• Structural Engineering and Mechanics
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• v.78 no.1
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• pp.23-30
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• 2021

In this paper, we established the generalized thermoelasticity phenomenon in an isotropic elastic medium considering the electromagnetic field, rotation and two-temperature. Three theories of generalized thermoelasticity have been applied: Lord-Shulman (one relaxation time), Green-Lindsay (two relaxation times), as well as the coupled theory. We discussed some particular cases in the context of the wave propagation phenomenon in thermoelasticity. From solving the fundamental equations, we arrived that there are three waves: P-, T- and SV-waves that we calculated their velocities. The boundary conditions for mechanical stress and Maxwell's stress and thermal insulated or isothermal have been applied to determine the amplitudes ratios (reflection coefficients) for P-, T - and SV waves. Some utilitarian aspects are obtained from the reflection coefficients, presented graphically, and the new conclusions have been presented. Comparisons are made for the results predicted by different theories (CT, LS, GL) in the absence and presence of the electro-magnetic field, rotation, as well as two-temperature on the reflection of generalized thermoelastic waves. The results obtained concluded that the external parameters as the angle of incidence, electromagnetic field, rotation as well as the theories parameters have strong effect on the phenomenon.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.7 no.1
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• pp.109-121
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• 2000

Increasingly nursing science is embracing the concepts and methodology derived from psycho-neuroimmunology. It has been previously shown that stress increases and immune function declines in students undergoing examinations. To date, however, no many studies have been reported on stress levels, immune function and interventions in Korean students undergoing their first clinical nursing rotation. It was proposed that nursing students during their first clinical rotation experience increase in stress because of the novelty of the situation and their lack of clinical knowledge. It was also hypothesized that biofeedback and progressive relaxation, methods of self-regulation of involuntary autonomic nervous system responses, would reduce the stress response. The purpose of this study is to test the effectiveness of progressive muscle laxation using biofeedback The effectiveness of the experimental methods was tested by measuring the degree of symptoms of stress (SOS) and the values of ephinephrine, pulse rate, blood pressure and natural killer cells. The subjects of this study were thirty nursing students divided into two groups: experimental group was progressive muscle relaxation group using biofeedback and control group. This study was conducted for 8 weeks of clinical practice. Biofeedback training was done by software developed by J&J company (1-410 form for progressive muscle training). Progressive muscle relaxation training according to Jacobson's Theory was done by messaged word from biofeedback. The data was analyzed using Chronbach' ${\alpha}$ and t-test of the SPSS program and the significance level of statistics was 5%. The results of the study were : 1) The progressive muscle relaxation training using biofeedback was effective for the reduction of symptoms of stress(t=-4.248, p<.001) under clinical practice stress conditions. 2) The progressive muscle relaxation training using biofeedback was not effective for the values of epinephrine(t=-1.294, p=.206). 3) The progressive muscle relaxation training using biofeedback was effective for the reduction of systolic blood pressure (t=-2.757, p=.01). 4) The progressive muscle relaxation training using biofeedback was effective for the reduction of diastolic blood pressure (p=-2.032, 0=.05). 5) The progressive muscle relaxation training using biofeedback was not effective for the reduction of pulse rate(t=-15, p=.988). 6) The progressive muscle relaxation training using biofeedback was effective for the maintenance of natural killer cells (t=2.381, p=02). The first clinical rotation for student nurses is a stressful experience as seen by the rise in the SOS in the control group. Biofeedback using progressive muscle relaxation were effective in preventing the rise of symptoms of stress and the blood pressure means when comparing the pre to post clinical experience, The mean natural killer cell count was depressed in the control group but not significantly different in the experimental groups, It is proposed here that stress via the hypothalamic - pituitary - adrenal axis suppressed the NK cell count whereas the relaxation methods prevented the rise in stress and the resulting immune depression. We recommend relaxation techniques using biofeedback as a health promotion technique to reduce psychological stress. In summary. the progressive muscle relaxation training using biofeedback was effective for the reduction of symptoms of stress under clinical practice stress conditions.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.81.2-81.2
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• 2014

To figure out the effect of rotation on the final mass of Pop III stars, 1D stellar evolution simulations of the evolution of mass-accreting protostars are performed, with zero metalicity and high constant mass accretion rates. The protostar reaches the Keplerian rotation very soon after the onset of mass accretion, but it may continue mass accretion via angular momentum transport induced by viscous stress or magnetic field. However, as the accreting star evolves, the envelope expands rapidly when the total mass reaches $5{\sim}6M_{\odot}$ and the corresponding Eddington factor sharply increases. Strong radiative pressure with rotation imposes different criteria for breakup at the stellar surface, and the so-called 'critical rotation (${\Omega}{\Gamma}$-limit)' is reached. As a result mass accretion rate has to be significantly lowered. This implies that characteristic masses of Pop III stars would be significantly lowered than the previous expectation.

• Korea-Australia Rheology Journal
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• v.21 no.2
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• pp.119-126
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• 2009

A numerical analysis is performed to investigate the effect of rotation on the blood flow characteristics with four different angular velocities. The artery has a cylindrical shape with 50% stenosis rate symmetrically distributed at the middle. Blood flow is considered a non-Newtonian fluid. Using the Carreau model, we apply the pulsatile velocity profile at the inlet boundary. The period of the heart beat is one second. In comparison with no-rotation case, the flow recirculation zone (FRZ) contracts and its duration is reduced in axially rotating artery. Also wall shear stress is larger after the FRZ disappears. Although the geometry of artery is axisymmetry, the spiral wave and asymmetric flow occur clearly at the small rotation rate. It is caused that the flow is influenced by the effects of the rotation and the stenosis at same time.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3105-3114
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• 1993

previously, several basic studies in the experimental analysis of stress intensity factors of cracks by slab analogy have been presented by authors. But, for the application of above mentioned method to the analysis of the arbitrarily distributed cracks, there still is several bottlenecks to be overcome in terms of its experimental process and data treatment. Moreover, authors recently proposed an improved experimental method to use the fixed slab analogy device which has promised more accurate measurement of S.I.F. of small cracks. In this paper, for the completion of slab analogy analysis of distributed cracks, a grating imaginary rotation method is introduced. And, to prove its validity, this combined method is applied to the determination of stress intensity factors of theoretically known distributed cracks. The results show good agreement with the existing theoretical solutions and physical crack propagation tendencies.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.693-698
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• 2019

In this study, the problem of axisymmetric deformation of prestressed $F{\ddot{o}}ppl-Hencky$ membrane under constrained deflecting was analytically solved and its closed-form solution was presented. The small-rotation-angle assumption usually adopted in membrane problems was given up, and the initial stress in membrane was taken into account. Consequently, this closed-form solution has higher calculation accuracy and can be applied for a wider range in comparison with the existing approximate solution. The presented numerical examples demonstrate the validity of the closed-form solution, and show the errors of the contact radius, profile and radial stress of membrane in the existing approximate solution brought by the small-rotation-angle assumption. Moreover, the influence of the initial stress on the contact radius is also discussed based on the numerical examples.

• Structural Engineering and Mechanics
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• v.6 no.1
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• pp.1-15
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• 1998

Experimental work undertaken to investigate the behaviour of lead-rubber bearings under compression and a combination of compression and shear or rotation has been reported on elsewhere. However, it is difficult to determine the state of stress within the bearings in terms of the applied forces and the interaction between the lead plug and the steel shims and elastomeric layers. In order to supply some of the missing information about the stress-strain state within the bearings, an analytical study using the finite element method was carried out. The available experimental results were used to validate the model and although agreement was not as good as expected (on account of difficulties in modelling the lead plug), the analyses did provide some information about the state of the stress within the bearing.

• Structural Engineering and Mechanics
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• v.5 no.4
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• pp.451-469
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• 1997

Experimental work undertaken to investigate the behaviour of laminated elastomeric bridge bearings under compression and a combination of compression and shear or rotation has been reported on elsewhere. However, it is difficult to determine the state of stress within the bearings in terms of the applied forces or the interaction between the steel shims and the rubber layers in the bearings. In order to supply some of the missing information about the stress-strain state within the bearings, an analytical study using the finite element method was carried out. The available experimental results were used to validate the model after which the analyses were used to provide further information about the state of stress within the bearing.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.546-551
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• 1997

New typology of failure mechanisms for uniform compression fields are presented based on the classical theory of plasticity, in particular th normality rule, and the limit theorem. The concrete is assumed as a rigid-perfectly plastic material obeying the modified Coulomb failure criteria with zero tension cut-off. The failure mechanisms are capable of explaining flexural types of crushing failure in uniaxial uniform compression stress fields which are called struts in truss models. The failure mechanisms consist of sliding failure along straight failure lines or hyperbolic failure curves and rigid body rotation. The failure mechanisms involving straight failure lines are explained by constant strain expansion in the first principal direction and rigid body rotation motion. The failure mechanisms presented are applied to the explanation of bond failure of bar combined with concrete crushing failure and flexural crushing failure of concrete.

• Steel and Composite Structures
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• v.26 no.6
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• pp.663-672
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• 2018

This paper contains a consistent couple-stress theory to capture size effects in Euler-Bernoulli nano-beams made of three-directional functionally graded materials (TDFGMs). These models can degenerate into the classical models if the material length scale parameter is taken to be zero. In this theory, the couple-stress tensor is skew-symmetric and energy conjugate to the skew-symmetric part of the rotation gradients as the curvature tensor. The material properties except Poisson's ratio are assumed to be graded in all three axial, thickness and width directions, which it can vary according to an arbitrary function. The governing equations are obtained using the concept of minimum potential energy. Generalized differential quadrature method (GDQM) is used to solve the governing equations for various boundary conditions to obtain the natural frequencies of TDFG nano-beam. At the end, some numerical results are performed to investigate some effective parameter on buckling load. In this theory the couple-stress tensor is skew-symmetric and energy conjugate to the skew-symmetric part of the rotation gradients as the curvature tensor.