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991.
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993.
A. A. Vertiy I. V. Ivanchenko N. A. Popenko S. I. Tarapov V. P. Shestopalov 《International Journal of Infrared and Millimeter Waves》1989,10(3):395-404
A radio spectrometer set suggesting wide fuctional possibilities and operating in the shortwave part of the millimeter band at temperatures below 1 K is described. The set is intended for analyzing materials of polarized nuclear targets under the conditions close to actual operation, with the use of magnetic resonance methods. The potential of spectrometer allows employing it in semiconductor physics, physics of disordered media, biology, et.c. 相似文献
994.
本文从理论和实验上研究了具有环状耦合、工作在稳定腔边缘的凹-凸型高功率激光稳定腔.在一台大激活体积万瓦级模流CO_2激光器上进行实验,获得了具有良好方向性的均匀的环状分布近场花样的7kw激光输出. 相似文献
995.
A.P. Sarvazyan 《Ultrasonics》1982,20(4):151-154
The application of ultrasonic methods to investigation of problems of molecular physics and molecular biology is greatly limited by the necessity of precise measurements of ultrasound velocity and absorption in small volumes of liquids. Fixed path interferometric methods are the most adequate for such measurements in the low MHz region.In this paper disadvantages of the present interferometric methods of ultrasonic measurements are considered and new resonator cells and a simple device for such measurements are described. Accuracies of 10?4% for the velocity change and to better than 1% for the attenuation change, at frequencies of about 7 MHz, are obtained by the device described. The volumes of the resonator cells vary within 0.1 to 0.8 ml depending on the purpose of investigation. 相似文献
996.
Multi-chamber perforated resonator (MCPR) is a kind of typical silencer element which can both attenuate broadband noise and satisfy specific installation requirements. The one-dimensional transfer matrix method (TMM) and finite element method (FEM) are widely used to predict the transmission loss of the resonators. This paper mainly focuses on the comparison between 1D TMM and FEM in which detailed perforation modeling is applied for the acoustic modeling of MCPRs. Five resonators with different acoustic attenuation frequency ranges are built for simulation and test. In order to verify the results of the above methods, a transmission loss test facility is designed based on two-load method. Through adjusting the distance between microphones, the facility’s effective measurement frequency can be changed. The results show that despite of the complex modeling and calculation, FEM with detailed perforation modeling shows good consistency with test results in both frequency and amplitude within entire frequency range. In comparison, TMM is limited by the cut-off frequency when calculating transmission losses. Besides, accuracy of TMM in low frequency range is also affected by perforation conditions. However, TMM is time-saving in calculation and structure optimization. In MCPRs’ development process, TMM can be used to quickly design and optimize structure parameters while FEM can be used to verify the acoustic performance before prototyping. 相似文献
997.
《Comptes Rendus Physique》2016,17(5):518-523
We explore experimentally the role played by diffraction in the phenomenon of acoustic shielding provided by a plate that is periodically perforated with subwavelength slits and immersed in water. We carried out ultrasonic transmission measurements for all directions of propagation in order to check the omnidirectionality of acoustic shielding. While a single slit acts as a Fabry–Perot resonator in the frequency range of interest, the coupling between adjacent slits provides an attenuation frequency band centered around the resonant frequency that is mostly independent of the angle of incidence. Beyond the incident angle of 45 degrees, however, we observe the appearance of scattered radiation that limits the attenuation of ultrasound. This spurious scattering is shown to arise from diffraction by the grating of slits. 相似文献
998.
A compact CO2–NH3 FIR laser system where an NH3 laser cavity was inserted in pump, three mirror CO2 laser cavity was designed. The total length of this system was about 1.8 m. Output energy of about 1 mJ (10 KW pea power) was obtained at the 152 m and 90 m lines in NH3. Power conversion efficiency of 1.7 percent was obtained at the 90 m line. 相似文献
999.
J. W. V. Storey D. M. Watson C. H. Townes 《International Journal of Infrared and Millimeter Waves》1980,1(1):15-25
A Fabry-Perot spectrometer for airborne observations of astronomical spectral lines has been designed for use in the 50 to 200 m region of the far-infrared. The spectrometer uses a fixed wavelength Fabry-Perot filter cooled to 4.2 K in conjunction with a high order scanning Fabry-Perot at room temperature. This arrangement provides high spectral resolution and also minimizes the thermal background radiation on the detector. The instrument has been successfully used to study all the presently detected fine structure lines between 50 and 120 m.Work supported in part by NASA Grant NGR 05-003-511 相似文献
1000.
A. A. Vertiy S. P. Gavrilov O. A. Tretyakov M. E. Özel 《International Journal of Infrared and Millimeter Waves》1996,17(9):1541-1556
Employment ofE
0np modes of cylindrical cavity resonator for measurement of electrodynamical parameters of dielectric pipe-shaped materials in millimeter wavelength band is suggested. Dielectric permittivity and conductivity of a sample can be found by measuring the frequency shift and theQ-factor change of the resonator.Method of mode basis is used for the calculation of sample permittivity and conductivity . Measurements were carried out at 8mm wavelength and related calculations have demonstrated use and possibilities of the method in studying the dielectric properties of samples of cylindrical and other forms. 相似文献