• Korean Journal of Crystallography
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• v.8 no.1
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• pp.64-65
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• 1997

A method for calculation of the estimated standard deviation (ESD) of physical quantities which are functions of experimentally observed variables has been shown.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.10a
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• pp.219-221
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• 2012

근접도 평가시 충돌(침범)확률이 0.0001이하면 안전하다고 판단한다. 하지만 안전진단서상 수치가 0에 수렴하는 경우가 많아 간과하기 쉬우며 이 값을 이해하기 어렵다. 이러한 문제점을 해결하기 위해 근접도 평가 결과를 손쉽게 평가하는 방법을 제안하고 평균값과 표준편차값이 갖는 의미를 해석하여 안전진단 검토 및 사전검토서 작성시 도움이 되고자 한다.

• Progress in Medical Physics
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• v.15 no.1
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• pp.45-53
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• 2004

SPM has been widely applied for comparison studios of the functional image data among groups of patients or individuals under different conditions and these images are from people ranging from children to adults. However, the analysis of children's brain images by using SPM can make children's brain images normalized to an adult's template image and this can result in some errors. So this study created the children's mean MR images based on the Magnetic Resonance Images of 36 normal children (age: 2～6, average age: 4.36, SD age: 1.41, M/F: 17/19), and the children's mean SPECT images by using SPECT images of 13 normal children (age: 2～6, average age: 4.80, SD age: 1.17, M/F: 10/3). We created the Korean children's brain template image, based on those mean images, and then we compared between the positions of the clusters, based on the blood flow, by normalizing ADHD children's SPECT image to Korean children's template image and SPM adult's template image. As a result of the analysis, the variation of the cluster positions was found to be a maximum of 25 ㎜. Therefore, we should be aware that we need to consider the template image and the p-value when we analyze the chlidren's brain image by using SPM.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.960-967
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• 2012

Wireless sensor network is used at the environment to obtain nearby information and since such information is transferred through wireless link, it causes unnecessary re-sending and disadvantage of big energy consumption at node. Because of this to select reliable, energy effective link, method of estimating quality on wireless link using RSSI(received signal strength indication), LQI(link quality indication), etc is needed on wireless link. To set up path extending survival time by reducing energy consumption of nodes at the wireless sensor network, the thesis selects with small standard deviation of LQI after obtaining LQI within each path. Additionally, LQI standard deviation routing algorithm is compared based on LQI algorithm such as minimum-LQI, hop-LQI weight and RF output -7dBm. According to the outcome, the algorithm suggested has superior characters such as the number of node, retransmission rate and network life span respectively compared to existing algorithm. Therefore, energy consumption can be efficiently reduced in case that LQI standard deviation routing scheme suggested by this paper is adapted to wireless sensor network.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.12
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• pp.1186-1192
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• 2008

The reliability of gas turbine engine blades was studied. Yield strength, Young’s modulus, engine speed and gas temperature were considered as statistically independent random variables. The failure probability was calculated using five different methods. Advanced Mean Value Method was the most efficient without significant loss in accuracy. When random variables were assumed to have normal, lognormal and Weibull distributions with the same means and standard deviations, the CDF of limit state equation did not change significantly with the distribution functions of random variables. The normalized sensitivity of failure probability with respect to standard deviations of random variables was the largest with gas temperature. The effect of means and standard deviations of random variables was studied. The increase in the mean of gas temperature and the standard deviation of engine speed increased the failure probability the most significantly.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.567-570
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• 2008

The present study investigated the applicability of the minium fludization velocity measuring method using linear regression analysis between the standard deviation of pressure fluctuation and gas velocity in multi-particle sand on a fluidized bed 0.109 in inner diameter. We measured minium fludization velocity according to the standard deviation of particle distribution in Gaussian distribution. The measured value compared with other researchers' equations. The minium fludization velocity derived from the linear regression analysis of the standard deviation of pressure fluctuation and pressure drop inside the bed. We also found that the minium fludization velocity of a multi-particle system using the standard deviation of pressure fluctuation must be measured at freely bubbling region.

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.175-181
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• 2002

BIS(Bus arrival Information System) is a system that informs Passengers waiting at bus stops of the bus arrival time of next buses. However, when operating this system, it is not exactly known what type of bus arrival information should be provided. The purpose of this paper is to develop a model of the optimal bus arrival time to be informed for BIS. Analyzing Efficiency in the Seoul's Urban Bus Industry Using Data Envelopment Analysis. Two basic types of bus arrival information can be considered. One is Bus Locations : Where next buses are located and under what situation they are, such as the next bus departed from the previous stop, The other is Expected Arrival Time. Time to the arrivals of next buses. Characteristics of these two types of bus arrival time information provided for passengers waiting at bus stops for BIS are examined. The waiting time of passengers at bus stops is derived as a function of the bus arrival time to be informed. Some basic principles about the optimal bus arrival time to be informed are found. Finally, a case study assuming several simplifications is performed. One of the key findings is that there exists optimal arrival time to be informed other than the average arrival time. The optimal arrival time to be informed should be closer to the average arrival time for small and very large standard deviations and be earlier for certain amounts of standard deviations.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.695-703
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• 2015

Acceptance criteria for chemical admixtures of cement concrete were investigated in domestic and international specifications. The reliability was verified for solid content test method of chemical admixture examined statistical analysis by round robin test. The applicability of FT-IR spectroscopy for qualitative measurement of multi-compound chemical admixtures verified. From solid content experimental results, outlier analysed using Cochran, Grubbs and Dickson's Q test. Repeatability and reproducibility standard deviation for solid content results showed 0.25 and 0.098% respectively according to KS A ISO 5725-2 procedure, it can be confirmed reliability of test methods. FT-IR spectrum of liquefied or oven-dried chemical admixtures condition showed big differences. It is needed that the FT-IR analysis is performed on dry material. However there's no difference with the applicability of FT-IR spectroscopy for multi-compound chemical admixtures. So the utility of method analysis could not identify.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.12
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• pp.1232-1237
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• 2009

The ICAO and FAA are developing and verifying of GBAS for civil aircraft landing and take-off. The guarantee of aircraft integrity issue is the important part of GBAS. To guarantee integrity, the GBAS ground facility broadcasts various informations to aircraft. The informations are related to the estimated accuracy of each pseudorange correction and the estimated error terms, for example B-value and standard deviation of the ground facility error. These parameters are used to calculate position error (estimated value of the user). If estimated position errors don't satisfy requirements, aircraft use alternate navigation means. In this paper, GBAS reference stations's real data, which operated by KARI (Korea Aerospace Research Institute) in Jeju international airport, are used to development of new ground facility error standard deviation model. We verify improvement of GBAS availability, with respected to vertical protection level, using B-value based a new ground facility error standard deviation model and a sigma inflation factor.

• Environmental and Resource Economics Review
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• v.16 no.2
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• pp.337-361
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• 2007

Using the sample of bituminous coal prices, this study calculates the cash flows of selective procurement strategies compared to the previous routine procurement strategies, and analyzes the revenue-improvement and revenue-stabilization effects of different procurement strategies. In empirical analyses, these effects of routine and selective procurement strategies are compared by forecasting model and forecasting period. The revenue-improvement and revenue-stabilization effects are analyzed to compare the distribution of return flows, that is the means and standard deviations of procurement revenue flows. The revenue-improvement and revenue-stabilization effects of selective procurement strategies compared to the previous routine procurement strategies are as follows. Compared with routine procurement strategies, the selective procurement strategies turn out to yield higher means of returns (except for some forecasting periods and models). On the contrary, the standard deviations of returns decrease. With longer forecasting periods, the amounts of increases in the means become larger, but the degrees of decreases in the standard deviations vary. Although there exist some variations, some forecasting models outperform the others in terms of means and standard deviations.