A solution to the hub center problem via a single-relocation algorithm with tabu search

Network designers for many transportation or telecommunication applications need to minimize the maximum (weighted) interaction time or distance in the networks, i.e., to solve the p-hub center problems. This study addresses the p-hub center problem. A single-relocation heuristic is proposed as a means of generating location-allocation strategies in a reasonable amount of time, and tabu search is superimposed on the underlying algorithm, so as to decrease the possibility of being trapped by local optima. Two single-allocation schemes are adapted from the literature, and a further one is developed specifically for the minimax objective function, for use in the evaluation phase of the algorithm. A greedy local search is employed to improve the resulting allocations. A number of strategies for choosing the initial hub locations are discussed and initial strategy - allocation scheme combinations are compared in terms of solution quality and pragmatic efficiency.     

A novel two‐part interconnector for solid oxide fuel cells

A two‐part interconnector is developed for solid oxide fuel cell stacks to reduce cost and to improve sealing. The novel interconnector involves a metallic core for current collection and gas distribution and a ceramic support to house the metallic core and to separate two short stacks. The new interconnector reduces usage of expensive metallic alloys and substantially reduce mismatch between stack components due to higher expansion coefficient of metals. The new interconnectors also improve sealing with glass–ceramics eliminating chromium evaporation which is a major reason for sealing failure in fully metallic interconnectors. A proof of concept short stack is manufactured and tested in this study. A comparable performance with a convectional interconnector is obtained with new interconnector, while substantially improving the sealing quality. Copyright © 2014 John Wiley & Sons, Ltd.     

超声波在纺织工业中的应用

超声波工艺使用极高强度和频率的声波(通常高出人的听力范围--大于20kHz或2万cycles/s)对材料进行改性.     

The effects of diets containing different levels of common vetch (Vicia sativa) seed on fattening performance,carcass and meat quality characteristics of Awassi male lambs

The experiment was carried out to evaluate the effect of common vetch seed (CVS), used at various levels (0, 15 and 25%), as a protein source in diets replacing different proportion of barley, wheat bran and soybean meal on fattening performance, carcass and meat quality characteristics of Awassi male lambs at approximately 8 months of age. The lambs were divided into three treatment groups, T1 (control, fed a diet without CVS; n = 12), T2 (15% CVS; n = 12) and T3 (25% CVS; n = 12), at the beginning of the fattening period. The T2 and T3 lambs were fed with a concentrate including 15 and 25% of ground CVS. The main protein source was soybean meal in T1 diet treatment, partially replaced by vetch in T2 and T3 diet treatments. All groups were fed a diet consisting of concentrate mixture offered ad libitum, and 300 g of grass hay per lamb per day during the 60 day fattening period. Daily feed intake, daily weight gain and feed conversion efficiency (concentrate and hay consumption for 1 kg of live weight gain) were 1.716 kg, 0.26 kg and 6.60 for T1, 1.756 kg, 0.28 kg and 6.27 for T2 and 1.806 kg, 0.29 kg and 6.23 for T3, respectively. Growth, carcass and meat quality traits were almost the same across the groups. In conclusion, CVS supplementation to diets of Awassi lambs at a 0, 15 and 25% rates showed no statistical differences in fattening performance, wholesale cuts of carcasses, meat color parameters (L* = lightness, a* = redness, b* = yellowness, H = huge angle and C = chroma) and pH values, but there were numerical differences (improvement) in feed conversion efficiency. Copyright © 2005 Society of Chemical Industry     

Understanding preservice teachers' technology use through TPACK framework

This study discusses preservice teachers' achievement barriers to technology integration, using principles of technological pedagogical content knowledge (TPACK) as an evaluative framework. Technology‐capable participants each freely chose a content area to comprise project. Data analysis based on interactions among core components of TPACK revealed that participants struggled with developing new knowledge. Lack of pedagogical experience limited development of appropriate technology integration approaches. Creating new knowledge bases based on different teaching components can be difficult for preservice teachers because it requires a deep understanding of core knowledge and interpretation of the teaching context and its dynamics. Developing pedagogical content knowledge (PCK) is an important factor in overall technology integration; teachers must make it a priority to acquire PCK before integrating technology. In preservice teacher education, PCK development must be supported with actual teaching experience. We believe that the results of the study may provide valuable insight with respect to proper focus on technology integration and recognizing limitations and challenges within TPACK principles to both those who teach technology integration and those who design TPACK‐based activities.