Nuclear β+\beta^+/EC decays in covariant density functional theory and the impact of isoscalar proton-neutron pairing

Self-consistent proton-neutron quasiparticle random phase approximation based on the spherical nonlinear point-coupling relativistic Hartree-Bogoliubov theory is established and used to investigate the $\beta^+$/EC-decay half-lives of neutron-deficient Ar, Ca, Ti, Fe, Ni, Zn, Cd, and Sn isotopes. The isoscalar proton-neutron pairing is found to play an important role in reducing the decay half-lives, which is consistent with the same mechanism in the $\beta$ decays of neutron-rich nuclei. The experimental $\beta^+$/EC-decay half-lives can be well reproduced by a universal isoscalar proton-neutron pairing strength.Comment: 12 pages, 4 figure

Searching for Dark Matter Signals in the Left-Right Symmetric Gauge Model with CP Symmetry

We investigate singlet scalar dark matter (DM) candidate in a left-right symmetric gauge model with two Higgs bidoublets (2HBDM) in which the stabilization of the DM particle is induced by the discrete symmetries P and CP. According to the observed DM abundance, we predict the DM direct and indirect detection cross sections for the DM mass range from 10 GeV to 500 GeV. We show that the DM indirect detection cross section is not sensitive to the light Higgs mixing and Yukawa couplings except the resonance regions. The predicted spin-independent DM-nucleon elastic scattering cross section is found to be significantly dependent on the above two factors. Our results show that the future DM direct search experiments can cover the most parts of the allowed parameter space. The PAMELA antiproton data can only exclude two very narrow regions in the 2HBDM. It is very difficult to detect the DM direct or indirect signals in the resonance regions due to the Breit-Wigner resonance effect.Comment: 24 pages, 8 figures. minor changes and a reference added, published in Phys. Rev.

Comprehensive influences measurement and analysis of power converter low frequency current ripple on PEM fuel cell

© 2019 Hydrogen Energy Publications LLC To deeply understand the influences of power converter's low frequency current ripple (LFCR) and harmonics on a proton exchange membrane fuel cell (PEMFC) in its power conditioning system (PCS), a comprehensive measurement and analysis of the influences of LFCR and harmonics on PEMFC's performance and durability is investigated in this paper. Based on an equivalent circuit model of PEMFC stack and a mechanism model for evaluating the LFCR effects on the PEMFC, this paper studies primarily and systematically the comprehensive influences of LFCR and harmonics on PEMFC performances and durability, such as (1) degrading the PEMFC performance, (2) shortening the lifetime of PEMFC, (3) reducing the stack output power, (4) lowing its availability efficiency, (5) producing more heat and raising the PEMFC temperature, (6) consuming more fuel, and (7) decreasing the fuel utilization. Finally, a Horizon 300 W PEMFC stack is implemented and tested

Fuzzy Adaptive PI Decoupling Control for Gas Supply System of Proton Exchange Membrane Fuel Cell

© 2018 KIEE EMECS (KIEE Electrical Machinery and Energy Conversion Systems). Aiming at the issues of nonlinear and strong coupling between hydrogen partial pressure and oxygen partial pressure in a proton exchange membrane fuel cell (PEMFC) and the poor control effect of traditional PID method, a fuzzy adaptive PID decoupling control method with simple rules is proposed in this paper. A fuzzy control algorithm is used to realize the adaptive adjustment of PID parameters online and the decoupling of the PEMFC gas supply system. According to the model established, the PEMFC gas supply system with fuzzy adaptive PID decoupling control is simulated. Simulation results show that the proposed control strategy can effectively reduce the pressure difference between hydrogen and oxygen supplies, prevent the PEMFC from degradation, and improve the output performance and lifetime of PEMFC

Asynchronous device detection for cognitive device-to-device communications

Dynamic spectrum sharing will facilitate the interference coordination in device-to-device (D2D) communications. In the absence of network level coordination, the timing synchronization among D2D users will be unavailable, leading to inaccurate channel state estimation and device detection, especially in time-varying fading environments. In this study, we design an asynchronous device detection/discovery framework for cognitive-D2D applications, which acquires timing drifts and dynamical fading channels when directly detecting the existence of a proximity D2D device (e.g. or primary user). To model and analyze this, a new dynamical system model is established, where the unknown timing deviation follows a random process, while the fading channel is governed by a discrete state Markov chain. To cope with the mixed estimation and detection (MED) problem, a novel sequential estimation scheme is proposed, using the conceptions of statistic Bayesian inference and random finite set. By tracking the unknown states (i.e. varying time deviations and fading gains) and suppressing the link uncertainty, the proposed scheme can effectively enhance the detection performance. The general framework, as a complimentary to a network-aided case with the coordinated signaling, provides the foundation for development of flexible D2D communications along with proximity-based spectrum sharing

Enhanced nutrient removal and mechanisms study in benthic fauna added surface-flow constructed wetlands: The role of Tubifex tubifex

© 2016 Elsevier Ltd This study designed a combined benthic fauna-T. orientalis-substrate-microbes surface-flow constructed wetlands (SFCWs) through the addition of T. tubifex. Results showed that, the removal efficiencies of nitrogen and phosphorus in the tested SFCWs achieved 81.14 ± 4.16% and 70.49 ± 7.60%, which were 22.27% and 27.35% higher than that without T. tubifex. Lower nitrate (2.11 ± 0.79 mg/L) and ammonium (0.75 ± 0.64 mg/L) were also observed in the tested SFCWs, which were 3.46 mg/L and 0.52 mg/L lower than that without T. tubifex. Microbial study confirmed the increased denitrifiers with T. tubifex. The lower nitrogen in effluent was also attributed to higher contents of nitrogen storage in sediment and T. orientalis due to the bioturbation of T. tubifex. Furthermore, with T. tubifex, higher proportions of particulate (22.66 ± 3.96%) and colloidal phosphorus (20.57 ± 3.39%) observed promoted phosphorus settlement and further absorption by T. orientalis. The outcomes of this study provides an ecological and economical strategy for improving the performance of SFCWs

Development of biochars from pyrolysis of lotus stalks for Ni(II) sorption: Using zinc borate as flame retardant

In this work, zinc borate (ZB) was employed as flame retardant for preparation of biochar (BC). A series of BC samples were generated by varying the ZB to lotus stalks (LS) ratio (0.25, 0.5 and 1.0) under different temperatures (300, 350 and 400 °C) for 1 h. The BCs were analyzed for their surface morphologies, surface areas, surface elemental compositions and yields. The results indicated that, after charring, ZB kept the structures of the produced BCs as its starting material (LS), dramatically enhancing their yields, and promoting their surface oxygen content. The BCs were used as adsorbent for removal of Ni(II) from aqueous solutions. Sorption of Ni(II) on the BCs was enhanced about 3-10 times compared with that of BCs derived from pyrolysis of LS without adding ZB. © 2014 Elsevier B.V

Potential benefits of limiting global warming for the mitigation of temperature extremes in China

In this study, we attempt to quantify the potential impacts of two global warming levels (i.e., 1.5 °C and 2.0 °C) on extreme temperature indices across China. The CMIP6 dataset is first evaluated against the CN05.1 observation for the historical period of 1995–2014. Then, future spatiotemporal patterns of changes in extreme temperature at two global warming levels under two shared socio-economic pathway scenarios (SSP245 and SSP585) are further analyzed. Overall, China will experience more frequent and intense high temperature events, such as summer days (SU), tropical nights (TR), warm days (TX90p) and nights (TN90p). On the other hand, under the SSP585, the number of icing days and frost days is projected to decrease at two global warming levels, with the maximal days of decrease (exceeding 20 days) seen in the west of China. Our results suggest that limiting global warming to 1.5 °C rather than 2.0 °C is beneficial to reduce extreme temperature risks. As temperature increases to 1.5 °C and then 2.0 °C above preindustrial levels, the most extreme temperature indices are expected to increase proportionately more during the final 0.5° than during the first 1.5° across most regions of China. For some warm indices, such as the warmest day (TXx), summer days (SU), and warm days (TX90p), the largest incremental changes (from 1.5° to 2.0°) tend to be found in the southwest. Under the SSP585, the incremental changes are similar to the change in the SSP245, but smaller magnitude and spatial extent

Chemical dynamics of triacetylene formation and implications to the synthesis of polyynes in Titan's atmosphere

For the last four decades, the role of polyynes such as diacetylene (HCCCCH) and triacetylene (HCCCCCCH) in the chemical evolution of the atmosphere of Saturn's moon Titan has been a subject of vigorous research. These polyacetylenes are thought to serve as an UV radiation shield in planetary environments; thus, acting as prebiotic ozone, and are considered as important constituents of the visible haze layers on Titan. However, the underlying chemical processes that initiate the formation and control the growth of polyynes have been the least understood to date. Here, we present a combined experimental, theoretical, and modeling study on the synthesis of the polyyne triacetylene (HCCCCCCH) via the bimolecular gas phase reaction of the ethynyl radical (CCH) with diacetylene (HCCCCH). This elementary reaction is rapid, has no entrance barrier, and yields the triacetylene molecule via indirect scattering dynamics through complex formation in a single collision event. Photochemical models of Titan's atmosphere imply that triacetylene may serve as a building block to synthesize even more complex polyynes such as tetraacetylene (HCCCCCCCCH)