• Geomechanics and Engineering
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• v.38 no.2
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• pp.165-177
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• 2024

Liquefaction phenomenon refers to a phenomenon in which excess pore water pressure occurs when a dynamic load such as an earthquake is rapidly applied to a loose sandy soil ground where the ground is saturated, and the ground loses effective stress and becomes liquid. The laboratory repetition test for liquefaction evaluation can be performed through a repeated triaxial compression test and a repeated shear test. In this regard, this study attempted to evaluate the effects of the relative density of sand on the liquefaction resistance strength according to particle size distribution using repeated triaxial compression tests, and additional experimental verification using numerical analysis was conducted to overcome the limitations of experimental equipment. As a result of the experiment, it was confirmed that the liquefaction resistance strength increased as the relative density increased regardless of the classification of soil, and the liquefaction resistance strength of the SP sample close to SW was quite high. As a result of numerical analysis, it was confirmed that the liquefaction resistance strength increased as the confining pressure increased under the same relative density, and the liquefaction resistance strength did not decrease below a certain limit even though the confining pressure was significantly reduced at a relatively low relative density. This is judged to be due to a change in confining pressure according to the depth of the ground. As a result of analyzing the liquefaction resistance strength according to the frequency range, it was confirmed that there was no significant difference from the laboratory experiment results in the basic range of 0.1 to 1.0 Hz.

• 연구논문집
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• s.34
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• pp.29-38
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• 2004

The objective of this study is to investigate the pressure drop and heat transfer characteristics of the micro-fin tubes before and after the tube-expansion process. Test tubes are single-grooved micro-fin tubes made of copper with an outer diameter of 9.52 mm before the tube-expansion. The direct heating method is applied in order to make the refrigerant evaporated in the micro-fin tubes. The test ranges of the heat flux, mass flux, and the saturation pressure are 5 to 15kW/$m^2$, 100 to 200 kg/$m^2s$ and 540 to 790 kPa, respectively. The effects of the mass flux, heat flux, and the saturation pressure of the refrigerant on the pressure drop and the heat transfer are presented for the refrigerant R22. In the test conditions of this study, the heat transfer coefficient for the micro-fin tube after the tube-expansion is about 16.5% smaller than that before the tube-expansion because the fin height of micro-fin is reduced and the fin shape becomes flatter. The micro-fin tube after the tube-expansion has about 7.7% greater average pressure drop than that before the tube-expansion process.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.18 no.1
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• pp.63-70
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• 2011

Purpose: This study was done to examine the effects of aroma inhalation therapy on pain post tonsillectomy. Method: A non-equivalent control group pre- and post-test design was used. The research instruments used in this study were a pain perception measurement and vital signs (systolic & diastolic blood pressure and pulse rate levels). Twenty-five patients in the experimental group went through aroma inhalation therapy for ten minutes after the tonsillectomy. The aroma inhalation therapy used was a blended oil, a mixture of Lavender and Loman chamomile in the ratio of 2:1. The 25 patients in the control group did not receive the therapy. Before and after the experiment, both groups were tested for pain (pain perception and vital signs). Collected data were processed with the SPSS WIN. Ver. 14.0 program and analyzed using frequencies, percentages, ${\chi}^2$-test, Fisher's exact test, t-test and ANCOVA. Results: Pain perception of patients was not significantly reduced. However systolic and diastolic blood pressure and pulse rate were significantly reduced. Conclusion: The results of the study indicate that aroma inhalation is a partially effective nursing intervention to reduce the post-operative tonsillectomy pain.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.303-309
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• 1999

Optimum tribological performance of the head/disk system is critical in maintaining reliable data processing in a hard disk drive. Particularly, as the flying height of the slider continues to decrease with increasing recording density, frictional interaction between the slider and the disk need to be better understood. In this work the effect of reduced ambient pressure on the tribological behavior of the head/disk interface is presented. It is found that surface damage of the components can be accelerated by reducing the ambient pressure. This method may be utilized to assess slider/disk compatibility of newly developed systems in short time.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2642-2649
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• 2023

A real-time unmeasured dynamic response prediction process for the nuclear power plant pressure pipeline is proposed and its performance is tested in the test-loop system (KAERI). The aim of the process is to predict unmeasurable or unreachable dynamic responses such as acceleration, velocity, and displacement by using a limited amount of directly measured physical responses. It is achieved by combining a well-constructed finite element model and robust inverse force identification algorithm. The pressure pipeline system is described by using the displacement-pressure vibro-acoustic formulation to consider fully filled liquid effect inside the pipeline structure. A robust multiphysics modal projection technique is employed for the real-time sensor synchronized prediction. The inverse force identification method is also derived and employed by using Bathe's time integration method to identify the full-field responses of the target system from the modal domain computation. To validate the performance of the proposed process, an experimental test is extensively performed on the nuclear power plant pressure pipeline test-loop under operation conditions. The results show that the proposed identification process could well estimate the unmeasured acceleration in both frequency and time domain faster than 32,768 samples per sec.

• Korean Journal of Community Nutrition
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• v.16 no.1
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• pp.62-74
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• 2011

This study was designed to implement and evaluate a nutrition education program for hypertensive patients aged between 50 and over. Nutrition education consisted of four sessions and, 35 out of 51 patients completed all education sessions at the public health center. To assess program effectiveness (effectively), data about blood pressure, blood cholesterol, anthropometry, nutrition knowledge, eating behavior and dietary intake were collected before and after nutrition education. Data were analyzed using SAS package (ver. 9.2) and significant difference was evaluated by paired t-test, x2-test and Wilcoxon signed rank test. Blood cholesterol was significantly reduced from 200.7 mg/dL to 188.7 mg/dL after nutrition education, although there were not significant changes in blood pressure or blood triglyceride level. Weight (p < 0.05), % body fat (p < 0.001), BMI (p < 0.05) were significantly reduced, especially in women, after nutrition education. Nutrition knowledge was increased significantly (p < 0.05), and some eating behaviors such as 'having fruits & vegetables for snack' and 'having brown rice, barley rice than white rice' were improved after nutrition education (p < 0.05). Sodium intake was reduced from 3,888.9 mg/day to 3,157.4 mg/day after nutrition education (p < 0.05). Except protein and iron intakes, the nutrient intake of hypertensive patients was much below the recommended level for Koreans. Dietary intakes of most of nutrients were not significantly different between pre-test and post-test. It appeared that nutrition education for the aged hypertensive patients was effective in reducing the percentage of % body fat and BMI, increasing the nutrition knowledge and some dietary behaviors. This nutrition education can be implemented at public health centers or senior centers for hypertensive patients.

• Wind and Structures
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• v.32 no.3
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• pp.227-238
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• 2021

This study analyzed the pressure patterns and local pressure of tall buildings with corner modifications (recessed and chamfered corner) using wind tunnel tests and proper orthogonal decomposition (POD). POD can distinguish pressure patterns by POD mode and more dominant pressure patterns can be found according to the order of POD modes. Results show that both recessed and chamfered corners effectively reduced wind-induced responses. Additionally, unique effects were observed depending on the ratio of corner modification. Tall building models with recessed corners showed fluctuations in the approaching wind flow in the first POD mode and vortex shedding effects in the second POD mode. With large corner modification, energy distribution became small in the first POD mode, which shows that the effect of the first POD mode reduced. Among building models with chamfered corners, vortex shedding effects appeared in the first POD mode, except for the model with the highest ratio of corner modifications. The POD confirmed that both recessed and chamfered corners play a role in reducing vortex shedding effects, and the normalized power spectral density peak value of modes showing vortex shedding was smaller than that of the building model with a square section. Vortex shedding effects were observed on the front corner surfaces resulting from corner modification, as with the side surface. For buildings with recessed corners, the local pressure on corner surfaces was larger than that of side surfaces. Moreover, the average wind pressure was effectively reduced to 88.42% and 92.40% in RE1 on the windward surface and CH1 on the side surface, respectively.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.3
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• pp.86-94
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• 2015

A series of injection and drainage test were conducted on an circular acrylic tube to investigate the pressure generated by the accumulated fill materials inside a circular acrylic tube structure. The acrylic tube was filled by means of gravity filling with a slurry material having an average water content of 700%. The water head during the filling process was 1.8m and the bottom pressure during initial filling was 20.18kPa. The recorded stress at the sides of the acrylic tube was 17.89kPa during the filling process and was reduced to 13.58kPa during the leaving process. Continuous drainage of the acrylic tube has greatly influenced the stresses around the tube structure. As the water is gradually allowed to overflow, the generated pressure at the topmost pressure sensor of the tube was reduced further to 2.17kPa. Eventually, the initially liquid state slurry material transforms into plastic state after water has dissipated and substantial soil particles are deposited in the acrylic tube. The final water content of the deposited silt inside the acrylic tube after the test was 42%. It was found that the state of stresses(geo-static earth pressures) in the acrylic tube was anisotropic rather than isotropic.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.3
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• pp.70-81
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• 1996

Solutions of geotechnical engineering problems require predictions of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such predictions even for complicated problems. To get accurate results, realistic stress-strain relationships of soils are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate stress-strain and volume change characteristics of Lade's single work hardening model dependant on the stress path. In order to predicted of stress-strain and volumetric strain behavior were determined the values of parameters for the mode by the computer program based on the regression analysis. Predicted stress-strain behavior of triaxial compression tests and optional stress path tests for increasing confining pressure with parameters obtained conventional triaxial compression tests agreed with several test results but the prediction results for decreasing confining pressure reduced triaxial compression tests make a little difference with test results.

• Journal of computational fluids engineering
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• v.1 no.1
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• pp.134-141
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• 1996

Wall interference is one of the major obstacles to increase the model size and data accuracy. There have been many treatments for wall interference including interference correction and adaptive wall test section. Recently, two-flexible-walled adaptive wall test section is concluded adequate for three-dimensional test. But proper location of target line and pressure holes are critical to its success. In this study, a new adaptive algorithm which dispenses target line and dependency of pressure hole distribution is suggested. The wind tunnel and free air tests are simulated by the numerical computation of Euler equations. The optimum wall shape is achieved by two variable optimization which is composed of two base streamlines. The wall interference is reduced well in the optimized result which is not sensitive to the base streamlines.