1,354,401 research outputs found
The air temperature conundrum
No full textMeasuring air temperature is far from a trivial task, as Andrea Merlone, Graziano Coppa and Chiara Musacchio explain
Impulsivity in Binary Choices and the Emergence of Periodicity
No full textBinary choice games with externalities, as those described by Schelling (1973, 1978), have been recently modelled as discrete dynamical systems (Bischi and Merlone, 2009). In this paper we discuss the dynamic behavior in the case in which agents are impulsive; that is; they decide to switch their choices even when the difference between payoffs is extremely small. This particular case can be seen as a limiting case of the original model and can be formalized as a piecewise linear discontinuous map. We analyze the dynamic behavior of this map, characterized by the presence of stable periodic cycles of any period that appear and disappear through
border-collision bifurcations. After a numerical exploration, we study the conditions for the creation and the destruction of periodic cycles, as well as the analytic expressions
of the bifurcation curves
Boltzmann: the genius of disorder
No full textThe tragedy and greatness of the contribution of Ludwig Boltzmann cannot be understood without taking into account the relevant scientific developments that took place in the nineteenth century, one of the most eventful periods in the history of science. The kinetic theory opened a new theoretical perspective in understanding natural phenomena. The introduction of new categories of order and disorder changed radically the point of view of those physicists that accepted Boltzmann’s thesis and led, at the same time, to strong opposition to the Viennese Scientist. In this paper, we present the academic situation, scientific theories, and disputes involving the Boltzmann’s theories. A short introduction on the birth of the atomistic theories opens the article, while a view on the evolution of the concept of temperature and the definition of its unit quantity closes it
Design and capabilities of the temperature control system for theItalian experiment based upon precision laser spectroscopy for anew determination of the Boltzmann constant
No full textThis article reports on the construction details of an isothermal cell, referenced to the triple point of water (TPW), together with characterization of its temperature uniformity and stability. The traceability of the temperature measurements is also defined and reported. The cell has an inner chamber of 15 mm diameter, and it is 150 mm long. Its temperature is actively controlled and maintained stable within 0.1 mK, for an unlimited time. The temperature gradient is limited to less than one millikelvin over the length of the cell which is kept in a horizontal position. This accurate temperature control is achieved by means of a series of three vacuum chambers, one inside the other. A special heater, reflectors, standard platinum resistance thermometers, several feedthroughs, an auxiliary thermostat, specific electronics, and dedicated software are used for the active control. The device represents a mixture of cryogenic and contact thermometry techniques, and it has been designed, assembled, and characterized at the Istituto Nazionale di Ricerca Metrologica. This temperature-stabilized cell is a part of a more complex experimental setup, based on near-infrared precision laser spectroscopy, devoted to the experimental determination of the Boltzmann constant
Thermal metrology for climate: a review of projects, activities and open issues
No full textOver the last decade, an increasing collaboration has been established between the metrology and the meteorology and climate communities. The International Committee for Weights and Measures and the World Meteorological Organization of the United Nations are jointly cooperating and driving the growing liaisons between national institutes of metrology and national meteorological and hydrological services. Thermal quantities play a key role among the Essential Climate Variables defined by the Global Climate Observing System in the terrestrial, atmospheric and marine domains. Improved understanding of ongoing and future climate variability and change through accurately monitoring temperature evolution requires metrological rigor to also enable early detection of trends. This is achieved through developing new measurement techniques and novel instruments; understanding uncertainty components both for laboratory calibration and for field conditions; accurately evaluating quantities of influence; and developing guidelines, best practices and recommendations. This paper reports an overview of the projects and activities involving the thermal metrology community under a growing collaboration with the researchers in climate and meteorology. A general vision on open issues and future perspectives is also presented
Temperature metrology needs for climate studies - CCT Recommendation to CIPM T3 (2010). Doc. CCT/10-09
No full textMemory effects on binary choices with impulsive agents: Bistability and a new BCB structure
No full textAfter the seminal works by Schelling, several authors have considered models representing binary choices by different kinds of agents or groups of people. The role of the memory in these models is still an open research argument, on which scholars are investigating. The dynamics of binary choices with impulsive agents has been represented, in the recent literature, by a one-dimensional piecewise smooth map. Following a similar way of modeling, we assume a memory effect which leads the next output to depend on the present and the last state. This results in a two-dimensional piecewise smooth map with a limiting case given by a piecewise linear discontinuous map, whose dynamics and bifurcations are investigated. The map has a particular structure, leading to trajectories belonging only to a pair of straight lines. The system can have, in general, only attracting cycles, but the related periods and periodicity regions are organized in a complex structure of the parameter space. We show that the period adding structure, characteristic for the one-dimensional case, also persists in the two-dimensional one. The considered cycles have a symbolic sequence which is obtained by the concatenation of the symbolic sequences of cycles, which play the role of basic cycles in the bifurcation structure. Moreover, differently from the one-dimensional case, the coexistence of two attracting cycles is now possible. The bistability regions in the parameter space are investigated, evidencing the role of different kinds of codimension-two bifurcation points, as well as in the phase space and the related basins of attraction are described
Reaching consensus on rumors
No full textAn important contribution in sociophysics is the Galam's model of rumors spreading. This model provides an explanation of rumors spreading in a population and explains some interesting social phenomena such as the diffusion of hoaxes. In this paper the model has been reformulated as a Markov process highlighting the stochastic nature of the phenomena. This formalization allows us to derive conditions for consensus to be reached and for the existence of some interesting phenomena such as the emergence of impasses. The proposed formulation allows a deeper and more comprehensive analysis of the diffusion of rumors
A New Mercury Gas-Controlled Heat Pipe for Temperature Amplifier and as Calibration Facility
No full textAt the Italian National Research Institute of Metrology the activities and studies on the Gas Controlled Heat Pipes are constantly increasing in terms of involved personnel, instrumentations and devices available. In last two years, among the other activities, a totally new Gas-Controlled Heat Pipe operating with mercury as working fluid has been designed, manufactured and completely characterised.
This Heat Pipe is made in stainless steel and provided with three thermometers wells. A dedicated furnace has been constructed too and specific software algorithms have been implemented for the temperature and pressure control. This device will be used as low temperature reference for the new “Temperature Amplifier” and, at the same time, as calibration facility for thermometers calibrations by comparison in the field between 220 °C and 450 °C. All details regarding this Heat Pipe, including assembly, filling and testing procedures, and the complete characterisation campaign are here summarised.
Results in terms of temperature stability, uniformity, time response are reported, and demonstrate the capabilities of this Gas Controlled Heat Pipe to be a useful device for researches and applications in contact thermometry.
A further Gas Controlled Heat Pipe operating with mercury has been manufactured, provided with six thermometer wells and will be characterised for the contact thermometry calibration laboratory on INRiM and for other calibration groups; this device is presented too
Construction and start up of a large-volume thermostat for dielectric-constant-gas-thermometry
No full textA liquid-bath thermostat with a volume of about 800 L was designed to provide a suitable thermal environment for a dielectric-constant gas thermometer (DCGT) in the range from the triple point of mercury to the melting point of gallium. In the paper, results obtained with the unique, huge thermostat without the DCGT measuring chamber are reported in order to demonstrate the capability of controlling the temperature of very large systems at a metrological level. First tests showed that the bath together with its temperature controller provide a temperature variation of less than ±0.5 mK peak-to-peak. This temperature instability could be maintained over a period of several days. In the central working volume (diameter 500 mm, height 650 mm), in which the vacuum chamber containing the measuring system of the DCGT will be placed later, the temperature inhomogeneity has been demonstrated to be also well below 1 mK
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