• 한국과학교육학회지
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• 제43권3호
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• pp.237-251
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• 2023

본 연구는 합성곱 신경망을 활용한 자동 채점 모델을 설계하고 학생의 운동학 그래프 답안에 적용함으로써, 과학 그래프 답안에 대한 자동 채점의 가능성을 탐색하였다. 연구자가 작성한 2,200개의 답안을 2,000개의 훈련 데이터와 200개의 검증 데이터로 데이터셋을 구성하고, 202개의 학생 답안을 100개의 훈련 데이터와 102개의 시험 데이터로 데이터셋을 구성하여 연구를 진행하였다. 먼저, 자동 채점모델을 설계하고 성능을 검증하는 과정에서는 연구자가 작성한 답안 데이터셋을 활용하여 그래프 이미지 분류에 최적화되도록 자동 채점모델을 완성하였다. 다음으로 자동 채점 모델에 훈련 데이터셋을 여러 유형으로 학습시키면서 학생의 시험 데이터셋에 대한 채점을 수행하여 훈련 데이터의 양이 많고 다양할수록 자동 채점 모델의 성능이 향상된다는 것을 확인하였고, 최종적으로 인간 채점과의 일치율은 97.06%, 카파 계수는 0.957, 가중 카파 계수는 0.968을 얻었다. 한편, 훈련 데이터로 학습되지 않은 유형의 답안의 경우 인간 채점자들 간에는 채점이 거의 일치하였으나, 자동 채점 모델은 일치하지 않게 채점하는 것을 확인하였다.

• 한국운동역학회지
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• 제24권3호
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• pp.301-308
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• 2014

The purpose of this study was to determine whether there are significant differences in kinematic variables and muscle activities of the thumb between two smartphone holding techniques. Twelve right handed university students(age $25.4{\pm}3.9yrs$, height $176.2{\pm}5.1cm$, weight $75.8{\pm}11.4kg$, hand length $19.2{\pm}1.1cm$) who have no musculoskeletal disorder were recruited as the subjects and had experience in using a smartphone for more than one year. Maximum joint angle, angular velocity, muscular activities were determined for each trial. For each dependent variable, paired t-test was used to determine whether there were significant differences between one hand (OH) and two hands ([TH], ${\rho}$ <.05). The results of this study showed that there were no significant differences between OH and TH in the maximum joint angle of the thumb. The angular velocity of each joint was not statistically significant between OH and TH. The statistical analysis revealed that the main effect of the smartphone holding conditions was significant in the peak normalized muscular activities of FDI and APL. Although smartphone holding technique doesn't affect on mobility and movement of the thumb joint, it may affect on active degree of the thumb and the upper extremity in directly and indirectly.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.26.2-26.2
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• 2011

Flyby anomaly (unexpected energy increase during Earth Gravity Assists) indicates existence of an unknown non-conservative perturbation which affects hyperbolic trajectories. This presentation focuses on first order position and velocity perturbation formulas derived in terms of classical orbital element variations for hyperbolic orbit. By using both the perturbation formulas and numerical approach, we analyze effects of hypothetical acceleration models proposed by Hasse (2009), Lewis (2009), Gerrad and Sumner (2008), and Busack (2007). Based on analysis of perturbation effect on low earth orbit, we find that typical position perturbation is about 10m which is much larger than current orbit determination accuracy. From this, we deduce that anomalous acceleration only affects hyperbolic orbit or behaves differently in bound orbit. On the other hand, based on analysis of perturbation effects on hyperbolic trajectories, we find that position and velocity perturbations are highly different from acceleration models, and all of proposed models fail to explain observed range and Doppler data. Thus, it can be concluded that not only energy variations but also kinematics gives us crucial clues on the flyby anomaly, and kinematical characteristic should be considered in modeling flyby anomaly.

• 전자공학회논문지SC
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• 제43권1호
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• pp.13-20
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• 2006

본 논문에서는 로봇 말단부에 장착된 카메라 환경에서 시각 궤환을 이용하는 로봇 매니퓰레이터의 자세제어 기법을 제안한다. 자세제어를 위한 기준 관절 속도와 관절 가속도는 외부루프의 특징점을 이용한 영상정보에서 생성된다. 영상평면상에서 특징점을 추종하기 위한 제어 입력은 로봇 동역학을 사용하였다. 영상평면상의 특징점과 관절 각속도 오차를 로봇 구동을 위한 제어입력에 포함시켜 파라미터 불확실성에 강인하도록 하였다. 시스템의 안정도는 Lyapunov 안정도 판별법을 이용하여 입증하였다. 제안된 제어기의 성능은 5-링크 2 자유도를 가지는 로봇에 대한 컴퓨터 시뮬레이션과 실험을 통해 검증하였다.

• 천문학회보
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• 제41권2호
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• pp.30.3-31
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• 2016

The M81 Group is the nearest among the known groups of galaxies. HI maps show that all main galaxies of this group are interacting, indicating that this group is in the active phase of formation. On the other hand, wide field imaging shows that globular cluster candidates are found not only in the member galaxies but also between the galaxies in this group. In this study we present preliminary results based on MMT/Hectospec spectroscopy of the globular cluster candidates in this group. We find that the intragroup globular clusters have mostly low metallicity, while the globular clusters in M81 have mostly high metallicity. We will discuss the implication of this result and the kinematics of the globular clusters in relation with the formation history of the M81 Group.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제6권1호
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• pp.22-29
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• 2003

This research aims at investigation of accuracy potential of RTK(Real-Time Kinematic) GPS in combination with Echo Sounder(E/S) for the coastal mapping. Apart from this purpose, the accuracy of ambiguity resolution with the OTF(On The Fly) method was tested with respect to the initialization time. The result shows that the accuracy is better than 1cm with 5-minute initialization in the distance of 10km baseline. The seaside topography was measured by the RTK GPS only, on the other hand the seafloor topography was surveyed in combination of RTK GPS and E/S. Comparing to the volume of seaside measured by RTK GPS and digital topographical map, the difference of only 2% was achieved. This indicates that the coastal mapping. As a result, it has been revealed that every possible noise in surveying could be corrected and the accuracy could be improved. The accuracy of GPS data acquired in real time was as good as that acquired by post processing. It is expected that it will be useful for the analysis of coastal geographic characteristics because DTM(Digital Terrain Model) can be also constructed for the harbor reclamation, the dredging, and the variation of soil movement in a river.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.449-454
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• 1994

The Stewart Platform is one example of a motion simulator which generater 6DOF motion in space by six actuators in parallel. The presented control methrol of 6DOF motion simulator is generally classified into two types, one is SISO and the other is MIMO control type. The SISO control can't compensate for external load variation and different dynamic behavior of 6DOF motion, trerefore this type don's control motion precisely. On the other hand, the MIMO control compensates for a interference of 6DOF motion because MIMO controller is designed with 6DOF motion simulator synamics. But MIMO control of motion simulator has a complexity of 6DOF displacement feedback, because in oder to obtain feedback value we must solve the forward kinematics using measurement of cylinder length or design a state estimator, unless measurement of 6DOF displacement is possible. In this paper, a multivariable controller using H .inf. optimal control theory is designed to consider a interference of 6DOF motion and to obtain robust,precise control of system. Also in order to solve the mentioned problem of MIMO control, this paper presents a modified MIMO control model which control 6DOF motion by using feedback of measurement od cylinder length.

• 한국해양공학회지
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• 제17권3호
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• pp.13-20
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• 2003

This research aims at investigation of accuracy potential of RTK(Real-Time Kinematic) GPS in combination with Echo Sounder(E/S) for the coastal mapping. Apart from this purpose, the accuracy of ambiguity resolution with the OTF(On The Fly) method was tested with respect to the initialization time. The result shows that the accuracy is better than 1cm with 5-minute initialization in the distance of 10km baseline. The seaside topography was measured by the RTK GPS only, on the other hand the seafloor topography was surveyed in combination of RTK GPS and E/S. Comparing to the volume of seaside measured by RTK GPS and digital topographical map, the difference of only $2\%$ was achieved. This indicates that the coastal mapping. As a result, it has been revealed that every possible noise in surveying could be corrected and the accuracy could be improved. The accuracy of GPS data acquired in real time was as good as that acquired by post processing. It is expected that it will be useful for the analysis of coastal geographic characteristics because DTM(Digital Terrain Model) can be also constructed for the harbor reclamation, the dredging, and the variation of soil movement in a river.

• 로봇학회논문지
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• 제18권1호
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• pp.37-47
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• 2023

This paper introduced how to construct Denavit-Hartenberg (DH) parameters from the Unified Robot Description Format (URDF). URDF is convenient for describing a robot even though the robot is very complex. On the other hand, DH convention is not an easy notation for many novices who want to describe a robot. Therefore, most vendors provide URDF and users prefer to use URDF to describe a robot. However, some controllers or algorithms are based on DH parameters to perform kinematics, dynamics, control, etc. To connect URDF and DH parameters, we present a three-step approach to construct DH parameters from URDF. The first step is to define the joint axis for constructing DH parameters. The second step is constructing DH parameters to define joint character. The final step is constructing DH parameters to define the coordinate frame of the child link. This approach is based on intuitive vector calculation and guarantees the uniqueness of DH parameters. To verify our approach, we applied our approach to a simple one-link robot, a manipulator with 6 DOF, and a quadruped robot with 3 DOF per leg. We verified that our approach worked well based on forward kinematic results.

• 천문학회보
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• 제46권2호
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• pp.81.1-81.1
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• 2021

Stellar kinematics is a useful tool to understand the formation and evolution of young stellar systems. Here, we present a kinematic study of the HII region, NGC 821, using the Gaia Early Data Release 3. NGC 281 contains the open cluster IC 1590. This cluster has a core and a low-stellar density halo. We detect a pattern of cluster expansion from the Gaia proper motion vectors. Most stars radially escaping from the cluster are distributed in the halo. We measure the 1-dimensional velocity dispersion of stars in the core. The velocity dispersion (1 km/s) is comparable to the expected virial velocity dispersion of this cluster, and therefore the core is at a virial state. The core has an initial mass function shallower than that of the halo, which is indicative of mass segregation. However, there is no significant correlation between stellar masses and tangential velocities. This result suggests that the mass segregation has a primordial origin. On the other hand, it has been believed that the formation of young stars in NGC 281 West was triggered by feedback from massive stars in IC 1590. We investigate the ages of stars in the two regions, but the age difference between the two regions is not comparable to the timescale of the passage of an ionization front. Also, the proper motion vectors of the NGC 281 West stars relative to IC 1590 do not show any systematic receding motion from the cluster. Our results suggest that stars in NGC 281 West might have been formed spontaneously. In conclusion, the formation of NGC 281 can be understood in the context of hierarchical star formation model.