Research on Signal Analysis Method based Wavelet Analysis and Grey Theory

Lijun Song,Hongxing Qu 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.9

In allusion to the shortcomings of the existing signal analysis method for high-frequency analysis, non-stationary signal analysis and so on, wavelet analysis and grey theory are introduced into the signal analysis, a new signal analysis method based wavelet analysis and grey theory is proposed in this paper. In this method, the wavelet packet is used to nonredundantly, lossless and orthogonally decompose different components of noise signals into different frequency bands with different scales, in order to realize the signal frequency band division with total energy conservation for obtaining the energy feature of each frequency band. Then these energy frequency bands are used to construct the feature vector. And the grey theory is used to analyze the correlation degree between the equipment states and system parameters in order to quickly and accurately determine the position of source. Finally, for a typical signal simulation and analysis, the effectiveness of the signal method is tested and verified.

Robust Model Predictive Control for Multi-phase Batch Processes with Asynchronous Switching

Hui Li,Lijun Song,Xueying Jiang,Huiyuan Shi,Chengli Su,Ping Li 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.1

A robust asynchronous switching model predictive controller is designed for multi-phase batch processes with uncertainties, unknown disturbances and time-varying set-point. Firstly, in view of the influence of timevarying set-point and disturbances, an asynchronous switching model with stable and unstable cases is established. Based on the switching model, a robust asynchronous switching model predictive control law is designed. Secondly, by using relevant theories and methods, the sufficient conditions with the form of linear matrix inequality (LMI) are given to ensure that the multi-phase batch processes are asymptotically stable at each phase and exponentially stable at each batch. Then, these LMI conditions are solved online to obtain the control gain of each phase, the shortest running time of each stable case, and the longest running time of each unstable case. Finally, the effectiveness and feasibility of the proposed method are verified by taking the injection molding process as an example.

A Numerical Method to Reduce the Stray Magnetic Field Around the Asymmetrical Wireless Power Transfer Coils for Electric Vehicle Charging

Zhang Wenjie,Song Jiancheng,Lin Lingyan,Ren Hui,Zheng Lijun,Gao Yunguang,Song Yuan 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.3

Wireless power transfer (WPT) is becoming increasingly popular in stationary electric vehicle charging. Unfortunately, the adverse health eff ects due to the stray magnetic fi eld created by the WPT coils have increasingly caused concern. However, the traditional stray magnetic fi eld optimization design method based on fi nite element simulation is time-consuming and resource intensive. In this paper, a numerical method to reduce the stray magnetic fi eld around the asymmetrical wireless power transfer coils is proposed while maintaining the transmission power constant. The formulas of the stray magnetic fi eld around the WPT coils are derived, and the distribution characteristics of the stray magnetic fi eld are analyzed in detail. The stray magnetic fi eld around the asymmetrical wireless power transfer coils is optimized by the numerical method, and the number of the turns for the WPT coils corresponding to the minimum stray magnetic fi eld intensity is obtained. The eff ectiveness of the numerical method is verifi ed via the fi nite element analysis tool JMAG, and it is proved that the numerical method require less computational time than the fi nite element simulation. The experiments have also been carried out to evaluate the validity of the theoretical analysis.

Thermal pretreatment of poplar sawdust at 100 °C in water or with microwave heating impacts the pyrolysis behaviors

Chao Li,Baihong Li,Guoming Gao,Lijun Zhang,Shu Zhang,Lei Zhang,Jun Xiang,Song Hu,Yi Wang,Xun Hu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.125 No.-

Drying at 100 C is a common practice for processing many biomasses for their further thermochemicalconversion via the routes such as pyrolysis. The drying temperature of 100 C is low, but might not be toolow to cause any impact on pyrolytic behaviors of a biomass feedstock. In this study, varied scenarios ofthermal pretreatment of poplar sawdust (oven-drying, boiling in water and microwave heating) at 100 Cwere screened for probing their potential influence on the pyrolytic behaviors at 500 and 750 C. Comparing with oven-drying, boiling in water (cooking) and microwave heating at 100 C could removesome oxygen-containing species, increasing carbon content of the pretreated sawdust and promotingcarbonization in pyrolysis. This enhanced formation of biochar, heavy p-conjugated organics in bio-oil,but suppressed generation of gas. The cooking or microwave heating pretreatment also promoted aromatizationto form the biochar of higher thermal stability, higher crystallinity, and higher aromatic degree,due to the enhanced deoxygenation reactions in the pyrolysis. The in-situ IR characterization suggestedthat microwave pretreatment promoted generation of unsaturated ketones and also the species with olefinicC = C, favoring their further aromatization. The cooking pretreatment impacted transformationroutes of the oxygen-containing organics, thus modifying pyrolysis behaviors of the pretreated sawdust.

Wear Resistance of Different Bionic Structure Manufactured by Laser Cladding on Ti6Al4V

Mengyao Wu,Xiaohong Zhan,Hengchang Bu,Lijun Liu,Yuanzeng Song,Yaping Li 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

In this study, the laser cladding system with an IPG YLS-6000 fber laser was used, and the WC–Ti6Al4V powder reinforcedcomposite coatings on Ti6Al4V titanium alloy with various bionic structures were innovatively fabricated. The microstructures and surface damage behavior of the coatings were characterized by scanning electron microscopy, energy dispersivespectroscopy, and X-ray difraction. Additionally, the wear resistance of diferent bionic structures was evaluated, which hadnot been comprehensively explored in the published literature. The results indicated that the un-melted WC particles in thecoatings act as a hard reinforcement, avoiding serious wear of the coating. In addition, the hard coatings exhibit excellentdeformation resistance and the soft substrate cushion the shear stress. So when the “Ratio”, which refers to the laser cladding area to sample area, is between 0.25 and 0.3, the sample has the highest wear resistance. Furthermore, the “Dot+Line”bionic structure has the best wear resistance compared with other structures. The separated line units and the addition of dotunits can improve the stress concentration state of bionic structure are conducive to release the stress to the substrate underthe cladding layer.

Correlation between Vitamin B12 and Mental Health in Children and Adolescents: A Systematic Review and Meta-analysis

Yongjun Tan,Li Zhou,Kaiqi Gu,Caihong Xie,Yuhan Wang,Lijun Cha,Youlin Wu,Jiani Wang,Xiaosong Song,Xia Chen,Hua Hu,Qin Yang 대한정신약물학회 2023 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.21 No.4

To conduct the association between vitamin B12 and mental health in children and adolescents. Five databases were searched for observational studies in any language reporting on mental health and vitamin B12 levels or intake in children and adolescents from inception to March 18, 2022. Two authors independently extracted data and assessed study quality. Qualitative and quantitative analysis of data were performed. The review was registered in the PROSPERO database (CRD42022345476). Fifty six studies containing 37,932 participants were identified in the review. Vitamin B12 levels were lower in participants with autism spectrum disorders (ASD) (standardized mean difference [SMD], −1.61; 95% confidence interval [95% CI], −2.44 to −0.79; p < 0.001), attention deficit hyperactivity disorders (SMD, −0.39; 95% CI, −0.78 to −0.00; p = 0.049) compared with control group. Vitamin B12 intake were lower in participants with ASDs (SMD, −0.86; 95% CI, −1.48 to −0.24; p = 0.006) compared with control group, but showed no difference between depression group (SMD, −0.06; 95% CI, −0.15 to 0.03; p = 0.17) and the control group. Higher vitamin B12 intake were associated with lower risk of depression (odds ratio [OR], 0.79; 95% CI, 0.63−0.98; p = 0.034) and behavioral problems (OR, 0.83; 95% CI, 0.69−0.99; p = 0.04). The vast majority of included studies supported potential positive influence of vitamin B12 on mental health, and vitamin B12 deficiency may be a reversible cause for some mental health disorders in children and adolescents.

THEORETICAL STUDY OF THE ADSORPTION AND DIFFUSION OF OXYGEN ATOM ON O-TERMINATED ZnO (000 ? 1) SURFACE

LIANG QIAO,YI ZENG,CHAOQUN QU,XIAOYING HU,LIJUN SONG,YONGMING SUI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.1

The adsorption and difusion of oxygen atom on the O-terminated ZnO ð 000?1 Þ surface havebeen systematically investigated based on ¯rst-principles density functional theory. The resultsshow that the surface relaxation of the ZnO ð 000?1 Þ surface is signi¯cant. In the view of themaximization of the adsorption energy, the preferred site for the adsorption of oxygen atom is thetop-O site above the oxygen atom of the ¯rst Zn – O bilayer. There is chemical bond formedbetween the adsorbed oxygen atom and the oxygen atom on the surface, which will result in theredistribution of the charges. The charges transfer from the ZnO surface to the adsorbed oxygenatom, which will heighten the surface potential of ZnO surface and increase the surface workfunction. Moreover, the di®usion of the oxygen atom on the ZnO surface has also been investi-gated, and the potential barriers of the difusion have been identi¯ed to reveal the adsorptionstability

Adsorption behaviour of film-forming amine on pre-oxidized carbon steel surface

Lin Genxian,Sun Yun,Liu Canshuai,Fang Jun,Song Lijun,Liu Bin 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.4

The maintenance of condenser main pipe is the key to achieve film-forming amine maintenance effectiveness. In this work, oxygen content, pH and temperature of the solution were controlled to simulatethe condition of condenser main pipe, and magnetite coated carbon steel sample was prepared by preoxidization. CAM was used to characterize the hydrophobicity of film formed samples. Hydrophobic filmwas formed on pre-oxidized carbon steel samples when octadecylamine concentration reaches 20 mg/kg. SEM, EDS, EIS, and PD were used to characterize the influence of octadecylamine concentration onmaintenance effectiveness. It was found that the maintenance effectiveness was enhanced and thecorrosion rate was suppressed with the increase of octadecylamine concentration. FIB and TEM wereused to detect the adsorbed octadecylamine film thickness founding that octadecylamine adsorbed ontothe surface of pre-oxidized carbon steel by multi-layer adsorption mechanism

Circuit Model for the Effect of Nonradiative Recombination in a High-Speed Distributed-Feedback Laser

Bowen Nie,Zhijuan Chi,Qing-an Ding,Xiang Li,Changqing Liu,Xiaojuan Wang,Lijun Zhang,Juan Song,Chaofan Li 한국광학회 2020 Current Optics and Photonics Vol.4 No.5

Based on single-mode rate equations, we present an improved equivalent-circuit model for distributedfeedback (DFB) lasers that accounts for the effects of parasitic parameters and nonradiative recombination. This equivalent-circuit model is composed of a parasitic circuit, an electrical circuit, an optical circuit, and a phase circuit, modeling the circuit equations transformed from the rate equations. The validity of the proposed circuit model is verified by comparing simulation results to measured results in the literature. The results show that the slope efficiency and threshold current of the model are 0.22 W/A and 13 mA respectively. It is also shown that increasing bias current results in the increase of the relaxation-oscillation frequency. Moreover, we show that the larger the bias current, the lower the frequency chirp, increasing the possibility of extending the transmission distance of an optical-fiber communication system. The results indicate that the proposed circuit model can accurately predict a DFB laser’s static and dynamic characteristics.

Joint optimization of source and relay precoding for AF MIMO relay systems

Li, Jun,Jiang, Xueqin,Song, Sangseob,Guo, Ying,Lee, Moon Ho SpringerOpen 2015 Eurasip Journal on Wireless Communications and Net Vol.2015 No.-