• Communications of the Korean Mathematical Society
• /
• v.29 no.2
• /
• pp.295-310
• /
• 2014

This paper provides a study of lightlike submanifolds of a generalized Robertson-Walker (GRW) space-time. In particular, we investigate lightlike submanifolds with curvature invariance, parallel second fundamental forms, totally umbilical second fundamental forms, null sectional curvatures and null Ricci curvatures, respectively.

• Bulletin of the Korean Mathematical Society
• /
• v.49 no.4
• /
• pp.863-874
• /
• 2012

We provide a study of lightlike hypersurfaces of a generalized Robertson-Walker (GRW) space-time. In particular, we investigate lightlike hypersurfaces with curvature invariance, parallel second fundamental forms, totally umbilical second fundamental forms, null sectional curvatures and null Ricci curvatures, respectively.

• The Korean Journal of Zoology
• /
• v.12 no.4
• /
• pp.123-134
• /
• 1969

細胞學의 發展은 電子顯微鏡의 分解能$(2.4\\mu 以上)$이 增加됨과 아울러 超薄切片法(Sjostrand 1953) 및 固定法의 改良(Palade 1952) 으로 細胞의 超微細構造를 追究하는 反面 物理化學的構成成分과 機能面에서 細胞生物學, 더 나아가 分子生物學으로 發展하였다. 細胞膜(原形質膜)의 分子的 構造는 二重의 脂質分子膜의 表面에 蛋白質分子가 結合하고 있는 單位膜(Robertson 1961, Danielli 1964)으로 되어있다. 이 單位膜構造는 모든 動植物 細胞의 表面膜만이 아니고 核膜, mitochondria, Golgi complex, 色素體等 細胞內 膜系가 同一하게 되어 있고(Robertson 1961), 膜의 무게는 位置(Sjostrand 1963) 및 小器官別(Yamamoto 1963)로 다르다. 또 各細胞는 그 機能에 따라 部分的으로 特殊하게 分化되어 있다.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.1
• /
• pp.61-70
• /
• 2004

In this paper, we propose the color-temperature conversion system with compensated X-chromaticity coordinate. It uses a linear regression to improve the error of color-temperatue calculation in conventional systems. It also extend the color-temperature range from 1,667K to 25,000K to Provide a wider color-temperature range. We show the effectiveness of the proposed method by comparing the performance of the proposed method with those of the Robertson's and the existing methods. The proposed method is experimetally verified by displaying the results on a TV system through the Xilinx FPGA XCV2000E-BG560.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.54.2-54.2
• /
• 2011

It is the conventional wisdom that the Poynting-Robertson effect is essentially the outcome of the interplay between absorption and reemission processes. For a better understanding of the motion of charged particles around a compact star with strong radiation, we reached an alternative interpretation for the Poynting-Robertson effect based on the covariant formalism and found that it is attributed to the combination of the aberration and the Lorentz transformation of the radiation stress-energy tensor. As a general relativistic application of the Poynting-Robertson effect, we studied the dynamics of test particles around the spinning relativistic star with strong radiation. We discovered that the combination of the angular momentum and the finite size of the star generates "radiation counter drag" which exerts on the test particle to enhance its specific angular momentum, contrary to the radiation drag. The balance of the radiation drag and the radiation counter drag renders the particle to hover around the spinning luminous star at the "suspension orbit". The radial position and the angular velocity of the particle on the "suspension orbit" are determined by the angular momentum, the luminosity, and the size of the central star only, and they are independent of the initial position and velocity of the particle.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.7
• /
• pp.1668-1672
• /
• 2009

In this study, the method by Robertson which has been most commonly used for classifying soils, using piezocone test results, was compared with that by Schneider which was most recently proposed. Both methods were applied to the soils in Gyeonggi province and the classifying results were investigated. It has been found that the difference between the results according to the methods was not so large and Schneider's method showed slightly better results for clay region and vice versa. Such factors as large field database, normalized tip resistance, pore water pressure, and drain condition were found to need further research for more reliable soil classification.

• Journal of the Korean Mathematical Society
• /
• v.19 no.2
• /
• pp.123-128
• /
• 1983

• The Bulletin of The Korean Astronomical Society
• /
• v.7
• /
• pp.8.4-8.4
• /
• 1982

• Proceedings of the Korea Contents Association Conference
• /
• 2003.11a
• /
• pp.367-372
• /
• 2003

In the framework of Lorentzian warped products, we study the Friedmann - Robertson - Walker cosmological model to investigate non-smooth curvatures associated with multiple discontinuities involved in the evolution of the universe. In particular we analyze non-smooth features of the spatially flat Friedmann-Robertson-Walker universe by introducing double discontinuities occurred at the radiation- matter and matter-lambda phase transitions in astrophysical phenomenology.

• International Journal of High-Rise Buildings
• /
• v.6 no.1
• /
• pp.73-82
• /
• 2017

Vertical shortening in tall buildings would be of little concern if all vertical elements shortened evenly. However, vertical elements such as walls and columns may shorten different amounts due to different service axial stress levels. With height, the differential shortening may become significant and impact the strength design and serviceability of the building. Sometimes column transfers or other vertical structural irregularities may cause differential shortening. If differential shortening is not addressed properly, it can impact the serviceability of the building. This paper takes the perspective of a structural engineer in planning the design, predicting the shortening and its effects, and communicating the information to the contractor.