An introduction to heat transfer

Common to liquids, solids and substances in between the former two is that if a stress is applied to them, they will strain. Stress may be visualized by placing a small amount of fluid between two parallel plates. When one plate slides over the other, forces act on the fluid dependent upon the rate of the plate movement. This causes a shear stress on the liquid. Recall laminar flow of fluids through a tubular vessel. Strain is the response to the stress. If solids are elastic, they deform and return to their original shape. Since fluids are not elastic and, hence, viscous, their deformation is irreversible.

Introduction to rheology

Commercially important edible nut seeds were analyzed for chemical composition and moisture sorption. Moisture (1.47-9.51%), protein (7.50-21.56%), lipid (42.88-66.71%), ash (1.16-3.28%), total soluble sugars (0.55-3.96%), tannins (0.01-0.88%), and phytate (0.15-0.35%) contents varied considerably. Regardless of the seed type, lipids were mainly composed of mono- and polyunsaturated fatty acids (>75% of the total lipids). Fatty acid composition analysis indicated that oleic acid (C18:1) was the main constituent of monounsaturated lipids in all seed samples. With the exception of macadamia, linoleic acid (C18:2) was the major polyunsaturated fatty acid. In the case of walnuts, in addition to linoleic acid (59.79%) linolenic acid (C18:3) also significantly contributed toward the total polyunsaturated lipids. Amino acid composition analyses indicated lysine (Brazil nut, cashew nut, hazelnut, pine nut, and walnut), sulfur amino acids methionine and cysteine (almond), tryptophan (macadamia, pecan), and threonine (peanut) to be the first limiting amino acid as compared to human (2-5 year old) amino acid requirements. The amino acid composition of the seeds was characterized by the dominance of hydrophobic (range = 37.16-44.54%) and acidic (27.95-33.17%) amino acids followed by basic (16.16-21.17%) and hydrophilic (8.48-11.74%) amino acids. Trypsin inhibitory activity, hemagglutinating activity, and proteolytic activity were not detected in the nut seed samples analyzed. Sorption isotherms (Aw range = 0.08-0.97) indicated a narrow range for monolayer water content (11-29 mg/g of dry matter). No visible mold growth was evident on any of the samples stored at Aw < 0.53 and 25 degrees C for 6 months.

Chemical composition of selected edible nut seeds

A paradigm shift has emerged over the last decade pointing to an exciting research area dealing with the harnessing of elastic structural instabilities for ‘smart’ purposes in a variety of venues. Among the different types of unstable responses, buckling is a phenomenon that has been known for centuries, and yet it is generally avoided through special design modifications. Increasing interest in the design of smart devices and mechanical systems has identified buckling and postbuckling response as a favorable behavior. The objective of this topical review is to showcase the recent advances in buckling-induced smart applications and to explain why buckling responses have certain advantages and are especially suitable for these particular applications. Interesting prototypes in terms of structural forms and material uses associated with these applications are summarized. Finally, this review identifies potential research avenues and emerging trends for using buckling and other elastic instabilities for future innovations.

https://iopscience.iop.org/article/10.1088/0964-1726/24/6/063001/pdf

Buckling-induced smart applications: recent advances and trends

Pasteurization process development for controlling Salmonella in in-shell almonds using radio frequency energy

The equilibrium moisture contents (EMC) of pistachio were determined using the standard static-gravimetric method at 15, 25, 35 and 40 °C for pistachio powder at 15, 35 °C for pistachio kernel and pistachio nut for water activity (a
 w) ranging from 0.11 to 0.9. At a given water activity, the results show that the moisture content decreases with increasing temperature. The experimental sorption curves are then described by the BET, GAB, Henderson, Oswin, Smith and Halsey models. A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. The Smith model was found to be suitable for describing the sorption curves. The isosteric heat of adsorption of water was determined as a function of moisture content from the equilibrium data at different temperatures using the Clasius–Clapeyron equation.

Moisture sorption isotherms and isosteric heat for pistachio

The results of an experimental study on the buckling behavior of thin-walled GFRP-stiffened cylindrical shells are presented. The buckling behavior of stiffened shells, with lozenge and triangular grids, and unstiffened shells were studied under quasi-static axial loading at room temperature. The effect of the number of helical ribs and grid shapes was thoroughly investigated. During the experimental study, local skin buckling mode was observed on all specimens. Based on the findings from this work, a minimum number of stiffeners should be present in a structure in order to play an effective role in its strength. Furthermore, it was concluded that under axial loading, increasing the number of helical ribs is more effective than adding hoop rings and changing the grid types.

The Effects of Helical Ribs’ Number and Grid Types on the Buckling of Thin-walled GFRP-stiffened Shells under Axial Loading

The equilibrium moisture contents of almond were determined using the gravimetric-static method at 15, 30, 55 and 75C for powder and 15, 55 and 75C for nut state of almond for water activity (aw) ranging from 0.11 to 0.87. At a given aw, the results show that the moisture content decreases with increasing temperature. The experimental sorption curves are then described by the BET, GAB, Henderson, Oswin, Smith and Halsey models. A nonlinear regression-analysis method was used to evaluate the constants of equations. The GAB model was found to be the most suitable for describing the sorption curves; the monolayer-content values for the sorption at different temperatures are calculated. Also, the isosteric heats of adsorption of water were determined as a function of moisture content from the equilibrium data at different temperatures using the Clasius-Clapeyron equation.

Moisture adsorption isotherms and isosteric energy for almond

In this study, ballistic behavior of multi-layered ceramic armors under high velocity impact is studied numerically. The model consists of 2D-axisymmetric Lagrangian approach with Johnson–Holmquist constitutive model for alumina ceramic tiles, Mie–Gruneisen equation of state for polymeric interlayers, and Johnson–Cook constitutive relation for Armor Piercing (AP) projectile. The finite element results obtained from various armor layups show the potentiality of multi-layered ceramic armor in extending conoid fracture through the ceramic layers, thus leading to the increase in the armor performance. It is illustrated that besides ceramic armor layup, interlayers of ceramic tiles have a significant role in increasing the armor performance. Finally, the effect of different polymeric interlayers on ballistic performance of multi-layered ceramic armors against AP projectile is investigated. In order to measure the ballistic performance of the armors, various criteria are introduced. Depth of penetration of the ...

Investigation on high-velocity impact performance of multi-layered alumina ceramic armors with polymeric interlayers

The results of an experimental study on the buckling behavior of thin-walled GFRP cylindrical shells are presented. The specimens were fabricated from continuous glass fiber using a specially-designed filament winding machine. The buckling behaviors of unstiffened shells and stiffened shells with lozenge, triangular and hexagonal grids were then studied under quasi-static axial loading at room temperature. Due to the thin skin of the shells, all specimens first experienced a general buckling mode as well as barreling under the applied loading. Following this general buckling damage, local buckling mode was seen on all specimens. Based on the experimental results, the critical buckling load was higher for the shells with hexagonal and triangular grids while the unstiffened shells and stiffened shells with lozenge grids exhibited much lower critical buckling load. On the other hand, in very small skin thicknesses, when the specific buckling loads for all specimens were compared, the unstiffened shells showed the highest specific buckling load.

	 

	Key words: Buckling load, composite shells, stiffened shells.

Mojtaba Yazdani

Papers

Moisture sorption isotherms and isosteric heat for pistachio

The Effects of Helical Ribs’ Number and Grid Types on the Buckling of Thin-walled GFRP-stiffened Shells under Axial Loading

Moisture adsorption isotherms and isosteric energy for almond

Investigation on high-velocity impact performance of multi-layered alumina ceramic armors with polymeric interlayers

An experimental investigation into the buckling of GFRP stiffened shells under axial loading