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51.
Jianmei Han Zhongyan Huang Jingsheng Miao Yuntao Qiu Ziyang Xie Chuluo Yang 《Chemical science》2022,13(12):3402
Blue thermally activated delayed fluorescence (TADF) emitters that can simultaneously achieve narrowband emission and high efficiency in nondoped organic light-emitting diodes (OLEDs) remain a big challenge. Herein, we successfully design and synthesize two blue TADF emitters by directly incorporating carbazole fragments into an oxygen-bridged triarylboron acceptor. Depending on the linking mode, the two emitters show significantly different photophysical properties. Benefitting from the bulky steric hindrance between the acceptor and terminal pendants, the blue emitter TDBA-Cz exhibited a high photoluminescence quantum yield (PLQY) of 88% in neat films and narrowband emission. The corresponding non-doped blue device exhibited a maximum external quantum efficiency (EQE) of 21.4%, with a full width at half maximum (FWHM) of only 45 nm. This compound is the first blue TADF emitter that can concurrently achieve narrow bandwidth and high electroluminescence (EL) efficiency in nondoped blue TADF-OLEDs.A donor–acceptor TADF emitter showed narrowband high-efficiency blue emission by fine molecular modulation. The corresponding OLEDs exhibited a maximum EQE of 21.4% and a small FWHM of 45 nm, representing the most efficient nondoped blue TADF-OLEDs. 相似文献
52.
A Q-switched mode-locking femtosecond all-fiber laser based on a 2 cm long homemade Er3+/Yb3+ codoped phosphate glass fiber has been reported. By using the nonlinear polarization evolution technique, a nearly 100% modulation
depth of mode-locking pulse train is achieved. At a pump power of 410 mW, the energy of each Q-switched envelope, whose width
is about 220 μs, is 10 μJ, while the duration of mode-locking pulse within the Q-switched envelope is 318-fs. 相似文献
53.
An upgraded external beam PIXE setup for multielemental analysis of atmospheric aerosol samples 下载免费PDF全文
The external beam particle‐induced X‐ray emission (PIXE) setup has been upgraded by introducing a new silicon drift detector with the aim of obtaining better minimum detection limits (MDLs) at the 2 × 1.7 MV Tandetron accelerator of the Beijing Normal University in China. The upgraded external beam PIXE setup is equipped with two silicon drift detectors for PIXE analysis of low and high Z elements. A surface barrier detector for Rutherford backscattering spectrometry monitors beam and helium flow. Two kinds of aerosol filter samples (quartz fiber filters and Teflon filters) were studied. A 200‐μm thick Mylar absorber in front of the medium‐high energy X‐rays detector was adopted, and it got the best MDLs for atmospheric aerosol samples analysis. Multielemental analysis of quartz fiber filter aerosol samples was achieved. For more accurate and better MDLs of low Z elements in PIXE analysis, it is necessary to keep sufficient helium flow behind the thin samples. 相似文献
54.
Sixteen groups of chinchillas (N=140) were exposed to various equivalent energy noise paradigms at 100 dB(A) or 103 dB(A) SPL. Eleven groups received an interrupted, intermittent, and time varying (IITV) non-Gaussian exposure quantified by the kurtosis statistic. The IITV exposures, which lasted for 8 hday, 5 daysweek for 3 weeks, were designed to model some of the essential features of an industrial workweek. Five equivalent energy reference groups were exposed to either a Gaussian or non-Gaussian 5 days, 24 hday continuous noise. Evoked potentials were used to estimate hearing thresholds and surface preparations of the organ of Corti quantified the sensory cell population. For IITV exposures at an equivalent energy and kurtosis, the temporal variations in level did not alter trauma and in some cases the IITV exposures produced results similar to those found for the 5 day continuous exposures. Any increase in kurtosis at a fixed energy was accompanied by an increase in noise-induced trauma. These results suggest that the equal energy hypothesis is an acceptable approach to evaluating noise exposures for hearing conservation purposes provided that the kurtosis of the amplitude distribution is taken into consideration. Temporal variations in noise levels seem to have little effect on trauma. 相似文献
55.
In order to achieve a higher lateral resolution required for ultraprecision measurement of microstructural workpieces, phase-only pupil filtering differential confocal microscopy (PFDCM), a new approach is proposed based on the differential confocal microscopy (DCM), which uses a three-zone phase-only pupil filter with lateral super-resolution capability obtained through optimized design to change the distribution of DCM three-dimensional point spread function, so that the DCM lateral resolution is therefore significantly improved while its axial resolution is slightly improved. Preliminary experimental comparison and analyses indicate that, the lateral and axial resolutions of PFDCM are better than 0.2 μm and 2 nm, respectively, when wavelength of incidence laser beam , numerical aperture of measuring lens NA=0.85, and lateral spot size with a three-zone phase-only pupil filter GT=0.65. It is therefore concluded that PFDCM is a new approach to further improvement of lateral resolution in laser probe measurement systems. 相似文献
56.
利用扭曲波方法计算类He离子的电子碰撞激发截面。靶波函数采用HFS自洽场波函数,本文计算了若干元素从基态(11S)到21S,21P,23S,23P的跃迁。计算结果以碰撞强度的形式给出。入射电子能量从激发阈能开始到x=10,计算结果与已有的结果作了比较,分析表明,在大多数情况下,结果是满意的。 相似文献
57.
Zhipeng Qiu 《Applied mathematics and computation》2010,216(5):1553-1565
In this paper, a 3(n+1) dimensional sexually transmitted disease model is studied. The model involves two competing strains 1 and 2, where females are divided into n different groups based on their susceptibility to two distinct pathogenic strains. The first and second reproduction numbers , which have their biological meaning, are defined for strain , respectively. With the non-degeneracy assumption (H), a complete classification for dynamics of this model in terms of is presented, which is based on the theory of type-K monotone dynamical systems. 相似文献
58.
进一步讨论亚纯函数的k阶导数具有公共小函数的唯一性问题,得到两个亚纯函数唯一性问题的结果,改进了李平的有关结果. 相似文献
59.
Infrared femtosecond laser pulse induced permanent reduction of Eu3+ to Eu2+ in a fluorozirconate glass 总被引:3,自引:0,他引:3
We report what is believed to be the first observation of permanent photoreduction of Eu(3+) to Eu(2+) in transparent and colorless Eu(3+) -doped fluorozirconate glass at room temperature, using an infrared femtosecond laser. Difference absorption and electron-spin-resonance spectra of the glass before and after laser irradiation showed that a portion of the Eu(3+) ions in the focused part of the laser inside the glass were reduced to Eu(2+) ions after laser irradiation. It is suggested that Eu(3+) ions act as electron-trapping centers, whereas active sites in the glass matrix act as hole-trapping centers, leading to the formation of Eu(2+) ions. The observed phenomenon is inferred to be useful in the fabrication of optical memory devices with high storage density and waveguide-type micro-optical devices. 相似文献
60.
Experimental Mechanics - Identification of impact force is essential for various engineering applications, such as performance evaluation, design optimisation, noise suppression, and vibration... 相似文献