• 항공우주기술
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• 제6권2호
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• pp.126-133
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• 2007

유공압 설비 설계에 있어서 중요한 요소인 유공압 구성품의 압력손실계수를 측정하기 위한 시험 설비의 설계, 제작 그리고 일련의 시험 내용 및 PS(Pyrostarter, 고체추진제 가스발생기) 연소시험 결과와의 비교 분석 내용을 정리한다. 최종적으로 blow-down 시스템을 이용하여 간단한 시험 설비를 구축하였으며 PS에 사용되는 필터들의 압력손실계수를 측정하였다. 시험 설비를 통해 PS의 CQSF 압력손실계수 K를 획득하였으며, PS 연소시험 결과와의 비교를 통해 2% 내외의 높은 신뢰도의 압력 손실 예측이 가능한 것으로 나타났다. 한편 PS 필터의 K와 PS 연소압과의 관계를 유도하여 PS 연소시험 결과와 일치함을 보였으며, 향후 PS 개발에서 필터의 K를 활용하여 PS 추진제의 연소속도를 향상시킬 수 있을 것으로 기대된다.

• 한국화재소방학회논문지
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• 제24권3호
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• pp.58-65
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• 2010

최근 들어 발생하고 있는 화재 사고는 재산 피해 및 인명 피해 측면에서 점점 대형화 되어가고 있는 추세지만, 이를 효과적으로 예방하고 조치할 수 있는 종합적인 차원의 화재안전기술 개발을 필요로 한다. 특히, 초고층 빌딩이 우후죽순으로 들어서고 있는 지금, 새로운 패러다임의 진보된 화재안전기술의 필요성이 대두되고 있다. 따라서, 본 논문에서는 세 가지 종류의 산소소모법 칼로리미터인 bench scale calorimeter(cone calorimeter/ISO 5660/Avg.500Kw), Medium scale calorimeter(Room corner tester, Single burning Item/ISO 9750, EN 13823/Avg.3MW), and large scale calorimeter(Industry calorimeter/Avg. 10MW)에 의한 열방출율 측정과 이때 발생된 연기발생량과의 상관관계를 찾고자 한다. 이렇게 찾아진 열방출율과 연기발생량과의 상관관계를 활용하여 새로운 개념의 연기감지기를 개발하여 화재 사고 시 인명피해 및 재산피해를 최소화 하고 궁극적으로 이러한 이론을 바탕으로 초고층화 되고 있는 건축물에 새로운 개념의 화재경보 및 피난 시스템의 개발 및 적용이 가능하리라 예상된다.

• 한국정보통신학회논문지
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• 제18권7호
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• pp.1757-1763
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• 2014

채널당 속도 10 Gb/s 인 8개의 NRZ 포맷을 가지는 파장다중화 광신호를 장거리 전송 링크에 적용시켜 720 km 를 전송하였다. 반복되는 링크구간은 80 km 단일모드광섬유, 완전 구간보상을 위한 분산보상광섬유, 어븀첨가 광섬유 증폭기들로 구성되었다. 전송 링크 구현을 위해 반복루프 실험 방법이 적용되었고 반복루프의 구조에 따른 신호 성능 차이가 조사되었다. 파장별 이득 평탄화는 고가의 평탄화 필터를 사용하지 않고 증폭기들의 이득 기울기를 서로 역으로 배치하여 구현하였다. 720 km 전송 후에 평균적인 OSNR 값은 22 dB 였고, 채널별로 OSNR 값의 최고 편차는 9.7 dB 였다. 이득 편차의 주원인은 Hole burning 효과에 의한 것임을 광스펙트럼 조사를 통해 확인했으며, 이득평탄화 필터 없이도 560 km 전송이 가능함을 확인했다.

• 한국추진공학회지
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• 제17권2호
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• pp.39-45
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• 2013

추진제를 고에너지 금속 분말 연소시스템에 점화원으로 적용을 위한 기초 연구로서 strand burner를 이용하여 HTPB/AP/Al, HTPE/AP/Al 추진제의 연소특성을 고찰하였다. 실험은 아르곤을 사용하여 ~300 psia 까지 가압하였으며, 2개의 석영창을 이용하여 가시화하였다. 추진제 점화를 위해서 10 W의 $CO_2$ 레이저를 사용하였으며, 연소 속도 측정은 초고속 카메라를 활용한 프레임 분석 기법 및 광다이오드를 이용한 연소시간 분석 기법을 적용하였다. 스펙트로메터를 이용하여 300 nm ~ 800 nm, 1500 nm ~ 5000 nm 의 방출 스펙트럼을 분석하여 추진제 연소반응 시 발생하는 화학종을 확인하였다.

• 대한기계학회논문집B
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• 제22권12호
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• pp.1691-1701
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• 1998

Fly ash produced in coal combustion is a fine-grained material consisting mostly of spherical, glassy, and porous particles. A study on the formation mechanism of the fly ash from coal particles in the pulverized coal power plant is investigated with a physical, morphological, and chemical characteristic analysis of fly ash collected from the Samchonpo power plant. This study may contribute to the data base of domestic fly ash, the improvement of combustion efficiency, fouling phenomena and ash collection in the electrostatic precipitator. The physical property of fly ash is determined using a particle counter for the measurement of ash size distribution. Morphological characteristic of fly ash is performed using a scanning electron micrograph. The chemical components of fly ash are determined using an inductively coupled plasma emission spectrometry(ICP). The distribution of fly ash size was bi-modal and ranged from 12 to $19{\mu}m$ in mass median diameter. Exposure conditions of flue gas temperature and duration within the combustion zone of the boiler played an important role on the morphological properties of the fly ash such as shape, particle size and chemical components. The evolution of ash formation during pulverized coal combustion has revealed three major mechanisms by large particle formation due to break-up process, gas to particle conversion and growth by coagulation and agglomeration.

• Advances in materials Research
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• 제4권2호
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• pp.97-111
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• 2015

Polypropylene short fiber (PP)-clay particulate-epoxy ternary composites were prepared by reinforcing PP short fiber and clay particles in the range of 0.1 phr to 0.7 phr into epoxy resin. Prepared hybrid composites were characterized for their mechanical, thermal and flame retardant properties. The obtained results indicated an increase in impact resistance, tensile strength, flexural strength and Young's modulus to an extent (up to 0.5 phr clay and 0.5 phr PP short fiber) and then decreases as the reinforcing phases are further increased. The thermal stability of these materials are found to increase up to 0.2 phr clay and 0.2 phr PP addition, beyond which it is decreased. Addition of clay is found to have the negative effect on epoxy-PP short fiber composites, which is evident from the comparison of mechanical and thermal properties of epoxy-0.5 phr PP short fiber composite and epoxy-0.5 phr PP short fiber-0.5 phr clay composite hybrid. UL-94 tests conducted on the composite hybrids have showed a reduction in the burning rate. Morphological observations indicated a greater fiber pull with the addition of clay. The performed tests in the present study indicated that materials under investigation have promising applications in construction, agriculture and decorative purposes.

• 한국연소학회지
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• 제19권3호
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• pp.44-52
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• 2014

Solid oxide fuel cell(SOFC) makes electric power using hydrogen or reformed from methane and emits high temperature products that contain flammable species like hydrogen, carbon monoxide and methane which varies with operation condition. SOFC/gas turbine integrated system which uses thermal and chemical energy of the discharges is more efficient than SOFC itself. Burning character of the SOFC products will affect the efficiency and stability of the system. Experiments were conducted to know the characteristics of the flame for two typical composition of SOFC products, i.e. start-up and steady state composition. When coflowing air temperature was higher than $600^{\circ}C$, auto-ignitin occurred for both fuels. Though start-up fuel has higher contents of hydrogen, it makes longer flame than steady state composition. It was inferred that the amount of oxidizer necessary to burn makes this phenomenon. Steady state composition fuel was unstable since it contains lots of water. Nozzle that had 6 holes, distance between each hole was 16.7 times of hole diameter, improved the stability of the flame.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.167-173
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• 2005

Thermal regeneration means burning-off and cleaning-up the particulate matters piled up in DPF(diesel particulate filter), and it requires both high temperature $(550\~600^{\circ}C)$ and appropriate concentration of oxygen at DPF entrance. However, it is not easy to satisfy such conditions because of the low temperature window of the HSDI(high speed direct injection) diesel engine(approximately $200\~350^{\circ}C$ at cycle). Therefore, this study is focused on the method to raise temperature using the trade-off relation between temperature, oxygen concentration, and the influence of many parameters of common rail injection system including post injection. After performing an optimal mapping of the common rail parameters for regeneration mode, the actual cleaning process during regeneration mode is investigated and evaluated the availability of the regeneration mode mapping through regenerating soot trapped in the DPF.

• International Journal of Contents
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• 제14권4호
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• pp.70-75
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• 2018

The purpose of this corpus-based study was to find 4-word lexical bundles in computer science research articles. As the demand for research articles (RAs) for international publication increases, the need for acquiring field-specific writing conventions for this academic genre has become a burning issue. Particularly, one area of burgeoning interest in the examination of rhetorical structures and linguistic features of RAs is the use of lexical bundles, the indispensable building blocks that make up an academic discourse. To illustrate, different academic discourses rely on distinctive repertoires of lexical bundles. Because lexical bundles are often acquired as a whole, the recurring multi-word sequences can be retrieved automatically to make written discourse more fluent and natural. Therefore, the proper use of rhetorical devices specific to a particular discipline can be a vital indicator of success within the discourse communities. Hence, to identify linguistic features that make up specific registers, this corpus-based study examines the types and usage frequency of lexical bundles in the discipline of CS, one of the most in-demand fields world over. Given that lexical bundles are empirically-derived formulaic multi-word units, identifying core lexical bundles used in RAs, they may provide insights into the specificity of particular CS text types. This will in turn provide empirical evidence of register specificity and technicality within the academic discourse of computer science. As in the results, pedagogical implications and suggestions for future research are discussed.

• Journal of Dental Anesthesia and Pain Medicine
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• 제22권5호
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• pp.323-338
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• 2022

Burning mouth syndrome (BMS) is a chronic oral disorder of unknown etiology which presents therapeutic challenges. Alpha-lipoic acid (ALA) has been studied as a potential treatment for BMS. The objective of this systematic review and meta-analysis was to evaluate the effectiveness of ALA compared to that of placebo or other interventions in individuals with BMS. Randomized controlled trials (RCT) using ALA to treat BMS were identified from MEDLINE, Cochrane Library, EMBASE, and Web of Science up to February 3, 2021. The assessment of the risk of bias in the included studies was based on the Cochrane guidelines. The primary outcome evaluated was the visual analog scale (VAS) pain intensity. ALA was compared with placebo, clonazepam, gabapentin, pregabalin, ALA plus gabapentin, capsaicin, Biotène^®, and laser therapy. Altogether, 137 records were scanned for inclusion/exclusion, and nine RCTs (two unclear and seven at high risk of bias) were included in the qualitative and quantitative analyses, with a total of 594 patients with BMS included in this review. All studies reported an improvement in VAS pain scores ranging from -0.72 to -2.77. Meta-analysis results showed a non-significant reduction in pain intensity for ALA (P = 0.616) compared to that of placebo on a VAS of 0-10. Patients taking ALA were 1.923 times more likely to show an improvement in self-reported BMS symptoms (P = 0.031) than those in the placebo group. Clonazepam and pregabalin showed a significant VAS pain reduction of 4.08 and 4.68 (P < 0.001), respectively, compared to that with ALA. Although ALA intervention provided a non-significant improvement in the pain score and was more likely to produce a reduction in BMS symptoms, the evidence was of low quality. Further research is needed to establish clear guidelines for the use of ALA for BMS treatment.