649 research outputs found
STSAT-2C mission achievements with on orbit verifications
No full textThe STSAT-2C is a small satellite with 100kg mass and was launched on 30 January 2013, on the third fight of the KSLV-1, Korean rocket. Lift of occurred from the Naro Space Centre in Korea, and the launch vehicle successfully deployed the satellite into at 297km by 1,512km Low Earth Orbit inclined at 80.3 degrees. The objectives of STSAT-2C consist of three missions. The first is to demonstrate the capability of the KSLV-I as a launch vehicle for LEO missions. The Second is observation of space environment. And the third is to perform new space technology demonstration in orbit. The STSAT-2C was developed very shortly in a year for the KSLV-1, which had previously failed to launch STSAT-2A in 2009 and STSAT-2B in 2010. The STSAT-2C is operated by Satellite Technology Research Center of KAIST and was achieved mission requirement successfully in orbit. It has new developed space technology include IR Sensor, Femto-Second Laser, Reaction Wheel and Li-Ion battery system using COTS devices and etc
Detection of fatigue crack on a rotating steel shaft using air-coupled nonlinear ultrasonic modulation
No full textRotating shafts in drop lifts of manufacturing facilities are susceptible to fatigue cracks as they are under repetitive heavy loading and high speed spins. However, it is challenging to use conventional contact transducers to monitor these shafts as they are continuously spinning with a high speed. In this study, a noncontact crack detection technique for a rotating shaft is proposed using air-coupled transducers (ACTs). (1) Low frequency (LF) and high frequency (HF) sinusoidal inputs are simultaneously applied to a shaft using two ACTs, respectively. A fatigue crack can provide a mechanism for nonlinear ultrasonic modulation and create spectral sidebands at the modulation frequencies, which are the sum and difference of the two input frequencies Then LF and HF inputs are independently applied to the shaft using each ACT. These three ultrasonic responses are measured using another ACT. (2) The damage index (DI) is defined as the energy of the first sideband components, which corresponding to the frequency sum and difference between HF and LF inputs. (3) Steps 1 and 2 are repeated with various combinations of HF and LF inputs. Crack existence is detected through an outlier analysis of the DIs. The effectiveness of the proposed technique is investigated using a steel shaft with a real fatigue crack
High Efficiency and High Power Density Weinberg Converter Reducing Conduction Loss and Output Current Ripple for Space Applications
No full textWeinberg converter is widely used to battery discharge regulator of satellite system because it guarantees soft-switching of all devices and has low output current ripple. However, due to leakage inductance of the coupled inductor and transformer, the voltage stress of powering diode and the output current spike are increased. To overcome these problems, weinberg converter with auxiliary switch and capacitor is presented in this paper. The proposed converter significantly reduces the voltage stress of powering diode. In additions, the output current spike is decreased by adopting auxiliary circuit. Thus, the conduction loss of the powering diode and output current ripple are reduced. As a results the proposed converter achieves high efficiency and high power density with the reduced output filter. The verification is performed with 400 W/50 V prototype
비접촉 내구 진단 장치 및 방법
No full textA non-contact durability diagnosis apparatus includes: (a) applying non-contactly and sequentially at least two excitation ultrasonic waves to an object and storing frequency signals generated from the object; (b) applying non-contactly and simultaneously the at least two excitation ultrasonic waves to the object and storing frequency signals generated from the object; (c) storing derived frequency signals remaining after removing an overlapping portion of the frequency signals of step (a) and the frequency signals of step (b); and (d) determining that the object is damaged when at least one of the generated frequency signals of step (c) is larger than a predetermined value
Topology optimization of hierarchical sensor fusion network considering time delay
No full textTime delay in sensor fusion is one of the main obstacles to situational awareness and can be mitigated through sensor network planning. This paper deals with topology optimization problem considering time delay in hierarchical sensor fusion network. For this purpose, the network utility maximization (NUM) problem is formulated by quantifying the gain from the information fusion of the local sensor nodes considering the time delay by borrowing the mutual information form, and the centralized optimization is performed using the genetic algorithm
mTORC1 accelerates retinal development via the immunoproteasome
No full textThe numbers and types of cells constituting vertebrate neural tissues are determined by cellular mechanisms that couple neurogenesis to the proliferation of neural progenitor cells. Here we identified a role of mammalian target of rapamycin complex 1 (mTORC1) in the development of neural tissue, showing that it accelerates progenitor cell cycle progression and neurogenesis in mTORC1-hyperactive tuberous sclerosis complex 1 (Tsc1)-deficient mouse retina. We also show that concomitant loss of immunoproteasome subunit Psmb9, which is induced by Stat1 (signal transducer and activator of transcription factor 1), decelerates cell cycle progression of Tsc1-deficient mouse retinal progenitor cells and normalizes retinal developmental schedule. Collectively, our results establish a developmental role for mTORC1, showing that it promotes neural development through activation of protein turnover via a mechanism involving the immunoproteasome.
Track management architecture for distributed multiple radar fusion system
No full text학위논문(석사) - 한국과학기술원 : 항공우주공학과, 2017.2,[iv, 41 p. :]다수 레이다를 통해 얻은 표적 정보의 융합은 통합 전장 상황 인식을 통해 작전수행능력의 향상을 가능하게 해준다. 따라서 이를 위한 다중 레이다 융합 시스템은 정보 처리 및 융합 성능 보장이 필수적이다. 분산형 융합 시스템을 위한 이전 연구 사례들은 최적성을 고려한 추적 연관 및 융합에 대한 접근법이 대부분이었다. 하지만 고 신뢰도를 요구하는 방공 레이다 융합 시스템에서는 다양한 상황에 대해 높은 안정성을 보장하기 위한 구조적, 관리적 접근이 필수적이라고 할 수 있다. 본 논문은 추적 연관, 추적 융합 기능을 포함하는 다중 레이다 융합 시스템을 위한 안정적 추적 관리 구조 선정을 목적 으로 한다. 이를 위해 다수의 하위 레이다와 상위 융합 센터 로 이루어진 분산형 다중 레이다 융합시스템에 알맞은 융합 구조 및 융합 기법을 선정하고 추적 병합 기능을 포함하는 안 정적 추적 관리 구조를 제시하였고, 다수 탄도 표적에 대한 시뮬레이션을 통해 검증하였다.한국과학기술원 :항공우주공학과
Highly reliable organic light-emitting diodes with optimized fill factor based on rotational membrane design for stretchable displays
No full textStretchable displays represent a critical advancement in next-generation wearable devices, attracting attention for their potential to address numerous challenges. This study introduces a novel stretching approach for stretchable devices through a rotational membrane design. Patterned substrates offer significant advantages in process compatibility and device performance among various fabrication methods. The rotational patterned substrate easily enables structural modifications, while vacuum deposition facilitates precise deposition of thin-film encapsulations and organic light-emitting diode (OLED) layers. The resulting stretchable OLED (SOLED) with optimized Al2O3/SiO2 nanolaminate/parylene-C-based multibarrier encapsulation demonstrates comparable luminance, current density, and operational lifespan to glass-based OLED devices. The innovative membrane rotation technique evenly distributes stress across the substrate, ensuring stability under high-strain conditions. Notably, the structure remained stable under a strain of 60%, exceeding twice the strain tolerance of previous designs. This approach addresses the strain fill-factor limitations observed in prior studies, achieving sufficient strain capacity for high-density displays. Consequently, SOLEDs with high fill-factors minimize non-emissive circuit areas, paving the way for high-luminance, reliable, and stretchable displays tailored for next-generation wearable technologies.
Unlocking Robotic Autonomy: A Survey on the Applications of Foundation Models
No full textThe advancement of foundation models, such as large language models (LLMs), vision-language models (VLMs), diffusion models, and robotics foundation models (RFMs), has become a new paradigm in robotics by offering innovative approaches to the long-standing challenge of building robot autonomy. These models enable the development of robotic agents that can independently understand and reason about semantic contexts, plan actions, physically interact with surroundings, and adapt to new environments and untrained tasks. This paper presents a comprehensive and systematic survey of recent advancements in applying foundation models to robot perception, planning, and control. It introduces the key concepts and terminology associated with foundation models, providing a clear understanding for researchers in robotics and control engineering. The relevant studies are categorized based on how foundation models are utilized in various elements of robotic autonomy, focusing on 1) perception and situational awareness: object detection and classification, semantic understanding, mapping, and navigation; 2) decision making and task planning: mission understanding, task decomposition and coordination, planning with symbolic and learning-based approaches, plan validation and correction, and LLM-robot interaction; 3) motion planning and control: motion planning, control command and reward generation, and trajectory generation and optimization with diffusion models. Furthermore, the survey covers essential environmental setups, including real-world and simulation datasets and platforms used in training and validating these models. It concludes with a discussion on current challenges such as robustness, explainability, data scarcity, and real-time performance, and highlights promising future directions, including retrieval augmented generation, on-device foundation models, and explainability. This survey aims to systematically summarize the latest research trends in applying foundation models to robotics, bridging the gap between the state-of-the-art in artificial intelligence and robotics. By sharing knowledge and resources, this survey is expected to foster the introduction of a new research paradigm for building generalized and autonomous robots.
근접한 사용자간의 간섭을 줄이기 위한 랜덤 안테나 선택 기법
No full text학위논문(석사) - 한국과학기술원 : 전기및전자공학과, 2014.2, [ iii, 32 p. ]Since millimeter (mm)-wave suffer significant path loss than microwave, beamforming which can obtain array gain is required. In this thesis, we consider analog beamforming with phase shifter supporting multiuser. Also, one phase shifter at each antenna is constraint in our system to reduce the hardware complexity. In multiuser analog beamforming system, management of interference from closely located users is important because interference from farther located users can be suppressed by using of beamforming. We propose beamforming with random antenna selection to mitigate interference from nearby users. Also, low rate spread code is adopted for reliable communication in case of main beams overlapping. In this thesis, we compare fixed and random antenna selections and analyze the interference and bit error rate (BER) with respects to user`s positions. Simulation and analysis indicate that beamforming with random antenna selections is advantageous when mitigating interference from closely located users.한국과학기술원 : 전기및전자공학과
- …
