Electric Current-Induced Stresses at the Crack Tip in Conductors

The electromagnetic and thermal effects on the stress distribution around the crack tip in conducting materials due to electric current are investigated. Emphases are placed on quantifying the crack growth behavior affected by the interplay between these effects. A two-dimensional finite element analysis is conducted to examine the coupled problems. The results show that the compressive stress state around the crack tip plays a decisive role in preventing the crack from further growth. The resulting normal stress in front of the crack tip caused by the Joule heat generation tends to suppress the crack growth, while the stress induced by the electromagnetic forces provides a tensile normal stress with smaller magnitude in the vicinity of the crack tip, hence promotes the crack growth. Favorable agreements between numerical analysis results and existing experimental results are achieved. By utilizing these phenomena, the electric current may be used to actively control the damage propagation, hence catastrophic failure can be prevented. This revised version was published online in July 2006 with corrections to the Cover Date.     

New frequency-domain technique for joint measurement of nonlineartransition shift and partial erasure

Nonlinear transition shift (NLTS) and partial erasure have been measured independently by traditional time- or frequency-domain techniques without considering the interference between the two. In some cases, such interference can severely distort the measurement results. To solve this problem, a new frequency-domain technique is proposed that measures NLTS and partial erasure jointly. At each given density, three specially constructed periodic data patterns are written and certain harmonics of the readback signals are measured and used to calculate the amount of NLTS and partial erasure simultaneously. The method is simple and easy to implement with a spectrum analyzer     

An investigation into vibration in switched reluctance motors

Two disadvantages of the switched reluctance motor (SRM) are its torque ripple and acoustic noise. Previous work on vibration modes and resonant frequencies of the laminations of an 8-6 SRM is extended here to include the effects of the frame. Both a smooth frame and a ribbed frame are examined, and the presence of numerous additional vibratory modes in the ribbed frame demonstrated. Accelerometer tests behind a pole verify some of the theoretical predictions     

Autonomy-supportive teachers: How they teach and motivate students.

The authors examined motivating style in terms of a teacher's disposition to control students or support their autonomy. In Study 1, 4 independent samples of preservice teachers completed the Problems in Schools (PS) questionnaire so the authors could critically evaluate the instrument to assess motivating style as an individual difference characteristic. In Study 2, preservice teachers taught a 10-min instructional episode as raters judged their language and style. In Study 3, elementary and high school teachers self-reported a recent attempt to teach and motivate one of their students. Compared with their controlling counterparts, autonomy-supportive teachers showed a distinctive motivating style as measured by their conversational behaviors, interpersonal style, and attempts to support students' intrinsic motivational and internalization processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

多种斜楔机构在一副模具中的应用

小巧实用的斜楔机构不仅占用空间小 ,而且使整副模具结构紧凑、美观。介绍了3种斜楔结构 ,以供借鉴     

铸轧工艺对产品质量的影响

讨论了铸轧区，铸轧速度，铸轧温度等对轧制力，铸轧板坯质量的影响，并根据实践对影响机理进行了探讨。     

Cleavage of Poly(A)-binding protein by coxsackievirus 2A protease in vitro and in vivo: another mechanism for host protein synthesis shutoff?

Infection of cells by picornaviruses of the rhinovirus, aphthovirus, and enterovirus groups results in the shutoff of host protein synthesis but allows viral protein synthesis to proceed. Although considerable evidence suggests that this shutoff is mediated by the cleavage of eukaryotic translation initiation factor eIF4G by sequence-specific viral proteases (2A protease in the case of coxsackievirus), several experimental observations are at variance with this view. Thus, the cleavage of other cellular proteins could contribute to the shutoff of host protein synthesis and stimulation of viral protein synthesis. Recent evidence indicates that the highly conserved 70-kDa cytoplasmic poly(A)-binding protein (PABP) participates directly in translation initiation. We have now found that PABP is also proteolytically cleaved during coxsackievirus infection of HeLa cells. The cleavage of PABP correlated better over time with the host translational shutoff and onset of viral protein synthesis than did the cleavage of eIF4G. In vitro experiments with purified rabbit PABP and recombinant human PABP as well as in vivo experiments with Xenopus oocytes and recombinant Xenopus PABP demonstrate that the cleavage is catalyzed by 2A protease directly. N- and C-terminal sequencing indicates that cleavage occurs uniquely in human PABP at 482VANTSTQTM downward arrowGPRPAAAAAA500, separating the four N-terminal RNA recognition motifs (80%) from the C-terminal homodimerization domain (20%). The N-terminal cleavage product of PABP is less efficient than full-length PABP in restoring translation to a PABP-dependent rabbit reticulocyte lysate translation system. These results suggest that the cleavage of PABP may be another mechanism by which picornaviruses alter the rate and spectrum of protein synthesis.     

油缸与其连接件的干涉

对工程安装中油缸杆端及尾部耳环与其连接件相对运动时相互干涉的原因进行了分析,并提出应采取的措施.     

MCM—41中孔分子筛的研究和开发

介绍了近期国内外中孔分子筛ＭＣＭ－４１的研究情况，阐述了其合成机理并简述了其性能和应用。     

产业化生产优质系列云母珠光颜料

常州涂料化工研究院以优质白云母为原料,开发出净化分级、云母活化、四氯化钛控制水解包膜 和连续化煅烧等技术,在100t/a工业装置上生产出系列优质云母珠光颜料,质量接近国外名牌产品水平,产品 性价比高,80％以上用来出口。