COMPARISON OF TIBIAL IMPACT ACCELERATIONS: VIDEO VS ACCELEROMETER

This study compared tibial axial accelerations measured by video analysis and accelerometry. Twenty-two recreationally active adults performed three countermovement jumps. The landing tibial axial accelerations were assessed with video and an accelerometer. High reliability was demonstrated for the root mean square error between the assessment methods (ICCave = 0.872). Repeated measures ANOVA results revealed no instrumentation differences in the magnitude of the two acceleration peaks (toe and heel contact) and no difference between trials. However, first and second peaks occurred 9.6 and 4.0 ms earlier, respectively, when assessed by video. Accelerometry is a valid and reliable alternative to video analysis for the assessment of tibial impact accelerations if temporal characteristics are not of interest

Precision VLBI astrometry: Instrumentation, algorithms and pulsar parallax determination

(Abridged) This thesis describes the development of DiFX, the first general-purpose software correlator for radio interferometry, and its use with the Australian Long Baseline Array (LBA) to complete the largest VLBI pulsar astrometry program undertaken to date in the Southern Hemisphere. This two year astrometry program has resulted in the measurement of seven new pulsar parallaxes, more than trebling the number of measured VLBI pulsar parallaxes in the Southern Hemisphere. The measurements included a determination of the distance and transverse velocity of PSR J0437-4715 with better than 1% accuracy, enabling improved tests of General Relativity, and the first significant measurement of parallax for the famous double pulsar system PSR J0737-3039A/B, which will allow tests of General Relativity in this system to proceed to the 0.01% level. The DiFX software correlator developed to enable this science has been extensively tested and is now an integral part of the upgraded LBA Major National Research Facility; furthermore, it has been selected to facilitate a substantial sensitivity upgrade for the US Very Long Baseline Array.Comment: PhD Thesis, Swinburne University, accepted January 2009. 202 pages, 51 figures. For a version with high resolution images, see http://www.aoc.nrao.edu/~adeller/AdamDellerPhDThesis.pd

Velocity Determination for an Inverted Pseudolite Navigation Reference System

As navigation systems continue to improve in performance and features, the Air Force must develop better Navigation Reference Systems (NRS) to keep pace with technology. Specifically, with the advent of enhanced, integrated Global Positioning System (GPS) and Inertial Navigation System (INS) navigators, emphasis is placed on the measuring performance in the presence of GPS jamming. To meet these needs, a new NRS, dubbed the Sub-Meter Accuracy Reference System (SARS), is being developed by the 746th Test Squadron, Holloman AFB, New Mexico. SARS uses a unique, inverted GPS pseudolite positioning system to determine a reference trajectory. This research investigates two post processing methods of determining velocity from a discrete position data at a constant data rate. The first method employs numerical differentiation along with digital filters provide noise reduction. The second method uses kinematic model based Kalman filter and smoothing to determine the reference velocity

Interactions between the Madden-Julian oscillation and mesoscale to global scale phenomena

2019 Summer.Includes bibliographical references.The Madden-Julian Oscillation (MJO) influences and interacts with atmospheric phenomena across the globe, from the tropics to the poles. In this two-part study, the interactions of the MJO with other phenomena across a broad range of scales are considered, including mesoscale convective structures within the tropics and global teleconnection patterns. While the two studies are distinct in the scales of the interactions they discuss, each highlights an aspect of the importance of interactions between the MJO and variability across a broad range of scales within the climate system. The study of such cross-scale interactions is important for understanding our climate system, as these interactions can transfer energy between phenomena of starkly different spatial and temporal scales. Part one of the study uses a cloud-resolving model, the Regional Atmospheric Modeling System, to consider the relationship between mesoscale convective structures within the Indo-Pacific region and the regional, intraseasonal anomalies associated with the MJO. The simulation captures the entirety of a canonical boreal summertime MJO event, spanning 45 days in July and August of 2016, during which the convective anomaly associated with the MJO propagated over the Maritime Continent. The convective cloud structures, or cells, within the simulation were tracked and logged according to their location relative to the regional convective anomaly of the MJO. Using both spectral analysis and phase compositing, it was found that a progressive relationship exists between the boreal summertime MJO and mesoscale deep convective structures within the Indo-Pacific region, specifically within the convectively enhanced region of the MJO, as follows: increased cell longevity in the initial phases of the MJO, followed by increased cell number in the intermediate phases, progressing into increased cell expanse in the terminal phases. This progressive relationship is connected back to the low-frequency atmospheric response to the MJO. It is suggested that the bulk thermodynamic and kinematic anomalies of the MJO are closely related to the convective cell expanse and longevity, although the number of convective cells appears to be tied to another source of variability not identified within this study. These findings emphasize that while the MJO is commonly defined as an intraseasonal-scale convective anomaly, it is also intrinsically tied to the mesoscale variability of the convective systems that constitute its existence. The second part of the study quantifies the prevalence of the MJO within the overall climate system, along with the dependence of its teleconnections on variability in another tropical phenomena on a larger scale than itself. It is well known that the MJO exhibits pronounced seasonality in its tropical and global signature, and recent research has suggested that its tropical structure also depends on the state of the Quasi-Biennial Oscillation (QBO). We therefore first quantify the relationship between 300-mb geopotential anomalies and the MJO across the globe, then test the dependence of the relationship on both the meteorological season and the QBO phase using a derivative of cross-spectral analysis, magnitude-squared coherence Coh2. It is found that the global upper-tropospheric signature of the MJO exhibits pronounced seasonality, but also that the QBO significantly modulates the upper-tropospheric tropical and extratropical anomalies associated with the MJO. Globally, variability in upper tropospheric geopotential linked to the MJO is maximized during the boreal summertime and wintertime of easterly QBO phases, which is consistent with previous research that has shown easterly QBO phases to enhance the persistence of tropical convection associated with the MJO. Additional features are identified, such as the global maximum in upper-tropospheric variability associated with the MJO occurring during boreal summertime, rather than boreal wintertime. Overall, the MJO explains seven to thirteen percent of intraseasonal atmospheric variability in 300-mb geopotential, depending on season and QBO phase. These results highlight the importance of considering the phase of the QBO in analyses related to either global or local impacts of the MJO, along with the importance of cross-scale relationships, such as those between the MJO and QBO, in governing the coupling between the MJO and teleconnections across the globe. This thesis considers the relationship between the MJO and processes that operate on both longer and shorter timescales than itself, including tropical convection and the Quasi-Biennial Oscillation. In doing so, this work highlights the importance of considering relationships between the MJO and atmospheric phenomena on different spatial and temporal scales and with origins distinct from the MJO itself. While theories exist describing the MJO as its own distinct entity, this research corroborates the idea that it is at its core fundamentally linked to the rest of the climate system, both modulating and being modulated by a broad range of atmospheric processes

THE IMPACT OF BODY MASS AND SKILL LEVEL ON ROWING KINEMATICS

Rowing is a non-weight-bearing aerobic full body exercise, which is often recommended for weight loss programs. Previous studies demonstrated that Body Mass Index (BMI) is correlated with changes in the kinematics of humans. We extend this area of research to compare the effect of both BMI and skill-level on the kinematics of the lower extremities during rowing. Findings highlight differences such as knee flexion, knee internal rotation, hip extension, hip external rotation between normal weight and obese individuals. These findings suggest that injury risks are correlated to body type and previous skill level. This research indicates the need for adjustable setups for the rowing ergometer. This recommendation would not only increase comfort for all types of athletes, but reduce risks of injury and create the necessary conditions to accomplish a proper technique

Control and Automation

Control and automation systems are at the heart of our every day lives. This book is a collection of novel ideas and findings in these fields, published as part of the Special Issue on Control and Automation. The core focus of this issue was original ideas and potential contributions for both theory and practice. It received a total number of 21 submissions, out of which 7 were accepted. These published manuscripts tackle some novel approaches in control, including fractional order control systems, with applications in robotics, biomedical engineering, electrical engineering, vibratory systems, and wastewater treatment plants. This Special Issue has gathered a selection of novel research results regarding control systems in several distinct research areas. We hope that these papers will evoke new ideas, concepts, and further developments in the field

Offshore Structures Exposed to Large Slamming Wave Loads

PhD thesis in Offshore technologyIn sloping shallow water regions, waves undergo different nonlinear transformations such as wave shoaling and breaking, due to the nonlinear wave interactions with the seabed. The forces from breaking waves are of concern for offshore structures installed in such regions. The wave breaking forces are large impulsive forces acting for short period of time. The substructures of offshore wind turbines are usually monopile, gravity-based, tripod and jackettype structures. Due to the simplicity in the design and installation, monopile structures are widely used for supporting offshore wind turbines. However, the operating water depths and turbine capacity of monopile substructures are limited. With the increase in the turbine capacity and use in larger water depths, the offshore wind industry has recently focused on rigid types of substructures, such as jackettype structures. In order to estimate the slamming forces due to wave breaking on offshore structures, many research studies have been conducted in the past. However, most of these studies were limited to simple structures such as monopiles. The empirical force models by Goda et al. [5] and Wienke and Oumeraci [7] are widely used in the industry to estimate the breaking wave forces on monopile structures. However, in the case of the jacket structures there have not been much research. Due to the complexity of jacket structures, it is more difficult to analyse the wave forces on a jacket compared to a monopile. The empirical force models developed for approximating the slamming forces on monopiles cannot be easily transferred to jacket structures due to the different member sizes and orientations. Moreover, the uncertainties in these empirical models need to be addressed while using them for jacket structures. In order to study breaking wave interactions with a jacket structure, high quality experimental data is required. Within the WaveSlam experiment ([4, 11]) carried out in a joint collaboration with the University of Stavanger, NTNU and the University of Hannover, a large-scale jacket structure of 1:8 scale was tested for a number of relevant breaking wave conditions. According to the author’s knowledge this is the first largescale experiment conducted to estimate the breaking wave forces on a jacket structure. This experimental dataset forms the basis for the present research. [...

A Methodology for the Identification of Helicopter Mathematical Models From Flight Data Based on the Frequency Domain

There is considerable need for the application of system identification techniques to helicopters. These include their use in the validation and improvement of existing theoretical flight-mechanics models, and for development flight testing. In both cases, estimates of stability and control parameters are sought. Most applications of system identification techniques to helicopters have involved time-domain methods which use reduced-order mathematical models representing six-degrees-of-freedom rigid-body motion. In this document, an identification methodology which uses the frequency-domain to obtain estimates of the stability and control parameters is advocated

Vibration, Control and Stability of Dynamical Systems

From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”