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Two wires exit a black box that has three exposed light bulbs connected together in an unknown configuration. The task for students is to determine the circuit configuration without opening the box. In the activity described in this paper, we navigate students through the process of making models, developing and conducting experiments that can support or falsify models, and confronting ways of distinguishing between two different models that make similar predictions. We also describe a twist that forces students to confront new phenomena, requiring revision of their mental model of electric circuits. This activity is designed to mirror the practice of science by actual scientists and expose students to the “messy” side of science, where our simple explanations of reality often require expansion and/or revision based on new evidence. The purpose of this paper is to present a simple classroom activity within the context of electric circuits that supports students as they learn to test hypotheses and refine and revise models based on evidence.
J. Christopher Moore; Louis J. Rubbo. Modeling Hidden Circuits: An Authentic Research Experience in One Lab Period. The Physics Teacher 2016, 54, 423 -426.
AMA StyleJ. Christopher Moore, Louis J. Rubbo. Modeling Hidden Circuits: An Authentic Research Experience in One Lab Period. The Physics Teacher. 2016; 54 (7):423-426.
Chicago/Turabian StyleJ. Christopher Moore; Louis J. Rubbo. 2016. "Modeling Hidden Circuits: An Authentic Research Experience in One Lab Period." The Physics Teacher 54, no. 7: 423-426.
Visualization is a common and important step in expert-like problem solving across multiple disciplines. Within the context of physics education, significant intervention is often required to develop visualization skills with novice problem solvers. In particular, dynamic multi-body problems require mental models that incorporate multiple objects time-varying in space, which may require significant development of spatial and/or other cognitive abilities. We have investigated student abilities in applying a dynamic visualization to solve a simple multi-body problem and that ability’s correlation with scientific reasoning (SR) cognitive ability as measured by Lawson’s Classroom Test of Scientific Reasoning (LCTSR). A broad population of students (N = 212) attending a regional comprehensive university in the USA were classified into four SR categories based on Piaget’s theory of cognitive development: (1) concrete operational, (2) early transitional, (3) late transitional, and (4) formal operational. A short problem was also administered that required students to construct a dynamic visualization to correctly answer. Specifically, the problem involved a situation where two trains leave opposite stations once per hour. The stations are 3 h apart. The task was to determine how many trains an observer on one of the trains would see during the 3-h trip between stations. Through analysis of expressed student reasoning, we have found that students answering with 3–4 trains typically have built a visualization based on at least one set of trains remaining stationary. Students answering 6–7 trains typically recognize the evolving nature of the problem and construct an appropriate dynamic visualization with both sets of trains in motion. Students struggle to deploy a successful dynamic visualization when classified below formal operational level. Formal operational reasoners within the population succeed almost universally in applying a successful dynamic visualization. This suggests an epistemological threshold may exist, whereby students struggle with constructing dynamic visualizations before reaching a high-formal level of reasoning ability. This has implications for instruction and textbook/classroom problem construction, especially considering that a significant majority of students enrolled in introductory physics courses within our population demonstrate late transitional and below SR levels.
James Christopher Moore; Josip Slisko. Dynamic Visualizations of Multi-body Physics Problems and Scientific Reasoning Ability: A Threshold to Understanding. Springer Proceedings in Physics 2016, 155 -164.
AMA StyleJames Christopher Moore, Josip Slisko. Dynamic Visualizations of Multi-body Physics Problems and Scientific Reasoning Ability: A Threshold to Understanding. Springer Proceedings in Physics. 2016; ():155-164.
Chicago/Turabian StyleJames Christopher Moore; Josip Slisko. 2016. "Dynamic Visualizations of Multi-body Physics Problems and Scientific Reasoning Ability: A Threshold to Understanding." Springer Proceedings in Physics , no. : 155-164.
The photocatalytic activity and stability of thin, polycrystalline ZnO films was studied. The oxidative degradation of organic compounds at the ZnO surface results from the ultraviolet (UV) photo-induced creation of highly oxidizing holes and reducing electrons, which combine with surface water to form hydroxyl radicals and reactive oxygen species. Therefore, the efficiency of the electron-hole pair formation is of critical importance for self-cleaning and antimicrobial applications with these metal-oxide catalyst systems. In this study, ZnO thin films were fabricated on sapphire substrates via direct current sputter deposition of Zn-metal films followed by thermal oxidation at several annealing temperatures (300–1200 °C). Due to the ease with which they can be recovered, stabilized films are preferable to nanoparticles or colloidal suspensions for some applications. Characterization of the resulting ZnO thin films through atomic force microscopy and photoluminescence indicated that decreasing annealing temperature leads to smaller crystal grain size and increased UV excitonic emission. The photocatalytic activities were characterized by UV-visible absorption measurements of Rhodamine B dye concentrations. The films oxidized at lower annealing temperatures exhibited higher photocatalytic activity, which is attributed to the increased optical quality. Photocatalytic activity was also found to depend on film thickness, with lower activity observed for thinner films. Decreasing activity with use was found to be the result of decreasing film thickness due to surface etching.
James C. Moore; Robert Louder; Cody V. Thompson. Photocatalytic Activity and Stability of Porous Polycrystalline ZnO Thin-Films Grown via a Two-Step Thermal Oxidation Process. Coatings 2014, 4, 651 -669.
AMA StyleJames C. Moore, Robert Louder, Cody V. Thompson. Photocatalytic Activity and Stability of Porous Polycrystalline ZnO Thin-Films Grown via a Two-Step Thermal Oxidation Process. Coatings. 2014; 4 (3):651-669.
Chicago/Turabian StyleJames C. Moore; Robert Louder; Cody V. Thompson. 2014. "Photocatalytic Activity and Stability of Porous Polycrystalline ZnO Thin-Films Grown via a Two-Step Thermal Oxidation Process." Coatings 4, no. 3: 651-669.
Ghusoon M. Ali; James C. Moore; Ahmed K. Kadhim; Cody Thompson. Electrical and optical effects of Pd microplates embedded in ZnO thin film based MSM UV photodetectors: A comparative study. Sensors and Actuators A: Physical 2014, 209, 16 -23.
AMA StyleGhusoon M. Ali, James C. Moore, Ahmed K. Kadhim, Cody Thompson. Electrical and optical effects of Pd microplates embedded in ZnO thin film based MSM UV photodetectors: A comparative study. Sensors and Actuators A: Physical. 2014; 209 ():16-23.
Chicago/Turabian StyleGhusoon M. Ali; James C. Moore; Ahmed K. Kadhim; Cody Thompson. 2014. "Electrical and optical effects of Pd microplates embedded in ZnO thin film based MSM UV photodetectors: A comparative study." Sensors and Actuators A: Physical 209, no. : 16-23.
Three methods were used to fabricate ZnO-based room temperature liquid petroleum gas (LPG) sensors having interdigitated metal-semiconductor-metal (MSM) structures. Specifically, devices with Pd Schottky contacts were fabricated with: (1) un-doped ZnO active layers; (2) Pd-doped ZnO active layers; and (3) un-doped ZnO layers on top of Pd microstructure arrays. All ZnO films were grown on p-type Si(111) substrates by the sol-gel method. For devices incorporating a microstructure array, Pd islands were first grown on the substrate by thermal evaporation using a 100 μm mesh shadow mask. We have estimated the sensitivity of the sensors for applied voltage from
Ghusoon M. Ali; Cody V. Thompson; Ali K. Jasim; Isam M. Abdulbaqi; James C. Moore. Effect of Embedded Pd Microstructures on the Flat-Band-Voltage Operation of Room Temperature ZnO-Based Liquid Petroleum Gas Sensors. Sensors 2013, 13, 16801 -16815.
AMA StyleGhusoon M. Ali, Cody V. Thompson, Ali K. Jasim, Isam M. Abdulbaqi, James C. Moore. Effect of Embedded Pd Microstructures on the Flat-Band-Voltage Operation of Room Temperature ZnO-Based Liquid Petroleum Gas Sensors. Sensors. 2013; 13 (12):16801-16815.
Chicago/Turabian StyleGhusoon M. Ali; Cody V. Thompson; Ali K. Jasim; Isam M. Abdulbaqi; James C. Moore. 2013. "Effect of Embedded Pd Microstructures on the Flat-Band-Voltage Operation of Room Temperature ZnO-Based Liquid Petroleum Gas Sensors." Sensors 13, no. 12: 16801-16815.
We present a phenomenological model for the photocurrent transient relaxation observed in ZnO-based metal-semiconductor-metal (MSM) planar photodetector devices based on time-resolved surface band bending. Surface band bending decreases during illumination, due to migration of photogenerated holes to the surface. Immediately after turning off illumination, conduction-band electrons must overcome a relatively low energy barrier to recombine with photogenerated holes at the surface; however, with increasing time, the adsorption of oxygen at the surface or electron trapping in the depletion region increases band bending, resulting in an increased bulk/surface energy barrier that slows the transport of photogenerated electrons. We present a complex rate equation based on thermionic transition of charge carriers to and from the surface and numerically fit this model to transient photocurrent measurements of several MSM planar ZnO photodetectors at variable temperature. Fitting parameters are found to be consistent with measured values in the literature. An understanding of the mechanism for persistent photoconductivity could lead to mitigation in future device applications.
James C. Moore; Cody V. Thompson. A Phenomenological Model for the Photocurrent Transient Relaxation Observed in ZnO-Based Photodetector Devices. Sensors 2013, 13, 9921 -9940.
AMA StyleJames C. Moore, Cody V. Thompson. A Phenomenological Model for the Photocurrent Transient Relaxation Observed in ZnO-Based Photodetector Devices. Sensors. 2013; 13 (8):9921-9940.
Chicago/Turabian StyleJames C. Moore; Cody V. Thompson. 2013. "A Phenomenological Model for the Photocurrent Transient Relaxation Observed in ZnO-Based Photodetector Devices." Sensors 13, no. 8: 9921-9940.
We have investigated the photoluminescence properties of ZnO grown on sapphire substrates via the thermal oxidation of Zn-metal films at various temperatures and thicknesses. X-ray diffraction (XRD) spectra indicate that the resulting films possess a polycrystalline hexagonal wurtzite structure without preferred orientation. For films having a thickness of 200 nm, crystal grain size was observed to decrease with increasing annealing temperature up to 600ºC, and then increase at higher temperatures. Thicker films demonstrated a modest increase in grain size as temperature increased from 300ºC to 1200ºC. The influence of film thickness on the optical properties was investigated using room temperature photoluminescence (PL). Specifically, PL spectra indicate four emission bands: excitonic ultraviolet, blue, and deep-level green and yellow emission. The strongest UV emission and narrowest full width at half maximum (0.09 eV) was observed for films having a thickness of 200 nm and annealed at low temperature (300ºC). As film thickness decreased, we observed the emergence of blue emission. The emergence of blue emission when depletion width grows relative to the bulk suggests that the origin of the blue emission is related to the negatively charged Zinc interstitials found within the deletion region near the interface.
L.R. Covington; R. Stansell; J.C. Moore. Emergence of blue emission with decreasing film thickness and grain size for ZnO grown via thermal oxidation of Zn-metal films. MRS Proceedings 2012, 1394, 1 .
AMA StyleL.R. Covington, R. Stansell, J.C. Moore. Emergence of blue emission with decreasing film thickness and grain size for ZnO grown via thermal oxidation of Zn-metal films. MRS Proceedings. 2012; 1394 ():1.
Chicago/Turabian StyleL.R. Covington; R. Stansell; J.C. Moore. 2012. "Emergence of blue emission with decreasing film thickness and grain size for ZnO grown via thermal oxidation of Zn-metal films." MRS Proceedings 1394, no. : 1.
We have investigated the photoluminescence (PL) properties of ZnO grown on sapphire substrates via the thermal oxidation of Zn‐metal films at various temperatures and having various thicknesses. PL spectra indicate four emission bands: excitonic ultraviolet (UV), blue, and deep‐level green and yellow emission. The ratio of deep‐level green emission to UV excitonic emission was observed to decrease with decreasing annealing temperature from 1200 to 300 °C, which is attributed to the generation of fewer oxygen vacancies () and interstitial oxygen ions () in the bulk. As film thickness decreased from approximately 600 to 200 nm, we observed the emergence of blue emission and a significant red shift (0.15 eV) in the bandgap. The emergence of blue emission and the corresponding decrease in emission associated with bulk defects when depletion width grows relative to the bulk suggests that the origin of the blue emission is related to the charged zinc interstitials () found within the deletion region near the interface.
J. C. Moore; L. R. Covington; R. Stansell. Affect of film thickness on the blue photoluminescence from ZnO. physica status solidi (a) 2012, 209, 741 -745.
AMA StyleJ. C. Moore, L. R. Covington, R. Stansell. Affect of film thickness on the blue photoluminescence from ZnO. physica status solidi (a). 2012; 209 (4):741-745.
Chicago/Turabian StyleJ. C. Moore; L. R. Covington; R. Stansell. 2012. "Affect of film thickness on the blue photoluminescence from ZnO." physica status solidi (a) 209, no. 4: 741-745.