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On the unsteady motion and stability of a heaving airfoil in ground effect

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Acta Mechanica Sinica 2011年第2期27卷 164-178页

作者： juan Molina David Angland School of Engineering Sciences University of Southampton Southampton SO17 1BJ UK

This study explores the fluid mechanics and force generation capabilities of an inverted heaving airfoil placed close to a moving ground using a URANS solver with the Spalart-Allmaras turbulence model. By varying the mean ground clearance and motion frequency of the airfoil, it was possible to construct a frequency-height diagram of the various forces acting on the airfoil. The ground was found to enhance the downforce and reduce the drag with respect to freestream. The unsteady motion induces hysteresis in the forces’ behaviour. At moderate ground clearance, the hysteresis increases with frequency and the airfoil loses energy to the flow, resulting in a stabilizing motion. By analogy with a pitching motion, the airfoil stalls in close proximity to the ground. At low frequencies, the motion is unstable and could lead to stall flutter. A stall flutter analysis was undertaken. At higher frequencies, inviscid effects overcome the large separation and the motion becomes stable. Forced trailing edge vortex shedding appears at high frequencies. The shedding mechanism seems to be independent of ground proximity. However, the wake is altered at low heights as a result of an interaction between the vortices and the ground.

关键词： Oscillating airfoil · Flutter · Wing in ground effect · Vortex shedding

Controlled Mean-Field Backward Stochastic Differential Equations with Jumps Involving the Value Function

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Journal of Systems Science & Complexity 2016年第5期29卷 1238-1268页

作者： LI juan MIN Hui School of Mathematics and Statistics Shandong University

This paper discusses mean-field backward stochastic differentiM equations （mean-field BS- DEs） with jumps and a new type of controlled mean-field BSDEs with jumps, namely mean-field BSDEs with jumps strongly coupled with the value function of the associated control problem. The authors first prove the existence and the uniqueness as well as a comparison theorem for the above two types of BSDEs. For this the authors use an approximation method. Then, with the help of the notion of stochastic backward semigroups introduced by Peng in 1997, the authors get the dynamic programming principle （DPP） for the value functions. Furthermore, the authors prove that the value function is a viscosity solution of the associated nonlocal Hamilton-Jacobi-Bellman （HJB） integro-partial differential equation, which is unique in an adequate space of continuous functions introduced by Barles, et al. in 1997.

关键词： Dynamic programming principle (DPP) Hamilton-Jacobi-Bellman (HJB) equation mean-field backward stochastic differential equation (mean-field BSDE) with jump Poisson random measure value function.

Structural and functional analysis of an asymmetric bidirectional promoter in Arabidopsis thaliana

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Journal of Integrative Plant Biology 2015年第2期57卷 162-170页

作者： Shi-juan Liu Qiu-juan Yue Wei Zhang Key Laboratory of Plant Cell Engineering and Germplasm Innovation Ministry of Education School of Life Sciences Shandong University College of Life Science Qufu Normal University

Bidirectional promoters are relatively abundant in eukaryotic genomes, suggesting that they have an important biological significance. As yet, few of these promoters have been characterized in detail. Here, using a promoter：：GUS transgene approach has revealed that the intergenic region of Arabidopsis thaliana divergent genes At1g71850 and At1g71860 is an asymmetric bidirectional promoter, which exhibits an orientation-dependent expression profile. The strength of the forward promoter was greater than that of the reverse promoter, and their tissue specificities were not identical. Deletion analyses revealed that this bidirectional promoter could be divided into three functional regions. The basal level and tissue specificity of the promoter in the reverse orientation were regulated positively by region II and negatively by region III, whereas promoter activity in the forward orientation was regulated negatively by region II and positively by region I. Thus the 52-bp stretch of region II had a dual function, enhancing expression in the reverse orientation and suppressing it in the forward orientation. These results demonstrated that the activity of the At1g71850-At1g71860 bidirectional promoter was modulated by complex interactions between both positive and negative cis-acting elements. These findings will enhance our understanding of the regulatory mechanisms of plant bidirectional promoters.

关键词： GUS (β-glucuronidase) positive and negative regulatoryelement promoter strength tissue-specific expression

Meniscus-Assisted Solution Printing Enables Cocrystallization in Poly(3-alkylthiophene)-based Blends for Field-Effect Transistors

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Chinese Journal of Polymer Science 2023年第8期41卷 1269-1276,I0009页

作者： Shu-Yin Zhu juan Peng State Key Laboratory of Molecular Engineering of Polymers Department of Macromolecular ScienceFudan UniversityShanghai 200438China

The formation of cocrystallization in two various conjugated components may endow the newly formed conjugated cocrystals with multiple functionalities and improved charge transport ***,compared to conjugated small molecules,this strategy is rather limitedly realized in conjugated ***,a simple meniscus-assisted solution printing(MASP)strategy is utilized to achieve the cocrystallization in the blends of two conjugated polymers,i.e.,poly(3-hexylthiophene)(P3HT)and poly(3-octylthiophene)(P3OT),and the cocrystalline structures are correlated closely to their charge *** P3HT/P3OT blends phase separate and crystallize individually in their drop-cast thin *** subjecting the P3HT/P3OT blended solution to MASP,the confined solvent evaporation between two nearly parallel plates triggers them to cocrystallize progressively when accelerating the moving lower *** cocrystallization kinetics and the changes in P3HT/P3OT molecular structures are ***,these different crystalline structures of P3HT/P3OT blends are applied in organic fieldeffect transistors,imparting the cocrystallization-enhanced charge transport than respective P3HT and P3OT crystal *** MASP method can be extended to craft cocrystals of other conjugated polymer blends for their diverse optoelectronic applications.

关键词： Conjugated polymer blends Polythiophene Cocrystallization Charge mobility Meniscus-assisted solution printing

Sparse recovery method for far-field and near-field sources localization using oblique projection

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The Journal of China Universities of Posts and Telecommunications 2013年第3期20卷 90-96页

作者： WANG Bo ZHAO Yan-ping LIU juan-juan College of Communication Engineering Jilin University

In this paper, we propose a novel source localization method to estimate parameters of arbitrary field sources, which may lie in near-field region or far-field region of array aperture. The proposed method primarily constructs two special spatial-temporal covariance matrixes which can avoid the array aperture loss, and then estimates the frequencies of signals to obtain the oblique projection matrixes. By using the oblique projection technique, the covariance matrixes can be transformed into several data matrixes which only contain single source information, respectively. At last, based on the sparse signal recovery method, these data matrixes are utilized to solve the source localization problem. Compared with the existing typical source localization algorithms, the proposed method improves the estimation accuracy, and provides higher angle resolution for closely spaced sources scenario. Simulation results are given to demonstrate the performance of the proposed algorithm.

关键词： array signal processing near-field far-field sparse signal recovery oblique projection

Medical Sign Recognition of Lung Nodules Based on Image Retrieval with Semantic Features and Supervised Hashing

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Journal of Computer Science & Technology 2017年第3期32卷 457-469页

作者： juan-juan Zhao Ling Pan Peng-Fei Zhao Kiao-Xian Tang College of Computer Science and Technology Taiyuan University of Technology Taiyuan 030024 China Shanxi Provincial People's Hospital Taiyuan 030012 China

Sign recognition is important for identifying benign and malignant nodules. This paper proposes a new sign recognition method based on image retrieval for lung nodules. First, we construct a deep learning framework to extract semantic features that can effectively represent sign information. Second, we translate the high-dimensional image features into compact binary codes with principal component analysis （PCA） and supervised hashing. Third, we retrieve similar lung nodule images with the presented adaptive-weighted similarity calculation method. Finally, we recognize nodule signs from the retrieval results, which can also provide decision support for diagnosis of lung lesions. The proposed method is validated on the publicly available databases： lung image database consortium and image database resource initiative （LIDC-IDRI） and lung computed tomography （CT） imaging signs （LISS）. The experimental results demonstrate our retrieval method substantially improves retrieval performance compared with those using traditional Hamming distance, and the retrieval precision can achieve 87.29%when the length of hash code is 48 bits. The entire recognition rate on the basis of the retrieval results can achieve 93.52%. Moreover, our method is also effective for real-life diagnosis data.

关键词： lung nodule medical sign recognition image retrieval supervised hashing adaptive weight

A novel simple procedure to consider seismic soil structure interaction effects in 2D models

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Earthquake Engineering and Engineering Vibration 2014年第3期13卷 535-543页

作者： juan Diego Jaramillo juan David Gómez Doriam Restrepo Santiago Rivera Universidad EAFIT Medellín Colombia INTEGRAL S.A Medellín Colombia

A method is proposed to estimate the seismic soil-structure-interaction （SSI） effects for use in engineering practice. It is applicable to 2D structures subjected to vertically incident shear waves supported by homogenous half-spaces. The method is attractive since it keeps the simplicity of the spectral approach, overcomes some of the difficulties and inaccuracies of existing classical techniques and yet it considers a physically consistent excitation. This level of simplicity is achieved through a response spectra modification factor that can be applied to the free-field 5%-damped response spectra to yield design spectral ordinates that take into account the scattered motions introduced by the interaction effects. The modification factor is representative of the Transfer Function （TF） between the structural relative displacements and the free- field motion, which is described in terms of its maximum amplitude and associated frequency. Expressions to compute the modification factor by practicing engineers are proposed based upon a parametric study using 576 cases representative of actual structures. The method is tested in 10 cases spanning a wide range of common fundamental vibration periods.

关键词： seismic soil structure interaction simplified procedures modified response spectra

A Note on Extreme Points in Dual Spaces

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Acta Mathematica Sinica,English Series 2013年第3期29卷 471-476页

作者： juan Francisco MENA-JURADO juan Carlos NAVARRO-PASCUAL Departamento de Análisis Matemático Facultad de Ciencias Universidad de Granada Departamento de lgebra y Análisis Matemático Universidad de Almería

Given a normed space X it can be easily proven that every extreme point in Bx＊, the unit ball of X＊, is the restriction of an extreme point in Bx Our purpose is to study when the restrictions of extreme points in B... 详细信息

关键词： Extreme point Ll-predual M-ideal

Large Deviations for Hitting Times of a Random Walk in Random Environment on a Strip

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Acta Mathematica Sinica,English Series 2014年第3期30卷 395-410页

作者： Mei juan ZHANG School of Statistics and Mathematics Central University of Finance and Economics

We consider a random walk in random environment on a strip, which is transient to the right. The random environment is stationary and ergodic. By the constructed enlarged random environment which was first introduced by Goldsheid （2008）, we obtain the large deviations conditioned on the environment （in the quenched case） for the hitting times of the random walk.

关键词： Random walk in random environment strip large deviations quenched enlarged randomenvironment