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91.
In this paper, we investigate the stability and robust stability criteria for genetic regulatory networks with interval time-varying delays and Markovian jumping parameters. The genetic regulatory networks have a finite number of modes, which may jump from one mode to another according to the Markov process. By using Lyapunov–Krasovskii functional, some sufficient conditions are derived in terms of linear matrix inequalities to achieve the global asymptotic stability in the mean square of the considered genetic regulatory networks. Two numerical examples are provided to illustrate the usefulness of the obtained theoretical results. 相似文献
92.
93.
X.S. Qin G.H. Huang G.M. Zeng A. Chakma Y.F. Huang 《European Journal of Operational Research》2007,180(3):182
Planning for water quality management systems is complicated by a variety of uncertainties and nonlinearities, where difficulties in formulating and solving the resulting inexact nonlinear optimization problems exist. With the purpose of tackling such difficulties, this paper presents the development of an interval-fuzzy nonlinear programming (IFNP) model for water quality management under uncertainty. Methods of interval and fuzzy programming were integrated within a general framework to address uncertainties in the left- and right-hand sides of the nonlinear constraints. Uncertainties in water quality, pollutant loading, and the system objective were reflected through the developed IFNP model. The method of piecewise linearization was developed for dealing with the nonlinearity of the objective function. A case study for water quality management planning in the Changsha section of the Xiangjiang River was then conducted for demonstrating applicability of the developed IFNP model. The results demonstrated that the accuracy of solutions through linearized method normally rises positively with the increase of linearization levels. It was also indicated that the proposed linearization method was effective in dealing with IFNP problems; uncertainties can be communicated into optimization process and generate reliable solutions for decision variables and objectives; the decision alternatives can be obtained by adjusting different combinations of the decision variables within their solution intervals. It also suggested that the linearized method should be used under detailed error analysis in tackling IFNP problems. 相似文献
94.
C*-代数的*-同构一定是(完全)等距映射,反之不然.本文证明了C*-代数的实完全等距映射能够完全决定C*-代数*-同构的结论. 相似文献
95.
针对圆柱形管道外部的流体与颗粒介质运动问题,提出了结合圆柱周围声辐射力和声流Stokes力的研究方法。从柱体外部声流方程出发,得到影响涡流结构的无量纲参数Rem≥325.27时,外涡最大流速大于内涡最大流速。在此基础上,采用Nyborg的边界滑移速度理论,获得管道外部声流的极限滑移速度,推导得出圆柱附近的声辐射力公式。基于此公式,在理论上推导出颗粒速度为0、声辐射力和声流Stokes力平衡时,颗粒临界直径的表达式。通过对圆柱位于不同位置时,圆柱外部的颗粒运动进行仿真模拟,得到与理论公式相一致的结论:颗粒的临界直径的大小与声波频率有关,当颗粒直径小于临界直径时,声流Stokes力为主导,颗粒随声流运动,颗粒直径大于等于临界直径时,声辐射力为主导,颗粒在声辐射力作用下逐渐向声辐射力的节点聚集。理论与仿真结果表明该方法可用于分析管道外颗粒的分布状态,其研究结果有助于解决电站中换热器的管道结垢、热交换率降低等问题。 相似文献
96.
《Proceedings of the Combustion Institute》2023,39(3):3303-3311
Lignin pyrolysis involves complex radical reactions, whereas the radical chain process, especially the influence of aliphatic substituents, has been rarely studied. Herein, the typical β-O-4 lignin dimer, phenethyl phenyl ether (PPE), and three aliphatic substituted derivatives of PPE, namely α-OH substituted, β-CH2OH substituted, and α,β-disubstituted PPE (αPPE, βPPE, and αβPPE) were employed as model compounds. DFT calculations, electronic analyses, and fast pyrolysis experiments were combined to investigate three core steps of the radical chain mechanism in lignin pyrolysis, i.e., homolysis, hydrogen abstraction, and radical decomposition. The pathway involving successive Cβ-O homolysis → α-hydrogen abstraction → Cβ-O breakage of α-dehydrogenated radical is dominated for the pyrolysis of aliphatic substituted β-O-4 linked lignin, with the formation of phenolics. The hydrogen abstraction reactions at the Cα site are obviously superior to those at other sites for PPE derivatives, due to the p-π conjugate stability. Notably, α-hydrogen abstraction can be significantly promoted by the π-electron-dispersing α-OH substitution. The decomposition step of dehydrogenated radicals can be facilitated by the electron-donating β-CH2OH substitution, where the Cβ-O breakage of the α-dehydrogenated radical is dominant. Totally, aliphatic substituents can improve the radical growth stage and change the competitiveness of the hydrogen abstraction and radical decomposition reactions. The fast pyrolysis experiments of PPE and αPPE gave direct proof that the generation of characteristic products from the radical chain process, i.e., benzaldehyde and phenylacetaldehyde, was enhanced by the α-OH substitution. The present work offers the potential to give a comprehensive image of the radical chain mechanism in lignin pyrolysis. 相似文献
97.
《Proceedings of the Combustion Institute》2023,39(4):4399-4407
Ammonia is a promising alternative clean fuel due to its carbon-free character and high hydrogen density. However, the low reactivity of ammonia and the potential high NOx emissions hinder its applications. Blending methane into ammonia can effectively improve the reactivity of pure NH3. In addition, lean combustion, as a high-efficiency and low-pollution combustion technology, is an effective measure to control the potential increase in NOx emissions. In the present work, the ignition delay times (IDTs) of NH3/CH4 mixtures highly diluted in Ar (98%) with CH4 mole fractions of 0%, 10%, and 50% were measured in a shock tube at an equivalence ratio of 0.5, pressures of 1.75 and 10 bar and a temperature range of 1421 K - 2149 K. A newly comprehensive kinetic model (named as HUST-NH3 model) for the NH3/CH4 mixtures oxidation was developed based on our previous work. Four kinetic models, the HUST-NH3 model, Glarborg model [19], Okafor model [7], and CEU model [10], were evaluated against the ignition delay times, laminar flame speeds, and species profiles of pure ammonia and ammonia/methane mixtures from the present work and literature. The simulation results indicated that the HUST-NH3 model shows the best performance among the above four models. Kinetic analysis results indicated that the absence of NH3 + M = NH2 + H + M (R819) and N2H2 + M = H + NNH + M (R902) in the CEU model and Okafor model cause the deviations between the experimental and simulation results. The overestimation of the rate constants of NH2 + NO = NNH + OH (R838) in the Glarborg model is the main reason for the overprediction of the NH3 laminar flame speeds. 相似文献
98.
99.
Yunlong Liu Prof. Chunfeng Zhang Rui Wang Bo Zhang Prof. Zhanao Tan Prof. Xiaoyong Wang Prof. Min Xiao 《Angewandte Chemie (International ed. in English)》2015,54(21):6222-6226
By creating two triplet excitons from one photo‐excited singlet exciton, singlet fission in organic semiconductors has drawn tremendous attention for its potential applications in boosting the efficiency of solar conversion. Here, we show that this carrier‐multiplication effect can also be used to dramatically improve the nonlinear optical response in organic materials. We have observed large optical nonlinearity with a magnitude of χ(3) up to 10?9 esu in pentacene films, which is further shown to be a result of singlet fission by monitoring the temporal dynamics. The potential application of such efficient nonlinear optical response has been demonstrated with a singlet‐fission‐induced polarization rotation. 相似文献
100.
Benke Hong Houhua Li Jinbao Wu Jing Zhang Prof. Dr. Xiaoguang Lei 《Angewandte Chemie (International ed. in English)》2015,54(3):1011-1015
Utilizing a late‐stage enamine bromofunctionalization strategy, the twelve‐step total synthesis of (?)‐huperzine Q was accomplished. Furthermore, the first total syntheses of (+)‐lycopladines B and C are described. An unprecedented X‐ray crystal structure of an unusual epoxyamine intermediate is also reported, and the synthetic application of this intermediate in natural product synthesis is demonstrated. 相似文献