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Design science in information systems research   总被引:1,自引:1,他引:0  
  相似文献   
34.
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence.  相似文献   
35.
Reports of failure of existing concrete structures due to a lack of durability, rather than a deficiency in structural strength, has made concrete technologists, engineers, and researchers focus research on the parameters influencing durability performance with respect to time. Systematic performance monitoring, with respect to chosen durability parameters of existing concrete structures, will decide the direction of future research in this area. Inferences based on laboratory simulations and testing need to be confirmed by in situ field measurements and studies. In situ condition rating and performance monitoring surveys have been conducted by many researchers, scientists, and professional associations, and reported in literature. Inferences of few such studies are summarized and discussed. Deterioration of concrete structures constructed in recent times is observed at relatively faster rates, and has been mainly attributed to cracking. Cracking is associated with the use of faster-hydrating portland cements with increased fineness and the tricalcium silicate (C3S) content to support the high speed of modern construction. In the present research, a case study of deteriorated water tank structures situated in the semitropical region of India is presented. Some selected parameters—such as concrete cover, carbonation depth, chloride concentration, compressive strength, etc. which influence long term durability of structures—have been measured.  相似文献   
36.
Summary The macroscopic behavior of materials subjected to large deformations is investigated by considering the structure and mechanics of the single slip. Physically based constitutive relations for the plastic flow and material spin are then rigorously derived by resorting to the concept of non-coaxiality; yielding a class of vertex-type plasticity models incorporating features like noncoaxiality and large material rotation. It is shown that these phenomena are inherently coupled through the concept of plastic spin as it relates to the persistence of noncoaxiality. The implication of such phenomena to large deformations is investigated by examining their influence on the development of axial effects accompanying finite shear deformation, as well as on the onset of localized shear bands.  相似文献   
37.
Zusammenfassung Man erh?lt kompakte Approximationen von Laplace-übergangsfunktionen, wenn die Koeffizienten des Nenners aus den Zeitkonstanten des Systems abgeleitet werden. (üblicherweise führt dies auf das Problem der Nullstellensuche einer transzendenten Funktion.) Es ist bekannt (Gough [1], Stephenson [2]), da? für die meisten W?nde drei Zeitkonstanten ausreichen, um hinreichend genaue übergansfunktionen zu erhalten. Die Taylor-Entwicklung der Kettenmatrix im Laplaceraum wird für beliebige W?nde mit eindimensionalem W?rmestrom mit der Picard'schen Methode berechnet. Für ebene Mehrschichtw?nde ist dafür eine explizite L?sung angegeben. Die ersten N Zeitkonstanten werden n?herungsweise aus der (N+1). Ordnung der Partial-Summe der Taylor-Entwicklung berechnet. Dies wird mit einer generalisierten Pade-Approximation bewerkstelligt, die eine Totzeit enth?lt und direkt auf ein Nennerpolynom führt (ohne transzendente Wurzeln). Die Wurzeln konvergieren geometrisch zu den Eigenwerten mit wachsendem N (die Eigenwerte stellen die reziproken Zeitkonstanten dar). Die Komplexit?t der gesamten Prozedur liegt kaum über derjenigen für ein System mit konzentrierten Parametern der Ordnung N+1. Es werden Beispiele angegeben, um mit den „exakten” Frequenzg?ngen zu vergleichen.  相似文献   
38.
Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion.  相似文献   
39.
Zusammenfassung Es werden die prinzipiellen Einsatzm?glichkeiten neuronaler Netwwerke zur Modellbildung, Steuerung und Regelung von Robotern sowie zur Unterstützung sensomotorischer Aktionen dargelegt. Einige ausgew?hlte neuronale Regelungskonzepte werden vorgestellt und auf ihre Stabilit?t, Robustheit, Genauigkeit sowie Echtzeitf?higkeit hin untersucht. Ferner wird gezeigt, wie sich neuronale Regelungskonzepte in industrielle Robotersteuerungen integrieren lassen.  相似文献   
40.
A numerical simulation of unsteady compressible flow induced by two high-speed trains in oncoming traffic within a tunnel is presented. The computations were carried out by means of a second-order accurate Harten-Yee type upwind TVD scheme. In order to take the effect of friction into account, a source term is included in the governing flow equations. In the computation, moving boundary configurations were used to simulate the two trains passing through the tunnel. As geometrical configuration, the Einmalberg tunnel, where experimental data are available, was selected. The computational results agree reasonably well with their experimental counter-part. The waves interaction and the waves propagation process at the tunnel entrance and exit as well as within the tunnel are addressed. Finally, the influence on the transmitted waves at the tunnel exit portal and the variation of the negative pressure drop during the passage of the two trains are discussed.  相似文献   
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