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The VIMOS Ultra-Deep Survey: ~10?000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2 < <i>z</i> ? 6
摘要： We present the VIMOS Ultra Deep Survey (VUDS), a spectroscopic redshift survey of ～10 000 very faint galaxies to study the main phase of galaxy assembly in 2 < z (cid:4) 6. The survey covers 1 deg2 in three separate ?elds: COSMOS, ECDFS, and VVDS-02h, with the selection of targets based on an inclusive combination of photometric redshifts and colour properties. Spectra covering 3650 < λ < 9350 ? are obtained with VIMOS on the ESO-VLT with integration times of 14h. Here we present the survey strategy, target selection, data processing, and the redshift measurement process with an emphasis on the speci?c methods used to adapt to this high-redshift range. We discuss the spectra quality and redshift reliability and derive a success rate in redshift measurement of 91%, or 74% by limiting the dataset to the most reliable measurements, down to a limiting magnitude iAB = 25. Measurements are performed all the way down to iAB = 27. The mean redshift of the main sample is z ～ 3 and extends over a broad redshift range mainly in 2 < z < 6. At 3 < z < 5, the galaxies cover a wide range of luminosities ?23 < MNUV < ?20.5, stellar mass 109 M(cid:5) < M? < 1011 M(cid:5), and star formation rates 1 M(cid:5)/yr < SFR < 103 M(cid:5)/yr. We discuss the spectral properties of galaxies using individual as well as stacked spectra. The comparison between spectroscopic and photometric redshifts as well as colour selection demonstrate the e?ectiveness of our selection scheme. From about ～90% of the data analysed so far, we expect to assemble >6000 galaxies with reliable spectroscopic redshifts in 2 < z < 6 when complete. This makes the VUDS the largest survey at these redshifts and o?ers the opportunity for unprecedented studies of the star-forming galaxy population and its distribution in large-scale structures during the main phase of galaxy assembly.
关键词： cosmology: observations,galaxies: formation,galaxies: evolution,surveys,large-scale structure of Universe,galaxies: high-redshift
更新于2025-09-04 15:30:14
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Nontopological Transformation of Hierarchical TiO2 by Self-regulated Etching and Capping Roles of F- for Photocatalytic H2 Evolution
摘要： In the past decade, crystal facet engineering of TiO2 though various controllable strategies has attracted a lot of attention due to its strong facet dependent photoactivities. In this work, we report on nontopological transformation of titanium oxydifluoride (TiOF2) to hierarchical TiO2 structures by hydrothermal tailoring. The fluorine-containing species in TiOF2 crystal perform the roles as either an etching agent or a capping agent, which can conveniently modulate morphologies and facets of TiO2 crystals via dissolution or oriented collapse under hydrothermal condition. The Wulff construction and different surface energies of shape and facet lead to the controlled formation of hierarchical TiO2, respectively with (101) faceted nanowalls, (001) and (111) faceted nanosheets, or their multi-facets. All TiO2 with single exposed facet exhibit higher photocatalytic H2 evolution performance than the commercial P25 TiO2. Moreover, the (101) faceted nanowalls demonstrate superior photocatalytic H2 evolution to (111) and (001) faceted TiO2 nanosheets in presence of hole scavenger (methanol) due to favoured hole transfer at (101) facet/methanol interface. This work presents novel methodology for shape and facet control of TiO2 towards solar to fuel conversion.
关键词： Charge separation,H2 evolution,Oriented collapse,Facet Engneering,Dissolution
更新于2025-09-04 15:30:14
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Outstanding hydrogen evolution performance of supported Pt nanoparticles: Incorporation of preformed colloids into mesoporous carbon films
摘要： Platinum is the best catalyst known so far for the hydrogen evolution reaction (HER) in acidic environments, but it is also a scarce and expensive resource. Maximizing its performance per metal atom is essential in order to reduce costs. The deposition of small Pt nanoparticles (2–3 nm) onto electrically conductive, highly accessible and stable carbon supports leads to active catalysts. However, blocking of pores and active sites by Na?on, which acts as a binding species, reduces the catalytic activity. Moreover, inaccessible Pt located in micropores diminishes an ef?cient exploitation of the noble metal. We report a new synthesis approach to ordered mesoporous carbon (OMC) coatings with preformed Pt nanoparticles. The particles are exclusively located inside the mesopores. Furthermore, no Na?on binder is needed. As a consequence, the PtNP/OMC catalyst ?lm outperforms Pt/C catalysts reported in literature particularly at high current densities. PtNP/OMC catalyst ?lms with a geometric Pt loading of 1.6 mgPt/cm2 achieve a current density of (cid:1)100 mA/cm2 at an overpotential of ca. (cid:1)70 mV.
关键词： Ordered mesoporous carbon,Noble metal colloids,Electrocatalysis,Mesoporous ?lms,Hydrogen evolution reaction
更新于2025-09-04 15:30:14
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Photocatalytic hydrogen evolution from water using fluorene and dibenzothiophene sulfone conjugated microporous and linear polymers
摘要： Three series of conjugated microporous polymers (CMPs) were studied as photocatalysts for hydrogen production from water using a sacrificial hole scavenger. In all cases, dibenzo[b,d]thiophene sulfone polymers outperformed their fluorene analogs. A porous network, S-CMP3, showed the highest hydrogen evolution rate of 6076 μmol h-1 g-1 (λ > 295 nm) and 3106 μmol h-1 g-1 (λ > 420 nm), with an external quantum efficiency of 13.2% at 420 nm. S-CMP3 outperforms its linear structural analog, P35, while in other cases, non-porous linear polymers are superior to equivalent porous networks. This suggests that microporosity might be beneficial for sacrificial photocatalytic hydrogen evolution, if suitable linkers are used that do not limit charge-transport and the material can be wetted by water as studied here by water sorption and quasi-elastic neutron scattering.
关键词： fluorene,sacrificial hole scavenger,conjugated microporous polymers,photocatalytic hydrogen evolution,dibenzo[b,d]thiophene sulfone
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Design of Wideband Circuit Analog Absorber with Improved Oblique Incidence Performance
摘要： Most of the previous circuit analog (CA) absorbers only consider the normal incidence. In this paper, a novel wideband absorber consisting of two dimensional array of conductive crossed dipoles with lumped resistors and a well-designed dielectric, working as the wide-angle impedance matching (WAIM) layer, is presented. Results show that the absorption under oblique transverse electrical (TE) incidence can be markedly improved due to the WAIM layer. Equivalent circuit (EC) and strict formula derivation are proposed to make the design more clear and straightforward. Evolutionary algorithm, to be specific, the differential evolution, is used to speed up the optimization process. The final results obtained by EC and simulation software show that the absorber offers the 10-dB reflection reduction bandwidth of at least 109.6%(2.6-8.9 GHz) when the angle of TE incidence is less than 60 degrees.
关键词： differential evolution (DE),microwave absorber,Circuit analog (CA) absorber,equivalent circuit
更新于2025-09-04 15:30:14
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3D reticulated carbon nitride materials high-uniformly capture 0D black phosphorus as 3D/0D composites for stable and efficient photocatalytic hydrogen evolution
摘要： Black phosphorus has recently emerged as an excellent 2D semiconductor with high charge-carrier mobility and wide tunable bandgap for photocatalysis. In the research, a simple method was developed to manufacture reticulated carbon nitride materials (CN-4N). Utilizing the self-capturing property of CN-4N to catch the black phosphorus quantum dots (BQ) that were uniformly dispersed in aqueous solution, the BQ were successfully implanted into the interior surface of CN-4N, to form a unique structure instead of the normal exterior surface contact pattern. The optimized CN-4N(BQ) showed good stability and achieved an excellent hydrogen production rate of 13.83 mmol h?1 g?1, which was is 3.3 and 35.5 folds larger than that of CN-4N and bulk CN (NCN), respectively. The experimental results illustrated that greatly improved photocatalytic performance of CN-4N(BQ) was attributed to the joint actions of the abundant active sites provided by ultra-porous structures, the excellent vis-NIR absorption capability, the spatially separated reactive sites for the redox reaction, and the greatly enhanced photoinduced electron-hole separation efficiency. This research provides a novel insight for the rational fabrication of CN-based hybrids for various applications.
关键词： Black phosphorus,carbon nitride,photocatalysis,quantum dots,hydrogen evolution
更新于2025-09-04 15:30:14
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Technology Evolution and Growth Potential for Printed Electronic Papers
摘要： Electronic paper is now closer than ever to changing the way we read, write, and study. This was hailed as a revolution so profound that some see it as second only to the invention of the printing press in the 15th century. In this study, four analytical methods, which included statistical analysis, technology decomposition, multistage technological evolution and growth potential analysis were used. Results showed that technological research on business has great potential for development and vast market, and it would be another 16 years before the limit could be reached for patents. A great deal of technology breakthrough has been achieved during 1992 and 2012. The four major countries for printed electronic paper development are Japan, USA, South Korea and China. However, China has a gap compared with other countries, as the key technology was held by large enterprises. The apparatus for printed electronic paper has been the major focus in China. The key point for research on printed electronic paper was focused on devices for presentation and light emission, and related semiconductor devices.
关键词： Patent Bibliometrics,Growth Potential,Technology Evolution,S Curve,Printed Electronic Paper
更新于2025-09-04 15:30:14
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Asymmetric light transmission effect based on an evolutionary optimized semi-Dirac cone dispersion photonic structure
摘要： In this paper, we present the numerical and experimental demonstration of asymmetric light transmission by a compact photonic crystal (PC) structure, which sustains semi-Dirac cone dispersion. The semi-Dirac point is obtained by exploiting plane-wave expansion method in a rectangular unit cell of a cylindrical dielectric rod, forming a PC structure. The preselected part of the corresponding PC structure is optimized via differential evolution to maximize the transmission efficiency in one direction, and to minimize in the opposite direction. In this regard, finite-difference time-domain method is integrated with the optimization algorithm to numerically design a compact PC structure with asymmetric light transmission effect. The detailed numerical investigation of the optimized PC structure is represented, and the experiments in the microwave regime are performed to verify the numerical results. The experimentally measured transmission efficiency reaches 78% for one direction, whereas in the opposite direction it reduces to 11%. The physical mechanism of asymmetric light transmission is related to differences of the projection of the wave incident from both directions into the eigenmodes of the photonic structure.
关键词： asymmetric light transmission,semi-Dirac cone dispersion,photonic crystal,differential evolution,finite-difference time-domain method
更新于2025-09-04 15:30:14
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Carbon nanosheet facilitated charge separation and transfer between molybdenum carbide and graphitic carbon nitride toward efficient photocatalytic H2 production
摘要： Interfacial manipulation of nanostructured heterojunction photocatalysts to enhance charge separation and transfer is highly desirable to achieve a high photocatalytic activity. In this work, a well-designed non-noble-metal Mo2C@C/g-C3N4 heterostructure is constructed, in which the intercalated carbon nanosheets serve as a binder to form an excellent interfacial contact between Mo2C and g-C3N4. In addition, large quantities of carbon quantum dotsare found to be homogeneously embedded in the carbon nanosheets. The as-obtained Mo2C@C/g-C3N4 hybrid exhibits a remarkably improved photocatalytic H2 evolution rate of 52.1 μmol h?1 under visible-light irradiation (λ ≥ 420 nm) without co-catalyst, which is up to nearly 260 times higher than that of pristine g-C3N4 (0.2 μmol h?1) under the same conditions. The significant increase in photocatalytic activity mainly results from the fast charge migration and separation between Mo2C and g-C3N4 facilitated by the conducting carbon nanosheets as an efficient electron mediator. Moreover, the carbon quantum dots embedded in the carbon support also promotes solar energy utilization. This work highlights a feasible strategy to explore highly efficient photocatalysts via interfacial engineering on heterojunction composites.
关键词： H2 evolution,Photocatalysis,Water splitting,Carbon nitride,Heterojunction
更新于2025-09-04 15:30:14
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Comparison of level set models in image segmentation
摘要： Image segmentation is one of the most important tasks in modern imaging applications, which leads to shape reconstruction, volume estimation, object detection and classification. One of the most popular active segmentation models is level set models which are used extensively as an important category of modern image segmentation technique with many different available models to tackle different image applications. Level sets are designed to overcome the topology problems during the evolution of curves in their process of segmentation while the previous algorithms cannot deal with this problem effectively. As a result, there is often considerable investigation into the performance of several level set models for a given segmentation problem. It would therefore be helpful to know the characteristics of a range of level set models before applying to a given segmentation problem. In this study, the authors review a range of level set models and their application to image segmentation work and explain in detail their properties for practical use.
关键词： topology problems,curve evolution,level set models,active segmentation,image segmentation
更新于2025-09-04 15:30:14