低逾渗MWCNTs-CB/UHMWPE导电复合材料的制备及性能

采用溶液法及机械共混法分别制备了均匀结构的炭黑(CB)/超高分子量聚乙烯(UHMWPE)及隔离结构的多壁碳纳米管(MWCNTs)-CB/UHMWPE复合薄膜。扫描电镜分析显示,虽然大部分CB均匀分散于UHMWPE基体中,但依然存在明显的局部团聚,而隔离结构中的MWCNTs-CB分布于UHMWPE界面间,更易形成导电通道。导电测试结果表明,复合材料的导电逾渗值由均匀分布的4.91%(体积分数)下降到隔离结构的0.42%。MWCNTs的加入完善了CB间的导电网络,使复合材料的逾渗值进一步下降,当CB∶MWCNTs=15∶1时,复合薄膜的逾渗值由0.42%(体积分数)下降到0.24%,然而混合填料中MWCNTs含量的进一步增加几乎对逾渗值没有影响。力学性能研究表明,隔离型复合材料的拉伸强度和断裂伸长率随填充剂含量的增加呈现出先上升后下降的趋势。     

丁苯橡胶/炭黑湿法预混胶的塑炼特性

基于胶乳/炭黑湿法混合的丁苯橡胶/炭黑湿法预混胶(P(SBR/CB))是一种在低剪切力环境下制备得到的炭黑在丁苯橡胶基体中分散优良的橡胶/炭黑预混胶,与采用传统机械混炼得到的充炭黑母胶相比,未经塑炼加工的P(SBR/CB)中的橡胶-炭黑相互作用较弱,故其加工行为表现出诸多新的特点。本文在分析P(SBR/CB)结构的基础上,采用实验室开炼机和Brabender转矩流变仪研究了其塑炼特性,探讨了开炼机薄通次数和密炼机塑炼工艺参数(循环油温、转速、塑炼时间等)对其塑炼特性(表观黏度、门尼黏度、排胶温度和结合胶含量)的影响规律,发现P(SBR/CB)的塑炼过程主要包括2个同时进行的进程,即炭黑网络的破坏和橡胶-炭黑相互作用的增强,且可通过调节密炼机塑炼参数,调控P(SBR/CB)混炼胶的门尼黏度和结合胶含量。     

Finding an Euclidean anti--centrum location of a set of points

An obnoxious facility is to be located inside a polygonal region of the plane, maximizing the sum of the k smallest weighted Euclidean distances to n given points, each protected by some polygonal forbidden region. For the unweighted case and k fixed an O(n²logn) time algorithm is presented. For the weighted case a thorough study of the relevant structure of the multiplicatively weighted order-k-Voronoi diagram leads to the design of an O(kn³+n³logn) time algorithm for finding an optimal solution to the anti-t-centrum problem for every t=1,…,k, simultaneously.     

江南传统民居建筑色彩的成因

民居建筑是在特定文化空间与特定地理环境内产生的独特文化现象。是民族智慧与审美的结晶。民居建筑的规模、结构、装饰的形成演变,是其民族文化发展历程的缩影。建筑与民族文化之间是互为因果的关系。"黑瓦白墙"作为江南传统民居中具有代表性的古典建筑风格,尤具有独特的文化内涵。本文以此为立足点,透过文化属性与地理环境等因素来探析江南传统民居建筑色彩的成因。     

PSO并行优化LSSVR非线性黑箱模型辨识

针对非线性黑箱系统辨识中存在不确定性、高阶次,采用常规辨识方法建立其精确数学模型十分困难等问题,提出一种基于自适应粒子群算法的最小二乘支持向量机回归(PSO-LSSVR)非线性系统辨识方法.该方法采用2组自适应粒子群算法并行计算模型,分别利用自适应粒子群算法对LSSVR中的参数进行自动选取和矩阵迭代求解,既克服了传统LSSVR参数难以确定的缺点,提高了辨识精度,同时避免了复杂矩阵求逆运算,加快了计算速度.将该方法应用于船舶操纵性模型非线性系统辨识,仿真结果表明,由该方法得到的LSSVR能够有效地对系统进行建模,仿真精度高,结构简单,具有一定的理论推广意义.     

On the decoding of binary cyclic codes with the Newton identities

We revisit in this paper the concept of decoding binary cyclic codes with Gröbner bases. These ideas were first introduced by Cooper, then Chen, Reed, Helleseth and Truong, and eventually by Orsini and Sala. We discuss here another way of putting the decoding problem into equations: the Newton identities. Although these identities have been extensively used for decoding, the work was done manually, to provide formulas for the coefficients of the locator polynomial. This was achieved by Reed, Chen, Truong and others in a long series of papers, for decoding quadratic residue codes, on a case-by-case basis. It is tempting to automate these computations, using elimination theory and Gröbner bases.Thus, we study in this paper the properties of the system defined by the Newton identities, for decoding binary cyclic codes. This is done in two steps, first we prove some facts about the variety associated with this system, then we prove that the ideal itself contains relevant equations for decoding, which lead to formulas.Then we consider the so-called online Gröbner basis decoding, where the work of computing a Gröbner basis is done for each received word. It is much more efficient for practical purposes than preprocessing and substituting into the formulas. Finally, we conclude with some computational results, for codes of interesting length (about one hundred).     

Identification and quantification of different vapours using a single polymer chemoresistor and the novel dual transient temperature modulation technique

This paper presents a novel signal processing technique for a square wave temperature modulated carbon black/polymer composite sensor. The technique consists of only two mathematical operations: summing the off- and on-transients of the conductance signals, and subtracting the steady-state conductance signal. The technique has been verified through its application to a carbon black/polyvinylpyrrolidone composite chemoresistor. Identification of water, methanol and ethanol vapours was successfully demonstrated using the peak time of the resultant curves. Furthermore, quantification of those vapours was found to be possible using the height of the peak heights, which was linearly proportional to concentration. The technique does not require zero-gas calibration and thus is superior to previously reported techniques.     

Quadratic optimal neural fuzzy control for synchronization of uncertain chaotic systems

This paper presents a novel quadratic optimal neural fuzzy control for synchronization of uncertain chaotic systems via H^∞ approach. In the proposed algorithm, a self-constructing neural fuzzy network (SCNFN) is developed with both structure and parameter learning phases, so that the number of fuzzy rules and network parameters can be adaptively determined. Based on the SCNFN, an uncertainty observer is first introduced to watch compound system uncertainties. Subsequently, an optimal NFN-based controller is designed to overcome the effects of unstructured uncertainty and approximation error by integrating the NFN identifier, linear optimal control and H^∞ approach as a whole. The adaptive tuning laws of network parameters are derived in the sense of quadratic stability technique and Lyapunov synthesis approach to ensure the network convergence and H^∞ synchronization performance. The merits of the proposed control scheme are not only that the conservative estimation of NFN approximation error bound is avoided but also that a suitable-sized neural structure is found to sufficiently approximate the system uncertainties. Simulation results are provided to verify the effectiveness and robustness of the proposed control method.     

Limitations of nonlinear discrete periodic control for disturbance attenuation and robust stabilization

This paper presents a performance analysis of nonlinear periodically time-varying discrete controllers acting upon a linear time-invariant discrete plant. Time-invariant controllers are distinguished from strictly periodically time-varying controllers. For a given nonlinear periodic controller, a time-invariant controller is constructed. Necessary and sufficient conditions are given under which the time-invariant controller gives strictly better control performance than the time-invariant controller from which it was obtained, for the attenuation of l_p exogenous disturbances and the robust stabilization of l_p unstructured perturbations, for all p[1,∞].