16,987 research outputs found
Meso-scale FDM material layout design strategies under manufacturability constraints and fracture conditions
In the manufacturability-driven design (MDD) perspective, manufacturability of the product or system is the most important of the design requirements. In addition to being able to ensure that complex designs (e.g., topology optimization) are manufacturable with a given process or process family, MDD also helps mechanical designers to take advantage of unique process-material effects generated during manufacturing. One of the most recognizable examples of this comes from the scanning-type family of additive manufacturing (AM) processes; the most notable and familiar member of this family is the fused deposition modeling (FDM) or fused filament fabrication (FFF) process. This process works by selectively depositing uniform, approximately isotropic beads or elements of molten thermoplastic material (typically structural engineering plastics) in a series of pre-specified traces to build each layer of the part. There are many interesting 2-D and 3-D mechanical design problems that can be explored by designing the layout of these elements. The resulting structured, hierarchical material (which is both manufacturable and customized layer-by-layer within the limits of the process and material) can be defined as a manufacturing process-driven structured material (MPDSM). This dissertation explores several practical methods for designing these element layouts for 2-D and 3-D meso-scale mechanical problems, focusing ultimately on design-for-fracture. Three different fracture conditions are explored: (1) cases where a crack must be prevented or stopped, (2) cases where the crack must be encouraged or accelerated, and (3) cases where cracks must grow in a simple pre-determined pattern. Several new design tools, including a mapping method for the FDM manufacturability constraints, three major literature reviews, the collection, organization, and analysis of several large (qualitative and quantitative) multi-scale datasets on the fracture behavior of FDM-processed materials, some new experimental equipment, and the refinement of a fast and simple g-code generator based on commercially-available software, were developed and refined to support the design of MPDSMs under fracture conditions. The refined design method and rules were experimentally validated using a series of case studies (involving both design and physical testing of the designs) at the end of the dissertation. Finally, a simple design guide for practicing engineers who are not experts in advanced solid mechanics nor process-tailored materials was developed from the results of this project.U of I OnlyAuthor's request
The Artist as Surveillant: The Use of Surveillance Technology in Contemporary Art
Artists have long been called observers, voyeurs, and watchers, and with a particular interest in human behavior and society, they frequently use unknowing passersby as their subjects for works. Curators and scholars explored how artists put citizens under surveillance with photography and videography, which dates back to the early 1900s, years before governments deployed surveillance systems. Since the 1980s, artists have explicitly explored surveillance technology and theory to alert viewers to the rise of surveillance. Today, this genre is called artveillance, a term coined by Andrea Mubi Brighenti in 2010 to categorize art that explicitly deals with surveillance. This genre developed parallel to the rise of mass surveillance which created the current-day surveillance state. Since artveillance dominates the contemporary art scene, I was interested in the history of surveillance technology and themes in art. Although that history is brief, there is a wealth of artworks and studies on the topic. This thesis explores artists who use surveillance technology, specifically close-circuit video, in their practice and how this work has changed over time compared to the rise of government surveillance systems. To properly examine the artwork, each artwork’s technological history and broader cultural context is considered, with careful attention to the artists’ intentions. The thesis starts in the 1970s with Bruce Nauman and Peter Campus’s closed-circuit video installations. The artists did not aim to create a surveillance area but wanted to explore the viewer’s identity with their moving image. In Chapter 2, Julia Scher and Lynn Hershman Leeson’s work from the 1980s and early 1990s is discussed. Created when state surveillance was on the rise, the artists’ work used surveillance technology to critique the systems. The third chapter explores surveillance in a post-9/11 state through Jill Magid and Laura Poitras’s work. The artists exploited and exposed government systems to show how the public’s privacy is invaded. Finally, the paper concludes with an investigation into the public’s relationship with video surveillance, which resembles an apathetic acceptance
A direct-laser-written heart-on-a-chip platform for generation and stimulation of engineered heart tissues
In this dissertation, we first develop a versatile microfluidic heart-on-a-chip model to generate 3D-engineered human cardiac microtissues in highly-controlled microenvironments. The platform, which is enabled by direct laser writing (DLW), has tailor-made attachment sites for cardiac microtissues and comes with integrated strain actuators and force sensors. Application of external pressure waves to the platform results in controllable time-dependent forces on the microtissues. Conversely, oscillatory forces generated by the microtissues are transduced into measurable electrical outputs. After characterization of the responsivity of the transducers, we demonstrate the capabilities of this platform by studying the response of cardiac microtissues to prescribed mechanical loading and pacing.
Next, we tune the geometry and mechanical properties of the platform to enable parametric studies on engineered heart tissues. We explore two geometries: a rectangular seeding well with two attachment sites, and a stadium-like seeding well with six attachment sites. The attachment sites are placed symmetrically in the longitudinal direction. The former geometry promotes uniaxial contraction of the tissues; the latter additionally induces diagonal
fiber alignment. We systematically increase the length for both configurations and observe a positive correlation between fiber alignment at the center of the microtissues and tissue length. However, progressive thinning and “necking” is also observed, leading to the failure of longer tissues over time. We use the DLW technique to improve the platform, softening
the mechanical environment and optimizing the attachment sites for generation of stable microtissues at each length and geometry. Furthermore, electrical pacing is incorporated into the platform to evaluate the functional dynamics of stable microtissues over the entire range of physiological heart rates. Here, we typically observe a decrease in active force and contraction duration as a function of frequency.
Lastly, we use a more traditional ?TUG platform to demonstrate the effects of subthreshold electrical pacing on the rhythm of the spontaneously contracting cardiac microtissues. Here, we observe periodic M:N patterns, in which there are ? cycles of stimulation for every ? tissue contractions. Using electric field amplitude, pacing frequency, and homeostatic beating frequencies of the tissues, we provide an empirical map for predicting the emergence of these rhythms
The Influence of Frontal and Axial Plane Deformities on Contact Mechanics during Squatting: A Finite Element Study
Knee Osteoarthritis (KOA) is a degenerative joint disease and a leading cause of disability worldwide. Lower limb malalignment was a risky factor leading to KOA, altering the load distributions. This study aimed to study the influence of knee deformities on knee contact mechanics and knee kinematics during squatting. A full-leg squat FE model was developed based on general open-source models and validated with in vivo studies to investigate the outputs under frontal malalignment (valgus 8° to varus 8°) and axial malalignment (miserable malalignment 30°). As a result, Varus-aligned and miserable aligned models increased medial tibiofemoral force and lateral patellar contact pressures, while the valgus-aligned model increased lateral tibiofemoral force medial patellar contact pressures with no effects on total contact loads. The Model with a higher medial force ratio (medial force/total force) induced a higher internal tibial rotation. In conclusion, we recommended that patients with knee malalignment be taken care of alignments in both frontal and axial planes
Visualisation of Fundamental Movement Skills (FMS): An Iterative Process Using an Overarm Throw
Fundamental Movement Skills (FMS) are precursor gross motor skills to more complex or specialised skills and are recognised as important indicators of physical competence, a key component of physical literacy. FMS are predominantly assessed using pre-defined manual methodologies, most commonly the various iterations of the Test of Gross Motor Development. However, such assessments are time-consuming and often require a minimum basic level of training to conduct. Therefore, the overall aim of this thesis was to utilise accelerometry to develop a visualisation concept as part of a feasibility study to support the learning and assessment of FMS, by reducing subjectivity and the overall time taken to conduct a gross motor skill assessment. The overarm throw, an important fundamental movement skill, was specifically selected for the visualisation development as it is an acyclic movement with a distinct initiation and conclusion. Thirteen children (14.8 ± 0.3 years; 9 boys) wore an ActiGraph GT9X Link Inertial Measurement Unit device on the dominant wrist whilst performing a series of overarm throws. This thesis illustrates how the visualisation concept was developed using raw accelerometer data, which was processed and manipulated using MATLAB 2019b software to obtain and depict key throw performance data, including the trajectory and velocity of the wrist during the throw. Overall, this thesis found that the developed visualisation concept can provide strong indicators of throw competency based on the shape of the throw trajectory. Future research should seek to utilise a larger, more diverse, population, and incorporate machine learning. Finally, further work is required to translate this concept to other gross motor skills
Strategies for Early Learners
Welcome to learning about how to effectively plan curriculum for young children. This textbook will address: • Developing curriculum through the planning cycle • Theories that inform what we know about how children learn and the best ways for teachers to support learning • The three components of developmentally appropriate practice • Importance and value of play and intentional teaching • Different models of curriculum • Process of lesson planning (documenting planned experiences for children) • Physical, temporal, and social environments that set the stage for children’s learning • Appropriate guidance techniques to support children’s behaviors as the self-regulation abilities mature. • Planning for preschool-aged children in specific domains including o Physical development o Language and literacy o Math o Science o Creative (the visual and performing arts) o Diversity (social science and history) o Health and safety • Making children’s learning visible through documentation and assessmenthttps://scholar.utc.edu/open-textbooks/1001/thumbnail.jp
Acute Effects of Velocity-Based Resistance Training on the Physical Functional Performance of Older Adults
International Journal of Exercise Science 15(3): 399-413, 2022. The aim of this study was to analyse the acute effects of velocity-based resistance training on the physical and functional performance of older adults. Twenty participants (70.4 ± 7.4 years) performed the deadlift exercise, in two different resistance training protocols. The moderate-velocity protocol (MV) predicted maximum loads so that the movement velocity during the concentric phase remained in the range of 0.5 to 0.7 m/s and the high-velocity protocol (HV) predicted maximum loads so that the movement velocity remained between 0.8 and 1.0 m/s. The jump height (cm), handgrip strength (kg), and time (s) to complete the functional tests were assessed before (baseline), and immediately (post), 24-h, and 48-h after the MV and HV protocols. Compared to baseline, both training protocols acutely led to a gradual reduction in walking velocity, with significant values 24 hours after training (p = 0.044), on the other hand, both protocols improved performance in the timed up and go test at post (p \u3c 0.001) and in the sit-to-stand test at 48-h (p = 0.024), although there were no significant differences between them for any times analysed (p \u3e 0.05). No other outcomes exhibited significant changes. Results indicate that neither of the protocols (MV and HV) led to significant impairments in physical function of the older adults, and can be recommended with the safety criterion of at least 48-h of rest between sessions
Latest Advances in Waste Plastic Pyrolytic Catalysis
With the increase in demand for plastic use, waste plastic (WP) management remains a challenge in the contemporary world due to the lack of sustainable efforts to tackle it. The increment in WPs is proportional to man’s demand and use of plastics, and these come along with environmental challenges. This increase in WPs, and the resulting environmental consequences are mainly due to the characteristic biodegradation properties of plastics. Landfilling, pollution, groundwater contamination, incineration, and blockage of drainages are common environmental challenges associated with WPs. The bulk of these WPs constitutes polyethene (PE), polyethene terephthalate (PET) and polystyrene (PS). Pyrolysis is an eco-friendly thermo-chemical waste plastic treatment solution for valuable product recovery, preferred over landfilling and incineration solutions. In this extensive review, a critical investigation on waste plastic catalytic pyrolysis (WPCP) is performed, including catalyst and non-catalyst applications to sustainably tackle WP management. Current catalysis techniques are revealed, and some comparisons are made where necessary. Common pyrolytic products and common shortcomings and errors related to WP catalysis were also identified. The benefits of catalysts and their applications to augment and optimise thermal pyrolysis are emphasised. With all these findings, and more, this paper provides reassurance on the significance of catalysis to industrial-scale applications and products and supports related WPCP research work concerning the environment and other beneficiaries
Exploring differences in electromyography and force production between front and back squats before and after fatigue and how this differs between the sexes
Limited research has been conducted to explore sex differences in biomechanical and physiological demands of the front and back squat, especially in response to fatigue where technique may be altered. Therefore, this study investigated differences in electromyography and force production in performance of back and front squats before and after a fatigue protocol and how this differed between males and females. 35 participants (5 female, 30 male) performed a fatigue protocol for back and front squats with measures of maximal performance pre and post. Main findings were that mean and peak activation of the semitendinosus was greater in the back squat than the front squat suggesting that the back squat has greater hamstring activation possibly for hip stabilisation and knee flexion (p < 0.05). There were no differences in quadricep activation between back and front squats, disputing the notion that front squats have a greater quadricep focus, however, lending support to the hypothesis that quadricep activation equal to the back squat can be achieved with lighter absolute load in a front squat. There were no differences in electromyography as a result of fatigue however force production decreased for back squats following fatigue (p < 0.01). This decrease could result from decreased acceleration out of the bottom position and into the concentric phase. This study also presents preliminary findings of greater mean and peak rectus femoris activation in females compared to males in both front (p < 0.01) and back squats (p < 0.05). This was suggested to be in order to support the knee and in an attempt to prevent knee valgus and excess hip adduction. These findings have implications in programming for both high performance sport and for rehabilitation of lower limb injuries
The culture of the perfect body: analysis of the use of dietary and anorectic elements to weight loss and eating disorders
Eating disorders are psychological disorders that directly affect the physical health of those who suffer from them, with a high mortality rate. Women are more prone to eating disorders than men, which is why most research focuses on women. Thus, 10% of patients with eating disorders are men. The results of bibliographical research are presented through in-depth interviews about the perception of the body that Social Work and Psychology professionals, who worked in both the public and private sectors, as an element that can influence eating disorders. This perception has been analyzed as an element that influences eating disorders. This research reaches three main conclusions: First, the body is considered by professionals as an instrument to stop time when personal identity problems arise, especially when the patient is a woman. Second, professionals perceive their patients' bodies as a responsibility in open conflict with social perceptions seen as something unattainable, ideal, and subject to unattainable parameters. Finally, the perception of the body is guided by social imaginaries in which morality (taboo and sin) and the biological are predominant
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