Efficient Visual Place Recognition by Adaptive CNN Landmark Matching

( Yutian Chen ),( Wenyan Gan ),( Yi Zhu ),( Hui Tian ),( Cong Wang ),( Wenfeng Ma ),( Yunbo Li ),( Dong Wang ),( Jixian He ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.11

Visual place recognition (VPR) is a fundamental yet challenging task of mobile robot navigation and localization. The existing VPR methods are usually based on some pairwise similarity of image descriptors, so they are sensitive to visual appearance change and also computationally expensive. This paper proposes a simple yet effective four-step method that achieves adaptive convolutional neural network (CNN) landmark matching for VPR. First, based on the features extracted from existing CNN models, the regions with higher significance scores are selected as landmarks. Then, according to the coordinate positions of potential landmarks, landmark matching is improved by removing mismatched landmark pairs. Finally, considering the significance scores obtained in the first step, robust image retrieval is performed based on adaptive landmark matching, and it gives more weight to the landmark matching pairs with higher significance scores. To verify the efficiency and robustness of the proposed method, evaluations are conducted on standard benchmark datasets. The experimental results indicate that the proposed method reduces the feature representation space of place images by more than 75% with negligible loss in recognition precision. Also, it achieves a fast matching speed in similarity calculation, satisfying the real-time requirement.

Identification and Determination of Oil Pollutants Based on 3-D Fluorescence Spectrum Combined with Self-weighted Alternating Trilinear Decomposition Algorithm

Pengfei Cheng,Yutian Wang,Zhikun Chen,Zhe Yang 한국광학회 2016 Current Optics and Photonics Vol.20 No.1

Oil pollution seriously endangers the biological environment and human health. Due to the diversityof oils and the complexity of oil composition, it is of great significance to identify the oil contaminants. The 3-D fluorescence spectrum combined with a second order correction algorithm was adopted to measurean oil mixture with overlapped fluorescence spectra. The self-weighted alternating trilinear decomposition(SWATLD) is a kind of second order correction, which has developed rapidly in recent years. Micellarsolutions of #0 diesel, #93 gasoline and ordinary kerosene in different concentrations were made up. The3-D fluorescence spectra of the mixed oil solutions were measured by a FLS920 fluorescence spectrometer. The SWATLD algorithm was applied to decompose the spectrum data. The predict concentration andrecovery rate obtained by the experiment show that the SWATLD algorithm has advantages of insensitivityto component number and high resolution for mixed oils.

Stability analysis of a novel mobile spray-painting robot for touch-up painting in vehicle repair plant

Ruijie Zhang,Jun Wu,Yutian Wang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

The stability of a mobile robot is important because it may tip over. This work proposes a hybrid spray-painting robot with high stiffness for touch-up painting in vehicle repair plant and investigates its stability. The distribution of the center of mass is studied based on the kinematics model, and the static stability of the mobile spray-painting robot is analyzed. A micro element method is proposed to accurately calculate the inertia force and the action point of each link in the robot. Zero-moment point (ZMP) is calculated, and the dynamic stability of the mobile robot is assessed using the ZMP criterion. The smallest reasonable width of AGV is obtained for the lightweight design of the robot. The static and dynamic stabilities of the mobile robot are compared with a traditional series mobile robot with the same workspace. Several case studies are conduct by ADAMS to verify the theoretical analysis.

A Novel Method of Phase-Shifted Full-Bridge Converter to Improve Efficiency under Light Load Condition

Lei Zhao,Haoyu Li,Yanxue Yu,Yutian Wang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

The main theme of this paper is to propose a novel peak current mode control method to reduce the loss of phase-shifted full-bridge (PSFB) converter under light load condition. The proposed control method can adjust the switching frequency of the converter to keep the on-time of switches fixed. According to the loss analysis model in discontinuous current mode operation, the switching frequency is proportional to load current and the efficiency is independent from the load. Moreover, the small signal model of the PSFB converter with the proposed control method is presented. A digital-controlled experimental system is set up. The proposed method is investigated and confirmed by experimental results. Experimental results show that the efficiency and dynamic performance can be improved. These results confirm the effectiveness of the proposed control method.

A novel recyclable nano-adsorbent for enhanced oil recovery with efficient removal of Ca2+ and Cr6+ from oilfield wastewater

Lei He,Yong Dai,Zhe Wang,Lutao Yang,Luxia Zhang,Pengpeng Hu,Yutian Lei,Hong Mo,Haomiao Zhu,Jun Zhang 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.8

Oilfield wastewater has a significantly negative influence on the recovery efficiency due to its hypersalinity. Therefore, magnetic graphene oxide (GO) modified with ethylene diamine tetraacetic acid (EDTA) and grafted bypolyethylene glycol (PEG) nano-adsorbent was prepared to remove the Ca2+ and Cr6+ in Jidong Oilfield wastewaterspecifically. It was noteworthy that PEG-g-EDTA/Fe3O4/GO nano-adsorbent had excellent adsorption performance,with removal ratios up to 71.6% for Ca2+ and 42.7% for Cr6+ at 30 min. After the fifth recycling run, the nano-adsorbentstill remained with high removal ratios (69.3% for Ca2+ and 30.5% for Cr6+) and high reuse rates (89.4% for Ca2+and 95.2% for Cr6+), indicating that the nano-adsorbent had outstanding adsorption-desorption efficacy and high reusability. The adsorption test results demonstrated that the total salinity of the treated oilfield wastewater decreased byabout 5,000 ppm, and the displacement efficiency further increased by 12.5% by chemical flooding compared with theuntreated wastewater. Therefore, PEG-g-EDTA/Fe3O4/GO nano-adsorbent is an adsorbent with excellent potentialwhich can effectively remove Ca2+ and Cr6+ in oilfield wastewater to enhance oil recovery (EOR).

Cactus-like double-shell structured SiO2@TiO2 microspheres: Fabrication, electrorheological performances and microwave absorption

Xuqiang Ji,Wenling Zhang,Wenpeng Ji,Xiaoxia Wan,Yutian Wang,Li Deng,Jingquan Liu 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.56 No.-

The cactus-like double-shell structured SiO2@TiO2 microspheres (CDS SiO2@TiO2 microspheres) withhigh dielectric properties were successfully fabricated and utilized as high-performance electrorheological(ER)fluids and microwave absorbing materials. The SiO2 nanospheres with average diametersof 190 nm were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS), and used as the core forthefirst coating layer of TiO2 achieved by sol-gel method. Thefinal cactus-like TiO2 layer was prepared viaa hydrothermal method. The morphology of the resultant samples was characterized via transmissionelectron microscopy (TEM), scanning electron microscopy (SEM) and scanning transmission electronmicroscopy (STEM). This novel CDS SiO2@TiO2 microspheres based suspension exhibited improved ERproperties compared to conventional bare SiO2 spheres.

HPLC Characterization of Hydrogenous Polystyrene<i>-block-</i>deuterated polystyrene Utilizing the Isotope Effect

Lee, Sanghoon,Lee, Hyojoon,Thieu, Lam,Jeong, Youncheol,Chang, Taihyun,Fu, Chao,Zhu, Yutian,Wang, Yongmei American Chemical Society 2013 Macromolecules Vol.46 No.22

<P>HPLC elution behavior of isotopically different block copolymers was investigated. A series of three diblock copolymers of hydrogenous polystyrene and deuterated polystyrene (hPS-<I>b</I>-dPS), in which the length of hPS-block is fixed at 18 kg/mol and the length of dPS-block is varied from 17 kg/mol to 80 kg/mol, was synthesized and their retention behavior in liquid chromatography at critical condition (LCCC) was investigated using a C18 coated silica stationary phase and a mixed solvent of CH<SUB>2</SUB>Cl<SUB>2</SUB> and CH<SUB>3</SUB>CN. At this LC separation condition, hPS is retained slightly longer than dPS. The LCCC separations were performed at both LCCC conditions of dPS and hPS established with the same stationary and mobile phases, but at different column temperatures. Since the chromatographic retention difference between dPS and hPS is very small, it was possible to elute the block copolymers at both exclusion and interaction modes at the critical condition of each individual block. We found that the block at its critical condition is not fully “invisible” in both cases. In the LCCC separation at the critical condition of dPS, hPS-<I>b</I>-dPS elutes after the injection solvent peak (interaction mode) due to the stronger interaction of the hPS block. Although they have the same hPS block, they do not coelute but elute in the order of decreasing total molecular weight like an elution in exclusion mode. It clearly demonstrates that the dPS block is not “invisible” at the critical condition but influences the retention of the block copolymers. Monte Carlo simulations of the partition coefficient of A-<I>b</I>-B into a slit pore were performed to give insight on the elution behavior of A-<I>b</I>-B at the critical condition of the B block. The simulation shows that a block under the critical condition influences the retention of the other “visible” block whether the “visible” block is eluted in exclusion or interaction mode. When A is eluted in the interaction mode and B is at its critical condition, the partition coefficient is found to decrease with the increase of the “invisible” B block length, conforming to the observed elution behavior in experiments.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2013/mamobx.2013.46.issue-22/ma4018247/production/images/medium/ma-2013-018247_0010.gif'></P>

Characteristics of vibration response of ball bearing with local defect considering skidding

Yu Tian,Changfeng Yan,Yaofeng Liu,Wei Luo,Jianxiong Kang,Zonggang Wang,Lixiao Wu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11

The occurrence and aggravation of local defects in ball bearings are closely linked to the skidding behavior of the ball. Previous studies have given less attention to investigating the impact of localized defects on the problem of bearing skidding. To investigate the dynamic response of defective bearings due to skidding, a dynamic model of the ball bearing is developed that considers various factors, including self-rotation, revolution, and radial motion of the ball, as well as the contact forces and friction forces of ball/cage and ball/race, time-varying displacement excitation, and elastohydrodynamic lubrication (EHL). Experimental signals collected from a machinery fault simulator test rig are used to validate the accuracy of the proposed model. The impact of race defects on the vibration characteristics of the bearing is analyzed, and the patterns of variation in contact and friction forces within one cycle of inner race rotation are described. The results indicate that the presence of defects intensifies the force fluctuation of the ball and causes it to deviate from its normal rolling condition. By comparing the skidding characteristics of a healthy bearing with a defective one under slippage, local defects will increase the skidding ratio of bearings. The proposed model can investigate the impact of race defects on the vibration response of ball bearings under the skidding condition.