Jae-Seok Kim

An overview of membership function generation techniques for pattern recognition

Abstract The estimation of membership functions from data is an important step in many applications of fuzzy theory. In this paper, we provide a general overview of several methods for generating membership functions for fuzzy pattern recognition applications. We discuss methods based on heuristics, probability to possibility transformations, histograms, nearest neighbor techniques, feed-forward neural networks, clustering, and mixture decomposition. We also illustrate these membership generation methods using synthetic and real data sets, and discuss the suitability and applicability of these membership function generation techniques to particular situations.

A novel architecture design for multicode CDMA rake receiver

We propose a new architecture design for the Multicode CDMA (MC-CDMA) rake receiver. It contains one searcher module, three independent fat finger modules, and one combiner for the demodulation of high-rate data. We compare the hardware complexity of the proposed architecture with a conventional CDMA rake receiver in terms of the number of Walsh code channels. The result shows that our proposed architecture has a 12% and 18.6% reduction in gate count when the number of Walsh code channels is 4 and 7, respectively.

Highly selective chemical mechanical polishing of Si3N4 over SiO2 using advanced silica abrasive

Highly selective chemical mechanical polishing (CMP) of Si3N4 over SiO2 is achieved by using a modified silica abrasive. Controlling the removal rate of Si3N4/SiO2, chemical reaction is a dominant factor for ceria abrasive, but physical force such as repulsion/attraction is a primary one for silica abrasive. In order to maximize mechanical action in CMP process using silica slurry, we modified the surface charge of silica abrasive into having more negative charge, which resulting in −50 mV of zeta potential in a low pH (< 3.0) slurry. This strong negative zeta potential of the modified silica abrasive enables enhancing attractive forces to Si3N4 and repulsive forces to SiO2 in a low pH environment. In addition, a cocoon shape silica abrasive shows 3 times higher Si3N4 RR than a spherical shape one. Consequently, selectivity of Si3N4 over SiO2 reaches 95.0, which is significantly improved from 0.0167 in the conventional silica abrasive case. When this modified silicon abrasive and the optimum pH condition are applied, in-chip uniformity at various pattern densities of Si3N4 (0, 12, and 32%) turns out to be well controlled under 100 A. This result is an acceptable level for our semiconductor device integration.