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991.
对承受内压、非等厚轴对称双曲薄壳,基于大塑性变形几何关系,通过严格的数学推导,建立了用微分代数方程组描述的数学模型。避免了Gleyzal等建立的变形几何关系采用Taylor展开,导致求解大应变问题精度较低的不足。采用可变步长和变阶的Klopfenstein-Shampine数值微分方法进行计算,可方便地获得该类结构应力、应变和位移等参量的变化规律。通过对比该数学模型和基于Gleyzal几何关系数学模型的数值计算结果与试验结果,验证了模型能较好地描述胀形双曲金属薄壳的大应变特性。 相似文献
992.
半纤维素基水凝胶是一种具有优异保水性、良好生物相容性和力学性能的三维网络状亲水聚合物,在软材料领域尤其是半纤维素基材料研究领域备受瞩目。本文综述了近年来半纤维素基水凝胶的研究进展,从化学交联和物理交联两个方面介绍了半纤维素基水凝胶的制备方法、形成机理和性能,比较了化学交联中光、酶、微波辐射和辉光放电电解等离子体等不同引发体系的差异,总结了半纤维素基水凝胶在药物控释、伤口敷料、高效吸附及3D打印等领域的最新应用和发展,并对半纤维素基水凝胶领域所面临的挑战进行了总结和展望,以期为新型半纤维素水凝胶的研究提供参考。 相似文献
993.
Hongyang Wang Baoqiang Feng Gang Song Liming Liu 《Materials and Manufacturing Processes》2018,33(7):735-742
The laser–tungsten inert gas hybrid welding method was adopted to realize the welding process between Q460 high-strength steel and 6061 aluminum alloy. The influence of the dual heat source on the mechanical properties and microstructure of the welded joints are discussed. In addition, the effects of including a copper–zinc interlayer on the microstructure, elemental distribution, and mechanical properties of welded joints are also studied. The results show that the mechanical properties of the welded joints are influenced by the relative heat inputs of the two heat sources and the Cu-Zn interlayer. The braze welded joint fabricated without a Cu-Zn interlayer fractured at an Al-Fe intermetallic compound (IMC) layer formed at the interface, whereas the braze welded joint fabricated with a Cu-Zn interlayer fractured at an Al-Cu IMC layer formed at the interface. Comparisons show that the maximum tensile shear load of the brazed welded joint with the Cu-Zn interlayer was increased by about 20% relative to that formed without the interlayer. The formation of Al-Fe IMC layer in the deep penetration joint was inhibited by the combined effect of the dual heating sources and the Cu-Zn interlayer. 相似文献
994.
本文利用均匀化方法预测复合材料导热性。采用这一方法给出了单向纤维复合材料沿纤维方向的导热性表达式;将该方法与有限元技术结合得到了在垂直于纤维方向上复合材料导热性数值形式的预测结果。根据这些结果我们用曲线形式给出了材料导热性同各组分体分比间的关系,分析了体分比、纤维截面形状和分布方式、纤维和基体间的相对导热系数等因素对材料整体导热性影响。注意到纤维分布的随机性,本文还研究了纤维相对位置对材料导热性的影响,指出相对位置的变化可导致材料的各向异性导热性。本文指出基体相导热性对材料整体导热性的影响比纤维相的影响更重要。和已有的理论和实验结果的比较说明,本文提出的方法是很有效的。 相似文献
995.
Fei Li Heqiu Zhang Lizhong Hu Yingmin Luo Yu Zhao Yu Qiu Jiuyu Ji Lunlun Yue 《Journal of Materials Science: Materials in Electronics》2013,24(12):4812-4816
One-dimensional (1D) ZnO microwires were successfully synthesized by chemical vapor deposition and their structural and morphological properties were analyzed by X-ray diffraction and scanning electron microscopy, demonstrating that the microwires were single crystalline with perfect hexagonal structure and smooth surface. Using these 1D microstructures, we fabricated a novel ZnO-based ethanol gas sensor. Operating at room temperature, the sensor was found to have good sensing characteristics. The reliability and stability of the sensor could be improved by connecting multiple 1-wire devices (1-WD) in parallel into a multi-wires device. In interior natural lighting environment and under 3 V bias, the response and recovery time of the 1-WD to 200 ppm ethanol gas were <10 s and about 300 s, respectively, and the minimum and maximum detection limit were about 2 and 200 ppm, respectively. A sensing model was proposed for discussing the performance of the sensor. The simplicity in fabrication, low power consumption and low cost make the sensor suitable for practical application in many fields, especially in identifying driving under the influence and chemical industry monitoring. 相似文献
996.
Bubble-liquid turbulent flow has an excellent heat and mass transfer behaviors than single gas or liquid flow. In order to analyze the effects of normal and reduced gravity on cold bubble-liquid two-phase turbulent flow in bubble column a second-order moment cold bubble-liquid two-phase turbulent model was developed to disclose the bubble dispersion characteristics. Under the reduced gravity condition, volume fraction caused by the decrease of buoyance force is larger than normal gravity level due to bigger bubble solid volume. In addition, bubble frequency is also decreased by in decrease of buoyance force. Normal and shear stresses have strongly anisotropic characteristics at every directions and have larger values under normal gravity than reduced gravity. The liquid turbulent kinetic energy has the two-peak bimodal distribution and weaker than bubble turbulent kinetic energy with one peak unimodal, which is caused by vigorous wake fluctuations. The correlation of fluctuation velocities between bubble and liquid has clearly anisotropic behaviors Under reduced gravity, the bubble motion has a little impact on liquid turbulent flow caused by slight buoyancy force, however, it will greatly reduce the liquid turbulent intensity due to energy cascade transport, which was transformed into bubbles or dissipated by interface friction. Bubble formation and detachment mechanisms affected by gravity conditions lead to the different levels of bubble dispersion distributions. 相似文献
997.
998.
Isolation and characterization of a nitrobenzene degrading yeast strain from activated sludge 总被引:2,自引:0,他引:2
Strain Z1 was isolated from nitrobenzene-contaminated sludge. Strain Z1 was able to utilize nitrobenzene as a sole source of carbon, nitrogen, and energy under aerobic condition. Based on the morphology, physiological biochemical characteristics, and 26S rDNA D1/D2 domain sequence, strain Z1 was identified as Rhodotorula mucilaginosa. Strain Z1 mineralized up to 450mg L(-1) nitrobenzene. Kinetics of nitrobenzene degradation was described using the Andrews equation. The kinetic parameters were as follows: q(max)=1.50h(-1), K(s)=31.31mg L(-1), and K(i)=101.34mg L(-1). Strain Z1 had a high-salinity tolerance. It degraded nitrobenzene effectively in 5% NaCl (quality concentration). Even in the presence of aniline or phenol, strain Z1 degraded nitrobenzene efficiently. Strain Z1 therefore could be an excellent candidate for the bio-treatment of nitrobenzene industrial wastewaters. 相似文献
999.
核-壳型磁性金属有机骨架材料Fe_3O_4@IRMOF-3的合成、表征及其催化反应研究 总被引:1,自引:0,他引:1
以Fe3O4为核心,以IRMOF-3为壳层,采用层层包裹的方法制备了核-壳结构的磁性Fe3O4@IRMOF-3材料。用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、透射电镜(TEM)、及扫描电镜(SEM)等手段对材料进行表征,并考察了材料在Knoevenagel缩合反应中的催化反应性能。实验结果表明,Fe3O4@IRMOF-3材料呈现出Fe3O4和IRMOF-3的双重功能,既可以磁性分离,又具有IRMOF-3的晶体结构、孔结构和催化性能,在Knoevenagel缩合反应中表现出较好的催化活性、选择性和稳定性。 相似文献
1000.