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991.
The recombination dynamics of singlet and triplet oppositely charged polarons under the influence of electron–electron (e–e) interactions in coupled polymer chains are investigated using a multi-configurational time-dependent Hartree–Fock (MCTDHF) method. During recombination processes, singlet and triplet intrachain excitons are important products. By calculating the yields of the singlet and triplet intrachain excitons as a function of the on-site and long-range e–e interactions, it is found that the yields of the singlet and triplet intrachain excitons both decrease with increasing on-site e–e interactions. On the other hand, as the long-range e–e interactions increase, the yields of singlet intrachain excitons initially increase and then maintain a constant value, while the yields of the triplet intrachain excitons decrease. Our results show that the long-range e–e interaction is of fundamental importance and improves the luminescence efficiency in coupled polymer chains. Finally, the influence of the polymer chain length on the yields of singlet and triplet intrachain excitons is discussed.  相似文献   
992.
Band structures of ni doped lattice-matched GaNAsBi/GaAs quantum wells are studied theoretically using a self-consistent calculation (based on the envelop function formalism) combined with the 16-band anti-crossing model. Operating at 1.55 μm, these QWs can represent active zones of temperature-insensitive optoelectronic device applications intended for optical fiber communications. We have calculated physical parameters of the structures such as the confining potential profiles, the Fermi level, the subband energies and their corresponding wavefunctions as well as the oscillator strength of inter-band transitions, the subband occupations, and the confined electrons density distributions. Finally, the absorption coefficient spectra of GaNAsBi-based QWs are also computed.  相似文献   
993.
工业锅炉炉膛内部是一个高温、高辐射、高灰度的环境,炉内燃料的燃烧过程伴随着剧烈而连续的发光发热的物理、化学反应。在锅炉火焰图像识别中,原始图像对该复杂环境变化非常敏感,并严重地影响图像的识别率。针对这一问题,本文介绍了一种提取锅炉火焰特征的最优阈值法。该方法依据统计学基本原理,对锅炉火焰自动识别的实际问题建立一个统计回归模型,并根据回归模型参数直接求取最优的分割阈值。  相似文献   
994.
The dynamic analysis of a generalized linear elastic body undergoing large rigid rotations is investigated. The generalized linear elastic body is described in kine-matics through translational and rot...  相似文献   
995.
Now a days, the convergence of wireless and optical network gaining popularity to enhance the data carrying capacity, QoS and to support future multimedia applications. The queue theory plays an important role for analytically evaluating such converged networks. In the everyday state of affairs, queue phenomena are observed in the several situations like the health clinic, railway reservation system, automobile laundry centre, bank cash counter, call centre, etc. Similarly, the phenomenon of congestion is ascertained in the telephone network, computer network, communication systems and the Internet wherever nonstop enhancements need to be created to stay up with the quickly growing demand. The subsistence of these adverse clogging effects has lead toward the improvement of queuing theory-based statistical models. Therefore, these queues based statistical models answering to optimising queries corresponding to the way for assigning resources in converged optical and wireless networks. During this paper, a review on the role of the queuing model in wireless & optical communication is presented that concentrate on the present and future aspects of research.  相似文献   
996.
Large-scale evacuations are a recurring theme on news channels, whether in response to major natural or manmade disasters. The role of warning dissemination is a key part in the success of such large-scale evacuations and its inadequacy in certain cases has been a ‘primary contribution to deaths and injuries’ (Hayden et al., 2007). Along with technology-driven ‘official warning channels’ (e.g. sirens, mass media), the role of unofficial channel (e.g. neighbours, personal contacts, volunteer wardens) has proven to be significant in warning the public of the need to evacuate. Although post-evacuation studies identify the behaviours of evacuees as disseminators of the warning message, there has not been a detailed study that quantifies the effects of such behaviour on the warning message dissemination. This paper develops an Agent-Based Simulation (ABS) model of multiple agents (evacuee households) in a hypothetical community to investigate the impact of behaviour as an unofficial channel on the overall warning dissemination. Parameters studied include the percentage of people who warn their neighbours, the efficiency of different official warning channels, and delay time to warn neighbours. Even with a low proportion of people willing to warn their neighbour, the results showed considerable impact on the overall warning dissemination.  相似文献   
997.
<正>Coarse-graining of some sort is a fundamental and unavoidable step in any attempt to derive the classical mechanical behavior from the quantum formalism.We utilize the two-mode Bose-Hubbard model to illustrate how different coarse-grained systems can be naturally associated with a fixed quantum system if it is compatible with different dynamical algebras.Alternative coarse-grained systems generate different evolutions of the same physical quantities,and the difference becomes negligible only in the appropriate macro-limit.  相似文献   
998.
This paper presents an empirical model to predict attenuation in forest environments considering parameters related to vegetation. Typically, environmental parameters are only included in theoretical models, but they are more difficult to apply. The developed model uses tree density, average tree canopy diameter and foliage density as input parameters. The foliage density is very difficult to determine since it depends on the characteristics of trees. A simple metric of this parameter was obtained by measuring the background light silhouetted by the canopy. The model was developed with measurements obtained in different forest environments for two frequencies within the UHF band (Ultra High Frequency). A procedure was also applied to extend the operating frequency range of the model.  相似文献   
999.
Thermospray nebulizer interfaced HPLC-Flame AAS was used to study the effect of heavy metals (Al, Cd, Cu, Hg and Zn) on the chlorophylls of duckweed. Flame AAS was used as a metal specific detector of HPLC. Study indicated that heavy metals promote the degradation of chlorophylls. No evidence of direct replacement of central magnesium with heavy metals was found.  相似文献   
1000.
随着核能事业的发展,高放废物的处理和处置问题日益突出.其中,研究高放废物在环境介质中的吸附、扩散和迁移行为是获取放射性核素对周围环境和人群健康影响的基础参数的最重要和最直接的途径.近年来,人们利用已有的实验数据及核素的基础热力学和动力学数据,附以相应的数学模型,建立了一些地球化学模拟软件,用于分析核素在地质介质中可能发生的连续性和长期性变化.目前,国内外常用的地球化学模拟软件有十多种.本文从热力学平衡计算原理、种态分布计算方法和表面配位模型假设等几个方面对地球化学模拟软件进行了简要介绍,对近年来地球化学模拟软件在核素种态分布计算和表面配位模型模拟两方面的应用进行了举例分析,并以Ca-U-CO3配合物为例,说明完备的热力学数据对地球化学模拟软件发展的重要性,以期促进我国地球化学模型的应用和发展.  相似文献   
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