• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.529-539
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• 1998

A quantitative study of impact damage of ${Al_2}}O_3}-TiO_2$ plasma coated soda-lime glasses was carried out and compared with that of the uncoated smooth glass specimen. The shape of cracks by the impact of steel ball was observed by stereo-microscope and the decrease of the bending strength due to the impact of steel ball was measured through the 4-point bending test. At the low velocity, cone cracks were occurred. As the impact velocity increases, initial lateral cracks were propagated on the slanting surface of a cone crack, and radial cracks were generated at the crushed site. When the impact velocity of steel ball exceeds the critical velocity, the contact site of specimen was crushed due to plastic deformation and then radial and lateral cracks were largely grown. Crack length of coated specimens was smaller than that of uncoated smooth specimen due to the effect of coating layer on the substrate surface. According to impact velocity, the bending strength of coated specimens had no significant difference, compared with that of the uncoated smooth specimen. But this represents that the bending strength of coated specimens was increased, considering the effect of sand blasting damage which was performed to increase the adhesion force of coating layer.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.40-44
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• 2000

The purpose of study was to measure the interrater reliability of the newly developed caries diagnostic instrument, Diagnodent(KaVo, Germany), using a new laser fluorescence techinique. One hundred and three extracted human premolars and molars were examined by Diagnodent, three times for fissures and five times for smooth surfaces. There was no significant difference among the three fissure means, but two combinations showed significant differences among the five smooth surface means. Correlation coefficients of Pearson and Spearman were all above 0.9(P<0.01). The $\alpha$ values from reliability analysis were 0.9980 or 0.9981 for fissures and 0.9992 for smooth surfaces.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.1055-1064
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• 2000

First, various specimen geometries, namely, coupon type, waisted type and dog-bone type, were examined to determine appropriate fatigue specimen of thermoplastic composite material AS4/PEEK and the n, fatigue strength of smooth and notched specimens of AS4/PEEK [-45/0/+45/90]2s was investigated. Fatigue tests were performed under load controlled condition at a stress ratio of 0. 1 at a frequency of 5Hz. Stiffness degradation of specimens with fatigue cycling was monitored using an automated unloading compliance technique. The waisted type specimen is found appropriate for smooth fatigue specimen geometry of AS4/PEEK. As for the effect of stress concentration, it is found that fatigue strength is higher for a 2mm-diameter hole notched specimen than a 5mm-diameter one. Fatigue notch factor decreases with the increase of fatigue life. These results are far different from the trend of fatigue strength of metallic materials. The stiffness variation of smooth specimen was only 4% at maximum until final fracture. On the other hand, the stiffness of hole notched specimen was reduced by 45% at maximum. Notched fatigue strength was compared between thermoplastic composite AS4/PEEK and thermosetting composite Graphite/Epoxy. In long-life fatigue (>104), the AS4/PEEK composite shows superior fatigue strength, but in short-life fatigue, the fatigue strength of the Graphite/Epoxy composite is nearly equal or somewhat higher than that of the AS4/PEEK composite.

• Journal of Food Hygiene and Safety
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• v.26 no.3
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• pp.187-191
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• 2011

Platelet derived growth factor (PDGF)-BB is one of the most potent vascular smooth muscle cell(VSMC) proliferative factors, and abnormal VSMC proliferation by PDGF-BB plays an important role in the development and progression of atherosclerosis. The aim of this study was to assess the effect of YP 12, a newly synthesized obovatol derivative, on the proliferation of PDGF-BB-stimulated rat aortic VSMCs. The anti-proliferative effects of YP 12 on rat aortic VSMCs were examined by direct cell counting and by using $[^3H]$ thymidine incorporation assays. It was found that YP 12 potently inhibited the growth of VSMCs. The pre-incubation of YP 12 (1-4 ${\mu}M$) significantly inhibited the proliferation and DNA synthesis of 25 ng/ml PDGF-BB-stimulated rat aortic VSMCs in a concentration-dependent manner. In accordance with these findings, YP 12 revealed blocking of the PDGF-BB-inducible progression through G0/G1 to S phase of the cell cycle in synchronized cells. Whereas, YP 12 did not show any cytotoxicity in rat aortic VSMCs in this experimental condition by WST-1 assay. These results also show that YP 12 may have potential as an anti-proliferative agent for the treatment of restenosis and atherosclerosis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1107-1113
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• 2002

This study presents the hydrogen emblittlement in the metal, which decreases the ductility and then induces the brittle fracture. The contribution deals with the effect of strain rate and notch geometry on hydrogen emblittlement of 1.25Cr-0.5Mo and 2.25Cr-1Mo steels, which are in use at high pressure vessel. Smooth and notched specimens were examined to obtain the elongation and tensile strength. For charging the hydrogen in the metal, the cathodic electrolytic method was used. In this process, current density is maintained constant. The amount of hydrogen penetrated in the specimen was detected by the hydrogen determenator(LECO RH404) with the various charging time. The distribution of hydrogen concentration penetrated in the specimen was obtained by finite element analysis. The amount of hydrogen is high in smooth specimen and tends to concentrate in the vicinity of surface. The elongation and tensile strength decreased with the passage of charging time in 1.25Cr-0.5Mo and 2.25Cr-1Mo steels. The elongation increased and tensile strength decreased as strain rate increased. As a result of this study, it is supposed that 1.25Cr-0.5Mo steel is more sensitive than 2.25Cr-lMo steel in hydrogen embrittlement. Hydrogen embrittlement susceptibility of notched specimen after hydrogen charging is more remarkable than that of smooth specimen.

• The Journal of Internal Korean Medicine
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• v.17 no.1
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• pp.210-217
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• 1996

Farfarae Flos, a traditional herb medicine, has been used in Korea and China for many centuries as a treatment for respiratory disease. The purpose of the present study was to determine the effect of Farfarae Flos on histamine-induced tracheal smooth muscle contraction in rats. Guinea pigs(500g, female) were killed by CO2 exposure and a segment (8-10mm) of the thoracic trachea from each guinea pig was cut into equal segments and mounted 'in pairs' in a tissue bath. Contractile force was measured with force displacement transducers under 0.5g loading tension. The dose of histamine which evoked 50% of maximal response (ED50) was obtained from cumulative dose response curves for histamine (10-7-10-4M). Contractions evoked by histamine(ED50) were inhibited significantly by Farfarae Flos. The mean percent inhibition was 8.7% after 1.5mg/ml Farfarae Flos, and 33.5% (p<0.05) after 5.0mg/ml Farfarae Flos. Propranolol (10-7M) slightly but significantly attenuated the inhibitory effects of Farfarae Flos. Following treatment with propranolol, the mean percent inhibition caused by 5.0mg/ml Farfarae Flos. Indomethacin and methylene blue (10-7M) did not significantly alter the inhibitory effect of Farfarae Flos. These results indicate that Farfarae Flos can relax histamine-induced contraction of guinea pig tracheal smooth muscle, and that this inhibition involves, in part, symphathetic nerve system.

• Journal of Korea Water Resources Association
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• v.39 no.9 s.170
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• pp.737-744
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• 2006

The velocity of the inner region of turbulent flow on a smooth bed has complex profile which can not be described with a simple formula. Though there have been a couple of formulas describing the profile, most of them have very complex forms, i.e., with many terms, with integration form, or with implicit forms. It means that it is hard to use them or it is difficult to estimate their parameters. A new single formula that describes the velocity profile of the inner region of the turbulent flow on a smooth bed was proposed. This formula has a form of the traditional log-law multiplied by a damping function. Introducing only one additional parameter, it can describe the whole inner range nicely. It approximates the law-of-the-wall in the vicinity of the bed and approaches to the log-law in the overlap region. The added parameter, damping factor, can be estimated very easily. It is not sensitive to the Reynolds number change and the velocity profile calculated by the formula does not change much due to the change of the parameter.

• Journal of Korean Society of Steel Construction
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• v.13 no.3
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• pp.301-311
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• 2001

For a rectangular-highrise building with aspect ratio about six, the resonant wind speed of wind-induced vibration or galloping start wing speed can be within the design wind speed. The wind-induced vibration and galloping of highrise building with aspect ratio $H/\sqrt{DB}=6$, side ratio D/B=1 to 2 at intervals of 1/4 D/B were investigated in smooth flow. For the reducing effect of wind-induced vibration of highrise building, rectangular-highrise building with corners cutting about side ratio D/B=2 were investigated. Experimental results show that in the smooth flow non corners-cutting cases have tendency of increasing wind-induced vibration and galloping vibration then corner-cutting section. Therefore, the wind-induced vibrations on rectangular-highrise buildings were reduced effectively by using corner cut method.

• Solar Energy
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• v.13 no.2_3
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• pp.91-106
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• 1993

The purpose of this study was to investigate the enhancement of heat transfer coefficient in double pipe fluidized bed heat exchangers. The inner tube used a smooth tube and a finned tube equipped with longitudinal fins. The heat transfer coefficients between the heated tube and fluidized bed of alumina beads were calculated as a function of fluidized velocity in various particle sizes($d_p$=0.41, 0.54, 0.65, 0.77mm) and static bed heights($H_o$=50, 100, 150, 200, 250mm). The coefficient for finned tube is higher than for smooth tube. And the maximum increasing rate is 7.8 times in smooth tube and 12.9 times in finned tube.

• The Korean Journal of Physiology
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• v.29 no.2
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• pp.233-241
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• 1995

The nonapeptide bradykinin has been shown to exhibit an array of biological activities including relaxation/contraction of various smooth muscles. In order to investigate the effects of bradykinin on the contractility and the electrical activity of antral circular muscle of guinea-pig stomach, the isometric contraction and membrane potential were recorded. Also, using standard patch clamp technique, the $Ca^{2+}-activated$ K currents were recorded to observe the change in cytosolic $Ca^{2+}$ concentration. $0.4 {\mu}M$ bradykinin induced a triphasic contractile response (transient contraction-transient relaxation-sustained contraction) and this response was unaffected by pretreatment with neural blockers (tetrodotoxin, atropine and guanethidine) or with apamin. Bradykinin induced hyperpolarization of resting membrane potential and enhanced the amplitude of slow waves and spike potentials. The enhancement of spike potentials was blocked by neural blockers. Both the bradykinin-induced contractions and changes in membrane potential were reversed by the selective $B_2$-receptor antagonist $(N{\alpha}-adamantaneacetyl-_{D}-Arg-[Hyp, Thy,_{D}-Phe]-bradykinin)$. In whole-cell patch clamp experiment, we held the membrane potential at -20 mV and spontaneous and transient changes of Ca-activated K currents were recorded. Bradykinin induced a large transient outward current, consistent with a calcium-releasing action of bradykinin front the intracellular calcium pool, because such change was blocked by pretreatment with caffeine. Bradykinin-induced contraction was also blocked by pretreatment with caffeine. From these results, it is suggested that bradykinin induces a calciumrelease and contraction through the $B_{2}$ receptor of guinea-pig gastric smooth muscle. Enhancement of slow wave activity is an indirect action of bradykinin through enteric nerve cells embedded in muscle strip.