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<p> The force-velocity and force-length relationships of skeletal muscle have been thoroughly investigated in the literature. Unfortunately many of the relationships that have been applied to models of the human anatomy have been based upon investigations that have been performed under in-vitro conditions. It was the intention of this study to investigate whether the relationships determined by in-vitro investigation and assumed to be correct could accurately and properly be applied to actual human examples. Previous investigation by Leedham and Dowling (1991) displayed that when investigating human elbow flexors and in particular the biceps brachii that the force-length relationship did not concur with in-vitro results. The purpose of this study was to investigate the relationships between length, velocity, EMG and force of the biceps muscle. </p> <p> Eight young adult males (22-26) were fastened into an isoveloci ty device ( CYBEX) which allowed only flexion and extension of the right elbow. The forearm was then rotated eccentrically or concentrically through a range of motion from 50 to 170 degrees of extension (or vice-versa). The biceps muscle was either maximally contracted voluntarily or was excited using electrical stimulation at 40 Hz. Using the constant angle torque (CAT) method and three dimensional surfaces the force-velocity, force-length and EMG-velocity relationships were investigated. <p> <p> The main conclusions of the study were that the neural drive provided by electrical stimulation over the motor point provided CMAPS of consistent amplitude regardless of the joint angle or angular velocity. The concentric force-velocity relationship of the biceps was in agreement with most accounts in the literature however the eccentric contraction condition displayed a peak force production at 30° Is then showed a slight decline to plateau across faster eccentric velocities. Increased eccentric force production was thought to be more mechanical than neurological in nature. </p> / Thesis / Master of Science (MSc)

Yes / Sedimentation processes are fundamental to solids/liquid separation in water and wastewater treatment, and therefore a robust understanding of the settlement characteristics of mass fractal aggregates (flocs) formed in the flocculation stage is fundamental to optimized settlement tank design and operation. However, the use of settling as a technique to determine aggregates’ traits is limited by current understanding of permeability. In this paper, we combine experimental and numerical approaches to assess settling velocities of fractal aggregates. Using a non-intrusive in situ digital image-based method, three- and two-dimensional fractal dimensions were calculated for kaolin-based flocs. By considering shape and fractal dimension, the porosity, density and settling velocities of the flocs were calculated individually, and settling velocities compared with those of spheres of the same density using Stokes’ law. Shape analysis shows that the settling velocities for fractal aggregates may be greater or less than those for perfect spheres. For example, fractal aggregates with floc fractal dimension, Df ¼ 2.61, floc size, df > 320 μm and dp ¼ 7.5 μm settle with lower velocities than those predicted by Stokes’ law; whilst, for Df ¼ 2.33, all aggregates of df > 70 μm and dp ¼ 7.5 μm settled below the velocity calculated by Stokes’ law for spheres. Conversely, fractal settling velocities were higher than spheres for all the range of sizes, when Df of 2.83 was simulated. The ratio of fractal aggregate to sphere settling velocity (the former being obtained from fractal porosity and density considerations), varied from 0.16 to 4.11 for aggregates in the range of 10 and 1,000 μm, primary particle size of 7.5 μm and a three-dimensional fractal dimension between 2.33 and 2.83. However, the ratio decreases to the range of 0.04–2.92 when primary particle size changes to 1.0 μm for the same fractal dimensions. Using the floc analysis technique developed here, the results demonstrate the difference in settlement behaviour between the approach developed here and the traditional Stokes’ law approach using solid spheres. The technique and results demonstrate the improvements in understanding, and hence value to be derived, from an analysis based on fractal, rather than Euclidean, geometry when considering flocculation and subsequent clarification performance / Rodrigo B. Moruzzi is grateful to São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP) Grant 2017/19195-7 for financial support and to CNPq for the fellowship Grant 301210/2018-7.

In recent times Jamaica has experienced an increase in infrastructure and mineral resource (bauxite) developments. As a result, quarrying activities have also increased to supply the needed construction material. Blasting has been the main technique for loosening insitu rock before transporting to construction site. Consequently there is a growing concern of the effects of blasting activities on the environment. These effects are normally nuisances to the neighbouring residence as they come in the form of: dust, toxic gases, noise, fly rocks and ground vibration. Of the set of nuisances the one that is of most concern is ground vibrations which can cause damage to structures. In most cases worldwide, after blasting activities there are the usual complaints about damage to residence, which is also a focus of the thesis. There have been researches on the subject of ground vibrations to help refute some of these complaints. The works of Lewis Oriard and Charles Dowding are the foundation on which standards and regulations are built as guides to assist blasters in the prevention of creating unnecessary nuisances. Most countries have developed their own regulations with respect to blasting and parameters are set according to the geological conditions. This is of importance as the rock structures determine the transmission of the peak particle velocity. However, most countries in the west adopt standards similar to ones put forward by the United States Bureau of Mines or The Office of Surface Mining. It is my opinion that a whole scale adoption should not take place, as the criteria used may not be suitable for other countries’ geological conditions. For this thesis the aim was to identify a vibration level that will not cause damage to structures close to a quarry. Based on the literature review it was revealed that there are a number of parameters that needed to be considered. These ranges: construction material, age of structures, distance from structures, geology of the location, type and quantities of explosives and the blast design. There was also the review of standards to building threshold with respect to the level of ground vibration. The case study with its main focus on vibration levels at structures in close proximity to the Bengal quarry revealed that a tolerable level can be determined which will not result in any form of damage to the structures. However, having established a PPV limit using the USBM and OSM standards that appears reasonable there is the need for criteria similar to those of the USBM and OSM using blasting and geological conditions in Jamaica. Due to the time constraints (20 wks) it is recommended that future research is carried out in this area especially in relation to assessing the performances of the structures. / <p>Validerat; 20101217 (root)</p>

There are millions of pieces of space debris in orbit around Earth that pose threats to operating spacecraft. Some of these debris can be attributed to satellite failure, or end-of-life protocols. With a continual increase in commercial satellite launches per year, decommissioned spacecraft act as more debris polluting the space environment. Not only can robotic arms assist with active orbital debris removal to be more sustainable, they also support robotic on-orbit servicing (OOS). Additionally, using a robotic manipulator enables different servicing operations to take place, allowing for life extension capabilities for expired spacecraft. These life extension services allow for a broader application for robotic arms, which includes rendezvous proximity operations and docking. Robotic arms can also be used for assembly and manufacturing cases, establishing a more sustained presence and creating permanent structures in space. When considering any robotic rendezvous maneuvers or servicing, assembly, and manufacturing tasks aboard a spacecraft, it is important for the parent satellite to maintain attitude throughout robot motion, as in a zero gravity setting, any forces created by the robot act as equal and opposite forces applied to the parent spacecraft. The research performed in this thesis aims to create a model to describe changes in attitude throughout planned robot motion, as well as introduce methods for compensating for potential disturbances. Additionally, methods for describing the kinematics of a robot manipulator are presented and the forces and torques experienced by each joint are calculated using Newton-Euler inverse dynamics. Based on a calculated trajectory of the end effector, these torques are propagated to the parent spacecraft to determine the change in angular velocity. The results of this analysis are used to determine the required angular velocity to apply to the parent spacecraft in order to maintain attitude. / Master of Science / There are millions of pieces of space debris in orbit that threaten operating spacecraft. Spacecraft that are no longer working, yet continue to orbit, are considered space debris. As commercial satellite launches increase each year, orbital debris becomes more of a problem. Instead of disregarding broken satellites and adding to the orbital debris problem, robotic arms can be used to help fix and extend the lives of these spacecraft through acts of refueling or docking with an expired satellite to assume control, as well as provide assistance with orbital debris removal. In a broader sense, robotic arms can help two satellites dock together as well as assist in proximity operations. Robotic arms can be used to manufacture parts and build space structures, establishing a more permanent human presence in space. Because these robot servicing tasks can be very precise, it is important for the attached spacecraft to maintain position and orientation. During any servicing, assembly, or manufacturing task, the motion of a robotic arm produces forces that propagate to the parent spacecraft. If the spacecraft were on the ground, these forces would absorb into the ground, not affecting the position or orientation of the spacecraft. In zero gravity, any forces created by the robot arm act as equal and opposite forces applied to the parent spacecraft. These forces can cause shifts in the satellites position and orientation which need to be compensated for. Methods for describing the motion of the robotic arm are presented, and a model for how the parent spacecraft reacts to this motion is created. The results from this analysis are used to determine the appropriate counterforce to apply to the parent spacecraft in order to maintain desired orientation.

Velocity tomography is a noninvasive technology that can be used to determine rock mass response to ore removal. Velocity tomography is accomplished by propagating seismic waves through a rock mass to measure velocity distribution of the rock mass. Tomograms are created by mapping this velocity distribution. From the velocity distribution relative stress in the rock mass can be inferred, and this velocity distribution can be mapped at specific time intervals. Velocity tomography is an appropriate technology for the study of rockbursts. Rockbursts are events that occur in underground mines as a result of excessive strain energy being stored in a rock mass and sometimes culminating in violent failure of the rock. Rockbursts often involve inundation of broken rock into open areas of the mine. They pose a considerable risk to miners and can hinder production substantially. The rock mass under investigation in this research is the strata surrounding an underground coal mine in the western United States, utilizing longwall mining. The mine has experienced rockbursts. Seismic data were collected over a nineteen day period, from July 20th, 1997 to August 7th, 1997, although only eighteen days were recorded. Instrumentation consistsed of sixteen receivers, mounted on the surface, approximately 1,200 feet above the longwall panel of interest. The system recorded and located microseismic events, and utilized them as seismic sources. The data were analyzed and input into a commercial program that uses an algorithm known as simultaneous iterative reconstruction technique to generate tomograms. Eighteen tomograms were generated, one for each day of the study. The tomograms consistently display a high velocity area along the longwall tailgate that redistributes with face advance. Numerical modeling and mine experience confirm that the longwall tailgate is subject to high stress. Additionally, microseismic events are correlated with the velocity tomograms. Velocity tomography proves to be an effective method for the study of stress redistribution and rockburst phenomena at underground longwall coal mines, because it generates images that are consistent with prior information about the stress state at the mine and with numerical models of the stress in the mine. / Master of Science