Filters








136 Hits in 0.97 sec

The Wear Behavior of Textured Steel Sliding against Polymers

Meiling Wang, Changtao Zhang, Xiaolei Wang
2017 Materials  
Artificially fabricated surface textures can significantly improve the friction and wear resistance of a tribological contact. Recently, this surface texturing technique has been applied to polymer materials to improve their tribological performance. However, the wear behavior of textured tribo-pairs made of steel and polymer materials has been less thoroughly investigated and is not well understood; thus, it needs further research. The aim of this study is to investigate the wear properties of
more » ... tribological contacts made of textured stainless steel against polymer surfaces. Three polymer materials were selected in this study, namely, ultrahigh molecular weight polyethylene (UHMWPE), polyoxymethylene (POM) and (polyetheretherketone) PEEK. Wear tests were operated through a ring-on-plane mode. The results revealed that the texture features and material properties affected the wear rates and friction coefficients of the textured tribo-pairs. In general, PEEK/textured steel achieved the lowest wear rate among the three types of tribo-pairs investigated. Energy dispersive x-ray spectroscopy (EDX) analysis revealed that the elements of C and O on the contacting counterfaces varied with texture features and indicated different wear behavior. Experimental and simulated results showed differences in the stress distribution around the dimple edge, which may influence wear performance. Wear debris with different surface morphologies were found for tribo-pairs with varying texture features. This study has increased the understanding of the wear behavior of tribo-pairs between textured stainless steel and polymer materials. polyoxymethylene (POM) and polypropylene (PP) significantly improved the tribological performance under dry friction [19] . The friction pair consisting of textured 316 stainless steel surfaces against polytetrafluoroethylene (PTFE) presented a reduced friction coefficient [20] . Textured UHMWPE reduced friction and increased wear resistance [21, 22] . Different from stiff materials, soft materials usually deform when they are subjected to forces. Thus, the tribological behavior of the counterfaces between stiff and soft materials are speculated to be different from those of stiff materials. The aims of this study are to investigate the wear behavior of textured stainless steel against polymer materials to understand wear behavior leading to better design of surface textures on soft counterfaces that prolongs the life of tribological contacts. Dimples were fabricated on 304 samples of stainless steel with varying parameters, namely, depth and area density. Wear tests were conducted with ring-on-plane testing. The friction coefficients and wear rates were measured. The worn surface morphologies of the counterfaces and wear debris were examined to assess the wear mechanism. Energy dispersive X-ray spectroscopy (EDX) was performed to investigate changes in the elements of C and O of the contacting counterfaces. Finite element analysis (FEA) was carried out to analyze the stress distribution of the mating contacts. Material and Methods Lithography-electrolytic technology was used to fabricate surface patterns on the stainless steel. The fabrication process is illustrated in Figure 1 . Firstly, the steel was ground and polished (Sa ≤ 50 nm). After cleaning the samples, they were evenly coated with a layer of photoresist on the specimens' surface using spin coating. Then, through exposing and developing, a layer of photoresist mask with certain patterns was formed on the specimen surface. Finally, redundant steel was removed by electrolytic etching to fabricate surface textures. The fabricated dimples are presented in Figure 2 . UHMWPE, POM, and (polyetheretherketone) PEEK are widely used polymers because of their low friction and superior mechanical properties and were studied in this work (Table 1 ). The geometrical parameters of the dimples are shown in Table 2 .
doi:10.3390/ma10040330 pmid:28772688 pmcid:PMC5506931 fatcat:5hlgq64etnddbmfvezjmsbp6mq

Super-resolution optical telescopes with local light diffraction shrinkage

Changtao Wang, Dongliang Tang, Yanqin Wang, Zeyu Zhao, Jiong Wang, Mingbo Pu, Yudong Zhang, Wei Yan, Ping Gao, Xiangang Luo
2015 Scientific Reports  
Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found
more » ... t fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems.
doi:10.1038/srep18485 pmid:26677820 pmcid:PMC4683440 fatcat:h6etydlmzralpddrfv3jnhnwoy

Anisotropic meta-mirror for achromatic electromagnetic polarization manipulation

Mingbo Pu, Po Chen, Yanqin Wang, Zeyu Zhao, Cheng Huang, Changtao Wang, Xiaoliang Ma, Xiangang Luo
2013 Applied Physics Letters  
Articles you may be interested in Using dual-band asymmetric transmission effect of 2D metamaterial to manipulate linear polarization state of electromagnetic waves AIP Advances 4, 097129 (2014); 10.1063/1.4896285 A linear-to-circular polarization converter with half transmission and half reflection using a single-layered metamaterial Appl. Phys. Lett. 105, 021110 (2014); 10.1063/1.4890623 Anisotropic electromagnetic properties of polymer composites containing oriented multiwall carbon
more » ... in respect to terahertz polarizer applications Demonstration of a nearly ideal wavelength-selective optical mirror using a metamaterial-enabled dielectric coating Appl. Phys. Lett. 102, 171114 (2013); 10.1063/1.4804140 Cross-polarization scattering from low-frequency electromagnetic waves in the GAMMA10 tandem mirror Rev. Sci. Instrum. 70, 991 (1999);
doi:10.1063/1.4799162 fatcat:6auzqyujnzad3nr4g3hflrcjnq

Sixty Years of the Chemistry of Rare-earth Organometallic Complexes

Changtao Qian, Chunhong Wang, Yaofeng Chen
2014 Huaxue xuebao  
Rare-earth elements include scandium, yttrium and fifteen lanthanides. Since Wilkinson and Birmingham reported the fist example of rare-earth organometallic complex, the chemistry of rare-earth organometallic complexes has had a great advance during the past sixty years. A variety of Cp containing rare-earth metal complexes, including mono-Cp, bis-Cp, and tri-Cp complexes, have been synthesized. Variation of the size of substituent on Cp ring, introducing the nitrogen or oxygen containing
more » ... t arm to Cp ring or using ansa bis-Cp ligands make the synthesis and stabilization of these three types of rare-earth metal Cp complexes available. The Cp related ligands, such as indenyl and fluorenyl, also have been applied for the rare-earth organometallic complexes. From 1990's, there was a tendency to explore the rare-earth organometallic complexes with ancillary ligands beyond Cp and its derivatives in order to search for more efficient rare-earth metal catalysts. Non-Cp ligands, such as biphenolates, β-diketiminates, amidinates, guanidinates, etc. have been introduced into the chemistry of rare-earth organometallic complexes, and a larger number of non-Cp rare-earth organometallic complexes have been synthesized and characterized. The application of non-cyclopentadienyl ligands not only resulted in the rare-earth organometallic complexes with new structural features, but also the catalysts with high activity and high selectivity for the polymer synthesis and organic synthesis. The rare-earth organometallic complexes catalyze homo-and co-polymerization of olefins as well as specific polymerization of dienes and polar monomers. The discovery of the catalytic system composed of the neutral rare-earth metal dialkyls/borate enables to synthesize some interesting polymers which are difficult to be prepared by using other catalytic system. The rare-earth organometallic complexes are also able to catalyze some important organic reactions, such as hydroamination, hydrophosphinylation, and hydroalkoxylation, etc. Different from the late-translation metal catalyzed organic reactions, most of the rare-earth metal catalyzed ones do not involve oxidative addition and reductive elimination steps. The review describes some important developments of the chemistry of rare-earth organometallic complexes in the past sixty years.
doi:10.6023/a14060434 fatcat:li7fzrn4yzea3jewtpnhexdv4a

The role of the gut microbiome and its metabolites in metabolic diseases

Jiayu Wu, Kai Wang, Xuemei Wang, Yanli Pang, Changtao Jiang
2020 Protein & Cell  
COMPLIANCE WITH ETHICS GUIDELINES Jiayu Wu, Kai Wang, Xuemei Wang, Yanli Pang, and Changtao Jiang declare that they have no conflict of interest.  ...  In contrast, other studies have observed changes in the fecal microbiome composition of probiotictreated individuals (Ferrario et al., 2014; Wang et al., 2015) .  ... 
doi:10.1007/s13238-020-00814-7 pmid:33346905 pmcid:PMC8106557 fatcat:3hyjr6panffsboj32lufs2qwva

Multimodal medical image fusion based on IHS and PCA

Changtao He, Quanxi Liu, Hongliang Li, Haixu Wang
2010 Procedia Engineering  
The fusion of multimodal brain imaging for a given clinical application is a very important performance. Generally, the PET image indicates the brain function and has a low spatial resolution, the MRI image shows the brain tissue anatomy and contains no functional information. Hence, a perfect fused image should contain both more functional information and more spatial characteristics with no spatial and color distortion. There have been a number of approaches proposed for fusing multitask or
more » ... ltimodal image information. But, every approach has its limited domain for a particular application. Study indicated that intensity-hue-saturation (IHS) transform and principal component analysis (PCA) can preserve more spatial feature and more required functional information with no color distortion. The presented algorithm integrates the advantages of both IHS and PCA fusion methods to improve the fused image quality. Visual and quantitative analysis show that the proposed algorithm significantly improves the fusion quality; compared to fusion methods including PCA, Brovey, discrete wavelet transform (DWT).
doi:10.1016/j.proeng.2010.11.045 fatcat:uuiyfm6rsfglfo7w3vnpevu5gu

Plasmonic Structures, Materials and Lenses for Optical Lithography beyond the Diffraction Limit: A Review

Changtao Wang, Wei Zhang, Zeyu Zhao, Yanqin Wang, Ping Gao, Yunfei Luo, Xiangang Luo
2016 Micromachines  
Wang et al. combined surface sinusoidal roughness with the additional loss and achieved flatter transfer function and 86% reduction of beam width compared to the lossless flat superlens [108] .  ...  Wang et al. combined surface sinusoidal roughness with the additional loss and achieved flatter transfer function and 86% reduction of beam width compared to the lossless flat superlens [108] .  ... 
doi:10.3390/mi7070118 pmid:30404291 pmcid:PMC6189824 fatcat:g347foaxxngltcci5yucpvnb2m

Metasurface-based broadband hologram with high tolerance to fabrication errors

Xiaohu Zhang, Jinjin Jin, Yanqin Wang, Mingbo Pu, Xiong Li, Zeyu Zhao, Ping Gao, Changtao Wang, Xiangang Luo
2016 Scientific Reports  
With new degrees of freedom to achieve full control of the optical wavefront, metasurfaces could overcome the fabrication embarrassment faced by the metamaterials. In this paper, a broadband hologram using metasurface consisting of elongated nanoapertures array with different orientations has been experimentally demonstrated. Owing to broadband characteristic of the polarizationdependent scattering, the performance is verified at working wavelength ranging from 405 nm to 914 nm. Furthermore,
more » ... tolerance to the fabrication errors, which include the length and width of the elongated aperture, the shape deformation and the phase noise, has been theoretically investigated to be as large as 10% relative to the original hologram. We believe the method proposed here is promising in emerging applications such as holographic display, optical information processing and lithography technology etc.
doi:10.1038/srep19856 pmid:26818130 pmcid:PMC4730226 fatcat:ubshtuj3ebhtdbklmaobo6ydnq

Spatially and spectrally engineered spin-orbit interaction for achromatic virtual shaping

Mingbo Pu, Zeyu Zhao, Yanqin Wang, Xiong Li, Xiaoliang Ma, Chenggang Hu, Changtao Wang, Cheng Huang, Xiangang Luo
2015 Scientific Reports  
The geometries of objects are deterministic in electromagnetic phenomena in all aspects of our world, ranging from imaging with spherical eyes to stealth aircraft with bizarre shapes. Nevertheless, shaping the physical geometry is often undesired owing to other physical constraints such as aero-and hydro-dynamics in the stealth technology. Here we demonstrate that it is possible to change the traditional law of reflection as well as the electromagnetic characters without altering the physical
more » ... ape, by utilizing the achromatic phase shift stemming from spin-orbit interaction in ultrathin space-variant and spectrally engineered metasurfaces. The proposal is validated by full-wave simulations and experimental characterization in optical wavelengths ranging from 600 nm to 2800 nm and microwave frequencies in 8-16 GHz, with echo reflectance less than 10% in the whole range. The virtual shaping as well as the revised law of reflection may serve as a versatile tool in many realms, including broadband and conformal camouflage and Kinoform holography, to name just a few. S pace-variant distribution of refractive index is the key of light shaping and forms the basis of various realms including optical imaging 1 , subwavelength focusing 2 and holography 3,4 . In the last decade, a vast range of novel devices have been demonstrated with the help of the newly emerging metamaterials 5,6 and transformation optics 7 . Among these diverse applications, the electromagnetic cloaks have attracted special attentions from both the microwave 8 and optical regimes 9-11 . Nonetheless, only narrow working bandwidth could be achieved at specific polarization state owing to the fundamental bandwidth-delay restriction in the cloaks 12 . In a general sense, the cloaks change the shape seen by electromagnetic detectors thus they actually belong to the context of virtual shaping technology used in the design of stealth aircrafts and ships 13 . Besides the gradient-index methodology, another promising approach utilizes the phase discontinuity at metasurface to control the motion of light 14-17 . Owing to the ultra-small thickness, these metasurfaces possess unprecedented advantages over traditional bulk optical elements. In principle, the abrupt change of phase is accompanied with polarization conversions from linear 14 or circular polarizations 16 to their cross-polarization states. Due to the equivalency of circular polarization and spin, the latter process is typically referred to as photonic spin-orbit interaction (PSOI) 18 . Nevertheless, previous structures for PSOI are often characterized by low efficiency and/or small working bandwidth. In this paper, we present for the first time the concept of broadband virtual shaping based on the phase shift induced by PSOI in spatially inhomogeneous and spectrally dispersive metasurfaces. Owing to the abrupt phase change, traditional law of reflection should be revised accordingly. Theoretical and experimental analyses in the optical and microwave frequencies demonstrate unambiguously the versatility of our approach. The results provided here may also stimulate the development of flat optics and electromagnetics 19 . Results Principle and numerical simulation. The modification of electromagnetic shape relies on the phase modulation of scattered wave upon structured surfaces. According to the generalized Snell's law 14,20 , a properly designed reflection phase would force the reflected beam to propagate in well-defined ways with respect to the specular reflection direction (Fig. 1a) 21 . In this way, traditional law of reflection is also broken. In the following, we focus on the geometric phase, a universal but not well-known property resulting from the PSOI in space-variant OPEN
doi:10.1038/srep09822 pmid:25959663 pmcid:PMC4426594 fatcat:5d5y6emny5ftph6iyxelxjrsmm

Chitosan Biguanidine/PVP Antibacterial Coatings for Perishable Fruits

Xiangyu Jiao, Jiaxuan Xie, Mingda Hao, Yiping Li, Changtao Wang, Zhu Zhu, Yongqiang Wen
2022 Polymers  
World hunger is on the rise, yet one-third of food is wasted. It is necessary to develop an effective food preservation method to reduce food waste. This article reports a composite film based on chitosan biguanidine hydrochloride(CBg) and poly (N-vinyl-2-pyrrolidone)(PVP) that can be used as a conformal coating for fresh produce. Due to the strong positive charge of CBg, the film has excellent antibacterial properties. Owing to the hydrogen bonds between CBg and PVP, the film has good
more » ... ty and mechanical properties. In addition, the coating is washable, transparent, and can reduce the evaporation of water. The above characteristics mean the film has broad application prospects in the field of food preservation.
doi:10.3390/polym14132704 pmid:35808748 pmcid:PMC9269116 fatcat:dk4tnwwpyjelnkhmpz4jwvn63m

Dispersion management of anisotropic metamirror for super-octave bandwidth polarization conversion

Yinghui Guo, Yanqin Wang, Mingbo Pu, Zeyu Zhao, Xiaoyu Wu, Xiaoliang Ma, Changtao Wang, Lianshan Yan, Xiangang Luo
2015 Scientific Reports  
Dispersion engineering of metamaterials is critical yet not fully released in applications where broadband and multispectral responses are desirable. Here we propose a strategy to circumvent the bandwidth limitation of metamaterials by implementing two-dimensional dispersion engineering in the meta-atoms. Lorentzian resonances are exploited as building blocks in both dimensions of the dedicatedly designed meta-atoms to construct the expected dispersion. We validated this strategy by designing
more » ... d fabricating an anisotropic metamirror, which can accomplish achromatic polarization transformation in 4-octave bandwidth (two times of previous broadband converters). This work not only paves the way for broadband metamaterials design but also inspire potential applications of dispersion management in nano-photonics.
doi:10.1038/srep08434 pmid:25678280 pmcid:PMC4326699 fatcat:4gmnusqiw5amjowxmeeos66j2q

Chemical proteomic profiling of protein N-homocysteinylation with a thioester probe

Nan Chen, Jinmin Liu, Zeyu Qiao, Yuan Liu, Yue Yang, Changtao Jiang, Xian Wang, Chu Wang
2018 Chemical Science  
Inspired by native chemical ligation, we apply thioester probes to profile protein N-homocysteinylation with chemical proteomics strategy.
doi:10.1039/c8sc00221e pmid:29732068 pmcid:PMC5914431 fatcat:dfsnaospsbabraybxkmwgbfm2i

Pyrolysis characteristics of a North Korean oil shale

Wei Wang, Shuyuan Li, Linyue Li, Yue Ma, Changtao Yue, Jilai He
2014 Petroleum Science  
It is found that the pyrolysis mechanisms of different oil shale are complex and their first-order kinetics parameters are different from each Zhou, 2009; Wang et al, 2010) .  ... 
doi:10.1007/s12182-014-0358-x fatcat:cj7iiu2c3fd3biprujv3ybhcnu

HIF1α-Induced Glycolysis Metabolism Is Essential to the Activation of Inflammatory Macrophages

Ting Wang, Huiying Liu, Guan Lian, Song-Yang Zhang, Xian Wang, Changtao Jiang
2017 Mediators of Inflammation  
Authors' Contributions Ting Wang and Huiying Liu contributed equally to this work.  ... 
doi:10.1155/2017/9029327 pmid:29386753 pmcid:PMC5745720 fatcat:fhm42th2avfzva6r7oyoudzluy

Experiment and numerical analysis on temporal stability of a bitter-like HTS magnet excited by MPFM

Xi Yuan, Yinshun Wang, Yueyin Wang, Yukai Qiao, Changtao Kan, Wei Pi
2019 AIP Advances  
doi:10.1063/1.5112148 fatcat:qd4qllvwffg75jr3assorc7tui
« Previous Showing results 1 — 15 out of 136 results