Sep 2010, Volume 4 Issue 3
    

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  • Research articles
    Introduction to the special section on the Symposium on Computational Fluid Dynamics and Molecular Simulation
    Tianwei TAN, Peiyong QIN,
    2010, 4(3): 241-241. https://doi.org/10.1007/s11705-009-0285-3
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  • Research articles
    CFD simulation of jet behaviors in a binary gas-solid fluidized bed: comparisons with experiments
    Pei PEI, Guiying WU, Bangting YU, Kai ZHANG, Jianchun JIANG, Dongsheng WEN,
    2010, 4(3): 242-249. https://doi.org/10.1007/s11705-009-0277-3
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    Based on the experimental observation of the fluidization characteristics of solid mixtures (resin and rapeseed) with different densities and sizes, the jet behaviours of the binary system are simulated in a two-dimensional jetting fluidized bed 0.30 m in width and 2.00 m in height. A simple mathematical model, by introducing two additional force terms in both gas and particle phase momentum equations of Gidaspow’s inviscid two-fluid model, is used to explore the effects of jet gas velocity and mixture combination on the jet penetration depth in the fluidized bed with a binary system. Experimental results show that there is a fluidization velocity interval (uif-uff) for the resin-on-rapeseed (flotsam-on-jetsam) segregated bed. The simulated jet penetration depth increases with the increase of jet gas velocity and the volume fraction of the flotsam (resin), which is in fair agreement with experimental data. The above findings show that the hydrodynamic model of Brandani and Zhang (2006), by introducing the average physical properties from Goossens et al.(1971), can be used to predict the jet behaviors of a well-mixing binary system.
  • Research articles
    Molecular size characterization of heavy oil fractions in vacuum and solution by molecular dynamic simulation
    Wenpo REN, Honggang CHEN, Chaohe YANG, Honghong SHAN,
    2010, 4(3): 250-256. https://doi.org/10.1007/s11705-009-0281-7
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    Two kinds of heavy oils were fractionated into eight fractions by Liquid-Solid Adsorption Chromatography, respectively, and samples were collected to measure properties. According to the elemental analysis, molecular weight and 1H-NMR data, average molecular structures of polycyclic aromatic and heavy resin were constructed with improved Brown-Ladner (B-L) method and several corrections. And then, the most stable conformations of polycyclic aromatic and heavy resin in vacuum and toluene solution were obtained by molecular dynamic simulation, and the molecular size was gotten via the radius of gyration analysis. The results showed that the radius of gyration of polycyclic aromatic and heavy resin was 0.55–0.70 nm in vacuum and 0.60–0.90 nm in toluene solution. With molecular weight increasing, the molecular size in vacuum and toluene solution also increased. Due to the swelling behavior of solvent, the alkyl side chains of heavy oil molecule in solution were more stretched. Thus, the molecular size in toluene solution was larger than that in vacuum.
  • Research articles
    Study on the gas permeabilities in styrene-butadiene rubber by molecular dynamics simulation
    Hailu LIU, Xuejia DING, Jun YI, Liqun ZHANG, Sizhu WU,
    2010, 4(3): 257-262. https://doi.org/10.1007/s11705-009-0270-x
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    In this research, molecular dynamics (MD)simulations were used to study the transport properties of small gas molecules in the butadiene-styrene copolymer(SBR). The condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field was applied. The diffusion coefficients were obtained from MD (NVT ensemble) and the relationship between gas permeability; the chemical structure and free volume of butadiene-styrene copolymer were investigated. The results indicated that the diffusion coefficient of oxygen declined with increasing styrene content. The fraction of free volume (FFV) in butadiene-styrene copolymer was calculated. It was concluded that diffusion coefficient increased as the FFV increases, which is in accordance with the analysis of the small molecular hop through the free volume in polymer matrix. Subsequently, the glass transition temperatures of these copolymers were calculated by MD. The result showed that the glass transition temperature increased with increasing styrene content in polymer.
  • Research articles
    Simulation of cottonseed cake melt flow in metering zone of a single screw extruder
    Hong HE, Jianguo ZHOU,
    2010, 4(3): 263-269. https://doi.org/10.1007/s11705-009-0276-4
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    Research on the extrusion of natural polymers (food, feed, etc.) is relatively new due to the complex physicochemical transformations of raw materials, although plastics melt conveying and transport have been well studied. The structure and composition, rheological behavior as well as extrusion processing of natural polymer are much more complicated. In this study, a quasi-three-dimensional (3D) fluid flow model for non-Newtonian, non-isothermal and undeveloped temperature was developed, the model prediction being in reasonably good agreement with the experiment. Results show that the influence of moisture content, among other process variables, is the most significant, followed by screw speed. Some interaction exists between these two variables and the screw speed effect becomes marginal at high moisture contents. In addition, viscosity change in the channel was studied.
  • Research articles
    Monte Carlo simulation of the diffusion-limited aggregating process of particle suspension systems
    Jiajing XU, Lin ZHANG, Yongjian TANG, Wei DAI, Wenwen SHAN,
    2010, 4(3): 270-274. https://doi.org/10.1007/s11705-009-0273-7
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    The aggregating process of particle suspension systems is a very universal phenomena and crucial for various processes both in nature and in industry. In this paper, the aggregating process was simulated with off-lattice diffusion-limited cluster-cluster aggregation (DLCA) Monte Carlo programs. The self-similar fractal structures of aggregates have been clearly demonstrated by the statistical analysis of gyration radius distribution and the existence of a scaling distribution of the reduced cluster size. The fractal dimension determined from the relationship between mass and gyration radius of aggregates was 1.80 or so. The fractal dimension of the aggregates drawn from the radial distribution function and structure factor of a single aggregate is about 1.90–2.10. It was also showed that, along with the increasing of particle volume fraction, the fractal dimension will increase in a nearly square root manner, and the spatial range of the fractal structure appearing becomes narrower. Also, the gelation transition can only occur in a particle suspension system where the particle volume fraction is greater than a critical value.
  • Research articles
    Simulating the air flow in the conveying pipe of the foreign fiber detection device
    Ting CHEN, Lili WU, Ke WANG,
    2010, 4(3): 275-279. https://doi.org/10.1007/s11705-009-0274-6
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    Cotton bales are frequently intermingled with foreign fibers which will interfere in the process of spinning, weaving and dyeing and will worsen the product quality. Nowadays, cotton fibers are sorted manually in most of the cotton textile mills with very low efficiency. There is a great demand for foreign fiber detection devices in Chinese cotton textile mills. The air flow in the conveying pipe of the device has an important effect on the image acquisition, image analysis and removal of foreign fibers. As a primary effort, the air flow in the conveying pipe of the foreign fiber detection device was simulated numerically. The effects of the inlet air velocity on the air turbulence intensity and air velocity along the detecting section were studied.
  • Research articles
    Many-body dissipative particle dynamics simulation of wetting phenomena
    Ying ZHAO, Ye YUE, Xianren ZHANG, Shuangyang LI, Atul SAJJANHAR,
    2010, 4(3): 280-282. https://doi.org/10.1007/s11705-009-0278-2
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    With the development of the simulation of particle dynamics, the traditional dissipative particle dynamics (DPD) method can not satisfy the needs of research in static or dynamic wetting phenomena. However, the Many-body DPD approach extends the ability of the traditional method to simulate the interface between solid and liquid or some other situation. In this paper, we propose a Many-body DPD program to simulate the solid-liquid interface and get satisfactory results.
  • Research articles
    Research on pedestrian escape route without visibility based on Markov chain model
    Xiaoping ZHENG, Lijuan DU, Hongjiang WANG,
    2010, 4(3): 283-289. https://doi.org/10.1007/s11705-009-0272-8
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    It is a pioneering work to use a Markov chain model to study the pedestrian escape route without visibility. In this paper, based on the Markov chain probability transition matrix, the algorithms with random numbers and the spatial-grid, an escape route in a limited invisible space is obtained. Six pace states (standing, crawling, walking, leaping, jogging, and running) are applied to describe the characteristics of pedestrian behaviors. Besides, eight main direction changes are used to describe the transition characteristic of a pedestrian. At the same time, this paper analyzes the escape route from two views, i.e., pedestrian pace states and directions. The research results show that the Markov chain model is more realistic as a means of studying pedestrian escape routes.
  • Research articles
    Elements’ important ranking of China drug safety management system: applying the non-structural fuzzy group decision method
    Xiaoping ZHENG, Xiaocui WANG, Tingkuan ZHONG,
    2010, 4(3): 290-299. https://doi.org/10.1007/s11705-009-0283-5
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    Drug safety management is an important issue in China drug management system and attracts great attentions from the whole society. In order to reduce drug incident, this study discusses some important elements associated with China drug safety management system and analyzes the data collected by questionnaires. Besides, a methodology for rating the important elements is described and applied. The non-structural fuzzy group decision method not only considers the insufficient precise information but also combines the opinions of different kinds of respondents in China’s four municipalities. The results indicate that the sample systems are the most important in these important elements, and the order of importance is sampling systems, licensing systems, traceability systems, transaction models, pharmacovigilance and emergence management. This study not only points out the important ranking of the pivotal elements in China drug safety management but also gives some specific proposals about how to enhance drug safety management in China.
  • Research articles
    Effect of PEG additives on properties and morphologies of polyetherimide membranes prepared by phase inversion
    Jian CHEN, Jiding LI, Xia ZHAN, Xiaolong HAN, Cuixian CHEN,
    2010, 4(3): 300-306. https://doi.org/10.1007/s11705-009-0280-8
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    This study investigated the effect of poly(ethylene glycol) (PEG) additive as a pore-former on the structure formation of membranes and their permeation properties connected with the changes in thermodynamic and kinetic properties in the phase inversion process. The membranes were prepared by using polyetherimide/N-methyl-2-pyrrolidone/PEG (PEI/NMP/PEG) casting solution and water coagulant. The resulting membranes, prepared by changing the ratio of PEG to PEI, were characterized by scanning electron microscope (SEM) observations, measurements of water flux and γ-globin rejection. The thermodynamic and kinetic properties of the membrane-forming system were studied through viscosity. The pore radius distribution curves were especially obtained by differential scanning calorimetry (DSC). Furthermore, the membranes were characterized for pure water flux and rejection of solute and by SEM observation. The filtration results agreed well with the SEM observations. As expected, PEG with a fixed molecular weight (PEG 600) acted as a pore forming agent, and membrane porosity increased as the PEG content of the casting solution increased.
  • Research articles
    Study on the microwave-assisted extraction of polyphenols from tea
    Liyun WANG, Peiyong QIN, Yan HU,
    2010, 4(3): 307-313. https://doi.org/10.1007/s11705-009-0282-6
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    This study demonstrated a promising method for quickly extracting tea polyphenol (TP) by microwave-assisted extraction (MAE) technology. Some influential parameters, including MAE temperature, microwave power, concentration of extraction solvent, MAE time and the solid/liquid ratio, were investigated. The optimum condition of MAE was obtained by dual extraction with 60% ethanol (v/v) and the solid/liquid ratio 1:12 g/mL at 80°C for 10 minutes under the microwave power 600 W. The yield of TP was 96.5% under the described condition. Compared with traditional methods, including hot reflux extraction (HRE), ultrasound-assisted extraction (UAE) and supercritical fluid extraction (SFE), the extraction time was saved 8 times than that of HRE, and the yield was increased by 17.5%. The extraction time at comparable levels of production was saved 2 times, and the energy consumption was one fourth that of UAE. The extraction time was saved 5 times than that of SFE, and the yield of TP was increased by 40%. Moreover, compared with MAE of TP studied by others, it decreased the solid/liquid ratio from 1 ∶ 20 to 1 ∶ 12 g/mL without 90-min pre-leaching time, and the yield of TP was increased by 6%–40%.
  • Research articles
    Desulfurization mechanism of FCC gasoline: A review
    Liang ZHAO, Yan CHEN, Jinsen GAO, Yu CHEN,
    2010, 4(3): 314-321. https://doi.org/10.1007/s11705-009-0271-9
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    This paper reviews the most important developments on the desulfurization mechanism of Fluid Catalytic Cracking (FCC) gasoline. First, the origin of sulfur compounds in FCC gasoline and the current developed desulfurization approaches and technologies are briefly introduced, and then the researches on desulfurization mechanism are summarized from experimental and theoretical perspectives. Further researches on the desulfurization mechanism will lay a foundation for optimizing desulfurization sorbents and technologies.
  • Research articles
    Simultaneous removal of trihalomethanes by bimetallic Ag/Zn: kinetics study
    Ahmed H A DABWAN, Satoshi KANECO, Hideyuki KATSUMATA, Kiyoyuki EGUSA, Tohru SUZUKI, Kiyohisa OHTA,
    2010, 4(3): 322-327. https://doi.org/10.1007/s11705-009-0261-y
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    In the present work, bimetallic silver/zinc was applied into the degradation of trihalomethanes, THMs: CHCl3, CHBrCl2, CHBr2Cl, and CHBr3. The kinetics reaction rates and removal efficiencies of the THM compound mixtures, in the aqueous solutions, were investigated. Batch experiments were conducted under mild conditions, ambient temperature, and pressure. The primary degradation reaction followed a pseudo-first-order kinetic law. The first-order rate constants and the degradation efficiencies followed the decreasing order of CHBr3>CHBr2Cl>CHBrCl2>CHCl3. The bond dissociation energy and hydrophilic/hydrophobic characteristics of the THM compounds may become the most important parameters affecting the degradation kinetics and efficiency by bimetallic Ag/Zn.
  • Research articles
    Dyeing fine denier polypropylene fibers with phenylazo- β -naphthol-containing sulfonamide disperse dyes
    Zhihua CUI, Weiguo CHEN, Jinzong YANG, Shufen ZHANG,
    2010, 4(3): 328-335. https://doi.org/10.1007/s11705-009-0216-3
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    A series of phenylazo-β-naphthol-containing sulfonamide disperse dyes were prepared from C.I. Acid Orange 7 by successive reactions of chlorination and amination, and their chemical structures were characterized by FTIR, 1H NMR, and mass spectrometry. The dyes were applied to coloring of knitted fabrics from fine denier polypropylene fibers by exhaust dyeing and their optimal dyeing conditions, such as dyebath pH, dyeing temperature, dyeing time, and dye concentration were investigated in detail. Then, dye exhaustion, color strength, and color fastnesses of the dyes on the fibers were assessed and summarized. In view of dye exhaustion and color strength of the sulfonamide dyes on fine denier PP fabrics, 90°C was selected as the best dyeing temperature at dye concentration below or equal to 3.0% owf. For achieving higher color strength, 130°C was the better choice when the dye concentration was above 3.0% owf. The sulfonamide dyes, especially secondary sulfonamide dyes, exhibited superior dye exhaustion and color fastnesses to washing, sublimation, and rubbing on fine denier PP fabrics in comparison to C.I. Solvent Yellow 14 bearing the same chromophore but without sulfonamide group.
  • Research articles
    Determination of the diffusion of poly(ethylene glycol) in polypropylene using ATR-FTIR
    Hanjia CHEN, Xuhua SHI, Yafei ZHU, Yi ZHANG, Jiarui XU,
    2010, 4(3): 336-341. https://doi.org/10.1007/s11705-009-0230-5
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    The diffusion of poly(ethy1ene glycol) (PEG) in polypropylene (PP) was investigated using attenuated total reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Atomic Force Micrograph (AFM), and Scanning Electron Microscopy (SEM). It has been found that the diffusion of PEG in PP was greatly affected by the annealing temperature and the molecular weight of PEG. Higher temperature was in favor of PEG to diffuse in PP with fast velocity and reached diffusion equilibrium with shorter time. PEG with higher molecular weight was distributed in PP with bigger phase domains and had lower diffusivity, which resulted in its lesser enrichment on the surface of the PP blend film.
  • Research articles
    Catalysis and deactivation of montmorillonite K10 in the aryl O -glycosylation of glycosyl trichloroacetoimidates
    Xiaoliu LI, Xinhao YAN, Zhiwei LI, Hua CHEN, Pingzhu ZHANG,
    2010, 4(3): 342-347. https://doi.org/10.1007/s11705-009-0279-1
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    The catalysis of montmorillonite K10 (MK10) for aryl O-glycosylation of glycosyl trichloroacetimidates was investigated. It was found that the catalyst MK10 is deactivated gradually in the recycle glycosylation. The fresh and the deactivated catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), and N2 adsorption-desorption. The results show that the eliminated trichloroacetamide molecule deposits on the MK10, which blocks and poisons the active sites, resulting in the deactivation of the catalyst. The regeneration of the deactivated MK10 by calcination was studied preliminarily.
  • Research articles
    Molecular dynamic simulation on the conformation of mouse muscle type nAChR
    Shengai SUN, Rilei YU, Yanhui ZHANG, Yanni LI,
    2010, 4(3): 348-352. https://doi.org/10.1007/s11705-009-0284-4
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    A mouse muscle type nAChR model ((α1)2βδγ) was built based on the cryoelectron microscopic structure of intact Torpedo marmorata nAChR and the high resolution crystal structure of nAChR-α1 subunit. The conformation of the pentameric nAChR model was investigated by molecular dynamic simulation. The function of water molecule in the hydrophilic interior was clarified. The reason for Tyr127 showing two alternative conformations was discussed in detail.
  • Research articles
    Residence time distribution and modeling of the liquid phase in an impinging stream reactor
    Xingjun WANG, Xianhui HU, Lishun HU, Guangsuo YU, Fuchen WANG,
    2010, 4(3): 353-359. https://doi.org/10.1007/s11705-009-0262-x
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    Based on some experimental investigations of liquid phase residence time distribution (RTD) in an impinging stream reactor, a two-dimensional plug-flow dispersion model for predicting the liquid phase RTD in the reactor was proposed. The calculation results of the model can be in good agreement with the experimental RTD under different operating conditions. The axial liquid dispersion coefficient increases monotonously with the increasing liquid flux, but is almost independent of gas flux. As the liquid flux and the gas flux increase, the liquid dispersion coefficient of center-to-wall decreases. The axial liquid dispersion coefficient is much larger than that of center-to-wall, which indicates that the liquid RTD is dominated mainly by axial liquid dispersion in the impinging stream reactor.
  • Research articles
    Experimental studies on extraction of cobalt ions from dilute aqueous solutions by using complexation-ultrafiltration process
    Jianxian ZENG, Junfeng LIU, Niandong HUANG,
    2010, 4(3): 360-366. https://doi.org/10.1007/s11705-009-0269-3
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    The extraction of cobalt ions from dilute aqueous solutions was investigated by ultrafiltration with the help of poly(acrylic acid) sodium salt (PAASS). Polysulfone and polyethersulfone hollow fiber ultrafiltration membranes were employed in this process. The kinetics of complexation reaction was studied for PAASS with Co2+. Results showed that, under a large excess of PAASS, it takes 65, 55 and 40 min at pH 5, 6 and 7, respectively, to get the equilibrium of complexation. The reaction kinetics can be described by a pseudo-first-order equation. Then, the effects of various parameters on the extraction of Co2+ were examined in detail. Results indicated that loading ratio, pH value and low-molecular competitive complexing agent affect significantly cobalt rejection coefficient R. Furthermore, a concentration experiment was carried out at pH 7. With increasing volume concentration factor, membrane flux declines slowly, and R value is always about 1. The concentrated retentate was used further for a decomplexation experiment. The decomplexation ratio of cobalt-PAASS complex reaches as high as 90.1%. After the decomplexation step, a diafiltration experiment was performed at pH 2.5. Cobalt ions can be extracted satisfactorily from the retentate, and a purified PAASS is obtained.
  • Research articles
    Study of ultrasound-promoted, lipase-catalyzed synthesis of fructose ester
    Kai ZHU, Hui LIU, Pingfang HAN, Ping WEI,
    2010, 4(3): 367-371. https://doi.org/10.1007/s11705-009-0312-4
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    The effect of low energy ultrasound in biochemistry and biotechnology has attracted great attention in recent years. It can enhance substrate dissolution and improve mass transfer within and outside of a cell, both of which are beneficial to the synthesis of fructose ester. Here we describe the experimental study of the effect of ultrasounds of different intensity on the lipase-catalyzed synthesis of fructose ester in the solvent butanone. The results were compared with control reactions performed with no ultrasound. High performance liquid chromatography (HPLC) and thin layer chromatography (TLC) were used for qualitative and quantitative analyses. The results show the following: 1) the concentration of mono-ester and diester increased with the reaction time, either with or without ultrasonic irradiation. Low energy ultrasound accelerated the reaction due to the effect of ultrasonic steady cavitations, and high energy ultrasound was not beneficial to the reaction. 2) The application of ultrasound played an important role in our lipase-catalyzed reaction. It decreased reaction time as compared to a reaction without ultrasound that resulted in the same yield, increased reaction rate, and enhanced the amount of fructose ester produced. When the frequency was 10 kHz and sound intensity was 0.16 W·m−2, the concentration of ester was twofold more than without ultrasonic irradiation after a reaction time of up to 12 h. With the proper ultrasonic parameters, the overall concentration of production appeared to increase exponentially with the reaction time. 3) Ultrasound had little effect on the initial reaction rate, and continuous ultrasonic irradiation was favorable for the reaction. The longer the reaction continued, the more obvious the effects of the ultrasound became in our experiments.
  • Research articles
    Surface modification of biomaterials by photochemical immobilization and photograft polymerization to improve hemocompatibility
    Yakai FENG, Haiyang ZHAO, Li ZHANG, Jintang GUO,
    2010, 4(3): 372-381. https://doi.org/10.1007/s11705-010-0005-z
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    Thrombus formation and blood coagulation are serious problems associated with blood contacting products, such as catheters, vascular grafts, artificial hearts, and heart valves. Recent progresses and strategies to improve the hemocompatibility of biomaterials by surface modification using photochemical immobilization and photograft polymerization are reviewed in this paper. Three approaches to modify biomaterial surfaces for improving the hemocompatibility, i.e., bioinert surfaces, immobilization of anticoagulative substances and biomimetic surfaces, are introduced. The biomimetic amphiphilic phosphorylcholine and Arg-Gly-Asp (RGD) sequence are the most effective and most often employed biomolecules and peptide sequence for improving hemocompatibility of material surfaces. The RGD sequence can enhance adhesion and growth of endothelial cells (ECs) on material surfaces and increase the retention of ECs under flow shear stress conditions. This surface modification is a promising strategy for biomaterials especially for cardiovascular grafts and functional tissue engineered blood vessels.