• Structural Engineering and Mechanics
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• 제82권2호
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• pp.245-258
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• 2022

Many Structural Health Monitoring (SHM) methods have been proposed for structural damage diagnosis and prognosis. However, SHM for pinched hysteretic structures can be problematic due to the high level of nonlinearity. The model-free hysteresis loop analysis (HLA) has displayed notable robustness and accuracy in identifying damage for full-scaled and scaled test buildings. In this paper, the performance of HLA is compared with seven other SHM methods in identifying lateral elastic stiffness for a six-story numerical building with highly nonlinear pinching behavior. Two successive earthquakes are employed to compare the accuracy and consistency of methods within and between events. Robustness is assessed across sampling rates 50-1000 Hz in noise-free condition and then assessed with 10% root mean square (RMS) noise added to responses at 250 Hz sampling rate. Results confirm HLA is the most robust method to sampling rate and noise. HLA preserves high accuracy even when the sampling rate drops to 50 Hz, where the performance of other methods deteriorates considerably. In noisy conditions, the maximum absolute estimation error is less than 4% for HLA. The overall results show HLA has high robustness and accuracy for an extremely nonlinear, but realistic case compared to a range of leading and recent model-based and model-free methods.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.167-176
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• 2023

This study presents the performance analysis of real-time orbit determination and prediction for navigation message generation of Regional Navigation Satellite System (RNSS). Since the accuracy of ephemeris and clock correction in navigation message affects the positioning accuracy of the user, it is essential to construct a ground segment that can generate this information precisely when designing a new navigation satellite system. Based on a real-time architecture by an extended Kalman filter, we simulated orbit determination and prediction of RNSS satellites in order to assess the accuracy of orbit and clock prediction and signal-in-space ranging errors (SISRE). As a result of the simulation, the orbit and clock accuracy was at 0.5 m and 2 m levels for 24 hour determination and six hour prediction after the determination, respectively. From the prediction result, we verified that the SISRE of RNSS for six hour prediction was at a 1 m level.

• 한국지형학회지
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• 제28권4호
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• pp.41-52
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• 2021

With the popularization of drones and the ease of use of the Global Navigation Satellite System (GNSS), drone photogrammetry for terrain information has been widely used. Drone photogrammetry enables the realization of high-accuracy three-dimensional topography for the entire area with less effort and time compared to the past direct survey using GNSS or total station. From 3-D topographic data, various topographical analysis is possible. To improve the accuracy of drone photogrammetry, direct GCP surveying in the field is essential, and the numbers and reasonable positioning of GCPs are very important. In the case of beaches or tidal flats on the west coast of Korea, the numbers and location of GCPs are important factors in efficient drone photogrammetry because of the size of the area, difficulties of movement, and the risk from tides. If the RTK (Real-time kinematic) or PPK (Post-processed kinematic) method is used, the increased accuracy of the drone's location enables high-accuracy photogrammetry with a small number of GCPs. This study presents an efficient drone photogrammetry method in terms of time and economy by comparing and analyzing the results of drone photogrammetry using Non-PPK with low-cost PPK-Kit, based on the tests of various numbers and locations of GCPs in the university field including various slopes and structures like coastal terrain.

• Tuberculosis and Respiratory Diseases
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• 제87권1호
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• pp.91-99
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• 2024

Background: Tuberculous pleural effusion (TPE) and parapneumonic effusion (PPE) are often difficult to differentiate owing to the overlapping clinical features. Observational studies demonstrate that the ratio of lactate dehydrogenase to adenosine deaminase (LDH/ADA) is lower in TPE compared to PPE, but integrated analysis is warranted. Methods: We conducted a systematic review to evaluate the diagnostic accuracy of the LDH/ADA ratio in differentiating TPE and PPE. We explored the PubMed and Scopus databases for studies evaluating the LDH/ADA ratio in differentiating TPE and PPE. Results: From a yield of 110 studies, five were included for systematic review. The cutoff value for the LDH/ADA ratio in TPE ranged from <14.2 to <25. The studies demonstrated high heterogeneity, precluding meta-analysis. Quality Assessment of Diagnostic Accuracy Studies Tool 2 assessment revealed a high risk of bias in terms of patient selection and index test. Conclusion: LDH/ADA ratio is a potentially useful parameter to differentiate between TPE and PPE. Based on the limited data, we recommend an LDH/ADA ratio cutoff value of <15 in differentiating TPE and PPE. However, more rigorous studies are needed to further validate this recommendation.

• 한국산학기술학회논문지
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• 제13권5호
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• pp.2298-2304
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• 2012

형광 X-선 스펙트럼을 분석 방법은 RoHS 성분 및 중금속 함량 분석 등 여러 분야에 응용이 가능하며 비교적 빠른 시간 안에 함량 분석 결과를 얻을 수 있다. 형광 X-선 스펙트럼에는 잡음 및 여러 요인이 포함되어 있어 분석 정확도를 떨어뜨린다. 본 논문에서는 여러 요인 중 잡음의 특징을 분석하여 형광 X-선 스펙트럼 분석의 정확도를 높이고자 한다. 형광 X-선 스펙트럼은 산탄잡음(푸아송 잡음)의 특징을 가지고 있으며, 따라서 작은 신호에서는 잡음의 크기가 상대적으로 크고, 큰 신호에서는 잡음의 크기가 상대적으로 작은 특징을 가지고 있다. 기존에 잡음을 분석하고 제거하는 방법 및 알고리즘은 이러한 특징을 반영하지 않은 일반적인 목적으로 사용되는 방법으로 일반적인 알고리즘을 사용하여 잡음을 제거하게 되면 왜곡된 결과를 얻게 된다. 정확한 잡음 분석을 기반으로 효율적인 잡음 제거 알고리즘을 설계할 수 있고, 또한 높은 정확도의 원소 함량 분석 결과를 기대할 수 있다.

• 한국콘텐츠학회논문지
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• 제16권10호
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• pp.393-402
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• 2016

기상청에서 현재 시행되고 있는 만족도 설문조사의 한계를 보완하기 위해 SNS를 통한 감성분석이 활용될 수 있다. 감성분석은 2011~2014년 동안 '기상청'을 언급한 트위터를 수집하여 나이브 베이즈 방법으로 긍정, 부정, 중립 감성을 분류하였다. 기본적인 나이브 베이즈 방법에 긍정, 부정, 중립의 각 감성에서만 출현한 형태소들로 추가사전을 만들어 감성분석의 정확도를 향상시키는 방법을 제안하였다. 분석결과 기본적인 나이브 베이즈 방법으로 감성을 분류할 경우 약 75%의 정확도로 학습데이터를 재현한데 반해 추가 사전을 적용할 경우 약 97%의 정확성을 보였다. 추가사전을 활용하여 검증자료의 감성을 분류한 결과 약 75%의 분류 정확도를 보였다. 낮은 분류 정확도는 향후 기상 관련의 다양한 키워드를 포함시켜 학습데이터 양을 늘려 감성사전의 질을 높임과 동시에 상시적인 사전의 업데이트를 통해 개선될 수 있을 것이다. 한편, 개별 어휘의 사전적 의미에 기반한 감성분석과 달리 문장의 의미에 기반하여 감성을 분류할 경우 부정적 감성 비율의 증가와 만족도 변화 추이를 설명할 수 있을 것으로 보여 향후 설문조사를 보완할 수 있는 좋은 수단으로 SNS를 통한 감성분석이 활용될 수 있을 것으로 사료된다.

• 한국운동역학회지
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• 제15권2호
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• pp.83-92
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• 2005

Computer-assisted motional analysis is a popular method in biomechanical studies. Validation of the specific system and its measurement are fundamental to its application in the areas. Because the accuracy and consistency of a particular system provide the researchers with critical information to assist in making judgements regarding the degree to which inferences can be drawn from measurement data. The purpose of this study was to assess the accuracy and consistency of the Kwon3D motion analysis system. Validation parameters were five lengths from eight landmarkers in combination with the DLT reconstruction error values, digitizing monitor resolutions, and numbers of control points. With the best setting, Kwon3D's estimations of 260cm, 200cm, 140cm, 100cm, and 20cm were $260.33{\pm}.688cm$, $199.98{\pm}.625cm$, $139.89{\pm}.537cm$, $99.75{\pm}.466cm$, $20.08{\pm}.114$, respectively. There was no significant DLT error value difference between two monitor resolutions, but 0.27cm significant difference in 260cm estimation. There were significant differences in 260cm and 200cm estimations between with 33-control-point DLT error and with 17-control-point DLT error, but no in 140cm, 100cm, and 20cm estimations. Test-retest results showed that Kwon3D measurements were highly consistent with reliability coefficients alpha of .9263 and above.

• 대한공간정보학회지
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• 제18권2호
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• pp.13-20
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• 2010

현재 국토지리정보원은 전국 44개의 상시관측소를 이용하여 VRS 서비스를 제공하고 있으며 이를 이용하여 짧은 시간 동안 취득된 자료의 처리를 통해 높은 위치정밀도의 획득이 가능하다. 그러나 공공기준점 측량을 위한 VRS 측량의 가용성 분석은 미비한 상태이다. 따라서 본 연구에서는 다양한 환경에서 데이터를 취득하여 공공기준점 측량에 대해 적용하기 위한 VRS 측량의 정확도를 분석하였다. 그 결과 85%의 데이터가 4cm 이내의 수평오차가 나타남으로써 VRS 측량에 적용할 수 있다고 판단되었고 좌표의 정확도를 판별하는 인자로 GDOP(Geometric Dilution of Precision)보다는 추정된 좌표의 분산을 나타내는 PQ(Position Quality)를 이용하는 것이 효율적임을 알수 있었다. 또한, 현재 대표적인 VRS 장비회사인 TRIMBLE, MAGELLAN, LEICA, TOPCON의 장비의 정밀도를 비교분석한 결과 수평위치의 표준편차가 3cm 미만으로 나타났으며, 회사 장비 별 정밀도는 비슷한 것으로 확인 되었으며, 공공기준점 측량에 VRS 측량을 적용하여도 무방하다고 사료된다.

• 한국환경보건학회지
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• 제35권6호
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• pp.461-467
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• 2009

Exposure analysis is a critical component of determining the health impact of pollutants. Global positioning systems (GPS) could be useful in developing time-location information for use in exposure analysis. This study compares four low cost GPS receivers with data logging capability (Garmin 60, Garmin Forerunner 201, GeoStats GeoLogger and Skytrx minitracker MT4100) in terms of accuracy, precision, and ease of use. The accuracy of the devices was determined at two known National Geodetic Survey points. The coordinates logged by the devices were compared when the devices were carried while walking and driving. The Garmin 60 showed better accuracy and precision than the GeoLogger when they were placed at the geodetic points. The Forerunner and Skytrx did not record when they were kept stationary. When the subject wore the devices while walking, the location of the devices differed by about 8 m on average between any two device combinations involving the four devices. The distance between the coordinates logged by the devices decreased when the devices were carried with their antennas facing the sky. All the devices showed similar routes when they were used in a car. All the devices except the Forerunner had satisfactory signal reception when they were worn and when they were carried in the car. The GeoLogger is less comfortable for the subject because of specific wearing requirements. This evaluation found that the Garmin 60 and the Skytrx may be useful in personal exposure analysis studies to record time-location data.

• 동의생리병리학회지
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• 제20권1호
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• pp.209-214
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• 2006

This study is validity study of the questionnaire for doctors for Sasang constituion diagnosis. (an objects of this study : 314 patients) We analyzed the results of questionnaires about 314 patients who were diagnosed in Department of Sasang Constitutional Medicine from June to November, 2004. The questionnaire for doctors consists of objective valuation about the patients for Sasang constituion diagnosis. In the analysis about all variables, we obtain the diagnosis accuracy of 92%. In the analysis about body type variable, we obtain the diagnosis accuracy of 44-48%. In the analysis about external appearance, mental characteristics, physiology & pathologic symptoms variables, we obtain the diagnosis accuracy of 46-72%. After all, in order to increase of the diagnosis accuracy, we have to analysis total variables(body type, external appearance, mental characteristics, physiology & pathologic symptoms) for sasang constituion diagnosis. Hereafter, We need many data and standardization for sasang constituion diagnosis.