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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Monostatic GTD Model for Double Scattering due to Specular Reflections or Edge Diffractions
摘要： GTD model is a good candidate to extract the features of radar targets, which describes the frequency dependence of scattering centers for many geometries or mechanisms and can represent the attribute information of the geometrical structures. The mechanisms associated with this model have been proven to include single reflection, single diffraction and multiple reflections from dihedral and trihedral corner reflectors. However, multi-scattering mechanisms from more complex structures are not studied adequately. In this paper, we expand the GTD model to any double scattering due to specular reflections or edge diffractions, and derive the related frequency-dependence factor. Finally, a simulation validates the theory.
关键词： specular reflection,multiple scattering mechanism,frequency-dependence factor,flat surface,straight edge,doubly-curved surface,GTD model,curved edge,edge diffraction,singly-curved surface
更新于2025-09-23 15:22:29
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Electrical Transport Properties of Thin Film Composed of a-ZnO Nanorods
摘要： Background: Due to its wide band gap, high exciton binding energy and high breakdown strength, the nanostructures of ZnO may find applications for electronic, photonic devices, and high-frequency applications. Objective: The aim of the present work is to study electrical transport of thin film composed of a-ZnO nanorods. Method: Physical vapour condensation method was employed to fabricate the nanorods of ZnO. The morphology of these nanorods was investigated with the help of scanning electron microscope. X-ray diffraction pattern of as-prepared thin film was recorded using X-ray diffractometer. For dc conductivity measurements, four-probe method was used. Result: The as-prepared ZnO nanorods have diameter ranging from 10-20 nm and the length is of order of few hundred nanometers. XRD pattern of film composed of ZnO nanorods suggests the amorphous nature. Temperature dependence of dc conductivity has been studied over the temperature range of (297- 4.2K). For the temperature range of 297-120K, Mott’s three dimensional variable range hopping (VRH) is applied to explain the electrical conduction. For lower temperature range (120 - 4.2K), 2D-variable-range hopping in localized states near the Fermi level may be responsible for the transport of carriers. Conclusion: Variable range hopping mechanism (VRH) has been suggested for the entire temperature range (298-4.2K) on the basis of temperature dependence of dc conductivity data, which changes from 3D to 2D on moving to lower temperatures side (below 125K).
关键词： physical vapour condensation technique,variable range hopping,XRD,ZnO nanorods,SEM,Mott’s parameters,electrical conduction mechanism
更新于2025-09-23 15:22:29
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Co <sub/>3</sub> (PO <sub/>4</sub> ) <sub/>2</sub> /Ag <sub/>3</sub> PO <sub/>4</sub> with Enhanced Simulated Sunlight Photocatalytic Activity toward Ofloxacin Degradation and Mechanism Insight
摘要： BACKGROUND: Ofloxacin is a frequently detected fluoroquinolone antibiotic in wastewater treatment plants effluents, sea waters and surface waters. Photocatalytic technology is considered to the most promising treatment technology for the removal of ofloxacin. However, it is a big challenge to exploit the novel sunlight driven photocatalyst and reveal the mechanism of the ofloxacin degradation. RESULTS: Co3(PO4)2/Ag3PO4 composites were prepared using a facile hydrothermal synthesis method. The structural, morphological, optical properties of the composites were well characterized. Both the degradation efficiency and cyclical stability of the Co3(PO4)2/Ag3PO4 composites increased significantly under simulated sunlight irradiation, when ofloxacin (OFX) or methyl orange (MO) was used as the target molecule, as compared to single-phase Ag3PO4 and Co3(PO4)2. The reduction of antimicrobial activity for 8%Co3(PO4)2/Ag3PO4 reached to 88.8% after 5 min sunlight irradiation. CONCLUSIONS: Co3(PO4)2 played a critical role in suppressing carrier recombination and provided a large number of photogenerated holes and ?O2- to oxide OFX or MO. The OFX degradation mechanism included piperazinyl dealkylation, decarboxylation, defluorination. The reduction of antimicrobial activity for degradation byproducts was obvious after simulated sunlight irradiation over Co3(PO4)2/Ag3PO4. Therefore, Co3(PO4)2/Ag3PO4 is an attractive candidate for the removal of OFX.
关键词： Antibacterial activity,Mechanism,Ofloxacin,Co3(PO4)2/Ag3PO4,Simulated sunlight
更新于2025-09-23 15:22:29
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Effects of Microsphere Size on the Mechanical Properties of Photonic Crystals
摘要： Photonic crystal (PC) thin films that are self-assembled from different-sized silica microspheres were prepared for studying mechanical properties via nanoindentation at the submicron scale. We found that the silica photonic crystals (PCs) possessed a face-centered cubic (FCC) microstructure and their elastic modulus and hardness were in the range of ~1.81–4.92 GPa and 0.008–0.033 GPa, respectively. The calculated results proved that there were size-dependent properties in the silica PCs, in that the elastic modulus and hardness increased as the diameter decreased from 538 nm to 326 nm. After studying the total work and plastic work in the progressive deformation of silica PCs during the nanoindentation tests, we developed a two-stage deformation model to explain how the microsphere size affects the mechanical properties of PC thin films. The phenomenon of 'smaller is stronger' is mainly due to the energy consumption, which combines the effects of microstructure collapse, microsphere slide, and reduced porosity during the whole loading and unloading process. In addition, the results of numerical simulation matched the experimental data and reflected the energy change rules of PCs during the indentation process. Furthermore, the study affords useful guidance for constructing high-performance films with proper design and potential application in next-generation PC materials.
关键词： photonic crystals,deformation mechanism,nanoindentation,size-dependent
更新于2025-09-23 15:22:29
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Binary-phase TiO2 modified Bi2MoO6 crystal for effective removal of antibiotics under visible light illumination
摘要： A series of binary-phase TiO2 modified Bi2MoO6 nanocrystals have been prepared via a solvothermal-calcination process. Trace TiO2 modification can effectively enhance the visible light catalytic activity of Bi2MoO6 to remove the antibiotics in aqueous solution. The obtained TiO2/Bi2MoO6 composites were investigated by some physicochemical techniques like XRD, N2 adsorption, SEM, TEM, UV–vis DRS, Raman, XPS, PL and Photo-electrochemical measurement. The presence of TiO2 nanoparticles (NPs) influenced the crystal growth of Bi2MoO6, decreasing the crystal size of Bi2MoO6 and effectively promoting its specific surface area. Moreover, the conduction band of TiO2 can serve as the electron transfer platform, which largely boosts the effective separation of photocarriers at TiO2/Bi2MoO6 heterojunction interface. With optimal TiO2 content (0.41 wt%), TiO2/Bi2MoO6 exhibited the best photocatalytic performance for different antibiotics degradation, e.g. ciprofloxacin, tetracycline and oxytetracyline hydrochloride under visible light irradiation. Moreover, the mechanism for enhanced photocatalytic performance in ciprofloxacin degradation was illuminated.
关键词： Mechanism,Binary-phase TiO2,Antibiotics,Photocatalytic degradation,Bi2MoO6
更新于2025-09-23 15:22:29
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Synthesis of Zr-based MOF nanocomposites for efficient visible-light photocatalytic degradation of contaminants
摘要： A novel ternary complex photocatalyst (UiO-66/g-C3N4/Ag) was fabricated by chemical protonation coating and photodeposition and its physicochemical parameters, crystal morphology, and electrochemical properties characterized using a series of techniques. Proper addition of g-C3N4 and Ag effectively enhanced the separation and mobility of photoinduced charge and improved the visible-light absorption and thereby the catalytic performance. Degradation experiments on target contaminants such as Rhodamine B (RhB) dye and 2,4-dichlorophenoxyacetic acid (2,4-d) showed that the photocatalytic ability of UiO-66/g-C3N4/Ag(15) was greatly increased compared with the parent material. Moreover, the composite could be regenerated by a simple ethanol washing process and exhibited stability and high reusability over six cycles. Finally, experiments on trapping of active species revealed that superoxide radicals (·O2?), holes (h+), and hydroxyl radicals (·OH) were primarily responsible for the photodegradation of RhB and 2,4-d.
关键词： UiO-66/g-C3N4/Ag,Photocatalysis,2,4-d,RhB,Catalytic mechanism
更新于2025-09-23 15:21:21
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A roller posture adjustment device with remote-center-of-motion for roll-to-roll printed electronics
摘要： Nonuniform web tension has a great negative effect on product quality of roll-to-roll printed electronics. In this paper, a roller posture adjustment device with remote-center-of-motion (RCM) characteristic is proposed to guarantee web tension uniformity. The device combines a high-stiffness spherical air bearing (SAB) and a multi-degree-of-freedom flexure-based mechanism. The nonuniform web tension in lateral direction can be divided into an equivalent force and two equivalent moments. The equivalent moments are caused by the nonuniformity of the web tension. By adjusting the roller angle around y and z-axes, the equivalent moments can be eliminated to guarantee the web tension uniformity. The multi-DOF flexure-based mechanism is composed of a linear mechanism, a rotary mechanism and a 3-DOF off-plane mechanism. Besides, the RCM characteristic of the proposed device is realized to eliminate extra parasitic movement when the roller posture is changed. Based on pseudo-rigid-body model (PRB-M) method, the theoretical analysis is conducted to evaluate the kinematics, stiffness and dynamics of the device. Moreover, the parameter optimization is conducted to maximize the first two resonance frequencies of the system. After that, finite element analysis is conducted to validate the established models. Finally, a prototype of the proposed device is fabricated performance verification. The experimental results show that the proposed device has a workspace of 10.22 mrad and 8.16 mrad about two working axes with center shifts of the RCM point less than 0.75%, which demonstrate the superior property of the proposed device.
关键词： Flexure-based mechanism,Micro-positioning,Roll-to-roll printed electronics,Remote-center-of-motion
更新于2025-09-23 15:21:21
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Gate Conduction Mechanisms and Lifetime Modeling of p-Gate AlGaN/GaN High-Electron-Mobility Transistors
摘要： The gate conduction mechanisms in p-gallium nitride (GaN)/AlGaN/GaN enhancement mode transistors are investigated using temperature-dependent dc gate current measurements. In each of the different gate voltage regions, a physical model is proposed and compared to experiment. At negative gate bias, Poole–Frenkel emission (PFE) occurs within the passivation dielectric from gate to source. At positive gate bias, the p-GaN/AlGaN/GaN “p-i-n” diode is in forward operation mode, and the gate current is limited by hole supply at the Schottky contact. At low gate voltages, the current is governed by thermionic emission with Schottky barrier lowering in dislocation lines. Increasing the gate voltage and temperature results in thermally assisted tunneling (TAT) across the same barrier. An improved gate process reduces the gate current in the positive gate bias region and eliminates the onset of TAT. However, at high positive gate bias, a sharp increase in current is observed originating from PFE at the metal/p-GaN interface. Using the extracted conduction mechanisms for both devices, accurate lifetime models are constructed. The device fabricated with the novel gate process exhibits a maximum gate voltage of 7.2 V at t1% = 10 years.
关键词： time-dependent breakdown (TDB),p-GaN gate,high-electron-mobility transistor (HEMT),enhancement mode,gallium nitride (GaN),Conduction mechanism
更新于2025-09-23 15:21:21
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Degradation of methylparaben using BiOI-hydrogel composites activated peroxymonosulfate under visible light irradiation
摘要： A novel hydrogel photocatalyst (p(HEA-APTM)-BiOI) was synthesized by irradiation polymerization and chemical precipitation method, while employed as peroxymonosulfate (PMS) activator to enhance methylparaben (MP) degradation. The structure, morphology and physicochemical properties of the prepared p(HEA-APTM)-BiOI were characterized by XRD, XPS, SEM, TEM, FTIR and BET. The experimental results revealed that the MP catalytic degradation by p(HEA-APTM)-BiOI activated PMS can achieve the best performance under the visible light irradiation. In addition, the parameters including the molar radio of [PMS]/[MP], initial pH, Cl- and HCO3- were also investigated in detail. It was worth noting that p(HEA-APTM)-BiOI also effectively eliminated MP in the absence of visible light. Based on the quenching experiment, 1O2, h+ and ?O2- were determined as the dominant active species contributing to the catalytic oxidation process in the p(HEA-APTM)-BiOI/PMS/Vis system, and the possible degradation mechanism was also elaborated. Eventually, the possible pathways of MP degradation were deduced from several intermediates identified by HPLC-MS.
关键词： Methylparaben,peroxymonosulfate,degradation mechanism,visible light,BiOI-hydrogel
更新于2025-09-23 15:21:21
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Insights into the element gradient in the grain and luminescence mechanism of the long afterglow material Sr2MgSi2O7: Eu2+,Dy3+
摘要： In the long afterglow luminescent material, the defects play an important role on the afterglow performance, but the understanding of the traps are still not uniform. In this research, the long afterglow material Sr2MgSi2O7: Eu2t,Dy3t is treated by the acid corrosion liquid with different times to research gradient distribution of elements from outside to inside the grain of the long afterglow materials, the effect of the gradient on the structure, photoluminescence performance, long afterglow properties as well as the mechanism of luminescence are discussed. When the grain surface is destroyed, the initial brightness falls sharply, but the decrease of decay times are not obvious, that is caused by the different distribution of defects. The amounts of element Sr and O increase, but the Eu and Dy decrease from the outside to the inside the grain, the aggregate defects (VO$$EuSr)n which act as shallow traps are proposed, and meanwhile the isolated defects VO$$ act as deep traps. A new luminescent model is put forward to account for the long afterglow photoluminescence phenomenon, the shallow traps and the deep traps play different roles on the long afterglow properties, and most of the problems that exist in the long afterglow materials can be explained by this model.
关键词： Luminescence,Mechanism of luminescence,Afterglow properties,Grain surface,Sr2MgSi2O7:Eu2t,Dy3t
更新于2025-09-23 15:21:21