基于灰度图像的秘密分享方案

目前像素的扩展问题成为可视秘密分享方案的重要问题。利用布尔运算给出一个可视的秘密分享方案,并且没有像素的扩展,恢复出的秘密图像质量很好。     

螺环结构膨胀单体的合成及膨胀性能研究

为解决环氧树脂固化时体积收缩带来的不良影响,用实验室合成的三元醇与二正丁基氧化锡反应制得螺环结构的膨胀单体3,9-二羟甲基-3,9-二(二甲基乙硫基)-1,5,7,11-四氧杂螺环[5,5]十一烷改性环氧树脂.产物经红外、核磁表征其结构.用膨胀剂跟踪测定阳离子引发膨胀单体开环聚合体积膨胀率为3.16%,考察预聚体改性环氧树脂体积膨胀率的变化,为1.194%.     

天然胶/杜仲胶共混硫化物结晶性对热致形变回复性能的影响

用XRD法分析天然胶/杜仲胶共混硫化胶的结晶性,研究其结晶性对天然胶/杜仲胶共混硫化胶的物理性能和热致形变性能的影响.实验结果表明:随着杜仲胶用量的增加,硫化胶在XRD图谱中的衍射峰强度增大,硫化胶的结晶性增大,硫化胶交联密度有明显减小.定伸应力和拉伸强度随杜仲胶用量的增加而增大,而拉断伸长率减小,热致回复温度降低,试样的最终形变率减小.     

Mechanical,electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver–palladium nanocomposite with CNT resulted in increases in the hardness and Young＇s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion（CTE）. The hardness and Young＇s modulus of the nanocomposites were increased by 30%？40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver–palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.     

Microstructure and properties of electronic packaging shell with high silicon carbide aluminum-base composites by semi-solid thixoforming

The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion（CTE） are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.     

特征线坐标系下柱对称超音速流膨胀波计算方法研究

在静压圆盘止推气体轴承柱对称超音速流膨胀波系的计算中,借鉴Liepmann的特征线坐标系与自然坐标系变换理论和Liepmann引入两个黎曼不变量的方法,使得边界条件的处理更为直观和简便。采用特征线坐标系下的特征线法,推导计算该膨胀波系所用到的基本计算公式,将其应用于 P-M 流动并与 P-M 流动理论解进行比较。结果表明,数值计算结果与P-M流动理论解吻合,该计算方法可行。     

TC10钛合金相变点的测定

分别用计算法、热膨胀法和连续升温金相法测定了TC10钛合金的β相转变温度.结果表明,计算法得到该合金相变点温度为936℃,热膨胀法测得该合金相变点温度为939.6℃,连续升温金相法测得该合金相变点温度为937.5℃.3种方法测得的结果相当接近,说明这3种方法可以相互结合使用.     

基于灰色关联的自密实混凝土配合比设计分析

由于自密实混凝土对工作性和耐久性的要求很高,其研究主要从自密实混凝土配合比设计考虑,通过对配合比的优化充分满足自密实混凝土的性能要求。根据灰色关联度分析法,概括了各主要材料用量对强度、坍落度和扩展度的影响,总结出自密实混凝土配制的影响因素,并对诸多因素进行排序,以便抓住主要影响因素。对自密实混凝土的配合比进行优化,以满足实际工程中配制自密实混凝土的需要。     

不同强度混凝土静态破碎试验研究

将静态破碎剂在相同用量及相同拌合水温条件下,倒入强度等级分别为C20、C30、C40的混凝土预留孔中进行静态破碎试验,观察混凝土表面裂缝的扩展情况并记录反应过程中混凝土外表面应变变化规律。结果表明：随着混凝土强度等级的提高,混凝土外表面开始出现裂缝的时间逐渐推迟,裂缝扩展的宽度以及混凝土外表面出现裂缝的条数都随着混凝土强度等级的提高而逐渐缩小和减少。在反应过程中,随着混凝土强度等级的提高,混凝土外表面的应变出现明显波动的时间逐渐滞后,不同强度等级的混凝土的四个侧面中,始终有一个侧面产生拉应变,其余三个侧面产生压应变。     

全长粘结式灌浆锚杆锈胀机制研究

针对埋设在地下特殊环境条件下全长粘结式灌浆锚杆存在因锈胀致裂,导致结构失效的实际情况,以弹性理论为基础,根据锚杆、灌浆材料以及围岩体三者之间变形协调关系、荷载平衡条件,研究了锚杆锈胀导致灌浆或岩体开裂,进而加速锚杆锈蚀破坏的机制问题,讨论了锚杆锈胀量、灌浆材料特性、保护层厚度以及围岩体力学性质对锚杆锈胀力的影响。结果表明:锚杆锈胀力随着钢筋锈蚀率的增加而增加,随钢筋保护层厚度的增加而减少;砂浆与围岩体之间的锈胀力随砂浆强度、围岩强度的增加而增加,钢筋与砂浆之间的锈胀力随围岩强度的增加而增加,随砂浆强度的增加而降低。