Environmental testing of high strength molding compounds

Tensile and short beam shear tests were performed on five high strength vinyl ester molding compounds after immersion in water at various temperatures. These tests were conducted in order to characterize the degradation of these properties with environmental exposure and to isolate problem areas which contribute to the degradation. Reductions of up to 70 percent were found for both tensile and short beam shear strength, when tested at high temperatures. This loss of properties is primarily a result of degradation of the glass/resin interface and is essentially irreversible.     

Flash pyrolysis of coals: behaviour of three coals in a 20 kg h−1 fluidized-bed pyrolyser

Flash pyrolysis of Loy Yang brown coal, and Liddell and Millmerran bituminous coals has been studied using a fluidized-bed reactor with a nominal throughput of 20 kg h^?1. The apparatus and its performance are described. The yields of tar and hydrocarbon gases are reported for each coal in relation to pyrolysis temperature, as also are analytical data on the pyrolysis products. The peak tar yields for the dry, ash-free Loy Yang and Millmerran coals were respectively 23% wt/wt (at ≈ 580 °C) and 35% wt/wt (at $\text{\$}\text{?}$600 °C). The tar yield from Liddell coal was 31% wt/wt at ≈ 580 °C. Hydro-carbon gases were produced in notable quantities during flash pyrolysis; e.g. Millmerran coal at 810 °C gave 6% wt/wt (daf) methane, 0.9% wt/wt ethane, 6% wt/wt ethylene, and 2.5% wt/wt propylene. The atomic $\text{H}\text{C}$ ratios and the absolute levels of hydrogen in product tars and chars decreased steadily with increasing pyrolysis temperature.     

Water quality of Scottish rivers: spatial and temporal trends

The Harmonised Monitoring Scheme (HMS) was initiated in 1974 and represents the best-organised source of temporal and spatial data describing water quality for the major mainland rivers of Scotland, England and Wales. This paper presents the first detailed analysis of HMS data for Scotland, and identifies temporal changes in water quality from 1974 to 1995. From a concomitant analysis of catchment land cover characteristics, water quality indices have been linked with potential 'drivers' of change, influencing both point and diffuse sources. Nitrate concentrations between rivers are highly correlated with the amount of arable land, and relationships exist between grassland cover, orthphosphate-P and suspended solids concentrations. Similarly, urban catchments are highly correlated with ammonium-N, orthophosphate-P and suspended solids. Spatial and temporal trends in water quality for the rivers of Scotland are discussed.     

Meat quality in pigs subjected to minimal preslaughter stress

The experiment compared meat quality in carcasses from pigs subjected to the absolute minimum of stress preslaughter with that from carcasses of pigs subjected to simulated commercial handling. A total of 120 pigs (85 kg) were used. They were a commercial hybrid and were processed in six equal batches. The minimal stress group were slaughtered with as little stress as possible. The simulated commercial handling group were mixed and transported for 2hr (80 km) and lairaged for 30 min. Simulated commercial handling increased plasma cortisol, plasma lactate, CPK and beta-endorphin. Muscle temperature measured in the m. longissimus dorsi (LD) at 45 min increased as did the ultimate pH in the m. adductor (AD). Overall eating quality was not affected. There were batch affects on most variables. Males were leaner and produced meat that had greater abnormal fat odour, darker cooked colour, poorer pork flavour, lower overall acceptability and was tougher.     

A 16 Gb/s adaptive bandwidth on-chip bus based on hybrid current/voltage mode signaling

This paper describes an adaptive bandwidth bus (ABB) architecture based on hybrid current/voltage mode repeaters for long global RC interconnect static busses that achieves high-data rates while minimizing the static power dissipation associated with current-mode signaling. Attaining a maximum aggregate bandwidth of 16 Gb/s (i.e., 1 Gb/s per line) across lossy on-chip interconnects spanning 1.75 cm in length, the bus core fabricated in 0.35 /spl mu/m CMOS technology dissipates approximately 93 mW with a supply of 2.5 V and signal activity of 0.5, equivalent to 5.71 pJ/bit. Experimental results using a 16-bit reference bus design that can be externally programmed to operate in voltage, current or adaptive modes indicate a 50% reduction in power dissipation over current-mode (CM) sensing, and an improvement in interconnection delay and signaling bandwidth of 35%-70% and 66% over voltage-mode (VM) sensing, respectively.     

Colloidal Processing of Zirconium Diboride Ultra‐High Temperature Ceramics

Colloidal processing of the Ultra‐High Temperature Ceramic (UHTC) zirconium diboride (ZrB₂) to develop near?net‐shaping techniques has been investigated. The use of the colloidal processing technique produces higher particle packing that ultimately enables achieving greater densification at lower temperatures and pressures, even pressureless sintering. ZrB₂ suspension formulations have been optimized in terms of rheological behavior. Suspensions were shaped into green bodies (63% relative density) using slip casting. The densification was carried out at 1900°C, 2000°C, and 2100°C, using both hot pressing at 40 MPa and pressureless sintering. The colloidally processed materials were compared with materials prepared by a conventional dry processing route (cold pressed at 50 MPa) and subjected to the same densification procedures. Sintered densities for samples produced by the colloidal route are higher than produced by the dry route (up to 99.5% relative density by hot pressing), even when pressureless sintering is performed (more than 90% relative density). The promising results are considered as a starting point for the fabrication of complex‐shaped components that can be densified at lower sintering temperatures without pressure.     

Problems in using a comb sample as a stress-free reference for the determination of welding residual stress by diffraction

Precise measurement of a stress-free reference lattice parameter is vital in the determination of residual stress by diffraction techniques using θ/2θ-based analyses. For the evaluation of the residual strain profile in fusion-welded material, it is particularly important to correct the measured strain point-by-point by a stress-free reference for each spatial location across the weld. This is to take into account the compositional and microstructural variation across the weld caused by the thermal cycle of welding, as local changes in solute content of the parent alloy cause changes in the stress-free lattice parameter.Although ideally such measurements should be obtained from small cubes machined from the weld, the use of a comb sample has previously been proposed as a macro-stress-free reference, with the assumption that each finger of the comb is of insufficient dimension to hold a macro-stress field. This paper presents an approach towards analysis of the stress-free reference values using a comb sample extracted from a variable polarity plasma arc (VPPA) welded plate. It is shown that there is inter-granular stress and retained macro-stress within the comb teeth, and an experimental approach to deal with the problem is proposed.     

Receive antenna selection for MIMO systems over correlated fading channels

In this letter, we propose a novel receive antenna selection algorithm based on cross entropy optimization to maximize the capacity over spatially correlated channels in multiple-input multiple-output (MIMO) wireless systems. The performance of the proposed algorithm is investigated and compared with the existing schemes. Simulation results show that our low complexity algorithm can achieve near-optimal results that converge to within 99% of the optimal results obtained by exhaustive search. In addition, the proposed algorithm achieves near-optimal results irrespective of the mutual relationship between the number of transmit and receive antennas, the statistical properties of the channel and the operating signal-to-noise ratio.