Laser interferometer is the common tool to measure the positioning error of CNC machine, and its measurement process will be affected by external factors. Therefore, it is very important to ensure ...the error accuracy which measured by laser interferometer for compensating the error of CNC machine tools. The positioning error of MVC850B CNC milling machine was measured by Renishaw laser interferometer. Firstly, the positioning error of it was measured in standard and actual environmental parameters, and measured results were comparatively shown in factors of temperature, air pressure and humidity. Secondly, the influence degree that in three conditions of feeding speed, interval distance and processing time was analyzed by the errors of reverse clearance and screw pitch cumulative. Finally, with the statistics of positioning errors measured in a certain period of time, this paper analyzed the reliability of positioning errors measured by laser interferometer and analyzed the variation of milling machine motion axis errors. Meantime, the possible location of machine errors can be predicted, and the positioning accuracy of CNC milling machine would be promoted.
The trade-off between the temporal and spatial resolutions, and/or the influence of cloud cover, makes it difficult to obtain continuous fine-scale satellite data for surface urban heat island (SUHI) ...analysis. To relieve these difficulties, this study employs multi-temporal and multi-sensor fusion methods for a long-term and fine-scale summer SUHI analysis of the city of Wuhan in China. By integrating several series of satellite images, we generated 26-year (1988 to 2013) high spatial resolution (Landsat-like) summer land surface temperature (LST) data. This series of data was then used for a qualitative and quantitative analysis of the SUHI patterns, evolution characteristics, and mechanisms. This study not only provides a generalized research framework for the long-term and fine-scale analysis of the SUHI effect, but also reveals several findings about the heat distribution and SUHI characteristics in Wuhan. Firstly, our results show that the high temperature and sub-high temperature areas were continuously concentrated from rural to urban areas, but the high temperature area within the old city zones showed an obvious decreasing tendency. Secondly, a more important finding is that the SUHI intensity first increased and then decreased over the 26years. The maximum temperature difference between the city zone and the rural area was in 2003 (7.19K for the old city zone, and 4.65K for the area within the third ring road). Finally, we confirm that the relationships between heat distribution and land cover (especially vegetation and impervious surfaces) were interannually stable, and that the influences of industry, businesses, and residential districts on the SUHI effect were in descending order in Wuhan.
•We solve the spatial–temporal discontinuity of remotely sensed LST data.•A long-term (26-years) and fine-scale summer LST data series has been generated.•This 26-year data is used for the analysis of the SUHI characteristic.
The spatial–temporal relationships are investigated from a 3D perspective.
We report the preparation of a furan polymer, poly(2,5-furandimethylene succinate) by means of a condensation reaction between bio-based monomers. A reversible Diels–Alder reaction between furan and ...maleimide groups allowed the formation of network polymers cross-linked by a bismaleimide. By controlling the amount of the bismaleimide, mechanical properties were varied widely. These network polymers healed well when their broken surfaces were activated by bismaleimide solutions or solvent. The polymers also displayed excellent self-healing ability without external stimulus. This polymer class offers a wide range of possibilities to produce materials from biomass that have both practical mechanical properties and healing ability. These materials have the potential to bring great benefits to our daily lives by enhancing the safety, performance, and lifetime of products.
This study aims to theoretically and numerically investigate the dispersion relations of Rayleigh waves propagating through vertical oscillators periodically distributed on stratified media. The ...classical elastodynamics theory and an effective medium approximation method are adopted to describe the dynamic behavior of metasurfaces and hybridization between the local oscillators and the foundational surface wave modes. The Abo‐zena algorithm and delta‐matrix method are combined to simplify the Eigen equation to overcome the accuracy problem in solving the closed‐form dispersion laws and improve the computational efficiency. Subsequently, plane‐strain finite element (FE) models with three configurations are developed to confirm the analytical predictions and obtain further insight into the resonator‐Rayleigh wave coupling mechanism. The numerical results are in good agreement with the analytical solutions, revealing that only the foundational mode is strongly coupled with the vertical resonators at resonance, while the surface wave band gap reported in homogeneous media is crossed by the remaining higher‐order surface modes. The attenuation performance and mechanical behavior of a finite‐length metasurface are investigated, and it is demonstrated that the output surface ground motion can be significantly reduced in a narrow frequency band near resonance. Moreover, a graded resonant metasurface with decreasing frequency is simulated to assess the feasibility of broadband attenuation. In summary, the aforementioned analytical framework and numerical simulation results show that the vertical oscillators placed atop a stratified soil system can be designed as resonant metasurfaces for shielding seismic surface waves to protect multiple large infrastructures or special structures from earthquake hazards.
Snow and glacier melting and accumulation are important processes of the hydrological cycle in the cryosphere, e.g., high‐mountain areas. Glaciers and snow cover respond to climate change notably ...over the Tibetan Plateau (TP) as the Earth's Third Pole where complex topography and lack of ground‐based observations result in knowledge gaps in hydrological processes and large uncertainties in model output. This study develops a snow and glacier melt model for a distributed hydrological model (Coupled Routing and Excess Storage model, CREST) using the Upper Brahmaputra River (UBR) basin in the TP as a case study. Satellite and ground‐based precipitation and land surface temperature are jointly used as model forcing. A progressive two‐stage calibration strategy is developed to derive model parameters, i.e., (1) snow melting processes (stage I) and (2) glacier melting and runoff generation and routing using multisource data (stage II). Stage‐I calibration is performed using the MODIS snow cover area (SCA) product and a blending snow water equivalent (SWE) product combined with partial in situ measurements. Stage‐II calibration is based on Gravity Recovery and Climate Experiment (GRACE) satellite‐derived total water storage (TWS) changes and streamflow observed at a gauging station of the lower reach of the UBR. Results indicate that the developed two‐stage calibration method provides more reliable streamflow, snow (both SCA and SWE), and TWS change simulations against corresponding observations than commonly used methods based on streamflow and/or SCA performance. The simulated TWS time series shows high consistency with GRACE counterparts for the study period 2003–2014, and overestimated melting rates and contributions of glacier meltwater to runoff in previous studies are improved to some degree by the developed model and calibration strategy. Snow and glacier runoff contributed 10.6% and 9.9% to the total runoff, and the depletion rate of glacier mass was ∼ −10 mm/a (∼ −2.4 Gt/a, Gt/a is gigaton (km3 of water) per year) over the UBR basin during the study period. This study is valuable in examining the impacts of climate change on hydrological processes of cryospheric regions and providing an improved approach for simulating more reliable hydrological variables over the UBR basin and potentially similar regions globally.
Key Points
There are trade‐offs between SCA and SWE in calibration
GRACE TWS changes provide useful information for glacier melting calibration
Calibration based only on streamflow can result in equifinality and overestimation of glacier mass depletion
Efficient photo‐ and piezoelectric‐induced molecular oxygen activation are both achieved by macroscopic polarization enhancement on a noncentrosymmetric piezoelectric semiconductor BiOIO3. The ...replacement of V5+ ions for I5+ in IO3 polyhedra gives rise to strengthened macroscopic polarization of BiOIO3, which facilitates the charge separation in the photocatalytic and piezoelectric catalytic process, and renders largely promoted photo‐ and piezoelectric induced reactive oxygen species (ROS) evolution, such as superoxide radicals (.O2−) and hydroxyl radicals (.OH). This work advances piezoelectricity as a new route to efficient ROS generation, and also discloses macroscopic polarization engineering on improvement of multi‐responsive catalysis.
Macroscopic polarization enhancement by V5+ replacement in the piezoelectric semiconductor BiOIO3 can greatly facilitate charge separation and provide efficient photo‐ and piezoelectric‐induced molecular oxygen activation. Powerful superoxide and hydroxyl radicals can be thereby produced in abundance.
Since the scan line corrector (SLC) of the Landsat Enhanced Thematic Mapper Plus (ETM+) sensor failed permanently in 2003, about 22% of the pixels in an SLC-off image are not scanned. To improve the ...usability of the ETM+ SLC-off data, we propose an integrated method to recover the missing pixels. The majority of the degraded pixels are filled using multi-temporal images as referable information by building a regression model between the corresponding pixels. When the auxiliary multi-temporal data cannot completely recover the missing pixels, a non-reference regularization algorithm is used to implement the pixel filling. To assess the efficacy of the proposed method, simulated and actual SLC-off ETM+ images were tested. The quantitative evaluations suggest that the proposed method can predict the missing values very accurately. The method performs especially well in edges, and is able to keep the shape of ground features. According to the assessment results of the land-cover classification and NDVI, the recovered data are also suitable for use in further remote sensing applications.
► We propose an integrated method to recover Landsat-7 ETM+ imagery. ► A weighted linear regression method using auxiliary data is proposed. ► We use a regularization algorithm to fill the remaining gaps.
One promising approach for robots efficiently learning skills is to learn manipulation skills from human tutors by demonstration and then generalize these learned skills to complete new tasks. ...Traditional learning and generalization methods, however, have not well considered human impedance features, which makes the skills less humanlike and restricted in physical human-robot interaction scenarios. In particular, stiffness generalization has not been well considered. This paper develops a framework that enables the robot to learn both movement and stiffness features from the human tutor. To this end, the upper limb muscle activities of the human tutor are monitored to extract variable stiffness in real time, and the estimated human arm endpoint stiffness is properly mapped into the robot impedance controller. Then, a dynamic movement primitives model is extended and employed to simultaneously encode the movement trajectories and the stiffness profiles. In this way, both position trajectory and stiffness profile are considered for robot motion control in this paper to realize a more complete skill transfer process. More importantly, stiffness generalization and movement generalization can be efficiently realized by the proposed framework. Experimental tests have been performed on a dual-arm Baxter robot to verify the effectiveness of the proposed method.
To develop a novel lignin-based highly efficient nitrogen fertilizer, the amination of the biorefinery technical lignin was conducted by Mannich reaction synergy with phenolation pretreatment. ...Subsequently, the structural transformations of lignin samples and the reaction mechanism were investigated in detail. The soil column leaching experiment was also performed to research the nitrogen release behavior of aminated lignin in soil. The results indicated that the amounts of active sites in lignin were significantly increased to 8.26 mmol/g from the original 2.91 mmol/g by phenolation. In addition, the Mannich reaction was highly selective for occurring at ortho- and para-positions of phenolic hydroxyl groups in the phenolated lignin, in which the latter was favored. Moreover, the nitrogen content in the aminated lignin was highly depended on the types of amination reagent instead of the proportion of reactants in this study. Under an optimal condition, aminated lignin with a high nitrogen content (10.13%) and low C/N ratio (6.08) could be obtained. Besides, it was especially noteworthy that the prepared APL in this study has a favorable nitrogen release behavior in soil. Thus, it is believed that these aminated lignin derivatives could be used for the preparation of various lignin-based highly efficient nitrogen fertilizer.
•The chemical reactivity of lignin was significantly improved by phenolation.•The nitrogen content of APL was highly depended on the types of amination reagent.•Ethanediamine is regarded as the most favorable among these selected amination reagents.•An optimum chemosynthesis condition of high N-containing APL was obtained.•A new approach was developed to prepare lignin-based highly efficient fertilizer.
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