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A simple iterative technique, which is free of certain shortcomings of the previous methods, is proposed for the approximation of large linear systems by a lower- order model. Here, the measure of the goodness of the approximate model is taken to be the value of the integral-square error between the step responses of the exact and the simplified systems. The proposed technique consists of a two-step iterative scheme. In the first step, the optimum residues are obtained by the minimization of the objective function, while the poles (or eigenvalues) are kept constant. In the second step, the poles are optimized while the residues remain fixed. This procedure is continued cyclically until the objective function is satisfactorily minimized. The necessary and sufficient conditions for existence of an optimum are satisfied in each step. The residues, poles and objective functions converge monotonically. The resulting reduced-order model obtained by this method is stable if the original system is stable. The method can also be applied to systems with repeated poles and to multivariable systems. The results are superior to those obtained previously in the steady-state, the point-by-point transient response, and the value of the integral-square error. Illustrative examples are presented. 相似文献
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The purpose of this study was to explore what salient characteristics can be found in some university teachers＇ approaches to teaching in Finland, Japan and India, and in what ways university teachers in Finland, India and Japan use ICTs （information and communication technologies） in their own teaching. Furthermore, this study aimed to investigate what ICT applications these same teachers use in their teaching. The data were collected via an electronic survey and interviews. The participants （N=21） were university teachers from Finland （N=8）, Japan （N=I0） and India （N=3）. Their approaches to teaching were explored by applying the ATI （approaches to teaching inventory） and its modified version focusing on the use of ICTs in teaching. The study reported in this paper was a pilot study, thus the results are based on the limited number of respondents. The ATI and ATI ICT subscales and ICT inventory applied in this study have been confirmed to be valid. The university teachers in Japan and Finland differed in their approaches to teaching： The Finnish teachers scored higher on the CCSF （conceptual change orientated, student-focused） approach to teaching than the Japanese teachers, while the Japanese teachers scored higher on the ITTF （information transmitting, teacher-focused） approach to teaching. Two Indian teachers were classified as having a teacher-focused approach to teaching, while the third was classified as having a student-focused approach to teaching. The teachers＇ differences in their use of ICTs related more to their disciplinary status than to their cultural background. 相似文献
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A two-step iterative method (1,2) for a reduction in the order of linear continuous-time systems, given in the state equation or the transfer function, is extended to reduce discrete-time systems. The method requires the optimization of the residues and eigenvalues (or poles) belonging to an objective function. The objective function to be minimized is chosen as the finite sum of the squares of the error between the step responses of the reduced model and the original system. This scheme is continued cyclically until the objective function is satisfactorily minimized. By investigating the initial selection of the eigenvalues in the reduced-order model, it is found that the dominant eigenvalues of the original system give a good approximation. Further, the resulting model is always stable, assuming the original system is stable. As shown in a numerical example, the proposed method is superior to the other methods of model reduction in both steady-state and transient responses, and in the value of the sum of the squares of the error. 相似文献
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Megan N. Shoji Anna R. Haskins David E. Rangel Kia N. Sorensen 《Early childhood research quarterly》2014
Scholars suggest that racial/ethnic and class disparities in school-based social capital contribute to educational inequalities. Previous studies demonstrate that social capital (relations of trust, mutual expectations, and shared values) between parents and schools supports children's development. Yet we know little about the emergence of social capital, that is, the processes through which it develops. In this study, we explore mechanisms of social capital emergence in predominantly low-income Latino school communities. We draw data from an experimental study that manipulated social capital through an after-school family engagement program. Based on interviews and focus groups with participating parents, teachers, and program staff in two elementary schools, we identified four types of interactions that act as mechanisms of social capital emergence: (1) responsive communication; (2) reciprocal communication; (3) shared experiences; and (4) institutional linkage. The article connects these mechanisms to theoretically linked sources of social capital and discusses implications for theory and practice. 相似文献
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A sequential and high-throughput single-cell manipulation system for a large volume of cells was developed and the successive manipulation for single cell involving single-cell isolation, individual labeling, and individual rupture was realized in a microhydrodynamic flow channel fabricated by using two-dimensional simple flow channels. This microfluidic system consisted of the successive single-cell handlings of single-cell isolation from a large number of cells in cell suspension, labeling each isolated single cell and the lysate extraction from each labeled single cell. This microfluidic system was composed of main channels, cell-trapping pockets, drain channels, and single-cell content collection channels which were fabricated by polydimethylsiloxane. We demonstrated two kinds of prototypes for sequential single-cell manipulations, one was equipped with 16 single-cell isolation pockets in microchannel and the other was constructed of 512 single-cell isolation pockets. In this study, we demonstrated high-throughput and high-volume single-cell isolation with 512 pocket type device. The total number of isolated single cells in each isolation pocket from the cell suspension at a time was 426 for the cell line of African green monkey kidney, COS-1, and 360 for the rat primary brown preadipocytes, BAT. All isolated cells were stained with fluorescence dye injected into the same microchannel successfully. In addition, the extraction and collection of the cell contents was demonstrated using isolated stained COS-1 cells. The cell contents extracted from each captured cell were individually collected within each collection channel by local hydrodynamic flow. The sequential trapping, labeling, and content extraction with 512 pocket type devices realized high-throughput single-cell manipulations for innovative single-cell handling, feasible staining, and accurate cell rupture. 相似文献
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F.F. Shoji 《Journal of The Franklin Institute》1982,313(5):267-271
This brief communication establishes a two-step iterative algorithm based on the orthogonal projection for reducing order of the high-order system transfer function or state variable equations. A two-step iterative algorithm which has been developed by the authors (1) consists of the residue and pole (or eigenvalue) optimization with respect to the objective function. Here, the optimum residues in the first step can be determined by using the reciprocal basis in the projection theorem. The reciprocal basis allows one to avoid performing the Grammian inversion. Selecting the new basis, the optimum poles in the second step can be also applied for the orthogonal projection. Although the resulting reduced-order models derived from this geometrical point of view are consistent with models of a two-step iterative algorithm, the algorithm is thus a computationally much simpler way to derive the formula. 相似文献
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