基于CAD/CAM模具设计与制造的研究

模具是技术密集、资金密集、劳动密集的产品.模具工业是国民经济的重要基础工业,模具的设计与制造水准直接影响产品的品质和生产效率.本文阐述了模具设计与制造中CAD/CAM技术应用的侧重点.强调CAM在模具设计与制造中的关键技术.给企业模具设计与制造以借鉴.     

特征提取与可制造性知识表达

针对零件的可制造性设计,研究制造信息的获取与表达方法.通过ACIS提取几何模型信息,建立制造特征库与采用基于规则的方法实现对制造特征的识别与重构.综合运用多种知识与推理机制,建立特征与制造资源、工艺知识的关联.解决了并行工程中的工艺性问题.开发的DFM系统验证了该方法的可行性.     

机械、仪表工业类核心期刊表

序号 l。刊名序号刊名机械工程学报15.润滑与密封机械设计16.压缩机技术中国机械工程17.工具技术起重运输机械18.机械设计与制造流体工程19.机床与液压工程机械20.机械机械工艺师21.液压与气动机床22.新技术新工艺轴承23.机械工程师机械制造24.齿轮组合机床与自动化加工技术25.液压工业国外工程机械26.重型机械风机技术27.阀门水泵技术28.模具工业序号 、刊,上海机械学机械强度摩擦学学报二工业仪表与自动化装置现代机械磨料磨具与磨削仪表技术与传感器分析仪器机械工业自动化压力容器机电工程机械设计与研究机械科学与技术仪器仪表学报 ...…     

条码图像模式识别的追溯系统设计与实现

为解决新能源汽车生产企业从车辆制造到售后服务产品生命周期内信息管理与质量追溯问题.利用条形码图像处理技术与图像模式识别算法对整车制造装配环节的重要零部件进行数据采集和信息绑定.采用.NET编程技术设计图像识别程序完成对零件条码图像自动识别分类工作.形成整车车辆识别代码与关键零部件物料信息结合的管理体系.最后通过企业ERP系统物料完成数据接口,承接起ERP系统零件管理功能向仓库和制造流程扩展的作用.物料流程追溯与质量信息管理功能实现验证了技术方案的可行性.通过对质量数据的管理提高了制造企业对质量问题的反馈和追踪能力.     

碳管纳米弹簧的轴向压缩刚度与失稳分析

分析轴向压缩载荷作用下碳管纳米弹簧的变形与失稳,给出碳管弹簧的轴向压缩刚度Kp与失稳临界载荷Pc的计算公式.为验证公式的有效性,将碳管纳米弹簧kp和Pc的理论解与相应的试验结果进行比较.结果发现,碳管纳米弹簧的K和P理论解与实验结果较为接近.文中碳管纳米弹簧的分析方法与Kp、Pe的公式对人们进一步探讨碳管纳米弹簧的力学特性具有参考意义.     

基于啁啾光栅的温度与应变测量解耦方法研究

实际环境中光纤光栅存在对应变与温度测量交叉敏感问题,提出了利用啁啾光纤光栅(CFBG)进行双参数同时测量的方法。通过将CFBG胶封于等强度梁上,利用CFBG反射谱的中心波长与带宽对温度与应变的灵敏度差异,组成系数解耦矩阵,实现对应变与温度的同时测量。室温下,CFBG的中心波长与带宽随应变变化的灵敏度分别为0. 79、1. 38 pm/με,线性度为0. 998 8、0. 999 3;在-20～60℃温度范围内,CFBG的中心波长与带宽随温度变化的灵敏度分别为22. 74、23. 97 pm/℃,线性度为0. 999 8、0. 997 0,表明使用单个CFBG可以实现同时测量应变与温度。     

数控加工中刀具的选择与切削用量分析

现代刀具的显著特点是结构创新速度加快.随着计算机应用领域的扩大,机械加工逐渐运用数控技术.这对刀具的选择与切削用量的确定提出了更高的要求.对数控加工中的刀具选择与切削用量分析给出原则,可供数控机床编程与操作人员的参考.     

基于虚拟仪器的车辆综合传动装置测试系统设计

为提高测试数据采集与处理的自动化和智能化程度,融合虚拟仪器、稳态与动态数据采集技术与办公自动化技术,在Visual Basic平台上自主开发了多参数车辆动力传动测试与故障诊断系统.该系统将多路传统仪器功能模块显示在同一窗口,采用数据库对测试项目、传感器与仪表的配置及标定、设备型号的选择等以适应各类不同功能与规模的测试项目.实现了多参量数据的自动采集,可进行各类数据处理及分析与定制格式试验报告的自动生成.实际应用表明,该系统工作可靠、操作便利.     

含裂纹构件塑性失效时载荷与位移关系的闭合解

对含裂纹构件的一种失效模式(韧带屈服)进行研究.将构件位移分成线弹性位移与塑性位移.在进行线弹性位移分析时,采用断裂力学中的能量差率方法与固体力学中的余能原理.在进行弹塑性位移分析时,建立三区力学模型,在此基础上得到载荷位移关系与构件承载能力表达式的闭合解.此解与试验结果具有很好的一致性.     

基于遗传算法和变邻域搜索的柔性作业车间同步调度方法

研究了现有的柔性作业车间问题求解算法中存在的计算等待时间与求解结果质量之间的矛盾.针对这一矛盾设计了一种名为同步调度的新型调度求解方法.同步调度实现了生产作业与调度计算同步进行,旨在同时满足零等待与精求解两大要求.基于遗传算法与变邻域搜索设计了两种同步调度算法.在静态与动态柔性作业车间问题上的仿真实验表明,同步调度算法...     

Histochemical and ultrahistochemical localization of heavy metals in calf organs

Cadmium, zinc, selenium, and copper were administered, singly or in combination, orally or subcutaneously. Experiment I included 32 calves of both sexes; six received Cd (two groups), Zn, Cd, and Zn, and Cd and Se (two groups) and one group was a control. In Experiment II (21 bulls), three were given Cd, Cd, and Cu, and Cd and Zn, respectively, and one group was a control. For light microscopy, in Experiment I the highest amounts of silver granules were present in the samples of liver, small intestine, and vesicular gland of all the exposed groups; in Experiment II the most affected organs were liver, kidney, and small intestine. For electron microscopy, in Experiment I, after administration of Cd and Zn, the highest amounts of granules were seen in the cytoplasm of hepatocytes and cells of the proximal and distal renal tubules and the lowest amounts were found in glandular cells of the pancreas. Administration of Cd and Se resulted in the presence of large numbers of granules in the nuclei and nucleoli of spermatogonies. In Experiment II, ingestion of Cd and Zn in feed led to the appearance of highest amounts of granules in the nucleoli, nuclei, and cytoplasm of cells in testes, kidneys, and pancreas. Following Cd intake, the highest accumulation of granules was observed in the nucleoli of hepatocytes and cells of the proximal and distal renal tubules. Combined Cd and Cu produced the highest number of granules in cells of the proximal and distal renal tubules and in the nucleoli and nuclei of germinal epithelium.     

Mechanotransduction-The relationship between gravity,cells and tensile loading in extracellular matrix

Gravity plays a central role in vertebrate development and evolution. Mechanotransduction involves the tensile tethering of veins and arteries, connections between the epidermis and dermis in skin, tensile stress concentrations that occur at tissue interfaces, cell-cell interactions, cell-collagen fiber stress transfer in extracellular matrix and fluid shear flow. While attention in the past has been directed at understanding the myriad of biochemical players associated with mechanotransduction pathways, less attention has been focused on determining the tensile mechanical behavior of tissues in vivo. Fibroblasts sit on the surface of collagen fibers in living skin and exert a retractile force on the fibers. This retractile force pulls against the tension in collagen fibers in skin. After fibroblast-collagen fiber interactions are altered either by changes in fibroblast adhesion or after formation of cancer associated fibroblasts, and changes in cell junctions, alterations in the retractive force leads to changes in mechanotransduction. The purpose of this paper is to present a model of tensile forces that occur at the fibroblast-collagen fiber interface and how these forces are important in extracellular matrix physiology in health and disease.     

The intracellular distribution of ions and water in rat liver and heart muscle

Local dry mass concentrations of intracellular compartments in rat heart muscle and liver cells were estimated by quantitative electron microscopy and X-ray microanalysis of ultrathin frozen-dried cryosections. The results were used to calculate elemental concentrations per litre of compartment water from the X-ray microanalytical data. Water fractions were between 80.3 ± 1.3% of wet weight in the decondensed chromatin and only 45.1 ± 1.7% in mitochondria of liver cells. The lowest water fraction in heart muscle cells was also found in mitochondria. The ionic concentrations found in the cytoplasm of liver cells and in the myofibrils are in accord with the electroneutrality rule and in osmotic equilibrium with the extracellular concentrations. The concentrations of Na, K, Cl and P both in the cytoplasm and in the regions of decondensed chromatin within the nuclei were found to be equal. However, in regions of condensed chromatin K⁺ concentrations were found to be much higher than expected for a Donnan distribution of ions free in solution. Most probably the activity coefficient for K⁺ is lower in the condensed chromatin than in the decondensed or in the cytoplasm. The same holds true for the A-band as compared to the I-band in heart muscle cells. A sequestration of K⁺ was measured also in the rough endoplasmic reticulum (RER) of hepatocytes. The Cl^? concentration in mitochondria both in heart muscle and liver cells has been measured far in excess of what might be expected from a Nernstian distribution. A coupled inward Cl^? transport in mitochondria must, therefore, be assumed.     

Ciliary neurotrophic factor increases the survival of magnocellular vasopressin and oxytocin neurons in rat supraoptic nucleus in organotypic cultures.

Organotypic cultures of the rat hypothalamus are very useful models for the long-term study of parvocellular vasopressin (VP) neurons in the paraventricular (PVN) and suprachiasmatic (SCN) nuclei. However, they do not preserve significant numbers of VP magnocellular neurons (VP-MCNs) in either the PVN or the supraoptic nucleus (SON). Vutskits et al. [(1998) Neuroscience 87:571-582] reported that ciliary neurotrophic factor (CNTF) was a selective survival factor for rat VP-MCNs in organotypic cultures of the rat hypothalamic paraventricular nucleus (PVN). We examined the effects of CNTF on the survival of these neurons in rat and mouse SONs. CNTF (10 ng/ml) in the culture media increased the survival of VP-MCNs by 6-fold and OT-MCNs by 3-fold. In the mouse, both OT- and VP-MCNs survive very well in organotypic cultures under standard culture conditions and the addition of CNTF had no further effect. Consistent with these results, in situ hybridization showed substantially higher levels of VP- and OT-mRNA in rat PVNs and SONs in the presence of CNTF, but produced no changes in these nuclei in the mouse. The optimum period for the survival effect of CNTF on MCNs in the rat hypothalamic cultures was in the first 7-10 days of culture and this effect is maintained for at least 5 additional days if CNTF is then removed from the medium. Therefore, using CNTF in the culture media can provide an opportunity for long-term studies of rat VP- and OT-MCNs in SONs in organotypic cultures.     

Gender-related changes in the avian vasotocin system during ontogeny

The arginine vasotocin (AVT) system of the avian brain includes a sexually dimorphic part that extends from the caudal part of preoptic region through the medial part of the bed nucleus of stria terminalis (BSTm) to the lateral septum. It is composed of the parvocellular neurons located in the BSTm and the dense innervation of the medial preoptic region and lateral septum. In this part of the brain, AVT expression is stronger in males than in females in a few bird species investigated to date. This review focuses on the ontogeny of sexual differences in the vasotocinergic system of two gallinaceous species, domestic chicken and Japanese quail, and on the role of gonadal hormones in organizing during development and maintaining in adulthood these differences. Parvocellular AVT neurons become discernible in the BSTm of males and females during the second half of embryonic development. These cells undergo a profound and irreversible sexual differentiation during ontogenetic development. Recent findings demonstrate a dual role of estrogens in the organization and activation of sex differences in the AVT system. During the embryonic period of ontogeny, estrogens differentiate the AVT system in a sexually dimorphic manner in parallel with the differentiation of sexual behavior, while in adulthood estrogens, locally produced from testosterone in the male brain, activate AVT synthesis in the BSTm. The sexually dimorphic part of the AVT system is sensitive to a number of abiotic factors such as light, temperature, and water availability. It is suggested that sex dimorphic vasotocinergic systems could be implicated in processes of social recognition in various behavioral contexts.     

轮轨关系研究中的力学问题

简单论述世界铁路发展状况和铁路交通运输的优越性。详细论述轮轨关系的研究问题,其研究包含轮轨滚动接触作用和稳定性问题、轮轨粘着和强度、接触表面磨损和滚动接触疲劳破坏、轮轨噪声、轮轨蠕滑率／力理论和轮轨三维弹塑性滚动接触问题。在这些问题研究中,蕴涵十分复杂的力学和强度问题。文中就这方面的研究现状和存在问题以及问题研究的难点进行讨论,并分析今后可能的研究方向。     

五自由度机器人的结构设计及其控制

介绍了串联五自由度机器人的机械结构和机器人控制系统的设计.文中设计的五自由度机器人既可以用于实际生产,也可以用于教学和科研.用于实际生产既可以执行点位控制下的操作,也可以执行连续轨迹控制下的操作;用于教学和科研时,该机器人可用于机器人结构分析、机构运动学分析及机器人控制系统的教学演示和实验操作.它具有结构简单、操控方便等特点,而且可以做进一步的研发.     

Sex differences in songbirds 25 years later: What have we learned and where do we go?

About 25 years ago, Nottebohm and Arnold reported that there are profound male-biased sex differences in volume in selected nuclei in telencephalic portions of the song control system. This review focuses on issues related to the cellular bases of these sex differences in volume and comparative studies that might elucidate the function of this variation between the sexes. Studies utilizing a variety of neurohistological methods in several different species to define the boundaries of two key telencephalic song nuclei HVc and the robust nucleus of the archistriatum (RA) all tend to find a sex difference in volume in agreement with Nissl-defined boundaries. Sex differences in volume in nuclei such as HVc and RA are associated with differences in cell size and cell number. Other attributes of the phenotype of cells in these nuclei are also different in males and females such as the number of cells expressing androgen receptors. Comparative studies have been employed to understand the function of these sex differences in the brain. In some songbird species, females sing rarely or not at all, and the brain nuclei that control song are many times larger volume in males than females. In other species, males and females sing approximately equally, and the brain nuclei that control song are approximately equal between the sexes. Recently, statistical methods have been employed to control for phylogenetic effects while comparing the co-evolution of traits. This analysis indicates that the evolution of sex differences in song has co-evolved with the evolution of sex differences in singing behavior in songbird species. Future studies should focus on the function of the smaller song control nuclei of females and investigate the role these nuclei might play in perception as well as in production. Microsc. Res. Tech. 54:327–334, 2001. © 2001 Wiley-Liss, Inc.     

Distribution of sex steroid hormone receptors in the avian brain: functional implications for neural sex differences and sexual behaviors

Developmental and seasonal changes in the production of androgens, estrogens, and progestins seem to control sex-specific differentiation and seasonal changes in appetitive and consummatory sexual behaviors of birds. This results in profound sex differences in the quality (sex-specific) or quantity (sex-typical) of behaviors such as courtship, territoriality, or copulation. Steroids affect the brain by binding to intracellularly located receptors. The same brain areas express androgen, estrogen, and progesterone receptors in male and female brains. Sex differences in these genetically determined patterns occur in the size of neuron populations that intrinsically express sex steroid receptors. Further permanent sex differences are subsequent to degenerative fates of receptor expressing neuron populations during ontogeny. Transient sex differences in receptor expression appear to be due to area-specific up- and down-regulation of receptor levels, reflecting transient changes in the level of circulating steroids, changes in environmental conditions, or in the physiological status of the individuals. In particular, intrinsic sex differences in the expression pattern of sex steroid receptors and steroid-independent regulation of the expression level of these receptors in the brain are limiting mechanisms for gonad-dependent sexual development and activities.     

Use of primary cell cultures and intact isolated glandular epithelia for X-ray microanalysis

Changes in the elemental composition of cells during isolation of glandular epithelia were studied by electron probe X-ray microanalysis. Fine chopping of rat submandibular gland followed by enzymatic treatment for 15 min caused marked increases in Na and Cl and a decrease in K concentrations in acinar cells. After enzymatic treatment for 50 min, Na, Cl and K concentrations returned to close to the control level. Mechanical disaggregation of the acinar clumps following enzymatic treatment resulted again in minor increases in Na and Cl and a marked decrease in K concentration. Exposure of isolated acini to cholinergic stimulation in vitro resulted in secretion of Cl and K from the acinar cells. Dissection of the sweat gland from human skin caused a decrease in the K/Na ratio. Incubation of the gland for 30–45 min with collagenase gave rise to a gradual decrease in the K/Na ratio. After mechanical separation of the gland into the secretory coil and reabsorptive duct, a further reduction of the K/Na ratio was seen. However, the duct cells had a much lower K/Na ratio and higher Ca concentration than the coil cells. In primary cultures, the K/Na ratios of the coil and duct cells returned to the in situ level. The elemental composition of sweat gland cells incubated in collagenase-containing medium was no different from that in cells incubated in collagenase-free medium. In the intact collagenase-isolated tissue, Cl^? secretion in the coil was elicited by carbachol but not by cAMP, whereas in the duct cells the reverse was the case. In primary cell cultures, Cl^? efflux in both coil and duct cells could be elicited by both carbachol and cAMP. In conclusion, although changes in elemental composition of gland cells during the isolation procedure occur, physiological responses can be detected. When primary cell cultures are used, it should be borne in mind that cultured cells may have physiological properties different from those of the intact tissue.