It is common practice for endurance athletes to manipulate training load prior to an important competition, known as tapering. An effective strategy aims to alleviate accumulated fatigue, whilst maximising physiological adaptation and facilitating a peak performance. Improvements in performance of 0.5 to 6.0% have been reported after a successful taper, a margin that could potentially have a dramatic influence on performance outcome at the elite level. This thesis explored the strategies currently employed by elite endurance athletes and investigated novel training manipulations during the taper to further enhance performance, to gain a more thorough understanding of the physiological mechanisms, and to identify a minimally invasive physiological biomarker capable of monitoring recovery status during the taper. Tapering strategies in elite endurance athletes were shown to be individualised and influenced by the preceding training load. Algorithms were developed, capable of explaining a large proportion of the variance (53-95%) in tapering strategy training variables (with the exception of interval volume), for a given pre-taper training load (Chapter III). A tapering strategy implemented using the algorithms was most likely to improve 1,500 m treadmill performance (ES = 0.53). When the intensity of final interval session was increased from 100% to 115% race speed, the effect on treadmill performance was unclear (ES = 0.22) and perhaps due to insufficient recovery to respond positively to the increased intensity interval session (Chapter IV). When continuous volume was reduced further (by 60%), the novel high intensity strategy was very likely to improve 1,500 m track performance (ES = 0.74), compared to the algorithm-derived taper (ES = 0.40) (Chapter VI). In middle-distance runners, training above race speed in the final days of the taper might be more beneficial than current practice, although training volume must be further reduced to compensate. It was possible to measure plasma concentrations of interleukin-6 and soluble interleukin-6 receptor from capillary samples (Chapter II), although these markers in addition to C-reactive protein, testosterone and cortisol were not sensitive enough to detect changes in recovery status during tapering (Chapters IV and V). Measures of muscle maximum voluntary contraction force (algorithm-derived taper: 9%; ES = 0.39; novel taper: 6%; ES = 0.29), and rate of force development (algorithm-derived taper: ES = 0.53; novel taper: ES = 0.26) improved in response to tapering (Chapter IV), and could represent alternative non-invasive markers of recovery and taper effectiveness to facilitate peak performance.

Les ressources techniques, tactiques, physiques et mentales sont autant d’éléments à prendre en compte pour accéder à la performance en compétition. Pour autant, la spécificité du rugby à 7 attribue à la dimension physique une place particulière. La planification de l’entraînement, et en particulier la façon de gérer la charge à l’approche d’une compétition, devient ainsi une préoccupation permanente. Le but de cette thèse était d’étudier la réponse de joueurs internationaux de rugby à 7 à une gestion stratégique de la charge d’entraînement à l’approche d’une compétition. Notre première étude a consisté à décrire la distribution de la charge de travail sur une saison et caractériser différents modèles de périodisation. Ce travail a permis d’identifier l’affûtage comme une stratégie largement utilisée avant chaque tournée pour optimiser la performance physique des joueurs. Notre deuxième étude a consisté à montrer les effets d’une période d’affûtage sur les qualités physiques. L’observation des cinétiques de surcompensation des qualités de force, de vitesse et de répétition de sprints a démontré qu’une fenêtre comprise entre 9 et 16 jours constituait une durée optimale pour maximiser les gains. Enfin, notre dernière étude a porté sur une stratégie de pré-conditionnement mise en œuvre le jour de la compétition. Il s’agissait d’expérimenter les effets d’une séance d’entraînement, réalisée 2 heures avant le premier match du tournoi, sur les réponses physiques et psycho-physiologiques des joueurs. La capacité à répéter des sprints et l’activité physique en match n’ont pas été améliorées mais l’état psychophysiologique a été positivement influencé par cette séance. A travers cette thèse, nous avons donc essayé de dessiner une image générale d’une saison internationale de rugby à 7 et de questionner la pertinence de stratégies de périodisation mises en œuvre par les entraîneurs de l’équipe de France à l’approche des compétitions. Les conclusions scientifiques issues de ces études doivent être appréhendées comme des orientations qui guident les entraîneurs dans la construction de leurs scénarios d’entraînement. / The technical, tactical, physical and mental resources of a team are key factors to access to the performance in competition, and the Rugby-7’s specificity attributes a particular place to the physical dimension. Training periodization and in particular the way to manage training load prior to competition, is a permanent concern. The aim of this thesis was to study the response of international Rugby-7s players to strategic training load management in the pre-competition phases. Our first study examined the workload distribution over a season and identified different periodization models. This work helped identify the tapering phase as a strategy widely used before each competition to optimize players’ physical performance. The second study investigated the effects of a tapering period on physical qualities. The supercompensation kinetics of strength, speed and repetition of sprints qualities showed that a window between 9 and 16 days was an optimal duration to maximize physical performance. The final study focused on a preconditioning strategy implemented on the day of the competition. The aim was to examine the effects of a morning training session, completed 2 hours before the first match of the tournament, on the physical and psycho-physiological responses of the players. The repeated sprinting ability and physical activity in match was not improved, but the psychophysiological state was positively influenced by this session. Through this thesis, a general picture of a Rugby-7s international season was drawn and the relevance of periodization strategies implemented by the French team coaches in the approach of competitions was questioned. The scientific findings from these studies could be used as guidelines for coaches in building their training programs.

Abstract available in the Medicine & Science in Sports & Exercise.

PURPOSE: To examine the effects of an overreaching week followed by a 3-week taper (ORT) on DI collegiate throwers after 8 weeks of in-season training. METHODS: Seven throwers (5 male, 2 female) (20.8 ± 1.1 years, 182.9 ± 7.6 cm, 100.6 ± 22.2 kg) were recruited for the study. Throwing performance (TP) was normalized across events using z-scores calculated from the top 500 throws/year in DI over the past 5 years (-1.28 ± 0.99). Athletes were tested on measures of vastus lateralis muscle thickness (MT) using B-mode ultrasound, countermovement jump peak power with 0kg (CMJPP0) on a force platform, overhead shot put throw (OHT) at baseline (T1), pre-taper (T2) and post-taper (T3). TP was measured at a conference meet and championships. Training load (TL=session RPE·duration) and strength training volume-load (VL) were monitored for 12 weeks at all training sessions and competitions. One-way repeated measures ANOVA and paired sample t-tests were used for analysis with alpha level set at p"0.05. RESULTS: There was a statistical reduction in weight training VL (d=1.21, 90% CI [0.58, 1.8], p=0.01) and TL (d=0.96 [0.26, 1.7], p=0.04) between in-season (T1 to T2) and OR-T (T2 to T3) training phases. There were statistical time effects for MT (p=0.02), CMJPP0 (p=0.02), and TP (p=0.04). Post-hoc analysis revealed statistical improvements in MT (T1-T2: d=0.28 [0.11, 0.45], p=0.02), CMJPP0 (T2-T3: d=0.27 [0.1, 0.44], p=0.02), OHT (T2-T3: d=0.49 [0.16, 0.82], p=0.03) and TP (T2-T3, d=0.57 [0.22, 0.93], p=0.02). CONCLUSIONS: The OR-T appeared to augment TP at conference championships and national ranking. Collegiate throwers may benefit from an OR-T phase where TL and VL are exponentially reduced prior to an important competition.

The purpose of this thesis was to observe psychological, physiological, and performance changes to determine when two high-level weightlifters were peaked for a major competition. We addressed this purpose by conducting a two-part case study series with one USA international level female and one USA national level male weightlifter. Both athletes were considered to be peaked on competition day. The results support our hypothesis that jumping performance would be peaked on competition day corresponding with an increased recovery and decreased stress state. However, contrary to our hypothesis, each athlete exhibited small decreases in muscle size leading into the competition relative to baseline values. Further, changes in inflammatory markers were inconsistent for each athlete and were not reduced as hypothesized. Based on our findings, this investigation supports the use of overreaching and tapering for individual strength-power athletes providing insight into underlying psychological and physiological basis for observed changes in performance.

In this thesis, we demonstrate, theoretically, that, by depositing a regular fused-silica fiber with optical nonlinear molecules, strong and thermodynamically stable SHG can be obtained. Our experiments also provide strong evidence for the theory. Start from the basic Maxwell equation, we derive the SHG efficiency that the excited power translates into the SHG signal. According to the SHG efficiency equation, a small radius and a long length will help to result in a high SHG efficiency, which also increases with the excited power. We fabricate silica fiber tapers with radius less than 5 μm through either wet etching or heating while stretching. Through improving the stretching setup, and adroitly manipulating both the stretching rate and the heating temperature, we are able to control the taper loss less than 1 dB. Then we dip taper part into cationic solution and anionic solution alternatively to have ISAM/CHISAM film on it. By improving the surface quality of film around a silica fiber taper, we are able to control film loss of PAH/PR film to less than 2 dB for 5 bilayers. We set up a SHG measurement stage for a nonlinear fiber, and develop a measurement method during the experiments. We have shown that by depositing (PAH/PB)10 films around a fiber taper with a diameter around 5 µm, we can obtain high SHG signal. The ratio of the obtained SHG signal to the excitation power for such a nonlinear fiber is more than 10 times of that of a 125 µm single mode fiber with the same length. Our experiment result provides strong evidence that centrosymmetric material can be used as SHG material. / Master of Science

Made available in DSpace on 2016-03-15T19:37:37Z (GMT). No. of bitstreams: 1 Rodrigo Mendes Gerosa.pdf: 5257410 bytes, checksum: d0ee4897567ff7f2299a46312ebcc2f1 (MD5) Previous issue date: 2011-01-27 / Fundo Mackenzie de Pesquisa / In this work two techniques are described for post-processing photonic crystal fibers (PCFs), which were developed to change their guidance properties. The first technique consists of selectively closing holes of the PCF microstructure, thus allowing, among other things, to fill in some holes with materials such as liquids, polymers and nanoparticles. The other technique consists of selectively collapsing holes in the PCF cross-section using differential pressure and an optical fiber fusion splicer, and is based on techniques previously demonstrated for PCF tapering. With the first technique a simple and effective way of sealing liquid core fibers is demonstrated, which avoids evaporation. The study of PCFs with complex cores formed by the original core of a solid-core fiber and an oil-filled hole adjacent to the core was also undertaken with this technique and provided a strong interaction between light and the filled channel, as well as a high sensitivity to temperature (displacement of 5.35 nm/°C in the observed spectral structures). With the use of the second technique, the collapse of a hole adjacent to the solid core of a PCF allowed the development of a modal Mach-Zehnder allfiber interferometer, with a spectral modulation depth of 9.5 dB, which is similar to that of other PCF modal interferometers reported in the literature, and a sensitivity to temperature of -54 pm/°C, which is about 4 times higher than that of Bragg gratings in conventional optical fibers. The same technique was used to obtain optical coupling between two cores of a photonic crystal fiber with 3 initially uncoupled cores. / Nesse trabalho são descritas duas técnicas de pós-processamento em fibras de cristal fotônico (PCFs, do inglês Photonic Crystal Fibers) desenvolvidas para alterar suas propriedades de guiamento. A primeira consiste em fechar seletivamente buracos da microestrutura das PCF possibilitando assim, entre outras coisas, o preenchimento de alguns buracos com materiais como líquidos, polímeros e nanopartículas. A outra técnica consiste em se colapsar seletivamente buracos da seção transversal da microestrutura de uma PCF utilizando pressão diferencial e uma máquina de emendas para fibras ópticas, sendo baseada em técnicas previamente demonstradas para o afilamento (tapering) de PCFs. Com a utilização da primeira dessas técnicas é apresentada uma maneira simples e eficiente de se vedar fibras com núcleo líquido, evitando-se assim a evaporação. O estudo de PCFs com núcleos complexos, formados pelo núcleo original de uma fibra de núcleo sólido e um buraco adjacente ao núcleo preenchido por óleo foi também realizado com essa técnica, proporcionando uma grande interação da luz com o canal preenchido e uma alta sensibilidade a temperatura (deslocamento de 5,35 nm/°C nas estruturas espectrais observadas). Utilizado-se a segunda técnica, o colapso de um buraco adjacente ao núcleo sólido de uma PCF permitiu o desenvolvimento de um interferômetro modal de Mach-Zehnder totalmente a fibra, apresentando uma profundidade de modulação espectral de 9,5 dB, semelhante à de outros interferômetros modais em PCFs reportados na literatura, e uma sensibilidade a temperatura de -54 pm/°C, cerca de 4 vezes maior do que a de redes de Bragg em fibras ópticas convencionais. A mesma técnica foi utilizada para se obter o acoplamento óptico entre 2 núcleos de uma fibra de cristal fotônico com 3 núcleos inicialmente desacoplados.

Laser-plasma accelerators are of great interest because of their ability to sustain extremely large acceleration gradients, enabling compact accelerating structures. Laser-plasma acceleration is realized by using a high-intensity short pulse laser to drive a large plasma wave or wakefield in an underdense plasma. This thesis considers the effect of axial plasma density upramps on laser wakefield acceleration. Theoretical groundwork shows that tapered plasma channels can be used to mitigate one of the main limitations of laser plasma acceleration, that is, dephasing of an electron beam with respect to the plasma wave. It is shown that it is possible to maintain an electron bunch at constant phase in the longitudinal electric fields of the laser wake field. This leads to an increased energy gain of an electron trapped in the wakefield. The required shape of the density slope is difficult to implement in experiments. Therefore, a linear density ramp is also considered which is predicted to also increase the energy gain beyond that possible in a uniform density plasma. Towards an experimental implementation it was studied how a suitable gas density profile can be established in a capillary. This was done employing simulations using the computational fluid dynamics tool kit OpenFoam and comparing these to measurements of the axial density profile based on Raman scattering. It was demonstrated that a linear density ramp could be established by applying different pressures on the capillary gas inlets. The dependence of the density profile on the capillary parameters, such as, capillary diameter and length and inlet diameter were also studied. The results of the simulations and the measurement showed excellent agreement and demonstrate that approximately linear density ramps can be generated by flowing gas along a capillary of constant cross-section Laser wakefield acceleration in plasmas with longitudinally varying density was investigated in an experiment at the Astra Laser at Rutherford Laboratories. The experiment utilised ionisation injection in order to operate in the mildly non-linear regime of laser-wakefield acceleration. The measured electron energies agree well with the theoretical predictions. It was demonstrated that an increase in the energy gain can be obtained by driving the accelerator in a ramped plasma, the electron spectrum is more narrow and the injected charge increases significantly. Measurements of the X-ray spectrum emitted by the betatron motion of the accelerated electron bunch allowed the transverse radius of the bunch to be deduced. These measurements showed that retrieved electron bunch radius is inversely proportional to the longitudinal density gradient, that is a plasma density upramp (downramp) has a decreased (increased) electron bunch radius.

An ID generating circuit is unquestionably the core of a chipless RFID tag. For convenience of printing process and cost consideration, the circuit should be kept as simple as possible. Based on the cognition, an 8-bit time-domain based ID generating circuit that merely consists of a ML and eight capacitors was offered, and implemented on photo-paper substrates via inkjet printing process. In addition to the experimental measurements, the circuit was also input into circuit simulators for cross-validation. The good agreement between simulations and measurements is observed, exhibiting the tag technical feasibility. Besides of low cost, the tag has wide compatibility with current licensed RFID spectrum, which will facilitate the future deployment in real applications. Compared   to  time-domain   based  chipless   tags,  frequency   signatures   based chipless RFID tags are expected to offer a larger coding capacity. As a response, we presented a 10-bit frequency-domain based chipless RFID tag. The tag composed of ten configurable LC resonators was implemented on flexible polyimide substrate by using  fast  toner-transferring  process.  Field  measurements  revealed  not  only  the practicability  of  the  tag,  but  also  the  high  signal  to  noise  ratio  (SNR).  Another frequency domain tag consists of a configurable coplanar LC resonator. With the use of all printing process, the tag was for the first time realized on common packaging papers.  The tag feasibility was confirmed by subsequent measurements. Owing to the ultra-low cost potential and large SNR, The tag may find wide applications in typical RFID solutions such as management of paper tickets for social events and governing of smart documents. Ultra wide band (UWB) technology possesses a number of inherent merits such as high speed communication and large capacity, multi-path immunity, accurate ranging and positioning, penetration through obstacles, as well as extremely low-cost and low- power transmitters. Thus, passive UWB RFIDs are expected to play an important pole in  the future identification applications for IoT. We explained the feature difference between  UWB  chipless  tags  and  chip  based  tags,  and  forecasted  the  applications respectively  based on the comparison  between the two technologies.  It is expected that the two technologies will coexist and compensate each other in the applications of IoT. Lastly, the thesis ends up with brief summary of the author’s contributions, and technical prospect for the future development of printable chipless RFID tags. / <p>QC 20140304</p>

During processing of data received by an airborne radar one of the issues is that the typical signal echo from the ground produces a large perturbation. Due to this perturbation it can be difficult to detect targets with low velocity or a low signal-to-noise ratio. Therefore, a filtering process is needed to separate the large perturbation from the target signal. The traditional method include a tapered Fourier transform that operates in parallel with a MTI filter to suppress the main spectral peak in order to produce a smoother spectral output. The difference between a typical signal echo produced from an object in the environment and the signal echo from the ground can be of a magnitude corresponding to more than a 60 dB difference. This thesis presents research of how the multitaper approach can be utilized in concurrence with the minimum variance estimation technique, to produce a spectral estimation that strives for a more effective clutter suppression. A simulation model of the ground clutter was constructed and also a number of simulations for the multitaper, minimum variance estimation technique was made. Compared to the traditional method defined in this thesis, there was a slight improvement of the improvement factor when using the multitaper approach. An analysis of how variations of the multitaper parameters influence the results with respect to minimum detectable velocity and improvement factor have been carried out. The analysis showed that a large number of time samples, a large number of tapers and a narrow bandwidth provided the best result. The analysis is based on a full factorial simulation that provides insight of how to choose the DPSS parameters if the method is to be implemented in a real radar system.