Carbon nanotubes growth on sub-surface catalyst layer of Cu–Ni nanoparticles thin film

Cu–Ni nanoparticles (NPs) thin films were prepared by Direct Current (DC) magnetron sputtering with Cu and Ni targets. The products were used as catalysts for Thermal CVD (TCVD) growing of carbon nanotubes (CNTs) from acetylene gas at 825°C. In order to characterize the nano catalysts, X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM) and to study the synthesized CNTs Scanning Electron Microscopy (SEM) and Raman Spectroscopy were applied. A remarkable CNT grown on the sub-surface of catalyst layer compared to its top is deduced from SEM images. Despite the poor catalytic activity of the top-surface, these considerations led us to conclude more catalytic activity of the sub-surface.     

Study of a novel and simple method of generating binary mask for microprism fabrication

A new and simple method for generating binary masks for fabrication of gray scale micro-optical elements is proposed and examined. In this technique the main idea is superimposing two or more gratings with slightly different pitches that depend on the considered gray tone level. This causes generation of a chirped binary mask in which the openings widths are changed from a maximum to minimum through considered steps. Furthermore, to show its capability, it was applied to fabricate some microprisms. In addition, influence of proximity gap, and designation parameters on the surface quality were studied. It is shown that surface deterioration is effectively modified by optimizing the designation parameters. In comparison to other techniques, one of the advantages of this method is to have an assortment of pulse modulated masks that are able to create a variety of gray tone levels. Other advantages are ease in designation and implementation, and the fact that surface roughness could be smoothed effectively by aptly optimized parameters. Theoretical approach, simulation works, and experimental results are presented.     

Effect of Particles Content on Microstructure,Mechanical Properties,and Electrochemical Behavior of Aluminum-Based Hybrid Composite Processed by Accumulative Roll Bonding Process

Metallurgical and Materials Transactions A - Effect of B4C/SiC particles content on the microstructure, deformation, and electrochemical behavior of aluminum-based hybrid composite processed by...     

Coordinated scheduling of a single machine with sequence-dependent setup times and time-window constraints

In this paper we consider the selection and scheduling of several jobs on a single machine with sequence-dependent setup times and strictly enforced time-window constraints on the start times of each job. We demonstrate how to develop network-based algorithms to sustain the desired work in process (WIP) profile in a manufacturing environment. Short-term production targets are used to coordinate decentralised local schedulers and to make the objectives of specific areas in line with the chain objectives. A wide range of test problems with two different network structures are simulated. The effectiveness, efficiency, and robustness of the proposed algorithms are analysed and compared with an exhaustive search approach.     

Shake Table Studies of a Concrete Bridge Pier Utilizing Pipe-Pin Two-Way Hinges

Pipe-pin two-way hinge details were recently developed by California Department of Transportation (Caltrans) to eliminate moments while transferring shear and axial loads from integral bridge bent caps to reinforced concrete bridge columns. The hinges consist of a steel pipe that is anchored in the column with an extended segment into the cap beam. There is no specific design guideline for these hinges, and the current design method is primeval and only controls shear failure of the steel pipe. In this study, a rational method is proposed on the basis of the possible limit states to obtain the lateral capacity of these hinges. To validate the proposed method, a large-scale two-column bridge pier model utilizing pipe-pin hinges was tested on a shake table. The model was subjected to increasing levels of one of the Sylmar-Northridge 1994 earthquake records. A comprehensive analytical modeling of the pier was also performed using OpenSees; for this purpose, a macro model was developed for pipe-pin hinges in this study. The experimental results confirmed that the hinges designed on the basis of the proposed guideline remain elastic with no damage. The good correlation between the analytical and experimental data indicated that the macro model and other modeling assumptions were appropriate.     

High velocity impact of metal sphere on thin metallic plate using smooth particle hydrodynamics (SPH) method

The modeling of high velocity impact is an important topic in impact engineering. Due to various constraints, experimental data are extremely limited. Therefore, detailed numerical simulation can be considered as a desirable alternative. However, the physical processes involved in the impact are very sophisticated; hence a practical and complete reproduction of the phenomena involves complicated numerical models. In this paper, we present a smoothed particle hydrodynamics (SPH) method to model two-dimensional impact of metal sphere on thin metallic plate. The simulations are applied to different materials (Aluminum, Lead and Steel); however the target and projectile are formed of similar metals. A wide range of velocities (300, 1000, 2000, and 3100 m/s) are considered in this study. The goal is to study the most sensitive input parameters (impact velocity and plate thickness) on the longitudinal extension of the projectile, penetration depth and damage crater.