• Steel and Composite Structures
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• 제31권4호
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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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• 제25권4호
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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.

• 한국식품과학회지
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• 제9권4호
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• pp.271-276
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• 1977

한우(韓牛)의 round muscke에 papain을 농도별(濃度別)로 증가(增加)시켜서 longitudinal section과 cross section하여 결체조직(結締組織)의 collagenous fibre와 elastic fibre를 각각(各各) 염색(染色)하여 현미경으로 관찰한 결과(結果)는 다음과 같다. 1. 효소(酵素) 농도(濃度)의 증가(增加)에 따라 비정형 상태로 뭉쳐져 있는 collagenous fibre는 점점 풀어지는 상태(狀態)를 지나 후에는 붕괴되며 또한 염색성(染色性)이 현저하게 약해졌다. 2. elastic fibre의 방향(方向)은 muscle fibre에 평행(平行)하게 존재(存在)하며 효소(酵素) 농도(濃度)의 증가(增加)에 따라 점차 탄성(彈性)을 잃고 loose헤지며 직선적(直線的)으로 보이고 fragment되는 것도 현저하다. 3. collagenous fibre와 elastic fibre 모두 효소(酵素) 처리구(處理區)가 대조구(對照區)에 비하여 조직변화(組織變化)가 현저하다.

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1994년도 교수 연수회(환경)
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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.

• 대한한의학회지
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• 제37권1호
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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.

• 한국지역사회생활과학회지
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• 제17권3호
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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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• 제53권5호
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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.

• 응용통계연구
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• 제27권7호
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• pp.1077-1095
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• 2014

관찰연구를 이용하여 인과관계를 추론할 경우 무작위 통제시험과는 달리 교란변수로 인한 편향을 제어하기 위한 통계적 전략이 필요하다. 최근에는 성향점수(propensity score) 를 이용한 짝짓기나 원인변수의 역확률을 가중치로 사용하는 주변구조모형이 제안되어 사용되고 있다. 이러한 인과관계 추론은 처치(treatment)가 명확히 주어진 경우에 교란변수를 통제하고 그 처치가 결과에 미치는 영향을 평가하는 방법에 초점이 맞추어져 있다. 하지만 기존의 방법의 경우 원인변수인 처치가 직접관측이 가능한 범주형 변수이고 결과변수 또한 직접관측이 가능한 변수인 경우에만 사용할 수 있는 한계를 갖고 있다. 본 연구에서는 원인변수인 처치와 결과변수의 결괏값의 직접적인 관측이 어려운 경우, 측정오차를 고려한 잠재범주모형(latent class analysis)의 변수로 모형화 함으로써 잠재범주 간의 원인적 영향력을 추정하는 방법을 제시하고자 한다. 그리고 미국의 The National Longitudinal Study of Adolescent Health 자료를 이용하여, 약물사용의 잠재범주에 대한 청소년기의 비행(delinquency)이라는 잠재범주의 원인적 영향력을 추정하였다.

• 한국전문물리치료학회지
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• 제23권4호
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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.

• 아동학회지
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• 제24권1호
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• pp.99-108
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• 2003

가족소득은 어머니의 교육수준과 밀접하게 관련되어 있다는 이전의 많은 연구들에 근거하여, 세대간 교육수준 순환의 가정하에 두 문제점들이 제기되었다 : (a) 어머니의 교육수준이 학령기 아동의 학업성적을 예측할 수 있는가? (b) 만약 예측되어진다면, 교육수준의 역순환은 부모의 경제적 수준상태에 의하여 이러한 영향을 상쇄시킬 수 있는가? 아동발달에 대한 보다 나은 이해를 추구하고자 종단적 데이타를 사용하였다. 즉, 아동이 2살일 때 부모의 경제적 수준상태가 측정되어졌으며, 아동들이 초등학교 1학년이 되었을 때 다시 담임선생에 의한 아동의 학업성적이 측정되어졌다. 이러한 데이타는 Structure equation modelling analyses 통계분석법을 이용하여, 본 연구는 어머니의 교육수준이 아동의 초등학교 1학년 때의 학업성적을 예측한다는 것을 검증하였으며, 이러한 관계는 부모의 경제적 수준상태에 의하여 상쇄될 수 있다는 것이 밝혀졌다. 그러므로, 이 연구는 어머니의 저교육수준에 따른 아동의 열등한 학업성적 순환고리는 부모의 경제적 수준의 영향에 의해 깨어질 수 있다는 가능성을 밝혀주었으며, 아동기 발달의 한 경로를 분명히 제시하였다.