• Title/Summary/Keyword: Longitudinal Stability

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Study of Longitudinal Stability of eVTOL UAM with Tilt Rotor and Tandem Wing (Tilt Rotor와 Tandem Wing을 적용한 eVTOL UAM의 세로안정성 연구)

  • Joo Chan-Young;Kim Ha-Min;Kim Min-Jae;Min Kyoung-Soon
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.6
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    • pp.941-946
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    • 2023
  • To improve the lift, cruise speed, and range of eVTOL aircraft, which are being considered as future transportation vehicles, this paper introduces the concepts of Tilt Rotor and Tandem Wing to the aircraft. We developed an aircraft and conducted flight experiments to obtain flight videos and flight logs. The results of the analysis of the flight videos and flight logs showed that the aircraft's moment was excessively forward and the attitude was not recovered. To address this problem, we modified the wing incidence angles and surface areas in XFLR5 to obtain the optimal pitching moment coefficients to ensure vertical stability. We then analyzed the redesigned aircraft, developed using CATIA, through XFLR5. The results of this study provide valuable insights, suggesting that the incorporation of Tilt Rotor and Tandem Wing designs can contribute to achieving stable pitching moment coefficients. This innovative approach offers a promising avenue to significantly enhance vertical stability in UAM vehicles, paving the way for future advancements in the field.

TWO-MODE NONLINEAR STABILITY ANALYSIS

  • Hyun-Gull Yoon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1997.04a
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    • pp.247-256
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    • 1997
  • A nonlinear mathematical model of longitudinal combustion instability appropriate for ramjets and augmentors was developed based on modal analysis. The model was limited to a two-mode formulation. The associated differential equations were solved both analytically and numerically and used to perform parametric studies.

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Stability evaluation of CWR on the bridge with lead Rubber Bearing(LRB) (LRB 교좌장치를 사용한 교량의 장대레일 축력안정성 평가)

  • Yang Sin-Chu;Yun Cheol-Kyun;Lee Jin-Woo
    • Proceedings of the KSR Conference
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    • 2004.10a
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    • pp.787-792
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    • 2004
  • LRB(Lead rubber bearing) has small resistance force against slowly acting loadings such as temporal and creep loadings vice versa large resistance force against rapid loadings such as earthquake and braking loadings. By those mechanical characteristics, it has the advantage to reduce longitudinal load acting on abutments and piers, and moreover to in1prove the running stability of train by restricting the behavior of bridge under the required level. In this study, a stability evaluation method of CWR on the bridge with LRB is presented. Several parametric studies are carried to investigate how LRB contributes to the improvement of CWR stability.

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Stability of tow-steered curved panels with geometrical defects using higher order FSM

  • Fazilati, Jamshid
    • Steel and Composite Structures
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    • v.28 no.1
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    • pp.25-37
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    • 2018
  • For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.

Parametric Study of Thermal Stability on Continuous Welded Rail

  • Choi, Dong-Ho;Na, Ho-Sung
    • International Journal of Railway
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    • v.3 no.4
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    • pp.126-133
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    • 2010
  • The thermal buckling analysis of curved continuous welded rail (CWR) is studied for the lateral buckling prevention. This study includes a thermal buckling theory which accounts for both thermal and vehicle loading effects in the evaluation of track stability. The parameters include rail size, track lateral resistance, track longitudinal and torsional stiffnesses, initial misalignment amplitude and wavelength, track curvature, tie-ballast friction coefficient and truck center spacing. Parametric studies are performed to evaluate the effects of the individual parameters on the upper and lower critical buckling temperatures. The results show that the upper critical buckling temperature is highly affected by the uplift due to vehicle loads. This study provides a guideline for the improvement of stability for dynamic buckling in curved CWR track.

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Design of a Stabilizing Controller for Hybrid systems with as Application to Longitudinal Spacing Control in a Vehicle Platoon (다중 Lyapunov 기방 하이브리드 시스템에 안정화 제어기 설계 및 군집 차량의 종방향 거리 제어시스템의 용용)

  • Kim, Jin-Byun;Park, Jae-Weon;Kim, Young-Ho
    • Journal of Institute of Control, Robotics and Systems
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    • v.7 no.6
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    • pp.477-486
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    • 2001
  • Many physical systems can be modeled by incorporating continuous and discrete event nature together. Such hybrid systems contain both continuous and discrete states that influence the dynamic be-havior of the systems. There has been an increasing interest in thers types of systems during the last dec-ade, mostly due to the growing usage of computers in the control of physical plants but also as a result of the hybrid nature of physical processes. The stability theory for hybrid systems is considered as extension of Lyapunov theory where the existence of an abstract energy function satisfying certain properties verifies stability, called multiple Lyapunov theory. In this paper, a hybrid stabilizing controller is proposed using the control Lyapunov function method and multiple Lyapunov theory, and the proposed method is applied to lon-gitudinal spacing control in a vehicle platoon for intelligent transportation systems(ITS).

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The Change of the Physical Properties of Rayon/Cotton Blend Fabrics Treated with Cellulase by Addition of Silicon (셀룰라아제 처리시 실리콘 첨가에 따른 레이온/면 혼방직물의 물성변화)

  • 이선화;송화순
    • Journal of the Korean Society of Clothing and Textiles
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    • v.22 no.8
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    • pp.1032-1042
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    • 1998
  • The purpose of this study is to measure, compare, and investigate the physical properties of rayon/cotton blend fabrics treated with cellulase and cellulase & specific degeneration silicon and to present basic data which is in development a value-added fabric. The results are as follows. The condition for the treatment of cellulase was at 55$^{\circ}C$, pH 4 and the weight loss increased as the concentration of cellulase and the treated time increased. On treatment with cellulase, the crossectional view & longitudinal view of fiber noticed remarkable crack as weight loss increased and tensile strength and elongation decreased, and pilling was enhanced remarkably. KOSHI was increased, NUMERI and FUKURAMI were decreased as weight loss increased. In the basic characteristic value of clothing wearning, shape stability and drapability were decreased, but air content was improved. On treatment with cellulase & silicon, the degree of damage in the crossectional view & longitudinal view of the fiber reduced. Tensile strength, elongation, moisture regain improved. KOSHI and FUKURAMI were reduced, NUMERI was improved rather than when it was treated with cellulase. Therefore handle was improved. In the basic characteristic value of the clothing wearing, shape stability, air content, drapability were improved.

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Investigation on the Behavior of Tunnel Face Reinforced with Longitudinal Reinforcements using Reduced-Scale Model Tests (모형실험에 의한 수평보강재로 보강된 터널 막장의 거동 분석)

  • Yoo, Chung-sik;Shin, Hyun-Kang
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.2 no.2
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    • pp.32-40
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    • 2000
  • This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A series of reduced-scale model tests was carried out to in an attempt to verify previously performed three-dimensional numerical modeling and to investigate effects of reinforcement layout on the tunnel face deformation behavior. The results of model tests indicate that the tunnel face deformation can significantly reduced by pre-reinforcing the tunnel face with longitudinal members and thus enhancing the tunnel stability. In addition, the model tests results compare fairly well with those from the previously performed three-dimensional finite element analysis. Therefore, a properly calibrated three dimensional model may effectively be used in the study of tunnel face reinforcing technique.

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A Study on the Effects of Side Jets to the Longitudinal Aerodynamics of Subsonic Missile (측방 제트가 아음속 유도탄 종방향 공력특성에 미치는 영향 연구)

  • GO, Beom Yong;HUR, Ki Hoon
    • Journal of the Korea Institute of Military Science and Technology
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    • v.20 no.3
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    • pp.393-404
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    • 2017
  • Side jet effect on the aerodynamic characteristics of a missile was investigated using experimental and computational methods. A couple of side jets were injected toward outward downstream at mid point of missile body. Cold air jet was used in the wind tunnel test, and cold and hot jet were used in the computation. Wind tunnel test was carried out with jet and without jet, and calculation was performed for three cases ; no jet, cold air jet, and hot mixture gas jet. From the comparison of measured and calculated data for all cases, two points could be deduced. Firstly, side jet made static stability to be unstable by increasing body normal force near the side jet exit and by decreasing tail normal force. Secondly, hot mixture gas had more significant effect on the static stability of a missile-type body than cold air jet.

Application of the Unstructured Finite Element to Longitudinal Vibration Analysis (종방향 진동해석에 비구조적 유한요소 적용)

  • Kim Chi-Kyung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.19 no.1 s.71
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    • pp.39-46
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    • 2006
  • This paper analyzes the continuous Galerkin method for the space-time discretization of wave equation. The method of space-time finite elements enables the simple solution than the usual finite element analysis with discretization in space only. We present a discretization technique in which finite element approximations are used in time and space simultaneously for a relatively large time period called a time slab. The weighted residual process is used to formulate a finite element method for a space-time domain. Instability is caused by a too large time step in successive time steps. A stability problem is described and some investigations for chosen types of rectangular space-time finite elements are carried out. Some numerical examples prove the efficiency of the described method under determined limitations.