62 research outputs found
The Author Book
No full textTéma mé diplomové práce zní autorská kniha. Popisuji v ní příběh svého rodnéha města Mostu, který byl v minulém století téměř kompletně zdemolován kvůli těžbě hnědého uhlí. Ačkoliv jsem tam prožil téměř celý svůj život, před touto prací jsem měl jen malou představu, jak staré město vypadalo, a to byl můj důvod, proč jsem si toto téma vybral.
Kniha je rozdělena na tři části. První hovoří o historii města, která sahá až do 12. století. Zaměřuje se především na druhou polovinu 20. století a pomocí autorských textů a dobových fotografií popisuje jeho vývoj. Ukazuje staré zchátralé město po 2. světové válce, jeho demolici, těžbu uhlí a nakonec stavbu nového modernistického města stejného jména jen o pár kilometrů vedle. Ve druhé části jsou vedle sebe porovnávány fotografie důležitých institucí minulosti a současnosti (náměstí, nádraží, budova soudu, atd.). Třetí část tvoří rozhovor s mou babičkou, která celý příběh zažila.
Nejdůležitějším grafickým prvkem je motiv prolínání fotografií. To symbolizuje vzájemnou provázanost na první pohled dvou úplně odlišných měst. Já je spojuji v jeden obraz a tím vzniká nekomprosmisní srovnání minulosti a současnosti.
Knihu doplňují další předměty. Plakáty a pohlednice využívají především motivu prolínání fotografií. Vytvořil jsem ještě jednu knihu, která obsahuje pouze doslovné úryvky kritických článků z doby demolice města.
Nechtěl jsem vytvořit obsáhlou encyklopedii historie Mostu. Kniha je určena především lidem, jako jsem já. Obyvatelům Mostu, kteří ví o historii svého města jen velmi málo a chtějí se dovědět víc. Kniha je vlastně záznamem procesu mého vlastního poznání.ObhájenoThe topic of my diploma thesis is Author book. In this work I describe story of my hometown Most which was almost completely destroyed during the last century because of brown coal mining. The main reason I chose this topic is that though I spent most of my life in this city I had very limited knowledge how the original old city looked like.
The book is divided into three parts. First part is focused on the history of town which goes to the 12th century. It describes mostly the second half of the 20th century and the city's evolution by primary sources as author's texts and photos. It shows old, dilapidated city after The World War II, its demolition, coal mining and the construction of the new modernistic city carrying the same name just few kilometers away. The second part of the book consists of historical and current photos of important buildings, places and institutions (the main square, the train station, the court, etc.). Third part is an interview with my grandmother who lived through this whole story.
The most important graphic element is the photos intermingling. It symbolizes the mutual connection on the first sight two completely different cities. I connect them into one picture and create an intransigent comparison of history and present.
The book is replenished by other things like posters and postcards which repeat the motive of intermingling of history and presence. I also created another book which consists solely of quotations of period articles that criticized the demolition of the city. My intention was not to create a comprehensive encyclopedia of the city Most but to create a book for people like myself for citizens of Most who know a little about their hometown history but they are seeking to learn more. This thesis is actually a record of my own seeking
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Unveiling the Dark Side of the Universe: Harnessing the Power of Big Data to Reveal a Hidden and Heavily Obscured AGN Population
No full textWe present a study of over 3000 X-ray A tive Galactic Nuclei (AGN) in the Stripe 82X field, analyzing their intrinsic properties and deriving model-independent obscured and unobscured AGN evolution up to redshift 4. Our findings reveal a discrepancy when tracing the black hole accretion density by comparing our results with current and up-to-date evolutionary models. Specifically, we find evidence for a heavily obscured, Compton-thick AGN population that remains undetected even when combining X-ray and infrared data at all redshifts. These results challenge our understanding of AGN evolution and suggest that Compton-thick sources play a larger role in the accretion history of AGN than previously thought.Building on these insights, we extend this work in two parallel endeavors: First, we introduce Stripe 82-XL (S82-XL), an extension of the Stripe 82X survey. Leveraging data from both XMM and Chandra source catalogs, S82-XL expands the survey area to a vast 57 square degrees, doubling the depth of its predecessor. Simultaneously, we are constructing the AGN-DataBase (AGN-DB), an archive for all the discovered AGN. AGN-DB offers a comprehensive catalog of AGN properties and classifications, leveraging the wealth of data from all the available archives and surveys. With this double approach, we can capture fainter, more obscured, and higher redshift AGN, further improving our understanding of AGN evolution
Fondamenti e applicazioni della plasmonica
No full textQuesto lavoro ha l’obbiettivo di analizzare i principi che stanno alla base della plasmonica, partendo dallo studio dei plasmoni di superficie fino ad arrivare alle loro applicazioni.
La prima parte di questa tesi riguarda l’aspetto teorico. Essendo essenzialmente eccitazioni collettive degli elettroni nell'interfaccia fra un conduttore ed un isolante, descritti da onde elettromagnetiche evanescenti, questi plasmoni superficiali, o polaritoni plasmonici di superficie (SPP), vengono studiati partendo dalle equazioni di Maxwell.
Viene spiegato come questi SPP nascano dall’accoppiamento dei campi elettromagnetici con le oscillazioni degli elettroni del materiale conduttore e, utilizzando l’equazione dell’onda, si descrivono le loro proprietà in singola interfaccia e in sistemi multistrato.
Il quinto capitolo analizza le metodologie di eccitazione di SPP. Sono descritte varie tecniche per l’accoppiamento di fase, per accennare poi a eccitazioni di SPP in guide d’onda, tramite fibra ottica.
L’ultimo capitolo della prima parte è dedicato alla seconda tipologia di plasmoni: i plasmoni di superficie localizzati (LSP). Questi sono eccitazioni a seguito dell’accoppiamento fra elettroni di conduzione di nanoparticelle metalliche e il campo elettromagnetico ma che, a differenza dei SPP, non si propagano. Viene esplorata la fisica dei LSP trattando prima le interazioni delle nanoparticelle con le onde elettromagnetiche, poi descrivendo i processi di risonanza in una varietà di particelle differenti in numero, forma, dimensione e ambiente di appartenenza.
La seconda parte della tesi riguarda invece alcune applicazioni. Vengono proposti esempi di controllo della propagazione di SPP nel contesto delle guide d’onda, analizzando l’indirizzamento di SPP su superfici planari e spiegando come le guide d’onda di nanoparticelle metalliche possano essere utilizzate per trasferire energia.
Infine, viene introdotta la teoria di Mie per la diffusione e l’assorbimento della luce da parte di nanoparticelle metalliche, per quanto riguarda la colorazione apparente, con esempi sulla colorazione vitrea, come la famosa coppa di Licurgo
AGN oscurati nel campo J1030: prospettiva in banda X e ottico/infrarossa
No full textIn questo lavoro di tesi si presenta uno studio multibanda di un campione di 30 candidati AGN oscurati, selezionati in banda X nel campo profondo centrato su J1030+0524 (J1030), un quasar a z=6.31. La selezione viene fatta tramite un Hardness Ratio (HR) >0, che può essere considerato come una sorta di indice di colore in banda X. La statistica del campione ha un valore mediano di 120 conteggi netti in banda 0.5-7 keV.
Con un totale di 500 ks osservati con il telescopio Chandra, il campo di J1030 è attualmente la quarta survey X più profonda mai osservata, il che la rende il laboratorio ideale per studiare oggetti deboli come gli AGN oscurati. Grazie alla profondità del campo, è stato possibile analizzare gli spettri X in cerca di features come la riga in emissione del ferro neutro a 6.4 keV e la edge del ferro a 7.1 keV.
Non avendo a disposizione la spettroscopia ottica, è stato ideato un metodo di indagine innovativo sulla base dei dati X: sono state elaborate simulazioni in modo da riprodurre gli spettri delle sorgenti osservate, per poter verificare la significatività delle features sopracitate. Inoltre, sempre tramite simulazioni, è stato verificato fino a che punto la statistica X possa essere utilizzata per ottenere indicazioni sul redshift delle sorgenti.
Per verificare i risultati ottenuti è stata utilizzata la tecnica dei redshift fotometrici, attraverso una procedura di SED fitting. Si è sfruttata l'ampia copertura fotometrica disponibile in J1030 nelle bande ottiche e infrarosse, utilizzato osservazioni (LBC/LBT, WIRCam/CFHT, la survey MUSYC e IRAC).
I risultati ottenuti con questa tecnica, seppur con incertezze non trascurabili, confermano le soluzioni trovate dall'analisi in banda X, verificando la bontà del metodo ideato
Testing the paradigm: First spectroscopic evidence of a quasar-galaxy Mpc-scale association at cosmic dawn
No full textState-of-the-art models of massive black hole formation postulate that quasars at z > 6 reside in extreme peaks of the cosmic density structure in the early universe. Even so, direct observational evidence of these overdensities is elusive, especially on large scales (≫1 Mpc) as the spectroscopic follow-up of z > 6 galaxies is observationally expensive. Here we present Keck/DEIMOS optical and IRAM/NOEMA millimeter spectroscopy of a z ̃ 6 Lyman-break galaxy candidate originally discovered via broadband selection, at a projected separation of 4.65 physical Mpc (13.94 arcmin) from the luminous z = 6.308 quasar J1030+0524. This well-studied field presents the strongest indication to date of a large-scale overdensity around a z > 6 quasar. The Keck observations suggest a z ̃ 6.3 dropout identification of the galaxy. The NOEMA 1.2 mm spectrum shows a 3.5σ line that, if interpreted as [C II], would place the galaxy at z = 6.318 (i.e., at a line-of-sight separation of 3.9 comoving Mpc assuming that relative proper motion is negligible). The measured [C II] luminosity is 3 × 108 L☉, in line with expectations for a galaxy with a star formation rate ̃15 M☉ yr-1, as inferred from the rest-frame UV photometry. Our combined observations place the galaxy at the same redshift as the quasar, thus strengthening the overdensity scenario for this z > 6 quasar. This pilot experiment demonstrates the power of millimeter-wavelength observations in the characterization of the environment of early quasar
E-Learning Experiences in the Computer Networks Course in Higher Education
No full textThis article examines the impact and benefits of e-learning in higher education, focusing on student experience in the Computer Networks course. To evaluate the meaning of e-learning, the author used a complex questionnaire, applied to 98 students from the Technical University of Moldova. The results highlighted the importance of course structure, reliance on deep study, lecturer training quality, feedback and interaction, and use of digital resources. The article argues that e-learning has significant potential to improve academic performance, save time and costs, and provide access to quality educational content. The study highlights the significant contribution of e-learning to improving the learning process in higher education and to meeting the evolving needs of students and labor market demands.Articolul de faţă examinează impactul și beneficiile e-learning în învăţământul superior, centrat pe experienţa studenţilor în cadrul cursului de Reţele de calculatoare. Pentru a evalua semnificaţia e-learning, autorul a folosit un chestionar complex, aplicat la 98 de studenţi ai Universităţii Tehnice a Moldovei. Rezultatele au scos în evidenţă importanţa structurii cursului, încrederea în studiul profund, calitatea pregătirii lectorilor, feedbackul și interacţiunea, precum și utilizarea resurselor digitale. Articolul argumentează că e-learning are un potenţial semnifi cativ de a îmbunătăţi performanţa academică, de a economisi timp și costuri și de a oferi acces la conţinut educaţional de calitate. Studiul evidenţiază contribuţia semnifi cativă a e-learning la îmbunătăţirea procesului de învăţare la nivelul învăţământului superior și la satisfacerea nevoilor în evoluţie ale studenţilor și cerinţelor pieţei muncii
On the Cosmic Evolution of AGN Obscuration and the X-Ray Luminosity Function: XMM-Newton and Chandra Spectral Analysis of the 31.3 deg2 Stripe 82X
No full textWe present X-ray spectral analysis of XMM-Newton and Chandra observations in the 31.3 deg ^2 Stripe-82X (S82X) field. Of the 6181 unique X-ray sources in this field, we analyze a sample of 2937 candidate active galactic nuclei (AGNs) with solid redshifts and sufficient counts determined by simulations. Our results show an observed population with median values of spectral index , column density log and intrinsic, de-absorbed, 2–10 keV luminosity log , in the redshift range 0–4. We derive the intrinsic, model-independent, fraction of AGNs that are obscured ( ), finding a significant increase in the obscured AGN fraction with redshift and a decline with increasing luminosity. The average obscured AGN fraction is 57% ± 4% for log L _X /erg s ^−1 > 43. This work constrains the AGN obscuration and spectral shape of the still uncertain high-luminosity and high-redshift regimes (log L _X /erg s ^−1 > 45.5, z > 3), where the obscured AGN fraction rises to 64% ± 12%. We report a luminosity and density evolution of the X-ray luminosity function, with obscured AGNs dominating at all luminosities at z > 2, and unobscured sources prevailing at log L _X /erg s ^−1 > 45 at lower redshifts. Our results agree with the evolutionary models in which the bulk of AGN activity is triggered by gas-rich environments and in a downsizing scenario. Moreover, the black hole accretion density (BHAD) is found to evolve similarly to the star formation rate density, confirming the coevolution between AGN and host galaxy, but suggesting different timescales in their growing history. The derived BHAD evolution shows that Compton-thick AGNs contribute to the accretion history of AGNs as much as all other AGN populations combined
X-ray properties and obscured fraction of AGN in the J1030 Chandra field
No full textThe 500ks Chandra ACIS-I observation of the field around the quasar
SDSS J1030+0524 is currently the 5th deepest extragalactic X-ray survey. The
rich multi-band coverage of the field allowed for an effective identification
and redshift determination of the X-ray source counterparts: to date a catalog
of 243 extragalactic X-ray sources with either a spectroscopic or photometric
redshift estimate in the range is available over a 355 arcmin
area. Given its depth and the multi-band information, this catalog is an
excellent resource to investigate X-ray spectral properties of distant Active
Galactic Nuclei (AGN) and derive the redshift evolution of their obscuration.
We performed a thorough X-ray spectral analysis for each object in the sample,
measuring its nuclear column density and intrinsic (de-absorbed)
2-10 keV rest-frame luminosity, . Whenever possible, we also used the
presence of the Fe K emission line to improve the photometric redshift
estimates. We measured the fractions of AGN hidden by column densities in
excess of and cm ( and ,
respectively) as a function of and redshift, and corrected for
selection effects to recover the intrinsic obscured fractions. At ,
we found and , respectively, in broad
agreement with the results from other X-ray surveys. No significant variations
with X-ray luminosity were found within the limited luminosity range probed by
our sample (log). When focusing on luminous AGN with
log to maximize the sample completeness up to large
cosmological distances, we did not observe any significant change in
or over the redshift range . Nonetheless, the obscured
fractions we measure are significantly higher than ...Comment: A&A, in pres
LBT-MODS spectroscopy of high-redshift candidates in the Chandra J1030 field. A newly discovered z2.8 large scale structure
No full textWe present the results of a spectroscopic campaign with the Multi-Object
Double Spectrograph (MODS) instrument mounted on the Large Binocular Telescope
(LBT), aimed at obtaining a spectroscopic redshift for seven Chandra J1030
sources with a photometric redshift >=2.7 and optical magnitude
r_AB=[24.5-26.5]. We obtained a spectroscopic redshift for five out of seven
targets: all of them have z_spec>=2.5, thus probing the reliability of the
Chandra J1030 photometric redshifts. The spectroscopic campaign led to the
serendipitous discovery of a z~2.78 large scale structure (LSS) in the J1030
field: the structure contains four X-ray sources (three of which were targeted
in the LBT-MODS campaign) and two non-X-ray detected galaxies for which a
VLT-MUSE spectrum was already available. The X-ray members of the LSS are
hosted in galaxies that are significantly more massive
(log(M_*/M_sun)=[10.0-11.1]) than those hosting the two MUSE-detected sources
(log(M_*/M_sun)<10). Both observations and simulations show that massive
galaxies, and particularly objects having log(M_*/M_sun)>10, are among the best
tracers of large scale structures and filaments in the cosmic web.
Consequently, our result can explain why X-ray-detected AGN have also been
shown to be efficient tracers of large scale structures.Comment: 16 pages, 9 Figures. Accepted for publication in Astronomy and
Astrophysic
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