Properties of Bi-doped PbTe layers grown by liquid phase epitaxy under controlled Te vapor pressure

Effects of Bi doping in PbTe liquid-phase epitaxial layers grown by the temperature difference method under controlled vapor pressure (TDM-CVP) are investigated. For Bi concentrations in the solution, x_Bi, lower than 0.2 at.%, an excess deep-donor level (activation energy E_d≈0.03–0.04 eV) appears, and Hall mobility is low. In contrast, for x_Bi>0.2 at.%, Hall mobility becomes very high, while carrier concentration is in the range of 10¹⁷ cm⁻³. Inductive coupled plasma (ICP) emission analysis shows that, for x_Bi=1 at.%, Bi concentration in the epitaxial layer is as high as N_Bi=2.3–2.7 × 10¹⁹ cm⁻³. These results indicate that Bi behaves not only as a donor but also as an acceptor, and the nearest neighbor or very near donor-acceptor (D-A) pairs are formed, so that strong self-compensation of Bi takes place. Carrier concentration for highly Bi-doped layers shows a minimum at a Te vapor pressure of 2.2 × 10⁻⁵ torr for growth temperature 470°C, which is coincident with that of the undoped PbTe.     

基于整体退火遗传算法的低功耗极性转换

针对n变量逻辑函数在不同极性下所对应REED-MULLER(RM)电路功耗和面积不问的特点,对信号几率传递算法、多输入XOR/AND(异或/与)门的低功耗分解算法和多成份极性转换算法进行了深入研究,成功地将整体退火遗传算法(whole annealing genetic algorithm,WAGA)应用于RM电路最佳极件的搜索.通过对8个MCNC Benchmark测试表明,算法搜索到的最佳极性,其所对应RM电路的SYNOPSYS综合结果,与极性0时相比,功耗、面积和最大延时的平均节省分别达到了77.2%,62.4%和9.2%.     

DNA Computing Boosted by a Cationic Copolymer

The huge information storage capability of DNA and its ability to self‐assemble can be harnessed to enable massively parallel computing in a small space. DNA‐based logic gates are designed that rely on DNA strand displacement reactions; however, computation is slow due to time‐consuming DNA reassembly processes and prone to failure as DNA is susceptible to degradation by nucleases and under certain solution conditions. Here, it is shown that the presence of a cationic copolymer boosts the speed of DNA logic gate operations that involve multiple and parallel strand displacement reactions. Two kinds of DNA molecular operations, one based on a translator gate and one on a seesaw gate, are successfully enhanced by the copolymer without tuning of computing conditions or DNA sequences. The copolymer markedly reduces operation times from hours to minutes. Moreover, the copolymer enhances nuclease resistance.     

水平井电缆牵引器滚轮与管壁压力的测量

水平井电缆牵引器滚轮与管壁之间的压力是进行牵引器结构设计和作业控制的一项关键参数。如果压力施加不当,滚轮将出现打滑或堵转。由于套管细长,滚轮与管壁的接触位置又不断在发生变化,因此压力测量的难度很大。笔者提出在套管上开窗口并用球头立柱支撑压板,使立柱与压板始终处于单面点接触状态,确保压板发生变形时立柱只受到压力。为防止压板从窗口掉入套管,将压板的两个侧立面加工为楔形,与窗口侧立面具有相同的锥度。研究介绍了测力系统的设计和工作原理,提出了有无预紧力2种情况下支撑立柱的压力计算模型,建立了测试系统,并对牵引器在套管内爬行时的压力进行了测量。根据得到的16根支撑立柱的应变值,计算和分析了压板和立柱上的压力分配。     

Efficient implementation of 3D filter for moving object extraction

In this paper the design and implementation of Multi-Dimensional (MD) filter, particularly 3-Dimensional (3D) filter, are presented. Digital (discrete domain) filters applied to image and video signal processing using the novel 3D multirate algorithms for efficient implementation of moving object extraction are engineered with an example. The multirate (decimation and/or interpolation) signal processing algorithms can achieve significant savings in computation and memory usage. The proposed algorithm uses the mapping relations of z-transfer functions between non-multirate and multirate mathematical expressions in terms of time-varying coefficient instead of traditional polyphase de- composition counterparts. The mapping properties can be readily used to efficiently analyze and synthesize MD multirate filters.     

100 Å-thick tunnel junction by double impurity doping liquid phase epitaxy for V-band TUNNETT oscillation

The tunnel injection transit time (TUNNETT) diodes with p⁺p⁺n⁺n⁻n⁺ structure were fabricated by liquid phase epitaxy (LPE). About 100 Å tunnel junction (p⁺n⁺) was successfully prepared by the double impurity diffusion of Ge and S during LPE growth. Continuous wave (CW) oscillation was realized at 51.520 GHz in the V-band cavity with the phase noise of −60 dBc/Hz at 1 kHz bandwidth.     

Effects of AsH3 surface treatment for the improvement of ultra-shallow area-selective regrown GaAs sidewall tunnel junction

Low-temperature (290°C) area-selective regrowth by molecular layer epitaxy (MLE) was applied for the fabrication of an ultra-shallow sidewall (50 nm) GaAs tunnel junction. Fabricated tunnel junctions have shown a record peak current density up to 35,000 A/cm². It is shown that the tunnel junction characteristics are strongly dependent on the sidewall orientation and the AsH₃ surface treatment conditions just prior to regrowth. The effects of AsH₃ surface treatment are discussed in view of the control of surface stoichiometry.     

Aggregate volumetric estimation based on PCA and momentum-enhanced BP neural network

This paper proposes a Back Propagation (BP) neural network with momentum enhance-ment aiming to achieving the smooth convergence for aggregate volumetric estimation purpose. Net-work inputs are first selected by optically measuring the eight geometry-related parameters from the given particle image. To simplify the network structure, principal component analysis technique is applied to reduce the input dimension. The specific network structure is finalized based on both em-pirical expertise and analysis on selecting the appropriate number of neurons in hidden layer. The network is trained using the finite number of randomly-picked particles. The training and test results suggest that, compared to the generic BP network, the training duration of the proposed neural network is greatly attenuated, the complexity of the network structure is largely reduced, and the es-timation precision is within 2%, being sufficiently up to technical satisfaction.