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- 摘要
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- 实验方案
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Fourier Optics of Fractal Structures
摘要： The scaling characteristics of Fourier spectra of fractal structures are determined. Their stability and influence on cognitive processes associated in particular with the aesthetic aspects of perceiving objects with self-similarity criteria are estimated. Evidence of their heuristic importance for Fourier analysis results is presented using an example in which the properties of aperiodic multilayer structures and chaotic processes are considered.
关键词： scaling characteristics,fractal structures,aperiodic multilayer structures,Fourier optics,cognitive processes,chaotic processes
更新于2025-09-04 15:30:14
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A revisit to atomic layer deposition of zinc oxide using diethylzinc and water as precursors
摘要： Nanophase zinc oxide (ZnO) has been widely studied as an important multi-functional material in many applications. Atomic layer deposition (ALD) is a unique thin-film synthesis technique, featuring its extreme uniformity, unrivaled conformal coverage, low deposition temperature, and precise controllability. Using diethylzinc (DEZ) and water as precursors, ALD has been reported previously for growing nanophase ZnO thin films. However, the growth characteristics and the resultant ZnO crystallinity have not been well characterized and understood. To this end, we revisited the ALD process of ZnO using DEZ and water. Through employing a suite of advanced characterization techniques, we systematically addressed the growth characteristics, morphological changes, and the crystallinity evolution of ZnO along with growth temperature in the range of 30–250 °C. The growth characteristics of the ALD ZnO films were investigated using in situ quartz crystal microbalance (QCM), scanning electron microscopy, atomic force microscopy, and synchrotron-based X-ray reflectivity. The crystallinity of the ALD ZnO films was determined using synchrotron-based X-ray diffraction and high-resolution transmission electron microscopy. In addition, through further analyzing QCM data, we proposed the adsorption-limited surface reaction for ALD ZnO growth with the temperature-dependent number of –OH surface group reacting with one DEZ molecule. Thus, this study contributes to offer new and deep insights on the fundamental ALD process of ZnO.
关键词： Atomic layer deposition,Water,Diethylzinc,Crystallinity,Zinc oxide,Growth characteristics
更新于2025-09-04 15:30:14
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Performance of resonant tunneling diodes based on the nonpolar-oriented AlGaN/GaN heterostructures
摘要： The performance of resonant tunneling diodes (RTDs) based on nonpolar-oriented AlGaN/GaN heterostructures has been theoretically investigated by numerical simulation. Simulation results show that the RTDs grown along the nonpolar orientation can yield the current–voltage (I–V ) characteristics with the peak current, the peak-to-valley ratio (PVCR), and the peak voltage of about 3.5 times and 1.5 times higher and 1.1 times lower than those of RTDs grown along the conventional polar orientation, respectively. The results also show excellent symmetry, high reproducibility of I–V characteristics, and high intrinsic response frequency.
关键词： current–voltage characteristics,resonant tunneling diodes,numerical simulation,AlGaN/GaN heterostructures,nonpolar orientation
更新于2025-09-04 15:30:14
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Load-Independent Wireless Power Transfer System for Multiple Loads Over a Long Distance
摘要： In this paper, a novel long-distance wireless power transfer (WPT) system using repeater coils is proposed to provide power supplies for the driver circuits in high voltage applications such as flexible alternative current transmission systems (FACTS). Different from most of the existing wireless repeater systems where the load is only connected to the last coil and the repeater coils function solely as power relays, in the proposed system, multiple loads are powered by the repeaters. The repeater coils transfer power not only to the subsequent coils but also to the loads connected to them. Dual coil design is proposed for the repeaters with which load-independent characteristics are obtained with a suitable design of coupling coefficients. As a result, the load power can be easily adjusted without affecting each other. Load current characteristics and system efficiency have been analyzed in detail. The power transfer capability of the proposed system is illustrated for different coil quality factors and coupling coefficients. An experimental setup with 10 loads has been built to validate the effectiveness of the proposed long-distance WPT system. The maximum reachable system efficiency is about 84%.
关键词： dual coil design,Wireless power transfer (WPT),constant load characteristics,current independent,long distance
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Non-linear Input Capacitance Determination of WBG Power FETs using Gate Charge Measurements
摘要： This paper discusses the measurement of the input capacitances Cgs and Cgd of SiC and GaN power FETs in order to implement simulation models with an improved mapping of the drain-source voltage vds and drain current id during the switching operation. Based on the gate charge characteristic measured at an inductive load condition using different drain current values and temperature settings, the gate current is allocated to the charging of the gate-drain capacitance Cgd and the gate-source capacitance Cgs. With this approach the capacitance characteristics Cgs(vgs) and Cgd(vgd) are determined in the full operating range of the gate-source voltage vgs and gate-drain voltage vgd.
关键词： wide-bandgap semiconductors,Inter-electrode capacitances,dynamic measurements,cgs,capacitance-voltage characteristics,cgd
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL) - Padua (2018.6.25-2018.6.28)] 2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL) - Characterization and Modeling of the Impact of the Substrate Potential in the Dynamic and Static Behavior of Power GaN-on-Si HEMTs
摘要： The maturity of GaN power transistors grown on conductive Si substrates permits today the integration of gate drivers and half bridges in a monolithic integrated chip. Among others, the back-gating effect arising from the substrate potential poses a challenge for circuit designers and hinders the development of this promising technology. In this paper, we characterize the effect of the substrate potential in the IV characteristics of a commercially available GaN power HEMT. A modified version of the ASM-HEMT compact transistor model which accounts for the effect of the substrate potential on IV and part of the CV characteristics is extracted from these measurements. Through transient simulations of the fitted transistor model, the impact of the bulk potential in the dynamic and static characteristics of power GaN-on-Si HEMTs is investigated.
关键词： substrate potential,power semiconductor device,semiconductor device modeling,Gallium Nitride,current-voltage characteristics,HEMTs
更新于2025-09-04 15:30:14
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[IEEE 2018 Global Smart Industry Conference (GloSIC) - Chelyabinsk, Russia (2018.11.13-2018.11.15)] 2018 Global Smart Industry Conference (GloSIC) - Diagnostics of External Defects of Railway Infrastructure by Analysis of its Images
摘要： An important component of the safe movement of the railway transport is the absence of visible rail defects. The external defects of the track infrastructure were analyzed according to the criteria of detection accuracy and the conditions of applicability of the methods of their detection. For the diagnostics of the railway track, a passive defectoscopy method, based on stereo vision and blur analysis, is proposed. This system can be implemented in a hardware-software control system and is located on ground transport-technological devices.
关键词： railway track,kinematic characteristics,stereo vision,image blur,distance estimation,control system,depth of field,video monitoring
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Substrate Bias Effect on E-Mode GaN-on-Si HEMT Cos<inf>s</inf> Losses
摘要： Previous work found large COSS losses in GaN-on-Si HEMTs used in soft-switched, MHz-frequency power converters. Here, we use a back-gate bias between the source and Si substrate to investigate the capacitance characteristics of commercially-available GaN HEMTs. The small-signal capacitance is reduced significantly – up to 2× for a 650 V HEMT and 4× for a 100 V HEMT – indicating that the drain-substrate capacitance is a significant portion of the total output capacitance. This portion of the capacitance appears responsible for trapping-detrapping with time constants on the order of seconds. We verify this by testing the 100 V GaN HEMT in the Sawyer-Tower circuit with negative substrate bias, finding that COSS losses are reduced by up to 30% compared to the shorted substrate condition.
关键词： Sawyer-Tower circuit,COSS losses,capacitance characteristics,GaN-on-Si HEMTs,substrate bias
更新于2025-09-04 15:30:14
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Intraoperative OCT imaging of the Argus II retinal prosthesis and its clinical significance
摘要： To report the clinical, multimodal imaging and genetic characteristics of patients with Enhanced-S-cone syndrome (ESCS) in a Tunisian cohort. Methods: Descriptive clinical and genetic study including patients with inherited retinal dystrophies who consulted the oculogenetics laboratory LR14SP01, at Hedi Rais Institute of ophthalmology. Results: A total of 9 patients from 6 consanguineous families were diagnosed with ESCS based on typical clinical and ERG abnormalities. All patients complaint from hemeralopia since childhood. Visual acuity ranged from light perception to 4/10. Fundus examination revealed variable abnormalities with radial yellow dots in the posterior pole in two patients, nummular yellow dots in one patient, minimal pigmentary changes along the arcades in five patients, nummular pigment clumping in 3 patients and peripheral retinal atrophy in one patient. One patient had macular atrophy and 8 had macular cysts confirmed by SS-OCT. Genetic analysis was contributive in 7 patients and revealed NR2E3 mutations in 5 patients and NR2E3 + RHO digenism in two patients from the same family. Conclusions: This is to our knowledge the first report on a Tunisian cohort with ESCS. The phenotype in ESCS is highly variable and multimodal imaging may help to the diagnosis in addition to electrophysiology results.
关键词： genetic characteristics,ESCS,multimodal imaging,Enhanced-S-cone syndrome,Tunisian cohort
更新于2025-09-04 15:30:14