• Korean journal of applied entomology
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• v.57 no.4
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• pp.261-269
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• 2018

The cowpea aphid Aphis craccivora Koch (Hemiptera: Aphididae) is a polyphagous species with a worldwide distribution. We investigated the temperature effects on development periods of nymphs, and the longevity and fecundity of apterous female of A. craccivora. The study was conducted at six constant temperatures of 10.0, 15.0, 20.0, 25, 30.0, and $32.5^{\circ}C$. A. craccivora developed successfully from nymph to adult stage at all temperatures subjected. The developmental rate of A. craccivora increased as temperature increased. The lower developmental threshold (LT) and thermal constant (K) of A. craccivora nymph stage were estimated by linear regression as $5.3^{\circ}C$ and 128.4 degree-days (DD), respectively. Lower and higher threshold temperatures (TL, TH and TH-TL, respectively) were calculated by the Sharpe_Schoolfield_Ikemoto (SSI) model as $17.0^{\circ}C$, $34.6^{\circ}C$ and $17.5^{\circ}C$. Developmental completion of nymph stages was described using a three-parameter Weibull function. Life table parameters were estimated. The intrinsic rate of increase was highest at $25^{\circ}C$, while the net reproductive rate was highest at $20^{\circ}C$. Biological characteristics of A. craccivora populations from different geographic areas were discussed.

• Korean Journal of Social Welfare Studies
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• v.48 no.3
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• pp.209-232
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• 2017

This study proposes supplemental security income programs for the elderly to reduce the serious elderly poverty in Korea. The experiences of the supplemental security income programs for the elderly among the developed countries were investigated. Based on this, the Korean supplemental security income models were proposed, and the effects of the programs on the poverty, inequality, and finance were analysed. The results suggest the following implications. First, the supplemental security income programs cover a sizable portion of the elderly in Korea, and reduce substantially the poverty and inequality problems among the elderly. Second, the supplemental security income programs are efficient compared to the increase of the basic pension. Third, the effects were varied among the combinations of the basic pension models and the supplemental security income models. Therefore Korea needs to introduce an adequate policy mix consisting of basic income and supplemental security income programs so as to construct solid basic income security systems for the elderly.

• Korean Journal of Culture and Social Issue
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• v.19 no.3
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• pp.389-407
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• 2013

This study investigated the mediating effects of depression on the relationship between perceived problem solving ability and suicidal ideation. 548 college students were examined with PSI(Problem Solving Inventory), BDI(Beck Depression Inventory) and SSI(Scale for Suicidal Ideation). To explore the relationship among these variables, correlation analysis was undertaken. Regression analysis was then applied to test the mediating effects of depression. In the results, perceived problem solving ability, depression and suicidal ideation were correlated positively. Depression operated as a factor to mediate between the perceived problem solving ability and suicidal ideation. This mean that perceived problem solving ability impact indirectly, rather than directly, on suicidal ideation. These results suggest the importance of psychological intervention to improve depression and perceived problem solving ability that affect suicidal ideation.

• Structural Engineering and Mechanics
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• v.49 no.1
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• pp.1-22
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• 2014

A seismic evaluation is made of the response to horizontal ground shaking of cantilever retaining walls using the finite element model in three dimensional space whose verification is provided analytically through the modal analysis technique in case of the assumptions of fixed base, complete bonding behavior at the wall-soil interface, and elastic behavior of soil. Thanks to the versatility of the finite element model, the retained medium is then idealized as a uniform, elastoplastic stratum of constant thickness and semi-infinite extent in the horizontal direction considering debonding behavior at the interface in order to perform comprehensive soil-structure interaction (SSI) analyses. The parameters varied include the flexibility of the wall, the properties of the soil medium, and the characteristics of the ground motion. Two different finite element models corresponding with flexible and rigid wall configurations are studied for six different soil types under the effects of two different ground motions. The response quantities examined incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that the wall flexibility and soil properties have a major effect on seismic behavior of cantilever retaining walls and should be considered in design criteria of cantilever walls. Furthermore, the results of the numerical investigations are expected to be useful for the better understanding and the optimization of seismic design of this particular type of retaining structure.

• Anxiety and mood
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• v.10 no.2
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• pp.151-156
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• 2014

Objective : The aim of this study is to analyze the relationship among job stress, depression, and suicidal ideation in firefighters, particularly the mediating effects of depression. Methods : The subjects were 2,136 firefighters in Gangwon-do, who completed the short form of Korean occupational stress scale (KOSS-SF), Korean version of the Beck depression inventory (K-BDI), and the revised scale for suicide ideation (SSI) online in mental health promotion service of firefighters. The data was analyzed with correlation analysis among the variables, and the multiple regression analysis method of Bar-on and Kenny (1986) was used. Results : Job stress showed positive correlations with depression (r=0.493, p <0.01) and suicidal ideation (r=0.296, p<0.01). Depression showed a positive correlation with suicidal ideation (r=0.561, p<0.01). The result of analyzing the mediating effect of depression showed that depression was a full mediator variable between job stress and suicidal ideation. Conclusion : Based on the results, it is very likely that job stress may affect suicidal ideation via depression. These results suggested that the preventive interventions emphasized on depression may be helpful for reduction of suicide in firefighters.

• Structural Engineering and Mechanics
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• v.89 no.4
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• pp.421-436
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• 2024

This research addresses experimentally the relationship between the excitation frequency and both hoop and axial wall stresses in a water storage tank. A low-density polyethylene tank with six different aspect ratios (water level to tank radius) was tested using a shake table. A laminar box with sand represents a soil site to simulate Soil-Structure Interaction (SSI). Sine excitations with eight frequencies that cover the first free vibration frequency of the tank-water system were applied. Additionally, Ricker wavelet excitations of two different dominant frequencies were considered. The maximum stresses are compared with those using a nonlinear elastic spring-mass model. The results reveal that the coincidence between the excitation frequency and the free-vibration frequency of the soil-tank-water system increases the sloshing intensity and the rigid-like body motion of the system, amplifying the stress development considerably. The relationship between the excitation frequency and wall stresses is nonlinear and depends simultaneously on both sloshing and uplift. In most cases, the maximum stresses using the nonlinear elastic spring-mass model agree with those from the experiments.

• Journal of The Korean Association For Science Education
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• v.42 no.1
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• pp.111-125
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• 2022

This study aims to investigate the effects of the ENACT project on promoting pre-service science teachers (PSTs)' views on the social responsibility of scientists and engineers. The ENACT project was designed to cultivate the social responsibility by integrating the theoretical framework of socioscientific issues (SSIs) education with problem-based inquiry approaches for the resolution of the issues. Thirty-two PSTs voluntarily participated in the project and completed the five stages over three months. Data was collected through a questionnaire to measure PSTs' view of the social responsibility of scientists and engineers (VSRoSE) and focus-group interviews. Results indicate that the PSTs presented statistically significant changes in their views of the social responsibility after the ENACT project. The mean scores of the five sub-dimensions of VSRoSE significantly increased. The interviews also supported that the PSTs had opportunities to seriously consider the social responsibility of scientists and engineers through epistemological exploration of science and technology (Cycle I), and problem-solving and action-taking (Cycle II). In particular, they agreed more on such responsibilities as consideration of societal needs and demands, pursuit of the common good, civic engagement and services using their expertise, communications with the public regarding potential risks, and participation in policy decision-making related to science and technology advances. Educational implications for SSI education and teacher education were suggested.

• Earthquakes and Structures
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• v.12 no.6
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• pp.689-697
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• 2017

Nowadays, there are a great number of various structures that have been retrofitted by using different FRP Composites. Due to this, more researches need to be conducted to know more the characteristics of these structures, not only that but also a comparison among them before and after the retrofitting is needed. In this research, a model steel structure is tested using a bench-scale earthquake simulator on the shake table, using recorded micro tremor data, in order to get the dynamic behaviors. Beams of the model steel structure are then retrofitted by using CFRP composite, and then tested on the Quanser shake table by using the recorded micro tremor data. At this stage, it is needed to evaluate the dynamic behaviors of the retrofitted model steel structure. Various types of methods of OMA, such as EFDD, SSI, etc. are used to take action in the ambient responses. Having a purpose to learn more about the effects of FRP composite, experimental model analysis of both types (retrofitted and no-retrofitted models) is conducted to evaluate their dynamic behaviors. There is a provision of ambient excitation to the shake table by using recorded micro tremor ambient vibration data on ground level. Furthermore, the Enhanced Frequency Domain decomposition is used through output-only modal identification. At the end of this study, moderate correlation is obtained between mode shapes, periods and damping ratios. The aim of this research is to show and determine the effects of CFRP Composite implementation on structural responses of the model steel structure, in terms of changing its dynamical behaviors. The frequencies for model steel structure and the retrofitted model steel structure are shown to be 34.43% in average difference. Finally, it is shown that, in order to evaluate the period and rigidity of retrofitted structures, OMA might be used.

• Wind and Structures
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• v.30 no.6
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• pp.633-648
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• 2020

The objective of this work was to investigate the interference effects of two-parallel bridge decks on aerodynamic coefficients, vortex-induced vibration, flutter instability and flutter derivatives. The two bridges have significant difference in cross-sections, dynamic properties, and flutter speeds of each isolate bridge. The aerodynamic static tests and aeroelastic tests were performed in TU-AIT boundary layer wind tunnel in Thammasat University (Thailand) with sectional models in a 1:90 scale. Three configuration cases, including the new bridge stand-alone (case 1), the upstream new bridge and downstream existing bridge (case 2), and the downstream new bridge and the upstream existing bridge (case 3), were selected in this study. The covariance-driven stochastic subspace identification technique (SSI-COV) was applied to identify aerodynamic parameters (i.e., natural frequency, structural damping and state space matrix) of the decks. The results showed that, interference effects of two bridges decks on aerodynamic coefficients result in the slightly reduction of the drag coefficient of case 2 and 3 when compared with case 1. The two parallel configurations of the bridge result in vortex-induced vibrations (VIV) and significantly lower the flutter speed compared with the new bridge alone. The huge torsional motion from upstream new bridge (case 2) generated turbulent wakes flow and resulted in vertical aerodynamic damping H1^* of existing bridge becomes zero at wind speed of 72.01 m/s. In this case, the downstream existing bridge was subjected to galloping oscillation induced by the turbulent wake of upstream new bridge. The new bridge also results in significant reduction of the flutter speed of existing bridge from the 128.29 m/s flutter speed of the isolated existing bridge to the 75.35 m/s flutter speed of downstream existing bridge.

• Anxiety and mood
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• v.16 no.2
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• pp.76-82
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• 2020

Objective : Previous studies have shown that depression, anxiety and embitterment are highly related to suicide. This study aims to investigate the mediating effect of embitterment between depression, anxiety and suicide. Methods : A total of 174 participants with depressive and anxiety disorders were evaluated with STAI-S, STAI-T, PHQ-9, PTED scale, SSI and suicide attempt history. A mediation analysis using bootstrapping was utilized in order to estimate the indirect effects of depression and anxiety on suicide through embitterment. Results : Embitterment significantly mediated the relationship between depression and suicidal ideation [b=0.291, 95% CI(0.18, 0.40)], and also it mediated the relationship between depression and suicide attempt [b=0.066, 95% CI(0.02, 0.16)]. Although a direct effect of anxiety on suicide attempt was not significant, but embitterment significantly mediated the relationship between anxiety and suicide attempt Conclusion : This suggests that embitterment may be a significant important factor to consider in the relationship between depression, anxiety and suicide. Understanding the mediating role of embitterment on suicide may helpful to prevent suicide.