Michell cantilevers constructed within trapezoidal domains

The paper concerns the Michell-like cantilevers transmitting a point load to a straight segment of a support. The feasible domain is of trapezoidal infinite shape, as in the previous parts of the paper. The ratio of allowable stresses in tension and compression is arbitrary, not necessarily equal to 1. The present, last part of the paper includes detailed geometric and static analyses of the optimal cantilevers for various admissible data, thus providing new benchmarks of topology optimization. All results are found by using analytical methods developed in the previous parts of the paper. Particular attention is put on the force field distribution within the fibrous domains. These force fields turn out to be defined in certain subdomains forming a static division. The volumes of the optimal cantilevers are computed in two manners: by direct integration of the density of fibres and summing it up with the volume of the reinforcing bars of finite cross sections, and by using the kinematic formula of Michell according to which the volume is proportional to the virtual work. The examples analysed prove that both approaches lead to identical results of the volumes, thus showing that the possible duality gaps vanish. The analytical solutions are verified by considering appropriately chosen sequences of trusses of finite number of joints converging to the exact Michell cantilevers.     

Michell cantilevers constructed within trapezoidal domains—Part III: force fields

This paper complements the analysis of geometric properties of the Hencky nets within the Michell cantilevers constructed in the trapezoidal domains by providing the analytical formulae for the force fields. The force field analysis introduces a new division of the cantilever domain and enables an alternative method for computing the optimal weights.     

Michell cantilevers constructed within trapezoidal domains—Part I: geometry of Hencky nets

The present paper is the first part of the four-part work on Michell cantilevers transmitting a given point load to a given segment of a straight-line support, the feasible domain being a part of the half-plane contained between two fixed half-lines. The axial stress σ in the optimal cantilevers is assumed to be bounded by −σ _C ≤σ≤σ _T , where σ _C and σ _T represent the allowable compressive and tensile stresses, respectively. The work provides generalization of the results of the article of Lewiński et al. (Int J Mech Sci 36:375–398, 1994a) to the case of σ _T ≠σ _C . The present, first part of the work concerns the analytical formation of the Hencky nets or the lines of fibres filling up the interior of the optimal cantilevers corresponding to an arbitrary position of the point of application of the given concentrated force.     

First results of ITC'99 benchmark circuits

The ISCAS circuits have long been used as design-for-testability benchmarks; however, recent progress in technology requires newer DFT standards. This look at the ITC'99 benchmarks reveals complexities that will serve as a starting point for other researchers     

The exact weight of discretized Michell trusses for a central point load

A discretized optimal structure is derived in a closed analytical form based on Michell truss. The result shows that the discretized optimal structure is most similar to Michell truss in topology and shape. The difference in volume, displacement and strain energy between the discretized optimal structure and Michell truss decreased sharply as the number of members increased in discretized structure. A discretized optimal structure may be obtained from Michell truss by using finite members. This work is meaningful for studying discretized optimal topology based on Michell truss. This result is useful for engineering structural design.     

Analysing singularities of a benchmark problem

The purpose of this paper is to analyze the singularities of a well known benchmark problem “Andrews’ squeezing mechanism.” We show that for physically relevant parameter values this system admits singularities, and describe explicit conditions for the parameters. The method is based on Gröbner bases computations and ideal decomposition. It is algorithmic and can thus be applied to study constraint singularities which arise in more general situations as well.     

Generalized Michell structures — exact least-weight truss layouts for combined stress and displacement constraints: Part II — Analytical solutions within a two-bar topology

Analytical solutions are obtained for least-weight trusses with a vertical support and a single point load in an arbitrary direction. The optimal layout is derived for displacement and stress constraints within a two-bar topology, with different permissible stresses for the two bars. The globality of the above solutions is verified by a numerical exploration of the design space. The results in this paper show a complete agreement with the general theory of plane generalized Michell structures outlined in Part I of this study.     

The Genesis distributed-memory benchmarks. Part 1: Methodology and general relativity benchmark with results for the SUPRENUM computer

This is the first of a series of papers on the Genesis distributed-memory benchmarks, which were developed under the European ESPRIT research program. The benchmarks provide a standard reference Fortran77 uniprocessor version, a distributed memory. MIMD version, and in some cases a Fortran90 version suitable for SIMD computers. The problems selected all have a scientific origin (mostly from physics or theoretical chemistry), and range from synthetic code fragments designed to measure the basic hardware properties of the computer (especially communication and synchronisation overheads), through commonly used library subroutines, to full application codes. This first paper defines the methodology to be used to analyse the benchmark results, and gives an example of a fully analysed application benchmark from General Relativity (GR1). First, suitable absolute performance metrics are carefully defined, then the performance analysis treats the execution time and absolute performance as functions of at least two variables, namely the problem size and the number of proecssors. The theoretical predictions are compared with, or fitted to, the measured results, and then used to predict (with due caution) how the performance might scale for larger problems and more processors than were actually available during the benchmarking. Benchmark measurements are given primarily for the German SUPRENUM computer, but also for the IBM 3083J, Convex C210 and a Parsys Supernode with 32 T800-20 transputers.     

An argument for abandoning the travelling salesman problem as a neural-network benchmark.

In this paper, a distinction is drawn between research which assesses the suitability of the Hopfield network for solving the travelling salesman problem (TSP) and research which attempts to determine the effectiveness of the Hopfield network as an optimization technique. It is argued that the TSP is generally misused as a benchmark for the latter goal, with the existence of an alternative linear formulation giving rise to unreasonable comparisons.     

The design of a scalable, fixed-time computer benchmark

By using the principle of fixed-time benchmarking, it is possible to compare a wide range of computers, from a small personal computer to the most powerful parallel supercomputer, on a single scale. Fixed-time benchmarks promise greater longevity than those based on a particular problem size and are more appropriate for “grand challenge” capability comparison. We present the design of a benchmark, SLALOM, that adjusts automatically to the computing power available and corrects several deficiencies in various existing benchmarks: it is highly scalable, solves a real problem, includes input and output times, and can be run on parallel computers of all kinds, using any convenient language. The benchmark provides an estimate of the size of problem solvable on scientific computers. It also can be used to demonstrate a new source of superlinear speedup in parallel computers. Results that span six orders of magnitude for contemporary computers of various architectures are presented.     

A hybrid feedback for a benchmark problem of idle speed control

The ever increasing demands on passengers' comfort, safety, emissions and fuel consumption imposed by car manufacturers and regulations call for advanced techniques and the use of cycle‐accurate models in automotive control. In this paper, we focus on such approach to the idle speed control. It is natural to resort to hybrid methodologies, because of the rich combination of time and event‐based behaviors exhibited by a controlled engine. A hybrid benchmark problem is considered and addressed first by analyzing the equilibria of the system and then testing a simple hybrid feedback strategy. Copyright © 2009 John Wiley & Sons, Ltd.     

Socializing artifacts as a half mirror of the mind

In the near future, our life will normally be surrounded with fairly complicated artifacts, enabled by the autonomous robot and brain–machine interface technologies. In this paper, we argue that what we call the responsibility flaw problem and the inappropriate use problem need to be overcome in order for us to benefit from complicated artifacts. In order to solve these problems, we propose an approach to endowing artifacts with an ability of socially communicating with other agents based on the artifact-as-a-half-mirror metaphor. The idea is to have future artifacts behave according to the hybrid intention composed of the owner’s intention and the social rules. We outline the approach and discuss its feasibility together with preliminary work.

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The specification and numerical solution of a benchmark swirling laminar flow problem

A primitive variable finite element method for solving swirling incompressible flow problems is presented. A flow problem of physical importance is analysed and the results are critically compared with an earlier solution. The numerical solution of a problem characterized by a particular choice of Reynolds number and swirl ratio is discussed in detail; this problem is proposed as a benchmark for general swirling flow calculations.     

Continuity of the spectral factorization on a vertical strip

The continuity of the mapping which associates a spectral factor to a spectral density is investigated. This mapping can be defined on several classes of spectral densities and spectral factors. For the usual largest class of spectral densities, i.e., essential bounded functions on the imaginary axis that are bounded away from zero, it is known that this mapping is not continuous. It is shown here that for slightly smaller, but still generic class the mapping becomes continuous.     

Design of a log periodic strip grating microstrip antenna

The design of a log periodic strip grating antenna is described. The 12-element antenna is compact and has a measured power bandwidth of 22%. The antenna elements are mounted on the top of the top layer of a two-layer structure with its feed line located between the two dielectric layers providing electromagnetic coupling. The structure was analyzed using PMESHD, a moment method code for two-layer passive structures. The analysis and measurements are in good agreement. © 1993 John Wiley & Sons. Inc.