• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.689-697
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• 2023

The high-pressure hydrogen valve is intended to supply hydrogen charged at high pressure in the hydrogen tank to the fuel cell stack, which decompresses high-pressure hydrogen gas to low pressure and primarily limits the excessive flow. It consists of a pilot valve, a main valve, and a excessive flow valve to operate in a wide pressure range from 2 to 70 MPa of charging pressure. The opening characteristics of the valve were confirmed by computation fluid dynamics applying the moving grid technique. The behavior of the valve was predicted by predicting the force acting on the valve over time. In addition, the difference in behavior according to supply pressure was compared.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.374-386
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• 2010

Recently, the theoretical and experimental research is being made actively in control character of waves of perforated-wall caisson breakwater like the slit caisson. This study showed that the character of reflection coefficient and the wave pressure acting on the front and inner of slit caisson were estimated in two and three dimensional numerical wave flume and compared each other. The numerical experiment was set and conducted by various cases as to a variety of wave steepness under 7 sec, 9 sec, 11sec and 13 sec period condition. In this study using a 2 and 3 dimensional numerical wave flume, it applied the Model for the immiscible two-phase flow based on the Naveir-Stokes Equations. This technique can easily reproduce a complicated physical phenomenon more than others and organize the program simply. According to the results of the experiment, the reflection coefficient was estimated high in short-period waves. However, 2-dimensional numerical experiment and 3-dimensional numerical experiment were the same in case of the long-period waves and high wave steepness. And to conclude in case of short-period waves the pressures were a relatively small difference between the two, but there was a big gap in longperiod waves and high wave steepness.

• Geomechanics and Engineering
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• v.35 no.2
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• pp.195-208
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• 2023

The nodular diaphragm wall (NDW) is a novel type of foundation with favorable engineering characteristics, which has already been utilized in high-rise buildings and high-speed railways. Compared to traditional diaphragm walls, the NDW offers significantly improved vertical bearing capacity due to the presence of nodular parts while reducing construction time and excavation work. Despite its potential, research on the vertical bearing characteristics of NDW requires further study, and the investigation and visualization of its displacement pattern and failure mode are scant. Meanwhile, the measurement of the force component acting on the nodular parts remains challenging. In this paper, the vertical bearing characteristics of NDW are studied in detail through the indoor model test, and the displacement and failure mode of the foundation is analyzed using particle image velocimetry (PIV) technology. The principles and methods for monitoring the force acting on the nodular parts are described in detail. The research results show that the nodular part plays an essential role in the bearing capacity of the NDW, and its maximum load-bearing ratio can reach 30.92%. The existence of the bottom nodular part contributes more to the bearing capacity of the foundation compared to the middle nodular part, and the use of both middle and bottom nodular parts increases the bearing capacity of the foundation by about 9~12% compared to a single nodular part of the NDW. The increase in the number of nodular parts cannot produce a simple superposition effect on the resistance born by the nodular parts since the nodular parts have an insignificant influence on the exertion and distribution of the skin friction of NDW. The existence of the nodular part changes the displacement field of the soil around NDW and increases the displacement influence range of the foundation to a certain extent. For NDWs with three different nodal arrangements, the failure modes of the foundations appear to be local shear failures. Overall, this study provides valuable insights into the performance and behavior of NDWs, which will aid in their effective utilization and further research in the field.

• Journal of the Korean Geotechnical Society
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• v.31 no.1
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• pp.5-14
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• 2015

Seabed may undergo large excess pore water pressure in the case of long duration of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. Thus, it is necessary to develop a numerical technique which can precisely evaluate the dynamic response of seabed due to wave action. In this study, a new numerical technique named mixed model (2D NIT & FLIP models) was proposed. The dynamic wave pressure and water flow velocity acting on the boundary between seabed and the wave field was estimated using 2D-NIT model. This result was used as input data in FLIP program for investigation of dynamic response of seabed. To secure the reliability of the mixed model, the numerical analysis results of the mixed model were compared with Yamamoto's solution and Chang's experiment results. The comparison results indicated that there were some differences between them, but the general trend of the effective stress increment and the excess pore water pressure along the depth of seabed was similar to each other. Thus, this study clearly supports the plausibility of the numerical analysis of the mixed model.

• International Journal of Oral Biology
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• v.33 no.1
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• pp.1-5
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• 2008

Adenosine 5'-triphosphate (ATP) is an important extracellular signaling molecule which is involved in a variety of physiological responses in many different tissues and cell types, by acting at P2 receptors, either ionotropic (P2X) or G protein-coupled metabotropic receptors (P2Y). P2X receptors have seven isoforms designated as $P2X_{1^-}P2X_7$. In this study, we investigated the electrophysiological and pharmacological properties of rat $P2X_{1^-}P2X_4$ currents by using whole-cell patch clamp technique in a heterologous expression system. When ATP-induced currents were analyzed in human embryonic kidney (HEK293) cells following transient transfection of rat $P2X_{1^-}P2X_4$, the currents showed different pharmacological and electrophysiological properties. ATP evoked inward currents with fast activation and fast desensitization in $P2X_{^1-}$ or $P2X_{3^-}$ expressing HEK293 cells, but in $P2X_{2^-}$ or $P2X_{4^-}$ expressing HEK293 cells, ATP evoked inward currents with slow activation and slow desensitization. While PPADS and suramin inhibited $P2X_2$ or $P2X_3$ receptor-mediated currents, they had little effects on $P2X_4$ receptor-mediated currents. Ivermectin potentiated and prolonged $P2X_4$ receptor-mediated currents, but did not affect $P2X_2$ or $P2X_3$ receptor-mediated currents. We suggest that distinct pharmacological and electrophysiological properties among P2X receptor subtypes would be a useful tool to determine expression patterns of P2X receptors in the nervous system including trigeminal sensory neurons and microglia.

• Journal of Digital Convergence
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• v.13 no.8
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• pp.101-112
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• 2015

The company's technical reserves in accordance with the internal skills and external technology commercialization capacity and to analyze the impact on the performance of technology commercialization and financial performance of the company. External technology funding, internal and external technologies marketing, internal and external technologies production, outside of the external Technology Commercialization technique was investigated to affect the financial performance. Financing, marketing capability, and the production base is completely mediated effect acting from within the technology business technical achievement, but funding and the regulation of full-mediated effects on the financial performance in the external action, technical marketing skills and capacity of external technology in part mediated effect was investigated by the effect on financial performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1174-1181
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• 2003

The flow around a circular cylinder was controlled by attaching O-rings to reduce drag force acting on the cylinder. Four experimental models were tested in this study; one smooth cylinder of diameter D (D=60mm) and three cylinders fitted with O-rings of diameters d=0.0167 D, 0.05D and 0.067 D with pitches of PPD=2D, 1D, 0.5D and 0.25D. The drag force, mean velocity and turbulence Intensity profiles in the near wake behind the cylinders were measured for Reynolds numbers based on the cylinder diameter in the range of Re$_{D}$=7.8$\times$10$^3$~1.2$\times$10$^{5}$ . At Re$_{D}$=1.2$\times$10$^{5}$ , the cylinder fitted with O-rings of d=0.0167D in a pitch interval of 0.25D shows the maximum drag reduction of about 5.4%, compared that with the smooth cylinder. The drag reduction effect of O-rings of d=0.067D is not so high. For O-ring circulars, as the Reynolds number increases, the peak location of turbulence intensity shifts downstream and the peak magnitude is decreased. Flow field around the cylinders was visualized using a smoke-wire technique to see the flow structure qualitatively. The size of vortices and vortex formation region formed behind the O-ring cylinders are smaller, compared with the smooth cylinder.der.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.151-158
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• 2009

To implement the insects' flapping flight for developing flapping MAVs(micro air vehicles), the unsteady flow characteristics of the insects' forward flight is investigated. In this paper, two-dimensional FSI(Fluid-Structure Interaction) simulations are conducted to examine realistic flow features of insects' flapping flight and to examine the flexibility effects of the insect's wing. The unsteady incompressible Navier-Stokes equations with an artificial compressibility method are implemented as the fluid module while the dynamic finite element equations using a direct integration method are employed as the solid module. In order to exchange physical information to each module, the common refinement method is employed as the data transfer method. Also, a simple and efficient dynamic grid deformation technique based on Delaunay graph mapping is used to deform computational grids. Compared to the earlier researches of two-dimensional rigid wing simulations, key physical phenomena and flow patterns such as vortex pairing and vortex staying can still be observed. For example, lift is mainly generated during downstroke motion by high effective angle of attack caused by translation and lagging motion. A large amount of thrust is generated abruptly at the end of upstroke motion. However, the quantitative aspect of flow field is somewhat different. A flexible wing generates more thrust but less lift than a rigid wing. This is because the net force acting on wing surface is split into two directions due to structural flexibility. As a consequence, thrust and propulsive efficiency was enhanced considerably compared to a rigid wing. From these numerical simulations, it is seen that the wing flexibility yields a significant impact on aerodynamic characteristics.

• The Journal of Art Theory & Practice
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• no.1
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• pp.7-22
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• 2003

What is 'Art Theory'? In the western sense, the term poses a vague ambiguity, and in the eastern, it is rather an abstract and metaphysical concept. As for etymology, theory is derived from theoria and theoria from theoros. It refers to an act of viewing or seeing, of course not in a metaphysical sense. Plato understood it as 'eide'. During the time of Plotinus, theoria encompassed gazing at every possible reality, and this gazing, that is theoria, is closely related to reality as aunit that theoriacan perceive. However, we tend to distinguish, as other scientists of dualism have done, studio art from theory since a pre-modern approach to art has been particularly tuned to studio practice, set apart from theory. Therefore, in studio classes, students are expected to learn the subject based on the foundational curriculum methods such as medium, genre, technique:, rather than bringing out their own interpretations and discussing theories. As a result, students have become artists, who are not able to understand their own art. Art professors who conduct class in studio are required to proceed with specific 'theories' as well as 'intellectual reflections'. In this respect, this thesis presents poiesis and an idea of 'acting out'. Although art history and aesthetic theory tend to view art as a finished product, actual art-making and related theories should not only be acknowledged as 'completion' (finition) but also be accompanied by theoretic interpretations of the act itself and process. Accordingly, it is to accept and appreciate art as finished result in view of current theory and aesthetics thus boils down to aisthesis. Likewise, poietics starts from a point where an artist is related to studio and examines the 'work process' that extends as far as to the exact end of work. Through the study of such relationship, it is possible that theory understands 'studio' and 'process', and an artist can grant an independent meaning to studio where s/he pours her/his heart out creating a work of art. Theory is a study on artistic discovery thus should be equipped with functions that can accommodate fortuity, imitation, thinking, culture, and surrounding.

• The Korean Journal of Pain
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• v.13 no.2
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• pp.182-186
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• 2000

Background: Ropivacaine is a new amide local anesthetics, having therapeutic properties similar to those of bupivacaine but less cardiovascular toxicity and motor blockade. The aim of this study was to evaluate the effects of ropivacaine used in stellate ganglion block (SGB) compared with those of lidocaine or bupivacaine. Methods: This prospective and crossover study performed in twenty patients with sudden sensory neural hearing loss. All patients received three times SGB, in the paratracheal approach using 8 ml of 1% lidocaine, 0.2% bupivacaine, and 0.2% ropivacaine respectively without any orders. Onset time and action duration of Horner's syndrome were observed after each SGB. Results: Onset time of ropivacaine was the middle of the three agents; earlier lidocaine and slower bupivacaine. Lidocaine ($3.0{\pm}1.9$ min), bupivacaine ($4.1{\pm}2.9$ min) and ropivacaine ($3.3{\pm}1.3$ min). But there were no significant differences; Action duration of Horner's syndrome of ropivacaine (223.6?105.2 min) was longer than lidocaine ($134.6{\pm}77.3$ min) and shorter than bupivacaine ($241.2{\pm}115.8$ min). There were significant differences in the action duration of each local anesthetics (P<0.05). There was no critical side effects and temporary foreign body sensation was the most common side effect. Conclusions: We conclude that ropivacaine is a good alternative in SGB instead of lidocaine or bupivacaine. Ropivacaine is a long acting local anesthetic similar to those of bupivacaine with wide margin of safety. However, optimal concentration and volume of ropivacaine in SGB should be studied.