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1.
A control system of an ODE and a diffusion PDE is discussed in this paper. The novelty lies in that the system is coupled. The method of PDE backstepping as well as some special skills is resorted in stabilizing the coupled PDE–ODE control system, which is transformed into an exponentially stable PDE–ODE cascade with an invertible integral transformation. And a state feedback boundary controller is designed. Moreover, an exponentially convergent observer for anti-collocated setup is proposed, and the output feedback boundary control problem is solved. For both the state and output feedback boundary controllers, exponential stability analyses in the sense of the corresponding norms for the resulting closed-loop systems are given through rigid proofs. 相似文献
2.
Although innovation diffusion is a central topic in policy and strategy, its measurement remains difficult – particularly in cases where the innovation is a complex and possibly ambiguous practice. In this paper, we develop four theoretical mechanisms that may bias diffusion markers by leading to the understatement and/or overstatement of diffusion at different points in time. Employing the case of “green chemistry,” we then compare three different diffusion markers – keywords, database index terms, and domain expert assessments – and we demonstrate how they lead to differing conclusions about the magnitude and timing of diffusion, organizational demography, publication outlets, and collaboration. We also provide suggestive evidence of extensive “greenwashing” by particular organization types and in particular countries. Building on these findings, we point to potential challenges with existing diffusion studies, and we make a case for the incorporation of practitioners in construct measurement and for the integration of comparative metrics in diffusion studies. 相似文献
3.
Many authors have proposed categorizations for approaches to Knowledge Management; outstanding prospects including functionalist and interpretativist. In the first approach, knowledge is considered as a “static object” that exists in a number of ways and locations; in the second one, knowledge does not exist independently of human experience, social practice, of knowledge itself and its use, where it is shared by the social practices of communities, because it is “dynamic and active”. These articles constitute an extensive review on the subject, focused in reviewing, analyzing and presenting a study of the interpretativist perspective, and describe a maturity model for KM operational from it. 相似文献
4.
A user study of aNobii was conducted with an aim to exploring possible criteria for evaluating social navigational tools. A set of measures designed to capture various aspects of the benefits provided by the tools was proposed. To test the applicability of these measures, a within-subject experimental design was adopted where fifty regular aNobii users searched alternately with three book-finding tools: browsing “friends’ bookshelves”, “similar bookshelves”, and “books by known authors”. Other than the self-report user experience and search result measures, the “choice set” model was used as a novel framework for navigational effectiveness. Further analyses were conducted to explore whether three aspects of reader preference, “preference insight”, “preference diversity”, and “reading involvement” might influence the performance of the tools. 相似文献
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6.
In the present paper, we study stochastic boundary control problems where the system dynamics is a controlled stochastic parabolic equation with Neumann boundary control and boundary noise. Under some assumptions, the continuity and differentiability of the value function are proved. We also define a new type of Hamilton–Jacobi–Bellman (HJB) equation and prove that the value function is a viscosity solution of this HJB equation. 相似文献
7.
《Journal of The Franklin Institute》2021,358(17):8943-8968
This paper addresses the stabilization issue of linear time delay system with input saturation and distinct input delays via predictor feedback boundary control algorithm by employing transport partial differential equations (PDEs). First, the addressed ordinary differential equation (ODE) system with input delay is equivalently represented as a cascade of an ODE and transport PDEs. Second, by employing the backstepping Volterra integral transformation technique, the equivalent cascade system is transformed into a stable target system, whose kernels are solved by the constraints satisfying transport PDEs. Third, based on the boundary conditions of the obtained invertible transformation, the proposed feedback control law can be formulated. Fourth, by applying semigroup operator theory, the well-posedness of the resulting system is proved and consequently, novel exponential stability conditions of the addressed system are established. Then, the domain of attraction region under the given actuator saturation constraints is estimated with the help of the solution of obtained stability conditions. Finally, a demonstrative simulation example is offered to verify the feasibility and usefulness of the results. 相似文献
8.
Martin Heidenreich 《Research Policy》2005,34(5):739-757
The innovativeness of a region depends on its ability to recombine technological, organisational and scientific capabilities. This recombination can be facilitated by regional policies. In the past, these policies provided a stable set of “local collective competition goods” supporting interorganisational patterns of cooperation, communication and competition. Given the increasing uncertainties of an internationalised knowledge society, these stable regional orders are challenged by new, more open-ended and experimental patterns of regional policies. These policies treat regions as social fields whose political and economic boundaries, identities, dominant coalitions and governance structures are constructed in bargaining and exchange relations. Also the type of collective competition goods required and their target groups are the result of negotiations involving not only political actors and business associations but also enterprises and trade unions. This shift to a discursive renewal of regional capabilities, as well as the difficulties and limitations encountered by such “experimental regionalism”, is illustrated on the basis of an East and a West German region. Leipzig had to create a new economic and business structure and to integrate the existing firms into regional networks in order to enhance its innovative capabilities. In Leipzig, these two challenges were met by separate, newly created institutions thus hampering the regional integration and innovativeness of the recently recreated industrial basis. In Nuremberg, the transformation of a traditional industrial region into a technology and service-based one was facilitated by a common vision, regional networks, new research facilities and favourable conditions for start-up activities. In this case, a new regional “steering committee” facilitated the integration and renewal of formerly isolated regional capabilities thus demonstrating the potential of a discursive renewal of regional innovation systems. 相似文献
9.
This study uses bibliometric analysis and citation context analysis to identify the influence of the main concepts embedded in Taylor’s 1968 classic article entitled Question-Negotiation and Information-Seeking in Libraries. This study analyses articles published between 1969 and 2010 which cite Taylor’s article. The results show that Taylor’s article on a question-negotiation model is increasingly visible and its influence is not limited to the discipline of library and information science. Of the 14 cited concepts identified, the concept of “four levels of information needs” was cited most (31.7%), followed by “question negotiation” (20.5%) and “other concepts relating to information needs” (17.9%). The results indicate an increasing trend in the citations of “four levels of information needs” and this concept also received the most attention from information retrieval research. A decreasing trend was evident for the concept of “question negotiation” and this concept was frequently cited by reference service researchers. In addition, among the 10 citation functions, “related literature” was dominant (30.8%). Both “evidence” and “views” were in second place with the same percentage (18.7%), followed by “terms” (9.2%) and “background information” (7.2%). A decreasing trend was identified in the top three citation functions, whereas an increasing trend was observed in the “term” and “background information” functions. 相似文献
10.
Innovation has moved to the foreground in regional policy in the last decade. Concrete policies were shaped by “best practice models” derived from high-tech areas and well performing regions. These are often applied in a similar way across many types of regions. Here an attempt is made to show that there is no “ideal model” for innovation policy as innovation activities differ strongly between central, peripheral and old industrial areas. In this paper we analyse different types of regions with respect to their preconditions for innovation, networking and innovation barriers. Based on this classification different policy options and strategies are developed. 相似文献
11.
Thomas K. Gaisser 《Journal of The Franklin Institute》2011,348(3):453-458
This award recognizes two specific discoveries that constitute the experimental discovery of neutrino oscillations. In 1998 the Super-Kamiokande group under the leadership of Yoji Totsuka published their paper, “Evidence for Oscillation of Atmospheric Neutrinos” in Physical Review Letters [1]. The paper describes a deficit of muon-type neutrinos from below the detector relative to those from above. It explains this “atmospheric neutrino anomaly” as a result of transformation of some of the muon neutrinos into another type of neutrino. Four years later, the group led by Arthur McDonald described “Direct Evidence for Neutrino Flavor Transformation from Neutral-Current Interactions in the Sudbury Neutrino Observatory” [2] in the same journal. This experiment detected lower energy neutrinos from deep inside the Sun. By measuring all flavors of neutrinos with large rates, the SNO collaboration showed definitively that the long-standing “solar neutrino puzzle” was another manifestation of neutrino oscillations. As a result of these two experiments, we now understand that neutrinos can change identities during propagation and that both the solar and atmospheric neutrino “problems” result from the same underlying phenomenon of oscillations. A consequence of neutrino oscillations is that neutrinos, previously thought to be massless, must have a non-zero rest mass. 相似文献
12.
To perform repetitive tasks, this paper proposes an adaptive boundary iterative learning control (ILC) scheme for a two-link rigid–flexible manipulator with parametric uncertainties. Using Hamilton?s principle, the coupled ordinary differential equation and partial differential equation (ODE–PDE) dynamic model of the system is established. In order to drive the joints to follow desired trajectory and eliminate deformation of flexible beam simultaneously, boundary control strategy is added based on the conventional joints torque control. The adaptive iterative learning algorithm for boundary control scheme includes a proportional-derivative (PD) feedback structure and an iterative term. This novel controller is designed to deal with the unmodeled dynamics and other unknown external disturbances. Numerical simulations are provided to verify the performance of proposed controller in MATLAB. 相似文献
13.
求解非线性偏微分方程的方法很多不同的方法用于不同的方程其有效性也各不相同．第一积分法是把非线性偏微分方程转换为常微分方程，应用交换挟代数理论中的Hibert-Nullstensatz定理，以及整除定理，根据待定系数法来获得非线性偏微分方程精确解的一种很好的方法。本文利用第一积分法具体讨论了二维KdV-Burgers型方程更具一般形式的精确解。 相似文献
14.
Despite a number of studies looking at Web experience and Web searching tactics and behaviours, the specific relationships between experience and cognitive search strategies have not been widely researched. This study investigates how the cognitive search strategies of 80 participants might vary with Web experience as they engaged in two researcher-defined tasks and two participant-defined information seeking tasks. Each of the two researcher-defined tasks and participant-defined tasks included a directed search task and a general-purpose browsing task. While there were almost no significant performance differences between experience levels on any of the four tasks, there were significant differences in the use of cognitive search strategies. Participants with higher levels of Web experience were more likely to use “Parallel player”, “Parallel hub-and-spoke”, “Known address search domain” and “Known address” strategies, whereas participants with lower levels of Web experience were more likely to use “Virtual tourist”, “Link-dependent”, “To-the-point”, “Sequential player”, “Search engine narrowing”, and “Broad first” strategies. The patterns of use and differences between researcher-defined and participant-defined tasks and between directed search tasks and general-purpose browsing tasks are also discussed, although the distribution of search strategies by Web experience were not statistically significant for each individual task. 相似文献
15.
Web search engines are beginning to offer access to multimedia searching, including audio, video and image searching. In this paper we report findings from a study examining the state of multimedia search functionality on major general and specialized Web search engines. We investigated 102 Web search engines to examine: (1) how many Web search engines offer multimedia searching, (2) the type of multimedia search functionality and methods offered, such as “query by example”, and (3) the supports for personalization or customization which are accessible as advanced search. Findings include: (1) few major Web search engines offer multimedia searching and (2) multimedia Web search functionality is generally limited. Our findings show that despite the increasing level of interest in multimedia Web search, those few Web search engines offering multimedia Web search, provide limited multimedia search functionality. Keywords are still the only means of multimedia retrieval, while other methods such as “query by example” are offered by less than 1% of Web search engines examined. 相似文献
16.
A numerical method is proposed for solving multi-dimensional hyperbolic–parabolic differential equations with the nonlocal boundary condition in t and Dirichlet and Neumann conditions in space variables. The first and second order of accuracy difference schemes are presented. The stability estimates for the solution and its first and second orders difference derivatives are established. A procedure of modified Gauss elimination method is used for solving these difference schemes in the case of a one-dimensional hyperbolic–parabolic differential equations with variable coefficients in x and two-dimensional hyperbolic–parabolic equation. 相似文献
17.
Raphael Kaplinsky 《Research Policy》2011,40(2):193-203
Innovation and technological change play an important role in poverty reduction through their contribution to growth, their use of factors of production, their environmental spillovers, the social relations associated with production and the characteristics of the products which they produce. It was only after the 1960s that these linkages were identified, with the recognition that much of global technological progress was directed to meet the needs of the global rich, and was best-suited to operation in high-income environments. The development and diffusion of “appropriate technologies” was an agenda largely pursued by the not-for-profit Appropriate Technology movement. However, with the global diffusion of innovative capabilities, and the rapid rise of incomes of the very poor - the “second bottom billion” - innovation for the poor and innovation appropriate for production in low-wage and poor-infrastructure environments has increasingly become an arena for profitable production. The very large size of China and India, coupled with their growing technological capabilities and the rapid growth of low-incomes, makes it likely that they will become the dominant sources of innovation for the poor. 相似文献
18.
This paper focuses on the role of capabilities in economic development. In recent years, the quality and availability of data on different aspects of development have improved, and this provides new opportunities for investigating the reasons behind the large differences in economic development. Using factor analysis on data for 25 indicators and 115 countries between 1992 and 2004, we identify four different types of “capabilities”: the development of the “innovation system”, the quality of “governance”, the character of the “political system” and the degree of “openness” of the economy. Innovation systems and governance are shown to be of particular importance for economic development. 相似文献
19.
Zhigang Ren Chao Xu Zhongcheng Zhou Zongze Wu Tehuan Chen 《Journal of The Franklin Institute》2019,356(1):173-195
In this paper, the boundary stabilization problem of a class of unstable reaction–advection–diffusion (RAD) systems described by a scalar parabolic partial differential equation (PDE) is considered. Different the previous research, we present a new gradient-based optimization framework for designing the optimal feedback kernel for stabilizing the unstable PDE system. Our new method does not require solving non-standard Riccati-type or Klein–Gorden-type PDEs. Instead, the feedback kernel is parameterized as a second-order polynomial whose coefficients are decision variables to be tuned via gradient-based dynamic optimization, where the gradients of the system cost functional (which penalizes both kernel and output magnitude) with respect to the decision parameters are computed by solving a so-called “costate” PDE in standard form. Special constraints are imposed on the kernel coefficients to ensure that the optimized kernel yields closed-loop stability. Finally, three numerical examples are illustrated to verify the effectiveness of the proposed approach. 相似文献
20.
This study examines how libraries within college and university settings in the United States have dealt with the influx of patron mobile telephone use. We contacted 150 colleges and universities throughout the United States and received 87 responses. These institutions were ranked by US News and World Report in their 2006 Edition of “America’s Best Colleges;” we sampled from their list stratified within the following categories: “top public universities;” “best liberal arts colleges;” “fourth tier liberal arts colleges;” “best national universities;” and “fourth tier national universities.” We found that those college and university libraries adopt an array of stances when approaching cell phone use within their library facilities. These approaches include structured guidelines that specifically address cell phone use posted on the library website, signs displayed throughout the library barring cell phone use, and signage that provides patrons with a list of areas in which use is permitted. Interestingly, we found that several libraries lack any kind of mobile phone policy and instead, assume all patrons will behave in a proper way. 相似文献