基于F^2OMCDM方法的在役挖掘机可靠性评价研究

针对可靠性评价中现场数据的模糊性、关联性和不一致性,在分析在役液压挖掘机可靠性影响因素的基础上,构建其可靠性评价指标体系,并讨论了指标间的交互作用;然后构建基于三角模糊数、模糊测度和有序加权平均算子(Ordered weighted average,OWA)的混合多指标评价方法(Hybrid multi-criteria decision making method involved triangular fuzzy number,fuzzy measure and OWA,F2OMCDM);分析了基于关联系数的指标权重计算方法;并探讨基于F2OMCDM的在役液压挖掘机可靠性评价方法;最后将该方法应用于无锡地区某型在役液压挖掘机可靠性评价中。计算结果显示用新方法计算的挖掘机可靠性为64%。由于考虑了指标的模糊性和关联性,评价结果更为科学合理,为降低其维护费用和施工风险提供了更可信的决策依据。此方法可应用于其他机械结构系统的可靠性评价。

Gain enhancement of perovskite nanosheets by a patterned waveguide:excitation and temperature dependence of gain saturation

Optical gain enhancement of two-dimensional CsPbBr3 nanosheets was studied when the amplified spontaneous emission is guided by a patterned structure of polyurethane-acrylate.Given the uncertainties and pitfalls in retrieving a gain coefficient from the variable stripe length method,a gain contour g((h))ω.x)was obtained in the plane of spectrum energy(hω)and stripe length(x),whereby an average gain was obtained,and gain saturation was analysed.Excitation and temperature dependence of the gain contour show that the waveguide enhances both gain and thermal stability due to the increased optical confinement and heat dissipation,and the gain origins were attributed to the two-dimensional excitons and the localized states.

Enhanced photoluminescence quantum yield of MAPbBr3 nanocrystals by passivation using graphene

Diminishing surface defect states in perovskite nancx^rystals is a highly challenging subject for enhancing optoelectronic device performance.We synthesized organic/inorganic lead-halide perovskite MAPbBr3(MA=methylammonium)clusters comprising nanocrystals with diameters ranging between 20 and 30 nm and characterized an enhanced photoluminescence(PL)quantum yield(as much as^7 times)by encapsulating the MAPbBr3 with graphene(Gr).The optical properties of MAPbBr3 and Gr/MAPbBr3 were investigated by temperature-dependent micro-PL and time-resolved PL measurements.Density functional theory calculations show that the surface defect states in MAPbBr3 are removed and the optical band gap is reduced by a 0.15 eV by encapsulation with graphene due to partial restoration of lattice distortions.

Coarse and fine-tuning of lasing transverse electromagnetic modes in coupled all-inorganic perovskite quantum dots

Inorganic perovskite lasers are of particular interest,with much recent work focusing on Fabry-P6rot cavity-forming nanowires.We demonstrate the direct observation of lasing from transverse electromagnetic(TEM)modes with a long coherence time-9.5ps in coupled CsPbBr_(3) quantum dots,which dispense with an external cavity resonator and show how the wavelength of the modes can be controlled via two independent tuning-mechanisms.Controlling the pump power allowed us tofine-tune the TEM mode structure to the emission wavelength,thus providing a degree of control over the properties of the lasing signal.The temperature-tuning provided an additional degree of control over the wavelength of the lasing peak,importantly,maintained a constant full width at half maximum(FWHM)over the entire tuning range without mode-hopping.

Strain-tunable optical microlens arrays with deformable wrinkles for spatially coordinated image projection on a security substrate

As a new concept in materials design,a variety of strategies have been developed to fabricate optical microlens arrays(MLAs)that enable the miniaturization of optical systems on the micro/nanoscale to improve their characteristic performance with unique optical functionality.In this paper,we introduce a cost-effective and facile fabrication process on a large scale up to~15 inches via sequential lithographic methods to produce thin and deformable hexagonally arranged MLAs consisting of polydimethylsiloxane(PDMS).Simple employment of oxygen plasma treatment on the prestrained MLAs effectively harnessed the spontaneous formation of highly uniform nanowrinkled structures all over the surface of the elastomeric microlenses.With strain-controlled tunability,unexpected optical diffraction patterns were characterized by the interference combination effect of the microlens and deformable nanowrinkles.Consequently,the hierarchically structured MLAs presented here have the potential to produce desirable spatial arrangements,which may provide easily accessible opportunities to realize microlens-based technology by tunable focal lengths for more advanced micro-optical devices and imaging projection elements on unconventional security substrates.

Optical shaping of the polarization anisotropy in a laterally coupled quantum dot dimer

We find that the emission from laterally coupled quantum dots is strongly polarized along the coupled direction[110],and its polarization anisotropy can be shaped by changing the orientation of the polarized excitation.When the nonresonant excitation is linearly polarized perpendicular to the coupled direction[110],excitons(X_(1) and X_(2))and local biexcitons(X_(1)X_(1) and X_(2)X_(2))from the two separate quantum dots(QD_(1) and QD_(2))show emission anisotropy with a small degree of polarization(10%).On the other hand,when the excitation polarization is parallel to the coupled direction [110],the polarization anisotropy of excitons,local biexcitons,and coupled biexcitons(X_(1)X_(2))is enhanced with a degree of polarization of 74%.We also observed a consistent anisotropy in the time-resolved photoluminescence.The decay rate of the polarized photoluminescence intensity along the coupled direction is relatively high,but the anisotropic decay rate can be modified by changing the orientation of the polarized excitation.An energy difference is also observed between the polarized emission spectra parallel and perpendicular to the coupled direction,and it increases by up to three times by changing the excitation polarization orientation from [110] to [110].These results suggest that the dipole-dipole interaction across the two separate quantum dots is mediated and that the anisotropic wavefunctions of the excitons and biexcitons are shaped by the excitation polarization.