4,953 research outputs found
Transient model of a Professional Oven
Tackling the climate change by reducing energy consumption is among the biggest, most urgent challenges society is facing and requires a continuous efficiency improvement of thermal systems. Appropriate design strategies, developed a priori and then experimentally validated according to suitable test protocols on a prototype, are needed in order to reach potential energy saving targets. These strategies can successfully be implemented in the food service sector, where cooking appliances, in particular, present many possibilities for improving energy savings. Therefore, a valuable design methodology should take into account not only steady state operating conditions but also the transient behaviours of the device, which must be described by means of specially developed theoretical dynamic models. The operating profile of an oven, for example, consists of a sequence of unsteady phases (cavity heating-up, food introduction and extraction, switching from one cooking mode to another) interspersed with steady cooking phases. The dynamic model presented in this paper defines the energy conservation equations of a professional oven, where a high temperature thermal source positioned inside its cavity produces thermal power radiated and modulated over time, according to a suitable control strategy. In particular, when the temperature in the cooking zone of the cavity has reached a specified set point, this is thermostatically controlled in time, depending on the cooking phase. The resulting equation system is then solved by means of numerical methods. With this code, it is possible to support the design phase of both the structure and the control strategy of the oven. It permits, for example, to get a general understanding of the best possible configurations and combinations of insulation materials for the cavity walls or, with reference to the control strategy, to simulate different cooking procedures, with the aim of optimizing the operating sequence of the oven, reaching the maximum energy saving without reducing the cooking quality. The code, validated by comparison with a set of experimental data obtained with a current production model, will be applied in the design phase of a new line of high efficiency professional ovens
Weakly bound states of polar molecules in bilayers
We investigate a system of two polarized molecules in a layered trap. The
molecules reside in adjacent layers and interact purely via the dipole-dipole
interaction. We determine the properties of the ground state of the system as a
function of the dipole moment and polarization angle. A bound state is always
present in the system and in the weak binding limit the bound state extends to
a very large distance and shows universal behavior.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
EFFECTS OF THE USE OF D-LIMONENE AS AN ADDITIVE TO DIESEL-BIODIESEL BLENDS ON EXHAUST GASES COMPOSITION OF COMPRESSION IGNITION ENGINES
The transesterification of vegetable oils results in methyl esters of fatty acid, known as biodiesel. This one presents similar features of diesel oil, such as cetane number, specific weight, heat of combustion and air-fuel ratio. However, arising problems from its higher viscosity leads to a poor spraying by the fuel injectors and so to a low-grade combustion, causing formation of undesirable deposits inside the engine, changes in the properties of the lubricating oil and in the composition of the exhaust gas. Owing to this issue, it is necessary to study an additive able to make biodiesel characteristics more appropriate to be used in compression ignition engines, as well as a monitoring of changes in exhaust gas composition. The chosen additive was d-limonene, a monocyclic terpene obtained as a byproduct of citriculture. This paper presents the preliminary results obtained from the tests in a stationary diesel engine fuelled with mixtures of diesel-biodiesel and d-limonene, in different concentrations, comparing to regular diesel fuel. Although it was used in low concentrations, the additive was efficient in the reduction of hydrocarbons, carbon monoxide and opacity
Topological p_x+ip_y Superfluid Phase of Fermionic Polar Molecules
We discuss the topological p_x+ip_y superfluid phase in a 2D gas of
single-component fermionic polar molecules dressed by a circularly polarized
microwave field. This phase emerges because the molecules may interact with
each other via a potential V_0(r) that has an attractive dipole-dipole 1/r^3
tail, which provides p-wave superfluid pairing at fairly high temperatures. We
calculate the amplitude of elastic p-wave scattering in the potential V_0(r)
taking into account both the anomalous scattering due to the dipole-dipole tail
and the short-range contribution. This amplitude is then used for the
analytical and numerical solution of the renormalized BCS gap equation which
includes the second order Gor'kov-Melik-Barkhudarov corrections and the
correction related to the effective mass of the quasiparticles. We find that
the critical temperature T_c can be varied within a few orders of magnitude by
modifying the short-range part of the potential V_0(r). The decay of the system
via collisional relaxation of molecules to dressed states with lower energies
is rather slow due to the necessity of a large momentum transfer. The presence
of a constant transverse electric field reduces the inelastic rate, and the
lifetime of the system can be of the order of seconds even at 2D densities ~
10^9 cm^{-2}. This leads to T_c of up to a few tens of nanokelvins and makes it
realistic to obtain the topological p_x+ip_y phase in experiments with
ultracold polar molecules.Comment: 15 pages, 9 figures, published versio
Designing spin-1 lattice models using polar molecules
We describe how to design a large class of always on spin-1 interactions
between polar molecules trapped in an optical lattice. The spin degrees of
freedom correspond to the hyperfine levels of a ro-vibrational ground state
molecule. Interactions are induced using a microwave field to mix ground states
in one hyperfine manifold with the spin entangled dipole-dipole coupled excited
states. Using multiple fields anistropic models in one, two, or three
dimensions, can be built with tunable spatial range. An illustrative example in
one dimension is the generalized Haldane model, which at a specific parameter
has a gapped valence bond solid ground state. The interaction strengths are
large compared to decoherence rates and should allow for probing the rich phase
structure of strongly correlated systems, including dimerized and gapped
phases.Comment: 24 pages, 5 figure
Internet of robotic things : converging sensing/actuating, hypoconnectivity, artificial intelligence and IoT Platforms
The Internet of Things (IoT) concept is evolving rapidly and influencing newdevelopments in various application domains, such as the Internet of MobileThings (IoMT), Autonomous Internet of Things (A-IoT), Autonomous Systemof Things (ASoT), Internet of Autonomous Things (IoAT), Internetof Things Clouds (IoT-C) and the Internet of Robotic Things (IoRT) etc.that are progressing/advancing by using IoT technology. The IoT influencerepresents new development and deployment challenges in different areassuch as seamless platform integration, context based cognitive network integration,new mobile sensor/actuator network paradigms, things identification(addressing, naming in IoT) and dynamic things discoverability and manyothers. The IoRT represents new convergence challenges and their need to be addressed, in one side the programmability and the communication ofmultiple heterogeneous mobile/autonomous/robotic things for cooperating,their coordination, configuration, exchange of information, security, safetyand protection. Developments in IoT heterogeneous parallel processing/communication and dynamic systems based on parallelism and concurrencyrequire new ideas for integrating the intelligent “devices”, collaborativerobots (COBOTS), into IoT applications. Dynamic maintainability, selfhealing,self-repair of resources, changing resource state, (re-) configurationand context based IoT systems for service implementation and integrationwith IoT network service composition are of paramount importance whennew “cognitive devices” are becoming active participants in IoT applications.This chapter aims to be an overview of the IoRT concept, technologies,architectures and applications and to provide a comprehensive coverage offuture challenges, developments and applications
COMBUSTION ANALYSIS OF D-LIMONENE AS AN ADDITIVE TO DIESEL-BIODIESEL BLENDS IN COMPRESSION IGNITION ENGINES
Vegetable oils, when subjected to transesterification process generate “vegetable oils esters”, with similar properties as density, cetane number, heating values, air-fuel ratio. However, problems resulting from the higher viscosity, leads to a worst spraying and combustion, formation of undesirable deposits on engine parts and contamination of the lubricant oil. Due to these problems, it is interesting to study an additive, also derived from biomass, to improve the characteristics of biodiesel for a suitable use in diesel engines. This paper proposes an additive (d-limonene obtained from orange peel) and preliminary results obtained from the tests in a stationary diesel engine fueled with mixtures of diesel/biodiesel/d-limonene, in different concentration to compare with a regular diesel-biodiesel blend and analyzes the influence of the additive on the combustion process. The diesel oil used was purchased from BR supply network (containing 7% biodiesel in its composition) and two blends with different concentrations of the additive (1% and 3% of d-limonene) were prepared and tested. Diesel without additive was also tested. The effects of the DS10 addititivation with d-limonene in the combustion process of a diesel engine have been analyzed, the results obtained were satisfactory showing the positive effects in the combustion process with the addition of d-limonene in diesel-biodiesel blends, decreasing the ignition delay around 2 degrees and showing an improvement in the cetane number of the fuel
On the segmentation of astronomical images via level-set methods
Astronomical images are of crucial importance for astronomers since they
contain a lot of information about celestial bodies that can not be directly
accessible. Most of the information available for the analysis of these objects
starts with sky explorations via telescopes and satellites. Unfortunately, the
quality of astronomical images is usually very low with respect to other real
images and this is due to technical and physical features related to their
acquisition process. This increases the percentage of noise and makes more
difficult to use directly standard segmentation methods on the original image.
In this work we will describe how to process astronomical images in two steps:
in the first step we improve the image quality by a rescaling of light
intensity whereas in the second step we apply level-set methods to identify the
objects. Several experiments will show the effectiveness of this procedure and
the results obtained via various discretization techniques for level-set
equations.Comment: 24 pages, 59 figures, paper submitte
Three-body interactions with cold polar molecules
We show that polar molecules driven by microwave fields give naturally rise
to strong three-body interactions, while the two-particle interaction can be
independently controlled and even switched off. The derivation of these
effective interaction potentials is based on a microscopic understanding of the
underlying molecular physics, and follows from a well controlled and systematic
expansion into many-body interaction terms. For molecules trapped in an optical
lattice, we show that these interaction potentials give rise to Hubbard models
with strong nearest-neighbor two-body and three-body interaction. As an
illustration, we study the one-dimensional Bose-Hubbard model with dominant
three-body interaction and derive its phase diagram.Comment: 8 pages, 4 figure
- …