• Bulletin of the Korean Mathematical Society
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• v.50 no.4
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• pp.1109-1126
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• 2013

Let $\mathbb{M}^3_q(c)$ denote the 3-dimensional space form of index $q=0,1$, and constant curvature $c{\neq}0$. A curve ${\alpha}$ immersed in $\mathbb{M}^3_q(c)$ is said to be a Bertrand curve if there exists another curve ${\beta}$ and a one-to-one correspondence between ${\alpha}$ and ${\beta}$ such that both curves have common principal normal geodesics at corresponding points. We obtain characterizations for both the cases of non-null curves and null curves. For non-null curves our theorem formally agrees with the classical one: non-null Bertrand curves in $\mathbb{M}^3_q(c)$ correspond with curves for which there exist two constants ${\lambda}{\neq}0$ and ${\mu}$ such that ${\lambda}{\kappa}+{\mu}{\tau}=1$, where ${\kappa}$ and ${\tau}$ stand for the curvature and torsion of the curve. As a consequence, non-null helices in $\mathbb{M}^3_q(c)$ are the only twisted curves in $\mathbb{M}^3_q(c)$ having infinite non-null Bertrand conjugate curves. In the case of null curves in the 3-dimensional Lorentzian space forms, we show that a null curve is a Bertrand curve if and only if it has non-zero constant second Frenet curvature. In the particular case where null curves are parametrized by the pseudo-arc length parameter, null helices are the only null Bertrand curves.

• Communications of the Korean Mathematical Society
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• v.15 no.2
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• pp.349-355
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• 2000

In this paper we generalize the Whitehead theorem which says that a homology equivalence implies a homotopy equivalence for nilpotent spaces. We make some theorems on a homotopy equivalence of non-nilpotent spaces, e.g., the solvable space or space satisfying the condition (T**) or space X with $\pi$1(X) Engel, or locally nilpotent space with some properties. Furthermore we find some conditions that the Wall invariant will be trivial.

• Korean Institute of Interior Design Journal
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• v.24 no.3
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• pp.38-47
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• 2015

This study evaluated non-liturgical space of catholic churches based on the four principles of universal design; accessible design, supportive design, safety-oriented design, and adaptable design. To design those spaces in terms of supportive design principle, diaper exchanging station needs to be placed in the restroom. Findings of this study are as follows: In terms of accessible design, valid width of entrance door to each room(more than 800mm), installation of elevator, height of riser in the stair, and width of step board were appropriate, but there were many spaces where door sils were not removed. In terms of supportive design, notice board at teacher's room and installation of storage closet, and width of passage to office(more than 1,200mm) were also appropriate, but storage closet at a meeting and prayer room, and space for storing flowers appeared inappropriate. To design those spaces in terms of supportive design principle, diaper exchanging station needs to be placed in the restroom. In terms of safety-oriented design, installation of round-edged furniture, use of non-slip flooring material, installation of safety emergency bell at a restroom, and installation of wall handle were required. In terms of adaptable design, space for wheelchair users at each room, installation of the furniture that can adjust the height, installation of desk with different height at an office, installation of toilet and basin considering children were considered to be necessary.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.34.2-34.2
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• 2010

Cosmic rays registered by Neutron Monitors on the surface of the Earth are believed to be coming from outer space, and sometimes also from the exotic objects of the Sun. Ground level enhancement (GLE) is the sudden, sharp and short-lived increase in cosmic rays originated from the Sun. Since GLE is the signature in solar cosmic ray intensity, different solar factors erupted from the Sun can be responsible for causing it. In this context, an attempt has been made to determine quantitative relationships of GLEs > 5% with simultaneous solar, interplanetary and geophysical factors from 1997 through 2006 thereby searching the perpetrators which seem to be causing them. The study has revealed that solar flares are stronger ($0.71{\times}10-4$ w/m2) during GLE peaks than the solar flares ($1.10{\times}10-5$ w/m2) during GLE non-peaks and backgrounds. On the average, the solar wind plasma velocity and interplanetary magnetic field are found stronger during the GLE peaks than the GLE non-peaks and backgrounds indicating that the solar flares, in conjunction with interplanetary shocks, sometimes may cause GLE peaks. Direct proportionality of GLE peaks to simultaneous solar energetic particle (SEP) fluxes imply that the GLE peaks may often be caused by SEP fluxes. Although the high intensity of SEP fluxes are also seen extended few minutes even after GLE peaks, the mean (373.62 MeV) of the GLE associated SEP fluxes is much stronger than the mean (10.35 MeV) of the non-GLE associated SEP fluxes. Evidences are also supported by corresponding SEP fluences that the the mean fluence (${\sim}5.32{\times}107/cm2$) across GLE event was more intense than the mean fluence (${\sim}2.53{\times}106/cm2$) of SEP fluxes across non-GLE event.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.12
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• pp.83-92
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• 2019

The purpose of this study is to analyze the continuous forms of time and space that work as architectural design principles of the Memorial to the Murdered Jews of Europe (Jewish Memorial). Continuity is divided into two, physical and non-physical attributes. The former extends from small installations to furnitures, finishes, spatial composition, and even spatial networks that complete architecture, and the latter is tied to time, from traditional to historical, developmental, commemorative or memorial elements. They are inherent in architecture as continuous forms. The Jewish Memorial is analyzed by the analysing framework of these two items. The analysis of the two layers can be summarized as follows; physical continuity is found in the space networks of the Memorial's inside and outside, the undulating spaces, the finishes, the small furnitures and installations, the entrances of staircases, the expanded underground of the ground order, and non-physical continuity manifests in the topological variation of spatiality, the morphological development of memorial architecture, the connection of semantic sense of space, and the superposition of historicity and modernity. These forms of continuity do not aestheticize the German enormity history, but make the meaning of the Memorial into non-superficial, in-depth architecture as a monument. Thus, the results of this study show that physical and non-physical continuity should be considered as the important design principles of architecture that makes the Memorial architecture possible.

• Journal of Multimedia Information System
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• v.6 no.4
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• pp.309-316
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• 2019

Virtual Reality is broadly recognized as an "empathy machine". This reputation is due to the feeling of 'presence' that it provides to users, which is the sensation of being bodily present in a space, even when that space is virtual. The possibility of complete immersion attracts many creators looking to induce empathy and awareness about the most diverse subjects. One of the first types of VR non-fiction productions to be released was in the morally sensitive humanitarian documentary genre. This research aims to explore how VR productions differ from non-VR productions with a focus on humanitarian communication. Rather than targeting mechanical aspects of VR technology, this article compares the visual and narrative storytelling characteristics in VR and non-VR media. First, humanitarian communication and its nuances are explained. Then, 360° video filming characteristics are analyzed, followed by a comparison table contrasting VR and non-VR non-fiction. After evaluating VR non-fiction empirical studies, a discussion is initiated over the betterment of VR non-fiction storytelling in a way that could help it generate more empathy, since many productions seem to purely rely on the technology as a production novelty, and end up lacking emotional depth and audience engagement through story.

• Journal of Astronomy and Space Sciences
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• v.7 no.1
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• pp.23-35
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• 1990

Resonance effect on the orbital elements of geosynchronous artificial satellite due to the non-zonal geopotential has been calculated. For the perturbation of a artificial satellite, perturbation effects due to the non-zonal geopotential is less than due to the $J_2$ or Luni-Solar perturbation, but non-zonal harmonics resonance exist. So, we calculate the perturbation of geosynchronous artificial satellite orbit due to the non-zonal harmonics resonance. The effect on the orbit eccentricity of non-zonal harmonics resonance is represented by a phase plane plot of ec. The effect on the orbit eccentricity of non-zonal harmonics resonance is represented by a phase plane plot of $e_c$ verse $e_s$. The evolution of mean longitude and semi-major axis are obtained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.269-275
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• 2022

In ideal configuration, elapsed-time method can measure the exact reaction wheel speed. But in real configuration, the speed measurement error exists due to tacho pulse non-uniformity. In this research, we study the method which overcome the non-uniformity effects. First, we introduce the method which spin the wheel at the specific speed and measure the non-uniformity. Then, we propose the real-time measurement error correction method which uses the obtained non-uniformity information. This method calculate the speed candidates from the elapsed-time method's counts and non-uniformity information, and choose the closest speed to the real speed. Through simulation, we show that proposed method measure the exact speed regardless of non-uniformity, and fast wheel speed control is possible.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1558-1565
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• 2004

It is important to determine supporting locations for structural stability when a structure is loaded with non-uniform load or supporting locations as well as the number of the supporting structures are restricted by the problem of space. Moreover, the supporting location optimization of complex structure in real world is frequently faced with discontinuous design space. Therefore, the traditional optimization methods based on derivative are not suitable Whereas, Genetic Algorithm (CA) based on stochastic search technique is a very robust and general method. The KSTAR in-vessel control coil installed in vacuum vessel is loaded with non- uniform electro-magnetic load and supporting locations are restricted by the problem of space. This paper shows the supporting location optimization for structural stability of the in-vessel control coil. Optimization has been performed by means of a developed program. It consists of a Finite Element Analysis interfaced with a Genetic Algorithm. In addition, this paper presents an algorithm to find an optimum solution in discontinuous space using continuous design variables.

• Smart Structures and Systems
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• v.14 no.1
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• pp.17-37
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• 2014

In this study, four widely accepted and used variants of Evolution Strategies (ES) are adapted and applied to the output-error state-space identification problem. The selection of ES is justified by prior strong indication of superior performance to similar problems, over alternatives like Genetic Algorithms (GA) or Evolutionary Programming (EP). The ES variants that are being tested are (i) the (1+1)-ES, (ii) the $({\mu}/{\rho}+{\lambda})-{\sigma}$-SA-ES, (iii) the $({\mu}_I,{\lambda})-{\sigma}$-SA-ES, and (iv) the (${\mu}_w,{\lambda}$)-CMA-ES. The study is based on a six-degree-of-freedom (DOF) structural model of a shear building that is characterized by light damping (up to 5%). The envisaged analysis is taking place through Monte Carlo experiments under two different excitation types (stationary / non-stationary) and the applied ES are assessed in terms of (i) accurate modal parameters extraction, (ii) statistical consistency, (iii) performance under noise-corrupted data, and (iv) performance under non-stationary data. The results of this suggest that ES are indeed competitive alternatives in the non-linear state-space estimation problem and deserve further attention.