• 한국측량학회지
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• 제25권5호
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• pp.399-405
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• 2007

정밀한 위치정보의 제공은 GPS가 갖는 가장 큰 특징 중의 하나이다. 기준국과 사용자의 공통된 관측정보를 이용하는 상대측위기법이 일반적으로 정밀위치 정보 산출에 사용되고 있다. 그러나 기준국과 사용자의 기선거리가 멀어지면 GPS 신호가 통과하는 공간상의 매질특성이 서로 다르기 때문에 이중차분에 의해서도 전리층과 대류층 등의 오차요인은 완전히 제거가 되지 않는다. 본 연구는 이러한 특성을 고려하여 전리층과 대류층에 대한 오차보정정보를 추가적으로 생성하여 자료처리에 적용하였다. 그 결과 실험지역 17곳 중 14곳은 오차보정정보 적용이후에 위치정확도가 향상되었음을 알 수 있었다. 또한 기선거리에 따른 위치정확도 향상정도를 분석하였다.

• Journal of Korean Neurosurgical Society
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• 제55권6호
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• pp.337-342
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• 2014

Objective : To determine deformity correction by postural correction and subsequent balloon inflation in acute vertebral compression fractures (OVCFs) and to examine the effect of bone mineral density on deformity correction. Methods : A totol of 50 acute OVCFs received balloon kyphoplasty. Lateral radiographs were taken and analyzed at five different time points : 1) preoperative, 2) after placing the patient in prone hyperextended position, 3) after balloon inflation, 4) after deposition of the cement, and 5) postoperative. All fractures were analyzed for height restoration of anterior (Ha), middle (Hm) and posterior (Hp) vertebra as well as Cobb angle and Kyphotic angle. The bone mineral density (BMD) of lumbar spine was measured by dual-energy X-ray absorptiometry. According to the T-score, the patients were divided into two groups which were osteoporosis group and osteopenia group. Results : Postoperative measurements of Ha, Hm and the Cobb angle demonstrated significant reduction of 4.62 mm, 3.66 mm and $5.34^{\circ}$ compared with the preoperative measurements, respectively (each p<0.05). Postural correction significantly increased Ha by 5.51 mm, Hm by 4.35 mm and improved the Cobb angle by $8.32^{\circ}$ (each p<0.05). Balloon inflation did not demonstrate a significant improvement of Ha, Hm or the Cobb angle compared with baseline prone hyperextended. Postural correction led to greater improvements of Ha, Hm and Cobb angle in osteoporosis group than osteopenia group (each p<0.05). Conclusion : In acute OVCFs, the height restoration was mainly attributed to postural correction rather than deformity correction by balloon inflation. BMD affected deformity correction in the process of postural correction.

• Journal of Positioning, Navigation, and Timing
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• 제7권1호
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• pp.43-52
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• 2018

In recent years, the need of high accuracy navigation for vehicles has increased due to the development of autonomous driving vehicles and increase in land transportation convenience. This study is performed for vehicle users to achieve a performance of centimeter-level positioning accuracy by utilizing Compact Network Real-time Kinematic (RTK) that is applicable as a national-level infrastructure. To this end, medium-baseline RTK was implemented in real time to estimate accurate integer ambiguities between reference stations for reliable generation of Network RTK correction using the linear combination of carrier-phase observations and L1/L2 pseudo-range measurements. The residual tropospheric error was estimated in real time to improve the accuracy of double-differenced integer ambiguity resolution between network configuration reference stations that have at least 30 km or longer baseline distance. In addition, C++ based software was developed to enable real-time generation and broadcasting of Compact Network RTK correction information by utilizing an accurately estimated double-differenced integer ambiguity values. As a result, the horizontal and vertical 95% accuracy was 2.5cm and 5.2cm, respectively, without performance degradation due to user's position change within the network.

• 한국멀티미디어학회논문지
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• 제25권3호
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• pp.493-501
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• 2022

This paper is a study on context-sensitive spelling error correction and uses the Korean WordNet (KorLex)[1] that defines the relationship between words as a graph to improve the performance of the correction[2] based on the vector information of the word embedded in the correction technique. The Korean WordNet replaced WordNet[3] developed at Princeton University in the United States and was additionally constructed for Korean. In order to learn a semantic network in graph form or to use it for learned vector information, it is necessary to transform it into a vector form by embedding learning. For transformation, we list the nodes (limited number) in a line format like a sentence in a graph in the form of a network before the training input. One of the learning techniques that use this strategy is Deepwalk[4]. DeepWalk is used to learn graphs between words in the Korean WordNet. The graph embedding information is used in concatenation with the word vector information of the learned language model for correction, and the final correction word is determined by the cosine distance value between the vectors. In this paper, In order to test whether the information of graph embedding affects the improvement of the performance of context- sensitive spelling error correction, a confused word pair was constructed and tested from the perspective of Word Sense Disambiguation(WSD). In the experimental results, the average correction performance of all confused word pairs was improved by 2.24% compared to the baseline correction performance.

• 천문학회지
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• 제48권5호
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• pp.229-236
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• 2015

We report results of investigation of amplitude calibration for very long baseline interferometry (VLBI) observations with Korean VLBI Network (KVN). Amplitude correction factors are estimated based on comparison of KVN observations at 22 GHz correlated by Daejeon hardware correlator and DiFX software correlator in Korea Astronomy and Space Science Institute (KASI) with Very Long Baseline Array (VLBA) observations at 22 GHz by DiFX software correlator in National Radio Astronomy Observatory (NRAO). We used the observations for compact radio sources, 3C 454.3, NRAO 512, OJ 287, BL Lac, 3C 279, 1633+382, and 1510–089, which are almost unresolved for baselines in a range of 350-477 km. Visibility data of the sources obtained with similar baselines at KVN and VLBA are selected, fringe-fitted, calibrated, and compared for their amplitudes. We find that visibility amplitudes of KVN observations should be corrected by factors of 1.10 and 1.35 when correlated by DiFX and Daejeon correlators, respectively. These correction factors are attributed to the combination of two steps of 2-bit quantization in KVN observing systems and characteristics of Daejeon correlator.

• 한국측량학회지
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• 제28권3호
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• pp.329-336
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• 2010

본 연구는 시간차방식(TOF: Time of flight)과 근적외선 파장대역(760-3000nm)을 사용하는 지상라이다를 이용해서 다양한 사용자 타깃에 대해 반사도와 거리정확도를 테스트하였다. 특별히 사용자 타깃에 대한 측점군의 반사도는 실내에서 독일 Gretag Macbeth사의 i1 분광광도계로 측정되었다. 그리고 지상라이다의 성능 평가를 위해 정밀 EDM 검기선장에서 지상라이다를 이용해서 타깃을 스캐닝 하여 기준표석간 이격거리를 측정하여 표준거리와 비교하였다. 테스트 결과로서, 약 10m 와 170m 기준표석간 이격거리에 설치된 흰색 수지 타깃을 제외하고, 실험에 이용된 다른 타깃들의 거리측정값은 기준거리와 수 mm 정확도 차이를 보였다. 향후 대기보정, 장비보정, 부가상수와 같이 거리정확도에 영향을 미치는 변수들에 대한 연구가 필요할 것으로 사료 된다.

• 대한원격탐사학회지
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• 제38권6_1호
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• pp.1081-1089
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• 2022

본 연구는 시계열 Small Baseline Subset (SBAS)-InSAR 기법을 이용하여 울산시의 지반 침하를 조사하였으며, 79개의 Sentinel-1 SAR 영상과 385개의 간섭도 영상(interferogram)을 사용하여 2015년 5월부터 2021년 12월 울산광역시의 지상 변위(surface displacement)를 추정하였다. 지반 침하율은 북구와 남구 삼산동 2지역에서 연 3.44 cm, 1.68 cm로 계측되었다. 또한 Generic Atmospheric Correction Online Service (GACOS)로 생성한 Zenith Total Delay (ZTD) 지도를 활용하여 unwrapping된 간섭도 위상에서 대기 지연(tropospheric delay)의 영향을 제거할 수 있는 가능성을 평가하였으며, GACOS ZTD 보정 전후의 SBAS-InSAR 지상 변위 측정의 차이가 연 1 mm 미만임을 발견하였다.

• 센서학회지
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• 제25권4호
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• pp.291-296
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• 2016

The ideal chemical sensor must show the similar result under the same condition for accurate measurement of gases regardless of time. However, the actual responses of chemical sensors have been shown the lacks of repeatability and reproducibility because of the drift which has been caused by aging and pollution of the sensor and the environment change such as temperature and humidity. If the problems are not properly taken into considerations, the stability and reliability of the system using chemical sensors would be decreased. In this paper, we analyzed the sensor's drift and applied the three different compensation methods(DWT( Discrete Wavelets Transform), Baseline Manipulation, Internal Normalization) for reducing the effects of the drift in order to improve the stability and the reliability of short term of the chemical sensors. And in order to compare the results of the methods, the standard deviation was used as a criterion. The sensor drift was analyzed by a trend line graph. We applied the three methods to the successive data measured for three days and compared the results. As a result of comparison, the standard deviation of DWT showed lowest value. (Before compensation: 7.1219, DWT: 1.3644, Baseline Manipulation: 2.5209, Internal Normalization: 3.1425).

• 소음진동
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• 제10권2호
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• pp.338-344
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• 2000

비선형 구조물에 대하여 미끄러짐 또는 기울어짐 해석을 수행할 때에는 수평 두 방향 입력을 동시에 고려하는 해석을 수행할 것을 추천한다. 그 이유는 단일 방향 입력만을 고려한 비선형 해석의 결과가 입력지진의 기준선 조정 여부에 아주 민감하고 자칫 과도하게 보수적이거나 또는 오히려 비보수적인 결과를 초래할 수 있기 때문이다. 특히, 오래 전에 작성되어 일차적 해석만 가능한 전산 프로그램을 사용하여 해석하는 경우 주의가 요구된다. 본 논문에서는 입력지진의 기준선조정에 의한 영향을 수평 단일방향 입력만을 고려하는 해석과 수평 두 방향 입력을 동시에 고려하는 해석에 대하여 살펴본다. 이를 위하여 자립형 계에 대한 예저 헤석을 수행한 결과, 단일방향 비선형 해석시 나타날 수 있는 이러한 불확실성을 피하기 위하여 두 방향 입력을 동시에 고려하는 해석이 필요하고 입력 지진의 기준선 조정과 연계된 표준화된 지침이 필요하다는 것을 알 수 있었다.

• Journal of Periodontal and Implant Science
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• 제44권4호
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• pp.201-206
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• 2014

Purpose: Aggressive periodontitis, especially in its severe form, was traditionally considered to have an unfavourable prognosis. It required a complex treatment and its stabilization was often achieved by surgical therapy. The aim of this study was to investigate the results of nonsurgical periodontal treatment in severe generalized forms of aggressive periodontitis. Methods: Patients with advanced generalized aggressive periodontitis were included in the study. Probing depth (PD) of pockets ${\geq}7mm$ and clinical attachment level (CAL) of sites with attachment loss ${\geq}5mm$ were measured at baseline before nonsurgical periodontal treatment, at re-evaluation, and after treatment. The following other parameters were recorded: resolution of inflammation and bone fill. We compared the baseline values with re-evaluation and posttreatment values using the Friedman test. The Wilcoxon test with the Bonferroni correction was used for both re-evaluation and posttreatment values. Results: Seven patients with 266 periodontal sites were examined. A significant difference was found between values, reported as medians with interquartile ranges, for PD at baseline (7.94 [7.33-8.19] mm) and both re-evaluation (4.33 [3.63-5.08] mm) and posttreatment (3.54 [3.33-4.11] mm) values (P=0.002). A significant difference was also found between values for CAL at baseline (9.02 [7.5-9.2] mm) and both re-evaluation (6.55 [6.30-6.87] mm) and posttreatment (6.45 [5.70-6.61] mm) (P=0.002). Inflammation was resolved and angular bone defects were repaired in all cases. Conclusions: These therapeutic results suggest that this form of periodontitis could have positive outcomes after nonsurgical periodontal treatment. The reparative potential of tissue affected by severe aggressive periodontitis should encourage clinicians to save apparently hopeless teeth in cases of this form of periodontitis.