[Foreword] Welcome to the Transactions on Media Technology and Applications:The Institute of Image Information and Television Engineers (ITE) has decided to launch a new open access journal, titled "Media Technology and Applications" (MTA).

PHDFS: Optimizing I/O performance of HDFS in deep learning cloud computing platform

Graphdiyne (g-CnH2n-2) is a new carbon material composed of sp and sp2 hybrid carbon atoms. Since the synthesis by Li's team, graphdiyne has been widely studied in other fields because of its excellent properties. In this paper, graphdiyne was synthesized from copper-containing materials and the composite GDY/CuI/MIL-53(Al) S-scheme heterojunction is prepared for photocatalytic cracking of water to produce hydrogen. First, GDY/CuI was prepared by organic synthesis, and then GDY/CuI was anchored on the surface of MIL-53(Al) by in situ ultrasonic stirring. After the continuous optimization of experimental conditions, the final hydrogen evolution rate is much higher than that of MIL-53(Al). This efficient photocatalytic performance can be attributed to the S-scheme heterojunction formed by the unique energy band arrangement. At the same time, the mechanism of charge transfer was demonstrated by in situ irradiation X-ray photoelectron spectroscopy. The strong interaction among the three strongly promotes the separation and transfer of photogenerated electron-hole pairs.

Graphdiyne (CnH2n-2)-Based GDY/CuI/MIL-53(Al) S-Scheme Heterojunction for Efficient Hydrogen Evolution.

Hadoop Perfect File: A fast and memory-efficient metadata access archive file to face small files problem in HDFS

Novel Preparation Strategy of Graphdiyn (Cnh2n-2): One-Pot Conjugation and S-Scheme Heterojunctions Formed with Mop Characterized with in Suit Xps for Efficiently Photocatalytic Hydrogen Evolution

: Industrialization undoubtedly boosts economic development and improves the standard of living; however, it also leads to some serious problems, including the energy crisis, environmental pollution, and global warming. These problems are associated with or caused by the high carbon dioxide (CO 2 ) and sulfur dioxide (SO 2 ) emissions from the burning of fossil fuels such as coal, oil, and gas. Photocatalysis is considered one of the most promising technologies for eliminating these problems because of the possibility of converting CO 2 into hydrocarbon fuels and other valuable chemicals using solar energy, hydrogen (H 2 ) production from water (H 2 O) electrolysis, and degradation of pollutants. Among the various photocatalysts, silicon carbide (SiC) has great potential in the fields of photocatalysis, photoelectrocatalysis, and electrocatalysis because of its good electrical properties and photoelectrochemistry. This review is divided into six sections: introduction, fundamentals of nanostructured SiC, synthesis methods for obtaining nanostructured SiC photocatalysts, strategies for improving the activity of nanostructured SiC photocatalysts, applications of nanostructured SiC photocatalysts, and conclusions and prospects. The fundamentals of nanostructured SiC include its physicochemical characteristics. It possesses a range of unique physical properties, such as extreme hardness, high mechanical stability at high temperatures, a low thermal expansion coefficient, wide bandgap, and superior thermal conductivity. It also possesses exceptional chemical characteristics, such as high oxidation and corrosion resistance. The synthesis methods for obtaining nanostructured SiC have been systematically summarized as follows: Template growth, sol-gel, organic precursor pyrolysis, solvothermal synthesis, arc discharge, carbon thermal reduction, and electrospinning. These synthesis methods require high temperatures, and the reaction mechanism involves SiC formation via the reaction between carbon and silicon oxide. In the section of the review involving the strategies for improving the activity of nanostructured SiC photocatalysts, seven strategies are discussed, viz. , element doping, construction of Z-scheme (or S-scheme) systems, supported co-catalysts, visible photosensitization, construction of semiconductor heterojunctions, supported carbon materials, and construction of nanostructures. All of these strategies, except element doping and visible photosensitization, concentrate on enhancing the separation of holes and electrons, while suppressing their recombination, thus improving the photocatalytic performance of the nanostructured SiC photocatalysts. Regarding the element doping and visible photosensitization strategies, element doping can narrow the bandgap of SiC, which generates more holes and electrons to improve photocatalytic activity. On the other hand, the principle of visible photosensitization is that photo-induced electrons move from photosensitizers to the conduction band of SiC to participate in the reaction, thus enhancing the photocatalytic performance. In the section on the applications of nanostructured SiC, photocatalytic H 2 production, pollutant degradation, CO 2 reduction, photoelectrocatalytic, and electrocatalytic applications will be discussed. The mechanism of a photocatalytic reaction requires the SiC photocatalyst to produce photo-induced electrons and holes during irradiation, which participate in the photocatalytic reaction. For example, photo-induced electrons can transform protons into H 2 , as well as CO 2 into methane, methanol, or formic acid. Furthermore, photo-induced holes can convert organic waste into H 2 O and CO 2 . For photoelectrocatalytic and electrocatalytic applications, SiC is used as a catalyst under high temperatures and highly acidic or basic environments because of its remarkable physicochemical characteristics, including low thermal expansion, superior thermal conductivity, and high oxidation and corrosion resistance. The last section of the review will reveal the major obstacles impeding the industrial application of nanostructured SiC photocatalysts, such as insufficient visible absorption, slow reaction kinetics, and hard fabrication, as well as provide some ideas on how to overcome these obstacles. photocatalysts.

Advances in Nanostructured Silicon Carbide Photocatalysts

Hadoop Distributed File System (HDFS) is designed to reliably storage and manage large-scale files. All the files in HDFS are managed by a single server, the NameNode. The NameNode stores metadata, in its main memory, for each file stored into HDFS. HDFS suffers the penalty of performance with increased number of small files. It imposes a heavy burden to the NameNode to store and manage a mass of small files. The number of files that can be stored into HDFS is constrained by the size of NameNode’s main memory. In order to improve the efficiency of storing and accessing the small files on HDFS, we propose Small Hadoop Distributed File System (SHDFS), which bases on original HDFS. Compared to original HDFS, we add two novel modules in the proposed SHDFS: merging module and caching module. In merging module, the correlated files model is proposed, which is used to find out the correlated files by user-based collaborative filtering and then merge correlated files into a single large file to reduce the total number of files. In caching module, we use Log - linear model to dig out some hot-spot data that user frequently access to, and then design a special memory subsystem to cache these hot-spot data. Caching mechanism speeds up access to hot-spot data.

Hadoop Massive Small File Merging Technology Based on Visiting Hot-Spot and Associated File Optimization

Semiconductor‐based photocatalytic solar‐to‐fuel conversion has proven an appealing strategy for achieving carbon‐neutral and green‐hydrogen production. However, almost all semiconductors exhibit unsatisfactory photocatalytic performance due to insufficient surface‐active sites, weak selectivity, and fast charge‐carrier recombination. For these reasons, cocatalyst loading has become an encouraging strategy for improving photocatalytic activity and selectivity. Owing to the scarcity, and cost of noble metal‐based cocatalysts, utilization of low‐cost noble‐metal‐free cocatalysts, such as metal carbide‐based cocatalysts, has aroused tremendous attention. This review highlights some recent crucial advances in active metal carbide‐based cocatalysts for photocatalytic solar‐to‐fuel conversion. First, the fundamentals of metal carbide‐based cocatalysts are presented, including the photocatalytic mechanism, advantages, drawbacks, and design rules. Second, three synthesis approaches of high‐active metal carbide‐based cocatalysts, namely constructing metal carbide nanostructures, epitaxial synthesis of metal carbides on nanostructured carbon, and crystal imperfection construction on metal carbides, are thoroughly addressed. Subsequently, applications of metal carbide‐based cocatalysts in photocatalytic hydrogen production, CO2 reduction, and nitrogen reduction are further discussed. Finally, the crucial challenges and important directions of metal carbide‐based cocatalysts for photocatalytic solar‐to‐fuel conversion are proposed. This review demonstrates some new options for rationally designing and developing novel and efficient metal carbide‐based cocatalysts for highly active and selective photocatalytic solar‐to‐fuel conversion.

Metal Carbide‐Based Cocatalysts for Photocatalytic Solar‐to‐Fuel Conversion

One of the most unique properties of two-dimensional carbides and nitrides of transition metals (MXenes) is their excellent water dispersibility and yet possessing superior electrical conductivity but their industrial-scale application is limited by their costly chemical synthesis methods. In this work, the niche feature of MXenes was capitalized in the packed-bed electrochemical reactor to produce MXenes at an unprecedented reaction rate and yield with minimal chemical waste. A simple NH4F solution was employed as the green electrolyte, which could be used repeatedly without any loss in its efficacy. Surprisingly, both fluoride and ammonium were found to play critical roles in the electrochemical etching, functionalization, and expansion of the layered parent materials (MAXs) through which the liberation of ammonia gas was observed. The electrochemically produced MXenes with excellent conductivity, applied as supercapacitor electrodes, could deliver an ultrahigh volumetric capacity (1408 F cm−3) and a volumetric energy density (75.8 Wh L−1). This revolutionary green, energy-efficient, and scalable electrochemical route will not only pave the way for industrial-scale production of MXenes but also open up a myriad of versatile electrochemical modifications for improved functional MXenes. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/cey2.295

Ke-jing He

Papers

Advances in Nanostructured Silicon Carbide Photocatalysts

Hadoop Massive Small File Merging Technology Based on Visiting Hot-Spot and Associated File Optimization

Metal Carbide‐Based Cocatalysts for Photocatalytic Solar‐to‐Fuel Conversion

Green and scalable electrochemical routes for cost‐effective mass production of MXenes for supercapacitor electrodes