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(1998)Journal ArticleThe first results obtained using a SOI device for microdosimetry applications are presented. Microbeam and broadbeam spectroscopy methods are used for determining minority carrier lifetime and radiation damage constants. A spectroscopy model is presented which includes the majority of effects that impact spectral resolution. Charge collection statistics were found to substantially affect spectral resolution. Lateral diffusion effects significantly complicate charge collection
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(1998)Journal ArticleSingle-address-space operating systems (SASOS) are an attractive model for making the best use of the wide address space provided by the latest generations of microprocessors. SASOS remove the address space boundaries which make data sharing between processes difficult and expensive in traditional operating systems. They offer the potential of significant performance advantages for applications where sharing is important, such as object-oriented databases or persistent programming systems. We have built the Mungi system to demonstrate that a SASOS can offer these performance advantages without resorting to special hardware. Mungi is a very `pure` SASOS, featuring an unintrusive protection model based on sparse capabilities, a fast protected procedure call mechanism, and uses shared memory as the exclusive inter-process communication mechanism, as well as for I/O. The simplicity of our model makes it easy to implement it efficiently on conventional architectures. Our implementation of Mungi for the MIPS R4600 64-bit microprocessor is presented, which is based on our port of the L4 microkernel. Mungi is shown to outperform, in some instances by more than an order of magnitude, two UNIX operating systems, Irix and Linux, in several important operations, such as task creation and inter-process communications, and on the OO1 object-oriented database benchmark. As well, we describe how our approach to key issues in SASOS design provides better performance than other systems, such as Opal. Our experience shows that the SASOS concept is viable, and that a well-designed microkernel is an excellent base on which to build high-performance operating systems.
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(1998)Conference PaperWe present the accounting system used for backing store management in the Mungi single-address-space operating system. The model is designed such that all accounting can be done asynchronously to operations on storage objects, and hence without slowing down such operations. It is based on bank accounts from which rent is collected for the storage occupied by objects. Rent automatically increases as available storage runs low, forcing users to release unneeded storage. Bank accounts receive regular income. A taxation system is used to prevent excessive buildup of funds on underutilised accounts. The accounting system is mostly implemented at user level, with minimal support from the kernel. As a consequence, the accounting model can be changed without modifying the Mungi kernel.
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(1998)Journal ArticleYBa2Cu3O7-y with high grain alignment has been successfully fabricated by a modified powder melting process at a temperature of ~930oC which is near the eutectic point of the starting materials Y2BaCuO5, BaCuO2, and CuO. In terms of the levitation force and YBa2Cu3O7-y grain alignment, the best result was shown in a sample having a Y2BaCuO5:BaCuO2:CuO molecular ratio of 1:3:5. In the present work, the Cu-surplus eutectic liquid was completely absorbed by use of a Y2BaCuO5 substrate, by which the final composition was driven to stoichiometric YBa2Cu3O7-y. The results were comparable to those obtained by the conventional melt-texture-growth process. A new invariant point apparently occurred at ~930-940oC owing to an interfacial reaction between YBa2Cu3O7-y matrix and Y2BaCuO5 substrate.
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(1998)Conference PaperRipple Down Rules (RDR) is a knowledge acquisition method for knowledge based systems (KBS) which facilitates incremental acquisition of knowledge and ensures that the previous performance of the KBS is not degraded by the incremental addition of the new knowledge. This approach is now well established for single classification tasks and more recently has been extended to multiple classification tasks. This paper describes the further extension of the approach to configuration tasks. The test domain for this study is the configuration of ion chromatography methods in analytical chemistry.
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(1998)Conference PaperThe major focus of recent knowledge acquisition research has been on problem-solving methods (PSM). This paper present results where a PSM developed for classification has been extended to handle a configuration or parametric design task, designing ion chromatography methods in analytical chemistry. Surprisingly good results have been obtained seemingly because any knowledge that has been added to the knowledge base, has been added precisely to overcome any limitations of the PSM. These results suggest a trade-off between domain knowledge and the power of the PSM and that greater use of domain knowledge would facilitate re-use by allowing PSMs to be used for a broader range of tasks.
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(1998)Conference PaperProducing vegetation maps is one of a myriad of uses that remotely sensed data is being used for. Low error rate classifers can be obtained from the training data generated from surveyed sites and expert knowledge. However, when these classifers are applied to an entire remotely sensed image to produce a map they contain at least many generalisations and at worst gross errors. This is, in part, due to the limited nature of spectral information and limited amounts of training data. In this paper we investigate a technique, called reinforcement classifcation, to generate more accurate classifcations of remotely sensed images. We demonstrate reinforcement classifcation using C4.5 although it is general enough to be applied to any domain and classifcation scheme.