• Title/Summary/Keyword: Curvature Theory

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A Case of Dieulafoy's Disease in a Child (소아의 Dieulafoy병 치험 1례)

  • Lee, Eui-Sung;Oh, Chang-Hee;Kim, Je-Woo;Chung, Ki-Sup;Han, Suk-Joo
    • Pediatric Gastroenterology, Hepatology & Nutrition
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    • v.2 no.1
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    • pp.80-84
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    • 1999
  • Dieulafoy's disease, a vascular anomaly mainly in the upper stomach, is a rare but potentially life-threatening cause of upper gastrointestinal bleeding. Pathogenesis is still controversial, but the most accepted theory is that a persistent caliber vessel in the submucosa is exposed by a small mucosal erosion leading to massive bleeding. The bleeding site is usually within 6 cm of the esophagogastric junction in the cardia or fundus of the stomach. The treatment of choice is therapeutic endoscopy or surgery. The age of patients reported is mainly between 50 and 70 years, and patients of pediatric age are extremely rare. We are reporting a 5-year-old male patient who had Dieulafoy's disease which was diagnosed by emergency upper gastrointestinal endoscopy. Endoscopic finding was a nodular lesion with an adherent clot on the lessor curvature of the stomach 2 cm below the esophagogastric junction. Epinephrine and $Beriplast^{(R)}$ was injected in the lesion. On the second day after endoscopic sclerotherapy, the patient had recurred massive hematemesis and accompanying shock. So we performed gastrotomy and ligation. After the operation, he showed an improved general condition and was discharged at the 12th hospital day.

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A Study on Behavior of Anisotrpic Circular Cylingdrical Shell including Large Deformation Effects (대변형 효과를 고려한 비등방성 원통형 쉘의 거동에 관한 연구)

  • Chun, Kyoung Sik;Son, Byung Jik;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.14 no.4
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    • pp.489-497
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    • 2002
  • Nonlinear behavior and large deformation cannot be analyzed using techniques based on linear theory. Nonetheless, they are emerging as gradually huge and complex structures. In addition, the optimum design of structure is necessary in the development of high-performance computation and numerical methods. as well as stricter design-criterion. Therefore, the structural problems in engineering that are limited to the linear region must be extended to the nonlinear region. Likewise, structural behavior must be accurately analyzed. In turn, this requires considering the expected problems beforehand. Only then can an efficient, economical, and optimized structure be designed. This paper presents the solution of the geometrical nonlinear problem of anisotropic cylindrical shell. The characteristics of the geometrical nonlinear behavior of anisotropic circular cylindrical shells may vary according to several causes. e.g., change of fibers, curvature in the circumferential direction, subtended angle, aspect, etc. Parametric studies were conducted to determine the effect of factors on the large deflection behavior of laminated shells, with interesting observations.

An evaluation of curve of Spee using cone beam computerized tomography in Korean (한국인에서 콘빔형 전산화단층영상을 이용한 스피만곡 평가)

  • Oh, Sang-Chun;Kim, Seul-Gi;Kim, Yu-Jin
    • Journal of Dental Rehabilitation and Applied Science
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    • v.30 no.2
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    • pp.93-101
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    • 2014
  • Purpose: The aim of this study is to investigate the typical shape of the curve of Spee in Korean and analyze the curve of Spee according to gender, age, and left and right. Materials and Methods: Among the patient of Wonkwang University Sanbon Dental Hospital taking cone beam computerized tomography, the images of 500 Koreans (311 males and 189 females) who qualifies the criteria of this study were selected and their curve of Spee were analysed in sagittal plane. Results: The mean radius of curve of Spee in Korean was 91.4 mm. There was statistically significant difference between male (94.6 mm) and female (86.1 mm) by gender, but not significant differences by age and between right and left side. Conclusion: Within the limitation of this study, the smaller radius (91.4 mm) of Korean than the 4-inch (101.6 mm) value advocated by Monson was meaned that it would be need to reconsider the application of the curve of Spee in all cases when occlusal plane is reconstructed in Korean.

Generation of Subdivision Surface and First-order Shear Deformable Shell Element Based on Loop Subdivision Surface (서브디비전의 다중해상도 기능을 이용한 곡면의 모델링과 유한요소 해석)

  • 김형길;서홍석;조맹효
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.2
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    • pp.151-160
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    • 2004
  • In the present study, Loop scheme is applied to generate smooth surfaces. To be consistent with the limit points of target surface, the initial sampling points are properly rearranged. The pointwise errors of curvature and position in the sequence of subdivision process are evaluated in the Loop subdivision scheme. A first-order shear deformable Loop subdivision triangular element which can handle transverse shear deformation of moderately thick shell are developed. The developed element is more general than the previous one based on classical shell theory, since the new one includes the effect of transverse shear deformation and has standard six degrees of freedom per node. The quartic box spline function is used as interpolation basis function. Numerical examples for the benchmark static shell problems are analyzed to assess the performance of the developed subdivision shell element and locking trouble.

FE Based Numerical Model to Consider Bond-slip Effect in Composite Beams (합성보의 부착슬립 효과를 고려한 유한요소 기반의 수치해석모델)

  • Kwak, Hyo-Gyoung;Hwang, Jin-Wook
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.1
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    • pp.95-110
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    • 2010
  • A numerical model to simulate bond-slip behavior of composite beam bridges is introduced in this paper. Assuming a linear bond stress-slip relation along the interface between the slab and girder, the slip behavior is implemented into a finite element formulation. Adopting the introduced model, the slip behavior can be taken account even in a beam element which is composed of both end nodes only. Governing equation of the slip behavior, based on the linear partial interaction theory, can be determined from the force equilibrium and a constant curvature distribution across the section of a composite beam. Since the governing equation for the slip behavior requires the moment values at both end nodes, the piecewise linear distribution of the constant bending moment in an element is assumed. Analysis results by the model are compared with numerical results and experimental values, and load-displacement relations of composite beams were then evaluated to verify the validity of the proposed model.

Effects of Fuel Nozzle Diameter in the Behavior of Laminar Lifted Flame (노즐 직경 변화가 층류부상화염 거동에 미치는 영향)

  • Kim, Tae-Kwon;Um, Hyen-Soo;Kim, Kyung-Ho;Ha, Ji-Soo;Park, Jeong
    • Journal of the Korean Institute of Gas
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    • v.12 no.2
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    • pp.77-84
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    • 2008
  • Experimental study was conducted to clarify the importance of buoyancy effects in laminar lifted flames which have been well understood by cold jet similarity theory. To evaluate buoyancy effects, lifted flame behaviors were systematically observed in methane and propane lifted flames diluted with He as changing the fuel nozzle diameter from 0.1 to 6 mm. Important physical parameters such as fuel strength, flame stretch and flame curvature, which were derived through simple physical scaling laws, were estimated. It is experimentally proven that buoyancy effects are important in relatively large fuel nozzle diameter and large fuel dilution with He. The results of Chen et al., which displayed the existence of stably lifted flames for 0.5

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Stochastic hygrothermoelectromechanical loaded post buckling analysis of piezoelectric laminated cylindrical shell panel

  • Lal, Achchhe;Saidane, Nitesh;Singh, B.N.
    • Smart Structures and Systems
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    • v.9 no.6
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    • pp.505-534
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    • 2012
  • The present work deals with second order statistics of post buckling response of piezoelectric laminated composite cylindrical shell panel subjected to hygro-thermo-electro-mechanical loading with random system properties. System parameters such as the material properties, thermal expansion coefficients and lamina plate thickness are assumed to be independent of the temperature and electric field and modeled as random variables. The piezoelectric material is used in the forms of layers surface bonded on the layers of laminated composite shell panel. The mathematical formulation is based on higher order shear deformation shell theory (HSDT) with von-Karman nonlinear kinematics. A efficient $C^0$ nonlinear finite element method based on direct iterative procedure in conjunction with a first order perturbation approach (FOPT) is developed for the implementation of the proposed problems in random environment and is employed to evaluate the second order statistics (mean and variance) of the post buckling load of piezoelectric laminated cylindrical shell panel. Typical numerical results are presented to examine the effect of various environmental conditions, amplitude ratios, electrical voltages, panel side to thickness ratios, aspect ratios, boundary conditions, curvature to side ratios, lamination schemes and types of loadings with random system properties. It is observed that the piezoelectric effect has a significant influence on the stochastic post buckling response of composite shell panel under various loading conditions and some new results are presented to demonstrate the applications of present work. The results obtained using the present solution approach is validated with those results available in the literature and also with independent Monte Carlo Simulation (MCS).

Model for fiber Cross-Sectional Analysis of FRP Concrete Members Based on the Constitutive Law in Multi-Axial Stress States (다축응력상태의 구성관계에 기초한 FRP 콘크리트 부재의 층분할 단면해석모델)

  • 조창근;김영상;배수호;김환석
    • Journal of the Korea Concrete Institute
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    • v.14 no.6
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    • pp.892-899
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    • 2002
  • Among the methods for enhancement of load-carrying capacity on flexural concrete member, recently, a concept is being investigated which replaces the steel in a conventional reinforced concrete member with a fiber reinforced polymer(FRP) shell. This study focuses on modeling of the structural behavior of concrete surrounded with FRP shells in flexural bending members. A numerical model of fiber cross-sectional analysis is proposed to predict the stress and deformation state of the FRP shell and concrete. The stress-strain relationship of concrete confined by a FRP shell is formulated to be based on the constitutive law of concrete in multi-axial compressive stress state, in assuming that the compression response is dependent on the radial expansion of the concrete. To describe the FRP shell behavior, equivalent orthotropic properties of in-plane behavior from classical lamination theory are used. The present model is validated to compare with the experiments of 4-point bending tests of FRP shell concrete beam, and has well predicted the moment-curvature relationships of the members, axial and hoop strains in the section, and the enhancement of confinement effect in concrete surrounded by FRP shell.

Influence of Detailed Structure and Curvature of Woven Fabric on the Luminescence Effect of Wearable Optical Fiber Fabric (직물의 세부 구조 및 굴곡이 웨어러블 광섬유의 발광 효과에 미치는 영향)

  • Yang, Jin-Hee;Cho, Hyun-Seung;Kwak, Hwy-Kuen;Oh, Yun-Jung;Lee, Joo-Hyeon
    • Science of Emotion and Sensibility
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    • v.21 no.4
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    • pp.55-62
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    • 2018
  • The two main requirements of wearable optical fiber fabrics are that they must presuppose a high degree of flexibility and they must maintain the luminance effect in both flat and bent conformations. Therefore, woven optical fiber fabrics that satisfy the above conditions were developed by both weaving and by using computer embroidery. First, we measured the brightness of the wearable optical fiber fabric in the flat state at a total of 10 measurement points at intervals of 1 cm. Second, the wearable optical fiber fabric was placed horizontally on the forearm, where three-dimensional bending occurs, and the luminance values were recorded at the same 10 measurement points. For the woven fabric in the flat state, the maximum, minimum, average, and standard deviation luminance values were $5.23cd/m^2$, $2.74cd/m^2$, $3.56cd/m^2$, and $1.11cd/m^2$, respectively. The corresponding luminance values from the bent forearm were $7.92cd/m^2$ (maximum), $2.37cd/m^2$ (minimum), $4.42cd/m^2$ (average), and $2.16cd/m^2$ (standard deviation). In the case of the computer-embroidered fabric, the maximum, minimum, average, and standard deviation luminance values in the flat state were $7.56cd/m^2$, $3.84cd/m^2$, $5.13cd/m^2$, and $1.04cd/m^2$, respectively, and in the bent forearm state were $9.6cd/m^2$, $3.63cd/m^2$, $6.13cd/m^2$, and $2.26cd/m^2$, respectively. Therefore, the computer-embroidered fabric exhibited a higher luminous effect than the woven fabric because the detailed structure reduced light-loss due to the backside fabric. In both types of wearable optical fiber fabric the luminance at the forearm was 124% and 119%, respectively, and the light emitting effect of the optical fiber fabric was maintained even when bent by the human body. This is consistent with the principle of Huygens, which defines the wave theory of light, and also the Huygens-Fresnel-Kirchhoff principle, which states that the intensity of light increases according to the magnitude of the angle of propagation of the light wavefront (${\theta}$).

Free Vibration Analysis of Horizontally Curved I-Girder Bridges using the Finite Element Method (유한요소법을 이용한 수평곡선 I형교의 자유진동해석)

  • Yoon, Ki Yong;Kang, Young Jong
    • Journal of Korean Society of Steel Construction
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    • v.10 no.1 s.34
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    • pp.47-61
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    • 1998
  • The behavior of horizontally curved I-girder bridges is complex because the flexural and torsional behavior of curved girders are coupled due to their initial curvature. Also, the behavior is affected by cross beams. To investigate the behavior of horizontally curved I-girder bridges, it is necessary to consider curved girders with cross beams. In order to perform free vibration analyses of horizontally curved I-girder bridges, a finite element formulation is presented here and a finite element analysis program is developed. The formulation that is presented here consists of curved and straight beam elements, including the warping degree of freedom. Based on the theory of thin-walled curved beams, the shape functions of the curved beam elements are derived from homogeneous solutions of the static equilibrium equations. Third-order hermits polynomials are used to form the shape functions of the straight beam elements. In the finite element analysis program, global stiffness and mass matrix are composed, based on the Cartesian coordinate system. The Gupta method is used to efficiently solve the eigenvalue problem. Comparing the results of several examples here with those of previous studies, the formulation presented is verified. The validity of the program developed is shown by comparing results with those analyzed by the shell element.

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