Bounds for closed-loop transfer functions of multivariable systems

A multivariable feedback system y(s)=G(s)x(s), x(s) = u(s)- F(s)y(s) is treated where G(s) ≜ (gkl(s)) is the transfer function matrix of a plant and F(s) ≜ diag(f1(s),...,fn(s)) is that of a controller. A new bound for the transfer function hj(s) that relates yj(s) to uj(s) when fj(s)≡ 0 is given. The main result reads |hj(s)- gjj(s)| < aj(s) if |fk(s)^-1+ gkk(s)| > ak(s) for k = 1,... ,n; k≠j. Here, A ≜ diag(a1(s),...,an(s)) is a diagonal matrix which makes A-B a semi-M-matrix where B ≜ (bkl) is given by bkk=0, bkl= |gkl(s)| (k≠l). A similar result is also obtained for the inverse transfer function.     

Localization-based sensor validation using the Kullback-Leibler divergence

A sensor validation criteria based on the sensor's object localization accuracy is proposed. Assuming that the true probability distribution of an object or event in space f(x) is known and a spatial likelihood function (SLF) psi(x) for the same object or event in space is obtained from a sensor, then the expected value of the SLF E[psi(x)] is proposed as a suitable validity metric for the sensor, where the expectation is performed over the distribution f(x). It is shown that for the class of increasing linear log likelihood SLFs, the proposed validity metric is equivalent to the Kullback-Leibler distance between f(x) and the unknown sensor-based distribution g(x) where the SLF psi(x) is an observable increasing function of the unobservable g(x). The proposed technique is illustrated through several simulated and experimental examples.     

Cr(CO)_n(n=1-5)与C_6 H_6相互作用的密度泛函研究

用密度泛函理论在B3LYP/LANL2DZ基组水平上对(η~x-C_6H_6)Cr(CO)_n(x=1-6;n=1-5)复合物体系的可能构型进行了自由优化及相互作用能的计算,研究了不同羰基数对复合物稳定性、苯和羰基铬相互作用的影响,并对苯和羰基铬相互作用进行了NBO分析。得到以下结论:(1)当n≤3时,苯与Cr(CO)_n以η~6配位;当n≥4时,苯与Cr(CO)_n以η~2配位;(2)最稳定复合物中随羰基数的增加Cr-C_(benzene)平均键长增长,最大二面角H-C-C-H偏离碳环的角度随复合物对称性降低而逐渐增大;(3)当n为奇数时,复合物相互作用主要表现为苯C-C键的π轨道和Cr-CO键的σ反键轨道;当n为偶数时,复合物相互作用主要表现为苯C-C键的π轨道或π~*轨道与Cr的孤对电子轨道;(4)复合物羰基数越多,最稳定复合物的相互作用能数值越大,稳定性越小。     

The Explanatory Role of Computation in Cognitive Science

Which notion of computation (if any) is essential for explaining cognition? Five answers to this question are discussed in the paper. (1) The classicist answer: symbolic (digital) computation is required for explaining cognition; (2) The broad digital computationalist answer: digital computation broadly construed is required for explaining cognition; (3) The connectionist answer: sub-symbolic computation is required for explaining cognition; (4) The computational neuroscientist answer: neural computation (that, strictly, is neither digital nor analogue) is required for explaining cognition; (5) The extreme dynamicist answer: computation is not required for explaining cognition. The first four answers are only accurate to a first approximation. But the ??devil?? is in the details. The last answer cashes in on the parenthetical ??if any?? in the question above. The classicist argues that cognition is symbolic computation. But digital computationalism need not be equated with classicism. Indeed, computationalism can, in principle, range from digital (and analogue) computationalism through (the weaker thesis of) generic computationalism to (the even weaker thesis of) digital (or analogue) pancomputationalism. Connectionism, which has traditionally been criticised by classicists for being non-computational, can be plausibly construed as being either analogue or digital computationalism (depending on the type of connectionist networks used). Computational neuroscience invokes the notion of neural computation that may (possibly) be interpreted as a sui generis type of computation. The extreme dynamicist argues that the time has come for a post-computational cognitive science. This paper is an attempt to shed some light on this debate by examining various conceptions and misconceptions of (particularly digital) computation.     

Cooperative path planning with priority target assignment and collision avoidance guidance for rescue unmanned surface vehicles in a complex ocean environment

In this paper, a novel cooperative path planning scheme of unmanned surface vehicles (USVs) for rescuing targets in a complex ocean environment is proposed. The primary objective of the rescue USVs is to bring all targets back safely on the premise of first rescuing priority targets, while optimizing the path length, the navigation time and the angular energy. The main contributions of this paper are as follows: (1) The proposed K-means-division (KMD) algorithm is able to identify a complex ocean environment with collision-free zone and static-obstacles zone; (2) The proposed path planning method with fast-marching-method-based ellipse guidance range (E-FMM) is able to optimize the angular energy while ensuring safety; (3) The proposed cooperative management system (including priority-target-assignment (PTA) with reward-mechanism genetic-optimization (RM-GO) and collision-avoidance (CA) guidance law with Tangent-based surge-varying wave-disturbances-observer (Tangent-SV-WDO)) can accomplish the mission of the rescue USVs. Comparative studies with the state-of-the-art methods demonstrate that the proposed cooperative path planning scheme is superior in terms of priority-target-assignment (PTA) and collision-avoidance (CA) of the actual rescue work.     

对偶关系与不确定系统的状态估计

本文讨论如下系统状态估计问题, x=A(t)x+B1(t)u(t)+B2(t)w y=C(t)X+D1(t)u(t)+D2(t)w 其中u(t)为已知输入向量,w为不确定向量.假定w为时间t 的函数,对它只知道其可能的变化范围,不知道其具体实现.问题是根据量测y(t),0tT,如何去估计状态变量 x(T)?我们用[1]中所建立的对偶关系式解决了状态的min-max估计问题.在二次型限制之下的min-max状态估计与卡尔曼滤波完全一致.这里所用的方法比起[4]中的方法简单得多.     

Fodor and Pylyshyn on connectionism

Fodor and Pylyshyn (1988) have argued that the cognitive architecture is not Connectionist. Their argument takes the following form: (1) the cognitive architecture is Classical; (2) Classicalism and Connectionism are incompatible; (3) therefore the cognitive architecture is not Connectionist. In this essay I argue that Fodor and Pylyshyn's defenses of (1) and (2) are inadequate. Their argument for (1), based on their claim that Classicalism best explains the systematicity of cognitive capacities, is an invalid instance of inference to the best explanation. And their argument for (2) turns out to be question-begging. The upshot is that, while Fodor and Pylyshyn have presented Connectionists with the important empirical challenge of explaining systematicity, they have failed to provide sufficient reason for inferring that the cognitive architecture is Classical and not Connectionist.     

FPGA based area efficient RS(23, 17) codec

Generally in digital communication systems and storage mediums, Reed–Solomon (RS) codes are employed to detect and correct errors. RS code is a promising code for Ultra Wide Band (UWB) which is ideally suitable for wireless application. Design of compact, high-speed and low-power RS(23, 17) code is challenging for today’s wireless communication systems. Here, an optimization algorithm is introduced which is very simple and it is employed to reduce the number of XOR gates required to design constant Galois Field (GF) multipliers. In this paper, a compact RS(23, 17) encoder and decoder circuit is designed and implemented for Ultra Wide Band(UWB) application. The number of two input XOR gates is reduced by 29.27 (20.00) and 56.10 (66.15) % respectively for local and global optimization compared to unoptimized RS encoder (syndrome block) without increasing its delay. The proposed algorithm is also employed to design the RS(204, 188) and RS(255, 223) encoder. All designs are simulated and synthesized for Vertex4 FPGA platform. Proposed algorithm is also used for the design of Chien Search and Forney blocks. Implemented RS(23, 17) codec requires lesser number of slices and LUTs over the unoptimized RS codec. The synthesis results reflect that the proposed design is suitable for resource constraint applications.

     

谐波影响下的高压直流输电系统运行特性分析

随着多馈入直流工程的不断发展,换流站发生谐波扰动的概率大大增加.通过分析换流母线谐波对锁相环和换相过程的影响,研究了高压直流输电系统的控制器在谐波扰动下的运行特性.通过减少电流偏差控制器的输出量以减少定熄弧角控制器在谐波扰动中的稳态误差,提高了直流系统传输容量.最后提出了谐波扰动中系统运行点的计算方法.PSCAD软件的仿真结果证明了分析和计算方法的准确性.     

Bifurcations in a stock market model

A theoretical framework is laid out, where a Stock Exchange is represented as a process under decentralized control. Attention is devoted to a specific case, in which the trading activity is described by a second order dynamical system. Three economically significant modes of behavior are identified. The stock market can (1)_adjust to a stable equilibrium, (2) approach a stable limit cycle, (3) diverge to infinity. The transition from mode (1) to mode (2) is a supercritical Hopf bifurcation, whereas the transition from mode (2) to mode (3) is a homoclinic bifurcation.     

Analysis of the interaction between the dendritic conductance density and activated area in modulating alpha-motoneuron EPSP: statistical computer model

Five reconstructed alpha-motoneurons (MNs) are simulated under physiological and morphological realistic parameters. We compare the resulting excitatory postsynaptic potential (EPSP) of models, containing voltage-dependent channels on the dendrites, with the EPSP of a passive MN and an active soma and axon model. In our simulations, we apply three different distribution functions of the voltage-dependent channels on the dendrites: a step function (ST) with uniform spatial dispersion; an exponential decay (ED) function, with proximal to the soma high-density location; and an exponential rise (ER) with distally located conductance density. In all cases, the synaptic inputs are located as a gaussian function on the dendrites. Our simulations lead to eight key observations. (1) The presence of the voltage-dependent channels conductance (g(Active)) in the dendrites is vital for obtaining EPSP peak boosting. (2) The mean EPSP peaks of the ST, ER, and ED distributions are similar when the ranges of G (total conductance) are equal. (3) EPSP peak increases monotonically when the magnitude of g(Na_step) (maximal g(Na) at a particular run) is increased. (4) EPSP kinetics parameters were differentially affected; time integral was decreased monotonically with increased g(Na_step), but the rate of rise (the decay time was not analyzed) does not show clear relations. (5) The total G can be elevated by increasing the number of active dendrites; however, only a small active area of the dendritic tree is sufficient to get the maximal boosting. (6) The sometimes large variations in the parameters values for identical G depend on the g(Na_step) and active dendritic area. (7) High g(Na_step) in a few dendrites is more efficient in amplifying the EPSP peak than low g(Na_step) in many dendrites. (8) The EPSP peak is approximately linear with respect to the MNs' R(N) (input resistance).     

Analysis of sparse representation and blind source separation

In this letter, we analyze a two-stage cluster-then-l(1)-optimization approach for sparse representation of a data matrix, which is also a promising approach for blind source separation (BSS) in which fewer sensors than sources are present. First, sparse representation (factorization) of a data matrix is discussed. For a given overcomplete basis matrix, the corresponding sparse solution (coefficient matrix) with minimum l(1) norm is unique with probability one, which can be obtained using a standard linear programming algorithm. The equivalence of the l(1)-norm solution and the l(0)-norm solution is also analyzed according to a probabilistic framework. If the obtained l(1)-norm solution is sufficiently sparse, then it is equal to the l(0)-norm solution with a high probability. Furthermore, the l(1)- norm solution is robust to noise, but the l(0)-norm solution is not, showing that the l(1)-norm is a good sparsity measure. These results can be used as a recoverability analysis of BSS, as discussed. The basis matrix in this article is estimated using a clustering algorithm followed by normalization, in which the matrix columns are the cluster centers of normalized data column vectors. Zibulevsky, Pearlmutter, Boll, and Kisilev (2000) used this kind of two-stage approach in underdetermined BSS. Our recoverability analysis shows that this approach can deal with the situation in which the sources are overlapped to some degree in the analyzed domain and with the case in which the source number is unknown. It is also robust to additive noise and estimation error in the mixing matrix. Finally, four simulation examples and an EEG data analysis example are presented to illustrate the algorithm's utility and demonstrate its performance.     

Investigation on uplink collaborative contention-based bandwidth request for WiMAX three hop relay networks

This paper suggests a collaborative contention bandwidth request (BR) mechanism for worldwide interoperability for microwave access (WiMAX) three-hop relay networks. By complimenting message and code BR in three hops of a link, the proposed framework enables low block error rate (BLER), packet dropping and signaling overhead while preserving the connection throughput and access delay requirements of best effort (BE) services. With three hops between base station (BS) and mobile station (MS) via relay station 1 (RS1) and relay station 2 (RS2), there take place eight possible BR mechanisms with message and code BR. Among eight BR mechanisms, message-message-code (MMC) BR performs better with message dominant BR and code-message-code (CMC) BR performs better with code dominant BR. Further, with CMC BR, the BLER is reduced by 5.88%, packet dropping is reduced by 8.68%, medium access control (MAC) overhead is reduced by 7.6%, MAC wastage is reduced by 4.47%, connection delay is reduced by 28.30%, queuing delay is reduced by 8.65%, queue size is reduced by 15.25% and throughput is improved by 11.51% than MMC BR mechanism.     

The Noisy Substring Matching Problem

Let T(U) be the set of words in the dictionary H which contains U as a substring. The problem considered here is the estimation of the set T(U) when U is not known, but Y, a noisy version of U is available. The suggested set estimate S*(Y) of T(U) is a proper subset of H such that its every element contains at least one substring which resembles Y most according to the Levenshtein metric. The proposed algorithm for-the computation of S*(Y) requires cubic time. The algorithm uses the recursively computable dissimilarity measure Dk(X, Y), termed as the kth distance between two strings X and Y which is a dissimilarity measure between Y and a certain subset of the set of contiguous substrings of X. Another estimate of T(U), namely SM(Y) is also suggested. The accuracy of SM(Y) is only slightly less than that of S*(Y), but the computation time of SM(Y) is substantially less than that of S*(Y). Experimental results involving 1900 noisy substrings and dictionaries which are subsets of 1023 most common English words [11] indicate that the accuracy of the estimate S*(Y) is around 99 percent and that of SM(Y) is about 98 percent.     

线性控制系统闭环稳定的结构稳定性

设反馈控制系统为 y(s)=G(s,θ)u(s)(1) u(s)=-K(s)y(s)+v(s). (2) 本文的主要结果如下: 当G(s,θ)在θ=θ0处零实部不升阶时,存在反馈控制(2),使得闭环稳定θ=θ.处 是结构稳定的一个充分必要条件为G(s,θ)在θ=θa处,正实部不是本质的升阶;当G(s,θ) 的零实部升阶时,这条件仅是必要的.     

基于区分服务的主动队列管理算法研究

分析了几种主动队列管理算法。RIO算法是用于支持区分服务确保转发逐跳行为的主动队列管理算法,它是对RED算法的简单扩充,但是该算法的性能对配置参数敏感。PI算法是基于控制论的主动队列管理算法,具有队列长度抖动小的特点。PIP算法是PI算法的改进,比PI算法具有更快的收敛速度。为了更好地满足AF PHB的要求,基于PIP算法,结合三色标记器的功能,提出一个新的主动队列管理算法PIPGYR（PIP with Green ＆ Yellow ＆ Red）。通过仿真验证,该算法队列长度抖动小,同时能够保护高优先级分组。     

Compressed sensing-based time-domain channel estimator for full-duplex OFDM systems with IQ-imbalances

In full-duplex orthogonal frequency-division multiplexing (OFDM) systems with in-phase and quadrature (IQ) imbalances, a time-domain least squares (TD-LS) channel estimator is proposed for estimating both the source-to-destination (intended) and the destination-to-destination (self-interference) channels. To further improve the performance, an adaptive orthogonal matching pursuit (OMP) is proposed and its sparsity is estimated by a threshold method. Finally, the full-duplex interference is removed using serial interference cancellation and sphere decoding is used to complete the maximum likelihood detection. Simulation results demonstrate that in terms of both the mean square error (MSE) and the bit error rate (BER), the proposed adaptive OMP performs better than the TD-LS by exploiting the sparse property of the channel. Additionally, compared to the gradient projection, the proposed adaptive OMP is better in the low and medium signal-to-noise ratio (SNR) regions and marginally worse in the high SNR region.     

基于混合微粒群优化的多目标柔性Job-shop调度

应用传统方法求解多目标柔性Job-shop调度问题是十分困难的,微粒群优化采用基于种群的搜索方式,融合了局部搜索和全局搜索,具有很高的搜索效率.模拟退火算法使用概率来避免陷入局部最优,整个搜索过程可由冷却表来控制.通过对这两种算法的合理组合,建立了一种快速且易于实现的新的混合优化算法.实例计算以及与其他算法的比较说明,该算法是求解多目标柔性Job-shop调度问题的可行且高效的方法.     

Rooted Maximum Agreement Supertrees

Given a set $\T$ of rooted, unordered trees, where each $T_i \in \T$ is distinctly leaf-labeled by a set $\Lambda(T_i)$ and where the sets $\Lambda(T_i)$ may overlap, the maximum agreement supertree problem~(MASP) is to construct a distinctly leaf-labeled tree $Q$ with leaf set $\Lambda(Q) \subseteq $\cup$_{T_i \in \T} \Lambda(T_i)$ such that $|\Lambda(Q)|$ is maximized and for each $T_i \in \T$, the topological restriction of $T_i$ to $\Lambda(Q)$ is isomorphic to the topological restriction of $Q$ to $\Lambda(T_i)$. Let $n = \left| $\cup$_{T_i \in \T} \Lambda(T_i)\right|$, $k = |\T|$, and $D = \max_{T_i \in \T}\{\deg(T_i)\}$. We first show that MASP with $k = 2$ can be solved in $O(\sqrt{D} n \log (2n/D))$ time, which is $O(n \log n)$ when $D = O(1)$ and $O(n^{1.5})$ when $D$ is unrestricted. We then present an algorithm for MASP with $D = 2$ whose running time is polynomial if $k = O(1)$. On the other hand, we prove that MASP is NP-hard for any fixed $k \geq 3$ when $D$ is unrestricted, and also NP-hard for any fixed $D \geq 2$ when $k$ is unrestricted even if each input tree is required to contain at most three leaves. Finally, we describe a polynomial-time $(n/\!\log n)$-approximation algorithm for MASP.     

MWNTs与GNPs—CHIT修饰的过氧化氢生物传感器

在玻碳电极（GCE）上自组装一层多壁碳纳米管（MWNTs）,构建负电荷的界面,然后,静电吸附一层阳离子电子媒介体硫堇（Thi）,再由共价键作用自组装一层纳米金（GNPs）,壳聚糖（CHIT）混合溶液的复合薄膜,通过静电吸附辣根过氧化物酶（HRP）制得过氧化氢（H2O2）生物传感器。采用循环伏安法和计时电流法考察了该生物传感器的电化学性质,并研究了该修饰电极对H2O2的催化还原作用。生物传感器的响应电流与H2O2浓度在8．2×10^-6～1．1×10^-3mol／L范围内呈现线性关系,检出限为5．8×10^-7mol／L,达到95％稳态响应时间约为15s。将此生物传感器用于H2O2的检测,结果令人满意。