• Journal of electromagnetic engineering and science
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• v.17 no.3
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• pp.165-167
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• 2017

We predict the electromagnetic wave propagation in space environments using geometrical optics. The effective indices of the troposphere, stratosphere, and ionosphere are computed, and the reflection, refraction, and attenuation of electromagnetic waves in space environments are calculated based on the ray tracing technique and geometrical optics. The influence of the refractive index and loss of atmosphere and the incident angle of the antenna on electromagnetic wave propagation is discussed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.1-5
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• 2011

In this thesis, we have developed novel geometrical analysis method for the double constraints linear constraint minimum variance (LCMV) beamforming algorithm. The proposed analysis method was matched well with the computer simulation result.

• Journal of Educational Research in Mathematics
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• v.23 no.4
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• pp.585-604
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• 2013

This study is based on the problem that most middle school students cannot recognize the generality of geometrical theorems even after having proved them. By considering this problem from the point of view of empirical verification, the particularity of geometrical representations, and the role of geometrical variables, we suggest that some experiences in dynamic geometry environment (DGE) can help students to recognize the generality of geometrical theorems. That is, this study aims to observe students' cognitive changes related to their recognition of the generality and to provide some educational implications by making students experience some geometrical explorations in DGE. To do so, we selected three middle school students who couldn't recognize the generality of geometrical theorems although they completed their own proofs for the theorems. We provided them exploratory activities in DGE, and observed and analyzed their cognitive changes. Based on this analysis, we discussed the effects of DGE on studensts' recognition of the generality of geometrical theorems.

• Proceedings of the Safety Management and Science Conference
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• 2007.11a
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• pp.319-322
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• 2007

This paper presents geometrical product specifications of acceptance and verification tests for coordinate measuring machines(CMM). These specifications include vocabulary, measuring size, rotary table with fourth axis, scanning measuring mode, multiple-stylus probing systems, measuring, and, estimation of errors in computing Gaussian associated features.

• Journal of architectural history
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• v.5 no.1 s.9
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• pp.73-86
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• 1996

This study is to analyze the geometrical composition system for the plan of S. Pietro by Michelangelo. In the result of study, the plan is based on the geometrical elements of circle square cross, and shaped to symbolize the Universe which consists of the Heaven the Earth the Man. The plan is constituted of the conception of composition into hierarchy and repetition intersecting 45 degree the same sized square with inscribed square in a circle. Such the geometrical composition system can be found out a large number of example to the geometrical composition of architecture and city planning from Vitruvius to Bramante and Da Vinci. This plan is disposed in balance as the regularly proportional system of 1:1, 1:2, 1:3, which is formed the principal space. And the interior space is constituted of the organic space system, expanding to the direction of horizontal, vertical(ascension), development for primary space and secondary space with center in the geometric composition system of altar.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1784-1788
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• 2003

For the improvement of geometrical accuracy in end milling, cutting method and cutting condition selection are investigated in this paper. As machining processes are composed of several steps such as roughing, semi-finishing. and finishing, cutting forces and tool deflection are calculated considering surface shape generated by the previous cutting. The effects of tool teeth numbers, tool geometry, and cutting conditions on the form error are analyzed. Using the from error prediction method from tool deflection, cutting condition for geometrical accuracy improvement is discussed. The characteristics and the difference of generated surface shape in up and down milling are dealt with and over-cut free condition in up milling is presented. The form error reduction method by alternating up and down milling is also suggested. The effectiveness of the presented method is examined from a set of cutting tests under various cutting conditions. This research contributes to cutting process optimization for the geometrical accuracy improvement in die and mold manufacture.

• Journal of the Korea Computer Graphics Society
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• v.4 no.1
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• pp.11-19
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• 1998

Non-manifold topological operations such as Euler and Boolean operations provide a versatile environment for modeling domains. The implementation of these operations raises geometrical issues that need to be addressed to ensure the topological validity of the underlying model, and they uses the glue operation which provides a basic method to modify the topology of non-manifold models when vertices, edges and faces are contacting each other. Topological information such as adjacency relationships should be inferred when gluing non-manifold models. Two methods of reasoning can be employed to find the topological information : topological reasoning and geometrical reasoning. The topological method can infer the adjacency relationships by using stored topological information. On the other hand, the geometrical method can find topological ambiguities by considering the geometrical shape at the local area of gluing when the topological relations were not stored. This paper describes the geometrical reasoning method.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1271-1276
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• 2020

The geometrical efficiency of a source-to-detector configuration is considered to be necessary in the calculation of the full energy peak efficiency, especially for NaI(Tl) and HPGe gamma-ray spectroscopy detectors. The geometrical efficiency depends on the solid angle subtended by the radioactive sources and the detector surfaces. The present work is basically concerned to establish a new mathematical approach for calculating the solid angle and geometrical efficiency, based on conversion of the geometrical solid angle of a non-axial radioactive point source with respect to a circular surface of the detector to a new equivalent geometry. The equivalent geometry consists of an axial radioactive point source with respect to an arbitrary elliptical surface that lies between the radioactive point source and the circular surface of the detector. This expression was extended to include coaxial radioactive circular disk source. The results were compared with a number of published data to explain how significant this work is in the efficiency calibration procedure for the γ-ray detection systems, especially in case of using isotropic radiating γ-ray sources in the form of point and disk shapes.

• Journal of the Korean Solar Energy Society
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• v.29 no.3
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• pp.1-11
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• 2009

Heliostat sun tracking accuracy could be the most important requirement in solar thermal power plant, since it determines the overall efficiency of power plant. This study presents the effect of geometrical errors on the heliostat sun tracking performance. The geometrical errors considered here are the mirror canting error, encoder reference error, heliostat position error. pivot offset and tilt error, gear backlash and mass unbalanced effect error. We first investigate the effect of each individual geometrical error on the sun tracking accuracy. Then, the sun tracking error caused by the combination of individual geometrical error is computed and analyzed. The results obtained using the solar ray tracing technique shows that the sun tracking error due to the geometrical error is varying almost randomly. It also shows that the mirror canting error is the most significant error source, while the encoder reference error and gear backlash are second and the third dominant source of errors.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.615-625
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• 2023

Initial geometrical imperfection is an important factor affecting the structural characteristics of plate and shell structures. Studying the effect of geometrical imperfection on the structural characteristics of cylindrical shell is beneficial to explore the thermal post-buckling response characteristics of cylindrical shell. Therefore, we devote to investigating the thermal post-buckling behavior of graphene platelets reinforced mental foam (GPLRMF) cylindrical shells with geometrical imperfection. The properties of GPLRMF material with considering three types of graphene platelets (GPLs) distribution patterns are introduced firstly. Subsequently, based on Donnell nonlinear shell theory, the governing equations of cylindrical shell are derived according to Eulerian-Lagrange equations. Taking into account two different boundary conditions namely simply supported (S-S) and clamped supported (C-S), the Galerkin principle is used to solve the governing equations. Finally, the impact of initial geometrical imperfections, the GPLs distribution types, the porosity distribution types, the porosity coefficient as well as the GPLs mass fraction on the thermal post-buckling response of the cylindrical shells are analyzed.