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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.
1481

Strain Rate Sensitivity of Ti-6Al-4V and Inconel 718 and its Interaction with Fatigue Performance at Different Speeds

Juratovac, Joseph M. January 2020 (has links)
No description available.
1482

Využití moderních metod echokardiografie a magnetické rezonance v diagnostice srdeční amyloidózy. / Novel echocardiographic and magnetic resonance methods in diagnostics of cardiac amyloidosis.

Fikrle, Michal January 2020 (has links)
Amyloidosis is a term used for a whole group of diseases caused by deposition of a substance called amyloid into different tissues. Amyloid may be produced by a range of pathologic processes. Heart affliction is typical for only several types of amyloidoses. Heart involvement is then the patient`s prognosis major limiting factor. Diagnosis of heart amyloidosis is difficult especially for nonspecific symptoms and nonspecific findings obtained during common diagnostic procedures. The aim of this thesis was to evaluate usefulness of novel diagnostic methods, namely cardiac magnetic resonance with gadolinium enhancement and a simplified echocardiographic evaluation of left ventricular longitudinal strain, in diagnosing amyloid cardiomyopathy. In our first study we examined 22 patients with light chain amyloidosis by echocardiography and also with cardiac magnetic resonance with late gadolinium enhancement. We compared morphologic and functional parameters acquired by magnetic resonance examination, which is considered a gold standard for morphologic and functional measurements, with values obtained by echocardiographic measurement. Afterwards we evaluated the presence and eventually pattern of late gadolinium enhancement during cardiac magnetic resonance exam. From acquired data we conclude that the...
1483

Using molecular dynamics to quantify biaxial membrane damage in a multiscale modeling framework for traumatic brain injury

Murphy, Michael Anthony 11 August 2017 (has links)
The current study investigates the effect of strain state, strain rate, and membrane planar area on phospholipid bilayer mechanoporation and failure. Using molecular dynamics, a 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) bilayer was deformed biaxially to represent injury-induced neuronal membrane mechanoporation and failure. For all studies, water forming a bridge through both phospholipid bilayer leaflets was used as a failure metric. To examine the effect of strain state, 72 phospholipid structures were subjected to equibiaxial, 2:1 non-equibiaxial, 4:1 non-equibiaxial, strip biaxial, and uniaxial tensile deformations at the von Mises strain rate of 5.45 × 108 s-1. The stress magnitude, failure strain, headgroup clustering, and damage behavior were strain state dependent. The strain state order of detrimentality in descending order was equibiaxial, 2:1 non-equibiaxial, 4:1 non-equibiaxial, strip biaxial, and uniaxial with failure von Mises strains of 0.46, 0.47, 0.53, 0.77, and 1.67, respectively. Additionally, pore nucleation, growth, and failure were used to create a Membrane Failure Limit Diagram (MFLD) to demonstrate safe and unsafe membrane deformation regions. This MFLD allowed representative equations to be derived to predict membrane failure from in-plane strains. To examine the effect of strain rate, the equibiaxial and strip biaxial strain states were repeated at multiple strain rates. Additionally, a 144 phospholipid structure, which was twice the size of the 72 phospholipid structure in the x dimension, was subjected to strip biaxial tensile deformations to examine planar area effect. The applied strain rates, planar area, and cross-sectional area had no effect on the von Mises strains at which pores greater than 0.1 nm2 were detected (0.509 plus/minus 7.8%) or the von Mises strain at failure (0.68 plus/minus 4.8%). Additionally, changes in bilayer planar and cross-sectional areas did not affect the stress response. However, a strain rate increase from 1.4 × 108 to 6.8 × 108 s-1 resulted in a yield stress increase of 44.1 MPa and a yield strain increase of 0.17. Additionally, a stress and mechanoporation behavioral transition was determined to occur at a strain rate of ~1.4 × 108 s-1. These results provide the basis to implement a more accurate mechano-physiological internal state variable continuum model that captures lower-length scale damage.
1484

Magnetic Domains and Domain Wall Oscillations in Planar and 3D Curved Membranes

Singh, Balram 30 August 2023 (has links)
This dissertation presents a substantial contribution to a new field of material science, the investigation of the magnetic properties of 3D curved surfaces, achieved by using a self-assembled geometrical transformation of an initially planar membrane. Essential magnetic properties of thin films can be modified by the process of transforming them from a 2D planar film to a 3D curved surface. By investigating and controlling the reasons that influence the properties, it is possible to improve the functionality of existing devices in addition to laying the foundation for the future development of microelectronic devices based on curved magnetic structures. To accomplish this, it is necessary both to fabricate high-quality 3D curved objects and to establish reliable characterization methods based on commonly available technology. The primary objective of this dissertation is to develop techniques for characterizing the static and dynamic magnetic properties of self-assembled rolled 3D geometries. The second objective is to examine the origin of shape-, size- and strain/curvature-induced effects. The developed approach based on anisotropic magnetoresistance (AMR) measurement can quantitatively define the rolling-induced static magnetic changes, namely the induced magnetoelastic anisotropy, thus eliminating the need for microscopic imaging to characterize the structures. The interpretation of the AMR signal obtained on curved stripes is enabled by simultaneous visualization of the domain patterns and micromagnetic simulations. The developed approach is used to examine the effect of sign and magnitude of curvature on the induced anisotropies by altering the rolling direction and diameter of the 'Swiss-roll'. Furthermore, a time-averaged imaging technique based on conventional microscopies (magnetic force microscopy and Kerr microscopy) offers a novel strategy for investigating nanoscale periodic domain wall oscillations and hence dynamic magnetic characteristics of flat and curved structures. This method exploits the benefit of a position-dependent dwell time of periodically oscillating DWs and can determine the trajectory and amplitude of DW oscillation with sub-100 nm resolution. The uniqueness of this technique resides in the ease of the imaging procedure, unlike other DW dynamics imaging methods. The combined understanding of rolling-induced anisotropy and imaging DW oscillation is utilized to examine the dependence of DW dynamics on external stimuli and the structure's physical properties, such as lateral size, film thickness, and curvature-induced anisotropy. The presented methods and fundamental studies help to comprehend the rapidly expanding field of 3-dimensional nanomagnetism and advance high-performance magneto-electronic devices based on self-assembly rolling.
1485

Spatial Analysis of Rock Textures

Basnet, Shiva 16 October 2012 (has links)
No description available.
1486

How the Illness Experience Predicts Key Psychosocial Outcomes in Veterans with Brain Injury

Tyler, Carmen M. 15 May 2017 (has links)
No description available.
1487

MULTISCALE MULTIPHYSICS THERMO-MECHANICAL MODELING OF AN MGB<sub>2</sub> BASED CONDUCTION COOLED MRI MAGNET SYSTEM

Amin, Abdullah Al 01 February 2018 (has links)
No description available.
1488

Balkböjning och signalbehandling / Beam bending and signal processing

Forsling Ekblom, Albin, Ohlén, Rickard January 2021 (has links)
I laborationssalarna på KTH i Södertälje, som i huvudsak används till elektrorelaterade ämnen, har det funnits ett antal balkmodeller med monterade töjningsgivare. Dessa har inte använts på många år och det saknas vidare uppgifter om modellerna. Uppdraget bestod av att utarbeta en laboration till KTH:s undervisning. Laborationen skulle handla om balkböjning och signalbehandling, med tonvikt på̊ det senare. Som hjälpmedel skulle vi använda oss av balkmodellerna. I uppdraget ingick det också att undersöka balkmodellernas elektriska och mekaniska egenskaper. Med teknisk balkteori skulle en möjlig relation mellan nedböjning och töjning tas fram. Med balkmodellen i en bryggkoppling kunde dess signal via ett DAQ-kort överföras till en PC och LabVIEW för vidare behandling. I LabVIEW kan ett anpassat gränssnitt tas fram och för visning av valda parametrar. Bryggkopplingen balanseras med hjälp av en potentiometer. I gränssnittet kan spänningsförändringen i bryggan observeras när balken påverkas av nedböjning. Efter kalibrering av systemet kan töjning och nedböjning presenteras efter beräkningar i LabVIEW. För att erhålla en så stabil och brusfri signal som möjligt har gruppen använt sig avbåde ett hårdvarufilter av lågpass-typ och ett mjukvarufilter i LabVIEW. Signalen förstärks med hjälp av en OP-förstärkare innan den matas in i DAQ-kortet. Trots sin ålder kunde balkmodellerna fortfarande användas och ge stabila signaler för vidarebehandling. Modellerna kan med fördel användas i en laboration för studenter och färdigt underlag finns för detta. Laborationen bör öka förståelsen för hur en signal från en givare kan förstärkas, filtreras och behandlas vidare i detta fall för grundläggande hållfasthetsberäkningar. / In the laboratory at KTH in Södertälje, which are mainly used for electro-related subjects, there are a number of beam models with mounted strain gauges. These have not been used for many years and there is no further information about the models. The assignment consisted of preparing a laboratory task for KTH's teaching. The laboratory would consist of beam bending and signal processing, with emphasis on the latter. As an aid, the beam models will be used, these consisted of a fixed aluminum beam with mounted strain gauges. The assignment also includes examining the electrical and mechanical properties of the beam models. With technical beam theory, a possible relationship between deflection and strain would be developed. With the beam model connected in a bridge connection, its signal could be transferred via a DAQ card to a PC and LabVIEW for further processing. In LabVIEW, a custom interface can be created and for displaying selected parameters. The bridge coupling is balanced with the help of a potentiometer. In the interface, the voltage change in the bridge can be observed when the beam is affected by deflection. After calibration of the system in the interface, strain and deflection can be presented according to calculations in LabVIEW. To obtain as stable and noise-free a signal as possible, the group has used both a low-pass hardware filter and a LabVIEW software filter. The signal is amplified by an OP amplifier before being fed into the DAQ card. Despite their age, the beam models could still be used and give stable signals for further treatment. The models can be used to advantage in a laboratory for students and there is a ready basis for this. The laboratory should increase the understanding of how a signal from a sensor can be amplified, filtered and further processed in this case for basic strength calculations.
1489

Modellering av grävpålar i Plaxis 2D : En parameterstudie applicerad på nya Vårbybron, Stockholm / Modelling of bored piles in Plaxis 2D : A parametric analysis applied at the new bridge Vårbybron, Stockholm

Johansson, Josefin, Wennberg, Matilda January 2021 (has links)
I samband med Förbifart Stockholm och Tvärförbindelse Södertörn förväntas en flaskhals skapas vid Vårbybron i södra Stockholm. För att förhindra överbelastning planeras en nybyggnation där pålgrundläggning med grävpålar föreslås. Markförhållanden är ovanliga i Stockholm, med över 100 meter ned till berg. Komplexa omständigheter i området gör det nödvändigt att analysera markrörelser som verkar på grundläggningen. Syftet med studien är att undersöka horisontella- och vertikala sättningar vid ett brolandfäste. Syftet är vidare att analysera vilken typ av numerisk konstitutiv modell som är lämplig med hänsyn till studiens specifika fall och område; Mohr-Coulomb (MC), Hardening Soil (HS) och Hardening Soil med small-strain stiffness (HSS). Slutligen ska jordparametrarnas väsentlighet avgöras i en parameterstudie. Sonderingsdata tillämpas i studien för att skapa en jordlagermodell i AutoCAD Civil 3D 2019 Metric och vidare simulering av sättningar i Plaxis 2D. Vid modellering av sättningar i förekommande geologi rekommenderas att en avancerad modell används, med fördel HSS. Däremot kräver mer avancerade modeller noggranna indata för tillförlitligt resultat och ytterligare tester för styvhetsparametrar bör utföras. I detta projekt kan dyrare tester tänkas sänka slutgiltig budget, eftersom underskattning av moduler i djupa och fast lagrade jordar baserade på konservativt valda moduler ger upphov till en dyrare konstruktion. / In conjunction with the opening of the Stockholm Bypass and Tvärförbindelse Södertörn, a bottleneck is expected at the bridge Vårbybron in southern Stockholm. To prevent traffic congestion, a new construction is planned where pile foundation consisting of bored piles is proposed. The ground conditions are unusual and not typical for Stockholm involving over 100 meters distance to rock. Complex circumstances in the area makes it complicated as well as necessary to analyze ground movements. The aim of the study is to investigate horizontal- and vertical settlements at a bridge abutment. The aim is further to analyze which type of numerical constitutive model that is appropriate with respect to the specific case and area; Mohr-Coulomb (MC), Hardening Soil (HS) and Hardening Soil with small-strain stiffness (HSS). Finally, the significance of the soil parameters is to be determined in a parameter analysis. Results from soundings are used to create a geological model in AutoCAD Civil 3D 2019 Metric. Furthermore, simulation of settlements in Plaxis 2D is performed. It is recommended to apply advanced models for this type of geology, advantageously HSS. However, more advanced models require accurate input data to obtain reliable results, and additional tests for stiffness parameters must be performed for accuracy in the results. In this project, more expensive tests can be thought of as lowering the final budget, as underestimation of modules in deep and stiff soils based on conservatively selected modules leads to an unnecessarily expensive construction.
1490

Konceptframtagning och mätning av laster på kingpin / Concept generation and measurement of loads on kingpin

Albeik, Dania January 2024 (has links)
Scania, ett världsledande företag inom lastbils- och busstillverkning, strävar efter att skapa hållbara och miljövänliga produkter genom noggrann forskning och testning. Denna rapport fokuserar på att mäta de dynamiska lasterna på en kingpin, en komponent som förbinder den dragande lastbilen med trailern. All horisontell kraft överförs via kingpin, vilket gör den avgörande för lastbilens säkerhet. Standardiserade tester säkerställer att komponenterna i kopplingen är tillräckligt starka för att klara de belastningar de utsätts för. Målet med detta examensarbete är att utveckla en mätmetod för att mäta de horisontella krafterna. Denna kunskap kommer att möjliggöra utvecklingen av både fysiska och virtuella provmetoder. Mätningen av dynamiska laster på en kingpin har alltid varit utmanande på grund av dess konstruktion, som är kort och har tre hävarmar som ständigt växlar mellan lasterna. Genom att förstå kraftöverföringen mellan lastbilen och trailern kan man möjliggöra vidareutveckling, såsom optimering av energi och effektivitet på till exempel eldrivna lastbilar. I detta projekt undersöktes olika metoder för att mäta lasterna på kingpin med hjälp av en chassi hållfasthetstestrigg (CH2-testrigg). Fördelen med CH2-testriggen är att lastbilsramen inte roterar, vilket underlättar utvecklingen av lösningar som är svåra att tillämpa vid verklig körning. Ett hinder för att bedöma lösningsförslagets praktiska effektivitet är om kingpinnen får tillräckliga töjningar på grund av sin komplexa konstruktion. Därför testades ett förenklat koncept med enbart en enkel töjningsgivare för att för att undersöka denna problematik. Resultatet visade att kingpinen fick tillräckliga töjningar, vilket innebär att ett mer avancerat koncept som ger mer detaljerade och noggrannare resultat nu kan genomföras. / Scania, a world-leading company in truck and bus manufacturing, strives to create sustainable and environmentally friendly products through careful research and testing. This report focuses on measuring the dynamic loads on a kingpin, a component that connects the towing truck to the trailer. All horizontal force is transmitted via the kingpin, making it essential for the safety of the truck. Standardized tests ensure that the strength of the coupling components is sufficient to withstand the loads they are subjected to. The aim of this thesis is to develop a measurement method for measuring the horizontal forces. This knowledge will enable the development of both physical and virtual testing methods. Measuring dynamic loads on a kingpin has always been challenging due to its design, which is short and has three levers that constantly switch between loads. Understanding the force transmission between the truck and the trailer can facilitate further development, such as optimizing energy and efficiency in electric trucks. In this project, various methods were investigated to measure the loads on the kingpin using a chassis strength test rig (CH2 test rig). The advantage of the CH2 test rig is that the truck frame does not rotate, which facilitates the development of solutions that are difficult to apply in real driving conditions. A challenge in assessing the practical effectiveness of the proposed solution is whether the kingpin experiences sufficient strains due to its complex design. Therefore, a simplified concept with only a basic strain gauge was tested to examine this issue. The results showed that the kingpin experienced sufficient strains, indicating that a more advanced concept that provides more detailed and accurate results can now be implemented.

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