用迭代法分析计算机床静压轴承-主轴系统的静态性能

本文参照文献[1] 的基本路线思路,构造了静压轴承--主轴系统的迭代计算方法。并联系机床中非常普遍的弹性两支承外伸轴系,以一台 MB1520型高速外圆磨床为例,考虑到该主轴系统径向轴承及推力轴承综合作用,用迭代法分析计算了该主轴部件的静态性能,一般情况下只需迭代1～3次,就可获得满意的结果。该方法计算效率高,占用计算机内存小,能在袖珍计算机上运算,为普及对机床主轴系统的静、动态特性研究及优化设计,提供了行之有效的方法。     

圆隙缝动静压轴承承载刚度分析

提出了一种新型动静压滑动轴承－圆隙缝动静压轴承，分析了该轴承的承载能力和刚度及刚度及设计参数对它们的影响，结果表明，该轴承性能优于传统的隙缝式轴承，且加工方便，很有应用前景。     

圆锥动静压轴承计算机辅助设计

对圆锥动静压轴承进行了有限元分析，利用ＡｕｔｔｏＣＡＤ软件编制程序绘制出轴承零件图，用ＡｕｔｏＬＩＳＰ语言实现了高级语言与ＡｕｔｏＣＡＤ联接。建立了圆锥动静压轴承计算机辅助设计系统。该系统具有连续性强，易于操作等优点。     

大型高速动静压轴承的试验研究

对一重型磨床上的大型特殊结构的动静压轴承进行了实验研究，完善了一大型高速动静压轴承试验台，改进了基于频谱分析动静压轴承动特性测试方法，实验中着重考虑了激振频率的影响，得出了一些有实用价值的结论。     

直驱式风电机组主轴系结构方案的分析与研究

使用Romax软件重点对两种直驱式风电机组主轴系的轴承寿命和承载范围进行了计算和分析.计算结果表明,双列圆锥滚子轴承存在两列滚子受力不均的缺陷,而使用两个直径较小的单列圆锥滚子轴承代替一个直径较大的双列圆锥滚子轴承作为主轴承是可行的.并从整机的角度对这两种轴系结构方案做了对比分析,对比结果表明,一个双列圆锥滚子轴承的主轴系比两个单列圆锥滚子轴承的主轴系具有更好的装配工艺性、机组可维护性和热特性.     

腔式平面静压推力轴承的压力跟踪供油特性

应用润滑理论建立了腔式平面静压推力轴承的数学模型，编写了计算机程序，计算结果表明，在变载荷情况下采用压力跟踪供油方式可例轴承始终处于良好的工作状态。     

动静压可倾瓦轴承有限元分析

对动静压可倾瓦轴承进行了有限元分析，同时还给出了孔式环面浅腔节流动静压可倾瓦轴承油腔尺寸的取值范围。     

定间隙核桃破壳机主轴的动态响应分析

通过对定间隙核桃破壳机主轴的动态响应分析,考虑到核桃破壳时挤压力在不断变化,主轴受力不均匀,综合其转速、材料和结构配置等因素,建立动态响应模型。结果表明,降低轴系固有频率,选择合适轴承,减轻主轴重量,采用对称设计,能够有效提高主轴的动态响应特性,改善破壳的质量和安全性能。     

TH 6350卧式加工中心主轴箱系统有限元建模及动态特性分析

通过合理设定主轴箱系统的边界条件，采用功能强大的I—deas8．0软件建立TH6350主轴系统的有限元模型，对有限元计算结果进行分析获得主轴系统的动态特性，据此可对机床的设计进行改进。     

圆锥动静压轴承有限元直接解法

对具有深浅腔的和志细管节流圆锥动静压混合轴承进行有限元分析，在用有限元法求解雷诺方程时，对流量连续方程进行了归并，并把计算结果与传统迭代法计算结果进行了比较。从而证明了此方法具有准确省时等优点。     

暗直榫欧式木窗专用数控机床主轴的有限元分析

通过主轴模型的建立、网格的划分、边界条件的设置和载荷的施加、刚度与强度分析以及模态分析,对暗直榫欧式木窗专用数控机床主轴的静态特性进行了有限元分析。结果表明:主轴加载后的最大位移出现在主轴最下端,且最大位移值为0.114 mm,是在误差的允许范围; 对主轴的应力、应变进行了分析,得到主轴的最大应力为282.76 MPa,小于主轴的许用应力[σ]=355 MPa,符合主轴的设计要求; 对主轴进行了模态分析,得到主轴前6阶固有频率,当机床工作时的固有频率低于主轴的1阶固有频率时,就不会引起机床的共振。并获得了主轴的位移云图、应力应变云图,验证其刚度在静态下均在许用范围内,可满足设计要求。     

Structure and organization of the living mitotic spindle of Haemanthus endosperm

New details of mitotic spindle structures in the endosperm of Haemanthus katherinae (Bak) have been demonstrated by differential interference microscopy. Spindle fibers are clearly seen in the living spindle extending from the kinetochores to the polar region. Individual spindle fibers consist of a bundle of smaller filaments which diverge slightly from the kinetochore and intermingle with filaments from other spindle fibers as they approach the polar region. The degree of intermingling increases during metaphase and anaphase. The chromosomes stop moving when the spindle fibers are still 5 to 10microns long; then the fibers disappear. These observations explain some aspects of spindle movements which were difficult to reconcile with earlier concepts of spindle organization.     

Anaphase inactivation of the spindle checkpoint

The spindle checkpoint delays cell cycle progression until microtubules attach each pair of sister chromosomes to opposite poles of the mitotic spindle. Following sister chromatid separation, however, the checkpoint ignores chromosomes whose kinetochores are attached to only one spindle pole, a state that activates the checkpoint prior to metaphase. We demonstrate that, in budding yeast, mutual inhibition between the anaphase-promoting complex (APC) and Mps1, an essential component of the checkpoint, leads to sustained inactivation of the spindle checkpoint. Mps1 protein abundance decreases in anaphase, and Mps1 is a target of the APC. Furthermore, expression of Mps1 in anaphase, or repression of the APC in anaphase, reactivates the spindle checkpoint. This APC-Mps1 feedback circuit allows cells to irreversibly inactivate the checkpoint during anaphase.     

A centrosome-independent role for gamma-TuRC proteins in the spindle assembly checkpoint

The spindle assembly checkpoint guards the fidelity of chromosome segregation. It requires the close cooperation of cell cycle regulatory proteins and cytoskeletal elements to sense spindle integrity. The role of the centrosome, the organizing center of the microtubule cytoskeleton, in the spindle checkpoint is unclear. We found that the molecular requirements for a functional spindle checkpoint included components of the large gamma-tubulin ring complex (gamma-TuRC). However, their localization at the centrosome and centrosome integrity were not essential for this function. Thus, the spindle checkpoint can be activated at the level of microtubule nucleation.     

On the mitotic movements of chromosomes

My conclusions, which, I confess, are tentative and based mainly on studies of one kind of cell, the grasshopper neuroblast, may be summarized as follows. The late prophase orientation of the chromosomes is a carry-over from the late telophase orientation. It is apparently maintained by means of the centromeres, which appear to be attached within a limited region of the nucleus throughout telophase, interphase, and prophase. Metaphase orientation of the chromosomes may be explained as the resultant of two forces: a force involving the centromere and spindle, which is responsible for keeping the centromeres in the equatorial plane of the spindle, and a repulsion force involving the noncentromeric portion of the chromosomes, which results in a tendency toward uniform spacing of the chromosomes outside the spindle. Anaphase separation of sister chromatids and their subsequent movement toward the poles of the spindle involves at least four distinct phases: (i) the initial poleward movement of the centromeres, which may be due to intrinsic repulsion or to a force acting between spindle and centromeres that produces an angle of almost 90 degrees between the separated and unseparated portions of the chromatids; (ii) the autonomous separation of the noncentromeric part of the chromosome; (iii) elongation of the spindle, beginning just after the sister chromatids are separated proximally and ending when the longer chromatids are about to lose contact distally; and (iv) the later movement apart of the daughter chromosomes, probably resulting from a pushing force exerted by elongation of the interzonal fibers.     

苹果不同树形树冠特性和果实品质的比较

为探讨渭北南部苹果产区矮化密植栽培的适宜树形,以11年生高纺锤形、自由纺锤形和开心形富士苹果树为试材,分别测定不同树形树体枝量及枝类组成、冠层特性、叶片光合特性、果实产量和品质相关指标。结果表明,高纺锤形枝类分布和组成及冠层特性指标优于自由纺锤形和开心形;高纺锤形和开心形的树冠光合优于自由纺锤形;3种树形的产量分别为56 428.6、43 523.8和28 952.4kg.hm-2。高纺锤形和开心形的品质优于自由纺锤形。综合分析表明,矮化密植栽培,高纺锤形优于开心形和自由纺锤形。     

小鼠输卵管卵母细胞的形态学研究

应用光、电镜技术研究发现:新排卵母细胞的纺锤体位于动物极质膜下,长轴与质膜平行,卵周隙狭窄,除纺锤体区外,微绒毛呈倒伏状遍布于卵细胞表面,皮质颗粒排列于质膜下,线粒体多分布于卵母细胞近中区及染色体旁;排卵后2～4h,纺锤体在质膜下旋转90°,卵周隙增宽,微绒毛逐渐竖起,少数皮质颗粒提前外排,线粒体趋于分散,排卵后8h,纺锤体内移,微绒毛趋于融合,皮质颗粒减少,线粒体退化。     

间作模式下四种扁桃树形结构间差异及对小麦生长的影响

[目的]通过对扁桃四种不同栽培树形的光合、冠层、微环境等指标及其对应间作区域光照和小麦生长情况的测定研究,旨在为南疆扁桃-小麦间作体系中,扁桃适宜树形的选择提供一定的理论依据.[方法]以10年生晚丰品种为试材,设主干分层形、纺锤形、高干圆头形和开心形四个处理,研究四个树形间的差异,调查间作区域光照分布和小麦生长情况.[结果]纺锤形处理单株负载量略低于主干分层形为1 184个/株,由于树冠体积小,单位投影面积负载量最高,达到94.8个/m2,是主干分层形的2.06倍;树冠内部光照情况优于其他三个处理,达到自然条件的31;;对间作区域遮阴影响程度较轻,且持续时间短,其整体和两侧近冠区域全天光照强度分别为自然条件的40.89;和34.57;.[结论]扁桃纺锤形树形负载量大,对间作区域影响小,适合应用于果粮间作立体复合种植体系中.     

数控铣齿机主轴系统温度场有限元分析

热误差是影响机床加工精度的主要因素之一。主轴的热变形是机床总的热变形的重要组成部分。因此本文在分析数控铣齿机主轴热源的基础上,计算发热量,确定边界条件,并利用有限元软件abaqus建立主轴系统的温度场模型并进行了数字模拟仿真,为主轴系统的进一步热变形控制提供了基础。     

不同树形矮化自根砧苹果的冠内光照及其生长和产量比较

【目的】研究矮化自根砧苹果2种砧木、6种树形的冠层内相对光照强度分布以及生长结果表现,明确西北黄土高原地区苹果矮化自根砧栽培的适宜树形。【方法】以富士苹果为试材,应用TES-1332A数字式照度计等仪器,观测矮化自根砧苹果2种砧木、6种树形的树体结构、冠层内相对光照强度、叶片营养、果实产量和品质等指标。【结果】4种纺锤形比V形和Y形的树体生长势强。高纺锤形/M26树冠内相对光照强度>30%的占79.6%,光截获能力强,枝量多,早期产量最高;V形树冠内相对光照强度仅次于Y形,早期产量仅次于高纺锤形;Y形/M26树冠内相对光照强度>30%的占91.8%,虽然光照条件较好,但枝量小、产量低。改良纺锤形、细长纺锤形、Y形和V形单果重较大,其次为高纺锤形,自由纺锤形单果重最小。V形、Y形的果皮色泽饱和度和可溶性糖含量显著高于其它树形。【结论】高纺锤形/M26的早期产量最高,V形产量仅次于高纺锤形,产量上升潜力大;V形和Y形的品质较好。