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Property Differences (property + difference)

Distribution by Scientific Domains
Chemistry40%

Selected Abstracts

Effects of Physical Property Differences on Blending

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2005
P. N. Jones
Abstract Within this study, the effects of viscosity differences between added and bulk liquids on mixing times were investigated. This was carried out in stirred tanks of diameter T,=,0.31, 0.61, 1.83,m to study the effect of scale. Different impeller types (hydrofoils, disc turbines, and pitched blade turbines) and sizes (D,=,T/2 and T/3) were employed. Operating conditions for which mixing time correlations for similar property liquids could be used were identified at scales relevant to industrial applications. Recommendations are made for improving blending under operating conditions where these correlations are not applicable as the mixing times are too long. [source]

Material properties are related to stress fracture callus and porosity of cortical bone tissue at affected and unaffected sites

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2009
Rachel C. Entwistle
Abstract Stress fractures are overuse injuries of bone that affect elite athletes and military recruits. One response of cortical bone to stress fracture is to lay down periosteal callus. The objectives of this study were to determine if material properties are different among bones with different stages of stress fracture callus, at both a callus site and at a distal site. Cortical specimens were mechanically tested to determine their stress,strain response. Material property differences were examined using nonparametric and regression analyses. At the callus site, material properties were low during the earliest stages of callus, higher with increasing callus maturity, but dropped at the late stage of callus. At the distal site, the material properties were low during early stages of callus and approached, or returned to, those of bones without callus during the late stages of callus. The effects of stress fracture and bone callus are not limited to the focal site of stress fracture. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1272,1279, 2009 [source]

An Information-Theoretic Approach to Descriptor Selection for Database Profiling and QSAR Modeling

MOLECULAR INFORMATICS, Issue 5 2003
Jeffrey
Abstract In order to rationalize the selection of molecular descriptors for QSAR and other applications, we have adapted the Shannon entropy concept that was originally developed in digital communication theory. The approach has been extended to facilitate the large-scale analysis of molecular descriptors and their information content in diverse compound databases. This has enabled us to identify descriptors with consistently high information content. Furthermore, it has been possible to select descriptors that are sensitive to systematic property differences in diverse compound collections (synthetic compounds, natural products, drug-like molecules, or drugs) and, in addition, to quantify such database-specific differences. Selection of descriptors based on information content has been proven useful for binary QSAR analysis. In this review, we describe the principles of entropy-based descriptor selection and discuss different applications. [source]

Finite element analysis of vent/hand hole designs for corrugated fibreboard boxes

PACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2007
Jongkoo Han
Abstract Corrugated fibreboard is an economical and efficient material for fabricating shipping containers that are widely used for the distribution, transportation and storage of goods. Corrugated fibreboard is usually considered to be an orthotropic material because the principal fibre directions, machine direction (MD) and cross-machine direction (CD), are identical to the fibres in paperboard, which has apparent directional property differences. The purpose of this study is to investigate the principal design parameters of ventilation holes and hand holes in the faces of the shipping container, (corrugated fibreboard boxes), using finite element analysis (FEA). Various designs of ventilation holes were studied with respect to stress distribution and stress level. It was found that the appropriate pattern and location of the ventilation holes were vertical oblong-shaped and symmetrically positioned within a certain extent of distance to the right and left from the centre of the front and rear faces of the boxes. On the other hand, the appropriate location and pattern of the hand holes were a short distance from the centre to the top of the boxes on both side faces. The appropriate pattern was a modified shape, such as the radius of curvature of both sides in horizontal oblong. The pattern and location of both the ventilation holes and the hand holes determined by the FEA simulation generally agreed well with laboratory experimental results. The decrease in compression strength of the box could be minimized with identical area of the ventilation holes if the length of the major axis of the ventilation hole is less than 1/4 of the depth of the box and the ratio of the minor axis to the major axis is 1/3.5,1/2.5, provided that even-numbered holes are located symmetrically. Copyright © 2006 John Wiley & son, Ltd. [source]

Monitoring epoxy and unsaturated polyester reactions under pressure,Reaction rates and mechanical properties

POLYMER ENGINEERING & SCIENCE, Issue 11 2009
Javier C. Cruz
The effects of pressure on reaction rates and final mechanical properties were studied for an unsaturated polyester (UP) and epoxy resin. A pressure chamber where reactions can be monitored by use of Raman spectroscopy has been built for these purposes. The chamber allows for pressures up to 13.8 MPa at 200°C. An advanced temperature control system has been adapted to the vessel to precisely control and monitor sample temperature variations and overshoots. It is described how for an accelerated UP reaction increasing pressure will result in a competing effect on the reaction rate where the rate will initially lower, but with increased pressures it may accelerate due to acceleration of the reaction rate constants. The final mechanical properties exhibit a similar behavior slightly increasing with pressure but lowering as pressure is raised further. For epoxy, it was shown that the reaction kinetics were accelerated by pressure although no mechanical property differences could be noted for the pressure ranges tested. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers. [source]