偶氮苯聚合物薄膜光致六角对称微结构

利用前向箭并四波混频光路,在偶氮苯聚合物薄膜表面制作出六角对称的晶体微结构,观察到多个相位共轭波,当三束入射光都处在p偏振态时,在样品表面可得到一维光栅,当三束入射光中有一束在p偏振态,另两束在s偏振态时,在样品表面上得到的是六角对称微结构,这一结果表明,光场强度周期性变化及光场偏振态对晶格微结构的形成非常重要。     

Ferroelectrics in Photocatalysis

The rapid development of industrialization and population has brought water, air-pollution and energy crises. Solar-driven catalysis is expected to relieve these issues. However, limited by poor light harvesting, serious charge recombination of semiconductors, and high surface reaction barriers, the low efficiency of solar conversion is far from satisfactory for industrial needs. Ferroelectrics are considered to be promising photocatalysts to overcome these shortcomings. Herein, perovskite ferroelectrics such as BaTiO₃, PbTiO₃, BiFeO₃ and LiNbO₃, layered bismuth-based ferroelectrics like Bi₂WO₆ and Bi₂MoO₆, and other ferroelectrics are introduced, and their crystal structure, polarity source and synthetic method are highlighted. Subsequently, research progress in ferroelectrics for photocatalysis is summarized, including pollution degradation, water splitting and CO₂ reduction. Finally, the current challenges and future prospects of ferroelectric photocatalysts are provided. The purpose of this review is not only to provide a timely summary for the application of ferroelectrics in photocatalysis, but also to present deep insight and a guideline for future research work into ferroelectrics.     

大气压射流等离子体中O及OH自由基的发射光谱在线诊断

OH自由基及氧原子在大气化学、表面处理及化学污染物分解等方面有着重要的作用。利用发射光谱技术在线测量了大气压射流等离子体中OH自由基紫外波段与O自由基777,844 nm波段的发射光谱。研究了OH自由基与氧原子光谱强度随放电功率及放电体系中所加入的氧浓度的变化。将实验测得的OH自由基光谱图与用Lifbase数据库模拟光谱图进行比较,估算了OH自由基的转动温度。结果表明:OH自由基的转动温度随放电功率的增加而增加,随工作气体流速的增加而减小。     

FAIR项目super-FRS超导磁体结构分析

 国际反质子与离子大科学工程项目中的超导super-FRS磁体包含2个超导线圈,最大磁场为1.6 T,这样大的磁场必然产生很大的电磁力。为了保证磁体运行时的机械稳定性,对项目中的超导super-FRS磁体进行了有限元结构的3维分析。结构分析中采用了ADINA和TOSCA两个有限元软件。ADINA软件主要用于结构中的应力应变计算,而TOSCA软件则主要用于电磁场的磁场强度和电磁力的计算。分析的结果显示super-FRS磁体采用铁芯及线圈盒长边中部加固结构时,其最大形变约0.19 mm,最大有效应力出现在长边中部的很小区域,约为92 MPa。由于线圈盒由316LN不锈钢制成,该结构是合理的。     

The Asymptotic Schottky Problem

Let ${\mathcal{M}_g}Let M_g{\mathcal{M}_g} denote the moduli space of compact Riemann surfaces of genus g and let A_g{\mathcal{A}_g} be the moduli space of principally polarized abelian varieties of dimension g. Let J : M_g ? A_g{J : \mathcal{M}_g \rightarrow \mathcal{A}_g} be the map which associates to a Riemann surface its Jacobian. The map J is injective, and the image J_g : = J(M_g){\mathcal{J}_g := J(\mathcal{M}_g)} is contained in a proper subvariety of A_g{\mathcal{A}_g} when g ≥  4. The classical and long-studied Schottky problem is to characterize the Jacobian locus J_g{\mathcal{J}_g} in A_g{\mathcal{A}_g}. In this paper we address a large scale version of this problem posed by Farb and called the coarse Schottky problem: What does J_g{\mathcal{J}_g} look like “from far away”, or how “dense” is J_g{\mathcal{J}_g} in the sense of coarse geometry? The large scale geometry of A_g{\mathcal{A}_g} is encoded in its asymptotic cone, Cone_￥(A_g){{\rm Cone}_\infty(\mathcal{A}_g)}, which is a Euclidean simplicial cone of real dimension g. Our main result asserts that the Jacobian locus J_g{\mathcal{J}_g} is “coarsely dense” in A_g{\mathcal{A}_g}, which implies that the subset of Cone_￥(A_g){{\rm Cone}_\infty(\mathcal{A}_g)} determined by J_g{\mathcal{J}_g} actually coincides with this cone. The proof shows that the Jacobian locus of hyperelliptic curves is coarsely dense in A_g{\mathcal{A}_g} as well. We also study the boundary points of the Jacobian locus J_g{\mathcal{J}_g} in A_g{\mathcal{A}_g} and in the Baily–Borel and the Borel–Serre compactification. We show that for large genus g the set of boundary points of J_g{\mathcal{J}_g} in these compactifications is “small”.     

A dual variant of Benson’s “outer approximation algorithm” for multiple objective linear programming

Outcome space methods construct the set of nondominated points in the objective (outcome) space of a multiple objective linear programme. In this paper, we employ results from geometric duality theory for multiple objective linear programmes to derive a dual variant of Benson’s “outer approximation algorithm” to solve multiobjective linear programmes in objective space. We also suggest some improvements of the original version of the algorithm and prove that solving the dual provides a weight set decomposition. We compare both algorithms on small illustrative and on practically relevant examples.     

Image matching using Gradient Orientation Selective Cross Correlation

Image matching has been an important topic in computer vision and image processing. A new approach named Gradient Orientation Selective Cross Correlation is proposed for image matching. In the new approach, a gradient orientation selectivity strategy is proposed to exclude the wrong points from correlation, especially for partial occlusion and some other ill-conditions. Experimental results are shown to demonstrate robustness, efficiency, and accuracy of the algorithm.     

Extraordinary Separation of Acetylene‐Containing Mixtures with Microporous Metal–Organic Frameworks with Open O Donor Sites and Tunable Robustness through Control of the Helical Chain Secondary Building Units

Acetylene separation is a very important but challenging industrial separation task. Here, through the solvothermal reaction of CuI and 5‐triazole isophthalic acid in different solvents, two metal–organic frameworks (MOFs, FJU‐21 and FJU‐22 ) with open O donor sites and controllable robustness have been obtained for acetylene separation. They contain the same paddle‐wheel {Cu₂(COO₂)₄} nodes and metal–ligand connection modes, but with different helical chains as secondary building units (SBUs), leading to different structural robustness for the MOFs. FJU‐21 and FJU‐22 are the first examples in which the MOFs’ robustness is controlled by adjusting the helical chain SBUs. Good robustness gives the activated FJU‐22 a , which has higher surface area and gas uptakes than the flexible FJU‐21 a . Importantly, FJU‐22 a shows extraordinary separation of acetylene mixtures under ambient conditions. The separation capacity of FJU‐22 a for 50:50 C₂H₂/CO₂ mixtures is about twice that of the high‐capacity HOF‐3, and its actual separation selectivity for C₂H₂/C₂H₄ mixtures containing 1 % acetylene is the highest among reported porous materials. Based on first‐principles calculations, the extraordinary separation performance of C₂H₂ for FJU‐22 a was attributed to hydrogen‐bonding interactions between the C₂H₂ molecules with the open O donors on the wall, which provide better recognition ability for C₂H₂ than other functional sites, including open metal sites and amino groups.     

Controllable synthesis of TiO2 nanoparticles employing substrate/dielectrophoresis/sol‐gel

Due to size‐dependent catalytic selectivity, the size and special morphology are of great importance to applications of TiO₂. The synthesis method of size and morphology control has been in need of innovation. In this study, TiO₂ nanoparticles(TiO₂‐NPs) with well‐defined morphology and homogenous size were synthesized using a novel method, in which bamboo substrate, dielectrophoresis (DEP) technology and a sol‐gel process were combined(substrate/ DEP/ sol‐gel). Powder X‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterize the TiO₂‐NPs. Further study showed that, with this combined method, the size and the uniformity of TiO₂‐NPs can be controlled by changing the voltage of DEP. The number and arrangement of TiO₂ nanorods can be controlled by changing the voltage. Substrate/ DEP/ sol‐gel proved to be an efficient way to form special morphologies of TiO₂‐NPs. A visible‐light catalytic activity experiment showed that among three preparation methods, the substrate/ DEP/ sol‐gel method made TiO₂‐NPs with the highest catalytic activity for degradation of methyl orange. TiO₂‐NPs produced by the DEP/ sol‐gel process presented higher catalytic activity than TiO₂‐NPs produced by only a sol‐gel process.