• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.50-56
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• 2010

Most mission trajectory design technologies for space exploration have been utilized the Patched Conic Approximation which is based on Hohmann transfer in two-body problem. The Hohmann transfer trajectory is basically an elliptic trajectory, and Patched Conic Approximation consists of Hohmann transfer trajectories in which each trajectory are patched to the next one. This technology is the most efficient method when considering only one major planet at each patch trajectory design. The disadvantages of the conventional Patched Conic Approach are more fuel (or mass) needed and only conic trajectories are designed. Recent space exploration missions need to satisfy more various scientific or engineering goals, and mission utilizing smaller satellites are needed for cost reduction. The geometrical characteristics of three-body dynamics could change the paradigm of the conventional solar system. In this theoretical concept, one can design a trajectory connecting around the solar system with comparably very small energy. In this paper, the basic three-body dynamics are introduced and a spacecraft mission trajectory is designed utilizing the three-body dynamics.

• Journal of the Korean Regional Science Association
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• v.37 no.1
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• pp.15-27
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• 2021

This study investigates the difference in income trajectories of the working poor and the non-working poor and explains the effects of socio-demographic (marriage, education) and regional (living in large cities) factors on intergroup differences. We use Seoul Survey data collected between 2009-2018 and the latent growth modeling approach. It was found that the trajectory difference between groups was statistically significant. Since 2016, the income gap widened as the income of the working poor stagnated. The three variables included in this model better explained the income trajectory of the working poor compared to the working non-poor. In particular, the change in income growth rate was positively related to whether they live in large cities. This suggests the possibility that living in a large city would act as an economic premium for the working poor. It is necessary to conduct follow-up studies on urban premiums for the working poor.

• Progress in Medical Physics
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• v.15 no.3
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• pp.121-127
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• 2004

The trajectories for high-energy electrons in water under magnetic fields were calculated approximately by numerical method. A differential equation for electrons under magnetic field was built and the calculation code was devised by Euler method. Using the code, the trajectories for electrons with energies of 3, 5, 10, and 15 MeV in water were calculated in the presence of magnetic fields parallel and perpendicular to the incident electrons. Since we considered only the energy loss and the directional change for primary electrons, there are errors in this calculation. However, based on the results we were able to explain the variation of dose distributions by the external magnetic fields in water.

• Journal of the Korean Society of Child Welfare
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• no.54
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• pp.145-172
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• 2016

The purpose of this study was to examine whether parenting attitudes would have an effect on the developmental trajectories of school adjustment for adolescents in out-of-home care. Additionally, we hypothesized that this model would be different between boys and girls. In this study, we analyzed three waves of data collected from 341 adolescents living in residential facilities, group homes or foster homes by using cluster sampling methods. Growth-curve longitudinal analysis was conducted, and the results indicated that levels of school adjustment had increased from the 1st through the 3rd grade of middle school. Positive parenting attitudes had a positive impact on initial school adjustment and rate of change, whereas negative parenting attitudes had a negative impact only on the initial school adjustment. Second, multi-group analysis revealed that there were group differences between boys and girls in their initial school adjustment by positive parenting attitudes. Based on these results, this study discussed further suggestions to increase school adjustments for adolescents in out-of-home care.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.30 no.2
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• pp.66-73
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• 2019

Objectives: This study aimed to investigate the trajectory of change of diverse attention and working memory in Koreans from 4 to 40 years of age. Methods: The data of 912 subjects from 4 to 15 years of age obtained from a previous standardization study of the computerized comprehensive attention test were merged with the newly obtained data of 150 subjects aged 16 to 40 years from this study. We evaluated the various kinds of attention, in which each subtest had five indicators. Working memory, with parameters such as number of correct responses and span, was also measured. Results: Our findings indicated that attention developed as age increased, and it decreased or was maintained after a certain age. Selective and sustained attention developed rapidly in children and adolescents, until mid-teens or 20 s when it ceased development. Divided attention, however, developed up to approximately age 20. In addition, working memory developed until mid-teens or 20 s. Conclusion: We presented the standardized data on diverse kinds of attention and working memory in children, adolescents, and adults in Korea. We could recognize any patterns of change in attention and working memory with increasing age.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.6
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• pp.494-500
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• 2015

It has been reported that a ship sailing in shallow water possesses better straight-line stability due to the change of fluid flow around the ship. This tendency affects manoeuvring characteristics of the ship. To investigate this phenomenon, indoor free running model test(FRMT) on KVLCC2 was carried out in three water depth conditions(H/T = 1.2, 1.5 & 2.0). Turning circle tests(± 35° ) and zigzag tests(± 20° /5° and ± 20° /10° ) were conducted with newly developed indoor FRMT system, and the manoeuvring results were compared with test results from other institutes. As the water depth decreased, the yaw rate of the ship decreased, and the distances of circular trajectories at the same heading angle increased in the turning circle tests. The first overshoot angles of the zigzag tests decreased. From both tests, the time for course change increased as the water depth decreased. These manoeuvring characteristics show that KVLCC2 in shallow water becomes more stable in terms of straight-line stability.

• Journal of Technology Innovation
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• v.14 no.2
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• pp.29-48
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• 2006

This paper analyzes organizational behavior of an established firm when disruptive innovation, a change in product architecture, occurs on a previous product. For the analysis, the paper analyzes and compares the behavior of an established fm through product trajectories between NEC (an established firm) and Toshiba (a new entrance) in the Japanese laptop computers industry. An established firm that has developed and produced a previous product is difficult in adapting to a disruptive innovation due to accumulated immense knowledge through a previous product. By using regression model in the product trajectory analysis, the paper analyzes the behavior of established firms. Product trajectory means a pattern of product strategy shown in a series of products. Two facts found in the paper are as follows. First, though NEC was able to develop a laptop computer at the same time with Toshiba, it was restricted by the resources of a previous product in the early stage. Second, possibility of teaming trap in the adapting process was found. The paper found the risk that too much commitment in one evolution stage would prohibit the adapting behavior in the next evolution stage.

• Journal of Science and Technology Studies
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• v.3 no.2 s.6
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• pp.61-82
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• 2003

In a new paradigm of competition, firms face a multiple industry in a generation and compete with existing capabilities and resources in a new industry. Firms need to increase dynamic capabilities to adjust to a radical change in terms of technologies for survival and sustainable growth in a new industry. But we lack a clear conceptual model explaining evolutionary process of firms facing a emerging industry with different experiences in a prior industry and where heterogeneity in firms' technological portfolios come from. How we explaining firms' heterogeneity arising in a new industiy? In this article, I suggest hypothesis explaining firms' heterogeneity in a new industry with the concept of existent industry's technological trajectories, available assets, core processes and show the possibility of model to explain the heterogeneity of firms.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.159-166
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• 2008

Video image processing systems (VIPS) offer numerous benefits to transportation models and applications, due to their ability to monitor traffic in real time. VIPS based on a wide-area detection algorithm provide traffic parameters such as flow and velocity as well as occupancy and density. However, most current commercial VIPS utilize a tripwire detection algorithm that examines image intensity changes in the detection regions to indicate vehicle presence and passage, i.e., they do not identify individual vehicles as unique targets. If VIPS are developed to track individual vehicles and thus trace vehicle trajectories, many existing transportation models will benefit from more detailed information of individual vehicles. Furthermore, additional information obtained from the vehicle trajectories will improve incident detection by identifying lane change maneuvers and acceleration/deceleration patterns. However, unlike human vision, VIPS cameras have difficulty in recognizing vehicle movements over a detection zone longer than 100 meters. Over such a distance, the camera operators need to zoom in to recognize objects. As a result, vehicle tracking with a single camera is limited to detection zones under 100m. This paper develops a methodology capable of monitoring individual vehicle trajectories based on image processing. To improve traffic flow surveillance, a long distance tracking algorithm for use over 200m is developed with multi-closed circuit television (CCTV) cameras. The algorithm is capable of recognizing individual vehicle maneuvers and increasing the effectiveness of incident detection.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.4
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• pp.426-432
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• 2009

In this paper, redundancy resolution of UVMS (underwater vehicle-manipulate. system) is addressed. In general, UVMS has redundant DOFs (degrees of freedom) as many as DOFs of manipulator and these redundant DOFs can be used to optimize the configuration of UVMS while satisfying given tasks. We propose a performance index for redundancy resolution which minimizes the restoring moments of UVMS. The restoring moment can cause unintentional change of poses of UVMS. If the restoring moments remain small, control effort for keeping the poses of UVMS decreases. This means that energy consumption can be reduced by minimizing the restoring moments during conducting tasks. Proposed performance measure is optimized by gradient projection method. Generated trajectories by this redundancy resolution are tracked by robust PID controller. Numerical simulations are presented to demonstrate performance of the proposed algorithm.