A variational energy approach for electromechanical analysis of thick piezoelectric beam

INTRODUCTION Piezoelectricity is an electromechanical phe- nomenon which couples elasticity and electricity through the existence of pressure induced electrical field or electric induced stress field. The piezoelectric materials are usually surface bonded in patches or fully embedded in the host structure, so that the structure becomes a laminated piezoelectric beam. Tzou and Gadre (1989), Lee (1990), Crawly and Lazarus (1991) developed laminated plate models incorporating the piezoelect…     

Assessment of the phase synchronization effect in modal testing during operation

The impact-synchronous modal analysis (ISMA), which uses impact-synchronous time averaging (ISTA), allows modal testing to be performed during operation. ISTA is effective in filtering out the non-synchronous cyclic load component, its harmonics, and noises. However, it was found that at operating speeds that coincide with the natural modes, ISMA would require a high number of impacts to determine the dynamic characteristics of the system. This finding has subsequently reduced the effectiveness and practicality of ISMA. Preservation of signatures during ISTA depends on the consistency of their phase angles on every time block but not necessarily on their frequencies. Thus, the effect of phase angles with respect to impact is seen to be a very important parameter when performing ISMA on structures with dominant periodic responses due to cyclic load and ambient excitation. The responses from unaccounted forces that contain even the same frequency as that contained in the response due to impact are diminished with the least number of impacts when the phase of the periodic responses is not consistent with the impact signature for every impact applied. The assessment showed that a small number of averages are sufficient to eliminate the non-synchronous components with 98.48% improvement on simulation and 95.22% improvement on experimental modal testing when the phase angles with respect to impact are not consistent for every impact applied.     

Development of instructional design strategies for integrating an online support system for creative problem solving into a University course

Asia Pacific Education Review - This study examined three cases in which an online support system was utilized to enhance creative problem solving (CPS) in a higher education setting. This study...     

Science learning and a Sense of Place in a Urban Middle School

This paper offers an analysis into low-income, urban middle school children's sense of place and what and how their sense of place matters in science learning by focusing on the following questions: In what ways is students' sense of place leveraged in a science classroom? How does the content and context of science class shape how students leverage their sense of place? What learning opportunities emerge when sense of place is leveraged in class? Drawing from an ethnographic investigation into an environmental statistics class in a mid-sized public middle school, we examined sense of place events from their source, process, and outcome perspectives. Our findings are presented from two aspects of sense of place events, (1) characterizing students' sense of place by exploring sources of the sense of place events, and (2) examining processes of how students' sense of place is being leveraged in the episodes. We also examine two kinds of tensions that emerge in the class when sense of place is leveraged by students and acknowledged by the teacher: epistemological tensions (related to what the students are learning) and procedural tensions (related to how they are learning).     

Critical thinking,social education and the curriculum: foregrounding a social and relational epistemology

In this article, I examine the extent to which, given how critical thinking has been most commonly conceptualised and taught in schools, the subject indeed develops modes of thinking, relating and reasoning that allow individuals to collectively work towards the appreciation and solution of social problems. In the first section, I outline a number of perspectives among social studies researchers and educators that demonstrate the importance of developing critical thinking capacities in students. This is followed by, in the next section, a close examination of two widely popular approaches through which critical thinking is taught – one in the general school curriculum and the other within social studies lessons. I argue that in their current forms and for a number of reasons these understandings of critical thinking fall short of developing the social and relational dimensions of thinking that are more than a little necessary in fulfilling the raison d’être of the subject. Towards this end, the final section presents a social epistemological framework for the teaching of critical thinking in the school curriculum, highlights a number of principles of its application and provides some examples of its use in classrooms.     

Chaotification of a class of linear switching systems based on a Shilnikov criterion

This paper proposes an approach for constructing and generating chaos from a class of three-dimensional linear switching systems via a heteroclinic loop based on the Shilnikov criterion. First, the existence of a switching rule for the system is derived by utilizing the Shilnikov heteroclinic criterion. Then a general design philosophy and its procedure of switching rule are provided to ensure that the proposed approach is applicable to engineering. Two numerical examples are presented to validate the main principle and the implementability of the scheme. Theoretical analysis and numerical simulation are used to demonstrate the feasibility and effectiveness of developed techniques.     

Dielectrophoretic capture voltage spectrum for measurement of dielectric properties and separation of cancer cells

In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius-Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis.     

Improving self-regulation, learning strategy use, and achievement with metacognitive feedback

Comprehension of science topics occurs when learners meaningfully generate relationships and conceptions about what they read. In this generation process, learners’ cognitive and metacognitive regulation is one of the most critical factors influencing learning. However, learners are not always successful in regulating their own learning, especially in computer-based learning environments (CBLEs) where they are alone. Based on this rationale, the present study was designed to examine the effects of two scaffolding strategies—generative learning strategy prompts and metacognitive feedback—on learners’ comprehension and self-regulation while learning the human heart system in a CBLE. Participants were 223 undergraduate student volunteers. Structural Equation Modeling (SEM) was employed to conceptualize and empirically test a model that explains mediating processes among variables. Results revealed that the combination of generative learning strategy prompts with metacognitive feedback improved learners’ recall and comprehension by enhancing learners’ self-regulation and better use of highlighting and summarizing as generative learning strategies.