Engineering

Modern development of power sources and our understanding of the forces governing metal transfer in welding processes is likely to continue to improve. The amount of possible combinations of pulsing parameters and current waveforms indicated that there is potentially an optimum parameter combination for every possible welding application. Proper selection of pulsing parameters has been proven to improve mechanical properties of the deposited weld metal. Most disadvantages of current welding processes can be eliminated by effective parameterization of the current waveform parameters. The prices of many advanced power sources have dropped significantly since their conception. The development of these waveform technologies is opening doors for experts in weld parameterization while making the actual operation of welding much easier, cheaper, and more effective. Welding was previously thought to have been a profession that was very limited in its ability to become automated, but these developments in our understanding of variables involved with metal transfer indicate the possibility of completely automating and/or manipulating welding processes.

Cognitive rehabilitation has the capacity to empower persons with brain-injuries and help them achieve heightened functional, personal, and social interactions within their environments. Interventions aimed at compensation for deficits and adaptation to cognitive disability can be aided through the use of assistive technology devices (ATD's). ATDs allow for their users to experience greater levels of independence, as well as social and vocational participation, which leads to a higher quality of life. The ISAAC system is a small, individualized, wearable cognitive prosthetic assistive technology system. Being fully individualized and very easy to use makes this system adaptable to, and appropriate for, patients with a wide variety of cognitive disabilities ranging from individuals with developmental disabilities to high functioning survivors of brain injury. The current article will discuss two cases that illustrate the effectiveness of the ISAAC system in assisting patients with generalization of rehabilitation to their home environments. Both patients incurred significant cognitive impairment, for which they were able to successfully compensate with the assistance of their ISAAC systems. These two case studies are typical examples of the functional independence that can be achieved through the use of the ISAAC system. When patients are properly selected for use of this system, appropriate content is authored, and sufficient training on the system is provided, the ISAAC system can prove very effective at improving patients' functional independence.

Cognitive rehabilitation has the capacity to empower persons with brain-injuries and help them achieve heightened functional, personal, and social interactions within their environments. Interventions aimed at compensation for deficits and adaptation to cognitive disability can be aided through the use of assistive technology devices (ATD's). ATDs allow for their users to experience greater levels of independence, as well as social and vocational participation, which leads to a higher quality of life. The ISAAC system is a small, individualized, wearable cognitive prosthetic assistive technology system. Being fully individualized and very easy to use makes this system adaptable to, and appropriate for, patients with a wide variety of cognitive disabilities ranging from individuals with developmental disabilities to high functioning survivors of brain injury. The current article will discuss two cases that illustrate the effectiveness of the ISAAC system in assisting patients wit...

Weight percentage gain (WPG), hydrophobicity and dimensional stability of Pinus radiata wood were examined after being heat-treated in raw linseed oil and left to cool in oil for 0 to 12 hours. The oil uptake percentage (OUP) in treated wood was determined after organic solvent extraction and compared with the weight percentage gain which was determined by difference in sample ovendry weight before and after heat treatment. The effect of solvent extraction on hydrophobicity of treated wood was also examined. The results show that WPG in wood increased significantly with increasing cooling times which in turn decreased the water absorption. However, comparatively, dimensional stability in treated wood was less affected by increased WPG as a result of the prolonged cooling time. The oil uptake percentages determined after organic solvent extraction were greater than the weight percentage gain determined by weighing after heat-treatment, indicating mass loss with the heat-treatment. The moisture excluding efficiency (MEE) of the heat-treated wood decreased with solvent extraction showing the influence of oil uptake on hydrophobicity of wood.

Pinus radiata wood specimens were heat-treated at 160–210°C in linseed oil and the effects of treatment on chemical composition, color, dimensional stability, and fungal resistance were examined. The degradation of hemicelluloses was the most remarkable feature, which is the principal reason for alterations in wood properties. Removal or migration of extractives, oil uptake and the accumulation of oil on the wood surface were observed. The color of heat-treated wood became more uniform and darker, and its dimensional stability (i.e., anti-swelling efficiency) and fungal resistance were improved by up to 60% and 36%, respectively. The viscosity of the oil after treatment was elevated with the treatment temperature and was higher in comparison to heated oil without wood present.

Radiata pine is a major plantation grown wood in the Southern hemisphere, but has inferior dimensional stability and low durability compared to other commercial species and the improvement of these features is the focus of this thesis. Specifically this thesis examines the dimensional stability, durability and mechanical properties of radiata pine after heat-treatment (160-210°C) in linseed oil. Changes in colour, micro-structure and chemistry with heat-treatment were studied. To optimise the treatment results, oil heat-treatment of wood was also carried out after thermo-mechanical compression of wood and the effect of the prior thermo-mechanical compression on stability, durability and mechanical properties were examined. The oil heat-treated wood turned uniformly darker in colour. The hydrophobicity (Water Repellence Efficiency-WRE up to 30%), dimensional stability (Ant-Swelling Efficiency-ASE up to 60%) and fungal resistance (up to 36%) were improved with the extent of the changes mainly depending on treatment temperature. However, the mechanical properties of oil heat-treated wood were reduced compared to the untreated control group. Accelerated UV weathering tests have shown that the oil heat-treated wood retained its colour and dimensional stability better than the untreated wood (the control group). The cell wall of treated wood was intact and no distinct structural changes were observed even at the most severe treatment (210°C for 6 hrs).The treatment resulted in changes to the wood chemical constituents, mainly the degradation of hemicelluloses which is believed to be principal reason for alterations in wood properties. Sailer M, Rapp AO, Leithoff H (2000a) Improved resistance of Scots pine and spruce by application of an oil-heat treatment. The International Research Group on Wood Preservation IRG/WP 00-40162.

Pinus radiata specimens with moisture content of 8-11% and dimensions of 90 × 35 × 200 mm 3 were heattreated in an oil bath of commercial grade raw linseed oil. The effect of oil aging was investigated under treatment condition of 180°C and 3 hours by using oil that had been preheated for 0, 3, 9, 15, 21, and 27 hours, respectively, before the wood treatment. After treatment using oils of varying ages, wood colour change was examined using a Minolta spectrophotometer through CIE 1976 (L * a * b) system. Water repellent efficiency and anti swelling efficiency in high humidity conditions were measured to determine the stability of the treated wood. The results show that stability of the treated wood was improved significantly compared to the matched untreated wood but the treated wood tended to be darker. Oil viscosity increased with the heating age resulting in slight decrease in weight percentage gain. Water repellent efficiency was decreased with an increase in heating age of oil. However no significant difference in total colour variation and wood stability (anti swelling efficiency) was observed between specimens treated with oils of varying heating age. Abbreviations ASE Anti-swelling Efficiency CIE Commission internationale de l'éclairage

Pinus radiata specimens with moisture content of 8-11% and dimensions of 90 × 35 × 200 mm 3 were heattreated in an oil bath of commercial grade raw linseed oil. The effect of oil aging was investigated under treatment condition of 180°C and 3 hours by using oil that had been preheated for 0, 3, 9, 15, 21, and 27 hours, respectively, before the wood treatment. After treatment using oils of varying ages, wood colour change was examined using a Minolta spectrophotometer through CIE 1976 (L * a * b) system. Water repellent efficiency and anti swelling efficiency in high humidity conditions were measured to determine the stability of the treated wood. The results show that stability of the treated wood was improved significantly compared to the matched untreated wood but the treated wood tended to be darker. Oil viscosity increased with the heating age resulting in slight decrease in weight percentage gain. Water repellent efficiency was decreased with an increase in heating age of oil. However no significant difference in total colour variation and wood stability (anti swelling efficiency) was observed between specimens treated with oils of varying heating age. Abbreviations ASE Anti-swelling Efficiency CIE Commission internationale de l'éclairage

The International Standard of Phytosanitary Measures No. 15 (ISPM-15) requires signatory countries of the International Plant Protection Convention to use approved treatment methods on wood packaging materials used in international trade to significantly reduce the risk of spreading alien species. One of the approved methods utilizes dielectric heating (DH) to raise the temperature in the wood to 60°C through the profile of the workload for 1 minute to eradicate pests. To improve the uniform distribution of heat within a wood workload using radio frequency, a form of DH, we tested the use of a wool blanket as a thermal insulation material for wood pallet components. Three species commonly used in the pallet industry—yellow poplar (Liriodendron tulipifera L.), northern red oak (Quercus rubra L.), and eastern white pine (Pinus strobus L.)—of low moisture content were used to generate matched sets of stringer samples. Internal wood temperatures were monitored continuously during treatm...

An instrumeni for prompt gamma-ray activation analysis is now in operation at the" NIST Cold Neutron Research Facility (CNRF). The cold neutron beam is relatively free of contamination by fast neutrons and reactor gamma rays, and the neutron fluence rate is 1.5 -10 s cm -2. s -1 (thermal equivalent). As a result of a compact target-detector geometry the sensitivity is better by a factor of as much as seven than that obtained with an existing thermal instrument, and hydrogen background is a factor of 50 lower. We have applied this instrument to multielement analvsis of the AUende meteorite and other materials.

The estimation of the number of inert gas atoms contained at equilibrium in microscale bubbles in a solid usually relies on a well-known formula equilibrating the internal pressure of He to the surface energy of the bubble. This approach evidences a strong variation with temperature of He content for a given bubble. At the opposite, at the Angstrom scale, ab initio calculations for He contained in vacancy assemblies neglect temperature effects. In this work, empirical potential molecular dynamics simulations are used to study, in the case of helium inserted in cubic silicon carbide, the variation of the He content of subnanoscale cavities with temperature. To do so free energy for He atoms inserted in cavities made of a few vacancies (up to 29) are calculated. One then evidences the existence of a sub-surface segregation in interstitial sites close to the surface of the cavity. The variation of the He content with temperature is observed to be negligible at the nanoscale, thus validating the ab initio approach.

Wet storage is synonymous with ensilage, a simple biotechnology that has been used to preserve forage for livestock feed for millennia. In this natural process, organic acids are produced by anaerobic microbial degradation of a small fraction of the biomass, and these acids reduce the pH to levels that minimize further microbial activity and can preserve the biomass for years as long as anaerobic conditions are maintained. These organic acids also result in mild pretreatment with potential to enhance downstream conversion processes, making this an effective storage strategy. However, the degree and significance of this natural pretreatment capability of ensiled storage on downstream processes has not previously been quantified across a range of storage conditions. In this study, the degree of pretreatment was investigated by measuring the reactivity of corn stover fiber to cellulolytic enzymes. Although the results indicated significant improvement in hydrolytic outcomes after wet storage, by a factor of up to 2.4, saccharification of cellulose to sugar monomers was still limited. The results also show that dominance of lactic acid in the ensilage process is key to wet storage (pretreatment) effectiveness as in the livestock feed industry. Lactic acid pKa value is lower than the pKa of other silage acids and lower than typical silage pH. This gives lactic acid the advantage of being in the more dissociated form, with more protons available to facilitate pretreatment hydrolysis. However, unlike the livestock feed industry, where quality feedstock is attainable within very narrow storage moisture range, for biofuel purposes, a wider range of 35-65% is appropriate in achieving a similar quality outcome. This is true both for the immediate fiber response to enzymes and with subsequent pretreatment. This wider moisture range implies more flexibility in harvest schedule without sacrificing feedstock quality, thus alleviating concerns over feedstock quality that biomass suppliers or biorefineries may have.

Organic acids produced during ensiled wet storage are beneficial during the storage process, both for biomass preservation, and to aid in mild in-situ pretreatment. However, there is concern these acids could later have negative impacts on downstream processes, especially microbial fermentation. Organic acids can inhibit microbial metabolism or growth, which in turn could affect biofuel productivity or yield. This study investigated the interaction of organic acids produced during ensiled storage with subsequent pretreatment of the resulting corn stover silage, as well as the potential for interference with downstream ethanol fermentation. Interaction with pretreatment was observed by measuring xylan and glucan removal and the formation of inhibitors. The results indicated that organic acids generally do not impede downstream processes and in fact can be beneficial. The levels of organic acids produced during 220 days of storage jar tests at 23 • C or 37 • C, and their transformation during pretreatment, remained below inhibitory levels. Concentrations of individual acids did not exceed 6 g per liter of the pretreated volume, and < 5% on a dry matter basis. Whereas, unensiled corn stover required 15 min of 190 • C pretreatment to optimize sugar release, ensiled corn stover could be treated equally effectively at a lower pretreatment duration of 10 min. Furthermore, the different organic acid profiles that accumulate at various storage moisture levels (35-65%) do not differ significantly in their impact on downstream ethanol fermentation. These results indicate biorefineries using ensiled corn stover feedstock at 35-65% moisture levels can expect as good or better biofuel yields as with unensiled stover, while reducing pretreatment costs.

This paper provides a general overview of U.S. housing policy, with emphasis on state and local programs. Despite the focus on local programs we also discuss the broader national policy environment. This broader context is necessary because national policies play a crucial role in shaping the country's housing markets. We briefly trace out some of the key features of the housing market, highlighting tenure distributions, housing conditions and costs. Particular emphasis is given to the role of increasing housing costs and the housing opportunities of the poor. The paper also describes: (1) the nation's housing finance and tax systems, focusing on the different ways the government uses the tax code to subsidize homeowners and renters; and (2) state and local government programs, often implemented in the close collaboration of nonprofit organizations. A final section provides a brief overview of the strengths and weaknesses of U.S. housing policy and the evolving role of sub-national governments.

In this paper, a novel MoM-based procedure is developed for efficient treatment of scattering problems over a wide frequency band, including very low frequencies where many of the conventional algorithms often fail. The proposed approach, based on closed-form expressions for the evaluation of the fields radiated by rooftop basis functions, is demonstrated to be universally applicable to conducting and dielectric objects without having to address the singularity issues associated with the conventional MoM approach. Furthermore, an equivalent rooftop type of basis function is introduced for handling curved surfaces. Illustrative examples demostrating the reliability and the efficiency of the described procedures are included.

In this paper, we present a novel procedure for an efficient and accurate electromagnetic simulation of microstrip circuits and printed antennas etched in layered media. The proposed approach, based on a new algorithm referred to herein as the equivalent medium approach (EMA), is applied for a rapid design of the preliminary desired circuit prototype. The illustrated technique yields reliable results and reduces the computational time in comparison with the conventional method of moments (MoM). Some examples that demonstrate the accuracy and the efficiency of the described procedure are included.

In this paper, a numerical dosimetric analysis has been carried out through CST Microwave Studio® 2009. The homogeneity of the SAR distribution and the coupling of EM fields within the liquid in the presence of a glass slide as support for living cells, has been investigated as a function of the incident field polarization.

Tower cranes are the centerpiece of production on today's typical building construction sites. Tower cranes hoist and transport a variety of loads near and above people, working under crowded conditions, occasionally with overlapping work zones, and often under time, budget, and labor constraints. This work regime further increases the safety risk on sites that are inherently hazardous workplaces. This paper presents the results of a study that identified the major factors affecting safety in tower-crane environments and evaluated the degree to which each factor influences ongoing safety on site. Use of statistical data on accidents was ruled out as a source of information due to the countless number of incidents that go unreported, the common inability of statistics to provide root causes, and the questionability of statistics as a predictor of accidents. The research methodology was therefore based on comprehensive questioning of an expert team that included the safety managers and equipment managers of leading construction companies. With the limited resources available for safety improvement and accident prevention, greater attention must be paid by all parties involved to those factors evaluated as highly affecting site safety due to tower-crane work.

We have collected peer-assessment (PA) and self-assessment (SA) data from two resident sections of a software construction course. This course is a core requirement in a graduate program in software engineering at a large research university. While the body of research gives strong evidence that there are many benefits to implementing peer and self-assessment, concerns remain. Two concerns are that students will inflate their evaluation of themselves and that they may collude to give each other high ratings ("cronyism"). These concerns motivated this exploratory study of student bias in peer and selfassessment in a graduate engineering program. Our results confirm previous research that students tend to rate themselves higher than their peers, but we found no evidence of cronyism.