摘要：This paper deals with optimal training design and placement over multiple orthogonal frequency division multiplexing(OFDM) symbols for the least squares(LS) channel estimation in multiple-input multipleoutput(MIMO) OFDM ***,the optimal pilot sequences over multiple OFDM symbols are derived by co-cyclic Jacket matrices based on the minimum mean square error(MSE) of the LS channel ***,an enhanced channel estimation method using sliding window is proposed to improve further the performance for the optimal pilot sequences in fast-varying *** results show that the enhancedmethod can efficiently improve the performances for the optimal pilot sequences over two and four OFDM symbols,especially in fast-varying channels.

摘要：The use of a reconfigurable intelligent surface(RIS)in the enhancement of the rate performance is considered to involve the limitation of the RIS being a passive *** address this issue,we propose a RIS-aided amplify-and-forward(AF)relay network in this *** jointly optimizing the beamforming matrix at AF relay and the phase-shift matrices at RIS,two schemes are put forward to address a maximizing signal-to-noise ratio(SNR)***,aiming at achieving a high rate,a high-performance alternating optimization(AO)method based on Charnes–Cooper transformation and semidefinite programming(CCT-SDP)is proposed,where the optimization problem is decomposed into three subproblems solved using CCT-SDP,and rank-one solutions can be recovered using Gaussian ***,the optimization variables in the CCT-SDP method are matrices,leading to extremely high *** reduce the complexity,a low-complexity AO scheme based on Dinkelbachs transformation and successive convex approximation(DT-SCA)is proposed,where the variables are represented in vector form,and the three decoupling subproblems are solved using *** results verify that compared to three benchmarks(i.e.,a RIS-assisted AF relay network with random phase,an AF relay network without RIS,and a RIS-aided network without AF relay),the proposed CCT-SDP and DT-SCA schemes can harvest better rate ***,it is revealed that the rate of the low-complexity DT-SCA method is close to that of the CCT-SDP method.

摘要：增材制造技术凭借其生产几何复杂结构(如晶格结构)的能力而广受欢迎.在航天航空和汽车领域轻量化设计中,晶格结构具有极大的优势.众所周知,振动问题是航天航空结构设计广泛关注的问题之一,为了避免结构动力破坏,有必要开展结构振动频率研究,尤其是结构自振频率研究.本文针对一阶频率最大化问题,提出了一种维诺梯度随机晶格结构多尺度优化设计方法.首先,在微观尺度上进行了维诺随机晶格微观结构生成和分析.然后,采用无惩罚密度法进行宏观结构优化.最后,基于得到的相对密度分布和映射关系,重构了全尺度维诺梯度随机晶格结构.数值算例验证了该方法在维诺梯度随机晶格结构设计中的正确性和有效性,振动试验也验证了所提出的多尺度方法的有效性和优化的梯度晶格结构在结构动力响应方面的优势.

摘要：A wedge shape Si LED is designed and fabricated with 0.35 μm double-grating standard CMOS technology. The device structure is based on the N-well-P+ junction. The P+ has a wedge shape and is surrounded by the N-well. The micrographs of Si LEDs' emitting and layout are captured. The I-V characteristic and spectra of the Si LED are tested. Under room temperature and backward bias, its radiant luminosity is 12 nW at 100 mA, and the wavelength of the emitting peak is located at 764 nm.

摘要：This paper presents a hardware efficient high definition television (HDTV) encoder for H.264/AVC. We use a two-level mode decision (MD) mechanism to reduce the complexity and maintain the performance, and design a sharable architecture for normal mode fractional motion estimation (NFME), special mode fractional motion estimation (SFME), and luma motion compensation (LMC), to decrease the hardware cost. Based on these technologies, we adopt a four-stage macro-block pipeline scheme using an efficient memory management strategy for the system, which greatly reduces on-chip memory and bandwidth requirements. The proposed encoder uses about 1126k gates with an average Bjontegaard-Delta peak signal-to-noise ratio (BD-PSNR) decrease of 0.5 dB, compared with JM15.0. It can fully satisfy the real-time video encoding for 1080p@30 frames/s of H.264/AVC high profile.

摘要：This paper presents an embedded SRAM design for write buffer applications in flash *** write buffer is implemented with a newly proposed self-adaptive timing control circuit,an area-saving sense-latch circuit and 6 T SRAM cell units.A 2 kb SRAM macro with the area of 135μm×180μm is implemented in and applied to a 128 Mb NOR flash memory with the SMIC 65 nm NOR flash memory *** simulation and chip test results show that the SRAM write buffer is beneficial to high-density flash memory design.

摘要：目的:Karhunen-Loève变换(KLT)核矩阵含有无理数而需要整数化。但整数化过程通常会削弱KLT对视频信号去相关能力,同时整数KLT的非正交性也会带来失真。因而需要一个评价模型来指导整数KLT的设计。创新点:综合考虑KLT在视频压缩中所起作用,分别对整数KLT矩阵的可逆程度和其变换编码增益(TCG)进行建模,并形成可逆-增益模型。用该模型进行KLT的整数化设计,得到的整数KLT矩阵在视频压缩效率上都高于其他整数化方法得到的矩阵。方法:首先,充分考虑KLT的正交性,分析无量化情形下整数变换编码过程中失真的来源及其与整数变换核矩阵的解析关系,并利用此解析关系为整数KLT矩阵的可逆程度进行建模(式15)。然后,由于KLT可以最大化TCG,我们对KLT在整数化过程中的TCG损失率进行建模(式16),并分析整数余弦变换的TCG损失率(表1),以作为参考。最后,联合变换的可逆程度和TCG损失率,形成一个指导整数KLT设计的可逆-增益模型(式18):在给定TCG损失率约束下,具有最佳可逆程度的整数KLT即是对给定KLT进行整数化的最优结果。结论:在视频压缩中,给定任意KLT矩阵和倍乘因子下,利用本文提出的可逆-增益模型指导该KLT的整数化,能得到在压缩效率上最优的整数KLT矩阵。

摘要：最新视频编码标准——高效视频编码(HEVC)——获得了远高于之前视频编码标准的编码效率。特别是,在使用分级B帧预测结构时,HEVC可显著去除临近图像间的时间冗余。实际中,消费者使用的视频——例如电视剧、电影和脱口秀等——通常包含了很多重复镜头。据我们观察,这些视频在分级B帧结构下使用HEVC编码时,每个镜头的时域相关性可以得到很好利用。然而,重复镜头之间的长期相关性并未被使用。我们提出一种长期预测方案,以利用视频中重复镜头之间的长期时域相关性。首先,聚类源视频中的相似镜头并从中抽取代表性图像作为长期参考帧。然后,使用长期参考帧对分级B帧的编码结构进行调整,以实现长期时域预测。最后,为长期参考帧设计一种自适应量化方法,以提高整体的视频编码效率。实验表明,提出的新编码方案可获得高达22.86%的编码性能增益。

摘要：In this paper,we present the design of a new photonic crystal fiber(PCF)gas sensor for evanescent-field sensing in terahertz(THz)wave *** sensor can be used to identify the gas,and its size is very large,so that it is beneficial to fill it with the test *** on simulation,we demonstrate that the gas sensor using PCFs with four noncircular large holes in the cladding has high sensitivity and low loss,the confinement loss is less than 0.007 dB/m,and the bending loss is very *** new PCF gas sensor can detect kinds of gases,for example,if test gas is water vapor,it has obvious absorption peaks in THz band,and the sensitivities of gas sensor are 64%and 73%at 1.097 THz and 0.752 THz,*** to the ultra-low loss and high sensitivity of the model,the novel steering-wheel structured fiber is very suitable for evanescent-field sensing and the detection of chemical and biological products.

摘要：Differential modulation was widely used for wireless networks in which channel estimation was *** on orthogonal design,a novel distributed differential space-time coding/decoding scheme forM-PSK modulations was proposed,which had a high code rate of 2/3 and second-order diversity for thetwo-user cooperative *** performance of decode-and-forward (DF) protocols was *** show that the differential space-time modulation scheme in this paper has better bit error rate(BER) performance or higher code rate than the schemes proposed by Tarasak and Wang when interuserchannel states are good *** impacts of transmission error between two users for the whole systemBER performance were also investigated.