• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.10
• /
• pp.1179-1185
• /
• 2011

Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ${\Delta}P-N_f$ relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.80-97
• /
• 2010

With the hubbing strategy, construction of "Incheon Airport Railroad(AREX)" was proceeded to expand the accessibility at the level of airports in rivalry like Kansai and Chek Lap Kok. At the present 1st phase which routes from Incheon Airport to Kimpo Airport is opened March 2007. 2nd phase which is planned from Kimpo Airport to Seoul station will be opened at the end of October 2010. But the accessibilty to AREX is delinquent because it is connected only in Seoul station and the maximum operation speed is 110km/h which downgrade the time competitiveness with airport limousine. In addition, transfering of user is necessary to access to AREX from Kyungbu KTX. With these reasons, travel demand in 1st phase section is low(7%). According to reestimation of travel demand, demand analysis result compared with convention condition is insufficient, so required annual average government grant-in-aid amounts to 200 billions won, and it is right time to develop the method for revitalization of Incheon airport railroad. In this paper, facilities plan and operating plan to make new travel demand by speed-up which is able through substitution train now running with high speed train(EMU, 180km/h) and direct connection of KTX, will be suggested. This will contribute to offering high speed railroad service to customers and the reduction of government grant-in-aid by way of demand expansion.

• Journal of Veterinary Clinics
• /
• v.32 no.1
• /
• pp.9-15
• /
• 2015

Purpose of this study is to determine the reasonable portal approach for thoracoscopic right middle lung lobectomy in small sized dogs under 10 kg. Ten healthy beagle dogs weighing $8.67{\pm}0.49kg$ were included. Under general anesthesia, one-lung ventilation (1LV) was achieved using endobronchial blocker with guidance of fiber-optic bronchoscope. Two portal approaches were used; 8-6-10 intercostal space (ICS) and 8-6-5 ICS approach. Thoracoscopic right middle lung lobectomy was performed using endoscopic linear self-cutting stapler and specimen retrieval bag. Each approach was evaluated by scoring 0; bad, 1; endurable, 2; good, 3; excellent in following five category, 1) visualization, 2) triangulation; instrumental sword fighting in the thoracic cavity, 3) approach to hilar pedicle; application of stapler, 4) any obstacles in applicating Lap Bag, and 5) the operator's convenience. Favorable working space was secured by 1LV and thoracoscopic right middle lung lobectomy was successfully completed in all dogs. There was no need to change the portal location and iatrogenic complication. Most of scores were good to excellent in both approaches. Consequently, both approaches are feasible methods for thoracoscopic right middle lung lobectomy with one lung ventilation using endoscopic linear self-cutting stapler in dogs weighing less than 10 kg.

• Journal of Science and Technology Studies
• /
• v.18 no.1
• /
• pp.219-265
• /
• 2018

Recently, interest in energy tranisition is rising. Energy transition requires active participation and cooperation of diverse stakeholders, including users / citizens, in that it requires not only changes in technological factors but also changes and coordination of various social factors. Living labs are attracting attention as one of the ways to do this. This article is a detailed analysis of the activities of the mini-PV living lab in the urban area from 2016 to 2017 at the Seoul, Sung Dae Goal. Through the Living Lab, mini PV DIY products, backup centers, local financial services, and the development of a variety of education and training strategies have been achieved. These activities and achievements were analyzed through questions raised on strategic, tactical, and operational levels, as well as through multi-level perspective and interaction between initiative, regime, and niche. In conclusion, this living lab activity confirmed the possibility of a 'transition lap' to solve social problems such as sustainability of energy production and utilization. In particular, it gained remarkable results in terms of the operational leves of transition management governance, that is, transition experiment, and it was also remarkable in that it was the initiative of citizens. However, it did not proceed without difficulty. In particular, structural problems such as the conflict between the flexibility inherent in living lab and the bureaucratic rigidity of the financial support organization have appeared. There was also a limitation that there was no 'transition field' on the strategic level necessary to replicate and expand strategic niches while spreading the knowledge gained from the transition experiment, forming the vision of transition.

• Korean Journal of Materials Research
• /
• v.9 no.7
• /
• pp.747-752
• /
• 1999

The interfacial reaction and joint properties of Sn-3.5Ag/Cu and Sn-3.5Ag-1Zn/Cu joint were studied. Modified double lap shear solder joints of Sn-3.5Ag and Sn-3.5Ag- lZn solder were aged for 60days at $100^{\circ}C$ and $150^{\circ}C$ and then loaded to failure in shear. The Sn-3.5Ag/Cu had a fast growth rate of the reaction layer in comparison with the Sn-3.5Ag-lZn at the aging temperature of $150^{\circ}C$ Through the SEM/EDS analysis of solder joint, it was proved that intermatallic layer was $Cu_{6}Sn_5$ phase and aged specimens showed that intermatallic layer grew in proportion to $t_{1/2}$, and the precipitate of $Ag_3Sn$ occur to both inner layer and interface of layer and solder. In case of Zn-containing composite solder, $Cu_{6}Sn_{5}$ phase formed at the side of substrate and $Cu_{5}Zn_{8}$ phase formed at the other side in double layer. The shear strength of the Sn-3.5Ag/Cu joint improved by addition of IZn. The strength of the joint increases with strain rate and decreases with aging temperature

• Korean Journal of Veterinary Research
• /
• v.36 no.3
• /
• pp.551-563
• /
• 1996

This study investigated the properties of primary cultured proximal tubule cells in hormonally defined(insulin, transferrin, and hydrocortisone), serum-free medium or 10% serum-supplemented medium. The growth rate of the primary cultured proximal tubule cells was lower in the hormonally defined, serum-free medium than in the 10% serum- supplemented medium(p < 0.05), while the activities of brush border marker enzymes, alkaline phosphatase(AP), leucine aminopeptidase(LAP), and y-glutamyl transpeptidase(${\gamma}$-GTP) were increased(p < 0.05). The activities of these enzymes, however, decreased with the lapse of incubation time to 50-70% after 6 days culture compared to those of the freshly-prepared proximal tubules. The enzymatic activities of the primary cultured proximal tubul cells on 6, 9, 12, and 15 days of culture were significantly increased in the hormonally defined, serum-free medium compared to the 10% serum-supplemented medium(p < 0.05). The functional differentiation of the primary culture was examined by observing multicellular domes of the confluent monolayer, which is indicative of transepithelial solute transport. The dome formation by the proximal tubule cultures occurred at a higher frequency in the hormonally defined, serum-free medium than in the 10% serum-supplemented medium(p < 0.05). Upon electron microscopic examination, an increased density of the brush border was observed in the hormonally defined, serum-free medium compared to the cells grown in 10% serum-supplemented medium. The activities of $Na^+$glucose cotransporter($^{14}C$-a-MG uptake), $Na^+$phosphate cotransportere($^{32}P$ uptake) and $Na^+$ transporter($^{22}Na^+$ uptake) in the brush border membrane, and of $Na^+/K^+$-ATPase($^{86}Rb$ uptake) in the basolateral membrane were significantly stimulated in the hormonally defined, serum-free medium than in 10% serum-supplemented medium(p < 0.05). In conclusion, the primary cultured proximal tubule cells grown in the hormonally defined, serum-free medium demonstrated a slower growth rate, but the functions of cell were enhanced.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.4
• /
• pp.413-420
• /
• 2012

An aluminum foil-laminated sheet is a laminated steel sheet on which aluminum foil is adhesively bonded. It is usually used on the outer panel of home appliances to provide an aluminum feeling and appearance on the surface of the product. The delamination of aluminum foil is one of the main problems during the stretch forming process. The purpose of this study is was to determine the delamination limit of an aluminum foil-laminated sheet in the stretch forming process. The delamination was dependent on the bonding strength between aluminum foil and steel sheet. The fracture behavior of the interface between the aluminum foil and the steel sheet was described by a cohesive zone model. A finite element was conducted with the cohesive zone model to analyze the relationship between the delamination limit and the bonding strength of the interface. The interface bonding strength was evaluated by lap shear and T-peel test. The delamination limit of the aluminum foil-laminated sheet was determined by using the bonding strength of the steel sheet. The delamination limit was also verified by the Erichsen test.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.5
• /
• pp.82-90
• /
• 2018

The nuclear structures are composed of large diameter bars over No.36. If the hooked bars are used for anchorage of large diameter bars, too long length of the tail extension of the hook plus bend create congestion and make an element difficult to construct. To address those problems, headed bars were developed. Provisions of ACI 318-08 specify the development length of headed bars and ignore the effect of transverse reinforcement based on the background researches. However, if headed bars are used at the cut-off or lap splice, longitudinal reinforcements, which are deformed in flexural members, induce tensile stress in cover concrete and increase the tensile force in the transverse reinforcement. The object of this research is to evaluate the effects of transverse reinforcement on the anchorage capacity of headed bar so anchorage test with variable of transverse rebar spacing was conducted. Specimens, which can consider the behavior at the cut-off, were tested. Test results show that failure of specimen without transverse reinforcement was sudden and brittle with concrete cover lifted and developed stress of headed bars was less than half of yield strength of headed bars. On the other hand, in the specimen with transverse reinforcement, transverse rebar directly resist the load of free-end so capacity of specimens highly increased.

• Korean Journal of Plant Resources
• /
• v.19 no.1
• /
• pp.76-82
• /
• 2006

Genetic variation of two Juniperus chinensis var. sargentii populations in Mt. Seorak and Mt. Halla was investigated by isozyme analysis at reproducible 11 loci of 7 isozyme systems(Aat-1, Aat-2, Gdh, Idh, Lap, Mdh-1, Mdh-2, Mdh-3, 6Pgd, Pgi-1, and Pgi-2), of which 7 loci were polymorphic. The levels of genetic diversity of two populations were A=2.2, $A_e=1.61,\;P_{95}=54.5,\;H_{o}=0.179,\;H_e=0.287$(Mt. Seorak population) and A=2.1, $A_e=1.48,\;P_{95}=63.6,\;H_{o}=0.270,\;H_e=0.250$(Mt. Halla population), respectively. These values were similar to and/or somewhat higher than those observed in other Korean native conifers. Moderately low degree of genetic differentiation was observed between 2 analyzed populations ($F_{ST}=0.039$). Heterozygosity of the population in Mt. Seorak was significantly lower than expected, and much high level of inbreeding coefficient(F=0.376) was observed. Considering the limited population size and distribution range of the population, the population seemed to be influenced by inbreeding and/or random genetic drift, Consequently, Mt. Seorak population should be considered to be a more important candidate for the conservation of J. chinensis var. sargentii.

• Journal of Chest Surgery
• /
• v.30 no.11
• /
• pp.1069-1076
• /
• 1997

There remains controversy regarding the appropriate surgical treatment for coarctation of the aorta because of relatively high rate of recoartation and high mortality in the cases associated with complex anomalies. We evaluated 31 consecutive patients who underwent surgical repair of coarctation of the aorta from May 1992 through June 1996. Nineteen patients(61.3%) were neonates and 26(83.9%) were under three months. Nine patients did not have major associated anom lies(Group I), 15 patients had ventricular septal defect(Group II), and 7 patients had major complex anomalies(Group III). 35.5% of the patients had arch hypoplasia. Surgical procedures performed were as follows: extended end-to-end anastomosis in 17 patients, combined resection-flap procedure in 7 patients, and subclavian flap aortoplasty in 7 patients. Residual coarctation occurred in 7(25%) of 28 patients; 2 after subclavian (lap aortoplasty(2/6, 33.3%), none after combillrd resection-flap procedure(0/7, 0%), and 5 after extended end-to-end anastomosis(5/15, 33.3%). Higher incidence of residual coarctation was noticed in the group with arch hypoplasia. The incidence of postoperative coarctation at a mean follow-up of 20.5 months in survivals was 12.0%(3/25); 2 cases after subclavian flap aortoplasty(2/6, 33.3%), none after combined resection-flap procedure(017, 0%), and one after endtoend anastomosis(1/12, 8.3%). The mortality rate related to coarctation repair was 9.7%(3 patients all in Group III). This study revealed that isolated coarctation of aorta and coarctation with ventricular septal di3fect(groups I & ll) can be repaired with low mortality, but repair of coarctation with complex anomaly had a high operative mortality Also the patients with arch hypoplasia had higher incidence of post-operative residual coarctation.