This paper presents some methods to improve the image quality obtained with volume rendering. By computing the opacity, color and gradient of each sample point directly at the sample position, the image quality has improved over methods which compute these values at the voxel positions. A new method for calculating the gradient is presented. These improvements result in small details becoming clearly visible. It also allows high zoom rates without generating blurry images. The opacity is corrected for the sample rate, allowing a consistent translucency setting.

Experimental single-chip LISP processors are already being build, but high performance processor-intensive architectures, which might be used for CPU-intensive tasks in computer algebra are still in the early stages of design. Parallelism will be needed to extend the power of computer algebra systems. Implementation of a parallel EVAL scheme is one of the most frequently mentioned options. The implementation of special purpose parallel hardware with a thight coupling between storage and computational units, was proposed recently under the name systolic array. The actual introduction of a flexible, general purpose, processor-intensive computer partition as a part of a large scale multiprocessor Computer Algebra system, depends heavily on the progress made in design and technology needed to develop these computational structures. This paper describes ideas for the design of a fully programmable processor-intensive computer partition, which can be (micro)programmed from a high level language.

Synthetic-numeric methods can be very instrumental in engineering and scientific research as well. We examplify this by considering the computational aspects of the analysis of a transmission line network, as occurring in micro-wave technology. We comparatively discuss the (dis)advantages of symbolic and numeric approaches for this specific problem, with emphasis on the synthetizing power of symbolically preparing programs for the production of reliable numerical results.

An algorithm for very accurate visualization of an iso- surface in a 3D medical dataset has been developed in the past few years. This technique is extended in this paper to several kinds of measurements in which exact geometric information of a selected iso-surface is used to derive volume, length, curvature, connectivity and similar geometric information from an object of interest. The actual measurement tool described in this paper is fully interactive. The highly accurate iso-surface volume- rendering algorithm is used to describe the actual measurement that should be performed. For instance, objects for which volumes should be calculated, or paths from which the length should be calculated can be selected at sub-voxel resolution. Ratios of these quantities can be used to automatically detect anomalies in the human body with a high degree of confidence. The actual measurement tool uses a polygon-based algorithm that can distinguish object connectivity at sub-voxel resolution, in exactly the same manner as the iso-surface algorithm. Segmentation based on iso-surfaces geometrical topology can be done at this point. The combination of the iso-surface volume-rendering algorithm and the polygon-based algorithm makes it possible to achieve both visual interaction with the dataset and highly accurate measurements. We believe that the proposed method contributes to the integration of visual and geometric information and is helpful in clinical diagnosis.

This paper discusses reconfigurability issues in lowpower hand-held multimedia systems, with particular emphasis on energy conservation. We claim that a radical new approach has to be taken in order to fulfill the requirements - in terms of processing power and energy consumption - of future mobile applications. A reconfigurable systems-architecture in combination with a QoS driven operating system is introduced that can deal with the inherent dynamics of a mobile system. We present the preliminary results of studies we have done on reconfiguration in hand-held mobile computers: by having reconfigurable media streams, by using reconfigurable processing modules and by migrating functions.

Medical application of volume-rendering techniques requires algorithms with a very high spatial accuracy. In this paper, a new volume-rendering method called 'Iso-Surface Volume Rendering' will be introduced. This method is able to visualize an iso-surface in a volumetric dataset with the highest possible accuracy. Furthermore, this new method is very fast, allowing interactive visualization on low-cost workstations without compromising quality. Given the point- spread function and the sample distance (voxel distance) of the acquisition device it is possible to calculate the spatial error that is made when the surface of an object is estimated by an iso-surface. It will be shown that this error depends on the sample distance, the sample location, and the interpolation function used. When the sample distance is very small, the error approaches zero.

Mobile personal computers will be a vital technology for making electronic information processing available to people on the move. We expect personal mobile computers, 'mobile digital companions', to be small enough that they can be carried along all day, versatile enough that they can be used for all kinds of information processing -- diary, notebook, pager, telephone, walk man, dictation, e-mail, e-money, keys, ID -- and frugal enough that they can be used all day without recharging. This paper reports ongoing work on Moby Dick, a research project that addresses fundamental issues in the architecture, design and implementation of lowpower hand-held computers, with particular emphases on energy conservation and security. The goal is to investigate architectural issues in hardware and software design in concert, so that opportunities in hardware design can be exploited by supportive software.

The ca lculation o f the e nergy consumption o f an algorithm can b e performed analytically for the ca se of r andom data on all signals within a circuit. The statistical properties of the signals in an application n eed however not be of a random nature. Hence there is a need for tools which help the user to find either spots in a c ircuit which consume c onsiderably more e nergy than the lower bound for f ully random data, or spots which dissipate considerably less energy, due to correlation's in the signals. Low power design methods (1) are of major importance for the utilization of all features offered b y a sub-micron p rocess. A posteriori simulation is the most common method used for power simulation today. This method has as has major disadvantage that t he ac tual energy consumption can on ly be calculated after the completion of the particular design, and through the application o f a rather specific stimulus. It i nvolves, in almost all cases, lengthy simulations in which all glitches at all l ocations in the c ircuit are taken into account. The elimination of characterization arbitrariness due to the selection of specific amplitudes of digital signals makes it necessary to use e ither multiple input sequences or even longer input stimuli and/or simulations at different amplitude levels. The methodology introduced in section 2, separates glitch p ropagation within arithmetic blocks on on e hand, from signal statistics and op erator- interaction on the other hand. The approach taken is analytic & constructive as opposed to the empiric nature of the dual-bit type approach (2), in which a mathematical model for the energy consumption is matched to the energy consumption measured for a given multiplier and/or adder design. It differs also substantial from straightforward simulations of synthesized descriptions (4, 5). Another high-level simulator with an empiric nature, which takes a non-synthesized VHDL as input t o p redict t he e nergy consumption of the modeled circuit, is introduced in (3)

In this paper we give a detailed overview of the ASIC design course as it is being given at the Department of Electrical Engineering of the University of Twente. This course covers the complete trajectory from system design via circuit design and actual implementation to testing. Design and testing are not limited to the digital field only, but contain also a substantial analogue and mixed-signal part.

A survey of the basic issues in low power design is presented, including techniques for the analysis of energy consumption in the early design phase of analog and digital circuits. The concept of energy complexity will be introduced in conjunction with techniques for parameterized energy management. The technique of energy consumption management will be applied to some analog and digital designs, to show how the designer can identify design bottlenecks and develop design alternatives, before starting any tedious design steps.

| Architectural synthesis for digital signal pro- cessing (DSP) is the automatic generation of a VLSI imple-mentationof a DSP algorithm. In this process, it is desirable to estimate the power consumption of potential solutions. The estimation should be fast and accurate. The dual-bit- type estimation method known from literature was taken as a basis and adapted for the goals of this research. Experi- mental results show that the followed approach gives useful results.

Architectural synthesis for digital signal processing(DSP) is the automatic generation of a VLSI implementationof a DSP algorithm. In this process, it is desirableto estimate the power consumption of potential solutions.The estimation should be fast and accurate. The dual-bittype estimation method known from literature was taken asa basis and adapted for the goals of this research. Experimentalresults show that the followed approach gives usefulresults.I.

To what extent can the exact size and form of an object be reconstructed from volume data? Why can the rendering of a 3D dataset performed with a super-resolution volume rendering algorithm be magnified beyond the dimensions of the individual voxels without introduction of artefacts and/or unsharpness? These topics are covered with clear examples and new ways to present fundamental issues related to the reconstruction of 3D objects from grey-values on a 3D grid. Application areas are 3D rendering of medical, seismic and geometrical data, as well as the rendering of surface textures.

Volume visualization is the technique of displaying two dimensional projections of three dimensional data. The data is acquired from a medical scanner, like MRI, CT, SPECT, or US scanners. Visualizing a given three dimensional medical dataset can be done by surface rendering algorithms or by direct volume rendering algorithms. Surface rendering algorithms require an intermediate geometric representation and are therefore less attractive. In our approach volume rendering is used. To improve image quality of such projections of the volume data, special care should be taken to (a) the interpolation step, (b) the estimation of the local gradient and (c) the assignment of opacity values at sample positions. These aspects are addressed in this paper.