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1.
Let f(χ) together with its first two derivatives be continuous in the domain D and additionally let χM?D be an extremum (or turning point) of this function. Also, let χn+1 = T (χn,χn-1,χn-2) be Jarratt's Method for computing the extremum (or turning point) of a function. Criteria are demonstrated which insure that, for any triple of initial assumptions (χ1,χ0,χ-1)?D, Jarratt's Method, converges to the extremum of f(χ), and that from and after some n = N0, the rate of convergence of this method increases steadily, finally becoming unbounded when the solution χM is attained.  相似文献   

2.
A new method for the calculation of time responses of lumped time invariant networks is presented. It is based on the numerical inversion of the Laplace transform and involves the computation of the frequency domain function at pre-assigned complex points and forming a weighted sum. The method exactly inverts a certain number of terms of the Taylor expansion of the time response and is thus equivalent to the methods used for the integration of differential equations. This equivalence is established on two examples. The order of integration can be changed between 1 and 46 without any difficulty. Additional properties resulting from the application of the numerical Laplace transform inversion are also discussed and some novel applications indicated.  相似文献   

3.
For singular systems, i.e. for systems of the form E[xdot] = Ax + Bu, with E singular, the problem of computing the transfer function matrix has been studied. An algorithm is developed which is similar to the corresponding algorithm proposed by Faddeev or Leverrier for regular systems. The present results involve the Drazin inverse and yield an expression for the transfer function matrix suitable for computer use.  相似文献   

4.
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5.
Given the linear system x = Ax - bu, y = cTx, it is shown that, for a certain non-quadratic cost functional, the optimal control is given by uopt(x) = h(cTx), where the function h(y) must satisfy the conditions ky2?h(y)y>0 for y≠0, h(0) = 0 and existence of h-1 everywhere. The linear system considered must satisfy the Popov condition 1/k + (1 +?ωβ) G(?ω)>0 for all ω, G(s) being the y(s)/u(s) transfer function.  相似文献   

6.
Most existing consensus control in multi-agent systems (MASs) require agents to update their state synchronously, which means that some agents need to wait for all individuals to complete the iteration before starting the next iteration. To overcome this bottleneck, this paper studied asynchronous consensus problems of second-order MASs (SOMASs) with aperiodic communication. An asynchronous pulse-modulated intermittent control (APIMC) with heterogeneous pulse-modulated function and time-varying control period, which can unify impulsive control and sampled-data control, is proposed for the consensus of SOMASs. A time-varying discrete system is constructed to describe the evolution of the sample values of position and velocity of the SOMAS. Then, by the analysis tools from the stochastic matrix and the properties of the Laplace matrix of graph, some effective conditions are obtained to show the relationship between the convergence of the controlled SOMASs and the control parameters. Finally, a 300-node SOMAS whose topology is a random geographic network is included to verify the feasibility of the proposed control and the correctness of the theoretical analysis.  相似文献   

7.
Azotobacter vinelandii is a gram-negative soil bacterium that produces two biopolymers of biotechnological interest, alginate and poly(3-hydroxybutyrate), and it has been widely studied because of its capability to fix nitrogen even in the presence of oxygen. This bacterium is characterized by its high respiration rates, which are almost 10-fold higher than those of Escherichia coli and are a disadvantage for fermentation processes. On the other hand, several works have demonstrated that adequate control of the oxygen supply in A. vinelandii cultivations determines the yields and physicochemical characteristics of alginate and poly(3-hydroxybutyrate).Here, we summarize a review of the characteristics of A. vinelandii related to its respiration systems, as well as some of the most important findings on the oxygen consumption rates as a function of the cultivation parameters and biopolymer production.How to cite: Castillo T, García A, Padilla-Córdova C, et al. Respiration in Azotobacter vinelandii and its relationship with the synthesis of biopolymers. Electron J Biotechnol 2020;48. https://doi.org/10.1016/j.ejbt.2020.08.001  相似文献   

8.
The need for collaborative ventures in Europe has long been stressed in the editorial pages of this journal, and more than ten years ago (Endeavour, 28, 54, 1969) we gave strong support for a proposal to establish a European Laboratory of Molecular Biology. For this we then incurred some criticism, on the ground that such a laboratory would weaken national academic institutes striving to establish themselves in this rapidly developing field. Nevertheless, we continued to maintain (30, 2, '71) ‘the great political and scientific importance of this [concept]—and of other such collaborative enterprises—if Europe is to maintain the initiative in fields where the great institutions of the United States have established a dominant position.’ In the event, the Laboratory was established at Heidelberg in 1974, though not formally opened until 1978. The Director-General, Sir John Kendrew, here surveys the policy and achievements of this important new institute.  相似文献   

9.
This paper derives an optimal homomorphic tomographic filter, to restore tomographic images of blurred radiographs, by taking into account the noise contributed by the other layers. The method is based on the homomorphic deconvolution technique, which is well-known for its performance in image restoration. A computer simulation of the procedure is presented. The results are compared with those obtained by using inverse filtering (3, IEEE Trans on Medical Imaging, Vol. 2, pp. 89–102, 1983) and Wiener filtering (4, Proc. Digitech '84). The paper shows that homomorphic filtering is a suitable and often preferable technique for the tomographic filtering of radiographs.  相似文献   

10.
Suppose that AXB=C is a consistent matrix equation and partition its solution X into a 2×2 block form. In this article we give some formulas for the maximal and minimal ranks of the submatrices in a solution X to AXB=C. From these formulas, we derive necessary and sufficient conditions for the submatrices to be zero and nonsingular, respectively. As applications, we give a group of formulas for the maximal and minimal ranks of submatrices in generalized inverses of matrices and their properties.  相似文献   

11.
Mathematical results are derived, which enable one to find a vector of parameters k0 such that (P1(s,k0)?H)∩(P2(k0)=0), where P1(s,k) is a polynomial in s and in the components of k,P2(k) is a polynomial in the components of k, and H is the set of Hurwitz polynomials. The algorithm is based on an extension of the root locus technique to the multiparameter case. The design problem of coupling networks between a resistive generator and a passive load, under prescribed power gain characteristics, is translated into the above formulation. A numerical example is provided.  相似文献   

12.
This paper is to study the mean square stabilizability and regional stability of discrete-time mean-field stochastic systems. Firstly, a necessary and sufficient condition is presented via the spectrum of linear operator to illustrate the stabilizability of discrete-time mean-field stochastic systems. B(0, γ)-stabilizability is introduced and transformed into solving linear matrix inequalities (LMIs). Secondly, BM-stability is characterized, especially, the stabilities of circular region, sector region and annulus regions are discussed extensively. Finally, as applications, it is shown that B(0, γ1; γ2)-stability has close relationship with the decay rate of the system state response and the Lyapunov exponent.  相似文献   

13.
The objective of the paper is to demonstrate how a sensemaking model of knowledge enables better and deeper understanding of knowledge management (KM) processes in organisations and the role of information technologies (IT) in these processes. Inspired and informed by a sensemaking view of organisations, the model identifies four types of knowledge, corresponding to four sensemaking levels: the individual, collective, organizational, and cultural. Each knowledge type, as the paper shows, is of different nature and has different characteristics but is constituted and affected by all other knowledge types. An organisation is thus seen as a ‘distributed knowledge system’ composed of numerous instances of these four knowledge types and their dynamic interplay. By drawing from three empirical studies, the paper illustrates how the sensemaking model of knowledge can be applied to investigate different ways companies (try to) manage knowledge and use IT-based systems to improve KM and ultimately company performance. A deeper understanding of these processes through the lens of the model reveals mechanisms and forces underlying KM phenomena that help explain why some processes were successful and others failed. The paper intends to make the following contributions: propose a theoretical framework of knowledge and KM in organizations, which is reasonably comprehensive and empirically grounded and also demonstrate its relevance and usefulness to both researchers and practitioners as they investigate and make sense of specific KM processes and IT applications in practice.  相似文献   

14.
BackgroundThe effects of dietary nutrition on tail fat deposition and the correlation between production performance and the Hh signaling pathway and OXCT1 were investigated in fat-tailed sheep. Tan sheep were fed different nutritional diets and the variances in tail length, width, thickness and tail weight as well as the mRNA expression of fat-related genes (C/EBPα, FAS, LPL, and HSL) were determined in the tail fat of sheep at three different growth stages based on their body weight. Furthermore, the correlations between tail phenotypes and the Hedgehog (Hh) signaling pathway components (IHH, PTCH1, SMO, and GLI1) and OXCT1 were investigated.ResultsC/EBPα, FAS, LPL, and HSL were expressed with differences in tail fat of sheep fed different nutritional diets at three different growth stages. The results of the two-way ANOVA showed the significant effect of nutrition, stage, and interaction on gene expression, except the between C/EBPα and growth stage. C/EBPα, FAS, and LPL were considerably correlated with the tail phenotypes. Furthermore, the results of the correlation analysis demonstrated a close relationship between the tail phenotypes and Hh signaling pathway and OXCT1.ConclusionsThe present study demonstrated the gene-level role of dietary nutrition in promoting tail fat deposition and related tail fat-related genes. It provides a molecular basis by which nutritional balance and tail fat formation can be investigated and additional genes can be identified. The findings of the present study may help improve the production efficiency of fat-tailed sheep and identify crucial genes associated with tail fat deposition.How to cite: Zeng J, Zhou S, Yang Y, et al. Effect of dietary nutrition on tail fat deposition and evaluation of tail-related genes in fat-tailed sheep. Electron J Biotechnol 2020;46. https://doi.org/10.1016/j.ejbt.2020.05.004.  相似文献   

15.
This year marks the 25th anniversary of the discovery of crown ethers by C. J. Pedersen (see Mary R. Truter and C. J. Pedersen Endeavour, 30, 142, 1971). This article reviews some new developments in this important field. New crown ether and related ligand systems that contain organometallic redoxactive groups can complex and electrochemically detect cations (metals, ammonium) and anions (halide, nitrate) in polar solvents. Thus, they represent prototypes of novel molecular sensory devices of the future.  相似文献   

16.
Recently, a massive amount of position-annotated data is being generated in a stream fashion. Also, massive amounts of static data including spatial features are collected and made available. In the Internet of Things (IoT) environments, various applications can get benefits by utilizing spatial data streams and static data. Therefore, IoT applications typically require stream processing and reasoning capabilities that extract information from low-level data. Particularly for sophisticated stream processing and reasoning, spatiotemporal relationship (SR) generation from spatial data streams and static data must be preceded. However, existing techniques mostly focus solely on direct processing of sensing data or generation of spatial relationships from static data. In this paper, we first address the importance of SRs between spatial data streams and static data and then propose an efficient approach of deriving SRs in real-time. We design a novel R-tree-based index with Representative Rectangles (RRs) called R3 index and devise an algorithm that leverages relationships and distances between RRs to generate SRs. To verify the effectiveness and efficiency of the proposed approach, we performed experiments using real-world datasets. Through the results of the experiments, we confirmed the superiority of the proposed approach.  相似文献   

17.
Matrix factorization-based methods become popular in dyadic data analysis, where a fundamental problem, for example, is to perform document clustering or co-clustering words and documents given a term-document matrix. Nonnegative matrix tri-factorization (NMTF) emerges as a promising tool for co-clustering, seeking a 3-factor decomposition X≈USV?X≈USV? with all factor matrices restricted to be nonnegative, i.e., U?0,S?0,V?0.U?0,S?0,V?0. In this paper we develop multiplicative updates for orthogonal NMTF where X≈USV?X≈USV? is pursued with orthogonality constraints, U?U=I,U?U=I, and V?V=IV?V=I, exploiting true gradients on Stiefel manifolds. Experiments on various document data sets demonstrate that our method works well for document clustering and is useful in revealing polysemous words via co-clustering words and documents.  相似文献   

18.
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19.
In this paper, a novel decentralized adaptive neural control approach based on the backstepping technique is proposed to design a decentralized H∞ adaptive neural controller for a class of stochastic large-scale nonlinear systems with external disturbances and unknown nonlinear functions. RBF neural networks are utilized to approximate the packaged unknown nonlinearities. A novel concept with regard to bounded-H∞ performance is proposed. It can be applied to solve an H∞ control problem for a class of stochastic nonlinear systems. The constant terms appeared in stability analysis are dealt with by using Gronwall inequality, so that H∞ performance criterion is satisfied. The assumption that the approximation errors of neural networks must be square-integrable in some literature can be eliminated. The design process for decentralized bounded-H∞ controllers is given. The proposed control scheme guarantees that all the signals in the resulting closed-loop large-scale system are uniformly ultimately bounded in probability, and each subsystem possesses disturbance attenuation performance for external disturbances. Finally, the simulation results are provided to illustrate the effectiveness and feasibility of the proposed approach.  相似文献   

20.
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