AC measurement of heat capacity and magnetocaloric effect for pulsed magnetic fields

International audienceA new calorimeter for measurements of the heat capacity and magnetocaloric effect of small samples in pulsed magnetic fields is discussed for the exploration of thermal and thermodynamic properties at temperatures down to 2 K. We tested the method up to 0H=50 T, but it could be extended to higher fields. For these measurements we used carefully calibrated bare-chip Cernox® and RuO2 thermometers, and we present a comparison of their performances. The monotonic temperature and magnetic field dependences of the magnetoresistance of RuO2 allow thermometry with a precision as good as 4 mK at T=2 K. To test the performance of our calorimeter, heat capacity and magnetocaloric effect for the spin-dimer compound Sr3Cr2O8 and the triangular lattice antiferromagnet RbFe MoO4 2 are presented

Mobile Communication Device Usage: Perceptions of Non-Supervisory Employees

The increased usage of mobile communication devices (MCDs) in the workplace has been controversial regarding whether they increase or decrease productivity, whether work-life balance is affected by use, and whether employers have the right to monitor usage. This paper includes research that addressed each of these three issues linked to employee use of MCDs. Past research provided conflicting results in three areas - work-life balance, productivity, and employee monitoring. A quantitative study of 60 non-supervisory employees in Arizona, Michigan, and Illinois, consisting of an online survey, was carried out to determine perceptions of whether use of MCDs for work purposes affects work-life balance or productivity and perceptions on employers monitoring usage of work-issued MCDs. Sixty-seven percent of respondents stated that their duties require the use of MCDs and, of those 62%, each stated that his or her MCD is a Smartphone. The majority stated that Smartphones were MCDs given to them by the employer. Other MCDs were cell phones and tablets which, combined, accounted for 35% of the responses. Fifty-three percent of the respondents stated that the use of the MCD did not impact work-life balance, eighty-eight percent stated that the use of the MCD increased productivity, and eighty-seven percent stated that their employer does not monitor usage of their MCD. Research findings may vary and depend on participants. Supervisors may have different viewpoints. However, the required use of these devices in the workplace keeps increasing, so it is appropriate for employers to clearly find a benefit for their use

Management-dependent effects of pollinator functional diversity on apple pollination services: A response–effect trait approach

Data available via the Dryad Digital Repository https://doi.org/10.5061/dryad.63xsj3v39 (Roquer-Beni et al., 2021).Functional traits mediate the response of communities to disturbances (response traits) and their contribution to ecosystem functions (effect traits). To predict how anthropogenic disturbances influence ecosystem services requires a dual approach including both trait concepts. Here, we used a response–effect trait conceptual framework to understand how local and landscape features affect pollinator functional diversity and pollination services in apple orchards. We worked in 110 apple orchards across four European regions. Orchards differed in management practices. Low-intensity (LI) orchards were certified organic or followed close-to-organic practices. High-intensity (HI) orchards followed integrated pest management practices. Within each management type, orchards encompassed a range of local (flower diversity, agri-environmental structures) and landscape features (orchard and pollinator-friendly habitat cover). We measured pollinator visitation rates and calculated trait composition metrics based on 10 pollinator traits. We used initial fruit set as a measure of pollination service. Some pollinator traits (body size and hairiness) were negatively related to orchard cover and positively affected by pollinator-friendly habitat cover. Bee functional diversity was lower in HI orchards and decreased with increased landscape orchard cover. Pollination service was not associated with any particular trait but increased with pollinator trait diversity in LI orchards. As a result, LI orchards with high pollinator trait diversity reached levels of pollination service similar to those of HI orchards. Synthesis and applications. Pollinator functional diversity enables pollinator communities to respond to agricultural intensification and to increase pollination function. Our results show that efforts to promote biodiversity provide greater returns in low-intensity than in high-intensity orchards. The fact that low-intensity orchards with high pollinator functional diversity reach levels of pollination services similar to those of high-intensity orchards provides a compelling argument for the conversion of high-intensity into low-intensity farms.This research (EcoFruit project) was funded through the 2013–2014 BiodivERsA/FACCE-JPI joint call (2014-74), Spanish MinECo (PCIN-2014-145-C02), German BMBF (PT-DLR/BMBF, 01LC1403) and Swedish Research Council Formas (2014-1784) by Formas (2013-934 to M.T.), Stiftelsen Lantbruksforskning (H1256150 to M.P.), INIA (RTA2013-00039-C03-00 to G.A. and M.M.), MinECo/FEDER (CGL2015-68963-C2-2-R to D.G.), FI-AGAUR (to L.R.-B.) and MinECo (RYC-2015-18448 to X.A.)

Study liquid length penetration results obtained with a direct acting piezo electric injector

A state of the art prototype common rail injector featuring direct control of the needle by means of a piezo stack (direct acting) has been tested. Liquid phase penetration of the sprays in diesel engine-like conditions has been studied via imaging technique in a novel continuous flow test chamber that allows an accurate control on a wide range of thermodynamic conditions (up to 1000 K and 15 MPa). This state of the art injector fitted with a 7-hole nozzle, allows a fully flexible control on the nozzle needle movement, enabling various fuel injection rates typology. The temporal evolution of the seven sprays has been studied recording movies of the injection event in evaporative conditions via Mie scattering imaging technique and using a high speed camera. The results showed a strong influence of needle position on the stabilized liquid length while the effect of the injection pressure is negligible: the decrease of the needle lift causes a pressure drop in the needle seat and thus a reduction in the effective pressure upstream of the orifices (in the nozzle sac). According to known literature the stabilized liquid-length depends mainly on effective diameter, spray cone-angle and fuel/air properties and does not depend on fuel velocity at the orifice outlet. Therefore, due to small change in the spray cone-angle, higher injection pressures give slightly lower liquid length. However, partial needle lifts has an opposite effect: when needle is partially lifted a dramatic increase of the spray cone-angle and a consequent reduction of the liquid length are observed. A deeper analysis revealed that low charges are linked also to higher hole to hole dispersion and flow instabilities. Needle vibrations caused by the fuel-needle interactions with fuel flow at partial needle lift and the onset of cavitation in the needle seat are likely the causes of this unexpected behavior. Finally, the effect of injection rate shaping on the transient liquid penetration is presented, showing the capability of the injector to control the liquid length along the injection event. This feature, when applied in a real engine, yields to develop new injection strategies to avoid fuel wall impingement.This work was sponsored by General Motors R&D, Warren, MI. The authors would like to thank Jose Enrique del Rey and David Fuertes Munoz for their precious work in the laboratory during the tests.Payri, R.; Gimeno, J.; Bardi, M.; Plazas, AH. (2013). Study liquid length penetration results obtained with a direct acting piezo electric injector. Applied Energy. 106:152-162. doi:10.1016/j.apenergy.2013.01.027S15216210

An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators

A one-dimensional model of a parallel-plate active magnetic regenerator (AMR) is presented in this work. The model is based on an efficient numerical scheme which has been developed after analysing the heat transfer mechanisms in the regenerator bed. The new finite difference scheme optimally combines explicit and implicit techniques in order to solve the one-dimensional conjugate heat transfer problem in an accurate and fast manner while ensuring energy conservation. The present model has been thoroughly validated against passive regenerator cases with an analytical solution. Compared to the fully implicit scheme, the proposed scheme achieves more accurate results, prevents numerical errors and requires less computational effort. In AMR simulations the new scheme can reduce the computational time by 89%.B. Torregrosa-Jaime acknowledges the Spanish Ministry of Education, Culture and Sport (Ministerio de Educacion, Cultura y Deporte) for receiving the Research Fellowship FPU ref. AP2010-2160.Torregrosa Jaime, B.; Corberán Salvador, JM.; Payá Herrero, J.; Engelbrecht, K. (2015). An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators. International Journal of Refrigeration. 58:121-130. https://doi.org/10.1016/j.ijrefrig.2015.06.007S1211305

Transport properties of strongly correlated metals:a dynamical mean-field approach

The temperature dependence of the transport properties of the metallic phase of a frustrated Hubbard model on the hypercubic lattice at half-filling are calculated. Dynamical mean-field theory, which maps the Hubbard model onto a single impurity Anderson model that is solved self-consistently, and becomes exact in the limit of large dimensionality, is used. As the temperature increases there is a smooth crossover from coherent Fermi liquid excitations at low temperatures to incoherent excitations at high temperatures. This crossover leads to a non-monotonic temperature dependence for the resistance, thermopower, and Hall coefficient, unlike in conventional metals. The resistance smoothly increases from a quadratic temperature dependence at low temperatures to large values which can exceed the Mott-Ioffe-Regel value, hbar a/e^2 (where "a" is a lattice constant) associated with mean-free paths less than a lattice constant. Further signatures of the thermal destruction of quasiparticle excitations are a peak in the thermopower and the absence of a Drude peak in the optical conductivity. The results presented here are relevant to a wide range of strongly correlated metals, including transition metal oxides, strontium ruthenates, and organic metals.Comment: 19 pages, 9 eps figure

I feel you: the design and evaluation of a domotic affect-sensitive spoken conversational agent

We describe the work on infusion of emotion into a limited-task autonomous spoken conversational agent situated in the domestic environment, using a need-inspired task-independent emotion model (NEMO). In order to demonstrate the generation of affect through the use of the model, we describe the work of integrating it with a natural-language mixed-initiative HiFi-control spoken conversational agent (SCA). NEMO and the host system communicate externally, removing the need for the Dialog Manager to be modified, as is done in most existing dialog systems, in order to be adaptive. The first part of the paper concerns the integration between NEMO and the host agent. The second part summarizes the work on automatic affect prediction, namely, frustration and contentment, from dialog features, a non-conventional source, in the attempt of moving towards a more user-centric approach. The final part reports the evaluation results obtained from a user study, in which both versions of the agent (non-adaptive and emotionally-adaptive) were compared. The results provide substantial evidences with respect to the benefits of adding emotion in a spoken conversational agent, especially in mitigating users' frustrations and, ultimately, improving their satisfaction

Martensitic accommodation strain and the metal-insulator transition in manganites

In this paper, we report polarized optical microscopy and electrical transport studies of manganese oxides that reveal that the charge ordering transition in these compounds exhibits typical signatures of a martensitic transformation. We demonstrate that specific electronic properties of charge-ordered manganites stem from a combination of martensitic accommodation strain and effects of strong electron correlations. This intrinsic strain is strongly affected by the grain boundaries in ceramic samples. Consistently, our studies show a remarkable enhancement of low field magnetoresistance and the grain size effect on the resistivity in polycrystalline samples and suggest that the transport properties of this class of manganites are governed by the charge-disordered insulating phase stabilized at low temperature by virtue of martensitic accommodation strain. High sensitivity of this phase to strains and magnetic field leads to a variety of striking phenomena, such as unusually high magnetoresistance (10^10 %) in low magnetic fields.Comment: Short paper, 4 figures, to appear in Rapid Communicatio