• 자원ㆍ환경경제연구
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• 제18권4호
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• pp.767-785
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• 2009

본 연구에서는 수질배출부과금제도의 부과체계를 분석하고 개선 방안을 연구하였다. 수질배출부과금제도는 환경오염 원인자에게 처리비용을 부담시켜 환경자원을 효율적으로 사용하도록 하는 경제적 유인 목적을 가지고 있으나 현행 수질배출부과금제도는 행정 규제적 성격이 강하다. 즉, 배출허용기준을 설정하여 이를 위반한 배출업소에 대하여 사업장 규모, 지역, 위반 횟수, 오염물질별 초과율을 고려한 누증적 부과계수를 적용하여 실제 환경오염 비용을 훨씬 초과하는 형벌적 성격의 부과금을 부과하고 있다. 그러나 과도한 부과금 부과로 배출부과금 징수율은 환경관련 부과금 중 가장 낮은 수준이다. 따라서 본 연구에서는 규제적 성격의 부과체계를 개편하여 경제적 유인제도로 수질배출부과금제도를 개편하는 부과체계 개편안을 연구하였으며 이에 따른 부과액 및 징수액 변화 효과를 추정하였다. 추정 결과를 보면 현행 부과금 부과액은 오염물질 처리단가의 약 4배 이상을 부과하고 있어 환경자원의 비효율적 배분을 초래하고 있음을 보여준다. 아울러 과도한 부과금 부과체계를 개선하는 경우에는 징수율도 제고되어 수질배출부과금제도의 기능을 회복할 수 있음을 보여준다.

• 한국군사과학기술학회지
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• 제20권4호
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• pp.528-535
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• 2017

Fuel cells have been spotlighted in the world for being highly efficient and environmentally friendly. A hydrogen which is the fuel of fuel cell can be obtained from a number of sources. Hydrogen source for operating the polymer electrolyte membrane fuel cell(PEMFC) in the current underwater environment, such as a submarine and unmanned underwater vehicles are currently from the metal hydride cylinder. However, metal hydride has many limitations for using hydrogen carrier, such as large volume, long charging time, limited storage capacity. To solve these problems, we suggest diesel reformer for hydrogen supply source. Diesel fuel has many advantages, such as high hydrogen storage density, easy to transport and also well-infra structure. However, conventional diesel reforming system for PEMFC requires a large volume and complex CO removal system for lowering the CO level to less than 10 ppm. In addition, because the preferential oxidation(PROX) reaction is the strong exothermic reaction, cooling load is required. By changing this PROX reactor to hydrogen separation membrane, the problem from PROX reactor can be solved. This is because hydrogen separation membranes are small and permeable to pure hydrogen. In this study, we conducted the pressurized diesel reforming and water-gas shift reaction experiment for the hydrogen separation membrane application. Then, the hydrogen permeation experiments were performed using a Pd alloy membrane for the reformate gas.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.176.2-176.2
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• 2013

Property of optical diagnostics for pulse-discharged plasma in liquid and its biological applications to proteins are investigated by making use of high voltage Marx generator. The Marx generator has been consisted of 5 stages, where each charging capacitor is 0.5 ${\mu}F$, to generate a high voltage pulse with rising time of $1{\mu}s$. We have applied an input voltage of 6 kV to the each capacitor of 0.5 ${\mu}F$. High voltage pulsed plasma has been generated inside a polycarbonate tube by a single-shot operation, where the breakdown voltage is measured to be 7 kV, current of 1.2 kA, and pulse width of ~ 1 ${\mu}s$ between the two electrodes of anode-cathode whose material is made of tungsten pin, which are immersed into the liquids. We have investigated the emitted hydrogen lines for optical diagnostics of high voltage pulsed plasma. The emission line of 656.3 nm from $H-{\alpha}$ and 486.1 nm from $H-{\beta}$ have been measured by a monochromator. If we assumed that the focused plasma regions satisfy the local thermodynamic equilibrium conditions, the electron temperature and density of the high voltage pulsed plasma in liquid could be obtained by the Stark broadening of optical emission spectroscopy. For the investigation of the influence of pulsed plasma on biological proteins, we have exposed it onto the proteins such as hemoglobin and myoglobin. The structural changes in these proteins and their analysis have also been obtained by circular dichroism (CD) and ultraviolet (UV) visible spectroscopy.

• Journal of Welding and Joining
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• 제31권6호
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• pp.112-118
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• 2013

In this study, constant loading test (CLT) was performed to evaluate the hydrogen embrittlement resistance for multipass FCA weld metals of 600MPa tensile strength grade. The microstructures of weld metal-2 having the smallest carbon equivalent (Ceq=0.37) consisted of grain boundary ferrite and widmanstatten ferrite in the acicular ferrite matrix. The weld metal-1 having the largest Ceq=0.47, showed the microstructures of grain boundary ferrite, widmanstatten ferrite and the large amount of bainite (vol.%=19%) in the acicular ferrite matrix. The weld metal-3 having the Ceq=0.41, which was composed of grain boundary ferrite, widmanstatten ferrite, and the small amount of bainite (vol.%=9%) in the acicular ferrite matrix. Hydrogen desorption spectrometry (TDS) used to analyze the amount of diffusible hydrogen and trapping site for the hydrogen pre-charged specimens electrochemically for 24 hours. With increasing the current density of hydrogen pre-charging, the released amount of diffusible hydrogen was increased. Furthermore, as increasing carbon equivalent of weld metals, the released diffusible hydrogen was increased. The main trapping sites of diffusible hydrogen for the weld metal having a low carbon equivalent (Ceq=0.37) were grain boundaries and those of weld metals having a relatively high carbon equivalent (Ceq: 0.41~0.47) were grain boundaries and dislocation. The fracture time for the hydrogen pre-charged specimens in the constant loading test was decreased as the carbon equivalent increased from 0.37 to 0.47. This result is mainly due to the increment of bainite that is vulnerable to hydrogen embrittlement.

• 한국가스학회지
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• 제25권2호
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• pp.28-33
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• 2021

최근 친환경 자동차에 대한 관심이 높아짐에 따라 공해물질을 배출하지 않는 수소연료전지 차량에 대한 관심과 구매가 증가하고 있다. 최근 정부의 수소에너지 보급정책에 따라 수소충전소의 확충과 핵심부품의 국산화를 지원하고 있다. 본 연구에서는 그중에서도 수소 유량제어 밸브의 차압에 따른 유동특성을 연구하였다. 차압이 높아 짐에 따라 질량유량과 유량계수는 체적유량과 다른 경향을 보임을 확인하였다. 그리고 병목 구간에서의 노즐효과로 인해 수소온도에 영향을 주게되고, 밀도의 변화를 일으켜 질량유량에 영향을 주게 되는 것을 확인 하였다.

• 대한조선학회논문집
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• 제58권4호
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• pp.225-233
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• 2021

Conventional submarine propulsion batteries have mainly used lead acid batteries, which have proved relatively safe, but in recent years, research on mounting lithium-ion batteries to improve the underwater operation capability of submarines is underway in advanced countries such as Japan. Korea has world-class technology in the development of electric vehicles and lithium-ion batteries for energy storage, but fire safety accidents continue to occur in electric vehicles and energy storage lithium-ion batteries. In order to mount the lithium-ion battery in a submarine, it is necessary to check the safety as well as whether the performance is improved compared to the lead acid battery. Through the charge/discharge experiment of this lithium-ion battery module unit, it was possible to measure how much performance was improved compared to the lead acid battery. Safety tests were conducted on the lithium-ion battery module assuming that it was mounted on a submarine, and it was confirmed that safety was secured when applied to a submarine. Since many modules are mounted on actual submarines, it has been confirmed that it can be applied to submarine systems by simulating charge/discharge characteristics through Hardware-in-the Loop(HILS). Through the results of this study, the application of lithium-ion batteries to submarines is expected to significantly improve the sustainability of underwater operations.

• 한국가스학회지
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• 제24권6호
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• pp.91-97
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• 2020

리튬이온 배터리(LIB)는 다른 배터리에 비해 수명이 길고, 에너지 밀도가 높으며, 자체 방전율이 낮아, 에너지 저장장치(ESS)로 선호되고 있다. 하지만, 2017~2019년 기간 동안 국내에서만도 28건의 화재사고가 발생하였으며, LIB의 운영 중 안전성 및 신뢰성을 보장하기 위해 LIB의 정확한 용량추정은 필수요소이다. 본 연구에서는 LIB의 충방전 cycle에 따른 용량변화를 예측하는 기계학습 기반 모델의 설계에 있어 중요한 요소인 최적 머신러닝 모델의 선정을 위해, Decision Tree, 앙상블학습법, Support Vector Regression, Gaussian Process Regression (GPR) 각각을 이용한 예측모델을 구현하고 성능비교를 실시하였다. 학습을 위해 NASA에서 제공하는 시험데이터를 사용하였으며, GPR이 가장 좋은 예측성능을 보였다. 이를 바탕으로 추가 시험데이터 학습을 통해 개선된 LIB 용량예측과 잔여 수명추정 모델을 개발하여, 운영 중 이상 감지 및 모니터링 성능을 높여, 보다 안전하고 안정된 ESS 운용에 활용하고자 한다.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.330-338
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• 2021

An integral electrode-bipolar plate assembly, which is composed of electrode, conductive adhesive film (CAF) and bipolar plate, has been developed and evaluated for application with a vanadium redox flow battery (VRB) to decrease contact resistance between electrode and bipolar plate. The CAF, made of EVA (ethylene-vinyl-acetate) material with carbon black or CNT (Carbon Nano Tube), is applied between the electrode and the bipolar plate to enable an integral assembly by adhesion. In order to evaluate the integral assembly of VRB by adhesive film, the resistivity of integral assembly and the performance of single cell were investigated. Thus, it was verified that the integral assembly is applicable to redox flow battery. Through resistance and contact resistance of bare EVA and CAF films on bipolar plate were changed. Among the adhesive films, CAF film coated with carbon black showed the lowest value in through resistance, and CAF film coated with CNT showed the lowest value in contact resistance, respectively. The efficiency of VRB single cell was improved by applying CAF films coated with carbon black and CNT, resulting in the reduced overvoltage in charging process. Therefore, the energy efficiency of both CAF films, about 84%, were improved than that of blank cell, about 79.5 % under current density at 40 mA cm^-2. The energy efficiency of the two cells were similar, but carbon black coated CAF improved the coulomb efficiency and CNT coated CAF improved the voltage efficiency, respectively.

• 전력전자학회논문지
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• 제26권6호
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• pp.421-428
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• 2021

Lithium-ion secondary batteries exhibit advantageous characteristics such as high voltage, high energy density, and long life, allowing them to be widely used in both military and daily life. However, the lithium-ion secondary battery does have its limitation; for example, the output power and capacity are readily decreased due to the increased internal impedance during discharging at a lower temperature (-32℃, military requirement). Also, during charging at a lower temperature, lithium dendrite growth is accelerated at the anode, thereby decreasing the battery capacity and life as well. This paper describes a study that involves increasing the internal temperature of lithium-ion secondary battery by energy circulation operation in a low-temperature environment. The energy circulation operation allows the lithium-ion secondary battery to alternately charge and discharge, while the internal resistance of lithium-ion battery acts as a heating element to raise its own temperature. Therefore, the energy circulation operation method and device were newly designed based on the electrochemical impedance spectroscopy of the lithium-ion secondary battery to mediate the battery performance at a lower temperature. Through the energy circulation operation of lithium ion secondary battery, as a result of the heat generated from internal resistance in an extremely low-temperature environment, the temperature of the lithium-ion secondary battery increased by more than 20℃ within 10 minutes and showed a 75% discharging capacity compared with that at room temperature.

• 한국가스학회지
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• 제26권3호
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• pp.38-44
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• 2022

전세계적으로 저탄소 친환경에너지로 다변화 정책이 진행되고 있으며, 그 정책 중 하나가 수소경제 활성화이다. 수소경제 활성화 정책으로 수소 공급을 위한 수소충전소의 보급이 가속화됨에 따라 사고발생의 위험도 커지고 있다. 수소의 폭발사고는 대부분 대형사고로 이어지기 때문에 수소에너지를 사용함에 있어 안전성을 확보하는 것은 매우 중요하다. 수소에너지를 활용하기 위해서는 액화수소의 생산, 저장, 운송 등에 사용될 수소저장 용기의 안전성 확보는 반드시 필요하다. 본 논문에서는 수소충전용 압력용기의 구조안전성을 평가하기 위해 가스 압력에 대한 거동특성을 유한요소해석으로 분석하였다. 압력용기의 재료는 SA-372 Grade J / Class 70을 사용하였고, 해석모델은 압력용기가 축대칭 형상이므로 1/4 형상만 고려하여 6면체 메쉬를 적용하였다. 수소가스 압력용기를 사용 최고 압력에서 유한요소해석을 하였으며, 해석 결과인 용기의 von Mises Stress와 변형량, 변형률 에너지 밀도를 관찰하였다.