Semiclassical theory of persistent current fluctuations in ballistic chaotic rings

The persistent current in a mesoscopic ring has a Gaussian distribution with small non-Gaussian corrections. Here we report a semiclassical calculation of the leading non-Gaussian correction, which is described by the three-point correlation function. The semiclassical approach is applicable to systems in which the electron dynamics is ballistic and chaotic, and includes the dependence on the Ehrenfest time. At small but finite Ehrenfest times, the non-Gaussian fluctuations are enhanced with respect to the limit of zero Ehrenfest time.Comment: 9 pages, 3 figures; submitted as invited contribution to a special issue in Physica E in memory of Markus Buettike

Determinants of the innovative ability of SMEs

Onderzoek naar de factoren die het innovatievermogen van midden- en kleinbedrijven bepalen. De conclusie luidt dat ondernemers zelf behoorlijke invloed kunnen uitoefenen op het innovatievermogen van hun bedrijf. Aan bod komen het innovatievermogen in relatie tot onder meer ondernemerseigenschappen, strategie, ondernemingscultuur, -structuur en marktkarakteristieken.

Spin-wave-induced correction to the conductivity of ferromagnets

We calculate the correction to the conductivity of a disordered ferromagnetic metal due to spin-wave-mediated electron--electron interactions. This correction is the generalization of the Altshuler-Aronov correction to spin-wave-mediated interactions. We derive a general expression for the conductivity correction to lowest order in the spin-wave-mediated interaction and for the limit that the exchange splitting $\Delta$ is much smaller than the Fermi energy. For a "clean" ferromagnet with $\Delta\tau_{\rm el}/\hbar \gg 1$, with $\tau_{\rm el}$ the mean time for impurity scattering, we find a correction $\delta \sigma \propto -T^{5/2}$ at temperatures $T$ above the spin wave gap. In the opposite, "dirty" limit, $\Delta\tau_{\rm el}/\hbar \ll 1$, the correction is a non-monotonous function of temperature.Comment: 9 pages, 6 figure

Spin-wave-induced corrections to the electronic density of states in metallic ferromagnets

We calculate the correction to the electronic density of states in a disordered ferromagnetic metal induced by spin-wave mediated interaction between the electrons. Our calculation is valid for the case that the exchange splitting in the ferromagnet is much smaller than the Fermi energy, but we make no assumption on the relative magnitude of the exchange splitting and the elastic electronic scattering time. In the "clean limit", where the exchange splitting is much larger than the electronic scattering rate, we find a correction with a T^{d/2} temperature dependence, where d is the effective dimensionality of the ferromagnet. In the opposite "dirty limit" the density-of-states correction is a non-monotonous function of energy and temperature.Comment: 8 pages, 4 figure

A non-discrimination principle for rankings in app stores

The gatekeeper position of app store operators gives them the power to favour their own and the most popular applications in the rankings of search results. Based on parallels with the non-discrimination principle in the European Union's Regulation on Open Internet Access, this article formulates a list of permitted and forbidden ranking rationales for app store operators. Permitted ranking rationales include text relevance, price, quality and the legality of content. These rationales contrast with the forbidden ranking rationales, such as those based on self-favouring without objective justification and the popularity of applications, which potentially limit consumer choice and distort the digital level playing field.Peer reviewe

Zelfbouw in reflectie: evaluatie SEV-experimenten (C)PO/MO

Dit rapport betreft een evaluatie van circa 60 projecten die de Stuurgroep Experimenten Volkshuisvesting (SEV) in de afgelopen 10 à 15 jaar heeft ondersteund met betrekking tot (collectief) particulier en medeopdrachtgeverschap in de woningbouw. Aanleiding daartoe werd gevormd door de algemene behoefte aan meer keuzevrijheid en meer markt in de Nederlandse woningbouw. Tegelijkertijd werd indertijd verondersteld dat particulier opdrachtgeverschap beter aan zou sluiten bij de behoefte van de woonconsumenten, alsmede sneller en goedkoper te realiseren zou zijn dan de reguliere seriematige nieuwbouw. Als zodanig stonden deze doelstellingen ook centraal in de VROM beleidsnota „Mensen, Wensen, Wonen‟ van 2000. Mede naar aanleiding van de in de Tweede Kamer algemeen aanvaarde motie Van Gent/Duivesteijn, werd zelfs beoogd om vanaf 2005 ongeveer 1/3 van de nieuw te bouwen woningen in particulier opdrachtgeverschap te realiseren. Desalniettemin hebben (collectief) particulier en medeopdrachtgeverschap sindsdien niet zo‟n hoge vlucht gekend als beoogd. Het richtgetal van 33,3% van de totale bouwproductie is bij lange na niet gehaald. Sterker nog, daar waar midden jaren negentig van de afgelopen eeuw 17% van de totale Nederlandse bouwproductie in particulier opdrachtgeverschap werd gerealiseerd, is dit thans nog slechts een ruime 10%. Ook het aandeel van de verhuisgeneigden, die zeggen voor (C)PO/MO te willen gaan is in de afgelopen vier jaar afgenomen van 36% naar 28%

Continuous athlete monitoring in challenging cycling environments using IoT technologiesis

Internet of Things (IoT)-based solutions for sport analytics aim to improve performance, coaching, and strategic insights. These factors are especially relevant in cycling, where real-time data should be available anytime, anywhere, even in remote areas where there are no infrastructure-based communication technologies (e.g., LTE and Wi-Fi). In this article, we present an experience report on the use of state-of-the-art IoT technologies in cycling, where a group of cyclists can form a reliable and energy efficient mesh network to collect and process sensor data in real-time, such as heart rate, speed, and location. This data is analyzed in real-time to estimate the performance of each rider and derive instantaneous feedback. Our solution is the first to combine a local body area network to gather the sensor data from the cyclist and a 6TiSCH network to form a multihop long-range wireless sensor network in order to provide each bicycle with connectivity to the sink (e.g., a moving car following the cyclists). In this article, we present a detailed technical description of this solution, describing its requirements, options, and technical challenges. In order to assess such a deployment, we present a large publicly available data-set from different real-world cycling scenarios (mountain road cycle racing and cyclo-cross) which characterizes the performance of the approach, demonstrating its feasibility and evidencing its relevance and promising possibilities in a cycling context for providing low-power communication with reliable performance

A model-based exploration of farm-household livelihood and nutrition indicators to guide nutrition-sensitive agriculture interventions

AbstractAssessing progress towards healthier people, farms and landscapes through nutrition-sensitive agriculture (NSA) requires transdisciplinary methods with robust models and metrics. Farm-household models could facilitate disentangling the complex agriculture-nutrition nexus, by jointly assessing performance indicators on different farm system components such as farm productivity, farm environmental performance, household nutrition, and livelihoods. We, therefore, applied a farm-household model, FarmDESIGN, expanded to more comprehensively capture household nutrition and production diversity, diet diversity, and nutrient adequacy metrics. We estimated the potential contribution of an NSA intervention targeting the diversification of home gardens, aimed at reducing nutritional gaps and improving livelihoods in rural Vietnam. We addressed three central questions: (1) Do 'Selected Crops' (i.e. crops identified in a participatory process) in the intervention contribute to satisfying household dietary requirements?; (2) Does the adoption of Selected Crops contribute to improving household livelihoods (i.e. does it increase leisure time for non-earning activities as well as the dispensable budget)?; and (3) Do the proposed nutrition-related metrics estimate the contribution of home-garden diversification towards satisfying household dietary requirements? Results indicate trade-offs between nutrition and dispensable budget, with limited farm-household configurations leading to jointly improved nutrition and livelihoods. FarmDESIGN facilitated testing the robustness and limitations of commonly used metrics to monitor progress towards NSA. Results indicate that most of the production diversity metrics performed poorly at predicting desirable nutritional outcomes in this modelling study. This study demonstrates that farm-household models can facilitate anticipating the effect (positive or negative) of agricultural interventions on nutrition and the environment, identifying complementary interventions for significant and positive results and helping to foresee the trade-offs that farm-households could face. Furthermore, FarmDESIGN could contribute to identifying agreed-upon and robust metrics for measuring nutritional outcomes at the farm-household level, to allow comparability between contexts and NSA interventions