道路环形交叉口机动车冲突风险区识别模型研究

为定量识别城市非信控环形交叉口区域内的机动车冲突风险易发生点,降低环形交叉口的事故发生率,本文构建针对非信控环形交叉口机动车冲突风险识别模型。首先,利用无人机采集高精度、连续的多车辆轨迹视频,结合Kinovea视频运动分析软件实现运行车辆状态识别与跟踪,并记录车辆每一帧的运动数据;其次,基于交通冲突识别指标TTC(Time to Collision),提出适应环形交叉口道路线形特征的车辆TTC计算方法,并使用累计频率法确定严重、一般和轻微冲突的阈值分别为1.2,2.8,4.4 s;最后,通过绘制高峰和平峰交通冲突空间异步图,并结合交通冲突数和严重冲突率,对环形交叉口的36个子区段进行交通冲突风险等级评定。研究结果显示:在高峰时段,某一子区段的平均交通冲突发生次数约为15次,严重冲突率为17.45%;在平峰时段,某一子区段的平均交通冲突发生次数约为8次,严重冲突率为8.28%。重度风险区域在高峰时段占比达到50%,而在平峰时段为8.33%,这些重度风险区域主要集中在交织区段。因此,环形交叉口在高峰时段且位于交织区段的情况更易发生交通事故。本文研究成果有助于交通管理部门了解环形交叉口在不同时段和区段上的交通冲突情况和特征,以便采取相应的预警和管理措施。

基于轨迹数据的非机动车左转信号灯安全效应评估

【目的】对城市交叉口采用的左转非机动车信号灯设施进行交通安全性量化评估。【方法】提出一种基于拓展碰撞时间(extended time to collision,ETTC)指标的左转非机动车信号灯安全效应评估方法。针对现有的碰撞时间(time to collision,TTC)指标不适于评估交叉口左转非机动车冲突的问题,考虑非机动车车辆尺寸与加速度对交通冲突的影响,采用拓展碰撞时间指标,评估交叉口非机动车交通冲突。收集长沙市4个信号交叉口的视频大数据,利用视频软件Tracker提取车辆微观轨迹后,开展案例分析。【结果】左转非机动车信号灯在时间上明确了非机动车的通行权,其设置能显著降低非机动车冲突率,在平峰、高峰时段非机动车冲突率分别降低了40.11%、25.27%。在直行相位末期、左转相位即将启亮时,设置组的左转非机动车在待行区等待,冲突率降为0;而对比组近50%的非机动车违规左转,冲突严重。设置左转非机动车信号灯的改善效果随非机动车流量的增大呈先增加后降低趋势,而随机动车流量的增大呈逐步波动下降趋势。【结论】本研究揭示了非机动车左转信号灯的设置对减少交叉口交通冲突的影响,可为城市交叉口非机动车交通安全管控提供有益参考。

基于Time Petri Nets的实时系统资源冲突检测

Time Petri Nets在实时系统的建模和性能分析中得到广泛应用,而冲突是Petri网及其扩展模型的重要行为,解决冲突是正确分析模型动态行为的关键.目前随机Petri网、混合Petri网和区间速率连续Petri网的冲突检测方法由于没有考虑到时间约束因此无法在TPN网中使用.时间约束的引入使得Time Petri Nets模型的使能和触发语义比Petri网模型的语义复杂,冲突检测变得更加困难.为了计算冲突发生的时间和概率,首先根据时间约束,给出了变迁持续使能时延迟区间的计算方法,并证明了该方法的合理性和完备性;然后在此基础上定义并证明了Time Petri Nets模型中不冲突的检测方法;并提出了Time Petri Nets模型的冲突检测方法,给出了冲突时间区间和变迁实施概率的计算方法;最后通过实例验证说明了该方法的正确性和有效性.

车辆轨迹数据驱动的急弯路段追尾冲突风险时空演化规律

为有效揭示急弯路段上车辆间追尾冲突风险的形成与变化态势,选取典型事故多发急弯路段使用无人机航拍等方式采集交通流数据,利用Tracker软件提取车辆轨迹信息,构建急弯路段追尾冲突后侵入时间PET判别指标,结合冲突先导车LV与跟随车FV的速度、加速度变化划分追尾冲突模式,进而界定临界冲突点、冲突风险范围及PET变化率指标DPET,运用回归分析量化LV与FV的速度、加速度、速度差及加速度差对DPET的影响,阐明临界冲突点及主要追尾冲突模式的微观变化特性及时空演化规律。结果表明:车辆追尾冲突存在空间集聚性,主要集中在入弯缓和曲线上游、曲中标志断面下游及出弯缓和曲线下游;在潜在追尾冲突的九大类别中发生频率最高的四大类冲突数量占比高达83.24%;PET在冲突临界点和冲突风险范围内均下降,导致DPET均为负值,在冲突临界点PET快速下降,其下降程度显著大于冲突风险范围;FV速度、加速度及LV、FV间速度差、加速度差四个指标显著影响追尾冲突临界点的DPET变化;T10模式(LV减速、FV加速)冲突过程中的DPET均值最小,PET序列下降最为剧烈,危险性显著高于其他冲突模式。

基于时空棱锥的航迹冲突解脱策略研究

航空运输业新技术的发展推动了基于航迹的精细化管理,使航空器冲突解脱成为重要课题。以时空棱锥为基础,深入探究航空器巡航阶段下的时空棱锥运行机理,旨在研究航迹冲突解脱策略。结果显示飞行速度、时间预算和起终点距离对航空器运行轨迹具有重要影响。通过分析航空器的时空运行特征和冲突解脱需求,提出了综合考虑时间窗口、安全间隔等约束条件的解脱策略,并采用3D Dijkstra算法搜索满足约束条件的最短时空路径,通过调整航速和航向获得多种解脱方案。各方案在燃油消耗和空域资源利用等方面存在差异,选择时需综合考虑实际利益和管制偏好。研究为航空器冲突解脱提供了参考,有助于提高航空运输系统的效率和安全性。

Improved Parallel Three-List Algorithm for the Knapsack Problem without Memory Conflicts

Based on the two-list algorithm and the parallel three-list algorithm, an improved parallel three-list algorithm for knapsack problem is proposed, in which the method of divide and conquer, and parallel merging without memory conflicts are adopted. To find a solution for the n-element knapsack problem, the proposed algorithm needs O（2^3n/8） time when O（2^3n/8） shared memory units and O（2^n/4） processors are available. The comparisons between the proposed algorithm and 10 existing algorithms show that the improved parallel three-fist algorithm is the first exclusive-read exclusive-write （EREW） parallel algorithm that can solve the knapsack instances in less than O（2^n/2） time when the available hardware resource is smaller than O（2^n/2） , and hence is an improved result over the past researches.

Solution to Beacon Conflict Based on IEEE 802.15.4

One main issue of degrading IEEE 802.15.4performance is the beacon conflict which increases the energy consumption.However,IEEE 802.15.4does not address a solution to avoid the beacon conflict.In order to reduce this beacon conflict,an individual time division(ITD)algorithm based on IEEE 802.15.4is proposed.In this algorithm,a coordinator assigns the time division(TD)for each associated coordinator so that different coordinators transmit a beacon frame at different time slice.In this way,the beacon conflict is decreased substantially.The experimental results show that ITD reduces both the beacon conflict and the network energy consumption,and improves the network performance.

Analysis of occupation time of vehicles at urban unsignalized intersections in non-lane-based mixed traffic conditions

In India, traffic flow on roads is highly mixed in nature with wide variations in the static and dynamic characteristics of vehicles. At unsignalized intersections, vehicles generally do not follow lane discipline and ignore the rules of priority. Drivers generally become more aggressive and tend to cross the uncontrolled intersections without considering the conflicting traffic. All these conditions cause a very complex traffic situation at unsignal- ized intersections which have a great impact on the capacity and performance of traffic intersections. A new method called additive conflict flow （ACF） method is suitable to determine the capacity of unsignalized inter- sections in non-lane-based mixed traffic conditions as prevailing in India. Occupation time is the key parameter for ACF method, which is defined as the time spent by a vehicle in the conflict area at the intersection. Data for this study were collected at two three-legged unsignalized intersections （one is uncontrolled and other one is semi- controlled） in Mangalore city, India using video-graphic technique during peak periods on three consecutive week days. The occupation time of vehicles at these intersections were studied and compared. The data on conflicting traffic volume and occupation time by each subject vehicle at the conflict area were extracted from the videos using image processing software. The subject vehicles were divided into three categories： two wheelers,cars, and auto-rickshaws. Mathematical relationships were developed to relate the occupation time of different cate- gories of vehicles with the conflicting flow of vehicles for various movements at both the intersections. It was found that occupation time increases with the increasing con- flicting traffic and observed to be higher at the uncontrolled intersection compared to the semicontrolled intersec- tion. The segregated turning movements and the presence of mini roundabout at the semicontrolled intersection reduces the conflicts of vehicular movements, which ulti- mately reduces the occupation time. The proposed methodology will be useful to determine the occupation time for various movements at unsignalized intersections. The models developed in the study can be used by practitioners and traffic engineers to estimate the capacity of unsignalized intersections in non-lane-based discipline and mixed traffic conditions.

基于自动化码头的改进Dijkstra算法路径规划研究

针对自动化码头多路径规划中Dijkstra算法存有路径冲突的问题,引入时间窗防冲突判断模型对其进行改进。在Dijkstra算法从源节点向其他各节点逐步遍历的过程中,将时间窗冲突判断模型加到各路径节点上。通过改变规划中的路径节点向量,将每一个节点的所有前节点记录在路径节点向量中,在所有的路径中,搜索出一条最短路径,保证此最短路径与其他路径无冲突。在计算机上运用Matlab仿真软件进行算法验证,仿真结果显示,算法经过改进后,在规划多路径任务中能够得到预期效果。

Dwell time estimation models for bus rapid transit stations

Bus rapid transit （BRT） systems have been shown to have many advantages including affordability, high capacity vehicles, and reliable service. Due to these attractive advantages, many cities throughout the world are in the process of planning the construction of BRT systems. To improve the performance of BRT systems, many researchers study BRT operation and control, which include the study of dwell times at bus/BRT stations. To ensure the effectiveness of real-time control which aims to avoid bus/BRT vehicles congestion, accurate dwell time models are needed. We develop our models using data from a BRT vehicle survey conducted in Changzhou, China, where BRT lines are built along passenger corridors, and BRT stations are enclosed like light rails. This means that interactions between passengers traveling on the BRT system are more frequent than those in traditional transit system who use platform stations. We statistically analyze the BRT vehicle survey data, and based on this analysis, we are able to make the following conclusions： （ I ） The delay time per passenger at a BRT station is less than that at a non-BRT station, which implies that BRT stations are efficient in the sense that they are able to move passengers quickly. （II） The dwell time follows a logarithmic normal distribution with a mean of 2.56 and a variance of 0.53. （III） The greater the number of BRT lines serviced by a station, the longer the dwell time is. （IV） Daily travel demands are highest during the morning peak interval where the dwell time, the number of passengers boarding and alighting and the number of passengers on vehicles reach their maximum values. （V） The dwell time is highly positively correlated with the total number of passengers boarding and alighting. （VI） The delay per passenger is negatively correlated with the total number of passengers boarding and alighting. We propose two dwell time models for the BRT station. The first proposed model is a linear model while the second is nonlinear. We introduce the conflict between passengers boarding and alighting into our models. Finally, by comparing our models with the models of Rajbhandari and Chien et al., and TCQSM （Transit Capacity and Quality of Service Manual）, we conclude that the proposed nonlinear model can better predict the dwell time at BRT stations.

生活时间贫穷对工作-家庭冲突的影响机理——基于C公司的案例分析

经济的快速发展催生了不断加快的社会节奏,生活时间贫穷业已成为人们普遍面临的新常态和新困境。从微观个体层面探索了生活时间贫穷对个体工作-家庭冲突的影响及其内在机制。运用案例分析方法,从时间的质量维度和数量维度出发,揭示了生活时间贫穷与工作-家庭冲突3个维度间的内在联系,并基于此构建了一个生活时间贫穷对工作-家庭冲突影响的整合理论框架。案例研究发现:生活时间贫穷会直接引发基于时间维度的工作-家庭冲突,这种时间维度上的冲突包含了基于物理的时间冲突和基于心理的时间冲突;生活时间贫穷在心理能量损耗的作用下会间接引发基于压力的工作-家庭冲突,心理能量的损耗主要源于工作时间的压力和负面情绪的压力;生活时间贫穷在稀缺心态的作用下主要通过“专注”和“管窥”两条路径间接引发基于行为的工作-家庭冲突。本研究丰富和拓展了生活时间贫穷的研究思路和影响范围,同时也有望对组织和个人的时间管理实践,以及如何化解生活时间贫穷这一难题提供新的理论和实践启示。

高拱坝施工的缆机碰撞概率实时分析模型研究

【目的】缆机是高拱坝建设中的主要施工机械之一,然而复杂的交叉作业和大风等不利环境为缆机的安全运行带来了巨大挑战。针对上述问题,基于实时采集的缆机定位监测数据,预测吊罐未来的运行轨迹,以吊罐与其他施工实体之间的距离以及距离变化速率定义碰撞概率,并以此实时分析吊罐的未来运行轨迹,为缆机防撞控制以及避障方案选择提供数据基础。【方法】首先,根据缆机的实时监测数据分析缆机的运行趋势,预测小车在未来一段时间内的运行轨迹,并综合考虑缆机速度变化和大风环境对吊罐的影响,进而计算吊罐的预测运行轨迹;其次,计算吊罐在预测运行轨迹上与其他施工实体之间的最小距离以及最小距离变化速率,据此计算吊罐在预测运行轨迹上与其他施工实体发生碰撞的概率;最后,取两段白鹤滩水电站吊罐的实测运行轨迹计算其预测运行轨迹,分别计算碰撞概率并进行对比分析,以验证该碰撞概率分析模型的有效性。【结果】结果显示,预测运行轨迹碰撞概率与实际运行轨迹碰撞概率的平均绝对误差为0.36%,均方误差为0.0010%。【结论】结果表明,可以使用该模型实时分析缆机的碰撞概率,为缆机防撞控制和路径优化提供数据支持。

ACTIVE-A Real Time Commit Protocol

Many existing real time commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. They block the borrower from sending WORKDONE/PREPARED message and restrict them from lending data so that transaction abort chain is limited to one. Thus, transaction execution time increases. This paper proposes a modified real time commit protocol for distributed real time database systems (DRTDBS), Allow Commit Dependent and in Time borrowers for Incredible Value added data lending without extended abort chain (ACTIVE), where borrower cohorts are categorized as commit and abort dependent. Further, the commit dependent borrowers can lend data to executing cohorts with still limiting the transaction abort chain to one only and reducing the data inaccessibility. Also, an incoming executing cohort having borrowing factor greater than one can only borrow the dirty data items from lender. This minimizes the fruitless borrowing by the cohort. The performance of ACTIVE is compared with PROMPT, 2SC and SWIFT protocols for both main memory resident and disk resident databases with and without communication delay. Simulation results show that the proposed protocol improves the system performance up to 4% as transaction miss percentage.

道路急弯路段追尾冲突分析预测

为实现急弯路段的追尾碰撞风险主动防控,提出了一种基于多源数据融合的追尾冲突动态预测方法。首先,基于无人机、毫米波雷达等采集的车辆运行数据,提出了适用于急弯路段交通流特征的追尾冲突判别模型及冲突等级阈值划分标准,分析了急弯路段的追尾冲突空间分布特征。然后,筛选车型、大车比率、断面速度差等13个交通流特征指标作为输入变量,以粒子群算法为基础,分别构建了其与BP神经网络、随机森林、支持向量机算法的追尾冲突动态组合预测模型,并根据混淆矩阵和曲线下面积评估各模型的预测性能,利用黑箱解释方法分析冲突发生概率的显著性影响因素及影响程度。结果表明:相较于平直或一般弯道路段,急弯路段的追尾冲突TTC(Time to Collision)值更小,出弯缓和曲线段冲突更为严重,且弯道内侧碰撞风险最高;粒子群-随机森林模型的追尾冲突预测性能最佳,灵敏度达90.70%;急弯路段追尾冲突受车辆平均车头间距的影响程度最大,当平均车头间距为25 m左右时,冲突发生概率最小,向心加速度均值、速度均值等因素亦对其有显著影响。

基于差分粒子群算法的装配式建筑时空冲突优化研究

由于装配式建筑施工的特殊性,相比于传统建筑施工,更易发生施工工作之间的时空冲突。结合建筑项目施工工作时空冲突研究以及进度管理需求,以施工进度、安全管理要求为总体目标,以时空冲突程度最小化为目标函数建立冲突优化模型,并提出冲突工作开始时间与完成时间的调整方法。针对问题需求,使用差分粒子群算法(DEPSO)求解模型,以某项目为例,进一步验证冲突优化模型的可行性,并使用蒙特卡洛方法仿真模拟分析时空冲突的优化效果。实验证明,该模型可有效减小时空冲突,优化比例维持在45%,相较传统解决时空冲突方法,能够合理保障工期,为装配式建筑施工管理提供更优的方案。

基于证据一致性检验的目标属性序贯辨识

针对信息不确定、不完备引起的识别证据动态变化、冲突悖论等问题,提出了一种基于证据一致性检验的目标属性序贯辨识改进方法。首先采用顺序滑动窗口构建时序证据体,再通过证据一致性检验,快速定位冲突证据并动态重构出一致性证据体,最后利用证据理论合成获得目标序贯辨识结果。经仿真数据验证表明,该方法能有效积累时序证据能量、抑制冲突悖论,提高目标属性辨识的准确性和稳定性。

双重就业样态群体的副业内在动机与主业工作绩效

新就业样态迅速兴起背景下,员工从事兼职是否会对其主业工作产生不利影响是实践界和学术界共同关心的问题。在对283名兼职员工的问卷调查的基础上,研究基于身份过程理论构建员工副业内在动机影响主业工作绩效的双中介模型,探讨员工调节焦点的调节作用。研究表明:身份冲突和身份增强在员工副业内在动机对主业工作绩效的影响中起到中介作用,且促进焦点能提高员工副业内在动机对主业工作绩效的正向影响,防御焦点则强化了二者之间的负向影响。研究结果有助于全面揭示副业内在动机对主业工作绩效的影响,为组织管理实践提供有益借鉴。

基于人车冲突的右转机动车信号配时优化方法

为了缓解人车冲突,增加行人过街安全性,在界定右转机动车与行人冲突区的基础上,以红灯期间等待过街的行人群体通过冲突区的时间为依据,对右转机动车进行信号控制,建立右转机动车禁行时间计算模型,并以长春市自由大路和同志街交叉口为例,应用Webster延误模型对右转机动车信号配时方案进行验证。结果表明,交叉口总延误降低20%,同时在很大程度上缓解了右转机动车与行人之间的延误。

基于改进A^(*)算法的多AGV路径规划研究

自动导引车AGV(Automated guided vehicle,AGV)的路径规划问题是工业生产和物流领域的关键问题,其中多AGV无碰撞路径规划是研究的难点。本文以实际工业生产现场为背景,提出一种改进的A^(*)算法,该算法利用切比雪夫距离对传统A^(*)算法的启发函数进行加权,显著地减少了A^(*)算法的搜索时间和搜索节点数,提高了传统A^(*)算法的路径搜索效率,并将改进的A^(*)算法和时间窗模型结合,通过时间窗模型提前预判多AGV路径上节点占用情况,根据生产任务需求和AGV离终点的远近程度,动态调整AGV的优先级,有效地解决了多AGV同时行驶时产生的死锁,碰撞冲突问题。试验结果表明,该算法在多AGV进行动态路径规划时,路径的搜索效率得到显著的提高,路径冲突问题也得到有效的解决。

基于色彩地址空间转换与多版本策略的复杂位图协同模型与一致性维护算法

调色编辑在现有位图协同模型下存在数据发送量大、编辑灵活性差、操作重叠易冲突、生成版本多、站点存储压力大等问题,针对这些问题提出了一种面向复杂位图的调色协同编辑模型。协同操作仅发送坐标与色彩变化量的协同操作,具有数据量小、多维编辑粒度、位置可重叠等特性;增加了时空关系的四维位图协同架构,只保存已编辑的像素点数据可减少数据存储量;采用空间转换的副本状态控制算法,通过回溯重构历史版本,可以确保协同操作总是在正确的副本状态上执行;根据当前状态与策略配置,动态生成分支版本的算法,可以解决此前模型分支版本过多的问题。最后,基于CCI(causality-preservation,convergence,intention-preservation)模型进行正确性推论,开发协同编辑器原型Co-Pixel,随机生成的操作集设计实验,对照Adobe Lightroom模拟实际编辑行为。结果显示提出的模型可有效减少操作产生冲突,降低一致性维护过程中的算法开销,灵活调整用户执行意图维护工作的结果版本。