Modeling and simulation of water-gas shift in a heat exchange integrated microchannel converter

The aim of this study is to analyze the operation of a heat exchange integrated, Pt-CeO₂/Al₂O₃ washcoated microchannel water-gas shift (WGS) reactor under fuel processing conditions by mathematical modeling techniques. In this context, operation of a single microchannel is modeled, whose outcomes are compared with experimental data obtained from the literature. Simulations show good agreement with the experimental data, with an error below 4%. Upon its validation, single channel model is used to simulate a heat exchange integrated microchannel reactor, which involves periodically located groups of reaction and air-fed cooling channels. The integrated reactor is modeled by 2D Navier-Stokes equations together with reactive transport of heat and mass. Incorporation of heat exchange function minimizes the impact of thermodynamic limitations on WGS by precise regulation of reaction temperature and gives 77.6% CO conversion, which is 67.4% in the absence of cooling. Improvement in conversion from 69.2% to 77.6% is observed upon increasing feed temperature of the reaction stream from 565 to 595 K, above which the reaction is controlled by equilibrium. Coolant feed temperature, however, changes conversion only by <1%. Isothermal conditions are obtained upon feeding reaction and coolant channels at 595 K and 587 K, respectively. Changes in the thickness and material of the wall between the channels give limited deviations in conversion. An integrated reactor with 2.37 L volume is sufficient for supplying H₂ necessary to drive a 1 kW PEMFC unit.     

Catalytic graphitization and formation of macroporous-activated carbon nanofibers from salt-induced and H2S-treated polyacrylonitrile

We present here a facile method to produce macroporous-activated carbon nanofibers (AMP-CNFs) by post-treating electrospun cobalt(II) chloride (CoCl₂) containing polyacrylonitrile (PAN/CoCl₂) nanofibers with hydrogen sulfide (H₂S) followed by carbonization. A range of techniques including scanning and transmission electron microscopy, FTIR and Raman spectroscopy is used to examine and characterize the process. Because of the phase behavior between carbon and cobalt, cobalt particles are formed in the nanofibers, some of which leave the fibers during the heat treatment process leading to macroporous fibrous structures. The number of the macroporous increase significantly with increasing CoCl₂ concentration in the precursor H₂S-treated PAN/CoCl₂ nanofibers. The cobalt phase in the fibers also leads to catalytic graphitization of the carbon nanofibers. The produced AMP-CNFs may be a promising candidates in many applications including anode layer in lithium ion batteries, air and liquid purifiers in filters, as well as in biomedical applications.     

Optimization of surface roughness in end milling Castamide

Castamide is vulnerable to humidity up to 7%; therefore, it is important to know the effect of processing parameters on Castamide with and without humidity during machining. In this study, obtained quality of surface roughness of Castamide block samples prepared in wet and dry conditions, which is processed by using the same cutting parameters, were compared. Moreover, an artificial neural network (ANN) modeling technique was developed with the results obtained from the experiments. For the training of ANN model, material type, cutting speed, cutting rate, and depth of cutting parameters were used. In this way, average surface roughness values could be estimated without performing actual application for those values. Various experimental results for different material types with cutting parameters were evaluated by different ANN training algorithms. So, it aims to define the average surface roughness with minimum error by using the best reliable ANN training algorithm. Parameters as cutting speed (V _c), feed rate (f), diameter of cutting equipment, and depth of cut (a _p) have been used as the input layers; average surface roughness has been also used as output layer. For testing data, root mean squared error, the fraction of variance (R ²), and mean absolute percentage error were found to be 0.0681%, 0.9999%, and 0.1563%, respectively. With these results, we believe that the ANN can be used for prediction of average surface roughness.     

Robust Recursive Inverse Adaptive Algorithm in Impulsive Noise

The recently proposed Recursive Inverse (RI) algorithm has shown a significant performance improvement compared to that of the Recursive Least Squares (RLS) algorithm, in various noise environments. However, both algorithms fail to converge in certain impulsive noise environments, especially if the Signal-to-Noise Ratio (SNR) is low. In this paper, a Robust RI algorithm is proposed. Analytical results show that robustness against impulsive noise is achieved by choosing the weights on the basis of the L ₁ norms of the autocorrelation matrix and the cross-correlation vector. Simulation results confirm that the proposed algorithm provides an improved performance, with a reduction in computational complexity, compared to those of the RLS and the Robust RLS in white and correlated impulsive noise.     

DEVELOPMENT OF SYNERGISTIC HEAT STABILIZERS FOR PVC FROM ZINC BORATE-ZINC PHOSPHATE

The importance of flame-retardant and smoke-suppressed poly(vinyl chloride) (PVC) compositions is increasing gradually in the polymer industry since PVC releases smoke and toxic gases (hydrogen chloride, HCl) during heating at temperatures above 140°C with the result of dehydrochlorination reaction. In this study, the synergistic effects of zinc borate (ZB)-zinc phosphate (ZP) on the thermal stability of PVC were investigated using thermal techniques. The induction and stability time values of PVC plastigels were obtained at 140° and 160°C. The results revealed that PVC plastigels having only ZP and ZB retarded dehydrochlorination of PVC compared with the unstabilized sample. However, the plastigels with both ZB and ZP had a superior synergistic effect on char formation of PVC. Since the induction periods of the samples having both ZB and ZP were higher than those of the unstabilized samples having only ZB or only ZP, the synergistic effect was observed.     

Analysis of the effect of a new process control agent technique on the mechanical milling process using a neural network model: Measurement and modeling

In this study, a new process control agent (PCA) technique called as gradual process control agent technique was developed and the new technique was compared with conventional process control agent technique. In addition, a neural network (ANN) approach was presented for the prediction of effect of gradual process control agent technique on the mechanical milling process. The structural evolution and morphology of powders were investigated using SEM and particle size analyzer techniques. The experimental results were used to train feed forward and back propagation learning algorithm with two hidden layers. The four input parameters in the proposed ANN were the milling time, the gradual PCA content, previous PCA content and gradual PCA content. The particle size was the output obtained from the proposed ANN. By comparing the predicted values with the experimental data it is demonstrated that the ANN is a useful, efficient and reliable method to determine the effect of gradual process control agent technique on the mechanical milling process.     

Esterification reaction of oleic acid with a fusel oil fraction for production of lubricating oil

In this study, the esterification of oleic acid with a fraction of fusel oil was investigated. The variables that affect ester yield, such as temperature, molar ratio of oleic acid to alcohol, and amount of catalyst, were determined. Powdered silica gel was chosen to remove water instead of granular silica gel, magnesium sulfate, or benzene. The behavior of amyl alcohols and the fusel oil fraction was compared. The esterification reaction was carried out under the reaction conditions selected as optimal, and the ester conversion of the reaction was 97.3%. The product mixture compressed products, excess reactants, catalyst, and desiccant. Oleate ester and oleic acid (2.7%) were obtained using the refinement steps of filtration, evaportation, washing with distilled water, and drying over sodium sulfate.     

Simulation of exhaust gas reforming of propane in a heat exchange integrated microchannel reactor

Exhaust gas reforming of propane to a hydrogen-rich mixture in a single, heat-exchange integrated, adiabatic, catalytic microchannel is modeled and simulated at different exhaust gas compositions from conventional gasoline and diesel fueled engines. Propane is considered as the model hydrocarbon for the complex fuels such as gasoline and diesel. The single microchannel is considered to be the characteristic unit of the catalytic exhaust gas reformer involving identical channels located parallel to each other. Steady-state simulations, carried out by the finite volume method, involve parametric variations of the total feed flow rate, and the amounts of propane and steam injected externally into the exhaust gas (reformer feed) stream. The results show that effective heat transfer and uniform temperature distribution, which are critical for the successful operation of the exhaust gas reformer, can be obtained in the microchannel configuration even at low gas hourly space velocities (GHSVs) at which the conventional packed-bed reformers usually lead to remarkable hot-spot formation. Production of H₂ and CO is favored by the addition of higher amounts of propane and steam into the reformer feed. Increasing the total feed flow rate, hence the GHSV is found to improve heat distribution along the microchannel at the expense of reduced product yields due to insufficient contact time.     

Comprehensibility of universal healthcare symbols for wayfinding in healthcare facilities

Healthcare facilities are often complex and overwhelming for visitors, and wayfinding in healthcare facilities can be challenging. As there is an increasing number of global citizens who travel to seek medical care in another country, it is critical to make wayfinding easy for visitors who are not familiar with the language in a foreign country. Among many wayfinding aids, symbols are helpful for those visitors who have limited ability to understand written language. This study tested universal healthcare symbols in the United States, South Korea, and Turkey to compare the comprehension of symbols cross-country and identify predictors of the correct comprehension. To explore statistically significant relationships between symbol comprehension and countries, Pearson's Chi-square tests, logistic regression, and ANOVA were conducted. The test results showed that ten symbols among 14 tested have significant relationship with countries. Results of this study demonstrate that symbol comprehension can be varied significantly in different countries.     

Guanine oxidation signal enhancement in single strand DNA with polyacrylonitrile/polyaniline (PAN/PAni) hybrid nanofibers

Pure polyacrylonitrile (PAN) and polyacrylonitrile/polyaniline (PAN/PAni) hybrid nanofibers (NFs) were produced via electrospinning and used to monitor guanine oxidation in single strand DNA (ssDNA) by electrochemical methods. Two different methodologies were conducted. First, pre‐synthesized PAni was added into electrospinning PAN solution and electrospun into composite PAN/PAni nanofibrous structure on cylindrical pencil graphite (PGE) surface. In the second route, PAN NFs were electrospun on a PGE surfaces and polymerization of PAni was conducted on the surfaces of the as‐spun PAN NFs. NFs were kept at ?18 °C in a refrigerator for several days. ssDNA was immobilized on the prepared NFs and guanine oxidation signals were observed for each system. The results revealed that use of PAN NFs enhanced signal intensity from 0.92 µA (PGE) to 1.04 µA (PAN NFs). Addition of PAni to PAN increased signal intensity to 1.23 µA. When the PAN NF surfaces were coated with PAni, signal enhancement continued to increase up to 4.19 µA for fourth day and decreased again when PAni‐coated NFs were kept at ?18 °C in the refrigerator. Since the prepared system is fast and cheap, it is promising for application in DNA biosensor devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45567.