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With the aim of reducing fan performance failure, an effective method of fan reliability analysis based on a hybrid uncertainty model was investigated using a combination of orthogonal test design, an approximation model, and computational fluid dynamics (CFD) simulation and analysis technology. By introducing interval uncertainty, this method can effectively solve the problem of quantifying model uncertainty owing to the lack of experimental samples and can greatly expand the applicability of reliability analysis technology in fluid machinery research. Random and interval uncertainty parameters were introduced to describe the fan system and a mixed random-interval reliability analysis model of fan performance was established based on the traditional first-order reliability analysis method. Using CFD analysis of the renormalization group (RNG) model, the flow, pressure, shaft power, efficiency, and other fan performance parameters were calculated, and the performance function was obtained. Owing to the low efficiency of the CFD calculation, the effective iterative algorithm of response surface to solve hybrid reliability model was studied, and the failure probability interval of fan performance was calculated. The method was used to study the fan performance of a rail transit train, and the failure probability, reliability index, and performance parameter sensitivity and uncertainty were analyzed. The influence of parameter uncertainty on system reliability was determined, and the engineering measures necessary to improve the fan’s performance reliability were proposed.

Because of the working in the bad environment, the fan of rail train is greatly influenced by the environment, especially with the increase of the year. Impeller structure often fails in the design life cycle. According to the uncertainty and self-dependence of structure size, material and load, the time variant reliability analysis of the impeller structure is carried out. Based on the time-dependent reliability analysis technique, an efficient method for analyzing the time-dependent reliability of fan blade structure is presented, which the time varying reliability is converted to the traditional static reliability problem, and the random process is discretized in time. Based on the analysis of the Pneumatic Elasticity, the reliability index and failure probability of the impeller structure under different damping coefficients are obtained, which can provide reference for the practical engineering application. Compared with the analysis results of without considering the aeroelasticity, the conclusion is that the reliability index of aerodynamic elasticity is much smaller than that without considering the aeroelastic reliability index. Without consideration of aeroelastic analysis, the reliability and safety of the impeller structure can be easily overestimated. By analyzing the influence of aerodynamic elasticity on the structure reliability of the impeller, it is very important and necessary to analyze the dynamic elasticity of the impeller.

A kind of modified epoxy resin sheet molding compounds of the impeller has been designed. Through the test, the non-metal impeller has a better environmental aging performance, but must do the waterproof processing design. In order to improve the stability of the impeller vibration design, the influence of uncertainty factors is considered, and a multi-objective robust optimization method is proposed to reduce the weight of the impeller. Firstly, based on the fluid-structure interaction, the analysis model of the impeller vibration is constructed. Secondly, the optimal approximate model of the impeller is constructed by using the Latin hypercube and radial basis function, and the fitting and optimization accuracy of the approximate model is improved by increasing the sample points. Finally, the micro multi-objective genetic algorithm is applied to the robust optimization of approximate model, and the Monte Carlo simulation and Sobol sampling techniques are used for reliability analysis. By comparing the results of the deterministic, different sigma levels and different materials, the multi-objective optimization of the SMC molding impeller can meet the requirements of engineering stability and lightweight. And the effectiveness of the proposed multi-objective robust optimization method is verified by the error analysis. After the SMC molding and the robust optimization of the impeller, the optimized rate reached 42.5%, which greatly improved the economic benefit, and greatly reduce the vibration of the ventilation system.

A rapid in situ immobilization process was developed based on conventional separation technique of immobilized metal affinity chromatography (IMAC) and was studied in the case of D-amino acid oxidase (DAAO) with binding-enhancing Heli-tag (His-Arg-Asn-Tyr-Gly-Gly-Cys-Cys-Gly). A recombinant Escherichia coli strain JM105 (Δase)/pGEMK-R-DAAO-Heli was successfully constructed to synthesize chimeric protein DAAO-Heli. Without additional purification procedure, the tagged enzyme DAAO-Heli could be directly immobilized to EP-IDA-Ni(2+) support with purity of 90 % and DAAO activity of over 70 U/g support. Experimental results showed that the immobilized DAAO-Heli was 73 times more thermally stable than free enzyme. Besides, it remained 67 % of initial activity after 100 cycles of batch catalysis and its operational stability was improved 36 times than that of the previously IMAC-immobilized DAAO-His. Furthermore, the epoxy (EP) support could be easily recovered and repeatedly used with simple steps, which could reduce the immobilization costs significantly.

A comprehensive study on the liquid mixing with/without instantaneous reactions was conducted using planar laser induced fluorescence (PLIF) technique, where a novel reactive PLIF technique was adopted to quantitatively visualize the dynamic variation of the concentration of fluorescence dye due to signal quenching by a Fenton reaction. The factors (e.g., tracer injection direction, tracer injection position, impeller speed) influencing the reactive and non-reactive mixing processes were investigated, and the mixing performances were characterized by non-reactive mixing times (τ95 and τ99), and reactive mixing time (θ99), respectively. The experimental results from the 2-D measurements of liquid mixing behavior emphasized the significance of the understanding on the spatio-temporal mixing patterns: not only did the tracer injection position affect the mixing performances in the stirred tank, but also the sampling position to monitor the mixing status would lead to a large difference in evaluating the mixing performance. For the stirred tank with fast reactions, the reactive mixing performance had a strong interplay with the non-reactive mixing.

ZSM-5 zeolites were modified with alkyltrichlorosilanes of various chain lengths (octyltrichlorosilane, decyltrichlorosilane, dodecyltrichlorosilane and hexadecyltrichlorosilane) and characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermal gravimetric analysis (TGA) and contact angle measurements (CA). The results showed that a closely packed and hydrophobic layer was presented at the particles surface and the surface wetting property varied from hydrophilic to hydrophobic, even to superhydrophobic. It was interesting to notice that the hydrophobic properties of modified ZSM-5 particles could be tuned by varying the chain length of chlorosilane and changing the pretreatment temperature before silanization. With increasing the alkyl chain length of trichlorosilane, the hydrophobicity increased. However, with an increase in the pretreatment temperature, the hydrophobicity decreased. Moreover, the relationship between the wetting properties and thermal stability was also investigated, the results showed that the modified ZSM-5 particles possessed good hydrophobicity at a temperature below 250 °C in air. These modified ZSM-5 particles may be utilized for many potential applications, such as membrane fillers, selective adsorbents, catalysts, chromatographic supports and so on.

In this study, poly(dimethyl siloxane) (PDMS)/poly(vinylidene fluoride) (PVDF), poly(phenyl methyl siloxane) (PPMS)/PVDF, poly(ethoxy methyl siloxane) (PEOMS)/PVDF, and poly(trifluropropyl methyl siloxane) (PTFMS)/PVDF composite membranes were prepared. The different functional compositions of these membranes were characterized by Fourier transform infrared spectroscopy. The surfaces and sections of these membranes were investigated by scanning electron microscopy. The hydrophobicity at the membrane surface was assessed with contact angle measurement. Swelling experiments were carried out to investigate the swelling behavior of these membranes. The composite membranes prepared in this study were used in the pervaporation separation of ethanol/water mixtures, and their separation performances were compared. The results show that the separation performances of these membranes were strongly related to the silicone rubber components and composition, the total fluxes decreased in the following order: PDMS > PPMS > PEOMS > PTFMS. The separation factor followed the following order: PPMS > PEOMS > PDMS > PTFMS (5 wt % ethanol at 40°C). In addition, the effects of the feed temperature (40–70°C) and feed composition (5–20 wt %) on the separation efficiency were investigated experimentally. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Configurational-bias Monte Carlo simulations in the isobaric-isothermal ensemble using the TraPPE-UA force field were performed to study the microscopic structures and molecular interactions of mixtures containing supercritical carbon dioxide (scCO(2)) and ethanol (EtOH). The binary vapor-liquid coexisting curves were calculated at 298.17, 333.2, and 353.2 K and are in excellent agreement with experimental results. For the first time, three important interactions, i.e., EtOH-EtOH hydrogen bonding, EtOH-CO(2) hydrogen bonding, and EtOH-CO(2) electron donor-acceptor (EDA) bonding, in the mixtures were fully analyzed and compared. The EtOH mole fraction, temperature, and pressure effect on the three interactions was investigated and then explained by the competition of interactions between EtOH and CO(2) molecules. Analysis of the microscopic structures indicates a strong preference for the formation of EtOH-CO(2) hydrogen-bonded tetramers and pentamers at higher EtOH compositions. The distribution of aggregation sizes and types shows that a very large EtOH-EtOH hydrogen-bonded network exists in the mixtures, while only linear EtOH-CO(2) hydrogen-bonded and EDA-bonded dimers and trimers are present. Further analysis shows that EtOH-CO(2) EDA complex is more stable than the hydrogen-bonded one.

A millisecond mixing process for liquids was implemented using a new mixer design, i.e., a jet nozzle connected with a trumpet -shaped module. The jet nozzle can facilitate two or three liquid channels, performing an initial impingement mixing of liquid sheets in the thickness at millimeters. Then, the joint liquids sheet out of the jet nozzle was stretched thinner and thinner on the expanded solid surface of the trumpet -shaped module, which significantly intensified the liquid mixing process. Accordingly, dual controls on the liquid mixing can be accomplished flexibly by optimizing the operating conditions and the module configuration. Experiments were carried out to investigate the influencing factors on the mixing performance, where the planar laser induced fluorescence (PLIF) technique was used to measure the mass transport of fluorescent dye between the liquids. The intensity of segregation ( IOS ) and 95% mixing time ( τ 9 5 ) were employed to characterize the mixing performance. The results showed that the module with a greater curvature surface possessed a better mixing performance owing to the rapid reduction of the liquid sheet thickness, which strengthened the mixing process in the lateral direction along the flow development. The mixing behaviors are greatly influenced by the flow rate ratio between the liquids. An optimum mixing state could be achieved when Q S 1 /Q S 2 is 1:1. An increase of Q T under the same flow rate ratio does not affect the mixing pattern in space, but the corresponding τ 95 is almost linearly shortened. By splitting one liquid stream into two surrounding streams, the so called Sandwich operation brought further improved mixing performance compared with the two liquids mixing process. Using the novel jet nozzle design, millisecond(s) mixing of liquids can be easily achieved with flexible control.

Correlations between positron annihilation lifetime spectroscopy (PALS) measurement and diffusivities in polymer solutions were established, with the help of the Simha–Somcynsky (SS) equation-of-state (EOS) and the free-volume theory. Mean hole volume probed by PALS was employed to predict the free volume available for solvent transport and solvent diffusion coefficient. The predictions of infinite dilution diffusion coefficients of four organic solvents in two common polymers were generally consistent with the published experimental values. Hole size distribution from PALS results was also investigated to prove the reliability of this new approach.

By use of PCR, the genes encoding d -carbamoylase from A. radiobacter TH572 were cloned in plasmid pET30a and transformed into Escherichia coli BL21 (DE3) to overexpress d -carbamoylase. However, almost all of the protein remained trapped in inclusion bodies. To improve the expression of the properly folded active enzyme, a constitutive plasmid of pGEMT-DCB was constructed using the native hydantoinase promoter (PHase) whose optimal length was confirmed to 209 bp. Furthermore, the RBS region in the downstream of PHase was optimized to increase the expression level, so the plasmid pGEMT-R-DCB was constructed and transformed into E. coli strain Top10F′. The enzyme activity of Top10F′/pGEMT-R-DCB grown at 37 °C was found to be 0.603 U/mg (dry cell weight, DCW) and increase 58-fold over cells of BL21 (DE3) harboring the plasmid pET-DCB grown at 28 °C.

The catalytic activity of four liquid organic amines, triethylamine (TEA), diethylamine (DEA), ethylenediamine (EDA) and monoethanolamine (MEA), in the transesterification reaction of rapeseed oil in supercritical methanol was studied in this paper. The results showed that the order of the catalytic activity was DEA > TEA > MEA > EDA. The effect of the molar ratio of methanol to oil on the reaction was involved. Further, with TEA as the catalyst, the effect of the reaction pressure on this reaction was investigated. Pressure had a positive effect on this reaction. Additionally, the efficiency of the co-solvent, including ethyl acetate, propylene oxide, tetrahydrofuran and cyclohexanone, was studied, showing that ethyl acetate had a positive effect on this reaction. The overall results suggested that the methyl ester yield in a continuous reactor was inferior to that in a batch reactor, mainly because of the poor mutual solubility between the oil and methanol. Furthermore, possible mechanisms for this amine-catalyzed reaction were proposed.

d -Hydantoinase and d -carbamoylase genes from Agrobacterium radiobacter TH572 were cloned by polymerase chain reaction (PCR). The plasmid pUCCH3 with a polycistronic structure that is controlled by the native hydantoinase promoter was constructed to co-express the two genes and transformed into Escherichia coli strain JM105. To obtain the highest level of expression of the d -carbamoylase and avoid intermediate accumulation, the d -carbamoylase gene was cloned closer to the promoter and the RBS region in the upstream of it was optimized. This resulted in high active expression of soluble d -hydantoinase and d -carbamoylase that is obtained without any inducer. Thus, by the constitutive recombinant JM105/pUCCH3, d - p -hydroxyphenylglycine ( d -HPG) was obtained directly with 95.2% production yield and 96.3% conversion yield.

A modified free-volume model was developed to predict solvent diffusion coefficients in amorphous rubbery polymers, with the introduction of the Sanchez-Lacombe equation-of-state (EOS) into the free-volume theory. The characteristic parameters of the EOS are the only introduced parameters, and they can be determined with the knowledge of polymer structural units. Since all of the parameters with respect to the polymer can be determined by the group contribution method, this model provides feasibility to correlate the solvent diffusivities with polymer structures, without the knowledge of any diffusion or viscoelastic data. The calculations of infinite dilution diffusion coefficients and solvent self-diffusion coefficients for seven kinds of organic solvents in seven kinds of polymers were generally consistent with the published experimental results.

Transesterification of the crude Jatropha curcas L. oil catalyzed by micro-NaOH in supercritical/subcritical methanol was studied. The effects of various reaction variables such as the catalyst content, reaction temperature, reaction pressure and the molar ratio of methanol to oil on the conversion of crude Jatropha curcas L. oil to biodiesel were investigated. The results showed that even micro-NaOH could noticeably improve this reaction. When NaOH was added from 0.2 to 0.5 to 0.8 wt-%o of triacylglycerols, the transesterification rate increased sharply; when the catalyst content was further increased, the reaction rate was just poorly improved. It was observed that increasing the reaction temperature had a favorable influence on the methyl ester yield. For the molar ratio ranging from 18 to 36, the higher the molar ratio of methanol to oil was charged, the faster the transesterification rate seemed. At the fixed stirring rate of 400 rpm, when the catalyst content, reaction temperature, reaction pressure and the molar ratio of methanol to oil were developed at 0.8 wt-%o NaOH, 523 K, 7.0 MPa and 24 :1, respectively, the methyl ester yield could reach 90.5% within 28 min. Further, the kinetics of this reaction was involved and the results showed that it was a pseudo-first-order reaction whose apparent activation energy was 84.1 kJ/mol, and the pre-exponential factor was 2.21 x 10 5 .

Transesterification reaction of the crude oil of rapeseed with supercritical/subcritical methanol in the presence of a relatively low amount of NaOH was successfully carried out, where soap formation didn't occur. The main factors affecting the methyl ester yield during the transesterification reaction were the catalyst content, the reaction temperature, the molar ratio of alcohol to oil and the water content. High methyl ester yield and fast reaction rate could be obtained even if the reaction pressure was relatively low. In addition, kinetics of the transesterification reaction was also discussed.

A modified free-volume model was proposed to predict the solvent diffusion coefficient in rubbery polymers without knowledge of any diffusion data. With the introduction of the Sanchez–Lacombe (SL) equation-of-state (EOS) into the Vrentas–Duda model, this model is an attempt to bridge the gap between the thermodynamic and transport properties of polymer solutions. The free volume provided by polymers for solvent diffusion can be estimated solely using the parameters of the SL EOS characteristics and the polymer glass transition temperature; thus the proposed model avoids the need to use polymer viscoelastic data in determination of polymer free-volume parameters. The other parameters in the Vrentas–Duda model remain applicable. Calculated results of solvent self- and mutual-diffusion coefficients of four common solvents in two polymers indicated that the modified model can give reliable predictions. In addition, it can reflect the effect of pressure on solvent diffusivity for concentrated polymer solutions.

Nano-MgO can apparently improve the transesterification reaction of soybean oil with supercritical/subcritical methanol. The variables affecting the yield of methyl ester during the transesterification reaction, such as the catalyst content, reaction temperature and the molar ratio of methanol to soybean oil were investigated and compared with those of non-catalyst. When nano-MgO was added from 0.5 wt% to 3 wt%, the transesterification rate increased evidently, while the catalyst content was further enhanced to 5 wt%, little increased in yield. It was observed that increasing the reaction temperature had a favorable influence on methyl ester yield. In addition, for molar ratios of methanol to soybean oil ranging from 6 to 36, the higher molar ratios of methanol to oil was charged, the faster transesterification rate was obtained. When the temperature was increased to 533 K, the transesterification reaction was essentially completed within 10 min with 3 wt% nano-MgO and the methanol/oil molar rate 36:1. Such high reaction rate with nano-MgO was mainly owing to the lower activation energy (75.94 kJ/mol) and the higher stirring.

Solid state fermentation is an attractive process to produce cellulase economically due to its lower financial investment and lower operating costs. Generally available natural materials in our study included vinegar residue, wheat bran, rice bran and wheat straw. Cellulase production was carried out by solid state fermentation using these materials as the substrate of Trichoderma koningii. The ingredients of natural materials, associated with the effects of water content, time and nitrogen sources on cellulase synthesis were studied. A comparatively high cellulase activity (>4 IU·g−1 SDM) was obtained in the fermentation batch. The optimum culture time of vinegar residue, wheat bran and wheat straw were 72 hours, but that of rice bran was 60 hours. Total water contents of wheat bran, rice bran and wheat straw should not exceed 50% and that of vinegar residue should not be more than 60%. It was also shown that nitrogen salts contributed much to fermentation. (NH4)3PO4 and urea achieved good results in promoting enzyme activity.

Monte Carlo simulations have been carried out to investigate supercritical ethanol using the OPLS–UA [W.L. Jorgensen, Optimized intermolecular potential functions for liquid alcohols, J. Phys. Chem. 90 (1986) 1276–1284] and TraPPE–UA [B. Chen, J.J. Potoff, J.I. Siepmann, Monte Carlo calculations for alcohols and their mixtures with alkanes. Transferable potentials for phase equilibria. Part 5: united-atom description of primary, secondary, and tertiary alcohols, J. Phys. Chem. B 105 (2001) 3093–3104] force fields. Two potentials were compared and TraPPE potential performed better in reproducing densities as a function of pressure, so, it was selected in further structural analysis. The pair distribution functions were obtained and their pressure and temperature dependence were analyzed. In addition, a serial two dimensional distribution functions were plotted to depict the detailed structure of liquid and supercritical ethanol. Based on a widely used geometric criterion, hydrogen bonding statistical results showed that the hydrogen bonds become weaker but still exist under supercritical condition, which are in good agreement with recent experimental measurements. The hydrogen bonds of water, methanol and ethanol were compared and ethanol has nearly the same behavior as methanol under supercritical conditions.

The preparation of polystyrene (PS)/montmorillonite (MMT) composites in supercritical carbon dioxide (SCCO2) was studied. Lipophilic organically modified MMT can be produced through an ion-exchange reaction between native hydrophilic MMT and an intercalating agent (alkyl ammonium). PS/clay composites were prepared by free-radical precipitation polymerization of styrene containing dispersed clay. X-ray diffraction and transmission electron microscopy indicated that intercalation of MMT was achieved. PS/clay composites have a higher thermal decomposition temperature and lower glass-transition temperature than pure PS. The IR spectrum analysis showed that the solvent of SCCO2 did not change the structures of the PS molecules, but there were some chemical interactions between the PS and the clay in the composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 22–28, 2005

The esterification of lactic acid with ethanol was carried out in the presence of five different cation-exchange resins. The effect of catalyst type, catalyst loading, and temperature on reaction kinetics was evaluated. In order to study which components had the strongest adsorption strength on the resin surface, two simplified mechanisms based on Langmuir–Hinselwood model were compared by correlating the experimental data. FTIR method was used to verify the rationality of the mechanism. Nonideality of the liquid phase was taken into account by using activities, which were predicted by UNIFAC method instead of concentrations. The thermal stability and mechanical strength of the resin catalysts were tested by SEM.

The phase structure development in the surface of poly(methyl methacrylate)/polystyrene (PMMA/PS) blend thin film in the presence of supercritical carbon dioxide (SCCO 2 ) was studied by means of phase contrast microscopy and atomic force microscopy. The surface structures obtained after spin-coating are far from thermodynamic equilibrium. A stable surface structure, which the PS-rich phase is elevated by PMMA-rich phase, is formed after annealed in supercritical CO 2 . The structure can be explained by the different aggregation of the PMMA and PS in the two interfaces: air-polymer and substrate-polymer. The different surface structures are investigated as a function of treatment pressure and temperature of supercritical CO 2 . A critical phase structure transition temperature/pressure was found at an explicit pressure/temperature by adjusting the condition of the supercritical CO 2 . The phase structure transition point indicates a glass transition point could be found by tuning the working condition of SCCO 2 . Due to the experimental difficulties in the measurement of T g of the thin films in supercritical CO 2 , this study, by observing the resulting surface structure formed in supercritical CO 2 , provides us a new angle to look at the problem.

Superabsorbent resins prepared by ultraviolet radiation-inducing polymerization techniques with acrylic acid/acrylamide were treated with supercritical carbon dioxide (SC-CO2). The water-absorbing properties of the treated resins were greatly improved. The water-absorbing properties of resins treated with SC-CO2 in the pressure range of 10–35 MPa and the temperature range of 40–60°C were studied. The effects of the treatment time and depressurizing speed of CO2 after treatment were also examined. Obviously, different results were found for particles of different sizes. Smaller particles were more efficient under the same treatment conditions. Samples were tested with differential scanning calorimetry. The results showed that the plasticizing effect of CO2 reduced the glass-transition temperature of the polymer, and it was proposed that the plasticization effect might have led to polymer chain redistribution and better flexibility. Minor changes in the surface morphology of the particles were observed with scanning electron microscopy. The extraction of the unpolymerized monomers by SC-CO2 was also studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2272–2278, 2002

The effect of hydrogen-bond cooperativity on self- and cross-aggregation of multiple polar species in supercritical carbon dioxide was investigated using both ab initio calculations and Monte Carlo simulations. Ab initio calculations indicate that hydrogen-bond cooperativity has a significant impact on the cluster size, but does not greatly influence the composition of clusters. The microscopic structures in the ethanol + CO(2) and acetic acid + CO(2) binary mixtures were first studied using Monte Carlo simulations with a strict set of criteria for hydrogen bonding, and a satisfactory agreement with experimental data was achieved. The state of microscopic phase separation in the ethanol + water + CO(2) and acetic acid + water + CO(2) ternary mixtures was then extensively investigated, indicating that the size and composition of aggregates are strongly dependent on the mixing ratio. Moreover, hydrogen-bond cooperativity must be considered to acquire more thorough understanding of the hydration process. On the basis of the detailed distributions of aggregate size and structure, a new two-staged hydration mechanism was finally proposed for the ternary solutions.

To express high-active soluble D-amino acid oxidase (DAAO), a constitutive plasmid that is regulated by a native hydantoinase promoter (P(Hase)), was constructed. A D-amino acid oxidase gene (dao) was ligated with the P(Hase) and cloned into pGEMKT to constitutively express protein of DAAO without the use of any inducer such as isopropyl beta-D-1-thiogalactopyranoside which is poisonous to the cells and environment. The ribosome binding site region, host strain, and fermentation conditions were optimized to increase the expression level. When cultivated in a 5-m(3) fermenter, the enzyme activity of JM105/pGEMKT-R-DAAO grown at 37 degrees C was found to be 32 U/mL and increase 16-fold over cells of BL21(DE3)/pET-DAAO grown at 28 degrees C. These results indicate the success of our approaches to overproducing DAAO in soluble form in Escherichia coli.