共查询到17条相似文献,搜索用时 656 毫秒
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开关磁阻式平面电动机及其控制 总被引:7,自引:6,他引:7
该文提出了一类新颖结构的平面电动机,这类电动机采用开关磁阻电动机的工作原理,结构简单、适用性强,可产生直接驱动的平面运动;在对平面电动机特性分析的基础上,进行了速度自抗扰控制研究;采取的特殊结构使半面电动机两个方向的运动解耦,使平面电动机的平面运动控制等效为两个直线电动机的运动控制;利用扩张状态观测器对扰动的观测和补偿,实现了速度的自抗扰控制;在进行控制器设计时,采用力分配函数的方法,即减小了纹波推力扰动,又使控制器的设计简单和易于实现;实验结果验证了所用方法的可行性和有效性。 相似文献
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R. Zambrano 《组合铁电体》2013,141(1):247-255
Ferroelectric memories (FeRAMs) are more and more using stack cells in 1T1C configuration. While none of these are already in real production, a great progress has been made when comparing these with strapped cells in 2T2C configuration. However the FeRAM community must be ready to face another challenging step in the evolution, i.e. the transition from planar to 3D capacitors. There's no consensus on the best approach to address this issue, which is probably a must at the 130 nm node. This paper reviews the limitations of the most popular approaches, then starts comparing two possible 3D FeCap structures (pin and cup-shaped). The final sections are dedicated to the introduction of a different strategy, trying to use a evolutionary approach. This is pursued starting with the development of a “quasi planar” FeCap in 0.35 μm technology that can evolve into a “quasi 3D” one at 0.18 μm node, and in a true one for 0.13 μm (or finer) rules. 相似文献
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Lethmate R Ratiney H Wajer FT Crémillieux Y van Ormondt D Graveron-Demilly D 《Magma (New York, N.Y.)》2003,16(1):21-28
A method—PA-keyhole—for 2D/3D dynamic magnetic resonance imaging with radial scanning is proposed. PA-keyhole exploits the
inherent strong oversampling in the center of k-space, which contains crucial temporal information regarding contrast evolution. The method is based on: (1) a rearrangement
of the temporal order of 2D/3D isotropic distributions of trajectories during the scan into subdistributions according to the desired time resolution, (2) a new post-acquisition keyhole approach based on the replacement of the central disk/sphere in k-space using data solely from a subdistribution, and (3) reconstruction of 2D/3D dynamic (time-resolved) images using 2D/3D-gridding
with Pipe's approach to the sampling density compensation and 2D/3D-IFFT. The scan time is not increased with respect to a
conventional 2D/3D radial scan of the same spatial resolution; in addition, one benefits from the dynamic information. The abilities of
PA-keyhole and the sliding window techniques to restore simulated dynamic contrast changes are compared. Results are shown
both for 2D and 3D dynamic imaging using experimental data. An application to in-vivo ventilation of rat lungs using hyperpolarized
helium is demonstrated.
Electronic Publication 相似文献
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D2D通信是允许两个相邻用户在通过基站的控制下共享蜂窝用户的频谱资源来直接通信的技术。D2D用户与蜂窝用户共享资源而引入的额外干扰会降低系统的性能,因此资源分配成为D2D通信的一个重要问题。针对D2D用户密集场景下最大可接入数量问题提出了一种基于图着色的资源分配算法,其中将D2D用户对视为一个顶点,蜂窝用户的资源视为一个个簇,对顶点进行着色即对其分簇。仿真分析可以看出,所提出的方案能够增加网络最大可接入的D2D用户对的数量,有效提高了系统容量。 相似文献
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2D sense for faster 3D MRI 总被引:10,自引:0,他引:10
Sensitivity encoding in two spatial dimensions (2D SENSE) with a receiver coil array is discussed as a means of improving
the encoding efficiency of three-dimensional (3D) Fourier MRI. it is shown that in Fourier imaging with two phase encoding
directions, 2D SENSE has key advantages over one-dimensional parallel imaging approaches. By exploiting two dimensions for
hybrid encoding, the conditioning of the reconstruction problem can be considerably improved, resulting in superior signal-to-noise
behavior. As a consequence, 2D SENSE permits greater scan time reduction, which particularly benefits the inherently time-consuming
3D techniques.
Along with the principles of 2D SENSE imaging, the properties of the technique are discussed and investigated by means of
simulations. Special attention is given to the role of the coil configuration, yielding practical setups with four and six
coils. The in vivo feasibility of the two-dimensional approach is demonstrated for 3D head imaging, permitting four-fold scan
time reduction.
Presented in parts at the 16th meeting of the ESMRMB, Sevilla, September, 1999. 相似文献
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在电力物联网中为了提高D2D(device-to-device)网络的频谱效率和系统能效,考虑不完美信道状态信息(channel state information, CSI)的影响,提出了一种鲁棒能效最大的资源分配算法。考虑D2D用户最大发射功率约束、蜂窝用户功率约束和共道干扰功率约束,建立下垫式频谱共享模式下混合蜂窝/D2D通信的上行传输资源分配模型;考虑蜂窝用户干扰中断约束,基于最小最大概率机和辅助变量法,将原非凸优化问题转换为凸优化求解。基于凸优化理论,获得鲁棒资源分配问题的解析解。仿真结果表明所提算法的有效性。 相似文献