智慧城市建设过程中宽带接入网全光化的必要性与对策

随着我国经济的发展,人们生活水平的提高,人们对于居住的环境的要求也越来越高,随之智慧城市的理念被提出。在智慧城市的建设当中对于相应的通讯技术提出了比较高的要求,特别是对于宽带入网的建设提出了更高的要求,这给行业的生厂商和运用商提出了比较高的挑战,从而就出现了全光宽带接入网,其在智慧城市建设中的运用对其有很重要的意义。文章主要对智慧城市建设过程中宽带接入网全光化的必要性与对策作分析介绍。

智慧城市建设中宽带接入网全光化问题研究

本文以智慧城市建设中宽带接入网全光化问题研究为题展开论述。首先,分析了当前我国宽带接入网全光化建设中存在的问题。然后,结合实际的个工作经验,提出了加快宽带接入网全光化建设的对策。希望可以解决宽带接入网中存在的问题,促进通信技术的快速发展,加快智慧城市建设的速度。

浅谈现代通信技术的未来发展方向

现代信息社会发挥趋势下,通信技术作为信息技术中的重要的组成部分。在现实生活中极为重要,过去,人们主要通过人力、信件方式来达到信息的联络传达,而这种时代早已成为历史,现代电子信息技术的发展改变了人类的生活,电子通信技术的发明是人类发展史上的又一重大突破,让人与人之间,信息与信息之间的通信变得更加快速与安全。而未来随着人们通信生活方式的不断提高,会对通信技术的速度和安全性带来更大的要求,因此,传输信息的方式会有所改变,本文主要就现代通信技术的未来发展方向进行分析。

Importance, features and uses of metal oxide catalysts in heterogeneous catalysis

This short review paper aims at assembling the present state of the art of the multiuses of metal oxides in heterogeneous catalysis, concerning liquid and gaseous phases of the reactant mixtures on solid catalysts. It includes the description of the main types of metal oxide catalysts, of their various preparation procedures and of the main reactions catalysed by them (acid-base type, selective and total oxidations, bi-functional catalysis, photocatalysis, biomass treatments, environmental catalysis and some of the numerous industrial applications). Challenges and prospectives are also discussed.

Water oxidation sites located at the interface of Pt/SrTiO_(3) for photocatalytic overall water splitting

When a proton reduction cocatalyst is loaded on an n-type semiconductor for photocatalytic overall water splitting(POWS),the location of water oxidation sites is generally considered at the surface of the semiconductor due to upward band-bending of n-type semiconductor which may ease the transfer of the photogenerated holes to the surface.However,this is not the case for Pt/SrTiO_(3),a model semiconductor based photocatalyst for POWS.It was found that the photogenerated holes are more readily accumulated at the interface between Pt cocatalyst and SrTiO_(3) photocatalyst as probed by photo-oxidative deposition of PbO_(2),indicating that the water oxidation sites are located at the interface between Pt and SrTiO_(3).Electron paramagnetic resonance and scanning transmission electron microscope studies suggest that the interfacial oxygen atoms between Pt and SrTiO_(3) in Pt/SrTiO_(3) after POWS are more readily lost to form oxygen vacancies upon vacuum heat treatment,regardless of Pt loading by photodeposition or impregnation methods,which may serve as additional support for the location of the active sites for water oxidation at the interface.Density functional theory calculations also suggest that the oxygen evolution reaction more readily occurs at the interfacial sites with the lowest overpotential.These experimental and theoretical studies reveal that the more active sites for water oxidation are located at the interface between Pt and SrTiO_(3),rather than on the surface of SrTiO_(3).Hence,the tailor design and control of the interfacial properties are extremely important for the achievement or improvement of the POWS on cocatalyst loaded semiconductor photocatalyst.

Design of p-n homojunctions in metal-free carbon nitride photocatalyst for overall water splitting

Two-dimensional(2D)carbon nitride(CN)photocatalysts are attracting extensive attention owing to their excellent photocatalytic properties.In this study,we successfully prepared CN materials with heterogeneous structures via hydrothermal treatment,high-temperature roasting,ball milling,sintering,and other processes.Benefitting from interface interactions in hybrid architectures,the CN photocatalysts exhibited high photocatalytic activity.The rate of hydrogen production using these CN photocatalysts reached 17028.82μmol h^(−1)g^(−1),and the apparent quantum efficiency was 11.2%at 420 nm.The ns-level time-resolved photoluminescence(PL)spectra provided information about the time-averaged lifetime of fluorescence charge carriers;the lifetime of the charge carriers causing the fluorescence of CN reached 9.99 ns.Significantly,the CN photocatalysts displayed satisfactory results in overall water splitting without the addition of sacrificial agents.The average hydrogen and oxygen production rates were 270.95μmol h^(−1)g^(−1)and 115.21μmol h^(−1)g^(−1)in 7 h,respectively,which were promising results for the applications of the catalysts in overall water splitting processes.We investigated the high efficiency of the prepared CN photocatalysts via a series of tests(UV-vis diffuse reflectance spectroscopy,photocurrent response measurements,PL emission spectroscopy,time-resolved PL spectroscopy,and Brunauer-Emmett-Teller analysis).Furthermore,the Mott-Schottky plot and current-voltage curve were acquired via electrochemical tests.The fabricated CN photocatalyst had a small p-n junction in its heterogeneous structure,which further enhanced its photocatalytic efficiency.Therefore,this work can promote the development of CN photocatalysts.

Noble metal-like behavior of plasmonic Bi particles deposited on reduced TiO2 microspheres for efficient full solar spectrum photocatalytic oxygen evolution

Herein, novel plasmonic Bi metal in situ deposited in reduced Ti O2 microspheres(Bi@R-Ti O2) are fabricated via a bimetallic MOF-derived synthesized strategy by adjusting the synthesizing temperature. Different characterization techniques, including XRD, SEM, TEM, XPS, DRS, PL, EIS, and photocurrent generation, are performed to investigate the structural and optical properties of the as-prepared samples. The results indicate that the Bi particles are generated inside and outside of reduced Ti O2 microspheres via the reduction of Ti4+ and Bi3+ by ethylene glycol. When the annealing temperature is controlled at 300 o C, the corresponding Bi@R-Ti O2-300 sample with an appropriate amount of Bi nanoparticles exhibits the highest full solar spectrum photocatalytic oxygen evolution activity(4728.709 μmol h–1 g–1), which is 5.9 and 9.5 times higher than that of pure Ti O2 and Bi-Ti bimetal organic frameworks(Bi-Ti-MOFs). Several reasons are suggested for the above results:(1) Bi metal behaves as an "electron acceptor" to accelerate the charge carrier transfer from Ti O2 to Bi;(2) The surface plasmon resonance effect of loaded metallic Bi particles can enhance the visible and NIR light absorption capacity;(3) The generation of Ti3+ further narrows the band gap of TiO2.

Ti_(3)C_(2)T_(x)MXene doped by W atoms for full-spectrum photofixation of nitrogen

Full-spectrum photofixation of N_(2) with remarkable NH_(3) production rate of 228μmol/(g·h)was achieved by W atoms doped Ti_(3)C_(2)T_(x)MXene(W/Ti_(3)C_(2)T_(x)-U)catalyst without sacrificial agents at room temperature.The effects of W doping and ultrasonic intercalation of Ti_(3)C_(2)T_(x)MXene were studied.Scanning transmission electron microscope,electron spin resonance spectra,X-ray photoemission spectroscopy,UV-Vis spectrophotometer,temperature programmed adsorption analyzer and density functional theory calculation were used to characterize the obtained catalysts.Results showed that Ti_(3)C_(2)T_(x)MXene harvested ultraviolet-visible and near-infrared light to generate hot electrons.In addition,the doped W atoms played an effective role in adsorbing and activating N_(2) molecules by donating electrons to the anti-bonding orbital of N_(2) molecules to elongate the bond length of N≡N.

Noble-metal-free plasmonic MoO_(3-x)-based S-scheme heterojunction for photocatalytic dehydrogenation of benzyl alcohol to storable H2 fuel and benzaldehyde

Simultaneous generation of H_(2) fuel and value-added chemicals has attracted increasing attention since the photogenerated electrons and holes can be both employed to convert solar light into chemical energy.Herein,for realizing UV-visible-NIR light driven dehydrogenation of benzyl alcohol(BA)into benzaldehydes(BAD)and H_(2),a novel localized surface plasmon resonance(LSPR)enhanced S-scheme heterojunction was designed by combining noble-metal-free plasmon MoO_(3-x) as oxidation semiconductor and Zn_(0.1)Cd_(0.9)S as reduction semiconductor.The photoredox system of Zn_(0.1)Cd_(0.9)S/MoO_(3-x) displayed an unconventional reaction model,in which the BA served as both electron donor and acceptor.The S-scheme charge transfer mechanism induced by the formed internal electric field enhanced the redox ability of charge carriers thermodynamically and boosted charge separation kinetically.Moreover,due to the LSPR effect of MoO_(3-x) nanosheets,Zn_(0.1)Cd_(0.9)S/MoO_(3-x) photocatalysts exhibited strong absorption in the region of full solar spectrum.Therefore,the Zn_(0.1)Cd_(0.9)S/MoO_(3-x) composite generated H_(2) and BAD simultaneously via selective oxidation of BA with high production(34.38 and 33.83 mmol×g^(–1) for H_(2) and BAD,respectively)upon full solar illumination.Even under NIR light irradiation,the H_(2) production rate could up to 94.5 mmol×g^(–1)×h^(–1).In addition,the Zn_(0.1)Cd_(0.9)S/MoO_(3-x) composite displayed effective photocatalytic H_(2) evolution rate up to 149.2 mmol×g^(–1)×h^(–1) from water,which was approximate 6 times that of pure Zn_(0.1)Cd_(0.9)S.This work provides a reference for rational design of plasmonic S-scheme heterojunction photocatalysts for coproduction of high-value chemicals and solar fuel production.

Complete removal of phenolic contaminants from bismuth-modified TiO2 single-crystal photocatalysts

Exploring low-cost and highly active photocatalysts is very urgent to accomplish complete removal of phenolic contaminants and overcome the limitations of the existing photocatalysts.In this study,we designed and synthesized noble metal-free TiO2 photocatalysts by introducing bismuth nanoparticles as modifiers of a TiO2 single crystal(Bi-SCTiO2).The Bi-SCTiO2 can make full use of the synergistic effect of a small band overlap and low charge carrier density(Bi)with a high conductivity(single crystal),significantly boosting the separation and migration of the photogenerated charge pairs.Therefore,the Bi-SCTiO2 photocatalyst exhibits a significantly enhanced degradation rate(12 times faster)of 4-nitrophenol than a TiO2 single crystal under simulated sunlight irradiation.Notably,the complete removal of phenolic contaminants is achieved in various water matrices,which not only successfully overcomes the incomplete degradation in many reported photocatalytic systems,but also manifests a significant practical potential for sewage disposal.Therefore,this work presents a new insight in designing and constructing noble metal-free decorated semiconductor single-crystal photocatalysts with excellent activity and cyclability.

Visible light induced TiO_2 pillared MMT photocatalyst coupling-doped with S and N

Visible light induced titanium dioxide (TiO2) pillared montmorillonite clay (MMT) photocatalyst coupling-doped with S and N elements was prepared by the two-step ad- sorption method.The photocatalyst was characterized by X-ray photoelectron spectros- copy (XPS) and ultraviolet-visible (UV-vis) absorption spectroscopy.The photocatalysic ef- ficacy of the prepared photocatalyst for degrading gaseous formaldehyde was evaluated under visible light irradiation.The degrading rate of gaseous formaldehyde is nearly 85% in 300 min visible light irradiation.The results demonstrate that the much higher visible light photocatalytic activity of the photocatalyst is due to the synergistic effects of coupling- doping of S and N elements to TiO2,extensive specific surface area of MMT and quantum sized efficacy between layers of MMT.

Global Water Vapor Content Decreases from 2003 to 2012： An Analysis Based on MODIS Data

Water vapor in the earth′s upper atmosphere plays a crucial role in the radiative balance, hydrological process, and climate change. Based on the latest moderate-resolution imaging spectroradiometer(MODIS) data, this study probes the spatio-temporal variations of global water vapor content in the past decade. It is found that overall the global water vapor content declined from 2003 to 2012(slope b = –0.0149, R = 0.893, P = 0.0005). The decreasing trend over the ocean surface(b = –0.0170, R = 0.908, P = 0.0003) is more explicit than that over terrestrial surface(b = –0.0100, R = 0.782, P = 0.0070), more significant over the Northern Hemisphere(b = –0.0175, R = 0.923, P = 0.0001) than that over the Southern Hemisphere(b = –0.0123, R = 0.826, P = 0.0030). In addition, the analytical results indicate that water vapor content are decreasing obviously between latitude of 36°N and 36°S(b = 0.0224, R = 0.892, P = 0.0005), especially between latitude of 0°N and 36°N(b = 0.0263, R = 0.931, P = 0.0001), while the water vapor concentrations are increasing slightly in the Arctic regions(b = 0.0028, R = 0.612, P = 0.0590). The decreasing and spatial variation of water vapor content regulates the effects of carbon dioxide which is the main reason of the trend in global surface temperatures becoming nearly flat since the late 1990 s. The spatio-temporal variations of water vapor content also affect the growth and spatial distribution of global vegetation which also regulates the global surface temperature change, and the climate change is mainly caused by the earth's orbit position in the solar and galaxy system. A big data model based on gravitational-magmatic change with the solar or the galactic system is proposed to be built for analyzing how the earth's orbit position in the solar and galaxy system affects spatio-temporal variations of global water vapor content, vegetation and temperature at large spatio-temporal scale. This comprehensive examination of water vapor changes promises a holistic understanding of the global climate change and potential underlying mechanisms.

Towards full-spectrum photocatalysis： Achieving a Z-scheme between Ag2S and TiO2 by engineering energy band alignment with interfacial Ag

A Z-scheme is a promising approach to achieve broad-spectrum photocatalysis. Integration of TiO2 with another semiconductor with a band gap of -1.0 eV would be ideal to harvest both ultraviolet and visible-near infrared light for photocatalysis; however, most narrow-bandgap semiconductors have straddling band structure alignments with TiO2, constituting an obstacle to forming the Z-scheme for photocatalytic hydrogen production. In this communication, we demonstrate Ag2S as a model system where the energy band upshift of the narrow-bandgap semiconductor that shares an interface with a metal can overcome this limitation. To fabricate the design, we developed a unique approach to synthesize Ag2S-Ag-TiO2 hybrid structures. The obtained ternary hybrid structures exhibited dramatically enhanced performance in photocatalytic hydrogen pro- duction under full-spectrum light illumination. The activities were significantly higher than the sum of those of Ag2S-Ag-TiO2 structures under λ〈 400 nm and λ 〉 400 nm irradiation as well as those of their counterparts under any light illumination conditions.

Recent progress on advanced design for photoelectrochemical reduction of CO_2 to fuels

The energy crisis and global warming become severe issues. Solar-driven CO2 reduction provides a promising route to confront the predicaments, which has received much attention. The photoelectrochemical（PEC） process,which can integrate the merits of both photocatalysis and electrocatalysis, boosts splendid talent for CO2 reduction with high efficiency and excellent selectivity. Recent several decades have witnessed the overwhelming development of PEC CO2 reduction. In this review, we attempt to systematically summarize the recent advanced design for PEC CO2 reduction. On account of basic principles and evaluation parameters, we firstly highlight the subtle construction for photocathodes to enhance the efficiency and selectivity of CO2 reduction, which includes the strategies for improving light utilization, supplying catalytic active sites and steering reaction pathway.Furthermore, diversiform novel PEC setups are also outlined.These exploited setups endow a bright window to surmount the intrinsic disadvantages of photocathode, showing promising potentials for future applications. Finally, we underline the challenges and key factors for the further development of PEC CO2 reduction that would enable more efficient designs for setups and deepen systematic understanding for mechanisms.

Quantum field entropy of the system with interaction between moving Bell-state atoms and coherent light field

The field entropy of the system with two moving atoms interacting with the coherent state is investigated by means of the full quantum theory. Under the different initial states with two atoms, the influences of the light field intensity and the atomic motion on the field entropy are discussed. The results indicate that the motion of the atoms leads to strict periodicity in the field entropy evolution. When the two atoms are in the Bell state ｜β11〉 initially, the system is in a completely disentangled state. For the atoms initially at other Bell states, the field periodically entangles with the atoms.