• 한국음향학회지
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• 제15권4호
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• pp.32-35
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• 1996

0.4~1.6kJ의 비교적 낮은 전기에너지를 갖는 수중 전기방전 시스템으로부터 발생하는 음파의 파형을 깊이별, 거리별로 관측하였다. 파형의 특성은 이미 보고된 에너지와 수심 의존도를 그대로 유지하고 있으나, 다른 두가지 특징적인 현상들이 관측되었다. 첫째는 내파에 의한 1차 bubble 펄스들의 피크 음압이 초기 충격파의 것보다 높게 관측되었는데, 이것은 10kJ 이상의 고에너지 방전시스템에서만 뚜렷하게 나타나던 현상이다. 둘째는 음향에너지 변환효율이 통상 5kJ에서 0.02, 1kJ에서 0.01로 저에너지대에서 그효율이 감소하는 경향을 보인다고 보고되었으나 1kJ의 부근에서는 0.01로 그 효율이 다시 일정하게 유지되고 있음이 확인되었다.

• KIEAE Journal
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• 제10권5호
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• pp.115-121
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• 2010

Lime was the solidifier mostly used at the fields of construction and civil works in the past. however, the development of Portland cement remarkably reduced the use of it. Recently as the concernment on circumstances gets higher, lime wined attention again as an eco-friendly material and was used at earth-using construction. This study examined the physical and chemical capacity of lime complexes with lime capacity improved, and performed fundamental study on the way to concretize by mixing it with earth. As a result, lime complex pressure strength was lower than cement pressure strength but it showed the possibility that its strength was improved by W/B control. The measurement of XRD after paste formation confirmed a compound generated by the reaction of Ca2+ion and Si, Al, and Fe from pozzolan reaction. A earth wall experiment by using lime complexes and earth showed that the higher, WB or the lower the quantity of unit combined materials, the lower the pressure strength was. The maximum pressure strength was maximum 11MPa when the quantity of unit combined materials was 450. It is because the composed earth particles had a high content of micro powder less than silt, so a lot of combination are demanded to secure fluidity. As a result of peptization experiment, after hardening, the material was not dissolved, which informed of the possibility of use as an outer subsidiary material. If the material is hardened by mold formation method, natural hardening crack appears. Cast expresses smart surface quality and enables to design for multiple purpose. The result shows the possibility of construction of low-story structures by using earth wall made of lime complexes and earth.

• 대한화학회지
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• 제61권3호
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• pp.112-121
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• 2017

본 연구는 수압 공식을 이용한 설명 대신, 밀도와 중력의 개념을 연결한 설명이 뜨거나 가라앉는 현상에 대한 학생들의 대안 개념에 어떠한 영향을 미치는가를 알아보고자 하였다. 연구 대상은 강원도에 위치한 한 고등학교 2학년 4개반, 140명의 학생들이었으며, 이들을 실험집단과 비교집단의 두 집단으로 나누었다. 실험집단에는 밀도와 중력 개념을 연계한 설명을 도입한 수업을, 비교집단은 교과서에 제시된 수압 공식을 이용한 설명을 도입한 수업을 각각 실시하였다. 사전검사 결과를 공변수로 하여 공변량분석(ANCOVA)을 한 결과, 물질의 특성과 관련된 3 문항 중 2개 문항은 두 집단 간 차이가 통계적으로 유의하지 않았으나, 1개 문항은 수업의 작은 효과크기(Hedges' g=0.327)를 보였다. 그리고 대안개념 변화 추이에서도 두 집단 사이에 유의미한 차이가 없었다. 반면, 물과 물체와의 상대적 무게 관계와 관련된 문항에서는 3개 문항 모두 두 집단 간 차이가 통계적으로 유의미한 효과크기(0.286~0.502)를 나타내었다. 뿐만 아니라 사후에 실험집단의 압력과 관련된 대안개념의 빈도수가 비교집단에 비해 상당히 감소하였다. 따라서 이 연구에서 제안한 무게와 밀도를 연계한 설명 방식은 뜨고 가라앉는 현상에 대한 학생들의 대안개념을 제거하고 과학적 개념을 형성하는데 효과적임을 알 수 있다.

• 한국산업융합학회 논문집
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• 제19권4호
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• pp.185-192
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• 2016

Low operational cost and high efficiency is absolute requirements in the mass production of the ship engine. Increasing the performance of the fuel injection system in the diesel engine is one kind of solution to improve the efficiency. Modern diesel engines are using electronic control module as the main controller in the fuel injection control system, however the mechanical system still involved in the modern control system. In modern ship engine, a control valve was used in injection fuel to regulate the flow of the fuel. High pressure and friction are intensively occur within this part, therefore high wear resist and low friction coefficient material including fine lubricating are needed. This study is to figure out the wear resist material and proper lubricant in the control valve fuel injection. The experiment has been tested using pin on disk in several treatments those are used various lubricants and non-lubricant condition. Two kinds of lubricant were used in this experiment such as INDERIN AW-32 and paraffin oil. INDERIN AW-32 has a better result compared to non-lubricant condition, which are 20% performance increases than non-lubricant condition. SCM 440 was providing small friction coefficient in the lower velocity. The friction coefficient was constantly maintains at 0.1 m/s of velocity or above respectively with the increment of the loads. Using INDERIN AW-32 and paraffin oil the lowest friction coefficient occurred at the lower load, and increases side by side with the increment of loads.

• 생물환경조절학회지
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• 제16권3호
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• pp.174-179
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• 2007

참외 발효과 발생에 영향을 미치는 증산과 관련된 몇 가지 요인을 검토한 결과는 다음과 같다. 참외의 증산율은 지온이 높고 토양수분 함량이 많을수록 높았으며, 광도가 약하여 온도가 낮을 경우 증산율과 기공 전도도가 낮아졌고, 저온 다습한 기상조건에 의한 증산의 억제는 식물체와 대기사이의 증기압기울기가 낮아지는 것으로 생각된다. 발효과 발생은 과실의 비대가 느린 착색기 이후에 토양수분이 -10 kPa로 많고, 저온 다습하여 참외와 대기 사이에 증기압기울기가 낮게 형성되어 증산이 억제될 때 발생하였다. 따라서 참외의 발효과 발생은 착색기 이후 참외의 과실 비대가 지연되는 반면 지온이 높아 뿌리로부터 지상부로 수분의 공급이 원활하고, 저온 다습한 기상조건하에 수분의 증산이 억제되어 수분이 태좌부로 유입되면 발효과가 발생되는 것으로 생각된다.

• 한국약용작물학회지
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• 제18권3호
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• pp.157-167
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• 2010

We investigated a method to improve anticancer activities of Acer mono wood extracts by ultra high pressure extraction process. The A. mono was extracted by water at $40^{\circ}C$ and 300 MPa for 15 min (High Pressure Extraction, HPE). The extraction yield by ultra high pressure extraction process was 5.42%. The cytotoxicity on human normal lung cell (HEL299) of the extracts from HPE showed 21.54% lower than that from conventional water extraction at $100^{\circ}C$ in adding the maximum concentration of 1.0 mg/$m{\ell}$. Ultra high pressure extracts process for 15 minutes extracts (HPE15) showed more potent scavenging effect than the control, BHA. On SOD-like test, the HPE15 showed highest activity as 32.4% at 1.0 mg/$m{\ell}$ concentration. Human stomach adenocarcinoma, liver adenocarcinoma, breast adenocarcinoma and lung adenocarcinoma cell growth were inhibited up to about 67~79%, in adding 1.0 mg/$m{\ell}$ of extracts from HPE. HPE was 20~25% higher than conventional water extraction. It was interesting that, among several cancer cell lines (stomach adenocarcinoma, liver adenocarcinoma), the growth of digestive related cancer cells were most effectively inhibited as about 75~79%. On in vivo experiment using ICR mice, the variation of body weight of mice group treated A. mono wood extracts from HPE of 100 mg/kg/day concentration was very lower than control and other group. The survival times of group treated this extracts was 61.96% longer than that of the control group and this extracts showed the lower tumor weight, which were 10.49 g than positive control as 16.17 g. Based on these results, we could tell that the HPE wood extracts of A. mono had higher anticancer activity than conventional water extraction. The results of HPE showed obvious advantages in higher efficiency, shorter extraction time, at lower energy costs.

• International Journal of Fluid Machinery and Systems
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• 제4권4호
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• pp.360-366
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• 2011

Thin circular-arc blade is often used as a guide vane, a deflecting vane, or a rotating blade of low pressure axial-flow turbomachine because of its easy manufacture. Ordinary design of the blade elements of these machines is done by use of the carpet diagrams for a cascade of circular-arc blades. However, the application of the carpet diagrams is limited to relatively low cambered blade operating under optimum inlet flow conditions. In order to extend the applicable range, additional design data is necessary. Computational fluid dynamics (CFD) is a promising method to get these data. In this paper, two-dimensonal cascade performances of circular-arc blade are widely analyzed with CFD. The results have been compared with the results of experiment and potential theory, and useful information has been obtained. Turning angle and total pressure loss coefficients are satisfactorily predicted for lowly cambered blade. For high camber angle of $67^{\circ}$, the CFD results agree with experiment for the angle of attack less than that for shockless inlet condition.

• 한국수소및신에너지학회논문집
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• 제16권2호
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• pp.180-190
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• 2005

The PSA cycle was performed for the separation of binary gas mixture $H_2/Ar$ (80%/20%) using the six-step two-bed process. Adsorption equilibrium contains a LRC model for equilibrium adsorption isotherms and a LDF model for mass transfer. Aspen ADSIM, simulator was applied to predict the separation performance. The effect of cycle parameters such as feed rate, adsorption pressure and P/F ratio on the separation of hydrogen has been studied in experiment and simulation. In the results, maximize the recovery of hydrogen as a high purity was 13LPM feed flowrate, 120sec adsorption time, 11atm adsorption pressure and 0.1 P/F ratio in a cyclic steady-state come out since 10th cycle.

• 소성∙가공
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• 제28권1호
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• pp.15-20
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• 2019

The superplastic forming/diffusion bonding process has been developed to fabricate a core frame structure with joint nodes out of tubes, for the development of a titanium high performance bicycle. The hydroforming process has been applied for bulging of a tube in the superplastic condition before, and during the diffusion bonding process. In this experiment, a commercial Ti-3Al-2.5V tube was selected as raw material for the study. The forming experiment has been performed using a servo-hydraulic press with a capacity of 200 ton. Next, nitrogen gas was used to acquire necessary pressure for the bulging and bonding of the tubes to fabricate the joint nodes. The pertinent processing temperature was $870^{\circ}C$ for the superplastic hydroforming/diffusion bonding (SHF/DB) process, using the Ti-3Al-2.5V tube. The bonding quality and the progress of bulging and diffusion bonding have been observed by the investigation of the joining interfaces at the cross section of the joint structure. The control of the nitrogen pressure throughout the SHF/DB process, was an important factor to avoid any significant defects in the joint structure. The whole progress stage of the diffusion bonding could be observed at a joint interface. A core structure with 5 joint nodes to manufacture a titanium bicycle could be obtained in a SHF/DB process.

• 한국기계가공학회지
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• 제20권8호
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• pp.74-79
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• 2021

This study focuses on designing a filter case using a water pump for application in eDNA filtering systems. Filter cases, channel type and net type were designed based on the flow field and made using a 3D printer for metal. Flow analysis was conducted for each filter case, and the results were consistent with the pressure experiment results. Furthermore, the water sampling performance test showed that the channel-type filter case exhibited a high flow rate and low pressure through the filter. The eDNA extraction experiment showed that the channel type exhibited improved capture ability compared to the net type.