• Title/Summary/Keyword: Space-Time

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Hybrid Algorithm of Space Time and Space Frequency Block Coding Technique using Alternate Time Switch (교번 스위치를 활용한 시공간 및 주파수공간 블록 코딩의 하이브리드 알고리즘)

  • Jung, Hyeok Koo
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.1
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    • pp.48-52
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    • 2017
  • This paper proposes a hybrid algorithm of space-time block coding and space-frequency block coding using alternate time switch. The traditional alternate time-switched space-time or space-frequency block coding technique for orthogonal frequency division multiplexing system does not provide a good performance with a variety of communication environments. This hybrid algorithm has searched good performance ranges in various environments in view points of mobile speed and doppler frequency. In this paper, we investigate better performance ranges for two algorithms, suggest a hybrid algorithm for dynamically changing communication environments, propose a structure for transmitter and receiver, and show that its performance is better than the traditional algorithm by simulations.

Noncoherent Unitary Space-Time Modulated DSSS Systems in Multipath Channels

  • Cheun, Kyung-Whoon;Kim, Jeong-Chang;Kim, You-Han;Choi, Soong-Yoon
    • Journal of Communications and Networks
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    • v.14 no.2
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    • pp.206-212
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    • 2012
  • In this paper, in order to effectively apply unitary space-time modulation to the direct-sequence spread-spectrum multiple-access (DSSS-MA) networks, we propose a low-rate, noncoherent, unitary, and space-time modulated DSSS system supporting any number of transmit antennas based on Walsh matrices. The proposed scheme simultaneously performs bandwidth spreading and space-time coding and outperforms those using high-rate, conventional unitary space-time constellations. Furthermore, the proposed scheme allows for a simple detector structure based on fast Walsh transforms.

Space-time cluster research of R&D industry in Seoul, Korea (서울시 R&D 산업체의 시공간 클러스터 분석)

  • Park, Sun-Young;Kim, Youngho
    • Journal of the Economic Geographical Society of Korea
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    • v.16 no.3
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    • pp.492-511
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    • 2013
  • According to IASB(International Accounting Standards Board), R&D(Research and Development) is defined as a tertiary sector industry combining research and development. Many studies investigated R&D industry clusters in the form of high-tech cluster(Coe et al., 2007). However, these studies only generalized various spatial cluster of R&D industries. In particular, the studies could not considers cluster formation process over time lacking statistical significance in space-time perspectives. This study, therefore, indicates the limitation of recent R&D cluster literature which only considers either time or space. In addition, this study explores space-time clusters in R&D industry together with textile and cloth industry for comparison. Discovering the existence and location of clusters, this study utilized space-time K function and space-time scan statistics. The result shows that R&D industry presents significant clusters only in spatial dimension. No significant clusters were found in space-time dimension. However, textile and clothing industry presents significant clusters in both spatial and space-time dimensions.

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Automatic real-time system of the global 3-D MHD model: Description and initial tests

  • Park, Geun-Seok;Choi, Seong-Hwan;Cho, Il-Hyun;Baek, Ji-Hye;Park, Kyung-Sun;Cho, Kyung-Suk;Choe, Gwang-Son
    • Bulletin of the Korean Space Science Society
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    • 2009.10a
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    • pp.26.2-26.2
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    • 2009
  • The Solar and Space Weather Research Group (SOS) in Korea Astronomy and Space Science Institute (KASI) is constructing the Space Weather Prediction Center since 2007. As a part of the project, we are developing automatic real-time system of the global 3-D magnetohydrodynamics (MHD) simulation. The MHD simulation model of earth's magnetosphere is designed as modified leap-frog scheme by T. Ogino, and it was parallelized by using message passing interface (MPI). Our work focuses on the automatic processing about simulation of 3-D MHD model and visualization of the simulation results. We used PC cluster to compute, and virtual reality modeling language (VRML) file format to visualize the MHD simulation. The system can show the variation of earth's magnetosphere by the solar wind in quasi real time. For data assimilation we used four parameters from ACE data; density, pressure, velocity of solar wind, and z component of interplanetary magnetic field (IMF). In this paper, we performed some initial tests and made a animation. The automatic real-time system will be valuable tool to understand the configuration of the solar-terrestrial environment for space weather research.

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Onset time comparison of solar proton event with coronal mass ejection, metric type II radio burst, and flare

  • Cho, Kyung-Suk;Hwang, Jung-A;Bong, Su-Chan;Marubashi, Katsuhide;Rho, Su-Lyun;Park, Young-Deuk
    • Bulletin of the Korean Space Science Society
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    • 2010.04a
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    • pp.38.3-39
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    • 2010
  • While major solar proton events (SPEs) come from the coronal mass eject (CME)-driven shocks in solar wind, there are many evidences that potentiality of CMEs to generate SPEs depends on its early evolution near the Sun and on different solar activities observed around the CME liftoff time. To decipher origin of SPE release, we have investigated onset time comparison of the SPE with CME, metric type II radio burst, and hard X-ray flare. For this, we select 30 SPEs observed from 1997 to 2006 by using the particle instrument ERNE onboard SOHO, which allows proton flux anisotropy measurement in the energy range ~10 - 50MeV. Onset time of the SPEs is inferred by considering the energy-dependent proton transport time. As results, we found that (1) SPE onset time is comparable to that of type II but later than type III onset time and HXR start time, (2) SPE onset time is mostly later than the peak time of HXR flare, (3) almost half of the SPE onsets occurred after the HXR emission, and (4) there are two groups of CME height at the onset time of SPE; one is the height below 5 Rs (low corona) and the other is above 5Rs (high corona). In this talk, we will present the onset time comparison and discuss about the origin of the SPE onset.

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Space-Time Warp Curve for Synthesizing Multi-character Motions

  • Sung, Mankyu;Choi, Gyu Sang
    • ETRI Journal
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    • v.39 no.4
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    • pp.493-501
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    • 2017
  • This paper introduces a new motion-synthesis technique for animating multiple characters. At a high level, we introduce a hub-sub-control-point scheme that automatically generates many different spline curves from a user scribble. Then, each spline curve becomes a trajectory along which a 3D character moves. Based on the given curves, our algorithm synthesizes motions using a cyclic motion. In this process, space-time warp curves, which are time-warp curves, are embedded in the 3D environment to control the speed of the motions. Since the space-time warp curve represents a trajectory over the time domain, it enables us to verify whether the trajectory causes any collisions between characters by simply checking whether two space-time warp curves intersect. In addition, it is possible to edit space-time warp curves at run time to change the speed of the characters. We use several experiments to demonstrate that the proposed algorithm can efficiently synthesize a group of character motions. Our method creates collision-avoiding trajectories ten times faster than those created manually.

Space-Time Finite Element Analysis of Transient Problem (동적 문제의 공간-시간 유한요소해석)

  • Kim, Chi-Kyung;Lim, Hong-Bin
    • Journal of the Korean Society of Safety
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    • v.8 no.4
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    • pp.201-206
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    • 1993
  • A space-time finite element method was presented for time dependent problem. The method which treat both the space and time unformly were proposed and numerically tested. The weighted residual process was used to formulate a finite element method in a space-time domain based upon continuous Galerkin method. This method leads to a conditional stabie high-order accurate solver.

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The 𝒲-curvature Tensor on Relativistic Space-times

  • Abu-Donia, Hassan;Shenawy, Sameh;Syied, Abdallah Abdelhameed
    • Kyungpook Mathematical Journal
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    • v.60 no.1
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    • pp.185-195
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    • 2020
  • This paper aims to study the 𝒲-curvature tensor on relativistic space-times. The energy-momentum tensor T of a space-time having a semi-symmetric 𝒲-curvature tensor is semi-symmetric, whereas the whereas the energy-momentum tensor T of a space-time having a divergence free 𝒲-curvature tensor is of Codazzi type. A space-time having a traceless 𝒲-curvature tensor is Einstein. A 𝒲-curvature flat space-time is Einstein. Perfect fluid space-times which admits 𝒲-curvature tensor are considered.

A Study on the set-up of Time Range for Typology of Space Observation Characters (공간주시특성의 유형화를 위한 시간범위설정에 관한 연구)

  • Kim, Jong-Ha;Jung, Jae-Young
    • Korean Institute of Interior Design Journal
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    • v.21 no.4
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    • pp.87-95
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    • 2012
  • This study is for the analysis to which element of space the users observing the lobby at a public space pay more attention for their visual perception. It is focused on the typology process of observation characters. The subjects, in the observation process, came to be interested in the circumstantial clues for space perception and the detailed characters drawing their interest. I could analyze the observation characters of the subjects observing the space by the comprehension and typology of their observation characters. First, from the viewpoint of successive 9 times of observations, each subject observed for 0.32 second to get the visual perception in the applied space, but spent another 0.39 second for the exploration of another observation object or the space roaming. The observation character of the subjects at the lobby of the public space selected for this experiment was that they spent more time on space exploration than on concentration on a point in the space. Second, I analyzed the typology process through the time range. Since the subjects' frequency varied depending on the way to set up the time range, the necessity was proposed that the time range for the analysis of observation characters should be set up more objectively. Third, in case of analyzing the observation characters by 10-second-unit time range, the concentration in the beginning and the middle was 25%, and that in the beginning and the final 41.7%, which showed that 75% of the subjects concentrated in the beginning of the observation time when the concentration in the beginning is added to it. Fourth, the type 3 categorized as "concentration in the beginning and the middle" is the group 47.1 percent of the subjects belong to, and each subject concentrated 1.1 times in the beginning and 2.1 times in the final, which showed that the concentration in the final was 1.75 times as high as that in the beginning.

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A Study of Time and Image of the Paintings in the Late $20_{th}$ Century (20세기 후기(後期) 회화(繪畵)의 시간(時間)과 이미지)

  • Shim Jung-Rhee
    • Journal of Science of Art and Design
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    • v.1
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    • pp.165-188
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    • 1999
  • When we think about visual art, we can't pass over the matter of images and spaces. An image is fixed in a painting space. If the image were posited in the river of time, it would be changed as time flowed on. Its image might be created, rigged, transfigured or it might vanish or remain as traces. The image is changed through the process of expressing them on the painting surfaces. In paintings the changing of the image is caused not only by working processes but also recognizing the objects. In modernist painting, the idea of space was important, but in postmodernist view, the idea of time becomes essential. In this thesis I will focus on the matter of time and image of painting in the late 20th century. Studying the relationship of image and time is not familiar because we had considered the space as being more related to painting distinction than time. Presently, the concept of space can't be divided from that of time. In Physics, they recently called it as a united concept- time-space. Painting space also becomes one asking and recieve the concept of time actively. Now in painting, time is no more a supporting matter but becomes a major matter. In the late 20th century, we can find many trials to catch the change of images as time flowes on and express them as a trace through using verioty media. One of the way to drawing the change of images as time passes could be seen through various joint images in one painting space and another in the traces of one image. The other could be done by using new media such as computer in the example of fractal art. It shows the images chainging of practically as time changes. New understanding about time of this era has to be affirmatively accepted because it reflects the contemporary cultural situation and in art, the concern about the possiblity of it and finding new medias which has to go on.

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