茶叶辐照的热释光分析研究

不采用二次辐照,将TL 分析法应用于辐照茶叶的定性鉴定。分离并收集茶叶中黏附的硅酸盐,采用热释光剂量仪测量获得硅酸盐的热释光发光曲线,比较未辐照与辐照不同剂量茶叶的热释光发光曲线的积分强度、峰值和峰值温度等特征参数。未辐照茶叶的热释光发光曲线的积分强度小于50、峰值小于0.4、峰值温度大于260℃;反之,辐照茶叶的热释光发光曲线的积分强度大于50000、峰值大于600、峰值温度位于160～190℃。TL 分析法能判别出茶叶的辐照与否,尤其对不能满足参比剂量辐照条件的样品很有帮助。     

前躯体浸渍法制备VO_x/Al_2O_3及其催化二甲醚制甲醛性能

采用前躯体浸渍法合成了VOx/Al2O3催化剂,并采用XRD、Uv-Vis、H2-TPR、NH3-TPD以及吡啶吸附红外等技术对催化剂材料的结构和性能进行了表征,同时考察了催化剂上二甲醚制备甲醛的反应性能。XRD的测试表明,V的氧化物在载体上处于高度分散状态,没有独立的V2O5晶相峰存在。Uv-Vis的测试表明,前躯体浸渍法制备的催化剂较之常规浸渍法制备的催化剂位于更高波数,因而VOx物种在载体表面的分散更加均一。H2-TPR的结果表明前躯体浸渍法制备的催化剂,相对更加容易还原,催化氧化能力更强。NH3-TPD以及吡啶吸附红外的结果表明前躯体浸渍法制备的催化剂相对具有较少的B酸和较弱的酸性。前躯体浸渍法制备的VOx/Al2O3催化剂在DME选择氧化制备甲醛的过程中,具有更高的甲醛的选择性和收率,选择催化的性能更佳。     

准噶尔盆地乌夏地区稠油稠变阶段及其成藏特征分析

乌夏地区稠油分布于距油源玛湖凹陷远距离的断裂上盘中生界超覆尖灭带上,埋深浅,构造简单。表现出高密度、高粘度、高沥青质、高酸值、低蜡、较高凝固点的特征,体现了生物降解原油的基本特征。根据其饱和烃色质谱特征、生物标志化合物降解程度、三环萜烷和孕甾烷含量等将其降解稠变过程划分为4个阶段。长距离通过不整合面运移遭受水洗、生物降解是导致原油稠变的主要因素,其成藏主要与不整合和浅部正断层有关,在后期成藏中对油气有重要的封堵作用。     

视觉文档图像中反渗噪声的去除方法

提出根据直方图特征去除视觉文档图像反渗噪声的方法.对于灰度直方图呈双峰特性的噪声图像,选取适当区域分别进行增强或归一化处理以达到去除反渗噪声的目的;而对于直方图呈单峰特性的含反渗噪声图像,建立了一种基于背景分离的新算法.实验结果表明,该方法可以有效去除视觉文档图像中的反渗噪声.     

一种新的基于相位调制跟踪的电源并联控制方法

研究了抗干扰能力强、控制可靠性高的数字化并联控制技术，提出了一种数字均流控制方法一相位调制跟踪法。该方法将每个模块有功功率、无功功率和同步信号通过相位调制的方法变换为相位变化的周期脉冲信号，然后通过锁相同步的方法使所有并联逆变器模块都跟踪相位最超前，即输出功率最大模块的脉冲信号，从而实现功率均分。该方法具有控制信号分辨率高，抗干扰能力强以及稳定性好等优点，提高了系统均流控制精度；同时，自然实现了民主主从控制，具有好的控制冗余性。克服了线路阻抗变化对系统均流精度的影响。实验结果表明，该方法能较好地实现逆变模块的功率均分，模块间输出电流偏差小于1％。     

Polymer microlayer structures with anisotropic conductivity

Continuous layer-multiplying coextrusion offers a new approach for processing metal-filled polymers into conducting structures. In this process, filled and unfilled polymers are combined into unique structures with many alternating layers of two or more components. The total number of layers can range from tens to thousands. The ability of microlayering to organize anisotropic particles was used to obtain metal-filled polypropylene tape with highly anisotropic electrical properties. Orientation of metal flakes by microlayering increased the anisotropy in resistivity by two orders of magnitude over compression molding. Isolation of individual filled layers by alternating filled and unfilled layers resulted in materials with many independent conducting pathways. Filled layers with 10% (v/v) copper flakes or 15% (v/v) nickel flakes were conductive only if the filled layers were thick compared to the thickness of the flake particles. When the thickness of the filled layers approached the particle thickness, the conductive properties were lost. This behavior was understood by comparing the three-dimensional arrangement of flakes in thick conductive layers with the two-dimensional particle layout of thin non-conductive layers.     

Herringbone fracture of a polycarbonate/ABS blend

Tensile fracture mechanisms in single edge notched injection-moulded specimens of a polycarbonate/ABS 30/70 wt% blend have been studied by fractography. When the tensile force was applied parallel to the injection direction, a herringbone pattern could be observed on the fracture surface, while for the perpendicular case, a reverse herringbone pattern was seen. At the same testing condition, the former was tougher than the latter. Fracture images and two-dimensional temperature profiles in the thickness direction were used to locate the crack initiation sites. Herringbone fracture occurred when the main crack repeatedly interacted with secondary cracks initiated along the centreline. Reverse herringbone fracture was formed in a similar mechanism but secondary cracks initiated near the edge. Anisotropy of the fracture modes was attributed to the processing-induced orientation of the polycarbonate phase near the edge.     

Comparison of left anterior oblique, anterior, and geometric mean methods in gastric emptying assessment of postpancreaticoduodenectomy patients

Although left anterior oblique (LAO) gastric emptying studies appear to be an adequate alternative to geometric mean (GM) measurements in patients with normal gastric anatomy, it is not clear whether they can be used after gastric or duodenal surgery. In this study, dual-phase gastric emptying studies with combined solid-liquid meal were performed in 54 patients who had undergone pancreaticoduodenectomy (Whipple procedure). Gastric emptying was studied with GM, LAO, and anterior (ANT) methods. T1/2 and percent gastric retention at 10, 30, 60, 90, and 120 minutes were calculated. Results from the three methods were compared using correlation analysis and the t test. The t test showed no significant difference in T1/2 and percent retention values between the GM and LAO or ANT views. The solid emptying T1/2 showed a better correlation between GM and LAO values (r = 0.824) than between GM and ANT (r = 0.589). For the liquid T1/2, the reverse was true. Correlation between GM and ANT (r = 0.939) was better than between GM and LAO (r = 0.839); however, both LAO and ANT views correlated well with GM liquid emptying. It is concluded that the LAO view can replace GM gastric emptying methods in postpancreaticoduodenectomy patients for evaluation of both solid and liquid emptying, although the ANT view appears completely adequate for the study of liquid emptying.