The Force Concept Inventory (FCI) is a 30-question multiple-choice assessment that has been a building block for much of the physics education research done today. In practice, there are often concerns regarding the length of the test and possible test-retest effects. Since many studies in the literature use the mean score of the FCI as the primary variable, it would be useful then to have different shorter tests that can produce FCI-equivalent scores while providing the benefits of being quicker to administer and overcoming the testretest effects. In this study, we divide the 1995 version of the FCI into two half-length tests; each contains a different subset of the original FCI questions. The two new tests are shorter, still cover the same set of concepts, and produce mean scores equivalent to those of the FCI. Using a large quantitative data set collected at a large midwestern university, we statistically compare the assessment features of the two halflength tests and the full-length FCI. The results show that the mean error of equivalent scores between any two of the three tests is within 3%. Scores from all tests are well correlated. Based on the analysis, it appears that the two half-length tests can be a viable option for score based assessment that need to administer tests quickly or need to measure short-term gains where using identical pre-and post-test questions is a concern.
The pupil size is an important parameter in different studies on vision and ophthalmology. A pupil size estimation model is constantly needed when actual measurements are unavailable. The reported pupil estimation models commonly adopt the product of light intensity and viewing field area, supposing the light contributes uniformly across the spatial domain. In this paper, the pupil diameters were measured for stimuli with different intensities and different sizes. Spatially varying effect were observed, especially for large field stimuli and annular bright stimuli. A spatially weighted flux density is proposed which shows a high correlation with pupil diameters. A hyperbolic equation is fitted to estimate the natural pupil diameter with independent light spatial distributions. The goodness of fit R 2 reaches 0.97. The accuracy of the model is further verified with a natural indoor scene for different viewing distances and different illumination levels. The model predicted pupil diameters show a high correlation with the measured data.
A neon plasma jet was generated in air, driven by a 9 kHz sinusoidal power supply. The characteristics of the plasma plume and the optical spectra with plasma propagation for different applied voltages were investigated. By increasing the applied voltage, the plasma plume first increases and then retracts to become short and bulky. The shortened effect of Ne plasma plume (about 10 mm) for the further voltage increasing is more apparent than that of He (about 3 mm) and Ar (about 1 mm). Emission intensity of the N2 (337 nm) increases with the applied voltage, gradually substituting the emission intensity of Ne (702 nm and 585 nm) as the noticeable radiation. At the nozzle opening, the Ne (702 nm) emission dominates, while the Ne (585 nm) emission is most noticeable around the tip of the plasma plume. The spatial distribution of the three spectral lines indicates that Ne (702 nm) emission decreases dramatically with plasma propagation while Ne (585 nm) and N2 (337 nm) emissions reach their maxima at the middle of the plasma plume. The results indicate that the Ne (702 nm) emission is much more sensitive to the average electron temperature and the density of the high-energy electrons, so it changes greatly at the tube nozzle and little at the tip region as the voltage increases. The population of high-energy electrons, the average electron temperature, the collision with air molecules and the Penning effect between Ne metastables and air molecules may explain their different variations with plasma propagating and voltage increasing.
Bragg scattering mechanism has been probed by a fully digital ultra-high-frequency (UHF) radar system. The system is based on studies of UHF radio wave (340 MHz) scattering from small-amplitude water waves. First-order radar cross section Doppler spectra have been measured. Comparing them with theoretical models, good agreement has been found. The amplitude ratio (dB) of the cross section between incident and reflected waves is 14.7 dB, and its deviation is 0.68%. The expectation of the normalized Doppler frequency shift of first-order peaks is 0.9850, and the deviation is 1.5%. Keywords: UHF radar, Bragg scattering, radar cross section Classification: Microwave and millimeter-wave devices, circuits, and modules References
Abstract-The research of stock price prediction is very important. Traditionally, the stock price is usually processed as a time series. However, the modelling of such time series is extremely important and vital, and has been attracting the attention of both practitioners and researchers. In this paper, the dynamic neural network model and the OU process with jumps are used to analyze the stock prices respectively, and the two models are compared by fitting and prediction performance. The experimental results show that the OU process with jumps is superior to the dynamic neural network for stochastic time series prediction.
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