• Title/Summary/Keyword: PO Method

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Comparative Evaluation of Two Analytical Models for Microwave Scattering from Deciduous Leaves

  • Oh, Yi-Sok
    • Korean Journal of Remote Sensing
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    • v.20 no.1
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    • pp.39-46
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    • 2004
  • The generalized Rayleigh-Gans (GRG) approximation is usually used to compute the scattering amplitudes of leaves smaller or comparable to a wavelength, while the physical optics (PO) approach with the resistive sheet approximation is commonly used for leaves larger or comparable to the wavelength. In this paper, the scattering amplitudes of an elliptical leaf are computed using those theoretical scattering models (GRG and PO) at different frequencies. The accuracies of the analytical models for microwave scattering from deciduous leaves are investigated by comparison with the precise estimation by the method of moment (MoM). It was found that both the PO approach and the GRG approximation can be used alternatively for computing the scattering matrices of natural deciduous leaves at P-, L-, C- and X-band frequencies.

Development of Radar Cross Section Analysis Program for Complex Structures (복합 구조물의 레이더 반사면적 해석 프로그램 개발)

  • Kwon, Hyun-Wung;Hong, Suk-Yoon;Song, Jee-Hun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.20 no.4
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    • pp.435-442
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    • 2014
  • In this paper, radar cross section (RCS) analysis program, RACSAN has been developed to predict RCS of complex structures. RACSAN is based on the high frequency range analysis method of Kirchhoff approximation in physical optics (PO). This program can present RCS including multi-bounce effect in complex structures by combination of geometric optics (GO) and PO method. GO method has a concern in the evaluation of the effective area, and PO method is involved in the calculation of RCS for the final effective area that is evaluated by GO method. Comparisons of the predicted results and analytical solutions showed that the developed program could be an effective tool for predicting RCS in complex structures.

Preparation of the Nano Cobalt Powder by Wet Chemical Reduction Method (액상환원공정을 이용한 나노 코발트 분말의 합성)

  • Hong, Hyun-Seon;Ko, Young-Dae;Kang, Lee-Seung;Kim, Geon-Hong;Jung, Hang-Chul
    • Journal of Powder Materials
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    • v.18 no.3
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    • pp.244-249
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    • 2011
  • Spherical nanosized cobalt powder with an average size of 150-400 nm was successfully prepared at room temperature from cobalt sulfate heptahydrate ($CoSO_4{\cdot}7H_2O$). Wet chemical reduction method was adopted to synthesize nano cobalt powder and hypophosphorous acid ($H_3PO_2$) was used as reduction agent. Both the HCP and the FCC Co phase were developed while $CoSO_4{\cdot}7H_2O$ concentration ranged from 0.7 M to 1.1 M. Secondary phase such as $Co(OH)_2$ and $CO_3O_4$ were also observed. Peaks for the crystalline Co phase having HCP and FCC structure crystallized as increasing the concentration of $H_3PO_2$, indicating that the amount of reduction agent was enough to reduce $Co(OH)_2$. Consequently, a homogeneous Co phase could be developed without second phase when the $H_3PO_2/CoSO_4{\cdot}7H_2O$ ratio exceeded 7.

The Analysis of Weibull Distribution on the Accelerated Aging Test in Polymer Insulation (EPDM 및 실리콘 애자의 가속실험에 대한 와이블 분포해석)

  • Lim, Jang-Seob;Kim, Jin-Gook;Park, Beom-Su;Keun, Song-Il;Lee, Jae-Bong
    • Proceedings of the KIEE Conference
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    • 2003.10a
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    • pp.25-28
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    • 2003
  • Fractal mathematics is being highlighted as a research method for classification of image. But the application of Fractal dimension(FB) has been required the complicated calculation method because of its complex repetition progressing. In this paper, it has been developed the new approach method to express the Fractal Dimension(FB) for aging level calculation and estimation system of outside insulator using special image processing algorithm. As a result after FD testing, the recognized aging estimation of FD has a very characteristics compared to the conventional visual inspection.

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2-Dimensional Analysis of Fresnel Zone Plate Antenna (2차원 프레넬 존 플레이트 안테나 해석)

  • Kim, Tae-Yong;Jo, Heung-Kuk
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2011.05a
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    • pp.55-57
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    • 2011
  • TLM method to analyize receiver gain characteristic of the FZPL antenna which is operated at 12GHz and can be applied to satellite TV system, radio telescope, and Geodetic System. Some numerical results computed by TLM method are compared with Kirchhoff's approximation and PO method. As a result, receiver gain characteristic on main axis of the 12GHz FZPL antenna is shown at the front side, which means that the focal length is 15% shorter than designed focal length.

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Design of Predistortive Mixer (전치 왜곡 혼합기 설계)

  • 정용채
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.2
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    • pp.197-205
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    • 2000
  • The back-off input power level method is generally used for design of high linear mixer. In this paper, the predistortive mixer design method which attaches the predistortor in front of mixer is proposed to compensate the nonlinear characteristics of mixer and the predistortor has inverse nonlinear characteristics of mixer. The proposed method improves C/I ratio of mixer by 22 dB (@Po=-20 dBm/tone), 21.7 dB(@Po=-17 dBm/tone) with two tones of RF at 1852.5MHz, 1857.5MHz and LO at 2015MHz, respectively.

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Evaluation of local and global ductility relationships for seismic assessment of regular masonry-infilled reinforced concrete frames using a coefficient-based method

  • Su, R.K.L.;Tang, T.O.;Lee, C.L.
    • Earthquakes and Structures
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    • v.5 no.1
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    • pp.1-22
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    • 2013
  • Soft storey failure mechanism is a common collapse mode for masonry-infilled (MI) reinforced concrete (RC) buildings subjected to severe earthquakes. Simple analytical equations correlating global with local ductility demands are derived from pushover (PO) analyses for seismic assessments of regular MI RC frames, considering the critical interstorey drift ratio, number of storeys and lateral loading configurations. The reliability of the equations is investigated using incremental dynamic analyses for MI RC frames of up to 7 storeys. Using the analytical ductility relationship and a coefficient-based method (CBM), the response spectral accelerations and period shift factors of low-rise MI RC frames are computed. The results are verified through published shake table test results. In general applications, the analytical ductility relationships thus derived can be used to bypass the onerous PO analysis while accurately predicting the local ductility demands for seismic assessment of regular MI RC frames.

Treatment of Frozen Shoulder under the Arthroscopic Capsular Release Combined with Manipulation (관절경하 관절낭 유리술과 강압교정술을 병용한 동결견의 치료)

  • You Yeun-Sik;Lee Young-Hyun;Lee Sang-Soo;Nam I1-Hyun
    • Clinics in Shoulder and Elbow
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    • v.4 no.2
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    • pp.166-172
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    • 2001
  • Purpose: To evaluate effectiveness of arthroscopic capsular release combined with manipulation in frozen shoulder. Material and Method: 15 patient who had failed to respond to physical therapy were evaluated, which were treated with arthroscopic capsular release combined with manipulation, from July 1998 to March 2000. Result: At a mean of fifteen months(range, six to twenty four) after the combined procedure, the improvement in the score of Constant and Murley averaged 45 points. The mean improvement in motion was 76 degrees for abduction; 40 degrees and 65 degrees for external rotation in adduction and abduction. Conclusion : Arthroscopic capsular release with manipulation is useful method to treatment the frozen shoulder which was not respond to conservative treatment.

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Preparation Nanosized TPA-Silicalite-1 with Different Silica Sources and Promoters (다양한 실리카 원과 결정화 촉진제를 이용한 나노크기의 TPA-Silicalite-1 제조)

  • Jung, Sang-Jin
    • Applied Chemistry for Engineering
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    • v.25 no.3
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    • pp.286-291
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    • 2014
  • In this study, nanosized TPA-silicalite-1 was synthesized with a suitable molar composition of TPAOH: $SiO_2$: $H_2O$ for the development of zeolite ceramic membranes to utilize as gas separation. As silica sources, TEOS, LUDOX AS-40 and CAB-O-SIL were used with the starting material of TPAOH. $NaH_2PO_4$, and a variety of acids and bases were used as promoters after TPAOH, $SiO_2$, $H_2O$ gel synthesis. To decrease synthesis time, a two step temperature change method was applied to the synthesis of TPA-silicalite-1 at a low temperature. TPA-silicalite-1 synthesized was analyzed with XRD, SEM, BET and TGA. As a result, TPA-silicalite-1 powders with a particle size of 100 nm and a specific surface area of $416m^2/g$ were obtained as optimum synthesis conditions when the two stage temperature change method was used with $NaH_2PO_4$ as promoter.

Development of IoT Device Management System Using Blockchain DPoS Consensus Algorithm (블록체인 DPoS 합의 알고리즘을 활용한 IoT 장치 관리 시스템 개발)

  • Kim, Mihui;Kim, Youngmin
    • Journal of IKEEE
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    • v.23 no.2
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    • pp.508-516
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    • 2019
  • Smart home with various IoT devices provides convenient and efficient services. However, security is important because sensitive information such as private video and audio can be collected and processed, as well as shared over the Internet. To manage such smart home IoT devices, we use blockchain technology that provides data integrity and secure management. In this paper, we utilize a PoS(Proof of Stake) method that verifies the block through the accumulated stake in the network rather than the computation power, out of the PoW(Proof of Work) block chain, in which the computation for the existing verification must be continuously performed. Among them, we propose a blockchain based system with DPoS(Delegated Proof of Stake) method to actively solve the scalability part, for security that is suitable for smart home IoT environment. We implement the proposed system with DPoS based EOSIO to show realization, and we show performance improvement in terms of transaction processing speed.