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- 2018
- Solar Photovoltaic (SPV)
- Fuzzy Logic Control (FLC)
- MATLAB/Simulink
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- Electrical Engineering and Automation
- Cochin University College of Engineering
- T.K.M College of Engineering
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An X-band single-layer waveguide directional filter with compact size and low insertion loss
摘要： A novel waveguide directional ?lter with compact-size and low insertion loss is proposed in this letter. The basic structure consists of a pair of rectangular waveguides placed parallel to each other along their narrow side and two identical band-pass ?lters connect them via two coupling slots. For easy of fabrication and assembling, all the band-pass ?lters and wave-guides have a uniform height, that is all the components of the directional ?lter are in a single-layer waveguide. It is easy machining by standard computer numerical controlled (CNC) techniques to match the requirement for low cost. For veri?cation purpose, an X-band single-layer waveguide directional ?lter has been manufactured and measured. The measured results show a insertion loss better than 0.1 dB, a return loss lower than ?17.5 dB and a isolation better than ?22.5 dB, good band-pass and band-elimination responses are also obtained over the frequency range from 7.25 GHz to 9.75 GHz. The good agreement has been found between the simulated and measured results.
关键词： waveguide directional ?lter,X-band,compact-size,low insertion loss,single-layer
更新于2025-09-19 17:13:59
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Size and Shape Evolution of GaAsSb-Capped InAs/GaAs Quantum Dots: Dependence on the Sb Content
摘要： Capping InAs/GaAs quantum dots (QDs) with a thin GaAsSb layer alters the QDs structural properties, leading to considerable changes in their optical properties. The increase of the Sb content induces a redshift of the emission energies, indicating a change in the buried QDs shape and size. The presence of well-defined ground- and excited-state emission bands in all the photoluminescence spectra allow an accurate estimation of the buried QDs size and shape by numerical evaluation and tuning of the theoretical emission energies. For an Sb content below 14%, the QDs are found to have a type I band alignment with a truncated height pyramidal form. However, for higher Sb content (22%), the QDs are present in a full pyramidal shape. The observed behavior is interpreted in terms of increasing prevention of InAs QDs decomposition with increasing the Sb content in the cap layer.
关键词： size,GaAsSb,InAs quantum dots,modeling,shape
更新于2025-09-19 17:13:59
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Optimizing the Phase-Separated Domain Size of the Active Layer via Sequential Crystallization in All-Polymer Solar Cells
摘要： Proper domain size of the active layer plays a key role in determining the exciton dissociation and charge transport in all polymer solar cells (all-PSCs). However, fine-tuning the domain size remains challenging due to low glass transition temperature and negligible mixing entropy in polymer blends. Herein, we systematically studied the influence of “crystallization kinetics” on the domain size and proposed that if donor and acceptor crystallize simultaneously, it is prone to form large domain size; while if sequential crystallization of donor and acceptor occurs, a fine phase separation structure with proper domain size can be obtained. Taking PBDB-T/PNDI blends for instance, the domain size was decreased by using sequential crystallization, meanwhile, the crystallinity and molecular orientation were optimized as well, boosting the power conversion efficiency (PCE) from 6.55% to 7.78%. This work provides a novel way to finely tune the heterojunction phase separation structures.
关键词： domain size,crystallization kinetics,sequential crystallization,all-polymer solar cells,phase separation
更新于2025-09-19 17:13:59
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Precise size separation of water-soluble red-to-near-infrared-luminescent silicon quantum dots by gel electrophoresis
摘要： A gel electrophoresis, which is a standard method for separation and analysis of macromolecules such as DNA, RNA and proteins, is applied for the first time to silicon (Si) quantum dots (QDs) for the size separation. In the Si QDs studied, boron (B) and phosphorus (P) are simultaneously doped. The codoping induces negative potential on the surface of a Si QD and makes it dispersible in water. Si QDs with different B and P concentrations and grown at different temperatures (950°C - 1200°C) are studied. It is shown that a native polyacrylamide gel electrophoresis can separate codoped Si QDs by size. The capability of gel electrophoresis to immobilize size-separated QDs in a solid matrix makes detailed analyses of size-purified Si QDs possible. For example, photoluminescence (PL) studies of dried gel of Si QDs grown at 1100°C demonstrate that a PL spectrum of a Si QDs solution with the PL maximum around 1.4 eV can be separated into more than 15 spectra with the PL maximum changing from 1.2 to 1.8 eV depending on the migration distance. It is found that the relation between the PL peak energy and the migration distance depends on the growth temperature of Si QDs as well as the B and P concentration. For all the samples with different impurity concentrations and grown at different temperatures, a clear trend is observed in the relation between the full width at half maximum (FWHM) and the peak energy of the PL spectra in a wide energy range. The FWHM increases with increasing the peak energy and it is nearly twice larger than those observed for undoped Si QDs. The large PL FWHM of codoped Si QDs suggests that excitons are further localized in codoped Si QDs due to the existence of charged impurities.
关键词： codoping,size separation,silicon quantum dots,photoluminescence,gel electrophoresis
更新于2025-09-19 17:13:59
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Realization of Low-loss Epsilon-near-zero Properties Using PT-symmetric Metasurfaces
摘要： A circularly polarized patch antenna for future fifth-generation mobile phones is presented in this paper. Miniaturization and beamwidth enhancement of a patch antenna are the two main areas to be discussed. By folding the edge of the radiating patch with loading slots, the size of the patch antenna is 44.8% smaller than a conventional half wavelength patch, which allows it to be accommodated inside handsets easily. Wide beamwidth is obtained by surrounding the patch with a dielectric substrate and supporting the antenna by a metallic block. A measured half power beamwidth of 124? is achieved. The impedance bandwidth of the antenna is over 10%, and the 3-dB axial ratio bandwidth is 3.05%. The proposed antenna covers a wide elevation angle and complete azimuth range. A parametric study of the effect of the metallic block and the surrounding dielectric substrate on the gain at a low elevation angle and the axial ratio of the proposed antenna are presented.
关键词： microstrip patch antennas,Antenna radiation patterns,satellite antennas,size reduction,beamwidth enhancement
更新于2025-09-19 17:13:59
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Impact of grain growth of silver reflective electrode by electron bombardment on external quantum efficiency of III-nitride micro-light-emitting diode arrays
摘要： The effect of electron-beam irradiation (EBI) on Ag reflector is investigated in order to improve the efficiency of flip-chip InGaN/GaN multiple-quantum-wells micro light-emitting diode (μ-LED) arrays. After EBI, small size grains are diffused and then become larger grain. Therefore, grain boundaries are reduced which originates the crystal quality and reflectance of Ag reflect to improve. Grain size of Ag reflector is increased with the increase in EBI time that is consistently observed by different kinds of material characterizations. 5 minutes EBI-based Ag reflector shows higher reflectance (~91 %) at 450 nm than without EBI sample (~84 %). Finally, without and with EBI on Ag reflector-based μ-LED arrays are fabricated. After EBI, there is no change in forward bias voltage except optical performances. At driving current, Ag reflector with EBI-based μ-LEDs has higher light-output-power, electroluminescence intensity and electroluminescence distribution over the chip area compared to without EBI-based μ-LEDs. Usually, increased light-extraction-efficiency causes the external-quantum-efficiency of the μ-LEDs to increase. These enhanced optoelectronic performances are consistently described by using microscopic and macroscopic characterizations.
关键词： Ag reflector,Electron-beam irradiation,reflectance,micro light-emitting diodes,grain size
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Local Laser Heating of Biological Tissue
摘要： The mathematical model of the process of heating of biological media by continuous and pulsed laser radiation was created and investigated. The dimensions of the heated area, the time of heating are determined. It is necessary use blue or green laser radiation for creating a local area. The thermal time constant of the process is a few minutes. Therefore, the radiation of the pulse-modulated radiation differs from the constant power only with periodic of pulses more than 1 minute.
关键词： size,biological tissue,time constant,heating,radiation,laser
更新于2025-09-19 17:13:59
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COMPACT SINGLE-LAYER BALANCED EIGHTH-MODE SUBSTRATE INTEGRATED WAVEGUIDE BANDPASS FILTER WITH HIGH SELECTIVITY
摘要： This letter proposes a compact single-layer balanced bandpass ?lter (BPF), which is realized by a new arrangement of eighth-mode substrate integrated waveguide (EMSIW) cavities. Under di?erential-mode (DM) operation, the half bisection topology of the proposed EMSIW ?lter can be equivalent to a quadruplet scheme based on four coupled EMSIW cavities. The negative cross coupling can be easily realized by the nature of the fringe electric ?elds of opened ends of EMSIW cavities. For the demonstration, a balanced EMSIW ?lter with the operating frequency at 2.4 GHz is designed, fabricated, and measured.
关键词： eighth-mode substrate integrated waveguide,compact size,high selectivity,balanced bandpass filter
更新于2025-09-19 17:13:59
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - An Improved UWB Bandpass Filter with a Notch-band Based on Asymmetric Parallel-coupled Line with Compact Size
摘要： This letter presents an improved UWB bandpass ?lter with sharp selectivity and a notch-band. Its fundamental structure is mainly based on a half-wavelength resonator using asymmetric parallel-coupled line. A center-tapped short-stub is connected at the symmetrical plane of the ?lter. As a result, two transmission zeros at the lower and upper passband/stopband edges are obtained. Moreover, one open parallel-coupled line is introduced to achieve a notch-band. Measured results indicate that the proposed ?lter has achieved a bandwidth of 110.6% from 3.05 to 10.6 GHz with a notch-band at 8.5 GHz. In addition, this ?lter can o?er some other advantages such as sharp roll-o? and compact size (0.63λg × 0.33λg), which make it attractive for the practical applications in UWB systems.
关键词： asymmetric parallel-coupled line,compact size,UWB bandpass filter,notch-band
更新于2025-09-19 17:13:59
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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) - Development of An Electron-Beam Pumped, Argon Fluoride Laser for Inertial Confinement Fusion
摘要： Snow changes its morphology permanently from the moment a snow flake touches the ground. Under the influence of meteorological factors such as temperature, humidity, and wind, snow grains form complex structures of ice bonds enclosing variable portions of air. The characteristics of such structures are important for the formation of snow avalanches. Certain snow types such as surface hoar, ice crusts, or windblown snow play a major role in the formation of weak layers and slabs, which are precondition for dangerous slab avalanches. The reflection properties of snow depend on the optical equivalent grain size of the ice particles that constitute the snow cover. High spatial resolution remote sensing instruments with near-infrared (0.7–1.4 μm) bands are able to detect such differences in the optical reflection of snow. We use normalized difference index band ratios from a spaceborne and an airborne remote sensing instrument to distinguish and map different snow-surface types in the neighborhood of Davos, Switzerland, enabling a valuable visualization of the spatial variability of the snow surface.
关键词： snow,snow avalanches,snow grain size,optical,Near infrared (NIR)
更新于2025-09-19 17:13:59