• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.4
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• pp.245-254
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• 2018

Impact of tropospheric correction techniques on accuracy of the GPS (Global Positioning System) derived ellipsoidal heights has been experimentally assessed in this paper. To this end, 247 baselines were constructed from a total of 88 CORS (Continuously Operating Reference Stations) in Korea. The GPS measurements for seven days, acquired from the so-called integrated GNSS (Global Navigation Satellite Systems) data center via internet connection, have been processed by two baseline processing software packages with an application of the empirical models, such as Hopfield, modified Hopfield and Saastamoinen, and the estimation techniques based on the DD (Double-Differenced) measurements and the PPP (Precise Point Positioning) technique; hence a total number of the baseline processed and tested was 8,645. Accuracy and precision of the estimated heights from the various correction schemes were analyzed about baseline lengths and height differences of the testing baselines. Details of these results are summarized with a view to hopefully providing an overall guideline of a suitable selection of the modeling scheme with respect to processing conditions, such as the baseline length and the height differences.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.75-85
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• 2017

A method to estimate hourly temperature profiles on calm and clear nights was developed based on temporal changes of inversion height and strength. A meteorological temperature profiler (Model MTP5H, Kipp and Zonen) was installed on the rooftop of the Highland Agriculture Research Institute, located in Daegwallyeong-myeon, Pyeongchang-gun, Gangwon-do. The hourly vertical distribution of air temperature was measured up to 600 m at intervals of 50 m from May 2007 to March 2008. Temperature and relative humidity data loggers (HOBO U23 Pro v2, Onset Computer Corporation, USA) were installed in the Jungdae-ri Valley, located between Gurye-gun, Jeollanam-do and Gwangyang-si, Jeollanam-do. These loggers were used to archive measurements of weather data 1.5 m above the surface from October 3, 2014, to November 23, 2015. The inversion strength was determined using the difference between the temperature at the inversion height, which is the highest temperature in the profile, and the temperature at 100 m from the surface. Empirical equations for the changes of inversion height and strength were derived to express the development of temperature inversion on calm and clear nights. To estimate air temperature near the ground on a slope exposed to crops, the equation's parameters were modified using temperature distribution of the mountain slope obtained from the data loggers. Estimated hourly temperatures using the method were compared with observed temperatures at 19 weather sites located within three watersheds in the southern Jiri-mountain in 2015. The mean error (ME) and root mean square error (RMSE) of the hourly temperatures were $-0.69^{\circ}C$ and $1.61^{\circ}C$, respectively. Hourly temperatures were often underestimated from 2000 to 0100 LST the next day. When temperatures were estimated at 0600 LST using the existing model, ME and RMSE were $-0.86^{\circ}C$ and $1.72^{\circ}C$, respectively. The method proposed in this study resulted in a smaller error, e.g., ME of $-0.12^{\circ}C$ and RMSE of $1.34^{\circ}C$. The method could be improved further taking into account various weather conditions, which could reduce the estimation error.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.4
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• pp.75-83
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• 2023

Apart from implementing hardware solutions like raising the crest freeboard of coastal structures to efficiently counter wave-overtopping, there is a simultaneous requirement for software-driven disaster mitigation strategies. These tactics involve the swift and accurate dissemination of wave-overtopping information to the inland regions of coastal zones, enabling the regulation of evacuation procedures and movement. In this study, a method was proposed to estimate wave-overtopping by utilizing the temporal variation of wave heights exceeding the structure's crown level, with the aim of developing an on-site wave measurement system for providing wave-overtopping information in the field. Laboratory model experiments were conducted on vertical seawall structures to measure wave-overtopping volumes and wave runup heights under different wave conditions and structural freeboard variations. By assuming that the velocity of water inundation on the top of the structure during wave-overtopping events is equivalent to the long-wave velocity, an overtopping discharge coefficient was introduced. This coefficient was utilized to estimate the rate of wave-overtopping based on the temporal changes in wave runup heights measured at the top of the structure. Upon reasonably calculating the overtopping discharge coefficient, it was verified that the estimation of wave-overtopping could be achieved solely based on the wave runup heights.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.661-668
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• 2009

The slosh natural frequencies, damping ratio, slosh mass and slosh force applying point of the liquid in cylindrical tank are estimated using the nonlinear least squares method in time domain. The estimated slosh model parameters are in good agreement with the results of the theoretical calculations for various liquid depths. Furthermore, this methodology will be applied to predict the sloshing parameters for a liquid propellant tank using ground experimental test-bed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.419-421
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• 2022

어선은 어획물로 인한 무게 변화 및 어구 사용에 의한 외력으로 GM이 변화한다. 하지만 실시간으로 변화하는 GM을 추정하는 것은 어려우며, 현재 적용되는 추정식은 어선에 대입하기에 정확성이 떨어진다. 이에 본 논문은 어선의 GM 추정식 개발에 기여하기 위해 어선의 Roll 운동응답을 분석하고, 실험과 시뮬레이션의 GM과 파경사 관계를 밝히고자 한다. 7톤 급의 실제 운항 중인 어선의 모델선 GM을 변화시키면서 파경사별 Roll 운동응답 데이터를 수집한다. GM 변화의 경우 선박 무게중심부에 높이 방향으로 추를 조절할 수 있도록 했으며, 파경사는 동일 주기 4가지 파경사를 선정하였다. GM과 파경사가 커질수록 Roll 응답이 증가하는 경향을 보이며, GM과 파경사가 커짐에 따라 기울기가 비선형성을 보이며 증가하는 것을 확인하였다. 본 연구를 통해서 어선의 GM과 파경사의 관계를 파악하고, GM추정에 사용할 수 있느 보정 계수를 도출할 수 있다. 추후에 본 연구 내용을 활용하여 운항 중인 어선의 실시간 GM 추정시스템 개발에 기여가 가능할 것으로 생각한다.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.374-381
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• 2023

The travel time of flash floods along mountain streams is mainly governed by reach-average velocity, rather than by the point velocity of the locations of interest. Reach-average velocity is influenced by various factors such as stream geometry, streambed materials, and the hydraulic roughness of streams. In this study, the reach-average velocity in mountain streams was measured for storm periods using rhodamine dye tracing. The point cloud data obtained from a LiDAR survey was used to extract the average hydraulic roughness height, such as R_a, R_max, and R_z. The size distribution of the streambed materials (D₅₀, D₈₄) was also considered in the estimation of the roughness height. The field experiments revealed that the reach-average velocities had a significant relationship with flow discharges (v = 0.5499Q^0.6165 ), with an R² value of 0.77. The root mean square error in the roughness height of the R_a-based estimation (0.45) was lower than those of the other estimations (0.47-1.04). Among the parameters for roughness height estimation, the R_a -based roughness height was the most reliable and suitable for developing the reach-average velocity equation for estimating the travel time of flood waves in mountain streams.

• Journal of Korea Multimedia Society
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• v.16 no.2
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• pp.131-137
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• 2013

Zoom motion estimation of video sequence is very complicated for implementation. In this paper, we propose a method to implement the zoom motion estimation using together the depth camera and color camera. Depth camera obtains the distance information between current block and reference block, then zoom ratio between both blocks is calculated from this distance information. As the reference block is appropriately zoomed by the zoom ratio, the motion estimated difference signal can be reduced. Therefore, the proposed method is possible to increase the accuracy of motion estimation with keeping zoom motion estimation complexity not greater. Simulation was to measure the motion estimation accuracy of the proposed method, we can see the motion estimation error was decreased significantly compared to conventional block matching method.

• Journal of the Korean Geographical Society
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• v.34 no.4
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• pp.371-384
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• 1999

디퓨젼 공식 모형은 한국 하천의 중.상류 지역의 하안 단구의 단구애와 같은 삭박 사면에 대한 연대 측정에 유용하게 적용될 수 있다. 지형 연대 측정 방법은 최대 사면각, 사면의 높이 등과 같은 사면단면에 대한 측정된 자료를 사용하는 보조적 연대 측정법의 하나이다. 토탄층에 대한 탄소연대측정법 또는 화분분석과 같은 방법으로 잘 통제되어진 연대를 이 모형에 적용하여 생성 연대를 모르는 다른 사면의 연대를 추정하는데 사용될수 있다. 적용사례로 경북 영양의 연지 저위단구에서 구해진 연대값 6ka를 이용하여, 최대 사면각과 사면의 높이간의 모의실험을 통해 연지 단구의 저위면/중위면 사이의 단구애 상의 삭박률 100 10-4m2/yr.을 구할수 있었다. 이 삭박률을 영춘 단구의 저위면/중위면 사이의 단구애의최대 사면각과 사면 연대간의 모의실험에 적용하여 영춘 단구의 저위면/중위면 사이의 단구애의 형성 시기를 약 37,000년 전으로 구할 수 있었다. 그러나 보다 정밀한 값을 얻기 위해서는 남한강 중.상류의 단구 지역에 대한 적절한 사면 측정 자료가 요구된다.

• The Korean Journal of Applied Statistics
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• v.24 no.6
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• pp.1115-1128
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• 2011

Cut-off sampling that discards a part of the population from the sampling frame, is a widely used method for a highly skewed population like a business survey. Usually to the estimate of population total, we need to estimate the total of the take-nothing stratum. Many estimators have been developed to estimate the total of the take-nothing stratum. In this paper, we suggest a new composite estimator which combines the estimator suggested by Sarndal et al. (1992) and a ratio estimator obtained by small samples from the take-nothing stratum. Small simulation studies are performed for the comparison of the estimators and we confirm that the new suggested estimator is superior to the others.

• The Korean Journal of Financial Management
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• v.14 no.3
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• pp.263-287
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• 1997

본 연구에서는 국내은행의 위험도가 반영된 보험요율을 Merton에 의해 처음으로 제시된 예금보험요율 결정모형을 이용하여 추정하였다. 실증분석 결과에 의하면 표본은행간의 예금보험요율의 추정치에는 횡단면적 차이가 있는 것으로 나타나 표본기간 중 여러 은행들이 공격적 경영을 취함으로써 은행파산의 위험도를 높이는 도덕적 위해의 문제를 발생시켰음을 보여주고 있다. 본 연구는 상관관계 분석을 통하여 추정된 보험요율이 Moody's사의 국내은행에 대한 장기신용등급과 재무건전도등급, 그리고 은행규모, 수익성, 자본적정성, 자산건전성을 나타내는 지표들과 어떠한 관계에 있는 지를 살펴보았다. 분석결과에 의하면 Moody's사의 국내은행에 대한 장기신용등급, 재무건전도등급과 보험요율 사이에는 통계적으로 유의한 관계가 있는 것으로 나타나 추정된 보험요율이 이들 지표와 마찬가지로 위험도를 적절히 반영하는 것으로 나타났다. 또한 보험요율은 은행규모, ROA, ROE들과는 음의 관계가 있는 것으로 나타났으나, BIS기준 자기자본비율, 부실여신비율과는 양의 관계가 있는 것으로 나타났다. 그러나 자기자본비율이나 부실여신비율이 은행의 신용도나 위험도를 적절하게 반영하지 못하는 것으로 나타남으로써 이들 비율에 대한 회계방식의 개선이 요구됨을 본 연구의 결과는 보여주고 있다.