• The Korean Journal of Physiology
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• v.23 no.2
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• pp.351-361
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• 1989

The contraction of renal arterial strip by no.epineph.me (NE) or 40 mM $K^+$ were Significantly attenuated after histamine $(10^{-5}\;M)-induced$ contraction. The mechanisms of this phenomenon were investigated in the helical strips of isolated renal artery with the measurement of isometric tension. The arterial strip was immersed in the tris-buffered Tyrode's solution which was equilibrated with 100% $O_2\;at\;35^{\circ}C$. The contraction was induced by NE or 40 mM $K^+$ during the recovery from the histamine-induced contraction which lasted for 15 minutes. The contraction by NE was also attenuated in the $Ca^{2+}-free$ Tyrode's solution and the increase of contraction by addition of 2 mM $Ca^{2+}$ was attenuated as well. This attenuation phenomenon was not observed in the presence of low concentration $(3{\times}10^{-7}\;M)$ of histamine. This attenuation was not affected by destruction of endothelium, pretreatment with papaverine or propranolol. This attenuation was partially inhibited by pretreatment of ouabain or in low $K^+(0.5 mM)$ Tyrode's solution. But the attenuation in the $Ca^{2+}-free$ Tyrode's solution was not inhibited. Furthermore this attenuation was completely blocked by pretreatment of djphenhydramine $(H_1-receptor blocker)$ and potentiated by pretreatment of cimetidine $(H_2-receptor\;blocker)$. This attenuation Phenomenon was disappeared after recovery of 1 hour. From the above results, it is suggested that the attenuation phenomenon may be resulted partially from the activation of $Na^+-K^+$ exchange pump and partially from the depletion of intracellular $Ca^{2+}$ pool after the histamine-induced contraction mediated through $H_1-receptor$ function.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.315-325
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• 2018

This paper predicts the flexural behaviour of reinforced concrete (RC) beams strengthened with a precast strip of ultra-high performance fiber-reinforced concrete (UHPFRC). In the first phase, ultimate load capacity of preloaded and strengthened RC beams by UHPFRC was predicted by using various analytical models available in the literature. RC beams were preloaded under static loading approximately to 70%, 80% and 90% of ultimate load of control beams. The models such as modified Kaar and sectional analysis predicted the ultimate load in close agreement to the corresponding experimental observations. In the second phase, the famous fatigue life models such as Papakonstantinou model and Ferrier model were employed to predict the number of cycles to failure and the corresponding deflection. The models were used to predict the life of the (i) strengthened RC beams after subjecting them to different pre-loadings (70%, 80% and 90% of ultimate load) under static loading and (ii) strengthened RC beams after subjecting them to different preloading cycles under fatigue loading. In both the cases precast UHPFRC strip of 10 mm thickness is attached on the tension face. It is found that both the models predicted the number of cycles to failure and the corresponding deflection very close to the experimental values. It can be concluded that the models are found to be robust and reliable for cement based strengthening systems also. Further, the Wang model which is based on Palmgren-Miner's rule is employed to predict the no. of cycles to failure and it is found that the predicted values are in very good agreement with the corresponding experimental observations.

• The Korean Journal of Physiology
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• v.29 no.1
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• pp.61-67
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• 1995

The extract of Ginkgo bibloba (EGb) is a complex mixture of natural products from the Ginkgo leaves and clinically used for the treatment of cerebral and peripheral circulatory disturbances due to its combined activity of several vasoactive principles. In this study we investigated the action of EGb and its mechanism in isolated rabbit corporal smooth muscle to evaluate the possibility of using this material as a pharmacoerecting agent. Strips of rabbit corpus cavernosum were mounted in organ chambers to measure isometric tension. EGb began to exert an relaxing effect at 1 mg/ml in the submaximally precontracted muscle strips with phenylephrine $(PHE,\;5{\times}10^{-6}\;M)$; causing concentration-dependent relaxation with maximal effect at $3{\sim}5\;mg/ml$. That relaxation was partially inhibited by removal of the smooth muscle endothelium or by pretreatment with a NO scavenger, pyrogallol $(10^{-4}\;M)$ or the guanylate cyclase inhibitor, methylene blue $(10^{-4}\;M)$. Pretreatment with EGb (3 mg/ml) inhibited PHE- $(5{\times}10^{-6}\;M)$ or KCI- (20 and 40 mM) induced contraction of muscle strip. In calcium-free high potassium solution EGb depressed the basal tone of the depolarized muscle strip and inhibited calcium-induced contraction when $CaCl_2$ $(10^{-4}\;M)$ was added. These results suggest that EGb relaxes rabbit corpus cavernosal smooth muscle through multiple action mechanisms that include increasing the release of nitric oxide from the corporal sinusoidal endothelium, sequestration of intracytosolic calcium, and maybe a hyperpolarizing action.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.413-416
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• 2007

In general, by means of the electrodepositing technique, a copper foil sample was prepared with a high purity and a high density. But the mechanical properties of the electrodepositing copper foil was lower than it's the rolling copper foil. However, the production of copper foil with approximately 36 microns thick in rolling process was very difficult. This paper describes the outline of the high accuracy cold rolling in 6 high mill which was developed for the purpose of rolling very thin accurate gauge copper foil(36 micron thick), and give several rolling characteristic of 600 mm wide copper foil. a) Large strain can be accumulated pass by pass in industrial multi-pass rolling processing to overcome large critical strain for thickness accuracy through optimization of rolling schedule. b) Also, permissible tension for rolling 0.45 $\sim$ 0.036 mm thick copper strip stably in accordance with the each pass work had been established by FEM simulation results. c) During the plate rolling process, considerable values of the forces of material pressure on the tool occur. These pressures cause the elastic deformation of the roll, thus changing the shape of the deformation region. A numerical simulation of roll deflection during cold rolling is presented in the paper. d) The proposed pass schedule can roll very thin copper foil of 36 micron thickness to a tolerance of ${\pm}1$ microns. The validity of simulated results was verified into rolling experiments on the copper foil.

• The Korean Journal of Physiology
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• v.7 no.2
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• pp.49-58
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• 1973

The distensibility of the major arteries has been investigated extensively, but the value expressed as Young Modulus varies widely by the different schools of the investigators, the major reason undoubtedly being the difficulties encountered in the measurement. In the present study, an attempt was made to elucidate the distensibility of the external carotid artery of the rabbit, which was placed in saline immediately after removing from the apparently healthy, normal rabbit without anesthesia. The circular section strip and longitudinal section strip were made from the whole artery, and Young Modulus of the whole artery, circular section and longitudinal section strips was calculated from the length-tension curve of each sample. Also, the similar samples of the artery seperately obtained were placed in ATP solution in the concentration of 0.15 mM and 0.30 mM, and Young Modulus was similary calculated. Experiments were performed at 15,45 and 75 min after the artery was removed from the rabbit, and the results thus obtained are summarized as follows. 1) Young Modulus of the whole external carotid artery of the rabbit in saline was $4.74{\times}10^7dyne/cm^2$ at 15 min, but lower values were obtained at 45 and 75 min, Young Modulus being $4.62{\times}10^7dyne/cm^2\;and\;4.13{\times}10^7dyne/cm^2$, respectively. When the arterial samples were placed in ATP solutions, Young Modulus did not change much throughout the experiment, and lower Young Moduli were obtained in 0.30 mM ATP solution than in 0. 15 mM ATP solution. 2) Young Modulus Of the Circular Section Strip in Saline was $4.11{\times}10^7dyne/Cm^2,\;3.75{\times}10^7dyne/cm^2\;and\;3.90{\times}10^7dyne/cm^2,$ respectively, at 15, 45 and 75 min, the value at 15 min being the highest. However, when the strip was placed in ATP solutions, no appreciable change was observed throughout the experiment, and Young Moduli were lower in 0.30 mM ATP solution than in 0.15 mM ATP solution. 3) Young Modulus of the longitudinal section strip in saline was $2.12{\times}10^7dyne/cm^2,\;2.48{\times}10^7dyne/cm^2\;and\;2.46{\times}10^7dyne/cm^2$, respectively, at 15, 45 and 75 min, Young Modulus being slightly elevated in the latter part of the experiment. A similar tendency was observed when the strip was placed in ATP solutions.

• The Korean Journal of Physiology
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• v.23 no.2
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• pp.263-275
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• 1989

Mechanical contractions and electrical activities of the fundic longitudinal and antral circular muscle fibers were investigated in order to elucidate topical differences of gastric motility. K-induced contracture was produced by exposure of muscle strips to high K Tyrode solution. Membrane potential and mechanical contraction were simultaneously recorded by conventional glass microelectrode method and single sucrose-gap technique. All experiments were performed in tris-buffered Tyrode solution which was aerated with $100%\;O_2\;and\;kept\;35^{\circ}C$. The results obtained were as follows: 1) The resting membrane potential of circular muscle cells in the antral region was about 10 mV more negative than that in the fundic region. 2) The membrane potentials decreased almost linearly as the extracellular KCI concentration was increased both in antral circular muscle cells and in fundic longitudinal muscle cells. 3) The thresholdal K concentration of K-contracture was 15 mM (membrane potential, -48 mV) for the antral circular muscle strip and 20 mM for the fundic longitudinal muscle cells. 4) The ratio of membrane permeability coefficient for $Na^+\;and\;K^+,\;P_{Na}/P_K\;({\alpha})$ was 0.065 for antral circular muscle cells and was 0.108 for fundic longitudinal muscle cells. 5) K-contracture of antral and fundic smooth muscle strips showed the contracture composed of phasic and tonic components. The amplitude of the phasic component increased sigmoidally in a dose-dependent manner, whereas that of the tonic component was maximal at a concentration of 40 mM KCI and at the concentrations above or below 40 mM KCI the amplitude was reduced. 6) The inverse relationship between the amplitude of tonic component and extracellular KCI concentration in the range of 40 to 150 mM KCI was more prominent in the antral circular muscle strip than in the fundic longitudinal muscle strip, where the amplitude of the tonic component decreased less steeply and was maintained higher at the same high K concentrations. 7) The tonic component was totally dependent on the external $Ca^{2+}$ and completely abolished by verapamil, while tile phasic component was far less dependent on the external $Ca^{2+}$ and partially suppressed by verapamil. From the above results, the following conclusions could be made. 1) The phasic component of K-contracture is produced both by intracellular $Ca^{2+}$ mobilization and by $Ca^{2+}$-influx from outside, while the tonic component is generated and maintained by the $Ca^{2+}-influx$ through the potential-dependent $Ca^{2+}$ channel. 2) The mechanism of reducing the free $Ca^{2+}$ concentration in the myoplasm seems to be more developed in the antral circular muscle than in the fundic longitudinal muscle. 3) The lower resting membrane potential of the fundic longitudinal muscle cell reflects a relatively high $P_{Na}/P_K$ ratio of about 0.108.

• Transactions of Materials Processing
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• v.16 no.7
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• pp.516-520
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• 2007

As the springback of sheet metal during unloading nay cause deviation from a desired shape, accurate prediction of springback is essential for the design of sheet stamping operations. On the removal of the applied load the specimen loses its elastic strain by contracting around the contour of the block, the radius $\rho$ can be determined by the residual differential strain. Therefore in this study the springback estimated by the residual differential strain is experimentally validated through the comparison with those obtained by U-bending test. The springback characteristics of two analytical models are also estimated at various processing conditions such as thickness, curvature of radius and drawing strain. The model based on residual differential strain has an applied transition strain where the springback undergoes a dramatic decrease. Both models show that springback decreases with increased strip thickness and with decreased radius of curvature. For no applied tension, the model based on residual differential strain predicts more springback as compared to the moment based model.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.29-35
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• 2015

In this study, a FEM analysis is undertaken of a rubber sleeve which is mounted onto a spreading mandrel so as to avoid marking the first wrappings of coils (known as the 'end-mark'), as occasionally occurs when a concentrated load is placed on the edge of a steel sheet, significantly reducing its quality. A commercial numerical package, ANSYS, was utilized to analyze the structural behavior of the rubber sleeve. In general, the strain of the sleeve increases as the thickness of the rubber layer (H) covering the tubes increases, thus also increasing the surface of the sleeve for a constant boundary condition, and decreasing the pitch (P) between each tube, resulting in an increase in the strain on the surface of the sleeve for all rubber thickness conditions tested here. In a comparison of two different materials, rubber and urethane, when H=3 mm and P=1.1D, the maximum total deformations in these cases are 0.12669 mm and 0.086623 mm, respectively.

• Biomolecules & Therapeutics
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• v.9 no.3
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• pp.224-230
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• 2001

DKY is an oriental drug preparation composed of 17 natural products and is known to have antihyperglycemic action at 100 mg/kg po in animal tests. The general pharmacological properties of DKY preparation were investigate in mice, rats, guinea pigs and rabbits. This preparation did neither show any effects on central nervous system, nor effects on algesia, nor epilepsia at the large doses of 3000 mg/kg po in mice or rats. However, the preparation showed hypothermic action at the doses of 330 and 1000 mg/kg po. In the guinea pig ileum, rat fundus strip and estrogenized rat uterus, DKY did not influence their tension at a concentration of 3$\times$10$^{-3}$ g/ml, and the spasmogenic actions produced by histamine, ACh and 5-HT were not blocked in the presence of DKY at 3$\times$10$^{-3}$ g/ml. The blood pressure and respiration were not considerably influenced at 10 mg/kg iv of DKY in rabbits. It did not influence the intestinal propulsion of mice and the normal gastric secretion of rats. These results may suggest that DKY preparation have little effects on central nervous, autonomic and gastrointestimal systems, except hypothermic action.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.9
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• pp.52-57
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• 2010

The analysis of a crack in a bone-like material is performed numerically. The bone-like material is hierarchically structured and each hierarchy is structured by mineral platelets and protein matrix through staggered arrangement. Mechanical behavior of the composite can be analyzed using tension shear chain model. The Dugdale model is adopted to evaluate the fracture energy of Bone-like material. The fracture energy dissipation is assumed to concentrate within a strip near the crack tip along the prospective crack path. Fracture criterion of the bone-like material is estimated by using J integral. Effects of hierarchical level, ratio of elastic modulus of mineral to protein, aspect ratio of mineral platelet and volume fraction on J integral are investigated. It is found that the J integral decreases as elastic modulus ratio and hierarchy level increase. It is also shown that the J integral increases as the volume fraction and aspect ratio decrease.