Defining Nafion Ionomer Roles for Enhancing Alkaline Oxygen Evolution Electrocatalysis

The electrocatalytic oxygen evolution reaction (OER) is not strictly a surface reaction, because it takes place in a thin hydrous electrical double layer (EDL). In this work, we perform an in-depth study of Nafion ionomer functions in both catalyst inks and catalyst layers (CL) for high-efficiency OER in alkaline media. Based on cyclic voltammetry results, an analysis method is developed to characterize pseudocapacitance and EDL charging capacitance independently. This enables accurate quantification of interfacial charge transport behavior and active sites for OER. Zeta potential measurements confirm that Nafion ionomer serves as a stabilizing and binding agent in catalyst-solvent inks. The data obtained from the half-cell tests in 1 M KOH reveal that increasing ionomer content in CL reduces OER performance due to higher mass transport resistance and less active sites. The sample with I/C = 1/24 (weight ratio of Nafion ionomer to IrOx catalyst) exhibits an approximately 1.7-times higher OER activity than that of I/C = 2/1. Furthermore, the ionomer blocking effect is found to be a common phenomenon, which was observed in a wide range of catalyst loadings and three different catalyst materials. Nevertheless, as demonstrated by Nafion-free samples, the addition of Nafion is indispensable for efficient catalyst utilization. Our study shows that the optimized ionomer content in the CL is 10-30 wt % of catalyst loading. Within this range, Nafion, catalyst particles, and electrolyte solution form efficient interaction, resulting in good connectivity of the charge conduction paths without inhibiting the gas diffusion

ADRC-based model predictive current control for PMSMs fed by three-phase four-switch inverters

© 2016 IEEE.A novel automatic disturbances rejection control (ADRC)-based model predictive current control (MPCC) strategy is developed for permanent magnet synchronous motors (PMSMs) fed by three-phase four-switch inverters, an after-fault-topology for fault-tolerant three-phase six-switch inverters. The mathematical model of a PMSM fed by a three-phase four-switch inverter is built firstly. Then the ADRC and MPCC are respectively designed, with the former being used to realize disturbance estimation and disturbance compensation while the latter being used to reduce stator current ripple and improve the quality of the torque and speed control. The resultant ADRC-based MPCC PMSM fed by an unhealthy inverter has fault-tolerant effective with dynamical performance very close to an ADRC-based MPCC PMSM fed by a healthy inverter. On the other hand, compared with PI-based MPCC PMSM fed by an unhealthy inverter, it possesses better dynamical response behavior and stronger robustness as well as smaller THD index of three-phase stator current in the presence of variation of load torque. The simulation results validate the feasibility and effectiveness of the proposed scheme

Study on anti-atherosclerotic effect of suxiao jiuxin pill and its mechanism.

Background: Suxiao Jiuxin Pill is composed of Ligusticum wallichii, Borneolum Syntheticum and other drugs; it has qi promoting and blood circulation activating, meridian dredging and pain relieving efficacies. The objective of this paper is to study the effect of Suxiao Jiuxin Pill (quick-acting heart reliever), in atherosclerosis (AS) rat model and explore the mechanism for its prevention and treatment of AS.Materials and Methods: AS rat model was established by high cholesterol diet and single intra-peritoneal injection of increased dose of vitamin D3.Results: Compared with the model group, Suxiao Jiuxin Pill medium- and high-dose groups and atorvastatin group can effectively regulate lipid metabolism.Conclusion: We conclude that Suxiao Jiuxin Pill has a good hypo-lipidemic effect, and can inhibit the occurrence and development of AS.Keywords : Suxiao Jiuxin Pill; atherosclerosis; atorvastati

A current transformer energy harvester with stable output based on the saturable magnetic core

One of the major bottlenecks of the traditional current transformer energy harvester (CTEH) is the instable output induced by the wide-range variations of the current in transmission lines. In this work, a novel CTEH capable of generating a stable output is demonstrated by using a core fabricated with saturable magnetic material. The stable output of the CTEH is enabled by the constant voltage-time product in its saturable characteristic. The proposed CTEH is implemented with a resistive load representing the load of electronic devices. When the current in the primary side of the CTEH's increases from 1 to 1000 A, the maximum power on the load can reach about 0.5 W, demonstrating the feasibility of using the CTEH with the saturable magnetic core as a quasi-stable power supply

Parallelization of Kinetic Theory Simulations

Numerical studies of shock waves in large scale systems via kinetic simulations with millions of particles are too computationally demanding to be processed in serial. In this work we focus on optimizing the parallel performance of a kinetic Monte Carlo code for astrophysical simulations such as core-collapse supernovae. Our goal is to attain a flexible program that scales well with the architecture of modern supercomputers. This approach requires a hybrid model of programming that combines a message passing interface (MPI) with a multithreading model (OpenMP) in C++. We report on our approach to implement the hybrid design into the kinetic code and show first results which demonstrate a significant gain in performance when many processors are applied.Comment: 10 pages, 3 figures, conference proceeding

The Minimal Solution to the mu/B_mu Problem in Gauge Mediation

We provide a minimal solution to the mu/B_mu problem in the gauge mediated supersymmetry breaking by introducing a Standard Model singlet filed S with a mass around the messenger scale which couples to the Higgs and messenger fields. This singlet is nearly supersymmetric and acquires a relatively small Vacuum Expectation Value (VEV) from its radiatively generated tadpole term. Consequently, both mu and B_mu parameters receive the tree-level and one-loop contributions, which are comparable due to the small S VEV. Because there exists a proper cancellation in such two kinds of contributions to B_mu, we can have a viable Higgs sector for electroweak symmetry breaking.Comment: 15 pages, 2 figures, version published on JHE

Intergrain Effects in the AC Susceptibility of Polycrystalline LaFeAsO_{0.94}F_{0.06}

The AC susceptibility, chi, at zero DC magnetic field of a polycrystalline sample of LaFeAsO_{0.94}F_{0.06} (Tc ≈ 24 K) has been investigated as a function of the temperature, the amplitude of the AC magnetic field (in the range Hac = 0.003 Oe - 4 Oe) and the frequency (in the range f = 10 kHz - 100 kHz). The chi(T) curve exhibits the typical two-step transition arising from the combined response of superconducting grains and intergranular weak-coupled medium. The intergranular part of chi strongly depends on both the amplitude and the frequency of the AC driving field, from few Kelvin below Tc down to T = 4.2 K. Our results show that, in the investigated sample, the intergrain critical current is not determined by pinning of Josephson vortices but by Josephson critical current across neighboring grains