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Visar resultat 1 - 5 av 484 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Dynamical Analysis of Terahertz Quantum Cascade Lasers

   Författare :Denizhan Ekin Önder; NanoLund: Centre for Nanoscience; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Terahertz; quantum cascade lasers; electric field domains; chaos; simulation; Fysicumarkivet A:2023:Önder;

   Sammanfattning : This thesis focuses on various aspects in terahertz quantum cascade lasers such as high temperature performances, electrical instabilities and chaos. In the first part of the thesis, an introduction to the topic and the non equilibrium Green's function package applied is given with particular emphasise on the inhomogeneous domain model and the chaos theory. LÄS MER

3. 2. Carbon Dioxide in Supermarket Refrigeration

   Författare :Samer Sawalha; Björn Palm; Eckhard Groll; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; CO2; carbon dioxide; refrigeration system; supermarket; cascade; indirect; trans-critical; modelling; simulation; experiment; safety analysis; comparison; Mechanical energy engineering; Mekanisk energiteknik;

   Sammanfattning : This thesis theoretically and experimentally investigates different aspects of the application of CO2 in supermarket refrigeration. Theoretical analysis has been performed using computer simulation models developed to simulate CO2 indirect, NH3/CO2 cascade, CO2 trans-critical and direct expansion (DX) R404A systems. LÄS MER

4. 3. Dynamic properties of two-dimensional and quasi-geostrophic turbulence

   Författare :Andreas Vallgren; Erik Lindborg; Guido Boffetta; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; two-dimensional turbulence; decaying turbulence; quasi-geostrophic turbulence; direct numerical simulation DNS ; coherent vortices; energy cascade; enstrophy cascade; intermittency; massively parallel simulations; locality iii; Non-linear dynamics; chaos; Icke-linjär dynamik; kaos;

   Sammanfattning : Two codes have been developed and implemented for use on massively parallelsuper computers to simulate two-dimensional and quasi-geostrophic turbulence.The codes have been found to scale well with increasing resolution and width ofthe simulations. LÄS MER

5. 4. The role of young-of-the-year fish in lake ecosystems

   Författare :Pia Romare; Biologiska institutionen; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Hydrobiology; Rutilus rutilus; Perca fluviatilis; diet-dependent growth; density dependent growth; behavioural cascade; 0 fish behaviour; horizontal echo sounding; biomanipulation; trophic cascade; predation pressure; young-of-the-year fish; trophic interactions; marine biology; aquatic ecology; limnology; Marinbiologi; limnologi; akvatisk ekologi; Ecology; Ekologi;

   Sammanfattning : Food chain theory is based on consumption; that is, presupposing that the only important interaction between organisms is that they actually meet in an unstructured environment and that one of them is consumed. Recently, studies, including biomanipulation projects, have indicated that trophic interactions are more complex than predicted by food chain theory. LÄS MER

7. 5. GaN HEMT Low Noise Amplifiers for Radio Base Station Receivers

   Författare :Pirooz Chehrenegar; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; gallium nitride GaN ; radio base station receiver; cascode; high linearity; robustness.; cascade; high electron mobility transistor HEMT ; low noise; low noise amplifier;

   Sammanfattning : Gallium nitride (GaN) high electron mobility transistor (HEMT) has been introduced as the technology of choice for high power microwave applications due to its material properties including high saturation electron velocity and breakdown field together with excellent thermal conductivity and robustness.It is also a promising candidate for receiver front-ends in the radio base station(RBS) where low noise figure and high linearity are key issues for low noiseamplifier (LNA) design. LÄS MER