Time series models for forecasting: Testing or combining?

In this paper we systematically compare forecasting accuracy of hypothesis testing procedures with that of a model combining algorithm. Testing procedures are commonly used in applications to select a model, based on which forecasts are made. However, besides the well-known difficulty in dealing with multiple tests, the testing approach has a potentially serious drawback: controlling the probability of Type 1 error at a conventional level (e.g., 0.05) often excessively favors the null, which can be problematic for the purpose of forecasting. In addition, as shown in this paper, testing procedures can be very unstable, which results in high variability in the forecasts. Selecting a candidate forecast by testing and combining forecasts are both useful but for complementary situations. Currently, there seems to be little guidance in the literature on when combining should be preferred to selecting. We propose instability measures that are helpful for a forecaster to gauge the difficulty in selecting a single optimal forecast. Based on empirical evidences and theoretical considerations, we advocate the use of forecast combining when there is considerable instability in model selection by testing procedures. On the other hand, when there is little instability, testing procedures could work well or even better than forecast combining in terms of forecast accuracy

Design of a large dynamic range readout unit for the PSD detector of DAMPE

A large dynamic range is required by the Plastic Scintillator Detector (PSD) of DArk Matter Paricle Explorer (DAMPE), and a double-dynode readout has been developed. To verify this design, a prototype detector module has been constructed and tested with cosmic rays and heavy ion beams. The results match with the estimation and the readout unit could easily cover the required dynamic range

A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona

We present a comprehensive radiative magnetohydrodynamic simulation of the quiet Sun and large solar active regions. The 197 Mm wide simulation domain spans from the uppermost convection zone to over 100 Mm in the solar corona. Sophisticated treatments of radiative transfer and conduction transport provide the necessary realism for synthesizing observables to compare with remote sensing observations of the Sun. This model self-consistently reproduces observed features of the quiet Sun, emerging and developed active regions, and solar flares up to M class. Here, we report an overview on the first results. The surface magnetoconvection yields an upward Poynting flux that is dissipated in the corona and heats the plasma to over one million K. The quiescent corona also presents ubiquitous propagating waves, jets, and bright points with sizes down to 2 Mm. Magnetic flux bundles generated in a solar convective dynamo emerge into the photosphere and gives rise to strong and complex active regions with Over $10^{23}$ Mx magnetic flux. The coronal free magnetic energy, which is about 18\% of the total magnetic energy, accumulates to about $10^{33}$ erg. The coronal magnetic field is not forcefree, as the Lorentz force needs to balance the pressure force and viscous stress as well as to drive magnetic field evolution. Emission measure from $\log_{10}T = 4.5$ to $\log_{10}T > 7$ provides a comprehensive view on structures and dynamics in the active region corona, such as coronal loops in various lengths and temperatures, mass circulation by evaporation and condensation, and eruptions from jets to large-scale mass ejections.Comment: 39 Pages, 17 figures, submitted to Ap

A Survey Study: The Correlation between Introversion/Extroversion and Oral English Learning Outcome

Introversion/extroversion is generally considered to be one of the most important factors affecting the success of foreign language learning, especially spoken language. Extroverts are usually thought to be better at learning a foreign spoken language than introverts. With the intention of finding out whether extroverts are better learners of spoken English (learned as a foreign language in China) than introverts, this study investigated 117 English majors’ personality types (in terms of introversion and extroversion) in Chongqing (a municipality city in China), and their spoken English performance through a spoken English test. With the data collected, this paper analyzes the correlation between introversion/extrusion and spoken English performance. The result shows that the two are not correlated. The author discusses factors leading to this phenomenon from various aspects of learning environment, motivation, language intake and output, culture, and concludes that introversion/ extroversion is not a key factor contributing to the success of spoken English learning. The research result is of great significance to both English teachers and learners, especially those who are concerned about their personality (introversion) being a barrier to their oral English learning. What matters most in spoken English learning probably are the strategies that learners employ to improve it, which is well worth researching