共查询到20条相似文献,搜索用时 31 毫秒
1.
在气流温度传感器风洞校准试验中,由于试验成本高、校准试验环境与实际使用环境差距大等原因,有必要构建气流温度传感器数值校准虚拟风洞,实现极限非常规校准工况的气流温度传感器误差修正及虚拟校准,并通过气流温度传感器的虚拟校准数值风洞获取仿真结果,尽可能地减少实物校准的工况数量,同时也从理论层面为气流温度传感器的设计与校准提供... 相似文献
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以CPR1000核电站R55区穹顶为研究对象,基于计算流体力学(CFD)技术,应用P-1辐射模型对穹顶内部温度场进行了3D稳态数值模拟与实验验证。结果表明:6月26日6个时刻,空穹顶内Z=11m处的温度模拟值与实测值吻合良好,最大相对误差为3.23%,平均相对误差为1.05%;9:00穹顶内垂直方向温度分布梯度明显,最大温差达到6℃。P-1辐射模型模拟太阳辐射对核电站穹顶内热环境的影响是可行的。 相似文献
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A copper disk pyrheliometer has been designed and constructed that utilizes a new methodology to measure solar radiation. By operating the shutter of the instrument and measuring the heating and cooling rates of the sensor at the very moment when the sensor is at the same temperature, the solar radiation can be accurately determined with these rates. The method is highly accurate and is shown to be totally independent of the loss coefficient in the measurement. The pyrheliometer has been tested using a standard irradiance lamp in the laboratory. The uncertainty of the instrument is identified to be +/-0.61%. Field testing was also conducted by comparing data with that of a calibrated (Eppley) Normal Incidence Pyrheliometer. This paper spells out details of the construction and testing of the instrument; the analysis underlying the methodology was also covered in detail. Because of the high accuracy, the instrument is considered to be well suited for a bench standard for measurement of solar radiation. 相似文献
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为实现太阳能光伏板最佳倾角的设计及优化,通过Matlab建立倾斜放置的光伏板表面接收太阳辐射能模型,计算得到光伏板上的辐射能,推导出光伏板的年最佳倾角和季节最佳倾角.为使光伏板最大限度地接收太阳辐射能,在对传统季节区段重新划分的基础上,优化了季节最佳倾角.结合杭州本地情况,实测光伏板接收的太阳能日辐射量,对不同倾角下的日辐射能进行计算和分析.研究表明,根据季节调整倾角的光伏板接收的年辐射能,与水平和年最佳倾角放置的光伏板相比,分别提高了11.5%和4.1%,水平光伏板辐射能的理论值与实验值误差在5%以内,完全能满足一般太阳能工程研究的需要. 相似文献
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Multiaccess interference in a non-line-of-sight ultraviolet optical wireless sensor network 总被引:2,自引:0,他引:2
Kedar D 《Applied optics》2007,46(23):5895-5901
The concept of exploiting both the scattering properties and the absence of solar radiation in the "solar blind ultraviolet" spectral range for achieving a non-line-of-sight (NLOS) communication link for wireless sensor networks has been discussed in scientific literature. We address the issue of the multiaccess interference (MAI) that would be encountered in a simple and low-cost sensor network operating on the above NLOS principle, for different sensor node densities and traffic levels, and use a Poisson model for the sensor node distribution. A metric for evaluation and comparison of sensor node distribution scenarios is derived and used to discuss the performance limitations of NLOS wireless sensor networks operating in the solar blind ultraviolet spectrum. Guidelines for NLOS wireless sensor network design are outlined taking into consideration the cumulative effect of interference from distant sensor nodes, the expected number of hops, and the trade-off between node redundancy and node isolation. The significant contribution of network traffic control to system operability is demonstrated. 相似文献
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P. K. Narasimharaghavan Hari Om Yadav T. S. Varadarajan L. N. Patnaik S. Das 《Journal of Materials Science》1991,26(17):4774-4786
Results of our experiments on the dark and photoconduction studies in two p-dimethylamino styryl dyes derived from pyridine-2
(PDMS-P2) and pyridine-4 (PDMS-P4) in their pure form without any dopant or additive are reported. Measurements on surface-type
(raster pattern) cells show that the dark and photocurrents are dependent on the applied potential, temperature, and the photocurrent
on the intensity of the incident radiation and the wavelength. Action spectra of the samples could not be recorded as the
intensity of the monochromatic radiation from the monochromator reaching the sample was too low to induce any noticeable photocurrent.
The compounds show a low dark conductivity. The dark and photocurrents show a perfect ohmic behaviour in the temperature range
studied (288–328 K). Since photoconduction could only be observed in a vacuum, this clearly indicates that the compounds are
n-type semiconductors. The observed rise and decay kinetics of the photocurrents indicate the presence of traps in the forbidden
zone. The dyes show an enhanced photoconduction on illumination with visible radiation only. The marked open circuit voltage
and the short-circuit current observed in these compounds indicate a possible application in solar photovoltaics. 相似文献
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利用 ANSYS 热分析模块分别对天线主副反射面板结构和天线的杆系结构建立有限元模型, 计算夏季7月15 日晴天无云这一最不利气候之一的天气各时刻的空气对流换热、太阳辐射、环境长波辐射换热以及阴影遮挡等各种边界条件, 研究分析了主面板、副面板在日照作用下的温度场分布, 特别是由于主面板反射太阳辐射热量并聚焦于副面板从而使副面板温度剧增的“太阳灶”现象;同时为获取天线结构在日照下指向误差变化规律, 还对天线杆系结构进行了日照非均匀热变形分析, 给出日照下主反射面型面精度随时间的变化规律。结果表明:主副面板之间存在的“太阳灶”效应使的副面板最高温度达135℃, 由于日照非均匀温度场的作用, 杆系结构中最大温差达到10.8℃。太阳照射引起的阴阳面造成主反射面不均匀热变形, 在俯仰角90°工况下导致RMS(反射面表面各点误差平方和均方根)最大增加0.35mm。这些数据为下一步结构的施工、传感器的布设以及局部温度控制措施提供了参考信息。 相似文献
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日光模拟器对试验室内传热影响的数值分析 总被引:1,自引:0,他引:1
应用CFD技术对沙漠环境模拟试验室内的传热过程进行了模拟,分别比较了日光模拟器的高度和开启组数对室内温度场和地面辐射分布的影响。研究发现随着日光模拟器高度升高热气流越难被带走,地面太阳辐射值明显减小。随着灯的数量增加,室内上升气流的趋势越明显,地面太阳辐射值明显增大。将灯布置成“梅花状”,有利于辐射照度的均匀。 相似文献
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The influence of the temperature coefficient of resistance in the chemoresistive response of inherently conductive polymer (ICP) sensors in the performance of an artificial neural network (ANN) e-natural olfactory sensor emulator (e-NOSE) system is evaluated. Temperature was found to strongly influence the response of the chemoresistors, even over modest ranges (ca. 2/spl deg/C). An e-NOSE array of eight ICP sensor elements, a relative humidity (RH/spl plusmn/0.1%) sensor, and a resistance temperature device (RTD/spl plusmn/0.1/spl deg/C) was tested at five different RH levels while the temperature was allowed to vary with the ambient. A temperature correction algorithm based on the temperature coefficient of resistance /spl beta/ for each material was independently and empirically determined then applied to the raw sensor data prior to input to the ANN. Conversely, uncorrected data was also passed to the ANN. The performance of the ANN was evaluated by determining the error found between the actual humidity versus the calculated humidity. The error obtained using raw input sensor data was found to be 10.5% and using temperature corrected data, 9.3%. This negligible difference demonstrates that the ANN was capable of adequately addressing the temperature dependence of the chemoresistive sensors once temperature was inclusively passed to the ANN. 相似文献
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Lima A.M.N. Deep G.S. Neto J.S.R. Freire R.C.S. Lobo P.C. 《IEEE transactions on instrumentation and measurement》1994,43(2):133-138
An identification procedure to estimate the parameters of a thermoresistive solar radiation sensor is presented. The proposed technique employs only electrical excitation for the sensor. The estimation algorithm is recursive and is applied to the sensor model derived from the thermodynamic equilibrium differential equations. The simulation and the experimental results demonstrate the validity of the proposed approach 相似文献
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M. J. Lourenço S. C. S. Rosa C. A. Nieto de Castro C. Albuquerque B. Erdmann J. Lang R. Roitzsch 《International Journal of Thermophysics》2000,21(2):377-384
The transient heating in an unsymmetrical, coated, hot-strip sensor was simulated with a self-adaptive finite-element method (SAFEM). The first tests of this model show that it can be used to determine, with a small error, the thermal conductivity of liquids, from the transient temperature rise in the hot strip, which is deposited in a substrate and coated by an alumina spray. 相似文献
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This study reports the direct thermal observation of the junction temperature and determination of the thermal resistance in a commercial solar cell package under actual operating conditions. A thermal transient method was the key method that was utilized for the thermal characterization of the device. Sunlight directed into the solar cell package was found to increase significantly the heat generation inside the solar cell package. It was shown that the operation of the solar cell package with sunlight of 1 sun resulted in a junction temperature of about 113 degrees C. The simulation data were in good agreement with the measured values. Detailed thermal performance of the solar cell package was projected using a Computational Fluid Dynamics (CFD) method under various operating conditions. Thermal resistance was determined under various operating conditions. 相似文献
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Transfer alignment is used to initialize SINS (Strapdown Inertial Navigation System) in motion. Lever-arm effect compensation is studied existing in an AUV (Autonomous Underwater Vehicle) before launched from the mother ship. The AUV is equipped with SINS, Doppler Velocity Log, depth sensor and other navigation sensors. The lever arm will cause large error on the transfer alignment between master inertial navigation system and slave inertial navigation system, especially in big ship situations. This paper presents a novel method that can effectively estimate and compensate the flexural lever arm between the main inertial navigation system mounted on the mother ship and the slave inertial navigation system equipped on the AUV. The nonlinear measurement equation of angular rate is derived based on three successive rotations of the body frame of the master inertial navigation system. Nonlinear filter is utilized as the nonlinear estimator for its capability of non-linear approximation. Observability analysis was conducted on the SINS state vector based on singular value decomposition method. State equation of SINS was adopted as the system state equation. Simulation experiments were conducted and results showed that the proposed method can estimate the flexural lever arm more accurately, the precision of transfer alignment was improved and alignment time was shortened accordingly. 相似文献
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建立了关节臂式坐标测量机(AACMM)结构参数热变形误差的运动学方程,研究了在实验温度约为20 ℃时关节臂式坐标测量机主要结构参数的温度变化规律和测量误差的变化趋势,建立了基于多元线性回归方法的热变形误差补偿模型并进行验证。实验结果表明:AACMM工作温度上升值最大可达3℃,测量误差随温度上升呈增大趋势,最大长度测量误差可达0.115 mm。实现了AACMM热变形误差补偿,平均测量误差从0.071 5 mm降到0.033 5 mm,在一定程度上提高了AACMM的测量精度。 相似文献
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为了考察不同强度等级混凝土路面板不同季节、不同浇注时间的温度变化规律,建立了基于有限差分方法的综合考虑水化放热以及太阳辐射、大气温度变化等环境作用下路面板温度场数值计算模型。计算结果显示:混凝土路面板温度受太阳辐射和大气温度影响呈周期性变化,白天主要受太阳辐射影响,夜间主要受大气温降影响,浇注初期的水化放热亦对早期温升有贡献。混凝土路面板顶面与底面温度差以1d 为周期正负循环。其中温度变化幅度及上下面最大温差以夏季最大、秋冬次之、冬季最小。下午2 点浇注和采用较低强度的混凝土可抑制路面板的早期温升和温度梯度。 相似文献