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In this article, the energy efficiency (EE) of an intelligent reflecting surface (IRS)-aided downlink multiuser multiple-input single-output (MISO) system is investigated. In order to maximize the system EE, the transmit beams at the access point (AP), and the phase shifts at the IRS are jointly optimized, while satisfying power and phase constraints. Since these two variables are coupled together and the problem is nonconvex, an alternating optimization framework is used as the algorithmic framework in order to decouple them, and for optimizing the phase shift, we use the successive convex approximation (SCA) approach to convert the original nonconvex objective function into a series of convex subproblems and solve them with the CVX toolbox. In order to reduce the complexity of the design, minimum mean square error (mmse) beamforming is used at the AP, so that only the power allocation needs to be optimized. The numerical results show that the proposed SCA-mmse method exhibits the superiority in terms of system EE, compared with a few benchmark schemes.

Resistive-type superconducting fault current limiters (R-SFCL) can limit the short-circuit fault current (SCFC). But superconducting tapes can not quickly recover to the superconducting state after deep quench. In response to minimizing the problem, this paper proposes a new resistive-inductive superconducting fault current limiter (RI-SFCL) and the current limiting transfer characteristics and investigates the recovery characteristics of it. The results show that RI-SFCL improves the fault current limit rate and significantly delays the emergence of sub-peaks of limiting current, reducing the rise rate of limiting current. Moreover, the recovery time of RI-SFCL can be less than 300 ms at 13 times the Critical expected SCFC. From the experimental results, the HTS tapes can be recovered within 300 ms when the heat generated during the current limiting process is not more than 215 J/m. Finally, the relation between the inductance and recovery time is given to provide a basis for the RI-SFCL design.

With the ability of fast and automatically response between zero resistance and current-limiting resistance, resistive type superconducting fault current limiter (R-SFCL) is considered a valid way to solve the excessive fault current in short circuit. But seconds recovery time is acquired for a R-SFCL to return superconductivity after quenching. A variable resistive type SFCL (VR-SFCL) has been proposed to achieve fast recovery after quenching. In this paper, to design the superconducting tape length in VR-SFCL, a VR-SFCL model in AC 10 kV/630 A system was built, and the influence of the main coil and limiting coil lengths on the current-limiting characteristics was investigated. From the simulation results of VR-SFCL, the main coil and limiting coil length can be designed through the demands of recovery and withstanding, separately. To achieve recovery in 300 ms and safety of superconducting tape, the length of the main coil and limiting coil should be longer than 235 m and 150 m, which can decrease the length of VR-SFCL by 59.9% compared with R-SFCL.

Resistive type superconducting fault current limiter (R-SFCL) can be used to suppress the fault current with low loss in normal conditions and fast response time in fault conditions. To meet the demand of reclosing, the fast recovery is required. However, the requirements of current limiting and recovery are contradictory in superconducting tape. To meet faster recovery in a variable resistance SFCL (VR-SFCL), superconducting tape branches with different layer parameters are used in the flowing branch. The effects of the copper and SS 316L thickness on the current limiting and recovery characteristics of the VR-SFCL are investigated through experiment. Results show that with the same critical current and room temperature resistance, the flowing branch of VR-SFCL with thicker SS 316L and thinner copper can recover faster with close current limiting ratio. The results can be helpful for the superconducting tape selection in VR-SFCL.

Neuronal ion channels of different types often do not function independently but will inhibit or potentiate the activity of other types of channels, a process called cross-talk. The N-methyl-D-aspartate receptor (NMDA receptor) and the γ-aminobutyric acid type A receptor (GABAAreceptor) are important excitatory and inhibitory receptors in the central nervous system, respectively. Currently, cross-talk between the NMDA receptor and the GABAAreceptor, particularly in the central auditory system, is not well understood. In the present study, we investigated functional interactions between the NMDA receptor and the GABAAreceptor using whole-cell patch-clamp techniques in cultured neurons from the inferior colliculus, which is an important nucleus in the central auditory system. We found that the currents induced by aspartate at 100 μmol L−1were suppressed by the pre-perfusion of GABA at 100 μmol L−1, indicating cross-inhibition of NMDA receptors by activation of GABAAreceptors. Moreover, we found that the currents induced by GABA at 100 μmol L−1(IGABA) were not suppressed by the pre-perfusion of 100 μmol L−1aspartate, but those induced by GABA at 3 μmol L−1were suppressed, indicating concentration-dependent cross-inhibition of GABAAreceptors by activation of NMDA receptors. In addition, inhibition of IGABA by aspartate was not affected by blockade of voltage-dependent Ca2+channels with CdCl2in a solution that contained Ca2+, however, CdCl2effectively attenuated the inhibition of IGABAby aspartate when it was perfused in a solution that contained Ba2+instead of Ca2+or a solution that contained Ca2+and 10 mmol L−1BAPTA, a membrane-permeable Ca2+chelator, suggesting that this inhibition is mediated by Ca2+influx through NMDA receptors, rather than voltage-dependent Ca2+channels. Finally, KN-62, a potent inhibitor of Ca2+/calmodulin-dependent protein kinase II (CaMKII), reduced the inhibition of IGABAby aspartate, indicating the involvement of CaMKII in this cross-inhibition. Our study demonstrates a functional interaction between NMDA and GABAAreceptors in the inferior colliculus of rats. The presence of cross-talk between these receptors suggests that the mechanisms underlying information processing in the central auditory system may be more complex than previously believed.