Dayong J.,Xian Research Institute of High Technology
Journal of biomedicine & biotechnology | Year: 2011
A novel biodiesel named rapeseed oil monoester of ethylene glycol monomethyl ether is developed. This fuel has one more ester group than the traditional biodiesel. The fuel was synthesized and structurally identified through FT-IR and P(1P)H NMR analyses. Engine test results show that when a tested diesel engine is fueled with this biodiesel in place of 0# diesel fuel, engine-out smoke emissions can be decreased by 25.0%-75.0%, CO emissions can be reduced by 50.0%, and unburned HC emissions are lessened significantly. However, NOx emissions generally do not change noticeably. In the area of combustion performance, both engine in-cylinder pressure and its changing rate with crankshaft angle are increased to some extent. Rapeseed oil monoester of ethylene glycol monomethyl ether has a much higher cetane number and shorter ignition delay, leading to autoignition 1.1°CA earlier than diesel fuel during engine operation. Because of certain amount of oxygen contained in the new biodiesel, the engine thermal efficiency is improved 13.5%-20.4% when fueled with the biodiesel compared with diesel fuel.
Hu X.,Harbin Institute of Technology |
Hu X.,Xian Research Institute of High Technology |
Wu L.,Harbin Institute of Technology |
Hu C.,Xian Research Institute of High Technology |
Gao H.,Harbin Institute of Technology
Journal of the Franklin Institute | Year: 2012
This paper is concerned with the adaptive sliding mode control (ASMC) design problem for a flexible air-breathing hypersonic vehicle (FAHV). This problem is challenging because of the inherent couplings between the propulsion system, the airframe dynamics and the presence of strong flexibility effects. Due to the enormous complexity of the vehicle dynamics, only the longitudinal model is adopted for control design in the present paper. A linearized model is established around a trim point for a nonlinear, dynamically coupled simulation model of the FAHV, then a reference model is designed and a tracking error model is proposed with the aim of the ASMC problem. There exist the parameter uncertainties and external disturbance in the model, which are not necessary to satisfy the so-called matched condition. A robust sliding surface is designed, and then an adaptive sliding mode controller is designed based on the tracking error model. The proposed controller can drive the error dynamics onto the predefined sliding surface in a finite time, and guarantees the property of asymptotical stability without the information of upper bound of uncertainties as well as perturbations. Finally, simulations are given to show the effectiveness of the proposed control methods. © 2011 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
Hao L.,Xian Research Institute of High Technology |
Yao M.,Xian Research Institute of High Technology
Simulation Modelling Practice and Theory | Year: 2011
A novel step tracking algorithm for Ku-band mobile satellite communication that will be used in mobile direct broadcasting satellite (DBS) reception is presented in this paper. The main idea for this improved step tracking algorithm is to use a highly efficient simultaneous perturbation approximation to the gradient using only two noisy measurements of the received signal strength. The antenna beam can be steered to coincide with the direction of DBS in both azimuth and elevation planes simultaneously in the direction of gradient using the novel step tracking algorithm. Computer simulations verify this improved step tracking algorithm is indeed robust and effective. © 2010 Elsevier B.V. All rights reserved.
Kong X.,Xian Research Institute of High Technology |
Hu C.,Xian Research Institute of High Technology |
Han C.,Xian Jiaotong University
IEEE Transactions on Signal Processing | Year: 2012
The dual purpose principal and minor subspace gradient flow can be used to track principal subspace (PS) and if altered simply by the sign, it can also serve as a minor subspace (MS) trackor. This is of practical significance in the implementations of algorithms. In this paper, a unified information criterion is proposed and a dual purpose principal and minor subspace gradient flow is derived based on the information criterion. In this dual purpose gradient flow, the weight matrix length is self-stabilizing, i.e., moving towards unit length in each learning step. The energy function associated with the dual purpose gradient flow for tracking PS and MS is given, and it exhibits a unique global minimum attained if and only if its state matrices span the PS or MS of the autocorrelation matrix of a vector data stream. The other stationary points of its energy function are (unstable) saddle points. The proposed dual purpose gradient flow can efficiently track an orthonormal basis of the PS or MS, which is illustrated through simulation experiments. © 2006 IEEE.
Zhang Z.,Xian Research Institute of High Technology |
Liu X.,Xian Research Institute of High Technology |
Wang X.,Xian Research Institute of High Technology |
Wu Y.,HIGH-TECH |
Li R.,Xian Research Institute of High Technology
Journal of Alloys and Compounds | Year: 2012
Nd-Co-substituted M-type strontium hexaferrites were prepared by sol-gel-autocombustion method. Crystalline structure, morphology, magnetic properties, and microwave absorption properties of Sr 1-xNd xFe 12-xCo xO 19 (x = 0-0.4) were studied via X-ray diffraction, scanning electron microscope, vibrating sample magnetometer, and vector network analyzer, respectively. Single-phase M-type strontium hexaferrites, with a chemical composition of Sr 1-xNd xFe 12-xCo xO 19 (x = 0-0.3), were formed by being heated at 1200 ̊C for 3 h in air. Saturation magnetization and coercivity reached a maximum at x = 0.2. For samples with x = 0.2, a minimum reflection loss of -22 dB was obtained at 16.2 GHz for a layer of 1.9 mm in thickness. The reflection loss of Sr 0.8Nd 0.2Fe 11.8Co 0.2O 19 ferrite (1.5-3.0 mm in thickness) is less than -10 dB over the range of 9.8-18 GHz. It indicates that the substituted Nd-Co can greatly improve the microwave absorption properties of SrFe 12O 19 hexaferrites. © 2011 Elsevier Ltd. All rights reserved. All rights reserved.