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91.
采用尿素调节三水醋酸钠的相变温度到合适范围再添加膨胀石墨来降低过冷度,研制了高性能的三水醋酸钠-尿素-膨胀石墨混合相变材料,并对其在电地暖中的应用性能进行了研究。结果表明,当尿素质量分数为36.5%、膨胀石墨添加量为4%(质量)时,所得混合相变材料的熔化焓高达209.1 J/g,熔点在31.98℃,过冷度仅为2.04℃,热导率为2.349 W/(m·K),热可靠性良好;将用该混合相变材料制成的相变板安装在实验房的电地暖中时,实验房的热舒适度随着相变材料层厚度的增加而增加,但也带来加热时间和用电量的增加;当相变材料层厚度为10 mm时,电加热温度适宜设置在45℃;在热舒适度相当的条件下,有相变板的实验房与无相变板的参比房相比具有用电量小及电费低的优势。 相似文献
92.
《International Journal of Hydrogen Energy》2020,45(32):15915-15923
The exploration of photocatalytic transformation of solar energy into H2 through water splitting is an important direction towards sustainable and non-polluting energy in order to cover energy necessity partially. Ternary transition metal chalcogenides have been attracted attention among the other chalcogenides due to their potential applications in the photocatalytic and electrocatalytic hydrogen evolution. Herein, Cu2WS4 nanocubes and Cu2WSe4 nanosheets have been synthesized through a facile hot-injection method to benefit from the advantages such as minimizing the required pressure and reaction time by this technique. The photocatalytic hydrogen evolution activities of Cu2WS4 and Cu2WSe4 have been investigated under the visible light irradiation by using eosin-Y (EY) dye and triethanolamine (TEOA) as a photosensitizer and an electron donor, respectively. Cu2WS4 nanocubes have exhibited higher photocatalytic activity and stability than Cu2WSe4 nanosheets. The photocatalytic HER rates of Cu2WS4 and Cu2WSe4 have been determined as 1260 μmol g−1 h−1 and 861 μmol g−1 h−1, respectively. Photocatalytic HER activities were figured out in the order of Cu2WS4 > Cu2WSe4 which could be attributed to differences between proton reduction potential and the conduction band energy levels. 相似文献
93.
《International Journal of Hydrogen Energy》2020,45(15):8094-8106
A titanium Porous Transport Layer (PTL) is usually used at the anode side of PEM water electrolyzers to ensure both the gas/water transport and the electric charges transfer. In this paper, four different sintered Ti powder PTLs were characterized to determine some properties, such as the pore size distribution, the porosity, and the permeability. Their influence on the electrolysis performance was investigated by using a 30 cm2 segmented cell which allowed measuring the current density distribution, while controlling temperature and pressure conditions. For a better understanding, in-situ techniques such as the Polarization Curves and the Electrochemical Impedance Spectroscopy (EIS) were used. A local characterization of mass transport limitations caused by oxygen saturation was carried out, paying special attention to the pressure influence when using a PTL with very small pores. The results showed that current density heterogeneities can be explained by microstructure changes along the PTL. The optimal geometric characteristics of the PTL depend not only on the operating conditions such as current density, pressure, and temperature but also on the catalyst layer properties. A new model for the constriction resistance between the catalyst layer and the PTL was proposed. 相似文献
94.
In this work, CuInS2/multiwalled carbon nanotube (MWCNT) layers are fabricated by the sol–gel spin-coating method. We introduce two forms of MWCNTs into a CIS2 solution, washed functional multiwalled carbon nanotubes (W-FMWCNTs) and unwashed-functional multiwalled carbon nanotubes (UW-FMWCNTs), in order to investigate the effects of MWCNTs and an acidic environment on the physical properties of the CIS2 absorber layers. The structure and morphology of the samples are investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The XRD study shows that all samples crystallize in a tetragonal structure. The results obtained from the optical, thermo-electric, and electrical measurements indicate that the two groups of CIS2 layers prepared using W- and UW-FMWCNTs show the opposite behaviors. The Seebeck coefficient (SC) measurements indicate possible formation of a p–n junction. 相似文献
95.
An improved multi-recessed 4H–SiC metal semiconductor field effect transistor (MRD-MESFET) with double-recessed p-buffer layer (DRB-MESFET) is proposed in this paper. By introducing a double-recessed p-buffer layer, the gate depletion layer is further modulated, and higher drain saturation current and DC transconductance are obtained compared with the MRD-MESFET. The simulations show that the drain saturation current of the DRB-MESFET is about 42.4% larger than that of the MRD-MESFET. The DC transconductance of the DRB-MESFET is almost 15% higher than that of the MRD-MESFET and very close to that of double-recessed structure (DR-MESFET) at the bias conditions of Vgs=0 V and Vds=40 V. The proposed structure has an improvement of 26.1% and 74.2% in the output maximum power density compared with that of the MRD-MESFET and DR-MESFET, respectively. In the meanwhile, the proposed structure possesses smaller gate-source capacitance, which results in better RF characteristics. 相似文献
96.
Graphene oxide (GO) is widely used as an interfacial material in applications such as organic light emitting diodes and photovoltaic devices. Herein we report a layer-by-layer (LbL) assembled GO thin film as an anode interfacial layer (AIL) for efficient polymer solar cells (PSCs). The GO thin film is fabricated by alternately depositing cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDDA) and GO on ITO/glass substrate, which possesses controllable thickness by adjusting LbL deposition frequency. The presence of ultrathin GO films improves the work function of ITO, leading to a better contact between the active layer and ITO anode. With the optimized number of deposition times, the efficiency of 6.04% for the PSC with PDDA-GO bilayer (GO-2) as the AIL was achieved. 相似文献
97.
介绍了高压变频调速变压器及高压变频器系统的基本原理及结构,详细论述了系统各组成部分的功能,并进行了举例说明。 相似文献
98.
介绍了基准光传输设备的基本组成和原理,指出低相噪长距离光纤传输中的问题所在,并提供了解决问题的方法,即数模混合器件的选择及改进滤波器设计. 相似文献
99.
向家坝水电站二期纵向围堰上游段座落于厚达45~62 m的覆盖层上,为提高接头段深厚覆盖层地基承载力,且保证导流期不同江水位时的堰体稳定,优化调整方案为,将接头段和导水段改为柔性结构。详细介绍了柔性结构段基础处理中所涉及的施工程序、施工技术和异常情况处理等。二纵围堰经过了2009年和2010年两个汛期的考验,安全监测显示与实际运行表明,柔性结构体结构稳定。将导水结构堰体改为柔性结构体,不仅节约了投资,而且保证了二期截流工程按施工总进度计划实施。 相似文献
100.
The present investigation is aimed at studying the deformation in thermo-microstretch elastic medium occuping the region y ? 0 with a stable internal heat source. A nonviscous fluid layer of height h is overlying the thermoelastic medium and a mechanical source of constant magnitude is applied along the fluid/solid interface. The normal mode analysis is used to obtain the exact expressions for displacement components, force stress, and temperature distribution. The numerical results are given and presented graphically for the Green–Lindsay theory of thermoelasticity. The variations of the considered variables through the horizontal distance are illustrated graphically. Comparisons are made with the results in the presence and absence of microstretch and microrotation parameters. 相似文献