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Fast Sampling-Based Cost-Aware Path Planning With Nonmyopic Extensions Using Cross Entropy
Suh, Junghun,Gong, Joonsig,Oh, Songhwai IEEE 2017 IEEE TRANSACTIONS ON ROBOTICS Vol.33 No.6
<P>This paper presents a cost-effective motion-planning method for robots operating in complex and realistic environments. While sampling-based path-planning algorithms, such as a rapidly exploring random tree (RRT) and its variants, have been highly effective for general path-planning problems, it is still difficult to find the minimum cost path in a complex space efficiently since RRT-based algorithms extend a search tree locally, requiring a large number of samples before finding a good solution. This paper presents an efficient nonmyopic path-planning algorithm by combining RRT* and a stochastic optimization method, called cross entropy. The proposed method constructs two RRT trees: The first tree is a standard RRT* tree, which is used to determine the nearest node in the tree to be extended to a randomly chosen point, and the second tree contains the first tree with additional long extensions. By maintaining two separate trees, we can grow the search tree nonmyopically to improve the efficiency of the algorithm while ensuring the asymptotic optimality of RRT*. From an extensive set of simulations and experiments using mobile and humanoid robots, we demonstrate that the proposed method consistently finds low-cost paths faster than the existing algorithms.</P>
Efficient Environmental Monitoring Using Cost-Aware Path Planning
Junghun Suh,Songhwai Oh 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
This paper presents an efficient environmental monitoring strategy that considers the information gain along the trajectory of a robot. In order to monitor environmental parameters such as temperature and chemical concentration, an estimation method based on Gaussian process regression is used. The goal of this paper is to model accurate spatio-temporal phenomena by reducing the uncertainty over the surveillance region. A cost-aware path planning based environmental monitoring is desirable for mobile sensor networks since robots are coordinated to follow a trajectory with the maximum accumulated information gain, as well as the traveling distance. The proposed method with respect to different sampling methods is demonstrated in simulations.
Cleavage Agents for Soluble Oligomers of Amyloid β Peptides
Suh, Junghun,Yoo, Sang Ho,Kim, Min Gyum,Jeong, Keunhong,Ahn, Jae Young,Kim, Myoung-soon,Chae, Pil Seok,Lee, Tae Yeon,Lee, Jaehwa,Lee, Jeongkuk,Jang, Yun Ah,Ko, Eun Hwa WILEY-VCH Verlag 2007 Angewandte Chemie Vol.46 No.37
<B>Graphic Abstract</B> <P>Clearing the mind: Peptide-cleaving agents for amyloid β-42 (Aβ<SUB>42</SUB>) oligomers (see scheme), the intermediate neurotoxic species in the pathology of Alzheimer's disease, have been obtained from a combinatorial library built using the Co<SUP>III</SUP> complex of 1,4,7,10-tetraazacyclododecane as the reaction center. Effective cleavage of the Aβ<SUB>42</SUB> oligomers occurs at submicromolar concentrations of the agents. <img src='wiley_img/14337851-2007-46-37-ANIE200702399-content.gif' alt='wiley_img/14337851-2007-46-37-ANIE200702399-content'> </P>
Vision-Based Coordinated Localization for Mobile Sensor Networks
Junghun Suh,Seungil You,Sungjoon Choi,Songhwai Oh IEEE 2016 IEEE transactions on automation science and engine Vol.13 No.2
<P>In this paper, we propose a coordinated localization algorithm for mobile sensor networks with camera sensors to operate under Global Positioning System (GPS) denied areas or indoor environments. Mobile robots are partitioned into two groups. One group moves within the field of views of remaining stationary robots. The moving robots are tracked by stationary robots and their trajectories are used as spatiotemporal features. From these spatiotemporal features, relative poses of robots are computed using multiview geometry and a group of robots is localized with respect to the reference coordinate based on the proposed multirobot localization. Once poses of all robots are recovered, a group of robots moves from one location to another while maintaining the formation of robots for coordinated localization under the proposed multirobot navigation strategy. By taking the advantage of a multiagent system, we can reliably localize robots over time as they perform a group task. In experiment, we demonstrate that the proposed method consistently achieves a localization error rate of 0.37% or less for trajectories of length between 715 cm and 890 cm using an inexpensive off-the-shelf robotic platform.</P>
서정헌,Junghun Suh,Emil Thomas Kaiser Korean Chemical Society 1978 대한화학회지 Vol.22 No.3
상온에서 카르복시펩티다제 A에 의한 에스테르 기질의 가수분해 반응을 여러가지 외부 시약의 존재하에 행하였다. 산무수물 형태의 아실-효소중간체가 외부시약에 의해 공격받는다면 아실 부분에 포획된 생성물이나 효소부분에 포획된 생성물이 형성될 것이다. 반응생성물의 분광도와 효소활성도의 변화를 조사한 결과 포획반응의 생성물은 검출되지 않았다. 또한, O-(o-hydroxyphenylacetyl)-L-${\beta}$-phenyllactate가수분해에 대한 효소 반응속도변수를 측정하였다. 이 기질의 o-히드록시기가 분자내 포획기로서 작용하여 산무수물형태의 아실-효소중간체를 공격하여 20coumaranone이 형성되었나를 조사하였으나 분자내 포획반응이 일어났다는 증거는 얻지 못하였다. 이러한 중간체 포획반응의 실패는 포획용 시약이 아실-효소 중간체의 무수산기에 접근할때 입체적 방해를 받거나 중간체의 가수분해 단계도 효소에 의해 촉매되기 때문이라고 생각된다. Carboxypeptidase A-catalyzed hydrolysis of ester substrates was carried out at room temperature in the presence of a number of external reagents. If the acyl-enzyme intermediate, an anhydride, is attacked by the external reagents, products formed by trapping at the acyl portion or at the enzyme portion of the anhydride group can be obtained. Examination of the uv/vis spectral properties of the reaction products and of changes in enzyme activity indicated that such trapping reactions did not occur. Also performed was evaluation of enzymatic rate parameters for the the hydrolysis of O-(o-hydroxyphenylacetyl)-L-${\beta}$-phenyllactate. Detection of 2-coumaranone possibly formed by attack of the o-hydroxy group as an intramolecular trapping group at the acyl-enzyme intermediate was tried, but no evidences for the intramolecular trapping reaction were obtained. Failure to trap the intermediate was discussed in terms of steric hindrance imposed on the approach of the trapping reagents to the anhydride group of the acyl-enzyme intermediate and of the fast enzymatic breakdown of the intermediate.
류정헌(Junghun Ryu),이준호(Junho Lee),서혁(Hyuk Suh),장기원(Kiwon Jang),김용욱(Yongwook Kim),오승협(Seunghyub Oh) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.11
국가 우주개발 중장기 계획에 따라 수행중인 한국형우주발사체(KSLV-1) 개발사업 중 2단에 사용할 Kick Motor(이하 KM)는 작동고도가 약 300km이므로 진공의 환경과 유사하다. 고고도에서 작동하는 로켓은 성능을 최대한 향상시키기 위해서 노즐의 팽창비를 상대적으로 크게 설계하며, 동일한 로켓으로 지상에서 연소시험 할 경우 노즐에서 박리가 발생하여 정확한 추력을 예측할 수가 없다. 본 논문에서는 고고도에서 KM 추력성능을 입증하기 위하여 수행한 시험설비의 설계/구축과정과 그 결과를 다루고 있다. The 2nd stage Kick Motor under the national aerospace middle and long term plan operates over the height of 300Km. Rocket Motors, designed for operation in high altitude, need nozzles with large expansion ratio to improve thrust efficiency. Hence, to evaluate the performance of such rocket motors on the ground, similar low pressure with the operating condition has to be made for the ground test to prevent flow separation in the nozzle. This study is for the installation of the high altitude test facility and test result for Kick Motor.
펄스분리장치를 적용한 소형 추진기관의 설계, 제작 및 시험평가
류정헌(Junghun Ryu),이원복(Wonbok Lee),서혁(hyuk Suh),김원훈(Wonhoon Kim),오종윤(Jongyun Oh) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.5
하나의 고체 추진기관에서 이중펄스 추력을 발생시키는 기술은 기존의 일회성 추력발생 방식에 비하여 여러 가지 장점이 있다. 추진기관에 펄스분리장치를 적용하면 적절한 추력배분을 통하여 유도탄의 사거리 연장 및 종말속도를 향상시킨다. 본 연구에서는 격벽형 펄스분리장치의 성능을 검증하기 위하여 소형 추진기관을 설계, 제작하여 지상연소시험을 수행하였다. 이를 통하여 펄스분리장치의 파열특성, 구조적 안전성 및 내열특성 등을 확인하였으며 향후 실물형 이중펄스 추진기관 설계 시 필요한 데이터 등을 확보하였다. A dual pulse solid rocket motor has several advantages compared to the single one. The range and the terminal velocity of the guided missile can be remarkably increased by the application of the pulse separation device(PSD) to the solid rocket motor which resulted in appropriate thrust distribution. In this study, the subscale dual pulse solid rocket motor with the bulkhead type PSD was designed, manufactured, and fire-tested. The bursting pressure, thermal characteristics, and the structural safety of the PSD were obtained by the tests and the results will be applied to the design of full-scale dual pulse rocket motor.