舰船大功率柴油机技术发展

介绍了舰船大功率柴油机的发展现状,单机功率、平均有效压力、强载度等参数提高的趋势。分析并比较了当前发展的在降低排放上的各种技术措施,以及燃油系统、增压系统、电子控制系统的技术发展方向。     

大功率单相完全有源功率因数校正器的实现

首先基于现有的、典型的模拟PFC控制芯片,较为详细地描述了单级升压变换的单相AC—DC变换器领域几种基本的有源功率因数校正技术,其中包括传统有源PFC技术、跟随有源PFC技术和单周期有源PFG技术。最后基于PFC控制芯片L4981B详细地介绍了支持较大功率输出的有源PFC电路设计过程,并给出部分实验结果。     

大功率内燃机润滑油30年

由于大功率内燃机在构造、设计以及用途、燃料等方面的不同,对润滑油的性能要求差异很大,也很难形成统一的润滑油产品质量规范。多为发动机OEM、用户和润滑油公司针对发动机的类型、设计特点、燃料情况以及使用工况合作开发润滑油产品并进行技术确认。本文结合我国大功率内燃机的发展,介绍了我国大功率内燃机润滑油的发展历程以及今后努力的方向。     

大功率柴油机的发展与可持续性

本文从柴油机的经济性、可靠性、减少环境污染及设计更简洁使其零部件数量较少等方面,阐述了研制柴油机中需要考虑的因素。强调柴油机的研制应针对不同的用户需求,在多参数中作出选择,做到综合平衡,而不应片面强调某一指标的最佳。文中还列举了瓦锡兰公司在这方面的一些实例。     

虚阴极高功率微波发生器的粒子模拟

本文简述了PIC模拟(Particle—in-cell Simulation,简称粒子模拟——Particle Simu—lation)的基本方法,全面评述了用粒子模拟方法研究虚阴极高功率微波发生器的历史、现状、基本方法、优点和模拟结果。     

兆瓦级变频调速综合分析

为了节约电能,提高生产效率和改善产品质量,兆瓦级变频调速系统目前正在被广泛地用于工业中.本文对由全球各大公司生产的各种大功率交流传动系统作了综合分析,对各类多电平电压型和电流型逆变器进行了解剖和分析,同时对这些传动系统的优缺点作了总结.本文还论述了适用于大功率变流器的各种脉宽调制方式,并用计算机模拟和实验结果对一些重要的概念进行了论证.     

The superior lithium storage capabilities of ultra-fine rutile TiO2 nanoparticles

The lithium storage capabilities of ultra-fine rutile TiO₂ nanoparticles have been studied. Ultra-fine rutile TiO₂ nanoparticles with only several nanometers in size have been prepared by a modified wet-chemical method with a high yield. Unexpectedly, the rutile TiO₂ nanoparticles with 3 nm in size exhibit superior lithium storage properties. Specifically, they show long term cycling stability upon extended cycling for at least 300 cycles with a capacity loss of only 0.17% per cycle, and good rate capability up to a 30 C rate. The excellent reversible lithium storage capabilities could be attributed to the ultra-fine size giving rise to a very short diffusion path, and the relatively large surface area which provides more sites for lithium insertion.     

Weld appearance prediction with BP neural network improved by genetic algorithm during disk laser welding

The appearance of welds is the external manifestation of welding quality. The morphology of molten pools is significantly associated with the weld appearance, but the approach to measure the morphology of molten pools during laser welding remains an outstanding challenge up to now. In this study, the shadows of molten pools were formed to describe the morphology of molten pools. Principal components analysis (PCA) is applied to analyze the characteristics of the molten pools’ shadow in order to reduce their redundancy. Then BP neural network improved by genetic algorithm (GABP) is established to model the relation between welding appearance and the characteristics of the molten-pool-shadows. The effectiveness of the established model is analyzed through two different welding speed experiments, and the results verify its prediction performance. The work provides an effective way to predict the weld appearance and assess the welding quality in real-time.     

炼钢电弧炉高功率变压器的低功率使用

就炼钢电弧炉提高变压器功率后其供电曲线与节电之间的关系进行了系统分析，提出不同冶炼时期电弧热利用率不同，输入炉内的电功率也应随之进行调整。一座５ｔ炼钢电弧炉，通过改造使变压器扩容后，加之供电曲线选择适当，在其它条件相同下，单位电耗降低了１０４ｋＷ·ｈ／ｔ。     

Mathematical modeling of high-power-density insertion electrodes for lithium ion batteries

Theoretical calculations are compared with well-controlled experiments conducted on a high-surface area, small diameter lithiated-carbon electrodes. The electrodes are shown to yield very high current densities and exhibit little interfacial kinetics resistance or intercalate diffusion resistance. The mathematical treatment describes quantitatively a wide range of electrochemical experiments. The application of the model to the experimental data is facilitated by the use of a reference electrode. Initial cycling behavior of the high-surface-area electrode is elucidated, including clarification of the first-cycle coulombic inefficiency. Nitrogen absorbtion and scanning electron micrographs are utilized to ascertain the microstructural characteristics that distinguish the active electrode material. An asymptotic analysis is used to indicate when diffusion resistance within host particles is negligible; this fact simplifies model calculations and contributes to our overall understanding of insertion processes associated with host particles of very small dimensions.