• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.179-184
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• 2016

The interface between the surface of a cathode material and the electrolyte gives rise to surface reactions such as solid electrolyte interface (SEI) and chemical side reactions. These reactions lead to increased surface resistance and charge transfer resistance. It is consequently necessary to improve the electrochemical characteristics by suppressing these reactions. In order to suppress unnecessary surface reactions, we coated cathode material using polypropylene (PP). The PP coating layer effectively reduced the SEI film that is generated after a 4.3 V initial charging process. By mitigating the formation of the SEI film, the PP-coated Li[(Ni_0.6Co_0.1Mn_0.3)_0.36(Ni_0.80Co_0.15Al0.05)_0.64)]O₂(NCS) electrode provided enhanced transport of Li⁺ ions due to reduced SEI resistance (R_SEI) and charge transfer resistance (R_ct). The initial charge and discharge efficiency of the PP-coated NCS electrode was 96.2 % at a current density of 17 mA/g in a voltage range of 3.0 ~ 4.3 V, whereas the efficiency of the NCS electrode was only 94.7 %. The presence of the protective PP layer on the cathode improved the thermal stability by reducing the generated heat, and this was confirmed via DSC analysis by an increased exothermic peak.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.4
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• pp.199-206
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• 2022

제주공항은 슬롯 증대사업을 통한 정시성 개선 노력에도 불구하고 항공 교통량의 확대에 따른 혼잡도의 증가가 지속되고 있다. 제주공항 혼잡도의 근본적인 해소를 위해서 추진되고 있는 신공항 건설이 여러 가지 사유로 지연되고 있으며, 실제 건설계획이 확정되더라도 정상적인 공항 운영까지 상당 기간의 시간이 소요될 것으로 예상된다. 따라서 제주 신공항 건설이라는 대규모 신규 투자와는 별개로 신공항 개항 전, 기존 제주공항을 운영하면서 혼잡도를 해소할 수 있는 중단기적 대안을 마련할 필요가 있다. 이에 국토교통부와 한국공항공사는 제주공항에 소형기보다는 최대이륙중량 100톤 이상의 대형항공기(통상 270석 이상 공급) 투입을 유도하는 착륙료 감면 조치를 시행하였으며, 최초 착륙료 10% 감면에서 추가 활성화를 위하여 착륙료 20% 감면으로 확대하여 운영 중이다. 항공사는 착륙료 감면 비율 상향을 통해 대형기 투입에 따른 실질적인 비용이 절감된다면 상기 정책에 적극 동참하게 될 것이다. 본 논문에서는 제주공항에서 실시 중인 착륙료 감면율 확대 조정이 항공사의 대형기 배정에 미치는 효과를 분석하여 정책의 실효성을 고찰하였으며 이에 따른 개선책을 제시하였다.

• Macromolecular Research
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• v.14 no.6
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• pp.630-633
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• 2006

In heterojunction photovoltaic devices of $ITO/TiO_2/poly$(3-alkylthiophene)/Au, the photo current was characterized at different temperatures for different alkyl chain lengths and regioregularities: regiorandom, regioregular poly(3-hexylthiophene), and regioregular poly(3-dodecylthiophene). The regioregularity and alkyl chain length affected the photovoltaic characteristics due to differences in hole-carrier transportation. The drift charge mobilities of these devices were analyzed by the space-charge-limited current theory using the relation between the dark current and the bias voltage. The photocurrent in the devices based on poly(3-alkylthiophene)s decreased rapidly below the temperature at which the drift charge mobility was $10^{-5}\;cm^2/V{\cdot}s$.

• Journal of Korean Society of Transportation
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• v.3 no.1
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• pp.46-57
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• 1985

The objective of this paper is to derive a optimum distance and time taxi fare structure based on social costs. Social costs expressed in terms of congestion and vehicle operating costs were successfully internalized. Speed and volume data for three major arterials in Seoul CBD were used. Optimum congestion charge turned out to be 97.01 Won/Km which can be regarded as congestion tax in the context of Seoul CBD. This congestion tax can possibly be incorporated into time-based taxi fare structure. Congestion is likely to be reduced as a result of imposition of time-based taxi fare which reflects social costs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.4
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• pp.733-739
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• 2017

Research on fuel cell systems attracting attention as an environmentally friendly energy source has been actively conducted. And research is being conducted on railway vehicles that use direct current power generated by a fuel cell as an energy source. In this paper, a two-phase interleaved bidirectional DC-DC converter has been proposed which can supply electric energy of a battery to a traction motor during powering and charge the battery with regenerative energy during braking. Therefore, the topology of the energy storage system applied to the railway vehicle was analyzed, and the simulation was performed by constructing the power conversion system by this topology. Experiments were also conducted through hardware design and fabrication based on the simulation analysis results, and the validity of the hardware implementation was verified.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.91-96
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• 2006

최근 예부선 결합선박에 대한 해양사고가 빈발하고 있다. 어선을 제외한 선박사고 중 36% 로 가장 높은 비율을 차지하고 있으며, 매년 예부선에 의한 해양사고가 증가하고 있다. 예부선에 의한 해양사고는 증가하고 있으나 예부선의 안전 운항 방안에 대한 체계적인 방안 마련이 부족한 실정이다. 본 연구에서는 예부선의 안전운항 방안 중에서 인적요소부분의 문제점을 도출하고 그에 대한 개선방안을 제시하여 예부선에 의한 해양사고를 방지하는데 목적이 있다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1577-1578
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• 2015

전세계적으로 신재생 에너지를 활용한 기술에 대한 관심이 대두되고 있는 가운데, 국내외에서 활발히 연구 중인 연료전지를 철도차량에 적용하는 연구를 수행하였다. 연료전지를 동력으로 사용하는 철도 차량시스템은 계통에서 전력을 공급받아 구동하는 철도차량과 달리 배터리를 적용한 토폴로지를 사용한다. 배터리는 역행시 철도차량 견인전동기를 구동하거나 회생시 발생되는 전류를 저장한다. 본 논문은 수소연료전지 발전시스템을 적용시 사용되어야하는 배터리 시스템의 충방전 토폴로지에 대해 분석하였다. 견인전동기 역행 및 회생특성을 반영하여 배터리 충방전 토폴로지 적용가능성을 분석하였고 시뮬레이션을 통해 제어 특성을 확인하였다.

• Journal of Institute of Convergence Technology
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• v.11 no.1
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• pp.19-23
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• 2021

These days, sales of battery electric vehicles have been rapidly increasing due to the strict CO₂ regulations. However, since it take too long to measure the energy economy of electric vehicles, it has been required to improve the procedure of energy economy measurement. In order to improve this problem, the present study analyzed the battery charge/discharge pattern according to the changes in battery SOC (state of charge). In general, the energy economy test is started with a battery SOC charged to 100 %. However, it was identified that when the battery is fully charged, it can actually be charged over the 100 % (e.g., 100.5 %). This can induce errors in the energy economy measurement. Therefore, the present study recommend to start the test at SOC 99.9 %. The regenerative braking was partly restricted for the SOC over 90 %. This made it difficult to estimate the overall energy economy of the electric vehicle. However, it was identified that there was no change in the battery charge/discharge characteristics under the SOC 90 %. Therefore, the energy economy test can be shortened by predicting the overall energy economy through a short mileage test.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.313-322
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• 1999

Pusan the principal port of South Korea, has opened its door since 1876. Currently, the four-stage port construction project is under way to handle ever-growing marine transportation volume. While the port unloading capabilities are increasing the infrastructure to deal with all the transportation volume failed to catch up with them. Accordingly the city had to suffer from worst traffic congestion on due to the increasing container traffic volume causing logistical costs to rise. This study was designed to inspect the enforcement of infrastructure construction plan and suggest systematical and effective ways to improve the plan. The study focused on :\circled1The decision-making procedure, \circled2Financial resource for the plan, \circled3Effectiveness of the project enforcement, and \circled4Who will be in charge of the project. As a result from the study, these followings were suggested to improve the plan. First, Pusan Port Infrastructure consisting of (Inter-city Free way, Belt Highway and Outer Highway) should be immediately legally-regulation project. Second, the method to finance the project should be deter-mined and investment consultation among the central government the city government and private sector should be also made. Measures to make the central government budget allocation for the project mandatory should be discussed. Third, Effectiveness of the project can be doubled by gradually or partialyl opening the routes based on long-term or short-term operating plans. Fourth, The organizer of the project should be appointed, or a special task-force team in charge of the plan can be formed.

• Journal of Korean Society of Transportation
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• v.14 no.1
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• pp.7-27
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• 1996

It is very costly to construct transportation facilities such as roads, bridges, tunnels, and public parking lots mainly because land price is very high in metropolis like Seoul. Private car oweners use these facilities more extensively than public transportation users. However, the government does not impose proper charges for using these facilities. Such improper charge causes traffic congestion and then decreases social welfare in efficiency and equity. To solve problem, many traffic demand management policies are used. Traffic management policies which are currently used or under consideration by the City Government of Seoul include the imposition of road tolls, increase of parking fees in public parking lots, increase of gasoline taxes, expanded implementation of bus only lanes, and shippujae, which requires one(1) non-driving day for 10 calendar days. This study examined the impacts of such policies on the different income classes using simulation analysis. We found that the impacts of market-oriented policies such as the imposition of road tolls and the increase of gasoline taxes is regressive. Also, we found that while the low and middle income private car users have incentive have incentive for public transportation use, the high income private car users have no incentive for public transportation use in many cases.