• 한국정밀공학회지
• /
• 제29권3호
• /
• pp.334-338
• /
• 2012

Electrical isolation of Ag nanowire, which is one of the candidates as electrode for display devices, on polymer with femtosecond pulse laser has been investigated. Line patterning to Ag nanowire with various pulse energy and scan speed were experimented. Duo to the results of the line patterning experiment, we fabricated the isolated squares and measured electrical resistance. The profile of the selectively ablated area was analyzed with AFM(Atomic Force Microscope). The width of the patterned line was $1.8\;{\mu}m$ and the depth was $1.6\;{\mu}m$. We demonstrated electrical isolation of the Ag nanowire using femtosecond laser by evaluating the electrical resistance of the sample between isolated and opened area.

• 한국정밀공학회지
• /
• 제26권6호
• /
• pp.50-58
• /
• 2009

Micro laser fabrication techniques can potentially be used for the manufacture of microstructures on the thin flat surfaces with large diameter that are frequently used in semiconductor industries. However, the large size of wafers can cause the degraded machining accuracy of the surface because it can be tilted or distorted by geometric errors of machines or the holding fixtures, etc. To overcome these errors the off-line focusing error compensation method is proposed. By using confocal autofocus system, the focusing error profile of machined surface is measured along the pre-determined path and can be compensated at the next machining process by making the corrected motion trajectories. The experimental results for silicon wafers and invar flat surfaces show that the proposed method can compensate the focusing error within the level of below $6.9{\mu}m$ that is the depth of focus required for the laser micromachining process.

• 천문학회보
• /
• 제35권2호
• /
• pp.73.2-73.2
• /
• 2010

In order to understand internal dynamics of starless cores, molecular line emissions are usually observed. From profiles of the molecular lines, internal motions of starless cores have been deduced using a simple radiative transfer model such as the two-layer model (Myers et al.1996). This brings complexities arising from the chemical evolution. The motivation of this study is to follow the chemical evolution of a starless core that goes through gravitational contraction. For this purpose, we have performed hydrodynamical simulations with a marginally unstable Bonnor-Ebert sphere as an initial condition. We follow the chemical evolution of this core with changing conditions such as the chemical reaction rate at the dust surface and the strength of radiation field that penetrate into the core. At the core center, the molecules suffer from a higher degree of molecular depletion on the dust covered by ice rather than on the bare silicate dust. The stronger radiation field dissociates more molecules at the core envelope. From analysis on the line profile using the two-layer model, we found that the speed of inward motion deduced from the HCN F = 2-1 line adequately traces the true infall speed, when the dust is covered by ice and the core is exposed to the diffuse interstellar radiation field. Under different conditions, the two-layer model significantly underestimate the infall speed.

• 천문학회보
• /
• 제36권2호
• /
• pp.97.2-97.2
• /
• 2011

Rims of solar filaments often appear brighter than the background chromosphere, but their physical nature is still poorly known. Last year, we observed a filament with a bright rim. The rim was bright in H alpha but not in Ca II 8542 line. Using the cloud model, we inferred physical parameters of the region from the spectral profiles. As a result, we found that the Doppler width of the H alpha line is very large, which implies temperature as high as 50000K. In addition, the value of the source function of the H alpha line is 0.7 times the continuum intensity of background profile. These results suggest that the bright rims might be a region of intense heating, probably associated with a current sheet. To further investigate this possibility, we carried out more observations this summer. We will present new results obtained from the analysis of these observations and discuss the physical implication of these measurements on the nature of bright rims and the filaments.

• 한국전자파학회논문지
• /
• 제10권2호
• /
• pp.291-301
• /
• 1999

원하는 역산란 패턴을 만족시키는 일차원 비선형 분포함수를 합성하는 방법을 제안하였다. 이 방법은 일차 원 역산란 문제로부터 유도된 Riccati 방정식의 해의 역변환에 기본을 두고 있다. 그 해는 collinear 배열 안테 나에서의 배열인자 혹은 정규화된 공간인자와 유사한 형태를 가지므로 연관된 비선형 분포함수를 구하기 위 해 line-source 법에 입각한 패턴 합성법을 사용하였다. 이 과정들은 최적화 기법에 의해 수행되며, 분산특성 을 갖는 매질내에서 임의의 전송선로를 특정 주파수 대역내에서 합성하는 예와 저항성 스트립의 산란패턴 제어 등의 예로부터 제안한 방법의 타당성을 수치적으로 입증하였다.

• 한국전기전자재료학회논문지
• /
• 제14권8호
• /
• pp.634-639
• /
• 2001

We investigated the etching characteristics of chromium films by using Cl$_2$/O$_2$ gas mixtures with electron cyclotron resonance plasma. In order to examine the chemical etch characteristics of Cr films by using Cl$_2$/O$_2$ gas plasma, we obtained the etch rate with various gas mixing ratios. By X-ray photoelectron spectroscopy, the surface reaction on the chromium films during the etch was examined. From narrow scan analyses of Cr, Cl, and O, it was confirmed that a chromium oxychlorie (CrCl$_{x}$O$_{y}$) layer was formed on the surface by the etch using Cl$_2$/O$_2$ gas mixtures. We observed a new characteristic emission line during the etch of chromium films using Cl$_2$/O$_2$ gas mixtures by an optical emission spectroscopy. It was found that the peak intensity of this emission line had a tendency compatible with the etch rate. The origin of this emission line was discussed in detail. At the same time, the etched profile was also examined by scanning electron microscope.e.e.

• International Journal of Contents
• /
• 제5권1호
• /
• pp.51-55
• /
• 2009

In this paper, we present a structure of personalized e-Learning system to study for a test formalized by uniform multiple-choice using on/off line mixed estimations as is the case of Driver :s License Test in Korea. Using the system a candidate can study toward the license through the Internet (and/or mobile instruments) within the personalized concept based on IRT(item response theory). The system accurately estimates user's ability parameter and dynamically offers optimal evaluation problems and learning contents according to the estimated ability so that the user can take possession of the license in shorter time. In order to establish the personalized e-Learning concepts, we build up 3 databases and 2 agents in this system. Content DB maintains learning contents for studying toward the license as the shape of objects separated by concept-unit. Item-bank DB manages items with their parameters such as difficulties, discriminations, and guessing factors, which are firmly related to the learning contents in Content DB through the concept of object parameters. User profile DB maintains users' status information, item responses, and ability parameters. With these DB formations, Interface agent processes user ID, password, status information, and various queries generated by learners. In addition, it hooks up user's item response with Selection & Feedback agent. On the other hand, Selection & Feedback agent offers problems and content objects according to the corresponding user's ability parameter, and re-estimates the ability parameter to activate dynamic personalized learning situation and so forth.

• 설비공학논문집
• /
• 제12권6호
• /
• pp.609-615
• /
• 2000

The energy conservation is one of the most important issues in recent years. Especially, the energy conservation through improved control strategies is one of the most highly possible area to be implemented in the near future. The energy conservation of the ice storage system can be accomplished through the improved control strategies. A real time building load prediction algorithm was developed. The expected highest and the lowest outdoor temperature of the next day were used to estimate the next day outdoor temperature profile. The measured dry bulb temperature and the measured building load were used to estimate system parameters by using the on-line weighted recursive least square method. The estimated hourly outdoor temperatures and the estimated hourly system parameters were used to predict the next day hourly building loads. In order to see the effectiveness of the building load prediction algorithm, two different types of building models were selected and analysed. The simulation results show less than 1% in error for the prediction of the next day building loads. Therefore, this algorithm may successfully be used for the development of improved control algorithms of the ice storage system.

• 천문학회보
• /
• 제36권1호
• /
• pp.52.1-52.1
• /
• 2011

Black hole masses of Active Galactic Nuclei (AGN) are one of the most important parameters in AGN physics. Based on the virial assumption, black hole masses can be determined from the product of the width of the broad emission lines and the continuum/line luminosities. Using the Low Resolution Imaging Spectrometer(LRIS) at the Keck telescope, we obtained high quality spectra (S/N~100), covering 2300-5500A in the rest-frame, for a sample of 37 intermediate-luminosity AGN at z~0.4, in order to calibrate various black hole mass estimators based on the Mg II (2798A) and the Hbeta (4861A) emission lines. After subtracting continuum and complex FeII emission under Mg II and Hbeta, we fit the broad emission lines using high order Guass-Hermite models to best constrain the profile and the width of the emission lines. Combining the SDSS spectra covering Halpha emission line with the Keck spectra, we determine a set of 6 black hole masses for each object, based on the line width (MgII, Hbeta, and Halpha) and the luminosity (LMgII, LHbeta, LHalpha, L3000, L5100), and calibrate each black hole mass estimator. We will present uncertainties and limitations of each mass estimator.

• Journal of Electrical Engineering and Technology
• /
• 제11권4호
• /
• pp.878-888
• /
• 2016

Cogging torque has a negative impact on the operation of permanent magnet machines by increasing torque ripple, speed ripple, acoustic noise and vibration. In this paper Magnet Shifting Method has been used as a tool to reduce the cogging torque in inset Line Start Permanent Magnet Synchronous Motor (LSPMSM). It has been shown that Magnet Shifting Method can effectively eliminate several lower-order harmonics of cogging torque. In order to implement the method, first the expression of cogging torque is studied based on the Fourier analysis. An analytical expression is then introduced based on Permanent Magnet Shifting to reduce cogging torque of LSPMS motors. The method is applied to some existing machine designs and their performances are obtained using Finite Element Analysis (FEA). The effect of magnet shifting on pole mmf (magneto motive force) distribution in air gap is discussed. The side effects of magnet shifting on back-EMF, core losses and torque profile distortion are taken into account in this investigation. Finally the experimental results on two prototypes 24 slot 4 pole inset LSPMS motors have been used to validate the theoretical analysis.