共查询到19条相似文献,搜索用时 187 毫秒
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提出了一种基于Fabry-Perot板干涉的角位移测量新方法。此方法采用函数近似,只需将初始入射角确定在40°到50°之间,即可由角位移与干涉信号条纹数变化间的函数关系,高精度测量角位移。解决了采用F-P板干涉法测量角位移需精确确定入射光初始角的问题。使用计算机处理采集的干涉信号,对干涉条纹进行细分,实现干涉信号相位测量的高分辨力。理论模拟和实验结果得出本方法可以实现精度为10-5rad数量级的角位移测量。该方法的测量装置采用带尾纤的半导体激光作为光源,由自聚焦透镜准直,出射光束直径为0.5mm,使探测头为小光斑。该装置结构简单,能实现小型化。 相似文献
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《中国测试》2019,(12):20-24
针对当前测量车辆通过角的手段较为复杂,对便携式双板测量的有效范围及测量偏差进行研究。首先基于几何关系分析有效测量条件,进而计算适用的测量板尺寸及有效测量范围,确定装置的设计和选用条件;然后求解测量失效时的实测角和精确角,并分析参数对测量偏差的影响;最后提出一种修正方法以补偿测量偏差,提升装置测量较小角度的适用性。结果表明:当待测角不小于装置临界角时,测量结果有效;待测角小于临界角时,测量结果失效,应通过不同参数下的修正表进行角度补偿;测量临界角与装置和车辆的尺寸参数相关,且测量板厚度越小,临界角越小,装置有效测量范围越大。研究可为双板测量装置的工程实用化奠定理论基础。 相似文献
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锶(Sr)掺杂羟基磷灰石(HA)在生物材料中得到广泛应用。在此研究中, 使用水热合成的方法制备HA和Sr掺杂HA的纳米颗粒。通过实验和计算机模拟的方法研究Sr掺杂对HA化学成分、结晶度、晶格参数、形貌和形成能的影响。实验结果表明, Sr掺杂后的HA纳米颗粒晶格参数和晶体尺寸增大。随着Sr离子浓度的增加, Sr 掺杂HA的纳米颗粒的结晶度没有显著变化。模拟结果验证了实验得到的Sr 掺杂HA纳米颗粒晶格参数的准确性, 且进一步表明Sr 离子掺杂后纳米颗粒的形成能较低, 结构更稳定。当Sr掺杂浓度为10%时, Sr掺杂的优先位点是Ca(1); Sr掺杂浓度为50%时, Sr混合掺杂到Ca(1)和Ca(2)位点为更优先的掺杂模式。 相似文献
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辐射源尺寸效应(SSE)是辐射测温的重要不确定度来源,本文设计了辐射温度计实验测试装置,在理论分析的基础上通过改变孔径光阑设置,研究辐射温度计SSE的变化。孔径适宜的孔径光阑在光轴任意位置都能起到限制接收立体角的作用,但实验表明设置在会聚透镜之后的SSE明显小于其他位置。本实验研究结果可为辐射温度计和绝对辐射法热力学温度测量的SSE优化设计提供参考依据。 相似文献
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本文介绍了空分装置用冷凝蒸发器结构改进的结果,示出了五种板翅式冷凝蒸发器组装的结构型式和各种型式冷凝蒸发器的结构参数,同时指出,对于新型空分装置,最有发展前途的是采用具有多孔复盖层管式冷凝蒸发器和板翅式冷凝蒸发器。图1、表1。 相似文献
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Minkin L 《Radiation protection dosimetry》2003,106(3):267-272
Based on the non-intersection model of cylindrical capillaries, the mean radius of the pores of some soils and building materials are estimated. In size, the above-mentioned radii are usually of the order of the free path of gas molecules at atmospheric pressure. A review of pore size distribution data also reveals that a large fraction of concrete pores belong to Knudsen's region. This fact indicates that the thermal gradient in these media must cause gas (radon) transport. The interpretation of the experimental data concerning the rate of emanation of 222Rn from a concrete-capped source subjected to a sudden increase in temperature is given, based on irreversible thermodynamics theory. The calculations given here for radon flux, caused by concentration and thermal gradients, are in satisfactory agreement with the experimental data. It is shown that thermodiffusion can significantly contribute to radon flux in concrete. The need to include the thermodiffusion radon flux in the radon entry model is discussed. 相似文献
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Voltaggio M 《Radiation protection dosimetry》2012,150(3):334-341
During atmospheric thermal inversions, dew and hoarfrost concentrate gamma emitting radionuclides of the short-lived (222)Rn progeny ((214)Pb and (214)Bi), causing an increase in the total natural gamma background from the ground. To highlight this phenomenon, a volcanic zone of high (222)Rn flux was studied during the winter season 2010-11. High-specific short-lived radon progeny activities up to 122 Bq g(-1) were detected in hydrometeors forming at the earth's surface (ESHs), corresponding to a mean increase of up to 17 % of the normal gamma background value. A theoretical model, depending on radon flux from soil and predicting the radon progeny concentrations in hydrometeors forming at the ESHs is presented. The comparison between model and field data shows a good correspondence. Around nuclear power plants or in nuclear facilities that use automatic NaI or CsI total gamma spectroscopy systems for monitoring radioactive contamination, hydrometeors forming at the ESHs in sites with a high radon flux could represent a relevant source of false alarms of radioactive contamination. 相似文献
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Albarracín D Font L Amgarou K Domingo C Fernández F Baixeras C 《Radiation protection dosimetry》2002,102(4):359-364
High indoor radon concentration means an increased risk of developing lung cancer. When high radon levels are present in a dwelling, the major source is normally the soil. Therefore, it is useful to know the radon concentration field in the soil underneath a building. A steady-state two-dimensional radon transport model has been used to calculate the effect of a reference building on the soil radon concentration, and the influence of soil parameters on radon entry through a single crack in the basement. Both advective and diffusive flows are considered. Away from the building, the well-known undisturbed soil radon concentration profile has been obtained, while under the house the radon level is increased. A variability analysis around the reference site has shown that the most relevant soil parameters on the radon flux at the top of the crack are, in this case, effective diffusion coefficient, soil gas-permeability and deep soil radon concentration. 相似文献
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Pressyanov D Georgiev S Dimitrova I Mitev K Boshkova T 《Radiation protection dosimetry》2011,145(2-3):123-126
This paper describes a method for determination of the diffusion coefficient and the solubility of radon in plastics. The method is based on the absorption and desorption of radon in plastics. Firstly, plastic specimens are exposed for controlled time to referent (222)Rn concentrations. After exposure, the activity of the specimens is followed by HPGe gamma spectrometry. Using the mathematical algorithm described in this report and the decrease of activity as a function of time, the diffusion coefficient can be determined. In addition, if the referent (222)Rn concentration during the exposure is known, the solubility of radon can be determined. The algorithm has been experimentally applied for different plastics. The results show that this approach allows the specified quantities to be determined with a rather high accuracy-depending on the quality of the counting equipment, it can be better than 10 %. 相似文献
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I.S. Kim A. Appleby G.H. Sigel Jr. 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1997,390(3):749-422
We report the observation of the trapping of radioactive inert gas radon (222Rn) on oxide glass under ambient air temperature and pressure of 300 K and 760 Torr, respectively. Radon diffuses from the source, through two macroporous scintillating-glass-fiber bundle alpha detectors in series, to the end of the linear closed system filled with ambient air. The strategy is to provide radon atoms and alphas emitted from radon and its progeny with large accessible scintillating glass surface areas for efficient trapping and detection, respectively. Diffusion-only transport mechanism could not explain the experimental observations, strongly suggesting the trapping of radioactive inert gas radon (222Rn) on oxide glass. 相似文献
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Malki A Lavi N Moinester M Nassar H Neeman E Piasetzky E Steiner V 《Radiation protection dosimetry》2012,150(4):434-440
Building regulations in Israel require the insulating of buildings against radon (222)Rn penetration from soil. In radon-prone areas membranes stretched between the soil and the building foundation are used, together with sealing other possible penetration routes. Designing the radon mitigation procedure requires checking that all sealing materials are practically, radon tight, having a thickness of at least three times the radon diffusion length. In this work, a very simple technique to evaluate the radon diffusion length in thin membranes, using a radon source of known activity and an activated charcoal canister as radon detector is presented. The theoretical formalism and measurement results for polyethylene membranes of different densities obtained in a recent comparison exercise are presented. 相似文献
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A theoretical model based on Fourier optics and the power-coupling overlap integral is built to investigate the interchannel response in a micro-electro-mechanical systems 1xN(2) wavelength-selective switch. The simulation results demonstrate that the interchannel response depends significantly on the output port location and the radius of curvature of the micromirrors. For the output originally aligned with the input along the dispersion direction, it is possible to achieve interchannel-response suppression by rotating the two-dimensional (2D) collimator array by a slight angle, e.g., 20 degrees. Experimental results under different conditions are also shown. 相似文献
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This work was aimed at studying the behaviour of 222Rn in an experimental underground copper mine in Brazil with a single entrance. The 222Rn concentrations, meaured by using a dynamic radon measuring technique. varied between 30.5 Bq.m(-3), during ventilated conditions applied to the mine galleries, and 19.4 x 10(3) Bq.(-3) for non-ventilated conditions and when operational mining activities were conducted inside. High radon concentration surges were observed after blasting and drilling activities. In the cases of inadequate ventilation, it was estimated that workers could be subjected to exposures as high as 10 microSv.h(-1), only due to 222Rn and its short-lived progeny. The results show the importance of real-time measurements to evaluate radon dynamics during mining operations. 相似文献
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The National Institute of Standards and Technology (NIST) polyethylene-encapsulated 226Ra/222Rn emanation (PERE) standards (old SRM 4968 and new SRMs 4971, 4972, and 4973) provide precise radon emanation rate, certified to a high degree of accuracy (approximately to 2%). Two new SRM 4973 standards containing totally 1036 Bq (0.028 microCi) of 226Ra, emanate 0.114 Bq (3.08 pCi) of 222Rn per min. Air passing over such sources at a flow rate of 1 l min(-1) will have a radon concentration of 114 Bq m(-3) (3.08 pCi l(-1)). This paper describes a practical calibration system and the actual calibration verification data obtained at different flow rates, for E-PERM passive radon monitors, Femto-Tech and Alpha Guard Continuous Radon Monitors. The use of such an affordable and easy to use system by the manufacturers and users of radon measurement devices will bring uniform standards with traceability to a NIST standard source and is considered an important step in standardising radon measurement methods. 相似文献