Traditionellt har större fartyg bestyckade med ekolod använts för att utföra batymetriska mätningar av sjö- och havsbottnar. Att utföra mätningar i grunda vatten har varit problematiskt eftersom större fartyg inte kan nå dessa grunda vatten. För att tackla det problemet har mindre obemannade ytfarkoster (USV) utvecklats för att mäta grunda vatten. Dessa USVs hjälper även till vid områden nära stenar som inte har fått uppdaterade djupvärden. Den här undersökningens syfte är att utvärdera hur en Seafloor HydroLite TM enkelstrålsekolod monterad på en USV skiljer sig från insamlingsmetoderna GNSS och med måttband. Den syftar även till att utvärdera vilken interpolationsteknik som är mest lämpad för skapande av djupmodeller med enkelstrålsekolodsdata. Det kommer också studeras hur tvärsektioner påverkar djupmodellerna skapade med enkelstrålsekolod. De experimentella mätningarna med GNSS, måttband och enkelstrålsekolod utfördes i sjön Öjaren som ligger utanför Sandviken. I undersökningen inmättes totalt 91 punkter med GNSS och måttband samt 8 mätstråk och 9 tvärsektioner med enkelstrålsekolod monterad på en USV. Djupmodellerna skapades i Surfer 10 med interpolationsteknikerna kriging, natural neighbor och triangulation with linear interpolation. Alla beräkningar genomfördes i Microsoft Excel och data insamlat med måttband ansågs vara det sanna värdet vid jämförelsen mellan insamlingsmetoderna. Resultaten visade att djupmodellerna skapade med GNSS-data är snarlika till djupmodellerna skapade med måttbandsdata samt att djupmodellerna med GNSS-data visar på den minsta skillnaden mot djupmodellerna skapade med enkelstrålsekolodsdata. Resultatet från jämförelsen mellan interpolationsteknikerna visar på att användandet av de olika interpolationsteknikerna inte har en signifikant påverkan på djupmodellen. Våra slutsatser av undersökningen blev att användande av ett enkelstrålsekolod kan bidra till att skapa en mer detaljerad djupmodell än om enbart GNSS eller måttbandsdata används. Det är också en mer kostnadseffektiv metod eftersom mer data kan samlas in på kortare tid. Det kan dock uppstå felmätningar vid insamlade av data med enkelstrålsekolod som kan vara svåra att upptäcka. Tilläggande av tvärsektioner kan bidra till att skapa en ännu mer detaljerad djupmodell och kan användas som kontrollpunkter vid kontroll av enkelstrålsekolodsdata. / Traditionally, large vessels armed with echo sounders have been used to conduct bathymetric surveys of the seas and oceans. Conducting surveys of shallow water have been troublesome since larger vessels cannot reach and survey shallow waters. To tackle that problem smaller unmanned surface vessels (USV) have been developed to survey shallow waters. It also helps in the areas closest to rocks that do not have updated depth measurements. This study aims to assess how a Seafloor HydroLite TM single-beam echo sounder mounted on a USV differs from other surveying methods. It also aims to evaluate which interpolation methods is most suitable for creating depth models by utilizing single-beam echo sounder data. It will also be studied how cross section lines affect the created depth using the USV. The experimental surveys with GNSS, measuring tape and single-beam echo sounder were used in the lake Öjaren that is located outside of Sandviken. In this study a total of 91 points were collected with GNSS and measuring tape and 8 sounding lines and 9 cross sections lines were collected using echo sounder mounted on the USV. The depth models were created in Surfer 10 using different interpolation methods i.e. kriging, natural neighbor and triangulation with linear interpolation. All calculation were performed in Microsoft Excel and the measurements collected with measuring tape were assumed as a “true” value to evaluate the different surveying techniques. The results showed that the depth model obtained using GNSS data is close to the depth model created using measuring tape data and shows lowest difference in comparison to the USV technique. The results from the comparison between interpolation methods showed that the use of different interpolation methods not have a significant impact on the depth model. The study concludes that the use of a single-beam echo sounder can help to create a more detailed depth model than using GNSS or measuring tape. It is also a cost effective method that helps collect more data in a short time. Though, some errors can appear in the data collected using the single-beam echo sounder that can be hard to detect. The cross section lines can contribute to a more detailed depth model and can be used as control points.

The soft x-rays (wavelengths less than 30 nm) emitted by the sun are responsible for the production of high energy photoelectrons in the D and E regions of the ionosphere, where they deposit most of their energy. The photoelectrons created by this process are the main drivers for dissociation of nitrogen ($N_2$) molecules in the altitude range below 200 km. The dissociation of $N_2$ is one of main mechanisms responsible for the production of nitric oxide (NO) at these altitudes. These processes are important to understand because NO plays a critical role in controlling the temperatures of various regions of Earth's atmosphere. In order to estimate the dissociation rate of $N_2$ we need its dissociation cross-sections. The dissociation cross-sections of $N_2$ due to inelastic collisions with electrons is primarily es- timated from the cross-sections of its excitation states (using predissociation factors) and dissociative ionization channels. Predissociation is the transition without emission of radi- ation from a stable excited state to an unstable excited state of a molecule that leads to dissociation. Unfortunately, the lack of cross-section data, particularly at high electron en- ergies and of higher excited states of N 2 and N 2 + , introduces uncertainty in the dissociation cross-section and subsequently the dissociation rate calculation, which leads to uncertainties in the NO production rate. We have updated a photoelectron model with thoroughly-revised electron impact cross- section data of all major species and experimentally determined predissociation factors. The dissociation rates of $N_2$ using this model are compared to the dissociation rates obtained using another existing (Solomon and Qian [2005]) model. A parameterized version of the updated dissociation rates are used in a one-dimensional global average thermospheric/ ionospheric model, ACE1D (Atmospheric Chemistry and Energetics), to obtain the updated production rates of NO. In the final chapter, we use the ACE1D model to show that the energies deposited by the solar soft x-rays in the lower thermosphere at altitudes between 100 -150 km affect the temperature of the Earth's thermosphere at altitudes well above 300 km. By turning off the input solar flux in the different wavelength bins of the model iteratively, we are able to demonstrate that the maximum change in exospheric temperature is due to changes in the soft solar x-ray bins. We also show, using the thermodynamic heat equation, that the molecular diffusion via non-thermal photoelectrons is the main source of heat transfer to the upper ionosphere/thermosphere. Moreover, these temperature changes and heating effects of the solar soft x-rays are comparable to that of the much stronger He II 30.4nm emission. Finally, we show that the uncertainties in the solar flux irradiance at these soft x-rays wavelengths result in corresponding uncertainties in the modeled exospheric temperature, and these uncertainties increase substantially with increased solar activity. / Doctor of Philosophy / The radiation from the sun covers a wide range of the electromagnetic spectrum. The soft x-rays with wavelengths less than 30 nm are the most energetic and variable part of the spectrum, and would have detrimental effects on humans were they not absorbed by the atmosphere. The absorption of soft x-rays by the Earth's atmosphere at altitudes near 100- 150 km creates ionized and energized particles. These energetic changes can affect and even damage the satellites in low Earth orbit, and can cause radio communication blackouts and radiation storms (large quantities of energetic particles, protons and electrons accelerated by processes at and near the Sun). Therefore, we need to have good models that can quantify these changes in order to correctly predict their effects on our atmosphere, and help to mitigate any harmful effects. The soft x-rays and the extreme ultraviolet (EUV) are responsible for ionization of the major neutral species, $N_2$ , $O_2$ and O, in the Earth's atmosphere, which leads to the production of ions and energetic photoelectrons. These high energy photoelectrons can cause further ion- ization, excitation and dissociation. We study the dissociation of $N_2$ by these photoelectrons to create neutral N atoms. The N atoms created via this process combine with the $O_2$ in the atmosphere to produce nitric oxide (NO), which is one of the most important minor constituents because of its role in regulating atmospheric heating/cooling. The production of NO peaks near 106 km altitude, where most of the energy of the soft x-rays are deposited. However, they also affect the temperature of the upper atmosphere well above this altitude. This is because the energy of the photoelectrons is conducted to the upper atmosphere by collisions of electrons and ions with ambient neutral atoms and molecules, thus increasing their temperature. In this study, we use modeling of soft x-ray irradiance, photoelectron ionization, excitation and dissociation rates and atmospheric neutral temperature to quantify the effects of soft x-rays on the Earth's atmosphere.

The AASHTO LRFD design specifications and the AASHTO manual for bridge evaluation are consistently revised using knowledge of previous bridge failures. Although modern steel structures are designed to resist fatigue cracking from service loads, cracks in the tension flanges of steel bridge girders have been observed as a result of stress concentrations, design errors, welding quality control, and vehicular impacts. Cracks can grow in size with time and active cyclic live loads and may result in a member fracture. Fracture is a dangerous limit state which occurs with little to no warning. One method to quantify the stress field in the vicinity of a crack tip is by calculating the Stress Intensity Factor (SIF) around the crack tip. Finding SIFs for a cracked geometry may help an engineer to determine the fracture potential based on crack dimensions found during the inspection. Rolled I-beam and steel plate girders are extensively used as bridge superstructure members to efficiently carry live loads. This research was focused on determining Stress Intensity Factors (SIFs) of partially cracked I-sections using Finite Element Analysis. Two different tension flange crack profiles were studied: edge cracks, and full-width cracks. The SIF solutions were further used to study the fracture behavior and stress redistribution in the partially cracked flexural I-shaped members. / Master of Science / Steel is one of the fundamental materials used in the construction of bridge structures, and steel girder bridges are one of the most common types of bridge structures seen in the United States. Past bridge failures have helped engineers to understand shortcomings in design specifications, and AASHTO codes have been developed and revised over the years to reflect an improved understanding and evolution of engineering behavior. Engineers must make sure that a design is robust enough for functional use of the component during its service life. It is also equally important to understand the potential chances of failure and make the structure strong enough to overcome any failure mechanisms. Fracture is one structural failure mode which occurs with little to no warning and hence is very dangerous. One efficient way to quantify the stress field in the vicinity of a crack tip is by calculating the Stress Intensity Factor (SIF) around a crack tip. Fracture literature is available which describes different methods of determining SIFs for cracked members. However, there are no solutions available to find a SIF of a partially cracked flexural I-shaped members. This research was focused on determining Stress Intensity Factors and studying the fracture behavior of partially cracked I-sections using Finite Element Analysis. The resulting SIF solutions were further used to study the fracture behavior and stress redistribution in partially cracked flexural I-shaped members.

Oxidation flow reactors (OFRs) using low-pressure Hg lamp emission at 185 and 254 nm produce OH radicals efficiently and are widely used in atmospheric chemistry and other fields. However, knowledge of detailed OFR chemistry is limited, allowing speculation in the literature about whether some non-OH reactants, including several not relevant for tropospheric chemistry, may play an important role in these OFRs. These non-OH reactants are UV radiation, O(¹D), O(³P), and O₃. In this study, we investigate the relative importance of other reactants to OH for the fate of reactant species in OFR under a wide range of conditions via box modeling. The relative importance of non-OH species is less sensitive to UV light intensity than to water vapor mixing ratio (H₂O) and external OH reactivity (OHR_ext), as both non-OH reactants and OH scale roughly proportionally to UV intensity. We show that for field studies in forested regions and also the urban area of Los Angeles, reactants of atmospheric interest are predominantly consumed by OH. We find that O(¹D), O(³P), and O₃ have relative contributions to volatile organic compound (VOC) consumption that are similar or lower than in the troposphere. The impact of O atoms can be neglected under most conditions in both OFR and troposphere. We define “riskier OFR conditions” as those with either low H₂O (< 0.1 %) or high OHR_ext ( ≥  100 s⁻¹ in OFR185 and > 200 s⁻¹ in OFR254). We strongly suggest avoiding such conditions as the importance of non-OH reactants can be substantial for the most sensitive species, although OH may still dominate under some riskier conditions, depending on the species present. Photolysis at non-tropospheric wavelengths (185 and 254 nm) may play a significant (> 20 %) role in the degradation of some aromatics, as well as some oxidation intermediates, under riskier reactor conditions, if the quantum yields are high. Under riskier conditions, some biogenics can have substantial destructions by O₃, similarly to the troposphere. Working under low O₂ (volume mixing ratio of 0.002) with the OFR185 mode allows OH to completely dominate over O₃ reactions even for the biogenic species most reactive with O₃. Non-tropospheric VOC photolysis may have been a problem in some laboratory and source studies, but can be avoided or lessened in future studies by diluting source emissions and working at lower precursor concentrations in laboratory studies and by humidification. Photolysis of secondary organic aerosol (SOA) samples is estimated to be significant (> 20 %) under the upper limit assumption of unity quantum yield at medium (1 × 10¹³ and 1.5 × 10¹⁵ photons cm⁻² s⁻¹ at 185 and 254 nm, respectively) or higher UV flux settings. The need for quantum yield measurements of both VOC and SOA photolysis is highlighted in this study. The results of this study allow improved OFR operation and experimental design and also inform the design of future reactors.

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