Current Issue : July - September Volume : 2019 Issue Number : 3 Articles : 5 Articles
The occurrence of adverse weather exacerbates traffic flow conditions, often leading to\nsevere traffic congestions. Many studies have been conducted based on field-collected data to obtain\nthe effects of weather on traffic flow characteristics. However, there is a limitation for filed data-based\nstudies, in that weather conditions and traffic conditions are both noncontrollable and nonrepeatable,\nmaking it difficult to comprehensively assess the influence of weather conditions, especially the rare\nextreme weather conditions, on traffic flow characteristics. This paper proposes to assess these effects\nwith the combination of driving simulator and traffic simulation. A driving simulator can collect\ndriving behavior by conducting weather-related driving simulation experiments, while a microscopic\ntraffic simulation program can evaluate the changes in traffic flow characteristics by inputting driving\nbehavior parameters coming from the driving simulator. The proposed method can overcome the\nlimitation of the field data-based approach. In this paper, the structure of the assessment platform is\nintroduced at first. Then a verification experiment is conducted to measure the influences of adverse\nweather conditions on traffic flow characteristics. The verification experiment results show that\nthe influences of adverse weather on traffic flow characteristics have consistent tendencies with\noutcomes from previous research and demonstrate that the method is practicable for the analysis of\nthe influence of weather on traffic flow characteristics. This paper provides a practical way to analyze\nthe influence of weather on traffic flow from driving behaviorâ??s point of view....
It is important to develop a reliable and high-throughput simulation method for predicting airflows in the installation planning\nphase of windmill power plants. This study proposes a two-stage mesh generation approach to reduce the meshing cost and\nintroduces a hybrid parallelization scheme for atmospheric fluid simulations. The meshing approach splits mesh generation into\ntwo stages: in the first stage, the meshing parameters that uniquely determine the mesh distribution are extracted, and in the\nsecond stage, a mesh system is generated in parallel via an in situ approach using the parameters obtained in the initialization\nphase of the simulation. The proposed two-stage approach is flexible since an arbitrary number of processes can be selected at run\ntime. An efficient OpenMP-MPI hybrid parallelization scheme using a middleware that provides a framework of parallel codes\nbased on the domain decomposition method is also developed. The preliminary results of the meshing and computing performance\nshow excellent scalability in the strong scaling test....
The propagation approach of a botnet largely dictates its formation, establishing a foundation of bots for future exploitation. The\nchosen propagation method determines the attack surface and, consequently, the degree of network penetration, as well as the\noverall size and the eventual attack potency. It is therefore essential to understand propagation behaviours and influential factors\nin order to better secure vulnerable systems.Whilst botnet propagation is generally well studied, newer technologies like IoT have\nunique characteristicswhich are yet to be thoroughly explored. In this paper, we apply the principles of epidemic modelling to IoT\nnetworks consisting of wireless sensor nodes. We build IoT-SIS, a novel propagation model which considers the impact of IoTspecific\ncharacteristics like limited processing power, energy restrictions, and node density on the formation of a botnet. Focusing\non worm-based propagation, this model is used to explore the dynamics of spread using numerical simulations and the Monte\nCarlo method to discuss the real-life implications of our findings....
The centrifugal model test system is utilized to reappear the breaching process of a tailings dam. The results show that there are\nsignificant differences in breaching processes between tailings dams and earth-rockfill dams. Influenced by the special physical\nand mechanical properties of tailings, the breaching processes of tailings dams are of short duration, and the flood flow through\nthe breach increase rapidly. Based on the centrifugal test results, considering the special physical and mechanical properties of\ntailings, a mathematical model for tailings dam breaching is established. In the model, the vertical undercutting and horizontal\nexpansion are simulated utilizing the erosion rate formula which is derived from shear stress principle of water flow; limit\nequilibrium method is used to analyze the breach slope stability. In addition, the model adopts iterative calculation method to\nsimulate the whole breaching process. The analysis results show that, the proposed model is applicable in modeling the dam\nbreaching process for tailings dam due to overtopping....
In this study, a cryogenic turbo-based refrigerator, with high-speed foil gas bearing\nturboexpander and plate-fin heat exchanger, was presented. For the cooling process of a cryogenic\nrefrigerator is long and complex, the efficient simulation of the dynamic performance is vital for its\nevaluation and operation. It is difficult to achieve this purpose. Because the cryogenic refrigerator\nwill go through great temperature changes, resulting in dynamic performances of components\ngoing to complexity. In this article, the turboexpander was simulated using CFX, and the matching\nmodels with expansion works of consumption and utilization were unified and modified. With\nnumerical calculation of heat exchanger, the dynamic simulation model of the refrigerator was\nimproved via MATLAB code. The calculation method of the required input energy of the\nrefrigerator in cooling processes was proposed based on the simulation and integration. The energy\nefficiency and economy cost of the refrigerator were evaluated under different operation modes.\nThe refrigerator with a motor was more stable than the one with a blower. The refrigerator was\ntested under different conditions, the results of which agreed well with simulation data. The\nsimulation method is efficient to serve practical applications, improve energy efficiency and reduce\ncosts....
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