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高功率光纤激光器阵列的下一代大模式区域纤维技术
This program has successfully accomplished its main objective in that large core single-mode Ge-doped and Yb-doped CCC fibers have been developed as a platform for monolithically-integrated building blocks (individual laser channels) of high power beam-combined fiber laser arrays. Robust single-mode performance of CCC fibers with core sizes of up to approximately 60m has been rigorously demonstrated. Various CCC fiber based high power lasers have been also demonstrated, including 600W SBS-free single-frequency linearly-polarized cw fiber MOPA system, mJ pulsed and high-pwer ultrashort-pulse CPA systems. Accurate numerical modeling tools for designing CCC structures have been developed. Fabrication of CCC fibers reached such a degree of maturity that they have become available commercially. Furthermore, this program resulted in a successful demonstration of SBS suppression in acoustic-guidance tailored fibers with up to 13dB SBS threshold increase, which to our knowledge constitutes one of the largest SBS suppression achieved to date. UUIC group also performed an extensive study of SBS gain coefficient magnitude and spectrum in a variety of fiber glass materials.
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内螺纹小通道冷却板的流体过渡以冷却混合电力电子产品
Forced flow of fluids undergoing phase change in traditional single- phase cold plates is an effective way to manage waste heat removal of vehicle power electronics. Such cold plates come in a variety of standard styles, ranging from circular-tubed cold plates and flat-tube cold plates, to more exotic designs such as louvered and offset fin cold plates. The mechanisms of heat transfer in a two-phase system are different than single-phase, and as such, improvement can be made by custom designing cold plates for two-phase operation. Past research has focused on surface modifications that enhance nucleate boiling, convective vaporization, or both during two-phase operation. The method that has gained the most attention is the use of inner grooved tubes for performance improvement in refrigeration applications. Despite the popularity of inner grooved tubes, the flow mechanisms that deliver performance enhancement are not fully understood. The absence of phenomenological insights and physical models makes it difficult to transition inner grooved tube technology from conventional refrigeration equipment to cold plates. Therefore, understanding the physical mechanisms underpinning two-phase performance enhancement in inner grooved tubes is at the heart of this report.
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高功率光纤激光器
This program focused on new materials and fiber designs towards the realization of 100+ kW class eye-safe fiber lasers based on the following guiding principles: large mode area, single mode, purity of polarization state, minimization of nonlinear effects, compatibility with all-fiber pumps, and high temperature buffer coatings. Over the duration of this program the most significant findings are discussed below in the following sections: (1) Gain guided index anti guided fiber lasers; (2) High temperature fiber coatings; (3) Tm doped fiber lasers 4. Tm doped Photonic Crystal Fiber (PCF) lasers.
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单片微波集成电路(MMIC)宽带功率放大器
A broadband power amplifier design approach was used to design several monolithic microwave integrated circuits (MMICs) using a 0.13- m gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (PHEMT) process from TriQuint Semiconductor. The design and fabrication of these circuits were performed as part of the fall 2011 Johns Hopkins University (JHU) MMIC Design Course, taught by the author. The design approach is taught by Dale Dawson in the JHU Power MMIC Design Course. This approach is useful for designing relatively broadband amplifiers that are limited only be the active transistor's 'Q'.
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公共交通系统运营决策的混合预测控制
The optimization of the real-time operations associated with a bus system is formulated under a hybrid predictive control (HPC) approach. Both the objective function and the predictive model are essential for HPC design. For the sake of simplicity, in this work, the HPC framework is constructed for a single-loop bus system, although it could be extended to more complex systems according to a similar modeling framework. The system is represented in Fig. 4.1. The network is a one-way loop route with P equidistant stops and b buses running around the loop under the control of the dispatcher.
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射频功率放大器和线性化技术
The radio frequency (RF) power amplifier (PA) is one of the most critical components in designing transmitters in wireless communication systems, and its efficiency dominates the overall efficiency of the transmitter. On one hand, the PA is most power consuming ; for example, in a cellular phone, the battery life is largely determined by the power efficiency of the PA. On the other hand, it is desirable to have the ability to transmit data at the highest possible rate for a given channel bandwidth, i.e., to have high spectral efficiency [1].
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大功率板坯耦合的光波导激光器和放大器
The development of a high-brightness semiconductor diode laser/amplifier concept, which utilizes a slab-coupled optical waveguide (SCOW) region to achieve several important advances in performance, has been presented. SCOW devices are capable of single-spatial-mode operation with a single-lobed, large-area, low-aspect-ratio beam that is easily coupled to a single-mode fiber with high-coupling efficiency. The SCOW concept is applicable to a wide variety of semiconductor material systems and wavelengths of interest.
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光伏阴影模块级电力电子实验平台
This document describes a repeatable test procedure that attempts to simulate shading situations, as would be experienced by typical residential rooftop photovoltaic (PV) systems. This type of shading test is particularly useful to evaluate the impact of different power conversion setups, including microinverters, DC power optimizers and string inverters, on overall system performance. The performance results are weighted based on annual estimates of shade to predict annual performance improvement. A trial run of the test procedure was conducted with a side by side comparison of a string inverter with a microinverter, both operating on identical 8kW solar arrays. Considering three different shade weighting conditions, the microinverter was found to increase production by 3.7under light shading, 7.8under moderate shading, and 12.3under heavy shading, relative to the reference string inverter case. Detail is provided in this document to allow duplication of the test method at different test installations and for different power electronics devices.