Vanadium oxide films with improved characteristics for ir microbolometric matrices

Vanadium oxide (VO_x) films intended for use in uncooled IR microbolometric matrices were deposited by reactive magnetron sputtering on silicon substrates. Optimum deposition conditions were determined, which provide for the obtaining of films possessing a current 1/f noise level 3–10 times lower, extended dynamic range, and increased working temperature interval. It was found that the 1/f noise level of the VO_x films depends on the VO₂ phase content and grain size. It is suggested that the observed 1/f noise is caused by the martensite transformation characteristic of the semiconductor-metal phase transition in VO₂.     

Calculation of a conical anode radiator

A method of determining the dimensions of a minimum-weight anode radiator of a five-element thermionic generator for certain cases of variation of the cross-sectional area of the radiator is described.     

耐高温缩水甘油胺型环氧树脂的化学流变特性

采用流变仪测试耐高温缩水甘油胺型环氧树脂体系的黏度-温度和黏度-时间特性曲线,考察了树脂体系的化学流变特性,建立并对比树脂体系在等温条件下黏度特性曲线的Daul Arrhenius模型和工程黏度模型,提出了一种二阶指数黏度模型预测体系的黏度变化规律。结果表明:二阶指数黏度模型的预测精度和适用范围均优于Daul Arrhenius模型和工程黏度模型,预测黏度与实验值具有良好的一致性,根据建立的黏度随温度和时间变化的唯象关系式,可方便准确地预报树脂体系的工艺窗口,指出了其在工程应用中必须改善的工艺问题。      

Peculiarities of the current-voltage characteristics of a Josephson medium in a YBCO high-temperature superconductor

The influence of a weak magnetic field (H < 150 Oe) on the current-voltage (I-U) characteristic of a YBa₂Cu₃O_{7 ? x} (YBCO) high-temperature superconductor (HTSC) near the superconducting transition temperature has been studied. It is established that there exist narrow (<0.2 K) temperature regions where the I-U curve exhibits sharp bending for H < 30 Oe and the ohmic behavior changes to a quadratic dependence of the voltage on current in a region of several milliamperes. At higher temperatures, the I-U curve bending exhibits smearing. This behavior is observed at a temperature below that corresponding to a zero critical current. Above a certain current, the temperature and magnetic field exhibit equivalent effects on the I-U curve of YBCO. Experimental results are explained by a sharp decrease in the critical currents of intergranular Josephson junctions under the action of magnetic field and by the current-induced formation of uncoupled (with respect to the order parameter) superconducting grains. Characteristic currents for the transition of the intergranular Josephson medium into an incoherent state are determined and the first critical fields in YBCO are evaluated.     

Multi-objective design optimization of a new space radiator

In this work different multi-objective techniques are used to the conceptual design of a new kind of space radiator. Called VESPAR (Variable Emittance Space Radiator), the radiator has an effective variable emittance which makes it able to reduce or avoid the demand for heater power to warm up equipment during cold case operations in orbit. The multi-objective approach was aimed on obtaining a radiator that minimize its mass while at the same time minimize the need for heater power during cold case. Four multi-objective algorithms were used: Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II), Multi-Objective Genetic Algorithm (MOGA), Multi-Objective Simulating Annealing (MOSA) and Multi-Objective Generalized Extremal Optimization (M-GEO). The first three algorithms were used under the modeFrontier^® optimization software package, while M-GEO is a recently proposed multi-objective implementation of the Generalized Extremal Optimization (GEO) algorithm. The Pareto frontier showing the trade-off solutions between radiator mass and heater power consumption is obtained by the four algorithms and the results compared. An assessment of the performance of M-GEO on this problem, compared to the other well-known multi-objective algorithms is also made.     

On a modified Kim-Anderson model of the current-voltage characteristics of high-temperature superconducting ceramics

In comparison with the classical Kim-Anderson model for the current-voltage characteristics of type-II superconductors, another model with a less sharp pinning potential is presented. In addition to the approximate solution, for currents close to the critical one, a complete solution of this model is derived, which better fits the experimentally obtained current-voltage characteristics.     

Extracting surface impedance model parameters of a high-temperature superconductor from experimental characteristics of a microstrip resonator

We describe a method for extracting the model parameters of a high-temperature superconductor (HTSC) film from experimental resonance characteristics of a microstrip resonator. The method is based on a correct phenomenological model of the surface impedance of an HTSC film and the exact calculation of the microstrip resonator characteristics. The procedure of extracting the model parameters from experimental data is realized by using a genetic algorithm. Based on the models described, a special program implementing this mathematical algorithm was written, which allows the HTSC model parameters to be determined from experimental data.     

Effect of the geometric characteristics of a multijet mixing chamber on high-temperature heat exchange in a channel

The work entailed the experimental determination of the effect of the ratio of the diameters of the nozzles of electric-arc gas heaters to the channel diameter of a multijet mixing chamber on the heat exchange of a high-temperature air stream with the channel walls.     

棒形超声辐射器的特性

基于一维振动理论和有限元分析,研究了两种结构棒形超声波辐射器,在空载和水负载下的振动特性以及振幅和应力分布。用有限元对辐射器的声场进行了模拟。理论分析结果进行了实验验证。研究表明棒形辐射器有很好的辐射效果,其辐射声场与结构有关,因而合理的设计可以得到满意的辐射声场。     

Refining the high-temperature strength characteristics of composite materials under bending

On the basis of the complete equation of bending, we establish the refined mechanical characteristics of a carbon-filled plastic under bending as functions of temperature by taking into account the effect of rotation of reactions in the supports. We also show that friction in the supports affects the fracture process in specimen subjected to bending. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 1, pp. 139–141, January–February, 1999.     

A radiator system for cooling a short cylindrical body

A solution is given for the heat loss and optimal design of radial cones (solid and hollow) that lie in the same plane.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 18, No. 4, pp. 737–739, April, 1970.     

Mathematical modeling of high-temperature thermophysical characteristics of rubber-like thermal protection materials

Based on analyzing and generalizing results of theoretical and experimental investigations of main regularities of heat transfer in the thermal protection of the combustion chamber, the mathematical and computer models of high-temperature characteristics of rubber-like thermal protection materials are formulated. The distinctive feature of the models is taking into account the change in the composition and structure of the destructing material in the process of heating up to high temperatures. Results of the numerical simulation satisfactorily agree with experimental data.     

Local characteristics of heat-radiation superconductor detectors based on high-temperature superconductor films

Relations are proposed for evaluating the local values of the thermal sensitivity, speed of response, and resolution of a heat radiation detector based on high-temperature superconductor films.Moscow Institute of Engineering Physics. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 6, pp. 873–877.