ADVANCE IN Ti_3 Al AND TiAl INTERMETALLICS RESEARCH IN CISRI

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郑州国际会展中心低收缩高防裂高耐久混凝土技术

郑州国际会展中心工程地下室底板为大体积超长混凝土结构,地下侧墙为薄壁超长混凝土结构,地上部分为超长超大面积混凝土薄板结构,设计采用低收缩高防裂高耐久混凝土技术。由于从原材料、混凝土配合比设计、施工、温度控制、养护等环节采取了有效的抗裂措施,工程达到了预期效果,混凝土质量优良。     

Efficiency of activated carbon to transform ozone into *OH radicals: influence of operational parameters

Based on previous findings (Jans, U., Hoigné, J., 1998. Ozone Sci. Eng. 20, 67-87), the activity of activated carbon for the transformation of ozone into *OH radicals including the influence of operational parameters (carbon dose, ozone dose, carbon-type and carbon treatment time) was quantified. The ozone decomposition constant (k(D)) was increased by the presence of activated carbon in the system and depending on the type of activated carbon added, the ratio of the concentrations of *OH radicals and ozone, the R(ct) value ([*OH]/[O3]), was increased by a factor 3-5. The results obtained show that the surface chemical and textural characteristics of the activated carbon determines its activity for the transformation of ozone into *OH radicals. The most efficient carbons in this process are those with high basicity and large surface area. The obtained results show that the interaction between ozone and pyrrol groups present on the surface of activated carbon increase the concentration of O2*- radicals in the system, enhancing ozone transformation into *OH radicals. The activity of activated carbon decreases for extended ozone exposures. This may indicate that activated carbon does not really act as a catalyst but rather as a conventional initiator or promoter for the ozone transformation into *OH radicals. Ozonation of Lake Zurich water ([O3] = 1 mg/L) in presence of activated carbon (0.5 g/L) lead to an increase in the k(D) and R(ct) value by a factor of 10 and 39, respectively, thereby favouring the removal of ozone-resistant contaminants. Moreover, the presence of activated carbon during ozonation of Lake Zurich water led to a 40% reduction in the content of dissolved organic carbon during the first 60 min of treatment. The adsorption of low concentrations of dissolved organic matter (DOM) on activated carbon surfaces did not modify its capacity to initiate/promote ozone transformation into *OH radicals.     

静态和疲劳荷载下带切口和无切口[0/±30/±60/90]_s玻纤增强/环氧组合的性能

主要研究带切口和无切口,折角[0/±30/±60/90]的玻纤增强环氧组合结构在静力和疲劳荷载下的弯曲性能。确定了带切口和无切口折角试件的静态和疲劳性能。为此,在试件中心钻了2,4.5,7,9mm的不同圆形切口。在零度低应力和25Hz下,进行了常规挠度弯曲疲劳试验,构建了玻纤增强环氧组合试件全截面与净截面的S-N图表。结果显示,带切口玻纤增强环氧组合试件最终挠度随着切口直径的增加而线性减小。对于全截面,随着切口尺寸减小,疲劳寿命增加;而无切口的试件具有较长疲劳寿命。另一方面,基于净截面的S-N图表显示折角组合结构对于切口尺寸的敏感性。对于复合材料这被认为是特殊的情况。结果也显示,在严格的107次循环之内,S-N图表没有任何的疲劳极限。     

Scanning the pressure-induced distortion of fingerprints

Fingerprint recognition technology is an important part of criminal investigations it is the basis of some security systems and an important tool of government operations such as the Immigration and Naturalization Services, registration procedures in the Armed Forces, and so forth. After the tragic events of September 11, 2001, the importance of reliable fingerprint recognition technology became even more obvious. In the current study, pressure-induced changes of distances between ridges of a fingerprint were measured. Using calibrated silicon pressure sensors we scanned the distribution of pressure across a finger pixel by pixel, and also generated maps of an average pressure distribution during fingerprinting. Emulating the fingerprinting procedure employed with widely used optical scanners, we found that on average the distance between ridges decreases by about 20% when a finger is positioned on a scanner. Controlled loading of a finger demonstrated that it is impossible to reproduce the same distribution of pressure across a given finger during repeated fingerprinting procedures.     

EBSD characterization of carbide–carbide boundaries in WC–Co composites

A sample of WC‐6wt%Co was investigated for grain boundary character distribution and occurrence of coincidence site lattice (CSL) boundaries on a statistical basis. For this purpose orientation measurements of the grains were carried out using electron back‐scattered diffraction (EBSD). The dominant misorientation relationships were determined by complementary EBSD data representation tools such as orientation maps, misorientation angle distribution histograms and the sectioned three‐dimensional misorientation space. It was found that the grain boundary character distribution of the material is nearly random and the CSL boundaries are not present in statistically significant amounts. It was also found that the amount of binder phase does not play a role in the formation of special boundaries. The paper focuses on the methodology of characterizing grain boundaries in a hexagonal material using EBSD.     

Experimental study of wear interaction between piston ring and piston groove in a radial piston hydraulic motor

The wear interaction between piston ring and piston groove in a radial piston hydraulic motor was studied in regard to mass loss and changes in form and surface roughness. A specially developed test rig that simulates the tilting movements of pistons at the end of strokes was used in the test. The results show that wear on the piston ring groove can be up to 10 times greater than the wear on the piston ring. For both interacting surfaces, the dominant wear mechanism was mild wear. The results from a factorial design show that the form of the piston groove significantly influences the amount of wear.     

Elastic–plastic solid disk with nonuniform heat source subjected to external pressure

The elastic–plastic stress distribution of a solid disk due to nonuniform heat source under external pressure is investigated in this work. The nonuniform heat generation rate is taken to be a function of the radial position in the form , where a denotes radius of the solid disk; q₀, n and s are constants. The exact solution presented is based on the usual assumptions of plane stress, Tresca's yield condition, its associated flow rule and linear strain hardening material behaviour. According to this analysis, the plastic core in the general case consists of three parts with different forms of the yield condition. The present solution is illustrated by numerical results and is compared with uniform heat generation case. This work provides the basis for a comprehensive investigation of the influence of nonuniform heat generation.     

Slope protection by membrane structures

Left uncontrolled the effects of weathering can lead to severe degradation of slopes. To assess these effects a field trial has been carried out involving both protected and unprotected slopes. In this trial two types of slope protection were investigated. The first was a simple synthetic mat installed directly over the exposed surface of the slope. The second was a more substantial geotextile reinforced fill facing, incorporating fillow bushes which generate root systems to aid long-term stability of the protective facing. Data are presented to show that appropriate protection systems do prevent significant deterioration in the slope. Also the combination of a geotextile and deep rooting vegetation produce robust structures which are able to withstand high loadings with acceptable deformations. The use of a geotextile reinforced protection system is illustrated through two examples. These show that protection of the face of fill slopes can be achieved either by encapsulating the fill in the geotextile reinforcing layers or by the use of a three-dimensional wire netting applied directly to the face.