• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.133-140
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• 2000

The objective of this study is to develop a damage model based on damage mechanics that can be used to analyze the mechanical behavior of structures with defects and the global behavior of damaged structures. A modified second order damage tensor that can be applied to finite element analysis is used to reflect the effect of damage. The damage stress computed from the effective stress is considered as an additional loading term acting on nodes and can represent the effect of crack surface. The accuracy of the proposed algorithm is verified by comparing the analysis results with the experimental data from other studies and the analysis results based on transverse isotropic theory. The developed damage model is applied to the analyses of structures with cracks under linear elastic condition. Numerical results show that the developed model can effectively analyze the global behavior of damaged structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.23-28
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• 1991

A simple, yet effective, material model of concrete is presented in this paper. Based on the orthotropic model in which the assumption of orthogonal principal strain axes is used, the incremental stress-strain relation of concrete is defined in the biaxial stress condition and the rotating crack model is adopted to represent realistically the change of the crack direction according to the different loading pad after cracking. Numerical results obtained from the finite element analysis are compared favourably with the available experimental data. By the parametric study, moreover, it was found that He most important factor in the structural behavior when the reinforced concrete structure is subjected to the dominent shear forces is the tension stiffening effect. The influences of the tension stiffening effect remarkably appears as the steel ratio decreases.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.1
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• pp.94-100
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• 2017

Stress drain bias dependent current model is proposed for sub-70-nm p-channel metal-oxide semiconductor field-effect transistors (pMOSFETs) under drain-avalanche-hot-carrier (DAHC-) mechanism. The proposed model describes the both on-current and off-current degradation by using two device parameters: channel length variation (${\Delta}L_{ch}$) and threshold voltage shift (${\Delta}V_{th}$). Also, it is a simple and effective model of predicting reliable circuit operation and standby power consumption.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.107-114
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• 2003

There are many problems in the prediction of dynamic behaviors of saturated soils because undrained excess pore water pressure builds up and then the strain softening behavior is occurred simultaneously. A few analytical constitutive models based on the effective stress concept have been proposed but most models hardly predict the excess pore water pressure and strain softening behaviors correctly In this study, the disturbed state concept (DSC) model proposed by Dr, Desai was modified to predict the saturated soil behaviors under the dynamic loads. Also, back-prediction program was developed for verification of modified DSC model. Cyclic triaxial tests were carried out to determine DSC parameters and test result was compared with the result of back-prediction. Through this research, it is proved that the proposed model based on the modified disturbed state concept can predict the realistic soil dynamic characteristics such as stress degradation and strain softening behavior according to dynamic process of excess pore water pressure.

• YAKHAK HOEJI
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• v.41 no.1
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• pp.38-47
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• 1997

Using a concentric cylinder type, rheometer. the steady shear flow properties of vaseline were measured over the temperature range of 20~70${\circ}$C. In this paper, the shea rate and temperature dependencies of its flow behavior were investigated and the validity of some flow models was examined. In addition, the flow characteristics over a wide temperature range were quantitatively evaluated by calculating the various material parameters. Main findings obtained from this study can be summarized as follows: (1) At relatively lower temperature range, vaseline is a plastic fluid with a yield stress and its flow behavior shows shear-thinning characteristics. (2) As the temperature increases, the value of a yield stress and the degree of shear-thinning become smaller, consequently, the Newtonian flow behavior occurs at a lower shear rate range. (3) At temperature range lower than 45${\circ}$C, the flow behavior shows much stronger temperature dependence, and a larger activation energy is needed for flow. (4) The Herschel-Bulkley model is the most effective one g$^3$ to predict the flow behavior of vaseline having a yield stress. The validity of the Bingham and Casson models becomes more available with increasing temperature. The flow behavior of vaseline at temperature range higher than 45${\circ}$C can be perfectly described by the Newton model.

• Journal of the Korean Home Economics Association
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• v.45 no.5
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• pp.121-133
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• 2007

The purpose of this study was to investigate the psychological wellbeing as applied to the bioecological family life welfare model, concerning individual attributes, family backgrounds, and family processes across the family life cycles. Based on Bronfenbrenner's bioecological perspective, the "bioecological family welfare model", which includes person (individual attributes), context (family background), process (mechanism - family process), and time (the family life cycles), was applied as a research paradigm for this study. The sample for the questionnaire study comprised for 900 families, considering the family life cycle in Busan and the Kyungnam area. The families were categorized into 6 family life cycles based on Duvall and Hill's family life cycle. For the final analysis, 628 families were used. According to the path analysis results, the length of commitment before marriage and self-esteem had significant effects on the stress coping ability. Several individual attributes and family backgrounds such as age, length of marriage, family life cycle, self-esteem and stress coping ability had significant effects on marital adjustment. The family life cycle and age were significant variables on family function. The significant variables on psychological wellbeing were monthly income, length of commitment before marriage, stress coping ability and marital adjustment. The regression model showed that the variables of the individual attributes, context and family process accounted for 51% of the psychological wellbeing. The results show that the suggested research model was significant and effective to explain the mechanism of psychological wellbeing. Individual attributes and family context have an impact on stress coping, marital adjustment, and family function, which in turn affect psychological wellbeing.

• Journal of the Korean Geotechnical Society
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• v.30 no.3
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• pp.47-58
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• 2014

To investigate the unsaturated characteristics of the tailings obtained from the waste dump at Imgi mine, matric suction and volumetric water content were measured in both drying and wetting processes using Automated Soil-Water Characteristics Curve Apparatus. Based on the measured result, Soil Water Characteristic Curves (SWCC) were estimated by van Genuchten model. According to the unsaturated soil classification method, the tailings of the waste dump correspond to clayey sand. As a result of Suction Stress Characteristic Curve (SSCC) by Lu and Likos model, SSCC has a shape of S which is similar to SWCC. The hysteresis phenomenon occurred in SSCCs, which means the suction stress of drying path is larger than that of wetting path in the same effective degree of saturation. The effective stress of unsaturated soil is equal to that of saturated soil when matric suction is less than Air Entry Value (AEV). However, the effective stress of unsaturated soil is larger than that of saturated soil when matic suction is more than AEV. Meanwhile, unsaturated hydraulic conductivity by van Genuchten model decreased with increasing matric suction, and the hydraulic conductivity of drying path is larger than that of wetting path.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.134-153
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• 1988

This paper was carried out to investigate the existence of a unique stress- strain behavior by obtaining some factors influencing the time dependent stress- strain behavior of clay. The results obtained from this study were summarized as follows ; 1. The relationship between stress ratro and strain in normally consolidated clay was in- dependent on pre-shear consolidation pressure. Therefore, shear strain could be expressed as a function with stress ratio. 2. The constitutive equation of shear strain on Modified Carn Clay Model coincided better with the observed value than Cam Clay Model. 3. The relationships between deviator stress and shear strain, between pore water pressure and shear strain were unified by the mean equivalent pressure. 4. The shear strain contour in norrnally consolidated clay was increased linearly through origin, but that in overconsolidated clay was not in accordance with the result of the former. 5. Because the effective stress path of normally consolidated clay was unified by the mean equivalent pressure, state boundary surface in (e,p,q) space was transformed into two dimensional surface. But it was considered to be suitable that the unified stress- strain in overconsolidated clay be expressed by a function with overconsolidation ratio. 6. The deviator for constant strain was increased linearly with increment of strain rate ($\varepsilon$) on semi-log scale, but pore water pressure was decreased. 7. The behavior of stress relaxation was transformed from linear to curvilinear with inc - rement of strain rate before stress relaxation test, and pore water pressure was increased in total range. 8. The strain of creep was increased linearly with increment of time on semi-log scale. The greater the strain rate before creep test became, the greater the increment of strain of creep became. And the pore water pressure during creep test was increased generally with increment of time on semi-log scale.

• Journal of the Korean Geotechnical Society
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• v.34 no.2
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• pp.5-17
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• 2018

In this study, the in-situ stress, strength and stress-strain characteristics with shear parameters (UU, CU, ${\bar{CU}}$) are analytically evaluated and the stability analyses are carried out under loading/unloading conditions. The in-situ stress and the stress-strain behaviour may become different according to input shear parameters in finite element analyses with construction step, Especially, if the internal friction angle in Mohr-Coulomb model is set to zero, the in-situ stress and the stress-strain behaviour might not be properly predicted. The results from CU parameter of total stress analysis have no significant difference with the results from CU of effective stress analysis. Therefore, in the numerical analysis for soft ground, CU parameters can be applied to predict in-situ stress and stress-strain behaviors. In addition, the calculation method was proposed to determine the shear parameter of Mohr-Coulomb model, which is corresponding to the shear strength equivalent to that of in-situ soil.

• Journal of Korean Academy of Nursing
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• v.35 no.2
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• pp.239-251
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• 2005

Purpose: This study was designed to construct a structural model for explaining mental health status in middle - aged women. Methods: The data was collected by self - reported questionnaires from 206 middle - aged women in Seoul. Data analysis was done with the SAS pc program for descriptive statistics and a PC - LISREL Program for finding the best fit model which assumes causal relationships among variables. Results: The overall fit of the hypothetical model to the data was good, but paths and variables of the model were modified by considering theoretical implications and statistical significances of parameter estimates. Thus it was modified by excluding 3 paths, The modified model showed was good fit to the data($x^2=177.55$, p=.00), GFI=0.908, AGFI=0.860, RMR=0.013, NFI=0.972, NNFI=0.982). Perceived stress, anger expression method, and self -esteem were found to have direct effects on mental health status in middle - aged women. These predictive variables of mental health status explained $66.6\%$ of the model. Conclusion: Programs to enhance mental health status in middle - aged women should include stress management skill, anger expression skill, and self -esteem enhancement skills to be effective.