• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.942-947
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• 2006

In KOWACO, flow measurement system using PDA has been developed and used since 2004. Even though this system has improved the reliability of the measured flow data, it still has some problems caused by the internet-based data manipulation scheme. We found that this kind of data handling method is not suitable because it causes frequent communication problems especially in fringe areas. To solve this problem, the structure and algorithms of existing system has been analyzed and an improved system is proposed. Besides, improvement study on the rate of change and the uncertainty of the flow data have been performed as well as the communication method between the Microwave Water Surface Current Meter and PDA adopting the state-of-the-art IT technology.

• Korean Journal of Agricultural and Forest Meteorology
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• v.4 no.2
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• pp.103-113
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• 2002

Calibration experiments were executed to document pertinent calibration methods for open-path infrared gas analyzer (OP-2) in field operations and to quantify their performance characteristics in continuous long-term flux measurements. Based on our results, we concluded: (1) flow rate of 2.0 L min$^{-1}$ can be used for calibration instead of the recommended 0.5 L min$^{-1}$ . Such faster flow rate brings the sampled air in the calibration hood at equilibrium within 5 min for $CO_2$ and 10 min for $H_2O$; (2) after reaching equilibrium, two-minute average sampling for related variables per each concentration may be sufficient; (3) use of four concentration is needed to derive the nonlinear calibration equation for water vapor with 1% uncertainty of flux measurement; and (4) the resultant calibration interval for OP-2 for both $CO_2$ and $H_2O$ is approximately one month.

• Journal of Korea Port Economic Association
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• v.34 no.1
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• pp.99-110
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• 2018

This study empirically examines simple methodology to quantify the risk resulted from the uncertainty of bunker price and foreign exchange rate, which cause main resources of the cost in shipping industry during the periods between $1^{st}$ of January 2010 and $31^{st}$ of January 2018. To shed light on the risk measurement in cash flows we tested GBM(Geometric Brownian Motion) frameworks such as the model with conditional heteroskedasticity and jump diffusion process. The main contribution based on empirical results are summarized as following three: first, the risk analysis, which is dependent on a single variable such as freight yield, is extended to analyze the effects of multiple factors such as bunker price and exchange rate return volatility. Second, at the individual firm level, the need for risk management in bunker price and exchange rate is presented as cash flow. Finally, based on the scale of the risk presented by the analysis results, the shipping companies are required that there is a need to consider what is appropriate as a means of risk management.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1046-1053
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• 2006

In the large scale recent reclaiming works performed within the wide spatial boundary, evaluation of long-term consolidation settlement and residual settlement of the whole construction area is sometimes made with the results of the limited ground investigation and measurement. Then the reliability of evaluation has limitations due to the spatial uncertainty. Additionally, in case of large scale deep excavation works such as urban subway construction, there are a lot of hazardous elements to threaten the safety of underground pipes or adjacent structures. Therefore it is necessary to introduce a damage prediction system of adjacent structures and others. For the more accurate analysis of monitoring information in the wide spatial boundary works and large scale urban deep excavations, it is necessary to perform statistical and spatial analysis considering the geographical spatial effect of ground and monitoring information in stead of using diagrammatization method based on a time-series data expression that is traditionally used. And also it is necessary that enormous ground information and measurement data, digital maps are accumulated in a database, and they are controlled in a integrating system. On the abovementioned point of view, we developed Geomonitor 2.0, an Internet based real time monitoring program with a new concept by adding GIS and geo-statistical analysis method to the existing real time integrated measurement system that is already developed and under useful use. The new program enables the spatial analysis and database of monitoring data and ground information, and helps the construction- related persons make a quick and accurate decision for the economical and safe construction.

• STI Policy Review
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• v.4 no.2
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• pp.41-54
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• 2013

R&D is inherently an uncertain endeavor, yet now more than ever those performing R&D with public funding are called upon to clarify the utility of their research. Calls for public accountability are mounting with the increase in constraints on government budgets due to the recent worldwide economic recession, in response to which both policymakers and researchers pay much more attention to rigorously assessing publicly funded R&D. A key issue complicating R&D evaluation in these circumstances is how to adequately account for the nature and degree of risk involved in a given R&D program or project. This study deliberates on certain issues involving the measurement of ex-ante risk in public R&D evaluation: (i) information asymmetry between R&D sponsors and performers, (ii) ambiguity in the measurement of returns in both prospective and retrospective evaluation, and (iii) the dilemma between measurement error and omitted variable bias for empirical estimation of R&D performance. The study then presents an analysis of hypothetical evaluation results that apply risk-relevant weights to the annual evaluation outcomes of South Korea's national R&D programs funded during 2006~2012. In this counterfactual re-evaluation of public R&D program performance, high-risk R&D programs turn out to receive higher evaluation than non-high-risk programs. The current study suggests that R&D evaluation ignoring ex-ante risk is not only conceptually invalid since R&D activities are intrinsically uncertain endeavors, but unfair as R&D performers are asked to be accountable for the results that were in fact out of their reach.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.453-460
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• 2014

We analyze fault detection algorithm of ephemeris included in navigation message, which is one of the GNSS risk factors. This algorithm uses carrier-phase measurement and baseline vector of two reference stations and is alternative method for uncertainty condition of previous ephemeris. Even though same ephemeris fault is occurred, the geometry condition, between baseline vector of reference stations and satellites, effects on performance of algorithm. Also, we introduce the suitable geometry of reference stations, threshold and performance index (MDE : Minimum Detectable Error) in jeju international airport.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.35-40
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• 2011

The low caloric LNG, which didn't meet the gas interchangeability of Korea, has been imported from 2005 winter season. Amount of this LNG imports has been increased from year to year. In the near future, very low caloric LNG (calorific value ${\leq}$ 9,500 kcal/$Nm^3$) such as CBM, Shale LNG will be imported large amounts. For this reason, we need a method for monitoring live calorific values(CV) of LNG in each storage tank to supply gasified LNG with interchangeable CV at LNG receiving terminal. This study was conducted to develope the method for measuring the live CVs of LNG in each storage tank using LNG densitometer. For this purpose, the accurate correlation between CV and density of LNG was derived and the uncertainty of this method was evaluated and also the measuring system for CVs was constructed at LNG receiving terminal. To verify this method, the results of measurement using this method were compared with the field data of LNG analysis and the results showed that the deviations were 0.17~0.47%.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.60-68
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• 1997

Rayleigh Scattering Cross Sections($\sigma$i) of various gases and the temperature distributions of premixes C3H8/O2 flame are measured by high power KrF(248nm) Exci- mer laser and ICCD camera. Results show that $\sigma$i of O2 and Propane(C3H8) gases agree well in the 5% error range, but of H2 has the more or less difference from the calcul- ated value by other groups. This is attributed to the low RS signal of H2 to Nosie level(S/N ratio). The temperature distributions of flame range out between 300K in the air and about 2000K in the burned area. In this temperature range, out system has the about 250K temperature resolution. Because low RS signals in the reaction area with high temperature are affected highly by noises, temperature uncertainty of this area is relatively high to another part of flame. Experimental results show that UV Rayleigh Scattering can be used for the measurement of mixing ratio of mixed gases and the temperature distributions of flame. Especially, this technique can be applied for the measurement of the mixing ratio of air/fuel before the ignition and the flame structure after the ignition inside the Engine.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.201-206
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• 2008

Determining the coefficient of weathering(CW) for stone heritage plays very important role in investigation and conservation plan. In most case, CW is obtained from the empirical relation, which use the difference between sonic velocities of fresh and weathered rocks. In this paper, we measured sonic velocities for the samples from Iksan, Geochang, Wonju, Goesan and Chungju of which our stone heritages are made. We first investigate the uncertainty of velocity by portable measurement by comparing it to lab measurement. There were small difference, but we conclude that the difference is not major. However, the velocity of fresh rock differs significantly among samples: ranging from 3200 to 4400m/s. This cause a lot of error in CW estimation if we use typical fresh rock velocity as of 5000m/s. Thus accurate measurement of the velocity of fresh rock is crucial to CW estimation.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.216-222
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• 2006

We propose the use of the Gaussian-curve fitting algorithm for the improvement of measurement accuracy in wavelengthscanned Fabry-Perot filter based demodulation systems. The peak locations of FBG sensors were calculated from the fitted curves rather than from distorted PD profiles, resulting in much better measurement accuracy than that of the highest-peak search algorithm. Also, the algorithm was proved to minimize measurement uncertainty of spectrally-distorted grating sensors. From our experimental results, a temperature resolution as small as ${\sim}0.3^{\circ}C$ was readily achieved by use of the Gaussian-curve fitting algorithm whereas the highest-peak search algorithm gave a temperature resolution larger than ${\sim}4^{\circ}C$.