融入现代物流体系壮大铁路多元经营

近几年铁路货运的快速发展，为推进传统铁路运输企业向现代物流企业转型奠定了基础。向社会提供全方位的综合物流服务是铁路货运发展的必然选择。多元经营作为铁路工作的重要组成部分，与运输主业相辅相成、互为促进。现代社会物流的快速发展向多经企业提出了巨大挑战，也使企业发展面临新的环境，同时，铁路货运现代化进程的深入推进为多经企业提供了重大发展机遇。铁路多经企业要正视挑战，抓住货运改革发展的机遇，适应现代物流的发展要求，积极参与物流基础设施建设，全面发展物流增值服务，完善服务手段，提高企业管理水平。     

精密控制测量中两套施工坐标系重叠区域投影变形分析

以隧道洞外精密控制测量为例,阐述了同一工程项目中两套施工坐标系的建立及其重叠区域控制网内相同边角在两个投影面上的投影变形情况.     

城市复杂环境下大断面隧道施工技术

介绍了大断面市政隧道在复杂环境下，针对不同隧道围岩地质条件，因地制宜采取三台阶法和“导洞先行、后续扩挖法”，并采用动态监测手段，从而既有效控了制地表构筑物变形，又确保了隧道施工安全、快速顺利地通过浅埋段。     

Design of an adaptive controller for dive-plane control of a torpedo-shaped AUV

Underwater vehicles operating in complex ocean conditions present difficulties in determining accurate dynamic models. To guarantee robustness against parameter uncertainty, an adaptive controller for dive-plane control, based on Lyapunov theory and back-stepping techniques, was proposed. In the closed-loop system, asymptotic tracking of the reference depth and pitch angle trajectories was accomplished. Simulation results were presented which show effective dive-plane control in spite of the uncertainties in the system parameters.     

基于XML工艺全域信息模型的CAPP与PDM集成技术研究

采用XML技术进行系统集成具有平台无关性和良好的可移植性,是目前实现CAPP与PDM集成的首选技术,针对现有XML工艺信息模型中无法表示工艺卡片样式的问题,提出了通过虚拟打印的方式将工艺卡片转换成PDF格式文件,并通过BASE64编码将其嵌入到XML工艺信息模型中的方法,通过该方法构建的XML工艺全域信息模型可以表示任...     

船舶电气自动化设备产业发展研究

船舶电气自动化设备是船舶配套设备的重要组成部分。本文论述了我国乃至我省船舶配套产品,特别是船舶电气及自动化产品的现状,总结了船舶电气自动化设备组成和分类;指出船舶电气及自动化系统发展趋势;最后针对船舶电气自动化设备的技术引进、消化吸收与开发创新提出一些想法与具体建议。     

Experimental research on dynamic vibration absorber with negative stiffness for longitudinal vibration control of propulsion shafting system北大核心CSCD

［Objectives］In order to control the first longitudinal vibration mode of propulsion shafting systems, a dynamic vibration absorber with disc spring negative stiffness is proposed and its experimental verification carried out. ［Methods］A test bench is established for the propulsion shafting system containing a dynamic vibration absorber with negative stiffness. According to the first longitudinal vibration mode of the shafting, a dynamic vibration absorber with negative stiffness integrated into the thrust bearing is developed. Vibration transmission tests under different rotational speeds, static thrusts and negative stiffness are then carried out, and acceleration response data on the thrust bearing foundation and shafting is obtained. ［Results ］ The results show that the developed dynamic vibration absorber with negative stiffness can achieve vibration suppression of 7.8 dB for the thrust bearing foundation in the first longitudinal mode of the propulsion shafting with a mass ratio of 1.6%, and the vibration control effect of the negative stiffness dynamic vibration absorber is maintained at 3.3 dB when the natural frequency changes by 5% and the thrust changes by 40%. The vibration response on the thrust bearing foundation and shafting do not deteriorate even at non-optimal negative stiffness. ［Conclusions］This study shows that a dynamic vibration absorber with negative stiffness can effectively suppress vibration transmission at the first longitudinal mode of a shafting under different rotational speeds. © 2023 Authors. All rights reserved.     

飞燕式拱桥结构静动力特性分析

飞燕式拱桥具有跨越能力大、承载能力高、自平衡推力而地基适应能力强、造型优美的优点。以一座新建三跨连续自锚飞燕式提篮钢管混凝土拱桥为工程背景,通过有限元分析软件Midas Civil建立该大桥的空间杆系有限元模型,对该拱桥的空间受力特点进行分析,评定其结构静力、动力特性和施工过程以及成桥后的稳定性能。计算结果与分析表明,主拱肋及边跨各截面的抗力均大于组合轴力,同时各个主要施工阶段结构稳定安全系数均大于4。因此,该拱桥结构静动力性能优良,满足设计规范要求。     

英语背景知识对于提高英语听力的意义

加强英语背景知识的学习不仅对学生的学业有积极帮助,而且对全面提高学生素质、培养良好的道德风尚也会起到潜移默化的作用,英语背景知识的学习应引起足够的重视.     

一种水下目标识别方法──基于模糊理论的多种神经网络融合分类

在应用多种方法提取目标噪声中分类特征的研究基础上,本文设计出基于模糊理论的多神经网络融合分类器,其研究重点主要包括有监督分类的模糊聚类神经网络分类、多神经网络与模糊综合分析相结合的融合分类。基于大量海试实测信号样本的多组实验表明,该分类方法具有良好的工程应用前景。