Flexural traveling wave excitation based on shear-shear mode

This paper presents a new mechanism for circular flexture traveling wave excitation, which is based on a shear-shear mode in a single piezoelectric disc with a center hole was poled along its radial direction. Its bottom electrode was divided into four parts, and the top electrode acted as common ground. By use of a pair of alternating current (AC) voltage signals (sine and cosine), at the disc's resonance frequency, a flexural traveling wave was generated circumferentially. Both finite element modeling (FEM) analysis of transducers by integration of Laplace equations (ATILA) analysis and experimental results demonstrate the concept. As an application example, a shear-shear mode prototype was constructed and characterized.     

A Combinatorial Analysis of Boundary Data Structure Schemata

Speed up the software in geometric algorithms for solid modeling, CAD/CAM, and robotics applications. How? By using boundary data structures that are fast and use less storage.     

A Hybrid Feature Recognizer for Machining Process Planning Systems

We describe a hybrid feature recognition method for machining features that integrates three distinct feature recognition methods: graph matching, cell-based maximal volume decomposition, and negative feature decomposition using convex decomposition. Each of these methods has strengths and limitations, which are evaluated separately. We integrate these methods in a sequential workflow, such that each method recognizes features according to its strengths, and successively simplifies the part model for the following methods. We identify two anomalous cases in the application of maximal volume decomposition, and their cure by introducing limiting halfspaces. Feature volumes recognized by all three methods are then combined into a unified hierarchical feature representation, which captures feature interaction information, including geometry-based machining precedence relations.     

Multiplicative approximation of transfer functions with frequency weighting

An algorithm for transfer function order reduction is presented, which generalizes the balanced stochastic truncation algorithm to allow for input weighting. An example illustrates use of the algorithm to secure smaller dB error in selected frequency bands through the introduction of the weighting.     

Brequinar sodium inhibits interleukin-6-induced differentiation of a human B-cell line into IgM-secreting plasma cells

Brequinar sodium (BQR) has been shown recently to be a potent immunosuppressive agent. This property has been attributed to the capacity of BQR to inhibit de novo pyrimidine nucleoside biosynthesis and consequently, to blockade the synthesis both of DNA and RNA. The influence of this new immunosuppressant on lymphocyte function has not been fully characterized. To determine the potential efficacy of BQR for the control of antibody-mediated graft rejection, which is of particular significance in the context of xenotransplantation, we have examined the influence of the drug on interleukin-6-dependent IgM production by the human B-cell line, SKW 6.4. At concentrations up to 10 micrograms/ml, BQR did not affect concanavalin A (Con A)-induced human peripheral blood lymphocyte proliferation or IL-6 production by blood mononuclear leucocytes. In contrast, the drug was very effective in inhibiting IL-6-stimulated IgM production by SKW 6.4 cells, with an optimal inhibitory concentration of 0.3 microgram/ml. As expected, addition of exogenous uridine (0.1 mM), the precursor of uridine triphosphate (UTP), reversed the inhibitory effect of BQR on antibody production, while cytidine (0.1 mM) potentiated the inhibitory activity of the drug. It was further demonstrated that the inhibition of IgM production was unrelated to DNA synthesis, indicating that BQR may affect IL-6 signal transduction and IgM production in SKW 6.4 cells independent of any effect on cell proliferation.     

A 19-mW 2.6-mm/sup 2/ L1/L2 dual-band CMOS GPS receiver

This paper presents the design and implementation of an L1/L2 dual-band global positioning system (GPS) receiver. Dual-conversion with a low-IF architecture was used for dual-band operation. The receiver is composed of an RF preamplifier, down-conversion mixers, a variable-gain channel filter, a 2-bit analog-to-digital converter, and the full phase-locked-loop synthesizer including an on-chip voltage controlled oscillator. Fabricated in a 0.18-/spl mu/m CMOS technology, the receiver exhibits maximum gain of 95 dB and noise figures of 8.5 and 7.5 dB for L1 and L2, respectively. An on-chip variable-gain channel filter provides IF image rejection of 20 dB and gain control range over 60 dB. The receiver consumes 19 mW from a 1.8-V supply while occupying a 2.6-mm/sup 2/ die area including the ESD I/O pads.     

Tetrahedral mesh generation based on advancing front technique and optimization scheme

In recent years, demand for three‐dimensional simulations has continued to grow in the field of computer‐aided engineering. Especially, in the analysis of forming processes a fully automatic and robust mesh generator is necessary for handling complex geometries used in industry. For three‐dimensional analyses, tetrahedral elements are commonly used due to the advantage in dealing with such geometries. In this study, the advancing front technique has been implemented and modified using an optimization scheme. In this optimization scheme, the distortion metric determines ‘when and where’ to smooth, and serves as an objective function. As a result, the performance of the advancing front technique is improved in terms of mesh quality generated. Copyright © 2003 John Wiley & Sons, Ltd.