Highly reliable testing of ULSI memories with on-chip voltage-downconverters

Two testing techniques for ultra-large-scale integrated (ULSI) memories containing on-chip voltage downconverters (VDCs) are described. The first in an on-chip VDC tuning technique that adjusts internal V_CC to compensate for the monitored characteristics of the process parameters during repair analysis testing. The second is an operating-voltage margin test, performed at various internal V_CC levels during the water sort test (WT) and the final shipping test (FT)     

Computer analysis,design and simulation of horizontal ground heat exchangers

This paper presents a new computerized procedure for dealing with the design of horizontal ground heat exchangers (HGHE). The computer program is based on the transient model of coupled nonlinear partial differential equations governing heat and mass flow in soils. The model is two-dimensional and delineates the operation of ground heat storage with the HGHE and such phenomena as freezing/thawing and drying/rewetting of soil moisture. Comprehensive climatological data, such as ambient temperature, solar radiation, wind velocity, rainfall, snowfall, snow characterstics, and water vapour pressure is used to simulate conditions at the ground surface over any required length of time. The package can be applied to any geographical location by changing climatic and soil data input. The designer has the possibility of selecting any of 12 types of soils from sand to clay, 12 commercial heat pumps, nine different configurations of the HGHE, 16 plastic pipes for ground coils, and 13 ground coil fluids. The program, however, does not calculate the length of the HGHE but it evaluates the thermodynamic performance of a ground heat pump system and provides comprehensive data on thermal and hydraulic conditions in ground heat storage. The length of the ground heat exchanger is obtained from a line source theory model or from site dimensions and pipe spacing. Computed results for ground heat exchanger operation correlate fairly well with experimental data. Simulation of temperature and moisture content in the ground for natural conditions (no heat extraction/deposition) showed a fair agreement with field data. The entire computer program is user-friendly, interactive, menu-driven, and written in FORTRAN 77.     

A BiCMOS dynamic carry lookahead adder circuit for VLSIimplementation of high-speed arithmetic unit

A BiCMOS dynamic carry lookahead circuit that is free from race problems is presented. A 16 b full-adder test circuit, which has been designed based on a 2 μm BiCMOS technology, shows a more than five times improvement in speed as compared to the CMOS Manchester carry lookahead (MCLA) circuit. The speed advantage of the BiCMOS dynamic carry lookahead circuit is even greater in a 32- or 64-b adder     

Influence of doping on the electronic structure of (La,Sr)2CuO4

High-statistics (>4 × 10⁸ counts), room-temperature measurements of the electron-positron momentum density of La_2?x Sr _x CuO₄ have been performed for samples with Sr concentrations of x=0.0, 0.1, 0.13, and 0.2. These spectra have been analyzed in conjunction with theoretical calculations of the electron-positron momentum density. The metallic samples show features consistent with the presence of a Fermi surface, but its evolution with increasing Sr concentration does not follow the predictions of band theory. These results may indicate the effects of electron-electron correlation on the electron momentum distribution in the Cu-O plane.     

Ceramic Composites Fabricated by Selective Laser Sintering

Selective laser sintering (SLS) uses a computer controlled laser beam to create objects directly from the CAD data without part-specific tooling. In this paper, the effect of material and processing parameters on the microstructure and mechanical properties of an alumina/aluminum phosphate composite fabricated by SLS is described. The precursor material is a blend of alumina and ammonium phosphate powder. This paper deals primarily with the effect of alumina particle size and material composition on the strength of the composite. A constitutive equation is also proposed to relate the mechanical properties of the composite to its microstructural characteristics.     

Wideband HEMT MMIC low-noise amplifier with temperaturecompensation

A wideband low-noise pseudomorphic HEMT MMIC variable-gain amplifier has been designed and fabricated. The amplifier has a nominal gain of 13 dB across the band 2-20 GHz, with gain flatness better than ±0.4 dB. The noise figure is less than 3 dB across the band 6-16 GHz. An on-chip temperature-sensing diode is used to provide a linear temperature correction which has been used to reduce the gain variation of the amplifier by a factor of 2 across the temperature range -50°C to +95°C     

Performance of asynchronous DS-CDMA system with long and shortspreading codes

The effect of spreading code length on the BER performance of an asynchronous DS-CDMA system is studied by means of Monte Carlo simulation. The probability of the crosscorrelation value between segments of long sequences is also discussed. Results indicate that the system performance with very long codes is ~1 dB worse compared to that of short CDMA codes     

A little less sodium is not without hazard

Surgical thrombectomy is not a rational approach to neonatal renal vein thrombosis since the occlusion mainly involves intrarenal branches rather than the main renal vein, which is even patent in some instances. Conservative management combines supportive therapy for renal failure and systemic hypertension, if needed, and either heparin or thrombolytic agents. Streptokinase has proven difficult to handle in neonates and should not be used. Urokinase has been used in 18 patients but results are difficult to interpret because these cases occurred over an 18-year period. Plasminogen tissue activator, the latest thrombolytic agent developed, has been used in few pediatric patients. An international task force is currently studying whether or not a randomized study is warranted to provide data for standardizing thrombolytic therapy in pediatric renal vein thrombosis.     

D-lactic acidosis: a treatable encephalopathy in pediatric patients

Isolation of Salmonella from the feces of impounded dogs was carried out to make clear the recent microbiological condition of dogs introduced into our facilities. Salmonella was isolated from 10 out of 283 samples (3.5%). Inparticular, during the first week after introduction, Salmonella was isolated from nine out of 74 dogs (12.2%). The isolation rate during the first week after introduction was significantly higher than that for dogs introduced later. No isolates were detected from dogs reared for more than 3 weeks after introduction. This study indicates that impounded dogs had the highest risk of infecting a person with Salmonella during the first week after introduction into our laboratory animal facilities, and that we need to pay attention to this fact when handling them.