13,895 research outputs found
The Effect of Varied Gender Groupings on Argumentation Skills among Middle School Students in Different Cultures
The purpose of this mixed-methods study was to explore the effect of varied gender groupings on argumentation skills among middle school students in Taiwan and the United States in a project-based learning environment that incorporated a graph-oriented computer-assisted application (GOCAA). A total of 43 students comprised the treatment condition and were engaged in the collaborative argumentation process in same-gender groupings. Of these 43 students, 20 were located in the U.S. and 23 were located in Taiwan. A total of 40 students comprised the control condition and were engaged in the collaborative argumentation process in mixed-gender groupings. Of these 40 students, 19 were in the U.S. and 21 were in Taiwan. In each country, verbal collaborative argumentation was recorded and the students’ post essays were collected. Among females in Taiwan, one-way analysis of variance (ANOVA) indicated that statistically a significant gender-grouping effect was evident on the total argumentation skills outcome, while MANOVA indicated no significant gender-grouping effect on the combined set of skill outcomes. Among females in the U.S., MANOVA indicated statistically significant gender-grouping effect on the combined set of argumentation skills outcomes Specifically, U.S. female students in mixed-gender groupings (the control condition) significantly outperformed female students in single-gender groupings (the treatment condition) in the counterargument and rebuttal skills. No significant group differences were observed among males. A qualitative analysis was conducted to examine how the graph-oriented computer-assisted application supported students’ development of argumentation skills in different gender groupings in both countries. In each country, all teams in both conditions demonstrated a similar pattern of collaborative argumentation with the exception of three female teams in the U.S. Female teams, male teams, (the treatment condition) and mixed-gender teams (the control condition) demonstrated metacognition regulation skills in different degrees and with different scaffolding
Design of a Novel Antenna Array Beamformer Using Neural Networks Trained by Modified Adaptive Dispersion Invasive Weed Optimization Based Data
A new antenna array beamformer based on neural networks (NNs) is presented. The NN training is performed by using optimized data sets extracted by a novel Invasive Weed Optimization (IWO) variant called Modified Adaptive Dispersion IWO (MADIWO). The trained NN is utilized as an adaptive beamformer that makes a uniform linear antenna array steer the main lobe towards a desired signal, place respective nulls towards several interference signals and suppress the side lobe level (SLL). Initially, the NN structure is selected by training several NNs of various structures using MADIWO based data and by making a comparison among the NNs in terms of training performance. The selected NN structure is then used to construct an adaptive beamformer, which is compared to MADIWO based and ADIWO based beamformers, regarding the SLL as well as the ability to properly steer the main lobe and the nulls. The comparison is made considering several sets of random cases with different numbers of interference signals and different power levels of additive zero-mean Gaussian noise. The comparative results exhibit the advantages of the proposed beamformer
Vertically coupled double quantum rings at zero magnetic field
Within local-spin-density functional theory, we have investigated the
`dissociation' of few-electron circular vertical semiconductor double quantum
ring artificial molecules at zero magnetic field as a function of inter-ring
distance. In a first step, the molecules are constituted by two identical
quantum rings. When the rings are quantum mechanically strongly coupled, the
electronic states are substantially delocalized, and the addition energy
spectra of the artificial molecule resemble those of a single quantum ring in
the few-electron limit. When the rings are quantum mechanically weakly coupled,
the electronic states in the molecule are substantially localized in one ring
or the other, although the rings can be electrostatically coupled. The effect
of a slight mismatch introduced in the molecules from nominally identical
quantum wells, or from changes in the inner radius of the constituent rings,
induces localization by offsetting the energy levels in the quantum rings. This
plays a crucial role in the appearance of the addition spectra as a function of
coupling strength particularly in the weak coupling limit.Comment: 18 pages, 8 figures, submitted to Physical Review
Electronic structure of few-electron concentric double quantum rings
The ground state structure of few-electron concentric double quantum rings is
investigated within the local spin density approximation. Signatures of
inter-ring coupling in the addition energy spectrum are identified and
discussed. We show that the electronic configurations in these structures can
be greatly modulated by the inter-ring distance: At short and long distances
the low-lying electron states localize in the inner and outer rings,
respectively, and the energy structure is essentially that of an isolated
single quantum ring. However, at intermediate distances the electron states
localized in the inner and the outer ring become quasi-degenerate and a rather
entangled, strongly-correlated system is formed.Comment: 16 pages (preprint format), 6 figure
Nucleation in dilute 3He-4He liquid mixtures at low temperatures
We present a study of phase separation from supersaturated 3He-4He liquid
mixtures at low temperatures addressing both the degree of critical
supersaturation Dx and the thermal-to-quantum crossover temperature T* for the
nucleation process. Two different nucleation seeds are investigated, namely 3He
droplets and 4He vortex lines with cores filled with 3He. We have found that
the experimental T* is reproduced when we consider that nucleation proceeds
from 3He droplets, whereas Dx is reproduced when we consider 4He vortex lines
filled with 3He. However, neither nucleation configuration is able to
simultaneously reproduce the current experimental information on Dx and T*.Comment: To appear in J. of Low Temp. Physic
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