• Journal of Institute of Control, Robotics and Systems
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• v.13 no.10
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• pp.962-969
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• 2007

In this paper, an approach is developed for relative state estimation of satellite formation flying. To estimate relative states of two satellites, the Extended Kalman Filter Algorithm is adopted with the relative distance and speed between two satellites and attitude of satellite for measurements. Numerical simulations are conducted under two circumstances. The first one presents both chief and deputy satellites are orbiting a circular reference orbit around a perfectly spherical Earth model with no disturbing acceleration, in which the elementary relative orbital motion is taken into account. In reality, however, the Earth is not a perfect sphere, but rather an oblate spheroid, and both satellites are under the effect of $J_2$ geopotential disturbance, which causes the relative distance between two satellites to be on the gradual increase. A near-Earth orbit decays as a result of atmospheric drag. In order to remove the modeling error, the second scenario incorporates the effect of the $J_2$ geopotential force, and the atmospheric drag, and the eccentricity in satellite orbit are also considered.

• Journal of Korea Port Economic Association
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• v.39 no.3
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• pp.155-178
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• 2023

The purpose of this study is to derive factors that affect the acceptance of digital transformation in ports and empirically analyze the impact of these factors on the acceptance of digital transformation through a survey of port workers. Additionally, we test whether acceptance attitude plays a mediating role in the relationship between these factors and digital transformation acceptance. The variables used in this study are as follows. First, knowledge, self-efficacy, and involvement were included as variables related to individual characteristics, relative advantages, complexity, observability were included as variables related to innovation characteristics, and government regulations and competitor pressure were included as variables relate to environmental characteristics, so that a total of eight latent variables were selected. The results of this study are summarized as follows. First, two variables among individual characteristics, self-efficacy and involvement, were able to confirm a positive(+) causal relationship with the attitude of accepting digital transformation, and knowledge initially expected a positive(+) causal relationship with the attitude of accepting digital transformation, but the result was a negative(-) causal relationship, so that the hypothesis was rejected. Second, among the characteristics of innovation, complexity has a negative(-) causal relationship with the attitude of accepting digital transformation, and relative advantages and technological innovation have a positive(+) causal relationship with the attitude of accepting digital transformation. Finally, among the environmental characteristics, government regulations and competitor pressure, confirmed a positive(+) causal relationship with the attitude of accepting digital transformation. In addition, it was found that the attitude of accepting digital transformation had a positive(+) causal relationship with personal acceptance and social acceptance of digital transformation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.219-229
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• 2018

This paper proposes Kalman Filter-based relative navigation algorithms for proximity tasks such as rendezvous/docking/cluster-operation of spacecraft using PSD Sensors and Infrared Beacon Modules. Numerical simulations are performed for comparative analysis of the performance of each relative-navigation technique. Based on the operation principle and optical modeling of the PSD Sensor and the Infrared Beacon Module used in the relative navigation algorithm, a measurement model for the Kalman filter is constructed. The Extended Kalman Filter(EKF) and the Unscented Kalman Filter(UKF) are used as probabilistic relative navigation based on measurement fusion to utilize kinematics and dynamics information on translational and rotation motions of satellites. Relative position and relative attitude estimation performance of two filters is compared. Especially, through the simulation of various scenarios, performance changes are also investigated depending on the number of PSD Sensors and IR Beacons in target and chaser satellites.

• International Journal of Control, Automation, and Systems
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• v.6 no.6
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• pp.859-872
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• 2008

In this paper, the problem of partial asymptotic stabilization of nonlinear control cascaded systems with integrators is considered. Unfortunately, many controllable control systems present an anomaly, which is the non complete stabilization via continuous pure-state feedback. This is due to Brockett necessary condition. In order to cope with this difficulty we propose in this work the partial asymptotic stabilization. For a given motion of a dynamical system, say x(t,$x_0,t_0$)=(y(t,$y_0,t_0$),z(t,$z_0,t_0$)), the partial stabilization is the qualitative behavior of the y-component of the motion(i.e., the asymptotic stabilization of the motion with respect to y) and the z-component converges, relative to the initial vector x($t_0$)=$x_0$=($y_0,z_0$). In this work we present new results for the adding integrators for partial asymptotic stabilization. Two applications are given to illustrate our theoretical result. The first problem treated is the partial attitude control of the rigid spacecraft with two controls. The second problem treated is the partial orientation of the underactuated ship.

• Fashion & Textile Research Journal
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• v.15 no.5
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• pp.815-824
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• 2013

This study divides female consumers according to eco-friendly attitudes and the purchase frequency of eco-clothing products; in addition, it analyzes the characteristics of each group in terms of LOHAS lifestyles, the attitudes for eco-clothing products, and satisfaction. Eco-clothing attitudes of female consumers were lower than eco-friendly attitudes. A total of 360 female consumers were divided into 4 group according to purchase frequency and the eco attitude, Type 1: survival (33.0%), Type 2: wellbeing (25.6%), Type 3: curious (15.0%), Type 4: LOHAS (26.4%); in addition, age, income, marit alstatus, occupation, LOHAS lifestyle and shopping places were differentiated by type. Type 1 (low eco attitude and low eco-clothing purchase) were composed of the youngest, college students, low income, low level of LOHAS lifestyles and low level of eco-clothing attitude. Type 2 (high eco attitude and low eco-clothing purchase) were interested in healthy eating & exercise among LOHAS lifestyles; in addition, Type 1 & 2 showed alow level of eco-clothing satisfaction. Type 3, low eco attitude and high eco-clothing purchase, were characterized with high expenditures on clothing relative to income as well as lower levels of family activities and leisure life than LOHAS Type 4. Type 4 (high eco attitude and high eco-clothing purchase) were the oldest group and mostly composed of married workers (the highest income) with the highest LOHAS lifestyles and the highest level of eco-clothing satisfaction.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.3
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• pp.369-375
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• 2010

Since multi-view images can be utilized for 3D visualization and surveying as well, a system calibration is an essential procedure. The cameras in the system are mounted to the holder and their locations and attitudes are relatively fixed. Therefore, the locations and the attitudes of the perspective centers of the four oblique looking cameras can be calculated using the location and attitude of the nadir looking camera and the boresight values between the cameras. In this regard, this research is focusing on the analysis of the relative location and attitude between the nadir and oblique looking cameras based on the results of the exterior orientation parameters after the aerial triangulation of the real multiview images. We acquired high standard deviations of the relative locations between the nadir and oblique cameras. Standard deviations of the relative attitudes between the cameras were low when only the exterior orientations of the oblique looking cameras were allowed to be adjusted. Moreover, low standard deviations of the relative attitudes came when we considered not all the exterior orientations of the cameras but the attitudes of them only.

• Journal of Astronomy and Space Sciences
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• v.36 no.4
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• pp.235-248
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• 2019

This paper suggests a relative orbit control strategy for the CubeSat Astronomy by NASA and Yonsei using Virtual Telescope Alignment eXperiment (CANYVAL-X) mission whose main goal is to demonstrate an essential technique, which is an arrangement among two satellites and a specific celestial object, referred to as inertial alignment, for a next-generation virtual space telescope. The inertial alignment system is a relative orbit control system and has requirements for the relative state. Through the proposed orbit control strategy, consisting of separation, proximity keeping, and reconfiguration, the requirements will be satisfied. The separation direction of the two CubeSats with respect to the orbital plane is decided to provide advantageous initial condition to the orbit controller. Proximity keeping is accomplished by differential atmospheric drag control (DADC), which generates acceleration by changing the spacecraft's effective cross section via attitude control rather than consuming propellant. Reconfiguration is performed to meet the requirements after proximity keeping. Numerical simulations show that the requirements can be satisfied by the relative orbit control strategy. Furthermore, through numerical simulations, it is demonstrated that the inertial alignment can be achieved. A beacon signal had been received for several months after the launch; however, we have lost the signal at present.

• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.387-393
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• 2015

This study presents a precise relative navigation algorithm using both laser and Global Positioning System (GPS) measurements in real time. The measurement model of the navigation algorithm between two spacecraft is comprised of relative distances measured by laser instruments and single differences of GPS pseudo-range measurements in spherical coordinates. Based on the measurement model, the Extended Kalman Filter (EKF) is applied to smooth the pseudo-range measurements and to obtain the relative navigation solution. While the navigation algorithm using only laser measurements might become inaccurate because of the limited accuracy of spacecraft attitude estimation when the distance between spacecraft is rather large, the proposed approach is able to provide an accurate solution even in such cases by employing the smoothed GPS pseudo-range measurements. Numerical simulations demonstrate that the errors of the proposed algorithm are reduced by more than about 12% compared to those of an algorithm using only laser measurements, as the accuracy of angular measurements is greater than $0.001^{\circ}$ at relative distances greater than 30 km.

• Journal of Astronomy and Space Sciences
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• v.29 no.4
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• pp.351-362
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• 2012

We made a study on real-time determination method for relative position using the laser-measured distance data between satellites. We numerically performed the determination of relative position in accordance with extended Kalman filter algorithm using the vectors obtained through nonlinear equation of relative motion, laser simulator for distance measurement, and attitude determination of chief satellite. Because the spherical parameters of relative distance and direction are used, there occur some changes in precision depending on changes in relative distance when determining the relative position. As a result of simulation, it was possible to determine the relative position with several millimeter-level errors at a distance of 10 km, and sub-millimeter level errors at a distance of 1 km. In addition, we performed the determination of relative position assuming the case that global positioning system data was not received for long hours to see the impact of determination of chief satellite orbit on the determination of relative position. The determination of precise relative position at a long distance carried out in this study can be used for scientific mission using the satellite formation flying.

• Journal of the Korea Safety Management & Science
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• v.17 no.4
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• pp.353-363
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• 2015

In unlimited competitive period changed every time, domestic manufacturing industry feels a crisis between China and Japan, who are leaping to manufacturing strong countries with worldwide manufacturing factories. In this situation, many companies make an effort to learn and introduce Toyota production method drawing innovation of production method and reduction of many costs for high quality, but most of cases were failed. The reason for the failure should be that correct understanding and application of TPS corporate culture were insufficient and job attitude was not considered when applying Toyota production system. Therefore, the purposes of this thesis are to arrange major contents based on relative documents of precedent researchers, conduct a survey for employees of middle and small scaled manufacturers who introduced Toyota production system, analyze changes of enterprises' job attitude by introduction of TPS corporate culture and the effects on company's management results through the various analyses for grasping relationship among TPS corporate culture, job attitude and management results, introduce Toyota production system more effectively and suggest measures to maximize company's long-term management results.