Bifurcation and chaos analysis of spur gear pair with and without nonlinear suspension

This study performs a systematic analysis of the dynamic behavior of a single degree-of-freedom spur gear system with and without nonlinear suspension. The dynamic orbits of the system are observed using bifurcation diagrams plotted using the dimensionless damping coefficient and the dimensionless rotational speed ratio as control parameters. The onset of chaotic motion is identified from the phase diagrams, power spectra, Poincaré maps, Lyapunov exponents and fractal dimension of the gear system. The numerical results reveal that the system exhibits a diverse range of periodic, sub-harmonic and chaotic behaviors. The results presented in this study provide an understanding of the operating conditions under which undesirable dynamic motion takes place in a spur gear system and therefore serve as a useful source of reference for engineers in designing and controlling such systems.     

Photocathodic protection properties of three-dimensional titanate nanowire network films prepared by a combined sol–gel and hydrothermal method

A combined sol–gel and hydrothermal method was developed for preparing a three-dimensional titanate nanowire network film on titanium substrates to achieve an especial photocathodic protection effect for 403 stainless steel. Photopotential measurements were performed to study the protection effect of the film. The results indicated that the titanate film exhibited a special all-dimensional uniform porous structure composed of branched titanate nanowires. When we coupled the steel in a 0.5 M NaCl solution to the titanate film photoanode in a 1.0 M NaOH solution under illumination, its potential decreased by 560 mV. Especially after the light source was cut off, the photopotential of the steel increased by only 50–145 mV, and kept at the lower values than the corrosion potential under dark conditions for over 10 h, indicating that the titanate nanowire network film could produce a striking photocathodic protection effect for 403 stainless steel under illumination and dark conditions.     

Developments of High-Efficiency Flexible Cu（In,Ga）Se2 Thin Film Solar Cells on a Polyimide Sheet by Sodium Incorporation

We present the fabrication of flexible Cu（In,Ga）Se2 （CIGS） solar cells on a polyimide （PI） sheet with and without Na incorporation. A sodium element is incorporated into the CIGS absorber by using a NaF precursor after Mo back contact deposition. X-ray diffraction patterns show that the （112） preferred orientation of the as-grown GIGS films is decreased by Na incorporation. The secondary phase of （Inx,Gal-x）zSe3 is observed for the CIGS films with Na. There is no significant difference in the grain size with and without Na incorporation from surface and cross-sectional SEM images. Additionally, the increase of carrier concentration and decrease of resistivity of CIGS absorber are induced by Na doping. Finally, the flexible CIGS solar cells on PI sheets with efficiency close to 11%, containing Na, are achieved. The improvement of cell efficiency can be attributed to the modified electrical properties of the CIGS film by Na incorporation.     

托卡马克装置中高能离子的直接损失

通过严格求解导心坐标系下的哈密顿方程,提出了托卡马克装置中离子的真实轨道理论,并利用此理论对国际热核聚变实验堆(ITER)中α离子的真实轨道进行了数值模拟研究,获得了驻点轨道和近期理论预言的半俘获轨道.根据此真实轨道理论计算了ITER中α离子的直接损失率.结果发现,与所提出的真实轨道理论相比,以前的回旋平均理论大幅度低估了α离子的直接损失率,两种理论的损失率差值可达14%,对此差异进行了详细的分析并给出了物理上的解释.     

Fabrication of transparent double-walled carbon nanotubes flexible matrix touch panel by laser ablation technique

This study reports on the fabrication of transparent double-walled carbon nanotubes (DWNTs) flexible matrix touch panel using the method of laser ablation. We employed an Nd:YAG laser (1064 nm) to pattern transparent DWNT thin film pre-coated on a PET substrate and successfully fabricated a flexible matrix touch panel. By increasing the laser energy, the ablation depth of transparent DWNT flexible thin film is increased but the sheet resistance (Ω/sq) is decreased. When the laser energy intensity reaches 117 mJ/cm², the DWNTs can be completely ablated from transparent DWNT flexible thin film. This method is rapid, simple, applicable to large-area processing and thus is potential for mass production.     

离子通道摇摆电子束流激发的纵向慢波不稳定性

考虑相对论电子束入射等离子体所产生的离子通道的具体结构,利用线性电磁流体力学理论对离子通道摇摆电子束激发的纵向慢波电磁不稳定性进行研究.通过对导出的系统色散关系的数值分析,给出了系统中电磁波、空间电荷波以及两者在一定条件下互作用形成的电磁-静电混合模式的传播特性.研究发现系统在慢波区域存在电磁不稳定性,并揭示此慢波不稳定性是由电子束的betatron振荡所导致,且系统的不稳定性程度与betatron振动频率密切相关.对betatron振荡激发的慢波电磁不稳定性物理机理进行了分析,并给出了不稳定性存在的条件 关键词： 离子通道 betatron振荡 电磁不稳定性     

A Monte Carlo study for the shielding of γ backgrounds induced by radionuclides for CDEX

The CDEX(China Dark matter EXperiment)Collaboration will carry out a direct search for WIMPs(Weakly Interacting Massive Particles)using an Ultra-Low Energy Threshold High Purity Germanium(ULE-HPGe)detector at the CJPL(China JinPing deep underground Laboratory).A complex shielding system was designed to reduce backgrounds and a detailed GEANT4 Monte Carlo simulation was performed to study the achievable reduction of T rays induced by radionuclides and neutron backgrounds by D(γ,n)p reaction.Furthermore,the upper level of allowed radiopurity of shielding materials was estimated under the constraint of the expected goal.Compared with the radiopurity reported by other low-background rare-event experiments,it indicates that the shielding used in the CDEX can be made out of materials with obtainable radiopurity.     

NONLINEAR NUMERICAL ANALYSIS OF A FLEXIBLE ROTOR EQUIPPED WITH SQUEEZE COUPLE STRESS FLUID FILM JOURNAL BEARINGS

This study performs a dynamic analysis of a rotor supported by two squeeze couple stress fluid film journal bearings with nonlinear suspension.The numerical results show that the stability of the system varies with the non-dimensional speed ratios and the dimensionless parameter l*.It is found that the system is more stable with higher dimensionless parameter l*. Thus it can conclude that the rotor-bearing system lubricated with the couple stress fluid is more stable than that with the conventional Newtonian fluid.The modeling results thus obtained by using the method proposed in this paper can be used to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided.     

碱金属原子的光激发与光电离

本文研究了碱金属原子在三步激光脉冲作用下的光激发和光电离过程的动力学特性, 重点关注和比较了锂和铯原子的异同. 针对多种激发模式, 本文不但建立了其原子布居数在各个跃迁态的速率方程组, 还给出了各相关态的光激发和光电离过程的解析解. 通过精心设计并选择了特殊情况, 显著简化了解析解的数学表达式, 从而凸显和讨论了其物理内涵. 通过自行编程, 系统地计算和观察了各种激发模式对锂原子的光激发和光电离过程的可能影响, 研究和讨论了电离率随激光参数的变化规律. 在相同激发模式下, 比较和分析了采用两种不同激发路径所导致的各态原子布居率的变化, 凸显了改变原子参数所产生的作用. 探讨了锂和铯原子在类似的激发条件下在电离率方面的差别. 最后, 基于本文的研究结果, 本文指出了优化电离率的多种途径.