数据中心交直流混合供电系统效率浅析

介绍了数据中心交直流混合供电系统方案产生的背景。针对目前认为交流直供承担所有负载效率最优化的观点,对交直流混合供电系统的效率进行了理论分析和试验验证,说明了交直流混合供电系统方案中系统效率的影响因素以及在现网机房中如何实现该方案的最佳效率点。作为简单的参考原则,在高压直流系统（HVDC）不休眠的情况下,在目前业界主流的产品配置下,推荐采用交流和高压直流系统（HVDC）均分负载的供电模式。     

从美国AHRI标准210/240中季节能效比的测试计算方法看房间空调器节能技术

本文从美国AHRI标准210/240中对房间空调器季节能效比(SEER)的定义以及测试试验、计算方法入手,阐述房间空调器提高季节能效比的若干方法与方向,在大力提倡节能降耗的新形式下,为提高现有中低能效房间空调器的季节能效比提供设计参考.     

风力发电机叶片变桨距偏离方式的受力分析

通过叶素理论及贝茨理论对两种风机叶片桨距角调节方法进行了对比,系统分析叶片桨距角偏离所引起的受力、边界层分离、攻角及桨距角等参数的变化,计算出叶片升力/阻力变化;通过求解流体边界层方程,揭示出叶片偏离最优桨距角之后产生的实际变化。得到下述结论:桨距角变大时,风机效率变化稳定但变化慢,桨距角调节范围较大;桨距角变小时,风机效率变化敏感,调整范围需要精密控制;该结论可为不同应用区域风机叶片参数调整方式的确定提供参考。     

长三角地区县域中小城市空间形态对碳排放效率影响研究

城市空间形态与碳排放效率存在密 切联系,探究两者间关系可以为县域中小城市 低碳发展提供指引,并为实现高质量发展提 供新参考。文章在大城市碳排放效率评价研 究的基础上结合县域中小城市特征,进行碳 排放效率评价指标选取及模型构建,通过建 立面板数据模型对2005—2020年间长三角 地区县域中小城市空间形态对碳排放效率影 响进行了实证研究,并分析了城市空间形态 对碳排放效率的影响机理。结果表明：城市 空间形态紧凑度、复杂度及破碎化程度与碳 排放效率密切相关;紧凑程度的提高对碳排 放经济效率具有促进作用,复杂程度和破碎 化程度的下降会对碳排放经济效率和碳排放 社会效率产生积极影响。总体而言,城市空间 形态主要通过影响交通碳排放进而对碳排 放效率产生影响,交通碳排放水平是长三角 地区县域中小城市碳排放经济效率和碳排放社会效率的首要影响因素。结合研究结论,本文提出强化结构性填充式开发以及调整空间组织 模式等策略,以期助力县域中小城市低碳发展。     

2~6 GHz紧凑型、高效率GaN MMIC功率放大器

基于0.25 μm SiC衬底的GaN高电子迁移率晶体管(HEMT)工艺,根据有源器件的G_max和输出功率密度,选择末级功率器件尺寸并确定其最优阻抗;采用三级放大器,其栅宽比为1:4:16,实现高功率增益和高效率;利用等Q匹配技术,把偏置电路融入匹配电路中,实现简单、低损耗和宽带阻抗变换;借助电磁场寄生参数提取技术实现紧凑型芯片版图,尺寸为2.8 mm×2.0 mm。测试结果表明,偏置条件漏极电压U_D=28 V、U_G=-2.2 V,在2~6 GHz频率范围内,功率放大器增益大于24 dB,饱和输出功率大于43 dBm,功率附加效率大于45%,可广泛应用于电子对抗和电子围栏等领域。     

A Comparative Study of Spouted and Spout-Fluid Beds for Tablet Coating

Abstract

The performance of spouted, spouted with auxiliary air supply, and spout-fluid beds for the coating of tablets was investigated. The gas–solid regimes of the three systems were confirmed by their hydrodynamic characteristic curves, e.g., pressure drop versus air flow rate. The coating study was developed following a central composite design and using flow regime, suspension feed rate and tablet load in the bed as factors. The dependent variables for the composite design of experiments were weight gain and efficiency. Other coat quality indexes, like tablet surface appearance, hardness, moisture content and gastric resistance are also discussed. The analysis of variance of the experimental data revealed that only the suspension feed rate affected the coating efficiencies and weight gain significantly. The coat quality, e.g., tablet moisture content, hardness, friability, and gastric resistance, were found to be unaffected by the factors studied, according to pharmaceutical standards. The results show that the gas–solid regimes do not affect coating performance.     

Impedance match for Stirling type cryocoolers

Impedance match in Stirling type cryocoolers is important for the compressor efficiency and available acoustic power. This paper generalizes the basic principles concerning the efficiency and acoustic power output of the linear compressor. Starting from basic governing equations and mainly from the viewpoint of energy balance, the physical mechanisms behind the principles are clearly shown. Specially, this paper focuses on the impedance match for an existing compressor, where the current limit and displacement limit should also be taken into consideration when selecting a suitable impedance. Some case studies based on a commercial compressor are also provided for a deep understanding.     

A roadmap towards intelligent net zero- and positive-energy buildings

Buildings nowadays are increasingly expected to meet higher and more complex performance requirements: they should be sustainable; use zero-net energy; foster a healthy and comfortable environment for the occupants; be grid-friendly, yet economical to build and maintain. The essential ingredients for the successful development and operation of net zero- and positive-energy buildings (NZEB/PEB) are: thermal simulation models, that are accurate representations of the building and its subsystems; sensors, actuators, and user interfaces to facilitate communication between the physical and simulation layers; and finally, integrated control and optimization tools of sufficient generality that using the sensor inputs and the thermal models can take intelligent decisions, in almost real-time, regarding the operation of the building and its subsystems. To this end the aim of the present paper is to present a review on the technological developments in each of the essential ingredients that may support the future integration of successful NZEB/PEB, i.e. accurate simulation models, sensors and actuators and last but not least the building optimization and control. The integration of the user is an integral part in the dynamic behavior of the system, and this role has to be taken into account. Future prospects and research trends are discussed.