• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.91-99
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• 2002

In this study, a new methodology for the assessment of liquefaction potential is proposed. Since there is no data on the liquefaction damage in Korea, the dynamic behavior of fully saturated soils is characterized through laboratory dynamic tests. There are two experimental parameters related to the soil liquefaction resistance characteristics : the one is the index of disturbance determined by $G/G_{max}$ curve and the other is a plastic shear strain trajectory evaluated from stress-strain curve. The proposed methodology takes advantage of the site response analysis based on real earthquake records to determine the driving effect of earthquake. In the evaluation of liquefaction resistance characteristics, it is verified experimentally that the magnitude of cyclic shear stress has no influence on the critical value of plastic shear strain trajectory at which the initial liquefaction occurs. Cyclic triaxial tests under the conditions of various cyclic stress ratios and torsional shear tests are carried out far the purpose of verification. Through this study, the critical value at the initial liquefaction is found unique regardless of the cyclic stress ratio. It is also f3und that liquefaction resistance curve drawn with disturbance and plastic shear strain trajectory can simulate the behavior of fully saturated soils under dynamic loads.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.492-506
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• 2013

The historical accounts and materials about the eruption of Mt. Baekdusan as observed by the geological survey is now showing some signs of waking from a long slumber. As a response of the volcanic eruption of Mt. Baekdusan, water release may occur from the stored water in Lake Cheonjii caldera. The volcanic flood is crucial in that it has huge potential energy that can destruct all kinds of man-made structures and that its velocity can reach up to 100 km $hr^{-1}$ to cover hundreds of kilometers of downstream of Lake Cheonji. The ultimate goal of the study is to estimate the level of damage caused by the volcanic flood of Lake Cheon-Ji caldera. As a preliminary study a scenario-based numerical analysis is performed to build hydrographs as a function of time. The analysis is performed for each scenario (breach, magma uplift, combination of uplift and breach, formation of precipitation etc.) and the parameters to require a model structure is chosen on the basis of the historic records of other volcanos. This study only considers the amount of water at the rim site as a function of time for the estimation whereas the downstream routing process is not considered in this study.

• Nutrition Research and Practice
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• v.9 no.1
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• pp.22-29
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• 2015

BACKGROUND/OBJECTIVES: Recently, anthocyanins have been reported to have various biological activities. Furthermore, anthocyanin-rich purple corn extract (PCE) ameliorated insulin resistance and reduced diabetes-associated mesanginal fibrosis and inflammation, suggesting that it may have benefits for the prevention of diabetes and diabetes complications. In this study, we determined the anthocyanins and non-anthocyanin component of PCE by HPLC-ESI-MS and investigated its anti-diabetic activity and mechanisms using C57BL/KsJ db/db mice. MATERIALS/METHODS: The db/db mice were divided into four groups: diabetic control group (DC), 10 or 50 mg/kg PCE (PCE 10 or PCE 50), or 10 mg/kg pinitol (pinitol 10) and treated with drugs once per day for 8 weeks. During the experiment, body weight and blood glucose levels were measured every week. At the end of treatment, we measured several diabetic parameters. RESULTS: Compared to the DC group, Fasting blood glucose levels were 68% lower in PCE 50 group and 51% lower in the pinitol 10 group. Furthermore, the PCE 50 group showed 2-fold increased C-peptide and adiponectin levels and 20% decreased HbA1c levels, than in the DC group. In pancreatic islets morphology, the PCE- or pinitol-treated mice showed significant prevention of pancreatic ${\beta}$-cell damage and higher insulin content. Microarray analyses results indicating that gene and protein expressions associated with glycolysis and fatty acid metabolism in liver and fat tissues. In addition, purple corn extract increased the phosphorylation of AMP-activated protein kinase (AMPK) and decreased phosphoenolpyruvate carboxykinase (PEPCK), glucose 6-phosphatase (G6pase) genes in liver, and also increased glucose transporter 4 (GLUT4) expressions in skeletal muscle. CONCLUSIONS: Our results suggested that PCE exerted anti-diabetic effects through protection of pancreatic ${\beta}$-cells, increase of insulin secretion and AMPK activation in the liver of C57BL/KsJ db/db mice.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.183-190
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• 2015

An ejector is a type of non-powered pump that is used to supply a secondary flow via the ejection of a primary flow. It is utilized in many industrial fields, and is used for fueling the vehicle because of less failures and simple structure. Since most of ejectors in industry are gas-to-gas and liquid to gas ejector, many research activities have been reported in optimization of gas ejector. On the other hand, the liquid ejector is also applied in many industry but few research has been reported. The liquid ejector occurs cavitation, and it causes damage of parts. Cavitation has bees observed at the nozzle throat at the specified pressure. In this study, a two-dimensional axisymmetric simulation of a liquid-liquid ejector was carried out using five different parameters. The angle of the nozzle plays an important role in the cavitation of a liquid ejector, and the performance characteristics of the flow ratio showed that an angle of $35^{\circ}$ was the most advantageous. The simulation results showed that the performance of the liquid ejector and the cavitation effect have to be considered simultaneously.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.7
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• pp.1156-1166
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• 2020

Objective: The aim of this study was to evaluate the effects of compound organic acid calcium (COAC) on growth performance, hepatic antioxidant status and intestinal barrier of male broilers under high ambient temperature (32.7℃). Methods: Nine hundred healthy one-d-old Cobb-500 male broiler chicks were randomly assigned into three groups with six replicates of 50 birds each. A basal diet supplemented with 0% (control), 0.4% and 0.8% COAC, respectively were fed to birds for 6 weeks. All treatments were under high ambient indoor temperature of 32.7℃, and had a constant calcium and available phosphorus ratio. Results: The results showed that, compared with control, the average daily gain of broilers in 0.4% and 0.8% was significantly increased and the ratio of feed to gain in in 0.4% and 0.8% was significantly decreased at 1 to 21, 22 to 42 and 1 to 42 days of age (p<0.05). Compared with control, 0.8% COAC slightly decreased (p = 0.093) the content of malondialdehyde in liver at 42 days of age while 0.4% COAC significantly decreased (p<0.05) the activity of alkaline phosphatase. Furthermore, 0.4% COAC significantly enhanced the intestinal barrier function via increasing jejunal and ileal ocln transcription, promoting jejunal mucin 2 transcription at 42 days of age (p<0.05), and decreasing jejunal toll-like receptor 2 (TLR-2) and ileal TLR-15, inducible nitric oxide synthase compared with control group (p<0.05). Whereas, no significant differences on the transcription of interleukin-1β in jejunum and ileum were observed among three treatments (p>0.05). Overall, heat stress caused by high natural environment temperature may induce the damage to hepatic antioxidation and intestinal barrier. Conclusion: Dietary inclusion of COAC can improve the tolerance of broilers to thermal environment through the modification of antioxidative parameters in liver and the mRNA expression of genes in intestinal barrier, resulting in an optimal inclusion level of 0.4%.

• Tribology and Lubricants
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• v.36 no.2
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• pp.105-115
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• 2020

This paper presents a numerical study on the rotordynamic analysis of a dual-spool turbofan engine in the context of blade defect events. The blades of an axial-type aeroengine are typically well aligned during the compressor and turbine stages. However, they are sometimes exposed to damage, partially or entirely, for several operational reasons, such as cracks due to foreign objects, burns from the combustion gas, and corrosion due to oxygen in the air. Herein, we designed a dual-spool rotor using the commercial 3D modeling software CATIA to simulate blade defects in the turbofan engine. We utilized the rotordynamic parameters to create two finite element Euler-Bernoulli beam models connected by means of an inter-rotor bearing. We then applied the unbalanced forces induced by the mass eccentricities of the blades to the following selected scenarios: 1) fully balanced, 2) crack in the low-pressure compressor (LPC) and high pressure compressor (HPC), 3) burn on the high-pressure turbine (HPT) and low pressure compressor, 4) corrosion of the LPC, and 5) corrosion of the HPC. Additionally, we obtained the transient and steady-state responses of the overall rotor nodes using the Runge-Kutta numerical integration method, and employed model reduction techniques such as component mode synthesis to enhance the computational efficiency of the process. The simulation results indicate that the high-vibration status of the rotor commences beyond 10,000 rpm, which is identified as the first critical speed of the lower speed rotor. Moreover, we monitored the unbalanced stages near the inter-rotor bearing, which prominently influences the overall rotordynamic status, and the corrosion of the HPC to prevent further instability. The high-speed range operation (>13,000 rpm) coupled with HPC/HPT blade defects possibly presents a rotor-case contact problem that can lead to catastrophic failure.

• Food Science and Preservation
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• v.19 no.1
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• pp.1-6
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• 2012

The effect of the packing methods for enhancing the shelf life and improving the postharvest quality of the $tah$ $tasai$ Chinese cabbage baby leaf vegetable was studied during storage. Fresh baby leaf vegetables were packed in four commercial packaging types: (1) a non-perforated bag with a 0.03-mm oriented polypropylene (OPP) film; (2) a perforated bag with 1.0-mm-diameter holes on an OPP film; (3) a 0.40-mm polyethylene terephthalate (PET) container with a hinged lid; and (4) an expanded polystyrene (EPS) tray wrapped with a 0.02-mm polyvinyl chloride (PVC) film. The quality parameters, such as the weight loss, moisture content change, color difference, and appearance of the baby leaf vegetables were investigated. The baby leaf vegetables in the PET container and in the non-perforated OPP film bag showed relatively low weight loss, high moisture content, and good external appearance compared to those in the EPS tray and in the perforated OPP film bag during limited storage periods, at $16^{\circ}C$. The PET container also protected the baby leaf vegetables from physical damage. The study results will enable the selection of a better packaging system for extending the freshness and increasing the market ability of baby leaf vegetables.

• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.67-75
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• 2014

In this study, the staged seismic performance evaluations were conducted to the 91 high speed railway tunnels in use for checking whether to comply with the recent design criteria or not. In addition, the seismic fragility functions of the tunnels were developed to allow the probabilistic risk assessment. The results of the staged seismic performance evaluations which consist of a preliminary assessment and a detailed assessment, show that the tunnels comply with the recent design criteria. With reference to the results of previous studies, a form of the proposed seismic fragility functions was set as a log-normal distribution by PGA, and the parameters of the functions were determined by using the probability of damage for the design PGA level. The seismic fragility functions were developed for each types (Cut & Cover, NATM) of tunnels. The seismic fragility functions from this study and the existing research results (FEMA, 2004) were compared to evaluate the seismic performance level of the tunnels, as a result the tunnels of this study were relatively superior to the ASSM tunnels on the seismic performance.

• The Journal of Internal Korean Medicine
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• v.25 no.3
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• pp.461-472
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• 2004

Objectives : For the screening of neuroprotective effects of medicinal herbs, the complex system of animal models suffer some disadvantages in controlling critical parameters such as blood pressure and body temperature. Additionally, application of drugs to the appropriate brain area sometimes is difficult, due to poor permeability though the blood brain barrier, and so potential protective effects might be masked. Methods : Organotypic hippocampal slice culture (OHSC) method has the advantages of being relatively easy to prepare and of maintaining the general structure, including tissue integrity and the connections between cells. Drugs can easily be applied and neuronal damage can easily be quantified by using tissues and culture media. This study demonstrates neuroprotective effects of Puerariae radix (葛根, PR), Salviae miltiorrhizae radix (丹蔘, SR), Rhei rhizoma (大黃, RR), and Bupleuri radix (柴胡, BR). These were screenedand compared to MK-801, antagonist of NMDA receptors, by using OHSC of 1 week-old Sprague-Dawley rats. Oxygen/glucose deprivation (OGD) were conducted in an anaerobic chamber $(85%\;N_2,\;10%\;CO_2\;and\;5%\;H_2)$ in a deoxygenated glucose-free medium for 60 minutes. Water extracts of each herbs were treated to culture media with $5\;{\mu}g/ml$ for 48 hours. Results : Neuronal cell death in the cultures was monitored by densitometric measurements of the cellular uptake of propidium iodide (PI). PI fluorescence images were obtained at 48 hours after the OGD and medicinal herb treatment. Also TUNEL-positive cells in the CAI and DG regions and LDH concentrations in culture media were measured at 48 hours after the OGD. According to measured data, MK-801, PR, SR and BR demonstrated significant neuroprotective effect against excessive neuronal cell death and apoptosis induced by the OGD insult. Especially, PR revealed similar neuroprotective effect to MK-801 and RR demonstrated weak neuroprotective effect. Conclusions : These results suggest that OHSC can be a suitable method for screening of neuroprotective effects of medicinal herbs. (This work was supported by the research program of Dongguk University and Grant 01-PJ9-PG1-01CO03-0003 from Ministry of Health & Welfare.)

• Smart Structures and Systems
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• v.4 no.2
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• pp.221-232
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• 2008

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.