• 전자공학회논문지A
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• 제33A권11호
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• pp.60-69
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• 1996

In this study, when the coherent detector has been developed and manufactured in the receiver of radar system, we have suggested and realized the 'Frequecny-Feedback correction (FFC)' that extracts its errors affecting the performance of radar, such as amplitude imbalances (k), phase imbalance ($\varphi$) between channels and offset votlages and corrects them to improve radar performances. Applying the FFC proposed, we analyzed sthe properties of the coherent detector and compared its perfomances after and before correction procdure. After the correction sequence, the amplitude imbalance was improved upt o 2dB and the phase imbalance over 9$^{\circ}$. The image rejection ratio (IRR), one of the figures of merit of radar system, was made better above 9 dB after correcting the coherent detector which possessed 23 dB before.

• 대한수학교육학회지:학교수학
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• 제3권2호
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• pp.447-473
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• 2001

Since the greater part of mathematical concepts have been developed in the direction of “from the concrete and realistic aspects to the abstract level”, children should be secured to learn mathematics genetically with various manipulative materials. The aim of this study is to instigate the active use of geoboards in mathematics classroom. To achieve this arm, we first embodied the several significances on the use of geoboards in mathematics instruction. And we then performed an instruction that children discover and justify the formula related to the area of trapezoid by exploring with geoboards, and analyzed the instructional episode to support our assertion about some secure merit accompanied by using geoboards. From this study, we obtained the conclusion that geoboard activity contains many significances such as children can explore congruence, symmetry, similarity, fundamental properties of figures, and pattern. Futhermore, geoboard activity enable children to transform a figure into other equivalently, develop spatial sense, have basic experiences for coordinate geometry, build a concrete model to explain abstract ideas, and foster the ability of problem solving and mathematical thinking.

• 에너지공학
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• 제7권1호
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• pp.57-64
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• 1998

폴리에스터와 스테인레스스틸섬유를 재료로 제조된 제전사여과포에 대한 물리화학적 특성시험 및 여과포성능 기초시험을 수행하였다. 실험용먼지로 제철.제강, 시멘트제조, 열공급시설 및 폐기물공정에서 채취된 먼지를 처리하여 사용하였다. 제전사여과포의 물리화학적 특성 실험에서는 산성분위기하에서 인장강도 및 초기탄성계수변화를 조사하였고, Automated Permporometer를 이용하여 평균흐름세공압력, 기포점 세공지름, 평균흐름세공지름 및 세공크기분포를 구하였다. 또한 벤처규모의 여과포 기초성능 시험장치를 이용하여 먼지부하에 따른 압력손실, 먼지통과율 및 여과포성능 평가지표를 산출하였다. 산성가스 및 분위기하에서 제전사여과포의 인장강도는 온도 및 노출시간과 깊은 관련이 있었다. 압력손실은 여과속도와 먼지부하가 증가함에 따라 증가하였으며 증가형태는 먼지의 종류에 따라 달랐다. 먼지 통과율은 먼지종류에 관계없이 먼지부하의 증가에 따라 급격히 감소하는 경향을 나타내었다. 여과포성능지표는 먼지 포집 초기에는 증가했다가 급격히 감소하여 일정하게 유지되었다.

• 한국진공학회지
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• 제6권1호
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• pp.69-76
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• 1997

순간 증착법으로 $Bi_{0.5}Sb_{1.5}Te_3$(p형)와 $Bi_2Te_{2.4} Se_{0.6}$(n형) 박막을 제조하여 두께와 어닐 링 조건에 따른 Seebeck 계수, 전기전도도, carrier 농도 및 이동도, 열전도도, 성능지수의 변화 등 열-전기적 특성을 조사하였다. 473K에서, 1시간 진공 열처리한 결과 p형과 n형의 성능지구는 각각 $1.3{\times}10^{-3}K^{-1}$ 및 $0.3{\times}10^{-3}K^{-1}$으로 향상되었으며 두께에 크게 의존하지 않았 다. 이런 성질을 갖는 열전 박막을 소자화한 박막 온도 센서를 유리와 Teflon기판 위에 제 조하였으며, 이들의 온도 변화에 대한 열기전력, 민감도 및 시간 상수 등 센서 특성을 측정 하였다. p 및 n형의 leg 폭 1mm$\times$길이 16mm인 박막 온도 센서의 경우, Teflon 기판일 때 좋은 성능을 나타내었으며, 민감도는 2.91V/W, 시간 상수는 28.2초이었다.

• 한국전기전자재료학회논문지
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• 제23권10호
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• pp.767-770
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• 2010

In this work, we investigated the static characteristics of 4H-SiC vertical metal-oxidesemiconductor field effect transistors (VMOSFETs) by adjusting the doping level of n-epilayer and the effect of a current spreading layer (CSL), which was inserted below the p-base region with highly doped n+ state ($5{\times}10^{17}cm^{-3}$). The structure of SiC VMOSFET was designed by using a 2-dimensional device simulator (ATLAS, Silvaco Inc.). By varying the n-epilayer doping concentration from $1{\times}10^{16}cm^{-3}$ to $1{\times}10^{17}cm^{-3}$, we investigated the static characteristics of SiC VMOSFETs such as blocking voltages and on-resistances. We found that CSL helps distribute the electron flow more uniformly, minimizing current crowding at the top of the drift region and reducing the drift layer resistance. For that reason, silicon carbide VMOSFET structures of highly intensified blocking voltages with good figures of merit can be achieved by adjusting CSL and doping level of n-epilayer.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권1호
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• pp.66-74
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• 2012

In this paper, the impact of segregation layer density ($N_{DSL}$) and length ($L_{DSL}$) on scalability and analog/RF performance of dopant-segregated Schottky barrier (DSSB) SOI MOSFET has been investigated in sub-30 nm regime. It has been found that, although by increasing the $N_{DSL}$ the increased off-state leakage, short-channel effects and the parasitic capacitances limits the scalability, the reduced Schottky barrier width at source-to-channel interface improves the analog/RF figures of merit of this device. Moreover, although by reducing the $L_{DSL}$ the increased voltage drop across the underlap length reduces the drive current, the increased effective channel length improves the scalability of this device. Further, the gain-bandwidth product in a common-source amplifier based on optimized DSSB SOI MOSFET has improved by ~40% over an amplifier based on raised source/drain ultrathin-body SOI MOSFET. Thus, optimizing $N_{DSL}$ and $L_{DSL}$ of DSSB SOI MOSFET makes it a suitable candidate for future nanoscale analog/RF circuits.

• 한국세라믹학회지
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• 제55권5호
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• pp.419-439
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• 2018

Piezoelectric materials are essential parts of the electronics and electrical equipment used for consumer and industrial applications, such as ultrasonic piezoelectric transducers, sensors, actuators, transformers, and resonators. In this review, the development of piezoelectric materials and the figures of merit for various electromechanical applications are surveyed, focusing on piezoelectric crystals, i.e., the high-performance relaxor-$PbTiO_3$-based perovskite ferroelectric crystals and nonferroelectric high-temperature piezoelectric crystals. The uniqueness of these crystals is discussed with respect to different usages. Finally, the existing challenges and perspective for the piezoelectric crystals are discussed, with an emphasis on the temperature-dependent properties, from cryogenic temperatures up to the ultrahigh-temperature usage range.

• 천문학회보
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• 제40권1호
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• pp.67.1-67.1
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• 2015

In the past two decades, diverse methods and computer codes for reconstruction of coronal magnetic fields have been developed. Some of them can reproduce a known analytic solution quite well when the magnetic field vector is fully specified by the known solution at the domain boundaries. In practical problems, however, we do not know the boundary conditions in the computational domain except the photospheric boundary, where vector magnetogram data are provided. We have developed a new, simple variational method employing vector potentials. We have tested the computational code based on this method for problems with known solutions and those with actual photospheric data. When solutions are fully given at all boundaries, the accuracy of our method is almost comparable to best performing methods in the market. When magnetic field vectors are only given at the photospheric boundary, our method excels other methods in "figures of merit" devised by Schrijver et al. (2006). Our method is expected to contribute to the real time monitoring of the sun required for future space weather prediction.

• Transactions on Electrical and Electronic Materials
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• 제1권2호
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• pp.23-27
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• 2000

Indium in oxide(ITO) films have been deposited on PET and glass substrates by DC reactive magnetron sputtering without post-deposition thermal treatment, The high quality for microstructure, electrical and optical properties of the as-deposited ITO films on unheated substrates is dominated by the sputtering parameters, The influence of the working gas pressure, DC power and oxygen partial pressure has been systematically investigated, The lowest DC power, and oxygen partial pressure has been systematically investigated, The lowest resistivity of ITO films deposited on PET substrates was 6$\times$10$^{-4}$ $\Omega$cm. It has been obtained at a working pressure of 3 mTorr and DC power of 30 W. The sheet resistance and optical transmittance of these film were 22 $\Omega$/square and 84% respectively. The best values of figures of merit for the electrical and optical characteristics such as T/ $R_{sh}$ and $T^{10}$ / $R_{sh}$ are approximately 38.1 and 7.95($\times$10$^{-3}$ $\Omega$$^{-1}$ ), respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.350-350
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• 2010

Silicon carbide (SiC), one of the well known wide band gap semiconductors, shows high thermal conductivities, chemical inertness and breakdown energies. The design of normally-off 4H-SiC VJFETs [1] has been reported and 4H-SiC VJFETs with different lateral JFET channel opening dimensions have been studied [2]. In this work, 4H-SiC based VJFETs has been designed using the device simulator (ATLAS, Silvaco Data System, Inc). We varied the n-epi layer thickness (from $6\;{\mu}m$ to $10\;{\mu}m$) and the channel width (from $0.9\;{\mu}m$ to $1.2\;{\mu}m$), and investigated the static characteristics as blocking voltages, threshold voltages, on-resistances. We have shown that silicon carbide JFET structures of highly intensified blocking voltages with optimized figures of merit can thus be achieved by adjusting the epi layer thickness and channel width.