• Korean Journal of Applied Biomechanics
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• v.15 no.4
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• pp.25-42
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• 2005

The study was to investigate kinematic difference between flexed and extended type of knee during Jigeo-Cha-Gi in Taekwon-Do. For this subjects participated were consisted of weights of fin (1), bantam (1) and welter class(1) of male 3 national representative level skilled in two type(flexed and extended type) of Jigeo-Cha-Gi. 3D cinematography analysis was performed for motion analysis and Kwon 3D ver. 3.1) was used for 3D coordinates & analysis variables calculation. In Temporal variable there was no significant difference statistically in all phases & total elapsed time between flexed and extended type, but flexed type was delayed more 0.016 sec than extended type. In displacement of COG there was significant difference in level of p<.05 showing longer mean 6.13 cm in case of flexed type than extended type in displacement of COG during all phase and too significant difference in level of p<.01 showing longer mean 4.4 cm in case of flexed type than extended type in displacement of COG in follow through phase. In velocity of COG there was significant difference in level of p<.001 showing higher mean 15.53cm/s in case of flexed type than extended type in velocity of COG(Y direction) during targeting phase and peak velocity(Y) was more fast 8.74 cm/s in extended type than flexed type. In velocity of leading leg in forward direction(Y) there was significant difference in level of p<.05 showing higher thigh mean value in case of flexed type than extended type but showing higher foot mean value in extended type at level of p<.001 than flexed type in velocity of COG(Y direction). In velocity of leading leg in vertical direction(Z) there was no significant difference in the second & third phase in case of vertical velocity level, but momentum transferred efficiently form proximal to distal endpoint. In front-back & right-left orientation angle of trunk there was possibility of more stable Jigeo-Cha-Gi in extended than flexed type by decreasing in right-left orientation angle of trunk. In relative angle of lower leg(hip, knee, ankle) there was significant difference in level of p<.001 showing longer mean 32.74 deg. in case of flexed type than extended type in hip joint during the second phase but maintained insufficient extended knee of mean 168 deg. in targeting phase.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.11
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• pp.1434-1443
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• 1999

The turbulent fluctuations of temperature and two components of velocity have been measured with hot- and cold-wires in the Thermally Stratified Wind Tunnel(TSWT). Using the fin-tube heat exchanger type heaters and the neural network control algorithm, both stable ($dT/dz=109.4^{\circ}C$) and unstable ($dT/dz=-49.1^{\circ}C$) stratifications were realized. An ambient air jet was issued normally into the cross flow($U_{\infty}=1.0 m/s$) from a round nozzle(d = 6 mm) flushed at the bottom waII of the wind tunnel with the velocity ratio of $5.8(U_{jet}/U_{\infty})$. The characteristics of turbulent dispersion in the cross flow jet are found to change drastically depending on the thermal stratification. Especially, in the unstable condition, the vertical velocity fluctuation increases very rapidly at downstream of jet. The fluctuation velocity spectra and velocity-temperature cospectra along the jet centerline were obtained and compared. In the case of stable stratification, the heat flux cospectra changes Its sign from a certain point at the far field because of the restratification phenomenon. It is inferred that the main reason in the difference between the vertical heat fluxes is caused by the different length scales of the large eddy motions. The turbulent kinetic energy and scalar dissipation rates were estimated using partially non-isotropic and isotropic turbulent approximation. In the unstable case, the turbulent energy dissipation decreases more rapidly with the downstream distance than in the stable case.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.10
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• pp.710-718
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• 2010

A numerical study was performed to predict refrigerant charge amount in a mini-channel condenser for a R410A residential air-conditioning system. Multi-channel flat tubes with 12 mini-channels of 1.17 mm average hydraulic diameter for each tube were applied to the condenser. The condenser consisted of 3 passes, and the first, second, and third pass had 44, 19, and 11 tubes, respectively. Each pass was connected by a vertical header. In this study, the condenser was divided into 410 finite volumes, and analyzed by an $\varepsilon$-NTU method. With thermophysical properties and void fraction models for each volume element, the R410A amount distribution and a total charge amount in the condenser were calculated. The predicted total charge amount was compared with the experimentally measured charge amount under a standard ARI A condition. The developed model could predict the charge amount in the mini-channel condenser within prediction errors from -23.9% to -3.0%. Air velocity distribution at the condenser face was considered as non-uniform and uniform by the simulation model, and its results showed that the air velocity distribution could significantly influence the charge amount and vapor phase distribution in the condenser.

• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.130-140
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• 1997

The osteological features of Rhodeus uyekii were examined. In this study, the detailed descriptions of cranium, vertebra and fin skeleton of Rhodeus uyekii are presented. R. uyekii had the following characteristics ; there was no fontanell in the cranium ; there was no process of supraethmoid ; the free interneural spine was large and flat ; the dorsal process of the supraoccipital was high and triangular ; the fourth infraorbital was reduced ; in the urohyal, the hypohyal attachment is bifurcated, the horizontal and vertical plate has a elongated rhombus shape with posterior edge pointed ; there was no coracoid foramen in the shoulder girdle ; there was no uroneural in the first preural centrum.

• Korean Journal of Ichthyology
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• v.20 no.1
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• pp.66-69
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• 2008

A single specimen (351.1 mm SL) of the sleek unicornfish, Naso hexacanthus, belonging to Acanthuridae was firstly collected from the coastal waters of Jeju Island, Korea. The species is characterized by having brownish vertical bands on the dorsal fin and two pale purple bony plates on caudal peduncle. We add this species to the Korean fish fauna and propose its new Korean name, "Nam-bang-pyo-mun-jwi-chi."

• Korean Journal of Ichthyology
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• v.20 no.1
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• pp.74-77
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• 2008

Three juvenile specimens (38.8~51.5 mm SL) of the opistognathid fish, Opistognathus hongkongiensis Chan were collected off the Jeju Island, southern Korea. O. hongkongiensis is characterized by having a large mouth, dark brown vertical bands on sides, and yellow dorsal fin without a black blotch. We described it as the first record to Korean fish fauna, and proposed the new Korean name, "Jul-hu-ak-chi" for this species.

• Smart Structures and Systems
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• v.18 no.2
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• pp.249-265
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• 2016

A bimorph piezoelectric energy harvester is developed for harvesting energy under the vortex induced vibration and it is integrated to a host structure of a trapezoidal plate without changing its passive dynamic properties. It is aimed to select trapezoidal plate as similar to a vertical fin-like structure which could be a part of an air vehicle. The designed energy harvester consists of an aluminum beam and two identical multi fiber composite (MFC) piezoelectric patches. In order to understand the dynamic characteristic of the trapezoidal plate, finite element analysis is performed and it is validated through an experimental study. The bimorph piezoelectric energy harvester is then integrated to the trapezoidal plate at the most convenient location with minimal structural displacement. The finite element model is constructed for the new combined structure in ANSYS Workbench 14.0 and the analyses performed on this particular model are then validated via experimental techniques. Finally, the energy harvesting performance of the bimorph piezoelectric energy harvester attached to the trapezoidal plate is also investigated through wind tunnel tests under the air load and the obtained results indicate that the system is a viable one for harvesting reasonable amount of energy.

• Korean Journal of Ichthyology
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• v.36 no.3
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• pp.282-287
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• 2024

The Yellow-dotted butterflyfish, Chaetodon selene is newly reported from Korea based on a single juvenile specimen (28.6 mm SL) collected from rocky reef of the Jwasarido Island, southern Korea. The present specimen represents the first reliable record of C. selene from Korea supported by a voucher specimen. The specimen is characterized by having 12 spines of dorsal fin, and a dark lunate-shaped marking on posterior half of body as well as a vertical black bar crossing eye. A new Korean name, "No-rang-jeom-na-bi-go-gi", is adopted for the species.

• Applied Microscopy
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• v.52
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• pp.1.1-1.8
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• 2022

As semiconductor device architecture develops, from planar field-effect transistors (FET) to FinFET and gate-all-around (GAA), there is an increased need to measure 3D structure sidewalls precisely. Here, we present a 3-Dimensional Atomic Force Microscope (3D-AFM), a powerful 3D metrology tool to measure the sidewall roughness (SWR) of vertical and undercut structures. First, we measured three different dies repeatedly to calculate reproducibility in die level. Reproducible results were derived with a relative standard deviation under 2%. Second, we measured 13 different dies, including the center and edge of the wafer, to analyze SWR distribution in wafer level and reliable results were measured. All analysis was performed using a novel algorithm, including auto fattening, sidewall detection, and SWR calculation. In addition, SWR automatic analysis software was implemented to reduce analysis time and to provide standard analysis. The results suggest that our 3D-AFM, based on the tilted Z scanner, will enable an advanced methodology for automated 3D measurement and analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.35-42
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• 2020

Electromechanical Actuator(EMA) for flight vehicles generally serves to control the fin deflection angle or the thrust vector angle. This paper deals with design and development of EMA for both aerodynamic control and thrust vector control. In this paper, a novel compact EMA is proposed that can simultaneously control both the tail fin and the jet vane with one actuator and detach the jet vane after vertical launch and rapid turn of the flight vehicle so as to increase efficiency during flying to target. To do this, we designed the EMA using a push-push link mechanism and derived a mathematical model. The mathematical model is validated by comparing simulation result and experimental data. The performance and reliability of the proposed EMA have been verified through performance test, environmental test and ground test. The proposed EMA is expected to be useful as an EMA for flight vehicles because of its simple and compact structure, as well as its performance and reliability.