Target Vehicle Selection Algorithm for Adaptive Cruise Control Based on Lane-changing Intention of Preceding Vehicle

To improve the ride comfort and safety of a traditional adaptive cruise control(ACC)system when the preceding vehicle changes lanes,it proposes a target vehicle selection algorithm based on the prediction of the lane-changing intention for the preceding vehicle.First,the Next Generation Simulation dataset is used to train a lane-changing intention prediction algorithm based on a sliding window support vector machine,and the lane-changing intention of the preceding vehicle in the current lane is identified by lateral position offset.Second,according to the lane-changing intention and collision threat of the preceding vehicle,the target vehicle selection algorithm is studied under three different conditions:safe lane-changing,dangerous lane-changing,and lane-changing cancellation.Finally,the effectiveness of the proposed algorithm is verified in a co-simulation platform.The simulation results show that the target vehicle selection algorithm can ensure the smooth transfer of the target vehicle and effectively reduce the longitudinal acceleration fluctuation of the subject vehicle when the preceding vehicle changes lanes safely or cancels their lane change maneuver.In the case of a dangerous lane change,the target vehicle selection algorithm proposed in this paper can respond more rapidly to a dangerous lane change than the target vehicle selection method of the traditional ACC system;thus,it can effectively avoid collisions and improve the safety of the subject vehicle.

A new traffic model on compulsive lane-changing caused by off-ramp

In the field of traffic flow studies, compulsive lane-changing refers to lane-changing （LC） behaviors due to traffic rules or bad road conditions, while free LC happens when drivers change lanes to drive on a faster or less crowded lane. LC studies based on differential equation models accurately reveal LC influence on traffic environment. This paper presents a second-order partial differential equation （PDE） model that simulates both compulsive LC behavior and free LC behavior, with lane-changing source terms in the continuity equation and a lane-changing viscosity term in the momentum equation. A specific form of this model focusing on a typical compulsive LC behavior, the ＇off-ramp problem＇, is derived. Numerical simulations are given in several cases, which are consistent with real traffic phenomenon.

Modelling of vehicle interaction behavior during discretionary lane-changing preparation process on freeway

In order to increase the accuracy of microscopic traffic flow simulation,two acceleration models are presented to simulate car-following behaviors of the lane-changing vehicle and following putative vehicle during the discretionary lanechanging preparation( DLCP) process, respectively. The proposed acceleration models can reflect vehicle interaction characteristics. Samples used for describing the starting point and the ending point of DLCP are extracted from a real NGSIM vehicle trajectory data set. The acceleration model for a lanechanging vehicle is supposed to be a linear acceleration model.The acceleration model for the following putative vehicle is constructed by referring to the optimal velocity model,in which optimal velocity is defined as a linear function of the velocity of putative leading vehicle. Similar calibration,a hypothesis test and parameter sensitivity analysis were conducted on the acceleration model of the lane-changing vehicle and following putative vehicle,respectively. The validation results of the two proposed models suggest that the training and testing errors are acceptable compared with similar works on calibrations for car following models. The parameter sensitivity analysis shows that the subtle observed error does not lead to severe variations of car-following behaviors of the lane-changing vehicle and following putative vehicle.

A new traffic model with a lane-changing viscosity term

In this paper, a new continuum traffic flow model is proposed, with a lane-changing source term in the continuity equation and a lane-changing viscosity term in the acceleration equation. Based on previous literature, the source term addresses the impact of speed difference and density difference between adjacent lanes, which provides better precision for free lane-changing simulation; the viscosity term turns lane-changing behavior to a ＂force＂ that may influence speed distribution. Using a flux-splitting scheme for the model discretization, two cases are investigated numerically. The case under a homogeneous initial condition shows that the numerical results by our model agree well with the analytical ones; the case with a small initial disturbance shows that our model can simulate the evolution of perturbation, including propagation,dissipation, cluster effect and stop-and-go phenomenon.

Effects of Potential Lane-Changing Probability on Uniform Flow

In this paper, we use the car-following model with the anticipation effect of the potential lane-changing probability （Acta Mech. Sin. 24 （2008） 399） to investigate the effects of the potential lane-changing probability on uniform flow. The analytical and numerical results show that the potential lane-changing probability can enhance the speed and flow of uniform flow and that their increments are related to the density.

The Main Colors of the Forbidden City

The main colors of the Forbidden City are Red and Yellow,which can represent rich cultural deposits.According to the Chinese traditional culture,the Red of the Forbidden City has always been regarded as a positive color of celebration,conveying dignity and happiness.The Yellow color is usually considered as a promising color,and represents a bumper harvest.Based on the principle of the Five Elements,Fire is red,which means breeding and encouragement,and shows prosperity and a solid foundation for the country.Yellow represents Winged Dragon,belonging to the Center of the Earth,and symbolizes the divine right of emperors.Therefore,the color of the Forbidden City(see Figure 1)is of great significance to the development of history and the revival of culture.We still need to work determinedly for the protection of the cultural heritages,so that more people can have the opportunity to understand the brilliance of Chinese civilization.

青海湖高寒草原植被群落结构和水源涵养功能对禁牧封育的响应

【目的】探讨禁牧封育对青海湖植被群落结构和水源涵养功能的影响,对准确评估禁牧封育在青海湖退化草地恢复过程中的作用具有重要意义。【方法】对青海湖北岸高寒草原设置自由放牧及不同封育年限样地,分析封育措施对植物物种数、生物量、功能群、土壤容重、持水量及孔隙度等指标的影响。【结果】(1)随封育年限延长,青海湖北岸高寒草原物种数呈降低趋势,植被盖度、地上地下生物量均呈先增加后降低趋势,禾本科植物在群落中的重要值占比逐渐增加。(2)禁牧封育对青海湖北岸高寒草原土壤水分特征的影响主要集中在0—20 cm。随禁牧封育年限延长,0—20 cm土壤容重逐步降低,0—10 cm土壤饱和持水量、毛管持水量、田间持水量及总孔隙度均呈先增加后稳定趋势。(3)土壤容重是影响青海湖北岸高寒草原植被群落结构的最主要土壤水分特征因子。【结论】从植被群落结构的角度考虑,青海湖高寒草原禁牧封育年限不应超过7年,超过7年应进行适度干扰。

故宫古建筑油饰技艺中的传统材料研究

为更好地保护故宫古建筑,基于现场调查与分析论证相结合的方法,以油饰技艺中的传统材料为研究对象,即油饰技艺中地仗层之桐油、猪血、麻、砖灰、面粉,油皮层之光油,贴金层之黄金进行分析,讨论其运用方式和主要科学机理。结果表明:桐油、猪血、麻、面粉均有较好的胶结或拉接性能,有利于提升地仗层的防菌、防潮、防裂等性能;砖灰是地仗层的填充料,有利于与灰油等黏结材料进行调和;光油为油皮层黏结材料,且为贴金层用金胶油的主要材料;黄金以金箔的形式,用于贴金面层,使古建筑呈现金碧辉煌的视觉效果。上述传统材料在油饰技艺中的科学运用,体现了我国古代工匠卓越的建筑智慧。

明清紫禁城中轴线建筑形象的图像资料研究

紫禁城位于北京皇城与内城中心,其布局深受中国传统皇城规划思想的影响,中轴线上的建筑成为挑起整个城市的“脊梁”,然而六百年时光荏苒,一些建筑的空间格局和形象都发生了些许改变。文章从传统绘画、舆图及历史文献等各种资料中,探寻紫禁城中轴线建筑的形象变迁,并对其形制原型“三朝五门”进行探讨,可为理解明清时期紫禁城的都城政治空间格局及建筑体形环境的真实面貌提供一种较为生动全面的考察视角。

基于ITCM-CVM-IPA的文化遗产旅游地游憩价值评估与游客感知因素分析——以沈阳故宫为例

评估文化遗产旅游地游憩价值和深入分析游客感知因素,可促进旅游地资源合理开发与持续发展。以文化遗产旅游地沈阳故宫为例,通过ITCM(Individual Travel Cost Method)和CVM(Contingent Valuation Method)对其游憩价值进行评估,将游客感知因素根据IPA(Important-Performance Analysis)矩阵与IPA指数进行分析。结果表明:文化遗产旅游地沈阳故宫使用价值>非使用价值,游憩非使用价值中,遗产价值>存在价值>选择价值;在IPA分析中,游客预期与实际旅游体验差距较小。

几种元素掺杂二维MgCl_(2)单层的第一性原理计算

采用基于密度泛函理论的第一性原理赝势平面波方法对H,F,Al,K,Zn掺杂二维MgCl_(2)单层材料的几何结构和电子性质进行研究.结果表明:几种掺杂体系的晶体结构均有不同程度变化;由于H,Al,Zn的s态电子影响,这3种元素掺杂的MgCl_(2)在禁带中明显出现杂质能级,F和K掺杂体系的杂质能级出现在价带顶,与本征MgCl_(2)材料的5.996 eV带隙相比,H,F,Al,K,Zn掺杂体系的禁带宽度分别减小至5.665,5.903,4.409,5.802,5.199 eV;5种掺杂体系杂质原子周围的电荷均重新分布;电荷转移情况与差分电荷密度结果一致;与本征MgCl_(2)的功函数8.250 eV相比,H,F,Al,K,Zn掺杂体系的功函数分别减小至7.629,7.990,3.597,7.685,7.784 eV.

备案审查背景下婚检法律制度之重构

2003年国务院《婚姻登记条例》通过后,在实践层面取消了强制婚检制度,而母婴保健相关立法仍要求在婚姻登记前进行婚检,两者长期存在的冲突引发学界关注。《民法典》实施后,其作为调整民事关系的基本法律,为重构婚检法律制度提供了新的思路。从历史维度看,新中国婚姻登记制度以法治运动引导规则和实践变迁;在规范层面,婚检制度与婚姻登记中禁止性要件规定相关联。当《民法典》不再将身体疾病作为禁止结婚要件后,婚姻登记机关通过婚检干涉宪法上婚姻自由的正当性难以证成。为服务优生法治化的目标,建立婚前健康咨询、免费自愿婚检、个人声明制度等,保障当事人建立婚姻关系时的意思自治,是《民法典》实施背景下婚检法律制度构建的正当方式。

K^(+)掺杂双钙钛矿Cs_(2)AgInCl_(6)的发光性质

采用固相球磨法制备了K^(+)掺杂双钙钛矿Cs_(2)AgInCl_(6)纳米材料,该方法无需配体辅助,绿色环保。通过X射线衍射和拉曼光谱对晶体结构进行研究,通过激发光谱、发射光谱和时间分辨光谱对其发光性能进行研究。结果表明,Cs_(2)AgInCl_(6)为立方晶体,属于Fm3m空间群,由于宇称禁戒跃迁,其荧光量子产率(PLQY)低,小于0.1%。低于60%的K^(+)掺杂主要取代Ag^(+)的位置,引起Cs_(2)AgInCl_(6)的晶格膨胀,消除了晶格结构的反演对称性,打破了宇称禁戒跃迁,掺杂后Cs_(2)AgInCl_(6)的光致发光强度显著增强。K^(+)的最佳掺杂比例为40%,Cs_(2)Ag_(0.6)K_(0.4)InCl_(6)材料发射中心波长为640 nm,半高宽为180 nm,平均荧光寿命达到29.2 ns,PLQY达到10.5%。当K^(+)掺杂比例超过60%,K^(+)开始取代Cs+的位置,产物发生相变,出现立方相的Cs_(2-x)K_(1+x+y)AgyInCl_(6)和单斜相的Cs_(2-x)K_(1+x)InCl_(6)产物,这些产物由于强电子-声子耦合,非辐射复合占据主导地位。

NCRPE约束下具有周期性禁止时间窗口的项目群业主费用优化模型

具有周期性禁止时间窗口的合同项目(简称特殊合同项目)是影响项目群实施效果的关键因素之一,如何有效地控制具有周期性禁止时间窗口合同项目的进度既是一个理论问题,也是一个实践问题。首先界定了问题,分析了项目群业主费用优化原理,并将特殊合同项目分为在原时间窗口能够完成的合同项目和在下一个时间窗口能够完成的合同项目两类;其次,考虑具有周期性禁止时间窗口的合同项目的特殊性,构建了项目群实施前和项目群实施过程中的项目群业主费用优化模型;再次,结合项目群R开展案例分析,验证模型的可行性和有效性;最后,提出了管理启示。研究结果表明:在具有周期性禁止时间窗口的项目群中,合同项目延误给项目群带来的不利影响程度除了取决于给一般合同项目带来的不良影响程度,更多取决于特殊合同项目能否在原计划时间窗口内完成。为此,业主应通过安排项目群和特殊合同项目的开始时间,提高特殊合同项目在原时间窗口内完成的概率,以有效减少项目群业主费用。

“紫檀木边点翠金质山水图围屏”屏心的研究与修复

为了解故宫博物院藏文物“紫檀木边点翠金质山水图围屏”屏心的制作工艺,使用X射线荧光光谱仪、拉曼光谱仪、红外光谱仪及数码显微镜对文物进行检测,明确了屏风所用材质:满铺“卍”字纹点翠为基底,大面积山体使用纯金打造,细节装饰配件则用金银合金、金银铜合金和银等金属材料制成,金质嵌件用金属丝拴结的方式与点翠基底相连接。笔者以科学技术分析为依托,确定了屏风的制作工艺为:制作木板底纹—点翠—制作金属嵌件—金属部件组装固定。针对点翠脱落严重、灰尘堆积严重、金属部件脱落、点翠基底开裂等伤况,对文物进行了点翠加固、除尘、金属部件加固、基底修复四个步骤完成修复。此修复研究为了解清代宫廷大型屏风的制作工艺提供了实践依据,并为后期同类文物的修复提供经验支持。

畜禽禁养区政策对肉牛养殖成本效率的影响

文章基于2011—2021年30个省级行政区面板数据,借助双重差分模型实证检验畜禽禁养区政策对我国肉牛养殖成本效率的影响。结果显示,畜禽禁养区政策对我国肉牛养殖业成本效率具有明显的促进作用,其影响程度为0.074。交通基础设施、农户投资水平、肉牛出栏率和经济发展水平均对肉牛养殖成本效率具有显著正向影响,且交通基础设施的正向促进作用最强。畜禽禁养区政策对肉牛养殖成本效率的影响存在明显的区域差异,具体表现为对肉牛普通产区的促进作用更强。因此,文章提出合理划定畜禽禁养区、加速完善交通基础设施建设、因地制宜发展肉牛养殖业的政策建议,为加速推动肉牛养殖业高质量发展提供有益借鉴。

改进GWO算法求解柔性作业车间调度问题

针对以最小化最大完工时间为目标的柔性作业车间调度问题,设计一种改进的邻域搜索灰狼算法。设计一种适于灰狼算法的基于工序和机器的双层编码方案,改进种群初始化策略、灰狼变异操作以及种群更新机制;通过两点交叉操作、插入操作以及PR操作,得到GWO算法的全局搜索邻域,提出设计禁忌搜索邻域以增强GWO算法的局部开发能力。最后将所提算法在已知算例上进行仿真实验,并与其他算法进行对比。实验结果验证了改进GWO算法具有一定的优越性。

基于CFD数值模拟的古建筑群风场特性研究——以北京故宫建筑群为例

为研究我国古建筑群风场特性评估方法,基于计算流体动力学方法(Computational Fluids Dynamics,CFD),以北京故宫建筑群为例,通过对不同风向角工况下的故宫建筑群进行CFD数值模拟,获得全域流场信息,包括故宫中轴线主要建筑的表面风压分布情况、以及故宫建筑群环境风速分布情况.研究揭示了故宫建筑群内不同风向角下主要建筑表面的风压分布规律、中轴线建筑的不利风向角,并基于风环境评估理论对故宫建筑群内的行人风环境舒适性和安全性进行评估.研究结果表明:风压分布大致呈东西和南北对称分布形态;迎风面受较大正风压,侧风和背风面受较大负风压,负风压主要集中在靠近屋脊和墙面转角等气流分离区;主要建筑表面的正风压系数最值达1.0,负风压系数最值达2.2;六座大殿所受竖直方向的升力系数极值接近8,是水平方向的2倍;在水平和竖直方向上风压合力在斜风向下较大,其中在120°时的三向风压合力均达到极值;环境最大风速比在3~6之间,斜风向的最大风速比较大;垂直风向下,风速放大效应较弱,其中正南和正北风放大效应最弱,北京地区的主导风向是故宫建筑群的最优风向.研究成果可以为故宫建筑群的结构抗风保护以及行人防风措施提供科学依据和指导.

禁用两个子图的图的全控制数

设G=V(V,E)是一个简单无向图.一个点悬挂三个一度点的图称为爪图,D图是一个三角形其中两个点各悬挂一条长为2的路.如果图G的任何导出子图都不同构于爪图也不同构于D图,则称G为无爪和无D图.设S是V的非空子集,如果不在S的点一定与S中的某个点相邻,则称S为G的控制集.如果G中的点一定与S中的某个点相邻,则S称为G的全控制集.最小全控制集包含顶点的数目称为全控制数.给出了当G是N阶连通的无爪和无D图时全控制数紧的上界.

The characteristics of driver lane-changing behaviour in congested road environments

Lane-changing behaviour is one of the complex|driving behaviours.The lane-changing behaviour of drivers may exacerbate congestion,however driver behavioural characteristics are difficult to accurately acquire and quantify,and thus tend to be simplified or ignored in existing lane-changing models.In this paper,the Bik-means clustering algorithm is used to analyse the urban road congestion state discrimination method.Then,simulated driving tests were conducted for different traffic congestion conditions.Through the force feedback system and infrared camera,the data of driver lane-changing behaviours at different traffic congestion levels are obtained separately,and the definitions of the start and end points of a vehicle changing lanes are determined.Furthermore,statistical analysis and discussion of key feature parameters including driver lane-changing behaviour data and visual data under different levels of traffic congestion were conducted.It is found that the average lane-change intention times in each congestion state are 2 s,4 s,6 s and 7 s,while the turn-signal duration and the number of rear-view mirror observations have similar patterns of change to the data on lane-changing intention duration.Moreover,drivers’pupil diameters become smaller during the lane-changing intention phase,and then relatively enlarge during lane-changing;the range of pupil variation is roughly 3.5 mm to 4 mm.The frequency of observing the vehicle in front of the target lane increased as the level of congestion increased,and the frequency of observation in the driver’s mirrors while changing lanes approximately doubled compared to driving straight ahead,and this ratio increased as the level of congestion increased.