The renormalization of several composite operator insertions,Wilson expansions of composite operators,and the applications to short-distance behaviour

We examine the renormalization of composite operator insertions within a normal product framework, and prove various identities between composite operator insertions. In particular a proof of the Wilson expansion of composite operators in the presence of other composite operators is given. The analysis necessitates a re-examination of several physical processes, and it is shown in particular why the results for deep inelastic scattering still hold.     

Effect of multi-walled carbon nanotubes on dielectric and electro-optic properties of a high tilt antiferroelectric liquid crystal

By dispersing a small amount of multi-walled carbon nanotubes in a high tilt antiferroelectric liquid crystal, a nano composite is prepared. Though the phase sequence remains the same, the transition temperatures of the composite get changed, the stability of SmA* and SmC* phases increases whereas that of SmC_A* phase decreases. Pitch of the helicoidal structure shows a discontinuous change at SmC*–SmC_A* transition. Absorption strength and critical frequency of the anti-phase antiferroelectric mode are reduced in the composite. The dielectric increment of the Goldstone mode (GM) decreases and the critical frequency increases due to increased elasticity of the composite. A two-fold increase in the critical field for suppression of the GM is observed which signifies more stable helical structure in the composite. The switching time is reduced by 56% in the nano composite as a result of decrease in rotational viscosity but the high tilt remains intact. An observed lower value of conductivity indicates ion trapping in the composite.     

超高速碰撞下C-SiC复合材料双层防护结构的力学特性

 C-SiC复合材料是一种随着航空航天技术发展而研制开发的新型材料,具有优异的力学性能,可以很好地满足航天器防护系统的使用要求,因此其超高速碰撞力学性能研究具有重要意义。基于现有的有关C-SiC复合材料力学性能的实验数据和模拟结果,推导得到模拟C-SiC复合材料超高速碰撞时所需的一系列参数。利用AUTODYN进行数值模拟,获得了C-SiC复合材料双层防护结构在超高速碰撞下的特性及弹道极限曲线,总结得出预测C-SiC复合材料双层防护结构的弹道极限方程。     

二维光栅与周期性缝隙阵列组合薄膜结构的杂散光抑制

传统方格型二维光栅与周期性缝隙阵列的组合薄膜结构具有雷达和光学波段双带通的电磁特性. 但由于其杂散光能量集中分布而严重制约它在高精度探测以及成像领域中的应用. 本文提出了一种全新的组合薄膜结构, 即由满足一定约束条件的圆孔型二维光栅和十字缝隙阵列构成. 基于Fraunhofer衍射理论建立组合薄膜结构标量衍射模型, 通过对比两种组合薄膜结构的衍射光分布, 理论分析与实验测试均表明: 圆孔型光栅与十字缝隙阵列组合薄膜结构不仅能够提高其光学透过率, 而且还使其杂散光分布均匀, 降低了其杂散光总比率, 从而有效抑制杂散光, 进一步增强了二维光栅与周期性缝隙阵列组合薄膜结构在实际光学系统中的可靠性. 关键词： 二维光栅 组合薄膜结构 衍射光强 杂散光     

采用阶梯形弹性基底的磁致伸缩/压电复合结构磁电响应研究

利用阶梯形变幅杆的应变放大作用,构造了磁致伸缩/阶梯形弹性基底/压电复合结构. 采用等效电路法分析了沿长度方向振动复合结构的一阶磁电响应. 计算了Terfenol-D/阶梯形铍青铜基底/PZT-5H复合结构的磁电响应,并与实际结构的磁电响应进行了比较,由于理论分析中忽略了胶层产生的损耗,理论值和实验结果的变化规律相似,但是谐振频率点和磁电电压转换系数有一定的差异. 同时比较了阶梯形基底和等截面杆基底复合结构,分析表明前者具有更高的磁电电压转换系数. 研究了阶梯形弹性基底长度比及层厚比对复合结构纵振动一阶模 关键词： 磁电效应 磁致伸缩/压电复合结构 磁电响应     

Temperature dependence of the spin polarization of composite fermions

It is found that at a critical value of the magnetic field in which a system of composite fermions becomes completely spin-polarized, the temperature dependence of the electronic spin polarization is a linear function at low temperatures. It is shown that the slope of this dependence is determined by the Fermi energy of the composite fermions. This made it possible to measure the Fermi energy and the Zeeman splitting of the composite fermions. A large amplification of the spin splitting of composite fermions for complete spin polarization of the system is found. This makes it possible to measure the strength of the interaction between composite fermions. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 722–726 (10 December 1999)     

Current-induced suppression of superconductivity in a three-dimensional lattice of weakly linked indium grains in opal

The current-voltage characteristics of the metal-dielectric composite have been investigated in the range of the resistive state near the superconducting transition temperature T _c . The composite structure can be represented as a face-centered cubic lattice, which involves a large number of weakly linked indium nanograins and is stabilized in structural cavities of opal. The response to microwave radiation is used to characterize the resistive state of the composite. The comparative investigation into the current-voltage characteristics and the response of the composite to microwave radiation makes it possible to conclude that the weak links are superconducting in the region of critical current (I _c ) of the composite as a whole. The transition of weak links to the resistive state occurs at currents immediately preceding the transition of the composite from the resistive state to the ohmic state. The model of resistivity of the indium-opal composite is proposed on the basis of morphological examinations. According to this model, the energy dissipation in the resistive state is brought about by the quasi-discrete (due to the quantization of the magnetic flux in circuits of a three-dimensional lattice comprised of multiply connected grains) redistribution of transport current over the cross-section of composite.     

Tuneability amplification factor and loss of high-contrast composites

The problem of tuneability of nonlinear ferroelectric–dielectric composite materials is addressed. Attention is concentrated on the analysis of the tuneability amplification factor, K, of a composite material, which is introduced as the ratio of the effective tuneability of a composite material to the tuneability of its ferroelectric (tuneable) component. Previously, ferroelectric–dielectric composite materials have been designed with an effective tuneability amplification factor slightly greater than 1 (i.e. 1.1–1.4) [A.K. Tagantsev et al., J. Electroceramics 11 (2003) p.5; A.G. Kolpakov et al., J. Electroceramics 18 (2007) p.129]. It is demonstrated that the tuneability amplification factor can take values significantly greater than 1. Numerical prototypes (structural designs integrated with finite element method tools) of microstructures are presented with K in the range 3 to 30. The effective tuneability of nonlinear composite materials strongly depends on the microgeometry and microtopology of the material and, in general, cannot be described in terms of volume fraction of components of composite material. In the designs presented, the increased tuneability is due to concentration of the high electric field in narrow regions with carefully selected geometry. The problem of loss in ferroelectric–dielectric composite materials is discussed. In the general case, the loss tangent stays between that of the components of the composite. For high-contrast ferroelectric–dielectric composite materials, the effective loss tangent is practically equal to the loss tangent of the ferroelectric.     

Yb:Y3Al5O12/Y3Al5O12复合晶体的制作和光谱性能

采用热键合技术,制作中运用不同的工艺参量制作出12片Yb:Y3Al5O12/Y3Al5O12(Yb:YAG/YAG)复合.晶体.利用偏光显微镜对其键合界面进行了观察,研究了样品的透射光谱,从而确定出复合晶体合适的制作工艺.通过透射光谱的形状和透射率来表征复合晶体键合界面的质量.研究表明Yb:YAG/YAG复合晶体键合质量较好,可实现一体化.     

Free vibration of composite membranes with arbitrary shape

This paper is concerned with a method for solving problems of a composite membrane with an arbitrarily shaped outer boundary and an arbitrarily shaped inner boundary. The boundary conditions and the conditions of continuity are satisfied directly by using a Fourier expansion collocation method which has been given by Nagaya. The general equation for finding the natural frequencies of the composite membranes has been presented. As examples, numerical calculations have been carried out for composite polygonal membranes, composite elliptical membranes and composite circular membranes with eccentric circular boundaries.     

Relevance of inter-composite-fermion interaction to the edge Tomonaga-Luttinger liquid

It is shown that Wen's effective theory correctly describes the Tomonaga-Luttinger liquid at the edge of a system of noninteracting composite fermions. However, the weak residual interaction between composite fermions is found to be a relevant perturbation. The filling factor dependence of the Tomonaga-Luttinger parameter is estimated for interacting composite fermions in a microscopic approach and satisfactory agreement with experiment is achieved. It is suggested that the electron field operator may not have a simple representation in the effective one-dimensional theory.     

Optical characterisation and modelling for oblique near-infrared laser heating of carbon fibre reinforced thermoplastic composites

The optical behaviour of a carbon fibre reinforced thermoplastic composite material is investigated for a near infrared laser heating process applied to automated composite tape placement. A nip point heating strategy in laser tape placement results in a shadow before the nip point on both the incoming tape and substrate. The moderate laser angle relative to the surface of the composite leads to reflections in the cavity formed by the tape and the substrate, reducing the shadow. An optical ray tracing model can provide valuable insight to the interaction of the laser with the composite, as well as detailed estimation of the irradiance distributions. This paper provides the foundations for such a model, describing an optical characterisation process and formulation of appropriate models to capture the composite surface and laser source behaviour. A micro-half-cylinder surface treatment was shown to give a good approximation of the anisotropic scattering behaviour of the composite. Angular dependent reflectance was described well by Fresnel equations. An approximation of the laser beam profile and propagation is also presented.     

Structure and Properties of Self-Organized 2D and 3D Antimony/Carbon Composites

The conditions of synthesis of antimony/carbon composites by interlayer self-assembly from colloidal solutions and melts are discussed. The morphology and the structure of these composites are examined. The potential to produce composites of 2D and 3D morphologies is demonstrated. The 2D composite has a multilayer graphene structure with submicron antimony inclusions, while the 3D composite has a spheroidal shell structure with a deformed film-shell with carbon nanoinclusions. The difference in properties of these composites is demonstrated: the 2D composite is conductive, while the 3D composite has a nonlinear current–voltage characteristic that indicates the emergence of novel functional properties of the spheroidal antimony/carbon composite. A model of exfoliation of the layered precursor with covalent interlayer coupling is proposed. This model provides an explanation for the experimentally observed nonlinear hydrodynamic processes in the colloidal antimony solution.     

Superposition rule for light scattering by a composite particle

A superposition rule for light scattering by composite particles is presented that expresses the scattering amplitude of a composite particle as a superposition of that of the host particle and those of the shadowed inclusions. The superposition rule is derived for a soft composite particle but also provides insight into light scattering by a general composite scatterer. Favorable comparison with an exact numerical method demonstrates the usefulness of the rule in analyzing light scattering by composite particles such as biological cells.     

碳纳米管/聚苯胺纳米复合管的制备及其微波介电特性研究

用原位乳液聚合法在碳纳米管表面包覆聚苯胺，制备出了碳纳米管/聚苯胺一维纳米复合管.复合管的直径为50—80 nm，聚苯胺包覆层的厚度为20—30 nm，聚苯胺在碳纳米管表面以层状和枝晶状两种形态生长.研究了碳纳米管/聚苯胺复合管在2—18 GHz的微波介电特性.与纯碳纳米管相比，碳纳米管/聚苯胺复合管的介电常数的实部ε′和虚部ε″在2—18 GHz随频率变化较小，在低频波段介电常数值较小，作为微波吸收剂容易实现与自由空间的阻抗匹配，而且它的介电损耗角正切(tanδ=ε″/ε′)较高，是一种很好的微波吸收剂. 关键词： 碳纳米管 聚苯胺 微波介电特性 微波吸收剂     

Transverse tensile properties of spun-type carbon fabric/phenolic composites

The transverse tensile properties of phenolic composites reinforced with spun-type carbon fabrics (spun C/P composites) have been investigated in order to evaluate the adherent failure behavior of composites in the transverse (90°) direction due to tension. The transverse tensile strength of the spun C/P composite is about 3.4 times higher than that of the conventional composite reinforced with filament type carbon fabrics (filament C/P composites). It is found from stress–strain curve of composites that it exhibits above 4 times higher failure strain than the filament C/P composite. However, the transverse tensile modulus of the spun C/P composite is similar to that of the filament C/P composite. The results indicate that the protruded fibers of spun yarns between the interlaminar layers in the spun C/P composite play an important role in improving the transverse tensile properties by the effects of fiber bridging. Consequently, this result suggests that use of spun yarn type carbon fabrics as reinforcement in a phenolic composite may significantly contribute to improving the interfacial properties of carbon/phenolic composites.     

Study on the Compatibility of SMA and Composite Materials by Holographic Interferometry

With the help of holographic interferometry a study is conducted on the compatibility of SMA (shape memory alloy) and epoxy resin composite material. The paper gives experiment results and analysis which show that after coupling SMA with the composite material, the flexural rigidity of composite material is somewhat reinforced. Under certain conditions, SMA and the epoxy resin composite material are compatible.     

Study on the Compatibility of SMA and Composite Materials by Holographic Interferometry

With the help of holographic interferometry a study is conducted on the compatibility of SMA (shape memory alloy) and epoxy resin composite material. The paper gives experiment results and analysis which show that after coupling SMA with the composite material, the flexural rigidity of composite material is somewhat reinforced. Under certain conditions, SMA and the epoxy resin composite material are compatible.     

谱有限元数值分析各向异性复合板中导波色散特性

提出谱有限元方法研究层状各向异性复合板中导波的色散特性和波结构。基于三维弹性动力学方程,用有限元方法离散波导截面,波传播方向的位移用简谐波表示,得到了导波色散的特征方程。分析了单层和双层复合板中导波沿不同方向传播的色散特性和波结构,讨论了双层复合板中层厚比对相速度的影响。数值研究结果表明:导波的对称模态沿纤维方向传播时在较宽的频率范围内保持弱色散状态。双层复合板中导波基本模态的相速度在低频时受层厚比的影响较明显,随着频率的增加趋向于相速度较低的材料。数值模拟结果为导波用于复合材料定量无损检测和性能评价提供理论依据。      

Optical properties of metallic nanoshell composites: The effects of temperature and particle clustering

The optical properties of a metallic nanoshell composite are studied theoretically using different effective medium theories with particular focus on the effects of variation in temperature and particle clustering on these properties. One unique result from our modeling is the persistent manifestation of the single-particle resonances of the individual nanoshells which cannot be found in a composite of solid particles. In addition, we observe red-shifts in the composite plasmon modes, as well as damping in the dielectric function spectrum as the temperature increases. Furthermore, a much greater red-shift will occur when these nanoshells coalesce to form fractal clusters in the composite, with the value of this shift increasing with decrease in the fractal dimension or increase in the cluster size. We further calculate the transmission at normal incidence through such composite thin films as a demonstration of how these effects can be observed experimentally.