Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Study on the hole-type traps in BaFCl : Eu2+ phosphor

Optical absorption spectra of BaF2-xClx:Eu in different states of optical storage were investigated. Three new difference absorption spectra bands were observed in ultraviolet region, which centered at 270, 315, and 378 nm. The bands at 270 and 315 nm were attributed to H(F-2(-)) and O-F(-) centers, respectively. The band at 378 nm was tentatively attributed to hole-trap centers related to Cl- ions. (c) 2006 Elsevier B.V. All rights reserved

A Novel Closed-Loop System for Vehicle Speed Prediction Based on APSO LSSVM and BP NN

Vehicle speed prediction plays a critical role in energy management strategy (EMS). Based on the adaptive particle swarm optimization–least squares support vector machine (APSO-LSSVM) algorithm with BP neural network (BPNN), a novel closed-loop vehicle speed prediction system is proposed. The database of a vehicle internet platform was adopted to construct a speed prediction model based on the APSO-LSSVM algorithm. Furthermore, a BPNN is established according to the local high-precision nonlinear fitting relationship between the predicted value and error so as to correct the prediction value. Then, the results are returned to the APSO-LSSVM model for calculating the minimum fitness function, thus obtaining a closed-loop prediction system. Finally, equivalent fuel consumption minimization strategy (ECMS) based EMS was performed. According to the simulation results, the RMSE performance is 0.831 km/h within 5 s, which is over 20% higher than other performances. Additionally, the training time is 15 min within 5 s, which is advantageous over BPNN. Furthermore, fuel consumption increases by 6.95% compared with the dynamic-programming algorithm and decreased by 5.6%~10.9% compared with the low accuracy of speed prediction. Overall, the proposed method is crucial for optimizing EMS as it is not only effective in improving prediction accuracy but also capable of reducing training time

A Novel Closed-Loop System for Vehicle Speed Prediction Based on APSO LSSVM and BP NN

Vehicle speed prediction plays a critical role in energy management strategy (EMS). Based on the adaptive particle swarm optimization–least squares support vector machine (APSO-LSSVM) algorithm with BP neural network (BPNN), a novel closed-loop vehicle speed prediction system is proposed. The database of a vehicle internet platform was adopted to construct a speed prediction model based on the APSO-LSSVM algorithm. Furthermore, a BPNN is established according to the local high-precision nonlinear fitting relationship between the predicted value and error so as to correct the prediction value. Then, the results are returned to the APSO-LSSVM model for calculating the minimum fitness function, thus obtaining a closed-loop prediction system. Finally, equivalent fuel consumption minimization strategy (ECMS) based EMS was performed. According to the simulation results, the RMSE performance is 0.831 km/h within 5 s, which is over 20% higher than other performances. Additionally, the training time is 15 min within 5 s, which is advantageous over BPNN. Furthermore, fuel consumption increases by 6.95% compared with the dynamic-programming algorithm and decreased by 5.6%~10.9% compared with the low accuracy of speed prediction. Overall, the proposed method is crucial for optimizing EMS as it is not only effective in improving prediction accuracy but also capable of reducing training time

High open-circuit voltage in UV photovoltaic cell based on polymer/inorganic bilayer structure

Polymer/inorganic hybrid ultra violet (UV) photovoltaic device is fabricated by using poly(N-vinyl-carbazole) (PVK) and zinc sulfide (ZnS). The device shows promising photovoltaic characteristics with a high open-circuit voltage of 1.65 V, and a short-circuit current of 46.8 mu A/cm(2) under the illumination of 340 nm UV light with the intensity of 14 mW/cm(2). Besides, much correlative photocurrent spectra of the device under forward and reverse applied bias manifest the transport mechanism of charge carriers in PVK/ZnS bilayer systems. (c) 2006 Elsevier B.V. All rights reserved

Colour centres and energy transfer in BaF2-xClx: Eu2+ phosphors

The optical absorption spectra of BaF2-xClx:Eu2+ after ultraviolet (UV) light excitation were investigated. The differences between the absorption spectra after and before excitation (DAS) were observed. The DAS increase at both the high and the low energy side of F band in BaF2-xClx:Eu2+ after 245 nm UV light excitation. The bleach effect of UV light and the absorption of electrons in the valence hand may account for the former and the formation of F-a centres (association of F(Cl-) centres), whose absorption band matches the HeNe laser better, may explain the latter. In the write-in process, the transfer of electrons is via tunneling. In the readout process, the transfer of electrons captured in F(F-) and F-a centres is more likely via tunneling, and that of F(Cl-) centres is more likely via conduction band

A new promising X-ray storage phosphor BaBrCl: Eu2+

Photostimulated luminescence was observed in X-ray irradiated BaBrCl doped with Eu2+. It shows an emission band that peak at 413 nm, and two difference absorption spectra (DAS) bands that peak at similar to 550 nm and 675 nm respectively. The stimulation energy is lower than that of BaFX:Eu2+ (X = Cl, Br), and matches the cheaper, more portable, and more convenient semiconductor laser better. The results indicate that BaBrCl:Eu2+ shows positive potential as a promising X-ray storage phosphor for practical utilization

Numerical Study on the Fatigue Limit of Metallic Glasses under Cyclic Tension-Compression Loading

Numerical study was performed to determine the fatigue limit of metallic glass under tension-compression cyclic loading. A revised free-volume theory which considers the hydrostatic stress was utilized to make the predictions. Systematical simulations showed that a higher strain amplitude is prone to making the sample completely damaged earlier. However, lower strain fluctuations could result in a longer fatigue life. Shear banding evolution history described by free-volume localization could reasonably explain the mechanical responses of different samples. In addition, compressive loading could give rise to a higher stress than that under tensile loading because of hydrostatic stress contribution. In the end, a correlation between fatigue life and applied strain amplitude was plotted which could supply a guidance for designing the engineering application of metallic glass under periodic loading

Improving photovoltaic properties via electric-field-induced orientation of conjugated polymer

A high electric field is applied to polarize the undoped MEH-PPV and the MEH-PPV:C-60 composite thin film in the process of spin-coating. Due to the polarization causing the orientation of the MEH-PPV chains, the resulting thin-film devices show improved photovoltaic properties. For undoped MEH-PPV devices, oriented under the electric field of 6 x 103 V cm(-1), the short-circuit current (J(sc)) and the external quantum efficiency (EQE) are enhanced by a factor of 2.5 and 2, respectively. For MEH-PPV-fullerene composite devices, oriented under the same field, the J(sc) and the EQE are improved by a factor of 1.8 and 1.7, respectively. (c) 2006 Elsevier Ltd. All rights reserved

Enhanced photovoltaic properties of polymer-fullerene bulk heterojunction solar cells by thermal annealing

The effect of a thermal annealing treatment on the performance of bulk heterojunction photovoltaic cells based on poly [2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and fullerene (C-60) composites is investigated. Upon thermal annealing at 120 degrees C, short-circuit current (I-sc) and power conversion efficiency (eta) are more than tripled, while a sharp rise by eight times in I-sc and eta is found for the device annealed at 200 degrees C. It is concluded that the improved phase separation between MEH-PPV and C-60 leads to the enhancement of I-sc and eta at 120 degrees C, while thermodynamic molecule arrangement at the higher temperature of similar to 200 degrees C induces a significant increase in all photovoltaic parameters of composite devices except the open-circuit voltage (V-oc). (c) 2007 Elsevier Ltd. All rights reserved