To compensate the strong Troposheric impairments caused in the Ka frequency band, it is necessary to use Fade Mitigation Techniques. To develop and validate such techniques, time series of rain attenuation are needed. Nevertheless, these data are difficult to obtain. An alternative to using real rain attenuation time series is to develop a model of rain rate time series synthesizer. Nevertheless, real rain rate time series are needed to develop and validate this model. The aim of this internship is to provide real rain rate data useful for the development, parameterization and validation of this new model. In the first part of this report, different rain rate computation methods will be presented. Then, real data from a rain gauge located at Onera premises in Toulouse will be processed according to the presented methods and to a novel one. Results will be statistically analysed and finally a study of both the error of the methods and the uncertainty of the experimental devices and tools will be carried out. / <p>Validerat; 20120514 (anonymous)</p>

Yes / When ocean waves propagate over porous seabed, they cause variations of the pore pressure within seabed, leading to the possible wave attenuation and soil liquefaction. In order to advance and improve our understanding of the process of wave-induced seabed liquefaction and its impact on wave propagation, systematical experiments are carried out in a wave flume with a soil basin filled with silt. Both the pore pressures and water surface elevations are measured simultaneously, while the seabed liquefaction is videotaped using a high-speed camera. Laboratory measurements show that the pore pressure in surface layer mainly oscillates over time, while the wave period averaged pore pressure has little change. In the deep layer, however, the wave period averaged value of the pore pressure builds up dramatically. The results show that the wave height decreases rapidly along the direction of wave propagation when seabed liquefaction occurs. Such a wave attenuation is greatly enhanced when the liquefaction depth further increases. The experiments also demonstrate that the conditions (wave height and wave period) of incident waves have significant impacts on the wave-induced pore pressures, liquefaction depth and wave attenuation in a silt bed. / National Natural Science Foundation of China (Grant No. 51479053), the 111 Project (Grant No. B12032), the marine renewable energy research project of State Oceanic Administration (GHME2015GC01), the Fundamental Research Funds for the Central University, China (Grant No. 2013B31614), the Colleges and Universities in Jiangsu Province Plans to Graduate Research and Innovation (Grant No. B1504708), and Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University (Grant No: 2016491011).

<p> The principal subject of this thesis is to experimentally determine the beta attenuation patterns in tooth enamel layers, and to examine the predictions of two theoretical models which are involved in the beta dose calculations of ESR dating. One of the models is based on empirical equations (Yokoyama, 1982) and employed by R.Grün (1986) in the DATA software of ESR dating, the other is based on the "one group" transport theory which was incorporated in the ROSY dating programme (B.J. Brennan, et al., 1997).</p> <p> The theoretical bases of Grün's approximation (i.e. the empirical approach) and the "one group" transport theory are discussed. Their predictions of beta attenuation under 2-π geometry are compared with the results of Monte Carlo simulations, and were then compared with the results of our experimental work, which show clear inclination to the predictions of "one group" theory and Monte Carlo. The previous experiment of Aitken et al.(1985) is also described and its flawed geometric arrangement is discussed.</p> <p> In this study, two sets of experiments are performed. The first set used pitchblende as the irradiator and employed the configuration of irradiator-absorber-detector, which is aimed to reassess the experiment of Aitken et al. (1985). The second set of our experiments used a pure beta source of 90Sr(90Y) and employed the innovative configuration of tooth enamel pellets in a hole of tooth enamel holder, which substantially solved the problem encountered in the first set (e.g. gamma background subtraction and non-2π geometry, etc.).</p> <p> Based on our experimental results as well as the discussion of Aitken et al.'s experiment, a conclusion is drawn that the "one group" theory is more reliable in predicting beta doses in ESR dating samples, and consequently, it challenges the ESR ages calculated by DATA software which employs the empirical approach. The comparison of ESR ages calculated by the two dating programmes is shown, and some revisions of published ESR ages based on DATA programme demonstrate the great significance of our experimental results.</p> / Thesis / Master of Science (MSc)

This thesis investigates the implementation of a passive isolator with a pressurized air cushion for spacecraft payloads in mission architectures implementing in-space assembly technologies. A pressurized air bed capable of briefly surviving the space environment for cargo delivery was prototyped and experimentally evaluated for launch vehicle vibration dynamics resulting in a 72%, 93%, and 88% reduction in experienced GRMS loads for the X-Axis, Y-Axis, and Z-Axis, respectively. A preliminary Total Mass Loss evaluation of the Low-Density Polyethylene Film utilized for the air bed resulted in a mass loss of 0.7%, indicating that commercial off-the-shelf films might require minimal modification for flight readiness. An analytical model of a planar rectangular payload experiencing free vibrations with a Winkler foundation is generated and compared to the experimental results, showing a potential way for characterizing and designing such a foundation to reduce experienced vibrations. These preliminary results show a potential path for a non-cost-prohibitive method for space payloads to reduce loads experienced during launch as inspired by the successful hosted payloads program aboard the International Space Station.

Ground penetrating radar (GPR) is limited by the depth of penetration and signal-to-noise ratio (SNR), which both impact the ability to resolve subsurface features. GPR antennas are known to have limited depth penetration due to the noise and signal attenuated. The noise floor is the depth at which there is no discernable signal (Stec and Susek 2018). SNR is the comparison of desired signal to background noise, understanding that noise is any unwanted signal. Different objects in the environment can transmit frequencies that are recorded in data as background noise; this noise is considered to be external noise. Internal noise is noise which is generated by the internal components of the GPR system. Data processing such as filtering can reduce noise. Noise that occurs at the same frequency as the signal of interest, however, cannot be filtered out without also removing the signal of interest.

Detonation is the supersonic mode of combustion that occurs in munitions (military explosives and high explosives). These munitions result in blast waves that are hazardous to human life and structures. As a result, there is a high desire to mitigate these blast waves. One such method is to surround the explosive with mitigants (liquid, granular, and cellular porous material). For the safe storing and use of munitions, it is crucial to study the explosive dispersal of mitigant, the ensuing blast wave attenuation, and specifically, the mechanisms underlying this interaction. Current research involving mitigant blast wave attenuation is conducted in many configurations. The study aims to evaluate one configuration, shock tubes with particle suspension. Blast waves are simulated in the form of detonations initiated by DDT (deflagration-to-detonation) with mitigants in the form of dispersed particles. These dispersed particles included aluminum oxide, Al2O3, and aluminum, Al. The flame-flow interactions are experimentally studied using Particle Image Velocimetry (PIV) and pressure transducers. The effect of particle suspension on blast waves is revealed, portraying a decrease in mitigation performance.

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