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Unconventional spin-density wave in Bechgaard salt (TMTSF)2NO3
Get PDFBasletić, Mario; Korin-Hamzić, Bojana; Maki, Kazumi; Tomić, Silvi
Computer mouse as displacement sensor with application to torsion pendulum
No full textKružno ili torzijsko njihalo je tijelo učvršćeno tako da može rotirati oko jedne osi. Najvažniji dio kružnog njihala je spiralna opruga, koja skupa sa kotačem sačinjava harmonijski oscilator. Cilj rada je nadodavanje eksperimentalnom postavu kružnog njihala element koji prati i bilježi pomake kotača u vremenu te na taj način služi kao precizan mjerni uređaj za proučavanje oscilacija. Za ovu svrhu koristili smo računalnog miša. U radu su objašnjeni najvažniji dijelovi eksperimentalnog postava. Opisano je kako je računalni miš uklopljen u postav korištenjem računalnog programa. Navedena su mjerenja koja su rađena i dani su njihovi rezultati.The torsion pendulum is a body fixed so that it can rotate about one axis. The most important part of the torsion pendulum is the coil spring, which together with the wheel forms a harmonic oscillator. The aim of this paper is to add to the experimental setup of a torsion pendulum an element that monitors and records wheel movements over time and thus serves as a precise measuring device for studying oscillations. We used a computer mouse for this purpose. The paper explains the most important parts of the experimental setup. It is described how a computer mouse was incorporated into the setup using a computer program. The measurements that have been made are listed and their results are given
Road vehicle consumption optimization
No full textU ovom radu ćemo pokušati razviti model vožnje cestovnog vozila kojim bi se minimizirala potrošnja goriva na putu kojem se mijenja nagib ceste. U tu svrhu ćemo pretežito koristiti pojednostavljeni model puta i podatke o potrošnji goriva u ovisnosti o brzini i nagibu za stvarno vozilo. U sklopu rada ćemo razviti i program koji računa optimalne brzine kretanja po tom jednostavnom modelu puta i uštedu na tom putu.In this thesis, we will try to develop a driving model of a road vehicle that would minimize fuel consumption on a road with a changing slope. For this purpose, we will predominantly use a simplified road model and data on fuel consumption depending on speed and gradient for the actual vehicle. As part of this thesis, we will also develop a program that calculates the optimal speed of movement according to that simple road model and savings on that road
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Computerised experiments
Get PDFU ovom radu ćemo koristiti Arduino, model Leonardo, kako bi nam olakšao prikupljanje podataka tijekom izvođenja eksperimenta. Za prikupljanje podataka bit će nam potreban i nekakav senzor. Osim senzora potrebno je i napisati program na Arduinu koji će mu dati do znanja koje podatke da prikupi, koliko često da ih prikuplja te gdje i kad da ih šalje kad ih je prikupio. Na drugom kraju, kad smo te podatke primili, trebamo nešto s njima i napraviti. Za to nam služi računalo na kojem ćemo napisati program da dobivene podatke prikupi, obradi i prikaže u grafičkom sučelju te kad smo gotovi s eksperimentom obrađene podatke spremi u trajnu memoriju. U našem slučaju odlučili smo se usredotočiti na ultrazvučni senzor pomoću kojeg ćemo mjeriti udaljenost. Mjerenje udaljenosti ćemo iskoristiti kako bi promatrali gibanje utega, prvo kao njihanje na opruzi, a zatim kao osciliranje na niti. Razlog zašto smo se odlučili za ovakav izbor senzora i eksperimenta jest jednostavnija kontrola varijabli koja će nam omogućiti bolji pregled mogućnosti samog Arduina i njegovih granica. Tijekom provođenja eksperimenta također ćemo pripaziti na njegovu izvedivost u učionici unutar okvira nastavnog sata i na razumljiv prikaz sadržaja učenicima. Iz tog je razloga također titranje optimalan izbor.In this thesis we will be using the Arduino, model Leonardo, to facilitate the gathering of data during our experiment. To gather the data we will also be needing a sensor. It is also necessary to write a program on the Arduino to specify which data needs to be collected, how often it needs to be collected and where and when to send the data once it has been gathered. On the other end, once we've received our data, we need to do something with it. For that purpose we are using a computer on which we will write a program to gather, process and present the data in a graphical user interface. Once the experiment has been finished the program will store the processed data in the computers' permanent memory. In our case we decided to focus on the ultrasonic sensor with which we will be measuring distance. The distance measurement will be used to observe the movement of a weight, first as oscillations on a spring, and afterwards as swinging on a thread. The reason we opted for this particular choice of sensor and experiment is the ease of variable control which will give us a better overview of the Arduinos' possibilities and its limitations. During the experiment we will pay attention to the experiments' feasibility in the classroom during a lesson and to the understandable display of the content to the students. For that reason as well oscillations are the optimal choice
Toys in research-oriented physics teaching
No full textU sklopu ovog diplomskog rada igračke su upotrijebljene u istraživački usmjerenoj nastavi fizike u osmom razredu osnovne škole te u prvom razredu gimnazije. Ukupno je održano šest školskih nastavnih sati. Korištenjem vrlo poznatih igračaka (autić sa spustom, klaun koji iskače iz kutije, praćka, slink), kroz demonstracijske i učeničke pokuse, učenicima je pokazana pretvorba energije, zakon očuvanja energije te su uvedeni pojmovi longitudinalnog i transverzalnog vala. Nakon svakog odrađenog sata s igračkama, učenici su dobili izlaznu anketu koju su anonimno ispunili. Anketom se ispitivalo učeničko zadovoljstvo provedenim nastavnim satom. Rezultati ankete obrađeni su frekvencijskom analizom te ukazuju na učeničko zadovoljstvo uporabom igračaka u provedenom nastavnom satu.In this master thesis toys have been implemented as a part of inquiry – based learning of physics in the eight grade of primary school and first grade of high school. There were six lessons held. Pupils were shown energy transformation, law of energy conservation, as well as longitudinal and transverse waves during demonstration experiments and ones made by themselves. For this purpose some quite popular toys (hot wheel car, Jack in the box, slinky and sling) have been used. After each lesson for which toys were used pupils were given an anonymous exit poll. The aim of the poll was to measure the level of students’ satisfaction with the given lesson. The results of the poll were obtained through frequency analysis and indicate students’ satisfaction with usage of toys during the lesson
Magnetotransport properties ofanisotropic organic conductors (TMTTF)2ReO4 an alpha-(BEDT-TTF)2I3
No full textU ovom su radu izloženi rezulti mjerenja otpora, magnetootpora i Hallovog efekta na anizotropnim organskim vodičima (TMTTF)2ReO4 i α- (BEDT−TTF)2I3. Mjerenja su vršena u rasponu temperatura od 140 K, odnosno 60 K do sobne temperature i u magnetskim poljima do 5 T. Rezultati mjerenja otpora (TMTTF)2ReO4 pokazuju očekivano ponašanje sa dva vidljiva fazna prijelaza uzrokovana uredenjem aniona na nižim te uredenjem naboja na višim temperaturama. Izmjerena ovisnost Hallove konstante o temperaturi usporedena je s izmjerenom ovisnošću otpora o temperaturi. Korišten je najjednostavniji, klasični teorijski model koji omjer dobivenih ovisnosti povezuje s promjenom razlike pokretljivosti šupljina i elektrona (μh − μe), a dobivene vrijednosti magnetootpora s umnoškom pokretljivosti (μhμe). Teorijski izrazi izvedeni u ovom radu pokazuju povezanost Hallove konstante, otpora i magnetootpora, te omogućuju izračunavanje vrijednosti pokretljivosti i koncentracije nosioca naboja koja se razlikuje od standardne procjene za čak tri reda veličine. Rezultati mjerenja otpora α-(BEDT−TTF)2I3 pokazuju očekivano ponašanje s naglašenim metal-izolator faznim prijelazom. Izmjerena ovisnost Hallove konstante o temperaturi usporedena je s izmjerenom ovisnošću otpora o temperaturi te je uočena približna proporcionalnost. Za temperature iznad faznog prijelaza uočeno je vrlo dobro slaganje izmjerenih vrijednosti Hallove konstante, a time i proračunatih vrijednosti koncentracije naboja s teorijski predvidenim vrijednostima za metalnu fazu dobivenim iz vrijednosti parametara kristalne rešetke. Isto teorijsko predvidanje pokazalo se približno dobro i u (TMTTF)2ReO4. Primjećena je promjena predznaka Hallove konstante u α-(BEDT−TTF)2I3 ispod temperature faznog prijeleza što ukazuje na veću pokretljivost elektrona spram pokretljivosti šupljina u izolatorskoj fazi.In this thesis we present the measurements of resistance, magnetoresistance and Hall effect of the anisotropic organic conductors (TMTTF)2ReO4 and α-(BEDT−TTF)2I3 ˙ Measurements were conducted in temperature range from 140 K i.e. 60 K respectively, to room temperature and in magnetic fields to 5 T. The results of (TMTTF)2ReO4 resistivity show the expected behavior with two visible phase transitions caused by anion ordering at lower, and charge ordering at higher temperatures. The temperature dependence of Hall constants is compared with the measured temperature dependence of resistance. We use the simplest, classical theoretical model which relates the ratio of measured dependencies with changes in difference between hole and electron mobilities (μh − μe), and also the values of magnetoresistance with product of mobilities (μhμe). Theoretical expressions derived in this work show the connection between Hall constant, resistance and magnetoresistance and also enable the calculation of charge carriers mobility and concentration which differs from standard estimate for three orders of magnitude. Measurement results of α- (BEDT−TTF)2I3 resistivity show the expected behavior with metal-insulator phase transition. The temperature dependence of Hall constants is compared with the temperature dependence of resistance and we found that they are approximatly proportional. For temperatures above the phase transition, values of Hall constants, and thereby also carrier concentrations are in very good agreement with the theoretically predicted values for metallic phase, obtained from the values of crystal lattice parameters. The same theoretical predictions also proved to be relatively good for (TMTTF)2ReO4. We found sign change of Hall constant in α-(BEDT−TTF)2I3 under phase transition temperature, indicating the higher electron mobility versus hole mobility in insulator phase
Photograph artefacts
No full textU ovom radu se bavimo jednim artefaktom na fotografijama, krugom zamućenja. Uzrok nastajanja tog artefakta su sitne čestice van fokusa pri fotografiranju predmeta. Navedena pretpostavka se provjerila eksperimentom koji je uključivao fotografiranje predmeta, žice, na nekoliko udaljenosti s odredenim fokusnim duljinama. Promjer kruga zamućenja se odredio iz fotografija pomoću alata grafičkog programa Krita. Dobiveni podaci su potom prikazani u grafovima kako bi se potvrdile očekivane ovisnosti dobivene iz izvedenih izraza. Linearizirani grafovi dobivenih podataka i objašnjenja istih daju odgovor na pitanje slažu li se očekivanja s rezultatima provedenog eksperimenta.In this paper, we deal with one artefact in photography, the circle of confusion. The cause of this artefact are small particles out of focus when photographing the object. The aforementioned assumption was verified by an experiment that included photographing an object, a wire, at several distances with certain focal lengths. Diameter of a circle of confusion was determined from photographs using the tools of the graphics program Krita. The obtained data were then presented in graphs to confirm the expected dependencies obtained from derived expressions. The linearized graphs of the obtained data and their explanations provide an answer to the question of whether the expectations agree with the results of the conducted experiment
Transport and dielectric properties of selected BEDT-TTF organic materials
Get PDFIzvršena su mjerenja otpornosti i dielektrična spektroskopija pri niskim temperaturama na uzorcima kvazi-dvodimenzionalnih organskih vodiča koji su bazirani na organskoj molekuli bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF). Istraživanje spoja α -ET_2I_3 je provedeno kako bi se bolje razumjela feroelektrična priroda metalno-izolatorskog prijelaza na T_MI = 135K te pojava relaksacijskih modova u smjeru okomitom na vodljivu ravninu ispod tog prijelaza. Transportna mjerenja su pokazala promjenu vrijednosti energijskog procjepa na niskim temperaturama koja dosad nije razmatrana u literaturi. Također je izvedeno istraživanje svojstava nedavno sintetiziranog spoja κ-ET_2Ag_2(CN)_3 da bismo bolje razumjeli ponašanje srodnog κ -ET_2Cu_2(CN)_3 koji je istaknuti kandidat za pronalaženje osnovnog stanja kvantne spinske tekućine. U ovom radu je prezentirana prva dielektrična karakterizacija uzorka κ-ET_2Ag_2(CN)_3 koja je zabilježila pojavu većeg broja relaksacijskih modova.Resistance measurements and dielectric spectroscopy at low temperatures were performed on samples of quasi-two-dimensional organic conductors based on the organic molecule bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF). An investigation on the α – ET_2I_3 compound was conducted in order to better understand the ferroelectric nature of the metal-insulator transition at T_MI = 135K, as well as the appearance of out-of-plane relaxation modes below this transition temperature. Transport measurements have shown a change in energy gap values at low temperatures, which was not previously discussed in the literature. The properties of the newly synthesised compound κ – ET_2Ag_2(CN)_3 were also explored in order to better comprehend the behaviour of the related κ – ET_2Cu_2(CN)_3 which is a prominent candidate for finding a quantum spin liquid ground state. In this work the first dielectric characterization of a sample of κ – ET_2Ag_2(CN)_3 is presented which recorded an occurrence of multiple relaxation modes
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