• International Journal of Naval Architecture and Ocean Engineering
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• 제10권4호
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• pp.427-438
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• 2018

The reduction of $CO_2$ emissions has been a key target in the marine industry since the IMO's MEPC published its findings in 2009. Air lubrication method is one of the mature technologies for commercialization to reduce the frictional resistance and enhance fuel efficiency of ships. Air layer is formed by the coalescence of the injected air bubbles beyond a certain air flow rate. In this study, a model ship (${\lambda}=33.33$) of a 50,000 ton medium range tanker is equipped with an air lubrication system. The experiments were conducted in the 100 m long towing tank facility at the Pusan National University. By selecting optimal air injector configuration and distribution ratio between two injectors, the total resistance of model $R_{TM}$ was able to be reduced down to 18.1% in the model scale. Key issue was found to suppress the sideway leakage of injected air by appropriate injection parameters.

• Journal of Mechanical Science and Technology
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• 제14권12호
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• pp.1376-1385
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• 2000

This study investigates spray characteristics before and after wall impingingment of gasoline spray in suction air flow. For this study, a rectangular model intake port was made of acrylic glass, and suction air was generated by using the forced air blower contrariwise. The injector for this study was a pintle-type port gasoline injector in which an air-assist adaptor is installed to supply assisted air. A PDPA system was employed to simultaneously measure the size and velocity of droplets near the wall. Measured droplets are divided into "pre-impinging droplets"with positive normal velocity and "post-impinging droplets"were negative normal velocity for the suction flow. The velocities, size distributions and Sauter mean diameter(SMD) of pre-and post-impinging droplets for varions injection angles and air-assists are comparatively analyzed.

• 설비공학논문집
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• 제10권5호
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• pp.640-648
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• 1998

A numerical study has been conducted to investigate the effect of inflow supply air temperature and velocity on ventilation effectiveness in an underfloor air conditioning space. A low Reynolds number k-$\varepsilon$ model is implemented to calculate steady state turbulent velocity distributions. A step-down injection method is used to calculate local and room mean ages from transient concentrations based on the concept of the age of air. Results show that there is a significant effect of Archimedes number on ventilation effectiveness especially for cooling conditions. Reynolds number shows relatively minor effect on velocity distribution and ventilation effectiveness especially for isothermal and heating conditions. It can be concluded that underfloor air conditioning system provides good ventilation characteristics for cooling conditions because of temperature stratification in the space.

• 전기화학회지
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• 제8권4호
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• pp.149-154
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• 2005

연료전지의 안정성 여부를 장시간에 걸쳐 측정하기 위한 stability test logic을 LabVIEW 기반으로 설계하여 개선된 평가 system을 구성하였다. 일반적으로 사용되어온 logic에서 탈피하여 다량의 데이터 수집을 통한 평균값과 표준편차를 도출함으로서 연료전지 성능 데이터의 안정성 검증과 신뢰도를 대쪽 향상시킬 수 있었다. 가습의 새로운 개념인 water injection system방법을 제시하였으며 양측가습의 경우와 비교할 때 4% 이하의 미미한 성능 차이를 보였다. Water injection system의 경우 가습에 필요한 에너지를 최소화할 수 있으므로 전체적인 에너지효율을 높일 수 있고 system을 소형화할 수 있다는 장점이 있다. 영하의 조건에 연료전지를 방치한 후 실험을 수행한 경우 성능이 다소 감소하였으며, 이와 같은 현상은 MEA의 구조 및 제조사에 따라 영향을 받는 것으로 사료된다. 연료전지 운전 후 영하의 상태로 내려가기 전에 가스를 사용하여 내부의 물을 제거하는 방법에 대한 실험을 수행하였다. 저온방치 전 건조실험에서 전극면적이 $25cm^2$인 경우에 성능저하가 거의 없었다.

• 한국도로학회논문집
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• 제19권1호
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• pp.1-9
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• 2017

PURPOSES : The objective of this study is to develop an optimized method of mix design for rapid-set lightweight-formed mortar mix. To achieve this objective, the workability, setting time, and compressive strength of mixes under various conditions of mix design were evaluated. METHODS : The water-bonder ratio, fly-ash substitution ratio, and forming agent injection amount were selected as design variables in the study. The fluidity, setting time, density, and strength of the mortar mix were considered as major evaluation criteria of the mixture, and were subsequently utilized to evaluate the characteristics of the mortar mix under various conditions. RESULTS : The observations made from the mix design process are as follows: 1) the air content and fluidity increase as the forming agent ratio and forming agent ratio increase, respectively; 2) the maximum air content is approximately 20%; 3) the accelerating agent decreases the fluidity of the mortar mix by 15% on average; 4) the forming agent injection ratio and fly-ash substitution ratio yield significant effects on the initial and final set times of the mortar mix; 5) as the forming agent injection ratio and fly-ash substitution ratio increase, the compressive strength of the mortar mix decreases; and 6) the 28-day compressive strengths of the forming agent injection ratio and fly-ash substitution ratio yield the most significant effects. CONCLUSIONS : It is concluded that the governing design variables for the rapid-set lightweight-formed mortar mix are the forming agent injection ratio and fly-ash substitution ratio.

• 한국분무공학회지
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• 제19권3호
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• pp.115-122
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• 2014

As a demand for an automobile increases, air pollution and a problem of the energy resources come to the fore in the world. Consequently, governments of every country established ordinances for green-house gas reduction and improvement of air pollution problem. Especially, as international oil price increases, engine using clean energy are being developed competitively with alternative transportation energy sources development policy as the center. Bio ethanol, one of the renewable energy produced from biomass, gained spotlight for transportation energy sources. Studies are in progress to improve fuel supply methods and combustion methods which are key features, one of the engine technologies. DI(Direct Injection), which can reduce fuel consumption rate by injecting fuel directly into the cylinder, is being studied for Green-house gas reduction and fuel economy enhancement at SI(Spark Ignition). GDI(Galoine Direct Injection) has an advantage to meet the regulations for fuel efficiency and $CO_2$ emissions. However it produces increased number of ultrafine particles, that yet received attention in the existing port-injection system, and NOX. As fuel is injected into the cylinder with high-pressure, a proper injection strategy is required by characteristics of a fuel. Especially, when alcohol type fuel is considered. In this study, we tried to get a base data bio-ethanol mixture in GDI, and combustion for optimization. We set fuel mixture rate and fuel injection pressure as parameters and took a picture with a high speed camera after gasoline-ethanol mixture fuel was injected into a constant volume combustion chamber. We figured out spraying characteristic according to parameters. Also, we determine combustion characteristics by measuring emissions and analyzing combustion.

• International Journal of Oral Biology
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• 제42권1호
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• pp.1-8
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• 2017

In the present study, we investigated the role of peripheral ionotropic receptors in artemin-induced thermal hyperalgesia in the orofacial area. Male Sprague-Dawley rats weighting 230 to 280 g were used in the study. Under anesthesia, a polyethylene tube was implanted in the subcutaneous area of the vibrissa pad, which enabled drug-injection. After subcutaneous injection of artemin, changes in air-puff thresholds and head withdrawal latency time were evaluated. Subcutaneous injection of artemin (0.5 or $1{\mu}g$) produced significant thermal hyperalgesia in a dose-dependent manner. However, subcutaneous injection of artemin showed no effect on air-puff thresholds. IRTX ($4{\mu}g$), a TRPV1 receptor antagonist, D-AP5 (40 or $80{\mu}g$), an NMDA receptor antagonist, or NBQX (20 or $40{\mu}g$), an AMPA receptor antagonist, was injected subcutaneously 10 min prior to the artemin injection. Pretreatment with IRTX and D-AP5 significantly inhibited the artemin-induced thermal hyperalgesia. In contrast, pretreatment with both doses of NBQX showed no effect on artemin-induced thermal hyperalgesia. Moreover, pretreatment with H-89, a PKA inhibitor, and chelerythrine, a PKC inhibitor, decreased the artemin-induced thermal hyperalgesia. These results suggested that artemin-induced thermal hyperalgesia is mediated by the sensitized peripheral TRPV1 and NMDA receptor via activation of protein kinases.

• 터널과지하공간
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• 제21권4호
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• pp.297-306
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• 2011

본 연구에서는 지하 압축공기에너지 저장공동 주변 지하수 및 압축공기의 유체유동과 열전달 거동 해석을 위한 다상다성분 열유동 해석 결과를 이용하여 지하 저장공동의 열역학적 에너지수지 분석을 통한 에너지 효율평가를 실시하였다. 복공재인 콘크리트 라이닝이 충분한 기밀성능을 발휘할 경우, 주입 압축과정에서 저장공동으로부터 손실되는 에너지의 대부분은 콘크리트 라이닝 및 주변 암반에의 열전도를 통해 발생함을 확인하였다. 지하 압축공기에너지 저장공동의 에너지 효율은 압축공기 주입온도에 민감한 결과를 보였으며, 주입온도가 주변 암반의 온도에 근사할 경우, 손실된 에너지의 대부분이 토출 팽창과정에서 저장공동으로 유입 회수되는 결과를 보였다. 한편, 콘크리트 라이닝의 열전도특성이 저장공동의 에너지효율에 미치는 영향은 크지 않았다.

• 대한환경공학회지
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• 제35권12호
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• pp.929-936
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• 2013

DAF (Dissolved air flotation) 공정에서 공기포화장치(Saturator)와 미세기포 발생노즐은 미세기포 형성에 중요한 영향을 미치는 장치이다. 미세기포 발생 효율을 증가시키기 위해서는 공기포화장치 용기 안에서 기-액 접촉 효율을 증가시키고, 미세기포 발생노즐까지 이송 배관 내 압력을 일정하게 유지해 주어야 한다. 본 연구에서는 공기포화장치 내 순환수 유입 분사노즐과 포화수 이송 배관, 미세기포 발생노즐에 의한 미세기포 발생에 미치는 영향을 공기체적법과 기포 크기, 기포의 잔류시간 측정을 통해 비교해 보았다. 순환수 유입 분사노즐을 설치하고, 포화수의 이송 배관 내 압력손실이 발생하지 않는 구조, 미세기포 발생노즐의 통과유속을 증가시킬 경우 미세기포 발생 성능이 증가하였다.

• 한국동물생명공학회지
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• 제38권2호
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• pp.84-88
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• 2023

Because multiple ovulation embryo transfer (MOET) in cattle includes several benefits such as wide spreading of genetically superior offspring for long distance, this biotechnological method has been widely applied to Hanwoo. When the recipients are not stayed close after embryo recovery from donor, the embryos are moved to other farms via several vehicles (car, train, and airplane). However, air travel induces lesser oxygen level, increased vibration, lower air pressure, higher noise, and increased exposure of cosmic radiation to living things than ground level. It was still unknown that fresh embryos obtained from multiple ovulation of Hanwoo could maintain their fertility after being transported via air plane, the present case report introduced a clinical case of MOET in Hanwoo after shipping fresh embryos via air transportation. The donor was multi-ovulated via follicle-stimulating hormone series of injection, which was followed by a gonadotrophin-releasing hormone injection and artificial insemination twice. The embryos were recovered by the uterine flushing, packed in ministraws, transported to recipients for 6 h including 1 h air flight, and then transferred to the synchronized recipients. During pregnancy diagnosis of early gestation period, 5 of 7 recipients (71.4%) presented no heat signs and showed fetal sacs with fluid under transrectal ultrasonography. After normal gestation period, all recipients naturally delivered healthy calves (male n = 2 and female n = 3) without abortion, stillbirth, and premature birth. The present case report indicated that transportation of fresh embryos for MOET via domestic flight in Korea did not affect to their fertility.