A Study of premixed propagating flame vortex interaction

Experimental data is presented for the interaction between a propagating flame and a simple vortex flow field structure generated in the wake of solid obstacles. The interaction between gas movement and obstacles creates vortex shedding forming a simple flow field recirculation. The presence of the simple turbulent structure within the gas mixture curls the flame front increasing curvature and enhancing burning rate. A novel twin camera Particle Image Velocimetry, PIV, was employed to characterise the flow field recirculation and the interaction with the flame front. The technique allowed the quantification of the flame/vortex interaction. The twin camera technique provides data to define the spatial variation of both the velocity of the flow field and flame front. Experimentally obtained values of local flame displacement speed and flame stretch rate are presented for simple flame/vortex interactions.     

Tunable properties of light propagation in photonic liquid crystal fibers

Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical results obtained are in good agreement with our earlier experimental results presented elsewhere [1].     

Experimental study of convection in a model Czochralski crucible using liquid crystal thermography

Steady state temperature distribution in a model Czochralski crucible has been mapped by liquid crystal thermography (LCT). The crucible is a water-filled glass beaker. Water is used as the test fluid because of ease of experimentation, as well as the availability of correct thermo-physical properties. In addition, the Prandtl number of water matches those of molten oxides. A copper cylinder whose diameter is smaller than that of the beaker is placed centrally at the water surface. Convection patterns are set up by applying constant temperature difference between the crucible wall and the cylinder surface, in the temperature range of the liquid crystals. The cylinder is given a fixed rotation, thus creating mixed convection conditions in the test fluid. The LCT images recorded in the present study clearly reveal convective rolls, and the interaction of buoyancy-driven convection in the crucible with cylinder rotation. The resulting temperature distributions match numerical simulation quite well. The pure buoyancy and pure rotation experiments result in axisymmetric temperature fields, while in mixed convection, the field is unsteady and three dimensional.     

Laser-induced breakdown threshold and fracture versus the nanostructure of two-phase glass

The radiation hardness and mechanical strength of single-and two-phase glasses are studied for the case when nanosecond laser pulses (λ= 1.06 μm, τ_0.5 ≈ 12.5 ns) are focused inside the material. Laser interferometry is applied to measure the displacement of the free surface, find optical breakage thresholds, and carry out the fractographic analysis of damaged regions. It is shown that breakdown channels and damage regions develop in a nonlinear manner according to optical breakdown mechanisms, changing each other with an increase in the laser energy. The strength of the two-phase glass is found to be more than four times that of the single-phase glass, although their elastic properties differ insignificantly. Such a considerable difference in the hardness of these materials with chemically similar constitutents is attributed to the presence of the double-lattice nanometer-scale structure of the two-phase glass.     

Near field imaging in microwave regime using double layer split-ring resonator based metamaterial

A planar metamaterial structure consisting of two layers of split-ring resonator (SRR) arrays is demonstrated to form the image of a point source with subwavelength resolution. The source frequency is swept through the resonance gap of the metamaterial layers and the lateral field intensity distribution is recorded on the transmission side of the metamaterial. When the source is tuned to the resonance frequency of SRRs, the metamaterial acts as a high permeability medium and a distinct image with subwavelength resolution in the lateral direction is obtained. Increasing the distance between the individual SRR layers reduces the interlayer coupling, and the intensity and spatial resolution of the image decrease rapidly.     

N-aryl-and N-vinyldiaza-18-crown-6: Synthesis and complexing ability

The nucleophilic aromatic and vinyl substitution using diaza-18-crown-6 as nucleophile afforded a number of its N,N’-diaryl-[aryl = 2,4-(NO₂)₂C₆H₃, 4-C₅F₄N, 4-CF₃C₆F₄] and N,N’-dialkenyl-substituted derivatives [alkenyl = PhC(O)CH=CH, MeOCOCH=CH, (EtO₂C)₂C=C(Ph), etc.]. Arylation of diaza-18-crown-6 with nonactivated aryl bromides, such as 4-Me₂NC₆H₄Br, 4-MeOC₆H₄Br, C₆H₅Br, and 4-CF₃C₆H₄Br, was effected under catalysis by palladium complexes. N,N’-Diaryldiaza-18-crowns-6 having electron-acceptor substituents in the aromatic rings turned out to be incapable of forming complexes with metal cations, while their analogs containing electron-donor para-methoxy and para-dimethylamino groups gave complexes with barium perchlorate.     

146Ce核的八级形变带和准γ带

通过测量²⁵²Cf自发裂变所产生的瞬发γ射线, 对¹⁴⁶Ce核的高自旋结构进行了重新研究, 结果更新了以前报道的能级纲图, 把八级形变集体带扩展到更高的自旋, 并且重新构建了可能的准γ带结构. 此外, 用反射不对称壳模型(RASM)对¹⁴⁶Ce核的八级形变带进行了计算, 低自旋处的计算结果与实验数据符合得很好.     

Electrical and magnetic properties of CoFeAlO thin films

Influences of oxygen-partial pressure and annealing on the electrical and magnetic properties of CoFeAlO thin films were systematically investigated by means of resistivity, permeability, magnetization and ferromagnetic resonance (FMR) measurements. It was found that, with increasing oxygen-partial pressure or under annealing, the electrical resistivity of the film increased and the magnetic softness decreased, which is attributed to the microstructural change of the film. Interestingly, an as-deposited Co_45.30Fe_20.65Al_19.34O_14.71 film was found to exhibit an inverted hysteresis loop with negative coercivity, and this peculiar phenomenon disappeared upon effects of oxygen-partial pressure and annealing. It was also found that the as-deposited films owned a narrow FMR line width that increased with increasing oxygen-partial pressure or under annealing.     

On diquark clustering in quark—gluon plasma

The possibility that pairs of quarks will form diquark clusters in the regime above deconfinement transition for hadron matter at finite density is revisited. Here we present the results on the diquark-diquark (dq-dq) interaction in the framework of constituent quark model taking account of spin, isospin and color degrees of freedom in the spirit of generalized Pauli principle. By constructing the appropriate spin and color states of the dq-dq clusters we compute the expectation values of the interaction Hamiltonian involving pairwise quark—quark interaction. We find that the effective interaction between two diquark clusters is quite sensitive to different configurations characterized by color and spin states, obtained after the coupling of two diquark states. The value of the coupling parameter for a particular color—spin state, i.e., -3, 1 is compared to the one obtained earlier by Donoghue and Sateesh,Phys. Rev. D38, 360 (1988) based on the effective Φ⁴-theory. This new value of λ derived for different color-spin dq-dq states, may lead to several important implications in the studies of diquark star and diquark gas.     

In situ observations of domain wall motion in Mn–Zn and Ni–Zn ferrites by Lorentz microscopy and electron holography

Domain wall motion in Mn–Zn and Ni–Zn ferrites with applied magnetic fields is investigated by in situ observations with Lorentz microscopy and electron holography. It is found that both Mn–Zn and Ni–Zn ferrites have a mean grain size of approximately 10 μm and several pores with sizes ranging from 0.2 to 1.1 μm. In situ observations by Lorentz microscopy with an applied magnetic field reveals that in Mn–Zn ferrite, the domain walls move easily across the grain boundary, while in Ni–Zn ferrite, the domain walls move along the grain boundary but are pinned at the grain boundary and pores. From in situ observations of Ni–Zn ferrite by electron holography, it is clarified that domain wall pinning at the grain boundary retards a sensitive increase in magnetic flux parallel to the applied field direction, which is considered to result in high hysteresis loss.