Driving force for γ→ε martensitic transformation and stacking fault energy of γ in Fe-Mn binary system

A regular solution model for the difference of the chemical free energy between γ and ε phases during γ→ε martensitic transformation in the Fe-Mn binary system has been reexamined and partly modified based on many articles concerning the M _s and A _s temperatures of Fe-Mn alloys. Using the regular solution model, the measured M _s temperatures, and a thermodynamic model for the stacking fault energy (SFE) of austenite (γ), the driving force for γ→ε martensitic transformation, and the SFE of γ have been calculated. The driving force for γ→ε martensitic transformation increases linearly from − 68 to − 120 J/mole with increasing Mn content from 16 to 24 wt pct. The SFE of γ decreases to approximately 13 at. pct Mn and then increases with increasing Mn content, which is in better agreement with Schumann’s result rather than Volosevich et al.’s result.     

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.     

Phase behaviors of polymer blend(PEO–PPO) electrolyte/LiCF3SO3 systems in lithium battery

Polymer blend (poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO)) systems with two different mole ratios, complexed with LiCF₃SO₃ salt, have been characterized at various temperatures and compositions using a thermo‐optical analysis (TOA) technique. We also developed a new melting point depression theory based on the modified perturbed hard sphere chain model to interpret phase behavior of polymer blend electrolyte systems. The obtained results show that the eutectic points move toward higher T_m and lower weight fraction of salt with decreasing PEO mole ratio and also indicate that the mole ratio of PEO–PPO for each polymer blend plays an important role in determining the eutectic point of the polymer blend system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2314–2319, 2005     

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.     

Preparation of Polymer-stabilized Palladium–silver Bimetallic Nanoparticles by γ-irradiation and their Catalytic Properties for Hydrogenation of cis,cis-1,3-Cyclooctadiene

Polyvinypyrrolidone (PVP)-stabilized Pd-Ag bimetallic colloids were successfully prepared in an acetone:2-propanol solution mixture of palladium acetate and silver perchlorate, and in an aqueous solution of palladium nitrate and silver nitrate by γ-irradiation. The prepared PVP-stabilized bimetallic nanoparticles were characterized by UV, TEM, XRD, and XPS. In Pd–Ag bimetallic nanoparticles, the XPS data indicated that the constituent elements were in the metallic state, and the palladium atoms were concentrated on the surface of the alloy cluster. These PVP-stabilized bimetallic nanoparticles were used as catalysts for hydrogenation of cis,cis-1,3-cyclooctadiene (COD).     

A fault isolation filter design using left eigenstructure assignment scheme

This paper presents a novel fault isolation filter design method using left eigenstructure assignment scheme proposed by the first author et al. The proposed method shows good performance of fault isolation with an exact eigenstructure assignment and guarantees that the corrupted γ faults can be isolated simultaneously when the number of available output measurements are equal to or larger than (γ+l). A numerical example for the fault isolation filter is also included.     

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.