求解旅行商问题的嵌入遗传算子启发式算法

算法复杂性理论中的NP完全问题是悬解的著名难题之一。旅行商问题作为经典的组合优化问题,实际中的应用非常广泛,但它却是一个NP完全问题。历年来,对它的一项主要研究工作,就是寻找一种既有高质量的解,又能快速收敛的近似算法。围绕这项研究,本文的主要创新是:首先,设计了求解该问题的一种嵌入遗传算子的启发式算法,它在本质上是经典插入算法的改良,但同时渗透了遗传算法思想;其次,对于这种近似算法,文章阐明算法具有多项式时间界O(n3),并且给出了评价其性能的不超过2的界估计及其严格的理论证明,因而它的算法理论基础是坚实的;最后,通过两个典型的算例计算结果的对比分析表明:该近似算法较之几种常用的启发式算法,其解的质量更高,又由于插入算法的程序设计方便快捷,因而它对于实际问题的计算需求无疑是极有意义的。     

Word 2003长文档的实用处理方法

针对打字印刷行业专业人员及其他人员在Word中长文档排版时遇到的困难,提出了一种适合各类人员使用长文档排版的行之有效的方法。指出了排版之后文件格式比较混乱且无法进行再次编辑的原因。提出了在Word2003中处理长文档时,按照文章的提示便能取得到一个专业的、完整的排版效果的一种实用方法。     

预制混凝土墙体U型筋搭接连接受拉承载性能研究

装配式剪力墙结构的预制墙体采用U型筋搭接连接可提高效率、降低造价.为研究上下预制墙体U型筋搭接连接时,上下钢筋传力性能及其影响因素,对16个采用U型筋搭接连接的上下预制墙体进行了轴拉试验,试验参数包括U型筋直径、搭接长度、水平插筋直径和U型筋位置.分析了各试件的裂缝开展、破坏模式、荷载-位移曲线和各特征点荷载值、变形值...     

基于B样条曲线节点插入算法的拟合优化

在逆向工程中对叶片进行非接触式测量,为了更好得到叶片型线的数据,需要用曲线对有序的点云进行拟合.为了满足精度要求,提出了用节点插入算法来对拟合出B样条曲线进行优化.该方法首先通过最小二乘法拟合出曲线,然后根据误差和曲率信息以及节点插入算法不断插入节点,所得结果与上一次进行对比,直到达到拟合要求.实验表明,该方法考虑到局部曲率及误差,得到的拟合曲线逼近效果更好.     

Solving the heterogeneous fixed fleet open vehicle routing problem by a combined metaheuristic algorithm

The vehicle routing problem (VRP) is a well-known combinatorial optimisation problem and holds a central place in logistics management. Many exact, heuristic and metaheuristic approaches have been proposed to solve VRP. An important variant of the VRP arises when a ?eet of vehicles is fixed and characterised by different capacities for distribution activities. The problem is known as the heterogeneous fixed fleet VRP (HFFVRP). The HFFVRP is a natural generalisation of the VRP with several vehicle types, each type being defined by a capacity, a fixed cost and a cost per distance unit, and can cover more practical situations in transportation. This problem consists of determining a set of vehicle trips of minimum total length in which a set of customers is to be satisfied in the demand constraints using identical vehicles with limited capacity. If open routes instead of closed ones are considered in the HFFVRP, the problem becomes a heterogeneous fixed fleet Open VRP (HFFOVRP) which has numerous applications in industrial and service problems. In this paper, a bone route algorithm which uses the tabu search as an improved procedure is utilised to solve the HFFOVRP. The proposed algorithm was tested empirically on a 24 of generated VRPs, and compared with elite ant system and ant colony system. In all cases, the proposed algorithm finds the best-known solutions within a reasonable time.     

双波段频率选择表面复合材料的性能研究

以三阶正十字分行贴片旋转45°得到的图形为基本周期单元,设计了一种新型周期图案的频率选择表面(FSS)。将FSS和聚甲基丙烯酰亚胺泡沫复合制备得到双波段频选复合材料,通过对频率选择表面尺寸和泡沫厚度的设计,研究了其在1～18 GHz内的电磁波插损。研究结果表明,当FSS厚为12 μm,边界宽为30 μm,两侧泡沫厚为5 mm时,双波段频率选择超材料在特定的频段内电磁波插损的实验值和仿真值基本一致,即在2.5~35 GHz及8.5~11 GHz频段内,90%频点插损值小于0.9 dB;随着电磁波入射角的偏移,带内插损值增大,有效带宽减小。     

北京国际机场周边地区建筑隔声测试与分析

为较好的分析飞机噪声对机场周围居民室内声环境的影响，研究选择不同类型的民居房、学校（多层建筑）、基层机关办公用房、商品房等为测试对象，对北京国际机场周边地区建筑物隔声特性（插入损失）进行监测与分析，结果表明：现有民居、学校、机关办公室的隔声特性较差，商品房的隔声效果较好。门窗和房顶是机场附近农村现有建筑物隔绝噪声的最薄弱环节。     

可适应多规格浅盘型纸盒插舌包装机的设计

目的设计一种应用于多规格浅盘蛋挞纸盒包装的包装机,以实现适应多规格浅盘纸盒的自动包装。方法基于浅盘纸盒的折叠工艺流程,将纸盒襟片、侧板、盖板的折叠运动轨迹等效为各面板沿折痕转动的运动模型,设计能适应不同规格浅盘纸盒包装的插舌包装机。将同轴布局5R机构作为盖板折叠装置,利用同轴布局5R机构运动轨迹的多样性及运动可控性,控制其末端输出运动轨迹,实现2粒、3粒、4粒、6粒规格浅盘纸盒的襟片、侧体板、盖板的折叠及插舌。结果样机有效工作空间为300 mm×200mm×50 mm,能够对外形尺寸在145 mm×78 mm×35 mm到230 mm×152 mm×37 mm的浅盘纸盒进行折叠插舌,纸盒完成折叠时间约15s。结论可以完成多种规格蛋挞纸盒的包装工作,实现了浅盘型纸盒折叠自动化包装;包装机占地面小、运动柔性可控,能快速适应规模定制产品的需求。     

Ultra-high Q Ba(Mg1/3Ta0.675)O3 microwave dielectric ceramics realized by slowly cooling step process and the simulation design for hairpin dielectric filters

With the development of 5G technology, it would inevitably lead to the problem of energy consumption owing to the massive construction of 5G base stations and the increase in the number of antenna channels. Dielectric filters as the core component in the base station, the energy consumption was closely related to its insertion loss, which could be achieved by reducing the dielectric loss (tanδ = 1/Q) of microwave dielectric ceramics. In this work, in order to further enhance the Q × f value, the slowly cooling step process was innovatively introduced to the Ba(Mg_1/3Ta_0.675)O₃ ceramic. The optimal microwave dielectric properties were obtained in Ba(Mg_1/3Ta_0.675)O₃ ceramic with the step temperature of 1500 °C: ε_r = 24.767, Q × f = 298,051 GHz, τ_f = ?0.66 ppm/°C. Based on ultra-high Q Ba(Mg_1/3Ta_0.675)O₃ ceramic, the hairpin dielectric filter with high integration and low insertion loss was designed and simulated. Compared with traditional RT/duroid5870 dielectric substrate, the circuit area was reduced by more than 6 times and the passband insertion loss (|S₂₁| < 1 dB) was decreased by more than 50%. The current work could provide a solution for the low-power applications of microwave dielectric devices in 5G base stations.     

Computational Mechanistic Investigations of Biocatalytic Nitrenoid C−H Functionalizations via Engineered Heme Proteins

Engineered heme proteins were developed to possess numerous excellent biocatalytic nitrenoid C−H functionalizations. Computational approaches such as density functional theory (DFT), hybrid quantum mechanics/molecular mechanics (QM/MM), and molecular dynamics (MD) calculations were employed to help understand some important mechanistic aspects of these heme nitrene transfer reactions. This review summarizes advances of computational reaction pathway results of these biocatalytic intramolecular and intermolecular C−H aminations/amidations, focusing on mechanistic origins of reactivity, regioselectivity, enantioselectivity, diastereoselectivity as well as effects of substrate substituent, axial ligand, metal center, and protein environment. Some important common and distinctive mechanistic features of these reactions were also described with brief outlook of future development.