Sedan människor började använda energetiska material har risken för oönskade explosioner alltid varit ett problem. Många produktionsanläggningar och förråd har förstörts på grund av oönskad antändning energetiska material. Idag är nitrocellulosa en komponent i de flesta kanonkrut. En negativ egenskap hos nitrocellulosa är att den bryts ner över tid och eftersom det är en naturprodukt så kommer det alltid att finnas en viss skillnad mellan olika batcher. Genom att ersätta nitrocellulosa med en produkt som inte bryts ner men som fortfarande ger liknande övriga egenskaper kan kanonkrutssäkerheten öka. Termoelaster undersöktes då de är smältbara och tåliga. Smältpunkt och glastransitionstemperaturen bestämdes med differentiell svepkalorimetri, viskositeten mättes vid flera temperaturer med en reometer och mekaniska egenskaper utvärderades i en dragprovningsmaskin. De två mest lovande polymererna blandades sedan med hexamin som är ett inert material för att simulera ett kompositkrut. Agglomerering av hexamin undveks genom tillsats av små mängder pyrogen kiseldioxid. Fyllnadsgraden i systemet nådde 70 viktprocent hexamin i en polymer. Kompositmaterialen dragprovades och resultaten jämfördes med motsvarande data för två nitrocellulosabaserat krut. Kompositmaterialen hade lägre brottgräns än det ena nitrocellulosabaserade krutet men högre brottgräns än det andra nitrocellulosabaserade krutet. Kompositmaterialen hade högre E-modul än det nitrocellulosabaserade krutet men lägre brottöjning. Resultaten är lovande och visar att termoelasterna har stor potential att användas i kompositkrut. Med fortsatt undersökning och optimering av kompositmaterialen kan ett säkrare alternativ till nitrocellulosa skapas.

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV / SOQPSK-TG is a highly bandwidth-efficient constant-envelope modulation so that it has been applied in airspace telemetry widely. We compare four types of coherent detectors for SOQPSK-TG, which are optimal detector, pulse truncation (PT) detector, standard OQPSK detector and modified OQPSK detector. The simulation and analysis results indicate that PT detector has the advantages of low complexity and good performance, so it has more practicality value.

Les conditions indispensables à l'émergence de la vie terrestre ont surement été réunies sur Mars au début de son histoire. Une forme de vie martienne aurait alors pu apparaître et des indices de cette dernière auraient pu perdurer. Dans le cadre de la recherche de ces indices sur Mars, nos travaux s'articulent autour de deux cibles d'intérêt exobiologique : les biominéraux carbonatés et la matière organique. Dans la première partie, nous avons fait l'hypothèse que les températures de résistance thermique de carbonates biogéniques et abiotiques diffèrent du fait de leurs particularités intrinsèques. Nous les avons comparées via des analyses thermiques TG-ATD et nous avons constaté qu'un écart de 15°C sépare les domaines biologiques et abiotiques. Par conséquent nous avons ainsi accès à une signature biologique non ambiguë. Dans la seconde partie, nous avons testé la photostabilité et l'évolution d'acides carboxyliques et d'un biomarqueur bactérien, soumis au rayonnement ultraviolet simulé du soleil à la surface de Mars. Pour cela, nous avons développé une expérience de simulation en laboratoire : M.O.M.I.E. (Martian Organic Molecules Irradiation and Evolution). Nous avons observé que la plupart des molécules organiques sont détruites. Une seule, l'acide mélitique, produit un ou des composés organiques résistants. Nous avons ainsi accès aux taux de matière organique potentiellement présent à la surface/sous-surface de Mars. Les deux axes de recherche que nous avons suivis sont donc d'un grand intérêt exobiologique, car ils nous permettent de définir les stratégies expérimentales à mettre en oeuvre pour tenter de détecter in situ une activité biologique martienne.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Data from existing research are linked together to produce an overview of the effects of chloride-induced corrosion on reinforced concrete structures. The effects of chloride-induced corrosion on the following mechanisms have been investigated: (i) Cracking. (ii) Bond strength. (iii) Flexural strength. (iv) Shear strength. (v) Column behaviour. Models have been developed to link material and structural aspects of deterioration. Despite the complexity of the behaviour, many of the models are modifications to existing procedures contained in UK codes. Material and structural models are integrated together in a spreadsheet for assessing the variation in load-carrying capacity with time. Time to cracking and residual load-carrying capacity are found to be sensitive to small variations in key parameters such as the cover and the surface chloride level. Predictions from a spreadsheet model indicate that structures designed and built to BS 8110 should achieve their design life without the need for significant repair. The predictions also indicate that the UK Highways Agency was justified in making BD 57 more onerous than BS 5400. With validation against further test data the procedures developed in this Thesis could form the basis for codes of practice for the assessment of corrosion-damaged concrete structures and the durability design of new concrete structures.

This research examines the effect of plan irregularities on the progressive collapse of steel structures. Firstly, 2, 3 and 5-storey steel structures, regular and irregular, located in regions with different seismic activity designed in accordance with AISC (20 I 0) and ASCE7 (20 I 0). Secondly, the effect of the four plan irregularities on the progressive collapse of braced and unbraced steel structures located in regions with different seismic activity assessed. The collapse patterns of the I4 buildings is analysed and compared under seven loading scenarios using nonlinear dynamic and static analyses. In the nonlinear dynamic analyses, node displacements above the removed columns and the additional force on the columns adjacent to them are discussed. Furthermore, the capacity of the columns is compared to determine their susceptibility to collapse. ln the nonlinear static analyses, the pushdown curve and yield load factor of the structures are obtained after column removal. The results indicate that an irregular structure designed in site class C seismic zone collapses in most of the column removal scenarios. Moreover, when comparing regular and irregular structures designed in site class E seismic zone, the demand force to capacity ratio (D/C) of the columns in the irregular structures is on average between I.5 and 2 times that of the regular ones has been discussed by Homaioon Ebrahimi et.al (20 I7). The lack of 2-storey building bearing capacity to withstand the removal of the column is lower than that of the 5-storey structure, which is due to the level of redundancy that characterises in the 5-storey structure.

To discover the potential of IR spectroscopy and explore the details of FTIR instrumentation, a FTIR was built from most basic parts to provide access to every aspect of a IR spectrometer including the hardware and software. The optical system followed the most widely used double-interferometer design. The software control system was developed with LabVIEW to perform data acquisition of the detectors, data processing and controls of the actuators. The FTIR built will be able to provide a full optical IR spectroscopy platform which has a complete control and data acquisition system and can be continuously improved in accuracy and resolution to reach high lab experiment class as the research keep going. The availability of the hardware setup and software source code allows updating of this system for many advanced IR spectroscopy like spatially resolved and time resolved applications. To achieve in-situ material characterization with multiple measurements, some instruments can be modified and integrated with experiments. This thesis provides a practical and useful example of measuring IR spectra and mass of the sample simultaneously during thermal reactions. This instrument was designed and build with a Fourier transform infrared spectrometer (FTIR) and a thermogravimetric analyzer (TGA). Diffuse reflectance Fourier transform (DRIFT) was equipped to a commercial FTIR to acquire the IR spectra. A micro-balance was taken from a TGA was refitted to this system to measure the sample mass. A series of LabVIEW applications was developed for the FTIR control and communication, TGA communication and temperature control. The system was successfully built and tested with calcium oxalate decomposition experiments. The data showed that the instrument has good accuracy and repeatability of both the IR and mass measurement. The analysis of the calcium oxalate data demonstrated good correlation between the IR, mass and temperature parameters.

Railroad bridges are the most important connection parts of railroad networks. These bridges are exposed to heavier train loads compared to highway bridges as well as various detrimental ambient conditions during their life span. The railroad bridges in Turkey are mostly constructed during the late Ottoman and first periods of the Turkish Republic / therefore, they are generally close to about 100 years of age / their inspection and maintenance works are essential. Structural health monitoring (SHM) techniques are widely used around the world in order to increase the effectiveness of the inspection and maintenance works and also evaluate structural reliability. Application of SHM methods on railway bridges by static and dynamic measurements over short and long durations give important structural information about bridge members&rsquo / load level and overall bridge structure in terms of vibration frequencies, deflections, etc. Structural Reliability analysis provides further information about the safety of a structural system and becomes even more efficient when combined with the SHM studies. In this study, computer modeling and SHM techniques are used for identifying structural condition of a steel truss railroad bridge in Usak, Turkey, which is composed of six spans with 30 m length each. The first two spans of the bridge were rebuilt about 50 years ago, which had construction plans and are selected as pilot case for SHM and evaluation studies in this thesis. Natural frequencies are obtained by using 4 accelerometers and a dynamic data acquisition system (DAS). Furthermore, mid span vertical deflection member strains and bridge accelerations are obtained using a DAS permanently left on site and then compared with the computer model analyses results. SHM system is programmed for triggering by the rail load sensors developed at METU and an LVDT to collect mid span deflection high speed data from all sensors during train passage. The DAS is also programmed to collect slow speed data (once at every 15 minutes) for determination of average ambient conditions such as temperature and humidity and all bridge sensors during long term monitoring. Structural capacity and reliability indices for stress levels of bridge members are determined for the measured and simulated train loads to determine structural condition of bridge members and connections. Earthquake analyses and design checks for bridge members are also conducted within the scope of this study.

In Turkey, big investments are made to improve the existing train lines for use of new high speed trains. Most of the bridges on the existing train lines are typical and in this thesis one of the standard types, the classic steel truss bridge is investigated. This thesis presents the dynamic investigation of standard type existing truss bridge for passenger comfort criteria under the high speed train loadings. Two different computational analysis models have been developed to idealize the vehicle-bridge modeling to evaluate the passenger comfort that were influenced by dynamic vibrations on bridges induced by trains. Field tests of this bridge have been conducted by two separate institutes, Middle East Technical University and Turkish State Railways, to determine the state of the bridge under existing low-speed train loadings. Eigenvalue and Time history analysis of the LARSA 4D structural analysis program has been used to investigate the vehicle bridge interactions. The solutions obtained from the analysis have been evaluated with the experimental results. Different rehabilitation options are analytically studied to improve the serviceability of standard steel truss bridges per Eurocode 1990:2002, Eurocode 1991-2:2003, UIC 774-3 and UIC 776-1. The focus of this research is to define a relationship between span weight per meter and passenger comfort as well as the stiffness of this type of bridge.

Recent devastating earthquakes revealed that bridges are one of the most vulnerable components of the transportation systems. These seismic events have emphasized the need to mitigate the risk resulting from the failure of the bridges. Depending on the seismicity of the bridge local site, seismic vulnerability assessment of the bridges can be done based on the fragility curves. These curves are conditional probability functions which give the probability of a bridge attaining or exceeding a particular damage level for an earthquake of a given intensity level. In this dissertation, analytical fragility curves are developed for the ordinary highway bridges in Turkey constructed after the 1990s to be used in the assessment of their seismic vulnerability. Bridges are first grouped into certain major bridge classes based on their structural attributes and sample bridges are generated to account for the structural variability. Nonlinear response history analyses are conducted for each bridge sample with their detailed 3-D analytical models under different earthquake ground motions having varying seismic intensities. Several engineering demand parameters are employed in the determination of seismic response of the bridge components as well as defining damage limit states in terms of member capacities. Fragility curves are obtained from the probability of exceeding each specified damage limit state for each major bridge class. Skew and single-column bent bridges are found to be the most vulnerable ones in comparison with the other bridge classes. Developed fragility curves can be implemented in the seismic risk assessment packages for mitigation purposes.