• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.629-632
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• 2003

This paper has been studied analysis and design of microstrip Rotman lens operating over wide band and wide steering angle by the contour integral method along with the segmentation method. All mutual coupling, internal reflections between ports with exponential taper are taken into account. Equally spaced ports are designed and realized which gives less amplitude ripple at array ports. The measured results of 12 input and 12 output lens show $\pm$1.8 dB insertion loss deviation over 6~18GHz wide frequency range and beam steering accuracy less than 1$^{\circ}$ over $\pm$53$^{\circ}$ angle and agrees well with the analysis results.

• Journal of Environmental Science International
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• v.33 no.7
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• pp.453-462
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• 2024

This study was carried out for the purpose of selecting the most appropriate taper equation for the actual stands of Pinus thunbergii in the southern coastal region of Korea and then developing a stem volume table to provide basic data for rational management. To develop a volume table of Pinus thunbergii in this region of Korea, 59 sample trees with various diameter distributions were selected and stem analysis was performed. As a result of stem analysis, two trees with abnormal diameter and height growth as the age increased were rejected, and 57 trees were analyzed. To develop the taper equation, seven major variable exponential equations were used, including Kozak 1988, 1994, 2001, 2002, Bi 2000, Muhairwe 1999, and Sharma and Parton 2009. As a result of parameter estimation and statistical verification, the Kozak 1988 model showed the highest goodness of fit with Fit I (Fit Index), RMSE 1.5620, Bias 0.0031, and MAD 1.0784. The diameter of each 10cm stem ridge for the selected model was estimated, and a stem volume table was produced using the mensuration of division (end area formula) using the Smalian equation. As a result of two-sample T-test for volume table of this study and current yield table, the volume for this study was found to be significantly larger at all observation points (p < 0.001). Even for the same tree species, it is judged that differentiated volume tables are needed for each growth environment characteristic.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.25-28
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• 2001

The problem considered is the buckling of a rectangular orthotropic plate, tapered in thickness in a direction parallel to two sides and compressed in that direction. Curves are presented showing the variation of buckling stress coefficient with the special loads. The type of thickness variation is exponential. While this paper is presented how to design for an efficient orthotropic plate taper from physical consideration.

• Journal of electromagnetic engineering and science
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• v.4 no.2
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• pp.68-71
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• 2004

The limitation of telegrapher's equations for analysis of nonuniform transmission lines is investigated here. It is shown theoretically that the input impedance of a nonuniform transmission line cannot be derived uniquely from the Riccati equation only except for the exponential transmission line of a particular frequency-dependent taper. As an example, the input impedance of an angled two-plate transmission line is calculated by solving the telegrapher's equations numerically. The numerical results suffer from larger deviation from its rigorous solution as the plate angle increases.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.3
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• pp.105-109
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• 2017

In this paper is proposed wide band reconfiguration antenna by using PIN diode. The proposed antenna consisted of elliptical dipole and exponential taper balun. The proposed new matching method was exponential tapered balun in this paper. The research paper comprised of two PIN diode and Elliptical dipole. This paper used CPW to CPS feed. We obtained a good band width characteristics result by simulating. This antenna is designed to apply ISM and WiFi band.

• Advances in aircraft and spacecraft science
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• v.10 no.1
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• pp.19-49
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• 2023

The present study proposes a theoretical and numerical investigation on the dynamic response behaviour of a functional graded (FG) ceramic-metal tapered rotor shaft system, by the differential quadrature finite elements method (DQFEM) to identify the natural frequencies for modelling and analysis of the structure with suitable validations. The purpose of this paper is to explore the influence of heat gradients on the natural frequency of rotation of FG shafts via three-dimensional solid elements, as well as a theoretical examination using the Timoshenko beam mode, which took into account the gyroscopic effect and rotational inertia. The functionally graded material's distribution is described by two distribution laws: the power law and the exponential law. To simulate varied thermal conditions, radial temperature distributions are obtained using the nonlinear temperature distribution (NLTD) and exponential temperature distribution (ETD) approaches. This work deals with the results of the effect on the fundamental frequencies of different material's laws gradation and temperature gradients distributions. Attempts are conducted to identify adequate explanations for the behaviours based on material characteristics. The effect of taper angle and material distribution on the dynamic behaviour of the FG conical rotor system is discussed.

• Journal of Korean Society of Forest Science
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• v.106 no.4
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• pp.480-486
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• 2017

This study was conducted to develop the merchantable stem volume models to predict the volume up to upper diameter or upper height out of the total stem volume, targeting on Pinus densiflora, Pinus koraiensis, and Larix kaempferi in South Korea. The 131 stemmed sample trees for stem analysis were used as the data for developing the models. The six kinds of merchantable volume equations including merchantable volume ratio form, ratio form, and exponential ratio form were examined to develop the best models. The two models were finally selected as the best models to predict the merchantable volume: $V_d=V_t\{{\exp}[{\alpha}_1(d^{{\alpha}_2}/D^{{\alpha}_3})]\}$ for upper diameter and $V_h=V_t\{1+{\beta}_1(P^{{\beta}_2}/H^{{\beta}_3})\}$ for upper height. By rearranging the best model equations, implicit taper functions were derived, and the estimation was performed for the upper height by upper diameter and upper diameter by upper height. Because of not only the high accuracy but also the convenience, the models developed in this study were considered to be easily applicable in the field of forestry.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.769-776
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• 2003

This paper presents analysis and design of microstrip Rotman lens operating over wide band and wide steering angle by the contour integral method along with the segmentation method. All mutual coupling, internal reflections between ports and the discontinuity at every junction are taken into account. Equally spaced ports are designed and realized, which make suppress output ripple through the array ports. Impedance matching and mutual coupling between ports are analyzed and optimized using 12 input and 12 output exponential tapers. The measured results of fabricated lens show ${\pm}$ 1.8 dB insertion loss deviation over 6∼18 GHz wide frequency range and beam steering accuracy less than 1$^{\circ}$over ${\pm}$53$^{\circ}$angle and agrees well with the analysis results.

• Structural Engineering and Mechanics
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• v.66 no.6
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• pp.737-748
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• 2018

The current study presents a new technique in the framework of the nonlocal elasticity theory for a comprehensive buckling analysis of Euler-Bernoulli nano-beams made up of bidirectional functionally graded material (BDFGM). The mechanical properties are considered by exponential and arbitrary variations for axial and transverse directions, respectively. The various circumstances including tapering, resting on two-parameter elastic foundation, step-wise or continuous variations of axial loading, various shapes of sections with various distribution laws of mechanical properties and various boundary conditions like the multi-span beams are taken into account. As far as we know, for the first time in the current work, the buckling analyses of BDFGM nano-beams are carried out under mentioned circumstances. The critical buckling loads and mode shapes are calculated by using energy method and a new technique based on calculus of variations and collocation method. Fast convergence and excellent agreement with the known data in literature, wherever possible, presents the efficiency of proposed technique. The effects of boundary conditions, material and taper constants, foundation moduli, variable axial compression and small-scale of nano-beam on the buckling loads and mode shapes are investigated. Moreover the analytical solutions, for the simpler cases are provided in appendices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.836-844
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• 2006

In this paper, we designed and fabricated the wideband probe with double ridged waveguide for Near-field Measurement. An exponential taper ridge in the rectangular waveguide was implemented for wideband impedance matching. It has wideband characteristics and its measured impedance bandwidth ratio is approximately 2.2:1 from 8.2 GHz to 18 GHz for $VSWR\leq2.2$. It maintains about the same radiation pattern over the entire bandwidth and has more than 4.5 dBi peak radiation gain. Our designed probe was applied to near-field measurement. A good agreement has been found between simulated and measured results.