共晶强制性熔化的界面形态

对透明共晶系ＣＢｒ４－８．４ｗｔ－％Ｃ２Ｃ１６生长的典型层片共晶组织强制熔化进行实时实地观测．表明相对于强制生长时的“界面滞后”现象，熔化界面温度高于静止时界面温度，熔化界面比静止界面更靠近热端，称为“界面超前”．随熔化速度增大，“界面超前量”增大；共晶组织分层熔化，出现两个熔化界面，α和β相熔化秩序不同，α，β相分别单独熔化，两熔化界面的相对位置由α，β相成分，熔化速度和共晶相间距等因素决定．     

Poly(oxyphosphazenes): A unifying look at structure and morphology

Variations in thermotropic behavior have been investigated for many crystalline polyphosphazenes. Experimental results obtained from DSC, solid-state MAS NMR, dilatometry, mechanical property (creep and dynamic) measurements, birefringence, X-ray (wide and small-angle), and electron diffraction have been made as a function of temperature in an attempt to elucidate the structure-morphology behavior in these polymers. Initially all polyphosphazenes described in this study crystallize from dilute or moderately concentrated solutions in the monoclinic form with relatively low crystallinity (50%). When heated, these specimens expand atT(1) and adopt a chain-extended 2D mesophase morphology in order to relieve congestion. Above this first-orderT(1) temperature a chain-extended –P=N– chain backbone morphology transforms into an isotropic phase at the melting temperatureT _m. When cooled, samples transform into the mesostate. However, crystallization from the mesophase belowT(1) takes place into a 3D orthorhombic state. These two modes of ordering/disordering are in accordance with (i) a hexatic chain packing [betweenT(1) andT _m] with variously mobile side groups that also exhibits smectic features when mesogenic side groups are present and (ii) a 3D orthorhombic structure of high crystallinity belowT(1). The initial monoclinic phase is accessible only via a solution crystallization route. Solid-state MAS NMR, crystallization kinetic measurements, and optical microscopy studies obtained from oriented and unoriented polymers have been especially germane in providing a unifying picture for mesophase formation and ordering in polyoxyphosphazenes. X-ray and electron diffraction evidence is complicated by critical overlapping peaks that are found under these same conditions. They demonstrate that (a) positional disorder exists along the chain direction and (b) the side chain above, as well as below, theT(1) transition is governed by the mobility, size, and type of side group in circumstances where phase transformations occur.     

改进的形态学运算在声纳图像生成中的应用

声纳技术应用日益广泛,已成为海洋测量的重要工具,而去除噪声处理是对声纳图像进行正确判读的前提,本文采用了改进的形态学算法减少声纳图像中噪声的影响,对图像进行预处理,采用Matlab图形图像处理工具对处理的算法进行仿真的方式,从而使处理效果达到最佳。     

Formation of WC/Ni hard alloy coating by laser cladding of W/C/Ni pure element powder blend

WC/Ni coating was formed by laser cladding of a W/C/Ni powder blend. The formed WC crystals have rectangular or quadrangle cross-section shapes with size of 2–30 μm. Step, twist and cross growth morphologies of WC formation were observed. The coating contains WC, CW_3, WNi, FeW₃C, Fe₆W₆C, W₃O, W, C, and (Fe,Ni) phases.     

钢表面化学气相沉积TiC晶体的择优取向

本文用化学气相沉积(CVD)法,以TiCl_4-CH_4-H_2为原料气体,在不锈钢表面获得了致密的TiC膜.研究了TiC的成膜速度、表面形貌和晶体择优取向与沉积条什的关系.结果表明,沉积温度T_(dep),碳钛比CH_4/TiCl_4强烈地影响了TiC的成膜速度、表面形貌和晶体择优取向.CH_4/TiCl_4低时,TiC晶体的择优取向为(220):而CH_4/TiCl_4高时,TiC晶体的择优取向为(200).TiC晶体的择优取向主要取决于气氛中活性碳的平衡浓度。     

多壁碳纳米管/聚酰亚胺复合材料制备及其性能研究

聚酰亚胺的前聚体,聚酰胺酸,是通过4,4-二氨基二苯醚(ODA)与3,3,4,4二苯甲酮四羧酸二酐(BTDA)反应制备的。未改性的、酸改性和胺改性的多壁碳纳米管(MWCNT)被分别地单独加入到聚酰胺酸溶液中,并加热至300℃,从而制成聚酰亚胺/碳纳米管复合材料。扫描型电子显微镜(SEM)和透射电子显微镜(TEM)的显微照片表明,酸改性的多壁碳纳米管和胺改性多壁碳纳米管在聚酰亚胺基体中被均匀一致地分散开。通过对酸和胺改性的多壁碳纳米管MWCNTS对多壁碳纳米管/聚酰亚胺复合材料的表面和体积电阻率的影响进行了研究。了解到该纳米复合材料的表面电阻率ITES从1.28×10^(15)Ω/cm^(2)(纯聚酰亚胺),降到7.59×10^(6)Ω/cm^(2)(26.98%的未改性的多壁碳纳米管含量)。除此之外,添加多壁碳纳米管影响了纳米复合材料的玻璃化转变温度。改性多壁碳纳米管意义就是提高了纳米复合材料的机械性能。多壁碳纳米管/聚酰亚胺复合材料的拉伸强度从10^(2)MPa(纯的聚酰亚胺)增加到134 MPa(6.98%酸改性多壁碳纳米管/聚酰亚胺复合材料)。     

基于LCZ的湿热地区典型城市局部空间格局特性研究

城市化建设的快速发展使得城市街区尺度区域形成了复杂多样的空间格局, 影响了城市局部区域的微气候特性。本文从量化城市地表要素对局地气候影响的视角出发, 提出了基于街区边界和区域内空间特性指标计算的局部气候分区(Local Climate Zone, LCZ)划分方法, 该方法面向街区单元, 较好地描述了街区尺度局部区域的精细化空间格局。以湿热地区典型的人工生态城区(广州大学城)及典型中心商务区(珠江新城)为例, 利用所提出的LCZ划分法构建了两个案例区域的LCZ分布图, 以及建筑空间形态与下垫面布局特性指标分布图集。从图集对比结果可知, 大学城主要以开敞式中层建筑为主, 而珠江新城则以紧凑型高层建筑为主。城市区域LCZ空间特性参数的可视化表达将为街区小气候分布规律的量化研究和气候适宜型生态城市建设提供数据基础和理论依据。     

超声辅助激光修复镍基高温合金V形槽

为了提高失效零件的修复质量,以V形槽为修复对象开展研究,在修复过程中引入超声振动. 耦合声场、温度场与流场建立超声辅助激光修复V形槽的非线性瞬态模型,对修复过程熔池形貌及其温度场进行数值模拟,并开展相关实验研究,分析超声对修复区组织及性能的影响机制. 数值模拟结果表明,超声振动能加速熔池流动与散热,提高熔深,细化晶粒并改善V形槽底部难熔区域的修复效果. 金相、扫描电子显微镜和电子背散射衍射分析结果表明,在超声作用下,晶粒尺寸和一次枝晶间距得到细化,Laves相更加弥散,Nb元素的富集受到抑制;常温和高温硬度在超声作用下分别提高了11.1%、10.4%. 研究表明,超声振动能有效改善镍基高温合金V形槽激光修复区的微观形貌,提高力学性能.     

钼对渗碳过程中碳化物形态的影响

通过萃取复型观察和对衍射花样的标定，研究了深层渗碳过程中析出碳化物的形态和分布。实验结果表明：渗碳过程中析出的形态较好的碳化物，象点状、球状和椭球状碳化物均为钼的碳化物；而形态较差的针状、网状则为（Cr、Fe）7C3和（Fe，M）3C。并对其形成机理进行了初步探讨。     

基于数学形态学的运动估计及VLSI设计*

提出的基于数学形态学的运动估计算法,采用四场的SAD比较进行运动估计,并且对运动向量进行数学形态学滤波处理(先进行腐蚀,再进行扩散处理),削弱噪声影响,提高运动估计的精度.在VLSI实现中采用外挂SDRAM作为帧存储器,存储前两场图像数据和运动信息.本算法和VLSI设计经过FPGA验证,取得了很好的效果,并且已经被成功地应用于基于SMIC 0.18 μm CMOS工艺的数字视频处理芯片中.