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Experimental study on temperature stress calculation and temperature control optimization of concrete based on early age parameters
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作者 HU Yintao ZHOU Qiujing +3 位作者 YANG Ning QIAO Yu JIA Fan Xin Jianda 《中国水利水电科学研究院学报(中英文)》 北大核心 2023年第6期586-597,共12页
Temperature control curve is the key to achieving temperature control and crack prevention of high concrete dam during construction,and its rationality depends on the accurate measurement of temperature stress.With th... Temperature control curve is the key to achieving temperature control and crack prevention of high concrete dam during construction,and its rationality depends on the accurate measurement of temperature stress.With the simulation testing machine for the temperature stress,in the present study,we carried out the deformation process tests of concrete under three temperature curves:convex,straight and concave.Besides,we not only measured the early-age elastic modulus,creep parameters and stress process,but also proposed the preferred type.The results show that at early age,higher temperature always leads to greater elastic modulus and smaller creep.However,the traditional indoor experiments have underestimated the elastic modulus and creep development at early age,which makes the calculated value of temperature stress too small,thus increasing the cracking risk.In this study,the stress values of the three curves calculated based on the strain and early-age parameters are in good agreement with the temperature stress measured by the temperature stress testing machine,which verifies the method accuracy.When the temperature changes along the concave curve,the law of stress development is in consistent with that of strength.Under this condition,the stress fluctuation is small and the crack prevention safety of the concave type is higher,so the concave type is better.The test results provide a reliable basis and support for temperature control curve design and optimization of concrete dams. 展开更多
关键词 concrete dam temperature control curve early-age parameters temperature stress testing machine elastic modulus
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Using modified Soil Conservation Service curve number method to simulate the role of forest in flood control in the upper reach of the Tingjiang River in China 被引量:3
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作者 LIN Wei YANG Fan +2 位作者 ZHOU Liang XU Jian-gang ZHANG Xing-qi 《Journal of Mountain Science》 SCIE CSCD 2017年第1期1-14,共14页
To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based... To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based on the Soil Conservation Service curve number(SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario,namely a coniferous forest covering 59.35km^2 is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75km^2 bamboo forest replaced by broad-leaved forest,the reduction of flood peak discharge and flood volume could be improved significantly. Specifically,flood peak discharge of 10-year return period event was reduced to 7-year event,and the reduction rate of small flood was 21%-28%. Moreover,the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods,respectively. The resultssuggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR,the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities. 展开更多
关键词 Flood control Soil Conservation Service curve number method Forest type change Scenarios simulation Tingjiang River
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Vector Field Based Sliding Mode Control of Curved Path Following for Miniature Unmanned Aerial Vehicles in Winds 被引量:9
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作者 WANG Yajing WANG Xiangke +1 位作者 ZHAO Shulong SHEN Lincheng 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2018年第1期302-324,共23页
In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles(UAVs) in winds with constant speed and altitude is developed. Different to the widely considered line or orbit followin... In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles(UAVs) in winds with constant speed and altitude is developed. Different to the widely considered line or orbit following, the curved path to be followed is defined in terms of the arc-length parameter, which can be straight lines, orbits, B-splines or any other curves provided that they are smooth. The proposed path following control algorithm, named by VF-SMC, is combining the vector field(VF) strategy with the sliding mode control(SMC) method. It is proven that the designed algorithm guarantees the tracking errors to be a bounded ball in the presence of winds, with the aid of the Lyapunov method and the BIBO stability. The algorithm is validated both in Matlab-based simulations and high-fidelity semi-physical simulations. In Matlab-based simulations, the proposed algorithm is verified for straight lines, orbits and B-splines to show its wide usage in different curves.The high-fidelity semi-physical simulation system is composed of actual autopilot controller, ground station and X-Plane flight simulator in-loop. In semi-physical simulations, the proposed algorithm is verified for B-spline path following under various gain parameters and wind conditions thoroughly.All experiments show the accuracy in curved path following and the excellent robustness to wind disturbances of the proposed algorithm. 展开更多
关键词 curved path following miniature UAVs sliding mode control vector field wind disturbance
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On global asymptotic controllability of planar affine nonlinear systems 被引量:4
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作者 SUN Yimin GUO Lei 《Science in China(Series F)》 2005年第6期703-712,共10页
In this paper, we present a necessary and sufficient condition for globally asymptotic controllability of the general planar affine nonlinear systems with single-input. This result is obtained by introducing a new met... In this paper, we present a necessary and sufficient condition for globally asymptotic controllability of the general planar affine nonlinear systems with single-input. This result is obtained by introducing a new method in the analysis, which is based on the use of some basic results in planar topology and in the geometric theory of ordinary differential equations. 展开更多
关键词 affine nonlinear system globally asymptotic controllability STABILIZATION vector field Jordan curvetheorem control curve
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Optimal Transportation for Generalized Lagrangian
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作者 Ji LI Jianlu ZHANG 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2017年第3期857-868,共12页
This paper deals with the optimal transportation for generalized Lagrangian L = L(x, u, t), and considers the following cost function: c(x, y) = inf x(0)=x x(1)=y u∈U∫0^1 L(x(s), u(x(s), s), s)ds, w... This paper deals with the optimal transportation for generalized Lagrangian L = L(x, u, t), and considers the following cost function: c(x, y) = inf x(0)=x x(1)=y u∈U∫0^1 L(x(s), u(x(s), s), s)ds, where U is a control set, and x satisfies the ordinary equation x(s) = f(x(s), u(x(s), s)).It is proved that under the condition that the initial measure μ0 is absolutely continuous w.r.t. the Lebesgue measure, the Monge problem has a solution, and the optimal transport map just walks along the characteristic curves of the corresponding Hamilton-Jacobi equation:Vt(t, x) + sup u∈U = 0,V(0, x) = Φ0(x). 展开更多
关键词 Optimal control Hamilton-Jacobi equation Characteristic curve Viscosity solution Optimal transportation Kantorovich pair Initial transport measure
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