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oe1(光电查) - 科学论文

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出版时间
  • 2019
研究主题
  • photovoltaic power generation system
  • sensitivity analysis
  • Monte Carlo
  • fuzzy layering evaluation method
应用领域
  • Electrical Engineering and Automation
机构单位
  • Xi’an Jiaotong University
798 条数据
?? 中文（中国） ▾

  • Performance of a modified solar chimney power plant for power generation and vegetation

    摘要： This paper develops a mathematical model to investigate the performance of a modified solar chimney power plant (MSCPP) for purposes of both power generation and vegetation. It then estimates the net added benefit. Results show that with the vegetation area enlarging, the MFR of the vapor increases, and more heat is used as the latent heat for water evaporation, leading to considerable reduction of the power. Condensation from the saturated air occurs only for very large vegetation area. On a cooler day, the plant produces less power and the condensation occurs for smaller vegetation area. Higher relative humidity of ambient air results in clear reduction of the MFR of the vapor evaporating from the vegetation area, and accordingly the great enhancement of the power. The benefit from agricultural products is larger than the benefit loss caused by the electricity loss, and the benefit of fresh water condensed from the saturated air is negligible. This leads to net added benefit for the MSCPP compared to the conventional plant. The net added benefit becomes greater with larger vegetation area. When the chimney is heightened from 1000 m to 1500 m, the power is enhanced greatly; however, the net added benefit becomes smaller.

    关键词： Vegetation,Solar collector,Latent heat,Fresh water,Solar chimney,Power generation

    更新于2025-09-23 15:23:52

  • High-order harmonic generation of pulses with multiple timescales: selection rules, carrier envelope phase and cutoff energy

    摘要： High harmonic generation (HHG) is sensitive to the carrier envelope phase (CEP) of its driving laser field if it is a sufficiently short pulse (several-cycle pulse). Here we show that strong CEP effects can also be found in HHG from long duration multi-cycle pulses (up to 200 fs at 800 nm central wavelength). We find that HHG from multi-cycle pulses may be CEP dependent when the driving pulse exhibits two distinct timescales (multi-timescale pulse): (i) a short timescale associated with the average frequency, and (ii) a long timescale associated with the pulse’s temporal periodicity. The interplay of these timescales results in significant changes to both the cutoff frequency, and the appearance of symmetry allowed harmonics in the spectrum as function of CEP, similar to HHG from several-cycle pulses. We relate this effect to the multi-timescale intensity variations in the driving pulse, and construct an analytical condition to access the phenomenon. Lastly, we numerically demonstrate reconstruction of the CEP through HHG from long duration multi-timescale pulses. Our work may be useful in several areas of strong-field physics and attosecond science, for example, allowing spectroscopy of multi-timescale processes (e.g. HHG from vibrationally active media), and paving the way towards CEP characterisation using long pulses.

    关键词： carrier-envelope phase,dynamical symmetry,High harmonic generation

    更新于2025-09-23 15:23:52

  • ZnIn2S4 nanosheets decorating WO3 nanorods core-shell hybrids for boosting visible-light photocatalysis hydrogen generation

    摘要： We here report the fabrication of a core-shell WO3@ZnIn2S4 heterostructure by an interfacial seeding growth strategy, which is implemented by direct growth of ZnIn2S4 nanosheets on the surface of WO3 nanorods with forming a strong electronic interaction between two semiconductors that are beneficial for promoting the interfacial charge transfer. Systematic studies demonstrate that the WO3@ZnIn2S4 nanohybrids hold superior performance for photocatalytic hydrogen generation under visible light irradiation with a production rate of 3900 mmol g-1 h-1. This work provides an effective approach to construct the direct Z-scheme photocatalytic systems for efficient photocatalytic hydrogen evolution, which would be significant for the design of more direct Z-scheme system for various photocatalytic applications.

    关键词： ZnIn2S4 nanosheets,WO3 nanorods,Photocatalytic H2 generation,Visible light,Z-scheme

    更新于2025-09-23 15:23:52

  • Pressure dependence of high order harmonic generation in nitrogen molecular gas and atmospheric air

    摘要： The effect of the variation of the gas pressure on the high harmonic generation (HHG) from nitrogen molecular gas (N2) and atmospheric air with ultrashort intense laser pulses is measured. The optimum pressure in the interaction region of a gas jet for maximizing the HHG yield is determined for both gases. Enhancement of the HHG output and its extension to higher harmonic orders are observed around the optimum pressure value of 0.33 bar. Theoretical calculations based on one-dimensional models explain this effect and provide reasonable agreement with experimental results.

    关键词： Femtosecond laser,Conversion efficiency,High-order harmonic generation (HHG),Phase matching,XUV radiation,Pressure optimization

    更新于2025-09-23 15:23:52

  • [IEEE 2018 12th International Conference on Communications (COMM) - Bucharest (2018.6.14-2018.6.16)] 2018 International Conference on Communications (COMM) - Supervized Change Detection for SAR Imagery Based on Processing of a Low Size Training Data Set by an Ensemble of Self-Organizing Maps

    摘要： This paper presents a new method to improve accuracy of supervised change detection in Synthetic Aperture Radar (SAR) imagery. The model is based on the idea to apply a low size labeled dataset to the input of an Ensemble of Self-Organizing Maps (ESOM) for training data generation (TDG). The resulted synthetic data set produced by ESOM substitutes the initial authentically labeled sample set and it is used to train a supervised change detection classifier. The proposed method is evaluated using a TerraSAR-X image of 400x400 pixels acquired in the Fukushima region, Japan, before and after tsunami. As change detection classifiers we have comparatively considered Support Vector Machine (SVM), Nearest Neighbor (NN), the three-Nearest Neighbors (3-NN), and Likelihood Bayes classifier. The experimental results have confirmed the effectiveness of the proposed approach using only 100 authentic labeled pixels.

    关键词： SAR images,ensemble of self-organizing maps (ESOM),virtual training data generation(VTDG),change detection

    更新于2025-09-23 15:23:52

  • Synthesis, crystal structures, second harmonic generation response and temperature phase transitions of two noncentrosymmetric Cu(II)-hybrid halides compounds: [(R)-C7H16N2][CuX4] (X?= Cl or Br)

    摘要： (R)-(+)-3-aminoquinuclidine was used in the synthesis of [(R)-C7H16N2][CuCl4] (1) and [(R)-C7H16N2][CuBr4] (2), which both contain similar [CuX4]2- anions (X = Cl or Br). The structures of the two compounds were determined using single-crystal X-ray diffraction. The use of enantiomerically pure sources of (R)-C7H14N2 forces crystallographic noncentrosymmetry. These materials crystallize in the chiral space group P212121 (No. 19), which exhibits the enantiomorphic crystal class 222 (D2). In the molecular arrangement, the [CuX4]2- anions are linked to the organic cations through N-H...X and C-H...X hydrogen bonds to form cation-anion-cation molecular units, which are held together by means of offset face-to-face interactions giving a three-dimensional network. Thermal stability of the crystals was ascertained by TG measurement. Compounds (1) and (2) display several phases transition with higher transition temperature at T = 100°C. The Kurtz and Perry powder method using Nd:YAG laser shows that their second harmonic generation (SHG) efficiencies are about 0.81 and 0.82 times as large as that of KH2PO4 (KDP), respectively. Such a chiral hybrid metal halides skeleton could provide a new platform for future engineering in the areas including information storage, light modulators and optoelectronic functionalities.

    关键词： nonlinear optics,second harmonic generation,crystal structure,chiral hybrid halide,phase transitions

    更新于2025-09-23 15:23:52

  • RF Characterization of NiO and TiO <sub/>2</sub> Based Metal-Insulator-Metal (MIM) Diodes on Flexible Substrates

    摘要： This paper presents the fabrication and characterization of metal-insulator-metal (MIM) diodes on flexible substrates for RF and microwave circuit applications. Diodes using two types of insulators, titanium dioxide (TiO2) and nickel oxide (NiO), are investigated. These insulators are obtained using different oxidation techniques, i.e., in-situ oxidation for TiO2 and plasma oxidation for NiO. Asymmetric metal contacts (Ti-TiO2-Pd and Ni-NiO-Mo) are utilized to achieve nonlinear I–V characteristics. The fabricated diodes show strong non-linearity, high current densities, and low turn-ON voltage. The diodes show RF to dc rectification with near-ideal behavior and rectification sensitivity of 22 V/W (18 GHz) and 46 V/W (18 GHz) for TiO2 and NiO, respectively. NiO-based diodes barrier shows higher current density and higher cutoff frequency in comparison with TiO2 as expected diodes due to thinner oxide and lower dielectric constant. The diodes also work well as frequency doublers over a wide frequency range of 1–4 GHz for TiO2 and 2–10 GHz for NiO-based diodes. Good dc and RF performance of diodes indicate that good quality oxide can be achieved on plastic substrates and MIM devices can provide a perfect solution for RF and microwave circuits on a flexible substrate.

    关键词： MIM diodes,rectification,Flexible electronics,harmonic generation,thin film devices,microwave circuits

    更新于2025-09-23 15:23:52

  • Local structural changes due to the electric field-induced migration of oxygen vacancies at Fe-doped SrTiO <sub/>3</sub> interfaces

    摘要： We report on our study of dc voltage-induced structural changes at reduced and oxidized Fe-doped SrTiO3 (Fe:STO) electrode interfaces using second harmonic generation (SHG) together with photoluminescence (PL) method. We show that oxygen vacancy defects play a critical role in determining the local electrical and structural properties of interfacial depletion regions at Schottky junctions. The SHG results show that the dc electric field causes oxygen ions and vacancies to displace toward the anode and cathode in the low field regime, respectively. This process forms electrostrictive distortions within local interfacial depletion regions which are described by Fe:Ti-O bond stretching and bending. Differences in the EFISHG responses from the oxidized and reduced crystal interfaces are explained according to local oxygen vacancy concentrations and dynamics and their effects on the Schottky barrier heights and depletion region widths at each interface. These results are further supported by our PL measurements. Oxygen ion migration towards the Fe:STO surface leads to enhanced fluorescence intensities from in-gap acceptor states. We demonstrate that SHG and PL measurements are well suited for understanding and resolving the underlying causes of dielectric breakdown processes and device failure brought on by dc electric field and ionic defect migrations in perovskite-type electroceramics.

    关键词： Photoluminescence,Oxygen Vacancy,Electroceramic,Second Harmonic Generation

    更新于2025-09-23 15:23:52

  • Application of a New Method of Spectral Analysis for Detecting Synchronous Processes in Heliobiology

    摘要： Until now, the sum of periodic variations was the main carrier of information in biological and helio-geophysical signals. However, not all of the time series of interest contain dominant periodic components. The relaxation analysis used in this paper makes it possible to generalize the “spectral” formalism to signals that cannot be represented as a sum of a limited number of quasiperiodic components. An algorithm for filtering noise and long-period trends is developed based on the separation of the original signal into rapidly and slowly relaxing components. The main theorem that guarantees the operability of the algorithm is proven. A method for constructing an orthonormal basis whose components have a strictly defined relaxation time is described. The result of the signal expansion over this basis is called the relaxation spectrum. It can be used to divide the time series into signal-to-noise or oscillation-trend if there are no adequate Fourier or stochastic models. The hypothesis that geomagnetic rhythms with periods of about 7 and 9 days have the most significant influence on physiological indicators of biological objects (including those of the population as a whole), as was stated earlier by the heliobiologists, is confirmed based on an automatic algorithm for extracting reliable spectral peaks of population and heliogeomagnetic time series and detecting similar peaks using the S?rensen measure.

    关键词： orthonormal basis generation,signal filtering,heliobiophysics,spectral formalism generalization

    更新于2025-09-23 15:23:52

  • Photocathodic hydrogen evolution from catalysed nanoparticle films prepared from stable aqueous dispersions of P3HT and PCBM

    摘要： Photo-assisted hydrogen evolution is achieved on photocathodes comprising of nanoparticles of poly(3-hexylthiophene) (npP3HT) and nanoparticles of phenyl-C61-butyric acid methyl ester (npPCBM) onto which ultra-low loadings of Pt nanoparticles are deposited. The nanoparticles, npP3HT and npPCBM, are prepared individually via miniemulsion using surfactants of opposite head group polarity. Aqueous dispersions of npP3HT:npPCBM, devoid of organic solvent, are cast conformally onto ITO-coated glass to yield water-insoluble bulk-heterojunction films. Pt is deposited photoelectrochemically onto ITO/npP3HT:npPCBM photocathodes and found to nucleate preferentially on PCBM nanoparticles. ITO/npP3HT:npPCBM/Pt photocathodes produce 65 μA/cm2 photocurrent under 100 mW/cm2 of visible light at 0.0 VSHE and liberate H2 gas. The photocurrents observed for electrodes prepared using npP3HT:npPCBM are twice as large, and the onset potential is ～0.4 V more positive than analogous photocathodes cast from nanoparticles each comprising an intimate blend of P3HT and PCBM. These are encouraging results for large scale synthesis of organic photoelectrochemical devices, given the simplicity of the photoelectrode, i.e., prepared from aqueous solutions and devoid of vacuum-deposited films such as charge transport layers and protective films.

    关键词： Polymer nanoparticle,Photoelectrochemistry,P3HT: PCBM bulk-heterojunction,Solar hydrogen generation,Organic semiconductor,Mini-Emulsion

    更新于2025-09-23 15:23:52