• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.2
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• pp.49-60
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• 2011

Instant Messenger is one of the most popular communication service when translating message or data each other through Internet. For digital crime investigation, therefore, it is obviously important to obtain communication trace and contents derived from Instant Messenger. This is because that gathering traditional communication histories also have been important until now. However, extracting communication trace and contents are not easy because they are generally encrypted or obfuscated in local system, futhermore, sometimes they are located at server computer for Instant Messenger. This paper researches on extracting communication histories against NateOn, BuddyBuddy, Yahoo! messenger and Mi3 messenger, and obtaining user password or bypassing authentication system to Instant Messenger Service when a user use auto-login option.

• Journal of Chest Surgery
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• v.42 no.1
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• pp.22-27
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• 2009

Background: Coronary artery bypass grafting (CABG) is the standard surgical treatment for coronary artery disease. Although there are many clinical reviews of the long term results after CABG in the Western countries, not many such studies have been done for Korea. Therefore, we reviewed the long term clinical results for the patients who underwent CABG at our hospital. Material and Method: We retrospectively reviewed the medical records of 342 patients who underwent CABG at our hospital from February 1984 to December 2006, which is when CABG was first performed in our institution. A total of 286 patients (83.6%) were able to be followed-up, and the mean follow-up period was $75.7{\pm}46.1$ months. Result: The early mortality rate was 5.6%, and late mortality rate was 23.1%. The one-year survival rate, the five-year survival rate, the ten-year survival rate and the fifteen-year survival rate were 91.5%, 82.1%, 60.7% and 50.0%, respectively. The survival rate was significantly lower for the patients over the age of 60 (p=0.002) and for those with diabetes mellitus (p=0.000), hypertension (p=0.002), multivessel disease (p=0.006) and left ventricular dysfunction (p=0.015). No significant difference was observed between the genders. Multivariate analysis showed that the statistically significant risk factors were diabetes mellitus (p=0.001), age (p=0.005) and those cases for which the left internal thoracic artery was not used (p=0.037). Conclusion: CABG is the effective method of treatment for coronary artery disease. Therefore, active usage of the internal thoracic artery and appropriate medical treatment after surgery, and especially for diabetes mellitus patients, are mandatory for achieving good long-term survival.

• Journal of Chest Surgery
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• v.36 no.7
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• pp.504-509
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• 2003

Although arterial grafts are widely used due to the advantage of long-term patency in coronary bypass surgery, greater saphenous vein is still an important additional conduit. It was reported that preservation of the adventitia of vein graft and the adjacent tissues may bring the improved long-term graft patency. The aim of this study is to look for a harvest technique that can reduce vein injury and wound complications. Material and Method: In thirty-four patients that vein grafts were used for coronary bypass surgery, 50 harvest sites were included for the study. In 25 harvest sites in calf below knee (group 1), vein was exposed through a long incision and then clearly dissected from the adjacent tissue. Ten endoscopic vein harvests were performed in the thighs (group 2). Fifteen other vein grafts that were bluntly dissected were harvested from the thighs through three separate incisions (group 3). Result: Vein harvest time was longest in endoscopic harvest group (44.7$\pm$9.8 minutes) and shortest in group 3 (24.2$\pm$5.9 minutes) (p＝0.000). Most avulsion injuries of vein branches happened in the endoscopic group. Sequential grafting numbers per vein were 1.72$\pm$0.98 with thigh vein graft and 1.16$\pm$0.37 with calf vein (p＝0.02). Swelling of foot and/or leg, which was the most common wound complication after vein harvest, was most commonly presented in group 1 (20/25 sites; p＝0.000). Tingling, the most common neurologic complication, was also most prevalent in group 1 (7/25 sites; p＝0.013). The risk factor of the wound complication was vein harvest from calf, and the vein harvest technique was not a risk for wound complication. Conclusion: Vein harvest technique through three separate incisions from thigh presented shorter harvest time and less vein injury and wound complication compared with the endoscopic harvest technique from thigh or the harvest through a long incision from calf.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.139-148
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• 2011

Asphalt concrete overlay method is used by general maintenance and rehabilitation of construction for aged concrete pavement in Korea. However, in case of the AC overlay method to extend service life of the existing concrete pavements, various distresses of reflection crack, pothole and rutting are the typical problems of the asphalt overlay on existing concrete pavement since it has different physical characteristics between asphalt overlay and existing concrete pavement. To achieve this, application of concrete overlay method is required instead of AC overlay method. Concrete overlay method has advantages that can reduce maintenance cycle and costs since it has excellent bearing value for heavy vehicles and no rutting. However, technical problems of detour road construction, traffic control and other disadvantages happened by long curing time. Thus, in this study and experimental research were launched to evaluate the workability, durability and resistance against environmental loading of Very Rapid Hardening Acrylic Polymer Modified Concrete(VRH-APMC) for application of bonded concrete overlay method. Test results showed that the compressive and bond strength were exceed 21MPa and 1.4MPa of target strength after four hours for rapid traffic opening properties. And tests of resistance against environmental loading results showed that VRH-APMC secured excellent durability. Thus, it was known that VRH-APMC was suitable material for large scale bonded concrete overlay method, and it was possible to use maintenance and rehabilitation method which needs enough workability and rapid traffic opening.

• Journal of Chest Surgery
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• v.31 no.3
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• pp.262-265
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• 1998

A retrospective analysis was performed on the 72 cases of peripheral artery occlusive disease treated at Yonsei Medical School Yongdong Severance Hospital, from March 1, 1990, through July 31, 1992, focusing on the operative procedures, surgical results and perioperative complications. The etiologic causes of vascular obstruction were atherosclerosis in 28 cases, Buerger's disease in 31, traumatic orgin in 7, operative complications in 4, and malignancy and arteritis in one case each. Treatment modalities, actually performed include bypass graft.(27), infusion of PGE1 (23), Embolectomy (16), Sympathectomy (4) and end-to-end anastomosis (2). There were 21 satisfactory cases and 9 unsatisfactory cases of atherosclerotive occlusive disease, defining the operative outcome as“satisfactory”if the obstructive symptoms disappeared completely and “unsatisfactory”if they did not. The patients of TAO induced Buerger's disease with preoperative Foutain class III or IV were surgically converted to class 0 in 14 cases, class I in 12 and class II in 3.

• 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 Korea Multimedia Society
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• v.12 no.11
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• pp.1593-1608
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• 2009

If a certain relay node in multi-hop wireless networks might become a malicious node that does not cooperate with other nodes or a selfish node, network throughput will be dramatically decreased. Most of existing ad hoc routing protocols assuming that the nodes will fully cooperate with other nodes do not resolve the problem of network performance degradation due to malicious and selfish nodes. This paper presents the CARE (Cooperative Ad hoc routing protocol based REputation) scheme incorporating the reputation management that can achieve a multi-hop wireless network with high throughput performance. The proposed scheme provides the horizontal cross-layer approach which can identify misbehaving malicious, selfish nodes dropped out of the hop-by-hop based packet processing in the network and then set up an optimal packet routing path that will detour misbehaving nodes. And the vertical cross-layer approach contained in the CARE scheme attempts to improve the quality of routing paths by exploiting the quality of link information received from the MAC layer. Besides, it provides high TCP throughput by exploiting the reputation values of nodes acquired from the network layer into the transport layer. A case study on experiments and simulations shows that the CARE scheme incorporating vertical and horizontal cross-layer approaches yields better performance in terms of the low rate of packet loss, fast average packet delivery time, and high TCP throughput between end-to-end nodes.

• Journal of Korean Society of Transportation
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• v.29 no.2
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• pp.91-100
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• 2011

Hub network design for freight transportation is a decision process that determines hub locations together with freight transportation routes among shippers so as to ultimately minimize total logistics cost. This study presents the optimal location of hubs by strict hub network design policy with single allocation, which overcomes the limitation of Kim et al. (2008) that does not allow direct transportation among shippers. The greedy-interchange algorithm is employed for hub location decision process, and EMME/2 is adopted for the route searching process. Application of the processes to the nationwide highway network shows that the best hub locations in order are Seoul metropolitan, GyeongNam, Chung-nam, Jeon-Nam, Gyeong-Buk, Chung-Buk, and the locations are concentrated on the Seoul-Busan corridor. The strict hubnetwork design policy with single allocation increases the transportation distance but decreases the transportation cost by passing through the hubs instead of direct transportation. The reduction in total transportation cost can be achieved as the number of hubs increases, but the amount of the reduction gradually decreases because the cost reduction from the decrease in detour transportation distance between non-hubs and hubs becomes less than the discount reduction from dispersion of inter-hubs transportation volumes.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.1
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• pp.276-290
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• 2023

Several efforts in Korea are currently underway with the goal of commercializing autonomous vehicles. Hence, various studies are emerging on autonomous vehicles that drive safely and quickly according to operating guidelines. The current study examines the path search of an autonomous vehicle from a microscopic viewpoint and tries to prove the efficiency required by learning the lane change of an autonomous vehicle through Deep Q-Learning. A SUMO was used to achieve this purpose. The scenario was set to start with a random lane at the starting point and make a right turn through a lane change to the third lane at the destination. As a result of the study, the analysis was divided into simulation-based lane change and simulation-based lane change applied with Deep Q-Learning. The average traffic speed was improved by about 40% in the case of simulation with Deep Q-Learning applied, compared to the case without application, and the average waiting time was reduced by about 2 seconds and the average queue length by about 2.3 vehicles.

• Journal of Korean Society of Transportation
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• v.29 no.5
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• pp.121-138
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• 2011

More affordable and available cutting-edge technologies (e.g., wireless vehicle communication) are regarded as a possible alternative to the fixed infrastructure-based traffic information system requiring the expensive infrastructure investments and mostly implemented in the uninterrupted freeway network with limited spatial system expansion. This paper develops an advanced decentralized traveler information System (ATIS) using vehicle-to-vehicle (V2V) communication system whose performance (drivers' travel time savings) are enhanced by three complementary functions (autonomous automatic incident detection algorithm, reliable sample size function, and driver behavior model) and evaluates it in the typical $6{\times}6$ urban grid network with non-recurrent traffic state (traffic incident) with the varying key parameters (traffic flow, communication radio range, and penetration ratio), employing the off-the-shelf microscopic simulation model (VISSIM) under the ideal vehicle communication environment. Simulation outputs indicate that as the three key parameters are increased more participating vehicles are involved for traffic data propagation in the less communication groups at the faster data dissemination speed. Also, participating vehicles saved their travel time by dynamically updating the up-to-date traffic states and searching for the new route. Focusing on the travel time difference of (instant) re-routing vehicles, lower traffic flow cases saved more time than higher traffic flow ones. This is because a relatively small number of vehicles in 300vph case re-route during the most system-efficient time period (the early time of the traffic incident) but more vehicles in 514vph case re-route during less system-efficient time period, even after the incident is resolved. Also, normally re-routings on the network-entering links saved more travel time than any other places inside the network except the case where the direct effect of traffic incident triggers vehicle re-routings during the effective incident time period and the location and direction of the incident link determines the spatial distribution of re-routing vehicles.