VLSI chip set for 2D HDTV subband filtering with on-chip linememories

A chip set for 2D subband filtering of HDTV signals has been designed, fabricated and successfully tested. The two chips perform 10*14 quadrature mirror filtering for analysis filtering at the coder and synthesis filtering at the decoder. In order to achieve a very compact realization, the architectures utilize all a priori known properties of the filter algorithm. A 2D polyphase filter structure reduces the processing clock rate from the 72-MHz sampling rate to a moderate 18 MHz. The memory for vertical filtering is realized by on-chip parallel shift registers with multiphase clocking. A small silicon area for the filter arithmetic is achieved by application of carry save adder trees with fixed filter coefficients represented by canonical signed digits. A complete filterbank for luminance and chrominance signals consists of four identical chips, each with 450 000 transistors on 92 mm²     

The tone sense multiaccess protocols with partial collisiondetections (TSMA/PCD) for packet satellite communications

The tone sense multiaccess with partial collision detection (TSMA/PCD) protocol is particularly suitable for a packet satellite system serving an area with a dense population of earth stations. By incorporating a narrowband ground radio channel for broadcasting busy ones, the earth stations are able to avoid packet collisions by sensing for the absence of busy tones before transmitting packets. Partial collision detection capability can also be achieved. Single-tone TSMA/PCD gives 97% of the carrier-sense multiaccess with collision detection (CSMA/CD) throughput when N=10 tones are used, while for multitone and slot-by-slot announcement TSMA/PCD protocols only N=8 and N=2, respectively, are sufficient to drive the system to the CSMA/CD performance     

Occupational stress, social support, and the costs of health care.

Relationships among health care costs, social support, and occupational stress are investigated. Health care cost data were collected over two years for 260 working individuals. Multiple regression analyses were used to control for initial health care costs, age, and gender in predicting later costs; independent variables were stress, strain, social support, and their interactions. Main effects and interactions each accounted for significant proportions of the variance in various health care costs.     

On basic definitions of unified fracture mechanics terminology

The adoption of unified fracture mechanics terminology (UFMT) will promote efficient communication between specialists in different fields of fracture research, harmonization of national and international standards relating to fracture mechanics, and last but not least improvement of the existing methodology for teaching and education in fatigue and fracture. In this paper the definitions of some basic and related terms included in different standards on fracture mechanics terminology are confronted with one another. Alternative definitions of the same terms are offered. By this strategy the author tries to show that the definitions of basic and related terms appropriate for the UFMT should emerge as a consequence of harmonizing a crack model with an actual crack and then both taken together with a fracture model, laboratory test methods, and failure assessment codes.Published in Problemy Prochonsti, No. 1, pp. 17–29, January, 1996.This paper is published as a matter of discussion.     

The effect of particle distribution on damage formation in particulate reinforced metal matrix composites deformed in compression

Image analysis results are reported on the generation of damage in particulate reinforced metal matrix composites during compressive deformation. The technique allows the automated collection of data on the incidence of particle fracture and void formation in the matrix as a function of important microstructural parameters such as local particle volume fraction and particle size. There is a strong relationship between damage and the local volume fraction of the reinforcement proving that damage formation is accentuated in regions of particle clustering. With the SiC reinforced materials examined, there was observed to be a change in dominance of damage mechanism from particle fracture at low local volume fractions to void formation in the matrix within strongly clustered regions. The results are compared with finite element (FE) modelling of the compressive deformation of clustered particles using a simple cluster of equi-spaced particles. The FE results suggest that plastic flow is generally inhibited in clustered regions. In certain highly clustered configurations shielding is such that flow does not occur in the heart of the cluster even at high levels of average plastic strain. The modelling suggests that the change in dominance of damage mechanism is related to the dramatic increase in tensile hydrostatic stresses in the matrix with higher levels of particle clustering.     

Experimental investigation of systems for synchronizing time scales by means of the Quasar satellite communication system network

Experiments conducted at ground stations of the Quasar satellite communication network using both a null base as well as a base of around 2000 km is described. In experiments with a null base, the time scale transmission error was 1 nsec. Comparison of the results of collocation with data cbtained by the GLONASS system in the course of experiments using a 2100-km base demonstrated a divergence of the results of from 5 to 25 nsec. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 35–38, April, 1996.     

Inertia and Change in the Early Years: Employment Relations in Young, High Technology Firms

This paper considers processes of organizational imprintingin a sample of 100 young, high technology companies. It examinesthe effects of a pair of initial conditions: the founders' modelsof the employment relation and their business strategies. Ouranalyses indicate that these two features were well alignedwhen the firms were founded. However, the alignment has deterioratedover time, due to changes in the distribution of employmentmodels. In particular, the ‘star’ model and ‘commitment’model are less stable than the ‘engineering’ modeland the ‘factory’ model. Despite their instability,these two blueprints for the employment relation have strongeffects in shaping the early evolution of these firms. In particular,firms that embark with these models have significantly higherrates of replacing the founder chief executive with a non-founderas well as higher rates of completing an initial public stockoffering. Some implications of these findings for future studiesof imprinting and inertia in organizations are discussed.     

A dislocation shielding prediction of the toughness transition during cleavage of semibrittle crystals

An interconnected set of observations assesses current equilibrium models of the ductile-brittle-transition temperature (DBTT). This involvesin situ transmission electron microscopy (TEM) studies of crack-tip dislocations in single and polycrystals and bulk fracture toughness tests at various temperatures. Beyond K_I values of 8 MPa · m^1/2 in both iron-base single and polycrystals, large numbers of redundant dislocations are created, as postulated recently by Weertman. [38] Still, the necessary shielding dislocations, as required by equilibrium, can be detected at values as high as 20 and 40 MPa · m^1/2 byex situ TEM and electron channeling, respectively. In addition, the close approach of dislocations to the crack tip in some of the studies, as opposed to others, suggests that large dislocation free zones (DFZ) are a thin-film artifact. However, a failure criterion based partly on the Rice-Thomson model’21 is both consistent with the absence of a large DFZ and observed fracture toughness variations with test temperature. It is emphasized that this toughness transition is entirely in the semibrittle regime where cleavage is the failure mode. Nevertheless,K _lc values increase from 3 to 60 MPa·m^1/2 with an increase in test temperature. This article is based on a presentation made in the symposium “Quasi-Brittle Fracture” presented during the TMS fall meeting, Cincinnati, OH, October 21–24, 1991, under the auspices of the TMS Mechanical Metallurgy Committee and the ASM/MSD Flow and Fracture Committee.     

Molecular genetics in Saccharomyces kluyveri: The HIS3 homolog and its use as a selectable marker gene in S. kluyveri and Saccharomyces cerevisiae

We cloned the Saccharomyces kluyveri HIS3 homolog, k-HIS3, and made a partial deletion of the gene. The k-HIS3 gene complemented a HIS3 deletion in S. cerevisiae. The DNA sequences of the open reading frames (ORFs) of the HIS3 homologs are 70% identical at the DNA level and 83% identical at the deduced amino acid level. The ORF upstream of the k-HIS3 gene is related to the PET56 gene of S. cerevisiae found upstream of the HIS3 gene of S. cerevisiae. The ORF downstream from the k-HIS3 gene is not related to the DED1 gene found downstream of the HIS3 gene in S. cerevisiae.