基于悬臂梁的光纤光栅线性调谐

理论上对不同厚度的“凸”字形悬臂梁的调谐能力进行了分析,实验中选用适当尺寸的悬臂梁,对粘贴基上的光纤光栅的反射波长实现了线性调谐,并观察到由于梁轴向应力的梯度分布造成的啁啾输出现象,指出选用长度较短的光栅可以减小谱的展宽量。     

Measurement of direct photon emission in K+-->pi(+)pi(0)gamma decay

We have performed a measurement of the K+-->pi(+)pi(0)gamma decay and have observed 2x10(4) events. The best fit to the decay spectrum gives a branching ratio for direct photon emission of (4.7+/-0.8+/-0. 3)x10(-6) in the pi(+) kinetic energy region of 55 to 90 MeV and requires no component due to interference with inner bremsstrahlung.     

Sn/Ge(111) surface charge-density-wave phase transition

Angle-resolved photoemission has been utilized to study the surface electronic structure of 1 / 3 monolayer of Sn on Ge(111) in both the room-temperature (sqrt[3]xsqrt[3] )R30 degrees phase and the low-temperature ( 3x3) charge-density-wave phase. The results reveal a gap opening around the ( 3x3) Brillouin zone boundary, suggesting a Peierls-like transition despite the well-documented lack of Fermi nesting. A highly sensitive electronic response to doping by intrinsic surface defects is the cause for this unusual behavior, and a detailed calculation illustrates the origin of the ( 3x3) symmetry.     

d-band quantum well states

Observations of d-band quantum well states are made for atomically uniform Ag films on Fe(100) using angle-resolved photoemission. For increasing film thicknesses, quantum well peaks within the small 4d bandwidth multiply rapidly and merge into a bulklike spectrum at approximately 25 monolayers. An analysis of the peak positions yields a highly accurate bulk band structure of Ag. A very narrow d-band peak width (13 meV) is observed at the band top.     

Measurement of structure-dependent K+ --> &mgr;(+)nu(&mgr;)gamma decay

We report the first measurement of a structure-dependent component in the decay K+-->&mgr;(+)nu(&mgr;)gamma. Using the kinematic region where the muon kinetic energy is greater than 137 MeV and the photon energy is greater than 90 MeV, we find that the absolute value of the sum of the vector and axial-vector form factors is |F(V)+F(A)| = 0.165+/-0.007+/-0.011. This corresponds to a branching ratio of B(SD+) = (1.33+/-0.12+/-0.18)x10(-5). We also set the limit -0. 04相似文献   

Two-phase heat transfer characteristics for R-22/R-407C in a 6.5-mm smooth tube

Two-phase friction and heat transfer characteristics for R-22/R-407C inside a 6.5-mm smooth tube are reported in this study. The heat transfer results for G=100 and 400 kg/m² s were reported in the present study, and the adiabatic frictional pressure drop was recorded in the range of 100 to 700 kg/m² s. It is found that the development of flow pattern for R-407C falls behind R-22. This may explain the lower pressure drops for R-407C. The major heat transfer mechanism at low mass flux is nucleate boiling, and virtually becomes the convective evaporation as mass flux increase to G=400 krg/m² s, Meanwhile, the reduction of heat transfer coefficients for R-407C mixtures are especially profound at low mass flux, and the reduction of heat transfer coefficient decreases with the increase of mass flux.     

Enhanced birefingence of MgF2 thin film at 193 nm by serial bideposition

Magnesium fluoride films were coated by serial bideposition with a varying number of sub-deposited layers. The deposition angle 70° remained constant throughout the process by a single electron-beam source. One, 4, 20, and 100 sub-deposition layers were prepared. The microstructure, residual stress, absorption of water, and linear birefringence of serial bideposition of anisotropic thin film at 193 nm were investigated and discussed. Microstructures of the films were observed by scanning electron microscopy. The residual stress was measured by phase-shifting interferometer. The water absorption bands of the thin films were measured by Fourier transform infrared (FTIR) spectroscopy, and refractive indices in two different directions (S- and P-polarized) were determined from a spectrometer equipped with a polarizer. The linear birefringence would increase and the stress would decrease when the sub-deposited layers were increased. When the number of layers was 100, the difference between the refractive indices for two different polarizations was able to reach 0.082.     

A 2$,times,$ 2 Mechanical Optical Switch With a Thin MEMS Mirror

This paper presents the design, fabrication, alignment and experimental tests of a 2times2 mechanical optical switch. The key component of the mirror device is fabricated by the MEMS process that coats both sides with an ultrathin high reflection Au/Cr film (thickness less than 1.8 microns and roughness 5.7 nm) to allow double-sided reflection. The mirror is mounted on a thin metal arm, which is switched by a mechanical relay. Compared to the 4-mirror type of single-sided reflector which is used by other 2times2 optical switches, this configuration significantly reduces the size and number of the components. The optical alignment and the component assembly can rapidly be accomplished by two stages: visual coarse alignment and automatic fine alignment. Due to the feature of an adjustable mirror positioning and orientation, insertion losses can be reduced to a very low level. Experimental results show that the insertion losses, crosstalk, switching time and long-cycle test can all meet the Bellcore 1073 specification requirements.     

Mechanical modeling of flexible OLED devices

General expressions are deduced for the stresses developed in the individual thin layers of a multi-layer structure as a result of bending to a specified radius. These are appropriate for analysing flexible organic light emitting diode (FOLED) devices on flexible substrates. Residual stress (caused internally by temperature change and differential thermal expansion) after material deposition and return to ambient temperatures is not considered. The reduced elastic modulus of the typical small molecule OLED materials: N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPD) and tris-(8-hydroxyquinoline)aluminum (Alq₃) are measured as thin-films using nano-indentation techniques. A conventional device: polyethylene terephthalate (PET)/Buffer layer (BL)/ITO/OLED/Al is considered from a modeling standpoint, as a preliminary to actual fabrication and subsequent comparative testing of OLED performance on rigid and flexible supports.     

Laboratory and modeling study on modulated wave properties

Development of Benjamin?Feir instability is investigated under laboratory conditions and by analytical modeling. Nonlinear properties of the wave train with discrete spectrum are also investigated. The mechanically generated waves are composed of several discrete waves, while the newly generated harmonics are still combined into discrete spectra with the same frequency step. The technique proposed in this study allows us to study accurately the nonlinear variations in main properties of each harmonic with fixed frequency, such as amplitude, phase speed, and wavenumber along the wave tank together with velocities of wave packet crests, especially for the large transient waves. The phase speeds of short waves increase near large transient waves, and the velocities of longer waves are close to the values determined by the linear theory of waves. The relative long wave accompanied by short waves can dramatically change the local kurtosis and skewness of the wave field. They may play an important role for the generation of large transient wave and provide an opportunity for triggering of the freak waves.