• Geomechanics and Engineering
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• v.20 no.3
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• pp.243-254
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• 2020

Due to the permanent damage to structures during earthquakes, soil liquefaction is an important issue in geotechnical earthquake engineering that needs to be investigated. Typical examples of soil liquefaction have been observed in many earthquakes, particularly in Alaska, Niigata (1964), San Fernando (1971), Loma Prieta (1989), Kobe (1995) and Izmit (1999) earthquakes. In this study, liquefaction behavior of uniform sands of different grain sizes was investigated by using the energy-based method. For this purpose, a total of 36 deformation-controlled tests were conducted on water-saturated samples in undrained conditions by using the cyclic simple shear test method and considering the relative density, effective stress and mean grain size parameters that affect the cumulative liquefaction energy. The results showed that as the mean grain size decreases, the liquefaction potential of the sand increases. In addition, with increasing effective stress and relative density, the resistance of sand against liquefaction decreases. Multiple regression analysis was performed on the test results and separate correlations were proposed for the samples with mean grain size of 0.11-0.26 mm and for the ones with 0.45-0.85 mm. The recommended relationships were compared to the ones existing in the literature and compatible results were obtained.

• Korean Journal of Clinical Laboratory Science
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• v.43 no.1
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• pp.6-11
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• 2011

In clinical chemistry tests, the interfering substances such as hemoglobin, lipid, bilirubin, and drugs, etc. can cause the changes of test results performed by spectrophotometrical methods. We evaluated the effects of interfering substances on the test results by adding interfering substances on the samples in the 19 kinds of clinical chemistry tests such as aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase, gamma-glutamyltransferase, total protein, albumin, glucose, total cholesterol, total bilirubin, triglyceride, uric acid, calcium, inorganic phosphours, high density lipoprotein cholesterol, low density lipoprotein cholesterol, creatinine, blood urea nitrogen, and C-reactive protein using newly implemented automatic chemical analyzer Toshiba TBA-C8000 under the direction of CLSI EP07-A guideline. Hemolytic samples show increased concentration of total protein, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase and reduced concentration of total bilirubin, alkaline phosphatase by interfering effect. Hyperlipemic samples show increased concentration of total protein and alkaline phosphatase and reduced concentration of low density lipoprotein cholesterol. The samples with conjugated bilirubinemia show increased concentration of inorganic phosphours, otherwise the samples with unconjugated bilirubinemia show no interference or allowable range in the test result.

• Journal of the Korean Geotechnical Society
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• v.25 no.4
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• pp.105-112
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• 2009

In this study, a series of direct shear tests were performed to investigate the characteristics of friction angles for sands and interface friction angle between sands and construction materials with respect to different relative density of the Nak-dong River sands and shearing velocity. The result of the test shows that friction angles of sands are always higher than interface friction angle between sands and construction materials. As the shearing velocity get faster, the friction angles of sand became higher. With respect to the density of sand by reducing void ratio, friction angles increase linearly, and relevant equations were proposed to calculate the friction angle by changing void ratio and relative density of sand. The interface roughness of construction materials was also an important factor in interface friction angle.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.43.5-44
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• 2021

In the local Universe, the gravitational effects of mass density fluctuations exert perturbations on galaxies' redshifts on top of Hubble's Law, called 'peculiar velocities'. These peculiar velocities provide an excellent way to test the cosmological model in the nearby Universe. In this talk, we present new cosmological constraints using peculiar velocities measured with the 2MASS Tully-Fisher survey (2MTF), 6dFGS peculiar-velocity survey (6dFGSv), the Cosmicflows-3 and Cosmicflows-4TF compilation. Firstly, the dipole and the quadrupole of the peculiar velocity field, commonly named 'bulk flow' and 'shear' respectively, enable us to test whether our cosmological model accurately describes the motion of galaxies in the nearby Universe. We develop and use a new estimators that accurately preserves the error distribution of the measurements to measure these moments. In all cases, our results are consistent with the predictions of the Λ cold dark matter model. Additionally, measurements of the growth rate of structure, fσ8 in the low-redshift Universe allow us to test different gravitational models. We developed a new estimator of the "momentum" (density weighted peculiar velocity) power spectrum and use joint measurements of the galaxy density and momentum power spectra to place new constraints on the growth rate of structure from the combined 2MTF and 6dFGSv data. We recover a constraint of fσ8=0.404+0.082-0.081 at an effective redshift zeff=0.03. This measurement is also fully consistent with the expectations of General Relativity and the Λ Cold Dark Matter cosmological model.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.83-86
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• 2008

This paper deals with the experimental works for the correlations of ice resistance for icebreaker with synthetic(model) ice in general towing tank and with refrigerated ice in ice tank. In order to find out the correlation, the density variation is mainly focused in the present study. The model of Terry-Fox ice breaker has been used for the present correlation study because many data are available to be compared. According to the increase of density, the correlation becomes better quantitatively as well as qualitatively. Other parametric studies such as an ice size, a friction coefficient, a bending moment, etc., are also expected to be carried out to have better correlation in a near future. This research could be the basis for the possibility of resistance test using a synthetic ice in a general towing tank instead of an expensive ice tank.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1791-1795
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• 2007

Small ions generated at conductor corona sources remain in the atmosphere until they recombine with ions of opposite polarity, attach to aerosols, or make contact with an object. Ion current density is major factor to design conductor configuration of DC overhead transmission line. Several techniques have been used to measure the ion current of HVDC overhead transmission line. In this study, the ion current density was measured by a plate electrode made of a metal flat board at DC corona cage. The sensitivity of the plate electrode is $0.156uA/m^2/V$. To obtain an useful database on corona discharge, it is necessary to do corona test on several kinds of conductor bundles. Therefore, a number of experiments were conducted on several kinds of conductor bundles. To reliably analyze ion effects, corona cage test data were obtained over a long period of time under various weather conditions and expressed as a statistical distribution. Ion current density distribution in foul weather shows a significant increase in levels over the corresponding fair weather. Based on this results, we evaluated the environmental characteristic caused by ion flow of three candidated conductor bundles.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.209-226
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• 2002

When predicting unsteady flow and pressure fields around a structure in a turbulent boundary layer by Large Eddy Simulation (LES), velocity fluctuations of turbulence (inflow turbulence), which reproduce statistical characteristics of the turbulent boundary layer, must be given at the inflow boundary. However, research has just started on development of a method for generating inflow turbulence that satisfies the prescribed turbulence statistics, and many issues still remain to be resolved. In our previous study, we proposed a method for generating inflow turbulence and confirmed its applicability by LES of an isotropic turbulence. In this study, the generation method was applied to a turbulent boundary layer developed over a flat plate, and the reproducibility of turbulence statistics predicted by LES computation was examined. Statistical characteristics of a turbulent boundary layer developed over a flat plate were investigated by a wind tunnel test for modeling the cross-spectral density matrix for use as targets of inflow turbulence generation for LES computation. Furthermore, we investigated how the degree of correspondence of the cross-spectral density matrix of the generated inflow turbulence with the target cross-spectral density matrix estimated by the wind tunnel test influenced the LES results for the turbulent boundary layer. The results of this study confirmed that the reproduction of cross-spectra of the normal components of the inflow turbulence generation is very important in reproducing power spectra, spatial correlation and turbulence statistics of wind velocity in LES.

• Research in Community and Public Health Nursing
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• v.27 no.1
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• pp.51-59
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• 2016

Purpose: The purpose of this study is to provide a disease management, nutrition education, and group exercise program for three months to the moderately frail elderly whose physical functions have deteriorated, and to investigate its effects in order to develop an intervention program. Methods: As a quasi-experiment, this study was conducted based on non-equivalence studies designed as a similar experiment. The milk intake group and calcium intake group participated in the disease education, individual nutrition education, and group exercise program for three months, and the control group was visited once in the three months by a nurse who provided disease education, nutrition education, and oral instruction of exercise, and asked them to exercise on their own every day. For the data analysis, ${\chi}^2$-test, ANOVA and $Scheff{\acute{e}}$ test were used. Results: After three months of intervention, there was a significant difference in the frailty level (p=.029) and bone density (p=.001) between the groups. Conclusion: The comprehensive intervention program had an effect on the bone density and the frailty level of the socially-vulnerable and moderately frail elderly, suggesting that the program can be used as a nursing intervention to prevent functional deterioration and damage of the moderately frail elderly.

• Journal of Korean Biological Nursing Science
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• v.10 no.2
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• pp.105-112
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• 2008

Purpose: The purpose of this study was to investigate the difference in the incidence of diarrhea among the subjects given hypertonic and isotonic nutrients to the nasogastric tube feeding patients in the a critical care setting. Methods: This study is aquasi-experimental study with a pre & post-test design. The sample size of 40 was calculated based on Cohen's formula (1988). The total of 40 subjects who signed the informed consent were randomly selected and divided evenly into two groups, experimental and control group. Results: There are no significant differences between the two groups in homogeneity test (sex, age, albumin level, the use of antibiotics, antacid, and $H_2$ blocker). However, the frequencies of occurrence in diarrhea according to the density of nutrients formulation indicated a statistical difference at the level of .005 (p=.001): diarrhea occurred in four of 20 (20%) of the experiment group, but 14 (70%) of the control group. Also the onset date of diarrhea in the experiment group is later than that of the control group. Conclusion: The research findings suggest that we should begin with low density nutrients for nasogastric tube feeding, and increase its density gradually to decrease diarrhea incidence in the critical care setting.

• Journal of the Korean Society of Safety
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• v.21 no.5 s.77
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• pp.6-11
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• 2006

This study aims to measure a smoke density and velocity by using the PIV method in case a fire occurs in tunnels. By doing so, this will estimate a critical velocity, examine its appropriateness, and present the basic materials necessary for designing a smoke control equipment. For this study, a visualization test was conducted based on the 1/20 miniature of a real tunnel according to the Froude scaling. As a part of basic experiments, a correlation between smoke density and brightness was analyzed here, and a critical velocity was estimated on the condition that a fire breaks out in tunnels. As a result, this study finds that there is a correlation between smoke density and brightness within a range of 100% to 30% transmittance, from which a quantitative smoke density can be obtained. The study also suggests that a critical velocity calculated from the Kennedy formula shows about 10% difference from that estimated in the test.