Numerical simulation of the flow field in a reactor for titanium dioxide production

A physicochemical and fluid dynamic model is formulated for the numerical simulation of the flow field in a reactor for titanium dioxide production, the turbulence motion is described by theKε equation, the governing equations are solved by the SIMPLER algorithm devised by Partankar and Spalding. The velocity, tmperature and concentration fields are obtained for three cases: A) with chemical reaction and thermal insulation on the walls; B) with chemical reaction and wall temperature is 450K; C) without chemical reaction and thermal insulation on the walls, and the physicochemical numerical simulation for the titanium dioxide production has been done. The results of the paper can be used as a theoretical guide for the engineers in the design of such reactors.     

Operation analysis of natural resources and their pan-weighted network models

In this paper, we propose a competition-share 3-category principle, on which we unite the problems of natural resources, energy, population and environment and so on into a mutual scheme, and provide a united model for the comprehensive research on these problems. This makes the idea of operation analysis of natural resources clearer and the relationships between each of their parts more obvious. On the basis of the above discussion, we propose mathematical models for the operation analysis of multi-networks and the solution of the above global comprehensive problems. We discuss, especially, Shengke (growth and restraint) relationships between two networks of natural resources and share-competitors and their analysis models, providing mathematical tools for solving the problems of the resource-population and the resource-economy, etc. Supported by Science Fund of Lanzhou University.     

城区爆破作业对环境的影响

本文用一个城区爆破作业的实例说明,只要采取可靠的技术措施,就可将爆破对环境的影响,如振动、噪声、飞石等,控制在允许的范围内,从而可以在人口稠密的城区顺利地进行较大规模的爆破施工,加快工程进度。     

A fractional order hyperchaotic system derived from Liu system and its circuit realization

In this paper we propose a novel four-dimensional fractional order hyperchaotic system derived from Liu system. Electronics workbench (EWB) and Matlab simulations show the dynamical behavior of the proposed four-dimensional fractional order hyperchaotic system. Finally, after separately using EWB and Matlab, an electronic circuit is designed to realize the novel four-dimensional fractional order hyperchaotic system and the experimental circuit results are obtained which are identical to software simulations.     

Full relativistic calculations of the quadrupole and electric field gradients for C2, N2, and O2

In the present work we calculate the energies,quadrupole moments,and electric field gradients(EFGs) of molecules C2,N2,and O2 based on the DIRRCI method with basis aug-cc-pVTZ-DK.We prove that the quadratic force constant k2 is the product of charge and EFG at its equilibrium nuclear distance.The dipole charge distributions for these symmetrical molecules are all in equilibrium,however,the quadrupole charge distributions are far from equilibrium;among these,there is the most remarkable deviation from equilibrium for N2,for its many charges concentrate on two sides of the molecule,which is in agreement with the well-known characteristic of the nitrogen molecule.The relativistic effect is remarkable even for the same period.     

Estimation of temperature elevation generated by ultrasonic irradiation in biological tissues using the thermal wave method

In most previous models,simulation of the temperature generation in tissue is based on the Pennes bio-heat transfer equation,which implies an instantaneous thermal energy deposition in the medium.Due to the long thermal relaxation time τ(20 s-30 s) in biological tissues,the actual temperature elevation during clinical treatments could be different from the value predicted by the Pennes bioheat equation.The thermal wave model of bio-heat transfer(TWMBT) defines a thermal relaxation time to describe the tissue heating from ultrasound exposure.In this paper,COMSOL Multiphysics 3.5a,a finite element method software package,is used to simulate the temperature response in tissues based on Pennes and TWMBT equations.We further discuss different factors in the bio-heat transfer model on the influence of the temperature rising and it is found that the temperature response in tissue under ultrasound exposure is a rising process with a declining rate.The thermal relaxation time inhibits the temperature elevation at the beginning of ultrasonic heating.Besides,thermal relaxation in TWMBT leads to lower temperature estimation than that based on Pennes equation during the same period of time.The blood flow carrying heat dominates most to the decline of temperature rising rate and the influence increases with temperature rising.On the contrary,heat diffusion,which can be described by thermal conductivity,has little effect on the temperature rising.     

SiN自由基X2∑+, A2Π和B2∑+ 电子态的光谱常数研究

采用内收缩多参考组态相互作用(MRCI)方法, 结合价态范围内的最大相关一致基aug-cc-pV6Z, 计算了SiN自由基X²∑⁺, A²Π 和B²∑⁺电子态的势能曲线. 采用Davidson修正来避免由于MRCI方法本身的大小一致性缺陷产生的误差. 为了提高计算精度, 进一步考虑了相对论修正和核价相关修正对势能曲线的影响. 本文的相对论修正是利用二阶Douglas-Kroll 哈密顿近似在cc-pV5Z基组水平进行的; 同时核价相关修正是在cc-pCV5Z基组水平进行的. 对这些势能曲线进行拟合, 得到各种水平下三个电子态的光谱常数(T_e, R_e, ω_e, ω_ex_e, α_e和B_e), 并详细分析了Davidson修正、相对论修正和核价相关修正对光谱常数的影响. 与其他理论结果和实验数据进行比较, 可知本文的结果更精确、更完整.     

碳纳米管锁模双包层光纤激光器的实验研究

本文采用双包层掺镱光纤作为增益介质,用单壁碳纳米管作为饱和吸收体,获得最高输出功率为336 mW的锁模脉冲激光.用飞秒激光诱导水击穿法直接在单模光纤上制备出D形区,通过在D形光纤上滴涂单壁碳纳米管溶液,成功制备出碳纳米管饱和吸收体,并对其饱和吸收特性进行测试,发现其调制深度为27％.利用该饱和吸收体作为锁模器件,制备出具有环形腔结构的锁模光纤激光器.当抽运功率为4W时,获得了脉宽为93.8 fs,中心波长为1083.8 nm,3 dB谱宽为8.6 nm,重复频率为5.59 MHz,平均功率为336 mW的飞秒脉冲激光输出.     

金属催化制备石墨烯的研究进展

石墨烯作为一种新兴的碳素材料,从一出现就引起了众多学者的关注.石墨烯具有许多新奇的特性,使得石墨烯在光电领域及微电子工业等有极大的应用潜力.但是目前难以实现大尺寸、高质量、宏量石墨烯的可控制备,限制了石墨烯的广泛应用.本文分析了各种石墨烯制备方法的利弊,重点从层数控制及大面积制备等方面对金属催化法进行了阐述,固态碳源金属催化法可以实现宏量制备大尺寸、高质量、薄且均匀的石墨烯.综述了金属催化制备石墨烯的相关机理研究,指出了目前研究的局限,并对石墨烯相变机理的下一步研究方向进行了展望.     

不同周期信号激励下分数阶线性系统的响应特性分析

研究了含分数阶导数阻尼的一类线性系统在不同周期信号激励下系统的响应问题.首先在简谐信号的激励下,利用谐波平衡法得到了系统响应的近似解,这一结果和已有文献(申永军,杨绍普,邢海军2012物理学报61 110505)的结果完全相同,但本文的求解过程大为简化,而且本文进一步扩展了分数阶导数阻尼微分阶数的取值范围.接着,利用傅里叶级数展开法和线性系统的叠加原理,求得了一般周期信号激励下系统响应的近似解,并以周期方波信号和周期全波正弦信号为例进行了说明.本文的结果表明,分数阶导数阻尼的微分阶数影响系统响应中各阶谐波的共振频率和共振振幅.系统响应的幅值与分数阶导数阻尼的微分阶数之间的单调关系主要受外激信号频率的影响.除解析分析外,本文还用数值模拟对相关结论进行了验证,两种结果符合良好,表明本文的分析方法是可行的.