• Journal of Korean Society on Water Environment
• /
• v.30 no.5
• /
• pp.477-485
• /
• 2014

Imha Reservoir is connected to Andong Reservoir via a diversion tunnel allowing water to pass between. The diversion tunnel is equipped with screens to exclude exotic largemouth bass due to their predatory impacts on prey assemblages resulting in a degradation of species richness of local fish fauna and extinction of local fish populations in Korea. Flow pattern changes resulting from the fish screens and trash racks were investigated using a computational fluid dynamics (CFD) model. Numerical simulations showed that the decrease in the discharge capacity of the tunnel is approximately 8.6% and the headloss coefficient for fish screen at Andong intake tower was determined to be 1.5. In order not to allow the small fishes enough to pass through the wire openings enter into Imha Reservoir through tunnel, the velocity in the tunnel should be greater than 1.48 m/s which is a critical ascending velocity of the bass. This study suggests that it can keep the velocity higher enough to exclude largemouth bass when a gate opens with the condition of 1.0m difference in water stage between two reservoirs.

• Magazine of the Korea Concrete Institute
• /
• v.8 no.6
• /
• pp.141-149
• /
• 1996

The reinforced high-strength-concrete beam subjected to flexure moment behaves more brittly than the moderate-strength-concrete beam reinforced with equal reinforcement ratio($\rho$/$\rho_b$). Test results show that when the concrete strength exceeds 830kg/$cm^2$, the maximum reinforcement ratio should be less than $0.6{\rho}_b$ for ductile behavior (${\rho}_b$=balanced steel ratio). The ratio of flexural strength between experimental results and analytical results with rectangular stress block decrease as the compressive strength of concrete increase. The shape of the compressive stress block distributed triangularly. because the ascending part of the stress-strain curve shows fairly linear response up to maximum stress in contrast to the nonlinear behavior of the medium and low strength specimens.

• Food Science and Preservation
• /
• v.20 no.4
• /
• pp.592-596
• /
• 2013

To stabilize the basal extraction conditions of Leonuri herbal products, three kinds of Leonurus sibiricus water extracts were prepared with different extraction conditions (boiling extraction (I), high thermal process & boiling extraction (II), and wet grinding & boiling extraction (III)), and their physiological properties were investigated. The extraction yields of the L. sibiricus water extracts were from 13.02 to 15.90%, with no significant difference among them. The polyphenol contents were significantly high in extracts (II) and (III) than in extract (I). The $IC_{50}$ for the electron-donating ability was the smallest in extracts (II), (III) and (I) in ascending order. The ABTS radical scavenging ability was significantly higher in extracts (II) and (III) than in extract (I). Also, the ACE in hibition ability for 5 mg/mL of each extract was high in extracts (II) and (III), but there was no significant difference among the three extracts in terms of their nitrite scavenging abilities. Extraction processes (II) and (III) were shown to be useful for preparing Leonurus sibiricus water extracts with healthful properties.

• Journal of Ocean Engineering and Technology
• /
• v.30 no.4
• /
• pp.268-276
• /
• 2016

This paper presents a study on the crashworthiness of the scaled-down stiffened panels used on a Korean icebreaker. In order to validate the crashworthiness of the panels, this paper provides various mechanical properties such as the results of a CVN test, quasi-static tensile test, and high-speed tensile test at arctic temperatures. Two types of steels (EH32 and FH32) were chosen for the material tests. CVN tests revealed that the two steels were equivalent up to −60℃ in terms of their impact energy absorption capacity. However, the toughness of FH32 was significantly superior to that of EH32. EH32 showed slightly higher flow stresses at all temperature levels compared to FH32. The improvement ratios of the yield strengths, tensile strengths, plastic hardening exponents, etc. for FH32, which were obtained from quasi-static tensile tests, showed an apparent ascending tendency with a decrease in temperature. Dynamic tensile test results were obtained for the two temperatures levels of 20℃ and −60℃ with two plastic strain rate levels of 1 s⁻¹ and 100 s⁻¹. A closed form empirical formula proposed by Choung et al. (2011;2013) was shown to be effective at predicting the flow stress increase due to a strain rate increase.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.5
• /
• pp.17-26
• /
• 2020

This study examined the structural effectiveness of the unbonded technique originally developed for seismic strengthening of unreinforced masonry walls on the basis of the prestressed steel bars and glass fiber (GF) grids. The masonry walls were strengthened by using individual steel bars or GF grids and their combination. Test results showed that the proposed technique was favorable in enhancing the strength, stiffness, and ductility of the masonry walls. When compared with the lateral load capacity, stiffness at the ascending branch of the lateral load-displacement curve, and energy dissipation capacity of the unstrengthened control wall, the increasing ratios were 110%, 120%, and 360%, respectively, for the walls strengthened with the individual GF grids, 140%, 130%, and 510%, respectively, for the walls strengthened with the individual steel bars, and 160%, 130%, and 840%, respectively, for the walls strengthened with the combination of steel bars and GF grids. The measured lateral load capacities of masonry walls strengthened with the developed technique were in relatively good agreement with the predictions by the equations proposed by Yang et al. Overall, the developed technique is quite promising in enhancing the seismic performance of unreinforced masonry walls.

• Sleep Medicine and Psychophysiology
• /
• v.5 no.2
• /
• pp.119-133
• /
• 1998

Attentional processes facilitate cognitive and behavioral performance in several ways. Attention serves to reduce the amount of information to receive. Attention enables humans to direct themselves to appropriate aspects of external environmental events and internal operations. Attention facilitates the selection of salient information and the allocation of cognitive processing appropriate to that information. Attention is not a unitary process that can be localized to a single neuroanatomical region. Before the cortical registration of sensory information, activation of important subcortical structures occurs, which is called as an orienting response. Once sensory information reaches the sensory cortex, a large number of perceptual processes occur, which provide various levels of perceptual resolution of the critical features of the stimuli. After this preattentional processing, information is integrated within higher cortical(heteromodal) systems in inferior parietal and temporal lobes. At this stage, the processing characteristics can be modified, and the biases of the system have a direct impact on attentional selection. Information flow has been traced through sensory analysis to a processing stage that enables the new information to be focused and modified in relation to preexisting biases. The limbic and paralimbic system play significant roles in modulating attentional response. It is labeled with affective salience and is integrated according to ongoing pressures from the motivational drive system of the hypothalamus. The salience of information greatly influences the allocation of attention. The frontal lobe operate response selection system with a reciprocal interaction with both the attention system of the parietal lobe and the limbic system. In this attentional process, the search with the spatial field is organized and a sequence of attentional responses is generated. Affective, motivational and appectitive impulses from limbic system and hypothalamus trigger response intention, preparation, planning, initiation and control of frontal lobe on this process. The reticular system, which produces ascending activation, catalyzes the overall system and increases attentional capacity. Also additional energetic pressures are created by the hypothalamus. As psychophysiological measurement, skin conductance, pupil diameter, muscle tension, heart rate, alpha wave of EEG can be used. Event related potentials also provide physiological evidence of attention during information process. NI component appears to be an electrophysiological index of selective attention. P3 response is developed during the attention related to stimulus discrimination, evaluation and response.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.6
• /
• pp.226-234
• /
• 2021

The objective of this study is to establish the fundamental design data for axial load-displacement relationship under axial monotonic or cyclic responses of seismic damping·isolation (SDI) units developed for ceiling structures. The main parameters include the installation of a spring, the number of rubber layer, prestress stress of bolts for connector between the spring and rubbers, and loading type. Test results showed that SDI units with a spring in the core and higher prestress stress of bolts tended to be higher stiffness at the ascending branch and more ductile behavior at the descending branch. This trends more notable for the specimens under monotonic load rather than cyclic loads. Consequently, the energy dissipation of SDI unit can be optimally designed with the following conditions: installation of a spring within 3-layer rubbers and prestress applied to the bolts at 10% of their yielding strength . When compared with the experimental tension capacity of the developed SDI units, the predictions by JIS B 2704-1 and KDS 31 00 are conservative under monotonic loading but higher by approximately 10% under cyclic loading.

• Journal of the Korean Society of Radiology
• /
• v.13 no.6
• /
• pp.879-887
• /
• 2019

The purpose of this study is to establish a physiological injection protocol according to body weight, in order to minimize amount of contrast medium and optimize contrast enhancement in pediatric patients performing thoracic CT examinations. The 80 pediatric patients under the age of 10 were studied. Intravenous contrast material containing 300 mgI/ml was used. The group A injected with a capacity of 1.5 times its weight, and groups B, C and D added 5 to 15 ml of normal saline with a 10% decrease in each. The physiologic model which can be calculated by weight about amount of injection of contrast medium and normal saline, flow rate and delay time were applied. To assess image quality, measured average HU value and SNR of superior vena cava, pulmonary artery, ascending and descending aorta, right and left atrium, right and left ventricle. CT numbers of subclavian vein and superior vena cava were compared to identify the effects of reducing artifacts due to normal saline. Comparing SNR according to the contrast medium injection protocol, significant differences were found in superior vena cava and pulmonary artery, descending aorta, right and left ventricle, and CT numbers showed significant differences in all organs. In particular, B group with a 10% decrease in contrast medium and an additional injection of saline showed a low degree of contrast enhancement in groups with a decrease of more than 20%. In addition, the group injected with normal saline greatly reduced contrast enhancement of subclavian vein and superior vena cava, and the beam hardening artifact by contrast medium was significantly attenuated. In conclusion, the application of physiological protocol for injection of contrast medium in pediatric thoracic CT examinations was able to reduce artifacts by contrast medium, prevent unnecessary use of contrast medium and improve the effect of contrast enhancement.

• Journal of Chest Surgery
• /
• v.37 no.8
• /
• pp.632-643
• /
• 2004

Background: The Histidine-Tryptophan-Ketoglutarate (HTK) solution has been shown to provide the excellent myocardial protection as a cardioplegia. The HTK solution has relatively low potassium as an arresting agent of myocardium, and low sodium content, and high. concentration of histidine biological buffer which confer a buffering capacity superior to that of blood.. Since HTK solution has an excellent myocardial protective ability, it is reported to protect myocardium from ischemia for a considerable time (120 minutes) with the single infusion of HTK solution as a cardioplegia. The purpose of this study is to evaluate the cardioprotective effect of HTK solution on myocardium when the ischemia is. exceeding 120 minutes at two different temperature (10 to 12$^{\circ}C$, 22 to 24$^{\circ}C$) using the Langendorff apparatus, Material and Method: Hearts from Sprague-Dawley rat, weighing 300 to 340 g, were perfused with Krebs-Henseleit solution at a perfusion pressure of 100 cm $H_2O$. After the stabilization, the heart rate, left ventricular developed pressure (LVDP), and coronary flow were measured. Single dose of HTK solution was infused into the ascending aorta of isolated rat heart and hearts were preserved at four different conditions. In group 1 (n=10), hearts were preserved at deep hypothermia (10∼12$^{\circ}C$) for 2 hours, in group 2 (n=10), hearts were preserved at moderate hypothermia (22∼24$^{\circ}C$) for 2 hours, in group 3 (n=10), hearts were preserved at deep hypothermia for 3 hours, and in group 4 (n=10), hearts were preserved at moderate hypothermia for 3 hours. After the completion of the preservation, the heart rate, left ventricular developed pressure, and coronary flow were measured at 15 minutes, 30 minutes, and 45 minutes after the initiation of reperfusion to assess the cardiac function. Biopsies were also done and mitochondrial scores were counted in two cases of each group for ultrastructural assessment. Result: The present study showed that the change of heart rate was not different between group 1 and group 2, and group 1 and group 3. The heart rate was significantly decreased at 15 minutes in group 4 compared to that of group 1 (p<0.05 by ANCOVA). The heart rate was recovered at 30 minutes and 45 minutes in group 4 with no significant difference compared to that of group 1. The decrease of LVDP was significant at 15 minutes, 30 minutes and 45 minutes in group 4 compared to that of group 1 (p < 0.001 by ANCOVA). Coronary flow was significantly decreased at 15 minutes, 30 minutes, and 45 minutes in group 4 compared to that of group 1 (p < 0.001 by ANCOVA). In ultrastructural assessment, the mean myocardial mitochondrial scores in group 1, group 2, group 3, and group 4 were 1.02$\pm$0.29, 1.52$\pm$0.26, 1.56$\pm$0.45, 2.22$\pm$0.44 respectively. Conclusion: The HTK solution provided excellent myocardial protection regardless of myocardial temperature for 2 hours. But, when ischemic time exceeded 2 hours, the myocardial hemodynamic function and ultrastructural changes were significantly deteriorated at moderate hypotherma (22∼ 24$^{\circ}C$). This indicates that it is recommended to decrease myocardial temperature when myocardial ischemic time exceeds 2 hours with single infusion of HTK solution as a cardioplegia.