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Chen F.,Bei Hang University | Ding X.,Bei Hang University | Lodhi E.,Bei Hang University
Energy Procedia | Year: 2016

With the expanding power demands and increasing use of renewable energy resources, microgrids have been widely supported. The wide bandgap semiconductor devices with higher blocking voltage capabilities and higher switching speed such as silicon carbide (SiC) devices will become a critical component in building the microgrid. In this paper, the power loss and current harmonics of both Si-IGBT and SiC-MOSFET based inverters are investigated and compared in low voltage (LV) microgrid applications, respectively. And the experimental results show that the application of SiC devices greatly increases the energy efficiency and improves the power quality in microgrid. © 2016 The Authors.

Jian W.,CAS Institute of Automation | Feng Q.,CAS Institute of Automation | Cheng X.-M.,Bei Hang University
Proceedings of the 28th Chinese Control and Decision Conference, CCDC 2016 | Year: 2016

This paper proposes an optimal guidance method which can give a certain orbit injection time, and satisfy the six terminal constraints of velocity and position at the same time. An optimal control problem of fixed-time and fixed-point orbit injection is established for the launch vehicle whose size of engine thrust and direction are controllable. The problem is proved to be solvable by introducing a new control variable, transforming the problem with equality constraints into control variable unconstrained problem, and deriving formulas. Numerical algorithm can be used to calculate seven co-state variables, then the size and direction of thrust is obtained. The simulations reveal that the guidance method this paper presented can put the rocket into the target orbit from the specified orbit injection point at the specified time. © 2016 IEEE.

Lu Y.-F.,Bei Hang University | Yin Y.-F.,Bei Hang University
19th International Conference on Industrial Engineering and Engineering Management | Year: 2013

Software testing is becoming a relatively independent activity of software development process. To estimate the cost of software testing is an important part of project management. The researchers have focused on the software cost and treated software testing cost as a part of the total software development cost for several years. Few researchers consider software testing as a separate process to estimate its' cost. This paper proposed a new constructive cost model for software testing project management (CCMST) which contains the main cost divers of software testing. The cost drivers included in this model is more comprehensive than former models. Application case study proved the model is usable and valid. © 2013 Springer-Verlag Berlin Heidelberg.

Qin B.,Bei Hang University
ICMET 2010 - 2010 International Conference on Mechanical and Electrical Technology, Proceedings | Year: 2010

Single-cylinder piston engine power constraint (Electric Power Confined Piston Engine) combine the traditional internal combustion engine - generator system and the set of power piston engine as a whole, and directly use traditional internal combustion engines reciprocating motion of the piston. With the fuel combustion energy conversion into electrical energy and output it. Constrained by single-cylinder piston engine power structure and working mechanism of the in-depth study ,it has establish a system and dynamic model on the basis of the power piston engine in the motor part to establish parameters and know the conditions of the power constraint in the linear motor piston engine The finite element model use AVL boost power constraint on the single-cylinder piston engine thermodynamic process simulation, and the combustion chamber gas pressure curve was created. © 2010 IEEE.

Li H.G.,Bei Hang University | Yin X.Y.,Bei Hang University | Zhang Z.Y.,Bei Hang University
IEEE/OSA Journal of Display Technology | Year: 2015

This paper proposes an 8-bit grayscale AMOLED driver IC with a mixed modulation DAC. This architecture maintains a digital logic component, high-precision 8-bit compensated gamma correction and an output amplifier buffer with low-complexity configuration for the AMOLED display panel. The proposed driver IC with gamma correction consists of a 6-bit resistor-string DAC and a 2-bit polynomial interpolation current-modulation sub-DAC. The two-stage DAC leads to a more compact die size than conventional 8-bit resistor-string DAC, and the polynomial interpolation method provides higher accuracy gray level voltages than linear methods. The source driver IC of the 240 RGB AMOLED display was implemented in the 0.35 $\mu$m CMOS process with a die area of 2.95$\times$ 8.9 mm$2 , including a digital core area of approximately 7.0$\times$1.0 mm$2. The DNL and INL of the proposed mixed modulation DAC are of 0.43 LSB and, 0.4 LSB, respectively. © 2005-2012 IEEE.

Tongguang C.,Bei Hang University | Changhui W.,Bei Hang University | Wentong H.,Bei Hang University
Procedia Engineering | Year: 2015

Channeling centerbody provides a wide variation in throat area, which makes it possible to start the inlet at lower velocity and get high performance at cruise conditions. We developed a new method to design the channels and performed three-dimensional computational fluid dynamics analysis. We found that the starting characteristics of the channeled centerbody inlet are different from that of the equivalent centerbody inlet The unchanneled parts of the inlet are still unstarted at low Mach numbers, and the aerodynamic performance of the channeled parts of the inlet are apparently affected by the channels. Boundary layer separation developed seriously due to abruptly turning down of the channel contour, and it decreased the available cross-section area of the channel seriously. © 2015 The Authors.

Luo X.,Chongqing University | Luo X.,Bei Hang University | Ouyang Y.,Bei Hang University | Zhang X.,Bei Hang University
International Journal of Information Technology and Decision Making | Year: 2011

One of the most popular approaches to Collaborative Filtering is based on Matrix Factorization (MF). In this paper, we focus on improving MF-based recommender's accuracy by homogeneous ensemble methods. To build such ensembles, we investigate a series of methods primarily in two aspects: (i) manipulating the training examples, including bagging, AdaBoost, and Forward Stepwise Additive Regression; (ii) injecting randomness to the base models' training settings, including randomizing the initializing parameters and randomizing the training sequences. Each method is evaluated on two large, real datasets, and then the effective methods are combined to form a cascade MF ensemble scheme. The validation results on experiment datasets demonstrate that compared to a single MF-based recommender, our ensemble scheme could obtain a significant improvement in the prediction accuracy. © 2011 World Scientific Publishing Company.

Bi H.X.,Bei Hang University | Yao J.Y.,Bei Hang University | Li Y.,Bei Hang University
Procedia Engineering | Year: 2011

The working principle, failure modes and failure causes of the jet pipe servo valve has been analyzed. Get the main failure modes of the servo valve, which is caused by wear. The influences of the arris edge geometric error on the performance of the servo valve been analyzed. Get the wearing capacity equal to the edge arris geometric error. It provides an estimation method of the arris edge geometric error, which could be use to analysis the wearing capacity of the servo valve. © 2011 Published by Elsevier Ltd.

Meng H.J.,Bei Hang University | Wang Z.L.,Bei Hang University
Applied Mechanics and Materials | Year: 2014

With the development of oil field production demand today, pumping unit is developing towards the direction of energy saving, intelligent. According to the present status of the oilfield, this paper designed a kind of intelligent energy saving pumping unit system, the system acceleration and deceleration process is very short, most of their working time in uniform motion in a stroke, and the beam pumping unit has been alternating deceleration process all the time compared with good energy saving effect. Energy store system is designed, the system not only reduces energy consumption, and make the motors can be started with initial velocity, shorten the motor start-up time, the motor starting current is stable running current of 4 to 7 times, so that reduces the starting current impact. To test this idea, modeling of motor, and the simulation analysis, the results confirmed the idea very well. Finally, in the principle of the pumping unit system prototype experiments, the experimental results show that the pumping unit system has significant energy-saving effect and the intelligent characteristics. © (2014) Trans Tech Publications, Switzerland.

Han Q.,Bei Hang University | Wang J.,Bei Hang University | Li Q.,Bei Hang University
Journal of Vibration and Acoustics, Transactions of the ASME | Year: 2010

The frequency response characteristic of a general time-invariant system has been extensively analyzed in literature. However, it has not gained sufficient attentions in the parametrically excited system. In fact, due to the parametric excitation, the frequency response of time-periodic system differs distinctly from that of the time-invariant system. Utilizing Sylvester's theorem and Fourier series expansion method, commonly used in the spectral decomposition for matrix, the frequency response functions (FRFs) of a single-degree-of-freedom (SDOF) parametrically excited system are derived briefly in the paper. The external resonant condition for the system is obtained by analyzing the specific expressions of FRFs. Then, a spur-gear-pair with periodically time-varying mesh stiffness is selected as an example to simulate the frequency response characteristics of parametric system. The effects of parametric stability, periodic mesh stiffness parameters (mesh frequency and contact ratio), and damping are considered in the simulation. It is shown from both theoretical and simulation results that the frequency response of parametric system has the following properties: there are multiple FRFs even for a SDOF periodic system as the forced response contains many frequency components and each FRF is corresponding to a certain response spectrum; the system has multiple external resonances. Besides the resonance caused by the external driving frequency equals to the natural frequency, the system will also be external resonant if external frequency meets the combination of natural frequency and parametric frequency. When the system is in external resonant state, the dominant frequency component in the response is the natural frequency; damping makes the peak values of FRFs drop evidently while it has almost no impact on the FRFs in nonresonant regions. Copyright © 2010 by ASME.

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