溅射压强和退火气氛对Mg0.2Zn0.8O∶Al紫外透明导电薄膜结构与性能的影响

以自制Mg0.2Zn0.8O∶Al陶瓷为靶材,采用室温溅射后续退火磁控溅射工艺制备了Mg0.2Zn0.8O∶Al紫外透明导电薄膜.研究了溅射压强和退火气氛对Mg0.2Zn0.8O∶Al薄膜结构和光电性能的影响.结果表明:溅射氩气压强不影响薄膜的相结构,但对薄膜的取向生长和结晶质量有一定影响;薄膜的方块电阻随溅射压强的增加先大幅减小后有所增大,溅射气压为2.0 Pa时,薄膜的方块电阻最低;不同溅射气压下制备薄膜的透光范围均已扩展到了紫外区域,而且具有85;以上的高透射率,但溅射气压对薄膜的带隙宽度和透光率没有明显影响;室温下溅射制备的薄膜经真空退火处理后其导电性能显著提高,但在空气中退火处理后其导电性能反而有所下降.     

Strain effect on the electronic properties of 1T-HfS2 monolayer

We perform first-principles based on the density function theory to investigate electronic and magnetic properties of 1T-HfS₂ monolayer with biaxial tensile strain and compressive strain. The results show that HfS₂ monolayer under strains doesn’t display magnetic properties. When the strain is 0%, the HfS₂ monolayer presents an indirect band gap semiconductor with the band gap is about 1.252 eV. The band gap of HfS₂ monolayer decreases quickly with increasing compressive strain and comes to zero when the compressive strain is above −7%, the HfS₂ monolayer system turns from semiconductor to metal. While the band gap increases slowly with increasing tensile strain and comes to 1.814 eV when the tensile strain is 10%. By comparison, we find that the compressive strain is more effective in band engineering of pristine 1T-HfS₂ monolayer than the tensile strain. And we notice that the extent of band gap variation is different under tensile strain. The change of band gap with strain from 1% to 5% is faster than that of the strain 6–10%. To speak of, the conduction band minimum (CBM) is all located at M point with different strains. While the valence band maximum (VBM) turns from Γ point to K point when the strain is equal to and more than 6%.     

An intelligent approach for engine fault diagnosis based on Hilbert–Huang transform and support vector machine

Based on the techniques of Hilbert–Huang transform (HHT) and support vector machine (SVM), a noise-based intelligent method for engine fault diagnosis (EFD), so-called HHT–SVM model, is developed in this paper. The noises of a sample engine under normal and several fault states are first measured and denoised by using the wavelet packet threshold method to initially lower the noise level with negligible signal distortion. To extract fault features of the engine, then, the HHT is selected and applied to the measured noise signals. A nine-dimensional vector, which consists of seven intrinsic mode functions (IMFs) from the empirical mode decomposition (EMD), maximum value of HHT marginal spectrum and its corresponding frequency component, is specified to represent each engine fault feature. Finally, an optimal SVM model is established and trained for engine failure classification by using the fault feature vectors of the noise signals. Cross-validation results show that the proposed noise-based HHT–SVM method is accurate and effective for engine fault diagnosis. Due to outstanding time–frequency characteristics and pattern recognition capacity of the HHT and SVM, the newly proposed HHT–SVM can be used to deal with both the stationary and nonstationary signals, and even the transient ones. In the view of applications, the HHT–SVM technique may be suggested not only to detect the abnormal states of vehicle engines, but also to be extended to other fields for failure diagnosis in engineering.     

Passively Q-switched diode-pumped Raman laser with third-order Stokes eye-safe oscillation

We demonstrate a passively Q-switched all-solid-state laser system with intracavity Raman frequency conversion to the eye-safe spectral region. Laser oscillation at the 1.064 μm wavelength with a pulse repetition rate of several kilohertz was provided by a Nd:YAG crystal and a Cr:YAG passive absorber. Third Stokes oscillations at the 1.599 and 1.494 μm wavelengths were obtained in Ba(NO₃)₂ and PbWO₄ crystals with output pulse energies of 5 μJ and 6 μJ, respectively. The results of the numerical simulation of the pulse dynamics are in good agreement with the experimental data.     

Trapping colloidal dielectric microparticles with overlapping evanescent optical waves

We experimentally demonstrate the creation of a stable surface trap for colloidal microparticles in a high-intensity evanescent optical field that is produced by total internal reflection of two counter-propagating and mutually incoherent laser beams. While the particles confined in the trap undergo fast Brownian motion, they never “stick” to the surface – not even at high optical powers – but rather levitate above the surface. If many particles are stored in the trap, they tend to form a well ordered self-organized array. We apply a numerical model based on the general energy-momentum tensor formalism to evaluate the overall optical force acting on a trapped particle. The optical-field parameters are calculated using the finite element method. The simulations show that for small particles a sharp repulsive potential at the surface – required for the levitation – can have neither optical nor light-induced thermal origin. Among the possible non-optical forces, electrostatic double-layer repulsion is often considered to be the origin of the levitation. We find, however, that the experimentally observed levitation of small particles in a high-intensity evanescent-wave trap cannot be explained by this effect.     

On the axial propagation of kink bands in fiber composites : Part ii analysis

A new micromechanical model is presented to simulate the steady-state axial propagation of kink bands investigated experimentally in the accompanying paper (Part I) . The fibers are in a hexagonal array and are assumed to be isotropic and linearly elastic, while the matrix is modeled as an elastic-powerlaw viscoplastic solid. Matrix properties for the model are determined from shear tests on the composite and compression tests on neat PEEK. The model is used to predict the propagation stress (σ_P) of the AS4⧹PEEK composite and to investigate the sensitivity of σ_P to band inclination, matrix properties, and loading rate. A simple model recently reported in the literature is calibrated to the current material system and compared with the present experimental data and model predictions. The micromechanical model is found to predict the propagation stress reasonably well and to capture the rate dependence of the composite. The simple model is found to capture the trends of the behavior.     

Sensitivity analysis in linear programming: just be careful!

In this paper we review the topic of sensitivity analysis in linear programming. We describe the problems that may occur when using standard software and advocate a framework for performing complete sensitivity analysis. Three approaches can be incorporated within it: one using bases, an approach using the optimal partition and one using optimal values. We elucidate problems and solutions with an academic example and give results from an implementation of these approaches to a large practical linear programming model of an oil refinery. This shows that the approaches are viable and useful in practice.     

双功能电极改善有机发光器件效率滚降的研究

针对磷光器件存在严重的效率滚降,进而制约有机电致发光器件的实用化进程的问题,提出采用超声喷涂Poly(3,4-ethylenedioxythiophene)Polystyrene Sulfonate(PEDOT:PSS)作为透明电极,制备了红、绿、蓝三色有机电致发光器件.利用超声喷涂工艺材料利用率高的特点,起绝缘作用的水溶性PSS分子链在PEDOT:PSS透明电极中得到保留,使该透明电极具有空穴缓冲作用.这种双功能性,提高了器件在高电流密度下的载流子平衡性,降低了红、绿、蓝三色发光层中的极化子浓度,改善了红、绿、蓝三色器件的效率滚降问题,从最高外量子效率所在亮度到10000cd/m^2的电流效率滚降分别仅为14.9%、12.4%和16.0%.该结果表明,双功能性电极的引入显著改善了有机电致发光器件中载流子平衡性,具有降低三基色器件效率滚降的普适性,对实现高亮度、高效率发光器件具有重要意义.     

A new fluorescent quinoline derivative toward the acid-responsivity in both solution and solid states

In this article, an acid-responsive luminescent material, 1,4-di(quinoline-6-yl)buta-1,3-diyne (DQBD) is designed and synthesized. Upon different pH values, gradual changes of fluorescence colors for DQBD in both solution and solid phases are demonstrated due to the protonation effect. Moreover, such responsive characteristics can also be reversible, suggesting DQBD as a promising fluorescent material with great potential for reusable- and accurate-pH sensors in the future.