Chemically functionalized carbon nanotubes and their characterization using thermogravimetric analysis, fourier transform infrared, and raman spectroscopy

This article reports key findings on the chemical functionalization of carbon nanotubes (CNT). The functionalization of chemical vapor-deposited CNT was carried out by treating tubes with polyvinyl alcohol through ultrasonication in water with the aid of a surfactant. The surfactant is expected to promote the unbundling of aggregated CNT. The characterization of functionalized samples using thermogravimetric analysis, Fourier transform infrared spectroscopy, and Raman spectroscopy revealed that the CNT were functionalized by the interaction of carboxylic acid and hydroxyl groups. From the characterization studies, it is apparent that there is a strong interaction between these functional groups and the covalently bonded carbon in the CNT network. The functionalization process enabled good CNT dispersion in the solution, and the CNT remained in suspension for many days. To support the effective functionalization of the tubes, the interaction of functionalized CNT with Ni ions is also demonstrated. This paper was presented at the fourth International Surface Engineering Congress and Exposition held August 1–3, 2005 in St. Paul, MN.     

复合钎料的特点及研究现状

为缓解钎焊接头的列余应力，人们提出了在普通钎料中加入一定体积比的作为增强相的各种形态的高温合金、碳纤维及陶瓷颗粒等形成复合钎料方法。该钎料不仅具有较好的填缝能力，同时获得的钎缝接头具有良好的高温强度和抗冲击性能，复合钎料钎焊方法是一种很有潜力的钎焊陶瓷与金属的方法。     

Hydrothermal formation of dispersive Mg（OH）2 particles in NaOH solution

The hydrothermal modification of Mg(OH)2 crystals in NaOH solution was investigated. The aggregated Mg(OH)2 particles with irregular shape are converted to regular Mg(OH)2 hexagonal plates after hydrothermal treatment. The prolongation of reaction time from 1-4 h or the increase of temperature from 140℃ to 200℃ can promote the formation of Mg(OH)2 plates with big particle size but small cluster size. The dispersion characteristics of the hydrothermal products are improved owing to the improvement of Mg(OH)2 crystalline degree and the in-crease of I（001)/I（101） ratio. The proper hydrothermal modification condition is as follows: solid content 0. 075 g/mL,NaOH concentration 5.0 mol/L, temperature 200℃ and time 4 h. Thermodynamic analysis indicates that the increase of MgOH^ concentration at elevated temperature or the increase of OH^- concentration in concentrated NaOH solution is favorable for the hydrothermal formation of Mg(OH)2 particles.     

Low-melting-point titanium-base brazing alloys—part 1: Characteristics of two-, three-, and four-component filler metals

The melting point, microstructure, phase, and electrochemical behavior of Ti-21Ni-15Cu alloy, together with two-, three-, and four-component low-melting-point titanium-base brazing alloys, are presented in this paper. Five filler metals were selected for the study, in which melting points were measured by differential thermal analysis, phases identified by x-ray diffractometry, and corrosion behaviors tested by potentiodynamic polarization. The experimental results show that the three-component Ti-15Cu-15Ni and the newly developed Ti-21Ni-14Cu alloys exhibit the combination of lower melting point and superior corrosion resistance compared to the two-and four-component titanium alloys, 316L stainless steel, and a Co-Cr-Mo alloy in Hank’s solution at 37 °C. On a short time basis, the presence of Ti₂Ni and Ti₂Cu intermetallics in the Ti-15Cu-15Ni and Ti-21Ni-14Cu alloys should not be preferentially dissolved in galvanic corrosion with respect to the dissimilar Ti-6Al-4V alloy.     

The impact of global dispersion on coordination,team performance and software quality – A systematic literature review

ContextGlobal software development (GSD) contains different context setting dimensions, which are essential for effective teamwork and success of projects. Although considerable research effort has been made in this area, as yet, no agreement has been reached about the impact of these dispersion dimensions on team coordination and project outcomes.ObjectiveThis paper summarizes empirical evidence on the impact of global dispersion dimensions on coordination, team performance and project outcomes.MethodWe performed a systematic literature review of 46 publications from 25 journals and 19 conference and workshop proceedings, which were published between 2001 and 2013. Thematic analysis was used to identify global dimensions and their measures. Vote counting was used to decide on the impact trends of dispersion dimensions on team performance and software quality.ResultsGlobal dispersion dimensions are consistently conceptualized, but quantified in many different ways. Different dispersion dimensions are associated with a distinct set of coordination challenges. Overall, geographical dispersion tends to have a negative impact on team performance and software quality. Temporal dispersion tends to have a negative impact on software quality, but its impact on team performance is inconsistent and can be explained by type of performance.ConclusionFor researchers, we reveal several opportunities for future research, such as coordination challenges in inter-organizational software projects, impact of processes and practices mismatches on project outcomes, evolution of coordination needs and mechanism over time and impact of dispersion dimensions on open source project outcomes. For practitioners, they should consider the tradeoff between cost and benefits while dispersing tasks, alignment impact of dispersion dimensions with individual and organizational objectives, coordination mechanisms as situational approaches and collocation of development activities of high quality demand components in GSD projects.     

一种基于群组判断离差的偏好集结方法

针对群决策偏好集结中违反Pareto 最优性的情况, 设计一种基于群组判断几何离差的同质性集结方法. 该方法在集结前进行几何离差测试, 以确定个体决策信息的离差水平. 离差较小时, 可基于几何平均集结; 对于离差较大且修正复杂度较高的决策信息, 采用主成分分析(PCA) 从高维决策信息中提取大多数相关信息, 在不依赖主观分析的情况下进行加权集结. 仿真实验表明, 所提出的方法能够在不违背Pareto 最优性的基础上集结离差较大的群决策信息.

     

定长槽单向弥散方程的理论解及其应用

论文导出了定长槽的单向弥散方程解。解包含槽下游封闭和开敞并伴有流速的两种条件。根据定长槽和半无限长槽单向弥散方程解的比较结果,只要弥散系数D和流速u相等,且弥散前锋尚未到达定长槽下游边界以前,那么两者相对浓度C/C0的分布相同。据此,可取定长槽进行试验,而用相应于半无限长的简单公式计算分析。     

Mathematical model to identify nitrogen variability in large rivers

The river Swale in Yorkshire, northern England has been the subject of many studies concerning water quality. This paper builds on existing data resources and previous 1D river water quality modelling applications at daily resolution (using QUESTOR) to provide a different perspective on understanding pollution, through simulation of the short‐term dynamics of nutrient transport along the river. The two main objectives are (1) building, calibration and evaluation of a detailed mathematical model (Advection‐Dispersion Model: ADModel), for nutrient transport under unsteady flow conditions and (2) the development of methods for estimating key parameters characterizing pollutant transport (velocity, dispersion coefficient and transformation rates) as functions of hydrological parameters and/or seasonality. The study of ammonium and nitrate has highlighted temporal variability in processes, with maximum nitrification and denitrification rates during autumn. Results show that ADModel is able to predict the main trend of measured concentration with reasonable accuracy and accounts for temporal changes in water flow and pollutant load along the river. Prediction accuracy could be improved through more detailed modelling of transformation processes by taking into account the variability of factors for which existing data were insufficient to allow representation. For example, modelling indicates that interactions with bed sediment may provide an additional source of nutrients during high spring flows. Copyright © 2010 John Wiley & Sons, Ltd.     

高密度机柜散热策略分析与实现

随着数据中心机房内高密度机柜的不断增加,设备的集成度越来越高,散热问题已成为数据中心机房管理的主要难题。该文中讲述了五种应对高密度机柜散热问题的策略,总结了应用高密度计算的最佳散热策略,最后介绍了提高冷却效率和冷却能力以及提高现有数据中心密度的具体措施。     

求解弹头散布均匀度的分布估计算法

未来空域窗射击体制是一种新型的高炮射击体制, 这种射击体制对近程防空反导具有显著的效果. 在对未来空域窗进行设计和评价时, 必须计算未来空域窗内弹头散布的均匀度, 并要求算法具有全局收敛以及解的精度高. 文章描述了未来空域窗弹头散布均匀度的问题, 提出了一种求解弹头散布均匀度的分布估计算法; 然后, 提出了一种变焦算法用来提高算法的搜索效率和解的精度, 并给出了混合算法的流程图. 仿真结果表明, 混合算法具有全局收敛、解的精度高以及搜索效率高的优点, 适合于在实际工程中用来求解弹头散布均匀度.