• 대한기계학회논문집B
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• 제25권4호
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• pp.561-571
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• 2001

The standard uncertainty of flowrate measurement is obtained by combining that of independent variables. Gravimetric and volumetric method were applied to determine the flowrate and the standard uncertainties of flowrate measurement by both methods were evaluated in accordance with the procedure recommended by International Organization for Standardization. The combined standard uncertainties of determining the flowrate were estimated from the sensitivity coefficient and the standard uncertainty of independent variables. For practical application, the methods for evaluating and expressing uncertainty in flow measurement were discussed. It was found that the uncertainties of the weighing and time measurement in gravimetric method, the volume and time measurement in volumetric method have dominant influence on that of flowrate measurement. With the quantitative analysis of the sensitivity coefficient, the contribution of the each variable uncertainty to the combined standard uncertainty of flowrate measurement is shown clearly.

• 한국경영과학회지
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• 제20권3호
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• pp.17-29
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• 1995

Recently, neural network models have been employed as an alternative to regression analysis for point estimation or function fitting in various field. Thus far, however, no theoretical or empirical guides seem to exist for selecting the tool which the most suitable one for a specific function-fitting problem. In this paper, we evaluate performance of three major function-fitting techniques, regression analysis and two neural network models, back-propagation and linear-Hebbian-learning neural networks. The functions to be fitted are simple linear ones of a single independent variable. The factors considered are size of noise both in dependent and independent variables, portion of outliers, and size of the data. Based on comutational results performed in this study, some guidelines are suggested to choose the best technique that can be used for a specific problem concerned.

• International Journal of Control, Automation, and Systems
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• 제6권2호
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• pp.263-268
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• 2008

An improved linear matrix inequality (LMI) representation of delay-independent $H_2$ performance analysis is introduced for linear delay systems with delays of any size. Based on this representation we propose a new $H_2$ memoryless state feedback design. By introducing a new matrix variable, the new LMI formulation enables us to parameterize memoryles s controllers without involving the Lyapunov variables in the formulations. By using a parameter-dependent Lyapunov function, this new representation proposed here provides us the results with less conservatism.

• 한국안전학회지
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• 제27권3호
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• pp.161-166
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• 2012

This study deals with the accident of roundabout. The objective is to analyze the traffic accidents occurred in 3-legged and 4-legged roundabouts through the developed models. In developing the multiple linear regression models, this study uses the number of traffic accidents as a dependent variable and such the variables as geometric structures, traffic characters and others as the independent variables. The correlation and multicollinearity of variables were analyzed using SPSS17.0. The main results are as follows. First, R-square value of developed models were analyzed to be 0.851(3-leg) and 0.689(4-leg), respectively. Second, the independent variables in the 3-legged roundabout accident model were analyzed to be the traffic volume and number of crosswalk, and the variables in the 4-legged roundabouts were evaluated to be the traffic volume and signal. Finally, the paired t-test shows that the predicted values and observed values are not statistically different.

• 제어로봇시스템학회논문지
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• 제18권3호
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• pp.230-236
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• 2012

Shielding the air-gap magnetic field of the electrodynamic wheel below a conductive plate and opening the shielding plate partially, a thrust force and a normal force generate on the conductive plate at the open area. But, as only the variable controlling both forces is a rotating speed of the electrodynamic wheel, it is very difficult to control the forces independently by the speed. So, we discuss a novel method controlling the forces effectively through manipulating a size of the open area. The independent control is made possible by virtue of the feature that the relative ratio between both forces is irrelevant to an air-gap length and determined uniquely for a specific rotating speed of the wheel. Therefore, the rotating speed and the size of open area become new control variables. The feasibility of the method is verified experimentally. Specially, the controllable magnetic forces are used in a noncontact conveyance of the conductive plate.

• 한국수소및신에너지학회논문집
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• 제30권6호
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• pp.614-620
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• 2019

In the present study, the wind characteristics were analyzed according to the time averages to evaluate the performance of small wind turbines required for the development of energy independent village. Measuring data of wind speed were recorded between January 2016 and April 2016 every second. Experimental data is averaged out using 5, 10, 15, 20 and 30 minute time steps. Throughout the experimental data analysis, 5 minutes averaged data is used to analyze the performance of the wind turbine, because it produces a minimum turbulence intensity in wind speed. The measuring power of the wind turbine is less than the designed value due to the unsteady nature wind of sudden changes in magnitude of wind speed and wind angle. Detailed wind conditions are also analysed using two variable Weibull probability density functions.

• 한국인구학
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• 제11권2호
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• pp.3-10
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• 1988

This study is a replication of Clemente and Sturgis' study conducted among 600 American cities in 1972. The impact of population size, physical density, social density, and age of 56 Korean cities upon the extent of their industrial diversification was analyzed. Hypotheses concerning each independent variable were generated from the theory of the development of the division of labor proposed by Durkheim and subsequently adopted by human ecologists. Zero-order correlation analysis and regression analysis were employed to test the hypotheses. The standardized partial regression coefficients indicated that social density and age of cities exert significant positive impact upon industrial diversification. On the other hand, population size showed a significant negative impact upon industrial diversification. In addition, it was discovered that the combined influence of the independent variables account for 34.6 percent of the variation in industrial diversification. The findings of this study were compared with the results of Clemente and Sturgis' study. Some suggestions for future research are presented and discussed.

• 한국병원경영학회지
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• 제26권2호
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• pp.17-26
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• 2021

Purposes: This study aims to identify factors affecting dental university hospitals' profitability and understand recent their business condition. Methodology: Data from 2016 to 2019 was collected from financial statement, public open data in 8 dental university hospitals. For the study, multiple regression test with stepwise selection was applied. Findings: First of all, 9 out of 19 independent variables were selected by stepwise selection. As a result of multiple regression test with selected independent variables and the dependent variable(operating profit margin ratio), the factors affecting hospitals' profitability were the number of dental unit chair, hospital location, debt ratio, total capital turnover ratio, employment cost rate, material cost rate, management expense rate, the number of patient per a dentist. Practical Implication: To improve dental university hospitals' profitability, hospitals specifically analysis and manage their cost such as employment, material and management cost and seek effectiveness by managing the proper number of patient per a dentist.

• Asian Pacific Journal of Cancer Prevention
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• 제15권19호
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• pp.8101-8105
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• 2014

Background: Although mucinous adenocarcinoma has been recognized for a long time, whether it is associated with a poorer prognosis in colorectal cancer patients is still controversial. Many studies put emphasis on mucinous adenocarcinoma containing mucin component ${\geq}50%$. Only a few studies have analyzed cases with a mucin component <50%. Objectives: This study aimed to analyze the prognostic value of different mucin component proportions in patients with stage III rectal cancer. Materials and Methods: Clinical, pathological and follow-up data of 136 patients with the stage III rectal cancer were collected. Every variable was analyzed by univariate analysis, then multivariate analysis and survival analysis were further performed. Results: Univariate analysis showed pathologic T stage, lymphovascular invasion, and histological subtype were statistically significant for DFS. Pathologic T stage was significant for OS. Histological subtype and lymphovascular invasion were independent prognostic factors in multivariate analysis for DFS, and histological subtype was the only independent prognostic factor for OS. Survival curves showed the survival time of mucinous adenocarcinoma (MUC) was shorter than non-MUC (adenocarcinomas with a mucin component <50% and without mucin component). Conclusions: Histological subtype (tumor with different mucin component) was an independent prognostic factor for both DFS and OS. Patients with MUC had a worse prognosis than their non-MUC counterparts with stage III rectal carcinoma.

• 한국항공운항학회지
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• 제19권1호
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• pp.66-73
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• 2011

According to U.S. NTSB, from 1989 to 1992, Situation Awareness(SA) was a major factor causing 80% of all aircraft accidents in scheduled airlines. Therefore, the prevention of accidents through effective training in SA became a pivot in aviation safety. Furthermore, during the past 10 years, since all helicopter accidents in Korea were caused by the factors related to SA, an appropriate countermeasure has been required. This study, which uses survey data, examines various factors related to SA that could affect helicopter pilots. Common characteristics of situation awareness factors are that the result from the independent variables which are flight time, duty period and age of a first officer is statistically significant with the result from the independent variables of an instructor pilot's. However, only experience is statistically significant independent variable for factors influencing decision making in emergency situations, but anxiety, expectation and comprehension are not significant.