Constructal design of tree-shaped microchannel disc heat sink with wavy walls北大核心CSCD

［Objective］To meet the efficient thermal management needs of electronic devices such as ships and underwater vehicles, this study focuses on the constructal design of a tree-shaped microchannel disc heat sink with wavy walls. ［Method］A design prototype of the heat sink with wavy walls is first proposed. Based on constructal theory, the amplitude and wavelength of the wavy walls are designed under the constraints of fixed heat sink volume and fixed microchannel volume by maximizing the comprehensive performance evaluation criteria (PEC) while considering both heat transfer and flow pressure drop. ［Results］The results show that the wavy walls increase the heat transfer surface areas and generate vortices in their cavities, effectively reducing the maximum temperature. When the inlet Reynolds number is fixed at 700, 900 or 1100 respectively, the maximum temperature is reduced by 13.5 K by increasing the amplitude of the wavy walls, while the pressure drop increases significantly; and the maximum temperature is reduced by 4.7 K by reducing the wavelength of the wavy walls, while the pressure drop increases slightly. There are optimal amplitudes that raise the comprehensive performance evaluation criteria to extreme values for given larger wavelengths, while the comprehensive performance evaluation criteria increase monotonously as the amplitude increases for given smaller wavelengths. ［Conclusion］Wavy walls can significantly improve the thermal performance of tree-shaped microchannel disc heat sinks, and the use of constructal design can realize optimal geometric constructs with optimal comprehensive performance evaluation criteria. © 2023 Authors. All rights reserved.     

Analysis of naval warship blast and shock resistance technology system北大核心CSCD

舰船抗爆和抗冲击技术概念宏观,内涵广泛,对其认识理解、设计研究都需要技术体系的顶层划分和牵引。首先,基于武器攻击对舰船的爆炸毁伤类型,对舰船抗爆与抗冲击这两个概念进行划分;然后,基于舰船总体抗爆抗冲击设计技术需求,区分不同的研究对象及技术的基础理论,提出包含6大类型的舰船抗爆抗冲击技术体系的划分方案,即水上/水下防护结构设计、新型抗爆结构与毁伤分析、设备系统及人员抗冲击、舰船抗爆抗冲击试验验证及技术标准规范;最后,分别对舰船抗爆和抗冲击技术内涵进行详细阐述。所做研究可为我国舰船抗爆抗冲击技术体系的形成提供一个初步构想,供从事舰船抗爆抗冲击设计、研究及管理人员参考。     

Robust adaptive course-keeping control of under-actuated ships with the rudder failure北大核心CSCD

[目的]针对舵机故障、控制增益未知和海洋环境干扰情况下的欠驱动船舶航向保持问题,设计一种考虑舵机故障的船舶鲁棒自适应航向保持控制算法。[方法]通过结合鲁棒神经阻尼技术和自适应方法,对繁重的神经网络权值进行横向压缩,仅需设计2个自适应学习参数对未知增益和舵机故障参数在线补偿,以确保船舶在舵机故障的情况下能够有效执行航向保持任务。通过李雅普诺夫理论,证明所提出的控制器半全局最终一致稳定有界(semi-global uniform and ultimately bounded,SGUUB)。最后以“育鲲”轮为仿真对象,建立非线性Nomoto数学模型,在海洋干扰下进行对比仿真试验验证。[结果]结果表明,在此策略下,“育鲲”轮在舵机故障情况下平均舵角输出比仿真试验中所对比的传统方法降低了51%,可改善航向保持控制效果。[结论]研究结果可为欠驱动船舶的航向保持控制问题提供借鉴。