High-performance flat-panel solar thermoelectric generators with high thermal concentration

The conversion of sunlight into electricity has been dominated by photovoltaic and solar thermal power generation. Photovoltaic cells are deployed widely, mostly as flat panels, whereas solar thermal electricity generation relying on optical concentrators and mechanical heat engines is only seen in large-scale power plants. Here we demonstrate a promising flat-panel solar thermal to electric power conversion technology based on the Seebeck effect and high thermal concentration, thus enabling wider applications. The developed solar thermoelectric generators (STEGs) achieved a peak efficiency of 4.6% under AM1.5G (1 kW m(-2)) conditions. The efficiency is 7-8 times higher than the previously reported best value for a flat-panel STEG, and is enabled by the use of high-performance nanostructured thermoelectric materials and spectrally-selective solar absorbers in an innovative design that exploits high thermal concentration in an evacuated environment. Our work opens up a promising new approach which has the potential to achieve cost-effective conversion of solar energy into electricity.     

All Inorganic Halide Perovskites Nanosystem: Synthesis,Structural Features,Optical Properties and Optoelectronic Applications

The recent success of organometallic halide perovskites (OHPs) in photovoltaic devices has triggered lots of corresponding research and many perovskite analogues have been developed to look for devices with comparable performance but better stability. Upon the preparation of all inorganic halide perovskite nanocrystals (IHP NCs), research activities have soared due to their better stability, ultrahigh photoluminescence quantum yield (PL QY), and composition dependent luminescence covering the whole visible region with narrow line‐width. They are expected to be promising materials for next generation lighting and display, and many other applications. Within two years, a lot of interesting results have been observed. Here, the synthesis of IHPs is reviewed, and their progresses in optoelectronic devices and optical applications, such as light‐emitting diodes (LEDs), photodetectors (PDs), solar cells (SCs), and lasing, is presented. Information and recent understanding of their crystal structures and morphology modulations are addressed. Finally, a brief outlook is given, highlighting the presently main problems and their possible solutions and future development directions.     

Greatly Enhanced Anticorrosion of Cu by Commensurate Graphene Coating

Metal corrosion is a long‐lasting problem in history and ultrahigh anticorrosion is one ultimate pursuit in the metal‐related industry. Graphene, in principle, can be a revolutionary material for anticorrosion due to its excellent impermeability to any molecule or ion (except for protons). However, in real applications, it is found that the metallic graphene forms an electrochemical circuit with the protected metals to accelerate the corrosion once the corrosive fluids leaks into the interface. Therefore, whether graphene can be used as an excellent anticorrosion material is under intense debate now. Here, graphene‐coated Cu is employed to investigate the facet‐dependent anticorrosion of metals. It is demonstrated that as‐grown graphene can protect Cu(111) surface from oxidation in humid air lasting for more than 2.5 years, in sharp contrast with the accelerated oxidation of graphene‐coated Cu(100) surface. Further atomic‐scale characterization and ab initio calculations reveal that the strong interfacial coupling of the commensurate graphene/Cu(111) prevents H₂O diffusion into the graphene/Cu(111) interface, but the one‐dimensional wrinkles formed in the incommensurate graphene on Cu(100) can facilitate the H₂O diffusion at the interface. This study resolves the contradiction on the anticorrosion capacity of graphene and opens a new opportunity for ultrahigh metal anticorrosion through commensurate graphene coating.     

K-NN与SVM相融合的文本分类技术研究

提出了一种改进的K-NN(K Nearest Neighbor)与SVM(Support Vector Machine)相融合的文本分类算法。该算法利用文本聚类描述K-NN算法中文本类别的内部结构,用sigmoid函数对SVM输出结果进行概率转换,同时引入CLA(Classifier’s Local Accuracy)技术进行分类可信度分析以实现两种算法的融合。实验表明该算法综合了K-NN与SVM在分类问题中的优势,既有效地降低了分类候选的数目,又相应地提高了文本分类的精度,具有较好的性能。     

超声波流量测量技术及发展

本文叙述了超声波流量测量的原理、基本测量方法以及传统的多普勒和时差法超声波流量计的缺陷和测量局限性，分析了超声波流量测量最新进展所采取的新的测量技术和方法，并介绍了超声波相关流量计的原理和技术特点．     

现代包装机械设计质量综合评价体系研究

目的研究面向现代包装机械的设计质量综合评价体系。方法根据包装机械的性能要求、结构特征和相对应的质量特性,参照机械产品的评价体系,构建面向包装机械的设计质量综合评价体系。然后利用层次分析法确定指标的主观权重,利用熵值法确定指标的客观权重,通过主客观权重综合得到评价体系设计质量指标的综合权重,并以案例进行分析验证。结果案例分析证明,该评价体系和评价方法可行。结论使用该套包装机械设计质量评价体系,即可提高包装机械设计质量,又能降低成本。     

酸催化溶胶-凝胶法Eu2+、Gd3+共掺杂TiO2的制备及光催化活性

采用酸催化溶胶-凝胶法制备了Gd³⁺、Eu²⁺两种稀土金属离子混合掺杂的复合TiO₂光催化剂, 通过TEM、XRD、UV-Vis等分析手段对产物进 行了表征, 结果表明: 样品均呈锐钛矿型结构, 颗粒尺寸的变化只与掺杂离子总量有关, 掺杂量为1.0%时达最小值; 一定比例Eu²⁺、Gd³⁺的混合掺杂, 能增强可见光范围内光响应. 以甲基橙为目标降解物研究了不同比例Eu²⁺、Gd³⁺混合掺杂对纳米二氧化钛光催化活性的影响, Gd³⁺、Eu²⁺适合掺杂量范围分别为0.1%～1.0%和0.5%～1.5%. Eu²⁺、Gd³⁺混和掺入TiO₂光催化剂中产生协同效应, 探讨了Eu²⁺和Gd³⁺与TiO₂之间的相互作用, 讨论了光催化活性与催化剂性质的关系.     

Band Structure Engineering of Interfacial Semiconductors Based on Atomically Thin Lead Iodide Crystals

To explore new constituents in two‐dimensional (2D) materials and to combine their best in van der Waals heterostructures is in great demand as being a unique platform to discover new physical phenomena and to design novel functionalities in interface‐based devices. Herein, PbI₂ crystals as thin as a few layers are synthesized, particularly through a facile low‐temperature solution approach with crystals of large size, regular shape, different thicknesses, and high yields. As a prototypical demonstration of band engineering of PbI₂‐based interfacial semiconductors, PbI₂ crystals are assembled with several transition metal dichalcogenide monolayers. The photoluminescence of MoS₂ is enhanced in MoS₂/PbI₂ stacks, while a dramatic photoluminescence quenching of WS₂ and WSe₂ is revealed in WS₂/PbI₂ and WSe₂/PbI₂ stacks. This is attributed to the effective heterojunction formation between PbI₂ and these monolayers; type I band alignment in MoS₂/PbI₂ stacks, where fast‐transferred charge carriers accumulate in MoS₂ with high emission efficiency, results in photoluminescence enhancement, and type II in WS₂/PbI₂ and WSe₂/PbI₂ stacks, with separated electrons and holes suitable for light harvesting, results in photoluminescence quenching. The results demonstrate that MoS₂, WS₂, and WSe₂ monolayers with similar electronic structures show completely distinct light–matter interactions when interfacing with PbI₂, providing unprecedented capabilities to engineer the device performance of 2D heterostructures.