The superior lithium storage capabilities of ultra-fine rutile TiO2 nanoparticles

The lithium storage capabilities of ultra-fine rutile TiO₂ nanoparticles have been studied. Ultra-fine rutile TiO₂ nanoparticles with only several nanometers in size have been prepared by a modified wet-chemical method with a high yield. Unexpectedly, the rutile TiO₂ nanoparticles with 3 nm in size exhibit superior lithium storage properties. Specifically, they show long term cycling stability upon extended cycling for at least 300 cycles with a capacity loss of only 0.17% per cycle, and good rate capability up to a 30 C rate. The excellent reversible lithium storage capabilities could be attributed to the ultra-fine size giving rise to a very short diffusion path, and the relatively large surface area which provides more sites for lithium insertion.     

高速铁路飞快建基础可靠最关键——台达UPS电源[铁路行业]解决方案

本文对高速铁路信号电源系统采用大功率UPS并联冗余供电的安全、可靠及高效节能方面进行了分析,详细介绍了采用台达NT系列UPS的解决方案.     

大功率单相完全有源功率因数校正器的实现

首先基于现有的、典型的模拟PFC控制芯片,较为详细地描述了单级升压变换的单相AC—DC变换器领域几种基本的有源功率因数校正技术,其中包括传统有源PFC技术、跟随有源PFC技术和单周期有源PFG技术。最后基于PFC控制芯片L4981B详细地介绍了支持较大功率输出的有源PFC电路设计过程,并给出部分实验结果。     

1500MVA大容量自耦变压器调压方式选择

对自耦变压器采用有载和无励磁调压两种调压方式进行对比分析;并对1500MVA大容量变压器采用中压侧线端调压、中性点调压、串联绕组末端调压等方式的可行性及合理性进行论述分析。     

回旋管电子枪的发展及其评述

回旋管电子枪是一种具有重要发展前景的高功率微波源(HPM)电子枪。该文简要介绍了回旋管电子枪的结构和设计原理,并且评述了国际上加旋管电子枪的发展状况及趋势,着重介绍了大回旋电子枪的发展状况及趋势,并指出了回旋管电子枪发展中存在的一些关键问题及一些建议。     

高负载能力电压电流标准源的研究

在多年计量检测经验的基础上,从电工仪表分析,以及仪表检测的要求入手,介绍一种高负载能力电压电流标准源的具体实现过程、工作原理,以及适应检测工作的各种设计等。最终实现模拟式、数字式电压、电流仪表检测目的。     

Unstained and in vivo fluorescently stained bacterial nucleoids and plasmolysis observed by a new specimen preparation method for high-power light microscopy of metabolically active cells

Microscope slides were coated with a layer of gelatin, the thickness of the gelatin increasing linearly along the long axis. The bacterial suspension is applied to the dried gelatin and covered by a coverslip. The medium is absorbed by the gelatin and thus the cells applied against the coverslip. By this method, cultures of concentrations below 10⁸ cells/ml provide statistically relevant numbers for observation without prior concentration steps. It is easier to apply than the existing methods for the observation of bacterial nucleoids by phase contrast imaging. Because the cells are maintained in growing conditions the method is useful for the vital fluorescence DAPI-staining of various bacterial species and for observations of plasmolysis and its reversal at different physiological conditions and extracellular osmolalities. The previously generally assumed view that the plasmolytic changes of the cell morphology are immediate upon the hyperosmotic shock and are rapidly repaired when the cell is able to metabolize actively was confirmed; this is in contrast to some recent claims.     

基于微处理器和PWM的船用大功率直流电机起动与调速研究

采用PWM脉宽调制改变直流电压的控制方式,具有效率高、电压连续可调等优点,已广泛应用于大功率直流电机的调速中。本文对直流电动机调速驱动方式中存在的问题进行了分析,应用微处理器对驱动模块进行适时检测与自动切换,保证驱动系统的工作连续性和安全稳定性;对操作人员非正常操作或误动作产生的错误指令给以合理的修正,提高系统的操作客...     

大功率机电伺服系统关键驱动技术研究

10kW级的大功率机电伺服系统的电源电压达到500VDC,且对动态特性要求很高,在这种伺服系统中,高速大功率开关器件的可靠工作是实现系统功能的基本保证。本文在系统研究IGBT失效模式的基础上确定了基于M57962L的IGBT功率驱动电路设计。本文的研究工作解决了大功率机电伺服系统控制驱动器的驱动技术,切实提高了对功率器件的保护,提高了功率驱动电路的安全性,提高了控制驱动器的工作性能。     

On-board non-linear circuitry for Ku-band active arrays

Active phased arrays will play an important role in future satellite communications, because of the system flexibility and potential reconfigurability that they may provide. Therefore, an investigation of the relationship existing between payload characteristics and the synthesis parameters of this kind of antenna may constitute a helpful tool. To this end, a parametric analysis of the on-board non-linear circuitry of the transmitting system (power and up-converter sections) has been carried out, establishing the dependence of the mass and DC power demand on the number of beams and feeds of the transmitting phased array. The parametric investigation has been, in particular, applied to an active imaging phased array and an active direct radiating phased array whose suitability to provide a multibeam coverage of Western Europe at K_u band has been demonstrated within an ESA/ESTEC contract. This paper describes the parametric approach followed in the investigation of the on-board non-linear subsystems of the active transmitting phased arrays. The assumed circuitry configurations are widely commented, and the parametric curves for the case of imaging and direct radiating phased arrays are reported.