共查询到20条相似文献，搜索用时 24 毫秒
1.
Guy Jumarie 《Journal of The Franklin Institute》2010,347(10):1797-1813
The usual model for (Poissonian) linear birth-death processes is extended to multiple birth-death processes with fractional birth probabilities in the form λi(Δt)α+o((Δt)α, 0<α<1. The probability generating function for the time dependent population size is provided by a fractional partial differential equation. The solution of the latter is obtained and comparison with the usual model is made. The probability of ultimate extinction is obtained. One considers the special case of fractional Poissonian processes with individual arrivals only, and then one outlines basic results for continuous processes defined by fractional Poissonian noises. The key is the Taylor’s series of fractional order f(x+h)=Eα(hαDxα)f(x), where Eα(·) is the Mittag-Leffler function, and Dxα is the modified Riemann-Liouville fractional derivative, as previously introduced by the author. 相似文献
2.
Motivated by the work in [1] of Abualrub and Siap (2009), we investigate (1+λu)-constacyclic codes over Fp[u]/〈um〉 of an arbitrary length, where λ is a nonzero element of Fp. We find the generator polynomials of (1+λu)-constacyclic codes over Fp[u]/〈um〉, and determine the number of (1+λu)-constacyclic codes over Fp[u]/〈um〉 for a given length, as well as the number of codewords in each such code. Some optimal linear codes over F3 and F5 are constructed from (1+λu)-constacyclic codes over Fp+uFp under a Gray map. 相似文献
3.
This paper concentrates on computing the stabilizing region
of PDμ controller for fractional order system with general interval uncertainties and an interval delay. The stabilizing region means the complete/approximate set of PDμ controllers that stabilize the given closed-loop control system. General interval uncertainties refer to both coefficients and orders of the fractional system suffer from interval uncertainties. Interval delay indicates that the delay also vary in a specified interval.Firstly, a method is presented to calculate the stabilizing region for general interval fractional system with an interval
time-constant delay. Based on a novel mapping function and the concept of critical controller parameters, the stabilizing region can be determined numerically. Secondly, the stabilizing region computation problem for general interval fractional system with an interval time-varyingdelay is considered. By applying a revised small-gain theorem, the stabilizing region can be calculated like the time-constant delay case. Thirdly, two alternative methods are proposed to improve the computational efficiency of stabilizing region calculation. Both methods can reduce the number of polynomials which are used to determine the stabilizing region. Examples are followed to illustrate the proposed results. 相似文献
4.
A novel adaptive control with σ-modification for uncertain nonlinear systems is proposed in the paper. The application of conventional adaptive control is severely limited by the problems of construction of Lyapunov function and parameter drift because of non-parametric uncertainties. The proposed adaptive control that is on the basis of the immersion and invariance theory and σ-modification can be used to deal with these problems to some extent. It turns out to be a structured design method without requiring a Lyapunov function in the design level and robust to non-parametric uncertainties. Moreover, constrained command filter backstepping is adopted to meet the amplitude and rate constraints on the states and actuators. The uniformly ultimately bounded stability of the closed-loop system has been analyzed by Lyapunov theory with parametric and non-parametric uncertainties of the controlled model. To demonstrate the design flexibility, the method is applied to the position tracking control system design of a mass-damper-spring system and the flight control system design of a scramjet-powered air-breathing hypersonic vehicle. Finally, the effectiveness of the proposed adaptive control method is illustrated by numerical simulations. 相似文献
5.
The sampled-data H∞ filtering for a continuous-time Takagi–Sugeno fuzzy system with an interval time-varying state delay is investigated, where the measurement outputs from the plant to the filter are assumed to be sampled at discrete instants with a variable period. Firstly, by means of a newly proposed inequality bounding technique and a new Lyapunov–Krasovskii functional, the fuzzy sampled-data H∞ filtering performance analysis is carried out such that the resultant filter error system is asymptotically stable with a prescribed H∞ attenuation performance index. Secondly, sufficient conditions on the existence of fuzzy sampled-data H∞ filters are derived in the simultaneous presence of the time-varying state delay and the variable sampling period. The proposed bounding inequality lies in its more tightness and alleviates the enlargement of some inverse “coefficients” resulting from the utilization of the well-known Jensen integral inequality . Compared with some existing Lyapunov–Krasovskii functionals, more information about the relationship among the current state and its delayed state is considered. The upper bound of the derivative of the time-varying state delay is not required to be less than one. Different from some existing results in the literature, by applying the proposed results, each different value of such an upper bound (greater than one) leads to a different H∞ disturbance attenuation level. Finally, a numerical example and a modified continuous stirred tank reactor system are given to show the effectiveness of the proposed results. 相似文献
6.
Extending previous investigations by Loeb of mobilities in gaseous mixtures using his procedure except that the auxiliary field in these measurements was made equal to the advancing field thus giving absolute values of the mobilities, measurements of mobilities were made in mixtures of CH3NO2H2 and CH3CNH2. The mobilities in H2 were 7.12 for the positive ions and 10.46 for the negative ions in cm./sec. per volt/cm. Those in CH3NO2 were 0.221 cm./sec. per volt/cm. for both ions and in CH3CN they were 0.234 cm./sec. per volt/cm. for both ions. Both ion mobilities deviated from Blanc's law in CH3NO2 indicating the formation of complexes with the CH3NO2 ions somewhat greater in size than the normal ions in H2. The molecules attached to negative ions somewhat less readily than to the positive ions but both final ions were of the same size. In CH3CN mixtures both positive and negative ions deviated from Blanc's law, the positive ion showing more ready attachment of CH3CN. The negative ion had consistently a higher mobility than the positive ion, a circumstance indicating a smaller ion and suggesting that the attaching molecule might not be CH3CN but some impurity. Both ion addition products in CH3CN are larger than the normal ion in H2 but smaller than those in CH3NO2 as was to be expected. 相似文献
7.
Yuxiang Shen Tianfu Liu Rongtan Li Houfu Lv Na Ta Xiaomin Zhang Yuefeng Song Qingxue Liu Weicheng Feng Guoxiong Wang Xinhe Bao 《国家科学评论(英文版)》2023,(9):37-45
Solid oxide electrolysis cells provide a practical solution for the direct conversion of CO2 to other chemicals(i.e.CO),however,an in-depth mechanistic understanding of the dynamic reconstruction of active sites for perovskite cathodes during CO2 electrolysis remains a great challenge.Herein,we identify that iridium-doped Sr2Fe1.45Ir0.05Mo0.5O6-δ(SFIrM) perovskite displays a dynamic electrochemical reconstruction feature during CO... 相似文献
8.
本文采用高温熔融法制备了SiO2-Bi2O3-Sb2O3-Er2O3玻璃。测量和研究了样品的吸收光谱和发射光谱。结果表明,Ω2的值和1.5μm附近的发射带宽均随着Er3+浓度的升高而增大。 相似文献
9.
This paper concerns the problem of designing a robust observer-based modified repetitive-control system with a prescribed H∞ disturbance rejection level for a class of strictly proper linear plants with unknown aperiodic disturbances and time-varying structural uncertainties. A correction to the amount of the delay in the repetitive controller is introduced that leads to a significant improvement in tracking performance. An integrated performance index is defined to quantify the overall effect of rejecting the aperiodic disturbances and tracking the periodic reference input. A Lyapunov functional with two tuning parameters is used to derive a linear-matrix-inequality based robust stability condition for the system with a prescribed disturbance-rejection bound. Combining the performance indices, an optimization algorithm that searches for the best combination of state-observer gain and the feedback control gains is developed. A numerical example illustrates the design procedure and demonstrates the effectiveness of the method. 相似文献
10.
Ti基准晶由于其特殊的晶体结构而成为具有前途的新型贮氢材料。Ti45Zr38Ni17准晶最大吸氢量时,氢原子与金属原子比约等于2,明显高于普通金属间化合物贮氢材料,但其平台压力低,氢很难放出。为了改善准晶的气态放氢性能,Takasaki等采用机械合金化及热处理的方法制备了Ti45Zr38Ni17准晶粉末。该粉末达到最大贮氢量时,氢原子与金属原子比等于1.5,这可能是由于准晶中含有少量的Ti2Ni型晶体相的原因。同时,在充放氢过程中,准晶相不稳定。Majzoub等采用电化学方法氢化Ti45Zr38Ni17准晶,贮氢量最大时氢原子与金属原子比为1.9,并且在充氢过程中无晶体相生成。到目前为止,准晶作为镍氢电池负极材料的电化学贮氢性能的研究未见报道。在本章中,将研究Ti45Zr38Ni17Cu3准晶作为镍氢电池负极时的最大放电容量和循环稳定性。为了对比,也研究了非晶合金的相关电化学性能。 相似文献
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采用两种方法:甘氨酸-硝酸盐法和新型的溶胶凝胶法,制备纳米级的钙钛矿型氧化物Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF)。所得到的BSCF粉末的结构和表面形态采用XRD和SEM表征,结果表明得到的BSCF粉末均呈现纯的立方钙钛矿结构和多孔的结构,平均粒径分别为15.6和53nm,均在纳米量级。将由这两种方法制备的BSCF粉末用做IT-SOFC的阴极,在650℃分别获得了1.28和1.24W/cm2的功率密度。 相似文献
13.
This paper focuses on the problem of H∞ filter design for continuous-time Takagi and Sugeno (T–S) fuzzy systems with time-varying delays. The partitioning time delay technique is used to construct the Lyapunov–Krasovskii functional, furthermore, a novel delay-dependent H∞ filter design approach is proposed based on the matrix decoupling approach, and the filter parameters can be obtained by solving a set of linear matrix inequalities (LMIs). The numerical examples show that the proposed method is of less conservativeness than the existing methods. 相似文献
14.
通过固相反应法合成Co Fe1.9Nb0.1O4物相,Rietveld精修表明该材料具有立方尖晶石结构,空间群为Fd-3m.Nb主要占据尖晶石的B位,部分取代Fe,这一取代对材料的磁电性能产生显著影响.与Co Fe2O4相比,Co Fe1.9Nb0.1O4的铁磁性减弱,而介电性能提高,表现出明显的介电弛豫行为.Nb掺杂导致Fe离子变价是造成极化增大和介电弛豫的主要原因.由于材料的漏导过大,无法通过P-E曲线直接证明材料的铁电性. 相似文献
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文章通过共沉淀法合成了正极材料Li1.2Mn0.54Ni0.13Co0.13O2所需球形前驱体。采用碳酸盐及氢氧化物两种沉淀剂,通过颗粒密度,颗粒粒径,SEM形貌表征手段研究了共沉淀实验条件对所制备前驱体理化性质的影响。结果表明:加料速度对颗粒密度,颗粒粒度,颗粒形貌有较大的影响,随着加料速度的增大颗粒密度增大,粒度增大,颗粒形貌趋于球形且表面缺陷完善;在颗粒形貌方面,碳酸盐沉淀剂体系更容易获得球形颗粒,颗粒表面光滑;氢氧化物沉淀体系颗粒形貌不易控制,但颗粒表面能直观地呈现出单晶形貌。 相似文献
18.
《Information processing & management》2023,60(1):103155
This paper presents a continuous delivery/continuous verifiability (CD/CV) method for IoT dataflows in edge–fog–cloud. A CD model based on extraction, transformation, and load (ETL) mechanism as well as a directed acyclic graph (DAG) construction, enable end-users to create efficient schemes for the continuous verification and validation of the execution of applications in edge–fog–cloud infrastructures. This scheme also verifies and validates established execution sequences and the integrity of digital assets. CV model converts ETL and DAG into business model, smart contracts in a private blockchain for the automatic and transparent registration of transactions performed by each application in workflows/pipelines created by CD model without altering applications nor edge–fog–cloud workflows. This model ensures that IoT dataflows delivers verifiable information for organizations to conduct critical decision-making processes with certainty. A containerized parallelism model solves portability issues and reduces/compensates the overhead produced by CD/CV operations. We developed and implemented a prototype to create CD/CV schemes, which were evaluated in a case study where user mobility information is used to identify interest points, patterns, and maps. The experimental evaluation revealed the efficiency of CD/CV to register the transactions performed in IoT dataflows through edge–fog–cloud in a private blockchain network in comparison with state-of-art solutions. 相似文献
19.
本文考察了添加不同助剂对Ni/Al2O3催化剂对乙醇水蒸气重整反应性能的影响,结果表明,添加K助剂可以改进催化剂活性并提高了反应稳定性。 相似文献
20.
M.R.D. Al-Mothafar 《Journal of The Franklin Institute》2012,349(1):260-283
A procedure is established for the small-signal modelling of n-connected current-programmed parallel-input/series-output pulse-width modulated bridge-based buck dc–dc converters operating in the continuous-current conduction mode. State-space averaging is used to represent the power stage while current-mode control is modelled using a modified new continuous-time technique. Approximate analytical expressions of the major small-signal transfer functions that include the number of modules as a variable are proposed. PSpice simulations are carried out to validate the analysis. 相似文献