Journal Research - SIJR this editorial, the editors make a special appeal to all the research...

Sahyadri Journal of Research

TM

DECEMBER 2015VOL.1 ISSUE 1

SIJRJournal

Research

Research Papers

Review Papers

Scientific Articles

International

Advisors

Editorial Board

Members

Dr. D L Prabhakara (Director)

Dr. Umesh M Bhushi (Principal)

Dr. C Ranganathaiah (Director – Research)

Dr. Manjappa Sarathi (Director-Consultancy)

Dr. Richard Pinto (Editor-in-Chief)

Dr. Jayarama A (Editor)

Dr. Rathishchandra Gatti (Dept. of ME)

Dr. Manoj Kumar A P (Dept. of ME)

Dr. Sarvesh Vishawakarma (Dept. of CSE)

Mr. Shamanth Rai (Dept. of CSE)

Mr. Harisha, (Dept. of CSE)

Ms. Srinidhi (Dept. of CSE)

Mr. Duddela Sai Prashanth (Dept. of CSE)

Mr. Vasudeva Rao P V (Dept. of CSE)

Mr. Naitik S T (Dept. of ISE)

Mr. Ashwath Rao (Dept. of ECE)

Mr. Steven L Fernandes (Dept. of ECE)

Mr. Sunil Kumar (Dept. of Civil E)

Mr. Likith (Dept. of Civil E)

Dr. Navin N. Bappalige (Dept. of Phy.)

Dr. Niraj Joshi (Dept. of Phy.)

Mr. Bharath Bhushan (Dept. of MCA)

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and opinions published in SIJR express solely the opinions of

the respective authors. Authors are responsible for citing of

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Although every effort will be made by the editorial board to

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Contents

SAHYADRI International Journal of Research | Vol 1 | Issue 1 | December 20152

Contents

Research Articles

Scientific Articles

Editorial 3

Identification of Lymphocytes from

Lymph node Images 4-7

Simulation and fabrication

considerations of P(VDF-TrFE) cantilevers 8-10

Growth kinetics, Spectral and

Optical properties of

Glycine mixed Sodium Nitrate crystal 11-15

Simulation study of proton

exchange membrane thickness on

cell voltage in micro methanol fuel cells 16-17

A Triple-band Circular-shaped Patch Antenna for

2.4/3.5/5.8 Ghz Wireless Communication System 18-20

Thickness dependence properties of

spin coated ZnO nano crystalline films 21-24

The puzzle of neutrino

– an elementary particle in the Universe 25

General Guidelines 26

Vol. 1 Issue 1ISSN Pending (Print)ISSN Pending (Online)

Mailing Address:Editor Sahyadri International Journal of ResearchSahyadri campus, Adyar, Mangalore - 575 007, IndiaE-mail: [email protected]: www.sijr.in

SAHYADRIInternational Journal of Research

It gives us immense pleasure to bring out the Volume 1 of Sahyadri International

Research. During a meeting held on September 10, 2015 the research community decided

that it is better to give a new name to the journal namely ‘Sahyadri International Journal of

Research'. The members present in this meeting unanimously accepted this suggestion. So

the erstwhile e-journal has appeared as 'Sahyadri International Journal of Research', Vol.1,

Issue1, 2015.

During the subsequent meetings we have finalized the advisors and editorial board of

'Sahyadri International Journal of Research' and implemented improvements. The journal

will have research papers, review papers and scientific articles which will be interesting to

research community. In this editorial, the editors make a special appeal to all the research

community to contribute original research papers and review papers on a regular basis.

There will be one volume with two issues every year starting from 2016. We hope that this

journal will provide a strong platform to both students and faculties to publish their

research results.

- Editorial Board

Journal of

Editorial

3SAHYADRI International Journal of Research | Vol 1 | Issue 1 | December 2015

Identification of Lymphocytes from Lymph node Images.1 2 1Ashwath Rao , S. N. Bharath Bhushan and Steven Lawrence Fernandes

1E & C Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-5750072MCA Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-575007

Email: [email protected], Mob: +91-9986224816

Abstract

Manual counting of lymphocytes is a tedious job and also time

consuming. Because of these drawbacks, an automated tool is

essential for segmenting and counting the lymphocytes. The

objective of this work is to develop an automated tool which

segments and counts lymphocytes from lymph nodes. The

dataset contains 25 stained lymphocyte images which are

obtained from five different parts of the human body. These

images are captured from scanning electron microscope

(SEM) and camera fitted microscopes. These images are

converted to gray scale images, and then edges are detected

from canny edge detection method. Using morphological

operators on the edge images we extract the contour

boundary of the lymphocytes and count the number of

lymphocytes. The proposed algorithm results with 76.00% of

accuracy.

Keywords; White blood cells, lymphocytes, lympho node,

segmentation, Lymphocytes count.

1. Introduction

Leukocyte cells composition reveals important diagnostic

information to the doctors about the patients. Globally, blood

is categorized into three different groups, erythrocytes,

leukocytes and thrombocytes. Leukocytes are having the

classification based on its Pathological (nucleus and

cytoplasm) characteristics. They are granulocytes and

agranulocytes, again the granulocytes contains three kinds,

those are Neutrophil, Basophil and Eosinophil and

agranulocytes contains LYMPHOCYTES and Monocytes as

referred in figure 1. Here we are more concentrating on

Lymphocytes. Lymphocytes are developed from the

haemocytoblast (Stem cells) in the red bone marrow of the

human body, and then spread in the blood to lymphoid tissue

elsewhere in the body also. The lymphocytes are having large

nuclei and cytoplasm. There are two functionally distinct

types: T-Lymphocytes and B-Lymphocytes. These are present

great in numbers in the lymphatic tissue. Out of 100 WBC cells

lymphocytes are present in the range of 30 to 35 and it is the

normal healthy person’s lymphocytes range, else treated as

cancer cell. These cancer lymphocyte cells combine to form a

tissue called LYMPH NODES. Hence calculating the number of

lymphocyte cells is an important task. Conventionally

lymphocytes are counted by pathologist.

Pathologists make use of differential count (DC) and newbaur

counting chamber (NCC) for manual counting of blood cells. In

the literature of manual blood counting NCC stands at the first

place and DC is at the second place. Till today DC is used for

manual counting of blood cells. DC is a type of manual

counting technique, where blood smears are viewed with the

help of a microscope and cells are classified manually by the

doctors. Doctors make use of five counters, which count the

five different leukocytes cells. On the other hand in Newbaur

Counting Chamber a grid structure is over lied on the image,

which may be of the length and width about 1mm size. Then

select any one grid area of an image, again divide it into

number of subparts by putting the grid lines. Finally it ends

with a microscopically one small region of an image. Count

the number of cells present in that respective region of the

microscopic image, then multiply it with that of one of gridded

portion, again multiply it with the whole grids of an image.

Finally, the result gives the number of cells present in an entire

image respectively.

Both manual counting techniques have their own drawbacks.

Each technique will consume more time and require more

number of cytotechnicians. Sometimes these methods may

not give required accuracy result. In some situations cells may

be in confusion (illumination inconsistency) state. Because of

this, ambiguity arises about the classification and counting of

leukocyte cells. To overcome all these limitations we are

proposing a novel automated algorithm for segmentation of

lymphocytes and counting of lymphocytes in the image.

The rest of paper is organized as follows. In section 2 we

provide a brief literature survey on segmentation of cells in

the blood. In section 3 we discuss about the dataset. The new

methodology proposed for segmentation of lymphocytes in

the lymph node image with experimental results is provided

in section 4. The paper is concluded in section 5.

2. Literature Survey

Many automatic segmentation methods have been proposed,

most of them based on geometrical features and local image

information such as shape, size, texture and histogram

equalizations respectively.

Research Paper


Neelam et al [1] suggests a method for segmenting the blood

cells using expectation maximization (EM) algorithm. Two

part segmentation system enables to distinguish white blood

cells into nucleus and cytoplasm from the color HSV images.

Segmentation is done by 3D Gaussian distribution and

clustering by K-mean clustering on the 3D feature vector. The

respective scheme provide good results, as which is applied

for 115 peripheral blood smears. Baldo et al [2] reported a

novel method to segment nucleus and cytoplasm of white

blood cells. WBC changes their shape in the level of

maturation. Baldo et al use morphological operators and

explore the scale-space properties of a toggle operator to

improve the segmentation accuracy. The rate of

segmentation mainly depends on selection of geometrical

structure of the cell. Nipon Theera-Umpon [3] proposed a

new method to segment single cell images of white blood cells

in bone marrow into two regions, i.e., nucleus and non-

nucleus. The method is based on fuzzy c-means clustering and

mathematical morphology. WBC present in bone marrow is

classified according their maturation. Though maturation is

continuous, WBC are classified into discrete classes. The fuzzy

clustering of pixels provides the over segmentation in which

several patches are generated. These patches are then

combined to form two segments of nucleus and non-nucleus

regions depending upon their similarities. Farnoosh et al [4]

projected WBC segmentation scheme, which is slightly

different from other work, because the images are captured

using L2 microscopic image for segmentation. All these

schemes mainly contain edge and border detection, region

growing, filtering, mathematical morphology, and watershed

clustering. The result of the proposed framework is able to

extract the nucleus and cytoplasm region in a WBC image

sample. Ravi Kumar et al [5] proposed cell segmentation using

Teager energy operator (TEO) method. TEO is used to

differentiate the nucleus and cytoplasm present in the

leucocytes. Nucleus is identified by high pass filtering

property of TEO and cytoplasm is segmented by

morphological operators.

Joost et al [6] proposed a method to segment the erythrocytes

using the SEM images. Joost et al concentrate to segment the

overlapped erythrocytes, i.e. only the upper most cells.

Simple Greedy Contour technique is used for the

segmentation. Duanggate et al [7] reported the scheme for

automatic Pap smear screening process. This is developed

over the manual count of nuclei and the cytoplasm of the

cervical cancer smear. For the isolation of nuclei and

cytoplasm using the dual wavelength method, as well for the

segmentation process using the color model, genetic

algorithm, fuzzy logics and Hough transformations are the

techniques used sequentially for Pap smear screening. For

classification purpose Duanggate et al used KNN classified

and Tabu search methods.

Nilsson et al [8] proposed the method for leukocytes

clustering. So many algorithms have been developed on the

pair of normal leukocytes clustering. Aim of this work is to

cluster the complex and abnormal leukocyte cells. The

process is done on the base of morphological operators.

Clustering is done using moving interface model based on

combinatorial model optimization system. Hiremath et al [9]

suggested a method for identification and classification of

leukocyte cells. Many papers are developed over the same

process based on the histogram analysis, measurement of

distance among nuclei and segmentation based on Graham

Schmidt orthogonalization process for amplifying color

vectors. The method adopted is developed by using the

histogram equalization, thresholding and edge detection

methods and results with high accuracy, by the comparison of

manual count done by pathologists. Animesh et al [10]

suggested a method on circulating peripheral blood plasma

cells as a prognostic indicator in patients with primary

systemic amyloidosis (AL). Data set consists of two varieties of

plasma cells i.e., peripheral blood plasma cells (PBPCs) and

the bone marrow plasma cells (BMPCs). These two varieties of

data set can be processed by the technique called sensitive

slide-based immunofluorescence. By this process circulating

peripheral blood plasma cells (PBPCs) as a prognostic

indicator in patients’ blood plasma, this technique gives the

count of absolute circulating plasma cell count was

determined. Domenico et al [11] proposed a method for

correction of the motion blur alternation in the Human

Lymphocyte Micro-Nucleus Image Based on Weiner’s

deconvolution. These corrections are always based on the

Weiner’s deconvolution, but evaluation of the point–spread

function (PSF) of the image is performed by taking into

account the motion angle. The image is altered by motion blur

a proper index is defined. The theme of this paper is to reduce

the number of rejected images for correct detection of Micro-

Nucleus into human lymphocytes respectively. The proposed

correction operates with the conjunction with spatial filters,

pointed out to correct the bad exposure, the Gaussian out of

focus and the Gaussian noise and the Weiner’s devolution

with PSF particular for the Gaussian out of focus alternation

with high intensity. Kind of Morphological operators is used to

develop this project. Miguel et al [12] designed the concept

on the morphological Operators. This paper provides the

relationship among the Medical image processing and the

Mathematical Operators. The datasets are converted to polar

logarithmic by morphological operators. To detect the

Erythrocytes, Inclusions and Extrusions Extraction algorithm

technique was used. Finally the fundamental idea here

presented is that the conversion of image into other intuitive

geometrical representation can be provided over the

traditional Cartesian representation. The conversion of Polar-

Logarithm coordinates as well as derived cyclic morphology

appears this is the result of this paper.


3. Dataset

3.1. About the dataset :

Collection of data set is one of the challenging tasks. Here we

have created our own image data set. We have collected

lymph node images from five different parts of the human

body, from each part of the body, randomly selected images

are taken. They are head and neck, breast, respiratory, soft

tissues and cardiovascular system.

The data set images are captured from SEM and camera fitted

microscopes. SEM is nothing but scanning electron

microscope. SEM can be controlled over a range of up to 6

orders of magnitude from about 10 to 5,00,000 times. These

microscopic images are having high accuracy compared other

microscopic images.

4. Proposed Model

Automatic identification of lymphocytes from lymph node

images consists of four steps, including pre-processing,

histogram equalization, edge detection and morphological

operations. The pre-processing stage includes image

enhancement of the dataset images. Edges are detected from

the image using canny edge detection. The post-processing

steps involves morphological operations namely dilation and

erode.

The proposed method for lymphocyte

segmentation is given below:

Algorithm: Lymphocytes Detection from Lymph node image.

Step 1: I ← Input color Image.

Step 2: Igray Ùw Convert the color image to gray scale.

Step 3: Thersholding is applied separately all places ie red,

green, and blue plain.

Step 4: Three plains are concatenated then once aging global

Thersholding is applied.

Step 5: Edges are detected by Canny Method.

Step 6: Idilate Dilation is applied on Iedge_detected Image.

Step 7: Iimerode is applied in Idilate.

Step 8: Finally lymphocytes are detected from lymph node

image.

For the purpose of experimentation five different parts of

human body lymph node images are considered.

Preprocessing is done on all images, then they are subjected

to canny edge detection. Morphological operators namely

dilation is applied on edge detected images. The simulation is

done for different threshold values. Figure 2 shows sample

image of our database.

Table 1: Accuracy Resulting Table.

Threshold Single cell Combined cell

Value detection detection

0.2 60.08 34.40

0.25 53.92 32.12

0.3 63.04 35.12

0.35 19.56 22.48

0.40 12.48 18.28

The table 1. Represents the rate of detection of lymphocyte

cells for different threshold values. Table 1 shows the rate of

detection of lymphocytes cells for different threshold values.

We have calculated two types accuracy i.e., single cell

detection and combined cell detection. The former one gives

accuracy of single cell detection whereas later one gives

accuracy based on single and combined cell detection in

which two or more cells are detected as a single cell. Figure 3

represents single cell detection and figure 4 represents

combined cell detection.

Table 2: Experimental Results

Threshold Value Average Result.

0.20 76.00%

0.25 75.78%

0.30 76.00%

0.35 36.00%

0.40 26.00%


Figure 1 : Different types of WBC

Figure 2: Sample Image from our dataset

Figure 3 Single Cell Detection

Figure 4. CombinedCell Detection.

Table 2. Represents the experimental result of the proposed

method. The same average result is getting for two different

threshold values i.e., 0.20 and 0.30. As like pathologist, we are

also more concentrating on single cell detection. Single cells

detection is high in threshold value 0.30 as compared with

0.20. The result of the 0.3 threshold value is considered as

final result of the proposed algorithm.

5. Conclusion And Future Work

We have proposed a method for segmenting lymphocyte. The

proposed method made to work on lymphocyte images which

are taken from the five different parts of the human body;

they are collected from head and neck, breast, respiratory

system, soft tissues and cardiovascular system. In differential

counting, pathologists are more concentrate on single cells.

As like pathologist we are also concentrating on single cell

segmentation, and then only we give preference to combined

cell segmentation. The profiling is done on all five classes of

images with 76.00% accuracy. From that, the result of 0.2 and

0.3 threshold values are same, but we conclude that 0.3

threshold value is the higher accuracy, because rate of single

cell segmentation is high compared 0.2.

We have successfully segmented the lymphocytes from the

lymphnodes. The same idea can be further extended to

remaining all types of blood cells. This idea leads to a great

thought, anyone can think of developing a device like

multimedia card reader. As like card reader, it should read the

blood smear and give the count of different types of blood

cells automatically.

References

[1] N. Sinha and A.R.Ramakrishnan. “Blood cell Segmentation using EM algorithm”. The III Indian Conference on Computer Vision, Graphics and Image Processing, Space Applications Centre (ISRO, Ahmedabad, India, Online ICVGIP-2002 Proceedings, December 16-18, 2002.

[2] L. B. Dorini, R. Minetto, and N. J. Leite, “White blood cell segmentation using morphological operators and scale-space analysis,” in Proc.20th Brazilian Symp. Comput. Graph. Image Process., pp. 100–107, 2007.

[3] N. Theera-Umpon, "Patch-Based White Blood Cell Nucleus Segmentation Using Fuzzy Clustering," ECTI Transactions on Electrical Engineering, Electronics, and Communications Vol.3, No.1, pp.15–19, February 2005.

[4] F.Sadeghian, Z.Seman, A. R. Ramli, B. H. Abdul Kahar, and M-Iqbal Saripan. “A Framework for White Blood Cell Segmentation in Microscopic Blood Images Using Digital Image Processing”. Biol Proced Online, Jun 11: pp. 196–206, 2009.

[5] B. Ravi Kumar, D. K. Joseph and V. Sreenivas, “Teager Energy Based Blood Cell Segmentation”. 14th International Conference on Digital Signal Processing. DSP 2002, 1-3 July, Santorini,Greece, vol. 2, pp. 619 -622, 2002.

[6] J. Vromen and B. McCane, "Red Blood Cell Segmentation from SEM Images", Conference on Image and Vision Computing New Zealand, Wellington, November 2009.

[7] C. Duanggate; B, Uyyanonvara; and T. Koanantakul, “A review of image analysis and pattern classification techniques for automatic pap smear screening process”, In Proceedings of the 2008 International Conference on Embedded Systems and Intelligent Technology (ICESIT 2008) [CD-ROM], 27-29 Bangkok, Thailand. pp. 212-217, February 2008.

[8] B. Nilsson and A. Heyden, "Model-based Segmentation of Leukocytes Clusters", 16th International Conference on Pattern Recognition (ICPR'02) - ICPR, vol. 1, pp.10727, 2002.

[9] P. S. Hiremath, Parashuram and S. Geetha “Automated Identification and classification of White Blood Cells (Leukocytes) in Digital Microscopic Images”. IJCA,Special Issue on RTIPPR (2), pp. 59–63, 2010.

[10] A. Pardanani, T. E. Witzig, G. Schroeder, E. A. McElroy, R. Fonseca, A. Dispenzieri, M. Q. Lacy, J. A. Lust, R. A. Kyle, P. R. Greipp, M. A. Gertz, and S. Vincent Rajkumar “Circulating peripheral blood plasma cells as a prognostic indicator in patients with primary systemic amyloidosis”, Blood Journal, Vol.101 Issue 3, pp. 827-830, Feb 1 2003.

[11] Domenico, Lamonaca and Carmelo, “Correction of the Motion Blur Alternation in the Human lymphocyte M i c ro - N u c l e u s I m a g e B a s e d o n W i e n e r ' s

thDeconvolution”, 16 IMEKO TC4 Symposium, Exploring New Frontiers of Instrumentation and Methods for Electrical and Electronics Measurements, Florence, Italy, Sept 22-24, 2008.

[12] M. A. Luengo-Oroz1, J. Angulo1, G. Flandrin, and J. Klossa, “Mathematical Morphology in Polar-Logarithmic Coordinates Application to Erythrocyte Shape Analysis” (Eds.): IbPRIA 2005, LNCS 3523, pp. 199–206, 2005.


Abstract

This paper presents des ign and s imulat ion of

polyvinylidenefluoride (PVDF) cantilever. However, poly

(vinylidenefluoride-trifluroethylene) P(VDF-TrFE) has better

piezoelectric properties than PVDF. In view of this,

piezoelectric â-phase of P(VDF-TrFE) which is essential for

energy harvesting has been investigated. The spin coated

films of P(VDF-TrFE) were heat-treated at various

temperatures to realize â-phase. The results indicate the

presence of â-phase in films heat-treated at 115oC for one

hour confirmed using high resolution X-ray diffraction

technique. Through Solidworks-simulation software, we

show that for a unimorph cantilever with design dimensions

45mm x 30 mm x 3.5 mm and 12mm thick proof mass a

fundamental vibrational frequency of 50 Hz (which is required

for body energy harvesting) is achievable.

1. Introduction

There has been an increase in wearable devices such as

external wearable medical devices, mobile phones, wireless

electronic devices etc. due to advancement in wireless

technology and low power electronics. Major sources of

energy that can be used are environmental vibrations and

motion of biological systems; these sources are ideal for

piezoelectric materials which have the ability to convert

mechanical energy into electrical energy with high conversion

efficiency [1]. The concept of utilizing piezoelectric materials

for energy generation has been studied greatly over past

decades [2, 3]. One ambient vibration energy source is human

movement [4], with energy available in breathing, blood

pressure/pulse and body movements. Approximately

60–70W of power is consumed during walking and a

piezoelectric material in a shoe with a conversion efficiency of

12.5% could produce 8.4W of power. On the other hand,

intelligent clothing with flexible piezoelectric materials

integrated into fabrics such as gloves [5], may be able to

convert a portion of mechanical energy associated with daily

activities into electric energy. Converted electrical energy can

be used to charge wearable mediums giving greater battery

life, or in an ideal scenario, a self-maintaining power supply.

Wearable devices will undoubtedly multiply in the years to

come due to a constant decrease in size and power

requirements of electronic systems.

Smart systems such as wireless sensing nodes etc., can be

powered by the energy from the ambient motion of the body,

eliminating the need for periodic battery replacements [6, 7].

The power generation in the harvester can be realized by

exploiting electromagnetic, electrostatic or piezoelectric

effect. The required voltages are generated directly in

piezoelectric and electromagnetic conversion mechanisms,

while in electrostatic generators, the conversion process is

initiated by a separate voltage source. While electromagnetic

generators are suitable for generating energy at high

frequencies, piezoelectric harvesters can outperform the

electromagnetic generators at low frequencies [8]. In

Addition, the volume occupied by the piezoelectric

generators is smaller than that of the electromagnetic

harvesters for a given normalized power density [9]. Hence

piezoelectric conversion is a better mechanism to harvest

energy at frequencies below 100 Hz.

However, there is a limited choice of piezoelectric materials

suitable for low frequency resonator designs [10]. PVDF is an

attractive piezoelectric material for harvesters owing to its

low elastic stiffness allowing the design of resonators with the

fundamental mode of vibration below 100Hz Recently it has

been reported that Poly(v iny l idenef luor ide-co-

trifluoroethylene P(VDF-TrFE) has better piezoelectric

properties than PVDF. One of the most efficient

configurations for a body energy harvesting device is a

cantilever with low natural frequency. A piezoelectric

harvester with the cantilever configuration having a single

layer of piezoelectric material is called a unimorph and that

with two layers is called a bimorph [11]. The energy harvester

so developed could be integrated with wireless sensor node

for in-vitro applications such as monitoring patient health like

heartbeat. Energy harvesters have wide ranging potential

such as in-vivo applications for powering pacemakers etc. The

in-vivo applications though are challenging due to the

biocompatibility issues of the energy harvester. Nevertheless,

the first set of in-vitro applications appear to be realistic. In

this paper, simulation, design and identification of PVDF-TrFE

in its piezoelectric phase for the fabrication of unimorph

cantilever has been presented.

Simulation and fabrication considerations of P(VDF-TrFE) cantilevers 1 2 3 1 1 1 4 5K.R. Rashmi , Swathi Rai , Rathishchandra R. Gatti , A. Jayarama , Navin Bappalige , Niraj Joshi , R.Pinto , S.P. Duttagupta

1Physics Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-5750072E & C Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-575007

3Mechanical Engg. Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-5750074CENT, Sahyadri College of Engineering & Management, Adyar, Mangalore-575007

5Electrical Engineering Department, IIT Bombay, Mumbai-400050Email: [email protected], Mob.: +91-8105284348

Research Paper


Design of unimorph cantilever: In order to harvest the energy

from body vibration, d33 mode for the higher voltage power

generation from the flexible material PVDF-TrFE is designed

and depicted in figure 1.

2. Simulation of the cantilever device

One of the most important design parameters in designing a

vibration energy harvesting device is resonant frequency. The

power density would be maximum when the vibration

frequency of the source matches the resonant frequency of

piezoelectric generator. The power density decreases when

source frequency deviates from the resonant frequency [6].

The frequency range of common body vibrations is between

40 Hz and 60 Hz. Moreover acceleration decreases with

higher modes of frequencies [6]. Therefore, fundamental

mode is considered in designing the cantilever.

We use the natural frequency of the proposed cantilever as 75

Hz, which nearly matches with the body vibrations at certain

points. Preliminary results are obtained with simulations of

the piezoelectric cantilever device using Solidworks-

simulation software. The design parameters are as shown in

figure 2. The mode list and material parameters are shown in

Table 1-2. The simulated cantilever vibrational frequencies

are shown in figure 3a-b. In order to identify the vibrational

frequencies and amplitudes at a given point on the body,

measurements have been carried out using inbuilt

accelerometer in i-phone. For this we used i-phone app

d o w n l o a d e d f r o m R e a l v i b r a t i o n s d a t a b a s e

(realvibrations.nisplab.org) and is shown in figure 4.

Figure 2. Basic cantilever design parameters (dimensions in

mm) for PVDF used for simulation

Figure 3. PVDF Cantilever device designed with numerical

simulation for frequency 50Hz (a) Frequency 1-Amplitude-

Amplitude1, (b) Frequency 1-Amplitude-Amplitude2

Figure 4. Vibrational frequencies and amplitudes at two

points on the body obtained by inbuilt accelerometer in i-

phone using NISP lab - real vibrations database

app[http://realvibrations.nipslab.org/node/178].

Figure 1. Schematic of d33 mode `of piezoelectric cantilever with metallic interdigitated pattern for energy extraction

(a) (b)


Table 1: Mode list

Frequency

Number

1 316.28 50.338 0.019866

2 1350.3 214.9 0.0046533

3 3001.1 477.64 0.0020936

4 7823.4 1245.1 0.00080313

5 8903.5 1417 0.0007057

Table 2: Material Properties

3. Sample preparation

P(VDF-TrFE) 70:30 is purchased from solvay chemicals. 10

wt% P(VDF-TrFE) solution has been prepared using N, N

dimethyl acetamide as solvent. The solution is ultrasonicated

for 2hours. 2 inch quarter wafers cleaned with RCA and

coated 240nm SiO2 using wet oxidation technique. The owafers were kept on hotplate at 120 C for 30 min to remove all

the impurities. P(VDF-TrFE) solution was spun on quarter

wafers at 1000 rpm for 30 sec to obtain films. The spun P(VDF-

TrFE) samples were heated on hotplate at various o o o otemperatures 105 C, 115 C, 125 C and 135 C for 1 hr. The

thickness of films was measured using dektak profilometer

and found to be approximately 1 micrometer.

Rad/sec Hertz Seconds

Piezoelectric Phase identification: To identify the piezoelectric

â phase and identify the functional groups of P(VDF-TrFE), high

resolution x-ray diffraction (HRXRD) technique is used. XRD

spectra of P(VDF-TrFE) films heat-treated at various

temperatures are shown in figure 5. A Rigaku diffractometer

with monochromated Cu Ká radiation of wavelength

1.54184A was the source of the X-ray generator. The data has obeen collected in the range of 15 to 25 C.

4. Summary

Design and simulation of PVDF cantilever which has low

resonant frequency but high piezo-electric constant has been

carried out. The ß-phase of PVDF and P(VDF-TrFE) are essential

for realizing piezoelectric properties. This paper presents work

on realization ß-phase of P(VDF-TrFE) films obtained by oannealing the films in the temperature range 105 to 135 C.

oXRD results indicate the annealing temperature 115 C is the

optimum.

References [1] M. Umeda, K. Nakamura and S. Ueha, “Energy storage

characteristics of a piezo-generator using impact induced vibration”, Japan. J. Appl. Phys. vol. 36, pp. 3146–51, 1997.

[2] N. G. Elvin, A. A. Elvin and M. Spector, “A self-powered mechanical strain energy sensor”, Smart Mater. Struct. vol. 10, pp. 293–9, 2001.

[3] E. Hausler and L. Stien, “Implantable physiological power supply with PVDF film” Ferroelectrics, vol. 60, pp. 277–282, 1984.

[4] T. Starner and J. A. Paradiso “Human generated power for mobile electronics Low-Power Electronics”, ed C Piguet (Boca Raton, FL: CRC Press) Chapter 45, pp. 1–35, 2004.

[5] E. Siores and L. Swallow, “Detection and suppression of muscle tremors”, Greater Manchester, UK, Patent GB0623905.7, 2006.

[6] S. Roundy, P. Wright, and J. Rabaey, "A Study of Low Level Vibrations as a Power Source for Wireless Sensor Nodes," Computer Communications, vol. 26, pp. 1131-1144, 2003.

[7] S.P. Beeby, M.J. Tudor, and N.M. White, "Energy Harvesting Vibration Sources for Microsystems Applications," Measurement Science and Technology, vol. 17, pp. 175-195, 2006.

[8] P. D. Mitcheson, E. K. Reilly, P. K. Wright and E. M. Yeatman, “Transduction mechanisms and power density for MEMS inertial energy scavengers”, Proc. Power MEMS, 2006.

[9] S. P. Beeby, R. N. Torah, M. J. Tudor and P. Glynne-Jones, T. O. Donnell, C. R. Saha, S. Roy, “A micro electromagnetic generator for vibration energy harvesting”, J. Micromech. Microeng, vol. 17, pp. 1257-1265, 2007.

[10] Y. Jeon, R. Sood, J. –h. Jeong, and S. G. Kim, “MEMS power generator with transverse mode thin film PZT”, Sens. and Actuators A., vol. 122, pp. 16-22, 2005.

[11] S. R. Anton and H. A. Sodano, “A review of power harvesting using piezoelectric materials (2003–2006)”, Smart Mater. Struct., vol. 16, R1-21. 2007.

SolidBody 1

(Boss-Extrude1)

(PVDF_cantilever)

Name: PVDF

Model type: Linear

Elastic Isotropic

Tensile strength:52 N/mm^2

Mass density:1770 kg/m^3

Elastic modulus:2450 N/mm^2

Poisson's ratio:0.18

Model

Reference Properties Components


Figure 5: XRD pattern of P(VDF-TrFE) films

heat-treated at various temperatures

Abstract

Single crystals of glycine mixed sodium nitrate (GSN) have

been grown by isothermal solvent evaporation technique at

ambient temperature. Crystal growth parameters such as

growth rate, metastable zone width and nucleation

parameters for GSN have been determined. Spectral and

optical characteristics of GSN have been investigated. The

optical energy gap of GSN crystal is 4.034eV. GSN crystal is

optically transparent in the visible region with lower

transmission cutoff at 265 nm.

Key words: spectral, optical crystal growth, glycine complex

PACs No:

1. Introduction

Considerable interest in some optically nonlinear semi-

organic crystals has developed in recent years due to their

important role in electro-optic modulators, high density

optical memories color displays, in the realization of signal

processing devices involving the generation of new

frequencies, signal amplification emission or oscillation etc.

[1]. The basic requirement for a material to be suitable for

nonlinear optical (NLO) applications is that it must have very

high nonlinearity. Although many materials have high

nonlinearity, their practical application is limited because of

their inherent limitations. Currently the concentration is more

on amino acids and their complexes because they combine

the advantages of organic crystals among with that of the

inorganic materials.

Glycine has the distinction of being the only amino acid which

forms many addition compounds with inorganic acids and

salts, besides forming metallic complexes. Most of the glycine

complexes show ferro electricity at high temperature [2-4].

Glycine mixed sodium nitrate viz: glycine mixed sodium

nitrate (GSN) is a nonlinear optical crystal [5]. The crystal

structure of GSN [6] has been determined. It has been

reported that GSN has optical nonlinearity comparable to that

of KDP. However no investigation has been made on the

growth kinetics, spectral and optical properties of GSN crystal.

This paper presents the results and analysis of our study on

GSN crystals.

2. Experimental procedure

2.1 Crystal Growth kinetics

GSN crystals were grown from aqueous solution by slow

evaporation technique at ambient temperature. The starting

materials were analytical grade reagents glycine and sodium

nitrate. They are taken in the molar ratio of 1:1 and dissolved

in double distilled water. The solution was heated on a water

bath maintained at a temperature of 34oC until the volume

was sufficiently reduced. Small transparent single crystals

with perfect external form were obtained through

spontaneous nucleation after three days of solution

evaporation. In order to confirm the phase purity of GSN X-ray

powder diffraction was recorded using SCINTAG powder x-ray

diffractometer with Cu Ká radiation (ë =1.5418A) and index othem. The sample was scanned in the 2è values from 10 to

o o50 at a rate of 2 /min. The observed XRD pattern was identical

with the XRD data reported [5], confirming the phase purity of

the crystal. The powder XRD of GSN (figure 1) is entirely

different from the XRD pattern of ã - glycine (figure 2) .

1 2 1 4S. Satheeshchandra , A. Jayarama , Nandakumar Shetty , S M Dharmaprakash1Physics Dept., S. D. M College (Autonomous), Ujire 574 240, India

2 Physics Dept., Sahyadri College of Engineering & Management, Mangalore-575007, India3Physics Dept., St. Aloysius College (Autonomous), Mangalore 575 003, India

4Physics Dept., Mangalore University, Mangalagangotri 574199, India.Email: [email protected], Mob.: +91- 9448549376

2 3B. Sunil Kumar , M. Narayana Bhat ,

Growth kinetics, Spectral and Optical properties of Glycine mixed Sodium Nitrate crystal

Research Paper

Figure 1. Powder XRD pattern of GSN

Figure 2. Powder XRD pattern of ã - glycine


Defect free crystals were selected as seeds and suspended in

the mother solution maintained at constant temperature of o34 C which was allowed to evaporate in a crystal growth

apparatus. Good crystals with larger dimensions were

obtained within a week. The crystal faces were indexed using

Enraf CAD4 diffractometer along with a four circle

goniometer. GSN crystal with well developed surfaces was

mounted on the goniometer and the various faces of the

crystal were indexed.

In solution growth technique, the size of a crystal depends on

the amount of the material available in the solution which in

turn is decided by the solubility of the material in that solvent.

The solubility of synthesized pure glycine and sodium nitrate

mixed glycine has been determined in water. This was

performed by adding water maintained at constant

temperature to a known quantity of the material till the

material was completely dissolved.

Good quality GSN and ã-glycine crystals were collected and

finely powdered.. Two hundred milliliters of saturated GSN

and ã-glycine solution was prepared in accordance to the

solubility diagram and loaded in a constant temperature bath.

The solutions were stirred continuously for five hours for

stabilization. While stirring the solution the temperature of othe bath was reduced at the rate of 5 C per hour. The

temperature at which the first speck of the particle has been

observed corresponds to the width of metastable zone. The

experiment was repeated for saturated solutions at otemperatures 35, 40, 45, 50 C.

Attempts were made to find the growth rate of the crystal

along a and c-axis of the GSN crystal. For this the seed crystal

was monitored continuously. The dimensions of the crystal

along the a and c-axis were measured at regular time

intervals.

The optical transmission of glycine mixed sodium nitrate for

the wavelengths between 200 – 2500nm was recorded using

Varian Cary 5E UV-VIS-NIR spectrometer. Laser Raman spectra

is used to confirm the presence of functional groups in glycine

mixed sodium nitrate crystals. Laser Raman spectra was -1recorded in the range 400-4000cm . In order to qualitatively

analyze the presence of functional groups in GSN, Fourier

transform infrared (FTIR) spectrum was recorded in the range

400-4000 cm-1 using the Perkin Elmer grating Infrared

spectrometer. The sample used was in pellet form in KBr

phase. The characteristic absorption peaks were observed in -1the range from 400 to 3000cm .

3. Results and Discussion

The morphological analysis reveals that the GSN crystal is a

polyhedron with 12 developed faces. The crystal was found to

be transparent and was bound by 100, 111, 11 , 00 , 1 , 11

faces, There is a pair of parallel faces, which is a pinacoid and

indexed as 100. This is the most prominent face and

dominates the crystal morphology. The other pinacoids are

111 and 111. They are inclined with 100 face. Different faces of

the crystal in the order of prominence are as follows:

100>111>111>001>111>111. The morphology of the grown

crystal is shown in Figure 3.

The variation of solubility of pure glycine and GSN with o otemperature between (30 C and 60 C) is shown in Figure 4.

The solubility data could be fitted to an equation of the form S

= AT2+BT+C where A,B, and C values for pure glycine and GSN

Figure 3. Morphology of Glycine mixed sodium nitrate

Figure 4. Solubility of glycine and Glycine mixed Sodium Nitrate


From the UV-VIS-NIR studies we observed that the crystal is

found to be transparent in the entire UV & visible spectral

regions extending between 1000 and 2000nm, the

absorbance is minimum, suggesting that the crystal is highly

transparent and it is very much required for NLO applications.

Above 2000nm slight increase in the absorbance is observed.

Hence GSN crystal is optically transparent in the UV- visible

region with lower transmission cutoff is observed at 265 nm.

The plot of transmittance vs wavelength (nm) is shown in

Figure 7.

Optical properties of crystalline materials give information

regarding the composition nature and quality of the crystal. In

a crystalline material the region of transparency to

electromagnetic radiation defines the intrinsic loss

mechanisms and also theoretical transmittance achievable

within this region. The transparent spectral region in

insulators is defined at short wavelengths by electronic

transitions across the band gap and at long wavelengths by

lattice vibrations. The band gap of the material Eg, sets the

transmittance limit at short wavelength cut off (ë ) is defined c

by ë = hc/E in which h is Plank’s constant and c is the velocity c g

of light. The optical band gap Eg as given by Tauc’s graph [7]

between the product of absorption coefficient and the 1/2 incident photon energy (áhí) with the photon energy hí at

room temperature shows a linear behavior that can be

considered as the proof for direct transition. Hence assuming

a direct transition between valence and conduction bands,

the optical energy gap (Eg) is estimated by the extrapolation 1/2 of the linear portion of the curve to a point at which (áhí) is

equal to zero [8,9]. The optical energy gap has been estimated

using the Tauc’s method and the optical energy band gap has 1/2been found to be 4.03eV. The variation of (áhí) vs energy is

shown in Figure 8.

samples were given in Table 1. S and T are the solubility

expressed in gm/100cm3 and temperature in degree Celsius

respectively. The solubility of GSN was found to be

63gm/100cc of water and that of pure glycine is

12.5gm/100cc. GSN has a positive temperature coefficient of

solubility. Therefore, slow cooling of aqueous solution of GSN

could be attempted to grow bulk crystals.

Table 1: Solubility data of ã-glycine and GSN

Sample A B C

Glycine 0.01002 0.23321 11.60298

GSN 0.01333 0.44762 43.89286

The metastable zone width of GSN and ã-glycine for different

saturation temperatures are shown in Figure 5. The

metastable zone width of ã-glycine was found to be less than

that of GSN. It is obvious from the figure that the zone width

for both solutions decreases as the temperature decreases.

The variation of the growth rate of the crystal with time is

shown in the Figure 6. From the graph it follows that, along c-

axis the crystal grows rapidly in the beginning and it grows at a

lower rate after 6 hours. However the growth rate along a -

axis is very less than c-axis.

Figure 5. Metastable zone width of Glycine mixed sodium nitrate

Figure 6. Growth rate of Glycine sodium Nitrate crystal.

Figure7. UV VIS IR Spectra of glycine mixed sodium nitrate


In Laser Raman spectra the peaks observed at 591.9 and -1683cm are attributed to carboxylate groups while the

-1absorption peak at 3027.8 cm is NH stretching attributed to

NH3 group. Of the remaining peaks, those at 901.5, 1334.6, -1and 2973.1 cm are attributed to CH2 group while the peaks at

-11057.8 and 1454 cm are assigned to NO3 and CH groups

respectively. The characteristic peaks of laser raman spectra

are shown in Figure 9.

From the FTIR spectra the characteristic absorption peaks -1were observed in the range from 400 to 3000cm and are

shown in Figure 10.

Free glycine exists as zwitterions in which carboxyl group is

present as carboxylate ion and amino group exists as

ammonium ion. The absorption due to carboxyl ate group of -1 -1GSN are observed at 503.4, 605.6 cm and 887.2 cm

respectively. The symmetric and asymmetric modes of COO- -1are observed at 1585.4 and 1390.6 cm . The absorption

peaks due to NH + group of GSN are observed at 2171.7, 3

-12603.7, and 2754.2cm . The asymmetric and symmetric NH -1bends of NH + are positioned at 1124 and 1487cm 3

respectively. Nevertheless, from the presence of carboxylate

ion it may be concluded that glycine molecules exists in

zwitterionic form in GSN. The presence of NO - group in GSN 3

-1is confirmed by the absorption peak at 1041.5cm . Other -1 -1 -1peaks at 925.8cm , 1326.9cm , and 2887.2cm are attributed

to CH groups from a comparison of spectra with that of 2

glycine [10]. The position of the peaks with the proposed

assignments is shown in Table 2.

Table 2: Laser Raman and IR frequencies of Glycine mixed

Sodium nitrate crystals (Wave number in cm)

Infrared LaserRaman Assignment

3755.1 - Combination band

3687.7 - Combination band+3107.1 3027.8 NH3

2887.2 2973.1 CH2

+2754.2 - NH3

+2603.7 - NH3

+2171.7 - NH3

-1585.4 1621.4 COO+1487 454.5 NH3

-1390.6 - COO

1326.9 1334.6 CH2

+1124.4 1123.1 NH3

1041.5 1057.8 NO3

-925.8 901.5 COO-887.2 - COO

- 727.5 CH2

684.7 683 COOH-605.6 591.9 COO

503.4 515.3 COO-

Fig. 8. Optical Energy gap of Glycine mixed sodium nitrate

Figure 9. Laser Raman Spectra of Glycine mixed sodium nitrate

Figure10. FTIR Spectra of glycine mixed sodium Nitrate.


4. Conclusion

The morphological analysis reveals that the crystal is a

polyhedron with 12 developed faces. The optical energy gap

of GSN crystal is 4.03eV. GSN crystal is optically transparent in

the visible region with lower transmission cutoff at 265 nm.

The growth rate of GSN along a –axis is very less than c-axis.

The metastable zone width of ã-glycine was found to be less

than that of GSN.

References

[1] D.S. Chemla J. Zyss Eds, Nonlinear optical properties of

organic molecules & crystals vols. 1 & 2, Academic

press, New york 1987.

[2] B. T. Matthias, C.E. Miller and J.P. Remeika,

“Ferroelectricity of Glycine Sulfate”, Phys. Rev. vol. 104,

pp. 849, 1956.

[3] S. Hoshino, T. Mitsui, F. Jona and R. Pepinsky, “Dielectric

and thermal study of tri-glycine sulfate and try-glycine

fluoberyllate, Phy. Rev., vol. 107, pp. 1255, 1957.

[4] R. Pepinsky, Y. Okaya and F. Jona, “Ferroelectricity and

structure of tri-glycine fluoberyllate” Bull. Amer. Phys.

Sol. vol. 2, pp.220, 1957.

[5] M. Narayana Bhat, S. M. Dharmaprakash, “New

nonlinear optical material: glycine sodium nitrate”

Journal of Crystal Growth, vol. 235 pp. 511-516, 2002.

[6] R. V. Krishnakumar, M. Subha Nandhini, S. Natarajan, K.

Sivakumar and Babu Varghese, “Glycine sodium

nitrate”, Acta Cryst., vol. C57, pp. 1149-1150, 2001.

[7] J. Tauc, R. Grigorovici and A. Vance, “Optical Properties

and Electronic Structure of Amorphous Germanium”,

Phys. Stat. Sol., vol. 15, pp. 627-637, 1966.

[8] G. P. Joshi, N. S Saxena, T. P Sharma, V. Dixit, S. C. K.

Misra, “Bandgap determination of chemically doped

polyaniline materials from reflectance measurements”

Indian J. Pure Appl. Phys. vol. 41, pp. 462-465, 2003.

[9] E. A. Davis, N. F. Mott, “Conduction in non-crystalline

systems V. Conductivity, optical absorption and

photoconductivity in amorphous semiconductors”,

Philosophical Magazine, vol. 22, pp. 903-922, 1970.

[10] R.S Krishnan, P.S. Narayanan, “Crystallography and

Crystal Perfection”, Academic Press, London, pp. 329,

1963.


of proton exchange membrane thickness on cell voltage in micro methanol fuel cells is presented.

Basic design considerations of DMFCsThe basic design of DMFC has a membrane layer, primarily Nafion is sandwiched between two electrode assemblies anode and cathode; this Membrane Electrode Assembly (MEA) is the heart of the fuel cell as shown in figure 1. Methanol diffuses through the micro-porous layer (which regulates the transport of methanol) to the catalyst which generates protons. The protons then diffuse through the membrane to the cathode. The proton reacts with oxygen at the cathode to form water.

The equations for the process are as below: The entire MEA is sandwiched between two silicon chips with micro channels which contain the flow of methanol at the anode and flow of air at cathode. The negative charge collected by the metallic electrode moves into the external circuit from anode to cathode, thus balancing the charge transfer process.

SimulationA 3 dimensional model of a proton exchange membrane /polymer electrolyte membrane fuel cell (PEMFC) [7-9] is implemented using COMSOL Multiphysics 5.0.

AbstractProton exchange membranes (PEMs) are important components of fuel cells in which either hydrogen or methanol are used as fuels. In this paper we propose to use methanol as fuel to realize micro direct methanol fuel cells (µ-DMFC). The membrane electrode assembly (MEA) of µ-DMFC consists of a micro-porous layer which regulates the flow of methanol to the catalyst at the anode, a high efficiency

+catalyst layer for the generation of protons (H ) from methanol, a high conductance membrane layer for the transfer of protons and a high efficiency catalyst at the

+cathode for the conversion of oxygen and H into water. Simulation results indicate that the cell voltage decreases with increase in membrane thickness from 50ìm to 200 ìm

IntroductionThe fuel cell technology has been considered as a promising alternative for future energy needs and cleaner environment. Among the several kinds of fuel cells, proton-exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) are known to utilize the proton exchange membranes [1-5]. A proton exchange membrane or polymer electrolyte membrane (PEM) is a semipermeable membrane generally made from ionomers and designed to conduct protons while being impermeable to gases such as oxygen or hydrogen [6]. This is their essential function when incorporated into a membrane electrode assembly (MEA) of a proton exchange membrane fuel cell i.e. separation of reactants and transport of protons. Direct-methanol fuel cells (DMFCs) are a subcategory of proton-exchange fuel cells in which methanol is used as the fuel. Their main advantage is the ease of transport of methanol, energy-dense yet reasonably stable liquid at all environmental conditions. Efficiency is quite low for these cells, so they are targeted especially to portable applications, where energy and power density are more important than efficiency. Current DMFCs are limited in the power they can produce, but can still store high energy content in a small space. This means they can produce a small amount of power over a long period of time. Military applications of DMFCs are an emerging application since they have low noise and thermal signatures and no toxic effluent. These applications include power for man-portable tactical equipment, battery chargers, and autonomous power for test and training instrumentation. In this paper, simulation study

Simulation study of proton exchange membrane thickness oncell voltage in micro methanol fuel cells

Research Paper

1 2 3 2 4 5Swathi Rai , K. R. Rashmi , M. B. Savitha , A. Jayarama , R.Pinto , S.P. Duttagupta1E & C Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-575007

2Physics Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-5750073Chemistry Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-575007

4CENT, Sahyadri College of Engineering & Management, Adyar, Mangalore-5750075Electrical Engineering Department, IIT Bombay, Mumbai-400050

Email: [email protected], Mob.: +91- 9008928153

Figure 1 Basic structure of DMFC


+ - Anode reaction: CH OH + H O 6 H + 6e + CO (Oxidation)3 2 2

+ - Cathode reaction: O + 6 H + 6e 3H O (Reduction)2 232

Overall reaction: CH OH + 3 O 2H O + CO (Overall reaction) 2 2 2

32

The present model is established based on the following assumptions: • Flow is laminar everywhere due to small gas pressure

gradient. • Reactant gases behave as the ideal gas mixture. • The electrodes and membrane are made of homogeneous

materials. • The temperature distribution across the cell is uniform. • Water exists only in the gas phase in the fuel cell. • The polymer electrolyte membrane is impermeable to

reactant gases. • Protons can only transport through the electrolyte, and

electrons through the solid phase. • Three species including oxygen, water and nitrogen are

considered on the cathode side while only hydrogen and water are considered on the anode side.

• The fuel cell is operating at the steady state.

Figure 2 shows the schematic structure of the PEMFC model simulated using Comsol Multiphysics 5.0. The top part is the anode side and bottom part is the cathode side.

The following are the design parameters of the model.

• Cell Length 20.0mm

• Channel height 1.0mm

• Channel width 0.7mm

• Rib width 0.9mm

• GDL width 0.3mm

• Contact dimension for 1 contact 200ìm

• Porous electrode thickness 0.5mm

• Membrane thickness 0.05mm

• GDL Porosity 0.4

• GDL electric conductivity 1000S/m

• Contact electric conductivity 100000S/m

• Inlet H2 mass fraction (anode) 0.743

• Inlet H2O mass fraction (cathode) 0.023

• Inlet oxygen mass fraction (cathode) 0.228

• Anode inlet flow velocity 0.2m/s

• Cathode inlet flow velocity 0.5m/s - 5• Anode viscosity 1.19?10 Pa.s- 5•Cathodeviscosity 2.46?10 Pa.s- 12• Permeability (porous electrode) 2.36?10 m2

• Membrane conductivity 10 S/m

Effect of membrane thickness: Effect of membrane thickness on the PEM fuel cell performance is studied by keeping the parameters mentioned above as constant. As shown in Figure 3, the cell voltage decreases with increase in membrane

thickness from 50ìm to 200ìm. This is due to decrease in proton conductivity with the increase of membrane thickness. This result is important for designing minimum membrane thickness for maximum proton conductivity and

with minimum permeability in the case of ì-DMFCs. Figure 3: Variation of cell voltage with respect to cell membrane thickness

ConclusionA 3-dimensional model for DMFC fuel cell is validated under the experimentally feasible assumptions. The effect of channel width on the fuel cell performance is studied by considering various channel widths employing different distributions and dimensions. It is observed that the voltage of the cell decreases as the thickness of the membrane is increased from 50µm to 200µm.

References:[1] Y. Lim, H. Lee, S. Lee, H. Jang, M. A. Hossain, Y. Cho, T. Kim, Y. Hong,

W. Kim, “Synthesis and properties of sulfonated poly(phenylene sulfone)s without ether linkage by Diels–Alder reaction for PEMFC application” Electrochim Acta vol. 119, pp. 16–23 February 2014.

[2] U. Thanganathan, S. L. Ghatty, “Effects of humidity and temperature on the electrochemical activities of H2/O2 PEMFCs using hybrid membrane electrolytes” J. Solid State Electrochem. vol. 18, pp. 285-290, 2014.

[3] S. Martemianov, V. A. Raileanu Ilie, C. Coutanceau, “Improvement of the proton exchange membrane fuel cell performances by optimization of the hot pressing process for membrane electrode assembly” J. Solid State Electrochem., vol. 18, pp. 1261-1269 2014.

[4] U. Thanganathan, M. Nogami, “Proton conductivity and structural properties of precursors mixed PVA/PWA-based hybrid composite membranes” J. Solid State Electrochem. vol. 18, pp. 97-104, 2014.

[5] S. Neelakandan, P. Kanagaraj, R. M. Sabarathinam, A. Muthumeenal, Nagendran, “SPEES/PEI-based highly selective polymer electrolyte membranes for DMFC application” Solid State Electrochem., vol. 19, Issue 6, pp 1755-1764, June 2015.

[6] M. Tohidian, S. R. Ghaffarian, S. E. Shakeri, E. Dashtimoghadam, M. M. Hasani-Sadrabadi, “Organically modified montmorillonite and chitosan–phosphotungstic acid complex nanocomposites as high performance membranes for fuel cell applications”, J. Solid State Electrochem., vol. 17, 2123-2137, 2013.

[7] P. Ramesh, S. S. Dimble, S. P. Duttagupta, “Study of the Effect of Channel Width and Rib Width on Micro Fuel Cell Performance using 3D Modelling”, IJECT vol. 2, Issue 4, Oct. - Dec. 2011.

[8] P. Ramesh, S. P. Duttagupta, “Effect of Segmented Current Collection Contacts Attached to Gas Diffusion Layer in Micro PEM Fuel Cells with Ceramic Flow Field Plates” Int. J. Electrochem. Sci. vol. 9, pp. 4331-4344, 2014.

[9] T. C. Patil, S. P. Duttagupta, “Portable Micro–Solid Oxide Fuel Cell Testing Setup (Indian Patent Pending [2129/MUM/2014] Filed In July 2014.Figure 2: Schematic of PEMFC


A TRIPLE-BAND CIRCULAR-SHAPED PATCH ANTENNA FOR 2.4/3.5/5.8 GHZ WIRELESS COMMUNICATION SYSTEM

1 1 1 2 1 1Harisha , R. B. Shamanth , D. S. Prashanth , Mukul Anand. , B. N. Sunil , Shobhan1CS & Engg. Dept., Sahyadri College of Engineering & Management, Adyar, Mangalore-575007

2Information Technology Dept. IIIT AllahabadE-mail: [email protected], Mob.:+918861361233

ABSTRACT

In this paper a triple-band circular-shaped patch antenna for

wireless communication system is designed and simulated.

Proposed antenna is suitable for wireless application which

uses the frequencies 2.4GHz, 3.5GHz and 5.2GHz. Proposed

antenna is made up of two different types of material with

silicon as substrate and copper as a patch of antenna. This

proposed antenna comprises of four circular patches and one

I-shaped patch to control the performance of antenna. The

return loss, S parameter, gain , current distribution and 1,1

VSWR are analyzed through the simulation result and also

presented as same in this paper .

KEYWORDS: MICROSTRIP PATCH ANTENNA, RETURN LOSS,

GAIN, BANDWIDTH, WLAN.

1. INTRODUCTION

In the modern era communication devices are part and parcel

of life. In the field of wireless communication, data transfer

between the devices are done through a wireless medium;

where antenna is being used to transmit and receive

electromagnetic waves[1]. Antennas are available in variety

[1], depending on the performance and working frequency,

we use them for different applications. In the field of mobile

cellular technology there are many manufacturers producing

a variety of mobile phones and the other communication

devices like tablet, where data transfer facilities such as 3G,

4G and WLAN are being supported. For such devices,

thewidth is continuously increasing,while the thickness is

decreasing. Even the Portable Computers are manufactured

with smaller sizes, which incorporates antenna for accessing

Wireless LAN [2].

In the early generation of wireless communication,

perpendicular hardwired antennas were used on printed

circuit boards, these antenna's were very bulky and used to

occupy more area. The bulkier antennas were prone to

breakage by some obstructions such walls, tables and other

materials. This problem is solved by patch antenna, which is

easily mountable on the printed circuit boards with low

conformal properties [1] [3]. One of the main inventions in the

field of antenna is microstrip patch antenna suitable for low

energy devices. These antennas can be built on different

substrate which is having variable thickness and shape [4] [5].

By creating slots or changing thickness of the patch, the

performance of antenna can be enhanced. There are different

types of slots like L shape, U shape and H shape that can made

on the patches [5-9]. Intensive research has been done to

develop a dual band, triple band and multiband antennas

[10]. For WLAN many researchers have proposed an antenna

with flexible substrate for dual band showing that it is easy to

mount a patch antenna on RFID circuit [11]. Apart from

substrate, different feeding mechanisms can be used to

enhance the performance of antenna [12].

The prominent challenge faced by WLAN is the design of

antenna. In WLAN, antenna should be more efficient and it

should work in a certain range of frequencies [6][8]. In the

past few decades E-shape micro-strip patch antenna has

gained importance, due to its good gain and polarisation

properties. Initially, E-shaped patch antenna were developed

for the broadband application but later many researchers

worked on it to improve the performance by changing its

shape [9]. As per the 802.11 standards, WLAN will work in the

frequencies of 5-6GHz. For WLAN and WiMax new antenna

has been proposed and simulated and results are presented in

the paper.

2. RELATED WORK

In [7] , Hussein and Luhaib, proposed a new antenna design

for WLAN applications, where the design includesmultilayer

of substrate silicon/glass/silicon with dielectric constant 11.9

and 4.6 respectively. The proposed antenna shows bandwidth

of 920MHz with gain 2.8dB and return loss -20. There are

many types of antenna that have been proposed for multiple

frequency band operations like Wi-Fi, WiMax, ISM band etc.

[16][17].

Authors in [13] claim that staked configuration on patch

antenna can increase the bandwidth and that can be used for

WiFi, WiMax.

The antenna performance can be improved by inset feeding

mechanism and substrate materials play major role in it [14].

For example 'Rogers' which is used as substrate material of an

antenna has higher possibilities of good results like s11

Research Paper


parameters gain and return loss [15]. Electromagnetic waves

are scattered by many ways so it is very important to have

good transmitter and receiver. Itneeds to consider the

polarization and other QoS parameters of antenna [19].

3. Proposed Design

The proposed antenna has a thickness of 0.618mm, width

22mm and height 29mm as shown in fig1. The antenna

comprises of material silicon with dielectric constant 11.9.

The proposed antenna has a thickness of 0.618mm, width

22mm and height 29mm as shown in fig1. The antenna

comprises of material silicon with dielectric constant 11.9.

Three circular Patch each having thickness 0.1mm and width

1mm separated by 0.1mm gap are used. Feed to the antenna

is given through I shaped patch with thickness 1mm and

length of 3mm constructed on the substrate 0.508mm.

4. Simulation And Result

Simulation results are displayed in fig 2. It shows that return

loss is -15dB at frequency 2.4GHz, -20dB at frequency 3.5GHz

and -18dB at frequency 5.8GHz that shows antenna is suitable

for ISM band 2.4GHz/5.8GHz.

The proposed antenna has the gain of 3.0dB. The radiation

pattern is shown in fig 3.

Radiation pattern (2D) is shown in fig 4. It shows that radiation

will be distributed on the upper and lower side of the antenna.

Directivity of the antenna is one of the important parameters

which are used for the WLAN. In this case, directional antenna

may lead to more collision because of the hidden terminal

problem [18].

VSWR is the voltage standing wave ratio. Here VSWR of the

antenna should be less than 2V for safety purpose and the

proposed antenna has VSWR ~1.03V.


Figure 1: Proposed Design

Fig.4 Simulation results of the radiation pattern (3D)

Fig.5 Simulation results of the radiation pattern (2D)

Fig.2 Simulation result showing S parameter1,1

L= L -2eff

The actual length (L) of patch is obtained by:

Width of patch antenna will be

The effective of the dielectric constant

The effective length (L eff) is given by

The length extension (?L) is given by

5. CONCLUSIONIn this paper a triple band antenna has been designed and simulated which works in the frequencies 2.4/3.5/5.8 GHz. Proposed antenna shows a gain of 3.5dB, and it is suitable for ISM band.

REFERENCES

[1] C. Balanis, , Antenna Theory, Analysis, and Design , 1997 :Wiley

[2] L. Chen; K. Wong, "2.4/5.2/5.8 GHz WLAN antenna for the ultrabook computer with metal housing," Microwave Conference Proceedings (APMC), 2012 Asia-Pacific , vol., no., pp.322,324, 4-7 Dec. 2012

[3] R. Garg, Microstrip antenna design handbook: Artech House.

[4] X. Liu, Y. Chen, Y. Jiao and F. Zhang, "Conformal Low-profile E-shaped Patch Antenna with Unequal Thickness Substrate", 2007 International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, 2007.

[5] F. da Costa Silva, S. Barroso de Assis Fonseca, A. Soares and A. Giarola, "Analysis of microstrip antennas on circular-cylindrical substrates with a dielectric overlay", IEEE Trans. Antennas Propagat., vol. 39, no. 9, pp. 1398-1404, 1991.

[6] L. Kong, J. Pei and X. Guo, "A new dual-frequency broadband L-slot mixed E-shaped patch antenna", 2008 Global Symposium on Millimeter Waves, 2008.

[7] A. Hussein and S. Luhaib, "Designing E-Shape microstrip patch antenna in multilayer structures for WiFi 5GHz network", 2012 20th Telecommunications Forum (TELFOR), 2012.

[8] R. Gyawali, P. Kumar Penta and V. Sudha, "CPW-FED S-shaped single band WLAN antenna", 2011 International Conference on Emerging Trends in Electrical and Computer Technology, 2011.

[9] F. Yang, X. Zhang, X. Ye and Y. Rahmat-Samii, "Wide-band E-shaped patch antennas for wireless communications", IEEE Trans. Antennas Propagat., vol. 49, no. 7, pp. 1094-1100, 2001.

[10] W. Mok, S. Wong, K. Luk and K. Lee, "Single-Layer Single-Patch Dual-Band and Triple-Band Patch Antennas", IEEE Trans. Antennas Propagat., vol. 61, no. 8, pp. 4341-4344, 2013.

[11] C. Hsuan-Yu, C. Sim and L. Ching-Her "Compact size dual-band antenna printed on flexible substrate for WLAN operation," Antennas and Propagation (ISAP), 2012 International Symposium on , vol., no., pp.1047,1050, Oct. 29 2012-Nov. 2 2012

[12] V. Singh, Z. Ali and A. Singh, "Dual Wideband Stacked Patch Antenna for WiMax and WLAN Applications", 2011 International Conference on Computational Intelligence and Communication Networks, 2011

[13] M. Sharma, A. Katariya and R. Meena, "E Shaped Patch Microstrip Antenna for WLAN Application Using Probe Feed and Aperture Feed", 2012 International Conference on Communication Systems and Network Technologies, 2012.

[14] Z. Ali, V. Singh, A. Singh and S. Ayub, "Wide Band Inset Feed Microstrip Patch Antenna for Mobile Communication", 2013 International Conference on Communication Systems and Network Technologies, 2013.

[15] Z. Ali, V. Singh, A. Singh and S. Ayub, "E-Shaped Microstrip Antenna on Rogers Substrate for WLAN Applications", 2011 International Conference on Computational Intelligence and Communication Networks, 2011.

[16] Z. Ali, V. Singh, A. K. Singh and etal., “Compact Dual Band Microstrip Patch Antenna for WiMAX lower band Application” In the proceedings of IEEE International Conference on Control, Computing, Communication and Materials-2013

[17] M. Siddhartha, K. Akash and A. K. Singh, “Dual Band Textile Antennas for ISM Bands” In the proceedings of IEEE International Conference on Control, Computing, Communication and Materials-2013.

[18] M. Umehira and Y. Ohtomo "Impact of antenna directivity for carrier sensing in high density WLAN using adaptive directional antenna," Applied Sciences in Biomedical and Communication Technologies (ISABEL), 2010 3rd International Symposium on , vol., no., pp.1,5, 7-10 Nov. 2010.

[19] J. Rodrigues, S. Fraiha, J. Araujo, H. Gomes, C. Frances and G. Cavalcante, "Influenceof polarization effects of the antennas in a WLAN coverage area", 2011 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC 2011), 2011.


Thickness dependence properties of spin coatedZnO nano crystalline films

1 2Felcy Jyothi Serrao and S.M. Dharmaprakash .1. Department of Physics, Sahyadri College of Engineering and Management, Mangalore 575007, India.

2. Department of studies in Physics, Mangalore University, Mangalagangothri 574199, India.E-mail: [email protected]

Abstract

Transparent, conducting undoped ZnO thin films were

prepared by optimized sol-gel spin coating technique. The

influence of film thickness on the structural, optical and

electrical properties of ZnO films was investigated. The

structural characteristics of the samples were analyzed by X-

ray diffractometer and an atomic force microscope. XRD

studies revealed the polycrystalline nature of the films with a

hexagonal (wurtzite) structure and a preferred orientation

with c-axis. The grain size and the surface roughness were

found to increase with increased film thickness. The optical

properties were studied using a UV-visible spectroscopy. The

average optical transmittance in the visible region of all the

films was over 80%. The optical band gap (E ) values g

decreased from 3.224 to 3.148 when the film thickness was

increased from 112 nm to 348nm. A lowest resistivity of 1.46 -2x 10 Ù cm was obtained from the film of thickness 384 nm.

From the results, it can be concluded that the structural,

optical and electrical properties of ZnO thin films can be tuned

by varying thickness of the films, making it suitable for

optoelectronic device applications.

Keywords: ZnO, sol-gel, thin film, optical properties, electrical

properties

1. Introduction

In recent years, the inexpensive, nontoxic and abundant zinc

oxide (ZnO) has received extensive attention because of its

novel properties such as direct energy wide band gap

(3.37eV), large exciton binding energy (60 meV), high thermal

and chemical stability and environmental friendly

applications It is a promising material that possesses

various applications such as optoelectronic devices like flat

panel displays, light-emitting diodes and transparent

antireflection coatings for electrodes in solar cells and gas

sensors A variety of techniques have been used to

fabricate ZnO thin films such as chemical vapor deposition

(CVD), RF sputtering, spray pyrolysis, thermal vapor

deposition and sol-gel process Among these methods,

the sol-gel method is widely used due to several advantages in

comparison with other deposition methods such as its low

cost of the apparatus and raw materials, safety, simplicity,

homogeneity, its excellent control of stoichiometry, ability to

[1].

[2-5].

[6-10].

prepare high quality thin films in large scale etc. It is well

known that the deposition parameters and the preparation

method can have an important influence on the properties of

the thin film. The device applications mainly depend on the

characteristics such as high optical transmittance in the visible

region and high conductivity of the film. These parameters are

highly influenced by the thickness of the film. Therefore,

thickness dependent study of ZnO is essential.

In the present work, ZnO thin films have been prepared by

cost effective sol-gel method and the influence of the

thickness on the structural, optical and electrical properties

were discussed.

2. Materials and Methods

ZnO thin films were deposited by sol-gel spin coating method

on glass substrate. The precursor solution was prepared by

dissolving an appropriate amount of zinc acetate dehydrate in

2-methoxyehanol. Monoethanolamine (MEA) was used as a

sol stabilizer. The total concentration of the sol was -1maintained at 0.5 mol L and the molar ratio of MEA to zinc

acetate was maintained at 1.0. The resulting mixture was 0then stirred at 60 C for 1 hour using a magnetic stirrer to form

a clear and transparent homogeneous mixture and was aged ofor 48 hours at 30 C. The glass substrate was cleaned with

standard cleaning procedure and then ZnO films were spin

coated on glass substrate at room temperature with a rate of

3000 rpm for 30s. The deposited thin films were preheated at 0350 C for 15 min, to evaporate the solvent and to remove

organic residuals. The films with desired thickness were

achieved by multiple spin-bake process and then the films 0were annealed in air at 500 C for an hour.

The structural characteristics were investigated by Rigaku

Miniflex 600 PXRD. Crystallite size is estimated from XRD data

using the Debye-Scherrer formula. The surface topography of

the ZnO films was studied using AFM. The thickness of ZnO

films was measured by an ellipsometer. Optical properties of

the films were measured by a UV-visible spectrophotometer

(SHIMADZU 1800) in the wavelength range 300-800nm.

Electrical characterization of the films was carried out by the

current-voltage measurements using Keithley 236 source

measure unit.

Research Paper


3. Results and Discussion

3.1 Structural properties

The X-ray diffraction patterns of ZnO films with different

thickness are indicated in Figure 1. XRD patterns show that all

spin coated ZnO films are polycrystalline with hexagonal

wurtzite structure. For all the samples, (100), (101) and (002)

diffraction peaks are observed in the XRD pattern, showing

the growth of ZnO crystallites along different directions. The

existence of very strong peak along (002) plane indicates that

the films are oriented along c-axis It can be seen that the

intensity of the (002) peak is increased and FWHM is

decreased, as the thickness increased from 112 nm to 384 nm.

This indicates that within a certain range of thickness, the

crystallinity and the crystallite size increases with film

thickness (Table 1). The grain size of the ZnO films was

calculated using the Debye-Scherrer formula

1

Where D is the grain size, ë is the X-ray wavelength (0.154059

nm), â is the full width at half maximum of the peaks in radians

and è is the angle of diffraction. The position of the (002) peak

depends greatly on the film thickness and shifts from 34.339

to 34.524 when the thickness of the film increased from 112

nm to 384 nm. This can be attributed to the better crystallinity

and the relaxation of the lattice strain. The strain along c-axis

(å) and the dislocation density (ä) of films were estimated

using the equations and tabulated in Table 1.

2

3

It can be observed that the values of strain and dislocation

density, which indicates the defects in the film, decreases with

film thickness and the strain relaxation was found to be

maximum for the ZnO film of thickness 384 nm for which the

crystallite size was maximum

[11].

[12]

Figure 2. AFM image of ZnO thin films

with thickness (a) 112 nm (b) 243 nm (c) 384 nm

Figure 2 shows the 2 μm × 2μm AFM images of ZnO thin

films for different thicknesses. It can be seen that all the films

consist of uniform and spherical like nanoparticles and the

grain size increased with film thickness. The grain size is found

maximum for the ZnO film of thickness 384nm. As expected,

the surface roughness (Sa) also is maximum for the same film

(Table.1). These results agree with the XRD results. Thus, in

the present investigation, we found that with increase in the

film thickness the structural properties of the films improved.

3.2 Optical properties

Figure 3 shows the optical transmittance spectra of ZnO thin

films between 300-800 nm wavelengths. The loss due to the

plane glass substrate was removed during the measurement.

The average transmittance of all the films over visible

wavelengths decreased from 89% to 80% with increasing in

film thickness. This decrease in the optical transmittance can

be attributed to the better crystallization of the film and the

dense microstructure of the thicker film as seen in the AFM

image (Figure 2). It can also be seen that the transmission in

the visible region decreases considerably at shorter

wavelengths near the ultra-violet range of all the films. The

absorption coefficient α was estimated using the Beer-

Lambert relation

4

Where T is the transmittance and d is the thickness of the film.

The optical band gap (Eg) was estimated using the relatio

[13]

5

Where h is Planck’s constant, ν is the frequency of the

incident photon and c is the proportional constant. Since ZnO

film is a direct transition semiconductor, the values of energy

gap (E ) of the samples could be estimated by extrapolating g

2the straight line portion at (αhν) =0 as shown in the Figure

4. It can be observed that the optical energy gap deceased

with the film thickness indicating the weak Burstein-Moss

effect.


Figure 1. XRD spectrum of the ZnO films

Figure 4. (αhν)2 vs. (hν) curves of the ZnO films

3.4 Electrical properties

The sheet resistance (Rs) of the films was measured by

soldering two wires to the ends of the films with silver

contacts. I-V characteristics of the samples were recorded

using Keithley 236 measuring unit. Then by using I-V data, the

sheet resistance of the films was calculated by the relation,

6

Where V is the applied voltage and I is the measured current.

Then the resistivity of the ZnO films were determined by the

relation [14]

7

The dependence of electrical resistivity (p) on film thickness is

shown in Figure 5. It can be seen that the resistivity decreases

with an increase in the film thickness. A lowest resistivity of

1.46×10-2 Ù cm was obtained from the film of thickness 384

nm. This may be because the crystalline size increases with

increasing film thickness, which reduces the grain boundary

scattering. From the obtained results, it is clear that the film

resistivity strongly depends on the film thickness.

4. Conclusion

ZnO thin films with different thickness were prepared by cost

effective sol-gel spin coating method. Structural analysis

revealed the polycrystalline nature of the films. The grain size

was found to increase with increasing film thickness. The

optical transmittance of all the films was above 80%. The

optical energy gap was decreased from 3.224 to 3.148 when

the thickness of the film was increased from 112 nm to 384

nm. The lowest electrical resistivity of 1.46×10-2 Ω cm was

obtained from the film of 384 nm thickness. We observed that

the structural, optical and electrical properties of synthesized

ZnO thin films were dependent on the film thickness and can

be tuned by selecting the appropriate thickness. The good

performance of ZnO thin film indicates that it can be used as

promising materials for optoelectronic applications.

Acknowledgement

The authors gratefully acknowledge the Coordinator, DST FIST

and UGC SAP, Department of Physics, Mangalore University

for providing facilities for the characterization of thin films

and technical support to carry out the work.

Reference

[1] T.V. Vimalkumar, N. Poornima, C. Sudha Kartha, K.P.

Vijayakumar, “Effect of precursor medium on structural

electrical and optical properties of spray polycrystalline

ZnO thin films”, J.Mat Sci Eng B, Vol.175, pp.29–35, 2010

[2] A. Farooq, M. Kamran, “ Effect of Sol Concentration on

Strctural and Optical Behaviour of ZnO Thin Films

Prepared by Sol-Gel Spin Coating”, International Journal

of Applied Physics and Mathematics, Vol. 2, pp.430-432,

2012

[3] E. Burunkaya, N. Kiraz, O. Kesmez, H. E. Camurlu, M.

Asilturk, E. Arpac, “ Preparation of aluminum-doped zinc

oxide (AZO) nano particles by hydrothermal synthesis”,

J.Sol-Gel Sci Technol, Vol. 55, pp.171-176, 2010

[4] Y. Xiaolu, H.Dan, L. Hangshi, L. Linxiao, C.Xiaoyu, Y.Wang, “

Nanostructure and optical properties

of M doped ZnO (M=Ni, Mn) thin films prepared by sol–gel

process”, Physica B, Vol. 406, pp. 3956– 3962, 2011


Table 1. Characteristic properties of ZnO thin films.

Figure 5.

Dependence of Electrical resistivity on thickness of the film

[5] B. Baruwati, D.K. Kumar, S.V. Manorama , “ Hydrothermal

synthesis of highly crystalline ZnO nanoparticles: A

competitive sensor for LPG and EtOH ”, Sensor Actuat, Vol.

119, pp.676-682, 2006

[6] M.R. Waugh, G. Hyett, I.P. Parkin, “Zinc Oxide Thin Films

Grown by Aerosol Assisted CVD” Chem. Vap. Deposition,

Vol. 14, pp.366, 2008

[7] D. I. Son, J. W. Lee, D. U. Lee, T. W. Kim, “Structural And

Optical Properties Of Zno Thin Films Grown on Flexible

Polyimide Substrates”, Surf. Rev.Lett, Vol.14 pp.

801–805,2007

[8] B. Xiao, Z.Z. Ye, Y.Z. Zhang, Y.J. Zeng, L.P. Zhu, B.H. Zhao,

“Fabrication of p-type Li-doped ZnO films by pulsed laser

deposition”, Appl. Surf. Sci, Vol. 253, pp. 895, 2009

[9] P.P. Sahay, S. Tewari, R.K. Nath, “Optical and electrical

studies on spray deposited ZnO thin films”, Cryst. Res.

Technol, Vol. 42, pp. 723–729, 2007

[10] G.T. Delgado, C.I.Z. Romero, S.A.M. Hernández, R.C.

Pérez, O.Z. Angel, “Optical and structural properties of

the sol–gel-prepared ZnO thin films and their effect on the

photocatalytic activity”, Sol. Energy Mater. Sol. Cells, Vol.

93, pp.55, 2009

[11] S.Ilican, Y.Caglar, M.Caglar, “Preparation and

characterization of ZnO thin films deposited by sol-gel

spin coating method”, J. Optoelectron. Adv. M, Vol.10, pp.

2578-2583, 2008

[12] S.A.Kamaruddin, K.Y.Chan, H. K.Yow, M. Z. Sahdan, H.

Saim, D. Knipp, “Zinc oxide films prepared by sol–gel spin

coating technique”, Appl Phys A, Vol. 104, pp. 263-268,

2011

[13] N. Shakti, P.S Gupta, “Structural and Optical Properties of

Sol-gel Prepared ZnO Thin Film”, Applied Physics

Research, Vol.2, pp.19-28, 2010

[14] M.C. Jun, S.U. Park, J. Hyukkoh, “Comparative studies of

Al-doped ZnO and Ga-doped ZnO transparent conducting

oxide thin films”, Nanoscale Res.Lett. Vol. 7, pp.639, 2012


Pauli stated that “I have done a terrible thing, I have postulated a particle that cannot be detected”. This was the theoretical birth of an electrically neutral, weakly interacting and very light particle called neutrino. But as the time elapsed this tiny particle revolutionised both particle physics and cosmology.

In Italian language neutrino means "little neutral one”!!. Pauli postulated the emission of neutrino particle in a desperate attempt to explain conservation of energy in beta decay as there was discrepancy in energy and momentum during beta (â) decay. In a research paper in December 1930, he suggested that some of the energy is carried away by the â particle during the radioactive decay process. The word "neutrino" entered the international vocabulary through Enrico Fermi, who used it during a conference in Paris in July 1932.

The original equation of â decay, n p+ e ( â), is Fermi,s theory of â decay and indicates that an electron i.e., â particle is emitted during the radioactivity due to the conversion of neutron into proton in the nucleus. However it has taken a quarter of a century for the discovery of neutrino particle with the streaming of the neutrinos from nuclear power plants then being built in 1950’s. In June 1956, two American physicists, Frederick Reines and Clyde Cowan sent a telegram to Wolfgang Pauli stating the neutrinos had left traces in their detector. This discovery showed that the ghostly neutrino, or Poltergeist as it had been called, was a real particle. Frederick Reins and Clyde Cowan were jointly awarded the Nobel Prize in Physics in the year 1995 for the discovery of leptons and neutrino particle.

Solar neutrino problem

In fact we live in a world of neutrinos. Billions of neutrinos are flowing through our body every second. We cannot see them and do not feel them. Neutrinos rush through space almost at the speed of light and hardly ever interact with matter and the question is where do they come from? Some were created already in the Big Bang, others are constantly being created in various processes in space and on Earth – from exploding supernovas, the death of massive stars, to reactions in nuclear power plants and naturally occurring radioactive decays. Even inside our bodies an average of 5,000 neutrinos per second is released when an isotope of potassium decays. The majority of those that reach the Earth originate in nuclear reactions ins ide the Sun. Second only to part ic les of light[electromagnetic spectrum]- photons, the neutrinos are the most numerous particles in the entire universe.

Since the 1960s, scientists had theoretically calculated the number of neutrinos [using energy mass relation] that are

created in the nuclear reactions that make the Sun shine. But while carrying out measurements on Earth, up to two thirds of the calculated number of neutrino was missing. Where did the neutrinos go? One suggestion was that there was some error in the theoretical calculations of how the neutrinos are produced in the Sun. Second suggestion that came to solve the solar neutrino puzzle was that the neutrinos change identities. According to the Standard Model of particle physics there are three types of neutrinos – electron-neutrinos, muon-neutrinos and tau-neutrinos. The second suggestion was more realistic as explained later.

In order to detect the neutrinos , the search was on day and night, in colossal detectors built deep underground, in order to shield out noise from cosmic radiation from space and from spontaneous radioactive decays in the surroundings.

Following this search, in 1998 Takaaki Kajita presented the discovery that neutrinos seem to undergo metamorphosis i.e., they switch identities during their passage in the Super-Kamiokande underground detector in Japan. The neutrinos captured there are created in reactions between cosmic rays and the Earth’s atmosphere.

Meanwhile, scientists at the Sudbury Neutrino Observatory in Canada, SNO, were studying neutrinos coming from the Sun. In 2001, the research group led by Arthur B. McDonald proved that these neutrinos, too, switch identities.

Together, the two experiments have discovered a new phenomenon – neutrino oscillations. A far-reaching conclusion of the experiments is that the neutrino, for a long time considered to be massless, must have a mass. This is of great importance for particle physics and for our understanding of the universe.

In summary, the neutrino particle took birth in *Pauli’s theory to explain the discrepancy in the explanation of beta decay. At that time this massless particle was only a hypothesis. Pauli himself expressed the doubt about its real existence. Later, Frederick Reines and Clyde Cowan proved the existence of the neutrino particle. But the massless assumption of the neutrino particle again created the problem of number or quantity of the particle as the energy has to be conserved. Last year, Takaaki Kajita and Arthur B. McDonald with their discovery of neutrino oscillations showed that neutrinos indeed have mass. For solving the neutrino puzzle they were jointly awarded with the Nobel Prize in Physics 2015.

*Pauli got the Nobel prize in 1946 not for his prediction of beta particle but for the discovery of exclusion principle.

Sources: nobelprize.org

The puzzle of neutrino – an elementary particle in the Universe- Navin N Bappalige


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