Output voltage regulation of a k15 mode piezoelectric transformer by an external L/C component

Smooth regulation of output voltage of piezoelectric transformers can significantly widen the application range of piezoelectric transformers. So far the driving frequency of piezoelectric transformers has been used to regulate the output voltage at a matching load. However, the regulation range of voltage gain achieved by the method is usually very narrow within the acceptable range of efficiency. In this work, we investigate the possibility to regulate the output voltage of a k₁₅ mode piezoelectric transformer by an external L/C component. The effects of an L/C component in series or parallel with the input and output ports on the voltage gain are investigated theoretically and experimentally. It is found that the voltage gain can be smoothly regulated in a relatively wide range by a tunable inductor that is in series with the input port. At a matching load of 80 Ω, the voltage gain can be regulated between 0.31 and 0.94 with efficiency larger than 90% and between 0.34 and 1.18 with efficiency about 80%. It is also found that a tunable capacitor in parallel or series with the output port can be used to regulate the voltage gain with efficiency higher than 90%.     

光波导短程透镜焦点特性的分析

利用波导短程透镜的几何光学性质, 给出了短程透镜的等效光线追迹图和相位传递函数, 得到短程透镜焦点的模场分布表达式. 理论得出的焦斑光强分布和实验测得的光强分布一致.     

A Comparison of Numbers in Chinese and English Culture

This thesis introduces the relationship between number and culture. Numbers are an important part of culture. With the development of human civilization, in different countries or nationalities, numbers have different implications and characteristics.From the expression of quantity, specific things and proportion, we can find the differences of culture.The focus is on ＂Mode Numbers＂ in Chinese and English culture.     

Dynamic response of a rotating disk submerged and confined. Influence of the axial gap

In this paper, the natural frequencies and mode shapes of a rotating disk submerged and totally confined inside a rigid casing, have been obtained. These have been calculated analytically, numerically and experimentally for different axial gaps disk-casing. A simplified analytical model to analyse the dynamic response of a rotating disk submerged and confined, that has been used and validated in previous researches, is used in this case, generalised for arbitrary axial gaps disk-casing. To use this model, it is necessary to know the averaged rotating speed of the flow with respect to the disk. This parameter is obtained after an analytical discussion of the motion of the flow inside the casing where the disk rotates, and by means of CFD simulations for different axial positions of the disk. The natural frequencies of the rotating disk for the different axial confinements can be calculated following this method. A Finite Element Model has been built up to obtain the natural frequencies by means of computational simulation. The relative velocity of the flow with respect to the disk is also introduced in the simulation model in order to estimate the natural frequencies of the rotating disk. Experimental tests have been performed with a rotating disk test rig. A thin stainless steel disk (thickness of 8 mm, (h/r<5%) and mass of 7.6 kg) rotates inside a rigid casing. The position of the disk can be adjusted at several axial gaps disk-casing. A piezoelectric patch (PZT) attached on the rotating disk is used to excite the structure. Several miniature and submergible accelerometers have measured the response from the rotating frame. Excitation and measured signals are transmitted from the rotating to the stationary frame through a slip ring system. Experimental results are contrasted with the results obtained by the analytical and numerical model. Thereby, the influence of the axial gap disk-casing on the natural frequencies of a rotating disk totally confined and surrounded by a heavy fluid is determined.     

首都科技条件平台与科技创新基地对接模式研究

首都科技条件平台的建设几年来取得了巨大成绩,但却未能很好地解决与北京科技研发机构和北京市重点实验室、北京市工程技术研究中心等科技创新基地实现有效对接的问题。解决这一问题的关键在于探索出多元联合互动与政府主导相结合的有效对接模式。     

论CDIO对高职院校思想政治理论课改革的意义

思想政治理论课是对大学生进行思想政治教育的主要渠道,是高校学生综合素质教育的核心。实践育人是思想政治理论课教学不可缺少的重要任务。CECL实践教学模式是目前解决思想政治理论课实践教学不完善,教学资源和资金不足等问题的主要方法。CDIO教学模式对于思想政治教育实践教学由专家主导型向基层主导型转变都具有重要意义。     

中国管理模式的时代功能

在新的历史社会条件下,深化中国管理模式研究,推进中国管理模式,具有重要意义。这是因为,中国管理模式具有重要的时代功能。具体来看,推进中国管理模式,对于促进中国经济发展,推进中国文化发展,实现社会发展,加强政治文明建设,提升中国的核心竞争力,都有积极作用。     

Eu（Ⅲ）（EB）3配合物与DNA的相互作用模式研究

应用荧光光谱法得Eu(Ⅲ)(EB)3配合物与DNA可形成摩尔比为41的复合物,通过磷酸盐实验与阴离子猝灭剂实验可知其相互作用为混合模式,包括嵌插作用、沟渠作用和静电作用。由双倒数法求得ΔrHmΘ=1.11×105 J/mol,ΔrGmΘ28℃=-3.24×104 J/mol,ΔrSmΘ28℃=475.08 J/(mol.K),可知该反应为熵驱动反应。     

A magnetically tunable non-Bragg defect mode in a corrugated waveguide filled with liquid crystals

A magnetically tunable, non-Bragg defect mode (NBDM) was created in the terahertz frequency range by inserting a defect in the middle of a periodically corrugated waveguide filled with liquid crystals (LCs). In the periodic waveguide, non-Bragg gaps beyond the Bragg ones, which appear in the transmission spectra, are created by different transverse mode resonances. The transmission spectra of the waveguide containing a defect showed that a defect mode was present inside the non-Bragg gap. The NBDM has quite different features compared to the Bragg defect mode, which includes more complex, high-order guided wave modes. In our study, we filled the corrugated waveguide with LCs to realize the tunability of the NBDM. The simulated results showed that the NBDM in a corrugated waveguide filled with LCs can be used in filters, sensors, switches, and other terahertz integrated devices.     

Recent progress in optical devices for mode division multiplex transmission system

The idea of adopting the space domain as the next frontier for optical communication has received increasing attention in the last few years. Optical devices are the integral parts of a mode division multiplexing (MDM) transmission. Therefore, conducting an intensive study on the devices is paramount to the successful realization of the overall system. This paper presents a review of the recent advances in the inline components of an MDM system, consisting of mode converters, spatial (de) multiplexers, optical amplifiers, and few-mode fibers (FMFs). Also presented are different mode conversion and multiplexing schemes. Recent techniques of minimizing differential mode gain (DMG) in the optical amplifiers are also reviewed. The review covers other types of amplification schemes and their current standing in the MDM system. These include optical semiconductor amplifiers (OSAs), and the Raman amplifiers (RAs). Finally, the review also highlights the role of FMF, multicore fiber and their relationship with fan-in/fan-out devices.