The future of U.S. natural gas production,use, and trade

Two computable general equilibrium models, one global and the other providing U.S. regional detail, are applied to analysis of the future of U.S. natural gas. The focus is on uncertainties including the scale and cost of gas resources, the costs of competing technologies, the pattern of greenhouse gas mitigation, and the evolution of global natural gas markets. Results show that the outlook for gas over the next several decades is very favorable. In electric generation, given the unproven and relatively high cost of other low-carbon generation alternatives, gas is likely the preferred alternative to coal. A broad GHG pricing policy would increase gas use in generation but reduce use in other sectors, on balance increasing its role from present levels. The shale gas resource is a major contributor to this optimistic view of the future of gas. Gas can be an effective bridge to a lower emissions future, but investment in the development of still lower CO₂ technologies remains an important priority. International gas resources may well prove to be less costly than those in the U.S., except for the lowest-cost domestic shale resources, and the emergence of an integrated global gas market could result in significant U.S. gas imports.     

圆弧焊接薄壁圆筒残余应力场的分析研究

由于圆弧焊接的薄壁圆筒在高科技工程,如航空机器、压力容器和核工程中的广泛应用,对焊接导致的如焊接变形和残余应力等缺陷的研究就显得非常重要。介绍了一个计算程序,用以分析低碳钢薄壁圆筒在圆弧焊接中的温度分布以及随后将产生的残余应力场。基于数值模拟的参数研究用于分析焊接所产生的残余应力中的关键参数的影响。考虑了低碳钢、焊丝和双椭圆热源模型的基于温度的热机械性能。通过全尺寸焊接试验中的瞬时温度分布和残余应力场证实了有限元模拟方法的精确性。其目的在于提供数据以证实薄壁圆筒现有焊接工艺的有效性,从而将预加应力导致的结构在使用期间失效的可能性降至最低。     

Silver nanoparticles and silver salt (AgNO3) elicits morphogenic and biochemical variations in callus cultures of sugarcane

The research work was arranged to check the role of AgNPs and silver ions on callus cells of sugarcane (Saccharum spp. cv CP‐77,400). AgNPs were synthesized chemically and characterized by UV‐Vis spectra, XRD and SEM. AgNPs and silver ions were applied in various concentrations (0, 20, 40, 60 ppm) to sugarcane calli and the induced stress was characterized by studying various morphological and biochemical parameters. AgNPs and silver ions treatments produced high levels of malondialdehyde, proline, proteins, TP and TF contents. Similarly, CAT, SOD and POX activity was also significant in both treatments. The lower concentration of AgNPs and silver ions (20 ppm) provided maximum intracellular GSH level. This work mainly showed effects of AgNPs and silver ions on sugarcane calli in terms of morphological aberrations and cell membrane damage due to severe oxidative stress and production of enhanced levels of enzymatic and non‐enzymatic antioxidants as self‐defence to tolerate oxidative stress by scavenging reactive oxygen species. These preliminary findings will provide the way to study ecotoxicity mechanism of the metal ions and NPs in medicine industry and in vitro toxicity research. Furthermore, silver ions alone and their chemically synthesised AgNPs can be used for various biomedical applications in future.Inspec keywords: nanoparticles, biomedical materials, X‐ray diffraction, scanning electron microscopy, silver, molecular biophysics, toxicology, enzymes, visible spectra, nanofabrication, ultraviolet spectra, microorganisms, nanotechnology, plant diseases, crops, agricultural safetyOther keywords: silver nanoparticles, silver salt, scanning electron microscopy, total flavonoid contents, callus cultures, sugarcane cultivation, Saccharum spp, UV‐visible spectroscopy, X‐ray diffraction analysis, malondialdehyde, proline, proteins, total phenolic content, catalase, superoxide dismutase, peroxidases activities, scavenging reactive oxygen species, biomedical applications, microbial disease resistance, AgNO₃ , Ag     

Seed germination and biochemical profile of Citrus reticulata (Kinnow) exposed to green synthesised silver nanoparticles

The biosynthesis of silver nanoparticles (AgNPs) is substantial for its applications in different fields. The Moringa oleifera leaves were used as reducing and stabilising agent for the biosynthesis of AgNPs. The synthesised AgNPs were characterised through UV–visible spectroscopy, zeta analyser, scanning electron microscopy (SEM) and energy dispersive Xray (EDX). In this study, effects of the synthesised AgNPs were also evaluated on nucellus tissues germination frequency and biochemical parameters of plant tissues. Nucellus tissues of Citrus reticulata were inoculated on MS medium supplemented with 10, 20, 30 and 40 µg/ml suspension of the synthesised AgNPs. Green synthesised AgNPs enhanced the in vitro germination because of low toxicity and nonfriendly issues. Significant results were obtained for germination parameters i.e. root and shoot length and seedling vigour index in response to 30 µg/ml suspension of green synthesised AgNPs. The 30 µ/ml suspension of AgNPs also enhanced antioxidant activity (41%) and SOD activity (0.36 nM/min/mg FW) while total phenolic content (4.7 µg/mg FW) and total flavonoid content (1.1 µg/mg FW) was significantly high when MS medium was fortified with 40 µg/ml suspension of the synthesised AgNPs. The content of total protein was significant (558 µg/BSA Eq/mg FW) in control plantlets as compared to the other treatments.Inspec keywords: antibacterial activity, ultraviolet spectra, X‐ray chemical analysis, proteins, microorganisms, biochemistry, nanofabrication, silver, nanotechnology, visible spectra, surface plasmon resonance, nanoparticles, suspensions, nanomedicine, scanning electron microscopy, electrokinetic effectsOther keywords: green synthesised silver nanoparticles, superoxide dismutase activity, biochemical profile, UV–visible spectroscopy, Citrus reticulata, green synthesised suspension, EDX detector, zeta potential, scanning electron microscopy, SEM, energy dispersive X‐ray, EDX, total phenolic content, total flavonoid content, size 423.0 nm to 425.0 nm, size 8.0 nm to 28.0 nm     

Analysis of weld-induced residual stresses and distortions in thin-walled cylinders

Circumferential weld specifically in thin-walled structures is a common joint type in the fabrication of structural members in aerospace, aeronautical and pressure vessel industries. This type of weld joint suffers various types of weld-induced residual stress fields (hoop and axial) and deformation patterns (axial shrinkage, radial shrinkage). These imperfections have negative effects on fabrication accuracies and result in low strength welded structures that can lead to premature failures. To precisely capture the distortions and residual stresses, computational methodology based on three-dimensional finite element model for the simulation of gas tungsten arc welding in thin-walled cylinders is presented. Butt-weld geometry with single “V” for a 300 mm outer diameter cylinder of 3 mm thick is used. The complex phenomenon of arc welding is numerically solved by sequentially coupled transient, non-linear thermo-mechanical analysis. The accuracy of both the thermal and structural models is validated through experiments for temperature distribution, residual stresses and distortion. The simulated result shows close correlation with the experimental measurements. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Naeem Ullah Dar received the B.Sc. and M.S. degrees in mechanical engineering from the Univer-sity of Engineering & Technology, Taxila, in 1989 and 2004 respectively. Presently, he is PhD scholar in mechanical engineering at UET, Taxila. His publications are over 25 in different Int. journals and conferences. His research includes manufacturing process (GTAW welding process, HSM process, abrasive waterjet process, incremental forming etc), welding simulations, optimization, and expert system. He spent more than 16 years in different mechanical manufacturing fields. He also received MBA degree in project management and six sigma black belt from SQII in 2005. Ejaz M. Qureshi is currently a graduate student working for his PhD in computational weld mechanics at National University of Sciences and Technology (Pakistan). After receiving his B.S. degree in Mechanical Engineering in 1997, he worked for five years in an industrial manufacturing setup producing hi-tech welded structures. Qureshi has published numerous technical papers in professional refereed journals and conferences of international repute. He has also been an active referee for several conferences and journals. His current research interests include: manufacturing processes simulation, structural integrity of welded structures and computational plasticity of cylinders/pressure vessels. M.M.I. Hammouda received the B.Sc. and M.Sc. degrees in mechanical engineering from Al Azhar University, Cairo, Egypt in 1970 and 1975 respectively. He received his PhD degree in mechanical engineering from Cambridge University, England in 1978. His has more than 35 publications in different International journals and conferences. The research includes mechanical behavior of engineering materials, linear elastic and elastic-plastic fracture mechanics, manufacturing process modeling and simulations. Presently being a foreign faculty professor in mechanical engineering department of UET, Taxila, Pakistan, he spent more than 25 years in academic and teaching. He is a member of the Editorial Board of the International Journal of Fatigue and Fracture of Engineering Materials and Structures. [www.blackwell-science.com].     

Quality Management in Pakistan's Readymade Garments' Industry

Pakistan's readymade garments' industry is a key player in Pakistan's industry in general, and its textile industrial output and exports in particular. In a liberalizing international trade regime, quality will be a critical success factor in the international competitiveness of Pakistan's readymade garments. Research in quality management in Pakistan's readymade garments' industry was undertaken. To gain further information, a postal self-completion questionnaire was mailed to 101 members of the Pakistan Readymade Garments' and Exporters' Association (PRGMEA). The response rate was 32%. It was found that while this industrial segment was in various stages of development, it needs to graduate fast to advanced quality management concepts of Kaizen and total quality management in order to maintain its competitive advantage in an environment that will soon be liberalized fully.     

Effect of microvoid formation on the tensile properties of dual-phase steel

A steel containing 0.32 wt.% C, 0.88 wt.% Mn, 0.99 wt.% Si, 0.9 wt.% Ni, and 0.9 wt.% Cr was intercritically annealed at different temperatures from 775 to 870 °C and quenched in oil to produce dual-phase steel microstructure. Tensile testing of these samples gave a series of strengths and ductilities. The tensile strength increased with the increased annealing temperatures and the martensite percentage increased with a reduction in ductility. Microvoids were formed near the fracture surfaces. The morphology of the microvoids changed with the martensite percentage from decohesion of the martensite particles to the intergranular and transgranular cracks, which defined the ultimate fracture mode of the specimens. The change in the morphology of microvoids may be due to a high percentage of carbon in the steel, which produced stresses in the matrix (ferrite) during phase transformation.     

Limonoids as cancer chemopreventive agents

Nutritional research on the health benefits of substances in plant foods has recently advanced to a new stage. The research frontier has moved from study of classical vitamin deficiency diseases to study of the thousands of phytochemicals that may have important physiological effects. Recent research suggests that citrus fruit consumers may be getting another health benefit from orange juice and other citrus products called limonoids, which appear to possess substantial anticancer activity. Limonoids are highly oxidized triterpenes present in Rutaceae and Maliaceae families. Several citrus limonoids have recently been subjected to anticancer screening utilizing laboratory animals and human breast cancer cells. The experimental results described that citrus limonoids may provide substantial anticancer actions. The compounds have been shown to be free of toxic effects in animal models, so potential exists for the use of limonoids against human cancer in either natural fruits, in citrus fortified with limonoids, or in purified forms of specific limonoids. Although the initial studies are very promising they have been conducted primarily with in vitro cell culture and animal models. Thus, research is needed to determine whether the limonoids may be useful in preventing or treating cancer in humans. Copyright © 2005 Society of Chemical Industry     

An investigation of LPCVD and PECVD of in situ doped polycrystalline silicon for VLSI

In general, high-temperature processes cause thermal stresses and diffusion of dopants, resulting in reduced device yields. It is thus desirable to reduce the number of high-temperature steps and the use of an in situ doping technique eliminates one such step. In this investigation, low-pressure chemical vapour deposition (LPCVD) and plasma-enhanced chemical vapour deposition (PECVD) have been utilised to deposit in situ doped polycrystalline silicon films. The process characteristics and properties such as spreading resistance, grain structure, etch rate using a plasma and dopant concentrations of these films have been investigated and explained using a simple model for dopant activation and grain growth. It is shown that good-quality films suitable for VLSI can be produced.     

16-Mb synchronous DRAM with 125-Mbyte/s data rate

In order to keep up with the growing need for memory bandwidth at low cost, a new synchronous DRAM (SDRAM) architecture is proposed. The SDRAM has programmable latency, burst length, and burst type for wide variety of applications. The experimental 16M SDRAM (2M×8) achieves a 125-Mbyte/s data rate using 0.5-μm twin well CMOS technology