• Title/Summary/Keyword: Wave models

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Effect of Ground Boundary Condition on Evaluation of Blast Resistance Performance of Precast Arch Structures (지반경계조건이 프리캐스트 아치구조물의 폭발저항성능 평가에 미치는 영향)

  • Lee, Jungwhee;Choi, Keunki;Kim, Dongseok
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.32 no.5
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    • pp.287-296
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    • 2019
  • In this study, the effect of ground boundary conditions on the evaluation of blast resistance performance of precast arch structures was evaluated by a numerical analysis method. Two types of boundary conditions, namely, fixed boundary conditions and a perfectly matched layer (PML) were applied to numerical models. Blast loads that were much higher than the design load of the target structure were applied to compare the effects of the boundary conditions. The distribution and path of the ground explosion pressure, structural displacement, fracture of concrete, stress of concrete, and reinforcing bars were compared according to the ground boundary condition settings. As a result, the reflecting pressure shock wave at the ground boundaries could be effectively eliminated using PML elements; furthermore, the displacement of the foundation was reduced. However, no distinct difference could be observed in the overall structural behavior including the fracture and stress of the concrete and rebar. Therefore, when blast simulations are performed in the design of protective structures, it is rational to apply the fixed boundary condition on the ground boundaries as conservative design results can be achieved with relatively short computation times.

What Makes Sick Workers Go To Work? A Study of Occupational Environment and Presenteeism (무엇이 아픈 노동자들을 출근하도록 만드는가? 직업환경과 프리젠티즘(presenteeism)에 대한 연구)

  • Shin, Heeju
    • Korean Journal of Labor Studies
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    • v.24 no.3
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    • pp.35-71
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    • 2018
  • The purpose of this study is to examine which job-related factors are associated with presenteeism, which is defined as attending work while ill. Although presenteeism is a relatively new concept in academic research, it should be regarded as an important social issue in that presenteeism threatens employees' job prospects and quality of life as well as it causes loss of work productivity. I analyzed a cross-sectional survey of 24,571 wage workers over 15 from the fourth wave of the Korean Working Conditions Survey in 2014. Five logistic regression models were analyzed on experience of presenteeism, and work hours and private life, occupational environment, job insecurity, rewards and welfare were assessed as key predictors of presenteeism. I found that 1) work hours with bad fit with private life, 2) high level of work time-pressure, and low job satisfaction 3) job insecurity, and 4) low benefits are associated with experience of presenteeism. The findings are fairly consistent with the theory of job-person mismatch, which explains that workers tend to preserve their personal resources by going to work while ill (presenteeism) when job demands or work conditions do not match with their level of personal expectation and, thus, workers are afraid of loss of personal resources. Presenteeism influences worker's long-term health and quality of life negatively as well as causes serious social costs. Therefore, we need organizational efforts to prevent the negative effects of presenteeism on society as well as workers.

Types of Retirement Satisfaction and Life Satisfaction among Middle and Older Adults: Focusing on Gender Differences (중고령자의 은퇴 만족 유형과 삶의 만족도 : 성별에 따른 차이를 중심으로)

  • Cho, Kyuyoung;Jun, Hey Jung;Lee, Eun Jee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.371-381
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    • 2019
  • This study explored how retirement satisfaction or dissatisfaction influences on retirees' life satisfaction, comparing to workers and the gender differences were examined. The study sample was 2,609 persons (1,886 workers, 723 retirees) aged 45 or older who participated in the 1-2 waves of the Korean Longitudinal Study of Ageing (KLoSA), and the retirees were classified into continuously dissatisfied retirees and satisfied retirees during wave 1 and 2. Using SPSS 21.0, the multiple regression models were examined, and in order to clarify the gender difference, the multi-group analysis and the wald-test were conducted to test the difference of the regression coefficients according to gender using Mplus 7.3. According to the results, the life satisfaction of dissatisfied retirees was lower than that of the employed, but when satisfied with retirement, the life satisfaction was higher than that of the employed. In addition, the dissatisfied retirees in both gender were less satisfied with life than the employed, and this effect was greater in female group. However, the life satisfaction of female satisfied with retirement was higher than that of the employed, whereas the evidence of the male influence was not found to be significant. Based on the results of this study, discussion about heterogeneity of retirees and gender differences in life span were presented.

Development and Validation of the GPU-based 3D Dynamic Analysis Code for Simulating Rock Fracturing Subjected to Impact Loading (충격 하중 시 암석의 파괴거동해석을 위한 GPGPU 기반 3차원 동적해석기법의 개발과 검증 연구)

  • Min, Gyeong-Jo;Fukuda, Daisuke;Oh, Se-Wook;Cho, Sang-Ho
    • Explosives and Blasting
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    • v.39 no.2
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    • pp.1-14
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    • 2021
  • Recently, with the development of high-performance processing devices such as GPGPU, a three-dimensional dynamic analysis technique that can replace expensive rock material impact tests has been actively developed in the defense and aerospace fields. Experimentally observing or measuring fracture processes occurring in rocks subjected to high impact loads, such as blasting and earth penetration of small-diameter missiles, are difficult due to the inhomogeneity and opacity of rock materials. In this study, a three-dimensional dynamic fracture process analysis technique (3D-DFPA) was developed to simulate the fracture behavior of rocks due to impact. In order to improve the operation speed, an algorithm capable of GPGPU operation was developed for explicit analysis and contact element search. To verify the proposed dynamic fracture process analysis technique, the dynamic fracture toughness tests of the Straight Notched Disk Bending (SNDB) limestone samples were simulated and the propagation of the reflection and transmission of the stress waves at the rock-impact bar interfaces and the fracture process of the rock samples were compared. The dynamic load tests for the SNDB sample applied a Pulse Shape controlled Split Hopkinson presure bar (PS-SHPB) that can control the waveform of the incident stress wave, the stress state, and the fracture process of the rock models were analyzed with experimental results.

Effects of siblings characteristics on living arrangements between married children and their parents (기혼자녀와 부모의 거주형태에 영향을 미치는 형제자매의 특성)

  • Choi, Heejeong
    • Journal of Family Relations
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    • v.21 no.2
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    • pp.129-147
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    • 2016
  • Objective: This study examined the role of siblings with respect to living arrangements between married children and their parents. Previous studies have rarely considered the possibility that family context such as siblings may be associated with intergenerational residential proximity. Method: Using data from first wave of the Korean Longitudinal Study of Ageing (2006), I investigated if, among married children, their sibling characteristics may be associated with the probability of their coresiding with the parent(s), living nearby (within a 30-minute distance from parent(s) by public transportation), or living further away. Specifically, the total numbers of sisters and brothers, the numbers of siblings coresiding with the parent(s) and living nearby, their relative position in the sibling network (first-born son, later-born son, first-born daughter, later-born daughter), and sibship existence and gender configurations (only child, son with brother(s) only, son with sister(s) only, son with both brother(s) and sister(s), daughter with brother(s) only, daughter with sister(s) only, daughter with both brother(s) and sister(s)) were evaluated in the study. For data analysis, multinomial logit models with robust standard errors were estimated using the Stata mlogit procedure. Results: Results suggest that the probability of a married child living together with the parent(s), relative to living close by, was significantly higher the more sisters he or she has. Being a son, especially first-born son, was associated with a higher probability of intergenerational coresidence compared to near residence, respectively. Also, the numbers of siblings coresiding with the parent(s) and living in close proximity were linked to a higher risk of intergenerational coresidence and near residence. Supplementary analyses revealed that the last finding was held over and above the total number of siblings, their relative position in the sibling network, as well as sibling existence and gender configurations. Conclusion: Overall, the study findings indicate that sibling characteristics have significant impacts on intergenerational living arrangement. The influence of traditional patrilineal norm of intergenerational coresidence and a trend towards modified extended family have emerged when siblings characteristics are taken into consideration as determinants of intergenerational living arrangement.

Development of integrated disaster mapping method (I) : expansion and verification of grid-based model (통합 재해지도 작성 기법 개발(I) : 그리드 기반 모형의 확장 및 검증)

  • Park, Jun Hyung;Han, Kun-Yeun;Kim, Byunghyun
    • Journal of Korea Water Resources Association
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    • v.55 no.1
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    • pp.71-84
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    • 2022
  • The objective of this study is to develop a two-dimensional (2D) flood model that can perform accurate flood analysis with simple input data. The 2D flood inundation models currently used to create flood forecast maps require complex input data and grid generation tools. This sometimes requires a lot of time and effort for flood modeling, and there may be difficulties in constructing input data depending on the situation. In order to compensate for these shortcomings, in this study, a grid-based model that can derive accurate and rapid flood analysis by reflecting correct topography as simple input data was developed. The calculation efficiency was improved by extending the existing 2×2 sub-grid model to a 5×5. In order to examine the accuracy and applicability of the model, it was applied to the Gamcheon Basin where both urban and river flooding occurred due to Typhoon Rusa. For efficient flood analysis according to user's selection, flood wave propagation patterns, accuracy and execution time according to grid size and number of sub-grids were investigated. The developed model is expected to be highly useful for flood disaster mapping as it can present the results of flooding analysis for various situations, from the flood inundation map showing accurate flooding to the flood risk map showing only approximate flooding.

Living Arrangement and Health Behavior Profiles Among Midlife and Older Adults (중노년기 거주형태에 따른 건강행동프로파일 유형화)

  • Kim, Bon;Oh, Seung-Eun;Min, Joohong
    • 한국노년학
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    • v.40 no.4
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    • pp.691-706
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    • 2020
  • This study aims to explore health behavior profiles and the association between the derived profiles and living arrangement among middle-aged and older adults. Using data from wave 6 (2016) of the Korean Longitudinal Study of Aging, latent profile analyses were applied to identify patterns of health behaviors and multinomial logistic regression models were conducted to predict profile membership using living arrangement (i.e., living alone, living with spouse only, living with family members) and sociodemographic characteristics. A sample of 7,048 respondents aged 55 and older were included in the study. Results revealed that Korean middle-aged and older adults can be grouped into four health behavior profiles: "High health-compromising" (4%), "Moderate health-compromising" (28%), "Low health-compromising" (65%), and "High physical activity" (3%). Also, living arrangement showed significant profile differences. Compared to the respondents living alone, those living with spouse only were more likely to belong to low and moderate levels of health-compromising behavior profiles than the "High physicial activity profile". Respondents living with family members were more likely to belong to the "High health-compromising profile" than the "High physical activity profile" compared to those living with spouse only. These findings indicate that living arrangement needs to be taken into consideration when developing health promoting programs and supports. Moreover, policy interventions suiting the needs of various sociodemographic subgroups are recommended.

The mediation effect of grip strength trajectory on the association between exercise participation and life satisfaction among couples (중노년기 부부의 운동참여가 삶의 만족도에 미치는 영향에 관한 악력 궤적의 매개효과)

  • Joo, Susanna;Jun, Hey Jung
    • 한국노년학
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    • v.40 no.1
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    • pp.91-109
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    • 2020
  • This study aims to investigate the interdependence of Korean middle and old-aged couples in the association between exercise and life satisfaction through grip strength trajectory. Data were drawn from the nationally representative Korea Longitudinal Study of Aging (KLoSA) collected from 2006 to 2016. The sample included couples over 45 years of age in the first wave and participated in all six waves of the survey (Ncouple=1,997). There were three steps for analyses: correlation, parallel latent growth curve model, tests of indirect effects of the mediation paths. Covariates included in the models were husbands and wives' characteristics (age, education, work status, chronic diseases, marital satisfaction, contact frequency with friends or neighbors) and couple's household income. Results showed husbands' and wives' life satisfaction and grip strength were interdependent upon each other. Also, exercise participation of both husbands and wives was associated with both husbands' and wives' life satisfaction via the initial level of grip strength of husbands. Moreover, exercise participation of only husbands was associated with wives' life satisfaction through the initial grip strength of husbands. These results suggest the aging processes of middle and old-aged couples need to be understood in the context of gender dynamics and couple interdependence.

Effects of exploration and molecular mechanism of CsV on eNOS and vascular endothelial functions

  • Zuo, Deyu;Jiang, Heng;Yi, Shixiong;Fu, Yang;Xie, Lei;Peng, Qifeng;Liu, Pei;Zhou, Jie;Li, Xunjia
    • Advances in nano research
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    • v.12 no.5
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    • pp.501-514
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    • 2022
  • This study aimed to investigate the effects and potential mechanisms of Chikusetsusaponin V (CsV) on endothelial nitric oxide synthase (eNOS) and vascular endothelial cell functions. Different concentrations of CsV were added to animal models, bovine aorta endothelial cells (BAECs) and human umbilical vein endothelial cells (HUVECs) cultured in vitro. qPCR, Western blotting (WB), and B ultrasound were performed to explore the effects of CsV on mouse endothelial cell functions, vascular stiffness and cellular eNOS mRNA, protein expression and NO release. Bioinformatics analysis, network pharmacology, molecular docking and protein mass spectrometry analysis were conducted to jointly predict the upstream transcription factors of eNOS. Furthermore, pulldown and ChIP and dual luciferase assays were employed for subsequent verification. At the presence or absence of CsV stimulation, either overexpression or knockdown of purine rich element binding protein A (PURA) was conducted, and PCR assay was employed to detect PURA and eNOS mRNA expressions, Western blot was used to detect PURA and eNOS protein expressions, cell NO release and serum NO levels. Tube formation experiment was conducted to detect the tube forming capability of HUVECs cells. The animal vasodilation function test detected the vasodilation functions. Ultrasonic detection was performed to determine the mouse aortic arch pulse wave velocity to identify aortic stiffness. CsV stimulus on bovine aortic cells revealed that CsV could upregulate eNOS protein levels in vascular endothelial cells in a concentration and time dependent manner. The expression levels of eNOS mRNA and phosphorylation sites Ser1177, Ser633 and Thr495 increased significantly after CsV stimulation. Meanwhile, CsV could also enhance the tube forming capability of HUVECs cells. Following the mice were gavaged using CsV, the eNOS protein level of mouse aortic endothelial cells was upregulated in a concentration- and time-dependent manner, and serum NO release and vasodilation ability were simultaneously elevated whereas arterial stiffness was alleviated. The pulldown, ChIP and dual luciferase assays demonstrated that PURA could bind to the eNOS promoter and facilitate the transcription of eNOS. Under the conditions of presence or absence of CsV stimulation, overexpression or knockdown of PURA indicated that the effect of CsV on vascular endothelial function and eNOS was weakened following PURA gene silence, whereas overexpression of PURA gene could enhance the effect of CsV upregulating eNOS expression. CsV could promote NO release from endothelial cells by upregulating the expression of PURA/eNOS pathway, improve endothelial cell functions, enhance vasodilation capability, and alleviate vessel stiffness. The present study plays a role in offering a theoretical basis for the development and application of CsV in vascular function improvement, and it also provides a more comprehensive understanding of the pharmacodynamics of CsV.

Study on the Shape of Appendage for the Reduction of Motion of Floating Wind Turbine Platforms (부유식 풍력 하부구조물의 운동 저감을 위한 부가물 형상 연구)

  • Dae-Won Seo;Jaehyeon Ahn;Jungkeun Oh
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.28 no.7
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    • pp.1201-1208
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    • 2022
  • In general, to maximize the supply and efficiency of floating offshore wind power generation energy, the motion caused by wave attenuation of the substructure must be reduced. According to previous studies, the motion response was reduced due to the vortex viscosity generated by the damping plate installed in the lower structure among the waves. In this study, a 5 MW semi-submersible OC5 platform and two platforms with attenuation plates were designed, and free decay experiments and numerical calculations were performed to confirm the effect of reducing motion due to vortex viscosity. As a result of the model test, when the heave free decay tests were conducted at drop heights of 30 mm, 40 mm, and 50 mm, compared with the OC5 platform, the platform with two types of damping plates attached had relatively improved motion damping performance. In the model test and numerical calculation results, the damping plate models, KSNU Plate 1 and KSNU Plate 2, were 1.1 times and 1.3 times lower than OC5, respectively, and the KSNU Plate 2 platform showed about two times better damping performance than OC5. This study shows that the area of the damping plate and the vortex viscosity are closely related to the damping rate of the heave motion.