Vibration of vehicle–pavement coupled system based on a Timoshenko beam on a nonlinear foundation

This paper focuses on the coupled nonlinear vibration of vehicle–pavement system. The pavement is modeled as a Timoshenko beam resting on a six-parameter foundation. The vehicle is simplified as a spring–mass–damper oscillator. For the first time, the dynamic response of vehicle–pavement coupled system is studied by modeling the pavement as a Timoshenko beam resting on a nonlinear foundation. Consequently, the shear effects and the rotational inertia of the pavement are included in the modeling process. The pavement model is assumed to be a linear-plus-cubic Pasternak-type foundation. Furthermore, the convergent Galerkin truncation is used to obtain approximate solutions to the coupled vibratory response of the vehicle–pavement coupled system. The dynamic responses of the vehicle–pavement system with the asphalt pavement on soft soil foundation are investigated via the numerical examples. The numerical results show that the calculation for the coupled vibratory response needs high-order modes. Moreover, the coupling effects between the pavement and the vehicle are numerically examined by using the convergent modal truncation. The physical parameters of the vehicle–pavement system such as the shear modulus are compared for determining their influences on the coupled vibratory response.     

Recreational runners with patellofemoral pain exhibit elevated patella water content

Increased bone water content resulting from repetitive patellofemoral joint overloading has been suggested to be a possible mechanism underlying patellofemoral pain (PFP). To date, it remains unknown whether persons with PFP exhibit elevated bone water content. The purpose of this study was to determine whether recreational runners with PFP exhibit elevated patella water content when compared to pain-free controls. Ten female recreational runners with a diagnosis of PFP (22 to 39 years of age) and 10 gender, age, weight, height, and activity matched controls underwent chemical-shift-encoded water-fat magnetic resonance imaging (MRI) to quantify patella water content (i.e., water-signal fraction). Differences in bone water content of the total patella, lateral aspect of the patella, and medial aspect of the patella were compared between groups using independent t tests. Compared with the control group, the PFP group demonstrated significantly greater total patella bone water content (15.4 ± 3.5% vs. 10.3 ± 2.1%; P = 0.001), lateral patella water content (17.2 ± 4.2% vs. 11.5 ± 2.5%; P = 0.002), and medial patella water content (13.2 ± 2.7% vs. 8.4 ± 2.3%; P < 0.001). The higher patella water content observed in female runners with PFP is suggestive of venous engorgement and elevated extracellular fluid. In turn, this may lead to an increase in intraosseous pressure and pain.     

垂直场下磁性薄膜中的铁磁共振现象

将铁磁共振频率看成外磁场的函数, 讨论了垂直场下磁性膜中的铁磁共振现象. 结果显示: 当外磁场平行于膜面, 并考虑磁膜具有垂直磁晶各向异性情形时, 其磁共振频率随外磁场的变化分为高频支和低频支两种情况, 具体的依赖关系取决于磁膜内磁晶的各向异性; 当外磁场垂直于膜面, 其磁共振频率随外磁场的关系仅存在一支, 一般地, 磁共振频率随外磁场的增加单调地非线性减小, 但当立方磁晶各向异性场H_k1 与单轴磁晶各向异性场H_a之比值介于2/3 < H_k1/H_a <1时, 其磁共振频率随外磁场的增加单调增加, 这与相关的实验结果一致. 研究结果表明: 磁薄膜中有无垂直于膜面的磁各向异性可以通过其磁共振谱的测量进行辨析.     

热带低层弱涡旋中扰动的快速发展及其向中心传播的特征

台风发生的必要条件是热带低层具有气旋式扰动, 从卫星云图和诊断分析看,许多低层涡旋中存在分立的云团或中尺度系统. 这些涡旋能否发展成为台风,取决于其中的中尺度波动是否发展集合组成密闭云带. 本文利用柱坐标下的两层动力模式,研究了低层弱涡旋中第二类条件不稳定 机 制驱动下的波动的发展和移动问题. 结果表明:热带弱涡旋中的低层基本流垂直切变 可以很大地加强波动的不稳定性; 波动的相速度和群速度都指向涡旋中心, 波动向中心传播,能量向中心频散. 实例和数值研究也都表明,低层涡旋中的中尺度扰动会迅速发展并且向 中心靠近,促使台风形成.     

A novel optical beam splitter based on photonic crystal with hybrid lattices

A novel optical beam splitter constructed on the basis of photonic crystal(PC) with hybrid lattices is proposed in this paper.The band gap of square-lattice PC is so designed that the incident light is divided into several branch beams.Triangular-lattice graded-index PCs are combined for focusing each branch.Computational calculations are carried out on the basis of finite-different time-domain algorithm to prove the feasibility of our design.The waveguide is unnecessary in the design.Thus the device has functions of both splitting and focusing beams.Size of the divided beam at site of full-width at half-maximum is of the order of λ/2.The designed splitter has the advantages that it has a small volume and can be integrated by conventional semiconductor manufacturing process.     

HT-7托卡马克slide-away放电充气对等离子体行为的影响

本文研究了slide-away放电条件下的等离子体约束性能;分析了充气对等离子体约束性能以及反常多普勒共振不稳定性的影响.研究了等离子体密度的提升对slide-away放电过程中逃逸电子辐射行为的影响.研究结果发现:slide-away放电充气可以抑制逃逸电子反常多普勒不稳定性,但是使得等离子体约束状态变差,逃逸电子辐射增强.     

Edge states at the interface between monolayer and bilayer graphene

The electronic properties for monolayer-bilayer hybrid graphene with zigzag interface are studied by both the Dirac equation and numerical calculation in zero field and in a magnetic field. Basically there are two types of zigzag interface dependent on the way of lattice stacking at the edge. Our study shows they have different locations of the localized edge states. Accordingly, the energy-momentum dispersion and local density of states behave quit differently along the interface near the Fermi energy EF=0.     

一种用于土壤非金属养分测试的光纤探头式分光光度计

针对测土配方施肥技术中要求快速、便捷、高效地进行土壤养分测试的需求,文章基于浸入式光纤探头、平场凹面全息光栅、二极管线阵检测器开发了一种光纤探头式分光光度计用于土壤养分中非金属元素的快速、准确测试。基于国家计量检定规程JJG 178—2007对紫外、可见、近红外分光光度计的性能检测方法测试的该仪器的波长最大允许误差与波长重复性、基线平直度、透射比最大允许误差与透射比重复性均达到了国标第Ⅲ级别标准,其最小光谱带宽、噪声与漂移、杂散光基本达到了国标第Ⅳ级别标准。基于该仪器测试的土壤硝态氮、铵态氮、有效磷、有效硫、有效硼、和有机质含量与基于商用的国产单光束和进口双光束分光光度计测试的结果呈极显著的线性相关关系,其回归方程的斜率接近于1,且对比数据之间无显著性差异。因此,该光纤探头式分光光度计可用于土壤非金属养分的快速、准确测试。     

ICP-MS法测定不同采收时间宽叶荨麻中微量元素含量

采用微波消解,ICP-MS法分析不同采收时间宽叶荨麻中18种微量元素Al,Ba,Ca,Co,Cr,Cu,Fe,K,Li,Mg,Mn,Mo,Na,Ni,P,Pb,S和Zn的含量。该方法的相对标准偏差在1.2%～5.3%之间,加标回收率在95.4%～101.2%之间。结果表明宽叶荨麻中K,P,S,Ca,Na含量较高;Fe,Mg,Mn,Zn含量次之;有潜在生理毒性的元素Al,Cr,Pb的含量较低,并且在宽叶荨麻中微量元素呈现明显的季节性动态变化,此结果为进一步研究宽叶荨麻药理药效与微量元素的关系以及更好的开发这一资源提供理论数据。     

拱形激光二极管侧抽运Nd:YAG固体激光器的实验研究

详细阐述了同心抽运、同心冷却的激光二极管紧包侧抽运Nd：YAG激光器的实验研究工作。这种抽运结构使晶体内的增益场与谐振腔基模实现了良好的匹配,易于得到良好的光束质量和大能量输出,基模提取效率高。模拟分析了晶体内的增益场以及横截面内的温度分布,从不同角度探讨了激光二极管的温度特性对器件工作的影响。研究了晶体的热致退偏效应对器件调Q工作的影响．并且初步探讨了不同腔长、不同腔型下器件的工作情况,这些实验结果对进一步优化使用这种抽运结构有指导意义。所设计的激光器在工作频率6Hz时．得到了斜效率为44．3％的多模调Q输出。在抽运能量735mJ时,得到最大输出能量135mJ,脉宽7．6ns的调Q脉冲,光光效率为18．4％,插头效率为11．0％,光束发散角小于1．5mrad。