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A novel scheme for precise diagnostics and effective stabilization of currents in a fuel cell stack
(2010)
A novel scheme for detecting inhomogeneous internal currents in a fuel cell stack is presented. In this paper the scheme is investigated for the case that the flow field plates consist of graphite. Then plates of high conductivity, e.g. aluminium between the flow field plates together with small slits in these plates have three effects: (a) Whenever a local inhomogeneity of the electric current occurs at a particular cell in the stack, this will induce a surface current close to that cell perpendicular to the averaged current. This current can be detected. (b) The plates of high conductivity completely prevent the inhomogeneities from spreading to neighbouring cells. (c) Even at the particular cell the inhomogeneity is suppressed as far as possible. Thus this scheme leads to much better diagnostic possibilities and at the same time reduces electric instabilities to an extent, where they probably become harmless. This scheme will first be explained for a simple model to clarify the idea. However, very precise three dimensional computations using realistic parameters are presented, corroborating the results of the simple model.
The mission of the COMPASS-1 picosatellite is to take pictures of the earth, to validate a space-borne GPS receiver developed by the German Aerospace Center, and to verify the proper operation of the magnetic attitude control system in orbit. The spacecraft was launched on April 28, 2008 from the Indian space port Sriharikota, as part of the PSLV-C9 world record launch that simultaneously brought ten satellites into orbit. The mission operations were carried out from the ground stations in Aachen and Tainan. Arising difficulties in the communication link were overcome with the support of individuals from the amateur radio community. After several months of mission operation, abundant housekeeping and mission data has been commanded, received and analyzed and is presented in this paper.
A novel tomographic scheme for analysing the state of any single membrane electrode assembly (MEA) in a stack is suggested. Plates of very high conductivity placed between every fuel cell and slitted in an appropriate manner cause surface currents at well-defined locations of the stack. We show that knowing these surface currents, information about anomalies of the currents in a MEA can be obtained using the methods of tomography. The results are mathematically not unique. However, when assuming plausible defect structures, one can exclude improbable deficiencies by applying a special form of simulated annealing. We present numerical calculations of typical examples demonstrating that the essential defects of the MEA in any single cell of the stack can be detected and their extent can be determined.
Comparison of intravenous immunoglobulins for naturally occurring autoantibodies against amyloid-β
(2010)
Intravenous immunoglobulins (IVIG) are currently used for therapeutic purposes in autoimmune disorders. Recently, we demonstrated the presence of naturally occurring antibodies against amyloid- β (nAbs-Aβ) within the pool of IVIG. In this study, we compared different brands of IVIG for nAbs-Aβ and have found differences in the specificity of the nAbs-Aβ towards Aβ1–40 and Aβ1–42 . We analyzed the influence of a pH-shift over the course of antibody storage using ELISA and investigated antibody dimerization at acidic and neutral pH as well as differences in the IgG subclass distributions among the IVIG using both HPLC and a nephelometric assay. Furthermore, we investigated the epitope region of purified nAbs-Aβ. The differences found in Aβ specificity are not directly proportionate to the binding nature of these antibodies when administered in vivo. This information, however, may serve as a guide when choosing the commercial source of IVIG for therapeutic applications in Alzheimer's disease
Since the 80s power production with solar thermal power plants has been a way to substitute fossil fuels. By concentrating direct solar radiation from heliostats very high temperatures of a thermal fluid can be reached. The resulting heat is converted to mechanical energy in a steam cycle which generates electricity.
High efficiencies and fast start-up are reached by using air as a heat medium, as well as using porous ceramic materials as solar receiver of the concentrated sunlight.
In Germany the construction of a 1.5 MWe solar tower power plant began in 2008. It is operational since December 2008 and started production of electricity in the spring of 2009.
In Greece and Cyprus, countries with high solar potential, the development of this competitive solar thermal technology is imperative, since it has already been implemented in other Mediterranean countries.
Capacitive field-effect electrolyte-diamond-insulator-semiconductor (EDIS) structures with O-terminated nanocrystalline diamond (NCD) as sensitive gate material have been realized and investigated for the detection of pH, penicillin concentration, and layer-by-layer adsorption of polyelectrolytes. The surface oxidizing procedure of NCD thin films as well as the seeding and NCD growth process on a Si-SiO2 substrate have been improved to provide high pH-sensitive, non-porous thin films without damage of the underlying SiO2 layer and with a high coverage of O-terminated sites. The NCD surface topography, roughness, and coverage of the surface groups have been characterized by SEM, AFM and XPS methods. The EDIS sensors with O-terminated NCD film treated in oxidizing boiling mixture for 45 min show a pH sensitivity of about 50 mV/pH. The pH-sensitive properties of the NCD have been used to develop an EDIS-based penicillin biosensor with high sensitivity (65-70 mV/decade in the concentration range of 0.25-2.5 mM penicillin G) and low detection limit (5 μM). The results of label-free electrical detection of layer-by-layer adsorption of charged polyelectrolytes are presented, too.
Urinary stone formation has been evolved to a widespread disease during the last years. The reason for the formation of urinary stones are little crystals, mostly composed of calcium oxalate, which are formed in human kidneys. The early diagnosis of the risk for urinary stone formation of patients can be determined by the “Bonn-Risk-Index” method based on the potentiometric detection of the Ca2+-ion concentration and an optical determination of the triggered crystallisation of calcium oxalate in unprocessed urine. In this work, miniaturised capacitive field-effect EMIS (electrolyte-membrane-insulator-semiconductor) sensors have been developed for the determination of the Ca2+-ion concentration in human native urine. The Ca2+-sensitive EMIS sensors have been systematically characterised by impedance spectroscopy, capacitance–voltage and constant–capacitance method in terms of sensitivity, signal stability and response time in both CaCl2 solutions and in native urine. The obtained results demonstrate the suitability of EMIS sensors for the measurement of the Ca2+-ion concentration in native urine of patients.
A handheld sensor system for the online measurement of hydrogen peroxide (H2O2) in aseptic sterilisation processes has been developed. It is based on a calorimetric-type gas sensor that consists of a differential set-up of two temperature sensors, of which one is catalytically activated and the second one is passivated and used as reference. The sensor principle relies in detecting a rise in temperature on the active sensor due to the exothermic reaction of H2O2 on the catalytic surface. To characterise the sensor system towards H2O2 sensitivity and other influencing factors, measurements have been carried out both at an experimental set-up and a manufacturer's sterilisation machine. Physical sensor characterisation was done by means of the optical microscopy.
The chemical imaging sensor is a semiconductor-based chemical sensor that can visualize the spatial distribution of chemical species. For the practical application of this sensor, artifacts in the chemical images due to defects of the semiconductor substrate and contamination of the sensing surface etc. have been a major problem. An image correction method was developed to eliminate the influence of nonuniformity of individual sensor plate.
A novel strategy for enhanced field-effect biosensing using capacitive electrolyte–insulator–semiconductor (EIS) structures functionalised with pH-responsive weak polyelectrolyte/enzyme or dendrimer/enzyme multilayers is presented. The feasibility of the proposed approach is exemplarily demonstrated by realising a penicillin biosensor based on a capacitive p-Si–SiO2 EIS structure functionalised with a poly(allylamine hydrochloride) (PAH)/penicillinase and a poly(amidoamine) dendrimer/penicillinase multilayer. The developed sensors response to changes in both the local pH value near the gate surface and the charge of macromolecules induced via enzymatic reaction, resulting in a higher sensitivity. For comparison, an EIS penicillin biosensor with adsorptively immobilised penicillinase has been also studied. The highest penicillin sensitivity of 100 mV/dec has been observed for the EIS sensor functionalised with the PAH/penicillinase multilayer. The lower and upper detection limit was around 20 µM and 10 mM, respectively. In addition, an incorporation of enzymes in a multilayer prepared by layer-by-layer technique provides a larger amount of immobilised enzymes per sensor area, reduces enzyme leaching effects and thus, enhances the biosensor lifetime (the loss of penicillin sensitivity after 2 months was 10–12%).
Gas sensor investigation based on a catalytically activated thin-film thermopile for H2O2 detection
(2010)
In aseptic filling systems, hydrogen peroxide vapour is commonly used for the reduction of microbial contaminations in carton packages. In this process, the germicidal efficiency of the vapour depends especially on the H₂O₂ concentration. To monitor the H₂O₂ concentration, a calorimetric H₂O₂ gas sensor based on a catalytically activated thin-film thermopile is investigated. Two different sensor layouts, namely a circular and a linear form, as well as two various material pairs such as tungsten/nickel and gold/nickel, have been examined for the realization of a thin-film thermopile. Additionally, manganese oxide and palladium particles have been compared as responsive catalysts towards H₂O₂. The thin-film sensors have been investigated at various H₂O₂ concentrations, gas temperatures and flow rates.
pH-sensitive properties of barium strontium titanate (BST) high-k thin films as alternative gate material for field-effect capacitive (bio-)chemical sensors based on an electrolyte-insulator-semiconductor system have been investigated. The BST films of different compositions (Ba0.31Sr0.69TiO3, Ba0.25Sr0.75TiO3 and Mg-doped Ba0.8Sr0.2Mg0.1Ti0.9O3) were deposited by pulsed laser deposition technique from targets fabricated by self-propagating high-temperature synthesis. The realised sensors have been electrochemically characterised by means of impedance-spectroscopy, capacitance–voltage and constant-capacitance method. The sensors possess a Nernstian-like pH sensitivity in the concentration range between pH 3 and 11 with a response time of 5–10 s. An equivalent circuit model for the BST-based capacitive field-effect sensor is discussed.
Simultaneous detection of cyanide and heavy metals for environmental analysis by means of µISEs
(2010)
In environmental analysis, cyanide and heavy metals play an important role, because these substances are highly toxic for biological systems. They can lead to chronic and acute diseases. Due to the chemical properties of cyanide it is frequently used for industrial processes such as extraction of silver and gold. Heavy metals can be found as trace elements in nature and are often applied in industries e.g., galvanization processes. Up to now, cyanide and heavy metals can be detected by several sensors separately and their detection is often limited to laboratory investigations. In this publication, with regard to an in situ analysis, a new miniaturized silicon-based sensor system for the simultaneous detection of cyanide and heavy metals in aqueous solutions is presented that is based on chalcogenide glass-based micro ion-selective electrodes (µISEs). The µISEs are incorporated into a specially designed measuring system for the simultaneous detection of heavy metals and cyanide in solutions and validated by simultaneous measurements of Cu2+- and CN−-ions, Cd2+- and CN−- ions and Pb2+- and CN−-ions. The particular sensor system has shown good sensor properties in the µ-molar ion-concentration range. For simultaneous measurements in complex heavy metal and cyanide solutions an intelligent software using fuzzy logic is discussed.
The control of molecular architecture provided by the layer-by-layer (LbL) technique has led to enhanced biosensors, in which advantageous features of distinct materials can be combined. Full optimization of biosensing performance, however, is only reached if the film morphology is suitable for the principle of detection of a specific biosensor. In this paper, we report a detailed morphology analysis of LbL films made with alternating layers of single-walled carbon nanotubes (SWNTs) and polyamidoamine (PAMAM) dendrimers, which were then covered with a layer of penicillinase (PEN). An optimized performance to detect penicillin G was obtained with 6-bilayer SWNT/PAMAM LbL films deposited on p-Si-SiO2-Ta2O5 chips, used in biosensors based on a capacitive electrolyte-insulator-semiconductor (EIS) and a light-addressable potentiometric sensor (LAPS) structure, respectively. Field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) images indicated that the LbL films were porous, with a large surface area due to interconnection of SWNT into PAMAM layers. This morphology was instrumental for the adsorption of a larger quantity of PEN, with the resulting LbL film being highly stable. The experiments to detect penicillin were performed with constant-capacitance (ConCap) and constant-current (CC) measurements for EIS and LAPS sensors, respectively, which revealed an enhanced detection signal and sensitivity of ca. 100 mV/decade for the field-effect sensors modified with the PAMAM/SWNT LbL film. It is concluded that controlling film morphology is essential for an enhanced performance of biosensors, not only in terms of sensitivity but also stability and response time.
C-terminal truncation of a metagenome-derived detergent protease for effective expression in E. coli
(2010)
Recently, a new alkaline protease named HP70 showing highest homology to extracellular serine proteases of Stenotrophomonas maltophilia and Xanthomonas campestris was found in the course of a metagenome screening for detergent proteases (Niehaus et al., submitted for publication). Attempts to efficiently express the enzyme in common expression hosts had failed. This study reports on the realization of overexpression in Escherichia coli after structural modification of HP70. Modelling of HP70 resulted in a two-domain structure, comprising the catalytic domain and a C-terminal domain which includes about 100 amino acids. On the basis of the modelled structure the enzyme was truncated by deletion of most of the C-terminal domain yielding HP70-C477.
This structural modification allowed effective expression of active enzyme using E. coli BL21-Gold as the host. Specific activity of HP70-C477 determined with suc-l-Ala-l-Ala-l-Pro-l-Phe-p-nitroanilide as the substrate was 30 ± 5 U/mg compared to 8 ± 1 U/mg of the native enzyme. HP70-C477 was most active at 40 °C and pH 7–11; these conditions are prerequisite for a potential application as detergent enzyme. Determination of kinetic parameters at 40 °C and pH = 9.5 resulted in KM = 0.23 ± 0.01 mM and kcat = 167.5 ± 3.6 s⁻¹. MS-analysis of peptide fragments obtained from incubation of HP70 and HP70-C477 with insulin B indicated that the C-terminal domain influences the cleavage preferences of the enzyme. Washing experiments confirmed the high potential of HP70-C477 as detergent protease.
The integration of nanostructured films containing biomolecules and silicon-based technologies is a promising direction for reaching miniaturized biosensors that exhibit high sensitivity and selectivity. A challenge, however, is to avoid cross talk among sensing units in an array with multiple sensors located on a small area. In this letter, we describe an array of 16 sensing units of a light-addressable potentiometric sensor (LAPS), which was made with layer-by-layer (LbL) films of a poly(amidomine) dendrimer (PAMAM) and single-walled carbon nanotubes (SWNTs), coated with a layer of the enzyme penicillinase. A visual inspection of the data from constant-current measurements with liquid samples containing distinct concentrations of penicillin, glucose, or a buffer indicated a possible cross talk between units that contained penicillinase and those that did not. With the use of multidimensional data projection techniques, normally employed in information visualization methods, we managed to distinguish the results from the modified LAPS, even in cases where the units were adjacent to each other. Furthermore, the plots generated with the interactive document map (IDMAP) projection technique enabled the distinction of the different concentrations of penicillin, from 5 mmol L−1 down to 0.5 mmol L−1. Data visualization also confirmed the enhanced performance of the sensing units containing carbon nanotubes, consistent with the analysis of results for LAPS sensors. The use of visual analytics, as with projection methods, may be essential to handle a large amount of data generated in multiple sensor arrays to achieve high performance in miniaturized systems
Background: To elaborate the impact of new haemostatic agents we developed an instrument for the pressure-controlled induction of blunt liver injuries in a porcine animal model. Materials and Methods: A dilutional coagulopathy of 80% of animal blood volume was induced in 9 anaesthetized pigs. Animals were randomly assigned to be injured with a force of 112 Newton (N) (n = 1), 224 ± 19 N (n = 4) or 355 ± 35 N (n = 4). The impact of injury was measured by blood loss, survival time and coagulation parameters. Liver histology was obtained to evaluate the degree of liver injury. Results: The profound haemodilution resulted in a significant alteration of all coagulation parameters. After inflicting the injury with 355 ± 35 N, both the survival time (30 ± 9 min; p = 0.006) and blood loss (68 ± 16 ml min–1, p = 0.002) were significantly different as compared to injuries with 224 ± 19 N (survival time: 76 ± 20 min, blood loss: 23 ± 4 ml min–1). In contrast, an injury with 112 N led to an insignificant blood loss of only 239 ml. Conclusion: We developed a pressure-controlled clamp that allows for the induction of blunt liver traumas with highly reproducible injuries with a positive correlation with blood loss and survival.
With the final objective of optimizing the "Micromix" hydrogen combustion principle, a round jet in a laminar cross-flow prior to its combustion is investigated experimentally using Stereoscopic Particle Image Velocimetry. Measurements are performed at a jet to cross-stream momentum ratio of 1 and a Reynolds number, based on the jet diameter and jet velocity, of 1600. The suitability to combine side, top and end views is analyzed statistically. The statistical theory of testing hypotheses, pertaining to the joint distribution of the averaged velocity along intersecting observation planes, is employed. Overall, the averaged velocity fields of the varying observation planes feature homogeneity at a 0.05 significance level. Minor discrepancies are related to the given experimental conditions. By use of image maps, averaged and instantaneous velocity fields, an attempt is made to elucidate the flow physics and a kinematically consistent vortex model is proposed. In the time-averaged flow field, the principal vortical systems were identified and the associated mixing visualized. The jet trajectory and physical dimensions scale with the momentum ratio times the jet diameter. The jet/cross-flow mixture converging upon the span-wise centre-line, the lifting action of the Counter Rotating Vortex Pair and the reversed flow region contribute to the high entrainment and mixedness. It is shown that the jet width is larger on the downstream side as compared to the upstream side of the centre-streamline. The deepest penetration of the particles on the outer boundary occurs in the centre-plane. Meanwhile, with increasing off-centre position, the boundaries all lay further from the centre-line position than does the boundary in the centre-plane, corresponding to a kidney-like shape of the flow cross-section. The generation of the Counter Rotating Vortex Pair and the instability mechanism is documented by instantaneous image maps and vector fields. The necessary circulation for the Counter Rotating Vortex Pair originates from a combined effect of steady in-hole, hanging and wake vortices. The strong cross-flow and jet interaction induces a three-dimensional waving, the stream-wise Counter Rotating Vortex Pair pair, leading to the formation of Ring Like Vortices. A secondary Counter Rotating Vortex Pair forms on top of the primary Counter Rotating Vortex Pair, resulting in mixing by "puffs". Overall, Stereoscopic Particle Image Velocimetry proofed capable of elucidating the Jet in Cross-Flow complex flow field. The gained insight in the mixing process will definitely contribute to the "Micromix" hydrogen combustion optimization.
For more than a decade up to now there is an ongoing interest in small gas turbines downsized to micro-scale. With their high energy density they offer a great potential as a substitute for today’s unwieldy accumulators, found in a variety of applications like laptops, small tools etc. But micro-scale gas turbines could not only be used for generating electricity, they could also produce thrust for powering small unmanned aerial vehicles (UAVs) or similar devices. Beneath all the great design challenges with the rotating parts of the turbomachinery at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. With the so called regular micromix burning principle for hydrogen successfully downscaled in an initial combustion chamber prototype of 10 kW energy output, this paper describes a new design attempt aimed at the integration possibilities in a μ-scale gas turbine. For manufacturing the combustion chamber completely out of stainless steel components, a recuperative wall cooling was introduced to keep the temperatures in an acceptable range. Also a new way of an integrated ignition was developed. The detailed description of the prototype’s design is followed by an in depth report about the test results. The experimental investigations comprise a set of mass flow variations, coupled with a variation of the equivalence ratio for each mass flow at different inlet temperatures and pressures. With the data obtained by an exhaust gas analysis, a full characterisation concerning combustion efficiency and stability of the prototype chamber is possible. Furthermore the data show a full compliance with the expected operating requirements of the designated μ-scale gas turbine.
Among many approaches to address the high-level decision making problem for autonomous robots and agents, the robot program¬ming and plan language Golog follows a logic-based deliberative approach, and its successors were successfully deployed in a number of robotics applications over the past ten years. Usually, Golog interpreter are implemented in Prolog, which is not available for our target plat¬form, the bi-ped robot platform Nao. In this paper we sketch our first approach towards a prototype implementation of a Golog interpreter in the scripting language Lua. With the example of the elevator domain we discuss how the basic action theory is specified and how we implemented fluent regression in Lua. One possible advantage of the availability of a Non-Prolog implementation of Golog could be that Golog becomes avail¬able on a larger number of platforms, and also becomes more attractive for roboticists outside the Cognitive Robotics community.
Aims: Thrombotic complications due to activation of platelets and plasmatic clotting factors belong still to the most investigated topics in the field of study of patho-physiological mechanisms. Mathematical modeling of thrombotic reactions is established and validated in test cases. Aim of this study is to experimentally evaluate and computationally simulate platelets under the influence of well-defined shear flow conditions. Platelet behaviour and reactions are experimentally reproduced, measured and used for validation of the numerical simulation. Methods: A mathematical model of platelet activation, adhesion and aggregation has been implemented into a finite element CFD (Computational Fluid Dynamics) code. The approach is based on the advective and diffusive transport equations for resting platelets, activated platelets and platelet released agonists. Adhesion rates for the reactive surfaces depend on the hemocompatibility properties of the surface and the local shear rate. Experiments with citrate-anticoagulated freshly-drawn whole blood are performed in a perfusion flow chamber as well as in a system of rotating cylinders for Couette and Taylor-vortex flow. Different biomaterials are used. The activation, drop of platelet concentration, adhesion and aggregation are quantified using scanning electron microscopy (SEM) and flow cytometry. Results: Regions and flow conditions with a high potential for thrombus growth could be identified. The experiments clearly show the influence of the blood contacting material and flow properties. By means of SEM diverse platelet adhesion patterns are observed. Numerical analysis can explain the patterns and the degree of thrombus formation. Conclusion: The numerical method shows good agreement with experimental data indicating a possible prediction of initiation of activation and detection of the local adhesion areas in connection with the role of Von-Willebrand-Factor.
Purpose of Study: Thrombosis-related complications are among the leading causes for morbidity and mortality in patients who depend on artificial organs. For the prediction of platelet behavior both the flow conditions inside the device and the thrombogenic properties of the blood-contacting surfaces must be considered. Platelet reactions under the influence of well-defined shear rates are experimentally evaluated and numerically simulated. The approach is intended for the analysis of VAD and oxygenator design.
Methods Used: A mathematical model of platelet activation, adhesion and aggregation has been implemented into a finite element CFD (Computational Fluid Dynamics) code. The approach is based on the advective and diffusive transport equations for resting and activated platelets and platelet released agonists. Experiments with citrate-anticoagulated freshly-drawn whole blood are performed in a perfusion flow chamber as well as in a system of rotating cylinders for Couette and Taylor-vortex flow. Different biomaterials are used. The activation, adhesion and aggregation are quantified using scanning electron microscopy and flow cytometry.
Summary of Results: Regions and flow conditions with a high potential for thrombus growth could be identified. The experiments clearly show the influence of the blood contacting material and governing shear rates. Numerical analysis can explain observed adhesion patterns and the degree of thrombus formation
The idea of component-based software engineering was proposed more that 40 years ago, yet only few robotics software frameworks follow these ideas. The main problem with robotics software usually is that it runs on a particular platform and transferring source code to another platform is crucial. In this paper, we present our software framework Fawkes which follows the component-based software design paradigm by featuring a clear component concept with well-defined communication interfaces. We deployed Fawkes on several different robot platforms ranging from service robots to biped soccer robots. Following the component concept with clearly defined communication interfaces shows great benefit when porting robot software from one robot to the other. Fawkes comes with a number of useful plugins for tasks like timing, logging, data visualization, software configuration, and even high-level decision making. These make it particularly easy to create and to debug productive code, shortening the typical development cycle for robot software.
The high-level decision making process of an autonomous robot can be seen as an hierarchically organised entity, where strategical decisions are made on the topmost layer, while the bottom layer serves as driver for the hardware. In between is a layer with monitoring and reporting functionality. In this paper we propose a behaviour engine for this middle layer which, based on formalism of hybrid state machines (HSMs), bridges the gap between high-level strategic decision making and low-level actuator control. The behaviour engine has to execute and monitor behaviours and reports status information back to the higher level. To be able to call the behaviours or skills hierarchically, we extend the model of HSMs with dependencies and sub-skills. These Skill-HSMs are implemented in the lightweight but expressive Lua scripting language which is well-suited to implement the behaviour engine on our target platform, the humanoid robot Nao.
In order to allow an autonomous robot to perform non-trivial tasks like to explore a foreign planet the robot has to have deliberative capabilities like reasoning or planning. Logic-based approaches like the programming and planing language Golog and it successors has been successfully used for such decision-making problems. A drawback of this particular programing language is that their interpreter usually are written in Prolog and run on a Prolog back-end. Such back-ends are usually not available or feasible on resource-limited robot systems. In this paper we present our ideas and first results of a re-implementation of the interpreter based on the Lua scripting language which is available on a wide range of systems including small embedded systems.
We propose a formalism for reasoning about actions based on multi-modal logic which allows for expressing observations as first-class objects. We introduce a new modal operator, namely [o |α], which allows us to capture the notion of perceiving an observation given that an action has taken place. Formulae of the type [o |α]ϕ mean ’after perceiving observation o, given α was performed, necessarily ϕ’. In this paper, we focus on the challenges concerning sensing with explicit observations, and acting with nondeterministic effects. We present the syntax and semantics, and a correct and decidable tableau calculus for the logic
In this paper, we will provide a feasible mission design for a multiple-rendezvous mission to Jupiter's Trojans. It is based on solar electric propulsion, as being currently used on the DAWN spacecraft, and other flight-proven technology. First, we have selected a set of mission objectives, the prime objective being the detection of water -especially subsurface water -to provide evidence for the Trojans' formation at large solar distances. Based on DAWN and other comparable missions, we have determined suitable payload instruments to achieve these objectives. Afterwards, we have designed a spacecraft that is able to carry the selected payload to the Trojan region and rendezvous successively with three target bodies within a maximum mission duration of 15 years. Accurate low-thrust trajectories have been obtained with a global low-thrust trajectory optimization program (InTrance). During the transfer from Earth to the first target, the spacecraft is propelled by two RIT-22 ion engines from EADS Astrium, whereas a single RIT-15 is used for transfers within the Trojan region to reduce the required power. For power generation, the spacecraft uses a multi-junction solar array that is supported by concentrators. To achieve moderate mission costs, we have restricted the launch mass to a maximum of 1600 kg, the maximum interplanetary injection capability of a Soyuz/Fregat launcher. Our final layout has a mass of 1400 kg, yielding a margin of about 14%. Nestor (a member of the L4-population) was determined as the first mission target. It can be reached within 4.6 years from launch. The fuel mass ratio for this transfer is about 35%. The stay time at Nestor is 1.2 years. Eurymedon was selected as the second target (transfer time 3.5 years, stay time 3.0 years) and Irus as the third target (transfer time 2.2 years). The transfers within the Trojan L4-population can be accomplished with fuel mass ratios of about 3% for each trajectory leg. Including the stay times in orbit around the targets, the mission can be accomplished within a total duration of about 14.5 years. According to our mission analysis, it is also feasible to fly to the L5-population with similar flight times. It has to be noted that -for a first analysis -we have taken only the named targets into account. Allowing also rendezvous with unnamed objects will very likely decrease the mission duration. Based on a scaling of DAWN's mission costs (due to comparable scientific instruments and mission objectives), and taking into account the longer mission duration and the potential re-use of already developed technology, we have estimated that these three rendezvous can be accomplished with a budget of about 250 Million Euros, i.e. about 25% of ROSETTA's budget.
The Solar-Institute Jülich (SIJ) has initiated the construction of the first and only German solar tower power plant and is now involved in the accompanying research. The power plant for experimental and demonstration purposes in the town of Jülich started supplying electric energy in the beginning of 2008. The central receiver plant features as central innovation an open volumetric receiver, consisting of porous ceramic elements that simultaneously absorb the concentrated sunlight and transfer the heat to ambient air passing through the pores so that an average temperature of 680°C is reached. The subsequent steam cycle generates up to 1.5 MWe. A main field of research at the SIJ is the optimization of the absorber structures. To analyze the capability of new absorber specimens a special test facility was developed and set up in the laboratory. A high-performance near-infrared radiator offers for single test samples a variable and repeatable beam with a power of up to 320 kW/m² peak. The temperatures achieved on the absorber surface can reach more than 1000°C. To suck ambient air through the open absorber - like on the tower - it is mounted on a special blower system. An overview about the test facility and some recent results will be presented.
The importance of validating and reproducing the outcome of computational processes is fundamental to many application domains. Assuring the provenance of workflows will likely become even more important with respect to the incorporation of human tasks to standard workflows by emerging standards such as WS-HumanTask. This paper addresses this trend by an actor-based workflow approach that actively support provenance. It proposes a framework to track and store provenance information automatically that applies for various workflow management systems. In particular, the introduced provenance framework supports the documentation of workflows in a legally binding way. The authors therefore use the concept of layered XML documents, i.e. history-tracing XML. Furthermore, the proposed provenance framework enables the executors (actors) of a particular workflow task to attest their operations and the associated results by integrating digital XML signatures.
Lightning safety guidelines
(2010)
This paper introduces lightning to the layman, noting the right behaviour in front of thunderstorms as well as protective measures against lightning. It also contributes to the prevention of lightning injuries and damages. This report was prepared by the authors inside the AHG1 Group for IEC TC81 (Lightning Protection).
Large power plants can be endangered by lightning strikes with possible consequences regarding their safety and availability. A special scenario is a lightning strike to the HV overhead transmission line close to the power plant's connection to the power grid. If then additionally a so-called shielding failure of the overhead ground wire on top of the overhead transmission line is assumed, i.e. the lightning strikes directly into a phase conductor, this is an extreme electromagnetic disturbance. The paper deals with the numerical simulation of such a lightning strike and the consequences on the components of the power plant's auxiliary power network connected to different voltage levels.
Planning the air-terminations for a structure to be protected the use of the rolling-sphere method (electro-geometrical model) is the best way from the physics of lightning point-of-view. Therefore, international standards prefer this method. However, using the rolling-sphere method only results in possible point-of-strikes on a structure without giving information about the probability of strikes at the individual points compared to others.
Currently, most workflow management systems in Grid environments provide push-oriented job distribution strategies, where jobs are explicitly delegated to resources. In those scenarios the dedicated resources execute submitted jobs according to the request of a workflow engine or Grid wide scheduler. This approach has various limitations, particularly if human interactions should be integrated in workflow execution. To support human interactions with the benefit of enabling inter organizational computation and community approaches, this poster paper proposes the idea of a pull-based task distribution strategy. Here, heterogeneous resources, including human interaction, should actively select tasks for execution from a central repository. This leads to special demands regarding security issues like access control. In the established push-based job execution the resources are responsible for granting access to workflows and job initiators. In general this is done by access control lists, where users are explicitly mapped to local accounts according to their policies. In the pull-based approach the resources actively apply for job executions by sending requests to a central task repository. This means that every resource has to be able to authenticate against the repository to be authorized for task execution. In other words the authorization is relocated from the resources to the repository. The poster paper introduces current work regarding to the mentioned security aspects in the pull-based approach within the scope of the project “HiX4AGWS”.
In steps of the production chain of carbide inserts, such as unloading or packaging, the conformity test of the insert type is done manually, which causes a statistic increase of errors due to monotony and fatigue of the worker and the wide variety of the insert types. A machine vision system is introduced that captures digital frames of the inserts in the production line, analyses inspects automatically and measures four quality features: coating colour, edge radius, plate shape and chip-former geometry. This new method has been tested on several inserts of different types and has shown that the prevalent insert types can be inspected and robustly classified in real production environment and therefore improves the manufacturing automation.
Biomechanics studies biological soft tissue materials (growth, remodeling) in vivo. For this objective, the detailed information of material properties must be well defined to construct reliable constitutive models. In the paper, the bulge test is carried out with elastomers in order to develop a test method. Then, application of the test for soft tissue materials is straightforward due to the similarities between elastomers with soft tissue materials as proved in Holzapfel 2005, Ogden 2009. It means, after the preliminary experiments and parameter identification with rubber materials has been setup, experiments on soft tissue materials can be similarly carried out. Elastomers have a complex behavior which strongly depends on the largest previous load cycle. For simplicity we consider only the first loading.