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Chinese Journal of Chemical Engineering 2016年第11期24卷 1522-1526页

作者： Changhai Li Dongmei jia Department of Chemical Engineering Binzhou University Binzhou 256603 China Research Center of Chemical Engineering and Technology Binzhou University Binzhou 256603 China

Commercial grade weakly basic resin D301 was impregnated with iron through a simple method using ferric chloride. Experiments for single, bisolute and trinary competitive adsorption were carried out to investigate the adsorption behavior of 2-naphthalenesulfonic acid(NSA), sulfuric acid and sulfurous acid from their solution at 298 K onto the novel hybrid iron impregnated D301(Fe-D301). Adsorption affinity of NSA on Fe-D301 was found to be much higher than that of sulfuric acid, while adsorption affinity of sulfuric acid was slightly higher than that of sulfurous acid. The data of single-solute adsorption were fitted to the Langmuir model and the Freundlich adsorption model. The non-ideal competitive adsorbed model coupled with the single-solute adsorption models were used to predict the bisolute and trinary-solute competitive adsorption equilibria. The NICM coupled with the Langmuir model yields the favorable representation of the bisolute and trinary-solute competitive adsorption behavior.

关键词： 2-naphthalenesulfonic acid Hybrid iron impregnated D301 Adsorption Non-ideal competitive adsorbed model Model Equilibrium

A QR DECOMPOSITION BASED SOLVER FOR THE LEAST SQUARES PROBLEMS FROM THE MINIMAL RESIDUAL METHOD FOR THE SYLVESTER EQUATION

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Journal of Computational Mathematics 2007年第5期25卷 531-542页

作者： Zhongxiao jia Yuquan Sun Department of Mathematical Sciences Tsinghua University Beijing 100084 China

Based on the generalized minimal residual （GMRES） principle, Hu and Reichel proposed a minimal residual algorithm for the Sylvester equation. The algorithm requires the solution of a structured least squares problem. They form the normal equations of the least squares problem and then solve it by a direct solver, so it is susceptible to instability. In this paper, by exploiting the special structure of the least squares problem and working on the problem directly, a numerically stable QR decomposition based algorithm is presented for the problem. The new algorithm is more stable than the normal equations algorithm of Hu and Reichel. Numerical experiments are reported to confirm the superior stability of the new algorithm.

关键词： Least-squares solution Preconditioning Generalized singular value decomposition.

Machine Learning for Many-Body Localization Transition

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Chinese Physics Letters 2020年第8期37卷 12-18页

作者： Wen-jia Rao School of Science Hangzhou Dianzi UniversityHangzhou 310027China

We employ the methods of machine learning to study the many-body localization(MBL)transition in a 1D random spin *** using the raw energy spectrum without pre-processing as training data,it is shown that the MBL transition point is correctly predicted by the *** structure of the neural network reveals the nature of this dynamical phase transition that involves all energy levels,while the bandwidth of the spectrum and nearest level spacing are the two dominant patterns and the latter stands out to classify *** further use a comparative unsupervised learning method,i.e.,principal component analysis,to confirm these results.

关键词： spectrum transition Transition

SAR imaging method based on coprime sampling and nested sparse sampling

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Journal of Systems Engineering and Electronics 2015年第6期26卷 1222-1228页

作者： Hongyin Shi Baojing jia School of Information Science and Engineering Yan Shan University

As the signal bandwidth and the number of channels increase, the synthetic aperture radar （SAR） imaging system produces huge amount of data according to the Shannon-Nyquist theorem, causing a huge burden for data transmission. This paper concerns the coprime sampl which are proposed recently but ng and nested sparse sampling, have never been applied to real world for target detection, and proposes a novel way which utilizes these new sub-Nyquist sampling structures for SAR sampling in azimuth and reconstructs the data of SAR sampling by compressive sensing （CS）. Both the simulated and real data are processed to test the algorithm, and the results indicate the way which combines these new undersampling structures and CS is able to achieve the SAR imaging effectively with much less data than regularly ways required. Finally, the influence of a little sampling jitter to SAR imaging is analyzed by theoretical analysis and experimental analysis, and then it concludes a little sampling jitter have no effect on image quality of SAR.

关键词： synthetic aperture radar (SAR) imaging compressivesensing coprime sampling nested sparse sampling.

Decentralized adaptive sliding mode control of a space robot actuated by control moment gyroscopes

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Chinese Journal of Aeronautics 2016年第3期29卷 688-703页

作者： jia Yinghong Xu Shijie School of Astronautics Beihang University

An adaptive sliding mode control （ASMC） law is proposed in decentralized scheme for trajectory tracking control of a new concept space robot. Each joint of the system is a free ball joint capable of rotating with three degrees of freedom （DOF）. A cluster of control moment gyroscopes （CMGs） is mounted on each link and the base to actuate the system. The modified Rodrigues parameters （MRPs） are employed to describe the angular displacements, and the equations of motion are derived using Kane＇s equations. The controller for each link or the base is designed sep- arately in decentralized scheme. The unknown disturbances, inertia parameter uncertainties and nonlinear uncertainties are classified as a ＂lumped＂ matched uncertainty with unknown upper bound, and a continuous sliding mode control （SMC） law is proposed, in which the control gain is tuned by the improved adaptation laws for the upper bound on norm of the uncertainty. A gen- eral amplification function is designed and incorporated in the adaptation laws to reduce the control error without conspicuously increasing the magnitude of the control input. Uniformly ultimate boundedness of the closed loop system is proved by Lyapunov＇s method. Simulation results based on a three-link system verify the effectiveness of the proposed controller.

关键词： Adaptation law Ball joint Control moment gyroscopes Sliding mode control Space robot Trajectory tracking

Experimental study of wave propagation characteristics on a simplified coral reef

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Journal of Hydrodynamics 2020年第2期32卷 385-397页

作者： jia-yi Xu Shu-xue Liu Jin-xuan Li Wei jia State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian116024China

The wave transformation over slope topography is widely studied,but most of studies are for common coastal *** paper presents an experimental study of 2-D regular and irregular wave transformations on a simplified coral reef with a steep slope of 1:5 and a horizontal reef flat,focusing on the characteristics of the waves that break on the reef *** analyzed results show that the estimates of the wave breaking made by using the well-known previous formulae do not agree completely with the experimental *** the waves break on a reef flat,the relative breaking wave height(H/d)b is related to the incident deep-water wave steepness and the relative water depth db/***,a new criterion for breaking waves on a reef flat is ***,in view of the fact that the local Ursell number is commonly used to parameterize the wave nonlinearity,the relationships among the skewness,the asymmetry,and the local Ursell number are also *** data confirm that when the Ursell number is greater than 30,the absolute values of the skewness and the asymmetry on a reef flat are greater than those on a steep slope.

关键词： Coral reef bathymetry wave breaking wave height attenuation representative wave parameter nonlinear parameters

Ultrawide-band radar imagery from multiple incoherent frequency subband measurements

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Journal of Systems Engineering and Electronics 2011年第3期22卷 398-404页

作者： Xiaojian Xu jia Li School of Electronic and Information Engineering Beihang UniversityBeijing 100191P.R.China Department of Electrical Computer and Systems EngineeringRensselaer Polytechnic InstituteTroy NY12180USA

The problem of combined radar imagery from multiple sparse frequency subbands initially incoherent to each other is of practical importance for radar target discrimination.A new coherent processing technique based on probability density analysis of the subband data is proposed,which is applicable for radar imaging from measurements of two or more initially incoherent radar *** coherence parameters for both amplitude and phase are obtained by combining modern spectral analysis with probability density *** major advantage of the proposed technique lies in that it enables much more robust cohering for the sparse subband data of real-world complex targets.

关键词： radar imagery coherent processing subband spectral analysis.

Research for patient benefit： an interview with Dr. Alim Louis Benabid

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Science Bulletin 2017年第24期62卷 1619-1621页

作者： Xuming jia Science China Press Beijing 100717 China

Dr. Alim Louis Benabid is a world-renowned French neurosurgeon who has had a global impact on the development of deep brain stimulation （DBS） for Parkinson＇s disease （PD） and other movement disorders. Dr. Benabid was awarded the 2014 Albert Lasker Award in Clinical Medicine and the 2015 Breakthrough Price. DBS, which delivers constant stimulation to small targets in the brain, is currently the most effective neurosurgical procedure for restoring patients＇ motor function. Since marketing approval for the use of DBS as a PD treatment was granted in Europe in 1998, DBS has been administered to over 150,000 patients, and it has become a standard treatment worldwide.

关键词： Research for patient benefit an interview Dr. Alim Louis Benabid

Thermoelastic analysis of multiple defects with the extended finite element method

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Acta Mechanica Sinica 2016年第6期32卷 1123-1137页

作者： Honggang jia Yufeng Nie School of Mathematics and Statistics Xuchang University School of Science Northwestern Polytechnical University

In this paper, the extended finite element method (XFEM) is adopted to analyze the interaction between a single macroscopic inclusion and a single macroscopic crack as well as that between multiple macroscopic or microscopic defects under thermal/mechanical load. The effects of different shapes of multiple inclusions on the material thermomechanical response are investigated, and the level set method is coupled with XFEM to analyze the interaction of multiple defects. Further, the discretized extended finite element approximations in relation to thermoelastic problems of multiple defects under displacement or temperature field are given. Also, the interfaces of cracks or materials are represented by level set functions, which allow the mesh assignment not to conform to crack or material interfaces. Moreover, stress intensity factors of cracks are obtained by the interaction integral method or the M-integral method, and the stress/strain/stiffness fields are simulated in the case of multiple cracks or multiple inclusions. Finally, some numerical examples are provided to demonstrate the accuracy of our proposed method.

关键词： Multiple defects Stress intensity factors extended finite element method (XFEM) Thermoelastic

Numerical Investigation of the Interaction between Mainstream and Tip Shroud Leakage Flow in a 2-Stage Low Pressure Turbine

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Journal of Thermal Science 2014年第3期23卷 215-222页

作者： jia Wei LIU Huoxing National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power Engineering Beihang University

The pressing demand for future advanced gas turbine requires to identify the losses in a turbine and to understand the physical mechanisms producing them. In low pressure turbines with shrouded blades, a large portion of these losses is generated by tip shroud leakage flow and associated interaction. For this reason, shroud leakage losses are generally grouped into the losses of leakage flow itself and the losses caused by the interaction between leakage flow and mainstream. In order to evaluate the influence of shroud leakage flow and related losses on turbine performance, computational investigations for a 2-stage low pressure turbine is presented and discussed in this paper. Three dimensional steady multistage calculations using mixing plane approach were performed including detailed tip shroud geometry. Results showed that turbines with shrouded blades have an obvious advantage over unshrouded ones in terms of aerodynamic performance. A loss mechanism breakdown analysis demonstrated that the leakage loss is the main contributor in the first stage while mixing loss dominates in the second stage. Due to the blade-to-blade pressure gradient, both inlet and exit cavity present non-uniform leakage injection and extraction. The flow in the exit cavity is filled with cavity vortex, leakage jet attached to the cavity wall and recirculation zone induced by main flow ingestion. Furthermore, radial gap and exit cavity size of tip shroud have a major effect on the yaw angle near the tip region in the main flow. Therefore, a full calculation of shroud leakage flow is necessary in turbine performance analysis and the shroud geometric features need to be considered during turbine design process.

关键词： tip shroud leakage flow entropy rise low pressure turbine aerodynamic loss