• Title/Summary/Keyword: 모우멘트

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Analysis on the Dynamic Respone of the Hull Structure due to Slamming Impact - By Finite Element Method - (슬래밍 충격을 받는 선체의 동적 응답해석 -유한요소법으로-)

  • Hong, Bong-Ki;Moon, Duk-Hong;Bae, Dong-Myung
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.19 no.2
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    • pp.117-124
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    • 1983
  • In rough seas, actual behaviours of a ship may not be estimated by the linear strip theory, because of Nonlinearities due to the hull shape, bottom slamming and bottom and/or bow-flare slamming. In case of slamming, impulsive hydrodynamic pressure occurs on the fore body surface of the ship, resulting hull vibration called whipping, by which the ship may suffer from serious structural damages and the impact pressure, depends critically on the relative velocity at re-entry. In this paper, the Time history of impact froce at each station, the longitudinal distribution of impact force at critical time, the Time history of acceleration at F.P. and the Time history of Bending moment at midship are illustrated. That is, authors analyzed Dynamic response of container ship to be subjected slamming impact force.

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The Analysis and Implementation of Cavity-backed Circular Microstrip Patch Antenna (원형 공진기 구조 마이크로스트립 안테나 해석 및 구현 방법 연구)

  • Park, Gyeong-Bin;Jeong, Yeong-Bae;Choe, Dong-Hyeok;Park, Seong-Ok;Mun, Yeong-Chan;Jeon, Sun-Ik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.37 no.12
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    • pp.1-8
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    • 2000
  • The analysis of cavity-backed circular microstrip antenna is performed, based on the method of moments, and verified with experimental results. The proposed algorithm was used to analyze the return loss and radiation characteristics of antenna by the variation of each associated parameter. This result was used to provide the optimum design guideline. Finally active reflection coefficient of infinite cavity-backed microstrip away was calculated to show the effect of suppressing surface wave to eliminate scan blindness.

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Solution Algorithm of Unsteady Flow in a Dendritic Channel System (수지형 하천에서의 부정류 흐름의 해석 알고리즘)

  • Choi, Gye Woon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.4
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    • pp.839-846
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    • 1994
  • This paper presents a simultaneous solution algorithm for one-dimensional unsteady flow routing through a dendritic channel system. This simulations solution algorithm is based on the double-sweep method and utilizes separate recursion equations for continuity, momentum and energy equations for each of the individual components of a dendritic channel system. Through separate recursion equations for each of the components. the new algorithm converts a dendritic channel network problem into a single-channel problem. The new algorithm is utilized in conjunction with a linearized unsteady flow model using full dynamic flow equations. The required computer storage for the coefficient matrix of the whole system is reduced significantly from the $2N{\times}2N$ matrix to a $2N{\times}4$ matrix, where N is the number of cross sections used in the computation of flow variables in a dendritic channel system. The algorithm presented in this paper provides an efficient and accurate modeling of unsteady flow events through a dendritic channel system.

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Efficient Performance Evaluation Method for Digital Satellite Broadcasting Channels (효율적인 디지틀 위성방송채널 성능평가 기법)

  • 정창봉;김준명;김용섭;황인관
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.6A
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    • pp.794-801
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    • 2000
  • In this paper, the efficient new performance evaluation method for digital communication channels is suggested and verified its efficiency in terms of simulation run-tim for the digital satellite broadcasting satellite TV channel. In order to solve the difficulties of the existing Importance Sampling(IS) Technics, we adopted the discrete probability mass function(PMF) in the new method for estimating the statistical characteristics of received signals from the measured Nth order central moments. From the discrete probability mass function obtained with less number of the received signal than the one required in the IS technic, continuous cumulative probability function and its inverse function are exactly estimated by using interpolation and extrapolation technic. And the overall channel is simplified with encoding block, inner channel performance degra-dation modeing block which is modeled with the Uniform Random Number Generator (URNG) and concatenated Inverse Cummulative Pr bility Distribution function, and decoding block. With the simplified channel model, the overall performance evaluation can be done within a drastically reduced time. The simulation results applied to the nonlinear digital satellite broadcasting TV channel showed the great efficiency of the alogrithm in the sense of computer run time, and demonstrated that the existing problems of IS for the nonlinear satellite channels with coding and M-dimensional memory can be completely solved.

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Hydroelastic Responses for a VLFS close to a Breakwater by the Velocity Potential Continuation and Singularity Distribution Method (속도포텐셜접속법과 특이점분포법에 의한 방파제에 근접한 부유식 해상공항에 대한 유탄성 응답 해석)

  • Ho-Young Lee;Young-Ki Kwak;Jong-Hwan Park
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.2
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    • pp.11-18
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    • 2002
  • In this paper, the method calculating hydroelastic responses of very large floating structure close to a breakwater in waves is presented. The source-dipole distribution method is used to calculate the generalized radiation problem considering breakwater effects and the diffraction problem is analyzed by using the source-dipole distribution andvelocity potential continuation method. The response of a VLFS is approximated by anexpansion in terms of a free-free beam. Calculated model is a VLFS with 1000m in length in a sea with a straight breakwater. The vertical displacements and bonding moments around a VLFS are calculated by variations for distance between a VLFS and a breakwater and incident wave angle to know the effect of a breakwater.

Configuration and Design of the Large Multi-Electromagnetic Shaking System (대형 멀티 전자기 가진 시스템의 구성 및 설계)

  • 우성현;김홍배;문상무;김영기;임종민
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.618-622
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    • 2004
  • The vibration test system of SITC(Satellite Integration and Test Center) at KARI(Korea Aerospace Research Institute) has been used successfully for the environmental tests of a majority of korean space programs, such as KOMPSAT, Koreasat KITSAT, STSAT and KSR program since 1996. To meet the recent needs of large size test facility available for the vibrational tests of the huge launch vehicles and tole-communication satellites which will be developed in the near future, KARI undertook to construct the large size multi-electromagnetic shaking system with 3 $\times$ 3m head expander system. The new system will consist of three electromagnetic shakers which has 160 kN thrust force individually, and be able te sustain up to 8 tons test load and 300 kNm overturing moment. And to avoid the tremendous cost and effort to furnish the seismic block with large size and weight, it will adopt a Lin-E-Air type configuration with which the seismic block is less severe than a Solid-Truninon type. In addition, to fulfill the strong requirement of high overturning moment the additional guidance system including a central bearing system on a central support and several pad bearings around the head expander body is now considered. This paper describes the configuration and the design parameters of the multi-shaking system which is under development by KARI's engineers.

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Content-based Image Retrieval using the Color and Wavelet-based Texture Feature (색상특징과 웨이블렛 기반의 질감특징을 이용한 영상 검색)

  • 박종현;박순영;조완현;오일석
    • Journal of KIISE:Databases
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    • v.30 no.2
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    • pp.125-133
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    • 2003
  • In this paper we propose an efficient content-based image retrieval method using the color and wavelet based texture features. The color features are obtained from soft-color histograms of the global image and the wavelet-based texture features are obtained from the invariant moments of the high-pass sub-band through the spatial-frequency analysis of the wavelet transform. The proposed system, called a color and texture based two-step retrieval(CTBTR), is composed of two-step query operations for an efficient image retrieval. In the first-step matching operation, the color histogram features are used to filter out the dissimilar images quickly from a large image database. The second-step matching operation applies the wavelet based texture features to the retained set of images to retrieve all relevant images successfully. The experimental results show that the proposed algorithm yields more improved retrieval accuracy with computationally efficiency than the previous methods.

Numerical Analysis of Rarefied Hypersonic Flows Using Generalized Hydrodynamic Models for Diatomic Gases (이원자 기체 일반유체역학 모델을 이용한 극초음속 희박 유동장 해석)

  • Myong, Rho-Shin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.5
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    • pp.32-40
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    • 2002
  • The study of nonlinear gas transport in rarefied condition or associated with the microscale length of the geometry has emerged as an interesting topic in recent years. Along with the DSMC method, several fluid dynamic models that come under the general category of the moment method or the Chapman-Enskog method have been used for this type of problem. In the present study, on the basis of Eu's generalized hydrodynamics, computational models for diatomic gases are developed. The rotational nonequilibrium effect is included by introducing excess normal stress associated with the bulk viscosity of the gas. The new models are applied to study the one-dimensional shock structure and the multi-dimensional rarefied hypersonic flow about a blunt body. The results indicate that the bulk viscosity plays a considerable role in fundamental flow problems such as the shock structure and shear flow. An excellent agreement with experiment is observed for the inverse shock density thickness.

A Method for Calculation of Compressive Strength of a One-Sided Stiffened Plate (편면 보강판의 압축강도 해석을 위한 한 방법)

  • C.D. Jang;S.I. Seo
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.1
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    • pp.117-124
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    • 1991
  • In this paper, a method to overcome inefficiency of the finite element method in the calculation of compressive strength of one-sided stiffened plates, is proposed. In this method the collapse modes of stiffened plates are assumed as follows. a) Overall buckling $\rightarrow$ Overall collapse b) Local buckling $\rightarrow$ Overall collapse c) Local buckling $\rightarrow$ Local collapse In each collapse mode, shape of deflection is assumed, and then elastic large deformation analysis based on the Rayleigh-Ritz method is carried out. One-sided stiffening effect is considered by taking into account of the moment due to eccentricity. Plastic analysis by assuming hinge lines is also carried out. The ultimate strength of a stiffened plate is obtained as the point of intersection of the elastic analysis curve and the plastic one. From this study, it is concluded that the angles between the plastic hinge lines in plastic collapse mode are determined as the ones which give the minimum collapse load, and these angles are different from the ones assumed in the previous studies. Minimum stiffness ratios can also be calculated. Calculated results according to this method show good agreements with the results by the finite element method.

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Three Dimensional Correction Factors for the Added Mass Moment of Inertia of Ships in Torsional Vibration (선체(船體)비틂진동(振動)에 있어서의 부가관성(附加慣性)모우멘트 3차원수정계수(次元修正係數))

  • K.C.,Kim;H.S.,Lee
    • Bulletin of the Society of Naval Architects of Korea
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    • v.11 no.2
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    • pp.15-22
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    • 1974
  • As for the added mass moment of inertia of ships in torsional vibration, it seems that the works by T. Kumai[1,2] are the only systematic one available currently. The work[1] is for the calculation of the two dimensional correction factors with finitely-long elliptic cylinders as the mathematic model. In this work the authors recalculated the above factors, $J_{\tau}$, with the same mathematic model and the same problem formulation, and presented the numerical results in Fig. 1. The reason why the reinvestigation was done was that in Kumai's work he obtained the solutions of the Mathieu equations, which was derived from the problem formulation for the velocity potential, under the assumption that the dummy constant q involved in the equations was always far less than unity, whereas in fact it takes values within the region of $0<q{\leq}{\infty}$ in sequence. As a result the authors found two remarkable differences in general features of $J_{\tau}$(refer to Fg.3); one that the authors' numerical results are considerably higher than the results given in [2], and the other that for a given number of node those have properties of decreasing monotonically with increase of the beam-draft ratio while these rapidly decrease from a maximum value of near at B/T=2.00 with B/T becoming greater or less than ratio. It seems that the latter trend was resulted from the fact that the assumption of $q{\ll}1$ employed in [2] was more closely satisfied in the vicinity of B/T=2.00.

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