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Numerical study of heat-transfer in two-and quasi-two-dimensional Rayleigh–Bénard convection

Chinese Physics B 2018年第10期27卷 405-412页

作者： Zhen-Yuan Gao Jia-Hui luo Yun bao Department of Mechanics Sun Yat-Sen UniversityGuangzhou 510275China

A detailed comparative numerical study between the two-dimensional（2 D） and quasi-two-dimensional（quasi-2 D）turbulent Rayleigh–B＇enard（RB） convection on flow state, heat transfer, and thermal dissipation rate（TDR） is made. The Rayleigh number（Ra） in our simulations ranges up to 5×10^10 and Prandtl number（Pr） is fixed to be 0.7. Our simulations are conducted on the Tianhe-2 supercomputer. We use an in-house code with high parallelization efficiency, based on the extended PDM–DNS scheme. The comparison shows that after a certain Ra, plumes with round shape, which is called the ＂temperature islands＂, develop and gradually dominate the flow field in the 2 D case. On the other hand, in quasi-2 D cases, plumes remain mushroom-like. This difference in morphology becomes more significant as Ra increases, as with the motion of plumes near the top and bottom plates. The exponents of the power-law relation between the Nusselt number（Nu） and Ra are 0.3 for both two cases, and the fitting pre-factors are 0.099 and 0.133 for 2 D and quasi-2 D respectively,indicating a clear difference in magnitude of the heat transfer rate between two cases. To understand this difference in the magnitude of Nu, we compare the vertical profile of the horizontally averaged TDR for both two cases. It is found that the profiles of both cases are nearly the same in the bulk, but they vary near boundaries. Comparing the bifurcation height zb with the thermal boundary layer thickness dq, it shows that zb 〈 δθ（3 D）〈 δθ（2 D） and all three heights obey a universal power-law relation z ~Ra^-0.30. In order to quantify the difference further, we separate the domain by zb, i.e., define the area between two zb（near top and bottom plates respectively） as the ＂mid region＂ and the rest as the ＂side region＂, and integrate TDR in corresponding regions. By comparing the integral it is found that most of the difference in TDR between two cases, which is connected to the heat transfer rate, occurs within the thermal b

关键词： Rayleigh-Benard convection Nusselt number turbulence thermal dissipation

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Numerical simulation on characteristics of COREX shaft furnace with central gas distribution

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Journal of Iron and Steel Research International 2019年第6期26卷 567-577页

作者： Xing-sheng Zhang Zong-shu Zou Zhi-guo luo Department of Ferrous Metallurgy School of Metallurgy Northeastern University Shenyang 110819 Liaoning China Key Laboratory of Ecological Utilization of Multi-metallic Mineral of Education Ministry Northeastern University Shenyang 110819 Liaoning China

A three-dimensional steady-state mathematical model, considering the chemical reactions and transfers of momentum, heat and mass between the gas and solid phases, was developed to investigate the characteristics of the shaft furnace with the central gas distribution (CGD) device. The model was verified by the practical production data of a COREX-3000 shaft furnace, and then, it was used to study the inner characteristics of the shaft furnace with CGD. The results show that, compared with the COREX shaft furnace without CGD, the gas utilization rate (UR) and solid metallization rate (MR) increase from 33.66% to 34.18% and 60.4% to 61.8%, respectively. Especially, the standard deviation of solid MR decreases from 6.9% to 0.8%, which means that the MR of direct reduced iron from the furnace with CGD is more uniform than that without CGD. Additionally, the effects of operational conditions and CGD design on gas UR, solid MR and direct reduced iron uniformity were further discussed and the optimized conditions were suggested.

关键词： COREX shaft furnace Central gas distribution Gas utilization Solid metallization Direct reduced iron uniformity

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Learning Rates for Least Square Regressions with Coefficient Regularization

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Acta Mathematica Sinica,English Series 2012年第11期28卷 2205-2212页

作者： bao Huai sheng Pei Xin YE Jian Li WANG Department of Mathematics Shaoxing College of Arts and Sciences School of Mathematical Sciences and LPMC Nankai University

We analyze the learning rates for the least square regression with data dependent hy- pothesis spaces and coefficient regularization algorithms based on general kernels. Under a very mild regularity condition on the regression function, we obtain a bound for the approximation error by esti- mating the corresponding K：-functional. Combining this estimate with the previous result of the sample error, we derive a dimensional free learning rate by the proper choice of the regularization parameter.

关键词： Least square regressions coefficient regularization general kernel M-functional learningrates

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Simultaneous determination of seven flavonoids in Epimedium by liquid chromatography-tandem mass spectrometry method

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Chinese Chemical Letters 2008年第3期19卷 329-332页

作者： Cai sheng Wu bao Lin Guo Yu Xin sheng Jin Lan Zhang Institute of Materia Medica Chinese Academy of Medical Sciences Peking Union Medical College Beijing 100050 China Institute of Medicinal Plant Development Chinese Academy of Medical Sciences Peking Union Medical College Beijing 100094 China

In this paper, a sensitive and specific liquid chromatography-electrospray ionisation-mass spectrometry （LC-ESI-MS） method has been developed and validated for the identification and determination of seven flavonoids, namely epimedin A, epimedin B, epimedin C, icariin, sagittatoside B, 2＂-O-rhamnosyl icariside II, and baohuoside I in Epimedium from different sources.

关键词： Flavonoids Epimedium Liquid chromatography-electrospray ionization-mass spectrometry Quantitative determination

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Experiments and model development of p-nitrochlorobenzene and naphthalene purification in a continuous tower melting crystallizer

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Chinese Journal of Chemical Engineering 2023年第12期64卷 9-17页

作者： Wenlong Xiao Yonglin Li Zhengming Yi sheng Yang He’an luo School of Chemical Engineering Xiangtan UniversityXiangtan 411105China School of Energy Science and Engineering Central South UniversityChangsha 410083China College of Materials and Chemical Engineering Hunan Institute of EngineeringXiangtan 411105China

With the increasing demand for high-purity products,the industrial application of melt crystallization technology has been highly *** this study,the purification process of nitrochlorobenzene binary eutectic system(NBES)and naphthalene–benzothiophene solid solution system(NBSSS)in tower melting crystallizer is analyzed,and a mathematical model of crystallization process is *** key parameters in terms of feed concentration,crystal bed height,reflux ratio and stirring speed effi-ciency on purification effects were discussed by the established *** results show that the concentration of p-nitrochlorobenzene was purified from 90.85%to 99.99%,when the crystal bed height is 600 mm,the reflux ratio is 2.5,and the stirring speed is 12 rmin^(-1).The naphthalene concentration is purified from 95.89%to 99.99%,when the crystal bed height is 400 mm,the reflux ratio is 1.43,and the stirring speed is 16 rmin^(-1).The quality of the model is evaluated by the ARD(average relative deviation).The minimum ARD values of the NBES and NBSSS are 2.39%and 5.22%,respectively,indicating the model satisfactorily explains the purification process.

关键词： Crystallization Separation Mathematical modeling Crystallizer Purification

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A fine acquisition algorithm based on fast three-time FRFT for dynamic and weak GNSS signals

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Journal of Systems Engineering and Electronics 2023年第2期34卷 259-269页

作者： PAN YI ZHANG sheng WANG Xiao LIU Manhao luo Yiran Key Laboratory of Advanced Sensor and Integrated System Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China Department of Aeronautical and Aviation Engineering Hong Kong Polytechnic UniversityHong Kong 999077China

As high-dynamics and weak-signal are of two primary concerns of navigation using Global Navigation Satellite System(GNSS)signals,an acquisition algorithm based on threetime fractional Fourier transform(FRFT)is presented to simplify the calculation ***,the correlation results similar to linear frequency modulated(LFM)signals are derived on the basis of the high dynamic GNSS signal ***,the principle of obtaining the optimum rotation angle is analyzed,which is measured by FRFT projection lengths with two selected rotation ***,Doppler shift,Doppler rate,and code phase are accurately estimated in a real-time and low signal to noise ratio(SNR)wireless communication *** theoretical analysis and simulation results show that the fast FRFT algorithm can accurately estimate the high dynamic parameters by converting the traditional two-dimensional search process to only three times *** the acquisition performance is basically the same,the computational complexity and running time are greatly reduced,which is more conductive to practical application.

关键词： Global Navigation Satellite System(GNSS)signal fractional Fourier transform(FRFT) acquisition high-dynamics weak-signal

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Soil profile characteristics of high-productivity alluvial cambisols in the North China Plain

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Journal of Integrative Agriculture 2015年第4期14卷 765-773页

作者： LIU Hai-tao LI bao-guo REN Tu-sheng College of Resources and Environmental Sciences China Agricultural University

The North China Plain（NCP） is one of major breadbaskets in China. Crop growth and grain yield differ significantly with spatial variations of soil properties. This study aims to identify the key soil properties in relation to the grain yield for the winter wheat（Triticum aestivum L.）-maize（Zea mays L.） cropping system in a high-productivity farmland of the NCP. The field trials were conducted in three fields with different grain yield levels in Tai＇an City, Shandong Province, China, during the 2009–2012 period. Consistent field management strategies were applied in the three fields. Fifty-one physical and chemical indicators of the soil profile as related to grain yield were evaluated. An approximate maximum of 17.8% annual average grain yield difference was observed in the fields during the period of 2009–2012. The soil indicators were classified into three clusters with specific functions using cluster analysis, and three key indicators were extracted from each cluster to characterize the different soil properties of three fields. The first cluster represented soil water retention capacity, and the key indicator was available soil water（ASW）, which ranged from 153 to 187 mm in the 1.2 m profile and was correlated positively with grain yield. The second cluster represented soil water conductivity, as measured by saturated hydraulic conductivity（K s）. The higher yield field had a greater capacity to retain topsoil water for its lower K s（1.9 cm d^–1） in the 30–70 cm soil layer as compared to the lower yield field. The third cluster represented nutrient storage and supply, as indicated by the ratio of nutrient content to silt＋clay content of the top soil layer. The ratio of soil organic matter（OM）, total nitrogen（TN）, available P, exchangeable K＋ to silt＋clay content in the 0–20 cm soil layer were 19.0 g kg^–1, 1.6 g kg^–1, 94.7 mg kg^–1, 174.3 mg kg^–1 in the higher yield field, respectively, and correlated positively with the grain yield. By characterizing the diff

关键词： soil quality assessment cluster analysis grain yield key soil indicators

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Numerical realization of the conditions of Max Nther's residual intersection theorem

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Applied Mathematics(A Journal of Chinese Universities) 2014年第4期29卷 481-502页

作者： luo Zhong-xuan FENG Er-bao ZHANG Jie-lin School of Software Dalian University of Technology School of Mathematical Sciences Dalian University of Technology

The aim of this paper is to study numerical realization of the conditions of Max Nother＇s residual intersection theorem. The numerical realization relies on obtaining the inter- section of two algebraic curves by homotopy continuation method, computing the approximate places of an algebraic curve, getting the exact orders of a polynomial at the places, and determin- ing the multiplicity and character of a point of an algebraic curve. The numerical experiments show that our method is accurate, effective and robust without using multiprecision arithmetic, even if the coefficients of algebraic curves are inexact. We also conclude that the computational complexity of the numerical realization is polynomial time.

关键词： algebraic curve Puiseux expansion place homotopy continuation multiple root.

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2T-PERIODIC SOLUTION FOR m ORDER NEUTRAL TYPEDIFFERENTIAL EQUATIONS WITH TIME DELAYS

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Applied Mathematics and Mechanics(English Edition) 2002年第1期23卷 100-106页

作者： ZHANG bao-sheng(张保生) ZHU Guang-hui(朱光辉) Department of Mathematics Yunnan Nationalities InstituteKunming 650031 P R China Department of Mathematics Yunnan Nationalities InstituteKunming 650031 P R China

Periodic solution of m order linear neutral equations with constant coefficient and time delays was studied. Existence and uniqueness of 2 T-periodic solutions for the equation were discussed by using the method of Fourier series. Some new necessary and sufficient conditions of existence and uniqueness of 2 T-periodic solutions for the equation are obtained. The main result is used widely. It contains results in some correlation paper for its special case, improves and extends the main results in them. Existence of periodic solution for the equation in larger number of particular case can be checked by using the result, but cannot be checked in another paper. In other words, the main result in this paper is most generalized for (1) the better result cannot be found by using the same method.

关键词： neutral type equation 2T-periodic solution Fourier series

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Multiple temporal scale relationships of bankfull discharge with streamflow and sediment transport in the Yellow River in China

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International Journal of Sediment Research 2013年第4期28卷 496-510页

作者： Yan-yan ZHANG De-yu ZHONG bao-sheng WU State Key Laboratory of Hydroscience and Engineering Tsinghua University Pearl River Hydraulic Research Institute Pearl River Water Resources Commission

This paper presents a study on the characteristics of multiple time scales of bankfull discharge and its delayed response to changes of tlow conditions using continuous wavelet analysis for data from selected hydrologieal stations in the Yellow River *** showed that bankfull discharge series had one or two dominant lime *** example,the Huayuankou station in the lower reach of the Yellow River had two dominant time scales of 19 20 years and 5 6 *** dominant time seales of the bankfull discharge series were generally consistent with the dominant time scales of water discharge and sediment concentration series,indicating thai the channel morphology inherits the characteristics of the hydrologieal system in terms of multiple time *** addition,the wavelet coefficients of the bankfull discharge series had a phase difference in relation to those of the sediment concentration series,with a delay time that varied from 3 to 16 years at different *** delay time or relaxation lime is a result of the delayed response of bankfull discharge to How conditions,which was significant for channel adjustments in response lo changes of tlow *** findings of the multiple lime scales and the delayed response are of importance for further study of channel morphology of fluvial systems.

关键词： Multiple time scales wavelet analysis bankfull discharge river morphology fluvial processes Yellow River

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