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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Linjering av ett mikro-CT-system

Trowald, Jacob, Lundahl, Alexander January 2015 (has links)
At the School of Technology and Health (STH) on KTH, a micro- CT is beeing build. The micro-CT-system need to be aligned in order to function correctly. The purpose of this bachelor thesis was to create an application that, from the micro-CT images, could calculate all the necessary parameters to make the alignment pos- sible. During the projekt, LabView-code for aligning a micro-CT system has been modified to being compatible with the micro-CT at the School of Technology and Health (STH) on KTH. The code has also partly been translated into the open-source and platform independent programming language Java. Due to delays in building the micro-CT at STH, neither the LabView- or Javacode could be validated with it. However, successful attempts have been made with images from another micro-CT and on simulated images of a phantom in a micro-CT.
12

Att läsa genetik: bättre än sitt rykte?

Bradley, Hanna January 2009 (has links)
Ett stort antal studier har gjorts där man konstaterat och ringat in svårigheter med att som elev förstå undervisning i genetik, och att som lärare bedriva densamma. Denna studie har jämfört två grupper av elever som båda läst kursen genetik & mikrobiologi på Naturbruksprogrammet inriktning djurvård. Med den ena gruppen (1) bedrevs undervisningen på sedvanligt sätt enligt skolans traditionella stoffordning och undervisningsmetoder. Med den andra gruppen (2) förändrades undervisningen genom att ett antal nya kursinslag skapades. Stoffordningen var dock i stort densamma mellan grupperna. De nya kursinslagen bestod bl.a. i filminslag, laborationer och ett tydligare avstamp i elevernas vardag och ting de kan tänkas känna igen. Det övergripande syftet med studien har varit att hitta metoder för ökad måluppfyllelse i genetik. Detta har gjorts genom att ta reda på vilka förväntningar som generellt sett finns på denna kurs bland de elever som väljer att läsa den. Jag ville också ta reda på vilken känsla kursen givit de elever som läst den, och om denna känsla skiljer sig åt mellan de två elevgrupperna. Med känsla menas här såväl den emotionella upplevelsen, som upplevelsen av användbarhet, nytta och anknytningar till ett framtida yrkesliv. Studien genomfördes under HT08/VT09 genom kvalitativt inriktade intervjuer.I studien har det visat sig att medan kurs 1 beskriver ord och begrepp man minns, kan kurs 2 beskriva mer av rum, händelser och bilder, det vill säga både det fysiska rummet –var vi befann oss- och vad vi som hände där. Eleverna i kurs 2 kunde lättare och mer spontant ge exempel på problem och situationer de med sina nya kunskaper nu kunde lösa. Eleverna från kurs 1 var mer bundna till kursens konkreta innehåll och de frågor vi diskuterat där.Den genomgående förväntan på kursen, har i studien varit att kursen skulle vara ”svår” –ett ord som återkom många gånger under intervjuerna. Denna förväntan har dock inte infriats, utan i efterhand förmedlar båda elevgrupperna en känsla av att man verkligen lärt sig något nytt, man har ytterligare ett perspektiv att lägga på sin framtida yrkesroll och man tycker inte kursen varit så svår som man förväntade sig.
13

Vliv řízeného naplynění hliníkových slitin na strukturu a vlastnosti odlitků / Influence of directed gassing of aluminium alloys on structure and properties of castings

Hotař, Jan January 2012 (has links)
This thesis examines the influence of directed gassing of aluminium alloys on structure and properties of castings. Cast and tests were made of gravity castings in metak molds. The aim is to compare the properties of castings and without the use of Probat-Fluss Mikro 100.
14

Konstrukce zařízení pro modifikaci topografie třecích povrchů / Design of Equipment for Surface Topography Modification

Kománek, Jiří January 2013 (has links)
This master thesis is focused on design and construction of laboratory shot peening machine. This machine is determined for modification of the topography of the friction surfaces specimens. Two types of specimens are used. The first specimen is sphere with diameter 20-40 mm. The second specimen is cylinder with 9.6 mm diameter. In this thesis the setting parameters of shot peening for creation of surface with the micro-texture was described. Influence of the micro-texture to the coefficient of friction was investigated under mixed lubrication and slip condition.
15

Catalytic Tubular Micro-Jet Engines

Solovev, Alexander Alexandrovich 26 July 2012 (has links) (PDF)
This dissertation offers demonstrations of autonomous catalytic microtubes (microjet engines) with tunable diameters ranging from micro- to nanoscale and lengths from 50 μm to 1 mm. These results open the door to effective microengines and represent the entry in the Guinness Book of World Records for “the smallest man-made jet engine.” Several attractive methodologies of machine-based functions at the micro- and nanoscale are shown. For instance, catalytic Ti/Cr/Pt microjets, which are integrated on a planar substrate, can operate as “on chip” chemical micropumps by decomposition of hydrogen peroxide fuel into oxygen bubbles and water. When released from a substrate, microjets self-propel autonomously in solution. The incorporation of ferromagnetic layer (Fe) into the rolled-up geometry enables their remote control using external magnetic field. Such microjets were used to load, transport, deliver and assemble multiple cargo particles, including biological cells in bulk solutions and microfluidic channels. Furthermore, it is demonstrated that for microjets that are fixed to or self-propelled above a platinum patterned surface, the microengine power/speed can be controlled using a white lightsource. A change in intensity of the white light leads to a controllable switching “off” and “on” of the microengine power on demand. Light degrades a local concentration of the hydrogen peroxide fuel and surface tension and subsequently suppresses the generation of oxygen microbubbles. In the next step, the diameter of the microjets was rigorously reduced to 250 nm by using hybrid heteroepitaxial/catalytic InGaAs/GaAs/Cr/Pt nanotubes. Due to asymmetry of the rolled-up layers, these nanojets move in corkscrew-like motions and act as “self-propelled nanotools,” which were used in the next step to transport yeast cells and drill into fixed cancer Hela cells. Although it is well-known that hydrogen peroxide cannot be used to sustain viable cellular function, it is however conceivable that alternative fuels, such as glucose, might enable operation of such nanotools under biologically compatible conditions. As a first step to achieve this goal, demonstrations were made using metal-enzyme biocatalytic Ti/Au/SAM/Catalase microengines. Synthetic components with competing interactions are well-suited to study the emergence of their collective behavior, such as swarms of large numbers of individuals. Microengines’ self-organization in bistable swarms is shown at the air-liquid interface of the mixture of propylene carbonate and hydrogen peroxide. Microengines act as “water striders.” Buoyed by oxygen bubbles, they self-propel via the microbubble recoiling mechanism and, depending on the bubbles’ sizes, self-organize into swarms due to the meniscus climbing effect. These reversible swarms depend on the microengine power, which competes against attracting surface tension force. The demonstrated microjet engines show great promise for emerging applications, including biomedical, on-chip, environmental, and robotic micromachines. Furthermore, a key method discovered, entitled “rolled-up nanotechnology on polymers,” allowed for the fabrication of highly parallel arrays of microtubes with multiple functionalities and aimed for different purposes.
16

Moderní trendy v třískovém obrábění - frézování a mikrofrézování / Modern manufacturing trends in chip machining - milling and micromachining

Tkadlec, Jiří January 2019 (has links)
The thesis is focused on the research on micro-milling with the aim to specify the latest findings and trends in milling and micro-milling. The introduction consists of the specification of micro-milling and its comparison with conventional milling. The main goal of the thesis is to interpret modern trends in micro-milling technology, such as machine modernization, advanced machining strategies and the latest CAD/CAM software. The second part deals with the influence of cutting parameters on the overall workpiece quality. The final part is devoted to the application and use of micro-milling technology.
17

Studium genetických změn u dětí s akutními lymfoblastickými leukémiemi (ALL) za využití metod mFISH/mBAND a čipových technologií. / The study of genetic changes of children patients suffering from the acute lymphoblastic leukemia (ALL) using mFISH / mBAND and micro-arrays.

Bártů, Linda January 2012 (has links)
Acute lymphoblastic leukemia is the most common malignancy in children. The most important examination at the time of diagnosis includes karyotype of leukemic cells which divides patients into prognostic groups according to cytogenetic finding. In up to 90 % of patients the chromosomal aberrations with well known clinical significance are designated. One of cytogenetic type is high hyperdiploid ALL (51-68 chromosomes) associated with favorable prognosis. Nevertheless, relapses of the disease occur even in these children. One possible reason why this happens could be an increased genomic instability of leukemic cells that causes cryptic structural rearrangements. In a retrospective study, we examined a total of 232 children with newly diagnosed B-ALL using conventional cytogenetic analyses and interphase fluorescence in situ hybridization (I-FISH) with a panel of DNA probes (Abbott Vysis) in order to detect heteroploid cells. In patients with suspect cryptic structural chromosome aberrations, we analyzed the karyotypes in detail by multicolor FISH and multicolor banding (mFISH/mBAND; MetaSystems). The extent of aberrations was determined by comparative genomic hybridization on BAC arrays (array CGH; BlueGnome). Cell clones with high hyperdiploid karyotype were detected in a total of 102 children (44 %). In...
18

Att arbeta med CSR : En studie om relationen mellan CSR-arbete och chefers motivation

Svensson, Hanna, Hedström, Linda January 2019 (has links)
Medvetenheten och kraven på hållbarhet växer ständigt i samhället. Corporate social responsibility (CSR) är aktuellt för företag att arbeta med för att bemöta de externa påtryckningarna. När CSR undersöks på individnivå kallas det Mikro-CSR. Vidare forskning om hur CSR påverkar individers motivation fordras. Särskilt på chefsnivå, då att vara motiverad anses av betydande vikt när mobilisering och involvering av andra ingår i yrkesrollen. Syftet med denna studie har således varit att undersöka hur individer i chefsposition upplever att deras motivation påverkas av deras individuella CSR-arbetet. För att besvara detta undersöktes om behovet av prestation, behovet av makt och behovet av tillhörighet tillfredsställs. En fallstudie på fem chefer genomfördes. Analysen av data kodades med inspiration från tidigare forskning. Undersökningen visar att chefer upplever deras individuella CSR-arbete som endast delvis motiverande. Det finns svårigheter i att förstå, hantera och mäta CSR-arbetet, vilket är faktorer som påverkar upplevelsen av relationen mellan CSR-arbete och motivation negativt och ger sig uttryck i de vi benämner som CSR-paradoxen. Slutligen visar studien att en respondent särskiljer sig från övriga då han anses omotiverad av CSR-arbetet han utför, vilket anses kunna förklaras av att hans upplevelser av CSR-arbetet står i konflikt med yrkesrollens arbetsuppgifters karaktär.
19

Revision i små och mikro aktiebolag : lagstadgad eller självvald / Audit in small and micro joint stock companies : statutory by law or self chosen

Westerlind, Ann, Ståhlberg, Emma January 2007 (has links)
<p>Syftet med denna uppsats är att undersöka om revisionsplikten för små och mikro AB bör finnas kvar eller inte. Inom den Europeiska Unionen (EU) är det endast Sverige och Malta som i nuläget har plikten kvar fullt ut. För att få en uppfattning om vad debatten handlar om har vi i första hand studerat aktuella artiklar. Vi har även använt oss av två olika forskarrapporter inom området och litteratur. Åsikter i debatten har vi även tagit del av genom sju stycken olika intervjuer med anställda hos banker, Skatteverket, revisionsbyråer och ägare i små och mikro AB. Genom vår studie har vi kommit fram till att fördelar med en revisionsplikt är att den fungerar som ett kontrollinstrument för intressenter och bidrar till en kvalitetsstämpel för bolagen. Vi har dock sett att det viktigaste inte är själva plikten, utan revisionen i sig. De främsta intressenterna av revision är kreditgivarna och dessa kommer troligtvis att kunna kräva reviderat material, även om plikten avskaffas. Med andra ord är inte kreditgivarna beroende av en revisionsplikt. Vi anser därför att det är bättre att revision är självvald. Detta tror vi bidrar till en ökad status för revisorn och en högre kvalitetsstämpel för revisionen i sig.</p> / <p>The purpose with this paper is to examine whether the audit duty for small and micro joint stock companies should be in existence or not. Within the European Union (EU) it´s only Sweden and Malta who now a days still has the duty fully in existence. To get an apprehension on what the debate is about have we first of all studied current articles. We have also used two different sciencesreports within the subject and literature. We have also taking part of opionions in the debate through seven different interviews with employees at banks, tax authorities, firms of accountants and owners in small and micro joint stock companies. Through our study we have seen that the advantages with an auditduty is that it works as a controlinstrument for partners and contribute to an qualitystamp for the companies. We have although seen that the most important isn´t the duty, but instead the audit it self. The leading partners of audit is the creditgivers and they will probably be able to demand audited material anyway, even if the duty abolish. With other words, the creditgivers, is not depended on a auditduty. Our opinion is therefore that it´s better if audit is self-chosen. We think that it contributes to an increased status for the auditor and a higher qualitystamp for the audit it self.</p>
20

Magnetic jets from accretion disks : field structure and X-ray emission

Memola, Elisabetta January 2002 (has links)
Astrophysikalische Jets sind stark kollimierte Materieströmungen hoher Geschwindigkeit. Sie stehen im Zusammenhang mit einer Fülle verschiedener astrophysikalischer Objekte wie jungen Sternen, stellaren schwarzen Löchern ('Mikro-Quasare'), Galaxien mit aktivem Kern (AGN) und wahrscheinlich auch mit dem beobachteten intensiven Aufblitzen von Gamma-Strahlung (Gamma Ray Bursts). Insbesondere hat sich gezeigt, dass die Jets der Mikro-Quasare wahrscheinlich als kleinskalige Version der Jets der AGN anzusehen sind. <br /> <br /> Neben den Beobachtungen haben vor allem auch theoretische Überlegungen gezeigt, dass Magnetfelder bei der Jetentstehung, -beschleunigung und -kollimation eine wichtige Rolle spielen. Weiterhin scheinen Jets systematisch verknüpft zu sein mit dem Vorhandensein einer Akkretionsscheibe um das zentrale Objekt. Insbesondere wenn ein schwarzes Loch den Zentralkörper darstellt, ist die umgebende Akkretionsscheibe der einzig mögliche Ort um Magnetfeld erzeugen zu können. <br /> <br /> Wir sind speziell interessiert am Entstehungsprozess hoch relativistischer Jets wie sie bei Mikro-Quasaren und AGN beobachtet werden. Insbesondere untersuchen wir die Region, in der der Jet kollimiert, eine Region, deren räumliche Ausdehnung extrem klein ist selbst im Vergleich zur Auflösung der Radioteleskope. Dies ist ein Grund, wieso zum heutigen Zeitpunkt für die meisten Quellen die theoretische Modellierung die einzige Möglichkeit darstellt, um Information über die physikalischen Prozesse in der innersten Region der Jetentstehung zu erhalten. <br /> <br /> Uns ist es zum ersten Mal gelungen, die globale zwei-dimensionale Magnetfeldstruktur stationärer, axialsymmetrischer, relativistischer und stark magnetisierter (kräfte-freier) Jets zu berechnen, die zum einen asymptotisch in einen zylindrischen Jet kollimieren, zum anderen aber in einer differential rotierenden Akkretionsscheibe verankert sind. Damit erlaubt dieser Ansatz eine physikalische Verkn&#168;upfung zwischen Akkretionsscheibe und dem asymptotischen Jet. Nimmt man also an, dass die Fußpunkte der Magnetfeldlinien mit Keplergeschwindigkeit rotieren, so kann man eine direkte Skalierung der Jetmagnetosphere mit der Größe des Zentralobjektes erhalten. Unsere Resultate zeigen eine gute Übereinstimmung zwischen unserem Modell und Beobachtungen des Jets von M87. <br /> <br /> Für das Beispiel eines relativistischen Mikroquasarjets haben wir die Röntgenemission im Bereich von 0.2-10.1 keV berechnet. Dafür haben wir in der Literatur aus den relativistischen magnetohydrodynamischen Gleichungen berechnete Jetgrößen (Dichte-, Geschwindigkeits-, und Temperaturprofil) verwendet und das Spektrum für jeden Punkt entlang der Jetströmung abgeleitet. Das theoretische thermische Röntgenspektrum des innersten, heißen Teils des Jets erhalten wir zusammengesetzt aus den spektralen Anteilen der einzelnen Volumenelemente entlang des Jets. Um relativistische Effekte wie Dopplerverschiebung und -verstärkung (boosting) aufgrund der Jetbewegung zu untersuchen, haben wir für verschiedene Inklinationswinkel des Jets zur Sichtlinie berechnet, wie die erhaltenen Spektren davon beeinflusst werden. <br /> <br /> Unsere Spektren zeigen deutlich die hochionisierten Eisen-Emissionslinien, die in den galaktischen Mikroquasaren GRS 1915+105 und XTE J1748-288 andeutungsweise beobachtet wurden.<br /> Eine Dopplerverschiebung dieser Linien ist in unseren Spektren deutlichzu sehen. Da die innerste, Röntgenstrahlung emittierende Region des magnetohydrodynamischen Jets allerdings noch unkollimiert ist, spielt Dopplerboosting in unseren Spektren, abhängig vom Sichtwinkel, keine große Rolle. Mit unseren Resultaten konnte zum ersten Mal ein Röntgenspektrum gewonnen werden, das auf der numerischen Lösung eines magnetohydrodynamischen Jets beruht. / Jets are highly collimated flows of matter. They are present in a large variety of astrophysical sources: young stars, stellar mass black holes (microquasars), galaxies with an active nucleus (AGN) and presumably also intense flashes of gamma-rays. In particular, the jets of microquasars, powered by accretion disks, are probably small-scale versions of the outflows from AGN. <br /> <br /> Beside observations of astrophysical jet sources, also theoretical considerations have shown that magnetic fields play an important role in jet formation, acceleration and collimation. Collimated jets seem to be systematically associated with the presence of an accretion disk around a star or a collapsed object. If the central object is a black hole, the surrounding accretion disk is the only possible location for a magnetic field generation. <br /> <br /> We are interested in the formation process of highly relativistic jets as observed from microquasars and AGN. We theoretically investigate the jet collimation region, whose physical dimensions are extremely tiny even compared to radio telescopes spatial resolution. Thus, for most of the jet sources, global theoretical models are, at the moment, the only possibility to gain information about the physical processes in the innermost jet region.<br /> <br /> For the first time, we determine the global two-dimensional field structure of stationary, axisymmetric, relativistic, strongly magnetized (force-free) jets collimating into an asymptotically cylindrical jet (taken as boundary condition) and anchored into a differentially rotating accretion disk. This approach allows for a direct connection between the accretion disk and the asymptotic collimated jet. Therefore, assuming that the foot points of the field lines are rotating with Keplerian speed, we are able to achieve a direct scaling of the jet magnetosphere in terms of the size of the central object. We find a close compatibility between the results of our model and radio observations of the M87 galaxy innermost jet.<br /> <br /> We also calculate the X-ray emission in the energy range 0.2--10.1,keV from a microquasar relativistic jet close to its source of 5 solar masses. In order to do it, we apply the jet flow parameters (densities, velocities, temperatures of each volume element along the collimating jet) derived in the literature from the relativistic magnetohydrodynamic equations. We obtain theoretical thermal X-ray spectra of the innermost jet as composition of the spectral contributions of the single volume elements along the jet. Since relativistic effects as Doppler shift and Doppler boosting due to the motion of jets toward us might be important, we investigate how the spectra are affected by them considering different inclinations of the line of sight to the jet axis. <br /> <br /> Emission lines of highly ionized iron are clearly visible in our spectra, probably also observed in the Galactic microquasars GRS 1915+105 and XTE J1748-288. The Doppler shift of the emission lines is always evident. Due to the chosen geometry of the magnetohydrodynamic jet, the inner X-ray emitting part is not yet collimated. Ergo, depending on the viewing angle, the Doppler boosting does not play a major role in the total spectra. This is the first time that X-ray spectra have been calculated from the numerical solution of a magnetohydrodynamic jet.

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