- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGe <sub/><i> <i>n</i> </i> </sub> S <sub/> 2( <i> <i>n</i> </i> +1) </sub> ( <i>n</i> = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications
摘要： AgGaGenS2(n+1) crystal is a series of quaternary for mid-IR laser applications of nonlinear optical materials converting a 1.064 μm pump signal (Nd:YAG laser) to 4?11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with di?erent cooling processes. High-resolution X-ray di?raction analysis and re?nement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modi?ed Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20?40 mm length have been grown. We have discussed the structure and composition of AgGaGenS2(n+1) by XPS spectra and analyzed the three kinds of vibration modes of tetrahedral clusters by the Raman spectra. The Hall measurement indicates that the AgGaGenS2(n+1) single crystals are p-type semiconductor, and the carrier concentration decreases with the increasing n value. All the transmittances of as-grown AgGaGenS2(n+1) samples exceeds 60% in the transparent range, especially the transmittance of AgGaGe2S6, is up to 70% at 1064 nm, and the band gap of as-grown crystal increases from 2.85 eV for AgGaGe2S6 to 2.92 eV for AgGaGe5S12. After a thermal annealing treatment, the absorptions at 2.9, 4, and 10 μm have been eliminated, and the band gap changed into the range of 2.89?2.96 eV.
关键词： Hall measurement,nonlinear optical materials,thermal annealing treatment,vapor transport,AgGaGenS2(n+1),Bridgman method,Raman spectra,mid-IR laser applications,XPS spectra,mechanical oscillation method
更新于2025-11-14 15:27:09
-
Backward wave oscillation suppression study of the helix travelling wave tube
摘要： In this paper, the effect of backward wave oscillation (BWO) on helix slow wave structure performance for TWT has been described. In this paper both the cases tapered and untapered helix slow wave structure (SWS) have been analyzed, caused by BWO for high gain helix TWT. In house developed the one-dimensional (SUNRAY-1D) large signal analysis model has been used for stability analysis of the helix SWS. The analysis on backward wave amplifier gain has been carried out as a function of the taper parameter and frequency parameter. The position and nature of tapering also affect the electronic efficiency as well as the start oscillation current. Hence, position and nature of tapering have been optimized.
关键词： backward wave oscillation (BWO),support rods,instability,Slow wave structure (SWS)
更新于2025-09-23 15:23:52
-
Importance of electron correlations in understanding photoelectron spectroscopy and Weyl character of
摘要： We study the role of electron correlations in the presumed type-II Weyl semimetallic candidate γ-MoTe2 by employing density functional theory (DFT) where the on-site Coulomb repulsion (Hubbard U) for the Mo 4d states is included within the DFT+U scheme. We show that pure DFT calculations fail to describe important features of the light-polarization dependence of the angular resolved photoemission intensity which can be accounted for by including the role of the Hubbard U. At the same time, while pure DFT calculations cannot explain the angular dependence of the Fermi surface as revealed by quantum oscillation experiments (a fact which had raised doubt about the presence of the Weyl physics in γ-MoTe2), inclusion of such on-site Coulomb repulsion can. We find that while the number of Weyl points (WPs) and their position in the Brillouin zone change as a function of U, a pair of such WPs very close to the Fermi level survive the inclusion of these important corrections. Our calculations suggest that the Fermi surface of γ-MoTe2 is in the vicinity of a correlations-induced Lifshitz transition, which can be probed experimentally and its interplay with the Weyl physics might be intriguing.
关键词： electron correlations,Lifshitz transition,angular resolved photoemission,MoTe2,DFT+U,Hubbard U,quantum oscillation,Weyl semimetal,photoelectron spectroscopy
更新于2025-09-23 15:23:52
-
Simultaneous Fast Frequency Control and Power Oscillation Damping by Utilizing PV Solar System as PV-STATCOM
摘要： This paper presents a novel fast frequency response and power oscillation damping control by large-scale PV plants controlled as STATCOM, termed PV-STATCOM, to simultaneously enhance frequency regulation and small signal stability of power systems. Frequency deviations typically occur together with power oscillations in large power systems. The proposed controller comprises: i) Power Oscillation Damping (POD) controller based on reactive power modulation; and ii) Fast Frequency Response (FFR) controller based on real power modulation, both of which are applied to the plant level controller of PV-STATCOMs. The proposed composite control is shown to successfully reduce frequency deviations, damp power oscillations and provide voltage regulation both during over-frequency and under-frequency events. The proposed smart inverter control makes effective utilization of the PV inverter capacity and available solar power. For large power flows, the proposed control is shown to be superior than the conventional droop control recommended by North American Electric Reliability Corporation (NERC) for generating plants. Matlab/Simulink based simulations are conducted on two-area power system using generic PV plant dynamic models developed by Western Electricity Coordinating Council (WECC), for a wide range of system operating conditions. Such grid support functionality is expected to bring new revenue making opportunities for PV solar farms.
关键词： Power Oscillation Damping,Frequency control,Smart Inverters,Photovoltaic power plant
更新于2025-09-23 15:22:29
-
Emission of dispersed-type inorganic EL devices with frequency-variable high-voltage oscillation circuit
摘要： Dispersed‐type inorganic electroluminescent (EL) devices composed of a transparent electrode, a phosphor, a dielectric, and a back electrode were prepared under various conditions using a zinc sulfide (ZnS)‐based phosphor. Additionally, a voltage/frequency variable circuit was designed. A compact high‐voltage/frequency variable circuit including three modules for boosting, frequency conversion, and voltage conversion was designed. A 140 Vpp voltage and a frequency in the range of 270 Hz to 2.4 kHz can be controlled by this circuit. The emission has begun to be observed at a voltage about 60 Vpp and a frequency of 400 Hz, at a voltage about 40 Vpp and a frequency of 1.4 kHz, 2.4 kHz, respectively. The emission intensity increased with an increase in frequency; emission with a wavelength of 450 nm was strongly influenced by the frequency. The luminescence and the electrical properties were affected by the preparation conditions including device structures, dispersion of ZnS:Cu, and Cl particles because of the current path generated by defects in the EL cell.
关键词： inorganic,organic dye,electroluminescence,ZnS:Cu,Cl,oscillation circuit,driver circuit
更新于2025-09-23 15:22:29
-
Graphene field-effect transistors with high extrinsic fT and fmax
摘要： In this work, we report on the performance of graphene field-effect transistors (GFETs) in which the extrinsic transit frequency (fT) and maximum frequency of oscillation (fmax) showed improved scaling behavior with respect to the gate length (Lg). This improvement was achieved by the use of high-quality graphene in combination with successful optimization of the GFET technology, where extreme low source/drain contact resistances were obtained together with reduced parasitic pad capacitances. GFETs with gate lengths ranging from 0.5 μm to 2 μm have been characterized, and extrinsic fT and fmax frequencies of up to 34 GHz and 37 GHz, respectively, were obtained for GFETs with the shortest gate lengths. Simulations based on a small-signal equivalent circuit model are in good agreement with the measured data. Extrapolation predicts extrinsic fT and fmax values of approximately 100 GHz at Lg=50 nm. Further optimization of the GFET technology enables fmax values above 100 GHz, which is suitable for many millimeter wave applications.
关键词： field-effect transistor,scaling,graphene,maximum frequency of oscillation,transit frequency
更新于2025-09-23 15:22:29
-
Electric-Field Control of Dirac Two-Dimensional Electron Gas in PbTe/CdTe Heterostructures
摘要： Two-dimensional electron gases (2DEGs) confined to quantum wells trigger rich emergent phenomena and serve as a host for high-speed electronics. 2DEG in PbTe/CdTe heterostructure was predicted to be Dirac electrons and confirmed by recent experiments. Here, we demonstrate the manipulation of electrical transport properties of this 2DEG with extremely high mobility and unique electron structure by ionic liquid-gating. The extreme capacitance of carrier modulation enables to tune the band structure. With a change of the gate voltage, the Fermi level moves to the conduction band and crosses the Dirac Point, leading to the shift of quantum oscillation. Our results may offer new insight toward electronic application with on-demand properties.
关键词： Fermi surface,molecular beam epitaxy,ionic liquid gating,quantum oscillation,two-dimensional electron gas
更新于2025-09-23 15:22:29
-
A Light-activated Polymer Composite Enables On-demand Photocontrol of Biomimetic Swimming Towards Transportation at Liquid/Air Interface
摘要： Swimmers at liquid/air interface have drawn enormous attention for their potential applications while conventional devices face problems such as dependence on fuel, difficulty in motion control and accompanying high temperature. Herein, we show one novel light-driven swimmer based on bimorph composite structure of photoresponsive liquid-crystalline polymer network and commercially available polyimide (Kapton) whose motion is highly controllable with photoirradiation. The bilayer-structured film shows quickly photoinduced bending towards the Kapton side on exposure to UV light and recovers immediately after removal of light. When placed on liquid surface, the swimmer propels itself continually though rhythmic beating the liquid like a dolphin moving forward with its tail fin. Besides, light-powered rotation of the swimmer is successfully achieved by simply changing the length-width ratio and the irradiation site, mimicking the function of a dolphin’s pectoral fin. Combining the together, on-demand forward movement and rotation motion directional control of the photo-driven swimmer can be readily obtained at room temperature, showing promising for miniaturized transportation.
关键词： bionic motion,azobenzene,miniaturized transportation,light-driven device,photomechanical oscillation
更新于2025-09-23 15:22:29
-
[IEEE 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - Portland, OR, USA (2018.9.23-2018.9.27)] 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - Power Factor Operation of a Boost Integrated Three-Phase Solar Inverter using Current Unfolding and Active Damping Methods
摘要： This paper proposes a three-phase solar inverter with integrated boost function. The circuit operating principle is based on current unfolding and injection method. This approach requires only two high frequency switches for the boost function as well as shaping its output currents, thus leading to a significant reduction in switching losses. Other switches only operate at line frequency to unfold the output currents to sinusoidal three-phase currents, and thus can be optimized to reduce conduction losses. The proposed inverter therefore could deliver high efficiency. This paper discusses the basic operating principle and control method for the inverter. The paper proposes an active damping method to overcome intrinsic oscillation due to overlapping time in switching operation. It also shows that the inverter is capable of supplying reactive power up to a limit of 0.866 power factor. Stable operation of the proposed inverter is confirmed by both simulation and experiment.
关键词： current unfolding,active damping,three-phase inverter,oscillation
更新于2025-09-23 15:22:29
-
A Light-activated Polymer Composite Enables On-demand Photocontrol of Biomimetic Swimming Towards Transportation at Liquid/Air Interface
摘要： Swimmers at liquid/air interface have drawn enormous attention for their potential applications while conventional devices face problems such as dependence on fuel, difficulty in motion control and accompanying high temperature. Herein, we show one novel light-driven swimmer based on bimorph composite structure of photoresponsive liquid-crystalline polymer network and commercially available polyimide (Kapton) whose motion is highly controllable with photoirradiation. The bilayer-structured film shows quickly photoinduced bending towards the Kapton side on exposure to UV light and recovers immediately after removal of light. When placed on liquid surface, the swimmer propels itself continually though rhythmic beating the liquid like a dolphin moving forward with its tail fin. Besides, light-powered rotation of the swimmer is successfully achieved by simply changing the length-width ratio and the irradiation site, mimicking the function of a dolphin’s pectoral fin. Combining the together, on-demand forward movement and rotation motion directional control of the photo-driven swimmer can be readily obtained at room temperature, showing promising for miniaturized transportation.
关键词： bionic motion,azobenzene,photomechanical oscillation,miniaturized transportation,light-driven device
更新于2025-09-23 15:22:29