Dual-jet plasmatron for medical applications

We present a design for a dual-jet arc plasmatron operating at a frequency of 66 kHz in an argon flow at atmospheric pressure. We present the results of determination of the temperature, electron concentration, and electrode erosion obtained by atomic emission spectral analysis. The proposed convenient design for a dualjet plasmatron and the low erosion of the copper electrodes in the plasma make it possible to use it for medical purposes. Report given at the Fifth International Conference on Plasma Physics and Plasma Technologies (PPPT-5), 18–22 September 2006, Minsk, Belarus. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 139–140, January–February, 2007.     

Corrosive behavior of chromium carbide-based films formed on steel using a filtered cathodic vacuum arc system

The formation of chromium carbide-based hard-coatings on steels using a 90°-bend filtered cathodic vacuum arc (FCVA) has extensive industrial applications; such coatings are free of macroparticles and exhibit excellent characteristics. In this investigation, a working pressure of C₂H₂/Ar was adopted to synthesize amorphous chromium carbide film (a-C:Cr) and crystalline chromium carbide film (cryst-Cr₃C₂) from a Cr target (99.95%) at 500 °C under a substrate voltage of −50 V. The corrosion behavior of a-C:Cr coated on steel (a-C:Cr/steel) and cryst-Cr₃C₂ coated on steel (cryst-Cr₃C₂/steel) were compared in terms of open-circuit potentials (OCP) and polarization resistance (R_p) in an aerated 3.5 wt% NaCl aqueous solution, as determined by electrochemical impedance spectroscopy (EIS). The XRD results indicated that the transformation of a-C:Cr to cryst-Cr₃C₂ is distinct as the working pressure declines from 1.2 × 10⁻² to 2.9 × 10⁻³ Torr. The OCP of a-C:Cr/steel and cryst-Cr₃C₂/steel resemble each other and both assembly are nobler than uncoated steel. The R_p of the coatings exceeds that of the uncoated steel. The SEM observation and the EIS results demonstrate that the cryst-Cr₃C₂/steel more effectively isolates the defects than dose a-C:Cr/steel.     

An investigation into EMI-induced noise in nanometer multi-quantum well InGaN LEDs

This study investigates the low-frequency noise induced by electromagnetic radiation interference (EMI) in a nanometer multi-quantum well InGaN LED (NMQLED). Theoretical models of the noise spectra and the EMI are constructed. In general, a good agreement is identified between the experimental and theoretical results. Both sets of results reveal that the magnitude of the EMI-induced noise is related to the pulse height, the output load, the parasitic capacitance, the interference frequency and the interference amplitude. It is shown that the harmonic noise increases with an increasing interference amplitude and frequency. The techniques presented in this study provide a systematic approach for obtaining the interference noise and signal-to-noise ratio (SNR) in LEDs and similar wavelength-based semiconductor devices.     

两相颗粒多孔材料导热系数研究

对固-气两相颗粒多孔材料导热系数的预测,尚未见以实验数据对其各预测模型进行分析及验证其准确度的相关文献。本文利用断电热线法测定石英砂、碳化硅、工程沙以及煤灰的导热系数;将模型预测结果与实验数据进行对比分析,结果表明,Kunii and Smith模型误差小;考虑孔隙率的影响,利用实测数据对Kunii and Smith模型进行修正,给出新的预测模型;通过与国外学者给出的实测导热系数的对比,验证了本文给出的修正模型的准确性。     

An algorithm for fitting circular arcs to data using the <Emphasis Type="Italic">l</Emphasis><Subscript><Emphasis Type="Italic">1</Emphasis></Subscript> norm

There are many applications of fitting circular arcs to data. We have for example, system control, using a computer controlled cutting machine, approximating hulls of boats, drawing and image techniques. Out of these applications comes the least squares norm to be the most commonly used criterion. This paper examines how the l ₁ norm is used which seems to be more appropriate than the use of least squares in the context of wild points in the data. An algorithm and different methods to determine the starting points are developed. However, numerical examples are given to help illustrate these methods.      

Influence of processing variables on the formation of La2Zr2O7 in transferred arc plasma torch processing

The transferred arc plasma (TAP) torch process has various noteworthy features such as extremely high temperatures, low environmental impact and short processing time which makes it the most suitable technique for synthesizing ceramic composite materials. Furthermore, it is a direct two-step technique which by its virtue of high temperature and power density paves way for high production rate. Hence in this study, an effort has been made to utilize the TAP torch processing technique for the bulk production of La₂Zr₂O₇ with time effectiveness from the mixture of La₂O₃ and ZrO₂ powders (1:2 mol ratios) which were ball milled for 4 h. For this purpose, transferred arc plasma torch was specially designed in laboratory scale level and the operating parameters were optimized in order to achieve maximum La₂Zr₂O₇ formation efficiency. In this study, the phase and microstructure formation of the processed samples was analyzed via X-ray diffraction (XRD) and scanning electron microscope (SEM) images respectively. Moreover, EDX analysis was incorporated to highlight the superior influence of the longer processing time on the stoichiometric ratio of ZrO₂/La₂O₃ in the processed sample as against input power and the gas flow rate.     

一种可调制的连续光谱点光源

短弧氙灯是一种发光强度高,具有从紫外到红外的连续光谱的点光源。本文介绍交流供电的短弧氙灯光源,用两电极短弧氙灯实现三电极短弧氙灯性能的方法。给出了用一个系统满足各种不同发光强度、不同调制波形、不同调制频率的要求,以及在制造和使用过程中应注意的事项。     

STABILITY OF A KIND OF COMPOUND BOUNDARY VALUE PROBLEM WITH RESPECT TO THE PERTURBATION OF BOUNDARY CURVE

In this paper, we discuss the stability of general compound boundary value prob-lems combining Riemann boundary value problem for an open arc and Hilbert bound-ary value problem for a unit circle with respect to the perturbation of boundary curve.     

A variable neighborhood search for the capacitated arc routing problem with intermediate facilities

The capacitated arc routing problem (CARP) focuses on servicing edges of an undirected network graph. A wide spectrum of applications like mail delivery, waste collection or street maintenance outlines the relevance of this problem. A realistic variant of the CARP arises from the need of intermediate facilities (IFs) to load up or unload the service vehicle and from tour length restrictions. The proposed Variable Neighborhood Search (VNS) is a simple and robust solution technique which tackles the basic problem as well as its extensions. The VNS shows excellent results on four different benchmark sets. Particularly, for all 120 instances the best known solution could be found and in 71 cases a new best solution was achieved.     

钢丝绳模型比较研究

将现有的各种钢丝绳计算模型进行比较研究，通过将数值结果与现有的实验数据进行比较可以看出，考虑绳芯变化并结合Love曲杆理论的JW和KC模型更适用于实际的钢丝绳结构。