20: Breaking Down Barriers to the Use of Technology for Teaching in Higher Education

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138866/1/tia200516.pd

Emulsion Electrospinning of Polytetrafluoroethylene (PTFE) Nanofibrous Membranes for High-Performance Triboelectric Nanogenerators

Electrospinning is a simple, versatile technique for fabricating fibrous nanomaterials with the desirable features of extremely high porosities and large surface areas. Using emulsion electrospinning, polytetrafluoro­ethylene/polyethene oxide (PTFE/PEO) membranes were fabricated, followed by a sintering process to obtain pure PTFE fibrous membranes, which were further utilized against a polyamide 6 (PA6) membrane for vertical contact-mode triboelectric nanogenerators (TENGs). Electrostatic force microscopy (EFM) measurements of the sintered electrospun PTFE membranes revealed the presence of both positive and negative surface charges owing to the transfer of positive charge from PEO which was further corroborated by FTIR measurements. To enhance the ensuing triboelectric surface charge, a facile negative charge-injection process was carried out onto the electrospun (ES) PTFE subsequently. The fabricated TENG gave a stabilized peak-to-peak open-circuit voltage (<i>V</i>_oc) of up to ∼900 V, a short-circuit current density (<i>J</i>_sc) of ∼20 mA m^–2, and a corresponding charge density of ∼149 μC m^–2, which are ∼12, 14, and 11 times higher than the corresponding values prior to the ion-injection treatment. This increase in the surface charge density is caused by the inversion of positive surface charges with the simultaneous increase in the negative surface charge on the PTFE surface, which was confirmed by using EFM measurements. The negative charge injection led to an enhanced power output density of ∼9 W m^–2 with high stability as confirmed from the continuous operation of the ion-injected PTFE/PA6 TENG for 30 000 operation cycles, without any significant reduction in the output. The work thus introduces a relatively simple, cost-effective, and environmentally friendly technique for fabricating fibrous fluoropolymer polymer membranes with high thermal/chemical resistance in TENG field and a direct ion-injection method which is able to dramatically improve the surface negative charge density of the PTFE fibrous membranes

Expanding the portfolio of tribo-positive materials: aniline formaldehyde condensates for high charge density triboelectric nanogenerators

The rapid uptake of energy harvesting triboelectric nanogenerators (TENGs) for self-powered electronics requires the development of high-performance tribo-materials capable of providing large power outputs. This work reports on the synthesis and use of aniline formaldehyde resin (AFR) for energy-harvesting applications. The facile, acidic-medium reaction between aniline and formaldehyde produces the aniline-formaldehyde condensate, which upon an in-vacuo high temperature curing step provides smooth AFR films with abundant nitrogen and oxygen surface functional groups which can acquire a tribo-positive charge and thus endow AFR with a significantly higher positive tribo-polarity than the existing state-of-art polyamide-6 (PA6). A TENG comprising of optimized thin-layered AFR against a polytetrafluoroethylene (PTFE) film produced a peak-to-peak voltage of up to ~1,000 V, a current density of ~65 mA m⁻², a transferred charge density of ~200 μC m⁻² and an instantaneous power output (energy pulse) of ~11 W m⁻² (28.1 μJ cycle⁻¹), respectively. The suitability of AFR was further supported through the Kelvin probe force microscopy (KPFM) measurements, which reveal a significantly higher average surface potential value of 1.147 V for AFR as compared to 0.87 V for PA6 and a step-by-step increase of the surface potential with the increase of energy generation cycles. The work not only proposes a novel and scalable mouldable AFR synthesis process but also expands with excellent prospects, the current portfolio of tribo-positive materials for triboelectric energy harvesting applications

Designing web-based instruction: A human-computer interaction perspective

This item is not the definitive copy. Please use the following citation when referencing this material: Dillon, A. and Zhu, E. (1997) Designing Web Based Instruction: A Human-Computer Interaction (HCI) Perspective. In: Khan (ed.) Web-Based Instruction. Englewood Cliffs. NJ: Educational Technology Publications, 221-225. Introduction: The general interest in the World Wide Web (WWW) as a medium for sharing and distributing textual and graphic information has brought about an increasing number of instruction-oriented web sites and web-based instructional pages. These range from offering supplemental (or even duplicate) instructional materials to students on campus to providing opportunities for off-campus individuals to complete courses via WWW. This chapter briefly discusses the design of web-based instruction from an HCI perspective, raising issues which instructors and designers need to consider in the design of web-based instruction, and suggesting ways in which instructors and designers can build optimal web instructional sites and pages

Data_Sheet_1_Development and validation of Child-Friendly School Environment Questionnaire from Chinese culture.pdf

In the context of building Child-Friendly Cities in China, child-friendly school environments are considered as having a profound impact on children’s development and growth. This study presents the development and validation of the Child-Friendly School Environment Questionnaire for assessing a child-friendly school environment. Utilizing open-ended questions and interviews, an initial questionnaire on the child-friendly school environment was compiled. An exploratory factor analysis of the preliminary test results with 696 primary school children in grades three to six was conducted to refine the questionnaire into a formal 19-item questionnaire. Subsequently, a confirmatory factor analysis was performed to analyze the evaluation results of 807 primary school children in grades three to six. The results indicated that a child-friendly school environment is a multi-dimensional construct encompassing Environment Friendly, Teaching Friendly, Peer Friendly, and Children Participation, with good reliability and validity. The promising outcomes of this study suggest that the Child-Friendly School Environment Questionnaire can be widely used as a powerful evaluation tool for the child-friendly school education practice in the future.</p

Quantized impedance dealing with the damping behavior of the one-dimensional oscillator

A quantized impedance is proposed to theoretically establish the relationship between the atomic eigenfrequency and the intrinsic frequency of the one-dimensional oscillator in this paper. The classical oscillator is modified by the idea that the electron transition is treated as a charge-discharge process of a suggested capacitor with the capacitive energy equal to the energy level difference of the jumping electron. The quantized capacitance of the impedance interacting with the jumping electron can lead the resonant frequency of the oscillator to the same as the atomic eigenfrequency. The quantized resistance reflects that the damping coefficient of the oscillator is the mean collision frequency of the transition electron. In addition, the first and third order electric susceptibilities based on the oscillator are accordingly quantized. Our simulation of the hydrogen atom emission spectrum based on the proposed method agrees well with the experimental one. Our results exhibits that the one-dimensional oscillator with the quantized impedance may become useful in the estimations of the refractive index and one- or multi-photon absorption coefficients of some nonmagnetic media composed of hydrogen-like atoms