HOMOGENIZATION OF A STATIONARY NAVIER-STOKES FLOW IN POROUS MEDIUM WITH THIN FILM

The article studies the homogenization of a stationary Navier-Stokes fluid in porous medium with thin film under Dirichlet boundary condition.At the end of the article,＂Darcy＇s law＂is rigorously derived from this model as the parameter ε tends to zero,which is independent of the coordinates towards the thickness.

Effect of Magnetohydrodynamic on Thin Films of Unsteady Micropolar Fluid through a Porous Medium

In This paper, we deal with the study of the effect of magnetohydrodynamic on thin films of unsteady micropolar fluid through a porous medium. These Thin films are considered for three different geometries. The governing continuity, momentum and angular momentum equations are converted into a system of non-linear ordinary differential equations by means of similarity transformation. The resulting system of coupled non-linear ordinary differential equations is solved numerically by using shooting method. A representative set of numerical results in the three thin film flow problems for velocity and micro-rotation profiles are discussed and presented graphically. A comprehensive parametric study is carried out to show the effects of the micropolar fluid parameters, magnetic field parameter, permeability parameter and etc. on the obtained solutions.

Evolution of Surface Oxide Film of Typical Aluminum Alloy During Medium-Temperature Brazing Process

The evolution of the surface oxide film along the depth direction of typical aluminum alloy under mediumtemperature brazing was investigated by means of X-ray photoelectron spectroscopy(XPS). For the alloy with Mg content below 2.0wt%, whether under cold rolling condition or during medium-temperature brazing process, the enrichment of Mg element on the surface was not detected and the oxide film was pure Al2O3. However, the oxide film grew obviously during medium-temperature brazing process, and the thickness was about 80 nm. For the alloy with Mg content above 2.0wt%, under cold rolling condition, the original surface oxide film was pure Al2O3. However, the Mg element was significantly enriched on the outermost surface during medium-temperature brazing process, and MgO-based oxide film mixed with small amount of MgAl2O4 was formed with a thickness of about 130 nm. The alloying elements of Mn and Si were not enriched on the surface neither under cold rolling condition nor during mediumtemperature brazing process for all the selected aluminum alloy, and the surface oxide film was similar to that of pure aluminum, which was almost entire Al2O3.

Hydromagnetic thin film flow of Casson fluid in non-Darcy porous medium with Joule dissipation and Navier＇s partial slip

In this paper, the effects of viscous and Ohmic heating and heat genera- tion/absorption on magnetohydrodynamic flow of an electrically conducting Casson thin film fluid over an unsteady horizontal stretching sheet in a non-Darcy porous medium are investigated. The fluid is assumed to slip along the boundary of the sheet. Similar- ity transformation is used to translate the governing partial differential equations into ordinary differential equations. A shooting technique in conjunction with the 4th order Runge-Kutta method is used to solve the transformed equations. Computations are car- ried out for velocity and temperature of the fluid thin film along with local skin friction coefficient and local Nusselt number for a range of values of pertinent flow parameters. It is observed that the Casson parameter has the ability to enhance free surface velocity and film thickness, whereas the Forchheimer parameter, which, is responsible for the inertial drag has an adverse effect on the fluid velocity inside the film. The velocity slip along the boundary tends to decrease the fluid velocity. This investigation has various applications in engineering and in practical problems such as very large scale integration （VLSI） of electronic chips and film coating.

Study of Ge_2Sb_2Te_5 Film for Nonvolatile Memory Medium

The amorphous Ge2Sb2Te5 film with stoichiometric compositions was deposited by co-sputtering of separate Ge, Sb, and Te targets on SiO2/Si (100) wafer in ultrahigh vacuum magnetron sputtering apparatus. The crystallization behavior of amorphous Ge2Sb2Te5 film was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). With an increase of annealing temperature, the amorphous Ge2Sb2Te5 film undergoes a two-step crystallization process that it first crystallizes in face-centered-cubic (fcc) crystal structure and finally fcc structure changes to hexagonal (hex) structure. Activation energy values of 3.636±0.137 and 1.579±0.005 eV correspond to the crystallization and structural transformation processes, respectively. From annealing temperature dependence of the film resistivity, it is determined that the first steep decrease of the resistivity corresponds to crystallization while the second one is primarily caused by structural transformation from 'fcc' to 'hex' and growth of the crystal grains. Current-voltage (Ⅰ-Ⅴ) characteristics of the device with 40 nm-thick Ge2Sb2Te5 film show that the Ge2Sb2Te5 film with nanometer order thickness is still applicable for memory medium of nonvolatile phase change memory.

草状氧化铝微结构渐变折射率的计算及实验研究

针对草状氧化铝的微纳结构对折射率的影响,采用台体计算法与柱体计算法计算氧化铝的体积,使用Clausius-Mossotti方程式与MATLAB软件拟合计算微纳结构的折射率变化,使用TFC软件进行拟合,最终计算出草状氧化铝的渐变折射率,研究其微结构的形貌特征及渐变折射率的分布,计算其可见光减反射性能。采用电子束沉积氧化铝薄膜,通过对沉积温度、水煮工艺等参数的优化,获得了不同结构的草状氧化铝纳米薄膜,制备了可见光波段420~680 nm的减反射薄膜。

高分辨率探测器短中波红外滤光片的设计及其光谱特性研究

短中波红外滤光片是航天光学遥感相机上的关键器件之一。高分辨率探测器的光谱响应由滤光片的光谱特性决定,其中短中波红外占有很大比重,传统方式制备的短中波红外滤光片与理论值存在差距,使得短中波红外滤光片发生光谱角漂或温漂等现象,在高分辨率探测器中形成高频和低频光谱混合叠加导致复原光谱失真。本文提出了一种高透过率低漂移高分辨率探测器短中波红外滤光片的设计及研制方法。为了达到短中波红外滤光片特定波长滤光特性的要求(在3.5~4.1μm波段范围内实现98%以上透过率,在2.4~3.35μm、4.25~6.4μm两个波段范围内实现截止),以Si材料为滤光片的基底材料,采用模拟染色体遗传交叉算法以带通滤光高低反射率膜堆结构进行了结构迭代设计,薄膜的高折射率材料采用TiO_(2),低折射率材料采用SiO_(2),该结构设计使得膜层数量大为减少,通过温漂测试、角漂测试、光谱特性分析及面形测试,短中波红外滤光片达到了前后双波段截止、高通带透过率的目标。环境测试试验表明,短中波红外滤光片膜层与基底材料匹配性适宜、膜层稳定性较高,适用于空间严酷的温度变化、高能粒子辐照环境。

超越景观的“词”与“物”:中国当代电影中风景的三重演绎

中国当代电影关于风景的讨论,常从“寄情于景”等美学意境层面展开,显然这一向度未能言及风景的文化实践、视觉批判等多重面向。对“风景与电影”进行不同层面的分析发现尚未形成一定的研究体系。在中国当代电影中承担着多重话语实践,影像中的风景既是“物”的呈现,又昭示着“词”的指向。当代电影中风景存在着三重演绎及其互动关系:作为“词”的风景,意在从人赋予“原初-大地”的主体意识、象征意涵、质料特质的“景”出发,探寻影像中的自身与主体隐喻之间的关联;作为“物”的风景,经由影像勾勒“器具-真实”的物之物象,来确认人与“世界”的连接;最后超越“词与物”的“真理-风景”,赋予了“我”与“世界”的“触媒”,是“敞开-境域”与想象能指。风景散溢在有限荧幕画幅内与无限延展空间外的双向维度上发出了超越“词”与“物”的影像表达与文化诘问。

Thin Film of Mesoporous MCM-41 Grown on Indium-Tin-Oxide Glass Substrate

From a basic solution containing celyltrimethylammonium cations as the template, thin film of mesoporous MCM-41 has been grown on the surface of a pre-treated indium-tin-oxide conducting glass substrate. The channel axis of the film is oriented parallel with the surface plane of the substrate, and the film is stable after careful removal of template in vacuum.

BIODEGRADATION OF REGENERATED CELLULOSE FILMS BY FUNGI

The biodegradability of Aspergillus niger (A. niger), Mucor (M-305) and Trichoderma (T-311) strains on regenerated cellulose films in media was investigated. The results showed that T-311 strain isolated from soil adhered on the cellulose film fragments has stronger degradation effect on the cellulose film than A. niger strain. The weights, molecular weights and tensile strengths of the cellulose films in both shake culture and solid media decreased with incubation time, accompanied by producing CO2 and saccharides. HPLC, IR and released CO2 analysis indicated that the biodegradation products of the regenerated cellulose films mainly contain oligosaccharides, cellobiose, glucose, arabinose, erythrose, glycerose, glycerol, ethanal, formaldehyde and organic acid, the end products were CO2 and water. After a month, the films were completely decomposed by fungi in the media at 30 degrees C.

Fabrication and photoluminescence characteristics of nonuniform Yb-Er codoped films

The nonuniform Yb-Er Codoped Al2O3 films were prepared on SiO2/Si substrates using a medium frequency magnetron sputtering system. Two asymmetry targets in the system were introduced to realize the nonuniform dopant. Some curves of Photoluminescence （PL） peak intensity were obtained by adjusting the deposition parameters, such as, the pillar number of erbium and ytterbium in the mixed target and the distance between a sample table and targets. Typically, the curve of PL peak intensity against the offset distance was approximately linear. The ratio of the PL intensity at the two ends of the same sample was 12.6 and the slope was 71.83/mm when the pillar numbers of the erbium and ytterbium in the mixed target are 5 and 60, respectively, and the distance between targets and the sample table is 2.9 cm.

6063铝合金阳极氧化膜中温无镍封孔工艺

以醋酸镁和醋酸锂为主盐,聚乙二醇600(PEG600)为表面活性剂,对6063铝合金阳极氧化膜进行封孔处理。研究了封孔时的pH、温度和时间对阳极氧化膜耐蚀性的影响,得到较优的封孔工艺参数为:Mg(CH_(3)COO)_(2)·4H_(2)O 3g/L,CH_(3)COOLi 7 g/L,三乙醇胺2 g/L,PEG 6006 g/L,苯并三氮唑(BTA)5 g/L,温度75℃,pH 6.1,时间30 min。采用扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、电化学测试等手段分析了阳极氧化膜封孔前后的微观形貌、元素组成和耐蚀性,并简要分析了封孔机理。在较优工艺条件下封孔后阳极氧化膜的微观表面更加粗糙,耐蚀性良好,封孔产物主要由Mg、Li和Al的氧化物与氢氧化物所组成。

非饱和颗粒材料的多孔连续体有效压力与有效广义Biot应力

多孔连续体理论框架下的非饱和多孔介质广义有效压力定义和Bishop参数的定量表达式长期以来存在争议,这也影响了对与其直接相关联的非饱和多孔介质广义Biot有效应力的正确预测.基于随时间演变的离散固体颗粒−双联液桥−液膜体系描述的Voronoi胞元模型,利用由模型获得的非饱和颗粒材料表征元中水力-力学介观结构和响应信息,文章定义了低饱和度多孔介质局部材料点的有效内状态变量:非饱和多孔连续体的广义Biot有效应力和有效压力,导出了其表达式.所导出的有效压力公式表明,非饱和多孔连续体的有效压力张量为各向异性,它不仅对非饱和多孔连续体广义Biot有效应力张量的静水应力分量的影响呈各向异性,同时也对其剪切应力分量有影响.文章表明,非饱和多孔连续体中提出的广义Biot理论和双变量理论的基本缺陷在于它们均假定反映非混和两相孔隙流体对固相骨架水力−力学效应的有效压力张量为各向同性.此外,为定义各向同性有效压力张量和作为加权系数而引入的Bishop参数并不包含对非饱和多孔连续体中局部材料点水力−力学响应具有十分重要效应的基质吸力.所导出的非饱和多孔介质广义Biot有效应力和有效压力公式(包括反映有效压力各向同性效应的有效Bishop参数)可在以协同计算均匀化方法为代表的非饱和颗粒材料计算多尺度方法中上传到在宏观非饱和多孔连续体设置了表征元的局部材料点.

一种即用液态型口服纤维素类胃超声显影剂制备的体外筛选实验

目的旨在制备一种使用便捷的、液态即用型基于纤维素类的口服胃超声显影剂。方法本研究通过大量的体外筛选实验,筛选了甲基纤维素、乙基纤维素、羧甲基纤维素、羟丙基甲基纤维素、聚葡萄糖、阿拉伯胶、微晶纤维素、胶态微晶纤维素等材料,通过筛选实验考察它们在不同温度水(凉水10℃、温水40℃和热水90℃)冲泡的难易程度、以及冲泡混合后的超声成像质量。为获得最佳的筛选实验结果,以目前使用市售产品做为参照对比研究。着重考察上述常见纤维素类物质单一和复配后水混悬液的超声成像效果,包括不同浓度和不同粒径纤维素的超声成像效果。其它评价试验还包括:沉降体积比的测定、离心稳定性测定、冻融循环稳定性试验、加水稀释试验等。结果根据上述筛选实验最终表明,发现选用2%微晶纤维素(优选粒径80~110μm)有很好的超声成像效果,胶态微晶纤维素Avicel CL-611(浓度为2.0%)对其具有极佳的助悬作用,因此微晶纤维素(优选粒径80~110μm)和胶态微晶纤维素分别作为本发明胃超声显影剂的超声成像颗粒和助悬增稠剂,最为理想。该理想配方的口服胃超声显影剂的物理性能指标分析结果:其沉降体积比为1.0,离心稳定不分层,冻融循环稳定不分层,加水稀释混匀时间为6 s。结论本研究通过大量筛选实验,提供一种使用便捷的、液态即用型口服胃超声显影剂配方及其制备方法。

高耐蚀Fe-Cr-Ni系中熵合金在H_(2)SO_(4)溶液中的腐蚀行为

开发了一种低成本Fe-Cr-Ni系中熵合金,通过与316L不锈钢进行对比研究了该中熵合金在0.1 mol·L^(-1) H_(2)SO_(4)溶液中的耐腐蚀性能,分析了其表面钝化膜的保护能力。结果表明:与316L不锈钢相比,试验合金的自腐蚀电位更高,自腐蚀电流密度更小,说明其腐蚀抗力更强,腐蚀速率更慢,耐腐蚀性能更好;试验合金表面钝化膜中的铬、镍元素含量更高,铁、锰元素含量更低,电荷转移电阻为316L不锈钢的8.1倍,说明合金表面形成了更具保护力的钝化膜;试验合金具有稳定的单相面心立方固溶体组织,元素偏析程度较低,使得合金钝化能力提高、腐蚀敏感性降低,从而保证了钝化膜的稳定性和保护能力。

Fe_(60)Cr_(18)Cu_(3)(MnCoNiMoAlTi)_(19)中熵合金时效硬化与耐蚀性能

采用真空电弧炉熔炼制备Fe_(60)Cr_(18)Cu_(3)(MnCoNiMoAlTi)_(19)中熵合金,研究了合金的时效硬化机理和耐腐蚀性能。结果表明,中熵效应使合金凝固组织具有简单的BCC固溶体结构。HRTEM研究发现,超饱和固溶体基体高晶格畸变有利于合金时效后纳米有序B2共格相大量弥散析出,最高时效硬度达到621HV_(0.5)。特别是抗热硫酸腐蚀和NaCl溶液点蚀性能与相同Cr、Ni含量的时效硬化不锈钢17-4PH相比均获得了大幅提升,表现为更宽、更稳定的阳极钝化区和显著较低的腐蚀溶解速度。XPS分析结果表明,高含量Cr_(hy)^(3+)、Cr_(ox)^(3+)、Cu_(ox)^(+)、Ti_(ox)^(4+)、Al_(ox)^(3+)和Mo_(ox)^(6+)耐蚀元素离子组成的多元钝化膜是其抑制Cl-点蚀坑形核和扩展的重要原因。

PVDF薄膜传感器用于测试块状岩石表面爆炸应力的研究

采用PVDF(聚偏二氟乙烯)薄膜传感器对岩石表面爆炸应力进行测量,并分析炮孔内不同填塞介质对爆炸应力波在岩石介质中传播的影响。在直径为28 mm、孔深为25 cm的炮孔内填塞不同的介质(空气、水或沙子),采用不同的装药结构分别进行爆破试验,通过PVDF薄膜传感器得到了不同工况下岩石表面应力波时程曲线。分析炮孔内不同填塞介质对爆炸应力波透射的影响发现,水作为炮孔填塞介质时,爆炸应力波透射能力强,炸药爆炸产生的能量用于岩石破碎的比例高。水作为炮孔填塞介质时,为达到岩石开裂效果,装药结构设计为1发8^(#)雷管加2 g传爆药(聚黑-14);当沙子作为炮孔填塞介质时,为达到岩石的开裂效果,装药结构设计为1发8^(#)雷管、2 g传爆药(聚黑-14)和20 g炸药(聚黑-2);前者炸药用量仅为后者的15.3%。炸药使用量减少,也降低了爆破次生危害的影响程度。用PVDF薄膜传感器在岩石表面直接测量爆炸应力的方法是可行的。

FeCrNi中熵合金薄膜电沉积工艺正交优化及其耐蚀性

采用电化学沉积法在铜基体上制备FeCrNi中熵合金薄膜,以沉积速率和电流效率为评价指标,通过四因素三水平正交试验得到电沉积的较优工艺条件为:电流密度200 mA/c^(2)或100 mA/c^(2),温度30℃,时间15 min。采用X射线衍射仪(XRD)、场发射电子探针显微镜(EF-EPMA)分析了较优条件下所得FeCrNi中熵合金薄膜的显微组织和元素分布,并采用电化学方法研究了其在3.5%NaCl溶液中的耐蚀性。结果表明,所得FeCrNi中熵合金薄膜由大量球状颗粒组成,为非晶态结构,表面存在大量微裂纹,Fe、Cr、Ni三种元素在薄膜中分布均匀。综合考虑电沉积速率、电流效率及FeCrNi中熵合金薄膜的耐蚀性后确定电沉积的最佳电流密度为100 mA/c^(2)。

石榴组培苗试管外生根条件探究

目的:筛选石榴组培苗试管外生根的最适条件,为石榴工厂化育苗奠定理论基础。方法:以‘白花玉石籽’石榴组培苗为试验材料,研究不同因素对石榴组培苗试管外生根的影响,筛选最适试管外生根条件。结果:最适石榴试管外生根条件培养石榴组培苗生根率及移栽成活率均达到100%,且比试管内生根培养节约了30 d的时间,移栽成活率提高了14.79%。结论:培养15 d的石榴组培苗移栽到基质(草炭∶蛭石=1∶4)中,用WPM+0.8 mg/L IBA浇透基质,覆膜12 d,在温度25℃、光照强度2000 lx、光照10 h条件下培养,提高了石榴组培苗的生根率及移栽成活率。

成膜介质和还原剂对大豆分离蛋白膜性能的影响

研究了成膜介质和还原剂对大豆分离蛋白膜(SPI)性能的影响。结果表明,大豆分离蛋白在自制玻璃板上成膜效果最好;亚硫酸钠可明显提高SPI膜的抗拉强度,对透气度和透光率影响不显著;添加0.1%亚硫酸钠的SPI膜抗拉强度最大,超过0.1%,抗拉强度下降明显。