• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.9
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• pp.714-719
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• 2013

A turboprop aircraft for this study is required to operate at icing condition in order that it performs its given mission. So an air intake system of the turboprop aircraft should be designed and verified not only to provide the maximum possible total pressure at engine inlet at normal flight condition, but also to include an inertial separator which protects Foreign Object Debris (FOD) like ice or snow at icing condition from entering into the engine inlet screen which can cause or lead an catastrophic engine failure like engine flame-out or severe damage. So an air intake assembly incorporating a variable geometry inertial separator has been designed and then CFD/structural analysis for the assembly was performed to see its design results. Then 35% scaled model of the air intake assembly was manufactured and wind tunnel test was done. This paper describes the detailed design results for the aerodynamic design, analysis and wind tunnel testing during the development process of the air intake assembly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.641-648
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• 2016

In this study, the effect of injection nozzle shape on the supersonic film cooling performance is analyzed using CFD. The design parameters are inside and outside angles of upper plate of nozzle and nozzle tip thickness. It is observed that the mass flow rate of film cooling decreases with increase of inside angle, while the effect of the change of mass flow rate on the film cooling effectiveness is relatively small. In addition, cooling performance is generally reduced, except ahead of the local region where shock wave interaction with film cooling occurs, in accordance with the growth of the outside angle and tip thickness. In this paper, the CFD simulation is performed using a commercial software, ANSYS Fluent V15.0, and the CFD model is validated by comparing it with the experimental data shown in preceding research.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1496-1502
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• 2012

The fuel pump mounted on the engine in the vehicle is consist of the outer and inter rotors, and which inhales fuel from the inlet port and supplies it to the outlet port. In this study, it is carried out the analysis and test of the fuel pump with rotors to evaluate its performance. It is analyzed the flow characteristics of the fuel pumps with numerical simulation in their inlet-outlet angles of 0, 15, 30 degree. After it is determined whether it has the best flow characteristics, its vibration characteristics is analyzed. The flow rate of a pump in the inlet-outlet angles of 0 degree is 191.0 LPH(Liter per hour) which is the largest. and its vibration is calculated to be 0.866 $^m/s^2$. In the results of vibration test, it is known that the vibration of the research pump is smaller than that of the existing one. And the natural frequencies of two pumps is nearly same. Therefore it is known that the performance of the research pump is superior.

• Korean Journal of Microbiology
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• v.39 no.2
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• pp.114-117
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• 2003

In molecular biology, it is necessary to develop an easy and rapid method to identify a specific DNA sequence. Though Southern and Northern blot techniques have been used widely for the analysis of gene structure and function, those methods are inconvenient in the points that we need to control incubation temperature, time, and other parameters to get the final result. In this study, we report a new method for the rapid analysis of specific DNA sequence with the modification of an immunochromatographic method. The lateral flow DNA analysis strip is composed of a sample pad, a nitrocellulose membrane for the separation and propagation of analytes, and an absorption pad for the generation of capillary action. Capture DNA was immobilized on the membrane by UV cross-linking and target DNA was labeled with Cy-5 for signaling. The samples containing target DNA were applied onto the sample pad, incubated for 15 min for separation, and scanned with a GSI fluorescence scanner. Though the hybridization reaction occurs in a short time without any washing steps, there appears to be little cross hybridization between the different sequences. The result showed a possibility that the new method can be used for the rapid identification of specific DNA sequence among the samples.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.9
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• pp.766-774
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• 2017

When a plume flow exhausted from a lunar lander descent engine impinges on the lunar surface, regolith particles on the lunar surface will be dispersed due to a plume-surface interaction. If the dispersed particles collide with the lunar lander, some adverse effects such as a performance degradation can be caused. Thus, this study tried to predict the plume flow behaviors using the CFD methods. A nozzle inside region was analyzed by a continuum flow model based on the Navier-Stokes equations while the plume behaviors of the outside nozzle was performed by comparing and analyzing the individual results using the continuum flow model and the DSMC method. As a result, it was possible to establish an optimum procedure of the plume analysis for the lunar lander descent engine in the vacuum condition. In the future, it is expected to utilize the present results for the development of the Korean lunar lander.

• Korean Journal of Food Science and Technology
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• v.25 no.5
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• pp.558-564
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• 1993

The drying characteristics of fluidized bed drying with different drying conditions using naked barley were carried out. This fluidized drying mechanism of naked barley was consisted of consecutive two falling rate parts, first falling rate period and second falling rate period without showing constant rate period. The drying rate constant was increased with decreasing charged amount and relative humidity and increasing air temperature and air velocity. Since the drying rate constant expressed by Arrhenius type equation in the falling rate period showed good linearity, the falling rate period was considered as the controlling step. The activation energy of first falling step was 1,900 cal/gmol, while for second falling step the values showed 2,500 cal/gmol.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.156-156
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• 2003

유럽의 여러나라들의 경우 토양내 중금속의 허용치는 그 사용 목적에 따라 다르게 책정되고 있으며 1999년에 제정된 독일의 새로운 토양보전법에서도 토양의 사용목적별로 중금속 허용치를 달리 정하고 있다. 여기서 중금속 농도를 측정하기 위한 방법으로는 DIN(독일 공업규격)에서 정하고 있는 증류수추출법과 왕수추출법이 채택되고 있다. 그러나 이 2가지 방법들은 토양의 중금속분석에서 가장 큰 factor로 작용하는 것이 pH인데 반하여 pH가 7인 증류수와 pH가 0인 왕수를 사용함으로써 실제환경에 적용하기에는 많은 무리수를 내포하고 있으며 차츰 적당치 못한 것으로 판명되고 있다. 실질적인 중금속의 유해성 여부는 토양에서의 그 중금속의 용해도와 유동성으로 결정되는데 강한 산성비가 내린다고 가정하였을 때 비의 pH가 약 4 정도이고 이 경우 식물 뿌리 부분의 pH는 5 정도가 되므로 pH를 기준으로 할 때 잠재적으로 유동가능한 중금속을 분석하는 데에는 pH 4.5 에서 EDTA 추출이 가장 적당하고 또한 이를 토대로 토양내 중금속 허용치를 정하는 것이 합리적이라고 하겠다. 그러나 EDTA는 pH 4에서 부분적으로 Proton과 결합되어 Metal Chelate로의 능력을 잃게 되고 또한 식물 뿌리의 중금속 흡착을 Simulation할 수 없어 불리한 점이 있다. 또한 EDTA는 분해기간이 길고 인체에 해롭다는 것이 알려지고 있어 점점 사용이 어려워지고 있다. 본 연구에서는 토양에 함유된 유동가능한 중금속농도분석을 보다 적절히 하기 위한 방법으로 EDTA와 같이 Carboxyl기가 결합된 고분자 자성체를 이용해 토양의 중금속을 분석하는 것을 제안하였고 분석을 위한 중금속 추출 시 토양시료와 증류수 그리고 고분자 자성체만을 사용하여 근본적으로 토양에서 유동 가능성이 있는 중금속만을 추출하였다. 분석실험은 토양의 Cd2+ 와 Pb2+를 대상으로 행하여졌으며, 여러 토양에서 추출 분석한 결과를 EDTA분석결과와 비교하였다. 실험결과, 중금속은 매우 신속하게 고분자 자성체와 결합하였고, 그 후 자성체를 외부 자장으로 모은 후 산으로 용해시키고, 결합된 중금속은 Graphite furnace AAS로 분석함으로써 빠르고 효율적으로 분석실험을 수행할 수 있음을 알 수 있었다. 한편, 실험에서 나타난 수치들을 비교 검토한 결과 토양 분석시 sandy soil에서는 자성체를 이용한 분석이 EDTA에 의한 방법보다 더 높은 추출도를 보인 반면, silt 함량이 많은 토양의 경우에서 EDTA분석에서 더 높은 중금속 추출도를 보였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.999-1003
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• 1992

Because of low noise and small size with huge capacity, a centrifugal fan is widely used for ventilation, air-conditioner and so on, which are very near to human life. Because of the complexity of its vibration and noise generation mechanics, most of researches on them are based on experimental methods. This study is to characterize the centrifugal fan noise and vibration. It is considered that noise is composed of the structural vibration noise and the air flow induced aerodynamic noise. To decouple the structural vibration noise the centrifugal fan is masked with an adhesive tape, such that air blowing is prohibited thus only the structural vibration noise is extracted. The noise level and characteristics in the frequency domain are verified and compared with those of total mixed one. This study shows some significant results that the structural vibration noise has relatively narrow band power spectrum compared with the total mixed one and has a strong periodicity. The sound level is lowered about 5dB by the removal of air flow with the masked fan for an air-conditioner used in this study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.73-84
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• 2003

A transient analysis on fuel temperatures in an aircraft was studied using the finite difference method. Numerical calculation was performed by an explicit method of modified Dufort-Frankel scheme. Among various missions, close air support mission was considered with 20% hot day ambient condition in subsonic region. The aircraft was assumed to be in turbulent flow. The fuel system model with additional fuel supplies and return concept was considered. As a result of this analysis, the fuel tank temperatures have increased with the increase of the additional fuel supplies. In contrast to tank temperatures, the fuel temperature at the engine inlet has decreased with the increase of additional fuel supplies except in some in-flight phases having high engine fuel flow. From this analysis, the fuel system with the additional fuel supplies and return concept has been shown to be an effective method to decrease the engine inlet fuel temperature. Also, it has been shown that fuel flow rate through fuel/oil heat exchanger is a key factor influencing fuel temperature.

• Journal of the Korean GEO-environmental Society
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• v.12 no.8
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• pp.39-50
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• 2011

Nowadays, H-piles are usually used as temporary retaining walls, and sometimes buried in the ground after construction. The purpose of this study is the development of flowable fill materials that are easy to fill holes of retaining wall structure and minimize friction during pulling out H-pile. The first test was performed to decide mix proportion that is reasonable for purpose, in the second test, direct shear test was performed to get pullout resistance between flowable fills material and H-pile, and one dimensional consolidation test was performed to analyze the compressibility. In the test result, it showed that flowable fill material mix proportion is 350-450% of water, 70-100% of cement and 70-100% of sand based on the bentonite weight.