Control of spatially homogeneous distribution of heteroatoms to produce red TiO2 photocatalyst for visible-light photocatalytic water splitting

The authors thank National Natural Science Fundation of China (Nos. 51825204, 51572266, 21633009, 51629201), the Major Basic Research Program, Ministry of Science and Technology of China (2014CB239401), the Key Research Program of Frontier Sciences CAS (QYZDB-SSW-JSC039) for the financial support. G. L. is grateful for the award of the Newton Advanced Fellowship.The strong band-to-band absorption of photocatalysts spanning the whole visible light region (400-700 nm) is critically important for solar-driven photocatalysis. Although it is actively and widely used as photocatalyst for various reactions in the past four decades, TiO2 has a very poor ability to capture the whole-spectrum visible light. Here, by controlling the spatially homogeneous distribution of boron and nitrogen heteroatoms in anatase TiO2 microspheres with a predominance of high-energy {001} facets, a strong visible light absorption spectrum with a sharp edge beyond 680 nm is achieved. The red TiO2 with the homogeneous doping of boron and nitrogen obtained shows no increase in defects like Ti3+ that are commonly observed in doped TiO2. More importantly, it has the ability to induce photocatalytic water oxidation to produce oxygen under the irradiation of visible light beyond 550 nm and also photocatalytic reducing water to produce hydrogen under visible light. These results demonstrate the great promise of using the red TiO2 for visible light photocatalytic water splitting and also provide an attractive strategy for realizing the wide-spectrum visible light absorption of wide-bandgap oxide photocatalysts.PostprintPeer reviewe

SPOC learner's final grade prediction based on a novel sampling batch normalization embedded neural network method

Recent years have witnessed the rapid growth of Small Private Online Courses (SPOC) which is able to highly customized and personalized to adapt variable educational requests, in which machine learning techniques are explored to summarize and predict the learner's performance, mostly focus on the final grade. However, the problem is that the final grade of learners on SPOC is generally seriously imbalance which handicaps the training of prediction model. To solve this problem, a sampling batch normalization embedded deep neural network (SBNEDNN) method is developed in this paper. First, a combined indicator is defined to measure the distribution of the data, then a rule is established to guide the sampling process. Second, the batch normalization (BN) modified layers are embedded into full connected neural network to solve the data imbalanced problem. Experimental results with other three deep learning methods demonstrates the superiority of the proposed method.Comment: 11 pages, 5 figures, ICAIS 202

Homogeneous doping of substitutional nitrogen/carbon in TiO2 plates for visible light photocatalytic water oxidation

The authors thank National Natural Science Foundation of China (Grant Nos. 51825204, 51572266, 21633009, and 51629201), the Key Research Program of Frontier Sciences CAS (QYZDB‐SSW‐JSC039) for the financial support. G.L. is grateful for the award of the Newton Advanced Fellowship.Extending the light absorption range of wide‐bandgap photocatalysts into the visible light region is significant in terms of fully harvesting and converting solar light. The desirable band‐to‐band redshift of the absorption edge of semiconducting binary metal oxides such as prototypical photocatalyst TiO2 by doping is long targeted but remains a challenge, up to date. Here, by taking the advantage of abundant 1D diffusion channels with rhombus‐like cross‐sections along the c‐axis in the crystal structure of titanium oxalate hydrate to promote the entrance of nitrogen dopant species into the bulk and subsequent thermal topotactic transition in an atmosphere of gaseous ammonia, homogeneous doping of substitutional carbon/nitrogen for oxygen in the TiO2 decahedral plates with a dominant anatase phase is obtained for the first time. The resultant TiO2−x(CN)y with an unusual band‐to‐band visible light absorption spectrum can induce photocatalytic water oxidation to release oxygen under visible light irradiation. This study provides not only a promising visible light–responsive TiO2 photocatalyst, but also an important strategy for developing other solar‐driven photocatalysts.PostprintPeer reviewe

Smoothed Finite Element Methods for Predicting the Mid to High Frequency Acoustic Response in the Cylinder-Head Chamber of a Diesel Engine

Modeling and simulation of the acoustic response in enclosed cavities of a diesel engine are of great significance for optimal design of an engine to achieve a better acoustic performance. Nevertheless, the use of the traditional finite element method (FEM) for the mid to high frequency acoustic prediction is limited by the well-known numerical dispersion errors and the tedious preprocessing of the model. Smoothed finite element methods (SFEMs) proposed originally for solid mechanics have been employed for the modeling of acoustic problems in the low to medium frequency ranges whilst acoustic modeling in the mid to high frequency range remains untouched. This paper comprehensively investigates into the performance of SFEMs in modeling and simulation of mid to high frequency acoustic problems. It is shown that the mass-redistributed edge-based smoothed finite element method (MR-ES-FEM) can yield an excellent prediction result in the mid to high frequency range in terms of accuracy, efficiency and robustness. The MR-ES-FEM is also used to simulate sound propagation in a cylinder head chamber of a four-cylinder diesel engine to prove its effectiveness. The findings presented in this paper offer an in-depth insight for engineers to select suitable numerical methods for solving mid to high frequency acoustic problems in the design of diesel engines.</p

Marine Coastline Polygonal Ridges and Surface Roughness Development on a Salt-Crusted Playa: Recognition by Structure-from-Motion Photogrammetry

Salt crust is a normal landform in drying-out salt lake basins or marine regression coastlines, but the surface evolution processes over a decadal or even centenary period are not well understood due to poor data records. Microrelief characteristics control erodibility and erosivity, which will significantly influence wind erosion and dust emission. It is essential to classify the microrelief pattern of salt crust for mapping its spatial distribution and evaluating the environmental process. A desiccated inland tail-end lake would be an example of the coastline surface evolution after regression and represent a good case study of salt crust because of the fewer exogenic process interruptions. For this paper, field work was performed in the Lop Nur playa in China, about 90&#176; E, 40&#176; N, which used to be a salt lake half a century ago. Ground-based photos of the salt crust were acquired and imported into structure-from-motion (SfM) software to produce a fine centimeter-scale digital elevation model (DEM). Two indexes were introduced and extracted from the digital elevation model to classify various types of salt crust: roughness was calculated to evaluate the magnitude and the gray-level co-occurrence matrix (GLCM) score was derived to describe the structure pattern of the salt crust. Moreover, in this paper, sedimentary features during different parts of a playa evaporation cycle are reviewed and peculiar kinds of salt crust found on Lop Nur are further discussed

On the use of a 2D-carbon microfiber fractionation system to improve flow-injection QTOF-HRMS analysis in complex matrices: the case of Abelmoschus manihot flower extracts

A two-dimensional microscale carbon fiber/active carbon fiber system combined with a quadrupole time of flight high-resolution mass spectrometer (2DCFs-QTOF-HRMS) system is proposed to rapidly identify polar, medium polar and weakly polar constituents in complex matrices strongly mitigating ionic suppression effects. The 2DCFS-QTOF-HRMS capabilities have been proven analysing the composition of Abelmoschus manihot flower extracts, allowing in a single run the detection of 41 known substances and the presence of 6 compounds never revealed before in these samples. 2DCFS-QTOF-HRMS has been compared with traditional HPLC-MS, showing higher versatilities, and a significant reduction of both analysis time (70 min to 5 min) and solvent consumption (35 mL to 1.5 mL). A comparison with results obtained by direct flow-injection MS analyses demonstrated that 2DCFS-QTOF-HRMS lead to a more comprehensive analysis and to an improved detection sensitivity. The proposed method can be considered suitable for rapid and comprehensive analysis of food, environmental and pharmaceutical complex samples. 2DCFs-QTOF-HRMS can be then considered a rapid, versatile, reliable, high-throughput and economical technique, that allows to obtain information on polar, semipolar, and weakly polar component in complex matrices

Circular Nonuniform Electric Field Gel Electrophoresis for the Separation and Concentration of Nanoparticles

A circular nonuniform electric field strategy coupled with gel electrophoresis was proposed to control the precise separation and efficient concentration of nano- and microparticles. The circular nonuniform electric field has the feature of exponential increase in the electric field intensity along the radius, working with three functional zones of migration, acceleration, and concentration. The distribution form of electric field lines is regulated in functional zones to control the migration behaviors of particles for separation and concentration by altering the relative position of the ring electrode (outside) and rodlike electrode (inner). The circular nonuniform electric field promotes the target-type and high-precision separation of nanoparticles based on the difference in charge-to-size ratio. The concentration multiple of nanoparticles is also controlled randomly with the alternation of radius, taking advantage of vertical extrusion and concentric converging of the migration path. This work provides a brand new insight into the simultaneous separation and concentration of particles and is promising for developing a versatile tool for the separation and preparation of various samples instead of conventional methods