Occurrence Of Collisions Research Articles

Practical Point-to-Point Multiple-Goal Task Realization in a Robot Arm with a Rotating Table

This study presents a multiple-goal task realization in a system composed of a 6-d.o.f. robot arm and a one-axis rotating table. The problem is complex due to the existence of multiple goals and the kinematic redundancy of the system. We propose a design approach integrating the base placement, task sequencing and motion coordination methods. We show that this approach reduces the task completion time of the robot arm; the motion planning is realized through straight-line paths in the configuration space despite collision occurrences. Furthermore, we introduce a hybrid graph-search method combining the greedy nearest-neighbor method and the Dijkstra method to solve the motion coordination of the robot arm and the table. We show the effectiveness of the design approach and the search method through a time-constrained simulation-based optimization.

Mining Microscopic Data of Vehicle Conflicts and Collisions to Investigate Collision Factors

Road collisions lead to great human and financial costs for society. Although some progress has been made, this worldwide issue needs more attention, as the costs increase. Proactive methods for road safety analysis that do not depend on collision occurrences are needed. Collection and analysis of microscopic data (road user trajectories) about all traffic events with and without a collision are the only ways to gain insight into collision factors and processes; that is, the chains of events that lead to collisions. The first phase of the project reported in this paper used microscopic data extracted from video sensors and data mining techniques to identify patterns in the traffic event database. Decision trees, the k-means algorithm, and the hierarchical agglomerative clustering method were used to analyze the relationship between interaction attributes and outcome (collision or not) and identify groups of interactions with similar attributes. This approach was demonstrated on a data set collected in Kentucky of 295 traffic events and contained 213 conflicts and 82 collisions. The decision tree confirmed the importance of evasive action in the interaction outcome. Three clusters were found from speed indicators extracted from road users' trajectories: the cluster containing the fewest collisions had the lowest speeds of the three. This result hints at the existence of conflicts that are dissimilar from most collisions and may therefore not be suitable for surrogate safety analysis.

Energy-Efficient Receiver-Driven Wireless Mesh Sensor Networks

A major challenge in wireless sensor networks research is energy efficiency. In the intermittent receiver-driven data transmission (IRDT) protocol, which aims at saving energy, communication between two nodes commences when multiple receiver nodes transmit their own IDs and the sender nodes receive them. This protocol can be used to construct a mesh network which is robust against node failure and wireless channel fluctuations. In our work, we improve this protocol by implementing a collision avoidance method for control packets. First, we refer to the probability of control packet collision as a function of the intermittent interval. We then introduce procedures to determine the interval which decreases or minimizes this probability. Afterwards, we include a data aggregation mechanism into IRDT to reduce data transmission frequency and the occurrence of control packet collisions. Through computer simulation, we show that IRDT can offer greater reduction of the average energy consumption compared with RI-MAC and X-MAC, especially at small loads, and we also demonstrate that IRDT with collision avoidance for control packets can attain higher performance than the original IRDT. This method ensures a packet collection ratio of more than 99% and an average energy consumption 38% lower than that of EA-ALPL and 90% lower than that of the original IRDT.

SIMULATION STUDY OF TRAFFIC ACCIDENTS IN BIDIRECTIONAL TRAFFIC MODELS

Conditions for the occurrence of bidirectional collisions are developed based on the Simon–Gutowitz bidirectional traffic model. Three types of dangerous situations can occur in this model. We analyze those corresponding to head-on collision; rear-end collision and lane-changing collision. Using Monte Carlo simulations, we compute the probability of the occurrence of these collisions for different values of the oncoming cars' density. It is found that the risk of collisions is important when the density of cars in one lane is small and that of the other lane is high enough. The influence of different proportions of heavy vehicles is also studied. We found that heavy vehicles cause an important reduction of traffic flow on the home lane and provoke an increase of the risk of car accidents.

A framework for geocoding traffic collision data

BackgroundCollision geocoding is the process of assigning latitude and longitude coordinates to a traffic collision record. In California and most other US states, collision location is recorded on police reports...

Transferability of Community-Based Collision Prediction Models for Use in Road Safety Planning Applications

Collision prediction models (CPMs) are statistically developed mathematical models that relate the occurrence of traffic collisions to various traits or explanatory variables of locations and zones. This paper describes the use of several recently developed community-based, macro-level CPMs and model-use guidelines in a CPM transferability case study for spatial and temporal transferability. The objective was to test the model-use guidelines in an application that involved transferring CPMs developed using 1996 data for the Greater Vancouver Regional District (GVRD) for use in the Central Okanagan Regional District (CORD) using 2003 data. The GVRD and CORD are regions located 400 km apart in the Province of British Columbia, Canada. The case study was carried out in two parts. First, CPMs were developed using 2003 data for the City of Kelowna following recommended community-based, macrolevel collision prediction model development guidelines. Second, existing CPMs were transferred from the GVRD to the CORD, using the recommended transferability guidelines. An analysis of the results revealed that macrolevel CPM transferability was possible and no more complicated than microlevel CPM transferability. To facilitate the development of reliable community-based macrolevel collision prediction models, it is recommended that CPMs be transferred rather than developed whenever and wherever communities lack sufficient data of adequate quality.

Red Light Cameras: Do They Change Driver Behavior and Reduce Accidents?

: Installation of red light cameras (RLC) at intersections associated with a high number of traffic accidents are currently in use to reduce the number of traffic collisions. The primary objective of this study was to evaluate the sustained effect of RLC on driver behavior. The secondary objective was to evaluate the number of collisions before and after RLC implementation. : For the primary objective, an 8-month prospective observational study after installation of RLC in September 2007 was undertaken at the intersection with the highest incidence of traffic accidents in the State of Louisiana. For the secondary objective, collision occurrences were collected 10 months before and after RLC installation. The mean number of citations was calculated by month, and the statistical significance of trend was obtained from a linear regression model across the study period and by t test to compare before and after citations were issued. The number of traffic collisions was compared using chi. : During the initial 30 days, 2,428 violations per week were recorded, whereas in the subsequent 30 days, there were 534 citations per week issued (p < 0.001). After eight months, the number of citations was reduced to an average of 356 citations per week (p < 0.01). Mean number of citations decreased significantly during implementation of RLC. Three drivers received more than one citation. Although there was a trend in reduction of collisions from 122 to 97 before and after RLC, this did not reach statistical significance; p = 0.18. : A significant and sustained reduction in the number of citations occurred as driving behavior was modified. Despite reducing the number of cars entering this intersection during a red light, RLC do not seem to prevent traffic collisions at this monitored intersection. Alternative means of injury prevention must be investigated.

Fatal Wrong‐Way Collisions on New Mexico’s Interstate Highways, 1990–2004

Medical examiner files from 1990 through 2004 were reviewed to identify fatalities caused by drivers traveling the wrong direction on interstate highways and identify risk factors and prevention strategies. Other fatal nonpedestrian interstate motor vehicle crashes served as a comparison group. Data abstracted included decedent demographics, driver/passenger status, seatbelt use, blood alcohol concentration, weather and light at time of occurrence and types of vehicles involved. Of 1171, 79 (6.7%) interstate motor vehicle fatalities were because of drivers traveling against the posted direction in 49 crashes, with one to five fatalities per crash. Wrong-way collisions were significantly more likely to occur during darkness (p < 0.0001) and involve legally intoxicated drivers (p < 0.0001). In 29/49 (60%) wrong-way crashes, alcohol was a factor. Prevention strategies aimed at reducing the incidence of driving while intoxicated, as well as improved lighting and signage at ramps, could help reduce the occurrence of fatal wrong-way collisions on interstates.

Geocoding police collision report data from California: a comprehensive approach

BackgroundCollision geocoding is the process of assigning geographic descriptors, usually latitude and longitude coordinates, to a traffic collision record. On California police reports, relative collision location is recorded using a highway postmile marker or a street intersection. The objective of this study was to create a geocoded database of all police-reported, fatal and severe injury collisions in the California Statewide Integrated Traffic Records System (SWITRS) for years 1997-2006 for use by public agencies.ResultsGeocoding was completed with a multi-step process. First, pre-processing was performed using a scripting language to clean and standardize street name information. A state highway network with postmile values was then created using a custom tool written in Visual Basic for Applications (VBA) in ArcGIS software. Custom VBA functionality was also used to incorporate the offset direction and distance. Intersection and address geocoding was performed using ArcGIS, StreetMap Pro 2003 digital street network, and Google Earth Pro. A total of 142,007 fatal and severe injury collisions were identified in SWITRS. The geocoding match rate was 99.8% for postmile-coded collisions and 86% for intersection-coded collisions. The overall match rate was 91%.ConclusionsThe availability of geocoded collision data will be beneficial to clinicians, researchers, policymakers, and practitioners in the fields of traffic safety and public health. Potential uses of the data include studies of collision clustering on the highway system, examinations of the associations between collision occurrence and a variety of variables on environmental and social characteristics, including housing and personal demographics, alcohol outlets, schools, and parks. The ability to build maps may be useful in research planning and conduct and in the delivery of information to both technical and non-technical audiences.

Advanced and Applications in Vehicular Ad Hoc Networks

Recently there is a strong interest in developing networking techniques and important applications for moving vehicles, to enable wireless communication between roadside and vehicles or between vehicles. Vehicular ad hoc networks (VANETs) using all kinds of wireless technologies has recently received considerable attention. The goal of this special issue is to explore the development of wireless vehicular ad hoc network technologies about communication, networking, and applications. The communication protocol design will affect the performance results. A good communication protocol design can achieve highly reliable, highly scalable, and high performance. In aspect of networking, there are many challenges that how to offer quality of service, build high performance routing, provide mobility management, and create secure vehicular ad hoc networks. VANET safety applications include safety warnings and collision avoidance. It is important to improve the non-safety applications and reduce the occurrence of collision. VANETs present a highly active field of research, development, standardization and field trials. Throughout the world, there are many national/ international projects from government, industry, and academia devoted to VANETs, for example consortia like VSC (US), C2CCC (Europe) and InternetITS (Japan), standardization efforts like IEEE 802.11p (WAVE) and field trials like the large-scale Vehicle Infrastructure Integration Program (VII) in the US. The call for papers for this Special Issue attracted more than 50 submissions from Asia, Europe, and the US covering many topics this Special Issue focuses on. Each paper was carefully evaluated by at least two reviewers. Based on the review results, we selected 13 high quality research papers to be included in this Special Issue. We strongly believe that the selected papers will make a significant contribution to researchers, practitioners, and students working in the area of the VANET. Our special thanks go to Dr. Imrich Chlamtac (Editor-inChief) and Katiuscia Buonaiuto for their valuable support throughout the preparation of this Special Issue. We would like to thank all authors who have submitted papers to the Special Issue and in particular those whose papers have been accepted for this Special issue. Assistance from the editorial staff of the Mobile Networks and Applications journal is also very much appreciated. Finally, the Guest Editors wish to gratefully acknowledge all those who have generously given their time to review the papers submitted for consideration for this SI. The thirteen accepted papers are divided into three categories. Two papers relate to channel modeling or access. “Channel Modeling and Inter-Carrier Interference Analysis for V2V Communication Systems in FrequencyDispersive Channels” by Hsiao-Hwa Chen et al. presents a practical model to characterize V2V communication channel and its corresponding Doppler spread spectrum is derived. “Cooperative and Opportunistic Channel Access for Vehicle to Roadside (V2R) Communications” by Wanjiun Liao et al. proposes a new mechanism called Proxy-based Vehicle to exploit cooperative and opportunistic forwarding between any H.-C. Chao (*) National Ilan University, I-Lan, Taiwan e-mail: hcc@niu.edu.tw

Stability Analysis of Passive Dynamic Walking of Quadrupeds

We introduce a detailed numerical simulation and analysis framework to extend the principles of passive dynamic walking to quadrupedal locomotion. Non-linear limit cycle methods are used to identify possible gaits and to analyze the stability and efficiency of quadrupedal passive dynamic walking. In doing so, special attention is paid to issues that are inherent to quadrupedal locomotion, such as the occurrence of simultaneous contact collisions and the implications of the phase difference between front and back leg pairs. Limit cycles identified within this framework correspond to periodic gaits and can be placed into two categories: in-phase gaits in which front and back legs hit the ground at roughly the same time, and out-of-phase gaits with a ±90° phase shift between the back and front leg pairs. The latter are, in comparison, energetically more efficient but exhibit one unstable eigenvalue that leads to a phase divergence and results in a gait-transition to a less efficient in-phase gait. A detailed analysis examines the influence of various parameters on stability and locomotion speed, with the ultimate goal of determining a stable solution for the energy-efficient, out-of-phase gait. This was achieved through the use of a wobbling mass, i.e. an additional mass that is elastically attached to the main body of the quadruped. The methods, results, and gaits presented in this paper additionally provide a point of departure for the exploration of the considerably richer range of quadrupedal locomotion found in nature.

Making Explicit the Contention in Hospice Care

At the core of hospice remains the defining nature of mortals tending to other mortals facing diagnosed terminality. Such situations are pregnant with meanings. As mortals are subjective beings, social engagements become inundated with meaning differences. This alludes to the inescapable occurrence of collisions and conflicts in meaning. It would behoove us to make explicit the contention that exists in hospice care, given that death is the nonnegotiable outcome to be diversely faced by all involved persons whose lived approaches related to death issues may characteristically lack unanimity. Toward elucidating the inherently contentious nature of hospice care, the dynamical influence of external forces that overlie thanatological matters in society and the complex human dynamic in hospice care situations are discussed. Practice suggestions for hospice staff are offered.

Preamble allocation scheme using trajectory information for mobile relay stations

We propose a novel preamble allocation scheme for mobile relay stations (MRS) in order to reduce the occurrence of preamble collision. We calculate the probability of preamble collision based on trajectory information of MRSs. Then, we select a preamble considering not only the probability of preamble collision but also interference from other base stations (BS) and relay stations (RS). Simulation results show that the proposed scheme significantly reduces the occurrence of preamble collision.

A Comparison of Data Sets Varying in Spatial Accuracy Used to Predict the Occurrence of Wildlife-Vehicle Collisions

Wildlife-vehicle collisions (WVCs) pose a significant safety and conservation concern in areas where high-traffic roads are situated adjacent to wildlife habitat. Improving transportation safety, accurately planning highway mitigation, and identifying key habitat linkage areas may all depend on the quality of WVC data collection. Two common approaches to describe the location of WVCs are spatially accurate data derived from global positioning systems (GPS) or vehicle odometer measurements and less accurate road-marker data derived from reference points (e.g., mile-markers or landmarks) along the roadside. In addition, there are two common variable types used to predict WVC locations: (1) field-derived, site-specific measurements and (2) geographic information system (GIS)-derived information. It is unclear whether these different approaches produce similar results when attempting to identify and explain the location of WVCs. Our first objective was to determine and compare the spatial error found in road-marker data (in our case the closest mile-marker) and landmark-referenced data. Our second objective was to evaluate the performance of models explaining high- and low-probability WVC locations, using congruent, spatially accurate (<3-m) and road-marker (<800-m) response variables in combination with field- and GIS-derived explanatory variables. Our WVC data sets were comprised of ungulate collisions and were located along five major roads in the central Canadian Rocky Mountains. We found that spatial error (mean +/- SD) was higher for WVC data referenced to nearby landmarks (516 +/- 808 m) than for data referenced to the closest mile-marker data (401 +/- 219 m). The top-performing model using the spatially accurate WVC locations contained all explanatory variable types, whereas GIS-derived variables were only influential in the best road-marker model and the spatially accurate reduced model. Our study showed that spatial error and sample size, using road-marker data for ungulate species, are important to consider for model output interpretation, which will impact the appropriate scale on which to apply modeling results. Using road-marker references <1.6 km or GPS-derived data locations may represent an optimal compromise between data acquisition costs and analytical performance.

Collective motion in non-reciprocal swarms

This paper studies a non-reciprocal swarm model that consists of a group of mobile autonomous agents with an attraction-repulsion function governing the interaction of the agents. The function is chosen to have infinitely large values of repulsion for vanishing distance between two agents so as to avoid occurrence of collision. It is shown analytically that under the detailed balance condition in coupling weights, all the agents will aggregate and eventually form a cohesive cluster of finite size around the weighted center of the swarm in a finite time. Moreover, the swarm system is completely stable, namely, the motion of all agents converge to the set of equilibrium points. For the general case of non-reciprocal swarms without the detailed balance condition, numerical simulations show that more complex self-organized oscillations can emerge in the swarms. The effect of noise on collective dynamics of the swarm is also examined with a white Gaussian noise model.

The influence of meteorological factors on the occurrence of trauma and motor vehicle collisions in Tokyo

Background:Previous studies have suggested a possible association between meteorological factors and the occurrence of trauma, but with conflicting results. This study investigated the relation of the occurrence of trauma with...

Sea breeze simulation over the Malay Peninsula in an intermonsoon period

This study presents a characteristic intermonsoon weather situation over the Malay Peninsula. The Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) is used to investigate the mesoscale details of the simulated sea breeze circulations over the Malay Peninsula on 23 April 2002. The occurrence of sea breeze collisions occurring in the inland region of the southern Malay Peninsula is noted. On the peninsula‐scale, convection was first initiated along the low‐level convergence line that became established along the west coastal region of the Malay Peninsula in the early afternoon. Deep clouds that led to thunderstorms developed in the northwestern part of the Malay Peninsula after the sea breeze encountered the mountain wave induced under the ambient easterlies above the mountain ridge line. The convective activity was further enhanced over the central Malay Peninsula because of the interaction between sea breeze front and gap winds from the mountains. This case study suggests that the Malay Peninsula is a potentially fertile ground for many dynamically interesting case studies of land–sea breeze circulations.

Toward Reliable and Efficient Reporting in Wireless Sensor Networks

Energy-efficiency is one of the major concerns in wireless sensor networks since it impacts the network lifetime. In this paper, we investigate the relationship between sensor network performance, particularly its lifetime, and the number of active reporting nodes N by using both analytical and simulation approaches. We first demonstrate that decreasing the number of reporting nodes increases the number of reports that need to be sent to the sink in order to achieve the desired information reliability regarding a detected event. On an other side, we show that reducing the number of reporting nodes reduces the probability of collision occurrence. Based on these results, and as a first main contribution, we derive the optimal number of reporting nodes Nopt_energy that minimizes the energy consumed to report reliably the occurrence of an event. In other words, we prove that limiting the reporting tasks of a detected event to a small subset of sensor nodes (i.e., Nopt_energy), instead of using all the sensor nodes in the event area, enables significant energy conservation.

Trust Model Based on Minimal Uncertainty Metric in Wireless Mesh Network

PDF HTML阅读 XML下载 导出引用 引用提醒 无线网状网基于不确定性度量极小化信任模型 DOI: 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: Supported by the National Natural Science Foundation of China under Grant Nos.60673142, 60473090 (国家自然科学基金) Trust Model Based on Minimal Uncertainty Metric in Wireless Mesh Network Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:WMN(wireless mesh network)网络环境中,网络拓扑结构的改变或无线冲突的发生,都可能导致作为信任值评估证据的样本空间不一定完整和可靠,使得现有的信任评估模型不能应用其上.为了解决WMN网络节点间信任评估问题和建立信任关系,在研究现有信任模型并分析其存在问题的基础上,提出了基于不确定性度量极小化的信任模型.模型引入可信任度因子,根据网络实际情况,弱化证据样本空间不一定完整和可靠对信任值评估的影响,使得信任评估值的修正量在全局范围内达到最小.仿真实验与基于证据理论的信任评估模型进行了对比 Abstract:In wireless mesh networks, the sample space of evidence may be not integrative or reliable because of the change of network topology and the occurrence of wireless collision. It makes the existing trust evaluation models inapplicable. To evaluate trust values of nodes and establish trust relationship in nodes, a trust model is proposed on the basis of the analyses of the existing trust models and the minimal principle of uncertainty metric. The model reduces the influence of the non-integrated and unreliable sample space through importing a credible parameter. According to the real situation of networks, the model can minimize the amendment of evaluation values in the whole scope. Contrasted with the evidence-based trust model, the simulation results show that the proposed model is effective. 参考文献 相似文献 引证文献

Risk of Pedestrian Collision Occurrence

This individual-level case control study analyzed the risk of occurrence of a pedestrian–motor vehicle collision at a given location on a state route in King County, Washington. With the full sample of collisions (1999-2004), binomial logit models estimated the odds of collision occurrence as related to the road and the neighborhood environments and adjusting for exposure. Separate models were run for SR-99, the principal transregional arterial with four-plus lanes ( n = 826), and for all the other state routes ( n = 1,602). The strongest significant correlates of the risk of collision occurrence were the presence of crosswalks with or without traffic signals, the facility's number of lanes, and the presence of nearby retail uses. Also positively significant were the number of traffic signals and the street-block size near the location and being located outside the city of Seattle. Exposure variables including road-level measures such as average daily traffic and posted speed and neighborhood-level measures such as the number of residential units and bus ridership were significant in at least one of the models. Employment density appeared to be an unreliable measure of exposure. Other pedestrian activity generators such as educational facilities were not significantly associated with the risk of collision occurrence. The strong significance of crosswalks, whether signalized or not, indicated that engineering approaches to safety should likely be complemented by education- and enforcement-based measures. Similarly, facilities in areas with concentrations of retail should become the targets of future safety programs.