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Search Results: 1 - 10 of 12092 matches for " Jose Ignacio Robla "
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Variations in the Electrical Resistivity of Vapour Grown Carbon Fibres by Effect of Successive Operations of Intake and Outgassing of Hydrogen
Cesar Mota,Antonio Madronero,Jose Maria Amo,Jose Ignacio Robla
Journal of Materials Science Research , 2012, DOI: 10.5539/jmsr.v2n1p163
Abstract: The aim of this work is to study the behaviour of Vapour Growth Carbon Fibres (VGCF) with different treatments after the intake and outgassing of hydrogen takes place. The VGCFs are prepared via catalyzed decomposition of a mixture of hydrogen and methane. The catalyst was minute particles of iron. The fibre thickness was about 10 to 20 microns and they have a trunk-tree inner structure. Two different treatments are tested to improve the properties of the as grown samples: a heat treatment under vacuum conditions and an acid etching with nitric acid. The desorption kinetics of the three type of samples is studied measuring the electrical resistivity during the hydrogen outgassing. As a result, the surface treatment with acid etching seems to be an efficient method to improve the kinetics of the hydrogen sorption in the first hydrogenation cycle.
Effects of Gamma Irradiation on the Kinetics of the Adsorption and Desorption of Hydrogen in Carbon Microfibres  [PDF]
Cesar Mota, Mario Culebras, Andrés Cantarero, Antonio Madro?ero, Clara Maria Gómez, Jose María Amo, Jose Ignacio Robla
Advances in Materials Physics and Chemistry (AMPC) , 2013, DOI: 10.4236/ampc.2013.32021

In this study, three types of carbon fibres were used, they were ex-polyacrylonitrile carbon fibres with high bulk modulus, ex-polyacrylonitrile fibres with high strength, and vapour grown carbon fibres. All the samples were subjected to a hydrogen adsorption process at room temperature in an over-pressured atmosphere of 25 bars. The adsorption process was monitored through electrical resistivity measurements. As conditioning of the fibres, a chemical activation by acid etching followed by γ-ray irradiation with 60Co radioisotopes was performed. The surface energy was determined by means of the sessile drop test. Both conditioning treatments are supplementary; the chemical activation works on the outer surface and the γ-irradiation works in the bulk material as well. Apparently, the most significant parameter for hydrogen storage is the crystallite size. From this point of view, the most convenient materials are those with small grain size because hydrogen is accumulated mainly in the grain boundaries.

Testing ZigBee Motes for Monitoring Refrigerated Vegetable Transportation under Real Conditions
Luis Ruiz-Garcia,Pilar Barreiro,Jose Ignacio Robla,Loredana Lunadei
Sensors , 2010, DOI: 10.3390/s100504968
Abstract: Quality control and monitoring of perishable goods during transportation and delivery services is an increasing concern for producers, suppliers, transport decision makers and consumers. The major challenge is to ensure a continuous ‘cold chain’ from producer to consumer in order to guaranty prime condition of goods. In this framework, the suitability of ZigBee protocol for monitoring refrigerated transportation has been proposed by several authors. However, up to date there was not any experimental work performed under real conditions. Thus, the main objective of our experiment was to test wireless sensor motes based in the ZigBee/IEEE 802.15.4 protocol during a real shipment. The experiment was conducted in a refrigerated truck traveling through two countries (Spain and France) which means a journey of 1,051 kilometers. The paper illustrates the great potential of this type of motes, providing information about several parameters such as temperature, relative humidity, door openings and truck stops. Psychrometric charts have also been developed for improving the knowledge about water loss and condensation on the product during shipments.
Revisiting the Classics to Recover the Physical Sense in Electrical Noise  [PDF]
Jose-Ignacio Izpura
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.26055
Abstract: This paper shows a physically cogent model for electrical noise in resistors that has been obtained from Thermodynamical reasons. This new model derived from the works of Johnson and Nyquist also agrees with the Quantum model for noisy systems handled by Callen and Welton in 1951, thus unifying these two Physical viewpoints. This new model is a Complex or 2-D noise model based on an Admittance that considers both Fluctuation and Dissipation of electrical energy to excel the Real or 1-D model in use that only considers Dissipation. By the two orthogonal currents linked with a common voltage noise by an Admittance function, the new model is shown in frequency domain. Its use in time domain allows to see the pitfall behind a paradox of Statistical Mechanics about systems considered as energy-conserving and deterministic on the microscale that are dissipative and unpredictable on the macroscale and also shows how to use properly the Fluctuation-Dissipation Theorem.
On the Absence of Carrier Drift in Two-Terminal Devices and the Origin of Their Lowest Resistance Per Carrier Rk=h/Q2  [PDF]
Jose Ignacio Izpura
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.38100
Abstract: After a criticism on today’s model for electrical noise in resistors, we pass to use a Quantum-compliant model based on the discreteness of electrical charge in a complex Admittance. From this new model we show that carrier drift viewed as charged particle motion in response to an electric field is unlike to occur in bulk regions of Solid-State devices where carriers react as dipoles against this field. The absence of the shot noise that charges drifting in resistors should produce and the evolution of the Phase Noise with the active power existing in the resonators of L-C oscillators, are two effects added in proof for this conduction model without carrier drift where the resistance of any two-terminal device becomes discrete and has a minimum value per carrier that is the Quantum Hall resistance Rk=h/q2 Ω
Electrical Noise, Brownian Motion and the Arrow of Time  [PDF]
Jose-Ignacio Izpura
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.62018
Abstract: The origin of the Johnson noise of resistors is reviewed by a new model fitting in the Fluctuation-Dissipation framework and compared with the velocity noise in Brownian motion. This new model handling both fluctuations as well as dissipations of electrical energy in the Complex Admittance of any resistor excels current model based on the dissipation in their conductance. From the two orthogonal currents associated to a sinusoidal voltage in an electrical admittance, the new model that also considers the discreteness of the electrical charge shows a Cause-Effect dynamics for electrical noise. After a brief look at systems considered as energy-conserving and deterministic on the microscale that are dissipative and unpredictable on the macroscale, the arrow of time is discussed from the noise viewpoint.
A Review of Wireless Sensor Technologies and Applications in Agriculture and Food Industry: State of the Art and Current Trends
Luis Ruiz-Garcia,Loredana Lunadei,Pilar Barreiro,Ignacio Robla
Sensors , 2009, DOI: 10.3390/s90604728
Abstract: The aim of the present paper is to review the technical and scientific state of the art of wireless sensor technologies and standards for wireless communications in the Agri-Food sector. These technologies are very promising in several fields such as environmental monitoring, precision agriculture, cold chain control or traceability. The paper focuses on WSN (Wireless Sensor Networks) and RFID (Radio Frequency Identification), presenting the different systems available, recent developments and examples of applications, including ZigBee based WSN and passive, semi-passive and active RFID. Future trends of wireless communications in agriculture and food industry are also discussed.
A Fluctuation-Dissipation Model for Electrical Noise  [PDF]
Jose-Ignacio Izpura, Javier Malo
Circuits and Systems (CS) , 2011, DOI: 10.4236/cs.2011.23017
Abstract: This paper shows that today’s modelling of electrical noise as coming from noisy resistances is a non sense one contradicting their nature as systems bearing an electrical noise. We present a new model for electrical noise that including Johnson and Nyquist work also agrees with the Quantum Mechanical description of noisy systems done by Callen and Welton, where electrical energy fluctuates and is dissipated with time. By the two currents the Admittance function links in frequency domain with their common voltage, this new model shows the connection Cause-Effect that exists between Fluctuation and Dissipation of energy in time domain. In spite of its radical departure from today’s belief on electrical noise in resistors, this Complex model for electrical noise is obtained from Nyquist result by basic concepts of Circuit Theory and Thermo-dynamics that also apply to capacitors and inductors.
Thermodynamical Phase Noise in Oscillators Based on L-C Resonators  [PDF]
Javier Malo, Jose-Ignacio Izpura
Circuits and Systems (CS) , 2012, DOI: 10.4236/cs.2012.31009
Abstract: Using a new Admittance-based model for electrical noise able to handle Fluctuations and Dissipations of electrical energy, we explain the phase noise of oscillators that use feedback around L-C resonators. We show that Fluctuations produce the Line Broadening of their output spectrum around its mean frequency f0 and that the Pedestal of phase noise far from f0 comes from Dissipations modified by the feedback electronics. The charge noise power 4FkT/R C2/s that disturbs the otherwise periodic fluctuation of charge these oscillators aim to sustain in their L-C-R resonator, is what creates their phase noise proportional to Leeson’s noise figure F and to the charge noise power 4kT/R C2/s of their capacitance C that today’s modelling would consider as the current noise density in A2/Hz of their resistance R. Linked with this (A2/Hz?C2/s) equivalence, R becomes a random series in time of discrete chances to Dissipate energy in Thermal Equilibrium (TE) giving a similar series of discrete Conversions of electrical energy into heat when the resonator is out of TE due to the Signal power it handles. Therefore, phase noise reflects the way oscillators sense thermal exchanges of energy with their environment.
Thermodynamical Phase Noise in Oscillators Based on L-C Resonators (Foundations)  [PDF]
Jose-Ignacio Izpura, Javier Malo
Circuits and Systems (CS) , 2012, DOI: 10.4236/cs.2012.31008
Abstract: By a Quantum-compliant model for electrical noise based on Fluctuations and Dissipations of electrical energy in a Complex Admittance, we will explain the phase noise of oscillators that use feedback around L-C resonators. Under this new model that departs markedly from current one based on energy dissipation in Thermal Equilibrium (TE), this dissipation comes from a random series of discrete Dissipations of previous Fluctuations of electrical energy, each linked with a charge noise of one electron in the Capacitance of the resonator. When the resonator out of TE has a voltage between terminals, a discrete Conversion of electrical energy into heat accompanies each Fluctuation to account for Joule effect. This paper shows these Foundations on electrical noise linked with basic skills of electronic Feedback to be used in a subsequent paper where the aforesaid phase noise is explained by the new Admittance-based model for electrical noise.
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