1,720,964 research outputs found
Metodi matematici nelle scienze fisiche. Praxis: software per la simulazione del comportamento delle molecole magnetiche
No full textNella moderna e attuale ricerca di prodotti sempre più piccoli, più veloci, più efficienti e
selettivi, la realizzazione di materiali con arrangiamenti spaziali microscopici ben definiti,
è di vitale importanza per la creazione di nuovi dispositivi elettronici, ottici o magnetici.
Un modo potenzialmente attraente di assemblaggio e mantenimento di strutture
microscopicamente controllate è quello di utilizzare materiali a base molecolare. La
ricerca nel campo del magnetismo molecolare è principalmente focalizzata a sistemi
molecolari contenenti un numero finito di ioni magnetici accoppiati. Questo tipo di
nano-molecole magnetiche, chiamate magneti a singola molecola (in inglese single
molecole magnets SMMs) si trovano nella linea di confine tra a fisica classica e
quantistica. Infatti, da un punto di vista esse mostrano fenomeni classici come il lento
rilassamento della magnetizzazione e un’isteresi magnetica molto estesa. Dall’altro tali
strutture sono di dimensioni tali da mostrare fenomeni quantistici. I materiali magnetici
molecolari, in particolare le SMMs, mostrano fenomeni di bistabilità magnetica e il più
importante fenomeno di tunnelling magnetico. Che è un puro fenomeno quantistico.
Sono queste caratteristiche fisiche quelle che permettono le numerose applicazioni di tali
strutture ma soprattutto il loro utilizzato come strumenti di immagazzinamento dati di
dimensioni nanometriche o qbits per la realizzazione di computer quantistici.
In base al tipo di applicazione tecnologica richiesta, è possibile, ad oggi, realizzare una
struttura molecolare ad hoc, in grado di sopperire a tutte richieste funzionali. Per
raggiungere un tale obiettivo è necessario conoscere e capire appieno il comportamento
di tali molecole e per questo, sono necessarie sia informazioni ottenute da metodi
sperimentali, sia informazioni ottenute da modellizzazione. L’argomento principale della
mia ricerca si basa sull’implementazione di un semplice strumento di simulazione – al
quale ho assegnato il nome PRAXIS – che permette di simulare e comprendere e le
principali proprietà termodinamiche e magnetiche delle SMMs.
PRAXIS è stato sviluppato facendo uso di un accurato schema basato sulle metodologie
del software engineering e con due ben precisi scopi: il primo, è quello di verificare i dati
ottenuti sperimentalmente mentre, il secondo, è quello di prevedere il comportamento di
tali strutture magnetiche in differenti situazioni in modo da rendere più adeguata la loro
sintesi per specifiche applicazioni tecnologiche. Come ulteriore sviluppo delle sue
funzionalità, c’è la possibilità di auto-assemblare teoricamente un gran numero di
molecole e di simulare il loro comportamento in una vasta gamma di differenti situazioni
Possible Evidence of Piezonuclear Alpha Emission
No full textCompression cycles at different loading speeds, each followed by a rapid stress release, were applied to cylindrical AISI 304 steel bars with 500 g mass, 2 cm diameter and 20 cm height. Three ZnS scintillators and a Geiger counter were placed around the samples. The emission of ionizing particles was both recorded by the Geiger and by the alpha particles counters during the compression and decompression phases. The recorded counts-rates as a function of the load are here shown and commented
DEFORMED SPACE-TIME OF THE PIEZONUCLEAR EMISSIONS
No full textIn this paper, an experimental verification of the relationship between the deformed Minkowsky space-time and the piezonuclear emission has been obtained by testing several cylindrical steel bars cyclically loaded in a mechanical fatigue machine. During the compression cycles, α-particles have been both detected by a ZnS(Ag) scintillator and a Geiger counter. Taking into account the theory of the deformed special relativity, we report that the emission only occurs after a specific value of energy is overcome. This value is strictly related to the weak and strong nuclear interactions, which in turn define the regions of Minkowsky and non-Minkowsky space-time
Statistics of piezonuclear emissions: early results
No full textMeasurements of ionizing and nonionizing particles are performed during the rupture tests of steel rods having different diameter. A ZnS(Ag) alpha detector, a Geiger counter and a 3He proportional counter for neutrons are used. From the distributions of the recorded intensity maxima, different particles emissions are suggested to occur in broken and nonbroken samples. A hint for the emission of neutrons at rupture is also obtained. Such neutron emissions are predicted in the framework of the piezonuclear theory
U-SANS Analysis of as-sintered and IECT-treated NiTi SMA produced by Metal Injection Moulding.
No full textChemical changes induced by ultrasound in iron
No full textThe focus of this work is a careful chemical investigation of structural damage produced by the exposure of an iron bar to pressure waves generated using an ultrasound machine (called the R-1-S reactor).
In addition to the emission of neutron bursts, the ultrasound treatment caused the appearance of zones of macroscopic damage (∼1 mm in size) on the exterior of the bar. Reflected-light optical and environmental scanning electron microscopy (ESEM) has shown that these external damage zones are characterized by microcraters and are covered by a thin layer of cracked amorphous material. Under back scattered electron (BSE) observation, this material shows a lower brightness than the intact ferrite surface. In addition, a zone with a high density of deformed cavities (∼1300 per mm2) with irregular walls and a maximum size of 10 μm was found inside the bar. These deformed microcavities are partially filled with a material composed of a chaotic assemblage of submicron-sized (most likely amorphous) particles.
A careful compositional investigation of the chaotic material inside the microcavities using the semi-quantitative data obtained with the ESEM X-ray Energy Dispersive System (EDS) has shown that it is primarily composed of carbon, manganese and chromium. These elements are also found in lower amounts within the intact ferrite matrix. In contrast, the damaged surface surrounding the craters is characterized by elements not found in the ferrite at all (i.e., O, Cl, K, Cu); elements the presence of which cannot be attributed to the occurrence of non-metallic inclusions or to contamination during fabrication.
These results are also difficult to explain using the generally accepted laws of physics; however, they do appear to agree with a recent theory predicting the deformation of the local spacetime and the violation of the Local Lorentz Invariance. Such a violation should occur following the collapse of micron-sized discontinuities internal to the materials (micropores) exposed to ultrasonic pressure waves resulting in an energy density to time ratio large enough to overcome the threshold predicted by the deformed spacetime theory, triggering, in this way, a new kind of nuclear reaction. Following this theory, the C-, Mn- and Cr-rich chaotic material inside the microcavities is the product of the spherically symmetrical collapse of micropores internal to the ferrite while the presence of new elements within the cratered damage zones on the ferrite surface can be attributed to the catastrophic collapse of the subsurface pore walls resulting from microexplosions
Piezonuclear reactions and DST-reactions
No full textOver the past two decades a great deal of evidence has been gathered about the existence and the possible energetic exploitation of a new type of reactions predicted by the Deformed Special Relativity, which is an extension of Special Relativity. According to that theory, the energy of every physical phenomenon determines, by deforming it, the space-time in which the same phenomenon evolves. The practical consequences of this theoretical prediction are that mechanical machines, such as ultrasound generators or other compressing equipments, can also induce nuclear reactions on systems consisting of stable atoms such as iron, if they are able to trigger some particular physical effects able to concentrate an adequate amount of energy in an adequate space-time region. The experimental research aims at converting those predictions into experimental results and, in perspective, into industrial prototypes for a following commercial use. The evidence of nuclear transmutation of elements is among the most interesting possible results. Neutron and alpha particles emission are also reported
Defect analysis on optical waveguide arrays by synchrotron radiation microtomography
Full text linkIn recent years, great attention has been devoted to the study
and realization of polymeric optical waveguides embedded in printed
circuit boards due to the increasing need of transferring large amounts
of data at high speed within computer and telecommunication devices.
Nonuniform microstructural defects that can be induced during the manufacturing
process can dramatically influence the waveguide performance.
The synchrotron radiation computed microtomography technique was
used to obtain 3-D microstructural information, specifically to observe
small defects, such as porosities, in a nondestructive way. Porosity level
and pore size range were evaluated
U-SANS analysis of as-sintered and PEC-treated NiTi SMA produced by metal injection moulding
Full text linkUsing ultra-small angle neutron scattering method, we have analyzed sizes of pores of 100 nm–
25 m in diameter in specimens from NiTi shape memory alloys produced by metal injection
moulding before and after pulse electric current treatment. Such treatment invokes coalescence of
pores with diameter smaller than 4 m and size reduction of pores with diameter exceeding 4 m
Characterization of Porosity in a Laser Sintered MMCp Using X-Ray Synchrotron Phase Contrast Microtomography
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