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.     

Design of Feedback Shift Register of Against Power Analysis Attack

Stream ciphers based on linear feedback shift register (LFSR) are suitable for constrained environments, such as satellite communications, radio frequency identification devices tag, sensor networks and Internet of Things, due to its simple hardware structures, high speed encryption and lower power consumption. LFSR, as a cryptographic primitive, has been used to generate a maximum period sequence. Because the switching of the status bits is regular, the power consumption of the LFSR is correlated in a linear way. As a result, the power consumption characteristics of stream cipher based on LFSR are vulnerable to leaking initialization vectors under the power attacks. In this paper, a new design of LFSR against power attacks is proposed. The power consumption characteristics of LFSR can be masked by using an additional LFSR and confused by adding a new filter Boolean function and a flip-flop. The design method has been implemented easily by circuits in this new design in comparison with the others.     

汽轮机运行调节方式优化策略探析

分析了汽轮机的喷嘴调节、节流调节、旁通调节、定压调节和滑压调节等几种基本调节方式的特点,指出现役燃煤火电机组多因调节方式单一而普遍存在着调峰能力不足、负荷响应迟缓以及因长期偏离设计工况致使运行安全经济性下降等诸多问题,提出了通过调节方式的优化组合,采用(节流)定压-滑压-(喷嘴)定压-旁通调节的复合调节方式,以实现煤电机组安全、经济、灵活、快速地参与电网的深度调峰,破解具有强随机波动性的新能源电量规模化并网的困境。