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<p>Human body models (HBMs) have been present in the automotive industry for simulating automotive related injury since the turn of the century and have in recent years found a place in assessment of soldier and sports related injury prediction and assessment. This issue is the lack of models that lie outside of the 50th percentile. By a simple application of physics, it is evident that acceleration or force will affect people of varying weights differently. To this end, having the ability to scale a 50th percentile HBM to targets for weight and stature would allow for better characterization on how an impact or acceleration event will affect people of differing size, especially when ~90% of males can fall outside the 50th percentile for weight and stature and HBMs models from vendors exist in only a few variations outside the 50th percentile [1]. Using Corvid Technologies’ 50th percentile model CAVEMAN (capable of being repositioned) as a base, scaled model from the 5th to 95th percentiles of stature and weight were generated based on ANSURII metrics, using a combination of 1D and 3D scaling transformations. These models met their stature and weight metrics when standing and weight metrics when positioned. </p> <p>After creation of a framework to scale the CAVEMAN HMB, creation of a digital twin to the HIRRT Lab helmet testing model commenced. With the HIRRT Lab’s history of experimental testing of football helmets, a natural turn of events was to bring helmet performance testing into the computational space. This digital twin was a natural evolution and addition to the HIRRT Lab’s helmet testing as it would enable manipulation of helmets that would be infeasible experimentally. After calibration of the barehead using experimental data, helmeted simulation began. Angle of impact, while it was found to effect peak translational acceleration, was found to profoundly effect peak rotational acceleration. With this in mind, various angles of impact were simulated to produce curves similar to experimental results. Helmeted simulations were qualitatively dissimilar to experimental data, prompting a modification of the padding material used by the models. Following various modifications of the padding material model, these inconsistencies between simulated helmets and experimentally tested helmets persisted. These inconsistencies highlight a need for better characterization of material, such as foam, and more thorough validation of simulated helmet models. The results of the helmeted simulations are difficult to quantify, as the evaluation criteria used for the BioCore model did not include rotational acceleration, indicating a need for further research and simulation is necessary. </p>

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Finite element human body models have in recent years become widely used in the area of vehicle safety evaluations. They make it possible to predict injury risk in specific areas, down to the organ level in the human body. An existing human body model, SAFER HBM includes a rib cage representing an average male. However, humans have a large variability in rib geometry and material properties leading to uncertainties in non-linear phenomena such as rib fracture risk. Hence, it cannot be known if predictions based on an average male representation are applicable to other similar individuals. In simulation studies with the SAFER HBM, rib cortical bone thickness, rib cross-sectional width, and rib cortical bone material properties have been identified as the most influential for the magnitude of rib strains and thus, they have a large influence on the strain-based rib fracture risk. This means that the predicted injury outcome is sensitive to the particular rib properties of an individual, and in a real-world scenario, a distribution of injury outcomes is expected across a population. Knowledge of the injury risk distribution can aid vehicle designers in developing safer vehicles. This distribution can be found through repeated human body model simulations with various rib properties, but due to the lengthy simulation times, this is not feasible. This thesis aims to predict human body model rib strain histories, given variations in the three biomechanical parameters, rib cortical bone thickness, rib cross-section width and rib cortical bone material with the help of graph neural networks (GNNs) for both single and mixed impact scenarios. Several variations of GNNs were used and implemented with help of PyTorch and PyTorch Geometric. An extensive hyperparameter study was performed on a small part of one human body model rib, to find the optimal combinations of hyperparameters and GNNs. The data used in training and evaluation of the networks was generated in LS-DYNA with SAFER HBM v10 and post-processed in Meta post processor. To be able to generate many training examples, the HBM was subjected to a simplified impact scenario consisting of a pendulum impact to the chest. As final verification, the trained GNNs were applied to predict rib strains in a vehicle impact scenario. Evaluation of the GNNs' prediction accuracy on the whole rib cage for all impact scenarios was made by studying the root mean square error along with differences in predicted and actual peak strain, rib fracture risk, time the peak strain occurs and the euclidean distance between the locations within the rib of real and predicted peak strains. The results showed that it is possible to accurately predict strain histories. Further, a multilayer perceptron (MLP) model consistently achieved the lowest errors in all measurements for mixed impacts. However, the trained model produced slightly unexpected errors for test data extracted from vehicle simulations compared to simplified simulations. This is an indication that retraining the model on data from vehicle simulations may be necessary. In conclusion, this thesis has shown the possibility to predict strain histories from a SAFER HBM rib cage extracted from simplified simulations and simulations including the full vehicle model, the SAFER HBM and all safety systems, to investigate the effects of human variability in the rib cage.

A finite element human body model (FE HBM) is a detailed virtual model of the human body that, for example, is used for simulating traffic accidents. A problem with HBMs is that there is no simple way to position the HBMs in non-standard positions. As different postures during an impact will affect the body in different ways it is vital to have the ability to position the HBMs. In this project it was investigated if it is possible to position a HBM from THUMS, by first positioning only the skin and skeleton, as control points, in the 3D-graphics program Blender. Thereafter a radial basis function interpolation is utilised to morph the rest of the HBM into the new position. The results indicate that in theory, it is possible to position a HBM using a 3D-graphics software. However, the method developed in this project resulted in a disfigurement of the morphed model. The disfigurement is possibly due to the change in distance between the skin and skeleton when positioning those body parts in Blender. / En finit element människokroppsmodell (FE HBM) är en detaljerad virtuell modell av människokroppen som exempelvis används för att simulera trafikolyckor. Ett problem med HBM:er är att det inte finns något enkelt sätt att positionera dem i annat än standardpositioner. Eftersom olika kroppsställningar påverkar kroppen på olika sätt under en kollision är det viktigt att ha möjlighet att kunna positionera en HBM. I detta projekt undersöktes om det är möjligt att positionera en HBM från THUMS, genom att först positionera endast huden och skelettet, som kontrollpunkter, i 3D-grafikprogrammet Blender. Därefter användes en radiell basfunktionsinterpolation för att flytta resten av HBM till den nya positionen. Resultaten indikerar att det är möjligt att positionera en HBM med hjälp av ett 3D-grafikprogram. Metoden som utvecklades i detta projekt resulterade dock i en deformering av den positionerade modellen. Deformeringen beror möjligen på att avståndet mellan hud och skelett ändrades vid positioneringen av dessa kroppsdelar i Blender.

Men who have sex with men (MSM) are disproportionately affected by HIV infection and account for more than half of all new HIV infections diagnosed in the U. S. The purpose of this study was to explore factors that influence sexual behavior among sexually active HIV positive MSM using constructs from the health belief model (HBM). A cross-sectional, correlational study was conducted with a non-randomized sample of 216 HIV positive MSM. Participants were predominantly Black/African American (85.6%). The mean age of the sample was 43.02 years (SD = 9.74) and ages ranged from 19 to 66. More than 90% reported a high school educational level or greater; and nearly half (47.2%) had been diagnosed with HIV for more than 10 years. The overall model predicted that participants who had perceived less severity of living with HIV and who had a positive attitude toward condom use were more likely to practice safer sex, accounting for 24% of the variance in sexual behavior (p < .001). When controlling for demographic characteristics (age, number of years diagnosed as HIV positive, number of recent sexual partners, and current antiretroviral medication use), the overall model accounted for 41% of the variance (p < .001). Participants who had a fewer number of recent sex partners and who had a positive attitude toward condom use were more likely to practice safer sex. Additionally, those who practiced safer sex (n = 58, 27%) reported significantly higher levels of perceived severity of living with HIV (p = .037), perceived benefits of safe sex (p = .018), perceived barriers to safe sex (p < .001), and self-efficacy for negotiating safe sex (p = .013) compared to those who did not practice safer sex (n = 157, 73%). Results from the study indicated there was a high prevalence of unsafe sexual practices among the participants. These findings support the need for additional research to explore factors that influence sexual behavior among HIV positive MSM with an emphasis on testing interventions that support safe sex practices.

In modern integrated circuits, electrostatic discharge (ESD) is a major problem that influences the reliability of operation, yield and cost of fabrication. ESD discharge events can generate static voltages beyond a few kilo volts. If these voltages are dissipated in the chip, high electric field and high current are generated and will destroy the gate oxide material or melt the metal interconnects. In order to protect the chip from these unexpected ESD events, special protection devices are designed and connect to each pin of the IC for this purpose. With the scaling of nano-metric processing technologies, the ESD design window has become more critical. That leaves little room for designers to maneuver. A good ESD protection device must have superior current sinking ability and also does not affect the normal operation of the IC. The two main categories of ESD devices are snapback and non-snapback ones. Non-snapback designs usually consist of forward biased diode strings with properties, such as low heat and power, high current carrying ability. Snapback devices use MOSFET and silicon controlled rectifier (SCR). They exploit avalanche breakdown to conduct current. In order to investigate the properties of various devices, they need to be modeled in device simulators. That process begins with realizing a technology specific NMOS and PMOS in the device simulators. The MOSFET process parameters are exported to build ESD structures. Then, by inserting ESD devices into different simulation test-benches, such as human-body model or charged-device model, their performance is evaluated through a series of figures of merit, which include peak current, voltage overshoot, capacitance, latch-up immunity and current dissipation time. A successful design can sink a large amount of current within an extremely short duration, while it should demonstrate a low voltage overshoot and capacitance. In this research work, an inter-weaving diode and SCR hybrid device demonstrated its effectiveness against tight ESD test standards is shown.

In modern integrated circuits, electrostatic discharge (ESD) is a major problem that influences the reliability of operation, yield and cost of fabrication. ESD discharge events can generate static voltages beyond a few kilo volts. If these voltages are dissipated in the chip, high electric field and high current are generated and will destroy the gate oxide material or melt the metal interconnects. In order to protect the chip from these unexpected ESD events, special protection devices are designed and connect to each pin of the IC for this purpose. With the scaling of nano-metric processing technologies, the ESD design window has become more critical. That leaves little room for designers to maneuver. A good ESD protection device must have superior current sinking ability and also does not affect the normal operation of the IC. The two main categories of ESD devices are snapback and non-snapback ones. Non-snapback designs usually consist of forward biased diode strings with properties, such as low heat and power, high current carrying ability. Snapback devices use MOSFET and silicon controlled rectifier (SCR). They exploit avalanche breakdown to conduct current. In order to investigate the properties of various devices, they need to be modeled in device simulators. That process begins with realizing a technology specific NMOS and PMOS in the device simulators. The MOSFET process parameters are exported to build ESD structures. Then, by inserting ESD devices into different simulation test-benches, such as human-body model or charged-device model, their performance is evaluated through a series of figures of merit, which include peak current, voltage overshoot, capacitance, latch-up immunity and current dissipation time. A successful design can sink a large amount of current within an extremely short duration, while it should demonstrate a low voltage overshoot and capacitance. In this research work, an inter-weaving diode and SCR hybrid device demonstrated its effectiveness against tight ESD test standards is shown.

Low back pain is a common cause of disability and work inability, often associated with intervertebral disc degeneration. The current understanding of disc degeneration is limited and none of the available treatments is entirely effective. The work described herein investigates potential strategies for the biological herapeutic restoration of disc degeneration. Firstly, an in vitro study to investigate the effects of BMP-7 on human discal cellular viability was performed. Cultured cells were treated with TNF-a or H202 to induce apoptosis, resulting in the down regulation of extracellular matrix proteins, decreased cell viability, morphological changes and activation of caspase-3; however, addition of BMP-7 alone prevented the observed effects, demonstrating the ability of BMP-7 to prevent apoptosis of human disc cells in vitro. Secondly, the differentiation potential of stem cells towards disc-like cells was studied. Rodent mesenchymal stem cells (rMSCs) were cultured alone or co-cultured with rat disc tissue. Differentiation potential of rMSCs was evaluated by mRNA and protein expression, cellular function and morphological studies. The co-culture conditions led to the expression of chondrocytic markers in rMSCs, whereas rMSCs cultured alone did not express the chondrocytic markers. Cellular contact between the co-cultured rMSCs and the discal tissue were observed. This study demonstrated that rMSCs can differentiate into functional disc-like cells in a tissue influenced co-culture environment. Finally, the survival and differentiation of CD34+ or CD34?? bone marrow (hBM) cells, in an intra-discal xenogeneic transplantation rat model was investigated. Human CD34+ or CD34?? cells were isolated, fluorescent-labelled and injected into rat coccygeal discs. The survival of transplanted cells was confirmed by fluorescent positive cells as well as a human nuclear specific marker. Interestingly, CD34?? cells survived until day 42 in the injected discs, and differentiated into cells ex:pressing a chondrocytic phenotype. In contrast, CD34+ cells could not be detected by day 21. This data suggests that transplanted hBM CD34?? cells, in contrast to CD34+ cells, were able to survive and differentiate within the intervertebral disc. Together, the results of these studies can both encourage and contribute to the basis of potential biological therapies in the restoration of intervertebral disc degeneration.

No description available.