Effect of notches and glass fiber reinforcement on fatigue behavior of polycarbonate

In order to investigate the effect of a notch on the tensile properties of polycarbonate and 30% glass fiber-reinforced polycarbonate, two types of notched specimens were prepared. These notches were a sharp 60° notch and a dull notch with rounded tip 1.5 mm in radius at the base of the 60° notch. The notches decreased the tensile strength of polycarbonate. The sharp notch reduced tensile strength more effectively than the dull notch. In 30% glass fiber-reinforced polycarbonate, even the dull notch decreased the tensile strength considerably. Unnotched polycarbonate was subjected to cyclic tensile loading of 10⁴ cycles at 10 Hz, with varying cyclic stress. It was found that the elongation at break decreased rapidly with increase in cyclic stress. The notches considerably decreased the tensile fatigue strengths of polycarbonate and glass fiber-reinforced polycarbonate in 10⁴ cycles at 10 Hz.     

Characterization of starch based nanocomposites

The goal of this study was to characterize the nanostructure and the properties of starch based nanocomposites with either cellulose nano whiskers (CNW) or layered silicates (LS) (synthetic hectorite) as reinforcements. Modified potato starch was used as matrix with water and sorbitol as plasticizers and with 5 wt.% of either of the reinforcements. Two methods were explored to prepare samples for transmission electron microscopy (TEM) examination; chemical fixation and freeze etching. It was possible to characterize the nanostructure both parallel and perpendicular to the nanocomposite surface by the freeze etching technique. Both nanocomposites showed well-distributed reinforcements in the starch matrix. Dynamic mechanical thermal analysis showed that the storage modulus was significantly improved at elevated temperatures, especially for the layered silicate nanocomposite. Both nanocomposites showed a significant improvement in tensile properties compared to the pure matrix.     

Disconnection detection using earth capacitance measurement in photovoltaic module string

A disconnection detection method using an earth capacitance measurement in photovoltaic (PV) module string was experimentally studied. In the experiments with disconnections between PV modules in the string, the earth capacitance of the string was increased in proportion to the module number, and this feature resulted in that the disconnection position between the modules could be estimated by comparing the earth capacitance value of the failed string with that of the good string. Since the earth capacitance was not affected by the irradiance change, the detection method could be applied anytime to locate the disconnection position in the string without the effect of the irradiance change. Moreover, this method could be applied not only to the string consisting of the crystalline Si modules but also to the string consisting of the amorphous Si modules. Copyright © 2008 John Wiley & Sons, Ltd.     

Transport of carnitine and acetylcarnitine by carnitine/organic cation transporter (OCTN) 2 and OCTN3 into epididymal spermatozoa

Carnitine and acetylcarnitine are important for the acquisition of motility and maturation of spermatozoa in the epididymis. In this study, we examined the involvement of carnitine/organic cation transporter (OCTN) in carnitine and acetylcarnitine transport in epididymal spermatozoa of mice. Uptake of both compounds by epididymal spermatozoa was time-dependent and partially Na(+)-dependent. Kinetic analyses revealed the presence of a high-affinity transport system in the spermatozoa, with K(m) values of 23.6 and 6.57 muM for carnitine and acetylcarnitine respectively in the presence of Na(+). Expression of OCTN2 and OCTN3 in epididymal spermatozoa was confirmed by immunofluorescence analysis. The involvement of these two transporters in carnitine and acetylcarnitine transport was supported by a selective inhibition study. We conclude that both Na(+)-dependent and -independent carnitine transporters, OCTN2 and OCTN3, mediate the supply of carnitine and acetylcarnitine to epididymal spermatozoa in mice.     

基于问题解决的建构体育层级教学理论与实践

建构主义者提出了诸多创新教学思路和设想,而基于问题解决来促进知识的建构,则是其中的一条核心思路。按照问题及其解决方式的不同,基于问题解决体育知识、技能的建构有3种基本途径,即巩固／熟练、深化／整合、建构,技能。针对建构体育教学的问题解决,层级教学这一思路的实践性以及学生主动参与,自我建构制订锻炼方案和计划,并进行自我检测与评价其锻炼效果,提出了一些观点和建议。     

几株采油菌驱油性能的物模试验

对B1-4、Ⅳ、TB褐、长Ⅱ、DY一1、LJ1、Z-2六株菌开展了单一菌种和复配菌种岩心驱替模拟实验.首先,开展了单菌种在不同驱油阶段的岩心驱油模拟实验.在整个驱替阶段无论发酵原液或稀释液均可以提高原油采收率,因此,从经济方面考虑微生物驱宜采用培养基稀释的茵液.其次,通过复配菌种模拟实验,确定了微生物和弱凝胶联合作用时,不同段塞微生物的选择和配比.通过开展岩心模拟实验,为今后开展微生物驱油和弱微联作提供可借鉴的有利信息,为华北油田微生物采油的发展提供有力的支持.