Probe measurements in the normal electric arc

Probe measurements have been made in cadmium, thallium and carbon arcs by sweeping the probe through the arc at a constant velocity and measuring the current collected by the throw on a ballistic galvanometer with different probe potentials applied. The voltage-current characteristic was analyzed to get a measure of the positive ion concentration, the average electron temperature and the space potential by the Langmuir method. The cathode falls found were each equal to, or only slightly higher than, the ionization potential of the active gas, and were 9.0 volts in the cadmium arc, 6.5 volts in the thallium arc and 5.0 volts in the carbon arc. The last value is to be compared with the ionization potential of the cyanogen molecule of 4.4 volts. The anode fall found in the carbon arc was 16.5 volts. These values for the carbon are agree almost exactly with the “forward” and “back” E.M.F.'s measured by Duddell and others at the cathode and the anode but not identified by them as the cathode and anode falls. The electron velocities were found to be Maxwellian with average velocities sufficiently high to account for the ionization known to exist. Over parts of the are stream where the fields were found to be large the electrons showed corresponding increases in average temperature and evidence that only about three-quarters of the energy gained by the electrons from the field between collisions is lost by the lectrons while the remaining quarter is retained and made evident by the steady increase in the electron temperature. As the current flowing through the arc was increased, the radiation per unit volume and also the positive ion current per unit length of the probe were found to increase very rapidly indicating an increase in the efficiency of the ionization process as the current increases. It is thought that this observation is closely related to the fact that the voltage drop across the arc decreases as the arc current increases.     

The magnetic deflection experiments of Curtiss and of Mott-Smith

We have carried out a geometrical analysis which applies to that type of cosmic ray deflection experiment in which an extended region of magnetic field lies between the lower two of three or more Geiger-Mueller counters arranged in line for counting coincident discharges. It is apparent that charged particles of sufficiently low energy will be deviated away from the last counter and that the counting rate will therefore be reduced by application of the field. This paper presents a method for computing what proportion of electrons of a given energy will be eliminated by application of the field. The method is extended to include a constant loss of energy per unit path length as the particle traverses an iron core. The results of the experiments of Curtiss and of Mott-Smith are interpreted in the light of these calculations. Curtiss' result could be explained if all rays were electrons of 4 × 10⁸ volts energy. One may conclude from his observation that if all the radiation consists of positive or negative electrons, the fraction between 2 × 10⁷ volts and 1.5 × 10⁸ volts is less than 30 per cent. of the total above 2 × 10⁷, and that the fraction between 2 × 10⁷ and 10⁹ is greater than 30 per cent. A comparison of Curtiss' and Mott-Smith's experiments yields no reason for doubting the correctness of using the magnetic induction B when computing the deflection within iron. Nor does it necessarily sustain this procedure. An experiment by W. F. G. Swann and the writer is at present under way for the purpose of securing, if possible, more conclusive evidence on this point.     

Electron diffusion,electron attachment,and the aging of negative ions in commercial nitrogen at atmospheric pressure

A criticism by Loeb and Bradbury of my interpretation of the experimental results of that part of a previous paper which dealt with the aging of negative ions in commercial nitrogen is shown to be invalidated by a mistake in their analysis and by assumptions which do not represent facts with sufficient accuracy. A more extended analysis of the previous work and new evidence which is given confirm the correctness of the former contention that the negative ions in question changed in size with age. The lateral spread, owing to diffusion, of a stream of electrons in this nitrogen at atmospheric pressure, when moving in an electric field of about 100 volts/cm., was found to be very nearly the same as that for positive ions under like conditions. The average energy losses of the electrons at collision with the molecules must therefore have nearly balanced the gains from the electric field and hence were greater than would result from purely elastic collisions. The experimental results indicate that in fields down to at least 20 volts/cm. nearly all of the attachment of electrons to molecules in the gas used occurred close to the place of their liberation.     

The blackening of photographic plates by positive ions of the alkali metals

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.     

Critical ionization potentials by positive-ion impact

The experiments of several previous investigators were repeated in substance with apparatus designed to make it possible to distinguish between ionization and certain spurious factors which have made questionable much of the existing evidence relating to ionization by positive-ion impact. A great many current-potential measurements and curves were obtained at different gas pressures and with a variety of electrical arrangements. The data and curves thus obtained present direct evidence (a) that the previously so-called “ionization current” is due to a secondary electron emission from the platinum walls of the ionization chamber, (b) that this secondary electron emission is produced by the impact of the positive ions with these metal walls, (c) that either there is no ionization in hydrogen gas by the impact of the positive ions accelerated by potential differences up to 925 volts, or that if this phenomenon exists, as is indicated by visual and spectroscopic evidence, its effects are so small at relatively low pressures (.012 mm.) that it is completely masked by secondary phenomena which make its detection by the ordinary direct methods problematic, and (d) that it seems possible that at relatively high gas pressures (considerably above .012 mm.), ionization by positive ions might be an important factor with accelerating potential differences between the ends of their M.F.P. well within this same range of voltages.     

On the rôle of tube walls,and surface and space charges in electrical discharges through rarefied gases

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.     

基于技术进步的中国能源消耗与经济增长：前后两个30年的比较

本文依据1953年-2009年统计数据,以单位产值能源消耗为指标,将新中国划分为两个阶段（1953年-1977年和1978年-2009年）,比较了两个阶段能源消耗与经济增长的关系。结果显示：从1953年-1977年,随着人均GDP的升高,人均能源呈同步增长;单位产值能耗从6.76t标准煤增长到17.9t标准煤,能源消耗弹性从3.59下降到-0.58,两者呈现反相关性;从1978年-2009年,随着人均GDP的增大,人均能源消耗波动上升;单位产值能源消耗从17.50t标准煤下降到5.05t标准煤,而能源消耗弹性波动较大。本文依据IPAT方程从广义技术角度对其进行了理论分析,结果表明在前30年经济增长对能源消耗依赖性较大,对技术依赖性较小;而后30年经济增长对能源消耗依赖性减弱,对技术依赖性增强;技术转变与技术进步是引起这种变化的关键因素。     

锂同位素在气溶胶特性示踪研究中的应用

以热表面电离质谱计为分析手段，采用6Li稳定同位素示踪了爆炸过程中放射性气溶胶粒子悬浮、沉积和在毛细管中扩散行为。实验结果表明：爆炸后100h，气溶胶粒子悬浮份额占10-5；沉积量占绝大多数，且各部位沉积量存在明显差异；即使在无压力推动下，仍明显观察到了气溶胶粒子在毛细管中的扩散，对于d25μm×2cm 毛细管通道而言，穿透率为1.5×10-10 / h。研究结果对于正确评估放射性气溶胶粒子在爆炸过程中的行为有一定的价值。     

论《憩园》中巴金的自我斗争

《憩园》是巴金在20世纪40年代由尖锐张扬过渡到内敛深沉的代表作。本文旨在通过以下几个方面说明《憩园》中巴金的矛盾和潜意识,即寒儿执著寻父的源头,寒儿、＂哥哥＂和黎先生的实质关系,巴金本身的现实生活状态。     

Mica and the Mica industry

The instrument described is an ammeter for measuring currents flowing in the secondary circuits of induction coils.A D'Arsonval system is used, modified by placing a small condenser in parallel with the moving coil and its calibration shunt to compensate for the high rate change of current, and by a ground on one side of the system to prevent sparking between the meter parts.The instrument is especially adapted for use in X-ray work, because it was found that the quantity of X-rays was directly proportional to the current flowing in the tube.     

资源型城市生态效率评价

本文引入生态效率概念,基于能值生态足迹法,评价我国资源型城市的生态效率,兼与宜居城市进行比较分析,以探讨资源型城市可持续发展状况。研究发现,与宜居城市相比,资源型城市生态效率低下;资源类型和城市规模对生态效率影响较大,二产比重、单位GDP能耗与生态效率负相关;城市人均绿地面积、建成区绿化覆盖率则正相关。因此,延长产业链,提高资源使用效率,发展循环经济,缓解生态压力,对于提高生态效率,至关重要。     

Secondary electron emission from oxide-coated cathodes

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. δ_K° ? δ_300°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.     

苏州市与徐州市耕地资源变化与经济发展关系的对比分析

不同的区域耕地资源变化与经济发展的关系具有明显的差异性。本文采用1978～2006年江苏省苏州市与徐州市的统计数据,分析不同区域中耕地资源变化的特点,并定量分析了耕地资源变化与经济发展的关系,对不同区域GDP增加的耕地占用量进行了对比研究。结果表明:①苏州的耕地面积经历了3次明显的流失高峰,年递减率高达1.34%,而徐州市的耕地面积变化则相对缓和,年递减率只有0.33%,人均耕地面积也有类似的变化趋势;②不同区域的耕地资源面积随着GDP的增加均呈指数递减趋势,用模拟的指数方程对耕地面积的估算值和实际值比较误差较小,证明用指数递减方程预测耕地占用面积随着GDP的变化是可行的;③在不同的区域每单位的GDP增长所消耗的耕地面积随着经济的增加均呈下降趋势,但下降速度不同;④徐州市每增加1×10⁸元所消耗的耕地面积在1978年～1999年,要高于苏州市的水平;在2000年～2006年,则低于苏州市的水平。     

The potential fall between striæ in electrical discharges through rarefied hydrogen

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.     

中国耕地压力指数时空规律分析

耕地压力指数是指最小人均耕地面积与实际人均耕地面积之比。文章通过对改革开放以来我国耕地压力指数的测算，发现耕地压力指数在1981年～1996年间呈下降趋势，主要原因是由于期间最小人均耕地面积减少速度大于实际人均耕地面积的减少速度；1996年后耕地压力指数整体处于上升趋势，这主要是由于期间实际人均耕地面积急剧减少所致。通过对2004年各省份压力指数的测算，发现有21个省份的耕地压力指数大于1，其中上海的耕地压力指数达到了2.84；即便是在无明显压力的5个省份中，其压力指数也均在0.78以上，区域耕地压力非常明显。导致各省份耕地压力指数过大的主要原因有3个：一是由于耕地大量被占用，实际人均耕地面积偏小而导致的压力指数过大；二是因单产水平过低而导致最小人均耕地面积偏大，从而使压力指数偏大；三是粮食主产区由于要承担国家商品粮任务，使区域粮食自给率过高，导致最小人均耕地面积过大，从而使耕地压力指数偏大。通过控制耕地面积减少速度、提高农业科技水平可以有效缓解耕地压力状况。     

The control of current across a spark gap by means of an external magnetic field

An experimental study was made of the electrical discharge between parallel plates when the pressure between the plates had been reduced to a value slightly less than the critical pressure—i.e. to the condition when a tube begins to harden. Under these conditions the application of a transverse magnetic field will produce a discharge between the electrodes for potentials less than the normal potential required. It is believed that this is due to the lengthening of the path traversed by the ions in crossing the gap. The results obtained may be harmonized by means of the values found by Carr (Proc. Roy. Soc. 1903) who made a study of Paschen's Law in the region of critical pressure. In general it is found possible, under the conditions studied, to start a discharge and control the value of the current through a circuit of which the gap is a part by means of varying the magnetic field superposed on the gap and without altering either the impressed E.M.F. or the ohmic resistance of the circuit.This control is effected by altering the effective length of the spark gap in the circuit by means of the external magnetic field.     

基于MFA方法的陕西省物质减量化分析

运用MFA方法，依据欧盟统计局推荐的MFA基本指标和Schmidt-Bleek关于可持续发展的指标，设计了5类9个指标及7种可以直接采集数据的变量；在分析陕西省1996年～2003年生产、消费领域的物质输入、输出量的相关数据的基础上，推导并描述了陕西省当前发展阶段的物质输入、输出相关变量的函数关系；预测了陕西省物质输入、输出的发展态势。进一步证明了下述结论：①陕西省经济增长方式表现出典型的粗放型特征；②陕西省经济发展的弱可持续性趋势明显；③陕西省物质减量的潜力巨大。认为如果陕西省不从根本上改变现行经济增长方式，物质生产力将面临持续下降趋势。因此，发展循环经济，转变经济增长方式,实行源头控制，以期减少物质投入，提高物质利用强度，是陕西省实现可持续发展的根本途径。     

A circuit for the limitation of discharge in G-M counters

A simple two tube feedback arrangement to limit the discharge in a counter to a small segment of its length subsequently restoring all but a small portion of the tube to full sensitivity in about a microsecond, has been achieved. The procedure results in a marked reduction in dead-time, and a correspondingly large increase in life. For example, a 20-cm. counter may be operated at a rate of 20,000 counts per second with a loss no greater than that normally encountered at 1000 counts per second. Counting rate data are given along with studies of the discharge distribution with and without the cut-off procedure. Alteration in the dead-time picture is illustrated by oscillograms.     

电除尘三、四电场节能调整及成效

针对电除尘器在运行中出现的一些问题,主要从运行节能的角度来分析其产生高耗电率的原因;结合运行可操作的方法,从运行调整、及调试上分析原因,并提出相应的改进措施,以提高除尘效率,达到环境保护的要求;调整后,每台炉,每天可节电：11572KWH,使每台机组的厂用电率降低：0．1052％。     

Residual currents in A.C. discharges.

A point by point determination is made of the residual current flowing during the reignition period of an a.c. arc between pure graphite electrodes in atmospheric air.The air pressure is varied from 0.14 to 5.4 atmospheres absolute and the gap varied from 1/4 to 5 mm. Alternating current of 6o cycles per second is supplied to the arc by a io Kv. power transformer and the r.m.s. discharge current is limited by ohmic resistance to values between o.o5 and 2 amperes. The residual current rises to a peak shortly after the voltage reverses and the current then decreases as the recovery voltage increases to its reignition value. The peak of the residual current increases directly with the r.m.s. current of the arc, and is essentially independent of both the length of the gap and the pressure of the gas. The reignition voltage is shown to be a function of the value of residual current existing just prior to ignition. The rate of decay of residual current decreases as gas pressure and gap length are increased.