共查询到20条相似文献，搜索用时 156 毫秒
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研究了部分相干贝塞尔光束经过光阑透镜聚焦后的光强分布。研究表明．部分相干贝塞尔光束在几何焦点附近的光强分布不仅取决于阶数和贝塞尔光束系数,还与相干度有关。据此,可以通过选择合适的参数。产生部分相干局域空心光束。产生的局域空心光束运用广泛,如微粒导引,捕获和诱导旋转等等。还有一些研究者采用局域空心光束来构成激光导管、光学镊子和光学扳手,从而实现微观粒子的精确、无接触操纵和控制。 相似文献
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基于矢量德拜理论,研究了双环角向偏振涡旋光束经大数值孔径透镜的聚焦,且在聚焦场中考虑存在两种不同介质。研究表明当涡旋光束的拓扑电荷数为1,且当透镜孔径半径与入射双环角向偏振涡旋光束的束腰半径之比为1.5时,聚焦光束可得到一个尺寸只有零点几个波长的局域空心光束。局域空心光斑的横向半径仅为0.38λ,而空心长度为2.37λ。此外还研究了透镜的数值孔径以及光束的入射拦截比对不同介质引起聚焦光束焦移的影响。 相似文献
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袁素真 《安阳师范学院学报》2009,(2)
本文简单介绍了光场角动量的基本概念.概括了具有轨道角动量的特殊光束-高斯拉盖尔光束的特点及产生方式,在其产生过程中总结出带角动量的光束和物质相互作用时角动量发生转移.给出了不具有螺旋相位结构却有轨道角动量的椭圆光束.这些带有角动量的光束与微米粒子相互作用时所产生的微小的力可以起到对微米粒子的囚禁和旋转作用,这就为生物细胞的光学导引、囚禁与操控领域提供了广阔应用前景. 相似文献
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理论分析了光束具有的自旋角动量传递给晶体并导致其旋转的机理。并以碳酸钙粒子为例从理论上的分析了有效功率,粒子形状和大小,以及粘滞系数对旋转角速度的影响。对实验中如何提高晶体旋转角速度具有一定参考价值。 相似文献
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《实验室研究与探索》2017,(6):58-61
设计了一种大气环境散射率测量装置,用于测量普通大气环境中粒子对激光散射率,用以反映测量环境对光束的散射程度,进而评估测量环境能否满足散射测量。该装置以稳功率激光器为光源,让光束穿过积分球空腔,使空腔内的粒子在空腔内发生散射,从而散射光都被积分球所收集,再使用光电倍增管测量积分球收集的散射光强,并采用相关检查方法进行信号处理,有效去除背景噪声。在实验室环境进行了测量,结果表明,测量精度最高可达0.1×10~(-6),装置误差达到±2%,实现了散射率的高精度测量。 相似文献
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袁洪彬 《数理化学习(高中版)》2006,(4)
1．为什么天空总是蔚蓝色的?为什么早晨或傍晚看到的太阳呈红色而中午的太阳呈白色?如果地球表面没有大气,天空将是什么样子?宇航员在太空中看到的天空又是什么样子? 解析:以上这些现象都是由于光的散射造成的．光的散射是由于介质中存在微小粒子或分子对光的作用,使光束偏离原来的传播方向而向四周传播的现象．当光束通过光学性质均匀的介质(如玻璃、纯水)时,在光束的侧面观察,几乎看不到光．但当一束太阳光射人有烟雾的室内或混浊 相似文献
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郎雷鸣 《南京晓庄学院学报》2012,(6):60-64
该文主要采用简单的溶剂热和水热法通过控制不同条件如硫源和表面活性剂合成了多种形貌的硫化镍纳米材料,在使用L-胱氨酸,硫代乙酰胺作为硫源以及PEG2000作为表面活性剂时,分别获得了规整的硫化镍实心球,海胆状硫化镍空心微球以及由纳米粒子组成的空心球,分别测定了三者的电化学性能,结果表明海胆状硫化镍空心微球的循环性能较好,循环30次以后放电容量保持在200 mAhg-1左右. 相似文献
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基于交叉谱密度函数的传输定律及相干与偏振的统一理论,研究了部分相干径向偏振光在自由空间中的传输。结果表明：由于相干诱导作用,部分相干径向偏振光在自由空间中传输时其光强与偏振度都发生了变化,传输过程中径向偏振光的光强由原来的空心逐渐变为平顶接着变为高斯型,而不同的相干度下光束的偏振度在传输过程中的变化情况不同。 相似文献
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A type of hollow cylinder joints connected with H-shaped beams is proposed for spatial structures. Based on von Mises yield
criterion and perfect elasto-plasticity model, a series of finite element models of the joints is established, in which the
effect of geometric nonlinearity is taken into account. Then mechanical behavior and load-carrying capacity of the joints
were investigated, which were subjected to axial load, in- and out-plane bending moments, and their combinations. The results
show that the ultimate loads of the joints are determined by the maximum displacement. Furthermore, the case of one joint
connected with multiple beams was discussed. Experiments on a set of typical full-scale joints were conducted to understand
the structural behavior and the failure mechanism of joint, and also to validate the finite element models. Finally, the practical
calculation method was established through finite elements analysis (FEA) results and numerical fitting. The results show
that the joints are more ductile and materially economical than welded hollow spherical joints, and the practical calculation
method can provide a reference for direct design and the revision of relevant design codes. 相似文献
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主要介绍汽车自动弯道照明系统结构、原理.通过在车辆内部增加一套机构实现前照灯的随动转向,使得大灯能够根据夜间行驶道路的弯道情况,随时自动调整弯道照明的光束方向,减少弯道内侧出现的盲区,以便及时发现障碍物和行人,从而增强夜间驾驶的主动安全性. 相似文献
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为了解玻璃纤维(GFRP)布与钢筋混凝土梁界面之间的粘结性能,进行了7根GFRP布加固的钢筋混凝土梁与2根对比梁的试验研究.试验的变化参数为GFRP布层数、粘结长度及配筋率.试验结果表明,GFRP布加固的钢筋混凝土梁极限荷载显著提高,但是发生剥离破坏的试验梁极限荷载有所降低,粘结长度是影响加固梁剥离破坏的主要因素.根据试验结果提出了GFRP布与钢筋混凝土梁界面粘结剪应力的试验分析方法并分析了界面间粘结剪应力的分布.同时,提出了GFRP布加固的钢筋混凝土梁剥离正应力与粘结剪应力的理论分析方法.最后,给出了GFRP布加固钢筋混凝土梁剥离荷载的计算方法.为验证理论分析方法的正确性,计算了试验梁界面间的粘结剪应力、剥离正应力及剥离荷载.计算结果表明,所提出的理论分析方法与试验值吻合较好. 相似文献
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A study of the behaviour of constructional cold-formed stainless steel beams at elevated temperatures was conducted in this paper. An accurate finite element model （FEM） for stainless steel beams was developed using the finite element program ABAQUS. Stainless steel beams having different cross-sections were simulated in this study. The nonlinear FEM was verified against the experimental results. Generally, the developed FEM could accurately simulate the stainless steel beams. Based on the high temperature stainless steel material test results, a parametric study was carried out on stainless steel beams at elevated temperatures using the verified FEM. Both high strength stainless steel EN 1.4462 and normal strength stainless steel EN 1.4301 were considered. A total of 42 stainless steel beams were simulated in the parametric study. The effect of temperatures on the behaviour of stainless steel beams was investigated. In addition, a limiting temperature for stainless steel beams was also proposed. 相似文献
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叶海青 《五邑大学学报(社会科学版)》1993,(3)
为了确保计算稳定性和提高计算精度,本文改进了砼梁单元在双向应力作用下的本构关系,自编了钢筋砼梁非线性平面有限元计算程序RCNFEA,对简支梁和两跨连续梁进行了非线性全过程分析,着重研究了连续梁的内力重分布规律,并详细分析了弯矩调幅对低配筋连续梁使用阶段裂缝宽度和挠度的影响,所得结果与试验分析结果基本一致。 相似文献
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通过含有钢筋混凝土连梁、钢连梁与新型组合钢连梁的结构进行试验对比,利用ANSYS软件建立试验模型,进行模拟试验分析,研究新型组合钢连梁在弹性状态下的抗震性能。试验结果表明:小跨高比连梁采用新型组合钢连梁具有明显的减振效果,抗震性能好,适宜剪力墙结构采用。 相似文献
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Hai-tao Li Andrew John Deeks Li-xin Liu Dong-sheng Huang Xiao-zu Su 《浙江大学学报(A卷英文版)》2012,13(3):165-173
Hollow core slabs are becoming of increasing interest as the construction industry attempts to minimise the impact of its
activities on the environment. By forming voids in the interior of a concrete slab, the amount of concrete used can be reduced
without significantly altering the capacity of the structure. In this study, we examined the inner force transfer mechanism
of a column-supported cast-in-situ hollow core slab using finite element analysis. Both a hollow core slab and the corresponding
solid slab were analysed using ANSYS and the results were compared. The orientation of the tube fillers causes the stiffness
of the hollow slab to be orthotropic, potentially changing the distribution of load carried in the two orthogonal directions.
Both the cross-section’s moments in the column strip and near the columns in the hollow core slab become larger than that
in the solid floor. As well, the cross-section’s stiffness along the tube arrangement direction is larger than that of the
radial cross-section, which causes the direction along the hole of the hollow core slab to carry more moment than the radial
direction. The conversion factors of the two directions are proposed from the comparison for four typical areas of the hollow
core slab, as are the moment distribution coefficients. 相似文献
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INTRODUCTION The aging or deterioration of existing R. C.(reinforced concrete) or P. C. (prestressed concrete)structures is one of the major problems that modernengineers have to face. If the flexural or shear strengthof R. C. or P. C. structures is not sufficient to maintaintheir service functions, strengthening of these struc-tures becomes necessary. To date, steel plates havebeen used to strengthen concrete members. Usingcomposite plates to strengthen R.C. or P.C. structures… 相似文献
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ＮＴＲＯＤＵＣＴＩＯＮＴｅｍｐｅｒａｔｕｒｅｆｉｅｌｄｃｈａｎｇｅｗｉｌｌｐｒｏｄｕｃｅｔｈｅｒ ｍａｌｓｔｒｅｓｓｅｓｉｎｓｔｒｕｃｔｕｒｅｓ.Ｉｔｉｓｗｅｌｌｋｎｏｗｎｔｈａｔｄｉｆｆｅｒｅｎｔｍａｔｅｒｉａｌｓｇｅｎｅｒａｔｅｄｉｆｆｅｒｅｎｔｓｔｒｅｓｓｒｅ ｓｐｏｎｓｅｓ ,ａｎｄｔｈａｔｉｎｓｏｍｅｃａｓｅｓ,ｔｈｅｒｍａｌｓｔｒｅｓｓ ｅｓａｒｅｌａｒｇｅｅｎｏｕｇｈｔｏｃａｕｓｅｓｔｒｕｃｔｕｒｅｆａｉｌｕｒｅ .Ｓｏｉｔｉｓｍｅａｎｉｎｇｆｕｌａｎｄｉｍｐｏｒｔａｎｔｔｏｓｔｕｄｙｄｙ… 相似文献
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研究Mathieu-Gauss(MG)光束通过光阑透镜分离系统的焦开关现象.由Collins公式,推导出了MG光束轴上光强分布公式,在此基础上作了大量的数值分析.研究发现,在光束参数和截断参数的适当取值下,MG光束存在焦开关现象.产生焦开关现象的条件是:光阑和透镜相对间距为1,光束参数必须大于其相应的临界值,而截断参数则须在它的两个临界值之间. 相似文献