增强型三线圈电磁斥力机构的运动特性分析

为进一步优化高压直流断路器的刚分速度和始动时间,改善电磁斥力机构的运动特性,本文提出增加电磁吸力作为驱动力的增强型三线圈电磁斥力机构,采用运动学、瞬态电磁场以及电路理论进行数学模型耦合分析,运用有限元分析软件建立二维模型,求解其运动特性,最后通过仿真试验进行验证。首先,本文分析了不同参数对其运动特性的影响,其次,分析了合闸线圈介入时刻对其运动特性的影响,最后,对比分析了增强型三线圈模型与双线圈模型的运动特性差异。结果表明：增加电容容值和电容电压可以缩短行程时间,提高刚分速度,且三个线圈中改变运动线圈驱动电路参数的优化效果最佳;适当增加线圈匝数和截面宽度可以增大电磁驱动力,缩短始动时间;从0时刻介入可以最大限度提高机构的运动速度;同参数条件下,三线圈模型可在2ms内完成25mm行程,对应的双线圈模型在2ms内只能完成16mm行程。     

基于合成孔径雷达干涉测量的高速铁路下伏老采空区稳定性监测分析

揭示老采空区现有变形规律是老采空区的稳定性分析的关键,而合成孔径雷达干涉测量(interferometric synthetic aperture radar,InSAR)技术对于广域地表变形监测有着传统测量技术无法比拟的优势.针对贵南高铁穿越大盘井采煤沉陷区的地表监测,采用最新的永久散射体对合成孔径雷达干涉测量(pe...     

旋转激励振动载荷对平面摩擦副的影响实验

振动可以减小摩擦,利用自制的旋转激励环境下摩擦力测试实验装置研究了旋转激励振动载荷的幅值和频率对不同材料平面摩擦副摩擦力的影响。实验表明:旋转激励振动载荷降低了平面摩擦副的摩擦系数。相同激振频率下,随着名义振幅的增大,摩擦系数不断减小,且二者呈现近似线性关系。相同名义振幅条件下,Q235A-Q235A平面摩擦副摩擦系数减小率最大,Q235A-花岗岩平面摩擦副摩擦系数减小率次之,Q235A-400目砂纸平面摩擦副摩擦系数减小率最小。相同名义振幅下,随着激振频率的增大,摩擦系数亦呈现减小的趋势;在激振频率为15 Hz以前,摩擦系数减小速率较快,当激振频率超过15Hz后,摩擦系数减小速率变慢。     

基于纠缠见证的路径纠缠微波检测方法

提出了一种基于纠缠见证的路径纠缠微波信号检测方法.路径纠缠微波是微波频段上的连续变量纠缠,介绍了利用微波压缩态和微波分束器制备路径纠缠微波的方法.根据部分转置正定判据以及2?2纠缠态密度矩阵的部分转置具有负本征值的性质,分别对常见的两种2?2纠缠进行了纠缠见证算符的构造,用于对两路信号是否为纠缠态进行判定.将连续变量纠缠的路径纠缠微波分解为大量2?2纠缠子系统叠加的纠缠态,证明其能够利用所构造的2?2纠缠见证算符来检测路径纠缠微波.同时分析了微波分束器的作用,并利用微波分束器设计了一种用于检测路径纠缠微波信号的实验方案,并在理论上分析了纠缠检测所得到的结果.结果表明,该方法能够有效检测路径纠缠微波信号,降低了检测的复杂度和计算量.本文的研究为纠缠微波的检测提供了思路.     

Tetra­aqua(2,2′‐bi­pyridine)­nickel(II) terephthalate

The reaction of nickel(II) nitrate with terephthalic acid and 2,2′‐bi­pyridine in di­methyl­form­amide solution gives the title complex, [Ni(C₁₀H₈N₂)(H₂O)₄](C₈H₄O₄). The Ni^II ion is octahedrally coordinated to one 2,2′‐bi­pyridine and four water mol­ecules and does not coordinate to the terephthalate anion. Hydro­gen bonds between the terephthalate anions and the [Ni(2,2′‐bipy)(H₂O)₄]²⁺ cations produce a two‐dimensional hydrogen‐bonding architecture with double sheets.     

Stacked-ring electrostatic ion guide

In 1969 Bahr, Gerlich, and Teloy introduced an rf device that consisted of a stack of ring electrodes, with charge sign alternation between neighboring rings, to store or transport ions. Here we propose to operate such a device with electrostatic potentials rather than rf potentials: ions that move axially along the center of the guide are thereby subjected to an oscillating electrical potential similar to the sinusoidal rf potential in familiar rf-only multipole ion guides. The oscillating potential of the stacked-ring static ion guide focuses ions by exerting a field gradient force on the ions so as to push ions toward the central axis where the field is weakest. The stacked-ring ion guide produces an effectively static “pseudopotential” that is much steeper at the edge (potential varies as e ^r) compared to a quadrupole or octupole guide (for which the potential varies as r ² or r ⁶, where r is radial position) and that is much flatter near the center of the guide (for potentially higher ion flux). Advantages of the new ion guide include static rather than rf potential, low electrical noise, a large field-free region near the central axis of the guide, and simple mechanical construction. A disadvantage of the stacked-ring ion guide is that high ion axial kinetic energy is required; ions with axial kinetic energy that is too low may be trapped in the shallow pseudopotential well between adjacent ring electrodes.     

Enhancement of the effective resolution of mass spectra of high-mass biomolecules by maximum entropy-based deconvolution to eliminate the isotopic natural abundance distribution

Although high-resolution Fourier transform ion cyclotron resonance mass spectrometry can resolve individual isotopic masses for biomolecules of more than 100 ku, its effective mass accuracy is limited by the distribution of naturally occurring rare isotopes (¹³C, ¹⁵N, ¹⁸O, ³⁴S, etc.). In this article, we compare least-squares and maximum entropy methods for deconvolution of the isotopic natural abundance distribution to narrow the mass spectral isotopic abundance envelope for greatly enhanced effective mass resolution. We apply both methods to yield deconvolved high-resolution deuterium distributions for peptides and proteins subjected to H/D exchange prior to electrospray Fourier transform ion cyclotron resonance mass analysis. In addition, we show that even unresolved isotopic envelopes from a quadrupole mass spectrometer can be narrowed for considerably improved resolution there as well.     

Structural Analysis of Saccharomyces cerevisiae Dihydroorotase Reveals Molecular Insights into the Tetramerization Mechanism

Dihydroorotase (DHOase), a dimetalloenzyme containing a carbamylated lysine within the active site, is a member of the cyclic amidohydrolase family, which also includes allantoinase (ALLase), dihydropyrimidinase (DHPase), hydantoinase, and imidase. Unlike most known cyclic amidohydrolases, which are tetrameric, DHOase exists as a monomer or dimer. Here, we report and analyze two crystal structures of the eukaryotic Saccharomyces cerevisiae DHOase (ScDHOase) complexed with malate. The structures of different DHOases were also compared. An asymmetric unit of these crystals contained four crystallographically independent ScDHOase monomers. ScDHOase shares structural similarity with Escherichia coli DHOase (EcDHOase). Unlike EcDHOase, ScDHOase can form tetramers, both in the crystalline state and in solution. In addition, the subunit-interacting residues of ScDHOase for dimerization and tetramerization are significantly different from those of other DHOases. The tetramerization pattern of ScDHOase is also different from those of DHPase and ALLase. Based on sequence analysis and structural evidence, we identify two unique helices (α6 and α10) and a loop (loop 7) for tetramerization, and discuss why the residues for tetramerization in ScDHOase are not necessarily conserved among DHOases.     

Interfacial self-assembly growth of mesoporous polydopamine nanofilms for formaldehyde sensing

Mesoporous polymer nanofilms combine the advantages of the unique structure of mesopores, the quasi-2D configuration of the films, and the inherent properties of polymers, and have become a kind of ideal candidate for the high-performance micro-nano devices due to their highly accessible surface area and exposed active sites. However, the facile preparation of polymer nanofilms with well-defined mesostructures has remained a great challenge due to the lack of synthetic strategies. In this study, we developed a simple soft-template interfacial co-assembly strategy to in-situ construct mesoporous polydopamine nanofilms with uniform thickness (30 nm) and regularly distributed mesopore arrays (average pore size of 12 nm) on surfaces with different types and morphologies. Furthermore, a single-layer mesoporous polymer nanofilm was directly grown on a quartz crystal microbalance substrate and its performance for sensing formaldehyde was studied. The resulted sensor showed excellent sensing response, fast response/recovery dynamics, and great stability, presenting a great promising landscape for trace detection of formaldehyde gas.     

Surface Charge‐Reversible Tubular Micromotors for Extraction of Nucleic Acids in Microsystems

Extraction of nucleic acids in microsystems is of significance for biomedical applications, but the current extraction methods generally require sophisticated microchannels and external equipment, hindering their practical applications. In this work, we have demonstrated a simple, versatile and efficient approach to extract nucleic acids in microsystems by developing cationic branched polyethyleneimine (PEI)‐functionalized tubular micromotors. The as‐developed tubular micromotors are fabricated by a two‐step process combining the template‐assisted electrodeposition and carbodiimide chemistry, and contain an inner catalytic Pt layer, a middle magnetic Ni layer and an outer cationic PEI layer. They exhibit autonomous bubble‐propelled motion in aqueous hydrogen peroxide solutions, which can be guided by an external magnetic field, and the surface charges can be reversibly modulated by changing the pH value of the solution. Consequently, the as‐developed tubular micromotors can selectively absorb nucleic acids from acidic solutions and desorb them into alkaline solutions, leading to the extraction of nucleic acids with high efficiency without external stirring. Furthermore, they can be operated in a microchannel chip without the aid of a pumping system. Our results indicate that this PEI‐functionalized tubular micromotor platform provides a novel, simple and versatile microsystem nucleic acid extraction technology, holding considerable promise for important practical applications.