• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.235-240
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• 2010

Transpiration cooling is the most effective cooling technique for liquid rocket and air-breathing engines operating in aggressive environments with higher pressures and temperatures. Combustor liners and turbine vanes are cooled by the coolant(air or fuel) passing through their porous walls and also the exit coolant acting as an insulating film. However, its practical implementation has been hampered by the limitations of available porous materials. The search for more practical methods of increasing the internal heat transfer within the walls has led to the development of multi-laminate porous structures, such as Lamilloy$^{(R)}$ and Transply$^{(R)}$. This paper reviews recent research activities of transpiration cooling for the propulsions of liquid rocket, gas turbine, and scramjet.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.275-282
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• 2010

The effect of swirl flow on NOx in a nonpremixed turbulent hydrogen jet with coaxial air was studied. The swirl vane angle was varied from $30^{\circ}$ to $90^{\circ}$. The fuel jet air velocity and coaxial air velocity were varied in an attached flame region as $u_F=85{\sim}160m/s$ and $u_A=7{\sim}14m/s$. The objective of the current study was to analyze the characteristics of nitrous oxide emission in a swirl flow and to propose a new parameter for EINOx scaling. The experimental results show that EINOx decreases with the swirl vane angle and increased with flame length. Further, EINOx scaling factors can be determined by considering the effective diameter ($d_{F,eff}$) in a far field concept. The EINOx increased in proportion to the flame residence time (${\sim}{\tau_R}^{1/2.8}$) and the global strain rate (${\sim}{S_G}^{1/2.8}$).

• Explosives and Blasting
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• v.39 no.1
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• pp.1-9
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• 2021

As the national economic growth and the rapid increase in industrial structures are aging, the demand for removing steel structures is increasing, and research on improving the penetration performance of the linear shape charge explosives. In the study, numerical analyses were performed on the effect of the type of explosive used in the self-made shape charging container and the initiation method on the cutting performance of the steel plate and the effect on the shaped explosive installed close to it. ANSYS LS-DYNA, which can analyze the large deformation problem of materials due to explosion, was used, and an ALE(Arbitrary-Lagrange-Eulerian) model was applied that enables interlocking analysis of gases, liquids, and solid.

• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.595-605
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• 2023

With the escalating prevalence of modular construction projects, there is a concurrent surge in scholarly and industrial intrigue in this domain, leading to a broadened spectrum of its applications. Modular construction, inherently facilitated by controlled factory settings, boasts the capability to consistently deliver edifices of superior quality. To optimize this advantage, the judicious integration of quality assurance methodologies during the site-specific phases of lifting and assembly is non-negotiable. This research embarked on a survey directed at project stakeholders, aiming to gauge the perceived significance and efficaciousness of prevailing quality preservation and oversight protocols during the aforementioned site stages, subsequently employing the Importance-Performance Analysis(IPA) for data interpretation. The findings elucidated that, while a majority of quality assurance procedures were adeptly executed, perceptual disparities existed among stakeholders regarding certain aspects, prompting recommendations for enhancement. This investigative endeavor lays a foundation, aiding future studies in amplifying the quality assurance cognizance among professionals during modular construction's site-assembly phase.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.127-134
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• 2020

High supersonic aircraft are exposed to high temperature environments by aerodynamic heating during supersonic flight. Thermal protection system structures such as double-panel structures are used on the skin of the fuselage and wings to prevent the transfer of high heat into the interior of an aircraft. The thin-walled double-panel skin can be exposed to acoustic loads by supersonic aircraft's high power engine noise and jet flow noise, which can cause sonic fatigue damage. Therefore, it is necessary to examine the behavior of supersonic aircraft skin structure under thermal-acoustic load and to predict fatigue life. In this paper, we designed and fabricated thermal-acoustic test equipment to simulate thermal-acoustic load. Thermal-acoustic testing of the titanium specimen under thermal-acoustic load was performed. The analytical model was verified by comparing the thermal-acoustic test results with the finite element analysis results.

• Clean Technology
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• v.25 no.2
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• pp.161-167
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• 2019

Several types of reactors have been used during the past decade to perform fast pyrolysis of biomass. Among the developed fast pyrolysis reactors, fluidized bed reactors have been widely used in the fast pyrolysis process. In recent years, experimental studies have been conducted on the characteristics of biomass fast pyrolysis in a spouted bed reactor. The fluidization characteristics of a spouted bed reactor are influenced by particle properties, fluid jet velocity, and the structure of the core and annulus. The geometry of the spouted bed reactor is the main factor determining the structure of the core and annulus. Accordingly, to optimize the design of a spouted bed reactor, it is necessary to study the pyrolysis characteristics of biomass. However, no detailed investigations have been made of the fast pyrolysis characteristics of biomass in accordance with the geometry of the spouted bed reactor. In this study, fast pyrolysis experiments using Jatropha curcas L. seed shell cake were conducted in a conical spouted bed reactor to study the effects of reaction temperature and reactor cone angle on the product yield and pyrolysis oil quality. The highest energy yield of pyrolysis oil obtained was 63.9% with a reaction temperature of $450^{\circ}C$ and reactor cone angle of $44^{\circ}$. The results showed that the reaction temperature and reactor cone angle affected the quality of the pyrolysis oil.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.223.2-223.2
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• 2010

용융탄산염 연료전지(MCFC)는 $650^{\circ}C$에서 작동하는 고온형 연료전지 시스템이다. 이 시스템은 천연가스 등을 개질하여 생산된 수소를 바로 전기로 생산할 수 있는 시스템으로 열효율이 높으며, 현재 대체 발전시스템으로 각광을 받고 있다. MCFC는 개질방식에 따라 내부개질 방식과 외부개질 방식이 있다. 내부개질 방식은 수소를 생산하는 개질기가 스택내부에 장착된 형식으로 천연가스를 스택내부에서 개질하여 바로 전기를 생산하는 방식이다. 이 내부개질반응에 사용되는 촉매로는 알루미나에 담지된 니켈(Ni) 계열촉매이 주로 쓰이고 있다. 또한 내부개질촉매의 형태는 작은 원주형의 촉매형태로 성형되어 사용된다. 이 성형된 촉매의 크기가 바로 내부개질 스택의 크기를 결정하는 중요한 요소이다. 그래서 촉매의 크기는 되도록이면 작게 성형하는 것이 중요하다. 그러나 촉매의 크기가 너무 작으면 촉매를 성형하는데 큰 어려움이 생기게 된다. 본 연구에서는 니켈 촉매를 공침법이 아닌 균일용액침전법을 이용하여 제조하였으며, 이 촉매를 이용하여 지름이 약 2 mm 이하로 촉매를 압출성형하는 방법을 연구하였다. 먼저 요소(urea)를 이용한 균일용액침전법으로 촉매를 제조하였다. 최적의 촉매 합성조건을 살펴보기 위해서, 반응 온도를 80, 85, 90, 95, $100^{\circ}C$로 변화 시키면서 제조된 촉매의 특성을 살펴보았다. 그리고 촉매의 적절한 니켈 양을 알아보기 위해서 니켈의 양을 30, 40, 50, 60, 70 wt%로 변화 시켰으며, 조촉매로 사용되는 MgO 양을 5, 10, 15, 20 wt%로 변화 시켜서 제조된 촉매의 특성을 살펴보았다. 물성을 비교하기 위해서, X-선 회절분석(XRD) 및 TPR, 물리화학흡착을 하였다. 그 결과 침전반응온도가 $80^{\circ}C$에서 촉매가 가장 좋은 물성을 보였으며, 우수한 개질성능을 보였다. 그리고 촉매 활성물질인 니켈의 함량은 50 wt% 정도가 가장 적절한 함량이었으며, MgO의 함량이 15 wt%일 때 가장 우수한 물성과 개질 성능을 보여주었다. 이 촉매들은 공침법으로 제조된 상용촉매와 비교하였을 때, 보다 우수한 물성과 개질성능 보였다. 그래서 이 촉매를 균일침전법을 이용하여 대량으로 제조한 다음 압출성형 방법을 이용하여 촉매를 원주형으로 제조하였다. 먼저 제조된 촉매는 별도의 분쇄작업(볼밀 혹은 제트밀)을 거치지 않아도 입자사이즈가 약 $4{\mu}m$ 수준이 나오도록 촉매 제조조건을 조절 하였다. 그리고 소량의 Methyl cellulose(MC) 바이더와 물만 사용하여 촉매를 혼합한 다음 스크류 압출기를 이용하여 촉매를 성형하였다. 이 촉매는 지름이 약 2 mm 이하로 제조할 수 있었으며, 기계적 강도는 타정기로 성형한 상용촉매보다 우수하였다. 그리고 촉매 성능 또한 상용촉매와 비교하였을 때, 우수한 성능 보였다. MCFC용 내부개질 촉매로 균일용액침전법을 사용한 촉매가 적합하다고 판단되며, 압출성형에도 적합하다고 판단되었다.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.424-431
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• 2018

Stormwater runoff containing considerable amounts of pollutants such as particulates, organics, nutrients, and heavy metals contaminate natural bodies of water. At present, best management practices (BMP) intended to reduce the volume and treat pollutants from stormwater runoff were devised to serve as cost-effective measures of stormwater management. However, improper design and lack of proper maintenance can lead to degradation of the facility, making it unable to perform its intended function. This study evaluated an infiltration trench (IT) that went through a series of maintenance operations. 41 monitored rainfall events from 2009 to 2016 were used to evaluate the pollutant removal capabilities of the IT. Assessment of the water quality and hydrological data revealed that the inflow volume was the most relative factor affecting the unit pollutant loads (UPL) entering the facility. Seasonal variations also affected the pollutant removal capabilities of the IT. During the summer season, the increased rainfall depths and runoff volumes diminished the pollutant removal efficiency (RE) of the facility due to increased volumes that washed off larger pollutant loads and caused the IT to overflow. Moreover, the system also exhibited reduced pollutant RE for the winter season due to frozen media layers and chemical-related mechanisms impacted by the low winter temperature. Maintenance operations also posed considerable effects of the performance of the IT. During the first two years of operation, the IT exhibited a decrease in pollutant RE due to aging and lack of proper maintenance. However, some events also showed reduced pollutant RE succeeding the maintenance as a result of disturbed sediments that were not removed from the geotextile. Ultimately, the presented effects of maintenance operations in relation to the pollutant RE of the system may lead to the optimization of maintenance schedules and procedures for BMP of same structure.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.2
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• pp.115-125
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• 2022

The purpose of this study was to examine the effect of packaging on quality maintenance of paprika (Capsicum annuum L. cv. Nagano RZ) stored at three different temperatures. In Korea, paprika is stored and distributed under ambient conditions. To ensure the freshness maintenance, determining optimal storage temperature is necessary. Paprika were unpacked (control) or packed with polyamide film and stored at 5℃, 10℃ and 20℃ for 35 days. Quality characteristics such as weight loss and appearance were examined. Paprika packed with polyamide film showed less quality changes compared to unpacked paprika under all the storage temperatures. The commercial properties tended to decrease rapidly during storage at 20℃ regardless of packing. The degree of weight loss was significantly lower in packed paprika compared to unpacked paprika. It was found that soluble solids, pigments, hardness, etc. were complexly affected by storage temperature and film packaging. For paprika, the storage temperature of 5℃ or 10℃ was effective in maintaining freshness; paprika packed in polyamide film packing maintained greater freshness than unpacked paprika. Our results showed that, packaging is required to preserve the freshness and to improve the marketability of paprika in the domestic market. It seems that it is necessary to continuously search for an effective packaging method.

• The Korean Journal of Air & Space Law and Policy
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• v.30 no.2
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• pp.37-81
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• 2015

AirAsia QZ8501 Jet departed from Juanda International Airport in, Surabaya, Indonesia at 05:35 on Dec. 28, 2014 and was scheduled to arrive at Changi International Airport in Singapore at 08:30 the same day. The aircraft, an Airbus A320-200 crashed into the Java Sea on Dec. 28, 2014 carrying 162 passengers and crew off the coast of Indonesia's second largest city Surabaya on its way to Singapore. Indonesia's AirAsia jet carrying 162 people lost contact with ground control on Dec. 28, 2014. The aircraft's debris was found about 66 miles from the plane's last detected position. The 155 passengers and seven crew members aboard Flight QZ 8501, which vanished from radar 42 minutes after having departed Indonesia's second largest city of Surabaya bound for Singapore early Dec. 28, 2014. AirAsia QZ8501 had on board 137 adult passengers, 17 children and one infant, along with two pilots and five crew members in the aircraft, a majority of them Indonesian nationals. On board Flight QZ8501 were 155 Indonesian, three South Koreans, and one person each from Singapore, Malaysia and the UK. The Malaysia Airlines Flight 370 departed from Kuala Lumpur International Airport on March 8, 2014 at 00:41 local time and was scheduled to land at Beijing's Capital International Airport at 06:30 local time. Malaysia Airlines also marketed as China Southern Airlines Flight 748 (CZ748) through a code-share agreement, was a scheduled international passenger flight that disappeared on 8 March 2014 en route from Kuala Lumpur International Airport to Beijing's Capital International Airport (a distance of 2,743 miles: 4,414 km). The aircraft, a Boeing 777-200ER, last made contact with air traffic control less than an hour after takeoff. Operated by Malaysia Airlines (MAS), the aircraft carried 12 crew members and 227 passengers from 15 nations. There were 227 passengers, including 153 Chinese and 38 Malaysians, according to records. Nearly two-thirds of the passengers on Flight 370 were from China. On April 5, 2014 what could be the wreckage of the ill-fated Malaysia Airlines was found. What appeared to be the remnants of flight MH370 have been spotted drifting in a remote section of the Indian Ocean. Compensation for loss of life is vastly different between US. passengers and non-U.S. passengers. "If the claim is brought in the US. court, it's of significantly more value than if it's brought into any other court." Some victims and survivors of the Indonesian and Malaysia airline's air crash case would like to sue the lawsuit to the United States court in order to receive a larger compensation package for damage caused by an accident that occurred in the sea of Java sea and the Indian ocean and rather than taking it to the Indonesian or Malaysian court. Though each victim and survivor of the Indonesian and Malaysia airline's air crash case will receive an unconditional 113,100 Unit of Account (SDR) as an amount of compensation for damage from Indonesia's AirAsia and Malaysia Airlines in accordance with Article 21, 1 (absolute, strict, no-fault liability system) of the 1999 Montreal Convention. But if Indonesia AirAsia airlines and Malaysia Airlines cannot prove as to the following two points without fault based on Article 21, 2 (presumed faulty system) of the 1999 Montreal Convention, AirAsia of Indonesiaand Malaysia Airlines will be burdened the unlimited liability to the each victim and survivor of the Indonesian and Malaysia airline's air crash case such as (1) such damage was not due to the negligence or other wrongful act or omission of the air carrier or its servants or agents, or (2) such damage was solely due to the negligence or other wrongful act or omission of a third party. In this researcher's view for the aforementioned reasons, and under the laws of China, Indonesia, Malaysia and Korea the Chinese, Indonesian, Malaysia and Korean, some victims and survivors of the crash of the two flights are entitled to receive possibly from more than 113,100 SDR to 5 million US$ from the two airlines or from the Aviation Insurance Company based on decision of the American court. It could also be argued that it is reasonable and necessary to revise the clause referring to bodily injury to a clause mentioning personal injury based on Article 17 of the 1999 Montreal Convention so as to be included the mental injury and condolence in the near future.