Proposing a New Model of Hangers in Pedestrian Suspension Bridges to Solve Hangers Slackness Problem

The hangers of suspension bridges can be placed in two forms: vertical or inclined form. Inclined hangers are more liable to fatigue. Vertical hangers are subjected to greater fluctuations of stress resulting from bridge wind loads. To improve aerodynamic stability, inclined hangers can be used instead of vertical ones. Some inclined hangers show considerable signs of distress and some of them show slackness due to their location against loads. In this paper a pedestrian suspension bridge with vertical hangers has been studied as a case study. Then, the same bridge has been studied with inclined hangers. To reduce internal forces, fatigue and slackness in hangers, horizontal cables have been added to inclined hangers. This modification is proposed by the present authors. The added horizontal cables transfer the tensile load from overstressed hangers to adjacent slacked hangers. Three different hanger patterns have been analyzed under nonlinear static analysis for symmetrical and nonsymmetrical live load plus dead load. Results showed that the modified hanger system had been improved considerably in comparison with vertical or inclined hangers and wherever that there is no improvement some solutions have been proposed.

Pitfalls and Remedies in DEA Applications: How to Handle an Occurrence of Zero in Multipliers by Strong Complementary Slackness Conditions

This study discusses a guideline on a proper use of Data Envelopment Analysis (DEA) that has been widely used for performance analysis in public and private sectors. The use of DEA is equipped with Strong Complementary Slackness Conditions (SCSCs) in this study, but an application of DEA/SCSCs depends upon its careful use, as summarized in the guideline. The guideline consists of the five suggestions. First, a data set used in the DEA applications should not have a ratio variable (e.g., financial ratios) in an input(s) and/or an output(s). Second, radial DEA models under variable and constant Returns to Scale (RTS) need a special treatment on zero in a data set. Third, the DEA evaluation needs to drop an outlier. Fourth, an imprecise number (e.g., 1/3) may suffer from a round-off error because DEA needs to specify it in a precise expression to operate a computer code. Finally, when a large input or output variable may dominate other variables in DEA computation, it is necessary to normalize the data set or simply to divide each observation by its average. Such a simple treatment produces more reliable DEA results than the one without any data adjustment. This study also discusses how to handle an occurrence of zero in DEA multipliers by applying SCSCs. The DEA/SCSCs can serve for a multiplier restriction approach without any prior information. Thus, the propesed DEA/SCSCs can provide more reliable results than a straight use of DEA.

The influence of AAR coupler features on estimation of in-train forces

Inadequate management of large in-train forces transferred through coupler systems of a railway train leads to running and structural failures of vehicles.Understanding these phenomena and their mitigation requires accurate estimation of relative motions and in-train forces between vehicle bodies.Previous numerical studies have ignored inertia of coupling elements and the impacts between couplers.Thus,existing models underestimate the additional dynamic variations in in-train forces.Detailed multi-body dynamic models of two AAR(Association of American Railroads)coupler systems used in passenger and freight trains are developed,incorporating coupler inertia and various slacks.Due to the modeling and simulation com-plexities involved in a full train model,with such details of coupler system,actual longitudinal train dynamics is not studied.A system comprising only two coupling units,inter-connecting two consecutive vehicles,is modeled.Considered system has been fixed at one end and an excitation force is applied at the other end,to mimic a relative force transmission through combined coupler system.Simulation results obtained from this representative system show that,noticeable influence in in-train forces are expected due to the combined effect of inertia of couplers and intermittent impacts between couplers in the slack regime.Maximum amplitude of longitudinal reaction force,transferred from draft gear housing to vehicle body,is expected to be significantly higher than that predicted using existing models of coupler system.It is also observed that the couplers and knuckles are subjected to significant longitudinal and lateral contact forces,due to the intermittent impacts between couplers.Thus,accurate estimation of draft gear reaction force and impact forces between couplers are essential to design vehicle and coupler components,respectively.

Investigating the Effects of Slack Bus Selection in Load Flow Studies: A Comparative Analysis of Robust and Weak Grids

Load flow studies play a critical role in the analysis of power systems. They enable the computation of voltage, current, and power flows in a power system. They provide valuable insights into the steady-state performance of the power system under different operating conditions. Choosing a slack bus is a vital step in conducting load flow simulations. A slack bus is a PV bus that includes a generator and is used to balance real and reactive power during load flow studies. Many studies have been conducted on the selection of slack buses in load flow analysis. However, varied conclusions regarding the impact on system losses and power flows were obtained during these studies. Therefore, using the IEEE-14 bus test system, this study investigated the effects of slack bus selection in strong and weak grids by alternating slack buses among PV buses and observing the effects on bus voltage magnitude, bus voltage phase angle, total power flows, and active and reactive power losses. The study noted that the effect of slack bus selection on these system quantities is contingent upon the voltage stability of the grid. Whereas in a robust grid, system losses and power flows remained constant irrespective of the choice of slack bus, a weak grid experienced some variations in these system quantities under similar circumstances. The simulation results led to the conclusion that, to a large extent, the voltage stability of the grid plays a significant role in determining the degree to which slack bus selection affects system losses and other quantities in load flow studies.

计算机系统信息隐藏反取证技术

研究了现代计算机系统信息隐藏的各种可能方式.运用HPA和DCO、隐藏分区等技术分析了磁盘驱动的数据隐藏,运用簇分配、Slack空间等技术分析了NTFS文件系统的各种信息隐藏方法,以及各种方法可能的检测手段.分析各种隐藏技术作为计算机反取证手段,给计算机取证带来的巨大影响.

基于SBM-Tobit模型的中部6省环境效率分析

环境保护是事关社会发展与人类生存的重大问题.选取80个地级以上城市2014-2018年的面板数据,定量测度了中部6省的环境效率及其影响因素.结果表明:①整体上中部6省的环境效率值偏低,且存在环境EKC(Environmental Kuznets Curve)曲线,6省环境效率呈现一定的空间溢出效应和集聚效应.②湖南和湖北为典型的高环境效率高差异省份,安徽为典型的低环境效率低差异省份.③中部6省的全要素环境效率发生了由衰退到提升的演变,其诱因由技术进步的单因素驱动演变为技术进步、技术效率提升兼有的双因素驱动.④产业结构和人均GDP对环境效率有促进作用,财政支出、研发投入强度与外商直接投资对环境效率有抑制作用.

环境约束下中国与世界主要国家技术效率和生产率的测度与比较

运用含非期望产出的超效率SBM(slack based measure)模型和GML(global Malmquist-Luenberger)指数,对中国与世界主要国家1991—2016年的分别在考虑和不考虑环境约束下的技术效率和全要素生产率进行测度与比较。研究发现,不考虑环境约束的测度结果忽略了一国发展所造成的污染损失,导致技术效率与生产率被高估;中国的技术效率在考虑环境因素后显著下降,总效率排名从样本中的第16位下降至第40位。时间趋势上,中国的环境效率与技术效率的差距呈现先扩大后缩小,且近年来有逐渐趋同的态势;动态视角上,不考虑环境约束时中国的全要素生产率变化总体呈现增长趋势,但在考虑环境因素后中国的环境全要素生产率转变为下降趋势,这其中,技术进步的下降是影响环境全要素生产率变化的主要因素。

Environmental Flows from Alternate Land Uses in the Delta, Pacific, and the Southeastern States: 1947-2007

Land use policy involves allocating land between production alternatives to meet society’s wants and desires. Increase in the affluence in the United States has increased the demand for environmental flows that could be met from public ownership or as joint products of private ownerships. The empirical results of this study indicated that land use patterns remained relatively unchanged between 1947 and 2007. The lack of change suggests that a large part of the demand for environmental services is being as byproducts of other commercial decisions.

考虑碳排放的长三角机场运营效率研究

传统的机场运营效率研究忽视了非期望产出对机场运营效率的影响,且对有效单元无法进一步排名,基于此,采用长江三角洲16个机场2015~2019年的面板数据,将碳排放量和旅客投诉数量作为非期望产出指标,通过模型对比分析非期望产出的必要性,利用GML(Global Malmquist-Luenberger)指数刻画出机场全要素生产率的时空特性.结果表明,考虑非期望产出后,机场的静态运营效率和动态全要素生产率均产生变化.2015~2019年,长三角机场运营效率呈现波动上升,小型机场受非期望产出影响较大;2015~2019年,长三角机场全要素生产率受技术效率和技术进步共同影响,非期望产出影响技术进步上升的机场数量较多,但是对机场的技术效率影响更大.

Bimanual motor skill learning and robotic assistance for chronic hemiparetic stroke: a randomized controlled trial

Using robotic devices might improve recovery post-stroke, but the optimal way to apply robotic assistance has yet to be determined. The current study aimed to investigate whether training under the robotic active-assisted mode improves bimanual motor skill learning(biMSkL) more than training under the active mode in stroke patients. Twenty-six healthy individuals(HI) and 23 chronic hemiparetic stroke patients with a detectable lesion on MRI or CT scan, who demonstrated motor deficits in the upper limb, were randomly allocated to two parallel groups. The protocol included a two-day training on a new bimanual cooperative task, LIFT-THE-TRAY, under either the active or activeassisted modes(where assistance decreased in a pre-determined stepwise fashion) with the bimanual version of the REAplan? robotic device. The hypothesis was that the active-assisted mode would result in greater biMSkL than the active mode. The biMSkL was quantified by a speed-accuracy trade-off(SAT) before(T1) and immediately after(T2) training on days 1 and 2(T3 and T4). The change in SAT after 2 days of training(T4/T1) indicated that both HI and stroke patients learned and retained the bimanual cooperative task. After 2 days of training, the active-assisted mode did not improve biMSkL more than the active mode(T4/T1) in HI nor stroke patients. Whereas HI generalized the learned bimanual skill to different execution speeds in both the active and active-assisted subgroups, the stroke patients generalized the learned skill only in the active subgroup. Taken together, the active-assisted mode, applied in a pre-determined stepwise decreasing fashion, did not improve biMSkL more than the active mode in HI and stroke subjects. Stroke subjects might benefit more from robotic assistance when applied "as-needed." This study was approved by the local ethical committee(Comité d'éthique médicale, CHU UCL Namur, MontGodinne, Yvoir, Belgium;Internal number: 54/2010, Eudra CT number: NUB B039201317382) on July 14, 2016 and was registered with ClinicalTrials.gov(Identifier: NCT03974750) on June 5, 2019.

电子取证中的隐形数据及其相关处理技术探究

随着社会信息化程度越来越高,电子取证中的证据来源逐渐成为大家关注的一个热点。本文提出在计算机及其相关存储设备中,存在着一些不太显而易见的电子证据来源隐形数据,对它们的产生和数据形式进行了分析,并介绍了几种重要的隐形数据分析处理技术。

TIMING SLACK OPTIMIZATION APPROACH USING FPGA HYBRID ROUTING STRATEGY OF RIP-UP-RETRY AND PATHFINDER

To improve the path slack of Field Programmable Gate Array(FPGA), this paper proposes a timing slack optimization approach which utilizes the hybrid routing strategy of rip-up-retry and pathfinder. Firstly, effect of process variations on path slack is analyzed, and by constructing a collocation table of delay model that takes into account the multi-corner process, the complex statistical static timing analysis is successfully translated into a simple classical static timing analysis. Then, based on the hybrid routing strategy of rip-up-retry and pathfinder, by adjusting the critical path which detours a long distance, the critical path delay is reduced and the path slack is optimized. Experimental results show that, using the hybrid routing strategy, the number of paths with negative slack can be optimized(reduced) by 85.8% on average compared with the Versatile Place and Route(VPR) timing-driven routing algorithm, while the run-time is only increased by 15.02% on average.

数据库基于Slack Bot的实时监控和预警平台

为了能够有效的监控和预警生产环境中数据库的运行状态,及时的解决因为数据库无法响应或者数据库硬件损坏导致的损失,基于数据库的实时预警系统尤为重要。传统的监控和预警平台通常采用的是自动化脚本＋邮件和短信提醒的方式,虽然解决了预警的及时性问题,但是并不能支持可配置性和实时查询。因此有必要搭建一套实时的数据库监控和预警系统来保证线上数据库的正常运行。该文采用了最近逐渐开始流行的Slack作为消息推送平台,通过研究Slack实时消息API,并且与Jira,LDAP等企业管理工具的集成,实现了一套部署在生产环境数据库之上的基于Slack Bot的实时监控和预警系统。最后通过比较评估了实际效果。

Further studies on stability analysis of nonlinear Roesser-type two-dimensional systems

This paper is concerned with further relaxations of the stability analysis of nonlinear Roesser-type two-dimensional （2D） systems in the Takagi-Sugeno fuzzy form. To achieve the goal, a novel slack matrix variable technique, which is homogenous polynomially parameter-dependent on the normalized fuzzy weighting functions with arbitrary degree, is developed and the algebraic properties of the normalized fuzzy weighting functions are collected into a set of augmented matrices. Consequently, more information about the normalized fuzzy weighting functions is involved and the relaxation quality of the stability analysis is significantly improved. Moreover, the obtained result is formulated in the form of linear matrix inequalities, which can be easily solved via standard numerical software. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed result.

RHEOLOGICAL FRACTURE ANALYSIS OF CABLE BY CONSIDERING THE SECOND ORDER EFFECTS OF RANDOM SLACK

In this paper we consider the cable as a bundle consisting of x sub-bundles, with m parallel tension members per sub-bundle, and the tension members themselves are polymeric yarns impregnated with a resin matrix. The nonfailad members at any instant must share an applied system load according to some rule, since there is a clearly expressed dependence of the fracture on the duration on the duration and character of the loading. So then, the fracture of cable is a process of nonlinear dynamic evolution, which accommodates to the non-equilibrium thermodynamics of irreversible processes by itself. Let us assume that the polymeric yarns art as viscoelastic solid, under certain probabilistic assumptions, according to the principles of rheology of bodies with defects, the relationship between the single member loading and failure and the bundle loading are investigated. It can be shown that the bundle failure time is asymptotically normally distributed as the number of members grows large. After a study of the second order effects of random slack, it is known that the asymptotic mean and variance are functions of the parameters of loading and single member theological behavior. Hence the loss in the asymptotic bundle strength mean brought about by random member and sub-bundle slack, L(s), and the loss in the asymptotic bundle strength variance caused by random member slack, Delta(s), are determined. And finally, if is known that the asymptotic time of failure can make up a considerable part of the fracture of cable, and the fracture of cable is a time-dependent process of rheological fracture.

Energy Efficient On-Chip Communications Implementation Based on Power Slacks

The quest for energy efficiency has growing importance in high performance many-core systems. However, in current practices, the power slacks, which are the differences observed between the input power budget and the actual power consumed in the many-core systems, are typically ignored, thus leading to poor energy efficiency. In this paper, we propose a scheme to effectively power the on-chip communications by exploiting the available power slack that is totally wasted in current many-core systems. As so, the demand for extra energy from external power sources （e.g., batteries） is minimized, which helps improve the overall energy efficiency. In essence, the power slack is stored at each node and the proposed routing algorithm uses a dynamic programming network to find the globally optimal path, along which the total energy stored on the nodes is the maximum. Experimental results have confirmed that the proposed scheme, with low hardware overhead, can reduce latency and extra energy consumption by 44% and 48%, respectively, compared with the two competing routing methods.

Thermal transport property of Ge_(34) and d-Ge investigated by molecular dynamics and the Slack's equation

In this study, we evaluate the values of lattice thermal conductivity κL of type Ⅱ Ge clathrate （Ge34） and diamond phase Ge crystal （d-Ce） with the equilibrium molecular dynamics （EMD） method and the Slack＇s equation. The key parameters of the Slack＇s equation are derived from the thermodynamic properties obtained from the lattice dynamics （LD） calculations. The empirical Tersoff＇s potential is used in both EMD and LD simulations. The thermal conductivities of d-Ge calculated by both methods are in accordance with the experimental values. The predictions of the Slack＇s equation are consistent with the EMD results above 250 K for both Ge34 and d-Ge. In a temperature range of 200-1000 K, the κL value of d-Ge is about several times larger than that of Ge34.

The Treatment of Non-zero Slacks in Data Envelopment Analysis

The paper studies the non-zero slacks in data envelopment analysis. A procedure is developed for the treatment of non-zero slacks. DEA projections can be done just in one step.

Research and Test of Three-Pulley Noncircular Synchronous Pulley Transmission Mechanism with Minimum Slack

The noncircular synchronous belt drive mechanism has demonstrated certain achievements and has been used in special fields.Research regarding noncircular synchronous belt drive mechanisms has focused on optimization design and kinematic analysis in China,whereas two pulley noncircular synchronous belt transmissions have been developed overseas.However,owing to the noncircular characteristics of the belt pulley,the real-time variation in the belt length slack during the transmission of the noncircular synchronous belt is significant,resulting in high probabilities of skipping and vibration.In this study,a noncircular tensioning pulley is added to create a stable three-pulley noncircular synchronous belt driving mechanism and a good synchronous belt tensioning,with no skipping;hence,the non-uniform output characteristic of the driven pulley is consistent with the theoretical value.In the circular noncircular noncircular three-pulley noncircular synchronous belt mechanism,the pitch curve of the driving synchronous belt pulley is circular,whereas those of the driven synchronous belt and tensioning pulleys are noncircular.To minimize the slack of the belt length of the synchronous belt and the constraint of the concavity and circumference of the tensioning pulley,an automatic optimization model of the tensioning pulley pitch curve is established.The motion simulation,analysis,and optimization code for a three-belt-pulley noncircular synchronous belt drive mechanism is written,and the variation in belt length slack under different speed ratios is analyzed based on several examples.The testbed for a circular-noncircular-noncircular three-pulley noncircular synchronous belt transmission mechanism is developed.The test shows that the three-pulley noncircular synchronous belt drives well.This study proposes an automatic optimization algorithm for the tensioning pulley pitch curve of a noncircular synchronous belt transmission mechanism;it yields a stable transmission of the noncircular synchronous belt transmission mechanism as well as non-uniform output characteristics.

Spatio-temporal Evolution of the Agricultural Eco-efficiency Network and Its Multidimensional Proximity Analysis in China

As a traditional agricultural country,China has always prioritized agricultural development,and has increasingly focused on green and sustainable agricultural development.Based on the inter-provincial panel data for China from 1997 to 2019,this study divided these data into five periods according to the Five-Year Plan(FYP)of China,measured the agricultural eco-efficiency(AEE)values using the Super-SBM model,and then determined the spatial association network of the inter-provincial AEE of China using the improved gravity model.Finally,social network analysis(SNA)was used to further analyze the evolution process of AEE,and we de-veloped a framework of how multidimensional proximity,which includes geographical,economic,technological,cognitive,and institutional proximity,made an influence on the formation of AEE spatial relation network.The findings indicated that:1)in 1997−2019,the AEE in China was present in some spatial and temporal differences characteristics at the provincial scale,and we specifically found that national macro-regulation and policy incentives played a positive role in the long-term development of AEE.2)The spatial correlation of AEE development among provincial regions were becoming closer and exhibits obvious spatial correlation and spillover effects.The evolution of the AEE network has clearly observable trends of hierarchization and aggregation,and the complexity of the correlation network continues to increase and exhibits spatial clustering characteristics that are dense in the east and sparse in the west.The network structure has changed from monocentric radiation to a multicentric network,and network nodes select the more advantageous nodes with which to connect.3)Finally,the geographical proximity had a significant negative effect;the economic,technological,and institutional proximities were all observed to contribute to the AEE network formation,and cognitive proximity did not significantly influence this network formation.