• 생태와환경
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• 제43권2호
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• pp.199-211
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• 2010

The objectives for this study were to evaluate spatial and temporal characteristics of water quality, based on long-term water quality monitoring data during 1993~2008. We found that physico-chemical and ecological conditions in the Daecheong Reservoir (DR) were modified by the construction of upper dam (i.e., Yongdam Reservoir). total phosphorus (TP), Secchi depth (SD), and chlorophyll-a (CHL) in the DR showed significant longitudinal decreases along the headwater-to-the downlake, indicating a large spatial variation, and this gradient was more intensified during the high-flow season (monsoon). Nutrient-rich water containing high nitrogen and phosphorus in the monsoon season (July~August) passed through the reservoir as a density current in the metalimnetic depth, and also high suspended solids increased in the metalimnetic depth, especially during the monsoon. According to the deviation analysis of Trophic State Index (TSI), >50% of TSI (CHL)-TSI (SD) and TSI (CHL)-TSI (TP) values were negatives, so that inorganic suspended solids (non-votatile solids) influenced the underwater light regime against phytoplankton growth. Also, ratios of CHL:TP after the dam construction evidently increased, compared to the values before the upper dam constructions, indicating a greater yield of phytoplankton in the unit phosphorus. Overall data showed that ecological and functional changes in Daecheong Reservoir occurred after the construction of upper dam (Yongdam Reservoir).

• 한국보육지원학회지
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• 제18권5호
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• pp.57-77
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• 2022

Objective: The purpose of this study was to analyze the causal relationship between parenting knowledge, parenting stress, and parenting behavior of mothers with infants and to confirm the longitudinal mediating effect of parenting stress in the relationship between parenting knowledge and parenting behavior. Methods: This study used data collected through the Panel Study on Korean Children from 2008 to 2010 and the participants were 1,444 mothers with infants. The data were analyzed through technical statistics, correlations and multivariate potential growth models using SPSS 28.0 and AMOS 26.0. Results: Parenting knowledge and parenting stress of mothers gradually increased, and positive parenting behavior gradually decreased. Having a lot of parenting knowledge reduced mother's parenting stress. Mother's parenting stress reduced positive parenting behavior, and as parenting stress increased, positive parenting behavior decreased significantly. However, the relationship between parenting knowledge and parenting behavior was not significant. In addition, the mediating effect of parenting stress was confirmed in the relationship between parenting knowledge and parenting behavior of mothers. Conclusion/Implications: The results of this study suggest the need to reduce parenting stress and promote positive parenting behavior along with the systematization of parent education programs in order for mothers with infants to acquire parenting knowledge.

• 한국보육지원학회지
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• 제20권1호
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• pp.39-53
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• 2024

Objective: The purpose of this study is to investigate whether emotionality at age three predicts early school-age media overdependence and to examine the potential mediating role of internalizing behavior problems in children. Methods: This study employed data from the 4th and 10th waves of the Panel Study of Korea Children, comprising a sample of 1,270 children. Assessments of emotionality (4th wave), media overdependence (10th wave), and internalizing behavior problems (10th wave) were conducted. Data analysis utilized SPSS and the Process Macro. Results: At age 3, heightened emotionality was found to directly contribute to an increased tendency for media overdependence in early school age. Internalizing behavior problems played a significant mediating role in the relationship between emotionality and media overdependence. Conclusion/Implications: This study validated a significant longitudinal connection between emotionality and the inclination to excessively rely on media, highlighting the role of internalization behavior problems in this relationship. It is essential to provide focused attention, especially to children displaying heightened emotionality in early childhood, in order to proactively prevent internalization behavior problems and the undue dependence on media.

• 한국콘텐츠학회논문지
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• 제19권1호
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• pp.339-349
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• 2019

본 연구는 노인가구 노인의 삶의 만족도 변화에 미치는 영향 요인을 분석하는데 연구 목적이 있다. 연구를 위해 노인 1인가구와 노인 부부가구를 노인 가구라고 정의하여, 한국고용정보원이 제공하고 있는 고령화 연구패널자료(Korean Longitudinal Survey of Ageing: KLoSA)의 2, 3, 4차 자료를 활용 했으며, 65세 이상 3차시 모두 설문에 응답한 677명을 최종 분석대상으로 활용하였다. 노인가구의 삶의 만족도 수준의 종단적 연구에서 시간이 지날수록 개인별 만족도 수준이 낮아지고 있음을 확인하였고, 잠재성장모형의 조건부 모형을 통해 노인가구의 삶의 만족도 수준의 종단 변화에 영향을 미치는 요인을 분석하였다. 분석 결과, 가구유형, 주택소유유무, 주관적 건강상태 등이 노인가구의 삶의 만족도 초기값에 영향을 미치는 것으로 나타났으며, 가구유형, 생활수준 기대감 등이 노인가구의 삶의 만족도 변화율에 영향을 미치는 요인으로 나타났다. 이러한 연구 결과를 통해 노인가구의 자아실현 기회를 높여 노년 시대의 삶의 만족도 향상이 필요하며, 정책적 접근에 있어 다양한 유형을 고려한 선별적 접근이 필요함 등을 제언하였다.

• Asian Journal of Business Environment
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• 제9권2호
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• pp.5-15
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• 2019

Purpose - The present study endeavours to investigate the impact of intellectual capital (IC) and its components on corporate sustainable growth in India. In addition, this study aims to find out the most influential component of IC on corporate sustainable growth in India. Research design, data, and methodology - A sample size of top 139 NSE listed non-financial companies over a time period of five years has been used in this monograph. The impact of intellectual capital and its components on corporate sustainable growth has been examined using the longitudinal data analysis technique. Results - The findings of this study bring to light that intellectual capital (IC) as measured by the M-VAIC model demonstrates a significant impact on corporate sustainable growth. Considerably, the results also reveal that almost all the explanatory variables viz. Physical Capital, Relational Capital, Innovation Capital, and Process Capital exercise notable influence in explaining corporate sustainable growth. Moreover, the results demonstrate Innovation Capital (controlling the effect of Physical Capital) represents the most influential component of IC on corporate sustainable growth. Conclusions - The research findings show that in the Indian context, both physical capital, and IC (overall), as well as its components, play a crucial role to explain corporate sustainable growth.

• 한국소음진동공학회논문집
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• 제20권9호
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• pp.863-875
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• 2010

The vibration of a cylindrical shell is generated due to elastic waves propagating on the shell. Those elastic waves include propagating waves such as flexural, longitudinal and shear waves. Those also include non-propagating decaying waves, i.e. evanescent waves. In order to separate contributions of each type of waves to the data for the vibration of the cylindrical shell, spatial signal processing techniques for wavenumber analysis are investigated in this paper. Those techniques include Fast Fourier transform(FFT) algorithm, Extended Prony method and Overdetermined Modified Extended Prony method(OMEP). Those techniques have been applied to identify the waves from simulated vibration signals with various signal-to-noise ratios. Futhermore, the experimental data for in-plane vibration of the cylindrical shell has been processed with those techniques to identify propagating waves(longitudinal, shear and flexural waves) and evanescent waves.

• 대한간호학회지
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• 제35권2호
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• pp.382-389
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• 2005

Purpose: This longitudinal study was done to investigate critical thinking dispositions and critical thinking skills of nursing students enrolled in a 4-year baccalaureate program at a university in Korea. Method: The study used a longitudinal design. A convenience sample of 32 nursing students who were completing their 1st, 2nd, 3rd, and 4th year in a baccalaureate program at a selected university was included. The subjects completed the California Critical Thinking Dispositions Inventory (CCTDI), the California Critical Thinking Skill Test (CCTST), and a demographic questionnaire. Data was analyzed by descriptive statistics, repeated ANOVA, adjusted p-values, and Pearson's correlation coefficient with SAS 8.12. Results: There was statistically significant improvement according to academic year in the CCTDI total mean score (F=7.54, p= .0001) and subscales of Open-mindedness, Self-confidence, and Maturity. Contrarily, no statistically significant difference was found in the CCTST total mean score and subscales' score except Analysis. Conclusion: There is no significant correlation between critical thinking dispositions and skills, so it will be necessary to repeat a study like this, and the translated instruments should be modified by considering Korean culture.

• Earthquakes and Structures
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• 제7권4호
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• pp.463-484
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• 2014

Solid piers with a rounded rectangular cross-section are widely used in railway bridges for high-speed trains in China. Compared to highway bridge piers, these railway bridge piers have a larger crosssection and less steel reinforcement. Existing material models cannot accurately predict the seismic behavior of this kind of railway bridge piers. This is because only a few parameters, such as axial load, longitudinal and transverse reinforcement, are taken into account. To enable a better understanding of the seismic behavior of this type of bridge pier, a simultaneous influence of the various parameters, i.e. ratio of height to thickness, axial load to concrete compressive strength ratio and longitudinal to transverse reinforcements, on the failure characteristics, hysteresis, skeleton curves, and displacement ductility were investigated. In total, nine model piers were tested under cyclic loading. The hysteretic response obtained from the experiments is compared with that obtained from numerical studies using existing material models. The experimental data shows that the hysteresis curves have significantly pinched characteristics that are associated with small longitudinal reinforcement ratios. The displacement ductility reduces with an increase in ratio of axial load to concrete compressive strength and longitudinal reinforcement ratio. The experimental results are largely in agreement with the numerical results obtained using Chang-Mander concrete model.

• 동력기계공학회지
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• 제18권5호
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• pp.66-73
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• 2014

This study was considered to occur the local wall thinning at elbow which is flowing the steam and high-pressure water of high-temperature. The angle of elbow is ${\Theta}=45^{\circ}$ and $67.545^{\circ}$. The damage behaviors of inner or outer wall thinning elbow under internal pressure were calculated by FEA(finite element analysis). We compared the simulated results by FEA with experimental data. The FEA results are as follows: In the FEA results of three types of wall thinning ratio, the circumferential and longitudinal stresses show the similar values regardless of the angle of elbow, respectively. The circumferential strain was greater at elbow of small angle, but the longitudinal strain was nearly same. The FEM stress of outer wall thinning elbow was slightly higher than that of the inner wall thinning elbow, and strain was also slightly higher. In the experiments, the circumferential strain was increased with the increase in the internal pressure, and increased rapidly on about 0.2% of strain. The longitudinal strain was small. The strain at break was much smaller than 0.2%. In the relation between pressure and eroded ratio, the criteria that can be used safely under operating pressure and design pressure were obtained. The results of FEA were in relatively good agreement with those of the experiment.

• Structural Engineering and Mechanics
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• 제11권4호
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• pp.357-372
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• 2001

In this paper, cantilevered tall structures are treated as cantilever bars with varying cross-section for the analysis of their free longitudinal (or axial) vibrations. Using appropriate transformations, exact analytical solutions to determine the longitudinal natural frequencies and mode shapes for a one step non-uniform bar are derived by selecting suitable expressions, such as exponential functions, for the distributions of mass and axial stiffness. The frequency equation of a multi-step bar is established using the approach that combines the transfer matrix procedure or the recurrence formula and the closed-form solutions of one step bars, leading to a single frequency equation for any number of steps. The Ritz method is also applied to determine the natural frequencies and mode shapes in the vertical direction for cantilevered tall structures with variably distributed stiffness and mass. The formulae proposed in this paper are simple and convenient for engineering applications. Numerical example shows that the fundamental longitudinal natural frequency and mode shape of a 27-storey building determined by the proposed methods are in good agreement with the corresponding measured data. It is also shown that the selected expressions are suitable for describing the distributions of axial stiffness and mass of typical tall buildings.