Microstructures and electrical properties of La0.8Sr0.2MnO3 films synthesized by sol-gel method

La_0.8Sr_0.2MnO₃ (LSMO) thin films were fabricated on alumina substrates by an improved sol-gel dip-coating process. It was found that multiple dip-coating process could not be performed until the pre-firing temperature reached 600 °C. Different amounts of LSMO powders were added to precursor solution with an aim to avoid cracks in LSMO thin films during calcining caused by the shrinkage mismatch between the film and the substrate. The structure and surface morphology of the films prepared from precursors with and without LSMO powders were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the addition of 56.4 wt.% LSMO powders into the sol-gel precursor solution significantly modified the microstructure of films. A single LSMO perovskite phase was obtained on alumina substrate after calcining at 800 °C for 4 h by the improved sol-gel method. The sheet resistance of the films prepared with different processing parameters was measured by four-point dc method. Results indicated that the sheet resistance of films decreased with increasing the number of coating applications and the amount of LSMO powders.     

Investigation of all-solid photonic bandgap fiber with low losses in low-order bandgaps

We report synoptically an investigation of design, fabrication and characterization of a new all-solid photonic bandgap fiber. By introducing an index depressed layer around a high index core in every unit cell of photonic crystal cladding, a novel all-solid bandgap fiber is predicted to obtain low confinement and bend losses within low-order bandgaps. After optimizing the structure parameters, we fabricate a batch of rods used for cladding cells, select a pure-silica rod for core cell and an inner-hexagonal jacket tube. We demonstrate an all-solid bandgap fiber with the transmission loss as low as 2 dB/km at 1,310 nm and a bandwidth of over 700 nm within the first bandgap. The guiding properties are also measured, respectively, such as transmission spectrum, attenuation spectrum, bend loss, mode field intensity profile, and chromatic dispersion.     

北京同步辐射装置3W1B软X射线光束线偏振特性测量

应用自行研制的Mo/Si周期多层膜作为起偏器和检偏器的光学元件, 测量了北京同步辐射装置3W1B束线的偏振状态. 通过数据分析, 得到了3W1B软X射线的有关偏振参数, 在86—89eV能区经过起偏器后的偏振度超过98%, 圆偏振分量介于1%—3%之间.     

少子寿命和表面形貌与多孔硅发光性能的关系

研究了不同时间腐蚀的多孔硅的光致发光性能与多孔硅的表面形貌和少子寿命之间的关系。结果表明,多孔硅的发光来自与氧空位有关的缺陷,而多孔硅表面的氢原子能够钝化多孔硅表面的非辐射中心从而提高多孔硅的发光效率。多孔硅的空隙度随腐蚀时间的延长而增大,这也导致了多孔硅的少子寿命的降低,从而造成多孔硅的光致发光效率随多孔硅空隙度的增大以及少子寿命的降低而提高。另外,原子力显微照片表明长时间的腐蚀使多孔硅表面层被化学腐蚀,从而降低了多孔硅表面的粗糙度。     

射流注入角对平板气膜冷却特性影响的实验研究

本文对不同射流注入角的典型单排孔冷却结构的平板气膜冷却特性进行了实验研究,研究对象为轴线与主流来流方向分别成30°、60°、90°的射流孔板,对它们在吹风比为0.5、1.0、1.5条件下的射流孔下游的绝热气膜冷却效率分布特性进行了分析.在吹风比M=0.5时,三个射流注入角条件下近孔区域都能形成较好的冷气覆盖效果;M=1.0时,三者的下游横向平均冷却效率基本相同;M=1.5时,注入角60°的条件下冷却效果最好.     

Microstructure of yttric calcium phosphate bioceramic coatings synthesized by laser cladding

The yttric calcium phosphate (CaP) coatings were in situ prepared on pure titanium substrate by laser cladding. The morphologies and phases constitution of CaP coatings were studied by electron probe microanalysis, X-ray diffraction and so on. The bonding state between the coating and the substrate is fine metallurgical combination, and the addition of yttria can fine the structure and increase the tensile strength of the coatings. The X-ray result shows that the coating is composed of the phases of HA, α-Ca₂P₂O₇, β-Ca₂P₂O₇ and CaTiO₃.     

Re-examining generalized teleportation protocol

We present an explicit generalized protocol for probabilistic teleportation of an arbitrary N-qubit GHZ entangled state via only one non-maximally two-qubit entangled state. Without entanglement concentration, using standard Bell-state measurement and classical communication one cannot teleport the state with unit fidelity and unit probability. We show that by properly choosing the measurement basis it is possible to achieve unity fidelity transfer of the state. Compared with Gordon et al’s protocol [G. Gordon, G. Rigolin, Phys. Rev. A 73 (2006) 042309], this protocol has the advantage of transmitting much less qubits and classical information for teleporting an arbitrary N-qubit GHZ state.     

Optimization on Synchrotron Radiation Lattice of BEPCII

The Beijing Electron and Positron Collider II （BEPCII） is a double ring electron positron collider, which can also be used as a synchrotron radiation （SR） light source. Since the BEPCII will start commissioning with SR mode in November 2006, it is essential to have a satisfying SR lattice. Here we first perform frequency map analysis on the original BEPCII SR lattice. The result shows that the resonance is really severe in the lattice and the transverse motion of particles is unstable. Then a new SR lattice is designed to obtain a large dynamic aperture and much more stable transverse motion. The dynamic aperture of the new lattice including nonlinear wiggler effect is calculated to be very good. This new SR lattice can be used in the commissioning stage of the BEPCII.     

Thickness Determination for a Two-Layered Composite of a Film and a Plate by Low-Frequency Ultrasound

We present an ultrasonic method for determining the thickness of a composite consisting of a soft thin film attached to a hard plate substrate, by resonance spectra in the low frequency region, The interrogating waves can be incident only to the two-layered composite from the substrate side. The reflection spectra are obtained by FFT analysis of the compressive pulsed echoes from the composite, and the thicknesses of the film and the substrate are simultaneously inversed by the simulated annealing method from the resonant frequencies knowing other acoustical parameters in prior. The sensitivity of the method to individual thickness, its convergence and stability against experimental noises are studied, Experiment with interrogating wavelength 4 times larger than the film thickness in a sample of a polymer film （0.054mm） on an aluminium plate （6.24mm） verifies the validity of the method. The average relative errors in the measurement of the thicknesses of the film and the substrate are found to be -4.1% and -0.62%, respectively.     

Electronic Structure of Si1-xⅣx/Si Superlattices on Si （001）

We have preformed systematical ab initio studies of the structural and electronic properties of short-period Si1-xⅣx/Si （x = 0.125, 0.25, 0.5, Ⅳ=Ge, Sn） superlattices （SLs） grown along the [001] direction on bulk Si. The present calculations reveal that the Si0.875Ge0.125/Si, Si0.75Ge0.25/Si and Si0.875Sn0.125/Si are the F-point direct bandgap semiconductors. The technological importance lies in the expectation that the direct gap Si1-xⅣx/Si SLs may be used as components in integrated optoelectronic devices, in conjunction with the already well-established and highly advanced silicon technology.