Statističke analogije između potresa, mikropotresa u metalima i lavina u 1D Burridge-Knopoff modelu

Universalities and intriguing analogies in the statistics of avalanches are revealed for three physical systems defined on largely different length and energy scales. Earthquakes induced by tectonic scale dynamics, micro-scale level quakes observed from slipping crystallographic planes in metals and a one-dimensional, room-scale spring-block type Burridge-Knopoff model is studied from similar statistical viewpoints. The validity of the Gutenberg-Richter law for the probability density of the energies dissipated in the avalanches is proven for all three systems. By analysing data for three different seismic zones and performing acoustic detection for different Zn samples under deformation, universality for the involved scaling exponent is revealed. With proper parameter choices the 1D Burridge-Knopoff model is able to reproduce the same scaling law. The recurrence times of earthquakes and micro-quakes with magnitudes above a given threshold present again similar distributions and striking quantitative similarities. However, the 1D Burridge-Knopoff model cannot account for the correlations observed in such statistics.Univerzalnosti i intrigantne analogije u statistici lavina otkrivene su za tri fizička sustava definirana na uvelike različitim duljinama i energijskim skalama. Potresi uzrokovani dinamikom na tektonskoj skali, mikro-potresi koji nastaju na klizećim kristalografskim ravnina u metalima i jednodimenzionalni Burridge-Knopoffov model opruga i blokova na skali sobe proučeni su sa sličnih statističkih stajališta. Valjanost Gutenberg-Richterove relacije za gustoću vjerojatnosti energija disipirane u lavinama dokazana je za sva tri sustava. Analizom podataka za tri različita seizmički aktivna područja i detekcijom akustičkih valova za različite uzorke Zn pod deformacijom, otkrivena je univerzalnost za uključeni eksponent skaliranja. S pravilnim izborom parametara 1D Burridge-Knopoffov model može reproducirati isti zakon skaliranja. Vremena ponavljanja potresa i mikropotresa s magnitudama iznad zadanog praga opet predstavljaju slične distribucije i zapanjujuće kvantitativne sličnosti. Međutim, 1D Burridge-Knopoffov model ne može objasniti korelacije opažene u takvim statistikama

Irradiation-induced strain localization and strain burst suppression investigated by microcompression and concurrent acoustic emission experiments

Plastic deformation of microsamples is characterised by large intermittent strain bursts caused by dislocation avalanches. Here we investigate how ion irradiation affects this phenomenon during single slip single crystal plasticity. To this end, in situ compression of Zn micropillars oriented for basal slip was carried out in a scanning electron microscope (SEM). The unique experimental setup also allowed the concurrent recording of the acoustic emission (AE) signals emitted from the sample during deformation. It was shown that irradiation introduced a homogeneous distribution of basal dislocation loops that lead to hardening of the sample as well as strain softening due to dislocation channeling at larger strains. Under the loading conditions imposed in the present work, the intensity of strain bursts was found to decrease during channeling. The concurrently recorded AE events were correlated with the strain bursts and their analysis provided additional information of the details of collective dislocation dynamics. It was found that the rate of AE events decreased significantly upon irradiation, however, other statistical properties did not change. This was attributed to the appearance of new type of dislocation avalanches which is dominated by short-range dislocation-obstacle interactions that cannot be detected by AE sensors

Alkalmazásfejlesztés REST alapokon

Dolgozatom témájaként egy olyan web-alkalmazás elkészítését tűztem ki, amely megfelelően alkalmazkodik a különböző képernyő felbontásokhoz, kellőképpen interaktív, eseményvezérelt, a legmodernebb technológiákat alkalmazza, és eleget tesz a REST architektúra megszorításainak. A TicketRadar fejlesztési folyamatainak bemutatása során nyilvánvalóvá válik, hogy a számos modern technológia segítségével mily módon lehet könnyen és gyorsan webalkalmazásokat fejleszteni. A felhasznált rendszerekről megállapítható, hogy minden egysége egy-egy jól megtervezett munka eredménye. Munkám során rengeteg új szemléletmódot ismertem meg – REST architektúra, MVC minta – és már magabiztosan használom a tárgyalt rendszereket. Symfony 2 és Angular JS keretrendszerek használatakor rájöttem, hogy mennyire egyszerűen megoldhatóak, olyan feladatok melyek korábbi webfejlesztési tapasztalataim során nehézséget okoztak. A REST architektúrának köszönhetően sikerült teljesen szétválasztanom a szerver- és kliens oldali feladatokat, valamint az MVC mintának köszönhetően a felhasználói felületek és a működés szétválasztását is sikerült megoldanom, így egy igazán flexibilis és jól bővíthető alkalmazást hoztam létre. Szakdolgozatomban részletesen, kódokkal szemléltetve is bemutattam, hogyan lehet Symfony 2 segítségével szerveroldali, AngularJS segítségével pedig kliensoldali alkalmazásokat létrehozni, valamint bemutattam e két rendszer integrálását és a további hasznos modul telepítését, használatát, mint pl. a Jade, amely leegyszerűsítette a HTML kódok írását, a Coffee Script, amely megkönnyítette a JavaScript fejlesztést, vagy a Bootstrap, amely segítette egy egyszerű, letisztult és responsive interfész kialakítását. Természetesen az elkészített alkalmazásomhoz még rengeteg fejlesztési ötletem van, mint pl. a regisztráció beiktatása, egy felhasználó kezelés kialakítása, valamint a RESTful kialakítás, de ezidáig is sikerült olyan szintre fejlesztenem, amely már éles környezetben is megállja a helyét. További hiányosság még az adatbázis mérete, ami idővel bővülni fog nem csak az általam feltöltött, hanem a látogatók által beküldött adatokkal is. Úgy gondolom, hogy sikerült egy olyan alkalmazást készítenem, amely nagyban segítheti a TicketRadar felhasználók országszintű tájékozódását a mindennapi rohanó élet során.BSc/BAMérnök Informatiku

Statistical properties of fractal type dislocation cell structures

International audienceThe dislocation microstructure developing during plastic deformation strongly influences the stress-strain properties of crystalline materials. Resent theoretical investigations based on the 2D continuum theory of straight parallel edge dislocations were able to predict a periodic dislocation microstructure. The results obtained, however, can only be considered as a very first step toward the understanding of the origin of dislocation patterning. One of the most challenging problems is the modeling of the formation of the fractal like dislocation microstructure. So, it is crucial to determine the statistical properties of such a structure developing at ideal multiple slip orientation. In the paper, by x-ray line profile analysis and the method of high resolution electron backscatter diffraction (HR-EBSD) a complex experimental characterization of dislocation microstructure developing in uniaxially compressed Cu single crystals is presented. With these methods, the maps of the internal stress, the Nye tensor, and the geometrically necessary dislocation (GND) density were determined at different load levels. It is found from the fractal analysis of the GND maps that the fractal dimension of the cell structure is decreasing with increasing average spatial dislocation density fluctuation. Moreover, it is shown that the evolution of different types of dislocations can be successfully monitored with the HR-EBSD-based technique

Nanomechanical, Structural and Electrochemical Investigation of Amorphous and Crystalline MoO3 Thin-Film Cathodes in Rechargeable Li-Ion Batteries

In this work, a comprehensive investigation of amorphous and crystalline modification of identical electrode active material as a thin-film electrode for a future all-solid-state Li-ion battery application is presented and discussed. Using the proposed micro-battery system, we aim to unravel the effect of the crystallinity of the positive electrode material on the intrinsic durability of all-solid-state thin-film Li-ion batteries during prolonged electrochemical cycling. We demonstrate the preparation, structural-, nanomechanical and electrochemical characteristics of molybdenum (VI) oxide (MoO3) thin-film cathodes based on their different crystallinity. The nanomechanical properties of the electrode layers were determined using nanoindentation along with acoustic emission studies. Based on the electrochemical test results, as-prepared thin films that did not go under any heat treatment showed the best performance and stability throughout cycling around 50 μAh initial capacity when cycled at C/2. This suits well their nanomechanical properties, which showed the highest hardness but also the highest flexibility in comparison with the heat-treated layers with lower hardness, high brittleness, and numerous cracks upon mechanical loads. According to our results, we state that amorphous-type electrode materials are more durable against electro-chemo-mechanical-aging related battery performance loss in all-solid-state Li-ion batteries compared to their crystalline counterparts