Calculation of sub-surface-initiated fatigue fractures in gears

Power-transmitting gears are typically heat-treated, most often case-hardened, to improve the fatigue strength and therefore to ensure higher fatigue life. The heat treatment causes higher hardness in the surface area as well as compressive residual stresses in the hardened layer. The near-surface compressive residual stresses are compensated by tensile stresses in higher depths of the gear volume. Pitting and tooth root breakage are the most common failure modes of gears, which are well researched and are also addressed in ISO 6336 [14]. The assessment of these failure modes provides the basis for the dimensioning of gears in the design phase. However, subsurfaceinitiated failures, like tooth flank fracture (TFF), can also appear at loads below the allowable level of loading for pitting and tooth root bending. TFF is a fatigue damage with crack initiation in the region of the transition between compressive and tensile residual stresses and usually leads to a total loss of drive. The existing calculation models for fatigue strength of gears with regard to TFF consider residual stresses differently. The base of the investigated calculation models is a local comparison of the occurring stresses and the strength value in the gear volume. The outcome of the calculation model from Oster [26] is highly influenced by the residual stress state. However, the material-physical model by Hertter [10] is more tolerant to slightly varying residual stresses. Further approaches such as Weber [34] and Konowalcyk [18] are based on the ideas of Oster and Hertter. The verification of the models is complicated due to the lack of residual stress measurements in larger depths under the gear flank surface. For example, residual stress measurement by Xray diffraction is only possible up to depths of approximately one millimeter. Therefore, tensile residual stresses in the inner tooth volume are considered zero in the common residual stresses calculation of Lang [19] and are not considered in the current calculation approach of ISO/DTS 6336-4 [15]. The paper describes local calculation approaches for the fatigue strength of gears with different consideration of residual stresses. Furthermore, the crack initiation point, which is mandatory for the validation of an approach, is examined. The failure mode TFF is hereby the key

Labor Pooling in R&D Intensive Industries

We investigate firms’ incentives to locate in the same region to gain access to a large pool of skilled labor. Firms engage in risky R&D activities and thus create stochastic product and implied labor demand. Agglomeration in a cluster is more likely in situations where the innovation step is large and the probability for a firm to be the only innovator is high. When firms cluster, they tend to invest more and take more risk in R&D compared to spatially dispersed firms. Agglomeration is welfare maximizing, because expected labor productivity is higher and firms choose a more effcient, technically diversified portfolio of R&D projects at the industry level.

Labor Pooling in R&D Intensive Industries

We investigate firms’ incentives to locate in the same region to gain access to a large pool of skilled labor. Firms engage in risky R&D activities and thus create stochastic product and implied labor demand. Agglomeration in a cluster is more likely in situations where the innovation step is large and the probability for a firm to be the only innovator is high. When firms cluster, they tend to invest more and take more risk in R&D compared to spatially dispersed firms. Agglomeration is welfare maximizing, because expected labor productivity is higher and firms choose a more efficient, technically diversified portfolio of R&D projects at the industry level.

Influence of Larval Gizzard Shad (Dorosoma cepedianum) Density on Piscivory and Growth of Young-of-Year Saugeye (Stizostedion vitreum x S. canadense)

Abstract in English and French.Growth and survival of young-of-year saugeye (Stizostedion vitreum x S. canadense) (stocked into Ohio reservoirs to create sport fisheries) are probably influenced by prey availability, variations in which may account for historically documented variability in stocking success. Because saugeye switch from a diet of zooplankton to fish once stocked, we sought to determine experimentally if saugeye size and available ichthyoplankton, i.e., larval gizzard shad (Borosoma cepediaraum), affected this switch and whether piscivory improved saugeye growth. In an enclosure experiment, saugeye (33.9 mm TL) immediately switched to piscivory when exposed to ichthyoplankton densities of 20 and l00m^-3, growing faster when more gizzard shad were available. In another enclosure experiment, saugeye 30-49 mm TL consumed 14-mm gizzard shad. In ponds (N = 4 ponds-treatment-1) containing zooplankton and chironornids, we compared saugeye growth with and without larval gizzard shad and found, as in the first enclosure experiment, that piscivory improved saugeye growth. Neither saugeye size nor ichthyoplankton density influenced how quickly saugeye switched to piscivory. We conclude that managers should stock saugeye >=30 mm 1-2 wk before peak ichthyoplankton densities to improve saugeye growth and survival by enhancing opportunities for exploitation of young-of-yeas gizzard shad.This work was funded by the Federal Aid in Sport Fish Restoration Program (F-57-R, Evaluation of Fish Management Techniques), administered jointly by the U.S. Fish and Wildlife Service and the Ohio Division of Wildlife

Goverment-to-Business in Deutschland

Beim Angebot elektronischer Verwaltungsdienstleistungen hinkt Deutschland weit hinterher. Bei internationalen Vergleichen belegt Deutschland nur Plätze im Mittelfeld. Insbesondere auf Ebene der Länder und der Kommunen besteht noch Nachholbedarf. Mangelnde Kundenorientierung in der Umsetzung beeinträchtigt die Akzeptanz der Angebote. Unabgestimmte Einzelprojekte verhindern die Ausschöpfung von Synergiepotenzialen. Die Rahmenbedingungen für weitere Angebote haben sich jedoch bereits deutlich verbessert. Mit DeutschlandOnline existiert eine ebenenübergreifende E-Government-Strategie. Im Bündnis für elektronische Signaturen wird die Schaffung der erforderlichen Sicherheits-Infrastruktur vorbereitet. Basiskomponenten und einzelne Best-Practice-Lösungen können bei zukünftigen Angeboten wieder verwendet werden. Erfolgreiches E-Government erfordert eine Neuausrichtung der öffentlichen Verwaltung. Die verwaltungsinternen Prozesse müssen grundlegend überarbeitet werden. Optimale Lösungen setzen eine Bündelung der Ressourcen voraus. Durch Zusammenarbeit mit privaten Anbietern können Win-Win-Situationen generiert werden. Die globale Wirtschaft erfordert länderübergreifende E-Government-Services

Advanced Mirror Technology Development (AMTD) Thermal Trade Studies

Advanced Mirror Technology Development (AMTD) is being done at Marshall Space Flight Center (MSFC) in preparation for the next Ultraviolet, Optical, Infrared (UVOIR) space observatory. A likely science mission of that observatory is the detection and characterization of 'Earth-like' exoplanets. Direct exoplanet observation requires a telescope to see a planet that is 10-10 times dimmer than its host star. To accomplish this using an internal coronagraph requires a telescope with an ultra-stable wavefront. This paper investigates two topics: 1) parametric relationships between a primary mirror's thermal parameters and wavefront stability, and 2) optimal temperature profiles in the telescope's shroud and heater plate that minimize static wavefront error (WFE) in the primary mirror

Predictive Thermal Control (PTC) Technology to Enable Thermally Stable Telescopes: First Two Year Status

Predictive Thermal Control Technology (PTCT) development project is a multiyear effort initiated in Fiscal Year (FY) 2017, to mature the Technology Readiness Level (TRL) of critical technologies required to enable ultra-thermally-stable ultraviolet/optical/infrared (UVOIR) space telescope primary-mirror assemblies for ultra-high-contrast observations of exoplanets. Key accomplishments of 2017 to 2019 include: creating a high-fidelity STOP (Structural, Thermal, and Optical Performance) model of the AMTD-2 (Advance Mirror Technology Development) 1.5-meter Ultra-Low Expansion (ULE) mirror (manufactured by Harris Corp) by merging 3D X-Ray computed tomography data of the as-built mirror and coefficient of thermal expansion (CTE) data maps for each of the 18 core elements; partially validating this model by measuring the mirrors response to bulk temperature changes and lateral thermal gradients; designed and built (with PTC partner Harris Corp) a 1.5-meter enclosure with 26 actively-control thermal zones; and defined specifications for a potential 4-meter primary mirror thermal enclosure for the Habitable Exoplanet (HabEx) Imager mission

Year in review 2009: Critical Care - shock

The research papers on shock that have been published in Critical Care throughout 2009 are related to four major subjects: first, alterations of heart function and, second, the role of the sympathetic central nervous system during sepsis; third, the impact of hemodynamic support using vasopressin or its synthetic analog terlipressin, and different types of fluid resuscitation; as well as, fourth, experimental studies on the treatment of acute respiratory distress syndrome. The present review summarizes the key results of these studies together with a brief discussion in the context of the relevant scientific and clinical background published both in this and other journals

Von der Landeskunde zum interkulturellen Lernen – mit Werbung?

Der Beitrag bietet Überlegungen zum Einsatz von Werbematerial im Fremdsprachenunterricht. Im Fokus steht dabei das Potenzial von Werbung für landeskundliches und interkulturelles Lernen aufgrund ihrer kulturellen Determiniertheit.The article offers reflections on the use of advertising material in foreign language teaching. The focus is the potential of advertisement for cultural and intercultural learning due to the cultural determination