Solvent-Processible Polymer Membrane-Based Reference Electrodes for Miniature Chemical Sensors

We have recently developed a new type of liquid junction-free reference electrode that is suited for fabrication of miniature ion sensor devices. The proposed reference electrode system employs a solvent-processible polymer membrane, and the best performance membrane so far is formulated with an aromatic type polyurethane,synthesized with 4,4'- methylenebis(phenyl isocyanate) and poly(tetramethylene ether glycol).     

光敏络合催化光解水析氢的电化学模拟

Durham等^[1]曾利用Pt(黑)|lN HCl‖Ru(bipy)₃²⁺、MV²⁺、EDTA(pH=9)|Pt(网)电池模拟光解水析氢反应。但该装置的左、右二半电池中溶液的pH值相差9以上,相当于外加0.5V以上的偏压,因此,不能真实地模拟自发的光解水析氢过程。     

Postsynthetically Modified Alkoxide-Exchanged Ni2(OR)2BTDD: Synergistic Interactions of CO2 with Open Metal Sites and Functional Groups

Postsynthetic modifications (PSMs) of metal–organic frameworks (MOFs) play a crucial role in enhancing material performance through open metal site (OMS) functionalization or ligand exchange. However, a significant challenge persists in preserving open metal sites during ligand exchange, as these sites are inherently bound by incoming ligands. In this study, for the first time, we introduced alkoxides by exchanging bridging chloride in Ni₂Cl₂BTDD (BTDD=bis (1H-1,2,3,–triazolo [4,5-b],–[4′,5′-i]) dibenzo[1,4]dioxin) through PSM. Rietveld refinement of synchrotron X-ray diffraction data indicated that the alkoxide oxygen atom bridges Ni(II) centers while the OMSs of the MOF are preserved. Due to the synergy of the existing OMS and introduced functional group, the alkoxide-exchanged MOFs showed CO₂ uptakes superior to the pristine MOF. Remarkably, the tert-butoxide-substituted Ni_T exhibited a nearly threefold and twofold increase in CO₂ uptake compared to Ni₂Cl₂BTDD at 0.15 and 1 bar, respectively, as well as high water stability relative to the other exchanged frameworks. Furthermore, the Grand Canonical Monte Carlo simulations for Ni_T suggested that CO₂ interacts with the OMS and the surrounding methyl groups of tert-butoxide groups, which is responsible for the enhanced CO₂ capacity. This work provides a facile and unique synthetic strategy for realizing a desirable OMS-incorporating MOF platform through bridging ligand exchange.     

Mechanism on oscillating lifted flames in nonpremixed laminar coflow jets

The oscillating lifted flame in a laminar nonpremixed nitrogen-diluted fuel jet is known to be a result of buoyancy, though the detailed physical mechanism of the initiation has not yet been properly addressed. We designed a systematic experiment to test the hypothesis that the oscillation is driven by competition between the positive buoyancy of flame and the negative buoyancy of a fuel stream heavier than the ambient air. The positive buoyancy was examined with various flame temperatures by changing fuel mole fraction, and the negative buoyancy was investigated with various fuel densities. The density of the coflow was also varied within a certain range by adding either helium or carbon dioxide to air, to study how it affected the positive and negative buoyancies at the same time. As a result, we found that the range of oscillation was well-correlated with the positive and the negative buoyancies; the former stabilized the oscillation while the latter triggered instability and became a source of the oscillation. Further measurements of the flow fields and OH radicals evidenced the important role of the negative buoyancy on the oscillation, detailing a periodic variation in the unburned flow velocity that affected the displacement of the flame.     

Multiphysics Simulation Combining Large-Eddy Simulation,Wall Heat Conduction and Radiative Energy Transfer to Predict Wall Temperature Induced by a Confined Premixed Swirling Flame

A multi-physics simulation combining large-eddy simulation, conjugate heat transfer and radiative heat transfer is used to predict the wall temperature field of a confined premixed swirling flame operating under atmospheric pressure. The combustion model accounts for the effect of enthalpy defect on the flame structure whose stabilization is here sensitive to the wall heat losses. The conjugate heat transfer is accounted for by solving the heat conduction within the combustor walls and with the Hybrid-Cell Neumann-Dirichlet coupling method, enabling to dynamically adapt the coupling period. The latter coupling procedure is enhanced to determine statistics (mean, RMS, \(\ldots \)) in a permanent regime accurately and efficiently thanks to an acceleration technique which is derived and validated. The exact radiative heat transfer equation is solved with an advanced Monte Carlo method with a local control of the statistical error. The coupled simulation is carried out with or without accounting for radiation. Excellent results for the wall temperature are achieved by the fully coupled simulation which are then further analyzed in terms of radiative effects, global energy budget and fluctuations of wall heat flux and temperature.     

A method to stabilize the incident X‐ray energy for anomalous diffraction measurements

A method to calibrate and stabilize the incident X‐ray energy for anomalous diffraction data collection is provided and has been successfully used at the single‐crystal diffraction beamline 1W2B at the Beijing Synchrotron Radiation Facilities. Employing a feedback loop to control the movement of the double‐crystal monochromator, this new method enables the incident X‐ray energy to be kept within a 0.2 eV range at the inflection point of the absorption edge.     

飞机舱音记录器背景声的联合时频分析研究

飞机舱音记录器记录的舱音主要是由话语音、噪声和具有不同物理意义的背景声组成的复杂混合体,用传统的辨听和分析方法难以获取较多的舱音特征参数。本文以一个舱音记录器记录的主告警声为例,针对传统短时傅立叶变换在舱音辨听、分析的不足,将联合时频分析引入到飞机舱音分析中,扩展了舱音分析方法。对比分析结果表明:时频分布及其重排,在时频分辨率、时频凝聚性、交叉项干扰的抑制上各有所长,都适合分析非平稳舱音背景声,从而为飞行事故调查提供一种值得采用的方法。