Protection of Aluminum Foils against Environmental Corrosion with Graphene-Based Coatings

Commercial aluminum foils were coated by graphene oxide, and its functionalized derivatives and the corrosion performance of the coated specimens were examined in acidic conditions (lithium perchlorate and sulfuric acid). Electrochemical experiments have shown that all graphene oxide-coated specimens provided up to 96% corrosion inhibition efficiency with a corresponding lower corrosion rate compared to the bare aluminum foil. Our results clearly show that graphene-related materials offer viable alternatives for the protection of aluminum, and this opens up a number of possibilities for its use in a number of commercial applications

Development of the Turgo Impulse turbine:past and present

The Turgo Impulse turbine provides a unique and novel solution to increasing the capacity of a hydraulic impulse turbine while maintaining the nozzle and spear injector system (as used in Pelton turbines) for flow regulation. This has produced a turbine which operates in the higher flow ranges usually reserved for Francis machines while maintaining a relatively flat efficiency curve, characteristic of impulse machines. Since its invention nearly 100 years ago, the Turgo turbine has been installed in thousands of locations across the globe. The majority of the development of the Turgo turbine design has been through the use of paper based and experimental studies however recent advances in computational fluid dynamics (CFD) tools have allowed the simulation of the complex, highly turbulent, multiphase flows associated with impulse turbines and some work has been done in applying this to the Turgo design. This review looks at the development of the of the Turgo turbine since its invention in 1919 and includes the paper-based analyses, experimental studies and the more recent CFD analyses carried out on the design

Fault tolerant computer control for a Maglev transportation system

Magnetically levitated (Maglev) vehicles operating on dedicated guideways at speeds of 500 km/hr are an emerging transportation alternative to short-haul air and high-speed rail. They have the potential to offer a service significantly more dependable than air and with less operating cost than both air and high-speed rail. Maglev transportation derives these benefits by using magnetic forces to suspend a vehicle 8 to 200 mm above the guideway. Magnetic forces are also used for propulsion and guidance. The combination of high speed, short headways, stringent ride quality requirements, and a distributed offboard propulsion system necessitates high levels of automation for the Maglev control and operation. Very high levels of safety and availability will be required for the Maglev control system. This paper describes the mission scenario, functional requirements, and dependability and performance requirements of the Maglev command, control, and communications system. A distributed hierarchical architecture consisting of vehicle on-board computers, wayside zone computers, a central computer facility, and communication links between these entities was synthesized to meet the functional and dependability requirements on the maglev. Two variations of the basic architecture are described: the Smart Vehicle Architecture (SVA) and the Zone Control Architecture (ZCA). Preliminary dependability modeling results are also presented

Flow modeling in Pelton turbines by an accurate Eulerian and a fast Lagrangian evaluation method

The recent development of Computational Fluids Dynamics (CFD) has allowed the flow modeling in impulse hydro turbines that includes complex phenomena like free surface flow, multi fluid interaction, and unsteady, time dependent flow. Some commercial and open-source CFD codes, which implement Eulerian solving methods, have been validated against experimental results showing satisfactory accuracy. Nevertheless, further improvement of the flow analysis accuracy is still a challenge, while the computational cost is very high and unaffordable for multi-parametric design optimization of the turbine’s runner. In the present work, a CFD Eulerian approach is applied at first, in order to simulate the flow in the runner of a Pelton turbine model installed at the laboratory. Then, a particulate method, the Fast Lagrangian Simulation (FLS), is used for the same case, which is much faster than the Eulerian approach, and hence potentially suitable for numerical design optimization, providing that it can achieve adequate accuracy. The results of both methods for various operation conditions of the turbine, as also for modified runner and bucket designs, are presented and discussed in the paper. In all examined cases the FLS method shows very good accuracy in predicting the hydraulic efficiency of the runner, although the computed flow evolution and torque curve during the jet-runner interaction exhibit some systematic differences from the Eulerian results

Empirical Investigation of Factors influencing Function as a Service Performance in Different Cloud/Edge System Setups

Experimental data can aid in gaining insights about a system operation, as well as determining critical aspects of a modelling or simulation process. In this paper, we analyze the data acquired from an extensive experimentation process in a serverless Function as a Service system (based on the open source Apache Openwhisk) that has been deployed across 3 available cloud/edge locations with different system setups. Thus, they can be used to model distribution of functions through multi-location aware scheduling mechanisms. The experiments include different traffic arrival rates, different setups for the FaaS system, as well as different configurations for the hardware and platform used. We analyse the acquired data for the three FaaS system setups and discuss their differences presenting interesting conclusions with relation to transient effects of the system, such as the effect on wait and execution time. We also demonstrate interesting trade-offs with relation to system setup and indicate a number of factors that can affect system performance and should be taken under consideration in modelling attempts of such systems.Comment: 24 pages, 14 Figures, Journal pape