Numerical simulation of fully nonlinear sloshing waves in three-dimensional tank under random excitation

Xu, Gang,Hamouda, A.M.S.,Khoo, B.C. Techno-Press 2011 Ocean systems engineering Vol.1 No.4

Based on the fully nonlinear velocity potential theory, the liquid sloshing in a three dimensional tank under random excitation is studied. The governing Laplace equation with fully nonlinear boundary conditions on the moving free surface is solved using the indirect desingularized boundary integral equation method (DBIEM). The fourth-order predictor-corrector Adams-Bashforth-Moulton scheme (ABM4) and mixed Eulerian-Lagrangian (MEL) method are used for the time-stepping integration of the free surface boundary conditions. A smoothing scheme, B-spline curve, is applied to both the longitudinal and transverse directions of the tank to eliminate the possible saw-tooth instabilities. When the tank is undergoing one dimensional regular motion of small amplitude, the calculated results are found to be in very good agreement with linear analytical solution. In the simulation, the normal standing waves, travelling waves and bores are observed. The extensive calculation has been made for the tank undergoing specified random oscillation. The nonlinear effect of random sloshing wave is studied and the effect of peak frequency used for the generation of random oscillation is investigated. It is found that, even as the peak value of spectrum for oscillation becomes smaller, the maximum wave elevation on the side wall becomes bigger when the peak frequency is closer to the natural frequency.

Customer Sentiment Analysis: Take Restaurant Online Reviews as an Example

Xu Gang 사단법인 미래융합기술연구학회 2020 아시아태평양융합연구교류논문지 Vol.6 No.6

The customer's sentiment analysis can fully grasp the customer's consumption trends and the popularity of the product. This article takes the restaurant's online reviews as an example and uses machine learning algorithms to analyze the customer's sentiment tendency. The research describes the overall process of sentiment analysis, and discusses the implementation methods of corpus acquisition, feature extraction, feature selection, expanded sentiment dictionary construction, and determination of class labels. The training method of machine learning sentiment analysis model is analyzed. After the experimental analysis of the obtained corpus, the experimental results are given through the chart. The C4.5, Bagging, Multinomial naïve bayes algorithm has achieved good results.

Imide-functionalized Polymers for High-performance Organic Thin-film Transistors and Polymer Solar Cells

Xugang Guo 한국고분자학회 2018 한국고분자학회 학술대회 연구논문 초록집 Vol.43 No.2

Bithiophene-Imide-Based Polymeric Semiconductors for Field-Effect Transistors: Synthesis, Structure−Property Correlations, Charge Carrier Polarity, and Device Stability

Guo, Xugang,Ortiz, Rocio Ponce,Zheng, Yan,Hu, Yan,Noh, Yong-Young,Baeg, Kang-Jun,Facchetti, Antonio,Marks, Tobin J. American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.5

Performance evaluation of inerter-based damping devices for structural vibration control of stay cables

Zhiwen Huang,Xugang Hua,Zhengqing Chen,Huawei Niu 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.6

Inerter-based damping devices (IBBDs), which consist of inerter, spring and viscous damper, have been extensively investigated in vehicle suspension systems and demonstrated to be more effective than the traditional control devices with spring and viscous damper only. In the present study, the control performance on cable vibration reduction was studied for four different inerter-based damping devices, namely the parallel-connected viscous mass damper (PVMD), series-connected viscous mass damper (SVMD), tuned inerter dampers (TID) and tuned viscous mass damper (TVMD). Firstly the mechanism of the ball screw inerter is introduced. Then the state-space formulation of the cable-TID system is derived as an example for the cable-IBBDs system. Based on the complex modal analysis, single-mode cable vibration control analysis is conducted for PVMD, SVMD, TID and TVMD, and their optimal parameters and the maximum attainable damping ratios of the cable/damper system are obtained for several specified damper locations and modes in combination by the Nelder-Mead simplex algorithm. Lastly, optimal design of PVMD is developed for multi-mode vibration control of cable, and the results of damping ratio analysis are validated through the forced vibration analysis in a case study by numerical simulation. The results show that all the four inerter-based damping devices significantly outperform the viscous damper for single-mode vibration control. In the case of multi-mode vibration control, PVMD can provide more damping to the first four modes of cable than the viscous damper does, and their maximum control forces under resonant frequency of harmonic forced vibration are nearly the same. The results of this study clearly demonstrate the effectiveness and advantages of PVMD in cable vibration control.

Consensus-Based Finite-Time Cooperative Guidance with Field-of-View Constraint

Shuai Ma,Xugang Wang,Zhongyuan Wang,Qi Chen 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.5

The problem of cooperative guidance of multiple missiles with field-of-view constraint is addressed based on consensus theory. Considering the singularity problem when the second-order consensus algorithm is directly applied to missile guidance, a novel finite-time consensus algorithm with field-of-view constraint is derived and proved. The singularity problem is also avoided. Cooperative guidance law under 2D and 3D engagement is designed using a two-stage guidance scheme. In the first stage, a decentralized guidance law is designed based on the derived finite-time consensus algorithm to provide the latter stage’s desired initial conditions, and proportional navigation guidance law is used in the second stage. The proposed cooperative guidance law requires neither time-to-go estimation nor controllable velocity magnitude. Compared with other two-stage guidance schemes, the proposed cooperative guidance law can provide better initial conditions for the second stage. Numerical simulation and comparison work demonstrate the effectiveness and superiority of the proposed cooperative guidance law.

An empirical model for amplitude prediction on VIV-galloping instability of rectangular cylinders

Huawei Niu,Zhengqing Chen,Xugang Hua,Shuai Zhou 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.1

Aerodynamic forces of vortex-induced vibration and galloping are going to be coupled when their onset velocities are close to each other, which will induce the cross-wind amplitudes of the structures increased continuously with ever-increasing wind velocities. The main purpose of the present work is going to propose an empirical formula to predict the response amplitude of VIV-galloping interaction. Firstly, two typical mathematical models for the coupled oscillations, i.e., Tamura & Shimada model and Parkinson & Corless model are comparatively summarized. Then, the key parameter affecting response amplitude is determined through comparative numerical simulations with Tamura & Shimada model. For rectangular cylinders with the side ratio from 0.5 to 2.5, which are actually prone to develop the VIV and galloping induced interaction responses, an empirical amplitude prediction formula is proposed after regression analysis on comprehensively collected experimental data with the predetermined key parameter.

Mitigation of wind-induced vibrations of bridge hangers using tuned mass dampers with eddy current damping

Huawei Niu,Zhengqing Chen,Xugang Hua,Wei Zhang 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.6

To mitigate vibrations, tuned mass dampers (TMD) are widely used for long span bridges or high-rise buildings. Due to some durability concerns, such as fluid degradation, oil leakage, etc., the alternative solutions, such as the non-contacted eddy current damping (ECD), are proposed for mechanical devices in small scales. In the present study, a new eddy current damping TMD (ECD-TMD) is proposed and developed for large scale civil infrastructure applications. Starting from parametric study on finite element analysis of the ECD-TMD, the new design is enhanced via using the permanent magnets to eliminate the power need and a combination of a copper plate and a steel plate to improve the energy dissipation efficiency. Additional special design includes installation of two permanent magnets at the same side above the copper plate to easily adjust the gap as well as the damping. In a case study, the proposed ECD-TMD is demonstrated in the application of a steel arch bridge to mitigate the wind-induced vibrations of the flexible hangers. After a brief introduction of the configuration and the installation process for the damper, the mitigation effects are measured for the ambient vibration and forced vibration scenarios. The results show that the damping ratios increase to 3% for the weak axis after the installation of the ECD-TMDs and the maximum vibration amplitudes can be reduced by 60%.

Nicotinamide Mononucleotide Adenylyl Transferase 2 Inhibition Aggravates Neurological Damage after Traumatic Brain Injury in a Rat Model

Xiaoyu Gu,Haibo Ni,XuGang Kan,Chen Chen,Zhiping Zhou,Zheng Ding,Di Li,Bofei Liu 대한신경외과학회 2023 Journal of Korean neurosurgical society Vol.66 No.4

Objective : Nicotinamide mononucleotide adenylyl transferase 2 (NMNAT2) is a crucial factor for the survival of neuron. The role of NMNAT2 in damage following traumatic brain injury (TBI) remains unknown. This study was designed to investigate the role of NMNAT2 in TBI-induced neuronal degeneration and neurological deficits in rats. Methods : The TBI model was established in Sprague-Dawley rats by a weight-dropping method. Real-time polymerase chain reaction, western blot, immunofluorescence, Fluoro-Jade C staining, and neurological score analyses were carried out. Results : NMNAT2 mRNA and protein levels were increased in the injured-side cortex at 6 hours and peaked 12 hours after TBI. Knocking down NMNAT2 with an injection of small interfering RNA in lateral ventricle significantly exacerbated neuronal degeneration and neurological deficits after TBI, which were accompanied by increased expression of BCL-2-associated X protein (Bax). Conclusion : NMNAT2 expression is increased and NMNAT2 exhibits neuroprotective activity in the early stages after TBI, and Bax signaling pathway may be involved in the process. Thus, NMNAT2 is likely to be an important target to prevent secondary damage following TBI.

Lipid-coated ZnO nanoparticles synthesis, characterization and cytotoxicity studies in cancer cell

Cao Dingding,Shu Xugang,Zhu Dandan,Liang Shengli,Hasan Murtaza,Gong Sheng 나노기술연구협의회 2020 Nano Convergence Vol.7 No.14

ZnO nanoparticles are widely used in biological, chemical, and medical fields, but their toxicity impedes their wide application. In this study, pristine ZnO NPs (~ 7 nm; ~ 18 nm; ~ 49 nm) and lipid-coated ZnO NPs (~ 13 nm; ~ 22 nm; ~ 52 nm) with different morphologies were prepared by chemical method and characterized by TEM, XRD, HRTEM, FTIR, and DLS. Our results showed that the lipid-coated ZnO NPs (~ 13 nm; ~ 22 nm; ~ 52 nm) groups improved the colloidal stability, prevented the aggregation and dissolution of nanocrystal particles in the solution, inhibited the dissolution of ZnO NPs into ­Zn 2+ cations, and reduced cytotoxicity more efficiently than the pristine ZnO NPs (~ 7 nm; ~ 18 nm; ~ 49 nm). Compared to the lipid-coated ZnO NPs, pristine ZnO NPs (~ 7 nm; ~ 18 nm; ~ 49 nm) could dose-dependently destroy the cells at low concentrations. At the same concentration, ZnO NPs (~ 7 nm) exhibited the highest cytotoxicity. These results could provide a basis for the toxicological study of the nanoparticles and direct future investigations for preventing strong aggregation, reducing the toxic effects of lipid-bilayer and promoting the uptake of nanoparticles by HeLa cells efficiently.