Investigation of the performance of bipolar transverse plate ESP in the sintering flue control

In order to improve the particle collection efficiency of the electrostatic precipitator (ESP), a transverse plate ESP with bipolar discharge electrodes is proposed. The simulations of the velocity distribution have shown that when the inlet velocity is 1 m/s, within the range of 40 mm from electrode plate, the average velocities of windward side and leeward side are less than 0.7 m/s and 0.3 m/s respectively. It is clear that the velocity near the collection electrode plate of this bipolar ESP is much lower than that of the ordinary ESP at the same inlet velocity. This low velocity can lead to higher efficiency for fine dust collection due to the less dust re-entrainment in ESP. It is also found that the average velocities are getting lower when the distance between plates electrodes are greater than 150 mm in accordance with the simulations. The voltage current characteristics of the bipolar ESP are superior to the ordinary ESP. The pressure drop of the bipolar ESP is about 30% higher than that of the ordinary one. The dust penetration of the bipolar ESP is about 54% less than that of the ordinary ESP when the sintering dust with 25.405 μm mass median diameter is used as the test particulate under the condition of the electric field from 2.1 kV/cm to 3.2 kV/cm and the velocity from 1.0 m/s to 1.5 m/s.     

旋转荷电球体外部引力场中引力效应

以实验粒子的短程线方程为出发点，计算了由旋转参量与电荷参量所引起的近日点进动效应．当粒子绕行方向与场源旋转方向一致时，与Kerr场中情况相比修正项将使进动效应增大．此外，通过引入局域洛伦兹空间截面，可给出该场中运动物体上加速度．显然在随动系中（vⁱ=0），从极轴方向和赤平面粒子均不能到达场源，而是分别停滞在r＝k＋(k²+4m²a²)^1/2/2m和r=k/m处．此时可以计算对星系尘埃的吸积作用，即尘埃的分布状况．最后还讨论了赤平面上作圆周运动物体（仅v³≠0）的类柯里奥利加速度 关键词：     

Experiments of all-optical switching due to cross-phase modulation in fiber grating coupler by lock-in amp. detection scheme

We report results of experiments examining cross-phase modulation effect on fiber grating coupler (FGC). All-optical switching are observed in both cases of high pump pulses emitted from high-power Nd:YAG laser and mode-locked EDF laser. Based on coherent detection using a lock-in amplifier, the red-shift of the Bragg wavelength for a FGC was estimated to be 0.04-0.06 nm/1.5-1.7 kW peak power of EDF pump light at 1.55 μm. To avoid mixture of pump pulse and signal light at 1.55 μm, we have also performed the experiment using high power Nd:YAG laser as a pump power. For a Nd:YAG laser, the red-shift of Bragg wavelength is estimated to be 0.06 nm at maximum pump power of 2.1 kW. A simple model for the proposed detection scheme is given and the resultant red-shift is analyzed numerically.     

2μm人眼安全波段太阳光抽运激光器的理论研究

太阳光直接抽运激光器在空间光通信、遥感等领域有着重要的潜在应用,但是一直以来人们对太阳光抽运激光器的研究局限于以掺Nd3+粒子为增益介质的1μm波段.通过对现有固体激光工作物质的吸收谱进行分析,发现掺Tm3+离子在太阳辐射较强的可见光波段具有强的吸收峰,使2μm人眼安全波段实现太阳光直接抽运激光输出成为可能.本文对Tm:YAG和Tm:YAP两种常见晶体的吸收谱与太阳光谱匹配度进行了分析计算,得出两种材料用于太阳光抽运激光器的阈值抽运功率密度分别为1.14和1.434 kW/cm3.选择与抽运阈值功率密度低的Tm:YAG晶体作为增益介质,使用TracePro软件建立太阳光抽运激光器的二级抽运模型,并对模型进行优化,得到了锥形腔窗口与菲涅耳透镜的最佳距离、晶体棒的最佳长度以及锥形腔最佳锥度.本文的工作为实现太阳光直接抽运2μm激光输出做了理论上的准备.     

Radar studies of ionospheric dusty plasma phenomena

We discuss the influence of charged dust on radar observations in the Earth ionosphere. This region in the upper Earth atmosphere can be described as a partially ionized, low‐temperature plasma. Plasma parameters vary by orders of magnitude spatially and in time. Dust particles influence the charge balance, in some cases dusty plasma condition is met. The polar mesospheric echoes are an example of dust plasma interactions observed with radar. The mesosphere is a region where atmospheric temperature decreases with altitude and can reach frost point temperature. The formation of the polar mesospheric radar echoes involves neutral atmosphere dynamics, which is latitude dependent and it involves charged dust particles, especially icy dust that forms in the polar summer mesosphere. Charged dust can also influence incoherent scatter that results from electromagnetic waves scattering off electrons, where the electrons are coupled to other charged components. Observers rarely report charged dust signatures in the incoherent scatter spectra; we show that there is a good chance for doing so with improved observations. The incoherent scatter can possibly also be used to estimate the amount of charged dust in the direct vicinity of a meteor, as we show based on the order of magnitude considerations. This prospect of new observational results makes theoretical investigations of radio‐wave scattering in the presence of charged dust with size distributions worthwhile.     

Ultrasonic resonance regulated near-field scanning optical microscope and laser induced near-field optical-force interaction

We have developed a novel sample-tip regulation for a near-field optical microscope: an ultrasonic resonance regulation method. The regulation range is from 0 to 50 nm. It shows not only stability, simplicity in construction, but also versatility in vacuum, magnetic field, and low temperature environments. The main advantage of this technique is that it is a non-optical detecting scheme, which is very important for near-field spectroscopy. Such construction can also be used as a force microscope to study the topography of insulating samples. The laser light induced force interaction in the near-field range has been observed for the first time, showing that aided by laser radiation, the shear force between sample and tip can be changed depending on the type of sample. This can be interpreted as the light induced optical tip-sample interaction of light pressure effect. The van der Waals dispersion energy and the optical binding energy induced by laser beam between dielectric tip and samples play important role. The effect confirms a theoretical prediction. This new technique and phenomenon will add new aspects to near-field optics.     

Phase-coupling-induced ultraslow light propagation in solids at room temperature

We show that the group velocities of light pulses can be decelerated dramatically by the use of a dispersive phase-coupling effect through a wave mixing process. We have observed experimentally such a phase-coupling-induced ultraslow light propagation with a group velocity as low as 0.05 m/s in a photorefractive Bi12SiO20 crystal at room temperature. Moreover, the ultraslow light is amplified in the Bi12SiO20 crystal because of the unidirectional energy transfer from a coupling beam to the ultraslow light. This technique to produce ultraslow light propagation is valid for all nonlinear wave mixing processes with a dispersive phase-coupling effect.     

Distribution of charged lunar dust in the south polar region of the moon

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon. In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software. The distribution of dust and plasma at low solar altitude angles of 20° and 0° was studied, and the spatial density of lunar dust was ~10^10.4 m^-3 and ~10^11.5 m^-3, respectively. This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust. The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied. We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater, and the dust density was about a magnitude lower than that in other regions. The dust risk to a spacesuit is much lower on the nightside than on the dayside, but there is severe charged lunar dust transport in the region between light and shade, which is dominated by the difference in surface and plasma potential caused by photoelectrons.     

沙尘气溶胶粒子群的散射和偏振特性

根据Mie散射理论,以对数正态分布函数描述沙尘气溶胶粒子群的粒径尺度分布,计算了沙尘气溶胶粒子群在0.2～40μm波段间对太阳短波辐射和地球大气长波辐射的单次散射反照率、散射相矩阵函数,揭示了不同相对湿度时,沙尘粒子群对入射辐射的散射和偏振的特征。结果表明,沙尘粒子群的单次散射反照率随着入射波长的增加有较大起伏,不同相对湿度条件下,变化趋势基本一致;在可见光、近红外波段单次散射反照率随湿度增加而变大,湿度95%时非常接近于1;大于10μm的热红外波段单次散射反照率随相对湿度增加而减小,具有较强的吸收辐射能力。散射辐射强度受湿度影响较小,随散射角的增加呈现先减小后增大的趋势,且增大的趋势随着波长的增加而减弱;不同波段上,线偏振和圆偏振随散射角和相对湿度变化存在差异;在前向和后向仅对入射辐射为圆偏振辐射产生圆偏振散射;散射光的偏振特性及其湿度差异主要表现在后向散射区,多以拱形形式体现。拱顶峰值散射角位置存在差异,且峰值散射角随相对湿度的降低向后向漂移。     

X荧光分析法测定地表灰尘和空调灰中重金属含量

使用X荧光分析法对地表灰尘和空调滤网灰中所含金属元素(Mn,Fe,Cu,Zn,Pb)做了定量分析.结果表明,5种元素在空调灰中的含量都大于其在地表灰尘中的含量,其中Cu,Zn,Pb 3种元素在地表灰尘和空调灰中的含量远远大于四川省表层土壤中对应的平均含量.通过对不同粒径组地表灰尘中重金属含量的分析表明,地表灰尘中五种元素的含量在测量范围内随灰尘直径的变化规律大致相同.     

Giant nonlinear optical properties of bismuth thin films grown by pulsed laser deposition

Thin films of Bi were grown by pulsed laser deposition on glass substrates at room temperature. The thickness and roughness of the films were characterized by grazing-incidence x-ray reflectivity, and the complex refractive indices were measured in the range from 1.5 to 4 eV by spectroscopic ellipsometry. We performed Z-scan measurements to study the third-order optical nonlinearity of the films. It was found that the Bi films exhibited an unusually large nonlinear refractive coefficient, n(I)~1.24x10(-1) cm(2)/kW and nonlinear absorption coefficient, alpha(I)~-3.97 cm/W , at low laser intensity, ~60 kW/cm(2) . This anomaly is believed to have an origin related to melting of the Bi films at the focus spot by the laser beam.     

The role of dust particles with large gyroradii in the `2/3'fall-down process

The authors consider the Alfven-Arrhenius fall-down process and propose a mechanism whereby the Rosseland electric field (the field needed to maintain quasineutrality) may be responsible for the capture and confinement of large-gyroradius dust particles within a plasma shell stratified along the direction of the magnetic-field lines. For these particles, the effect of the magnetic force is rather weak, and they move with a constant z component of the angular momentum in a one-dimensional equivalent potential (gravitational plus centrifugal). This has a maximum at the equator and a minimum at the `2/3' points, i.e. the points where the field-aligned components of the gravitational and centrifugal forces balance. It is shown that under suitable initial conditions these are points of maximum dust density and minimum plasma density. The plasma-planetisemal transition is therefore expected to take place at the `2/3' points in accordance with the Alfven-Arrhenius mechanism. It is also shown that the fraction of infalling dust particles that can accrete onto the equatorial plane by the Alfven-Arrhenius and Rosseland mechanisms is rather small (~(L/ R_e)≪1), L being the thickness of the plasma shell, and R_e, a characteristic length scale of the field line     

Observation of laser-pulse-induced traveling microbubbles in dusty plasma liquids

We report a direct experimental observation of traveling microbubbles induced by intense laser pulses in strongly coupled dusty plasma liquids. The dense plasma ablated from a suspended dust particle generates a spherical plasma bubble with a low dust density, in the quiescent regime before a transition to self-organized longitudinal dust density waves. It travels downwards at a velocity about 6 cm/sec inside the dust liquid. Dust density fluctuations trailing the bubble are also observed. The bubble generated in the high pressure dissipative regime collapses right after formation.     

High-power CO(2) laser with a Gauss-core resonator for high-speed cutting of thin metal sheets

A novel resonator, the Gauss-core resonator, based on a stable resonator configuration designed to yield a highly focusing beam operating in a large-volume TEM(00) mode, is presented. A 6.2 kW linearly polarized output beam with an M(2) factor of 1.7 is obtained experimentally for a high-power cw CO(2) laser. The capability of the Gauss-core resonator to process laser materials is also studied. We can cut 1-mm-thick mild (soft) steel with a maximum cutting speed of 58 m/min at 5.6 kW and 0.2-mm-thick steel 145 m/min at 2.8 kW.     

微燃机稳压箱的计算分析

本文对自行设计的100 kW微型燃气轮机的稳压箱进行了数值模拟,并将结果与国外某75 kW微型燃气轮机的稳压箱的数值模拟结果进行了对比。然后对结果进行分析,从中发现,自行设计的微型燃气轮机的稳压箱与国外同功率级的稳压箱相比,总压恢复系数有所提高,流动损失较小,因此具有更优良的气动性能。计算表明,进口处流动方向变化较大,流动损失也较大,并且流动复杂,有漩涡产生,流场具有复杂的结构,必须在设计时引起足够的重视。     

Optically pumped InGaN/GaN MQW lift-off lasers grown on silicon substrates

Chemical etching and removal of the silicon substrate was used for the creation of optically pumped lift-off InGaN/GaN multiple quantum well (MQW) lasers from heterostructures grown on silicon substrate by MOVPE. Luminescence and laser properties of these heterostructures on silicon substrates as well as those of MQWs lifted-off from their substrate by chemical etching were investigated. The lowest value of the lasing threshold of the lift-off lasers at room temperature was about 205 kW/cm² for a laser wavelength of 463 nm and about 360 kW/cm² for a wavelength of 475 nm. It was shown theoretically that the reduction of internal losses, caused by the absence of absorption in the substrate (resulting from its removal) is most significant for the high order modes having lower values of mirror losses and can lead to a 50% reduction of the threshold (or material gain in InGaN necessary to achieve the threshold).     

纯相稀土硫化物红色发光材料的高温微波合成及其光谱性质

采用工业频率为2.45 GHz的高温微波法制备了纯基质相的CaS∶Eu2+红色发光材料,激发波段为410~580 nm,发射峰值波长为654 nm。在微波输入功率为1.0~1.1 k W的条件下,可以获得纯基质相CaS∶Eu2+发光材料;在1.2~1.3 k W功率范围,获得的样品中含有Ca O杂质相,且颗粒团聚严重。其中,1.1 k W制备的CaS∶Eu2+样品相纯度最高,发光性能最优。微波功率的变化本质上揭示了固体颗粒的介电损耗因子及其加热特性的变化,体系涉及的非平衡反应机制促使了纯基质相的形成,并影响材料晶相结构、粒径、形貌和发光性能。结果显示,高温微波制备技术通过控制输入功率及其物料的介电损耗性质,能够获得纯基质相并且颗粒小、团聚少的荧光粉。     

普通单模石英光纤中频率上转换过程的研究

介绍了在普通通讯用单模ＧｅＯ２／ＳｉＯ２石英光纤中从近红外到可见光的频率上转换过程。利用１．３１３μｍ的调Ｑ锁模Ｎｄ：ＹＬＦ激光脉冲泵浦单模石英光纤，产生了５８８ｎｍ的黄光，峰值功率达２０Ｗ，对应０．０９％的转换效率。     

T-matrix approach to calculating circular polarization of aggregates made of optically active materials

Optical activity is a typical property of the biological materials where left-handed amino-acids and right-handed carbohydrates dominate (so called homochirality). Observationally, optically active materials reveal themselves through the circular polarization in the light they scatter. Thus, circular polarization produced by the optically active particles can serve as a biomarker. It is known that biological (e.g. colonies of bacteria) and pre-biological (e.g. dust in comets) particles often have a complex structure that can be modeled presenting them as aggregates of small monomers. This motivated the development of the T-matrix code presented in this paper, which enables calculation of the scattering matrix - including circular polarization - of the light scattered by aggregated optically active particles. The code can be used for modeling the light scattering by biological objects (e.g. colonies of bacteria, blood cells) and for interpretation of the circular polarization produced by the cosmic dust that contains (pre)biological organic, e.g. comet dust or planetary aerosols.     

Dynamics of Macroparticles in a Quasi-Two-Dimensional Dust–Plasma System under Directed External Action: Simulation Results

The action of the light pressure force on a bounded region of a 2D system of dust macroparticles is simulated using the molecular dynamics method. The dynamics of dust macroparticles in the quasi-2D structure (trajectories of particles, their mean square displacement, and kinetic energy) is analyzed for various values of the nonideality parameter and laser radiation power. It is shown that by varying the radiation power, it is possible to influence the self-diffusion processes and the value of chaotic velocity of particles. Analysis is performed for different initial values of the nonideality parameter of the unperturbed dust subsystem. It is found that the interparticle interaction results in an increase in the kinetic energy of particles in the region of action, as well as beyond it.