• Advances in concrete construction
• /
• v.7 no.1
• /
• pp.31-37
• /
• 2019

This paper evaluates the workability and hardened properties of self-compacting concrete (SCC) containing silica fume as the partial replacement of cement. SCC mixtures with 0, 2, 4, 6, 8 and 10% silica fume were tested for fresh and hardened properties. Slump flow with $T_{500}$ time, L-box and V-funnel tests were performed for evaluating the workability properties of SCC mixtures. Compressive strength, splitting tensile strength and modulus of rupture were performed on hardened SCC mixtures. Experiments revealed that replacement of cement by silica fume equal to and more than 4% reduced the slump flow diameter and increased the $T_{500}$ and V-funnel time linearly. Compressive strength, splitting tensile strength and modulus of rupture increased with increasing the replacement level of cement by silica fume and were found to be maximum for SCC mixture with 10% silica fume. Further, residual hardened properties of SCC mixture yielding maximum strengths (i.e., SCC with 10% silica fume) were determined experimentally after heating the concrete samples up to 200, 400, 600 and $800^{\circ}C$. Reductions in hardened properties up to $200^{\circ}C$ were found to be very close to normal vibrated concrete (NVC). For 400 and $600^{\circ}C$ reductions in hardened properties of SCC were found to be more than NVC of the same strength. Explosive spalling occurred in concrete specimens before reaching $800^{\circ}C$.

• Korean Journal of Pharmacognosy
• /
• v.50 no.3
• /
• pp.165-174
• /
• 2019

Oregonin is known as a representative active substance of plants of the Alnus species. In this study, we will show the results of establishing a method for extracting trace amounts of useful substances in plants. Additionally, a variety of physiological activity studies were conducted with extracts containing high content of useful substances. In this study, anti-oxidant, anti-inflammatory and anti-allergic activities of supercritical fluid residue 60% EtOH extracts of Alnus sibirica (ASCFR) were investigated in vitro. To explore anti-oxidant and anti-inflammatory characteristics of supercritical extract, DPPH radical scavenging, and ABTS radical scavenging activity, inhibition of nitric oxide production in LPS-stimulated RAW 264.7 cells and ${\beta}$-hexosaminidase release in IgE-stimulated RBL-2H3 cells were examined, respectively. Results showed a concentration-dependent increase in DPPH and ABTS radical scavenging activity. Cells stimulated with LPS produced more nitric oxide than normal control cells. However, cells treated with supercritical fluid residue 60% EtOH extract decreased production in a concentration-dependent manner. In anti-allergic activity studies, ASCFR showed concentration-dependentanti-allergic activity. Based on results and strong antioxidant activity, ASCFR has potential as basic research materials for development of therapeutic supplements-based medicines or functional cosmetics related to chronic inflammatory skin immunity diseases.

• Korean Journal of Applied Biomechanics
• /
• v.29 no.3
• /
• pp.137-143
• /
• 2019

Objective: Ligament laxity and hypotonia are characteristics of Down syndrome patients. The aim of this study was to compare the landing pattern between Down syndrome patients and typically developing subjects. To compare the landing pattern, variables related to ligament laxity and hypotonia i.e. vertical stiffness and lower extremities kinematics were investigated. Method: Five subjects with Down syndrome (age: $14.6{\pm}1.8years$, mass: $47.6{\pm}6.94kg$, height: $147.9{\pm}6.0cm$) and six able-bodied subjects (age: $13.2{\pm}0.4years$, mass: $54.7{\pm}6.7kg$, height: $160.1{\pm}9.8cm$) participated in this study. Results: The vertical displacement of the center of mass, vertical reaction force, leg stiffness and range of ankle angle range among Down syndrome patients were significantly different than typically developing group. The youth with Down's syndrome appeared to receive greater vertical impact force at landing than normal youth. Conclusion: The differences in the biomechanical characteristics suggest the delay in motor development among Down syndrome patients and an increased risk of injury to the lower extremity during movement execution such as drop landing.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.58.2-58.2
• /
• 2018

Theoretically, the magnetic helicity transport flux through the solar surface into the upper atmosphere can be estimated indefinitely precisely by magnetic field footpoint tracking if the observational resolution is infinitely fine, even with magnetic flux emergence or submergence. In reality, the temporal and spatial resolutions of observations are limited. When magnetic flux emerging or submerging, the footpoint velocity goes to infinity and the normal magnetic field vanishes at the polarity inversion line. A finite observational resolution thus generates a blackout area in helicity flux estimation near the polarity inversion line. It is questioned how much magnetic helicity is underestimated with a footpoint tracking method due to the absence of information in the blackout area. We adopt the analytical models of Gold-Hoyle and Lundquist force-free flux ropes and let them emerging from below the solar surface. The observation and the helicity integration can start at different emerging stages of the flux rope, i.e., the photospheric plane initially cuts the flux rope at different levels. We calculate the magnetic helicity of the flux rope below the photospheric level, which is eventually to emerge, except the helicity hidden in the region to be swept by the blackout area with different widths. Our calculation suggests that the error in the integrated helicity flux estimate is about half of the real value or even larger when small scale magnetic structures emerge into the solar atmosphere.

• Earthquakes and Structures
• /
• v.16 no.5
• /
• pp.547-561
• /
• 2019

In this work, a new analytical approach using a theory of a high order hyperbolic shear deformation theory (HSDT) has been developed to study the free vibration of plates of functionally graduated material (FGM). This theory takes into account the effect of stretching the thickness. In contrast to other conventional shear deformation theories, the present work includes a new displacement field that introduces indeterminate integral variables. During the manufacturing process of these plates defects can appear as porosity. The latter can question and modify the global behavior of such plates. The materials constituting the plate are assumed to be gradually variable in the direction of height according to a simple power law distribution in terms of the volume fractions of the constituents. The motion equations are derived by the Hamilton principle. Analytical solutions for free vibration analysis are obtained for simply supported plates. The effects of stretching, the porosity parameter, the power law index and the length / thickness ratio on the fundamental frequencies of the FGM plates are studied in detail.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.33.2-33.2
• /
• 2018

Fossil galaxy cluster has a dominant central elliptical galaxy (${\Delta}M12$ >2 in 0.5Rvir) embedded in highly relaxed X-ray halo, which indicates dynamically stable and passively evolved system. These features are expected as a final stage of the cluster evolution in the hierarchical structure formation paradigm. It is known that Abell 2261(A2261 hereafter) is classified as a fossil cluster, but has unusual features such as a high central X-ray entropy (i.e., non-cool core system), which is not expected in normal fossil clusters. We perform a kinematic study with a spectroscopic data of 589 galaxies in the A2261 field. We define cluster member galaxies using the caustic method and discover a new second bright galaxy at ~1.5 Rvir (nearly the splash-back region). It implies the current fossil state of the cluster can break in the near future. In addition, with three independent substructure finding methods, we find that A2261 has many substructures within 3 Mpc from the center of the cluster. These findings support that A2261 is not in a dynamically stable state. We argue that A2261 is in a transitional phase of dynamical evolution of the galaxy cluster and maybe previously defined fossil cluster does not mean the final stage of the evolution of galaxy clusters.

• Pediatric Infection and Vaccine
• /
• v.26 no.1
• /
• pp.66-70
• /
• 2019

Trans-placental neonatal human immunodeficiency virus (HIV) infection is common in Africa; however, it is not yet reported in the Republic of Korea. With the increasing incidence of HIV infection, especially in the reproductive age group, the risk of the vertical transmission of HIV is also increasing. We report the first case of HIV infection acquired in-utero in a newborn in Korea. The baby is growing well with normal development.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.24 no.6
• /
• pp.501-509
• /
• 2021

Extensive studies have shown that breast milk is the best source of nutrition for infants, especially during the first six months, because it fulfills almost all of their nutritional needs. Among the many functional building blocks in breast milk, human milk oligosaccharides (HMOs) have been receiving more attention recently. Furthermore, it is the third most common group of compounds in human milk, and studies have demonstrated the health benefits it provides for infants, including improved nutritional status. HMOs were previously known as the 'bifidus factor' due to their 'bifidogenic' or prebiotic effects, which enabled the nourishment of the gastrointestinal microbiota. Healthy gastrointestinal microbiota are intestinal health substrates that increase nutrient absorption and reduce the incidence of diarrhea. In addition, HMOs, directly and indirectly, protect infants against infections and strengthen their immune system, leading to a positive energy balance and promoting normal growth. Non-modifiable factors, such as genetics, and modifiable factors (e.g., maternal health, diet, nutritional status, environment) can influence the HMO profile. This review provides an overview of the current understanding of how HMOs can contribute to the prevention and treatment of nutritional issues during exclusive breastfeeding.

• Journal of Animal Science and Technology
• /
• v.63 no.4
• /
• pp.892-903
• /
• 2021

The objective of this study is to investigate effect of air cleaner operated during pig breeding period on stress hormones of pigs and their pork quality. The stress hormones (cortisol, epinephrine and norepinephrine) in blood sample of pigs reared in the housing rooms with or without air cleaner have been measured according to a pig's rearing stage: 0 day (farrowing), 21st day (farrowing-weaning), 70th day (weaning-nursery), 140th day (nursery-growing), and 180th day (growing-fattening). The comparison of pork quality according to the application of an air cleaner was performed through the carcass analysis of the pigs shipped from swine house. The levels of cortisol, epinephrine, and norepinephrine in pigs reared in housing rooms with and without air cleaners were found to be within the range of normal reference values. Among pork quality evaluation items, the thickness of intermuscular fat and final carcass grade of pigs raised in housing room with air cleaner was generally superior to those of pigs raised in housing room without air cleaner (p < 0.05). Based on the results obtained from this study, it is concluded that air cleaner does not have a significant effect on reducing pig stress but contributes to improving pork quality in pig breeding.

• Structural Engineering and Mechanics
• /
• v.78 no.4
• /
• pp.439-453
• /
• 2021

In this work, quasi three-dimensional (quasi-3D) shear deformation theory is presented for bending and dynamic analysis of functionally graded (FG) plates. The effect of varying material properties and volume fraction of the constituent on dynamic and bending behavior of the FG plate is discussed. The benefit of this model over other contributions is that a number of variables is diminished. The developed model considers nonlinear displacements through the thickness and ensures the free boundary conditions at top and bottom faces of the plate without using any shear correction factors. The basic equations that account for the effects of transverse and normal shear stresses are derived from Hamilton's principle. The analytical solutions are determined via the Navier procedure. The accuracy of the proposed formulation is proved by comparisons with the different 2D, 3D and quasi-3D solutions found in the literature.