共查询到20条相似文献,搜索用时 15 毫秒
1.
A new method is described for measuring an impedance accessible only through an unknown 2-port linear system. Four calibrating impedances are used: a known resistance, a short circuit and two other unknown reactances. The value of impedance is calculable directly from the input measurements using simple step-by-step formulas. 相似文献
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Starting with powdered Hg1−xCdxTe, several tie-lines at 500 and 560°C were established using an energy dispersive spectrometer on a scanning electron microscope
for the quantitative analysis. After holding at 500 or 560°C for time periods based upon the powder size and the published
interdiffusion constant, then water quenching to room temperature, the primary grains were found to be uniform in composition
and covered with a 5-6 μ layer of HgTe or low x Hg1−xCdxTe. The primary grain and overall compositions establish directions for tie-lines that are in good agreement with published
experimental and theoreti-cal results. 相似文献
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X. J. Liu H. S. Liu I. Ohnuma R. Kainuma K. Ishida S. Itabashi K. Kameda K. Yamaguchi 《Journal of Electronic Materials》2001,30(9):1093-1103
The phase equilibria of the Cu-In-Sn system were investigated by means of the diffusion couple method, differential scanning
calorimetry (DSC) and metallography. The isothermal sections at 110–900 C, as well as vertical sections at 10wt.%Cu–70wt.%Cu
were determined. It was found that there are large solubilities of In in the ε(Cu3Sn), δ(Cu41Sn11), and η phases in the Cu-Sn system, and large solubilities of Sn in the γ, η, and δ(Cu7In3) phases in the Cu-In system. The η phase was found to continuously form from the Cu-In side to the Cu-Sn side, and a ternary
compound (Cu2In3Sn) was found to exist at 110 C. Thermodynamic assessment of the Cu-In-Sn system was also carried out based on experimental
data of activity and phase equilibria using the CALPHAD method, in which the Gibbs energies of the liquid, fcc and bcc phases
are described by the subregular solution model and that of compounds, including two ternary compounds, are represented by
the sublattice model. The thermodynamic parameters for describing the phase equilibria were optimized, and agreement between
the calculated and experimental results was obtained. 相似文献
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A prototype of a 'real-time' 64-channel spherical measurement system for determining the complex radiated far fields of active mobile terminals is presented. The system does not require any RF feed cables to be connected to the mobile terminal. Test measurements show that the complex far field can be determined with an acceptable accuracy. The system thus provides, together with the radio-channel data, a basis for realistic and fast estimation of MIMO performance of a mobile terminal. 相似文献
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基于基尔霍夫定律,利用半导体激光器InGaAs/I及钽酸锂热释电探测器设计了一种实用化的实时测温系统。基于该系统A/D转换器件的分辨率、V(T)-T曲线的温度灵敏度及其与测温范围间的制约关系,确定了系统应选用16位的芯片为其A/D转换器件;基于该系统的测温精度、V(T)-T曲线的相对温度灵敏度及其与波长间的关系,对其工作波长的优化选择进行了进一步的讨论;基于探头的温度分辨力、A/D转换器件的分辨率以及与V(T)-T曲线的温度灵敏度间的制约关系,对其波长带宽的优化设计进行了进一步的分析,并给出了系统在673K~1473K内的测温灵敏度。对系统进行优化设计后,在测温范围的低温段,其灵敏度不低于0.5K;在测温范围的高温段,则不低于0.1K。在673K~1473K内,其测温不确定度不低于0.3%。 相似文献
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A human intervention is essential for human–machine system and human operator’s skill affects deeply achievement of the control purpose. By keeping the human operation easy, an operator can concentrate on more advanced decision so that the operation performance is improved. In this paper, a new concept of human-oriented compensator is proposed for improving the human–machine system, which is named “collaborater”. The design approach exists in human dynamics, and 2DOF structure is introduced. The simulation results confirm that the time and frequency responses are improved. Moreover the experimental results also confirm the similar effect of proposed method. 相似文献
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K. -F. Schuster H. Rothermel 《Journal of Infrared, Millimeter and Terahertz Waves》1996,17(2):333-344
We present a simple method to determine the spectral response of an SIS detector in the millimeter and submillimeter wavelength range from its current response to a chopped cold-load. This direct detection response is also a good indicator of quantum efficiency and mixer noise temperature when using the SIS junction in heterodyne mode. A simple experimental setup without local oscillator, cryogenic IF-amplifier or any quasioptical interferometer allows a quick diagnosis of integrated planar impedance matching structures. 相似文献
9.
设计并搭建了半球空间内收发同轴的目标表面后向散射特性测量系统,以1 550 nm线偏振、窄线宽激光为光源,在0°~±60°入射角度范围内,通过对具有不同表面微观形貌(研磨、立铣和平铣加工表面)的典型粗糙度比较样块进行后向散射特性的测量,探讨了入射光偏振方向、入射方位角、入射角和表面微观形貌的变化对后向散射特性的影响,分析了这些影响产生的原因,并分析了后向散射场偏振特性的变化。结果表明这些影响因子均对表面后向散射特性产生规律性影响,既有共性规律,也有个性规律.其中,表面微观形貌又决定着入射方位角、入射角等变量变化时对后向散射场能量分布及偏振性质的改变所产生的影响。这一结果为无合作目标测量领域及其他表面测量特性研究领域提供参考及应用价值。 相似文献
10.
X. J. Liu Y. Inohana Y. Takaku I. Ohnuma R. Kainuma K. Ishida Z. Moser W. Gasior J. Pstrus 《Journal of Electronic Materials》2002,31(11):1139-1151
The phase equilibria of the Sn-Ag-In system were investigated by means of differential scanning calorimetry (DSC) and metallography.
The isothermal sections at 180–600°C, as well as some vertical sections, were determined. Thermodynamic assessment of this
system was also carried out based on the experimental data of thermodynamic properties and phase equilibria using the calculation
of phase diagram (CALPHAD) method, in which the Gibbs energies of the liquid, fcc, and hcp phases are described by the subregular
solution model, and those of compounds are represented by the sublattice model. The thermodynamic parameters for describing
the phase equilibria were optimized, and reasonable agreement between the calculated and experimental results was obtained.
The maximum bubble-pressure method and dilatometric method have been used in measurements of the surface tension and density
of the binary In-Sn and ternary (Sn-3.8Ag)eut + In (5 at.% and 10 at.%) liquid alloys, respectively. The experiments were performed in the temperature range from 160–930°C.
The experimental data of the surface tension were compared with those obtained by the thermodynamic calculation of Butler’s
model. 相似文献
11.
本文应用芯片技术设计了棒球测速系统,首先阐述了该系统的工作原理,并对系统需求进行了分析,然后设计了硬件系统和软件系统,硬件系统的加速度传感器采用ADXL345,单片机采用ST7LITE49M,软件系统主要设计了1COSMIC C编译器,最后对该系统进行了系统测试,结果较满意。 相似文献
12.
A new antenna-pattern measurement method for antennas with large far-field distances is proposed. The method is applicable to conventional antenna ranges with two axis mounts and with pattern recording in amplitude only, It requires only a few minor items of additional equipment. A computer simulation has been carried out and the results are presented. 相似文献
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《IEEE instrumentation & measurement magazine》2005,8(1):54-59
There are many ways to measure the magnitude of the frequency response of a system. The authors consider three methods and explain why they are not optimal. Then a method that uses pseudorandom sequences and explains why this method is optimal is considered. The authors discuss pseudorandom sequences and show how their properties make them nearly ideal for measuring the magnitude of the frequency response of a system. Several implementations of pseudorandom sequence generators is described. Finally, an example of a measurement made using a pseudorandom sequence is provided. Pseudorandom sequences are used in audio applications to measure the properties of loudspeakers and of rooms. Additionally pseudorandom sequences are made use of in direct sequence spread spectrum. 相似文献
17.
Zink M. Ottl H. Freeman A. 《Geoscience and Remote Sensing, IEEE Transactions on》1994,32(6):1198-1201
Terrain height variations in mountainous areas cause problems in the radiometric correction of SAR images. The authors propose a novel SAR system which exploits the monopulse principle to determine the elevation angle and thus the height at the different parts of the image. From the ratios of images radiometrically modulated by the difference and sum antenna pattern in cross-track direction, the authors can calculate the appropriate elevation angle at any point in the image. In this paper, they present design considerations for an array antenna for DLR's airborne X-band SAR system and give estimates of the error due to system noise and azimuth ambiguities as well as the expected performance and precision in topographic mapping 相似文献
18.
《Electronics letters》1967,3(10):446
The use of a Markov model is a valuable aid in the analysis of many systems. The purpose of this work is the establishment of a response for this type of system based on the use of an impulse function. The response of the system is obtained with the impulse as an excitation while utilising the Markov property of the system. 相似文献
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