Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental stu...Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental studies of the hysteresis of friction force are presented in this paper. A model, which is based on the stripe theory and the simplified theory of rolling contact, is built to describe the transient hysteresis of the friction force. Then, the model is modified by taking the anelasticity effect into consideration. Experimentally, a linear motor direct-drive setup is utilized to measure the transient asymmetrical hysteresis of the friction force in the pre-rolling region of an LRG. The influences of the pre-rolling displacement and the dwelling time on the asymmetrical hysteresis of the friction force are studied. The numerical and experimental results are well correlated, which shows good accuracy of the model. The transient asymmetrical hysteresis of friction force in the pre-rolling region of LRGs can thus be determined using the model.展开更多
文摘Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental studies of the hysteresis of friction force are presented in this paper. A model, which is based on the stripe theory and the simplified theory of rolling contact, is built to describe the transient hysteresis of the friction force. Then, the model is modified by taking the anelasticity effect into consideration. Experimentally, a linear motor direct-drive setup is utilized to measure the transient asymmetrical hysteresis of the friction force in the pre-rolling region of an LRG. The influences of the pre-rolling displacement and the dwelling time on the asymmetrical hysteresis of the friction force are studied. The numerical and experimental results are well correlated, which shows good accuracy of the model. The transient asymmetrical hysteresis of friction force in the pre-rolling region of LRGs can thus be determined using the model.
文摘目的研究慢性甲基苯丙胺(methamphetamine,MA)成瘾小鼠神经突触可塑性基因的表达变化情况。方法选用C57BL/6J小鼠,模拟人类药物成瘾模式,分段渐进性腹腔注射给药5 mg/kg、10 mg/kg或者生理盐水。选取小鼠的大脑皮质和海马组织,通过亚硫酸氢盐处理基因组DNA和甲基化特异性PCR(methylmion specific PCR,MSP)对突触可塑性基因表达水平进行检测,运用BiQ-Analyzer软件对测序结果进行比对和DNA甲基化分析。结果相比盐水处理组小鼠,MA成瘾组小鼠大脑皮层的Egr2(P=0.064)基因启动子CpG位点的甲基化修饰增加,而Eln(P=0.083)基因启动子的甲基化修饰降低;海马组织中,Arc(P=0.025)、Egr2(P=0.034)基因甲基化修饰增加,而Eln(P=0.063)基因甲基化修饰降低。结论突触可塑性基因的甲基化修饰可能参与MA成瘾机制的形成。
