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Stable expression and control parameters in the numerical simulation of unsaturated flow

Zhiyuan ZHANG; Xu LI; Yongkang WU; Xiaokang LI

《结构与土木工程前沿（英文）》 2022年 第16卷 第12期   页码 1501-1514 doi: 10.1007/s11709-022-0893-2

摘要： The Richards’ equation describes the flow phenomenon in unsaturated porous media and is essential to hydrology and environmental science. This study evaluated the numerical stability of two different forms of the Richards’ equation. Sensitivity analyses were performed to investigate the control parameters of the equation. The results show that the h-form Richards’ equation has better applicability for calculating variable saturation flows than the θ-form Richards’ equation. For the h-form Richards’ equation, the hydraulic conductivity of the soil in the low-suction range and the specific moisture capacity in the high-suction range primarily influenced the solution. In addition, sensitivity analyses indicated that the saturated hydraulic conductivity, initial condition, and air-entry pressure have a higher sensitivity to the simulation results than the saturated water content, rainfall intensity, and decline rate of hydraulic conductivity. Moreover, their correctness needs to be guaranteed first in numerical simulations. The research findings can provide a helpful reference for improving the reliability of numerical simulations of unsaturated flows.

关键词： Richards’ equation     sensitivity analysis     unsaturated soil     hydraulic diffusivity     seepage simulation    

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Solubility and diffusivity of CO

Guilan Chen, Xingfu Song, Shuying Sun, Yanxia Xu, Jianguo Yu

《化学科学与工程前沿（英文）》 2016年 第10卷 第4期   页码 480-489 doi: 10.1007/s11705-016-1603-1

摘要： The absorption of CO in insoluble organic amine is crucial for understanding the mechanism of coupled reaction-extraction-crystallization process between aqueous chloride and CO . In this study, the solubility and diffusivity of CO in -butanol+ N235 system were measured and reported. The absorption of CO in the system is a physical absorption behavior and the solubility of CO decreases with the increase of the mass fraction of N235. The diffusivity of CO increases firstly and then decreases with the increase in the mass fraction of N235. Moreover, the absorption mechanism of CO in the coupled reaction-extraction-crystallization process was investigated and identified by experiments. The results indicated that in the coupled reaction-extraction-crystallization process, CO is absorbed by the aqueous phase rather than by the organic phase and further transferred into the aqueous phase.

关键词： carbon dioxide     N235     solubility     diffusivity     coupled process    

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Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

Yiqun HUANG, Yiran LI, Man ZHANG, Boyu DENG, Hao KONG, Junfeng WANG, Junfu LYU, Hairui YANG, Lingmei WANG

《能源前沿（英文）》 2021年 第15卷 第2期   页码 320-327 doi: 10.1007/s11708-020-0674-3

摘要： Diffusion of oxygen in the ash layer usually dominated the combustion of oil shale semicoke particles due to the high ash content. Thus, effective diffusivity of oxygen in the ash layer was a crucial parameter worthy of careful investigation. In this paper, the effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke was measured directly using an improved Wicke-Kallenbach diffusion apparatus. The experimental results showed that higher temperature would lead to a higher effective diffusivity and a thicker ash layer had the negative effect. Especially, the effective diffusivity along the direction perpendicular to bedding planes was much lower than that along the direction parallel to bedding planes. In addition, an effective diffusivity model was developed, which could be used to describe the mass transfer of oxygen in the ash layer of oil shale semicoke.

关键词： oil shale semicoke     diffusivity     pore structure     ash layer    

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Molecular dynamics simulation of diffusivity

LIU Juanfang, ZENG Danling, LI Qin, GAO Hong

《能源前沿（英文）》 2008年 第2卷 第3期   页码 359-362 doi: 10.1007/s11708-008-0039-9

摘要： Equilibrium molecular dynamics simulation was performed on water to calculate its diffusivity by adopting different potential models. The results show that the potential models have great influence on the simulated results. In addit

关键词： diffusivity     Equilibrium molecular     influence     potential    

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Multiobjective trajectory optimization of intelligent electro-hydraulic shovel

《机械工程前沿（英文）》 2022年 第17卷 第4期 doi: 10.1007/s11465-022-0706-2

摘要： Multiobjective trajectory planning is still face challenges due to certain practical requirements and multiple contradicting objectives optimized simultaneously. In this paper, a multiobjective trajectory optimization approach that sets energy consumption, execution time, and excavation volume as the objective functions is presented for the electro-hydraulic shovel (EHS). The proposed cubic polynomial S-curve is employed to plan the crowd and hoist speed of EHS. Then, a novel hybrid constrained multiobjective evolutionary algorithm based on decomposition is proposed to deal with this constrained multiobjective optimization problem. The normalization of objectives is introduced to minimize the unfavorable effect of orders of magnitude. A novel hybrid constraint handling approach based on -constraint and the adaptive penalty function method is utilized to discover infeasible solution information and improve population diversity. Finally, the entropy weight technique for order preference by similarity to an ideal solution method is used to select the most satisfied solution from the Pareto optimal set. The performance of the proposed strategy is validated and analyzed by a series of simulation and experimental studies. Results show that the proposed approach can provide the high-quality Pareto optimal solutions and outperforms other trajectory optimization schemes investigated in this article.

关键词： trajectory planning     electro-hydraulic shovel     cubic polynomial S-curve     multiobjective optimization     entropy weight technique    

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Effects of slip length and hydraulic diameter on hydraulic entrance length of microchannels with superhydrophobic

Wenchi GONG, Jun SHEN, Wei DAI, Zeng DENG, Xueqiang DONG, Maoqiong GONG

《能源前沿（英文）》 2020年 第14卷 第1期   页码 127-138 doi: 10.1007/s11708-020-0661-8

摘要： This paper investigated effects of slip length and hydraulic diameter on the hydraulic entrance length of laminar flow in superhydrophobic microchannels. Numerical investigations were performed for square microchannels with Re ranging between 0.1 and 1000. It is found that superhydrophobic microchannels have a longer hydraulic entrance length than that of conventional ones by nearly 26.62% at a low Re. The dimensionless hydraulic entrance length slightly increases with the increasing slip length at approximately Re<10, and does not vary with the hydraulic diameter. A new correlation to predict the entrance length in square microchannels with different slip lengths was developed, which has a satisfying predictive performance with a mean absolute relative deviation of 5.69%. The results not only ascertain the flow characteristics of superhydrophobic microchannels, but also suggest that super hydrophobic microchannels have more significant advantages for heat transfer enhancement at a low Re.

关键词： laminar flow     hydraulic entrance length     super hydrophobic surface     slip length     hydraulic diameter    

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Modelling the thresholds of nitrogen/phosphorus concentration and hydraulic retention time for bloom

《环境科学与工程前沿（英文）》 2022年 第16卷 第10期 doi: 10.1007/s11783-022-1564-1

摘要：

● A new model for bloom control in open land scape water was constructed.

关键词： Reclaimed water landscape     Algal bloom     Nitrogen and phosphorus     Hydraulic retention time     Threshold     Control model    

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Hydromechanical model for hydraulic fractures using XFEM

Bo HE

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 240-249 doi: 10.1007/s11709-018-0490-6

摘要： In this study, a hydromechanical model for fluid flow in fractured porous media is presented. We assume viscous fluids and the coupling equations are derived from the mass and momentum balance equations for saturated porous media. The fluid flow through discrete cracks will be modelled by the extended finite element method and an implicit time integration scheme. We also present a consistent linearization of the underlying non-linear discrete equations. They are solved by the Newton-Raphson iteration procedure in combination with a line search. Furthermore, the model is extended to includes crack propagation. Finally, examples are presented to demonstrate the versatility and efficiency of this two-scale hydromechanical model. The results suggest that the presence of the fracture in a deforming, porous media has great impact on the fluid flow and deformation patterns.

关键词： multi-phase medium     porous     fracture     multi-scale method    

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Review of fluid and control technology of hydraulic wind turbines

Maolin CAI, Yixuan WANG, Zongxia JIAO, Yan SHI

《机械工程前沿（英文）》 2017年 第12卷 第3期   页码 312-320 doi: 10.1007/s11465-017-0433-2

摘要：

This study examines the development of the fluid and control technology of hydraulic wind turbines. The current state of hydraulic wind turbines as a new technology is described, and its basic fluid model and typical control method are expounded by comparing various study results. Finally, the advantages of hydraulic wind turbines are enumerated. Hydraulic wind turbines are expected to become the main development direction of wind turbines.

关键词： wind turbine     hydraulic system     fluid model     control technology    

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Simulation analysis of pressure regulation of hydraulic thrust system on a shield tunneling machine

Zhibin LIU, Haibo XIE, Huayong YANG

《机械工程前沿（英文）》 2011年 第6卷 第3期   页码 377-382 doi: 10.1007/s11465-011-0226-y

摘要：

Hydraulic thrust system is an important system in a shield tunneling machine. Pressure regulation of thrust cylinders is the most important function for thrust system during tunnel excavation. In this paper, a hydraulic thrust system is explained, and a corresponding simulation model is carried out in order to study the system characteristics. Pressure regulation of a certain group’s cylinders has little influence on regulation of the other groups’ cylinders. The influence will not affect the process much during tunnel excavation. Pump displacement may have a greater effect on pressure regulation and oil supply flow rate should be adaptive to the system’s demand. A exacting situation is simulated to explain how pressure regulation works during tunnel excavation.

关键词： tunnel     hydraulic thrust system     pressure regulation     simulation    

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A novel high-temperature and high-pressure hydraulic pump based on mononeuron control

Linhui ZHAO, Xin FANG

《机械工程前沿（英文）》 2009年 第4卷 第2期   页码 219-223 doi: 10.1007/s11465-009-0024-y

摘要： Based on structures and characteristics of traditional hydraulic pumps, this paper proposes a novel high-temperature and high-pressure hydraulic pump (HHHP) that can work under 150°C and 28 MPa to overcome problems of traditional high-temperature plunger pumps. The HHHP is designed with the structure of mechanical division and double cylinder parallel. The control signals of two cylinders are two separate triangle waveforms with 90° phase difference. Because the output waveforms of two cylinders have the same characteristics as the control signals, the HHHP can obtain a stable output after two separate waveforms are superposed. A mononeuron self-adaptive PID control algorithm is also improved by modifying parameters and . Two improved controllers are used to control the two cylinders, respectively, making two displacements of plungers match each other. Therefore, reduced fluctuations and stable pressure output is obtained. Besides simulation, tests on the built prototype test system are carried out to verify the performance of HHHP. Results show that the improved control approach can limit fluctuations to a lower level and the HHHP system attains good outputs under different signal periods and different pressures.

关键词： mononeuron PID control     hydraulic pump     pressure fluctuation    

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Distributed monitoring and diagnosis system for hydraulic system of construction machinery

Xiaohu CHEN, Wenfeng WU, Hangong WANG, Yongtao ZHOU,

《机械工程前沿（英文）》 2010年 第5卷 第1期   页码 106-110 doi: 10.1007/s11465-009-0089-7

摘要： This paper mainly presents a distributed monitoring and diagnosis system for the hydraulic system of construction machinery based on the controller area net (CAN) field bus. The hardware of the distributed condition monitoring and fault diagnosis system is designed. Its structure including the sensors, distributed data acquisition units, central signal processing unit, and CAN field bus is introduced. The software is also programmed. The general software design and its realization are studied in detail. The experiments and applications indicate that the distributed condition monitoring and fault diagnosis system can effectively realize its function of real-time online condition monitoring and fault diagnosis for the hydraulic system of construction machinery.

关键词： construction machinery     hydraulic system     distributed condition monitoring     controller area net (CAN) field bus     fault diagnosis    

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Passive convergence-permeable reactive barrier (PC-PRB): An effective configuration to enhance hydraulic

《环境科学与工程前沿（英文）》 2022年 第16卷 第12期 doi: 10.1007/s11783-022-1591-y

摘要：

● A novel PRB configuration based on passive convergent flow effect was proposed.

关键词： Passive convergence-permeable reactive barrier (PC-PRB)     Permeable reactive barrier configuration     Numerical simulation     Hydraulic performance evaluation     Sensitivity analysis    

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Vehicle roll stability control with active roll-resistant electro-hydraulic suspension

Lijun XIAO, Ming WANG, Bangji ZHANG, Zhihua ZHONG

《机械工程前沿（英文）》 2020年 第15卷 第1期   页码 43-54 doi: 10.1007/s11465-019-0547-9

摘要： This study examines roll stability control for vehicles with an active roll-resistant electro-hydraulic suspension (RREHS) subsystem under steering maneuvers. First, we derive a vehicle model with four degrees of freedom and incorporates yaw and roll motions. Second, an optimal linear quadratic regulator controller is obtained in consideration of dynamic vehicle performance. Third, an RREHS subsystem with an electric servo-valve actuator is proposed, and the corresponding dynamic equations are obtained. Fourth, field experiments are conducted to validate the performance of the vehicle model under sine-wave and double-lane-change steering maneuvers. Finally, the effectiveness of the active RREHS is determined by examining vehicle responses under sine-wave and double-lane-change maneuvers. The enhancement in vehicle roll stability through the RREHS subsystem is also verified.

关键词： electro-hydraulic suspension     roll stability     LQR     experiment    

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Tomographic diagnosis of defects in hydraulic concrete structure

ZHAO Mingjie, XU Xibin

《结构与土木工程前沿（英文）》 2008年 第2卷 第3期   页码 226-232 doi: 10.1007/s11709-008-0027-5

摘要： The ultrasonic tomographic technology is applied to diagnose the defects in hydraulic concrete structure. In order to improve the precision of diagnoses, the wavelet transformation is used in the processing of ultrasonic signals. The influences of water, scale and orientation of defect, processing methods and theoretical model on image resolution are investigated. The experimental results indicate that the result of the tomographic diagnosis of a single defect is sensitive and the boundary can be clearly determined. However, the image resolution of multiple defects is not satisfactory. The water content and scale of a defect may significantly affect the imaging resolution. Defects with the orientation perpendicular to the direction of the diagnosis may have higher precision in diagnosing. The wavelet transformation technology can elevate the imaging resolution. The applied calculation model plays a very important role in improving the accuracy of detection.

关键词： satisfactory     processing     orientation     tomographic diagnosis     orientation perpendicular    

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标题 作者 时间 类型 操作

Stable expression and control parameters in the numerical simulation of unsaturated flow

Zhiyuan ZHANG; Xu LI; Yongkang WU; Xiaokang LI

期刊论文

Solubility and diffusivity of CO

Guilan Chen, Xingfu Song, Shuying Sun, Yanxia Xu, Jianguo Yu

期刊论文

Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

Yiqun HUANG, Yiran LI, Man ZHANG, Boyu DENG, Hao KONG, Junfeng WANG, Junfu LYU, Hairui YANG, Lingmei WANG

期刊论文

Molecular dynamics simulation of diffusivity

LIU Juanfang, ZENG Danling, LI Qin, GAO Hong

期刊论文

Multiobjective trajectory optimization of intelligent electro-hydraulic shovel

期刊论文

Effects of slip length and hydraulic diameter on hydraulic entrance length of microchannels with superhydrophobic

Wenchi GONG, Jun SHEN, Wei DAI, Zeng DENG, Xueqiang DONG, Maoqiong GONG

期刊论文

Modelling the thresholds of nitrogen/phosphorus concentration and hydraulic retention time for bloom

期刊论文

Hydromechanical model for hydraulic fractures using XFEM

Bo HE

期刊论文

Review of fluid and control technology of hydraulic wind turbines

Maolin CAI, Yixuan WANG, Zongxia JIAO, Yan SHI

期刊论文

Simulation analysis of pressure regulation of hydraulic thrust system on a shield tunneling machine

Zhibin LIU, Haibo XIE, Huayong YANG

期刊论文

A novel high-temperature and high-pressure hydraulic pump based on mononeuron control

Linhui ZHAO, Xin FANG

期刊论文

Distributed monitoring and diagnosis system for hydraulic system of construction machinery

Xiaohu CHEN, Wenfeng WU, Hangong WANG, Yongtao ZHOU,

期刊论文

Passive convergence-permeable reactive barrier (PC-PRB): An effective configuration to enhance hydraulic

期刊论文

Vehicle roll stability control with active roll-resistant electro-hydraulic suspension

Lijun XIAO, Ming WANG, Bangji ZHANG, Zhihua ZHONG

期刊论文

Tomographic diagnosis of defects in hydraulic concrete structure

ZHAO Mingjie, XU Xibin

期刊论文