• Korean Journal of Materials Research
• /
• v.22 no.3
• /
• pp.123-129
• /
• 2012

The microstructures and mechanical properties of friction stir welded lap joints of Inconel 600 and SS 400 were evaluated; friction stir welding was carried out at a tool rotation speed of 200 rpm and welding speed of 100 mm/min. Electron back-scattering diffraction and transmission electron microscopy were introduced to analyze the grain boundary characteristics and the precipitates, respectively. Application of friction stir welding was notably effective at reducing the grain size of the stir zone. As a result, the reduced average grain size of Inconel 600 ranged from $20{\mu}m$ in the base material to $8.5{\mu}m$ in the stir zone. The joint interface between Inconel 600 and SS 400 showed a sound weld without voids and cracks, and MC carbides with a size of around 50 nm were partially formed at the Inconel 600 area of lap joint interface. However, the intermetallic compounds that lead to mechanical property degradation of the welds were not formed at the joint interface. Also, a hook, along the Inconel 600 alloy from SS 400, was formed at the advancing side, which directly brought about an increase in the peel strength. In this study, we systematically discussed the evolution of microstructures and mechanical properties of the friction stir lap joint between Inconel 600 and SS 400.

• Korean Journal of Ichthyology
• /
• v.6 no.1
• /
• pp.51-59
• /
• 1994

Morphology of glochidia of two species of Unionidae mussels, Unio douglasiae and Anodonta woodiana were studied based on SEM, and their attachment on Acheilognathus yamatsutae(Acheilognathinae) was observed in the experimentally infected fishes. The glochidia were round-triangle in shape and possessed larval threads, hooks, hooklets, and sensory hairs. Glochidal attachment and cyst formation of the fish were observed without regard to feeding habit and habitat. Density of glochida on the fish (Acheilognathus yamatsutae) was in the order of pectoral fin, dorsal fin, gill and caudal fin. The host fish became encysted about 5-10 hours to the glochidia, and the glochidia detached about 5-6 days after attachment at water temperature $26{\pm}1^{\circ}C$.

• Ocean Systems Engineering
• /
• v.3 no.2
• /
• pp.97-122
• /
• 2013

For the optimization design and strength evaluation of the umbilical cable, the calculation of cross section stress is of great importance and very time consuming. To calculate the cross section stress under combined tension and bending loads, a new integrated analytical model of umbilical cable is presented in this paper. Based on the Hook's law, the axial strain of helical components serves as the tensile stress. Considering the effects of friction between helical components, the bending stress is divided into elastic bending stress and friction stress. For the former, the elastic bending stress, the curvature of helical components is deduced; and for the latter, the shear stress before and after the slipping of helical components is determined. This new analytical model is validated by the experimental results of an umbilical cable. Further, this model is applied to estimate the extreme strength and fatigue life of the umbilical cable used in South China Sea.

• Animal Systematics, Evolution and Diversity
• /
• v.23 no.2
• /
• pp.229-235
• /
• 2007

Two euplotid ciliates collected from the estuarine littorals in Korea were identified as Euplotes vannus ($M\ddot{u}ller$, 1786) and E. parawoodruffi Song and Bradbury, 1997. These species are reported taxonomically for the first time from Korea. These two species are redescribed with illustrations, photos and biometry based on live and silver impregnated specimens. Diagnostics of each species are as follows. E. vannus: size in vivo $94-111{\times}55-75{\mu}m$ (average $103{\times}60{\mu}m)$, adoral zone of membranelles (AZM) 70% of cell length with 57-74 adoral membranelles (AM) and terminating close to hook-shape, macronucleus (Ma) C-shaped with twisted foot-like, 10 frontoventral (FVC), 5 transverse (TC), 4-7 (average 5) caudal cirri (CC), 9-10 dorsal kineties (DK), mid dorsal kinety with 15-22 cilia; silver-line system single vannus type. E. parawoodruffi: size in vivo $125-163{\times}72-100{\mu}m$, (average $141{\times}87{\mu}m$), dorsally strongly arched, body shaped reserved triangular. AZM 67-83% of cell length with 60-85 AMs, 9 FVC, 5 TC, 4 CC, 9 DK; mid-dorsal kinety with 20-30 cilia, double-eurystomus type, T-shaped Ma with equal sized right and left arms or right arm shortened slightly.

• Journal of Welding and Joining
• /
• v.30 no.5
• /
• pp.34-39
• /
• 2012

This study was conducted to investigate the microstructure and mechanical properties of friction stir lap joints. Invar 42 and SS 400 were selected as the experimental materials, and friction stir welding was carried out at a tool rotation speed of 200 rpm and welding speed of 100 mm/min. The application of friction stir welding to Invar 42 effectively reduced the grain size in the stir zone; the average grain size of Invar 42 was reduced from $11.5{\mu}m$ in the base material to $6.4{\mu}m$ in the stir zone, which resulted in an improvement in the mechanical properties of the stir zone. The joint interface between Invar 42 and SS 400 showed a relatively sound weld without voids and cracks, and the intermetallic compounds with $L1_2$ type in lap jointed interface were partially formed with size of 100 nm. Moreover, the hook in the advancing side of Invar 42 was formed from SS 400, which contributed to maintenance of the tensile strength. The evolution of microstructures and mechanical properties of friction stir lap jointed Invar 42 and SS 400 are also discussed herein.

• Clinics in Shoulder and Elbow
• /
• v.12 no.1
• /
• pp.80-83
• /
• 2009

Purpose: A triple labral lesion represents a combination of injuries of the anterior, posterior and superior glenoid labrum. The injury mechanism and symptoms is not completely understood. Materials and Methods: We encountered a triple labral injury in a 39-year-old male complaining pain and active abduction difficulty after a motor vehicle accident. Currently, he does not complain any instability symptoms. The labrum was repaired using bio-absorbable suture anchors and a suture hook. Results: Eighteen months following surgery, the active range of motion was restored and he had no difficulty in his daily activities.

• Clinics in Shoulder and Elbow
• /
• v.22 no.3
• /
• pp.146-148
• /
• 2019

We report a simple technique for repairing capsular tear, using only a hook-like, cannulated instrument and braided sutures without relaying steps. A No. 2 braided suture is passed through the lumen of the instrument. Under direct arthroscopic view, the tip of the instrument is passed through the side of the capsule that has previously been separated with the probe. One end of the suture is retrieved with a grasper through a separate portal. The tip is moved back without withdrawing through the skin, and reinserted into the other side of the capsule. Holding the end retrieved earlier, the other end of the suture is retrieved with a suture retriever. After complete removal of the instrument, the suture is tied through a cannula using the standard knot tying techniques. The same procedures are repeated for other required knots.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.180-185
• /
• 2001

In the life assessment for plant structural component, the research on deterioration of toughness and material properties occurred in weldments has been considered as very important problems. In general, the microstructures composed in weldments are hugely classified with weld metal(W.M), fusion line(F.L), heat affected zone(HAZ), and base metal(B.M). It has been reported that the creep characteristics on weldments having variable microstructures could be unpredictably changed. Furthermore, it is also known that HAZ adjacent to F.L exhibits the decreased creep strength compared to those in base or weld metals, and promotes the occurrence of Type III and Type IV cracking due to the growth of grains and the coarsening carbides precipitated in ferritic matrix by welding and PWHT processes. However, the lots of works reported up to date on creep damage in power plant components have been mostly conducted on B.M and the creep properties on a localized microstructures in weldments have not as yet been throughly investigated. In this paper, for various microstructures such as coarse grain HAZ(CGHAZ), W.M and B.M in X20CrMoV121 steel weldment, the small punch-creep(SP-Creep) test using miniaturized specimen(t=0.5mm, 0.25mm) is performed to investigate a possibility for creep characteristics evaluation.

• Journal of agricultural medicine and community health
• /
• v.4 no.1
• /
• pp.62-70
• /
• 1979

In order to evaluate the present status of hook-worm infection in the rural areas in Korea, stool examinations were undertaken in several selected rural villages in each year of 1970 and 1977. The methods employed were cellophane thick smear technique and brine floatation technique in 3,454 specimens collected from 7 different rural villages for the prevalence rate of hookworm infection and Stoll's dilution egg counting technique for the intensity of hookworm infection. The incidences of Ancylostoma duodenale and Necator americanus infections were determind by polyethylene tube coproculture and by the evacuated adult worms after treatment with anthelmintics to the patients who were infected by hookworms. The results are as follows : 1) In 1970, 323(18.6%) out of 1,737 specimens collected from 4 different rural areas were positive for hook worm infection and the ranges of prevalence rates in those suveyed areas were shown as 6.9 to 38.2 per cent. On the other hand, 144(8.2%) out of 1,717 specimens collected from 3 different rural areas in 1977 were shown as positive for hookworm infection and 7.5 to 10.6 per cent of prvalence rates were shown in the surveyed areas. 2) In the age group under 10 years, there was no infection of hookworm in the studied areas in 1977, however in 1970 the prevalence of the hookworm infection was shown as very low in the age group of 5~9. On the whole, the hookworm prevalence steadily increased from the age of 15 in the studied areas in 1970, however in 1977 the prevalence increased from the age of 20 to the older age groups. 3) There was not observed much differences in the intensity of hookworm infection among the studied areas in 1970 and 1977. The mean EPG in each studied areas were shown under 1,000 EPG and mean numbers of evacuated worms per infected persons were counted as 9.4 to 15. 1. 4) Both A.duodenale and N.americanus have been found in all studied areas but the incidences and st-ate of distribution of two species of hookworn were shown as different in each localities.

• The korean journal of orthodontics
• /
• v.46 no.4
• /
• pp.242-252
• /
• 2016

Objective: Orthodontic mini-implants (OMI) generate various horizontal and vertical force vectors and moments according to their insertion positions. This study aimed to help select ideal biomechanics during maxillary incisor retraction by varying the length in the anterior retraction hook (ARH) and OMI position. Methods: Two extraction models were constructed to analyze the three-dimentional finite element: a first premolar extraction model (Model 1, M1) and a residual 1-mm space post-extraction model (Model 2, M2). The OMI position was set at a height of 8 mm from the arch wire between the second maxillary premolar and the first molar (low OMI traction) or at a 12-mm height in the mesial second maxillary premolar (high OMI traction). Retraction force vectors of 200 g from the ARH (-1, +1, +3, and +6 mm) at low or high OMI traction were resolved into X-, Y-, and Z-axis components. Results: In M1 (low and high OMI traction) and M2 (low OMI traction), the maxillary incisor tip was extruded, but the apex was intruded, and the occlusal plane was rotated clockwise. Significant intrusion and counter-clockwise rotation in the occlusal plane were observed under high OMI traction and -1 mm ARH in M2. Conclusions: This study observed orthodontic tooth movement according to the OMI position and ARH height, and M2 under high OMI traction with short ARH showed retraction with maxillary incisor intrusion.