Electromagnetism-like algorithms for optimized tool path planning in 5-axis flank machining

Optimization of tool path planning using metaheuristic algorithms such as ant colony systems (ACS) and particle swarm optimization (PSO) provides a feasible approach to reduce geometrical machining errors in 5-axis flank machining of ruled surfaces. The optimal solutions of these algorithms exhibit an unsatisfactory quality in a high-dimensional search space. In this study, various algorithms derived from the electromagnetism-like mechanism (EM) were applied. The test results of representative surfaces showed that all EM-based methods yield more effective optimal solutions than does PSO, despite a longer search time. A new EM-MSS (electromagnetism-like mechanism with move solution screening) algorithm produces the most favorable results by ensuring the continuous improvement of new searches. Incorporating an SPSA (simultaneous perturbation stochastic approximation) technique further improves the search results with effective initial solutions. This work enhances the practical values of tool path planning by providing a satisfactory machining quality.     

Fabrication of novel silicon carbide-based nanomaterials with unique hydrophobicity and microwave absorption property

Novel SiC-based nanomaterials, namely the nitrogen and aluminum co-doped SiC@SiO₂ core-shell nanowires and nitrogen-doped SiO₂/Al₂O₃ nanoparticles, have been fabricated through a facile thermal treatment process based on the chemical vapor deposition and vapor-liquid reaction. These nanomaterials show remarkable hydrophobicity with a water contact angle (CA) over 140°, which are aroused by the surface zigzag morphology of the nanostructures and the hydrocarbyl groups generated during the preparation process. Moreover the nanocomposites also exhibit relatively prominent microwave absorption (MA) properties in the frequency range of 2.0-18.0 GHz. The minimum reflection loss (RL) value as low as −23.68 dB can be observed at 14.16 GHz when the absorber thickness is 2.6 mm with a loading rate of 16.7 wt%. And the nanocomposites-based absorbent can achieve an effective absorption bandwidth (RL < −10 dB) of 4.48 GHz with the absorbent thickness of 2.5 mm. This enhanced microwave attenuation performance can be attributed to multiple polarizations and perfect impedance matching conditions, as well as multiple internal reflections. These marvelous properties make these N and Al co-doped SiC@SiO₂ core-shell nanowires and N-doped SiO₂/Al₂O₃ nanoparticles display extensive application potential as MA materials in harsh environment.     

《数据结构》课程设计实验教学创新模式探索

《数据结构》课程设计可以使学生巩固数据结构的理论、方法和应用,激发学生学习和研究的兴趣。通过《数据结构》课程设计综合创新型实验科研培养学生的创新能力、竞争意识和团队精神。为了提高《数据结构》课程设计的教学效果,从课程设计项目的提出、项目的组织与实施、项目的验收与考核等方面提出一些可行方法和建议。重点对《数据结构》课程设计的实际教学过程进行探讨和实践研究。     

Optical properties and cooling performance analyses of single-layer radiative cooling coating with mixture of TiO2 particles and SiO2 particles

Radiative cooling can achieve cooling effect without consuming any energy by delivering energy into outer space(3K) through"atmospheric window"(8–13 μm). Conventional radiative cooling coating with multi-layer structure was severely restricted during application due to its complex preparation process and high cost. In this study, a single-layer radiative cooling coating with mixture of TiO_2 particles and SiO_2 particles was proposed. The algorithm for calculating the radiative properties of the multi-particle system was developed. Monte Carlo ray-tracing method combined with that algorithm was used to solve the radiative transfer equation(RTE) of the single-layer radiative cooling coating with mixture of TiO_2 particles and SiO_2 particles.The effects of particle diameter, volume fraction and coating thickness on radiative cooling performance were analyzed to obtain the best radiative cooling performance. The numerical results indicated that the average reflectivity of the single-layer radiative cooling coating with mixture of TiO_2 particles and SiO_2 particles in the solar spectrum can reach 95.6%, while and the average emissivity in the "atmospheric window" spectrum can reach 94.9% without additional silver-reflectance layer. The average reflectivity in the solar spectrum and average emissivity in the "atmospheric window" spectrum of the single-layer radiative cooling coating with mixture of TiO_2 particles and SiO_2 particles can increase 4.6% and 4.8% compared to the double-layer radiative cooling coating. This numerical research results can provide a theoretical guidance for design and optimization of single-layer radiative cooling coatings containing mixed nanoparticles.     

基于贪婪算法无线传感器网络中继节点布局的研究

为实现远距离的无线通信, 在网络中添加中继节点, 采用多跳路由传输数据。对于中继节点的布局问题, 依据线性结构使网络整体能量消耗最小的特征, 提出一种中继节点贪婪布局算法。该算法通过最近贪婪策略、中继节点通信容量、传感器节点数据转发跳数等约束方法限制中继节点的布局位置。理论分析和实验验证了该算法能够有效减少能量消耗, 延长网络寿命。     

Reaction-formed W2B5/C composites with high performance

Highly densified W₂B₅/C composites with W₂B₅ content from 30 to 70 vol% were fabricated by reaction hot pressing of the powder mixture of B₄C, WC and carbon black. The reaction products were identified by XRD analysis to consist of only W₂B₅ and carbon, regardless of carbon content. The reaction formed composites have excellent mechanical properties (the maximum flexural strength and fracture toughness of 786 MPa and 8.9 MPa m^1/2 respectively), electrical conductivity (the highest electrical conductivity of 1.64 × 10⁶ Ω⁻¹ m⁻¹), and resistance to both wear and oxidation because of the presence of the plate-like W₂B₅ grains. In this paper, the preparation, microstructure and properties of this new composite are investigated, and the strengthening, toughening, conduction mechanisms are discussed.     

铸钢件黑色磷化工艺的研究

通过对黑色磷化各种工艺因素的研究,确定了铸钢件锰系中温黑色耐磨磷化工艺的最佳方案.采用体视显微镜研究了磷化膜表面微观形貌;采用X射线荧光光谱法(XRF)对磷化膜的厚度和成分进行了测定;采用点蚀法对磷化膜的耐蚀性进行了研究.结果表明,磷化膜性能好,磷化液污染小,便于维护和调整;温度适中,节约能源.本文还对磷化液中各成分作用进行了理论分析.     

Residual strength model for composite laminates

To research the approach of predicting composites fatigue life,the cumulative fatigue damage of fiber-reinforced plastic laminates(FRP) was investigated,and based on the complex exponential function,the residual strength model was obtained. This model can accurately describe the propagation of cumulative fatigue damage of FRP in three stages,especially in the initial stage and the ceasing stage. Applying this model in the experiment with two loading cycles,it can be found that the prediction result has good coincidence with experimental data. So a reliable residual strength model can be provided for studying the cumulative fatigue damage of FRP.     

底框砌体剪力墙震损房屋抗震加固拟动力子结构试验

在完成了3层足尺底框配筋砌块短肢砌体剪力墙震损房屋损伤程度的评估、加固的基础上,通过对加固后的3层房屋进行拟动力抗震性能试验,研究了震后受损结构构件所用加固方法的适用性和加固对恢复结构抗震性能的效果,为寻求震损结构加固修复的方法提供理论依据,并为汶川地震受损底框房屋的结构修复提供参考。     

一种基于扩展UML的企业应用软件PIM模型

针对UML在企业应用软件建模中可用性差和效率低的问题,提出一种基于扩展UML的企业应用软件PIM模型.通过对企业应用软件特点的分析,建立了一个以业务对象为中心的多视图集成PIM模型,对UML进行扩展,在它的元模型中增加了描述企业应用软件PIM模型中的概念及其之间关系的元类、版型和标记,并采用包对这些概念和关系进行不同视点的划分.基于扩展UML的企业应用软件PIM模型通过业务对象的丰富语义实现了UML中各种图之间基于语义的集成,改善了UML的可用性,提高了企业应用软件的建模效率.结果表明:通过实际案例验证了该模型的可行性和有效性.