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1.
It has been shown that electrons with 11.5 volts energy can dissociate a hydrogen molecule into its two constituent atoms, but up until recently no experiments have been performed to see whether fast positive ions are able to dissociate hydrogen.In the present experiments Li or Cs positive ions of various velocities are produced in a tube containing hydrogen molecules. The tube is immersed in liquid air, and the rate of decrease of pressure of hydrogen is measured as a function of the velocity of the positive ions. It is found that with no positive ions entering the tube there is a certain decrease in the pressure of the hydrogen due to its thermal dissociation on the hot filament and its subsequent condensation on the cold walls of the tube. With ions of energies from 15 to 320 volts flowing in the tube the rate of decrease of pressure is greater, showing a formation of some condensible product due to the action of the ions.The rate of pressure decrease with the voltage applied has been found to be proportional to the ion current flowing. The rate per unit current is proportional to the pressure; and the rate per unit current per unit pressure is practically independent of the voltage for Li and Cs ions of energies from 15 to 320 volts.The effect has been shown not to be due to secondary electrons.The process may be due to the formation of alkali hydrides in the gas phase. The number of hydrogen molecules disappearing per positive ion entering the tube varies from 0.01 to 0.5. No critical potentials have been found in this experiment, in disagreement with recent experiments of Leipunsky and Schechter.  相似文献   

2.
The secondary electron emission from alkaline-earth oxide-coated cathodes has been investigated under both continuous and pulsed bombardment. Various factors affecting the yield, such as dependence upon primary voltage, collecting voltage, temperature, time, and angle of incidence, are noted, and the present state of the theory is discussed.Experiments have been performed with three types of apparatus. Yield vs. Energy data reveal values of δ of 4–7 at room temperature, with a more or less flat maximum at approximately 1,000 volts primary energy.The yield increases with temperature in an exponential manner, and plots of log Δδ (i.e. δK° ? δ300°K) vs. 1/T give straight lines. Values of Q1 between 0.9 – 1.5 eV. are generally indicated, and from extrapolation of these curves, yields exceeding 100 at 850° C. are deduced. The secondary emission depends upon the degree of activation, and increases with enhancement of the thermionic emission characteristics. Short-time effects such as growth or decay of secondary current after the onset of primary bombardment or persistence after the cessation of bombardment have not been observed, and values of yield obtained by pulsed methods are in accord with those obtained under D.C. conditions. Tail phenomena reported by J. B. Johnson and interpreted as “enhanced thermionic emission” from oxidecoated cathodes become manifest only under experimental conditions characterized by certain space-charge effects, and have been effectively simulated by bombarding a tantalum target adjacent to an electron-emitting tungsten filament. Various measurements of the energy distribution of secondary electrons as a function of primary voltage and temperature have been obtained. It was observed that the average energy of the secondary electrons decreases with temperature at a rate which more than compensates for the increase in the number of secondaries emitted per incident primary. The mechanism of the observed dependence of yield upon temperature is not well understood. Various alternative explanations are discussed and, in the light of the present state of our knowledge, regarded as untenable.  相似文献   

3.
Throughout this paper data have been presented showing that the apparent inconsistency of the reported dielectric strength behavior of insulating liquids can be satisfactorily correlated if proper consideration be given to the state of the “purity” of the liquid itself. As a result it is suggested that insulating liquids should be classified as (a) “pure,” indicating those liquids free from dissolved gases as primary “impurities”; and (b) “impure,” including those liquids which contain dissolved gas. The breakdown mechanism depends on the distinctive behavior of these two general classes. “Pure” liquid breakdown is a function of charged particle formation. In part, this may be caused by the assumption of a charge by molecular aggregates, colloidal-like in nature. In part, the charge may arise from molecular ionization by collision. The latter occurs chiefly in the voltage range immediately preceding electrical rupture and is the chief cause of “pure” liquid insulation failure. The presence of the first type of charge—that is, the existence of a difference of potential between molecular aggregates and the liquid—is chiefly responsible for the variation in the time factor to breakdown.The breakdown of “impure” liquids is a function of dissolved gas elimination. This dissolved gas is eliminated as a result of changing solubility produced (a) by electro-striction effects, or (b) by changing pressure or temperature. The presence of secondary impurities such as dust particles and fibers, acts chiefly through the effect on increasing gassing tendencies.It is suggested further that the localization of dielectric breakdown in liquids, irrespective of the type or degree of “purity,” is chiefly in the “neutral membrane” located near the electrodes and formed by the discharge of particles. Such a “neutral membrane” results in a space charge effect giving marked drop in potential and as a result promoting ionization by collision effects in “pure” liquids and electro-striction effects in “impure” liquids.  相似文献   

4.
A study was made of the variation with gas pressure of the potential fall between striæ in the positive column of a discharge through hydrogen because in this gas the distances between the striæ change with pressure in an anomalous manner first noted by Willows. With decrease of pressure the stria distances at first increase, pass through a maximum value and then through a rather sharp minimum value at a pressure between 1 mm. and 2 mm. The color of the striæ was found to be bluish in the pressure region of minimum separation and reddish at other pressures.  相似文献   

5.
A short review is included of previous work on the blackening of photographic plates by positive rays and rays of an analogous nature.The blackening of Eastman x-ray plates, by positive ions, has been measured as a function of the energy of the ions of Li, Na, K, Rb, and Cs. The energy of the ions required to produce a photographic density of D = 0.3 with a one minute exposure at a current density of 1.32 × 10?8 amperes per cm.2 ranged from 1420 electron-volts in the case of cæsium to 860 electron-volts in the case of Li7. Approximately 105 ions are required at these energies to render developable one silver-halide grain. For a threshold density, D = 0.04, under the same conditions the energy ranged from approximately 920 to 460 electron-volts for Cs and Li7 respectively.Sensitivity comparisons were made between x-ray plates and process and schumannized process plates. Potassium ions with an energy as low as 137 electron-volts were recorded on Schumann plates, and it is possible that positive ions of one-third this energy can be recorded.  相似文献   

6.
The ratio of the number of electrons striking a surface to the number leaving it was determined under various conditions for a number of metals contaminated by the condensation of grease vapors on them.The curves showing the variation of secondary emission with incident electron energy (evidently characteristic of the contamination rather than of the metals) are similar for all the targets and resemble the results obtained by Gehrts. Reducing the amount of the contamination by heating the metals at first reduces the secondary emission until it falls below that expected from a clean metal. The emission then increases with further heating and the characteristics of the metal appear. The variation of the work function during the “outgassing” process is indicated by this increase of the secondary emission followed by a decrease of the secondary emission as the process continues.  相似文献   

7.
若干氢键团簇的纳秒和飞秒激光光电离及从头计算研究   总被引：1，自引：0，他引：1  
利用纳秒和飞秒激光及飞行时间质谱仪对氮化苯 溶剂分子团簇的多光子电离和离解进行了研究。通过解决实验中的技术难题,实现了在气相条件下实验研究嘧啶与水团簇的多光子电离。首次观测到该团簇的多光子电离质谱,发现电离后形成了质子化团簇系列,通过团簇浓度随激光强度的变化以及理论计算,阐明了团簇内质子转移过程,以及电荷分布和质子转移过程随着团簇尺寸的变化;首次观测到吡啶团簇在飞秒光电离过程中的质子化和非质子化团簇离子共存的现象。非质子化吡啶二聚体离子的存在及高水平下理论计算表明,吡啶分子之间可以形成C -H N氢键,对文献中报道的结果给予了纠正,提供了弱氢键团簇中质子转移的一个极佳范例;首次研究并获得了嘧啶 甲醇以及哒嗪 甲醇氢键团簇的多光子实验研究结果.实验发现团簇经激光电离后只产生质子化产物,并从理论计算得到各种团簇的稳定构型,阐明了团簇发生电离后质子转移反应的过程和机理  相似文献   

8.
Spatially varied surface treatment of a fluorescently labeled Bovine Serum Albumin (BSA) protein, on the walls of a closed (sealed) microchannel is achieved via a well-defined gradient in plasma intensity. The microchips comprised a microchannel positioned in-between two microelectrodes (embedded in the chip) with a variable electrode separation along the length of the channel. The channel and electrodes were 50 μm and 100 μm wide, respectively, 50 μm deep, and adjacent to the channel for a length of 18 mm. The electrode separation distance was varied linearly from 50 μm at one end of the channel to a maximum distance of 150, 300, 500, or 1000 μm to generate a gradient in helium plasma intensity. Plasma ignition was achieved at a helium flow rate of 2.5 ml/min, 8.5 kVpk-pk, and 10 kHz. It is shown that the plasma intensity decreases with increasing electrode separation and is directly related to the residual amount of BSA left after the treatment. The plasma intensity and surface protein gradient, for the different electrode gradients studied, collapse onto master curves when plotted against electrode separation. This precise spatial control is expected to enable the surface protein gradient to be tuned for a range of applications, including high-throughput screening and cell-biomolecule-biomaterial interactions.  相似文献   

9.
Several matters pertaining to the part played by tube walls, and surface and space charges in electrical discharges through rarefied gases, are briefly discussed, and experiments are described which throw light on some of the processes involved in such discharges. Measurements made under identical conditions of the falls of potential between striæ in the positive columns of discharges in hydrogen at various pressures in two glass tubes of different diameters showed that for pressures above 1.1 mm. these falls were increasingly greater in the larger tube. The results of experiments done with discharges produced under unusual conditions and bearing on the radial and axial fields present in the positive columns of discharges are described, and photographs of some of the discharges are reproduced in a part of which the positive column was made to pass through a long metal tube placed inside of the glass discharge tube, the two ends of the metal tube being at times both open and at other times both closed with wire gauzes of fine mesh. The potential assumed by the metal tube and the current flowing through its walls were measured, and special experiments were done to elucidate the process by which the current manages to penetrate the more or less field-free space inside the metal cylinder. The distributions of the space and surface charges along the length of a glass discharge tube were measured separately, at least roughly, and the nature of these distributions was found to depend markedly upon whether the anode or the cathode of the discharge tube was connected to earth, although the combined effects of the two charges of necessity produced the same field distribution within the discharge tube in both cases. The gases used in the experiments were air and hydrogen.  相似文献   

10.
陈洁  焦建玲  李方一  李兰兰 《资源科学》2016,38(7):1373-1382
确定行业二氧化碳减排的优先次序并实施差别对策对减排目标的实现具有重要意义。本文基于投入产出Ghosh模型和敏感性分析,从结构减排、技术减排两个方面,提出了国家或区域行业二氧化碳减排优先次序确定的一般方法。将该方法应用到中国行业减排,采用2002年和2012年全国投入产出表和行业碳排放数据,依据各行业的经济增长贡献率、感应度系数、边际增长的完全碳排放量、二氧化碳排放强度年均下降率和二氧化碳排放强度-增加值弹性5个代表性指标,确定行业减排的优先次序,并提出差别的减排对策建议。结果表明：在考察的40个行业中,技术减排优先级I的行业包括非金属矿物制品业在内共18个,结构性减排优先级I的行业包括石油和天然气开采业在内共13个,针对行业技术减排和结构减排的三级优先次序,可以确定四类减排对策。应用研究一方面证明了本文设计的一般方法的实用性和科学性,另一方面为中国制定分行业的减排政策提供了参考。  相似文献   

11.
This article examines the financial impact of software patent subject matter eligibility by analyzing divergent legal practices by courts and administrative bodies. We illustrate these effects by empirical evidence relating to case-law decisions, notably Alice Corp. Pty. v. CLS Bank International (hereafter, Alice v. CLS Bank or Alice). In order to eliminate the ambiguity of legal practice of these two systems in relation to patent law, the patent office has been inspired by and aligned with the work of the judicial system and developed an analytical model concerning the application of the law. The effectiveness of this workable standard is then evaluated on the basis of its influence on firm value. The results suggest that the publication of the workable standard, the United States Patent and Trademark Office (USPTO) Interim Guidance, has had a significant positive impact on companies which have completely modified their patent strategies in line with the new USPTO policy. We conclude that the uniformity of legal approach by the judicial and administrative systems decreases legal uncertainty and contributes to financial performance. Consequently, a workable standard with clear and precise legal approaches enables the patent system to develop efficiently.  相似文献   

12.
Tunable resistive pulse sensing (TRPS) has emerged as a useful tool for particle-by-particle detection and analysis of microparticles and nanoparticles as they pass through a pore in a thin stretchable membrane. We have adapted a TRPS device in order to conduct simultaneous optical measurements of particles passing through the pore. High-resolution fluorescence emission spectra have been recorded for individual 1.9 μm diameter particles at a sampling period of 4.3 ms. These spectra are time-correlated with RPS pulses in a current trace sampled every 20 μs. The flow rate through the pore, controlled by altering the hydrostatic pressure, determines the rate of particle detection. At pressures below 1 kPa, more than 90% of fluorescence and RPS events were matching. At higher pressures, some peaks were missed by the fluorescence technique due to the difference in sampling rates. This technique enhances the particle-by-particle specificity of conventional RPS measurements and could be useful for a range of particle characterization and bioanalysis applications.  相似文献   

13.
周五七  聂鸣 《科研管理》2013,34(6):50-57
本文利用1985-2009年的时间序列数据,运用ARDL模型与边界检验方法,就结构性因素及专利对中国碳排放强度变动的动态效应进行计量检验。研究发现,碳排放强度与人均收入显著负相关,与煤炭消费比重显著正相关,人均收入增长有利于促进碳排放强度下降,但人均收入对碳排放强度的边际影响低于煤炭比重的边际影响,煤炭比重对碳排放强度的短期影响明显弱于长期影响。在不同模型中,第三产业比重对碳排放强度的影响结果不一致,表明第三产业内部发展不均衡,因此,产业结构调整的目标不仅仅在于提高第三产业的比重,更需要加快其向资源节约与环境友好型发展方式转变。专利对碳排放强度的短期影响不显著,其对碳排放强度的影响具有时间滞后性,从长期来看,碳排放强度与专利总量、实用新型专利和外观设计专利显著负相关,与发明专利显著正相关,发明专利对碳排放强度下降尚未起到显著促进作用。  相似文献   

14.
BackgroundResidual oils were characterized according to their physicochemical properties, i.e. acidity, iodine value, peroxide value and saponification number, to evaluate the degradation level and viability for biodiesel production.ResultsThe methyl esters of fatty acids (FAME) from samples of residual bovine, chicken and soybean oils were quantified by using four transesterification methods, using acidic and basic catalysis and, gas chromatography with flame ionization detector (GC–FID). Methods that used acidic catalysis at a lower temperature were the most efficient. Methyl biodiesel samples were synthesized by basic catalysis (KOH) for all quantified oils and the physicochemical properties of the biofuel were evaluated, i.e. viscosity, flash and fire points, density, water content, iodine and acidity numbers.ConclusionsThe obtained results suggesting that it is possible to take advantage of these residues for biodiesel production as the obtained products were approved according to the rules established by the National Association of Petroleum (ANP); the bovine samples were the exception regarding moisture and acidity.  相似文献   

15.
Reducing the NOx emissions from Diesel engines remains as a challenging issue as the emission standards for Diesel engine powered vehicles have become more stringent than ever before. Urea-based selective catalytic reduction (SCR) systems have emerged as a promising technique in addressing this issue. However, the SCR performance in terms of NOx reduction and ammonia slip continues as an ongoing challenge due to the engine exhaust gas temperature variations, Diesel emission characteristics (especially high NO/NO2 ratio), and immature SCR controls. The purpose of this study is to improve the SCR performance by feeding the SCR system with exhaust gas having the desired NO/NO2 ratio. The proposed complete active NO/NO2 ratio control consists of a low-level adaptive NO/NO2 ratio controller and a high-level nonlinear soot mass controller. The low-level controller utilizes the pre-SCR catalysts such as Diesel oxidation catalyst (DOC) to convert part of NO into NO2, while the high-level controller was designed and coordinated with the low-level controller to avoid NO2 reduction through the Diesel particulate filter (DPF). Simulation and experimental results show that the proposed active NO/NO2 ratio control has the potentials of regulating the NO/NO2 ratio to the desired value and thus considerably improving the SCR performance. Simulation results also illustrate that the active NO/NO2 ratio control can enable the SCR system size reduction by a half without a significant sacrifice on the overall tailpipe emission control performance. Such an integrated aftertreatment system control can be instrumental in reducing the cost and improving the performance of SCR systems, especially in low-temperature operations.  相似文献   

16.
A method is presented that allows the computation of the impulse strength of insulating oil and of solid and gas-filled cables. The principle of the calculation is that breakdown is initiated by currents due to an electronic emission from the cathode; in gas-filled cables these currents are increased by means of gaseous ionization in the butt spaces. Approximate equations are deduced and numerical impulse strength values for insulating oil and solid cable computed, resulting in fair agreement with experimental observations. Extending the equations to gas-filled cables, numerical impulse data for varying gas pressure and for varying radial butt-space alignment are evaluated.  相似文献   

17.
The way in which bacterial communities colonize flow in porous media is of importance, but basic knowledge on the dynamic of these phenomena is still missing. The aim of this work is to develop microfluidic experiments in order to progress in the understanding of bacteria capture in filters and membranes. PDMS microfluidic devices mimicking filtration processes have been developed to allow a direct dynamic observation of bacteria across 10 or 20 μm width microchannels. When filtered in such devices, bacteria behave surprisingly: Escherichia coli, Pseudomonas aeruginosa or Staphylococcus aureus accumulate in the downstream zone of the filter and form large streamers which oscillate in the flow. In this study, streamer formation is put in evidence for bacteria suspension in non nutritive conditions in less than 1 h. This result is totally different from the one observed in same system with “inert” particles or dead bacteria which are captured in the bottleneck zone and are accumulated in the upstream zone. Observations within different flow geometries (straight channels, connected channels, and staggered row pillars) show that the bacteria streamer development is influenced by the flow configuration and, particularly by the presence of tortuosity within the microchannels zone. These results are discussed at the light of 3D flow simulations. In confined systems and in laminar flow, there is secondary flow (z-velocities) superimposed to the streamwise motion (in xy plane). The presence of the secondary flow in the microsystems has an effect on the bacterial adhesion. A scenario in three steps is established to describe the formation of the streamers and to explain the positive effect of tortuous flow on the development kinetics.  相似文献   

18.
Polymer stretching in two-phase microfluidics is investigated by dissipative particle dynamics. The flow patterns can be controlled by wall wettability, flowrate ratio between two phases, and Reynolds number (Re). For neutral and partially wettable walls, segmented flows are formed and polymer stretching can be controlled by Re and segment length. At high Re, stratified flows are observed and the extension ratio can be tuned by the flowrate ratio. For nonwettable walls, slug flows are formed and polymer stretching can be controlled by Re and slug length. At high Re or flowrate ratio, annular flows are observed and high extension ratio can be easily attained.  相似文献   

19.
朱泳丽  丁利杰 《资源科学》2022,44(7):1373-1387
长三角城市群协同发展背景下,城市间产业转移频繁,伴随经济和碳排放的连接,对城市碳排放强度产生的影响成为区域低碳发展需要考虑的重要战略问题。本文采用动态偏离-份额模型测度城市间产业转入和转出量。基于空间全局自相关、反距离空间权重和经济地理权重矩阵下的空间杜宾模型,对2005—2017年26个长三角城市的产业转移动态、碳排放强度的时空演变特征进行研究,在空间溢出视角下对城市碳排放强度的影响因素进行分析。结果表明：①碳排放强度存在显著的空间自相关性,具有明显的空间溢出效应。②长三角城市群内频繁转移的产业多数为非能源密集型产业,产业转移并未产生显著“碳减排”效应。值得注意的是,产业转移的经济影响开始显现,产业转移实际上不利于长三角城市群整体碳排放量减少。③人均GDP与碳排放强度呈现“倒U型”,技术水平与碳排放强度呈现“U型”,存在“技术进步的反弹效应”,人口数的增加降低了碳排放强度,二产比重正向作用于碳排放强度。因此在制订碳减排计划时,需要考虑不同区域生产效率、能耗强度、人力资本等因素,做好产业转入、转出的碳排放强度监测,避免盲目进行产业转移;壮大优势产业,改善产业结构,培育新增长点,发展符合城市自身禀赋的低能耗产业。  相似文献   

20.
熊爱华  丁友强  胡玉凤 《资源科学》2020,42(11):2184-2195
在碳减排门槛效应下,考察了绿色创新与低碳补贴对全要素生产率的影响,揭示了从高碳向低碳转变的制约因素。考虑了企业与政府的碳决策目标差异,将全要素生产率分为不含环境因素的企业全要素生产率和包含环境因素的绿色全要素生产率。基于中国2006—2017年省际及重点碳源行业A股上市公司的面板数据进行门槛效应检验,结果显示：①在绿色创新与低碳补贴对全要素生产率的影响中,碳减排具有显著的门槛效应;②当碳排放总量处于低位时,绿色创新与低碳补贴对企业全要素生产率有促进作用,超出碳高位的补贴将会失效;当碳排放强度处于中位时,低碳补贴对绿色全要素生产率有积极影响;③碳减排与绿色全要素生产率呈“S”型关系,与企业全要素生产率呈正“U”型关系,绿色全要素生产率与企业全要素生产率也有正“U”型关系。因此,绿色创新与低碳补贴应契合碳减排的阶段性特征,选择有效路径,为全要素生产率协调增长提供重要借鉴。  相似文献   

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