Highly Dispersed and Small‐Sized Nickel(II) Hydroxide Co‐Catalyst Prepared by Photodeposition for Hydrogen Production

Photodeposition has been widely used as a mild and efficient synthetic method to deposit co‐catalysts. It is also worth studying how to synthesize non‐noble metal photocatalysts with uniform dispersion. Different synthetic conditions in photodeposition have a certain influence on particle size distribution and photocatalytic activity. Therefore, we designed experiments to prepare the inexpensive composite photocatalyst Ni(OH)₂/g‐C₃N₄ by photodeposition. The Ni(OH)₂ co‐catalysts disperse uniformly with particle sizes of about 10 nm. The photocatalytic hydrogen production rate of Ni(OH)₂/g‐C₃N₄ reached about 19 mmol g^?1 h^?1, with the Ni(OH)₂ deposition amount about 1.57 %. During 16 h stability testing, the rate of hydrogen production did not decrease significantly. The composite catalyst also revealed a good hydrogen production performance under sunlight. The Ni(OH)₂ co‐catalyst enhanced the separation ability of photogenerated carriers, which was proved by surface photovoltage and fluorescence analysis.     

Effect of energy dependent cross-section on flow velocity measurements with charge exchange spectroscopy in magnetized plasma

Charge exchange spectroscopy (CXS) is widely used to measure plasma flow velocity. Accurate measurement is heavily affected by energy dependent cross section between neutral atoms and impurity ions. One symmetric layout of poloidal CXS is applied on Large Helical Device. Correction velocity due to the cross section is exacted from total velocity when actual plasma flow velocity is acquired with the benefit of this layout. A linear relationship between correction velocity and ion temperature is observed. Abundant discharges with wide plasma conditions are investigated and the ratio of correction velocity to ion temperature with the same beam energy shows the normal distribution. The impact of beam energy on the ratio of correction velocity to ion temperature of the carbon system and the hydrogen system is discovered based upon the statistics. Effective emission coefficient (Q) from Atomic Data and Analysis Structure (ADAS) is utilized to study the dependence of correction velocity on Q. The relationship in which the ratio of correction velocity to ion temperature increases linearly with the increasing normalized effective emission coefficient ((1/Q)dQ/dv) is observed. Experimental (1/Q)dQ/dv is obtained according to this observation, and comparison with different fractions of n?=?2 excited state is also discussed. The influence of different receivers (carbon and hydrogen) is also presented. The experimental (1/Q)dQ/dv from the carbon system decreases with beam energy decreasing when beam energy is less than 30 keV/amu. This tendency of (1/Q)dQ/dv at low beam energy indicates the existence of the contribution of n?=?2 excited state donors to the cross section.     

Controllable wave propagation in a weakly nonlinear monoatomic lattice chain with nonlocal interaction and active control

The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is derived with the consideration of both the nonlocal and the active control effects. The numerical results show that the nonlocal effect can effectively enhance the frequency in the middle part of the dispersion curve.When the nonlocal effect is strong enough, zero and negative group velocities will be evoked at different points along the dispersion curve, which will provide different ways of transporting energy including the forward-propagation, localization, and backwardpropagation of wavepackets related to the phase velocity. Both the nonlinear effect and the active control can enhance the frequency, but neither of them is able to produce zero or negative group velocities. Specifically, the active control enhances the frequency of the dispersion curve including the point at which the reduced wave number equals zero, and therefore gives birth to a nonzero cutoff frequency and a band gap in the low frequency range. With a combinational adjustment of all these effects, the wave propagation behaviors can be comprehensively controlled, and energy transferring can be readily manipulated in various ways.     

Experimental study on flow control of the turbulent boundary layer with micro-bubbles

The effect of micro-bubbles on the turbulent boundary layer in the channel flow with Reynolds numbers (Re) ranging from \(0.87\times 10 ^{5}\) to \(1.23\times 10^{5}\) is experimentally studied by using particle image velocimetry (PIV) measurements. The micro-bubbles are produced by water electrolysis. The velocity profiles, Reynolds stress and instantaneous structures of the boundary layer, with and without micro-bubbles, are measured and analyzed. The presence of micro-bubbles changes the streamwise mean velocity of the fluid and increases the wall shear stress. The results show that micro-bubbles have two effects, buoyancy and extrusion, which dominate the flow behavior of the mixed fluid in the turbulent boundary layer. The buoyancy effect leads to upward motion that drives the fluid motion in the same direction and, therefore, enhances the turbulence intense of the boundary layer. While for the extrusion effect, the presence of accumulated micro-bubbles pushes the flow structures in the turbulent boundary layer away from the near-wall region. The interaction between these two effects causes the vorticity structures and turbulence activity to be in the region far away from the wall. The buoyancy effect is dominant when the Re is relatively small, while the extrusion effect plays a more important role when Re rises.     

Hybrid continuum–coarse-grained modeling of erythrocytes

The red blood cell (RBC) membrane is a composite structure, consisting of a phospholipid bilayer and an underlying membrane-associated cytoskeleton. Both continuum and particle-based coarse-grained RBC models make use of a set of vertices connected by edges to represent the RBC membrane, which can be seen as a triangular surface mesh for the former and a spring network for the latter. Here, we present a modeling approach combining an existing continuum vesicle model with a coarse-grained model for the cytoskeleton. Compared to other two-component approaches, our method relies on only one mesh, representing the cytoskeleton, whose velocity in the tangential direction of the membrane may be different from that of the lipid bilayer. The finitely extensible nonlinear elastic (FENE) spring force law in combination with a repulsive force defined as a power function (POW), called FENE–POW, is used to describe the elastic properties of the RBC membrane. The mechanical interaction between the lipid bilayer and the cytoskeleton is explicitly computed and incorporated into the vesicle model. Our model includes the fundamental mechanical properties of the RBC membrane, namely fluidity and bending rigidity of the lipid bilayer, and shear elasticity of the cytoskeleton while maintaining surface-area and volume conservation constraint. We present three simulation examples to demonstrate the effectiveness of this hybrid continuum–coarse-grained model for the study of RBCs in fluid flows.     

掺磷TiO_2优化TiO_2/MBA/Ag三明治结构的SERS性能

本文以磷酸为磷源,通过溶胶水热法制备磷掺杂TiO_2,利用Lee和Meisel的方法制备银溶胶,以4-巯基苯甲酸(MBA)为探针分子,通过构建TiO_2/MBA/Ag三明治结构,研究磷掺杂二氧化钛对该基底表面增强拉曼(SERS)性能的提升。通过TEM、XRD、XPS、DRS和拉曼光谱图表征二氧化钛的形貌结构、化学组成、光学和拉曼性能,结果表明,制备出的磷掺杂二氧化钛为锐钛矿型纳米颗粒,粒径范围6~12nm,XPS显示磷以P~(5+)替代了Ti~(4+),形成O-P-O键掺入TiO_2的晶格中,当磷的掺杂量在1.77%时,TiO_2/MBA/Ag三明治体系具有最佳的SERS信号,这是因为适量的磷掺杂降低了TiO_2的能带间隙,丰富TiO_2的表面态,这能促进TiO_2向MBA分子的电荷转移。     

同轴周期慢波结构色散特性的通用数值解法

 运用场匹配法和傅里叶级数理论,提出一种原则上可数值求解任意同轴周期慢波结构色散特性的方法,给出了同轴慢波结构TM_0n模的色散方程。基于该方法,编制了Matlab程序,给出了同轴波纹波导和同轴双波纹波导色散特性,以算例形式分析计算了同轴盘荷波导的色散特性。数值计算结果与多维全电磁模拟软件结果进行比较,证明了该数值算法的准确性和可靠性。     

Study on the morphology, crystalline structure and thermal properties of yellow ginger starch acetates with different degrees of substitution

Yellow ginger starch acetates with different degrees of substitution (DS) were prepared by reacting native starch with glacial acetic acid/acetic anhydride using sulfuric acid as catalyst. X-ray diffraction (XRD) of acetylated starch revealed that the crystal structure of native starch was disappeared and new crystalline regions were formed. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm⁻¹, as well as the reduced hydroxyl groups, in the Fourier transform infrared spectroscopy (FT-IR). The scanning electron microscopy (SEM) suggested most of the starch granules disintegrated with many visible fragments along with the increasing DS. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), it was observed that the thermal stability of acetylated starch depends on the degree of substitution. Thermal stability of high DS acetylated starch is much better than that of the original starch when DS reached to 2.67.     

Thermal degradation of star-shaped poly(?-caprolactone)

Thermal degradation of a serials of star-shaped poly(?-caprolactone) (PCL) with well-defined arm numbers and arm length was investigated. The weight loss of star-shaped PCL during heating process showed a two-stage character, and its dependence on molecular weight and multi-armed structure was well discussed. It was found that the thermal stability could be improved not only by increasing molecular weight but also by increasing arm numbers when the molecular weight is in a certain range. Based on the analyses of pyrolytic products by ¹H NMR and TGA-FTIR, two mechanisms of thermal degradation for the random cleavage of ester bonds of PCL chains were proposed. Ester bonds were pyrolyzed into alkene and carboxyl functional groups in mechanism I while they were pyrolyzed into ketene and hydroxyl functional groups in mechanism II. The effects of multi-armed structure of star-shaped PCL on the cleavage of ester bonds of PCL chains were discussed in terms of the limitation of central “core” on mobility of each PCL arm. Combined the results of viscosity analysis with thermal analysis, it could be concluded that both thermal stability and processability of PCL materials can be improved by controlling the multi-armed structures.     

开放实验室教学模式的实践与思考

山东大学化学与化工学院开放实验室自2003年5月份开始向二、三年级本科生进行全天候开放。由本科生自主组成课题组,经院专家组筛选后进入开放实验室。目前这种教学模式已经纳入正常教学工作,对学生的培养已经产生和正在产生着较大的影响。