复杂岩基地质海上风电高桩承台基础关键技术研究及应用

本文针对福建海域复杂的地质特点,以岩基海床高桩承台基础为研究对象,对基础的承台选型、承台结构设计进行分析,结合基础的载荷计算、结构的内力建模、基础的实际监测数据,研究表明高桩中承台嵌岩基础满足设计规范要求。同时,以嵌岩基础施工为例,从桩基施工、承台施工2方面详细阐述了基础施工工艺,实践表明,采用打桩架固定式沉桩、整体式嵌岩平台、装配式预制钢套箱工艺可显著提高施工效率,满足工程建设要求。该高桩承台基础设计和施工方案可为东南沿海类似工程提供参考。     

基于功频下垂控制的光伏并网发电系统惯量阻尼机理研究

针对光伏以低惯量、弱阻尼的特征大规模接入电网，给电网稳定性带来不利影响的问题，基于功频下垂控制的光伏并网发电系统，借鉴经典电气转矩分析法，从物理机制层面上分析影响系统惯量、阻尼以及同步能力的作用规律。研究结果表明对于控制参数的影响规律而言，惯量特性主要受功率环的比例系数Kp影响，且随Kp的增大而增强；阻尼特性受频率下垂系数Dp影响比较明显，且随Dp的增大而减弱；同步特性只受功率环的比例积分系数Ki影响，且随Ki的增大而增强。通过仿真验证了理论分析的正确性。     

"人机环管"在煤矿供电安全管理中的应用

制定供电过程中消除安全隐患的针对性措施,可以为矿井安全生产提供必要保障。为探究煤矿供电管理中安全隐患的具体分析方法,首先介绍“人机环管”管理体系的建立过程和核心内容,接着以“人机环管”的管理方法分析了供电管理中的普遍问题。在分析供电管理中的具体问题时,分别得出了“人”“机”“环”“管”4方面的具体措施。分析认为,“人机环管”方法可以有效查找出存在的安全隐患,进而保证煤矿供电系统的安全可靠。     

Multi-objective optimization for efficient modeling and improvement of the high temperature PEM fuel cell based Micro-CHP system

Fuel cells due to different useful features such as high efficiency, low pollution, noiselessness, lack of moving parts, variety of fuels used and wide range of capacity of these sources can be the main reasons for their tendency to use them in different applications. In this study, the application of a high temperature proton exchange membrane fuel cell (HT-PEMFC) in a combined heat and power (CHP) plant has been analyzed. This study presents a multi-objective optimization method to provide an optimal design parameters for the HT-PEMFC based micro-CHP during a 14,000 h lifetime by considering the effect of degradation. The purpose is to optimize the net electrical efficiency and the electrical power generation. For the optimization process, different design parameters including auxiliary to process fuel ratio, anodic stoichiometric ratio, steam to carbon ratio, and fuel partialization level have been employed. For optimization, A new technique based on Tent mapping and Lévy flight mechanism, called improved collective animal behavior (ICAB) algorithm has been employed to solve the algorithm premature convergence shortcoming. Experimental results of the proposed method has been applied to the data of a practical plant (Sidera30) for analyzing the efficiency of the proposed ICAB based system, it is compared with normal condition and another genetic algorithm based method for this purpose. Final results showed that the difference between the maximum electrical power production under normal condition and ICAB based condition changes from 2.5 kW when it starts and reaches to its maximum value, 3.0 kW, after 14,000 h lifetime. It is also concluded that the cumulative average for the normal and the ICAB based algorithm are 24.01 kW and 27.04 kW, respectively which showed about 3.03 kW cumulative differences.     

公民新闻与权力变移

公民新闻的诞生源于信息网络技术的推动,同时也得力于媒介接近权的付诸实践。结合国内外学者的网络社会学主要研究成果,本文着重探索和分析了媒介权力变移所呈现出来的知识化、扁平化和分散化的趋向,并分析研究了现今阶段公民新闻在媒介权力变移过程的所面临的问题。     

一种二线制无极性数字称重传感器

现有的数字传感器至少由2根数据线和2根电源线共4根线组成,每根线均有明确的分工和极性,不能接错和短路,否则易损坏设备,需专业人员才能安装和维护;数据传输加密方式有限,易破解。利用本公司研发的"智能终端整机供电用二线制数据/电源共线传输装置及方法",将数字传感器的连线减至2根,且无极性、可短路,简化了系统的连接,提高系统的可靠性,使安装和维护变得极为简便。数据传输采用特殊的加密方式,极难破解。     

A methodology to assess suitability of a site for small scale wet and dry CSP systems

This study presents a methodology to assess suitability of a site for small scale concentrated solar power (CSP) systems for its energy conversion efficiency and make‐up water requirement. Energy conversion efficiency of CSPs relies not only on the level of direct solar radiation but also on the performance of the cooling system. Regions with high solar potential have to deal with heat rejection at elevated temperatures which causes reduced energy conversion efficiencies due to high condenser temperatures. It is desirable to utilize wet cooling systems as they can achieve temperatures lower than the dry bulb temperature by evaporative cooling. On the other hand, such regions usually lack water resources which deteriorate the sustainable nature of CSP applications. This study combines various available models for both solar resource estimation and cooling systems' performance considering (i) the influence of ambient temperatures, and (ii) the influence of humidity levels. These models are integrated together to analyze the use of dry or wet cooling systems in terms of overall energy output and water consumption at a selected site in northern Cyprus. The model inputs consist of only annual hourly surface weather data and the location of the site of interest. The results show that dry cooling unit at northern Cyprus is capable of saving water about 18.7 ton/MWh while it produces 27% less energy compared to the wet cooling alternative for the representative annual weather data. Copyright © 2015 John Wiley & Sons, Ltd.     

Voltage reference architectures for low-supply-voltage low-power applications

This paper presents a voltage reference generator architecture and two different realizations of it that have been fabricated within a standard 0.18 μm CMOS technology. The architecture takes the advantage of utilizing a sampled-data amplifier (SDA) to optimize the power consumption. The circuits achieve output voltages on the order of 190 mV with temperature coefficients of 43 ppm/°C and 52.5 ppm/°C over the temperature range of 0 to 120°C without any trimming with a 0.8 V single supply. The power consumptions of the circuits are less then 500 nW while occupying an area of 0.2 mm² and 0.08 mm², respectively.     

Application of an empirical model in CFD simulations to predict the local high temperature corrosion potential in biomass fired boilers

To gain reliable data for the development of an empirical model for the prediction of the local high temperature corrosion potential in biomass fired boilers, online corrosion probe measurements have been carried out. The measurements have been performed in a specially designed fixed bed/drop tube reactor in order to simulate a superheater boiler tube under well-controlled conditions. The investigated boiler steel 13CrMo4-5 is commonly used as steel for superheater tube bundles in biomass fired boilers. Within the test runs the flue gas temperature at the corrosion probe has been varied between 625 °C and 880 °C, while the steel temperature has been varied between 450 °C and 550 °C to simulate typical current and future live steam temperatures of biomass fired steam boilers. To investigate the dependence on the flue gas velocity, variations from 2 m·s⁻¹ to 8 m·s⁻¹ have been considered. The empirical model developed fits the measured data sufficiently well. Therefore, the model has been applied within a Computational Fluid Dynamics (CFD) simulation of flue gas flow and heat transfer to estimate the local corrosion potential of a wood chips fired 38 MW steam boiler. Additionally to the actual state analysis two further simulations have been carried out to investigate the influence of enhanced steam temperatures and a change of the flow direction of the final superheater tube bundle from parallel to counter-flow on the local corrosion potential.     

Power generation characteristics of a sandwich‐type self‐heating thermoelectric generator with spatially varying embedded heat source

Power generation characteristics of a sandwich‐type thermoelectric generator in which the heat source is embedded into thermoelectric elements are investigated. Our previous work on a similar concept only considered a uniform heat source distribution inside thermoelectric elements. In this work, the effect of the spatial distribution of a heat source is examined. In particular, the effect of the concentration of heat source near the one end, that is, the hot end, is intensively studied as a potential means of improving the efficiency of the device. Although the effects of heat source concentration in impractical cases without heat transfer limitations on the cold side remain ambiguous, it become clear that heat source concentration indeed has positive effects in more realistic cases with finite heat transfer coefficients imposed on the cold side. Because of the relatively low efficiency of typical thermoelectric generation, a significant amount of heat must be dissipated from the cold end of the thermoelectric element. Greater heat source concentration near the hot end leads to more effective utilization of available heat source, reduces the amount of heat rejected at the cold end, and lowers the hot end temperature of the thermoelectric element. Overall, it is suggested that heat source concentration can be used as a method to achieve more efficient operation and better structural integrity of the system. Copyright © 2015 John Wiley & Sons, Ltd.