Performance Analysis of RFID Framed Slotted Aloha Anti-Collision Protocol

In this paper, we develop a novel mathematical model to estimate the probability distribution function of the number of tags discovered after a certain number of interrogation rounds. In addition, the pdfs of the number of rounds needed to discover all the tags are also calculated. The estimation of such pdfs will be helpful in estimating the number of interrogation rounds and the optimal parameter configuration of the RFID system which in turn will be helpful in estimating the time needed to discover all tags. Our results show that the proposed model accurately predicts the tags detection probability. We then use the proposed model to optimally configure the reader parameters (i.e. the frame size and the number of interrogation rounds).

Distance-Measuring Technology Using LD for Auto Anti-Collision

Auto anti-collision technology is one of the main research subjects of automobiles’ safety technology. Aiming at the key technology of Auto anti-collision, measuring the distance from obstacles, based on the theory of phase laser distance ranging, Laser Diode (LD) distance-measuring system for auto anti-collision has been developed to solve the problem of on-line measuring distance technology in middle to long distance utilizing the good characteristics of LD when modulating its optical intensity and adopting typical kinds of filter techniques in this paper. By theoretical analysis, adopting typical kinds of filter techniques can reduce the interference of strong light, so distance-measuring range can be 0.5–100 m in daytime or 1–200 m at night. And more, from theoretical analysis and experiment result, it can guarantee the high measuring resolution which can be less than 24.5 mm, utilizing the method of two Laser Diode optical intensity modulating wavelength and complimenting precise calibration and revision. The idea of LD distance-measuring technology is novel and feasible and this technology can be applied in Auto anti-collision. Key words laser diode - phase laser distance ranging - filter techniques - auto anti-collision CLC number TH 161 Foundation item: Supported by the National Natural Science Foundation of China (59675080, 59805006) and Wuhan Chenguang Foundation (20025001001)Biography: Zhang Xin-bao (1965-), male, Associate professor, research direction: precise mechanism and instrument.

Ultra-low power anti-crosstalk collision avoidance light detection and ranging using chaotic pulse position modulation approach

A novel concept of collision avoidance single-photon light detection and ranging（LIDAR） for vehicles has been demonstrated, in which chaotic pulse position modulation is applied on the transmitted laser pulses for robust anti-crosstalk purposes. Besides, single-photon detectors（SPD） and time correlated single photon counting techniques are adapted, to sense the ultra-low power used for the consideration of compact structure and eye safety. Parameters including pulse rate, discrimination threshold, and number of accumulated pulses have been thoroughly analyzed based on the detection requirements, resulting in specified receiver operating characteristics curves. Both simulation and indoor experiments were performed to verify the excellent anti-crosstalk capability of the presented collision avoidance LIDAR despite ultra-low transmitting power.

Geochemistry and Sr,Nd Istopes of Granitoids from the Lac Ifni Area(Sirwa Massif-Anti-Atlas Morocco):A Geodynamic Setting for the Post-collisional Ediacaran Magmatic Chain of the Anti-Atlas

The plutonic rocks of the westernmost part of the Sirwa massif belong to the Ediacaran post-collisional magmatic chain of the Anti-Atlas.The geochemistry of major and trace elements attests that the fractional crystallization cannot account for the variations between the granitoids and the associated MME.They represent two contemporaneous but independent magmatic tendencies.However,Sr and Nd configur data argue for a similar and juvenile material

Novel Tag Anti-Collision Algorithm with Adaptive Grouping

For RFID tags, a Novel Tag Anti-collision Algorithm with Grouping (TAAG) is proposed. It divides tags into groups and adopts a deterministic method to identify tags within group. TAAG estimates the total number of tags in systems from group identifying result and then adjusts the grouping method accordingly. The performance of the proposed TAAG algorithm is compared with the conventional tag anti-collision algorithms by simulation experiments. According to both the analysis and simulation result, the proposed algorithm shows better performance in terms of throughput, total slots used to identify and total cycles.

Application of Ship Maneuvering Simulator's Technology on Research of Vessels Automatic Anti-Collision

In this paper, the authors make a summary of current situation of research on the Auto Anti-Collision, briefly introduce the components and functions of the NSACA Simulation Platform and bring forward the project to realize the simulation of an Automatic Anti-Collision control, based on the NSACA Simulation Platform. Finally give typical examples from a great deal of simulating tests and analyze them.

Synchronous Dynamic Adjusting: An Anti-Collision Algorithm for an RF-UCard System

An RF-UCard system is a contactless smartcard system with multiple chip operating systems and multiple applications. A multi-card collision occurs when more than one card within the reader’s read field and thus lowers the efficiency of the system. This paper presents a novel and enhanced algorithm to solve the multi-card collision problems in an RF-UCard system. The algorithm was originally inspired from framed ALOHA-based anti-collision algorithms applied in RFID systems. To maximize the system efficiency, a synchronous dynamic adjusting (SDA) scheme that adjusts both the frame size in the reader and the response probability in cards is developed and evaluated. Based on some mathematical results derived from the Poisson process and the occupancy problem, the algorithm takes the estimated card quantity and the new arriving cards in the current read cycle into consideration to adjust the frame size for the next read cycle. Also it changes the card response probability according to the request commands sent from the reader. Simulation results show that SDA outperforms other ALOHA-based anti-collision algorithms applied in RFID systems.

Simulation Analysis on Navigation Indexes of Wanzhou Yangtze River Highway Bridge after the Anti-Collision Device Construction by Ship Model Test

After the anti-collision facility construction of Wanzhou Yangtze River Highway Bridge, the conditions of navigation in bridge area are complex. In order to study the navigation conditions of the reach and layout optimization measures, ensuring the safety of the ship navigation test has been carried out on the ship model navigation in the bridge area. According to the requirements of the maximum safety limit of the ship model test, the paper puts forward the best route, the control method and the difficulty of navigation through the analysis of the test results, and finally gives the recommendations and suggestions.

A collision recovery algorithm using optimal Q parameter based on BIBD in RFID

In this work,an optimal Q algorithm based on a collision recovery scheme is presented. Tags use BIBD-( 16,4,1) codes instead of RN16 s. Therefore,readers can make a valid recognition even in collision slots. A way of getting the optimal slot-count parameter is studied and an optimal Q algorithm is proposed. The theoretical and simulation results show that the proposed algorithm can improve reading efficiency by 100% more than the conventional Q algorithm. Moreover,the proposed scheme changes little to the existing standard. Thus,it is easy to implement and compatible with ISO 18000-6C.

基于性能的通航桥梁抗船撞评估方法及应用研究

为合理有效地开展通航桥梁抗船撞性能评估,提出基于性能的桥梁抗船撞标准化评估方法。基于现行《公路桥梁抗撞设计规范》(JTG/T 3360-02-2020),从抗撞性能等级确定、设防代表船型确定、船撞力计算、船撞效应计算以及抗撞性能验算等方面,采用结构性能目标作为评估准则,建立桥梁抗撞性能评估各环节流程的标准化评估方法。以江苏扬中三桥为应用实例,运用该方法进行该桥20号墩抗撞性能评估,结果表明:20号墩桩基顺桥向抗弯性能不满足JX1级要求,其余验算结果满足要求,桥墩抗撞性能综合评估结果为不满足要求。参照评估结果该桥加装了浮动式防撞设施。桥梁抗撞性能评估标准化,可准确高效实现桥梁抗撞性能等级确定、船撞效应计算、抗撞性能验算等预期的评估功能要求。

基于混沌控制的采摘机器人防碰撞系统设计

针对采摘机器人在作业过程中遇到障碍物导致路径规划出现混沌现象的问题,基于混沌控制对采摘机器人防碰撞系统进行设计,并采用模糊自适应控制算法和滑模变结构控制算法结构的方式对系统进行控制。为了验证防碰撞系统的有效性,对采摘机器人进行了防碰撞和采摘仿真试验,结果表明:采摘机器人在作业过程中可以避开障碍物,按照规划路线到达预设位置,完成果蔬的采摘。

桥墩倾斜方向对自浮式防撞装置防护效果影响研究

随着航道上大跨度桥梁的建设愈加广泛,其桥墩在水面附近往往具有一定的倾斜角度。为研究桥墩倾斜方向对自浮式防撞装置防护效果的影响,文章基于装备自浮式防撞装置的2种倾斜方向的桥墩与6000DWT级散货船为研究对象进行非线性有限元仿真碰撞计算,分析桥墩倾斜方向对不同航速船舶撞击下桥墩撞击力、系统能量转换、船艏结构破坏的影响。结果表明:外倾式桥墩受到撞击力更小,其防撞装置通过变形吸收能量更多、防护效果更好。研究成果可为大跨度桥墩设计与防撞装置的开发提供重要的参考价值。

钢橡胶组合防撞装置试验与动力性能研究

为减少船桥撞击损伤,提出一种新型的钢-橡胶组合防撞装置.首先设计3组大比例试验构件,通过拟静力试验研究装置整体受力性能、破坏模式以及承载力;然后通过试验验证有限元模型,明确了焊缝对结构受力的影响,进行了装置整体动力性能分析.结果表明:钢-橡胶组合防撞装置由于填充轮胎的支撑作用,承载能力明显高于空筒防撞装置;钢-橡胶组合防撞装置具有很好的缓冲消能效果,在正撞和20°斜撞工况下耗能均达到35%以上,满足阻碍船舶与桥墩撞击的功能;回收轮胎不仅实现了一定的拨转功能,还起到耗能作用,轮胎填充能提升耗能5%以上,对船有回弹作用;同时,轮胎的填充不仅能提升自浮性能,更提升了装置整体性能.

既有防撞设施桥梁抗撞性能评估方法及应用

如何合理有效地开展桥梁抗撞性能评估,特别是准确评价防撞设施的防护效果,是已建桥梁进行船撞桥隐患整治的难题之一。为准确评估已建桥梁加装防撞设施后的抗撞性能,基于现有规范及相关研究成果,结合大量工程项目经验,从抗撞性能评估总体环节、抗撞性能标准确定、设防代表船型确定、船舶撞击力计算、防撞设施防护效果分析、桥墩船撞效应计算及抗撞性能验算等方面,建立了既有防撞设施桥梁抗撞性能评估方法的标准化框架流程。以某长江公路大桥3~#主墩为例,运用上述方法进行桥梁抗撞性能评估。结果表明:典型计算工况下,防撞设施较好地发挥了耗能缓冲防护效果,延长了撞击时间,削减了船舶撞击力,对船舶正撞及侧撞峰值力削减率分别为47.2%和51.6%;不考虑防撞设施防护效果时,3~#主墩抗撞性能不满足要求,主要表现为墩身及桩基横桥向抗剪性能不足;考虑防撞设施防护效果后,墩身及桩基横桥向抗剪性能不足得到改善,桥墩抗撞性能可满足要求。既有防撞设施桥梁抗撞性能评估方法的标准化框架流程系统全面,可用于已建桥梁防撞设施评价及抗撞性能评估。

多胞体汽车后防撞吸能器耗能机制研究与结构优化设计

为有效提升后防撞系统耐撞性能以满足碰撞冲击载荷作用下的车辆被动安全需求,研发了6种正多边形镶嵌的多胞体薄壁吸能器。基于简化超折叠单元理论分析了截面参数和肋板连接方式对薄壁吸能器的能量耗散途径与影响机制;采用ABAQUS数值仿真探究了各种吸能器吸能特性,同时揭示了正八边形截面、肋板对边连接的薄壁吸能器吸能特性优异;依托拉丁超立方试验方法和基于Kriging代理模型的NSGA-II遗传算法进行多目标优化,确定了吸能器内薄壁管截面尺寸、管壁和肋板厚度分别为18.073 mm、1.669 mm、1.924 mm。结果分析表明,参数优化后的正八边形多胞体吸能器压溃吸能过程平稳可靠,能够为后防撞系统吸能器的结构设计提供参考。

基于空闲时隙探测机制的分组帧时隙标签防碰撞算法

多标签碰撞是射频识别系统中无法避免的问题,大量的标签碰撞会增加系统的能量消耗和时间开销,严重影响系统的识别效率。为此提出一种新型的标签防碰撞算法,该算法结合了传统帧时隙算法简单易实施的优点,同时引入了分组和空闲时隙探测机制,以极小的探测时隙开销,消除了识别过程中的空闲时隙,同时减低了标签冲突概率。仿真结果显示,相对于FuzzyQ算法和帧时隙ALOHA算法,本算法平均吞吐率提高了22.64%和61.74%,系统通信传输量平均节省了16.73%和30.41%。

弧形自浮式防撞装置运动响应及受力特性分析

针对弧形自浮式防撞装置导向机构在日常运行过程中易发生塑性变形的问题,建立了基于三维势流理论的弧形自浮升降式防撞装置水动力分析模型,对不同入射角的波浪与水流共同作用条件下装置的运动响应及导向机构的受力特性进行分析,结果表明:水流的持续作用有利于减小防撞装置的运动响应;浮筒下游侧导向机构的刚度较大导致了该部分机构受力过于集中而其他导向机构未受力或者受力较小的现象;波浪入射角对导向机构的受力影响较大,当波浪入射角与水流流向的夹角较小时,波流的叠加效应会增大,造成下游侧导向机构受力陡增。

大跨梁-拱组合刚构桥船撞力和抗撞性能研究

梁-拱组合刚构桥是一种新桥型,船撞研究较少。该文以礼嘉嘉陵江大桥为工程背景,研究大跨度上承式梁-拱组合刚构桥梁的船撞力标准值和抗撞性能。首先确立了代表船型和船撞计算工况,利用ANSYS/LS-DYNA非线性有限元瞬态动力软件模拟了单墩模型在各工况下船桥碰撞过程,并对比了船撞力有限元仿真结果与多种经验公式计算结果。最后利用全桥模型和验算截面的极限承载力反推得到桥墩的极限抗船撞力,对桥墩的抗撞性能进行了评估。结果表明:船撞力具有很强的非线性波动特征,船艏最大撞深发生时刻滞后于最大撞击力发生时刻,船桥碰撞过程中的系统能量主要是由船舶动能转化为船艏局部变形内能;不同的船撞力经验公式的计算结果相差较大,推荐采用动力仿真模拟值;极限抗船撞力验算结果表明礼嘉嘉陵江大桥主墩的抗撞性能满足要求。

警务车辆特种驾驶“防冲撞”专项培训课程研究

警务车辆“防冲撞”驾驶专项训练是全警实战大练兵活动的重要内容之一。依托于公安部警务车辆特种驾驶培训基地这一平台,通过多年来积累的警用车辆安全驾驶和特种驾驶教学经验,结合当前车辆冲撞类案件的特点,以及应急处置的不同临战状态,研究搭建了以单车最小作战单元现场处置为基础,双车、多车配合相辅助,以不同情境条件下车辆的追击、控制、截停等为技战术要点的一门针对性强、全面完整、及时有效的特种驾驶“防冲撞”专项培训课程。

桥墩被动防船撞设施发展评述

桥梁被动防船撞装置通过缓冲和吸收撞击能量,是保障桥梁在船舶撞击下结构安全的重要措施之一。由于各类防船撞设施的结构差异较大,其防护、维护等功能需求以及对航道环境的影响都存在较大差异。为此,首先梳理了被动防船撞装置的分类方法,针对钢浮箱、复合材料浮箱、钢围堰、普通橡胶护舷等各类防船撞装置的防护性能与研究应用现状进行了分析。结合对国内外35座特大桥梁开展的防撞措施应用状况调查,总结归纳了各类防船撞装置的特点与适用场合,梳理了当前各类防撞装置面临的技术问题。最后,针对未来被动防船撞设施的发展提出了钛钢复合板材和FRP复合钢板等高性能复合金属材料应用、GFRP部件连接新工艺与新形式研发、拦截索网自适应技术及其恒定阻力装置研发等有待进一步研究的问题和展望。调研与分析结果表明:通航孔桥墩以采用直接型防撞装置为主,对于非通航孔桥墩则采用间接型防撞装置,独立防撞钢管桩适用于内河航道非通航孔桥且水中桥墩较少的情形,人工岛目前应用较少。未来被动防船撞措施在强耐久性、高耗能以及受力稳定性方面,仍需进一步深入研究和改进,以提高桥梁被动防船撞措施的防护性能。