Effect of thermal oxidation on the corrosion resistance of Ti6Al4V alloy in hydrochloric and nitric acid medium

The characteristics of Ti6Al4V alloy subjected to thermal oxidation in air atmosphere at 650 °C for 48 h and its corrosion behavior in 0.1 and 4 M HCl and HNO₃ medium are addressed. When compared to the naturally formed oxide layer (～4–6 nm), a relatively thicker oxide scale (～7 µm) is formed throughout the surface of Ti6Al4V alloy after thermal oxidation. XRD pattern disclose the formation of the rutile and oxygen‐diffused titanium as the predominant phases. A significant improvement in the hardness (from 324 ± 8 to 985 ± 40 HV_0.25) is observed due to the formation of hard oxide layer on the surface followed by the presence of an oxygen diffusion zone beneath it. Electrochemical studies reveal that the thermally oxidized Ti6Al4V alloy offers a better corrosion resistance than its untreated counterpart in both HCl and HNO₃ medium. The uniform surface coverage, compactness and thickness of the oxide layer provide an effective barrier towards corrosion of the Ti6Al4V alloy. The study concludes that thermal oxidation is an effective approach to engineer the surface of Ti6Al4V alloy to increase its corrosion resistance in HCl and HNO₃ medium.     

The effect of call admission policies on the system benefit of CDMA communication networks

Previous studies of call admission control (CAC) in mobile communication networks focused on call blocking and call dropping mechanisms. However, achieving global optimization of the system benefit is a complicated process. In this paper, we propose a benefit optimization model that accommodates as many users as possible, while simultaneously maintaining system-wide quality of service (QoS) in terms of admission control. To clarify the CAC concept, we construct a framework of CAC policies, derive associated interference models based on the framework, and then investigate the effects of the policies on the system benefit. In addition, to solve the complicated integer programming problem, we adopt the Lagrangean relaxation approach, and employ Lagrangean multipliers to perform sensitivity analysis of several parameters. The contribution of this study is twofold: the novel problem formulation and the improvement in the system benefit. The computational results demonstrate that the system accrues more benefit as new traffic is loaded and the number of users increases. Meanwhile, the sensitivity analysis shows that proper assignment of the strength of power-controlled signals is a key factor in the global optimization of the system benefit.     

宁波财富中心灯光景观光照对室内影响的分析

本文介绍了笔者主持创作的宁波财富中心外立面灯光景观项目光照对室内影响的分析。     

A Chiral Salen-type Schiff Base Cu<Superscript>2+</Superscript> Complex for the Vinylic-type Polymerization of Norbornene

Abstract  

The chiral Salen-type Schiff base ligand H ₂ L (H ₂ L = (s)-(+)2,2′-bis(2-hydroxy-3-methoxybenzylideneamino)-1,1′-binaphthyl), was selected to obtain the new chiral Cu²⁺ complex CuL (1), which was found to catalyze the polymerization of norbornene (NBE). The complex shows the distinctively distorted geometry from a square-planar reactive center, this feature being suggested to account for the efficient catalysis on the vinylic-type polymerization of NBE, with moderate molecular weights and narrow molecular weight distributions.     

Chaotic bubbles and phase locking for a shaker system in the vicinity of three coexisting critical points

In this paper, the dynamical model of the shaker system, Poincaré maps, Jacobian matrix and power spectrum are established. Different phase-locking phenomena and chaotic bubbles are investigated in the vicinity of three coexisting critical points including Hopf–Hopf bifurcation point, 1:3 resonance point and 1:4 resonance point. In two strong resonance cases, phase-locking dynamics and associated bifurcations are easily to occur. Coexisting attractors have also been introduced to provide mechanisms for chaotic bubbles with connections between pieces. The occurrence of phase locking on doubling torus to multi-period leads to interruption of torus-doubling bifurcation. Isolated chaotic bubbles are birth via period-doubling bifurcation of such a multi-period. Phase-locking phenomena on T² torus are also observed in such a neighborhood of critical points. The number of periods on torus by phase locking can be identified by power spectrum methods. The system parameters may be optimized by studying of phase-locking dynamics of this system.     

大型深基坑顺、逆作结合施工技术

对上海浦东三林城居住区中心工程西块大面积深基坑施工难的问题,采用了对基坑中心岛顺作、周边逆作相结合的施工新工艺,并采取了若干技术措施确保了基坑的安全开挖施工。该技术既缩短了总工期,又节约了项目成本,且对周边环境影响较小,可供类似工程参考。     

基于统计分析的发酵溶解氧与二氧化碳关系的研究

由理论分析及经验得到溶解氧与尾气二氧化碳模型,通过布拉酵母菌发酵得到实测溶解氧及尾气二氧化碳检测数据,依据经验模型计算出近似溶解氧值。应用统计分析软件SPSS得到实测溶解氧与二氧化碳及计算溶解氧的Pearson相关系数分别为-0.632和0.862,说明溶解氧与尾气二氧化碳之间存在负相关关系,而经验模型计算的溶解氧值与实际溶解氧之间具有较强的相关性。进一步采用曲线拟合对计算溶解氧值进行修正,使其更接近实际溶解氧。     

Streaming currents in microfluidics with integrated polarizable electrodes

A surface in contact with an aqueous solution is electrically characterized by the zeta potential. One way of determining indirectly the zeta potential of a surface is by measuring the streaming currents generated by a Poiseuille flow through a capillary channel with charged walls. We report measurements of streaming current in individual rectangular glass/PDMS microchannels with integrated miniaturized electrodes. Experiments performed using solutions with different salt concentrations and different electrode materials showed that the measured electrical current depends on the electrode material and in general differs from the real value of the streaming current. To determine the streaming current from the experimental data, an equivalent circuit model is proposed. The extracted value of the streaming current is proportional to the flow rate of electrolyte and the calculated glass/PDMS zeta potential scales linearly with the logarithm of the salt concentration. This work offers a thorough analysis of the effects that come into play during streaming current measurements and, in particular, it describes potential sources of error that can affect the streaming current measurements and suggestions on how to correct the measured values.     

Provenance and temporal variations in selected flavonoids in leaves of Cyclocarya paliurus

Cyclocarya paliurus is a well-known multiple function plant in China. To reveal the provenance variation of selected flavonoids in leaves of C. paliurus and changes of their level during the growing season, twelve provenances were grown in a field trial and sampled five times at approximately 1 month intervals. The levels of flavonoids varied significantly in leaves of C. paliurus from different provenances, and isoquercitrin represented the largest component of the selected compounds, followed by kaempferol and quercetin. The growing season also significantly affected the concentration of total flavonoids and its composition. In most cases, the greatest concentration was observed in July and October, showing a bimodal temporal variation pattern. Results not only demonstrated that leaves of C. paliurus exhibited commendably higher levels of quercetin, kaempferol and isoquercitrin, but also provided a basis for breeding strategies, selecting superior provenances, and choosing harvesting time for producing specific flavonoids for the food industry.     

为什么会有“西部建筑”

相对于东部而言,我国西部建筑正以一种集体姿态引起更多的关注.需要对“西部”这一概念进行清晰而深入的剖析,以增进对“西部建筑”更为深刻的理解.西部建筑是一种姿态与精神,而不是某种具体类型.当前它所面临的最根本问题,是迅猛的经济发展与必须深思慎行的地域可持续性之间的矛盾.建筑的设计与建造必须在满怀理想的同时面对现实,避免简单粗暴地套用形式语言,以务实的态度处理好西部建筑中遭遇的各种具体问题,并从“在西部、为西部、属西部”三个层次实现西部建筑的品质进化.