• Title/Summary/Keyword: multi-reflection

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Optimization of a Broadband Waveguide Magic-T for X-Band Monopulse Tracking Radars (X-Band 모노펄스 추적 레이더를 위한 광대역 도파관 Magic-T 최적화 설계)

  • Hwang, Keum-Cheol
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.10
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    • pp.1042-1049
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    • 2009
  • Design and optimization of a broadband waveguide magic-T was performed for X-Band tracking radars. A multi-stepped conducting cylinder was used to enhance the bandwidth performance of the conventional waveguide magic-Ts. Particles swarm optimization in conjunction with genetic algorithm was employed to obtain the optimized geometrical parameters. The optimized design exhibits low reflection coefficient below -20 dB at all waveguide ports with frequency bandwidth of 12%. The transmission loss and difference are within 0.2 dB and 0.1 dB, respectively. Measured results are also shown to be in good agreement with the simulated results. Finally, the bandwidth performances for five and seven-stepped conducting cylinders are also investigated.

A Study on the Guided Wave Mode Conversion using Self-calibrating Technique (자가교정기법에 의한 유도초음파 모드전이에 관한 연구)

  • Park, Jung-Chul;Cho, Youn-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.3
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    • pp.206-212
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    • 2000
  • The guided wave mode conversion phenomena were investigated for the NDE of a plate-like structure with thickness variation. The ratios of reflection and transmission (R/T) were measured via the self-calibrating procedure which allows us to obtain experimental guided wave data in a more reliable way regardless of the coupling uncertainty between transducer & specimen. The results on R/T could be used to determine the thickness reduction of the structure. It was shown that not only the incident modes but also the converted ones need to be considered in the self-calibrating guided wave inspection to extract a reasonable correlation between experimental data & the thickness variation. Through this study, the potential of guided wave inspection as a quantitative NDE technique was explored based on the combined concept of self-calibration & multi-mode conversion in guided wave scattering problems.

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Potential of gas generation and/or natural gas hydrate formation, and evidences of their presence in near seafloor sediments of the southwestern Ulleung Basin, East Sea (동해 울릉분지 남서부 천부 퇴적층에서의 가스 생성 및 천연가스 하이드레이트 형성 잠재력과 이들의 부존 증거)

  • Ryu, Byong-Jae;Lee, Young-Joo;Kim, Ji-Hoon;Riedel, M.;Hyndman, R.D.;Kim, Il-Soo
    • 한국신재생에너지학회:학술대회논문집
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    • 2006.11a
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    • pp.50-53
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    • 2006
  • Regional geophysical surveys and geological cal studies on natural gas hydrate (NGH) in the East Sea were carried out by the Korea Institute of Geoscience and Mineral Resources (KIGAM) from 2000 to 2004. 16 piston cores, 2270 L-km of multi-channel reflection seismic (MCRS) data and 730 L-km of 3.5kHz Chirp data obtained from the southwestern part of the deep-water Ulleung Basin were analyzed in this study. In piston cores, cracks generally developed parallel to bedding suggest significant gas content. The core analyses showed high total organic carbon (TOC) content, sedimentation rate and heat flow of sediments. These are in favor of the general ion of substantial biogenic methane, which can form the NGH within the stability zone of the near seafloor sediments in the study area. The cores generally show also high residual hydrocarbon gas concentrations for the formation of natural gas hydrates The geophysical indicators of the presence of gas and/or NGH such as bottom simulating reflectors (BSRs), seismic blank Bones, pockmarks and gas seeping features were well defined on the MCRS and Chirp data.

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Symbolic Values of Fur in Fashion Since 1990s - An Analysis under the Theories of Fetishism -

  • Hahn, Soo-Yeon;Yang, Sook-Hi
    • Journal of Fashion Business
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    • v.5 no.5
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    • pp.49-64
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    • 2001
  • Fur is conceived as a material signifier, not only with its commodity value as luxury goods but also as its symbolic value as objects invested by one's libidinal desire. In this study, complex meanings of fur as multi-layered signs of political and sexual power focusing on fetishism shall be explored, especially on the spectacle fetishism acted by mass media during the anti-fur movement in the 1980s. In conjuction herewith, a highlight shall also be made to the symbolic value in fashion design since 1990s. In this study, first, as a theoretical investigation, fetishism, that has been traditionally considered only as sexual fetishism in fashion discourse will be explored in socio-economic level. Second, in historical context, how the meanings and values of fur have become realized in various cultural spaces, such as literature, art, film and finally, fashion will be viewed. In fashion, fur is a product of desire and power influenced by commodity fetishism as well as sexual fetishism. During the anti-fur movement, mass media has developed the concept of spectacle fetishism. Fur is a sign of animal-victim, and fur-clad women is viewed with images full of imperialsm, sexism and racism, thus act as derisive spectacles of consumerism. Since 1990s as a reflection on anti-fur movement, fetishistic characteristics, which challenge traditional operation method, are expressed by disguise, parody, and returning to the nature. First, fur as disguise is intended to hide sexually perverse, decadent characteristics and expensiveness of fur by texturing or patterning techniques. Second, fur as parody uses fake fur or dyed fur in order to satirize erotically and ethnographically fetishized meanings of fur. Third, aboriginal design of fur is adapted to use symbolic values outside the West, which can potentially mobilize antagonistic oppositions out of their fetishistic regimes. In conclusion, fur as sign of female sexuality and its libidinal profits of exchange, has significant symbolic values expressed in fashion.

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A Study on Expressive Aspects of Subversive Mimesis Found in Architectural Design - With a Focus on the Concepts of Appropriation and Détournment - (건축디자인에 나타난 전복적 미메시스의 표현특성 연구 - 전유, 전용을 중심으로 -)

  • Park, Young-Tae
    • Korean Institute of Interior Design Journal
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    • v.22 no.2
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    • pp.68-80
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    • 2013
  • This study is about expressive aspects of subversive mimesis found in architectural design under 2nd Modernity. Architectural works under 2nd Modernity are described based on pseudo-scientific positivism and philosophical ontology of Deleuze. However, subversiveness found in works of arts by architects such as Rem Koolhaas present a few complexities to relay on such a description. This is about 'subversiveness' which absorbs the positive and negative factors of modernity which has been multi-layered as 'cultural capital'. This study aims to identify meta-phenomenon as well as the specific correlations between expression and purposes of any work of art that is presented in the form of subversiveness. To achieve this aim, this study approached with the concepts of appropriation and detournment based on Adorno's subversive mimesis concept. Meta-phenomena of architectural design methods occur from relations of three, which are social reality, artist, and work of art. This was connected to productivity of mimesis practice of self-reference and self-examination, which was then, summed up from the perspectives of appropriation in pure arts and d$\acute{e}$tournment of situationalists. Based on this work, subversive expressive characteristics of architecture under 2nd Modernity were framed from the perspectives of the absorption of cultural capital, reflection and negation, autonomy, instrumentality, and meta properties. In this way, this study found that Adorno's subversiveness should be effective for creative and methodological systemization in terms of interpretation of cognition, practice, and effect after materialization.

The Detection of Yellow Sand Using MTSAT-1R Infrared bands

  • Ha, Jong-Sung;Kim, Jae-Hwan;Lee, Hyun-Jin
    • Proceedings of the KSRS Conference
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    • v.1
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    • pp.236-238
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    • 2006
  • An algorithm for detection of yellow sand aerosols has been developed with infrared bands from Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-functional Transport Satellite-1 Replacement (MTSAT-1R) data. The algorithm is the hybrid algorithm that has used two methods combined together. The first method used the differential absorption in brightness temperature difference between $11{\mu}m$ and $12{\mu}m$ (BTD1). The radiation at 11 ${\mu}m$ is absorbed more than at 12 ${\mu}m$ when yellow sand is loaded in the atmosphere, whereas it will be the other way around when cloud is present. The second method uses the brightness temperature difference between $3.7{\mu}m$ and $11{\mu}m$ (BTD2). The technique would be most sensitive to dust loading during the day when the BTD2 is enhanced by reflection of $3.7{\mu}m$ solar radiation. We have applied the three methods to MTSAT-1R for derivation of the yellow sand dust and in conjunction with the Principle Component Analysis (PCA), a form of eigenvector statistical analysis. As produced Principle Component Image (PCI) through the PCA is the correlation between BTD1 and BTD2, errors of about 10% that have a low correlation are eliminated for aerosol detection. For the region of aerosol detection, aerosol index (AI) is produced to the scale of BTD1 and BTD2 values over land and ocean respectively. AI shows better results for yellow sand detection in comparison with the results from individual method. The comparison between AI and OMI aerosol index (AI) shows remarkable good correlations during daytime and relatively good correlations over the land.

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Optimal Shape Design of Dual Reflector Antenna Based on Genetic Algorithm (유전 알고리즘 기반의 이중 반사경 안테나 형상최적화 기법)

  • Park, Jung-Geun;Chung, Young-Seek;Kang, Won-June;Shin, Jin-Woo;So, Joon-Ho;Cheon, Chang-Yul
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.5
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    • pp.445-454
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    • 2015
  • In this paper, we propose an optimal design method for a dual reflector antenna(DRA) using the Genetic algorithm. In order to reduce the computational burden during the optimal design, we exploit the iterative physical optics(IPO) to calculate the surface current distribution at each reflector antenna. To improve the accuracy, we consider the shadow effect by the structure and the coupling effect by the multi-reflection based on the iterative MFIE(Magnetic Field Integral Equation). To reduce the number of design variables and generate a smooth surface, we use the Bezier function with the control points, which become the design variables in this paper. We adopt the HPBW(Half Power Beam Width), the FNBW(First Null Beam Width), and the SLL(Side Lobe Level) as the objective or cost functions. To verify the results, we compare them with the those of the commercial tool.

Study of Microwave Propagation Characteristics of Matching Liquids for the Microwave Cancer Detection System (유방암 진단 시스템을 위한 정합 액체의 전파 특성에 관한 연구)

  • Kim, Jang-Yeol;Minz, Laxmikant;Lee, Kwang-Jae;Son, Seong-Ho;Jeon, Soon-Ik
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.4
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    • pp.442-450
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    • 2014
  • This paper is a study of the propagation characteristic of matching liquids in the skin-covered breast model. In order to evaluate the matching liquids, we investigated six kinds of matching liquids applied to proposed 1-D breast model from frequency range of 3~6 GHz. A uniform plane wave is projected / transmitted inside the multi-layered breast model. Then the propagation characteristics inside the model and the transmission loss of each matching liquids were analyzed. The studying method presented in the paper can be used in the breast cancer detection system, the field of cancer detection using human tissue and the field of other medical devices. This paper was applied to the breast cancer detection system. Consequently, these studies could be used to determine the suitable type of matching liquids for breast cancer detection system and to apply useful for performance analysis.

Molecular Beam Epitaxial Growth of Oxide Single Crystal Films

  • Yoon, Dae-Ho;Yoshizawa, Masahito
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • 1996.06a
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    • pp.508-508
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    • 1996
  • ;The growth of films have considerable interest in the field of superlattice structured multi-layer epitaxy led to realization of new devices concepts. Molecular beam epitaxy (MBE) with in situ observation by reflection high-energy electron diffraction (RHEED) is a key technology for controlled layered growth on the atomic scale in oxide crystal thin films. Also, the combination of radical oxygen source and MBE will certainly accelerate the progress of applications of oxides. In this study, the growth process of single crystal films using by MBE method is discussed taking the oxide materials of Bi-Sr-Ca-Cu family. Oxidation was provided by a flux density of activated oxygen (oxygen radicals) from an rf-excited discharge. Generation of oxygen radicals is obtained in a specially designed radical sources with different types (coil and electrode types). Molecular oxygen was introduced into a quartz tube through a variable leak valve with mass flowmeter. Corresponding to the oxygen flow rate, the pressure of the system ranged from $1{\;}{\times}{\;}10^{-6}{\;}Torr{\;}to{\;}5{\;}{\times}{\;}10^{-5}$ Torr. The base pressure was $1{\;}{\times}{\;}10^{-10}$ Torr. The growth of Bi-oxides was achieved by coevaporation of metal elements and oxygen. In this way a Bi-oxide multilayer structure was prepared on a basal-plane MgO or $SrTiO_3$ substrate. The grown films compiled using RHEED patterns during and after the growth. Futher, the exact observation of oxygen radicals with MBE is an important technology for a approach of growth conditions on stoichiometry and perfection on the atomic scale in oxide. The oxidization degree, which is determined and controlled by the number of activated oxygen when using radical sources of two types, are utilized by voltage locked loop (VLL) method. Coil type is suitable for oxygen radical source than electrode type. The relationship between the flux of oxygen radical and the rf power or oxygen partial pressure estimated. The flux of radicals increases as the rf power increases, and indicates to the frequency change having the the value of about $2{\times}10^{14}{\;}atoms{\;}{\cdots}{\;}cm^{-2}{\;}{\cdots}{\;}S^{-I}$ when the oxygen flow rate of 2.0 seem and rf power 150 W.150 W.

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Solar Cell Efficiency Improvement using a Pre-deposition Temperature Optimization in The Solar Cell Doping Process (도핑 공정에서의 Pre-deposition 온도 최적화를 이용한 Solar Cell 효율 개선)

  • Choi, Sung-Jin;Yoo, Jin-Su;Yoo, Kwon-Jong;Han, Kyu-Min;Kwon, Jun-Young;Lee, Hi-Deok
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.244-244
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    • 2010
  • Doping process of crystalline silicon solar cell process is very important which is as influential on efficiency of solar. Doping process consists of pre -deposition and diffusion. Each of these processes is important in the process temperature and process time. Through these process conditions variable, p-n junction depth can be controled to low and high. In this paper, we studied a optimized doping pre-deposition temperature for high solar cell efficiency. Using a $200{\mu}m$ thickness multi-crystalline silicon wafer, fixed conditions are texture condition, sheet resistance($50\;{\Omega}/sq$), ARC thickness(80nm), metal formation condition and edge isolation condition. The three variable conditions of pre-deposition temperature are $790^{\circ}C$, $805^{\circ}C$ and $820^{\circ}C$. In the $790^{\circ}C$ pre-deposition temperature, we achieved a best solar cell efficiency of 16.2%. Through this experiment result, we find a high efficiency condition in a low pre-deposition temperature than the high pre-deposition temperature. We optimized a pre-deposition temperature for high solar cell efficiency.

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