超薄弹性层超声反射波频域测厚法

为了克服超声体积波测量方法只适用于测试厚度大于声波波长的弹性层的缺点,提出了频域相对传递函数法测量超薄弹性层的厚度的新方法.在推导超薄弹性层相对反射传递函数的基础上,用相对反射传递函数幅度谱、相位谱和复谱定征超薄弹性的厚度,分析了影响估计准确性的各种因素,研究了相对反射传递函数对厚度的灵敏度函数在误差传递中的意义.实验结果表明:相对传递函数法能够测量厚度为波长百分之一的铝薄层的厚度,相对误差小于2.5%,其中用幅度谱定征得到的结果最准确.这表明相对传递函数法可以有效地测量超薄弹性层的厚度,在实际应用中更加实用,其定征的准确性主要由相对传递函数对厚度灵敏度函数和测量误差共同决定.     

超薄单向纤维增强复合材料低频多模式超声兰姆波定征方法

提出低频多模式超声兰姆波定征方法来估计超薄层状单向纤维增强复合材料的密度、厚度、弹性常数等参数。这里"超薄"的概念是指材料厚度h远小于材料中的声波波长λ,导致在时域上材料前后界面的各次回波信号相互混迭。分析了沿平行和垂直于纤维两个方向上,在超薄层状单向纤维增强复合材料中传播的低频兰姆波色散特性,提出在最小二乘意义下以材料色散曲线为基础的反向算法对材料参数进行了估计。文中分析了影响估计准确性的各种因素,研究了该方法对材料参数的灵敏度及其在误差传递中的意义。结合超声漏兰姆波频域分析方法,并使用超声耦合剂耦合方式和一对中心频率为2MHz的宽带纵波换能器,实验结果证实,该方法能够准确估计h<0.05 λ的单向玻璃纤维增强双酚A型聚砜(PSF)复合材料的材料参数。      

低频多模式超声兰姆波超薄弹性层定征方法

提出了用低频多模式超声兰姆波定征方法来估计超薄弹性层的纵波声速、横波声速、厚度和密度等参数。这里“超薄”是指材料厚度ｈ远小于材料中的声波波长λ,由此导致地时域上材料前后界面的各次回波信号相互混选。中采用水浸耦合方式,结合空间波场设计和泄漏兰姆波频域分析方法获取了材料零阶对称与反对称模式兰姆波色散曲线,并以色散特性为基础的零阶对称模式兰姆波定征方法、简化方法、零阶反对称模式兰姆波定征方法和最小二乘     

弹性波传播到声发射传感器的声压透射系数研究

研究固体中弹性波在媒介分界面的透射规律,以提高声发射检测的精度与效率。基于声学理论推导出了三种典型耦合状态的声压透射系数计算公式,明确了各参数对透射系数的影响;搭建了声发射波透射试验研究平台,分别对上述典型状态下的声压透射理论计算系数进行验证;基于建立的声压透射系数计算方法分析了耦合层的声阻抗、厚度值以及耦合层材料的内外位置等对声压透射系数的影响。研究结果表明,理论计算结果与试验检测结果吻合较好,建立的声压透射系数计算公式有助于指导声发射传感器增强对弹性波的拾取。     

超薄覆层低频超声类瑞利波定征方法

本文提出低频超声类瑞利波定征方法来估计覆层/基层层状复合结构超薄覆层的纵波声速、横波声速、厚度和密度等参数。这里“超薄”的概念是指覆层厚度h远小于覆层中的声波波长λ,导致在时域上覆层前后界面的各次回波信号相互混迭。文章采用水楔耦合方式,利用超声漏类瑞利波频域分析方法获取层状复合结构超声类瑞利波色散曲线,提出以色散特性为基础的低频超声类瑞利波覆层定征方法和在最小二乘意义下以色散曲线为基础的反向算法对覆层进行了参数估计。文中分析了影响估计准确性的各种因素,研究了低频超声类瑞利波定征方法对覆层各参数的灵敏度及其在误差传递中的意义。实验结果证实,对于银箔/玻璃层状复合结构,该方法能够准确估计厚度小到26μm银箔覆层的声学参数。     

超薄覆层低频超声类瑞利波定征方法

本文提出低频超声类瑞利波定征方法来估计覆层／基层层状复合结构超薄覆层的纵波声速,横波声速,厚度和密度等参数。这里“超薄”的概念是指覆层厚度ｈ远小于覆层中的声波波长λ,导致在时域上覆层前后界面的各次回波信号相互混迭。文章采用水楔耦合方式,利用超声漏类瑞利波频域分析方法获取层状复合结构超声类瑞利波色散曲线,提出以色散特性为基础的低频超声类瑞利波覆层定征方法和在最小二乘意义下以色散曲线为基础的反向算法对     

基于互功率谱相位谱的混凝土结构中应力波波速的估计

在应用冲击反射法进行无损估计时，应力波波速测量是一项非常重要的工作。本文研究了时间延迟估计方法中用互功率谱的相位谱进行时间延迟估计的算法，并将其应用到波速估计中，取得了比较满意的结果。     

液浸多层薄膜-基底结构中Scholte界面波特性研究

多层薄膜-基底结构在工业领域有广泛应用，其中薄膜的厚度与弹性参数等特性对结构与器件性能有显著影响。但对多层薄膜材料参数进行无损定征较为困难。考虑界面波对界面附近材料特性敏感的特点，以及分层薄膜导致液固界面Scholte波频散与分层材料速度分布密切相关等因素，文章首先利用全局矩阵理论分析了分层结构中的声传播，并给出界面上脉冲激励的声压表达式，据此对水浸双层薄膜-基底三层结构材料声速呈正梯度、负梯度、随机分布三种结构中液固界面Scholte波的频散曲线进行数值计算。进一步详细计算了法向脉冲线源激发的界面波瞬态信号随薄膜厚度的变化。结果显示，三种结构中两层薄膜厚度均对液-固界面波频散特性有显著影响，同时不同膜厚对不同频段的Scholte波的“捕获”作用(频率选择性)十分明显。该结果为进一步利用Scholte波频散特性进行多层薄膜厚度定征提供了理论依据。     

超薄SIMOX材料的Pseudo-MOSFET电学表征

介绍了一种表征SOI材料电学性质的手段,并对三种不同顶层硅厚度的SIMOX材料进行测试、提取参数,分析材料制备工艺对性能产生的影响。研究结果表明,标准SIMOX材料通过顶层硅膜氧化、腐蚀等减薄工艺制得的顶层硅厚度小于100nm的超薄SIMOX材料,其顶层硅与BOX层界面有更多的缺陷,会影响到在顶层硅膜上制得的器件的性能,引起NMOSFET的阈值电压升高、载流子迁移率降低。Pseudo-MOSFET方法能够在晶圆水平上快捷有效地表征超薄SIMOX材料的电学性质。     

毛面球墨铸铁的球化质量无损评价研究

采用水浸透射法测量球墨铸铁材料的声传播速度,克服毛面球墨铸铁件表面较粗糙耦合困难的问题,避免人为因素引起的耦合补偿对声速影响的不确定性,实现不测量工件厚度测出未知厚度的工件声速,从而进行球墨铸铁球化率等级的评定,这为自动化球化率等级评定装置的研制提供基础.实验对多种球墨铸铁试样进行球化率测量评定,测量结果与实际情况基本一致.对球墨铸铁球化质量的无损评价有重要意义.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Effect of Permeable Crystalline Material on Steel Reinforcement Corrosion of Concrete

Permeable crystalline materialcan permeate into pores and cracks of concrete and catalyze the reaction between Ca(OH) 2and unhydrated cement to generate a great quantity needle non-soluble crystals, which can stop up the pores and cracks of concrete, and increase the impermeability of concrete. This paper reported the results of a study conducted to evaluate steel reinforcement corrosion of concrete specimens uncoated and coated with permeable crystalline material as well as mixed with the permeable crystalline material. The properties evaluated for corrosion test were water impermeability, water absorption, compressive strength and potential. The results of water impermeability, water absorption, compressive strength clearly showed that the permeable crystalline material could prohibit water, any soluble salts and moisture from penetrating the concrete to cause corrosion, leaking, and other problems, and it did increase the compressive strength, which was favorable for protection of corrosion of reinforcing steel. Moreover, it was concluded from the potential-time curve that the steel reinforcement of uncoated specimen was in the state of activation whereas that of other specimens coated and mixed with the permeable crystalline material was in the state of inactivation. Above all, it was indicated that the permeable crystalline materialis very effective to protect the steel reinforcement of concrete from corrosion.     

The Research and Application About "Dry Peeling Off" Technology for Airplane Surface Paint Layer

In this paper, the principle of spurting take off lacquer were introduced; and with orthogonal method the unsaturate polyester was prepared ;it was easy to peel airplane paint layer off with this material and equipment.     

Quality Study of Honeycomb Core Shaping Without Wax Stabilization

Sandwich panels utilizing honeycomb cores result in lightweight, high-strength units that are very rigid. Indeed, they give honeycomb panels the best strength-to-weight ratio of any construction type available. Conventionally, the wax is poured into the cell of the core to strengthen the structure and prevent the core from being crushed during milling. Much time and labor is required to wax, mill, and clean the cores. In this study, the process of pouring wax into the core was skipped. In other words, the cutter directly milled the core. Experiments showed that the compressive strength of the core produced without wax stabilization was only 3% lower than that of cores produced using the traditional method. In addition, the drum peel strengths of cores produced without wax stabilization were 38.4% higher than cores produced using the traditional method, in which residual wax seriously polluted the adhesive. It was also found that eliminating the wax process can reduce costs.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

In-process thermal treatment of polylactic acid in fused deposition modelling

Polylactic acid (PLA) is one of the most widely used open source fused filament fabrication materials due to its ease of extrusion, biodegradability, and mechanical strength. The mechanical strength of PLA largely depends on the proper growth of its semi-crystalline structure, which can be severely impaired by a low rate of crystallization, particularly in open source printers. This can be further aggravated by the non-uniform thermal distribution of heat that causes improper curing among the extruded beads of the printing material. As a result, PLA printed on open source printers does not achieve the best mechanical properties. This research, for the first time, proposes an additive-free solution implemented through a detailed set of experimentation to improve the curing rate through in-process temperature variations to cure the joints among the beads. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy is used to confirm the improvements in the bead joints. This work is conducted in two phases of experiments. In the first phase, a full factorial ANOVA is used to investigate various process parameters and the important variables are used in the second phase to print test specimens in four different sets.