Immobilization of Metalloporphyrin on Functionalized Magnetic Nanoparticles as a Catalyst in Oxidation of Cyclohexene: Novel Modified Fe3O4 Nanoparticles with Triethoxysilane Agent

Magnetic nanoparticles, Fe₃O₄, have been prepared and functionalized by (N-(3-(triethoxysilyl)propyl)isonicotinamide) and characterized by infrared spectroscopy, thermal analysis (TGA/DTA), X-ray powder diffraction, scanning electron microscopy, elemental analysis and BET surface area measurement. The functionalized Fe₃O₄ nanoparticles were used as a support to anchor metalloporphyrin. Application of immobilized metalloporphyrin as a heterogeneous catalyst in the oxidation of cyclohexene was explored. Effect of various parameters such as solvent and temperature on immobilization process and also various parameters (solvent, time, oxidant and axial group effect) on oxidation of cyclohexene has been investigated. The result showed that the immobilized metalloporphyrin on functionalized magnetic nanoparticles is an efficient and reusable catalyst for oxidation of cyclohexene.     

A novel modular fretting wear test rig

A novel modular experimental apparatus was designed and developed to measure and visualize fretting wear and friction for Hertzian circular and elliptical contacts and flat on flat contacts. The experimental apparatus utilizes a magnetostrictive actuator to reciprocate a flat, ball, or cylinder between two fixed specimens. Two stationary flat or cylindrical specimens mounted on a rotary table clamp the reciprocating specimen from the top and bottom to generate the fretting contact. The two stationary test specimens installed on the rotary table perpendicular to the moving specimen form a crossed cylinder geometry which creates a well-defined circular contact. An elliptical contact with different aspect ratios can be obtained by varying the angle between the fixed and the moving specimens. Dead weights placed on top of the upper stationary specimen provide the normal load. A force sensor located in line between the actuator output shaft and the specimen is used to measure friction. The test rig's modular design allows it to be configured for Hertzian circular (ball-on-flat, crossed cylinder), elliptical (crossed cylinder), and conformal (flat-on-flat) contacts. In the ball on flat configuration a steel flat or sapphire window is used in contact with the reciprocating ball. When the sapphire window is used a microscope and high speed camera is employed for in situ visualization and recording of the contact.     

A highly sensitive and selective electrochemical sensor for determination of Cr(VI) in the presence of Cr(III) using modified multi-walled carbon nanotubes/quercetin screen-printed electrode

A novel screen-printed carbon electrode modified with quercetin/multi-walled carbon nanotubes was fabricated for determination of Cr(VI) in the presence of excess of Cr(III) without any pretreatment. The method is based on accumulation of the quercetin–Cr(III) complex generated in situ from Cr(VI) at the modified electrode surface in an open circuit followed by differential pulse voltammetry detection. The new method allowed selective determination of Cr(VI) in the presence of Cr(III). The influence of various parameters affecting the adsorptive stripping voltammetry performance was investigated. Under the optimum conditions, the calibration plot was found to be linear in the Cr(VI) concentration range from 1.0 to 200 μmol^? 1 with a limit of detection(S/N = 3) of 0.3 μmol L^– 1. The relative standard deviation (RSD%) of seven replicates of the current measurements for a 50 μmol^? 1 of Cr(VI) solution was 3.0%. The developed electrode displayed a very low or no sensitivity to alkali, alkali-earth and transition metal cations and was successfully applied for the determination of Cr(VI) in drinking water samples.     

An improved process simulation system for ball-end milling of sculptured surfaces

A simulation system is developed in this paper, which deals with the geometry and mechanics of machining with ball-end milling cutters. The geometry of the workpiece, the cutter, and the cutter/workpiece engagement is modeled using a geometric simulation system. This module uses a commercial solid modeler (ACIS) as a geometric engine and automatically extracts the critical geometric information required for the physical simulation system. To calculate the instantaneous cutting forces, a new mechanistic force model is developed. This force model takes into account the variations of the cutting coefficients along the cutting edge, and considers the variations of the rake angle and the chip flow direction on the rake face. The calibration of the developed model is performed for half-immersion ball-end milling operation. The applicability of the developed system is verified experimentally for various up-hill angles. It is shown that as the up-hill angle increases, the ball-nose tip engagement decreases which in turn significantly affects the magnitude of the resultant forces. Also, lower cutting forces and powers are experienced if cutting with the vicinity of the tool tip is avoided.     

The influence of heat treatment and hot deformation conditions on γ′ precipitate dissolution of Nimonic 115 superalloy

In precipitation hardenable materials, it is desirable to determine the precipitate dissolution temperature for homogenizing the microstructure by controlling the size and distribution of the precipitates. In this research, the influence of various heat treatment and hot deformation conditions on the kinetics of γ′ dissolution and its morphological evolution in Nimonic 115 was studied. In addition, hot deformation behavior of the material was investigated using hot compression experiments at varying temperature (between 1,050°C and 1,175°C) and strain rates (between 0.01 and 1 s^?1) up to a true strain of 0.8. The values obtained for the solvus temperature of γ′ precipitates by two methods are all in agreement indicating this temperature at approximately 1,165?±?5°C. Through examination of the influence of temperature and strain rate on the hot deformation behavior, it was determined that the experimental flow stress observations could be effectively related to the processing parameters using an Arrhenius relationship. The results indicate that dynamic recrystallization is the main softening mechanism during the high temperature deformation of Nimonic 115, and it can be effectively promoted by increasing the deformation temperature. By deformation at temperatures higher than 1,125°C, a completely recrystallized microstructure is obtained.     

Microstructure and Mechanical Properties of CP-Titanium Processed by ECAP Followed by Warm Caliber Rolling

In this study, microstructural evolution and mechanical properties of commercial purity titanium after a combined equal channel angular pressing (ECAP) and warm caliber rolling (WCR) was investigated. The ECAP process was applied to enhance the hardness and strength of the specimen by decreasing the grain size and producing UFG microstructure. WCR was applied to reduce cross-section and increase the ductility of the ECAPed specimens. Results show that WCR reduces the work-hardening rate by increasing grain size and also increases elongation and workability while it reduces the yield and ultimate tensile strength. It has been shown that the strength ratio (\({{\sigma_{UTS} } \mathord{\left/ {\vphantom {{\sigma_{UTS} } {\sigma_{y} }}} \right. \kern-0pt} {\sigma_{y} }}\)) and strain ratio (\({{\varepsilon_{UTS} } \mathord{\left/ {\vphantom {{\varepsilon_{UTS} } {\varepsilon_{t} }}} \right. \kern-0pt} {\varepsilon_{t} }}\)) of the processed samples are comparatively larger than all previously post processed ECAPed materials at lower temperatures.     

Effective thermal conductivity and thermal contact resistance of gas diffusion layers in proton exchange membrane fuel cells. Part 1: Effect of compressive load

Heat transfer through the gas diffusion layer (GDL) is a key process in the design and operation of a PEM fuel cell. The analysis of this process requires determination of the effective thermal conductivity as well as the thermal contact resistance associated with the interface between the GDL and adjacent surfaces/layers.In the present study, a custom-made test bed that allows the separation of effective thermal conductivity and thermal contact resistance in GDLs under vacuum and ambient conditions is described. Measurements under varying compressive loads are performed using Toray carbon paper samples with a porosity of 78% for a range of thicknesses. The measurements are complemented by compact analytical models that achieve good agreement with experimental data. A key finding is that thermal contact resistance is the dominant component of the total thermal resistance; neglecting this phenomenon may result in significant errors in evaluating heat transfer rates and temperature distributions.     

Technology selection in the presence of fuzzy data and dual-role factors

Technology selection is an important part of management technology. One of the models which is used for technology selection is data envelopment analysis (DEA). Conventional DEA models require input and output data to be precisely known, and also they assume that decision making units do not have dual-role factor, but this is not always the case in real applications, such as technology selection. In this regard, a model for technology selection in the presence of fuzzy data and dual-role factors is developed in the present study. A numerical example demonstrates the application of the proposed method.     

Preparation and investigation of properties of deproteinized natural rubber nanocomposites incorporating functionalized nano-alumina by in situ emulsion polymerization

The present study reports the preparation, characterization, and investigation of properties of DNR/f-Al₂O₃ nanocomposites through an in situ emulsion polymerization technique. The method consists of the dispersion of pretreated nano-alumina (f-Al₂O₃ NPs) onto deproteinized natural rubber (DNR) latex, followed by the polymerization reaction with the K₂S₂O₈/K₂S₂O₅ redox initiation system, after deproteinization of natural rubber using urea in the presence of a surfactant. To improve the compatibility and reactivity of the nanofillers with DNR latex, the nano-alumina surface was treated with 3-methacryloxypropyltrimethoxysilane (MPS) to produce f-Al₂O₃ NPs. The thermo-gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy approved that the MPS was bound onto the surface of Al₂O₃ NP. The resulting nanocomposites were characterized using standard techniques for physical properties and structural morphology, including X-ray diffraction (XRD) analysis, FTIR spectroscopy, scanning electron microscopy (SEM), and TGA. The SEM images showed a homogeneous distribution of f-Al₂O₃ NPs throughout DNR matrix. Due to such monodisperse particles, the DNR/f-Al₂O₃ nanocomposite films revealed significant enhancement in thermal stability with increasing nano-alumina loading as compared with the neat DNR.     

Systemic reliability of bridge networks with mobile sensing-based model updating for postevent transportation decisions

This paper proposes the upscaling of conventional individual bridge health monitoring problems into urban regions and transportation networks via mobile and smart sensing techniques together with an innovative reconnaissance procedure. The paper associates structural failure probabilities with systemic features and proposes decision criteria to optimize postdisaster actions. Twenty bridges constituting transportation network infrastructure compose the testbed region and utilize smartphone accelerometers for dynamics characterization in a vibration-based framework. In this framework, reconnaissance output serves for model development, and mobile sensor data enable finite element model updating. Structural reliability analyses merged in a chain setting generate the systemic behavior of cascaded bridge performance. Combining systemic reliability with transportation and health services demand, one can optimize the response strategies of the bridge population and strategize disaster-related decisions in a postevent assessment setting. Based on a testbed region with remote access to nearby vicinities, 18 earthquake scenarios are conducted to visualize the optimal evacuation strategies on the network, taking systemic bridge performance into consideration. Cost-free mobile sensing support adds one more fundamental information source for reducing the uncertainty of the models and, therefore, improves associated mitigation actions.