共查询到20条相似文献，搜索用时 62 毫秒
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利用Bridge乘积定理得到了线阵组合平面阵的指向性函数,并运用MATLAB软件绘制出该阵列的三维指向性图.借助于此图分析了线阵组合平面阵的指向性特点,以及声波的波长、阵列的尺寸对指向性的影响.该研究对线阵组合平面阵的设计提供了参考. 相似文献
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ZHANG Chen-xi CHEN Ya-zhu 《浙江大学学报(A卷英文版)》2007,8(8):1237-1245
A 3D ultrasound thermal model with a 3D finite element representation for modeling the thermal diffusion effects for hepatic ablation induced by spherical-section ultrasound phased array was developed. The model was first validated against available published measured data in rat liver. Using the validated model,effects of blood perfusion and heating schemes on lesion formation were studied for both single focus and split-focus intensity patterns. It was shown that for single focus sonication pattern the short-duration(～2 s) and high-intensity(～1250 W/cm2) heating scheme can completely reduce the cooling effect of the blood perfusion. The lesion shape and size were significantly altered by perfusion for split-focus pattern even with a rapid heating scheme when the focus spacing was larger than 2.4 mm. Underdosed areas might be present between two foci. Prolonging ex-posure time or shortening focus spacing can reduce the cool region between two foci. In addition,the influences of thermal and acoustic parameters were also studied. When the therapy depth is short(<5 cm) ,the lesion size monotonically increases with increasing attenuation coefficient that ranges from 5.4 to 11 Np/(m?MHz) . 相似文献
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STL模型的分层处理是RPM前处理部分的重要内容,分层软件的速度对快速成形的整体效率有重要影响.本文在现有切片算法的基础上,提出了基于分组的切片算法,该算法使三角面片排序的运算量小,建立拓扑关系便捷.并据此开发了切片软件. 相似文献
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传统的太阳跟踪方式多采用光电跟踪或视日跟踪,跟踪精度低,存在累积误差。为了改进对太阳的跟踪精度和消除累积误差,计算各种太阳角,提出以光电跟踪为主要的跟踪方式,同时设置视日跟踪控制,通过两种跟踪方式互补,可以让光伏阵列在昼夜更替以及任何气候条件下得到稳定而可靠的跟踪控制,完成光伏阵列跟踪控制过程的设计。 相似文献
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由于现实中同步与互斥问题复杂多样,如果都使用普通信号量机制来实现,显得灵活复杂、非常不便.本文在普通信号量机制的基础上,对带标记信号量和带标记数组型信号量进行了研究,提出了带标记多维数组型信号量机制,可以很好地解决原有信号量难以解决的复杂问题,拓宽了信号量机制在同步与互斥环境下的使用范围. 相似文献
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为了探讨随机谐振现象的发生对信号、非线性系统和噪音的依赖性,特别是对噪音的依赖性,以互信息量为测度研究了二进制信号在非线性门限阵列的传输问题.在高斯混合噪音下计算了单门限系统和门限阵列的互信息量.通过研究得到:高斯混合噪音能改善信息的传输;随机谐振和超门限随机谐振现象不但在单门限系统中而且在门限阵列中存在;噪声分布中的参数影响随机谐振和超门限随机谐振现象的出现;随着门限阵列中门限单元数的增加,门限阵列能大大地改善信息的传输效果.这些结果进一步说明随机谐振和超门限随机谐振现象对噪声分布特性的依赖,同时也拓展了随机谐振和超门限随机谐振在信息传输中的应用. 相似文献
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在圆柱形介质谐振器天线单元分析的基础上,设计了一种4单元介质谐振器天线阵列。天线阵采用微带线馈电网络,保证单元之间满足相位匹配关系,使该天线阵列具有良好的定向辐射特性,而且在带宽方面满足要求。 相似文献
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1 Introduction Bothoutputover samplingandinputholdingschemesareeffectiveinmanysystemidentificationproblems ,especiallyinaclassofblindsystem/channelidentifi cation problemsthatcannotoraredifficulttobesolvedbyconventionalapproaches .Neverthelesstherearestillagreatnumberofsystemstowhichnei theranoutputover samplingschemenoraninputholdingschemeisapplicable .Certainlysuchablindi dentificationproblemmaybesolvedusinghigh orderstatisticsbasedalgorithms (HOS) [1] .However ,ifmultiplesensorscanbeuse… 相似文献
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王辉静 《深圳信息职业技术学院学报》2008,6(2):59-62
本文设计了一种基于MEMS技术的柔性触觉感知阵列。通过将MEMS传感器单元与柔性基板相结合,实现三维曲面上的分布力的测量。该触觉感知阵列适台安装于智能机器人手爪上,为机器人系统高效率地获取物体形状、位置和姿态信息、实现智能操作物体提供了有效的手段。 相似文献
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RAID磁盘阵列技术在高职图书馆的应用 总被引：1，自引：0，他引：1
黄浏展 《宁波职业技术学院学报》2006,10(2):28-30
针对高职院校图书馆在存储方案选取上盲目性的问题,结合目前常用RAID技术及高职图书馆信息资源的特点,权衡存储设备性价比,来解决高职图书馆如何选取存储方案的问题。 相似文献
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An efficient adaptive approximation demosaicking algorithm based on the sampled edge pattern was presented for mosaic images from Bayer color filter array. The proposed algorithm determined edge patterns by four nearest green values surrounding the green interpolation location. Then according to the edge patterns, different adaptive interpolation steps were applied. Simulations on 12 Kodak photos and 15 IMAX high-quality images showed that the proposed method outperformed the other four demosaicking methods (bilinear, effective color interpolation, Lu’s method and Chen’s method) for average color peak signal to noise ratios and maintained a relatively low complexity owing to constant color-difference interpolation step and a reasonable terminating condition of iteration. 相似文献
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The authors have fabricated bottom gate amorphous silicon thin film transistor (a-Si TFT) array using five-step lithography process.The device shows a field effect mobility of 0.43 cm 2 /(V·s),on/off ratio of 7.5×10 6 and threshold voltage of 0.87 V.The instability of a-Si TFT is ascribed to the defect state in the a-Si channel and SiNx/a-Si interface.The present a-Si TFT array with SiN x insulator could be a significant step towards the commercialization of active matrix organic lighting diode (AM-OLED) te... 相似文献
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A low-sidelobe circularly-polarized （CP） microstrip patch array for 2.4 GHz radio frequency identification （RFID） readers is presented. The antenna array with a Chebyshev current distribution is composed of 6 microstrip elements. The CP operation is obtained by the quasi-square patch with difference in lengths of the two sides. The antenna has been investigated numerically and experimentally. Measured results show that the array has a Chebyshev pattern with the sidelobe level of -23 dB, the half-power beamwidth of 16° and an impedance bandwidth （S11 ≥-10 dB） of 130 MHz, which is suitable for RFID reader applications. 相似文献
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A 16×16 micro-strip antenna array with high gain characteristic was proposed for the 5.5 GHz WiMAX application. The T-junctions with a power ratio of 2∶1 were used to design the feed network. To correct the stepped discontinuity of impedance change in common multi-section impedance transformer, exponential line matching transformers were adopted in the WiMAX frequency band. The reflection coefficient was lower than-15 dB from 5.08 GHz to 5.87 GHz. The measured gain of the antenna array achieved 29.8 dBi on E-plane at 5.8 GHz. 相似文献
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This paper proposes a new multitarget constant modulus array structure for code division multiple access (CDMA) systems. The new algorithm for the structure is called pre-despreading and wavelet denoising constant modulus algorithm (D-WD-CMA). In the new algorithm, the pre-despreading is applied to multitarget arrays to remove some multiple access inter- ferences. After that the received signal is subjected to wavelet de-noising to reduce some noise, and used in CMA adaptive iteration … 相似文献
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A compact wideband microstrip array antenna with a squint beam is introduced without the matched load. Its measured beam is
at 10° offset to the broadside with a measured gain of 12 dB at 10 GHz. The measured impedance bandwidth (voltage standing
wave ratio (VSWR)⩽2) is over 16%, which agrees well with the simulated one. It is a low-cost wideband design with compact
simple structure, suited for military and commercial application. 相似文献
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Redundant array of inexpensive disk (RAID)10 is known as the most reliable disk array architecture to tolerate up to half of total disk failures, but failure of two disks in the same mirror set still results in data loss. In this paper, we propose a new disk array architecture, mirroring and parity protected RAID (MP-RAID), which combines both mirroring and parity techniques to further improve reliability of disk arrays. The main idea behind MP-RAID is to protect the data by both mirroring and parity techniques: keep two copies of data in the same mirror set and update the parity block in the log disk within the same parity groups. Reliability analysis shows that the reliability of MP-RAID, in terms of mean time to data loss (MTTDL), is much better than RAID10 and RAID5. 相似文献