Enrico Campari - Academia.edu (original) (raw)
Papers by Enrico Campari
Il circuito di figura 2 è una stella a 5 punte inscritta in un cerchio di raggio r= 0,5 m e perco... more Il circuito di figura 2 è una stella a 5 punte inscritta in un cerchio di raggio r= 0,5 m e percorso in senso antiorario da una corrente di 0,5 A. Si determini il campo magnetico B prodotto dalla corrente nel centro della figura (Suggerimento: si può procedere considerando ogni segmento oppure applicando la formula per il campo magnetico prodotto da un segmento rettilineo sia ai segmenti che uniscono i vertici della stella sia a quelli che formano il pentagono interno).
Il progetto, realizzato per il gruppo CNI-MUSA di Alfonsine (RA), ha comportato la progettazione ... more Il progetto, realizzato per il gruppo CNI-MUSA di Alfonsine (RA), ha comportato la progettazione e realizzazione di un prototipo di camera iperspettrale operante nell'intervallo di lunghezze d'onda 450-900 nm. La ipercamera potr\ue0 essere utilizzata per attivit\ue0 industriali quali il riconoscimento del grado di maturazione della frutta o la separazione di plastiche conferite come rifiuti
Applicazione di un sistema ottico basato sull'uso di lenticole per permettere il riconoscimen... more Applicazione di un sistema ottico basato sull'uso di lenticole per permettere il riconoscimento dell'avvenuta apertura di un contenitore con tappo o per creare effetti ottici sul medesimo. La parte meccanica dei tappi \ue8 interamente da Sacmi, quella ottica \ue8 stata sviluppata dei ricercatori unibo
Physica status solidi, Mar 16, 1991
The anelastic stress relaxation is measured at room temperature on amorphous alloys of different ... more The anelastic stress relaxation is measured at room temperature on amorphous alloys of different chemical composition obtained by melt spinning. It is found that the load relaxation vs. time behavior depends considerably on the strain rate at which the samples are anelastically deformed at a fixed strain before the relaxation tests. It is suggested that it is possible, in principle, by performing stress relaxation tests after loading the specimens in a wide range of strain rates, to obtain indications of the activation energy spectrum for relaxation and of the dependence on the strain rate of the characteristic relaxation times of the shear processes (two level systems), responsible for anelasticity. Unelastische Spannungsrelaxation wird bei Zimmertemperatur an Melt-Spin-Proben amorpher Legierungen verschiedener chemischer Zusammensetzung gemessen. Es wird gefunden, das das Relaxations-Zeit-Verhalten der Belastung wesentlich von der Deformationsrate abhangt, bei der die Proben vor dem Relaxationsversuch bei einer festen Spannung anelastisch deformiert werden. Es wird angenommen, das es im Prinzip moglich ist, durch Spannungsrelaxationstests nach Belastung der Proben in einem weiten Bereich der Deformationsraten Hinweise auf das Spektrum der Aktivierungsenergie fur die Relaxation zu erhalten, sowie uber die Abhangigkeit der charakteristischen Relaxationszeiten der Scherprozesse (Zweiniveausysteme) von der Deformationsrate, die fur die Anelastizitat verantwortlich sind.
Journal of Alloys and Compounds, Aug 1, 2021
Abstract he anelastic behavior of 5N-Al thin foils with three different thicknesses (10, 50 and 1... more Abstract he anelastic behavior of 5N-Al thin foils with three different thicknesses (10, 50 and 125 µm) was investigated in the temperature range from 300 to 720 K through Mechanical Spectroscopy (MS) measurements performed by using a completely automated vibrating reed analyser. Two relaxation peaks P1 and P2 and a relevant high temperature background were observed in the thinnest samples whereas only the grain boundary peak (PGB) was observed in the thickest ones. Detailed TEM observations and X-ray diffraction (XRD) measurements indicate that defective structures depend on foil thickness and suggest that the origin of P1 and P2 peaks is connected to the vibration dynamics of isolated dislocations not organized in networks. P1 has been attributed to the combination of dislocation motion through the stress field of other dislocations and thermally activated cross slip, while P2 is due to the movement of jogs assisted by pipe diffusion. In addition to anelastic effects due to dislocation vibration, permanent grain boundary sliding seems to contribute to the high temperature background observed in the thinnest foils.
Physical review, 1995
Neutron-diffraction data collected under vacuum at 680 and 695 K have been compared with elastic ... more Neutron-diffraction data collected under vacuum at 680 and 695 K have been compared with elastic energy dissipation and dynamic Young's modulus measurements in YBa2Cu3O6+x. The orthorhombic to tetragonal phase transition has been observed in isothermal conditions. The data suggest that a phonon softening occurs at the oxygen disordering, which, in these experimental conditions, precedes the phase transition. The elastic energy dissipation presents a peak above room temperature. Its origin and behavior are discussed in terms of an oxygen atom repopulation model, with activation energy depending on the orthorhombic strain and oxygen ordering in the basal plane.
Journal of The Less Common Metals, Oct 1, 1990
Physica C-superconductivity and Its Applications, Jun 1, 1992
Elastic energy dissipation measurements were carried out using the vibrating reed and torsional p... more Elastic energy dissipation measurements were carried out using the vibrating reed and torsional pendulum techniques on polycrystalline YBa2Cu3Ov_x specimens in different stoichiometric conditions. In the 300-900 K range two relaxational damping peaks, Po~ and Poz, can be observed. The relaxation strength depends considerably on the oxygen deficiency x. As the value of x increases, the intensity of peak PoJ decreases while that of Po2 increases. The two relaxation processes have activation energies H~ = (1.54 + 0.09) eV and//2 = (1.3 _+ 0.1) eV, respectively. Models for the relaxation involving the dynamics of oxygen atoms in the Cu-O basal plane and along the twinned interfaces are examined.
Physica C-superconductivity and Its Applications, Sep 1, 1991
Dynamic Young's modulus measurements, have been performed by the vibrating reed technique (1... more Dynamic Young's modulus measurements, have been performed by the vibrating reed technique (102-104 Hz) on polycrystalline YBa2Cu3O7-x samples in the temperature range 300-900 K. A strong modulus softening, indicative of a phase transition, is measured at about x = 0.45. DTG measurements versus temperatures show in correspondence a maximum in the oxygen desorption rate. Long time modulus isotherms display an exponential trend linked to a thermally activated structural process with activation energy H = 0.9 +/- 0.1 eV. On the basis of the experimental results a model for the structural transformation linked to the twinned interfaces mobility and to oxygen diffusion is presented and discussed.
Journal de physique, Nov 1, 1993
Astract-Measurements of the elastic energy dissipation coefficient and of the dynamic Young's mod... more Astract-Measurements of the elastic energy dissipation coefficient and of the dynamic Young's modulus were performed on polycrystalline YBa2C~307-~ by the vibrating reed technique and torsional pendulum, in the frequency range 1-5000 Hz. The stoichiomehy of the samples was varied in the range x = 0.02-0.7. From the isothermal modulus measurements a strong softening stage characterizing the onset of the ortho-tetragonal transformation was observed. The long time isotherms give an activation energy of 0.9 = 0.1 eV. Two relaxational damping peaks have been observed and attributed to the short range oxygen dynamics in the well oxygenated and oxygen deficient superconducting phases. On the basis of these results models for the structural transformation linked to oxygen out diffusion and for the oxygen dynamics in different stoichiometric conditions are discussed.
Journal of Alloys and Compounds, Sep 1, 1994
A pulse echo technique was employed to measure the ultrasonic attenuation and velocity in the 120... more A pulse echo technique was employed to measure the ultrasonic attenuation and velocity in the 120-340 K temperature range on Nd2Cul_~ZnxO4 with x = 0, 0.02 and 0.05. A marked hysteresis in the velocity vs. temperature trend was observed. The Zn doping results in a reduction in the hysteresis loop area. Strong attenuation maxima were observed at 210 and 260 K. The results are discussed in terms of magnetoelastic interaction across the N6el temperature.
La presente invenzione riguarda la produzione di indumenti per stampa additiva ed il processo di ... more La presente invenzione riguarda la produzione di indumenti per stampa additiva ed il processo di loro produzione
Verificare la realizzabilit\\ue0 e la successiva ingegnerizzazione di snodi per linee di trasferi... more Verificare la realizzabilit\\ue0 e la successiva ingegnerizzazione di snodi per linee di trasferimento ad una sola pista di sfere che migliorino l'esistente in termini di ingombro e di prestazioni. Tali giunti troveranno impiego primario nelle linee di trasferimento di carburanti, ma potranno essere prodotti in una versione compatibile con le esigenze del trasferimento di fluidi alimentari. Verranno ricercate soluzioni ad una serie di problemi: (1) individuare i materiali pi\\uf9 adatti per permettere allo snodo di poter essere esercito fino a -55 \\ub0C; (2) realizzare trattamenti o ricoprimenti superficiali con soluzioni anti-usura, efficaci sull\\u2019intero intervallo delle temperature di esercizio; (3) inserire un rivelatore di perdite per verificare la funzionalit\\ue0 della tenuta primaria; (4) studiare la possibilit\\ue0 di utilizzare lo snodo con GPL; (5) realizzare una versione dello snodo adatta anche per il campo alimentare, individuando i rivestimenti ed i trattamenti da eseguire nella parte dello snodo a contatto con l'alimento, i grassi di lubrificazione utilizzabile in campo alimentar
Journal of Alloys and Compounds, Sep 1, 1994
2111212 (1994) 314-317 JALCOM I39 in transition Measurements of the elastic energy dissipation co... more 2111212 (1994) 314-317 JALCOM I39 in transition Measurements of the elastic energy dissipation coefficient and of the dynamic Young modulus were performed on polycrystalline YBCO samples by the vibrating-reed technique and torsional pendulum, in the frequency range 5-5000 Hz. Two relaxational damping peaks with activation energy H,,, = (1.5 f 0.1) eV and H,,z = (1.3 f 0.1) eV have been observed above room temperature and their origin is discussed in terms of the short-range oxygen dynamics. The dynamic modulus shows a relaxation in correspondence to the two peaks and a softening attributed to the orthorhombic-to-tetragonal phase transition.
Il circuito di figura 2 è una stella a 5 punte inscritta in un cerchio di raggio r= 0,5 m e perco... more Il circuito di figura 2 è una stella a 5 punte inscritta in un cerchio di raggio r= 0,5 m e percorso in senso antiorario da una corrente di 0,5 A. Si determini il campo magnetico B prodotto dalla corrente nel centro della figura (Suggerimento: si può procedere considerando ogni segmento oppure applicando la formula per il campo magnetico prodotto da un segmento rettilineo sia ai segmenti che uniscono i vertici della stella sia a quelli che formano il pentagono interno).
Il progetto, realizzato per il gruppo CNI-MUSA di Alfonsine (RA), ha comportato la progettazione ... more Il progetto, realizzato per il gruppo CNI-MUSA di Alfonsine (RA), ha comportato la progettazione e realizzazione di un prototipo di camera iperspettrale operante nell'intervallo di lunghezze d'onda 450-900 nm. La ipercamera potr\ue0 essere utilizzata per attivit\ue0 industriali quali il riconoscimento del grado di maturazione della frutta o la separazione di plastiche conferite come rifiuti
Applicazione di un sistema ottico basato sull'uso di lenticole per permettere il riconoscimen... more Applicazione di un sistema ottico basato sull'uso di lenticole per permettere il riconoscimento dell'avvenuta apertura di un contenitore con tappo o per creare effetti ottici sul medesimo. La parte meccanica dei tappi \ue8 interamente da Sacmi, quella ottica \ue8 stata sviluppata dei ricercatori unibo
Physica status solidi, Mar 16, 1991
The anelastic stress relaxation is measured at room temperature on amorphous alloys of different ... more The anelastic stress relaxation is measured at room temperature on amorphous alloys of different chemical composition obtained by melt spinning. It is found that the load relaxation vs. time behavior depends considerably on the strain rate at which the samples are anelastically deformed at a fixed strain before the relaxation tests. It is suggested that it is possible, in principle, by performing stress relaxation tests after loading the specimens in a wide range of strain rates, to obtain indications of the activation energy spectrum for relaxation and of the dependence on the strain rate of the characteristic relaxation times of the shear processes (two level systems), responsible for anelasticity. Unelastische Spannungsrelaxation wird bei Zimmertemperatur an Melt-Spin-Proben amorpher Legierungen verschiedener chemischer Zusammensetzung gemessen. Es wird gefunden, das das Relaxations-Zeit-Verhalten der Belastung wesentlich von der Deformationsrate abhangt, bei der die Proben vor dem Relaxationsversuch bei einer festen Spannung anelastisch deformiert werden. Es wird angenommen, das es im Prinzip moglich ist, durch Spannungsrelaxationstests nach Belastung der Proben in einem weiten Bereich der Deformationsraten Hinweise auf das Spektrum der Aktivierungsenergie fur die Relaxation zu erhalten, sowie uber die Abhangigkeit der charakteristischen Relaxationszeiten der Scherprozesse (Zweiniveausysteme) von der Deformationsrate, die fur die Anelastizitat verantwortlich sind.
Journal of Alloys and Compounds, Aug 1, 2021
Abstract he anelastic behavior of 5N-Al thin foils with three different thicknesses (10, 50 and 1... more Abstract he anelastic behavior of 5N-Al thin foils with three different thicknesses (10, 50 and 125 µm) was investigated in the temperature range from 300 to 720 K through Mechanical Spectroscopy (MS) measurements performed by using a completely automated vibrating reed analyser. Two relaxation peaks P1 and P2 and a relevant high temperature background were observed in the thinnest samples whereas only the grain boundary peak (PGB) was observed in the thickest ones. Detailed TEM observations and X-ray diffraction (XRD) measurements indicate that defective structures depend on foil thickness and suggest that the origin of P1 and P2 peaks is connected to the vibration dynamics of isolated dislocations not organized in networks. P1 has been attributed to the combination of dislocation motion through the stress field of other dislocations and thermally activated cross slip, while P2 is due to the movement of jogs assisted by pipe diffusion. In addition to anelastic effects due to dislocation vibration, permanent grain boundary sliding seems to contribute to the high temperature background observed in the thinnest foils.
Physical review, 1995
Neutron-diffraction data collected under vacuum at 680 and 695 K have been compared with elastic ... more Neutron-diffraction data collected under vacuum at 680 and 695 K have been compared with elastic energy dissipation and dynamic Young's modulus measurements in YBa2Cu3O6+x. The orthorhombic to tetragonal phase transition has been observed in isothermal conditions. The data suggest that a phonon softening occurs at the oxygen disordering, which, in these experimental conditions, precedes the phase transition. The elastic energy dissipation presents a peak above room temperature. Its origin and behavior are discussed in terms of an oxygen atom repopulation model, with activation energy depending on the orthorhombic strain and oxygen ordering in the basal plane.
Journal of The Less Common Metals, Oct 1, 1990
Physica C-superconductivity and Its Applications, Jun 1, 1992
Elastic energy dissipation measurements were carried out using the vibrating reed and torsional p... more Elastic energy dissipation measurements were carried out using the vibrating reed and torsional pendulum techniques on polycrystalline YBa2Cu3Ov_x specimens in different stoichiometric conditions. In the 300-900 K range two relaxational damping peaks, Po~ and Poz, can be observed. The relaxation strength depends considerably on the oxygen deficiency x. As the value of x increases, the intensity of peak PoJ decreases while that of Po2 increases. The two relaxation processes have activation energies H~ = (1.54 + 0.09) eV and//2 = (1.3 _+ 0.1) eV, respectively. Models for the relaxation involving the dynamics of oxygen atoms in the Cu-O basal plane and along the twinned interfaces are examined.
Physica C-superconductivity and Its Applications, Sep 1, 1991
Dynamic Young's modulus measurements, have been performed by the vibrating reed technique (1... more Dynamic Young's modulus measurements, have been performed by the vibrating reed technique (102-104 Hz) on polycrystalline YBa2Cu3O7-x samples in the temperature range 300-900 K. A strong modulus softening, indicative of a phase transition, is measured at about x = 0.45. DTG measurements versus temperatures show in correspondence a maximum in the oxygen desorption rate. Long time modulus isotherms display an exponential trend linked to a thermally activated structural process with activation energy H = 0.9 +/- 0.1 eV. On the basis of the experimental results a model for the structural transformation linked to the twinned interfaces mobility and to oxygen diffusion is presented and discussed.
Journal de physique, Nov 1, 1993
Astract-Measurements of the elastic energy dissipation coefficient and of the dynamic Young's mod... more Astract-Measurements of the elastic energy dissipation coefficient and of the dynamic Young's modulus were performed on polycrystalline YBa2C~307-~ by the vibrating reed technique and torsional pendulum, in the frequency range 1-5000 Hz. The stoichiomehy of the samples was varied in the range x = 0.02-0.7. From the isothermal modulus measurements a strong softening stage characterizing the onset of the ortho-tetragonal transformation was observed. The long time isotherms give an activation energy of 0.9 = 0.1 eV. Two relaxational damping peaks have been observed and attributed to the short range oxygen dynamics in the well oxygenated and oxygen deficient superconducting phases. On the basis of these results models for the structural transformation linked to oxygen out diffusion and for the oxygen dynamics in different stoichiometric conditions are discussed.
Journal of Alloys and Compounds, Sep 1, 1994
A pulse echo technique was employed to measure the ultrasonic attenuation and velocity in the 120... more A pulse echo technique was employed to measure the ultrasonic attenuation and velocity in the 120-340 K temperature range on Nd2Cul_~ZnxO4 with x = 0, 0.02 and 0.05. A marked hysteresis in the velocity vs. temperature trend was observed. The Zn doping results in a reduction in the hysteresis loop area. Strong attenuation maxima were observed at 210 and 260 K. The results are discussed in terms of magnetoelastic interaction across the N6el temperature.
La presente invenzione riguarda la produzione di indumenti per stampa additiva ed il processo di ... more La presente invenzione riguarda la produzione di indumenti per stampa additiva ed il processo di loro produzione
Verificare la realizzabilit\\ue0 e la successiva ingegnerizzazione di snodi per linee di trasferi... more Verificare la realizzabilit\\ue0 e la successiva ingegnerizzazione di snodi per linee di trasferimento ad una sola pista di sfere che migliorino l'esistente in termini di ingombro e di prestazioni. Tali giunti troveranno impiego primario nelle linee di trasferimento di carburanti, ma potranno essere prodotti in una versione compatibile con le esigenze del trasferimento di fluidi alimentari. Verranno ricercate soluzioni ad una serie di problemi: (1) individuare i materiali pi\\uf9 adatti per permettere allo snodo di poter essere esercito fino a -55 \\ub0C; (2) realizzare trattamenti o ricoprimenti superficiali con soluzioni anti-usura, efficaci sull\\u2019intero intervallo delle temperature di esercizio; (3) inserire un rivelatore di perdite per verificare la funzionalit\\ue0 della tenuta primaria; (4) studiare la possibilit\\ue0 di utilizzare lo snodo con GPL; (5) realizzare una versione dello snodo adatta anche per il campo alimentare, individuando i rivestimenti ed i trattamenti da eseguire nella parte dello snodo a contatto con l'alimento, i grassi di lubrificazione utilizzabile in campo alimentar
Journal of Alloys and Compounds, Sep 1, 1994
2111212 (1994) 314-317 JALCOM I39 in transition Measurements of the elastic energy dissipation co... more 2111212 (1994) 314-317 JALCOM I39 in transition Measurements of the elastic energy dissipation coefficient and of the dynamic Young modulus were performed on polycrystalline YBCO samples by the vibrating-reed technique and torsional pendulum, in the frequency range 5-5000 Hz. Two relaxational damping peaks with activation energy H,,, = (1.5 f 0.1) eV and H,,z = (1.3 f 0.1) eV have been observed above room temperature and their origin is discussed in terms of the short-range oxygen dynamics. The dynamic modulus shows a relaxation in correspondence to the two peaks and a softening attributed to the orthorhombic-to-tetragonal phase transition.