Teaching computer design using virtual prototyping

The rapid increase in complexity and size of digital systems has reduced the effectiveness of old design methodologies based on physical prototyping. Prototyping via simulation must be used to achieve design cost and time-to-market goals when designing large digital systems. This virtual prototyping design methodology often permits the first physical prototype to be a manufacturable product. A two-course sequence has been developed to introduce students to this design paradigm. These courses teach virtual prototyping techniques and allow the students to use these techniques to develop a simple computer. The students simulate their designs, and then they implement their designs in hardware using field programmable hardware. This allows the students to complete an entire design cycle from idea to actual hardware implementation and compare their physical results to their simulated results.     

Assessing of long-distance background nutrient loading to the Archipelago Sea, northern Baltic, with a hydrodynamic model

Nutrient concentrations have increased in the Archipelago Sea during recent years. This is probably caused by growth in the loads from agriculture, air, fish farming and the Baltic proper. The Archipelago Sea acts like a nutrient filter between the Baltic proper and the Bothnian Sea; part of some of the externally input nutrients are retained within this area. Previously only rough estimates of the amount of the background load have been given. In this study the amount of net nutrient inflow from the Baltic proper was estimated with the aid of a three-dimensional hydrodynamic model for the years 1993–1997. Our model suggests that the role of background nutrient load from the Baltic proper may sometimes be decisive in the eutrophication process. For example, in June 1993 the background load of phosphorus was 300 000 kg in one month, i.e. about threefold compared to the total phosphorus load from fish farming during this whole year. Nutrient inflow varies a lot during open water seasons and therefore more detailed studies are highly recommended. If all other local loading sources were included in the dynamic nutrient balance model we could calculate actual nutrient concentrations at any given time in the Archipelago Sea.     

Preface

ThisspecialissueoftheJournalofComputerScienceandTechnologycontainsthePro-ceedingsoftheinternationalSummerSchoolandWorkshoponFormalModelsofProgram-mingandtheirApplications,heldinBeijingonSeptember17-20,1997.ThiseventwaspartoftheKIT(KeepinTouch)ProjectSYMSEMoftheEuropeanUnion,andwasjointlyorganizedwithLaboratoryofComputerScience,InstituteofSoftware.'KeepinTouch'isaprogrammeaimedatmaintainingandenhancingthelinksbetweennon-EuropeanscientistsandEuropeaninstitutions.Thepartnersofthissp…     

Monadic second-order definable text languages

Atext is a word together with a (additional) linear ordering. Each text has a generic tree representation, called itsshape. Texts are considered in a logical and in an algebraic framework. It is proved that, for texts of bounded primitivity, the class of monadic second-order definable text languages coincides with both the class of recognizable text languages and the class of text languages generated by right-linear text grammars. In particular it is demonstrated that the construction of the shape of a text can be formalized in terms of our monadic second-order logic. This approach can be extended to the case of graphs. This research was supported by the EBRA Working Group ASMICS 2.     

A mixture-of-experts framework for adaptive Kalman filtering

This paper proposes a modular and flexible approach to adaptive Kalman filtering using the framework of a mixture-of-experts regulated by a gating network. Each expert is a Kalman filter modeled with a different realization of the unknown system parameters such as process and measurement noise. The gating network performs on-line adaptation of the weights given to individual filter estimates based on performance. This scheme compares very favorably with the classical Magill filter bank, which is based on a Bayesian technique, in terms of: estimation accuracy; quicker response to changing environments; and numerical stability and computational demands. The proposed filter bank is further enhanced by periodically using a search algorithm in a feedback loop. Two search algorithms are considered. The first algorithm uses a recursive quadratic programming approach which extremizes a modified maximum likelihood function to update the parameters of the best performing filter in the bank. This particular approach to parameter adaptation allows a real-time implementation. The second algorithm uses a genetic algorithm to search for the parameter vector and is suited for post-processed data type applications. The workings and power of the overall filter bank and the suggested adaptation schemes are illustrated by a number of examples.     

Adaptive combination of PCA and VQ networks

In this paper we consider the principal component analysis (PCA) and vector quantization (VQ) neural networks for image compression. We present a method where the PCA and VQ steps are adaptively combined. A learning algorithm for this combined network is derived. We demonstrate that this approach can improve the results of the successive application of the individually optimal methods.     

Converter configurations and switching frequency for a GTO reactivepower compensator

This paper compares two converter configurations for a multi-10 MVA gate-turn-off (GTO) reactive power compensator (STATCOM) from the viewpoints of converter connection and switching frequency. One is a single-bridge system consisting of a three-phase bridge converter unit and a transformer. Its pulsewidth modulation (PWM) frequency varies from 450 to 1800 Hz, and its line frequency is 50 Hz. The other is a multiconnected converter system consisting of plural, single-, or three-phase converter units and transformers. Its switching frequencies are chosen to be the lowest possible. The evaluated items are harmonic distortion, power loss, GTO utilization factor, and control response. Our simulation study shows that the multiconnected converter system with the lowest switching frequency is superior to the single-bridge system with the higher switching frequency in every case, even when there are severe line faults requiring very quick response. A new control strategy is adopted for obtaining quick response     

An electrostatic microactuator using LIGA process for a magnetic head tracking system of hard disk drives

 We demonstrate an electrostatic micro actuator which is fabricated by LIGA process. The actuator is designed for a magnetic head tracking system of hard disk drives (HDDs). The actuator is essential to achieve very high track density of HDDs. We realize the aspect ratio of 125 by the LIGA process using a Si-Au mask. We propose to use PMMA molds both as the mechanical structure and as the insulator between electrodes. We believe there are great opportunity for the LIGA process in making micro actuators of HDDs. Received: 25 August 1997 / Accepted: 24 October 1997