- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Recent Problems of Heat-Transfer Simulation in Technological Processes of Selective Laser Melting and Fusion
摘要： The thermal processes arising upon the implementation of the additive technologies of selective laser melting and the fusion of metals and alloys are analyzed. An adequate description of the heat transfer upon the implementation of additive technological processes associated with high-intensity local heating by a moving laser beam and the phase transitions generated by a semifinished powder product, crystallization, and the concomitant effects in the growing element is the key to gaining insight into the microstructure and the efficient properties of the obtained material and the prevention of residual deformation (shrinkage) of the item. Currently, the main causes of unpredictable production defects are deviations of the shape of the final item from the preset geometry and high-amplitude residual stresses, which can initiate destruction of the item under loads significantly lower than those calculated, as well as the occurrence of the microscopic defects (pores, layer interfaces, etc.) are. The development of mathematical models that, on the one hand, are sufficiently accurate to predict the listed phenomena and, on the other hand, allow practical implementation in engineering calculations is the basis for the further development of the laser-melting and fusion of metal materials. At the same time, analysis of the current state of the problem shows that development of efficient numerical methods providing acceptable computational costs while maintaining accuracy is the key element in the practical implementation of the models. A method based on multiscale, interconnected modeling of the mechanical and the thermal state of the growing body—at the local level in the melt pool domain, at the intermediate level in the vicinity of the melt pool and the adjacent layers, and at the level of the entire product as a whole—seems to be efficient; here, the computing process at the global level can be based on a combination of the finite-element method (indisputable in practice) and analytical calculations providing local refinement of the solution.
关键词： numerical methods,heat-transfer simulation,microstructure,residual deformation,mathematical models,fusion,thermal processes,selective laser melting,additive technologies
更新于2025-09-23 15:19:57
-
Efficient predictive models for characterization of photovoltaic module performance
摘要： This paper presents simple, e?cient and general mathematical models for predicting the I-V characteristics of any Photovoltaic (PV) module at any irradiance and temperature values without any need to estimate the parameters of the PV circuit model. The prediction of the I-V characteristics in this paper is mainly dependent on building general mathematical models for ten key points selected from the I-V characteristics. To generalize these models and make them applicable for any PV module, twenty di?erent PV modules covering a wide range of PV modules with di?erent temperature and irradiance values are selected for training data generation. All simulations are performed in MATLAB/SIMULINK. The training process and models development are built using EUREQA software. The performance of the developed models is tested by comparison with simulation data, experimental data, and di?erent recent research articles. The assessments have shown e?cient prediction capability of all models to predict the I-V curves for any PV module, at any weather condition, without evaluating the PV circuit model parameters. The models have also exceeded various algorithms used in the literature in terms of accuracy of I-V characteristics estimation with less execution time.
关键词： MPP,I-V curve,Mathematical models,PV,EUREQA
更新于2025-09-23 15:19:57
-
[Springer Series on Atomic, Optical, and Plasma Physics] Gaseous Ion Mobility, Diffusion, and Reaction Volume 105 || Ab Initio Calculations of Transport Coefficients
摘要： There are two main philosophies behind theoretical calculations. The one illustrated in Chap. 9 is to use models of physical phenomenon, specifically mathematical models, that can be solved exactly, either analytically or by numerical methods. Such models often involve adjustable parameters whose values are fit by comparing model results to experimental values; once the parameters are determined, the models are then used to make similar calculations for other situations, ones that were not part of the set used to determine the parameters. The philosophy illustrated in this chapter is to start from our best theories and, as necessary, make approximations to reduce the equations to forms that are practical to solve, again either analytically or numerically. The hope is that, with time, the approximations will improve such that the calculated values match experimental results without using adjustable parameters. In short, the first philosophy is to make exact calculations with approximate theories, while the second is to make approximate calculations with theories that one believes to be exact.
关键词： experimental results,approximations,mathematical models,adjustable parameters,theoretical calculations
更新于2025-09-23 15:19:57
-
The Method of Integral Equations in Problems of Wave Diffraction in Waveguides
摘要： This paper studies the propagation of steady-state oscillations in an irregular rectangular waveguide. The irregularity of the waveguide is caused by the presence inside it of a metallic inclusion in the form of a cylindrical inductive cylinder. To solve the problem in a complete electrodynamic formulation, it is necessary to investigate the boundary problem for the system of Maxwell equations. To study the waveguide system consisting of a waveguide with a well-conducting inclusion, the method of integral equations was applied. The cores of the integral equations are defined through the Green functions of the unfilled waveguide, written in terms of the waveguide modes. Algorithms for their calculation are developed on the basis of the selection of a logarithmic singularity, and algorithms for summing up the series belonging to them are created. The possibilities of the method of integral equations are illustrated with examples of calculating the reflection and transmission coefficients from inductive pins.
关键词： numerical results,mathematical models,reflection and transmission coefficients of the electromagnetic field,rectangular waveguide,integral equations,inductive cylinder
更新于2025-09-19 17:13:59
-
Solar Engineering of Thermal Processes, Photovoltaics and Wind || System Thermal Calculations
摘要： In Chapters 6 through 9 we have developed mathematical models for two of the key components in solar energy systems: collectors and storage units. In this chapter we show how other components can be modeled and how the component models can be combined into system models. With information on the magnitude and time distribution of the system loads and the weather, it is possible to simultaneously solve the set of equations to estimate the thermal performance of a solar process over any time period. These estimates (simulations) are usually done numerically and provide information on the expected dynamic behavior of the system and long-term integrated performance.
关键词： mathematical models,solar energy systems,simulations,thermal performance,collectors,storage units
更新于2025-09-16 10:30:52
-
Bioelectrochemical Interface Engineering || Quantum Dots for Bioelectrochemical Applications
摘要： In this chapter, the structure, characteristics, and synthesis processes of QDs were summarized. The most common electrochemical methods for QDs were also represented by reviewing their potential applications in biosensor technology. Many specific applications have been realized by utilizing the unique characteristics of QDs. However, their limited commercial availability; requirements of demanding synthesis procedures, analysis of multicomponent complex samples, and in situ analysis; and lack of validation with real samples are other disadvantage of QDs. The design of QD-based biosensors is also complicated due to limitedly defined redox behavior of nanocrystals resulting in difficulty with probing their redox levels. Therefore, extensive investigations are needed on the redox properties of QDs, despite having a large amount of literature on their synthesis, properties, and applications. The interactions between the system parameters can be clarified by using the mathematical models. To solve the model equations analytically, it is introduced to equivalent systems having identical spectra and wave functions, and these forms have to satisfy the solvability conditions. 3D QDs can be modeled by an ODE accurately, when the dimension of the cross section is very small and the energy levels are low. To obtain high accuracy of the effective mass approximation model, sizes of the QDs should be 10–20 nm. Optimum design problems for QD systems generally have discrete search spaces and involve highly nonlinear terms. Therefore, the selection of any traditional optimization methods to solve optimization problems is not appropriate. In these circumstances, it is useful to perform modern optimization algorithms such as the GA, DE, and SA methods. By incorporating mathematical models and optimization approximations to QD-based bioloelectrochemical systems, their performances will excel far beyond the current state in the near future.
关键词： Optimization Algorithms,Mathematical Models,Bioelectrochemical Applications,Electrochemical Methods,Biosensor Technology,Quantum Dots
更新于2025-09-11 14:15:04