• Journal of IKEEE
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• v.27 no.4
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• pp.518-523
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• 2023

The diagnosis of Inter Turn Short Circuits (ITSC) in induction motors is critical due to the escalating severity of faults resulting from even minor disruptions in the stator windings. However, diagnosing ITSC presents significant challenges due to similarities in noise and losses shared with 3-phase induction motors. Although artificial intelligence techniques have been explored for efficient diagnosis, practical applications heavily rely on model-based methods, necessitating further research to enhance diagnostic performance. This study proposed a diagnostic method applied the Clarke Transformation approach, focusing solely on current components while disregarding changes in rotating flux. Experimental results conducted over a 30-minute period, encompassing both normal and ITSC conditions, demonstrate the effectiveness of the proposed approach, with FAR(False Accept Rates) of 0.2% for normal-to-ITSC FRR(False Rejection Rates) and 0.26% for ITSC-to-normal FRR. These findings underscore the efficacy of the proposed approach.

• Tribology and Lubricants
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• v.39 no.6
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• pp.235-243
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• 2023

This paper presents the fabrication process of water-lubricated plastic bearings. Plastic bearings require good mechanical properties and tribological properties as well as elasticity and shock resistance, especially when lubricated in dirty water conditions. In this study, sleeve-type plastic bearings are produced by winding a prepreg sheet, which primary contains nitrile rubber (NBR)-modified epoxy, self-lubricating fillers, and various types of lattice-structured reinforcing fibers such as carbon, Aramid, and polyethylene terephthalate. A thermosetting epoxy is chemically modified with NBR to impart elasticity and low-friction characteristics in water conditions. Experimental investigations are conducted to examine the mechanical and tribological characteristics of the developed bearing materials, and the results are compared with the characteristics of a commercial plastic bearing (Thordon SXL), well known as a water-lubricated bearing. A Thordon bearing (mainly composed of polyurethane) exhibits an extremely low load-bearing capacity and is thus only suitable for medium loading (1~10MPa). The tribological characteristics of the test materials are evaluated through Falex block-on-ring (LFW-1) friction and wear tests. The results indicate that friction exhibited by the carbon-fiber-reinforced NBR-10wt.%-modified epoxy composite material, incorporated with the addition of 20wt.% UHMWPE and 6wt.% paraffin wax, is lower than that of the Thorden bearings, whereas its wear resistance surpass that of Thorden ones. Because of these features, the load carrying capacity of the fabricated composite (>10MPa) is higher than that of the Thorden bearings. These results confirm the applicability of water-lubricated plastic bearing materials developed in this study.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.32 no.3
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• pp.1-9
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• 2014

This article is the results of excavation data and it aims to interpret the composition facilities of the Royal garden at the Wanggung-ri site. The base of research was prepared through excavation and study on the royal garden at the Wanggung-ri site, which was constructed in Sa-bi period of Baek-je. The elements for the royal garden at the Wanggung-ri site were divided in 3 parts. - 1) Stonework facility 2) Installation for conveyance of water : Large moat-shaped ditch and Winding waterway(1~6 and water catchment) 3) Square cornerstone building. In this article, I arrange the basic data about facilities and function of the royal garden for making recovery of original form. First of all, I reason that stonework facilities were in charge to make space for catchment and boundary. Especially the Round angel rectangular stonework facility took charge of complex roles as catchment and water conveyance, and water can be transferred to the large moat-shaped ditch through joint between them. I confirmed that the round angel rectangular stonework facility and the large moat-shaped ditch which were connected by joint are one of the facilities in the royal garden. The large moat-shaped ditch protected the eastern, the northern walls and workshop site under the inclined plane to minimize the damage. Also, the large moat-shaped ditch took several roles, especially water catchments and landscaping. The large moat-shaped ditch was continually used from the period of Baek-je to the unified Silla, as a result it was completely deposited inside. After that, the 6 winding waterway were built in the western inclined plane with similar needs with the large moat-shaped ditch, and the square cornerstone building was built in same time. I noticed that the square cornerstone building was built as a part of the royal garden in Sa-bi period of Baek-je through the remains of Baek-je tiles around the building. After that, the square cornerstone building was built in same place as reconstruction.

• Horticultural Science & Technology
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• v.30 no.4
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• pp.449-462
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• 2012

The objectives of this study were to measure the range of motion for joints and muscle activation of upper limb for flower arrangement tasks for physical rehabilitation and to test horticultural therapy programs using flower arrangement tasks for improving upper limb function of the patients with stroke. Major flower arrangement tasks were classified with eight tasks (cutting 1, thick stem; cutting 2, thin stem; fixing 1, long stem; fixing 2, short stem; rolling a leaf; bending 1, thick stem; bending 2, thin stem; and winding, using a wire) based on the occupational analysis. When eight male university students (mean age $24.1{\pm}2.5$ years) conducted the eight flower arrangement tasks, range of motion for joints and muscle activation of upper limb were measured by a 3D motion analyzer and electromyography, respectively. Based on the results of the range of motion and muscle activation of upper limb, horticultural therapy programs using flower arrangement tasks (total 33 sessions) for improving upper limb function of the patients with stroke was conducted at a rehabilitation hospital, Seoul, South Korea and then the range of motion, grip strength, and upper limb function of the patients were tested. Among the eight flower arrangement tasks, cutting 1, winding, and bending 1 induced the highest value for the range of motion in joints of shoulder, elbow, and wrist, respectively (P < 0.001). In terms of muscle activation, eight flower arrangement tasks performed in this study showed various patterns of muscle activation and several muscles were simultaneously used for each task (P < 0.001). In addition, thickness and length of the materials used in a task had a prominent effect on the range of motion for joints and muscle activation of upper limb (P < 0.001). The stroke patients had positive effects for their range of motion of upper limb (shoulder, forearm, and elbow), grip strength, and overall upper limb function through the horticultural therapy program. Thus, this study suggested that flower arrangement tasks would be a potential horticultural activity for physical rehabilitation program. It would be interesting to apply a customized horticultural therapy program using flower arrangement tasks according to the symptoms of patient for physical rehabilitation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.351-373
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• 2019

The cold eddies around the Ulleung Basin in the East Sea were identified from satellite altimeter sea level data using the Winding-Angle method from 1993 to 2015. Among the cold eddies, the Dokdo Cold Eddies (DCEs), which were formed at the first meandering trough of the East Korea Warm Current (EKWC) and were pinched off to the southwest from the eastward flow, were classified and their migration patterns were analyzed. The vertical structures of water temperature, salinity, and flow velocity near the DCE center were also examined using numerical simulation and observation data provided by the Hybrid Coordinate Ocean Model and the National Institute of Fisheries Science, respectively. A total of 112 DCEs were generated for 23 years. Of these, 39 DCEs migrated westward and arrived off the east coast of Korea. The average travel distance was 250.9 km, the average lifespan was 93 days, and the average travel speed was 3.5 cm/s. The other 73 DCEs had moved to the east or had hovered around the generated location until they disappeared. At 50-100 m depth under the DCE, water temperature and salinity (T < $5^{\circ}C$, S < 34.1) were lower than those of ambient water and isotherms made a dome shape. Current faster than 10 cm/s circulates counterclockwise from the surface to 300 m depth at 38 km away from the center of DCE. After the EKWC separates from the coast, it flows eastward and starts to meander near Ulleungdo. The first trough of the meander in the east of Ulleungdo is pushed deep into the southwest and forms a cold eddy (DCE), which is shed from the meander in the south of Ulleungdo. While a DCE moves westward, it circumvents the Ulleung Warm Eddy (UWE) clockwise and follows U shape path toward the east coast of Korea. When the DCE arrives near the coast, the EKWC separates from the coast at the south of DCE and circumvents the DCE. As the DCE near the coast weakens and extinguishes about 30 days later after the arrival, the EKWC flows northward along the coast recovering its original path. The DCE steadily transports heat and salt from the north to the south, which helps to form a cold water region in the southwest of the Ulleung Basin and brings positive vorticity to change the separation latitude and path of the EKWC. Some of the DCEs moving to the west were merged into a coastal cold eddy to form a wide cold water region in the west of Ulleung Basin and to create a elongated anticlockwise circulation, which separated the UWE in the north from the EKWC in the south.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.106-112
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• 2016

In this study, circular concrete column specimens confined by carbon sheet tube with different winding angles and different number of carbon sheet plies(3T, 5T and 7T) were tested to propose design equations and a strength reduction factor. Specimens were designed by 300 mm diameter and 600 mm height with $90^{\circ}{\pm}0^{\circ}$, $90^{\circ}{\pm}30^{\circ}$, $90^{\circ}{\pm}45^{\circ}$, $90^{\circ}{\pm}60^{\circ}$, $90^{\circ}{\pm}75^{\circ}$ and $90^{\circ}{\pm}90^{\circ}$ carbon fiber angles. A 10,000 kN UTM was used for compressive strength test of specimens by displacement control method with 0.01 mm/sec velocity. Estimation equations of compressive strength and ultimate strain of circular concrete column specimens confined by carbon sheet tube using a regression analysis and a strength reduction factor to apply ultimate strength design method of concrete were proposed. The strength reduction factor(${\phi}$) of circular concrete columns confined by carbon sheet tube was estimated as 0.64 by the Monte Carlo Analysis Method. Manufacture and construction process have to be perfectly managed by construction managers because the structural capacities of carbon tubes were depends on construction abilities of manufacturing operators.

• Composites Research
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• v.18 no.4
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• pp.1-7
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• 2005

In-situ structural health monitoring of filament wound pressure tanks were conducted during water-pressurizing test using embedded fiber Bragg grating (FBG) sensors. We need to monitor inner strains during working in order to verify the health condition of pressure tanks more accurately because finite element analyses on filament wound pressure tanks usually show large differences between inner and outer strains. Fiber optic sensors, especially FBG sensors can be easily embedded into the composite structures contrary to conventional electric strain gages (ESGs). In addition, many FBG sensors can be multiplexed in single optical fiber using wavelength division multiplexing (WDM) techniques. We fabricated a standard testing and evaluation bottle (STEB) with embedded FBG sensors and performed a water-pressurizing test. In order to increase the survivability of embedded FBG sensors, we suggested a revised fabrication process for embedding FBG sensors into a filament wound pressure tank, which includes a new protecting technique of sensor heads, the grating parts. From the experimental results, it was demonstrated that FBG sensors can be successfully adapted to filament wound pressure tanks for their structural health monitoring by embedding.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1265-1272
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• 2014

This study performed the progressive failure analysis of adhesive joints of a composite pressure vessel with a separated dome by using a cohesive zone model. In order to determine the input parameters of a cohesive element for numerical analysis, the interlaminar fracture toughness values in modes I and II and in the mixed mode for the adhesive joints of the composite pressure vessel were obtained by a material test. All specimens were manufactured by the filament winding method. A mechanical test was performed on adhesively bonded double-lap joints to determine the shear strength of the adhesive joints and verify the reliability of the cohesive zone model for progressive failure analysis. The test results showed that the shear strength of the adhesive joints was 32MPa; the experiment and analysis results had an error of about 4.4%, indicating their relatively good agreement. The progressive failure analysis of a composite pressure vessel with an adhesively bonded dome performed using the cohesive zone model showed that only 5.8% of the total adhesive length was debonded and this debonded length did not affect the structural integrity of the vessel.

• Journal of fish pathology
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• v.10 no.1
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• pp.53-63
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• 1997

In this study, poikilocyte rate and histopathological observation of flounder, Paralichthys olivaceus, treated with formalin, neutral-formalin(0, 50, 100, 150, 200, 300 ppm) at two different temperatures (15 and $25^{\circ}C$) were conducted to determine the time need for recovery. In all test chamber, formalin was more toxic than neutral-formalin and moderate lesions were not observed at low concentration of formalin and neutral-formalin(50~100 ppm). As expectedly, time need for recovery of gill and kidney tissues was lengthening as increasing chemical concentration and temperature. Treatments caused edema, winding of secondary gill lamella, seperation of epithelial layer and thrombosis of secondary gill lamella in the gill; edema, hydropic and hyaline droplet degeneration in the kidney. Representatively, recovery period of fish gill that had been exposed to 300 ppm formalin and neutral-formalin was about 120 and 72 hr($25^{\circ}C$). 72 and 48 hr($15^{\circ}C$). Recovery period of kidney was about 72 and 48 hr($25^{\circ}C$), 48 and 48 hr($15^{\circ}C$) respectively. Maximum value of poikilocyte rate(27.84%) was shown in formalin 300 ppm treated fish at $25^{\circ}C$. Tendency of decreasing poikilocyte rate was similiar to recovery of tissues in treated fish.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3176-3183
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• 2010

A multi-scale fatigue life prediction methodology of composite pressure vessels subjected to multi-axial loading has been proposed in this paper. The multi-scale approach starts from the constituents, fiber, matrix and interface, leading to predict behavior of ply, laminates and eventually the composite structures. The multi-scale fatigue life prediction methodology is composed of two steps: macro stress analysis and micro mechanics of failure based on fatigue analysis. In the macro stress analysis, multi-axial fatigue loading acting at laminate is determined from finite element analysis of composite pressure vessel, and ply stresses are computed using a classical laminate theory. The micro stresses are calculated in each constituent from ply stresses using a micromechanical model. Three methods are employed in predicting fatigue life of each constituent, i.e. a maximum stress method for fiber, an equivalent stress method for multi-axially loaded matrix, and a critical plane method for the interface. A modified Goodman diagram is used to take into account the generic mean stresses. Damages from each loading cycle are accumulated using Miner's rule. Monte Carlo simulation has been performed to predict the overall fatigue life of a composite pressure vessel considering statistical distribution of material properties of each constituent, fiber volume fraction and manufacturing winding angle.