Asymptotic expansions of the mergesort recurrences

This note provides exact formulae for the mean and variance of the cost of top-down recursive mergesort. These formulae improve upon earlier results of Flajolet and Golin. Received: 11 May 1998     

Analysis of sandwich sheet rolling by stream function method

A mathematical model for symmetrical sandwich sheet rolling is proposed by using the stream function method and the upper bound theorem to investigate the plastic deformation behavior of sheets at the roll-gap. The velocity fields derived from the newly proposed stream functions can automatically satisfy the volume constancy and the velocity boundary conditions within the roll-gap. Effects of various rolling conditions such as the thickness ratio and flow stress ratio of sheets, total thickness reduction, friction factor between the sheet and roll, etc., upon the thickness ratio of the rolled product, the relative length of the plastic region in each layer, rolling force and rolling power are discussed systematically. Furthermore, experiments on sandwich sheet rolling are also conducted by employing aluminium, mild steel and stainless steel as layers of sandwich sheets. It is found that the theoretical predictions of the thickness ratio of the rolled products and rolling force are in good agreement with the experimental measurements. Through the study, it becomes clear that the proposed analytical method is applicable for simulating the sandwich sheet rolling processes and is able to offer useful knowledge in manufacturing sandwich sheets.     

Contact technology for high performance scalable BiCMOS on TFSOI

A selective W contact layer is deposited on both poly and silicon electrodes to realize scalable, high performance TFSOI BiCMOS. A unique double spacer integration results in high performance MOS and bipolar operation while providing adequate separation between poly and silicon electrodes to prevent sidewall leakage. Switching speed more than twice that of comparable bulk circuits is demonstrated. Limitations imposed by conventional silicon- and metal-diffusing self aligned silicides (Ti and Pt) are described. Pt silicide limits scaling of the spacer width while Ti silicide limits scaling of the silicon thickness. Selective W is shown capable of maintaining good device and circuit performance while not imposing such limitations     

Scalable parallel computers for real-time signal processing

We assess the state-of-the-art technology in massively parallel processors (MPPs) and their variations in different architectural platforms. Architectural and programming issues are identified in using MPPs for time-critical applications such as adaptive radar signal processing. We review the enabling technologies. These include high-performance CPU chips and system interconnects, distributed memory architectures, and various latency hiding mechanisms. We characterize the concept of scalability in three areas: resources, applications, and technology. Scalable performance attributes are analytically defined. Then we compare MPPs with symmetric multiprocessors (SMPs) and clusters of workstations (COWs). The purpose is to reveal their capabilities, limits, and effectiveness in signal processing. We evaluate the IBM SP2 at MHPCC, the Intel Paragon at SDSC, the Gray T3D at Gray Eagan Center, and the Gray T3E and ASCI TeraFLOP system proposed by Intel. On the software and programming side, we evaluate existing parallel programming environments, including the models, languages, compilers, software tools, and operating systems. Some guidelines for program parallelization are provided. We examine data-parallel, shared-variable, message-passing, and implicit programming models. Communication functions and their performance overhead are discussed. Available software tools and communication libraries are also introduced     

A lattice realization for 2-D separable-denominator digital filters

New properties useful in connection with 1-D and 2-D lattice realizations are developed. These properties enable one to represent given, complicated 2-D separable-denominator digital filters in terms of simpler, more elemental building blocks which consist of two 1-D lattice realizations having dynamics in different directions and connected in a cascade form. The matrix-relationship between a 2-D discrete Schwarz form and a controller-observer canonical form is also derived. A notable property of the proposed 2-D lattice realization is that the impulse response energy of a 2-D separable-denominator digital filter can be readily obtained from the reflection coefficients and input/output tapped coefficients of the realization.This work was supported by the National Science Council of the Republic of China under Grant NSC79-0402-E0006-02, the US Army Research Office under Grant DAAL-03-91-G0106, and the NASA-Johnson Space Center under Grant NAG-9-380.     

A pregnancy-specific glycoprotein is expressed in the brain and serves as a receptor for mouse hepatitis virus

Mouse hepatitis virus (MHV), a murine coronavirus known to cause encephalitis and demyelination, uses murine homologues of carcinoembryonic antigens as receptors. However, the expression of these receptors is extremely low in the brain. By low-stringency screening of a mouse brain cDNA library, we have identified a member of the pregnancy-specific glycoprotein (PSG) subgroup of the carcinoembryonic antigen gene family. Unlike other PSG that are expressed in the placenta, it is expressed predominantly in the brain. Transfection of the cDNA into COS-7 cells, which lack a functional MHV receptor, conferred susceptibility to infection by some MHV strains, including A59, MHV-2, and MHV-3, but not JHM. Thus, this is a virus strain-specific receptor. The detection of multiple receptors for MHV suggests the flexibility of this virus in receptor utilization. The identification of this virus in receptor utilization. The identification of a PSG predominantly expressed in the brain also expands the potential functions of these molecules.     

Molecular Conformation and Applicaton of Stereoregular PMMA Langmuir-Blodgett Films

Molecular conformations of stereoregular poly(methyl methacrylate) (PMMA) monolayers have been investigated by scanning probe microscopes. Isotactic and syndiotactic PMMAs were found to have right and left hand helical structures, respectively. On the contrary atactic PMMA showed rather random arrangement of the chains. It has been demonstrated that the PMMA Langmuir-Blodgett(LB) films can be utilized to form nanoscale patterns down to 50 nm and to form a geodesic lens. It has also been manifested that the quantum efficiency of a polymer electroluminescent device can be significantly enhanced by inserting the PMMA LB films between the emitting layer and the cathode. All the applications utilize the unique characteristics of the LB films to form thin and uniform films in the molecular level.     

Asphyxiated bladder syndrome in a pediatric intensive care unit

Sixteen neonates and infants with asphyxiated bladder syndrome (ABS) were prospectively studied over a two-year period. Their transient urinary bladder distention had developed as a sequel of asphyxial events, and presented as delayed micturition in the absence of obstructive lesion. The incidence was 1.9 percent in this Pediatric Intensive Care Unit. Five cases occurred in the neonatal period. All patients were younger than three years of age (mean: 9.1 months), and the incidence of ABS was 2.8 percent within this age group. For intermittent decompression of the bladder, all responded successfully to the suprapubic bladder expression method (Crede's maneuver). Most (81.3%, 13/16) ABS cases coexisted with intestinal dysfunction as either paralytic ileus (62.5%, 10/16) or as gas-less abdomen (18.8%, 3/16). There was no evidence of association with either systemic or urinary bacterial infection. Normal spontaneous voiding and bowel function were regained in all cases except one, who died early. Mean (SD) duration of bladder dysfunction was 66.9 (40.3) hours. Sonography showed normal kidneys and collecting system in all patients both during and after ABS episodes. Half of the patients (8/16) died ultimately. No urinary tract abnormality was found in post-mortem examinations in five cases.     

Contrast enhancement for backpropagation

This paper analyzes the effect of data-contrast to a backpropagation (BP) network and introduces a data preprocessing algorithm that can improve the efficiency of the standard BP learning. The basic idea is to transform input data to a range that associates the high-slope region of the sigmoid function where a relatively large modification of weights occurs. A simple uniform transformation to such a desired range, however, can lead to a slow and unbalanced learning if the data distribution is heavily skewed. To facilitate data processing on such distribution, the authors propose a modified histogram equalization technique which enhances the sparing between the data points in the heavily concentrated regions of the distribution