• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.1
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• pp.1-5
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• 2001

This study was carried out to isolate saponin compounds from red-ginseng efflux, which was produced during the industrial processing of red-ginseng from fresh ginseng. We isolated crude saponin from the efflux extract (moisture content 35.0%) by using Diaion HP-20 adsorption method. Non-saponin fraction, which was adsorbed on Diaion HP-20 resin, was removed by eluating with $H_{2}O$ and 25% spirit. Then crude saponin was eluated with 95% spirit, continuously. Saponin in the eluated fractions was confirmed by TLC analysis. Crude saponin isolated from red ginseng efflux extract contained 12.10% of saponin. whereas those of white ginseng and red-ginseng were 3.30 and 3.39%, respectively. Ginsenoside contents showed the highest contents kin crude saponin from red ginseng efflux extract. Expacilly, the ginsenoside-$Rb_{1}$ and Re showed the highest contents in red-ginseng efflux extract when compared with those of white ginseng and red ginseng crude saponins. And the other ginsenosides except ginsenoside-$Rb_{1}$ and -Re also showed the highest contents in red ginseng efflux extract. However, the ratio of PD saponin (Panaxadiol saponin: $Rb_{1}+Rb_{2}$+Rc+Rd) to PT saponin (panaxatriol: $Re+Rg_{1}$) showed almost the same level when compared with those of ginseng saponin fractions. Ratio of PD/PT from red ginseng efflux extract was 1.99. Ratios of PD/PT from white ginseng and red ginseng were 1.85 and 1.84, respectively. Saponin purity, which was calculated by ratio percent of total ginsenoside to curde saponin content, was 45.90%. In case of white ginseng and red ginseng, the purities were 35.50 and 36.00%, respectively. However, by PHLC analysis, we confirmed that crude saponin isolated from red ginsengs. It suggested that crude saponin isolated from red ginseng ellux also would be useful component as ginseng saponins.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.230-240
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• 1997

An experimental research investigation of the fracture properties of polypropylene fiber reinforced concrete is reported. Fibers used in this experiment were two types, monofilament and fibrillated polypropylene fibers. Fiber length was 19 mm, and volume fractions were 0, 1, 2, and 3%. Also, as initial notch depths influence the fracture properties of fiber reinforced concrete, the notch depth ratios by specimen height were 0.15, 0.30 and 0.45. The main objective of this experimental program is to obtain the load-deflection and the load-CMOD curves, to investigate the fracture properties of the polypropylene fiber reinforced concretes. Therefore, the flexural specimen testings on the four-point bending were conducted. Then, the load-load point displacement and the load-crack mouth opening displacement curves were measured. The effects of different volume fractions of the monofilament and the fibrillated polypropylene fiber reinforced concrete on the compressive strength, flexural strength and toughness, stress intensity factor, and fracture energy were investigated through the experimental results.

• Advances in nano research
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• v.8 no.2
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• pp.135-148
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• 2020

The incorporation of carbon nanotubes in a polymer matrix makes it possible to obtain nanocomposite materials with exceptional properties. It's in this scientific background that this work was based. There are several theories that deal with the behavior of plates, in this research based on the Mindlin-Reissner theory that takes into account the transversal shear effect, for analysis of the critical buckling load of a reinforced polymer plate with parabolic distribution of carbon nanotubes. The equations of the model are derived and the critical loads of linear and parabolic distribution of carbon nanotubes are obtained. With different disposition of nanotubes of carbon in the polymer matrix, the effects of different parameters such as the volume fractions, the plate geometric ratios and the number of modes on the critical load buckling are analysed and discussed. The results show that the critical buckling load of parabolic distribution is larger than the linear distribution. This variation is attributed to the concentration of reinforcement (CNTs) at the top and bottom faces for the X-CNT type which make the plate more rigid against buckling.

• Journal of the Korean Society of Safety
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• v.24 no.6
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• pp.103-110
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• 2009

Since the mechanical properties of cement-based materials are time-dependent due to the prolonged cement hydration process, those of fiber reinforced concrete(FRC) may also be time-dependent. Toughness is one of important properties of FRC. Therefore, it should be investigated toughness development of FRCs with curing ages to fully understand the time-dependent characteristics of FRCs. To this end, the effect of curing ages on flexural toughness development of steel fiber reinforced concrete is studied. Three point bending test with notched beam specimen was adapted for this study. Hooked-end steel fiber(DRAMIX 40/30) was used as a fiber ingredient to investigate w/c ratio and fiber volume fraction effect on toughness development during curing. Three different water-cement ratios(0.44, 0.5 and 0.6) and fiber volume fractions(0%, 0.5% and 1%) were used as influence factors. Each mixture specimens were tested at five different ages, 0.5, 1, 3, 7 and 28 days. The study shows that flexure toughness development with age is quite different than other concrete material properties such as compressive strength. The study also shows that the toughness development trend correlates more closely to water/cement ratio than to fiber volume fraction.

• Journal of Microbiology and Biotechnology
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• v.13 no.1
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• pp.22-28
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• 2003

Increasing conjugated linoleic acid (CLA) content in dairy products has been a research Interest due to the potential health benefits resulted from consuming CLA. Attempts were made to obtain high level natural CLA containing fatty acid fractions from milk fat through bovine feeding of sunflower oil (SO) and urea fractionation. SO feeding changed the fatty acid profile of milk fat. increasing the CLA content five-fold at eight weeks of trial. Milk fat obtained from S0-fed cows was hydrolyzed to free fatty acids, which were then fractionated with urea at various ratios. The profiles of fatty acids were also greatly influenced by urea fractionation. Long-chain unsaturated fatty acids, Including CLA, were concentrated in milk fat after the fractionation, whereas saturated long-chain counterparts were eliminated. The highest level of CLA was achieved by the fractionation at 2:1 urea/fatty acid ratio (UFR2). CLA level was elevated 2.5-fold, and the Cl8:1/C18:0 fatty acid ratio was increased 120 times after the fractionation. The level of CLA in high CLA-milk fat (24mg/g fat) obtained from the feeding study was further increased through urea fractionation up to 52mg/g fat, 10 folds as high as CLA in the control milk fat (5mg/g fat).

• Steel and Composite Structures
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• v.19 no.3
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• pp.521-546
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• 2015

A new refined hyperbolic shear and normal deformation beam theory is developed to study the free vibration and buckling of functionally graded (FG) sandwich beams under various boundary conditions. The effects of transverse shear strains as well as the transverse normal strain are taken into account. Material properties of the sandwich beam faces are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. Equations of motion are derived from Hamilton's principle. Analytical solutions for the bending, free vibration and buckling analyses are obtained for simply supported sandwich beams. Illustrative examples are given to show the effects of varying gradients, thickness stretching, boundary conditions, and thickness to length ratios on the bending, free vibration and buckling of functionally graded sandwich beams.

• Advances in nano research
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• v.7 no.2
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• pp.109-123
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• 2019

In this article, the free vibration analysis of annular sandwich plates with various functionally graded (FG) porous cores and carbon nanotubes reinforced composite (CNTRC) facesheets is investigated based on modified couple stress theory (MCST) and first order shear deformation theories (FSDT). The annular sandwich plate is composed of two face layers and a functionally graded porous core layer which contains different porosity distributions. Various approaches such as extended mixture rule (EMR), Eshelby-Mori-Tanaka (E-M-T), and Halpin-Tsai (H-T) are used to determine the effective material properties of microcomposite circular sandwich plate. The governing equations of motion are extracted by using Hamilton's principle and FSDT. A Ritz method has been utilized to calculate the natural frequency of an annular sandwich plate. The effects of material length scale parameters, boundary conditions, aspect and inner-outer radius ratios, FG porous distributions, pore compressibility and volume fractions of CNTs are considered. The results are obtained by Ritz solutions that can be served as benchmark data to validate their numerical and analytical methods in the future work and also in solid-state physics, materials science, and micro-electro-mechanical devices.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.3
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• pp.85-94
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• 2006

Practially useful method of steel fiber for construction work is presented in this study. The most important purpose of this study is to develop a model which can predict mechanical behavior of the structure according to aspect ratio and volume fraction of steel fiber. Experiments on compressive strength, elastic modulus, and splitting strength were performed with self-made cylindrical specimens of variable aspect ratios and volume fractions. The experiment showed that compressive strength was not in direct proportion to volume fraction which doesn't seem to have great influence over compressive strength. However, splitting strength showed almost direct proportion to aspect ratio and volume fraction. Improvement of optimal efficiency was confirmed when the aspect ratio was 70. Experiments on flexural strength, fracture energy, and characteristic length were carried out with self-manufactured beams with notch. As a result, increases of flexural strength, fracture energy, and characteristic length according to increase of volume fraction tend to be prominent when aspect ratio is 70. The steel fiber improves concrete to be more ductile and tough. Moreover, regression analysis was the performed and predictable model was developed after determining variables. With comparison and analysis of suggested estimated values and measured data, reliance of the model was verified.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.4
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• pp.15-21
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• 2013

This study carried out finite element deflection analysis of cylindrical shell structures made of composite materials, which is based on the micro-mechanical approach for different fiber-volume fractions. The finite element (FE) models for composite structures using multi-scale approaches described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the effect of the material combination. New results reported in this paper are focused on the significant effects of the fiber-volume fraction for various parameters, such as fiber angles, layup sequences, and length-thickness ratios. It may be concluded from this study that the combination effect of fiber and matrix, largely governing the dynamic characteristics of composite shell structures, should not be neglected and thus the optimal combination could be used to design such civil structures for better dynamic performance.

• Steel and Composite Structures
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• v.33 no.6
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• pp.805-822
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• 2019

In this work, a simple four-variable integral plate theory is employed for examining the thermal buckling properties of functionally graded material (FGM) sandwich plates. The proposed kinematics considers integral terms which include the effect of transverse shear deformations. Material characteristics and thermal expansion coefficient of the ceramic-metal FGM sandwich plate faces are supposed to be graded in the thickness direction according to a "simple power-law" variation in terms of the "volume fractions" of the constituents. The central layer is always homogeneous and consists of an isotropic material. The thermal loads are supposed as uniform, linear, and nonlinear temperature rises within the thickness direction. The influences of geometric ratios, gradient index, loading type, and type sandwich plate on the buckling properties are examined and discussed in detail.