Synthesis of Ti2SnC from Ti/Sn/TiC powder mixtures by pressureless sintering technique

Ti/Sn/TiC powder mixtures were first employed to synthesize Ti₂SnC powder by pressureless sintering in the temperature range of 950–1250 °C at vacuum atmosphere. Ti₂SnC began to form at 950 °C, its content increased with increasing temperature. High purity of Ti₂SnC was obtained by sintering the mixtures with deficient Sn and TiC at 1200 °C for 15 min. A reaction mechanism was proposed to explain the formation of Ti₂SnC. The Ti₂SnC powder was characterized by scan electron microscopy (SEM) and X-ray diffraction (XRD). Using the above mixtures and process, the Ti₂SnC ceramic powder can be obtained on a larger scale.     

基于位置一步预测的核相关目标跟踪算法

针对视频机动目标跟踪过程中前后两视频帧间目标移动距离过大导致目标丢失问题,提出一种基于位置一步预测的核相关目标跟踪算法.首先,提取当前帧目标区域灰度以及颜色特征,并分别对灰度特征和颜色特征进行梯度及颜色直方图运算,得到FHOG特征向量和颜色直方图;然后根据颜色直方图引入粒子滤波对下一帧图像中目标位置进行一步预测;进而,...     

高温高压加热受试物对细菌回复突变试验结果的影响

目的研究高温高压加热灭菌对受试物进行细菌回复突变(Ames)试验,并评价其致突变作用结果稳定性的影响。方法以细菌回复突变试验推荐阳性物为研究对象,使用高压灭菌锅对阳性物进行加热灭菌处理。采用平板掺入法验证加热和未加热阳性物对菌株的诱导回变效率。进一步将推荐阳性物等体积配制为混合阳性物后,将其掺入到一种以中药颗粒为主的保健食品中配制为模拟阳性受试物,考察浓度和加热2个条件下混合阳性物的诱导回变效率。结果加热会明显降低推荐的单一阳性物诱变活力,混合阳性物在以保健食品为基质中的结果也基本一致,但受到阳性物浓度和基质浓度的影响。结论高压灭菌易导致阳性物的诱导效率下降,对Ames试验有一定程度的影响,特别是对保健食品的测试准确性具有影响;而开发新的前处理方法是避免上述问题的关键。     

亚磷酸法直接合成亚磷酸二辛酯的研究

采用辛醇和亚磷酸直接酯化法来制备亚磷酸二辛酯用正交试验法确定了适宜的合成条件:以二甲苯为溶剂,反应温度190℃,反应时间为6h,正辛醇和业磷酸的摩尔比为3∶1,合成产率可以达到95.4％,通过红外光谱仪对产品进 行了表征.     

苔藓结皮光谱的变异性研究

通过测定干、湿苔藓结皮光谱和不同季节的苔藓结皮光谱,研究了其水分变异性和季节变异性.研究得出,湿苔藓结皮光谱曲线与维管植物的光谱曲线相似,即苔藓在生命活动期的光谱曲线具有高等植物光谱曲线特征,干苔藓结皮光谱曲线特征与裸地土壤的光谱曲线相似;苔藓结皮光谱在苔藓营养发育期(7月)与生殖发育期(10月)存在较大差异,即苔藓结皮光谱也如维管植物一样存在季节变异.研究分析认为,苔藓结皮光谱与其所处环境的土壤水分有关,且苔藓结皮光谱象其他高等植物一样具有季节性变异,所以仅通过分析某一状态下的生物结皮的光谱与其他地物光谱的异同,构建的遥感解译方法很难具有普适性.由于湿苔藓结皮光谱与维管植物相似,苔藓结皮可能造成其盖度分布较大区域的植物指数的不稳定性和该区域植被生产力的过高估计.     

基于分布式光纤传感的热网膨胀节膨胀量测量方法

在热力管网中,膨胀节作为缓冲管道的关键部分,极易因变形扭曲引发泄漏故障,进而致使热网瘫痪.实时准确测量膨胀节的膨胀是评估管网健康状态的有效途径.对此,本文提出一种基于分布式光纤传感技术的膨胀节膨胀量的新型检测方法,建立了膨胀量检测模型,并通过实验验证了方法的有效性.研究结果表明,测量误差随着光纤绕制圈数增大而减小,通过调节绕制圈数,可以将误差范围控制在3%以内.这不仅为热网膨胀节的膨胀量检测提出了一种新思路,同时也为分布式光纤传感技术在热网健康状态检测领域的应用奠定了一定的理论基础.     

Cu/Ti3SiC2体系润湿性及润湿过程的研究

采用座滴法研究了温度及Ti₃SiC₂的两个组成元素Si和Ti对Cu/Ti₃SiC₂体系润湿性的影响。结果表明, Cu与Ti₃SiC₂之间有良好的润湿性, 且润湿过程属于反应性润湿。随着温度的升高, Cu与Ti₃SiC₂间的反应区扩大, 反应层深度增加, 润湿角减小, 温度超过1250℃后反应明显加快, 至1270℃时润湿角降至15.1°。物相分析与微观结构研究表明, Cu/Ti₃SiC₂界面区域发生了化学反应, 反应产物主要为TiC_x和Cu_xSi_y, 同时发生元素的互扩散, 形成反应中间层, 改变体系的界面结构, 促进了Cu和Ti₃SiC₂基体的界面结合, 从而改善了体系的润湿性。在Cu中添加Si抑制了Ti₃SiC₂的分解, 而添加Ti阻碍了Cu向Ti₃SiC₂的渗入, 均不利于Cu/Ti₃SiC₂体系润湿性的改善。     

高效液相色谱法同时测定食品中12种防腐剂和甜味剂

目的建立高效液相色谱法同时测定食品中12种防腐剂和甜味剂的含量。方法样品经甲醇-水(30:70,V:V)提取,经Agilent TC C_(18)色谱柱分离,以甲醇/20 mmol/L乙酸铵水溶液为流动相进行梯度洗脱,流速为1.0mL/min,采用二极管矩阵检测器进行检测,检测波长为230 nm。结果 12种防腐剂和甜味剂在0.2~20μg/mL的浓度范围内呈现良好的线性关系,r~2≥0.9992,回收率在70.9%~115.6%之间,方法的检出限为0.001~0.005 g/kg。结论该方法具有高通量、操作简便等优点,可适用于食品中12种防腐剂和甜味剂的检测。     

Formation of TiC hexagonal platelets and their growth mechanism

A large amount of TiC hexagonal platelets has formed on the surface of the sample made of Ti/Si/TiC/Al_0.2 after sintering at above 1450 °C in an Ar atmosphere. The basal plane of TiC platelets is (111) facet confirmed by X-ray diffraction. Small amounts of Si and Al elements dissolved in the TiC crystal structure, influencing the structure of TiC. The detailed structure and growth mechanism of the TiC platelets have been observed and analyzed. A model has been proposed to understand the formation of TiC hexagonal platelets.     

Controlling the oriented growth of Ti2SnC grains with carbon fiber as a reactive template in the Ti-Sn-C system

Carbon short fibers with a length of ∼3 mm used as a reactive template were mixed with Ti and Sn powders. The mixture was pressurelessly sintered at 1200 °C for 2 h in a vacuum atmosphere. The microstructure shows that Ti₂SnC grains with a plate-like shape grow along a preferred direction, forming a ‘string’ structure in which Ti₂SnC platelets pack themselves closely with a top-bottom-top-bottom sequence. With increasing the length of the C fibers, the length of the ‘string’ structures increases. A large amount of long and aligned ‘string’ structures have formed after sintering the samples prepared by infiltration of the carbon short fibers with a length of ∼50 mm in a Ti-Sn slurry and then stacking and cold pressing. X-ray diffraction and scanning electron microscopy, respectively were used to analyze and observe the phase composition and microstructure.