硅烷添加剂Y9669对STN液晶取向剂性能的影响

在工业生产中,STN液晶取向剂在以薄膜形式涂覆在玻璃基板表面并进行热固化后,需要用溶剂对其进行洗涤。在洗涤中,薄膜从玻璃基板上脱落的现象时有发生。针对这种现象,需要一种添加剂,在不影响STN液晶取向剂的粘度、外观、预倾角、硬度等性质的同时,提高其粘接性能。在液晶取向剂中引入了N-苯基-3-氨基丙基三甲氧基硅烷(Y9669)添加剂,将硅烷添加剂以不同添加比例与取向剂搅拌混合后,得到5份添加剂含量不同的溶液。表征并对比了含有不同含量添加剂的STN液晶取向剂的粘度、外观、预倾角、硬度、粘接性等性质。实验结果表明:对于STN液晶取向剂体系,硅烷添加剂Y9669的最佳添加比例为取向剂固含量的0.5%,此时得到的取向剂综合性能更加优异。硅烷添加剂Y9669基本能够达到在不影响取向剂其他性能的同时,提高其对基板粘接性能的要求。     

Circulant based extremal additive self-dual codes over GF(4)

It is well known that the problem of finding stabilizer quantum-error-correcting codes (QECC) is transformed into the problem of finding additive self-orthogonal codes over the Galois field GF(4) under a trace inner product. Our purpose is to classify the extremal additive circulant self-dual codes of lengths up to 15, and construct good codes for lengths 16/spl les/n/spl les/27. We also classify the extremal additive 4-circulant self-dual codes of lengths 4,6,8,12,14, and 16 and most codes of length 10, and construct good codes of even lengths up to 22. Furthermore, we classify the extremal additive bordered 4-circulant self-dual codes of lengths 3,5,7,9,11,13,15, and 17, and construct good codes for lengths 19,21,23, and 25. We give the current status of known extremal (or optimal) additive self-dual codes of lengths 12 to 27.     

Maximum likelihood localization of sources in noise modeled as astable process

This paper introduces a new class of robust beamformers which perform optimally over a wide range of non-Gaussian additive noise environments. The maximum likelihood approach is used to estimate the bearing of multiple sources from a set of snapshots when the additive interference is impulsive in nature. The analysis is based on the assumption that the additive noise can be modeled as a complex symmetric α-stable (SαS) process. Transform-based approximations of the likelihood estimation are used for the general SαS class of distributions while the exact probability density function is used for the Cauchy case. It is shown that the Cauchy beamformer greatly outperforms the Gaussian beamformer in a wide variety of non-Gaussian noise environments, and performs comparably to the Gaussian beamformer when the additive noise is Gaussian. The Cramer-Rao bound for the estimation error variance is derived for the Cauchy case, and the robustness of the SαS beamformers in a wide range of impulsive interference environments is demonstrated via simulation experiments     

多层单道电弧增材表面3-D重构方法研究

为了研究多层单道电弧增材表面3-D成形特征，采用激光视觉传感系统采集电弧增材制造表面条纹图像。提出基于边界约束条件的感兴趣区域(ROI)提取法对焊缝特征曲线进行定位，获取ROI的激光条纹像素坐标。进行了理论分析和实验验证，得到电弧增材表面的3-D离散点数据，采用Delaunay三角剖分对离散点拟合形成3-D实体表面。结果表明，锯齿靶标的线性标定方法，3-D重构精度在0.2mm以内; 基于边界约束条件的ROI提取方法能准确定位电弧增材上表面和侧表面的条纹特征曲线。这一结果对电弧增材表面的3-D成形检测是有帮助的。     

激光增材制造成形合金钢件质量特征及其检测评价技术现状(特邀)

无损检测技术是合金钢构件激光增材制造的重要技术支撑,是保证激光增材制造产品质量和在役安全性的关键技术,是贯穿产品全寿命安全保证的重要技术组成。金属激光增材制造合金钢件成形、组织和力学性能不同于传统技术制造构件性能,使得无损检测技术面临诸多挑战。综述了激光增材制造合金钢成形质量特性,包括成形缺陷和力学性能;基于无损检测技术,论述了无损检测技术在激光增材制造合金钢件质量评价中的应用,重点论述了无损检测技术在激光增材制造构件缺陷和力学性能中的应用现状;提出了基于超声和微磁检测技术评价材料力学性能的原理、标定方法和微磁传感器设计方案;最后总结了无损检测评价技术在激光增材制造合金钢件检测评价应用中面临的挑战和发展趋势。     

添加Li+的硫酸铵电解液超级电容器的研究

在电解液(NH4)2SO4中加入Li+添加剂,用以提高二氧化锰/活性炭混合超级电容器以及活性炭电容器的容量.测试结果表明,当在2 mol/L 的(NH4)2SO4溶液中添加0.37 mol/L的Li2CO3时,比容量提高幅度最大.添加剂在混合超级电容器中起的作用比在单纯活性炭超级电容器中大.对于混合超级电容器,加入Li+添加剂后比容量提高了77 %,且2 000次循环后比容量为30 F/g,仅衰减了2.9 %.     

Optimal coherent detection of FSK signals with imbalance amplitudes in the presence of colored gaussian noise

The problem of optimal coherent detection of frequency-shift keying (FSK) signals transmitted over an additive colored Gaussian noise channel with imbalance gains in different frequencies (IGDF-ACGN channel) is studied. The structure of the optimal coherent detector is derived. Theoretical analysis and computer simulation results show that the detector is optimal in either additive colored Gaussian noise environment or additive white Gaussian noise environment.     

二氧化铈掺杂锆钛酸钡陶瓷性能和结构的研究

采用传统电容器陶瓷制备工艺,研究了CeO2加入量对Ba(Zr,Ti)O3(BTZ)基电容器陶瓷性能的影响,得到了CeO2影响其性能的规律 ,当w(CeO2)为1.0%时相对介电常数最大(7193),当w(CeO2)为0.5%时介质损耗最小(0.0351)。CeO2有降低居里温度及展宽介电常数-温度峰和减小介电常数温度变化率的作用。利用SEM研究了CeO2对BTZ基陶瓷微观结构的影响,探讨了影响性能的机制,结果表明:CeO2是通过与BTZ形成缺陷固溶体、移峰、偏析晶界及抑制晶粒生长等来影响瓷料性能和结构的。     

The rank and kernel of extended 1-perfect /spl Zopf//sub 4/-linear and additive non-/spl Zopf//sub 4/-linear codes

A binary extended 1-perfect code of length n + 1 = 2/sup t/ is additive if it is a subgroup of /spl Zopf//sub 2//sup /spl alpha// /spl times/ /spl Zopf//sub 4//sup /spl beta//. The punctured code by deleting a /spl Zopf//sub 2/ coordinate (if there is one) gives a perfect additive code. 1-perfect additive codes were completely characterized and by using that characterization we compute the possible parameters /spl alpha/, /spl beta/, rank, and dimension of the kernel for extended 1-perfect additive codes. A very special case is that of extended 1-perfect /spl Zopf//sub 4/-linear codes.     

一种新的FSK最佳相干解调器

本文讨论在信号各频率振幅受到的衰减不一致并存在有色加性高斯噪声(IGDF-ACGN)信道条件下,FSK信号的最佳相干解调问题。基于矢量表示系统模型的方法,导出了最佳解调器的结构。从理论分析和计算机模拟实验结果都证明了所导得的最佳解调器,不仅在IGDF-ACGN信道条件下是最佳的,而且在加性高斯白噪声(AWGN)信道条件下也是最佳的。文中还导出了相应的误码率公式,给出了误码率数值计算和计算机模拟曲线。     

新型MFSK最佳相干解调器

本文推广了作者在1999年提出的方法和结论[1],讨论了在信号各频率振幅受到的衰减不一致并存在有色加性高斯噪声(IGDF-ACGN)信道条件下,M进制FSK(MFSK)信号的最佳相干解调问题。导出了最佳解调器的结构,说明了该解调器中有关参数的估计方法,以及实现时遇到的矢量、矩阵运算的有关快速算法。从理论和计算机模拟实验两方面说明了所导得的最佳解调器,不仅在IGDF-ACGN信道条件下是最佳的,而且在加性高斯白噪声(AWGN)信道条件下也是最佳的。文中给出了误码率的计算机模拟曲线。     

Structurally Constrained Receivers for Signal Detection and Estimation

A general approach to the problem of designing structurally constrained receivers for signal detection and estimation is proposed. The approach is based on the constrained Bayesian methodology wherein risk-minimizing inference (or decision) rules are modified (constrained) by replacement of true posterior probabilities with estimated posterior probabilities. The estimators are structurally constrained minimum-mean-squared-error (MMSE) estimators for random posterior probabilities. This methodology is, in essence, an extension and generalization of the well-known linear MMSE estimation methodology. The approach is employed to design linearly constrained coherent receivers for signals in additive and multiplicative noise, and quadratically constrained noncoherent receivers for signals in additive noise. An analysis of these receivers shows that they are very similar to those that are optimum for additive Gaussian noise. The methodology provides a unified theory of receiver design based on the constrained MMSE criterion. This unification yields new insight into this old approach, clarifying both strengths and weaknesses of the approach.     

Si_3N_4在BaTiO_3基低阻高性能PTCR陶瓷材料中的作用

要同时保证 PTCR材料和元件具有低室温电阻率和较高的 PTC特性 ,有较大难度。研究了添加 Si3N4作为烧结助剂 ,对 PTCR材料的显微结构和电学性能的影响。同添加 Si O2 作为烧结助剂相比 ,添加 1.0 %的 Si3N4的 PTCR材料更易同时满足低阻高性能要求。     

Performance evaluation of optical fiber transmission systems

A method is presented for evaluating of error probability for optical-fiber communication systems in the present of intersymbol interference and additive noise. It is based on deriving a best approximation, in a minimax sense, for the cumulative distribution function of the additive noise. The method takes into account the avalanche photodetector's non-Gaussian shot noise statistics. The additive noise is also not constrained to be Gaussian. Examples are presented for comparison to previously published techniques     

航空激光增材制造零部件潜在缺陷检测

传统的航空激光增材制造零部件潜在缺陷检测方法检测准确度低,图像特征查全率低。基于上述问题,提出一种基于图像识别技术的航空激光增材制造零部件潜在缺陷检测方法。采用红外成像技术进行航空激光增材制造零部件成像处理,提取航空激光增材制造零部件红外图像的缺陷区域特征点,对红外图像进行中值滤波降噪处理,利用扫描图像的纹理异常分布特性进行潜在缺陷的自适应定位检测,结合模板匹配和角点检测方法,实现对航空激光增材制造零部件潜在缺陷检测。仿真结果表明,采用该方法方法的图像特征提取查全率比传统方法提高了15%-20%,能够清晰检测到增材零件的潜在缺陷。说明进行航空激光增材制造零部件潜在缺陷检测的准确性较好,对缺陷部位定位的误差较小。     

Simulation Results for the Decision-Directed MAP Receiver for M-ary Signals in Mulitiplicative and Additive Gaussian Noise

Simulation results are presented for the error-rate performance of the recursive digital maximum a posteriori probability (MAP) detector for knownM-ary signals in multiplicative and additive Gaussian noise. The structure of the digital simulation of the optimum detector is generally described, with specific results obtained for a quaternary signal and 2500 digit per second transmission rate. The simulation is focused on the aeronautical multipath communication problem. Plots of detection error rate versus additive signal-to-noise ratio are given, with the power ratio of multiplicative process to desired signal as a parameter. Results are presented for the cases where the detector has perfect knowledge of the first- and second-order statistics of the multiplicative and additive processes and also where these statistics are estimated in near real time. For comparison, the error rates of conventional coherent and noncoherent digital MAP detectors are also obtained. It is shown that with nonzero multiplicative noise, the error rates of the conventional detectors saturate at a level that is irreducible for increasing additive signal-to-noise ratio. The error rate of the optimum detector having perfect statistical knowledge continues to decrease rapidly with increasing additive signal-to-noise ratio. In the absence of multiplicative noise, the conventional coherent detector and the optimum detector are shown to exhibit identical performance. Suboptimum detectors, having less than perfect statistical knowledge, yield error rates bounded below by the optimum detector rates and bounded above by the conventional detector rates.     

分形方法用于有噪图像边缘检测的研究

本文研究了加性高斯白噪声对于基于离散分数布朗随机场模型图像分形维数估计的影响，并将分形方法用于图像边缘检测，指出在加性高斯白噪声的情况下，分形方法用于图像边缘检测较之经典的基于梯度运算的边缘检测方法有好的抗噪性能，同时又能检测比较丰富的图像边缘细节。     

Locally optimum detection of signals in a generalized observationmodel: the known signal case

A generalized observation model for signal detection problems is proposed. The model allows consideration of several interesting special cases including additive noise, multiplicative noise, and signal-dependent noise, and includes both deterministic and random signals. Locally optimum (LO) detectors are interesting generalizations of those for the additive noise model. Under the proposed observation model the performance of the LO detectors is compared with that of other common detectors     

Effects of tetramethylene sulfone solvent additives on conductivity of PEDOT:PSS film and performance of polymer photovoltaic cells

A solvent additive in PEDOT:PSS solution is one of many methods to improve the conductivity of the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films. We explore a new type of the solvent additive, namely tetramethylene sulfone (TMS), for the fabrication of the PEDOT:PSS conductive layer in the ITO/PEDOT:PSS/P3HT:PCBM/TiO_x/Al polymer photovoltaic cells, in comparison to a more common dimethyl sulfoxide (DMSO) solvent additive. At optimal conditions, the TMS additive at 10 wt.% has been found to enhance the conductivity of pristine PEDOT:PSS films from 0.04 S/cm up to approximately 189 S/cm, compared with the highest conductivity for the case of the DMSO additive at 15 wt.% of 117 S/cm. Possible mechanisms of this conductivity enhancement, relating to the polymer conformation and the film morphology, have been investigated by Raman spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The performance of the polymer photovoltaic cells fabricated with the solvent additives PEDOT:PSS films follows a similar trend to the conductivity of the films as a function of the additive concentration. The additives mainly lead to greater short circuit current density (J_sc) of the photovoltaic cells. The highest power conversion efficiency (PCE) of 2.24% of the device has been obtained with the 10 wt.% TMS additive of, compared to the PCE of 1.48% for the standard device without solvent additive.     

Performance improvement of conventional and inverted polymer solar cells with hydrophobic fluoropolymer as nonvolatile processing additive

The morphology of the photoactive layer critically affects the performance of the bulk heterojunction polymer solar cells (PSCs). To control the morphology, we introduced a hydrophobic fluoropolymer polyvinylidene fluoride (PVDF) as nonvolatile additive into the P3HT:PCBM active layer. The effect of PVDF on the surface and the bulk morphology were investigated by atomic force microscope and transmission electron microscopy, respectively. Through the repulsive interactions between the hydrophilic PCBM and the hydrophobic PVDF, much more uniform phase separation with good P3HT crystallinity is formed within the active layer, resulting enhanced light harvesting and improved photovoltaic performance in conventional devices. The PCE of the conventional device can improve from 2.40% to 3.07% with PVDF additive. The PVDF distribution within the active layer was investigated by secondary ion mass spectroscopy, confirming a bottom distribution of PVDF. Therefore, inverted device structure was designed, and the PCE can improve from 2.81% to 3.45% with PVDF additive. Our findings suggest that PVDF is a promising nonvolatile processing additive for high performance polymer solar cells.