• 한국자동차공학회논문집
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• 제18권3호
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• pp.8-18
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• 2010

According to the needs of change to hybrid, fuel cell and electric vehicle, and to the increasing demand for safety and eco-friendliness, the necessity of Electro-Mechanical Brake(EMB) is being increased. But, one of the most important problems for realizing EMB to the practical use is that the required motor power for braking is too high. So the high braking efficient EMB is required. In recent years, the Electronic Wedge Brake(EWB) is noticeable for the high braking efficiency. In this research, we examine the improvable matter of the recent published EWB, and we propose the improved mechanism and the cost effective control method using this mechanism. And we test these feasibility by experiment and discuss these meaning and effect.

• Advanced Composite Materials
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• 제18권2호
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• pp.167-185
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• 2009

Environmental problems caused by extensive use of polymeric materials arise mainly due to lack of landfill space and depletion of finite natural resources of fossil raw materials like petroleum or natural gas. The substitution of synthetic petroleum-based resins with natural biodegradable resins appears to be one appropriate measure to remedy the above-mentioned situation. This study presents the development of a composite that uses environmentally degradable starch-based resin as matrix and natural mineral basalt fibres as reinforcement, and investigates the fibre's and the composite's mechanical properties. The tensile strength of single basalt fibres was verified by means of single fibre tensile tests and statistically investigated by means of a Weibull analysis. Prepreg sheets were manufactured by means of a modified doctor blade system and hot power press. The sheets were used to manufacture specimens with fibre volume contents ranging from 33% to 61%. Specimens were tested for tensile strength, flexural strength and interlaminar shear strength. Composites manufactured during this study exhibited tensile and flexural strength of up to 517 MPa and 157 MPa, respectively.

• 한국세라믹학회지
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• 제32권8호
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• pp.893-900
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• 1995

The porous wollastonite ceramics were fabricated after firing calcium silicates, obtained using natural resources and by-products of power plants by hydrothermal synthesis, without organic fibers or asbestos for reinforcement agent. A specimen from diatomite as a SiO2 staring raw material had the highest strength owing to normal grain growth and good densification from homogeneous sperhcial C-S-H hydrates. A specimen from SiO2 sol as a SiO2 starting raw material showed tobermolite, but fly ash and mixed system did xonotlite after hydrothermal synthesis. The specimen from fly ash showed the lowest firing shirikage and strength changes in the firing range from 50$0^{\circ}C$ to 120$0^{\circ}C$. The other phases in all specimens changed to wollastonite phase after firing at 100$0^{\circ}C$. Also the average pore size was distributed from 0.2${\mu}{\textrm}{m}$ to 2${\mu}{\textrm}{m}$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.760-762
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• 1998

Due to the reinforcement of government's DSM(Demand Side Management) policy. Solid State Meter was introduced in Korea since 1993 and it is applied to the high voltage customer exceeding 100kW in order to equalize daily load curve. In recent days, KEPCO has a Plan to use the Solid State Meter which has a data recording and remote meter-reading function for low voltage customer to introduce the real-time pricing system and reduce peak power in the near future. So, this paper suggests the specification and function of Solid State Meter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1343-1344
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• 2007

In this paper, we investigated mechanical characteristics about thermal properties in semiconductor layer of power cables. Method of specimen making used solution mixing and Tensometer 2000 of Alpha used for measurement of stress and strain. Semiconductor layer made an experiment on separately environmental temperature$[25^{\circ}C]$ and high temperature$[90^{\circ}C]$ which running temperature$[90^{\circ}C]$ of cables exposed. As a result, specimen of applicable DFS(Dual Filler System) could know mechanical superiority that its structural characteristics reinforcement considered thermal characteristics.

• Steel and Composite Structures
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• 제43권3호
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• pp.363-373
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• 2022

As a key reinforcement connection between a tower and a substructure in offshore wind turbine system, the transition piece is inevitably subjected to cyclic dynamic environmental loads such as wind, current and wave. Therefore, well designed transition piece with high strength and good fatigue resistance is of great significance to the structural safety and reliability of offshore wind power systems. In this study, the structural behavior of the transition piece was studied by an extensive sets of finite element analyses. Three widely used types of transition piece were considered. The characteristics of stress development, fatigue life and weight depending on the type of the transition piece were investigated in the ultimate limit state (ULS) and the fatigue limit state (FLS) of a 5-MW offshore wind turbine to be placed in Korea. An optimal form of the transition piece was proposed based on this parametric study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권3호
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• pp.551-569
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• 2024

With the rapid development of electric vehicles (EVs) industry, EV charging service becomes more and more important. Especially, in the case of suddenly drop of air temperature or open holidays that large-scale EVs seeking for charging devices (CDs) in a short time. In such scenario, inefficient EV charging scheduling algorithm might lead to a bad service quality, for example, long queueing times for EVs and unreasonable idling time for charging devices. To deal with this issue, this paper propose a Deep-Q-Network (DQN) based two-stage scheduling method for the large-scale EVs charging service. Fine-grained states with two delicate neural networks are proposed to optimize the sequencing of EVs and charging station (CS) arrangement. Two efficient algorithms are presented to obtain the optimal EVs charging scheduling scheme for large-scale EVs charging demand. Three case studies show the superiority of our proposal, in terms of a high service quality (minimized average queuing time of EVs and maximized charging performance at both EV and CS sides) and achieve greater scheduling efficiency. The code and data are available at THE CODE AND DATA.

• International Journal of Computer Science & Network Security
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• 제22권3호
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• pp.37-44
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• 2022

Plug-in Hybrid electric vehicles (PHEV) show great potential to reduce gas emission, improve fuel efficiency and offer more driving range flexibility. Moreover, PHEV help to preserve the eco-system, climate changes and reduce the high demand for fossil fuels. To address this; some basic components and energy resources have been used, such as batteries and proton exchange membrane (PEM) fuel cells (FCs). However, the FC remains unsatisfactory in terms of power density and response. In light of the above, an electric storage system (ESS) seems to be a promising solution to resolve this issue, especially when it comes to the transient phase. In addition to the FC, a storage system made-up of an ultra-battery UB is proposed within this paper. The association of the FC and the UB lead to the so-called Fuel Cell Battery Electric Vehicle (FCBEV). The energy consumption model of a FCBEV has been built considering the power losses of the fuel cell, electric motor, the state of charge (SOC) of the battery, and brakes. To do so, the implementing a reinforcement-learning energy management strategy (EMS) has been carried out and the fuel cell efficiency has been optimized while minimizing the hydrogen fuel consummation per 100km. Within this paper the adopted approach over numerous driving cycles of the FCBEV has shown promising results.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제12권10호
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• pp.299-308
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• 2023

다양한 서비스가 등장으로 인해 스펙트럼 부족 문제가 가속하됨에 따라, 면허 대역에서 통신하던 사용자들을 비면허 대역에서 통신하는 NR-U(New Radio-Unlicensed)가 등장하였다. 하지만 NR-U 네트워크 사용자로 인해 동일한 비면허 대역에서 통신하는 Wi-Fi 네트워크 사용자의 성능이 감소하게 된다. 본 논문에서는 NR-U 네트워크 사용자와 WiFi 네트워크 사용자가 공존해있는 비면허 대역의 처리량과 비면허 대역의 사용에 대한 공평성을 동시에 최대화하는 것을 목표로 한다. 먼저 비면허 대역에서 전송률 분할 다중 접속 기술을 활용한 NR-U 네트워크의 합-전송 속도 (Sum of Rate)를 최대화하기 위해 강화 학습의 몬테 카를로 정책 하강법(Monte Carlo Policy Gradient)을 활용한 최적의 전력 할당 기법을 제안하였다. 그 뒤, 동일한 비면허 대역에서 NR-U 네트워크와 WiFi 네트워크의 공존을 위해 시스템 처리량과 공정성을 동시에 최대화할 수 있는 게임 이론의 순차적 라이파 협상 해법(Sequential Raiffa Bargaining Solution)을 활용한 채널 점유 시간 분할 알고리즘을 제안하였다. 시뮬레이션 결과에서 동일한 전력 할당 기법을 사용하였을 때, 본 논문에서 제안한 전송률 분할 다중 접속 기술이 기존의 다중 접속 기술들보다 더 빠른 합-전송속도를 보임을 확인하였다. 또한 비면허 대역 네트워크의 전송량과 공평성을 비교해본 결과 본 논문의 순차적 라이파 협상 해법을 활용한 채널 점유 시간 분할 알고리즘이 타 알고리즘보다 처리량과 공정성을 동시에 만족함을 입증하였다.

• 접착 및 계면
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• 제13권1호
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• pp.45-50
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• 2012

폴리케톤(polyketone, PK) 섬유는 고무의 강화재로 사용하기 위해서 최근 개발되고 있는 소재이다. 섬유의 고무와의 접착성을 향상시키기 위하여 플라즈마로 표면을 개질하였다. 산소 플라즈마 처리에 의한 섬유표면의 물리적 형태변화를 관찰하기 위하여 주사전자현미경과 원자현미경을 이용하여 관찰하였다. 섬유표면의 화학적 조성변화를 XPS (X-ray photoelectron spectroscopy)를 이용하여 알아보았다. 최종적으로 이러한 변화가 PK 섬유와 고무와의 계면접착력에 어떠한 영향을 미치는지를 microdroplet debonding 시험을 통해 분석하였다. 플라즈마 처리에 의하여 섬유표면에 산소함유기들이 증가하는 결과를 보였으며, 처리시간과 처리전력이 증가함에 따라 에칭에 의한 표면조도(RMS roughness)가 증가하였다. 그러나 장시간의 플라즈마 처리조건에서는 표면에 degradation이 발생하여 오히려 표면조도가 감소하는 결과를 보였다. PK 섬유와 고무와의 계면전단강도는 처리시간 60 s의 80 W, 처리전력 60 W의 180 s에서 처리한 경우에 최대 계면전단강도를 나타내었다. 그러나 그 이상으로 증가하면 degradation이 발생하면서 계면전단강도가 감소하였다.