• Structural Engineering and Mechanics
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• v.74 no.1
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• pp.83-90
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• 2020

Several classical and higher order plate theories were used to study the buckling of functionally graded material (FGM) plates. In the great majority of research, a power function is used to represent metal and ceramic material transverse distribution (P-FGM). Therefore, the effect of having other transverse variation of material properties on the buckling behavior of thick rectangular FGM plates was not properly addressed. In the present work, this effect is investigated using the Third order Shear Deformable Theory (TSDT) for the case of simply supported FGM plate. Both a sigmoid function and an exponential functions are used to represent the transverse gradual property variation. The plate governing equations are combined with a Navier type expanded solution of the unknown displacements to derive the buckling equation in terms of the pre-buckling in-plane loads. Finally, the critical in-plane load is calculated for the different buckling modes. The model is verified by a comparison of the calculated buckling loads with available published results of Al-SiC P-FGM plates. The conducted parametric study shows that manufacturing FGM plates with sigmoid variation of properties in the thickness direction increases the buckling load considerably. This improvement is found to be more significant for the case of thick plates than that of thin plates. Results also show that this stiffening-like effect of the sigmoid function profile is more evident for cases where the in-plane loads are applied along the shorter edge of the plate.

• Preventive Nutrition and Food Science
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• v.19 no.4
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• pp.358-362
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• 2014

Flow and dynamic rheological properties of hot thickened soups for consumption by the elderly people with swallowing difficulty (dysphagia) were investigated at a serving temperature of $60^{\circ}C$. In this study, sea mustard soup (SMS) and dried pollock soup (DPS), which have been widely known as favorable hot soups provided in a domestic hospitals and nursing homes for dysphagic patients, were thickened with four commercial xanthan gum (XG)-based food thickeners (coded A~D) marketed in Korea. Thickened soups prepared with different thickeners showed high shear-thinning flow behaviors (n=0.15~0.21). Apparent viscosity (${\eta}_{a,50}$), consistency index (K), storage modulus (G'), and loss modulus (G") demonstrated differences in rheological behaviors between the XG-based thickeners. The magnitudes of (G') were much higher than those of (G") over the entire range of frequency (${\omega}$) with the high dependence on ${\omega}$, showing the rheological behavior similar to a weak gel. In general, all rheological parameter values of thickened DPS samples were higher when compared to the thickened SMS samples. These results indicate that flow and dynamic rheological properties of hot thickened soups containing commercial XG-based thickeners are strongly dependent on the type of thickener and soup.

• Journal of Korean Port Research
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• v.14 no.4
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• pp.451-461
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• 2000

The design and maintenance of navigation channel and water facilities of an harbor which is located at the mouth of river or at the estuary area are difficult due to the complexity of estuarial water and sediment circulation. Effects of deepening navigable waterways, of changing coastline configurations, or of discharging dredged material to the open sea are necessary to be investigated and predicted in terms of water quality and possible physical changes to the coastal environment. A borad analysis of the transport mechanism in the estuary area was made in terms of sediment property, falling velocity, concentration and flow characteristics. In order to simulate the transport processes, a two-dimensional finite element model is developed, which includes erosion, transport and deposition mechanism of suspended sediments. Galerkin’s weighted residual method is used to solve the transient convection-diffusion equation. The fluid domain is subdivided into a series of triangular elements in which a quadratic approximation is made for suspended sediment concentration. Model could deal with a continuous aggregation by stipulating the settling velocity of the flocs in each element. The model provides suspended sediment concentration, bed shear stress, erosion versus deposition rate and bed profile at the given time step.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1023-1026
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• 2010

In this paper, rheological property of polymer blends in a confined geometry was investigated. The shear viscosity was measured in a capillary rheometer incorporated with a specially designed piston and three slit dies having 0.1, 0.2 and 0.5 mm in thickness. It was observed that the viscosity of polymer blends does not depend on the die size when the phase of polymer blends is a sea-island structure. However, when the phase of polymer blends is a co-continuous structure, the viscosity of the blends was dependent on the die size. By additional investigations, this result is attributed to the slip phenomenon between polymer phases in the blends.

• Computers and Concrete
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• v.23 no.5
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• pp.351-359
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• 2019

In this study, the calcium hydroxide, an inherent product of cement hydration, was treated using biomimetic carbonation method of incorporating stearic acid to generate the hydrophobic calcium carbonate on concrete surface. Carbonation reaction was carried out at various $CO_2$ pressure and temperatures and utilizing the Scanning Electron Microscope (SEM), chloride-ion penetration test apparatus, and compression test machine to investigate the hydrophobicity, durability, and mechanical properties of the synthesized products. Experimental results indicate that the calcium stearate may change the surface property of concrete from hydrophilicity to hydrophobicity. Increasing reaction temperature can change the particles from irregular shapes to needle-rod structures with increased shear stress and thus favorable to hydrophobicity and microhardness. The contact angle against water for the concrete surface was found to increase with increasing $CO_2$ pressure and temperature, and reached to an optimum value at around $90^{\circ}C$. The maximum static water contact angle of 128.7 degree was obtained at the $CO_2$ pressure of 2 atm and temperature of $90^{\circ}C$. It was also found that biomimetic carbonation increased the permeability, acid resistance and chloride-ion permeability of the concrete material. These unique results demonstrate that the needle-rod structures of $CaCO_3$ synthetized on concrete surface could enhance hydrophobicity, durability, and mechanical properties of concrete.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.121-128
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• 2009

The strain, microstructure and mechanical properties through thickness of an oxygen free copper(OFC) processed by differential speed rolling(DSR) were investigated in detail. The OFC sample with thickness of 1 mm was rolled to 35% reduction at ambient temperature without lubrication changing the differential speed ratio from 1.0:1 to 2.2:1. The shear strain introduced by the conventional rolling showed positive values at positions of upper roll side and negative values at positions of lower roll side. However, it showed zero or positive values at all positions for the samples rolled by the DSR. The effects of strain distribution through thickness of the coper sheets on microstructure, texture and mechanical properties are discussed in the present study.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.101-108
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• 2010

The local structural states of amorphous alloys have been depicted previously via short-range orders (SROs). However, the concept of SROs alone is inadequate and sometimes insufficient to explain the structure-property relation of the amorphous alloys. In this study, we propose new types of medium-range building structures that affect the mechanical properties, plasticity in particular. Using a combination of molecular dynamics simulations and the Voronoi tessellation method, we demonstrate a three-dimensional configuration of icosahedral medium-range orders (I-MROs) and elucidate how these icosahedral orders evolve by the application of shear deformation. It was observed that the structural stability of the icosahedral orders relies largely on how they are linked via percolation and this linking is explained in detail.

• Food Science of Animal Resources
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• v.42 no.3
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• pp.411-425
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• 2022

Semi-dried restructured sausages are restructured meat products with a high nutritional and economic value. However, excessively long drying times can have negative effects on the energy consumption, texture, and sensory properties of semi-dried restructured sausages. The objective of this study was to investigate the effects of different water contents on the drying and physicochemical characteristics of semi-dried restructured sausages. Sausages were prepared with different initial moisture contents (0%-50%) and drying time (0-580 min). The drying characteristics, including the drying rate, effective moisture diffusivity, and water activity of sausage were significantly improved as the initial moisture content was increased. When the initial moisture content of the sausage was 50%, physicochemical properties, such as color, porosity, shear force, and volatile basic nitrogen, were improved the most along with the decreased drying time. Scanning electron microscopy data showed greater porosity and pore size in sausages with the increase of initial moisture content. Collectively, our data suggest that an increase in the initial moisture content of semi-dried restructured sausages improves their drying characteristics and physicochemical properties.

• Food Science of Animal Resources
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• v.43 no.3
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• pp.540-551
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• 2023

Milk protein concentrate (MPC) is widely used to enhance the stability and texture of fermented dairy products. However, most research has focused on yogurt products, and the effects of MPC on sour cream characteristics remain unknown. Therefore, we investigated the effects of different MPC levels (0%, 1%, 2%, and 3% w/w) on the rheological, physicochemical, microbiological, and aroma characteristics of sour creams in this study. We found that MPC supplementation stimulated the growth of lactic acid bacteria (LAB) in sour creams, resulting in higher acidity than that in the control sample due to the lactic acid produced by LAB. Three aroma compounds, acetaldehyde, diacetyl, and acetoin, were detected in all sour cream samples. All sour creams showed shear-thinning behavior (n=0.41-0.50), and the addition of MPC led to an increase in the rheological parameters (η_a,50, K, G', and G"). In particular, sour cream with 3% MPC showed the best elastic property owing to the interaction between denatured whey protein and caseins. In addition, these protein interactions resulted in the formation of a gel network, which enhanced the water-holding capacity and improved the whey separation. These findings revealed that MPC can be used as a supplementary protein to improve the rheological and physicochemical characteristics of sour cream.

• The Journal of the Acoustical Society of Korea
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• v.25 no.1
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• pp.1-6
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• 2006

The Possibility of using acoustic impedance as an input Parameter for computation of underwater acoustic field in shallow waters was investigated. Analysis of the acoustic reflection from the ocean bottom with shear wave effect showed that acoustic impedances below the critical grazing angle have nearly angle-independent property and could be approximated with a single value of near-grazing impedance $Z_0$. Computations of the Propagation loss based on the concept of 'effective depth' indicate that near-grazing bottom acoustic impedances could be used as an input parameter for simulation of the acoustic fields in shallow waters.