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关于准静态过程
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作者 刘咸定 《中国大学教学》 1990年第5期38-39,共2页
国内外热力学和工程热力学教材中,关于准静态过程的定义大体上有两种,其一为:过程的每一步,系统都处在平衡态的过程或由连续平衡态组成的过程(以下简称定义一);另一为:在无限小势差推动下进行的过程(以下简称定义二)。一般认为两种定义... 国内外热力学和工程热力学教材中,关于准静态过程的定义大体上有两种,其一为:过程的每一步,系统都处在平衡态的过程或由连续平衡态组成的过程(以下简称定义一);另一为:在无限小势差推动下进行的过程(以下简称定义二)。一般认为两种定义一致且正确。前者是实质定义,后者是发生定义,即定义一是准静态过程的表现,定义二是实现准静态过程的条件。对于可逆过程的定义,各种教材并无分歧。 展开更多
关键词 准静态过程 可逆过程 平衡态 工程热力学 耗散效应 刚性容器 势差 流动功 可逆 膨胀
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磁谐振式无线电能传输系统频率跟踪设计
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作者 徐桂芝 曹智阳 +1 位作者 石凯凯 刘璐 《现代电子技术》 北大核心 2020年第18期80-84,共5页
无线电能传输系统在传输过程中,针对系统失谐导致输出功率大大降低的问题,文章在Matlab/Simulink仿真库搭建了一套能够自动进行频率跟踪反馈的磁谐振式无线传能仿真系统,并对高频逆变电路触发脉冲信号发生器进行了设计与改进,使系统能... 无线电能传输系统在传输过程中,针对系统失谐导致输出功率大大降低的问题,文章在Matlab/Simulink仿真库搭建了一套能够自动进行频率跟踪反馈的磁谐振式无线传能仿真系统,并对高频逆变电路触发脉冲信号发生器进行了设计与改进,使系统能够在发射端实现电压电流接近同相位,从而使系统在收发端传输能量时,处于接近纯阻态特性,减小了谐振线圈之间的无功损耗,增加了系统传输效率。仿真数据表明,该系统能够实时对发射端电流进行检测,并通过数字锁相环电路的调节信号对高频逆变器进行调节,输出与发射端电流同相位的逆变电压,实时进行动态调节。 展开更多
关键词 频率跟踪 无线电能传输 系统设计 磁耦合谐振 触发脉冲信号 流动
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Flow characteristics of variable hydraulic transformer 被引量:2
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作者 杨冠中 姜继海 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第6期2137-2148,共12页
A new kind of hydraulic transformer, called variable hydraulic transformer(VHT), is proposed to control its load flow rate. The hydraulic transformer evolves from a pressure transducer to a power transducer. The flow ... A new kind of hydraulic transformer, called variable hydraulic transformer(VHT), is proposed to control its load flow rate. The hydraulic transformer evolves from a pressure transducer to a power transducer. The flow characteristics of VHT, such as its instantaneous flow rates, average flow rates, and flow pulsations in the ports, are investigated. Matlab software is used to simulate and calculate. There are five controlled angles of the port plate that can help to define the flow characteristics of VHT. The relationships between the flow characteristics and the structure in VHT are shown. Also, the plus-minus change of the average flow rates and the continuity of the instantaneous flow rates in the ports are presented. The results demonstrate the performance laws of VHT when the controlled angles of the port plate and of the swash plate change. The results also reveal that the special principle of the flow pulsation in the ports and the jump points of the instantaneous curves are the two basic causes of its loud noise, and that the control angles of the port plate and the swash plate and the pressures in the ports are the three key factors of the noise. 展开更多
关键词 hydraulic transformer ENERGY-SAVING instantaneous flow rate average flow rate flow pulsation noise
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Effect of graphene on mechanical properties of cement mortars 被引量:10
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作者 曹明莉 张会霞 张聪 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第4期919-925,共7页
Functionalized graphene nano-sheets(FGN) of 0.01%-0.05%(mass fraction) were added to produce FGN-cement composites in the form of mortars. Flow properties, mechanical properties and microstructure of the cementitious ... Functionalized graphene nano-sheets(FGN) of 0.01%-0.05%(mass fraction) were added to produce FGN-cement composites in the form of mortars. Flow properties, mechanical properties and microstructure of the cementitious material were then investigated. The results indicate that the addition of FGN decreases the fluidity slightly and improves mechanical properties of cement-based composites significantly. The highest strength is obtained with FGN content of 0.02% where the flexural strength and compressive strength at 28 days are 12.917 MPa and 52.42 MPa, respectively. Besides, scanning electron micrographs show that FGN can regulate formation of massive compact cross-linking structures and thermo gravimetric analysis indicates that FGN can accelerate the hydration reaction to increase the function of the composite effectively. 展开更多
关键词 functionalized graphene nano-sheets cement mortars mechanical strength microstmcture
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OLED-on-silicon chip with new pixel circuit 被引量:2
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作者 刘艳艳 耿卫东 代永平 《Journal of Central South University》 SCIE EI CAS 2012年第5期1276-1282,共7页
A low power 640×480 OLED-on-silicon chip design that used in microdisplay was presented. A novel pixel circuit was proposed to meet the special requirement of OLED-on-silicon. The novel pixel consists of three tr... A low power 640×480 OLED-on-silicon chip design that used in microdisplay was presented. A novel pixel circuit was proposed to meet the special requirement of OLED-on-silicon. The novel pixel consists of three transistors and one capacitor (3T 1C). It has simple structure and can effectively reduce the current glitch generated during the AC driving from 55 pA to 7.5 pA, so that it can improve the precision of grayscale of display as well as extend the lifetime of (])LED material. Except for the pixel array, low power row driver, column driver and other functional modules were also integrated on the chip. Several techniques were adopted to reduce the power consumption and frequency requirement of the chip. Finally, a 16×3×12 resolution chip was fabricated with standard 0.35 μm CMOS process of CSM and the chip can operate correctly. 展开更多
关键词 organic light-emitting diode (OLED) pixel circuit ac driving
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