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Experimental study of a controlled variable double-baffle distortion generator engine test rig

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Chinese Journal of Aeronautics 2018年第9期31卷 1880-1893页

作者： Aiguo XIA Xudong huang Wei TUO ming ZHOU School of Aerospace Engineering Tsinghua University Beijing Aeronautical Technology Research Center

In order to explore the total-pressure distortion test assessment method for a turbofan engine, a Controlled Variable Double-Baffle Distortion Generator(CVDBDG) with a horizontal symmetry moving form was developed, which can adjust the steady-state and time–variant distortion separately in real time. The inlet total-pressure distortion test was conducted on an afterburner turbofan engine. The distortion parameters of CVDBDG and the instability characteristics of the engine were measured. The experimental data were modeled and analyzed by using back propagation artificial neural networks, and the work envelope of CVDBDG was obtained. Based on the analysis of the data on the engine’s instability, the properties of CVDBDG used for the stability assessment were preliminarily evaluated. The results show that CVDBDG can simulate both steady-state and time–variant distortions simultaneously in a range determined by three *** the condition of symmetric double baffles, a critical depth of insertion exists, beyond which the symmetric baffles will generate an asymmetric flow field. In the case of double baffles, compared to a single baffle, the engine exhibited different instability characteristics. Based on CVDBDG, it is expected that more efficient engine stability and durability assessment methods can be developed.

关键词： Distortion generator Engine stability Inlet flow Inlet total-pressure distortion Turbofan engines

Experimental study of wind loads on gable roofs of low-rise buildings with overhangs

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Frontiers of Structural and Civil Engineering 2018年第3期12卷 300-317页

作者： Peng huang Ling TAO ming GU Yong QUAN i University Shanghai 200092China

Gable roofs with overhangs （eaves） are the common constructions of low-rise buildings on the southeastern coast of China, and they were vulnerable to typhoons from experience. The wind pressure distributions on gable roofs of low-rise buildings are investigated by a series of wind tunnel tests which consist of 99 test cases with various roof pitches, height-depth ratios and width-depth ratios. The block pressure coefficients and worst negative （block） pressure coefficients on different roof regions of low-rise buildings are proposed for the main structure and building envelope, respectively. The effects of roof pitch, height-depth ratio, and width-depth ratio on the pressure coefficients of each region are analyzed in detail. In addition, the pressure coefficients on the roofs for the main structure and building envelope are fitted according to roof pitch, height-depth ratio and width-depth ratio of the low-rise building. Meanwhile, the rationality of the fitting formulas is verified by comparing the fitting results with the codes of different countries. Lastly, the block pressure coefficients and worst negative pressure coefficients are recommended to guide the design of low-rise buildings in typhoon area and act as references for the future＇s modification of wind load codes.

关键词： low-rise building gable roof wind loads wind tunnel test block pressure coefficient load code

design and optimization of a novel electrically controlled high pressure fuel injection system for heavy fuel aircraft piston engine

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Chinese Journal of Aeronautics 2018年第9期31卷 1920-1928页

作者： Ke ZHANG Xudong huang Zhifeng XIE ming ZHOU School of Aerospace Engineering Tsinghua University

The heavy fuel compression ignition engines are widely equipped as aircraft piston engines. The fuel injection system is one of the key technologies that determines the performance of engine. One of the main challenges is to precisely control the injected fuel quantity and flow rate in the presence of pressure fluctuation. This challenge is even more serious for heavy fuel. An original design for electrically controlled high pressure fuel injection system called Multi-Pumppressure-reservoirs fuel injection System(MPS) was demonstrated to reduce the pressure fluctuation and help keep injection stable. MPS was compared with an ordinary high pressure Common Rail fuel injection System(CRS). This work established one-dimensional AMESim and mathematical models for both CRS and MPS to study the effect of different structures and geometric parameters on the pressure fluctuations. The calculations show that the average fuel pressure fluctuation of MPS can be reduced by 57% for the crankshaft speed of 1900 r/min, and the pressure fluctuation before injection reduced by 100%. It is concluded that the pressure performance of MPS is less sensitive to pressure reservoir volume than that of CRS, and there is an opportunity for further volume reduction.

关键词： Aircraft engines AMESim Common rail Fuel injection Mathematical models Pressure effects Structural design

A Novel Image Digital Rights Management Scheme with High-Level Security,Usage Control and Traceability

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Chinese Journal of Electronics 2016年第3期25卷 481-494页

作者： MA Zhaofeng huang Jianqing JIANG ming NIU Xinxin Information Security Center of Beijing University of Posts and Telecommunications Library of Beijing University of Posts and Telecommunications Audio and Video department the Third Research Institute of China Electronics Technology Group Corporation

Current methods of image protection based on chaos encryption can only provide security in Human visual system(HVS) level, however they can not provide usage control when the image is opened, printed or exported. To solve this problem, we proposed a novel image digital rights management scheme for Confidential image data security based on encryption and watermark(CIDSEW) with high-level security, usage control and traceability, in which we employed full content image encryption for confidentiality of the image to be protected, and we firstly proposed strict and detailed Usage control(UC) scheme for Confidential image data(CIData) usage password-based authentication, opening times, printing and exporting control. And when the CIData need to delivery or export to other users or domain, we proposed the secure export and misused tracing and detect approach, in which before the ciphered CIData is exported, we decrypted the CIData in a plain mode, and simultaneously we embedded user-identity-related and hardware-related information as robust watermark for traceability and responsibility confirmation. Finally, we evaluated the proposed CIDSEW by groups of variant size image data for security and efficiency,a large amount of groups of experiments manifest the proposed CIDSEW is secure, efficient, pervasive and robust for confident image data protection, usage control and misuse tracing.

关键词： Digital rights management Confidential image data security Encryption Watermark Usage control(UC) Traceability

Optimal bounded control for maximizing reliability of Duhem hysteretic systems

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Applied Mathematics and Mechanics(English Edition) 2015年第10期36卷 1337-1346页

作者： ming XU Xiaoling JIN Yong WANG Zhilong huang College of Metrology and Measurement Engineering China Jiliang University department of Engineering Mechanics Zhejiang University

The optimal bounded control of stochastic-excited systems with Duhem hysteretic components for maximizing system reliability is investigated. The Duhem hysteretic force is transformed to energy-depending damping and stiffness by the energy dissipation balance technique. The controlled system is transformed to the equivalent non- hysteretic system. Stochastic averaging is then implemented to obtain the It5 stochastic equation associated with the total energy of the vibrating system, appropriate for eval- uating system responses. Dynamical programming equations for maximizing system re- liability are formulated by the dynamical programming principle. The optimal bounded control is derived from the maximization condition in the dynamical programming equation. Finally, the conditional reliability function and mean time of first-passage failure of the optimal Duhem systems are numerically solved from the Kolmogorov equations. The proposed procedure is illustrated with a representative example.

关键词： optimal bounded control reliability Duhem hysteretic system stochastic dynamical programming principle

A Video Watermarking DRM Method Based on H.264 Compressed Domain with Low Bit-Rate Increasement

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Chinese Journal of Electronics 2016年第4期25卷 641-647页

It gets more and more important for video copyright protection,it is necessary to provide efficient H.264 compression domain watermarking for video Digital rights management(DRM).A new watermarking method based on H.264 compressed domain is proposed for video DRM,in which the embedding and extracting procedure are performed using the syntactic elements of the compressed bit *** this way,complete decoding is unnecessary in both embedding and extracting *** on the analysis of the time and space,some appropriate sub-blocks are selected for embedding watermarks,increasing watermark robustness while reducing the declination of the visual *** order to avoid bit-rate increasing and strengthen the security of the proposed video watermarking scheme,only a set of nonzero coefficients quantized in different parts of macroblocks is chosen for inserting *** experiment results show the proposed scheme can achieve excellent robustness against some common attacks,the proposed scheme is secure and efficient for video content DRM protection.

关键词： Video watermarking H.264 Temporal quality Compressed domain watermarking

Materials-oriented integrated design and construction of structures in civil engineering—A review

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Frontiers of Structural and Civil Engineering 2022年第1期16卷 24-44页

作者： Xing ming John C.huang Zongjin LI Institute of Applied Physics and Materials Engineering University of MacaoMacao SAR 999078China CHC Engineering LLCFairfaxVA 20030USA

design is a goal-oriented planning activity for creating products,processes,and systems with desired functions through *** is a decision-making exploration:the design outcome may vary greatly depending on the designer’s knowledge and *** design is one type of design philosophy that takes an interdisciplinary and holistic *** civil engineering,structural design is such an activity for creating buildings and ***,structural design in many countries has emphasized a performance-based philosophy that simultaneously considers a structure’s safety,durability,serviceability,and ***,integrated design in civil engineering has become more popular,useful,and ***-oriented integrated design and construction of structures(MIDCS)combine materials engineering and structural engineering in the design stage:it fully utilizes the strengths of materials by selecting the most suitable structural forms and construction *** paper will explore real-world examples of MIDCS,including the realization of MIDCS in timber seismic-resistant structures,masonry arch structures,long-span steel bridges,prefabricated/on-site extruded light-weight steel structures,fiber-reinforced cementitious composites structures,and fiber-reinforced polymer bridge ***,advanced material design methods such as bioinspired design and structure construction technology of additive manufacturing are briefly reviewed and discussed to demonstrate how MIDCS can combine materials and structures.A unified strengthdurability design theory is also introduced,which is a human-centric,interdisciplinary,and holistic approach to the description and development of any civil infrastructure and includes all processes directly involved in the life cycle of the ***,this paper lays out future research directions for further development in the field.

关键词： integrated design and construction fiber-reinforced concrete fiber-reinforced polymer light-weight steel structures digital fabrication composites

On parametric approach of aerial robots' visual navigation

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Journal of Systems Engineering and Electronics 2008年第5期19卷 1010-1016页

作者： Zhou Yu huang Xianlin Jie ming Yin Hang Harbin Inst. of Technology Harbin 150001 P. R. China

In aerial robots＇ visual navigation, it is essential yet very difficult to detect the attitude and position of the robots operated in real time. By introducing a new parametric model, the problem can be reduced from almost unmanageable to be partly solved, though not fully, as per the requirement. In this parametric approach, a multi-scale least square method is formulated first. By propagating as well as improving the parameters down from layer to layer of the image pyramid, a new global feature line can then be detected to parameterize the attitude of the robots. Furthermore, this approach paves the way for segmenting the image into distinct parts, which can be realized by deploying a Bayesian classifier on the picture cell level. Comparison with the Hough transform based method in terms of robustness and precision shows that this multi-scale least square algorithm is considerably more robust to noises. Some discussions are also given.

关键词： parametric model aerial robots visual navigation multi-scale least square.

A Scheduling Optimization Technique Based on Reuse in Spark to defend Against APT Attack

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Tsinghua Science and Technology 2018年第5期23卷 550-560页

作者： Jianchao Tang ming Xu Shaojing Fu Kai huang College of Computer National University of Defense Technology Changsha 410073 China Sate Key Laboratory of Cryptology Beijing 100878 China

Advanced Persistent Threat （APT） attack, an attack option in recent years, poses serious threats to the security of governments and enterprises data due to its advanced and persistent attacking characteristics. To address this issue, a security policy of big data analysis has been proposed based on the analysis of log data of servers and terminals in Spark. However, in practical applications, Spark cannot suitably analyze very huge amounts of log data. To address this problem, we propose a scheduling optimization technique based on the reuse of datasets to improve Spark performance. In this technique, we define and formulate the reuse degree of Directed Acyclic Graphs （DAGs） in Spark based on Resilient Distributed Datasets （RDDs）. Then, we define a global optimization function to obtain the optimal DAG sequence, that is, the sequence with the least execution time. To implement the global optimization function, we further propose a novel cost optimization algorithm based on the traditional Genetic Algorithm （GA）. Our experiments demonstrate that this scheduling optimization technique in Spark can greatly decrease the time overhead of analyzing log data for detecting APT attacks.

关键词： Spark Advanced Persistent Threat (APT) schedule reuse Resilient Distributed Dataset (RDD) Directed Acyclic Graph (DAG) Genetic Algorithm (GA)