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Fabrication of bilayered attapulgite for solar steam generation with high conversion efficiency
摘要： Solar steam generation has been attracting wide attention for boosting the evolution of solar-energy-harvesting technology. Here, we demonstrate the fabrication of a novel bilayer photothermal material based on attapulgite/poly acrylamide composite (APAC), which was prepared by the solution polymerization of acrylamide (AM) in the presence of attapulgite using N, N’ - Methylene bisacrylamide (MBA) as a crosslinker, for efficient solar steam generation. The APAC shows better thermal stability with a decomposition temperature of 250 oC, good mechanical property with a compress strength of up to 125 KPa at 75% strain and a low apparent density (0.0191 g·cm-3) with abundant porosity accompanying with a low thermal conductivity (0.07 W m-1 K-1). To enhance the light absorption of APAC, a thin carbon layer was created on the surface of APAC via a facile flame treatment. Under our conditions, the bilayered APAC shows a high vapor rate of 1.2 kg m-2 h-1 under 1 sun illumination, equal to 85% solar-to-vapor efficiency. With the merits of cost-efficient, scalable manufacture, high solar energy conversion efficiency, the APAC may hold the great potential as high-performance photothermal materials for solar energy generation.
关键词： conversion efficiency,Solar steam generation,attapulgite,bilayer
更新于2025-09-23 15:23:52
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Efficient photocatalytic debromination of 2,2?,4,4?-tetrabromodiphenyl ether by Ag-loaded CdS particles under visible light
摘要： Highly active and visible light-driven Ag-loaded CdS photocatalysts were prepared via a hydrothermal synthesis and photodeposition method. The removal and debromination of 2,2?,4,4?-tetrabromodiphenyl ether was achieved efficiently using this Ag-loaded CdS under visible light, with a removal efficiency of 100% and a debromination ratio of 44.3% being achieved within 30 min. Both the reaction solvent and the water content were found to have a strong influence on the removal efficiency and the debromination ratio. In addition, the stepwise debromination preference was ortho > para, thereby indicating that the main debromination pathway was electron reduction. The stability and efficiency of these Ag-loaded CdS photocatalysts for the removal of BDE47 were satisfactory, and so our results confirmed the development of a promising visible light-driven catalyst for the removal of polybrominated diphenyl ethers.
关键词： Debromination ratio,Visible light-driven,Ag-loaded CdS,Photocatalyst,Removal efficiency
更新于2025-09-23 15:23:52
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Numerical investigation of energy performance and cost analysis of Moroccan’s building smart walls integrating vanadium dioxide
摘要： Thermochromic materials such as vanadium dioxide (VO2) have the capability to regulate their infrared reflectivity depending on ambient temperature. Such smart materials are attractive for applications like smart windows and smart roofs. In this paper, we investigate numerically the impact of tungsten (W) doped VO2 application as a smart outdoor wall layer on the building energy consumption in the Mediterranean climate. Temperature distributions through wall configurations with and without W doped VO2 were calculated using finite differences method implemented in Matlab environment. Calculations take into consideration dynamic variations of W doped VO2 absorptivity depending on outdoor temperature variations. Decrement factor, time lag, transmission and peak loads of cooling and heating were calculated. Results have shown that the indoor surface temperature is attenuated during summer by 2–3 °C depending on orientation. Cooling energy saving due to the use of W doped VO2 in summer is around 70% monthly which is equivalent to save $21.6/month of electricity invoiced amount. During winter, W doped VO2 maintains the same value of absorptivity as the uninsulated wall. Thus, results show small differences for indoor surface temperature and heating energy consumption. The application of W doped VO2 in intelligent thermal wall insulation offers a real-time dynamic variation of building’s envelope solar absorptivity and makes smart walls concept more feasible.
关键词： Energy efficiency,Smart wall,Radiative thermal rectification,Thermochromic,Real-time dynamic absorptivity,Vanadium dioxide
更新于2025-09-23 15:23:52
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Scaling Relations of Plasmon Resonance Peak in Au@Fe3O4 Core-Shell Nanohybrids Structure
摘要： In this paper, we study the absorption efficiency spectra of Au nanoparticles enveloped with Fe3O4 nanoshell by applying the discrete dipole approximation method. Three kinds of Au@Fe3O4 core-shell nanohybrids (NHs) structure, including the same core with different shell thickness, the same outer shell with different core radius, and the same size of total radius, have been discussed in detail. The simulation results show that the square of localized surface plasmon resonance (LSPR) peak wavelength of NHs is linearly proportional with the volume fraction of the shell, regardless of the outer shell material properties. Compared to the plasmon resonance peak of the Au nanoparticles, the LSPR shift of the NHs is dependent on both the total particles size and the outer Fe3O4 shell thickness. Our calculation results would provide some key guidances to design the structure variables of NHs for a broad range of plasmon applications.
关键词： Nanohybrids,Discrete dipole approximation,Absorption efficiency
更新于2025-09-23 15:23:52
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Design and optimization of grid-tied and off-grid solar PV systems for super-efficient electrical appliances
摘要： Modeling, simulation, and optimization methods are used in the present study to design grid-tied and off-grid solar PV systems for super-efficient electrical appliances for residential buildings. The principal objective of this study is to design a renewable energy system to serve the electric load of super-efficient appliances with high penetration of renewable resources and low greenhouse gas emissions and cost of energy. Hourly calculations using optimization method are used to study the daily and yearly performance and the cost of the renewable energy systems. A comparison between the performance of the grid-tied and off-grid solar PV systems using conventional and super-efficient appliances in Dubai is presented. The comparison includes the total power production from the solar PV system, the power purchased from the grid, the extra power sold to the utility grid, the power used to meet the electrical load of the appliances, the excess power, the renewable fraction, the greenhouse gas emissions, and the levelized cost of energy. The results of the simulation show that the integration of super-efficient appliances powered with the grid-tied solar power system is a good option to control the energy consumption of the residential buildings and to reduce the cost of electricity and greenhouse gas emissions: low building energy consumption (reduction by half of the electrical power consumption: from 62.91 to 30.78 kWh/day using super-efficient appliances); all the electrical power demand for the building is met without shortage; the power systems produce low excess power (0.29–1.82%) compared to the off-grid power system; all the extra power from the solar PV is sold back to the grid to reduce the cost of energy, high renewable fraction (68% of the total energy served to the load is produced from solar PV), low-cost of electricity (12% reduction of the cost of energy compared to the utility grid), and low greenhouse gas emissions (45–51% reductions of the CO2, NOX, and SO2 emissions compared to the conventional electrical appliances).
关键词： Grid-tied solar PV,Off-grid solar PV,Super-efficient appliances,Energy efficiency,Renewable energy
更新于2025-09-23 15:23:52
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Investigative study of the thermal performance of a trial solar air heater
摘要： Solar collectors need to be inclined at the optimum angle to maximize the receiving energy. The evaluation of the thermal performance of solar air collectors is important for the proper design and sizing of the collector for a given application. In our experimental/theoretical study, which consists of a thermal performance investigation, we have sought to optimize the efficiency–temperature rise couple of the designed solar air heater by considering the appropriate assembling materials regarding the absorber, the glazing and the insulation. Obviously, efficiency is dependent on the orientation of solar collectors and the measured parameters climate conditions such as wind speed, solar radiation and ambient temperature. In order to achieve possible performance optimization of the receiver plane using a low number of variables and equations, the calculations were carried out considering four values of azimuth angle, γ = 0°, 22.5°, 45° and 67.5°, and by varying the tilt angle β by 5 degrees from 15° to 70°.
关键词： Insulation,Efficiency,Absorber,Optimization,Experimental solar air collector
更新于2025-09-23 15:23:52
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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
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Scalable modulation of reduced graphene oxide properties via regulating graphite oxide precursors
摘要： Here we demonstrate the scalable modulation of reduced graphene oxide (RGO) properties by regulating graphite oxide (GtO) precursors. Our findings show the thickness and loose degree of GtO precursors act as key roles in flame activation process. Interestingly, the looser GtO transforms into RGO with a lower specific surface area (SSA); RGO from the thinner GtO paper shows a higher SSA. By regulating GtO precursors, SSA from 1030.5 to 335.3 m2 g?1, defect degree, oxidation degree, and pore volume from 4.61 to 1.36 cm3 g?1 can be tuned. The corresponding structural properties are translated into unique supercapacitor (SC) performances such as high specific capacitance (the highest value of 576 F g?1) and coulombic efficiency. Additionally, this method indicates great potential to prepare RGO-based metal oxide composites with good homogeneity and good SC behaviors.
关键词： Flame,Energy efficiency,Reduced graphene oxide,Precursor,Supercapacitor
更新于2025-09-23 15:23:52
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Rephasing efficiency of sequences of phased pulses in spin-echo and light-storage experiments
摘要： We investigate the rephasing efficiency of sequences of phased pulses for spin echoes and light storage by electromagnetically induced transparency (EIT). We derive a simple theoretical model and show that the rephasing efficiency is very sensitive to the phases of the imperfect rephasing pulses. The obtained efficiency differs substantially for spin echoes and EIT light storage, which is due to the spatially retarded coherence phases after EIT light storage. Similar behavior is also expected for other light-storage protocols with spatial retardation or for rephasing of collective quantum states with an unknown or undefined phase, e.g., as relevant in single-photon storage. We confirm the predictions of our theoretical model by experiments in a Pr3+:Y2SiO5 crystal.
关键词： phased pulses,rephasing efficiency,electromagnetically induced transparency,light storage,EIT,spin echoes,Pr3+:Y2SiO5 crystal
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Signal Distortion Decreasing in Envelope Tracking Power Amplifiers
摘要： When amplifying signals with a high peak to average power ratio, the efficiency of linear radio frequency (RF) power amplifiers (PA) is reduced to about 30%. This flaw can be noticeably corrected by using envelope tracking technology. However, using switched mode PAs of envelope signal (ES) is accompanied by the emergence of nonlinear distortions, which can appear as undesirable components in the RF PA signal spectrum. One of the ways to reduce the negative influence of the switched mode is to use ES PA of multicell structure. The paper covers the issues of the ES PA number of cells influence on its efficiency and output signal distortion, as well as its influence on the efficiency and output signal distortion of the RF PA. It is shown that rational choice of the number of cells allows to increase the efficiency of ES PA from 94 through 98% and to reduce the level of intermodulation components in the envelope signal spectrum by 20 ... 25 dB.
关键词： envelope tracking,power amplifier,harmonic distortion,efficiency,multicell
更新于2025-09-23 15:23:52