表面活性剂溶液界面拉压驱动液滴浸润性响应

液体表面的流体铺展在许多工程领域中具有广泛的应用前景。本文提出通过挡板对底液表面的拉压实现液滴的动态浸润响应,以正十六烷为受驱动液滴、十二烷基硫酸钠溶液为基底溶液组成浸润实验体系。挡板向外拉伸时,表面活性剂分子面密度降低,铺展系数增大,液滴铺展;挡板向内挤压时,表面活性剂分子面密度增大,铺展系数减小,液滴收缩。挡板往复运动实现了液滴的浸润性响应调控,这一工作为实现界面液膜的调节提供了新的思路。

     

基于铅铟合金线的SFQ多芯片超导互连方法研究

用基于铅铟合金线的引线键合(WB)工艺对单磁通量子(SFQ)多芯片的超导互连方法进行了研究,将铅含量75%,铟含量25%的铅铟合金线制备成WB线材,用超声楔形焊工艺成功实现SFQ芯片I/O接口焊盘的超导互连.拉力测试表明室温下铅铟合金线键合强度与同线径金线相当,优于同线径铝线;用开尔文四端法测量了铅铟合金线互连的多级超导转变温度以及线材与超导芯片之间的接触电阻,结果表明该铅铟合金线的超导转变温度为6.63 K,当温度降低至6.63 K或更低时,铅铟合金线的线阻以及线材与SFQ芯片I/O接口焊盘的接触电阻为0,实现了超导互连;并通过热冲击实验验证该WB结构具有优异的热稳定性.     

开口圆环类声子晶体传播禁带特性研究

为衰减中低频振动噪声,本文设计了一种非严格对称的开口圆环类声子晶体结构,基于有限元法和弹性波理论分析了其禁带特性和各方向的振动衰减性能;结合系统的振动模态解释了带隙打开和关闭的原因,并分析了几何参数对带隙宽度的影响规律.结果表明:由于晶体的非严格对称,仅 ΓX方向的传输损耗和禁带特性吻合,且衰减性能优于MΓ 方向,禁带...     

Calibration of differential scanning calorimeter (DSC) for thermal properties analysis of phase change material

Journal of Thermal Analysis and Calorimetry - Phase change material (PCM) selection for particular applications mainly depends on its phase change temperature and latent heat, which were commonly...     

汽轮机小长径比静叶片的优化径向积叠

应用粘性流动数值计算对叶轮机械叶片进行设计，能够使设计者对几种不同设计方案进行分析以满足设计要求，并获得最佳设计方案．本文采用三维N．S方程组和Baldwin-Lomax湍流模型，对一个小长径比的汽轮机导叶进行三维粘性流场数值模拟．计算结果表明，采用合适的周向弯曲（优化径向积叠）同样可以提高短叶片的效率．本计算方法可用来分析和研究叶片径向积叠形式对径向和周向流量平均绝热效率的影响，以获得较优的积叠形式．     

The determination of ethanol in wine by voltammetry with an internal standard

A rapid method for the electroanalysis of ethanol is presented that incorporates flow extraction at room temperature, with voltammetric detection and potassium ferrocyanide [K₄Fe(CN)₆] as internal standard. In 0.1 M NaOH electrolyte, ethanol was oxidised at a platinum comb-shaped working electrode at −300 mV (vs. a Ag/AgCl reference electrode) and K₄Fe(CN)₆ was oxidized at +180 mV. The ratio of the anodic peak currents was linear with ethanol concentration in the range of 0.1 to 8.0% (v./v.), and the detection limit (calculated as 3 σ background) was 0.012 % (v./v.) for Osteryoung square wave voltammetry (OSWV) and 0.023 %(v./v.) for cyclic voltammetry (CV). The average extraction efficiency of ethanol from aqueous solutions, at 20 ± 1°C, was 8.5%. The repeatability was in the range of 2.5 to 3.3% RSD (n = 8), and accuracy was in the range of 95.2 to 104.7% for the determination of wine samples. Application to wines compared well with GC and HPLC methods and the nominal ethanol concentration determined by gravimetry. Analytical parameters in CV and OSWV are optimized, and the dependence of the extraction efficiency with temperature and nitrogen gas flow is presented.     

Self-Assembly of Helical Nanofibrous Chiral Covalent Organic Frameworks

Despite significant progress on the design and synthesis of covalent organic frameworks (COFs), precise control over microstructures of such materials remains challenging. Herein, two chiral COFs with well-defined one-handed double-helical nanofibrous morphologies were constructed via an unprecedented template-free method, capitalizing on the diastereoselective formation of aminal linkages. Detailed time-dependent experiments reveal the spontaneous transformation of initial rod-like aggregates into the double-helical microstructures. We have further demonstrated that the helical chirality and circular dichroism signal can be facilely inversed by simply adjusting the amount of acetic acid during synthesis. Moreover, by transferring chirality to achiral fluorescent molecular adsorbents, the helical COF nanostructures can effectively induce circularly polarized luminescence with the highest luminescent asymmetric factor (g_lum) up to ≈0.01.     

Parallel Computation and Measurement Uncertainty in Nonlinear Dynamical Systems

In certain physical systems measuring one variable of the system modifies the values of any number of other variables unpredictably. We show in this paper that under these conditions a parallel approach succeeds in carrying out the required measurement while a sequential approach fails. Specifically, we show that for a nonlinear dynamical system, namely, the Belousov–Zhabotinskii chemical reaction, measurement disturbs the equilibrium of the system and causes it to enter into an undesired state. If, however, several measurements are performed in parallel, the effect of perturbations seems to cancel out and the system remains in a stable state.Mathematics Subject Classifications (2000) 37-XX, 37C75, 68Q10, 68Q25, 68W10.This research was supported by the Natural Sciences and Engineering Research Council of Canada.     

A fluorescence reagent for the highly selective recognition and separation of lead ion (II) from aqueous solutions

A new fluorescence reagent, N,N-bi[4(1-pyrene)-butyroyl]-lysine (1) was synthesized. The new fluorescence sensor showed high sensitivity (detection limit up to 20.7 μg L⁻¹) and specific selectivity for Pb²⁺ over other metal ions examined in aqueous solutions. It could also be used to remove Pb²⁺ from aqueous solutions by filtering the insoluble 1–Pb²⁺ complex with sufficient reversibility.