临界电流密度的分布对高温超导体中传输交流损耗的影响

基于Norris方程和Bean临界态模型,假定临界电流密度沿高温超导圆柱体半径的非均匀分布方式,从定量的角度研究了临界电流密度沿高温超导圆柱体径向分布方式的不同对传输交流损耗的影响.考虑临界电流密度沿径向的包括阶梯式和逐点变化式等多种分布方式,通过引进表征超导体内临界电流密度非均匀分布的强弱差异程度的无量纲参数λ推导出临界电流密度非均匀分布方式下高温超导体中传输交流损耗的解析表达式.结果表明临界电流密度阶梯式分布对损耗的影响和临界电流密度逐点变化式分布的情况在损耗曲线的变化趋势和量级上有明显的区别并且随着传输电流的增加临界电流密度的非均匀分布方式对传输损耗的影响也越显著.     

基于遗传LM算法的涂层目标光谱偏振BRDF建模分析

通过比较测量方法测量得到绿漆涂层木板探测目标在400～720 nm的光谱偏振二向反射分布函数值,从获得的户外试验测量数据入手,分析与探测角、波长之间的关系,通过有限探测条件得到的光谱偏振二向反射分布函数值(BRDF)建立光谱偏振BRDF模型,来描述探测目标的偏振二向反射特性。其中利用基于小面元的模型建立光谱偏振BRDF模型,利用遗传算法和Levenberg-Marquardt(LM)算法相结合的优化算法来获得非线性模型参数。仿真实验结果表明采用的遗传LM优化算法具有较好的性能,能较快较准确得到非线性的模型参数。真实实验数据证明了基于小面元模型的正确性,表明光谱偏振二向反射分布函数建模方法结果的可靠性。最后与绿漆涂层铁板目标的模型反演参数进行比较得出：2种不同材质、相同颜色涂层的目标,具有较为接近的折射率,其较小差别可以理解为由涂层的厚度、均匀程度的不同导致,而非不同的材质所引起。     

利用高光谱红边与黄边位置距离识别小麦条锈病

研究的目的是利用高光谱遥感尽可能早地识别出健康与遭受条锈病胁迫的小麦。通过人工田间诱发不同等级条锈病,在不同生育期测定感染不同严重程度条锈病的冬小麦冠层光谱及病情指数(disease index,DI)。对测定的光谱进行平滑并计算一阶微分值,并用两种方法分别提取光谱红边位置(red edge position,REP)与黄边位置(yellow edge position,YEP)：(1)一阶微分最大值法;(2)Cho and Skidmore方法。研究表明随着病情严重度的增加,REP逐渐向短波方向移动,YEP逐渐向长波方向移动,而REP-YEP则迅速的减小。分别对比分析了REP,YEP以及REP-YEP预测DI的能力,结果表明,以REP-YEP为变量的模型预测DI的精度最好,模型估测绝对误差(RMSE)仅为6.22,相对误差(relative error,RE)为14.3%,且能够提前12 d识别出健康与病害胁迫的小麦。该研究不仅可为将来利用高光谱遥感大面积监测小麦病害提供理论与技术支持,而且对精准农业的实施也具有重要意义与实际应用价值。     

Dynamics of the geometric phase in the adiabatic limit of a quench induced quantum phase transition

The geometric phase associated with a many body ground state exhibits a signature of quantum phase transition. In this context, we have studied the behavior of the geometric phase during a linear quench caused by a gradual turning off of the magnetic field interacting with a spin chain.     

Radiative leptonic decay B-c→τ-(v)τγ in the standard model and the two-Higgs-doublet model

We analyze the radiative leptonic Be decay B-→τ-(v)τγ in the Standard Model and the twoHiggs-doublet model using the non-relativistic constituent quark model.The results confirm that this channel is experimentally promising in view of the large number of Bc mesons which are expected to be produced at future hadron facilities.We also find that this decay is sensitive to the parameters of the two-Higgs-doublet model,and it can be tested in future experiments.     

Topological structure of the solitons solution in SU(3) Dunne-Jackiw-Pi-Trugenberger model

By using φ-mapping topological current theory and gauge potential decomposition, we discuss the self-dual equation and its solution in the SU(N) Dunne-Jackiw-Pi-Trugenberger model and obtain a new concrete self-dual equation with a δ function. For the SU(3) case, we obtain a new self-duality solution and find the relationship between the soliton solution and topological number which is determined by the Hopf index and Brouwer degree of φ-mapping. In our solution, the flux of this soliton is naturally quantized.     

Quantal symmetries in the non-linear σ model with Maxwell and non-Abelian Chern-Simons terms

The quantal symmetry property of the CP1 nonlinear σ model with Maxwell non-Abelian ChernSimons terms in(2+1) dimension is studied.In the Coulomb gauge,the system is quantized by using the Faddeev-Senjanovic(FS) path-integral formalism.Based on the quantaum Noether theorem,the quantal conserved angular momentum is derived and the fractional spin at the quantum level in this system is presented.     

CRACK PROPAGATING IN FUNCTIONALLY GRADED COATING WITH ARBITRARILY DISTRIBUTED MATERIAL PROPERTIES BONDED TO HOMOGENEOUS SUBSTRATE

In this paper, a finite crack with constant length （Yoffe type crack） propagating in a functionally graded coating with spatially varying elastic properties bonded to a homogeneous substrate of finite thickness under anti-plane loading was studied. A multi-layered model is employed to model arbitrary variations of material properties based on two linearly-distributed material compliance parameters. The mixed boundary problem is reduced to a system of singular integral equations that are solved numerically. Some numerical examples are given to demonstrate the accuracy, efficiency and versatility of the model. The numerical results show that the graded parameters, the thicknesses of the interfacial layer and the two homogeneous layers, the crack size and speed have significant effects on the dynamic fracture behavior.     

Volatile surfactants: Characterization and areas of application

Amphiphilic aroma molecules, representatives of fragrance molecules, are introduced as dynamic volatile surfactants. Surface tension of their aqueous solutions proves to be a sensitive and revealing quantity, used for assessment of the adsorption-evaporation behavior both under equilibrium conditions and in regimes of no instantaneous equilibrium. Such volatile amphiphiles are characterized by fast adsorption from bulk solution at an air-water interface, on a timescale of tens of microseconds, and exhibit synergetic effect in mixtures with conventional micellar-forming surfactants. Their ability to evaporate from the interface on a time scale of minutes suggests their applications as “temporal” dynamic cosurfactants in technologies involving fast formation of new surfaces. Current challenges concern evaluation of specific material parameters of volatile aroma surfactants in order to enable their selection for targeted applications.     

Beyond green with synthetic chlorophylls – Connecting structural features with spectral properties

The distinct features of chlorophylls in photosynthesis have led to the formation of numerous derivatives for applications encompassing solar energy conversion, molecular photonics, photodynamic therapy, and molecular imaging. Synthetic chlorins created de novo and bearing a geminal dimethyl group in the reduced ring have proved invaluable for fundamental studies. Four decades of research have led to accumulation of tabulated spectra for > 400 such synthetic chlorins with distinct structural frameworks (17-oxochlorins, 13¹-oxophorbines, chlorinimides) and substituents (alkyl, aryl, ethynyl, phenylethynyl, acetyl, formyl) located at specific (meso, β) positions. In this review, spectral traces (324 absorption, 247 fluorescence) are assembled along with photophysical data including the molar absorption coefficient (ε), fluorescence quantum yield (Φ_f) and singlet excited-state lifetime (τ_s). The review uses the accumulated spectral data derived from chlorins all containing a uniform molecular scaffold to (1) highlight the effects of molecular structure on spectral features, and (2) identify trends including how ε, Φ_f and τ_s vary with wavelength and other features. Use of a common geminal-dimethyl-substituted chlorin scaffold – beginning with no substituents, to one substituent at designated sites, and to 2 or more substituents – provides a systematic Aufbau approach for understanding the absorption spectra of chlorins on a path to and beyond the native chlorophylls. The review provides insights concerning the rational design of potent analogues of Nature’s preeminent red-region absorbers for potential utilization in diverse applications and is aimed at multiple audiences: those interested in spectral properties, tetrapyrrole photophysics, and the molecular design of new chromophores.