16,916 research outputs found
A Reverse-Shock Model for the Early Afterglow of GRB 050525A
The prompt localization of gamma-ray burst (GRB) 050525A by {\em Swift}
allowed the rapid follow-up of the afterglow. The observations revealed that
the optical afterglow had a major rebrightening starting at days
and ending at days, which was followed by an initial power-law
decay. Here we show that this early emission feature can be interpreted as the
reverse shock emission superposed by the forward shock emission in an
interstellar medium environment. By fitting the observed data, we further
constrain some parameters of the standard fireball-shock model: the initial
Lorentz factor of the ejecta , the magnetic energy fraction
, and the medium density . These
limits are consistent with those from the other very-early optical afterglows
observed so far. In principle, a wind environment for GRB 050525A is
disfavored.Comment: 11 pages, 1 figure, accepted for publication in Ap
Power load forecasting
For the electric power factory, the power load forecasting problem, including load forecasting and consumption predicting, is crucial to work planning. According to the predicting time, it can be divided into long-term forecasting, mid-term forecasting, short-term forecasting and ultra-short-term forecasting. The long-term and mid-term forecasting are mainly used for macro control, and their forecasting time arrange are from one year to ten years and from one month to twelve months respectively. The short-term forecasting which prediction time is from one day to seven days is used in generators macroeconomic control, power exchange plan and some other areas. Predicting the situation in next 24 hours is named as the ultra-short-term forecasting which is used for failure prediction, emergency treatment and frequency control. In general, the forecast accuracy is different for different prediction time. The longer is the time, the lower accurate is the prediction.
As the unique power supplier in Huizhou (China), Huizhou Electric Power wants to know the solution to the problems: 1. Prediction of the total electrical consumption and the peak load of the city in 2006 based on the economy development and the feature of the city. 2. Monthly prediction of the consumption and peak load in 2006. 3. Daily prediction of the consumption and peak load from July 10th to 16th in 2006. 4. Prediction of the load every 15 minutes of July 10th. 5. Real-time forecasting which means to amend the existing load prediction for next 15 minute
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Rheo-processing of an alloy specifically designed for semi-solid metal processing on the Al-Mg-Si system
Semi-solid metal (SSM) processing is a promising technology for forming alloys and composites to near-net shaped products. Alloys currently used for SSM processing are mainly conventional aluminium cast alloys. This is an obstacle to the realisation of full potential of SSM processing, since these alloys were originally designed for liquid state processing and not for semi-solid state processing. Therefore, there is a significant need for designing new alloys specifically for semi-solid state processing to fulfil its potential. In this study, thermodynamic calculations have been carried out to design alloys based on the Al-Mg-Si system for SSM processing via the ‘Rheo-route’. The suitability of a selected alloy composition has been assessed in terms of the criteria considered by the thermodynamic design process, mechanical properties and heat treatability. The newly designed alloy showed good processability with rheo-processing in terms of good control of solid fraction during processing and a reasonably large processing window. The mechanical property variation was very small and the alloy showed good potential for age hardening by T5 temper heat treatment after rheo-processing
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