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[IEEE 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Orlando, FL, USA (2019.6.23-2019.6.29)] 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Wide Bandgap Photoconductive Switches Driven by Laser Diodes as a High-Voltage Mosfet Replacement for Bioelectrics and Accelerator Applications
摘要： We systematically study the analysis and simulation of ac-biased superconductor transition-edge sensor (TES) circuits. In these ac-biased circuits, the current and voltage of the TES experience large swings in both directions, and small-signal analysis around a dc steady state does not apply. To understand their electrical and thermal behavior, we rely on concepts and techniques from radio-frequency circuit simulation and introduce the periodic steady state and perform periodic ac analysis. We also construct TES device models based on a comprehensive two-?uid physical model and investigate the behavior of ac-biased TES circuits using advanced circuit simulators. By relating our ?ndings to results for the analysis of dc-biased TES circuits, we give appropriate de?nitions for the current and temperature sensitivity of the TES in ac-biased circuits. Our work not only builds a rigorous foundation for theoretical analysis of ac-biased TES circuits but also introduces powerful simulation techniques valuable for their design and research.
关键词： Circuit analysis,computer simulation,superconducting devices
更新于2025-09-19 17:13:59
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Study on the maximum electric power supplied to copper bromide vapor lasers
摘要： Copper and copper-compound vapor lasers are most powerful in the visible spectrum with output power over 100 W. They offer unique properties including a laser beam with high coherence and convergence and high average output powers with relatively small dimensions. Recently, these lasers, and in particular the copper bromide (CuBr) laser, have been widely used as radiation sources and vapor brightness amplifiers in a new type of laser active optical systems, designed for the visual monitoring and control of fast processes shielded by intense background lighting. However, new problems arise with the development of such optical systems, related to the laser technology and the optimization of their operating parameters. Important operating characteristics of copper lasers include the input electric power and the gas temperature of the discharge. The upper limit of the laser power that can be supplied to the gas discharge is studied herein by considering the permissible thermal population thresholds of the lower level of the λ = 510.6 nm laser line. The application of enhanced analytical models based on a steady-state heat conduction equation and computer simulations enables the development of a methodology to determine the maximum possible electric power that can be supplied to the gas discharge, taking into account its radial distribution across the tube cross-section. This methodology is then applied to the case of an actual small-bore CuBr laser used as a brightness amplifier.
关键词： Copper vapor laser,Gas temperature,Copper bromide (CuBr) laser,Computer simulation,Laser active optical system,Heat conduction
更新于2025-09-19 17:13:59
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Nonradiative Energy Transfer in a??Colloidal Quantum Dot Nanoclustera??Dyea?? Hybrid Nanostructures: Computer Experiment
摘要： A computer model of nonradiative electronic excitation energy transfer from nanoclusters of colloidal quantum dots of cadmium selenide to the meso-tetra(3-pyridyl)porphyrin molecule in hybrid nanostructures nanocluster–dye has been constructed and analyzed. The model uses the experimental luminescence and absorption spectra of quantum dots and the dye, takes into account heterogeneity of the properties of quantum dots in nanoclusters and the different location of the dye in the hybrid structure. It has been shown that, in the ideal case, due to such energy transfer, the intensity of the luminescent signal of the dye can be increased by five orders of magnitude. However, this value is significantly reduced due to nonluminescent particles, the presence of a protective ligand shell, a large size distribution of the particles, and the non-optimal geometric structure of the hybrid system.
关键词： porphyrin dye,colloidal quantum dots,F?rster resonance energy transfer,hybrid systems,cadmium selenide,computer simulation
更新于2025-09-19 17:13:59
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Numerical modeling of carbon distribution and precipitation during directional solidification of photovoltaic silicon
摘要： Numerical modeling is used to investigate carbon distribution and precipitation in directional solidification of multicrystalline silicon. Computations are performed for samples of 6 cm in diameter grown in a Vertical Bridgman Freezing (VGF) system starting from silicon feedstock with different grades of contamination in carbon. The value of the unknown reaction rate coefficient governing the carbon precipitation in the silicon melt was estimated in the present work by comparing the numerically computed concentration profiles to the experimental results taken from the literature. Numerical results show that the growth rate has a significant influence on the interface deflection, melt convection and carbon precipitation. It is found that the silicon samples grown from the melts of low carbon contamination (< 1018 at/cm3) exhibit low content in SiC precipitates, even if they are solidified at high growth rates (1–2 cm/h). The samples with high initial carbon contamination (5 × 1018 at/cm3) should be solidified at much lower rates (0.2 cm/h) in order to avoid the formation of SiC precipitates.
关键词： Carbon transport and precipitation,Directional solidification,Impurities,Semiconducting silicon,Computer simulation
更新于2025-09-16 10:30:52
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Computer Simulation and Investigations of the Roof Mount Photovoltaic System
摘要： The interest in the renewable energy sources is increasing due to the depletion of the conventional energy sources and the environmental pollution. In this paper we present a computer simulation and investigations of the roof mounted photovoltaic system. The results of the generated power of the 5kW built-in photovoltaic system by months over a period of 5 years are presented. Depending on the meteorological conditions, the investigated photovoltaic system generates year-round energy necessary for the needs of the household.
关键词： computer simulation inverters,photovoltaic systems,Computational modeling
更新于2025-09-12 10:27:22
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Computer simulation for formation of critical spaces in II–VI solid solutions
摘要： Predicting of optimal properties of II–VI materials is an important task in solving the problems of micro- and nanoelectronics. Multicomponent solid solutions based on such semiconductors are promising for modern optoelectronics, for they allow creating devices that operate in a wide spectral range. However, under certain conditions multicomponent solid solutions lose their thermodynamic stability, and thus the properties of the devices based on such materials degrade. Modern methods of computer simulation are used to analyze processes of formation of self-organizing ordered structures. The authors use di?erential topological approach to obtaining multicomponent phase diagrams taking into account the possibility of existence of bifurcation spaces, critical spaces, and spaces of phase coexistence of di?erent orders.
关键词： Solid solutions,Computer simulation,Semiconducting II–VI materials,Phase diagrams,Alloys
更新于2025-09-11 14:15:04
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Exploring effective pedagogies using computer simulations to improve Grade 12 learners’ understanding of the photoelectric effect
摘要： The study aimed to determine the most effective of three pedagogies to improve Grade 12 learners’ understanding of the photoelectric effect when the teaching was done using chalk and talk, guided learning with computer simulations (CS) as a demonstration tool and semi-autonomous learning where the learners used the CS individually with limited support. A randomised pre-/post-test control group design was implemented. A paired-sample t-test on the post-test scores indicated that the guided learning experimental group (N =10) performed better than the semi-autonomous learning experimental group (N =10) [ t-statistics, t(9) = ?6.135, p < 0.05]. Even the control group (N = 10) where the teacher used chalk and talk performed better than the semi-autonomous learning experimental group. An analysis of covariance on the post-test scores with learners’ pre-test scores showed a signi?cant effect on the instructional group favouring the guided learning experimental group. It is, therefore, suggested that guided learning where the teacher manipulates the CS is a better method for the effective teaching of the photoelectric effect.
关键词： photoelectric effect,Einstein’s photoelectric equation,inquiry-based learning,constructivist theory,Computer simulation
更新于2025-09-10 09:29:36
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Computational design of microstructures of textured ferroelectric ceramics by phase field simulation
摘要： Grain-oriented microstructure evolutions of ferroelectric ceramics were analyzed using phase field simulations. In templated grain growth, the coarsening behavior of the template particle was investigated in detail. Although a large grain boundary energy was set in the lateral direction along the casting plane, the template particle grew mainly in the vertical direction and gradually converted from a needle-like to rectangular grain. We demonstrated a critical interval of template particles for the preparation of highly textured ceramics. Therefore, different microstructures with high degrees of texture could be fabricated by adjusting and controlling the template size and fraction. Complementary experiments were guided by the computational design. Dense ferroelectric ceramics with high degrees of texture were obtained.
关键词： Templated grain growth,Ferroelectric ceramic,Textured ceramic,Computer simulation
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE PES/IAS PowerAfrica - Cape Town (2018.6.28-2018.6.29)] 2018 IEEE PES/IAS PowerAfrica - Design of a Solar Powered Desalination Plant
摘要： Owing to the lack of perennial streams in the semi-desert to desert parts, two-thirds of South Africa’s surface area is largely dependent on groundwater. This ground water may at times be found to be brackish. Thus, hampering the development economy. A reliable water purification process would be an invaluable tool to those who do not have access to clean drinking water. This paper sets out to trade off this requirement of fresh water with the practical considerations of water quality, quantity, and the energy requirement of affected communities. The goal is to present a meaningful design of a water desalination unit for use in remote and water scarce parts of RSA. The desalination plant will be designed using an outcomes focused methodology and an estimated MATLAB model will be formulated.
关键词： Energy Conversion,Computer Simulation,Water Storage,Desalination,Solar Heating
更新于2025-09-09 09:28:46
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - Transfer Learning from Synthetic to Real Images Using Variational Autoencoders for Precise Position Detection
摘要： Capturing and labeling camera images in the real world is an expensive task, whereas synthesizing labeled images in a simulation environment is easy for collecting large-scale image data. However, learning from only synthetic images may not achieve the desired performance in the real world due to a gap between synthetic and real images. We propose a method that transfers learned detection of an object position from a simulation environment to the real world. This method uses only a significantly limited dataset of real images while leveraging a large dataset of synthetic images using variational autoencoders. Additionally, the proposed method consistently performed well in different lighting conditions, in the presence of other distractor objects, and on different backgrounds. Experimental results showed that it achieved accuracy of 1.5mm to 3.5mm on average. Furthermore, we showed how the method can be used in a real-world scenario like a “pick-and-place” robotic task.
关键词： variational autoencoder,transfer learning,position detection,deep learning,computer simulation
更新于2025-09-09 09:28:46