• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1992년도 제2회 정기총회 및 추계학술 발표회 발표논문 초록
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• pp.12-12
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• 1992

This paper proposes an analysis method of Petri nets (PNs) using the relational algebra (RA). More specifically, we represent PNs in relations of the relational model. Based on such representation, we first develop an algorithms for analyzing properties of PNs, such as boundedness, conservation, coverability, reachability, and liveness. The advantage of this approach is as follows: First, the algorithms represented by RA can be easily converted to a query language such as SQL of the widely used, commercial relational database management systems (DBMSs). Second, we can alleviate the problem of state space explosion because relational DBMSs can handle large amounts of data efficiency. Finally, we can use the DBMS's query language to interpret the Petri nets and make simulation.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1997년도 특별강연 및 추계학술발표 개요집
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• pp.184-193
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• 1997

Aluminium and aluminium alloys have the high electrical and heat conductivity. It gives rise to difficulties for a choice of electrodes material for their contact electric welding. This paper describes the investigations performed to solve the above problem. The purpose of this investigation was to obtain dispersion-hardening alloys by the internal oxidation method, to optimize their contents and treatment modes, to produce electrodes of these alloys and to test them. The strengthing effect of alloys with oxide particles depends on their size stability at high temperatures. Despite of the fact, that oxides are the most stable of all the non-metallic phases their coagulation takes place. Based on the early results, we chose two types of alloys, first No. 1 Cu - 0,4%Al and second No. 2 Cu - 0,2%Be for production of electrodes. These alloys had not additional alloying elements. These alloys were prepared as 1 mm plates and flake-formed 200 m thick, and also No. 1 as a powder of size 100 mkm (received from Korea). The large samples for electrodes were produced by three methods : explosive welding method, dynamic one including the explosion compression of electrode blank and the quasi-dynamic method including the high-speed compression of dense briquest and the further hot extrusion of a rod.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1609-1611
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• 2007

The owner of underground metallic structures (gas pipeline, oil pipeline, water pipeline, etc) has a burden of responsibility for the corrosion protection in order to prevent big accidents like gas explosion, soil pollution, leakage and so on. So far, Cathodic Protection(CP) technology have been implemented for protection of underground systems. The stray current from DC subway system in Korea has affected the cathodic protection (CP) system of the buried pipelines adjacent to the railroads. In this aspect, KERI has developed a various mitigation method, drainage system through steel bar under the rail, a stray current gathering mesh system, insulation method between yard and main line, distributed ICCP(Impressed Current Cathodic System), High speed response rectifier, restrictive drainage system, Boding ICCP system. In this paper, the mechanism of mitigation method of DC stray current for underground metallic structures is described.

• 한국분말재료학회지
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• 제11권4호
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• pp.308-313
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• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

• Journal of Preventive Medicine and Public Health
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• 제21권2호
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• pp.238-244
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• 1988

This study was conducted to investigate the causes of burn and emergency cares taken on the spot for the burn patient. Study population included 161 burn patients admitted to 2 university hospitals and 1 general hospital in Taegu from November 1, 1987 to April 30, 1988. Patients or guardians were interviewed with a structured questionnare. Out of 161 burn patients 111(68.9%)were males and 50(31.1%) females. Preschool children of 1-4 years old accounted for 29.8% of the total patients. Burns of children under 15 years of age took place at home in 91.0%, while 48.3% of burns of adult (15 years and over)males occurred at the working place, and 68.0% of adult females occurred at the home. Out of total burns occurred at home 39.8% took place at kitchen/dining room and 24.1% in the room. The most common cause of burns in children was the boiling water or hot food (74.3%). In adults the common causes were electrical burn(22.4%), hot water or food(19.0%) and explosion(12.1%) for males, and hot water or food(32.0%) and explosion (20.0%) for females. Common emergency cares for the burn taken on the spot were undressing(64.6%), pouring Soju(liquor)(13.7%), and pouring cold water(5.0%). There were a few cases who applied ash, soy or salt. To prevent burn, it is recommended to remodel the traditional kitchen and coal-briquet hole, to strengthen the safety control of LP Gas and LN Gas supply, to educate the public for the handling method for such gases, to strengthen the occupational safety control, to improve the safety device for the electric wire and socket, and to limit the temperature of hot water at home and public baths.

• 한국분말재료학회지
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• 제11권5호
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• pp.376-382
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• 2004

Nanoscale Cu-Ni alloy nanopowders have been produced by a pulsed wire evaporation method in an inert gas. The effect of Cu-Ni alloy nanopowders as additives to motor oil on the tribological properties was studied at room temperature. The worn surfaces were characterized by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Cu-Ni alloy nanopowders as additives lowered coefficient of friction and wear rate. It was found that a copper containing layer on the worn surface was formed, and deposited layers of the metal cladding acted as lubricant on the worn surface, reducing the friction coefficient. It was clearly demonstrated that Cu-Ni alloy nanopowders as additives are able to restore the worn surface and to preserve the friction surfaces from wear.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1612-1614
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• 2007

The owner of underground metallic structures (gas pipeline, oil pipeline, water pipeline, etc) has a burden of responsibility for the corrosion protection in order to prevent big accidents like gas explosion, soil pollution, leakage and so on. So far, Cathodic Protection(CP) technology have been implemented for protection of underground systems. The stray current from DC subway system in Korea has affected the cathodic protection (CP) design of the buried pipelines adjacent to the railroads. In this aspect, KERI has developed a various mitigation method, drainage system through steel bar under the rail, a stray current gathering mesh system, insulation method between yard and main line, distributed ICCP(Impressed Current Cathodic System), High speed response rectifier, restrictive drainage system. We installed the mitigation system at the real field and test of its efficiency in Busan and Seoul, Korea. In this paper, the results of field test, especially, distributed ICCP system is described.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.308-311
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• 2012

A wide range of possible hazards existing in thermal batteries are mainly caused by thermal runaway, which results in overheating or explosion in extreme case. Battery separators ensure the separation between two electrodes and the retention of ion-conductive electrolytes. Thermal runaways in thermal batteries can be significantly reduced by the adoption of these separators. The high operating temperature and the violent reactivity in thermal batteries, however, have limited the introduction of conventional separators. As a substitute for separators, MgO powders have been mostly used as a binder to hold molten salt electrolyte. During recent decades the fabrication technology of ceramic fiber, which has excellent mechanical strength and chemical stability, has undergone significant improvement. In this study we adopted wet-laid nonwoven paper making method instead of the electrospinning method which is costly and troublesome to produce in volume. Polymeric precursor can readily be coated on the surface of wet-laid ceramic paper, and be formed into ceramic film after heat treatment. The mechanical strength and the thermo-chemical stability as well as the wetting behaviors of ceramic separators with various molten salts were investigated to be applicable to thermal batteries. Due to their excellent chemical, mechanical, and electrical properties, wet-laid nonwoven separators made from ceramic fibers have revealed positive possibility as new separators for thermal batteries which operate at high temperature with no conspicuous sign of a short circuit and corrosion.

• 해양환경안전학회지
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• 제28권4호
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• pp.610-619
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• 2022

수소는 산소와 반응하여 전기에너지를 만들고 부산물로 물을 생성하므로 친환경 선박의 대체 연료로 대두되고 있다. 그러나 수소는 일반 화석연료와는 달리 낮은 점화 에너지와 높은 가연성 범위로 인하여 폭발의 위험성이 높은 물질이다. 그래서 선박에서 사용되는 수소의 안전성을 확보하기 위해서 수소의 누출·확산에 관한 유동 특성을 연구하는 것은 매우 중요하다. 본 연구에서는 선박 내부와 같은 밀폐공간에서 수소가 누출되었을 때 누출량, 통풍량, 환기 방식 등이 환기 성능에 어떤 영향을 미치는지에 대하여 수치적 해석을 수행하였다. 수치해석에는 CFD 상용 소프트웨어인 ANSYS CFX ver 18.1을 이용하였다. 누출량은 1 q = 1 g/s로 하여 1 q, 2 q, 3 q로 변경하였고, 통풍량은 1 Q = 0.91 m/s로 하여 1 Q, 2 Q, 3 Q로 변경하였으며 환기 방식은 typeI, typeII, typeIII로 변경하면서 환기 성능을 분석하였다. 누출량이 1 q에서 3 q로 증가할수록 저장실 내의 수소 몰분율(HMF)는 약 2.4 ~ 3.0배 높게 나타났으며 통풍량 증가는 누출량에 대비하여 약 62.0 ~ 64.8 % 정도 환기 성능이 개선에 효과가 있었다. 그리고 폭발의 위험성을 낮추기 위한 통풍량은 최소 2 Q 이상 되어야 하며, 수소탱크 저장실 내부의 부압 형성을 위해서는 type III가 가장 적합한 방식이라고 판단하였다.

• 대한전자공학회논문지SD
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• 제37권11호
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• pp.9-17
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• 2000

폭발성 가스의 종류 및 그 양을 검지하기 위한 10개의 개별 센서가 한 기판위에 집적된 센서어레이를 개발했다. 이 센서어레이는 각종 가스에 대해 다양한 감도 패턴을 가지며, $SnO_2$를 모물질로 하는 10개의 산화물 반도체 가스센서로 구성하였다. 나노사이즈이며 큰 비표면적을 가진 모물질에 서로 다른 첨가물을 첨가하여 감지물질를 제작함으로써 저농도에 대한 감도 및 재현성을 높였고, 센서어레이 전반에서 균일한 온도 분포가 되도록 설계하였다. $400^{\circ}C$에서 동작하는 센서어레이로부터 얻은 감도를 이용하여 주성분 분석 기법을 통해 폭발 하한값의 범위에서 부탄, 프로판 그리고 메탄 등과 같은 폭발성 가스의 종류 및 양을 신뢰성 있게 식별할 수 있었다.