• The Korean Journal of Mycology
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• v.31 no.2
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• pp.89-93
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• 2003

In order to select suitable bioreactor type inhibiting cell stress during submerged culture of Tricholoma matsutake mycelium, the growth characteristics and ergosterol contents were investigated using the external-loop type of air-lift bioreactor (ETAB), balloon type of air bubble bioreactor (BTBB) and column type of air bubble bioreactor (CTBB). Dry weights of the T. matsutake in the BTBB, ETAB and CTBB were 12 g, 11.4 g, and 9.5 g per 1 litter, respectively. BTBB, ETAB and CTBB reached stagnant phases 16, 20, and 24 days after cultivation, respectively, The BTBB was more suitable for liquid culture of T. matsutake mycelium compared to other bioreactors owing to much mycelia product and short culture period. The ergosterol contents produced by the mycelium in the bioreactors were in sequence of BTBB, CTBB, and ETAB at every growth phase. BTBB might affect the mycelium on producing the smallest size of pellets. BTBB and CTBB got the mycelium precipitated and coagulated under operation of bioreactor sparser, whereas ETAB shown no effect of above phenomenon. A renovated bioreactor combined between a balloon shape of BTBB and an external-loop of ETAB was developed to enhance the efficiency of culture technique.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.377-386
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• 2010

This study was conducted to find out the characteristics of the expanded road embankment constructed by the lightweight air-mixed soil (slurry density $10kN/m^3$) for a short-term without any ground improvement. Compression strength, capillary rise height of the lightweight air-mixed soil and settlement behavior of soft ground were studied. Compression strengths of the specimens sampled at the site after 1 and 5 months of construction were all satisfied the required strength 500 kPa. However, it was not convinced the homogeneity construction, because the values of strength were depending on the sampled location. Also, strength difference between laboratory and site specimens were found about 19%, and thus it should be considered for mixing design. Capillary rise reached about 20 cm for 70 hours because of a numerous tiny pores existed inside the lightweight air-mixed soil. Relationship between settlement and time of the soft ground placed underneath the expanded embankment was estimated by using the measured data and back analysis technique. The current average consolidation ratio and the final settlement after 120 months later were estimated about 32% and 4.5cm, respectively. This settlement is much less value than the allowable settlement 10cm for this structure.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.511-511
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• 2017

하천에서 홍수 예방 및 가뭄재해 방지를 목적으로 최근 4대강 살리기 사업이 수행되었다. 특히, 안정적인 용수공급 및 다양한 수재해 피해를 최소화하기위해 다기능보가 설치되었다. 설치된 보는 고정보와 가동보로 구분되며 평상시에는 고정보를 넘어가는 월류흐름이 발생하며 홍수 시에는 추가적으로 가동보를 개방하여 오리피스 흐름이 발생한다. 최근 기후변화로 인해 집중호우가 빈번히 발생하며 이는 보 주변에서 빠르고 복잡한 흐름을 유발하게 된다. 이러한 흐름특성은 보하류의 세굴문제뿐만 아니라 물받이와 바닥보호공의 안전성에 영향을 미칠 수 있다. 본 연구에서는 영상기법을 활용하여 도수가 발생하는 조건에서 고정보 하류의 물받이공 및 바닥보호공에 난류흐름특성 및 압력분포를 분석하였다. 길이 8.0 m, 폭 0.3 m를 갖는 개수로에서 실험을 수행하였으며 0.2 m 높이의 고정보는 상류경계로부터 3.0 m지점에 위치하였다. 보 하류부에서 유속성분은 비접촉식 유속측정 기법인 입자영상유속계(Particle Image velocimetry, PIV)와 기포흐름을 측정할 수 있는 기포영상유속계(Bubble Image velocimetry, BIV)를 적용하였다. 그러므로 기포 존재유무와 관계없이 보 하류부 구간에 대한 유속장 성분을 취득하였다. 도수흐름은 물받이공 및 바닥보호공 영역의 바닥면을 따라 빠른 유속을 갖는 제트류가 발생하고 수면과 바닥으로 강한 진동이 발생하여 불안정한 흐름이 야기된다. 바닥면에 작용하는 압력을 측정하기 위해 흐름방향을 따라 피에조미터를 설치하였고 압력수두 분포를 초고속카메라로 촬영하여 그 특성을 분석하였다. 실험을 결과를 통해 보 하류부에 영향을 미치는 인자를 도출하였으며 향후 보 설계기준에 반영할 수 있을 것으로 기대된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.317-317
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• 2023

수자원의 확보와 어류 서식 환경보전이라는 두 가지 측면은 수자원 이용이라는 목적하에 합의되기 어려운 문제를 가지고 있다. 점차적으로 수자원이 고갈되는 현시점에 효율적 물관리를 위해 최근에는 단절된 하천을 연결하기 위한 기술들이 개발되고 있으며, 이중 안정적인 물공급 시스템을 구축하기 위한 수중터널이 그러한 기술 중 하나이다. 수자원의 확보 측면에서는 의미가 있는 방법일 수 있으나 물리적으로 동떨어져 있던 서로 다른 환경을 연결하는 문제로 인한 부작용이 발생하는데 이중 외래어종 유입으로 인한 수중생물의 환경변화가 가장 큰 문제로 대두되고 있다. 이러한 문제를 방지하기 위해 어류의 이동을 차단하는 기술 또한 개발되고 있으며 그물망, 버블스크린, 빛, 소리를 이용한 다양한 방법을 통해 어류의 접근을 방지하고자 노력하고 있다. 본 연구에서는 이러한 차단시설 중 기포를 이용한 버블스크린과 관련하여 효율성을 높이기 위한 방법을 모색하고자 실제 버블의 상승속도에 영향을 미치는 여러 가지 불확실성 인자들에 대한 상관성과 인과관계를 검토하고자 하였다. 이를 위해서 외부적 원인에 대한 오차요소를 확인하고 결과값에 영향을 미치는 여러 가지 변수에 대하여 검토하고자 하는 실험연구를 수행하였다. 버블실험을 위한 수로는 길이 15m, 폭 1.5m 의 제원을 가지는 직선수로에서 수행하였으며, 버블 발생을 위한 튜브는 PVC 재질이며, 5cm 간격으로 1mm 직경을 갖는 파이프를 제작하여 활용하였다. 실험의 분석은 이미지를 이용한 방법을 사용하였으며 분석위치 및 버블사이즈 그리고 해석격자 크기에 대한 상관분석 및 회귀분석을 통해 각각 인자들과의 관계를 규명하고자 하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.81-88
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• 2014

An experimental study is performed to obtain an average heat transfer coefficient around the perimeter of a near horizontal tube. For the test a stainless steel tube of 50.8 mm diameter submerged in water at atmospheric pressure is used. Both subcooled and saturated pool boiling conditions are considered and the inclination angle of the tube is changed from the horizontal position to $9^{\circ}$ in steps of $3^{\circ}$. In saturated water, the local boiling heat transfer coefficient at the azimuthal angle of $90^{\circ}$ from the tube bottom can be regarded as the average of the coefficients regardless of the tube inclination angles. However, when the water is subcooled the location for the average heat transfer coefficient depends on the inclination angle and the heat flux. It is explained that the major mechanisms changing the heat transfer are closely related with the intensity of the liquid agitation and the generation of big size bubbles through bubble coalescence.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.130-137
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• 2019

In this study, a centrifugal seawater cooling pump was analyzed to investigate its cavitation behavior over different operating flow rates. 3D two-phase simulations were carried out with ANSYS-CFX commercial code. The $k-{\varepsilon}$ turbulence and Rayleigh-Plesset cavitation models were employed in the simulations. A head drop characteristics curves for three discharge rates was built based on numerical predictions. At higher flow rates, the impeller was more vulnerable to bubble cavitation. The 3 % head drop points of the pump working at 0.7Q, Q, and 1.3Q (Q: design flow rate) corresponded with NPSHa 1.21 m, 1.83 m, and 3.45 m, respectively. The volume of vapor bubbles was estimated and cavitation locations were anticipated to visualize the development of the cavity within the impeller. Moreover, the distribution of pressure coefficient and a blade loading chart are specifically presented, bringing out the harmful impacts of cavitation on the pump operation.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.427-434
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• 2003

This paper describes a new method of detecting rotor position in switched reluctance motor(SRM), Some strategies of position sensorless control methods for the motor include the measurement of phase current and applied pulse voltage in an unexcited phase. The principle of the estimation of a rotor position is based on the detection of inductance by pulse currents. This sensorless method is very simple to compute rotor position estimation and gives efficient control of drive system. Suggested method is verified by some experimental tests.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.413-418
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• 2016

Recently, a mega project such as Korea-China or Korea-Japan undersea tunnel project has been emerged for detail discussion and the interest in undersea tunnel is on the rise. More severe damage by train fire is expected in undersea tunnel comparing to ground tunnel and thus the study on more efficient fire extinguishing system, besides existing disaster prevention design is underway. To that end, a full-scale fire tests using CAF fire extinguishing system which has been developed by modifying traditional foam fire extinguishing system for fire suppression at rescue station in timely manner were conducted over 7 times. The test was conducted after setting the rescue station in virtual tunnel with a car of KTX. As a result of using compressed air foam directly to the fire source, 30 liter of Heptane combustibles was extinguished within 1 minutes. Applicability of compressed air foam to train fire at rescue station in undersea tunnel was has been proven and further study is considered required while changing the nozzle angle and location so as to achieve quick and easy extinguishing goal, making use of the advantage of CAF, as well as to reduce the fire water and chemicals required.

• Journal of Korea Foundry Society
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• v.42 no.6
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• pp.331-336
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• 2022

In this study, we investigated the casting designs for fuel tank valves for LPG automobiles. The valves we studied have two cavities inside the part. There is inevitable air entrapment inside the cavities. In order to reduce this kind of casting defect, we carried out computer simulations of molten metal flow during the diecasting process of the target products. The main process parameters were the ingate position, product direction, and injection velocity. We also examined the possible use of vacuum diecasting. The position of the air entrapment was almost identical for all the ingate positions and product directions. We found that the change of the injection velocity affects the position of the air entrapment. In case of vacuum diecasting, the position of the air entrapment was similar to the previous cases, but it is expected that the air entrapment will be highly reduced in a real situation due to the vacuumed space.

• Journal of Chest Surgery
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• v.30 no.12
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• pp.1225-1231
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• 1997

Spontaneous pneumothorax is the sudden collapse of a lung usually caused by air leakage from a subvisceral pleural blob. Responses to closed thoracostomy,thoracentesls and simple observation are usually prompt and effective. But in some cases, these are unsucceful and open thoracotomy is indicated. A clinical evaluation was performed on 242 cases(236 patients) of open thoracotomy in spontaneous pneumoth rax who were admitted and treated at department of Thoracic and Cardiovascular Surgery. Masan Samsung General Hospital during the past 9 years from January 1988 to December 1996. The results were as follows 1. The sex ratio was male predominance(M:F=11.7:1) 2. The most common age group were 2nd, 3rd decades(2nd=29.3%, 3rd=30.2%). 3. The most common chief complaints were chest pain and dyspnea(chest pain=41.7%. dryspnea= 36.8). 4. The etiologic factors of spontaneous pneumothorax were primary spontaneous pneumothorax(86.4%), tuberculosis(9.1%), COPD(3.7%) and pleuritis(0.8%). 5. The site of spontaneous pneumothorax was 52.1% in right, 45.4% in left and 2.5% in both. 6. The common indications of open thoracotomy were recurrence(44.2%), persistent air leakage(31.8%) and inadequate expansion(15.7%). 7. The operative procedures were bullectomy or mechanical pleurodesis through posterolateral thoracotomy or median sternotomy. 8. The most frequent location of bulla or blob were apical segme t oi RUL(35.1%) and apicoposterior segment of LUL(41.3 %). 9. The number of bulla or blob were mainly 1 to 5(88%), and there were no significant differences among operation indications. 10. The size of bulla or bleb were mainly below 5cm(81%)and small bulla($\leq$1cm) were predominant in recurrence group but large bulla(>5cm)were predominant in persistent air leakage and inadequate expansion group. 11. The pleural adhesion was seen in 54.5%.(Recurrence group 64.1%,Persistent air leakage group 51.9%,Inadequate expansion group 47.4%).