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Additively manufactured parts produced using selective laser melting (SLM) are prone to defects created during the build process due to part shrinkage while cooling. Currently defects are found only after the part is removed from the printer. To determine whether cracks can be detected before a print is completed, this project developed print parameters to print a test coupon with inherent defects – warpage and cracking. Data recorded during the build was then characterized to determine when the defects occurred. The test coupon was printed using two sets of print parameters developed to control the severity of warpage and cracking. The builds were monitored using an accelerometer recording at 12500 samples per second, an iphone recording audio at 48000 samples a second, and a camera taking a photo every build layer. Data was analyzed using image comparison, signal amplitude, Fourier Transform, and Wavelet Decomposition. The developed print parameters reduced warpage in the part by better distributing heat throughout the build envelope. Reducing warpage enabled the lower portion of the part to be printed intact, preserving it to experience cracking later in the build. From physical evidence on the part as well as time stamps from the machine script, several high energy impulse events in the accelerometer data were determined to be when cracking occurred in the build. This project’s preliminary investigation of accelerometers to detect defects in selective laser melting will be used in future work to create machine learning algorithms that would control the machine in real time and address defects as they arise.

Purpose: The purpose of this study was to assess the relationship between intensity of physical activity and body composition in 239 young adult women. Methods: This study was cross-sectional. Participants were recruited from October 2009 to December 2011 and included women from 36 different states and 6 different countries. Physical activity was objectively measured using accelerometers worn for seven days. Body composition was measured using the BOD POD. Height, weight, and circumferences were assessed. Results: Participant's mean age was 20.6±1.6 years. Their mean BMI was 22.6±3.0 kg/m2 and mean body fat percentage was 26.4±6.3 %. Average total activity counts per day were 387,560 ± 172,000, with 61.6±22.5 min per day spent in MVPA, 169.4±43 min per day in light activity, 55.6±19 min per day in moderate activity, and 6±9.2 min per day in vigorous activity. Total activity counts per day were inversely correlated with body fat (r = -0.17, p = 0.007). Light activity was positively correlated with both BMI (r = 0.17, p = 0.007) and waist circumference (r = 0.15, p = 0.0164). Moderate activity was inversely associated with body fat (r = -0.18, p = 0.0051) and hip circumference (r = -0.12, p = 0.0459). MVPA was inversely associated with body fat (r = -0.19, p = 0.0026) and hip circumference (r = -0.14, p = 0.0291). Vigorous physical activity was inversely related to body fat (r = -0.20, p = 0.0023). Using stepwise regression, the best predictor of body fat was time spent in vigorous PA (F = 9.45, p = 0.0024). The best predictor of BMI was light activity per day, which was positively correlated with BMI (F = 7.5, p = 0.0066) followed by moderate activity per day which was negatively correlated (F = 4.25, p = 0.0403). Young adult women who spent no time performing vigorous PA had significantly higher body fat percentages than women who performed some vigorous PA. Young adult women who spent less than 30 minutes per day in MVPA had significantly higher body fat percentages and BMIs than those who obtained more than 30 minutes per day. For every 10 minutes spent in MVPA per day, the odds of being obese by body fat decreased by 33%. Conclusion: Vigorous PA and MVPA appear to be the most important aspects of PA associated with lower body fat and BMI levels. Young adult women should be encouraged to obtain at least 30 minutes of MVPA per day.

[pt] Em estudos de integridade estrutural devem-se realizar medições de deslocamentos, pois estes são diretamente relacionados aas deformações. Contudo, nos casos em que este estudo é realizado em grandes estruturas, como pontes e estádios, torna-se difícil realizar esta medição com os transdutores disponíveis, tais como medidores de deslocamento resistivos e LVDT’s, pois há necessidade de se ter uma referência fixa perto do ponto onde se deseja realizar a medição. Existem muitos transdutores novos que utilizam tecnologia laser para a realização destas medições, contudo, este tipo de transdutor é ainda relativamente caro. Outra forma de se obter deslocamentos é através da integração dupla de sinais acelerométricos, contudo os integradores duplos analógicos comerciais disponíveis apresentam muitos problemas relacionados à sua Resposta Dinâmica e não são uma boa solução. Dessa forma, nesta tese é proposta uma forma de se realizar esta integração dupla de forma digital,obtendo-se então um sistema de medição de deslocamentos que utiliza acelerômetros. / [en] The measurement of displacements is very important of structural integrity, because they are directly related to the deformations. However, when the measurements are supposed to be made in huge structures, as bridges and stadiums, it becomes very difficult, because the available transducers, like LVDT’s, need to be fastened to a fixed reference. There are many new transducers the use laser to make these measurements, but, this kind of transducer are still expensive. Another form to measure displacements is through the double integration of accelerometer signals, however the analog double irregrators available presents many problems related to its Dynamic Response and can’t be used for this purpose. In this thesis it is proposed a digital way of making this double integration, allowing us to obtain a displacement measurement system that uses accelerometers.

Today's Advance Technology Facilities require low noise levels and increased noise monitoring. Ambient noise can interfere with the accuracy and precision of experiments and manufacturing processes. Therefore preconstruction site surveys are needed to develop strategies for mitigating noise. Vibration and low frequency electromagnetic fields are particularly detrimental for sensitive instruments, and they are also difficult to mitigate. However a large part of these costs can be avoided or minimized if a quiet building site is selected in the first place. Accelerometers and gauss meters combined with a computer for acquisition and analysis provide a low cost method of evaluating noise levels at proposed building sites. This work examines low frequency vibration and electromagnetic fields at two proposed sites for the planned Physical Science Building at the University of Central Florida.

This work addresses the problem of localizing an impact in a dispersive medium (waveguide) using a network of vibration sensors (accelerometers), distributed at various locations in the waveguide, measuring (and detecting the arrival of) the impact-generated seismic wave. In particular, the last part of this document focuses on the problem of localizing footsteps using underfloor accelerometers. The author believes the outcomes of this work pave the way for realizing real-time indoor occupant tracking using underfloor accelerometers; a system that is tamper-proof and non-intrusive compared to occupant tracking systems that rely on video image processing. A dispersive waveguide (e.g., a floor) causes the impact-generated wave to distort with the traveled distance and renders conventional time of flight localization methods inaccurate. Therefore, this work focuses on laying the foundation of a new alternative approach to impact localization in dispersive waveguides. In this document, localization algorithms, including wave-signal detection and signal processing, are developed utilizing the fact that the generated wave's energy is attenuated with the traveled distance. The proposed localization algorithms were evaluated using simulations and experiments of hammer impacts, in addition to occupant tracking experiments. The experiments were carried out on an instrumented floor section inside a smart building. As will be explained in this document, energy-based localization will turn out to be computationally cheap and more accurate than conventional time of flight techniques. / PHD

This thesis investigates the problem of sensors used with mobile robots. Firstly, a colour sensor is considered, for its ability to detect objects having the three primary colours Red, Green and Blue (RGB). Secondly, an accelerometer was investigated, from which velocity was derived from the raw data using numerical integration. The purpose of the design and development of the sensors was to use them for robotic navigation and collision avoidance. This report presents the results of experiments carried out on the colour sensor and the accelerometer. A discussion of the results and some conclusions are also presented. It proved feasible to achieve the goal of detecting colours successfully but only for a limited distance. The accelerometer proved reliable but is not yet being applied in real time. Both the colour sensor and the accelerometer proved to be inexpensive. Some recommendations are made to improve both the colour sensor and the accelerometer sensors.

Background: Objectively tracking sedentary behavior (SB) and physical activity (PA) is becoming increasingly important as research continues to show the negative effects with increasing SB and decreasing PA. Objectives: The purpose of this study was to evaluate three commercial activity trackers with young adults regarding how they accurately measure SB and PA behaviors in a laboratory setting. Methods: 50 college-aged participants wore three wrist-based activity trackers (Fitbit Surge, Apple Watch, and Basis Peak) and two ActiGraph accelerometer devices during a series of SB and PA behaviors for five-minute intervals in a laboratory setting. The activity trackers were evaluated against direct observation and the ActiGraph devices, placed on the hip and wrist, which are consistent with the National Health and Nutrition Examination Survey (NHANES) standards of measure. Results: Overall accuracy during the SBs compared to direct observation was high, with Apple (99.0%), Basis (99.0%), and Fitbit (94.9%) performing similar to the Hip ActiGraph (95.1%) and markedly better than the Wrist ActiGraph (58.6%). Overall significant correlations (p ≤ 0.05) during the PAs were higher with the Wrist ActiGraph (66.7%) than with the Hip ActiGraph (8.3%). The Wrist and Hip ActiGraphs significantly correlated in three out of four SBs, but not in any PA behaviors.Discussion: Activity trackers are reliable when determining sedentary behavior, tend to overestimate step count during light walking, and underestimate activity level when biking. Also,the Wrist ActiGraph consistently underestimated both SB and PA step count compared to the Hip ActiGraph. While some variability is seen in the validity of the activity trackers, each activity tracker studied has its strengths and weaknesses. Understanding these strengths and limitations helps healthcare professionals more accurately interpret recorded data based on the patient specific device.

Microelectronic Measuring Systems (MEMS) are being used to capture kinematic data in real-world environments. The benefits of using MEMS are their small size, relatively low cost (compared to an Optical Motion Capture System) and the ability to capture real-time data in almost any environment. The accuracy and precision of MEMS can be influenced by elements in their surrounding environment such as building materials (i.e., reinforced steel) and structural components (i.e., elevators). Recognizing the influence of the environment on MEMS output is important if the MEMS are to be used in real-world environments where subjects could navigate between various environments. MEMS can also be affected by dynamic motion therefore testing of the MEMS in the same conditions in which they are to be used will help to identify any issues prior to data collection. The overall purpose of this thesis was to determine if the outputs of four Shimmer 2r MEMS were accurate and precise enough in static and dynamic conditions to use in a future study to assess gait activities of daily living in individuals with a unilateral transtibial amputation. In order to understand the effect of the environment on the MEMS, accuracy and precision were assessed in a rural environment (to reduce the effect of building materials and structural components) as well as the clinical environment where they will eventually be used for research. The MEMS were also evaluated in static and dynamic conditions to better understand how motion affected accuracy and precision. The results of this study confirmed that the clinical environment affected the MEMS outputs. During the dynamic condition, the gyroscope output of one MEMS sensor was significantly different than the other devices indicating recalibration or possible exclusion from future studies. Prior to using MEMS in research, it is advisable to investigate the effects of the environment on the sensor outputs as well as assess the performance of the individual sensors. / Thesis / Master of Science Rehabilitation Science (MSc) / The overall objective of this thesis was to determine if four Shimmer 2r Microelectronic Measuring Systems (MEMS) were accurate and precise enough in static and dynamic conditions prior to their use in a future study to assess seven activities of daily living (including level walking, ramp walking and stairs) in individuals with a unilateral transtibial amputation in a clinical environment. To understand the effect the environment has on the MEMS, they were assessed in both a rural environment to reduce the effect of building materials, as well as the clinical environment where they will eventually be used for research. This study confirmed that the clinical environment affected the MEMS outputs, although these effects were deemed to be clinically insignificant for the intended purpose of these MEMS. Calibration as well as accuracy and precision assessment of MEMS should be executed in the conditions and environments in which they are to be utilized.

Rockfall, which is the detachment of rocks from a mountain, is a major hazard in the mining industry. To help combat this issue, this thesis aims to develop a sensor platform that is able to detect both the potential risk for rockfall and if any rocks do hit the ground. The platform requires wireless communication in order to output relevant information and in order to be part of an IoT-network of sensors.The design of the platform used three different sensors, a geophone, an accelerometer and a microphone. The main focus of the design process was to keep the platform low power, enabling long operation times. The final design had data output from both the microphone and accelerometer, with the accelerometer able to pick up the impact from a falling barbell. Wireless transmission of data is possible for up to 7.5 meters using Bluetooth Low Energy. The low power design was met, with an average current consumption of 26 milliamperes during transmission using Bluetooth Low Energy. That gives a theoretical operation time of 27 days with the battery used. As the accelerometer can pick up a falling object and with a theoretical lifetime of 27 days for the platform, it can be argued that the goals, except for detecting potential risk for rockfall, were met. In order to properly function, however, the platform needs more development, but the most important conclusion of the work is that it seems possible to build this type of platform. Further research and development outside the scope of the thesis is connecting several platforms together.