• Journal of Korea Port Economic Association
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• v.32 no.3
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• pp.83-94
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• 2016

The primary purpose of this study is to analyze the impact of bilateral Free Trade Agreements on international trade volume of bulk shipment at the port of Busan in Korea using the Gravity Model. Most recently, the total of 15 Korea's FTAs have been enforced since Korea-Chile FTA in 2004 and more than 50 countries became member of Korea's FTAs. Therefore, aggregated trade volume of Korea's FTA members out of the total trade volume in Korea increased from 25% in 2011 to 67% in 2015. Five Korea's bilateral FTA members are concerned as experimental group while top 10 foreign countries base on trade volume of bulk shipment are applied to the model as control group and panel data was used in this study. According to the results, bilateral FTA, GDP and population have positive impacts on trade volume of bulk shipment at the port of Busan. On the other hand, distance between Korea and its trade partner has negative impact. In examining Hausman test and LR test, the random effect model is statistically more appropriate than the fixed effect model for this study.

• Journal of the Korea Society of Computer and Information
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• v.17 no.4
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• pp.147-153
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• 2012

This paper has investigated the impact of corporate donation expenditure which has recently drawn great attention in Korean society on businessl performance and conducted an empirical analysis on the causal relations. In addition, concurrent effect has been analyzed using cross-sectional data between two variables (corporate donation expenditure and business performance) while sequential effect has been examined using panel data. The result of this study can be summarized as follows: First, corporate donation expenditure had a positive impact on ROA and ROS. However, PER and ROE had no impact on corporate donation expenditure Second, cumulative effcet of corporate cash donation would have a bigger impact on short-term business performance than long-term performance. In the future, The results of this study is expect through cash donations in the social contribution to be more aggressive in carrying out social responsibilities.

• The Korean Journal of Applied Statistics
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• v.31 no.2
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• pp.229-239
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• 2018

This paper introduces how to adopt the concept of temporal hierarchies to forecast time series data. Similarly as in hierarchical cross-sectional data, temporal hierarchies can be constructed for any time series data by means of non-overlapping temporal aggregation. Reconciliation forecasts with temporal hierarchies result in more accurate and robust forecasts when compared with the independent base and bottom-up forecasts. As an empirical example, we forecast traffic accident counts with temporal hierarchies and observe that reconciliation forecasts are superior to the base and bottom-up forecasts in terms of forecast accuracy.

• Korean Journal of Construction Engineering and Management
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• v.6 no.1 s.23
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• pp.80-88
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• 2005

This research describes an interactive process of analysing the demand factors for apartment on Cheonan area Using subjective statistical data for demand factor the process are categorized into main factors explained for the sensitiveness of correlation coefficient. This investigation is based on an analysis of the work of time series data One of the propose of this research is determining the correlation factors that can be effectively used in the model of forcasting. The results show a significant correlation coefficient on correlation matrix to iud the optimum correlation factors. The paper thus shows how to gain greater influntial factors on principal component analysis Consequently, this paper provides useful information about correlationship, but has limit of regional boundary for effectiveness.

• Korea journal of population studies
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• v.30 no.1
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• pp.149-176
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• 2007

본 연구는 지난 30년간(1975-2004년) 한국의 경제성장과정에서 교육의 부문별(초등 중등 고등교육) 역할을 추정하는 데 주목적이 있다. 본 연구는 우선 신고전학파 Solow의 외생적 경제성장이론을 접목한 Cobb-Douglas 모형을 확장하여 1인당 경제성장 추정을 위한 내생성장모형을 제시하였다. 또한 자료 한계를 극복하기 위하여 동아시아 7개국 자료를 바탕으로 시계 및 횡단면 자료를 블록으로 구축하여 앞의 내생성장모형을 이용한 pooling방법으로 1인당 경제성장에 물적자본, 단순노동력, 인적자본, 지적자본(R&D), 초기년도의 기술수준 등의 기여분을 추정하였다. 이러한 각 생산요소의 직접적인 추정결과로부터 각 요소간(고등교육, 중등교육, 지적자본) 상호작용으로 인한 간접적인 기여분 추정을 위해 연립방정식체계를 구축하고 각 요소의 영향력을 재 추정하여 보정된 결과를 제시하였다. 1975-2004년간 한국의 경제성장 과정에 있어서 인적자본요소인 교육은 40.7%를 기여였으며 이를 다시 분해하면 중등교육이 가장 큰 87.0%, 초등교육이 6.6%, 중등교육에 간접적으로 기여한 대학교육이 -52.9%를 보였다. 물적자본이 39.6%, R&D자본이 24.1%들 보였으며 지식 정보기반사회에서 그 의미가 감소한 단순노동력은 -1.4%, 기술추격을 가능케 하는 1975년도 초기기술수준이 -3.0%의 추정결과를 보여주고 있다. 향후 정책연구 과제로는 한국미 지식기반사회에서 선진국으로 진입하기 위해서는 경제성장과정에서 대학의 역할을 제고할 필요성이 있음을 제안하고 있다. 이를 위해서는 기존 대학의 양적인 구조조정이 필요하다. 특히 대학의 질적 경쟁력을 높이기 위한 정부의 대학 지원 역할 역시 제고되어야 할 것이다. 또한 이 글은 교육시장과 노동시장을 어떠한 방법으로 연계 시키는가를 논의하고 세계시장의 급격한 기술변화와 체제변화에 따라 국내노동시장의 필요한 산업인력수요의 내용도 같은 속도의 변화를 요구하고 있음을 상기시키고 연계지원 정책을 주장하고 있다.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.377-377
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• 2015

부유사 자료는 유사이송해석에 필수적인 요소로 하천의 흐름 변화 및 하상 변동을 발생시키고, 하천 구조물의 설계, 수자원 개발 및 관리를 위한 하천계획의 전반에 있어 매우 중요한 자료이다. 부유사 농도는 수자원의 이용뿐만 아니라 하천 생태계에까지 피해를 미친다는 점에서 하천의 유지 관리 및 보수와도 밀접한 관련이 있다. 부유사량을 산정하는 방법에는 수리량 및 하상토 특성 자료를 유사량 공식에 대입하여 계산하는 간접적인 방법과 유사량을 직접 측정하는 방법으로 나뉜다. 현재 국내에서는 유사량 채집기를 사용하여 실제 하천의 유사량을 채집하는 방식으로 많이 사용되고 있으나, 많은 인력과 시간이 소모되기 때문에 다지점 계측과 지속적인 계측이 힘들다는 한계점를 보이고 있다. 또한 국내 하천에서는 홍수기를 거치면서 하천의 수리학적 특성이 변화하는 경향을 보여주고 있어 유량-부유사 관계식을 자주 갱신해야 한다는 어려움이 있다. 이에 본 연구에서는 현재 국내에서 사용하고 있는 직접적인 측정 방법의 한계점을 보완하고자 직접적인 측정 방법 중 초음파를 이용하여 횡단면 전체의 유사량 측정을 연속적으로 할 수 있는 수평초음파도플러유속계(H-ADCP)를 활용하여 유사량을 추정할 수 있는 기법을 개발하고자 한다. 본 연구의 연구는 건설기술연구원 하천실험센터의 직선수로에서 수행되었다. H-ADCP (SonTek SL3000, 셀 크기 4 cm)를 사용하여 자연상태 흐름조건 (유속 0.7 m/s)에서 초음파산란도(Backscatter, 혹은 신호대잡음비 SNR) 및 유속자료를 2분 간격으로 확보하였다. 그리고 부유사 농도(SSC)의 측정 정확도가 높다고 평가되고 있는 레이저부유사측정기(LISST-100)를 활용하여 부유사 농도를 실측하여 초음파산란도와 실측 SSC의 관계를 도출하고 그 경향을 분석하였다. 또한 초음파산란도의 흡수 등을 보정하고 실측 부유사자료와의 관계식을 기반으로 H-ADCP를 활용하여 실시간으로 부유사 농도를 산정할 수 있는 소프트웨어를 개발하였다.

• The Korean Journal of Nuclear Medicine
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• v.38 no.4
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• pp.318-324
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• 2004

Purpose: Philips GEMINI is a newly introduced whole-body GSO PET/CT scanner. In this study, performance of the scanner including spatial resolution, sensitivity, scatter fraction, noise equivalent count ratio (NECR) was measured utilizing NEMA NU2-2001 standard protocol and compared with performance of LSO, BGO crystal scanner. Methods: GEMINI is composed of the Philips ALLEGRO PET and MX8000 D multi-slice CT scanners. The PET scanner has 28 detector segments which have an array of 29 by 22 GSO crystals ($4{\times}6{\times}20$ mm), covering axial FOV of 18 cm. PET data to measure spatial resolution, sensitivity, scatter fraction, and NECR were acquired in 3D mode according to the NEMA NU2 protocols (coincidence window: 8 ns, energy window: $409[\sim}664$ keV). For the measurement of spatial resolution, images were reconstructed with FBP using ramp filter and an iterative reconstruction algorithm, 3D RAMLA. Data for sensitivity measurement were acquired using NEMA sensitivity phantom filled with F-18 solution and surrounded by $1{\sim}5$ aluminum sleeves after we confirmed that dead time loss did not exceed 1%. To measure NECR and scatter fraction, 1110 MBq of F-18 solution was injected into a NEMA scatter phantom with a length of 70 cm and dynamic scan with 20-min frame duration was acquired for 7 half-lives. Oblique sinograms were collapsed into transaxial slices using single slice rebinning method, and true to background (scatter+random) ratio for each slice and frame was estimated. Scatter fraction was determined by averaging the true to background ratio of last 3 frames in which the dead time loss was below 1%. Results: Transverse and axial resolutions at 1cm radius were (1) 5.3 and 6.5 mm (FBP), (2) 5.1 and 5.9 mm (3D RAMLA). Transverse radial, transverse tangential, and axial resolution at 10 cm were (1) 5.7, 5.7, and 7.0 mm (FBP), (2) 5.4, 5.4, and 6.4 mm (3D RAMLA). Attenuation free values of sensitivity were 3,620 counts/sec/MBq at the center of transaxial FOV and 4,324 counts/sec/MBq at 10 cm offset from the center. Scatter fraction was 40.6%, and peak true count rate and NECR were 88.9 kcps @ 12.9 kBq/mL and 34.3 kcps @ 8.84 kBq/mL. These characteristics are better than that of ECAT EXACT PET scanner with BGO crystal. Conclusion: The results of this field test demonstrate high resolution, sensitivity and count rate performance of the 3D PET/CT scanner with GSO crystal. The data provided here will be useful for the comparative study with other 3D PET/CT scanners using BGO or LSO crystals.

• Journal of Climate Change Research
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• v.4 no.4
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• pp.317-330
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• 2013

The yield of rice production is affected severely by abnormal weather events, such as flood, drought, high temperature etc. The objective of this paper is to assess impacts of abnormal weather events on rice production, using a panel model which analyzes both cross-section data and ti- me series data. Abnormal weather is defined as the weather event which goes beyond the range of ${\pm}2{\sigma}$ from the average of a weather factor. The result of an analysis on impacts of high temperature on rice production showed that the yield of rice was decreased 5.8% to 16.3% under the conditions of extremely high temperature, and it was decreased 8.8 to 20.8% under the conditions of both extremely high and heavy rain. Adaptation strategies, development of new varieties enduring high temperature and heavy rain, adaptation of crop insurance, modernization of irrigation facilities are needed to minimize the impacts of abnormal weather on rice production, and to stabilize farmers' income.

• Journal of Korea Water Resources Association
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• v.54 no.3
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• pp.203-215
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• 2021

In the present study, hydrologic data and topographical data from 2010 to 2019 were collected from three gauging stations placed in the watershed of Naeseong stream to determine changes and rates of changes in rainfall, water level & mean velocity, and water level & discharge, together with changes in rates of erosion and deposition at cross-sections of the river. Besides, effects of regulated and non-regulated rivers according to the presence of artificial regulation of flow rate of the river via artificial structure located at Seo stream (Yeongju si (Wolhogyo) station), the tributary free from construction of dams, were compared and analyzed. Results of analyses conducted in the present study revealed vegetational establishment and landforming due to increasing area of vegetational sandbar evolved in the flood plain (intermediate- or high- water level) by the drought sustained from 2013 to 2015. Continuous erosion of river bed was appeared because of narrowed flow area with low water level and increased velocity and tractive force on river bed.

• Journal of The Geomorphological Association of Korea
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• v.19 no.4
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• pp.109-122
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• 2012

Topographic changes in the foredune in Sohwang-ri, Boryeong, Chungnam Province was analyzed over the last two years. Seven cross-sections and one permanent plot ($20m{\times}50m$) were periodically studied based on erosion and deposition measurement, in addition to vegetation monitoring and measurement of wind using an automatic weather station. The sand dunes usually grew from late winter to spring and the growth occurred in a period of strong northwesterly winds. From March to April, heavy sedimentation was observed on the front section of the foredune and sand piled up to ca. 30cm to the ca. 25m landward from the high tide line. It is likely that increased wind force and growth of vegetation played a major role in transportation and sedimentation of sand. Meanwhile, the lower part of the sand dunes was eroded when typhoon and spring tide caused a rise in sea level. The transition zone of beach and dune was usually affected by sea water but some frontal slopes were entirely influenced, resulting in dune scarps. The eroded scarps were naturally restored to their original state as time passed.