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- van der Zwaag, B.J., et al.
(författare)
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Extracting Knowledge from Neural Networks in Image Processing
- 2003
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Ingår i: Innovations in Knowledge Engineering. ; , s. 107-127
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Despite their success-story, artificial neural networks have one major disadvantagecompared to other techniques: the inability to explain comprehensively how a trainedneural network reaches its output; neural networks are not only (incorrectly) seen as a “magic tool” but possibly even more as a mysterious “black box.” Although much research has already been done to “open the box,” there is a notable hiatus in known publications on analysis of neural networks. So far, mainly sensitivity analysis and rule extraction methods have been used to analyze neural networks. However, these can only be applied in a limited subset of the problem domains where neural network solutions are encountered. In this chapter we propose a wider applicable method which, for a given problem domain, involves identifying basic functions with which users in that domain are already familiar, and describing trained neural networks, or parts thereof, in terms of those basic functions. This will provide a comprehensible description of the neural network’s function and, depending on the chosen base functions, it may also provide an insight into the neural network’s inner “reasoning.” To illustrate our method, the elements of a feedforward-backpropagation neural network, that has been trained to detect edges in images, are described in terms of differential operators of various orders and with various angles of operation. The results are then compared with image filters known from literature, which we analyzed in the same way.
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- Willander, Magnus, et al.
(författare)
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Silicon germanium strained layers and heterostructures
- 2004
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Ingår i: Physica Scripta. - : Royal Swedish Academy of Sciences. - 0031-8949 .- 1402-4896. ; T114, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- The integration of strained-Si1-xGex into Si technology has enhanced the performance and extended the functionality of Si based circuits. The improvement of device performance is observed in both AC as well as DC characteristics of these devices. The category of such devices includes field effect as well as bipolar families. Speed performance in some based circuits has reached limits previously dominated by III-V heterostructures based devices. In addition, for some optoelectronics applications including photodetectors it is now possible to easily integrate strained-Si1-xGex based optical devices into standard Silicon technology. The impact of integrating strained and relaxed Si1-xGex alloys into Si technology is important. It has lead to stimulate Si research as well as offers easy options for performances that requires very complicated and costly process if pure Si has to be used. In this paper we start by discussing the strain and stability of Si1-xGex alloys. The origin and the process responsible for transient enhanced diffusion (TED) in highly doped Si containing layers will be mentioned. Due to the importance of TED for thin highly doped Boron strained-Si1-xGex layers and its degrading consequences, possible suppression design methods will be presented. Quantum well p-channel MOSFETs (QW-PMOSFETs) based on thin buried QW are solution to the low speed and weak current derivability. Different aspects of designing these devices for a better performance are briefly reviewed. Other FETs based on tensile strained Si on relaxed Si1-xGex for n-channel and modulation doped field effect transistors (MODFETs) showed excellent performance. Record AC performance well above 200GHz for f(max) is already observed and this record is expected to increase in the coming years. Heterojunction bipolar transistors (HPTs) with thin strained-Si1-xGex highly doped base have lead to optimize the performance of the bipolar technology for many applications easily. The strategies of design and the most important designs of HBTs for optimum AC as well as DC are discussed in details. This technology is now mature enough and that is manifested in the appearance in the market nowadays. Si1-xGex based FETs circuits compatible with standard Si CMOS processes are soon expected to appear in the market. Finally, we briefly discuss the recent advances in Si1-xGex based infrared photodetectors.
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