In the last decade acoustic noise has become more and more regarded as a problem. In cars, boats, trains and aircraft, low-frequency noise reduces comfort. Lightweight materials and more powerful engines are used in high-speed vehicles, resulting in a general increase in interior noise levels. Low-frequency noise is annoying and during periods of long exposure it causes fatigue and discomfort. The masking effect which low-frequency noise has on speech reduces speech intelligibility. Low-frequency noise is sought to be attenuated in a wide range of applications in order to improve comfort and speech intelligibility. The use of conventional passive methods to attenuate low-frequency noise is often impractical since considerable bulk and weight are required; in transportation large weight is associated with high fuel consumption. In order to overcome the problems of ineffective passive suppression of low-frequency noise, the technique of active noise control has become of considerable interest. The fundamental principle of active noise control is based on secondary sources producing ``anti-noise.'' Destructive interference between the generated and the primary sound fields results in noise attenuation. Active noise control systems significantly increase the capacity for attenuating low-frequency noise without major increase in volume and weight. This doctoral dissertation deals with the topic of active noise control within the passenger cabin in aircraft, and within headsets. The work focuses on methods, controller structures and adaptive algorithms for attenuating tonal low-frequency noise produced by synchronized or moderately synchronized propellers generating beating sound fields. The control algorithm is a central part of an active noise control system. A multiple-reference feedforward controller based on the novel actuator-individual normalized Filtered-X Least-Mean-Squares algorithm is introduced, yielding significant attenuation of such period noise. This algorithm is of the LMS-type, and owing to the novel normalization it can also be regarded as a Newton-type algorithm. The new algorithm combines low computational complexity with high performance. For that reason the algorithm is suitable for use in systems with a large number of control sources and control sensors in order to reduce the computional power required by the control system. The computational power of the DSP hardware is limited, and therefore algorithms with high computational complexity allow fewer control sources and sensors to be used, often with reduced noise attenuation as a result. In applications, such as controlling aircraft cabin noise, where a large multiple-channel system is needed to control the relative complex interior sound field, it is of great importance to keep down the computational complexity of the algorithm so that a large number of loudspeakers and microphones can be used. The dissertation presents theoretical work, off-line computer experiments and practical real-time experiments using the actuator-individual normalized algorithm. The computer experiments are principally based on real-life cabin noise data recorded during flight in a twin-engine propeller aircraft and in a helicopter. The practical experiments were carried out in a full-scale fuselage section from a propeller aircraft. / Buller i vår dagliga miljö kan ha en negativ inverkan på vår hälsa. I många sammanhang, i tex bilar, båtar och flygplan, förekommer lågfrekvent buller. Lågfrekvent buller är oftast inte skadligt för hörseln, men kan vara tröttande och försvåra konversationen mellan personer som vistas i en utsatt miljö. En dämpning av bullernivån medför en förbättrad taluppfattbarhet samt en komfortökning. Att dämpa lågfrekvent buller med traditionella passiva metoder, tex absorbenter och reflektorer, är oftast ineffektivt. Det krävs stora, skrymmande absorbenter för att dämpa denna typ av buller samt tunga skiljeväggar för att förhindra att bullret transmitteras vidare från ett utrymme till ett annat. Metoder som är mera lämpade vid dämpning av lågfrekvent buller är de aktiva. De aktiva metoderna baseras på att en vågrörelse som ligger i motfas med en annan överlagras och de släcker ut varandra. Bullerdämpningen erhålls genom att ett ljudfält genereras som är lika starkt som bullret men i motfas med detta. De aktiva bullerdämpningsmetoderna medför en effektiv dämpning av lågfrekvent buller samtidigt som volymen, tex hos bilkupen eller båt/flygplanskabinen ej påverkas nämnvärt. Dessutom kan fordonets/farkostens vikt reduceras vilket är tacksamt för bränsleförbrukningen. I de flesta tillämpningar varierar bullrets karaktär, dvs styrka och frekvensinnehåll. För att följa dessa variationer krävs ett adaptivt (självinställande) reglersystem som styr genereringen av motljudet. I propellerflygplan är de dominerande frekvenserna i kabinbullret relaterat till propellrarnas varvtal, man känner alltså till frekvenserna som skall dämpas. Man utnyttjar en varvtalssignal för att generera signaler, så kallade referenssignaler, med de frekvenser som skall dämpas. Dessa bearbetas av ett reglersystem som generar signaler till högtalarna som i sin tur generar motljudet. För att ställa in högtalarsignalerna så att en effektiv dämpning erhålls, används mikrofoner utplacerade i kabinen som mäter bullret. För att åstadkomma en effektiv bullerdämpning i ett rum, tex i en flygplanskabin, behövs flera högtalare och mikrofoner, vilket kräver ett avancerat reglersystem. I doktorsavhandlingen ''Active Control of Propeller-Induced Noise in Aircraft'' behandlas olika metoder för att reducera kabinbuller härrörande från propellrarna. Här presenteras olika strukturer på reglersystem samt beräkningsalgoritmer för att ställa in systemet. För stora system där många högtalare och mikrofoner används, samt flera frekvenser skall dämpas, är det viktigt att systemet inte behöver för stor beräkningskapacitet för att generera motljudet. Metoderna som behandlas ger en effektiv dämpning till låg beräkningskostnad. Delar av materialet som presenteras i avhandlingen har ingått i ett EU-projekt med inriktning mot bullerundertryckning i propellerflygplan. I projektet har flera europeiska flygplanstillverkare deltagit. Avhandlingen behandlar även aktiv bullerdämpning i headset, som används av helikopterpiloter. I denna tillämpning har aktiv bullerdämpning används för att öka taluppfattbarheten.

Quantum computers are appealing for their ability to solve some tasks much faster than their classical counterparts. In fact, they have a potential to perform the full configuration interaction (FCI) energy calculations with a polynomial scaling only. This is in contrast to con- ventional computers where FCI scales exponentially. We provide a detailed description of the quantum version of the FCI method and the results of numerical simulations of the ground and excited state energy calculations of the methylene molecule. We further generalize this method to the relativistic four component regime and show how to efficiently solve the eigenproblem of the Dirac-Coulomb(-Breit) Hamiltonian on a quantum computer. We demonstrate the func- tionality of the proposed procedure by numerical simulations of computations of the spin-orbit splitting in the SbH molecule. Finally, we propose quantum circuits with 3 qubits and 9 or 10 CNOTs, which implement a proof-of-principle relativistic quantum chemical calculation for this molecule and might be suitable for an experimental realization. 1

Une étude théorique ab initio des structures électroniques des molécules Diatomiques polaires BN, SiN et LaH dans la représentation 2s+1Λ(+/-)Ont été effectués par la méthode du champ auto-cohérent de l'espace Actif complet (CASSCF), suivie par l'interaction de la configuration multiréférence (MRSDCI). La correction de Davidson, notée (MRSDCI+ Q), a ensuite été appliquée pour rendre compte de clusters ou agrégats quadruples non liés. L'ensemble de l'espace de configuration de CASSCF a été utilisé comme référence dans le calcul MRCI, qui a été effectués en utilisant le programme de calcul de chimie physique MOLPRO et en tirant parti de l'interface graphique Gabedit. Quarante-deux de plus bas états électroniques dans la représentation 2s+1Λ(+/-)au-dessous de 95000 cm-1 ont été étudiés de la molécule BN. Alors que vingt-huit états électroniques dans les représentations 2s+1Λ(+/-) jusqu'à 70000 cm-1 de la molécule de SiN ont été étudiés. D'autre part, les vingt-quatre bas états électroniques de LaH dans les représentations 2s+1Λ(+/-) au-dessous de 70000 cm-1 ont été étudiées par deux méthodes différentes et en prenant en considération l'effet des spin-orbite de la molécule LaH et nous avons observé la division énergétique des huit états électroniques. Les courbes d'énergie potentielle ont été construites avec la fréquence co-harmonique ωe, la distance internucléaire de l'équilibre re, les constantes de rotation Be. L'énergie électronique par rapport à l'état fondamentale Te a été calculé pour les états électroniques considérés comme des BN, SiN et la molécule LaH respectivement. En utilisant l'approche des fonctions canoniques, les valeurs propres Ev, les constantes rotationnelles Bv, la constante de distorsion centrifuge Dv et les abscisses des points de retournement Rmin and Rmax ont été calculés pour les états électroniques au niveau de vibration v=51 pour LaH molécule. Dix-huit et neuf états électroniques ont été étudiées pour la molécule BN et SiN respectivement. Pour LaH, vingt-trois états électroniques de la molécule LaH et l'effet de spin-orbite de molécule LaH sont donnés ici pour la première fois. La comparaison avec les données expérimentales et théoriques pour la plupart des constantes calculées démontre une très bonne précision. Enfin, ces résultats devraient ainsi mener à des études expérimentales plus poussées pour ces molécules. Nos résultats ont été publiés dans le Canadian Journal of Chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer, nous avons deux autres articles en préparation à soumettre. / In the present work a theoretical investigation of the lowest molecular states of BN, SiN and LaH molecule, in the representation 2s+1Λ(+/-), has been performed via complete active space self-consistent field method (CASSCF) followed by multireference single and double configuration interaction method (MRSDCI). The Davidson correction noted as (MRSDCI+Q) was then invoked in order to account for unlinked quadruple clusters. The entire CASSCF configuration space was used as a reference in the MRCI calculation which has been performed via the computational chemistry program MOLPRO and by taking advantage of the graphical user interface Gabedit. Forty-two singlet, triplet, and quintet lowest electronic states in the 2s+1Λ(+/-) representation below 95000 cm-1 have been investigated of the molecule BN. While twenty-eight electronic states in the representation2s+1Λ(+/-)up to 70000 cm-1 of the SiN molecule have been investigated.On the other hand the Twenty four low-lying electronic states of LaH in the representation 2s+1Λ(+/-) below 35000 cm-1 have been studied by two different methods and by taking into consideration the spin orbit effect of the molecule LaH we give in the energy splitting of the eight electronic states. The potential energy curves (PECs) together with the harmonic frequency ωe, the equilibrium internuclear distance re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for the considered electronic states of BN, SiN and LaH molecule respectively. Using the canonical functions approach, the eigenvalues Ev, the rotational constants Bv ,the centrifugal distortion constants Dv and the abscissas of the turning points Rmin and Rmax have been calculated for electronic states up to the vibrational level v =51 for LaH molecule.Eighteen and Nine electronic states have been investigated here for the first time for the molecules of BN and SiN respectively, while for LaH, news results are performed for twenty three electronic states of LaH molecule and the spin-orbit effect of LaH molecule is given here for the first time. A comparison with experimental and theoretical data for most of the calculated constants demonstrated a very good accuracy. Finally, we expect that the results of our work should invoke further experimental investigations for these molecules. Our results have been published in Canadian journal of chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer and we have two other papers in preparation to submit.