Sicherheitskonzept von unterspannten Konstruktionen

Safety Concept for Cable Supported Structures Codes treat permanent actions and prestress as independent actions with different (partial) safety factors. However, for structures whose geometry is controlled during prestressing, there are proposals to consider dead load and prestress as one load case “permanent actions” with the same safety factor. Both approaches are compared systematically with regard to the structural safety. It is shown that combining dead load and prestress in one load case does not yield a sufficient safety level. The results of the investigations lead to a proposal which considers the influence of controlling the geometry during prestressing by modifying the partial safety factor for the action prestress. This results in a sufficient safety level while also permitting more efficient dimensioning.     

Überprüfung des Tragverhaltens der Talbrücke Altwipfergrund

Validation of the structural behaviour of the Altwipfergrund Bridge. At the middle of the eighties in France composite bridges with corrugated steel webs have been built for the first time. Just a few years later this principle was adopted in Japan and many bridges of this kind have been built. At the same time in Germany also, the first considerations about these bridges have been taken place, but unfortunately to this date only one construction has been built, i.e. the Altwipfergrund Bridge. A comprehensive research project is presently carried out for research on general behaviour and the detailing of bridges with corrugated steel webs. The results are accompanied by measurements at the Altwipfergrund Bridge. Thus it was possible to validate the results of numerical calculations and laboratory tests by the results of measurements. Based on this information, the potential of these structures regarding web thickness, amount and style of prestressing and reduction of composite joints can be identified.     

A function-oriented surface reconstruction framework for reverse engineering

Reverse engineering can be considered as the methodological process of analyzing and reconstructing a digital model of a physical asset. It has gained considerable interest with the advent of sophisticated sensors and data processing technologies hence becoming an important enabler for the product digital twin. However, while existing approaches to reverse engineering focus on the mere geometric reconstruction, this paper presents a novel paradigm called function-oriented surface reconstruction, that is capable of reconstructing the underlying part and surface function and thus outperforms existing methods. The applicability of the presented method is demonstrated through a case study of a gearbox.     

Hydrogen production and technology: today,tomorrow and beyond

Hydrogen is produced on a large scale by a wide variety of processes starting with feedstocks like natural gas, crude oil products to coal as well as water-using processes like steam reforming, partial oxidation, coal gasification, metal-water processes and electrolysis. Hydrogen is also recovered from various gas streams especially in refineries.Depending on the basic energy scenarios to be used, steam reforming natural gas will remain the major hydrogen source from today till tomorrow, i.e. the turn of the century. Coal gasification will significantly increase in its share for hydrogen production. This will be achieved via newly developed coal gasification processes.The development of thermochemical hydrogen production technology as well as biological hydrogen production technologies will progress, but their widespread application remains to be seen in the next century.     

Enhanced control over selective-area intermixing of In0.15Ga0.85As/GaAs quantum dots through post-growth exposure to radio-frequency plasma

Post-growth treatment with a low pressure, CF₄-plasma is demonstrated to reliably inhibit the interdiffusion of In and Ga atoms in In_0.15Ga_0.85As/GaAs self-assembled quantum dot wafer structures subjected to rapid thermal annealing temperatures between 700 °C and 800 °C for a duration of 20 s. Comparative studies of the effects of rapid thermal annealing were made on plasma treated samples and samples that were capped with either 200 nm of plasma enhanced chemical vapor deposited SiO₂ or 220 nm of thermally deposited TiO₂ prior to plasma exposure, as well as to uncapped, untreated control samples. Room-temperature photoluminescence spectra were acquired using a Ti-Sapphire laser operating at 742 nm as the excitation source. A bandgap differential of 84 meV (94 nm) was measured across a wafer sample annealed at 775 °C, when contrasting sections that were uncapped and treated with the CF₄-plasma versus sections that were annealed without any treatment to the surface. This was comparable to a sample that was capped with the TiO₂ film, which produced a 73.5 meV (82 nm) variance from the raw, annealed-only sample.     

Buprenorphine treatment of opioid dependence: A review.

Buprenorphine, a partial mu-agonist opioid, is a promising pharmacotherapy for the treatment of opioid dependence. One hundred and eight papers are organized according to 3 components essential to buprenorphine's use as a pharmacotherapy for opioid dependence: inducting patients onto buprenorphine, maintaining patients on buprenorphine, and discontinuing patients from buprenorphine treatment. The research suggests that inducting patients onto buprenorphine should lead to limited discomfort if appropriate procedures are followed. As a maintenance treatment, buprenorphine is as efficacious as methadone, blocks the effects of exogenously administered opioids, promotes treatment compliance, and, importantly, can support an alternate day dosing regimen by doubling the daily dose. Discontinuing buprenorphine treatment appears to result in a mild-to-moderate opioid withdrawal syndrome that is less severe than that observed with full-efficacy agonists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison between low-magnitude voucher and buprenorphine medication contingencies in promoting abstinence from opioids and cocaine.

This study compared the relative efficacy of low-magnitude, contingent monetary vouchers, contingent buprenorphine medication, and standard counseling in promoting abstinence from illicit opioids and cocaine among opioid-dependent adults. Following an 8-week baseline period during which participants received buprenorphine maintenance treatment with no contingencies in place, 60 participants were randomly assigned to one of 3 treatment groups for 12 weeks: (a) Participants in the voucher group earned vouchers for each opioid- and cocaine-negative urine sample, in accordance with an escalating schedule. Continuous abstinence resulted in voucher earnings equivalent to a total of $269, which participants could exchange for material reinforcers of their choice. (b) Participants in the medication contingency group received half their scheduled buprenorphine dose for clinic attendance and the other half for remaining abstinent from opiates and cocaine. Thus, they received only half of their scheduled dose on submission of an opioid- and/or cocaine-positive urine sample. (c) Participants in standard treatment did not receive programmed consequences contingent on urinalysis results. All participants were maintained with buprenorphine according to a 3-times-per-week dosing regimen and participated in behavioral drug counseling. Retention rate did not significantly differ across the groups; however, participants in the medication contingency group achieved significantly more weeks of continuous abstinence from opiates and cocaine compared with participants in the voucher group (Ms = 5.95 and 2.90, respectively). Results suggest that the use of medication-based contingencies in combination with behavioral therapy in promoting drug abstinence may have clinical utility. Limitations of the study are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling and simulation of milling processes including process damping effects

Especially in high speed milling of aluminum alloys in the aviation industry, chamfered milling tools have proven themselves. Due to the chamfer, an extended contact between the tool and the workpiece at the flank face is evoked, which leads to additional process damping forces opposed to tool vibrations. Hence, the cutting process shows improved stability characteristics. This article presents an approach for the identification and modeling of these process damping effects in transient milling simulations. For this purpose, a simulation- and experiment-based procedure for the identification of required simulation parameters depending on the tool chamfer geometry is introduced and evaluated. Finally, the identified parameters are used for transient simulations of milling processes with extended stability due to the tool chamfer. The suitability of the proposed identification method and simulation model for milling with process damping is finally proved by a comparison between simulations and experiments.     

Querbiegetragverhalten von Betondübeln bei Verbundtragwerken mit Trapezblechstegen

Die größere Querbiegesteifigkeit von Trapezblechstegen gegenüber herkömmlichen, ebenen Stegen führt zu konstruktiven und wirtschaftlichen Vorteilen im Verbundbrückenbau. Dadurch muss allerdings insbesondere bei Hohlkastenquerschnitten der Übertragung des Rahmeneckmomentes erhöhte Aufmerksamkeit geschenkt werden. Die Verbundfuge muss in der Lage sein, die auftretenden Querbiegemomente zu übertragen. Dadurch entstehen für die Verbundmittel Zusatzbeanspruchungen. Des Weiteren ist der Verzicht auf einen Stahlflansch, der hier im Wesentlichen als reiner Verbundmittelträger agiert, erstrebenswert, um das große wirtschaftliche Potential dieser Bauweise zu nutzen. Eine Verbundfugenausbildung bestehend aus einem in den Betongurt einbindenden Trapezblech und dem Betondübel als Verbundmittel erwies sich in Versuchen als sehr viel versprechend. Der vorliegende Aufsatz behandelt das Tragverhalten dieser Verbundfugenausbildung unter Querbiegebeanspruchung. Behavior of Composite Structures with Corrugated Steel Webs under Transverse Bending using Concrete Dowels Compared to plane webs, the use of corrugated steel webs in composite bridge constructions leads to economic and structural advantages due to their lateral stiffness. But, especially in corners of hollow box girders the attention has to be paid on the transfer of the bending moment from the concrete chord into the steel web. The composite joint must be able to bear this transverse bending moment. This leads to additional forces for the connectors. Furthermore, for an economical and more practicable connection method, a composite joint without a steel flange is necessary. Therefore, the connectors have to be fixed directly on the web and these connectors must transfer the transverse bending moment. This article deals with the load bearing behaviour of an embedded corrugated steel web in combination with concrete dowels under transverse bending.