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Indian Society for Non-Destructive Testing Hyderabad Chapter
Proc. National Seminar on Non-Destructive Evaluation Dec. 7 - 9, 2006, Hyderabad
NDE-2006
Development of an Automated - Ultrasonic Gauging System for Tubes and
Pipes
V.H. Patankar1, V.M. Joshi
1 and B.K. Lande
2
1Electronics Division, Bhabha Atomic Research Centre, Mumbai-400 085 2Electrical Engineering Department, V.J.T.I., Matunga, Mumbai-400 019
e-mail: [email protected]
Abstract
Tubes/Pipes employed in critical applications such as Power Plants, Petrochemical
industry and others, demand very stringent quality control. Various Non-Destructive
Testing (NDT) techniques are used for inspection of such objects both during
fabrication as well as in-service stages. Ultrasonic testing (UT) is a very popular NDT
technique adopted in such applications. Flaw detection and thickness gauging are the
main UT methodologies adopted in such inspections. Today, ultrasonic imaging
systems are also available and such a system can be utilized for complete volumetric
inspection of the desired tubes/pipes. In flaw detection, the prime objective is
detection of internal flaws, if any, where as gauging enables high resolution thickness
and dimension measurements. Imaging systems basically provide both the operations, though gauging using imaging technique may not provide very high resolution. An
advanced system capable of both, B/C-Scan imaging and high resolution gauging of
tubes/pipes has been developed at Electronics Division, B.A.R.C. The system is based
around an Industrial Personal Computer and all the electronics hardware needed for
imaging and gauging has been developed at B.A.R.C. Extensive application software
– based on Visual Basic and Visual C++, running under Windows98 – has been developed to provide realize an advanced system suitable for tube/pipe inspection and
gauging. A two axes motorized mechanical scanner has been fabricated and it
provides automated inspection of tubes from inside using water immersion technique,
under the control of host PC. Initial trials have been carried out using Zircaloy and
Stainless Steel sample tubes with artificial defects. This paper highlights the hardware
and software features of the ultrasonic system and includes a discussion on the trial
inspections carried out with the system.
Keywords: Ultrasonic Imaging, Ultrasonic gauging, A-Scan, B-Scan, C-Scan,
NDT/NDE, Wall Thickness, Tube/Pipe
1. Introduction
In industry, Ultrasonic Inspection/
Imaging (UI) of tubes and pipes is carried
out to meet stringent Quality Assurance
(QA) demands particularly when the
inspected tubes/pipes are constituents of
strategic equipments or critical plants. To
perform quality checks on tubes, UI and
gauging are preferred techniques. The UI
technique enables the NDT experts to
perform flaw detection and sizing. Full
volumetric inspection of the tube needs to be
carried out in order to follow the “zero error”
concept for tubes. The UI method is complex,
time consuming, costly but is fully suitable
for volumetric inspection of tubes. On the
other hand, the ultrasonic gauging method
V.H. Patankar, V.M. Joshi and B.K. Lande
NDE-2006 220
provides information regarding the Wall
Thickness (WT), Inner Diameter (ID) and
Outer Diameter (OD) of the tube and the
variation therein due to stresses and
corrosion. The gauging method is precise,
fast, reliable and economical but internal
defects cannot be detected with it.
Generally gauging technique is used to
confirm the dimensional integrity of the
tube and the UI technique is employed at
suspected locations.
Gauging of tubes can be performed
using contact or water immersion method.
Pulse-echo technique employs the same
transducer as a transmitter and receiver of
ultrasound and using direct contact
method, tubes with smooth surface and
with access either from OD or ID side can
be inspected. Here, a couplant
(oil/water/grease) is essential for good
coupling of ultrasound to the tube under
inspection. Water immersion method is
mostly preferred for inspection and
gauging of tubes. The tube to be inspected
is immersed into the water and using the
immersion transducers, the desired
inspection is carried out either manually or
by automation, without wear and tear of
the transducer face.
2. Ultrasonic Gauging / Dimension
Measurement
Thorough inspection of tubes/pipes,
employed in Nuclear, Petrochemical
Industries, Defence and Aviation, is a vital
task. This may be carried out routinely
during Pre-Service, In-Service and Post-
Service Inspection schedules. Immersion
based Pulse-Echo technique is widely used
to carry out wall thickness gauging as well
as Dimension measurement for tubes and
pipes. Generally, high frequency, focused -
immersion transducers are needed for this
purpose. The tubes can be gauged using
water immersion technique in two ways as
indicated in Fig. 1 and Fig. 2. In method I,
the tube to be inspected is filled with water
with an access from inside and the
immersion transducers are placed 1800 apart,
each facing the ID of the tube. In method II,
tube is placed into a pool of water with an
access from outside only and the immersion
transducers are placed 1800 apart, each facing
towards the OD of the tube. Using
automation, the entire transducer assembly or
the tube itself can be rotated and indexed
linearly to gauge the entire tube under
inspection.
Transducer
TR1
Transducer TR2
ID = WP1 + WP2 + S
OD= ID + WT1 + WT2
S
Tube is filled with water
Fig. 1: Inspection of Tube from Inside
Tube is placed inside
a water pool
OD= S - (WP1 + WP2)
ID= OD - (WT1 + WT2)
TR1
TR2
S
Fig. 2: Inspection of Tube from Outside
For Fig. 1 and Fig. 2, WT1= Wall
Thickness measured by TR1 or a transit time
measured between the echo signals
corresponding to ID and OD of tube. WT2=
Wall Thickness measured by TR2 or a transit
time measured between the echo signals
corresponding to ID and OD of tube. WP1=
Water Path measured on TR1 side or a transit
time between the transmit pulse and the
interface echo reflected either from ID of tube
for Fig. 1 or from OD of tube for Fig. 2.
WP2= Water Path measured on TR2 side or a
transit time between the transmit pulse and
the interface echo reflected either from ID of
tube for Fig. 1 or from OD of tube for Fig. 2.
S= Face to face separation between TR1 and
TR2. [1,2].
Development of an Automated - Ultrasonic Gauging System
NDE-2006 221
8 - C h a n n e l U l t r a s o n ic P u ls e r -
R e c e iv e r U n i t M u l t ic h a n n e l S e q u e n c e r B o a rd B o a r d
A m p l i f ie r B o a rd
1 0 0 M S P S D ig i t i z e r B o a r d
P C B U S
In d u s t r ia l P C
S t e p p e r
M o to r C o n t r o l
a n d D r i v e
U n i t
R S 4 8 5
L IN K
Z - T h e t a
S c a n n e r
T R 1 T R 8
T
U
B
E
R X 1 R X 8 T R G 1 T R G 8 T R G
V O V m u x
L im it S w i t c h e s F o r Z A x is a n d
- S h a f t E n c o d e r s & P r o x im it y D e t e c to r s
F o r Z a n d T h e t a A x e s
T o p T a n k
B o t t o m
T a n k
Fig. 3: Block Diagram of Multichannel Ultrasonic Imaging System–ULTIMA
89C51 RD2 Microcontroller
Board
(100MHz) High
Speed Counter
Board (CH1)
(100MHz) High
Speed Counter
Board (CH2)
Ultrasonic Spike
Pulser - Receiver Board (CH1)
Ultrasonic Spike
Pulser - Receiver Board (CH2)
Industrial PC Controller
& Drive Unit For Z - Theta Scanner
RS 485 Link
RS232 - RS485 Converter
Sample Tube/Pipe
TG1
TG2
TRG1
TRG2
RX - 1
RX - 2
COM 3 COM 4
TX - 2 TX - 1
Water
TR2 TR1
Fig. 4: Block Diagram of an Ultrasonic Tube Dimension Measurement System - UTDMS
V.H. Patankar, V.M. Joshi and B.K. Lande
NDE-2006 222
Fig. 5: B-Scan Images (a) to (C) are acquired by UTDMS using Gauging Technique. And B-
Scan Images and corresponding A-Scan waveforms (d) to (f) are acquired by ULTIMA
100M8, using ultrasonic imaging technique
3. Ultrasonic Systems for Inspection and
Gauging of Tubes
The metallic tubes are inspected under
automation, by ultrasonic imaging
techniques using A-Scan waveform and B
or C-scan image mode for detection of
internal flaws/defects and sizing of
defects, if any. On the other hand, the
integrity of tubes can be confirmed by
ultrasonic gauging technique. Two kinds
of ultrasonic systems are available for
testing of tubes where, the first kind of
system can carry out ultrasonic imaging
for flaw detection and the second kind of
system can perform ultrasonic gauging for
confirmation of dimensional integrity. It
has been observed that, there is a need of
the industry to develop an integrated
system, which can perform both ultrasonic
inspection and gauging. In order to
perform an automated ultrasonic imaging
and gauging operation for tubes/pipes,
Electronics Division, BARC has
developed an advanced system, which
integrates the imaging and gauging
requirements. The gauging system is linked to
the imaging system by RS485 interface. Both
the systems are capable of operating in
standalone mode also. The overall system
configuration is -
1. Multichannel Ultrasonic Imaging System
ULTIMA 100M8 and
2. Ultrasonic Tube Dimension Measurement
System UTDMS
The block diagram of ULTIMA 100M8
system has been shown in Fig. 3. The
ULTIMA 100M8 system consists of PC Add-
on Boards - 1) 100MSPS, 8 Bits Digitizer, 2)
Multichannel Sequencer, 3) Low noise -
Programmable gain Amplifier and 4) 8-
channel ultrasonic spike pulser-receiver unit.
The system is based on the Industrial PC for
shop-floor inspection activities. The Win98
compatible, “Ultrasonic Tube Imaging
Software” (UTIS) has specifically been
developed for this system using Visual Basic
and VC++ (6.0). The system captures the RF
Development of an Automated - Ultrasonic Gauging System
NDE-2006 223
echo signal in B/C-Scan imaging mode, in
synchronization with the ‘water-metal’
interface echo, for immersion mode. The B
and C-Scan cross-sectional images
respectively, are acquired and
reconstructed under automation and they
permit visualization and sizing of internal
defects. The ULTIMA 100M8 system’s
host PC communicates with the controllers
of a Z-Theta mechanical scanner, via
RS485 serial link. This scanner is
designed to inspect tubes from ID side.
With the help of eight immersion
transducers, mounted (45o apart) on the
inspection head, imaging of the selected
region of the tube can be performed, by
imparting linear and rotational movements
to the inspection head simultaneously.
[Ref. 4] The tube is held at both the ends
with the help of sealed jackets and the tube
and the jackets are filled with water during
testing.
The UTDMS is a two-channel tube
dimension measurement system, which is
based on 89C51RD2 micro-controller. The
block diagram of the UTDMS is shown in
Fig. 4. UTDMS consists of two PCBs
containing of High frequency ultrasonic
spike pulser – receiver and High-speed
counter for each transducer. The unit is
linked to the host PC via RS485 interface.
The firmware for the micro-controller is
developed using standard assemblers.
Win98 compatible data acquisition
software has been developed using VB 6.0
for the host PC. The UTDMS is capable of
measuring the wall thickness with 25
microns precision for Zircaloy tubes.
However, the ID and OD can be measured
with a precision of 100 microns. In
gauging also, the B-Scan view of the
selected region of the tube can be
synthesized by computing together the
values of WT, ID and OD and plotting
them over a full length of the tube.
Under automation, the ultrasonic tube
inspection and gauging is carried out by
ULTIMA 100M8 and UTDMS
respectively. For this purpose, a dedicated Z-
Theta mechanical scanner – has been
developed. The scanner enables the user to
test a metallic tube from inside, by ultrasonic
water immersion technique. The tube to be
inspected is clamped in the top and bottom
jackets. O-rings are used for obtaining a fully
watertight environment. Using a pump, the
tube is filled with degassed water. An
inspection Head carrying eight, line focused,
20MHz, immersion transducers are employed
to move the transducers in both rotary (Theta)
and linear (Z) directions with the help of two
stepper motors. The stepper motor controllers
are interfaced to host PC using RS485
protocol. Using +/- JOG, +/- Absolute MOVE
and +/- Immediate MOVE commands, the
inspection head can be positioned at desired
location in the tube. In both the inspection,
and gauging modes, the data acquisition is
always carried out when the transducer is
stationary. The B-Scan imaging is carried out,
by moving the inspection head along a single
axis (either in Z or Theta direction). The C-
Scan image acquisition is performed by a
combination of Z and Theta movements, for
covering the entire volume of the tube.
4. System Overview for UTDMS
Ultrasonic Tube Dimension Measurement
System has been configured in 4U x 19” rack
mounting format. This embedded system is
based on the Philips 89C51RD2 micro-
controller, and a multidrop interface for
stepper motor controllers and the host
computer, for automated data logging and
post acquisition analysis. As the UTDMS is
intended for precise dimension measurement
of Tubes, suitable automation has been
incorporated into the system. The hardware
constituents of the UTDMS are – 1)
89C51RD2 micro-controller board with
RS232 interfaces, 2) Ultrasonic Spike Pulser
and Receiver board (2 channels), 3) High
Speed counter board (2 channels), 4) RS232
To RS485 converter (commercially available)
module, 5) Host – Industrial computer with
two ports of RS485, 6) RS485 based 2-axes
stepper motor controller and drive unit; Z-
Theta mechanical scanner suitable for
V.H. Patankar, V.M. Joshi and B.K. Lande
NDE-2006 224
inspection of Tubes from ID side, under
immersion scanning mode; Ultrasonic
Inspection Head with facility to mount 8
nos. of immersion transducers; overhead
and bottom tanks with water pump for
closed loop water circulation.
The firmware for micro-controller
has been developed using standard
assembly tools of 89C51. The system
software, which runs on the Windows98
platform, has been designed with an
extensive GUI for user-friendly operation,
using VB (Ver. 6.0) to perform data
logging and analysis. The UTDMS
acquires and transmits the data with
appropriate headers, in response to the
command given by the host PC. The
stepper motor controllers have been
configured in closed loop mode with
associated feedback and safety elements.
Design details of the UTDMS are given in
the following sub sections.
4.1 89C51RD2 Micro Controller Board
Philips 89C51RD2 serves as the core
controller and controls the entire operation
of UTDMS. On the power on, the
microcontroller detects the presence of
stepper motor controller and then polls all
the keys, located on the system front panel.
The front panel has in all eight switches
for- +JOG1, STOP1, -JOG1 for Z-axis and
+JOG2, STOP2 and –JOG2 for Theta axis,
in order to position the transducer for
gauging and two keys for initiation of the
B-Scan and C-Scan image acquisition
modes. Pressing `B-scan’ push button
switch, the B-Scan mode of acquisition is
initiated. The data acquisition is always
performed in synchronization with the
movement of the transducer. The B-scan
image data can be acquired either
advancing the transducer in linear (Z) or in
rotary (Theta) direction. The `C-scan’
mode is initiated by pressing relevant push
button switch and the UTDMS moves the
transducers in a sequence of Z and Theta
axis increments in order to cover the user
specific region of the tube. When the
transducers are stationary, the data for wall
thickness and water path is acquired and
transmitted to COM3 of PC, for data storage.
The COM4 port of PC is utilized for post
acquisition analysis i.e. for bringing the
transducer back to the required location, for
confirmation of located defects in B and C-
Scan mode of acquisition. This feature is
called as ‘Return-On-Defect’ mode.
4.2 Ultrasonic Spike Pulser and Receiver
Boards
To achieve a high axial resolution, use of
high frequency and highly damped
transducers is imperative. To energise such
transducers, a spike pulse is suitable. As the
tubes under inspection have smaller wall
thicknesses (1-10 mm), a suitable wideband
Ultrasonic Spike Pulser and Receiver (UPR)
board has been developed. The UPR consists
of – 1) Trigger Section; 2) High Voltage
Spike Pulse Generator; 3) Limiting network
and Wideband Amplifier. For precise
measurement of WT, ID and OD of the tube,
two ultrasonic immersion transducers are
used and they are placed 180o apart. Instead
of multiplexers, two independent channels of
ultrasonic Pulser Receivers are employed for
excitation of these transducers.
4.3 High Speed Synchronous Counter Boards
The high-speed counter boards have been
developed to perform simultaneous precision
counting of WT & WP for two channels. The
functions of a counter board are broadly
classified into Digital Control Section; High-
speed counter section; Analog signal
conditioning and comparator section for
generation of pulses equivalent to WP&WT.
The Digital control section is further divided
into three subsections namely 1) Trigger
synchronization; 2) generation of a pulse,
whose width is equivalent to the water path
and 3) generation of one more pulse, whose
width is equivalent to the wall thickness of
the tube. The received RF echo signal has
three components viz. i) Initial ringing of the
transducer corresponding to transmit pulse, ii)
An interface echo corresponding to ID of the
Development of an Automated - Ultrasonic Gauging System
NDE-2006 225
tube and iii) The phase inverted RF Echo
signal corresponding to the back surface of
the tube (i.e. reflection from OD), as
shown in the Fig. 1. Using a transmit
trigger signal and the ID-echo signal, the
‘ID-pulse’ is generated whose width is
equivalent to the water path. The water
path is computed using a 10 MHz clock,
derived from the on board 100 MHz clock.
The 8 bits, high-speed counter measures
the water path delay precisely, with a
resolution of 100nsec. An ‘OD-pulse’,
whose width is equivalent to the wall
thickness, is generated using the ID-echo
signal and OD-echo signal. The wall
thickness is measured with a precision of
10nsec, by using 100 MHz clock and 8
Bits counter. Both the counters for WP and
WT are interfaced to the microcontroller in
memory mapped I/O manner. The count
values corresponding to WP and WT of
each channel are transmitted to PC for
storage purpose. The WP and WT values
along with the known separation between
the transducers are utilized to precisely
compute ID, OD and WT of the tube at
any location.
4.4 RS232 to RS485 Converter Module
The 89C51RD2 microcontroller has a
RS232 port for serial communication. The
data and commands are transmitted /
received between the two axes stepper
motor controllers and the host PC. To
translate the single ended RS232 signal of
the microcontroller into a differential
RS485 signal (for better noise immunity
over large distance), a commercially
available converter module has been used.
4.5 Host Computer with Two RS485 Ports
The microcontroller transmits the WT
and WP data to the COM3 port of the host
- Industrial PC along with suitable header,
in order to distinguish data from
commands. Scanner movement can either
be controlled by UTDMS or through the
COM4 port of the host PC. COM4 of the
PC is used to activate ‘Return on Defect’
mode, which provides confirmation of any
anomaly found during the gauging of a tube.
This feature can be invoked during the
retrieval of B and C-Scan images.
4.6 2-Axes Mechanical Scanner, Transducers
and Water Tanks and Pump Assembly
Suitable for Tube Inspection from ID Side by
Immersion Mode
A specialized Z-Theta mechanical scanner
has been designed exclusively for this work
and it has been used for ultrasonic imaging as
well as for gauging of tubes. The scanner is
capable of inspecting tubes and pipes from ID
side, under immersion mode. The multi-
channel approach for inspection and gauging
of tube, results in fetching substantial saving
of inspection time. In essence, the Z-Theta
mechanical scanner developed for tube
inspection from ID side enables to carry out:
(1) Volumetric inspection (i.e. flaw detection)
of tubes with the help of ULTIMA 100M8
and (2) On-line gauging (i.e. dimension
measurement) of tubes with the help of
UTDMS.
5. Experimental Results
For the evaluation of the ULTIMA 100M8
and UTDMS, sample tubes of Zircaloy and
Stainless Steel (SS) have been fabricated.
Inspection results are as follows:
The sample tube made of Zircaloy has
typical dimensions such as: ID = 103.4 +0.4/-
0 mm, OD = 112.7 +/- 0.3 mm and WT = 4.3
+/- 0.4 mm. On this tube, artificial defects in
the form of a groove and a Flat Bottom Hole
(FBH) are machined on the outer surface. The
groove is 2.75mm deep and 10 mm wide and
the hole is 2.75 mm deep and 4 mm in
diameter. The B-scan image data of a tube
covering these two defects has been acquired
using UTDMS. A B-Scan image of the same
zone of the tube has been acquired using
ULTIMA 100M8 system. The results are
shown in Fig. 5. It has been observed from
the Fig. 5 that, the results acquired using
Ultrasonic Imaging technique and Gauging
method matched very close with an accuracy
V.H. Patankar, V.M. Joshi and B.K. Lande
NDE-2006 226
of +/- 100 microns. The B-Scan image
acquired by ULTIMA 100M8 has
provided information regarding the
interiors of the tube along the wall-
thickness and about the orientation of
these defects. The gauging results also
provide a profile of ID, OD, and WT of the
tube under testing, over the same length.
[The groove is not machined, exactly
perpendicular, to the tube length and the
effect can be seen in the B-Scan images,
acquired using ultrasonic imaging system
and also in the form of an offset in the B-
Scan images acquired by UTDMS.]
The sample tube of SS has dimensions:
ID = 103.6mm, OD = 112.7mm and WT =
4.5mm. Two grooves have been machined
on the OD, as artificial defects. The first
groove has a depth of 1mm and a width of
20mm; the second groove is 10 mm away
from the first groove with 2mm depth and
15mm width. Experiments similar to
section 5.1 have been carried out by
acquiring the B-scan images using a
gauging and an ultrasonic imaging
technique.
The WT, ID and OD values for
Zircaloy tubes have been confirmed by the
digital vernier caliper with 10 microns
accuracy and the results derived from
inspection and gauging technique have
been found within 50 microns accuracy for
WT and within 100 microns accuracy for
ID and OD.
6. Discussion
The ultrasonic tube dimension
measurement system UTDMS has been
tested for gauging of various samples of
metallic tubes and the results have been
supplemented by the cross-sectional B-
Scan images acquired using a multichannel
ultrasonic imaging system ULTIMA
100M8. For the UTDMS, the wall
thickness measurement has a precision of
10 nanoseconds, which is equivalent to 24
microns in Zircaloy. (Noting that, the
acoustic velocity of Zircaloy is 4800m/s).
The water path is measured with a precision
of 100 nsec., which is equivalent to 75
microns in water, considering the acoustic
velocity of water as 1500m/s. In conclusion,
the UTDMS provides highly precise and
accurate measurements of dimensions for
metallic tubes/pipes. The total system is
extremely useful for establishing the
procedures for inspection and gauging of
metallic tubes and pipes. Tubes/Pipes of
longer length can be tested by using a
modified scanner capable of handling such
tubes, with a provision to compensate for
temperature variation.
7. Acknowledgements
Authors are extremely grateful to Shri.
M.D. Ghodgaonkar, Head, Electronics
Division, BARC, Dr. S.K.Kataria, Ex-
Associate Director (E), E&I Group, BARC
and Dr. Mrs. Dixit, Ex-Director, VJTI,
Mumbai for their encouragement and support
for this work. Authors wish to express their
thanks to Shri. S.P. Srivastava of CDM,
BARC for his valuable guidance in the
mechanical design of the scanner. Very useful
suggestions made by Shri. P.P. Nanekar and
Shri. M.D. Mangasulikar of AFD, BARC
regarding the procedures for ultrasonic NDT
of tubes, are also gratefully acknowledged.
Authors are also thankful to Mrs. Shewta
Rane, Mrs. P. Jyothi and Shri. L.V.
Muralikrishna of Electronics Division, BARC
for their technical assistance in the fabrication
and testing of system hardware and making
useful phantoms for system
calibration/checking.
8. References
1. Non Destructive Testing Hand Book, second
edition, Volume 7 – Ultrasonic Testing,
American Society for Non Destructive
Testing, 1991, ISBN-0-931403-04-09.
2. Kazys R., Mazeika L. et al. from Kaunas
University of Technology, Lithuania “
Ultrasonic Measurement of Zirconium Tubes
used in Channel Type Nuclear Reactors”,
NDT&E International, Vol. 29, No. 1, pp. 37-
49, Feb. 1996.
Development of an Automated - Ultrasonic Gauging System
NDE-2006 227
3. Patankar V.H., Agashe A.A., P. Jyothi,
Joshi V.M. “ ULTIMA 100M8 –
Multichannel Ultrasonic Imaging System
for NDE of Tubes/Pipes ”, Xth
National
Conference On Ultrasonics, Osmania
University, Hyderabad, India, March 15-
16, 2001.
4. Patankar V.H., Joshi V.M., Srivastava S.P.
“Development of a 4-Channel Ultrasonic
Imaging System for Volumetric Inspection
of Solid Cylindrical Forgings”, Journal
For Non Destructive Evaluation (JNDE)
Vol.2, Issue 3, pp 35-40, December, 2003.
5. Anish Kumar, Rajkumar K.V., Palanichamy
P.P., Jayakumar T., Patankar V.H., Joshi
V.M., Lande B.K., Chellapandian R.,
Kasiviswanathan K.V., Baldev Raj
“Development and Applications of C-Scan
Ultrasonic Facility”, Journal For Non
Destructive Evaluation (JNDE) Vol.4, Issue
1, pp 11-16, June, 2005.
6. Ph.D. Thesis of Patankar V.H., University of Mumbai, 2006.