• 대한조선학회지
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• 제19권4호
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• pp.39-45
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• 1982

A floating rig, which has been used to develop the ocean resources has a common characteristics with the catamaran ship that it is composed of the two simple hulls. So the motion responses of the floating rig can be predicted theoretically with the aid of the strip method as those of the catamaran. And for the strip method, the two-dimensional hydrodynamic coefficients are the most important inputs to predict the results accurately. In this report, a theoretical method is proposed for calculating two-dimensional hydrodynamic forces and moments acting upon arbitrary shaped twin-hull cylinders, which are forced to make a heaving, swaying and rolling oscillation about their mean position on the free surface of a finite depth water. The theoretical results by making use of the singularity distribution method are presented. The accuracy of the coefficients was confirmed to be reasonable by the comparison with the Ohkusu's results for two circular cylinders in an infinite depth water. The depth effects on two-dimensional hydrodynamic coefficients for two circular cylinders are also checked. In some range of wave numbers, large differences in the behavior of hydrodynamic coefficients between for a finite depth and for an infinite depth are shown.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권4호
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• pp.691-698
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• 2015

The hydrodynamic interaction forces and moments induced by the vicinity of bank on a passing vessel are known as wall effects. In this paper, the characteristics of interaction acting on a passing vessel in the proximity of a semi-circle bank wall are described and illustrated, and the effects of ship velocity, water depth and the lateral distance between vessel and semi-circle bank wall are discussed. For spacing between ship and semi-circle bank wall (SP) less than about 0.2 L and depth to ship's draft ratio (h/d) less than around 2.0, the ship-bank interaction effects increase steeply as h/d decreases. However, for spacing between ship and semi-circle bank wall (SP) more than about 0.3 L, the ship-bank interaction effects increase slowly as h/d decreases, regardless of the water depth. Also, for spacing between ship and semi-circle bank wall (SP) less than about 0.2 L, the hydrodynamic interaction effects acting on large vessel increase largely as ship velocity increases. In the meantime, for spacing between ship and semi-circle bank wall ($S_P$) more than 0.3 L, the interaction effects increase slowly as ship velocity increases.

• 한국전기전자재료학회논문지
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• 제12권1호
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• pp.18-26
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• 1999

In this study, the undoped amorphous layers and phosphorus doped amorphous layers are fabricated using LPCVD at 531$^{\circ}C$ with SiH$_4$ gas or at same temperature with PH$_3$ gas during deposition, respectively. The thickness of deposited amorphous layer from this experiments was 5000 ${\AA}$. In this experiments, undoped amorphous layers are deposited with SiH$_4$and Si$_2$H$\_$6/ gas in a low pressure reactor using LPCVD. These amorphous layers can be doped for poly-silicon by phosphorus ion implantation. The experiments of this study are carried out by phosphorus ion implantation with energy 40 keV into P doped and undoped amorphous silicon layers. The distribution of phosphorus profiles are measured by SIMS(Cameca 6f). Recoiling effects and two dimensional profiles are also explained by comparisions of experimental and simulated data. Finally range moments of SIMS profiles are calculated and compared with simulation results.

• Smart Structures and Systems
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• 제14권2호
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• pp.71-83
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• 2014

The purpose of this paper is to investigate the flexible structure of parabolic shell using photostrictive actuators. The analysis is made to know its dynamic behavior and light-induced control forces for coupled parabolic shell. The effects of an actuator location as well as membrane and bending components under the control action have been analyzed considering the approximate spherical model. The parabolic membrane shell accuracy is being mathematically approximated and validated comparing the light induced control forces using approximate equivalent spherical shell model. The parabolic shell with kapton smart material and photostrictive actuators has been used to formulate the governing equation in the transverse direction. The Kirchhoff-Love assumptions are used to obtain the governing equation of shell with actuator. The mechanical membrane forces and bending moments for parabolic thin shell with actuator is used to analyze the dynamic effect. The results show that membrane control action is much more significant than bending control action. Photostrictive actuators oriented along circumferential direction (actuator-2) can give better control effect than actuators placed along longitudinal direction (actuator-1). The slight difference is observed between spherical and parabolic shell for a surface with focal length to the diameter ratio of 1.00 or more than unity. Space applications often have the shape of parabolical shells or shell of revolution, due to their required focusing, aiming, or reflecting performance. The present approach is focused that photostrictive actuators can effectively control the vibration of parabolical membrane shell. Also, the actuator's location plays an important role in defining the control force.

• Wind and Structures
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• 제19권4호
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• pp.371-387
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• 2014

Probability plotting positions are popular and used as the basis for distribution fitting and for inspecting the quality of the fit because of its simplicity. The plotting positions that lead to excellent approximation to the mean of the order statistics should be used if the objective of the fitting is to estimate quantiles. Since the mean depends on the sample size and is not amenable for simple to use closed form solution, many plotting positions have been presented in the literature, including a new plotting position that is derived based on the weighted least-squares method. In this study, the accuracy of using the new plotting position to fit the Gumbel distribution for estimating quantiles is assessed. Also, plotting positions derived by fitting the mean of the order statistics for all ranks is proposed, and an approximation to the covariance of the order statistics for the Gumbel (and Weibull) variate is given. Relative bias and root-mean-square-error of the estimated quantiles by using the proposed plotting position are shown. The use of the proposed plotting position to estimate the quantiles of annual maximum wind speed is illustrated.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1403-1415
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• 2021

The transient capability of a SP₃ based pin-wise core analysis code SPHINCS is developed and verified through the analyses of the C5G7-TD benchmark. Spatial discretization is done by the fine mesh finite difference method (FDM) within the framework of the coarse mesh finite difference (CMFD) formulation. Pin size fine meshes are used in the radial fine mesh kernels. The time derivatives of the odd moments in the time-dependent SP₃ equations are neglected. The pin homogenized group constants and Super Homogenization (SPH) factors generated from the 2D single assembly calculations at the unrodded and rodded conditions are used in the transient calculations via proper interpolation involving the approximate flux weighting method for the cases that involve control rod movement. The simplifications and approximations introduced in SPHINCS are assessed and verified by solving all the problems of C5G7-TD and then by comparing with the results of the direct whole core calculation code nTRACER. It is demonstrated that SPHINCS yields accurate solutions in the transient behaviors of core power and reactivity.

• Wind and Structures
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• 제33권6호
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• pp.437-446
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• 2021

As wind turbine rotors increase, the overall loads and dynamic response become an important issue. This problem is augmented by the exposure of wind turbines to severe atmospheric events with unconventional flows such as tornadoes, which need specific designs not included in standards and codes at present. An experimental study was conducted to analyze the loads induced by a tornado-like vortex (TLV) on horizontal-axis wind turbines (HAWT). A large-scale tornado simulation developed in The Wind Engineering, Energy and Environment (WindEEE) Dome at Western University in Canada, the so-called Mode B Tornado, was employed as the TLV flow acting on a rigid wind turbine model under two rotor operational conditions (idling and parked) for five radial distances. It was observed that the overall forces and moments depend on the location and orientation of the wind turbine system with respect to the tornado vortex centre, as TLV are three-dimensional flows with velocity gradients in the radial, vertical, and tangential direction. The mean bending moment at the tower base was the most important in terms of magnitude and variation in relation to the position of the HAWT with respect to the core radius of the tornado, and it was highly dependent on the rotor Tip Speed Ratio (TSR).

• Wind and Structures
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• 제34권3호
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• pp.303-312
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• 2022

As wind turbine rotors increase, the overall loads and dynamic response become an important issue. This problem is augmented by the exposure of wind turbines to severe atmospheric events with unconventional flows such as tornadoes, which need specific designs not included in standards and codes at present. An experimental study was conducted to analyze the loads induced by a tornado-like vortex (TLV) on horizontal-axis wind turbines (HAWT). A large-scale tornado simulation developed in The Wind Engineering, Energy and Environment (WindEEE) Dome at Western University in Canada, the so-called Mode B Tornado, was employed as the TLV flow acting on a rigid wind turbine model under two rotor operational conditions (idling and parked) for five radial distances. It was observed that the overall forces and moments depend on the location and orientation of the wind turbine system with respect to the tornado vortex centre, as TLV are three-dimensional flows with velocity gradients in the radial, vertical, and tangential direction. The mean bending moment at the tower base was the most important in terms of magnitude and variation in relation to the position of the HAWT with respect to the core radius of the tornado, and it was highly dependent on the rotor Tip Speed Ratio (TSR).

• Structural Engineering and Mechanics
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• 제84권4호
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• pp.561-573
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• 2022

This paper presents a new model to obtain the minimum area of the contact surface for rectangular isolated footings, considering that the contact surface works partially to compression (a part of the contact surface of the footing is subjected to compression and the other is not in compression or tension). The methodology is developed by integration to obtain the axial load "P", moment around the X axis "M_x" and moment around the Y axis "M_y". This document presents the simplified and precise equations of the four possible cases of footing subjected to uniaxial bending and five possible cases of footing subjected to biaxial bending. The current model considers the contact area of the footing that works totally in compression, and other models consider the contact area that works partially under compression and these are developed by very complex iterative processes. Numerical examples are presented to obtain the minimum area of rectangular footings under an axial load and moments in two directions, and the results are compared with those of other authors. The results show that the new model presents smaller areas than the other authors presented.

• 한국자기학회지
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• 제21권6호
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• pp.198-203
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• 2011

연 x선 광흡수 분광법(soft x-ray absorption spectroscopy: XAS)과 연 x선 자기 원편광 이색성(soft x-ray magnetic circular dichroism: XMCD)을 이용하여 스피넬 준강자성 산화물인 $FeV_2O_4$의 전자 구조를 연구하였다. Fe 2p XAS와 V 2p XAS 측정으로 부터 $FeV_2O_4$에서 Fe 이온과 V이온의 고유한 원자가는 각각 약 $Fe^{2.3+}$의 혼합원자가 상태와 약 $V^{3+}$의 상태임을 알 수 있었다. 실험적으로 측정된 Fe 2p XMCD의 신호는 거의 $Fe^{2+}$ 상태에서 기인하였으며, $Fe^{3+}$ 상태는 Fe 2p XMCD의 신호에 거의 기여하지 않는다는 사실이 발견되었다. 그러므로 $FeV_2O_4$의 자성 특성을 결정함에 있어서 자기적으로 정렬된 $Fe^{2+}$ 상태 이온들이 중요한 역할을 한다고 생각된다.