• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.167-168
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• 2008

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.3 s.258
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• pp.338-343
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• 2007

Thermal deformation of cast iron exhaust manifold for turbo diesel engine is investigated by finite element analysis (FEA). The FE model included the temperature dependent material properties as well as the interactions between exhaust manifold, cylinder head and fasteners. It also considers the sliding behavior of the flanges of exhaust manifold on cylinder head when either expansion or contraction of the exhaust manifold exceeds the fastener pretension. The result of analysis revealed that remarkable thermal deformation along the longitudinal direction. Compressive plastic deformation at high temperature remained tensile stress in manifold and resulted in longitudinal contraction at ambient temperature. The amount of contraction at each fastener position was predicted and compared with experimental results. Analysis results revealed that the model predicted deformation qualitatively, but more elaborated cyclic hardening behavior would be necessary to predict the deformation quantitatively.

• Journal of IKEEE
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• v.12 no.2
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• pp.87-94
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• 2008

Pelvic floor muscle is the main subsystem that maintains urinary continence. It is possible to diagnose the degree of the stress urinary incontinence(SUI) by evaluating the contraction pressure of the pelvic floor muscle. Bio-signal measurement system was developed to measure the contraction pressure. Diagnostic parameters were drawn out by analyzing the measured data. Statistical evaluations were done to classify the all subjects with five groups each has similar characteristics. SUI diagnostic algorithm was implemented to each group separately. The accuracy of the algorithm was about 78.9% and utility was confirmed by clinical trial.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1362-1369
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• 2007

Seoul Metro continuously converted the standard rail into continuous welded rail since the later part of 1990's, and currently, most of the sectors of the Seoul Metro are continuous welded rails. As the continuous welded rail is inhibited by the contraction and expansion force of the rail as well as rail-bed, this force is stored as the internal stress of the rail with the exception of portion of the both ends of the continuous welded rail. If the contraction and expansion of the rail is restricted, the internal stress, that is, the force in the direction of the axis, is proportional to the cross-sectional area of the rail. Therefore, with regards to the temperature changes, the internal stress changes in accordance with the type of rail, bolting apparatus, railroad tie and rail-bed. As such, the rail temperature becomes important data in securing the gap at the adjoining section of the rail in the standard rail section, and to determine the setting temperature for the continuous welded rail. In addition, it becomes basic data for maintenance of the track. Accordingly, this thesis introduces cases of installation of rail temperature detector in order to prevent and manage track defectiveness due to increase in rail temperature, and to utilize as basic data at the time of various construction and maintenance. Furthermore, this thesis aims to assist maintenance of track through systematic temperature management in the future by looking into means of its utilization.

• Geomechanics and Engineering
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• v.25 no.4
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• pp.341-345
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• 2021

1D sand compression response to ko-loading experiences volume contraction from low to high effective stress regimes. Previous study suggested compressibility model with physically correct asymptotic void ratios at low and high stress levels and examined only for both remolded clays and natural clays. This study extends the validity of Enhanced Terzaghi model for different sand types complied from 1D compression data. The model involved with four parameters can adequately fit 1D sand compression data for a wide stress range. The low stress obtained from fitting parameters helps to identify the initial fabric conditions. In addition, strong correlation between compressibility and the void ratio at low stress facilitates determination of self-consistent fitting parameters. The computed tangent constrained modulus can capture monotonic stiffening effect induced by an increase in effective stress. The magnitude of tangent stiffness during large strain test should not be associated with small strain stiffness values. The use of a single continuous function to capture 1D stress-strain sand response to ko-loading can improve numerical efficiency and systematically quantify the yield stress instead of ad hoc methods.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.101-107
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• 2008

A composite mechanics for discontinuous fiber reinforced polymer matrix composites(PMC) is analysed in order to predict fiber axial stresses. In continuum approach. frictional slip which usually takes place between fibers and polymers is accounted to derive PMC equations. The interfacial friction stress is treated by the product of the coefficient of friction and the compressive stress norma1 to the fiber/matrix interface. The residual stress and the Poisson's contraction implemented by the rule of mixture(ROM) are considered for the compressive stress normal to the fiber/matrix interface. In addition. the effects of fiber aspect ratio and fiber volume fraction on fiber axial stresses are evaluated using the derived equations. Results are illustrated numerically using the present equations with reasonable materials data. It is found that the fiber axial stress in the center region shows no great discrepancy for different fiber aspect ratios and fiber volume fractions while some discrepancies are shown in the fiber end region.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.743-756
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• 2017

Laboratory investigation reveals that rockfills exhibit significant stress-path-dependent behavior during shearing, therefore realistic prediction of deformation of rockfill structures requires suitable constitutive models to properly reproduce such behavior. This paper evaluates the capability of a strain hardening model proposed by the authors, by comparing simulation results with large-scale triaxial stress-path test results. Despite of its simplicity, the model can simulate essential aspects of the shear behavior of rockfills, including the non-linear stress-strain relationship, the stress-dependence of the stiffness, the non-linear strength behavior, and the shearing contraction and dilatancy. More importantly, the model is shown to predict the markedly different stress-strain and volumetric behavior along various loading paths with fair accuracy. All parameters required for the model can be derived entirely from the results of conventional large triaxial tests with constant confining pressures.

• Women's Health Nursing
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• v.26 no.3
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• pp.205-212
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• 2020

Purpose: This study aimed to identify the components of preterm birth (PTB) through women's personal narratives and to visualize clinical symptom expressions (CSEs). Methods: The participants were 11 women who gave birth before 37 weeks of gestational age. Personal narratives were collected by interactive unstructured storytelling via individual interviews, from August 8 to December 4, 2019 after receiving approval of the Institutional Review Board. The textual data were converted to PDF and analyzed using the MAXQDA program (VERBI Software). Results: The participants' mean age was 34.6 (±2.98) years, and five participants had a spontaneous vaginal birth. The following nine components of PTB were identified: obstetric condition, emotional condition, physical condition, medical condition, hospital environment, life-related stress, pregnancy-related stress, spousal support, and informational support. The top three codes were preterm labor, personal characteristics, and premature rupture of membrane, and the codes found for more than half of the participants were short cervix, fear of PTB, concern about fetal well-being, sleep difficulty, insufficient spousal and informational support, and physical difficulties. The top six CSEs were stress, hydramnios, false labor, concern about fetal wellbeing, true labor pain, and uterine contraction. "Stress" was ranked first in terms of frequency and "uterine contraction" had individual attributes. Conclusion: The text network analysis of narratives from women who gave birth preterm yielded nine PTB components and six CSEs. These nine components should be included for developing a reliable and valid scale for PTB risk and stress. The CSEs can be applied for assessing preterm labor, as well as considered as strategies for students in women's health nursing practicum.

• Applied Microscopy
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• v.28 no.1
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• pp.21-38
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• 1998

The present study was performed to determine the effect of cold stress on myocardium of aging rat. Control groups, which aged 6, 12 and 24 months, were compared with age-matched experimental groups that were exposed to moderate cold stress for a hours daily in a week at laboratory cold room $(4{\pm}1^{\circ}C)$. The histological, histochemical and ultrastructural changes of myocardium were observed. The results were summarized as follow: 1. Age-dependent histological change of control groups was observed the formation of contraction band in 24months aged group. The experimental groups submitted to cold stress showed a similar change pattern as seen in control groups. However, the degree of change in the experimental groups was significantly larger than that of control groups. In the 34 months aged group the formation of hypercontraction band was observed. 2. Regarding age-dependent histochemical changes of control groups, we observed the increase activities of PAS and Masson's trichrome. In experimental groups the activities of PAS and Masson's trichrome were also increased with age. Compare with control group, the activities of PAS was increased but the activities of Masson's trichrome was decreased. 3. Age-dependent ultrastructural changes on vacuolization, lysosome were observed. In control groups the structural changes occur at 12 months. The accumulation of lipofuscin, contraction band, hypercontraction band and a component of connective tissue were observed in 24 months. However, the degree of change in the experimental groups was significantly larger than that of control groups. In contract, the myelin body in intercalated discs was observed in 24 months of experimental groups.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.310-315
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• 2000

We analyzed thermal stress of the STS VOD ladle by the variation of material property of refractory, and determined the location of back filler using FE analysis. Thermal distribution of refractory of ladle between hot face and back face were decreased by the increasing the thermal conductivity, and thermal stress of refractory were decreased about 2 to 4 times with the decreasing the young's modulus coefficients. Back filler, which is constructed to absorb the thermal expansion of dolomite refractory, has relatively low thermal conductivity. Inner side of refractory of ladle maintained high temperature, but temperature of outer side of ladle decreased low. Consequently, inner expansion and outer contraction were appeared. and thermal stress were increased, so thermal stress by the construction of back filler were increased.