• Structural Engineering and Mechanics
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• 제15권3호
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• pp.285-297
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• 2003

Complementing recent advances made in the field of structural health monitoring and damage detection, the concept of a wireless sensing network with distributed computational power is proposed. The fundamental building block of the proposed sensing network is a wireless sensing unit capable of acquiring measurement data, interrogating the data and transmitting the data in real time. The computational core of a prototype wireless sensing unit can potentially be utilized for execution of embedded engineering analyses such as damage detection and system identification. To illustrate the computational capabilities of the proposed wireless sensing unit, the fast Fourier transform and auto-regressive time-series modeling are locally executed by the unit. Fast Fourier transforms and auto-regressive models are two important techniques that have been previously used for the identification of damage in structural systems. Their embedment illustrates the computational capabilities of the prototype wireless sensing unit and suggests strong potential for unit installation in automated structural health monitoring systems.

• 한국환경과학회지
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• 제24권4호
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• pp.393-401
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• 2015

Rainfall-runoff model of Jeju Oedo Stream was used to compute the optimal unit hydrograph by HEC-HMS model that reflecting on watershed characteristics. Each rainfall event was comparatively analyzed with the actual flow measurement using Clark, Snyder and SCS synthetic methods for derived unit hydrograph. Subsequently, the null hypothesis was established as p-value for peak flow and peak time of each unit hydrograph by one-way ANOVA(Analysis of variance) was larger than significance level of 0.05. There was no significant difference in peak flow and peak time between different methods of unit hydrograph. As a result of comparing error rate with actual flow measurement data, Clark synthetic unit graph best reflected in Oedo Stream as compared to other methods, and error rate of Clark unit hydrograph was 0.02~1.93% and error rate at peak time was 0~2.74%.

• 한국병원경영학회지
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• 제25권3호
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• pp.14-28
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• 2020

Purpose: The purpose of this study was to calculate the total daily nursing workload and the optimum number of nurses per intensive care unit (ICU) based on the nursing intensity and the direct nursing time per inpatient using the patient classification. Methods: Two ICUs at one general hospital were investigated. To calculate the nursing intensity, patient classification according to the nursing needs was conducted for 10 days in each unit during September 2018. We performed patient classifications for a total of 167 patient-days in the Medical Intensive Care Unit (MICU) and 86 patient-days in the Surgical Intensive Care Unit (SICU). The total number of person-days for nurses who responded to the Nursing Time survey was 151 for MICU and 85 for SICU. In each unit, direct and non-direct nursing hours, nursing intensity score, and direct nursing hours were analyzed using descriptive statistics such as frequency, percentage, and average calculated using Microsoft Excel. The amount of nursing workload and the optimum number of nurses were calculated according to the formula developed by the authors. Findings: For the MICU, the average direct nursing time per patient was 5.59 hours for Group 1, 6.98 hours for Group 2, and 9.28 hours for Group 3. For the SICU, the average direct nursing time per patient was 5.43 hours for Group 1, 7.21 hours for Group 2, 9.75 hours for Group 3, and 12.82 hours for Group 4. Practical Implications: This study confirmed that the appropriate number of nurses was not secured in the nursing unit of this study, and that leisure time such as meal time during nursing work hours was not properly guaranteed. The findings suggest that to create working environments where nurses can serve for extended periods of time without compromising their professional standards, hospitals should secure an appropriate number of nurses.

• Journal of the Korean Statistical Society
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• 제27권1호
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• pp.57-66
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• 1998

In the analysis of time series it is an important issue to determine whether a time series under study is stationary. For the test of the stationary of the time series the Dickey-Fuller (DF) type tests have been mainly used. In this paper, we consider the regular unit root tests and seasonal unit root tests based on the generalized Durbin-Watson (DW) statistics when the errors are independent. The limiting distributions of the proposed DW-type test statistics are the functionals of standard Brownian motions. We also obtain the finite distributions and powers of the DW-type test statistics and compare the performances with the DF-type tests. It is observed that the DW-type test statistics have good behaviors against the DF-type test statistics especially in the nonzero (seasonal) mean model.

• 대한임베디드공학회논문지
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• 제17권6호
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• pp.355-365
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• 2022

This paper addresses the problem of real-time tracking a high-speed ballistic target. Particle filters can be considered to overcome the nonlinearity in motion and measurement models in the ballistic target. However, it is difficult to apply particle filters to real-time systems because particle filters generally require much computation time. This paper proposes an accelerated particle filter using graphics processing unit (GPU) for real-time ballistic target tracking. The real-time performance of the proposed method was tested and analyzed on a widely-used embedded system. The comparison results with the conventional particle filter on CPU (central processing unit) showed that the proposed method improved the real-time performance by reducing computation time significantly.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권2호
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• pp.57-66
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• 2012

In this paper, we consider the periodic preventive maintenance model for a repairable system following the expiration of replacement-repair warranty. Under this preventive maintenance model, we derive the expressions for the expected cycle length, the expected total cost and the expected cost rate per unit time. Also, we determine the optimal preventive maintenance period and the optimal preventive maintenance number by minimizing the expected cost rate per unit time. Finally, the optimal periodic preventive maintenance policy is given for Weibull distribution case.

• Water Engineering Research
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• 제2권4호
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• pp.219-229
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• 2001

Synthetic unit hydrograph equations for rainfall run-off characteristics analysis and estimation of design flood have long and quite frequently been presented, the Snyder and SCS synthetic unit hydrograph. The major inputs to the Snyder and SCS synthetic unit hydrograph are lag time and peak coefficient. In this study, the methods for estimating lag time and peak coefficient for small watersheds proposed by Zhao and McEnroe(1999) were applied to the Kum river basin in Korea. We investigated lag times of relatively small watersheds in the Kum river basin in Korea. For this investigation the recent rainfall and stream flow data for 10 relatively small watersheds with drainage areas ranging from 134 to 902 square kilometers were gathered and used. 250 flood flow events were identified along the way, and the lag time for the flood events was determined by using the rainfall and stream flow data. Lag time is closely related with the basin characteristics of a given drainage area such as channel length, channel slope, and drainage area. A regression analysis was conducted to relate lag time to the watershed characteristics. The resulting regression model is as shown below: ※ see full text (equations) In the model, Tlag is the lag time in hours, Lc is the length of the main river in kilometers and Se is the equivalent channel slope of the main channel. The coefficient of determinations (r$^2$)expressed in the regression equation is 0.846. The peak coefficient is not correlated significantly with any of the watershed characteristics. We recommend a peak coefficient of 0.60 as input to the Snyder unit-hydrograph model for the ungauged Kum river watersheds

• Journal of the Korean Data and Information Science Society
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• 제14권4호
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• pp.889-901
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• 2003

In this paper, we consider the optimal replacement policies following the expiration of the combination warranty. The combination warranty can be divided into the renewing combination warranty and the non-renewing combination warranty. The criterion used to determine the optimal replacement period is the overall value function based on the expected cost and the expected downtime. Thus, we obtain the expected cost rate per unit time and the expected downtime per unit time for our model. And then the overall value function suggested by Jiagn and Ji(2002) is applied to obtain the optimal replacement period. The numerical examples are presented for illustrative purpose.

• 한국군사과학기술학회지
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• 제22권5호
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• pp.705-715
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• 2019

The purpose of this study is to analyze the necessity of organizing an exclusive unit to perform the division Engineering Reconnaissance, and how to organize exclusive unit. To this end, first, it was analyzed whether exclusive unit organization was necessary by using organization-conditions and AHP. Next, through ARENA model simulation and task-analysis, it was determined how many people would be organized, and how the class structure would be appropriate. As a result, first, it is reasonable to organize the Engineering Reconnaissance unit as an exclusive unit, and the best way is to organize all-time(war/peace time). Second, the exclusive unit should be organized into a total of 10 persons(2~3 cadres, 7~8 soldiers). We hope that the research will contribute to the rational procedure of our military unit structure organization and set the standards for applying the quantitative methodology.

• 제어로봇시스템학회논문지
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• 제11권1호
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• pp.84-91
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• 2005

In this paper, we describe the real-time parallel processing simulator developed for the use of performance analysis of rolling missiles. The real-time parallel processing simulator developed here consists of seeker emulator generating infrared image signal on aircraft, real-time computer, host computer, system unit, and actual equipments such as auto-pilot processor and seeker processor. Software is developed from mathematic models, 6 degree-of-freedom module, aerodynamic module which are resided in real-time computer, and graphic user interface program resided in host computer. The real-time computer consists of six TIC-40 processors connected in parallel. The seeker emulator is designed by using analog circuits coupled with mechanical equipments. The system unit provides interface function to match impedance between the components and processes very small electrical signals. Also real launch unit of missiles is interfaced to simulator through system unit. In order to apply the real-time parallel processing simulator to performance analysis equipment of rolling missiles it is essential to perform the performance verification test of simulator.