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이건민(Gun-Min Lee),김종찬(Jong-Chan Kim) 한국자동차공학회 2017 한국자동차공학회 학술대회 및 전시회 Vol.2017 No.11
Control performance is significantly affected by two control parameters, sampling frequency and sensing to actuating delay. Higher sampling frequency and shorter delay makes better control performance, however, it makes the system difficult to schedule in a multitasking environment, where multiple control tasks share CPU resource. To maintain high frequency and short delay, task periods and deadlines should be kept very short that eventually leads to system unschedulability. Making the problem more complex, in AUTOSAR-based vehicle control systems, a large number of small functions runnables are mapped to periodic tasks that matches each runnable’s own period and data flow between sensing and actuation goes through a sequence of runnables with different periods. With this motivation, we present a novel algorithm that determines runnable periods that provides both the optimal control performance and system schdulability for AUTOSAR. Assuming that control performance is given as a linear function of frequency and delay, we use Lagrange multiplier to find the set of optimal periods with a constraint that the system utilization is less than 100% with EDF scheduling algorithm.
멀티코어를 이용한 운전자보조시스템의 모델기반 설계 및 검증
이건민(Gun-Min Lee),김종찬(Jong-Chan Kim) 한국자동차공학회 2017 한국자동차공학회 부문종합 학술대회 Vol.2017 No.5
As the demand of Advanced Driver Assistance System (ADAS) increases, the computing power requirements are also increasing in the automotive system. Moreover, the problem of too much energy consumption and manufacturing cost of the current singlecore computing environment is forcing the OEMs and suppliers to adapt multicore ECUs in their E/E architecture. In this paper, we first propose a model-based design and validation process on multicore ECUs for ADAS and show how much control performance improvement can be made by our method compared to the singlecore case. Also we conduct an empirical study regarding how the task-to-core mapping and the resulting inter-core data dependency affects the control performance.
전기방사를 이용한 Pullulan Electrospun Fiber Webs의 제조 및 특성
손태원(Tae Won Son),이건민(Gun Min Lee),이동원(Dong Won Lee),이주현(Ju Hyun Lee),임학상(Hak Sang Lim) 한국고분자학회 2012 폴리머 Vol.36 No.2
전기방사는 휘발성 용매에 녹아있는 다양한 물질들을 마이크로 크기의 섬유로 제조하는데 사용되고 있다. 이 번 연구에서는 물을 용매로 사용하여 pullulan을 전기 방사하였다. 부드러운 섬유를 얻기 위하여 pullulan 농도와 전 압을 최적의 조건으로 설정하였다. Pullulan 농도는 pullulan 용액의 점도와 표면 장력에 큰 영향을 받는다. Bead 형태 의 pullulan 전기방사 섬유는 5 wt%이하의 농도에서 얻어진다. Pullulan 용액의 농도가 10 wt%로 유지되고, 전압이 15 kV에 고정되었을 때, pullulan 섬유의 평균 직경은 200 nm로 감소하였다. Pullulan electrospun 섬유는 높은 용해도, 유연성, 부드러움과 강한 접착성을 보여준다. Electrospinning is a versatile process used to prepare micro or nano sized fibers from various materials dissolved in volatile solvents. This study reports electrospun pullulan fibrous webs fabricated through electrospinning using water as a solvent. The electrospinning conditions such as pullulan (PUL) concentration and applied voltage were optimized in order to obtain smooth electrospun fibers. The concentration of PUL greatly influenced the viscosity and surface tension of PUL solution. PUL beaded electrospun fibers were obtained from PUL solutions with concentrations lower than 5 wt%, while homogenous electrospun fibers were prepared from solutions with high concentration and high viscosity. The average diameters of PUL fibers were decreased to 200 nm when the polymer concentration was kept at 10 wt% and the applied voltage was fixed at 15 kV during electrospinning. PUL electrospun fiber exhibited higher solubility, flexibility, softness and adhesive strength.
최대호(Daeho Choi),이건민(Gun-Min Lee),전우태(Wootae Jeon),김종찬(Jong-Chan Kim) 한국자동차공학회 2020 한국 자동차공학회논문집 Vol.28 No.1
In control applications, control performance is affected by the control frequency and the sensor-to-actuator delay. In particular, automobile control applications should extract the best performance through limited hardware resources such as CPU. Under this motivation, we developed a control performance-aware AUTOSAR scheduling method. More specifically, we tried to find the optimal runnable periods that exploit the underlying hardware resource as best as possible to improve control performance. Thus, we defined control cost and schedulability constraint as functions of AUTOSAR runnable periods. Then, the Lagrange multiplier method is used to determine optimal runnable periods. Experimental results show that our method can develop a near-optimal solution with under 2 % performance loss, compared to the optimal result with under 1 ms of required computation time for practical size systems.
유연쇄를 사용한 개질 폴리에스터 공중합체의 제조와 그 특성(II) -Neopentyl glycol 단위체를 함유한 공중합 폴리에스터의 결정화 거동-
손태원,한송정,고재왕,이건민,Son, Tae-Won,Han, Song-Jung,Ko, Jae-Wang,Lee, Gun-Min 한국섬유공학회 2009 한국섬유공학회지 Vol.46 No.6
Poly(ethyleneterephthalate)(PET) was chemically modified through copolymerization of bis(2-hydroxyethyl) terephthalate (BHET) and neopentyl glycol (NPG). NPG was used as flexible chain moiety to enhance spinnability by retarding the stress-induced crystallization during spinning. The properties of the copolyester were investigated by using GPC, DSC(differential scanning calorimetry), TGA(thermogravimetry analysis), and $^1H-NMR$. From the result of GPC, it was found that the copolyesters were able to get higher molecular weight and narrower molecular weight distribution than those of PET obtained from BHET alone. Non-isothermal crystallization behavior of the copolymers was investigated by differential scanning calorimetry (DSC). Non-isothermal crystallization measurements showed that, with increasing the amount of comonomer, Tcm decreased.. It seems that the rate of crystallization of copolymer might be retarded during melt-spinning. Isothermal melt-crystallization measurement demonstrated that the rate of crystallization and the Avrami index were reduced with increasing the amount of comonomer.
차기구축함 통합마스트에 적용을 위한 전자기파 메타물질 흡수체의 온도 환경 내구성 검증
라영은(Young-Eun Ra),김용준(Yongjune Kim),정현준(Hyun-June Jung),박평원(Pyoungwon Park),조정대(Jeongdai Jo),이준식(Joonsik Lee),김명준(Myungjoon Kim),정준교(Joonkyo Jung),이건민(Gun-Min Lee),이종학(Jong-Hak Lee),이학주(Hak-Joo Lee) 한국전기전자학회 2020 전기전자학회논문지 Vol.24 No.1
본 논문에서는 차기구축함에 탑재될 통합 마스트의 레이더 반사면적을 감소시킬 수 있는 스텔스 기술로 응용하기 위해 해양 환경이 모사된 온도 환경 조건에서 전자기파 메타물질 흡수체의 내구성을 검증하였다. 이를 위해 미국 군사 규격인 MIL-STD-810H의 Method 501.7 중 Procedure I 조건에 따라 주기적으로 온도를 조절할 수 있는 항온 챔버에 저장 후 전자기파 메타물질 흡수체의 반사도를 측정하였다. 고온 환경시험 전과 후 모두 X 밴드 전체에서 스텔스 성능을 충족시킬 수 있는 -10 dB 미만의 반사도가 확인되었다. In this paper, the durability of an electromagnetic metamaterial absorber is verified in a temperature varying condition mimicking a maritime environment for the purpose of applying it to reduce the radar cross section of an integrated mast of the next-generation destroyer. To validate the durability, the reflectance of the electromagnetic metamaterial absorber was measured after storing it in a chamber that can control the temperature according to Procedure I of Method 501.7 included in MIL-STD-810H. Before and after the environmental test, both of the measured reflectances were retained less than -10 dB over the X band, that can guarantee the stealth functionality.