共查询到13条相似文献,搜索用时 0 毫秒
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YANG MinDong TENG Bin XIAO LongFei NING DeZhi SHI ZhongMin QU Yan 《中国科学:物理学 力学 天文学(英文版)》2014,57(1):152-165
A new full time-domain nonlinear coupled method has been established and then applied to predict the responses of a Truss Spar in irregular wave.For the coupled analysis,a second-order time-domain approach is developed to calculate the wave forces,and a finite element model based on rod theory is established in three dimensions in a global coordinate system.In numerical implementation,the higher-order boundary element method(HOBEM)is employed to solve the velocity potential,and the 4th-order Adams-Bashforth-Moultn scheme is used to update the second-order wave surface.In deriving convergent solutions,the hull displacements and mooring tensions are kept consistent at the fairlead and the motion equations of platform and mooring-lines/risers are solved simultaneously using Newmark-integration scheme including Newton-Raphson iteration.Both the coupled quasi-static analysis and the coupled dynamic analysis are performed.The numerical simulation results are also compared with the model test results,and they coincide very well as a whole.The slow-drift responses can be clearly observed in the time histories of displacements and mooring tensions.Some important characteristics of the coupled responses are concluded. 相似文献
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在分析显微物镜成像原理的基础上,提出并实现了一种微操作机器人系统光轴方向深度测量方法,该方法通过显微物镜离焦光学传递函数(optical transfer function, OTF)建立物方离焦程度与显微图像模糊程度的关系,由此实现深度测量.由于考虑了透镜参数与衍射效应的影响,方法具有较高的测量精度和较好的线性度,同时利用条状物体快速辨识算法,对原始方法进行了简化,使深度测量可在线完成.进一步,将上述方法应用于实际微操作机器人系统,通过离焦状态双针互插实验验证了方法的有效性,同时拓展了微操作机器人系统的有效操作空间.
关键词:
深度测量
微操作机器人
显微镜系统成像模型
光学传递函数 相似文献
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利用电压/电流探头和数字示波器实现了脉冲调制射频功率测量。电压/电流探头输出的电压、电流信号由数字示波器采集存储,电压、电流的幅值及相位差由FFT分析得到。在不同频率下,对电压、电流幅值及相位差进行标定,获得计算射频功率的标定参数。分析表明电压、电流相位差是影响标定系数的主要因素,FFT方法处理非稳态调幅电压、电流时存在问题,只有在零无功功率处才能获得可信的吸收功率。 相似文献
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在LabVIEW开发环境下,基于虚拟仪器和PXI总线,采用National Instrument(NI)公司的数据采集卡,设计了一个空间相机试验测控系统,实现了硬件设计和软件功能。该系统具有多个通道,可测试温度、应力、应变等多种参数,能实现测控参数设置、数据采集与处理、数据及曲线显示、信号分析与处理、远程通信等多种功能。在某空间相机分系统热平衡试验中,用于测试、控制36个热敏电阻测温点和14个热电偶测温点的温度。结果表明,系统达到了0.5℃的控温要求;热电偶的标定和标准水银温度计的比对结果表明,本系统测温精度可达到0.15℃。与传统的文本语言相比,利用LabVIEW节省了大约80%的时间。本系统具有延续开发能力和可移植性,其设计方法能为其它测控系统的开发提供参考。 相似文献
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Volker Sick 《Proceedings of the Combustion Institute》2019,37(4):4945-4953
This study investigates the influence of large-scale flow features, including flow structure and velocity magnitude, on the early-burn period variability in a homogenous-charge spark-ignited engine fueled with premixed propane-air mixture. Particle image velocimetry and in-cylinder pressure measurement data from a previous study - were processed to enable simultaneous flow characterization and flame-front tracking as well as apparent heat-release analysis. By combining probability analysis of flame development with conditional sampling of fast and slow early-burn cycles using 10% fuel mass fraction burned, it is shown that an undesirable flow structure produces an asymmetric flame development at the initial flame growth period. This asymmetric flame structure persists through the whole initial-to-turbulent transition period until the flame becomes fully turbulent. The undesirable flow condition is characterized by large-scale convective flows near spark plug rather than flows that lead to increased flame spread in multiple directions. The simultaneous flow and flame characterization enables the quantifications of flame-front propagation speed, unburned fuel-air mixture velocity ahead of flame front and local burning velocity at flame surface. Here the local burning velocity is referred to as laminar or turbulent flame speed. A simplified approach is introduced to derive integrated values for these quantities per crank-angle-degree, enabling the quantitative comparison of the trend-wise difference in these integrated metrics between fast and slow early-burn cycles. It is revealed that for the transition period, the CCV in the velocity magnitude of unburned fuel-air mixture ahead of the flame front accounts for nearly 50% to the variability of flame propagation speed. The burning velocity provides the remaining source of the flame propagation variability in this period. The flame propagation variations in the initial flame growth and fully turbulent periods are smaller than those in the transition period and are primarily dependent on the variability of large-scale flow features. 相似文献
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Effect of the nonlinearity of the CCD in Fourier transform profilometry on spectrum overlapping and measurement accuracy 下载免费PDF全文
In Fourier transform profilometry (FTP), we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device (CCD) and increase the measurement accuracy of the object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and a simple physical explanation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the proposed theory and method. 相似文献
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直流电弧全谱直读原子发射光谱法(DC-Arc-AES)测定地球化学样品中痕量硼、钼、银、锡、铅的方法研究 总被引:2,自引:0,他引:2
建立了直流电弧全谱直读原子发射光谱法(DC-Arc-AES)测定地球化学样品中痕量硼、钼、银、锡、铅的分析方法。所使用直流电弧全谱直读原子发射光谱仪采用大面积固态检测器,具有全谱直读功能,并能实时背景校正。通过研究提出了新的电极和新的缓冲剂配方,方法采用内标法,以Ge元素作内标元素,同时选择了合适的分析线对。电流程序研究中设置多级电流,每级电流设置不同保持时间,升电流时选择连续升电流方式,可以有效消除试样的飞溅。以氩气为保护气消除CN带的产生并减少光谱背景,选择氩气流量为3.5 L·min-1。作各元素的蒸发曲线,得出各元素的蒸发行为基本一致,同时结合摄谱时间对各元素强度和背景的影响,得出最佳的设谱时间为35 s。方法选择国家一级地球化学标准物质作为标准系列,标准系列中包括了不同性质、不同含量的标准物质,满足地球化学样品中痕量硼、钼、银、锡、铅的测定。在优化的实验条件下,方法检出限为:B: 1.1 μg·g-1,Mo: 0.09 μg·g-1,Ag: 0.01 μg·g-1,Sn: 0.41 μg·g-1,Pb: 0.56 μg·g-1,精密度为(RSD, n=12):B: 4.57%~7.63%,Mo: 5.14%~7.75%,Ag: 5.48%~12.30%,Sn: 3.97%~10.46%,Pb: 4.26%~9.21%,准确度通过国家一级地球化学标准物质验证,结果与标准值相符。本方法简便、快速,是测定地球化学样品中痕量硼、钼、银、锡、铅的一种先进的分析方法,具有一定的实用性。 相似文献
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A method for independent control of the particle size and distance is presented for rhodium epitaxy on TiO2(110)-(1×2) surface. The real space imaging of the surface morphology was performed by scanning tunneling microscopy. The amount of the deposited rhodium was checked by Auger electron spectrometry. The method consists of two steps: (i) evaporation of 0.001–0.050 ML equivalent of rhodium at room temperature with a post-annealing at 1100 K (“seeding”); (ii) post-deposition of rhodium for growing of the Rh nanoparticles formed in step (i) (“growing”). The mechanism of this procedure is based on the large difference of the surface diffusion coefficient between Rh adatoms and Rh nanocrystallites larger than 1–2 nm. In the first step the average distance between the metal particles is controlled in the range 5–200 nm, the second step determines the particles size (2–50 nm). This work demonstrates that the diffusion processes of metal nanoparticles of different sizes and the growing modes of the crystallites can be studied in detail by application of seeded surfaces. 相似文献