基于前端LCL谐振式推挽变换器

提出了一种前端LCL谐振式变换器,其前级为功率因数校正（PFC）,后级为采用数字控制的逆变器。设计并制作了一台AC220V输出的1kW试验样机,对实验样机测试的结果表明,前级升压电路实现了零电压开通（ZVS）,后级电路实现了闭环控制,整个系统动态与稳态性能均较好,理论分析正确。     

拱桥节段施工斜拉扣挂索力仿真计算研究

斜拉扣挂在缆索吊装中经常运用 ,但扣索索力多采用手工计算 ,且多用于 5段以内的吊装 ,计算复杂 ,精度低 .本文提出“零弯矩法” ,可计算任意多段扣索索力 ,既可计算拱肋在施工过程中各节段临时铰接 ,又可计算各节段固结的情况 ,将两种连接方式统一成一种计算方法 ,力学概念清楚 ,计算简便 ,适宜编程 ,文中最后用示例证实本方法的正确性 .     

船舶三端口双向DC/DC变换器的能量控制

针对三端口双向DC/DC变换器在船舶电网中的应用,对其能量控制展开研究。以实现最小系统损耗为目的,对移相控制下的功率与移相比之间的关系进行分析,从而确定系统零循环功率时的移相范围,并通过解耦控制实现最小损耗。通过Matlab/Simulink仿真试验对控制策略进行验证,结果表明零循环功率控制可有效减小系统损耗。     

零航速下船舶减横摇控制策略研究

鉴于零航速下船舶横摇模型的不确定性,通过在线辨识确定船舶横摇运动数学模型.在此基础上采用改进型遗传算法和单纯形法相结合的优化策略对PID参数进行优化,使优化过程既具有遗传算法的全局性又具有单纯形算法的快速性,仿真显示按此种控制策略设计的控制系统对横摇模型的不确定性具有较强的自适应性,有一定的工程应用价值.     

仿生减摇鳍升力模型的数值模拟及分析

船舶在系泊或低航速状态下,发动机主机停止工作,船舶失去自控方向能力,船体随波浪左右摇晃,比航行时摇摆更为剧烈。因此,研究零航速减摇鳍非常重要。文章研究零航速时仿生减摇鳍产生升力的模型,其基础为Weis-Fogh机构理论。首先讨论如何旋转才能产生给定的升力。依据吕卡提方程理论,给出模型周期解的存在性和稳定性条件 采用单步Runge-Kutta方法求出模型的数值解,给出保证数值解稳定的条件。     

高速铁路偏压隧道高边坡零开挖进洞施工技术研究

零开挖进洞施工技术应用时必须对隧道洞口的地形、地质与隧道周边环境影响因素进行综合分析,使用不当容易产生地表沉陷、初期支护过量变形、衬砌间裂缝等诸多问题。为探究零开挖进洞施工技术在高速铁路偏压高边坡隧道的使用效果,以杭温铁路西安隧道洞口段施工为背景,理论分析表明偏压、高边坡和围岩差等不利因素是影响零开挖进洞施工技术的关键,现场采取抗滑桩防偏压、护拱补强、超前管棚预支护和注浆等措施,实现"零开挖"进洞的目标。     

A Step Zero Analysis of the Galapagos Marine Reserve

Contrary to common perceptions, the creation of protected areas does not start when they are officially declared but generally follows a long process. For instance, the Galapagos Marine Reserve (GMR) was not “born” when it was formally announced on March 18^th 1998, but several decades before that. Through document analysis and key informant interviews, we applied the “step zero” approach to examine what happened prior to the implementation of the GMR. This study reveals that the GMR did not arise from a social and political vacuum; rather, events took place in the distant past, even centuries ago, influenced the reserve's creation and current status. Its establishment was driven by complex geopolitical, economic, social, and environmental factors from both within and outside Galapagos. Additionally, the process of creating the GMR was convoluted, marked by hidden interests and conflictive political agendas that triggered controversies between users. The making of the GMR was also influenced by the interest in promoting “nature-based” tourism, and the regulations that followed had disadvantaged small-scale fishers. This knowledge about the reserve's pre-implementation phase enables a broader understanding of the current challenges facing the performance of the GMR and points to possible governance interventions needed to enhance its sustainability.     

Demand and welfare effects in recreational travel models: Accounting for substitution between number of trips and days to stay

In this paper we present a non-linear demand system for households’ joint choice of number of trips and days to spend at a destination. The approach, which facilitates welfare analysis of exogenous policy and price changes, is used empirically to study the effects of an increased CO₂ tax. In particular, we focus on the effect of including substitution between households choice of the number of trips and days to spend at a destination in the welfare analysis. The analysis reveals that the equivalent variation (EV) measure, for the count data demand system, can be seen as an upper bound for the households welfare loss. Approximating the welfare loss by the change in consumer surplus, accounting for the positive effect from longer stays, imposes a lower bound on the households welfare loss. The difference in the estimated loss measures, from the considered CO₂ tax reform, is about 20%. This emphasizes the importance of accounting for substitutions toward longer stays in travel demand policy evaluations.     

4000A舰船用智能型框架断路器

4000A舰船用智能型框架断路器是近期研制开发的舰船用新产品,具有容量大、短路分断能力高、零飞弧、能实现智能化保护的特点,介绍该产品的结构特点、基本参数、技术性能及主要应用．     

仿生减摇鳍升力数学模型的全局误差与稳定性

研究了零航速时仿生减摇鳍产生升力的数学模型,讨论了Weis-Fogh 机构如何旋转才能产生船舶减摇所需要的指定升力,其基础为Weis-Fogh 机构理论.首先把问题转化为求解微分方程问题,依据吕卡提方程,给出模型周期解的存在性和稳定性条件;然后采用单步Runge-Kutta方法求出模型的数值解,并分析数值解的全局误差;最后给出保证数值解稳定的条件,并用相应的数值试验予以验证.