Preparation of nano-TiO2/purified diatomite coating and its photocatalytic properties of formaldehyde degradation

Lijian Wang,Junwei Zhao,Yujiang Wang,Shuilin Zheng 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.6

The nano-TiO2/purified diatomite composite materials with core-shell structures were prepared by hydrolysis precipitationusing purified diatomite as carrier and titanium sulfate as precursor. The composite materials were characterized bytransmission electron microscope (TEM), X-ray diffraction (XRD), low temperature nitrogen adsorption and mercuryporosimetry. The photocatalytic composite coating based on the nano-TiO2/prified diatomite composite materials wasprepared and its properties of formaldehyde degradation were investigated. Meanwhile, the degradation mechanism offormaldehyde gas was discussed. The results showed that the nano-TiO2/prified diatomite composite materials were formedcore-shell structures, and the TiO2 nanoparticles were anatase with the average size of about 10 nm?The test results show thatthe formaldehyde purification performance of the coatings has met the technical requirements of Class I materials in theChinese national standard JC/T 1074-2008.

Step-by-step identification of industrial robot dynamics model parameters and force-free control for robot teaching

Binrui Wang,Junwei Fang,Shunan Qi,Ling Wang,Xiaolong Liu,Haijun Ren 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.7

In order to solve the problem of lack of flexibility in direct teaching of industrial robots under complex working conditions, dynamic inertia term compensation is combined with the traditional force-free control algorithm to reduce the traction in the teaching process in this paper. Firstly, considering the multi-dimensional, strongly nonlinear and multi-parameter characteristics of the 6-DOF manipulator dynamic model, a step-by-step parameters identification method based on genetic algorithm is proposed. This method can effectively reduce the computational complexity and improve the optimization speed of industrial robot dynamic model identification. Secondly, based on the internal torque analysis of industrial robot joints, a forcefree compensation control algorithm based on the torque control is designed. Finally, the effectiveness of the step-by-step robot dynamic model parameter identification method is verified by a traction teaching experiment. In the verification experiment, the relative error rate between the predicted torque and the actual torque calculated from the identification results is 1.64 % to 5.99 %. After increasing the inertia term compensation, the traction force of the teaching process is reduced by 28.6 %. The experimental results show that the identification result is more accurate, and the proposed force-free control algorithm significantly improves the compliance of the teaching process.

Dynamical Analysis of Memcapacitor Chaotic System and Its Image Encryption Application

Junwei Sun,Gaoyong Han,Yanfeng Wang 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.5

The prospective studies on memcapacitor models and potential applications are of importance due to its dynamical behavior. For this purpose, a memcapacitor model and a corresponding circuit model have been designed, whose characteristics have been investigated theoretically and experimentally. Based on the unique space conformation of DNA molecules and their unique information storage and processing ability, a memcapacitor chaotic image encryption algorithm combining with DNA sequence operations is proposed in the first time. DNA sequence operations and memcapacitor chaos iterations are used in the encryption process to strengthen the confusion and diffusion properties of the scheme. The simulation results and theoretical analysis show that the algorithm improves the sensitivity of key and the security of data transmission, and has better ability of the hacker attacks.

Mixed H2/H∞ Control for a Class of Nonlinear Networked Control Systems

Yanqian Wang,Junwei Lu,Ze Li,Yuming Chu 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.3

In this paper, the mixed H2=H∞ control problem is investigated for a class of nonlinear discrete-time networkedcontrol systems with random network-induced delays, stochastic packet dropouts and probabilistic sensorfaults. The packet dropouts process is modeled as a homogeneous Markov chains taking values in a finite statespace. Network-induced delays occur in a random way with known upper bound. A set of stochastic variablesare exploited to describe sensor faults with different probabilistic density functions. By using a delay-dependentLyapunov functional, a mode-dependent mixed H2=H∞ controller is designed to guarantee both stochastic stabilityof the closed-loop system and the prescribed H2, H∞ control performances. Sufficient conditions for the existenceof the mixed H2=H∞ controller are presented in terms of a series of LMIs. If these LMIs are feasible, then the modedependentmixed H2=H∞ controller can be obtained. A numerical example is given to demonstrate the effectivenessof the developed method.

Maximum Likelihood Recursive Generalized Extended Least Squares Estimation Methods for a Bilinear-parameter Systems with ARMA Noise Based on the Over-parameterization Model

Haibo Liu,Junwei Wang,Yan Ji 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.8

Maximum likelihood methods have wide applications in system modeling and parameter estimation. For the purpose of improving the precision of parameter estimation, this paper presents a maximum likelihood recursive generalized extended least squares (ML-RLS) algorithm for a bilinear-parameter system with autoregressive moving average noise based on the over-parameterization identification model. An over-parameterization-based recursive generalized extended least squares algorithm is presented to show the effectiveness of the proposed ML-RLS algorithm for comparison. The simulation test shows that the proposed algorithm has a higher estimation accuracy than the recursive least squares algorithm.

Fast numerical simulation of sheet metal forming using the program QuickForm

Yidong Bao,Junwei Chen,Zhiguo Wang,Wenliang Chen,Wing Lee 한국소성가공학회 2010 기타자료 Vol.2010 No.6

The fast numerical simulation system QuickForm has been self-developed specially for sheet metal forming with complex geometries. In order to resolve the convergence problem of static implicit method due to the change of contact state, the uncoupling solution method of the non-linear differential equations is used in QucikForm program. The bending effect and drawing effect during forming procedure are treated into two separate processes in QuickForm system, so this uncoupling solution has two basic steps. Firstly an approximate method named pre-stressed membrane element is used to achieve the intermediate configuration of sheet in this incremental step before incremental step iteration. The sheet shape of intermediate configuration depends on the current tooling position. Secondly the nonlinear material flow within this intermediate configuration is carried out, which means the nodes of deformed sheet can only slide on this form. The highly efficient iterative solver can be used to the solution of linear equations since the improved conditioning of the linear equations resulting from the uncoupling solution. Numerical simulation results of complex parts demonstrate the higher efficiency and accuracy of the proposed special purpose program.

Buckling Modes of Cold-Formed Thin-Walled Steel Beams Under Different Impact Positions

Chang Wu,Junwei Duan,Renhong Wang,Ziheng Yang 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

This paper aims to study the buckling mode of cold-formed thin-walled channel steel beams under different impact positions. The impact test of the thin-walled channel steel beams was carried out using a drop hammer to obtain the acceleration of the measuring point and the buckling mode of the member. The experimental results and ANSYS/LS-DYNA numerical simulation results are compared and analyzed. The results show that the acceleration curve change trend obtained from the test is similar to numerical simulation. The difference between the acceleration obtained by numerical simulation and the maximum value obtained by test accounts for 5.86% of the simulated value. Therefore, the dynamic response results of cold-formed thin-walled channel steel beams under numerical simulation can be effectively verified by the test. Numerical simulation methods are used to analyze the dynamic response of two groups of members under impact at different positions and the corresponding buckling modes. The results show that the buckling of the members at 1/2, 1/3, and 1/4 of the flange of the impact member is similar to the O-I mode under the same conditions. The buckling mode is half-O mode when the midpoint of the intersection line between flange and web is impacted. The buckling mode is U-shaped when the midpoint of the intersection line between flange and the curling edge is impact.

Weather Forecasting Using Ensemble of Spatial-Temporal Attention Network and Multi-Layer Perceptron

Yuanpeng Li,Junwei Lang,Lei Ji,Jiqin Zhong,Zaiwen Wang,Yang Guo,Sailing He 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.3

Weather forecasting is a challenging task, which is especially suited for artificial intelligence due to the large amount of data involved. This paper proposed an end-to-end hybrid regression model, called Ensemble of Spatial-Temporal Attention Network and Multi-Layer Perceptron (E-STAN-MLP), to forecast surface temperature, humidity, wind speed, and wind direction at 24 automatic weather stations in Beijing. Combining the data from historical observations with the data from the numerical weather prediction (NWP) system, our proposed model give better results than the NWP system or previously reported algorithms. Our E-STAN-MLP model consists of two parts. One is to use the spatial-temporal attention based recurrent neural network to model the time series of meteorological elements. The other is a simple but efficient multilayer perceptron architecture forecasts the regression value while ignoring time dependence. Results at each time stamp are integrated together using a step-wise fusion strategy. Moreover, we use a joint loss step integrating both the regression loss function and the classification loss function to simultaneously forecast the wind speed and direction. Experiments demonstrate that our proposed E-STAN-MLP model achieves state-of-the-art results in weather forecasting.

Phase behavior of aqueous two-phase systems of cationic and anionic surfactants and their application to theanine extraction

Qijun Peng,Junwei Zhang,Yan Wang 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.6

Phase behavior of aqueous two-phase systems (ATPS) containing cationic (SDS) and anionic (CTAB) surfactants and its application to theanine extraction was studied. Results indicated the ATPS could form under the certain SDS/CTAB molar ratio; there was a reasonable consistency between the conductivity and the formation region of ATPS,and the viscosity was higher in the formation region of ATPS. Additionally, the phase ratio increased with increase of CATB concentration, and the interfacial film between the top phase and the bottom phase was resilient. Moreover,the theanine extraction with ATPS was realized in the waste liquid of tea polyphenol production (WLTPP), and the partition coefficient of theanine decreased with increase of WLTPP concentration, whereas the extraction rate of theanine increased. The partition coefficient decreased with increasing SDS/CTAB molar ratio, and the extraction rate of theanine increased with increase of SDS/CTAB molar ratio.

Structure-activity correlations of LiNO3/Mg4AlO5.5 catalysts for glycerol carbonate synthesis from glycerol and dimethyl carbonate

Zhenmin Liu,Junwei Wang,Mao-qing Kang,Ning Yin,Xin-kui Wang,Yisheng Tan,Yulei Zhu 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

MgAl hydrotalcite synthesized via co-precipitation method from magnesium and aluminum nitrateswas calcined to produce Mg4AlO5.5 mixed oxides. The oxides were modified by introducing LiNO3 andapplied to the synthesis of glycerol carbonate from glycerol and dimethyl carbonate. The research resultsindicated that LiNO3/Mg4AlO5.5 was an efficient catalyst for the synthesis of glycerol carbonate. The fullconversion of glycerol and 96.28% yield of glycerol carbonate were obtained after reacting at 80 8C for1.5 h in the presence of LiNO3/Mg4AlO5.5. The structure and properties of the catalysts were studied bymeans of XRD, TGA, BET, CO2-TPD and Hammett indicator method. It was found that the basic strengthand the basicity of the catalysts were enhanced after addition of LiNO3. Over Mg4AlO5.5 oxides, LiNO3 waseasily converted to LiAlO2 which constituted new strong basic sites. Too high basic strength and basicityof catalysts may improve the conversion of glycerol at the cost of GC selectivity reduction.