• Journal of the Korean Society for Heat Treatment
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• v.23 no.6
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• pp.338-343
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• 2010

Mechanical properties and microstructures of medium carbon high manganese steels were investigated in terms of alloying elements such as Mn, C contents, and heat treatment condition. Austenite volume fraction was increased with increasing Mn content, leading to hardness decrease in the range of Mn content of above 10% after quenching and tempering. Such results are also supported by microstructural analysis and X-ray diffraction in that the increase in mangaese content results in the increase in austenite fraction. Studies on tempering condition indicated that not only hardness and tensile strength but also charpy impact values were reduced as tempering temperature were raised in the range of $250^{\circ}C$ to $600^{\circ}C$. It was also observed that fracture mode was changed from dimple to intergranular fracture. Such results are thought to be due to very fine carbide precipitation or impurity segreagation at grain boundaries as tempering temperature goes up. Heat treatment of Fe-5Mn-2Si-1Al-0.4C can be optimized by austenitizing at $850^{\circ}C$, air cooling and tempering at $250^{\circ}C$, resulting in 1950 MPa in Tensile strength, 17% in elongation and 23.3 $J/cm^2$ in charpy impact energy with high work hardening characteristics.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.600-603
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• 1995

A series of samples in the Sm1-xSrxCoO3-y(x=0.00, 0.25, 0.50, 0.75 and 1.00) system has been prepared at 1200 ℃ under ambient atmosphere. The X-ray diffraction patterns of the samples with x=0.00 and 0.25 are indexed with orthorhombic symmetry like GdFeO3 and x=0.50 appears to be perfectly cubic. In the tetragonal system (x=0.75), the structure is similar to that of SrCoO2.80. The composition of x=1.00, SrCoO2.52, shows the brownmillerite-type structure. The reduced lattice volume is increased with x value in this system. The chemical analysis shows the τ value (the amount of the Co4+ ions in the system) is maximized at the composition of x=0.50. Nonstoichiometric chemical formulas are determined by the x, τ and y values. The electrical conductivity has been measured in the temperature range of 78 to 1000 K. The activation energy is minimum for those of x=0.25 and x=0.50 with metallic behavior. First-order semiconductor-to-metal transition of SmCoO3 is not observed. Instead, a broad, high-order semiconductor-to-metal transition is observed. In general, the effective magnetic moment is increased with increasing τ values at low temperature. At high temperature, the magnetic moment is maximum for that of x=0.00. The 3d-electrons are collective and give ferromagnetism in x=0.50.

• Computers and Concrete
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• v.33 no.2
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• pp.163-173
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• 2024

Fiber-reinforced polymers (FRP) have a proven strength enhancement capability when installed into Reinforced Concrete (RC) beams. The brittle failure of traditional FRP strengthening systems has attracted researchers to develop novel materials with improved strength and ductility properties. One such material is that known as polyethylene terephthalate (PET). This study presents a numerical investigation of the flexural behavior of reinforced concrete beams externally strengthened with PET-FRP systems. This material is distinguished by its large rupture strain, leading to an improvement in the ductility of the strengthened structural members compared to conventional FRPs. A three-dimensional (3-D) finite element (FE) model is developed in this study to predict the load-deflection response of a series of experimentally tested beams published in the literature. The numerical model incorporates constitutive material laws and bond-slip behavior between concrete and the strengthening system. Moreover, the validated model was applied in a parametric study to inspect the effect of concrete compressive strength, PET-FRP sheet length, and reinforcing steel bar diameter on the overall performance of concrete beams externally strengthened with PET-FRP.

• Journal of Nutrition and Health
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• v.35 no.3
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• pp.394-401
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• 2002

The purpose of this study was to : (a) examine diabetic patients' sensory evaluation and food preferences, (b) analyze the portion sizes & plate wastes, (c) investigate the factors affecting plate wastes, and (d) determine the nutritional & mometary values of the plate wastes. A questionnaire for determining food preference and sensory evaluation was developed. Thirty-three diabetic patients who were hospitalized in Sanggye Paik hospital in Seoul were studied. Serving sizes and plate wastes were weighed by using an electric scale, and the CAN-Pro program was used to evaluate the nutritional value or the food consumed. The data were analyzed using the SAS package program for descriptive analysis, t-test, ANOVA, and the Pearson correlation. Using a five-point Likeu-type scale, the temperature s[ore ranged from 3.1 to 3.3 (1 : very poor, 5 : excellent), the preference store was 3.0-3.2 (1 : very dislike, 5:very like), the taste score was 2.9-3.2 (1 : very poor, 5 : excellent), and the amount of food served score was 2.8-3.0 (1 : too little, 5 : too much). Serving sizes were considered insufficient by patients because most of the DM diet was low in calories. Average plate waste for the DM diet was 26.2% of the total served, by weight, and was lower than that for patients consuming a normal diet, which was 30.3%, found in previous research. Those subjects who had been previously hospitalized and who wished to participate in a campaign for food waste reduction produced less plate waste than other groups (p<.05). Plate wastes of the DM diet were negatively correlated with taste, temperature, and preference, and were positively correlated with the amount served: however, these results were not statistically significant. It was found that diabetic patients consumed adequate levels of energy, protein, Ca, Fe, Vitamin B$_1$, Vitamin B$_2$, and niacin, but inadequate levels of Phosphorus, Vitamin A and Vitamin C. The plate wastes were calculated to be 26.2% of the total cost (￦ 3,489), which is ￦9l5. This represents a significant wastage of resources from the hospital. The results of this study could assist foodservice managers in both controlling food wastage, and improving the quality of hospital food services.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.3
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• pp.150-157
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• 2016

When blocks are supported on a dock, huge reaction forces concentrated at the supports cause structural damage owing to local stress concentrations. Thus, the supports should be arranged to avoid local failure from the reaction forces by redistributing those forces. Docking analyses to determine the proper blocks and their support arrangements are introduced so that the local stresses are minimized to warrant the safety of the docking supports. Local stresses enforced by the support arrangement should be evaluated by finite element analysis (FEA). However, it is difficult to consider an accurate 3D geometry of the blocks in the finite element model because the structural design information is too complicated to determine within several days using the FEA model. This paper presents a simplified FE model to evaluate the safety of the arrangement of supports using a simplified grillage element. The grillage element can be efficiently used to obrain the reaction forces in docking analysis becasuse the reaction forces at the supports are enough to assess the safety of block. Since a simplified grillage model of the entire ship cannot accurately calculate the local stresses, an optimized modeling method based on the grillage element was introduced. The local reaction forces obtained by the proposed approach and three-dimensional FEA were discussed for typical types of ships. It is shown that the reaction forces obtained by the present grillage model are in reasonably good agreement with the FEA model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.207-214
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• 2008

This study presents a way to validate the quality level of the proposed connection type and verify the experimental test, and performs a 3D nonlinear analysis corresponding to the experimental test. Two mixed-structure beams were cast and tested under a four-point static loading. Force-displacement relation, force-strain relation, force-opening width, and failure mode were observed from comparing the numerical results of the adopted FE model. Nonlinear analysis of mixed structures was carried out by utilizing the contact elements of a general purpose structural analysis computer program (ABAQUS). The results of numerical and experimental simulation show that the proposed L-shaped connection has greater stiffness under flexural loading and better structural performance with regard to the connection.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.37 no.4
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• pp.309-318
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• 2011

In this study, the antioxidative effect, antibacterial, inhibitory effects on tyrosinase, inhibitory effects on elastase and component analysis of Phellinus linteus (P. linteus) extracts were investigated. The ethyl acetate fraction of P. linteus extracts ($2.94\;{\mu}g/mL$) showed the highest free radical (1,1-diphenyl-2-picrylhydrazyl, DPPH) scavenging activity ($FSC_{50}$). Reactive oxygen species (ROS) scavenging activity ($OSC_{50}$) of P. linteus extracts on ROS generated in $Fe^{3+}$-EDTA/$H_2O_2$ system was investigated using the luminol-dependent chemiluminescence assay. The ethyl acetate fraction ($0.0072\;{\mu}g/mL$) showed the most prominent ROS scavenging activity. The protective effects of extract/fractions of P. linteus extracts on the rose-bengal sensitized photohemolysis of human erythrocytes were investigated. The P. linteus extracts showed cellular membrane protective effects in a concentration dependent manner ($5{\sim}50\;{\mu}g/mL$). The inhibitory effect ($IC_{50}$) on tyrosinase of P. linteus extract was the highest at 50 % ethanol extract ($6.34\;{\mu}g/mL$), and the inhibitory effect ($IC_{50}$) on elastase of P. linteus was the highest at ethyl acetate fraction ($14.08\;{\mu}g/mL$). TLC, HPLC chromatogram and LC/ESI-MS of the ethyl acetate fraction obtained from P. linteus extracts were identified interfungin A (PL RPT-1a). These results indicate that extract/fractions of P. linteus can function as antioxidants in biological systems, particularly skin exposed to UV radiation by scavenging ROS, and protect cellular membranes against ROS. Extract/fractions of P. linteus can be applicable to new cosmeceuticals for antioxidant, antiaging, antiwrinkle and whitening.

• Journal of Biomedical Engineering Research
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• v.38 no.1
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• pp.9-15
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• 2017

Recently, flexible cages have been introduced in an attempt to absorb and reduce the abnormal load transfer along the anterior parts of the spine. They are designed to be used with the pedicle screw systems to allow some mobility at the index level while containing ROM at the adjacent level. In this study, a finite element (FE) study was performed to assess biomechanical efficacies of the flexible cage when combined with pedicle screws with flexible rods. The post-operated models were constructed by modifying the L4-5 of a previously-validated 3-D FE model of the intact lumbar spine (L2-S1): (1) Type 1, flexible cage only; (2) Type 2, pedicle screws with flexible rods; (3) Type 3, interbody fusion cage plus pedicle screws with rigid rods; (4) Type 4, interbody fusion cage plus Type 2; (5) Type 5, Type 1 plus Type 2. Flexion/extension of 10 Nm with a compressive follower load of 400N was applied. As compared to the Type 3 (62~65%) and Type 4 (59~62%), Type 5 (53~55%) was able to limit the motion at the operated level effectively, despite moderate reduction at the adjacent level. It was also able to shift the load back to the anterior portions of the spine thus relieving excessively high posterior load transfer and to reduce stress on the endplate by absorbing the load with its flexible shape design features. The likelihood of component failure of flexble cage remained less than 30% regardless of loading conditions when combined with pedicle screws with flexible rods. Our study demonstrated that flexible cages when combined with posterior dynamic system may help reduce subsidence of cage and degeneration process at the adjacent levels while effectively providing stability at the operated level.

• Journal of Life Science
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• v.14 no.1
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• pp.82-90
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• 2004

This study was carried out to analysis the composition of fruit body of Morchella esculenta (MEF) to determine the possibility of medical and edible use. The nutritional compositions of MEF were as follows ; The contnt (g%) of crude fat, carbohydrate, crude protein were 3.8, 43.5 and 29.7, respectively. Potassium concentration in MEF was high up to 3558.0 mg% and Ca, Mg, Fe, Na and Zn were followed. There were 23 amino acids in MEF The content of glutamic acid was high up to 1433.0 mg% and leucine, alanine, arginine valine and theronine were followed. Since MEF contains 25 free amino acids, it will be a favorable food stuff. The content of Vitamin A, Vitamin $B_1$, , Vitamin$B_2$, Vitamin $B_6$, Vitamin C, Vitamin $BD_3$, Vitamin E and Vitamin $K_1$, were 2.23 $\mug%$, 0.13 mg%, 0.07 mg%, 0.27 mg%, 0.17 mg%, 52.27 $\mug%$, 5.26 mg% and 3.23 $\mug%$, respectively. MEF will have a good anti-aging effect due to content of Vitamin C and Vitamin E.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.452-460
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• 2018

This study was conducted to investigate the physiological activities of Houttuynia cordata extracts and fractions. H. cordata extracts were extracted with 50% ethanol and the ethyl acetate fractions were obtained from the extracts. Minimum inhibitory concentration (MIC) values of the ethyl acetate fraction for S. aureus and B. subtilis were $78{\mu}g/mL$ and $312{\mu}g/mL$, respectively, indicating the high activity against gram-positive bacteria. The free radical scavenging activity ($FSC_{50}$) for 1,1-diphenyl-2-picrylhydrazyl (DPPH) was higher in the ethyl acetate fraction with $12.00{\mu}g/mL$ compared to that of $27.15{\mu}g/mL$ for 50% ethanol extract. The total antioxidant activity ($OSC_{50}$) values for reactive oxygen species (ROS) produced in $Fe^{3+}-EDTA/H_2O_2$ system by a luminol-dependent chemiluminescence method were 2.91 and $0.983{\mu}g/ml$ for the 50% ethanol extract and ethyl acetate fraction, respectively. To investigate cellular protective effects on the HaCaT cell, the intracellular ROS scavenging activity was measured after UVB irradiation and the ethyl acetate fraction of H. cordata showed the activity in a concentration-dependent from $1.6{\mu}g/mL$ and a reduction rate of 54.3% at a maximum concentration of $12.5{\mu}g/mL$. Also, HaCaT cell protective effect against $H_2O_2$-mediated decreased the cell viability of the ethyl acetate fraction of H. cordata which significantly increased the cell viability from $0.8{\mu}g/mL$ and the maximum cell viability showed 86.9%. The ethyl acetate fraction of the H. cordata extracts was analyzed by TLC and HPLC. As a result, quercitrin, isoquercitrin, hyperoside, chlorogenic acid, neochlorogenic acid, cryptochlorogenic acid, rutin and afzelin were identified. From the above results, it was suggested that the extracts and fractions of H. cordata have a potential to be applied in the field of cosmetics as a natural antioxidant/preservative capable of protecting the cell membrane from the oxidative stress by eliminating ROS and exhibiting the antimicrobial effect.