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Abstract Every day and innumerably, road vehicles of different types pass flat roadside-placed elements like stable or temporary traffic signs, noise barriers, charge devices, etc. The elements are exposed to a vehicle-specific flow and pressure field, i.e. to transient loads. In order to quantify the involved phenomena, full-scale experiments were performed for six different vehicle types and three sizes of square plates, which were aligned in three different configurations with respect to the vehicle׳s track. For the measurement of loads effecting the plate, the pressure multi-tapping technique was implemented with high temporal and spatial resolution. The experiments delivered a broad database for the proper quantification of vehicle induced loads on flat elements as a function of vehicle type, vehicle velocity and passing distance to the plate, element size as well as spatial plate alignment with respect to the vehicle.

The combustion of coal is responsible for nearly 40% of the world's electricity production, and char combustion accounts for about half of that amount. Clearly, an understanding of the combustion mechanism of carbon is of great importance not only because of its industrial significance but because it is a model heterogeneous reaction. A number of recent studies have been concerned with ab initio molecular orbital calculations on graphite including model chemistry and the reactions with molecular oxygen. This study is concerned with oxidation steps involving the attachment of oxygen to a graphene layer at high temperature leading to the formation of carbon monoxide, and particular attention is paid to the subsequent oxidation reactions. In addition, the reaction of oxygen with carbon catalyzed by metals inherent within the char matrix and the reaction of molecular oxygen with the analogous biomass char are investigated and their reaction paths are discussed.

With the recent advancements in power electronics for wind turbines (WTs) and increasing penetration of wind energy, wind power plants (WPP) have become necessary contributors of reactive power support for the bulk power system. Balancing reactive power support with individual WT operating requirements in a cost-effective manner is a challenge for WPP designers. In this paper, we present a methodology to optimize the WPP reactive power capability as seen from the point of common coupling (PCC), accounting for steady-state operating capabilities of the WPP equipment. Thus, the proposed methodology determines the configuration of the tap-changing transformers within the WPP that maximizes the amount of reactive power the WPP can either consume or inject to the network, considering uncertain levels of wind power generation and voltage magnitudes at the PCC. The optimized reactive power capability (ORPC) problem is initially formulated as a mixed-integer nonlinear programming (MINLP) model. Then, a set of efficient linearization techniques are used to obtain a mixed-integer linear programming (MILP) model that can be solved via off-the-shelf mathematical programming solvers. Results demonstrate that the proposed MILP model is a scalable, flexible and accurate method to maximize the reactive power capability of WPP.

The operation of centrifugal pumps can generate instabilities and pressure pulsations that may be detrimental to the integrity and performance of the pump. In the present study a numerical investigation of the time variation of pressure within a complete centrifugal pump was undertaken. A range of parameters and three flow rates were investigated and the pulsations were extracted at 15 different locations covering important pump regions. The transient flow results compared reasonably with experimental data obtained in a limited experimental survey and clearly indicated the pump locations experiencing the largest pulsation levels. It was also noted that monitoring pulsations at the top dead centre of the pump volute casing would provide a better indication of internal pump pulsations than monitoring at the discharge.

Abstract A variety of novel, recyclable and reusable, construction materials has already been studied within literature during the past years, aiming at improving the overall energy efficiency ranking of the building envelope. However, several studies show that a delicate control of indoor climating elements can lead to a significant performance improvement by exploiting the building’s savings potential via smart adaptive HVAC regulation to exogenous uncertain disturbances (e.g. weather, occupancy). Building Optimization and Control (BOC) systems can be categorized into two different groups: centralized (requiring high data transmission rates at a central node from every corner of the overall system) and decentralized 1 (assuming an intercommunication among neighboring constituent systems). Moreover, both approaches can be further divided into two subcategories, respectively: model-assisted (usually introducing modeling oversimplifications) and model-free (typically presenting poor stability and very slow convergence rates). This paper presents the application of a novel, decentralized, agent-based , model-free BOC methodology (abbreviated as L4GPCAO) to a modern non-residential building (E.ON. Energy Research Center’s main building), equipped with controllable HVAC systems and renewable energy sources by utilizing the existing Building Management System (BES). The building testbed is located inside the RWTH Aachen University campus in Aachen, Germany. A combined rule criterion composed of the non-renewable energy consumption (NREC) and the thermal comfort index – aligned to international comfort standards – was adopted in all cases presented herein. Besides the limited availability of the specified building testbed, real-life experiments demonstrated operational effectiveness of the proposed approach in BOC applications with complex, emerging dynamics arising from the building’s occupancy and thermal characteristics. L4GPCAO outperformed the control strategy that was designed by the planers and system provider, in a conventional manner, requiring no more than five test days.

Abstract This paper investigates the hydrodynamics of a seabed-mounted, bottom-hinged, flap-type wave energy converter in shallow water. A conceptual model of the hydrodynamics of the device has been formulated and shows that, as the motion of the flap is highly constrained, the magnitude of the wave force on the flap is the key determinant of power capture. The results from a physical modelling program have been used in conjunction with numerical data from WAMIT to validate the conceptual model. The work finds that designing the device to increase the wave force is more profitable than designing it to be tuned to the incident wave climate. As wave force is the primary driver of device performance it is shown that the flap should fill the water column and pierce the water surface to reduce decoupling due to wave overtopping. It is concluded that, in order to maximize capture factor at a typical North Atlantic site, the flap should be approximately 20–30 m wide, with large diameter rounded side edges, having its pivot close to the seabed and its top edge piercing the water surface.

Abstract Stable aqueous TiO2 nanofluids with different particle (agglomerate) sizes and concentrations are formulated and measured for their static thermal conductivity and rheological behaviour. The nanofluids are then measured for their heat transfer and flow behaviour upon flowing upward through a vertical pipe in both the laminar and turbulent flow regimes. Addition of nanoparticles into the base liquid enhances the thermal conduction and the enhancement increases with increasing particle concentration and decreasing particle (agglomerate) size. Rheological measurements show that the shear viscosity of nanofluids decreases first with increasing shear rate (the shear thinning behaviour), and then approaches a constant at a shear rate greater than ∼100 s−1. The constant viscosity increases with increasing particle (agglomerate) size and particle concentration. Given the flow Reynolds number and particle size, the convective heat transfer coefficient increases with nanoparticle concentration in both the laminar and turbulent flow regimes and the effect of particle concentration seems to be more considerable in the turbulent flow regime. Given the particle concentration and flow Reynolds number, the convective heat transfer coefficient does not seem to be sensitive to the average particle size under the conditions of this work. The results also show that the pressure drop of the nanofluid flows is very close to that of the base liquid flows for a given Reynolds number.

We investigated the solid state reaction of 30-nm and 100-nm-thick silicide layers on single-crystalline silicon in the temperature range between 650 and 800°C using transmission electron microscopy and atomic force microscopy. Sheet resistance measurements were used to observe the effect of the reaction temperature on the layer properties and to perform a systematic study on the thermal stability. At the lower reaction temperature good quality layers were produced with quite small grains. The specific resistivity is as low as 15 μΩ cm and the interface to the silicon substrate is quite flat. These favourable properties lead to a high thermal stability. The processed layers are stable in the temperature range between 850 and 950°C. When the layer thickness is increased to 100 nm, the stability range extends by about 250°C. The deterioration rate of 30-nm and 100-nm-thick silicide layers was deduced from sheet resistance measurements. The activation energy for the electrical degradation of the layer due to layer agglomeration was found to be nearly independent of the thickness.

We present the determination of the alkaloid hordenine and its forensic relevance as a qualitative and quantitative marker for beer consumption. A simple, rapid and sensitive ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS) method for the determination of hordenine in human serum samples was developed and validated. The application was tested with serum samples after enzymatic cleavage. After addition of the synthesized internal standard hordenine-D 4, a liquid-liquid extraction with dichloromethane and diethyl ether was performed. Chromatographic separation was conducted with a Waters Acquity® UPLC system with gradient elution on an Agilent Eclipse XDB-C18 column (4.6 mm × 150 mm, 5-μm particle size). For quantification, a Waters Acquity® TQ detector (version SNC 627) with a positive electrospray ionization probe and multiple reaction monitoring mode was used. A flow rate of 0.4 ml/min was applied. The retention time for both the analyte and the internal standard was 3.67 min. Linearity was demonstrated from 0.2 to 16 ng/ml (R(2) > 0.999). The lower limit of quantification was 0.3 ng/ml in serum. Matrix effects and extraction recoveries for low and high concentrations were within acceptable limits of 75-125% and 50%, respectively. To the best of our knowledge there is no corresponding method for the determination of hordenine by UPLC-MS/MS in serum. By our drinking studies we demonstrate that beer consumption leads to detectable hordenine concentrations in serum and observed a linear elimination of total hordenine correlating to blood alcohol concentration, which shows that hordenine can be used as a reliable qualitative and quantitative marker for beer consumption. The validated method was successfully applied to serum from actual forensic cases.