Sound can propagate for long distances with a low loss of intensity in objects whose geometry acts as a guide for the sound waves; a phenomenon that can be utilised for long range testing of structures. The guided sound waves can be used to conduct materials evaluation or to detect flaws, which can be done for a relatively large region of coverage from a relatively small region of access. In particular this technology can be used to inspect or monitor large engineering structures whose structural integrity is critical for safety and the environment, such as wind turbine towers, ship hulls, and pipelines. The use of guided waves for structural inspection is complicated by the existence of many wave modes. In this thesis, the Macro Fiber Composite (MFC) is characterised for its frequency, wavelength, wave mode and direction dependent sensitivity. These devices are flexible, light and thin, and, here have been shown to have wave mode sensitivity characteristics that are favourable for some applications. The MFC is a piezoelectric actuator that can be used to excite and sense in-plane vibrations at a structures surface. The surface area of an MFC is significantly large with respect to typical wavelengths used in ultrasonic guided wave applications, which combined with their in-plane extensional nature gives rise to a significantly wave mode, frequency and direction dependent sensitivity. This can limit their application, but can also potentially be exploited for greater wave mode control. A method for simulating the output from hypothesised transducer behaviour is shown and validated for the MFC. This allows their behaviour to be predicted for new structures. It is shown that their frequency response can depend on the waveguide and can vary with direction, which can lead to wave mode transmission and reception characteristics that may be advantageous for some methods of application and detrimental to others. A novel method of adapting a flexible transducer, such as the MFC, has been developed and its characterisation is given. It is shown that through the use of a decoupling membrane, an MFC can be caused to have very different wave mode sensitivity characteristics whilst retaining their light and flexible nature. These altered characteristics are favourable for applications where shear horizontal wave modes are required. Both fully coupled MFC transducers and the adapted MFC transducers are considered for application to pipeline testing. Fully coupled MFC transducers are used for inspection using longitudinal waves, whilst the adapted MFC transducers are used with torsional waves. These arrays are compared to a current commercial tool.

There is a strong push worldwide to develop multi-Joule femtosecond duration laser pulses at wavelengths around 3.5-4 and 9-11 mu m within important atmospheric transmission windows. We have shown that pulses with a 4 mu m central wavelength are capable of delivering multi-TW powers at km range. This is in stark contrast to pulses at near-IR wavelengths which break up into hundreds of filaments with each carrying around 5 GW of power per filament over meter distances. We will show that nonlinear envelope propagators fail to capture the true physics. Instead a new optical carrier shock singularity emerges that can act to limit peak intensities below the ionization threshold leading to low loss long range propagation. At LWIR wavelengths many-body correlations of weakly-ionized electrons further suppress the Kerr focusing nonlinearity around 10 mu m and enable whole beam self-trapping without filaments.

No description available.

The aim of this study was to examine if perfluorinated alkylated substances (PFASs) reaches north of Sweden by long-range atmospheric transport. This was done by monitoring the levels of PFASs in reindeer livers at two locations in 2002 and 2010, respectively. The reindeers have lived all of their lives in the mountains and therefore the main source of exposure for PFASs is through air. The samples were extracted and analysed for 24 different PFASs using ultra performance liquid chromatography tandem mass spectrometer (UPLC-MS/MS). The most significant change concerns perfluorooctane sulfonic acid (PFOS) which decreased significantly from 6.1 ng/g at the most northern location (Ammarnäs/Biergenis) in 2002 to 0.87 ng/g 2010. At the other sampling location, Glen, PFOS decreased from 5.0 to 3.2 ng/g during the eight years. Mainly PFOS and longer chain carboxylates were found. The results revealed that the levels of many compounds decreased in time. The location seems to have an impact on the level of perfluorinated compounds present and most likely the distribution of them in the air, since certain PFASs have increased and decreased differently in time between the two locations. Since PFASs are non-volatile, they are believed to be degradation products of volatile compounds such as fluorotelomer alcohols (FTOHs) and perfluoroalkylated sulfonamido alcohols (FOSEs). FTOHs and FOSEs are released, translocated by long-range atmospheric transport and degraded to perfluorinated compounds in organisms or atmosphere.

Long-range surface plasmon-polaritons are transverse-magnetic polarized optical surface waves formed through the interaction of photons with free electrons at the surface of metal slabs or stripes. They play important roles in a variety of field such as integrated optics, amplifiers and lasers, optical sensing, modulation, etc. Due to their longer propagation length and deeper penetration depth compared to those of single-interface surface plasmon-polaritons, they have become increasingly promising in optical sensing. In sensing applications, it is necessary to reduce the noise level in order to obtain a lower detection limit. One way to achieve this is to use dual- or triple-output Mach-Zehnder interferometers so that the common perturbations among the outputs can be suppressed. The objective of this thesis is to provide deeper insights on the performances of dual- and triple-output Mach-Zehnder interferometers in thermo-optic and optical bulk sensing applications, theoretically and experimentally, and to demonstrate their ability to suppress common perturbations and lower the detection limit. On the theoretical side, the objective is approached by constructing a model for the transfer characteristic. For dual-output Mach-Zehnder interferometers, the plane-wave model is used to develop a general model for thermo-optic sensing and an unbalanced model for optical bulk sensing. For triple-output ones, local normal mode theory is used with modal analysis for the 3×3 coupler portion of the structure. Quantitative methods to analyze and compare different detection schemes are developed. The minimum detectable phase shift is determined for the case of thermo-optic sensing while the detection limit is determined for optical bulk sensing. On the experimental side, the objective is approached by providing a direct experimental demonstration of the transfer characteristics at an optimized operating wavelength for the coupler portion of the device, then comparing to theory. Time traces are carried out and various detection schemes are applied to suppress common perturbations among the outputs, and to improve the minimum detectable phase shift or the detection limit.

Diplomová práce je zaměřena na oblast rozpočtů ve firmě DATEV.cz s.r.o. V teoretické části práce je rozebrán koncept rozpočetnictví a následně je zařazen do současných teoretických rámců. Analýza problému a současné situace popisuje současný stav finančního plánování ve firmě a analyzuje firmu z pohledu manažerského účetnictví. V kapitole návrhů a přínosů řešení je navržen dlouhodobý finanční rozpočet firmy včetně investičního projektu. Cílem práce je zlepšit rozpočetnictví ve firmě na základě analýzy současné situace s přihlédnutím k současné finanční krizi.

With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. with this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. the first part (chapters 2 & 3) of the dissertation deals with the emerging field of plasmonics. Researchers have come up with various designs in an efort to fabricate efficient plasmonic waveguides capable of guiding plasmonic signals. However, the inherent dissipation in the form of Joule losses limits efficient usage of surface plasmon signal. a dielectric-metal-¬dielectric planar structure is one of the most practical plasmonic structures that can serve as an efficient waveguide to guide electromagnetic waves along the metal-dielectric boundary. I present here a theoretical study of propagation of surface plasmons along a symmetric dielectric-metal-dielectric structure and show how proper orientation of the optical axis of the anisotropic substrate enhances the propagation length. an equation for propagation length is derived in a wide range of frequencies. I also show how the frequency of coupled surface plasmons can be modulated by changing the thickness of the metal film. I propose a Kronig-Penny model for the plasmonic crystal, which in the long wavelength limit, may serve as a homogeneous dielectric substrate with high anisotropy which do not exist for natural optical crystals. in the second part (chapters 4 & 5) of the dissertation, I discuss an interesting effect of extraordinary absorption of acoustic energy due to resonant excitation of Rayleigh waves in a narrow water channel clad between two metal plates. Starting from the elastic properties of the metal plates, I derive a dispersion equation that gives resonant frequencies, which coincide with those observed in the experiment that was performed by Wave Phenomena Group at Polytechnic University of Valencia, Spain. Two eigenmodes with different polarizations and phase velocities are obtained from the dispersion equation. at certain critical aperture of the channel, an interesting cutoff effect, which is unusual for an acoustic wave, is observed for one of the eigenmodes with symmetric distribution of the pressure field. the theoretical prediction of the coupling and synchronization of Rayleigh waves strongly supports the experimentally measured shift of the resonant frequencies in the transmission spectra with channel aperture. the observed high level of absorption may find applications in designing metamaterial acoustic absorbers.

Ab initio alloy theory, formulated within the exact muffin-tin orbitals method in combination with the coherent-potential approximation, is used to determine the effect of long range order on the elastic properties. The lattice parameters and single-crystal elastic constants of Cu3Au are calculated for different partially ordered structures ranging from the fully ordered L12 to the random face centered cubic lattice. Special attention is put on the chemical and magnetic effects and on the interplay between these two degrees of freedom. For non-magnetic Cu3Au, it was found that the lattice parameters and single-crystal elastic constants follow a clear trend with the degree of chemical order: namely, C11 and C12 decrease slightly, whereas C44 remains nearly constant with increasing disorder. As none of the single-crystal elastic constants were modified significantly due to the long-range-order, the polycrystalline elastic moduli of Cu3Au also keep nearly constant upon ordering. The Debye temperature does not show a strong chemical order dependence either. Using the calculated Debye temperatures, we find that for the entropy change upon order-disorder transition varies between −0.018 kB and 0.022 kB, the upper value being surprisingly close to 0.023 kB observed in experiments. However, some of the elastic constants of ferromagnetic Ni3Fe, adopting the same crystal lattice as Cu3Au, were affected considerably. For the lattice parameter a, the main effect of magnetism is concentrated in the chemically dis-ordered region, with long-range order parameter S below ∼ 0.6 and the effect gradually disappears with increasing S. In the ferromagnetic state, the lattice parameter is almost constant as a function of the degree of order. Out of the three single-crystal elastic constants, only C11 and C12 are found to be affected by magnetism in the ordered state, however, their combined effect results in a nearly constant bulk modulus as a function of S. C44 changes slightly with S and magnetic state. The tetragonal shear elastic constant C´ , the Young’s modulus E and the shear modulus G increase significantly with the degree of order in the ferromagnetic state, but the effect becomes weak as the system approaches the random regime. Especially the C´ shear elastic constant depends strongly on the magnetic state and the degree of order. As a result, the Zener anisotropy ratio C44/C´ and the Possion’s ratio are strongly affected by the long-range order in the ferromagnetic state. Nevertheless, the actual values for the Pugh ratio and the Cauchy pressure remain far from their critical values, indicating that the ductility of Ni3Fe is not influenced by the chemical/magnetic ordering. Interestingly, the ferromagnetic L12 system possesses ∼5.4% larger elastic Debye temperature than the paramagnetic one, which in turn has similar ΘD as the chemically disordered face centered cubic phase being in either ferro-or paramagnetic state. The implications of the chemical/magnetic order on the mechanical properties and order-disorder transition is discussed. / <p>QC 20140929</p>

Using the ARFIMA-FIGARCH model, this dissertation examines the efficiency of Botswana's bond market. It focuses on the properties of the return and volatility of the Fleming Asset Bond Index (the main aggregate fixed income benchmark index in Botswana) over the period September 2009 to May 2019. The weak-form version of efficient market hypothesis (EMH) is used as a criterion to investigate the existence of long memory in both bond returns and volatility. The results of our study indicate that the Botswana bond market data follow, to a great extent, the long-range dependence which negates the precepts of the efficient market hypothesis. Furthermore, policy reforms intended to stimulate bond market reform and related efficiency gains appear not to have produced the desired outcomes as the existence of long memory is found across all sample periods. Further remedial policies are suggested to enhance market dynamism.

Bulk atmospheric deposition samples were taken every two months for a year in 2009-2010 at two sites in northern Sweden and analyzed for a suite of legacy and emerging persistent organic chemicals including legacy organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs)  and novel flame retardants (NFRs).  To further investigate the urban occurrence and contribution to remote contamination of flame retardants, indoor air, ventilation system air, and dust were sampled in several microenvironments in Stockholm during the winter of 2012 for analysis of PBDEs, isomer-specific hexabromocyclododecane (HBCDD), and NFRs.  Outdoor air and soil samples were also sampled around the same time period for analysis of the same compounds.  Five emerging pollutants were detected in atmospheric deposition: the current-use pesticides trifluralin and chlorothalonil; and the NFRs 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), 1,2-bis(tribromophenoxy)ethane (BTBPE), and Dechlorane Plus (DP).  A decrease in the fraction of the anti isomer of DP was observed at the more remote site, indicating isomer-selective degradation or isomerization during long range atmospheric transport.  The more remote site also received more total deposition of organic pollutants despite its receiving less precipitation.  Although PBDEs and emerging organic pollutants were detected, the bulk of the deposition consisted of PCBs and hexachlorocyclohexanes (HCHs) at both sites.   Several NFRs were identified in indoor and ventilation air samples including TBECH, pentabromotoluene (PBT), hexabromobenzene (HBB), 1,2-bis(pentabromodiphenyl)ethane (DBDPE), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EHTBB), and bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (TBPH).  There was no significant difference between concentrations of contaminants in ventilation system air and indoor air indicating that the flame retardants included in this study reach the outdoor environment via ventilation systems.  Dust and outdoor air samples have only been analyzed for HBCDDs so far.  HBCDD concentrations in apartments, offices, and schools were lower than reported concentrations for other countries in similar microenvironments.   However, an enrichment of α-HBCDD compared to γ-HBCDD was observed in dust taken from near treated products in stores when compared to dust taken directly from those products.  Very low concentrations of HBCDDs were detected in outdoor air.