• Journal of Korean society of Dental Hygiene
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• 제7권4호
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• pp.569-582
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• 2007

The author aims at first securing basic material required for developing and operating proper oral health care education programs though making an investigation into the undergraduates of S College of Education on the actual status of oral health care and perceptions of oral health care education. The obtained results were as follows 1. In the actual status of oral care based on whether or not they have experiences in taking oral health care education, undergraduates with teeth brushing for more than three minutes a time were found to be 25.9% and 15.7% respectively according to the existence and nonexistence of experiences in the education(pM0.020), and undergraduates with teeth brushing in a circular motion was found to be 64.7% and 51.7% respectively, showing statistically significant differences(pM0.015). 2. In the actual status of preventative oral care according to whether or not they have experiences in taking oral care education, degrees of awareness of the usefulness of dental cleansers among the undergraduates were found to be 37.6% and 21.5% respectively according to the existence and nonexistence of experiences in the education(pM0.001), undergraduates with experiences in scaling were found to be 51.8% and 34.9% respectively(pM0.002) and undergraduates with experiences in having dental sealants were found to be 26.5% and 16.9%(pM0.031), showing statistically significant differences. 3. In the survey on perceptions of oral health care according to the existence and nonexistence of experiences in oral health care education, it was revealed that the case that they indicated 'the necessity of oral health care education' was 87.1% and 64.0% respectively according to the existence and nonexistence of the experience(pM0.000), and undergraduates intended to 'participate in oral care education for students(at mid and high schools and so on) after being teachers' were 77.6% and 65.7% respectively, showing statistically significant differences(pM0.011). 4. In general characteristics according to awareness of the necessity of cultivating oral health professionals, groups with awareness of the necessity consisted of 31.8% of freshmen and juniors(pM0.001), 55.69b of female undergraduates(pM0.001), 80.8% of non-smokers(pM0.012), 38.9% of large city residents(pM0.002) and 32.3% of undergraduates living in their own houses (pM0.028), showing statistically significant differences.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제43권9호
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• pp.765-772
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• 2015

Aerodynamic force measurements and phase-locked PIV study were carried out to check the bio-mimetic MAV applicability of a swift flight. Two-rotational DOF robotic wing model and blowing-type wind tunnel were employed. The amplitude of twist angle were ${\pm}0$, ${\pm}5$, ${\pm}10$, and ${\pm}20$ deg. and stroke angles were manipulated by simple harmonic function with out-of-phase in regards to the stroke motion. It is acknowledged that the time-varying lift coefficients in accordance with the change of the twist angle did not result in any noticeable differences, just the small decrease and delay. However, the drag exhibited that the small change of the twist angle can produce large thrust. These findings imply why a swift uses small twist angle during flight. The PIV results displayed that the delay of aerodynamic forces is highly associated with the vortical structures around the wing. It is therefore indicated that a process of designing a swift-based Micro Air Vehicle should take the twist angle into consideration, as the essential parameter.

• Journal of the Korean Society for Marine Environment & Energy
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• 제9권4호
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• pp.225-234
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• 2006

Using the data from the sea water monitoring system installed at the Ieodo Ocean Research Station, we have analyzed the water properties around the station as well as the characteristics of the fresh water from the Changjiang River and the influence of typhoons on the sea water. In general, the accuracy and stability of the temperature data are high, but those of the salinity data are worse than the specification of the instruments. The daily variation of temperature and salinity is mainly controlled by the vertical motion of a water column due to semi-diurnal tide and diurnal change in the solar insolation. Seasonal change is prominent in temperature data. The freshwater from the Changjiang River is the main cause of large salinity variation. In August 2003 and August 2004, about 10 days before fresh water was observed near the Jeju Island, low salinity water was observed at the Ieodo Station. On the other hand, in July 2005 fresh water was observed at the station but not at around the Jeju Island. In other words, the fresh water observed at the Ieodo Station does not always expand to the Jeju Island. Two strong typhoons passed by the station in September 2003 and August 2004. The effects of the typhoons were lasted for 3 to 4 days.

• Journal of the Society of Naval Architects of Korea
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• 제28권1호
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• pp.38-52
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• 1991

In this paper, a semi-Lagrangian method is used to solve the nonlinear hydrodynamics of a three-dimensional body beneath the free surface in the time domain. The boundary value problem is solved by using the boundary integral method. The geometries of the body and the free surface are represented by the curved panels. The surfaces are discretized into the small surface elements using a bi-cubic B-spline algorithm. The boundary values of $\phi$ and $\frac{\partial{\phi}}{\partial{n}}$ are assumed to be bilinear on the subdivided surface. The singular part proportional to $\frac{1}{R}$ are subtracted off and are integrated analytically in the calculation of the induced potential by singularities. The far field flow away from the body is represented by a dipole at the origin of the coordinate system. The Runge-Kutta 4-th order algorithm is employed in the time stepping scheme. The three-dimensional form of the integral equation and the boundary conditions for the time derivative of the potential Is derived. By using these formulas, the free surface shape and the equations of motion are calculated simultaneously. The free surface shape and fille forces acting on a body oscillating sinusoidally with large amplitude are calculated and compared with published results. Nonlinear effects on a body near the free surface are investigated.

• Journal of Korean Academy of Fundamentals of Nursing
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• 제8권1호
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• pp.81-94
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• 2001

The purpose of this study was to identify levels of activity of daily living, self-efficacy. stroke specific quality of life and need for self-help management program for patients with hemiplegia in the home. Data were collected from June to November, 2000 and subjects were 88 poststroke patients who lived in Seoul and Kyunggi-do. The questionnaire consisted of 5 scales: activities of daily living, self-efficacy, stroke specific qulaity of life and need for a self-help management program. Data were analyzed using frequencies, percent, paired t-test, and Pearson's correlation coefficient with the SAS(version 6.12) program. The results are as follows ; 1) Most of subjects were Partially independent in ADL, but they needed assist once to do dressing, bathing meal preparation and house keeping work. 2) The mean self-efficacy score was 54.89(range : 1 to 80) and the individual differences were large. 3) Subjects responded that they were satisfied on the stroke specific quality of life scale totaled 65.8%. This value is comparatively low, especially for social role(51.4%), family functioning(58.3%) and mood (62.2%). 4) The highest needs for self-help management programs were for physical therapy, stress management, and range of motion exercise and the lowest needs were for elimination management and training, family counseling, and speech therapy. 5) On the demographic variables, sex showed significant differences for the dependent variables. Females had higher scores than males for IADL, self-efficacy, stroke-specific quality of life, and need for self-help management. 6) Age had high negative correlation with ADL, self-efficacy and stroke specific quality of life. Age was also correlated with need for self-help management. In conclusion, there was a high correlation for ADL, Self-efficacy and Quality of life in poststroke patients of home. The patient with a stroke also had a strong need for self-help management programs especially physical therapy and stress management. Therefore rehabilitation programs based on self-efficacy enhancement need to be developed in order to promote independent living for patients with hemiplegia.

• Journal of the Korean Chemical Society
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• 제62권4호
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• pp.288-298
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• 2018

In this study, we surveyed pre- and post-perceptions of fourteen science teachers related to the atmosphere composition of molecules with different masses by the developed test. As a result of the test, the teachers were classified into two types of thoughts; One of them is considered the atmosphere to be a homogeneous solution, and the other is a thought that the composition ratio of the atmosphere was not homogeneous considering the different weights of particles. The two types were reclassified into three categories; one of them is considering large gravity effect, another is considering small gravity effect, and the other is considering medium scale gravity effect. Total six types of thoughts were found from the pre-test. After introducing crosscutting concepts which are related to the composition of atmosphere. The teachers discussed the phenomena with the molecular motion by weights of atoms and temperature, the homogeneity of the solution of air in chemistry domain. They also discussed with the relationship between mass and gravity and distance in physics domain. And the discussion included distribution of the atmosphere, convection phenomena, etc. After the discussion, the teachers changed their pre-conceptions to post-concoctions considering combined perspectives of gravity, mass, temperature, altitude etc. Through these changes, we are able to confirm the importance of crosscutting concepts covered in various disciplines. In the integrated science, we should help teachers to provide students with these types of thinking in order to form a coherent world-view and to carry out inquiry thinking as an intellectual tool.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제21권5호
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• pp.465-474
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• 2008

The real-time hybrid testing method(RT-HYTEM) is a structural testing technique in which the numerical integration of the equation of motion for a numerical substructure and the physical testing for an experimental substructure are performed simultaneously in real-time. This study presents the quantitative evaluation of the seismic performance of a building structure installed with an passive and semi-active MR damper by using RT-HYTEM. The building model that was identified from the force-vibration testing results of a real-scaled 5-story building is used as the numerical substructure, and an MR damper corresponding to an experimental substructure is physically tested by using the universal testing machine(UTM). The RT-HYTEM implemented in this study is validated because the real-time hybrid testing results obtained by application of sinusoidal and earthquake excitations and the corresponding analytical results obtained by using the Bouc-Wen model as the control force of the MR damper respect to input currents were in good agreement. Also for preliminary study, some semi-active control algorithms were applied to the MR damper in order to control the structural responses optimally. Comparing between the test results of semi-active control using RT-HYTEM and numerical analysis results show that the RT-HYTEM is more resonable than numerical analysis to evaluate the performance of semi-active control algorithms.

• Structural Engineering and Mechanics
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• 제15권4호
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• pp.381-394
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• 2003

While constructing multistorey buildings with reinforced concrete framed structures it is a common practice to provide parking space for vehicles at the ground floor level. This floor will generally consist of open frames without any infilled walls and is called an open-storey. From a post disaster damage survey carried out, it was noticed that during the January 26, 2001 Bhuj (Gujarat, India) earthquake, a large number of reinforced concrete framed buildings with open-storey at ground floor level, suffered extensive damage and in some cases catastrophic collapse. This has brought into sharp focus the need to carry out systematic studies on the seismic vulnerability of such buildings. Determination of vulnerability requires realistic structural response estimations taking into account the stochasticity in the loading and the system parameters. The stochastic finite element method can be effectively used to model the random fields while carrying out such studies. This paper presents the details of stochastic finite element analysis of a five-storey three-bay reinforced concrete framed structure with open-storey subjected to standard seismic excitation. In the present study, only the stochasticity in the system parameters is considered. The stochastic finite element method used for carrying out the analysis is based on perturbation technique. Each random field representing the stochastic geometry/material property is discretised into correlated random variables using spatial averaging technique. The uncertainties in geometry and material properties are modelled using the first two moments of the corresponding parameters. In evaluating the stochastic response, the cross-sectional area and Young' modulus are considered as independent random fields. To study the influence of correlation length of random fields, different correlation lengths are considered for random field discretisation. The spatial expectations and covariances for displacement response at any time instant are obtained as the output. The effect of open-storey is modelled by suitably considering the stiffness of infilled walls in the upper storey using cross bracing. In order to account for changes in soil conditions during strong motion earthquakes, both fixed and hinged supports are considered. The results of the stochastic finite element based seismic analysis of reinforced concrete framed structures reported in this paper demonstrate the importance of considering the effect of open-storey with appropriate support conditions to estimate the realistic response of buildings subjected to earthquakes.

• Geophysics and Geophysical Exploration
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• 제10권4호
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• pp.241-251
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• 2007

The observed spectra from Odaesan earthquake were fitted to a point-source spectral model to evaluate the source spectrum and spatial features of the modelling error. The source spectrum was calculated by removing from the observed spectra the path and site dependent responses (Yun, 2007) that were previously revealed through an inversion process applied to a large accumulated spectral dataset. The stress drop parameter of one-corner Brune's ${\omega}^2$ source model fitted to the estimated source spectrum was well predicted by the scaling relation between magnitude and stress drop developed by Yun et al. (2006). In particular, the estimated spectrum was quite comparable to the two-corner source model that was empirically developed for recent moderate earthquakes occurring around the Korean Peninsula, which indicates that Odaesan earthquake is one of typical moderate earthquakes representative of Korean Peninsula. Other features of the observed spectra from Odaesan earthquake were also evaluated based on the commonly treated random error between the observed data and the estimated point-source spectral model. Radiation pattern of the error according to azimuth angle was found to be similar to the theoretical estimate. It was also observed that the spatial distribution of the errors was correlated with the geological map and the $Q_0$ map which are indicatives of seismic boundaries.

• Journal of the Korean Chemical Society
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• 제64권5호
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• pp.304-317
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• 2020

This study was conducted on four 11^th grade students at a high school in a small town to determine the effectiveness of responsive teaching. The three phases of the responsive teaching method proposed in the previous study were subdivided into six stages; Step 1 is elicitation of students' thoughts related to macroscopic world, Step 2 is drawing of students' early thoughts related to microscopic world, Step 3 is disciplinary connections with ideas of the particle, Step 4 is to clarify the learner's thoughts on the particle by the teacher's involvement, Step 5 is deepening students' thoughts, and Step 6 is expanding ideas. In Step 4, students came to the recognition that the cause of mass was atoms and that the cause of volume was molecules. In Step 5, students led to a shift in thinking that could ignore the volume of the molecules themselves through the properties of protons and neutrons that affect mass from a particle perspective. In the Step 6 of expanding ideas, students explained molecular motion by the concept of material point which ignores the volume of particles. This steps gave students perspectives on the relationship between the mass and volume of particles required by Avogadro's law. The students recognized that some systems could be studied only indirectly because they were too small, too large, too fast, or too slow to observe directly.