Impact of a polymer modifier on directing the non-classical crystallization pathway of TS-1 zeolite: accelerating nucleation and enriching active sites

The crystallization process directly affects the physicochemical properties and active centers of zeolites; however, controllable tuning of the zeolite crystallization process remains a challenge. Herein, we utilized a polymer (polyacrylamide, PAM) to control the precursor structure evolution of TS-1 zeolite through a two-step crystallization process, so that the crystallization path was switched from a classical to a non-classical mechanism, which greatly accelerated nucleation and enriched active Ti sites. The TS-1 crystallization process was investigated by means of various advanced characterization techniques. It was found that specific interactions between PAM and Si/Ti species promoted the assembly of colloidal precursors containing ordered structural fragments and stabilized Ti species in the precursors, leading to a 1.5-fold shortened crystallization time and enriched Ti content in TS-1 (Si/Ti = 29). The PAM-regulated TS-1 zeolite exhibited enhanced catalytic performance in oxidative reactions compared to conventional samples.

Polyacrylamide (PAM) was utilized to switch the crystallization pathway of TS-1 zeolite from classical to non-classical by virtue of the specific interaction between PAM and Si/Ti species, thus accelerating nucleation and enriching active sites.     

In原子在GaAs(001)表面的成核与扩散研究

近年来,半导体量子点特别是InAs量子点的基本物理性质和潜在应用得到了广泛研究。许多研究者利用InAs量子点结构的改变以调制其光电特性。本文采用液滴外延法在GaAs(001)表面沉积了不同沉积量的In(3 ML、4 ML、5 ML),以研究In的成核机制和表面扩散。实验发现,随着In沉积量的增加,液滴尺寸(包括直径、高度)明显增大。不仅如此,在相同的衬底温度下,沉积量越大,液滴密度越大。利用经典成核理论,计算了GaAs(001)表面In液滴形成的临界厚度为0.57 ML,计算的结果与已报道的实验一致。从In原子在表面的迁移和扩散,以及衬底中Ga和液滴中的In之间的原子互混原理解释了In液滴形成和形貌演化的机理。实验中得到的In液滴临界厚度以及In液滴在GaAs(001)上成核机理,可以为制备InAs量子点提供实验指导。     

声矢量锥形阵的高阶累积量波达方向估计

为解决信源在较低信噪比情况下的测向分辨率问题,提出阵列可扩展的声矢量锥形阵测向算法。算法基于四阶累积量的阵列扩展和高斯噪声抑制特性,计算声矢量传声器不同输出分量的四阶累积量,使其在三维方向上扩展与原阵型结构相同的虚拟阵,从而构造包含角度信息的旋转不变矩阵进行测向。推导给出了算法的克拉美罗界,理论分析了算法性能受信噪比、采样快拍以及入射声源俯仰角的影响。仿真实验验证了该算法较常规声矢量阵ESPRIT算法有更优的噪声抑制能力及更高分辨的DOA估计性能。     

次声试验系统及次声对人体生理功能影响的试验方法

研制了一种在试验室内可提供次声环境的次声舱,测量的次声波特性曲线和其空间均匀性表明,在6~20Hz频率范围内的试验结果是令人满意的。设计的次声对人体生理功能影响的试验研究方法具有可行性。     

Effects of initial conditions on the synchronization of the coupled memristor neural circuits

Nonlinear Dynamics - The fourth basic two-terminal circuit element has been called the memristor because its resistance (conductance) depends on the complete past history of the memristor current...     

小流量条件下汽轮机多级三维粘性流场的数值分析

1绪言小流量条件下汽轮机内部流动具有比设计条件下更为复杂的特征，最突出的表现是随冲角的增大而出现的分离流、先速流。这种流态不仅影响汽轮机的运行效率，更重要的是它还与汽轮机的安全可靠性密切相关，它可能诱发叶片的失速颤振而使叶片断裂。虽然大的负攻角所引起的本级叶片的脱流现象已成共识，但对小流量条件下汽轮机内部流动的认识只有一些实验观测到的现象和二维的数值分析，并且只限于末级叶片。在文献＊中，我们对某一汽轮机低压缸末级和次末级叶片在0．35小流量工况下的两级流场进行了三维粘性数值分析，计算得到的分离流态同…     

Gr-凝聚环的小有限分次投射维数gr.fp.dimR

文 [1],[2 ]分别研究了Gr NoetherGr 局部 (半局部 )环的同调维数 ,本文主要进一步讨论Gr 凝聚Gr 半局部环的同调性质 .在§ 1中 ,主要刻画交换Gr 凝聚Gr 半局部环R的分次弱整体维数gr.gl.w .dimR ;在§ 2中 ,定义了分次环R的小有限分次投射维数gr.fp .dimR .刻画了gr.fp .dimR =gr .gl.w .dimR的Gr 凝聚环 .由于Gr Noether环是Gr 凝聚的 ,因而本文所得的结果对于Gr Noether环是自然成立的 .同时 ,本文所得的结果 ,也可视为文 [4 ]关于一般交换凝聚环相应结论的推广 .     

An Extra‐Large‐Pore Zeolite with 24×8×8‐Ring Channels Using a Structure‐Directing Agent Derived from Traditional Chinese Medicine

Extra‐large‐pore zeolites have attracted much interest because of their important applications for processing larger molecules. Although great progress has been made in academic science and industry, it is challenging to synthesize these materials. A new extra‐large‐pore zeolite SYSU‐3 (Sun Yat‐sen University no. 3) has been synthesized by using a novel sophoridine derivative as an organic structure‐directing agent (OSDA). The framework structure was solved and refined using continuous rotation electron diffraction (cRED) data from nanosized crystals. SYSU‐3 exhibits a new zeolite framework topology, which has the first 24×8×8‐ring extra‐large‐pore system and a framework density (FD) as low as 11.4 T/1000 ų. The unique skeleton of the OSDA plays an essential role in the formation of the distinctive zeolite structure. This work provides a new perspective for developing new zeolitic materials by using alkaloids as cost‐effective OSDAs.     

钴与5－Cl－PADAB反应机理及其应用的研究

对钴与４－［（５－氯－２－吡啶）偶氮］－１，３－二氨基苯（５－Ｃｌ－ＰＡＤＡＢ）形成络合物的吸收光谱进行探讨，结果表明：试剂及络合物在不同酸度条件下形成不同型体。在酸性条件下，络合物为大阳离子，钴离子以三价形式存在，钻与试剂的络合比为１：２。在强酸性介质中，将此络合物用于光度测定钻，方法选择性及稳定性好，且灵敏度极高。对水、粮食、土壤、茶叶及维生素Ｂ＿（１２）中微量钻进行直接测定，获得满意结果。