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1.
Bellman's dynamic programming equation for the optimal index and control law for stochastic control problems is a parabolic or elliptic partial differential equation frequently defined in an unbounded domain. Existing methods of solution require bounded domain approximations, the application of singular perturbation techniques or Monte Carlo simulation procedures.In this paper, using the fact that Poisson impulse noise tends to a Gaussian process under certain limiting conditions, a method which achieves an arbitrarily good approximate solution to the stochastic control problem is given. The method uses the two iterative techniques of successive approximation and quasi-linearization and is inherently more efficient than existing methods of solution. 相似文献
2.
《Journal of The Franklin Institute》2021,358(18):9890-9908
This paper aims at establishing necessary and sufficient conditions of exponential stability for linear discrete-time systems with multiple delays. Firstly, we introduce a new concept—Lyapunov matrix, and investigate its properties, existence and uniqueness by: (i) characterizing the solution of a boundary value problem of matrix difference equations; and (ii) constructing complete type Lyapunov–Krasovskii functionals with pre-specified forward difference. Secondly, a new constructive analysis methodology, named Lyapunov matrix approach, is proposed to establish necessary and sufficient exponential stability conditions for discrete-time systems with multiple delays. Finally, two numerical examples are presented to illustrate the effectiveness of the theoretical results. It is worth emphasizing that, from a view of computation, the Lyapunov matrix approach proposed here is concerned with three key steps: (i) solve a systems of linear equations; (ii) check whether a constant matrix is of full-column-rank, and (iii) judge whether a constant matrix is positive definite. All of these can be easily realized by using the tool software—MATLAB. 相似文献
3.
This paper deals with optimal controls that maximize the expectation of first passage time of the state, of a stochastic non-linear system, to the complement of an open and bounded domain. The performance index includes a penalty on the magnitude of the deviation of the first passage time from its expectation. The nonlinear system considered here is subjected to two different kinds of perturbations. The first kind of perturbation is represented by a vector of independent standard Wiener processes and the second kind by a vector of a generalized type of Poisson process.By using a variational approach, necessary conditions on the optimal controls are derived. These conditions are given by a set of four coupled nonlinear partial integro- differential equations. A nonlinear stochastic third-order system is given as a test case, and a numerical method for the computation of its optimal controls, is suggested. The efficiency and applicability of this method are demonstrated with examples. 相似文献
4.
O. Yassine C. P. Gooneratne D. Abu Smara F. Li H. Mohammed J. Merzaban J. Kosel 《Biomicrofluidics》2014,8(3)
This study describes the development and testing of a magnetic microfluidic chip (MMC) for
trapping and isolating cells tagged with superparamagnetic beads (SPBs) in a microfluidic
environment for selective treatment and analysis. The trapping and isolation are done in two
separate steps; first, the trapping of the tagged cells in a main channel is achieved by soft
ferromagnetic disks and second, the transportation of the cells into side chambers for isolation is
executed by tapered conductive paths made of Gold (Au). Numerical simulations were performed to
analyze the magnetic flux and force distributions of the disks and conducting paths, for trapping
and transporting SPBs. The MMC was fabricated using standard microfabrication processes. Experiments
were performed with E. coli (K12 strand) tagged with 2.8 μm SPBs.
The results showed that E. coli can be separated from a sample solution by trapping
them at the disk sites, and then isolated into chambers by transporting them along the tapered
conducting paths. Once the E. coli was trapped inside the side chambers, two
selective treatments were performed. In one chamber, a solution with minimal nutrition content was
added and, in another chamber, a solution with essential nutrition was added. The results showed
that the growth of bacteria cultured in the second chamber containing nutrient was significantly
higher, demonstrating that the E. coli was not affected by the magnetically driven
transportation and the feasibility of performing different treatments on selectively isolated cells
on a single microfluidic platform. 相似文献
5.
以我国ICT领域产学研联合申请的SIPO授权专利为样本,按照专利申请人(专利权人)的组织类型区分产学研合作模式,首先从宏观上分析比较我国ICT产业产学研合作模式的演进路径;然后利用社会网络分析方法从微观上研究产学研合作网络整体结构及其时空演化,进而对产学研合作深度、广度及效率等进行分析。研究结果表明:我国ICT产业的创新主体已由大学转变为企业,产学研合作模式经历了由以大学、研究所为核心的合作模式到以企业为主导的合作模式的转变。产学研合作网络呈逐渐增大趋势,且整体上表现出较明显的核心—边缘结构。网络集聚程度较低,但网络连接效率较高。说明我国ICT产业中参与合作研发的大学、研究所、企业数量日益增多,知识转移效率较高的产学研合作网络已形成,这为充分调动各创新主体的积极性,开展更加广泛、紧密、深入的合作奠定了良好基础。 相似文献
6.
In atmospheric and oceanic studies, it is important to investigate the uncertainty of model solutions. The conditional non-linear optimal perturbation (CNOP) method is useful for addressing the uncertainty. This paper reviews the development of the CNOP method and its computational aspects in recent years. Specifically, the CNOP method was first proposed to investigate the effects of the optimal initial perturbation on atmosphere and ocean model results. Then, it was extended to explore the influences of the optimal parameter perturbation, model tendency perturbation and boundary condition perturbation. To obtain solutions to these optimal perturbations, four kinds of optimization approaches were developed: the adjoint-based method, the adjoint-free method, the intelligent optimization method and the unconstrained optimization method. We illustrate the calculation process of each method and its advantages and disadvantages. Then, taking the Zebiak–Cane model as an example, we compare the CNOPs related to initial conditions (CNOP-Is) calculated by the above four methods. It was found that the dominant structures of the CNOP-Is for different methods are similar, although some differences in details exist. Finally, we discuss the necessity and possible direction for designing a more effective optimization approach related to the CNOP in the future. 相似文献
7.
《Journal of The Franklin Institute》2022,359(9):4331-4345
This paper is concerned with the stability of sampled-data systems with constant delay. Firstly, by dividing the interval of sampling periods in two subintervals, two separate looped functionals are employed in each of these subintervals. Then, a new Lyapunov functional that combines classical Lyapunov functionals and looped-functionals is constructed. Furthermore, several zero equalities which consider the intrinsic relationships of state vectors in the system are introduced into the derivative of the constructed functional, and some stability criteria with less conservatism are obtained in forms of linear matrix inequalities (LMIs). Finally, two numerical examples are carried out as to verify the effectiveness and advantages of our method. 相似文献
8.
Quasi-power functionals have been traditionally derived through the Method of Weighted Residuals (MWR) and used as the starting formulation for the finite element method. In this paper, we derive similar but more complete functionals for potential fields through a novel approach. We first form discrete quasi-power functions by applying Tellegen's theorem to the Graph-Theoretic Field Model (GTFM) and then obtain the continuous model quasi-power functionals by applying a limiting process to the discrete counterpart. The procedure herein is in marked contrast to the MWR whereby quasi-power functionals are derived by applying mathematical operations to the partial differential system. The procedure can be used with fields with anisotropy, non-linearities and coupled processes, although the example fields used within are linear and isotropic. This paper is a sequel to similar derivations for Green's identities and variational formulations. 相似文献
9.
Felichism W. Kabo Natalie Cotton-Nessler Yongha Hwang Margaret C. Levenstein Jason Owen-Smith 《Research Policy》2014
This paper uses path overlap, an innovative measure of functional proximity, to examine how physical space shaped the formation and success of scientific collaborations among the occupants of two academic research buildings. We use research administration data on human subject protection, animal use management, and grant funding applications to construct new measures of collaboration formation and success. The “functional zones” investigators occupy in their buildings are defined by the shortest walking paths among assigned laboratory and office spaces, and the nearest elevators, stairs, and restrooms. When two investigators traverse paths with greater overlap, both their propensity to form new collaborations and to win grant funding for their joint work increase. This effect is robust across two very differently configured buildings. Implications for scientific collaboration and the design and allocation of research space are considered. 相似文献
10.
11.
Technological paradigms and technological trajectories: A suggested interpretation of the determinants and directions of technical change 总被引：1，自引：0，他引：1
Giovanni Dosi 《Research Policy》1982,11(3):147-162
The procedures and the nature of “technologies” are suggested to be broadly similar to those which characterize “science”. In particular, there appear to be “technological paradigms” (or research programmes) performing a similar role to “scientific paradigms” (or research programmes). The model tries to account for both continuous changes and discontinuities in technological innovation. Continuous changes are often related to progress along a technological trajectory defined by a technological paradigm, while discontinuities are associated with the emergence of a new paradigm. One-directional explanations of the innovative process, and in particular those assuming “the market” as the prime mover, are inadequate to explain the emergence of new technological paradigms. The origin of the latter stems from the interplay between scientific advances, economic factors, institutional variables, and unsolved difficulties on established technological paths. The model tries to establish a sufficiently general framework which accounts for all these factors and to define the process of selection of new technological paradigms among a greater set of notionally possible ones.The history of a technology is contextual to the history of the industrial structures associated with that technology. The emergence of a new paradigm is often related to new “schumpeterian” companies, while its establishment often shows also a process of oligopolistic stabilization. 相似文献
12.
The paper is concerned with the diffusion and adoption of innovations within the United Kingdom textile chemicals and dyestuffs industry. The authors chose this industry for investigation chiefly because of the rapid increase in dyestuffs output over recent years despite evidence that the market for dyestuffs had declined over that period.Two surveys are described, the first of which involved an attempt to personally interview all United Kingdom manufacturers of, and agents for, textile chemicals. A second survey, taken from a 10% systematic sample of firms engaged in the use of textile chemicals is then described. Comparisons were made between the results of the two surveys.Areas covered in the surveys were the identification of innovators and the influence that these innovators have in initiating the diffusion process; product characteristics affecting the diffusion process and the role of research and development; competitive and speciality products and pressure from consumers. Characteristics having an inhibiting effect upon the diffusion process were also examined.It was found that the communications approach did not satisfactorily explain the diffusion of new textile chemicals and dyestuffs in the United Kingdom textile industry which was due particularly to the infrequent incidence of inter-firm opinion leadership. It was concluded that there were more favourable positive characteristics than unfavourable negative characteristics which aided diffusion and so accounted for the growth of textile chemicals and dyestuffs. 相似文献
13.
本文以国家重点实验室科研工作者为研究样本,分析了政策助推、创新搜索机制对科研绩效的影响。建立了以问题界定和跨界搜索两种创新搜索机制为中介构念的政策助推影响科研绩效单中介和双中介模型,并采用Bootstrap法和PRODCLIN法检验了三个假设模型。研究发现：政策助推对科研绩效具有正向影响作用;创新搜索机制在政策助推影响科研绩效的过程中发挥完全中介作用,问题界定机制和跨界搜索机制的中介路径均具有统计显著性,但是问题界定机制的中介效果明显小于跨界搜索机制。研究丰富了创新搜索机制的前置要素分析,并增强对政策影响个体行为的关注。 相似文献
14.
15.
为了防止数据库在非法使用过程中造成数据泄露、更改或破坏,本文提出了数据库安全性控制的一般方法,具体阐述了用户标识和鉴定、存取控制、定义视图、数据加密和审计几类安全性措施。 相似文献
16.
Betzalel Avitzur Walter C. Hahn Samy Iscovici 《Journal of The Franklin Institute》1975,299(5):339-358
A variety of mathematical models may be used to analyse plastic deformation during a metal-forming process. One of these methods—limit analysis—places the estimate of required power between an upper bound and a lower bound. The upper and lower bound analyses are designed so that the actual power or forming stress requirement is less than that predicted by the upper bound and greater than that predicted by the lower bound. Finding a lower upper bound and a higher lower bound reduces the uncertainty of the actual power requirement. Upper and lower bounds will permit the determination of such quantities as required forces, limitations on the process, optimal die design, flow patterns, and prediction and prevention of defects.Fundamental to the development of both upper bound and lower bound solutions is the division of the body into zones. For each of the zones there is written either a velocity field (upper bound) or a stress field (lower bound). A better choice of zones and fields brings the calculated values closer to actual values.In the present work, both upper and lower bound solutions are presented for axisymmetric flow through conical converging dies. For the upper bound triangular velocity fields have been solved and compared to previously published work on spherical velocity fields. It is found that each type provides a lower solution over a part of the range of process variables. A previously published lower bound solution for axisymmetric flow is refined. 相似文献
17.
A class of nonlinear singularly perturbed systems with delayed impulses is considered. By delayed impulses we mean that the impulse maps describing the state's jumping at impulsive moments are dependent on delayed state variables. Assuming that each of two lower order subsystems possesses a Lyapunov function, exponential stability criteria for all small enough values of singular perturbation parameter are obtained. It turns out that the achieved exponential stability is robust with respect to small impulse input delays. A stability bound on perturbation parameter is also derived through using those Lyapunov functions. Additionally, for a class of singularly perturbed Lur'e systems with delayed impulses, an LMI-based method to determine stability and an upper bound of the singular perturbation parameter is presented. The results are illustrated by an example for the position control of a dc-motor with unmodelled dynamics. 相似文献
18.
In this paper, on the basis of the theories and methods of ecology and ordinary differential equation, an ecological model consisting of two preys and one predator with impulsive control strategy and seasonal effects is established. Conditions which guarantee the global asymptotical stability of the prey-eradication periodic solution are obtained using the theory of impulsive equations, small amplitude perturbation skills, and comparison techniques. Further, the influences of the impulsive perturbation and seasonal effects on the inherent oscillation are studied numerically. These show to be consistent with the theoretical analysis and rich complex population dynamics, such as species extinction and permanence. Moreover, the population dynamical behavior of the model is demonstrated by the computed largest Lyapunov exponent. By investigating the strange attractors through their computed Fourier spectra, we know that seasonality has a profound effect on the population dynamical behavior. All these results are expected to be of use in the study of dynamic complexity of ecosystems. 相似文献
19.
通过构造V函数法及细致的分析得到系统的一致持续性,在种群一致持续性前提下,利用Brouwer不动点定理证明系统至少存在一个正周期解,并通过构造Lyapunov泛函和运用微分不等式,稳定性理论及Barbalat’s引理得到了判定正周期解的全局渐近稳定性和全局吸引的充分条件。 相似文献
20.
W.F.G. Swann 《Journal of The Franklin Institute》1930,209(2):151-200
Measurements have been made of the residual ionization in a closed vessel of steel one inch thick, shielded by a two inch casing of lead, over a range of pressure from atmospheric to one thousand pounds per sq. inch, at Pike's Peak (alt. 14,000 ft.), Colorado Springs (alt. 6,ooo ft.), and New Haven (alt. 6,000 ft.). The ionization-pressure curves presents features of interest in relation to the interpretation of the processes associated with ionization in the vessel. However, in the present investigation they are used simply to obtain average relative value of the ionization due to the cosmic rays at the three altitudes concerned. A method of correcting the observations for absorption by the iron sphere, the lead case, and the walls of the buildings, has been developed. It is found that the data for the three stations can be correlated by the assumption of a pair of frequencies in the original cosmic radiation; and, as a matter of fact, an infinite number of such pairs are possible. They are represented in graphical form in Fig. 7 If we permit the assumption of three different frequencies in the cosmic radiation, it is possible in general to assign two of the frequencies, and determine an infinite number of possibilities as regards the third, distributed over a definite range. The possibilities inherent in the assumption of three frequencies are contained in tabular form in Table XVII. Of course, the inclusion of observations from more than three altitudes would serve to fix more definitely the possibility as regards the analysis. However, the result of the analysis for the three stations concerned is possibly of interest for comparison with other data, and as an indication of the kind of information which it is possible to extract from observations of this kind. It is probable that the very large range of possibilities inherent in a solution with three coefficients of absorption will be rather surprising to anyone who considers a situation of this kind for the first time.In addition to those whose assistance has already been acknowledged, I wish to acknowledge the assistance of Professor J. W. Broxon, who visited me while on Pike's Peak, and assisted in setting up the apparatus; and my thanks are due to Mr. C. A. Kotterman, and particularly to Mr. Andrew Longacre, and Mr. W. E. Ramsey for assistance in the reduction of the observations, and in the computational work. 相似文献