基于激光吸收光谱开放式长光程的空气中甲烷在线监测及分析

研制了一套基于可调谐半导体激光吸收光谱(TDLAS)技术的开放式长光程甲烷(CH4)浓度实时监测系统,系统采用波长调制和二次谐波探测相结合,并利用光强归一化的方法消除光强波动对测量结果产生的影响,实验证明采用消除光强波动的方法后使测量结果的误差小于2%.然后利用该系统在往返750 m的光程上,对合肥市董铺岛进行了为期1周的大气CH4浓度测量.测量结果表明董铺岛CH4浓度有明显的H变化趋势,白天浓度低,夜间浓度高,日平均浓度(1.8～3.4)×10-6,H最小值(1.8～2.2)× 10-6 ,日最大值(3.0～3.4)×10-6.通过分析,可实现1～2 km范围的空气中CH4浓度的实时在线监测,为生态系统的区域排放通量监测提供了有效的方法,也为卫星遥感提供了可行的地面校准方法.     

Dynamical Suppression of Nonlocal Decoherence in Two-State Quantum Systems

Nonlocal decoherence of two qubits due to Pure phase damping has been investigated. We have proposed a scheme to keep the entanglement of two qubits from nonlocal decoherence. By applying a series of ±π pulses, nonlocal decoherence can be thoroughly suppressed.     

Calibration of a single-point laser range finder and a camera

Laser and visual imagery have been broadly utilized in computer vision and mobile robotics applications because these sensors provide complementary information. Since the single-point laser range finder can provide depth information of a single pixel in the observed image, its price and size is very suitable for handheld devices or very lightweight robotic platforms. So the combination of a single-point laser range finder and a camera has become increasingly useful in recent report and industrial applications. In this paper, we propose two accurate calibration methods for determining the position and direction of the laser range finder relative to the camera. Furthermore, we can accomplish calibration even without observing the laser spot in camera image. We evaluate the two methods through experiments which demonstrate their efficiency and high reliability.     

A hemicyanine and cucurbit[n]uril inclusion complex: competitive guest binding of cucurbit[7]uril and cucurbit[8]uril

The interaction between the hemicyanine indole derivative H and the cucubit[n]urils Q[7] and Q[8] has been studied using ¹H NMR and UV spectroscopy as well as by fluorescence experiments. Competitive studies on the inclusion of H by Q[7] and Q[8] have also been conducted, and reveal that on changing the size of the Q[n] cavity, the binding behaviour can be very different.     

超弹性镍钛形状记忆合金单轴相变棘轮行为的宏观唯象本构模型

超弹性镍钛形状记忆合金因其良好的力学性能以及独特的超弹性和形状记忆效应已广泛应用于土木工程、航空航天和生物医疗等多个领域,在实际服役环境中超弹性镍钛合金元件不可避免地会承受不同应力水平的循环载荷作用,亟待建立描述相变棘轮行为(即峰值应变和谷值应变随着正相变和逆相变循环的进行不断累积)的循环本构模型.为此,基于已有的超弹性镍钛形状记忆合金在不同峰值应力下的单轴相变棘轮行为实验研究结果,在广义黏塑性框架下,对Graesser等提出的通过背应力非线性演化方程反映超弹性镍钛形状记忆合金超弹性行为的一维宏观唯像本构模型进行了拓展,考虑了正相变和逆相变过程中特征变量的差异及其随循环的演化,以非弹性应变的累积量为内变量引入了正相变开始应力、逆相变开始应力、相变应变和残余应变的演化方程,同时通过峰值应力与正相变完成应力的比值来确定演化方程中的相关系数,建立了描述超弹性镍钛合金单轴相变棘轮行为的本构模型.将模拟结果与对应的实验结果进行对比发现,建立的宏观唯像本构模型能够合理地描述超弹性镍钛形状记忆合金的单轴相变棘轮行为及其峰值应力依赖性,模型的预测结果和实验结果吻合得很好.     

带扰流小槽道内单相流动阻力特性实验

采用水作为工质, 实验研究入口或出口端加入圆柱扰流的不同高宽比多槽道散热器的压降特性; 结果表明: 单位长度压降随雷诺数成线性关系. 提出了雷诺数、水力学直径和槽道高宽比的拟合准则; 拟合公式在实验数据误差范围内很好反应类似系统的流阻特性. 对于线切割小槽道, 其摩阻系数和雷诺数成反比, 且较圆管理论值偏大; 对线切割槽道阻力特性分析发现, 表面粗糙度是其最主要的影响因素, 而扰流对其影响较小; 在槽道前部设置扰流柱可以增强换热.      

Modification and intercalation of layered zirconium phosphates: a solid‐state NMR monitoring

Several layered zirconium phosphates treated with Zr(IV) ions, modified by monomethoxy‐polyethyleneglycol‐monophosphate and intercalated with doxorubicin hydrochloride have been studied by solid‐state MAS NMR techniques. The organic components of the phosphates have been characterized by the ¹³C{¹H} CP MAS NMR spectra compared with those of initial compounds. The multinuclear NMR monitoring has provided to establish structure and covalent attachment of organic/inorganic moieties to the surface and interlayer spaces of the phosphates. The MAS NMR experiments including kinetics of proton‐phosphorus cross polarization have resulted in an unusual structure of zirconium phosphate 6 combining decoration of the phosphate surface by polymer units and their partial intercalation into the interlayer space. Copyright © 2016 John Wiley & Sons, Ltd.     

Total Synthesis of Rishirilide B by Organocatalytic Oxidative Kinetic Resolution: Revision of Absolute Configuration of (+)-Rishirilide B

Described herein is the enantioselective syntheses of (+)- and (−)-rishirilide B from the corresponding optically active β-substituted tetralones, which were obtained by oxidative kinetic resolution based on α-hydroxylation in the presence of a chiral guanidine-bisurea bifunctional organocatalyst. Benzylic oxidation of the tetralones at C1 followed by regioselective isomerization of the oxabenzonorbornadiene structure led to rishirilide B. Our findings lead to the revision of the previously proposed (2R,3R,4R) absolute configuration of (+)-rishirilide B to (2S,3S,4S).     

Voltammetric determination of paracetamol using a glassy carbon electrode modified with Prussian Blue and a molecularly imprinted polymer,and ratiometric read-out of two signals

The authors report on a ratiometric electrochemical sensor for paracetamol (PR) which was fabricated by successively electropolymerizing a layer of Prussian blue (PB) and a layer of molecularly imprinted polypyrrole (MIP) on the surface of a glassy carbon electrode (GCE). The binding of PR molecules to the MIP has two effects: The first is an increase of the oxidation current for PR at 0.42 V (vs. SCE), and the second is a decrease in the current for PB (at 0.18 V) due to partial blocking of the channels which results in reduced electron transmissivity. Both currents, and in particular their ratio, can serve as analytical information. Under optimized conditions, the sensor displays enhanced sensitivity for PR in the 1.0 nM to 0.1 mM concentration range and a 0.53 nM lower limit of detection. The sensor was applied to the determination of PR in tablets and urines where it gave recoveries in the range between 94.6 and 104.9 %. This dual-signal (ratiometric) detection scheme (using electropolymerized Prussian Blue and analyte-specific MIP) in our perception has a wide scope in that it may be applied to numerous other electroactive species for which specific MIP can be made available.

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Graphical Abstract Prussian blue (PB) and molecularly imprinted polymer (MIP) were combined to fabricate an electrochemical sensor for paracetamol (PR) detection. The ratio of both currents, increase of PR current and decrease of PB current, was employed for PR selective detection with enhanced sensitivity.

     

Hexagonal hollow mesoporous TiO2/carbon composite as an advanced anode material for lithium-ion batteries

Journal of Solid State Electrochemistry - Exploring the fast-charge anodes is crucial to meet the needs of lithium-ion battery (LIB) markets. Here, a hollow hexagonal mesoporous TiO2/carbon...