Note: Interpolation for evaluation of a two-dimensional spatial profile of plasma densities at low gas pressures

An interpolation algorithm for the evaluation of the spatial profile of plasma densities in a cylindrical reactor was developed for low gas pressures. The algorithm is based on a collisionless two-dimensional fluid model. Contrary to the collisional case, i.e., diffusion fluid model, the fitting algorithm depends on the aspect ratio of the cylindrical reactor. The spatial density profile of the collisionless fitting algorithm is presented in two-dimensional images and compared with the results of the diffusion fluid model.     

液压缸低速爬行动力学研究

分别建立了横、垂向液压缸的低速爬行动力学模型，研究了不同要素对横、垂向液压缸低速特性的影响规律，并提出提高液压缸低速控制精度的方法。研究结果表明，减小液压缸活塞倾斜角度、静动摩擦因数差、摩擦降落系数、活塞质量，增大液压油阻尼系数、排除油液中的空气时可以改善液压缸低速爬行特性。     

Supercritical droplet dynamics and emission in low speed cross-flows

Droplet dynamics and emission of a supercritical droplet in crossing gas stream are numerically investigated. Effects of ambient pressure and velocity of nitrogen gas on the dynamics of the supercritical oxygen droplet are parametrically examined. Unsteady conservative axisymmetric Navier-Stokes equations. in curvilinear coordinates are preconditioned and solved by dual-time stepping method. A unified property evaluation scheme based on a fundamental equation of state and extended corresponding-state principle is established to deal with thermodynamic non-idealities and transport anomalies. At lower pressures and velocities of nitrogen cross flows, both the diffusion and the convection are important in determining the droplet dynamics. Relative flow motion causes a secondary breakup and cascading vortices, and the droplet lifetime is reduced with increasing in ambient pressure. At higher ambient pressures and velocities, however, the droplet dynamics become convection-controlled while the secondary breakup is hindered by reduced diffusivity of the oxygen. Gas-phase mixing depends on the convection and diffusion velocities in conjunction with corresponding droplet deformation and flow interaction. Supercritical droplet dynamics and emission is not similar with respect to the pressure and velocity of the ambient gas and thus provides no scale.     

Fatigue failure at low temperatures

The fatigue failure of steel 20 at low temperatures is considered. Strain hardening of the surface layers is found to occur in adiabatic conditions at low temperatures. That increases the fatigue strength. Fatigue cracks form and grow along the grain boundaries. The influence of impurities on the fatigue failure of low-carbon steel is studied.     

Friction of materials at low temperatures

The friction of some commercially pure metals and stainless steel was investigated in vacuum and gaseous helium from room temperature to liquid helium temperature. No appreciable change in the coefficient of friction was observed for the metals as the temperature was reduced. In ultrahigh vacuum the coefficient of friction of copper reached 2.79. Test equipment including a magnetic clutch for transmission of a rotary motion into ultrahigh vacuum with the ability to record a moment of friction of the specimens was developed.     

Velocity-map imaging at low extraction fields

We present a velocity-map imaging (VMI) setup for photoelectron imaging that utilizes low electric extraction fields. This avoids any complications that could arise from electrostatic interactions between the extraction field and the molecular properties that are probed and has a minimal effect on the trajectory of ions in ion beam experiments. By using an attractive potential supplied to the detector, and keeping the electrodes at ground (zero) potential, we show that fringe fields between the VMI arrangement and the vacuum chamber can be eliminated, which is important in experiments on ions.     

Rotating sample holder at low temperature

A low temperature rotary device (cryoturbine) for use in extended x-ray-absorption fine structure measurements in fluorescence mode has been designed and manufactured. The instrument works at a temperature close to liquid Nitrogen and can reach frequencies up to 100 Hz with good stability. The rotation speed is measured with a light-emitting diode driven in stroboscopic mode by a simple electronic circuit.     

Protecting centrifugal pumps at low flow

Centrifugal pumps which operate under variable flow rates often require protection against prolonged operation at low flow rates. Determining the flow rate at which protection is required and the type of protection required is as important as the actual provision of low flow protection. This discussion deals with the correct application of low flow protection of centrifugal pumps and does not address the determination of the flow rate below which low flow protection is required.     

Monitoring low cycle fatigue damage in turbine blade using vibration characteristics

A finite element based approach is used to simulate the evolution of low cycle fatigue damage in a turbine blade. The turbine blade is modelled as a rotating Timoshenko beam with taper and twist. A damage growth model for low cycle fatigue damage developed using a continuum mechanics approach is integrated with the finite element model. Numerical results are obtained to study the effect of damage growth on the rotating frequencies. It is found that low cycle fatigue causes sufficient degradation in blade stiffness for changes in rotating frequency to be used as an indicator to track damage growth. Continuum damage mechanics models in conjunction with finite element analysis are used to develop thresholds for damage indicators. By placing suitable threshold on the frequency change, it is possible to detect the onset of the final stage of damage in the structure before failure occurs.     

Pumpability of engine oils at low temperatures

The pumpability of various engine oils at low temperatures has been investigated using a Haake-Rotovisko RV2 viscometer, a test engine and a laboratory pumping rig. The cold flow and cold pumpability properties of polymer-thickened engine oils can be predicted from the flow curves at low temperatures. Correlation was found between viscosity data and the cold pumpabiiity behaviour of an oil in an engine. The best evaluation of the low temperature pumpability of multigrade oils in the engine used was given by a specially developed laboratory pumpability rig.     

Vibration monitoring of bearings at low speeds

Some experimetnal observations and results are given comparing acceleration shock pulse transducer, acoustic emission and jerk measurements from slightly damaged bearings at medium to low speeds. Additional results showing defects at very low speeds with an acoustic emission transducer are not easily explained     

Radiation damage to microdroplets at low temperature

The effect of low temperatures on the stability of characteristic signals during electron probe analysis of microdroplets was investigated. The kinetics of the characteristic Na, K and Cl signals from lyophilized droplets of either KCl or NaCl salts were observed for 1200 s in an electron microprobe whose specimen stage temperature was either 133 K or room temperature. Samples were irradiated with 15 keV electrons, at beam current densities ranging from 7 to 70 A m^?2. Initial count rates were lower for the same samples at 133 K than at room temperature. At 133 K all the signals measured increased at the start and then, in some cases, decreased. Increases were more pronounced for measurements made at the lowest beam current density (i.e. the lowest electron dose), and for samples with the highest mass thickness; they were also more marked for KCl than for NaCl samples. At 133 K, measurements after 10 s irradiation showed no proportionality between X-ray intensity and the concentration of the elements, and proportionality was only restored when droplets had been irradiated for some time and count rates became nearer to the values measured at room temperature. Whether or not these observations reveal the existence of a fundamental physical process or a technical failure is still unknown. In no case was characteristic signal stability improved by the use of a cold stage.     

PLC为核心的实时监测系统

介绍了由多台可编程控制器（PLC）作为下位机与上位微机构成的远程自动监测系统。利用下位机与上位机的串行通讯，使所有的数据传到上住微机集中处理，并打印成报表。下住机的数字显示用传感器的变送器完成，显示汉字及数据。本系统也可扩展A／D、D／A，并行接口等用于其他适合主从多机系统的数据采集与控制。     

数控车床低速车削三角螺纹

介绍数控车床低速斜进车削三角螺纹的方法 ,着重阐述斜进借刀原理 ,并以 BKC- A数控系统加工 M2 4三角螺纹为例 ,具体分析螺纹粗精车进刀方法、局部螺纹循环程序的实现方法、螺纹加工程序的编制和调整方法     

Mechanical properties of Stycast-1266 at low temperatures

Young's modulus, the critical tensile stress, and the fracture stress of Stycast-1266 have been determined by the tension test as functions of temperature between room temperature and 2.2 K.     

Sensitive temperature gradiometer for use at low temperatures

A device capable of very sensitive temperature gradient measurements in the presence of relatively large ambient temperature fluctuations is described. The device uses a pair of 'matched' superconducting thin films in a bridge arrangement, with a SQUID magnetometer probe as the null detector.     

防锈铝合金5083锻件的焊接方法

介绍了防锈铝合金5083的力学性能,分析了其在低温阀门上尤其是在空气分离设备上应用的特点。论述了铝合金阀门的焊接工艺方法。     

The efficiency of X-ray production at low energies

The absolute efficiency of X-ray production has been determined for the K-lines of Al, Si and Cu; for the L-lines of Fe, Co, Cu, Ge and As; and for the M-lines of Hf, Ir, Pt, Au and Bi, using overvoltage ratios in the range 1–10. These emissions, with the exception of the Cu K, have critical excitation energies below 2.6 keV and are therefore typical of the lines used for X-ray microanalysis at low beam energies. For K-lines it is found that the experimental results are in good agreement with a Bethe, or a Casnati, cross-section model. For the L- and M-lines a Monte Carlo technique has been used to find an effective X-ray generation cross-section for each of the elements. The functional forms of these cross-sections are found to be in general agreement with proposed theoretical models.