• Computers and Concrete
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• v.30 no.4
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• pp.269-276
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• 2022

In this paper, frequency vibrations of double-walled carbon nanotubes (CNTs) has been investigated based upon nonlocal elastic theory. The inference of small scale is being perceived by establishing nonlocal Love shell model. The wave propagation approach has been operated to frame the governing equations as eigen value system. An innovational nonlocal model to examine the scale effect on vibrational behavior of armchair, zigzag and chiral of double-walled CNTs. An appropriate selection of material properties and nonlocal parameter has been considered. The influence of dimensionless nonlocal parameter has been studied in detail. The dominance of end condition via nonlocal parameter is explained graphically. The results generated furnish the evidence regarding applicability of nonlocal shell model and also verified by earlier published literature.

• Advances in concrete construction
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• v.13 no.6
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• pp.451-459
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• 2022

In present study, the nonlocal Flügge shell model based is utilized to investigate the vibration characteristics of armchair and chiral single-walled carbon nanotubes with impact of small-scale effect subjected to two boundary supports. The wave propagation approach is employed to determine eigen frequencies for armchair and chiral tubes. The fundamental frequencies scrutinized with assorted aspect ratios by varying the bending rigidity. The raised in value of nonlocal parameter reduces the corresponding fundamental frequency. It is investigated with higher aspect ratio, the boundary conditions have a momentous influence on vibration of CNT. It is concluded that frequencies would increase by increasing of the bending rigidity. Solutions of the frequency equation have determined by writing in MATLAB coding.

• Journal of Wind Energy
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• v.4 no.2
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• pp.17-24
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• 2013

Idealized PID-controlled rotor-speed error for blade pitch control of wind turbines responds as a second-order system with natural frequency and damping ratio for closed-loop system. RISO National Laboratory has recommended specific natural frequency(=0.6 rad/s) and damping ratio(=0.7) for 2 MW wind turbine. The baseline controller for 5 MW wind turbine of NREL(National Renewable Energy Laboratory) is designed based on the same values of RISO recommendation. This study investigates the effect of the natural frequency and damping ratio of the controller for NREL 5 MW wind turbine. It is confirmed that RISO recommendation shall be tuned for each wind turbine.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.3
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• pp.165-170
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• 2013

In spatial, desired target direction of arrival estimation is to find a incidental signal direction on receive antennas. In this paper, we were an estimation a desired target direction of arrival using maximum likelihood method. Direction of arrival estimation method estimated a desired target calculating the maximum likelihood sensitivity using singular value decomposition above threshold signals among receive signals in maximum likelihood method. Through simulation, we were analysis a performance to compare existing method and proposal method. In direction of arrival estimation, proposed method is effectivity to decrease processing time because it is not doing an eigen decomposition in direction of arrival estimation, and desired target correctly estimated. We showed that proposal method improve more target estimation than general method.

• Journal of Families and Better Life
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• v.6 no.1
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• pp.205-221
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• 1988

The purpose of this study is to classify several variable which were assumed to have relationship with the college students behavior of Hyo, to see their possible correlation with demographic characteristics, and to proved some useful data for their possible correlation with demographic characteristics. and to provide some useful data for their sound value system. The data for this study was obtained form the survey of the 477 students who reside in the city of Seoul by using questionnaire methods. The frequency of variables was statistically analyzed to see the general character of the samples and factor analysis was made for classification of the college student's behavior of Hyo. In order to study th characteristic of demographic variables, t-test and ANOVA were conducted The major findings of this study can be summarized as follows. 1) As the result of factor analysis about behavior of Hyo, six factors (Which Eigen value was above 1.0) out of 64 questions were extracted : 'respect' familiarity' 'family consciousness' 'serve' self-preservation, establishmence of them-selves in life' and 'self-reliance' were selected. 2)In general, it can be said that the college students' behavior of Hyo varies by demographic variables. 3) By surveying the level of actualizing Hyo of the college students' all of factors ranged from 'the middle' to 'the high level'. The result confirmed that students fulfilled the behavior of Hyo to their parents in all items.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.1837-1846
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• 2016

Background: Colon cancer screening (CRCS) uptake is markedly affected by public awareness of the disease. This study was conducted to assess levels of knowledge of CRC, to explore the pattern of CRCS uptake and identify possible barriers to screening among Saudis older than 50 years of age and primary care providers (PCPs) in Al Hassa region, Saudi Arabia. Materials and Methods: This cross-sectional study was conducted in randomly selected primary health care (PHC) centers, 884 Saudis and 39 PCPs being enrolled for data collection. Structured interviews were conducted to obtain information regarding socio-demographic characteristics, personal information relevant to CRC, awareness about early signs/symptoms and risk factors, and barriers to CRCS. Also, a self- administered data collection form was used to assess barriers to CRCS from the physicians' perspectives. Results: More than 66% of participants were lacking knowledge about CRC. Participants with higher educational levels, having ever heard about CRC, and having relatives with CRC had a significantly higher awareness of the disease. The rate of reported CRCS was low (8.6%). After conducting a logistic regression analysis, it was observed that female gender (OR=0.28; 95% CI=0.14-0.57; P=0.001), being unmarried (OR=0.11; 95% CI=0.10-0.23; P=0.001), lower levels of education (OR=0.36; 95% CI=0.16-0.82; P=0.015), and having no relatives with CRC (OR=0.30; 95% CI=0.17-0.56; P=0.001) were significantly associated with a lower CRCS uptake. There was a significant difference between most of the perceived barriers to CRCS and gender. Exploratory factor analysis showed that personal fear (especially fear of the screening results and shyness) was the major factor that hindered CRCS with high loading Eigen value of 2.951, explaining 34.8% of the barriers of the included sample toward utilization of CRCS, followed by lack of awareness of both person and providers (high Eigen value of 2.132, and explaining 23.7% of the barriers). The most frequently cited barriers to CRCS from the physicians' perspectives were lack of public awareness, lack of symptoms and signs, and fear of painful procedures. Conclusions: Poor levels of knowledge about CRC were found among older Saudis attending PHC centers in Al Hassa, Saudi Arabia. It is crucial to implement an organized national screening program in Saudi Arabia to increase public awareness.

• Water for future
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• v.25 no.1
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• pp.93-100
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• 1992

A study on the Derivation of the Unit Hydrograph using Multiple Regression Moe이. The purpose of this study is to deriver an optimal unit hydrograph suing the multiple regression model, particularly when only small amount of data is available. The presence of multicollinearity among the input data can cause serious oscillations in the derivation of the unit hydrograph. In this case, the oscillations in the unit hydrograph ordinate are eliminated by combining the data. The data used in this study are based upon the collection and arrangement of rainfall-runoff data(1977-1989) at the Soyang-river Dam site. When the matrix X is the rainfall series, the condition number and the reciprocal of the minimum eigenvalue of XTX are calculated by the Jacobi an method, and are compared with the oscillation in the unit hydrograph. The optimal unit hydrograph is derived by combining the numerous rainfall-runoff data. The conclusions are as follows; 1)The oscillations in the derived unit hydrograph are reduced by combining the data from each flood event. 2) The reciprocals of the minimum eigen\value of XTX, 1/k and the condition number CN are increased when the oscillations are active in the derived unit hydrograph. 3)The parameter estimates are validated by extending the model to the Soyang river Dam site with elimination of the autocorrelation in the disturbances. Finally, this paper illustrates the application of the multiple regression model to drive an optimal unit hydrograph dealing with the multicollinearity and the autocorrelation which cause some problems.

• Journal of Korean Association for Spatial Structures
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• v.15 no.1
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• pp.65-73
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• 2015

This paper presents the structural model verification process of whole wind turbine blade including blade model which proposed in Part1 paper. The National Renewable Energy Laboratory (NREL) Phase VI wind turbine which the wind tunnel and structural test data has publicly available is used for the study. In the Part1 of this paper, the processes of structural model development and verification process of blade only are introduced. The whole wind turbine composed by blade, rotor, nacelle and tower. Even though NREL has reported the measured values, the material properties of blade and machinery parts are not clear but should be tested. Compared with the other parts, the tower which made by steel pipe is rather simple. Since it does not need any considerations. By the help of simple eigen-value analysis, the accuracy of structural stiffness and mass value of whole wind turbine system was verified by comparing with NREL's reported value. NREL has reported the natural frequency of blade, whole turbine, turbine without blade and tower only models. According to the comparative studies, the proposed material and mass properties are within acceptable range, but need to be discussing in future studies, because our material properties of blade does not match with NREL's measured values.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.117-124
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• 2003

Wind-induced motions, like acceleration for instance, often influence designs for high-rise buildings. As a consequence, correct assessment of natural frequency becomes important. The empirical expressions used to quantify this parameter at the design phase tend to yield values that are significantly different from each other. This paper is concerned with the natural periods of steel buildings. It describes the vibration measurement methods that were employed for testing buildings. This paper will also present reliable methods of assessing the natural period from ambient vibration tests. Data from measurements on 21 buildings in Seoul were provided while 21 buildings were tested by ambient vibration measurements to obtain the natural periods. While regression formulas of natural periods for steel-frarried tall buildings were suggested,the obtained formula was compared with the empirical expressions of structural standards and the Eigen-value analysis.

• The Journal of the Acoustical Society of Korea
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• v.16 no.4
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• pp.5-10
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• 1997

In this paper, a new time delay estimation algorithm, WTD-LMSTDE was proposed. This method has great improvement in convergence rate relative to the time domain approach by decreasing the eigen value spread of input signal autocorrelation matrix. The performance of the algorithm was evaluated for the cases of time invariant time delay and time varying time delay. In the case of time invariant time delay, the estimation accuracy of WTD-LMSTDE was better than that of LMSTDE from 3.3% to 12.5% with respect to SNR. In the case of time varying time delay, the mean error power of WTD-LMSTDE in linear increased delay environment was decreased about 2.4dB compared to that of LMSTDE under noise-free condition. As a result, we showed that the performance of WTD-LMSTDE is better than of LMSTDE.