Quantized control settings based tuning of a heaving wave energy converter in irregular seas

The increasing awareness of environmental issues attracts more attention on environmentally friendly energy sources. This leads to increasing research on effective use of renewable energy sources. Among them, wave energy offers a high potential. The wave energy converter systems used for transforming the wave energy into electrical energy have been a main research topic for decades. However, only a few of these systems has been successfully implemented. There seems to be some technical problems one of which is on their control applications. It has been reported that by means of appropriate control implementation, the performance of the wave energy converter system could be improved considerably. In literature, many different control techniques are reported. They appear to be weak due to implementation related restrictions. The present study proposes a novel control technique that is far more practical based on quantization of control settings. Various quantization levels and their effect on system power capture performance are studied. The technique assumes use of realistic off-the-shelf components with realistic features. The proposed method utilizes time-series-analysis technique with online parameter estimation feature. This new method does not require any knowledge of previous or future states of any of the system or sea state parameters, but only the currently available and measurable ones. The approach of the new control technique sets it apart from most of the previously reported ones. Therefore, the proposed technique is not only very much practical but also very much useful in improvement of the system power performance relative to passive techniques.     

对脉冲电流探头的时域标定方法的探讨

根据Rogowski线圈原理自制自积分式脉冲电流探头,研究了脉冲电流探头时域标定的方法,验证了线圈工作于自积分状态,并最终得出标定系数。     

一种连接器振动故障分析

目的 分析得出轴向弹性触碰式连接器内导体失效的主要原因。方法 以某机载电子模块的连接器在功能振动试验后出现的故障为研究对象,对其进行目测检查、随机振动仿真分析和受力分析,定位故障原因,随后结合应力应变关系公式、高斯区间法和Miner累积损伤定律,推导内导体的疲劳寿命计算公式。结果计算得到内导体自身的振动响应应力仅为0.26 MPa,不足以产生疲劳破坏,但在振动激励下,连接器随模块的振动位移较大,超出了连接器的间隙容差范围,致使受压的内导体端面出现较大的往复动摩擦力,而摩擦力引起内导体根部的应力（250.13 MPa）超过了材料的疲劳极限,内导体有疲劳断裂的风险。进一步计算出内导体的振动疲劳寿命为0.67 h,小于功能振动试验时间,证实是振动位移引起的摩擦导致了内导体的疲劳断裂。结论 轴向弹性触碰式连接器必须要重视摩擦力的危害,提高模块的安装刚度,可以有效地提高连接器的可靠性。     

Influence of type of MVC test on electromyography measures of biceps brachii and triceps brachii

Objective. This study aimed to investigate the amplitude and frequency measures of the electromyography (EMG) signal in agonistic and antagonistic muscles (biceps brachii, triceps brachii). Methods. Fifteen males (22.9?±?2.1 years old) took three isometric maximum voluntary contraction (MVC) tests. Two tests were typical MVC tests for biceps brachii and triceps brachii. The third was a test often used to obtain MVC for forearm muscles (arm and forearm hanging down). The EMG signal was recorded during three isometric MVC muscle contractions and during a relaxation test. Results. There were no differences in amplitude between relaxation and MVC antagonist in static contraction, with higher values for frequency measures in relaxation. When biceps brachii and triceps brachii act as antagonists in an MVC test, frequency measures present lower values than when the muscles act as agonists. Biceps brachii shows much lower amplitude than during an agonist MVC contraction with similar spectral measures. Triceps brachii presents much higher values of spectral measures than during an agonist MVC test. Conclusion. The type of exerted force, i.e., if a muscle acted as an agonist, antagonist or stabilizer, affects the relationship between the time and frequency domain measures.     

Coastal protected area management and multi-tiered governance: the Cape Cod Model

Policy tools that allow for the coordination of various authorities at different levels of government are important for coastal protected areas. Frequently, multiple authorities manage these areas with varied and sometimes conflicting goals. This study examines a regulatory model implemented on the Cape Cod National Seashore in the US that uses federally-approved zoning to regulate private uses for protection of natural coastal resources. Local authorities implement the zoning which is designed to support national resource protection goals making this a prime model of cross-level governance for conservation. I use case study analysis to evaluate the program’s effectiveness by focusing on implementation and compliance in the context of multi-jurisdictional (i.e., national to local) relations. The analysis and subsequent discussion highlight the difficulties associated with implementation of intergovernmental mandates. Also, theoretical perspectives on compliance give insights about the implementation challenges of this model. The model’s limitations have implications for policymakers considering similar schemes implemented by split and hierarchical authorities with different, and possibly conflicting, coastal management goals.

基于文献计量与共词分析法的企业安全文化研究述评

为了揭示国内企业安全文化的研究现状,并为后续研究指明方向,采用文献计量分析法、共词分析法对选取的2 474篇文献进行分析并利用NetDraw软件输出关键词知识图谱。结果表明:企业安全文化的文献量与研究内容呈阶段性特征,以2002,2011年为界划分为3个阶段;研究机构众多且主要研究者的研究方向存在差异;研究重点集中在企业安全文化内涵与层次结构、建设与评价实证研究以及与其他变量的关系3个方面;存在研究行业过于集中,安全文化评价方法与现实存在“脱节”等问题。     

基于注意力机制的人群计数方法

为准确预测固定场景中的人群计数,在人群分析领域,采用一种融合注意力机制的卷积神经网络(CNN)进行人群计数,该模块结合空间域注意力和通道域注意力,空间域注意力可以编码整个图像的像素级上下文信息,以更准确地表达像素级别的密度图,而通道域注意力可以在不同的通道中提取更多的区分特征使网络显著表达人群的局部区域,并在多个公开数...     

现行土层地震反应分析存在的问题

工程上广泛应用的现行土层地震反应分析方法即为借助快速傅里叶变换和迭代法的等效线性化频域方法.简要介绍了现行土层地震反应分析方法,结合具体算例,再现了现行土层地震反应分析方法在实际应用中存在的四个问题,一是对个别输入加速度时程的离散点个数无效,二是底部存在软夹层计算结果异常,三是输入地震动较大、场地较软时计算结果不合理,四是可能出现死循环现象.针对这四个问题提出了现行土层地震反应分析方法改进的方向,对以后土层地震反应分析方法的发展进行了展望.     

基于熵权物元可拓模型的城市大气质量评价

本文分析城市大气环境的多耦合性与复杂动态性,识别城市环境质量中评价主体及环境要素的不确定性;确定城市大气污染评价因子及其评价等级的界定;实现可拓论经典集合中"属于"和"不属于"集合的定性描述扩展到精准定量描述,并将可拓工程方法与聚类分析相结合,依据大气质量等级标准和大气质量影响因子构造经典域物元和节域物元;实现关联函数逻辑域由(0,1)到(-∞,+∞)的扩展;并采用层次分析法(AHP)确定特征加权,建立变权可拓论的大气质量评价模型。新模型不仅可以体现大气质量整体等级水平,而且通过质量与等级的关联度可以辨识影响大气质量的主次要污染因子。以阜新市2010年大气环境质量为应用评价对象,将应用评价结果与上海大气质量指数法、模糊综合评判法的结果比较,给出新模型在大气质量评价应用中的适用性。