The electrochemical behavior of Pd(Ⅱ) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid has been studied on Pt working electrodes at 298 K by cyclic voltammetry(CV), polarization curve and galvanostatic transient techniques.Cycli...The electrochemical behavior of Pd(Ⅱ) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid has been studied on Pt working electrodes at 298 K by cyclic voltammetry(CV), polarization curve and galvanostatic transient techniques.Cyclic voltammogram of Pd(II) in [EMIm]NTf2consists of two cathodic current peaks located at 1.37 V(E pc2),corresponding to Pd2+/Pd+, and at 0.69 V(E pc1) corresponding to Pd+/Pd. The transfer coefficient α was calculated by the Tafel extrapolation from the polarization curves to be 0.306, which is in agreement with the value reported in an aqueous solution system. For Rh(Ⅲ) in [EMIm]NTf2, a cathodic current peak(E pc) was observed at-0.39 V, corresponding to Rh3+/Rh, and two oxidation peaks were observed at-0.13 V(E pa1) and0.37 V(E pa2) during the reverse scan. A significantly negative shift in the cathodic peak potential was observed with the increase of the scan rate, indicating that the reduction of Pd(II) and Rh(Ⅲ) on the Pt electrode involves kinetic complications. By using the galvanostatic transient technique, the diffusion coefficients of Pd(II) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid solution were found to be ～ 10-7cm2/s. The potential difference between the reduction of Pd(II) to Pd and the reduction of Rh(Ⅲ) to Rh obtained from the CV curves of the Pd(II) and Rh(Ⅲ) co-existing [EMIm]NTf2solution is found to be about 0.74 V, which makes it possible to electrodeposit Pd(II) and Rh(Ⅲ) separately.展开更多
Iron disulfide(FeS_2)cathode active material was prepared from iron and sulfur at room temperature by high energy mechanical alloying.Modified FeS_2 composites containing Co or Ni transition metal powders as additives...Iron disulfide(FeS_2)cathode active material was prepared from iron and sulfur at room temperature by high energy mechanical alloying.Modified FeS_2 composites containing Co or Ni transition metal powders as additives were also prepared by the same method.Lithium cells with these FeS_2 cathodes were studied for charge-discharge properties at room temperature using 0.5M LiTFSI in tetra(ethylene glycol)dimethyl ether(TEGDME)solvent.Cyclic voltammetry showed two anodic oxidation peaks at 1.8 and 2.5V and two cathodic reduction peaks at 2.0 and 1.3 V for FeS_2 with metal additives.The addition of 5wt% Co and 3wt% Ni resulted in an enhancement of the first discharge capacity giving 571 and 844mAh/g respectively at 0.1C-rate.The cycle performance was also enhanced remarkably by the addition of these electrically conductive transition metals in the active material.FeS_2 with 5wt% Co exhibited a stable cycle performance delivering a reversible capacity of 338mAh/g(37.8% of theoretical capacity)after 20 cycles.展开更多
A new aromatic diamine,3,5-diaminobenzoylpiperazine （3,5-DABP）,was synthesized from 3,5-diaminobenzoic acid and 1-formyl piperazine.The structure of 3,5-DABP was identified by FT-IR spectra and 1H NMR spectra.With 3...A new aromatic diamine,3,5-diaminobenzoylpiperazine （3,5-DABP）,was synthesized from 3,5-diaminobenzoic acid and 1-formyl piperazine.The structure of 3,5-DABP was identified by FT-IR spectra and 1H NMR spectra.With 3,5-DABP as aqueous monomer and trimesoyl chloride （TMC） as organic monomer,thin film composite （TFC） nanofiltration membranes were prepared by interfacial polymerization technology.The salt rejection order of these TFC membranes is Na2SO4MgSO4MgCl2NaCl.This sequence indicates that the membranes are negatively charged.展开更多
The elastic behavior of arteries is nonlinear when subjected to large deformations. In order to measure their anisotropic behavior, planar biaxial tests are often used. Typically, hooks are attached along the borders ...The elastic behavior of arteries is nonlinear when subjected to large deformations. In order to measure their anisotropic behavior, planar biaxial tests are often used. Typically, hooks are attached along the borders of a square sample of arterial tissue. Cruciform samples clamped with grips can also be used. The current debate on the effect of different biaxial test boundary conditions revolves around the uniformity of the stress distribution in the center of the specimen. Uniaxial tests are also commonly used due to simplicity of data analysis, but their capability to fully describe the in vivo behavior of a tissue remains to be proven. In this study, we demonstrate the use of inverse modeling to fit the material properties by taking into account the non-uniform stress distribution, and discuss the differences between the three types of tests. Square and cruciform samples were dissected from pig aortas and tested equi-biaxially. Rectangular samples were used in uniaxial testing as well. On the square samples, forces were applied on each side of edge sample attached with hooks, and strains were measured in the center using optical tracking of ink dots. On the cruciform and rectangular samples, displacements were applied on grip clamps and forces were measured on the clamps. Each type of experiment was simulated with the finite element method. The parameters of the Mooney-Rivlin constitutive model were adjusted with an optimization algorithm so that the simulation predictions fitted the experimental results. Higher stretch ratios (>1.5) were reached in the cruciform and rectangular samples than in the square samples before failure. Therefore, the nonlinear behavior of the tissue in large deformations was better captured by the cruciform biaxial test and the uniaxial test, than by the square biaxial test. Advantages of cruciform samples over square samples include: 1) higher deformation range;2) simpler data acquisition and 3) easier attachment of sample. However, the nonuniform stress distribution in cruciform samples requires the use of inverse modeling adjustment of constitutive model parameters.展开更多
The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-...The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-1,5-di-furanyl catalyzed by DBU reached 98.0% under optimized conditions. According to the kinetic analysis, the reaction order of furfural was estimated as 1.0, the apparent activation energy was 17.7 kJ.mol.1, and the pre-exponential factor was 2.67 L.min.1 in fitting with the Arrhenius equation, which explains the high efficiency of the DBU catalyst. DBU-catalyzed aldol condensation with free solvent offers an alternative route to simplify aldol condensation and separation into a single step.展开更多
Bubbly gas-liquid Taylor-Couette vortex flow has been the subject of several recent investigations both because of interest in bubble-induced drag reduction and because such devices have potential applications to a va...Bubbly gas-liquid Taylor-Couette vortex flow has been the subject of several recent investigations both because of interest in bubble-induced drag reduction and because such devices have potential applications to a variety of chemical and biochemical processing problems. In order to quantitatively describe the hydrodynamics of highly turbulent two phase Taylor-Couette flow, a rigorous two-fluid computational fluid dynamics （CFD） model was developed and compared with previously published experimental data. This model includes a comprehensive description of the constitutive closure for inter-phase forces and turbulence was simulated using both the k- and k-to models. In addition, the mechanism by which the dispersed fluid attains a non-uniform radial and axial distribution is analyzed and the relative importance of various interphase forces is discussed. Lastly the model was validated by comparison of simulation predictions with experimental data, and it is shown that the CFD model correctly predicts phase velocity, velocity fluctuation, and gas distribution, and may provide guidance for reactor design and scale-up.展开更多
In this study,the electrochemical behavior of Pd(II)in nitric acid media was investigated using various electrochemical techniques.By analyzing the cyclic voltammogram of Pd(II)recorded at Pt electrode,a series of ele...In this study,the electrochemical behavior of Pd(II)in nitric acid media was investigated using various electrochemical techniques.By analyzing the cyclic voltammogram of Pd(II)recorded at Pt electrode,a series of electrochemical reactions associated with palladium were recognized,indicating that Pd(II)undergoes a single step two-electrons irreversible process.Electroreduction reaction of Pd(II)and auto-catalytic reactions of nitrous acid are supposed to play a leading role in low and high concentrations of nitric acid,respectively.Stirring could facilitate the reduction of Pd(II)in relatively low nitric acid concentration(3 mol/L).The value of charge transfer coefficient was determined to be 0.18 for the measurements at 298 K.The diffusion coefficient of Pd(II)increased from 1.89×10 8cm2/s at 288 K to 4.23×10 8cm2/s at 318 K,and the activation energy was calculated to be 21.5 kJ/mol.In electrowinning experiments,SEM images of palladium obtained by electrolysis reveal the dendrite growth in all cases,which is uniform all over the entire surface of Pt electrode.The recovery ratios of Pd at different nitric acid concentrations are high,and the faradic efficiency of electrolysis decreases with increasing the nitric acid concentration.When stirring was introduced during electrolysis,the electrodeposition rate of Pd increased substantially.展开更多
Palladium（II） and chloride ions tend to form complexes in aqueous solution. Both theoretical and experimental （by UV spec- trum） results indicate that there are four complexes formed in aqueous solution containing...Palladium（II） and chloride ions tend to form complexes in aqueous solution. Both theoretical and experimental （by UV spec- trum） results indicate that there are four complexes formed in aqueous solution containing 3 mol/L hydrochloric acid and 20 mmol/L PdC12. This work evaluates the kinetics of electrochemical deposition of palladium on a Platinum electrode. For this purpose, palladium electrodeposition was investigated by means of cyclic voltammetry （CV）, potentiostatic current-time tran- sients （CTTs） and Tafel curve. By CTTs curves, the regions corresponding to the charge transfer control, mixed control and diffusion control were identified. In the diffusion control region, palladium electrodeposition mechanism was characterized as progressive nucleation with three-dimensional （3D） growth under diffusion control; as for the mixed control region, an adsorp- tion （1Ads）, ion transfer （liT）, and nucleation and growth （ING） model were proposed to analyze the current-time transients quan- titatively, which could separate the IAds, lit and IN~ perfectly.展开更多
The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as researc...The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as research transitions from petrochemistry to biorenewable chemistry. Compared to petrochemisty, the selective conversion of biomass-derived carbohydrates requires most catalytic reactions to take place at low temperatures (< 300 °C) and in the condensed phase to prevent reactants and products from degrading. The stability of heterogeneous catalysts in liquid water above the normal boiling point represents one of the major challenges to overcome. Herein, we review some of the latest advances in the field with an emphasis on the role of carbon materials and carbon nanohybrids in addressing this challenge.展开更多
Various published data show the amount of crop residue available annually in India may range from a low of 90 to a high of 180 million tonnes. Different types of crop residue are collected from farmers depending on th...Various published data show the amount of crop residue available annually in India may range from a low of 90 to a high of 180 million tonnes. Different types of crop residue are collected from farmers depending on the geography and crop pattern for instance, in north India rice straw and cotton stalks are collected while in central India soya husk and sugarcane tops are collected. Baling and transporting straw from the field, though appear to be an option for safe disposal, will be feasible only when alternate, effective and economically viable usage methods are identified and facilities and infrastructure for ex-situ management methods are created. One immediate short term use of the residue is to replace 5% - 7% of the 670 million tonnes of coal India currently consumes to generate power. The farmers will benefit from the sale of their excess crop residue. The scheme will reduce pollution due to residue burning practices. Replacing coal will cut the GHG emissions. The challenge is to mobilize the crop residue collection and timely delivery to power plants. The data and calculations in this monogram show that it is economical for the farmer to remove the crop residue from the field quickly by using modern balers, to pelletize the biomass in small-scale distributed pellet plants, to store pellets in the modern steel bins and finally to deliver the pellets to coal plants by using rail transport. The delivered cost is estimated at around Rp 6.78/kg. The Government of India encourages the power plants to pay at least Rp 10/kg for the delivered biomass in the form of pellets. The current monogram analyzes the organization of an efficient supply chain in the State of Haryana India to ensure a sustainable modern enterprise.展开更多
The relationship between the rheological properties of nylon-6,6 solutions and the morphology of their electrospun nanofibers was established. The viscosity of nylon-6,6 in formic acid （90%） was measured in the conc...The relationship between the rheological properties of nylon-6,6 solutions and the morphology of their electrospun nanofibers was established. The viscosity of nylon-6,6 in formic acid （90%） was measured in the concentration range of 5 wt%-25 wt% using a programmable viscometer. Electrospinning of nylon-6,6 solutions was carried out under controlled parameters. The chemical structure, morphology and thermal properties of the obtained nanofibers were investigated using Fourier transform infrared spectroscopy （FTIR）, scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）, respectively, Entanglement concentration （ce） was found to be 15 wt% and a power law relationship between specific viscosity and solution concentration was observed with exponents of 2.0 and 3.3 for semi-dilute unentangled （c 〈 ce） and semi-dilute entangled （c 〉 ce） regimes, respectively. The diameter and uniformity of the nanofibers were found to be dependent on the viscosity. Moreover, the average diameter of electrospun nanofibers was found to be dependent on zero shear rate viscosity and normalized concentration （c/ce） in a power law relationship with exponents of 0.298 and 0.816, respectively. For nylon-6,6 solutions, the entanglement concentration （ce = 15 wt%） provides the threshold viscosity required for the formation of a stable polymeric jet during electrospinning and producing uniform beadless fibers. For concentrations less than ce, beaded fibers with some irregularities are formed. DSC analysis showed an increase in crystallinity of all electrospun samples compared to original polymer. Furthermore; Based on FTIR spectroscopy, α phase is dominant in electrospun nanofibers and minor amount offland ）,phases is also available.展开更多
Operation of a dual fluidized bed, consisting of a riser as combustor and bubbling bed as gasifier, for synthesis gas production from a solid fuel requires determination of the solids circulation rate and char transfe...Operation of a dual fluidized bed, consisting of a riser as combustor and bubbling bed as gasifier, for synthesis gas production from a solid fuel requires determination of the solids circulation rate and char transfer rate. The performance relies on supplying sufficient heat from the combustor to the gasifier by circulation of solids between these two reactors. The flow rate of char is required to track the heat generated in the combustor, which supports endothermic reactions in the gasifier. Direct measurement of these two critical parameters is difficult, with the number of reported techniques capable of working at high temperatures extremely small. An indirect method was developed, using mass and energy balances over the entire system and individual reactors, to estimate the solids circulation rate and char transfer rate. There was general agreement between heat losses estimated from energy-balance calculations and from direct measurement of the outer reactor surface temperature. Under typical gasification conditions, the solids circulation fluxes were estimated to be 45.2 and 55.6 kg/(m^2 s) in two independent tests, which were in good agreement with values obtained using a thermal tracer;char transfer rates were calculated to be 1.2 and 0.6 kg/h, which were in reasonable agreement with average biomass feed rates. This method can be applied to dual gasification systems at any temperature or flow rate.展开更多
To date, few reports have been concerned with the physical properties of the liquid phases of imidazoles and benzimidazoles- potential starting materials for a great number of ionic liquids. Prior research has indicat...To date, few reports have been concerned with the physical properties of the liquid phases of imidazoles and benzimidazoles- potential starting materials for a great number of ionic liquids. Prior research has indicated that alkylimidazole solvents exhibit different, and potentially advantageous physical properties, when compared to corresponding imidazolium-based ionic liquids. Given that even the most fundamental physical properties of alkylimidazole solvents have only recently been reported, there is still a lack of data for other relevant imidazole derivatives, including benzimidazoles. In this work, we have synthesized a se- ries of eight 1-n-alkylbenzimidazoles, with chain lengths ranging from ethyl to dodecyl, all of which exist as neat liquids at ambient temperature. Their densities and viscosities have been determined as functions of both temperature and molecular weight. Alkylbenzimidazoles have been found to exhibit viscosities that are more similar to imidazolium-based ILs than al- kylimidazoles, owed to a large contribution to viscosity from the presence of a fused ring system. Solubilities of CO2 and SO2, two species of concern in the emission of coal-fired power generation, were determined for selected alkylbenzimidazoles to understand what effects a fused ring system might have on gas solubility. For both gases, alkylbenzimidazoles were deter- mined to experience physical, non-chemically reactive, interactions. The solubility of CO2 in alkylbenzimidazoles is 10%-30% less than observed for corresponding ILs and alkylimidazoles. 1-butylbenzimidazole was found to readily absorb at least 0.333 gram SO2 per gram at low pressure and ambient temperature, which could be readily desorbed under an N： flush, a behavior more similar to imidazolium-based ILs than alkylimidazoles. Thus, we find that as solvents for gas separations, benzimidazoles share characteristics with both ILs and alkylimidazoles.展开更多
The destruction of hexafluoroethane (C2F6), also known as R-116, was investigated in a nonthermal plasma reactor packed with dielectric pellets. The effects of the feed gas composition and the input power on the destr...The destruction of hexafluoroethane (C2F6), also known as R-116, was investigated in a nonthermal plasma reactor packed with dielectric pellets. The effects of the feed gas composition and the input power on the destruction of C2F6 were examined. The feed gas composition was varied by changing the oxygen content, the argon content and the initial C2F6 concentration. An increased input power led to increased C2F6 destruction as a result of promoting the electron-molecule collisions to dissociate C2F6 molecules. The addition of argon to the feed gas greatly improved the C2F6 destruction by reducing the energy losses due to vibrational excitation and dissociation of N2 molecules, while the increases in the oxygen content and the initial C2F6 concentration decreased the destruction efficiency. The byproducts including CO2, CO, COF2, CF4, SiF4, NO2, and N2O were identified, and the destruction mechanisms were elucidated, referring to these compounds. The most abundant byproduct was found to be carbonyl fluoride (COF2), indicating that it serves as an important medium to convert C2F6 into CO2. The energy requirement for the C2F6 destruction was in the range of 8.2–45.3 MJ/g, depending on the initial concentration.展开更多
The serial model of Epstein et al. （1981） is demonstrated to predict successfully the overall voidage of the mixed layer of incompletely segregated binary and ternary mixtures of liquid-fluidized solids that differ ...The serial model of Epstein et al. （1981） is demonstrated to predict successfully the overall voidage of the mixed layer of incompletely segregated binary and ternary mixtures of liquid-fluidized solids that differ only in shape. Some speculations are then offered on the conditions for the success and failure of this model. Finally, methods proposed in the literature for estimating the deviations from the serial model for a binary-solids bed, which manifest themselves as a bed contraction, are discussed, with emphasis on packing models.展开更多
This work describes the performance of the direct carbon fuel cell(DCFC)fuelled by ash-free coal.Employing coal in the DCFC might be problematic,mainly because of the ash deposition after the cell reactions.In the stu...This work describes the performance of the direct carbon fuel cell(DCFC)fuelled by ash-free coal.Employing coal in the DCFC might be problematic,mainly because of the ash deposition after the cell reactions.In the study,the carbonaceous ash-free component of coal is obtained,which is then evaluated as the DCFC fuel and compared with raw coal,active carbon,carbon black,and graphite.The electrolyte-supported SOFC structure is adapted to build the DCFC.The DCFC based on the ash-free coal fuel exhibits good performance with regard to the maximum power density,day-by-day measurements,and durability at continuous run.When the carbon fuels are internally gasified to H2 and CO,the power density is generally much improved,compared to N2 pyrolysis environment.The power generation is most likely related to the concentration of pyrolyzed gases as well as the electrochemical reactivity of the solid carbon.展开更多
This review discusses the recent reports on one-dimensional(1D) nanostructures with unusual flexibility.We discuss the importance that flexibility could have in future applications of nanowires and other nanostructure...This review discusses the recent reports on one-dimensional(1D) nanostructures with unusual flexibility.We discuss the importance that flexibility could have in future applications of nanowires and other nanostructures,and detail the two main approaches that have been followed to this day to synthesize highly flexible 1D nanostructures.One approach is based on making crystals in which one or two dimensions of the structure are comparable in size with the unit cell.Such thinness has been shown to provide unusual flexibility.The other approach conjoins hard nanostructures with flexible joints.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.91026019 and 91126006)
文摘The electrochemical behavior of Pd(Ⅱ) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid has been studied on Pt working electrodes at 298 K by cyclic voltammetry(CV), polarization curve and galvanostatic transient techniques.Cyclic voltammogram of Pd(II) in [EMIm]NTf2consists of two cathodic current peaks located at 1.37 V(E pc2),corresponding to Pd2+/Pd+, and at 0.69 V(E pc1) corresponding to Pd+/Pd. The transfer coefficient α was calculated by the Tafel extrapolation from the polarization curves to be 0.306, which is in agreement with the value reported in an aqueous solution system. For Rh(Ⅲ) in [EMIm]NTf2, a cathodic current peak(E pc) was observed at-0.39 V, corresponding to Rh3+/Rh, and two oxidation peaks were observed at-0.13 V(E pa1) and0.37 V(E pa2) during the reverse scan. A significantly negative shift in the cathodic peak potential was observed with the increase of the scan rate, indicating that the reduction of Pd(II) and Rh(Ⅲ) on the Pt electrode involves kinetic complications. By using the galvanostatic transient technique, the diffusion coefficients of Pd(II) and Rh(Ⅲ) in [EMIm]NTf2ionic liquid solution were found to be ～ 10-7cm2/s. The potential difference between the reduction of Pd(II) to Pd and the reduction of Rh(Ⅲ) to Rh obtained from the CV curves of the Pd(II) and Rh(Ⅲ) co-existing [EMIm]NTf2solution is found to be about 0.74 V, which makes it possible to electrodeposit Pd(II) and Rh(Ⅲ) separately.
文摘Iron disulfide(FeS_2)cathode active material was prepared from iron and sulfur at room temperature by high energy mechanical alloying.Modified FeS_2 composites containing Co or Ni transition metal powders as additives were also prepared by the same method.Lithium cells with these FeS_2 cathodes were studied for charge-discharge properties at room temperature using 0.5M LiTFSI in tetra(ethylene glycol)dimethyl ether(TEGDME)solvent.Cyclic voltammetry showed two anodic oxidation peaks at 1.8 and 2.5V and two cathodic reduction peaks at 2.0 and 1.3 V for FeS_2 with metal additives.The addition of 5wt% Co and 3wt% Ni resulted in an enhancement of the first discharge capacity giving 571 and 844mAh/g respectively at 0.1C-rate.The cycle performance was also enhanced remarkably by the addition of these electrically conductive transition metals in the active material.FeS_2 with 5wt% Co exhibited a stable cycle performance delivering a reversible capacity of 338mAh/g(37.8% of theoretical capacity)after 20 cycles.
基金Supported by the National Natural Science Foundation of China（21076176） the Research and Development Project of Tangshan（10140201C-3）+1 种基金 the Research and Development Project of Hebei Province（07275113） the Research Fund of Tangshan Normal College
文摘A new aromatic diamine,3,5-diaminobenzoylpiperazine （3,5-DABP）,was synthesized from 3,5-diaminobenzoic acid and 1-formyl piperazine.The structure of 3,5-DABP was identified by FT-IR spectra and 1H NMR spectra.With 3,5-DABP as aqueous monomer and trimesoyl chloride （TMC） as organic monomer,thin film composite （TFC） nanofiltration membranes were prepared by interfacial polymerization technology.The salt rejection order of these TFC membranes is Na2SO4MgSO4MgCl2NaCl.This sequence indicates that the membranes are negatively charged.
文摘The elastic behavior of arteries is nonlinear when subjected to large deformations. In order to measure their anisotropic behavior, planar biaxial tests are often used. Typically, hooks are attached along the borders of a square sample of arterial tissue. Cruciform samples clamped with grips can also be used. The current debate on the effect of different biaxial test boundary conditions revolves around the uniformity of the stress distribution in the center of the specimen. Uniaxial tests are also commonly used due to simplicity of data analysis, but their capability to fully describe the in vivo behavior of a tissue remains to be proven. In this study, we demonstrate the use of inverse modeling to fit the material properties by taking into account the non-uniform stress distribution, and discuss the differences between the three types of tests. Square and cruciform samples were dissected from pig aortas and tested equi-biaxially. Rectangular samples were used in uniaxial testing as well. On the square samples, forces were applied on each side of edge sample attached with hooks, and strains were measured in the center using optical tracking of ink dots. On the cruciform and rectangular samples, displacements were applied on grip clamps and forces were measured on the clamps. Each type of experiment was simulated with the finite element method. The parameters of the Mooney-Rivlin constitutive model were adjusted with an optimization algorithm so that the simulation predictions fitted the experimental results. Higher stretch ratios (>1.5) were reached in the cruciform and rectangular samples than in the square samples before failure. Therefore, the nonlinear behavior of the tissue in large deformations was better captured by the cruciform biaxial test and the uniaxial test, than by the square biaxial test. Advantages of cruciform samples over square samples include: 1) higher deformation range;2) simpler data acquisition and 3) easier attachment of sample. However, the nonuniform stress distribution in cruciform samples requires the use of inverse modeling adjustment of constitutive model parameters.
文摘The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-1,5-di-furanyl catalyzed by DBU reached 98.0% under optimized conditions. According to the kinetic analysis, the reaction order of furfural was estimated as 1.0, the apparent activation energy was 17.7 kJ.mol.1, and the pre-exponential factor was 2.67 L.min.1 in fitting with the Arrhenius equation, which explains the high efficiency of the DBU catalyst. DBU-catalyzed aldol condensation with free solvent offers an alternative route to simplify aldol condensation and separation into a single step.
基金Supported by the National Science Foundation(CBET-1236676)
文摘Bubbly gas-liquid Taylor-Couette vortex flow has been the subject of several recent investigations both because of interest in bubble-induced drag reduction and because such devices have potential applications to a variety of chemical and biochemical processing problems. In order to quantitatively describe the hydrodynamics of highly turbulent two phase Taylor-Couette flow, a rigorous two-fluid computational fluid dynamics （CFD） model was developed and compared with previously published experimental data. This model includes a comprehensive description of the constitutive closure for inter-phase forces and turbulence was simulated using both the k- and k-to models. In addition, the mechanism by which the dispersed fluid attains a non-uniform radial and axial distribution is analyzed and the relative importance of various interphase forces is discussed. Lastly the model was validated by comparison of simulation predictions with experimental data, and it is shown that the CFD model correctly predicts phase velocity, velocity fluctuation, and gas distribution, and may provide guidance for reactor design and scale-up.
基金supported by the National Natural Science Foundation of China(91026019,91126006)
文摘In this study,the electrochemical behavior of Pd(II)in nitric acid media was investigated using various electrochemical techniques.By analyzing the cyclic voltammogram of Pd(II)recorded at Pt electrode,a series of electrochemical reactions associated with palladium were recognized,indicating that Pd(II)undergoes a single step two-electrons irreversible process.Electroreduction reaction of Pd(II)and auto-catalytic reactions of nitrous acid are supposed to play a leading role in low and high concentrations of nitric acid,respectively.Stirring could facilitate the reduction of Pd(II)in relatively low nitric acid concentration(3 mol/L).The value of charge transfer coefficient was determined to be 0.18 for the measurements at 298 K.The diffusion coefficient of Pd(II)increased from 1.89×10 8cm2/s at 288 K to 4.23×10 8cm2/s at 318 K,and the activation energy was calculated to be 21.5 kJ/mol.In electrowinning experiments,SEM images of palladium obtained by electrolysis reveal the dendrite growth in all cases,which is uniform all over the entire surface of Pt electrode.The recovery ratios of Pd at different nitric acid concentrations are high,and the faradic efficiency of electrolysis decreases with increasing the nitric acid concentration.When stirring was introduced during electrolysis,the electrodeposition rate of Pd increased substantially.
基金supported by the National Natural Science Foundation of China(91026019,91126006)
文摘Palladium（II） and chloride ions tend to form complexes in aqueous solution. Both theoretical and experimental （by UV spec- trum） results indicate that there are four complexes formed in aqueous solution containing 3 mol/L hydrochloric acid and 20 mmol/L PdC12. This work evaluates the kinetics of electrochemical deposition of palladium on a Platinum electrode. For this purpose, palladium electrodeposition was investigated by means of cyclic voltammetry （CV）, potentiostatic current-time tran- sients （CTTs） and Tafel curve. By CTTs curves, the regions corresponding to the charge transfer control, mixed control and diffusion control were identified. In the diffusion control region, palladium electrodeposition mechanism was characterized as progressive nucleation with three-dimensional （3D） growth under diffusion control; as for the mixed control region, an adsorp- tion （1Ads）, ion transfer （liT）, and nucleation and growth （ING） model were proposed to analyze the current-time transients quan- titatively, which could separate the IAds, lit and IN~ perfectly.
基金supported by the National Science Foundation under NSF Grant Number EEC-0813570the Iowa Energy Center under IEC Grant Number 13-01supported by the U.S. Department of Energy-Laboratory Royalty Revenue through Contract No. DE-AC02-07CH11358.
文摘The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as research transitions from petrochemistry to biorenewable chemistry. Compared to petrochemisty, the selective conversion of biomass-derived carbohydrates requires most catalytic reactions to take place at low temperatures (< 300 °C) and in the condensed phase to prevent reactants and products from degrading. The stability of heterogeneous catalysts in liquid water above the normal boiling point represents one of the major challenges to overcome. Herein, we review some of the latest advances in the field with an emphasis on the role of carbon materials and carbon nanohybrids in addressing this challenge.
文摘Various published data show the amount of crop residue available annually in India may range from a low of 90 to a high of 180 million tonnes. Different types of crop residue are collected from farmers depending on the geography and crop pattern for instance, in north India rice straw and cotton stalks are collected while in central India soya husk and sugarcane tops are collected. Baling and transporting straw from the field, though appear to be an option for safe disposal, will be feasible only when alternate, effective and economically viable usage methods are identified and facilities and infrastructure for ex-situ management methods are created. One immediate short term use of the residue is to replace 5% - 7% of the 670 million tonnes of coal India currently consumes to generate power. The farmers will benefit from the sale of their excess crop residue. The scheme will reduce pollution due to residue burning practices. Replacing coal will cut the GHG emissions. The challenge is to mobilize the crop residue collection and timely delivery to power plants. The data and calculations in this monogram show that it is economical for the farmer to remove the crop residue from the field quickly by using modern balers, to pelletize the biomass in small-scale distributed pellet plants, to store pellets in the modern steel bins and finally to deliver the pellets to coal plants by using rail transport. The delivered cost is estimated at around Rp 6.78/kg. The Government of India encourages the power plants to pay at least Rp 10/kg for the delivered biomass in the form of pellets. The current monogram analyzes the organization of an efficient supply chain in the State of Haryana India to ensure a sustainable modern enterprise.
基金financially supported by the Universiti Teknologi Malaysia,(UTM) for providing IDF
文摘The relationship between the rheological properties of nylon-6,6 solutions and the morphology of their electrospun nanofibers was established. The viscosity of nylon-6,6 in formic acid （90%） was measured in the concentration range of 5 wt%-25 wt% using a programmable viscometer. Electrospinning of nylon-6,6 solutions was carried out under controlled parameters. The chemical structure, morphology and thermal properties of the obtained nanofibers were investigated using Fourier transform infrared spectroscopy （FTIR）, scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）, respectively, Entanglement concentration （ce） was found to be 15 wt% and a power law relationship between specific viscosity and solution concentration was observed with exponents of 2.0 and 3.3 for semi-dilute unentangled （c 〈 ce） and semi-dilute entangled （c 〉 ce） regimes, respectively. The diameter and uniformity of the nanofibers were found to be dependent on the viscosity. Moreover, the average diameter of electrospun nanofibers was found to be dependent on zero shear rate viscosity and normalized concentration （c/ce） in a power law relationship with exponents of 0.298 and 0.816, respectively. For nylon-6,6 solutions, the entanglement concentration （ce = 15 wt%） provides the threshold viscosity required for the formation of a stable polymeric jet during electrospinning and producing uniform beadless fibers. For concentrations less than ce, beaded fibers with some irregularities are formed. DSC analysis showed an increase in crystallinity of all electrospun samples compared to original polymer. Furthermore; Based on FTIR spectroscopy, α phase is dominant in electrospun nanofibers and minor amount offland ）,phases is also available.
文摘Operation of a dual fluidized bed, consisting of a riser as combustor and bubbling bed as gasifier, for synthesis gas production from a solid fuel requires determination of the solids circulation rate and char transfer rate. The performance relies on supplying sufficient heat from the combustor to the gasifier by circulation of solids between these two reactors. The flow rate of char is required to track the heat generated in the combustor, which supports endothermic reactions in the gasifier. Direct measurement of these two critical parameters is difficult, with the number of reported techniques capable of working at high temperatures extremely small. An indirect method was developed, using mass and energy balances over the entire system and individual reactors, to estimate the solids circulation rate and char transfer rate. There was general agreement between heat losses estimated from energy-balance calculations and from direct measurement of the outer reactor surface temperature. Under typical gasification conditions, the solids circulation fluxes were estimated to be 45.2 and 55.6 kg/(m^2 s) in two independent tests, which were in good agreement with values obtained using a thermal tracer;char transfer rates were calculated to be 1.2 and 0.6 kg/h, which were in reasonable agreement with average biomass feed rates. This method can be applied to dual gasification systems at any temperature or flow rate.
基金supported by ION Engineering, LLCUnited States Department of Energy-National Energy Technology Laboratory(DE-FE00005799)the National Science Foundation Research Experiences for Undergraduates Program (EEC-1062705)
文摘To date, few reports have been concerned with the physical properties of the liquid phases of imidazoles and benzimidazoles- potential starting materials for a great number of ionic liquids. Prior research has indicated that alkylimidazole solvents exhibit different, and potentially advantageous physical properties, when compared to corresponding imidazolium-based ionic liquids. Given that even the most fundamental physical properties of alkylimidazole solvents have only recently been reported, there is still a lack of data for other relevant imidazole derivatives, including benzimidazoles. In this work, we have synthesized a se- ries of eight 1-n-alkylbenzimidazoles, with chain lengths ranging from ethyl to dodecyl, all of which exist as neat liquids at ambient temperature. Their densities and viscosities have been determined as functions of both temperature and molecular weight. Alkylbenzimidazoles have been found to exhibit viscosities that are more similar to imidazolium-based ILs than al- kylimidazoles, owed to a large contribution to viscosity from the presence of a fused ring system. Solubilities of CO2 and SO2, two species of concern in the emission of coal-fired power generation, were determined for selected alkylbenzimidazoles to understand what effects a fused ring system might have on gas solubility. For both gases, alkylbenzimidazoles were deter- mined to experience physical, non-chemically reactive, interactions. The solubility of CO2 in alkylbenzimidazoles is 10%-30% less than observed for corresponding ILs and alkylimidazoles. 1-butylbenzimidazole was found to readily absorb at least 0.333 gram SO2 per gram at low pressure and ambient temperature, which could be readily desorbed under an N： flush, a behavior more similar to imidazolium-based ILs than alkylimidazoles. Thus, we find that as solvents for gas separations, benzimidazoles share characteristics with both ILs and alkylimidazoles.
文摘The destruction of hexafluoroethane (C2F6), also known as R-116, was investigated in a nonthermal plasma reactor packed with dielectric pellets. The effects of the feed gas composition and the input power on the destruction of C2F6 were examined. The feed gas composition was varied by changing the oxygen content, the argon content and the initial C2F6 concentration. An increased input power led to increased C2F6 destruction as a result of promoting the electron-molecule collisions to dissociate C2F6 molecules. The addition of argon to the feed gas greatly improved the C2F6 destruction by reducing the energy losses due to vibrational excitation and dissociation of N2 molecules, while the increases in the oxygen content and the initial C2F6 concentration decreased the destruction efficiency. The byproducts including CO2, CO, COF2, CF4, SiF4, NO2, and N2O were identified, and the destruction mechanisms were elucidated, referring to these compounds. The most abundant byproduct was found to be carbonyl fluoride (COF2), indicating that it serves as an important medium to convert C2F6 into CO2. The energy requirement for the C2F6 destruction was in the range of 8.2–45.3 MJ/g, depending on the initial concentration.
文摘The serial model of Epstein et al. （1981） is demonstrated to predict successfully the overall voidage of the mixed layer of incompletely segregated binary and ternary mixtures of liquid-fluidized solids that differ only in shape. Some speculations are then offered on the conditions for the success and failure of this model. Finally, methods proposed in the literature for estimating the deviations from the serial model for a binary-solids bed, which manifest themselves as a bed contraction, are discussed, with emphasis on packing models.
基金supported by the New&Renewable Energy Development Program of the Korea Institute of Energy Technology Evaluation and Planning(KETEP)Grant Funded by the Korean Government’s Ministry of Knowledge Economy(20113020030010)
文摘This work describes the performance of the direct carbon fuel cell(DCFC)fuelled by ash-free coal.Employing coal in the DCFC might be problematic,mainly because of the ash deposition after the cell reactions.In the study,the carbonaceous ash-free component of coal is obtained,which is then evaluated as the DCFC fuel and compared with raw coal,active carbon,carbon black,and graphite.The electrolyte-supported SOFC structure is adapted to build the DCFC.The DCFC based on the ash-free coal fuel exhibits good performance with regard to the maximum power density,day-by-day measurements,and durability at continuous run.When the carbon fuels are internally gasified to H2 and CO,the power density is generally much improved,compared to N2 pyrolysis environment.The power generation is most likely related to the concentration of pyrolyzed gases as well as the electrochemical reactivity of the solid carbon.
基金supported by Iowa State University of Science and Technology through startup funds
文摘This review discusses the recent reports on one-dimensional(1D) nanostructures with unusual flexibility.We discuss the importance that flexibility could have in future applications of nanowires and other nanostructures,and detail the two main approaches that have been followed to this day to synthesize highly flexible 1D nanostructures.One approach is based on making crystals in which one or two dimensions of the structure are comparable in size with the unit cell.Such thinness has been shown to provide unusual flexibility.The other approach conjoins hard nanostructures with flexible joints.
