Process capability indices for skewed populations

This paper proposes a new method of constructing process capability indices (PCIs) for skewed populations. It is based on a weighted standard deviation method which decomposes the standard deviation of a quality characteristic into upper and lower deviations and adjusts the value of the PCI using decomposed deviations in accordance with the skewness estimated from sample data. For symmetric populations, the proposed PCIs reduce to standard PCIs. The performance of the proposed PCIs is compared with those of standard and other PCIs, and finite sample properties of the estimates are investigated using Monte Carlo simulation. Numerical studies indicate that considerable improvements over existing methods can be achieved by the use of the weighted standard deviation method when the underlying distribution is skewed. Copyright © 2002 John Wiley & Sons, Ltd.     

EMG pattern classification using SOFMs for hand signal recognition

 We propose a method of pattern classification of electromyographic (EMG) signals using a set of self- organizing feature maps (SOFMs). The proposed method is simple to apply in that the EMG signals are directly input to the SOFMs without preprocessing. Experimental results are presented that show the effectiveness of the SOFM based classifier for the recognition of the hand signal version of the Korean alphabet from EMG signal patterns.     

An Improved Pinchoff Equivalent Circuit Model for Determining PHEMT Model Parameters for Millimeterwave Application

An improved equivalent circuit model under pinchoff condition for extracting parasitic model parameters for Double Heterojunction δ-doped PHEMTs is presented. Good prediction for S parameters and noise performance are obtained up to 40GHz. A modified parameter extraction technique based on this new model was use to determine a PHEMT equivalent circuit model. Signification improvements of the accuracy of S parameters are obtained by using the new pinchoff model.     

Equivalent Circuit Model for Si Avalanche Photodetectors Fabricated in Standard CMOS Process

We present an equivalent circuit model for CMOS-compatible avalanche photodetectors. The equivalent circuit model includes an inductive component for avalanche delay, a current source for photogenerated carriers, and several components that model the device structure and parasitic effects. The model provides accurate impedance characteristics and photodetection frequency responses.     

Laser Process Proximity Correction for Improvement of Critical Dimension Linearity on a Photomask

We report on the improvement of critical dimension (CD) linearity on a photomask by applying the concept of process proximity correction to a laser lithographic process used for the fabrication of photomasks. Rule‐based laser process proximity correction (LPC) was performed using an automated optical proximity correction tool and we obtained dramatic improvement of CD linearity on a photomask. A study on model‐based LPC was executed using a two‐Gaussian kernel function and we extracted model parameters for the laser lithographic process by fitting the model‐predicted CD linearity data with measured ones. Model‐predicted bias values of isolated space (I/S), arrayed contact (A/C) and isolated contact (I/C) were in good agreement with those obtained by the nonlinear curve‐fitting method used for the rule‐based LPC.     

Creep Behavior of Nickel-Copper Solid Solution Alloys below 0. 55 Tm

In two recent creep studies of inhomogeneous nickelcopper solid solution alloys,i.e. cast weld metal with solidification-induced composition gradients^[1] and nickelcopper laminate composites with controlled composition gradients across the layers,^[2] the creep rates at an intermediate temperature (500 °C) were shown to decrease with an increase in homogenization. The creep behavior in inhomogeneous alloy systems reflects the composite effects of position-dependent creep properties as controlled by solid solution alloy content. To utilize composite modeling techniques in creep analyses of materials with composition gradients, creep data of homogeneous materials as a function of alloy content are required. Therefore, this study was undertaken to evaluate the creep behavior of nickel-copper solid solution alloys at intermediate temperatures and to provide a base set of data to evaluate the effect of gradients described above.^[1,2] I. D. CHOI, formerly Graduate Research Assistant, Colorado School of Mines.     

Constructing Internet coordinate system based on delay measurement

In this paper, we consider the problem of how to represent the locations of Internet hosts in a Cartesian coordinate system to facilitate estimation of network distances among arbitrary Internet hosts. We envision an infrastructure that consists of beacon nodes and provides the service of estimating network distance between pairs of hosts without direct delay measurement. We show that the principal component analysis (PCA) technique can effectively extract topological information from delay measurements between beacon hosts. Based on PCA, we devise a transformation method that projects the raw distance space into a new coordinate system of (much) smaller dimensions. The transformation retains as much topological information as possible and yet enables end hosts to determine their coordinates in the coordinate system. The resulting new coordinate system is termed as the Internet Coordinate System (ICS). As compared to existing work (e.g., IDMaps and GNP), ICS incurs smaller computation overhead in calculating the coordinates of hosts and smaller measurement overhead (required for end hosts to measure their distances to beacon hosts). Finally, we show via experiments with both real-life and synthetic data sets that ICS makes robust and accurate estimates of network distances, incurs little computational overhead, and its performance is not susceptible to the number of beacon nodes (as long as it exceeds a certain threshold) and the network topology.     

Effect of tetragonality ratio on photo-induced domain switching in poled (Pb1-xLax)TiO3 ferroelectric ceramics

The effect of the tetragonality (c/a) ratio on photo-induced domain switching in (Pb_1-xLa_x)TiO₃ ferroelectric ceramics preliminarily poled at 1.5kVmm^-1 was investigated by measuring photovoltaic current and acoustic emission (AE) signals. Results of total increment of photovoltaic current (J_pv), total AE event count and AE energy distribution showed that non-steady state behavior of J_pv was dominantly dependent on the activity of 90° domain switching during illumination. The activity of photo-induced domain switching was explained in terms of the coercive field and the space charge field. It was confirmed that the magnitudes of the space charge field and coercive field were found to be optimal for the photo-induced 90° domain switching at a c/a of 1.021.     

A study on robust design optimization of layered plate bonding process considering uncertainties

Design optimization of layered plate bonding process is conducted by considering uncertainties in a manufacturing process, to reduce the crack failure arising due to the difference of thermal expansion coefficients of the adherents. Robust optimization is performed to minimize the mean and variance of the residual stress, which is the major cause of the failure, while constraining the distortion and the instantaneous maximum stress to the allowable limits. In this optimization, the dimension reduction (DR) method is employed to quantify the uncertainty of the responses in the bonding process. It is expected that the DR method benefits the optimization from the perspectives of efficiency, accuracy, and simplicity. Response surface method (RSM) combined with sequential approximate optimization (SAO) technique is employed as an optimization tool. The obtained robust optimal solution is verified by the Monte Carlo simulation.