http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Optimized Transient Modulation Control of Bidirectional Full-Bridge DC-DC Converter
Qinglei Bu,Huiqing Wen,Jiacheng Wen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
To eliminate the dc-bias current in the transient-state (TS) of the dual-active-bridge (DAB) DC-DC converter with the load change demand, this paper proposed an optimized transient modulation (OTM) control strategy under triplephase-shift (TPS) control for transient response. Compared with the traditional optimized algorithm in TS, a fixed switching state is applied to increase the transition speed and simplify the complexity of calculations. Because of the fixed switching state, the gradient of the inductor current is modified to the maximum value rather than piecewise linear relationship within the transient period, which shorten the settling time significantly. Besides, compared with the dedicated method for specific phaseshift control of traditional optimization, OTM control is not only suitable for TPS control, but can be utilized for other phaseshift control easily as well, such as extended-phase-shift (EPS) and single-phase-shift (SPS). Finally, the experimental results are given to verify the proposed OTM methods.
Rules Placement with Delay Guarantee in Combined SDN Forwarding Element
( Qinglei Qi ),( Wendong Wang ),( Xiangyang Gong ),( Xirong Que ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.6
Recent studies have shown that the flow table size of hardware SDN switch cannot match the number of concurrent flows. Combined SDN Forwarding Element (CFE), which comprises several software switches and a hardware switch, becomes an alternative approach to tackle this problem. Due to the limited capacity of software switch, the way to route concurrent flows in CFE can largely affect the maximum delay that a flow suffers at CFE. As delay-guarantee is a nontrivial task for network providers with the increasing number of delay-sensitive applications, we propose an analytical model of CFE to evaluate a rules placement solution first. Next, we formulate the problem of Rules Placement with delay guarantee in CFE (RPCFE), and present the genetic-based rules placement (GARP) algorithm to solve the RPCFE problem. Further, we validate the analytical model of CFE through simulations in NS-3 and compare the performance of GARP with three benchmark algorithms.
Fluid-structure interaction analysis of annular seals and rotor systems in multi-stage pumps
Qinglei Jiang,Lulu Zhai,Leqin Wang,Dazhuan Wu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.7
Annular seals play an important role in determining the vibrational behavior of rotors in multi-stage pumps. To determine the critical speeds and unbalanced responses of rotor systems which consider annular seals, a fluid-structure interaction (FSI) method was developed,and the numerical method was verified by experiments conducted on a model rotor. In a typical FSI process, rotor systems are modeled based on a node-element method, and the motion equations are expressed in a type of matrix. To consider the influence of annular seals,dynamic coefficients of annular seals were introduced into the motion equations through matrix transformation. The test results of the model rotor showed good agreement with the calculated results. Based on the FSI method proposed here, the governing equations of annular seals were solved in two different ways. The results showed that the Childs method is more accurate in predicting a rotor’s critical speed. The critical speeds of the model rotor were calculated at different clearance sizes and length/diameter ratios. Tilting coefficients of long seals were added to the dynamic coefficients to consider the influence of tilting. The critical speeds reached their maximum value when the L/D ratio was around 1.25, and tilting enhanced the rotor’s stability when long annular seals were located in either end of the shaft.
Impact of rock microstructures on failure processes - Numerical study based on DIP technique
Yu, Qinglei,Zhu, Wancheng,Tang, Chun'an,Yang, Tianhong Techno-Press 2014 Geomechanics & engineering Vol.7 No.4
It is generally accepted that material heterogeneity has a great influence on the deformation, strength, damage and failure modes of rock. This paper presents numerical simulation on rock failure process based on the characterization of rock heterogeneity by using a digital image processing (DIP) technique. The actual heterogeneity of rock at mesoscopic scale (characterized as minerals) is retrieved by using a vectorization transformation method based on the digital image of rock surface, and it is imported into a well-established numerical code Rock Failure Process Analysis (RFPA), in order to examine the effect of rock heterogeneity on the rock failure process. In this regard, the numerical model of rock could be built based on the actual characterization of the heterogeneity of rock at the meso-scale. Then, the images of granite are taken as an example to illustrate the implementation of DIP technique in simulating the rock failure process. Three numerical examples are presented to demonstrate the impact of actual rock heterogeneity due to spatial distribution of constituent mineral grains (e.g., feldspar, quartz and mica) on the macro-scale mechanical response, and the associated rock failure mechanism at the meso-scale level is clarified. The numerical results indicate that the shape and distribution of constituent mineral grains have a pronounced impact on stress distribution and concentration, which may further control the failure process of granite. The proposed method provides an efficient tool for studying the mechanical behaviors of heterogeneous rock and rock-like materials whose failure processes are strongly influenced by material heterogeneity.
Bing Xiao,Qinglei Hu,Aihua Zhang 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.1
This work explores a novel efficient and low-cost control scheme for rigid spacecraft attitude stabiliza-tion problem, in which the unavailability of angular velocity measurements is considered. The resulting controller is independent on spacecraft inertia parameters, and explicit accounts for control input saturation with angular velocity measurements eliminated. Moreover, the proposed control law allows L2 gain of the closed-loop attitude system to be chosen arbitrarily small so as to achieve any level of L2 disturbance attenuation. Numerical simulation results are also presented to highlight those highly desirable features.
Miao Cui,Qinglei Bu,Yutao Cai,Ruize Sun,Wen Liu,Huiqing Wen,Sang Lam,Yung. C. Liang,Ivona Z. Mitrovic,Stephen Taylor,Paul R. Chalker,Cezhou Zhao 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This study proposed a 100 kHz, 5V/11V boost converter with an integrated gate driver for a power switching device using recessed E-mode MIS-HFETs. The integrated gate driver consisting of multi-stages DCFL (Direct-Coupled FET Logic) inverters and a buffer stage, has large input swing (up to 10 V) and wide noise margin with gate dielectric, which benefits applications requiring large gate swing without any additional drivers or level shifters. The impact of transistor size on rise times and fall times have been studied. Either buffer stage or larger width of DCFL inverter can reduce rise times from 2.4 μs to less than 0.5 μs at 100 kHz, so the output voltage of boost converter is increased by 10 % at a duty cycle of 0.7. However, large buffer width can result in high gate overshoot and oscillation, indicating careful design to balance switching speed and oscillation.