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- 实验方案
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Misfit-Dislocation Distributions in Heteroepitaxy: From Mesoscale Measurements to Individual Defects and Back
摘要： We provide an in-depth characterization of the dislocation distribution in partially relaxed Si0.92Ge0.08/Si(001) films. This is achieved by an innovative and general method, combining two state-of-the-art characterization techniques through suitable modeling. After having inferred the dislocation positions from transmission-electron-microscopy images, we theoretically reproduce scanning-x-ray-diffraction-microscopy tilt maps measured on the very same region of the sample. We obtain a nearly perfect match between model predictions and experimental data. As a result, we claim that it is possible to establish a local, direct correlation between the dislocations revealed by the transmission-electron-microscopy analysis and the measured lattice tilt distribution.
关键词： heteroepitaxy,dislocation distribution,scanning x-ray diffraction microscopy,transmission electron microscopy,lattice tilt distribution
更新于2025-09-23 15:21:01
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Theoretical model and experimental analysis of non-uniform material removal during full-aperture polishing
摘要： Full-aperture polishing is a key process in the fabrication of large flat optical elements with a high-precision surface figure. Controlling of the surface figure, which is primarily dependent on the material removal distribution, during the polishing process is challenging. In this study, a novel model is proposed to calculate the material removal distribution and the resultant surface figure. The model determines the material removal amount of points on the workpiece by considering the kinematic parameters and pressure distribution along the sliding trajectory relative to the pad. Moreover, the pressure distribution during the polishing process is acquired from the mechanical and morphological characteristic of polishing pad. With this model, the final surface figures under several polishing conditions were simulated and were found to be in close agreement with the experimental results.
关键词： Full-aperture polishing,Surface figure,Pressure distribution,Material removal distribution
更新于2025-09-23 15:21:01
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BER Performance Analysis of an Orthogonal FDM Free Space Optical Communication System with Homodyne Optical Receiver over Turbulent Atmospheric Channel
摘要： Atmospheric turbulence induced fading may severely impair free-space optical (FSO) communication systems, affecting the quality of the propagated laser beam and lead to significant performance degradation. Recent research works reveal that performance can be improved by using orthogonal FDM. In this paper, an analytical approach is presented to evaluate the bit error rate performance of an OFDM FSO link with optical intensity modulation and coherent homodyne receiver taking into consideration the effect of strong atmospheric turbulence. The turbulence effect is modeled as gamma-gamma distribution and the performance results are evaluated in terms of average CNR and BER. Power penalty suffered by the system due to the effect of turbulence at a given BER is evaluated for several system parameters viz. link distance, local oscillator turbulence parameter, power etc. It is noticed that effect of turbulence can be significantly reduced by increasing the number of OFDM subcarrier. For example, power penalty for BER of 10–9 at a link distance of 3,600 m is 6 dB when number of subcarrier is 4 and can be reduced to 0.5 dB by increasing the number of subcarrier to 64. In addition, by utilizing coherent optical receiver and synchronous demodulation at the receiving end, we have introduced local oscillator (LO) for both Optical and RF state which have ability to track the signal’s phase changes over time relative to the LO’s phase and helps the system to remain stable.
关键词： subcarrier multiplexer,carrier to noise ratio (CNR),coherent optical receiver,free space optical (FSO) communication,gamma-gamma distribution
更新于2025-09-23 15:21:01
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Data-driven uncertainty analysis of distribution networks including photovoltaic generation
摘要： This paper investigates residential distribution networks with uncertain loads and photovoltaic distributed generation. An original probabilistic modeling of consumer demand and photovoltaic generation is presented that is based on the analysis of large set of data measurements. It is shown how photovoltaic generation is described by complex non-standard distributions that can be described only numerically. Probabilistic analysis is performed using an enhanced version of the Polynomial Chaos technique that exploits a proper set of polynomial basis functions. It is described how such functions can be generated from the numerically available data. Compared to other approximate methods for probabilistic analysis, the novel technique has the advantages of modeling accurately truly nonlinear problems and of directly providing the detailed Probability Density Function of relevant observable quantities affecting the quality of service. Compared to standard Monte Carlo method, the proposed technique introduces a simulation speedup that depends on the number of random parameters. Numerical applications to radial and weakly meshed networks are presented where the method is employed to explore overvoltage, unbalance factor and power loss, as a function of photovoltaic penetration and/or network configuration.
关键词： Photovoltaic generation,Data-driven models,Polynomial chaos,Unbalanced distribution networks,Probabilistic load flow,Uncertainty Analysis
更新于2025-09-23 15:21:01
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[IEEE 2019 4th International Conference on Information Technology, Information Systems and Electrical Engineering (ICITISEE) - Yogyakarta, Indonesia (2019.11.20-2019.11.21)] 2019 4th International Conference on Information Technology, Information Systems and Electrical Engineering (ICITISEE) - The Mapping of Lighting Intensity from the Light Distribution on LED and CFL Lamps
摘要： Electricity is an essential need for humans, specifically for the lighting function. Lighting is needed to aid humans visually perceive objects in areas that require lighting, both at night and during the day. At this day, there are two type of lamps that are extensively employed, paticularly the type of Light-Emitting Diode (LED) and Compact Fluorescent Lamp (CFL). The adoption of lights in an area takes a lot of energy, so it is particularly crucial to choose the appropriate type of lamp that is adequate to perform effectively and efficiently. To determine the light distribution of the two types of lights, it is crucial to investigate the distribution of light. The investigation was carried out by the direct measurement technique on 6 and 8 watt LED lamps, as well as on CFL lamps 11 and 14 watt using luxmeter in an area projecting 3x4 meters. The analysis range is varied in several horizontal and vertical points. From the assessment results it was noticed that the LED and CFL lamps the value of the light intensity reduces if the horizontal and vertical distance of the measurement point are far from the lamp. The ends of the light distribution mapping discovered that the light distribution on the LED lights is better indeed and brighter at each point. This is because all the electrons recombine with holes. Whereas in the CFL lamp there has been a filament heating and ionization between the electrons with argon gas and mercury vapor which generates another energy which is relatively large heat energy.
关键词： CFL,Light Distribution,Lighting Intensity,Mapping,LED
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - System Level Assessment of the Impact of High Penetration of PV Inverters with Grid Support Capability on Distribution Networks
摘要： Power systems simulations using PSCAD have been performed to evaluate the impact to the distribution grid of high photovoltaic (PV) penetration. Voltage regulation at load nodes, feeder short-circuit currents and power losses have been analyzed for penetration level up to 60% and compared with a baseline case referring to as no PV. Results show that high PV penetration impacts residential area and non-residential area networks differently. Also, depending on the grid strength, the performance of the network is different. PV micro-inverters, in some cases, can prevent voltage excursion beyond tolerance limits however, they are more effective for power losses reduction. Overall, up to 15% in energy losses can be saved at very high penetration levels. Regarding the short-circuit levels no adjustment in the network infrastructures is required as the PV systems will have inconsequential contribution in feeder short-circuit currents.
关键词： power distribution,Power conversion,Photovoltaic power systems
更新于2025-09-23 15:21:01
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Multipoint Nanolaser Array in an Individual Core-Shell CdS Branched Nanostructure
摘要： Nanoscale laser arrays are attractive for their potential applications in highly integrated nanodevices, which are always obtained by nanowire arrays with complicated fabrication techniques. Here, a quite different nanolaser array is successfully realized based on a highly ordered core–shell CdS branched nanostructure with implanted Sn nanoparticles in junctions that split the individual multichannel nanostructures to various microcavities with effective light confinement and oscillation, thus to achieve a multipoint nanolaser array. Under the excitation of an ultraviolet laser, the strong band-edge emission can be well reflected between Sn nanoparticles at junctions and effectively scattered into branch segments due to Sn nanoparticles existence in junctions, furthermore oscillating in various microcavities along trunks or branches to form multipoint lasing from Fabry-Pérot (F-P) mode with a quality factor up to 990 and the low threshold at around 3.78 MW cm?2. The corresponding fluorescent microscope images further demonstrate the formation of multipoint F-P lasing at various segments. The theoretical simulation indicates that implanted Sn nanoparticles work as hot point to enhance the confinement of light around the Sn centers. The existence of surface plasmon from the Sn metal particles is further confirmed by the polarization dependent photoluminescence measurement. The results provide a new way to realize nanolaser arrays.
关键词： core–shell structures,CdS branched nanostructure,nanolaser arrays,electric field distribution
更新于2025-09-23 15:21:01
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Development of threea??phase unbalanced power flow using local control of connected photovoltaic systems
摘要： With the increased number of installations of distributed photovoltaic (PV) systems within electricity distribution systems, power flow analysis is required to handle multiple PV systems. At present, PV systems are equipped with a local control function (LCF). The conventional algorithm is then applied for power flow analysis with the LCF of each PV system, where the power output of LCF of each PV system is calculated and used in the power flow calculation. The conventional algorithm is terminated when the voltage at each iteration of the power flow algorithm is converged. However, the conventional algorithm inevitably requires a lengthy calculation. This paper proposes a power flow algorithm that applies the Newton–Raphson technique to handle multiple PV systems with an LCF for a faster calculation. The LCF is approximated to have a continuous characteristic. The developed power flow algorithm can be used for a three-phase unbalanced distribution system and its effectiveness was demonstrated in a modified 19-node distribution system.
关键词： PV system,local control function,power flow algorithm,three-phase unbalanced distribution system
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Power & Energy Society General Meeting (PESGM) - Atlanta, GA, USA (2019.8.4-2019.8.8)] 2019 IEEE Power & Energy Society General Meeting (PESGM) - A New Remote Tap Position Estimation Approach for Open-Delta Step-Voltage Regulator in a Photovoltaic Integrated Distribution Network
摘要： We describe the general concept and practical feasibility of a dc-based open energy system (OES) that proposes an alternative way of exchanging intermittent energy between houses in a local community. Each house is equipped with a dc nanogrid, including photovoltaic panels and batteries. We extend these nanogrids with a bidirectional dc–dc converter and a network controller so that power can be exchanged between houses over an external dc power bus. In this way, demand-response fluctuations are absorbed not only by the local battery, but can be spread over all batteries in the system. By using a combination of voltage and current controlled units, we implemented a higher-level control software independent from the physical process. A further software layer for autonomous control handles power exchange based on a distributed multiagent system, using a peer-to-peer like architecture. In parallel to the software, we made a physical model of a four-node OES on which different power exchange strategies can be simulated and compared. First results show an improved solar replacement ratio, and thus a reduction of ac grid consumption thanks to power interchange. The concept’s feasibility has been demonstrated on the first three houses of a full-scale OES platform in Okinawa.
关键词： microgrid,power transmission,power system control,dc interconnected power system,smart grid,dc power distribution,DC–DC converter
更新于2025-09-23 15:21:01
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Phase-locked Strategy of Photovoltaic Connected to Distribution Network with High Proportion Electric Arc Furnace
摘要： With the rapid development of industrialization, the proportion of electric arc furnaces (EAF) in distribution networks is getting higher and higher. Aiming at the problem that grid voltage is distorted by a large number of arc furnace nonlinear loads accessing to distribution networks, it is crucial to make dynamic analysis of distribution network voltage and adopt a control strategy of grid-connected converter based on the new phase-locked loop (PLL) technology. As a result, the harmonic distortion rate is reduced and the quality of grid-connected current and voltage is improved. In this paper, photovoltaic (PV) system model and the typical dynamic model of the EAF are established. By analyzing the influence of the EAF model on the PV grid-connected converter with the traditional phase-locked loop while connected to distribution network, a control strategy of the PV grid-connected converter with the self-adjusting double SOGI (MAF-SASOGI) phase-locked loop with the ideal low-pass filter is proposed. Through the simulation analysis, it is verified that precise phase locked can be realized and harmonic content of the system can be reduced by the PLL strategy proposed in this paper. Therefore, the quality of PV grid-connected voltage and current is improved.
关键词： Electric arc furnaces (EAF),Photovoltaic(PV) grid-connected,Voltage distortion,Distribution network,Phase-locked strategy
更新于2025-09-23 15:21:01