• Journal of KIISE:Databases
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• v.35 no.6
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• pp.459-468
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• 2008

A data stream which is a massive unbounded sequence of data elements continuously generated at a rapid rate. Many recent research activities for emerging applications often need to deal with the data stream. Such applications can be web click monitoring, sensor data processing, network traffic analysis. telephone records and multi-media data. For this. data processing over a data stream are not performed on the stored data but performed the newly updated data with pre-registered queries, and then return a result immediately or periodically. Recently, many studies are focused on dealing with a data stream more than a stored data set. Especially. there are many researches to optimize continuous queries in order to perform them efficiently. This paper proposes a query optimization algorithm to manage continuous query which has multiple join operators(Multi-way join) over data streams. It is called by an Extended Greedy query optimization based on a greedy algorithm. It defines a join cost by a required operation to compute a join and an operation to process a result and then stores all information for computing join cost and join cost in the statistics catalog. To overcome a weak point of greedy algorithm which has poor performance, the algorithm selects the set of operators with a small lay, instead of operator with the smallest cost. The set is influenced the accuracy and execution time of the algorithm and can be controlled adaptively by two user-defined values. Experiment results illustrate the performance of the EGA algorithm in various stream environments.

• Journal of Chest Surgery
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• v.40 no.1 s.270
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• pp.79-82
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• 2007

Tracheobronchial rupture due to blunt chest trauma is an uncommon injury although the incidence is increasing. Early diagnosis and primary repair of tracheobronchial rupture not only restore a normal lung function but also avoid the difficulties and complications associated with delayed diagnosis and repair We present one case of the tracheal transsection caused by traffic accident. Patient suffered from progressive dyspnea, subcutaneous emphysema on the neck and anterior chest wall and tension pneumothorax at both sides were noted. Although both closed thoracostomy were done, massive air leakage through the chest tube continued and subcutaneous emphysema spread to the anterior abdominal wall and scrotum and the degree of dyspnea aggravated. With the impression of tracheobronchial injury, we performed the emergency operation. Preoperative bronchoscopy at the operation room was proceeded, which revealed the trachea was near totally transsected in transverse direction. Operation was performed through collar incisiion on the anterior neck, and the trachea was anastomosed with 4-0 $Vicryl^{(R)}$ interruptedly. Postoperative course were uneventful and patient discharged without any complications.

• Journal of Korean Society of Transportation
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• v.35 no.3
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• pp.197-209
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• 2017

With the advent of age that people spend more time and money on leisure activities, there is increasing interest in professional sport games. The location of large scale sport facilities has substantial impacts on existing transportation pattern because the facility attracts and generates massive traffic volume within a short period of time. This study aims to develop a mode choice model of leisure trips of which the destinations are a sport facility. A structured SP (stated preference) survey questionnaires were developed through an experimental design, and professional sport spectators were asked to state their preference in the choice of transport mode to the sport facility. The survey results show that public transportation is preferred to passenger cars for their trip to big sports event, implying that the convenience of back home trip after the event is an important factor of their mode choice. This study is a rare research on the trip pattern to sports complex in Korea, which provides policy implications on the provision of mass transit including subway system to large scale sport complexes. And it is also expected that this study contributes to future researches on leisure trip pattern.