Systematic optimization of corrosion,bioactivity, and biocompatibility behaviors of calcium-phosphate plasma electrolytic oxidation (PEO) coatings on titanium substrates

To optimize the corrosion, bioactivity, and biocompatibility behaviors of plasma electrolytic oxidation (PEO) coatings on titanium substrates, the effects of five process variables including frequency, current density, duty cycle, treatment time, and electrolyte Ca/P ratio were evaluated. In our systematic study, a Taguchi design of experimental based on an L16 orthogonal array was used. For this, the coatings characteristics such as the surface roughness, wettability, rutile to anatase and Ca/P ratios, and corrosion polarization resistance were investigated. After determining the optimum process variables for each response, the apatite forming ability in SBF (bioactivity behavior) and MG63 cell attachment and flattening (biocompatibility behavior) for two groups of coatings were examined. The first group was optimized based on the maximum corrosion polarization resistance and the variables were set as the frequency of 2000 Hz, the current density of 5 A/dm², the duty cycle of 30%, the treatment time of 5 min, and the Ca/P ratio of 0.65 at. % in the electrolyte. For the second group, the maximum surface roughness, greatest Ca/P ratio, and highest wettability as well as the minimum rutile to anatase ratio in coatings, could be obtained when the variables were set as the frequency of 10 Hz, the current density of 12.5 A/dm², the duty cycle of 50%, the treatment time of 12.5 min, and the Ca/P ratio of 1.70 at. % in the electrolyte. The results showed that while both groups of coatings indicated a significant apatite forming ability and can serve as bioactive coatings, a proper attachment and flattening of cells and consequently, the favorable biocompatibility properties were seen only in the first group.     

MG—375/750采煤机液压系统的污染控制

介绍了MG— 375 75 0采煤机液压系统污染危害的种类及控制方法 ,并收到了良好效果     

基于MG811探头的二氧化碳采集系统设计

二氧化碳采集系统以德州仪器公司的MSP430F169为主要控制芯片,采用MG811二氧化碳气体感应探头检测二氧化碳气体浓度。通过HT1621来驱动段式LCD,显示测量的二氧化碳浓度数据,系统外扩M25P80芯片,实现对测量数据的存储,并可通过USB与上位机进行通信。实验证明,该系统设计工作稳定、结构简单、便于携带,有良好的推广前景。     

基于ZigBee的多机器人通信系统的设计

为解决多机器人协作的问题,设计了可以让机器人之间基于ZigBee网络进行通信的通信方案。机器人硬件系统中引入了ZigBee节点,多个机器人依赖ZigBee形成一个星型网络,每个机器人可以通过中心节点保持通信。实验结果表明,机器人之间可以可靠地进行通信,能够显著提高机器人的工作效率。     

车载Ad Hoc网络中基于移动网关的数据传输

由于车载Ad hoc网络拓扑的动态变化及车载节点的快速移动,应用现有传输方法在其上进行Internet接入点向移动车辆(Infrastructure-to-Vehicle,I2V)数据传输时成功率较低,而且传输延迟高、延迟抖动大.为了解决这一问题,文中利用公交车路线固定、运行特征可预测、节点及线路分布稠密等特性,将公交车作为移动网关(Mobile Gateway,MG),提出了一种新的基于MG转发的I2V数据传输方法(Mobile Gateway based Forwarding,MGF).文中首先将公路网模型化为状态-空间图,再运用马尔可夫决策方法建立了一种基于MG转发的I2V数据传输优化模型,然后通过对模型求解得出I2V数据传输的最优转发决策,最优转发决策指的就是每个状态下对应的最优动作序列,最后在目的车辆行驶轨迹上选取满足传输成功率阈值,并使I2V传输延迟最小的路口节点作为数据包与目的车辆的最优汇聚节点,即目标节点.应用MGF方法,MG节点将以最优概率转发序列向目标节点转发数据包.文中利用模拟平台对MGF方法的传输性能进行了评估,结果表明该方法在满足传输成功率阈值前提下,能够获得最小传输延迟期望.理论分析同样也证明了该方法的有效性.     

下一代网络中网关控制协议对比研究

媒体网关控制协议是通信网络由PSTN向下一代网络(NGN)演进中必不可少的协议。该文在研究现有的两种相关协议MGCP和Megaco的基础上,结合软交换(Softswitch)系统开发中的实践经验,从系统的层次对它们做了较深入的对比。     

pH and heat-induced structural changes of bovine apo-α-lactalbumin

The effects of pH and thermal treatments on conformation and association state of Ca²⁺-depleted bovine α-lactalbumin (apo-α-LA) have been studied by fluorescence spectroscopy, and molecular modelling. The experimental results demonstrate a third-state model for heat-induced unfolding of apo-α-LA, at pH 2.0, and an all-or-none transition of apo-α-LA, at pH 4.5 and 7.0, respectively. The heat-induced changes in the secondary and tertiary structure of α-LA were outlined after running molecular dynamics simulations at 25 °C and 80 °C, at neutral pH, therefore supporting the experimental observations. Our data provides insight into the mechanism of pH- and heat-dependent structural changes and oligomerization of α-LA, and will be helpful in understanding the ability of this protein to interact with certain compounds of biological interest.     

Column solid‐phase extraction of sunset yellow and spectrophotometric determination of its use in powdered beverage and confectionery products

A new and simple solid‐phase extraction method for the determination of trace levels of sunset yellow has been developed on Diaion HP 2MG column system. The adsorbed sunset yellow on the resin was eluted with 3 mL of methanol and determined by UV–Vis spectrophotometry at 484 nm. Various experimental parameters such as pH, amount of sunset yellow, flow rates of sample and eluent solutions, resin amount, sample volumes, etc. were investigated. The influences of some alkali, alkali earth and transition metals on the recoveries of sunset yellow were investigated. The recovery values for sunset yellow were higher than 95%. Preconcentration factor was found as 150. The detection limit (three sigma) of the reagent blank for sunset yellow was 5.2 μg L^?1. The relative standard deviations (RSD) of the procedure were found as 3.9%. The validation of the presented procedure was performed by the method of standard addition. The procedure was successfully applied to the determination of trace levels of sunset yellow in powdered beverage and confectionery products.     

Microstructural and textural evolution during large strain hot rolling (LSR) of Mg–Al (AZ31) alloy

Abstract

Grain refinement has been achieved through large strain rolling (LSR) in Mg AZ31 alloy. The evolution of microstructure and texture has been found to be dependent on the amount of reduction. After the critical amount of reduction, grain refinement proceeds through continuous dynamic recrystallisation (CDRX).     

采煤机调高泵替换技术研究

MG2×125/560采煤机适用于薄煤层开采,近年来随着机组过度的服役,以及产品的更新换代,因齿轮泵全局短缺,配件无法得到保证。为了解决调高系统的事故频发问题,决定对其进行改造,把MG250/591采煤机调高泵更换在MG2×125/560采煤机机组。通过实验模拟与现场使用,证明改造技术切实可行,能够很好地进行摇臂升降。同时,改造后的调高系统能够节省设备费、增加煤炭产值、减少停工损失等费用共计约843 250元,具有良好的社会效应和明显的经济效益。