GIEF - Grup Innovació Educativa a la Física
http://hdl.handle.net/2117/3301
2024-03-28T11:46:05ZFront form and point form formulation of predictive relativistic mechanics. Noninteraction theorems
http://hdl.handle.net/2117/400177
Front form and point form formulation of predictive relativistic mechanics. Noninteraction theorems
Jaen Herbera, Javier; Molina, A; Iranzo Fernández, Vicente
The front form and the point form of dynamics are studied in the framework of predictive relativistic mechanics. The noninteraction theorem is proved when a Poincare-invariant Hamiltonian formulation with canonical position coordinates is required.
2024-01-24T14:40:07ZJaen Herbera, JavierMolina, AIranzo Fernández, VicenteThe front form and the point form of dynamics are studied in the framework of predictive relativistic mechanics. The noninteraction theorem is proved when a Poincare-invariant Hamiltonian formulation with canonical position coordinates is required.Relationship between climate variability indices and airborne pollination in Catalonia (NE Iberian Peninsula)
http://hdl.handle.net/2117/27348
Relationship between climate variability indices and airborne pollination in Catalonia (NE Iberian Peninsula)
Alarcón Jordán, Marta; Belmonte, Jordina; Majeed, Husam Tareq; Periago Oliver, M. Cristina; Izquierdo Miguel, Rebeca
Here we explore the effect of climatic variability on the airborne pollen series recorded in Catalonia (NE Iberian Peninsula) considered of high interest due to abundance, landscape importance and/or allergenic significance. In this sense, the relationship between the annual and winter (December to March) phases of the North Atlantic Oscillation (NAO), the Western Mediterranean Oscillation (WeMO) and the Arctic Oscillation (AO) and the Annual Pollen Index (API), the start, the end and the length of the pollination seasons of 22 taxa collected at 6 aerobiological stations in Catalonia during the 18 years-period 1994-2011 have been computed. In addition, daily back-trajectories cluster analysis has been carried out in order to determine the influence of climatic indices on the main atmospheric transport routes frequencies and the long range pollen transport. Our aim is to determine the respective vulnerability of taxa to climate variability, taking also into account the pollen provenance area.
Climatic indices showed significant negative correlations with the parameters API (except for Corylus) and pollination start (except for Ambrosia, Castanea, Fagus and Betula, the latter being Eurosiberian taxa often long range transported) of most taxa, while significant positive correlations with the end of the pollination period of most taxa. The most vulnerable taxa (more significant correlations) with regard to API were Corylus, Olea, Platanus and Quercus deciduous type.
2015-04-15T10:38:46ZAlarcón Jordán, MartaBelmonte, JordinaMajeed, Husam TareqPeriago Oliver, M. CristinaIzquierdo Miguel, RebecaHere we explore the effect of climatic variability on the airborne pollen series recorded in Catalonia (NE Iberian Peninsula) considered of high interest due to abundance, landscape importance and/or allergenic significance. In this sense, the relationship between the annual and winter (December to March) phases of the North Atlantic Oscillation (NAO), the Western Mediterranean Oscillation (WeMO) and the Arctic Oscillation (AO) and the Annual Pollen Index (API), the start, the end and the length of the pollination seasons of 22 taxa collected at 6 aerobiological stations in Catalonia during the 18 years-period 1994-2011 have been computed. In addition, daily back-trajectories cluster analysis has been carried out in order to determine the influence of climatic indices on the main atmospheric transport routes frequencies and the long range pollen transport. Our aim is to determine the respective vulnerability of taxa to climate variability, taking also into account the pollen provenance area.
Climatic indices showed significant negative correlations with the parameters API (except for Corylus) and pollination start (except for Ambrosia, Castanea, Fagus and Betula, the latter being Eurosiberian taxa often long range transported) of most taxa, while significant positive correlations with the end of the pollination period of most taxa. The most vulnerable taxa (more significant correlations) with regard to API were Corylus, Olea, Platanus and Quercus deciduous type.Homothetic motions and Newtonian cosmology
http://hdl.handle.net/2117/26879
Homothetic motions and Newtonian cosmology
Jaen Herbera, Javier; Molina Compte, Alfred
We construct a homothetic covariant Newtonian gravitation theory which unifies inertial homothetic forces and gravitational fields. This is achieved through an equivalence principle based on a local homothetic frame of motion. As a consequence, we can obtain a coherent Newtonian cosmology which admits a cosmological principle and leads to the Friedman equations for a dust universe. Finally we prove that this gravity theory can be obtained as the non-relativistic limit of a class of metrics in General Relativity. The Friedmann–Lemaître–Robertson–Walker metric and its limit are also studied.
2015-03-20T10:00:17ZJaen Herbera, JavierMolina Compte, AlfredWe construct a homothetic covariant Newtonian gravitation theory which unifies inertial homothetic forces and gravitational fields. This is achieved through an equivalence principle based on a local homothetic frame of motion. As a consequence, we can obtain a coherent Newtonian cosmology which admits a cosmological principle and leads to the Friedman equations for a dust universe. Finally we prove that this gravity theory can be obtained as the non-relativistic limit of a class of metrics in General Relativity. The Friedmann–Lemaître–Robertson–Walker metric and its limit are also studied.A conceptual discussion on electromagnetic units - Extending mechanical units towards a global system of units
http://hdl.handle.net/2117/23306
A conceptual discussion on electromagnetic units - Extending mechanical units towards a global system of units
Jaen Herbera, Javier; Bohigas Janoher, Xavier; Pejuan Alcobé, Arcadi
A comparative review of the different systems of units that are most usual in electromagnetism leads to the proposal of a new system of units. In this system, the gravitational constant acquires the role of an interaction constant, both for gravitational and electromagnetic interaction, as a result of a redefinition of electric charge. In this way, the new system of units extends in a natural manner to mechanics. The comparison between the gravitational and electromagnetic interactions is of particular relevance.
2014-06-26T09:59:52ZJaen Herbera, JavierBohigas Janoher, XavierPejuan Alcobé, ArcadiA comparative review of the different systems of units that are most usual in electromagnetism leads to the proposal of a new system of units. In this system, the gravitational constant acquires the role of an interaction constant, both for gravitational and electromagnetic interaction, as a result of a redefinition of electric charge. In this way, the new system of units extends in a natural manner to mechanics. The comparison between the gravitational and electromagnetic interactions is of particular relevance.La cara oculta del gasto militar. El presupuesto militar de 2014
http://hdl.handle.net/2117/21737
La cara oculta del gasto militar. El presupuesto militar de 2014
Ortega, Pere; Doe, John; Bohigas Janoher, Xavier
Análisis del presupuesto militar del Estado español, a partir de los Presupuestos Generales de l Estado 2014
2014-02-25T08:35:20ZOrtega, PereDoe, JohnBohigas Janoher, XavierAnálisis del presupuesto militar del Estado español, a partir de los Presupuestos Generales de l Estado 2014Una ojeada al terrorismo nuclear
http://hdl.handle.net/2117/21632
Una ojeada al terrorismo nuclear
Bohigas Janoher, Xavier
2014-02-18T10:32:35ZBohigas Janoher, XavierRigid motions and generalized Newtonian gravitation
http://hdl.handle.net/2117/20838
Rigid motions and generalized Newtonian gravitation
Jaen Herbera, Javier; Molina Compte, Alfred
In an effort to contribute to a better understanding of General Relativity,
here we lay the foundations of generalized Newtonian gravity, which unifies inertial
forces and gravitational fields. We also formulate a kind of equivalence principle for
this generalized Newtonian theory. Finally, we prove that the theory we propose here
can be obtained as the non-relativistic limit of General Relativity.
2013-11-28T15:01:09ZJaen Herbera, JavierMolina Compte, AlfredIn an effort to contribute to a better understanding of General Relativity,
here we lay the foundations of generalized Newtonian gravity, which unifies inertial
forces and gravitational fields. We also formulate a kind of equivalence principle for
this generalized Newtonian theory. Finally, we prove that the theory we propose here
can be obtained as the non-relativistic limit of General Relativity.Comparative study of three audio processors as environments for laboratory activities on wave physics and acoustics
http://hdl.handle.net/2117/17172
Comparative study of three audio processors as environments for laboratory activities on wave physics and acoustics
Pejuan Alcobé, Arcadi; Bohigas Janoher, Xavier; Jaen Herbera, Javier; Periago Oliver, M. Cristina
Audio processors allow to implement laboratory activities specially on acoustics. We have
evaluated three audio processors (Audacity, WaveLab, and Adobe Audition). Although an overall grade was
also calculated as a guideline (not a statement of ‘‘the best’’), the decision about the most suitable one depends on each particular laboratory activity.
2012-12-20T12:19:40ZPejuan Alcobé, ArcadiBohigas Janoher, XavierJaen Herbera, JavierPeriago Oliver, M. CristinaAudio processors allow to implement laboratory activities specially on acoustics. We have
evaluated three audio processors (Audacity, WaveLab, and Adobe Audition). Although an overall grade was
also calculated as a guideline (not a statement of ‘‘the best’’), the decision about the most suitable one depends on each particular laboratory activity.Misconceptions about sound among engineering students
http://hdl.handle.net/2117/17097
Misconceptions about sound among engineering students
Pejuan Alcobé, Arcadi; Bohigas Janoher, Xavier; Jaen Herbera, Javier; Periago Oliver, M. Cristina
Our first objective was to detect misconceptions about the microscopic nature of sound among senior university students enrolled in different engineering programmes
(from chemistry to telecommunications). We
sought to determine how these misconceptions are expressed (qualitative aspect) and, only very secondarily, to gain a general idea of the extent to which they are held
(quantitative aspect). Our second objective was to explore other misconceptions about wave aspects of sound. We have also considered the degree of consistency in the
model of sound used by each student. Forty students answered a questionnaire including open-ended questions.
Based on their free, spontaneous answers, the main results were as follows: a large majority of students answered most of the questions regarding the microscopic model of
sound according to the scientifically accepted model; however, only a small number answered consistently. The main model misconception found was the notion that sound
is propagated through the travelling of air particles, even in solids. Misconceptions and mental-model inconsistencies tended to depend on the engineering programme in which
the student was enrolled. However, students in general were inconsistent also in applying their model of sound to individual sound properties. The main conclusion is that
our students have not truly internalised the scientifically accepted model that they have allegedly learnt. This implies a need to design learning activities that take these
findings into account in order to be truly efficient.
2012-12-11T12:06:27ZPejuan Alcobé, ArcadiBohigas Janoher, XavierJaen Herbera, JavierPeriago Oliver, M. CristinaOur first objective was to detect misconceptions about the microscopic nature of sound among senior university students enrolled in different engineering programmes
(from chemistry to telecommunications). We
sought to determine how these misconceptions are expressed (qualitative aspect) and, only very secondarily, to gain a general idea of the extent to which they are held
(quantitative aspect). Our second objective was to explore other misconceptions about wave aspects of sound. We have also considered the degree of consistency in the
model of sound used by each student. Forty students answered a questionnaire including open-ended questions.
Based on their free, spontaneous answers, the main results were as follows: a large majority of students answered most of the questions regarding the microscopic model of
sound according to the scientifically accepted model; however, only a small number answered consistently. The main model misconception found was the notion that sound
is propagated through the travelling of air particles, even in solids. Misconceptions and mental-model inconsistencies tended to depend on the engineering programme in which
the student was enrolled. However, students in general were inconsistent also in applying their model of sound to individual sound properties. The main conclusion is that
our students have not truly internalised the scientifically accepted model that they have allegedly learnt. This implies a need to design learning activities that take these
findings into account in order to be truly efficient.Refredament magnètic: ordre i desordre d'imants atòmics
http://hdl.handle.net/2117/13608
Refredament magnètic: ordre i desordre d'imants atòmics
Bohigas Janoher, Xavier
S’ha comprovat que la refrigeració magnètica que utilitza un sistema magnètic és energèticament
eficient i competitiva amb la tecnologia refrigerant basada en la compressió de
gasos en el rang de temperatures proper a la temperatura ambient. En aquest article se’n
mostren el fonaments.
2011-10-21T09:21:34ZBohigas Janoher, XavierS’ha comprovat que la refrigeració magnètica que utilitza un sistema magnètic és energèticament
eficient i competitiva amb la tecnologia refrigerant basada en la compressió de
gasos en el rang de temperatures proper a la temperatura ambient. En aquest article se’n
mostren el fonaments.