• 천문학회지
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• 제37권5호
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• pp.501-507
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• 2004

The uniquely large dimensions of Giant radio galaxies (GRGs) make it possible to probe for stringent limits on total energy content, Faraday rotation, Alfven speeds, particle transport and radiation loss times. All of these quantities are more stringently limited or specified for GRG's than in more 'normal' FRII radio sources. I discuss how both global and detailed analyses of GRG's lead to constraints on the CR electron acceleration mechanisms in GRG's and by extension in all FRII radio sources. The properties of GRG's appear to rule out large scale Fermi-type shock acceleration. The plasma parameters in these systems set up conditions that are favorable for magnetic reconnection, or some other very efficient process of conversion of magnetic to particle energy. We conclude that whatever mechanism operates in GRG's is probably the primary extragalactic CR acceleration mechanism in the Universe.

• 한국물환경학회지
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• 제23권6호
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• pp.906-912
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• 2007

A lab-scale thermophilic aerobic digestion (TAD) system was operated at $64^{\circ}C$ with mixed primary and secondary sludges taken from a large wastewater treatment plant. The semi-continuously operated reactor at HRTs of 1, 3 and 6 days indicated that longer HRT could stabilize sludge organics and solids comparable to anaerobic digestion. It has been found that reduced HRT of 3 and 1 day produced the effluent with highly biodegradable soluble organics, indicating the possibility of energy recovery in TAD. No proof of biological nitrification was observed at thermophilic operating temperature of $64^{\circ}C$, while nitrogen removal seemed due to nitrogen exertion during the aerobic thermophilic cell synthesis as well as ammonia stripping.

• 천문학회지
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• 제23권1호
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• pp.15-29
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• 1990

The magnetic reconnection mechanism is a primary candidate for "flare" processes in solar coronal regions. Numerical simulations of two-dimensional magnetic reconnection are carried out for four different cases: (1) adiabatic condition with constant resistivity, (2) adiabatic condition with temperature-dependent resistivity, (3) energetics with radiation loss and constant resistivity and (4) energetics with radiation loss and temperature-dependent resistivity. It is found that the thermal instability prompts the magnetic reconnection process, thus increasing the conversion rate of magnetic energy into kinematic energy of the fluid. We demonstrated that the observed microflares can be accounted for by our magnetic reconnection models, when the effects of the radiation loss and the temperature-dependent resistivity are taken into account.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권8호
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• pp.416-422
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• 2006

With the increasing demand for renewable energy, distributed power included in fuel cells have been studied and developed as a future energy source. For this system, a power conversion circuit is necessary to interface the generated power to the utility. In many cases, a high step-up dc/dc converter is needed to boost low input voltage to high voltage output. Conventional methods using cascade dc/dc converters cause extra complexity and higher cost. The conventional topologies to get high output voltage use flyback dc/dc converters. They have the leakage components that cause stress and loss of energy that results in low efficiency. This paper presents a high boost converter with a voltage multiplier and a coupled inductor. The secondary voltage of the coupled inductor is rectified using a voltage multiplier and series-connected with the boost voltage of primary voltage of the coupled inductor. Therefore, high boost voltage is obtained with low duty cycle. Theoretical analysis and experimental results verify the proposed solutions using a 300W prototype.

• 신재생에너지
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• 제19권4호
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• pp.35-45
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• 2023

Global efforts are focused on achieving carbon neutrality due to the increases in the levels of greenhouse gases. Moreover, the greenhouse gases generated from the disposal of municipal solid waste (MSW) are the primary sources of emissions in South Korea. In this study, we conducted the biological conversion of syngas (CO, H₂, and CO₂) generated from MSW gasification. The MSW-derived syngas was used as a feed source for cultivating Eubacterium limosum KIST612, and pressurization was employed to enhance gas solubility in culture broth. However, the pH of the medium decreased owing to the pressurization because of the CO₂ in the syngas and the cultivation-associated organic acid production. The replacement of conventional HEPES buffer with a phosphate buffer led to an approximately 2.5-fold increase in acetic acid concentration. Furthermore, compared with the control group, the pressurized reactor exhibited a maximum 8.28-fold increase in the CO consumption rate and a 3.8-fold increase in the H2 consumption rate.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.283-288
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• 2005

A portable primary inductance standard set that includes a Maxwell-Wien bridge and a 10 mH standard inductor installed in a thermostat has been developed at KRISS. Two auxiliary resistance capacitance networks (analogous to a 'Wagner ground') provide excellent stability of the bridge balance and impose less strict requirements on the components of these networks. Removable capacitance and ac-dc resistance standards used in the bridge arms made it possible to reproduce 10 mH and 100 mH inductance values in the frequency range of 500 Hz to 3 kHz. From investigations of this standard and preliminary comparison with VNIIM (D. I. Mendeleyev Institute for Metrology), the results have demonstrated that the bridge can be used as a part of the transportable inductance standard with a measurement uncertainty within (1-3) $\mu$H/H at frequencies of 1 kHz and 1.6 kHz. The application of the bridge as a constituent part of the transportable standard gives us an opportunity to eliminate the influence of the standard inductors.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.33-36
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• 2014

Gasification of biomass produces syngas containing CO, $H_2$ and/or $CH_4$, which can then be converted into energy or value-added fuels. One of key issues for efficient gasification is to minimize tar concentration in the syngas for use in a final conversion device such as gas engine. This study investigated the decomposition of primary tar by catalytic cracking using char as catalyst, of which the feature can be integrated into a fixed bed gasifier design. The pyrolysis vapor containing tar from pyrolysis of wood at $500^{\circ}C$ was passed through a reactor filled with or without char at $800^{\circ}C$ for a residence time of 1, 3 or 5 sec. Then, the condensable vapor (water and tar) and gases were analyzed for the yields and elemental composition. Four types of char particles with different microscopic surface area and pore size distribution: wood, paddy straw, palm kernel shell and activated carbon. The results were analyzed for the mass and carbon yields of tar and the composition of product gases to conclude the effects of char types and residence time.

• 한국수산과학회지
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• 제24권4호
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• pp.266-271
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• 1991

연근해 생물생산의 가시적 주체가 되는 초식어류의 잠재생산력을 연역적방법으로 추정하려 할 때, 기초생산력으로부터의 에너지 전환효율의 추정이 중심과제가 된다. 이 과제에 관련한 지금까지의 연구성과 중에서 아직 그 방법에 정론이 없는, 이른바 해수중의 '먹이감'에서 herbivores 소화관내의 '먹은 것'으로의 변환효율$(K_i)$에 관한 부분을 고찰하였다. 해수 중 먹이생물의 종별조성 r과 herbivores 소화관내의 종별조성 p를 사용하는 Ivlev와 Sorygin의 계수들이$(K_i)$로 사용되기에는 부적당함을 지적하면서, 그대신 유사도 지수의 하나인 CCOS를 $(K_i)$로 가공하여 사용할 수 있는 가능성을 제시한다.

• 청정기술
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• 제12권3호
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• pp.138-144
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• 2006

저압에서 용량성 라디오 주파수 방전을 이용하여 메탄을 합성가스로 전환시키는 반응을 고찰하였다. 플라즈마에서 발생된 높은 에너지를 갖는 전자들이 메탄분자와 산소를 함유하고 있는 기체 분자들과 충돌에 의해 합성가스로 전환되었다. 입력전력, 함산소화합물의 종류, 함산소화합물과 메탄의 조성이 메탄 전환율 및 수소와 일산화탄소의 수율에 미치는 영향을 살펴보았다. 메탄 전환율은 최대 100%이었으며, 합성가스이외의 다른 화합물들은 거의 생성되지 않았다. 입력전력이 증가함에 따라 메탄전환율과 합성가스의 수율이 증가하였으며, 함산소화합물의 종류에 따라 각각 다른 조성의 합성가스를 생성할 수 있었다. 메탄과 함산소화합물을 함께 반응시킴으로써 순수한 합성가스를 제조할 수 있었는데 함산소화합물의 종류에 따라 합성가스의 조성을 조절할 수 있었으며 불순물이 거의 없는 순수한 생성물을 얻을 수 있었다.

• 에너지공학
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• 제19권3호
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• pp.195-202
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• 2010

최근 국내 연간 1차 에너지 사용량의 약 30% 이상이 폐열로 손실되어지고 있다. 이러한 현실을 타개하기 위하여, 본 논문에서는 장거리 열수송시 에너지 손실을 최소화할 수 있는 신기술로 화학 열변환을 이용한 장거리 열수송 기술을 채택하여, 화학 열변환에 있어서의 최적조건 도출을 목적으로 하였다. 화학 열변환을 위한 반응에 대해서는 많은 연구와 기술개발이 이루어지고 있으며, 그 중 물질이 안정하고, 값이 저렴하며, 생성물이 가스인 메탄올 분해 합성 반응이 가장 타당한 것으로 판단되었다. 본 연구에서는 장거리 열수송 기술 개발에 필요한 메탄올 분해 합성 반응 촉매를 각각 선정하여, 열수송 시스템 구축을 위한 메탄올 분해 합성 반응의 최적화 조건 도출을 위한 실험 연구를 수행하였다. 메탄올 합성 반응에서는 온도, 압력, $H_2$/CO ratio, 공간 속도, 촉매 형태에 따른 영향을 보았고, 메탄올의 분해 반응에서는 온도, 공간속도, 촉매 형태를 변수로 하여 상압에서 영향을 분석하여 메탄올 분해 합성 반응의 최적화 조건을 제시하였다.