Automatic synthesis of analog layout : a survey

A review of recent research in the automatic synthesis of physical geometry for analog integrated circuits is presented. On introduction, an explanation of the difficulties involved in analog layout as opposed to digital layout is covered. Review of the literature then follows. Emphasis is placed on the exposition of general methods for addressing problems specific to analog layout, with the details of specific systems only being given when they surve to illustrate these methods well. The conclusion discusses problems remaining and offers a prediction as to how technology will evolve to solve them. It is argued that although progress has been and will continue to be made in the automation of analog IC layout, due to fundamental differences in the nature of analog IC design as opposed to digital design, it should not be expected that the level of automation of the former will reach that of the latter any time soon

A Genetic Algorithm based Approach for Topological Optimization of Interconnection Networks

AbstractThe paper addresses the two terminal reliability while designing the interconnection networks. Thus a topological optimization problem is defined as the existence of at least a reliable path between a pair of nodes satisfying the predefined cost of the network. A new method based on Genetic Algorithm is proposed to solve the above said problem. In the proposed method the chromosome as well as the genes are efficiently encoded so that the cross over provides the optimal solution with better convergence rate. The reliability of some benchmark interconnection networks are evaluated by the proposed method. The population size and the computational time of the said networks as reported in this paper ensures that the proposed method converges to it's optimal solution in very few cpu secondss, while maximizing the value of the reliability of the said network to a greater extent

Генетический алгоритм синтеза топологической структуры сети передачи данных

В данной работе предложен генетический алгоритм синтеза топологии сети передачи данных, который отличается от известных тем, что для определения значения оптимальности получаемых топологий используется модель стоимости, в которой решается задача распределения информационных потоков в сети по кратчайшим путям, а также задача выбора оптимальных пропускных способностей каналов связи

Performance enhancement of active structures during service lives

This thesis describes a successful application of advanced computational methods to tasks in the field of active structural control. The control-task involves finding good control movements for a highly coupled, non-linear structure. It is demonstrated how these methods improve the accuracy of the analytical model. Also, stochastic search techniques are compared for the same task. Furthermore, the performance of the system can be enhanced during service life by storing, retrieving and adapting good solutions. The structure studied, a Tensegrity, is a special type of cable structure. Tensegrities stimulate the imagination of artists, researchers and engineers. Varying the amount of selftress changes structural shape as well as the load-bearing capacity. They offer unique applications, as deployable structures in the context of aerospace applications and more generally, as actively controlled structures. However, the non-linear behavior of tensegrities is difficult to model. Aspects of this work involve subjects such as tensegrity structures, active structural control, search algorithms and artificial intelligence. The focus of this thesis is on the last two subjects. This work demonstrates how advanced computing techniques can be used in order to increase solution quality. A hybrid approach, employing neural networks, increases the accuracy of the analytical model that is employed for simulating tensegrity structures. A comparison of three stochastic search techniques shows that computational time, first estimated to take centuries when adapting a "brute-force" approach, can be reduced to hours. Case-based reasoning (CBR) is used for a further tenfold decrease in computation time. The time needed to find good control solutions decreased from hours, when stochastic search is used, to minutes with CBR. CBR also provides possibilities for improving performance over service life. Successfully solved situations are stored as cases in a case-base. In new situations, a case close to the new situation is retrieved and then adapted. By storing additional cases, the system is able to retrieve better cases for adaptation. With increasing case-base size, adaptation time decreases. The combination of these techniques has much potential for improving the performance of complex structures during service lives. Results should contribute to the development of innovative structural solutions. Finally, it is expected that the findings in this thesis will become points of departure for subsequent studies

Reliability and Cost Evaluation of Third-Generation Wireless Access Network Topologies: A Case Study

Abstract-The "explosive growth in bursty traffic" changes the network dynamics and requires a good evaluation of various classes of service when designing an access network. From a topological standpoint, the multiservice networks in this paper are heterogeneous systems which integrate both a core and some wireless access networks into an infrastructure similar to third-generation wireless networks. Such networks require reliable and cost-effective solutions to the problem of selecting access technologies for satisfying performance and quality of service requirements related to the services and applications envisioned. This paper analyzes the reliability aspects of some access network topologies to insure a certain level of quality of service at the lowest cost for the end users. It considers a mass market equivalent to 1.6 million subscribers, the objective being to determine the cost the users are ready to pay to benefit from services and applications provided by these multiservice networks. For these purposes, the relative behavior of 3 access-network topologies are studied: the tree with parallel backup links, the ring, and the partially meshed topologies. In ring topology, simulation results show that a great connectivity in the access network is not justified in terms of reliability requirements; the partially meshed topology, even if it has redundant links which affect its cost, outperforms the tree with parallel backup links; and the ring topology is more reliable in terms of disconnected sessions than the tree topology. By considering both reliability and cost, a tree with parallel backup links appears the best topology for the access network and its cost is acceptable for the end user. This study can be extended by: 1) establishing the cost as a function of the quality of service; 2) optimizing the partially meshed topology for more reliable networks; and 3) defining a (shaping) policy to deal with a variety of traffic schemes. Index Terms-Access network, cost evaluation, multi-service network, quality of service, third-generation wireless network, topological design. ACRONYMS AND ABBREVIATIONS 1 ADSL asymmetric digital subscriber line AR access router ATM asynchronous transfer mod

Collision-free path planning for robots using B-splines and simulated annealing

This thesis describes a technique to obtain an optimal collision-free path for an automated guided vehicle (AGV) and/or robot in two and three dimensions by synthesizing a B-spline curve under geometric and intrinsic constraints. The problem is formulated as a combinatorial optimization problem and solved by using simulated annealing. A two-link planar manipulator is included to show that the B-spline curve can also be synthesized by adding kinematic characteristics of the robot. A cost function, which includes obstacle proximity, excessive arc length, uneven parametric distribution and, possibly, link proximity costs, is developed for the simulated annealing algorithm. Three possible cases for the orientation of the moving object are explored: (a) fixed orientation, (b) orientation as another independent variable, and (c) orientation given by the slope of the curve. To demonstrate the robustness of the technique, several examples are presented. Objects are modeled as ellipsoid type shapes. The procedure to obtain the describing parameters of the ellipsoid is also presented

AUTOMATED ANALYSIS OF NEURONAL MORPHOLOGY: DETECTION, MODELING AND RECONSTRUCTION

Ph.DDOCTOR OF PHILOSOPH

The AddACO: A bio-inspired modified version of the ant colony optimization algorithm to solve travel salesman problems

The Travel Salesman Problem (TSP) consists in finding the minimal-length closed tour that connects the entire group of nodes of a given graph. We propose to solve such a combinatorial optimization problem with the AddACO algorithm: it is a version of the Ant Colony Optimization method that is characterized by a modified probabilistic law at the basis of the exploratory movement of the artificial insects. In particular, the ant decisional rule is here set to amount in a linear convex combination of competing behavioral stimuli and has therefore an additive form (hence the name of our algorithm), rather than the canonical multiplicative one. The AddACO intends to address two conceptual shortcomings that characterize classical ACO methods: (i) the population of artificial insects is in principle allowed to simultaneously minimize/maximize all migratory guidance cues (which is in implausible from a biological/ecological point of view) and (ii) a given edge of the graph has a null probability to be explored if at least one of the movement trait is therein equal to zero, i.e., regardless the intensity of the others (this in principle reduces the exploratory potential of the ant colony). Three possible variants of our method are then specified: the AddACO-V1, which includes pheromone trail and visibility as insect decisional variables, and the AddACO-V2 and the AddACO-V3, which in turn add random effects and inertia, respectively, to the two classical migratory stimuli. The three versions of our algorithm are tested on benchmark middle-scale TPS instances, in order to assess their performance and to find their optimal parameter setting. The best performing variant is finally applied to large-scale TSPs, compared to the naive Ant-Cycle Ant System, proposed by Dorigo and colleagues, and evaluated in terms of quality of the solutions, computational time, and convergence speed. The aim is in fact to show that the proposed transition probability, as long as its conceptual advantages, is competitive from a performance perspective, i.e., if it does not reduce the exploratory capacity of the ant population w.r.t. the canonical one (at least in the case of selected TSPs). A theoretical study of the asymptotic behavior of the AddACO is given in the appendix of the work, whose conclusive section contains some hints for further improvements of our algorithm, also in the perspective of its application to other optimization problems

Modified mass-spring system for physically based deformation modeling

Mass-spring systems are considered the simplest and most intuitive of all deformable models. They are computationally efficient, and can handle large deformations with ease. But they suffer several intrinsic limitations. In this book a modified mass-spring system for physically based deformation modeling that addresses the limitations and solves them elegantly is presented. Several implementations in modeling breast mechanics, heart mechanics and for elastic images registration are presented