• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.385-389
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• 2004

Test facilities for the wind turbine performance monitoring and mechanical load measurements are installed in Vestas 100 kW wind turbine in Wollyong test site, Jeju island. The monitoring system consists of Garrad-Hassan T-MON system, telemetry system for blade load measurement, various sensors such as anemometer, wind vane, strain gauge, power meter, and etc. The experimental procedure for the measurement of wind turbine loads, such as edgewise(lead-lag) bending moment, flapwise bending moment, and tower base bending moment, has been established. Strain gauges are on-site calibrated against load cell prior to monitoring the wind turbine loads. Using the established monitoring system, the wind turbine is remotely monitored. From the measured load data, the load analysis has been performed to obtain the load power spectral density and the fatigue load spectra of the wind turbine.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.140-149
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• 2011

For a certain operating point of a horizontal shaft bulb turbine (i.e. volume flow, net head, blade angle, guide vane angle) the efficiency for different pressure levels (i.e. different Thoma-coefficient ${\sigma}$) is calculated using a commercial Computational Fluid Dynamics (CFD-)-code including two-phase flow and a cavitation model. The results are compared with experimental results achieved at a closed loop test rig for model turbines. The comparison of the experimentally and numerically obtained efficiency and the visual impression of the cavitation show a good agreement. Especially the drop in efficiency is calculated with satisfying accuracy. This drop in efficiency in combination with the visual impression is of high practical importance since it contributes to determine the admissible cavitation in a bulb-turbine. It is seen that the incipient cavitation in Kaplan type turbines has no major importance in determing this admissible amount of cavitation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 가을 학술발표회 논문집
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• pp.293-298
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• 2001

N-value is usually used to assume the displacement depth of embankment on the soft marine clay. But N-value of the soft marine clay tend to underestimate unlike overestimating of general cases. In general case, if the length of rod is more long then N-value is more large because it is under the influence of energy loss of hammer blow. So it is reasonable to correct N-value down. But in the case of soft marine clay, N-value must not be correct down. Especially to assume the displacement depth of embankment on the soft marine clay, it must be used laboratory test results or CPT, Vane Test than N-value. In this study, it is compared with two field cases that design displacement method of embankment.

• 한국지반공학회논문집
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• 제24권4호
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• pp.89-100
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• 2008

국외에서 개발한 상관식이나 도표 등을 활용하여 국내 지반특성을 반영함에 있어 이를 그대로 국내지반에 적용하는 데에는 한계가 있다. 따라서 국내에 적합한 피에조콘계수 활용을 위해서는 국내 지반에 대한 시험결과를 직접적으로 이용하여 피에조콘계수를 결정할 필요가 있다. 이에 본 연구에서는 서해안 시화호 주변에 광범위하게 분포하고 있는 연약지반을 대상으로 실내시험 및 현장시험을 수행한 결과를 피에조콘 관입시험과 비교 분석하고, 비배수전단강도와 콘 관입저항력과의 상관성 분석을 통하여 피에조콘계수를 산정하였다. 또한 산정된 결과의 신뢰성 확보를 위하여 통계분석 기법을 활용하여 연구대상 지역에 적합한 피에조콘계수를 재산정해 보았다.

• Ocean and Polar Research
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• 제25권spc3호
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• pp.353-360
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• 2003

Estimation of undrained shear strength $(S_u)$ of clayey soils from piezocone penetration test (CPTu), which has widely been known as one of very promising in situ test methods, requires piezocone factors. Empirical correlations are generally utilized to derive piezocone factors, but previous studies on the empirical piezocone factors are site-specific and in some cases need engineering characteristics, which should be obtained from additional laboratory tests. In this study, empirical cone factors were evaluated by comparing 6 CPTu results at Shihwa region in Korea with reference $S_u$ values obtained from field vane test (FVT). From previous CPTu results of other regions in Korea as well as the results herein, the correlations between piezocone factor, $N_{kT}$ and CPTu results were investigated and three simplified evaluation methods of $S_u$ using only CPTu results were presented. The $S_u$ values estimated by $(q_T-{\sigma}_v)/{\sigma}'_v$ method shows better matches with those obtained from laboratory tests for marine clays at Shihwa region.

• 한국지반공학회논문집
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• 제22권5호
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• pp.5-12
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• 2006

본 연구에서는 점토질 지반의 강도를 증진시키기 위해, 일련의 동전기 현상을 이용한 주입 실험을 수행하였다. 이를 위해 실내 Bench scale 실험을 실시하여 적용성을 파악하였다. 또한 확산의 영향에 의한 지반개량효과를 파악하기 위해 실험 종료 후 5일 간격으로 25일 동안 데인 실험을 실시하여 강도증진효과를 파악하였으며, 처리기간에 따른 영향을 고려하기 위해 5일 간격(5, 10, 15, 20, 25)으로 처리기간을 설정한 후 동전기 주입 실험을 실시하였다. 주입제 종류에 따른 실험결과, 초기 강도치와 비교하여 약 $2\sim7$배 정도의 강도증진효과가 발생하였으며, 특히 양극에 규산나트륨을 주입하고 음극에 인산을 주입한 경우 약 7배 정도의 강도증진효과가 발생하였다. 또한 확산과 함수비 감소에 따른 강도값을 분석해본 결과 시간경과에 따라 강도 값이 일정한 값으로 수렴하는 양상을 띠었으며, 함수비 감소에 의한 강도 증가치 보다 동전기 주입과 확산에 의한 영향으로 발생되는 강도증가치가 약 $700\sim1000%$ 높게 나타났다. 처리기간에 따른 실험결과, 처리기간이 증가함에 따라 동전기 주입에 의한 강도증진효과가 크게 나타났으며, 함수비 감소에 의한 강도증가치보다 대략 $3\sim4$배 정도 높게 나타남을 파악할 수 있었다.

• 한국수소및신에너지학회논문집
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• 제31권4호
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• pp.387-394
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• 2020

A parametric study of a 2.5 kW class propeller type micro hydraulic turbine was performed. In order to analyze the internal flow characteristics in the hydraulic turbine, three dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used and the hexahedral grid system was used to construct computational domain. To secure the reliability of the numerical analysis, the grid dependency test was performed using the grid convergence index method based on the Richardson extrapolation, and the grid dependency was removed when about 1.7 million nodes were used. For the parametric study, the axial distance at shroud span (L) between the inlet guide vane and the runner, and the inlet and outlet blade angles (β₁, β₂) of the runner were selected as the geometric parameters. The inlet and outlet angles of the runner were defined in the 3 spans from the hub to tip, and a total of 7 geometric parameters were investigated. It was confirmed that the outlet angles of the runner had the most sensitive effect on the power and efficiency of the micro hydraulic turbine.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.341-346
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• 2001

The gun-type gas burner adopted in this study is generally composed of some slits and swirl vanes. Therefore, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate $450\;{\ell}/min$, which is equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. When the burner has only swirl vanes, the axial mean velocity component shows the characteristic that spreads more remarkably toward radial direction than axial one, but when it has only slits, that is developed spreading more toward axial direction than radial one. Therefore, because the biggest speed is spurted in slits and it derive main flow toward axial direction encircling rotational flow that comes out from swirl vane that is situated on the inside of slits, both slits and swirl vanes composing of cone type gas burner act role that decreases the speed near slits and increases the flow speed in the central part of a burner. Moreover, because rotational flow by swirl vanes and fast jet flow by slits increase turbulent intensities effectively coexisting, the turbulent kinetic energy is distributed with a bigger size fairly near slits than burner models which have only slit or swirl vanes within X/R<0.6410.

• International Journal of Fluid Machinery and Systems
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• 제3권1호
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• pp.11-19
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• 2010

The performance of the crossover system of a centrifugal compressor stage consisting of static components of $180^{\circ}$ U-bend, return channel vanes and exit ducting with a $90^{\circ}$ bend is investigated. This study is confined to the assessment of performance of the crossover system by varying the shape of the return channel vanes. For this purpose two different types of Return Channel Vanes (RCV1 and RCV2) were experimentally investigated. The performance of the crossover system is discussed in terms of total pressure loss coefficient, static pressure recovery coefficient and vane surface pressure distribution. The experimentation was carried out on a test setup in which static swirl vanes were used to simulate the flow at the exit of an actual centrifugal compressor impeller with a design flow coefficient of 0.053. The swirl vanes are connected to a mechanism with which the flow angle at the inlet of U-bend could be altered. The measurements were taken at five different operating conditions varying from 70% to 120% of design flow rate. On an overall assessment RCV1 is found to give better performance in comparison to RCV2 for different U-bend inlet flow angles. The performance of RCV2 was verified using numerical studies with the help of a CFD Code. Three dimensional sector models were used for simulating the flow through the crossover system. The turbulence was predicted with standard k-$\varepsilon$, 2-equation model. The iso-Mach contour plots on different planes and development of secondary flows were visualized through this study.

• Geomechanics and Engineering
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• 제24권2호
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• pp.129-141
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• 2021

The vacuum preloading method has been used in many countries for soil improvement and land reclamation. However, the treatment time is long and the improvement effect is poor for the straight-line vacuum preloading method. To alleviate such problems, a novel combined air booster and straight-line vacuum preloading method for shallow ground treatment is proposed in this study. Two types of traditional vacuum preloading and combined air booster and straight-line vacuum preloading tests were conducted and monitored in the field. In both tests, the depth of prefabricated vertical drains (PVDs) is 4.5m, the distance between PVDs is 0.8m, and the vacuum preloading time is 60 days. The prominent difference between the two methods is when the preloading time is 45 days, the injection pressure of 250 kPa is adopted for combined air booster and straight-line vacuum preloading test to inject air into the ground. Based on the monitoring data, this paper systematically studied the mechanical parameters, hydraulic conductivity, pore water pressure, settlement and subsoil bearing capacity, as determined by the vane shear strength, to demonstrate that the air-pressurizing system can improve the consolidation. The consolidation time decreased by 15 days, the pore water pressure decreased to 60.49%, and the settlement and vane shear strengths increased by 45.31% and 6.29%, respectively, at the surface. These results demonstrate the validity of the combined air booster and straight-line vacuum preloading method. Compared with the traditional vacuum preloading, the combined air booster and straight-line vacuum preloading method has better reinforcement effect. In addition, an estimation method for evaluating the average degree of consolidation and an empirical formula for evaluating the subsoil bearing capacity are proposed to assist in engineering decision making.