Spin waves in magnetic quantum wells with Coulomb interaction and sdsd exchange coupling

We theoretically describe the spin excitation spectrum of a two dimensional electron gas embedded in a quantum well with localized magnetic impurities. Compared to the previous work, we introduce equations that allow to consider the interplay between the Coulomb interaction of delocalized electrons and the $sd$ exchange coupling between electrons and magnetic impurities. Strong qualitative changes are found : mixed waves propagate below the single particle continuum, an anticrossing gap is open at a specific wavevector and the kinetic damping due to the electron motion strongly influences the coupling strength between electrons and impurities spins

Creating and Capturing Value Through Sustainability: The Sustainable Value Analysis Tool. A new tool helps companies discover opportunities to create and capture value through sustainability.

Recent research and practice have shown that business model innovation can be one way to create and capture new value and drive production and consumption toward sustainability. However, business model tools typically do not create a space to consider how sustainability concerns may be integrated into the innovation process. To address this gap, this article describes a tool that can help companies identify new opportunities to create and capture value through sustainability by analyzing value captured and uncaptured for key stakeholders across the product life cycle. The Sustainable Value Analysis Tool is shown to help companies recognize value uncaptured and turn it into opportunities; it facilitates sustainability-focused business model innovation by identifying value uncaptured—and hence, opportunities for innovation—associated with environmental and social sustainability in production, use, and disposal.This study was supported by the EPSRC Centre for Innovative Manufacturing in Industrial Sustainability (grant EP/I033351/1) and the EPSRC project Business Models for Sustainable Industrial Systems (grant EP/L019914/1)

Creating and capturing value through sustainability: the Sustainable Value Analysis Tool

This is the author accepted manuscript. The final version is available from Taylor & Francis (Routledge) via the DOI in this record.Recent research and practice have shown that business model innovation can be one way to create and capture new value and drive production and consumption toward sustainability. However, business model tools typically do not create a space to consider how sustainability concerns may be integrated into the innovation process. To address this gap, this article describes a tool that can help companies identify new opportunities to create and capture value through sustainability by analyzing value captured and uncaptured for key stakeholders across the product life cycle. The Sustainable Value Analysis Tool is shown to help companies recognize value uncaptured and turn it into opportunities; it facilitates sustainability-focused business model innovation by identifying value uncaptured—and hence, opportunities for innovation—associated with environmental and social sustainability in production, use, and disposal.This study was supported by the EPSRC Centre for Innovative Manufacturing in Industrial Sustainability (grant EP/I033351/1) and the EPSRC project Business Models for Sustainable Industrial Systems (grant EP/L019914/1

An Internal Perspective of Business Model Innovation in Manufacturing Companies

Business model innovation is increasingly being used as a concept in different academic fields, although it is still missing a ground theoretical conceptualization. This work aims at advancing the understanding of business model innovation from an internal perspective in manufacturing companies. It builds on a literature review regarding two main concepts – business model and business architecture – and proposes a set of key areas for internally-driven business model innovation. Six main areas have been identified: i) strategy & business goals; ii) organizational culture; iii) product and service management; iv) technology management; v) operations management; vi) performance management systems. Further research will analyze the innovation processes within each area, based on existing theoretical foundations and empirical studies. Moreover, new empirical studies will be performed to further investigate different potential pathways for business model innovation.This work builds on research initially undertaken on SustainValue project which received funding from the European Community´s Seventh Framework Programme (FP7/2007-2013) under grant agreement n°262931. Further review and analysis leading to these results was supported by the EPSRC Centre for Innovative Manufacturing in Industrial Sustainability (grant n° EP/I033351/1).This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/CBI.2015.4

Nuclear spin-lattice relaxation in p-type GaAs

Spin-lattice relaxation of the nuclear spin system in p-type GaAs is studied using a three-stage experimental protocol including optical pumping and measuring the difference of the nuclear spin polarization before and after a dark interval of variable length. This method allows us to measure the spin-lattice relaxation time $T_1$ of optically pumped nuclei "in the dark", that is, in the absence of illumination. The measured $T_1$ values fall into the sub-second time range, being three orders of magnitude shorter than in earlier studied n-type GaAs. The drastic difference is further emphasized by magnetic-field and temperature dependences of $T_1$ in p-GaAs, showing no similarity to those in n-GaAs. This unexpected behavior is explained within a developed theoretical model involving quadrupole relaxation of nuclear spins, which is induced by electric fields within closely spaced donor-acceptor pairs.Comment: 9 pages, 8 figure

On the existence of traveling waves in the 3D Boussinesq system

We extend earlier work on traveling waves in premixed flames in a gravitationally stratified medium, subject to the Boussinesq approximation. For three-dimensional channels not aligned with the gravity direction and under the Dirichlet boundary conditions in the fluid velocity, it is shown that a non-planar traveling wave, corresponding to a non-zero reaction, exists, under an explicit condition relating the geometry of the crossection of the channel to the magnitude of the Prandtl and Rayleigh numbers, or when the advection term in the flow equations is neglected.Comment: 15 pages, to appear in Communications in Mathematical Physic

Flame Enhancement and Quenching in Fluid Flows

We perform direct numerical simulations (DNS) of an advected scalar field which diffuses and reacts according to a nonlinear reaction law. The objective is to study how the bulk burning rate of the reaction is affected by an imposed flow. In particular, we are interested in comparing the numerical results with recently predicted analytical upper and lower bounds. We focus on reaction enhancement and quenching phenomena for two classes of imposed model flows with different geometries: periodic shear flow and cellular flow. We are primarily interested in the fast advection regime. We find that the bulk burning rate v in a shear flow satisfies v ~ a*U+b where U is the typical flow velocity and a is a constant depending on the relationship between the oscillation length scale of the flow and laminar front thickness. For cellular flow, we obtain v ~ U^{1/4}. We also study flame extinction (quenching) for an ignition-type reaction law and compactly supported initial data for the scalar field. We find that in a shear flow the flame of the size W can be typically quenched by a flow with amplitude U ~ alpha*W. The constant alpha depends on the geometry of the flow and tends to infinity if the flow profile has a plateau larger than a critical size. In a cellular flow, we find that the advection strength required for quenching is U ~ W^4 if the cell size is smaller than a critical value.Comment: 14 pages, 20 figures, revtex4, submitted to Combustion Theory and Modellin