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Overcoming doping bottleneck by using surfactant and strain

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Frontiers of Materials Science 2011年第4期5卷 335-341页

作者： Junyi ZHU Su-huai WEI National Renewable Energy Laboratory Golden Colorado 80401 USA

Overcoming the doping bottleneck in semiconductors, especially in wide band gap semiconductors, has been a challenge in semiconductor physics for many years. In this paper, we review some recent progresses in enhancing doping by surfactant and strain. We show that surfactant and strain are two effective approaches to enhance dopant solubility in epitaxial growth. The surfactant can introduce an energy level deep inside the band gap, making the host compound less stable, thus lower the formation energy of the intentional dopant. The strain enhanced doping is based on the observation that dopant induces volume change in the host. If the external strain is in the same direction as the dopant induced volume change, the formation energy of the dopant is reduced. This effect can be used to tune doping sites, thus doping type, in a host. A hybrid method to both include strain and surfactant is proposed, which can be a promising general method to further enhance doping.

关键词： semiconductor surfactant strain doping band gap

Concentrated Trading and the Survival of Overconfident Traders

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Acta Mathematicae Applicatae Sinica 2019年第4期35卷 753-760页

作者： huai-nian ZHANG De-qing ZHOU Mathematics School & Institute Jilin University Changchun 130012 China Department of Mathematics and Physics Beijing Institute of Petrochemical Technology Beijing 102617 China School of Finance Central University of Finance and Economics Beijing 100081 China

We build a strategic trading model where the overconfident trader earns more than the rational trader and the mechanism for this result differs from that of Kyle and Wang(1997). In this paper, discretionary and nondiscretionary liquidity traders coexist. The overconfident insider is less worried by the market maker and thus induces a lower liquidity cost. In this way, he attracts all the trading from the discretionary liquidity traders, which enables the survival of the overconfident trader.

关键词： strategic trading concentrated trading overconfidence

3D MHD simulation of the double-gradient instability of the magnetotail current sheet

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Science China(Technological Sciences) 2018年第9期61卷 1364-1371页

作者： DUAN AiYing ZHANG huai LU Hao Yu Key Laboratory of Computational Geodynamics University of Chinese Academy of Sciences State Key Laboratory of Space Weather Chinese Academy of Sciences School of Space and Environment Beihang University

Flapping motion of the current sheet(CS) is an important physical process in the Earth's magnetotail. The magnetic doublegradient model, which includes both the instability and wave modes, offers a reasonable explanation for the exciting and propagation of the flapping wave. In this paper, we apply an advanced numerical magnetohydrodynamic(MHD) scheme(conservation element and solution element(CESE)-MHD) to simulate the magnetic double-gradient instability in an idealized current sheet that mimics the magnetotail configuration. We initialize the simulations with a numerically relaxed magnetotail equilibrium, in which the normal component of the magnetic field has a tailward gradient. It is confirmed in our simulation that the instability develops in the current layer. The growth rate of the instability yielded from the simulation is very close to the prediction of theory, with a relative deviation of only ten percent. The results demonstrate that the CESE-MHD scheme is very powerful in numerical study of the double-gradient mechanism of the CS flapping mode, and can be used for further investigations of the flapping motion in more realistic CS configurations.

关键词： Earth's magnetotail current sheet flapping magnetohydrodynamic numerical simulation

Cryptographic protocol security analysis based on bounded constructing algorithm

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Science in China(Series F) 2006年第1期49卷 26-47页

作者： LI Xianxian huai Jinpeng School of Computer Beihang University Beijing 100083 China

An efficient approach to analyzing cryptographic protocols is to develop automatic analysis tools based on formal methods. However, the approach has encountered the high computational complexity problem due to reasons that participants of protocols are arbitrary, their message concurrent. We propose an efficient structures are complex and their executions are automatic verifying algorithm for analyzing cryptographic protocols based on the Cryptographic Protocol Algebra （CPA） model proposed recently, in which algebraic techniques are used to simplify the description of cryptographic protocols and their executions. Redundant states generated in the analysis processes are much reduced by introducing a new algebraic technique called Universal Polynomial Equation and the algorithm can be used to verify the correctness of protocols in the infinite states space. We have implemented an efficient automatic analysis tool for cryptographic protocols, called ACT-SPA, based on this algorithm, and used the tool to check more than 20 cryptographic protocols. The analysis results show that this tool is more efficient, and an attack instance not offered previously is checked by using this tool.

关键词： cryptographic protocol formal analysis security verification.

Preprocessing photospheric vector magnetograms for nonlinear force-free field extrapolation of the global corona

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Research in Astronomy and Astrophysics 2018年第7期18卷 113-124页

作者： Ai-Ying Duan huai Zhang Key Laboratory of Computational Geodynamics University of Chinese Academy of Sciences SIGMA Weather Group State Key Laboratory for Space Weather National Space Science Center Chinese Academy of Sciences Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology

Nonlinear force-free magnetic field （NLFFF） extrapolation based on the observed photo- spheric magnetic field is the most important method to obtain the coronal magnetic field nowadays. However, raw photospheric magnetograms contain magnetic forces and small-scale noises, and fail to be consistent with the force-free assumption of NLFFF models. The procedure for removing the forces and noises in observed data is called preprocessing. In this paper, we extend the preprocessing code of Jiang ＆ Feng to spherical coordinates for a full sphere. We first smooth the observed data with Gaussian smoothing, and then split the smoothed magnetic field into a potential field and a non-potential field. The potential part is computed by a numerical potential field model, and the non-potential part is prepro- cessed using an optimization method to minimize the magnetic forces and magnetic torques. Applying the code to synoptic charts of the vector magnetic field from SDO/HMI, we find it can effectively reduce the noises and forces, and improve the quality of data for a better input which will be used for NLFFF extrapolations applied to the global corona.

关键词： magnetic fields - magnetohydrodynamics (MHD) - methods numerical - Sun corona

Collection efficiency in a three-dimensional randomly arranged dual-layer granular bed filter

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Particuology 2020年第2期18卷 88-94页

作者： Junlin Chen Xunfeng Li Xiulan huai Jingzhi Zhou Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The dual-layer granular bed filter packed with randomly arranged granules was simulated to study the effects of bed depth of the lower layer of fine granules and the inlet gas velocity on the collection *** computational results show that the collection efficiency is much better from this granular bed than a single-layer granular bed,especially for particle diameters of 1-10μ*** inlet gas velocity has less effect on the grade collection efficiency of the dual-layer granular bed than of the single-layer granular *** dual-layer granular bed provides a high collection efficiency and low pressure *** relationship between the grade collection efficiency and the Stokes number(St)based on the inlet gas velocity is *** St is below a threshold,the grade collection efficiency remains stable;if St is in value above threshold,the grade collection efficiency increases linearly with lg(St).As the bed depth of the lower layer of fine granules increases,the threshold for St shifts forward.

关键词： Dual-layer granular bed filter Pressure drop Grade collection efficiency Stokes number

Coupling dynamic characteristics of simplified model for tethered satellite system

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Acta Mechanica Sinica 2021年第8期37卷 1245-1254,I0001页

作者： Weipeng Hu Yulu huai Mengbo Xu Zichen Deng School of Civil Engineering and Architecture Xi’an University of TechnologyXi’an 710048China State Key Laboratory of Eco?Hydraulics in Northwest Arid Region of China Xi’an University of TechnologyXi’an 710048China School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China

connecting wires are the main manifestations of the coupling dynamic effects on the orbit evolution,the attitude adjusting and the flexible vibration of the tethered satellite *** investigate attitude evolution of the tethered system and the mechanical energy transfer/loss characteristics between the bus system and the solar sail via the connecting wires,a structure-preserving method is developed in this *** the tethered satellite system as a composite structure consisting of a particle and a flexible thin panel connected by four special springs,the dynamic model is deduced via the Hamiltonian variational principle ***,a structure-preserving approach that connects the symplectic Runge-Kutta method and the multi-symplectic method is *** excellent structure-preserving property of the numerical scheme constructed is presented to illustrate the credibility of the numerical results obtained by the constructed structure-preserving *** the numerical results on the mechanical energy transfer/loss in the composite structure,it can be found that the mechanical energy transfer tendency in the tethered system is dependent of the initial attitude angle of the system while the total mechanical energy loss of the system is almost independent of the initial attitude *** addition,the special stiffness range of the spring is found in the attitude angle evolution of the system,which provides a structural parameter design window for the connecting wires,that is,the duration needed to arrive the stable attitude is short when the stiffness of the wire is designed in this special range.

关键词： Tethered satellite system Non-smooth model Structure-preserving approach Hamiltonian

A Study of Ca-Mg Silicate Crystalline Glazes——An Analysis on Forms of Crystals

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Chemical Research in Chinese Universities 2004年第2期20卷 200-204页

作者： LIUPei-de YUPing-li WUJi-huai InstituteofMaterialPhysicalChemistry HuaqiaoUniversityQuanzhou362011P.R.China

In the study on Ca-Mg silicate crystalline glazes, we found some disequilibrated crystallization phenomena, such as non-crystallographic small angle forking and spheroidal growth, parasitism and wedging-form of crystals, dendritic growth, secondary nucleation, etc. Those phenomena possibly resulted from two factors: (1) partial temperature gradient, which is caused by heat asymmetry in the electrical resistance furnace, when crystals crystalize from silicate melt; (2) constitutional supercooling near the surface of crystals. The disparity of disequilibrated crystallization phenomena in different main crystalline phases causes various morphological features of the crystal aggregates. At the same time, disequilibrated crystallization causes great stress retained in the crystals, which results in cracks in glazes when the temperature drops. According to the results, the authors analyzed those phenomena and displayed correlative figures and data.

关键词： Crystalline glaze Costitutional supercooling Heat dynamical condition Disequilibrated crystallization Morphological feature of crystal aggregates

A revisit to MacKay algorithm and its application to deep network compression

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Frontiers of Computer Science 2020年第4期14卷 39-54页

作者： Chune LI Yongyi MAO Richong ZHANG Jinpeng huai School of Computer Science and Engineering Beihang UniversityBeijing100191China School of Electrical Engineering and Computer Science University of OttawaOttawaK1N6N5Canada

An iterative procedure introduced in MacKay’s evidence framework is often used for estimating the hyperparameter in empirical *** with the use of a particular form of prior,the estimation of the hyperparameter reduces to an automatic relevance determination model,which provides a soft way of pruning model *** the effectiveness of this estimation procedure,it has stayed primarily as a heuristic to date and its application to deep neural network has not yet been *** paper formally investigates the mathematical nature of this procedure and justifies it as a well-principled algorithm framework,which we call the MacKay *** an application,we demonstrate its use in deep neural networks,which have typically complicated structure with millions of parameters and can be pruned to reduce the memory requirement and boost computational *** experiments,we adopt MacKay algorithm to prune the parameters of both simple networks such as LeNet,deep convolution VGG-like networks,and residual netowrks for large image classification *** results show that the algorithm can compress neural networks to a high level of sparsity with little loss of prediction accuracy,which is comparable with the state-of-the-art.

关键词： deep learning MacKay algorithm model compression neural network