METHOD FOR STARTING GROUP CHAT AMONG USERS IN PROXIMITY

A method for starting group chat among users using proximity sensing in a communication device is disclosed. The application will allow quick formation of a group using proximity sensing that can be used for communication among the group members. The application for creating groups using the method illustrated can be implemented in any communication device such as phone, computer, laptop etc. or any wearable communication device such as a watch

Characterisation of the oxidation and creep behaviour of novel Mo-Si-Ti alloys

The oxidation and creep behaviour of novel eutectic-eutectoid Mo-Si-Ti alloys were studied and compared to previously investigated entirely eutectic Mo-20Si-52.8Ti (at%) and eutectoid Mo-21Si-34Ti reference alloys [Schliephake et al. in Intermetallics 104 (2019) 133-142]. While the latter reference alloys showed either outstanding oxidation behaviour in the temperature range of 800 to 1200 °C (eutectic alloy) or reasonable creep resistance (eutectoid alloy), a combination of both was successfully achieved in a Ti-rich alloy variant (Mo-21Si-43.4Ti). The ubiquitous catastrophic oxidation (“pesting”) of Mo-based alloys at 800 °C is suppressed in this alloy and reasonable oxidation resistance at higher temperatures is observed. For the first time, the unexpected oxidation resistance of the alloys exhibiting eutectic volume fractions of more than 50 vol% is rationalised by a systematic deconvolution of mass gain by scale formation and mass loss by evaporation of volatile species. Furthermore, creep is revealed to be based on similar creep mechanisms throughout the alloy series. Therefore, the observed improvement in creep resistance of the pesting-resistant Ti-rich alloy variant over the eutectic alloy is attributed to the decreasing homologous temperature when testing both at 1200 °C

Gefügeverfeinerung durch mechanische Zwillingsbildung in Kupfer und Kupfermischkristalllegierungen

Die vorliegende Arbeit zeigt einen Weg, Kupfer und einphasige Kupferlegierungen mit stark verzwillingten Gefügen durch ein technisch relevantes Umformverfahren herzustellen. Der Drahtzug bildet dabei aufgrund seines Spannungszustands und der entsprechenden Texturentwicklung in kubischflächenzentrierten Metallen ein ideales Umformverfahren, um einen Großteil des Gefüges durch mechanische Zwillingsbildung zu verfeinern. Für die Aktivierung der Zwillingsbildung in reinem Kupfer unter den untersuchten Werkstoffvarianten sind Temperaturen nahe der Temperatur des flüssigen Stickstoffs notwendig. Um den Drahtzug in flüssigem Stickstoff umzusetzen, wurden verschiedene Feststoffschmiermittel auf ihre Eignung hin getestet. Die Textur der mit Stickstoffkühlung hergestellten Halbzeuge ist durch eine dreifache Fasertextur bestehend aus -, - und -Fasertexturkomponente charakterisiert. Anhand der strengen Orientierungsverhältnisse konnte der Volumenanteil von verzwillingtem Material bestehend aus Matrixkörnern und Verformungszwillingen auf 71 vol% durch röntgenografische Globaltexturmessungen abgeschätzt werden, wobei das Volumenverhältnis von Zwillingen zu Matrix bei knapp 0,7:1 liegt. Die Zwillinge zeigen eine breite Zwillingslamellenweitenverteilung von wenigen Nanometern bis einige 100 nm im höchstverformten Stadium. Durch die Absenkung der Umformtemperatur und die daraus resultierende Aktivierung der Zwillingsbildung kann die Zugfestigkeit von reinem Kupfer um 140 MPa im Vergleich zu einem ohne Kühlung hergestellten Draht auf 582 MPa erhöht werden. Dabei reduziert sich die elektrische Leitfähigkeit um 6,5% gegenüber einem grobkorngeglühten Kupfer. Eine Absenkung der Stapelfehlerenergie auf 30 mJ/m² in CuAl2 führt zur Aktivierung der mechanischen Zwillingsbildung beim Drahtzug ohne Kühlung. Durch diese Aktivierung der Zwillingsbildung kann bei fortschreitender Verringerung der Stapelfehlerenergie wie in CuAl7 die Zugfestigkeit des umgeformten Drahtes auf weit über 1 GPa erhöht werden. Das entsprechende Gefüge ist dabei ultrafeinkörnig

Dark-matter sterile neutrinos in models with a gauge singlet in the Higgs sector

Sterile neutrino with mass of several keV can be the cosmological dark matter, can explain the observed velocities of pulsars, and can play an important role in the formation of the first stars. We describe the production of sterile neutrinos in a model with an extended Higgs sector, in which the Majorana mass term is generated by the vacuum expectation value of a gauge-singlet Higgs boson. In this model the relic abundance of sterile neutrinos does not necessarily depend on their mixing angles, the free-streaming length can be much smaller than in the case of warm dark matter produced by neutrino oscillations, and, therefore, some of the previously quoted bounds do not apply. The presence of the gauge singlet in the Higgs sector has important implications for the electroweak phase transition, baryogenesis, and the upcoming experiments at the Large Hadron Collider and a Linear Collider.Comment: 12 pages, 7 figure

Microstructural changes in CoCrFeMnNi under mild tribological load

The lack of a principle element in high-entropy alloys (HEA) leads to unique and unexpected material properties. Tribological loading of metallic materials often results in deformed subsurface layers. As the microstructure feedbacks with friction forces, the microstructural evolution is highly dynamic and complex. The concept of HEAs promises high solid solution strengthening, which might decrease these microstructural changes. Here, we experimentally investigated the deformation behavior of CoCrFeMnNi in a dry, reciprocating tribological contact under a mild normal load. After only a single stroke, a surprisingly thick subsurface deformation layer was observed. This layer is characterized by nanocrystalline grains, twins and bands of localized dislocation motion. Twinning was found to be decisive for the overall thickness of this layer, and twin formation within the stress field of the moving sphere is analyzed. The localization of dislocation activity, caused by planar slip, results in a grain rotation. Fragmentation of twins and dislocation rearrangement lead to a nanocrystalline layer underneath the worn surface. In addition, oxide-rich layers were found after several sliding cycles. These oxides intermix with the nanocrystalline layer due to material transfer to the counter body and re-deposition to the wear track. Having revealed these fundamental mechanisms, the evolution of such deformation layers in CoCrFeMnNi under a tribological load might lead to other HEAs with compositions and properties specifically tailored to tribological applications in the future