Publications
Book Chapters
- Tarek F. Abdelzaher and Chengdu Huang, "Security and Web Quality of
Service," The Handbook of Information Security,
John Wiley and Sons, expected in 2005.
- Tarek Abdelzaher, John Stankovic, Sang Son, Brian Blum,
Tian He, Anthony Wood, and Chanyang Lu, "Real-Time Communication
and Programming Abstractions for Sensor Networks,"
Handbook of Sensor Networks: Compact Wireless and
Wired Sensing Systems, CRC Press, July 2004.
- Tarek F. Abdelzaher, "Web Quality of Service", The Internet
Encyclopedia, John Wiley and Sons, December 2003.
Papers by Area
Color coding of publications is by venue:
- black: journal, blue: conference,
green: workshop.
Sensor Networks
- Tian He, Sudha Krishnamurthy, Liqian Luo, Ting Yan, Lin Gu, Radu Stoleru,
Gang Zhou, Qing Cao, Pascal Vicaire, John A. Stankovic,
Tarek F. Abdelzaher, Jonathan Hui, Bruce Krogh, "VigilNet: An Integrated
Sensor Network System for Energy-Efficient Surveillance,"
ACM Transactions on Sensor Networks, to appear in 2005.
-
L. Gu, D. Jia, P. Vicaire, T. Yan, L. Luo, A. Tirumala, Q. Cao,
J. A. Stankovic, T. Abdelzaher, and B. Krogh, "Lightweight Detection
and Classification for Wireless Sensor Networks in Realistic
Environments", SenSys, San Diego, CA, November 2005.
- Shashi Prabh and Tarek Abdelzaher, ``Energy-Conserving Data Cache
Placement in Sensor Networks,'' ACM Transactions on Sensor
Networks, to appear in 2005.
-
Tian He, Liqian Luo, Ting Yan, Lin Gu, Qing Cao, Gang Zhou,
Radu Stoleru,
Pascal Vicaire, Qiuhua Cao, John A. Stankovic, Sang H. Son and
Tarek F. Abdelzaher, "An Overview of the VigilNet Architecture,"
11th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications,
Hong Kong, August 2005. Invited.
-
Qing Cao, Ting Yan, Tarek Abdelzaher and John Stankovic, "Analysis of
Target Detection Performance for Wireless Sensor Networks," International
Conference on Distributed Computing in Sensor Networks,
Marina Del Rey, CA, June 2005.
-
Liqian Lu, Tian He, Tarek Abdelzaher, John Stankovic, "Design and
Comparison of Lightweight Group Management Strategies in EnviroSuite,"
International
Conference on Distributed Computing in Sensor Networks,
Marina Del Rey, CA, June 2005.
-
Qing Cao, Tarek Abdelzaher, Tian He, John Stankovic, "Towards Optimal Sleep
Scheduling in Sensor Networks for Rare-Event Detection,"
International Conference on Information Processing in
Sensor Networks (IPSN'05), Los Angeles, CA, April 2005.
- Tian He, John A. Stankovic, Chenyang Lu, and Tarek F. Abdelzaher,
"A Spatiotemporal Protocol for Wireless Sensor Network," IEEE Transactions on Parallel and
Distributed Systems, to appear in 2005.
- Hyung Seok Kim, Tarek Abdelzaher, Wook Hyun Kwon
"Dynamic Delay-constrained Minimum-Energy Dissemination in
Wireless Sensor Networks,"
ACM transactions on Embedded Computing Systems,
to appear in 2005.
- Tian He, Chengdu Huang, Brian Blum, John Stankovic, Tarek Abdelzaher,
"Range-Free Localization and its Impact on Large-scale Sensor Networks,"
ACM Transactions on Embedded Computing Systems, to appear in 2005.
-
Gang Zhou, Tian He, John Stankovic, Tarek Abdelzaher,
"RID: Radio Interference Detection in Wireless Sensor Networks,"
IEEE Infocom, Miami, FL, March 2005.
-
Qing Cao, Tarek Abdelzaher, "A Scalable Logical Coordinates
Framework for Routing in Wireless Sensor Networks,"
IEEE Real-time Systems Symposium,
Lisbon, Portugal, December 2004.
-
Tarek Abdelzaher, Tian He, John Stankovic,
"Feedback Control of Data Aggregation in Sensor Networks,"
43rd IEEE Conference on Decision and Control,
Paradise Island, Bahamas, December 2004.
-
Tian He, Sudha Krishnamurthy, John A. Stankovic, Tarek Abdelzaher,
Liqian Luo, Radu Stoleru, Ting Yan, Lin Gu, Jonathan Hui,
Bruce Krogh,
"An Energy-Efficient Surveillance System for Sensor Networks,"
MobiSys, Boston, MA, June 2004.
- Tian He, Brian M. Blum, John A. Stankovic, Tarek F. Abdelzaher
"AIDA: Adaptive Application Independent Data Aggregation in Wireless
Sensor Networks," ACM Transactions on Embedded Computing
Systems, Vol. 3, No. 2, May 2004.
-
Tarek Abdelzaher et al., "EnviroTrack:
Towards an Environmental
Computing Paradigm for Distributed Sensor Networks,"
IEEE International Conference
on Distributed Computing Systems, Tokyo, Japan,
March 2004.
-
Hyung Seok Kim, Tarek Abdelzaher, Wook Hyun Kwon,
"Minimum-Energy
Asynchronous Dissemination to Mobile Sinks in Wireless Sensor
Networks," ACM SenSys, Los Angeles, CA, November,
2003.
-
Tian He, Chengdu Huang, Brian Blum, John Stankovic,
Tarek Abdelzaher, "Range-Free Localization Schemes for Large
Scale Sensor Networks," The 9th Annual International
Conference on Mobile Computing and Networking (Mobicom),
San Diego, CA, September 2003.
- John A. Stankovic, Tarek Abdelzaher, Chenyang Lu, Lui Sha,
Jennifer Hou, "Real-Time
Coomunication and Coordination in
Embedded Sensor Networks," Proceedings of the IEEE,
Vol. 91, No. 7, July 2003.
-
Tian He, John Stankovic, Chenyang Lu, Tarek Abdelzaher
"SPEED: A Stateless Protocol for Real-Time Communication
in Sensor Networks," International Conference on
Distributed Computing Systems, Providence, Rhode Island,
May 2003.
-
Tarek Abdelzaher, John Stankovic, Sang Son, Brian Blum, Tian He,
Anthony Wood, Chanyang Lu, "A Communication
Architecture and Programming Abstractions for Real-Time Embedded
Sensor Networks,"
Workshop on Data Distribution for Real-Time Systems
(in conjunction with ICDCS 2003), Providence, Rhode Island,
May 2003. Invited Paper
-
Sagnik Bhattacharya, Hyung Kim, Shashi Prabh, Tarek Abdelzaher
"Energy-Conserving Data Placement
and Asynchronous Multicast in Wireless Sensor Networks,"
The First International Conference
on Mobile Systems, Applications, and Services (MobiSys),
San Francisco, CA, May 2003.
-
Brian Blum, Prashant Nagaraddi, Anthony Wood, Tarek Abdelzaher,
Sang Son, John Stankovic,
"An Entity Maintenance and Connection
Service for Sensor Networks,"
The First International Conference
on Mobile Systems, Applications, and Services (MobiSys),
San Francisco, CA, May 2003.
-
Chenyang Lu, Brian Blum, Tarek Abdelzaher, John Stankovic,
and Tian He, "RAP: A Real-Time Communication
Architecture for Large-Scale Wireless Sensor Networks,"
Real-Time Technology and Applications Symposium,
San Jose, CA, September 2002.
Aperiodic Schedulability Analysis
- Lui Sha, Tarek Abdelzaher, Karl-Eric Arzen, Anton Cervin,
Theodore Baker, Alan Burns, Giorgio Buttazzo, Marco Caccamo,
John Lehoczky, Aloysius K. Mok, "Real Time Scheduling Theory: A Historical Perspective,"
Journal of Real-time Systems (invited paper), December 2004.
-
Tarek F. Abdelzaher, Shashi Prabh, Raghu Kiran,
"On Real-time Capacity Limits of Multihop Wireless Sensor
Networks," IEEE Real-time Systems Symposium,
Lisbon, Portugal, December 2004.
-
Tarek Abdelzaher, Gautam Thaker, Patrick Lardieri,
"A Feasible Region for Meeting
Aperiodic End-to-end Deadlines
in Resource Pipelines," IEEE International Conference
on Distributed Computing Systems, Tokyo, Japan,
March 2004.
- Tarek Abdelzaher, Vivek Sharma, Chenyang Lu, ``A
Utilization Bound for
Aperiodic Tasks and Priority Driven Scheduling,''
IEEE Transactions on Computers, Vol. 53, No. 3, March
2004.
-
Tarek Abdelzaher and Vivek Sharma,
``A Synthetic Utilization Bound
for Aperiodic Tasks with Resource Requirements,''
5th Euromicro Conference on Real-Time Systems,
Porto, Portugal, July 2003.
-
Bjorn Andresson, Tarek Abdelzaher, and Jan Jonsson,
``Partitioned Aperiodic Scheduling on
Multiprocessors,'' International Parallel and
Distributed Processing Symbosium, Nice, France, April 2003
-
Bjorn Andresson, Tarek Abdelzaher, and Jan Jonsson,
``Global Priority-Driven Aperiodic
Scheduling on Multiprocessors,'' International Parallel and
Distributed Processing Symbosium, Nice, France, April 2003
-
Tarek Abdelzaher, Bjorn Anderson, Jan Jonsson, Vivek Sharma
and Minh Nguyen, ``The Aperiodic
Multiprocessor Utilization
Bound for Liquid Tasks,'' Real-Time Technology
and Applications Symposium, San Jose, CA, September 2002.
-
Tarek Abdelzaher, Chenyang Lu,
``Schedulability Analysis and Utilization
Bounds for Highly Scalable Real-Time Services,''
IEEE Real-Time Technology and Applications
Symposium, TaiPei, Taiwan, June 2001.
Feedback-Contol of QoS
- Chenyang Lu, Ying Lu, Tarek F. Abdelzaher, John A. Stankovic, Sang H. Son,
``Feedback Control Architecture and Design Methodology for Service Delay
Guarantees in Web Servers,'' IEEE Transactions on Parallel and
Distributed Systems, to appear in 2005.
- Chengdu Huang and Tarek Abdelzaher, ``Bounded-Latency
Content Distribution: Feasibility and Evaluation,'' IEEE Transactions on
Computers, to appear in 2005.
- Chengdu Huang, Seejo Sebastine, Tarek Abdelzaher, ``Design,
Implementation and Evaluation of a Real-Time Active Content
Distribution Service,''
Journal of Real-time Systems, Vol. 30, No. 1-2,
May 2005.
- Ronghua Zhang, Sujay Parekh,
Yixin Diao, Maheswaran Surendra,
Tarek Abdelzaher, John Stankovic, ``Control of Weighted
Fair Queueing: Modeling, Implementation, and
Experiences,'' 9th IFIP/IEEE International
Symposium on Integrated Network Management,
Nice, France, May 2005.
-
Chengdu Huang, Seejo Sebastine and Tarek Abdelzaher,
``An Architecture for On-Demand
Active Web Content Replication,''
16th Euromicro Conference on
Real-Time Systems, Catania, Italy, July 2004.
-
Dan Henriksson, Ying Lu, Tarek Abdelzaher,
``Improved Prediction for Web Server
Delay Control,'' 16th Euromicro Conference on
Real-Time Systems, Catania, Italy, July 2004.
-
Chengdu Huang and Tarek Abdelzaher, ``Towards Content Distribution
Networks with Latency Guarantees,''
IWQoS, Montreal, Canada, June, 2004.
-
Tarek Abdelzaher, Ying Lu, Ronghua Zhang, Dan Henriksson,
``Practical Application of Control
Theory to Web Services,'' Invited paper,
American Control Conference, Boston, MA,
June 2004.
- Ying Lu, Tarek F. Abdelzaher, Avneesh Saxena,
``Design, Implementation,
and Evaluation of Differentiated Caching Services,''
IEEE Transactions on Parallel and Distributed Systems
Vol. 15, No. 5, pp. 440-452, May 2004.
-
Ronghua Zhang, Tarek Abdelzaher, John Stankovic,
``Efficient TCP
Connection Failover in Server Clusters,''
Infocom, Hong Kong, March 2004.
-
Vivek Sharma, Arun Thomas, Tarek Abdelzaher, Kevin Skadron,
``Power-aware QoS
Management in Web Servers,''
Real-Time Systems Symposium, Cancun, Mexico,
December 2003.
Best Student Paper Award.
-
Ying Lu, Tarek Abdelzaher, Chenyang Lu, Lui Sha, Xue Liu,
``Feedback Control with
Queueing-Theoretic Prediction for
Relative Delay Guarantees in Web Servers,'' Real-Time and
Embedded Technology and Applications Symposium, Toronto,
Canada, May 2003.
-
Ronghua Zhang, Tarek F. Abdelzaher, and John A. Stankovic,
``Kernel Support for Open QoS-Aware
Computing,''
Real-Time and Embedded Technology and Applications
Symposium, Toronto, Canada, May 2003.
-
Ying Lu, Tarek F. Abdelzaher, Gang Tao, ``Direct Adaptive
Control of a Web Cache System,'' American Control
Conference Denver, CO, June 2003.
- Tarek F. Abdelzaher, John A. Stankovic, Chenyang Lu, Ronghua Zhang,
and Ying Lu, ``Feedback Performance
Control in Software Services,'' IEEE Control Systems Magazine,
Vol 23, No. 3, June 2003.
- Tarek Abdelzaher, Kang G. Shin, Nina Bhatti,
``User-Level QoS-Adaptive Resource Management in Server
End-Systems,'' IEEE Transactions on Computers,
Vol. 52, No. 5, May 2003.
-
Lui Sha, Xue Liu, Ying Lu, Tarek Abdelzaher, ``Queuing Model
Based Network Server Performance Control,''
Real-Time Systems Symposium, Austin, TX, December
2002.
-
Ying Lu, Gang Tao, and Tarek Abdelzaher, ``LDU
Parametrized
Discrete Time Multivariable MRAC and Application to a Web Cache
System,'' IEEE Conference on Decision and Control,
Las Vegas, Nevada, December 2002.
-
Ronghua Zhang, Chenyang Lu, Tarek F. Abdelzaher, John A. Stankovic,
``ControlWare: A Middleware Architecture
for Feedback Control of Software Performance,''
International Conference on Distributed
Computing Systems, Vienna, Austria, July 2002.
-
Kyoung-Don Kang, Sang Son, John Stankovic, Tarek Abdelzaher,
``A QoS-Sensitive Approach for Timeliness and
Freshness Guarantees in Real-Time Databases,''
Euromicro, Vienna, Austria, June 2002.
-
Nicolas Christin, Jorg Liebeherr, Tarek Abdelzaher,
``A Quantitative
Assured Forwarding Service,'' IEEE INFOCOM,
New York, NY, June 2002.
-
Ying Lu, Chanyang Lu, Tarek Abdelzaher, Gang Tao,
``An
Adaptive Control Framework for QoS Guarantees and its
Application to Differentiated Caching Services,''
IWQoS, Miami Beach, FL, May 2002.
-
Sivakumar Velusamy, Karthik Sankaranarayanan, Dharmesh Parikh,
Tarek Abdelzaher, Kevin Skadron, ``Adaptive
Cache Decay using Feedback Control,''2nd Annual
Workshop on Memory Performance Issues Anchorage,
Alaska, May 2002.
-
Kevin Skadron, Tarek Abdelzaher, and Mircea Stan,
``Control-Theoretic
Techniques and Thermal RC Modeling for Accurate and Localized Dynamic
Thermal Mangement,'' International Symposium on High
Performance Computer Architecture, Cambridge, MA,
February 2002.
-
Tarek Abdelzaher, Kang G. Shin, Nina Bhatti,
``Performance Guarantees
for Web Server End-Systems: A Control-Theoretical Approach,''
IEEE Transactions on Parallel and Distributed Systems
, Vol. 13, No. 1, Jan 2002.
-
Seejo Sebastine, Kyoung-Don Kang, Tarek F. Abdelzaher, Sang H. Son,
``A Scalable Web-Based Real-Time Information
Distribution Service for Industrial Applications,'' The
27th Annual Conference of the IEEE Industrial Electronics
Society, Denver, Colorado, December 2001.
-
John Stankovic, Tian He, Tarek Abdelzaher, Mike Marley, Gang Tao,
Sang Son, ``Feedback Control
Scheduling in Distributed Systems,'' IEEE Real-Time
Systems Symposium, London, UK, December 2001.
-
Chenyang Lu, Tarek Abdelzaher, Jack Stankovic, Sang Son,
``A Feedback Control Approach for
Guaranteeing Relative Delays in Web Servers,''
IEEE Real-Time Technology and Applications
Symposium, TaiPei, Taiwan, June 2001.
-
Ying Lu, Avneesh Saxena, and Tarek F. Abdelzaher,
``Differentiated
Caching Services; A Control-Theoretical Approach,''
International
Conference on Distributed Computing Systems, Phoenix, Arizona,
April 2001.
-
Tarek F. Abdelzaher and Chenyang Lu,
``Modeling and Performance Control of Internet Servers,''
Invited Paper, 39th IEEE Conference on
Decision and Control, Sydney, Australia, December 2000.
-
Chenyang Lu, John A. Stankovic, Tarek F. Abdelzaher, Gang Tao,
Sang H. Son and Michael Marley,
``Performance Specifications and Metrics for Adaptive Real-Time
Systems,'' IEEE Real-Time Systems Symposium,
Orlando, Florida, December 2000.
-
Tarek F. Abdelzaher,
``An Automoated Profiling Subsystem for QoS-Aware Services,''
IEEE Real-Time Technology and
Applications Symposium, Washington D.C., June 2000.
-
Tarek F. Abdelzaher and Kang G. Shin,
``QoS Provisioning with qContracts in Web and Multimedia Servers,''
IEEE Real-Time Systems Symposium,
Pheonix, Arizona, December 1999.
-
Tarek F. Abdelzaher, Nina Bhatti,
``Adaptive Content Delivery for Web Server QoS,''
International Workshop on Quality of Service,
London, UK, June 1999.
-
Tarek F. Abdelzaher, Nina Bhatti,
``Web Content Adaptation to Improve Server Overload Behavior,''
International World Wide Web Conference,
Toronto, Canada, May 1999.
-
Tarek F. Abdelzaher, Kang G. Shin,
``End-host Architecture for QoS-Adaptive Communication,''
IEEE Real-Time Technology and
Applications Symposium, Denver, Colorado, June 1998.
QoS-Sensitive Communication
-
Kang Shin, Tarek Abdelzaher, Seungjae Han, John Reumann, and Emmanuel
Abram-Profeta,
``Multimedia-Friendly Server and Communication Design,''
IEEE Multimedia, Vol. 6, No. 2, April 1999.
-
A. Mehra, A. Shaikh, T. Abdelzaher, Z. Wang, and K. Shin,
``Realizing Services for Guaranteed-QoS
Communication on a Microkernel Operating System,''
IEEE Real-Time
Systems Symposium, Madrid, Spain, December 1998.
-
Tarek Abdelzaher, Anees Shaikh, Farnam Jahanian, and Kang Shin,
``RTCast: Lightweight Multicast for Real-Time Process Groups,''
IEEE Real-Time Technology and Applications
Symposium, Boston, MA, June 10-12, 1996.
Winner of the 1996 RTAS Best Student Paper Award
(Earlier
version appears in Tech Report CSE-TR-291-96,
Department of Electrical Engineering and Computer Science,
University of Michigan, March, 1996.
OS and Middleware Solutions for QoS Management
-
Ella M. Atkins, Tarek F. Abdelzaher, Kang G. Shin, and
Edmund H. Durfee, ``Planning and Resource Allocation for
Hard Real-Time, Fault-Tolerant Plan Execution,''
Journal of Autonomous Agents and Multi-Agent
Systems, March 2001. (Earlier version appeared in
Third International Conference on
Autonomous Agents (Agents '99), Seattle, Washington,
May 1-5, 1999.)
-
Tarek F. Abdelzaher, Ella M. Atkins, and Kang Shin,
``QoS Negotiation in Real-Time Systems and its Application
to Automated Flight Control''
IEEE Transactions on Computers, Vol. 49, No. 11,
November 2000. (Earlier version appeared in
IEEE Real-Time Technology and Applications Symposium,
Montreal, Canada, June 9-11, 1997. 1997 RTAS Best Student
Paper Award Nominee)
-
Tarek F. Abdelzaher,
``QoS Adaptation in Real-Time Systems,''
Ph.D. Thesis, University of Michigan, August 1999.
-
Abdelzaher, Bjorklund, Dawson, Feng, Jahanian, Johnson,
Marron, Mehra, Mitton, Shaikh, Shin, Wang, Zou,
``ADMADA Middleware and Communication
Services,'' Journal of Real-Time Systems,
Vol. 16, No. 1, January 1999.
-
Abdelzaher, Dawson, Feng, Jahanian, Johnson, Mehra, Mitton,
Shaikh, Shin, Wang, Zou, ``ARMADA Middleware Suite,''
IEEE Workshop on Middleware for Distributed Real-Time
Systems and Services, San Francisco, California,
December 1997.
-
Tarek F. Abdelzaher, and M. A. Sheirah,
"New Hard Real-Time Kernel for Embedded Computing Systems,"
Proceedings of the 7th Mediterranean Electrotechnical
Conference - MELECON, Antalya, Turkey, 1994, pp. 1193-1196
-
M.A. Sheirah, Tarek F. Abdelzaher,
"Embedded Real Time Systems," in
proc. Symposium on New Horizons in Computers and Information
Systems, Cairo, Jan 26-28, 1993.
Real-Time Scheduling Theory
-
Tarek F. Abdelzaher and Kang G. Shin,
``Period-Based Partitioning and
Assignment for Large Real-Time Applications,''
IEEE Transactions on Computers, Vol. 49, No. 1,
January 2000.
-
Tarek F. Abdelzaher, Kang G. Shin, ``Optimal
Combined Task and Message Scheduling in Distributed
Real-Time Systems,''
IEEE Transactions on Parallel and Distributed Systems,
November, 1999. (Earlier version published in IEEE
Real-Time Systems Symposium, Italy, Pisa, Dec. 5-7, 1995.)
-
D.T. Peng, K.G. Shin, T.F. Abdelzaher,
``Assignment and Scheduling of Communicating Periodic Tasks in
Distributed Real-Time Systems''
IEEE Transactions on Software Engineering,
Vol. 23, No. 12, December 1997.
-
Tarek F. Abdelzaher, Kang G. Shin,
``Comment on 'A Pre-Run-Time Scheduling Algorithm for Hard Real-Time
Systems,''' IEEE Transactions on
Software Engineering, Vol. 23, No. 9, September, 1997.
-
Tarek F. Abdelzaher, A.M. Salem, S.A. Hammad and M.A. Sheirah ``A
Priority-Based Scheduler for Dynamic Real-Time Tasks with Simple
Resourse Requirements'' Proceedings of 3rd IASTED International
Conference, Cairo, Egypt, December, 1994.
Industrial Control Systems
-
Tarek F. Abdelzaher, S.A. Hammad, A.Z. Badr and M.A. Sheirah
"Experimental Validation for Modeling and Identification of a Pilot
Industrial Process" in Proc 3rd IASTED International
Conference, Cairo, Egypt, December, 1994.
-
Tarek F. Abdelzaher, "Design and Implementation of a Real-Time
Multiprocessor-Based Distributed Control System",
M.Sc. thesis, Dec. 1993.
-
M.A. Sheirah et. al.,
"Design and Manufacturing of Prototypes for Universal
Microprocessor Industrial Controller,"
Egyptian Academy of Scientific Research and Technology,
Tech. Report No. 3, June 1993.
-
M.A. Sheirah, Tarek F. Abdelzaher, "Embedded Real Time Systems," in
proc. Symposium on New Horizons in Computers and Information
Systems, Cairo, Jan 26-28, 1993.
-
M.A. Sheirah et. al.,
"Design and Manufacturing of Prototypes for Universal
Microprocessor Industrial Controller,"
Egyptian Academy of Scientific Research
and Technology,
Tech. Report No. 2, May 1992.
-
Tarek F. Abdelzaher, M.A. Sheirah, "Identification Algorithm for
Multicapacity Systems with Dead Time,"
Proceedings of the Second
IASTED International Conference,
Alexandria, Egypt, May 5-7, 1992.
-
Tarek F. Abdelzaher, M.A. Sheirah, "Generalized PID Tuning Method,"
Proceedings of the Second IASTED International Conference,
Alexandria, Egypt, May 5-7, 1992.
-
M.A. Sheirah et. al.,
"Design and Manufacturing of Prototypes for Universal
Microprocessor Industrial Controller," Egyptian Academy of
Scientific Research and Technology, Tech. Report No. 1,
July 1991.