• Journal of Welding and Joining
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• v.27 no.1
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• pp.95-101
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• 2009

In case of manufacturing the high quality welds or pipeline, the full penetration weld has to be made along the weld joint. Thus the root pass welding is very important and has to be selected carefully. In this study, an experimental method for the selection of optimal welding condition was proposed in the root pass welding which was done along the V-grooved butt weld joint. This method uses the response surface analysis in which the width and height of back bead were chosen as the quality variables of the weld. The overall desirability function, which is the combined desirability function for the two quality variables, was used as the objective function for getting the optimal welding condition. In the experiments, the target values of the back bead width and the height are 6mm and zero respectively for the V-grooved butt weld joint of 8mm thickness mild steel. The optimal welding conditions could predict the back bead profile(bead width and height) as 6.003mm and -0.003mm. From a series of welding test, it was revealed that a uniform and full penetration weld bead can be obtained by adopting the optimal welding condition which was determined according to the method proposed.

• Design & Manufacturing
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• v.10 no.2
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• pp.44-49
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• 2016

The roll forming produces mass products using the continuous production process. Also we need the process that continuous long material or goods cutting into a desired length. Our study uses 3-D driving cutter and roll forming material as SPCC to investigate this. When we cut the material using the process of roll forming, the shear resistance is raised at the cutting punch's edge. The result is remained the trouble about burr and progressive deformation on the material. This study shows the method minimizing the above trouble. The material of punch was considering heat generated on the continuous production process. So we used the type of STD 61 for the material of punch and had the vacuum heat treatment for the surface hardness of HRC 53. The structure of the mold is designed with forming a double cam die at the upper punch and the both sides of central core. We conducted the experiment three times. In the result when had to make V-groove within the angle between 105 and 110 on the punch front end, we could get the minimum shear resistance on the punch front end. Also with the same condition we minimizes the material jams in the continuous production process.

• Journal of The Geomorphological Association of Korea
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• v.19 no.4
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• pp.27-37
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• 2012

This study investigated granite landforms formed by Hantan-gang fluvial erosion and deposition, or by weathering in the area neighboring the Seungil-gyo bridge in Cheorwon-gun Gangwon-do Korea, in which the contact zone of Myeongseongsan granite and Cheorwon lava plateau creates a unique landform. Major granite landforms are deeply weathered hill, sheet erosional landform, paleo-landform surface and paleosoil, micro-fluvial landforms such as pothole and groove, granite rampart, sand bar and boulder bar, former riverbed. And river cliffs on a weakly weathered dome act as a barrier to lateral shifting of the river.

• Archives of Plastic Surgery
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• v.33 no.5
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• pp.541-545
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• 2006

Purpose: There are many methods for the reconstruction of the facial defect after an excision of a skin cancer; such as skin graft, local flap, free flap, etc... Skin graft has its' limitations; it could remain in different color with in regards of the recipient to donor, with an unfavorable scar. Free flap can lead to big donor site morbidity with long operation time and uncontrolled scar as a disadvantage factor. Compared to the prior, local flap offers several merits; sufficient blood supply, good tissue quality and short operation time. We revised 'V-Y-S flap' for the facial defect, which proved to have favorable outcomes. Methods: Total 7 V-Y-S flaps were performed to patients with skin cancers(six squamous cell carcinoma and one basal cell carcinoma). Two of these flaps were combined with composite grafts, one with full thickness skin graft. Six patients were female and one male. The average diameter of defects after excision was 2.3 cm. The follow-up period was 18 months maximally. Results: We treated seven facial skin cancers with 'V-Y-S flap'. There were no flap necrosis, cancer recurrence and scar contracture as a result. Furthermore, this method also offers a favorable central scar line that is parallel to the nasolabial fold and the nasojugal groove, especially in the nasolabial area and superomedial side of the cheek. With this method, we could cover a maximum diameter of 4cm facial defect. Conclusion: In conclusion, it is suggested that V-Y-S flap is a useful method to cover facial defects after the excision of a skin cancer.

• Tribology and Lubricants
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• v.34 no.1
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• pp.33-41
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• 2018

This paper describes a new test rig for identification of rotordynamic force coefficients of squeeze film dampers (SFDs) in automotive turbochargers (TCs). Prior studies have mainly concentrated on relatively large-sized SFDs used in aircraft engines, turbocompressors, and turbopumps. The main objective of the current study is to propose a test rig for identification of dynamic force coefficients of small-sized SFDs (a journal diameter of ~11 mm). The current test rig consists of a journal, a SFD cartridge, four support rods, an upper structure, a data acquisition (DAQ) system, and an oil circulation unit. The annular gaps between the journal outer surface and SFD cartridge inner surface create SFD film lands. The damper has two parallel film lands separated by a central groove, having an axial length and depth of 3 mm. Each film land has a length of 4 mm with a $40{\mu}m$ radial clearance. The static load and dynamic impact tests identify the structural characteristics (i.e., stiffness and natural frequency) of the journal and assembled test rig. The measurements show good agreement with predictions. The SFD performance data from this test rig will be used to develop innovative TC rotor systems with improved NVH and reliability characteristics incorporating advanced SFD technology.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.4
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• pp.795-804
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• 1997

Developmental dental morphological anomalies are fusion, gemination, twinning, concrescence and etc. They may cause many problems in conservative, periodontal and esthetic aspects. Fusion is a condition where two separate tooth buds unite at some stage in their development to form a bifid crown. If tooth contact occurs early, at least before the start of calcification, the two teeth may be completely unites to form a single large tooth. If tooth contact occurs after the time when a portion of the tooth crown has completed its formation, there may be union of the roots only. In fusion the dentin is always confluent. Fusion teeth is more common in the deciduous than in the permanent dentition. Fused teeth are relatively rare, and are mostly mandibular anterior teeth. Fusion of normal and supernumerary teeth or between normal teeth may occurs. The exact etiology factor of fusion is unknown, but genetic and environmental factors seems to be related. A variety of complications and subsequent treatments have been suggested on this teeth. Periodontal conditions may arise due to a groove formed at the line of fusion of the two teeth. Crowding or Protrusion with potential for malocclusion or delayed eruption of adjacent teeth. Fusion teeth appear in the anterior region, they usually cause esthetic problems. Treatments vary depending on the problem, the location, and the extent of fusion. Treatment of fused teeth has been reported from endodontic, orthodontic, periodontic, surgical and multidisciplinary. This report presents the esthetic improvements by separation of two clinical crowns. Bone reduction or endodontic treatments are not required.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.3
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• pp.219-237
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• 2003

he purpose of this study was to compare the fracture resistance of the IPS Empress ceramic crown with 1.0mm width rounded shoulder, which is usually recommended in all ceramic crown, and 0.5mm width chamfer finish lines on the maxillary first premolar. 30 sound maxillary first premolars were selected and then storaged in 5% NaOCl and saline. 15 teeth were performed preparation for each group(1.0mm rounded shoulder, 0.5mm chamfer). After 30 stone dies were made for each group, the IPS Empress ceramic crowns were fabricated and cemented with resin cement(Bistite resin cement, Tokuyama Soda Co. LTD., Japan) on the natural teeth. The cemented crowns were mounted on the positioning jig and the universal testing machine(Zwick Z020, Zwick Co., Germany)was used to measure the fracture strength, with stress loading on the occlusal surface between buccal and lingual cusp. And also, three-dimensional finite element model was used to measure the stress distribution with two types of the finish lines(1.0mm rounded shoulder, 0.5mm chamfer) and two loading conditions(both buccal and lingual cusp inclination, lingual cusp inclination only). The result of the this study were as follows. In the fracture resistance experiment according to the finish line, the mean fracture strength of rounded shoulder(842N) showed higher value than that of the chamfer(590N) (p<0.05). In the three dimensional finite element analysis of all ceramic crown, metal die and natural teeth model did not show any differences in stress distribution between finish lines. Generally, when force was loaded on the occlusal inclination of buccal and lingual cusp, the stress was concentrated on the loading point and the central groove of occlusal surface. When force was loaded only on the occlusal inclination of lingual cusp, the stress was concentrated on the lingual finish line and loading point.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.1
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• pp.119-125
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• 2009

Fusion and gemination are irregularities in tooth development. It is often difficult to differentiate between gemination and fusion and it is common to refer to these anomalies as 'double teeth'. The deciduous teeth are most commonly involved, but in 0.1% of cases permanent teeth are affected, in which case aesthetic, funtional and periodontal problems can result. Double teeth present great difficulties in management and required a multidisciplinary approach. The central groove on the labial and palatal surfaces of a double tooth is extremely prone to caries, therefore early 'fissure sealing' is essential. In permanent dentition, surgical separation of fused teeth may be possible with subsequent orthodontic alignment and restorative treatment as needed to reshape the crown. Reshaping or reduction of a double tooth with a single canal may be attempted by modifying the appearance of the labial groove and the use of composite tints but is often impossible and extraction may be the only alternative. Orthodontic treatment and prosthetic replacement is then required. Implants may be an option for adolescents. The present study describes three clinical cases of double teeth in the position of the maxillary permanent incisors. The first case demonstrates an example of multidisciplinary care including surgical intraoral hemisection, root canal therapy, restorative and orthodontic treatment. The second and third cases describe the external and internal morphology of the two fused teeth by means of three dimensional dental computer tomography.

• Korean Journal of Veterinary Research
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• v.36 no.2
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• pp.255-264
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• 1996

This studies were carried out to identify the characteristics of the tongue of Korean native goat(Capra hircus) by macroscopy, microscopy and scanning microscopy. Korean native goat had torus linguae, median lingual sulcus, lingual fossa and ventral median fissure but did not have glossoepiglottic fold and terminal sulcus in the tongue. The whole length of tongue was $11.51{\pm}0.76cm$. The length of tongue apex, tongue body, tongue root and the torus linguae were $2.62{\pm}0.28$, $7.39{\pm}0.27$, $1.56{\pm}0.26$ and $6.37{\pm}0.29cm$, respectively. The width of tongue apex, torus linguae and tongue root were $3.41{\pm}0.24$, $3.74{\pm}0.29$ and $3.68{\pm}0.11$, respectively. The thickness of tongue apex was $1.60{\pm}0.10$, and the height of torus linguae was $1.52{\pm}0.15cm$. Filiform papillae were present at the tongue apex and the tongue body rostral to torus linguae. Fungiform papillae were scattered from tongue apex to rostral portion of torus linguae, being in abundance at the tongue apex. Vallate papillae were showed at the lateral portion of torus linguae, while lentiform papillae were present at its central portion. Conical papillae were located between vallate and lentiform papillae. The numbers of filiform, fungiform, conical, vallate and lentiform papillae were $46,980{\pm}1070.98$, $446.8{\pm}36.97$, $818.4{\pm}43.99$, $34.8{\pm}2.77$, and $255.6{\pm}39.30$, respectively. The average numbers of taste bud were $8.3{\pm}2.04$ in a fungiform papilla and $247.3{\pm}37.44$ in a vallate papilla. The filiform papilla had secondary and tertiary papillae. The height of filiform papilla was about $150{\mu}m$ and the diameter was $100{\mu}m$. The diameters of fungiform papillae were 350 to $550{\mu}m$. The long and short diameters of maximum-sized lentiform papilla were 4000 and $3000{\mu}m$, respectively, while those of minimum-sized papilla were 700 and $600{\mu}m$, respectively. The height of conical papillae was 450 to $600{\mu}m$ and diameter was 250 to $450{\mu}m$. The vallate papilla was round or oval in shape and its diameter was 500 to $850{\mu}m$. It had well-developed papillary groove around itself. The modified conical papillae were not observed in the tongue of Korean native goat.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.31-41
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• 2019

The toxic dinoflagellate Gymnodinium catenatum isolated from the southern coast of Korea was described under light and scanning electron microscopy, and its large subunit (LSU) rDNA was sequenced. In addition, the effects of temperature and salinity on its growth were investigated. The cells of G. catenatum, as viewed under the electronic microscope, were green-brown color, $38.1-77.4{\mu}m$ in length and $26.1-40.8{\mu}m$ in width. The epicone was conical, while the hypocone was trapezoidal. The nucleus was located at the central part of the cell. The apical groove was horseshoe-shaped and small pores were irregularly distributed on the cell surface. Molecular phylogeny based on LSU rDNA gene sequences showed that the Korean G. catenatum and previously reported species formed a monophyletic clade within Gymnodinium sensu stricto clade. The maximum growth rate of $0.37day^{-1}$, was obtained at $25^{\circ}C$ and 35 psu, and the maximum cell density of $1,073cells\;mL^{-1}$, was observed at $20^{\circ}C$ and 25 psu. However, G. catenatum did not grow at temperature < $15^{\circ}C$ and < $30^{\circ}C$. These results suggest that environmental conditions of summer and autumn in the southern coast of Korea may be favorable for the growth of G. catenatum.