A Novel Hyperbranched Phase Transporter for Extraction of Water‐soluble Dyes in Industrial Wastewater

Methacrylated hyperbranched polyglycerol (HPG‐MA) is successfully synthesized through transesterification by controlling the ratio of HPG to glycidyl methacrylate (GMA). The concentration of the dye or phase transporter, temperature, contact time, and molecular weight of phase transporter were taken into consideration to evaluate the removal ratio and transfer capability. With malachite green optimized as a model dye, HPG‐MA could reach a maximum adsorption of 990 mg/g at the feed concentration of 1 g/L, and the removal ratio is 99% compared with ~20 h for other reported phase transporters, which indicates that HPG‐MA is a novel phase transporter. HPG‐MA can absorb dyes in aqueous solutions, which can be ascribed to the existence of a cavity structure and abundant ether groups. We believe that HPG‐MA can have potential applications in the removal of dyes from aqueous solutions due to its high adsorption capacity and eco‐friendly nature.     

Numerical investigation of the passive control of cavity flow oscillations by a dimpled non-smooth surface

Computational investigations are conducted to determine the effectiveness of a passive control technique, which was employed to decay the pressure oscillations induced by a subsonic flow over a cavity. This work focuses on a cavity with a small opening but a large volume. The passive control technique is employed by introducing a dimpled non-smooth surface, which is installed at the upstream of the cavity. Large eddy simulation is used to investigate the flow field and flow instability around the cavity for the smooth and non-smooth cases. Experiments are conducted in an acoustic wind tunnel for the smooth case to validate the computational scheme. Flow visualizations revealed that the dimpled surface located upstream effectively suppresses cavity flow oscillations. Finally, the control mechanism of cavity oscillation with the dimpled non-smooth surface is also determined based on the comparison of the flow field structure between the smooth and non-smooth cases.     

Trace Moisture Measurement with 5. 2 mu m Quantum Cascade Laser Based Continuous-Wave Cavity Ring-Down SpectroscopyEI北大核心CSCD

Trace moisture concentration in high-purity gases is an important parameter in semiconductor manufacturing because many manufacturing processes are sensitive to moisture even on the level of parts per billion by volume (ppbv). Detection of trace moisture in mid-infrared spectral region is beneficial due to more abundant and stronger spectral lines in this region. Recently, Quantum cascade lasers (QCLs) with high output power, narrow line-width, and high reliability have been developing rapidly and have become promising light sources for sensitive spectroscopic measurements. By employing a 5. 2 mu m external-cavity tunable quantum cascade laser, a continuous-wave cavity ring-down spectroscopy (CRDS) experimental setup is established and applied to detect trace moisture in high-purity nitrogen gas. In the experiment, the CRDS signal is averaged to improve the detection sensitivity, and the optimal averaging number is determined by Allan variance calculation to be 602. For trace moisture detection, the absorption cross-section of H2O in the spectral range between 1 905 and 1 925 cm(-1) is simulated according to the HITRAN database and the optimal detection spectral line is chosen. Detected at 1 918 cm(-1) absorption line at 296 K temperature and 1 atm pressure, the measured moisture concentration is in good agreement with the nominal value, and the minimum detectable moisture concentration of 24. 8 ppbv is achieved when cavity mirrors with reflectance of 99.93% are used. The experimental results show that mid-infrared cavity ring-down spectroscopy technique has great potential in a wide variety of applications, such as industrial production control, environmental monitoring and health diagnosis, etc.     

5.2μm量子级联激光器光腔衰荡光谱技术的痕量水汽检测

高纯气体中水汽含量是半导体工业生产中的一个重要参数,气体中残余水汽含量即使是ppbv量级也会对产品质量产生影响。气体在中红外区域具有更丰富的特征谱线,在该区域对水汽含量进行检测十分必要。宽调谐范围、高输出功率和窄线宽量子级联激光器的快速发展,推动了该区域红外光谱检测技术的发展。首次在中红外波段,采用5.2μm可调谐量子级联激光器,基于连续光腔衰荡光谱技术建立了痕量水汽的检测装置,并开展了痕量水汽检测实验。通过阿伦方差分析系统噪声水平,确定了光腔衰荡信号最优平均次数为602次。根据HITRAN数据库,模拟实验条件下1 905~1 925cm~(-1)范围内水汽的吸收截面,选取最佳的检测谱线位置。在常压和室温下,对1 918cm~(-1)附近的水汽吸收光谱进行测量,测定高纯氮气中的痕量水汽浓度,检测结果与标称值一致。在腔镜反射率为99.93%时水汽的检测灵敏度达到24.8ppbv。分析结果表明,中红外高灵敏痕量气体检测技术在工业监测、环境检测以及医学诊断等领域具有很好的应用前景。     

光纤耦合双光学腔系统的相干动力学

为了研究量子相干性在腔量子电动力学系统中的动力学和分布特性,基于两个各自捕获原子系综的光学腔建立了双光学腔系统,腔与腔之间由光纤耦合.利用相对熵度量的量子相干性,引入量子相干非平衡性的概念,分析了系统中相干动力学和光纤-腔耦合强度对相干性分布的影响.结果表明:在强耦合极限下,光纤-腔耦合强度的增加有利于保持两腔中的原子的整体相干性;光纤-腔耦合强度、原子-腔耦合强度以及原子数三个参数之间满足特定条件时,腔内的原子相干性可以传输至另一个腔.考虑腔、光纤及原子都存在耗散的情形,对比了不同耗散速率和非耗散情形下的相干性演化,发现耗散使得耦合双腔系统的相干性以及各个腔中的原子相干性发生衰减.     

Optical switching of electron transport in a waveguide-QED system

Electron switching in waveguides coupled to a photon cavity is found to be strongly influenced by the photon energy and polarization. Therefore, the charge dynamics in the system is investigated in two different regimes, for off-resonant and resonant photon fields. In the off-resonant photon field, the photon energy is smaller than the energy spacing between the first two lowest subbands of the waveguide system, the charge splits between the waveguides implementing a $\sqrt{\mathrm{NOT}}$-quantum logic gate action. In the resonant photon field, the charge is totally switched from one waveguide to the other due to the appearance of photon replica states of the first subband in the second subband region instigating a quantum-NOT transition. In addition, the importance of the photon polarization to control the charge motion in the waveguide system is demonstrated. The idea of charge switching in electronic circuits may serve to built quantum bits.     

Entropy Changes in Aqueous Solutions of Non-polar Substances and in Bio-complex Formation

The entropy changes, ΔS _app, (i) for dissolution in water of non-polar substances and (ii) for protein-ligand complexation show linear dependences on the logarithm of the absolute temperature. For every compound, the slope m _(S)=ΔC _p for the line ΔS _app=f(ln T) depends on the size of the molecule and is exactly equal to the slope m _(H)=ΔC _p found in the diagram ΔH _app=f(T). This means that the slopes are rigorously proportional (with a ratio m _(S)/n _w=C _p,w) where n _w is the number of involved water molecules as determined from the enthalpy change ΔH _app=f(T). It is also worth noting that the value of n _w is positive (as well as m _(S) and m _(H)) in the dissolution of non-polar substances, whereas it is negative (as well as m _(S) and m _(H)) in bio-complex formation and in micelle formation. The number n _w (n _w>0) involved in the dissolution of non-polar substances depends on the size of the cavity (excluded volume) formed in the structure of water. These water molecules that have been excluded from the structure of the solvent absorb thermal energy that compensates for the negative enthalpy change, whereas the formation of the cavity implies there should be a large negative entropy contribution. The low solubility of non-polar substances in water depends on the highly negative entropy effect due both to cavity formation and to loss of configurational entropy by the gas trapped in a cage of water molecules. In processes involving association, as in micelle formation and in protein complexation, the cavities surrounding the separate units coalesce and the resultant cavity is smaller than the sum of the previous ones. The n _w water molecules (n _w<0) needed to fill the excess cavity return to the structure of the bulk solvent and release thermal energy, which compensates for the endothermic enthalpy. The affinity in the association processes is bound, for the most part, to the entropy produced by occupation of part of the cavity by condensation of water molecules. The association processes are therefore entropy driven.     

Potential flow model of cavitation-induced interfacial fracture in a confined ductile layer

Fracture of a thin ductile layer sandwiched between stiff substrates often results from growth and coalescence of microscopic cavities ahead of an extending crack. Cavitation induced by plastic flow in a confined, ductile layer is analyzed here to evaluate the interfacial fracture toughness of such sandwich structures. For rigid-plastic materials, a new method is proposed in which the potential flow field of a fluid is used to approximate the plastic deformation. The principle of virtual work rate is applied to determine the equivalent traction-separation law. The method is demonstrated and validated for spherically symmetric cavity growth, for which an exact solution exists. We then study in detail the growth of an initially spherical cavity in a cylindrical bar of finite length subject to uniform traction at its ends. The results show that the stress-separation curves depend strongly on initial cavity size and the strain-hardening exponent, and weakly on the nominal strain. The method has clear advantages over numerical methods, such as finite-element analysis, for parametric study of cavity growth with large plastic deformation.     

A Taylor–Galerkin-based algorithm for viscous incompressible flow

In this paper the development and behaviour of a new finite element algorithm for viscous incompressible flow is presented. The stability and background theory are discussed and the numerical performance is considered for some benchmark problems. The Taylor–Galerkin approach naturally leads to a time-stepping algorithm which is shown to perform well for a wide range of Reynolds numbers (1 ? Re ? 400).

1 A conventional definition for Re is assumed.

Various modifications to the algorithm are investigated, particularly with respect to their effects on stability and accuracy.     

光腔衰荡光谱方法探测痕量一氧化碳气体

基于通讯波段的分布式反馈半导体激光器(DFB),搭建了一套光腔衰荡光谱仪(CRDS)。衰荡光腔由一对反射率高于99.997%的高反镜组成,衰荡腔长约为130 cm,空腔衰荡时间约为150 μs。当光谱平均次数达到1 000次时,光谱仪灵敏度(最小可探测吸收系数)达到5×10-12 cm-1。利用热隔绝的方式稳定衰荡腔长,并使用衰荡光腔自身作为光学标准具,来标定光谱的频率：利用反馈式光谱扫描程序步进改变激光器频率,使之与衰荡腔的纵模频率逐一匹配,从而实现所测得光谱的自动标定。通过测量一氧化碳分子在1.565 μm附近的吸收光谱,测定气体中一氧化碳的含量。将光谱测量结果和标准样品中的一氧化碳含量进行对比,对装置的定量精度进行了检验,表明其对一氧化碳的探测极限达4 ppbv。利用该装置对实际大气中一氧化碳的含量进行了实时监测。