• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.834-842
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• 1998

This paper examines the crack growth behavior of 7075-T651 and 5052-H32 aluminum alloy under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure ae investigated by compliance method. The applied stress ratios are R=0.15, 0.0, -0.15 and R=-0.15, 0.0, 0.15. The crack growth rate was found to increase as the load amplitude increases. However,${\bigtriangleup}K_eff$ was almost independent on the stress ratio. The experimental constants of 7075-T651 and 5052-H32 in Paris law were c`=1-1.3${\times}{10^-7},m`=3~3.2 and c`=4~6{\times}{10^-9}, m`=4.3-4.8$, respectively. $K_op$ of 7075-T651 and 5052-H32 becomes smaller as the stress ratio decreases. It seems that the crack closure affects $K_op$.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2159-2167
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• 2006

In order to find out a physical quantity which controls the fatigue life of a structure and to predict the fatigue life of tires, a finite element simulation methodology to use the cracking energy density (CED) and the virtual crack closure technique (VCCT) was proposed and applied to three different tires of a similar size. CED was calculated to predict the location of a crack initiation, and VCCT was used to obtain the strain energy release rate (SERR) at the tip of an initiated crack. Finite element simulations showed that SERR oscillated in the circumferential direction with its minimum occurring just before the contact zone and its maximum occurring just after the center of the contact zone, and SERR was affected significantly by the frictional force acting on the crack surface. In addition, a durability test was conducted to measure the fatigue life of the three tires. The comparison of SERR values with the test data revealed that the fatigue life increased as the amplitude of SERR decreased or as the R-ratio of SERR increased.

• Journal of the Korean Mathematical Society
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• v.54 no.6
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• pp.1733-1757
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• 2017

Let $R={\oplus}_{{\alpha}{\in}{\Gamma}}R_{\alpha}$ be an integral domain graded by an arbitrary torsionless grading monoid ${\Gamma}$, ${\bar{R}}$ be the integral closure of R, H be the set of nonzero homogeneous elements of R, C(f) be the fractional ideal of R generated by the homogeneous components of $f{\in}R_H$, and $N(H)=\{f{\in}R{\mid}C(f)_v=R\}$. Let $R_H$ be a UFD. We say that a nonzero prime ideal Q of R is an upper to zero in R if $Q=fR_H{\cap}R$ for some $f{\in}R$ and that R is a graded UMT-domain if each upper to zero in R is a maximal t-ideal. In this paper, we study several ring-theoretic properties of graded UMT-domains. Among other things, we prove that if R has a unit of nonzero degree, then R is a graded UMT-domain if and only if every prime ideal of $R_{N(H)}$ is extended from a homogeneous ideal of R, if and only if ${\bar{R}}_{H{\backslash}Q}$ is a graded-$Pr{\ddot{u}}fer$ domain for all homogeneous maximal t-ideals Q of R, if and only if ${\bar{R}}_{N(H)}$ is a $Pr{\ddot{u}}fer$ domain, if and only if R is a UMT-domain.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.80-85
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• 2014

Side jet thruster using nozzle closure separation device provides a solid rocket with a trajectory shift function. Side jet thruster consists of low combustion temperature propellant, neutral type propellant grain and nozzle closure separation device. If a trajectory shift is required, side jet thrust is generated on the rocket by separating some nozzle closures located in the opposite direction to thrust. After completing trajectory shift, the other nozzle closures located in the thrust direction are separated to cease side jet thrust. The operation process is verified through ground static test. The result in this study can be applied to changing rocket trajectory by controlling side jet thrust through nozzle closure separation.

• Journal of applied mathematics & informatics
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• v.32 no.5_6
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• pp.649-663
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• 2014

Presence of eyelid on anterior ocular surface and its thermal effects play significant role in maintaining eye temperature. In most of the literatures of thermal modeling in human eye, the eyelid is not considered as an eye component. In this paper, finite element model is developed to investigate the thermal effects of eyelid closure and opening in human eye. Based on different properties and parameter values reported in literatures, the bio-heat transfer process is simulated and compared with experimental results in steady and transient state cases. The sensitivity analysis using various ambient temperatures, evaporation rates, blood temperatures and lens thermal conductivities is carried out. The temperature values so obtained in open eye show a good agreement with past results. The closure of eyelid is found to increase/decrease the eye temperature significantly than its opening, when the parameter values are considered to be at extreme.

• Journal of the Korean Society of Safety
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• v.6 no.3
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• pp.21-26
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• 1991

In this study, a crack closure behavior of Al-alloy 5052-H38 was investigated. The fatigue test was performed by the four-point bending test under the contast amplitude load. Stress ratio R was changed from-1.0 to 0.5. To mcasure the fatigue crack opening point, the graph of load vs. subtracted displacement by computer program was obtained from the X - Y plotter. In order to gain the displacement data, a strain gage was attached at the back surface against the notched side. Uslng the conception of crack closure and influence of on crack growth rate a model for crack growth rate is developed for Al-alloy 5052-H38.

• Journal of Korean Institute of Industrial Engineers
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• v.43 no.3
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• pp.176-183
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• 2017

In recent years, studies about multitasking becomes more important. During multitasking, operators can feel frustration when they are interrupted during the task and frustration can affect operator's emotional state and performance. However there is no research on measuring the frustration quantitatively in multitasking environment. In this paper, we suggested quantitative measurement of frustration during multitasking. In order to measure the frustration, we made a mathematical representation with emotional decay model and the initial intensity of frustration based on cognitive closure theory. The amount of initial intensity could be represented as the ratio of actual remaining time to expected remaining time. By the experiment, we measured the frustration during the experiment and compared this values with values of frustration dimension of NASA-TLX. Finally we got the linear regression model with a good accuracy ($R^2=0.986$). This study contributes to measuring the emotion quantitatively by the relation of expected and actual remaining time in multitasking environment.

• Journal of Chest Surgery
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• v.25 no.6
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• pp.593-597
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• 1992

The bronchopleural fistula[BPF] due to bronchial stump disruption after pneumonec-tomy has remained one of the most dreadful complications to now. The management of the BPF with empyema thoracis are still therapeutic dilemma even though a various surgical methods for the control of BPF with or without empyema thoracis. We have experienced the successful treatment of BPF & empyema thoracis with transsternal transpericardial approach. The patient was a 54 years old male who was taken left pneumonectomy at W. Medical Center at sept, 19th. 1991. He was suffered from the BPF R empyema thoracis and so was transferred to our hospital at Nov. 19th. 1991. We treated the patient with transsternal transpericardial bronchial closure for BPF, and put clagett procedure for empyema thoracis in 2 weeks. We think this kind of surgical techniques is one of the relatively simple and effective method for the control of BPF and empyema thoracis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.4 no.2
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• pp.47-53
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• 1980

Kikukawa-Compliance method using a conventional clip-on gauge was employed to investigate fatigue crack growth and crack closure in 2017-T3 aluminum alloy. The crack growth rate plot against stress intensity range .DELTA.K on a log-log diagram exhibits a bilinear form with a transition at the growth rate of 10$\^$-4/ mm/cycle. The bilinear form appears still in the plot of growth rate versus effective stress intensity range .DELTA.K$\_$eff/. Fatigue crack growth rate could be well represented by .DELTA.K$\_$eff. The experimental results indicate that the effective stress intensity range ratio U depends on the maximum stress intensity factor K$\_$max/, but the stress ratio R does not affect U. The crack opening stress intensity factor K$\_$op/ tends to increase with increasing K$\_$max/ and decrease with increasing .DELTA.K.

• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.629-632
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• 1991

The rate constants for the formation and dissociation of nickel(II) and cobalt(II) complexes with mandelate have been determined by the pressure-jump relaxation study. The forward and reverse rate constants for the mandelate complex formation reactions were obtained to be $k_f=3.60{\times}10^4\;M^{-1}s^{-1}$ and $k_r=1.73{\times}10^2\;s^{-1}$ for the nickel(II), and $k_f=1.75{\times}10^5\;M^{-1}s{-1}$ and $2.33{\times}10^3\;s^{-1}$ for the cobalt(II) in aqueous solution of zero ionic strength ($(\mu{\to}0)\;at\;25^{\circ}C$. The results were interpreted by the use of the multistep complex formation mechanism. The rate constants evaluated for each individual steps in the multistep mechanism draw a conclusion that the rate of the reaction would be controlled by the chelate ring closure step in concert with the solvent exchange step in the nickel(II) complexation, while solely by the chelate ring closure step for the cobalt(II) complex.