• Title/Summary/Keyword: Beam Element

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Torque control during lingual anterior retraction without posterior appliances

  • Mo, Sung-Seo;Kim, Seong-Hun;Sung, Sang-Jin;Chung, Kyu-Rhim;Chun, Yun-Sic;Kook, Yoon-Ah;Nelson, Gerald
    • The korean journal of orthodontics
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    • v.43 no.1
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    • pp.3-14
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    • 2013
  • Objective: To evaluate the factors that affect torque control during anterior retraction when utilizing the C-retractor with a palatal miniplate as an exclusive source of anchorage without posterior appliances. Methods: The C-retractor was modeled using a 3-dimensional beam element (0.9-mm-diameter stainless-steel wire) attached to mesh bonding pads. Various vertical heights and 2 attachment positions for the lingual anterior retraction hooks (LARHs) were evaluated. A force of 200 g was applied from each side hook of the miniplate to the splinted segment of 6 or 8 anterior teeth. Results: During anterior retraction, an increase in the LARH vertical height increased the amount of lingual root torque and intrusion of the incisors. In particular, with increasing vertical height, the tooth displacement pattern changed from controlled tipping to bodily displacement and then to lingual root displacement. The effects were enhanced when the LARH was located between the central and lateral incisors, as compared to when the LARH was located between the lateral incisors and canines. Conclusions: Three-dimensional lingual anterior retraction of the 6 or 8 anterior teeth can be accomplished using the palatal miniplate as the only anchorage source. Using LARHs at different heights or positions affects the quality of torque and intrusion.

Evaluation on Structural Safety for Bearing seat according to Replacement of Bridge Bearing (교량받침 교체에 따른 보자리 구조 안전성 평가)

  • Choi, Jung-Youl;Lee, Hee-Kwang;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
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    • v.6 no.4
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    • pp.753-760
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    • 2020
  • In this study, the structural safety of the bearing support was analysed by applying the vertical load (bearing design load) and horizontal load (horizontal force generated during an earthquake) using a precise three-dimensional numerical model. The results of stress and displacement of newly-poured concrete and welded rebars were confirmed numerically. Numerical results show that the increase in the horizontal force and the height of the beam causes the concrete cracking and the stress increase of the rebar connections due to the increase of the stress at the new concrete interface. Therefore, it was analyzed that the increase in the height of bearing support is directly related to the horizontal force and it is necessary to apply the bearing support height appropriate for the bearing support capacity. It was proposed that a method of setting the height of the bearing support suitable for the bearing capacity and determining the reinforcement by presenting the guideline with the correlation between the horizontal force acting on the bearing support and its height.

Developmentof Dual Polarized Base station Antenna with Electrical Down tilting (전기적 다운 틸팅 기능을 갖는 이중 편파 기지국 안테나 개발)

  • Lee, Chang-Eun;Yun, Jong-Sup;Moon, Young-Chan;Hur, Jung
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.41 no.7
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    • pp.81-88
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    • 2004
  • In case of mechanical down tilting, a horizontal pattern is distorted and beam width widens whenincreasing tilt angle, which causes an expansion of hand off region and burden base station equipment. In contrast, electrical down tilting has advantage that horizontal HPBW is kept constant with down tilting. In this paper, based on a phased array technology, dual polarized base station antenna with electrical down tilting was developed at 800MHz band. The antenna has down tilting range of 0$^{\circ}$ to 14$^{\circ}$, and 15㏈i gain. We use stacked microstrip patch as a radiated element and apply balanced feed technique to improve isolation between ports and discrimination of cross polarization. The effect of electrical down tilting was verified by field test.

Two-Axis Rotational Micro-Mirror for High-Capacity Optical Cross-Connect Switch (대용량 광 스위치를 위한 2축 자유도 마이크로 미러)

  • 김태식;이상신
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.40 no.8
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    • pp.543-548
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    • 2003
  • In this paper, we have proposed and fabricated a two-axis rotational micro-mirror with large tilt angle. Such a micro-mirror is a key element for N$\times$N high capacity optical cross-connect switches. The micro-mirror is required to have large tilt angle to increase the capacity of the cross-connect switches. For larger micro-mirror tilt angle between the grounded mirror plate and the bottom electrode is to be large enough to provide space for the tilting of the mirror. For our proposed structure, the gap was produced in such a way that the grounded mirror plate and the bottom electrode were made separately in different substrates by using the bulk micromachining technology, and combined later by employing self-align technique. As a result, a large tilt angle has been achieved without using additional actuators. The measured tilt angles were as large as $\pm$5.5$^{\circ}$ and $\pm$8.4$^{\circ}$ in the x and y direction respectively, and the pull-in voltages for the two directions were 380 V and 275 V respectively. Finally the fabricated mirror was successfully utilized to steer the optical beam. To our knowledge, our micro-mirror has the best performance among the micro-mirrors reported internationally so far.

Delamination Analysis of Orthotropic Laminated Plates Using Moving Nodal Modes (이동절점모드를 사용한 직교이방성 적층평판의 층간분리해석)

  • Ahn, Jae-Seok
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.4
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    • pp.293-300
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    • 2012
  • In this study, the delamination analysis has been implemented to investigate the initiation and propagation of crack in composite laminates composed of orthotropic materials. A simple modeling was achieved by moving nodal technique without re-meshing work when crack propagation occurred. This paper aims at achieving two specific objectives. The first is to suggest a very simple modeling scheme compared with those applied to conventional h-FEM based models. To verify the performance of the proposed model, analysis of double cantilever beams with composite materials was implemented and then the results were compared with reference values in literatures. The second one is to investigate the behavior of interior delamination problems using the proposed model. To complete these objectives, the full-discrete-layer model based on Lobatto shape functions was considered and energy release rates were calculated using three-dimensional VCCT(virtual crack closure technique) based on linear elastic fracture mechanics.

Lateral Stiffness and Natural Period Evaluation of Flat Plate Tall Buildings for Wind Design (내풍설계를 위한 초고층 무량판 건축물의 횡강성 및 고유주기 산정)

  • Park, Je-Woo;Kim, Hong-Jin;Jo, Ji-Seong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.1
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    • pp.73-80
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    • 2010
  • Wind-induced vibration is one of the important structural design factors for serviceability of tall buildings. In order to evaluate the reliable wind-loads and wind induced-vibration, it is necessary to obtain the exact natural period of buildings. The discrepancy in the natural period estimation often results in the overestimation of wind loads. In this study, the effectiveness of lateral stiffness estimation method for tall buildings with flat plate system is evaluated. For this purposed, the results of finite element analysis of three recently constructed buildings are compared with those obtained from field measurement. For the analysis, factors affecting on the lateral resistance such as cracked stiffness of vertical members, elastic modulus of concrete, effective slab width, and cracked stiffness of link beam are considered. Form the results, it is found that the use of non-cracked stiffness and application of dynamic modulus of elasticity rather than initial secant modulus yields closer analysis result to the as-built period.

Development of Main Wing Structure of Long Endurance Electric Powered UAV (24시간 장기체공 전기 동력 무인항공기 주익 구조 개발)

  • Park, Sang Wook;Shin, Jeong Woo;Park, Ill Kyung;Lee, Mu-Hyoung;Woo, Dae Hyun;Kim, Sung Joon;Ahn, Seok Min
    • Aerospace Engineering and Technology
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    • v.12 no.1
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    • pp.1-9
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    • 2013
  • In order to increase endurance flight efficiency of long endurance electric powered UAV with solar cell, the light weight airframe design techniques are important. In this paper, the design of the main wing of electric powered UAV manufactured using Mylar film and fiber reinforced composite was conducted in order to achieve weight reduction and structural integrity of the structure. The shape of spar and size were determined using beam theory analysis. The finite element analysis of the wing was performed under various load condition derived from flight environment of EAV-2H. Finally, the static strength test of the main wing was conducted to verify structural integrity. It was found that the developed main wing weigh less than 42% than the previous EAV-2 and the main wing passed static strength test under ultimate load.

Performance Analysis of Low-level Radiation Shielding Sheet with Diamagnetic Nanoparticles

  • Cho, Jae-Hwan;Kim, Myung-Sam
    • Journal of Magnetics
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    • v.20 no.2
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    • pp.103-109
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    • 2015
  • In this study, the authors attempted to produce a medical radiation shielding fiber that can be produced at a nanosize scale and that is, unlike lead, harmless to the human body. The performance of the proposed medical radiation shielding fiber was then evaluated. First, diamagnetic bismuth oxide, an element which, among elements that have a high atomic number and density, is harmless to the human body, was selected as the shielding material. Next, 10-100 nm sized nanoparticles in powder form were prepared by ball milling the bismuth oxide ($Bi_2O_3$), the average particle size of which is $1-500{\mu}m$, for approximately 10 minutes. The manufactured bismuth oxide was formed into a colloidal solution, and the radiation shielding fabric was fabricated by curing after coating the solution on one side or both sides of the fabric. The thicknesses of the shielding sheets prepared with bismuth oxide were 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 1.0 mm. An experimental method was used to measure the absorbed dose and irradiation dose by using the lead equivalent test method of X-ray protection goods presented by Korean Industrial Standards; the resultant shielding rate was then calculated. From the results of this study, the X-ray shielding effect of the shielding sheet with 0.1 mm thickness was about 55.37% against 50 keV X-ray, and the X-ray shielding effect in the case of 1.0 mm thickness showed shielding characteristics of about 99.36% against 50 keV X-ray. In conclusion, it is considered that nanosized-bismuth radiation shielding fiber developed in this research will contribute to reducing the effects of primary X-ray and secondary X-ray such as when using a scattering beam at a low level exposure.

Analysis of the Reinforced I section UHPCC (Ulrea High Performance Cementitous Composites) beam without stirrup (전단철근이 없는 I형 휨보강 UHPCC 보의 거동해석)

  • Kim Sung Wook;Han Sang Muk;Kang Su Tae;Kong Jeong Shick;Kang Jun Hyung;Jun Sang Eun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.409-412
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    • 2004
  • Over last decade extensive researches have been undertaken on the strength behaviour of Fiber Reinforced Concrete(FRC) structures. But the use of Ultra-High Strength Steel Fiber Cementitious Concrete Composites is in its infancy and there is a few experiments, analysis method and design criteria on the structural elements constructed with this new generation material which compressive strength is over 150 MPa and characteristic behaviour on the failure status is ductile. The objective of this paper is to investigate and analyze the behaviour of reinforced rectangular structural members constructed with ultra high performance cementitious composites (UHPCC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The variables of test specimens were shear span ratio, reinforcement ratio and fiber quantity. Even if there were no shear stirrups in test specimens, most influential variable to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone could be defined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

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A Study on the Work Breakdown Structure of Agricultural Facilities for Developing a Construction and Maintenance Information System -Focused on Vinyl house, Glass greenhouse, Cattle shed- (농촌시설물 시공 및 유지관리 정보화 시스템 구축을 위한 작업분류체계 구축에 관한 연구 -비닐하우스, 유리온실, 축사를 중심으로-)

  • Choi, Oh-Young;Kim, Tae-Hui;Kim, Jae-Yeob;Kim, Gwang-Hee;Choi, Eung-Kyoo
    • Journal of the Korea Institute of Building Construction
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    • v.9 no.4
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    • pp.147-155
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    • 2009
  • Recently, the scale and technical complexity of agricultural production has been growing. Therefore, agricultural facilities are being gradually diversified, expanded, and made more complex. To furnish Korea's agricultural industry with international competitiveness, it is thus necessary to introduce new management techniques. The PCM (procurement-construction-maintenance) information management system for agricultural facilities is established by setting up its WBS (work breakdown structure). In this study, the WBS of a facility such as facility, space, element, works, and resources is analyzed. Following this analysts, a WBS of an agricultural facility that is appropriate for the PCM information system of an agricultural facility, is proposed by deriving it from actual WBS.