查看更多>>摘要：The paper presents a unique application of artificial neural networks (ANN) for replicating the predictions of Persson's flash-temperature viscoelastic friction model. This allows the efficient calculation of the coefficient of friction between a tyre and the road surface, given the operating conditions, the tread material properties, and the power spectral density of road roughness. This is important because it allows the update of friction in a computationally efficient manner and therefore presents an opportunity for carrying out vehicle simulations on several road surfaces, without the requirement for tyre testing on every surface. To this end, a method is also proposed for integrating the most successful ANN configuration with a tyre model that had its baseline parameters identified by flat-track testing on a sandpaper surface. It is shown that the ANN-enhanced tyre model operates several times faster than real-time, predicting reduced peak and asymptotic tyre forces, as expected in most cases when moving from sandpaper to regular asphalt. The enhanced tyre model is further integrated with a vehicle model to illustrate the significant effect of reduced friction in stopping distance and handling dynamics.
查看更多>>摘要：This paper proposes a hybrid metaheuristic based resource allocation framework named RAFL for load balancing in cloud computing environment. The objective is to proactively minimize the load imbalance across active physical machines and among their considered resource capacities (e.g., CPU and RAM). This prevents overloading/underloading of active physical machines and utilizes their considered resource capacities in a balanced manner. In the proposed framework, a phasor particle swarm optimization and dragonfly algorithm based hybrid optimization algorithm named PPSO-DA is used to generate an optimal resource allocation plan for balancing the load. Simulation experiments are performed using CloudSim simulator to measure the metrics of load imbalance across active physical machines and among their considered resource capacities. Results show that the proposed PPSO-DA algorithm outperforms phasor particle swarm optimization, dragonfly algorithm, comprehensive learning particle swarm optimization, memory based hybrid dragonfly algorithm, sine cosine algorithm, and elephant herding optimization, in finding an optimal resource allocation for balancing the load. The statistical analysis and benchmark testing also validates the relative superiority of PPSO-DA.
查看更多>>摘要：In rock engineering, blasting works are often carried out near the existing underground caverns, like tunnels, mine roadways and storage caverns. Moreover, the natural fractures and joints within rock mass are also inevitable. In order to explore the characteristics of rock fragmentation in blasting scenarios for jointed rock mass of underground space, four series of bonded particle models were created with an opening and a set of preexisting discontinuities. The crack propagation process was evaluated with the principal stress evolution, contact forces between particles and the particle velocity as well as changes in the discontinuity inclination angle. For the specimens containing horizontal and vertical discontinuities, it is found that cracks firstly initiate from the borehole and the time of crack initiation and peak stress comes latter. However, for the specimens containing inclined discontinuities, cracking starts from the discontinuity immediately after detonation. It is found that the proposed numerical method is useful in depicting the fragmentation features of rock with discontinuities under blasting disturbance.
O Y.R.Chakraborty A.K.Bhowmik A.R.Chatterjee S....
12页
查看更多>>摘要：Fast and reliable protection schemes, with accurate fault detection methodology, turn out to be one of the key endeavours in microgrids for improved operation and control strategies. Identification of fault at a very initial stage might result in rapid isolation, fault interruption, and reclosure of the faulty section. Reconfiguration of the network sections depends on the performance of the transient detection technique. In this paper, a protection application case-study for rapid fault identification, exploiting the natural frequency oscillation of a network, has been proposed for a standalone low-voltage DC-microgrid system (LV DCmG) network. The proposed method makes the use of distortion in the fault current spectrum for fault detection empirically. The rapid fault detection using suitable sampling frequency depicts the robustness of proposed approach. The proposed fault detection scheme has been corroborated for a standalone LV DCmG consisting of solar photovoltaics and energy storage devices. Wide range of test cases for fault and no-fault scenarios have been analysed and verified by shuffling different fault events (pole-ground, pole-pole), fault locations, and fault resistances. The proposed method utilizes local measurements solely which increases the admissibility of the fault detection scheme proposed in this paper. A test model has been constructed in MATLAB/ Simulink platform, and further verified on a real-time environment with OPAL-RT OP4510.
查看更多>>摘要：Security is one of the most important criteria in the management of cloud resources. In Mobile Cloud Computing (MCC), secure allocation of tasks remains challenging due to the limited storage, battery life and computational power of mobile devices connected to the core cloud cluster infrastructure. Secure wireless communication channels and protocols for protecting the data and information sent to the cloud, and remote access to secure cloud services, are other important problems related to task scheduling and processing in dynamic MCC. In this paper, we developed a new security-aware task allocation model strategy in Mobile Cloud Computing. In this model, we define an allocation algorithm which generates an optimal and secure configuration of communication protocols in order to meet the specific data confidentiality requirements defined by end users. Resource utilization is predicted using Machine Learning methods, and the optimal secure service for task execution is selected. We developed a simulation environment (MocSecSim) for the evaluation of the algorithms proposed in several scenarios based on the users’ requirements. The results of simulations and experiments have demonstrated that the model proposed significantly improves the level of security of calculations in comparison with a configuration where processing time and energy consumption are the main criteria for optimizing task allocation.
查看更多>>摘要：This paper presents an agent-based model of cybersecurity as a participatory public good. Ineffective cybersecurity measures pose serious threats and risks to the development and stability of information societies in the world. Various doctrines and thesis explore how this domain should be treated by the public and private stakeholders. One of these doctrines is cybersecurity as a public good. In this paper, we highlight divergent views about the type of cybersecurity as an economic good. Then, the paper proposes an agent-based simulation model of a repeated public goods game among a set of defenders that are in an uncertain environment with incomplete and imperfect information. In the model, defenders have a probability to choose contribution or being a free-rider, depending on their own preferences and facing with revealed preferences of other defenders. This model implements a utility maximization that applies to each individual, modeling the existence of free-riders, punishments, and interdependency of decisions under a polycentric governance structure. The results of this simulation model show that, over time, defenders update their preferences in reaction to the behavior of other defenders and the experience of cyber-attacks. They indicate a high level of contribution to the provision of cybersecurity as a public good and the effectiveness of decentralized punishment on increasing the contributions. The consistency of the pattern of our results across different empirical studies lends us some reassurance that our model behavior is in quantitative agreement with empirical macro-structures. Furthermore, implementation of a polycentric structure challenges all the relevant agents to take action, and provides more robust environment.
查看更多>>摘要：Non-pneumatic tires (NPTs) have gained more and more attention in recent years due to the advantages of no run-flat, maintenance-free and excellent load-bearing capacity. In this paper, a mechanical model of rhombic porous structure was derived based on the theory of the hexagonal honeycomb structure, and the difference of mechanical characteristics for rhombic NPT tread on horizontal pavement as well as complex pavement was studied. The results show that the average contact pressure of NPT with rhombic structure on horizontal road is much lower than that of pneumatic tire, the shape of its spoke bearing area is inverted trapezoid, and the stress concentration phenomenon is formed in the contact part corresponding to the connection between spokes and tread at different contact positions. Furthermore, the vertical displacement and contact pressure of NPT are decoupled on complex pavement. The maximum stress concentration point is shifted from the tire surface to the spoke-tread connection and then to the spokes of the rhombic bearing structure as the contact area between the tire and the ground increases. This study provides guidance for structural optimization of NPT applied to complex working conditions.
查看更多>>摘要：This study provides a deeper knowledge of the usage of finite integration techniques (FIT) and the finite element method (FEM) for analyzing various microstrip antenna shapes such as rectangular, circular and triangular patches. These patch shapes are fabricated practically and the efficiency of both mentioned methods have been identified through the evaluation of the microstrip antenna parameters such as, gain, bandwidth, VSWR, return loss S11, directivity and ration pattern operating at 28 GHz. Comparison between measured and simulated results with both techniques reveals that the FIT better for all types of microstrip antennas patch shapes whereas FEM is only reliable for rectangular microstrip antennas shape due to its regularity in its configuration. In addition, a good agreement between the results of the proposed antenna parameters with previously research works operating at the same frequency are also identified. Beside of this, our proposed antenna has the advantage of small size of the order of (5.2 mm3) which is compact and suitable for the 5 G wireless communication system applications. Furthermore, with this small profile configuration, the antennas still provide high radiation performance with a bandwidth of the order of (900 MHz), gain of (6 dB) and directivity of the order of (7 dB).
NSTL
Elsevier