Negation as failure for disjunctive logic programming

We generalize the Negation-as-Failure procedure for disjunctive logic programming. Then we compare our method with related methods in the literature. We also propose a new completion theory for disjunctive logic programs which allows some program clauses to have inclusive meaning and the others exclusive meaning.     

Adaptive space-time reduced-length MMSE receiver for interferencesuppression in DS/CDMA

The authors present an adaptive space-time reduced-length minimum mean-squared error (MMSE) receiver to suppress co-channel interference in the near-far environment for an asynchronous direct-sequence code-division multiple-access (DS/CDMA) system. Simulation results show that better bit-error rate and faster and more stable convergence are achieved over the existing full- and reduced-length MMSE receivers     

Ovarian aging and hormone replacement therapy. Hormonal levels, symptoms, and attitudes of African-American and white women

The purpose of the study was to identify psychiatric symptoms, neurological impairments, and situational factors associated with the emergence of violence and with its persistence. Psychiatric symptoms were assessed in newly admitted physically assaultive psychiatric patients and nonviolent controls. Patients were than evaluated for 4 weeks to determine the persistence or resolution of these physical assaults. Patients who showed marked resolution of assaults were classified as transiently violent (n = 41), and those who remained assaultive throughout were categorized as persistently violent (n = 34). At the end of 4 weeks, all patients received a comprehensive psychiatric and neurological assessment. Physical assaults were associated initially with prominent positive psychotic symptoms. Both transiently and persistently violent patients were more psychotic than the nonviolent controls; however transiently violent patients showed better resolution of these symptoms over the 4 weeks. They also evidenced less frontal lobe impairment on the neurological examination than the persistently violent patients. The two violent groups differed in their susceptibility to environmental influences: the surrounding ward agitation fostered physical assaults in transiently but not in persistently violent patients. This differentiation between transiently and persistently violent patients has major implications for the comprehensive treatment of violent behavior.     

Development of low loss organic-micromachined interconnects on silicon at microwave frequencies

We present the design and development of an ultra-violet (UV) LIGA (a German acronym for electroplating, lithography and molding) micromachining process on silicon substrates at microwave/millimeter wave frequencies. The process employs an ultra-thick negative photoresist SU-8 that can be spin-coated and processed using conventional lithography techniques. Using this process, we have developed micromachined coplanar waveguide (CPW) interconnects on Si substrates. The conductor-backed micromachined CPW on Si (7.2 /spl Omega/-cm) achieves a measured attenuation of 0.18 dB/cm at 20 GHz.     

A 2.2 W, 80 MHz superscalar RISC microprocessor

A 28 mW/MHz at 80 MHz structured-custom RISC microprocessor design is described. This 32-b implementation of the PowerPC architecture is fabricated in a 3.3 V, 0.5 μm, 4-level metal CMOS technology, resulting in 1.6 million transistors in a 7.4 mm by 11.5 mm chip size. Dual 8-kilobyte instruction and data caches coupled to a high performance 32/64-b system bus and separate execution units (float, integer, loadstore, and system units) result in peak instruction rates of three instructions per clock cycle. Low-power design techniques are used throughout the entire design, including dynamically powered down execution units. Typical power dissipation is kept under 2.2 W at 80 MHz. Three distinct levels of software-programmable, static, low-power operation-for system power management are offered, resulting in standby power dissipation from 2 mW to 350 mW. CPU to bus clock ratios of 1×, 2×, 3×, and 4× are implemented to allow control of system power while maintaining processor performance. As a result, workstation level performance is packed into a low-power, low-cost design ideal for notebooks and desktop computers     

A study of solid circulation rate in a circulating fluidized bed

An experimental investigation under cold condition was made to study the effects of some operating/design parameters and non-mechanical L valve configuration on the solid circulation rate in a 4.5 m tall, 0.15 m diameter circulating fluidized bed with riser flow rate varying from 1400 litres/min to 2000 litres/min and bed inventory from 15 kg to 25 kg of sand of average sizes 200 μm, 400 μm and 500 μm. Solid circulation rate was estimated by measuring velocity of sand particle travelling through a vertical Perspex tube section at the bottom of the return leg. It was found to be in the range of 2.8 to 12.3kg/m²s, 0.07 to 9.1kg/m²s and 0.12 to 2.23kg/m²s for sand sizes of 200 μm, 400 μm and 500 μm, respectively for a horizontal L valve. Two mathematical correlations have been developed from the experimental results to predict solid circulation rate as a function of riser flow rate, aeration flow rate, total bed inventory and particle size used.     

Effect of surface-modifying macromolecules and solvent evaporation time on the performance of polyethersulfone membranes for the separation of chloroform/water mixtures by pervaporation

Polyethersulfone (PES) membranes using different evaporation periods were fabricated by the phase-inversion method. Pervaporation experiments were conducted for chloroform/water mixtures to determine the selectivity of the PES membranes. It was found that chloroform could be concentrated in the permeate from chloroform/water binary feed mixtures by PES membranes prepared using longer evaporation periods, and that the selectivity of PES membranes in pervaporation could be reversed by shorter evaporation periods. This study also showed that by adding surface-modifying macromolecules (SMM) up to 1 wt % into the casting solution, chloroform enrichment in the permeate could be increased by 50%. Chloroform enrichment increased with increasing SMM concentration until an optimal value, after which the enrichment decreased. © 1994 John Wiley & Sons, Inc.     

Continuous hydrogen evolution from cyclohexanes over platinum catalysts supported on activated carbon fibers

The continuous production of hydrogen from cyclohexanes is achieved effectively using Pt/ACF (ACF = activated carbon fiber) catalysts in a fixed-bed flow reactor. The Pt catalysts are more effective than a Pd/ACF catalyst for the reaction. Besides cyclohexane, methylcyclohexane, 1,4-dimethylcyclohexane, and p-menthane can also be employed as hydrogen source in the reaction system.     

Coating of carbon-fiber surface by silicon carbide via sol-gel mixtures of tetraethyl orthosilicate and phenolic resin

The preparation of a SiC coating on a carbon fiber surface using a sol-gel mixture of tetraethyl orthosilicat (TEOS) and phenolic resin was studied. FTIR and SEM investigations indicated that the SiC coating can be formed by carbothermal reduction of the sol-gel mixture at 1420°C for 15–20 min in an argon atmosphere. TGA of the coated fiber was also performed, showing that the SiC coating improves the thermooxidative stability of the carbon fiber. With the thickness of the obtained coating of 0.47 μm using a C/Si ratio of 4, this treatment does not affect the carbon fiber strength.