Study on transient performance of tilting-pad thrust bearings in nuclear pump considering fluid-structure interaction

Qiang Li,Bin Li,Xiuwei Li,Quntao Xie,Qinglei Liu,Weiwei Xu Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6

To study the lubrication performance of tilting-pad thrust bearing (TPTBs) during start-up in nuclear pump, a hydrodynamic lubrication model of TPTBs was established based on the computational fluid dynamics (CFD) method and the fluid-structure interaction (FSI) technique. Further, a mesh motion algorithm for the transient calculation of thrust bearings was developed based on the user defined function (UDF). The result demonstrated that minimum film thickness increases first and then decreases with the rotational speed under start-up condition. The influence of pad tilt on minimum film thickness is greater than that of collar movement at low speed, and the establishment of dynamic pressure mainly depends on pad tilt and minimum film thickness increases. As the increase of rotational speed, the influence of pad tilt was abated, where the influence of the moving of the collar dominated gradually, and minimum film thickness decreases. For TPTBs, the circumferential angle of the pad is always greater than the radial angle. When the rotational speed is constant, the change rate of radial angle is greater than that of circumferential angle with the increase of loading forces. This study can provide reference for improving bearing wear resistance.

A Novel Adaptive Sliding Mode Control of Microbial Fuel Cell in the Presence of Uncertainty

Xiuwei Fu,Li Fu,Hashem Imani Marrani 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.6

Model-based control strategies for microbial fuel cell are able to create a balance between fuel supply, mass, charge and electric charge, performance effi ciency. This paper designs a new adaptive sliding mode control scheme of single chamber single population microbial fuel cell. The adaptive method estimates parametric uncertainty and nonlinear terms while the sliding mode method achieves microbial fuel cell performance targets. The signifi cant advantage of the suggested scheme is its capability to provide robustness against parametric uncertainties and handle systems nonlinearity. The Lyapunov technique has been used to demonstrate robust stability in the face of nonlinearity and uncertainty. Numerical simulations confi rms that the proposed control method is able to meet the desired specifi cation in the presence of varieties of parametric uncertainty.

Finite Time Robust Controller Design for Microbial Fuel Cell in the Presence of Parametric Uncertainty

Fu Li,Fu Xiuwei,Imani Marrani Hashem 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1

Microbial fuel cells are one of the most important elements in the renewable energy supply chain. To increase the effi ciency and performance of the fuel cell, designing a suitable control method is essential to achieve reliable performance and output stability. By considering the parametric uncertainties on the microbial fuel cell model as well as nonlinear terms, this paper presents a novel fi nite time adaptive sliding mode control method that achieves optimal performance of fuel cell in a fi nite time and also ensures the stability of the closed loop system. Sliding mode method without linearization or elimination of nonlinear terms has been used as a robust method to overcome uncertainty eff ects and guarantees proper operation of the fuel cell in the presence of the eff ects. The fi nite time convergence of the states is also assured by using of the proposed method. Furthermore, it uses an adaptive method to determine the sliding mode control coeffi cients which eliminates the necessity to know the upper bound of uncertainty. Finally, the simulation results show the effi ciency and stability of the proposed method in diff erent operating conditions.

Retraction Note: A Novel Adaptive Sliding Mode Control of Microbial Fuel Cell in the Presence of Uncertainty

Fu Xiuwei,Fu Li,Marrani Hashem Imani 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.5

.

The application of modified isochronal well test in a low-permeability condensate gas field

Zhaojing Zhou,Xiuwei Wang,Xue Miao,Kangning Qian,Lijian Li,Peng Xu,Xiuqin Lu 한국자원공학회 2019 Geosystem engineering Vol.22 No.6

The modified isochronal well test is a deliverability test method suitable for gas wells in low-permeability gas reservoirs. Generally, the absolute open flow of gas wells is determined by modified isochronal well test, thereby establishing a reasonable working system for gas wells. It is also possible to obtain gas layer physical parameters, gas reservoir engineering parameters, heterogeneity, boundary characteristics, etc. In this paper, the actual test data of a condensate gas field are applied. By modified isochronal well test analysis, not only the deliverability equation of the gas well is obtained, but also the absolute open flow is determined. At the same time, the formation parameters such as reservoir permeability and skin factor are obtained and the acidification effect is evaluated.

Energy-efficient Power Allocation based on worst-case performance optimization under channel uncertainties

( Xin Song Li Dong ),( Xue Huang Lei Qin ),( Xiuwei Han ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.11

In the practical communication environment, the accurate channel state information (CSI) is difficult to obtain, which will cause the mismatch of resource and degrade the system performance. In this paper, to account for the channel uncertainties, a robust power allocation scheme for a downlink Non-orthogonal multiple access (NOMA) heterogeneous network (HetNet) is designed to maximize energy efficiency (EE), which can ensure the quality of service (QoS) of users. We conduct the robust optimization model based on worse-case method, in which the channel gains belong to certain ellipsoid sets. To solve the non-convex non-liner optimization , we transform the optimization problem via Dinkelbach method and sequential convex programming, and the power allocation of small cell users (SCUs) is achieved by Lagrange dual approach. Finally, we analysis the convergence performance of proposed scheme. The simulation results demonstrate that the proposed algorithm can improve total EE of SCUs, and has a fast convergence performance.

Gallic Acid Ameliorates Cognitive Impairment Caused by Sleep Deprivation through Antioxidant Effect

Pang Xiaogang,Xu Yifan,Xie Shuoxin,Zhang Tianshu,Cong Lin,Qi Yuchen,Liu Lubing,Li Qingjun,Mo Mei,Wang Guimei,Du Xiuwei,Shen Hui,Li Yuanyuan 한국뇌신경과학회 2023 Experimental Neurobiology Vol.32 No.4

Sleep deprivation (SD) has a profound impact on the central nervous system, resulting in an array of mood disorders, including depression and anxiety. Despite this, the dynamic alterations in neuronal activity during sleep deprivation have not been extensively investigated. While some researchers propose that sleep deprivation diminishes neuronal activity, thereby leading to depression. Others argue that short-term sleep deprivation enhances neuronal activity and dendritic spine density, potentially yielding antidepressant effects. In this study, a two-photon microscope was utilized to examine the calcium transients of anterior cingulate cortex (ACC) neurons in awake SD mice in vivo at 24-hour intervals. It was observed that SD reduced the frequency and amplitude of Ca2+ transients while increasing the proportions of inactive neurons. Following the cessation of sleep deprivation, neuronal calcium transients demonstrated a gradual recovery. Moreover, whole-cell patch-clamp recordings revealed a significant decrease in the frequency of spontaneous excitatory post-synaptic current (sEPSC) after SD. The investigation also assessed several oxidative stress parameters, finding that sleep deprivation substantially elevated the level of malondialdehyde (MDA), while simultaneously decreasing the expression of Nuclear Factor erythroid 2-Related Factor 2 (Nrf2) and activities of Superoxide dismutase (SOD) in the ACC. Importantly, the administration of gallic acid (GA) notably mitigated the decline of calcium transients in ACC neurons. GA was also shown to alleviate oxidative stress in the brain and improve cognitive impairment caused by sleep deprivation. These findings indicate that the calcium transients of ACC neurons experience a continuous decline during sleep deprivation, a process that is reversible. GA may serve as a potential candidate agent for the prevention and treatment of cognitive impairment induced by sleep deprivation.