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Transient process of methane-oxygen diffusion flame-street establishment in a microchannel

Frontiers in Energy 2022年第6期16卷 988-999页

作者： xin kang Yu WANG School of Civil Engineering and Architecture Wuhan University of TechnologyWuhan 430070China School of Automotive Engineering Wuhan University of TechnologyWuhan 430070China

“Flame-street”is an interesting diffusion flame behavior in which a series of flame-segments is separately distributed along the mixing layer in a narrow *** experimental phenomenon was experimentally and numerically investigated with the focus on the steady-state,thermo-chemical flame structures in previous *** the present paper,the dynamic formation process of a methane-oxygen diffusion flame-street structure was simulated with a reacting flow solver developed based on the open-source framework *** imposing a certain amount of ignition-energy near the channel outlet,a reaction-kernel was formed and ***,three separate flames were consecutively generated from this kernel and propagated within the *** whole process was completed within 15 ms and all the discrete flames were eventually in a ***,different propagation features were observed for the three flame segments:The leading flame experienced a flame shape/type change from a tribrachial structure in its fastpropagating phase to a long,trailing diffusion tail after being anchored to the *** successive flame had a much lower propagation speed,keeping its two wing-like(fuel-lean premixed and fuel-rich premixed)structure while moving toward its stabilization location,which was approximately in the middle of the *** last flame,after the ignition source was turned-off,was immediately convected a bit downstream,and eventually featured a similar two-branch-like structure as the second ***,chemical insights for the premixed and diffusion branches of the leading flame were also provided with the change of significance of some key elementary reactions focused on,in order to attain a detailed profiling of the flame-type *** paper is a first-ever one discussing the transient formation of flame-streets in literature and is believed to be useful for obtaining a comprehensive understanding of this unique flame characte

关键词： micro-combustion flame-street diffusion flame mixing layer flame propagation speed

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Exploring Latent Semantic Information for Textual Emotion Recognition in Blog Articles

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IEEE/CAA Journal of Automatica Sinica 2018年第1期5卷 204-216页

作者： xin kang Fuji Ren Yunong Wu Faculty of Engineering Tokushima University 2-1 Minamijyousanjima-cho Tokushima 770-8506 Japan IEEE

Understanding people's emotions through natural language is a challenging task for intelligent systems based on Internet of Things(Io T). The major difficulty is caused by the lack of basic knowledge in emotion expressions with respect to a variety of real world contexts. In this paper, we propose a Bayesian inference method to explore the latent semantic dimensions as contextual information in natural language and to learn the knowledge of emotion expressions based on these semantic dimensions. Our method synchronously infers the latent semantic dimensions as topics in words and predicts the emotion labels in both word-level and document-level texts. The Bayesian inference results enable us to visualize the connection between words and emotions with respect to different semantic dimensions. And by further incorporating a corpus-level hierarchy in the document emotion distribution assumption, we could balance the document emotion recognition results and achieve even better word and document emotion predictions. Our experiment of the wordlevel and the document-level emotion predictions, based on a well-developed Chinese emotion corpus Ren-CECps, renders both higher accuracy and better robustness in the word-level and the document-level emotion predictions compared to the state-of-theart emotion prediction algorithms.

关键词： Bayesian inference emotion-topic model emotion recognition multi-label classification natural language understanding

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Numerical Simulation of Macrosegregation Caused by Thermal–Solutal Convection and Solidification Shrinkage Using ALE Model

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Acta Metallurgica Sinica(English Letters) 2019年第11期32卷 1396-1406页

作者： kang-xin Chen Hou-Fa Shen Key Laboratory for Advanced Materials Processing Technology Ministry of Education School of Materials Science and Engineering Tsinghua University

Solidifi cation shrinkage has been recognized as an important factor for macrosegregation formation. An arbitrary Lagrangian–Eulerian(ALE) model is constructed to predict the macrosegregation caused by thermal–solutal convection and solidi-fi cation shrinkage. A novel mesh update algorithm is developed to account for the domain change induced by solidifi cation shrinkage. The velocity–pressure coupling between the non-homogenous mass conservation equation and momentum equation is addressed by a modifi ed pressure correction method. The governing equations are solved by the streamline-upwind/Petrov–Galerkin-stabilized fi nite element algorithm. The application of the model to the Pb-19.2 wt%Sn alloy solidifi cation problem is considered. The inverse segregation is successfully predicted, and reasonable agreement with the literature results is obtained. Thus, the ALE model is established to be a highly effective tool for predicting the macrosegregation caused by solidifi cation shrinkage and thermal–solutal convection. Finally, the effect of solidifi cation shrinkage is analyzed. The results demonstrate that solidifi cation shrinkage delays the advance of the solidifi cation front and intensifi es the segregation.

关键词： Macrosegregation Solidification shrinkage Finite element method Arbitrary Lagrangian–Eulerian(ALE)

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A Versatile Numerical Tool for Simulating Combustion Features at Small-Scales

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Journal of Thermal Science 2021年第1期30卷 343-361页

作者： kang xin DENG Youcheng WANG Jianyong FAN Aiwu School of Civil Engineering and Architecture Wuhan University of TechnologyWuhan 430070China School of Energy and Power Engineering Wuhan University of TechnologyWuhan 430063China School of Mechanical&Mining Engineering The University of QueenslandQLD 4072Australia School of Energy and Power Engineering Huazhong University of Science and TechnologyWuhan 430074China

A versatile numerical tool based on the open-source framework Open FOAM has been developed in this paper for modeling time-accurate,low-Mach number reacting flows,with a particular interest in small-scale *** tool consists of a gas-phase Navier-Stokes solver and a solid-wall heat conduction solver which can be implemented alone,or used together in a coupled means to reveal the small-scale combustion’s characteristics of significantly enhanced flame-wall thermal *** works has proved that the tool is capable of reproducing experimental flames at various scales(from conventional to small scales),including well-recognized micro-flame features in literature such as three modes of premixed flame dynamics(weak flames,flames with repetitive extinction and ignition,and stable flames).Then,an experimentally-already-found but rarely-simulated unique phenomenon of diffusion flame street is successfully reproduced with well-captured flame ***,the conjugate heat transfer model with the specific formulation of solid-wall heat conduction enables an attempt to simulate a novel,thermally-orthotropic combustor with its axial thermal conductivities superior to the transverse ***,computational performance of the developed Open FOAM solver is compared to that of the previously-used compressible flow solver *** Open FOAM solver is found to show better wave-damping abilities for overcoming acoustic wave effects at the initial stage of simulations,and is much more efficient in terms of the computational cost.

关键词： micro-combustion Open FOAM conjugate heat transfer thermally orthotropic combustor flame streets

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Nonlinearity analysis of piezoelectric micromachined ultrasonic transducers based on couple stress theory

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Acta Mechanica Sinica 2012年第1期28卷 104-111页

作者： xin kang Fu-Jun Yang Xiao-Yuan He Department of Applied Mechanics Nanjing University of Science and Technology210094 NanjingChina Department of Mechanical and Aeronautical Engineering University of CaliforniaDavis95616US Institute of Engineering Mechanics Southeast University210096 NanjingChina

This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is evaluated using the couple stress theory. The results show that the optimal ratio of the top electrode diameter and the membrane diameter is around 0.674. It is also found that this optimal value does not depend on any other parameters if the thicknesses of the two electrodes are negligible compared with those of the piezo- electric and passive layers. In addition, the nonlinearities of the piezoelectric layer will become stronger along with the increase of the electric field, which means that softening of the membrane stiffness occurs when a strong external electric field is applied. Meanwhile, the optimal thickness ratio for the passive layer and the piezoelectric layer is not equal to 1.0 which is usually adopted by previous researchers. Because there exists size dependence of membrane deforma-tion, the optimal value of this thickness ratio needs to be greater than 1.0 on the microscale.

关键词： Piezoelectric micromachined ultrasonic trans- ducer (PMUT) Couple stress theory Static deformation - Nonlinearity analysis

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Estimation of non-point source pollution loads with flux method in Danjiangkou Reservoir area,China

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Water Science and Engineering 2017年第2期10卷 134-142页

作者： Xiao-kang xin Wei Yin Ke-feng Li State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Changjiang Water Resources Protection Institute Changjiang Water Resources Commission

The estimation of non-point source pollution loads into the Danjiangkou Reservoir is highly significant to environmental protection in the watershed. In order to overcome the drawbacks of traditional watershed numerical models, a base flow separation method was established coupled with a digital filtering method and a flux method. The digital filtering method has been used to separate the base flows of the Hanjiang,Tianhe, Duhe, Danjiang, Laoguan, and Qihe rivers. Based on daily discharge, base flow, and pollutant concentration data, the flux method was used to calculate the point source pollution load and non-point source pollution load. The results show that:(1) In the year 2013, the total inflow of the six rivers mentioned above accounted for 95.9% of the total inflow to the Danjiangkou Reservoir. The total pollution loads of chemical oxygen demand(CODMn) and total phosphorus(TP) from the six rivers were 58.20 103 t and 1.863 10~3 t, respectively, and the non-point source pollution loads were 39.82 10~3 t and 1.544 10~3 t, respectively, indicating that the non-point source pollution is a major factor(with a contribution rate of 68.4% for CODMnand 82.9% for TP).(2) The Hanjiang River is the most significant contributor of pollution loads to the Danjiangkou Reservoir, and its CODMnand TP contribution rates reached 79.3% and 83.2%, respectively. The Duhe River took the second place.(3) Non-point source pollution mainly occurred in the wet season in 2013, accounting for 80.8% and 90.9% of the total pollution loads of CODMnand TP, respectively. It is concluded that the emphasis of pollution control should be placed on non-point source pollution.

关键词： Danjiangkou Reservoir Non-point source pollution Base flow separation Digital filtering method (DFM) Flux method

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Quantitative division of succession and spatial patterns among different stand developmental stages in Changbai Mountains

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Journal of Mountain Science 2019年第9期16卷 2063-2078页

作者： GONG Zhi-wen kang xin-gang GU Li College of Economics and Management Research Center of Resource Economics and Environment Management Northwest A8J7 University Yangling 712100 China College of Forestry Northwest A&F University Yang ling 712100 China College of Forestry Beijing Forestry University Beijing 100083 China

Broadleaf-Korean pine forests exhibit high species richness and distinctive species composition, which are currently becoming more dominant among natural forests in Changbai Mountains of northeastern China. Understanding the ecological process of restored vegetation is quite important for ecosystem reconstruction. Distinguishing stand development stages and analyzing the dynamic spatial patterns could provide insights into significant community coexistence mechanisms. In the present study, eight permanent study areas were established according to the substituting space for time method in Changbai Mountains of north-eastern China. The optimal division method was used to quantify the successional series into different stand development stages, and the point pattern analysis method(L(r) function) was used to analyse the dynamic changes in spatial patterns and interspecific associations. Our results suggested that:(1) The stand development process was divided into five stages: the first three stages were poplar-birch secondary forests in different stages of recovery, the fourth stage was thespruce-fir mixed forest, and the last stage was the primary broadleaf-Korean pine forest;(2) The spatial pattern showed an aggregated distribution at a small scale and changed to a random distribution as the scale increased in poplar-birch secondary forests, but the spatial pattern appeared to be randomly distributed in spruce-fir mixed forest and broadleafKorean pine forest;(3) The interspecific associations between pioneer species and climax species changed from negative to positive among the different stand stages, and environmental resources were shared among these species. Interspecific differences in shade tolerance among the tree species were key determinants of forest dynamics and structure. Our study is vital to the understanding of the forest development;thus, the spatial change features should receive greater attention when forest management is being planned and restoratio

关键词： Dynamic spatial patterns Interspecific association Optimal division method Stand developmental stages Space for time substitution

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Distribution Patterns and Associations of Dominant Tree Species in a Mixed Coniferous-Broadleaf Forest in the Changbai Mountains

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Journal of Mountain Science 2015年第3期12卷 659-670页

作者： ZHANG Meng-tao kang xin-gang MENG Jing-hui ZHANG Li-xin Key Laboratory for Silviculture and Conservation Ministry of Education Beijing Forestry University Yunnan Forest Institute

In 2012 a plot was established with 1-ha area in a mixed coniferous-broadleaf forest in the Changbai Mountains, northeastern China for examining local forest processes, structure and succession. A method of O-ring statistics （pair- correlation function） was applied to analyze the spatial patterns and associations of the dominant species within different vertical layers. After the evaluation by their importance values, six tree species （or group）（i.e. Abies nephrolepis, Picea jezoensis, Pinus koraiensis, Tilia amurensis, and species group of Betula ssp. and species group of Acer ssp.） were determined as dominant trees species. It was found that some of these species exhibited closely clustered distributions at fine distances. As spatial distance increased, a random or even regular distribution gradually appeared with the exception of the upper layers of A. nephrolepis and P. koraiensis, and the lower layers of P. jezoensis, P. koraiensis and Betula ssp., which were substantially randomly distributed. Intra- and inter-species spatial associations varied in accordance with species, tree height and reciprocal distances. Positive associations were observed between the lower and upper height classes of trees of the same species （except for that of P. jezoensis） at fine distances. This may be owing to limited seed dispersal and geological heterogeneity. The aggregation intensity declines with increasing distances and this consistent with the predictions of self-thinning. Some coniferous trees （e.g. Pinus koraiensis） in the lower height class were positively associated with T. amurensis and group of Betula ssp. of the upper height class at some distances, suggesting that saplings of coniferous trees occupy a broader niche and can grow well under the canopy of the adult of broad-leaved trees. Negative associations were observed between upper coniferous trees and lower broad-leaved trees and between upper P. jezoensis and lower P. koraiensis, suggesting that a canopy of thes

关键词： Mixed coniferous-broadleaf forest O-ring statistics Spatial pattern Spatial association Null model

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Reservoir operation schemes for water pollution accidents in Yangtze River

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Water Science and Engineering 2012年第1期5卷 59-66页

作者： Xiao-kang xin Wei YIN Meng WANG Changjiang Water Resources Protection Institute Changjiang Water Resources CommissionWuhan 430051P.R.China

After the Three Gorges Reservoir starts running, it can not only take into consideration the interest of departments such as flood control, power generation, water supply, and shipping, but also reduce or eliminate the adverse effects of pollutants by discharge regulation. The evolution of pollutant plumes under different operation schemes of the Three Gorges Reservoir and three kinds of pollutant discharge types were calculated with the MIKE 21 AD software. The feasibility and effectiveness of the reservoir emergency operation when pollution accidents occur were investigated. The results indicate that the emergency operation produces significant effects on the instantaneous discharge type with lesser effects on the constant discharge type, the impact time is shortened, and the concentration of pollutant is reduced. Meanwhile, the results show that the larger the discharge is and the shorter the operation duration is, the more favorable the result is.

关键词： water pollution accident emergency operation water environment model, Three Gorges Reservoir

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DFF-ResNet: An Insect Pest Recognition Model Based on Residual Networks

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Big Data Mining and Analytics 2020年第4期3卷 300-310页

作者： Wenjie Liu Guoqing Wu Fuji Ren xin kang the School of Information Science and Technology and School of Transportation and Civil Engineering Nantong UniversityNantong 226019China the Faculty of Engineering Tokushima UniversityTokushima 770-8506Japan the School of Information Science and Technology Nantong UniversityNantong 226019China

Insect pest control is considered as a significant factor in the yield of commercial ***,to avoid economic losses,we need a valid method for insect pest *** this paper,we proposed a feature fusion residual block to perform the insect pest recognition *** on the original residual block,we fused the feature from a previous layer between two 11 convolution layers in a residual signal branch to improve the capacity of the ***,we explored the contribution of each residual group to the model *** found that adding the residual blocks of earlier residual groups promotes the model performance significantly,which improves the capacity of generalization of the *** stacking the feature fusion residual block,we constructed the Deep Feature Fusion Residual Network(DFF-ResNet).To prove the validity and adaptivity of our approach,we constructed it with two common residual networks(Pre-ResNet and Wide Residual Network(WRN))and validated these models on the Canadian Institute For Advanced Research(CIFAR)and Street View House Number(SVHN)benchmark *** experimental results indicate that our models have a lower test error than those of baseline ***,we applied our models to recognize insect pests and obtained validity on the IP102 benchmark *** experimental results show that our models outperform the original ResNet and other state-of-the-art methods.

关键词： insect pest recognition deep feature fusion residual network image classification

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