A Method for the Estimation of the Interface Temperature in Ultrasonic Joining

Ultrasonic joining of copper foil to 1100 aluminum sheet at nominal joining temperatures of 298 K to 413 K (25 °C to 140 °C) for 1.25 second caused significant copper diffusion into the aluminum sheet, indicating very high diffusivity (D) values of 1.54 × 10^?13 to 2.22 × 10^?13 m²/s. The D values reflect high excess vacancy concentrations caused by the rapid plastic deformation in the joining surfaces. A method is presented to estimate the actual values of interface temperature from the diffusion data and expected values of vacancy concentrations. The estimated values of interface temperature were about 390 to 410 deg below the equilibrium melting point of aluminum, and in agreement with reported experimental values.     

Electrochemical,continuous-flow determination of p-benzoquinone on a gold nanoparticles poly(propylene-co-imidazole) modified gold electrode

A novel continuous flow biosensor based on gold nanoparticles and poly(propylene-co-imidazole) was developed for the online determination of p-benzoquinone. The amperometric response was measured as a function of p-benzoquinone concentration at an applied potential of ?50 mV. The hydrogen peroxide concentration was optimized and fixed at 1 mM in samples. The mass transfer resistance of the copolymer film was minimized, and the flow cell was regenerated quickly at 1 mL/min. The resulting device provided good analytical performance based on a linear dynamic range from 5–100 µM, a short response time of 3 s, a detection limit of 3.3 µM, excellent repeatability with a relative standard deviation of 0.82%, long-term stability of 95% after four weeks, and an accuracy of 105%. The gold nanoparticles enhanced the electron transfer rate on the electrode. The apparent Michaelis-Menten constant was 4 mM, showing that the enzyme retained catalytic specificity and provided high activity for p-benzoquinone.     

Growth of NBT template particles through topochemical microcrystal conversion and their structural characterization

In this study, uniform rectangular plate‐like perovskite Na_0.5Bi_0.5TiO₃ templates were obtained by molten salt synthesis method in three steps. Perovskite plate‐like Na_0.5Bi_0.5TiO₃ templates were synthesized from bismuth‐layered Na_0.5Bi_4.5Ti₄O₁₅ by topochemical microcrystal conversion method at the third and final step. The most important point was that the plate‐like morphology remained as desired, but templates were obtained in cubic perovskite structure. The Na₂CO₃ excess in the third step was the main controlling parameter. The crystalline orientation of the particles was investigated by electron backscatter diffraction analysis. The results indicated that the particles are single crystalline in nature. In the case of the 90 mol% excess of the stoichiometric Na₂CO₃ ratio, the NBT platelets had highly regular, rectangular prismatic morphology and single‐crystal nature. The structure was also confirmed through high‐resolution transmission electron microscope and selected area electron diffraction analysis.     

Polymeric amylase nanoparticles as a new semi-synthetic enzyme system for hydrolysis of starch

α-Amylase (EC 3.2.1.1; α-d-1,4,glucan glucanohydrolase) catalyzes the hydrolysis of α-d-(1,4)-glucosidic linkages in starch, glycogen, and various malto-oligosaccharides, by releasing α-anomeric products. In this study, a novel method has been developed to prepare nanoprotein particles that carry α-amylase as a monomer by using a photosensitive microemulsion polymerization process. The nanostructured α-amylase with photosensitive features have been characterized by fluorescence spectroscopy, transmission electron microscopy (TEM) and Zeta Sizer. The fluorescence intensity of amylase nanoparticles was determined to be 658 a.u. at 610 nm and the average particle size of nanoamylase was found to be about 71.8 nm. Both free α-amylase and nanoparticles were used in the hydrolysis of starch under varying reaction conditions such as pH and temperature that affect enzyme activity and the results were compared to each other. K_m values were 0.26 and 0.87 mM and V_max values were 0.36 IU mg^? 1 and 22.32 IU mg^? 1 for nanoenzyme and free enzyme, respectively. Then, thermal stability, storage stability and reusability were investigated and according to the results, activity was preserved 60% at 60 °C; 20% at 70–80 °C temperature values and 80% after 105 days storage. Finally after 10 cycles, the activity was preserved 90% and this novel enzymatic polymeric amylase nanoparticle has showed considerable potential as reusable catalyst.     

Conceptualizing manufacturing flexibility: An operational approach and a comparative evaluation

An operational approach to conceptualization and the measurement of manufacturing flexibility is presented. A critical review of selected measures from the literature is provided in the context of the operational approach. A flexibility measure is proposed. A formulation and the features of the proposed measure are discussed. An application of the measure is demonstrated through a hypothetical example. Using the same example, selected flexibility measures from the literature are evaluated. The performance of the measures and the proposed measure are compared.     

High-Strain-Rate Material Behavior and Adiabatic Material Instability in Impact of Micron-Scale Al-6061 Particles

Impact of spherical particles onto a flat sapphire surface was investigated in 50-950 m/s impact speed range experimentally and theoretically. Material parameters of the bilinear Johnson–Cook model were determined based on comparison of deformed particle shapes from experiment and simulation. Effects of high-strain-rate plastic flow, heat generation due to plasticity, material damage, interfacial friction and heat transfer were modeled. Four distinct regions were identified inside the particle by analyzing temporal variation of material flow. A relatively small volume of material near the impact zone becomes unstable due to plasticity-induced heating, accompanied by severe drop in the flow stress for impact velocity that exceeds ~?500 m/s. Outside of this region, flow stress is reduced due to temperature effects without the instability. Load carrying capacity of the material degrades and the material expands horizontally leading to jetting. The increase in overall plastic and frictional dissipation with impact velocity was found to be inherently lower than the increase in the kinetic energy at high speeds, leading to the instability. This work introduces a novel method to characterize HSR (10⁹ s^?1) material properties and also explains coupling between HSR material behavior and mechanics that lead to extreme deformation.     

Reactive red 120 and NI(II) derived poly(2‐hydroxyethyl methacrylate) nanoparticles for urease adsorption

Non‐porous poly(2‐hydroxyethyl methacrylate) [p(HEMA)] nanoparticles were prepared by surfactant free emulsion polymerization. The p(HEMA) nanoparticles was about 200 nm diameter, spherical form, and non‐porous. Reactive Red 120 (RR 120) was covalently attached to the p(HEMA) nanoparticles and Ni(II) ions were incorporated to attach dye molecules. Urease was immobilized onto RR120‐Ni(II) attached p(HEMA) nanoparticles via adsorption. The maximum urease adsorption capacity of RR120‐Ni(II) attached p(HEMA) nanoparticles was 480.01 mg g^?1 nanoparticles at pH 7.0 in phosphate buffer. It was observed that urease could be repeatedly adsorbed and desorbed without significant loss in adsorption amount. K_m values were 21.50 and 34.06 mM for the free and adsorbed enzyme. The V_max values were 4 U for the free enzyme and 3.3 U for the adsorbed enzyme. The optimum pH was 25 mM pH 7 phosphate buffer for free and adsorbed enzyme. The optimum temperature was determined at 35°C and 55°C for the free and adsorbed enzyme, respectively. These findings show considerable promise for this material as an adsorption matrix in biotechnological applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39757.     

New generation polymeric nanospheres for lysozyme adsorption

Novel hydrophobic nanospheres with an average size of 100 nm utilizing N‐methacryloyl‐(l)‐tryptophan methyl ester (MAT) as a hydrophobic monomer were prepared by surfactant free emulsion polymerization of 2‐hydroxyethyl methacrylate (HEMA) and MAT. MAT was synthesized using methacryloyl chloride and l‐tryptophan methyl ester. Specific surface area of the nonporous nanospheres was found to be 1914 m²/g. Poly(HEMA–MAT) nanospheres were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Average particle size, size distribution, and surface charge measurements were also performed. Elemental analysis of MAT for nitrogen was estimated as 1.95 mmol/g polymer. Then, poly(HEMA–MAT) nanospheres were used in the adsorption of lysozyme in batch system. Using an optimized adsorption protocol, a very high loading of 1075 mg lysozyme/g nanosphere was obtained. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption amount or enzyme activity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mathematical simulation and long-term monitoring of leachate components from two different landfill cells

In this study we monitored for 920 days the sulfate (SO(4)(2-)), chloride (Cl(-)), chemical oxygen demand (COD) and biological oxygen demand (BOD) parameters in leachate produced in two large-scale test cells at the Odayeri Sanitary Landfill, Istanbul, Turkey. We present a mathematical model of these parameter concentrations in leachates of two test cells with one being the control (C1) and the other (C2) leachate recirculation. The relationship between these parameters and refuse age is simulated by a mathematical formula. The unknown constants of the simulation formula are solved by the least squares method, which minimizes the squared total of deviation from the model of the actual data using a MATLAB computer program. A good fit was obtained between the measured data and model simulations. COD concentrations in leachate from C1 and C2 rapidly attained their maximum values of 75 and 70 g/l, respectively, after 1 month of landfilling. BOD to COD ratios are around 0.8 for both test cells during the acidogenic phase; this ratio then decreased to 0.06. A sharp decrease in the concentration of Cl(-) from 14 to 15 g/l was observed after approximately 2 months of operation, followed by a slow decrease. SO(4)(2-) concentrations rapidly reached a maximum value of 2000 mg/l within 45 days; development of anaerobic conditions caused a sharp decrease to around 75 mg/l for C2 and 450 mg/l for C1 after 5 months of operation. The results showed that there appeared to be little improvement in leachate quality by leachate recirculation in terms of COD and BOD values, however, it is determined that the pollution loads more rapidly reached minimum values within the C2 test cell.     

Simultaneous hydrogen gas formation and COD removal from cheese whey wastewater by electrohydrolysis

Cheese whey (CW) was subjected to DC voltages between 0.5 and 5 V for hydrogen gas production with simultaneous COD removal by electrohydrolysis of CW organics. Hydrogen gas formation and COD removal were investigated at different DC voltages using aluminum electrodes. The highest cumulative hydrogen production (5551 mL), hydrogen yield (1709 mL H₂ g⁻¹ COD), hydrogen gas formation rate (913 ml d⁻¹), and percent hydrogen (99%) in the gas phase were obtained with 5 V DC voltage within 158 h. Energy conversion efficiency reached the highest level (80.7%) at 3 V DC voltage with cumulative hydrogen production of 4808 mL and hydrogen yield of 1366 mL H₂ g⁻¹ COD. Hydrogen gas was mainly produced by electrohydrolysis of CW organics due to low H₂ gas production in water and CW control experiments. The highest COD removal (22%) was also obtained with 3 V DC voltage. Major COD removal mechanism was anaerobic degradation of carbohydrates producing volatile fatty acids (VFA) and CO₂. Hydrogen gas was produced by reaction of protons released from VFAs and electrons provided by DC current. Hydrogen gas production by electrohydrolysis of CW solution was proven to be an effective method with simultaneous COD removal.