A generalized timed Petri net representation is defined and several time Petri net models compared. By introducing a new way to include a time variable in the Petri net and the firing rules, the authors realized a new...
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A generalized timed Petri net representation is defined and several time Petri net models compared. By introducing a new way to include a time variable in the Petri net and the firing rules, the authors realized a new timed Petri net that includes the other two principal types of timed Petri nets. This new timed Petri net seems to take a more general form than other types of time Petri nets defined so far. Therefore, complex systems are expected to be modeled with it. The authors present a model to represent a timer in order to model real communication systems properly. An example is given in which the timed Petri net representation and the timer model are applied to a communication protocol. With the results provided, communication protocols involving timers and transmission errors can be modeled.< >
The authors address a requirement for providing secure fully connected data processing services at a local site that may be spread out over several buildings of a campus environment. The network might consist of any v...
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The authors address a requirement for providing secure fully connected data processing services at a local site that may be spread out over several buildings of a campus environment. The network might consist of any variety of vendor terminals, workstations, hosts, or intermediate processors. Users are logically members of the same working community although they might reside in different locations throughout the site. The authors describe an ongoing program of architectural design, network performance modeling, and simulation intended to provide a better understanding of complex networks both during equipment development and during network implementation.< >
The NTB (national test bed) is a primary element of the five-year, SDI (strategic defense initiative) effort. It is actually a concept of facility utilization, rather than only a nationwide network of research facilit...
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The NTB (national test bed) is a primary element of the five-year, SDI (strategic defense initiative) effort. It is actually a concept of facility utilization, rather than only a nationwide network of research facilities. Its purpose is to study concepts and technologies of ballistic missile defense using computer simulations built from very large databases. Various aspects of NTB development are briefly discussed; the national test facility (NTF), its hardware basis, is described in detail. The wideband telecommunications links, the assessment of NTB accuracy, and NTF processing requirements are all covered.< >
It is shown that the antijamming (AJ) performance of binary FH-DPSK systems is, for all practical purposes, equivalent to (4-ary) FH-DQPSK and that an 8-ary FH-DPSK system has approximately 1.5-dB worse performance re...
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It is shown that the antijamming (AJ) performance of binary FH-DPSK systems is, for all practical purposes, equivalent to (4-ary) FH-DQPSK and that an 8-ary FH-DPSK system has approximately 1.5-dB worse performance relative to binary FH-DPSK. In addition, it is shown that an optimized partial-band multitone jammer (PBMJ) and a partial-band noise jammer (PBNJ) yield essentially equivalent AJ performance in the absence of thermal noise. The present results diverge from those of M.K. Simon et al. (1982, 1985) who concluded that the PBMTJ is 4.4 dB more effective than PBNJ. It is concluded that the differences between the present results and those of Simon et al. are attributable to the fact that they did not use the entropy of a frequency-hopping carrier as a design parameter to be optimized.< >
This paper presents a generalized linear programming (LP) and farm budget model for optimization of on-farm irrigation benefits resulting from variations in irrigation project size. The paper also summarizes applicati...
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ISBN:
(纸本)0872626091
This paper presents a generalized linear programming (LP) and farm budget model for optimization of on-farm irrigation benefits resulting from variations in irrigation project size. The paper also summarizes applications of the model to two proposed projects - the Lake Andes-Wagner, South Dakota, and Columbia Basin, Washington irrigation projects.
Nitrate-N, Ammonium-N and Phosphate-P concentrations were measured from shallow subsurface wells and outlets of a drainage-subirrigation system in the Georgia flatwoods for comparison to adjacent forested and cleared ...
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ISBN:
(纸本)0872626091
Nitrate-N, Ammonium-N and Phosphate-P concentrations were measured from shallow subsurface wells and outlets of a drainage-subirrigation system in the Georgia flatwoods for comparison to adjacent forested and cleared areas. Nitrate-N concentrations did not exceed 10 mg/1 from any of the outflow samples. However, Nitrate-N concentrations were significantly higher in the drained-subirrigated area than in the forested and cleared areas. Ammonium-N and Phosphate-P concentrations were relatively low and do not appear to be a problem based on the limited data available. Additional monitoring and modeling are required to form more definite conclusions.
Although it is recognized that a two-stage (indirect) evaporative cooler (EC) can deliver colder supply air than a single-stage (direct) EC, few guidelines exist to describe how large each component in the two-stage s...
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ISBN:
(纸本)0841209863
Although it is recognized that a two-stage (indirect) evaporative cooler (EC) can deliver colder supply air than a single-stage (direct) EC, few guidelines exist to describe how large each component in the two-stage system should be to optimize performance on the basis of minimum cost. The authors consider the cost function of an indirect EC and establish necessary constraints on performance. The cost function is then minimized to help develop guidelines for systemoptimization. A sample calculation illustrates the technique.
The authors outline the modeling process of a multikilowatt spacecraft power system comprised of eight solar-powered converter/battery channels, three control loops including the peak power tracker, and a common outpu...
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ISBN:
(纸本)0841209863
The authors outline the modeling process of a multikilowatt spacecraft power system comprised of eight solar-powered converter/battery channels, three control loops including the peak power tracker, and a common output bus. The computer models predict small signal stability margins, bus impedances, and fault-induced voltage transients. Unless the designer seeks exact transfer function pole and zero locations, the collection of SPICE programs appears to be the best general-purpose program for this application. However, the authors found it quicker to write their own programs rather than alter the SPICE programs to implement their models of a current sensor, nonideal harness, and the peak power tracker.
Key factors in the optimization of a dynamic isotope power system (DIPS) are identified, and tradeoffs between these factors discussed. The primary areas of concern regarding integration of a DIPS into a satellite are...
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ISBN:
(纸本)0841209863
Key factors in the optimization of a dynamic isotope power system (DIPS) are identified, and tradeoffs between these factors discussed. The primary areas of concern regarding integration of a DIPS into a satellite are presented, includng configuration, dynamic interaction, power processing, safety, satellite cooling, and launch vehicle integration.
The authors describe a small-scale dc motor-pump system powered by a 300-W (peak power) photovoltaic generator. The system consists of a solar cell array (or a simulator of a solar cell array), a permanent-magnet dc m...
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ISBN:
(纸本)0841209863
The authors describe a small-scale dc motor-pump system powered by a 300-W (peak power) photovoltaic generator. The system consists of a solar cell array (or a simulator of a solar cell array), a permanent-magnet dc motor, and a centrifugal or piston-type pump. Characteristics of the components and of the whole system are presented. The performance of the two types of system, using either the centrifugal or the piston pump, is compared. The measured results and the results obtained from a mathematical model of the system are shown to be in good agreement. An optimized system of this type could be used for pumping water in remote areas with enough solar energy.
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