This thesis presents theoretical work on the propagation of ultra high energy cosmic rays, from their source to Earth. The different energy loss processes, resulting from cosmic ray interactions with the radiation fields, are addressed. The subsequent uncertainties in the energy loss rates and the effect produced on the arriving cosmic ray spectrum are highlighted. The question of the composition of ultra high energy cosmic rays remains unresolved, with the range of possibilities leading to quite different results in both the secondary fluxes of particles produced through cosmic ray energy loss interactions en route, and the arriving cosmic ray spectra at Earth. A large range of nuclear species are considered in this work, spanning the range of physically motivated nuclear types ejected from the cosmic ray source. The treatment of cosmic ray propagation is usually handled through Monte Carlo simulations due to the stochastic nature of some of the particle physics processes relevant. In this work, an analytic treatment for cosmic ray nuclei propagation is developed. The development of this method providing a deeper understanding of the main components relevant to cosmic ray nuclei propagation, and through its application, a clear insight into the contributing particle physics aspects of the Monte Carlo simulation. A flux of secondary neutrinos, produced as a consequence of cosmic ray energy loss through pion production during propagation, is also expected to be observed at Earth. This spectrum, however, is dependent on several loosely constrained factors such as the radiation field in the infrared region and cosmic ray composition. The range of possible neutrino fluxes obtainable with such uncertainties are discussed in this work. High energy cosmic ray interactions with the radiation fields present within the source may also occur, leading to cosmic ray energy loss before the cosmic ray has even managed to escape. The secondary spectra produced are investigated through the consideration of three candidate sources. A relationship between the degree of photo-disintegration in the source region and the neutrino flux produced through p γ interactions is found.

<p>High-energy neutrinos are capable of carrying information over vast distances, and neutrino telescopes such as AMANDA-II provide the means to probe deep inside the violent and energetic interior of the universe. AMANDA-II is located in the glacial ice at South Pole in Antarctica and is optimised to detect Cherenkov emission from neutrino-induced muon tracks with energies above 100 GeV. </p><p>Data acquired in 2003 with the AMANDA-II detector were searched for a non-localised flux of neutrinos with energies in excess of 1 PeV. Because of the energy dependence of the neutrino mean free path, the Earth is essentially opaque to neutrinos above PeV energies. Combined with the limited overburden of the AMANDA-II detector (about 1.5 km), this means that a potential ultra-high energy neutrino signal will be concentrated at the horizon. The background for the analysis consists of large bundles of muons produced in atmospheric air showers. Owing to their energy losses, muons cannot penetrate the Earth, and the background will be downwards moving. </p><p>After applying different selection criteria, one event was observed in the final data sample, while 0.16±0.04 background events are expected. The corresponding 90% confidence level upper limit is 4.3. The expected number of neutrino signal events for a 10^-6 <i>E</i>^-2 GeV/(s sr cm² ) flux assuming a Φ(ν_e) : Φ(ν_μ) : Φ(ν_τ) = 1:1:1 flavour ratio is 4.1±0.2, yielding an upper limit on the all-flavour neutrino flux of <i>E</i>² Φ₉₀ ≤ 1.1∙10^-6 GeV/(s sr cm² ), including systematics and with the central 90% of the signal found in the energy range 480 TeV - 1.6 EeV. </p>

The width of an ultra high-power laser diode is greater than 50 £gm and more than 20 times of low-power laser diode.The core diameter of Erbium Doped Fiber Amplifier fiber (EDFA) is 4~6 £gm and it is a single-mode fiber (SMF).However¡Athe ultra high-power laser diode is multi-mode laser. Therefore¡Athe mismatch between high-power laser and SMF resulting in low coupling efficiency. We improve coupling efficiency by using a wedge-shaped graded-index fiber (GIF) tip spliced to a SMF then fused a fiber bragg grating (FBG) to form an external cavity laser. The GIF is a focusing action like a graded-index fiber. From near-field pattern (NFP)¡Awe find the best GIF length is 400 £gm. The coupling efficiency between ultra high-power laser diode and wedge-shape lensed fiber is only 5% .

Current thinking suggests that specialised modules process visual information in a hierarchical manner, using local circuitry in order to maximise efficiency both in terms of wiring costs and stimulus coverage (Reichl et al. (2012)). The resulting organisation has been shown to contain structure in the form of stripes, columns and pinwheels, which in animal models have been linked to functional segregation and specificity. In human cortex, post-mortem investigations have assisted in the visualisation of two such key features: ocular dominance columns (ODC) within V1, and a stripe system within V2 (Adams et al. (2007); Hockfield et al. (1990)). However, functional observations in humans have until recently been beyond the investigatory scope of in-vivo methodology, and as such, a role of these networks has yet to be conclusively determined. In the small number of instances of in-vivo investigations of human ODC and V2 stripes (Cheng et al. (2001); Yacoub et al. (2001); Nasr et al. (2016)), data have been acquired for a small number of carefully selected participants over long scan durations. I aimed to overcome these limitations and explore the functional similarities further, employing a novel, ultra-high resolution fMRI sequence to do so. I measured the cortical response to monocular stimulation and recorded a robust response within V1. However, the regular and repeating functional patterns of ODCs were not observed. Using multivariate techniques I concluded, based on robust classification, that reliable monocular signals were present but that they were subtle and difficult to differentiate from noise. I then investigated the segregation of colour, form and motion within V2, where I found evidence for spatially segregated signals in response to colour and motion, but not to form. I hypothesised that the form stimulus was sub-optimal in driving the neural population of the associated stripes. Based on a limited number of samples, activity in response to colour and motion stimulation conformed on average to the neuroanatomical profile of the V2 stripe system. I suggest that my results offer encouragement for in-vivo investigations of small-scale functional organisation in visual cortex.

The concrete technology has during the last century changed dramatically where the concept of high strength concrete has gone from 30MPa to well over 100MPa. UHPC has many areas of application and is used more and more frequently in all manner of structures. It is also a suitable concrete in areas and environments that are demanding and harsh for the concrete due to its overall excellent durability properties which suggest lifespans of reinforced structure elements that far exceeds what is economically available to design for today with a low cost of maintenance. The aim of this research was to produce Ultra High-Performance Concrete using mostly locally available materials. Tests were made on the binary materials where the particle packing was optimized through the Punkte method. A series of smaller mortar mixes was made where the effect of different proportions of i.e. silica fume, flyash, superplasticizer had on the concrete mix. The fresh and hardened properties of the mix as mini cone flow, slump flow, density, compressive strength and flexural strength was evaluated to obtain a mix which exhibited the properties sought for, high strength and good workability. The results showed that it is difficult to find an optimum mixture since the design of a recipe always has compromises and rarely all criteria’s can be met fully. The concrete produced had a W to C ratio between 0,21, 20wt% of silica fume, 4,5wt% of superplasticizer and max filler size of 1mm. Some mixes of the concrete were also produced with flyash replacement and with steel fibers. This resulted in concretes exhibiting compressive strength over 140MPa, flexural strength of 18MPa without fiber reinforcement and with self-consolidating properties. The replacement of cement with 30wt% of flyash resulted in better workability and long term(1year) compressive strength almost equaled the concrete without flyash replacement.

Yes / This paper evaluates the influence of mineral admixtures partially replacing cement, sea sand replacing quartz, sea water replacing fresh water on ultra-high performance concrete (UHPC). The fluidity and mechanical properties were studied. Besides, the impermeability, chloride resistance and freeze-thaw resistance were investigated. Failure modes, scanning electron microscope (SEM) analysis, mass loss, relative dynamic modulus of elasticity and mechanical properties of UHPCs after freeze-thaw cycles were conducted. The results showed the fluidity of UHPC paste gradually increases with the improvement of water-binder ratio. It is recommended that the water-binder ratio of UHPC be set at 0.19. The fluidity also increases with the improvement of the content of slag, fly ash and water reducer, but decreases with the improvement of silica fume content. The flexural and compressive strengths of UHPC enhance with the improvement of the content of silica fume, but reduce with the improvement of the content of fly ash and slag. The UHPCs made of quartz sand, river sand and sea sand, all, achieve a high strength. UHPCs prepared at standard curing conditions, with or without steel fibers, mixed by artificial seawater and made of sea sand, exhibited excellent impermeability and chloride resistance. The frost resistant grade of all UHPC specimens prepared by standard curing are greater than F500 exhibiting excellent freeze-thaw resistance and sustainability.

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Understanding mechanisms at the molecular level is essential for interpreting and predicting the outcome of processes in all fields of chemistry. Insight into gas-surface reaction dynamics can be gained through molecular beam scattering experiments combined with classical trajectory simulations. In particular, energy exchange and thermal accommodation in the initial collision, the first step in most chemical reactions, can be probed with these experimental and computational tools. There are many questions regarding the dynamic details that occur during the interaction time between gas molecules and organic surfaces. For example, how does interfacial structure and density affect energy transfer? What roles do intramonolayer forces and chemical identity play in the dynamics? We have approached these questions by scattering high-energy, rare gas atoms from functionalized self-assembled monolayers. We used classical trajectory simulations to investigate the atomic-level details of the scattering dynamics. We find that approximately six to ten carbon atoms are involved in impulsive collision events, which is dependent on the packing density of the alkyl chains. Moreover, the higher the packing density of the alkyl chains, the less energy is transferred to the surface on average and the less often the incident atoms come into thermal equilibrium with the surface. In addition to the purely hydrocarbon monolayers, organic surfaces with lateral hydrogen-bonding networks create more rigid collision partners than surfaces with smaller inter-chain forces, such as van der Waals forces. Finally, we find some interesting properties for organic surfaces that possess fluorinated groups. For argon scattering, energy transfer decreases with an increasing amount of surface fluorination, whereas krypton and xenon scattering transfer most energy to monolayers terminated in CF₃ groups, followed by purely hydrocarbon surfaces, and then perfluorinated surfaces. / Ph. D.