Mehdi Najafi

A dynamic dispatching and routing model to plan/ re-plan logistics activities in response to an earthquake

The unpredictable nature and devastating impact of earthquakes enforce governments of disaster-prone regions to provide practical response plans to minimize damage and losses resulting from earthquakes. Logistics management is one of the key issues that should be considered for an appropriate response, in particular, the planning of the transport of commodities required during response and the evacuation of injured people. This paper develops a dynamic model for dispatching and routing vehicles in response to an earthquake. We focus on the transport of both commodity towards affected areas and injured people to hospitals. The proposed model is capable of receiving updated information at any time and adjusting plans accordingly. Since speed is a key to a successful earthquake response, the model hierarchically minimizes the total time until arrival at a hospital for injured people, as well as the total lead-time to fulfill commodity needs. We designed experiments to investigate the effect of the network topology on earthquake response rapidity to improve the quality of earthquake response.

Location and distribution management of relief centers: a genetic algorithm approach (online article)

Humanitarian logistics is regarded as a key area for improved disaster management efficiency and effectiveness. In this study, a multi-objective integrated logistic model is proposed to locate disaster relief centers while taking into account network costs and responsiveness. Because this location problem is NP-hard, we present a genetic approach to solve the proposed model.

On the outflow conditions for spectral solution of the viscous blunt-body problem

The purpose of this paper is to study and identify suitable outflow boundary conditions for the numerical simulation of viscous supersonic/hypersonic flow over blunt bodies, governed by the compressible Navier-Stokes equations, with an emphasis motivated primarily by the use of spectral methods without any filtering. The subsonic/supersonic composition of the outflow boundary requires a dual boundary treatment for well-posedness. All compatibility relations, modified to undertake the hyperbolic/parabolic behaviour of the governing equations, are used for the supersonic part of the outflow. Regarding the unknown downstream information in the subsonic region, different subsonic outflow conditions in the sense of the viscous blunt-body problem are examined. A verification procedure is conducted to make out the distinctive effect of each outflow condition on the solution. Detailed comparisons are performed to examine the accuracy and performance of the outflow conditions considered for two model geometries of different surface curvature variations. Numerical simulations indicate a noticeable influence of pressure from subsonic portion to supersonic portion of the boundary layer. It is demonstrated that two approaches for imposing subsonic outflow conditions namely (1) extrapolating all flow variables and (2) extrapolation of pressure along with using proper compatibility relations are more suitable than the others for accurate numerical simulation of viscous high-speed flows over blunt bodies using spectral collocation methods.

Application of a shock-fitted spectral collocation method for computing transient high-speed inviscid flows over a blunt nose

Interaction of freestream disturbances with high-speed inviscid flow over a blunt nose is simulated utilizing a shock-fitted spectral collocation method. The unsteady flow computations are made through solving the 2D Euler equations by virtue of such a dissipation-free numerical algorithm for precise unsteady flow simulations. A shock-fitting technique is employed to accurately compute the unsteady shock motions and its interaction with monochromatic freestream disturbances of different conditions. A symmetry condition is proposed to accurately model the both steady and unsteady characters of the symmetry boundary, which allows the use of halved geometries and avoids the extra computational cost. The computational results for a cylinder at Mach 8.03 are presented and verified through comparisons with other numerical and promising analytical solutions. The stagnation line where the most energetic interactions take place is inspected carefully. The study shows the significant influence of the shock on its subsequent flow field in unsteady simulations and notable ability of the shock-fitted spectral collocation method implemented for the study of such problems.

Location and distribution management of relief centers: a genetic algorithm approach

Humanitarian logistics is regarded as a key area for improved disaster management efficiency and effectiveness. In this study, a multi-objective integrated logistic model is proposed to locate disaster relief centers while taking into account network costs and responsiveness. Because this location problem is NP-hard, we present a genetic approach to solve the proposed model.

A dynamic dispatching and routing model to plan/replan the logistical activities in the response phase of an earthquake

The unpredictable nature and devastating impact of earthquakes enforce governments of disaster-prone regions to provide practical response plans to minimize damage and losses resulting from earthquakes. Logistics management is one of the key issues that should be considered for an appropriate response, in particular, the planning of the transport of commodities required during response and the evacuation of injured people. This paper develops a dynamic model for dispatching and routing vehicles in response to an earthquake. We focus on the transport of both commodity towards affected areas and injured people to hospitals. The proposed model is capable of receiving updated information at any time and adjusting plans accordingly. Since speed is a key to a successful earthquake response, the model hierarchically minimizes the total time until arrival at a hospital for injured people, as well as the total lead-time to fulfill commodity needs. We designed experiments to investigate the effect of the network topology on earthquake response rapidity to improve the quality of earthquake response.

A dynamic dispatching and routing model to plan/re-plan the logistics activities in response to an earthquake

The unpredictable nature and devastating impact of earthquakes enforce governments of disaster-prone regions to provide practical response plans to minimize damage and losses resulting from earthquakes. Logistics management is one of the key issues that should be considered for an appropriate response, in particular, the planning of the transport of commodities required during response and the evacuation of injured people. This paper develops a dynamic model for dispatching and routing vehicles in response to an earthquake. We focus on the transport of both commodity towards affected areas and injured people to hospitals. The proposed model is capable of receiving updated information at any time and adjusting plans accordingly. Since speed is a key to a successful earthquake response, the model hierarchically minimizes the total time until arrival at a hospital for injured people, as well as the total lead-time to fulfill commodity needs. We designed experiments to investigate the effect of the network topology on earthquake response rapidity to improve the quality of earthquake response.

Receptivity of Hypersonic Flow over Blunt-Noses to Freestream Disturbances Using Spectral Methods

The receptivity of supersonic/hypersonic flows over blunt noses to freestream disturbances is performed by means of spectral collocation methods. The unsteady flow computations are made through solving the full Navier-Stokes equations in 2D. A shock-fitting technique is used to compute unsteady shock motion and its interaction with freestream disturbances accurately in the receptivity study. The computational results for receptivity of a semi-cylinder at Mach 8 is presented and validated by comparison with available theoretical and numerical results. The study shows significant effects of the viscosity on the receptivity process.