一种新的组合权重集结方法及合理性评价研究

针对多属性决策中的组合赋权问题,提出了一种新的多属性决策权重集结方法.该方法综合考虑权本身具有的随机性以及权向量之间的一致性要求,建立约束非线性优化模型.在分析和借鉴现有方法的基础上,设计一种改进粒子群优化算法进行求解.在决策矩阵已知的情况下,讨论不同组合赋权方法的合理性评价问题.最后,将本文提出的方法与已有组合赋权方法进行比较,结果表明该方法有效且比另外两种组合赋权方法更加合理.     

ISAR target recognition based on non-negative sparse coding

Aiming at technical difficulties in feature extraction for the inverse synthetic aperture radar (ISAR) target recognition, this paper imports the concept of visual perception and presents a novel method, which is based on the combination of non-negative sparse coding (NNSC) and linear discrimination optimization, to recognize targets in ISAR images. This method implements NNSC on the matrix constituted by the intensities of pixels in ISAR images for training, to obtain non-negative sparse bases which characterize sparse distribution of strong scattering centers. Then this paper chooses sparse bases via optimization criteria and calculates the corresponding non-negative sparse codes of both training and test images as the feature vectors, which are input into k neighbors classifier to realize recognition finally. The feasibility and robustness of the proposed method are proved by comparing with the template matching, principle component analysis (PCA) and non-negative matrix factorization (NMF) via simulations.     

平流层飞艇变质心姿态运动仿真

针对平流层飞艇工作高度空气密度低,飞行速度低的特点,提出了变质心姿态控制的方案。在机体坐标系下,采用牛顿—欧拉方法建立了浮空器的动力学方程,并分析了变质心动力学模型的特性,给出了质量滑块的参数化驱动方法。采用了ADAMS动力学分析软件,进行了不同飞行条件下的变质心动力学仿真。仿真结果显示了滑块质量、位移、速度以及飞艇速度等条件的改变对姿态控制的影响,结果表明:滑块的质量比和移动距离是影响变质心姿态控制能力的主要因素,滑块的速度决定系统的响应特性;变质心操纵能力不受飞行速度的影响,因此在低速飞行时具有很强的适应性。     

柔性空间机械臂的模糊控制及抑振最优控制

讨论了载体位置不受控、姿态受控的情况下,漂浮基柔性空间机械臂系统的轨迹跟踪和振动抑制问题。对系统进行输入输出反馈线性化,并采用奇异摄动理论,得到了慢变子系统和快变子系统。然后,设计了两种时间尺度的模糊逻辑控制器,以控制柔性空间机械臂的载体姿态和机械臂关节铰协调地来完成各自在关节空间的期望运动。慢变子系统用模糊控制来进行轨迹跟踪,而快变子系统用最优线性二次型控制来主动抑制柔性杆的振动。系统仿真结果说明了控制器的可靠性和有效性。     

Novel reference range selection method in InlSAR imaging

Aiming at the reference range selection for different antennas in interferometric inverse synthetic aperture radar (InISAR) systems, this paper proposes a respective focusing (RF) method. The reference ranges for echoes of different antennas are selected respectively for RF, which is different from the traditional uniform focusing (UF) with the same reference range applied to all the antennas. First, a comparison between UF and RF for InISAR signal model considering the ranging error is given. Compared with RF, UF has an advantage in overcoming the ranging error differences between different antennas. Then the influence of ranging error upon the interferometric imaging with RF is investigated particularly, and it is found that the ranging error differences between different antennas are far smaller than the wavelength, which is advantageous to imaging. By comparing the capabilities of interferometric imaging between RF and UF, it is concluded that RF is a better choice in conquering problems such as image mismatching and phase ambiguity even with ranging errors. Simulations demonstrate the validity of the proposed method.     

改进的舰船维修费案例调整模型

为提高舰船维修费案例的调整效果,遵循着调整知识产生、调整知识约简和调整知识推理的建模过程,提出了一种改进的舰船维修费案例调整模型。在该模型中,采用Policastro的重构方式,利用目标案例的直接和间接相似案例集,产生舰船维修费案例的调整知识;针对调整知识中可能存在冗余、相关性、知识量过于庞大不便于推理等问题,提出了一种既能有效约简调整知识、又能准确衡量调整知识重要度的改进规则约简方法,并给出了具体的实现算法;为提高知识推理的效率,采用具有强泛化能力和出色学习能力的最小二乘支持向量机（least square support vector machine,LSSVM）,构建了舰船维修费案例调整知识推理模型,并基于遗传算法（genetic algorithm,GA）和交叉验证方法,对推理模型的有关参数进行了优化。实例结果表明,与其他案例调整模型相比,所提模型在调整精度上要远远好于其他模型,所提模型是科学、有效的。     

SER analysis and power allocation for hybrid cooperative transmission system

The symbol-error-rate(SER) and power allocation for hybrid cooperative(HC) transmission system are investigated.Closed-form SER expression is derived by using the moment generating function(MGF)-based approach.However,the resultant SER contains an MGF of the harmonic mean of two independent random variables(RVs),which is not tractable in SER analysis.We present a simple MGF expression of the harmonic mean of two independent RVs which avoids the hypergeometric functions used commonly in previous studies.Using the simple MGF,closed-form SER for HC system with M-ary phase shift keying(M-PSK) signals is provided.Further,an approximation as well as an upper bound of the SER is presented.It is shown that the SER approximation is asymptotically tight.Based on the tight SER approximation,the power allocation of the HC system is investigated.It is shown that the optimal power allocation does not depend on the fading parameters of the source-destination(SD) channel and it only depends on the source-relay(SR) and relay-destination(RD) channels.Moreover,the performance gain of the power allocation depends on the ratio of the channel quality between RD and SR.With the increase of this ratio,more performance gain can be acquired.     

Superconvergence of mixed covolume method on quadrilateral grids for elliptic problems

This paper considers the mixed covolume method for the second-order elliptic equations over quadrilaterals.Superconvergence results are established in this paper on quadrilateral grids satisfying the h~2-parallelogram condition when the lowest-order Raviart-Thomas space is employed in the mixed covolume method.The authors prove O(h~2) accuracy between the approximate velocity or pressure and a suitable projection of the real velocity or pressure in the L~2 norm.Numerical experiments illustrating the theoretical results are provided.     

一种基于分片模板的自适应运动目标跟踪算法

分块跟踪算法是一种非常鲁棒的模板匹配算法,特别适合解决部分遮挡问题,但是该算法框架下的模板更新策略无法解决场景中的目标外观变化和遮挡问题,为此,提出一种分块跟踪框架下的带有遮挡检测的模板更新算法。算法将目标分为多个小片,根据各小片匹配的情况检测目标是否被部分遮挡。如果目标被遮挡,使用能精确反映目标信息的参考模板进行匹配;否则使用能反映目标变化的临时模板,并提出了相应的模板更新算法。大量的实验证明了本算法的有效性。     

Game-theoretic approach to power and admission control in hierarchical wireless sensor networks

Power efficiency and link reliability are of great importance in hierarchical wireless sensor networks (HWSNs),especially at the key level,which consists of sensor nodes located only one hop away from the sink node called OHS.The power and admission control problem in HWSNs is comsidered to improve its power efficiency and link reliability.This problem is modeled as a non-cooperative game in which the active OHSs are considered as players.By applying a double-pricing scheme in the definition of OHSs’ utility function,a Nash Equilibrium solution with network properties is derived.Besides,a distributed algorithm is also proposed to show the dynamic processes to achieve Nash Equilibrium.Finally,the simulation results demonstrate the effectiveness of the proposed algorithm.