A resonant cavity operating in TE011 mode was used to study the adsorption response of single walled carbon nanotubes (SWCNTs) and other nanomaterials for different types of gas molecules. The range of the frequency signal as a probe was chosen as geometry dependent range between 9.1 -9.8 GHz. A highly specific range can be studied for further experiments dependent on the type of molecule being investigated. It was found that for different pressures of gases and for different types of nanomaterials, there was a different response in the shifts of the probe signal for each cycle of gassing and degassing of the cavity. This dissertation suggests that microwave spectroscopy of a complex medium of gases and carbon nanotubes can be used as a highly sensitive technique to determine the complex dielectric response of different polar as well as non-polar gases when subjected to intense electromagnetic fields within the cavity. Also, as part of the experimental work, a range of other micro-porous materials was tested using the residual gas analysis (RGA) technique to determine their intrinsic absorption/adsorption characteristics when under an ultra-high vacuum environment. The scientific results obtained from this investigation, led to the development of a chemical biological sensor prototype. The method proposed is to develop operational sensors to detect toxin gases for homeland security applications and also develop sniffers to detect toxin drugs for law enforcement agency personnel.

On considère un écoulement compressible bidimensionnel, autour d'une cavité ouverte. Des d'instabilité, auto-entretenues par l'effet de rétroaction de l'écrasement de la couche de cisaillement sur le bord aval de la cavité, génèrent des émissions acoustiques qu'il faut réduire. Des simulations numériques directes (DNS) permettent d'obtenir, avec ou sans actionnement, un modèle précis de l'écoulement. A partir des champs issus de la simulation, des décompositions orthogonales de modes propres (POD) sont proposées pour bâtir, par projection de Galerkin sur les équations isentropiques, des modèles d'ordre réduit non linéaires en prenant en compte l'actionnement (le contrôle). Pour éviter la divergence temporelle, les coefficients du système dynamique non forcé sont calibrés par diverses approches originales dont une basée sur la sensiblité modale. A partir du système dynamique forcé par un actionnement multifréquentiel (présent aussi dans les DNS), un contrôle en boucle fermée linéaire quadratique gaussien est proposé sur un système linéarisé. La reconstruction de l'état est basée sur une estimation stochastique linéaire sur 6 points de pression. Le contrôle optimal obtenu s'avère être périodique à la fréquence du second mode de Rossiter, qui est exactement celles des instabilits auto-entretenues dans la cavité. Par introduction de ce contrôle dans les simulations numériques directes, nous avons obtenu une réduction du bruit (faible) sur la fréquence du contrôle. / We consider a two dimensional compressible flow around an open cavity. The Flow around a cavity is characterised by a self-sustained mechanism in which the shear layer impinges on the downstream edge of the cavity resulting in an acoustic feedback mechanism which must be reduced. Direct Numerical Simulations (DNS) of the flow at a representative Reynolds number has been carried to obtain pressure and velocity fields, both for the case of unactuated and multi frequency actuation. These fields are then used to extract energy ranked coherent structures also called as the Proper Orthogonal Decomposition (POD) modes. A Reduced Order Model is constructed by a Galerkin projections of the isentropic compressible equations. The model is then extended to include the effect of control. To avoid the divergence of the model while integrating in time various calibration techniques has been utillized. A new method of calibration which minimizes a linear functional of error, based on modal sensitivity is proposed. The calibrated low order model is used to design a feedback control of the Linear Quadratic Gaussian (LQG) type, coupled with an observer. For the experimental implementation of the controller, a state estimate based on the observed pressure measurements at 6 different locations, is obtained through a Linear Stochastic Estimation (LSE). The optimal control obtained is periodic with a frequency corresponding to the second Rossiter mode of the cavity. Finally the control obtained is introduced into the DNS to obtain a decrease in spectra of the cavity acoustic mode.

To build multi story buildings out of timber is of a common interest in the building sector. Timber as a building material has many profits, such as the low cost, the availability and the ability to recycle it, the low carbon footprint and the workability. Although, when it comes to fire protection of buildings with a timber based structure there are challenges regarding prevention of the spread of fire while timber surface is exposed to fire. There have been cases in which timber buildings have caught fire leading to severe fire spread and ruined buildings. One example concerns a student modulus accommodation in Luleå that caught fire in august 2013. The fire started on the fourth floor after which a vertical fire spread occurred in concealed spaces between the volume modules. According to the fire investigation lack of knowledge regarding performance of detailed building solutions has led to the poor fire performance of the building. This master thesis mainly consists of a model scale tests that is prepared and performed according to the standard EN 1363-1. The purpose of the test is to investigate the performance of various cavity barriers exposed to fire. The main objective is to examine which temperatures that can be expected at different positions at various cavity barriers when using model scale test as a test method. There are two main kinds of cavity barriers: barriers that are airtight and closed inside the voids of the construction; and ventilated barriers. The most common cavity barriers are the ones that are airtight and closed. The material can be solid wood, gypsum board or mineral wool. The installation areas for these cavity barriers are anywhere, besides where the concealed spaces shall be ventilated and in every joint that shall be sealed using sealant. The ventilated cavity barriers are mounted in concealed spaces where the ventilating function is provided. These concealed spaces are often situated in, for example, ventilated attics, facades and roofs. The purpose of the ventilated barriers is to maintain the air flow in the cavity during regular conditions but also to form a protecting barrier between fire compartments when exposed to fire. The model scale test includes test apparatuses such as thermocouples and a fire resistance furnace with plate thermometers and burners. In addition, a test rig consisting of test specimens and the products to be tested are essential.  In this report, two model scale tests have been performed and prepared according to EN 1363‑1. The test period endured for four hours and the thermocouples measured the temperatures during the whole time. During the first hour the test specimens were exposed to the standard ISO 834 fire curve by controlling the burners in the furnace. After one hour the burners were turned off and the specimens were no longer exposed to fire. The measurements of the temperatures continued during three more hours. After the first two of these three hours the furnace was opened to confer more oxygen in the purpose to record any changes in the temperatures. Results of the performed experiments have indicated parameters that affect the performance of the cavity barriers. The cavity surface itself has an influence to the fire spread. The number of barriers in the cavity and the material properties of the material that is used as the cavity barrier lead to the different protection by those cavity barriers. Some of the tested barriers were plastic covered, which had effect on the performance of the cavity barriers. The dimensions of the barriers, moreover the width and the thickness, are important parameters for the proper function of the barrier. The test results indicate that glowing combustion occurs in the cavity between various cavity barriers.  It can be seen that the temperature rises when the furnace is opened. This indicates the appearance of smouldering since the combustion increases when the amount of oxygen increases, which leads to a temperature rise. Furthermore, the appearance of smouldering (glowing combustion) can be indicated by the observation of the damages of the specimens after the test. The temperatures that may be expected at the unexposed side of the cavity barrier depend on the surface material of the cavity, dimensions, and the material of the cavity barriers. Smouldering is a consequence of the temperature rise in closed cavities between cavity barriers. The performed test endured for approximately four hours and this indicates that fires in cavities can stay for a long time. To ensure the performance of various cavity barriers and verification by a model scale test it is important to perform further experiment and analyses to investigate the effects of the various parameters. To ensure the effectiveness of the performance of the cavity barriers they should be tested in cavities with various widths and various heights. Further investigation of the risk for smouldering is needed with measuring the amount of oxygen and the pressure.

<p>Atomic ions trapped in microfabricated surface traps can be utilized as a physical platform with which to build a quantum computer. They possess many of the desirable characteristics of such a device, including high fidelity state preparation and readout, universal logic gates, and long coherence times, and can be readily entangled with each other through photonic interconnects. The use of optical cavities integrated with trapped ion qubits as a photonic interface presents the possibility for order of magnitude improvements in performance in several key areas for their use in quantum computation. The first part of this thesis describes the design and fabrication of a novel surface trap for integration with an optical cavity. The trap is custom made on a highly reflective mirror surface and includes the capability of moving the ion trap location along all three trap axes with nanometer scale precision. The second part of this thesis demonstrates the suitability of small microcavities formed from laser ablated, fused silica substrates with radii of curvature in the 300-500 micron range for use with the mirror trap as part of an integrated ion trap cavity system. Quantum computing applications for such a system include dramatic improvements in the photon entanglement rate of up to 10 kHz, the qubit measurement time down to 1 microsecond, and the qubit measurement error rate down to the 1e-5 range. The final part of this thesis describes a performance simulator for exploring the physical resource requirements and performance demands to scale a quantum computer to sizes capable of implementing quantum algorithms beyond the limits of classical computation.</p> / Dissertation

A dual-wavelength mode-locked semiconductor vertical-external-cavity-surface-emitting laser is demonstrated. A semiconductor saturable absorber mirror allows for simultaneous mode locking of pulses centered at two center wavelengths with variable frequency spacing. The difference-frequency control is achieved with an intracavity etalon. Changing the finesse of the etalon enables the adjustment of the pulse duration between 6 and 35 ps. The emitted two-color pulses are modulated by a beat frequency in the terahertz range. Self-starting mode-locking with 0.8-W average output power is demonstrated.

Cavity quantum electrodynamics (cavity QED) with single atoms and single photons provides a promising route toward scalable quantum information processing (QIP) and computing. A strongly coupled atom-cavity system should act as a universal quantum interface, allowing the generation and storage of quantum information. This thesis describes the realisation of an atom-cavity system used for the production and manipulation of single photons. These photons are shown to exhibit strong sub-Poissonian statistics and indistinguishability, both prerequisites for their use in realistic quantum systems. Further, the ability to control the temporal shape and internal phase of the photons, as they are generated in the cavity, is demonstrated. This high degree of control presents a novel mechanism enabling the creation of arbitrary photonic quantum bits.

Cavity enhanced absorption spectroscopies have earned themselves a place as one of the methods of choice for sensitive absorption measurements on gas-phase samples, but their application to liquid samples has so far been more limited. Sensitive short pathlength analysis of liquid samples is required for online analysis of microfluidic samples, which are processed in channels with dimensions of tens to hundreds of micrometres. Microfluidics is important for a range of applications including drug discovery and environmental sensing. This thesis explores the application of cavity enhanced absorption spectroscopies to short pathlength (0.010 mm to 2 mm) analysis of sub-microlitre volumes of liquids. Three experimental set-ups have been been examined. Firstly, a single-wavelength cavity ringdown (CRD) spectrometer operating at 532 nm was assembled using two 99.8% reflectivity mirrors. High optical quality flow cells with short pathlengths ranging from 0.1 mm to 2 mm were inserted into this cavity at Brewster’s angle. The detection limit of the set-up with each inserted flow cell was established using a concentration series of aqueous potassium permanganate (KMnO₄) solutions. For the 1 mm flow cell, a detection limit of 29 nM KMnO₄ or 1.4 x 10⁻⁴ cm⁻¹ was established. Several different types of microfluidic devices were also inserted into the cavity, and it was found that the losses arising from the inserted chip were highly dependent on the method of chip manufacture. The CRD set-up with inserted 1 mm flow cell was applied to the detection of two important species, nitrite and iron(II), via analyte-specific colourimetric reactions. Detection limits of 1.9 nM nitrite and 3.8 nM iron(II) were established. The second experimental set-up utilised broadband, supercontinuum light generated in a 20 m length of nonlinear photonic crystal fibre. Broadband mirrors with around 99% reflectivity over the wavelength range from 400 to 800 nm were used to form the cavity, and a miniature spectrometer was used to wavelength-resolve the time-integrated cavity output. Flow cells and microfluidic chips were inserted into the cavity either at normal incidence or at Brewster’s angle. This set-up was employed for reaction analysis of an iron complexation reaction with bathophenanthroline, and for a model organic reaction, the Diels-Alder reaction between anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione. The same broadband set-up was also used for pH measurements using bromocresol green indicator solution. Using dual-wavelength CRD spectroscopy, the pH sensitivity was established to be around a few milli pH units. Finally, an alternative type of cavity, formed from a loop of optical fibre has been investigated. A novel light-coupler was designed and fabricated in 365 μm core diameter multimode optical fibre. Sample designs employing both direct and evanescent wave absorption were investigated in small-core and large-core optical fibres, and the lowest detection limit of 0.11 cm⁻¹ was determined in direct absorption measurements, with a pathlength of 180 μm, using our novel light coupler in 365 μm core diameter optical fibre.

The frequency shifts and Q changes of a resonant microwave cavity were utilized as a basis for determining microwave properties of solids and liquids. The method employed consisted of varying the depth of penetration of a cylindrical sample of the material into a cavity operating in the TM0 1 0 Mode. The liquid samples were contained in a thin-walled quartz tube. The perturbation of the cavity was achieved by advancing the sample into the cavity along the symmetry axis by employing a micrometer drive appropriately calibrated for depth of penetration of the sample. A differentiation method was used to obtain the half-power points of the cavity resonance profile at each depth of penetration. The perturbation techniques for resonant cavities were used to reduce the experimental data obtained to physical parameters for the samples. The probing frequency employed was near 9 gHz.

Whether caused by trauma, internal diseases, or spontaneously; pneumothorax and hemothorax are potentially life threatening illnesses. They are currently primarily diagnosed with x-rays, CT scans, and ultrasound imaging. While these methods are generally reliable, they are not always available to the injured patient. Life threatening pneumothoraces, such as tension pneumothorax, must be treated quickly. When diagnosed correctly, pneumothorax and hemothorax can be quickly mended through insertion of chest tubes. X-rays, CT scans, and ultrasound imaging require large scale equipment and are not always dependable. There is a more reliable, portable, and faster result producing method to diagnose pneumothorax. Vibro-acoustic waves can be sent through the chest and the resulting wave can be measured. By analyzing attenuation characteristics determined by the geometry of the chest structures, it can be determined if the patient's pleural space is healthy, contains air (pneumothrax), or contains fluid (hemothorax).

Flow control is a key factor in optimizing the performance of any vehicle moving through fluids. Particularly, in aerodynamics there are many potential benefits for implementing synthetic jets to achieve aircraft designs with less moving parts, uper- maneuverability, and separation control for fuel economy. Piezoelectric synthetic jets are of special interest because of their lightweight and low power consumption. Numerous publications on such jets are available. Actuator properties and boundary conditions relevant to this particular application however are often overlooked. The focus of this project is to numerically model synthetic jets in quiescent air to study the influence of cavity geometry and boundary conditions of the piezoelectric diaphragm on jet velocity. Numerical simulation is performed for two synthetic jet cavities of different height and orifice diameter. The numerical modeling utilizes a turbulent RNG κ – ε model and a moving boundary condition with two oscillating deflection profiles, parabolic and logarithmic, applied to the diaphragm. The actuators modeled are typical Bimorph and Thunder piezoelectric actuators. The initial conditions for the actuators are obtained experimentally resulting in 0.396mm and 0.07mm respectively when driven with a sinusoidal wave input at 1524 V/m and 4064 V/m. Although the velocity boundary numerical model gave overall better results than the current moving-boundary numerical model, the moving-boundary model is more accurate since it better approximates the movement of the diaphragm. From an optimizing viewpoint the moving boundary is more suitable to attempt to optimize the design because displacement magnitude of the diaphragm can be measured directly from experiments. For the higher displacement Bimorph actuator, a logarithmic profile matches the experimental results, whereas the parabolic profile provided better results for the relatively small displacement Thunder actuator. It is thus hypothesized that both tested actuators, Bimorph and Thunder, oscillate according to the specified logarithmic and parabolic profile respectively. Cavity height was briefly investigated for the Bimorph actuator. Results show that cavity height did not make a difference in the centerline velocity for the numerical model. The model fails to consider the important effect of the dynamic coupling of the actuator displacement and the pressure that develops inside the cavity. The pressure values obtained are comparable to the theoretical blocking pressure for the Bimorph in the cavity. The results of this study show that jet formation and development has unique characteristics for each actuator and cavity configuration. The smaller orifice cavity configuration produced a faster, longer, thinner jet with larger vortices than the bigger orifice. During max expulsion, t = 0.25T, and max ingestion, t = 0.75T, a low-pressure area localized at the corners of the orifice, inlet and exit respectively, were observed. All cavity configurations passed all three known jet formation criterions that include, Lo/Do>1, Re > 50, and Re/S2 > 0.16.