在团队合作中培养学生的创新实践能力

介绍在实践课程中采用团队合作方式进行教学改革,总结在实践课程中激发学生的创新意识及培养学生动手能力的经验,提出在大学前期阶段安排学生在团队合作中进行自主创新实践。     

基于拓扑优化方法的大型液压挖掘机斗杆新型结构

以斗杆结构强度为基准,采用结构优化的方法,设计了大型液压挖掘机正铲工作装置斗杆新结构。采用离散元方法,构建矿山岩石模型,获得铲斗挖掘阻力;采用多体动力学方法,搭建大型液压挖掘机正铲工作装置刚柔耦合动力学模型,获得挖掘机斗杆挖掘工况斗杆动态载荷,并对斗杆进行动态结构强度分析;采用SIMP插值函数的变密度拓扑优化方法,在有限元中对斗杆结构进行拓扑优化设计,获得大型液压挖掘机正铲工作装置新型斗杆结构;对新型斗杆结构进行动态结构强度分析,斗杆结构强度保持原有水平。研究结果表明,通过拓扑优化后得到的新型斗杆,结构强度与类比设计一致,但质量减小。     

CRDMAC的设计与评价: 基于循环RTR的无线自组网络的定向MAC协议

Using directional antennas in Wireless Ad hoc Networks (WANETs) offers great potential of reducing the radio interference, and improving the communication throughput. Directional antennas, however, introduces new problems in the wireless Media Access Control (MAC), that is, the deafness and new hidden terminal problem, which may cause severe performance degradation. To solve the problems, we propose an effective Circular RTR Directional MAC (CRDMAC) protocol for WANETs by using a sub-transmission channel and Ready to Receive (RTR) packets, which modifies the IEEE 802. 11 Distributed Coordinated Function (DCF). The sub-channel avoids collisions to other ongoing transmission, and the RTR packets notify the neighbor nodes that the mutual transmission has been finished. We evaluate the CRDMAC protocol through simulations and the results show that the proposed protocol outperforms existing DMAC (directional MAC) protocol and the CRCM (Circular RTS and CTS MAC) protocol in terms of throughput and packet drop rate.     

导电聚苯胺电极材料在超级电容器中的应用及研究进展

超级电容器用导电聚苯胺电极材料具有高比容量、化学稳定性好、价格低廉等优点,目前已成为超级电容器研究的一个新方向.简述了导电聚苯胺的制备与储能机理,从纯聚苯胺电极材料、¨离子掺杂聚苯胺电极材料、C/聚苯胺复合电极材料、聚苯胺混杂型电容器以及聚苯胺全固态超级电容器5个方面详细论述了导电聚苯胺电极材料在超级电容器中的具体应用,并对聚苯胺今后的发展方向给予了评论.     

超级电容器复合电极材料的研究进展

超级电容器作为一种新型的储能元件,具有高功率密度和高循环寿命等优点,在许多领域特别是混合电动汽车领域具有广阔的应用前景.而电极材料是决定超级电容器性能的关键因素之一,高性能电极材料的合成和优化是目前超级电容器研究的重点.综述了超级电容器的储能原理、超级电容器复合电极材料的制备、性能、以及发展方向.     

矿粉对纳米SiO2-OPC-CSA体系耐盐渍土侵蚀性影响

研究了矿粉对纳米Si O2-普通硅酸盐水泥-硫铝酸盐水泥(纳米Si O2-OPC-CSA)复合体系抗硫酸盐侵蚀能力的影响规律,以试件表观形貌、质量、相对动弹性模量及抗压耐蚀系数的变化表征试件的损伤程度;采用X射线衍射(XRD)仪分析了硫酸盐-干湿循环作用下试样的水化产物,研究矿粉对纳米Si O2-OPC-CSA复合体系耐硫酸盐侵蚀性能的影响机理。结果表明,在硫酸盐-干湿循环作用下,水泥砂浆受到化学侵蚀和物理侵蚀的综合作用,其中物理侵蚀破坏更为严重;当矿粉掺量为10%时,消耗了体系中的氢氧化钙,提高了结构密实度,从而使复合体系的抗硫酸盐侵蚀能力最佳。     

基于频域水印的人脸图像窜改检测认证方法

以DeepFake为代表的AI换脸技术为人们的生活带来诸多负面影响,现有的人脸窜改检测算法鲁棒性较弱,缺乏可解释性。针对这一问题提出一种离散小波变换（DWT）、离散余弦变换（DCT）、奇异值分解（SVD）相结合的人脸频域水印算法（face frequency-domain watermarking,Face-FW）,通过提取图像人脸特征并压缩加密生成二值水印嵌入图像频域以达到检测人脸窜改、认证原人脸归属人的目的,同时提出动态特征融合算法以降低Face-FW适用范围。选取人脸图像标准数据集CASIA-FaceV5和IMDB-WIKI部分图像嵌入水印并窜改人脸生成测试集CASIA-DF和IMDB-DF。实验结果表明,Face-FW在两个测试集上分别有97.6%和96.9%的检测窜改成功率,优于对比方法,并且算法能够根据非特征融合水印提供人脸认证,具有较强的鲁棒性和可解释性。     

Theoretical Treatment of Target Coverage in Wireless Sensor Networks

The target coverage is an important yet challenging problem in wireless sensor networks,especially when both coverage and energy constraints should be taken into account.Due to its nonlinear nature,previous studies of this problem have mainly focused on heuristic algorithms;the theoretical bound remains unknown.Moreover,the most popular method used in the previous literature,i.e.,discretization of continuous time,has yet to be justified.This paper fills in these gaps with two theoretical results.The first one is a formal justification for the method.We use a simple example to illustrate the procedure of transforming a solution in time domain into a corresponding solution in the pattern domain with the same network lifetime and obtain two key observations.After that,we formally prove these two observations and use them as the basis to justify the method.The second result is an algorithm that can guarantee the network lifetime to be at least (1-ε) of the optimal network lifetime,where e can be made arbitrarily small depending on the required precision.The algorithm is based on the column generation(CG) theory,which decomposes the original problem into two sub-problems and iteratively solves them in a way that approaches the optimal solution.Moreover,we developed several constructive approaches to further optimize the algorithm.Numerical results verify the efficiency of our CG-based algorithm.     

基于可逆水印的神经网络模型完整性验证算法

针对深度神经网络模型易遭受完整性破坏问题,提出一种基于可逆水印和模型压缩剪枝理论的快速神经网络模型完整性验证算法Fast-MIV(model integrity verification)。基于模型压缩剪枝理论探究模型的冗余性,筛选对模型原始任务影响较小、且可被替代的权重参数进行预处理构建待嵌入参数序列;采用差值扩展可逆水印算法,在神经网络卷积层上嵌入对模型篡改敏感的神经网络水印,达到完整性验证的目的。基于ImageNet数据集,对VGG19、DenseNet-121、ResNet-50和Inception-v3等模型的实验验证结果表明,Fast-MIV在不影响模型原始分类任务精度的前提下,能够快速验证模型的完整性并报告模型的受损程度,可以应对数据中毒攻击和结构性破坏。     

变压器频率响应分析法测试结果的影响因素分析

针对在现场应用频率响应分析法检测变压器绕组变形时干扰因素较多,若操作不当,会使测试结果失真,导致对绕组状态做出错误判断的问题,结合频率响应分析法的基本原理和现场实例经验,从测试系统、被测变压器两方面分析测试结果的影响因素,并提出提高测试结果的准确性的相关注意事项。