915 research outputs found

    Thermal Energy Storage as a Way to Improve Transcritical CO2 Heat Pump Performance by Means of Heat Recovery Cycles

    Get PDF
    Electrification of the heating sector is a major target of energy transition towards a more sustainable, efficient, and less polluted future. Heat pumps are considered more suitable than electrical heaters or fossil-fueled boilers; however, common refrigerants cause ozone layer depletion, which exacerbates the greenhouse effect. Natural refrigerants, such as CO2, perform comparably and even better than hydrofluorocarbons while minimizing the negative aspects. This study presents a model of a water-heater CO2 transcritical heat pump in a configuration that increases the overall coefficient of performance (COP) by introducing thermal energy storage (TES). The thermodynamic cycle was divided into two separate phases. After heating the TES (charging), warm water was used as the heating fluid in the evaporator to increase the evaporation temperature and pressure of CO2, which reduced the work of the compressor. As the water temperature decreased progressively, the discharge cycles improved the total COP. The case study focuses on dairy processes and suggests a more straightforward and cheaper method to improve cycle efficiency than the current processes, such as ejector-expansion systems or double compression

    Sulfoxonium Ylides in Aminocatalysis: An Enantioselective Entry to Cyclopropane-Fused Chromanol Structures

    Get PDF
    The 1,1a,2,7b-tetrahydrocyclopropa[c]chromene, aris-ing from fusion of chromane and cyclopropane rings is the core of medicinally relevant compounds. Engaging sulfoxonium ylides in enantioselective aminocatalytic reactions for the first time, a convenient entry to this scaffold is presented. Several ring-fused derivatives were obtained in moderate-to-good yields and enantiose-lectivities and with perfect diastereoselectivity at the cyclopropane, using an alpha,alpha-diphenylprolinol aminocatalyst. The versatility of the hemiacetal moiety in the products was leveraged to effect various synthetic manipulations

    Rotational barriers of biphenyls having heavy heteroatoms as ortho-substituents: experimental and theoretical determination of steric effects

    Get PDF
    The free energies of activation for the aryl-aryl rotation of 17 biphenyl derivatives, bearing a heavy heteroatom (S, Se, Te, P, Si, Sn) as ortho substituent, have been measured by variable temperature NMR. These numbers, so called B values, represent a meaningful measure of the steric hindrance exerted by the selected substituents. DFT computations match quite satisfactorily the experimental barriers and the ground state geometries as well (determined, in two cases, by X-ray diffraction). The present values extend the available list of B values and thus provide an enlarged basis for the compilation of the space requirements of standard substituents, based solely on experimental determinations

    Overview of Native Chicken Breeds in Italy: Conservation Status and Rearing Systems in Use

    Get PDF
    The ongoing loss of domestic animal breeds around the world is occurring at an alarming rate. Thus, the registration and preservation of native breeds is of great importance. The aim of this study, which forms part of a conservation program, was to provide an overview of the conservation statuses of native Italian poultry breeds being reared by local breeders in Italy. The data collected by means of a census questionnaire demonstrate the low population sizes of these breeds in Italy and highlight the need for campaigns aimed at publicizing and promoting the benefits of native breeds with the goal of increasing population sizes. Identifying strategies to facilitate breeders’ access to pure breed birds is also essential, and would require collaborative efforts of university research centers, public entities, and breeders

    Overview of Native Chicken Breeds in Italy: Small Scale Production and Marketing

    Get PDF
    The intensive use of high-performing strains in poultry production has led to the extinction of several autochthonous chicken breeds and, consequently, loss of genetic variability. Interest in saving biodiversity is growing rapidly and has become a major objective worldwide. The aim of this study was to shed light on the production trends of native Italian poultry breeds and the related market. A questionnaire, which asked about the production cycles, the number of animals and table eggs produced per year and their retail prices was completed by 121 breeders across Italy. The surveyed breeders were divided into two categories: breeders conducting an agrozootechnical farm, referred to as ‘farmers’ (F); and breeders keeping chickens as backyard poultry, referred to as ‘fancy breeders’ (FB). Analysis of the data acquired indicated that animals were mainly slaughtered between 6 and 12 months of age, with F processing more animals per year. The same production trend was observed for table eggs. The recorded retail prices of native chicken products were higher than those for conventional products, but similar to those reported for valuable niche poultry products, such as the Poulet de Bresse in France and organic eggs. Knowledge about these highly valuable markets should be used to encourage the use of local breeds in alternative poultry farming and help protect biodiversity

    Color variations on Victoria quadrangle: support for the geological mapping

    Get PDF
    Mercury is the closest planet to the Sun. Its extreme thermal environment makes it difficult to explore onsite. In 1974, Mariner 10, the first mission dedicated to Mercury, covered 45% of the surface during of the three Hermean flybys [1]. For about 30 years after Mariner 10, no other mission has flownto Mercury. Many unresolved issues need an answer, and in recent years the interest about Mercury has increased. MESSENGER mission contributed to understand Mercury's origin, its surface structure, and the nature of its magnetic field, exosphere, and magnetosphere [1]. The Mercury Dual Imaging System (MDIS) provided a global coverage of Mercury surface with variable spatial resolution. MDIS is equipped with a narrow angle camera (NAC), dedicated to the study of the geology and a wide angle camera (WAC) with 12 filters useful to investigate the surface composition[2]. Mercury has been divided into 15 quadrangles for mapping purposes [3]. The mapping process permits integration of different geological surface information to better understand the planet crust formation and evolution. Merging spectroscopically data is a poorly followed approach in planetary mapping, but it gives additional information about lithological composition, contributing to the construction of a more complete geological map [e.g. 4]. Recently, [5] proposed a first detailed map of all the Victoria quadrangle (H2). Victoria quadrangle is located in a longitude range between 270°E and 360°E and a latitude range of 22.5°N and 65°N,and itwas only partially mapped by Mariner 10 data[3]. Here we investigate the lithological variation by using the MDIS-WAC data to produce a set of color map products which could be asupport to the geological mapping [5]. The future ESA-JAXA mission to Mercury, BepiColombo, will soon contribute to improve the knowledge of Mercury surface composition and geology thanks to the Spectrometer and Imagers for MPO BepiColombo-Integrated Observatory SYStem (SIMBIO-SYS)[6]

    SME Performance, Innovation and Networking - Evidence on Complementarities for a Local Economic System

    Full text link
    The paper addresses the relevancy of networking activities and R&D as main drivers of productivity performance and ouput innovation, for small and medium enterprises (SME) playing in a local economic system. Given the intangible nature of many techno organisational innovation and networking strategies, original recent survey data for manufacturing and services are exploited. The aim is to provide new evidence on the complementarity relationships concerning different networking activities and R&D in a local SME oriented system in Northern Italy. We first introduce a methodological framework to empirically test complementarity among R&D and networking, in a discrete setting. Secondly, we consequently present empirical evidence on productivity drivers and on complementarity between R&D and networking strategies, with respect to firm productivity and process/product output innovation. R&D is a main driver of innovation and productivity, even without networking. This may signify, in association with the evidence on complementarity, that firm expenditures on R&D are a primary driver for performance. The complementarity with networking is a consequential step. Networking by itself cannot thus play a role in stimulating productivity and innovation. It can be a complementary factor in situations where cooperation and networking are needed to achieve economies of scale and/or to merge and integrate diverse skills, technologies and competencies. This is compatible with a framework where networking is the public good part of an impure public good wherein R&D plays the part of the private-led driving force towards structural break from the business as usual scenario. Managers and policy makers should be aware that in order to exploit asset complementarity, possibly transformed into competitive advantages, both R&D and networking are to be sustained and favoured. our evidence suggests that R&D may be a single main driver of performance. Since R&D expenditures are associated with firm size, a policy sustain is to be directed towards firm enlargement. After a certain threshold firms have the force to increase expenditures. The size effect is nevertheless non monotonous. Then, but not least important, for the majority of firms still remaining under a critical size threshold, policy incentives should be directed to R&D in connection with networking, through which a virtuous circle may arise. It is worth noting that it is not networking as such the main engine. Networking elements are crucially linked to innovation dynamics; it is nevertheless innovation that explains and drives networking, and not the often claimed mere existence of local spillovers or of a civic associative culture in the territory. Such public good factors exist but are likely to evolve with and be sustained by firm innovative dynamics
    • …
    corecore