基于STC89C52单片机的可控旋转视觉试验台的设计

为实现对物体的不同角度、不同位置、不同速度的拍照,设计了一种基于STC89C52单片机的可控旋转视觉试验台.试验台由系统软件及硬件共同组成,实现了试验台角度的调节,正反转的控制、速度的控制.将两个CCD摄像机摆放在试验台的两侧,通过对试验台的控制,然后按照既定的条件触发摄像机拍照,将获得的图片传输至图像处理分析软件中进行分析处理.     

基于改进光流场和尺度不变特征变换的非刚性医学图像配准

该文对传统的变分光流模型进行了改进,结合尺度不变特征变换(SIFT)特征点提取提出一种新颖的非刚性医学图像配准算法。该算法模型使用亮度守恒与梯度守恒假设相结合的数据项,很好地解决了对医学图像中局部病灶异常、亮度不均匀等区域的处理问题;通过采用自适应的各向异性正则项,解决了传统光流模型中的过平滑所导致的图像严重模糊和重要细节丢失的问题;通过结合SIFT特征点提取,并采用多分辨率分层细化、内部不动点迭代以及由粗到细的变形技术求解策略,很好地解决了传统光流场模型无法对大形变医学图像以及细节进行配准的问题。实验证明：该文的模型和算法可以很好地实现对医学图像的非刚性配准。     

龙塘校区学生宿舍供水改造方案分析

分析了龙塘校区用水存在的供需矛盾,提出了建蓄水池、安装变频加压泵、改造供水管道等3项措施提高学院用水保证率。     

基于净图描述的通用隐写分析技术

针对互联网上大量的隐写软件利用数字图像隐藏秘密消息,文中提出了基于净图描述的通用隐写分析技术.这种隐写分析技术能有效地检测出图像是否含秘密信息,通过提取两种新颖特征,即纹理特征和虚特征值分解(IED)特征,对净图进行完整的定量描述,又经过降维处理,解决了维数灾难问题,提高了检测速度;并且设计了与特征相匹配的柔性化超椭球体一类分类器,提高了检测性能.     

基于深度学习的Linux内核引用计数字段识别方法

引用计数机制是现代软件中一种常见的内存管理技术.引用计数错误往往会导致内存泄露、释放后使用(useafterfree)等严重的安全问题.现有致力于提高引用计数安全性的工作都依赖于对引用计数的字段进行识别.然而,由于类似于Linux等软件系统的代码十分复杂,在代码中识别出引用计数字段是一项十分困难的工作.传统的基于代码模式匹配的引用计数字段识别方法一方面存在需要专家经验总结规则,人工开销大的问题;另一方面存在总结的模式无法覆盖所有情况,召回率较低等局限.针对这些问题,发现与字段有关的代码行为以及字段的名称可以用来表征这个字段的特征,帮助识别引用计数字段.基于这两个层面的特征,设计了一种基于多模态深度学习的引用计数字段识别方法,并面向Linux内核实现原型系统.测试数据表明:该原型系统的精确率、召回率分别为96.98%和93.54%,而传统的基于代码模式匹配的方法没有识别出任何引用计数字段.此外,在Linux内核上发现61个引用计数字段使用不安全的数据类型,并对其中21个向Linux内核社区提交数据类型转换补丁以提高引用计数字段的安全性,其中6个已经被合并到Linux内核代码主分支.     

“蒸汽相转化”法制备纳米多级Beta沸石催化材料

由于多级孔沸石具有实际及潜在的应用价值, 合成具有微孔-介孔孔道体系的多孔沸石引起了广泛关注。本研究在不添加二次模板剂的基础上, 采用“蒸汽相转化”法制备了多级孔Beta沸石催化材料, 对影响多级孔Beta沸石形成因素, 如凝胶碱度、模板剂用量、硅铝比、蒸汽压力和晶化时间等进行了讨论。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅立叶变换红外(FT-IR)光谱、拉曼(Raman)光谱、N₂吸附-脱附以及NH₃-TPD等表征手段对制备材料的结构性能进行了表征。在借助红外光谱、拉曼光谱及扫描电镜等表征手段的基础上, 对多级孔Beta沸石的形成机制进行了探索。结果表明: 通过“蒸汽相转化”法所制备的Beta沸石为纳米多晶聚集体, 这些多晶聚集体由粒径为10~40 nm的初级晶粒构成, 在初级纳米粒子之间形成了2~30 nm的介孔结构; 干胶制备过程中生成的初级和次级结构单元有利于快速形成大量的Beta沸石核, 较高的成核速率有利于Beta沸石纳米晶粒形成, 这些纳米晶粒相互聚集最终形成纳米多晶Beta沸石聚集体。     

Investigation on anti-wear properties of sulfide layer on bearing steel lubricated by oil-containing FeS particles

To enhance the anti-wear properties of the sulfide layer on the surface of 52100 steel under harsh conditions, FeS particles were mixed into the oil as additive. The anti-wear properties of plain surface and sulfurized surface under base oil and oil-containing FeS particles lubrication were investigated by a ball-on-disk tester. The composite effects of sulfide layer and FeS particles with different sizes and amounts in base oil were studied as well. The results showed that the anti-wear properties can be improved for sulfurized and plain steel surfaces after FeS particles were used as additive in oil. The composite effect of sulfide layer and FeS particles possessed very good anti-scuffing and anti-wear properties. The FeS particle could supplement the loss of sulfur from the sulfide layer in the wear process, so that the service life of FeS film can be prolonged under more harsh conditions. An appropriate addition amount of FeS is important for the composite effect.     

A dissipative particle dynamics study on the compatibilizing process of immiscible polymer blends with graft copolymers

The dissipative particle dynamics (DPD) is used to study the compatibilizing process of an immiscible polymer blend using a graft copolymer as a compatibilizer. Polystyrene (PS) and polyamide 6 (PA6) are chosen as the polymer components of the blend. The graft copolymer is composed of PS as the backbone and PA6 as the grafts. Mesoscale morphology, density distribution, end-to-end distance of PA6 and interfacial tension are investigated. Simulations show that the presence of a graft copolymer contributes to the formation of finer and more uniform dispersed domains by preventing them from collision and coalescence. In the presence of a graft copolymer, the density distribution is more uniform and the dynamic equilibrium of the blend morphology is reached more rapidly. For a given backbone and number of grafts per backbone, the compatibilizing efficiency of the graft copolymer first increases with increasing graft length. However, when the graft length exceeds a certain value, it starts decreasing.     

Addition of small amounts of BiFeO3 to (Li,K,Na)(Nb,Ta)O3 lead-free ceramics: Influence on phase structure,microstructure and piezoelectric properties

A small amount of BiFeO₃ (BF) was incorporated into lead-free Li_0.03(Na_0.53K_0.48)_0.97Nb_0.8Ta_0.2O₃ (LKNNT) piezoceramics for the purpose of property improvement via phase structure control. It was found that the addition of BF not only induced a series of phase transformations from orthorhombic to tetragonal and further to pseudocubic in LKNNT ceramics, but also enhanced its sintering densification behavior. Even tiny amount of BF addition down to 0.5 mol% could change the room-temperature phase structure from a dominant orthorhombic state to the coexistence of orthorhombic and tetragonal phases, resulting in peak piezoelectric properties of $d_{33}^{*}～340\text{pm/V}$, k_p ～ 47.0%. When the amount of BF was increased to 0.75 mol%, the tetragonal phase became dominant in the modified LKNNT ceramics, which exhibited excellent temperature stability, despite its slightly lowered piezoelectric coefficients.