• Journal of Environmental Health Sciences
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• v.37 no.1
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• pp.50-56
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• 2011

The adsorption capacity of charcoal is a function of the airborne concentration of the target chemical. To evaluate the adsorption capacity of charcoal packed in the cartridges of air purifying respirators, breakthrough tests were conducted with carbon tetrachloride for three commercial cartridges (3M models #7251, #6000 and AX) at 25, 50, 100, 250 and 500 ppm. Adsorption capacities were calculated using a mass transfer balance equation derived from the curve fitting to the breakthrough curves obtained experimentally. Carbon micropore volumes were estimated by iteration to fit the Dubinin/Radushkevich (D/R) adsorption isotherm. They were 0.6566, 0.5727 and 0.3087 g/cc for #7251, #6000 and the AX cartridge, respectively. Above 100 ppm (at high challenge concentrations), #7251 and #6000 showed higher adsorption capacities. However, as the challenge concentration decreased, the adsorption capacities of #7251 and #6000 sharply dropped. On the other hand, the adsorption capacity of the AX cartridge showed little change with the decrease of the challenge concentration. Thus, the AX showed a higher adsorption capacity than #7251 and #6000 at the 5-50 ppm level. It is concluded that service-life tests of cartridges and adsorption capacity tests of charcoal should be conducted at challenge concentration levels reflecting actual working environmental conditions. Alternatively, it is recommended to use the D/R adsorption isotherm to extrapolate adsorption capacity at low concentration levels from the high concentration levels at which breakthrough tests are conducted, at a minimum of two different concentration levels.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.3
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• pp.347-352
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• 2006

분자전해질연료전지 내의 다공성 기체확산층은 반응가스의 확산과 전자이동통로의 역할을 수행할 뿐만 아니라 전기화학반응에 의해 공기극에서 생성된 수분(기상 혹은 액상)을 반응면으로부터 분리판 채널 방향으로 이동시켜 배출시키는 중요한 역할을 한다. 따라서 물관리를 통한 성능향상을 위해서는 기체 확산층의 구조 및 재료특성에 대한 심도 릴은 연구가 필요하다. 실제 단위전지 체결시 기체확산층은 분리판의 리브(rib)에 의해 눌리게 되며, 그 부분의 기공 크기 분포의 변화를 야기한다. 또한 리브 전단부분에서 탄소 섬유가 손상을 입으며, 탄소 섬유를 감싸고 있는 PTFE coating이 벗겨지게 되어 표면화학적 특성이 달라진다. 본 연구에서는 단위전지 체결 시 분리판에 의해 눌리는 기체확산층의 기공 크기 분포 변화를 측정하였으며, 기공의 소수성에서 친수성으로의 변화를 알아보았다. Mercury 기공 측정기와 PMI 기공 측정기는 큰 기공 분포의 변화에, 질소의 흡/탈착을 이용한 BET 방식은 작은 크기의 기공 분포 변화 관찰에 사용되었다. 체결압에 의한 탄소섬유의 구조적 변화와 아울러 표면의 습윤 정도의 변화를 XPS와 물/알콜 Uptake를 이용해 알아보았다. 이 연구를 바탕으로 물관리를 통한 연료전지 성능 향상을 위한 최적 GDL 선정에 기반이 되는 자료를 도출하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.419-426
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• 2012

Fresh concrete has 10~20% extra water in it. As those water remain entrapped air in the concrete, life span of structures is reduced. For that reason, if extra water is eliminated, it will be useful to improve the durability of the structures. Though there were many reports about permeable formwork, the study on the properties of permeable liner itself has been insufficient. In addition, making holes on the form causes lowering of workability. Therefore, this study reviewed the properties of woven and non-woven permeable liner and formwork which has no holes on the form. For the woven and non-woven permeable liner, they showed great application with W/C decrease, lowering roughness, increased compressive strength of surface area and slight loss of cement paste, when the were applied to concrete. In addition, they showed different performance according to the density of woven liner or thickness of non-woven liner. Furthermore, when using the draining non-woven permeable liner which has drainage path inside, concrete surface showed required performance with high workability, without drilling the holes on the form.

• Journal of the Korean Wood Science and Technology
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• v.33 no.6 s.134
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• pp.17-24
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• 2005

Korean pine (Pinus koraiensis Sieb.et Zucc.) boards of 30 mm thickness were treated by steaming and four different drying methods. Small specimens were taken from the sapwoods of the treated boards and their longitudinal liquid permeability was measured according to Darcy's law. The specimens were also extracted with alcohol and aceton solutions to examine the mechanism of liquid flow in wood. It was observed that specific permeability drastically decreases with measurement time, resulting in violation of Darcy's law. It may be due to that air bubbles formed under vacuum block flow paths in resin canals. The average specific permeabilities of non-extracted and extracted specimens are different from one treatment to another. It is supposed that the properties of residual resin in resin canals change depending on the conditions of treatments. Anatomical examination was conducted with a scanning electron microscope.

• Journal of the Korean Society of Safety
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• v.26 no.2
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• pp.42-47
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• 2011

Going underwater is supposed to begin with the history of human beings. At first it was confined to relatively shallow level, less than several meters by holding breath. Recently, deep level diving has been necessary for such purpose as construction, maritime salvage, military operations, research and sports by using SCUBA(self-contained underwater breathing apparatus) equipment. As one goes down into water, the pressure on the diver is increased due to water pressure with depth, usually 1 atm for each 10 m water level. In deep water, mixed gas or nitrox(EAN, enriched air nitrox) could be applied for the divers lest they should get disease due to high pressure. Of these, the former is usually composed of oxygen and inert gas like helium or hydrogen, the latter contains higher oxygen content than that in normal air in which the oxygen concentration is designated by the character "EAN" followed by vol. % of oxygen, for example, "EAN 40" contains 40% of oxygen. In this case, a victim was found at the 39 m below the sea surface breathing air and nitrox in cylinder wrongly marked as EAN 36, which was analyzed to contain 63% of oxygen by GC/TCD. The cause of death could not be exactly related with the oxygen content in the nitrox cylinder, because the accurate depth for the victim to dive was not known, even though the victim was just found at the depth of 39 m. However, the wrongly marked nitrox could be believed to be the main cause of the death at the depth unless there happened any other accident except that during diving.

• Fire Science and Engineering
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• v.29 no.6
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• pp.98-108
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• 2015

An integrated command system is critical for the safety of firefighters and effective work in the headquarters of a special disaster areas such as natural disaster or large man-made hazard. The integrated command system requires environmental information such as temperature, humidity, and $CO_2$ levels, as well as personal physical information such as pulse and air respirator levels. An Analog to Digital Converter (ADC) chip converts sensed information into digital signals, and a Micro Controller Unit (MCU) transmits the digital signals to a transmission board using serial communication through a Serial Peripheral Interface (SPI). The digital signals are saved in a transmission board and transmitted to the integrated command system by a Radio Frequency (RF) unit. The location of fire-fighters in a building are determined using a gyro sensor and an inertial sensor. The collected information is applied to the integrated command system for firefighter safety and to ensure that they can effectively carry out their duties. Tthis study theoretically and experimentally investigated the technologies of RF transmission, indoor position, and an integrated command system that supports decision making using the transmitted information.

• Fire Science and Engineering
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• v.25 no.4
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• pp.89-93
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• 2011

It is not recommended that elevator use for egress at (super) high rise buildings because elevator shaft main roles to spread of fire smoke. But in North America used to protect this area by elevator shaft pressurization. These tests are performed at high rise apartment to verify that elevator shaft pressurization can protect to spread of fire smoke or not. and verify to used for egress at fire. Pressurization at elevator shaft make pressure difference of 50 Pa all floor at 150 CMM because this method have low friction loss from air flow. Also when dwelling door and elevator door are opened that critical velocity is performed to protect of back-layering from fire room for escape routs by 180 CMM. Therefore through out these pressurization tests by elevator shaft are estimated to have less overpressure because supply air difference are low between to satisfy critical velocity at one door opened and maintain to pressure difference all doors closed. Finally we verified that disable or residual people can use elevator for egress at fire by elevator shaft pressurization.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.155-162
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• 2011

The structures that use the bridge plates are considered to have advantages such as short work term, excellent economical efficiency and low maintenance cost. Bridge plates are being widely used for water ducts and eco-corridors as replacements of reinforced concrete ducts. Bridge plates are deep and have greater pitch as compare to conventionally deep corrugated steel plate. They are expected to be increasingly used in the future. The structures that use bridge plates have two forms, such as arch type and box type. The arch type structures are designed based on the compressive strength, and the box type structures, based on the moment in the plate member. In this study, the ultimate strength and moment strength of the connection part of the specimens were examined by their thickness. Static and bending tests used to evaluate the performance of bridge plate. Finally, These results were used in the design process.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.1-6
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• 2002

Micro engine that includes Micro scale combustor is fabricated. Design target was focused on the observation of combustion driven actuation in MEMS scale. Combustor design parameters are somewhat less than the size recommended by feasibility test. The engine structure is fabricated by isotropic etching of the photosensitive glass wafers. Electrode is formed by electroplating of the Nickel. Photosensitive glass can be etched isotropically with almost vertical angle. Bonding and assembly of structured photosensitive glass wafer from the engine. Combustor size was determined to be 1mn scale. Piston in cylinder moves by fuel injection and reaction. In firing test, adequate engine operation including ignition, flame propagation and piston motion was observed. Present study warrants further application research on MEMS scale internal combustion power units.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.3
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• pp.169-176
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• 2001

The purpose of study is to obtain low-emission and high-efficiency in LPG engine with hydrogen enrichment. The test engine was named heavy-duty variable compression ratio single cylinder engine (VCSCE). The fuel supply system provides LPG/hydrogen mixtures based on same heating value. Various sensors such as crank shaft position sensor (CPS) and hall sensor supply spark timing data to ignition controller. Displacement of VCSCE is $1858.2cm^3$. VCSCE was runned 1400rpm with compression ratio 8. Spark timing was set MBT without knocking. Relative air-fuel ratio(${\lambda}$) of this work was varied between 0.76 and 1.5. As a result, i) Maximum thermal efficiency occurred at ${\lambda}$ value 1.0. It was shown that thermal efficiency was increased approximately 5% with hydrogen enrichment at same ${\lambda}$ value. ii) Engine-out carbon monoxide (CO) emissions were decreased at a great rate under LPG/hydrogen mixture fuelling. iii) Total hydrocarbon (THC) emission was much exhausted in rich zone, same as CO. But THC was exhausted a little bit more in lean zone. iv) Finally, engine-out oxides of nitrogen (NOx) was increased with ${\lambda}$ value 1.0 zone at a greater rate with hydrogen enrichment due to high adiabatic flame temperature.