• Journal of Navigation and Port Research
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• v.40 no.1
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• pp.15-20
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• 2016

In this study we measured a differential ASF to improve the accuracy of time synchronization with the signal transmitted from Pohang 9930M Loran station. We obtained the differential ASF which is calculated from a difference of the TOA measurements between KRISS and Chungnam National University(CNU), and KRISS and National Maritime PNT Office respectively. The TOA measurement at KRISS was measured by UTC(KRIS) reference clock and other sites were measured by atomic clocks respectively. The time variations of differential ASF measurements at CNU and National Maritime PNT Office were within $0.1{\mu}s$ and $0.05{\mu}s$ respectively. And we found the time variations of $0.1{\mu}s$ depending on the surrounding radio-wave environments from the differential ASF measurements of 60 minute moving averages. We can improve the accuracy of time synchronization of the local clock to within 10 ns by compensating the differential ASF through removing the common component of ASF. And we measured the absolute ASF between the Pohang transmit station and KRISS by the measurement technique of absolute time delay using a cesium atomic clock. The average ASF between two points is about $3.5{\mu}s$.

• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.621-628
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• 2021

Prior studies on frequency-related image quality analysis of intravascular ultrasound catheters are lacking both in Korea and abroad. Therefore, this study was conducted to prepare a standard for measuring the image quality using the program and to suggest a measuring method to researchers related to the quality analysis of intravascular ultrasound images. For the target, the vessel lumen size is 3.0 - 4.0 mm. Before using intravascular ultrasound, thoroughly clean the ultrasound catheter so that no air or foreign substances enter it. Normal vascular images and lesion vascular images of sufficiently dilated images were used. As a standard image acquisition method, the image of the end-systolic section, which has the best evaluation of vascular lesions when using intravascular ultrasound, was acquired retrospectively through the DCAS PACS program to set the standard. When setting the measurement method criteria, we proposed a standard setting method that corresponds to the concentric and eccentric circles of normal and lesion vessels. By applying this criterion, we proposed a method for measuring the lumen and lateral cavities of normal and lesion vessels of interest and background area. In conclusion, if the image quality of intravascular ultrasonography is measured through the method devised by these researchers, consistent quality measurement is possible regardless of the type of intravascular ultrasound catheter. Therefore, it is thought that it can be applied as a guideline for the actual image quality measurement method in the study related to intravascular ultrasound image quality.

• Korean Journal of Optics and Photonics
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• v.19 no.6
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• pp.416-421
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• 2008

A scheme for predicting the concentration of a glucose solution based on its relative optical absorbance at multiple probe wavelengths was proposed and verified. The relative absorbance at each of the probe wavelength was obtained with respect to the absorbance at a reference wavelength. The single reference wavelength (1310 nm) and a group of four different probe wavelengths (1064, 1550, 1685, 1798 nm) were selected to exhibit the glucose absorbance with opposite signs, thereby enhancing the accuracy of the prediction. The final glucose concentration was estimated by taking the average of the predicted values provided by the four probe wavelengths. The absorbance of the glucose solution for the path length of 5 mm was $-1.42{\times}10^{-6}\;AU$/(mg/dL) at the reference wavelength of 1310 nm and peaked at $+8.12{\times}10^{-6}\;AU$/(mg/dL) at 1685 nm. The concentration of the glucose solution was decently predicted by means of the proposed scheme with the standard error of prediction of ${\sim}28\;mg/dL$. In addition, the influence of the ambient temperature and the fat thickness upon the prediction of the glucose concentration was examined. The absorption change with the temperature was $-9.1{\times}10^{-5}\;AU/^{\circ}C$ in the temperature range of $26{\sim}40^{\circ}C$ at the reference wavelength, and $-2.08{\times}10^{-2}\;AU/^{\circ}C$ at 1550 nm. And the absorption change with respect to the fat thickness was +1.093 AU/mm at the probe wavelength of 1685 nm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.128-133
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• 2020

This study was conducted to demonstrate the manufacturing process for producing high-quality solar salt. The design criteria of the manufacturing process, which was studied in a previous study, was applied to an actual manufacturing system to evaluate its performance. The design factors applied were the drying air temperature and the temperature of the washing water. They were 100℃ or less and 10℃ or less, respectively. Two standards were applied to the process performance evaluation. Standard (I) was the international food standard for solar salt, and standard (II) was the quality standard for high-quality solar salt production. The main quality evaluation items were the moisture content and salinity, and the color characteristics were also measured (p<0.05). The manufacturing process of solar salt consisted of five steps, and the quality change was measured for each step. The measured quality was appropriate to the standard (I) from the third-step process. In addition, the quality of the high-quality solar salt was suitable for the standard (II) from the fourth-step process. Therefore, the performance of the proposed solar salt production process met international standards. The improvements in the production of high-quality solar salt will improve international competitiveness in the future.

• Journal of Korean Society of Transportation
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• v.14 no.2
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• pp.191-222
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• 1996

현재 쓰이고 있는 무신호 교차로의 서비스수준 측정방법은 지체도에 의해서 판정 되어지고 있으며, 안전도를 기준으로 서비스수준을 측정하는 방법은 존재하지 않는다. 교차 로의 안전은 사고의 횟수를 기준으로 하거나, TCT(Traffic Conflict Technique)를 이용하여 측정되어지고 있다. 두 방법 모두 많은 시간과 인력이 요구되는 방법이다. 이에 많은 시간 과 인력투자 없이 교차로의 안전을 진단하는 방법을 개발하는데 이 연구의 목적이 있다. 무 신호 교차로의 안전에 영향을 미치는 요소로는 교차로의 시거, 운전자의 인지반응시간, 차 두간격, 차량속도, 차중, 노면상태, 날씨 등이 있다. 이 모든 요소들이 복합적으로 작용하여 사고를 유발한다. 이 연구에서는 위의 요소들을 모두 고려하여 무신호 교차로의 안전을 분 석하는 방법을 개발하고저 한다. 위의 요소들 중에서 교차로의 시거를 제일 주요한 요소로 보고 나머지 요소들을 첨가시켜서 분석하는 방법을 썼다. 위에 열거한 많은 요소들을 고려 하기 위해서는 Simulation 방법이 채택되었으며, 그 중에서도 Monte carlo Simulationah형 을 썼다. 이 연구에서는 무신호 4지교차로의 횡단차량에 대해서만 고려하였으며 이 연구에 서 개발된 Simulation 모델을 Conflict의 개수와 그때의 소모된 평균 운동에너지를 산출하여 위험도를 측정하는 기준으로 삼았다. 모델의 결과에 의하면 교차로 시거가 길수록 안전하 고, 상대적으로 시거가 짧을수록 위험하다고 나왔다. 또한 AASHTO의 교차로 시거 값은 약 간 하향 조정하여도 안전도에 있어서는 큰 변화가 없는 것으로 분석되었으며, 아울러 안전 에 의한 서비스수준(LOS. A~F)의 기준이 설정되었다. 모델의 결과에 의하여 교통 공학자들 은 어떤 무신호 교차로의 안전수준을 상대적으로 평가할 수 있으며, 교차로 시거의 개선 후 얻어질 편익을 미리 예상할 수 있다.

• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.643-648
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• 2003

The phase-shifting diffraction-grating interferometer proposed in the investigation uses a diffraction grating that performs manifold functions of beam splitting, beam recombination, and phase shifting. The reference and measurement waves generated by means of diffraction have different amplitudes depending on their orders of diffraction, so the interference fringe pattern resulting from the two waves tends to yield poor visibility. To cope with this problem, we select a phase grating of reflection type and attempt to improve the interference visibility with optimization of the groove shape of the grating through electromagnetic analysis.

• Journal of IKEEE
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• v.15 no.1
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• pp.1-9
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• 2011

Cable leakage criterion of technical regulations on CATV transmission system was reinforced considering interference against CDMA mobile communication system in 2007. The criterion is $3{\mu}V$/m(at 10m) over 824~849MHz. But generally it is difficult for us to decide if a given CATV transmission facilities conform to it or not through simple measurement methods. In this paper, the problems on measuring cable leakage is identified theoretically and the measuring model with spectrum analyzer, LNA, and antenna is proposed to settle the problems. Also, the model is proved to be useful by practically measuring outdoors and analysing the results and the process to decide to fit to the criterion or not is established.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.513-516
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• 2008

The risk in the constructions projects is extremely diverse because there are too many indefinite factors. Therefore, Performance Measurement Baseline(PMB) is needed regularly during the construction process. However, nowdays, the PMB in the constructions projects is for contractors' PMB and Performance Management(PM). Clients have a lot of difficulties to control and manage the projects. Therefore, this paper classifies schedule and cost data of the public apartments houses which is a actual cases into types and then conducts regression analysis and deduces a regression. In addition to this paper establishes the Work Breakdown Structure(WBS) and suggests the PMB for the clients through using that.

• The Korean Journal of Financial Studies
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• v.14 no.1
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• pp.119-158
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• 2008

본 연구에서는 복합금융그룹의 부실위험을 그룹전체기반 측도로 측정하는 방법론을 비교하고 국내 복합금융그룹의 자료를 이용하여 실증분석한다. Joint Forum(2001a) 방법은 연결기준을 사용하여 그룹내 자본의 중복요소들을 상계한 후 필요자본 대비 자기자본비율을 구한다. 신BIS 규제자본 방법은 Vasicek(1987)의 점근적 단일위험 모형을 가정하여 자산의 전체기반 위험을 측정하고 연결기준을 사용하여 자본의 중복계상을 배제하여 측정한다. 개별 경제적 자본 방법은 개별 경제적 위험을 수준별로 합산하여 전체기반 경제적 자본을 빌딩블록 방식으로 합산한다. 경제적 자본 방법은 위험 측정시 겪게 되는 극단적 손실 문제와 결합분포의 비대칭성을 반영할 수 있는 방법을 측정시 포함시킬 수 있다. 국내 복합금융그룹의 자료를 이용하여 실증분석을 한 결과, 첫째, 개별 재무지표에서 복합금융그룹 소속회사들의 ROA, ROA 변동성 그리고 총자산 대비 자기자본비율이 우량한 것으로 나타났다. 특히 가장 비중이 큰 은행산업에서 위 개별 재무지표는 복합금융그룹 소속회사에서 우량하게 나타난다. 둘째, 그룹전체기반 위험자본 측도로서 필요자본 대비 자기자본 비율과 연결기준 BIS비율을 살펴본 결과 은행계열 금융그룹의 부실위험이 낮은 것으로 판단된다. 전체적으로 국내 복합금융그룹의 부실위험은 높지 않은 것으로 판단된다. 이상의 결과를 바탕으로 복합금융그룹에 대한 리스크상시감시방안에의 시사점을 살펴보면, 첫째, 복합금융그룹 소속 금융회사에 대한 리스크 평가시 그룹전체기반 부실위험평가를 반영하여 이를 측정할 필요가 있다. 둘째, 권역별로 통일된 리스크감시를 위해 권역별 자기자본규제의 형평성을 제고할 필요가 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1255-1261
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• 2014

Based on the radio wave measurement of korean ocean-based DGPS by season, in this paper, the service coverages of ocean-based DGPS reference stations were analyzed according to the climate and season. The signal strengths and signal-to-noise ratios in the land service areas that are provided by ocean-based DGPS reference stations were measured. The ocean-based DGPS reference station except reference stations on the mountainous terrain and the low ground conductivity provide more than 68% service area in comparison with the designed land service coverage providing by the ocean-based DGPS reference stations. To provide the designed service area that is unrelated to a season, it is necessary to install and operate the DGPS reference station with good ground conductivity and high efficiency antenna. Also, the poor service regions which is generated by obstacles of electric wave on pathway can be resolved by the double service area providing by land-based DGPS reference stations.