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21.
Y. Yavin 《Journal of Optimization Theory and Applications》1984,44(1):159-179
Consider the random motion in the plane of a pointM, whose velocityv=(v
1,v
2) is perturbed by an 2-valued Gaussian white noise. Only noisy nonlinear observations taken on the point location (state) are available toM. The velocityv is of the formv(y)=
u
(u
1,u
2)
y
(du), wherey denotes the value of the observed signal,U is the range of the velocity, and, for eachy,
y
is a probability measure on (U). Using the available observations, the pointM wishes to steer itself into a given target set by choosing a randomized strategy ={
y
:y 2}. Sufficient conditions on weak optimal randomized strategies are derived. An algorithm for computing weak suboptimal randomized strategies is suggested, and the strategies are computed for a variety of cases.This work was partially supported by a grant from Control Data. 相似文献
22.
Yoshisuke Ueda 《Journal of statistical physics》1979,20(2):181-196
This paper deals with turbulent or chaotic phenomena which occur in the system governed by Duffing's equation, a special type of two-dimensional periodic system. By using analog and digital computers, experiments are carried out with special reference to the change of attractors and of average power spectra of the random processes under the variation of the system parameters. On the basis of the experimental results, an outline of the random process is made clear. The results obtained in this paper will be applied to various physical problems and will also serve as material for the development of a proper mathematics of this phenomenon. 相似文献
23.
Hong-Cheng Li Xun Tang Sheng-Yi Yang Yang-Kun Qu Zuo-Quan Jiang Liang-Sheng Liao 《中国化学快报》2021,32(3):1245-1248
Charge transfer via electron hopping from an electron donor (D) to an acceptor (A) in nanoscale, plays a crucial role in optoelectronic materials, such as organic light-emitting diodes (OLEDs) and organic photovoltaic cells (OPVs). Here, we propose a strategy for binding D/A units in space, where intramolecular charge-transfer can take place. The resulted material DM-Me-B is able to give bright emission in this molecular architecture because of the good control of D/A interaction and conformational rigidity. Moreover, DM-Me-B presents small singlet-triplet splitting energy, enabling thermally activated delayed fluorescence. Therefore, the DM-Me-B exhibits ~20% maximum external quantum efficiency and low efficiency roll-off at 1000 cd/m2, certifying an effective strategy in controlling D/A blocks through space. 相似文献
24.
We will focus on estimating the integrated covariance of two diffusion processes observed in a nonsynchronous manner. The observation data is contaminated by some noise, which possibly depends on the time and the latent diffusion processes, while the sampling times also possibly depend on the observed processes. In a high-frequency setting, we consider a modified version of the pre-averaged Hayashi–Yoshida estimator, and we show that such a kind of estimator has the consistency and the asymptotic mixed normality, and attains the optimal rate of convergence. 相似文献
25.
Andrew P. Jackson Brian J. Alloway 《International journal of environmental analytical chemistry》2013,93(3-4):119-131
Abstract Pressure decomposition in a microwave oven provides a rapid means of sample preparation for plant tissue analyses. The use of delayed atomisation cuvettes, Smith-Hieftje background correction and matrix/analyte modification enables accurate determinations of cadmium concentrations in plant materials to be made. However, care should be taken to restrict the concentrations of modifier used, as too high a concentration may lead to problems with both tube life and over-correction by the Smith-Hieftje background correction system. 相似文献
26.
Gintare Grybauskaite-Kaminskiene Dr. Dmytro Volyniuk Dr. Viktorija Mimaite Oleksandr Bezvikonnyi Dr. Audrius Bucinskas Dr. Gintautas Bagdziunas Prof. Juozas V. Grazulevicius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2018,24(38):9581-9591
Derivatives of 9-phenyl-9H-carbazole were synthesized as efficient emitters exhibiting both thermally activated delayed fluorescence and aggregation-induced emission enhancement. Effects of methoxy and tert-butyl substituents at the different positions of carbazolyl groups on the properties of the emitters were studied. Depending on the substitutions, photoluminescence quantum yields (PLQY) of non-doped solid films of the compounds ranged from 17 % to 53 % which were much higher than those observed for the solutions in low-polarity solvent toluene. Compounds substituted at C-3 and C-6 positions of carbazole moiety by methoxy- and tert-butyl- groups showed the highest solid-state PLQY. Ionization potentials of the studied derivatives in solid-state were found to be in the short range of 5.75–5.89 eV. Well-balanced hole and electron mobilities were detected for tert-butyl-substituted compound. They exceeded 10−4 cm2 (V×s)−1 at electric fields higher than 3×105 V cm−1. Two compounds with the highest solid-state PLQYs showed higher efficiencies in non-doped organic light-emitting diodes than in the doped devices. Maximum external quantum efficiency of 7.2 % and brightness of 15000 cd m−2 were observed for the best device. 相似文献
27.
Zhao-Long Hu Zhesi Shen Chang-Bing Tang Bin-Bin Xie Jian-Feng Lu 《Physics letters. A》2018,382(14):931-937
Locating sources in a large network is of paramount importance to reduce the spreading of disruptive behavior. Based on the backward diffusion-based method and integer programming, we propose an efficient approach to locate sources in complex networks with limited observers. The results on model networks and empirical networks demonstrate that, for a certain fraction of observers, the accuracy of our method for source localization will improve as the increase of network size. Besides, compared with the previous method (the maximum–minimum method), the performance of our method is much better with a small fraction of observers, especially in heterogeneous networks. Furthermore, our method is more robust against noise environments and strategies of choosing observers. 相似文献
28.
《Journal of computational and graphical statistics》2013,22(3):703-725
This article deals with the problem of local sensitivity analysis, that is, how sensitive are the results of a statistical analysis to changes in the data? A general methodology of sensitivity analysis is applied to some statistical problems. The proposed methods are applicable to any statistical problem that can be expressed as an optimization problem or that involves solving a system of equations. As some particular examples, the methodology is applied to the maximum likelihood method, the standard and constrained methods of moments and the standard and constrained probability weighted moments methods. Unlike the standard method of moments, the constrained method of moments ensures that the obtained estimates are always consistent with the data. Closed analytical formulas for the calculation of these local sensitivities are derived. The obtained sensitivities include: (a) the objective function sensitivities to data points and (b) the sensitivities of the estimated parameters to data points. The derived formulas for the sensitivities are based on recent results in the area of mathematical programming. Several examples of parameter estimation problems are used to illustrate the methodology. 相似文献
29.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(17):1989-1996
Formylphenyl has been demonstrated to act as an acceptor to construct thermally activated delayed fluorescence (TADF) emitter, and therefore a series of the TADF‐conjugated polymers with formylphenyl as pendant acceptor and carbazole/acridine as backbone donor are designed and synthesized. All polymers involve the twisted donor/acceptor structural moieties with the sufficiently spatial separation between the highest occupied molecular orbital and the lowest unoccupied molecular orbital as well as a small singlet/triplet splitting, and exhibit the legible TADF features confirmed by theoretical calculation and their transient decay spectra. The solution‐processed organic light‐emitting diodes using neat film of the polymers as emissive layer achieve excellent performance with the maximum external quantum efficiency (EQE) of up to 10.6%, the maximum current efficiency of up to 35.3 cd A−1 and the low turn‐on voltage of 2.7 V. Moreover, the EQE still remains 10.3% at the luminance of 1000 cd m−2 with the low driving voltage of 4.4 V and extremely small efficiency roll‐off. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1989–1996 相似文献
30.
Optimizing Optoelectronic Properties of Pyrimidine‐Based TADF Emitters by Changing the Substituent for Organic Light‐Emitting Diodes with External Quantum Efficiency Close to 25 % and Slow Efficiency Roll‐Off
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Kailong Wu Tao Zhang Lisi Zhan Dr. Cheng Zhong Prof. Shaolong Gong Prof. Nan Jiang Prof. Zheng‐Hong Lu Prof. Chuluo Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10860-10866
A series of green butterfly‐shaped thermally activated delayed fluorescence (TADF) emitters, namely PXZPM , PXZMePM , and PXZPhPM , are developed by integrating an electron‐donor (D) phenoxazine unit and electron‐acceptor (A) 2‐substituted pyrimidine moiety into one molecule via a phenyl‐bridge π linkage to form a D –π–A–π–D configuration. Changing the substituent at pyrimidine unit in these emitters can finely tune their emissive characteristics, thermal properties, and energy gaps between the singlet and triplet states while maintaining frontier molecular orbital levels, and thereby optimizing their optoelectronic properties. Employing these TADF emitters results in a green fluorescent organic light‐emitting diode (OLED) that exhibits a peak forward‐viewing external quantum efficiency (EQE) close to 25 % and a slow efficiency roll‐off characteristic at high luminance. 相似文献