• Title/Summary/Keyword: Closed-Structure

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On forced and free vibrations of cutout squared beams

  • Almitani, Khalid H.;Abdelrahman, Alaa A.;Eltaher, Mohamed A.
    • Steel and Composite Structures
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    • v.32 no.5
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    • pp.643-655
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    • 2019
  • Perforation and cutouts of structures are compulsory in some modern applications such as in heat exchangers, nuclear power plants, filtration and microeletromicanical system (MEMS). This perforation complicates dynamic analyses of these structures. Thus, this work tends to introduce semi-analytical model capable of investigating the dynamic performance of perforated beam structure under free and forced conditions, for the first time. Closed forms for the equivalent geometrical and material characteristics of the regular square perforated beam regular square, are presented. The governing dynamical equation of motion is derived based on Euler-Bernoulli kinematic displacement. Closed forms for resonant frequencies, corresponding Eigen-mode functions and forced vibration time responses are derived. The proposed analytical procedure is proved and compared with both analytical and numerical analyses and good agreement is noticed. Parametric studies are conducted to illustrate effects of filling ratio and the number of holes on the free vibration characteristic, and forced vibration response of perforated beams. The obtained results are supportive in mechanical design of large devices and small systems (MEMS) based on perforated structure.

A Study on the Establishment of Welfare Facilities for the Aged Using the Facilities Characteristics of Closed Schools - Focused on the Northern Area of Gyeonggi-Do - (폐교의 시설 특성을 활용한 노인복지시설 구축에 관한 연구 - 경기 북부지역을 중심으로 -)

  • Kim, Hak Cheol
    • Journal of the Korean Institute of Rural Architecture
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    • v.23 no.2
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    • pp.17-24
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    • 2021
  • Changes in the population structure caused by a decrease in the birthrate and an extension of life expectancy cause problems in utilization inefficiencies of closed schools and shortage welfare facilities for the aged. The closed schools have location characteristics that are close to the existing residence and facilities such as land and school buildings, so it is expected that the schools will be used as welfare facilities for the aged in the community. The purpose of this study is to compare and analyze the facility characteristics of closed schools in northern Gyeonggi-Do and present the types of aged welfare facilities that can be built, providing basic data for developing customized aged welfare facilities. The results of this study are summarized as follows: 1) The proportion of aged people in northern Gyeonggi-Do is higher than in southern Gyeonggi-Do, but welfare facilities for the aged are insufficient, so it is necessary to expand welfare facilities for the aged in northern Gyeonggi-Do. 2) Urban areas such as Paju and Goyang City have a lot of residential proximity, Dongducheon and Yangju have a lot of residential proximity, while schools located in urban and rural areas such as Yeoncheon have a lot of residential proximity. 3) Closed schools in urban areas such as Goyang City and Paju City are desirable to use them as residential facilities for senior citizens, day and night protection and short-term protection facilities, while closed schools in Namyangju City, Pocheon City, and Gapyeong County are desirable to use them as senior citizen centers and medical welfare facilities.

Strength Analysis and Standardization for Closed Chocks by Using the Finite Elements Method (유한요소법을 이용한 클로즈드 초크의 구조검증 및 표준화에 대한 연구)

  • Jung, Jae-Wook;Lee, Byung-Hoon
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.2
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    • pp.132-145
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    • 2012
  • Mooring fittings mean various devices and fittings to safely fasten vessels to quays, jetties and sea-floating buoys, etc. They include mooing winches, capstans, chocks, fairleads, guide rollers, bollards, and bitts. Not only the seats and reinforced parts for the installation of fittings but also ropes and chains for mooring and chain stoppers can be also considered. Because of damages to mooring fittings during mooring directly related to large-scale accidents such as the drifting of vessels, mooring fittings with strength appropriate for the physical features of the vessels must be installed. The reinforcement of the vessels on which the mooring fittings are installed must be designed to withstand the loads transferred from the fittings as well. Also mooring fittings with efficient strength should be required because damaged ships lead to sea pollution such as oil or fuel oil spillage. This study has been performed by the Finite Element Method for two aspects of closed chocks which are divided into structure-supporting shapes and working load. In the case of structure-supporting shapes, they have been performed in the field of sheet and bulwark. As for working load, it has been analyzed according to working load direction such as chock's side and below. At first, strength analysis for unique closed chocks has been carried out by using the Finite Element Method, they are applied for the situation when vessels pass by the panama canal. And then the experiment has been done to verify the analyzed date obtained by FEM. The experimental results were found to be similar to the numerical results with up to 16% difference. On the basis of the results obtained, standardization has been carried out by the Finite Element Method for various sizes of closed chocks.

Exploration of retention system for papermaking system closure (제지공정의 무방류화를 위한 보류시스템 탐색)

  • 이학래;함충현;이지영;황남선;이상길;김종민
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.33 no.2
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    • pp.1-7
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    • 2001
  • Use of high yield pulp and recycled fiber as raw materials and water system closure result in higher fines content and buildup of organic and inorganic contaminants in white water. These are detrimental for the effectiveness of chemical additives including retention aids. Thus it is imperative to employ a retention systems that maintains its efficiency in closed papermaking system for reducing fresh water consumption. The performance of four different microparticle retention systems including cationic polyacrylamide (C-PAM)/bentonite, highly charged cationic starch (HCS)/silica, C-PAM/micropolymer, cationic guar gum (CGG)/silica was evaluated and compared at three different levels of papermaking system closure. Buildup of detrimental substances in a closed white water system increased cationic demand and finally reduced the performance of retention systems. Cationic starch and guar gums maintained their effectiveness in retention in closed white water systems contaminated with anionic trashes because of their structural rigidity and hydrogen bonding ability. Particularly, cationic guar gums, due its stiffness of molecular structure, appeared perform better than catinonic starch.

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Interval finite element method for complex eigenvalues of closed-loop systems with uncertain parameters

  • Zhang, XiaoMing;Ding, Han
    • Structural Engineering and Mechanics
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    • v.26 no.2
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    • pp.163-178
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    • 2007
  • In practical engineering, the uncertain concept plays an important role in the control problems of the vibration structures. In this paper, based on matrix perturbation theory and interval finite element method, the closed-loop vibration control system with uncertain parameters is discussed. A new method is presented to develop an algorithm to estimate the upper and lower bounds of the real parts and imaginary parts of the complex eigenvalues of vibration control systems. The results are derived in terms of physical parameters. The present method is implemented for a vibration control system of the frame structure. To show the validity and effectiveness, we compare the numerical results obtained by the present method with those obtained by the classical random perturbation.

Development of a New Robot Manipulator Driven by the Closed-chain Actuator (폐체인 구조의 새로운 다관절 로봇 매니퓰레이터 개발)

  • 최형식;백창열
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.2
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    • pp.238-245
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    • 2003
  • To overcome the weakness in the load capacity of conventional robot manipulators actuated by motors with the speed reducer such as the harmonic driver, we proposed a new closed-chain type of the robot actuator which is composed of the four-bar-link mechanism driven by the ball screw. The robot manipulator is revolute-jointed and composed of four axes. The base axis is actuated by the lineal actuator such as the ball screw, and the others are actuated by the proposed actuator. We analyzed the mechanism of the actuators of the robot joints, and developed the dynamics model. The dynamics are expressed in the joint coordinates and then they are mapped into the sliding coordinates of the ball screw. We performed fundamental tests on the structure of the robot.

A Forward Closed-Form Position Solution, Kinematic Analysis And Implementation of a Translational 3-DOF Parallel Mechanism Formed by Constraining a Stewart Platform Structure (스트워트 플랫폼 구조를 구속하여 얻어지는 병진형 3 자유도 병렬 메커니즘의 정위치 해석해와 기구학 해석 및 구현)

  • Shin Dong-Min;Chung Jae-Heon;Oh Se-Min;Yi Byung-Ju;Kim Whee-Kuk
    • Journal of Institute of Control, Robotics and Systems
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    • v.12 no.10
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    • pp.1035-1043
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    • 2006
  • In this study, a translational 3-DOF parallel mechanism formed by constraining the Stewart Platform Mechanism is investigated. The translational 3-DOF parallel mechanism has three struts(3-UPS type serial subchains) and in addition, has a PPP type serial subchain in the middle of the mechanism. Firstly, the closed-form forward and reverse position solutions are derived for this mechanism. And analysis on kinematic characteristics using isotropic index of the Jacobian is conducted to examine effects of design parameters for the mechanism. Lastly, a prototype mechanism is implemented and the kinematic performance of the translational 3-DOF parallel mechanism was verified through experimental work.

A STUDY ON TEMPOROMANDIBULAR JOINT DYSFUNCTION WITH MAGNETIC RESONANCE IMAGING AND ARTHROGRAM (자기 공명 영상장치를 이용한 악관절 기능 장애에 관한 연구)

  • Kim Jae-Duk
    • Journal of Korean Academy of Oral and Maxillofacial Radiology
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    • v.23 no.1
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    • pp.7-14
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    • 1993
  • The Internal derangement of temporomandibular joint disc was evaluated by using magnetic resonance imaging and arthrogram in 5 patients having reciprocal clicking or locking and in 5 normal subjects. Parasagittal multisections on both closed and open mouth were serially obtained by using a 1.5 Tesla MR system and surface coil with CSMEMP, MPGR. MR images obtained were analized by correlating with images of arthrograms. The obtained results were as follows: 1. Displaced meniscus was clearly delineated as dark structure on MR images other than on arthrograms of closed mouth view of patient having clicking or locking. 2. The deltoid white images of synovial fluid were identified in the glenoid fossa and on the posterior surface of condyle on open mouth view and partly depicted on closed mouth view, of parasagittal sections by MPGR. 3. The greyish image of joint fluid was identified on the posterior surface of condyle on the open mouth view of parasagittal sections by CSMEMP. 4. The structural relationship among condyle, meniscus, and fluid showed the variety of images on each parasagitta1 view.

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Role of Open Channels in Overlapping Resonances Studied by Multichannel Quantum Defect Theory in Systems Involving 2 Nondegenerate Closed and Many Open Channels

  • Lee, Chun-Woo
    • Bulletin of the Korean Chemical Society
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    • v.31 no.11
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    • pp.3201-3211
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    • 2010
  • Previous work on the phase-shifted version of the multichannel quantum-defect theory (MQDT) for a system involving 2 closed and many open channels (Lee, C.-W. Bull. Korean Chem. Soc. 2010, 31, 1669) was extended to obtain the formulae of the spectral shape parameters with the structure of a pole extracted explicitly for general cases only limited by 2 non-degenerate closed channels. The theory was applied to the narrow $6p_{1/2,3/2}np$ J = 1 autoionizing Rydberg series in barium perturbed by the $6p_{3/2}nf$ states obtained by de Graaff et al.

An Improved Estimate of the Asymptotic Stability Region for the Uncertain Variable Structure Systems with Bounded Control (크기가 제한된 입력을 갖는 가변구조제어 시스템을 위한 개선된 안정 영역 추정값)

  • Choi Han Ho
    • Journal of Institute of Control, Robotics and Systems
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    • v.11 no.6
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    • pp.492-495
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    • 2005
  • This paper deals with the problem of estimating the asymptotic stability region(ASR) of uncertain variable structure systems with bounded control. Using linear matrix inequalities(LMIs) we estimate the ASR and we show the exponential stability of the closed-loop control system in the estimated ASR. We show that our estimate is always better than the estimate of [3].