• Korean Journal of Community Nutrition
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• v.20 no.1
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• pp.41-52
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• 2015

Objectives: Korean elderly people are known to consume diets high in carbohydrates low in vegetables compared to other age groups. This study evaluated the chronic disease risks and nutritional status in this group based on the percentage of energy from carbohydrates and the frequency of vegetable intake. Methods: Using the 2007~2009 Korean National Health Nutrition Examination Survey data, except those who were undergoing treatment for chronic disease, final 1,487 subjects aged 65 and older were divided into 4 groups: moderate carbohydrate energy ratio of 55~70% and low frequency of vegetable intake defined as less than 5 times per day (MCLV), moderate carbohydrate ratio and high frequency of vegetable intake more than 5 times (MCHV), high carbohydrate energy ratio above 70% and low frequency of vegetable intake less than 5 times (HCLV), and high carbohydrate ratio and high frequency of vegetable intake more than 5 times (HCHV). All data were analyzed after the application of weighted value, using a general linear model or logistic regression. Results: More than half of Korean elderly consumed diets with HCLV, and this group showed poor nutritional status and lower frequency of intake of most food items, but with no risk of chronic disease such as diabetes, obesity, hypertension, cardiovascular disease or anemia probably due to low intake of energy. On the contrary, MCHV group with a high percentage of energy from fat and protein showed the highest intake of energy and most nutrients, the highest frequency of intake of most of food items and a tendency of high risk of abdominal obesity, being followed by the MCLV group. Meanwhile, HCHV group showed a tendency of high risk of hypertension, followed by HCLV group with low frequency of intake of vegetables compared with the two moderate carbohydrate groups. Conclusions: The results suggested that the percentage of energy from carbohydrate and the frequency of vegetable intake affected the nutritional status, but not significantly affected the risk of chronic disease in Korean elderly. Further studies using more detailed category of % energy from carbohydrates and of type and amount of vegetables with consideration of individual energy intake level, excessive or deficient, are needed to confirm the results.

• Wind and Structures
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• v.5 no.1
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• pp.61-80
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• 2002

Wind tunnel aeroelastic model tests of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building were conducted using a three-degree-of-freedom base hinged aeroelastic(BHA) model. Experimental investigation into the effects of coupled translational-torsional motion, cross-wind/torsional frequency ratio and eccentricity between centre of mass and centre of stiffness on the wind-induced response characteristics and wind excitation mechanisms was carried out. The wind tunnel test results highlight the significant effects of coupled translational-torsional motion, and eccentricity between centre of mass and centre of stiffness, on both the normalised along-wind and cross-wind acceleration responses for reduced wind velocities ranging from 4 to 20. Coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness also have significant impacts on the amplitude-dependent effect caused by the vortex resonant process, and the transfer of vibrational energy between the along-wind and cross-wind directions. These resulted in either an increase or decrease of each response component, in particular at reduced wind velocities close to a critical value of 10. In addition, the contribution of vibrational energy from the torsional motion to the cross-wind response of the building model can be greatly amplified by the effect of resonance between the vortex shedding frequency and the torsional natural frequency of the building model.

• Smart Structures and Systems
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• v.31 no.3
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• pp.283-299
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• 2023

Structural stability of floating platforms has long since been a crucial issue in the field of marine engineering. Excessive motions would not only deteriorate the operating conditions but also seriously impact the safety, service life, and production efficiency. In recent decades, several control devices have been proposed to reduce unwanted motions, and an attractive one is the tuned heave plate (THP). However, the THP system may reduce or even lose its effectiveness when it is mistuned due to the shift of dominant wave frequency. In the present study, a novel adaptive tuned heave plate (ATHP) is proposed based on inerter by adjusting its inertance, which allows to overcome the limitation of the conventional THP and realize adaptations to the dominant wave frequencies in real time. Specifically, the analytical model of a representative semisubmersible platform (SSP) equipped with an ATHP is created, and the equations of motion are formulated accordingly. Two optimization strategies (i.e., J₁ and J₂ optimizations) are developed to determine the optimum design parameters of ATHP. The control effectiveness of the optimized ATHP is then examined in the frequency domain by comparing to those without control and controlled by the conventional THP. Moreover, parametric analyses are systematically performed to evaluate the influences of the pre-specified frequency ratio, damping ratio, heave plate sizes, peak periods and wave heights on the performance of ATHP. Furthermore, a Simulink model is also developed to examine the control performance of ATHP in the time domain. It is demonstrated that the proposed ATHP could adaptively adjust the optimum inertance-to-mass ratio by tracking the dominant wave frequencies in real time, and the proposed system shows better control performance than the conventional THP.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.571-575
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• 2000

The physical properties of the spatial model, mass, stiffness and damping matrix, can be defined by a specific natural frequency, damping ratio and mode shape. These modal parameters can be determined from a set of frequency response function(FRF) measured by exciting the structure and measuring the responses at various points around the structure. In this paper, The Transfer Matrix is obtained by experimental modal analysis for the 3-story scaled building model which TMD is installed on top and the physical properties of the spatial model is determined using the residue matrix and the location of poles from FRF measurement using polynomial curve fitting methods.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.984-989
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• 2008

An estimation of high-order damping in flexible multibody dynamic simulation is introduced in this paper. The suggested damping model based on the experimental modal analysis leads to more accurate correlation results comparing to the traditional linear damping model because it directly uses the modal parameters of each mode achieved from experiment even high frequency modes. The modal parameters until the 5th mode are extracted from the experimental modal testing of the flexible beam using a high speed camera. And using the measured damping ratio and natural frequency until the 5th mode, the generic damping model is constructed. Then, the ANCF (absolute Nodal Coordinate Formulation) simulation results are compared to experimental results until the 5th mode.

• 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 Korean Elementary Science Education
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• v.17 no.2
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• pp.55-65
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• 1998

This study was intended to suggest the desirable direction in the 7th national curriculum revision through the analysis of the elementary science textbooks in the 6th national curriculum. The analysis system was composed of three categories, (1)knowledge (2)inquiry process and (3)attitude. And knowledge was divided into fact, concept and rule. And inquiry process was divided into thirteen subcategories such as manipulating experimental apparatus, observing, measuring, recording data, classifying, interpreting/ predicting, determining relationship/ causal explanation, extrapolating/ interpolating, drawing conclusions/ formulating a generalization or model, evaluating, formulating a problem, generating a hypothesis and designing an experiment/ controlling variables. Each sentence in the textbooks was considered as an analyzing unit. The frequency and percentage of each category were counted and the ratios were calculated. The findings could be summarized as follows: 1. The content of the elementary science textbooks was composed of knowledge 10.3%, inquiry process 88.8%, attitude 0.8% respectively. 2. As increasing the grades, the ratio of knowledge showed high frequency, but that of attitude showed low frequency. 3. In All the grades, the ratio of observing was the highest in inquiry process. 4. In the domain of physics and chemistry, the manipulating experimental apparatus showed high frequency. In the domain of biology and earth science, the role of observing was emphasized.

• Smart Structures and Systems
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• v.26 no.4
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• pp.469-480
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• 2020

This is the first research on the smart control and vibration analysis of a Graphene nanoplatelets (GPLs) Reinforced Composite (GPLRC) porous cylindrical shell covered with piezoelectric layers as sensor and actuator (PLSA) in the framework of numerical based Generalized Differential Quadrature Method (GDQM). The stresses and strains are obtained using the First-order Shear Deformable Theory (FSDT). Rule of the mixture is employed to obtain varying mass density and Poisson's ratio, while the module of elasticity is computed by modified Halpin-Tsai model. The external voltage is applied to sensor layer and a Proportional-Derivative (PD) controller is used for sensor output control. Governing equations and boundary conditions of the GPLRC cylindrical shell are obtained by implementing Hamilton's principle. The results show that PD controller, length to radius ratio (L/R), applied voltage, porosity and weight fraction of GPL have significant influence on the frequency characteristics of a porous GPLRC cylindrical shell. Another important consequence is that at the lower value of the applied voltage, the influence of the smart controller on the frequency of the micro composite shell is much more significant in comparison with the higher ones.

• Journal of Korean Association for Spatial Structures
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• v.14 no.4
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• pp.39-46
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• 2014

In Seoul, total 27 places of foot-bridges were chosen to evaluate the damping ratio through vibration measurement by mobile-phone application. Model vibration test was performed to compare the natural frequency and damping ratio between the conventional accelerometer and mobile-phone application. Measured average damping was compared with the one of Bachmann. The relation between the damping ratio and span was also investigated. Measured average damping ratio was greater than that of Bachmann. It was shown that there is no distinct trend between damping and span.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.77-85
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• 2020

In this study, we proposed a method to replace the solid finite element model of the boiler membrane wall for coal-fired power plants using an equivalent shell model. The application of a bending load to the membrane wall creates greater displacement at both ends of the central portion when compared with the middle when an isotropic elastic constant is used in the shell model. This is inconsistent with the results of the solid model where the central portion is uniformly deformed. Here, we presented a method to determine the orthotropic elastic constants of the shell model in terms of bending stiffness and vibration characteristics to solve this problem. Our analysis of the orthotropic shell model showed that the error ratio was 0.9% for the maximum displacement due to the bending load, 0.3% for the first natural frequency, and 2.5% for the second natural frequency when compared with the solid model. In conclusion, a complicated boiler membrane wall composed of a large number of pipes and fins can be replaced with a simple shell model that shows equivalent bending stiffness and vibration characteristics using our proposed method.