Surface Tension Of Low-viscous Lubricants In High Pressure Carbon Dioxide Atmospheres

The optimization of refrigeration systems can be achieved by increasing the isentropic efficiency of the compressor. One possible way is the reduction of the friction and leakage losses which occur at the piston rings. The viscosity and the surface tension of the lubricant must be known for this purpose. From the literature only a small amount of measured values for the surface tension of commonly used lubricants are known. Additionally natural refrigerants like R-744 are more common according to the latest (European) environmental regulation. The thermophysical properties of lubricant-refrigerant-mixtures can currently only be calculated by generalized calculation methods. For specific mixtures, these equations need to be confirmed by measurements. In this paper the measurement results of the surface tension of different low-viscous lubricants are shown. A test bench was designed to measure the surface tension of different liquids especially under high pressure atmospheres. The investigation was performed by using the pendant drop method and analyzing the results with new algorithms for the solution of the Young-Laplace equation. Effects of the geometry of the used capillaries are discussed which leads to possible optimizations of this measurement method. Dilution effects of the surface tension of the lubricants in carbon dioxide atmospheres are shown and discussed. The effect of higher pressures and different temperatures on the surface tension is shown as well as a comparison of the measurements with generalized methods

The German ‘Appropriateness of Management Board Remuneration Act’: Impacts on German Executive and Supervisory Board Compensation – A Panel Data Approach

With the enactment of the VorstAG on 5.8.2009 the stock corporation act was changed leading to increased risk and uncertainty for executives and elevated complexity, responsibility, and liability for directors. Hence, the present paper focuses on investigating the impact of the VorstAG on executive and director compensation and composition. Thereby, a DID approach was applied to analyse the dataset consisting of 29 German DAX30-listed companies and 10 AEX-listed Dutch firms, which severed as a control group. This research produced a number of key findings: firstly, executive total compensation, base salary, and long-term compensation components show insignificant results whilst short-term compensation decreased significantly after the enactment of the VorstAG. However, long-term executive compensation shows a positive trend. Thus, executive compensation schemes tend to be increasingly long-term oriented after the enactment of the VorstAG. Secondly, total director compensation also remains unaffected by the VorstAG. Nevertheless, base salary considerably increased and variable compensation components significantly decreased. Hence, director compensation is characterised by a rather risk-averse design after the enacting of the VorstAG. Accordingly, the main conclusion drawn from this research was that total executive and director compensation remains unaffected by the VorstAG. However, the executive compensation composition tends to develop into a more long-term aligned structure while director compensation shows a decreasing trend for uncertain variable compensation components and increasing fixed compensation elements leading to a more risk-averse structure. Consequently, the VorstAG seems to have the desired effect on executive compensation. However, the impact of the VorstAG on director compensation towards more fixed compen-sation elements might show a precarious trend

Experimental Analysis Of Twisted Shaped Spot Evaporators At High Heat Fluxes

Devices for cooling high heat fluxes within small available spaces are called spot evaporators. Areas of application are for example the cooling of molds, power electronics or electrical mobility. The functionality of the spot evaporator bases on its geometry and is a combination of spray-cooling and pipe flow. Spray-cooling or jet impingement cooling is able to achieve high heat fluxes even at overcritical wall temperatures. To reach the same effects within the pipe-flow part of the spot evaporator, this part has to be twisted shaped. The paper focuses on the experimental analysis of the twisted shaped spot evaporator by varying fundamental parameters corresponding to the Model of Yagov. Two methods of generating the twist have been developed and compared to each other. The experimental results will be discussed. They show that the averaged critical heat flux can be raised up to 30 % compared to spot evaporators without twisted flow. As refrigerant R404A has been used

Porous translucent electrodes enhance current generation from photosynthetic biofilms.

Some photosynthetically active bacteria transfer electrons across their membranes, generating electrical photocurrents in biofilms. Devices harvesting solar energy by this mechanism are currently limited by the charge transfer to the electrode. Here, we report the enhancement of bioelectrochemical photocurrent harvesting using electrodes with porosities on the nanometre and micrometre length scale. For the cyanobacteria Nostoc punctiforme and Synechocystis sp. PCC6803 on structured indium-tin-oxide electrodes, an increase in current generation by two orders of magnitude is observed compared to a non-porous electrode. In addition, the photo response is substantially faster compared to non-porous anodes. Electrodes with large enough mesopores for the cells to inhabit show only a small advantage over purely nanoporous electrode morphologies, suggesting the prevalence of a redox shuttle mechanism in the electron transfer from the bacteria to the electrode over a direct conduction mechanism. Our results highlight the importance of electrode nanoporosity in the design of electrochemical bio-interfaces

Probing Convolutional Neural Networks for Event Reconstruction in {\gamma}-Ray Astronomy with Cherenkov Telescopes

A dramatic progress in the field of computer vision has been made in recent years by applying deep learning techniques. State-of-the-art performance in image recognition is thereby reached with Convolutional Neural Networks (CNNs). CNNs are a powerful class of artificial neural networks, characterized by requiring fewer connections and free parameters than traditional neural networks and exploiting spatial symmetries in the input data. Moreover, CNNs have the ability to automatically extract general characteristic features from data sets and create abstract data representations which can perform very robust predictions. This suggests that experiments using Cherenkov telescopes could harness these powerful machine learning algorithms to improve the analysis of particle-induced air-showers, where the properties of primary shower particles are reconstructed from shower images recorded by the telescopes. In this work, we present initial results of a CNN-based analysis for background rejection and shower reconstruction, utilizing simulation data from the H.E.S.S. experiment. We concentrate on supervised training methods and outline the influence of image sampling on the performance of the CNN-model predictions.Comment: 8 pages, 4 figures, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Busan, Kore

Autonomous guidewire navigation in a two dimensional vascular phantom

The treatment of cerebro- and cardiovascular diseases requires complex and challenging navigation of a catheter. Previous attempts to automate catheter navigation lack the ability to be generalizable. Methods of Deep Reinforcement Learning show promising results and may be the key to automate catheter navigation through the tortuous vascular tree. This work investigates Deep Reinforcement Learning for guidewire manipulation in a complex and rigid vascular model in 2D. The neural network trained by Deep Deterministic Policy Gradients with Hindsight Experience Replay performs well on the low-level control task, however the high-level control of the path planning must be improved further