• Geomechanics and Engineering
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• v.25 no.3
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• pp.195-205
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• 2021

Time effect on the deformation and strength characteristics of geogrid reinforced sand retaining wall has become an important issue in geotechnical and transportation engineering. Three physical model tests on geogrid reinforced sand retaining walls performed under various loading conditions were simulated to study their rate-dependent behaviors, using the presented nonlinear finite element method (FEM) analysis procedure. This FEM was based on the dynamic relaxation method and return mapping scheme, in which the combined effects of the rate-dependent behaviors of both the backfill soil and the geosynthetic reinforcement have been included. The rate-dependent behaviors of sands and geogrids should be attributed to the viscous property of materials, which can be described by the unified three-component elasto-viscoplastic constitutive model. By comparing the FEM simulations and the test results, it can be found that the present FEM was able to be successfully extended to the boundary value problems of geosynthetic reinforced soil retaining walls. The deformation and strength characteristics of the geogrid reinforced sand retaining walls can be well reproduced. Loading rate effect, the trends of jump in footing pressure upon the step-changes in the loading rate, occurred not only on sands and geogrids but also on geogrid reinforced sands retaining walls. The lateral earth pressure distributions against the back of retaining wall, the local tensile force in the geogrid arranged in the retaining wall and the local stresses beneath the footing under various loading conditions can also be predicted well in the FEM simulations.

• Journal of Gastric Cancer
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• v.24 no.2
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• pp.137-144
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• 2024

Purpose: Laparoscopic proximal gastrectomy (LPG) is a viable choice for treating proximal gastric lesions. However, the occurrence of severe reflux has limited its widespread adoption. To address this issue, the double flap technique (DFT), which incorporates artificial lower esophageal sphincteroplasty, has been developed to prevent reflux problems after proximal gastrectomy. In this study, we aimed to investigate the usefulness of this technique using high-resolution manometry (HRM), impedance pH monitoring, and esophagogastroduodenoscopy (EGD). Materials and Methods: The findings of pre- and postoperative 6-month HRM, pH monitoring, and EGD were compared for 9 patients who underwent LPG with DFT for various proximal gastric lesions at Incheon St. Mary's Hospital from January 2021 to December. Results: A total of 9 patients underwent proximal gastrectomy. Approximately half of the patients had Hill's grade under II preoperatively, whereas all patients had Hill's grades I and II in EGD findings. In the HRM test, there was no significant difference between distal contractile integral (1,412.46±1,168.51 vs. 852.66±495.62 mmHg·cm·s, P=0.087) and integrated relaxation pressure (12.54±8.97 vs. 8.33±11.30 mmHg, P=0.27). The average lower esophageal sphincter (LES) pressure was 29.19±14.51 mmHg preoperatively, which did not differ from 19.97±18.03 mmHg after the surgery (P=0.17). DeMeester score (7.02±6.36 vs. 21.92±36.17, P=0.21) and total acid exposure time (1.49±1.48 vs. 5.61±10.17, P=0.24) were slightly higher, but the differences were not statistically significant. Conclusions: There is no significant functional difference in HRM and impedance pH monitoring tests after DFT. DFT appears to be useful in preserving LES function following proximal gastrectomy.

• Geotechnical Engineering
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• v.10 no.4
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• pp.103-118
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• 1994

The rapid motion of granular material is microscopically observed, and investigated by continuum theory. From the binary collision phenomenon two different times are introduced : flying time and contact time. The former says the non -stationary motion and at a same time the variation of bulk volume. The latter is operative by a delayed time during the contact and describes the elastic properties of granular material. With both times a dynamic constitutive equation is postulated for four state variables : dispersive pressure, viscosity, thermal diffusivity and energy annihilation rate. The balance laws of mass, momentum and energy which are represented through above four variabls, are applied to the model, in which due to the elastic property the relaxation and energy absorption are explained.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.285-288
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• 2001

Hypereutectic Al-25Si-X alloys, expected to be applied to the cylinder-liner-part of the engine-block of an automobile due to the excellent wear resistance, low density and low thermal expansion coefficient has been fabricated through a spray forming process. The obtained microstructure of the hypereutectic Al-25Si-X alloy appeared to consist of Al matrix and equiaxed Si particles of average diameter of $5-7{\mu}m$. To characterize the deformation behavior of this alloy, a series of load relaxation and compression tests have been conducted at temperatures ranging from RT to $500^{\circ}C$. The strain rate sensitivity parameter (m) of this alloy has been found to be very low (0.1) below foot and reached 0.2 at $500^{\circ}C$. During the deformation above 300'c in compression, strain softening has been observed. The diagram of extrusion pressure vs. ram-speed has been constructed, providing the extrusion condition of Al-25Si-X alloys.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1699-1707
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• 2003

Coriolis mass flowmeter(CMF), which can measure the mass flow directly, is getting rapid attention for the industrial and custody transfer purpose. In order to study the characteristics and the applicability of CMF, it is tested with the national flow standard system. Two types of sensing tube, U-type and straight type, are employed in the test. Water, spindle oil and viscosity Standard Reference Material whose viscosities are 1, 20 and, 67 $\textrm{mm}^2$/s, respectively, are studied. It is shown that the linearity of CMF is getting deteriorated as the fluid viscosity increases, which is due to the zero drift and the relaxation time of the fluid. To test its applicability in the case of high pressured gas, it is calibrated using compressed air, It shows 1∼l.6 % deviations compared to the calibration results using water. It concludes that the fluid velocity in CMF should be lower than the sonic velocity. In addition, the effects of the vibration from the pipeline and pump on CMF as well as the long term stability are studied.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.62-70
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• 2009

In this paper, the fluid flow behavior past a pair of rectangular cylinders placed in a two dimensional horizontal channel has been investigated using Lattice-Boltzmann Method(LBM). The LBM has built up on the D2Q9 model and the single relaxation time method called the Lattice-BGK(Bhatnagar-Gross-Krook)model. Streamlines, velocity, vorticity and pressure contours are provided to analyze the important characteristics of the flow field for a wide range of non dimensional parameters that present in our simulation. Special attention is paid to the effect of spacing(d) between two cylinders and the blockage ratio A(=h/H), where H is the channel height and h is the rectangular cylinder height. for different Reynolds numbers. The first cylinder is called upstream cylinder and the second one as downstream cylinder. The downstream fluid flow fields have been more influenced by its blockage ratios(A) and Reynolds numbers(Re) whereas the upstream flow patterns(in front of downstream cylinder) by the gap length(d) between two cylinders. Moreover, it is observed that after a certain gap, both upstream and downstream flow patterns are almost similar size and shape. The simulation result has been compared with analytical solution and it is found to be in excellent agreement.

• Korean Journal of Pharmacognosy
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• v.16 no.4
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• pp.199-205
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• 1985

In order to investigate experimentally the clinical effects of Soeuminsohapwon that was prescribed to cure cerebral hemorrhage, palpitation etc, the author tested various activities of extract from the Soeuminsohapwhangwon by the method prescribed in the experimental part. The results of the studies were summarized as follows: Suppressive action was not shown on the convulsion induced by strychnine, but significant effect was noted on the convulsion induced by picrotoxin and caffeine. In acetic acid method, analgesic effect was noted. A prolongation of anesthetic time by pentobarbital sodium and antipyretic effect was observed. Relaxing action was noted on the ileum of mice, also same effect was recognized on contraction of the ileum due to acetylcholine, barium chloride and histamine. The expansion of blood vessels by relaxation of smooth muscle and hypotensive action were noted. According to the above results, effects based on oriental medical references were approximate to the actual experimental results.

• Korean Journal of Pharmacognosy
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• v.2 no.4
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• pp.163-172
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• 1971

This paper attempts to observe the histological structure of Korean Arisaema ringens $S_{CHOTT}{'s}$ rhizome, to identify it's constituent and to investigate the pharmacological action with it's alcohol extract. The results are : 1) The inner structure of rhizome on the transverse section is divided into external and internal tissues by the ring of intercellular secretary sac. Raphides of calcium oxalate contained in mucilage cell, collateral vascular bundle, are extremely similar to those contained in Pinellia ternata. 2) The organs of the pistillate Arisaema ringens are larger and more plentiful than those of the staminate Arisaema ringens. The sexual identification is easy in the flowering season. 3) The alkaloid is identified by Meyer reagent as white p.p.t. at pH 2 of sulfuric acid. 4) The saponin is indentified remarkably by means of foaming reaction, Lieberman-Burchard reaction and hemolytic reaction. 5) The effect of alcohol extract on the relaxation of the isolated intestine of the rabbit is remarkably shown at the concentration of $10^{-3}g/ml$. 6) The effect of alcohol extract on the isolated ractus muscle of the frog increases the constructive action of acetylcholine at the concentration of $10^{-3}g/ml$. 7) The effect of alcohol extract on the isolated heart movement of the frog is decreased remarkably at the concentration of $10^{-3}g/ml$. 8) The effect of alcohol extract on the blood pressure of the rabbit is decreased by an interavenous injection of $10^{-3}g/kg$.

• Korean Journal of Pharmacognosy
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• v.21 no.2
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• pp.163-172
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• 1990

These studies were conducted to investigate the effects of Tongkwan-San water extract on analgesic, sedatative, anti-inflammatory, blood pressure and vasodilating actions, the relaxing action of isolated ileums and actions on the contact dermatitis induced by picryl chloride and on the leakage of the dye into the peritoneal cavity. The results of these studies were summarized as follows: The analgesic effect of Tongkwan-San was noted. The prolongation of anesthetic time of Tongkwan-San was recognized. Spontaneous motilities of isolated ileum of mice were strongly suppressed by Tongkwan-San. It inhibited the contractions of isolated ileum of mice induced by acetylcholine and barium chloride and the contraction of isolated ileum of guinea-pig induced by histamine. Inhibition of the contact dermatitis induced by picryl chloride was recognized. Anti-inflammatory effects in the paw edema induced by histamine and dextran were significantly shown. The leakage of dye into the peritoneal cavity in mice was significantly inhibited. Hypotensive and vasodilating action due to vascular smooth muscle relaxation were noted in rats and rabbits.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.1-8
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• 2013

This study was performed for the purpose of analyzing the effect of tide on the stress-strain behavior in the boundary surface of sea dike embankment. Tide is a dynamic condition, but there are not suitable numerical models to solve the dynamic embankment condition caused by tide. So the analysis was simplified to quasi dynamic as follow. First, seepage by tide was analyzed according to elapsed time, and the results of the analysis at every hour during one periodic cycle time of 12 hours were applied to the pore water pressure conditions of stress-strain analysis with hyperbolic model by Duncan and Chang. The place at which maximum shear strain took place in the analysis result moved up and down repeatedly along the boundary of the dredged sand fill section and the crashed stone filter section. The value of maximum shear strain was large at high water level of tide. This result means that contraction and relaxation occur in turn repeatedly at every specific position along the boundary, and the repeated action compact loose position with sand moved down from the upper position by gravity. The experiment with the small sea dike model showed the result consistent with the numerical analysis. The surface of sea side on the dike collapsed at high water level after a couple of repetition of the rising and falling of water.