Experimentelle Untersuchungen zur radialen Durchschallung von Stämmen mittels variabler Frequenz

Zusammenfassung: Es wurden unterschiedliche Kenngrössen von Ultraschallsignalen für die Erkennung von Defekten in Stämmen getestet. Es zeigte sich, dass durch Messung der Schallgeschwindigkeit die besten Ergebnisse erzielt werden. Proben mit einer künstlich eingebrachten Bohrung mit 30mm Durchmesser konnten über die Schallgeschwindigkeit von solchen mit 100mm Durchmesser separiert werden. Das Füllen der Hohlräume mit Sägespänen bewirkte keinen Unterschied der Messergebnisse. Die Parameter RMS, Peak to Peak, Amplitude und Signalenergie erbrachten keine verwertbaren Ergebnisse. Die Signalamplitude korreliert stark mit der Dichte und der Holzfeucht

FACHBEITRAG Unleashing XQuery for Data-Independent Programming

an SQL equivalent for XML data, but its roots in functional programming make it also a perfect choice for processing almost any kind of structured and semi-structured data. Apart from standard XML processing, however, advanced language features make it hard to efficiently implement the complete language for large data volumes. This work proposes a novel compilation strategy that provides both flexibility and efficiency to unleash XQuery’s potential as data programming language. It combines the simplicity and versatility of a storage-independent data abstraction with the scalability advantages of set-oriented processing. Expensive iterative sections in a query are unrolled to a pipeline of relational-style operators, which is open for optimized join processing, index use, and parallelization. The remaining aspects of the language are processed in a standard fashion, yet can be compiled anytime to more efficient native operations of the actual runtime environment. This hybrid compilation mechanism yields an efficient and highly flexible query engine that is able to drive any computation from simple XML transformation to complex data analysis, even on non-XML data. Experiments with our prototype and stateof-the-art competitors in classic XML query processing and business analytics over relational data attest the generality and efficiency of the design

Bacterial Adhesion on Dental Polymers as a Function of Manufacturing Techniques

The microbiological behavior of dental polymer materials is crucial to secure the clinical success of dental restorations. Here, the manufacturing process and the machining can play a decisive role. This study investigated the bacterial adhesion on dental polymers as a function of manufacturing techniques (additive/subtractive) and different polishing protocols. Specimens were made from polyaryletherketone (PEEK, PEKK, and AKP), resin-based CAD/CAM materials (composite and PMMA), and printed methacrylate (MA)-based materials. Surface roughness (Rz; Ra) was determined using a laser scanning microscope, and SFE/contact angles were measured using the sessile drop method. After salivary pellicle formation, in vitro biofilm formation was initiated by exposing the specimens to suspensions of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Adherent bacteria were quantified using a fluorometric assay. One-way ANOVA analysis found significant influences (p < 0.001) for the individual parameters (treatment and material) and their combinations for both types of bacteria. Stronger polishing led to significantly (p < 0.001) less adhesion of S. sanguinis (Pearson correlation PC = −0.240) and S. mutans (PC = −0.206). A highly significant (p = 0.010, PC = 0.135) correlation between S. sanguinis adhesion and Rz was identified. Post hoc analysis revealed significant higher bacterial adhesion for vertically printed MA specimens compared to horizontally printed specimens. Furthermore, significant higher adhesion of S. sanguinis on pressed PEEK was revealed comparing to the other manufacturing methods (milling, injection molding, and 3D printing). The milled PAEK samples showed similar bacterial adhesion. In general, the resin-based materials, composites, and PAEKs showed different bacterial adhesion. Fabrication methods were shown to play a critical role; the pressed PEEK showed the highest initial accumulations. Horizontal DLP fabrication reduced bacterial adhesion. Roughness < 10 µm or polishing appear to be essential for reducing bacterial adhesion

A simple anisotropy correction procedure for acoustic wood tomography

Anisotropy of acoustic propagation velocities is a ubiquitous feature of wood. This needs to be considered for successful application of travel time tomography, an increasingly popular technique for non-destructive testing of living trees. We have developed a simple correction scheme that removes first-order anisotropy effects. The corrected travel-time data can be inverted with isotropic inversion codes that are commercially available. Using a numerical experiment, we demonstrate the consequences of ignoring anisotropy effects and outline the performance of our correction scheme. The new technique has been applied to two spruce samples. Subsequent inspection of the samples revealed a good match with the tomogram

Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Tailor-made lock protocols and their DBMS integration

ABSTRACT We outline the use of fine-grained lock protocols as a concurrency control mechanism for the collaboration on XML documents and show that their tailor-made optimization towards the access model used (e.g., DOM operations) pays off. We discuss how hard-wired lock services can be avoided in an XML engine and how we can, based on loosely coupled services, exchange lock protocols even at runtime without affecting other engine services. The flexible use of these lock protocols is further enhanced by enabling automatic runtime adjustments and specialized optimizations based on knowledge about the application. These techniques are implemented in our native XML database management system (XDBMS) called XTC MOTIVATION The hierarchical structure of XML documents is preserved in native XDBMSs. The operations applied to such tree structures are quite different from those of tabular (relational) data structures. Therefore, solutions for concurrency control optimized for relational DBMSs will not meet high performance expectations. However, efficient and effective transaction-protected collaboration on XML documents [11] becomes a pressing issue because of their number, size, and growing use. Tailor-made lock protocols that take into account the tree characteristics of the documents and the operations of the workload are considered a viable solution. But, because of structure variations and workload changes, these protocols must exhibit a high degree of flexibility as well as automatic means of runtime adjustments. Because a number of language models are available and standardized for XML Tailor-made Lock Protocols and their DBMS Integration FINE-GRAINED DOM-BASED LOCKING Because our XML documents are stored in a B*-tree structure [5], the question whether or not specific tree-based lock protocols can be used immediately arises. So-called B-tree lock protocols provide for structural consistency while concurrent database operations are querying or modifying database contents and its representation in B-tree indexes Hierarchical lock protocols [3] -also denoted as multi-granularity locking (MGL) -are used &quot;everywhere&quot; in the relational world. For performance reasons in XDBMSs, fine-granular isolation at the node level is needed when accessing individual nodes or traversing a path, whereas coarser granularity is appropriate when traversing or scanning entire trees. Therefore, lock protocols, which enable the isolation of multiple granules each with a single lock, are also beneficial in XDBMSs. Regarding the tree structure of documents, objects at each level can be isolated acquiring the usual locks with modes R (read), X (exclusive), and U (update with conversion option), which implicitly lock all objects in the entire subtree addressed. To avoid lock conflicts when objects at different levels are locked, so-called intention locks with modes IR (intention read) or IX (intention exclusive) have to be acquired along the path from the root to the object to be isolated and vice versa when the locks are released Using the IRIX protocol, a transaction reading nodes at any tree level had to use R locks on the nodes accessed thereby locking these nodes together with their entire subtrees. This isolation is too strict

Experimentelle Untersuchungen zur radialen Durchschallung von Stämmen mittels variabler Frequenz

ISSN:0018-3768ISSN:1436-736