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Many studies and experiments have been conducted over the years to find solutions to the electricity problem. This issue is not just related to how fossil fuels are dispensed. Also, the environmental concerns associated with using fossil fuels have become a severe issue, which is a major cause of environmental pollution and ozone layer damage. As such, the need for energy becomes one of the essential goals. Therefore, research has begun to revolve around thermoelectrics, which is a straightforward approach for generating energy, by converting heat directly into electricity. Cobalt antimonide (CoSb3) belongs to a broad family of materials with the skutterudite structure, which have been recently identified as potential new thermoelectric materials with high performance. The CoSb3 is one of the numerous promising thermoelectric materials in the intermediate temperature range. The binary CoSb3 is a narrow bandgap semiconductor with a relatively flat band structure and excellent electrical performance. The thermoelectric performance efficiency of binary CoSb3 is measured by its figure of merit. The figure of merit is important for thermoelectric materials and is primarily governed by the Seebeck coefficient because it exhibits a square dependence. The Seebeck coefficient of the CoSb3 can be affected by many factors that can either increase or decrease it. Strain is an important aspect for the transport properties, including the Seebeck coefficient. The goal of this thesis project is to study the effect of point defects and strain on the Seebeck coefficient of skutterudite CoSb3. The binary CoSb3 skutterudite was explored through density functional theory (DFT) to calculate the ground-state properties, in particular the Seebeck coefficient. Two different CoSb3 structures were considered, an ideal one (without any defects) and the other was termed real (containing defects). In both cases, the Seebeck coefficient and its response were studied while strain was applied by changing the volume of the structure. The non-equilibrium Green's function was used within a DFT simulation to get a transmission distribution, where it was essential for calculating the Seebeck coefficient. Moreover, oxygen molecules were placed over the (001) surface of 2 × 2 × 1 CoSb3 supercell to establish if oxidation leads to point defect formation. These simulations were carried out by DFT-based molecular dynamics. It is found that the strain affects the Seebeck coefficient in the ideal structure. At compression, the absolute value of the Seebeck coefficient increases.  By contrast, the Seebeck coefficient changed its sign from negative to positive and increased to 894 μVK−1at tension, which was unexpected. The electron density distribution map was explored to explain the behavior of the Seebeck coefficient at equilibrium, compression, and tension. It can be seen that the electron distribution between Co and Sb is increased at compression, implying an increased orbital overlap (covalent interaction). By contrast, the tension reduces the electron distribution between Sb and Co. The real structure induced by oxidation exhibits Sb vacancies. The See-beck coefficient is affected differently than that of the ideal structure. At equilibrium, the Seebeck coefficient increases to 151 μVK−1. The electron density distribution between Sb and Co is enhanced in the real structure compared to the ideal one. The most drastic change is found at tension, where the Seebeck coefficient reaches−270 μVK−1. It may be speculated that this occurs due to O which increases the orbital overlap. The strategy introduced in this work, an interplay of defects and strain effects, may be beneficial for other thermoelectric materials.

Vid träning av baksida lår kan det vara svårt att förstå hur muskeln aktiveras. Genom att visualisera de myoelektriska signalerna från biceps femoris och semimembranosus till den som tränar kan personen få en bättre mind-muscle connection. I examensarbetet har två teoretiska EMG sensorer skapats och simulerats, kod har skrivits för att filtrera fyra EMG signaler samt överföra dessa över BLE, kraftsensorer är kopplade och kod är skriven för att avgöra den kraftutveckling som sker i en kontraktion av baksida lår. EMG sensorerna har jämförts med SparkFuns MyoWear muskelsensor, OpenBCI Cyton board och BioNomadix BN-EMG2-T. Båda de teoretiska lösningarna anses likvärdiga med ett billigare alternativ till Cryton Board, en flerkanalig lösning till MyoWear, BN-EMG2-T är för dyr att realistiskt implementeras till examensarbetets syfte. Simuleringarna visar att kretsarna behandlar signalen enligt tänkt sätt men det gick inte att bygga en prototyp då en pandemi har begränsat KTH:s verksamhet / One difficulty when training hamstrings is the understanding of how the muscle is activated. Through visualization of the myoelectrical signals from biceps femoris and semimembranosus to the exerciser, a better mind-muscle connection can be achieved. In this bachelor thesis, two theoretical EMG sensors were created and simulated, code to filter four EMG signals and transmit them through BLE was written, also a way to calculate how much force is applied in a hamstring curl was constructed. Both EMG sensors have been compared against SparkFuns MyoWear muscle sensor, OpenBCI Cyton Board and BioNOmadix BN-EMG2-T. The theoretical EMG sensors are interconvertible to a cheaper Cyton Board, a multichannel alternative to MyoWear, the BN-EMG2-T is too expensive to be a realistic alternative for this bachelor thesis attended purpose. Simulations show that the EMG sensors behave as intended but because of a pandemic, a prototype could not be created.

This project involves the design and development of a cell stretching bioreactor device that can work in conjunction with a Random Positioning Machine (RPM) apparatus. Microgravity environments, such as in space, have been shown to induce alterations in cellular development due to inadequate mechanical loading of biological tissue. Because of this, long-term spaceflight has led to many health concerns, including osteoporosis and muscle atrophy. Space travel is rare and costly, making this research difficult to conduct, however; techniques to simulate microgravity on Earth can be achieved by using a Random Positioning Machine. This device has been a beneficial tool used to study the effect gravity has on cellular growth, yet certain tissues in the body, such as bone and muscle, require mechanical stress, strain, and mechanical loading to develop properly. Because of this, a device that can induce strain on cells while subjected to microgravity conditions is needed to further improve cellular research for space exploration. The constructed bioreactor consists of 3D printed and custom-made components that can induce uniaxial cyclic strain on cells adhered to an elastic membrane. Validation and testing of the device have shown that this bioreactor is suitable for cellular experimentation to work in conjunction with an RPM to deliver a controlled amount of strain while under microgravity conditions. / Bioengineering

The objective of this work is to develop an evolution equation for the ductile growth of a spherical void in a highly strain rate and temperature dependent material. The material considered in this work is stainless steel 304L at 982 °C. The material is characterized by a physically-based internal state variable model derived within consistent kinematics and thermodynamics — Evolving Microstructure Model for Inelasticity. Through this formulation, the degradation of the elastic moduli due to damage has been naturally acquired. An elastoviscoplasticity user material subroutine has also been developed and implemented into a commercially available finite element software ABAQUS. The subroutine utilizes a return mapping algorithm, where a purely elastic trial state (elastic predictor) is followed by a plastic corrector phase (return mapping). A conditionally stable fully-implicit scheme, derived from the backward Euler integration method, has been employed to calculate the values of the internal state variables in the elastoviscoplasticity integration routine. A repeating unit cell problem is set up by introducing a spherical void inside a matrix material that simulates a periodic array of voids in a component. Using finite element analysis, a database is generated by recording the responses of the unit cell under various combinations of loading conditions, porosity, and state variables. Functional forms of the void growth equations are constructed by utilizing normalization techniques to collapse all the data into master curves. The evolution equations are converted to a form consistent with the continuum damage variable in the complete thermal-elastic-plastic-damage version of the physically-based internal state variable model.

This research developed the quasi-static and dynamic equipment and protocols for tests of both Very-High-Strength Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC) to predict blast performance. VHSC was developed for high compressive strength (> 200 MPa). Using VHSC as the baseline material, HSHDC was developed and exhibits comparable compressive strength (> 150 MPa) and high tensile ductility (> 3% tensile strain). This research investigated quasi-static material properties including compression, tension, and flexure (third-point and pressure loadings). Additionally, dynamic blast load simulator (shock tube) tests were performed on simply-supported one-way panels in flexure. Subsequently, the material response in flexure was predicted using the Wall Analysis Code (WAC). Although VHSC has a higher peak flexural strength capacity, HSHDC exhibits higher ductility through multiple parallel micro-cracks transverse to loading. The equipment and test protocols proved to be successful in providing ways to test scaled concrete specimens quasi-statically and dynamically.

Commercial broilers are fed exclusively pelleted diets; this is due to research that has demonstrated numerous benefits to feeding pellets. The first objective was to investigate the effects of modest improvements in pellet quality on two modern broiler strains. Regardless of strain, feeding 80% pellets improved broiler performance from d 28 to 42. The second objective was to investigate the effects of feed form and liquid application method on feed augering segregation and subsequent broiler performance. In general, percent pellets steadily decreased across location throughout feed augering. Also, phytase segregation occurred throughout augering and was exacerbated in post-pellet liquid application diets. When the augered diets were fed to broilers, 75% pellets and post-pellet liquid application diets improved performance. The final objective was to investigate the change in percent pellets as feed was augered throughout an entire commercial poultry house. Ultimately, creating high-quality pellets decreases pellet attrition and improves broiler performance.

In this study, the teeth of the Carcharodon carcharias (Great White) and the Galeocerdo cuvier (Tiger) sharks were analyzed to examine their optimized structure-property relationships and edge serrations with regards to shearing. Structure-property analysis was conducted using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, X-ray diffraction, and optical microscopy to study the teeth using parametric optimization. Quantifying the structural properties also focused on the tooth serrations, which were captured in SEM and micrographs and were analyzed for geometric parameters using ImageJ software. Nanoindentation was performed to determine the material's mechanical properties. Further, finite element analysis (FEA) of the sharks' teeth serrations were carried out to quantify the optimum shearing performance of each serration type – zeroth (no serrations), first (a single array of serrations), and second (a secondary array of serrations upon the first array) order serration. Here, serration order, bite velocity, and angle-of-impact for ascertaining sharks' teeth shearing performance were analyzed. FEA results showed that serrated edges reduced the energy required to pierce and shear materials as the angle of penetration moved away from perpendicular to the surface. These bioinspired findings will help advance the design and optimization of engineered cutting tools.

The present study develops a phenomenological adaptation to an internal state variable (ISV) model that incorporates the influence of dynamic recrystallization (DRX) in a material’s evolving microstructure and flow stress response. During metal forming and joining processes that promote internal heat distributions and large strains, microstructural processes often occur that result in a transformation of the evolving microstructure away from the base distribution. In an effort to lower the stored energy accumulated in the material’s lattice and grain structure, the deformed material may undergo a type of dynamic recovery process, such as DRX. In this study, the ISV model’s flow stress output is modified to include a phenomenological DRX softening and hardening term internal to the isotropic hardening rate ISV. The flow stress thus directly includes the influence of microstructure evolution. The evolving grain size is modeled such that an inverse relation exists between strain hardening and average grain size.

Data from the McMaster Occupational Biomechanics Laboratory were consolidated to evaluate overall trends relating to tissue motion and blood flow in the carpal tunnel. Regarding tissue motion, displacements of the flexor digitorum superficialis (FDS) tendon and its subsynovial connective tissue (SSCT) were found to decrease with greater movement speed and a flexed wrist posture. Notably, changes to shear outcomes including relative tendon-SSCT displacement, the shear strain index (SSI), and maximum velocity ratio (MVR) demonstrate that greater movement speed contributes to SSCT damage according to the shear strain mechanism of injury theorised to promote carpal tunnel syndrome (CTS). Median nerve blood flow was also found to be implicated by wrist flexion, and appeared to decrease with greater CTS severity status. Finally, induced blood flow alteration of the carpal tunnel was found to elicit a median nerve blood flow response similar to the level found in CTS subjects, confirming its effectiveness as an intervention to study tissue motion in a CTS-like state. The influence of altered blood flow on tissue motion was differential, where the higher supradiastolic condition altered FDS displacement, and the lower subdiastolic condition affected SSCT displacement and SSI. These findings provide valuable evidence for changes in median nerve blood flow—and by extension, the local fluid environment within the carpal tunnel—not only being a consequence of SSCT fibrosis characteristic of CTS, but potentially also acting as a cause for said changes in carpal tunnel tissue motion. / Thesis / Master of Science in Kinesiology / This thesis aimed to evaluate and summarize key findings from the McMaster Occupational Biomechanics Laboratory relating to tissue motion and blood flow in the carpal tunnel. Performing repetitive finger movements faster and with a flexed wrist posture were found to decrease the distance travelled of the underlying finger tendon. Blood flow of the median nerve, which is implicated in carpal tunnel syndrome (CTS), is higher with forceful exertion and flexed wrist posture, and lower with greater severity of CTS. Finally, altering blood flow to the carpal tunnel was found to create a CTS-like environment, affected tissue motion in the carpal tunnel, and promoted movement disparity between these tissues that is associated with injury. This suggests that fluid/blood flow changes affecting the carpal tunnel is a plausible mechanism for increasing the likelihood of developing CTS.