Al2O3—SiO2—TiO2复合陶瓷薄膜的制备与结构

本文利用Ｓｏｌ－Ｇｅｌ法制备了Ａｌ２Ｏ－ＳｉＯ２－ＴｉＯ２复合陶瓷薄膜，讨论了主要内容是体系成分（Ａｌ：Ｓｉ：Ｔｉ摩尔比）对落膜制备过程及结构的影响。通过分步水解法可以得到稳定的Ａｌ２Ｏ３－ＳｉＯ２－ＴｉＯ２复合溶胶，进而制备复合陶瓷薄膜。组分间的静电作用是溶胶凝结的原因。三组分中，Ｓｉ／Ｔｉ摩尔比是决定溶胶稳定性的主要因素。通过ＸＲＤ对薄膜的相组成进行了分析，表明复合薄膜由Ａｌ４Ｔｉ２ＳｉＯ１２     

溶胶—凝胶法在玻璃表面涂膜

利用溶胶－凝胶法以浸涂方式在玻璃基体上制备了ＳｉＯ２薄膜，研究了某些工艺参数，尤其是加水量Ｒ（水与正硅酸乙酯的摩尔比）对薄膜形成过程及薄膜质量的影响，用ＳＥＭ观察了不同薄膜的微观结构，并结合ＳｉＯ２的溶胶－凝胶过程中聚合物的结构及涂膜特性进行了讨论。     

纳米微孔SiO2薄膜的Sol—Gel制备及气孔率控制

本文报道了纳米微孔ＳｉＯ２薄膜的溶胶－凝胶（ｓｏｌ－ｇｅｌ）制备工艺,利用椭圆偏振光测试仪（Ｅｌｌｉｐｓｏｍｅｔｅｒ）直接测量了薄膜的厚度、折射率、从而得到了ＳｉＯ２薄膜的气孔率及气孔大小分布。研究了合成工艺条件及浓Ｈ２ＳＯ４表面修饰对ＳｉＯ２薄膜气孔率及稳定性的影响。     

溶胶—凝胶法制备有机改性SiO2—TiO2涂层的研究

用溶胶－凝胶法在ＰＭＭＡ上制得ＳｉＯ２－ＴｉＯ２涂层。溶胶粘度分析表明，溶胶以线性生长方式凝胶，适宜于制备薄膜。ＦＴＩＲ对涂层的干燥和热处理过程研究表明，涂层中形成Ｓｉ－Ｏ－Ｔｉ－Ｏ－Ｓｉ无机网络结构。扫描电镜对涂层中Ｔｉ－Ｓｉ元素的分布进行了能谱分析，发现无机网络主要分布于涂层的表面及界面处。     

超细孔二氧化硅膜的制备研究

以正硅酸乙酯（ＴＥＯＳ）为原料，采用溶胶－凝胶技术在多孔陶瓷载体上制备出具有３．０ｎｍ孔径的ＳｉＯ２陶瓷膜。考察了制膜过程中ＴＥＯＳ、乙醇、水的相对量；酸碱催化和ｐＨ值；热处理温度及成膜助剂对膜性能的影响。在自制的单管膜分离器上，测定了Ｏ２、Ｎ２、ＣＯ２和ＣＨ４等气体在ＳｉＯ２陶瓷膜上的渗透性能。     

Si片上PbTiO3薄膜的XPS研究

用溶胶－凝胶方法在Ｓｉ上成功地制备了钙钛矿型的ＰｂＴｉＯ３薄膜。Ｘ射线衍射结果显示,在热处理温度为７５０￣９００℃范围内,随温度升高,薄膜由多晶转变为定向结晶。Ｘ射线光电子能谱分析发现,薄膜表面存在ＳｉＯ２薄层,其厚度大约为０．６ｎｍ,该薄层是在制膜过程中衬底Ｓｉ通过ＰｂＴｉＯ３薄膜扩散到表面与大气中的Ｏ２反应而形成的。在７５０℃热处理的薄膜,膜层中不含ＳｉＯ２,但温度升高,膜层中存在ＳｉＯ２成分     

医用NiTi合金表面溶胶-凝胶法制备TiO2-SiO2薄膜

采用溶胶－凝胶法在ＮｉＴｉ形状记忆合金表面制备了ＴｉＯ_２－ＳｉＯ_２复合薄膜,在提高医用ＮｉＴｉ合金的抗腐蚀性方面,收到了显著的效果．运用电化学方法对不同组成的ＴｉＯ_２－ＳｉＯ_２薄膜在模拟体液中的腐蚀行为进行了研究,结果表明,随薄膜中 Ｔｉ／Ｓｉ比的增加,ＴｉＯ_２－ＳｉＯ_２薄膜的抗腐蚀性增强．划痕试验表明 ＴｉＯ_２－ＳｉＯ_２（Ｔｉ／Ｓｉ＝４：１）膜与ＮｉＴｉ合金基体具有较高的界面结合强度．用原子力显微镜（ＡＦＭ）对ＴｉＯ_２－ＳｉＯ_２薄膜的表面形貌及表面粗糙度进行观察和分析,解释并讨论了ＴｉＯ_２－ＳｉＯ_２薄膜的配方组成与其抗腐蚀性的关系,ＳｉＯ_２含量较少时,薄膜结构致密,膜层均匀平滑,且膜基结合力好,作为医用ＮｉＴｉ合金的表面保护层,可以使其耐腐蚀性有显著提高．     

溶胶—凝胶法制备TiO2—SiO2复合薄膜的研究

采用溶胶－凝胶方法在单晶Ｓｉ基片上制备了ＴｉＯ２－ＳｉＯ２复合薄膜，研究了溶剂、ｐＨ值对先体溶液成胶时间的作用，溶液的浓度、甩胶时的旋转速度、涂覆层数以及热处理温度对薄膜厚度、光学性能的影响。薄膜的折射率随温度增大，其主要贡献来自于薄膜中结构的变化。并测量了薄膜的Ｉ－Ｖ、Ｃ－ｆ特性，由于薄膜中的热击穿效应而使得ＴｉＯ２含量较高的薄膜２的Ｉ－Ｖ呈非线性变化。     

溶胶－凝胶法制备薄膜湿敏元件的研究

用溶胶－凝胶法制备了Ｒ２Ｏ－Ａｌ２Ｏ３－ＳｉＯ２系（Ｒ＝Ｌｉ，Ｎａ，Ｋ）薄膜湿敏元件，研究了它们的感湿特性，对薄膜的结构、导电机理进行了讨论．获得的湿敏元件具有响应快、滞后小和灵敏度高等优点．     

快速热处理对PZT薄膜的微结构及电性能的影响

采用改进的溶胶一凝胶技术,在Ｐｔ／Ｔｉ／ＴｉＯ２／ＳｉＯ２／Ｓｉ（１００）基片上制备了太电ＰＺＴ薄膜,用ＸＲＤ和ＡＦＭ技术分析了不同热处理工艺条件下ＰＺＴ薄膜的微观形貌变化及相结构演化,系统测试了ＰＺＴ薄膜的铁电性能。工艺－结构－性能研究结果表明：快速热处理工艺（ＲＴＡ）有利于ＰＺＴ薄膜保持较低的漏电流密度,热处理温度是影响晶粒大小的主要因素,而保温时间则对ＰＺＴ薄膜的致密性、晶粒均匀度和晶界结合     

The effect of an inclusion or a hole on an approaching crack in the three-point bend specimen

A numerical finite element analysis of the influence of a disturbance: an inclusion or a hole on the stress intensity factor at the tip of an edge crack in a three-point bend specimen is presented. The effect of four parameters is considered: the crack length, the disturbance size and its distance from the crack tip, and the original neutral axis. It is found that both disturbances have an inverse effect on the stress intensity factor: the hole increases it, whereas the inclusion causes it to decrease. The magnitude of the effect depends on the above-mentioned parameters. The numerical results are found to be in good agreement with preliminary experimental findings.     

Metastable defects in hydrogenated amorphous silicon

The electronic structure of hydrogenated amorphous silicon (a-Si:H) is in a state of metastable equilibrium and can change upon application of external stimuli. We study the effect of thermal quenching and light soaking in lithium-doped a-Si:H, on its conductivity and thermopower. We present evidence showing that the metastable state obtained after fast quenching is different than that obtained after light exposure. Experiments on chalcogenides show that they are not affected by thermal quenching although they change upon light soaking. This is in contrast with lithium doped a-Si:H in which both effects are observed. Our experiments suggest that hydrogen present in a-Si:H plays an important role by controlling heterogeneities and potential fluctuations in a-Si:H. Light soaking appears to enhance these potential flucutations, whereas fast cooling seems to have little effect on them.     

Nonuniform electric fields in pulse heated wires

The influence of nonuniform electric fields on the measurement of the electrical conductivity in pulse-heated wires is studied analytically. Two causes for nonuniformity are considered: switching-on of an external voltage source (transient skin effect) and temperature-dependent change of the electrical conductivity. This problem usually has two strictly different time scales: a short one, on which the transient skin effect takes place, and a long one, on which heat conduction happens. Here, the short time scale is considered.Paper presented at the Third Workshop on Subsecond Thermophysics, September 17–18, 1992, Graz, Austria.     

声景观边缘效应对福州西湖公园声景观评价的影响

基于声景生态学,研究城市公园声景观边缘效应,以福州西湖公园为研究对象,采用实地调查法及语义差别法(Semantic Differential Method,SD),进行城市公园边界内外两侧空间的声景观评价。结果表明:(1)公园绿地边缘对声景观有优化作用,大部分情况下,声景观边缘效应在公园边缘外侧比内侧更明显,该效应一定程度上会影响景观使用者的心理感知;(2)公园不同质边缘的声景观边缘效应强度依次为:地形种植水体广场;(3)受声景观边缘效应影响较大的项目包括:噪声、气氛、美感、情绪、舒适度、愉悦度、吸引力。该研究将城市公园声景观评价由公园内部拓展到公园边缘及外部,为城市公园声景观的规划设计和声景观边缘效应研究提供了重要参考。     

Sustained release characteristics of tablets prepared with mixed matrix of sodium carrageenan and chitosan: effect of polymer weight ratio, dissolution medium, and drug type

The interpolymeric complexation of carrageenan and chitosan was investigated for its effect on drug release from polymeric matrices in comparison to single polymers. For this purpose, matrices with carrageenan: chitosan (CG:CS) ratios of 100%, 75%, 50%, 25%, and 0% were prepared at 1:1 drug to polymer ratio. The effect of dissolution medium and drug type on drug release from the formulations was addressed. Two model drugs were utilized: diltiazem HCl (DZ) as a salt of a basic drug and diclofenac Na (DS) as a salt of an acidic drug. Three dissolution media were used: water, simulated gastric fluid (SGF), and simulated intestinal fluid (SIF). Some combinations of the two polymers showed remarkable sustained release effect on DZ in comparison to the single polymers in water and SGF. However, no apparent effect for the combination on DZ release was shown in SIF. The medium effect was explained by the necessity of chitosan ionization, which could be attained by the acidic SGF or microacidic environment created by the used acidic salt of DZ in water, but not in SIF. An interaction between the medium type and CG:CS ratio was also found. With DS, the polymer combinations had similar dissolution profiles to those of the single polymers in water and SIF, which was explained by the lack of chitosan ionization by the medium or the drug basic salt. The dissolution profiles could not be obtained in SGF, which was attributed to the conversion of DS into diclofenac free acid. The importance of chitosan ionization for its interaction with CG to have an effect on the release of DS was demonstrated by performing dissolution of SGF presoaked tablets of DS in SIF, which showed an effect of combining the two polymers on sustaining the drug release.     

Study of the mechanical properties of Nd:YVO4 crystal by use of laser interferometry and finite-element analysis

A hybrid method that combines experimental and numerical approaches for determining the material properties of Nd:YVO(4) is reported. In the experimental investigations a laser interferometer is proposed for measuring the physical deformation of lasing materials at the end-pump surface. By matching with the measured end bulging, we have implemented a numerical solution with finite-element analyses to determine the Poisson ratio and Young's modulus of the crystal. The accuracy interval of the evaluated Poisson ratio of 0.33 and Young's modulus of 133 GPa is discussed numerically. Based on the mechanical properties obtained, the end effect is separated from thermal effects, and it shows that the end effect results in an approximate equal thermal lensing effect compared with the index parts for end-pumped Nd:YVO(4) lasers.     

Magnetoelectric coupling, efficiency, and voltage gain effect in piezoelectric-piezomagnetic laminate composites

The magnetoelectric (ME) effect of piezoelectric-magnetostrictive laminate composites, which is a product tensor, has been studied. Based on piezoelectric and piezomagnetic constituent equations, the longitudinal-mode vibration and equivalent circuits have been derived. The effective magnetoelectric coupling coefficient, voltage-gain, and output efficiency have been determined. Our results show: (i) that there is an extreme high voltage gain effect of >260 under resonance drive: the induced ME voltage is much higher than the input voltage to the coils for magnetic excitation; (ii) that there is an optimum ratio of the piezoelectric to piezomagnetic layer thicknesses, which results in maximum effective magnetoelectric coupling; and (iii) that the maximum output efficiency of magnetoelectric laminate at resonance drive is ∼98%, if eddy currents are neglected. This high ME voltage gain effect offers potential for power transformer applications.     

The Significance of Lead and Iron Ions for the Photographic Process

The method described previously for investigating the action of different addenda on the photosensitivity of silver bromide crystals has been used to study the effect of lead and iron ions on both stages of the photographic process. It is established that lead ions have a catalysing effect on the process of development and promote the latent image formation. Iron ions have an adverse effect on the two stages of the photographic process : although hindering the process of development, they have a strongly marked sensitizing effect on the latent image formation. The influence of iron ions on sensitized crystals has also been followed. The mechanism of the action of the addenda is discussed.     

风场类型对方形超高层建筑顺风向气动阻尼的影响研究

摘要：通过8个典型超高层建筑气动弹性模型的风洞试验,利用随机减量法从模型的风致加速度响应中识别了气动阻尼,并通过与前人相关研究成果及基于准定常理论的计算结果的比较,验证了识别结果的正确性。在此基础上,研究了典型超高层建筑顺风向气动阻尼比的变化规律,考察了风场类型对建筑结构顺风向气动阻尼比的影响。研究结果表明：在I－IV类风场下,建筑结构的气动阻尼比随折减风速增长的速度渐缓;在V－VIII类风场下,风场对顺风向气动阻尼比的影响不是很显著。基于大量矩形截面超高层建筑顺风向气动阻尼特性研究,并结合风场类型的影响,给出相应的经验公式,供工程设计人员参考。     

Effects of the transverse stress on biaxial fatigue crack growth predicted by plasticity-corrected stress intensity factor

The transverse stress has an important effect on the biaxial fatigue crack behavior. However, the experimental evidence has provided conflicting indications: it is sometimes considered to increase, decrease or have no effect. These complex phenomena cannot be rationally explained by the existing mechanical models. The effect of the transverse stress on the fatigue crack growth behavior is still one of the most puzzling questions in biaxial fatigue. Physically, this effect is a transverse stress induced plasticity phenomenon. In this paper, a plasticity-corrected stress intensity factor (PC-SIF) is proposed to describe the effect of transverse stress on biaxial fatigue. By use of this new crack driving force some important phenomena associated with transverse stress are predicted. Comparisons with experimental results showed that the PC-SIF as an effective mechanical parameter is capable of predicting the effects of the crack length, the stress level, cyclic stress ratio, biaxial stress ratio and phase difference on the biaxial fatigue crack growth. Consequently, the alleged conflicting experimental results have been rationally explained by the PC-SIF.