Solution‐Processed GaSe Nanoflake‐Based Films for Photoelectrochemical Water Splitting and Photoelectrochemical‐Type Photodetectors

Gallium selenide (GaSe) is a layered compound, which has been exploited in nonlinear optical applications and photodetectors due to its anisotropic structure and pseudodirect optical gap. Theoretical studies predict that its 2D form is a potential photocatalyst for water splitting reactions. Herein, the photoelectrochemical (PEC) characterization of GaSe nanoflakes (single‐/few‐layer flakes), produced via liquid phase exfoliation, for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both acidic and alkaline media is reported. In 0.5 m H₂SO₄, the GaSe photoelectrodes display the best PEC performance, corresponding to a ratiometric power‐saved metric for HER (Φ_saved,HER) of 0.09% and a ratiometric power‐saved metric for OER (Φ_saved,OER) of 0.25%. When used as PEC‐type photodetectors, GaSe photoelectrodes show a responsivity of ≈0.16 A W^?1 upon 455 nm illumination at a light intensity of 63.5 µW cm^?2 and applied potential of ?0.3 V versus reversible hydrogen electrode (RHE). Stability tests of GaSe photodetectors demonstrated a durable operation over tens of cathodic linear sweep voltammetry scans in 0.5 m H₂SO₄ for HER. In contrast, degradation of photoelectrodes occurred in both alkaline and anodic operation due to the highly oxidizing environment and O₂‐induced (photo)oxidation effects. The results provide new insight into the PEC properties of GaSe nanoflakes for their exploitation in photoelectrocatalysis, PEC‐type photodetectors, and (bio)sensors.     

Surge arresters for insulation coordination in UHV power systems—related problems and solutions

Surge arresters play an important role in the insulation coordination of ultra high-voltage (UHV) electric power systems. In this contribution the requirements on the surge arresters are discussed in comparison with those in conventional applications, and how surge arrester standards are being changed to cover these special requirements.     

Berechnung der Anlaufdaten von Asynchron-Käfigläufermotoren verschiedener Stabformen mit der Methode der finiten Differenzen

Übersicht Die spannungsabhängigen Anlaufströme und Drehmomente eines 2800 kW Asynchron-Käfigläufermotors werden mit der Methode der finiten Differenzen und einem neuen Block-SOR-Iterationsverfahren berechnet. Es wird ber die Ergebnisse für Rechteck-, Trapez- und andere Rotorstabformen berichtet. Die numerisch berechneten Daten werden mit den nach konventionellen Regeln ermittelten Zahlen verglichen. Der Sättigungseffekt ist unerwartet groß, als Folge des großen Nennstrombelages. Die ungesättigten werte stimmen sehr gut überein.

---

On the calculation of the starting data of A.C. squirrel-cage motors with different bar shapes by the method of finite differences

Contents The voltage dependent starting currents and torques of a 2,800 kW 3-phase a.c. squirrel cage motor are calculated by the method of finite differences using a new block-SOR iteration technique. The paper describes the results for different rotor bars with rectangular, trapezoidal and other shapes. The calculated data are compared with conventionally determined figures. The saturation effect is rather large due to the high values of the rated current loading per air gap periphery. The unsaturated values agree very good.

     

Managing fddi networks: The state of the standards

The third in a serieson the FDDI standard, this article looksatSMT–the Fibre Distributed Data Interface Station Management–and the directions for FDDI over copper cables.     

Kraftwerkseigenschaften von Windenergieanlagen hinsichtlich Kurzschlussverhalten, Engpass- und Blindleistungsmanagement sowie Spannungsregelung

The increasing number of wind turbines will lead to new demands for transmission and distribution system control in the years to come. In order to ensure a smooth integration of wind energy into an electrical energy system structure, wind farms will have to possess power plant properties and be able to provide ancillary services. The ENERCON concept offers solutions not only for critical situations, such as short-circuits and bottlenecks in the grid, but also for normal operation, such as reactive power management or voltage control. Wind farms will essentially function in a manner similar to conventional power plants and moreover offer additional advantages in the distribution grid.     

Internet traffic engineering

The main goal of Internet traffic engineering is to efficiently optimize the performance of operational networks in order to avoid the well-known shortcomings of the typical destination-based IP routing. Traffic engineering attempts to reduce or even avoid congestion hot spots and to improve resource utilization across the backbone IP network. During the last years traffic engineering has become an inevitable tool concerning performance optimization in large Internet backbones. The core objective of this paper is to give an overview of the architectures and mechanisms for traffic engineering.     

Nichtlinearer digitaler Reibungsbeobachter zur adaptiven Reibungskompensation bei Bewegungsregelungen

Friction can deteriorate the tracking behavior of motion control. By use of a friction observer an estimated value of the friction can be determined and through adaptive compensation of the friction its influence can be weakened. The following article developes a new digital nonlinear friction observer on ground of an already known continuous nonlinear friction observer, which can easily be parametrized. A mechanical model is used to compare this nonlinear friction observer with a linear one during simulations and real time investigation. The investigation shows that the effect of deterioration of the tracking behavior through friction is less significant with the new digital nonlinear friction observer than with the linear friction observer.     

Macrodiversity analysis of anM-ary noncoherent orthogonal DS/CDMA system on shadowed Rayleigh channels

DS/CDMA noncoherentM-ary orthogonal signaling is presented in a hexagonal cell with three and six corner-based antennas. Multipath Rayleigh channel with lognormal shadowing and perfect power control are assumed. The asynchronous case (uplink) is studied. Bit error rate analysis is carried out to investigate the benefits of combining theM-ary orthogonal signaling and macrodiversity techniques either with uncorrelated or correlated base stations. Comparative analysis between the one central antenna arrangement and the proposed one is presented. The results show that the combination ofM-ary signaling with multiple corner-based antennas improves system performance especially in terms of accommodating more users and supporting new services. The results also show that shadowing does not degrade system performance significantly.