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41.
The paper proposes a limit analysis approach to define the ultimate load capacity of orthotropic composite laminates under biaxial loading and plane stress conditions. A lower bound to the collapse load multiplier is computed by solving a maximization nonlinear problem, according to the static theorem of limit analysis. To set up the optimization problem a stress field distribution is hypothesized at lamina level, moreover inter-lamina stresses are also considered. The effectiveness and validity of the proposed approach is shown by comparing the obtained numerical predictions both with available experimental data and with other numerical results carried out by means of a different numerical lower bound approach. 相似文献
42.
This paper presents an experimental study of low velocity impact response of carbon/epoxy asymmetrically tapered laminates. The tests are realised at energy between 10 and 30 J on two types of layup with multiple terminated plies. The type and localisation of damage are analysed using C-scan and micrographs. Then, the data is compared with the response of corresponding respective plain laminate. The effects of some tapering parameters (taper angle, drop-off disposition and configuration) on the impact damage mechanisms are also investigated. Very similar impact damage phenomena are found between tapered and plain laminates. The presence of material discontinuity due to the resin pocket affects less the damage mechanism than the structural difference between the thick and the thin sections. 相似文献
43.
Adem Sreedhar I. Neelakanta Reddy Qui Thanh Hoai Ta Gitae Namgung Eunbin Cho Jin-Seo Noh 《Ceramics International》2019,45(6):6985-6993
In this paper, novel morphology correlation between silver nanowires (AgNWs) and cobalt (Co)-doped ZnO (Co-ZnO) flake-like thin films (nanowire/flake-like) has been proposed for enhanced photoelectrochemical (PEC) water splitting activity. Here in, high-quality AgNWs/Co-ZnO heterostructures enabled superior visible light water splitting activity compared to the pure ZnO and AgNWs/ZnO. To address the strategic effect of AgNWs coupling and transition metal (Co-2?at%) doping into the ZnO host lattice, we have carried out the X-ray diffraction, field emission scanning microscopy, X-ray photoelectron spectroscopy, UV–Vis transmittance, water contact angle and PEC analyses. In this way, PEC water splitting activity was mainly examined by linear sweep voltammetry (I-V), amperometric I-t and photoconversion efficiency (η) studies. The experimental results provide clear evidence of morphology correlation between AgNWs and Co-ZnO flake-like structures for strong visible light absorption. Specifically, AgNWs/Co-ZnO composites exhibited significant enhancement in the photocurrent density (7.0?×?10?4 A/cm2) than AgNWs/ZnO (3.2?×?10?4 A/cm2) and pure ZnO (1.5?×?10?6 A/cm2). As a result, detailed AgNWs/Co-ZnO geometry has great potential for photoconversion efficiency (0.73%). In a word, the merits of controllable AgNWs/Co-ZnO heterostructure are proposed to improve the visible light harvesting and charge carrier generation for energy conversion devices. 相似文献
44.
The main aim of this work is dual computer analysis of probabilistic coefficients for the homogenized tensor of the polymer filled with the rubber particles having randomized Poisson ratios of both constituents. The major issue is to verify an influence of a randomness in rubber Poisson ratio close to the compressibility limit on the uncertainty of the effective tensor probabilistic characteristics. Probabilistic analysis presented here is carried out using mainly the stochastic perturbation technique provided by the common application of the traditional FEM commercial code ABAQUS and the symbolic computations package MAPLE. This FEM-based technique employs polynomial response function of the optimum order recovered from the weighted least squares method and following a set of deterministic solutions obtained for various values of the randomized input parameter. Optimization procedure is released entirely into a symbolic environment, where maximization of the correlation factor together with minimization of the fitting variance and approximation error are applied. Homogenization technique consists in equating of deformation energies for the real composite and the artificial one characterized by the effective elasticity tensor with uncertainty. 相似文献
45.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献
46.
The lead-free piezoelectric ceramics (Na.47Bi.47Ba.06)1-xCaxTiO3 (x?=?0, 0.01, 0.02, 0.03, 0.05, and 0.08, abbreviated as BNBTC/0, BNBTC/1, BNBTC/2, BNBTC/3, BNBTC/5, and BNBTC/8, respectively) were obtained using the solid-state reaction method. The structure, electric conductivity, and dielectric, ferroelectric, and piezoelectric properties of the Ca2+-doped (Na.47Bi.47Ba.06)TiO3 ceramics were thoroughly investigated. The ceramics sintered at 1200?°C exhibit dense microstructures, having relative densities higher than 96%. The X-ray diffraction results demonstrate that all ceramics have a pure perovskite structure. The mean grain sizes of the ceramics are related to the Ca2+ quantity. A small quantity of Ca2+ ions (x?≤?0.03) improves the piezoelectric and ferroelectric properties of the samples. The dielectric behavior of the samples is sensitive to the Ca2+ content and electric poling. The results demonstrate that the electrical properties of the (Na.47Bi.47Ba.06)TiO3 lead-free ceramics can be well tuned by varying the Ca2+ quantity. 相似文献
47.
O.N. Kondrateva G.E. Nikiforova A.V. Tyurin M.A. Ryumin V.M. Gurevich A.P. Kritskaya K.S. Gavrichev 《Ceramics International》2018,44(15):18103-18107
The heat capacity of ytterbium orthovanadate was first measured by adiabatic calorimetry in the temperature range T?=?12.28–344.06?K. No obvious anomalies were observed on the curve obtained. The values of standard thermodynamic functions in the temperature range T?=?0–400 K were calculated. Based on low-temperature calorimetry data obtained, previously published data on the high-temperature heat capacity of ytterbium orthovanadate were corrected. The anomalous contribution to heat capacity for YbVO4 was compared with the data known for YbPO4. 相似文献
48.
Jeong Ha-Ram Cho Hye-Seung Cho Youn-Sup Kim Dae-Ok 《Food science and biotechnology》2020,29(12):1763-1770
Food Science and Biotechnology - Hardy kiwifruits (Actinidia arguta) contain various bioactive compounds such as vitamin C and phenolics and can withstand cold temperatures. Changes in soluble... 相似文献
49.
以废弃的流化催化裂化催化剂(简称SFCC)为载体、β-环糊精为金属络合剂、硝酸镍为镍源,采用湿法浸渍法制备β-环糊精修饰的Ni/SFCC催化剂(简称Ni/SFCC-CD催化剂),考察其对C9石油树脂的催化加氢性能。通过BET比表面积测试、H2程序升温还原、X射线光电子能谱等手段对催化剂的物相结构进行表征,研究β-环糊精的作用机理及其对催化剂加氢性能的影响。研究结果表明:在反应温度为260 ℃、反应压力为7 MPa、反应时间为2.0 h的最优条件下,采用Ni/SFCC-CD催化C9石油树脂加氢,可制得溴值为1.45 gBr/(100 g)、色号(加纳德)小于1的水白色氢化C9石油树脂,催化剂循环使用4次后仍保持良好活性;β-环糊精的作用机理是:β-环糊精与硝酸镍产生络合作用,抑制硝酸镍的分解、控制NiO的结晶过程和增强活性组分Ni与载体之间的相互作用力,从而提高了Ni/SFCC-CD的催化活性和稳定性。 相似文献
50.
Modern refractory castables contain between 3.5 and 5?wt.-% water that is necessary for sufficient flow during emplacement and for the formation of hydrate phases, necessary for the green strength of the material. Prior to the high temperature use of this material, it must be dried very carefully to avoid explosive spalling.This paper will demonstrate that beside conventional drying of pre-shaped materials in resistance furnaces microwave radiation is an energy saving and rapid method to remove pore water as well as hydrate bond water from the castable. In comparison to resistance furnaces, the use of microwave radiation does not affect the castable properties as there are mechanical strength (MOR, CCS), open porosity and pore size distribution. This study proved microwave radiation as valuable alternative with a series of tabular alumina based low cement castables (LLC) in which the water-to-cement-ratio (wcr = 0.64, 0.75, 0.82 and 1.13) was systematically altered by changing the cement concentration at constant mixing water concentration of 4.5%. 相似文献