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Intuitive Understanding (intuitive + understanding)
Selected AbstractsA perturbation analysis of harmonic generation from saturated elements in power systemsELECTRICAL ENGINEERING IN JAPAN, Issue 4 2010Teruhisa Kumano Abstract Nonlinear phenomena such as saturation of magnetic flux have considerable effects in power systems analysis. It is reported that a failure in a real 500-kV system triggered islanding operation, where resultant even harmonics caused malfunctions in protective relays. It is also reported that the major origin of this wave distortion is nothing but unidirectional magnetization of the transformer iron core. Time simulation is widely used today to analyze phenomena of this type, but it has basically two shortcomings. One is that the time simulation takes too much computing time in the vicinity of inflection points in the saturation characteristic curve because certain iterative procedures such as N-R (Newton,Raphson) must be used and such methods tend to be caught in an ill-conditioned numerical hunting. The other is that such simulation methods sometimes do not aid an intuitive understanding of the studied phenomenon because all of the nonlinear equations are treated in matrix form and are not properly divided into understandable parts, as is done in linear systems. This paper proposes a new computation scheme that is based on the so-called perturbation method. Magnetic saturation of iron cores in a generator and a transformer are taken into account. The proposed method has a special feature to deal with the first shortcoming of the N-R-based time simulation method stated above. The proposed method does not use an iterative process to reduce the equation residue, but uses perturbation series, so that it is free of the ill-conditioning problem. The user need only calculate the perturbation terms one by one until the necessary accuracy is attained. In a numerical example treated in the present paper, first-order perturbation can achieve reasonably high accuracy, which means very fast computing time. In a numerical study, three nonlinear elements are considered. The calculation results are almost identical to the conventional N-R-based time simulation, which shows the validity of the method. The proposed method can be effectively used in screening where many case studies are needed. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 35,42, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20895 [source] Modelling of source-coupled logic gatesINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2002M. Alioto Abstract In this paper, the modelling of CMOS SCL gates is addressed. The topology both with and without output buffer is treated, and the noise margin as well as propagation delay performance are analytically derived, using standard BSIM3v3 model parameters. The propagation delay model of a single SCL gate is based on proper linearization of the circuit and the assumption of a single-pole behaviour. To generalize the results obtained to cascaded gates, the effect of the input rise time and the loading effect of an SCL gate are discussed. The expressions obtained are simple enough to be used for pencil-and-paper evaluations and are helpful from the early design phases, as they relate SCL gates performance to design and process parameters, allowing the designer to gain an intuitive understanding of performance dependence on design parameters and technology. The model has been validated by comparison with extensive simulations using a 0.35-µm CMOS process. The model agrees well with the simulated results, since in realistic cases the difference is less than 20% both for noise margin and delay. Therefore, the model proposed can be profitably used for pencil-and-paper evaluations and for computer-based timing analysis of complex SCL circuits. Copyright © 2002 John Wiley & Sons, Ltd. [source] Supporting scientific discovery learning in a simulation environmentJOURNAL OF COMPUTER ASSISTED LEARNING, Issue 1 2003D.J. Reid Abstract Until recent times, most studies on supporting simulation-based scientific discovery learning adopted the ad hoc strategies-oriented approach. This paper makes a systematic analysis of the internal conditions of scientific discovery learning to propose a triple scheme for learning support design that includes interpretative support (IS), experimental support (ES), and reflective support (RS). The experiment was conducted with 78 students (aged from 12 to 13 years) to examine the effects of the IS and ES using a 2x2 between-subjects design. The main results were: significant effects were observed for IS on the post-test of intuitive understanding, flexible application and knowledge integration; no main effect was demonstrated for ES, and there was a marginally significant interactive effect for ES and IS on the intuitive understanding test. A process analysis showed that the successful learners had designed more well-controlled experiments than the failing ones. Learning support in a simulation environment should be directed toward the three perspectives to invite meaningful, systematic and reflective discovery learning. [source] Statistical determination of diagnostic species for site groups of unequal sizeJOURNAL OF VEGETATION SCIENCE, Issue 6 2006Lubomír Tichy Abstract Aim: Concentration of species occurrences in groups of classified sites can be quantified with statistical measures of fidelity, which can be used for the determination of diagnostic species. However, for most available measures fidelity depends on the number of sites within individual groups. As the classified data sets typically contain site groups of unequal size, such measures do not enable a comparison of numerical fidelity values of species between different site groups. We therefore propose a new method of measuring fidelity with presence/absence data after equalization of the size of the site groups. We compare the properties of this new method with other measures of statistical fidelity, in particular with the Dufrêne-Legendre Indicator Value (IndVal) index. Methods: The size of site groups in the data set is equalized, while relative frequencies of species occurrence within and outside of these groups are kept constant. Then fidelity is calculated using the phi coefficient of association. Results: Fidelity values after equalization are independent of site group size, but their numerical values vary independently of the statistical significance of fidelity. By changing the size of the target site group relative to the size of the entire data set, the fidelity measure can be made more sensitive to either common or rare species. We show that there are two modifications of the IndVal index for presence/absence data, one of which is also independent of the size of site groups. Conclusion: The phi coefficient applied to site groups of equalized size has advantages over other statistical measures of fidelity based on presence/absence data. Its properties are close to an intuitive understanding of fidelity and diagnostic species in vegetation science. Statistical significance can be checked by calculation of another fidelity measure that is a function of statistical significance, or by direct calculation of the probability of observed species concentrations by Fisher's exact test. An advantage of the new method over IndVal is its ability to distinguish between positive and negative fidelity. One can also weight the relative importance of common and rare species by changing the equalized size of the site groups. [source] The organizational influence of the Chief Technology OfficerR & D MANAGEMENT, Issue 4 2008John W. Medcof The proposition that the Chief Technology Officer's (CTO) primary bases for power and influence are in technical expertise and position power is critically analyzed from the perspective of upper echelons research. This fresh perspective suggests that CTOs who aspire to have significant influence in their organizations should also build their power bases on broad knowledge of the firm and its environment, a network of personal relationships inside and outside the firm, ownership position in the firm, and intuitive understanding of the business. The CEO's leadership style can also enhance or curtail the influence of the CTO. Research and managerial implications are drawn. [source] A molecular viewer for the analysis of TLS rigid-body motion in macromoleculesACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2005Jay Painter TLS (translation/libration/screw) models describe rigid-body vibrational motions of arbitrary objects. A single-group TLS model can be used to approximate the vibration of an entire protein molecule within a crystal lattice. More complex TLS models are broadly applicable to describing inter-domain and other internal vibrational modes of proteins. Such models can be derived and refined from crystallographic data, but they can also be used to describe the vibrational modes observed through other physical techniques or derived from molecular dynamics. The use of TLS models for protein motion has been relatively limited, partly because the physical meaning of the refined TLS parameters is not intuitive. Here, a molecular viewer, TLSView, is introduced using OpenGL and based on the mmLib library for describing and manipulating macromolecular structural models. This visualization tool allows an intuitive understanding of the physical significance of TLS models derived from crystallographic or other data and may be used as an interactive tool to display and interpret inter-domain or other motions in protein structural models. TLSView may also be used to prepare, analyze and validate TLS models for crystallographic refinement. [source] Holistic trajectories: a study of combined employment, housing and family careers by using multiple-sequence analysisJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2007Gary Pollock Summary., Social science applications of sequence analysis have thus far involved the development of a typology on the basis of an analysis of one or two variables which have had a relatively low number of different states. There is a yet unexplored potential for sequence analysis to be applied to a greater number of variables and thereby a much larger state space. The development of a typology of employment experiences, for example, without reference to data on changes in housing, marital and family status is arguably inadequate. The paper demonstrates the use of sequence analysis in the examination of multivariable combinations of status as they change over time and shows that this method can provide insights that are difficult to achieve through other analytic methods. The data that are examined here provide support to intuitive understandings of clusters of common experiences which are both life course specific and related to socio-economic factors. Housing tenure is found to be of key importance in understanding the holistic trajectories that are examined. This suggests that life course trajectories are sharply differentiated by experience of social housing. [source] | ||||||||||