Prevention and Mitigation Strategies to Address Recent Brittle Fractures in Steel Bridges

Brittle fracture results in unplanned loss of service, very costly repairs, concern regarding the future safety of the structure, and potential loss of life. These types of failures are most critical when there is no evidence of fatigue cracking leading up to the fracture and the fracture origin is concealed from view. Hence, the failure occurs without warning and the details are, essentially, noninspectable. In these cases, it appears desirable to take a proactive approach and introduce preventative retrofits to reduce the potential for future crack development. These efforts will help ensure that the likelihood of unexpected fractures is minimized. This paper examines the behavior of two bridge structures in which brittle fractures have developed in recent times, discusses the causes of the failures, and offers suggested design strategies for prevention and retrofit mitigation techniques. In situations where considerable uncertainty exists in the prediction of accumulated damage or in the ability to reliably inspect critical details, preemptive retrofit strategies appear to be highly desirable.     

Integrated cost/weight optimization of aircraft structures

A methodology for a combined cost/weight optimization of aircraft components is proposed. The objective function is formed by a simplified form of direct operating cost, i.e. by a weighted sum of the manufacturing cost and the component weight. Hence, the structural engineer can perform the evaluation of a design solution based on economical values rather than pure cost or weight targets. The parameter that governs the balance between manufacturing cost and weight is called weight penalty and incorporates the effect of fuel burn, environmental impact or contractual penalties due to overweight. Unlike previous work, the analytical cost model and structural models are replaced by commercially available software packages that allow a more realistic model of the manufacturing costs; further, arbitrary constraints for the structural analysis can be implemented. By means of parametric studies it is shown that the design solution strongly depends on the magnitude of the weight penalty.     

基于蓝牙的多机通信的实现及其应用

本文提出了一种基于蓝牙通信协议的PC机监控多台单片机控制系统的多机通信方案。针对蓝牙芯片PTR2000,对多机通信的设计方法、系统的组成原理进行了阐述;对上位机蓝牙接口电路、单片机蓝牙接口电路的实现过程进行了详细的说明;对蓝牙通信协议,特别是大数据传输协议进行了设计。以汉字传输过程为例,提出了一种提取汉字的点阵算法,对上下位机之间进行汉字传输的软件设计与实现过程进行了说明,对实验结果进行了分析。实验结果表明,上述通信方案是成功的和有效的。     

Rechtsprechung zum Datenschutz 2006 — Teil 1

Neben den Kontroversen um die Vorratsdatenspeicherung, den personenbezogenen Daten aus der Mautüberwachung und den Reaktionsm?glichkeiten gegenüber dem Terrorismus herrschte auch in der Judikatur zum Datenschutz rege Bewegung. Die davon betroffenen Rechtsgebiete waren mannigfaltig, was abermals unterstreicht, dass das Datenschutzrecht eine Querschnittmaterie darstellt. Dies ist der Anlass, die wichtigsten Entscheidungen des vergangenen Jahres kurz darzustellen.     

Rechtsprechung zum Datenschutz 2006 — Teil 2

Nachdem sich der erste Teil der Rechtsprechungsübersicht insbesondere der Judikatur des BVerfG und des BGH gewidmet hat, befasst sich der zweite Teil vornehmlich mit Entscheidungen aus dem Zeitraum Januar bis Anfang November 2006, die im Arbeitsrecht und dem Internetrecht sowie auf den Gebieten der Werbung und des Marketing ergangen sind.     

Routing on Meshes with Buses

We consider the problem of routing packets on an MIMD mesh-connected array of processors augmented with row and column buses. We give lower bounds and randomized algorithms for the problem of routing k-permutations (where each processor is the source and destination of exactly k packets) on a d-dimensional mesh with buses, which we call the (k,d)-routing problem. We give a general class of ``hard' permutations which we use to prove lower bounds for the (k,d)-routing problem, for all k,d≥ 1. For the (1,1)- and (1,2)-routing problems the worst-case permutations from this class are identical to ones published by other authors, as are the resulting lower bounds. However, we further show that the (1,d)-routing problem requires 0.72 ... n steps for d=3, 0.76 ... n steps for d=4, and slightly more than steps for all d≥ 5. We also obtain new lower bounds for the (k,d)-routing problem for k,d > 1, which improve on the bisection lower bound in some cases. These lower bounds hold for off-line routing as well. We develop efficient algorithms for the (k,1)-routing problem and for the problem of routing k-randomizations (where each processor has k packets initially and each packet is routed to a random destination) on the one-dimensional mesh and use them in a general (k,d)-routing algorithm which improves considerably on previous results. In particular, the routing time for the (1,d)-routing problem is bounded by steps with high probability (whp), whenever for some constant ε > 0, and the routing time for the (k,d)-routing problem is steps whp whenever for some constant ε > 0 and k≥ 3.6 ... d, matching the bisection lower bound. We then present a simple algorithm for the (2,2)-routing problem running in 1.39 ... n+o(n) steps whp. Finally, for the important special case of routing permutations on two-dimensional meshes with buses, the (1,2)-routing problem, we give a more sophisticated algorithm that runs in 0.78 ... n+o(n) steps whp. Received May 18, 1994; revised June 23, 1995.     

Evaluating the usability of natural language query languages and interfaces to Semantic Web knowledge bases

The need to make the contents of the Semantic Web accessible to end-users becomes increasingly pressing as the amount of information stored in ontology-based knowledge bases steadily increases. Natural language interfaces (NLIs) provide a familiar and convenient means of query access to Semantic Web data for casual end-users. While several studies have shown that NLIs can achieve high retrieval performance as well as domain independence, this paper focuses on usability and investigates if NLIs and natural language query languages are useful from an end-user's point of view. To that end, we introduce four interfaces each allowing a different query language and present a usability study benchmarking these interfaces. The results of the study reveal a clear preference for full natural language query sentences with a limited set of sentence beginnings over keywords or formal query languages. NLIs to ontology-based knowledge bases can, therefore, be considered to be useful for casual or occasional end-users. As such, the overarching contribution is one step towards the theoretical vision of the Semantic Web becoming reality.     

Routing in Polygons Without Rectilinearly Visible Corners

In this paper we present an algorithm for the routing problem in a routing region which is bordered by a simple polygonal line, such that there are no rectilinearly visible corners. The routing problem consists in finding pairwise edge-disjoint paths in the grid for the nets connecting some given pairs of boundary vertices. Whenever a solution exists our algorithm finds it in time O(U log²U), where U is the size of the boundary. This is a generalization of the algorithm for rectangle routing by Mehlhorn and Preparata (1986, J. Assoc. Comput. Mach.33, 60-85), which up to now has been the only method with sublinear running time in respect of the routing area.     

An extension of the Boyer-Moore Theorem Prover to support first-order quantification

We describe an implementation of an extension to the Boyer-Moore Theorem Prover and logic that allows first-order quantification. The extension retains the capabilities of the Boyer-Moore system while allowing the increased flexibility in specification and proof that is provided by quantifiers. The idea is to Skolemize in an appropriate manner. We demonstrate the power of this approach by describing three successful proof-checking experiments using the system, each of which involves a theorem of set theory as translated into a first-order logic. We also demonstrate the soundness of our approach.This research was supported in part by ONR Contract N00014-88-C-0454. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressed or implied, of Computational Logic, Inc., the Office of Naval Research or the U.S. Government.