Current/voltage-mode universal filter using FTFNs     

Mohd Amin Malik 《Journal of The Franklin Institute》2010,347(2):523-532

A new configuration realizing current/voltage-mode (CM/VM) universal filter using two four terminal floating nullors (FTFN) and four passive components is presented. The current-mode configuration has single input and three outputs and realises simultaneously lowpass (LP), bandpass (BP) and highpass (HP) responses from which allpass (AP) and notch functions can also be implemented. The voltage-mode filter has three inputs and two outputs and can be configured to realise all the five filtering functions. The circuit in current-mode uses grounded capacitors which are ideal for monolithic integration. Besides using a bare minimum number of passive components, the topology enjoys low active and passive sensitivity figures. Experimental and PSPICE simulation results are also included.  相似文献   

Developing and acting upon one's conception of the nature of science: A follow‐up study     

Randy L. Bell  Norman G. Lederman  Fouad Abd‐El‐Khalick 《科学教学研究杂志》2000,37(6):563-581

This study aimed to delineate the factors mediating the translation of preservice teachers' conceptions of the nature of science into instructional planning and classroom practice. Additionally, the study assessed the influence of temporally separating teaching preservice teachers about the nature of science and teaching them how to address it instructionally. This latter intervention was based on the results of a previous investigation. Prior to student teaching, the 13 participants responded to an open‐ended questionnaire designed to assess conceptions of the nature of science. Throughout student teaching, daily lesson plans, classroom videotapes, portfolios, and supervisors' weekly clinical observation notes were collected and searched for explicit instances of nature of science planning and/or instruction. Following student teaching, participants were interviewed to validate their responses to the open‐ended questionnaire, identify factors that mediate the translation of their conceptions of the nature of science into classroom teaching, and explicate their pedagogical preferences for teaching the nature of science. Participants possessed adequate understanding of several aspects of the nature of science and, contrary to the results of the earlier investigation, most did not conflate the nature of science with science processes. Furthermore, several participants explicitly addressed some aspects of the nature of science during classroom instruction. Participants, however, failed to include the nature of science among their instructional objectives and did not make a concerted effort to assess student understandings. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 563–581, 2000  相似文献