基于快速核独立分量分析的图像反光分离研究

透过玻璃对场景成像,图像由场景实像和反光虚像线性叠加而成,直接影响到图像分析处理和计算机视觉应用等,可采用盲源分离方法进行反光分离。图像成像过程中的非线性因素,会使线性独立分量分析(ICA)用于反光分离结果不够精确。采用基于Hilbert-Schmidt独立性判断准则的快速核独立分量分析(FastKICA)进行图像反光分离。实验表明,快速核独立分量分析用于图像反光分离,在分离精度和速度上优于线性独立分量分析和常规核独立分量分析(KICA)。

SrTiO3/BiOI heterostructure: Interfacial charge separation, enhanced photocatalytic activity, and reaction mechanism

Heterostructured photocatalysts provide an effective way to achieve enhanced photocatalytic performances through efficient charge separation.Although both wide-and narrow-band-gap photocatalysts have been widely investigated,the charge separation and transfer mechanism at the contacting interface of the two has not been fully revealed.Here,a novel SrTiO3/BiOI(STB)heterostructured photocatalyst was successfully fabricated by using a facile method.The heterostructure in the photocatalyst extends the photoabsorption to the visible light range,and thus,high photocatalytic NO removal performance can be achieved under visible light irradiation.A combination of experimental and theoretical evidences indicated that the photogenerated electrons from the BiOI semiconductor can directly transfer to the SrTiO3 surface through a preformed electron delivery channel.Enhanced electron transfer was expected between the SrTiO3 and BiOI surfaces under light irradiation,and leads to efficient ROS generation and thus a high NO conversion rate.Moreover,in situ diffused reflectance infrared Fourier transform spectroscopy revealed that STB can better inhibit the accumulation of the toxic intermediate NO2 and catalyze the NO oxidation more effectively.This work presents a new insight into the mechanism of the interfacial charge separation in heterostructures and provides a simple strategy to promote the photocatalytic technology for efficient and safe air purification.

Photosynthetic responses of thalli and isolated protoplasts of Bryopsis hypnoides(Bryopsidales,Chlorophyta)during dehydration

Bryopsis kypnoides Lamouroux is a unique intertidal siphonous green alga whose extruded protoplasm can aggregate spontaneously in seawater to form numerous new cells that can develop into mature algal thalli. In this study, the photosynthetic responses during dehydration of both the thalli and protoplasts isolated from B. kypnoides were measured using a Dual-PAM （pulse amplitude modulation）-100 fluorometer. The results show that the photosynthetic rates of B. kypnoides thalli were maintained for an initial period, beyond which continued desiccation resulted in reduced rates of PSI and PSII. However, the photosynthetic performances of the isolated protoplasts dehydrated in air （CO2 concentration 600-700 mg/L） showed a slight increase of Y（II） at 20% water loss, but the rates decreased thereafter with declining water content. When protoplasts were dehydrated in CO2 deficient conditions （CO2 concentration 40-80 mg/L）, the values of Y（II） declined steadily with increased dehydration without an initial rise. These results indicated that the thalli and isolated protoplasts of this alga can utilize CO2 in ambient air effectively, and the photosynthetic performances of the isolated protoplasts were significantly different from that of the thalli during dehydration. Thus the protoplasts may be an excellent system for the study of stress tolerance.

Progress in designing effective photoelectrodes for solar water splitting

Photoelectrochemical(PEC)water splitting process is regarded as a promising route to generate hydrogen by solar energy and at the heart of PEC is efficient electrode design.Great progress has been achieved in the aspects of material design,cocatalyst study,and electrode fabrication over the past decades.However,some key challenges remain unsolved,including the most demanded conversion efficiency issue.As three critical steps,i.e.light harvesting,charge transfer and surface reaction of the PEC process,occur in a huge range of time scale(from10-12s to100s),how to manage these subsequent steps to facilitate the seamless cooperation between each step to realize efficient PEC process is essentially important.This review focuses on an integral consideration of the three key criteria based on the recent progress on high efficient and stable photoelectrode design in PEC.The basic principles and potential strategies are summarized.Moreover,the challenge and perspective are also discussed.

Surface assembly of cobalt species for simultaneous acceleration of interfacial charge separation and catalytic reactions on Cd_(0.9)Zn_(0.1)S photocatalyst

Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit progress in solar energy conversion using semiconductor photocatalysts.Herein,we demonstrate a feasible strategy involving the surface assembly of cobalt oxide species(CoO_(x))on a visible-light-responsive Cd_(0.9)Zn_(0.1)S(CZS)photocatalyst to fabricate a hierarchical CZS@CoO_(x) heterostructure.The unique hierarchical structure effectively accelerates the directional transfer of photogenerated charges,reducing charge recombination through the smooth interfacial heterojunction between CZS and CoO_(x),as evidenced by photoluminescence(PL)spectroscopy and various electrochemical characterizations.The surface cobalt species on the CZS material also act as efficient cocatalysts for photocatalytic hydrogen production,with activity even higher than that of noble metals.The well-defined CZS@CoO_(x) heterostructure not only enhances the interfacial separation of photoinduced charges,but also improves surface catalytic reactions.This leads to superior photocatalytic performances,with an apparent quantum efficiency of 20%at 420 nm for visible-light-driven hydrogen generation,which is one of the highest quantum efficiencies measured among noble-metal-free photocatalysts.Our work presents a potential pathway for controlling complex charge separation and catalytic reaction processes in photocatalysis,guiding the practical development of artificial photocatalysts for successful transformation of solar to chemical energy.

Ar/N2/CH4 Glow Discharge at Low Pressures

Ar/N2/CH4 glow discharge at low-pressure are studied in a closed system. The plasma was produced in 79.6% N2-15.4% Ar- 5.0% CH4 ternary mixture at pressures between 0.5 and 10.0 Torr. The diagnostic has been made by optical emission spectroscopy （OES）. The principal species observed were： N2, N2＋, CH＋, CN, C2, C3, HI3, Ha, C＋ and At. It presents the behaviour of the bands and lines intensities as a function of the pressure. Also, it displays the ratios of intensities of N＋2 （391.44 nm）, CN （392.08 nm）, and H （486.13 nm） to that of the N2 （337.13 rim） as function of pressure. The ratios show a slow decreasing behavior as a function of the pressure. Being the CH/N2 ratio more highest and H/N2 ratio the lowest one. The variations of excited species at different pressures may change the subsequent chemical reactions in the gas phase significantly. The present results suggest that the ion-molecule and molecule-molecule reactions in the gas phase are likely to play a dominant role in the present pressures.

In situ FT-IR investigation on the reaction mechanism of visible light photocatalytic NO oxidation with defective g-C_3N_4

The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were analyzed with advanced tools. The results showed that the CN-U has a porous structure, a high specific surface area and a wide band gap in comparison with CN-T. The in situ FT-IR technique was used to monitor the adsorption and reaction process of visible photocatalytic NO oxidation on g-C_3N_4. The corresponding reaction mechanism was proposed based on the results of reaction intermediate observation and electron paramagnetic resonance(EPR) radical scavenging. It was revealed that(1) the presence of defective sites favored the adsorption of gas molecules and electronically compensated it leading to promoted formation of the final products;(2) the high separation efficiency of photogenerated electron-hole pairs enhanced the production of radicals during the photocatalytic reaction;(3) the hydroxyl radicals(-OH) are not selective for the decomposition of pollutants, which are favorable to the complete oxidation of the reaction intermediates. The above three aspects are the main reasons for the CN-U possessing the efficient visible light photocatalytic activity. The present work could provide new insights and methods for understanding the mechanism of photocatalysis.

Boosting visible-light-driven water splitting over LaTaON_(2) via Al doping

LaTaON_(2)is an attractive visible-light-active photocatalyst for water splitting due to its broad visible light absorption as far as 650 nm and proper band edge positions.Notwithstanding these promising properties,LaTaON_(2)generally exhibits poor photocatalytic activity because of its high defect concentration that severely hinders charge separation.Here,LaTaON_(2)has been modified by doping Al into the Ta sublattice,i.e.,LaTa_(1−x)Al_(x)O_(1+y)N_(2−y)(0≤x≤0.20).Al doping not only inhibits the defect concentration and increases surface hydrophilicity but also maintains the desired visible light absorption of LaTaON_(2).These important modifications substantially ameliorate the charge separation conditions within LaTaON_(2)and are responsible for a much enhanced photocatalytic performance for water redox reactions under visible light illumination.Under optimal conditions,the Al-doped LaTaON_(2)delivers an apparent quantum efficiency of 1.17%at 420±20 nm for water oxidation into O_(2),outperforming most LaTaON_(2)-based photocatalysts.These findings highlight Al as a useful dopant to open up the photocatalytic potential of metal oxynitrides whose activity is often undermined by a high defect concentration.