Current Issue : April - June Volume : 2021 Issue Number : 2 Articles : 5 Articles
GPU cards have been used for scientific calculations for many years. Despite their ever-increasing performance, there are cases where they may still have problems. This article addresses possible performance and memory issues and their solutions that may occur during GPU calculations of iterative algorithms. Specifically, the article focuses on the optimization of transient simulation of extra-large highly nonlinear time-dependent circuits in SPICE-like electronic circuit simulator core enhanced with NVIDIA/CUDA (Compute Unified Device Architecture) interface and iterative Krylov Subspace methods with emphasis on improved accuracy. The article presents procedures for solving problems that may occur during this integration and negatively affect either the simulation speed or the accuracy of the calculation. Finally, a comparison of the implementation of an iterative calculation procedure with the use of GPU cards, calculation by the direct method and calculation on the CPU only is presented....
The outdoor wind environment is one of the most important factors influencing the biological environment and human comfort. The campus of China University of Mining & Technology (Beijing) (CUMTB) is the case study for this research. PHOENICS simulation software was used to carry out a numerical simulation study of the outdoor wind environment. The pedestrian-level wind (PLW) environments for both winter and summer were investigated. Based on the numerical simulation results, the overall evaluation and subregional analysis of the campus’ current outdoor wind environment were carried out. Then, according to the results and problems of wind environment assessment, improvement measures and strategies of outdoor wind environment in universities are proposed from the aspects of campus planning, single building form, and greening configuration. The main goal is to further improve the outdoor space and environment of universities in Beijing and provide general guidelines to improve the quality of the universities’ wind environment effectively. The strategies can provide a reference for the same type of campus on wind environment renovation and improvement. This study can also provide data support and reference significance for outdoor thermal environment/pedestrian environment research....
With the constant expansion of the building sector as a major energy consumer in the modern world, the significance of energy-efficient building systems cannot be more emphasized. Most of the buildings are now equipped with an electric dashboard to record consumption data which presents a significant scope of research by utilizing those data in energy modeling. This paper investigates conventional regression modeling in building energy estimation and proposes three models with data classifications to improve their performance. The proposed models are regression models and an artificial neural network model with data classification for predicting hourly or sub-hourly energy usage in four different buildings. Energy data is collected from a building energy simulation program and existing buildings to develop the models for detailed analysis. Data classification is recommended according to the system operating schedules of the buildings and models are tested for their performance in capturing the data trends resulting from those schedules. Proposed regression models and an ANN model with the recommended classification show very accurate results in estimating energy demand compared to conventional regression models. Correlation coefficient and root mean squared error values improve noticeably for the proposed models and they can potentially be utilized for energy conservation purposes and energy savings in the buildings....
The new type of marine asynchronous shaft generator has the advantages of adjustable excitation and power factor, compared to the traditional synchronous shaft generator, and has been widely used. However, the traditional synchronous shaft generator simulation system is still used in domestic ship power station simulators, which seriously restricts the renewal of crew training. In order to overcome the shortage of the simulation system of doubly fed shaft generator for ship power plant simulator, in this paper, the mathematical model of marine doubly fed shaft system is established for the first time, according to the characteristics of doubly fed machine and marine shaft generator. This paper realizes power decoupling by stator flux orientation and simulates and analyses the asynchronous shaft generator under subsynchronous working conditions. The changing trend of each physical quantity in the simulation waveform meets the mathematical relationships of the actual physical quantity, which proves the correctness of the mathematical model and lays a theoretical foundation for the development of the simulation system of asynchronous shaft generator....
Thermophotovoltaic (TPV) systems generate electricity without the limitations of radiation intermittency, which is the case in solar photovoltaic systems. As energy demands steadily increase, there is a need to improve the conversion dynamics of TPV systems. Consequently, this study proposes a novel radiation-thermodynamic model to gain insights into the thermodynamics of TPV systems. After validating the model, parametric studies were performed to study the dependence of power generation attributes on the radiator and PV cell temperatures. Our results indicated that a silicon-based photovoltaic (PV) module could produce a power density output, thermal losses, and maximum voltage of 115.68W cm−2, 18.14Wcm−2, and 36 V, respectively, at a radiator and PV cell temperature of 1800 K and 300 K. Power density output increased when the radiator temperature increased; however, the open circuit voltage degraded when the temperature of the TPV cells increased. Overall, for an 80WPV module, there was a potential for improving the power generation capacity by 45% if the TPV system operated at a radiator and PV cell temperature of 1800 K and 300 K, respectively. The thermal efficiency of the TPV system varied with the temperature of the PV cell and radiator....
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