A Model for Type-IIP Supernovae with Medium Recombination Approximation

In this paper, we propose a new light-curve model for Type-IIP supernovae (SNe IIP) with an approximation of medium recombination. Recombination of hydrogen that takes place in the envelope is believed highly affect the light curves of SNe IIP. The propagation of the recombination wave through the expanding envelope is crucial to determine the temperature and the bolometric luminosity. Several approximations were made in previous works to determine the recombination front, which plays a role as the pseudo-photosphere. With the Eddington boundary condition, we let the actual photosphere be the boundary to determine the time evolution of temperature profile of the envelope and calculate the bolometric luminosity. A new approximation on the speed of recombination wave is introduced to get a closer result to the real situation. We abandon the non-self-consistent approximations made in former works and solve the initial hump problem in the previous attempt for the slow recombination approximation. The produced light curves show the necessity of this approximation and fit the observation well.Comment: 14 pages, 10 figures, 5 tables. Submitted to ApJ, welcome for comments

A target guided subband filter for acoustic event detection in noisy environments using wavelet packets

This paper deals with acoustic event detection (AED), such as screams, gunshots, and explosions, in noisy environments. The main aim is to improve the detection performance under adverse conditions with a very low signal-to-noise ratio (SNR). A novel filtering method combined with an energy detector is presented. The wavelet packet transform (WPT) is first used for time-frequency representation of the acoustic signals. The proposed filter in the wavelet packet domain then uses a priori knowledge of the target event and an estimate of noise features to selectively suppress the background noise. It is in fact a content-aware band-pass filter which can automatically pass the frequency bands that are more significant in the target than in the noise. Theoretical analysis shows that the proposed filtering method is capable of enhancing the target content while suppressing the background noise for signals with a low SNR. A condition to increase the probability of correct detection is also obtained. Experiments have been carried out on a large dataset of acoustic events that are contaminated by different types of environmental noise and white noise with varying SNRs. Results show that the proposed method is more robust and better adapted to noise than ordinary energy detectors, and it can work even with an SNR as low as -15 dB. A practical system for real time processing and multi-target detection is also proposed in this work

Influence of Tropical Cyclones in the Western North Pacific

The Western North Pacific (WNP) is the most favorable area in the world for the generation of tropical cyclones (TCs). As the most intense weather system, TCs play an important role in the change of ocean environment in the WNP. Based on many investigations published in the literature, we obtained a collective and systematic understanding of the influence of TCs on ocean components in the WNP, including sea temperature, ocean currents, mesoscale eddies, storm surges, phytoplankton (indicated by chlorophyll a). Some ocean responses to TCs are unique in the WNP because of the existence of the Kuroshio and special geographical configurations such as the South China Sea

A hierarchical control framework for autonomous decision-making systems: Integrating HMDP and MPC

This paper proposes a comprehensive hierarchical control framework for autonomous decision-making arising in robotics and autonomous systems. In a typical hierarchical control architecture, high-level decision making is often characterised by discrete state and decision/control sets. However, a rational decision is usually affected by not only the discrete states of the autonomous system, but also the underlying continuous dynamics even the evolution of its operational environment. This paper proposes a holistic and comprehensive design process and framework for this type of challenging problems, from new modelling and design problem formulation to control design and stability analysis. It addresses the intricate interplay between traditional continuous systems dynamics utilized at the low levels for control design and discrete Markov decision processes (MDP) for facilitating high-level decision making. We model the decision making system in complex environments as a hybrid system consisting of a controlled MDP and autonomous (i.e. uncontrolled) continuous dynamics. Consequently, the new formulation is called as hybrid Markov decision process (HMDP). The design problem is formulated with a focus on ensuring both safety and optimality while taking into account the influence of both the discrete and continuous state variables of different levels. With the help of the model predictive control (MPC) concept, a decision maker design scheme is proposed for the proposed hybrid decision making model. By carefully designing key ingredients involved in this scheme, it is shown that the recursive feasibility and stability of the proposed autonomous decision making scheme are guaranteed. The proposed framework is applied to develop an autonomous lane changing system for intelligent vehicles.Comment: 11 pages, 14 figures, submitted to Automatic

Effect of Corrosion on the Shear Transfer Behavior of Stud Shear Connectors

The effect of corrosion on the shear transfer behavior of stud shear connectors was investigated in this study. Experimental investigation was performed using an innovative test setup for single stud shear connector. Two series of specimens having different stud diameters were fabricated and tested. The test specimens were firstly corroded to different corrosion rates by electronic accelerating method. Loading test were then performed to obtain the load-slip curves and ultimate strengths of corroded test specimens. Corrosion rates were measured from the studs obtained from the failure test specimens. Test results were compared with standard push out test specimens having the similar corrosion rates. It is shown that the test results obtained from the single stud shear connectors are conservative compared with the corroded push test specimens, which prove the validation of single stud shear connector test method. The effect of corrosion on the shear transfer behavior of stud shear connectors was also presented