• Steel and Composite Structures
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• v.31 no.4
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• pp.387-396
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• 2019

This paper deals with the effect of ply orientation and control gain on tip transverse displacement of functionally graded beam layer for both active constrained layer damping (ACLD) and passive constrained layer damping (PCLD) system. The functionally graded beam is taken as host beam with a bonded viscoelastic layer in ACLD beam system. Piezoelectric fiber reinforced composite (PFRC) laminate is a constraining layer which acts as actuator through the velocity feedback control system. A finite element model has been developed to study actuation of the smart beam system. Fractional order derivative constitutive model is used for the viscoelastic constitutive equation. The control voltage required for ACLD treatment for various symmetric ply stacking sequences is highest in case of longitudinal orientation of fibers of PFRC laminate over other ply stacking sequences. Performance of symmetric and anti-symmetric ply laminates on damping characteristics has been investigated for smart beam system using time and frequency response plots. Symmetric and anti-symmetric ply laminates significantly reduce the amplitude of the vibration over the longitudinal orientation of fibers of PFRC laminate. The analysis reveals that the PFRC laminate can be used effectively for developing very light weight smart structures.

• Earthquakes and Structures
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• v.25 no.4
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• pp.283-296
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• 2023

This paper presents experimental and numerical studies of seismic performance on reinforced concrete (RC) wide beam (WB) joints. Two RC-WB joint specimens and one conventional RC joint specimen were fabricated using the reinforcing details of longitudinal reinforcing bars in a beam as a variable, and quasi-static cyclic loading tests were performed. The results were used to compare and analyze the load-drift ratio relationship, failure mode, and seismic performance of the specimens quantitatively. In addition, a finite element (FE) analysis of the RC-WB joint was conducted, and the rationality of the FE model was validated by comparing it with the test results. Based on the FE model, a parametric study was conducted, where the ratio of longitudinal reinforcing bars placed on the outer and inner parts of the joint (𝜌_ex/𝜌_in) was a key variable. The results showed that, in the RC-WB joint, an increase of 𝜌_ex/𝜌_in leads to more severe damage to concrete, which reduces the seismic performance of the RC-WB joints.

• Korean Journal of Food Science and Technology
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• v.9 no.4
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• pp.271-276
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• 1977

Treating with step concentration of papain, round mucle of Korean cattle were cut in longitudinal and cross section and stained. Collagenous fibre and elastic fibre of its connective tissue were observed microscopically. The results were as follows: 1) In proportion to the increase of enzyme concentration amorphous bundle of collagenous fibre were loosed gradually and destroyed in the long run and besides the property of this fibre stained became remarkably weak. 2) Elastic fibre was paralleled to muscle fibre and in proportion to the increase of enzyme concentration, it was lost elasticity, loosed, straightened and broken remarkably to pieces. 3) Histological variation of collagenous fibre and elastic fibre treated with enzyme was more remarkable than control.

• 대한예방의학회:학술대회논문집
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• 1994.02a
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• pp.577-584
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• 1994

The relation between lead in air (PbA) and lead in blood (PbB), concentrations was investigated among 44 workers in five major operations in a United States high volume, lead acid battery plant. The study covered a 30 month period in which workers received frequent PbA and PbB determinations, workers remained in a single job, and PbA concentrations averaged below the US Occupational Safety and Health Administration (OSHA) permissible exposure limit of $50{\mu}g/m^{3}$. In both univariate and multivariable linear regressions, longitudinal analyses averaging PbA concentrations over the 30 month study period appeared superior to cross sectional analyses using only six month PbA averages .to model PbB concentrations. The covariate adjusted coefficient ($\alpha$ value) for PbA($\mu/m^{3}$) in models of PbB (${\mu}g/100\;g$) was 1-14. This figure is strikingly higher than that reported in previous studies in the lead acid battery industry in all of which PbA concentrations were substantially higher than in the current study. Plausible explanations for the differences in a: values include non-linearity of the PbA-PbB curve, a higher fraction of large size particulate associated with higher PbA concentrations, survivor bias among workers exposed to higher PbA concentrations, and the cross sectional designs of most previous studies. Despite previously reported problems with the model used by OSHA to predict PbA-PbB relations, the findings of this study are in good agreement with the predictions of that model.

• The Journal of Korean Medicine
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• v.37 no.1
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• pp.41-52
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• 2016

Objectives: There are no studies which have investigated the health related quality of life(HRQOL) about stroke patients according to the medical care utilization behavior by longitudinal analysis. The purpose of this study is to analyze the quality of life(QOL) and quality adjusted life years(QALYs) of stroke patients of western and combined treatment group by longitudinal analysis. Methods: A retrospective cohort study was conducted among 37 new patients who initiated diagnosis with stroke in 2009 from Korea Health Panel Data. We analyzed the HRQOL of stroke patients and calculated the QALYs after medical use initiation for up to 3 years according to the medical care utilization behavior. Results: Overall, the quality of life of stroke patients was lowered somewhat from 0.8431 to 0.7864 in 2009~2012. Western treatment group was appeared slightly declined in from 0.8527 to 0.8231 and combined treatment group was shown to be falling from 0.8173 to 0.6875. The QALYs of total patients were calculated 2.3654 and western treatment group were 2.4436, combined treatment group were 2.1542 during the 4 year period. The difference of QALYs between two groups was 0.2894 QALYs. Conclusions: Although there was a small difference in QALYs of the two groups, it is not certain that the difference is come from medical care utilization behavior. Further studies should be needed to confirm the relation of the medical care utilization behavior and quality of life by considering severity of the stroke.

• The Korean Journal of Community Living Science
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• v.17 no.3
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• pp.109-121
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• 2006

This study examines the relationship between mother's stress and cortisol level during late pregnancy and how it changes into postpartum periods. Thirty one families were recruited from Daejeon and Incheon in South Korea. The major findings were as follows: (1) The level of mothers' cortisol followed the typical diurnal pattern of decline throughout the day. Further longitudinal analysis revealed that the level of Korean mothers' cortisol steadily lowered from the 8th prenatal month to the 6th postnatal month. (2) During pregnancy, mothers reported to experience changes in physical activities, daily routines, eating habits, types or amount of social activities and sleeping habits. Among these they were stressed the most by changes in physical activities and social activities. (3) The results of postpartum depression tests conducted at two months after giving birth showed mothers at this time were mostly stressed from difficulty sleeping and unnecessary self criticism. (4) The level of psycho social stress in mothers at six months after giving birth was mainly on social roles and the questions about self reliance marked the highest points. (5) Overall, there was a tendency for the level of maternal stress to decrease definitely from before and after the delivery and even though the level of stress was steadily decreasing up to 6th postpartum month it was not as sharp as those of before and after the birth of the babies. The level of cortisol analysis also showed the same obvious tendency.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.939-956
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• 2015

In this study, in order to propose an efficient model to predict the torque capacity of steel fiber reinforced concrete (SFRC) beams, the existing experimental data related to torsional response of beams is reviewed. It is observed that existing data neglects the effects of some parameters on the variation of torque capacity. Thus, an experimental research was also conducted to obtain the effects of neglected parameters. In the experimental study, a total of seventeen SFRC beams are tested against torsion. The parameters considered in the experiments are concrete compressive strength, steel fiber aspect ratio, volumetric ratio of steel fibers and longitudinal reinforcement ratio. The effect of each parameter is discussed in terms of torque versus unit angle of twist graphs. The data obtained from this experimental research is also combined with the data got from previous studies and employed in artificial neural network (ANN) analysis to estimate the ultimate torque capacity of SFRC beams. In addition to parameters considered in the experiments, aspect ratio of beam cross-section, yield strengths of both transverse and longitudinal reinforcements, and transverse reinforcement ratio are also defined as parameters in ANN analysis due to their significant effects observed in previous studies. Assessment of the accuracy of ANN analysis in estimating the ultimate torque capacity of SFRC beams is performed by comparing the analytical and experimental results. Comparisons are conducted in terms of root mean square error (RMSE), mean absolute error (MAE) and coefficient of efficiency ($E_f$). The results of this study revealed that addition of steel fibers increases the ultimate torque capacity of reinforced concrete beams. It is also found that ANN is a powerful method and a feasible tool to estimate ultimate torque capacity of both normal and high strength concrete beams within the range of input parameters considered.

• The Korean Journal of Applied Statistics
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• v.27 no.7
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• pp.1077-1095
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• 2014

Unlike randomized trial, statistical strategies for inferring the unbiased causal relationship are required in the observational studies. Recently, new methods for the causal inference in the observational studies have been proposed such as the matching with the propensity score or the inverse probability treatment weighting. They have focused on how to control the confounders and how to evaluate the effect of the treatment on the result variable. However, these conventional methods are valid only when the treatment variable is categorical and both of the treatment and the result variables are directly observable. Research on the causal inference can be challenging in part because it may not be possible to directly observe the treatment and/or the result variable. To address this difficulty, we propose a method for estimating the average causal effect when both of the treatment and the result variables are latent. The latent class analysis has been applied to calculate the propensity score for the latent treatment variable in order to estimate the causal effect on the latent result variable. In this work, we investigate the causal effect of adolescents delinquency on their substance use using data from the 'National Longitudinal Study of Adolescent Health'.

• Physical Therapy Korea
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• v.23 no.4
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• pp.27-37
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• 2016

Background: In previous studies regarding flexible pes planus, Foot orthosis, special shoes have been used as interventions for correcting malalignment and intrinsic muscles strengthening exercise have been regarded as interventions for foot function and supporting medial longitudinal arch during walking. However, some recent studies reported that strengthening extrinsic muscles as well as intrinsic muscles is more effective and active intervention for flexible pes planus. In particular, the tibialis posterior muscle of foot extrinsic muscles plays essential roles in maintaining the medial longitudinal arch during dynamic weight bearing and balance. In addition this muscle acts longer than other supination muscles during the stance phase in the gait cycle. Objects: This study aimed to investigate the effect of foot intrinsic muscle and tibialis posterior muscle strengthening exercise for plantar pressure and dynamic balance in adults with flexible pes planus. Methods: 16 young flexible pes planus adults (7 males, 9 females) were recruited and were randomized into two groups. The experimental group performed foot intrinsic muscle and tibialis posterior muscle strengthening training, the control group performed only foot intrinsic muscle strengthening training. All groups received strengthening training for 30 minutes five times a week for six weeks. Results: The experimental group had significantly lower plantar pressure of medial heel area than the control group in stand (p<.05). The experimental group had significantly higher dynamic balance ability than control group (p<.05). Conclusion: The results of this study provide evidence to suggest that foot intrinsic muscle and tibialis posterior muscle of extrinsic muscle strengthening exercises may improve plantar pressure distribution and dynamic balance ability in adults with flexible pes planus.

• Korean Journal of Child Studies
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• v.24 no.1
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• pp.99-108
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• 2003

This study was based on theories of the culture of poverty and the causes and consequences of poverty. The strong relationship of family income to mother's education presents the possibility of an intergenerational education cycle. Using a longitudinal approach, parental poverty status was measured by family income, welfare assistance, single parent, and occupation when children were 2 years of age; children's school performance was measured by teacher reports of their reading, mathematics, writing, and overall ability at grade 1. Data were analyzed by structure equation modeling. Results showed that mother's pre-childbearing level of education predicted child school performance in grade 1, confirming an intergenerational cycle. In addition, the results indicated that parental poverty acts as a mediator between the cycle.