All-solid-state tunable continuous-wave ultraviolet source with high spectral purity and frequency stability

We present a novel approach for the generation of higly frequency-stable, widely tunable, single-frequency cw UV light that is suitable for high-resolution spectroscopy. Sum-frequency generation (SFG) of two solid-state sources with a single cavity resonant for both fundamental waves is employed. Using a highly stable, narrow-linewidth frequency-doubled cw Nd:YAG laser as a master laser and slaving to it the SFG cavity and the other fundamental wave from a Ti:sapphire laser, we generate UV radiation of 33-mW output power around 313 nm. Alternatively, we use a diode laser instead of the Ti:sapphire laser and produce an output power of 2.1 mW at 313 nm. With both setups we obtain a continuous tunability of >15 GHz, short-term frequency fluctuations in the submegahertz range, a long-term frequency drift below 100 MHz/h, and stable operation for several hours. The theory of optimized doubly resonant SFG is also given.     

Protein identification by MALDI-TOF-MS peptide mapping: a new strategy

A new strategy for identifying proteins by MALDI-TOF-MS peptide mapping is reported. In contrast to current approaches, the strategy does not rely on a good relative or absolute mass accuracy as the criterion that discriminates false positive results. The protein sequence database is first searched for all proteins that match a minimum five of the submitted masses within the maximum expected relative errors when the default or externally determined calibration constants are used, for instance, +/-500 ppm. Typically, this search retrieves many thousand candidate sequences. Assuming initially that each of these is the correct protein, the relative errors of the matching peptide masses are calculated for each candidate sequence. Linear regression analysis is then performed of the calculated relative errors as a function of m/z for each candidate sequence, and the standard deviation to the regression is used to distinguish the correct sequence among the candidates. We show that this parameter is independent of whether the mass spectrometric data were internally or externally calibrated. The result is a search engine that renders internal spectrum calibration unnecessary and adapts to the quality of the raw data without user interference. This is made possible by a dynamic scoring algorithm, which takes into account the number of matching peptide masses, the percentage of the protein's sequence covered by these peptides and, as new parameter, the determined standard deviation. The lower the standard deviation, the less cleavage peptides are required for identification and vice versa. Performance of the new strategy is demonstrated and discussed. All necessary computing has been implemented in a computer program, free access to which is provided in the Internet.     

Comparison of analysis methods for package-induced stresses on moulded Hall sensors

Due to the piezoresistive and the piezo-Hall effect in semiconductor materials, Hall sensors show a strong temperature dependency and also a drift when subjected to temperature cycles Manic et al. (2000). Four factors mainly influence the mechanical stress in the sensitive layer. These are the geometry of the device, the differences of the coefficients of thermal expansion of the package materials, the temperature-dependent material properties and the time-dependent, viscous material properties. The objective of this investigation was to determine the mechanical stress in a moulded Hall sensor during the packaging process by finite-element simulation in comparison to experimental methods. It is shown that after each process-step the mechanical stress in the sensitive layer changes over time depending on the absolute value and the rate of the temperature change. Measurements of the inverse bending radius of glued and moulded chips show good agreement to the simulations.     

Semantics and Verification of Data Flow in UML 2.0 Activities

One of the major changes in going from UML 1.5 to UML 2.0 is the reengineering of activity diagrams. This paper examines activity diagramies as described in the current version of the UML 2.0 standard by defining a denotational semantics. It covers basic control flow and data flow, but excludes hierarchy, expansion nodes, and exception handling (see [Störrle, H., Semantics of Control-Flow in UML 2.0 Activities, in: P. Bottoni, C. Hundhausen, S. Levialdi and G. Tortora, editors, Proc. IEEE Symposium on Visual Languages and Human-Centric Computing (VL/HCC) (2004), pp. 235–242, Störrle, H., Semantics of Exceptions in UML 2.0 Activities (2004), submitted to Journal of Software and Systems Modeling, May, 9^th, available at www.pst.informatik.uni-muenchen.de/~stoerrle, Störrle, H., Semantics of Expansion Nodes in UML 2.0 Activities, in: I. Porres, editor, Proc. 2^nd Nordic Ws. on UML, Modeling, Methods and Tools (NWUML'04), 2004] for these issues). The paper shows, where the constructs proposed in the standard are not so easily formalized, and how the formalisation may be used for formal analysis.     

Semantic Based Prefetching in News-on-Demand Video Servers

In video databases, a video document has two abstractions. The high level abstraction corresponds to the view in which the contents of that video document are seen by end users, and the low level abstraction corresponds to the physical organization of that video document. Due to the huge size of continuous data, reducing I/O has become a key issue. The latter has been mostly addressed by developing appropriate buffering techniques. In addition, prefetching techniques play a major role to meet the video data requirements. In this paper, we propose a novel prefetching strategy based not only on run-time information (objects access frequencies for example) but also on knowledge about clips structures. The proposed technique merges the two views of a video document to trigger prefetching at the video server level. Simulation experiments for a News-on-Demand application performed on different request scenarios show an improvement of about 18% in the buffer hit-rate with respect, first to the available buffer size and second to the request arrival rate.     

Bundle event structures: A revised cpo approach

Bundle event structures equipped with a partial order ? have been used to give a true concurrency denotational semantics for LOTOS. This model has also been extended by time and stochastic information. Unfortunately it fails to yield a complete partial order (cpo) as we illustrate by an example.We propose a subset of all bundle event structures such that it forms a cpo. This subset is closed under the usual operators on bundle event structures. And as a consequence these operators are continuous. Therefore, this subset can be used to give a denotational semantics of LOTOS.     

Integrating Process Support and Knowledge Management for Virtual Software Development Teams

In this paper we describe how knowledge management and software process support can be integrated to improve the efficiency of virtual software teams. The approach presented here integrates a process enactment environment with an on-demand knowledge delivery strategy that is based on parameterized information needs models. The parameters in the information needs models are bound at project execution time to values extracted from the process enactment engine. Thus, the approach supports virtual teams by establishing a platform for systematic and task-specific knowledge exchange. The proposed approach is prototypically implemented in the MILOS system, an open source project of the University of Calgary (Canada) and the University of Kaiserslautern (Germany).     

An automated gantry crane as a large workspace robot

In the context of further automation of manufacturing processes, automated transportation of heavy weights using cranes becomes more and more important. Applying the skills of robots to crane automation, a wide market of new applications could be developed. The main idea is to interpret the crane as a large workspace-serving robot. The crane hook represents the effector of the robot. As an example for the effector, an automated storage and retrieval unit for rack operations by a crane with three active auxiliary effector axes has been developed and integrated into the control concept. The control has been realized for a reconstructed 5-t-bridge crane with workspace dimensions of 30 m×8.7 m×7 m.