Polymer nanocomposites based on epoxy resin and ATH as a new flame retardant for CFRP: preparation and thermal characterisation

Nanoscale aluminium trihydroxide (ATH) is examined to its suitability for carbon fibre reinforced plastics (CFRP) as a novel flame retardant. In particular the influence of particle size and concentration of ATH to the fire behaviour of epoxy polymer matrices is determined. The particle size is adjusted by means of different dispersing techniques. By SEM images and viscosity measurements the homogeneity of the produced ATH dispersions for the liquid ones and of cured epoxy–ATH nanocomposites is determined. Based on these pre-results, selected ATH dispersions are used for the manufacturing of CFRP which are produced by the proved injection technology. The thermal stability of the ATH nanocomposite plates and the corresponding CFRP plates are analyzed by means of quantitative single difference thermoanalysis (QSDTA). The fire behaviour is characterised by using the OSU chamber test. Both tests indicate a reduced heat release rate by decreasing the ATH particle size, i.e. the thermal load decreases. A combined fire protection mechanism is discussed for the improved fire protection through ATH nanoparticles.     

MRPC: A high performance RPC system for MPMD parallel computing

MRPC is an RPC system that is designed and optimized for MPMD parallel computing. Existing systems based on standard RPC incur an unnecessarily high cost when used on high‐performance multi‐computers, limiting the appeal of RPC‐based languages in the parallel computing community. MRPC combines the efficient control and data transfer provided by Active Messages (AM) with a minimal multithreaded runtime system that extends AM with the features required to support MPMD. This approach introduces only the necessary RPC overheads for an MPMD environment. MRPC has been integrated into Compositional C++ (CC++), a parallel extension of C++ that offers an MPMD programming model. Basic performance in MRPC is within a factor of two from those of Split‐C, a highly tuned SPMD language, and other messaging layers. CC++ applications perform within a factor of two to six from comparable Split‐C versions, which represent an order of magnitude improvement over previous CC++ implementations. Copyright © 1999 John Wiley & Sons, Ltd.     

Estimating the Optimal Margins of Embeddings in Euclidean Half Spaces

Concept classes can canonically be represented by matrices with entries 1 and –1. We use the singular value decomposition of this matrix to determine the optimal margins of embeddings of the concept classes of singletons and of half intervals in homogeneous Euclidean half spaces. For these concept classes the singular value decomposition can be used to construct optimal embeddings and also to prove the corresponding best possible upper bounds on the margin. We show that the optimal margin for embedding n singletons is and that the optimal margin for half intervals over {1,...,n} is . For the upper bounds on the margins we generalize a bound by Forster (2001). We also determine the optimal margin of some concept classes defined by circulant matrices up to a small constant factor, and we discuss the concept classes of monomials to point out limitations of our approach.     

Semantic-Web-Technologien in der Arbeitsplatzvermittlung

Zusammenfassung The importance of the Internet for job procurement is increasing for the reason that three quarters of the people in the employment age are online. On the other hand because ever more companies are publishing their job offers on the Web. However, due to the large number of openings published online it is almost impossible for job seekers and job portals to gain an overview of the entire employment market. Since job offers lack semantically meaningful annotations, the search and integration into databases are made highly difficult. Applying Semantic Web technologies to the e-recruitment process provides advantages for all participants in the market. In this paper we describe a method for analysing the domain-specific language of an application domain. We use this method to describe the e-recruitment process and the necessary ontologies for annotating job offers and job applications. In conclusion, we present the prototypical implementation of the scenario based on Semantic Web, especially semantic matching.     

Comparison of bronchial challenge with ultrasonic nebulized distilled water and hypertonic saline in children with mild-to-moderate asthma

There is still controversy about the most suitable method to measure bronchial hyperresponsiveness in children. In epidemiological surveys, nonisotonic aerosols are being used increasingly for bronchial provocation testing. Our aim was to study the acceptability, safety and correlation between two published bronchial challenge tests. Two standardized protocols--the inhalation of hypertonic saline (HS) and ultrasonically-nebulized distilled water (UNDW)--were performed in 36 children: 19 patients with the clinical diagnosis of mild-to-moderate asthma (7-12 yrs of age), and 17 control subjects (8-18 yrs of age). HS challenge involved stepwise inhalation of 4.5% saline (for 0.5, 1, 2, 4 and 8 min), whereas challenge with UNDW was performed as a single step protocol with 10 min inhalation of cold UNDW. Asthma medication was withheld prior to challenge testing. Thirty five subjects completed both challenge tests (one asthmatic patient did not return after UNDW challenge) in random order within a 7 day time interval. For HS a > or = 15% reduction in forced expiratory volume in one second (FEV1) from baseline was considered a positive response, and for UNDW a > or = 10% decrease. In 13 of the 19 asthmatic patients, but in none of the controls, a positive response was observed for UNDW. Fifteen out of 18 patients and one control subject had a positive response to HS. Twelve out of 18 asthmatic children responded to both challenges, three responded only to HS and three had no response to either challenge. There was a negative correlation between log provocative dose causing a 15% reduction in FEV1 (PD15) after HS and the maximum fall in FEV1 after UNDW (rs = -0.63; p < 0.005). The HS challenge had a lower acceptability than challenge with UNDW due to the unpleasant salty taste of HS. However, this did not inhibit the completion of the tests in any subject. The results of this study suggest a good correlation between response to hypertonic saline and ultrasonically-nebulized distilled water in children with mild-to-moderate asthma. A multiple step protocol might be safer when applied in field studies involving children.     

Interaction of a granular stream with an obstacle

We investigate numerically the interaction of a stream of granular particles with a resting obstacle in two dimensions. For the case of high stream velocity we find that the force acting on the obstacle is proportional to the square of the stream velocity, the density and the obstacle size. This behaviour is equivalent to that of non-interacting hard spheres. For low stream velocity a gap between the obstacle and the incoming stream particles appears which is filled with granular gas of high temperature and low density. As soon as the gap appears the force does not depend on the square of velocity of the stream but the dependency obeys another law.     

Test and evaluation of a solar powered gas turbine system

This paper describes the test and the results of a first prototype solar powered gas turbine system, installed during 2002 in the CESA-1 tower facility at Plataforma Solar de Almería (PSA) in Spain. The main goals of the project were to develop a solar receiver cluster able to provide pressurized air of 1000 °C and solve the problems arising from the coupling of the receivers with a conventional gas turbine to demonstrate the operability of the system. The test set-up consists of the heliostat field of the CESA-1 facility providing the concentrated solar power, a pressurized solar receiver cluster of three modules of 400 kWth each which convert the solar power into heat, and a modified helicopter engine (OST3) with a generator coupled to the grid. The first test phase at PSA started in December 2002 with the goal to reach a temperature level of 800 °C at the combustor air inlet by the integration of solar energy. This objective was achieved by the end of this test phase in March 2003, and the system could be operated at 230 kWe power to grid without major problems. In the second test phase from June 2003 to August 2003 the temperature level was increased to almost 1000 °C. The paper describes the system configuration, the component efficiencies and the operation experiences of the first 100 h of solar operation of this very successful first test of a solar operated Brayton gas turbine system.