Incremental Auto Regressive Prediction Models with External Variables of Greenhouse Air Temperature for Control Purposes

Zhenfeng Xu,Junjie Chen,Jingxia Zhang,Yuan Liu,Qiaowei Zhang 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.9

The impact of actuators should be considered in the prediction modeling of greenhouse air temperature. In this paper, the operating state of a greenhouse was divided into five sub-states based on the on-off characteristic of actuators. A group of novel incremental auto regressive models with external variables (IARX models) suitable for the five operat-ing sub-states were deduced from the mechanistic modeling of greenhouse air tempera-ture. The new IARX models have fewer coefficients than other known ARX models. In or-der to validate the IARX prediction models, the related environmental factors of a glass greenhouse were measured. The prediction results of the IARX models were compared with two typical ARX models. The maximum prediction errors and the mean square errors of the IARX models, under the three operating sub-states of passive state(all actuators are not working), mechanical ventilation and fan-pad cooling, are 0.1°C, 0.14°C, 0.7°C, and 0°C, 0.3°C, 0.4°C, respectively. The prediction results are much better than those of one compared model, while similar with the other.

Facial Synthesis of Zn-Doped Fe3O4 with Enhanced Electromagnetic Wave Absorption Performance in S and C Bands

Zhenfeng Liu,Honglong Xing,Lei Wang,Dexin Tan,Ying Gan,Xiaoli Ji,Guocai Xu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.8

In this study, Zn-doped Fe3O4 nanoparticles were successfully synthesized by a facile solvothermal method in the presence of sodium dodecyl sulfate (SDS). The morphology, magnetic properties and electromagnetic wave absorbing properties of these materials were characterized. Results showed that Zn2+ played a significant role in the formation of Zn-doped Fe3O4. With the protection of SDS, highly dispersed Fe3O4 nanoparticles were obtained. The nanoparticle size decreased after Zn2+ doping, and the dispersity deteriorated with increasing Zn2+ doping concentration. Zndoped Fe3O4 exhibited excellent electromagnetic wave absorbing property, which resulted in magnetic loss and dielectric loss at an appropriate doping concentration. The minimum reflection loss (RL) was approximately -27.2 dB at 16.9 GHz. As the coating layer thickness increased to 4.0 mm, the bandwidth was approximately 5.0 GHz corresponding to RL below -10 dB, which nearly covered the entire S band (2–4 GHz) and C band (4–8 GHz). The peak frequency of RL and the number of peaks matched the quarter-wave thickness criteria. It was believed that the Zndoped Fe3O4 could be a potential electromagnetic wave absorbing material in S and C bands.

State Observers for Suspension Systems with Interacting Multiple Model Unscented Kalman Filter Subject to Markovian Switching

Zhang Zipeng,Xu Nan,Chen Hong,Wang Zhenfeng,Li Fei,Wang Xinyu 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.6

This paper presents a novel model-based observer algorithm to address issues associated with nonlinear suspension system state estimation using interacting multiple model unscented Kalman Filters (IMMUKF) under various road excitation. Due to the fact that practical working condition is complex for the suspension system, e.g. additional load. Meanwhile, the changed sprung mass parameter will induce model changed of suspension system, and it can lead to state transition between various models. To tackle the mentioned issue, the models of road profile and suspension system are first established to describe the nonlinear suspension dynamics. Then, considering the variation of sprung mass under various movement conditions, an unscented Kalman Filter (UKF) algorithm is proposed to identify the sprung mass. Based on the interacting multiple model (IMM) and Markov Chain Monte Carlo (MCMC) theory, a novel IMMUKF observer is developed to estimate the movement state of suspension system. The stability conditions for the proposed observer is calculated using the stochastic stability theory. Finally, simulations and validations are performed on a quarter vehicle suspension system under various ISO road excitations, to validate the UKF and IMMUKF algorithms for acquiring suspension system states, and results illustrate that the maximum root mean square error of state estimation for the proposed algorithm is less than 7.5 %.

Synthesis and Excellent Microwave Absorption Properties of ZnO/Fe3O4/MWCNTs Composites

Lei Wang,Honglong Xing,Zhenfeng Liu,Ziyao Shen,Xiang Sun,Guocai Xu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.12

ZnO nanocrystals were introduced into Fe3O4/MWCNTs composites to improve the impedance matching and electromagnetic (EM) wave attenuation of the system. The as-synthesized ZnO/ Fe3O4/MWCNTs composites were characterized by X-ray diffraction, vibrating sample magnetometer, field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy. SEM and TEM images showed that Fe3O4 microspheres 100–200 nm in size connected MWCNTs. Analysis of EM parameters revealed that the impedance matching of the ZnO/Fe3O4/MWCNTs composites was considerably improved after ZnO nanocrystals were introduced. The ZnO/Fe3O4/MWCNTs composites exhibited a highly efficient microwave absorption (MA) capacity within the tested frequency range of 2–18 GHz. The optimal reflection loss of EM waves was -38.2 dB at 6.08 GHz with an absorber thickness of 3.5 mm. The excellent MA properties of the composites could be attributed to the improved impedance matching, interfacial polarization, and combined effects of dielectric and magnetic losses.

Improved DV-Hop Localization Algorithm Based on Bat Algorithm in Wireless Sensor Networks

( Yuan Liu ),( Junjie Chen ),( Zhenfeng Xu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1

Obtaining accurate location information is important in practical applications of wireless sensor networks (WSNs). The distance vector hop (DV-Hop) is a frequently-used range-free localization algorithm in WSNs, but it has low localization accuracy. Moreover, despite various improvements to DV-Hop-based localization algorithms, maintaining a balance between high localization accuracy and good stability and convergence is still a challenge. To overcome these shortcomings, we proposed an improved DV-Hop localization algorithm based on the bat algorithm (IBDV-Hop) for WSNs. The IBDV-Hop algorithm incorporates optimization methods that enhance the accuracy of the average hop distance and fitness function. We also introduce a nonlinear dynamic inertial weight strategy to extend the global search scope and increase the local search accuracy. Moreover, we develop an updated solutions strategy that avoids premature convergence by the IBDV-Hop algorithm. Both theoretical analysis and simulation results show that the IBDV-Hop algorithm achieves higher localization accuracy than the original DV-Hop algorithm and other improved algorithms. The IBDV-Hop algorithm also exhibits good stability, search capability and convergence, and it requires little additional time complexity and energy consumption.

Contact characteristics and interfacial motion states during sphere oblique impact with initial spin

Qingpeng Wang,Kai Zhang,Zhenfeng Wang,Heng Wang,Yufeng Sun,Xiankun Gao,Guangyin Xu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

The impact between a sphere and flat surface plays a significant role in the granular handling process. A method is proposed to investigate the evolution of interfacial states for the sphere oblique impact with initial spin. Firstly, the sphere with irregular surface structures is applied, and the imprinted surfaces are recorded with a thin carbon paper. Then the interfacial characteristics are analyzed in cases of impact angle, contact material and drop height, etc. The geometrical parameters decrease exponentially with impact angle and include three main stages: plateau, slow decrease and sharp decrease. The motional ratio corresponds to slow increase, steady state and sharp increase. For the no pre-spin, it goes through five interfacial states with impact angle. Comparatively, the forward spin decreases the critical angle, and the backward spin decreases the number of states. Furthermore, the parameters increase linearly with drop height, while the effect on interfacial states is very little.

Roles of cryo/thermal strength for redispersibility of drug nanocrystals: a representative study with andrographolide

YuanBiao Xie,YueQin Ma,JunNan Xu,JiXiu Dan,ZhenFeng Wu,Ming Yang,Qin Zheng 대한약학회 2016 Archives of Pharmacal Research Vol.39 No.10

Due to limited understanding about the effect of cryo/thermal strength from drying process on the redispersibility of drug nanocrystals, the impact of the different type and concentration of stabilizers and matrix formers on the redispersibility of nanocrystals were systematically investigated. Andro nanosuspensions were transformed into Andro nanocrystals (Andro-NC) via different drying process. The results demonstrated that the redispersibility of Andro-NC at the aggressive cryo-strength (meant higher freezing rate) was more excellent than those at conservative andmoderatecondition.Comparedtothethermalstressfrom drying, the employed amount and type of stabilizers more dramatically affected the redispersibility of Andro-NCP during lyophilization. The HPMC-sucrose and HPMC-sorbitol system achieved excellent performance that protected Andro-NC from crystal growth during lyophilization. During spray-drying, the impacts of types and amounts of stabilizers on the redispersibility of Andro-NCP were more significant compared to those induced by the thermal stress conditions. The polymers HPMC, PVPK30 and MCCS with high Tg played an outstanding role in preventing the AndroNCP from breakage during spray-drying, due to the firmly steric barrier effect of polymeric stabilizers. It is concluded that Andro-NCP is subjected to agglomeration or crystal growth due to cryo/thermal stresses during drying. The polymeric stabilizers are more effective to protect AndroNCP from the cryo/thermal damage during solidification process, which behaved strong surface adsorption and high glass transition property at different solidification stress.