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71.
In order to study cross flow induced vibration of heat exchanger tube bundles, a new fluid–structure interaction model based on surface vorticity method is proposed. With this model, the vibration of a flexible cylinder is simulated at Re=2.67 × 104, the computational results of the cylinder response, the fluid force, the vibration frequency, and the vorticity map are presented. The numerical results reproduce the amplitude‐limiting and non‐linear (lock‐in) characteristics of flow‐induced vibration. The maximum vibration amplitude as well as its corresponding lock‐in frequency is in good agreement with experimental results. The amplitude of vibration can be as high as 0.88D for the case investigated. As vibration amplitude increases, the amplitude of the lift force also increases. With enhancement of vibration amplitude, the vortex pattern in the near wake changes significantly. This fluid–structure interaction model is further applied to simulate flow‐induced vibration of two tandem cylinders and two side‐by‐side cylinders at similar Reynolds number. Promising and reasonable results and predictions are obtained. It is hopeful that with this relatively simple and computer time saving method, flow induced vibration of a large number of flexible tube bundles can be successfully simulated. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
72.
The Mach-Zehnder traveling-wave lithium niobate modulator is simulated by time domain finite difference (FDTD)method for different device geometry. The result is comparable to the reported value by finite element method. 相似文献
73.
Cellular neural network to detect spurious vectors in PIV data 总被引:2,自引:0,他引:2
74.
35Cr25Ni12奥氏体耐热钢中碳化物的电子显微分析 总被引:1,自引:0,他引:1
应用扫描电镜(SEM)和透射电镜(TEM)研究了长期使用前后的35Cr25Ni12奥氏体耐热钢中的碳化物演变行为;该钢固溶时效后的组织由初晶奥氏体及M23C6共晶碳化物组成,奥氏体基体中析出了二次M23C6,二次碳化物总是与基体保持立方-立方取向关系;长期使用(3、5年)后,奥氏体中析出的二次碳化物量明显增加,部分M23C6已转变为M6C,M6C与奥氏体基体以及二次碳化物M23C6保持[001]M6C//[221]A//[221]M23C6孪晶取向关系。 相似文献
75.
Au nanoparticles were precipitated inside Au+-doped glass samples after irradiation by femtosecond laser or x-ray. Femtosecond laser and X-ray irradiation result in decreasing of anneal temperature and critical size for the precipitation of Au nanoparticles. 相似文献
76.
GFFs with less than 0.4 dB peak-to-peak error functions are routinely fabricated using commercially available coating machines by utilizing the natural error compensation mechanism of wavelength variable turning point optical monitoring method. 相似文献
77.
Photonic devices based on III-nitrides offer benefits such as UV/blue emission, large band offsets of InN/GaN/AlN heterostructures allowing novel quantum well (QW) device design, and inherently high-emission efficiencies. Furthermore, due to their mechanical hardness and larger band gaps (when compared with conventional semiconductor devices), III-nitride-based devices may operate at much higher temperatures and voltages/power levels for any dimensional configuration and in harsher environments than other semiconductor devices and are expected to provide much lower temperature sensitivities. These are crucial advantages for many applications. Over the last decade, the physics of microsize photonic devices has been investigated. New physical phenomena and properties are expected to dominate as the device size scales down. The microsize light emitters offer benefits over edge emitters such as the ability to create arrays of individually controllable pixels on a single chip, enhanced quantum efficiency, and greatly reduced lasing threshold. Rapid progress in the area of III-nitride microphotonics has been made. The growth and fabrication of micron and submicron size photonic structures based on III-nitride wide bandgap semiconductors has been achieved, and the technology has made it possible to integrate arrays of optical elements to form active photonic-integrated devices. One example is an interconnected µ-LED with enhanced emission efficiency over the conventional LEDs for the same device area. Another example is a µ-LED array with independently addressed pixels or III-nitride microdisplay. III-nitride microdisplay may offer performance that is superior to microdisplays fabricated from liquid crystals and organic LEDs. The third example presented is III-nitride UV Focal Plane Arrays (UV-FPA) of detectors. So far, the operation of AlGaN UV-FPA with size up to 256×256 pixels with 30×30?μm2 unit cells has been demonstrated. Together with the nature of their two-dimensional array, these active micro-photonic devices show promise in many important applications, such as optical communications, signal and image processing, optical interconnects, computing, enhanced energy conversion and storage, chemical, biohazard substances, and disease detection, missile and shellfire, atmospheric ozone-level, and flame sensing. III-nitride microlens arrays have been fabricated successfully for blue and UV wavelength applications on GaN and AlN. The successful fabrication of microlens arrays based on III-nitride materials opens the possibility for monolithically integrating nitride-based micro-size photonic devices, as well as coupling light into, out of, and between arrays of III-nitride emitters and detectors, especially for short wavelengths covering the green-blue to deep UV (200?nm) region. Nanofabrication and characterization of photonic crystals with diameter/periodicity as small as 100/180?nm on InGaN/GaN MQW has been achieved. An unprecedented maximum enhancement factor of 20 was obtained under optical pumping. Single-mode ridged optical waveguide devices using GaN/AlGaN heterostructures have been designed, fabricated, and characterized for operation in 1550?nm wavelength window. The feasibility of developing novel photonic integrated circuits based on III-nitride wide bandgap semiconductors for fiber-optical communications has been investigated. 相似文献
78.
Hong Mao-Chun Huang Zhi-Ying Cao Rong Jiang Fei-Long Liu Han-Qin State Kev Laboratory of Structural Chemistry and Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou Fujian 《结构化学》1993,(5)
<正> [Au13Ag12(μ-Br)1(μ3-Br)2 (Ph3P)10Br2] Br, monoclinic. space group C2/m, a = 36. 496(17). b=16. 878(7), c-=19. 772(9) A , β=99. 87(5)°, V=11998. 9 A3.Z=2. The final R(Rw) is 0. 097(0. 109) for 3779 reflections with I>3σ(I). The structure can he considered as two icosahedral cluster units (AurAg6) sharing one vertex and linked hy six bromine atoms. The Au - Au, Au - Ag. and Ag-Ag distances fall in the ranges of 2. 69-2. 96. 2. 84-3. 02. and 2. 92-3. 26 A, respectively. 相似文献
79.
80.
在HL-1托卡马克上进行了辅助加热、加料、电流驱动的物理实验研究。在改善等离子体约束方面,某些实验取得了较好的结果。在适当的稳定放电条件下,低杂波电流驱动和弹丸注入辅助加料,均能使等离子体能量约束得到一定程度的改善,与相同密度条件下的欧姆加热放电相比,能量约束时间提高了约30%。在电子回旋共振加热等离子体实验中,等离子体总能量明显增加,但与相同密度条件下的欧姆加热放电相比,能量约束时间减少了约20%。 相似文献