• Journal of the Korea Society of Computer and Information
• /
• v.17 no.2
• /
• pp.149-157
• /
• 2012

In this thesis, the problem of computing approximate answers to continuous sliding-window joins over data streams when the available memory may be insufficient to keep the entire join state. One approximation scenario is to provide a maximum subset of the result, with the objective of losing as few result tuples as possible. An alternative scenario is to provide a random sample of the join result, e.g., if the output of the join is being aggregated. It is shown formally that neither approximation can be addressed effectively for a sliding-window join of arbitrary input streams. Previous work has addressed only the maximum-subset problem, and has implicitly used a frequency based model of stream arrival. There exists a sampling problem for this model. More importantly, it is shown that a broad class of applications for which an age-based model of stream arrival is more appropriate, and both approximation scenarios under this new model are addressed. Finally, for the case of multiple joins being executed with an overall memory constraint, an algorithm for memory allocation across the join that optimizes a combined measure of approximation in all scenarios considered is provided.

• The Journal of the Korean bone and joint tumor society
• /
• v.10 no.2
• /
• pp.71-78
• /
• 2004

Purpose: The purpose of this study is to investigate the characteristic of recurred giant cell tumor after bony curettage and cementation, and to review a way to prevent the recurrence. Materials and Methods : Thirty seven cases were analyzed, which were pathologically diagnosed giant cell tumor after diagnostic biopsy or surgical excision, followed by curative curettage, burring and cementation. Location, character, and time interval to recurrence were reviewed. Results: Thirteen out of thirty seven analyzed cases(35%) showed recurrence after primary curettage and cementation. The mean interval to recurrence was sixteen months(5 months to 43 months). Most of recurrence happened within the first two years except two cases. Among the recurred cases, eleven showed recurrence in the vicinity of window area. Two cases recurred in the depth of bone marrow, where cementation was made. The advantage of curettage and cementation is the immediate stability of the operation site, early rehabilitation, and early detection of recurrence. Furthermore, cementation is beneficial in that the cement-producing heat can eradicate the residual tumor burden. In this study, 85% of cases with insufficient curettage (for example, in cases where too small surgical window was made, or where there were anatomical difficulty in approaching the target tumor burden) showed recurrence. Conclusion: Bony curettage, burring and cementation is widely used as the primary curative modality for giant cell tumor. A few other modalities such as chemical cautery using phenol and $H_2O_2$; cryotherapy; and anhydroalcohol have also been introduced, but the benefit of these are still questionable. For some cases that relatively small surgical window was made due to anatomically complicated structures (such as ligament insertion or origin site) over the target tumor burden, unsatisfactory curettage and burring was made. This study showed high chance of recurrence after unsatisfactory curettage, and 85% of recurrence developed in the vicinity of the small window area. Most of the recurrence occurred within the first two years. It is concluded that sufficient window opening, extensive curettage and eradicative burring are key factors to prevent recurrence. Also, it should be reminded that careful and close observation should be made for at least the first two years after initial treatment for early detection of recurrence.

• KIPS Transactions on Software and Data Engineering
• /
• v.4 no.6
• /
• pp.253-260
• /
• 2015

When we buy items in online stores, it is common to face recommended items that meet our interest. These recommendation system help users not only to find out related items, but also find new things that may interest users. Recommendation system has been widely studied and various models has been suggested such as, collaborative filtering and content-based filtering. Though collaborative filtering shows good performance for predicting users preference, there are some conditions where collaborative filtering cannot be applied. Sparsity in user data causes problems in comparing users. Systems which are newly starting or companies having small number of users are also hard to apply collaborative filtering. Content-based filtering should be used to support this conditions, but content-based filtering has some drawbacks and weakness which are tendency of recommending similar items, and keeping history of a user makes recommendation simple and not able to follow up users preference changes. To overcome this drawbacks and limitations, we suggest weighted window assisted user history based recommendation system, which captures user's purchase patterns and applies them to window weight adjustment. The system is capable of following current preference of a user, removing useless recommendation and suggesting items which cannot be simply found by users. To examine the performance under user and data sparsity environment, we applied data from start-up trading company. Through the experiments, we evaluate the operation of the proposed recommendation system.

• Fire Science and Engineering
• /
• v.22 no.1
• /
• pp.105-114
• /
• 2008

This study investigated problems found with the installation of a descending life line which is one of the compulsory fire escape apparatuses required by the revised "Fire Service Act" of 2006 for multi-use facilities and multistory buildings. It presents an analysis of the causes and improvement details for the problems classified by type of item. To achieve the purpose, the total 367 problem points are indicated. The problems of Installation are unsuitable window glass using the descending life line(34%), required passage device is not attached(23.7%), the installation location is with required operation(20%) and damaged descending life line(20%) were investigated. In particular, the study looks at the stress analysis range for cracking window glass which is required for people to escape in an emergency. People have questioned unsuitable window glass for using the descending life line among the problems with the installation. As a result of stress analysis, window glass thickness of the place where the descending life line is installed must be 3 or 6 mm. In addition, this study indicates substantial improvement measures for installing the descending life line so I will actually be used as a fire escape apparatus to protect human lives, and not just to formally meet the Fire Service Act.

• Journal of KIISE:Databases
• /
• v.33 no.2
• /
• pp.201-213
• /
• 2006

A time-series database is a set of time-series data sequences, each of which is a list of changing values of the object in a given period of time. Subsequence matching is an operation that searches for such data subsequences whose changing patterns are similar to a query sequence from a time-series database. This paper addresses a performance issue of time-series subsequence matching. First, we quantitatively examine the performance degradation caused by the window size effect, and then show that the performance of subsequence matching with a single index is not satisfactory in real applications. We argue that index interpolation is fairly useful to resolve this problem. The index interpolation performs subsequence matching by selecting the most appropriate one from multiple indexes built on windows of their inherent sizes. For index interpolation, we first decide the sites of windows for multiple indexes to be built. In this paper, we solve the problem of selecting optimal window sizes in the perspective of physical database design. For this, given a set of query sequences to be peformed in a target time-series database and a set of window sizes for building multiple indexes, we devise a formula that estimates the cost of all the subsequence matchings. Based on this formula, we propose an algorithm that determines the optimal window sizes for maximizing the performance of entire subsequence matchings. We formally Prove the optimality as well as the effectiveness of the algorithm. Finally, we perform a series of extensive experiments with a real-life stock data set and a large volume of a synthetic data set. The results reveal that the proposed approach improves the previous one by 1.5 to 7.8 times.

• International Commerce and Information Review
• /
• v.18 no.2
• /
• pp.53-82
• /
• 2016

This article begins that previous literatures of South Korea's paperless trade differ from those of other developed countries' paperless trade. Some scholars in South Korea have studied on the relevance of documentary credit in the paperless trade and operability of electronic documentary credit. But Some other scholars in other developed countries have studied about e-customs and e-air logistics. As a result, The current situation of South Korea's paperless trade differs from that of other developed countries' paperless trade. The South Korea's paperless trade has tried to achieve the operation of electronic documentary credit as well as e-customs through the establishment of Korea Trade Network(KTNET) and Customs service's Single Window known as Uni-pass. and other developed countries's paperless trade has made an effort to develop an e-customs and e-air logistics through customs service's Single Window. So, this article describes the current status and characteristics of South Korea's paperless trade and next, this article aims to find out the obstacles and countermeasures in the operation of South Korea's paperless trade. Therefore this paper provides a clear understanding of the problems and solutions associated with South Korea's paperless trade.

• Journal of Korean Port Research
• /
• v.9 no.2
• /
• pp.9-24
• /
• 1995

The intensification of the competition among container terminals has led to important affect such as, decision making or aggressive intervention of customers for terminal operation. Therefore, in case of developed ports, the large transition of port operation is composed of the press of terminal customer than decision making of terminal manager. Overall port tariffs for using terminal is made out by the conference of terminal customers than the supreme headquarters of terminal operation, and the related investment of terminal has been made according to requisition or proposal of customers. Therefore, among decision making problems that shippers, shipping companies, and freight forwarder among decision making problems that shippers, shipping companies, and freight forwarder face, the choice of the container terminal is one of the most important problems. So, the decision making of the users seems to have a significant impact on the competitive power of container terminals. The main objective of this study is to design port marketing strategy for strengthening the competitive power of container terminals. The results of this study were found as follows: Firstly, port authority should establish user-oriented operation policy of terminal as the means of activating the opinion window, using terminal monitoring system(TMS). Secondly, terminal planning and development of government should be made to minimize the lead time, to induce the civil capital and to utilize the economies of scale. Thirdly, port authority needs to endeavor to analyze the information of competing foreign terminals as well to promote the concentrated marketing for the terminal on the users, to train the expert and to develop the new port charge system. Fourthly, to improve the competitive power of the container terminal, Port Authority should optimize the subsystems related to port marketing, far more these systems should be joined organically to work effectively. Finally, port authority system should be introduced, Namely, port should have the enterprise inclination as well s the public inclination.

• Journal of Chest Surgery
• /
• v.3 no.1
• /
• pp.3-12
• /
• 1970

During the last 10 years of period, one hundred patients with various pulmonary diseases were pneumonectomized upon at the Department of Chest Surgery of Pusan University Hospital. This paper is concerned with the clnical results of these patients along with the serious postoperative complications such as postoperative intrapleural infection and hemorrhage. The results were obtained as follows. 1.Left pneumonectomy was done in sixty-six of 100 patients [66 %] and the right one was done in the rest thirty-four[34 %]. The ratio between left and right was nearly 2:1. 2.Of all oostoperative complications, the intrapleural infection was most common, and these were 53 % in empyema thoracis and 12.7 % in pulmonary tuberculosis respectively. 3.More postoperative complications could be seen after right pneumonectomy than the left one. 4.It was thought that the postoperative intrapleural infection was closely correlated with the methods of pleural dissection at pneumonectomy,postoperatlve tube drainage, time of operation, massive hemorrhage during operation, prolongation of bleeding time, and dysfunction of the liver. 5.The repeated thoracenteses with infusion of neomycin into the infected thoracic cavity and intravenous administrations of the high units of penicillin were effective in treatment of the postoperative intrapleural infection, however, the refractory cases have to be cured by thoracoplasty with open window. 6.Immediate secondary open thoracotomy appears to be the method of choice in life saving who developed massive intrathoracic hemorrhage after pneumonectomy. 7.The mortality rate was 10 % in our cases and the main causes of death were postoperative respiratory insufficiency, pulmonary edema, hemorrhage and sudden cardiac arrest.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.32 no.4
• /
• pp.89-99
• /
• 2007

In this paper, an analytic model of a sleep mode operation in the IEEE 802.16e is investigated. A mobile subscriber station(MSS) goes to sleep mode after negotiations with the base station(BS) and wakes up periodically for a short interval to check whether there is downlink traffic to it. If the arrival of traffic is notified, an MSS returns to wake mode. Otherwise, it again enters increased sleep interval which is double as the previous one. In order to consider the situation more practically, we propose the sleep mode starting threshold, during which MSS should await packets before it enters the sleep mode. By modifying the M/G/l with multiple vacations model, energy consumption ratio(ECR) and average packet response time are calculated. Our analytic model provides potential guidance in determining the optimal parameters values such as sleep mode starting threshold, minimal sleep and maximal sleep window.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.1
• /
• pp.165-171
• /
• 2005

In this paper, the centralized dynamic load-balancing was processed effectively by using the network based parallel genetic algorithm. Unlike the existing method using genetic algorithm, the performance of central scheduler was improved by distributing the process for the searching of the optimal task assignment to clients. A roulette wheel selection and an elite preservation strategy were used as selection operation to improve the convergence speed of optimal solution. A chromosome was encoded by using sliding window method. And a cyclic crossover was used as crossover operation. By the result of simulation for the performance estimation of central scheduler according to the change of flexibility of load-balancing method, it was verified that the performance is improved in the proposed method.