• Transactions of Materials Processing
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• v.16 no.2 s.92
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• pp.101-106
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• 2007

Uniaxial displacement controlled tests were performed on annealed Type 304 stainless steel at room temperature. A servo-controlled testing machine and strain measurement on the gage length were employed to measure the response to a given input. The test results exhibit that the flow stress increases nonlinearly with the strain rate and the relaxed stress at the end of the relaxation periods depends strongly on the strain rate preceding the relaxation test. The rate-dependent inelastic deformation behavior is simulated using a new unified viscoplasticity model that has the rate-dependent format of nonlinear kinematic hardening rule, which plays a key role in modeling the rate dependence of relaxation behavior. The model does not employ yield or loading/unloading criteria and consists of a flow law and the evolution laws of two tensor and one scalar-valued state variables.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.21-26
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• 1988

Composition with O-3 connectivity were fabricated from PZT and phenolic resin powders. These composites were investigated for dielectric and pizoelectric properties with PZT-polymer interface porosity variation. The interface porosity dependence of dielectric and piezoelectric properties was especially discussed by porosity factors. The interface porosity dependence of piezoelectric constant was larger than that of dielectric constant. It was considered that the interface pore plays the role of a stress buffer. Thus the local stress applied on PZT particles in the composite was remarkably diminish.

• The Korean Journal of Emergency Medical Services
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• v.28 no.1
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• pp.21-34
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• 2024

Purpose: This study aimed to observe change in factors over time in the first cohort of the 2018 Children and Adolescent Panel Middle School. In addition, this study attempted to examine the causal relationship and influence between variables by setting a time gap between independent and dependent variables. Methods: Frequency and descriptive statistical analyses were conducted to determine the general characteristics of the study participants. Hierarchical regression analysis was conducted to analyze the effects of smartphone dependence on health, sleep quality, and depression. After inputting the control variables (Model 2), the influence of the variables was identified based on the input model. Results: Smartphone dependence positively impacted depression in both male and female students and negatively impacted sleep and health. Conclusion: Smartphones are closely associated with teenagers' lives. Additionally, as adolescents experience various psychological anxieties owing to rapid physical changes, there are concerns that psychological dependence may increase, considering that adolescence is the most emotionally unstable period. Therefore, the results of this study consistently prove that smartphone dependence has a causal relationship with emotion-related variables, such as emotional stress, depression, and anxiety.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1479-1492
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• 2015

This study evaluated the localized stress condition of the real corroded deck surface of an orthotropic steel bridge because severe corrosion damage on the deck surface and fatigue cracking were reported. Thus, a three-dimensional finite element (FE) analysis model was created based on measurements of the corroded orthotropic steel deck surface to examine the stress level dependence on the corrosion condition. Based on the FE analysis results, it could be confirmed that a high stress concentration and irregular stress distribution can develop on the deck surface. The stress level was also increased by approximately 1.3-1.5 times as a result of the irregular corroded surface. It was concluded that this stress concentration could increase the possibility of fatigue cracking in the deck surface because of the surface roughness of the orthotropic steel bridge deck.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.567-574
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• 1991

In this study thermal stress generated in three ingot moulds(GC25) during the solidification process of aluminum were analyzed by the two-dimensional thermo-elasto-plastic theory. In temperature analysis, all of the three models are shown steep temperature rising each case in initial stage of cooling. In thermal stress analysis, all of three models took compressible stress on inside wall of the mould, and tensible along with on out side. Model 2 take place less compressible, tensible stress then model 1. But model 3. have similar as thermal stress as model 2. The analysis will made one possible to calculate an optimum mould shape whose thermal stress gradient becomes minimum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.855-858
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• 2001

The stress induced leakage currents of thin silicon oxides is investigated in the VLSI implementation of a self learning neural network integrated circuits using a linearity synapse transistor. The channel current for the thickness dependence of stress current, transient current, and stress induced leakage currents has been measured in oxides with thicknesses between 41 ${\AA}$, 86${\AA}$, which have the channel width ${\times}$ length 10 ${\times}$1${\mu}$m, 10 ${\times}$0.3${\mu}$m respectively. The stress induced leakage currents will affect data retention in synapse transistors and the stress current, transient current is used to estimate to fundamental limitations on oxide thicknesses. The synapse transistor made by thin silicon oxides has represented the neural states and the manipulation which gaves unipolar weights. The weight value of synapse transistor was caused by the bias conditions. Excitatory state and inhitory state according to weighted values affected the channel current. The stress induced leakage currents affected excitatory state and inhitory state.

• Food Engineering Progress
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• v.13 no.1
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• pp.70-73
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• 2009

The yield stress of stirred yogurt was measured by the vane viscometer at different pre-shearing conditions, such as pre-shear speed, pre-shear time, and wait time, and temperature (12-38${^{\circ}C}$). The yield stress ranged from ~17.6 to 10 Pa and from 34.2 to 11.9 Pa, depending on the pre-shearing conditions and temperature, respectively. The preshear speed and the wait time significantly affected the yield stress. The temperature dependence of the yield stress was described by the Eyring's kinetic model. The linear function of the temperature on the yield stress was limited at the 22${^{\circ}C}$, and at the above 22${^{\circ}C}$, the yield stress was maintained to be a constant (~12.5 Pa).

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.2
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• pp.67-72
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• 2004

Electro-Rheological(ER) fluids consist of suspensions of fine polarizable particles In a dielectric oil, which upon application of an external electric field control take on the characteristics of the Bingham solid. In this study, the temperature dependence of the viscosity was Investigated for an ER fluid consisting of 35 weight % of zeolite particles in hydraulic oil 46cSt. Thermal activation analysis was performed by changing the ER fluid's temperature from $-10^{\circ}C$ to $50^{\circ}C$. According to the analysis, the activation energy for flow of the ER fluid was 79.6 kJ/mole without applying electric field. On the other hand, with the electric field of 2kV/mm, the linearity between viscosity and temperature was not existed By changing the temperatures the viscosity (or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to $200s^{-1}$ in 2 minutes. Generally, the hydraulic oil 46cSt will be operated at the temperature of about $40^{\circ}C$, thus, the ER fluid's electric field dependence of viscosity was examined at this temperature. Also, an influence of adding the dispersant(Carbopl 940) on ER effect was discussed.

• Advanced Composite Materials
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• v.17 no.1
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• pp.57-73
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• 2008

The present paper focuses on experimental verification of the ply-by-ply basis inelastic analysis of multidirectional laminates. First of all, rate dependence of the tensile behavior of balanced symmetric cross-ply T800H/epoxy laminates with a $[0/90]_{3S}$ lay-up under off-axis loading conditions at $100^{\circ}C$ is examined. Uniaxial tension tests are performed on plain coupon specimens with various fiber orientations $[{\theta}/(90-{\theta})]_{3S}$ ($\theta$ = 0, 5, 15, 45 and $90^{\circ}C$) at two different strain rates (1.0 and 0.01%/min). The off-axis stress.strain curves exhibit marked nonlinearity for all the off-axis fiber orientations except for the on-axis fiber orientations $\theta$ = 0 and $90^{\circ}$, regardless of the strain rates. Strain rate has significant influences not only on the off-axis flow stress in the regime of nonlinear response but also on the apparent off-axis elastic modulus in the regime of initial linear response. A macromechanical constitutive model based on a ply viscoplasticity model and the classical laminated plate theory is applied to predictions of the rate-dependent off-axis nonlinear behavior of the cross-ply CFRP laminate. The material constants involved by the ply viscoplasticity model are identified on the basis of the experimental results on the unidirectional laminate of the same carbon/epoxy system. It is demonstrated that good agreements between the predicted and observed results are obtained by taking account of the fiber rotation induced by deformation as well as the rate dependence of the initial Young's moduli.

• Journal of Practical Engineering Education
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• v.15 no.2
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• pp.459-466
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• 2023

This study was conducted to investigate the mediating effect of academic stress on the relationship between smartphone overdependence and the communication competence of nursing students. The research subjects were nursing students in cities A and Y. The research period was from March 2 to March 9, 2023, and the number of subjects analyzed was 139. Descriptive statistics, Pearson correlation were analyzed using SPSS/WIN 26.0, Process macro program the collected data. The results of the mediating effect of academic stress on the relationship between smartphone dependence and communication competence showed that academic stress (β=.226, p=.005) mediated the effect on the relationship between smartphone dependence and communication competence(Z=-3.131, p=.002). As a result, the combined explanatory power of the variables on nursing student's communication competence was 15.4%. In addition, in order to reduce nursing students' smartphone overdependence, it is necessary to educate them about smartphone use and develop self-control, provide interventions to cope with academic stress, and develop intervention programs to improve communication competence.