• Title/Summary/Keyword: Longitudinal Stability

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Flow Analysis Based on the Recovery of Lateral Connectivity in the River (하천 내 횡적 연결성 회복을 통한 흐름 해석)

  • Lee, Jin Woo;Chun, Seung Hoon;Kim, Kyu-Ho;Kim, Chang Wan
    • Journal of Wetlands Research
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    • v.16 no.2
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    • pp.213-220
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    • 2014
  • Recently, river maintenance is change due to concern for the environment increases. Thus, the river restoration and river environment is best part of river maintenance. In case of Korea, existing river is improvement straightly for flood control and transportation. When the stream channel is straightly, maintain stability is important. Thus, construction of levees along the river. The various river structures for the purpose of flood control and transportation are inhibit factors of longitudinal and lateral connectivity. Connectivity is defined as the maintenance of lateral, longitudinal, and vertical pathways for biological, hydrological, and physical processes. Long-term point of view, increased connectivity is very important for a healthy ecosystem composition. As the first step of river restoration, this study described theory and concept of river continuum and the numerical model was applied to a real topography to simulate the flow analysis with or without segregated and blocked space in the Mankyung river. The results of this study can be utilized to develop the watershed connectivity assessments methods in order to the river restoration.

Parameter Study of Track Deformation Analysis by Adjacent Excavation Work on Urban Transit (인접굴착공사에 따른 지하철 궤도 변형 해석을 위한 매개변수 연구)

  • Choi, Jung-Youl;Cho, Soo-Il;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
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    • v.6 no.4
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    • pp.669-675
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    • 2020
  • In this study, 3D analysis was compared in evaluating the track deformation of subway structures during adjacent excavation. For the 3D analysis model, the boundary conditions of the tunnel model and the application level of the ground water were analyzed as variables. As the result of the effects of track irregularity using the 3D model, the analysis model considering the site ground water level instead of the design values and changing the constraint of the boundary condition is more reasonable. In addition, the influence of track irregularity due to the boundary condition and load condition of the analytical model is more obvious in the factors directly affected by the longitudinal relative displacement of the rail, such as alignment, cross level and gauge irregularity. Therefore, the evaluation on track stability according to adjacent excavation work was appropriate to analysed the longitudinal deformation of the track by using 3D model that could be investigate the deformation of rail. In addition, the boundary condition and load condition(ground water level) of the numerical model was important for accurate analysis results.

A Causal Relationship between Family Social Capital and Self-Esteem using Autoregressive Cross-Lagged Modeling (가족 내 사회적 자본과 자아존중감과의 관계 -ARCL모델을 적용한 종단연구-)

  • Shin, Won-Young
    • Journal of the Korean Society of Child Welfare
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    • no.32
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    • pp.7-32
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    • 2010
  • The purpose of this research is to identify the longitudinal reciprocal relationship between family social capital and self-esteem of adolescents. Five waves of panel data from the Korea Youth Panel Survey were employed for this research. Korean Adolescents Policy Research Institute collected the first wave data in 2004 from elementary school children in 4th grade. Autoregressive cross-lagged modeling was performed to analysis the longitudinal reciprocal relationship between family social capital and self-esteem. The major findings were as follows. First, stability coefficient of family social capital and self-esteem showed that both variables were significantly stable over time. Secondly family social capital(t) had statistically significant effect on self-esteem(t+1), whereas self-esteem did not predict family social capital at a statistically significant level. These findings suggest that family social capital and self-esteem is stable overtime, and that obtaining family social capital and establishing positive self-esteem is important during this period in childhood. In addition, the results show that family social capital affects self-esteem, which highlights the importance of family social capital accumulation on the development of adolescent self-esteem.

Aerodynamic Design Optimization of Airfoils for WIG Craft Using Response Surface Method (반응표면법을 이용한 지면효과익기 익형의 공력 설계최적화)

  • Kim, Yang-Joon;Joh, Chang-Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.5
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    • pp.18-27
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    • 2005
  • Airfoils with improved longitudinal static stability were designed for a WIG craft through aerodynamic design optimization. The response surface method is coupled with NURBS-based shape functions and Navier-Stokes flow analysis. The procedure runs in the network-distributed design framework of commercial-code based automated design capability to enhance computational efficiency and robustness.Lift maximization design maintaining similar static margin to a DHMTU airfoil successfully produced a new airfoil shape characterized by pronounced front-loading and the well-known reflexed aft-camber line. Another airfoil design of lower variation in pitching moment during take-off showed weakened front-loaded characteristics and hence decreased lift slightly. Investigations using the present design methodology on an existing optimization result based on potential flow analysis and NACA-type geometry generation demonstrated significance of carrying various geometry generations and more realistic flow analysis with optimization.

Mixing Process of Double Diffusive Salt Wedge (이중확산의 영향을 받는 염수침입의 혼합과정 연구)

  • Hwang, Jin-Hwan
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.11 no.2
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    • pp.92-97
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    • 2008
  • Salt wedge into the river from the sea or fresh water flume (fresh wedge) in the ocean from the sea has density current characteristics. However, when temperature and salinity simultaneously determine the density of wedges, one of salinity and temperature can distributed in the reversed profiles against gravity, even though the density profile is stable. In this case, the double diffusive process is critical in determining mixing rate. The present work studies relative contribution of shear driven mechanical mixing component and double diffusive layering process, when warm salty denser water is introduced into the cold fresh lighter water column. Laboratory experiment releases warm salty denser water into cold fresh lighter water controlling discharge amount to achieve the steady state of density current. When longitudinal density rate becomes 15, the released amount ratio of salt and heat changes sharply and in the releasing point, vigorous mixing occurs with increase of discharged amount due to double diffusion. Double diffusion distabilizes gravitational stability and enhances the mixing rate up to $6{\times}10$ times at the lower density ratio comparing to the higher density ratio.

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A Study on Fire Resistance Character of a Tunnel and an Underground Structure (터널 및 지하구조물의 내화특성에 관한 연구)

  • Yoo, Sang-Gun;Kim, Jung-Joo;Park, Min-Yong;Kim, Eun-Kyum;Lee, Jun-Suk
    • Journal of the Korean Society for Railway
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    • v.13 no.2
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    • pp.194-200
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    • 2010
  • Recently, a longitudinal tunnel construction has increased because of subway construction extension, geomorphological effect and the development of construction Technologies etc. When the fire occurs in a tunnel and an underground structure, the many damage of human life and the economic losses are caused. In Korea, fire resistance character study of a tunnel and an underground structure is proceeding. However, when a concrete is exposed to high temperature, study of load carrying capacity reduction and stability evaluation for spalling of a concrete is not enough. Therefore in this study, fire resistance character of a concrete evaluated according to time heating temperature curve(RABT and RWS) and a result compared on virtual fire accident in order to apply fire scenario. Also this study performed thermo-mechanical coupled analysis of a FEM-based numerical technique and estimated fire-induced damage of a tunnel and an underground structure.

Aeroelastic Behaviors of Self-anchored Suspension Bridge with Lateral Sag of Main Cable(II) - Focused on the Behavior of Tower - (횡방향 새그를 가진 자정식 현수교의 공탄성 거동(II) - 주탑의 거동을 중심으로 -)

  • Kwon, Soon Duck;Chang, Sung Pil
    • Journal of Korean Society of Steel Construction
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    • v.9 no.2 s.31
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    • pp.269-275
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    • 1997
  • Wind tunnel test results and their interpretations, which were performed to study the aerodynamic stability of tower of self-anchored suspension bridge, are presented in this paper. Tower and full models were tested under smooth and turbulent flow conditions. In the case of the tower with inclined two columns, the vibration due to wakes were occurred at wide velocity zone because the wakes with various frequencies were generated by inclined upstream column. It has to be emphasized that the vibration characteristics of the tower in the self-anchored suspension bridge may be very sensitive to the longitudinal boundary conditions of the girder at the supports. Because of the two natural frequency of the tower, out-of-plane bending and torsional, were not well separated, coupled motions were observed in a wide range of wind velocity. The effectiveness of corner cut, countermeasure to reduce the tower vibrations, was also studied. It has been found that 1:10, comer cut size to column width, may be the most effective ratio for reducing the vibrations.

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Response of Gray Rock Cod to the Colored Lights (색광에 대한 볼낙의 반응)

  • YANG Yong-Rhim
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.16 no.4
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    • pp.330-334
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    • 1983
  • The author carried out an experiment to find out the response of gray rock cod, Sebastes inermis (Cuvier et Valenciennes) to the color light. The experimental tank ($360L{\times}50W{\times}55H\;cm$) was set up in a dark room. Six longitudinal sections with 60 cm intervals are marked in the tank to observe the location of the fish. Water depth in the tank was kept 50 cm level. Light bulbs of 20W at the both ends of the tank projected the light horizontally into the tank. Two different colored filters were selected from four colors of red, blue, yellow, and white, and they were placed in front of the light bulbs to make different colors of light. Light intensity were controlled by use of auxiliary filters intercepted between the bulb and the filter. The fishes were acclimatized in the dark for 50 minutes before they were employed in the experiment. Upon turning on the light, the number of fish in each section was counted 40 times in 30 second intervals, and the mean of the number of fish in each section was given as the gathering rate of the fish. The colors favourited by the fish was found in the order of white, blue, yellow and red. The gathering rate of fish on illumination period was small and comparatively fluctuated with stability. The difference of the gathering rates on two different colors of light was much greater, regardless of illumination period, in day time than in night time.

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Study on Forced Vibration Behavior of WIG Vehicle Main Wing Structure Excited by Propulsion System (프로펠러 엔진에 의해 가진되는 소형 위그선 주날개의 진동 거동 해석에 관한 연구)

  • Kong, Chang-Duk;Yoon, Jae-Huy;Park, Hyun-Bum
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2007.11a
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    • pp.7-12
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    • 2007
  • Previously study on structural design of the main wing of the twenty-seat class WIG (Wing in Ground Effect) craft. In the final design, three spars construction was selected for safety in the critical flight load, and the Carbon-Epoxy material was selected for lightness and structural stability. In this study, the forced vibration analysis was performed on the composite main wing structure of the twenty-seat class WIG craft with two-stroke pusher type reciprocating engine. The vibration analysis based on the finite element method was performed using a commercial FEM code, MSC/NASTRAN. Excitations for the frequency response analysis were assumed as the Y-mode (lateral mode), the Z-mode (vertical mode) and the $M_{xyz}$-mode (twisted mode) which are typical main vibration modes of engine. And excitations for the transient response analysis were assumed as the X-mode (longitudinal mode) with the oscillating propeller thrust which occurs in operation.

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Beam Profile Analysis of DFB Laser for High Speed Communications (고속 통신용 DFB 레이저의 빔 분포 해석)

  • Kwon, Keeyoung
    • The Journal of the Convergence on Culture Technology
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    • v.6 no.3
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    • pp.419-425
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    • 2020
  • In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB (Distributed Feedback) laser for a 1.55 um wavelength with two mirror surfaces without an anti-reflective coating, an analysis program was developed to determine the beam distribution of the oscillation mode in the longitudinal direction. As the phases of the index and gain gratings on the mirror faces are varied, the lasing gain and the beam profiles |R(z)| and |S(z)| of the lasing mode with the emitted power ratio Pl/Pr are analyzed and examined in case of δL<0. In order to reduce the threshold current of a oscillation mode and enhance the frequency stability, κL should be greater than 8, regardless of the grating phase values at the mirror surface.