Parallel kinematic concept for stationary high performance cutting in wood machining centers

In recent years parallel kinematic machines for wood machining have come into use more frequently. Despite first promising prototypes, these machines are single solutions for specific applications. To meet the requirements of shorter product life cycles and higher product diversity, high flexibility is demanded of the machining system. This paper presents a new wood machining center obtaining both, the reduction of the primary and secondary processing times. The machine concept, based on a parallel kinematic structure, allows high operating speeds and accelerations not only for workpiece machining but also for handling. Thus, the machine can be used without any external handling devices. The kinematic structure originates from a plane closed five-bar chain with two linear drives and additional drive axes for stroke and rotation. In order to increase the useable workspace a continuous motion between different assembly modes is realized. To guarantee a high feed rate and to minimize set-up times, an optimized dust exhaustion is included.     

Decentralized array processing using the MODE algorithm

Centralized methods for source location using sensor arrays have computational and communication burdens that increase significantly with the number of sensors in the array. Therefore, these methods may not be usable in the applications involving very large arrays. In such applications, the data processing may need to be decentralized. This paper introduces two methods for decentralized array processing, based on the recently proposed MODE algorithm. For prescribed nonoverlapping subarrays, both methods are shown to be statistically optimal in the sense that asymptotically they provide the most accurate decentralized estimates of source location parameters. The problem of subarray selection to further optimize the estimation accuracy is only briefly addressed. The two methods are intended for different types of applications: the first should be preferred when there exist significant possibilities for local processing or for parallel computation in the central processor; otherwise the second method should be preferred. The accuracy of the two decentralized methods is compared to the centralized Cramér-Rao bound, both analytically and numerically, in order to provide indications about the loss of accuracy associated with decentralized processing.The work of P. Stoica was supported by a grant from the Royal Swedish Academy of Engineering Sciences and by the Swedish Research Council for Engineering Sciences under contract 91-676. The work of A. Nehorai was supported by the Air Force Office of Scientific Research under grant no. AFOSR-90-0164, and by the Office of Naval Research under grant no. N00014-91-J-1298.on leave at the Department of Applied Electronics, Chalmens University of Technology, 2-41296 Göthensberg, Sweeden.     

Rekonstruktion von Barockspiegeln des Historischen Grünen Gewölbes im Dresdener Schloss

Reconstruction of Baroque Mirrors of the Historical Green Vault in the Dresden Royal Palace On the 1^st September 2006 the Federal Chancellor Dr. Angela Merkel inaugurated the reconstructed Historical Green Vault, the treasury museum of the Saxon electors and kings. Since its destruction on 13^th February 1945 two generations have been working scientific‐artistically in order to set the course for its reconstruction. The idea of a baroque mirror chamber has firstly been implemented on a sequence of 8 rooms in the Green Vault. The original mirrors, which were covered with tin amalgam, had a considerably lower reflexivity modern day silver mirrors. From originally 423 m² mirror surface, only 60 m² could be reused. For the restoration and reconstruction of the original mirrors extensive analytic investigations became necessary, which the state‐owned company Sächsisches Immobilien‐ und Baumanagement (SIB) commissioned the Fraunhofer Institute for Electron Beam and Plasma Technology (FEP). On basis of these results the responsible restoration commission decided to replace partly destroyed mirror surfaces using the historical tin amalgam mirror technology. The fully destroyed jewel room would be restored with mirrors including partial gold etching. Due to hygienical and temporal reasons those mirrors were coated through a mercury‐free vacuum thin film technology ‐ the magnetron sputtering. The results show that a layer system consisting of tin‐bronze‐titanium and protective lacquers represent an adequate replacement for the original tin amalgam mirrors. The procedure allows relatively uncomplicated partial silverings and a subsequent inserting of artistic gold etchings.     

Don't underestimate the problems of user centredness in software development projectsthere are many!

. On the basis of a longitudinal field study of 29 commercial software development projects, the pros and cons of user centredness in software development were analysed. We looked at two concepts: user participation-an organizational device-involving a user representative in the team, and user orientation-a cognitive-emotional concept-which pertains to positive attitudes towards users. Both were found to be associated with project difficulties relating to process and product quality as well as overall project success. We suggest that the issue is no longer whether or not to involve users, but instead to develop a realistic understanding of the difficulties associated with user centredness.     

The relationship among self-concept, self-efficacy, and performance in mathematics during secondary school.

The relationship among self-concept, self-efficacy, and performance in mathematics was examined among 416 high school students. Participants completed a questionnaire assessing mathematics self-concept and mathematics self-efficacy. Performance was assessed using end-of-term exam results in mathematics. Confirmatory factor analyses supported the existence of two self-concept components--a competency component and an affective component. Self-efficacy items and the competency items of self-concept also loaded on a single factor. Social comparison information was equally influential in the formation of each construct. Self-efficacy beliefs, however, were identified as most highly related with performance in mathematics and percentages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The transfer of infiltration measurement results to other sewers by means of discriminant analysis.

The cost-oriented and sustainable operation of sewer systems requires a comprehensive knowledge about the infiltration situation in the catchment. Owing to the high expenditures for infiltration measurements a reliable transfer of measurement results to other sewer sections would be highly beneficial. Assuming a functional relationship between sewer characteristics and infiltration rates can be identified, such a transfer can be realised by means of classification techniques. In this paper a method is introduced which is based on discriminant analysis and which allows for a transfer of measurement results to similar sub-catchments. The method was applied using two data sets with measured or virtual infiltration rates. It yields acceptable results as a total fraction of 50% to 75% of the investigated sub-catchments was assigned correctly. Furthermore, additional information to assess the results was provided. The quality of the transfer results depends strongly on the homogeneity of the considered sub-catchments. Due to this restriction the practical applicability of the method is restricted. Nevertheless, it might be used as a screening procedure for planning of effective detailed infiltration investigations.