Investigation of particle in-flight characteristics during atmospheric plasma spraying of yttria-stabilized ZrO2: Part 1. Experimental

A detailed investigation of the relationship between the parameters of the spray process and the in-flight properties of the particles was carried out using a multivariate statistical approach. A full factorial designed experiment concerning the spray process was performed, the spray gun parameters’ current, argon flow rate, hydrogen flow rate, and powder feed rate being selected to control the process. The particle properties, viz. velocity, temperature, and diameter, were determined using an optical measurement system, DPV 2000. In addition, the standard deviations of, and the correlations between, the measured particle properties were analyzed. The results showed current to have the strongest impact on particle velocity and particle temperature and argon flow rate to be the only parameter with an inverse effect on velocity and temperature.     

"技术性生态理念"在中国的尝试 --"沈阳中科院生态研究所主楼投标方案"

通过介绍德国魏斯玛大学设计的"沈阳中科院生态研究所主楼"方案,论述了技术性生态理念的细节和发展的重要性,及其在中国发展所存在的一些问题,号召建筑师和人们应从根本上应用和认识生态理念.     

The association of dental caries with blood lead in children when adjusted for IQ and neurobehavioral performance

Associations between childhood lead exposures and dental caries in children have been reported for over 30 years, with widely varying findings and conclusions, and using measures of lead exposure which ranged from food sources and water to tooth, hair or blood lead concentrations. OBJECTIVES: This study examined the relationship of lead exposure and dental caries in a population of normatively healthy children. METHODS: This cross-sectional study used a population of 507 children aged 8-12 who were participating in a clinical trial of dental materials to examine the relationship between lead and caries. Blood lead concentrations and dental caries were examined for association in both primary and permanent teeth. Because it is possible that neurobehavioral status could be associated with both lead exposure and dental caries prevalence, we also examined neurobehavioral status of the subjects. RESULTS: A gender-specific association (males only) between lead exposure and dental caries was found in primary teeth only. Neurobehavioral measures and IQ were not associated with caries status in this population. CONCLUSIONS: This study did not support neurobehavioral status as mediating any association between lead exposure and caries in a normatively healthy population. A gender-specific association between lead and caries not previously reported was found in primary teeth, and no biological explanation for this has been suggested. We conclude that this study provides only weak evidence, if any, for an association of low-level lead exposure with dental caries.     

Efficient optimization of single and multiple element transducers for the inspection of complex-shaped components

Ultrasonic inspection of components of complex geometry often suffers from loss of sensitivity, beam distortions and beam misorientations if the transducer is not perfectly matched to the specimen. A procedure is presented which allows to optimize single and multiple element transducers where—depending on the specific inspection configuration under concern—the shape of the piezoelement is determined to ensure a proper focusing of the beam field in the range of interest. The method is based on delay time calculation for multiple element transducers and employs a superposition technique for beam field calculation. The procedure is exemplified for a standard pipe inspection problem.     

Unexpected kinetic effect of MgB2 in reactive hydride composites containing complex borohydrides

Complex borohydrides of light metals are promising hydrogen storage materials due to their high hydrogen capacity. However, they exhibit two main drawbacks: their high thermodynamic stability and their slow kinetics. In the present work, the effect of various reactants on the formation kinetics of complex borohydrides is investigated. It is found that the kinetic barriers for the formation of LiBH₄, NaBH₄ and Ca(BH₄)₂ are drastically reduced when MgB₂ is used instead of B as starting material. Since this kinetic enhancement is observed in all borohydride studied so far, the observed effect is attributed to the higher reactivity of B in MgB₂ to form [BH₄]⁻ complexes. In addition, by using MgB₂ instead of elemental B, the corresponding reaction enthalpies are reduced by about 10 kJ/mol H, while the high gravimetric hydrogen capacities are largely preserved, i.e. LiBH₄ + MgH₂ with 11.4 wt%, Ca(BH₄)₂ + MgH₂ with 8.3 wt%, and NaBH₄ + MgH₂ with 7.8 wt%.     

Use of a minimum perturbation approach to predict TIM mutant structures

A minimum perturbation conformational search approach is usedto model the structures of the yeast triosephosphate isomerase(TIM) single mutant in which the catalytic base Glul65 is changedto Asp, and the double mutant in which Glul65 is changed toAsp and Ser96 to Pro. In chicken TIM this double mutant is referredto as a pseudo–revertant because some of the catalyticactivity lost due to the first mutation is regained when thesecond mutation occurs. Three minimum energy structures werecalculated for the Asp 165 conformation in the yeast TEM singlemutant and another three for the double mutant One of the calculatedminimum energy conformations for Aspl65 in the E165D structureagrees well with the X–ray structure. However, this conformationis not that of the lowest energy and is not one of the threemost common conformers for Asp found by Ponder and Richards.This suggests that when an amino acid is introduced it may notbe able to conform to the more general rules that apply to proteinstructures of evolutionary origin. While the van der Waals energylargely determines the allowed minima, the relative rankingof the final minima is determined by electrostatic effects andcan therefore be affected by the inclusion of crystal watersin the calculation. When the E165D calculation is repeated withan active–site water molecule fixed in its E165D X–raystructure position, the relative ranking of the minima shiftsand the X–ray conformation for Asp 165 is the lowest interactionenergy conformer. Two of the E165D calculated minimum energystructures are essentially identical to two of the S96P/E165Dminima. All of the calculated minima for both the E165D andS96P/E165D mutants position the Asp side chain such that theanti–orbital, and not the more basic syn–orbital,of the carboxylate would be utilized for proton abstraction.This observation may explain why the chicken TIM S96P/E165Dmutant, for which the X-ray structure indicates that the syn–orbitalis used, is a pseudo–revertant while the yeast TIM doublemutant is not; no X–ray structure is available for thelatter. The multiplicity of minima found in the present analysismakes clear that predicting the exact orientation of a singleside chain is not as simple as might be expected.     

Use of a theoretical model to investigate RF and DC reactive sputtering of titanium and chromium oxide coatings

An analysis of RF and DC reactive sputtering techniques is presented. The transition between a metal sputtering mode and a compound sputtering mode is usually noticed with a metallic target and an argon+oxygen gas mixture. The so-called hysteresis effect often observed for small amounts of reactive gas is explained in recent models. By considering gas kinetics parameters, it is possible to evaluate quite simple relationships between the main processing parameters. These theoretical calculations enable the prediction and aid the understanding of instability phenomena observed in reactive sputtering. In this paper, the effects of some parameters on the position and size of instability regions are discussed, and the difference between DC and RF reactive deposition is investigated. Simulations and experimental results are compared for the case of titanium and chromium oxide thin films prepared by DC and RF reactive sputtering. The influence of sputtering power on the position of the hysteresis loop is analysed theoretically and experimentally, and the changes observed between the reactive sputtering of titanium and chromium oxide materials are also discussed.     

Features of seismic hazard in large dam projects and strong motion monitoring of large dams

Earthquakes can affect large dam projects in many different ways. Usually, design engineers are focussing on ground shaking and neglect the other aspects. The May 12, 2008 Wenchuan earthquake has damaged 1803 dams and reservoirs, and 403 hydropower plants with an installed capacity of 3.3GW. Among these dams were the 132-m-high Shapai RCC arch dam and the 156-m-high Zipingpu concrete face rockfill dam. These recently completed dams are dam types which, up to now, have not experienced strong ground shaking. The widespread mass movements have caused substantial damage to dams and surface powerhouses in Sichuan. The different features of earthquake hazard are presented, i.e., ground shaking, faulting and mass movements. It is proposed to prepare project-specific safety plans for all dams, which consist of a matrix where the possible hazards and the corresponding countermeasures are listed. The earthquake behaviors of the Sefid Rud, Zipingpu and Shapai dams, which, in the past, have experienced strong ground shaking from nearby earthquakes, are discussed. Finally, the need for strong motion instrumentation of large dams is discussed. It is proposed that major dams with large damage potential, dams located in areas of high seismicity, and dams showing signs of abnormal behavior be equipped with strong motion instruments.     

钢混凝土组合桁架的纵向剪切力

钢混凝土组合桁架中钢和混凝土界面的纵向剪切分布一般是高度非均匀,在桁架节点出现峰值。对两个钢混凝土组合桁架梁的性能进行试验研究,所获试验结果对ANSYS软件包的非线性三维数值有限元模型进行校准。对30多个空腹板简支桁架中跨剪切变量进行研究,包括不同的荷载-滑移关系。在弹性阶段,尤其重要的是连接点受疲劳荷载导致塑性区的塑性重分配,使桁架节点连接处出现独特的剪切流峰值。数值结果与欧洲规范4进行比较,详细探讨了桁架节点剪切连接的增浓作用的影响。最后,对实际设计提出建议。