A constrained‐optimization methodology for the detection phase in contact mechanics simulations

The detection phase in computational contact mechanics can be subdivided into a global search and a local detection. When potential contact is detected by the former, a rigorous local detection determines which surface elements come or may come in contact in the current increment. We first introduce a rigorous definition of the closest point for non‐differentiable lower‐dimensional manifolds. We then simplify the detection by formulating an optimization problem subject to inequality constraints. The formulation is then solved using different techniques from the field of mathematical optimization, for both linear and quadratic finite element meshes. The resulting general and robust detection scheme is tested on a set of problems and compared with other techniques commonly used in computational geometry. Copyright © 2013 John Wiley & Sons, Ltd.     

Lateral Magnetic Near‐Field Imaging of Plasmonic Nanoantennas With Increasing Complexity

The design of many promising, newly emerging classes of photonic metamaterials and subwavelength confinement structures requires detailed knowledge and understanding of the electromagnetic near‐field interactions between their building blocks. While the electric field distributions and, respectively, the electric interactions of different nanostructures can be routinely measured, for example, by scattering near‐field microscopy, only recently experimental methods for imaging the magnetic field distributions became available. In this paper, we provide direct experimental maps of the lateral magnetic near‐field distributions of variously shaped plasmonic nanoantennas by using hollow‐pyramid aperture scanning near‐field optical microscopy (SNOM). We study both simple plasmonic nanoresonators, such as bars, disks, rings and more complex antennas. For the studied structures, the magnetic near‐field distributions of the complex resonators have been found to be a superposition of the magnetic near‐fields of the individual constituting elements. These experimental results, explained and validated by numerical simulations, open new possibilities for engineering and characterization of complex plasmonic antennas with increased functionality.     

Design,refinement, implementation and prototype testing of a reconfigurable lathe-mill

This article documents the design, refinement, and implementation of a reconfigurable machine tool that provides a flexible platform for turning and milling. Advances in the design and capabilities of machine tools drive modern industry. In fact, the expanding capabilities of the machines permit novel and economic changes in the manufacturing and design of products. After the flexible manufacturing (FMS) boom, a more recent, but no less significant, area of machine development involves the reconfiguration of milling machines. This reconfigurability can also be applied to lathe-mills. The present work demonstrates satisfactorily the reconfiguration characteristics of modularity, integrability, and convertibility. We prototype and test a completely functional bench top reconfigurable lathe mill machine implemented using a $10,000 USD budget and developed following a synthesized machine tool product development methodology that begins with concept design and cutting forces to end in prototyping. In addition to reasonable results in runout, positioning, and surface roughness, the machine demonstrates the capability to produce parts with a Cpk of 1.009, thereby demonstrating the ability to fabricate this type of machine in Mexico for the local jewelry industry.     

Phase and Rheological Behavior of Cetyldimethylbenzylammonium Salicylate (CDBAS) and Water

The temperature–composition phase diagram in the diluted region of the cationic surfactant cetyldimethylbenzylammonium salicylate/water system was studied with a battery of techniques. The Krafft temperature (T _k = 33 ± 1 °C) was measured by differential scanning calorimetry, polarizing microscopy, conductimetry, viscosimetry, and rheometry. The critical vesicle concentration (cvc, ~0.002 wt%) and a vesicle–micellar transition (cvm, ~0.005 wt%) was detected at a temperature of 35 °C. Below T _k and concentrations ≤2 wt%, a transparent solution is formed (I). Above 2–8.5 wt%, a lamellar (L₁) phase forms. At higher concentrations and up to 12 wt%, a second lamellar phase (L₂) is detected. From 12.4 to 15.5 wt%, an emulsion phase (E) is formed. Rheological dynamic measurements for the I phase indicate that the system exhibits a predominantly viscous behavior (G′ < G″) for concentrations lower than the overlap or entanglement concentration (C _e, ~0.75 wt%). At higher concentrations, wormlike micelles form and the elastic behavior predominates (G′ > G″). The elastic (G′) modulus collapses in a concentration–time master curve in the whole reduced frequencies range ωτ _c examined, whereas the viscous modulus (G″) collapses only at reduced frequencies lower than 0.1. Reduced stress plotted as a function of the reduced shear rate yields a good superposition of the curves at the different concentrations up to the onset of the non-linear behavior.     

Human critical success factors for kaizen and its impacts in industrial performance

This article presents the results of a survey with 13 main activities related to human factors that are executed during kaizen implementation process and were integrated in four independent latent variables (management commitment, education, communication and motivation) that are associated to 14 benefits obtained after its implementation that were grouped in three dependent latent variables (process, workers and customers). The survey was applied to persons with responsibilities in continuous improvement programs and projects in companies located in Mexico. Independent and dependent variables were integrated in a structural equation model that was evaluated using partial least squares algorithms WarpPLS® for finding causal relations among them. Results indicate that management commitment and education are the main factors that guarantee the success for kaizen implementation programs, but that is moderated by a good communication for having good operational process performance for better workers and customer satisfaction.     

Polyacrylamide-gelatin polymeric networks: effect of pH and gelatin concentration on the swelling kinetics and mechanical properties

This work presents the synthesis of polyacrylamide-gelatin (PAM-G) semi-interpenetrating hydrogels, as well as the study of the swelling capacity of this material at different pH’s, and we report its Young modulus. The hydrogels were crosslinked with N,N′-methylenebisacrylamide and synthesized at different acrylamide/gelatin weight relationship. It was observed that the swelling capacity of the hydrogels increases when the gelatin concentration is increased; while the Young modulus (at the swelling equilibrium) decreases lightly. Therefore, the gelatin has a small effect in the Young modulus, unlike its influence in the swelling ability. The swelling experiments reveal that the PAM-G hydrogels increase its swelling capacity in alkaline mediums because the presence of the hydrophobic functional groups (mainly COO⁻) in the gelatin structure.     

Numerical model of a planar jet wiping system for continuous strip lines

Journal of Mechanical Science and Technology - The present study focuses on the numerical modelling of gas-jet wiping process. Many processes involving liquids are necessary during steel...     

A Public Library for Matteson,Illinois

This project for the Matteson Public Library was developed through the utilization of three architectural language elements that defined the varied spaces required by the competition program: a large, light roof floating over the building, a system of brass columns defining a rhythmically punctuated space, and a non-structural wall creating the outer skin of the building. The poetically inflected relationship between these three elements articulates and defines the spaces of the library, generating high spatial tension at the corner of the site. As expected, the Community Meeting Room occupies this prominent urban position.