A power analysis and data acquisition system for ocean wave energy device testing

In the testing of ocean wave energy devices, the demand for a portable and robust data acquisition and electrical loading system has become apparent. This paper investigates the development of a 30 kW inclusive system combining loading capabilities, real-time power analysis, and data acquisition for the testing of deployed ocean wave energy devices. Hardware results for ocean testing are included.     

Zertifizierte Cloud durch das EuroCloud Star Audit SaaS

Es gibt wenige IT-Themen, die so kontrovers diskutiert werden wie Cloud Computing. Auf der einen Seite werden signifikante Einsparungen und eine flexible Nutzung von IT-Diensten prognostiziert, auf der anderen Seite sind die Bedenken zu Sicherheit, Datenschutz und der Ausgestaltung rechtlicher Anforderungen sehr ernst zu nehmen. Gerade für mittelst?ndische Unternehmen ist Cloud Computing eine h?chst attraktive M?glichkeit, ihre Wettbewerbsf?higkeit durch Einbinden von externen Serviceangeboten aufrecht zu erhalten und auszubauen. Jedoch verfügen diese Unternehmen oftmals nicht über ausreichende M?glichkeiten einer individuellen Prüfung potenzieller rechtlicher und technischer Problembereiche. Vor diesem Hintergrund bieten Zertifizierungen über das gesamte Spektrum der zu prüfenden Bereiche eine erhebliche Erleichterung bei der Auswahl von Anbietern. Hierzu hat EuroCloud Deutschland mit einer Vielzahl von Partnern das EuroCloud Star Audit System als Gütesiegel für die Cloud entwickelt.     

Erythropoietin Modulates Autophagy Signaling in the Developing Rat Brain in an In Vivo Model of Oxygen-Toxicity

Autophagy is a self-degradative process that involves turnover and recycling of cytoplasmic components in healthy and diseased tissue. Autophagy has been shown to be protective at the early stages of programmed cell death but it can also promote apoptosis under certain conditions. Earlier we demonstrated that oxygen contributes to the pathogenesis of neonatal brain damage, which can be ameliorated by intervention with recombinant human erythropoietin (rhEpo). Extrinsic- and intrinsic apoptotic pathways are involved in oxygen induced neurotoxicity but the role of autophagy in this model is unclear. We analyzed the expression of autophagy activity markers in the immature rodent brain after exposure to elevated oxygen concentrations. We observed a hyperoxia-exposure dependent regulation of autophagy-related gene (Atg) proteins Atg3, 5, 12, Beclin-1, microtubule-associated protein 1 light chain 3 (LC3), LC3A-II, and LC3B-II which are all key autophagy activity proteins. Interestingly, a single injection with rhEpo at the onset of hyperoxia counteracted these oxygen-mediated effects. Our results indicate that rhEpo generates its protective effect by modifying the key autophagy activity proteins.     

Young’s modulus of ceramic particle reinforced aluminium: Measurement by the Impulse Excitation Technique and confrontation with analytical models

Young’s modulus of particulate metal matrix composites with volume fractions of reinforcement ranging from 40% to 60% is measured with the Impulse Excitation Technique. Results are compared with predictions of four common micromechanical mean-field models. Good agreement is obtained with the Torquato identical hard spheres (TIHS) and the generalized self-consistent (GSC) model.     

Kinetics and dynamics of thermally-induced shape-memory behavior of crosslinked short-chain branched polyethylenes

Systematic investigation of the relation between shape-memory (SM) behavior and characteristics of the covalent network and the crystalline domains of a crosslinked polymer, i.e., crosslink density and crystallinity, respectively, was performed using homogeneous ethylene-1-octenecopolymers (EOC) as model polymers. The EOCs have been crosslinked by 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (DHBP) decomposition. Two EOCs with a degree of branching of 30 and 60 hexyl side chains per 1000C atoms with each four different crosslink densities were employed. The investigated EOCs differ significantly in crystallinity, melting temperature (T_m) and crosslink density. The crosslinked EOC undergone the programming at a strain of 100% showed high strain fixity ratio (R_f) and strain recovery ratio (R_r). The R_f and R_r values increase with increasing crystallinity and crosslink density, respectively, and decline only slightly in a subsequent SM cycle. The switching temperature (T_sw) is strictly related to T_m and decreases with increasing degree of branching as well as crosslink density in the temperature range of 101–63 °C. T_sw remains nearly unchanged when the programming temperature (T_pr) or the load during SM recovery is varied. The kinetics of SM recovery as characterized by the temperature dependence of recovery rate is controlled by the melting behavior. The specific work generated by the programmed specimen during thermally-induced recovery under constant load, gains with increasing crosslink density, and is proposed as dynamical characteristic of practical relevance. The opportunity of tailoring T_sw by variation of the degree of branching and crosslink density makes such polymers attractive candidates for applications requiring T_sw temperatures in the range from 60 to 100 °C.     

Experimental investigation of parameters influencing the freeze start ability of a fuel cell system

To improve the freeze start ability of a fuel cell system some significant influencing parameters are defined and investigated. Experiments with a fuel cell test system are carried out in a climate chamber at various conditions. The time interval until fuel cell stack power equals 50% of its maximum power is defined as an indicator for a successful freeze start as well as a value for comparison and evaluation of the results. The target of this work is the minimization of this freeze start time by avoiding the freezing of process water on the catalyst layer of the Membrane Electrode Assembly (MEA), since this leads to temporary performance losses.The shut down strategy of the fuel cell system is identified to be one of the main parameters influencing the freeze start. It is found that a higher degree of dryness in the stack leads to a significant improvement in the freeze start performance, since the water absorbing capacity of the membrane increases and therefore also the time until its saturation. If this saturation takes place after the temperature of the MEA reached 0 °C, no significant ice-formation occurs. It is shown that by improving the shut down strategy of the fuel cell system at T_Start = −6 °C a start without performance loss can be realized. At temperatures lower than that temporary performance losses occur.Even if a lower voltage leads to a higher current and therefore to a higher water production rate, its effect on the freeze start due to the increased heat of reaction is positive. Further investigated parameters, for example the volume of the coolant loop, also affect the freeze start ability, but it can be concluded that the shut down strategy is of main importance.     

A hybrid multi-level optimization approach for the dynamic synthesis/design and operation/control under uncertainty of a fuel cell system

During system development, large-scale, complex energy systems require multi-disciplinary efforts to achieve system quality, cost, and performance goals. As systems become larger and more complex, the number of possible system configurations and technologies, which meet the designer’s objectives optimally, increases greatly. In addition, both transient and environmental effects may need to be taken into account. Thus, the difficulty of developing the system via the formulation of a single optimization problem in which the optimal synthesis/design and operation/control of the system are achieved simultaneously is great and rather problematic. This difficulty is further heightened with the introduction of uncertainty analysis, which transforms the problem from a purely deterministic one into a probabilistic one. Uncertainties, system complexity and nonlinearity, and large numbers of decision variables quickly render the single optimization problem unsolvable by conventional, single-level, optimization strategies.To address these difficulties, the strategy adopted here combines a dynamic physical decomposition technique for large-scale optimization with a response sensitivity analysis method for quantifying system response uncertainties to given uncertainty sources. The feasibility of such a hybrid approach is established by applying it to the synthesis/design and operation/control of a 5 kW proton exchange membrane (PEM) fuel cell system.     

XPS analysis of wet chemical etching of GaAs(110) by Br2–H2O: comparison of emersion and model experiments

We have applied photoelectron spectroscopy to investigate the surface composition after different surface treatments involving Br₂–H₂O mixtures in order to study wet chemical etching. Emersion experiments from Br₂–H₂O solution are compared with model experiments, in which Br₂–H₂O adsorbate and coadsorbate mixtures react with clean GaAs(110) surfaces. Our results indicate that Ga- and As-bromides formed initially are hydrolyzed to form the respective oxides. Without addition of Br₂, only slight oxidation of the surface takes place. There is an enrichment of Ga due to loss of As both in adsorption as well as in emersion experiments. Since in emersion experiments only a final situation is analyzed, the relative influence of surface reactivity and subsequent solvation effects cannot be distinguished easily, while model experiments give clear information on reaction products formed intermediately. However, model experiments differ in environment and temperature from the real solid–liquid interface. The presented results demonstrate that a combination of emersion and model experiments provide valuable insight into the mechanism of wet chemical etching on a microscopic level.     

Nanopositioning using the spiral of Archimedes: The probe-based storage case

Micro-Electro-Mechanical-Systems (MEMS)-based scanning probes appear as potential candidates for a wide variety of emerging nanoscale applications, including ultra-high-density data-storage and surface imaging. In this work, a spiral trajectory nanopositioning scheme is proposed as an alternative to the conventional raster positioning pattern. The resulting positioning signal has an extremely narrowband frequency content, which shifts very slowly over time. These properties enable enhanced tracking performance and offer potentially uninterrupted high-speed operation. The mathematical analysis of the spiral positioning signal as well as its properties are presented. Experimental results obtained from applying the new nanopositioning scheme on a MEMS-based scanning-probe data-storage setup for thermomechanical storage on polymer medium are illustrated.