Background. Handball is a fast paced sport, with high velocity movements performed in a predominantly unilateral plane. In order to make training as specific as possible to on court movements, resistance training programmes should involve exercises that reflect the speed and stance of how they will be performed during gameplay however, working velocities are rarely prescribed due to the lack of research in the area. Aim. The aim of this study was (1) to determine the effect of three different training modes; unilateral high velocity (UHV), bilateral high velocity (BHV) and bilateral slow velocity (BSV) on vertical loaded and unloaded jumps, sprint, agility and balance. (2) To determine if any of these interventions had more of an effect when compared to each other. Methods. 29 women from four teams in the Swedish Elitserien participated in a 16-week intervention study. Teams were assigned to either UHV, who performed unilateral exercises with a high intended movement velocity, BHV, bilateral exercises at a high intended movement velocity, or BSV, who continued their regular bilateral slow velocity training. Power was assessed pre- and post-intervention by loaded vertical squat jump and countermovement jump (CMJ) both unilaterally and bilaterally. Performance assessments were conducted through 20m Sprints, agility T-test and Y-balance test. Effect sizes were calculated to determine the magnitude of differences from pre- to post-intervention in three training modes. One-way ANOVA determined if the group interactions were significant. Results. All three training modes increased their power output to varying levels and effect sizes. The UHV group demonstrated large effect sizes for all improvements in power output, whilst the BHV and BSV groups ranged from trivial to large. UHV got significantly faster at reaching time to peak velocity in unilateral and bilateral measures compared to both BHV and BSV (p=<0.05). Conclusion. The results suggest that a 16-week resistance training intervention regardless of stance improves power however to varying magnitudes. The high velocity groups showed greater improvements in measures of power and performance. This study suggests that resistance training at a high intended movement velocity may be beneficial for improving power and performance in elite women’s handball players.

In North America ice hockey is considered to be the fastest of all teamsports with high demands on leg strength and power. These two factors are crucial for acceleration and the total speed performance during a hockeygame. Skating performance requires a muscle engagement which also occurs during the Y-Balance Test (YBT). Some of the most active muscles during ice skating are biceps femoris, tibialis anterior and vastus medialis , these muscles are also some of the most active muscles during the YBT. The similarities between those two activities enable a possible relationship between skating velocity and YBT. This study investigated the relationship between dynamic postural control and on ice performance which includes 52 meter forward skating. The purpose of this study was to see if there is a significant correlation between skating velocity and the performance on YBT. Methods: 7 male ice hockey players in ages between 18-19 years performed a 52 meter forward skating test and a test for evaluating their dynamic postural control. The method used for measuring the dynamic postural control was the YBT. Results: There was no significant correlation between the YBT longitudinal directions, the total score and 52 meter forward skating. The strongest association (0,570) was shown between the YBT anterior longitudinal direction and 52 meter forward skating. The total score on YBT did not show a significant correlation with 52 meter forward skating, with a correlationcoefficient of 0,251. Conclusion: Due to several management errors during the YBT the results showed no significance. We can not for certain say that there is no significant correlation due to for instance management errors and the deficiency pf power. Future studies are needed to determine if there is a significant correlation between skating velocity and the performance on YBT.

Slug velocity measurement and flow regime recognition using acoustic emission technology are presented. Two non-intrusive and three intrusive methods were employed to detect the slug regime and measure its velocity using AE sensors. For the non-intrusive methods, AE sensors were placed directly on the exterior of the steel pipe section of the test rig with and without clamps. The intrusive method involved using different waveguide configurations with the AE sensors flush with the inner wall of the pipe. The experimental study presented investigated the application of Acoustic Emission (AE) technology for detecting slug velocity in addition to differentiating flow regime in two-phase (gas/liquid) flow in horizontal pipes. It is concluded that the slug velocity can be determined with acoustic emission (AE) sensors. The results were compared to slug velocities measured using high speed camera (HSC) and Ultrasound Transit Time (UST) techniques with good agreement between the three techniques at low gas void fraction (GVF). However, at high GVF (up to 95%) where the UST technique has limitations in application, the AE and HSC offered a good agreement. Flow regimes were also differentiated by using a combination of AE technology and Kolmogorov–Smirnov test technique. Stratified, slug and bubble regimes were recognised differentiated.

A study of the fluctuating wall pressure and unsteady velocity field in a flat plate turbulent boundary layer flow was conducted over a moderate range of Reynolds numbers to better understand the mechanisms by which the two fields are coupled. Individual and coincident measurements of the fluctuating pressure and velocity fields were acquired using a 20 element hydrophone array and a two-component Laser Doppler Anemometer, respectively. Estimates of the velocity power spectral density (PSD) revealed two primary trends predicted by turbulence theory, k⁻¹ in the region of (ky) = 10⁰ due to anisotropy of the large scales, and k⁻⁵/³ for larger values of (ky) where structures appear more isotropic. The mean velocity profiles, having been collapsed using outer scaling variables, exhibited the presence of a slightly adverse pressure gradient with a n = 6 power law shape. As for the fluctuating wall pressure, increased Reynolds numbers produced increases in the amplitude and frequency of the characteristic signatures from which the pressure spectral densities were also found to collapse reasonably well using outer scaling variables. The results suggest the location in the flow where the mechanisms responsible for driving the fluctuating wall pressure signatures reside. Space-time correlations and frequency-wavenumber analysis reveal a convective ridge in the fluctuating wall pressure corresponding to the passage of several organized structures at 75% of the free stream velocity for all Reynolds numbers tested. / text

Exoplanets are now known to be ubiquitous throughout the Galaxy. From the Kepler survey, we expect nearly every main-sequence star to form planetary systems during its formation phase. However, the detection limits of Kepler are confined to planets with short orbital periods, comparable to those in the inner solar system. Thanks to the long observational time baseline of the McDonald Observatory Radial Velocity (RV) Survey, we can identify gas giant planets in the outer regions of extrasolar planetary systems. The statistics of such planets are not well known, and are important for understanding the physics behind planet formation and migration. In this dissertation, I detail the discovery of five giant exoplanets on long-period orbits–so-called “Jupiter analogs.” For two systems of giant planets discovered through our survey, pairs of planets follow closely-packed orbits, creating the possibility for dynamical instability. I therefore examine the orbital resonances that allow these planets to avoid gravitational disruption. Because we see an abundance of small, potentially habitable exoplanets in the Kepler data set, current and upcoming exoplanet surveys concentrate on finding Earth-mass planets orbiting stars near enough to facilitate detailed follow-up observations. Particularly attractive targets are cool, low-mass “M dwarf” stars. Their low masses (and thus higher RV amplitudes from exoplanets) and close-in habitable zones allow for relatively quick detection of low-mass planets in the habitable zone. However, the RV signals of such planets will be obscured by stellar magnetic activity, which is poorly understood for M stars. In an effort to improve the planet detection capabilities of our M dwarf planet survey, I have conducted a detailed investigation of the magnetic behavior of our target stars. I show that, while stellar activity does not appear to systematically influence RV measurements above a precision level of ∼ 5 m/s, activity cycles can occasionally produce RV signals in excess of 10 m/s. Additionally, I show that long-term, solar-type stellar activity cycles are common amongst our M dwarf targets, although they are significantly less frequent than for FGK stars. In the case of GJ 328, I have discovered a magnetic activity cycle that appears in the RV data, causing the giant planet around the star to appear to be on a more circular orbit than indicated by the activity-corrected data. Such corrections are essential for the discovery of Earthlike exoplanets. / text

This study focuses on investigating the effect of the electronic spin transition of iron on the elasticity of the candidate lower mantle ferropericlase (Mg,Fe)O. This may be relevant to our understanding of the seismic velocity structures of the Earth’s lower mantle. The elastic constants of (Mg₀.₉₂Fe₀.₀₈)O at high-spin (HS) state, low-spin (LS) state, and through the pressure-induced HS-to-LS transition has been measured using both Brillouin Light Scattering (BLS) and Impulsive Stimulated Scattering (ISS). There is a large pressure range in which c₁₁ and c₁₂ exhibit a softening, while c₄₄ does not register such an anomaly. Compared with previously published data of ferropericlase with similar compositions ([Marquardt et al., 2009b], BLS measurement of (Mg₀.₉Fe₀.₁)O and [Crowhurst et al., 2008], ISS measurement of (Mg₀.₉₄Fe₀.₀₆)O), this study provides more reliable elastic constants measurements by taking the advantage of simultaneous measurements on Vp and Vs using both BLS and ISS. Our results show that bulk sound velocity of ferropericlase has a large but smooth softening in the spin transition pressure region. The elastic constants of ferropericlase at the spin transition region and the LS state have been well studied in this thesis, and a relaxation behavior has also been observed in this study. Those two subjects are not well documented in literature. The temperature effect of the spin state transition and its consequential effect on mineral’s elastic properties have not been studied in this project, but further research on this subject will follow. However, even in the room temperature, our results don’t show sudden changes in seismic velocities. Moreover, current theoretical and experimental studies [Sturhahn et al., 2005, Tsuchiya et al., 2006, Lin et al., 2007] indicate that the spin transition takes place over an extended range of depth along an expected lower-mantle geotherm, where sudden changes in compressional and bulk sound velocity are not expected. / text

L'objectif de cette thèse consiste en l'étude d'une stratégie de contrôle actif à faible autorité avec comme application le contrôle actif du rayonnement acoustique d'une plaque. Depuis l'essor du contrôle actif, son application aux problèmes acoustiques et vibracoustiques a été investiguée par de nombreux chercheurs, exploitant soit la théorie du contrôle optimal, soit des approches originales basées plus particulièrement sur la physique. Des notions spécifiques au contrôle vibroacoustique ont été développées comme, par exemple, les modes radiatifs pouvant caractériser le rayonnement acoustique d'une plaque d'une manière adaptée au contrôle. Le contrôle actif à faible autorité, pour lequel le Laboratoire de Structures Actives a développé une expertise dans le domaine de l'amortissement et du contrôle actif des vibrations, est une solution attractive par sa simplicité de mise en oeuvre. Le plus souvent implémenté sous la forme d'un contrôle décentralisé constitué de boucles indépendantes, le contrôle à faible autorité bénéficie de certaines garanties de stabilité et de robustesse. Bien que notre stratégie de contrôle puisse s'appliquer à n'importe quel type de plaque, l'application considérée dans ce travail a été motivée par le contexte socio-économique actuel en rapport avec les nuisances acoustiques. Il était en effet intéressant d'évaluer la stratégie de contrôle pour le problème de la transmission acoustique d'un vitrage. La stratégie de contrôle se divise en deux étapes. Tout d'abord le développement d'un capteur unique destiné à fournir une mesure représentative du bruit rayonné par une plaque en basse fréquence. Deux capteurs de vitesse volumétrique (l'un discret, l'autre distribué) ont ainsi été développés et évalués expérimentalement. Ensuite, une procédure d'optimisation de l'emplacement d'un ensemble d'actionneurs pilotés en parallèle est proposée. L'objectif de cette phase d'optimisation est de forcer la réponse fréquentielle du système à posséder les propriétés d'un système colocalisé. La stratégie de contrôle est ensuite évaluée sur deux structures expérimentales. / This thesis is concerned with a low authority active control strategy applied to the sound radiation control of a baffled plate. Since the development of active control , numerous researchers have studied its application to acoustical or vibroacoustical problems using either the modern control theory or other methods based rather on the understanding of the physics of the problem. Vibroacoustical active control has lead to the definition of radiation modes allowing to describe the radiated sound of a plate in an appropriate manner for active control purposes. Low autorithy control (LAC), for which the Active Structures Laboratory has gained an expertise for active vibration control applications is an interesting solution for its implementation simplicity. Most of the time it consists of several decentralized control loops, and benefits from guaranteed stability and robustness properties. Although our control strategy can be applied to any kind of plates, the application considered here has been motivated by the present socio-economical context related to noise annoyances. The active control strategy has been applied the problem of the sound transmission loss of glass plates (windows). This strategy is in two steps : first a volume velocity sensor is developed as to give a measure representative of the radiated sound at low frequencies. Two sensors have been developed (one discrete and one distributed) and experimentally tested. Next, an optimisation strategy is proposed which allow to locate on the plate a set of several actuators driven in parallel. The goal of this optimisation task is to obtain an open-loop frequency response which behave like a collocated system. The control strategy is finally evaluated on two plate structures.

The change of a vehicle’s velocity due to an impact, DeltaV (v) is often calculated and used in the scientific investigation of road traffic collisions. Two types of model are in common use to achieve this purpose, those based on the conservation of linear and angular momentum and the CRASH model which also considers the conservation of energy. It is shown that CRASH and major implementations of the momentum models are equivalent provided certain conditions are satisfied. Explicit conversions between the main variants of the models are presented. A method is also presented which describes a new formula for determining the total work performed in causing crush to a particular vehicle. This has the advantage of incorporating restitution effects and yields identical results to the momentum only models. Although the CRASH model has received adverse criticism due to perceived inaccuracies in the results, little work has been performed to determine the theoretical limitations on accuracy. This thesis rectifies that shortcoming. A Monte Carlo simulation and analytical model are developed here to provide two independent methods for determining the overall accuracy of the CRASH method. The principal direction of force was found to be the most likely to introduce error based on the CRASH assessment. It is shown how this and other sources of error in the CRASH model can be quantified for a particular collision suggesting priorities for minimising the overall uncertainty. The data from a series of well known crash tests are used with each of the models to provide comparison and validation data. It is recognised that without additional data velocity change is of limited use for forensic investigation. However DeltaV can be used as a proxy for acceleration and is particularly useful in studies involving injury causation. A method is also presented here which uses the change in velocity sustained by a vehicle in a planar collision to estimate the velocities of a vehicle before and after a collision. This method relies solely on conservation laws and is also applicable to situations where the coefficient of restitution is non-zero. An extension to the method is also described which allows an initial estimate to be modified to generate more realistic directions of force. This extension has the desirable effect of reducing uncertainty in the estimation of the direction of force which significantly improves the overall accuracy.

The aim of this project was to investigate the mechanics of the sprint start through the use of computer simulation. Experimental data was collected on one male athlete in accordance with a procedure agreed by Loughborough University Ethical Advisory Committee. The data provided subject specific data for the creation of a four and fourteen segment, angle and torque driven models of the sprint start. The models simulated the start from the moment of onset of force production until takeoff from the starting block. The four segment model comprised a head and trunk, thigh, shank and foot whilst the fourteen segment model also included a lower spine and pelvis, upper arms, forearms and hands, as well as the other leg including two segment feet. Subject specific torque data was combined with EMG data to provide input to the torque models Results from the four segment angle driven model demonstrated that the participant will benefit from using smaller joint angles than usual in the set position as this resulted in increased velocity on takeoff with minimal increase in movement time. The model also showed large joint torques during such starts and so suggested that this is likely to limit start performance. The four segment torque driven model also revealed that optimal joint angles exist for the hip and knee but such a result was not clear for the ankle. For this model the optimum angle at the hip was 73 (the smallest tested) and 108 at the knee which was the athlete's usual angle. Increasing the athlete's strength parameters resulted in a small increase in horizontal velocity on takeoff for some simulations and all simulations had enhanced acceleration. Increasing initial muscle activations didn't increase horizontal takeoff velocity but did also increase horizontal acceleration. The fourteen segment angle driven model was used to optimise spring parameters for input into a torque driven model. The fourteen segment torque driven model simulated movements and forces realistically but an adequate match was not found to the sprint start performance of the participant due to long simulation times and lack of computing power.

A major concern affecting the efficient use of composite laminates in aerospace industry is the lack of understanding of the effect of low-velocity impact (LVI) damage on the structural integrity. This project aims to develop further knowledge of the response and damage mechanisms of composite laminates under LVI, and to explore the feasibility of assessing the internal impact damage with a visually inspectable parameter. The response and damage mechanisms of composite laminates under LVI have been investigated experimentally and numerically in this project. Various parameters including the laminates thickness, lay-up configuration, repeated impact, and curing temperature have been examined. The concept and the phenomena of delamination threshold load (DTL) have been assessed in details. It was found that DTL exists for composite laminates, but the determination of the DTL value is not straightforward. There is a suitable value of range between the impact energy and the laminates stiffness/thickness, if the sudden load drop phenomenon in the impact force history is used to detect the DTL value. It is suggested that the potential menace of the delamination initiation may be overestimated. The composite laminates tested in this project demonstrate good damage tolerance capacity due to the additional energy absorption mechanism following the delamination initiation. As a result, the current design philosophy for laminated composite structure might be too conservative and should be reassessed to improve the efficiency further. To explore the feasibility of linking the internal damage to a visually inspectable parameter, quasi-static indentation (QSI) tests have been carried out. The dent depth, as a visually inspectable parameter, has been carefully monitored and assessed in relation to the damage status of the composite laminates. It is proposed that the damage process of composite laminates can be divided into different phases based on the difference in the increasing rate of dent depth. Moreover, the internal damage has been examined under the optical microscope (OM) and the scanning electron microscope (SEM). Residual compressive strength of the damaged specimen has been measured using the compression-after-impact (CAI) test. The results further confirm the findings with regard to the overestimated potential menace of the delamination initiation and the proposed damage process assumption. The proposed damage process assumption has great potential to improve the efficiency and accuracy of both the analytical prediction and the structural health monitoring for damages in composite laminates under low-velocity impact.