• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1254-1259
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• 2008

Recently, centrifuge tests have been widely used as tools in geotechnical engineering researches in domestic and foreign. However, the size of these centrifuge facilities is very large and thus the tests require for long time, high expense, and many labors. In this study, therefore, a small capacity(2g ton) of instructional centrifuge, which can conduct tests in a short period of time effectively, was introduced. The results of centrifuge tests conducted on the retaining wall both passive and active cases was used. Medium size of sand was used with sieve off fines in sand using #40 sieve. Based on the test results, this centrifuge facility introduced in here can be enough used for geotechnical engineering education for graduate and undergraduate students.

• Journal of Industrial Technology
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• v.23 no.A
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• pp.131-137
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• 2003

This thesis is results of centrifuge model experiments to investigate the behavior of replacement method in dredged and reclaimed ground. For experimental works, centrifuge model tests were carried out to investigate the behavior of replacement method in soft clay ground. Basic soil property tests were performed to find mechanical properties of clay soil sampled from the southern coast of Korea which was used for ground material in the centrifuge model tests. Reconstituted clay ground of model was prepared by applying preconsolidation pressure in 1g condition with specially built model container. Centrifuge model tests were carried out under the artificially accelerated gravitational level of 50g. Replacing material of leads having a certain degree of angularity was used and placed until the settlement of embankment of replacing material was reached to the equilibrium state. Vertical displacement of replacing material was monitored during tests. Depth and shape of replacement, especially the slope of penetrated replacing material and water contents of clay ground were measured after finishing tests. Model tests of investigating the stability of embankment after backfilling were also performed to simulate the behavior of the dike treated with replacement and backfilled with sandy material. As a result of centrifuge model test, the behavior of replacement, the mechanism of the replacing material being penetrated into clay ground and depth of replacement were evaluated.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.3
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• pp.143-146
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• 2009

Purpose: We use the centrifugation of refrigeration state in separation of blood serum, Anti-ds-DNA, Vitamin $B_{12}$/Folate and GAD-Ab assay. However, Cortisol urine and 25-Hydroxyvitamin $D_3$ ($25OHD_3$) are conducted centrifuge at room temperature. This is troublesome that change centrifugation temperature into room temperature due to using of most assays at cold temperature. Therefore when using centrifuge after extraction of Cortisol urine and $25OHD_3$, we conducted researches on effect of the centrifugation temperature in assay results. Materials and Methods: In Cortisol urine, add dichloromethane 1.0 mL in urine $500\;{\mu}L$, mix for 15 minutes, and then centrifuge for 8 minutes at 2600rpm. In $25OHD_3$ add acetonitrile 0.5 mL in serum $200\;{\mu}L$, and then centrifuge for 8 minutes at 2600rpm. Those experiments were conducted centrifuge at room temperature and $4^{\circ}C$. And experiments conducted immediately after centrifugation at $4^{\circ}C$ and standing for 20 minutes after centrifugation $4^{\circ}C$. Results: In Cortisol urine, room temperature result in 1.93, 2.18, 2.43, 9.45, 14.2 (${\mu}g/dL$). Experiments of performing immediately after centrifuge at $4^{\circ}C$ result in 1.8, 2.0, 2.3, 8.1, 13.7 (${\mu}g/dL$). Experiments of performing after 20 minutes result in 2.1, 2.1, 2.7, 9.95, 14.35 (${\mu}g/dL$). On the other hand, the $25OHD_3$ tests conducted at room temperature result in 7.13, 26.6, 35.8, 48.2, 74.8 (ng/dL). Experiments were conducted immediately by pipetting after $4^{\circ}C$ centrifugation result in 7.53, 30.9, 40.3, 61.5, 89.1 (ng/dL) as results are higher than experiments at room temperature. The experiments that conducted centrifuge at $4^{\circ}C$ and then left at room temperature for 20 minutes result in 7.40, 32.4, 41.3, 51.6, 85.6 (ng/dL). Conclusions: Experiments were conducted by using centrifuge at $4^{\circ}C$ are higher or lower than room temperature. The differences between results of standing for 20 minutes after centrifuge at $4^{\circ}C$ and those of centrifuge at room temperature are less than conducting immediately. It is concerned that experiments conducted immediately after centrifuge at $4^{\circ}C$ are incorrect, because tubes become dim due to temperature differences between $4^{\circ}C$ and room temperature. Therefore, it is desirable to centrifuge at room temperature as manual and we should pipet promptly without stopping.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.719-726
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• 2016

The problem of separation of isotopes in a concurrent gas centrifuge is solved analytically for an arbitrary binary mixture of isotopes. The separative power of the optimised concurrent gas centrifuges for the uranium isotopes equals to ${\delta}U=12.7(V/700m/s)^2(300K/T)(L/1m)kg{\cdot}SWU/yr$, where L and V are the length and linear velocity of the rotor of the gas centrifuge and T is the temperature. This equation agrees well with the empirically determined separative power of optimised counter-current gas centrifuges.

• Journal of Industrial Technology
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• v.31 no.A
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• pp.79-86
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• 2011

This paper is results of centrifuge model experiment of investigating geotechnical engineering behavior of waterproof dike, located in soft grounds, in Saemankem in progress of construction. Centrifuge test with artificially increased gravitational level of 50g were performed to find ground settlements and excess pore-pressures developed during construction of waterproof dike by simulating the construction stages being predicted to occur in field so that the stability of waterproof dike could be assessed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1C
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• pp.1-10
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• 2011

This paper simulates the piping effect, found levees with large difference in coefficient of permeability within the foundation such as the Gim-po Levee, via centrifuge model test which is a model test. We have also conducted a numerical analysis under the same conditions as the centrifuge model test to compare its results. First, we decided to use the centrifuge model based on the Gim-po Levee, and the tests were executed on a model levee with pore water pressure transducers. We have found that most of the water flows through the permeable layer and causes the piping effect. Via video camera footage, we have found that the piping effect occurred at the toe of the model levee. The characteristic of pressure head distribution, obtained from the pore water pressure transducers, also proves the occurrence of the piping effect. The numerical analysis results also showed the same results as the centrifuge model test. We have simulated the piping effect via centrifuge model test and believe that the centrifuge model test is viable for various tests, predictions and evaluation of the levee problems.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.51-58
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• 2008

The George Massey immersed tunnel passes the Fraser River near Vancouver, Western Canada. In this paper, dynamic analysis of the tunnel on sandy soils was performed using an effective stress constitutive model called UBCSAND. This model is able to calculate pore pressure rise and resulting tunnel deformation due to cyclic loading. Centrifuge tests conducted at RPI are used to verify the model performance. Centrifuge tests consist of 3 models: Model 1 is designed for an original ground condition, Model 2 for a ground improvement by compaction method, Model 3 for a ground improvement by gravel drainage. The results of centrifuge Model 1 are presented and compared with predictions of UBCSAND model. This model well captured the results of centrifuge test and therefore can be used to predict dynamic behavior of similar tunnels or underground structures on sandy soils.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.79-86
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• 2012

In this paper, centrifuge model tests and numerical analysis on the breakwater structure were performed to investigate the stability and behavior of breakwater in field. In centrifuge model tests, construction sequence of breakwater structure such as preparation of weathered rock and sand deposit, construction of D.C.M, rubble mound with crushed stones and installment of breakwater structure was reconstructed like field condition and the behavior of ground settlement and breakwater displacement during stage of construction was observed during tests. For the final stage of simulating the horizontal movement of breakwater due to wave force, horizontal load was applied by horizontal loading apparatus being specially designed so that horizontal displacement of structure could be observed. Numerical analysis were also carried out and its results were compared with test results to assess the property of centrifuge model tests with respect to the behavior of structure as well as ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1473-1478
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• 2010

For the cassion type of breakwater under the condition of large wave loads, stability about lateral movement of breakwater was investigated by performing centrifuge model experiments. Prototype of breakwater was modelled by scaling down to centrifuge model and the soft ground reinforced with grouting was also reconstructed in the centrifuge model experiments. Sandy ground beneath breakwater was prepared with a soil sampled in field so that identical value of internal friction angle could be obtained. Centrifuge model experiments were carried out to reconstruct the construction sequence in field. Lateral static wave load was applied to the model caisson after the final stage of construction sequence was rebuilt and the measured lateral movement of caisson was compared with allowable value by the code to assess the stability about lateral movement of the breakwater.

• Geomechanics and Engineering
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• v.12 no.2
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• pp.239-255
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• 2017

Various centrifuge model tests on the pile foundations were performed to investigate fundamental characteristics of a pile-soil-foundation system recently, but it is hard to find numerical analysis results of a pile foundation system considering the nonlinear behavior of soil layers due to the dynamic excitations. Numerical analyses for a pile-soil system were carried out to verify the experimental results of centrifuge model tests. Centrifuge model tests were performed at the laboratory applying 1.5 Hz sinusoidal base input motions, and nonlinear numerical analyses were performed utilizing a finite element program of P3DASS in the frequency domain and applying the same input motions with the intensities of 0.05 g~0.38 g. Nonlinear soil properties of soil elements were defined by Ramberg-Osgood soil model for the nonlinear dynamic analyses. Nonlinear numerical analyses with the P3DASS program were helpful to predict the trend of experimental responses of a centrifuge model efficiently, even though there were some difficulties in processing analytical results and to find out unintended deficits in measured experimental data. Also nonlinear soil properties of elements in the system can be estimated adequately using an analytical program to compare them with experimental results.