Lie group classifications and exact solutions for two variable-coefficient equations

In this paper, the Lie symmetry analysis and group classifications are performed for two variable-coefficient equations, the hanging chain equation and the bond pricing equation. The symmetries for the two equations are obtained, the exact explicit solutions generated from the similarity reductions are presented. Moreover, the exact analytic solutions are considered by the power series method.     

Travelling wave solutions of the Fornberg-Whitham equation

Zhou and Tian [J.B. Zhou, L.X. Tian, A type of bounded travelling wave solutions for the Fornberg-Whitham equation, J. Math. Anal. Appl. 346 (2008) 255-261] successfully found a type of bounded travelling wave solutions of the Fornberg-Whitham equation. In this paper, we improve the previous result by using the phase portrait analytical technology. Moreover, some smooth periodic wave, smooth solitary wave, periodic cusp wave and loop-soliton solutions are given, and the numerical simulation is made. The results show that our theoretical analysis agrees with the numerical simulation.     

Photocatalytic reaction and degradation of methylene blue on TiO2 films in vacuum: an X-ray photoelectron spectroscopy study

Photocatalytic reaction and degradation of methylene blue on TiO₂ films illuminated by ultraviolet light in air and in vacuum were studied by X-ray photoelectron spectroscopy (XPS). The results show that TiO₂ film has photocatalytic activity in high vacuum, while the oxygen-containing groups on TiO₂ film play a very important role in maintaining photocatalytic reaction, a certain nitrogenous group has been removed from the methylene blue molecule to make the atomic ratio of its N and S decrease from 2.83 to 2.09, and form the intermediate reaction products containing benzene ring and N, S heterocycle, which can be degraded incompletely.     

Experimental studies of biomass gasification with air

In this work,experimental studies of biomass gasification under different operating conditions were carried out in an updraft gasifier combined with a copper slag reformer.The influence of gasification temperature,equivalence ratio(ER) and copper slag catalyst addition on gas production and tar yield were investigated.The experimental results showed that the content of H2 and CO,gas yield and LHV increased,while the tar yield and the content of CO2,CH4 and C2Hx in the gas product decreased with the temperature.At 800C,with the increase of ER,the LHV,the tar yield and the content of H2,CO,CH4 and C2Hx in gas products decreased,while the gas yield and the content of CO2 increased.Copper slag was introduced into the secondary reformer for tar decomposition.The Fe3O4 phase in the fresh copper slag was reduced to FeO(Fe2+) and metallic Fe by the gas product.Fe species(FeO and metallic Fe) acted as the active sites for tar catalytic decomposition.The catalytic temperature had a significant influence on tar conversion and the composition of the gas product.Typically,the tar conversion of about 17%-54% could be achieved when the catalytic temperature was varied from 750 to 950 C.Also,the content of H2 and CO increased with the catalytic temperature,while that of CO2,CH4 and C2Hx in the gas product decreased.It was demonstrated that copper slag was a good catalyst for upgrading the gas product from biomass gasification.     

Band‐Edge Electronic Structure of β‐In2S3: The Role of s or p Orbitals of Atoms at Different Lattice Positions

As a promising solar‐energy material, the electronic structure and optical properties of Beta phase indium sulfide (β‐In₂S₃) are still not thoroughly understood. This paper devotes to solve these issues using density functional theory calculations. β‐In₂S₃ is found to be an indirect band gap semiconductor. The roles of its atoms at different lattice positions are not exactly identical because of the unique crystal structure. Additonally, a significant phenomenon of optical anisotropy was observed near the absorption edge. Owing to the low coordination numbers of the In3 and S2 atoms, the corresponding In3‐5s states and S2‐3p states are crucial for the composition of the band‐edge electronic structure, leading to special optical properties and excellent optoelectronic performances.     

原子轰击调制离子束溅射沉积Ge量子点的生长演变

采用离子束溅射沉积的方法在Si衬底上生长Ge量子点,观察到量子点的生长随Ge原子层沉积厚度θ的增加经历了两个不同的阶段.当θ在6—10.5个单原子层(ML)范围内时,量子点的平均底宽和平均高度随θ增加同时增大,生长得到高宽比较小的圆顶形Ge量子点,伴随着量子点的生长,二维浸润层的厚度同时增大,量子点的分布密度缓慢增加;当θ在11.5一17 ML范围内时,获得高宽比较大的圆顶形Ge量子点,量子点以纵向生长为主导,二维浸润层的离解促进量子点的成核和长大,量子点的分布密度随θ的增加快速增大;量子点在θ由10.5 ML增加到11.5 ML时由一个生长阶段转变到另一个生长阶段,其分布密度同时发生6.4倍的增加.离子束溅射沉积Ge量子点的生长演变与在热平衡状态下生长的量子点不同,在量子点的不同生长阶段,其表面形貌和分布密度的变化特点是在热力学条件限制下表面原子动态演变的结果,θ的变化是引起系统自由能改变的主要因素.携带一定动能的溅射原子对生长表面的轰击促进表面原子的扩散迁移,同时压制量子点的成核,在浸润层中形成超应变状态,因而,改变体系的能量和表面原子的动力学行为,对量子点的生长起重要作用.     

微波消解吸载乙醇活性炭出口浓度的近似法测定

设计了载乙醇活性炭微波解吸的实验流程。采用近似法测定载乙醇活性炭微波解吸的出口浓度曲线,对微波解吸的分离过程进行了分析。实验结果表明,中期乙醇出口浓度高于前后期;在320W微波功率下,90s即出现乙醇出口浓度的最高峰值;在680W微波功率下,60s即出现乙醇出口浓度的最高峰值;质量分数4%的低浓度乙醇水溶液经两次活性炭吸附-微波解吸循环后,乙醇出口质量分数的峰值可达94%以上。     

三元杂质砷锑钴对锌电沉积阴极过程的影响

采用电化学研究方法探讨了在锌电积过程中砷、锑、钴杂质对阴极极化过程的单一和共同影响,得出了单一杂质和三元杂质对锌电积过程影响的动力学方程及参数,并对其极化机理进行了研究.结果表明,含一元杂质的ZnSO4/H2SO4溶液的动力学参数与理论值基本一致,而含三元的ZnSO4/H2SO4溶液的传递系数α要比理论值小,说明杂质的存在及其含量的大小、品种的多少对锌电积影响程度不同.     

合成聚苯胺/碳化钨复合材料及聚合机理探讨

采用在原位聚合苯胺的反应介质中分散碳化钨(WC)的方法制备了掺杂聚苯胺/碳化钨(PANI/WC)复合物,并研究了苯胺在WC表面的聚合机理.通过扫描电镜(SEM)、透射电镜(TEM)、傅立叶红外光谱(FTIR)、拉曼光谱(Raman)和X射线衍射(XRD)对复合物进行了表征.结果表明,苯胺的聚合倾向于在WC颗粒表面进行,形成了PANI包覆WC的复合材料;WC粒子与PANI大分子之间存在强的相互作用,并且复合前后WC的晶型并未发生变化,WC的存在导致红外光谱有明显的蓝移现象,复合后在3446 cm-1处的红外吸收峰变得很弱;在拉曼光谱中,代表醌环C N键的伸缩振动峰红移了9 cm-1,并且强度也有很大程度提高.说明PANI与WC之间有化学键的作用,它们之间的化学键作用发生在C N键的N原子上.聚合反应优先在WC粒子表面进行,生成PANI包覆结构,并提出了PANI/WC复合物的形成机制.     

The self‐assembled of cyclic D,L‐α‐peptide systems: Insights into the structure and energetics

Cyclic D,L ‐α‐peptides are able to self‐assemble to nanotubes, although the inherent reason of the stability of this kind of nanotube as well as the intrinsic driving force of self‐assembly of the cyclic D ,L ‐α‐peptides still remain elusive. In this work, using several computational approaches, we investigated the structural and energy characteristics of a series of cyclo[(‐L ‐Phe‐D ‐Ala‐)₄] and cyclo[(‐L ‐Ala‐D ‐Ala‐)₄] oligomers. The results reveal that the thermodynamic stability, cooperativity, and self‐assembly patterns of cyclic D ,L ‐α‐peptide nanotubes are mainly determined by the interactions between cross‐strand side chains instead of those between backbones. For cyclo[(‐L ‐Phe‐D ‐Ala‐)₄] oligomers, the steric interaction between cross‐strand side chains, especially the electrostatic repulsion between the phenyls in Phe residues, brings anticooperative effect into parallel stacking mode, which is responsible for the preference of self‐assembling nanotube in antiparallel vs. parallel stacking orientation. Based on our results, a novel self‐assembling mechanism is put forward—it is the L ‐L antiparallel dimer of cyclo[(‐L ‐Phe‐D ‐Ala‐)₄], instead of the commonly presumed monomer, that acts as the basic building block in self assembly. It explains why these cyclic peptides uniquely self‐assemble to form antiparallel nanotubes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010