• Investigative Magnetic Resonance Imaging
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• 제19권3호
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• pp.178-185
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• 2015

Purpose: To compare the frequency of posterior globe flattening between two-dimensional T2-weighted imaging (2D T2WI) and three-dimensional (3D T2WI). Materials and Methods: Sixty-nine patients (31 female; mean age, 44.4 years) who had undergone both 5-mm axial T2WI and sagittal 3D 1-mm isovoxel T2WI of the whole brain for evaluation of various diseases (headache [n = 30], large hemorrhage [n = 19], large tumor or leptomeningeal tumor spread [n = 15], large infarct [n = 3], and bacterial meningitis [n = 2]) were used in this study. Two radiologists independently reviewed both sets of images at separate sessions. Axial T2WI and multi-planar imaging of 3D T2WI were visually assessed for the presence of globe flattening. The optic nerve sheath diameter (ONSD) was measured at a location 4 mm posterior to each globe on oblique coronal imaging reformatted from 3D T2WI. Results: There were significantly more globes showing posterior flattening on 3D T2WI (105/138 [76.1%]) than on 2D T2WI (27/138 [19.6%], P = 0.001). Inter-observer agreement was excellent for both 2D T2WI and 3D T2WI (Cohen's kappa = 0.928 and 0.962, respectively). Intra-class correlation coefficient for the ONSD was almost perfect (Cohen's kappa = 0.839). The globes with posterior flattening had significantly larger ONSD than those without on both 2D and 3D T2WI (P < 0.001; $6.14mm{\pm}0.44$ vs. $5.74mm{\pm}0.44$ on 2D T2WI; $5.90mm{\pm}0.47$ vs. $5.56mm{\pm}0.34$ on 3D T2WI). Optic nerve protrusion was significantly more frequent on reformatted 1-mm 3D T2WI than on 5-mm 2D T2WI (8 out of 138 globes on 3D T2WI versus one on 2D T2WI; P = 0.018). Conclusion: Posterior globe flattening is more frequently observed on 3D T2WI than on 2D T2WI in patients suspected of having increased intracranial pressure. The globes with posterior flattening have significantly larger ONSD than those without.

• Smart Structures and Systems
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• 제4권2호
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• pp.221-232
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• 2008

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.

• 한국인터넷방송통신학회논문지
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• 제15권2호
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• pp.31-37
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• 2015

사물인터넷(IoT)의 여러 분야에서 영상 정보의 보안은 매우 중요하며, 그 보안(저작권 등)을 표시하는 여러 방안을 연구하고 있다. 본 논문에서는 IoT에서 사용하는 영상 정보는 이산 코사인 변환(DCT)과 양자화를 통하여 계수값(QC)으로 변환된다. 그리고 워터마크(메시지)는 QR Code를 통하여 새로운 부호화된 메시지(WMQR)를 만든다. QC와 WMQR은 스테가노그래피 LSB 기법을 적용하고, 영상정보의 보안(저작권 등)을 얻을 수 있다. 스테가노그래피의 LSB 기법은 위치(Secret Key)의 결정에 따라 메시지를 삽입할 수 있다. 부호화된 영상은 인터넷을 통하여 수신자에게 전송하게 된다. 역 과정에서는 영상과 QR 코드, 워터마크(Message)를 얻을 수 있다. 영상정보의 보안에서 워터마크를 추출하는 방법은 부호화된 영상과 Secret Key 만을 사용하며, DCT와 양자화 과정을 통하여 워터마크(Message)를 분리하여 얻을수 있다. 본 논문에서 우리는 영상정보의 보안의 방법을 개선할수 있었으며, 이 모의실험을 통하여 영상의 화질(PSNR), 정규화 상관도(NC)를 통하여 높은 보안성을 얻을 수 있었다.

• Safety and Health at Work
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• 제10권4호
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• pp.452-460
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• 2019

Background: Monitoring and control of PM_2.5 are being recognized as key to address health issues attributed to PM_2.5. Availability of low-cost PM_2.5 sensors made it possible to introduce a number of portable PM_2.5 monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scatteringe-based PM_2.5 monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM_2.5 sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy. Methods: This study discussed the calibration of a low-cost PM_2.5-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM_2.5 sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM_2.5. Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference. Results: Based on the performance of ML algorithms used, regression of the output of the PMD to PM_2.5 concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 ㎍/㎥, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol. Conclusions: Calibration of a low-cost PMD, which is based on construction of PM_2.5 sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

• 한국조경학회지
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• 제37권3호
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• pp.1-10
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• 2009

학교숲은 도시숲의 유형중 하나이다. 도시학교는 적당한 거리에 적당한 면적을 유지하고 있어 학교숲의 조성은 도시에 많은 숲이 조성되는 효과를 준다. 또한, 학교는 학생들이 오랜 시간 머무르는 장소로 학생들의 환경교육의 장으로써의 역할을 수행할 수 있다. 그러나 현재 조성된 학교숲은 학생들의 요구나 참여가 배제된 채 결과 중심의 사업이 되고 있어 학생들의 환경교육에 큰 영향을 미치고 있지 못한 실정이다. 또한 설문조사를 바탕으로 분석하는 기존연구의 경우, 리커트척도를 활용하여 주관적 판단인 정성적 자료를 정량화 하였다는데 의의가 있으나, 인간의 주관적 판단은 모호한 경우가 많아 일반적으로 정량화하는데 문제가 있다. 이에 본 연구에서는 경상북도에 위치한 초등학교 학생들을 대상으로 학교숲에 대한 객관적인 만족도 평가를 위해 퍼지이론을 활용하여, 학교숲 만족도에 미치는 항목들을 알아보고자 하였다. 연구 결과, '학교 특색'과 '정서 함양' 항목의 산술평균값의 순위와 퍼지이론을 도입한 무게중심값의 순위가 변화됨을 알 수 있었다. 이는 퍼지이론이 인간의 사고와 같은 정성적 자료를 합리적으로 객관화 할 수 있다는 증거가 된다. 또한 학교숲 전체 만족도에 영향을 주는 요인은 '학교 특색' 항목의 회귀계수값이 0.159로 가장 높았으며, 다음으로 '수량 많음(0.142)', '자연 소중(0.136)', '정서 함양(0.120)'순으로 나타났다. 이 연구는 설문의 객관적 분석방법과 학교숲 조성을 위한 기초자료로 활용이 가능하리라 판단된다.

• 환경영향평가
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• 제22권5호
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• pp.455-466
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• 2013

The aim of this study is to seek application plans of National Ecosystem Survey database based on comparison and examination of feasible analysis methods for distribution characteristics of alien plants. In order to set up a correlation analysis method between alien plants and environmental factors, we had reviewed the 3rd National Ecosystem Survey guide book and consequently, two kinds of analysis method were tested. One was 1/25,000 scale map boundary based analysis and the other was representative mountain area based analysis. In this study we restricted the research area to select reliable surveyed database from whole "2011 National Ecosystem Survey flora database" according to two major criteria. First, an area defined by 1/25,000 scale map boundary and representative mountain area where the number of surveyed flora records should be within top 20%. Second, land cover map should also be built up inside that area. As a result, 25 map boundaries and 25 representative mountain areas were extracted to be analyzed. To limit a boundary for every representative mountain area we had analyzed distribution of environmental factors around that area by manual inspection with SPOT-5 remote sensed satellite image then designated 3km buffer zone from each alien plant location in that area. After then, naturalized index (NI) and urbanized index (UI) was calculated and correlations analysis was carried out. With the result of correlation analysis by map boundary only agricultural land area showed significant value of r (0.4~0.6, correlated) and the rest of factors did not. In the case of representative mountain area, the result showed that agricultural land, road and forest area showed significant value of r (0.6~0.8, highly correlated) which was corresponding to existing researches. Therefore, representative mountain area based method is preferable when using the alien plants database of National Ecosystem Survey for species distribution analysis. And also, considering the way of database utilization is strongly suggested at the first stage of survey planning for promoting active use of national ecosystem survey database.

• 대한교통학회지
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• 제29권1호
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• pp.17-27
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• 2011

본 연구에서는 교통수요분석의 중요한 오차요인 가운데 하나인 존 체계 구축에 따른 교통수요 추정 결과의 영향을 국가교통DB 전국 지역 간 자료를 이용하여 실증적으로 살펴보고 이를 통하여 현재 배포되는 Network 수준 및 해당사업(고속도로, 국도, 국지도 및 지방도 / 차로수)에 따른 적정 존 체계 수준, 내부 통행비율 수준 등에 대한 결과를 비교분석하였다. 더불어, 존 체계 수준에 따라 교통수요 추정 결과의 정확도가 도로위계, 도로용량별로 어떻게 달라지는지를 검토하였다. 마지막으로, 국가교통DB의 전국 지역 간 자료의 적정한 존 체계 수준을 제시해 보았다. 본 연구에서는 사회경제변수를 고려한 적정 Centroid의 위치와 Connector 연결지점 및 개수 등 존 체계를 구축하였으며, 존 체계 구축이 교통수요 추정에 어떤 영향을 미치는지를 살펴보기 위해 F-test와 상관계수 분석, 평균통행거리 및 통행시간분석, 오차율 분석, 총 주행거리 분석 등을 수행하였다. 분석 결과, 도로위계, 도로용량에 따라 적정 존체계 수준이 다양하게 나타났다. 즉, 현재의 시군구 단위 존 수준에서 추가적인 존 세분화를 수행할수록 국도, 국지도 및 지방도 / 편도 1차로 도로의 교통수요 추정 결과 신뢰성이 전반적으로 개선됨을 확인할 수 있었다. 특히, 신뢰성 높은 교통수요 추정 결과를 확보하기 위해서는 되도록 읍면동 단위의 존 수준까지 존 세분화를 수행할 필요가 있음을 확인할 수 있었다.

• 보건행정학회지
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• 제12권2호
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• pp.43-75
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• 2002

This study focuses on the factors that make the financial structure of hospitals in Korea different, and on recommended courses of action that could be very helpful to hospitals in maintaining a sound financial structure. Data used in this study were collected from 132 hospitals with complete general data of present conditions as well as financial statements. They were chosen from the 174 hospitals that passed the standardization audit undertaken by the Korean Hospital Association from 1996 to 2000 for the purpose of accrediting training hospitals. The dependent variable in this study is financial structure. It consists of liabilities as against total assets (total liabilities to total assets, short-term liabilities to total assets, long-term liabilities to total assets, short-term borrowings to total assets, long-term borrowings to total assets). The independent variables are ownership type, hospital type, location, whether or not a representative is a director of the hospital, the possibility of changing a hospital director, bed size, period of establishment, asset structure, profitability, growth, tax shields, business risk, competition. The factors that appear to have the strongest impact on the liabilities to total assets of all the hospitals sampled are ownership type, hospital type, profitability, tax shields, and business risk. It was found that not-for-profit private hospitals and for-profit private hospitals have more liabilities than public hospitals, and tertiary medical institutions have less liabilities than the secondary general hospitals. Moreover, hospitals earning more at the expense of high business risk have a distinct tendency to lower liabilities. Concerning the current ratio, it was found that factors such as ownership type, hospital type, period of establishment, asset structure, and business risk are the more significant variables. The current ratio of public hospitals is higher than that of both not-for-profit private hospitals and for-profit private hospitals, and the current ratio of tertiary medical institutions is higher than that of general hospitals. As business risk is higher in hospitals compared to other businesses, the current ratio becomes higher; this is because it is assumed that for fear of bankruptcy, hospitals lessen liabilities to total assets. On the other hand, as hospitals become older, the fixed assets to total assets become lower. It is remarkable that in hospitals, the factors affecting liabilities to total assets have an opposite regression coefficient sign against factors affecting current ratio. It brings out the same results borne out by the old financial theories and researches, in which a lot of the liabilities of hospitals are considered as the cause of worsening liquidity. Therefore, it is very important for hospitals to maintain a sound financial structure in order to survive using the rational acquisition and maintenance of capital.

• 한국항만경제학회지
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• 제28권1호
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• pp.263-288
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• 2012

본 연구는 새만금신항만을 건설함에 있어 국제적인 선사, 화주 및 포워더 유치를 위해 항만경쟁력 중 어떠한 국제경쟁력을 확보해야 새만금신항만의 활성화에 기여할 것인지 그 요인을 선정하는 것을 연구의 목적으로 하였다. 본 연구의 방법으로 요인분석 및 계층분석적 의사결정방법론(AHP)을 사용하였다. 선행연구를 통하여 짧은 입출입 항로, 주요 인프라 개발추진, 세제감면 및 규제완화를 비롯한 총 11가지의 측정변수를 선정하였고, 요인분석을 통해 '입지 및 시설', '주변 인프라 및 친수성', '지역 정책 및 환경'의 총 3가지의 상위평가 요인들을 그룹핑 하였다. 본 연구에서는 측정변수들의 신뢰성 검증을 요약 분석한 결과 총 11개의 측정변수의 Cronbach alpha 계수가 0.8 이상으로 나타나 신뢰성이 있다고 판단할 수 있다. 또한 일관성 검증 및 상위평가기준 중요도 분석과 측정변수별 중요도 분석을 실시하여 측정변수들의 우선순위를 산정한 결과 '주요 인프라 개발추진'이 가장 우선시 되는 측정변수로 선정되었으며 그 뒤를 이어 '중국 경제특구와의 인접성', '넓은 항만 배후부지', '공항과의 인접성', '국유지로 인한 국책사업의 가능성' 순으로 나타났다. 새만금신항만의 경쟁력 제고를 위한 활성화 방안으로는 새만금신항만을 환황해권 물류중심 허브항으로 건설하고 환경변화에 따른 대형선사를 유치해야 한다. 또한 새만금신항만의 시사점으로서 새만금신항만을 중량물 전용부두로 건설할 것을 제안해 보았다. 본 연구는 향후 개장 될 새만금신항의 국제경쟁력 요인 선정에 있어 중요한 지표로 사용될 수 있을 것이다.

• Journal of Korean Neurosurgical Society
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• 제49권3호
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• pp.147-152
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• 2011

Objective : The aim of this study was to evaluate the reliability and validity of the Pediatric Functional Assessment of Cancer Therapy Questionnaire Brain Tumor Survivor (version 2.0) Aged 13 years and older (Parent Form) (pedsFACT-BrS parent of adolescent). Methods : The pedsFACT-BrS parent of adolescent was translated and cross-culturally adapted into Korean, following standard Functional Assessment of Chronic Illness Therapy (FACIT) methodology. The psychometric properties of the pedsFACT-BrS parent of adolescent were evaluated in 170 brain tumor patient's mothers (mean age=43.38 years). Pretesting was performed in 30 mothers, and the results indicated good symptom coverage and overall comprehensibility. The participants also completed the Child Health Questionnaire Parent Form 50 (CHQ-PF-50), Neuroticism in Eysenck Personality Questionnaire, and Karnofsky score. Results : In validating the pedsFACT-BrS parent of adolescent, we found high internal consistency, with Cronbach's ${\alpha}$ coefficients ranging from 0.76 to 0.94. The assessment of test-retest reliability using intraclass correlation coefficient revealed satisfactory values with ICCs ranging from 0.84 to 0.93. The pedsFACT-BrS for parent of adolescent also demonstrated good convergent and divergent validities when correlated with the Child Health Questionnaire Parent Form 50 (CHQ-PF-50) and the Neuroticism in Eysenck Personality Questionnaire. The pedsFACT-BrS parent of adolescent showed good clinical validity, and effectively differentiated between clinically distinct patient groups according to the type of treatment, tumor location, shunt, and Karnofsky score of parent proxy report. Conclusion : We confirmed that this reliable and valid instrument can be used to properly evaluate the quality of life of Korean adolescent brain tumor patients by their parents' proxy report.