BUCKLING BEHAVIOR OF LONG ANISOTROPIC PLATES SUBJECTED TO RESTRAINED THERMAL EXPANSION AND MECHANICAL LOADS

An approach for synthesizing buckling results and behavior for thin balanced and unbalanced symmetric laminates that are subjected to nondestabilizing mechanical preloads, uniform heating or cooling, and elastically or totally restrained axial thermal expansion or contraction is presented. This approach uses a nondimensional analysis for infinitely long, flexurally anisotropic plates that are subjected to combined loads and is based on useful nondimensional parameters. In addition, a stiffness-weighted laminate coefficient of thermal expansion is derived and used to determine critical temperatures in terms of physically intuitive mechanical buckling coefficients, and the effects of membrane orthotropy and membrane anisotropy are included. Many results are presented for some common laminates that are intended to facilitate a structural designer's transition to the use of the generic buckling design curves that are presented in the article. Several generic buckling design curves are presented that provide physical insight into the buckling response in addition to providing useful design data. Examples are presented that demonstrate the use of the generic design curves. The analysis approach and generic results identify the effects and characteristics of laminate thermal expansion, membrane orthotropy and anisotropy, and flexural orthotropy and anisotropy in a very general and unifying manner.     

Non-destructive Visible/NIR Spectroscopy for Differentiation of Fresh and Frozen-thawed Fish

Nondestructive visible/near‐infrared (NIR) spectroscopy was evaluated to investigate whether fish has been frozen‐thawed. Fresh or frozen‐thawed red sea bream Pagrus major (n= 108) were scanned using a NIRSystems 6500 spectrophotometer equipped with a surface interactance fiber‐optic accessory then discriminated by soft independent modeling of class analogy (SIMCA) and linear discriminant analysis (LDA) based on principal component analysis (PCA) scores. The major effect of freeze‐thawing treatment involves a gross change in total reflectance after freezing and thawing; this arises from changes in light scatter presumably arising from alterations in the physical structure of at least the surface layer of fish. Untreated original absorbance spectra achieved much better (100%) classification accuracy for the prediction samples while the same figures for multiplicative scatter correction (MSC) treated spectra are considerably worse, indicating that scattering is the major information that makes classification work. No incorrect type of classification at all and also there are no samples classified to both groups either. This faster technique has the potential to differentiate fresh and frozen‐thawed fish and could be applied for online or at‐line processing control.     

Evolution of Extractive Composition During Thermal Treatment of Jack Pine

Abstract

The thermal treatment of wood has many benefits such as better dimensional stability and attractive dark color and does not use toxic chemicals. The resistance against biological decay can be improved when wood is not in contact with ground. On the other hand, after thermal transformation, wood becomes more fragile. The changes of the wood properties are related to the modification of the wood composition. During the thermal treatment, the evaporation of the moisture content is not the only event. Volatile extractives are evacuated from the wood, while new products and by-products of different chemical reactions appear. The comparison of the extracts obtained from untreated and treated wood can help to identify thermo-chemical reactions, taking place during the heat treatment. This article presents the analysis by Gas Chromatography–Mass Spectroscopy (GC-MS), High Performance Liquid Chromatography (HPLC), and Thin Layer Chromatography (TLC) of polar and non-polar extracts of untreated and heat-treated North American Jack pine (Pinus banksiana). The study of the impact of maximum heat treatment temperature on the composition of the Jack pine extracts showed that the major part of extractives leaves the wood under 200°C whereas most of the new products appear only above 200°C. While the extractives of the untreated Jack pine are dominated by non-polar components, the thermo-transformation seems to generate mainly polar compounds. However, presence of water vapor increases the portion of polar extractives in wood. Interestingly, an important decrease of concentration of phenolic compounds (such as pinosylvin, pinosylvin monomethyl ether, and pinobanksin) in Jack pine wood was observed between 160–200°C. On the other hand, 4-hydroxy-methylfurfural and vanillin have been identified as compounds generated by the heat treatment above 200°C. The identification of other by-products will be presented in a later paper.     

A retrospective analysis of 1570 appendiceal carcinoids

The design, synthesis and evaluation of transition metal containing combinatorial libraries has received much attention in the past few years. As a result, a variety of synthetic techniques have been developed, and rapid assays for metal ion binding have yielded new ligand classes displaying high affinity and selectivity. Research in catalysis has centered around lead optimization using much smaller parallel libraries because of the lack of a truly efficient reaction screening method. Materials science applications have also focused on spatially addressed libraries and have employed a variety of techniques to identify compounds with desired physical properties. Nonetheless, high-throughput characterization and reaction product detection methods must still be developed in order to realize the full potential of combinatorial chemistry for the discovery of novel metal-containing compounds.     

Kinetics of the heterogeneous catalytic decomposition of methane

Experiments have clearly demonstrated that dissociation of CH₄ on (supported) metal catalyst (e.g. Pt, Ru, Rh, Ir, Pd) occurs to give hydrogen, a small amount of ethane and surface carbonaceous species. For this catalytic decomposition of methane and its conversion into higher hydrocarbons (especially to ethane and surface carbon) model has been developed to investigate the kinetics. Rate constants of the elementary steps have been estimated. The problem with experimental data (especially for the surface species CH_m-s) is also treated for the sake of future improvement in the kinetics studies. A comparison with catalytic hydrogenolysis of ethane kinetics is also outlined.