Bi-level optimization for risk-based regional hurricane evacuation planning     

Pruttipong Apivatanagul  Rachel A. Davidson  Linda K. Nozick 《Natural Hazards》2012,60(2):567-588

Almost all engineering evacuation models define the objective as minimizing the time required to clear the region or total travel time, thus making an implicit assumption that who will or should evacuate is known. Conservatively evacuating everyone who may be affected may be the best strategy for a given storm, but there is a growing recognition that in some places that strategy is no longer viable and in any case, may not be the best alternative by itself. Here, we introduce a new bi-level optimization that reframes the decision more broadly. The upper level develops an evacuation plan that describes, as a hurricane approaches, who should stay and who should leave and when, so as to minimize both risk and travel time. The lower level is a dynamic user equilibrium (DUE) traffic assignment model. The model includes four novel features: (1) it refocuses the decision on the objectives of minimizing both risk and travel time; (2) it allows direct comparison of more alternatives, including for the first time, sheltering-in-place; (3) it uses a hurricane-scenario-based analysis that explicitly represents the critically important uncertainty in hurricane track, intensity, and speed; and (4) it includes a new DUE algorithm that is efficient enough for full-scale hurricane evacuation applications. The model can be used both to provide an evacuation plan and to evaluate a plan’s performance in terms of risk and travel time, assuming the plan is implemented and a specified hurricane scenario then actually occurs. We demonstrate the model with a full-scale case study for Eastern North Carolina.  相似文献   

On the coupling between vegetation and the atmosphere     

Isabella M. Angelini  Michael Garstang  Robert E. Davis  Bruce Hayden  David R. Fitzjarrald  David R. Legates  Steven Greco  Stephen Macko  Vickie Connors 《Theoretical and Applied Climatology》2011,105(1-2):243-261

Recent studies suggest that vegetation can drive large-scale atmospheric circulations and substantially influence the hydrologic cycle. We present observational evidence to quantify the extent of coupling between vegetation and the overlying atmosphere. Within the context of vegetation–atmospheric interactions, we reanalyze existing climatological data from springtime leaf emergence, emissivity, dew point temperatures, and historical records of precipitation and forest coverage. We construct new rainfall transects based on a robust global climatology. Using isotopic analysis of precipitation, we find that rain in Amazonia comes primarily from large-scale weather systems coupling interior regions to the ocean and is not directly driven by local evaporation. We find that changes in vegetative cover and state influence the temperature and moisture content of the surface and atmospheric boundary layer but are not reflected in observable precipitation changes. This analysis reaffirms the view that changes in precipitation over continental reaches are a product of complex processes only partly influenced but not controlled by local water sources or vegetation.  相似文献   

Triaxial shear testing of polished slickensided surfaces   总被引：1，自引：1，他引：0  

Christopher L. Meehan  Binod Tiwari  Thomas L. Brandon  J. Michael Duncan 《Landslides》2011,8(4):449-458

A series of consolidated-drained triaxial tests were performed on precut and polished clay specimens to measure their drained residual strength. Two soils were tested during this research program: Rancho Solano Clay and San Francisco Bay Mud. Specimens were tested using a specially modified triaxial compression device which was developed to minimize the effects of end-platen restraint on the measured strengths. Special attention was paid to the influence of changing specimen area and membrane effects during the test. Triaxial test results were compared with baseline measurements of drained residual shear strength that were made for each of the clay soils using Bromhead ring shear tests and polished-specimen direct shear tests. Residual strength values measured in the triaxial device were higher than the drained residual strengths measured in the Bromhead ring shear apparatus and the direct shear device, indicating that this test approach is more challenging than the use of direct shear tests conducted on polished slickensided surfaces. Comparison of single stage and multistage triaxial test data indicates that multistage triaxial testing may work well for specimens that fail along a well-defined plane, provided that careful attention is given to the effects of end platen restraint, membrane restraint, and changes in specimen area during shear.  相似文献   

A numerical study on the role of wind forcing,bottom topography,and nonhydrostacy in coastal upwelling     

Lide Jiang  Xiao-Hai Yan  Yu-Heng Tseng  Laurence C. Breaker 《Estuarine, Coastal and Shelf Science》2011

The responses of coastal upwelling to different magnitudes of wind stress over a narrow and a wide shelf are studied using a 3-D primitive equation numerical model. The results show that the position of the upwelling front depends on both the strength and the duration of the wind forcing. The comparison between different shelf widths shows that wide shelf will limit the cold water intrusion, so that the corresponding decrease in sea surface temperature is less compared to narrow shelves. Besides, the difference between hydrostatic and nonhydrostatic model results shows that nonhydrostatic effects will enhance the growth of surface meandering, and can be more pronounced near steep fronts. Although difference does exist, our results show that the nonhydrostatic effects are very small at least in this idealized study case.  相似文献   

Does sunspot number calibration by the “magnetic needle” make sense?     

K. Mursula  I. Usoskin  O. Yakovchouk 《Journal of Atmospheric and Solar》2009,71(17-18):1717-1726

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Satellite-based prediction of rainfall interception by tropical forest stands of a human-dominated landscape in Central Sulawesi,Indonesia     

Jens Nieschulze  Stefan Erasmi  Johannes Dietz  Dirk Hölscher 《Journal of Hydrology》2009,364(3-4):227-235

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Dynamo-generated magnetic fields at the surface of a massive star     

D. J. Mullan  James MacDonald 《Monthly notices of the Royal Astronomical Society》2005,356(3):1139-1148

Spruit has shown that an astrophysical dynamo can operate in the non-convective material of a differentially rotating star as a result of a particular instability in the magnetic field (the Tayler instability). By assuming that the dynamo operates in a state of marginal instability, Spruit has obtained formulae which predict the equilibrium strengths of azimuthal and radial field components in terms of local physical quantities. Here, we apply Spruit's formulae to our previously published models of rotating massive stars in order to estimate Tayler dynamo field strengths. There are no free parameters in Spruit's formulae. In our models of 10- and  50-M_⊙  stars on the zero-age main sequence, we find internal azimuthal fields of up to 1 MG, and internal radial components of a few kG. Evolved models contain weaker fields. In order to obtain estimates of the field strength at the stellar surface, we examine the conditions under which the Tayler dynamo fields are subject to magnetic buoyancy. We find that conditions for Tayler instability overlap with those for buoyancy at intermediate to high magnetic latitudes. This suggests that fields emerge at the surface of a massive star between magnetic latitudes of about 45° and the poles. We attempt to estimate the strength of the field which emerges at the surface of a massive star. Although these estimates are very rough, we find that the surface field strengths overlap with values which have been reported recently for line-of-sight fields in several O and B stars.  相似文献   

Vortex generation and evolution in water waves propagating over a submerged rectangular obstacle: Part II: Cnoidal waves     

《Coastal Engineering》2005,52(3):257-283

Vortex generation and evolution due to flow separation around a submerged rectangular obstacle under incoming cnoidal waves is investigated both experimentally and numerically. The Particle Image Velocimetry (PIV) technique is used in the measurement. Based on the PIV data, a characteristic velocity, phrased in terms of incoming wave height, phase speed, dimension of the obstacle, and a local Reynolds number are proposed to describe the intensity of vortex. The numerical model, which solves the two dimensional Reynolds Averaged Navier Stokes (RANS) equations, is used to further study the effects of wave period on the vortex intensity. Measurements for the mean and turbulent velocity fields further indicate that the time history of the intensity of fluid turbulence is closely related to that of the vortex intensity.  相似文献   

Residual currents in tidally dominated, well-mixed estuaries     

ROBERT K. MCCARTHY   《地球，A辑:动力气象学与海洋学》1993,45(4):325-340

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Radon modelling and the heat transfer surface area of the British hot dry rock geothermal reservoir     

N. Hussain 《Journal of Earth System Science》1991,100(1):1-11

A simple thermal model is developed to evaluate the heat exchange surface area of a hot dry rock geothermal reservoir. This model, in conjunction with the Rn model of Andrews and coworkers, is applied to RH12/RH15 system of the British HDR reservoir. Results suggest that although the estimated Rn transfer surface area represents the actual swept surface area, it is between 25 and 45 times larger than the heat transfer surface area. The difference is explained as due to clustering of several fractures within a range of thermal interaction, over the duration of the circulation. It is also shown that the decline in the measured temperatures of circulation fluids since 1985 to the present is consistent with the heat exchange surface area going through a maximum in 1987.  相似文献