• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.371-375
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• 2003

In this paper, a new design method for coupled-line filters with tapped input/output has been developed. The design equations for this tapped filter have been obtained using a new equivalent circuit model of tapped lines. From an edge coupled-line filter, tapped lines replaces the input/output coupled lines which tend to have very narrow gaps (few mils). Therefore, tapped coupled-line filters tend to be less sensitive to filter fabrication tolerances and to be easily fabricated using milling tools. The new filter design algorithm allows very accurate filter design for frequencies less than 20 GHz and bandwidth less than 20%. Above 20 GHz, the filter performance can be optimized starting from the filter design algorithm in this paper. Simulation problems with 2-D EM tools to characterize filter performance at high frequencies have shown to be solved by providing a channel for the filter to eliminate higher order modes.

• Steel and Composite Structures
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• 제22권4호
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• pp.889-913
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• 2016

Vibration analysis of embedded functionally graded (FG)-carbon nanotubes (CNT)-reinforced piezoelectric cylindrical shell subjected to uniform and non-uniform temperature distributions are presented. The structure is subjected to an applied voltage in thickness direction which operates in control of vibration behavior of system. The CNT reinforcement is either uniformly distributed or functionally graded (FG) along the thickness direction indicated with FGV, FGO and FGX. Effective properties of nano-composite structure are estimated through Mixture low. The surrounding elastic foundation is simulated with spring and shear constants. The material properties of shell and elastic medium constants are assumed temperature-dependent. The motion equations are derived using Hamilton's principle applying first order shear deformation theory (FSDT). Based on differential cubature (DC) method, the frequency of nano-composite structure is obtained for different boundary conditions. A detailed parametric study is conducted to elucidate the influences of external applied voltage, elastic medium type, temperature distribution type, boundary conditions, volume percent and distribution type of CNT are shown on the frequency of system. In addition, the mode shapes of shell for the first and second modes are presented for different boundary conditions. Numerical results indicate that applying negative voltage yields to higher frequency. In addition, FGX distribution of CNT is better than other considered cases.

• 한국초전도ㆍ저온공학회논문지
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• 제16권4호
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• pp.7-16
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• 2014

Rare-earth barium copper oxide (REBCO) coated conductor (CC) tapes have already been commercialized but still possess some issues in terms of manufacturing cost, anisotropic in-field performance, $I_c$ response to mechanical loads such as delamination, homogeneity of current transport property, and production length. Development on improving its performance properties to meet the needs in practical device applications is underway and simplification of the tape's architecture and manufacturing process are also being considered to enhance the performance-cost ratio. As compared to low temperature superconductors (LTS), high temperature superconductor (HTS) REBCO CC tapes provide a much wider range of operating temperature and a higher critical current density at 4.2 K making it more attractive in magnet and coil applications. The superior properties of the REBCO CC tapes under magnetic field have led to the development of superconducting magnets capable of producing field way above 23.5 T. In order to achieve its optimum performance, the electromechanical properties under different deformation modes and magnetic field should be evaluated for practical device design. This paper gives an overview of the effects of mechanical stress/strain on $I_c$ in HTS CC tapes due to uniaxial tension, bending deformation, transverse load, and including the electrical performance of a CC tape joint which were performed by our group at ANU in the last decade.

• KSBB Journal
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• 제5권4호
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• pp.335-339
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• 1990

전분으로 부터 에탄올을 생산하기 위한 경제적인 공정을 개발하기 위하여 Zymomonas mobilis와 당화효소(AMG)를 사용한 반 회분식 동시 당화 발효공정올 연구 하였다. 응집성 에탄올 균주인 Z. mobilis ZM40l과 침전조를 사용한 균체 재순환 방식에 의한 반회분식 동시 당화발효 공정에서는 에탄올 생산성이 제2차 및 제3차 발효에서 각각 4.1g / I / h 및 4.3 g / I / h이었다. 이에 비해 미세여과막(microfiltration) 장치에 의한 Z. mobilis ZM4의 재순환 방식을 사용하는 공정에서는 에탄올 생산성이 제2차 및 제3차 발효에서 모두 5.4 g / l / h로 더 높았다. 에탄올 생산 시설이 large-seale임을 고려할 때 미세여과막을 사용하는 반회분식 공정이 에탄올 생산성과 seale-up의 용이성 및 운전의 간편성등의 관점에서 가장 개발 가능성이 높은 공정인 것으로 판단되었다.

• 한국분무공학회지
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• 제22권4호
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• pp.185-189
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• 2017

In Korea, sales of passenger cars using diesel and LPG fuels were continuously increased in recent years. From now on 2030, the registrated vehicles will close in about twenty five million in Korea. From these reason, Investigation on the comparison of exhaust emission characteristics of passenger cars using LPG and Diesel fuel in variation of driving mode and ambient conditions were conducted in this study. Exhaust emission characteristics of test vehicles were measured and analyzed by using chassis dynamometer and emission analyzer. Also, test vehicles were selected on the diesel vehicle with 1.7L engine and LPG vehicle with 2.0L engine. In order to study on emission characteristics according to driving cycles, CVS-75, NEDC, US06, SC03, Cold-FTP and HWFET were applied and the test conditions were set up the cases of A/C on and hot start. From these results, it is revealed that the NOx emission of diesel vehicle was higher than that of LPG vehicle and the case of CO emission shows the opposite patterns. In the HC emission, the emission increasing patterns not showed but the NOx emission of diesel vehicle and CO emission of LPG vehicle were showed the variation patterns according to the various driving modes.

• 한국전자파학회논문지
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• 제10권3호
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• pp.440-448
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• 1999

본 논문에서는 무한 주기구조로 근사할 수 있는 전파 흡수체의 전파특성을 혼성 유한요소법을 이용하여 해석한 결과를 기술하였다. 가상의 경계면을 설정하여 유한한 영역을 정의하였고, 영역의 각각의 경계면에서 유효한 경계조건을 Floquet 이론으로부터 유도하였다. 고차 Floquet 모드가 사용되었으므로, 본 논문에서의 방법은 파장에 비교할 수 있을 정도로 큰 주기를 가진 구조의 경우에도 적용이 가능하다. 표면적분 계산의 어려움을 줄이기 위해 표면에 수직인 전자계 성분을 표면에 수평인 성분으로 표현하였다. 계산된 결과를 해석적인 해 또는 기존에 발표된 결과와 비교하여 해석의 유효성을 증명하였다.

• Journal of electromagnetic engineering and science
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• 제17권1호
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• pp.1-8
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• 2017

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

• Structural Engineering and Mechanics
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• 제6권2호
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• pp.143-159
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• 1998

The objective of this present work is to estimate the failure loads, associated maximum transverse displacements, locations and the modes of failure, including the onset of delamination, of thin, square symmetric laminates under the action in-plane positive (+ve) shear load. Two progressive failure analyses, one using the Hashin criterion and the other using a Tensor polynomial criterion, are used in conjunction with finite element method. First order shear deformation theory along with geometric non-linearity in the von Karman sense have been employed. Variation of failure loads and failure characteristics with five type of lay-ups and three types of boundary conditions has been investigated in detail. It is observed that the maximum difference between failure loads predieted by various criteria depends strongly on the laminate lay-up and the flexural boundary restraint. Laminates with clamped edges are found to be more susceptible to failure due to transverse shear (ensuing from the out of plane bending) and delamination, while those with simply supported edges undergo total collapse at a load slightly higher than the fiber failure load. The investigation on negative (-ve) in-plane shear load is in progress and will be communicated as part-II of the present work.

• Steel and Composite Structures
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• 제34권1호
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• pp.75-89
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• 2020

The current paper illustrates the effect of in-plane varying compressive force on critical buckling loads and buckling modes of sandwich composite laminated beam rested on elastic foundation. To generalize a proposed model, unified higher order shear deformation beam theories are exploited through analysis; those satisfy the parabolic variation of shear across the thickness. Therefore, there is no need for shear correction factor. Winkler and Pasternak elastic foundations are presented to consider the effect of any elastic medium surrounding beam structure. The Hamilton's principle is proposed to derive the equilibrium equations of unified sandwich composite laminated beams. Differential quadrature numerical method (DQNM) is used to discretize the differential equilibrium equations in spatial direction. After that, eigenvalue problem is solved to obtain the buckling loads and associated mode shapes. The proposed model is validated with previous published works and good matching is observed. The numerical results are carried out to show effects of axial load functions, lamination thicknesses, orthotropy and elastic foundation constants on the buckling loads and mode shapes of sandwich composite beam. This model is important in designing of aircrafts and ships when non-uniform compressive load and shear loading is dominated.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.421-426
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• 2003

Recently, mixers are being widely used in the water purification plant in order to increase the filtration efficiency. The mixer normally consists of impeller, shaft, hub, reduction gear, and the driving motor. It is one of the key design issues to confirm that the vibration caused by the rotation of the shaft should not coincide with the natural vibration frequency of the shaft itself. The vibration characteristics of the hydrofoil type mixer, which is the most widely used in real plants are evaluated through the finite element modeling and verified by experiment using the mock-up facility. The fundamental natural frequency of the mixer's shaft is found to be around 1.8 Hz which showed in good agreement with the experiment. The higher natural frequencies to the 2nd, 3rd, and 4th modes are also verified by the experiment. Thus the developed model is to be utilized for the structural design of the real mixer system.