Au@碳球复合结构中Au颗粒位置调控光吸收

采用时域有限差分（FDTD）法研究Au纳米颗粒@碳球（AuNPs@CS）复合结构的光吸收控制。发现Au纳米颗粒@碳球复合结构中Au颗粒的位置可以控制复合结构光吸收。模型计算中选取两粒Au纳米颗粒以最佳深度（0 nm）嵌入碳球表面。当两粒Au颗粒球心与碳球球心夹角为22.5°和45°时,复合结构光吸收较单一碳球光吸收明显增强;当夹角为315°、270°、180°、90°时,光吸收增量逐渐减小;当夹角为337.5°时,光吸收量低于单一碳球。这一结果主要归因于Au纳米颗粒位置变化可引起表面等离子体光强度和光散射方向的变化。改变碳球表面Au纳米颗粒的数量和位置,可以进一步调节AuNPs@CS复合结构的光吸收。     

A study on the flow field and local heat transfer performance due to geometric scaling of centrifugal fans

Scaled versions of fan designs are often chosen to address thermal management issues in space constrained applications. Using velocity field and local heat transfer measurement techniques, the thermal performance characteristics of a range of geometrically scaled centrifugal fan designs have been investigated. Complex fluid flow structures and surface heat transfer trends due to centrifugal fans were found to be common over a wide range of fan aspect ratios (blade height to fan diameter). The limiting aspect ratio for heat transfer enhancement was 0.3, as larger aspect ratios were shown to result in a reduction in overall thermal performance. Over the range of fans examined, the low profile centrifugal designs produced significant enhancement in thermal performance when compared to that predicted using classical laminar flow theory. The limiting non-dimensional distance from the fan, where this enhancement is no longer apparent, has also been determined. Using the fundamental information inferred from local velocity field and heat transfer measurements, selection criteria can be determined for both low and high power practical applications where space restrictions exist.     

石墨烯层层键合固相微萃取纤维的制备及对多环芳烃的检测

通过3-巯基丙基三甲氧基硅烷处理银层包裹的不锈钢纤维,得到Si-OH功能化的纤维,氧化石墨烯被层层键合到Si-OH功能化的纤维上,还原氧化石墨烯得到石墨烯层层键合的固相微萃取纤维。该方法制备的新型石墨烯层层键合的固相微萃取纤维具有制备简单,机械性能强,萃取涂层牢固,萃取能力强等优势。建立具有较宽线性范围(5~200μg/L)、较低检测限(0.007~0.09μg/L)的固相微萃取-气相色谱分析方法,用该方法测定河水和雨水中多环芳烃的含量。所制备的新型纤维重现性好、稳定性高、萃取能力强,可实现对多环芳烃的痕量检测。     

Differential equations for librational motion of gravity-oriented rigid body

We consider a gravity-oriented rigid body on a circular Keplerian orbit in a central gravitational field. The motion of the body is affected by a perturbation torque given by a cubic approximation. With the inclusion of the third infinitesimal terms, we introduce a new notation for the differential equations of disturbed motion. This form generalizes the familiar equations in canonical variations extending them to the case where both the potential and the non-potential disturbing forces are operative. This form is convenient for the analysis of non-linear oscillations of a body about its center of mass with the use of the asymptotic methods of non-linear mechanics.     

Aspects of Feynman Graphs

Points (vertices) and lines (edges) can be compared to the particles and waves in nature. Graphical, visual representations of objects and processes possess many properties which are quite advantageous and practically useful. Richard P. Feynman, made copious applications of the graph-theoretic language, ideas and methods for understanding the micro-world of elementary particles and their interactions. Here, we discus certain significant features of Feynman graphs or diagrams in the modern context. We make a novel observation that the CPT theorem is embedded in the space-time concepts of Feynman graphs and hence the success and precision of some the calculations of QED are in fact testament to the correctness and accuracy of this theorem.     

Ground State Structures,Electronic and Magnetic Properties of ScnFe (n=2–10) Clusters

The authors predict that the magnetic moment of the scandium clusters can not be efficiently enhanced with the encapsulation of Fe atom, which is different from previous works with Fe atom doped in B_n, Si_n, and Ge_n clusters. It was found that starting from n=6, the growth patterns of the ground state structures of the Sc_nFe clusters are dominated by the octahedron structures with Fe atom falling into the center of the host framework. The calculated results manifest that doping of the Fe atom contributes to strengthening the stabilities of the scandium framework. Maximum peaks are observed for clusters of n=3, 6 and 8 on the size dependence of the second‐order energy differences, implying that these clusters possess relatively higher stability. The HOMO‐LUMO gap of the Sc_nFe clusters exhibits an oscillational odd‐even character with the local peaks of n=4, 6 and 8. Especially, there is the largest oscillation of the gap with n=4 and 5. Additionally, the doped Fe atom exhibits the antiferromagnetic alignment at n=4, 5, 7 and 9. Also, the quench of the magnetic moments as n=6, 8 and 10 may be ascribed to the model of close‐shell electrons.     

带梯度项的半线性椭圆方程整体解的存在性

By a sub-supersolution method and a perturbed argument,we show the existence of entire solutions for the semilinear elliptic problem-△u + a(x)|▽u|~q = λb(x)g(u),u 0,x ∈ R~N,lim(|x|→∞) u(x) = 0,where q ∈(1,2],λ 0,a and b are locally Holder continuous,a ≥0,b 0,(?)x∈ R~N,arid g ∈ C~1((0,∞),(0,∞)) which may be both possibly singular at zero and strongly unbounded at infinity.     

Ground state solutions for a semilinear elliptic problem with a convection term

By a sub-supersolution method and a perturbed argument, we improve the earlier results concerning the existence of ground state solutions to a semilinear elliptic problem −Δu+p(x)q|∇u|=f(x,u), u>0, x∈RN, , where q∈(1,2], for some α∈(0,1), p(x)?0, ∀x∈RN, and f:RN×(0,∞)→[0,∞) is a locally Hölder continuous function which may be singular at zero.