This paper discusses the problem of optimizing the utilization of communication satellite capacity. The modem fixed satellite service provider seeks improved methods to optimize the amount of service demand that is ac...
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ISBN:
(纸本)097445592X
This paper discusses the problem of optimizing the utilization of communication satellite capacity. The modem fixed satellite service provider seeks improved methods to optimize the amount of service demand that is accommodated by capacity available on its satellite network. A mixed-integer programming (MIP) model is proposed for the solution of the problem, as part of a decision support tool. Such a tool integrates three system components, which are: a mathematical optimization model, an optimization algorithm, and a graphical user interface. This paper will discuss the design process associated with each component of the system and will conclude with preliminary results obtained from sample optimization runs.
作者：
Puri, RIBM Corp
TJ Watson Res Ctr Yorktown Hts NY 10598 USA
Power dissipation is becoming the most challenging design constraint in nanometer technologies. Among various design implementation schemes, standard cell ASICs offer the best power efficiency for high-performance app...
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ISBN:
(纸本)0780385284
Power dissipation is becoming the most challenging design constraint in nanometer technologies. Among various design implementation schemes, standard cell ASICs offer the best power efficiency for high-performance applications. The flexibility of ASICs allow for the use of multiple voltages and multiple thresholds to match the performance of critical regions to their timing constraints, and minimize the power every where else. We explore the trade-off between multiple supply voltages and multiple threshold voltages in the optimization of dynamic and static power. The use of multiple supply voltages presents some unique physical and electrical challenges. Level shifters need to be introduced between the various voltage regions. The physical layout needs to be designed to ensure the efficient delivery of the correct voltage to various voltage regions. More flexibility can be gained by using appropriate level shifters.
In this paper, design of diffractive optical element (DOE) for optical bubble creating and controlling with radially polarized incident beam focused by a high numerical aperture (NA) aplanatic lens is proposed and its...
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ISBN:
(纸本)0819454524
In this paper, design of diffractive optical element (DOE) for optical bubble creating and controlling with radially polarized incident beam focused by a high numerical aperture (NA) aplanatic lens is proposed and its application in optical trapping is discussed. We use a DOE to modify the phase of the incident radial polarization beam to form different kinds of optical bubbles. optimization algorithms are used to design the DOE to adjust the bubble size and depth to meet the requirements. The results show that the size of the bubble is inversely proportional to its depth. Owing to the overlapping of the field strengths around the focus, the bubble tends to merge into flattop distribution as it is getting smaller and smaller. With a fixed DOE design, bubbles with smaller size and larger depth can be generally obtained with higher NA, owing to a more confined field strength distribution from the strong longitudinal field component.
A new approach based on the decomposition, in position-time space, of operating functions (OFs) is proposed and various criteria of parameter identification like the output least squares (OLS) and the regularized leas...
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A new approach based on the decomposition, in position-time space, of operating functions (OFs) is proposed and various criteria of parameter identification like the output least squares (OLS) and the regularized least squares (RLS) are formulated and incorporated in the framework. Several optimization algorithms such as the Gauss-Newton, conjugate gradient and Levenberg-Marquardt are diligently modified and computed in order to search the performed algorithm to identify, in space and time, the numerical fields of the model parameters. Because the sensitivity of the criteria to the design variables plays a very important role in the optimization problem, various techniques such as finite difference method and direct differentiation method are tested. The enhanced performance of the model with the newly identified OFs is proved by a higher conformity of its predictions with the real data of drying wood systems (DWSs).
In this study, we compare the use of genetic algorithms (GAs) and other forms of heuristic search in the cryptanalysis of short cryptograms. This paper expands on the work presented at FLAIRS-2003, which established t...
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In this study, we compare the use of genetic algorithms (GAs) and other forms of heuristic search in the cryptanalysis of short cryptograms. This paper expands on the work presented at FLAIRS-2003, which established the feasibility of a word-based genetic algorithm (GA) for analyzing short cryptograms. 1 In this study the following search heuristics are compared both theoretically and experimentally: hill-climbing, simulated annealing, word-based and frequency-based genetic algorithms. Although the results reported apply to substitution ciphers in general, we focus in particular on short substitution cryptograms, such as the kind found in newspapers and puzzle books. Short cryptograms present a more challenging form of the problem. The word-based approach uses a relatively small dictionary of frequent words. The frequency-based approaches use frequency data for 2-, 3- and 4-letter sequences. The study shows that all of the optimization algorithms are successful at breaking short cryptograms, but perhaps more significantly, the most important factor in their success appears to be the choice of fitness measure employed.
Classical coverage models, adopted for second-generation cellular systems, are not suited for planning universal mobile telecommunication system (UNITS) base station (BS) location because they are only based on signal...
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Classical coverage models, adopted for second-generation cellular systems, are not suited for planning universal mobile telecommunication system (UNITS) base station (BS) location because they are only based on signal predictions and do not consider the traffic distribution, the signal quality requirements, and the power control (PC) mechanism. In this paper, we propose discrete optimization models and algorithms aimed at supporting the decisions in the process of planning where to locate new BSs. These models consider the signal-to-interference ratio as quality measure and capture at different levels of detail the signal quality requirements and the specific PC mechanism of the wideband CDMA air interface. Given that these UNITS BS location models are nonpolynomial (NP)-hard, we propose two randomized greedy procedures and a tabu search algorithm for the uplink (mobile to BS) direction which is the most stringent one from the traffic point of view in the presence of balanced connections such as voice calls. The different models, which take into account installation costs, signal quality and traffic coverage, and the corresponding algorithms, are compared on families of small to large-size instances generated by using classical propagation models.
We consider the problem of anatomy based dose optimization in brachytherapy. A calculation method for some objective functions and their derivatives is proposed which significantly reduces the number of required opera...
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We consider the problem of anatomy based dose optimization in brachytherapy. A calculation method for some objective functions and their derivatives is proposed which significantly reduces the number of required operations. The optimization in some cases, ignoring a preprocessing step, is independent of the number of sampling points. The idea is that some of the objectives and their derivatives used for dose optimization do not require the explicit calculation of dose values. Dose optimization with the new modified computation method for the objectives and derivatives is, depending on the number of sampling points, up to 100 times faster than the conventional method with dose calculation. (C) 2003 American Association of Physicists in Medicine.
Collision detection optimization in an event-driven simulation of a multi-particle system is one of the crucial tasks, determining the efficiency of the simulation. We present the event-driven simulation algorithm tha...
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Collision detection optimization in an event-driven simulation of a multi-particle system is one of the crucial tasks, determining the efficiency of the simulation. We present the event-driven simulation algorithm that employs dynamic computational geometry data structures as a tool for collision detection optimization (CDO). The first successful application of the dynamic generalized Voronoi diagram method for collision detection optimization in a system of moving particles is discussed. A comprehensive comparision of four kinetic data structures in d-dimensional space, performed in a framework of an event-driven simulation of a granular-type materials system, is supported by the experimental results.
The main problem of the traditional radiation pyrometry is that fatal errors will be caused by the unknown or varying emissivity. Based on the combined neural networks (CNNE model), we propose an improved method for e...
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The main problem of the traditional radiation pyrometry is that fatal errors will be caused by the unknown or varying emissivity. Based on the combined neural networks (CNNE model), we propose an improved method for emissivity modelling. The model structure and the optimum algorithm are described. This method being used, the spectral emissivity and temperature can be fast computed accurately from the spectral radiation measured.
Parallel manipulators have many advantages over traditional serial manipulators. These advantages include high accuracy, high stiffness and high load-to-weight ratio, which make parallel manipulators ideal for machini...
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Parallel manipulators have many advantages over traditional serial manipulators. These advantages include high accuracy, high stiffness and high load-to-weight ratio, which make parallel manipulators ideal for machining operations where high accuracy is required to meet the requirements that modern standards demand. Recently, the finite element method has been used by some workers to determine the stiffness of spatial manipulators. These models are mainly used to verify stiffness predicted using kinematic equations, and are restricted to relatively simple truss-like models. In this study, state-of-the-art finite elements are used to determine the out of plane stiffness for parallel manipulators. Euler-Bernoulli beam elements and flat shell elements with drilling degrees of freedom are used to model the platform assembly. The main objective of this study is to quantify the stiffness, particularly the out of plane stiffness, of a planar parallel platform to be used for machining operations. The aim is to obtain a design that is able to carry out machining operations to an accuracy of 10 mum for a given tool force. Reducing the weight of a parallel manipulator used in machining applications has many advantages, e.g. increased maneuverability, resulting in faster material removal rates. Therefore the resulting proposed design is optimized with respect to weight, subject to displacement and stress constraints to ensure feasible stiffness and structural integrity. The optimization is carried out by means of two gradient-based methods, namely LFOPC and Dynamic-Q. (C) 2003 Elsevier Inc. All rights reserved.
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