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Infrared thin layer drying of saffron(Crocus sativus L.) stigmas:Mass transfer parameters and quality assessment 被引量:2
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作者 Mehdi Torki-Harchegani Davoud Ghanbarian +1 位作者 Vida Maghsoodi Ahmad Moheb 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2017年第4期426-432,共7页
Saffron is the most precious and expensive agricultural product. A dehydration treatment is necessary to convert Crocus sativus L. stigmas into saffron spice. To the best of our knowledge, no information on mass trans... Saffron is the most precious and expensive agricultural product. A dehydration treatment is necessary to convert Crocus sativus L. stigmas into saffron spice. To the best of our knowledge, no information on mass transfer parameters of saffron stigmas is available in the literature. This study aimed at investigating the moisture transfer parameters and quality attributes of saffron stigmas under infrared treatment at different temperatures(60,70, …, 110 ℃). It was observed that the dehydration process of the samples occurred in a short accelerating rate period at the start followed by a falling rate period. The effective moisture diffusivity and convective mass transfer coefficient were determined by using the Dincer and Dost model. The diffusivity values varied from1.1103 × 10^-10m^2·s^-1to 4.1397 × 10^-10m^2·s^-1 and mass transfer coefficient varied in the range of 2.6433 × 10^-7–8.7203 × 10^-7m·s^-1. The activation energy was obtained to be 27.86 kJ·mol^-1. The quality assessment results showed that the total crocin content increased, when the temperature increased up to90 ℃ but, in higher temperatures, the amount of crocin decreased slightly. The total safranal content of the samples decreased slightly when drying temperature increased from 60 ℃ to 70 ℃ and then continuously increased up to 110 ℃. Also, the amount of picrocrocin increased from 83.1 to 93.3 as the drying temperature increased from 60 ℃ to 100 ℃. 展开更多
关键词 drying moisture Infrared expensive slightly convective varied dehydration spice convert
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The Stability Research for the Finite Difference Scheme of a Nonlinear Reaction-diffusion Equation 被引量:6
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作者 XU Chen-mei 《Chinese Quarterly Journal of Mathematics》 CSCD 北大核心 2008年第2期222-227,共6页
In the article, the fully discrete finite difference scheme for a type of nonlinear reaction-diffusion equation is established. Then the new function space is introduced and the stability problem for the finite differ... In the article, the fully discrete finite difference scheme for a type of nonlinear reaction-diffusion equation is established. Then the new function space is introduced and the stability problem for the finite difference scheme is discussed by means of variational approximation method in this function space. The approach used is of a simple characteristic in gaining the stability condition of the scheme. 展开更多
关键词 reaction-diffusion equation finite difference scheme stability research variational approximation method
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A Mass Transfer Model for Devolatilization of Highly Viscous Media in Rotating Packed Bed 被引量:13
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作者 李沃源 毋伟 +3 位作者 邹海魁 初广文 邵磊 陈建峰 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2010年第2期194-201,共8页
A mass transfer model for devolatilization process of highly viscous media in rotating packed bed(RPB) was developed based on penetration theory and mass conservation.Before establishing the model,some mass transfer e... A mass transfer model for devolatilization process of highly viscous media in rotating packed bed(RPB) was developed based on penetration theory and mass conservation.Before establishing the model,some mass transfer experiments of thin film were conducted in a designed diffusion cell including vacuum and feeding system. In this study,acetone was used as the volatile organic compound(VOC) and syrup as the highly viscous media.The thickness of thin film was changed by using different liquid distributor.It was found that bubbling played an important role in the devolatilization.The correlation of diffusion coefficient of acetone in highly viscous dilute solution was proposed.The relative error between predicted and experimental data was within the range of ± 30% for diffusion coefficient of acetone in syrup.A comparison of experimental data of RPB with model indicated that the relative error was within ± 30% for efficiency of acetone removal. 展开更多
关键词 mass transfer highly viscous liquid volatile organic compound diffusion coefficient rotating packed bed
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On Global Boundedness of Solutions for the Drift-diffusion Semiconductor Equations
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作者 GUO Xiu-lan ZHANG Yu-lan LI Gong-sheng 《Chinese Quarterly Journal of Mathematics》 CSCD 北大核心 2006年第4期590-596,共7页
This paper is devoted to the mixed initial-boundary value problem for the semiconductor equations. Using Stampacchia recurrence method, we prove that the solutions areglobally bounded and positive.
关键词 drift-diffusion model semiconductor equations global boundedness stampac-chia recurrence method
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Analysis of Linear Triangular Elements for Convection-diffusion Problems by Streamline Diffusion Finite Element Methods
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作者 ZHOU Jun-ming JIN Da-yong ZHANG Shu-hua 《Chinese Quarterly Journal of Mathematics》 CSCD 北大核心 2007年第1期43-51,共9页
This paper is devoted to studying the superconvergence of streamline diffusion finite element methods for convection-diffusion problems. In [8], under the condition that ε ≤ h^2 the optimal finite element error esti... This paper is devoted to studying the superconvergence of streamline diffusion finite element methods for convection-diffusion problems. In [8], under the condition that ε ≤ h^2 the optimal finite element error estimate was obtained in L^2-norm. In the present paper, however, the same error estimate result is gained under the weaker condition that ε≤h. 展开更多
关键词 CONVECTION-DIFFUSION streamline diffusion finite element methods linear triangular elements SUPERCONVERGENCE
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NONLINEAR ANALYSES OF VOID DIFFUSION MODEL AND ITS APPLICATION TO SUBSIDENCE PREDICTION
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作者 郝庆旺 马伟民 《Journal of China University of Mining and Technology》 1990年第1期101-108,共8页
The void diffusion model for mining-effected strata can be analyzed by means of a nonlinear finite element method. This paper presents the fundamental principles of the analyses. The key to the analyses is the determi... The void diffusion model for mining-effected strata can be analyzed by means of a nonlinear finite element method. This paper presents the fundamental principles of the analyses. The key to the analyses is the determination of roof subsidence and the nonlinear relationship between diffusion coefficient and subsidence. This paper discusses these problems and determines the coefficient for Pingdingshan mining district, with which several profiles are predicted. It is found that the predicted profiles are coincident with the corresponding field profiles. 展开更多
关键词 mine environment mining subsidence PREDICTION
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上海崇明东滩外来物种互花米草二次入侵过程 被引量:8
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作者 肖德荣 祝振昌 +1 位作者 袁琳 田昆 《应用生态学报》 CAS CSCD 北大核心 2012年第11期2997-3002,共6页
选取上海崇明东滩"刈割+水位调节"集成技术治理互花米草示范工程样地,对互花米草二次入侵过程进行了2年的监测.结果表明:大量互花米草实生苗在春季随潮水沿潮沟等通道向恢复自然水文区扩散定居,2年即可形成与周边群落无明显... 选取上海崇明东滩"刈割+水位调节"集成技术治理互花米草示范工程样地,对互花米草二次入侵过程进行了2年的监测.结果表明:大量互花米草实生苗在春季随潮水沿潮沟等通道向恢复自然水文区扩散定居,2年即可形成与周边群落无明显差异的二次入侵群落,而群落边缘通过无性繁殖的扩散距离有限.在保持淹水控制区,互花米草两年累计扩散距离小于1m.在物理隔离区,2年未监测到互花米草的二次入侵现象.实生苗在春季的快速拓植是互花米草实现种群二次入侵的关键.彻底消除治理区周边互花米草扩散源,设置隔离带以阻止其向治理区的扩散,或采用种植芦苇等土著物种进行生物替代,是防止互花米草二次入侵的主要措施. 展开更多
关键词 互花米草 二次入侵 有性扩散 无性繁殖 崇明东滩
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Positivity and boundedness preserving schemes for the fractional reaction-difusion equation 被引量:2
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作者 YU YanYan DENG WeiHua WU YuJiang 《Science China Mathematics》 SCIE 2013年第10期2161-2178,共18页
In this paper, we design a semi-implicit scheme for the scalar time fractional reaction-diffusion equation. We theoretically prove that the numerical scheme is stable without the restriction on the ratio of the time a... In this paper, we design a semi-implicit scheme for the scalar time fractional reaction-diffusion equation. We theoretically prove that the numerical scheme is stable without the restriction on the ratio of the time and space stepsizes, and numerically show that the convergence orders are 1 in time and 2 in space. As a concrete model, the subdiffusive predator-prey system is discussed in detail. First, we prove that the analytical solution to the system is positive and bounded. Then, we use the provided numerical scheme to solve the subdiffusive predator-prey system, and theoretically prove and numerically verify that the numerical scheme preserves the positivity and boundedness. 展开更多
关键词 time fractional reaction-diffusion equation subdiffusive predator-prey system POSITIVITY bound-edness
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Effect of dry density on ^(125)I diffusion in GMZ bentonite 被引量:12
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作者 WU Tao LI JinYing +5 位作者 DAI Wei XIAO GuoPing SHU FuJun YAO Jun SU YuLan SHI Lei 《Science China Chemistry》 SCIE EI CAS 2012年第9期1760-1764,共5页
Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for a potential repository in China. It is important to understand the diffusion behavior of ^125I in GMZ bentonite and compare t... Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for a potential repository in China. It is important to understand the diffusion behavior of ^125I in GMZ bentonite and compare the diffusion behavior in GMZ and other types of bentonite like MX-80, Avonlea, etc. Therefore, through- and out-diffusion experiments were conducted to obtain the effective diffusion coefficient (De) and distribution coefficient (Kd). A computer code named Fitting for diffusion coefficient (FDP) was used for the experimental data processing and theoretical modeling. At the dry density of GMZ bentonite from 1600-2000 kg/m^3, the De values of ^125I were (2.4-20.4)×10 ^-12 m^2/s and Ka values were constants. At dry density above 1800 kg/m^3, the diffusion behaviors were almost the same, indicating that the anion exclusion was ineffective. Out-diffusion results showed that the species of ^125I may be changed during the diffusion processing. It was probably caused by some organic mat- ters or reducing substances in GMZ bentonite. Since the main composition of bentonite is montmorillonite, similar diffusion parameters were obtained in GMZ and other types of bentonite. The relationship of DE and accessible porosity (εacc) could be described by Archie's law with exponent n = 1.2-2.8 for ^125I diffusion in bentonite, whereas n = 2.0 in GMZ bentonite. Fur- thermore, bentonite with the dry density of 1800 kg/m^3 was proposed as the backfilling materials used in the construction of high level radioactivity waste repository. 展开更多
关键词 ^125I DIFFUSION GMZ bentonite SPECIES distribution coefficient
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Wheat-Exuded Organic Acids Influence Zinc Release from Calcareous Soils 被引量:3
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作者 M.A.MAQSOOD S.HUSSAIN +1 位作者 T.AZIZ M.ASHRAF 《Pedosphere》 SCIE CAS CSCD 2011年第5期657-665,共9页
Rhizosphere drives plant uptake of sparingly soluble soil zinc(Zn).An investigation with three experiments was conducted to study organic acid exudation by two contrasting wheat genotypes(Sehar-06 and Vatan),Zn fracti... Rhizosphere drives plant uptake of sparingly soluble soil zinc(Zn).An investigation with three experiments was conducted to study organic acid exudation by two contrasting wheat genotypes(Sehar-06 and Vatan),Zn fractions in 10 different calcareous soils from Punjab,Pakistan,and release of different soil Zn fractions by organic acids.The two genotypes differed significantly in biomass production and Zn accumulation under deficient and optimum Zn levels in nutrient solution.At a deficient Zn level,Sehar-06 released more maleic acid in the rhizosphere than Vatan.Ten soils used in the present study had very different physicochemical properties;their total Zn and Zn distribution among different fractions varied significantly.Zinc release behaviour was determined by extracting the soils with 0.005 mol L-1 citric acid or maleic acid.The parabolic diffusion model best described Zn release as a function of time.Parabolic diffusion model fitting indicated more maleic acid-driven than citric acid-driven soil Zn mobility from different fractions.Cumulative Zn release in six consecutive extractions during 24 h ranged from 1.85 to 13.58 mg kg-1 using maleic acid and from 0.37 to 11.84 mg kg-1 using citric acid.In the selected calcareous soils,the results of stepwise linear regression indicated significant release of Fe-Mn oxide-bounded soil Zn by maleic acid and its availability to the Zn-effcient genotype.Hence,release of maleic acid by plants roots played an important role in phytoavailability of Zn from calcareous soils. 展开更多
关键词 citric acid maleic acid PHYTOAVAILABILITY plant uptake RHIZOSPHERE
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An island biogeography model for beta diversity and endemism: The roles of speciation, extinction and dispersal
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作者 Youhua Chen 《International Journal of Biomathematics》 2015年第1期137-148,共12页
A community composition island biogeography model was developed to explain and predict two community patterns (beta diversity and endemism) with the consideration of speciation, extinction and dispersal processes. R... A community composition island biogeography model was developed to explain and predict two community patterns (beta diversity and endemism) with the consideration of speciation, extinction and dispersal processes. Results showed that rate of speciation is positively and linearly associated with beta diversity and endemism, that is, increasing species rates typically could increase the percentage of both endemism and beta diversity. The influences of immigration and extinction rates on beta diversity and endemism are nonlinear, but with numerical simulation, I could observe that increasing extinction rates would lead to decreasing percentage of endemism and beta diversity. The role of immigration rate is very similar to that of speciation rate, having a positive relationship with beta diversity and endemism. Finally, I found that beta diversity is closely related to the percentage of endemism. The slope of this positive relationship is determined jointly by different combinations of speciation, extinction and immigration rates. 展开更多
关键词 Island biogeography model composition patterns ENDEMISM TURNOVER
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