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A longitudinal binary phase modulator (LBPM) based on the KTa1-xNbxO3 (KTN) crystal is proposed for laser speckle reduction. The actuation voltages are applied by two series of transparent electrodes consisted of interdigitated fingers. By sequentially changing the phase modulation depth of the LBPM pixel during the detector integration time, speckle reduction can be achieved. Due to the large Kerr coefficient of the KTN crystal, the LBPM is expected to work at low voltage levels. [ABSTRACT FROM AUTHOR]

Changes have been made to this article. See the full text for a description of the changes. [ABSTRACT FROM AUTHOR]

This paper describes a novel idea for reduction of speckle contrast in laser display projectors using the rotation of a diffraction pattern whose zeroth order has been canceled out without loosing power. The feasibility of the proposed method was investigated by illuminating gratings with a sinusoidal phase on two spatial light modulators (SLMs) in series for minimal intensity modulation, where the phase grating pattern was rotated with respect to the previous one on both SLMs. Two series of measurements were done with different periods of the sinusoidal grating. For each series, an image of the speckle pattern was recorded at discrete rotation angles of the phase grating, and then an average image was calculated. Experimental results were compared with a new theoretical model for speckle contrast of N partially correlated speckle patterns. The experimental measurement results compare well with the theoretical predictions resulting in a minimum speckle contrast of 0.36, with further reduction possible. Parameters necessary to achieve target contrast (0.08 or less) are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spatiotemporal heterogeneity of NEP mechanisms was explored. • Terrestrial ecosystems in study area showed a growing trend of carbon sinks. • Effects of natural factors was weakening, opposite for socioeconomic factors. • Eco-improvement benefited NEP, opposite for urban built-up area expansion. Urban cluster carbon sinks are key parts of the terrestrial carbon cycle, and play an important role in global climate change. Based on the inversion results of net ecosystem productivity (NEP) in Middle Reaches of the Yangtze River Urban Agglomeration (MRYRUA), this study considered the influence of both natural environmental and socioeconomic factors on NEP, and investigated the driving mechanism of carbon sink emphasizing spatial and temporal heterogeneity by the geographically and temporally weighted regression model (GTWR). Results demonstrated that (1) During 2008–2020, the annual average NEP was positive in MRYRUA, and the carbon sink effect of terrestrial ecosystem increased. (2) In MRYRUA, Precipitation and DEM were positively correlated with carbon sinks, opposite for temperature, percentage of water areas and population density. (3) During the study period, the influence of natural environmental factors, such as temperature and precipitation on NEP grew gradually weaker, whereas that of socioeconomic factors increased. The influence of urbanization rate, night lights index and factors of industrial structure changed from negative to positive, while percentage of built-up area had an increasing negative effect on NEP. Based on the conclusions above, this study proposed differentiated policy implications, including improving vegetation hydrothermal environment, controlling urban expansion and accelerating industrial transformation. It would provide empirical inspiration for attaining peak carbon, carbon neutrality, and sustainable development goals. [ABSTRACT FROM AUTHOR]

Hierarchical heterostructures have been proven to be the great material structures for the fabrication of gas sensors, due to they high surface area, well-aligned porosity and synergy effect. Here, ZnO hierarchical structures with various amount of Mn dopant were synthesized through a simple one-step solution route followed by annealing treatment. The characterization results demonstrated that Mn dopant existed in the forms of Mn 3 O 4 nanoparticles and lattice Mn2+ ions. The as-synthesized Mn 3 O 4 /ZnO hierarchical structures with abundant oxygen vacancies (Mn x ZnO with x values of 0, 0.25, 0.5, 1 and 3) were used as the sensing materials toward volatile organic compounds (VOCs) detection, illustrating that the introduction of Mn dopant can significantly improve the gas sensing performance. Especially, under optimal working temperature, Mn 0.5 ZnO hierarchical structures-based gas sensor exhibits the highest responses, fast response/recovery speed (2/9 s), a low detection limit (150 ppb), good selectivity and long-term stability toward acetone. In addition, the enhanced gas sensing mechanisms were explained by large surface area, oxygen vacancies and p-n heterojunction, boosting the surface reactions, which was further verified through DFT calculations. This work also confirmed that Mn element could be a promising dopant in metal oxides for high-performance VOCs gas sensors. [Display omitted] • Mn x ZnO hierarchical structures were synthesized through a simple solution route. • Mn 0.5 ZnO sensor exhibits high response, fast response/recovery speed, low detection limit toward acetone. • Sensing mechanisms were studied by large surface area, oxygen vacancies and p-n heterojunction. [ABSTRACT FROM AUTHOR]

Demands for highly deformable and responsive intelligent actuators are increasing rapidly. Herein, a photothermal bilayer actuator consisting of a photothermal-responsive composite hydrogel layer and a polydimethylsiloxane (PDMS) layer is presented. The photothermal-responsive composite hydrogel is prepared by compositing hydroxyethyl methacrylate (HEMA) and the photothermal material graphene oxide (GO) with the thermal-responsive hydrogel poly( N -isopropylacrylamide) (PNIPAM). The HEMA improves the transport efficiency of water molecules inside the hydrogel network, eliciting a fast response and large deformation, facilitating greater bending behavior of the bilayer actuator, and improving the mechanical and tensile properties of the hydrogel. Moreover, GO enhances the mechanical properties and the photothermal conversion efficiency of the hydrogel in the thermal environment. This photothermal bilayer actuator can be driven under various conditions, such as hot solution, simulated sunlight, and laser, and can achieve large bending deformation with desirable tensile properties, broadening the application conditions for bilayer actuators, such as artificial muscles, bionic actuators, and soft robotics., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A method to realize an equal-intensity beam splitter (EIBS) using wire grid polarizers (WGPs) is proposed. The EIBS consists of WGPs with predetermined orientations and high-reflectivity mirrors. We demonstrated the generation of three laser sub-beams (LSBs) with equivalent intensities using EIBS. The three LSBs were incoherent by introducing optical path differences larger than the laser coherence length. The LSBs were used to reduce speckle passively, where the objective speckle contrast was reduced from 0.82 to 0.5 when all three LSBs were used. The feasibility of EIBS in speckle reduction was studied using a simplified laser projection system. The structure of the EIBS implemented by WGPs is simpler than EIBSs obtained by other methods.

Traditional metal oxide semiconductor (MOS) gas sensors have limited applications in wearable devices owing to their inflexibility and high-power consumption by substantial heat loss. To overcome these limitations, we prepared doped Si/SiO 2 flexible fibers by a thermal drawing method as substrates to fabricate MOS gas sensors. A methane (CH 4 ) gas sensor was demonstrated by subsequently in situ synthesizing Co-doped ZnO nanorods on the fiber surface. The doped Si core acted as the heating source through Joule heating, which conducted heat to the sensing material with reduced heat loss; the SiO 2 cladding was an insulating substrate. The gas sensor was integrated into a miner cloth as a wearable device, and the concentration change of CH 4 was monitored in real time through different colored light-emitting diodes. Our study demonstrated the feasibility of using doped Si/SiO 2 fibers as the substrates to fabricate wearable MOS gas sensors, where the sensors have substantial advantages over tradition sensors in flexibility, heat utilization, etc.