蜗杆副传动接触线载荷的研究

建立了蜗杆副在常规的润滑与磨损传动条件下,齿面接触线载荷的计算模型,结合蜗杆副传动的润滑与磨损规律特点,阐明了蜗杆副传动中,弹性流体动力润滑油膜和齿面磨损状态对齿面接触线载荷变化规律的影响。     

Relationship between action potential, contraction-relaxation pattern, and intracellular Ca2+ transient in cardiomyocytes of dogs with chronic heart failure

Abnormalities of contractile function have been identified in cardiomyocytes isolated from failed human hearts and from hearts of animals with experimentally induced heart failure (HF). The mechanism(s) responsible for these functional abnormalities are not fully understood. In the present study, we examined the relationship between action potential duration, pattern of contraction and relaxation, and associated intracellular Ca²⁺ transients in single cardiomyocytes isolated from the left ventricle (LV) of dogs (n = 7) with HF produced by multiple sequential intracoronary microembolizations. Comparisons were made with LV cardiomyocytes isolated from normal dogs. Action potentials were measured in isolated LV cardiomyocytes by perforated patch clamp, Ca²⁺ transients by fluo 3 probe fluorescence, and cardiomyocyte contraction and relaxation by edge movement detector. HF cardiomyocytes exhibited an abnormal pattern of contraction and relaxation characterized by an attenuated initial twitch (spike) followed by a sustained contracture ('dome') of 1 to 8 s in duration and subsequent delayed relaxation. This pattern was more prominent at low stimulation rates (58% at 0.2 Hz, n = 211, 21% at 0.5 Hz, n = 185). Measurements of Ca²⁺ transients in HF cardiomyocytes at 0.2 Hz manifested a similar spike and dome configuration. The dome phase of both the contraction/relaxation pattern and Ca²⁺ transients seen in HF cardiomyocytes coincided with a sustained plateau of the action potential. Shortening of the action potential duration by administration of saxitoxin (100 nM) or lidocaine (30 μM) reduced the duration of the dome phase of both the contraction/relaxation profile as well as that of the Ca²⁺ transient profile. An increase of stimulation rate up to 1 Hz caused shortening of the action potential and disappearance of the spike-dome profile in the majority of HF cardiomyocytes. In HF cardiomyocytes, the action potential and Ca²⁺ transient duration were not significantly different from those measured in normal cells. However, the contraction-relaxation cycle was significantly longer in HF cells (314 ± 67 ms, n = 21, vs. 221 ± 38 ms, n = 46, mean ± SD), indicating impaired excitation-contraction uncou pling in HF cardiomyocytes. The results show that, in cardiomyocytes isolated from dogs with HF, contractile abnormalities and abnormalities of intracellular Ca²⁺ transients at low stimulation rates are characterized by a spike-dome configuration. This abnormal pattern appears to result from prolongation of the action potential. Received 22 January 1998; received after revision 16 March 1998; accepted 27 March 1998     

接触问题可靠度分析的随机有限元法

首次提出接触问题可靠度分析的随机有限元法,建立了可靠度计算的基本公式,研制了电算程序。通过两子结构接触问题可靠度分析算例,验证了本文所述方法的正确性和可行性,实际计算表明,该方法具有收敛快,精度高的优点,适用于大型复杂结构的接触问题可靠度计算,并可推广到三维多子结构的接触问题可靠度分析。     

北秦岭松树沟接触变质岩的形成温度研究

本文应用氧同位素和电子探针分析方法测定了北秦岭松树沟阿尔卑斯型超镁铁岩体接触变质带内角闪岩和及其原岩秦岭群斜长角闪片岩的形成温度．角闪岩的角闪石－石榴子石Ｆｅ－Ｍｇ配分温度计给出不同期次形成温度分别是：早期８１５～８５５℃，主期７００～７７０℃．矿物对氧同位素地质测温结果得到，角闪岩的主期变质温度为７４５～７７０℃，与其电子探针结果在误差范围内一致；斜长角闪片岩为５００～６０５℃，代表了秦岭群区域变质温度     

不带凸条件双曲守恒律熵解渐近行为

讨论了非凸双曲守恒律熵解的大时间渐近问题．若初值当｜ｘ｜充分大时为接触间断的Ｒｉｅｍａｎｎ数据时，熵解逼近相应Ｒｉｅｍａｎ问题解；当初值有紧支时，熵解以代数数率收敛于零．     

微晶CuCr材料的制备及电击穿性能的研究

根据真空断路器大功率、小型化发展趋势对触头材料的要求，探索用高能球磨制粉、热压烧结的方法制备微晶ＣｕＣｒ触头材料．结果表明，高能球磨能够制备出超细晶Ｃｕ－Ｃｒ合金粉．７５０℃热压时材料仍保持合金粉形貌，颗粒内发生部分过饱和固溶Ｃｕ与Ｃｒ的时效析出过程．９２０℃热压时Ｃｕ与Ｃｒ组元重新分布并发生了再结晶过程，晶粒尺寸为２～３μｍ，远远小于常规方法生产的ＣｕＣｒ材料．由于微晶ＣｕＣｒ材料中Ｃｒ相固溶度升高，使材料电击穿机制发生变化，首次击穿相从常规材料中的Ｃｒ相转移到Ｃｕ相上．     

25Cr2MoV离子渗氮齿轮疲劳强度的试验

本文对２５Ｃｒ２ＭｏＶ离子渗氮齿轮所进行的齿面接触疲劳和轮齿弯曲疲劳试验研究，得出了这种齿轮疲劳寿命分布规律和疲劳强度分布规律的结论，并求得这种齿轮的Ｒ－Ｓ－Ｎ线簇方程以及各种可靠度下的齿轮接触疲劳极限应力值和轮齿弯曲疲劳极限应力值。     

轧制应变速率参数ε的精确计算方法

该文采用精确接触弧参数方程，设定运动许可速度场与应变速率场，经参量积分与积分中值定理提出一个精确计算轧制应变速率ε的计算公式，经测试实例与目前各惯用公式进行了比较。     

滚动轴承接触问题的罚有限元分析

用罚有限元法分析了圆柱滚子轴承的接触非线性问题。应用所编程序计算出了有间隙圆柱滚子轴承的接触区与接触压力分布．所得结果同相应的实验结果较为一致．从而为进行轴承强度计算和优化设计提供了一种可靠的数值方法．     

板式楔横轧接触面的解析分析

在对板式楔横轧轧制过程进行分析基础上，建立了板式楔横轧的几何数学模型，确定了板式楔横轧模具与轧件轧制接触面的及边界方程，最后利用计算机辅助绘图技术，将结果以图形显示方式形象输出。