共查询到20条相似文献，搜索用时 49 毫秒
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针对手表主夹板精冲孔模结构进行改进,并对凸模固定板中少数坐标位置度超差孔进行精度修正,提高了手表主夹板精冲孔模具的冲孔坐标位置度精度及工作稳定性。 相似文献
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Willis G. Hazard 《Journal of The Franklin Institute》1934,217(5):571-590
An apparatus is described for recording general atmospheric dust. The full-scale range of the present model of approximately 120 × 106 particles per cubic foot of air may be increased or decreased as desired. The dust concentrations measured are far below smoke concentrations. The method is to impinge dust on a slowly moving strip of transparent film, and to measure the deposit by a comparison of two beams of light, one passing through the dusty film, the other through clean film. The decrease in transmitted light due to the dust is balanced automatically by a motor-driven optical wedge in the unobstructed beam. The position of this wedge is recorded on a chart. Dusty air is sampled continuously for long periods. Rapid fluctuations of a few minutes in length are registered. In this, and in the fact that it is direct-reading, without tedious laboratory quantitation, the recorder offers distinct advantages over the present dust determinators, almost all of which take momentary samples. A different calibration is needed for different dusts. The machine may be adapted to laboratory or field use. In factories, auxiliary blowers may be operated through relays, when the dustiness exceeds a specified level. 相似文献
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We have performed microfluidic experiments with erythrocytes passing through a network of microchannels of 20–25 μm width and 5 μm of height. Red blood cells (RBCs) were flowing in countercurrent directions through microchannels connected by μm pores. Thereby, we have observed interesting flow dynamics. All pores were blocked by erythrocytes. Some erythrocytes have passed through pores, depending on the channel size and cell elasticity. Many RBCs split into two or more smaller parts. Two types of splits were observed. In one type, the lipid bilayer and spectrin network were cut at the same time. In the second type, the lipid bilayer reconnected, but the part of spectrin network stayed outside the cell forming a rope like structure, which could eventually break. The microporous membrane results in multiple breakups of the cells, which can have various clinical implications, e.g., glomerulus hematuria and anemia of patients undergoing dialysis. The cell breakup procedure is similar to the one observed in the droplet breakage of viscoelastic liquids in confinement. 相似文献
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Jeroen A. van Kan Ce Zhang Piravi Perumal Malar Johan R. C. van der Maarel 《Biomicrofluidics》2012,6(3)
An easy method is introduced allowing fast polydimethylsiloxane (PDMS) replication of nanofluidic lab-on-chip devices using accurately fabricated molds featuring cross-sections down to 60 nm. A high quality master is obtained through proton beam writing and UV lithography. This master can be used more than 200 times to replicate nanofluidic devices capable of handling single DNA molecules. This method allows to fabricate nanofluidic devices through simple PDMS casting. The extensions of YOYO-1 stained bacteriophage T4 and λ−DNA inside these nanochannels have been investigated using fluorescence microscopy and follow the scaling prediction of a large, locally coiled polymer chain confined in nanochannels. 相似文献
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Brian Southworth 《Endeavour》1983,7(1):19-23
The unit of energy used in particle physics is the electronvolt (eV) which is the amount of energy picked up by an electron passing between the poles of a one-volt battery. Energies of a few eV are sufficient to pull electrons from atoms. Energies a million times higher (MeV,) are involved when dealing with nuclear phenomena such as fission in reactors. To study the constituent particles of the nucleus, energies at least a thousand times higher still (GeV), are needed. The CERN antiproton project described here makes possible the highest collision energies ever achieved, but the total energy in the proton and anti-proton beams is still very small. What is important is that this energy is concentrated in a tiny amount of matter in the particle beam. 相似文献
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E.W. Tschudi 《Journal of The Franklin Institute》1927,204(2):219-225
A cold cathode discharge tube has an auxiliary tube attached from which cathode-rays are projected against the main cathode. A photo-electric cell, attached to a monochromatic illuminator, is used to measure relative intensity distribution of Hγ and Hδ respectively, from the main cathode through the cathode dark space into the negative glow with and without excitation of the auxiliary tube. When the main cathode is bombarded by the electron stream the intensity of spectral illumination in the negative glow is increased by about 20 per cent. This increase does not result from the mere addition of an illumination, which appears when the auxiliary tube is alone excited, to the illumination of the main discharge, but may be attributed to the production of soft X-rays in the gas which are capable of exciting the gas molecules.R. Seeliger and co-workers have investigated spectrophotometrically the several characteristic sections of a cold cathode discharge tube. Their method consisted of an examination, with a microphotometer, of spectrograms taken at points along the discharge. The intensity distribution of any spectral line was found continuous in passing from one portion of the discharge to another, e.g., from the Faraday dark space into the positive column, and that the maxima of illumination for different lines appeared displaced relative to one another.A. Wehnelt and A. Jachan demonstrated with several experimental arrangements the effect of bombarding the cold cathode of an ordinary discharge tube with a beam of cathode-rays. There resulted an increase in the total intensity of illumination in the tube together with a shrinkage of the cathode dark space.The purpose of the present investigation was to examine the effect such an electronic bombardment would produce upon the spectral intensity distribution near the cathode of a hydrogen discharge in Hγ and Hδ alone were capable of investigation. 相似文献
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V.K. Zworykin 《Journal of The Franklin Institute》1933,215(5):535-555
For many experiments in physics and in some engineering applications, it is necessary to produce electron bundles, or as they are often called, “electron beams” of considerable intensities.Various methods have been used for directing a cloud of electrons evaporated from an emitting surface into a beam and then concentrating this beam to a desired degree. The concentration of electron beam in high vacuum depends entirely upon fields of force, either electric or magnetic, while in low vacuum or in rarified rare gas it depends also upon the action of the field of ionized gas molecules.In high vacuum the fields of force act upon the electron beam in a manner similar to the action of lenses upon a beam of light. An improperly shaped field produces effects similar to spherical aberration in poorly corrected lenses; non-uniform velocity of electrons in the beam results in effects similar to chromatic aberration of light.This optical analogy is not perfect.In the case of the electron beam the velocity varies continuously throughout most of the path and indices of refraction employed usually are greater than in the optical case. Moreover, space charge in beams of high intensity limits the concentration attainable; consequently, even theoretically, an electron beam can never be brought up to a mathematical point as in the case of light optics. Many secondary effects are present which complicate the problem still further.In focusing electron beams, both electrostatic and electromagnetic methods have been used extensively. The electrostatic method, however, seems to be preferable, especially when the beam is to be deflected. Precautions should be taken not to destroy the focusing of the beam during deflection. 相似文献
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根据火灾温度的变化,考虑火灾高温对结构钢屈服强度和梁塑性弯矩的影响,分析了火灾均布冲击荷载作用下简支钢梁的动力响应,计算了火灾场简支钢梁在均布冲击荷载作用下的残余变形,分析表明冲击荷栽和火灾高温钢梁的变形具有显著的影响。 相似文献
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目前,代表性国家形成合诉与分诉两种诉讼制度,不同的制度对专利侵权纠纷和解的影响并不相同,因此,分别构建合诉与分诉制度下专利权人和潜在侵权人之间专利诉讼的两回合博弈模型,通过逆向归纳法,从成本-收益角度对博弈模型进行求解及分析。结果表明：潜在侵权人和解率与和解金额负相关,与专利权人胜诉后的期望收益正相关;专利权人撤诉率与和解金额以及潜在侵权人和解费用负相关,与潜在侵权人诉讼费用正相关。与此同时,在分诉博弈模型中,潜在侵权人和解率还与专利权人赔偿诉讼费用负相关,专利权人撤诉率与潜在侵权人在侵权裁判后的市场损失正相关。因此,中国应提高专利侵权损害赔偿金额、适时借鉴分诉制度,企业也应当加大创新研发投入。 相似文献
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拍弦是网球传接球过程中直接的载体．它的好坏直接影响到传接球的质量和球员技术的发挥。通过对网球击球的力学分析以及拍弦种类、强度的了解,旨在提高网球爱好者对网球拍弦的认识,为网球爱好者在选择拍弦时提供参考。 相似文献
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本文分析了现代城市交通信号灯控制与管理的不合理性,进而提出一款更具人性化、智能化的城市交通灯控制系统的软硬件电路设计方案.该方案突破了传统固定时间模式,能根据车流量大小自动调节车辆通行时间,并考虑特殊车辆设置了紧急通道转换开关.最后通过PROTEUS仿真说明了系统制作过程与调试结果. 相似文献
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科学发现是贯穿于科学研究过程中的创新活动。关于科学发现的过程,历来是科学学、心理学、科学哲学等学科研究的中心课题。本文拟借鉴已有的研究成果,从创造心理学、科学哲学、科学知识社会学、科学史等方面对科学发现的过程与本质作点初步探讨。 相似文献
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文章通过对某商用微车的车架横梁进行结构优化,更改原堆材料式的结构方式,取消两层钣金零件大面贴合焊接的连接,从而使得车架横梁结构巧妙,材料利用率好,成本更低。对比原来设计,新的横梁在结构上更精简,同时有利提升横梁的刚度强度。 相似文献
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Nathaniel D. Poor 《The Information Society》2013,29(2):73-83
The Internet is not only an object of and a tool for study; it is also both simultaneously global and local. In order to address how global and how local it is, this study compares the news content of 1 week from four different computer news web sites in four different countries (using four different languages). These sites use the same code base and all strive to be the same in terms of computer culture. They are global in their reach and in the news they cover, yet they are all local in terms of language and geography. They are ideal locales to study how forces of the global and the local play out on the highly connected Internet, using Google language tools for translation. Findings were surprising in that they showed very little in terms of a pattern of any sort. This is similar to a 1953 UNESCO study of newspapers, but strange in that given the passing of 50 years and the connectedness of the Internet, greater overlap was expected. Link destinations for stories that were on more than one site were also examined, and the Japanese site had more in common with the American site while the two European sites were more alike in this lens. This is also surprising, given that an East/West split was expected. Little work in this specific area was found, and this study highlights some of the questions and methodological difficulties that need to be addressed. 相似文献
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中介语理论是从第二语言学习者的心理出发,结合其语言环境,创造性地建立一个新的语言系统,即学习者自己构建的一种在母语和目的标语之间的过渡性语言。这种过渡性的语言既非母语,又非目的语,而是介于二者之间的一种语言体系。在产生这种语言体系的同时也相应地产生一种区别于母语文化及目的语文化的"中介文化"。关注"中介文化"对于英语阅读能力的提高有一定启示。 相似文献