• The Transactions of the Korea Information Processing Society
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• v.1 no.4
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• pp.461-468
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• 1994

This paper describes the automatic extraction of collocations based on corpus. The collocations are extracted from corpus using cooccurrence frequency and mutual information between words. In English, 5 types of collocations are defined. These collocations are transitive verb and object, intransitive verb and subject, adjective and noun, verb and adverb, and adverb and adjective. In this paper another type of collocation is recognized and extracted, which consists of verb and preposition. So 6 types of collocations are extracted based on corpus.

• The Korean Journal of Applied Statistics
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• v.29 no.1
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• pp.221-230
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• 2016

This paper investigates volatilities of stock returns based on high frequency data from stock market. Incorporating the price duration as one of the factors in volatility, we employ the autoregressive conditional duration (ACD) model for the price duration in addition to the GARCH model to analyze stock volatilities. A combined ACD-GARCH model is analyzed in which a double-threshold is introduced to accommodate asymmetric features on stock volatilities.

• Journal of the Korean earth science society
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• v.31 no.7
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• pp.749-761
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• 2010

A relationship between cloud-to-ground lightning and rainfall was investigated by using the two-years (2006-2007) summer lightning data and the automatic weather stations (AWSs) data of the Korea Meteorological Administration. The negative lightning occurred at the core of highly concentrated convection, which is often accompanied with heavy rains. Whereas most positive lightning occurred at the anvil cloud with low density and light rains. The rainfall intensity is strongest when the negative and positive lightning occurred concurrently, and one with lightning is much stronger than that without lightning. A portion of the positive lightning of the total lightning was less than 10% during summer seasons, and the lightning without rains was about 34%. The rain rate was strongly correlated with the negative flash rate, and the correlation coefficients varied between 0.87 and 0.94 according to the co-location radius (5-15 km) of AWSs. Most of the lightning occurred 10 minutes before and/or concurrently occurred with rains. A portion of the convective rainfalls of the total rainfalls was at least 20% when we define the rainfalls with lightning as convective. The convective rainfall was greater during August than in June and July. In general, the portion of convective rainfalls showed a maximum diurnal variation during late afternoon as in the rains and lightning.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.6
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• pp.405-413
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• 2009

Tagging system is the system that allows internet users to assign new meta-data which is called tag to article, photo, video and etc. for facilitating searching and browsing of web contents. Tag cloud, a visual interface is widely used for browsing tag space. Tag cloud selects the tags with the highest frequency and presents them alphabetically with font size reflecting their popularity. However the conventional tag selection method includes known weaknesses. So, we propose a novel tag selection method Freshness, which helps to find fresh web contents. Freshness is the mean value of Kullback-Leibler divergences between each consecutive change of tag co-occurrence probability distribution. We collected tag data from three web sites, Allblog, Eolin and Technorati and constructed the system, 'Fresh Tag Cloud' which collects tag data and creates our tag cloud. Comparing the experimental results between Fresh Tag Cloud and the conventional one with data from Allblog, our one shows 87.5% less overlapping average, which means Fresh Tag Cloud outperforms the conventional tag cloud.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.288-288
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• 2017

최근 우리나라뿐만 아니라 세계에서는 기후가 변화함에 따라 다양한 문제들이 발생하고 있으며 복합적인 위험의 증가도 함께 나타났다. 이러한 기후의 변화로 인해 집중 호우가 발생하는 빈도가 많아지면서 여러 요인들의 의한 침수가 반복적으로 나타나고 있다. 침수의 요인으로는 크게 내수침수, 외수범람, 해수범람이 존재하게 된다. 내수침수의 경우는 펌프나 우수관 등의 문제로 제내지 배수 불량이 발생하여 물이 하천으로 배수 되지 못했을 때 발생하게 되고, 외수범람의 경우는 홍수나 폭우에 의해 하천의 수위가 높아져 제방을 월류할 때 발생, 해수범람은 해수위가 상승하여 발생하게 된다. 본 연구에서는 내수침수와 외수범람을 동시에 복합적으로 모의할 수 있는 2차원 동수역학모형인 HDM-2D(Song. 2011)를 확장하여 해수-외수-내수 연계 모듈을 개발하였다. 해수 유동 모의 결과를 별도의 입력 파일로 불러들여 ERG (Exponentially Growth Rate) 기법에 의한 내수침수 해석 모형과 Petrov 안정화 기법 기반 충격파의 해석이 가능한 외부 범람모형의 초기 및 경계조건으로 부여하여 동수역학적 연계 모듈을 구성하였다. 해수의 영향을 고려한 해수-외수-내수 연계 모의를 통해 시간에 따른 연안 도시 침수 발생 양상을 분석할 수 있었다. 본 연구는 기후변화에 따라 복합적인 침수가 많이 발생하는 연안도시 지역에서 침수의 복합원인을 찾아내고 침수 예상도를 작성하여 연안도시에 가해지는 피해를 분석하는데 도움이 될 것으로 판단된다.

• Journal of Convergence for Information Technology
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• v.12 no.2
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• pp.30-36
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• 2022

In this paper, when the lighting and communication functions of the visible light communication system are used at the same time, we propose a technique to reduce the dimming level and flicker of the lighting. Visible light communication must satisfy both communication and lighting performance. However, the existing data code method results in reducing the brightness of the entire lighting. This causes deterioration of lighting performance and flicker phenomenon. To solve this problem, in this paper, we propose an adaptive learning code allocation technique that allocates binary codes to transmitted characters and optimizes and matches the binary codes allocated according to the frequency of occurrence of alphabets in character strings. Through this, we studied a technique that can faithfully play the role of lighting as well as communication function by allocating codes so that the 'OFF' pattern does not occur continuously while maintaining the maximum dimming level of each character string. As a result of the performance evaluation, the frequency of occurrence of '1' increased significantly without significantly affecting the overall communication performance, and on the contrary, the frequency of consecutive '0' decreased, indicating that the lighting performance of the system was greatly improved.

• Journal of KIISE:Databases
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• v.33 no.1
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• pp.69-85
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• 2006

Broadcast has been often used to disseminate the frequently requested data efficiently to a large volume of mobile clients over a single or multiple channels. Conventional concurrency control protocols for mobile transactions are not suitable for the wireless broadcast environments due to the limited bandwidth of the up-link communication channel. In wireless broadcast environments, the server often broadcast different data items with different frequency to incorporate the data access patterns of mobile transactions. The previously proposed concurrency control protocols for mobile transactions in wireless broadcast environments are focused on the mobile transactions with uniform data access patterns. However, these protocols perform poorly when the data access pattern of update mobile transaction are not uniform but skewed. The update mobile transactions with skewed data access patterns will be frequently aborted and restarted due 4o the update conflict of the same data items with a high access frequency. In this paper, we propose an energy-efficient concurrence control protocol for mobile transactions with skewed data access as well as uniform data access patterns. Our protocol use a random back-off technique to avoid the frequent abort and restart of update mobile transactions. We present in-depth experimental analysis of our method by comparing it with existing concurrency control protocols. Our performance analysis show that it significantly decrease the average response time, the amount of upstream and downstream bandwidth usage over existing protocols.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2460-2468
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• 2014

A local rain that is concentrated in specific area in a short time frequently occurs due to recent abnormal weather. To prevent potential flood disasters, therefore, it is necessary to be established to the flood control system. Checking the river design standard, however, hydrologic design frequency of water gate is only marked as over 20 years, so this fact shows that the standard is unclear. The inland inundation modeling considering the stage in a river and quantitative assessment are required to reduce flood damage. The simulation for internal inundation is very complex and is time-consuming due to considering hydraulic hydrology characteristics at the same time. Using the already established river master plan, consequently, this study proposed the simple and convenient method for assessment of the internal inundation simulation. Using the proposed method in the upper and middle regions of a river, influences for design frequency or water gate location were assessed by applying the nine probability precipitation with design frequency and by targeting the water gates which are installed in five inlands.

• Annual Conference on Human and Language Technology
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• 2023.10a
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• pp.654-658
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• 2023

관계 추출은 질의응답이나 대화 시스템의 기반이 되는 지식을 구추하기 위한 작업으로, 정보 추출의 기초가 되는 기술이기도 하다. 최근 실세계 지식의 희소한 형태를 구현한 문서간 관계 추출 데이터셋이 제안되어, 여러 문서를 통해 분산되어 언급된 두 개체 사이의 관계 추론을 수행 및 평가할 수 있게 되었다. 이 작업에서 추론의 대상이 되는 개체쌍은 한 문서 안에 동시에 언급되지 않기 때문에 여러 문서에 언급된 중간 개체를 통하여 직/간접적으로 추론해야 하나, 원시 텍스트에서 이러한 정보를 수집하는 작업은 쉽지 않다. 따라서, 본 연구에서는 개체의 동시발생빈도에 기반하여 중간 개체의 중요도를 정량화하고, 이 중요도에 기반화여 중요한 문맥을 식별하는 방법론을 제안한다. 제안하는 방법론은 기존의 두 문서로 구성된 추론 경로를 식별된 중간 개체를 활용하여 확장하여, 관계 추론 모델의 수정 없이 추가된 문맥만을 활용하여 문서간 관계 추출 시스템의 성능을 개선할 수 있었다.

• Journal of Korea Water Resources Association
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• v.52 no.3
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• pp.173-185
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• 2019

The Korean Peninsula is considered as one of the most typhoon related disaster prone areas. In particular, the potential risk of flooding in coastal areas would be greater when storm surge and heavy rainfall occurred at the same time. In this context, understanding the mechanism of the interactions between them and estimating the risk associated with the concurrent occurrence are of particular interests especially in low-lying coastal areas. In this study, we developed a Poisson-Generalized Pareto (Poisson-GP) distribution based storm surge frequency analysis model to combine the occurrence of the exceedance of a threshold, that is the peaks over threshold (POT), within a Bayesian framework. The storm surge frequency analysis technique developed through this study might contribute to the improvement of disaster prevention technology related to storm surge in the coastal area.