A New Approach for Manufacturing a High Porosity Ti-6Al-4V Scaffolds for Biomedical Applications

Titanium and its alloys are currently considered as one of the most important metallic materials used in the biomedical applications, due to their excellent mechanical properties and superior biocompatibility. In the present study, a new effective method for fabricating high porosity titanium alloy scaffolds was developed. Porous Ti-6Al-4V scaffolds are successfully fabricated with porosities ranging from 30% to 70% using spaceholder and powder sintering technique. Based on its acceptable properties, spherical carbamide particles with different diameters （0.56, 0.8, and 1mm） were used as the space-holder material in the present investigation. The Ti-6Al-4V scaffolds porosity is characterized by using scanning electron microscopy. The results show that the scaffolds spherical-shaped pores are depending on the shape, size and distribution of the space-holder particles. This investigation shows that the present new manufacturing technique is promising to fabricate a controlled high porosity and high purity Ti-6Al-4V scaffolds for hard tissue replacement.     

新型稻田除草剂氟吡磺隆特性、作用机理及其除草效果

氟吡磺隆是由韩国LG公司生命科学有限公司研制的一种新型磺酰脲类除草剂，可用于移栽和直播水稻田；用于土壤或茎叶处理能有效防除稗草、阔叶和莎草科杂草；温室和田间试验表明，用于水稻田，在常规用量15～30g(有效成分，下同)／hm^2时，防效达90％以上，对水稻安全，对后茬作物无影响。文章还简述了药剂的分子结构、理化特性、毒性和作用机理等。     

Influence of stabilizers on Na-β′′-Al2O3 phase formation in Li2O(MgO)-Na2O-Al2O3 ternary systems

The influences of stabilizers on - and -Al2O3 phase formations in Li2O(MgO)-Na2O-Al2O3 systems were investigated. When stabilized with 4MgCO3Mg(OH)25H2O, most of the -Al2O3 phase formed below 1200°C and further - to -Al2O3 transformation with an increase of temperature was not observed. On the other hand, when stabilized with Li2CO3,-Al2O3 formation occurred by two steps. First, -Al2O3 was partly formed below 1200°C, and, second, noticeable transformation from -Al2O3 to -Al2O3 occurred at higher temperature ranges. It was shown that transient eutectic liquid in the Li2O-Na2O-Al2O3 system promoted the - to -Al2O3 transformation at higher temperatures. Uniform distribution of both Mg2+ and Li+ stabilizing ions enhanced -Al2O3 formation at low temperatures. In the Li-stabilized systems, however, homogeneous distribution of Li+ ions hindered both the formation of transient eutectic liquid and the second - to -Al2O3 phase transformation at high temperatures.     

Ka波段相控阵雷达TR组件幅相控制芯片的大功率微波非线性效应研究

采用实验测试和理论分析的方法研究了幅相控制芯片的大功率微波非线性效应.该芯片应用于Ka波段相控阵雷达收发组件中.测试平台利用固态源和脉冲磁控管来产生Ka波段大功率微波.随着输入功率幅值的提高,在实验中很明显地观测到了芯片的降级和毁伤现象.通过一系列的实验测试得到了芯片的全态相移特性和降级阈值,并通过图片给出了实验结果.最后,通过理论分析给出了该芯片的毁伤机理.     

Biomechanical features of level walking by transtibial amputees wearing prosthetic feet with and without adaptive ankles

This study aimed to evaluate the kinematics and kinetics of the lower limb in both the intact and amputated leg in individuals with transtibial amputations wearing Energy storage and return feet (ESRFs) with fixed ankles and Prosthetic feet with adaptive ankles (PFAAs) during level walking. Three individuals with transtibial amputations walked on level ground wearing their own ESRFs and PFAAs. Spatiotemporal parameters, kinematics, and kinetics of the lower-extremity joints were measured in the amputated and intact legs. There were differences in the kinematics of the joints in the amputated leg and of the ankle in the intact leg between ESRFs and PFAAs. Differences in joint moments, power, and stiffness in most joints in both legs and braking impulse were found between ESRFs and PFAAs. Thus, although it was a pilot study with three subjects, ankle angle control mechanisms (ESRFs: Fixed ankle vs. propriofoot: Mechanical motor vs. élan and echelon: Hydraulic actuator) might affect biomechanical features during level walking.

     

Processing and mechanical properties of porous 316L stainless steel for biomedical applications

Highly porous 316L stainless steel parts were produced by using a powder metallurgy process, which includes the selective laser sintering（SLS） and traditional sintering. Porous 316L stainless steel suitable for medical applications was successfully fabricated in the porosity range of 40%-50% （volume fraction） by controlling the SLS parameters and sintering behaviour. The porosity of the sintered compacts was investigated as a function of the SLS parameters and the furnace cycle. Compressive stress and elastic modulus of the 316L stainless steel material were determined. The compressive strength was found to be ranging from 21 to 32 MPa and corresponding elastic modulus ranging from 26 to 43 GPa. The present parts are promising for biomedical applications since the optimal porosity of implant materials for ingrowths of new-bone tissues is in the range of 20%-59% （volume fraction） and mechanical properties are matching with human bone.     

基于小波变换的埋地钢质管道外覆盖层缺陷定位技术研究

对小波变换检测信号奇异性理论进行阐述.以DCVG/CIPS组合仪器检测数据为对象,利用小波变换对阴极保护埋地管道通电电位、断电电位和电压梯度检测信号进行处理,根据小波变换模极大值对应着信号奇异点理论,实现了覆盖层缺陷点位置的准确定位.实验表明,该方法定位准确,具有一定的实用性.     

非对称双级环路行波热声热机的实验研究*

对于双级环路行波热声热机,两个热声核的相对位置直接影响到其起振温度,而热声热机的起振温差决定了其可利用的热源品位。基于线性热声理论分析,通过改变两个热声核的相对位置,研究了两个热声核的相对位置改变对其起振温差、压力振幅和压比等的影响。结果表明,双级环路行波热声热机的起振温度随着两个热声核从中心对称位置逐步靠近时先下降再上升,当两个热声核之间的谐振管长度比例为1:3.5时,系统获得最小的起振温差为59.6℃（工质为N₂,充气压力为2.5 MPa）。在相同温差下,该系统在谐振管长度比例为1:3.5的位置相较于其他位置具有较大的压力振幅和压比。     

克拉玛依油田八区下乌尔禾组层序地层学特征

克拉玛依油田八区下乌尔禾组为一套以砾岩为主的粗碎屑沉积,是该区最重要的含油层系。对其地层的划分与对比,是长期存在的一个问题。最近从深入进行层序地层学研究入手,着力识别层序界面,首次将其划分为2个三级层序,继而深入解剖层序构成．划分体系域、准层序组和准层序,较好地解决了地层划分和对比问题。在此基础上对层序的空间展布进行了讨论。     

Photocatalytic degradation of azo dye using TiO2 supported on spherical activated carbon

TiO₂ supported on spherical activated carbon (TiO₂/SAC) was prepared through an ion-exchange method followed by a heat-treatment process. The adsorption characteristic of TiO₂/SAC was evaluated using azo dye methyl orange (MO) as a target substance, and the photocatalytic degradation of MO under UV irradiation was also discussed. A synergistic effect of both the adsorption capacity of activated carbon and the photoactivity of TiO₂ on the removal of MO from aqueous solution was observed. Experimental results revealed that the photocatalytic degradation of MO improved with increasing photocatalyst dosage and followed a pseudo-first order kinetic. After five-cycle runs, TiO₂/SAC still exhibited relatively high photocatalytic characteristic for the degradation of MO. Besides, the prepared TiO₂/SAC can be helpful in the easy separation of photocatalyst from solution after photocatalysis of MO. Furthermore, the use of liquid chromatography/mass spectrometry (LC/MS) technique, identified three intermediates as degradation products during the photocatalytic reaction of MO with TiO₂/SAC.