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- 저자 : ( Donghua Liao ) (검색결과 3 건)
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( Donghua Liao ),( Christian Lottrup ),( Lotte Fynne ),( Barry P Mcmahon ),( Klaus Krogh ),( Asbjørn M Drewes ),( Jingbo Zhao ),( Hans Gregersen ) 대한소화기기능성질환·운동학회(구 대한소화관운동학회) 2018 Journal of Neurogastroenterology and Motility (JNM Vol.24 No.2
Background/Aims Efficient transport through the esophago-gastric junction (EGJ) requires synchronized circular and longitudinal muscle contraction of the esophagus including relaxation of the lower esophageal sphincter (LES). However, there is a scarcity of technology for measuring esophagus movements in the longitudinal (axial) direction. The aim of this study is to develop new analytical tools for dynamic evaluation of the length change and axial movement of the human LES based on the functional luminal imaging probe (FLIP) technology and to present normal signatures for the selected parameters. Methods Six healthy volunteers without hiatal hernia were included. Data were analyzed from stepwise LES distensions at 20, 30, and 40 mL bag volumes. The bag pressure and the diameter change were used for motion analysis in the LES. The cyclic bag pressure frequency was used to distinguish dynamic changes of the LES induced by respiration and secondary peristalsis. Results Cyclic fluctuations of the LES were evoked by respiration and isovolumetric distension, with phasic changes of bag pressure, diameter, length, and axial movement of the LES narrow zone. Compared to the respiration-induced LES fluctuations, peristaltic contractions increased the contraction pressure amplitude (P < 0.001), shortening (P < 0.001), axial movement (P < 0.001), and diameter change (P < 0.01) of the narrow zone. The length of the narrow zone shortened as function of the pressure increase. Conclusions FLIP can be used for evaluation of dynamic length changes and axial movement of the human LES. The method may shed light on abnormal longitudinal muscle activity in esophageal disorders. (J Neurogastroenterol Motil 2018;24:255-267)
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Behavior of Continuous Steel-concrete Composite Beams with Web Openings
Longqi Li,Wenyuan Liao,Jun Wang,Donghua Zhou 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.4
In order to investigate the mechanical performance and load carrying capacity of continuous steel-concrete composite beams with web openings, five continuous composite beams with web openings and a contrasting continuous composite beam without web openings were tested through two symmetric point loads. Nonlinear finite element analysis was also conducted, in which the slab thickness and the reinforcement ratio of slabs were selected as the major parameters. The main results of this test were concluded as follows: (1) Web openings not only decrease the stiffness and ultimate load carrying capacity of continuous composite beams but also give rise to the redistribution of vertical shear force between the cross section of the steel beam and the concrete slab at the web opening region. (2) The plane hypothesis is not satisfied at the web opening region. The failure mode of continuous composite beams with web openings is the shear failure of concrete slab in the region near the opening, and the result also indicates that the shear bearing capacity at the span with web openings become a critical factor in controlling design. (3) Meanwhile, by increasing the thickness and reinforcement ratio of a concrete slab, the ultimate load carrying capacity and ductility of continuous composite beams increased, which can be used to the enhancement of web opening region. (4) In addition, based on the experimental results, a finite element mode was established for composite beams with web openings, and good agreement was obtained between the tested results and the numerical results.
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Study on axial compressive behavior of quadruple C-channel built-up cold-formed steel columns
Shaofeng Nie,Tianhua Zhou,Fangfang Liao,Donghua Yang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.4
In this study, the axial compressive behavior of novel quadruple C-channel built-up cold-formed steel columns with different slenderness ratio was investigated, using the experimental and numerical analysis. The axial compressive capacity and failure modes of the columns were obtained and analyzed. The finite element models considering the geometry, material and contact nonlinearity were developed to simulate and analyze the structural behavior of the columns further. There was a great correlation between the numerical analyses and test results, which indicated that the finite element model was reasonable and accurate. Then influence of, slenderness ratio, flange width-to-thickness ratio and screw spacing on the mechanical behavior of the columns were studied, respectively. The tests and numerical results show that due to small slenderness ratio, the failure modes of the specimens are generally local buckling and distortional buckling. The axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns decrease with the increase of maximum slenderness ratio. When the screw spacing is ranging from 150mm to 450mm, the axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns change little. The axial compressive capacity of quadruple C-channel built-up cold-formed steel columns increases with the decrease of flange width-thickness ratio. A modified effective length factor is proposed to quantify the axial compressive capacity of the quadruple C-channel built-up cold-formed steel columns with U-shaped track in the ends.
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