SHS技术在制备金属—陶瓷复合材料中的应用

简要介绍了自蔓延高温合成技术的基本原理，简述了该技术在制备金属－陶瓷复合材料中的应用概况，并比较了ＳＨＳ技术与传统技术在制备金属－陶瓷复合材料中的优缺点。     

放电等离子烧结在金属-陶瓷复合材料制备中的应用

放电等离子烧结(SPS)是一种材料制备新技术。近年来，放电等离子烧结技术已成功用于制备金属-陶瓷复合材料，且在制备难熔化合物、纳米材料、梯度功能材料和开发新金属-陶瓷复合材料方面有其独特的优越性。综述了金属-陶瓷复合材料放电等离子烧结的最新研究进展，指出了放电等离子烧结金属-陶瓷材料的优缺点，并对今后的研究作了展望。     

陶瓷涂层材料的应用与发展

概述了表面工程的发展历史，陶瓷涂层的制备方法、种类及其在各领域中的应用。分析了陶瓷涂层存在的关键问题和目前所采取的措施，并对陶瓷涂层研究的发展趋势及Fe—Al金属间化合物／Al2O3陶瓷新型复合材料在表面工程中的应用前景进行了讨论。     

玻璃陶瓷复合材料的研究进展

玻璃陶瓷复合材料可以改善玻璃陶瓷的微观结构,消除结构缺陷,增强玻璃陶瓷的力学性能。对4类玻璃陶瓷复合材料,即纤维增强玻璃陶瓷复合材料、可用于牙科的玻璃陶瓷复合材料、玻璃陶瓷/金属复合材料和玻璃陶瓷/陶瓷复合材料研究进展进行了综述,并对玻璃陶瓷复合材料的制备、增强机理及应用前景进行了探讨。     

增强陶瓷汽车发动机

用金属和陶瓷的复合材料制造汽车发动机的汽缸,就会有较长的寿命。问题在于生产最耐磨的金属—陶瓷或陶瓷—陶瓷复合材料所用的陶瓷应满足两个要求:第一,它必需是已知的一种最硬的陶瓷,第二,它必需有适当的微形状,如象有了增强的金属钉形或针形。因     

复合材料PZT—PVDF和PT—P（VDF／TeFE）的压电性

本文报道了两种压电陶瓷—聚合物复合材料ＰＺＴ－ＰＶＤＦ和ＰＴ—Ｐ（ＶＤＦ／ＴｅＦＥ）的制备工艺，利用ＸＲＤ、ＳＥＭ和ＤＳＣ分析了压电复合材料的结构、形貌与相变，用ＬＣＲ法和Ｂｅｒｌｉｎｃｏｕｒｔ法测试了压电复合材料的介电性和压电性，最后讨论了压电复合材料的应用。     

先进陶瓷-金属复合材料在汽车制动系统应用研究

本文基于先进陶瓷-金属复合材料在汽车制动系统的应用前景,开展了教学方法的探索与实践。以培养适应社会发展的高水平人才为目标,通过及时优化教学方法来满足社会对人才的新需求。研究了先进复合材料在未来汽车领域的应用前景,重点分析先进材料在汽车制动系统的需求。通过真空热压烧结技术制备了性能优异的陶瓷-金属复合材料,根据制动系统对材料性能的要求,重点研究了复合材料的弯曲强度性能和摩擦磨损性能。引导学生以实际应用为驱动力,把学习与工程实践相联系,更好地掌握材料制备和性能优化的基本原理和方法。     

自蔓延高温合成技术及工艺研究

本论文以铝粉和三氧化二铁为主要原料,以二氧化硅、三氧化二铬等为添加剂,填涂在钢板上,并通过高温点燃的的形式,利用SHS技术和铝热反应,制备出陶瓷与金属结合的新型抗腐蚀材料。分析了实验的可行性及最终产物,研究了加热温度、粘合剂和添加剂以及不同的配比对反应和组织的影响,讨论了陶瓷和金属基体的界面结合机理。通过对材料各性能的综合分析,得出制备铁基复合材料的配比、制备工艺与材料的最佳性能之间的关系,为我们制备铁基复合材料提供理论指导。     

新型陶瓷-金属结合剂金刚石磨块的制备及磨削性能

设计并制备了一种新型陶瓷-金属结合剂金刚石磨块,测试了金刚石磨块的气孔率、体积密度和力学性能,并在相同条件下进行了陶瓷-金属结合剂金刚石磨块与陶瓷结合剂金刚石磨块磨削SiC增强高硅铝合金复合材料的对比试验。结果表明:陶瓷-金属结合剂对金刚石颗粒的把持力强;新型陶瓷-金属结合剂磨块的抗弯强度与硬度达到了66.02 MPa和74.6HRB;相同条件下,用陶瓷-金属结合剂金刚石磨块磨削SiC增强高硅铝合金复合材料,比用陶瓷结合剂金刚石磨块磨削得到的磨削表面质量更好,加工效率更高;当加工工件表面粗糙度为0.3μm时,新型陶瓷-金属结合剂磨块的材料去除率达到了普通陶瓷结合剂磨块的两倍,可以解决SiC增强高硅铝合金复合材料难加工的问题。     

FeAl/Al2O3陶瓷基复合材料--一种新型刀具材料

新型陶瓷刀具材料—— Fe Al金属间化合物 /Al2 O3 陶瓷复合材料的制备、性能以及新型陶瓷刀具的应用     

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.     

Changes in central steroid receptor expression, steroid synthesis, and dopaminergic activity related to the reproductive cycle of the ring dove

This review examines possible neural mechanisms involved in the expression of parental behavior in the ring dove, Streptopelia risoria. This avian species has proved an excellent animal model for studies concerning endocrine-behavior interactions for many years. Studies were performed to localize the expression of central androgen and progesterone receptor in both sexes. Expression of androgen receptor (androgen receptor immunoreactivity, AR-ir) was widespread but increased, similarly in both sexes, with increasing day-length. Progesterone receptor-immunoreactivity (PR-ir) was more localized in several discrete areas of the hypothalamus. Similarly, no sex differences were observed in PR-ir, and expression increased in birds maintained on long days. AR-ir demonstrated dramatic changes over the breeding cycle, being greatest in courting birds and almost undetectable in parenting birds of both sexes brooding their young. PR-ir showed a differential expression over the breeding cycle relative to its hypothalamic localization. PR-ir decreased in the tuberal hypothalamic area in brooding birds of both sexes; whereas in the preoptic area, PR-ir was maintained. Significant increases in dopaminergic activity during the parenting phase of the breeding cycle occurred in specific neural regions including the PVM and DMA. Studies demonstrated the ability of the diencephalon of both sexes of the ring dove brain to synthesize progesterone, with indications that in the male brooding dove, synthesis is increased. Finally, a model is presented that proposes a mechanism whereby these central systems may interact to result in the expression of full parental behavior in both sexes of the ring dove.     

Differential expression of CD95, Bcl-2, and Bax in rat gastric chief and parietal cells

Apoptotic cell death is common in the inflamed gastric mucosa, but its role in the regulation of cell homeostasis in normal gastric mucosa is unknown. We investigated the expression of CD95, Bcl-2, and Bax and their roles in the regulation of apoptosis in normal rat gastric mucosa and in cultures of highly enriched rat chief and parietal cells by immunostaining, Western blotting, and FACS. In intact tissue CD95, Bcl-2, and Bax were localized predominantly in the glandular base region in chief cells. In freshly isolated cells, expression of CD95, Bcl-2, and Bax was much more pronounced in chief cells than in parietal cells. A lower intracellular Bcl-2/Bax ratio suggesting a higher susceptibility to apoptosis was noticed in chief rather than in parietal cells. In extended cultures of parietal and chief cells, Bax expression was upregulated and Bcl-2 expression was downregulated. These regulatory changes, presumably caused by in vitro effects, were not associated with an increase in spontaneous apoptosis. Treatment of chief and parietal cells with Fas-ligand induced apoptosis of all CD95 expressing cells. Expression of CD95, Bcl-2, and Bax predominantly in chief cells suggests that in this cell type regulation of apoptosis may differ from that in parietal cells. Binding of FasL with functionally active CD95 receptors on chief and parietal cells may be relevant for induction of apoptosis in inflamed gastric mucosa.     

Extracellular breakdown of collagen by mice decidual cells. A cytochemical and ultrastructural study.

The interaction of antimesometrial decidual cells and collagen fibrils was studied by light microscopy and ultrastructural cytochemistry in fed and acutely fasted mice on days 9-11 of pregnancy. Fibrillar elements in the extracellular space consisted of collagen fibrils and filamentous aggregates (disintegrating collagen fibrils). Intracellular vacuoles exhibited typical collagen immersed in electron-translucent material (clear vacuoles) and faint cross-banded collagen immersed in electron-opaque material (dark vacuoles). Fibrillar elements showed extracellular acid phosphatase activity which was stronger in the region of mature decidua than in predecidual cells region in all animals; it was conspicuous in mature decidua of fasted animals. Intracellular acid phosphatase activity was observed in dark vacuoles and lysosomes, and was absent in clear vacuoles in all cells studied. Since acid phosphatase activity reflects the presence of lysosomal hydrolases in general, the results indicate that breakdown of extracellular collagen occurs by release of lysosomal enzymes by decidual cells and also by internalization of collagen for intracellular degradation in fed and fasted mice. Collagen breakdown may be part of the process of tissue remodeling in mature and predecidual regions, however, in mature decidua, collagen breakdown is enhanced and may therefore contribute to nutrition of the fetus, specially in acutely fasted mice.     

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.     

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.     

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.     

数字工厂--数字制造教学与研究中的技术个案

１IntroductionWiththeimpactofinformationtechnologyandcomputernetworking熏thecoreofmanufacturingactivitieshasshiftedfromphysicalproductiontosystematicprocessingofinfor鄄mation眼１演．Tocaterforthischange熏manufacturerstodaymustbewellversedwiththecomputerapplicationsinmanufacturing．Thiscoupleswiththeadventofhigh－resolu鄄tiongraphics熏high－speedcomputing熏anduserintegrationdevices鸦virtualmanufacturinghasemergedasamajornewtechnologyinrecentyears眼２演．Theimpactforthechangeisparticularlypromin…     

Immunohistochemistry of neuronal nitric oxide synthase and protein nitration in the striatum of the aged rat

To ascertain the possible implications of the nitric oxide (NO*) producing system in striatal senescence, and by using immunohistochemistry and image-processing approaches, we describe the presence of the enzyme nitric oxide synthase (NOS), the NADPH-diaphorase (NADPH-d) histochemical marker, and nitrotyrosine-derived complexes (N-Tyr) in the striatum of adult and aged rats. The results showed neuronal NOS immunoreactive (nNOS-IR) aspiny medium-sized neurons and nervous fibres in both age groups, with no variation in the percentage of immunoreactive area but a significant decrease in the intensity and in the number of somata with age, which were not related to the observed increase with age of the striatal bundles of the white matter. In addition, NADPH-d activity was detected in neurons with morphology similar to that of the nNOS-IR cells; a decrease in the percentage of area per field and in the number of cells, but an increase in the intensity of staining for the NADPH-d histochemical marker, were detected with age. The number of neuronal NADPH-d somata was higher than for the nNOS-IR ones in both age groups. Moreover, N-Tyr-IR complexes were observed in cells (neurons and glia) and fibres, with a significant increase in the percentage of the area of immunoreaction, related to the increase of white matter, but a decrease in intensity for the aged group. On the other hand, we did not detect the inducible isoform (iNOS) either in adult or in aged rats. Taken together, these results support the contention that NADPH-d staining is not such an unambiguous marker for nNOS, and that increased protein nitration may participate in striatal aging.     

Flow instability due to cryogenic cavitation in the downstream of orifice

Flow instability in LRE (liquid rocket engine) occurs due to various reasons such as flow interactions with valve, orifice and venturi, etc. The inception of cavitation, especially in the propellant feeding system, is the primary cause of mass and pressure oscillations because of the cyclic formation and depletion of cavitation. Meanwhile, the main propellant in a liquid rocket engine is the cryogenic fluid, which properties are very sensitive to temperature variation. And the change of propellant properties to temperature variation by thermodynamic effect needs to be properly taken into account in the flow analysis in order to understand basic mechanisms for cryogenic cavitation. The present study focuses on the formation of cryogenic cavitation by using the IDM model suggested by Shyy and coworkers. The flow instability was also numerically investigated in the downstream of orifice with a developed numerical code. Calculation results show that cryogenic cavitation can be a primary source of flow instability, leading to mass fluctuations accompanied by pressure oscillations. The prediction of cavitation in cryogenic fluid is of vital importance in designing a feeding system of an LRE. This paper was recommended for publication in revised form by Associate Editor Jun Sang Park Changjin Lee received his B.S. and M.S. degrees in Aeronautical Engineering from Seoul National University in 1983 and 1985. He then went on to receive his Ph.D. degree from University of Illinois at Urbana- Champaign in 1992. Dr. Lee is currently a Professor at the department of Aerospace Engineering at Konkuk University in SEOUL, Korea. His research interests are in the area of combustion instabilities of hybrid, liquid rocket and jet propulsions. Tae-Seong Roh received his B.S. and M.S. degrees in Aeronautical Engineering from Seoul National University in 1984 and 1986. He then went on to receive his Ph.D. degree from Pennsylvania State University in 1995. Dr. Roh is currently a Professor at the department of Aerospace Engineering at Inha University in Incheon, Korea. His research interests are in the area of combustion instabilities, rocket and jet propulsions, interior ballistics, and gas turbine engine defect diagnostics.