Hydrodynamic effects of reconnecting lake group with Yangtze River in China

The hydrodynamic effects of reconnecting a lake group with the Yangtze River were simulated using a three-dimensional hydrodynamic model. The model was calibrated and validated using the measured water temperature and total phosphorous. The circulation patterns, water temperature, and water exchange conditions between sub-lakes were simulated under two conditions: (1) the present condition, in which the lake group is isolated from the Yangtze River; and (2) the future condition, with a proposed improvement in which connecting the lake group with the Yangtze River will allow river water to be diverted into the lake group. The simulation period selected was characterized by extremely high temperature and very little rain. The results show that the cold inflow from the river has a significant effect on the water temperature only near the inlets, and the effect is more obvious in the lower water layers than that in the upper ones. The circulation pattern changes significantly and small-scale vortices only exist in part of the lake regions. The water exchange between sub-lakes is greatly enhanced with the proposed improvement. The water replacement rate increases with water diversion but varies in different sub-lakes. Finally, a new water diversion scheme was proposed to avoid contamination of some lakes in the early stage.

Non-dominated sorting culture differential evolution algorithm for multi-objective optimal operation of Wind-Solar-Hydro complementary power generation system

Due to the intermittency and instability of Wind-Solar energy and easy compensation of hydropower, this study proposes a Wind-Solar-Hydro power optimal scheduling model. This model is aimed at maximizing the total system power generation and the minimum ten-day joint output. To effectively optimize the multi-objective model, a new algorithm named non-dominated sorting culture differential evolution algorithm(NSCDE) is proposed. The feasibility of NSCDE was verified through several well-known benchmark problems. It was then applied to the Jinping Wind-Solar-Hydro complementary power generation system. The results demonstrate that NSCDE can provide decision makers a series of optimized scheduling schemes.

CONCEPTUAL ANALYSIS AND RANDOM ATTRACTOR FOR DISSIPATIVE RANDOM DYNAMICAL SYSTEMS

The aim of this work is to understand better the long time behaviour of asymptotically compact random dynamical systems(RDS),which can be generated by solutions of some stochastic partial differential equations on unbounded domains.The conceptual analysis for the long time behavior of RDS will be done through some examples. An application of those analysis will be demonstrated through the proof of the existence of random attractors for asymptotically compact dissipative RDS.

Investigation on hydrogen-induced cracking susceptibility of HG980D steel with yield strength 900 MPa

In this paper,the microstructure and hardness of HG980D heat-affected zone (HAZ) at different cooling rate t8/3 were studied,the implant critical fracture stress under three diffusible hydrogen conditions were measured,and the hydrogen-induced cracking (HIC) fractograph of steel HG980D were analyzed. The experimental results show that martensite exists in HAZ of HG980D till t8/3≥150 s,the harden quenching tendency of HG980D is greater; The implant critical fracture stress is related to diffusible hydrogen content significantly,at low hydrogen level,high restraint stress is needed to nucleate HIC,the fractograph is mainly microvoid coalescence,but at high hydrogen level,only small restraint stress can cause HIC occurrence,the fractograph is mainly quasicleavage. It is very important to choose ultra-low hydrogen welding consumable to weld steel HG980D to prevent hydrogen-induced cracking.

A Remote Sensing Image Semantic Segmentation Method by Combining Deformable Convolution with Conditional Random Fields

Currently,deep convolutional neural networks have made great progress in the field of semantic segmentation.Because of the fixed convolution kernel geometry,standard convolution neural networks have been limited the ability to simulate geometric transformations.Therefore,a deformable convolution is introduced to enhance the adaptability of convolutional networks to spatial transformation.Considering that the deep convolutional neural networks cannot adequately segment the local objects at the output layer due to using the pooling layers in neural network architecture.To overcome this shortcoming,the rough prediction segmentation results of the neural network output layer will be processed by fully connected conditional random fields to improve the ability of image segmentation.The proposed method can easily be trained by end-to-end using standard backpropagation algorithms.Finally,the proposed method is tested on the ISPRS dataset.The results show that the proposed method can effectively overcome the influence of the complex structure of the segmentation object and obtain state-of-the-art accuracy on the ISPRS Vaihingen 2D semantic labeling dataset.

Assessing Danger Degree of Soil Erosion in Rikaze Prefecture,Tibet

Ten indicators were selected in the present paper con-cerns current status of soil erosion and its driving forces. Synthe-sized evaluation model on danger degree of soil erosion(DDSE) was built and estimation on DDSE in Rikaze was carried out by analytical hierarchy process(AHP) . This evaluation model se-lected indicators scientifically and reasonably,which are easy to be caught,and played well in application. Results showed that a light erosion danger degree exists in Nanmulin,Xietongmen and Angren;Dingri,Sajia,Saga,Zhongba;Nielamu,Gangba,Kangma and Rikaze County share a moderate danger degree,while other counties own severe erosion,especially Dingjie and Lazi County. Ecological environment in Rikaze is frangible. Therefore,eco-restoration and corresponding countermeasures are urgently needed in this region to guarantee a regional eco-environment healthy.

EXPERIMENTAL FEEDBACK ON THE INVESTIGATION OF HYDRAULIC CHARACTERISTICS FOR THE SHIP-LOCK FILLING AND EMPTYING SYSTEM OF TGP

Where hydraulic characteristics of ship-lock filling and emptying system are concerned, there are much bigger differences between prototype and model experiments. Based on the results of the prototype experiments for the Three Gorges Project (TGP), experiments on the feedback model were conducted of the ship-lock filling and emptying system, by means of technologies of drag reduction, under similar conditions as the operation of the prototype project. The experimental results show that the difference of drag coefficient reached -44% between the prototype and the model for the filling and emptying system of the ship-lock No.3 for TGP and the difference of discharge coefficient was about 33% between them. The technologies of drag reduction are more efficient in the simulation of a ship-lock filling and emptying system in order to be consistent for discharge, water level, time average pressure and pulsating pressure between prototypes and models.

Vertical two-dimensional non-hydrostatic pressure model with single layer

The vertical two-dimensional non-hydrostatic pressure models with multiple layers can make prediction more accurate than those obtained by the hydrostatic pressure assumption. However, they are time-consuming and unstable, which makes them unsuitable for wider application. In this study, an efficient model with a single layer is developed. Decomposing the pressure into the hydrostatic and dynamic components and integrating the x-momentum equation from the bottom to the free surface can yield a horizontal momentum equation, in which the terms relevant to the dynamic pressure are discretized semi-implicitly. The convective terms in the vertical momentum equation are ignored, and the rest of the equation is approximated with the Keller-box scheme. The velocities expressed as the unknown dynamic pressure are substituted into the continuity equation, resulting in a tri-diagonal linear system solved by the Thomas algorithm. The validation of solitary and sinusoidal waves indicates that the present model can provide comparable results to the models with multiple layers but at much lower computation cost.

Mapping-Based 3D Hexahedral Finite Element Mesh Generation Method

Mapping mesh generation is widely applied in pre-processes of Finite Element Method (FEM). In this study, the basic 3D mapping equations by Lagrange interpolating function are founded. Based these equations, a mapping pattern library, which maps essential configurations e.g. line, circle, rotary body, sphere etc. to hexahedral FEM mesh, has been built. Then available FEM mesh will be generated by clipping and assembling the mapped essential objects. Study case illustrates that the proposed method is simple and efficient to generate valid FEM mesh for complex 3D engineering structure.

Terminal Sliding Mode Controllers for Hydraulic Turbine Governing System with Bifurcated Penstocks under Input Saturation

Terminal sliding mode controller method is introduced to enhance the regulation performance of the hydraulic turbine governing system(HTGS).For the purpose of describing the characteristics of controlled system and deducing the control rule,a nonlinear mathematic model of hydraulic turbine governing system with bifurcated penstocks(HTGSBF)under control input saturation is established,and the input/output state linearization feedback approach is used to obtain the relationship between turbine speed and controller output.To address the control input saturation problem,an adaptive assistant system is designed to compensate for controller truncation.Numerical simulations have been conducted under fixed point stabilization and periodic orbit tracking conditions to compare the dynamic performances of proposed terminal sliding mode controllers and conventional sliding mode controller.The results indicate that the proposed terminal sliding mode controllers not only have a faster response and accurate tracking results,but also own a stronger robustness to the system parameter variations.Moreover,the comparisons between the proposed terminal sliding mode controllers and current most often used proportional-integral-differential(PID)controller,as well its variant NPID controller,are discussed at the end of this paper,where the superiority of the terminal sliding mode controllers also have been verified.

A new depth-integrated non-hydrostatic model for free surface flows

A new depth-integrated model deploying a non-hydrostatic pressure distribution is presented.With the pressure divided into hydrostatic and dynamic components,the horizontal momentum equations were obtained by integrating the Navier-Stokes equations from the bottom to the free surface.The vertical momentum equation,in which the convective and viscosity terms were omitted,was approximated by the Keller-box scheme.The model has two steps.First,the dynamic pressure gradient terms were discretized semi-implicitly and the other terms were in explicit scheme.Second,the velocities expressed as the unknown dynamic pressure were substituted into the continuity equation,resulting in a five-diagonal symmetric matrix linear system that was solved by the conjugate gradient method.The model was validated with the propagation of a solitary wave and sinusoidal wave,indicating that it can predict free surface flows well.