• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2034-2036
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• 2003

본 논문에서는 21차 상태변수를 갖는 칼만필터 형태의 비행시험용 데이터 융합필터 알고리듬의 성능을 분석하였다. 실측 데이터에 대한 분석을 통하여 상태변수 선택의 적절성을 검증하였다. 공분산 해석기법을 통하여 기 개발된 데이터 융합 알고리듬의 추정값의 오차범위를 구하였다. 수치적인 성능값을 구하고자 간단한 시뮬레이터를 설계하였다. 20회 몬테칼로 시뮬레이션과 공분산 해석결과에 기반하여 필터 계수를 튜닝하였고 이를 기설계된 분산형 칼만필터에 적용하였다. 실시간 소프트웨어 모듈의 수행결과를 동일한 실측데이터를 적용한 후처리 실험결과와 비교하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.387-393
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• 2009

In this paper, we have considered the network performance of the VoIP service with the measurement by an emulator, and analyzed the major factors to affect its performance. Also, we have used the measured values to investigate the traffic variations, where their values were observed in the commercial operated network after the delay, jitter and packet loss, and loss compensation methods were applied as the dominant elements. It is expected that our presented results will be a good data to provide the high-quality of voice service in the Internet.

• 전기의세계
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• v.34 no.11
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• pp.654-665
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• 1985

현재 전자군의 매개변수해석에 많이 이용되고 있는 방법과 이들의 실측을 하기 위한 실험방법으로는 몇가지가 있다. 대체로 정상Townsend실험, 퍼스Townsend실험, 비행시간관측실험 등이 있으며, 본 고찰에서는 이들을 중심적으로 취급하였다. 그러나 이들은 측정실험방법이 각각 다름에 따라 이론적 해석방법도 다르다. 또한 본 논문에서는 에너지분포를 2차근사 방법으로 해석한 것을 서술하고, 그 이상의 고차항까지 고려하여 해석결과와 비교한예는 그림7과 같다. 이와 같이 기체방전현상의 이론적 해석이 실험치와 잘일치되는 것으로 보아 기체계의 절연설계나 특성 예측이 가능하기 때문에 공학적 응용이 기대되는 모델화도 이루어질 수가 있다. 기체방전simulation이 응용되어지고 있는 분야는 이외에도 가장 현대적인 응용인 gas laser의해석, laser조사에 의한 방전트리거기구의 해석 등 상당히 광범위하게 응용되어지고 있으므로 이에 대한 연구가 활성화되어져야 하겠다.

• Geotechnical Engineering
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• v.4 no.4
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• pp.51-60
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• 1988

기초지반에 대한 응력·변형률관계를 규명하기 위하여 소성론에 기초를 둔 구성방정식이 폭넓게 이용되고 있다. 본문은 성토나 강성기초와 같은 지반구조물을 연약점토지반에 축조하였을 때에 발생하는 변형에 관해 연구코저 한 것이다. 본 연구를 위하여 2차원모형토조를 제작, 재하실험한 시료를 재하실험을통하여 침하, 융기, 측방변위등을 측정하고 이들을 여러구함식과 비교고찰하였다. 구성식으로서는 한계상태개념에 근거를 둔 Cam-clay, Modified Cam-clay그리고 시간의존성을 고려한 탄·정감성 model인 Sakiguchi model을 이용하고 이들을 수치해를 통해 고찰하였다. 본 모형실험에 의하면 변형을 예측하는데 있어서 ModifiedICam-clay model이 Original Cam-clay"model 보다 실측치에 가까웠으며 또한 시간의존성을 고려한 탄·점견성 model인 Sekiguchi model'는 본 실험에서처럼 단기간의 실험에서는 변형의 creep조건을 만족시키지 못하므로 현장조건에 따라 잘- 판단하여 적용하여 야할 것으로 판단 된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.111-117
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• 2015

We investigate the influence of spatial rainfall distribution on hillslope soil erosion through laboratory experiments. Two distinct spatial distributions are examined in this study, i.e., rainfall concentrated on central area versus upper area of hillslope. During the entire period of 8 hours for each experiment, direct runoff, subsurface flow, and sediment yield are measured at high temporal resolution (10 minutes). Compared to the case that rainfalll concentrated on central area, upstream concentrated rainfall results in lower peak of the sediment yield curve while greater cumulative sediment yield. Cumulative sediment yield increases over time linearly but its growth rate shows a sudden decrease at around 2 hours. This should be taken into consideration when temporal variability of sediment yield is estimated from observed total amount, and demonstrates the necessity of measuring sediment yield at high temporal resolution.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.3
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• pp.161-169
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• 1999

In order to investigate the validity of acoustic tomography for current measurement, an experiment of reciprocal sound transmission was conducted in April, 1997 in the southern water of Koje island. This experiment was attempted as a preliminary field study on coastal ocean acoustic tomography for construction of real-time current observation system. Examining the physical oceanography environments, the current data obtained by travel time difference of reciprocal sound wave was compared with the data of Acoustic Doppler Current Profiler (ADCP). The result shows the correlation coefficient of 0.943, very good relation between the two data, and therefore the ocean acoustic tomography could be a useful method for current measurement in the coastal area.

• Journal of the Korean Geosynthetics Society
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• v.12 no.3
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• pp.75-79
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• 2013

The frost depth is one of important factors in the design of structures such as roadways, buried pipeline, and foundations. A frost indicator with methylene blue solution has several advantages with respect to installation cost, maintenance, and simple measurement. However, as a geotechnical engineering aspect, the accuracy of the frost indicator has not been proved yet. This paper presents experimental and field investigations of the accuracy of the frost indicator and contour maps of maximum frost depth. The contour maps of maximum frost depth can be applied to design geo-infrastructure in South Korea.

• Journal of Korea Water Resources Association
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• v.30 no.4
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• pp.335-346
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• 1997

This study aims at examining closely the scour around a pier due to irregular water stage changes during flood. At the Sangye bridge is located lowermost downstream of the Bocheong stream in the Kum River, the IHP experimental watershed. For this purpose, we have analyzed the change of scour depths due to stage hydrographs of experimental basin by a simulation. To examine the scour phenomenon around a pier due to irregular stage change in flood, we have analyzed the change of scour depth corresponding to stage hydrograph of field watershed after verification of model channel. From this study, the following conclusions are made: First, in case of predicting the maximum scour depth around a pier with stage hydrograph in the state of steady flow, we should choose the highest stage. Second, after increasing the stage, the equilibrium scour depth became smaller than the maximum scour depth. Therefore, in case of estimating the maximum scour depth in rivers, it is recommended that we should consider additional scour depth with is reduced by infilling the sediments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1779-1786
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• 2014

Artificial Intelligence-based techniques have been applied to problems where mathematical relations can not be presented due to complicatedness of the physical process. A representative example in hydraulics is the local scour around bridge piers. This study presents a GEP model for predicting the local scour around bridge piers. The model is trained by 64 laboratory data to build the regression equation, and the constructed model is verified against 33 laboratory data. Comparisons between the models with dimensional and normalized variables reveals that the GEP model with dimensional variables predicts better. The proposed model is now applied to two field datasets. It is found that the MAPE of the scour depths predicted by the GEP model increases compared with the predictions of local scours in laboratory scale. In addition, the model performance increases significantly when the model is trained by the field dataset rather than the laboratory dataset. The findings suggest that apart from the ANN model, GEP model is a sound and reliable model for predicting local scour depth.

• Water for future
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• v.29 no.2
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• pp.249-260
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• 1996

There have been easily found a number of examples that misleading or unreasonable measuring data set of physical variables are often produced in the field and the laboratory. The primary reason is that the specific requirements of civil engineers are initially disregarded in designing the experimental apparatus. It results from a lack of mutual understanding and co-operating between the user group and the maker. Therefore, their fundamental knowledge and apprehension become indispensible in order to obtain measuring data with high confidence and good quality In this study it is shortly explained the basic structure and the operation system of the experimental equipments commonly used at the present. A simple measuring set is developed which is quite easy for a general civil engineer to design and operate without any other specialty of mostly electricity electronics. Based upon this requirement, one of data logger named PPDL8 is newly designed by making use of the parallel port in the personal computer, consisting of multi-channels able to measure 8 different point values simultaneously. It can also use many valuable sub-programs existing in PC because the user makes his own programs necessary for measurement, by himself. Of all things, it has a great advantage to increase the applicability of field measurements much larger when adopting the notebook computer to operate with small battery only. In addition this study gives, in fact, the excellent agreements of in-situ field variables by showing their measuring results of temperature, distance and turbidity.