WSNs中优化移动信宿路径的数据收集算法

收集数据是部署无线传感网络(WSNs)的根本目的。采用移动信宿策略可有效缓解WSNs的能耗问题,信宿的移动路径是该策略的关键。为此,提出基于伪驻留点的数据收集(VRDC)算法。VRDC算法先依据驻留点规划信宿路径,再依据路径选择伪驻留点(VRPs)。VRPs可通过一跳直接向移动信宿传输数据,而其他的节点则将数据传输至最近的VRPs,进而减少传输跳数,降低能耗。仿真结果表明,提出的VRDC算法能有效降低能耗,并平衡节点间的能耗。     

捷联导引头延时引起的隔离度问题研究

研究了捷联导引头引起的隔离度问题,建立了捷联导引头延时造成的寄生回路模型,分析了捷联导引头延时引起隔离的机理,得到了捷联导引头延时引起的隔离度函数。研究了导引头延时造成寄生回路的稳定性,在制导参数取不同值情况下,绘制捷联导引头延时引起的寄生回路稳定区域。仿真结果表明:制导系统延迟环节动力学时间常数相对于弹体动力学时间常数越大,对系统克服导引头延时的影响越有利。减小弹体气动力时间常数,可以增强系统容忍导引头延时时间的能力。研究成果对于实现捷联导引头的工程应用具有重大意义。     

Improved electrical behavior of ZrO2-based MIM structures by optimizing the O3 oxidation pulse time

The influence of oxidation pulse during atomic layer deposition (ALD) process on electrical and dielectric properties of metal–insulator–metal (MIM) structures with different ZrO₂-based (e.g. pure ZrO₂, Al- and Si- doped ZrO₂) high-k dielectrics and different thicknesses has been investigated. Strongly pulse-time dependent as well as independent phenomena are observed and their thorough analysis has given more insight on the processes taking place in these structures thus allowing further optimization of their electrical performance. Longer oxidation pulses produce films with larger thicknesses which may be related to the incorporation of excess oxygen in the layers and the formation of less dense films. Incorporation of Al and 10 s pulse time are the most beneficial and provide structures with the lowest leakage current. At high positive voltages a significant increase of current and a change of I–V curve shape with increasing pulse time have been observed. The possible processes which provoke this change have been discussed. The analysis of leakage current mechanisms reveals that neither incorporation of Al or Si in ZrO₂ nor oxidation pulse time change the energy position of traps participating in the conduction process, hence the nature of these traps remains unaffected – it is a single positively charged oxygen vacancy in ZrO₂. The oxidation pulse time of 5–10 s is the optimal one which provides structures fulfilling the requirements for next generation MIM-based dynamic random access memories (DRAMs).     

Genetic algorithm for optimizing the nonlinear time alignment ofautomatic speech recognition systems

Dynamic time warping (DTW) is a nonlinear time-alignment technique for automatic speech recognition (ASR) systems. It had been widely used in many commercial and industrial products, ranging from electronic dailies/dictionaries to wireless voice digit dialers. DTW has the advantages of fast training and searching times, which makes it more popular than other available ASR techniques. However, there exist some limitations to DTW, such as the stringent rule on slope weighting, the nontrivial computation of the K-best paths, and the significant increase in computational time when the endpoint constraint is relaxed or the variations of the length of pattern increased. In this paper, a stochastic method called the genetic algorithm (GA), which is used to solve the nonlinear time alignment problem, is presented. Experimental results show that the GA has a better performance than the DTW. In addition, two derivatives of GA: the hybrid GA and the parallel GA are also presented     

基于禁止搜索的非线性时间匹配优化算法

动态时间规整算法DTW(Dynamic Time Warping)作为一种非线性时间匹配技术已成功地应用于语音识别系统中。DTW算法使用动态规划技术来搜索两个时间序列的最优规整路径,虽然这种算法计算量小,运算时间较短,但只是一种局部优化算法。禁止搜索TS(Tabu Search)算法是一种具有短期记忆的广义启发式全局搜索技术,适用于解决许多非线性优化问题。本文将该技术用于语音识别系统中,提出了基于禁止搜索的非线性时间规整的优化算法TSTW,使得时间规整函数尽可能逼近全局最优。仿真结果表明,TSTW比DTW有更高的识别率,且运行时间比遗传时间规整算法GTW大大减少。     

Two dynamic reconfiguration approaches for optimizing the restoration path length in p-cycle protection network

p-cycle is one of the most promising technique of span protection in optical transport networks with mesh-like efficiency and ring-like speed. Longer p-cycle provides better efficiency in term of spare capacity, but longer restored path increases end-to-end propagation delay, which reduces the reliability of the restored network. Hence, minimization of restoration path is a critical issue in p-cycle based protection network. In this paper, two new dynamic reconfiguration approaches namely inter-cycles switching (ICS) and local restoration paths (LRP) are discussed to reduce the length of restored paths in existing optimal spare capacity design of p-cycle. Both proposed approaches are meant to utilize the idle p-cycles thus significantly reducing the path length. This reduction in restored path length also releases the redundant spare capacity.     

Technology portfolio management: optimizing interdependent projectsover multiple time periods

In order to maintain competitiveness, companies need to continually invest in technology projects. However, resource limitations require an organization to strategically allocate resources to a subset of possible projects. A variety of tools and methods can be used to select the optimal set of technology projects. However, these methods are only applicable when projects are independent and are evaluated in a common funding cycle. When projects are interdependent, the complexity of optimizing even a moderate number of projects over a small number of objectives and constraints can become overwhelming. This paper presents a model developed for the Boeing Company, Seattle, WA, USA, to optimize a portfolio of product development improvement projects. Using a dependency matrix, which quantifies the interdependencies between projects, a nonlinear, integer program model was developed to optimize project selection. The model also balances risk, overall objectives and the cost and benefit of the entire portfolio. Once the optimum strategy is identified, the model enables the team to quickly quantify and evaluate small changes to the portfolio     

Fluctuations of the group path and the group-delay time of waves obliquely reflected by a plane-layered medium

The spatial correlation properties of the group path and the group-delay time of a radio signal leaving a random plane-layered reflecting medium similar to the ionosphere are considered. The spatial-correlation distances for the group path lying in the incidence plane and oriented perpendicularly to this plane are obtained for various angles of propagation of a wave entering the medium. It is shown that, when a radio signal is scattered by isotropic irregularities of the medium’s permittivity, regular refraction results in anisotropic fluctuations of the signal’s characteristics and the degree of anisotropy grows with the sounding angle.     

Dynamic connectivity and path formation time in Poisson networks

The connectivity of wireless networks is commonly analyzed using static geometric graphs. However, with half-duplex radios and due to interference, static or instantaneous connectivity cannot be achieved. It is not necessary, either, since packets take multiple time slots to propagate through the network. For example, if a packet traverses a link in one time slot, it is irrelevant if the next link is available in that time slot also, but it is relevant if the next hop exists in the next time slot. To account for half-duplex constraints and the dynamic changes in the transmitting set of nodes due to MAC scheduling and traffic loads, we introduce a random multi-digraph that captures the evolution of the network connectivity in a dynamic fashion. To obtain concrete results, we focus on Poisson networks, where transmitters form a Poisson point process on the plane at all time instants. We first provide analytical results for the degree distribution of the graph and derive the distributional properties of the end-to-end connection delay using techniques from first-passage percolation and epidemic processes. Next, we prove that under some assumptions, the delay scales linearly with the source–destination distance even in the presence of interference. We also provide simulation results in support of the theoretical results.