Comparing the Effects of Microwave and Conventional Heating Methods on the Evaporation Rate and Quality Attributes of Pomegranate (<Emphasis Type="Italic">Punica granatum</Emphasis> L.) Juice Concentrate

Pomegranate juice was concentrated by conventional heating and microwave heating at different operational pressures (12, 38.5, and 100 kPa), and their effects on evaporation rate and quality attributes of concentrated juice were investigated. The final juice concentration of 40° Brix was achieved in 140, 127, and 109 min at 100, 38.5, and 12 kPa, respectively, by using conventional heating. Applying microwave energy decreased required times to 118, 95, and 75 min. The changes in color, anthocyanin content, and antioxidant capacity during concentration processes were investigated. L*, a*, and b* parameters were measured to estimate the intensity of color loss. All Hunter color parameters decreased with time. Results showed that the degradation of color, anthocyanins, and antioxidant activity were more important in conventional heating compared to microwave heating method. Degradation rates increases by increasing process pressure. A first-order kinetics model was applied to modeling changes in total solid content, anthocyanin content, and antioxidant capacity.     

X-ray Photoelectron Spectroscopy of Cadmium Tin Oxide Ceramics in As-Fired and Electrochemically Reduced Forms

X-ray photoelectron spectroscopy (XPS) has been employed to investigate the chemical nature of samples of dicadmium stannate (Cd₂SnO₄) in the as-fired, electrochemically reduced, and reoxidized states. The reduction of Cd₂SnO₄ was found to be associated with a dramatic color change from bright yellow to dark green, a phenomenon commonly known as the electrochromic effect. Both quantitative XPS results and binding energy measurements proved that, upon exposure of the reduced ceramic bodies to air, the Sn²⁺ to Sn⁴⁺ transition readily took place to produce the intermediate compound, Cd₂SnO₃ with divalent tin. Prolonged exposure to the atmosphere did not result in further progress of reoxidation extending to monovalent cadmium. However, complete reoxidation of the reduced samples was possible by annealing in air at 350°C for a short period of time, e.g., 3 h, by which the original features of the as-fired state such as color and electrical conductivity were restored. The results also showed that reoxidized samples at high temperature assume the same XPS characteristics as those of as-fired ceramics.     

A jet mixing study in two phase gas-liquid systems

All studies concerned with jet mixing have been focused on liquid phase systems and no studies have been found on jet mixing for gas-liquid two phase systems. In the present study the use of jet fluid as a mixer in gas-liquid systems was proposed. Further by installing an experimental setup, the mixing behavior of liquid phase was studied. Gas flow and jet flow are injected to the mixing vessel countercurrently. In this study, the effect of jet injection, location of the conductivity probe, aeration rate and jet Reynolds number on the mixing time are investigated. The created flow pattern was extracted for each condition and the results often analyzed on the basis of them. It is observed that, for low aeration rates, the injection of jet decreases the mixing time considerably. By increasing the aeration rate, the difference in mixing times between the two cases of jet injection and without jet is reduced. Results also show that the closer the probe is to encounter location of the jet and airflow, the lower the mixing time obtained. Dependence of mixing time on the probe location decreases by increasing the mixing intensity and eliminating dead zones. It is obtained, on the basis of Re_j and the amount of jet travelling in the vessel, increasing the aeration rate has different effects on the performance of mixing. Generally, four different trends for the variation of mixing time with increasing the aeration rate are observed.     

利用扩展Tao-Mason状态方程预测天然气混合物容积特性(p-V-T)

A statistical-mechanical-based equation of state(EOS)for pure substances,the Tao-Mason equation of state,is successfully extended to prediction of the(p-v-T)properties of fourteen natural gas mixtures at temperatures from 225 K to 483 K and pressures up to 60.5 MPa.This work shows that the Tao-Mason equation of state for multicomponent natural gas is predictable with minimal input information,namely critical temperature,critical pressure,and the Pitzer acentric factor.The calculated results agree well with the experimental data.From a total of 963 data of density and 330 data of compressibility factor for natural gases examined in this work,the average absolute deviations(AAD)are 1.704%and 1.344%,respectively.The present EOS is further assessed through the comparisons with Peng-Robinson(PR)equation of state.For the all of mixtures Tao-Mason(TM)EOS outperforms the PR EOS.     

A nickel hexacyanoferrate and poly(1-naphthol) hybrid film modified electrode used in the selective electroanalysis of dopamine

A mixed-valent nickel hexacyanoferrate and poly(1-naphthol) hybrid (NiHCF–PNH) film was prepared on a gold (Au) electrode by a galvanostatic method, which led to stable and homogeneous hybrid film. The film was characterized using scanning electronic microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. This electrode showed excellent catalytic properties toward dopamine (DA) detection, using cyclic voltammetry and differential pulse voltammetry methods. The electrocatalytic oxidations of DA at different electrodes, such as a bare Au electrode or a poly(1-naphthol)/Au-, or NiHCF–PNH/Au-modified electrode, were investigated in a phosphate buffer solution (pH 7). Interestingly, the NiHCF–PNH-modified electrode facilitated the oxidation of DA, but it did not responded to other electroactive biomolecules, such as ascorbic acid and uric acid_. The DA electrochemical sensor exhibited a linear response from 0.1 to 4.3 μM (R² = 0.9984) and from 4.3 to 9.6 μM (R² = 0.9969), with a detection limit of 2.1 × 10^?8 M, and a short response time (3 s) for DA determination. In addition, the NiHCF–PNH-modified electrode exhibited distinct advantages by its simple preparation, specificity, and stability.     

Photoluminescence emission of nanoporous anodic aluminum oxide films prepared in phosphoric acid

The photoluminescence emission of nanoporous anodic aluminum oxide films formed in phosphoric acid is studied in order to explore their defect-based subband electronic structure. Different excitation wavelengths are used to identify most of the details of the subband states. The films are produced under different anodizing conditions to optimize their emission in the visible range. Scanning electron microscopy investigations confirm pore formation in the produced layers. Gaussian analysis of the emission data indicates that subband states change with anodizing parameters, and various point defects can be formed both in the bulk and on the surface of these nanoporous layers during anodizing.     

Effect of chlorine ion concentration on morphology and optical properties of Cl-doped ZnO nanostructures

Effect of Cl^?1 concentration on morphology and optical properties of Cl-doped ZnO nanostructures was studied. The Cl-doped ZnO nanostructures and undoped ZnO microstructures were grown on Si(1 1 1) substrates using a physical vapor deposition method. The ZnO nanostructures have been doped with different concentrations of chlorine. The Cl-doped ZnO nanostructures with 6% atom Cl, showed a nanodisk morphology with a hexagonal shape, while the Cl-doped ZnO nanostructures with 9% atom Cl, exhibited a stacked nanoplate morphology with smaller thickness in comparison to the Cl-doped ZnO nanodisks. In addition, with increasing Cl content to 13%, morphology of the products changed to more stacked nanoplates with nanoflakes morphology. X-ray diffraction results clearly showed a hexagonal structure for the all samples. Raman spectroscopy results showed a strong crystalline quality for the undoped ZnO microdisks and Cl-doped ZnO nanodisks; while these results indicated a weak crystalline quality for the Cl-doped ZnO nanoplates and nanoflakes. Photoluminescence (PL) studies also confirmed the Raman results and it exhibited a lower optical property for the Cl-doped ZnO nanoplates and nanoflakes in comparison to the undoped ZnO microdisks and Cl-doped ZnO nanodisks. Furthermore, the UV peak of the Cl-doped ZnO nanostructures was blue-shifted with respect to that of the undoped ZnO.     

Synthesis of polybutadiene nanoparticles by emulsion polymerization: The effect of electrolyte and initiator type on particle size and reaction kinetics

Emulsion polymerization of the butadiene (Bu) was performed in the presence of disproportionate potassium rosinate (DPR) as anionic emulsifier, potassium hydroxide (KOH), and potassium carbonate (K₂CO₃) as electrolytes, and three different initiators including potassium persulfate (KPS), 2,2^′-azobisisobutyronitrile (AIBN) or 4,4′-azobis(4-cyanovaleric acid) (ACVA, also known as VAZO) at 70 °C. Latexes were prepared with a solid content of about 30 wt%. The particle size and its distribution were measured by dynamic light scattering (DLS) analysis, while the polymerization conversion was determined gravimetrically at different time intervals. Results on the emulsion polymerization of Bu in the presence of KOH and K₂CO₃ co-electrolytes showed that adding KOH to the reaction media decreases the polymerization rate. Positive effect of co-electrolytes on the control over polybutadiene latex (PBL) particles size and its distribution was also confirmed, where K₂CO₃ played roles as electrolyte and pH buffer and KOH served double roles as electrolyte and alkaline supplier of the reaction media. Complete solubility of the AIBN in Bu resulted in higher rate of polymerization in the presence of AIBN in comparison to other initiators, i.e., VAZO or KPS. The results showed that initiator type plays a significant role on the formation of PBL nanoparticles and kinetics of the polymerization. The kinetic studies revealed that emulsion polymerization of Bu follows case 1 (i.e., \(\bar{n}\) ?0.5, where \(\bar{n}\) indicates average number of the propagating chains per particle) of the Smith-Ewart kinetics.     

Effect of annealing process on the growth and surface properties of Au–ZnO nanowire films grown by chemical routes

Au–ZnO nanowire films have been synthesized by chemical routes, electrochemical deposition (ECD) and chemical bath deposition (CBD) techniques, on zinc foil followed by annealing in air at 400 °C. X-ray diffraction patterns reveal formation of the ZnO wurtzite structure along with binary phases Au₃Zn and AuZn₃. Scanning electron microscopy shows the presence of ZnO nanowires having several micrometers in length and less than 120 nm in diameter synthesized by ECD and in the range of 70–400 nm using the CBD technique. During the annealing process, different surface morphologies originating from different catalytic effects of Au atoms/layers were observed. In addition, the effect of synthesis routes on crystalline quality and optical properties were studied by Raman and photoluminescence spectrometers indicating varying concentration of defects on the films. The Raman results indicate that Au–ZnO nanowire film prepared by chemical bath deposition route had better crystalline quality.     

Experiments Design for Hardness Optimization of the Ni-Cr Alloy Electrodeposited by Pulse Plating

The hardness of the Ni-Cr alloy which is electrodeposited in chloride solution,is optimized by design of experiment method(central composite design).Various parameters were evaluated in order to find significant factors in this process.Frequency,duty cycle,current density and temperature were selected as efective factors.Analyses of variance(ANOVA)were performed on the results of the designed experiments.The best model which can predict the hardness of the Ni-Cr alloy electrodeposits was found whereas the frequency and quadratic behaviour of the current density were the most significant model terms.Serious interaction of the current density with frequency and duty cycle also were found in this model.Finally the optimum conditions of the factors for obtaining the maximum hardness of the Ni-Cr alloy were found.Ni-Cr alloy with hardness828 HV(electrodeposited with frequency 63 Hz,current density 1800 A/m2,duty cycle 75%and temperature31℃ bath)were assessed as the optimum deposit.The deposit under the optimum condition was investigated by scanning electron microscopy(SEM),EDX analysis,polarization method and microhardness.