The immersed boundary (IB) method is a promising technique for the numerical simulation of complex microchannel flows. However, numerical tests revealed a loss of wall impermeability for certain flow cases leading to unphysical results when using a standard IB method. To solve this problem, we propose a novel artificial density technique incorporated in the pressure solution for IB methods. The pressure equation is modified by scaled density coefficients in IB domains, which reflects the effect the boundary screening. The proposed model is as simple and efficient as the original IB method, and it can eliminate the spurious velocity penetration. Numerical results are shown to justify this method. Its application to a branched microchannel is also presented in the last part of this study.
The effect of CO2 on the morphology of polyaniline (PANI) polymerized in the presence of compressed CO2 was investigated. Two dissimilar morphologies, nanorods and nanoparticles, were successfully obtained using polymerization with and without compressed CO2. The obtained nanorods and particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer, Emmett and Teller (BET) analysis, and scanning electron microscopy (SEM). FT-IR and XRD results showed the presence of polyaniline emeraldine salt form. The SEM images clearly showed PANI nanorods (PANNRs) and nanoparticles (PANNPs) in polymerized PANI. From SEM images, the average diameters of PANNPs and PANNRs were calculated to be 85 and 90 nm, respectively. BET analysis indicated the surface area of PANNRs to be 44% larger than that of the PANNPs. The adsorption performance of the prepared PANI was evaluated in a decolorization process of acid blue 25 dye (AB25). The PANNRs always showed better adsorption compared with PANNPs. The PANNRs recorded a higher decolorization rate, with 99.8% of the dye adsorbed within 8 min; whereas, PANNPs showed a rate of 99.38% decolorization in 16 min. The adsorption kinetics of both PANI were analyzed with both Freundlich and Langmuir models. As a result, the Langmuir isotherm model showed better agreement with the experimental data of the dye adsorption process than that of Freundlich model. Furthermore, it was found that the dye adsorption procedure onto the two fabricated PANI structures follows the pseudo-second-order model.
Multi-walled carbon nanotube (MWNT) was synthesized through flame in a diesel engine, in which normal dodecane/ethanol mixing fuel was employed as carbon and heat sources instead of gas oil. Ferrocene was used as a floating catalyst for MWNT formation and additives such as sulfur and molybdenum were employed as a promoter of MWNT formation. Mean adiabatic combustion temperatures of various experimental conditions were evaluated by measuring CO and CO2 amounts in the exhaust gas and carrying out a mass and heat balance at the inlet and outlet of an engine. These measurements revealed that not only a mean adiabatic combustion temperature but also CO amount during combustion may play a significant role in synthesizing CNT in a diesel engine.
Modern industrial power plants require continuous monitoring to ensure their safe and reliable operation. This monitoring depends heavily on accurate sensor readings from a large number of sensors, making sensors an important part of any plant. The possibility of more than a single sensor being simultaneously faulty should not be overlooked. In this paper, a nonlinear system data validation approach based on a robust input-training neural network is proposed for detecting, isolating, and reconstructing multiple sensor faults in a power plant. An influence factor function and reliability coefficients were introduced into an objective function for the purpose of inhibiting the influence of numerous failure data with significant errors. The proposed method was evaluated on a single-shaft gas turbine from a natural gas combined cycle power plant. The result shows that the proposed model has a high degree of accuracy in multiple sensor failure cases.
Quartz crystal microbalance (QCM) measurements of soft/wet materials during the freezing-thawing process were carried out by admittance analysis of the QCM oscillations using water as the soft/wet sample. The influence of the freezing and thawing of water on the QCM response was examined as a function of temperature based on the resonant frequency, fs, resonant resistance, R, and the equivalent circuit parameters of the QCM system determined by admittance analysis. The supercooled freezing and thawing behaviors of water were monitored from a viscoelastic point of view using the QCM. The QCM response and the liquid–solid phase changes in water were evaluated based on the LCR model through admittance analysis.
To promote the use of sewage sludge on farmland, a flocculant compatible with agricultural application is required. In general, an inorganic flocculant such as aluminium sulfate is used at large sewage disposal plants. However, there is concern that aluminium accumulates when it is returned to farmland, and therefore a biodegradable rather than an inorganic flocculant is required. To obtain biodegradable flocculants produced by microorganisms, the latter were isolated from soils and sewage sludges, and the flocculation activity of the culture broths was evaluated. Here, real sewage sludge was used for the evaluation because practical use was regarded as an important consideration. As a result, two strains, V13 and RK14, were selected and identified as Bacillus megaterium and Bacillus licheniformis, respectively. It was also found that flocculation was caused by poly-γ-glutamic acid (γ-PGA). γ-PGA from RK14 cells had considerably higher molecular weight than commercial γ-PGA, and the enantiomeric composition differed from that of γ-PGA from other B. licheniformis. To obtain mutants with high γ-PGA productivity, RK14 cells were treated with ethyl methanesulfonate, and a mutant (RK14-46) was selected. The culture medium suitable for γ-PGA production by RK14-46 cells was totally different from that by RK-14 cells. The γ-PGA production reached 21.1 g/L when RK14-46 cells were cultured in the optimum semi-synthetic medium at 30°C for 2 d. Furthermore, the combination of γ-PGA obtained from RK14-46 cells and chitosan, a cationic flocculant, was very effective for flocculation of real sewage sludge.
Solvent selection is one of the most important factors for the control of crystal habits. However, this relationship is poorly understood. The aim of this study was to determine the solvent selectivity to obtain a desired crystal habit using tert-butoxycarbonyl-L-asparagine (BocASN) as a model compound. The , , and  faces were dominant for the BocASN crystals obtained from acetone and ethanol. However, the , , and  faces were dominant for those obtained from methanol. The interactions between the solvent molecules and the functional groups exposed on the crystal surface were examined. The solvent-surface interactions on each surface of the BocASN crystal were dependent on the type of solvent. The different solvent-surface interactions along the a-, b-, and c-axes affected the growth rate and aspect ratio of the crystal. The analysis of the solvent-surface interactions is useful to predict the crystal habit.
Three K2CO3-MgO based solid sorbents were prepared with a spray drying method to prevent the degradation of the chemical reactivity of K2CO3-Al2O3 sorbents named KEP-CO2P, which were produced in bulk. Their physical properties and reactivity were screened to evaluate their applicability to a 0.5 MWe (2,000 Nm3/h) CO2 capture pilot plant built for Unit 3 and a 10 MWe (40,000 Nm3/h) CO2 capture pilot plant built for Unit 8 of the Hadong thermal power station. The CO2 sorption capacity and percentage utilization of K2CO3-MgO based sorbent, Sorb-KM2, was 8.6 wt% (g-CO2/100 g-sorbent) and 90%, respectively, along with good mechanical strength for fluidized-bed application. Sorb-KM2 was tested using a 2 Nm3/h circulating fluidized bed process to evaluate their applicability to a fluidized bed process, and the chemical and structural characteristics were investigated by PSA, FE-SEM, EPMA and XPS.
Chemical and instrumental analysis of humic acids (HAs) from four kinds of trees and soils in which the same trees were planted are performed using a chemical equilibrium model and UV-vis spectroscopies. First, the bindings of protons and copper ions to three types of binding sites in HAs were analyzed using the NICA-Donnan model. The model was used to formulate the binding of copper ions to HA at various pHs. The degree of darkness of the HAs, representing the number of the chromophores, including carboxyl and phenolic groups, are depended on the maximum adsorption quantities of copper ions analyzed by the equilibrium model. Therefore, we can partly estimate the copper adsorption amounts of humic acid by only using UV-vis spectroscopic analysis without employing further instrumental analysis or copper adsorption isotherm experiments.