• Journal of the Korean GEO-environmental Society
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• v.12 no.4
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• pp.5-15
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• 2011

This study is conducted to find out the effect of vibration on cure and compressive strength of lightweight Air Trapped Soil(ATS). If ATS is used next to a structure existed, the effect of vibration problems may be occurred, because there exist many sources of vibration such as pile driving, blasting and use of construction machinery. For example, if a road is expanded to reduce traffic congestion, it is expected that ATS's quality may be decreased due to vibration generated by cars moving on the road. Especially, because ATS has many air bubbles and needs a time for curing, the effect of vibration is more serious than we expected. So far, the effect of vibration on concrete has been conducted, but the study of ATS has not been conducted in detail. Therefore, for evaluating the effect of vibration on ATS during cure proceeds, unconfined compression tests are conducted on the samples prepared with different variables including vibration velocity, time when vibrated and mixing ratio. The results clearly show the effect of vibration on the characteristics of ATS.

• KSBB Journal
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• v.5 no.1
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• pp.59-67
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• 1990

Enzymatic hydrolysis of insoluble cellulose was performed in a bubble column with tangential flow ulrafiltration membrane unit. The reactor was operated in a batch mode as well as semi-continuous and continuous with continuous removal of products through the tangential flow ultrafiltration membrane. The optimum superficial gas velocity was 1-3cm / sec so as to avoid bubble coalescence and enzyme denaturation. In continuous and selni-cotinuous process, the conversion was gradually increased but the total reduced sugar concentration was drcastically dereased with the dilution rate. It was concluded that the bubble column attaching tangential flow ultrafiltration membrane unit was effective on continuous hydrolysis of cellulose and recovery of enzyme.

• Geophysics and Geophysical Exploration
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• v.26 no.1
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• pp.8-17
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• 2023

Various sources, such as wind, waves, ships, and gas leaks from the seafloor, forms bubbles in the ocean. Underwater bubbles cause signal scattering, considerably affecting acoustic measurements. This characteristic of bubbles is used to block underwater noise by attenuating the intensity of the propagated signal. Recently, researchers have been studying the large-scale release of methane gas as bubble plumes from the seabed. Understanding the physical properties and distribution of bubble plumes is crucial for studying the relation between leaked methane gas and climate change. Therefore, a water tank experiment was conducted to estimate the distribution of bubble plumes using seismic imaging techniques and acoustic signals obtained from artificially generated bubbles using a bubble generator. Reverse time migration was applied to image the bubble plumes while the acquired acoustic envelope signal was used to effectively estimate bubble distribution. Imaging results were compared with optical camera images to verify the estimated bubble distribution. The water tank experiment confirmed that the proposed system could successfully image the distribution of bubble plumes using reverse time migration and the envelope signal. The experiment showed that the scattering signal of artificial bubble plumes can be used for seismic imaging.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.357-358
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• 2013

본 논문에서는 커패시턴스를 이용해 수액 내에 있는 공기방울을 검출하고 수액의 성분을 구분 할 수 있는 측정기의 원리에 대해 제시해보려 한다. 이 측정기의 원리는 유전율의 변화를 감지하여 수액의 종류를 판단하고, 수액 내부의 기포를 검출해내는 등 의원성 사고를 근본적으로 막는 데에 그 의의가 있다. 실험결과 본 연구에서 제작한 측정기로 수액에 따른 값의 차이를 확인하였고, 발생한 기포에 대한 출력 결과를 확인할 수 있었다. 본 연구를 통해 커패시턴스 차폐의 정도가 결과의 신뢰도 측면에 중요한 요인으로 작용하고 있음을 확인 할 수 있었다. 향후 외부 간섭에 따른 노이즈에 대한 추가적인 커패시턴스 차폐 연구가 필요한 것으로 판단된다.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.3
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• pp.416-427
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• 2024

The wake-homing underwater guided weapon that detects and tracks wake generated during voyage of a surface ship is impossible to avoid with the present acoustic deception torpedo defense system. Therefore, research on bubble-generating wake decoy is necessary to deceive wake-homing underwater guided weapon. Experiments in various environments are required to verify the effective operation method and performance of the wake decoy, but performance verification through underwater experiment is limited. In this paper, we develop a simulator for an torpedo defense system of surface ship, which is applied bubble-generating wake decoy, against acoustic, wake, and hybrid homing underwater guided weapon attack. The simulator includes surface ship model, acoustic decoy(static, mobile) model, bubble-generating wake decoy model, search and motion model of underwater guided weapon and so on. By integrating various models, MATLAB GUI simulator was developed. Through the simulation results for various environmental variables by this simulator, it is judged that effective operation method and performance verification of the bubble-generating wake decoy can be performed.

• Journal of the Korean Society of Radiology
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• v.6 no.5
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• pp.351-356
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• 2012

Ultrasonic cavitation is a physical phenomenon that generates and collapses microbubbles in media (mainly fluids) under conditions of strong ultrasonic irradiation. In this study, changes in the ultrasonic acoustic characteristics of bubble clouds in relation to ultrasonic irradiation were observed by the quantitative evaluation of cavitation yields. Concave-type single ultrasonic transducers with center frequencies of 500 kHz and 1.1 MHz were used to produce cavitation, and 2.25 MHz interference ultrasonic waves that would traverse any bubble clouds generated were used to analyze the cavitation. The parameters used for the evaluation of cavitation yields (changes in the center frequency, attenuation characteristics, and the propagation time of penetrating waves) were analyzed in relation to the cavitation-generating conditions (irradiation intensity, excitation signal, and center frequency). On the basis of these results, correlations between the changes in the center frequency and irradiation intensity were identified. Although the correlation coefficient was low, notable changes were observed in the center frequency under certain irradiation conditions. Attenuation trends in the interference ultrasonic waves showed high correlations with all the irradiation conditions, and it was noted that these trends were not affected by the forms of cavitation generated. No differences in the propagation time were observed among different irradiation conditions. These findings suggest that bubble yields can be quantitatively evaluated effectively by evaluating the diverse irradiation conditions and that such a quantitative evaluation could be used to study the basic cavitation phenomenon occurring in high-intensity ultrasonic wave treatment.

• Journal of the Korea Institute of Building Construction
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• v.16 no.1
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• pp.35-43
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• 2016

Concrete is a representative heterogeneous material and mechanical properties of concrete are influenced by various factors. Due to the fact that pores in concrete affect determining compressive strength of concrete, studies which deal with distribution and magnitudes of pores are very important. That way, studies using picture imaging have been emerged. Studies on mechanical performance evaluation of structural lightweight foamed concrete and FEM analysis based on picture image are inadequate because lightweight foamed concrete has been researched for only non-structural. Therefore, in this study, cement paste with foaming agent to evaluate mechanical performance is made, FEM analysis with picture image is conducted and young's modulus of experiment and analysis are compared. In this study, dosage of foaming agent is determined 7 level to check pore distribution and water-binder ratio is determined 20% to progress research about structural light weight foamed concrete. Weight of unit volume is minimum at 0.8% of foaming agent dosage. However, weight of unit volume is increased over 0.8% of foaming agent dosage because of interconnection with independent pores. For FEM analysis, cement paste is photographed to use image analyzer(HF-MA C01). Consequently, the fact that Young's Modulus of experiment and FEM analysis are same is drawn by using OOF(Object Oriented Finite elements).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.447-450
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• 2012

An analysis of chill-down process was performed for 30 tonf Turbopump-Gas generator coupled tests. The chill-down process must be fulfilled before liquid rocket engine test using cryogenic propellant. Cavitation, damage and/or combustion instability due to bubble of propellant must be eliminated by chill-down process in a test specimen, especially cryogenic pump. The analysis of test data obtained by 30 tonf TP-GG coupled tests was performed in order to be based on the test process of KSLV-II liquid propellant rocket engine which will be developed. To macroscopically understand the process of chill-down from the viewpoint of test procedure the temperatures of important part and total time of chill-down process were analyzed.

• Korean Journal of Plant Tissue Culture
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• v.21 no.2
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• pp.77-84
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• 1994

To assess the feasibility of anthocyanin production in cell cultures of Euphorbia splendens Bojer the role of sucrose in pigment production was investigated and pilot scale cultures were attempted to establish mass production system. And also, several instrumental analyses were conducted to identify the pigment extracted from cultured rolls. Anthocyanin production was promoted prominently with concenetrations of sucrose ranging from 3% to 9% while cell growth was maximized at 3% of sucrose . This suggested that high osmolarity of sucrose enhance pigment production. When cells were cultured in two types of bioreactor better cell growth was achieved with draft-type air lift bioreactor than impeller type bioreactor and the pigment productivity was reached to 2.2 mg/L/day. The major pigment extracted from cultured cells was characterized as cyanidin-3-glucoside.

• Journal of Chest Surgery
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• v.32 no.6
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• pp.556-560
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• 1999

Background: The cause of spontaneous pneumothorax is not yet but it is certain that intrathoracic air comes from ruptured bulla. Video-assisted thoracoscopic surgery(VATS) or open thoracotomy is recommended for thoracic incision in recurrent pneumothorax. However, recurrent rate after bullectomy with the VATS is very high compared to mini-thoracotomy, 3% to 20% and below 2%, respectively. Material and Method: This retrospective analysis was performed on 16 re-operated cases among 446 surgically treated pneumothorax of the 737 cases of spontaneous pneumothorax diagnosed at Yongdong Severance Hospital from Nov. 1992 to June 1997. Result: Among the 446 surgically-treated patients in 737 case of spontaneous pneumothorax, 16 patients underwent re-operation, showing a 3.5% re-operation rate. Male-to-female ratio was 15 to 1 and mean age at initial attack was 20.2 years(ranging from 15 to 50). Mean hospital stay was 6.34 days(ranging from 2 to 20 days) and mean chest tube indwelling period was 4.2 days(ranging from 1-10 days). Median follow-up was 46 months(range 10-66 months). Three different surgical methods were applied : video-assisted thoracoscopic surgery(VAST) in 281 cases, of whom 2 underwent local anesthesia; subaxillary mini-thoracotomy in 159 cases and limited lateral thoracotomy in the remaining 6 cases. Three different re-operative surgical methods were applied ; video-assisted thoracoscopic surgery (VAST) in 6 cases, subaxillary mini-thoracotomy in 9 cases, and limited lateral thoracotomy in the remaining 1 case. The underlying etiological factors of the recurrent pneumothorax after bullectomy were o erlooking type(9) and new growing type(7). Mean recurrent period from previous operation was 1 month for overlooking type and 18 months for new growing type. Conclusion: The underlying etiological factors of recurrent pneumothorax lead to re-operation were new-growing and over-looking type. We need additional treatments besides resecting blebs of prevent the recurrence rate and more gentle handling with forceps due to less damage to the pleura.