Some social aspects of CAD

There is a widespread belief that automation, computerisation and the use of robotic devices will liberate human beings from routine, backbreaking, soul destroying tasks and leave them free to engage in more creative and worth-while activities. Actual experience does not support such a generalisation and there are growing grounds for believing the reverse is frequently the case.There are now grounds for believing that the computer, as the vehicle for technological change in the field of white collar and intellectual work, is bringing in its wake many of the contradictions experienced at an earlier historical stage when skilled manual work was subjected to mechanisation and automation.     

Some aspects of computer deadlocks

Modern multiprogramming systems are designed to support a high degree of parallelism by ensuring that as many system components as possible are operating concurrently. Deadlocks arise when members of a group of processes which hold resources are blocked indefinitely from access to resources held by other processes within the group. When no member of the group will relinquish control over its resources until after it has completed its current resource acquisition, deadlock is inevitable and can be broken only by the involvement of some external agency. In this paper we present a comprehensive study of the resource management problem in computer systems by critically reviewing the principles, techniques and tools involved in handling and avoiding deadlocks and by discussing the modelling techniques available for deadlock analysis. Toward the end we discuss the problem of on-line handling of deadlock in distributed computer networks.     

Some fundamental aspects of process-parameter estimation

The purpose of this paper is to give a coherent picture of the process-parameter estimation. It offers a philosophy by introducing a "generalized model." From this, two classes of schemes can be derived. In each class there is quite some freedom with respect to the choice of elements of the scheme, the choice of the error criterion, and the choice of signal representation (continuous, sampled, quantized, etc.). These choices account for a whole range of estimating systems. The dynamic properties of many of these systems can be studied by the approach presented in this paper. The extension to estimation of nonlinear processes is also discussed.     

Some practical aspects of covariance estimation

Vectorcardiogram (VCG) data often are analyzed using the Karhunen-Loéve expansion of the sample covariance matrix, S, as a method for discriminating between the VCG's of healthy pat unhealthy patients. The estimator, S, however, can be seriously effected by both atypical observations and the number of VCG's in the database relative to their dimension. In this paper it is shown that alternative robust estimators of the covariance matrix are appealing in analyzing VCG data when outliers are present in the sample. Also, it is demonstrated that sample sizes in such experiments should be greatly expanded in order to validate the asymptotic properties of S.     

Some legal aspects of expert systems

As expert systems become more popular, the possibility of lawsuits arising from their use becomes increasingly evident. The expert system developer needs to be aware of important legal concepts associated with an expert system's development and deployment. This paper will primarily explore the rights to intellectual property associated with an expert system and liability for malfunction of an expert system.     

Some aspects of the genesis of structures

Bendsøe and Kikuchi (1988) introduced a novel approach of distributing mass within a specified design domain utilizing a stiffness-density relation obtained by homogenization of a cellular microstructure. This approach was extended to multiple loading cases and three-dimensional applications by the author and his associates (Mlejnek and Schirrmacher 1989; Mlejnek 1990). Moreover the well-known concept of explicit convex behaviour approximation together with a dual solution scheme (Fleury and Smaoui 1988) was successfully introduced to this problem. Further objectives such as eigenvalues and displacements generalized the range of application. It is the aim of this paper, to develop a simplified procedure that can be easily integrated into a FEM-analysis package. Its application requires essentially not much more than the usual FEM-technology. Nevertheless a traceable mathematical base is still maintained. A series of examples demonstrates the suitability of this approach to the preliminary design of minimal compliance structures made of isotropic materials.Presented at NATO ASI Optimization of Large Structural Systems, Berchtesgaden, Germany, Sept. 23 – Oct. 4, 1991     

Some aspects of concurrent programming in CCNPASCAL

CCNPASCAL is a language derived from Pascal and Concurrent Pascal which has been used in the development of an operating system for a multiprocessor. This paper introduces some of the important features of the language and illustrates them with examples. The language provides mechanisms for interfacing separately compiled modules, for building abstractions of collections of resources and for efficient asynchronous communication.     

Some aspects of sorting in two dimensions

The subject of this paper is two dimensional sorting. First we shall examine the problem of determining a lower bound on worst case time complexity of any two dimensional sorting algorithm, with regard to the definition of two dimensional sorting we are interested in. Then we shall design a sorting algorithm working on an information structure, such as to allow access to a record only through the adjacent ones. The algorithm has been implemented by computer, and we shall report the results obtained about time complexity, which turns out to be logarithic. While examining the above algorithm, we shall examine some special cases of two dimensional sorting. This research has been supported by Comitato Nazionale per le Scienze Matematiche, C.N.R., under a scholarship for a thesis in computer science, and a research grant No. 75.01035.01.     

Some aspects of zoom lens camera calibration

Zoom lens camera calibration is an important and difficult problem for two reasons at least. First, the intrinsic parameters of such a camera change over time, it is difficult to calibrate them on-line. Secondly, the pin-hole model for single lens system can not be applied directly to a zoom lens system. In this paper, we address some aspects of this problem, such as determining principal point by zooming, modeling and calibration of lens distortion and focal length, as well as some practical aspects. Experimental results on calibrating cameras with computer controlled zoom, focus and aperture are presented     

Some computational aspects of the matrix exponential

Matrix norms that satisfy the Schwarz inequality are used to determine upper bounds for the error in some common computations involving the matrix exponential function.     

Some aspects of spatial aliasing in satellite altimetry

A detailed analysis on the effect of spatial aliasing associated with Topex/Poseidon-Jason, Geosat-GFO (Geosat Follow-On) and European Remote Sensing (ERS)-Envisat altimeters has been carried out. In the space domain, aliasing is characterized by a significant along-track (near meridional) and cross-track (near zonal) anisotropy in terms of alias wavelength, @_a . The former is practically limited by instrument noise at about 50 km, while the latter, ranging from 0 to ∞, is determined by the signal period, T_o . A striking feature of zonal alias wavelength is its step-like function with respect to signal period, which leads to a discrete distribution of the histogram of λ_a versus T_o . This explains the coincidence that the S2 tide is always aliased at a wavelength of about 180° of longitude, and K1 and P1 at about 360° of longitude for all three groups of altimeters concerned. Potential consequences of spatial aliasing in satellite altimetry are also discussed. It is speculated that the intrinsic asymmetry in zonal and meridional aliasing may introduce artificial anisotropy in altimeter-derived geophysical parameters. Furthermore, it is shown that the consequences of spatial aliasing can be modified by other physical or oceanic processes such as the Doppler effect.     

Some aspects of error bounds in feature selection

In this paper we discuss various bounds on the Bayesian probability of error, which are used for feature selection, and are based on distance measures and information measures. We show that they are basically of two types. One type can be related to the f-divergence, the other can be related to information measures. This also clarifies some properties of these measures for the two-class problem and for the multiclass problem. We give some general bounds on the Bayesian probability of error and discuss various aspects of the different approaches.     

Some mathematical and representational aspects of solid modeling

An approach is presented to the tripartite problem of modeling physical solids mathematically, representing the models in a computer, and using representations in geometric algorithms. Examples are primarily from the domain of manufacturing and design of discrete goods, but the results reported here have wider significance. Mathematical definitions can formalize many of our intuitions about three-dimensional (3-D) objects and operations on them. Representation-free (mathematical) models and functions allow formal properties to be defined for characterizing geometric representations. Three common representation schemes for 3-D objects are described briefly, along with some of their formal and informal properties. A rigorous, as opposed to ad hoc, approach to modeling has several advantages. Broadly, the conceptual complications and ambiguities which are endemic to ad hoc problem statements and solutions may be avoided by appealing to a precise mathematical semantics. Mathematical rigor is mandatory in applications such as automatic manufacturing in which correctness must be guaranteed and consistency and validity maintained.     

Some aspects of human-friendly control for movement-helping devices

Future welfare models should meet the needs of a large group of aged and disabled people. Present research and technology efforts in this direction are oriented toward the development of highly effective home-installed devices which will provide the user with continuous assistance in different everyday activities. The problems and needs of the elderly and the disabled vary from person to person over a large range, and with many serious requirements. Modern designs for such devices are oriented toward solutions where the user is less engaged in the control process, and the interaction between the device and the user ishuman-friendly, i.e., the devices should possess a high level of intelligence in their controls, actions, and interactions with the user, offering him/her a high level of comfort and functionality. This paper considers a mixed control mode as a better alternative for human-machine interactions for users with great movement disability. Some examples of easy direct control are discussed.