• Korean Journal of Optics and Photonics
• /
• v.16 no.5
• /
• pp.401-405
• /
• 2005

In this paper, we have presented mechanically formed long-period fiber gratings using periodically arrayed brass wires with a $250-{\mu}m$ diameter and realized the function of current-controlled wavelength-tuning. With the thermo-optic effect of the surrounding medium around the fiber cladding, the continuous displacement of the resonance wavelengths is achieved through the resistant heat of the wire which changes the refractive index of surrounding material. The tunability for each mode as a function of an applied electrical power is investigated. When the glycerin is used as a thermo-optic material, the measured tuning ranges of $LP_{03}$ and $LP_{04}$ within electrical power of 20 W reach to 14 nm and 48 nm, respectively. The experimental results are in good agreement with the theoretical that which is analyzed by a geometric-optics approximation.

• Communications of Mathematical Education
• /
• v.17
• /
• pp.17-29
• /
• 2003

수학이 일상생활에서 나날이 더욱 중요하게 변하고 있는 이런 시점에서 또 산업이나 새로 떠오르는 신기술에서 수학의 응용이 더욱 밀접하여지는 이러한 때에 수학을 공부하겠다는 학생의 숫자가 점점 줄어들고, 전체 학생들의 수학에 관한 관심도 낮아지는 징후가 있다. 학생들에게 수학은 미래 사회에서 근간을 이루고 있음을 보여줌으로써 수학에 대한 열광이 일어나게끔 새로운 접근을 시도하도록 교사들에게 용기를 북돋아 주어야 한다. 이러한 목표를 성취하기 위해서는 교사의 지식을 새롭게 하고, 교육 기술을 현대화할 수 있는 기회가 가능하도록 만들어야 한다. 이 글에서는 현실 세계 속에 있는 수학에 중점을 두고, 이를 스스로 학습이라든지 의사소통과 같은 좀 더 일반화된 교육 기술을 발전시키는 데 쓰도록 강조한다. 여기서 의사소통 이라든가 스스로 학습은 직업 현장에서 뿐만 아니라 고등 교육에 진학하는 준비 단계에서도 매우 중요한 부분이기도 하고 매우 요긴하다.

• Korean Journal of Soil Science and Fertilizer
• /
• v.14 no.4
• /
• pp.179-184
• /
• 1982

To describe a mathematical heat transfer model in saturated paddy soils, an analytical solution of the heat flow equation incorporated with the heat transfer by mass flow of water was obtained under the assumptions: 1) the diurnal (or annual) changes in temperature at a depth follow harmonic curves, 2) the temperature at the infinite depth be constant and 3) the temperatures of soil and water at the one depth be identical. The calculation of thermal diffusivities of the soil is possible with the known values of the physical parameters of each component in the soil matrix (heat capacity, density and porosity), percolation rate and the minimum and maximum temperatures at two different depths. The calculated thermal diffusivities using the solution were $9.5cm^2/hr$ for the loam soil with the percolation rate of 0.88cm/day and $13.9cm^2/hr$ for the sandy loam soil with the percolation rate of 2.64 cm/day.

• Korean Journal of Optics and Photonics
• /
• v.16 no.5
• /
• pp.469-475
• /
• 2005

An integrated photonic microwave bandpass filter has been proposed and demonstrated incorporating a coherently coupled microring resonator in low-loss polymers. The proposed device may feature compact site, simple structure, tuning via the thermooptic and electrooptic effect, and flexible integration with other electrical and optical devices. The resonator was designed to have an extremely small bandwidth so that it could be used to selectively pass the optical signal carrying the microwave signal to attain efficient bandpass filtering. We made and tested two resonators with a single ring and double rings, and performed a theoretical fitting of their measured transfer curves to predict the performance of the microwave filters based on them precisely. It was found that as the number of the rings used for the resonator increases, the bandwidth gets smaller, the rolloff sharper, and the band rejection higher. Finally our filter exhibited the center frequency of 10GHz, the 3-dB bandwidth of 1.0GHz, the corresponding quality (Q) factor of 10, and the rejection outside of the passband of more than 25dB.

• Journal of Korean Society for Atmospheric Environment
• /
• v.29 no.6
• /
• pp.722-733
• /
• 2013

Ground-based measurements were conducted from August 25 to September 8 of 2011 for understanding characteristics of carbonaceous aerosols measured at Gosan. Chemical components and their sources were discussed by analysis of organic compounds with identification of primary and secondary products in particulate matter. Thus, organic carbon (OC) and elemental carbon (EC) based on the carbonaceous thermal distribution (CTD), which provides detailed carbon signature characteristics relative to analytical temperature, was used to improve the carbon fractionation of the analytical method. In addition, organic compounds by gas chromatography technique with the backward trajectories were discussed for characteristics of carbonaceous aerosols. Different air-masses were classified related to the OC thermal signatures and the organic molecular markers such as aromatic acids and PAHs. We concluded that the aging process was influenced by the long-range transport from East Sea area.

• Journal of Science and Technology Studies
• /
• v.5 no.1 s.9
• /
• pp.125-148
• /
• 2005

This paper deals with public understanding of the stem cell cloning discussed in the Internet, based upon the case study of public discourse about Dr. Hwang's international publication of an advanced research of Stem Cell in Korean context. Public understanding of the stem cell cloning in Korea is characterized as follows: (1) it was defined as therapeutic cloning, (2) it was legitimized as a national pride and a potential vehicle for long-term economic performance, (3) ethical issues were criticized by the exclusion of early embryo from human life and the ubiquity of abortion in Korea.

• Korean Journal of Optics and Photonics
• /
• v.15 no.6
• /
• pp.591-596
• /
• 2004

In this paper, a photonic RF true-time delay based on a partially side-polished fiber Bragg grating with heating electrode has been proposed and fabricated. It features continuous voltage-controlled operation, requiring no mechanical perturbation and no moving parts. For an RF signal carried over an optical signal, the time delay has been obtained by controlling the voltage applied to the electrode and thus adjusting its reflection positions from the fiber grating via the thermooptic effect. The achieved time delay is about 100 ps with the electrical power consumption of 280 mW.

• Korean Journal of Optics and Photonics
• /
• v.18 no.1
• /
• pp.79-83
• /
• 2007

A reconfigurable photonic microwave (MW) channel selective filter was demonstrated incorporating a $1{\times}2$ switch based on two tunable polymeric resonators with different free spectral ranges. Each resonator, consisting of two cascaded rings with an electrode formed on one of them, plays a role as an on/off switch through the thermooptic effect. The optical signal carrying the MW signal is routed to either port of the switch and detected to show the filtered output at the frequency determined by the free spectral range of the corresponding resonator. When the channel centered at 10 GHz was chosen, the extinction ratio was ${\sim}30dB$, the bandwidth 1 GHz, and the electrical power consumption 4.1 mW. For the other channel located at 20 GHz, we have achieved the extinction ratio of ${\sim}30dB$, the bandwidth of 2 GHz, and the required power of 8.0 mW. Finally the crosstalk between the selected and blocked channels was higher than 24 dB.

• Archives of design research
• /
• v.17 no.1
• /
• pp.119-126
• /
• 2004

MMO RPG Online game as a new means of human computer interaction has been made rapid progress. Even though many kinds of online game have published, few games are being well received by its user. So we have a problem to be solved what is the fundamentals to attract game users. I will apply a game theory of the Roger Caillois who lived as an typical french thinker. Although Roger Caillois had never experienced a computer game since he died at 1978, his game theory was acknowledged that a game can be classified into four sections to grab the human's interest related with culture. Four sections of game were consisted of Ilinx, Mimicry, Alea, and Agon. The competition with people in game is essential to "Agon" that which stands on the basis of a pride when one is definitely superior to the others. In same way, "Alea" is that which stands on the basis of fortune, Mimicry is that which stands on the basis of simulation, Ilinx is that which stands on the basis of dizzy. In conclusion, I will explain that a game theory of the Roger Caillois is useful tool for deveoper to understand game fundamentals.d game fundamentals.

• Journal of Science and Technology Studies
• /
• v.17 no.2
• /
• pp.5-40
• /
• 2017

The purpose of this paper lies in summing up the historical stream of industrial revolutions and inspecting the place of so called 'the Fourth Industrial Revolution' set off by 2016 World Economic Forum. This paper examined the development of the First Industrial Revolution, the Second Industrial Revolution, the Third Industrial Revolution, and extracted the characteristics of each industrial revolution. Consequently, this paper certificated the history of industrial revolutions perceived by participants concerning the Fourth Industrial Revolution is problematic with reference to core technology and starting time. In addition, this paper raised a question whether the Fourth Industrial Revolution is another new industrial revolution or not, suggested some conditions required to bring industrial revolution into existence. In conclusion, the Fourth Industrial Revolution discussed enthusiastically in recent times is a sort of working hypothesis, and it is necessary to make future vision appropriate to Korean situation.