• Journal for History of Mathematics
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• v.28 no.1
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• pp.31-44
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• 2015

The cycloid curve had been studied by many mathematicians in the period from the 16th century to the 18th century. The results of those studies played important roles in the birth and development of Analytic Geometry, Calculus, and Variational Calculus. In this period mathematicians frequently used the cycloid as an example to apply when they presented their new mathematical methods and ideas. This paper overviews the history of mathematics on the cycloid curve and presents proofs of its important properties.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.335-342
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• 1986

The feasibility of simultaneous measurement of gas-liquid tow-phase flowrate and quality with a sharp-edged orifice has been investigated. Instantaneous pressure drop curves were monitored for various combinations of gas and liquid flowrates in the bubbly flow regime and some statistical properties of the curves were calculated. The time-averaged value of pressure drop increases with increasing gas and liquid flowrate, whereas the mean amplitude and the intensity of fluctuation monotonically increase as void fraction becomes larger in the flow regime. The statistical furctions for the instantaneous curves indicate a consistent pattern throughout the flow regime and the probability density function, which as a single-peaked and symmetrical distribution, is well predicted by the Gaussian distribution function. The results indicate that simultaneous determination of two-phase flowrate and quality may be possible based upon the statistical analysis of instaneous pressure drop curves measured in a sharp-edged orifice.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.4
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• pp.277-287
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• 1999

Quasi-static tests such as monotonic tension and loading/unloading tension were performed to investigate the bond characteristics and the failure processes for the T-joint specimens made from fiber/epoxy composite material. Two types of specimens, each consists of two components, e. g. skin and frame. were manufactured by co-curing and secondary bonding. During the monotonic tension test, AE instrument was used to predict AE signal at the initial and middle stage of the damage propagation. The damage initiation and progression were monitored optically using m (Charge Coupled Device) camera. And the internal crack front profile was examined using ultrasonic C-scan. The results indicate that the loads representing the abrupt increase of the AE signal are within the error range of 5 percent comparing to the loads shown in the load-time curve. Also it is shown that the initiation of crack occurred in the noodle region for both co-cured and secondarily bonded specimen. The final failure occurred in the noodle region for the co-cured specimen. but at the skin/frame termination point for the secondarily bonded specimen. Based on the results, it was found that two kinds of specimen show different failure modes depending on the manufacturing methods.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.67-78
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• 2008

In this study, artificial cemented sand made of a few portland cement and Nak-Dong river sand was researched closely to investigate cementing effect quantitatively through unconfined tests and triaxial tests. The peak strength and elastic modulus increased and dilation of cemented sand was restricted by the cementation, but after breakage of the cementation, dilation and negative excess pore water pressure increased. In stress-strain curve, strain-softening behavior appeared in drained condition but strain-hardening behavior was appeared in undrained condition as a result of the increase of effective stress. The test was quantitatively analyzed by multiple regression models, correlating each response variable with input variable. The equations are valid only over the range investigated. Its adjusted coefficient of determination was $0.81{\sim}0.91$, and dry density is important factor for estimating strength of cemented sand.

• The Korean Journal of Pharmacology
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• v.28 no.1
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• pp.27-40
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• 1992

The purpose of the present study is an attempt to investigate the effect of intraventricular taurine, which is a naturally occuring amino acid containing sulfur and has inhibitory action in brain, on heart rate and blood pressure in the urethane anesthetized rabbits and also to elucidate the mechanism of its cardiovascular actions. Taurine $(0.15{\sim}1.5\;mg)$ injected into the lateral ventricle of anesthetized normontensive rabbits produced a dose-related fall in arterial blood pressure and heart rate, which were marked and long-lasting along with considerable respiratory depression. However, the intravenous administration of taurine at the same dose with intraventricular injection did not induce any changes in blood pressure as well as heart rate. Depressor responses induced by taurine were inhibited significantly by pretreatment with chlorisondamine, clonidine, strychnine and bicuculline but not by atropine, vagotomy, propranolol and metoclopramide. Moreover, taurine did not affect the pressor responses of norepinephrine. Taurine-induced bradycardic effects were blocked clearly by pretreatment with chlorisondamine, propranolol, clonidine, strychnine and bicuculline, while they were not influenced by atropine, vagotomy and metoclopramide. These experimental results suggest that intraventricular taurine causes long-lasting hypotensive and bradycardic actions, and that these cardiovascular effects may be exerted through taurinergic (glycinergic) and GABAergic receptors which are associated with catecholaminergic neurons in brain.