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2010年 第18卷 第5期 刊出日期:2010-10-28
    A Reduced Mechanism for Flame Inhibition by Phosphorus-containing Compounds Based on Level of Importance Analysis
    蒋勇, 邱榕
    . 2010, 18(5):  711-720. 
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    A reduced mechanism for propane/air combustion and its flame inhibition by phosphorus-containing compounds (PCCs) is constructed with the level of importance (LOI) method. The analysis is performed on solutions of freely propagating premixed flames with detailed chemical kinetics involving 121 species and 682 reactions proposed by Jayaweera et al. For the non-homogeneous reaction-diffusion system, the chemical lifetime of each species is weighted by its diffusion timescale, and the characteristic flame timescale is used to normalize the chemical lifetime. The definition of sensitivity in LOI is extended so that multi-parameters can be used as sensitivity targets. Propane, oxygen, dimethyl methylphosphonate (DMMP), and flame speed are selected to be perturbed for sensitivity analysis, the species with low LOI index are removed, and reactions involving the redundant species are excluded from the mechanism. A skeletal mechanism is obtained, which consists of 57 species and 268 elementary reactions. Calculations for laminar flame speeds, key flame radicals and catalytic cycles using the skeletal mechanism are in good agreement with those by using the detailed mechanism over a wide range of equivalence ratio undoped and doped with DMMP.
    Experimental and Kinetic Study of Selective Catalytic Reduction of NO with NH3 over CuO/Al2O3/Cordierite Catalyst
    雷志刚, 龙爱斌, 贾美如, 刘学义
    . 2010, 18(5):  721-729. 
    摘要 ( 6257 )   PDF (595KB) ( 14 )  
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    The CuO/γ-Al2O3/cordierite catalyst, after being sulfated by sulfur dioxide (SO2) at 673 K, exhibits high activities for selective catalytic reduction (SCR) of nitrogen oxide (NO) with ammonia (NH3) at 573-723 K. The intrinsic kinetics of SCR of NO with NH3 over CuO/γ-Al2O3/cordierite catalyst has been measured in a fixed-bed reactor in the absence of internal and external diffusions. The experimental results show that the reaction rate can be quantified by a first-order expression with activation energy Ea' of 94.01 kJ·mol-1 and the corresponding pre-exponential factor A' of 3.39×108 cm3·g-1·s-1 when NH3 is excessive. However, when NH3 is not enough, an Eley-Rideal kinetic model based on experimental data is derived with Ea of 105.79 kJ·mol-1, the corresponding A of 2.94×109cm3·g-1·s-1, heat of adsorption ΔHads of 87.90 kJ·mol-1 and the corresponding Aads of 9.24 cm3·mol-1. The intrinsic kinetic model obtained was incorporated in a 3D mathematical model of monolithic reactor, and the agreement of the prediction with experimental data indicates that the present kinetic model is adequate for the reactor design and engineering scale-up.
    Kinetics of Reductive Leaching of Low-grade Pyrolusite with Molasses Alcohol Wastewater in H2SO4
    粟海锋, 刘怀坤, 王凡, 吕小艳, 文衍宣
    . 2010, 18(5):  730-735. 
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    The kinetics of reductive leaching of manganese from low grade pyrolusite in dilute sulfuric acid in the presence of molasses alcohol wastewater was investigated. The shrinking core model was applied to quantify the effects of reaction parameters on leaching rate. The leaching rate increases with reaction temperature, concentrations of H2SO4 and organic matter in molasses alcohol wastewater increase and ore particle size decreases. The leaching process follows the kinetics of a shrinking core model and the apparent activation energy is 57.5 kJ·mol-1. The experimental results indicate a reaction order of 0.52 for H2SO4 concentration and 0.90 for chemical oxygen demand (COD) of molasses alcohol wastewater. It is concluded that the reductive leaching of pyrolusite with molasses alcohol wastewater is controlled by the diffusion through the ash/inert layer composed of the associated minerals.
    Thermal Stability and Thermal Decomposition Kinetics of 1-Butyl-3-methylimidazolium Dicyanamide
    梁蕊, 杨美荣, 轩小鹏
    . 2010, 18(5):  736-741. 
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    Thermal stability and thermal decomposition kinetics of 1-butyl-3-methylimidazolium dicyanamide ([bmin+][N(CN)]2-) were investigated using both isothermal and non-isothermal thermogravimetric analyses (TGA) under high pure nitrogen as carrier gas. The long-term thermogravimetric studies revealed that the highest temperature used should be 110℃, at which ([bmin+][N(CN)]2-) lost less than 10% by mass in 10 hours. The non-isothermal activation energy values determined using Friedman and ASTM methods were (150±13) and (147±2) kJ·mol-1 , respectively. Multivariate non-linear-regression methods showed that expanded Fn and CnB models were the best fit models with highest correlation coefficient of 0.9994, and the apparent activation energies were consistent with iso-conversional methods.
    Methylation of 2-Methylnaphthalene with Methanol over NH4F and Pt Modified HZSM-5 Catalysts
    赵亮, 郭新闻, 刘民, 王祥生, 宋春山
    . 2010, 18(5):  742-749. 
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    Shape-selective methylation of 2-methylnaphthalene (2-MN) was carried out over NH4F and Pt modified HZSM-5 (SiO2 /Al2O3=83) catalysts in a fixed-bed down-flow reactor using methanol as methylating agent and 1,3,5-trimethylbenzene (1,3,5-TMB) as a solvent. Pt promoted HZSM-5 catalysts showed low concentration of coke-like polycondensed aromatics, NH4F modification decreased non-shape-selective acid sites. After Pt and NH4F comodification, both conversion of 2-MN and selectivity tO2,6-DMN were improved. 6% NH4F/0.5% Pt/HZSM-5 catalyst exhibited 13.8% of 2-MN conversion with 6.2% of 2,6-DMN yield after 7 h time on stream (TOS), and 2,6-/2,7-DMN ratio of 1.7 after 10 h of TOS.
    Isolation and Purification of Triptolide from the Leaves of Tripterygium wilfordii Hook F
    沈剑, 何潮洪
    . 2010, 18(5):  750-754. 
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    Triptolide is an important active component of Tripterygium wilfordii Hook F (TWHF) and possesses anti-inflammatory, immunosuppressive, male anti-fertility, and anticancer properties. A new method combining different techniques, including solid-liquid extraction, liquid-liquid partition, column chromatography and high-speed counter-current chromatography (HSCCC) but avoiding the use of chloroform, was developed for the isolation and purification of triptolide from the leaves of TWHF. 48 mg of triptolide at 96.5% purity was obtained from 1 kg of air-dried leaves of TWHF.
    Coupled Reaction/Distillation Process for Hydrolysis of Methyl Acetate
    赵素英, 黄镜钊, 王良恩, 黄国强
    . 2010, 18(5):  755-760. 
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    A process composed of a fixed-bed and a distillation column with a side withdraw, mainly methanol, is developed to hydrolyze methyl acetate (MA) as a typical byproduct in polyvinyl alcohol (PVA) and pure terephthalic acid (PTA) factory. The process is simulated by employing the equilibrium stage model RadFrac and plug flow model Rplug in Aspen Plus. Experiments are also carried out in a lab-scale to evaluate the process. The results show that at the molar ratio of water to methyl acetate about 4.0-5.0 in the feed stream and the volume ratio of distillate to feed MA above a critical value, the side product contains more than 80% (by mass) (MeOH) and less than 2% (by mass) MA, while the bottom contains more than 46% (by mass) acetic acid (HAc) and less than 0.5% (by mass) methanol with almost complete conversion of MA. Compared with the old catalytic distillation process we proposed before, this process can cut down 47.6% energy consumption and a distillation column.
    Effect of Additive EDTA on Crystallization Process of Magnesium Hydroxide Precipitation
    徐程浩, 汪芳, 刘代俊, 陈伟
    . 2010, 18(5):  761-766. 
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    The effects of additive ethylenediaminetetraacetic acid (EDTA) on crystallization process were investigated by the induction time of MgSO4-NaOH system. Nucleation and growth rates, growth mechanism and particle size distribution of magnesium hydroxide precipitation were involved with. The induction time in unseeded and seeded precipitation of magnesium hydroxide with and without additive EDTA was measured. The conductivity method was used to determine the induction period. Theoretical relations of the induction time and supersaturation ratio for different growth mechanisms and a combined analysis on the induction time were applied to determine nucleation and growth rates. The growth mechanism of magnesium hydroxide precipitation was disclosed by analyzing the experimental data with and without additive. The analysis on induction time indicated that additive EDTA had a significant influence on both nucleation and growth of magnesium hydroxide precipitation. The mechanism underlying the effect of EDTA on crystal growth was 2-dimension nucleation-mediated growth model.
    Caffeine Crystallization Induction Time Measurements Using Laser Scattering Technique and Correlation to Surface Tension in Water and Ethanol
    韩佳宾, 王静康
    . 2010, 18(5):  767-769. 
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    Caffeine nucleation induction times were measured at 30℃ and 40℃ in water and ethanol solvents employing laser light absorption technique. Supersaturation concentrations and liquid/solid phase surface tensions were calculated from crystallization induction times using classic homogeneous nucleation theory. Induction time and surface tension decreased at higher temperature.
    A Theoretical Model for the Size Prediction of Single Bubbles Formed under Liquid Cross-flow
    刘长军, 梁斌, 唐盛伟, 张海广, 闵恩泽
    . 2010, 18(5):  770-776. 
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    The size of initial bubbles is an important factor to the developed bubble size distribution in a gas-liquid contactor. A liquid cross-flow over a sparger can produce smaller bubbles, and hereby enhance the performance of contactor. A one stage model by balancing the forces acting on a growing bubble was developed to describe the formation of the bubble from an orifice exposed to liquid cross-flow. The prediction with this model agrees with the experimental data available in the literatures, and show that orifice size strongly affects the bubble size. It is showed that the shear-lift force, inertia force, surface tension force and buoyancy force are major forces, and a simplified mathematical model was developed, and the detachment bubble diameter can be predicted with accuracy of <±21%.
    A Novel Scheduling Strategy for Crude Oil Blending
    摆亮, 江永亨, 黄德先, 刘先广
    . 2010, 18(5):  777-786. 
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    For those refineries which have to deal with different types of crude oil, blending is an attractive solution to obtain a quality feedstock. In this paper, a novel scheduling strategy is proposed for a practical crude oil blending process. The objective is to keep the property of feedstock, mainly described by the true boiling point (TBP) data, consistent and suitable. Firstly, the mathematical model is established. Then, a heuristically initialized hybrid iterative (HIHI) algorithm based on a two-level optimization structure, in which tabu search (TS) and differential evolution (DE) are used for upper-level and lower-level optimization, respectively, is proposed to get the model solution. Finally, the effectiveness and efficiency of the scheduling strategy is validated via real data from a certain refinery.
    Run-to-run Optimization for Fed-batch Fermentation Process with Swarm Energy Conservation Particle Swarm Optimization Algorithm
    王建林, 薛尧予, 于涛, 赵利强
    . 2010, 18(5):  787-794. 
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    An iterative optimization strategy for fed-batch fermentation process is presented by combining a run-to-run optimization with swarm energy conservation particle swarm optimization (SEC-PSO). SEC-PSO, which is designed with the concept of energy conservation, can solve the problem of premature convergence frequently appeared in standard PSO algorithm by partitioning its population into several sub-swarms according to the energy of the swarm and is used in the optimization strategy for parameter identification and operation condition optimization. The run-to-run optimization exploits the repetitive nature of fed-batch processes in order to deal with the optimal problems of fed-batch fermentation process with inaccurate process model and unsteady process state. The kinetic model parameters, used in the operation condition optimization of the next run, are adjusted by calculating time-series data obtained from real fed-batch process in the run-to-run optimization. The simulation results show that the strategy can adjust its kinetic model dynamically and overcome the instability of fed-batch process effectively. Run-to-run strategy with SEC-PSO provides an effective method for optimization of fed-batch fermentation process.
    Noninvasive Flow Regime Identification for Wet Gas Flow Based on Flow-induced Vibration
    华陈权, 王昌明, 耿艳峰, 石天明
    . 2010, 18(5):  795-803. 
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    A novel noninvasive approach, based on flow-induced vibration, to the online flow regime identification for wet gas flow in a horizontal pipeline is proposed. Research into the flow-induced vibration response for the wet gas flow was conducted under the conditions of pipe diameter 50 mm, pressure from 0.25 MPa to 0.35 MPa, Lockhart-Martinelli parameter from 0.02 to 0.6, and gas Froude Number from 0.5 tO2.7. The flow-induced vibration signals were measured by a transducer installed on outside wall of pipe, and then the normalized energy features from different frequency bands in the vibration signals were extracted through 4-scale wavelet package transform. A "binary tree" multi-class support vector machine(MCSVM) classifier, with the normalized feature vector as inputs, and Gaussian radial basis function as kernel function, was developed to identify the three typical flow regimes including stratified wavy flow, annular mist flow, and slug flow for wet gas flow. The results show that the method can identify effectively flow regimes and its identification accuracy is about 93.3%. Comparing with the other classifiers, the MCSVM classifier has higher accuracy, especially under the case of small samples. The noninvasive measurement approach has great application prospect in online flow regime identification.
    Study on Excess Thermodynamic Parameters and Theoretical Estimation of Ultrasonic Velocity Using Scaled Particle Theory in Binary Liquid Mixtures of 2-Methyl-2-propanol and Nitriles at Different Temperatures
    K. Rajagopal, S. Chenthilnath
    . 2010, 18(5):  804-816. 
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    Density, ρ, ultrasonic speed, u, and viscosity, η, of binary mixtures of 2-methyl-2-propanol (2M2P) with acetonitrile (AN), propionitrile (PN) and butyronitrile (BN) including those of pure liquids are measured over the entire composition range at temperatures 298.15, 303.15 and 308.15 K. From these experimental data, the excess available volume, VaE, excess free volume, VfE, excess isothermal compressibility, βTE, excess thermal expansion coefficient, aE, and excess internal pressure, πiE, are calculated. The variation of these properties with composition and temperature are discussed in terms of molecular interactions between unlike molecules of the mixtures. It is found that the values of VaE, VfE, βTE and aE are positive and those of πiE are negative for all the mixtures at each temperature studied, indicating the presence of weak interactions between 2M2P and AN/PN/BN molecules. The variations of VaE, VfE, βTE, aE and πiE values with composition indicate that the interactions in these mixtures follow the order:AN<PN<BN, i.e., the 2M2P-nitrile interaction decreases with the increase of alkyl chain length in these nitrile molecules. In addition, the theoretical ultrasonic velocity is calculated using the scaled particle theory and compared with the experimental values.
    Prediction of Flash Point Temperature of Organic Compounds Using a Hybrid Method of Group Contribution+Neural Network+Particle Swarm Optimization
    Juan A. Lazzús
    . 2010, 18(5):  817-823. 
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    The flash points of organic compounds were estimated using a hybrid method that includes a simple group contribution method (GCM) implemented in an artificial neural network (ANN) with particle swarm optimization (PSO). Different topologies of a multilayer neural network were studied and the optimum architecture was determined. Property data of 350 compounds were used for training the network. To discriminate different substances the molecular structures defined by the concept of the classical group contribution method were given as input variables. The capabilities of the network were tested with 155 substances not considered in the training step. The study shows that the proposed GCM+ANN+PSO method represent an excellent alternative for the estimation of flash points of organic compounds with acceptable accuracy (AARD=1.8%;AAE=6.2 K).
    Purification and Characterization of a Versatile Peroxidase from Edible Mushroom Pleurotus eryngii
    陈敏, 姚善泾, 张虹, 梁新乐
    . 2010, 18(5):  824-829. 
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    A versatile peroxidase (VP-Peco60-7) was generated and purified from the liquid culture of Pleurotus eryngii. The purification procedure included ammonium sulfate precipitation, ion exchange chromatography, and gel chromatography. The molecular weight and isoelectric point (pI) of VP-Peco60-7 were determined to be approxi-mately 40 kDa and 4.1, respectively. By N-terminal sequence determination and peptide mapping analysis, VP-Peco60-7 was found to be similar to the versatile peroxidase isoenzyme VPL1, which was previously isolated from liquid cultures of the same species. However, the molecular weight and pI of VP-Peco60-7 were different from those of versatile peroxidases of liquid cultures, implying that the VP-Peco60-7 in this study is of a novel type. With 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) as a substrate, the maximal enzyme activity was obtained at 50℃ and pH 3.0. The catalysis of ABTS by VP-Peco60-7 was expressed by the Michaelis-Menten equa-tion. At 50℃ and pH 3.0, the maximum velocity (Vmax) was 188.68 U·mg-1 and the michaelis constant (Km) was 203.09 μmol·L-1.
    Analysis of Metabolic Products by Response Surface Methodology for Production of Human-like Collagen II
    郭佳庆, 骆艳娥, 范代娣, 高鹏飞, 马晓轩, 朱晨辉
    . 2010, 18(5):  830-836. 
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    Recombinant Escherichia coli BL21 is used to produce human-like collagen. The key constituents of media are optimized using response surface methodology (RSM). Before thermal induction, the highest biomass production and the lowest production of some hazardous by-products, especially acetic acid, were obtained in the media containing 0.085 mol·L-1 glucose and 0.019 mol·L-1 nitrogen (carbon-nitrogen ratio, 4.47:1). After thermal induction, when the concentrations of glucose and nitrogen in the media were 0.065 mol·L-1 and 0.017 mol·L-1, respectively (carbon-nitrogen ratio, 3.82:1), the productivity of human-like collagen per cell was the highest while that of acetic acid was the lowest. The extended analysis showed that the production of lactic acid and propionic acid increased while that of some intermediate acids of the tricarboxylic acid cycle decreased if the dose of glucose increased.
    Water-recycled Cassava Bioethanol Production Integrated with Two-stage UASB Treatment
    孙付保, 毛忠贵, 张建华, 张宏建, 唐蕾, 张成明, 张静, 翟芳芳
    . 2010, 18(5):  837-842. 
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    Considering limited success in target-hitting discharge from alcohol industry, our attention was directed toward a recycling use of distillery spentwash (DS) in cassava bioethanol production by using a two-stage up-flow anaerobic sludge blanket bioremediation (TS-UASBB). With the TS-UASBB,SO4-2, COD, N and P in the effluent from the DS degraded significantly and their concentrations were kept at 0.2 g·L-1, 2.0 g·L-1, 1.0 g·L-1 and 15 mg·L-1, respectively, in 13 batch processes for water-recycled ethanol fermentation. With the effluent used directly as dilution water, no heat-resistant bacteria were found alive. The thirteen-batch ethanol production individually achieved 10% after 48 h fermentation. The starch utilization ratio and total sugar consumption were 90% and 99.5%, respectively. The novel water-recycled bioethanol production process with ethanol fermentation and TS-UASBB has a considerable potential in other starchy and cellulosic ethanol production.
    On-line Measurement for Ohmic Resistance in Direct Methanol Fuel Cell by Current Interruption Method
    刘敏, 王金海, 王树博, 谢晓峰, 周涛, V.K.Mathur
    . 2010, 18(5):  843-847. 
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    Electrochemical impedance spectroscopy (EIS) is widely used in fuel cell impedance analysis. However, for ohmic resistance (RΩ), EIS has some disadvantages such as long test period and complex data analysis with equivalent circuits. Therefore, the current interruption method is explored to measure the value of RΩ in direct methanol fuel cells (DMFC) at different temperatures and current densities. It is found that RΩ decreases as temperature increase, and decreases initially and then increases as current density increases. These results are consistent with those measured by the EIS technique. In most cases, the ohmic resistances with current interruption (RiR) are larger than those with EIS (REIS), but the difference is small, in the range from-0.848% to 5.337%. The errors of RiR at high current densities are less than those of REIS. Our results show that the RiR data are reliable and easy to obtain in the measurement of ohmic resistance in DMFC.
    Synthesis of Petroleum Sulfonate Surfactant by Different Sulfonating Agent with Application of HIGEE Technology
    张迪, 张鹏远, 邹海魁, 初广文, 毋伟, 朱忠武, 邵磊, 陈建峰
    . 2010, 18(5):  848-855. 
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    With the application of HIGEE process intensification technology, petroleum sulfonate surfactant used for enhanced oil recovery was synthesized from petroleum fraction of Shengli crude oil with three sulfonating agents, including diluted liquid sulfur trioxide, diluted gaseous sulfur trioxide and fuming sulfuric acid. For each sulfonating agent, different operation modes (liquid-liquid or gas-liquid reaction with semi-continuous or continuous operation) were applied. The effects of various experimental conditions, such as solvent/oil mass ratio, sulfonating agent/oil mass ratio, gas/liquid ratio, gas concentration, reaction temperature, rotating speed, circulation ratio, reaction time and aging time, on the content of active matter and unsulfonated oil were investigated. Under relatively optimal reaction conditions, the target product was prepared with high mass content of active matter (up to 45.3%) and extremely low oil/water interfacial tension (4.5×10-3mN·m-1). The product quality and process efficiency are higher compared with traditional sulfonation technology.
    Proton Exchange Membrane Fuel Cell with Humidifying Zone
    吕维忠, 刘志祥, 王诚, 毛宗强, 张密林
    . 2010, 18(5):  856-862. 
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    Water management is of great importance to maintain performance and durability of proton exchange membrane fuel cells. This paper presents a novel proton exchange membrane (PEM) fuel cell with a humidification zone in the membrane electrode assembly (MEA) of each cell, in which the moisture of the cathode exhaust gas could transfer through the membrane to humidify anode or cathode dry gas. With a simple model, the relative humidity (RH) of the dry air exhaust from a membrane humidifier with 100% RH stream as a counter flow is calculated to be 60.0%, which is very close to the experimental result (62.2%). Fuel cell performances with hydrogen humidifying, air humidifying and no humidifying are compared at 50, 60 and 70℃ and the results indicate that humidifying is necessary and the novel design with humidifying zone in MEA is effective to humidify dry reactants. The hydrogen humidifying shows better performance in short term, while water recovered is limited and the stability is not as good as air humidifying. It is recommended that both air and hydrogen should be humidified with proper design of the humidifying zones in MEA and plates.
    Fluorescent Proteins as a Visible Molecular Signal for Rapid Quantification of Bioprocesses:Potential and Challenges
    张翀, 邢新会
    . 2010, 18(5):  863-869. 
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    Green fluorescent protein (GFP) and its variants/homolog proteins are generally called as GFP-like fluorescent proteins (FPs), which are widely used as visible molecular tools for monitoring a wide range of biological processes due to their capability of simple, accurate and real time quantification. The FPs-based molecular and visible quantification tools are giving more impact on bioprocess engineering, enabling the biomolecule-level dynamic information to be linked with the process-level events. In this review, different applications of FPs in biological engineering with emphasis on rapid molecular bioprocess quantification, such as quantification of the transcription efficiency, the protein production, the protein folding efficiency, the cell concentration, the intracellular microenvironments and so on, would be first introduced. The challenges of using FPs with respect to actual bioprocess applications for the precise quantification including the interaction of FPs and the fused partner proteins, the maturation of FPs, the inner filter effect and sensing technology were then discussed. Finally, the future development for the FPs used in molecular bioprocess quantification would be proposed.
    Enzymatic Synthesis of Fatty Acid Methyl Esters from Crude Rice Bran Oil with Immobilized Candida sp. 99-125
    李政, 邓利, 鲁吉珂, 郭小雷, 杨自信, 谭天伟
    . 2010, 18(5):  870-875. 
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    The non-edible crude rice bran oil was extracted from white rice bran, and then was catalyzed by immobilized lipase for biodiesel production in this study. The effects of water content, oil/methanol molar ratio, temperature, enzyme amount, solvent,number of methanol added times and two-step methanolysis by using Candida sp. 99-125 as catalyst were investigated. The optimal conditions for processing 1 g rice bran oil were:0.2 g immobilized lipase, 2 ml n-hexane as solvent, 20% water based on the rice bran oil mass, temperature of 40℃ and two-step addition of methanol. As a result, the fatty acid methyl esters yield was 87.4%. The immobilized lipase was proved to be stable when it was used repeatedly for 7 cycles.
    An Improved Method for Fullerol Preparation Based on Dialysis
    姚璐, 康峰, 彭琦云, 杨新林
    . 2010, 18(5):  876-879. 
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    A dialysis-based method was developed to remove Na ions in fullerol preparation by a conventional synthetic route. Fullerol was synthesized using a typical two-phase reaction in the presence of tetrabutylammonium hydroxide. Its structure was confirmed by UV spectra, Fourier transform infrared spectroscopy spectra, 1H nuclear magnetic resonance, and matrix-assisted laser desorption/ionization time of flight mass spectra. The content of Na element was determined by inductive coupled plasma atomic emission spectroscopy. The mass content of Na in the product obtained from the conventional route was about 10%, and it could be almost completely eliminated by dialysis with a membrane of molecular weight cut-off (MWCO) 8-15 kDa. The yield of fullerol by the dialysis method was slightly higher than by the conventional route. These results indicate that dialysis may have a potential application for fullerol preparation.
    Multi-scale Chaotic Analysis of the Characteristics of Gas-Liquid Two-phase Flow Patterns
    李洪伟, 周云龙, 孙斌, 杨悦
    . 2010, 18(5):  880-888. 
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    Using the high-speed camera the time sequences of the classical flow patterns of horizontal gas-liquid pipe flow are recorded, from which the average gray-scale values of single-frame images are extracted. Thus obtained gray-scale time series is decomposed by the Empirical Mode Decomposition (EMD) method, the various scales of the signals are processed by Hurst exponent method, and then the dual-fractal characteristics are obtained. The scattered bubble and the bubble cluster theories are applied to the evolution analysis of two-phase flow patterns. At the same time the various signals are checked in the chaotic recursion chart by which the two typical characteristics (diagonal average length and Shannon entropy) are obtained. Resulting term of these properties, the dynamic characteristics of gas-liquid two-phase flow patterns are quantitatively analyzed. The results show that the evolution paths of gas-liquid two-phase flow patterns can be well characterized by the integrated analysis on the basis of the gray-scale time series of flowing images from EMD, Hurst exponents and Recurrence Plot (RP). In the middle frequency section (2nd, 3rd, 4th scales), three flow patterns decomposed by the EMD exhibit dual fractal characteristics which represent the dynamic features of bubble cluster, single bubble, slug bubble and scattered bubble. According to the change of diagonal average lengths and recursive Shannon entropy characteristic value, the structure deterministic of the slug flow is better than the other two patterns. After the decomposition by EMD the slug flow and the mist flow in the high frequency section have obvious peaks. Anyway, it is an effective way to understand and characterize the dynamic characteristics of two-phase flow patterns using the multi-scale non-linear analysis method based on image gray-scale fluctuation signals.