Combining selection valve and mixing chamber for nanoflow gradient generation: Toward developing a liquid chromatography cartridge coupled with mass spectrometer for protein and peptide analysis

Toward developing a micro HPLC cartridge, we have recently built a high-pressure electroosmotic pump (EOP). However, we do not recommend people to use this pump to deliver an organic solvent directly, because it often makes the pump rate unstable. We have experimented several approaches to address this issue, but none of them are satisfactory. Here, we develop an innovative approach to address this issue. We first create an abruption (a dead-volume) within a fluid conduit. We then utilize an EOP to withdraw, via a selection valve, a train of eluent solutions having decreasing eluting power into the fluid conduit. When these solutions are further aspirated through the dead-volume, these solutions are partially mixed, smoothening concentration transitions between two adjacent eluent solutions. As these solutions are pushed back, through the dead-volume again, a smooth gradient profile is formed. In this work, we characterize this scheme for gradient formation, and we incorporate this approach with a high-pressure EOP, a nanoliter injection valve, and a capillary column, yielding a micro HPLC system. We then couple this micro HPLC with an electrospray ionization – mass spectrometer for peptide and protein separations and identifications.     

Wind turbine speed control of a contactless piezoelectric wind energy harvester

ABSTRACT

Wind turbine control is an important task to make the electricity generation secure in terms of energy demand and machine safety. It also yields to control the desired power level and optimized energy because of the assignment of turbine speed. The contactless piezoelectric wind energy harvester (CPWEH) used in this study has three piezoelectric layers located around the shaft with 120 degrees apart and they are buckled by the magnetic force without any physical contact. The superiority of this device is to generate energy for low wind speeds such as 1.5 m/s. However, for high speeds, high total harmonic distortions (THDs) govern the waveforms, thus controlling the turbine speed becomes necessary for optimizing the output power. Encouraged by this, a small low inertia dc generator is coupled with the wind turbine, and the generator terminals are connected to a resistor through a power switch to generate a braking torque that opposes to wind speed direction. By controlling the switch properly, turbine speed is ensured to remain within a certain band, which accordingly prevents the turbine from rotating very fast at damaging wind speeds. Several experiments are performed on the developed CPWEH with/without the presented control scheme which prove the existence of promising performance of our proposal.     

汽轮发电机组润滑油系统的故障诊断及分析

润滑油系统是汽轮发电机组中非常重要的辅助系统，该辅助系统的安全性直接关系到整个发电机组的工作效率和运行可靠性。润滑油系统在汽轮机中起到润滑、散热、减振的作用，因此，做好汽轮发电机组润滑油系统的故障诊断和分析工作至关重要。     

Random Variable Generation Using Concavity Properties of Transformed Densities

Abstract

Algorithms are developed for constructing random variable generators for families of densities. The generators depend on the concavity structure of a transformation of the density. The resulting algorithms are rejection algorithms and the methods of this article are concerned with constructing good rejection algorithms for general densities.     

宽频压电振动发电机阵列特性分析与实验

利用压电振动发电机可实现环境振动能量到电能的转化,压电振动发电机阵列可实现较宽频带的振动能量收集,压电振动发电机的特性研究通常采用机械分析方法,该文采用电路分析方法针对压电振动发电机阵列的串、并联方式进行了特性分析,利用电子电路仿真软件PSPICE对串、并联不同连接方式下压电发电机阵列的内阻及负载电压与负载功率进行了比较分析,最后设计了一台压电发电机阵列并进行了实验分析,验证了特性分析的正确性。     

V型双稳态压电发电机建模与输出特性分析

为对真实环境中宽带低频的振动能量实现有效收集,设计了一种不含磁铁的V型结构双稳态压电发电机,给出了压电发电机的机-电转换模型,并对输出特性进行了仿真分析。结果表明,初始夹角在一定范围内时,V型压电发电机发生随机共振,系统有效收集宽带低频的振动能量。该结构不含磁铁,有利于微型化和集成化。     

基于PIC24F的柴油发电机检测与自动化系统

针对原有柴油发电机组的专用控制器功能单一、集成度低、测量精度和响应速度低等问题,设计了一款基于PIC24F的柴油发电机检测与自动化系统。在该系统控制作用下,可实现市电故障检测以及无人值守条件下的自动运行。通过实验证明,文中所使用的差动式低通放大电路作为前置电压采样电路和软件补偿算法,可较好地抑制共模干扰信号,高频干扰信号,冲击噪声,提高了测量的准确性与可靠性。与以往的双电源供电和外置AD做法相比,文中所采用的单电源加偏置电压的信号采集电路成本降低,外围器件减少,且缩小了电路体积。     

核磁共振任意波形发生器的研制

任意波形发生器（又叫函数发生器）作为一种通用的信号源,在物理、电子、计算机等领域有着广泛的应用. 本文提出了一种不依赖PC机总线的、完全独立的、 可用于低场磁共振成像的多用途任意波形发生器（Arbitrary Waveform Generator, AWG）设计方案,围绕着这种方案,研制了80 MHz通用磁共振任意波形发生器. 并提供了实际测试数据和成像实验结果,对研制情况和实验结果进行了总结和讨论.     

基于STC89C52单片机的测速计设计

介绍了一种通过霍尔传感器采集数据,使用89C52单片机对信号进行计数的测速计,可以实现测转速、超速报警和调速的功能。该设计具有功耗低,价格低廉,可移植性高等优势。