This paper considers different cooling systems and investigates the most promising alternatives when solar energy is to be used to supply the cooling demand. All the systems are evaluated during a ...summer cooling season by the energetic and economic point of view by dynamic simulation for two different climates. For Milan (Cfb climate) the highest OSE (overall system efficiency) is reached by LiBr (lithium-bromide) double effect absorption chiller driven by parabolic through collector (0.53). In terms of the collecting surface area, the best systems for Milan feature 0.08 m2 MJ−1 per day both for electric system (mono-crystalline photovoltaic coupled to water cooled chiller) and thermal system (PTC (parabolic trough collectors) coupled to double effect water-LiBr absorption chiller). Southern latitudes like Trapani (Csa climate) allow a quite better performance for thermal solar cooling solutions. The NPV (net present worths) of electric solar cooling solutions are favorable with respect to the traditional solution and the DPV (discounted payback periods) are all lower than the period of economic analysis above all for water cooled chillers. Finally a sensitivity analysis of the specific investment cost (€ MJ−1 per day) is carried out regarding the investment cost of collectors, the solar ratio and the interest rate.
•Solar cooling is obtained with solar thermal or PV (photovoltaic) with easy available equipment.•In the past PV driven systems for solar cooling were not considered as too expensive.•An energy/economic comparison is carried out for the various solar cooling systems.•Sensitivity analyses are carried out varying different parameters.
•This work focuses on the study of the aqueous alteration process which acted in the main belt.•We present new visible spectra of 80 main belt primitive asteroids.•Statistical analysis on a sample of ...600 primitive main belt asteroids, including our and literature data.•The aqueous alteration process dominates in primitive asteroids located between 2.3 and 3.1AU.•The percentage of hydrated asteroids is strongly correlated with their size – around 50% of the observed C.•Type asteroids show absorption feature in the visible range due to hydrated silicates.
This work focuses on the study of the aqueous alteration process which acted in the main belt and produced hydrated minerals on the altered asteroids. Hydrated minerals have been found mainly on Mars surface, on main belt primitive asteroids and possibly also on few TNOs. These materials have been produced by hydration of pristine anhydrous silicates during the aqueous alteration process, that, to be active, needed the presence of liquid water under low temperature conditions (below 320K) to chemically alter the minerals. The aqueous alteration is particularly important for unraveling the processes occurring during the earliest times of the Solar System history, as it can give information both on the asteroids thermal evolution and on the localization of water sources in the asteroid belt.
To investigate this process, we present reflected light spectral observations in the visible region (0.4–0.94μm) of 80 asteroids belonging to the primitive classes C (prevalently), G, F, B and P, following the Tholen (Tholen, D.J. 1984. Ph.D. Dissertation, University of Arizona, Tucson). classification scheme. We find that about 65% of the C-type and all the G-type asteroids investigated reveal features suggesting the presence of hydrous materials, mainly a band centered around 0.7μm, while we do not find evidence of hydrated materials in the other low albedo asteroids (B, F, and P) investigated.
We combine the present observations with the visible spectra of asteroids available in the literature for a total of 600 primitive main belt asteroids. We analyze all these spectra in a similar way to characterize the absorption band parameters (band center, depth and width) and spectral slope, and to look for possible correlations between the aqueous alteration process and the asteroids taxonomic classes, orbital elements, heliocentric distances, albedo and sizes. Our analysis shows that the aqueous alteration sequence starts from the P-type objects, practically unaltered, and increases through the P→F→B→C→G asteroids, these last being widely aqueous altered, strengthening thus the results previously obtained by Vilas (Vilas, F. 1994. Icarus 111, 456–467). Around 50% of the observed C-type asteroids show absorption feature in the visible range due to hydrated silicates, implying that more than ∼70% of them will have a 3μm absorption band and thus hydrated minerals on their surfaces, based on correlations between those two absorptions (Howell, E.S. et al. 2011. EPSC-DPS Joint Meeting 2011, vol. 6. Abstracts, 637).
We find that the aqueous alteration process dominates in primitive asteroids located between 2.3 and 3.1AU, that is at smaller heliocentric distances than previously suggested by Vilas et al. (Vilas, F., Hatch, E.C., Larson, S.M., Sawyer, S.R., Gaffey, M.J. 1993. Icarus 102, 225–231). The percentage of hydrated asteroids is strongly correlated with their size. The aqueous alteration process is less effective for bodies smaller than 50km, while it dominates in the 50–240km sized primitive asteroids.
No correlation is found between the aqueous alteration process and the asteroids albedo or orbital elements. Comparing the ∼0.7μm band parameters of hydrated silicates and CM2 carbonaceous chondrites, the meteorites that have aqueous altered asteroids as parent bodies, we see that the band center of meteorites is at longer wavelengths than that of asteroids. This difference on center positions may be attributed to different minerals abundances, and to the fact that CM2 available on Earth might not be representative of the whole aqueous altered asteroids population.
ABSTRACT
We present new spectral observations using ground-based telescopes of 23 putative V-type asteroids, selected according to colour surveys in the visible from the Moving Objects Catalogue of ...the Sloan Digital Sky Survey and near-infrared from the Moving Objects VISTA catalogue. 10 asteroids are orbiting in the middle main belt, while five in the outer part of the main asteroid belt. For the observed asteroids, we assign a taxonomical classification and confirm the basaltic nature for 16 of them. The high-quality spectra in the UV range, obtained with the X-Shooter spectrograph at ESO, allowed the identification of the Fe2+ forbidden transition of pyroxene for 10 asteroids. This band is centred at 506.5 nm, and it is diagnostic of the Ca-content in the pyroxene form. We determined a low Fe-content composition for asteroids (2452) Lyot, (5758) Brunini, (7675) Gorizia, (9197) Endo, (22308) 1990 UO4, (36118) 1999 RE135, (66905) 1999 VC160, and (189597) 2000 WG119, and a composition more rich in Fe for asteroids (75661) 2000 AB79 and (93620) 2000 UQ70. We also present a dynamical investigation of V-type asteroids in the middle and outer main belt. The principal finding of these simulations is that the middle and outer V-types are more likely to be associated with some families, which were considered as possibly originated from the break up of a partially or totally differentiated parent body by diverse studies. This reinforces the hypothesis that the identified V-type in the region were not originated from (4) Vesta and that the number of differentiated objects in the middle and outer main belt must have been much larger than previously assumed.
Light spectral composition influences plant growth and metabolism, and has important consequences for interactions with plant-feeding arthropods and their natural enemies. In greenhouse horticulture, ...light spectral composition can be precisely manipulated by light-emitting diodes (LEDs), and LEDs are already used to optimize crop production and quality. However, because light quality also modulates plant secondary metabolism and defense, it is important to understand the underlying mechanisms in the context of the growth–defense trade-off. We review the effects of the spectral composition of supplemental light currently used, or potentially used, in greenhouse horticulture on the mechanisms underlying plant growth and defense. This information is important for exploring opportunities to optimize crop performance and pest management, and thus for developing resilient crop-production systems.
Light spectral composition influences plant morphology, physiology, and development by impacting on processes ranging from photosynthesis to secondary metabolism.Signaling pathways underlying growth and defense are linked, and light spectral composition therefore influences both processes.Light spectral composition influences the behavior of plant-feeding arthropods and their carnivorous enemies directly or via changes in plant morphology and physiology.Specific manipulation of light spectral composition in greenhouses through LEDs may optimize both crop production and crop protection, thus improving crop resilience.
Condensing boilers allow better performances when return temperatures from the plant are lower and above all when these temperatures are below the dew temperature of the smoke. That is the reason why ...many believe that condensing boiler is not suitable for the traditional heating plant terminals: the radiators. Instead the classic control system with weather compensation curve produces relatively low temperatures and an appreciable condensing operation during March, April, October and November. Moreover, condensing boilers allow a better performance than traditional boiler even when they do not perform condensing operation. However for the optimum exploitation of condensing boilers in a radiator plant, variable-flow-rate plants should be selected that permit every outside condition to maintain a high difference between delivery and return temperature. This control selection, which is fully consistent with the use of thermostatic valves, needs variable-flow-rate pumps and, if possible, with proportional head.
•We derived a global 3D shape model and the rotational parameters of comet 67P/C-G from high-resolution visible images collected aboard the Rosetta spacecraft.•Using this model, we could calculate ...accurate nucleus parameters including a volume of 18.8 ± 0.3 km3 and a density of 532 ± 7 kg m−3.•We could also retrieve the shape and the geometry of the two lobes using computer graphics tools.•A slight excitation of the spin state was detected, with a precession period of 11.5 ± 0.5 day.•The coordinates of the spin axis indicates a slight inhomogeneity of the density distribution.
The Rosetta spacecraft reached Comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) in August 2014 at an heliocentric distance of 3.6 a.u. and was then put in orbit around its nucleus to perform detailed observations. Among the collected data are the images acquired by the OSIRIS instrument up to the perihelion passage of the comet in August 2015, which allowed us to map the entire nucleus surface at high-resolution in the visible. Stereophotoclinometry methods have been used to reconstruct a global high-resolution shape model and to monitor its rotational parameters using data collected up to perihelion.
The nucleus has a conspicuous bilobate shape with overall dimensions along its principal axes of (4.34 ± 0.02) × (2.60 ± 0.02) × (2.12 ± 0.06) km. The best-fit ellipsoid dimensions of the individual lobes along their principal axes of inertia are found to be 4.10 × 3.52 × 1.63 km and 2.50 × 2.14 × 1.64 km. Their volume amounts to 66% and 27% of the total volume of the nucleus. The two lobes are connected by a “neck” whose volume has been estimated to represent ∼7% of the total volume of the comet. Combining the derived volume of 18.8 ± 0.3 km3 with the mass of 9.982 ± 0.003 × 1012 kg determined by the Rosetta/RSI experiment, we obtained a bulk density of the nucleus of 532±7kgm−3. Together with the companion value of 535±35kgm−3 deduced from the stereophotogrammetry shape model of the nucleus (Preusker et al. 2015 Astron. Astrophys. 583, A33), these constitute the first reliable and most accurate determination of the density of a cometary nucleus to date. The calculated porosity is quite large, ranging approximately from 70% to 75% depending upon the assumed density of the dust grains and the dust-to-ice mass ratio. The nature of the porosity, either micro or macro or both, remains unconstrained. The coordinates of the center of gravity are not compatible with a uniform nucleus density. The direction of the offset between the center of gravity and the center of figure suggests that the big lobe has a slightly higher bulk density compared to the small one. the center of mass position cannot be explained by different, but homogenous densities in the two lobes.
The initial rotational period of 12.4041 ± 0.0001 h of the nucleus persisted until October 2014. It then slightly increased to a maximum of 12.4304 h reached on 19 May 2015 and finally dropped to 12.305 h just before perihelion on August 10, 2015. A periodogram analysis of the (RA, Dec) direction of the Z-axis of the comet obtained in parallel with the shape reconstruction exhibits a highly significant minima at 11.5 ± 0.5 day clearly indicating an excited rotational state with an amplitude of 0.15 ± 0.03°.
Abstract
In this proceedings we describe the current development status and recent technical achievements of Qibo, an open-source framework for quantum simulation. After a concise overview of the ...project goal, we introduce the modular layout for backend abstraction released in version 0.1.7. We discuss the advantages of each backend choice with particular emphasis on hardware accelerators for quantum state vector simulation. Finally, we summarize the primitives and models currently available.
Aims. The Rosetta space probe accompanied comet 67P/Churyumov-Gerasimenko for more than two years, obtaining an unprecedented amount of unique data of the comet nucleus and inner coma. This has ...enabled us to study its activity almost continuously from 4 au inbound to 3.6 au outbound, including the perihelion passage at 1.24 au. This work focuses identifying the source regions of faint jets and outbursts and on studying the spectrophotometric properties of some outbursts. We use observations acquired with the OSIRIS/NAC camera during July–October 2015, that is, close to perihelion. Methods. We analyzed more than 2000 images from NAC color sequences acquired with 7–11 filters covering the 250–1000 nm wavelength range. The OSIRIS images were processed with the OSIRIS standard pipeline up to level 3, that is, converted in radiance factor, then corrected for the illumination conditions. For each color sequence, color cubes were produced by stacking registered and illumination-corrected images. Results. More than 200 jets of different intensities were identified directly on the nucleus. Some of the more intense outbursts appear spectrally bluer than the comet dark terrain in the visible-to-near-infrared region. We attribute this spectral behavior to icy grains mixed with the ejected dust. Some of the jets have an extremely short lifetime. They appear on the cometary surface during the color sequence observations, and vanish in less than some few minutes after reaching their peak. We also report a resolved dust plume observed in May 2016 at a resolution of 55 cm pixel−1, which allowed us to estimate an optical depth of ~0.65 and an ejected mass of ~2200 kg, assuming a grain bulk density of ~800 kg m−3. We present the results on the location, duration, and colors of active sources on the nucleus of 67P from the medium-resolution (i.e., 6–10 m pixel−1) images acquired close to perihelion passage. The observed jets are mainly located close to boundaries between different morphological regions. Some of these active areas were observed and investigated at higher resolution (up to a few decimeter per pixel) during the last months of operations of the Rosetta mission. Conclusions. These observations allow us to investigate the link between morphology, composition, and activity of cometary nuclei. Jets depart not only from cliffs, but also from smooth and dust-covered areas, from fractures, pits, or cavities that cast shadows and favor the recondensation of volatiles. This study shows that faint jets or outbursts continuously contribute to the cometary activity close to perihelion passage, and that these events are triggered byillumination conditions. Faint jets or outbursts are not associated with a particular terrain type or morphology.
The concept of a low energy building in a temperate climate (according to the Koppen climate classification) is based upon the following principles: reduction of heat losses through enhanced ...insulation; the inclusion of heat recovery on mechanical ventilation; and the use of high efficiency heating/cooling systems integrated with renewable technologies. It is almost impossible to achieve optimum results in terms of global energy efficiency if one of these elements is omitted from the design.
In 2009, a new school building, integrating these three key elements, was opened in Agordo town, located in northern Italy. The main design features of the building incorporate a well insulated envelope and a space heating and ventilation system driven by an innovative multisource heat pump system.
Outdoor air is a common heat source, although it does have widely documented limitations. Heat pump systems can utilise more efficient sources than air, including those of ground heat, solar heat, and heat recovery. The installed system within the school building incorporates these three sources. A multisource system aims to enhance the performance of the heat pump, both in terms of heating capacity and overall efficiency.
The present work includes evaluation and analysis of data obtained through real time monitoring of the working system in operation, for a period of approximately two heating seasons. During this time, the behaviour of the system was assessed and the incorrect settings of the plant were identified and subsequently adjusted as required. The energy balance indicates that the integration of different sources not only increases the thermal performance of the system as a whole, but also optimizes the use of each source. Further savings can be obtained through correct adjustment of the set point of the indoor temperature.
During the final stage of the study, the total energy consumption of the new building is calculated and compared to that of the former building that housed the same school, which had similar dimensions.
•We monitored an HVAC plant based on multisource heat pump for two years.•The electricity consumptions of auxiliaries (pumps etc) were taken into account.•A detailed first law energy balance of the plant was calculated on a monthly base, as well as a Primary Energy balance.•The use of more than one heat source at the evaporator level increases the efficiency of the heat pumps.
Abstract
We collect observational evidence that supports the scheme of mass transfer on the nucleus of comet 67P/Churyumov–Gerasimenko. The obliquity of the rotation axis of 67P causes strong ...seasonal variations. During perihelion the southern hemisphere is four times more active than the north. Northern territories are widely covered by granular material that indicates back fall originating from the active south. Decimetre sized chunks contain water ice and their trajectories are influenced by an antisolar force instigated by sublimation. OSIRIS observations suggest that up to 20 per cent of the particles directly return to the nucleus surface taking several hours of traveltime. The back fall covered northern areas are active if illuminated but produce mainly water vapour. The decimetre chunks from the nucleus surface are too small to contain more volatile compounds such as CO2 or CO. This causes a north–south dichotomy of the composition measurements in the coma. Active particles are trapped in the gravitational minimum of Hapi during northern winter. They are ‘shock frozen’ and only re-activated when the comet approaches the sun after its aphelion passage. The insolation of the big cavity is enhanced by self-heating, i.e. reflection and IR radiation from the walls. This, together with the pristinity of the active back fall, explains the early observed activity of the Hapi region. Sobek may be a role model for the consolidated bottom of Hapi. Mass transfer in the case of 67P strongly influences the evolution of the nucleus and the interpretation of coma measurements.
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