WAVE CURRENT FORCE COEFFICIENTS ON INCLINED CYLINDER AND A NEW ESTIMATION METHOD

Based on the review of present force coefficients estimation methods, a new method in the frequency domain, revised cross-spectrum estimation method, is presented in this paper. Some experiments on the wave-current force on inclined cylinders are also described and the wave current force coefficients are estimated by the revised cross-spectrum estimation method. From the results, it is found that the wave and current directions have some regular effect on the coefficients. According to the results, some empirical formulas are obtained for converting the wave-current force coefficients on inclined cylinders into a unified coefficient. Comparisons show that the unified coefficients are in good agreement with other results.

New Method for 3D Transient Eddy Current Field Calculation and Its Application in Magneto-Acoustic Tomography

A new method of 3D transient eddy current field calculation is proposed. The Maxwell equations with time component elimination （METCE） are derived under the assumption of magnetic quasi static approximation, especially for the sample of low conductivity. Based on METCE, we deduce a more efficient reconstruction algorithm of a 3D transient eddy current field. The computational burden is greatly reduced through the new algorithm, and the computational efficiency is improved. This new algorithm decompounds the space-time variables into two individual variables. The idea is to solve the spatial vector component firstly, and then multiply it by the corresponded time component. The iterative methods based on METCE are introduced to recover the distribution of conductivity in magneto-acoustic tomography. The reconstructed images of conductivity are consistent with the original distribution, which validate the new method.

A NEW APPROACH TO THE EQUATIONS FOR THE STEADY STATE CURRENTS AT MICROELECTRODES:EC'PROCESSES(SECOND ORDER REACTION)

With a new approach,the general current expressions of two typical second order catalytic reactions at microelectrodes are obtained.This allows the study of fast chemical reactions and systems where the reactants are present in similar concentrations.

On the Translation of New Words in Current Affairs

As China continues to open up to the outside world,new words in every aspect of our daily life are emerging at a rapid speed.However,the quality of translation at present is not very satisfactory.This paper analyzes the features of these words,the errors in their translation and discusses the translation strategies based on the Functional Theory of Germany.

Study on Short Circuit Current Calculation of Power System with UHVDC and New Energy Source

With the development of power system, the level of short circuit current will increase accordingly. In general, the influence of the HVDC system and the new energy source is not considered in the calculation of the short circuit current. For the power grid that short circuit current level closes to the interrupting capacity of circuit breaker, it’s necessary to fully consider all kinds of influence factors, careful checking, so as to obtain more accurate calculation results of short circuit current. In 2018, two ±800 kV high-power Ultra High Voltage Direct Current (UHVDC) transmission projects will be connected with Shaanxi power grid, accompanied by a lot of concomitant fossil-fuel generating plants as power resource, and also a large number of new energy source, includes wind power generation and photovoltaic power generation. Around one of the UHVDC converter stations, short circuit current may exceed the withstand limit of some certain circuit breakers. In order to get more accurate short circuit current calculation results, three measures are used: 1) contrastive calculation and analysis by algorithm based on schemes and algorithm based on power flow;2) analysis the influence of UHVDC by electromagnetic transient and electromechanical transient hybrid simulation;3) considered a detailed model of Doubly Fed Induction Generator (DFIG) with low voltage ride through characteristics. The calculation results shows that: in the typical operation mode of Shaanxi power grid of 2018, the original calculation results by conventional calculation method are coincident with the results by considering the influence of algorithms, UHVDC and DFIG in large, in which: the results of the algorithm based on power flow are smaller than that of the algorithm based on schemes about 2 - 8 kA;the steady values of the short circuit current provided by UHVDC converterstation (includes rectifiers and smoothing capacitors) are about 0 - 3 kA;the steady values of the short circuit current provided by DFIG are about 0 - 5 kA. The calculation results can provide reference for the selection of the circuit breaker, and it can be verified by fault recording data in the future.

Experimental Investigation of Local Scour Around A New Pile-Group Foundation for Offshore Wind Turbines in Bi-Directional Current

The local scour around a new pile-group foundation of offshore wind turbine subjected to a bi-directional current was physically modeled with a bi-directional flow flume. In a series of experiments, the flow velocity and topography of the seabed were measured based on a system composed of plane positioning equipment and an ADV.Experimental results indicate that the development of the scour hole was fast at the beginning, but then the scour rate decreased until reaching equilibrium. Erosion would occur around each pile of the foundation. In most cases, the scour pits were connected in pairs and the outside widths of the scour holes were larger than the inner widths. The maximum scour depth occurred at the side pile of the foundation for each test. In addition, a preliminary investigation shows that the larger the flow velocity, the larger the scour hole dimensions but the shorter equilibrium time. The field maximum scour depth around the foundation was obtained based on the physical experiments with the geometric length scales of 1:27.0, 1:42.5 and 1:68.0, and it agrees with the scour depth estimated by the HEC-18 equation.

一种低电流纹波高增益软开关直流变换器

提出了一种应用于新能源发电系统的低电流纹波高增益软开关直流变换器。在传统交错Boost变换器基础上,该变换器通过引入耦合电感和二极管、电容升压单元提高电压增益,耦合电感在整个开关周期过程中都传递能量,提高了磁芯利用率。输入侧工作在交错模式,两相电感电流纹波可以相互抵消,从而获得较低的输入电流纹波。由于耦合电感自身漏感的存在,减轻了整流二极管反向恢复问题,同时采用有源钳位电路回收利用漏感能量,实现了所有开关管零电压软开关,抑制了开关管关断电压尖峰,提高了变换器转换效率。详细分析了变换器的工作原理、电路特性以及软开关实现方法。最后,搭建了一台200 W的试验样机验证了理论分析的正确性。

串并联型海上风电场机组均压控制

针对串联型风机簇产生弃风的问题,在直流侧添加基于超级电容的储能单元,并在串联簇中设置一台参考机组,通过控制双向DC/DC变换器的吸收、释放电能,使同串联簇中除参考机组之外的其他机组向直流汇集母线上输出的功率相同,使直流风机风电功率和风机出口电压一致,实现基于超级电容储能的直流机组的均压控制,以此减少直流风机串联簇各机组间的风电功率差,降低弃风率。针对传统两相DC/DC变换器电感电流纹波大,两相电流不均衡等问题,采用了一种移相均流控制策略。最后,在Matlab/Simulink搭建了仿真模型,仿真结果验证了所提出的策略的有效性。

新时代文明实践中心建设现状及拓展路径

新时代文明实践中心建设是中国式现代化的重大探索,有助于丰富精神文明建设理论,提升全社会文明程度。该建设自试点及全面覆盖以来,在组织运行机制、中心建设标准、实践活动内容等方面取得积极成效,但也存在思想认识“泛化”“窄化”错误倾向、群众参与度还不够高、品牌化精准化水平亟待提升等问题。必须完善全员参与的运行机制、健全经费保障机制、创新文明实践组织形式、构建合理有效的监督考核体系,以推动新时代文明实践中心高质量发展。

新时代高校党员党性教育现状与对策研究

高校党性教育是党组织建设的重要组成部分,是不断壮大党的力量、强化党的领导,推进“党管教育事业”的基本工作。新时代推进高校党员党性教育是一个任重而道远的过程,但却普遍面临着重视程度不高、目标设置不强、党员主动性薄弱等问题,急需高校明确党性教育问题的基本原因,从斗争思维、整体思维、创新思维等维度出发,持续提升党员党性教育的实效性、规律性、紧迫性,从而办好社会主义大学,推动社会主义事业的现代化发展。

新媒体应用背景下档案专业服务大局的实践路径——基于“闻档察社”微信公众号的案例分析

本文介绍了依托新媒体平台能够捕捉时事并融合创作立体呈现、突破圈际以辐射多元阅读受众、传播高效以推动响应大政方针的客观优势,“闻档察社”原创微信公众号形成档案专业服务中心大局的特色实践,具体表现为密切追踪时事以专业视角切入、理论联系实践并多方协同思政、契合多元受众同时扩展辐射范围等。在此基础上,笔者从内容创作、运营主体、成果输出三个方面提出“闻档察社”在未来的发展目标,或可为其他同类型新媒体运作提供参考。

计及新能源幅相特性的新型多馈入短路比指标

为了合理评估高比例新能源并网的多馈入高压直流输电(multi-infeed HVDC,MIDC)系统电压支撑能力,该文首先分析MIDC系统结构特点,随后基于多馈入短路比(multi-infeed short circuit ratio,MISCR)指标,并结合新能源短路电流幅值和相位随机端电压变化的特性(以下简称“幅相特性”),提出多馈入暂态短路比(multi-infeed transient short circuit ratio,MITSCR)指标;其次,根据国家标准的要求分析以双馈风机(doubly-fed induction generator,DFIG)为代表的新能源在不同控制模式下的幅相特性,并通过MITSCR指标分析DFIG接入对MIDC系统节点电压支撑能力影响;最后,利用PSACD/EMTDC软件进行时域仿真分析,结果表明,MITSCR指标能有效表征节点的电压支撑能力,验证了该指标的有效性与优越性。

探讨新能源汽车电池类型现状及发展趋势

随着全球气候变化和环境问题日益严重,新能源汽车已成为未来可持续交通发展的重要方向。电池作为新能源汽车的核心组成部分,其性能、安全性、成本及寿命等方面会直接影响到新能源汽车的市场接受度和整体发展。结合针对当前新能源汽车电池类型现状的探析,汽车行业仍需加大研发与创新力度,从而进一步助推新能源汽车可持续发展,并创造更大的生态效益与经济效益。

辽宁新材料领域科技创新平台发展现状及对策

新材料领域科技创新平台的建设运行对促进新材料技术创新和产业发展具有重要的意义和作用。当前,辽宁新材料领域科技创新平台数量及类型初具规模、人才团队建设初现成效、经费投入来源广泛、科研成果大量涌现。针对其地域发展不均衡、研究方向不全面、企业创新力量较弱、创新服务能力有待提升等问题,未来应进一步优化顶层设计、强化人才支撑、强化资金支持、加强企业创新、促进开放合作,以促进辽宁新材料领域科技创新平台发展。

新型研发机构建设发展现状与建议

新型研发机构是科技创新的重要组织形式,在国家创新体系中的地位日益重要。本文从新型研发机构现状入手,查找问题,分析原因,提出推动新型研发机构良好健康发展的对策建议。

乡村振兴背景下新型职业农民培训现状与改进措施——以镇江市丹阳市为例

培训新型职业农民是乡村人才振兴的必然选择,有助于丰富农民的农业知识、提高农民的农业技能水平及综合素质。基于此,本研究详细介绍了丹阳市新型职业农民培训的现状和培训成效,指出了丹阳市农民培训过程中存在农民队伍文化素质整体不高、培训对象年龄结构偏大及培训和评估手段单一等问题,提出了丹阳市新型职业农民培训的整改措施,如加强组织管理,健全培训机制;线上服务、线下培训齐发力;多方位宣传发动,营造培训氛围;强化监督检查,规范培训管理等。研究结果表明,通过积极研究新型职业农民培训内容、拓展培训形式、探索培训评估方法,有助于构建出一套符合农民文化层次、能让农民更好接受的培训体系,为我国的新型职业农民培训工作添砖加瓦,助力乡村振兴。

新能源系统中性点设备的选型计算分析

阐述选择电力网中性点接地方式是一个综合性问题。分析单相接地电容电流计算、中性点设备选型计算。尽管接地故障电流选择1 300A,但测算得出跨步电压和接触电压能满足规程规范要求。

新型防蚊驱蚊产品的现状分析及管理建议

近年来,随着安全意识的提高和化工技术的发展,新型防蚊驱蚊产品市场逐渐扩大,包括驱蚊贴、驱蚊扣、驱蚊手环等。本文就新型防蚊驱蚊产品现状分析后发现,在其登记、生产、经营和使用中存在标签标识混乱、配方安全性未得到验证、误导消费者等问题,相关监管部门和生产企业应引起足够重视。为此,本文结合江苏省工作实践,对加强新型防蚊驱蚊产品监管提出若干建议。