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Granular Effects on Depositional Processes of Debris Avalanches
Yu-xiang Hu,Hai-bo Li,Shun-chao Qi,Gang Fan,Jia-wen Zhou 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.4
Debris avalanches generally have massive mobility and extensive deposited area, which have strong relation to the granular effect. The granular effect is an outcome from the interaction (based on frictional mechanism) among particles. Discrepancy of grain composition, for instance the difference of particle size and their proportion of particles, is a key factor to influence granular effect. A series of laboratory tests have been conducted to research the granular effects on depositional processes of debris avalanches containing fine- and coarse-grained particles. The velocity of debris front, the morphology characteristics and runout distance of the debris avalanche are considered in detail, and the mass parameter and the size parameter are introduced in analysis for the research of granular effect. The experimental results indicate that the granular effects can decrease the dissipation of momentum and increase the accumulation region, leading to further runout distance and more extensive deposited areas. Further, the velocity, the range of depositions of debris avalanches are larger than that in other conditions when the proportion of fine-grained particles is 30%, especially the materials consist of heterogeneous granular. It means there have a critical mass parameter in experiments which lead to the high efficiency of granular effects, and the granular effect is weakening in homogeneous granular composition.
Eye Fatigue State Recognition of Gabor Wavelet Optimization HMM Algorithm
Yu Xiang 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.9
It is easy for the internet learners to generate learning fatigue because of the long-term lack of emotional interaction in the learning process, and learning fatigue often manifests through the eye condition, in order to do effective monitoring for remote intelligent tutoring system, the learning fatigue eye state recognition algorithm is put forward based on Gabor wavelet and HMM. The algorithm has certain distinguishing characteristics aiming at the degree of eye openness of network learner under 3 learning states: normal learning, fatigue and confusion, first, it does gray difference disposal for eye image by Laplace operator in YCbCr color space, then, it selects two-dimension Gabor kernel function to build 48 optimal filters, obtain 48 characteristic values, these 48 characteristic values generate 48 eigenvectors, at last, it use a set of observation sequence O formed by eigenvector of HMM for eye state image to do eye state recognition. Experimental results show that the recognition rate of this algorithm for network learning reaches 95.68%, and this algorithm has a good robustness.
Numerical simulation on the coupled chemo-mechanical damage of underground concrete pipe
Xiang-nan Li,Xiao-bao Zuo,Yu-xiao Zou,Yu-juan Tang 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.86 No.6
Long-termly used in water supply, an underground concrete pipe is easily subjected to the coupled action of pressure loading and flowing water, which can cause the chemo-mechanical damage of the pipe, resulting in its premature failure and lifetime reduction. Based on the leaching characteristics and damage mechanism of concrete pipe, this paper proposes a coupled chemo-mechanical damage and failure model of underground concrete pipe for water supply, including a calcium leaching model, mechanical damage equation and a failure criterion. By using the model, a numerical simulation is performed to analyze the failure process of underground concrete pipe, such as the time-varying calcium concentration in concrete, the thickness variation of pipe wall, the evolution of chemo-mechanical damage, the distribution of concrete stress on the pipe and the lifetime of the pipe. Results show that, the failure of the pipe is a coupled chemo-mechanical damage process companied with calcium leaching. During its damage and failure, the concentrations of calcium phase in concrete decrease obviously with the time, and it can cause an increase in the chemo-mechanical damage of the pipe, while the leaching and abrasion induced by flowing water can lead to the boundary movement and wall thickness reduction of the pipe, and it results in the stress redistribution on the pipe section, a premature failure and lifetime reduction of the pipe.
New Method for Analysis of Sliding Cable Structures in Bridge Engineering
Xiang-min Yu,De-wei Chen,Zhi-zhou Bai 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.11
The Sliding Cable Structure (SCS) is widely used in bridge construction by cable crane method. The SCS generally consists of cables and fixed pulleys and the cables will slide around the pulleys when the cables are loaded until the balanced state is achieved. In this paper, an efficient Angle Bisector Method (ABM) is proposed for the mechanical analysis of SCS. The constraint effect of pulley on the cable is simulated by fixed hinge and the constraint force perpendicular to the angle bisector of cable elements adjacent to the pulley is therefore zero at balanced state. By utilizing “Unit Length Influence Matrix” (ULIM), the adjustment of unstressed length of each sub-cable can be determined. As the angle bisector at each pulley will change when the unstressed lengths of cables are changed, iterative procedures are necessary to find the convergence solutions. The proposed method is firstly verified by two examples and then applied to the analysis of cable crane during construction of the world’s longest steel truss cable-stayed bridge, namely Yachihe Bridge. Satisfactory numerical solutions can be obtained only with several iterations and are in good agreement with field measurements from the cable crane load tests, which confirms the accuracy and validity of the proposed method.
Xiang-Yu Guan,임정우,이수현,장호진,김정호,한수욱,유재수 한국물리학회 2016 Current Applied Physics Vol.16 No.2
The device performance improvement of ridge waveguide (RWG) laser diodes (LDs), operating at a wavelength (l) of ~960 nm, with a metal-dielectric high-reflection (HR) mirror consisting of Au/TieSiO2 layers on the back facet was demonstrated. To determine the optimum thickness of each layer, optical reflection calculations were performed using a rigorous coupled-wave analysis method, which leads to the resultant Au (80 nm)/Ti (5 nm)eSiO2 (164 nm) layers. The layers exhibited a broad high reflection band of >91% over a wavelength range of 920e1000 nm, indicating the reflectivity of ~91.2% at l ~ 960 nm. For 2 mm-cavity RWG LDs with the Au/TieSiO2 HR mirror, an enhanced maximum output power (Pmax) of 499.3 mW at an injection current of 3000 mA and a decreased threshold current (Ith) of 516 mA (i.e., Pmax ¼ 259.4 mW and Ith ¼ 650 mA for the uncoated LDs) were obtained, showing an increased slope efficiency percentage of 82%. The external differential quantum efficiency was also increased from ~17.1 to ~31.1%. Also, the full widths at half maximum values of beam divergences of the device were 38 (vertical direction) and 4 (horizontal direction).
Mechanical behavior of stud shear connectors embedded in HFRC
Yu-Liang He,Xu-Dong Wu,Yiqiang Xiang,Yu-Hang Wang,Li-Si Liu,Zhi-Hai He 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.24 No.2
Hybrid-fiber reinforced concrete (HFRC) may provide much higher tensile and flexural strengths, tensile ductility, and flexural toughness than normal concrete (NC). HFRC slab has outstanding advantages for use as a composite bridge potential deck slab owing to higher tensile strength, ductility and crack resistance. However, there is little information on shear connector associated with HFRC slabs. To investigate the mechanical behavior of the stud shear connectors embedded in HFRC slab, 14 push-out tests (five batches) in HFRC and NC were conducted. It was found that the stud shear connector embedded in HFRC had a better ductility, higher stiffness and a slightly larger shear bearing capacity than those in NC. The experimentally obtained ultimate resistances of the stud shear connectors were also compared against the equations provided by GB50017 2003, ACI 318-112011, AISC 2011, AASHTO LRFD 2010, PCI 2004, and EN 1994-1-1 (2004), and an empirical equation to predict the ultimate shear connector resistance considering the effect of the HFRC slabs was proposed and validated by the experimental data. Curve fitting was performed to find fitting parameters for all tested specimens and idealized load-slip models were obtained for the specimens with HFRC slabs.
Yu-Xiang Yang,Zhen-Hua Xu,Yu-Qian Zhang,Jing Tian,Li-Xing Weng,Lian-Hui Wang 한국미생물학회 2012 The journal of microbiology Vol.50 No.6
Quorum sensing (QS) has been a novel target for the treatment of infectious diseases. Here structural analogs of Pseudomonas aeruginosa autoinducer N-acyl homoserine lactone (AHL) were investigated for QS inhibitor (QSI) activity and a novel QSI was discovered, N-decanoyl-L-homoserine benzyl ester (C2). Virulence assays showed that C2 downregulated total protease and elastase activities, as well as the production of rhamnolipid, that are controlled by QS in P.aeruginosa wild-type strain PAO1 without affecting growth. C2 was also shown to inhibit swarming motility of PAO1. Using a microdilution checkerboard method, we identified synergistic interactions between C2 and several antibiotics, tobramycin, gentamycin, cefepime, and meropenem. Data from real-time RT-PCR suggested that C2 inhibited the expression of lasR (29.67%), lasI (21.57%), rhlR (28.20%), and rhlI (29.03%).