甲烷与氯气取代反应实验的创新设计*

基于甲烷氯代反应的机理,对物质体系、反应容器、光照条件、实验表征等进行分析,创新设计甲烷氯代反应实验,利用数字化实验的压强和温度传感器采集的实验数据为支持,更直观地多重表征甲烷与氯气发生的“取代”过程,对于成功实现甲烷氯代反应实验具有指导意义。     

用硝酸银溶液沉淀及分步沉淀卤素离子的数字化实验研究*

卤化银难溶电解质的沉淀溶解平衡是中学化学教学的重要知识点。应用本项目组研制的MXLab21先进数字化实验系统,结合银硫离子电极,测定AgNO₃溶液沉淀Cl^-,Br^-,I^-及其混合离子的沉淀曲线,即电动势(E)随AgNO₃溶液体积(V)变化的关系曲线。3种单一离子的沉淀曲线可以直观体现出滴定的电动势突跃范围与相应沉淀的溶度积大小的关系及其规律性变化。通过混合离子的沉淀曲线分析3种离子两两混合或3者混合时分步沉淀的可行性。Cl^-,Br^-,I^-的沉淀及分步沉淀的动态E-V曲线的建立,对中学化学教学具有重要作用,对化学学科核心素养的发展和培养具有重要价值。     

大学物理实验教学仪器的改进

通过仪器电路改进、程序编写等工作,成功改进了数字电流表。改进后的电流表具有量程自动切换功能,实现了对原有数字电流表的量程保护。经实验测试表明,改进后电流表运行稳定,测试结果正确。     

基于数学形态学的数字全息再现像融合方法

针对数字全息中不同再现距离获得的携带不同聚焦信息的再现像, 提出了一种基于数学形态学的多聚焦再现像融合方法, 以有效扩展成像景深。首先通过小波-Controulet变换获得源图像的高频和低频分量;然后, 针对数字全息中含散斑噪声的特点, 对高频分量采用基于数学形态学区域能量的方法进行融合, 对低频分量采用加权对比度法进行融合;最后, 将融合系数反变换得到融合图像。通过对算法的有效性分析和实验验证, 将本文提出的方法与不加入数学形态学的融合方法进行了对比研究。结果表明, 基于数学形态学的融合方法能充分抑制散斑噪声的影响, 保留更多细节信息, 有效扩展了成像景深范围达11.5 cm。其中, 对于表面粗糙且信息量较少的骰子, 基于数学形态学方法的空间梯度算子提高了11.8%, 熵值提高了2.7%;对于表面光滑且信息量较多的硬币, 其空间梯度算子提高了13.6%, 熵值提高了2.8%。     

Shape memory behavior in Fe3Al-modeling and experiments

The Fe₃Al alloy with D0₃ structure exhibits large recoverable strains due to reversible slips. Tension and compression experiments were conducted on single crystals of Fe₃Al, and the onset of slip in forward and reverse directions were obtained utilizing high-resolution digital image correlation technique. The back stress provides the driving force for reversal of deformation upon unloading, resulting in a superelastic phenomenon as in shape memory alloys. Using density functional theory simulations, we obtain the energy barriers (GSFE – generalized stacking fault energy) for {1?1?0}〈1?1?1〉 and {1?1?2}〈1?1?1〉 slips in D0₃ Fe₃Al and the elastic moduli tensor, and undertake anisotropic continuum calculations to obtain the back stress and the frictional stress responsible for reversible slip. We compare the theoretically obtained slip stress magnitudes (friction and back stress) with the experimental measurements disclosing excellent agreement.     

pH计检定仪期间核查方法

介绍pH计检定仪的4种期间核查方法:传递比较法、多台对比法、留样测量法、实验室间比对法。传递比较法能直接反应pH计检定仪的变化,适用于已建立pH计检定仪检定装置的单位;多台对比法与留样测量法方便、快捷,可操作性强,适合大多数单位进行pH计检定仪的期间核查;实验室间比对法对设备要求较低,但需要协调的单位较多,周期较长,费用较高,实用性差。     

Wavelet transforms in separation science for denoising and peak overlap detection

Wavelet transform is a versatile time‐frequency analysis technique, which allows localization of useful signals in time or space and separates them from noise. The detector output from any analytical instrument is mathematically equivalent to a digital image. Signals obtained in chemical separations that vary in time (e.g., high‐performance liquid chromatography) or space (e.g., planar chromatography) are amenable to wavelet analysis. This article gives an overview of wavelet analysis, and graphically explains all the relevant concepts. Continuous wavelet transform and discrete wavelet transform concepts are pictorially explained along with their chromatographic applications. An example is shown for qualitative peak overlap detection in a noisy chromatogram using continuous wavelet transform. The concept of signal decomposition, denoising, and then signal reconstruction is graphically discussed for discrete wavelet transform. All the digital filters in chromatographic instruments used today potentially broaden and distort narrow peaks. Finally, a low signal‐to‐noise ratio chromatogram is denoised using the procedure. Significant gains (>tenfold) in signal‐to‐noise ratio are shown with wavelet analysis. Peaks that were not initially visible were recovered with good accuracy. Since discrete wavelet transform denoising analysis applies to any detector used in separation science, researchers should strongly consider using wavelets for their research.     

Nonlinear resonant tunneling diode (RTD) circuits for microwave A/D conversion

Short-duration electrical pulses play important roles in ultrafast time-domain metrology: they are used to sample rapidly varying signals or as probe signals in ranging radars, time-domain reflectometry and in communication. In this work, we design a nonlinear transmission, which is loaded with resonant tunneling diode to be suitable for microwave A/D conversion. A resonant tunneling diode (RTD) has a negative differential resistance that means when the voltage increases the current decreases. The equivalent circuit of monostable line is given. The simulation is performed by using OrCad program. Results show that a spike is produced and after a charging time constant, another switching occurs. Hence – similar to a relaxation oscillator – the spiking period is determined by the amplitude and frequency of the input current. The transmission line itself ensures the generation and propagation of identical spikes, such as solitons formed after few diodes.     

Digital holographic cameras and data processing for remote monitoring and measurements of mechanical parts

Fast growing technology and requirements for testing of different types of materials and devices require new methods and systems for investigation of their parameters. Among the quantities of high interest are shape, deformation, roughness, local materials constants, displacement, and strain fields of elements under load. In the paper, we present novel solutions for digital holographic cameras, which allow for remote monitoring and measurement of the above mentioned quantities at small mechanical objects or at restricted areas of interest at big structures. The systems have compact design, “black box” measurement approach, and allows for fast and accurate measurements performed directly at the element and often in outdoor environment. The principles of digital and optoelectronic reconstruction and phase manipulation are described together with the exemplary measurement results obtained by means of the cameras presented.     

Simple and robust digital holography for high-resolution imaging

Based on the point spread function of holographic system,the lateral resolution of digital holographic imaging system without any pre-magnification is studied.The expression of resolution limitation of holographic imaging system is thus presented.We investigate the possibilities to improve the lateral resolution.The simple experimental setup with an off-axis arrangement is built.By using a U.S.Air Force(USAF)test target as microscopic object,the recorded holograms are reconstructed digitally based on the principle of Fresnel diffraction.The lateral resolution of 2.76 μm without any pre-magnification is demonstrated experimentally,which matches the theoretical prediction well.