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Experimental Study on Geometry Characteristics of Turbulent Premixed Flames for Natural Gas/Air Mixtures

Journal of Thermal Science 2025年第1期34卷 268-282页

作者： ZHENG Weilin WANG Qijiao XIAO Huahua CHEN Xiaoxiao XIE Fan ZENG Wen Liaoning Key lab of Advanced Test Technology for aerospace Propulsion System Shenyang Aerospace University State Key laboratory of Fire Science University of science and Technology of China AVIC Shenyang Aircraft Design and Research Institute

In this study,focusing on the geometry characteristics of spherical expanding flame,the turbulent premixed flames of natural gas/air mixtures were investigated in a fan-stirred turbulent *** effects of initial temperature（T=300-400 K）,initial pressure（P=0.1-0.3 MPa）,turbulence intensity（u'=1.0-2.7 m/s）,oxygen volumetric percentage(φ（O2）=15%-21%) and carbon dioxide volumetric percentage(φ（CO2）=0-20%)were delved *** flame profile under the Cartesian coordinate system was derived from the schlieren images taken by the high-speed ***,from both macroscopic and microscopic perspectives,the influence of experimental conditions on the flame geometry characteristics was explored through flame front extraction,wavelet decomposition and network *** results demonstrate that for significant flame wrinkling,changes in species concentrations and turbulence intensity have more pronounced effects on the flame wrinkling *** wrinkling of the flame front maintains a certain degree of similarity,as evidenced by the locally concentrated distribution of the angles of the maximum fluctuation *** disturbance energy under large-scale（D6-D8） disturbances exhibits relatively high values with a similar trend,exerting a significant impact on the geometry characteristics of the flame *** peaks of correlation degree are scattered either with the decomposition scale or the development of flame radius,indicating no linear correlation between different detail ***,the probability distribution of node degrees in key wrinkled regions exhibits different trends with that of large-scale wrinkling and disturbance energy,especially with changes in initial *** occurs because the number of key wrinkles varies based on the perturbation's strength or the region's ***,an increase in the fluctuation frequency of the flame's local radius may not necessarily lead to an increase in the number of key folded regions.

关键词： fan-stirred turbulent combustor geometry characteristics large-scale wrinkling network topology wavelet decomposition

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Evidential combination of augmented multi-source of information based on domain adaptation

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Science China(Information Sciences) 2020年第11期63卷 38-55页

作者： Linqing HUANG Zhunga LIU Quan PAN Jean DEZERT School of Automation Northwestern Polytechnical University onera-the french aerospace lab

In the applications of domain adaptation(DA), there may exist multiple source domains, and each source domain usually provides some auxiliary information for object classification. The combination of such complementary knowledge from different source domains is helpful for improving the accuracy. We propose an evidential combination of augmented multi-source of information(ECAMI) method. The information sources are augmented at first by merging several randomly selected source domains to generate extra auxiliary information. We can obtain one piece of classification result with the assistance of each information source based on DA. Then these multiple classification results are combined by belief functions theory, which is expert at dealing with the uncertain information. Nevertheless, the classification results derived from different information sources may have different weights. The optimal weights are calculated by minimizing an given error criteria defined by the distance between the combination result and the ground truth using some training data. For each object, the augmented information sources will produce multiple classification results that will be discounted by the learnt weights under the belief functions framework. Then the combination of these discounted results is employed to make the final class decision. The effectiveness of ECAMI is evaluated with respect to some related methods based on several real data sets, and the experimental results show that ECAMI can significantly improve the classification accuracy.

关键词： information fusion domain adaptation evidence theory belief functions pattern classification

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Revealing and predicting the long-term biomechanical response of orthokeratology by developing a patient-specific computational model

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 156-168页

作者： Yifeng Li Zhuoran Yang Ziming Yan Huibin Shi Zhanli Liu Kaijie Wang Department of Engineering Mechanics School of Aerospace Engineering Tsinghua University Beijing Tongren Eye Center Beijing Tongren Hospital Capital Medical University Beijing Ophthalmology & Visual Sciences Key Lab

Orthokeratology(OK) is widely used for effective myopia correction and control. However, the incomplete understanding of its biomechanical mechanisms makes OK lens fitting rely heavily on clinician judgment, complicating accurate predictions of treatment outcomes. In this paper, we performed clinical experiments and numerical analysis to study corneal deformation modes and long-term changes in central corneal thickness. Clinical experiments were conducted on 194 Chinese myopic patients under OK treatment for 3 months. Based on the experimental data, a patient-specific computational biomechanical model for OK was established and validated. Specifically, the anisotropic mechanical properties of the cornea were incorporated into the model to describe the significant difference between its shear modulus(29.5 kPa) and tensile modulus(768.4 kPa). Additionally, a viscohyperelastic material model with a prolonged corneal relaxation time of 5.6 h was developed to capture the long-term deformation response. The results show that corneal thickness reduction in OK is primarily due to out-of-plane shear deformation,influenced by the cornea's low shear resistance. Modeling the extended corneal relaxation time is crucial for predicting long-term biomechanical responses. The computational model effectively captures long-term changes in central corneal thickness, potentially improving OK lens fitting accuracy.

关键词： orthokeratology computational biomechanical model long-term viscoelasticity myopia correction

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Conservative Finite-Difference Scheme for High-Frequency Acoustic Waves Propagating at an Interface Between TwoMedia

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Communications in Computational Physics 2012年第2期11卷 351-366页

作者： J.Staudacher E.Savin onera–The french aerospace lab F-92322 ChatillonFrance

This paper is an introduction to a conservative,positive numerical scheme which takes into account the phenomena of reflection and transmission of high frequency acoustic waves at a straight interface between two homogeneous *** forms of the interpolation coefficients for reflected and transmitted wave vectors on a two-dimensional uniform grid are *** propagation model is a Liouville transport equation solved in phase space.

关键词： Acoustics high-frequency Liouville equation energy conservation reflection transmission

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Combination of classifiers with incomplete frames of discernment

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Chinese Journal of Aeronautics 2022年第5期35卷 145-157页

作者： Zhunga LIU Jingfei DUAN Linqing HUANG Jean DEZERT Yongqiang ZHAO School of Automation Northwestern Polytechnical UniversityXi’an 710072China onera–The french aerospace lab Palaiseau 91761France

The methods for combining multiple classifiers based on belief functions require to work with a common and complete(closed)Frame of Discernment(Fo D)on which the belief functions are defined before making their *** theoretical requirement is however difficult to satisfy in practice because some abnormal(or unknown)objects that do not belong to any predefined class of the Fo D can appear in real classification *** classifiers learnt using different attributes information can provide complementary knowledge which is very useful for making the classification but they are usually based on different Fo *** order to clearly identify the specific class of the abnormal objects,we propose a new method for combination of classifiers working with incomplete frames of discernment,named CCIF for *** is a progressive detection method that select and add the detected abnormal objects to the training data *** one pattern can be considered as an abnormal object by one classifier and be committed to a specific class by another one,a weighted evidence combination method is proposed to fuse the classification results of multiple *** new method offers the advantage to make a refined classification of abnormal objects,and to improve the classification accuracy thanks to the complementarity of the *** experimental results are given to validate the effectiveness of the proposed method using real data sets.

关键词： Abnormal object Belief functions Classifier fusion Evidence theory Detection

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An Unpreconditioned Boundary-Integral for Iterative Solution of Scattering Problems with Non-Constant Leontovitch Impedance Boundary Conditions

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Communications in Computational Physics 2014年第5期15卷 1431-1460页

作者： D.Levadoux F.Millot *** onera French Aerospace LabChemin de la humi`ere 91761 PalaiseauFrance. CERFACS 42 avenue G.Coriolis 31057 Toulouse France. onera French Aerospace Lab2 Avenue Edouard Belin31000 ToulouseFrance.

This paper concerns the electromagnetic scattering by arbitrary shaped three dimensional imperfectly conducting objects modeled with non-constant Leontovitch impedance boundary *** has two ***,the intrinsically wellconditioned integral equation(noted GCSIE)proposed in[30]is described focusing on its ***,we highlight the potential of this method by comparison with two other methods,the first being a two currents formulation in which the impedance condition is implicitly imposed and whose the convergence is quasioptimal for Lipschitz polyhedron,the second being a CFIE-like formulation[14].In particular,we prove that the new approach is less costly in term of CPU time and gives a more accurate solution than that obtained from the CFIE ***,as expected,It is demonstrated that no preconditioner is needed for this formulation.

关键词： Integral equation boundary element method impedance boundary equation preconditioner GMRES fast multipole method.

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De-combination of belief function based on optimization

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Chinese Journal of Aeronautics 2022年第5期35卷 179-193页

作者： Xiaojing FAN Deqiang HAN Yi YANG Jean DEZERT School of Automation Science and Engineering Xi’an Jiaotong UniversityXi’an 710049China SKLSVMS School of AerospaceXi’an Jiaotong UniversityXi’an 710049China onera The French Aerospace LabPalaiseau 91761France

In the theory of belief functions,the evidence combination is a kind of decision-level information *** two or more Basic Belief Assignments(BBAs)originated from different information sources,the combination rule is used to combine them to expect a better decision *** only a combined BBA is given and original BBAs are discarded,if one wants to analyze the difference between the information sources,evidence de-combination is needed to determine the original *** de-combination can be considered as the inverse process of the information *** paper focuses on such a defusion of information in the theory of belief *** is an under-determined problem if only the combined BBA is *** this paper,two optimization-based approaches are proposed to de-combine a given BBA according to the criteria of divergence maximization and information maximization,*** new proposed approaches can be used for two or more information *** numerical examples and an example of application are provided to illustrate and validate our approaches.

关键词： Belief functions De-combination Divergence maximization Information fusion Information maximization

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Novel moderate transformation of fuzzy membership function into basic belief assignment

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Chinese Journal of Aeronautics 2023年第1期36卷 369-385页

作者： Xiaojing FAN Deqiang HAN Jean DEZERT Yi YANG School of Automation Science and Engineering Xi’an Jiaotong UniversityXi’an 710049China onera The French Aerospace LabPalaiseau 91761France SKLSVMS School of AerospaceXi’an Jiaotong UniversityXi’an 710049China

In information fusion,the uncertain information from different sources might be modeled with different theoretical *** one needs to fuse the uncertain information represented by different uncertainty theories,constructing the transformation between different frameworks is *** transformations of a Fuzzy Membership Function(FMF)into a Basic Belief Assignment(BBA)have been proposed,where the transformations based on uncertainty maximization and minimization can determine the BBA without preselecting the focal ***,these two transformations that based on uncertainty optimization emphasize the extreme cases of *** avoid extreme attitudinal bias,a trade-off or moderate BBA with the uncertainty degree between the minimal and maximal ones is more *** this paper,two moderate transformations of an FMF into a trade-off BBA are *** is the weighted average based transformation and the other is the optimization-based transformation with weighting mechanism,where the weighting factor can be user-specified or determined with some prior *** rationality and effectiveness of our transformations are verified through numerical examples and classification examples.

关键词： Basic belief assignment Belief functions Fuzzy membership function Information fusion Moderate transformation

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Basic belief assignment approximations using degree of non-redundancy for focal element

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Chinese Journal of Aeronautics 2019年第11期32卷 2503-2515页

作者： Yi YANG Deqiang HAN Jean DEZERT SKLSVMS School of AerospaceXi'an Jiaotong UniversityXi'an 710049China Center for Information Engineering Science Research XVan Jiaotong UniversityXi'an 710049China onera The French Aerospace LabChemin de la HunierePalaiseau F-91761France

Dempster-Shafer evidence theory, also called the theory of belief function, is widely used for uncertainty modeling and reasoning. However, when the size and number of focal elements are large, the evidence combination will bring a high computational complexity. To address this issue,various methods have been proposed including the implementation of more efficient combination rules and the simplifications or approximations of Basic Belief Assignments(BBAs). In this paper,a novel principle for approximating a BBA into a simpler one is proposed, which is based on the degree of non-redundancy for focal elements. More non-redundant focal elements are kept in the approximation while more redundant focal elements in the original BBA are removed first. Three types of degree of non-redundancy are defined based on three different definitions of focal element distance, respectively. Two different implementations of this principle for BBA approximations are proposed including a batch and an iterative type. Examples, experiments, comparisons and related analyses are provided to validate proposed approximation approaches.

关键词： BBA approximation Belief functions Evidence theory Focal element Non-redundancy

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Spatially resolved investigation of flame particle interaction in a two dimensional model packed bed

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Particuology 2024年第2期85卷 167-185页

作者： Mohammadhassan Khodsiani Reza Namdar Fathollah Varnik Frank Beyrau Benoit Fond Institute of Fluid Dynamics and Thermodynamics Universitaetsplatz 2Magdeburg39106Saxony-AnhaltGermany Interdisciplinary Centre for Advanced Materials Simulation(ICAMS) Ruhr-University BochumBochum44801Germany onera The french aerospace lab Department of AerodynamicsAeroelasticity and Acoustics(DAAA)Paris-Saclay UniversityMeudon92190France

This study investigates the interaction between a premixed methane-air flame and particles inside a model packed *** opacity of the spherical packed beds to visible light poses a major barrier to the implementation of highly resolved optical diagnostics,so that no detailed experimental data were so far available for the validation of numerical ***,a two-dimensional cylindrical packed bed design is set up,which enables direct line-of-sight optical measurements without loss of spatial reso-lution over the fluid region between the *** this study,the case of cold metallic cylindrical particles(T=377 K)relevant to start-up of a reactor is investigated using internal particle cooling,which also allows cylinder specific heat transfer rate measurements by differential temperature measurements on the coolant *** two dimensional assumption is first verified by measuring the inflow ve-locity and cylinder temperature profile along the *** imaging is then per-formed using a telecentric lens to observe the position and geometry of the two-dimensional flame front with respect to the surrounding cylinders without loss of ***,the cylinder-specific flame to cylinder heat transfer rates and cylinder surface temperature are *** the flame is closely surrounded by the three cooled cylinders,intense heat transfer is observed in this region corresponding to 25±2.5%of the flame thermal *** were stabilised at different positions depending on inflow velocity and equivalence ratio,and a direct correlation between flame to cylinder stand-off distance and the heat transfer rate normalised to the flame thermal power was found for both top and side ***,sidewall quenching distances to the curved cylinder surfaces were evaluated,and seem to be influenced by the presence of a warm recirculation zone behind the *** investigation provides fully resolved flame front position and heat tra

关键词： Packed beds Flame-particle interaction Optical diagnostics Sidewall quenching

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