移动无线传感器网络中链路层连接变化分析

动态无线传感器网络中的一个关键问题就是节点移动对网络连接变化的影响.分析了移动无线传感器网络链路层中影响连接变化的因素,即节点移动速度和网络承载率,并以速度半径比的概念有效地描述节点在网络中的移动速度,研究了二者共同作用时的影响情况.通过对网络中链路层连接变化的深入研究和仿真实验得到的大量实验数据,最后得出连接变化率随着速度半径比增大而增大,随着网络承载率增大而减小的结论;该结论既可为无线传感器网络的实际应用提供依据,又可为上层协议的研究提供有价值的参考.

企业知识基础演变对技术创新绩效的影响

通过构建企业知识连接矩阵描绘企业知识基础,根据两阶段知识元素关系变化过程中涉及的知识元素类型(现存知识、旧知识、新知识)将企业知识基础演变进行分类,实证检验了现存知识连接变化、新知识与现存知识连接对企业技术创新绩效的影响。基于我国汽车产业1985~2011年278家企业26124条专利数据,应用负二项随机效应模型进行实证分析,研究结果表明:企业现存知识连接变化、新知识与现存知识连接均对技术创新绩效产生正向影响。

车载网运动模型的复杂网络解析方法

车载网快速移动的特点导致其结构具有强烈的复杂性,传统的网络研究方法无法对这种复杂性进行分析.针对此问题将复杂网络解析方法运用于车载网的研究之中,依据车载网组网过程建立车载网运动模型,通过复杂网络研究手段与运动模型相结合的方式对车载网的度分布、鲁棒性以及网络连接变化率进行分析与仿真实验.结果表明,所构建的运动模型能够反应车载网构网过程,复杂网络解析方法在车载网性质分析方面十分有效.

移动边缘计算环境下基于移动感知的工作流调度算法

移动边缘计算环境下,用户可将本地的计算密集型任务卸载至边缘服务器,从而缩短工作流的完工时间并节省设备能耗。然而,许多研究忽略了用户移动导致的网络连接变化对工作流调度的影响。针对现有算法中存在的卸载不合理问题,文中提出了基于移动感知的工作流调度算法MaWS。该算法通过预测用户移动轨迹得出未来可通信的基站集合,并融入遗传算法,制定合理的任务执行顺序和执行位置。仿真结果表明,相比HEFT和Greedy等算法,MaWS算法能够有效缩短10%~15%的工作流完工时间并降低8%~13%的设备能耗,为移动边缘计算下的工作流调度提出一种有效方案。

正念的脑机制

正念是对此时此刻状态的觉知,是有目的地、有意识地关注、觉察当下的一切,是一种专注于当前体验的非判断性关注。随着正念冥想训练在临床医学和心理治疗等领域的广泛应用及其疗效的凸显,越来越多的研究者开始对正念作用的机制感兴趣,特别是其脑机制。当前有关正念作用的脑机制研究主要集中于正念引起的大脑相关区域的激活以及功能连接性的变化。

Effects of temperature change on elastic behavior of steel beams with semi-rigid connections

Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loads and temperature change.Considering the non-uniform temperature distribution across the thickness of beams,the formulas for stresses and vertical displacements were presented.On the basis of a flowchart for analysis of the numerical example,the effect of temperature change on the elastic behavior of steel beams was investigated.It is found that the maximal stress is mainly influenced by axial temperature change,and the maximal vertical displacement is principally affected by temperature gradients.And the effect of temperature gradients on the maximal vertical displacement decreases with the increase of rotational stiffness of joints.Both the maximal stress and vertical displacement decrease with the increase of rotational stiffness of joints.It can be concluded that the effects of temperature changes and rotational stiffness of joints on the elastic behavior of steel beams are significant.However,the influence of rotational stiffness becomes smaller when the rotational stiffness is larger.

Walter Benjamin： A New Positive Concept of Destruction

The author＇s proposal is to show how an apparently marginal text by Walter Benjamin, ＂The Destructive Character＂, can be taken as a hermeneutic model for understanding the connection of Benjamin＇s with history and tradition and for characterizing his thought as philosophy of threshold. It is the author＇s intention to show how the destructive character, on the threshold between destruction and construction, succeeds in remaining in that transition area that announces a change, showing its creative and conservative features; thus it appears as a figure of coexistence between stillness and movement, passage and interruption, and past and future. What the author wants to point out is that, in the description of this figure, Benjamin is driven by a cognitive demand, which tends to focalize the process of destruction itself rather than the result of the destruction process. The space in which the destructive character is acting is the space of the possibility of change and emancipation, and the space where it is possible to keep together past and future, and memory and redemption. Starting from these reflections, an important question arises about the problem of the relation between history and tradition, and culture and its memory： Neither the destruction of memory by a culture nor its canonization is meaningful. The concept of destructive character then represents a preferential point of observation for analyzing the articulations of Benjamin＇s thought. From this perspective, a decisive point of Benjamin＇s reflection seems to emerge on one side, strengthened in the permeation of Hebraic ancestors between destruction and salvation; on the other side, some of the concepts and images of the Berliner philosopher seem to show up in a new light.

Application research of multivariate linkage fluctuation analysis on condition evaluation in process industry

Abnormal conditions are hazardous in complex process systems, and the aim of condition recognition is to detect abnormal conditions and thus avoid severe accidents. The relationship of linkage fluctuation between monitoring variables can characterize the operation state of the system. In this study,we present a straightforward and fast computational method, the multivariable linkage coarse graining(MLCG) algorithm, which converts the linkage fluctuation relationship of multivariate time series into a directed and weighted complex network. The directed and weighted complex network thus constructed inherits several properties of the series in its structure. Thereby, periodic series convert into regular networks, and random series convert into random networks. Moreover, chaotic time series convert into scale-free networks. It demonstrates that the MLCG algorithm permits us to distinguish, identify, and describe in detail various time series. Finally, we apply the MLCG algorithm to practical observations series, the monitoring time series from a compressor unit, and identify its dynamic characteristics. Empirical results demonstrate that the MLCG algorithm is suitable for analyzing the multivariable linkage fluctuation relationship in complex electromechanical system. This method can be used to detect specific or abnormal operation condition, which is relevant to condition identification and information quality control of complex electromechanical system in the process industry.

The variation of the estimated GPS instrumental bias and its possible connection with ionospheric variability

Based on the analysis of the satellite DCB data estimated by our method and the Center for Orbit Determination in Europe(CODE)from 1999 to 2011,the features of the temporal variation of differential code biases(DCB)are studied.Summarily,there are three types of variations in DCB on different time scales.The first one is the day-to-day variation that exhibits more obviously in solar maximum years.The second one is the variation with about one year periodic variation that behaves more obviously from 1999 to 2004.The last one is the monotonously descending tendency from 1999 to 2010.Considering the basic ionospheric approximation in DCB estimation method,the features of the variability of the ionospheric morphology from 1999to 2010 are also displayed based on the ionospheric characteristic parameters.It can be concluded that the day-to-day and annual variation of the estimated global positioning system(GPS).DCB is related to the ionospheric variability.The variation of DCBs on solar cycle time scale includes the real hardware DCBs and pseudo-DCBs induced by ionospheric variation.No doubt,these kinds of"pseudo"variations of DCB will affect the precision of ionospheric total electron content(TEC)derived from the GPS data.In addition,this study is helpful for evaluating the influence of ionospheric weather on TEC derivation and is also useful for developing one estimation method of DCB with more stability and precision through introducing a more practical ionospheric model.

Membrane nanotubes:Novel communication between distant cells

The many kinds of cell structures involved in cell-cell communication include tight junction,adherens junction and gap junction,but almost all are between adjacent cells.Recently,a general and dynamic membrane tether,termed tunneling nanotubes or membrane nanotubes(MNTs),was discovered to be involved in communication between distant cells.By facilitating intercellular communication,MNTs contribute to many biological functions and pathologic changes in cells.Many works have revealed the structure,formation and functional properties of MNTs.However,as novel structures,further research is needed.

Design for structural flexibility using connected morphable components based topology optimization

In topology optimization of structures considering flexibility, degenerated optimal solutions, such as hinges, gray areas and disconnected structures may appear. In this paper, built upon the newly developed morphable component based topology optimization approach, a novel representation using connected morphable components(CMC) and a linkage scheme are proposed to prevent degenerating designs and to ensure structure integrity. A lower bound condition of the thickness of each component is also incorporated to completely remove the smallest components in an optimal configuration. Designs of flexible structures, such as compliant mechanism design, maximum compliance structure design, and design of low-frequency resonating micro devices are studied to validate the proposed methodology. Our work demonstrates that the new methodology can successfully prevent degeneration solutions and possesses other advantages, such as minimum member size control in topology optimization of flexible structures.