Occurrence Of Collisions Research Articles

Models for Safety Analysis of Road Surface Transit

A study was done to explore the development of zonal- and arterial-level collision prediction models that incorporate characteristics applicable to urban transit planning. A generalized linear modeling approach with a negative binomial regression error structure was employed by using a data set from Toronto, Ontario, Canada. The zonal-level models indicate that vehicle kilometers traveled, bus or streetcar kilometers traveled, arterial road kilometers, bus stop density, percentage of near-sided stops, and average posted speed have significant associations with occurrences of transit-involved collisions. The arterial-level models, which were developed for collisions involving all motor vehicles, suggest that average annual daily traffic, transit frequency, segment length, presence of on-street parking, and percentage of near-sided stops are all associated with increased frequency of these collisions, whereas percentage of far-sided stops and average stop spacing are linked with reduced collision frequency. It is evident that models such as those developed in this study can provide transit agencies with decision-support tools for considering safety implications in the strategic and service-planning processes. These models can also be used as a tool to predict future levels of transit-involved collisions for an existing and a new transportation network or arterial route.

Experimental Reproduction of Accident Prone Area Using a Driving Simulator and Behavioral Analyses in Traffic Conflicts

The Meihan highway linking Kameyama in Mie Prefecture and Tenri in Nara Prefecture is one of most accident-prone areas in Japan. Representative accident factors that have been identified for the Meihan highway are chronic speeding and complex road alignments, including many sharp curves and steep slopes. One particular section is known as the “Omega curve” as the road shape is similar to the Greek character “Ω”. In this study, the probable effects of proposed plans to improve the road alignment of the Nakahata section are investigated by performing driving simulations to identify typical hazards, ranging from traffic conflicts to vehicle accidents. It was found that incidents that begin as a minor traffic conflicts can frequently escalate to become a fatal accidents. It was also found that improved road alignment generally reduces the required tire forces. For typical traffic conflict patterns reproduced using the driving simulator, it was found that road alignment resulted in considerable improvements in safety indexes which are effective indicators for the occurrence of rear-end collisions.

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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

Coupling constant behavior of eigenvalues of Zakharov-Shabat systems

We consider the eigenvalues of the non-self-adjoint Zakharov-Shabat systems as the coupling constant of the potential is varied. In particular, we are interested in eigenvalue collisions and eigenvalue trajectories in the complex plane. We identify shape features in the potential that are responsible for the occurrence of collisions and we prove asymptotic formulas for large coupling constants that tell us where eigenvalues collide or where they emerge from the continuous spectrum. Some examples are provided which show that the asymptotic methods yield results that compare well with exact numerical computations.

Effect of disorder on DNA electrophoresis in a microfluidic array of obstacles

The size-based separation of electrophoresing DNA chains of varying lengths has been experimentally achieved in microfluidic obstacle arrays. The separation is actuated by the occurrence of size-dependent chain-obstacle collisions and the subsequent formation of hooked chain configurations in the array. We investigate the role played by disorder in array geometry in determining chain dynamics in the array. As a prototypical example of a disordered post array, we select a self-assembled array of magnetic colloids, wherein the degree of disorder may be varied by varying the magnetic field strength under which the array is generated. We employ Brownian dynamics simulations of chain electrophoresis in the array to compute the mobility, dispersivity, chain-obstacle collision probability, and mean chain stretch in the device, and demonstrate the link between the orientational order of the array and the resulting chain dynamics.

Organization of size-selected platinum and indium clusters soft-landed on surfaces

Metal cluster cations are produced in a laser vaporization source, size selected in the gas phase by an electrostatic quadrupole deflector, and deposited on transmission electron microscopy grids coated with various substrates. The morphology of cluster assemblies is very dependent on the occurrence of diffusion, collision, and coalescence of incident particles on the surface. In this respect, indium and platinum clusters show very different behaviors: the former easily coagulate to form large entities when the latter do not coalesce and tend to form structured arrays with a uniform distance between first neighbors.

Reducing Treatment Selection Bias for Estimating Treatment Effects Using Propensity Score Method

Treatment selection bias leads to an inaccurate estimation of treatment effects as applied to specific sites or problem locations. Treatment selection bias is a major source of inconsistency in the results obtained from conventional before and after and cross-sectional models. One of the major expressions of treatment selection bias concerns the use of collision occurrence data in justifying intervention. For example, in highway safety field, a treatment is often introduced at a given site based on its high collision experience. Under normal conditions we would expect these collision numbers to return to a lower long term expected value, regardless of intervention. For treated sites, conventional observational models ascribe this reduction in collisions to the given treatment. This results in an overestimation of treatment effect. In this paper, a propensity score model is introduced that deals explicitly with treatment selection bias. The model is applied to Canadian highway–railway grade crossings data to estimate reductions in collision subject to upgrades in warning devices. The results of the propensity score model are compared for similar types of treatments to a number of before and after and cross-sectional models for both U.S. and Canadian data. The propensity score method is shown to reduce treatment selection bias and has probable merit that need to be further examined.

Interventions for increasing pedestrian and cyclist visibility for the prevention of death and injuries

Pedestrians and cyclists account for nearly one in three of all road users killed and seriously injured in road traffic crashes. Late detection of other road users is one of the basic driver failures responsible for collisions. Aids to improve pedestrians and cyclist visibility have been used to avert potential collisions. However, the impact of these strategies on drivers' responses, and on pedestrian and cyclist safety is not known. 1. To quantify the effect of visibility aids versus no visibility aids, and of different visibility aids on the occurrence of pedestrian and cyclist-motor vehicle collisions and injuries. 2. To quantify the effect of visibility aids versus no visibility aids, and of different visibility aids on drivers' detection and recognition responses. We searched the CENTRAL, the Cochrane Injuries Group specialised register, MEDLINE, TRANSPORT, National Research Register, PsycInfo and PsycLit. We searched the reference lists of included trials, contacted authors and searched the websites of relevant transport research organisations. The searches were last updated in April 2005. 1. Randomised controlled trials and controlled before-and-after studies of the effect of visibility aids on the occurrence of pedestrian and cyclist-motor collisions and injuries. 2. Randomised controlled trials of the effect of visibility aids on drivers' detection and recognition responses. This included trials where the order of presentation of visibility aids was randomised or balanced using a Latin square design. Two authors independently screened records, extracted data and assessed trial quality. We found no trials assessing the effect of visibility aids on pedestrian and cyclist-motor vehicle collisions and injuries. We identified 39 trials assessing the effect of visibility aids on drivers' responses. Fluorescent materials in yellow, red and orange colours improve detection and recognition in the daytime. For night-time visibility, lamps, flashing lights and retroreflective materials in red and yellow colours increase detection and recognition. Retroreflective materials arranged in a 'biomotion' configuration also enhance recognition. Substantial heterogeneity between and within the trials limited the possibility for meta-analysis. Summary statistics and descriptive summaries of the outcomes were presented for individual trials when appropriate. Visibility aids have the potential to increase visibility and enable drivers to detect pedestrians and cyclists earlier. Public acceptability of these strategies would merit further development. However, the effect of visibility aids on pedestrian and cyclist safety remains unknown. Studies which collect data on simple, meaningful outcomes are required.

Simulation of Fiber Suspensions—A Multiscale Approach

Abstract The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. The present approach is capable of coupling behaviors from the Kolmogorov turbulence scale through the full-scale system in which a fiber suspension is flowing. Here the key aspect is adaptive hierarchical modeling. Numerical results are presented for which focus is on fiber floc formation and destruction by hydrodynamic forces in turbulent flows. Specific consideration was given to dynamic simulations of viscoelastic fibers in which the fluid flow is predicted by a method that is a hybrid between direct numerical simulations and large eddy simulation techniques and fluid fibrous structure interactions will be taken into account. Dynamics of simple fiber networks in a shearing flow of water in a channel flow illustrate that the shear-induced bending of the fiber network is enhanced near the walls. Fiber-fiber interaction in straight ducts is also investigated and results show that deformations would be expected during the collision when the surfaces of flocs will be at contact. Smaller velocity magnitudes of the separated fibers compare to the velocity before collision implies the occurrence of an inelastic collision. In addition because of separation of vortices, interference flows around two flocs become very complicated. The results obtained may elucidate the physics behind the breakup of a fiber floc, opening the possibility for developing a meaningful numerical model of the fiber flow at the continuum level where an Eulerian multiphase flow model can be developed for industrial use.

Diesel–diesel and diesel–ethanol drop collisions

In view of the possible occurrence of unlike drop collisions in a diesel spray due to the increasing application of alcoholic fuels as supplementary fuels in diesel engines, collisions of a diesel drop with either a diesel drop or an ethanol drop were studied. Diesel drop collision results do not display appreciable difference, within experimental errors, from those of tetradecane drops except for very small Weber numbers. The collision of an ethanol drop with a diesel drop, when compared to binary diesel drop collisions, exhibits higher tendency towards reflex separation for near head-on collisions and lower tendency towards stretching separation for medium to high impact parameter collisions. These distinctions come from the spreading of ethanol over the diesel drop due to their difference in surface tension.

Computer simulation of flocs interactions: Application in fiber suspension

The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. Specific consideration was given to dynamic simulations of viscoelastic fibers in which the fluid flow is predicted by a method that is a hybrid between Direct Numerical Simulations (DNS) and Large Eddy Simulation techniques (LES), and fluid fibrous structure interactions (FSI) will be taken into account. Numerical results are presented for which focus is on fiber floc deformation by hydrodynamic forces in turbulent flows. Dynamics of simple fiber networks in a shearing flow of water in a channel flow illustrate that the shear-induced bending of the fiber network is enhanced near the walls. Fiber–fiber interaction in straight ducts is also investigated and results show that deformations would be expected during the collision when the surfaces of flocs will be at contact. Smaller velocity magnitudes of the separated fibers compare to the velocity before collision implies the occurrence of an inelastic collision. In addition because of separation of vortices interference flows around two flocs become very complicated. The results opening the possibility for developing a meaningful numerical model of the fiber flow at the continuum level where an Eulerian multi-phase flow model can be developed for industrial use.

Actual Safety Distance and Winding Tension to Manufacture Full Section Parts by Robotized Filament Winding

Robotized filament winding technology allows one to manufacture workpieces of high performances as a result of a robot placing fibers impregnated by resin (known as roving) along the directions of stresses the workpiece is subjected to in exercise; thus, robotized filament winding favors rigidity and strength of a workpiece along some preferential directions. A proper value of the winding tension has to be chosen and kept constant along the whole winding in order to limit the defects inside the composite workpieces. To keep the tension value on roving near to the nominal value, one must plan the value of the geometric parameters characterizing the winding trajectory. The same geometric parameters influence the value of the actual safety distance that may involve collisions among the deposition system and the components of the robotized cell. This work shows how to avoid the occurrence of collisions by planning the value of the actual safety distance through the definition of geometric parameters that characterize the winding trajectory. Moreover, the collision occurrence should be considered together with the control of the winding tension on the roving in the robotized filament winding planning stage. The present work shows how to solve both the problems previously defined (i.e., to keep the winding tension on roving near to the nominal value and to avoid collision occurrence), by the solution of a constrained optimization system.

An On-Demand Cluster Formation Scheme for Efficient Flooding in Ad-Hoc Networks

Flooding is usually utilized to find a multi-hop route toward a node which is not within transmission range. However, existing flooding schemes deteriorate the performance of network because of periodic message exchanges, frequent occurrence of collisions, and redundant packet transmission. To resolve the problem, a lightweight and novel flooding scheme is proposed in this paper. The scheme employs ongoing packets for constructing a cluster architecture as the existing on-demand clustering scheme. Unlike to the existing schemes, it makes use of unicast packet transmission to reduce the number of collisions and to find the flooding candidates easily. As a result, the proposed scheme yields fewer flooding nodes than other schemes. Simulation results prove that it causes fewer packet transmissions and fewer collisions than those of two other schemes.

A coloured Petri net model for automated storage and retrieval systems serviced by rail-guided vehicles: A control perspective

An Automated Storage and Retrieval System (AS/RS) automatically stores incoming material and retrieves stored parts with no direct human handling. This paper proposes a modular and unified modelling framework for heterogeneous automated storage and retrieval systems, comprising rail guided vehicles and narrow aisle cranes. We employ coloured timed Petri nets, representing a concise and computationally efficient tool for modelling the system dynamic behaviour, particularly suitable for real-time control implementation. Indeed, the model can be utilized in a discrete event simulation to apply control policies in order to solve scheduling problems, as well as to avoid deadlock and collision occurrences.

Effect of Ice Surface Size on Collision Rates and Head Impacts at the World Junior Hockey Championships, 2002 to 2004

To determine if collision rates and head impacts in elite junior hockey differed between games played on the small North American ice surface (85 ft wide), an intermediate-size Finnish ice surface (94 ft wide), and the large standard international ice surface (100 ft wide). Videotape analysis of all games involving Team Canada from the 2002 (large ice, Czech Republic), 2003 (small ice, Canada), and 2004 (intermediate ice, Finland) World Junior Championships. All collisions were counted and separated into various categories (volitional player/player bodychecks, into boards or open ice, plus accidental/incidental player/boards, player/ice, head/stick, head/puck). Further subdivisions included collisions involving the head directly or indirectly and notably severe head impacts. Small, intermediate, and large ice surface mean collisions/game, respectively, were 295, 258, 222, total collisions; 251, 220, 181, volitional bodychecks; 126, 115, 88, into boards; 125, 106, 93, open ice; 71, 52, 44, total head; 44, 36, 30, indirect head; 26, 16, 13, direct head; and 1.3, 0.5, 0.3, severe head (P < 0.05 for small-intermediate ice and intermediate-large ice differences in total collisions; P < 0.005 for small-large ice difference; P < 0.05 for small-intermediate ice differences in head impacts; P < 0.01 for small-large ice differences in total and severe head impacts). There is a significant inverse correlation between ice size and collision rates in elite hockey, including direct, indirect, and severe head impacts. These findings suggest that uniform usage of the larger international rinks could reduce the risk of injury, and specifically, concussions in elite hockey by decreasing the occurrence of collisions and head impacts.

Discrete-step evaporation of an atomic beam

We present a theoretical analysis of the evaporative cooling of a magnetically guided atomic beam by means of discrete radio-frequency antennas. First we derive the changes in flux and temperature, as well as in collision rate and phase-space density, for a single evaporation step. Next we show how the occurrence of collisions during the propagation between two successive antennas can be probed. Finally, we discuss the optimization of the evaporation ramp with several antennas to reach quantum degeneracy. We estimate the number of antennas required to increase the phase-space density by several orders of magnitude. We find that at least 30 antennas are needed to gain a factor $10^8$ in phase-space density.

Patient with immunoproliferative disease and lung carcinoma: A case report

There are a number of reports on collision occurrence of non-hematologic cancers and Non-Hodgkin's lymphoma (NHL) and multiple myeloma. In this report we present a case of patient with immunoproliferative disease, extramedullary plasmocytoma and NHL-lymphoplasmocytoid lymphoma (LPL) and squamous cell carcinoma of the lung. After diagnosis of extramedullary plasmocytoma cytostatic therapy was commenced and the patient was well. Five years after patient was clinically worse and diagnostic evaluation this time revealed lymphoplasmocytoid cells in bone marrow. Five months later malignant morphologically undifferentiated cells were found in bone marrow which were by immunocytochemistry established as CD38 positive. After the patient's death, disseminated NHL-LPL and squamous cell carcinoma of lung was confirmed. In the report, we compared clinical course and diagnostic findings of our patient with literature data. We have also discussed the possible relationship of multiple B-cell lymphoid tumors and squamous cell carcinoma concluding that multidiscplinary diagnostic tools are essential not only for carcinoma diagnosis and follow-up, but also for further understanding of carcinogenesis.

Collision Frequency Analysis Using Tree-Based Stratification

Although several factors are known to contribute to collisions at highway-railway grade crossings, the mixed effects of the control factors such as a highway class and other countermeasures on collision occurrence are less well explored. This study evaluates the relationship between countermeasures and collision occurrence by using a sequential analytic strategy that combines the tree-based data stratification method with the generalized linear regression technique. After the control factor effects were controlled with the use of the tree-based data partitioning method, stratified collision prediction models were developed, and the adjusted effect of the selected countermeasures was identified. The conventional statistical models were also provided for comparison with stratified models. The study used Canadian inventory and collision data to demonstrate the expected collision reductions resulting from changes in selected countermeasures, such as warning devices and posted speed limit.

Collision Frequency Analysis Using Tree-Based Stratification

Although several factors are known to contribute to collisions at highway–railway grade crossings, the mixed effects of the control factors such as a highway class and other countermeasures on collision occurrence are less well explored. This study evaluates the relationship between countermeasures and collision occurrence by using a sequential analytic strategy that combines the tree-based data stratification method with the generalized linear regression technique. After the control factor effects were controlled with the use of the tree-based data partitioning method, stratified collision prediction models were developed, and the adjusted effect of the selected countermeasures was identified. The conventional statistical models were also provided for comparison with stratified models. The study used Canadian inventory and collision data to demonstrate the expected collision reductions resulting from changes in selected countermeasures, such as warning devices and posted speed limit.

Evaluating Factors Affecting Safety at Highway–Railway Grade Crossings

Various countermeasures can be introduced to reduce collisions at highway–railway grade crossings. Existing improvements to crossings include the installation of flashing lights or gates, the addition of extra warning devices such as four-quadrant barriers or wayside horns, and the enforcement of speed limits on the approaching highway. Statistical models are needed to ensure that countermeasures introduced at a given crossing are both cost-effective and practicable. However, in large part because of issues of colinearity, poor statistical significance, and parametric bias, many existing statistical models are simple in structure and feature few statistically significant explanatory variables. Accordingly, they fail to reflect the full gamut of factor inputs that explain variation in collision frequency at individual crossings over a given period of time. Before statistical models can be used to investigate the cost-effectiveness of specific countermeasures, models must be developed that more fully reflect the complex relationships that link a specific countermeasure to collision occurrence. This study presents a sequential modeling approach based on data mining and statistical methods to estimate the main and interactive effects of introducing countermeasures at individual grade crossings. This paper makes use of Canadian inventory and collision data to illustrate the potential merits of the model in decision support.