Use of Petri nets for resource allocation in projects

Traditional models for project management have not adequately incorporated a number of factors that are important for resource allocation. This paper describes the use of Petri nets to facilitate resource allocation in projects under some conditions commonly encountered in practice. Petri nets provide a powerful formalism for representing and analyzing concurrent systems. To date, however, very little has been done to integrate this graphical and mathematical tool with the area of project management. Petri net models can be used to analyze interdependencies, criticality, substitution, conflicting resource priorities and variations in the availability of resources. This paper proposes a new model and demonstrates the usefulness of the model for real-time activity scheduling in a resource-constrained project environment. The model has been computerized using the C language, and a simple project is chosen as an example to provide step-by-step explanations of the simulation carried out. This paper also discusses the implications of the model and the analysis it supports     

Correctness within a constant of an optimal buffer allocation ruleof thumb

The problem is to allocate a fixed number of buffers among the nodes of an open network of exponential servers with Bernoulli routing and Poisson arrivals so as to optimize some performance criterion associated with the time to buffer overflow, such as maximizing its mean or maximizing the probability that it exceeds some value. In earlier work, the authors used pathwise probabilistic arguments to derive a simple rule of thumb for this problem: allocate the buffers in inverse proportion to the logarithms of the effective service rates at the nodes. Effective service rate denotes the ratio of the service rate to the stationary arrival rate in the network with infinite buffers. They showed that this rule of thumb is accurate to within a known constant times the logarithm of the number of buffers as the number of buffers to be allocated becomes large. In the present paper, the authors use time reversal and Poisson clumping arguments to show that their rule of thumb is, in fact, much better than previously demonstrated. They show that the optimal buffer allocation is within a constant of the rule of thumb as the number of buffers to be allocated becomes large, although now they cannot estimate the constant. In numerical terms, the earlier result reduced the search space for the optimal buffer allocation from O(N^J-1) to O((log N)^J-1), where J denotes the number of nodes and N the number of buffers to be allocated. The improvement reduces the search space to O(1)     

Surface properties of magnesium oxide obtained from basic magnesium carbonate: Influence of preparation conditions of magnesium carbonate

Surface area, total basicity and base strength distribution (weak, strong and intermediate strength basic sites) of magnesium oxide obtained from basic magnesium carbonate (by its decomposition at 873 K) prepared by precipitation using different magnesium slats, precipitating agents and precipitating conditions (viz. concentration of magnesium salt. pH, temperature, mode of mixing and ageing period) have been thoroughly investigated. The total basicity and base strength distribution of the different magnesium oxide samples have been determined by step-wise thermal desorption of carbon dioxide from 323 to 1253 K. The chemical composition of basic magnesium carbonate and the surface properties and carbon dioxide content of magnesium oxide are found to be strongly influenced by the aforementioned preparation conditions of basic magnesium carbonate.     

Kinetics and Sulfur fixation in the reduction or oxidation of metal Sulfides mixed with lime

A number of metallurgical processes involve roasting of metal sulfides with oxygen or reduction of metal sulfides with hydrogen. In each case sulfur-bearing gases are emitted. Lime can be used to capture these sulfur-bearing gases. A model of this reaction occurring in a pellet made up of grains of metal sulfide and lime is presented. Specifically, a pellet made up of a mixture of metal sulfide and lime surrounded by a lime layer is considered. The computational investigation shows the distribution of lime necessary to achieve the maximum fixation of sulfur-bearing gases in the shortest time.     

Self-created Rules and Conflict Management Processes: The Case of Water Users' Associations on Waghad Canal in Maharashtra,India

In India, community participation is receiving much importance in water planning and management. However, in the absence of effective institutional arrangements to govern the allocation and maintenance activities, it is more likely that such participation will fail to achieve the desired results. Therefore, the present study is an attempt to assess the self-created rules adopted by two Water Users' Associations (WUAs) in Maharashtra State, India, to govern the use and distribution of water resources. The paper describes the perception of the members with regard to some of these self-created rules. It was observed that both the WUAs studied had effectively enforced these rules, leading to improved water management and efficient conflict management process. Although preliminary, the findings indicate scope for designing strategies to achieve the objective of forming a federation — better planning and distribution of water among WUAs.     

An Experimental and Theoretical Study of the Flow of Xerographic Developer Powders from Small Hoppers

An experimental and theoretical study is presented which characterizes the flow of xerographic developer powders out of small hoppers. A small hopper in this reference is defined as one having a maximum height of 12 in. Two walls of the hopper converge at the gate and the remaining two walls are parallel to each other. The flow is studied as a function of the gate opening, hopper angle, particle size, the total height of the particulate material in the hopper, and the angle of repose. Experimental results are presented for particle diameters between 100 ? and 600 ?. A theory is presented to predict flow rates. The predicted functional dependence agrees very well with the observations. The predicted flow rates are about 3.75 times higher than the observed ones. It is suggested that this is due to a resistive force originating in particle interactions. Inclusion of this correction factor in the theory results in very good agreement between theoretical predictions and experimental observations.     

Alternate Testing of RF Transceivers Using Optimized Test Stimulus for Accurate Prediction of System Specifications

In the recent past, with the emergence of System-on-Chip (SoC), focus has shifted towards testing system specifications rather than device or module specifications. While the problem of test accessibility for test stimulus application and response capture for such high-speed systems remains a challenge to the test engineers, new test strategies are needed which can address the problem in a practical manner. In this paper, the problem of testing the transmitter and the receiver subsystems of a RF transceiver for system level specification is addressed. Instead of using different conventional test stimuli for testing each of the system level specifications of RF subsystems, a specially crafted test stimulus is used for testing all the specifications from the response of the subsystem-under-test. A new simulation approach has also been developed to perform fast behavioral simulations in frequency domain for the system-under-test. In the test method, frequency domain test response spectra are captured and non-linear regression models are constructed to map the spectral measurements onto the specifications of interest. In the presented simulation results, the test stimuli have been validated using netlist level simulation of the subsystem-under-test and specifications have been predicted within an error of ±3% of the actual value.Soumendu Bhattacharya was born in Calcutta, India, in 1978. He received his Bachelors degree from Indian Institute of Technology, Kharagpur, India, in 2000. In 2002, he received the M.S.E.E. degree in electrical engineering from Georgia Institute of Technology, Atlanta, USA. He is currently working toward his Ph.D. degree. In the summer of 2001, he worked as a summer intern in National Semiconductor, Santa Clara, CA, USA. His research interests are in the area of test generation for mixed-signal and RF circuits and systems and design-for-test.Achintya Halder received the B.S. degree in electronics and electrical communication engineering from the Indian Institute of Technology, Kharagpur, in 1998. He worked as an IC design engineer with Texas Instruments until 2000. Currently, he is a Ph.D. student and a research assistant with the School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta. His research area is analog/RF and mixed signal testing.Ganesh P. Srinivasan received the B.E. degree in Electronics and Communication Engineering from the National Institute of Technology and Science, University of Madras, Chennai (Madras), India, in 2002. He received the M.S. degree in Electrical and Computer engineering from the Georgia Institute of Technology, Atlanta, GA, in 2004 and is currently pursuing his Ph.D. degree in Electrical and Computer Engineering at the Georgia Institute of Technology, Atlanta, GA. His research interests include low cost testing approaches for analog/RF and mixed-signal circuits, and improving performance of low cost testers for enabling high quality tests.Abhijit Chatterjee received the Bachelor of Technology degree in electrical engineering from the Indian Institute of Technology, Kanpur, India, in 1981, the M.S. degree in electrical engineering and computer science from University of Illinois at Chicago in 1983 and the Ph.D. degree in electrical and computer engineering from the University of Illinois at Urbana-Champaign in 1990. Until December 1992, he was a Research Staff Member at the General Electric Research and Development Center in Schenectady, NY. His work has been cited by the Wall Street Journal and presented on a Japanese network TV program called High Tech Shower International. He is a collaborating partner in NASAs New Millennium Project. Dr. Abhijit Chatterjee is also the author of one U.S. patent and has over one hundred publications in referenced journals and conferences.