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《Computers & chemistry》1997,21(2):83-87
A program in Fortran has been created on the basis of programs LMDIF taken from the Minpack Library and also from the book Numerical Recipes in Fortran [Press et al. (1992), 2nd edn, Cambridge University Press, Cambridge]. The program permits the calculation of the structural parameters of adsorbents, including fractal dimension, and is based on the extension of the potential theory of adsorption (DA adsorption) given by Dubinin and Astakhov (1971) [Izv. AN. SSSR, Ser Khim. 5, 11–17]. To minimize the number of approximated parameters the program describes the cases where n (the parameter of the DA adsorption isotherm equation) can be different or equal to 2, but assumed “a priori”. In this case the number of parameters is equal to 4. However, for one system only was a reliable value of the fractal dimension obtained: the instance of adsorbate-adsorbent (zeolite NaA-water). For this reason we include a supplement to the program, which allows the calculation of structural parameters for the adsorbent on the basis of a five-parameter equation (N = 5) where n is approximated. In this case all obtained fractal dimension values are reliable and these suggest that among the zeolites investigated by us the deviation from planarity decreases in the order CaA > NaA > MgA > MgY > NH4Y.  相似文献   

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An algorithm to compute the curve skeleton of 3D objects in voxel images is presented. The skeleton is stable under isometric transformations of the object, since the algorithm is based on the use of the 〈3, 4, 5〉 weighted distance transform, which is a good approximation of the Euclidean distance transform. The 〈3, 4, 5〉 weighted distance transform is used both to identify suitable anchor points, and to efficiently check object voxels according to their distance to the background. The curve skeleton is symmetrically placed within the object, is topologically equivalent to the object, is unit-wide and provides a satisfactory representation of the object. Though the size of the object reconstructed from the curve skeleton via the reverse distance transformation is not as thick as that of the input, shape information is mostly retained by the skeleton, since all regions perceived as significant in the input can still be found in the reconstructed object.  相似文献   

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ity (≥ 9), high Ki-67 labeling index (≥ 42), and positivity of MUC1, cathepsin D, and MMP-7 showed a significantly high incidence of lymph node metastasis. Multivariate analysis revealed that hig  相似文献   

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Abstract

This paper describes a project designed to improve planning procedures, through the introduction of microcomputers into the Central Planning Division, Ministry of Finance, Government of Meridian. The first section places the logic of the computerization project within the context of a wider programme to upgrade skills and methodologies in Meridian, and the paper then discusses the background to the computerization proposal by way of explaining its aims and objectives.

The third section focuses on technical issues, and examines the particular virtues of microcomputers in this type of centralized planning division. The hardware, software and training requirements are considered, and the schedule and milestones of this particular project explained. Organizational issues are then examined, from which the sources of many of the problems encountered in this project can be identified. Actual progress to date is described in the light of both technical and organizational issues, and an attempt made to assess the effectiveness of the project as a whole. The paper ends by pointing to some broader conclusions on the potential of microcomputers in development planning and to issues which critically determine the effectiveness of their value in central planning agencies, such as that described here.  相似文献   

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In a key article (Walsham & Sahay, 2005) outlining research on information systems in developing countries and suggesting potential areas for future research, a notable omission was the issue of gender and gender relations. In this article, we draw on the substantial gender and development literature to demonstrate the centrality of gender to our understanding of information systems (IS) in developing countries. In particular, we consider the relationship among gender, information and communication technologies (ICTs), and globalization to illustrate how changes in the global economy both impact on and are influenced by changing gender identities and roles. © 2008 Wiley Periodicals, Inc.  相似文献   

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While the media industry may consider credibility its most valuable asset, scholars suggest there is a potential “dark side” to credibility: Perceptions of credibility of a source lead to selective exposure and selective avoidance, and both lead to increased fragmentation and polarization of social and political views. The link between credibility and selective exposure and avoidance has not received much academic attention, therefore this study employed a survey of politically interested Internet users during the 2008 presidential campaign to test the influence of credibility and reliance on selective exposure and avoidance after controlling for demographic and political factors. This study found little evidence of a dark side to credibility. Respondents who judge blogs as credible search for information that supports their point of view, as well as challenges their opinions.  相似文献   

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This research particularly aims to investigate how the individual differences in gender, age, and internet experience influence citizens’ trust in e-government’s adoption. The findings of the study revealed that females are confident and have a more positive evaluation of online services compared to males. Interestingly, this study found that old people display greater trust in e-government as compared to the levels of trust reported by younger people. The results also show that internet experience influences citizens’ trust positively.  相似文献   

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The teaching-learning process may have several obstacles; one of those would be a cultural situation of students but also the ICT (information and communication technologies) resource distribution per children. When we refer to cultural situation, we mean the language or dialect that they speak. In the state of Puebla, Mexico, there are primary schools in which courses are taught to students who do not speak Spanish and they only speak their own dialect. On the other hand, the use of information and communication technologies in primary schools in Puebla is a fact but a main concern in schools is that the languages in which are operated is Spanish. The present article will also deal with the distribution of enciclomedia sets per children population in the 217 communities of the state of Puebla. To analyze this situation, we find that turns out to be very important and with a negative effect on both the implementation and acceptance of a multimedia program in these schools, generating a technological gap between students. The government efforts are being decimated because of this cultural divide prevalent in many communities in the state of Puebla, Mexico.  相似文献   

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Radio frequency identification (RFID) technology dramatically increases the ability of the organization to acquire a vast array of data about the location and properties of any entity that can be physically tagged and wirelessly scanned within certain technical limitations. RFID can be applied to a variety of tasks, structures, work systems and contexts along the value chain, including business-to-business logistics, internal operations, business-to-consumer marketing, and after-sales service applications. As industry adoption of RFID increases there is an emerging interest by academic researchers to engage in scholarly investigation to understand how RFID relates to mobility, organizational and systems technologies (MOST). In this paper, we explore RFID and propose a research agenda to address a series of broad research questions related to how RFID technology: (1) is developed, adopted, and implemented by organizations; (2) is used, supported, and evolved within organizations and alliances; and (3) impacts individuals, business processes, organizations, and markets. As with many technological innovations, as the technical problems associated with implementing and using RFID are addressed and resolved, the managerial and organizational issues will emerge as critical areas for IS research.
Frederick J. RigginsEmail:
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Treating plant dynamics as an ideal integrator chain disturbed by the total disturbance is the hallmark of active disturbance rejection control (ADRC). To interpret its effectiveness and success, to explain why so many vastly different dynamic systems can be treated in this manner, and to answer why a detailed, accurate, and global mathematical model is unnecessary, is the target of this paper. Driven by a motivating example, the notions of normality and locality are introduced. Normality shows that, in ADRC, the plant is normalized to an integrator chain, which is called local nominal model and locally describes the plant’s frequency response in the neighborhood of the expected gain crossover frequency. Locality interprets why ADRC can design the controller only with the local information of the plant. With normality and locality, ADRC can be effective and robust, and obtain operational stability discussed by T. S. Tsien. Then viewing proportional-integral-derivative (PID) control as a low-frequency approximation of second-order linear ADRC, the above results are extended to PID control. A controller design framework is proposed to obtain the controller in three steps: (1) choose an integrator chain as the local nominal model of the plant; (2) select a controller family corresponding to the local nominal model; and (3) tune the controller to guarantee the gain crossover frequency specification. The second-order linear ADRC and the PID control are two special cases of the framework.  相似文献   

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To introduce this special issue of shared and cooperative control, we will look into history of tools in cooperation between humans and aim to unify the plethora of related concepts and definitions that have been proposed in recent years, such as shared control, human–machine cooperation and cooperative guidance and control. Concretely, we provide definitions to relate these concepts and sketch a unifying framework of shared and cooperative control that sees the different concepts as different perspectives or foci on a common design space of shared intentionality, control and cooperation between humans and machines. One working hypothesis which the article explores is that shared control can be understood as cooperation at the control layer, while human–machine cooperation can include shared control, but can also extend towards cooperation at higher layers, e.g., of guidance and navigation, of maneuvers and goals. The relationship between shared control and human–machine cooperation is compared to the relationship between the sharp, pointy tip and the (blunt) shaft of a spear. Shared control is where cooperation comes sharply into effect at the control layer, but to be truly effective it should be supported by cooperation on all layers beyond the operational layer, e.g., on the tactical and strategic layer. A fourth layer addresses the meta-communication about the cooperation and supports the other three layers in a traversal way.

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The NOAA-KLM satellites (NOAA-15 to 18) are the current polar-orbiting operational environmental satellites (POES) that carry the Advanced Very High Resolution Radiometer (AVHRR). This study examines the calibration stability and consistency of all three infrared channels (3.7, 11.0 and 12.0 μm) of AVHRR onboard NOAA-15 to 18. The short-term stability is examined from variations of the scan-by-scan gain response, while the long-term stability and calibration consistency are examined by tracking the trends of gain response and measured scene brightness temperatures. The relative differences of observed scene brightness temperatures among NOAA-15 to 18 AVHRR are determined using MODIS as a transfer radiometer based on observations from simultaneous nadir overpasses (SNO). Results show that variations of the scan-to-scan gain responses are within 0.10% under normal operational conditions, while long-term gain changes over six years from 2001 to 2006 vary from 2 to 4% depending on channel. Long-term trending results show that total six-year drifts in observed brightness temperature from NOAA-15 to 18 AVHRR are less than 0.5 K for a given scene temperature in the 250 to 270 K range for the 3.7, 11.0 and 12.0 μm channels, respectively. The calibration consistency is examined for a scene temperature range of 220 to 290 K. The temperature biases among NOAA-16 to 18 AVHRR are within ±0.5 K for the 11.0 and 12.0 μm channels. For NOAA-15 AVHRR, biases of –2.0 K at 11.0 μm and –1.5 K at 12.0 μm are found in comparison with others at the low end of the temperature range. For the 3.7 μm channel, relative biases up to a few degrees among NOAA-15 to 18 could be found at low brightness temperatures.  相似文献   

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