• 제목/요약/키워드: Large Objects

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Physical properties of Maria asteroid family

  • Kim, Myung-Jin;Choi, Young-Jun;Moon, Hong-Kyu;Brosch, Noah;Byun, Yong-Ik
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.1
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    • pp.101.2-101.2
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    • 2012
  • An asteroid family is a population of asteroids in the proper orbital element space (a, e, i), considered to have been produced by a disruption of a large parent body presumably through a catastrophic collision. Asteroid families offer unique opportunities to reconstruct and characterize the break-up history of airless bodies in the main-belt. The Maria family is a typical old population (~3${\pm}$1 Gyr) of asteroids that have undergone significant collisional and dynamical evolution in the history of the inner Solar System; it is also believed to be one of the candidate source regions for giant S-type near-earth asteroids (NEAs). However, to date, physical characteristics of this family members such as rotational periods have been known only for 61 of the larger asteroids among 3,230 objects, which accounts for less than 2 percent of the family. In this presentation, we provide some preliminary results of our recent study: out of more than dozen of the family members, lightcurves for eight objects have been obtained for the first time. We plan to increase the number of target objects, and investigate evidences for the Yarkovsky/YORP effect on Maria family based on our observations.

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Search for Dormant Comets in the Infrared Asteroidal Catalog

  • Kim, Yoonyoung;Ishiguro, Masateru;Usui, Fumihiko
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.1
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    • pp.67.2-67.2
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    • 2014
  • Comet nucleus is a solid body consisting of dark dust grains and ice. Cometary volatiles sublimate from subsurface layer by solar heating, leaving behind large dust grains on the surface. Eventually, the appearance could turn into asteroidal rather than cometary. It is, therefore, expected that there would be "dormant comets" in the list of known asteroids. Our research group has undertaken the research on the population of dormant comets. We applied a brand-new asteroidal catalog compiled from data garnered by three infrared astronomical observatories, AKARI, IRAS and WISE. We extracted objects which have comet-like orbits on the basis of their orbital properties (Tisserand parameters with respect to Jupiter, TJ, and aphelion distance, Q). We found that (1) there are a considerable number (>100) of asteroids in comet-like orbits, and (2) 80% of them have low albedo consistent with comets. This result suggest that these low albedo objects could be dormant comets. One unanticipated finding is that 20% of asteroids in comet-like orbit have high albedo similar to S-type asteroids. It is difficult to explain the population of S-type asteroids in comet-like orbits by the classical mechanics theory. We further found that these high-albedo objects are small (D < 2 km) bodies distributed in near-Earth space. We suggest that such high-albedo, small, near-Earth asteroids are susceptible to Yarkovsky effect and injected into comet-like orbits.

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Intergalactic Magnetic Field and Arrival Direction of Ultra-High-Energy Iron Nuclei

  • Ryu, Dongsu;Kang, Hyesung;Das, Santabrata
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.78.2-78.2
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    • 2012
  • We have studied how the intergalactic magnetic field (IGMF) affects the propagation of super-GZK iron nuclei that originate from extragalactic sources within the local GZK sphere. Toward this end, we set up hypothetical sources of ultra-high-energy cosmic-rays (UHECRs), virtual observers, and the magnetized cosmic web in a model universe constructed from cosmological structure formation simulations. We then arranged a set of reference objects at high density region to represent astronomical objects formed in the large scale structure (LSS). With our model IGMF, the paths of UHE iron nuclei are deflected on average by about 70 degrees, which might indicate a nearly isotropic distribution of arrival directions. However, the separation angle between the arrival directions and the nearest reference object on the LSS is only ~6 degrees, which is twice the mean distance to the nearest neighbors among the reference objects. This means that the positional correlation of observed UHE iron events with their true sources would be erased by the IGMF, but the correlation with the LSS itself is to be sustained. We discuss implications of our findings for correlations studies of real UHECR events.

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Practical Datasets for Similarity Measures and Their Threshold Values (유사도 측정 데이터 셋과 쓰레숄드)

  • Yang, Byoungju;Shim, Junho
    • The Journal of Society for e-Business Studies
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    • v.18 no.1
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    • pp.97-105
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    • 2013
  • In the e-business domain where data objects are quantitatively large, measuring similarity to find the same or similar objects is important. It basically requires comparing and computing the features of objects in pairs, and therefore takes longer time as the amount of data becomes bigger. Recent studies have shown various algorithms to efficiently perform it. Most of them show their performance superiority by empirical tests over some sets of data. In this paper, we introduce those data sets, present their characteristics and the meaningful threshold values that each of data sets contain in nature. The analysis on practical data sets with respect to their threshold values may serve as a referential baseline to the future experiments of newly developed algorithms.

The Control of A Ball Beam Using Fuzzy Control in Vision (화상의 퍼지 알고리즘 처리를 통한 공과 막대 시스템 제어)

  • Park, Seung-Hun;Joo, Han-Jo;Yim, Wha-Yoeng
    • Proceedings of the KIEE Conference
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    • 2003.11c
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    • pp.965-967
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    • 2003
  • Fuzzy Controller is a system that displays a person's thoughts using membership function and IF-THEN rules. With the help of specialists' knowledge, rule bases can be explained in easy language. Furthermore Fuzzy Controller has strong resistance against turbulence. Its performance is especially prominent when targets cannot be measured in mathematic methods because the fuzzy controller can measure the output using only the relations between the input and output. With the increasing influence of multimedia on our daily lives, vision plays bigger role both in industries and personal lives. Like wise vision is being used in many areas such as detecting and identifying objects. It is difficult to detect and control targets because there is a delay in the calculating when using vision in detecting and controlling objects in large quantity. In this paper we showed how to use fuzzy controller in minimizing the calculation process, controlling target objects and moving view window instead of applying input variation through vision. Ball beam, which has strong nonlinear, was used as the target object and DSP320C6711 IDK by TI(Texas Instruments) company was for the benefit of speedy calculation and vision data operation.

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Hierarchical Location Caching Scheme for Mobile Object Tracking in the Internet of Things

  • Han, Youn-Hee;Lim, Hyun-Kyo;Gil, Joon-Min
    • Journal of Information Processing Systems
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    • v.13 no.5
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    • pp.1410-1429
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    • 2017
  • Mobility arises naturally in the Internet of Things networks, since the location of mobile objects, e.g., mobile agents, mobile software, mobile things, or users with wireless hardware, changes as they move. Tracking their current location is essential to mobile computing. To overcome the scalability problem, hierarchical architectures of location databases have been proposed. When location updates and lookups for mobile objects are localized, these architectures become effective. However, the network signaling costs and the execution number of database operations increase particularly when the scale of the architectures and the numbers of databases becomes large to accommodate a great number of objects. This disadvantage can be alleviated by a location caching scheme which exploits the spatial and temporal locality in location lookup. In this paper, we propose a hierarchical location caching scheme, which acclimates the existing location caching scheme to a hierarchical architecture of location databases. The performance analysis indicates that the adjustment of such thresholds has an impact on cost reduction in the proposed scheme.

Research Trends on Engineering Education in the United States - Focus on Journal of Engineering Education - (미국 공학교육 연구 동향 - Journal of Engineering Education을 중심으로 -)

  • Wee, Seonbouk;Jo, Hanjin;Kim, Dongyoung;Byeon, Hyesoo;Kim, Taehoon
    • Journal of Engineering Education Research
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    • v.24 no.4
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    • pp.61-74
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    • 2021
  • The purpose of this study is to provide a direction for domestic engineering education research by analyzing the research trends of JEE(Journal of Engineering Education). The results of analyzing research trends regarding research topics, research objects and research methods are as follows. First, by research topic, 'Diffusion of Educational Innovation' was found to have the highest proportion with 52 articles(21%). Second, by research objects, 'university students' showed the highest proportion with 148 articles(53.6%). Third, by research method (large category), 'quantitative research' had the highest proportion with 132 articles(53.2%). By research method (medium category), 'survey research' had the highest proportion with 129 articles(33.5%). Based on the results of this study, future engineering education research should be conducted to contribute to holistic development through diversification of research topics, methods, and objects.

Selecting Representative Views of 3D Objects By Affinity Propagation for Retrieval and Classification (검색과 분류를 위한 친근도 전파 기반 3차원 모델의 특징적 시점 추출 기법)

  • Lee, Soo-Chahn;Park, Sang-Hyun;Yun, Il-Dong;Lee, Sang-Uk
    • Journal of Broadcast Engineering
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    • v.13 no.6
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    • pp.828-837
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    • 2008
  • We propose a method to select representative views of single objects and classes of objects for 3D object retrieval and classification. Our method is based on projected 2D shapes, or views, of the 3D objects, where the representative views are selected by applying affinity propagation to cluster uniformly sampled views. Affinity propagation assigns prototypes to each cluster during the clustering process, thereby providing a natural criterion to select views. We recursively apply affinity propagation to the selected views of objects classified as single classes to obtain representative views of classes of objects. By enabling classification as well as retrieval, effective management of large scale databases for retrieval can be enhanced, since we can avoid exhaustive search over all objects by first classifying the object. We demonstrate the effectiveness of the proposed method for both retrieval and classification by experimental results based on the Princeton benchmark database [16].

Motion Compensated Subband Video Coding with Arbitrarily Shaped Region Adaptivity

  • Kwon, Oh-Jin;Choi, Seok-Rim
    • ETRI Journal
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    • v.23 no.4
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    • pp.190-198
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    • 2001
  • The performance of Motion Compensated Discrete Cosine Transform (MC-DCT) video coding is improved by using the region adaptive subband image coding [18]. On the assumption that the video is acquired from the camera on a moving platform and the distance between the camera and the scene is large enough, both the motion of camera and the motion of moving objects in a frame are compensated. For the compensation of camera motion, a feature matching algorithm is employed. Several feature points extracted using a Sobel operator are used to compensate the camera motion of translation, rotation, and zoom. The illumination change between frames is also compensated. Motion compensated frame differences are divided into three regions called stationary background, moving objects, and newly emerging areas each of which is arbitrarily shaped. Different quantizers are used for different regions. Compared to the conventional MC-DCT video coding using block matching algorithm, our video coding scheme shows about 1.0-dB improvements on average for the experimental video samples.

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A Robust Algorithm for Tracking Non-rigid Objects

  • Kim, Jong-Ryul;Na, Hyun-Tae;Moon, Young-Shik
    • Proceedings of the IEEK Conference
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    • 2002.07a
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    • pp.141-144
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    • 2002
  • In this paper, we propose a new object tracking algorithm using deformed template and Level-Set theory, which is robust against background variation, object flexibility and occlusion. The proposed tracking algorithm consists of two steps. The first step is an estimation of object shape and location, on the assumption that the transformation of object can be approximately modeled by the affine transform. The second step is a refinement of the object shape to fit into the real object accurately, by using the potential energy map and the modified Level Set speed function. Experimental results show that the proposed algorithm can track non-rigid objects with large variation in the backgrounds.

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