• 제목/요약/키워드: Keeping performance

검색결과 617건 처리시간 0.026초

비행선의 정점체공 모드 자동조종장치 예비설계

  • 유혁;;김성필;주광혁;안이기
    • 항공우주기술
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    • 제2권1호
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    • pp.11-21
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    • 2003
  • 본 논문에서는 비행선의 정점체공을 위한 자동조종장치 예비 설계 결과를 다루었다. 이를 위해 비행선의 선형 운동방정식을 유도하였다. 그리고 선형 모형을 이용하여 비행선의 순항 모드의 정점 체공 모드에 적합한 제어 법칙을 제시하였다. 선형 시뮬레이션 결과를 통하여 정점 체공 자동비행이 가능함을 확인할 수 있었다.

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Formation Geometry Center based Formation Controller Design using Lyapunov Stability Theorem

  • Lee, Ji-Eun;Kim, Hyeong-Seok;Kim, You-Dan;Han, KiHoon
    • International Journal of Aeronautical and Space Sciences
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    • 제9권2호
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    • pp.71-78
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    • 2008
  • New formation flight controller for unmanned aerial vehicles is proposed. A behavioral decentralized control approach called formation geometry center control is adopted. Trajectory tracking as well as formation geometry keeping are the purpose of the formation flight, and therefore two controllers are designed: a trajectory tracking controller for reference trajectory tracking, and a position controller for formation geometry keeping. Each controller is designed using Lyapunov stability theorem to guarantee the asymptotic stability. Formation flight controller is finally obtained by combining the trajectory tracking controller and the formation geometry keeping controller using a weighting parameter that depends on the relative distance error between unmanned aerial vehicles. Numerical simulations are performed to validate the performance of the proposed controller.

Design and Application of an Adaptive Neural Network to Dynamic Positioning Control of Ship

  • Nguyen, Phung-Hung;Jung, Yun-Chul
    • 한국항해항만학회:학술대회논문집
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    • 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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    • pp.285-290
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    • 2006
  • This paper presents an adaptive neural network based controller and its application to Dynamic Positioning (DP) control system of ship. The proposed neural network based controller is developed for station-keeping and low-speed maneuvering control of ship. At first, the DP system configuration is described. And then, to validate the proposed DP system, computer simulations of station-keeping and low-speed maneuvering performance of a multi-purpose supply ship are presented under the influence of measurement noise, external disturbances such as sea current, wave, and wind. The simulations have shown the feasibility of the DP system in various maneuvering situations.

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Fresh Produce E-Commerce Supply Chain Coordination Considering Promotional and Freshness-Keeping Efforts

  • Xiaowei Hai;Tian Liao;Chanchan Zhao
    • Journal of Information Processing Systems
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    • 제19권4호
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    • pp.513-526
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    • 2023
  • Supply chain coordination plays a critical role in improving the enterprise performance and the competitive advantage of fresh e-commerce. This study explores the coordination problem of a two-echelon fresh produce e-commerce supply chain comprising a fresh e-commerce enterprise and a fresh supplier in a novel framework. In this framework, the fresh e-commerce sells fresh produce and provides promotion effort; meanwhile, the fresh supplier deliveries fresh produce and provides freshness-keeping effort. Specifically, the optimal decisions under centralized and decentralized decision-making are compared, and it is found that centralized decision-making is more profitable. Based on this work, we created a cost-sharing and revenue-sharing combination contract. This study demonstrates that this contract effectively coordinates the supply chain and makes both parties achieve Pareto optimization when the parameters meet certain conditions. Finally, the feasibility and validity of the contract are presented through a numerical example.

도로주행환경을 고려한 차선유지지원장치 성능 평가 (Performance Evaluation of Lane Keeping Assistance System)

  • 우현구;용부중;김경진
    • 자동차안전학회지
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    • 제6권2호
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    • pp.29-35
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    • 2014
  • Lane Keeping Assistance System(LKAS) is a kind of Advanced Driver Assistance Systems(ADAS) which are developed to automate/ adapt/ enhance vehicle systems for safety and better driving. The main system function of LKAS is to support the driver in keeping the vehicle within the current lane. LKAS acquires information on the position of the vehicle within the lane and, when required, sends commands to actuators to influence the lateral movement of the vehicle. Recently, the vehicles equipped with LKAS are commercially available in a few vehicle-advanced countries and the installation of LKAS increases for safety enhancement. The test procedures for LKAS evaluations are being discussed and developed in international committees such as ISO(the International Organization for Standardization). In Korea, the evaluations of LKAS for vehicle safety are planned to be introduced in 2016 KNCAP(Korean New Car Assessment Program). Therefore, the test procedures of LKAS suitable for domestic road and traffic conditions, which accommodate international standards, should be developed. In this paper, some bullet points of the test procedures for LKAS are discussed by extensive researches of previous documents and reports, which are released in public in regard to lateral test procedures including LKAS and Lane Departure Warning System(LDWS). Later, it can be helpful to make a draft considering domestic traffic situations for test procedures of LKAS.

인사동의 물리적 심리적 이미지의 평가 (An Evaluation on the Physical and Psychological Image of Insa-Dong)

  • 조정숙;김남조
    • 한국조경학회지
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    • 제30권2호
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    • pp.12-22
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    • 2002
  • This study examines the visitors'evaluations of tourism resources in Insa-dong, which the Seoul metropolitan government has improved recently. This study adopted the method of Importance-Performance Analysis by collecting data through questionnaires. A random sampling of visitors to Insa-dong was conducted in June and July,2001. The survey included questions on the physical and psychological components of Insa-dong's tourism resources. In the case of physical components, eight factors(ancient arts shop, art gallery, atelier, calligraphy shop, pottery arts, traditional tea house, antique shop, traditional clothes) out of thirteen were categorized as 'keeping up the good work'. None of the Physical components was shown as 'low priority'or'possible overkill'. In particular, four factors(restaurant, heritage, Korean-style house and alley, traditional cultural festival) need to be impoved most urgently in terms of visitors'satisfaction. Survey results realize them as high priority in importance but low in performance, thereby designated as, 'concentrate here'. An image of the 'street' showed to be high in importance and identical in performance, so can be categorized between'keeping up the good work'and 'concentrate here'. The results show that unusual outdoor spaces and the festivals of Insa-dong have a significant meaning to the visitors. In the case of psychological components, three factors(general atmosphere experience of unusual atmosphere, appropriateness of stroll time) out of seventeen were categorized as 'keeping up the good work'. Ore factor (shopping) was designated as 'low priority'and not found to be 'possible overkill'. Thirteen factors (various events, possibility of various activity, various flood, richness of play, new experience, education cultural inheritance, parking facilities, resting places, green spaces, meeting places, guide map and information, cleanliness of facilities/convenience) need to be improved mast urgently in terms of visitors' fulfillment. They are perceived as areas of 'concentrate here'. This confirms that attractive events are essential for the recent visitor satisfaction. Furthermore, visitors are not satisfied with its amenity and acccss in Insa-dong despite the improvements. In conclusion, positive impressions, both physical and psychological, should be maintained while factors mentioned to be lacking should be prioritized in order of necessity to improve the image of Insa-dong and solutions need to be found and implemented. The results of this study would be helpful in the planning and management of nsa-dong considering the visitors'requirements.

미소진동저감용 진동절연기의 성능유지를 위한 극저온 냉각용 압축기 조립체 열제어 설계 (Thermal Design of Cryogenic Compressor with Strategies for Keeping Performance of Micro-vibration Isolation System)

  • 오현웅;이경주;정석용;신소민
    • 한국항공우주학회지
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    • 제40권3호
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    • pp.237-242
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    • 2012
  • 극저온이 요구되는 우주용 탑재장비의 냉각을 위해 일반적으로 Pulse Tube-type 압축기가 적용되고 있으며, 궤도상에서 압축기의 냉각성능, 임무수명 및 비대칭 온도분포에 의한 미소진동발생 방지를 위해 압축기를 허용온도 범위로 유지하는 열제어가 필요하다. 압축기는 궤도 운용 시 미소진동을 발생하여 관측성능이 요구되는 탑재체의 지향성능을 저하시키는 원인으로 작용한다. 본 논문에서는 압축기의 미소진동 방지를 목적으로 적용된 진동절연기의 성능유지 및 압축기의 허용온도범위 유지를 위한 열제어 성능을 동시에 만족하는 우주용 압축기 조립체의 열설계를 제안하였으며, 설계의 유효성을 해석적으로 입증하였다.

NUMA 시스템에서 소유권에 근거한 원격 캐시 교체 정책 (Keeping-ownership Cache Replacement Policies for Remote Access Caches of NUMA System)

  • 신숭현;곽종욱;장성태;전주식
    • 한국정보과학회논문지:시스템및이론
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    • 제31권8호
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    • pp.473-486
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    • 2004
  • NUMA 시스템은 원격의 메모리에 반복적으로 접근하는 오버헤드를 피하기 위해 지역 노드내에 원격 캐시를 둔다. 이러한 원격 캐시를 사용하여 원격 메모리로의 접근 지연 시간을 감소시키고 네트워크 상의 트래픽 양을 줄이지 못한다면 다중 프로세서 시스템의 성능 저하는 명백하다. 성능 상의 여러 기준 중에서 메모리 시스템과 관련해서는 캐시 교체 정책에 관한 연구가 계속되었고, 그 중 다중 프로세서 시스템에서의 캐시 교체 정책에 관한 연구도 이어졌다. 본 논문에서는 캐시의 공유 상태에 기반을 둔 교체 정책을 제안한다. 소유권이 없는 캐시 라인을 먼저 교체하고, 이를 통해 소유권이 옮겨지는 오버헤드를 피하여 메모리 지연 시간을 줄인다. 또한 소유권이 없는 캐시 라인에 지나친 피해가 얼도록, “MRU를 사용한 소유권 유지 교체 정책(KOM)”과 “참조 비트를 사용한 소유권 유지 교체 정책(KORB)”를 제안하고, 이를 LRU, Pseudo LRU(PLRU)와 비교한다. KOM과 KORB는 PLRU에 비하여 수행 시간에서 25%, 13%씩 각각 향상을 보였다. 특히 KOM은 하드웨어 복잡도가 현저히 낮음에도 불구하고 LRU에 가까운 성능을 나타냈다.

Degradation Analysis of User Terminal EIRP and G/T due to Station-Keeping Variation of Stratospheric Platform

  • Ku, Bon-Jun;Ahn, Do-Seob;Baek, Dong-Cheol;Park, Kwang-Ryang;Lee, Seong-Pal
    • ETRI Journal
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    • 제22권1호
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    • pp.12-19
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    • 2000
  • Wireless communication systems using airship have been proposed in worldwide. The airship will be located at the stratosphere about $20{\sim}23\;km$ above the sea level. The position of airship will vary within the station keeping range with time due to the drag of the wind in the stratosphere. When the earth station antenna has a high gain without the tracking function, the antenna performance may be degraded by a small variation of the airship. This means that variation of airship location could result in serious degradation of the system performance. In this paper, degradation in earth station's Equivalent Isotropic Radiated Power (EIRP) and Gain to noise Temperature ratio (G/T) due to the stratospheric platform movements has been derived by calculating the deviation angle of the main beam directions between the earth station and the platform antenna. In this case, the antenna of the earth station has been assumed circular and/or patch array antennas.

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선체 운동 평가를 위한 다기능 계측시스템 개발에 관한 연구 (A Study On the Development of Multi-Purpose Measurement System for the Evaluation of Ship Dynamic Motion)

  • 이윤석;김철승;공길영;송재욱;엄필용
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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    • pp.1155-1160
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    • 2005
  • In order to evaluate the safety of navigation at sea and the safety of mooring ship on berthing, it is necessary that the wave and wind induced ship dynamic motion should be measured in real time domain for the validity of theoretical evaluation method such as sea-keeping performance and safety of mooring. In this paper, the basic design of sensors is discussed and some system configurations were shown. The developed system mainly consists of 4 kinds of sensors such as three dimensional accelerator, two dimensional tilt sensor, two displacement sensors and azimuth sensor. Using the this measuring system, it can be obtained the 6 degrees of freedom of ship dynamic motions at sea and on berthing such as rolling, pitching, yawing, sway, heave, surge under the external forces.

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