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简要叙述了X射线反射式衍射光学元件──Bragg-Fresnel多层膜元件产生和发展的过程.介绍了它的基本原理及它的设计和制作步骤.对其应用前景作了简要分析,并对开展这方面的研究工作提出了一些设想. 相似文献
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光学系统中的二元光学元件 总被引:7,自引:4,他引:7
本文回顾了二元光学元件的发展过程,简要介绍了用于校正光学系统象差的二元光学元件的设计及制作过程,对其应用领域,局限性和发展前景作了简要分析。 相似文献
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本文对挤压珩磨技术的基本原理、工艺特点等作了简要介绍,同时以某车辆传动装置中典型液压元件为例,阐述了挤压珩磨技术在液压元件清理上的应用。 相似文献
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将射流元件用于水力振荡器可以满足油井解堵对压力振荡幅度和频率的要求。主要介绍了射流元件的附壁切换原理和振荡解堵器的工作原理。详细阐述了射流元件的主要结构,以及喷嘴、控制道、位差、张角、劈尖、排空道和输出道的尺寸、方位等的设计方法,简要解释了各参数的概念及其对射流元件性能的影响。 相似文献
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超超临界锅炉是今后我国火电建设的发展趋势,蒸汽压力和温度的提高对受压元件金属材料的焊接工艺提出了特殊的要求.本文针对我国首台国产化百万等级超超临界锅炉机组研发和制造过程中遇到的各种新钢材特性做简要介绍和分析,通过工艺试验和焊接工艺评定,针对新钢材和不同种类的受压元件开发出了适合的焊接工艺,确保了超超临界锅炉受压元件的焊接质量,对今后类似炉型受压元件制造工艺具有一定的借鉴意义. 相似文献
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采用TD法在Cr12MoV冷作模具钢表面制备VC涂层,在摩擦磨损试验机上考察VC涂层与钢球、钢柱和陶瓷球配副时的摩擦磨损性能,利用扫描电镜、粗糙度测量仪和X射线衍射仪(XRD)分析涂层磨损前后表面及界面的形貌、表面粗糙度和物相组成.结果表明,与不同摩擦副配副时,VC涂层摩擦因数随着磨损时间增加先增大后趋于平稳,磨损率随着磨损时间增加而减小,其中与钢柱配副时摩擦因数最小,磨损率最低.与不同摩擦副配副时,VC涂层磨损机制与失效形式不同,与钢球配副时VC涂层磨损机制为磨粒磨损,失效形式为划痕和剥落坑;与钢柱配副时VC涂层磨损机制为黏着磨损和疲劳磨损,失效形式为犁沟和片层状剥落;与陶瓷球配副时VC涂层磨损机制为氧化磨损,失效形式为脆性断裂. 相似文献
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脉冲GMAW焊接极性对高压环境下焊缝成形的影响 总被引:1,自引:0,他引:1
高压环境会造成焊接电弧收缩,焊接过程较不稳定。鉴于脉冲熔化极气体保护焊(Pulsed gas metal arc welding,GMAW-P)具有热输入量可控、电弧挺度较好等特点,将其应用于高压环境下是一个有益尝试。开展压力在0.1~1.0 MPa范围内不同极性下的干法GMAW-P试验,分析随着环境压力升高电流电压波形图的变化趋势,由此确定焊接极性不同时焊接过程稳定性随环境压力升高的变化规律;在此基础上,对比分析不同极性下GMAW-P焊接飞溅及焊缝成形随压力升高的变化规律。随着环境压力增加,在直流反接情况下,电流电压波形周期性逐渐减弱,焊接过程趋于不稳定,飞溅逐渐增多,焊缝成形变差;而采用直流正接方式时,高压下电流电压波形的周期性虽然不及常压下稳定,但相较于同一压力下的直流反接方式,周期规律性有所增强,焊接过程相对稳定,且焊接时产生的飞溅比采用直流反接方式时的飞溅少且颗粒小。另外,随环境压力增加,两种极性GMAW-P焊缝宽度均有变窄的趋势,余高也随之增加。对高压环境下不同焊接极性GMAW-P的电弧形态及相应电弧力进行深入探讨,明确了上述现象出现的原因,为高压环境下焊接工艺的改进提供有效的理论依据。 相似文献
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研究了基于电火花机械复合磨削技术加工的反应烧结碳化硅(RB-SiC)陶瓷的表面特征。用电火花机械复合磨削(EDDG)、电火花磨削(EDG)以及普通磨削(CG)三种方法加工RB-SiC陶瓷,并采用激光共聚焦显微镜和扫描电子显微镜对加工后的SiC陶瓷的表面粗糙度、表面形貌及微观裂纹进行测量和对比试验,获得了RB-SiC陶瓷的EDDG加工特性。实验显示:EDDG加工的RB-SiC陶瓷的表面粗糙度优于EDG加工的表面粗糙度,为0.214 9μm,但比CG加工的表面粗糙度0.195 6μm略差。对加工后的SiC陶瓷表面形貌观察显示,传统磨削加工后的表面存在明显划痕,EDG加工表面主要由放电凹坑组成,而EDDG加工表面同时存在放电凹坑和磨削划痕;另外,传统磨削表面也存在磨削裂纹和晶界裂纹,但EDG加工后的表面只存在热裂纹,而EDDG加工后的表面存在磨削裂纹和热裂纹,不过热裂纹可以用金刚石磨粒磨削去除。对比实验显示RB-SiC陶瓷的EDDG加工与EDG和CG加工获得了不同的表面特征。 相似文献
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The psychological phenotype of females with fragile X syndrome (FraX) is discussed, focusing primarily on empirical findings over the past decade and on studies of probands with the full mutation (FM). A developmental approach is used to help characterize specific patterns of cognitive, neuropsychological, social, emotional, and behavioral functioning across the lifespan of females with FraX. Approximately half of females with the syndrome present with cognitive abilities that fall in the borderline to mentally retarded range, and the remaining females with average intellectual functioning may experience relative deficits in math achievement and problems with attention and executive functioning. Reports of socio-emotional functioning are somewhat inconsistent, due in part, perhaps, to methodological differences in study design. To date, much of what we understand about the psychological phenotype of FraX is based on cross-sectional studies of girls and women with the disorder. Symptoms associated with shyness, and social anxiety and avoidance have been reported in some school-age, adolescent, and adult females with FraX. Only recently have efforts begun to identify the developmental trajectory of FraX in infants and toddlers. There is a void of information specific to these developmental periods. Identifying key deficits in cognitive and socio-emotional functioning has important implications for early detection and intervention for girls with FraX. Directions for future research are discussed. 相似文献
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优化设计了频率带宽为1 Hz~10 k Hz的空心磁芯感应式磁传感器。首先提出空心结构的磁芯,分析空心磁芯的退磁因数和有效磁导率,并仿真、实测空心磁芯感应线圈的磁通,得出一定壁厚的空心磁芯感应线圈的磁通可以等于相同长径比棒状磁芯感应线圈的磁通。然后分析空心磁芯感应式磁传感器的灵敏度与噪声,通过数学算法优化噪声公式达到要求的噪声指标和较低的重量。为验证理论分析,设计空心磁芯感应式磁传感器,在屏蔽室对空心磁芯感应式磁传感器的性能进行测试,频率高于400 Hz时灵敏度为0.73 V/n T。100 Hz时噪声为0.06 p T/Hz1/2,总重量为80 g。实测的空心磁芯感应式磁传感器的灵敏度与噪声和理论分析一致。空心磁芯感应式磁传感器与THEMIS相比具有噪声低、重量轻的优点,能够满足空间电磁探测的实用条件。 相似文献
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提出一种高强钢/碳纤维增强复合材料(CFRP)的多材料零件连接成形一体化加工工艺,利用热冲压工艺对高强钢和CFRP预浸料进行连接并成形高强钢/CFRP多材料零件。研究热冲压过程中不同的淬火温度下多材料复合板的制备工艺,并对试样中钢板进行微观观测,最后对复合件进行弯曲试验。微观检测结果表明,该工艺下钢板组织为全马氏体组织。三点弯曲试验结果表明,未铺设CFRP试样、铺设2层CFRP试样和铺设4层CFRP试样的弯曲角度分别为130°、110°和104°。对弯曲试验的力位移曲线进行积分,计算试样的能量吸收量,得到如下结论:未铺设CFRP试样、铺设2层CFRP试样和铺设4层CFRP试样的能量吸收量分别为9410 J、9692 J和10 050 J;铺设2层CFRP的试样和铺设4层CFRP的试样相比于未铺设CFRP的试样,能量吸收量分别增加2.9%和6.8%。 相似文献
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Ricardo Paniagua Manuel Nistal Francisco J. Sez Benito Fraile 《Microscopy research and technique》1991,17(2):241-243
The ultrastructure of the progressive testicular involution with advancing age in men is reviewed. There is no definite age at which testicular involution begins, and the onset and severity of testicular lesions are subjected to pronounced individual variations. Hormone studies also indicate great individual variations, and subtle changes in both the testis and the pituitary develop progressively with age. Testicular size, sperm quality, and numbers of all germ cell types, Sertoli cells, and Ley dig cells decrease with age. The volume occupied by the seminiferous tubules decreases, whereas that occupied by the testicular interstitium remains constant. The most frequent histological pattern of the aging testis is a mosaic of different seminiferous tubule lesions, varying from tubules with complete, although reduced, spermatogenesis, to completely sclerosed tubules. The tubules with complete spermatogenesis may show numerous morphological abnormalities in the germ cells, including multinucleation. Abnormal germ cells degenerate causing Sertoli cell vacuolation. These vacuoles correspond to dilations of the extracellular spaces resulting from the premature exfoliation of germ cells. Degenerating cells that are phagocytosed by the Sertoli cells give rise to an accumulation of lipid droplets in the Sertoli cell cytoplasm. The loss of germ cells begins with the spermatids, but progressively affects the earlier germ cell types, and tubules with maturation arrest at the level of the spermatocytes or spermatogonia are observed. The Sertoli cells show morphological abnormalities such as dedifferentiation, mitochondrial metaplasia, and multinucleation. Germ cell loss is associated with thickening of the tunica propria. When all seminiferous epithelial cells have disappeared, only an intensely collagenized tunica propria with myoid cells remains (sclerosed tubules). The Ley dig cells progressively dedifferentiate with a decrease in the quantity of both smooth endoplasmic reticulum and mitochondria, together with an accumulation of lipid droplets, crystalline inclusions, and residual bodies, and formation of multinucleate cells. The development of tubular involution with age is similar to that observed after exprimental ischemia, suggesting that vascular lesions may play an important role in age-related testicular atrophy. 相似文献