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71.
In this work, different sol solutions with various titanium tetraisopropoxide (TIP)/glacial acetic acid ratios in 2‐propanol with 5 wt % poly(vinyl pyrrolidone) (PVP) (Mw = 360,000 g/mol) were prepared and electrospun. Composition of the prepared sols and as‐spun TiO2/PVP nanofibers were determined by Fourier transform infrared and Raman spectroscopy methods. Morphology of the electrospun TiO2/PVP nanofibers was studied by scanning electron microscopy and transmission electron microscopy (TEM) techniques. Rheometry measurements of the sol solutions showed decrease of viscosity upon the addition of TIP to the polymer solutions with constant polymer and acid concentrations. The sol solution having the lowest viscosity (at shear rate 10 s?1) but the highest TIP/glacial acetic acid ratio showed beaded nanofibers morphology when electrospun under 10 and 12 kV applied voltage while injection rate, needle tip to collector distance, and needle gauge were kept constant. However, smooth electrospun TiO2/PVP composite nanofibers with the average nanofibers diameters (148 ± 79 nm) were achieved under the same condition when applied voltage increased to 15 kV. TEM micrographs of the electrospun TiO2/PVP nanofiber showed that the TiO2 particles with continuous structure are formed at the middle of the nanofiber and distributed along its axis. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46337.  相似文献   
72.
In this work, the parameters of cobalt oxide suspension such as conductivity, zeta potential, particle size, stability, and finally the electrophoretic behavior of particles in the absence and presence of polyethylenimine (PEI) in acetone medium were investigated. Also, the effects of washing on the stability and electrophoretic deposition of Co3O4 were studied. Characterization of the obtained layer by optical microscopy revealed that there was no deposition in the suspension without PEI, while a uniform layer was formed in the presence of PEI additive. Scanning electron microscopy (SEM) results confirmed the uniformity of layer obtained in acetone using PEI additive. Moreover, SEM results demonstrated that more porous microstructures were obtained at longer deposition durations. The difference in the porosity of the layers, as indicated by the SEM micrographs, is attributed to increase in the deposition time.  相似文献   
73.
Carbon fiber reinforced aluminum laminates (CARALL) are one of the aluminum based Fiber metal laminates (FMLs) which, due to their high strength to weight ratio and good impact resistance are greatly replacing aluminum alloys in aircraft structures. In this research work, interlaminate shear strength of Vacuum assisted resin transfer molding (VARTM) manufactured CARALL has been investigated. Numerical simulation model incorporated with real time material data has been developed to predict the delamination behavior of CARALL laminates. Standard CARALL specimens with different surface morphologies were prepared by electric discharge machining, mechanical, chemical and electrochemical surface treatments. T-peel tests were carried out according to standard ASTM D1876-08 to find out inter laminate shear strength. FMLs made out of mechanically, chemically and electrochemically cleaned metal sheets depicted high interlaminate shear strength. SEM micrographs of failed surfaces verify the high adhesive strength of epoxy. Developed numerical simulation model accurately predicts the delamination behavior of CARALL as observed during experimentation.  相似文献   
74.
An abrasive free chemical mechanical planarization(AFCMP) of semi-polar(1122) AlN surface has been demonstrated. The effect of slurry pH, polishing pressure, and platen velocity on the material removal rate(MRR) and surface quality(RMS roughness) have been studied. The effect of polishing pressure on the AFCMP of the(1122) AlN surface has been compared with that of the(1122) AlGaN surface. The maximum MRR has been found to be ~562 nm/h for the semi-polar(1122) AlN surface, under the experimental conditions of 38 kPa pressure, 90 rpm platen velocity, 30 rpm carrier velocity, slurry pH 3 and 0.4 M oxidizer concentration. The best root mean square(RMS) surface roughness of ~1.2 nm and ~0.7 nm, over a large scanning area of 0.70×0.96 mm2, has been achieved on AFCMP processed semi-polar(1122) AlN and(AlGaN) surfaces using optimized slurry chemistry and processing parameters.  相似文献   
75.
Abstract

Surgical mesh is a porous fabric that is mainly produced from polymeric monofilaments using the warp-knitting method. Surgical mesh is used for healing hernia. Among the mechanical properties of the mesh, tensile and bursting strength have special significance. In this research, warp-knitted surgical meshes with five structures have been produced using polypropylene monofilament, and the effect of the fabric structure on the bursting characteristics of them has been investigated. All the meshes exhibited supraphysiologic bursting strength. quasi-Sandfly mesh demonstrated the highest, while quasi-Marqussite mesh exhibited the least bursting characteristics. The increase in the bursting characteristics of the meshes is attributed to the increase in the areal density and decrease in the porosity of them. Moreover, conformity between the bursting and tensile properties of them in bias direction has been observed. Overall, quasi-Marqussite mesh was proposed as the most desirable mesh in terms of porosity, weight, and bursting characteristics.  相似文献   
76.
Air-cored axial-flux permanent-magnet synchronous generators (AFPMSGs) are potential candidates for gearless direct-coupled wind turbines (DCWTs) owing to providing high efficiency and power density. The design of a DCWT generator is so complicated since the generator cost, dimension, and weight affected by gear elimination. Therefore, it is essential to find an optimal AFPMSG design at rated conditions. In this paper, an accurate procedure for the optimal design of an air-cored AFPMSG applicable for DCWTs is proposed. The genetic algorithm (GA) is used for multi-objective design optimization to reach the optimal configuration as well as system dimension in order to decrease the weight, increase the power density and enhance the effectiveness of the generator. To validate the efficiency of the suggested optimization proceducer, a 30 kW AFPMSG has been considered as a case study. The results of optimization have been investigated by finite element analysis (FEA). A prototype generator is also fabricated, and the test results are offered and compared with the numerical study. The outcomes show that there exists an acceptable agreement between FEA and experimental outcomes with the error percentage about of 1.35%.  相似文献   
77.
Deficiency of the placental hormone chorionic somatomammotropin (CSH) can lead to the development of intrauterine growth restriction (IUGR). To gain insight into the physiological consequences of CSH RNA interference (RNAi), the trophectoderm of hatched blastocysts (nine days of gestational age; dGA) was infected with a lentivirus expressing either a scrambled control or CSH-specific shRNA, prior to transfer into synchronized recipient sheep. At 90 dGA, umbilical hemodynamics and fetal measurements were assessed by Doppler ultrasonography. At 120 dGA, pregnancies were fitted with vascular catheters to undergo steady-state metabolic studies with the 3H2O transplacental diffusion technique at 130 dGA. Nutrient uptake rates were determined and tissues were subsequently harvested at necropsy. CSH RNAi reduced (p ≤ 0.05) both fetal and uterine weights as well as umbilical blood flow (mL/min). This ultimately resulted in reduced (p ≤ 0.01) umbilical IGF1 concentrations, as well as reduced umbilical nutrient uptakes (p ≤ 0.05) in CSH RNAi pregnancies. CSH RNAi also reduced (p ≤ 0.05) uterine nutrient uptakes as well as uteroplacental glucose utilization. These data suggest that CSH is necessary to facilitate adequate blood flow for the uptake of oxygen, oxidative substrates, and hormones essential to support fetal and uterine growth.  相似文献   
78.
Snap-through is an instability phenomenon that occurs in arch and dome-shaped structures, wherein the structure has to move from a stable equilibrium state through an unstable path into another stable equilibrated configuration in a jumping action. In this study, a linear elastic isotropic low arch is considered as a structure with power-law variable thickness. The phenomenon is investigated by considering the equation of the deflection for the variable thickness arch, solving it with an elegant analytical technique, and finding the snap-through critical load from an extreme condition. The effect of power-law exponent and geometry of the arch centerline on critical load is investigated and the constant thickness case and a very rare case of power-law thickness variation found in literature are considered for verification.  相似文献   
79.
In this work the fundamental problem of peristalsis with heat and mass transfer is investigated in the presence of a chemical reaction. An incompressible viscous fluid is considered in a channel with compliant walls. Mathematical modeling is based upon the laws of mass, linear momentum, energy and concentration. Analysis is presented not only for long wavelength and low Reynolds number but also for small Grashof number. The solutions are carried out for the stream function, temperature, concentration field and heat transfer coefficient. The results of various interesting parameters are plotted and discussed.  相似文献   
80.
The role of pH, solid content, water chemistry and ore mineralogy on the galvanic interactions between chalcopyrite and pyrite and low alloy steel balls were investigated in the grinding of Sarcheshmeh porphyry copper sulfide ore. All these factors strongly affect the galvanic current between the minerals and the steel during the grinding process. The galvanic current density decreased as the solution pH and percent solids increased. In addition, changing the water in the ball mill from tap to distilled water reduced the galvanic current between the minerals and the balls. Potentiodynamic polarization curves showed that pyrite and chalcopyrite demonstrated typical active-passive-transpassive anodic behavior in the grinding of copper ore. However, the nature of their transitions from the active to the passive state differed. This behavior was not seen in the grinding of pure minerals. In addition, an EDTA extraction technique was employed to quantify the amount of oxidized iron in the mill discharge. The amount of extractable iron was influenced by the same experimental factors and in the same way as the galvanic current.  相似文献   
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