• Journal of Korean Medicine Rehabilitation
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• v.20 no.4
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• pp.147-157
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• 2010

Objectives : The study is performed to investigate the influence of psychological stress on neck muscles tone and heart rate variability(HRV). Methods : This study was carried out with the data from stress response index score(SRI), surface electromyography(sEMG) and HRV. First subjects were divided into two group according to the SRI points. Subjects in group A had points of SRI in which lower than 30 points. Subjects in group B had points of SRI in which higher than 30 points. Then we investigated how to difference of the index of sEMG and HRV according to each groups. Results : In this study, the muscle contraction of both upper trapezius muscle in stress group were higher than non-stress group significantly. Complexity, root mean square of successive differences of R-R intervals(RMSSD), standard deviation difference between adjacent normal to normal intervals(SDSD), high frequency oscillation power(Ln(HF)), normalized HF(Norm HF) in stress group were lower than non-stress group significantly and normalized LF(Norm LF) was higher. Conclusions : This results show that the stress was associated with neck muscle condition and autonomic nervous system.

• Korean Journal of Metals and Materials
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• v.47 no.8
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• pp.466-473
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• 2009

Our group previously observed the intrinsic stress evolution of Cu thin films during deposition by changing the deposition rate. Intrinsic stress of Cu thin films, which show Volmer-Weber growth, is reported to display three unique stress stages, initial compressive, broad tensile, and incremental compressive stress. The mechanisms of the initial compressive stress and incremental compressive stages remain subjects of debate, despite intensive research inquiries. The tensile stress stage may be related to volume contraction through grain growth and coalescence to reduce over-accumulate Cu adatoms on the film surface. The in-situ intrinsic stresses behavior in Cu thin films was investigated in the present study using a multi-beam curvature measurement system attached to a thermal evaporation device. The effect of substrate surface roughness was monitored by observed the in-situ intrinsic stress behavior in Cu thin films during deposition, using $100{\mu}m$ thick Si(111) wafer substrates with three different levels of surface roughness.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.44-49
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• 2014

As expansion and contraction of bike disk brake are happened continuously by temperature at repeated urgent braking. In this study, 3 kinds of model are designed according to configurations of holes and thermal durabilities on bike disk brake are investigated by comparing 3 models through temperature and thermal analyses. Maximum thermal stress happened at the disk contacted with pad and the connection part fixing disk rotor. Instead of initial state, the temperature is uniformly distributed at transient state. As the area of hole at disk rotor face becomes wider, thermal stress becomes lower at the initial state. On the other hand, in case the number of holes increases, thermal stress becomes lower at the elapsed time of 100 seconds. The thermal durability of bike disk brake can be improved by applying this study result with configurations of holes.

• Journal of Life Science
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• v.13 no.5
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• pp.634-641
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• 2003

In order to examine whether arsenic, one of environmental stress, contribute to augumentation and relaxation of rat aorta, this study was performed in vivo and in vitro, using intacted or denuded rats aorta ring preparation, respectively. The carotid arterial pressure was recorded on an ink-writing physiograph(Grass Co. 79E) connected to strain gauge. The contractile response of vascular ring with or without endothelium preparation isolated from rat were determined in organ bath and was recorded on physiograph connected to isometric transducer. Vasopressin-,and phenylephrine- induced increase in arterial pressure significantly enhanced in arsenic-treated rats; increase of 19.1%, and 46.6%, respectively. Vascular contractile response was measured in vitro preparations exposed to 0, 0.5, 1, 2 and 4 mM of arsenic for 1, 3, 5 and 8 hours. The dose-vascular responses of phenylephrine augmented by increasing dose of arsenic in the strips exposed to arsenic for 8 hours, and did not augmented for 1, 3, 5 hours. The phenomenon was not affected by strips denuded endothelium. And the response of relaxation of rat aorta induced by nitroprusside was not influenced by arsenic stress, but acetylcholine was a little increased. compared to that of control. There were no significant difference in relaxation between control and arsenic treated rings with endothelium or denuded. All of the results, phenyleprine-induced vascular contraction was significantly enhanced in 4 mM arsenic-treated rat aortic rings compared with control, whether endothelium was present or denuded at 8 hours after arsenic treatment. It may be a mechanism by which long-term arsenic stresses play a role in development of hypertension.

• Speech Sciences
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• v.11 no.1
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• pp.73-83
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• 2004

Electromyographic studies of the cricopharyngeus muscle using hooked wire electrodes were performed in thyroidectomized patients. The shape of the cricoid cartilage and soft tissue thickness in the postcricoid area were evaluated during pitch elevation and pitch lowering using conventional neck lateral films. The cricopharyngeus muscle simultaneously activated in the initial task of speech and continuously activated. Its activity lessened in the interrogative stress contrast of sentence terminals and increased in the pitch lowered contrast of sentence terminal. On the radiologic findings the cricoid cartilage was tilted backward during high pitched phonation and tilted forward during low pitched phonation. The soft tissue thickness of postcricoid area was thicker at the low pitch than at high pitch. At low pitch the cricoid cartilage paralleled along the vertebral column. This result suggests that the bulging of cricopharyngeus muscle in contraction induce a thickened the postcricoid area thickened, and exert pressure anteriorly exerted on the cricoid cartilage. This contraction of the cricopharyngeus muscle may result in shortening the vocal fold and lowering pitch.

• Water Engineering Research
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• v.4 no.2
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• pp.99-109
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• 2003

Since bed elevation changes are mainly dependent on the flow velocity and corresponding shear stress, it is possible to predict bed elevation numerically using velocity components. For the scour analysis due to channel contraction, a bed load transport model is developed and applied to estimate scour depth around coffer dam in the Mississippi River. During Phase I of the Lock & Dam No. 26 replacement project, a coffer dam was constructed to reduce the flow area approximately by 50%. Flow velocity increases due to the flow area reduction yields significant lowering (erosion) of the channel bed elevation. The proposed numerical model solves the sediment continuity equation using the finite element method to evaluate scour process in the vicinity of the coffer dam

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2407-2417
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• 1993

Thermal deformations and stresses due to temperature changes are the serious problems in cryogenic structures such as the torque tube in a superconducting generator, In this paper, the equations of thermal expansion coefficients expressed only by material properties and winding angles are derived for the filament wound composite tubes. The experimental results of thermal contraction of CFRP tubes are compared with those from theoretical approach. Composite tubes with optimally regulated thermal expansion coefficient are designed on the basis of the study for the torque tube in the superconducting generator with temperature distributions varying from 300K to 4.2 K. The filament winding angle of composites resisting thermal stresses properly is sought by the finite element method using layered shell elements. The results show that the composite tubes designed for the requirements in cryogenic environments can effectively cope with the thermal stress problem.

• The Korean Journal of Rheology
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• v.2 no.1
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• pp.33-45
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• 1990

This study analyzes the planar 4:1 contraction flow of viscoelastic fluids with retardation time using finite volume method. To consider separately the elasticity effect of the viscoelastic fluid without shear thinn-ing effect, Oldroyd B liquid model is adopted for the numerical simulation. Instead of the stream function-vorticity formulation, SIMPLER algorithm with staggered grid system which incorporates primitive variable has been introduced in discretizing the momentum equations. An upwind corrected scheme has been used in discetizing the constitutive equations for the non-Newtonian part of the stress. The size of the corner vortex is shown to be slightly influenced by the Weissenberg number. However as the Weissenberg number is increased the chang-ing of the vortex shape agrees qualitatively well with some experimental studies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.187-194
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• 1999

In this study, a series of items on the safety and stability of cracked main structure in subway are investigated and analyzed. Cracks due to dry contraction under the construction can be found when a tensile stress of cross section is higher than tensile strength at a value of coefficient of dry contraction $200{\times}10^{-6}$. It is concluded that there is no problems when load carrying capacity, that is, an ability of resisting loads of structure is enough in this analytical model. Also, it is concluded that this model has a desirable serviceability because a width of bending crack is lower than allowable one.

• Journal of the Korean institute of surface engineering
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• v.37 no.4
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• pp.226-233
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• 2004

The residual stresses on the surfaces of low carbon 12Cr steels used as a nuclear steam turbine blade material have been studied by controlling the flame hardening surface treatments. The temperature cycles on the surfaces of 12Cr steel were controlled precisely as a function of both the surface temperature and cooling rate. The final residual stress state generated by flame hardening was dominated by two opposite competitive contributions; one is tensile stress due to phase transformation and the other is compressive stress due to thermal contraction on cooling. The optimum processing temperatures required for the desirable residual stress and hardness were in the range of $850^{\circ}C$ to $960^{\circ}C$ on the basis of the specification of GE power engineering. It was also observed that the high residual tensile stress generated by flame hardening induced the cracks on the surfaces, especially across the prior austenite grain boundaries, and the material failure virtually, which might limit practical use of the surface engineered parts by flame hardening.