Tool selection for optimal part production: a Lagrangian relaxation approach

This paper extends previous work on implementation problems associated with a flexible system that produces flat sheet-metal parts with interior holes. The paper makes four main contributions. First, we formulate the problem of selecting tooling and design standards to minimize the cost of producing parts as an optimization model. Second, we develop a projected subgradient algorithm for the Lagrangian relaxation of the problem by using the model's special structure to develop relationships between the Lagrangian multipliers. Third, we demonstrate that the algorithm produces close to optimal solutions (duality gap less than 2%) very quickly on a number of problems derived using a substantial data set obtained from a Chicago area firm. Fourth, an important variant of the traditional repair kit problem is shown to be a special case of the tool selection problem.     

Automated actuation of nasal spray products: effect of hand-related variability on the in vitro performance of Flonase nasal spray

Objective: To determine if patient-related variability for adults and children recorded during hand spraying of Flonase with an instrumented nasal spray results in significant differences in spray weight, droplet size or spray pattern.

Methods: Settings derived from adult and pediatric participants hand-spraying nasal sprays were implemented into force and velocity-controlled automated actuators. Spray weight, droplet size distribution and spray pattern tests were performed using iterations of actuation force (AF) and force rise, hold and fall times. Travel, actuation velocity and release velocity settings were also investigated.

Results: The variability measured in adult-derived actuator settings did not result in any differences in spray weight, but pediatric participants spraying with low AF and/or compression velocity (CV) were predicted to receive a partial dose or no dose at all under some circumstances. Droplet size characteristics were sensitive to the hand-based variability, with actuation force, force rise time and CV hand-related settings all resulting in significant differences in the droplet size.

Conclusions: This study demonstrated how variability in hand spraying by adults and pediatric patients could result in differences in nasal spray characteristics, thus demonstrating the importance of monitoring how the prospective patient groups are likely to use a nasal spray.     

Secondary hardened bainite

Abstract

The effect of Mo additions on the development of bainitic ferrite in hot rolled low carbon (0·05 wt-%C) Nb containing steel strips has been studied. The steel strips were fabricated by a combined process of controlled rolling and accelerated cooling. Microstructural characterisation and mechanical testing for the corresponding strips were investigated. The results indicated that a small amount of Mo addition (0·1–0·3 wt-%) causes the production of a high volume fraction of bainite, which undergoes significant secondary hardening after tempering treatment at 600°C for 1 h. It is noticeable that the secondary hardening effect provides an additional way to significantly increase the strength of low carbon Nb–Mo containing bainitic steels.     

Strain-induced D band observed in carbon nanotubes

We report the emergence of the D band Raman mode in single-walled carbon nanotubes under large axial strain. The D to G mode Raman intensity ratio (I _D/I _G) is observed to increase with strain quadratically by more than a factor of 100-fold. Up to 5% strain, all changes in the Raman spectra are reversible. The emergence of the D band, instead, arises from the reversible and elastic symmetry-lowering of the sp² bonds structure. Beyond 5%, we observe irreversible changes in the Raman spectra due to slippage of the nanotube from the underlying substrate, however, the D band intensity resumes its original pre-strain intensity, indicating that no permanent defects are formed.      

Mixed convection of micropolar fluids along a vertical wavy surface

Summary This paper presents numerical results for the steady-state mixed convection in micropolar fluids along a vertical wavy surface. The problem has been formulated by a simple trnasposition theorem, and the spline alternating-direction implicit method has been applied to solve the governing momentum, angular momentum and energy equations. The influence of the micropolar parameters (R and ), the amplitude-wave length ratio and the Gr/Re² number on the skin-friction coefficient and Nusselt number have been studied. Results demonstrate that the skin friction coefficient and local Nusselt number consist of a mixture of two harmonics in micropolar fluids and in Newtonian fluids. As the vortex viscosity parameter (R) increases, the heat transfer rate decreases but the skin friction increases. In addition, when the spin gradient viscosity parameter () increases, the heat transfer rate and the skin friction decreases. However, the heat transfer rate of a micropolar fluid is smaller than a Newtonian fluid, but the skin friction of a micropolar fluid is larger than a Newtonian fluid under all circumstances.     

Laser, buffer layer and CoCrPtOx-assisted low temperature fabrication process of a small-sized-CNT pattern by MPCVD

For improving compatibility with IC processes, this work presents a low temperature process (< 400 °C) to fabricate a small-sized-carbon nanotube (CNT) (< 6 graphene layers) pattern by buffer layer (AlN) and CoCrPtO_x catalyst precursor-assisted microwave plasma chemical vapor deposition (MPCVD). Without high temperature heating on the whole specimen, the low temperature process mainly results from selective local activation laser heating (≧ 600 °C) to form the catalyst nanostructures, which are beneficial to low temperature H-plasma treatment to form catalyst nanoparticles for CNT growth. The functions of the buffer layer and the catalyst precursor are to help the heat dissipation and the small-sized CNT formation.     

A generalized finite element formulation for arbitrary basis functions: From isogeometric analysis to XFEM

Many of the formulations of current research interest, including iosogeometric methods and the extended finite element method, use nontraditional basis functions. Some, such as subdivision surfaces, may not have convenient analytical representations. The concept of an element, if appropriate at all, no longer coincides with the traditional definition. Developing a new software for each new class of basis functions is a large research burden, especially, if the problems involve large deformations, non‐linear materials, and contact. The objective of this paper is to present a method that separates as much as possible the generation and evaluation of the basis functions from the analysis, resulting in a formulation that can be implemented within the traditional structure of a finite element program but that permits the use of arbitrary sets of basis functions that are defined only through the input file. Elements ranging from a traditional linear four‐node tetrahedron through a higher‐order element combining XFEM and isogeometric analysis may be specified entirely through an input file without any additional programming. Examples of this framework to applications with Lagrange elements, isogeometric elements, and XFEM basis functions for fracture are presented. Copyright © 2010 John Wiley & Sons, Ltd.     

Experimental study of the gas flow behavior in the inlet of a granular bed filter

The Moving Granular Bed Filter (MGBF) is an important apparatus being developed for filtration of the hot gas. Our research group demonstrated a good solution to diminish stagnant zones in MGBF during the filtration process. However, there still remain some systematic problems that have to be worked out prior to commercializing a whole facility.The design of the gas inlet component of the granular bed filter is important for achieving a uniform gas distribution and higher usage rate of the filter media. Non-uniformity may lead to a lower usage rate. The new gas inlet component design uses baffle devices in order to achieve a more uniform gas velocity distribution. Fixed bed and moving bed conditions were studied. The uniformity of the gas velocity distribution can be characterized by the standard deviation definitions and the differences in the mean velocities between the two filtration surfaces. The baffle lengths and angles affected the uniformity of gas velocity in inlet and filtration surfaces. The optimal experimental parameters were found by using different baffle lengths, angles and mass flow rate of filter media. The uniform gas velocity distributions were obtained by a series experiments. Furthermore, the results give important information about IGCC system that will be helpful for designing better models of moving granular bed filters in the future.