Calibration of hydrophones based on reciprocity and time delay spectrometry

A brief survey is given of the calibration methods for hydrophones in the ultrasonic frequency range. The methods presently used in the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, West Germany, for hydrophone calibrations in the frequency range from 1 to 15 MHz are the primary subject of concern. These methods are the two-transducer reciprocity method for the calibration at discrete frequencies, the time-delay-spectrometry substitution method for quasifrequency continuous calibrations, and the two-transducer reciprocity method with time-delay spectrometry, also for quasi-frequency continuous calibration. Compared with the calibration at discrete frequencies, the expenditure of time for a calibration is considerably reduced in the case of the last-mentioned method. The influencing parameters which affect the evaluation of the measurement uncertainty are briefly discussed for the calibration methods applied at the PTB.     

DMetabench—a metadata benchmark for distributed file systems

The performance of metadata processing in large distributed file systems currently presents larger challenges than scaling of data throughput. The paper presents a novel, distributed benchmark called DMetabench for measuring the performance of metadata operations. DMetabench runs in environments with potentially thousands of nodes and allows an assessment of the scalability of metadata operations. Additionally, precise run-time performance data is preserved which allows for a better understanding of performance artifacts. Example results from production file systems are provided and discussed. Possible applications of knowledge about metadata performance scaling include the choice of an optimal parallelization strategy for metadata-intensive workloads in a specific runtime environment.     

Function block applications in control systems based on IEC 61804

A variety of fieldbus technologies and digital fieldbus devices have been introduced within the process industries over the last ten years. There has been a gradual acceptance of the fact that a variety of communication technologies are needed to fully address the application requirements of a manufacturing facility. However, engineers responsible for the specification, engineering, and implementation of control systems require that a common interface and functionality be provided in the control system. This capability should be independent of the underlying fieldbus technology or manufacturer of the fieldbus device. The draft IEC 61804 standard defines how a control system can be structured to provide this flexibility in the utilization of fieldbus technology. In this paper, we discuss how a consistent function block capability may be provided for all fieldbus technology utilized in a control system. Examples will be given of how this standard has been applied in modern control systems to give a consistent interface to Foundation Fieldbus and PROFIBUS. Some detail will be presented on the standard means that is defined for manufacturers to describe function block capability of a field device. An analysis is given of the impact and benefit that the IEC 61804 standard will have on the process industry and on manufacturers of control systems.     

Novel Method for the Synthesis of Cholesteryl Glucosides starting from Disaccharides

Steryl glucosides (SG) and acylated steryl glucosides (ASG) are natural components of plant cell membranes and present in different concentrations in various plant foods. Currently, their positive effects on human health are under investigation. The present work presents a new and efficient synthesis method for cholesteryl glucosides starting from disaccharides. A five‐step synthesis protocol is done to obtain the desired product in 35% overall yield. In the first step, the hydroxy groups of the starting material sucrose are protected using benzyl ethers. After the subsequent acidic hydrolysis the obtained pyranosyl moiety of the disaccharide is transformed to its trichloroacetimidate derivative. Next, the formation of the glycosidic bond to cholesterol is performed and catalytic transfer hydrogenation in order to remove the protecting groups leads to the desired product. In this context, APCI‐MS‐TOF has turned out to be an excellent analytical tool for the high sensitive analysis of SG as well as intermediates. Practical Applications: Due to the comparatively high amounts of SG and ASG in seeds and oils, not only the food industry but also in biodiesel production, these natural compounds are of increasing interest. However, analysis of the compounds is difficult, commercially available pure standard materials are costly and their synthesis often requires time‐consuming work‐up procedures. The described preparation method allows the synthesis of cholesteryl glucosides which can be used as reference or standard material for the quantitative analysis of phytosteryl glucosides in plant derived samples. The general synthesis method could be also applied to other SG and ASG derivatives. Cholesteryl glucosides are synthesized using a new and efficient five‐step synthesis protocol starting from disaccharides. The preparation method provides products with good overall yield and high purity and, therefore, the synthesized glucosides can be used as reference or standard material for the quantitative analysis of phytosteryl glucosides in plant derived samples. APCI‐MS‐TOF is extensively used as analytical tool for the sensitive analysis of cholesteryl glucosides as well as intermediates.     

LIDAR and vision‐based pedestrian detection system

A perception system for pedestrian detection in urban scenarios using information from a LIDAR and a single camera is presented. Two sensor fusion architectures are described, a centralized and a decentralized one. In the former, the fusion process occurs at the feature level, i.e., features from LIDAR and vision spaces are combined in a single vector for posterior classification using a single classifier. In the latter, two classifiers are employed, one per sensor‐feature space, which were offline selected based on information theory and fused by a trainable fusion method applied over the likelihoods provided by the component classifiers. The proposed schemes for sensor combination, and more specifically the trainable fusion method, lead to enhanced detection performance and, in addition, maintenance of false‐alarms under tolerable values in comparison with single‐based classifiers. Experimental results highlight the performance and effectiveness of the proposed pedestrian detection system and the related sensor data combination strategies. © 2009 Wiley Periodicals, Inc.     

Thermodynamics and Phase Equilibria in the Sr─Cu─O System

Phase equilibria in the SrO─CuO─Cu system were determined at 1173 K from the results of X-ray diffraction measurements using specimens annealed under low oxygen partial pressure ( p o₂= 0.21–10⁻⁸ atm). Electromotive force (EMF) measurements using ZrO₂ solid electrolyte cells were carried out in the ternary phase equilibria. Gibbs free energies for five reactions in the cell electrodes were summarized by equations with linear temperature dependence. The standard free energies of formation for Sr₂CuO₃, SrCuO₂, Sr₁₄Cu₂₄O₄₁, and SrCu₂O₂ were derived. The stability conditions of all oxides are displayed in the p-T-x diagram using the new data.     

Physikalische messungen an einem kunststoff als optischem medium

The possibility of using polymers of diethylene glycol bisallyl carbonate as optical components is considered. The problems of material production and molding are presented. Characterization of polymer and such problems, as the control of the polymerization process or the resistance of polymer to mechanical surface damage and climatic influences are discussed. It is shown that diethylene glycol bisallylcarbonate is a valuable addition to the series of those plastics used so far in optics. It is shown that an improvement and further development in resistance to mechanical surface damage is possible; at the same time a contribution is made to the formulation and standardization of the term “wiping strength.”     

Some notes on the abstraction operation for multi-terminal binary decision diagrams

The starting point of this work are inaccurate statements found in the literature for Multi-terminal Binary Decision Diagrams (MTBDDs) (Bahar et al., Form. Methods Syst. Des. 10(2/3):171–206, 1997; Siegle, Behaviour analysis of communication systems: compositional modelling, compact representation and analysis of performability properties, 2002; Kuntz, Symbolic semantics and verification of stochastic process algebras, 2006) regarding the well-definedness of the MTBDD abstraction operation. The statements try to relate an operation ? on a set of terminal values M to the property that the abstraction over this operation does depend on the order of the abstracted variables. This paper gives a necessary and sufficient condition for the independence of the abstraction operation of the order of the abstracted variables in the case of an underlying monoid and it treats the more general setting of a magma.