• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.143-155
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• 2009

A dynamic traffic assignment (DTA) has recently been implemented in many practical projects. The core of dynamic model is the inclusion of time scale. If excluding the time dimension from a DTA model, the framework of a DTA model is similar to that of static model. Similar to static model, with given exogenous travel demand, a DTA model loads vehicles on the network and finds an optimal solution satisfying a pre-defined route choice rule. In most DTA models, the departure pattern of given travel demand is predefined and assumed as a fixed pattern, although the departure pattern of driver is changeable depending on a network traffic condition. Especially, for morning peak commute where most drivers have their preferred arrival time, the departure time, therefore, should be modeled as an endogenous variable. In this paper, the authors point out some shortcomings of current DTA model and propose an alternative approach which could overcome the shortcomings of current DTA model. The authors substitute a traditional definition for time-dependent OD table by a new definition in which the time-dependent OD table is defined as arrival time-based one. In addition, the authors develop a new DTA model which is capable of finding an equilibrium departure pattern without the use of schedule delay functions. Three types of objective function for a new DTA framework are proposed, and the solution algorithms for the three objective functions are also explained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.369-379
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• 2011

During the routing process between nodes on the CR(Cognitive Radio) network conducting for efficient use of limited frequency resources, spectrum handover process due to the appearance of the PU occupies most of the routing latency, and also decreases the reliability of the path. In this paper, a cooperative routing protocol in a multi-channel environment is proposed. The source node broadcasts a message with available channel lists and probability of PU appearance during its route guidance. The intermediate nodes re-transmit the message, received from the source node, and update and maintain the information, status table of the path. The destination node determines the optimal path and sends a reply message to the selected path after it receives the messages from the intermediate nodes. The average probability of the PU appearance and the average time of the PU appearance are updated while transferring data. During data transmission the channel with the lowest probability of appearance of the PU is selected dynamically and if a PU appears on the current channel partial repairment is performed. It is examined that reliability of the selected path considerably is improved and the routing cost is reduced significantly compared to traditional routing methods.

• Journal of Gastric Cancer
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• v.5 no.3 s.19
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• pp.139-145
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• 2005

Gastric cancer is the most prevalent cancer in Korea and comprises the second cause of cancer death. Surgery only can provide chance of cure, but most locally advanced cancers recur after a curative resection, even though important advances in the surgical and nonsurgical treatments of gastric cancer have taken place. Preoperative chemotherapy theoretically can provide the advantages of reducing the bulk of tumor, which might improve the R0 resection rate, and of treating micrometastases early. Also, preoperative chemotherapy is expected to render unresectable tumors resectable without increasing postoperative morbidity and mortality. There are many new chemo-therapeutic agents available for the treatment of advanced gastric cancer, but still the most effective agent, the optimal time and number of cycle for administration are still not known. The addition of postoperative chemotherapy through an intraperitoneal route and/or radiotherapy might affect the outcome of surgery favorably, but that hasn't been proved yet. A multicenter prospective randomized phase III trial should be peformed to answer for those questions and to improve the curability of gastric cancer treatment.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.30-36
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• 2008

The Spatial Image contents of Geomorphology 3-D environment is focused by the requirement and importance in the fields such as, national land development plan, telecommunication facility management, railway construction, general construction engineering, Ubiquitous city development, safety and disaster prevention engineering. The currently used DEM system using contour lines, which embodies geographic information based on the 2-D digital maps and facility information has limitation in implementation in reproducing the 3-D spatial city. Moreover, this method often neglects the altitude of the rail way infrastructure which has narrow width and long length. There it is needed to apply laser measurement technique in the spatial target object to obtain accuracy. Currently, the LiDAR data which combines the laser measurement skill and GPS has been introduced to obtain high resolution accuracy in the altitude measurement. In this paper, we tested of the railway facilities using laser surveying system, then we propose data a generation of spatial images for the optimal manage and synthesis of railway facility system in our 3-D spatial terrain information. For this object, LiDAR based height data transformed to DEM, and the realtime unification of the vector via digital image mapping and raster via exactness evaluation is transformed to make it possible to trace the model of generated 3-dimensional railway model with long distance for 3D tract model generation. As the results, We confirmed the solutions of varieties application for railway facilities management using 3-D spatial image contents.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.483-494
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• 2022

Owing to the saturation of ground spaces in downtown areas, underground spaces are being developed increasingly. Underground spaces are utilized for transportation, water supply and sewerage, communication zones, electric power zones, and various cultural complexes. In Korea, for excavating underground spaces, blasting methods using gunpowder such as the New Austrian Tunneling Method (NATM) are mainly used. However, the blasting method causes vibration and noise during tunnel excavation, generating many complaints from residents in the vicinity of the excavation site. To address this problem, various methods have been developed, and recently, vibration and noise have been reduced using deep excavation. This study predicts blast vibration changes according to the depth, under the same blasting and tunnel conditions, using numerical analysis based on the blast vibration measurement data of the GTX-A route, the tunnel cross-section drawings, and ground investigation reports. Furthermore, the necessary separation distance from densely populated areas such as residential areas is suggested by analyzing the trend of decreasing blast vibration according to the distance from ground surface directly above the blasting location.

• Journal of Service Research and Studies
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• v.8 no.4
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• pp.13-29
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• 2018

The final goal of this study was to develop an optimal service scenario to ensure that building occupants can be effectively evacuated from the building within the golden time without extra assistance in preparing and evacuating for fires. In addition, the research was carried out by dividing the current services into fire evacuation and preparedness phases by applying the Double Diamond process in order to find a way to better familiar them as a lifestyle and to always be prepared for fires. For the building occupants and managers, a total of 14 ideas were first suggested, including not only the services of how to evacuate from a fire, but also the life-style service functions associated with fire implementation technology in daily life. The 14 proposed ideas were conducted by the Service quality evaluation and Analytical Hierarchy Process(AHP) from the perspective of the service recipient, and those were finally prioritized from the service provider's perspective, taking into account the cost and practicality of the service provider. The results of this study show that differences in the importance of fire phases considered by stakeholders and the perception of fire generally vary considerably.

• Korean Journal of Remote Sensing
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• v.34 no.6_2
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• pp.1283-1298
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• 2018

KOPRI(Korea Polar Research Institute) have researhed Arctic sea ice by using satellite remote sensing data since 2017 as a mission of KOPRI. The title of the reseach is "Development of Satellite Observation and Analysis for Arctc sea-ice". This project has three major aims; 1) development of prototype satellite data archive/manage system for Arctic sea ice monitoring, 2) development of sea ice remote sensing data processing and analysis technique, and 3) development of international satellite observing network for Arcitc. This reseach will give us that 1) deveolpment of sea ice observing system for northern sea route, 2) development of optimal remote sensing data processing technique for sea ice and selected satelite sensors, 3) development of international satellite onbservation network. I hope that this letter of introducton KOPRI satellite program for Arctic will help to understand Arctic remote sensing and will introduce you to step into the Arctic remote sensing, which Iis like a blue ocean of remote sensing.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.5
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• pp.1-18
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• 2019

A short-turn bus is a bus that is operated within a subsection of an existing bus line. Previous studies regarding short-turn buses decided optimal turn-back points for a single bus line rather than a bus network. Also, in-vehicle crowding which has a significant impact on transit convenience was rarely considered. Therefore, this study aimed to develop a methodology to set priorities for the introduction of short-turn buses of bus lines and sections, considering crowding. To achieve this objective, we calculated occupancies and crowding alleviation benefits of existing bus lines overlapping a new short-turn route based on transit card data, before and after the introduction of short-turn strategy. Also, operator and social costs caused by the introduction of short-turn buses were calculated. Those procedures were iterated over bus lines and sections to operate a short-turn service, and a section whose benefit-to-cost ratio (B/C) is the largest in a line was selected to operate a short-turn service in the line. After, priorities of bus lines to introduce short-turn services could be determined based on B/C values, and the optimum total fleet size could be determined when a short-turn strategy is applied in multiple lines.

• Journal of Navigation and Port Research
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• v.44 no.6
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• pp.447-452
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• 2020

Extratropical cyclone in winter season is very important in safe operation of ships because it is a major cause of marine accidents due to its strong power. In this study, we used meteorological data, to analyze extratropical cyclones occurring near the 1st Pacific polar front from December 2019 to February 2020. The analysis results are as follows. During those three months, we recorded 41 extratropical cyclones, 8 of which were remarkably developed. The central pressure of the strongest cyclone was 947hPa. The highest number of cyclones were generated in the East P acific Ocean around J apan (16), followed by the areas around Korea, the East China Sea, and the southern Sea of J apan. The cyclones followed five major tracks with a common northeast pattern. We thus concluded that the optimal route for a ship encountering an extratropical cyclone in the North P acific in winter would be south of the cyclone's center traveling eastbound and north of the center traveling westbound.

• Journal of Korea Port Economic Association
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• v.38 no.3
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• pp.15-28
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• 2022

Bunkering refers to the supply of bunker fuel necessary for the ship operation, as well as minimizing the price and supply cost of fuel itself, and includes supplying good quality fuel oil in a timely manner and at the optimal port. Bunkering is an important criterion in terms of cost for shipping companies because bunkering involves a significant cost to the purchaser of bunkering from the time of initial purchase. This study aims to prioritize selection criteria for tramper companies to call port for bunkering. For this study, the variables were selected by analyzing the common criteria such as price, location, bunker quality and service and infrastructure etc. employed in previous studies. The AHP method was employed to prioritize the criteria in order. As a result of the analysis, the high level factors appeared in the order of price, location, bunkering quality and port service and infrastructure factors. The importance of price criterion and location criterion was found to be high. In the low level criterion of price, the bunker price per MT was ranked first in importance. In terms of location criteria, the location on the main trade route was high. In the low criteria of bunker quality and port service, the bunkering available types and bunker quality were found to be important factors, and in the low level criteria of infrastructure, anchorage and availability of bunkering during loading and discharging and port security factors were found to be important criteria. This study provides the guidelines for research designed to compare the bunkering port selection factors and to derive their importance suggesting the ways to enhance competitiveness as a bunkering port.