Injection locked multi-section gain-coupled dual mode DFB laser for terahertz generation

A dual mode multi-section gain-coupled distributed feedback laser with tunable mode spacing is subharmonically injection locked at 0.315 THz. The injected signal consists of an optical comb with harmonics 35 GHz apart and a bandwidth of approximately 1.9 THz. The optical comb is a result of strong four-wave mixing in a highly-nonlinear dispersion-shifted fiber. In order to observe locking of the multi-section laser, the output is optically downconverted to RF frequencies using the same optical comb. The locked multi-section DFB laser is a coherent and tunable optical source suitable for continuous-wave terahertz generation systems.     

Evaluation of elastic modulus of cantilever beam by TA-ESPI

The paper proposes an evaluation technique for the elastic modulus of a cantilever beam by vibration analysis based on time average electronic speckle pattern interferometry (TA-ESPI) and Euler-Bernoulli equation. General approaches for the measurement of elastic modulus of a thin film are the Nano indentation test, Buldge test, Micro-tensile test, and so on. They each have strength and weakness in the preparation of the test specimen and the analysis of experimental results. ESPI is a type of laser speckle interferometry technique offering non-contact, high-resolution and whole-field measurement. The technique is a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI can be used to find the resonance frequency for each vibration mode shape. And the elastic modules of a test material can be easily estimated from the measured resonance frequency and Euler-Bernoulli equation. The TA-ESPI vibration analysis technique can be used to find the elastic modulus of a material requiring simple preparation process and analysis.     

Frequency domain optical tomography using a conjugate gradient method without line search

A conjugate gradient method without line search (CGMWLS) is presented. This method is used to retrieve the local maps of absorption and scattering coefficients inside the tissue-like test medium, with the synthetic data. The forward problem is solved with a discrete-ordinates finite-difference method based on the frequency domain formulation of radiative transfer equation. The inversion results demonstrate that the CGMWLS can retrieve simultaneously the spatial distributions of optical properties inside the medium within a reasonable accuracy, by reducing cross-talk between absorption and scattering coefficients.     

Exchange coupled magnetic nanocomposites of Sm(Co1−xFex)5 / Fe3O4 with core/shell structure

Magnetic nanocomposites of Sm(Co_1−xFe_x)₅/Fe₃O₄ (x≈0.1) with the core/shell type structure were successfully fabricated using a two-step polyol process, where as-prepared SmCo_5(1−x) nanoparticles were used as seeds for the ferrite coating. The core/shell composites are quite stable in air and show a typical hysteric behavior of single component, yielding an enhanced coercivity of 2.2 kOe with a saturated magnetization of 130 emu/g at 5 T. The magnetization data clearly reveal the presence of effective exchange coupling between the hard-magnetic Sm(Co_1−xFe_x)₅ core and soft-magnetic Fe₃O₄ shell, suggestive of a single-phase structure rather than a distinctive two-phase one.     

Fabrication of electrode Pt nanotubes for semiconductor capacitors

Template-wetting process was used to fabricate Pt electrode nanotubes for the further application in 3D nanotube capacitors. Anodic alumina oxide (AAO) was used as a template, which can be fabricated by means of two-step anodization process. After the wetting process, released Pt nanotubes have been obtained by selective etching of the template using KOH solution. Pt nanotubes formation and tube walls morphology were investigated by FE-SEM technique. Furnace annealing (FA) effects at temperatures ranging from 200 to 600 °C with 100^oC step on nucleation and crystal growth condition of Pt nanotubes have been examined. Crystallization of the Pt nanotube inside the template has been examined by step-by-step annealing at different temperatures, and confirmed by XRD.     

Photoluminescence of ZnO nanowires grown on sapphire (1 1 2¯ 0) substrates

ZnO nanowires were fabricated on c-plane (0 0 0 1), a-plane (1 1 2¯ 0) sapphire, and boron doped p-type (1 0 0) Si substrates in vacuum furnace by simple physical vapor deposition. Room temperature photoluminescence spectra of the nanowires show the near band-edge emission and the deep-level green light emission. The ZnO nanowires formed on sapphire (1 1 2¯ 0) substrates exhibited enhancement on optical properties and better crystalline structures than those of nanowires grown on other substrates. The formation mechanism and the effect of substrate direction on structural and optical properties of the nanowires are discussed.     

二价金属元素掺杂对LiCoO2体系电子输运性质的影响

为了解释Ca掺杂与Mg掺杂在影响锂离子二次电池正极材料LiCoO2体系电子输运性质方面的不同效应,采用基于密度泛函理论的第一性原理方法研究了该体系的电子结构.计算结果表明,虽然在LiCoO2体系中用Ca或Mg替代Co都会在费米能级附近产生部分占据的受主带,但两者对应的电子态都具有明显的局域化特征;此外,与Mg掺杂体系明显不同的是,Ca掺杂体系的受主带与价带之间存在清晰的带隙.这一带隙的存在正是Ca掺杂不能明显提高LiCoO2体系电导率的主要原因.此外,Ca2+与Mg2+离子半径的较大差别也是造成这两个掺杂体系的电导率存在明显差异的一个重要因素.     

Time-resolved PIV investigation on the unsteadiness of a low reynolds number confined impinging jet

The flow characteristics in a confined slot jet impinging on a flat plate were investigated in low Reynolds number regime by using time-resolved Particle Image Velocimetry technique. The jet Reynolds number was varied from 404 to 1026, where it is presumed that the transient regime exists. We found that the vortical structures in the shear layer are developed with increase of Reynolds number and that the jet becomes remains steady at the Reynolds number of 404. Vortical structures and their temporal evolution are verified and the results were compared with previous numerical studies.     

The identification of tyre induced vehicle interior noise

Sound transmission into a vehicle is classified as either airborne or structure borne sound. From the point view of noise control, the reduction of noise transferred by different paths requires different solutions. Coherence function analysis is often used to identify transmission paths. However it can be difficult to separate the airborne from structure borne components. The principle of acoustic reciprocity offers a convenient method for overcoming this difficulty. The principal states that the transfer function between an acoustic volume velocity source and an acoustic receiver is independent of a reversal of the position of source and receiver. The work done on this study involves exciting a stationary tyre and measuring the surface velocity of the tyre at a number of discrete points. The acoustic transfer functions between each point on the tyre and a receiver point are measured reciprocally. Two sets of measurements are then combined to yield a measure of the sound pressure due to a point force on the tyre via the acoustic transmission path only. This technique also provides information on the relative contributions of various regions of the tyre wall to the resultant noise. Also the sound radiation characteristics, the horn effect, and resonance at the wheel housing are identified through the reciprocal measurement.     

Momentum-Kick Model Application to High-Multiplicity pp Collisions at s = 13 $\sqrt {s}=13$ TeV at the LHC

International Journal of Theoretical Physics - In this study, the momentum-kick model is used to understand the ridge behaviour in dihadron Δη–Δφ correlations recently...