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981.
Mapping evacuation risk on transportation networks using a spatial optimization model 总被引:2,自引:0,他引:2
The focus of this paper is on the development of a methodology to identify network and demographic characteristics on real transportation networks which may lead to significant problems in evacuation during some extreme event, like a wildfire or hazardous material spill. We present an optimization model, called the critical cluster model, that can be used to identify small areas or neighborhoods which have high ratios of population to exit capacity. Although this model in its simplest form is a nonlinear, constrained optimization problem, a special integer-linear programming equivalent can be formulated. Special contiguity constraints are needed to keep identified clusters spatially connected. We present details on how this model can be solved optimally as well as discuss computational experience for several example transportation networks. We describe how this model can be integrated within a GIS system to produce maps of evacuation risk or vulnerability. This model is now being utilized in several research projects, in Europe and the US. 相似文献
982.
Key to the predictive understanding of many nearshore marine ecosystems is the transport of larvae by ocean circulation processes. Many species release thousands to billions of larvae to develop in pelagic waters, but only a few lucky ones successfully settle to suitable habitat and recruit to adult life stages. Methodologies for predicting the larval dispersal are still primitive, and simple diffusive analyses are still used for many important applications. In this study, we investigate mechanisms of larval dispersal using idealized simulations of time-evolving coastal circulations in the California Current system with Lagrangian particles as models for planktonic larvae. Connectivity matrices, which describe the source-to-destination relationships for larval dispersal for a given larval development time course, are used to diagnose the time–space dynamics of larval settlement. The resulting connectivity matrices are shown to be a function of several important time scales, such as the planktonic larval duration, the frequency and duration of larval release events and inherent time scales for the coastal circulations. Many important fishery management applications require knowledge of fish stocks on a year-to-year or generation-to-generation basis. For these short time scales (typically less than 1 year), larval dispersal is generally far from a simple diffusive process and the consideration of the stochastic and episodic nature of larval dispersal is required. This work provides new insights into the spatial–temporal dynamics of nearshore fish stocks. 相似文献
983.
In this paper, we extend previous analyses of temporal effects by examining the factors associated with activity generation and duration over four waves of the Puget sound transportation panel survey (PSTPS). A Cox proportional hazards model was specified for each of five activities: visiting, appointment, free time, personal business, and shopping. For each activity, the duration times are modeled with an emphasis on examining important higher order interactions. The results suggest that activity durations have changed significantly over the survey period. Many of the differences in activity durations over time were significant, and often associated with increasing numbers of children in the household and higher order interactions between sex and the sequencing of activities. 相似文献
984.
985.
C. Sanchez-Rebollo A. Carnicero 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2013,51(4):554-569
Dynamic simulation methods have become essential in the design process and control of the catenary–pantograph system, overall since high-speed trains and interoperability criteria are getting very trendy. This paper presents an original hardware-in-the-loop (HIL) strategy aimed at integrating a multicriteria active control within the catenary–pantograph dynamic interaction. The relevance of HIL control systems applied in the frame of the pantograph is undoubtedly increasing due to the recent and more demanding requirements for high-speed railway systems. Since the loss of contact between the catenary and the pantograph leads to arcing and electrical wear, and too high contact forces cause mechanical wear of both the catenary wires and the strips of the pantograph, not only prescribed but also economic and performance criteria ratify such a relevance. Different configurations of the proportional-integral-derivative (PID) controller are proposed and applied to two different plant systems. Since this paper is mainly focused on the control strategy, both plant systems are simulation models though the methodology is suitable for a laboratory bench. The strategy of control involves a multicriteria optimisation of the contact force and the consumption of the energy supplied by the control force, a genetic algorithm has been applied for this purpose. Thus, the PID controller is fitted according to these conflicting objectives and tested within a nonlinear lumped model and a nonlinear finite element model, being the last one validated against the European Standard EN 50318. Finally, certain tests have been accomplished in order to analyse the robustness of the control strategy. Particularly, the relevance or the plant simulation, the running speed and the instrumentation time delay are studied in this paper. 相似文献
986.
A new method to calculate the anthropogenic CO2 (ΔDICant) within the water column of the North Atlantic Ocean is presented. The method exploits the equilibrium chemistry of the carbonate system with reference to temperature, salinity and the partial pressure of atmospheric CO2 (pCO2,atm). ΔDICant is calculated with reference to the ventilation ages of water masses derived from tracer data and to the time history of pCO2,atm. The method is applied to data recorded during the WOCE program on the WHP A1/E transect in the North Atlantic Ocean, where we characterise six key water masses by their relationships of dissolved inorganic carbon (DIC) and apparent oxygen utilisation (AOU). The error in determining ΔDICant is reduced significantly by minimising the number of values referred to, especially by avoiding any use of remineralisation ratios of particulate organic matter. The distribution of ΔDICant shows highest values of up to 45 μmol kg−1 in the surface waters falling to 28–33 μmol kg−1 in the Irminger Sea west of the Mid-Atlantic Ridge. The eastern basin is imprinted by older water masses revealing decreasing values down to 10 μmol kg−1 ΔDICant in the Antarctic Bottom Water. These findings indicate the penetration of the whole water column of the North Atlantic Ocean by anthropogenic CO2. 相似文献
987.
This paper presents an application of shallow water theory to describe the motion of floodwater inside a rolling ship in damage
condition. The time domain theoretical approach to the coupled problems of ship and water inside compartment motions is briefly
described, including the method used to solve for the water motion characteristics and forces exerted on the ship. This approach
is applied to the study of the behaviour of a passenger Ro–Ro ship in regular beam seas and numerical results are given for
the intact and damaged conditions. Comparison is made with experimental results. For the damaged condition, the characteristics
of the floodwater motion are studied in the time domain for a number of different wave frequencies. The shape of the free-surface
and phase of water motion in relation to the ship roll motion are shown for several wave frequencies. The dynamic floodwater
roll moment is also shown and compared with the static roll moment (flat horizontal free surface), allowing the conclusion
that the dynamic roll moment is much larger than the static roll moment, for high wave frequencies, and is in phase opposition
in relation to the roll motion. 相似文献
988.
Based on data available in mid-2006, the five cooperating international institutions of shipping — BIMCO, Intertanko, Intercargo, ICS, and ISF — produced a summary of factual information on 106 flag states. These international institutions intentionally avoided drawing conclusions on underperformance. This paper extends this assessment allowing for an in-depth empirical assessment of flags performance. Towards this end, the analysis uses weight factors reflecting the importance that an operator might wish to attach on the different variables before making his flag choice, and seeks to statistically (un)group ‘conventionally’ grouped flag states performance. The paper also examines whether IMO membership and/or active participation in the IMO is associated with a greater compliance of a flag-state to safety and relevant environment rules and thus to a better performance. The findings challenge the classic outright categorization of national flags as good performing ones and of commercial flags as those performing badly. The findings also support the suggestion that an active IMO participation, rather than a simple membership, enhances flag performance. 相似文献
989.
Z. Shi I. Legate F. Gu J. Fieldhouse A. Ball 《International Journal of Automotive Technology》2010,11(3):363-373
An Antilock Braking System (ABS) is one of the most important safety facilities equipped in modern vehicles. A self-test is
therefore embedded into its ECU to identify any electronic malfunction. However there is no effective method to predict or
check its mechanical conditions routinely to ensure its functionality. Because the ABS system is merely actuated above a particular
speed in emergency stops, the current brake test facilities are not adequate for ABS test. Because of the dangers involved
it would not be acceptable to use a public road to implement such a practice for fault detection so an alternative means must
be sought. To provide a safe and convenient solution this paper proposes a novel method to predict ABS faults whilst the vehicle
is stationary. In this situation a model-based approach is applied to predict various faults from the ABS, especially from
its hydraulic subsystem. As such, a mathematic model is developed to describe the operating processes of ABS including possible
faulty conditions. An autonomous control strategy is also designed to actuate the control module independently without the
knowledge of the control algorithms embedded in an ABS control module. This approach is evaluated through a Simulink simulation. 相似文献
990.