Sökning: "Boundary treatments"

Visar resultat 1 - 5 av 28 avhandlingar innehållade orden Boundary treatments.

1. 1. Perfectly Matched Layers and High Order Difference Methods for Wave Equations

   Författare :Kenneth Duru; Gunilla Kreiss; Jan Nordsröm; Ken Mattsson; Marcus Grote; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Elastic waves; Surface waves; Perfectly matched layers; High order difference methods; Stability; Summation-by-parts operators; Boundary treatments; Beräkningsvetenskap med inriktning mot numerisk analys; Scientific Computing with specialization in Numerical Analysis;

   Sammanfattning : The perfectly matched layer (PML) is a novel technique to simulate the absorption of waves in unbounded domains. The underlying equations are often a system of second order hyperbolic partial differential equations. In the numerical treatment, second order systems are often rewritten and solved as first order systems. LÄS MER

3. 2. Adhesion to machined and laser ablated wood surfaces

   Författare :Micael Stehr; KTH; []
   Nyckelord :LANTBRUKSVETENSKAPER; AGRICULTURAL SCIENCES; ablation; adhesion; checks; coating; cracks; excimer laser; gluing; IR laser; mechanical machining; mechanical weak boundary layer; microscopy; notched specimens; pine; planing; sample preparation; sawing; scanning electronmicroscopy; spruce; tip-cracks; UV laser; weak boundary layer; wood;

   Sammanfattning : This thesis is a contribution to the R&D-program ValueActivation at KTH,Division of Wood Technology and Processingand containsfive papers related to the evaluation and development ofmachining techniques (mechanical and irradiation treatments)whereby weak boundaries at the wood surfaces in the form of(mechanical) weak boundary layers and (micro) cracks due tomechanical treatment can be avoided.The first paper describes the development of a method–using a UV laser–to study the mechanically weakenedboundaries. LÄS MER

4. 3. Microstructure of Nickel-Chromium Superalloys

   Författare :Mattias Thuvander; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; segregation; TEM; nickel alloy; grain boundary; APFIM; SIMS; carbide; precipitation; ordering; boride;

   Sammanfattning : The microstructure of nickel-chromium superalloys has been investigated using several advanced microanalytical techniques; atom probe field ion microscopy (APFIM), transmission electron microscopy (TEM) together with energy dispersive X-ray analysis (EDX) and electron energy loss spectroscopy (EELS), secondary ion mass spectroscopy (SIMS) and optical microscopy (OM). The features primarily considered include precipitation, segregation and ordering. LÄS MER

5. 4. Absorption of Sound : On the effects of field interaction on absorber performance

   Författare :Anna Färm; Mats Åbom; Ragnar Glav; Susann Boij; Gareth Bennett; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Sound absorption; Porous absorbers; Bulk reaction; Local reaction; Boundary layer; Grazing flow; Temperature gradients; Surface impedance; Sound field; Pass-by noise; Vehicle and Maritime Engineering; Farkostteknik;

   Sammanfattning : Environmental noise has for decades been a well known problem, especially in urban areas. As noise requirements for vehicles are sharpened, noise reducing concepts are needed in early design stages requiring accurate simulations to support the design. LÄS MER

7. 5. Summation-by-parts formulations for flow problems

   Författare :Fredrik Laurén; Jan Nordström; Andrew Ross Winters; Martin Kronbichler; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : Many problems in engineering and physics can be described by partial differential equations (PDEs). Augmented with proper initial and boundary conditions, the PDE forms an initial-boundary value problem (IBVP). An IBVP is said to be well-posed if a unique solution bounded by the given data exists. LÄS MER