Time dependent response of polycarbonate and microcellular polycarbonate

Microcellular polycarbonate is a novel cellular material with cells on the order of 10 μm in diameter and a cell density on the order of 10⁹ cells per cm³. In this study the room temperature creep response of microcellular polycarbonate is experimentally determined and compared with the creep behavior of polycarbonate. The viscoelastic response of polycarbonate and microcellular polycarbonate is characterized using Schapery's theory of nonlinear viscoelasticity. Polycarbonate exhibited a nonlinear creep response at stress levels above 24.13 MPa, while the nonlinear behavior in microcellular polycarbonate was initiated at lower stress levels. Creep strains of microcellular polycarbonate contain a significantly higher viscoplastic component compared with the unfoamed material.     

Automatic Control Chart for Micropipet

Abstract

The control chart is defined and exemplified, and the importance of controlling the volume delivered by a micropipet is discussed. A LabVIEW VI is described, which automates control chart generation and routine use based on the gravimetric calibration of a micropipette, using a Sartorius balance. A user selects between creating a new control chart and adding a data point to the control chart. File storage and retrieval, and construction of the control chart are automated. A sample control chart for a micropipet is presented.     

The spinning circular disc with a radial edge crack; an exact solution

A circular disc of radius a, made of homogeneous, isotropic, linearly elastic material, contains a radial edge crack of length b. The disc is rotating with constant angular velocity about an axis through its centre and perpendicular to its plane. The problem of determining the resulting stress and displacement fields throughout the disc is solved (within the two-dimensional linear theory) exactly and in closed form. In particular the stress intensity factor and the crack opening displacement are evaluated for both the plane stress and plane strain cases with any crack length b (0<b<2a) and any values of the elastic constants.

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Résumé Un disque circulaire de rayon a, en un matériau homogène, isotrope et élastique linéaire, comporte une fissure radiale de bord de longueur b. Le disque tourne à vitesse angulaire constante autour d'un axe normal passant par son centre dans les limites de théorie linéaire à deux dimensions. On résout le problème de la détermination des champs de contraintes et déplacements dans le disque, sous une forme exacte ou sous une forme fermée. En particulier, le facteur d'intensité de contraintes et la COD sont évalués en condition d'état plan de tension et d'état plan de déformation pour toute longueur de fissure comprise entre 0 et 2a et pour toute valeur de constantes élastiques.

     

Chemical engineering research synergies across scientific categories

Chemical engineers operate industrial plants, design reactors and equipment, manage capital projects, estimate costs, project earnings, and drive efficiency through innovation while maintaining rigorous safety standards. The undergraduate curriculum includes mathematics, physics, chemistry, mechanics, biology, and management, much of which is common with other engineering departments. 1 However, chemical engineering research is more related to chemistry. Here, we show that chemical engineers cite journals in WoS’ chemical engineering category most, followed by physical chemistry, energy & fuels, multi‐disciplinary chemistry, environmental science, and multi‐disciplinary materials science. According to a bibliometric analysis, the major research poles include materials, biotechnology, catalysis, environment, and thermodynamics. The 5 top cited journals in 2012 were Ind. Eng. Chem. Res., J. Membrane Sci., Chem. Eng. Sci., J. Hazard. Mater., and J. Catal., which are not the journals with the highest impact factors of the category. Can. J. Chem. Eng. was ranked third among the 32 classical chemical engineering journals after AIChE J. and Chem. Eng. Sci. and with respect to the ratio of the number of citations accrued until August 2017 to the number of articles they published in 2012. Chinese researchers have authored more articles than any other nation and they co‐author research most with the USA and other Pacific Rim nations. Research collaborations between nations follow linguistic, geographical, and historical traditions.

     

Tough thiourethane thermoplastics for fused filament fabrication

Fused filament fabrication (FFF) is the most common form of additive manufacturing. Most FFF materials are variants of commercially available engineering plastics. Their performance when printed can widely vary, thus there is an increasing volume of research on alternative materials with thermal and mechanical performance optimized for FFF. In this work, thiol–isocyanate polymerization is used for the development of a one‐pot synthesis for polythiourethane thermoplastics for tough three‐dimensional (3D) printing applications. The thiol–isocyanate reaction mechanism allows for rapid polymer synthesis with minimal byproduct formation and few limitations on reaction conditions. The resulting elastomer has high toughness and a low melting point, making it favorable for use as a 3D printing filament. The elastomer outperforms commercial filaments in tension when printed. Considering the rapid advancement of additive manufacturing and the limitations of many engineering polymers with the 3D printing process, these results are encouraging for the development of bespoke 3D printing thermoplastics. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45574.     

Analysis of the dynamics of a slider-crank mechanism with hydrodynamic lubrication in the connecting rod-slider joint clearance

The conventional slider-connecting rod-crank mechanism is widely applied in mechanical systems. The use of hydrodynamic bearings in the mechanism joints is of particular interest in reducing friction, mainly in special conditions of lubrication such as the connecting rod-slider joint. This bearing belongs to a class of bearings with alternating rotational motion. This paper proposes a mathematical model for this particular problem, considering the dynamics of the slider-connecting rod-crank system interacting with the lubrication phenomenon in bearings with alternating motion. Two models were used to analyze the dynamics of the system. The first model (by Eksergian Equation of Motion) represents the system when the connecting rod end is in contact with the bearing surface, assuming, in this condition, the same behavior as that of rigid bearings (without clearance). The second model (by Lagrange Method) represents the system when the connecting rod end is in the hydrodynamic lubrication mode in the slider bore clearance. In this condition, the slider moves in relation to the connecting rod, presenting a problem of multi-degrees-of-freedom. The mathematic model of hydrodynamic lubrication was introduced to obtain more realistic results of the system's dynamic behavior.     

Statistical estimation of delay fault detectabilities and fault grading

In this paper we present a technique to statistically estimate transition delay and path delay fault coverage. The basic method is an extension of STAFAN to include delay faults. By partitioning a combinational circuit into non-overlapping fanout free logic cones, we accurately calculate the transition sensitization controllabilities of 0 1 and 1 0 transitions of the lines within a fanout free logic cone to the output of the fanout free logic cone for each fanout free logic cone. A strategy to calculate the transition observabilities of fanout stems is proposed. The detectability of a path delay fault is evaluated as the product of the observabilities of the input line to its head gate within each fanout free logic cone on the path multiplied by the transition controllability of the path. When compared with the fault simulations, the estimations of transition delay fault coverage are within 2.3%. Also, the technique gives reasonably good path delay fault coverage estimation for large fault set of the ISCAS85 benchmark circuits.     

Phase-only joint-transform correlator: analysis and experimental results

An analysis of the popular joint-transform optical correlator is presented for architectures employing spatial light modulators that operate only on the phase of the coherent light. Experimental results are also presented, for simple scenes that produce analytic solutions, which support the analysis.     

Optical wavelet transform by the phase-only joint-transform correlator

A method is presented that performs the optical wavelet transform with liquid-crystal televisions as spatial light modulators operating only on the phase of the incident coherent light. The architecture is the joint-transform correlator, and the wavelets and the image to be transformed are encoded in the input plane of the system. The mathematical formalism describing the adaptation of the joint-transform correlator to the wavelet transform is given and extended to the operation of the phase-only joint-transform correlator. A new wavelet is described for two-dimensional image processing, and experimental results are presented for optical wavelet transforms done in real time by use of this wavelet in the phase-only joint-transform-correlator architecture. The analysis is extended to multiwavelet (multispectral) analysis by the joint-transform correlator, and simulation results are given. Finally experimental results with the phase-only joint-transform correlator applied to multi-wavelet analysis are presented.