The majority of the physical properties of tissue depend directly on the interstitial or intracellular concentration of water within the epidermal and dermal layers. The relationship between skin constituent concentrations, such as water and protein, and the mechanical and optical properties of human skin is important to understand its complex nature. Localized mechanical loading has been proven to alter optical properties of tissue, but the mechanisms by which it is accomplished have not been studied in depth. In this thesis, skin's complex nature is investigated experimentally and computationally to give us better insight on how localized mechanical loading changes tissues water content and its optical properties. Load-based compression and subsequent increased optical power transmission through tissue is accomplished to explore a relationship between localized mechanical loading and tissue optical and mechanical properties. Using Optical Coherence Tomography (OCT), modification of optical properties, such as refractive index, are observed to deduce water concentration changes in tissue due to mechanical compression. A computational finite element model is developed to correlate applied mechanical force to tissue strain and water transport. Comprehensive understanding of the underlying physical principles governing the optical property changes within skin due to water concentration variation will enable future development of applications in the engineered tissue optics field. / Master of Science

The human body is a complicated dynamic system that is difficult to model because of the numerous interactions that occur between limbs during various tasks. There are documented movement differences when assessing movement in various populations, for example, joint angle and loading symmetry differences when comparing a clinical and healthy population. Symmetry deficits can impact quality of life and in some cases have been associated with an increase in injury risk. Therefore, it is essential to understand movement and loading symmetry in healthy individuals to facilitate the identification of rehabilitation targets. The purpose of this research was to assess the impact that task type and sex have on movement variability and load symmetry in healthy younger adults. The tasks included in this study represent activities of daily living such as level walking, stair ascent, stair descent and standing up from a chair. A wireless, single-sensor in-shoe force sensor allowed for data collection in a non-laboratory setting so that peak impact force and average loading rate could be evaluated across the different daily tasks. To assess movement variability, the coefficients of variation (CV) were determined for each task. The peak impact force (PIF) did not show a significant interaction between sex and task (p=0.627) or between sexes (p=0.685). The PIF did show significant between-task differences (p < 0.001), where the highest mean CV was observed in the sit-to-stand task and the lowest CV was observed during level walking. The variation between movements could be a result of the differential motor skill required to perform the task. The average loading rate (ALR) did not show a significant interaction between sex and task (p=0.069) or between sexes (p=0.624). The average loading rate showed significant between-task differences (p < 0.001), where the highest mean CV was observed in the sit-to-stand task and the lowest CV was observed during level walking. Based on these results, differences in movement type needs to be considered when evaluating average loading rate. To assess the impact of task type on load symmetry, the absolute symmetry index was calculated for the peak impact force and the average loading rate. For both parameters, only between task differences were identified (p < 0.001) and further analysis showed that sit-to-stand was significantly different from the other three movement tasks. The acceptable threshold for a healthy level of asymmetry has been defined in a clinical population to be less than 10%. Based on a chi square analysis, the 10% threshold accurately represents 95% of the population when used to measure peak impact force in level walking, stair ascent and stair descent. However, when assessing peak impact force symmetry during sit-to-stand or assessing average loading rate symmetry between tasks, the 10% threshold does not consistently represent 95% of the population. These results indicate that a threshold for a healthy symmetry may need to be redefined for bilateral movements and that the symmetry threshold may need to be specific to the outcome measure of interest. / Master of Science / When an individual completes a task there are many options for how they accomplish the movement each of which requires the different use of motor skills, these differences in how tasks are completed are called movement variability. A better understanding of these movement differences during various tasks in a healthy population then could help prevent long term injury and allow for the development of interventions to aid in recovery following injury. One way to assess measurements of the human body is to look at symmetry. Movements that are performed on a daily basis include walking, stair ascent, stair descent and standing up from a chair are considered activities of daily living throughout literature. Therefore, it is important to simulate these daily activities to assess a healthy population. Thus, this research aims to assess the impact that the type of task being completed has on the variability of movement and load symmetry in a healthy young adult population. Data collection was performed with an in-shoe measurement device that connects via Bluetooth to an iPad. These sensors allow for data to be collected outside of a laboratory setting allowing for the collection of a wider variety of tasks. The coefficient of variation (CV) was calculated for each task. This is a measure that allows for an understanding of the standard deviation of a measure in relation to the mean of the data. Differences in peak impact force and average loading rate variability were observed between tasks. For both parameters, the sit-to-stand task had the largest variability, most likely due to this being a task that allows for the use of limbs, which provides individuals with more flexibility in how they complete the movement. To assess load symmetry between tasks, the absolute symmetry index was calculated, a value that computes a percent difference between the right and left limbs. The peak impact force symmetry of the sit-to-stand task was different from the others because it requires the loading of both limbs simultaneously, which allows individuals to preferentially load one limb versus the other when completing this task. When evaluating load symmetry, clinicians have been using a threshold of 10% when defining a healthy symmetry benchmark when evaluating injury recovery. A difference greater than 10% between limbs may suggest a higher susceptibility to injury or a lack of recovery. This study evaluated if this 10% threshold accurately represents symmetry in peak impact force and average loading rate for 95% of the participants. While the 10% threshold does accurately describe the between limb differences in walking, stair ascent and stair descent tasks, the 10% threshold does not represent the results from 95% of those in this healthy population when standing up from a chair. Further, this 10% threshold did not accurately describe the symmetry discrepancies in average loading rate for any task evaluated in this study. These results suggest that a benchmark for defining healthy symmetry may need to be redefined for some tasks and outcome measures.

NAND flash-based Solid State Devices (SSDs) provide high performance and energy efficiency and at the same time their capacity continues to grow at an unprecedented rate. As a result, SSDs are increasingly being used in high end computing systems such as supercomputing clusters. However, one of the biggest impediments to large scale deployments is the limited erase cycles in flash devices. The natural skewness in I/O workloads can results in Wear imbalance which has a significant impact on the reliability, performance as well as lifetime of the cluster. Current load balancers for storage systems are designed with a critical goal to optimize performance. Data migration techniques are used to handle wear balancing but they suffer from a huge metadata overhead and extra erasures. To overcome these problems, we propose an endurance-aware write off-loading technique (EWO) for balancing the wear across different flash-based servers with minimal extra cost. Extant wear leveling algorithms are designed for a single flash device. With the use of flash devices in enterprise server storage, the wear leveling algorithms need to take into account the variance of the wear at the cluster level. EWO exploits the out-of-place update feature of flash memory by off- loading the writes across flash servers instead of moving data across flash servers to mitigate extra-wear cost. To evenly distribute erasures to flash servers, EWO off-loads writes from the flash servers with high erase cycles to the ones with low erase cycles by first quantitatively calculating the amount of writes based on the frequency of garbage collection. To reduce metadata overhead caused by write off-loading, EWO employs a hot-slice off-loading policy to explore the trade-offs between extra-wear cost and metadata overhead. Evaluation on a 50 to 200 node SSD cluster shows that EWO outperforms data migration based wear balancing techniques, reducing up to 70% aggregate extra erase cycles while improving the write performance by up to 20% compared to data migration. / Master of Science / Exponential increase of Internet traffic mainly from emerging applications like streaming video, social networking and cloud computing has created the need for more powerful data centers. Datacenters are composed of three main components- compute, network and storage. While there have been rapid advancements in the field of compute and networking, storage technologies have not advanced as much in comparison. Traditionally, storage consists of magnetic disks with magnetic parts which are slow and consume more power. However, Solid State Disks (SSDs) offer both better performance and lower energy. With the price of these SSDs being comparable to magnetic disks, they are increasingly being used in storage clusters. However, one of the biggest drawback of SSDs is the limited program erase (P/E) cycles. There is a need to ensure the uniform wearing of blocks in a SSD. While solutions for this do exist for a single SSD device, usage of these devices in a cluster poses new problems. This work introduces EWO which is a wear balancing algorithm that balances wear in a flash storage cluster. It carried out load balancing in a flash storage cluster while incorporating the wear characteristics as a cost function. EWO carries out lazy data migration also referred to as write offloading. To alleviate the metadata overhead, the migration is performed at the slice level. To evaluate EWO, a distributed key value store emulator was built to simulate the behavior of an actual flash storage cluster.

Much previous experimentation related to wood structures has employed monotonic loading to replicate static situations. However, instances of natural hazards have raised interest in the response of structural connections to dynamic loads. This increased interest led the Consortium of Universities for Research in Earthquake Engineering (CUREE) to develop a testing protocol for reverse-cyclic loading, which involves cycling loads through zero in order to test specimens in both tension and compression. With the CUREE testing protocol in place, recent research has been devoted to understanding the effects of reverse-cyclic loading on multiple-fastener connections. Experimentation by Heine (2001), Anderson (2002), Billings (2004) and others contributed to a better understanding of bolted connection behavior under reverse-cyclic loading. However, some questions remained. Billings was unable to consistently produce yield modes III and IV, meaning that her suggested bolt spacing of seven times the bolt diameter (7D) could not be applied to connections subject to these yield modes without further testing. In addition, the work of Anderson and Billings raised questions regarding the proper measurement of bending yield strength in bolts and the relationship between the bending yield strength and the tensile yield strength. These topics are each addressed by this project and thesis report. Results of the connection testing presented in this report can be used in conjunction with the work of Anderson and Billings to critically evaluate the 4D between-bolt spacing recommended by the National Design Specification (NDS) for Wood Construction (AF&PA, 2001). Results of the bolt testing provide a supplement to the search for a reliable method for the measurement of bending yield strength in bolts. / Master of Science

Background: Epidemiological studies suggest an increased incidence of osteoarthritis among workers in occupations requiring squat-lifting such as in construction, mining and farming. Squat-lifting postures can induce heavy mechanical loads on the joint, causing the articulating surfaces to deform. This can result in changes of vibration characteristics of the joint surfaces. Differences in the vibration characteristics of normal and pathological joints have been established and used in the past for classifying severity of disease. The purpose of this study was to examine the influence of cumulative mechanical load on the vibration properties of the knee joint and to gain an understanding of how these properties may relate to an increase in cumulative load placed on the joint. Methods: In this study, cumulative load was measured as the resultant knee joint torque during squat lifting, while a piezoelectric accelerometer was used to capture vibration signals from points on the knee during flexion and extension. Twelve university students were recruited for a repeated measures study. Each participant attended one session where they had to perform a series of six squat-lifting tasks on a force platform. Motion capture equipment was used to obtain kinematic data. The cumulative 3-D moment on the joint was calculated using inverse dynamics. Results: A visual inspection of an ensemble average constructed for the frequency spectrum of all participants revealed that differences may exist in the 750 Hz - 2000 Hz bandwidth for vibrations coming from the patella during flexion. Further statistical analysis by a t-test and ANOVA showed a decrease in the RMS power of the signal captured in this bandwidth before and after mechanical load was induced by squat lifting. A linear regression analysis indicated a significant correlation between cumulative 3-D moment on the knee joint and the median frequency of vibration signals from the patella during flexion in the 1000 Hz - 2500 Hz range. Conclusions: Overall, the results of this study indicate the possibility of a relationship between mechanical exposure on the knee joint and its vibration properties during joint movement. Despite the small sample size, a declining trend was observed in the normalized RMS power of signals with increase in loading. However, the quantitative nature of this relationship is not clear and the current study points towards a non-linear relationship between joint exposure and knee vibrations. Future studies must investigate this possibility using direct measures of joint loading, cartilage deformation and their relation to joint vibrations. / Master of Science

An experimental investigation was conducted to study the extended end-plate moment connections subjected to cyclic loading. Seven specimens representing three end-plate moment connection configurations commonly used in the pre-engineered building industry were used. The connections were designed using yield-line theory to predict end-plate yielding and the modified Kennedy method to predict maximum bolt force calculations including prying action. A displacement controlled loading history was used to load the specimens. The maximum moments obtained experimentally and the experimental bolt forces throughout loading were compared with analytical predictions and finite element model results. The inelastic rotation of connections was calculated and conclusions were drawn on the compliance of these connections with current AISC specifications. / Master of Science

Yes / Seabed consolidation state is one of important factors for evaluating the foundation stability of the marine structures. Most previous studies focused on the seabed consolidation around breakwaters standing on the seabed surface. In this study, a numerical model, based on Biot’s poro-elasticity theory, is developed to investigate the unsaturated seabed consolidation around a nearshore pile foundation, in which the pile inserted depth leads to a different stress distribution. Seabed instabilities of shear failure by the pile self-weight and the potential liquefaction under the dynamic wave loading are also examined. Results indicate that (1) the presence of the inserted pile foundation increases the effective stresses below the foundation, while increases and decreases the effective stresses around the pile foundation for small (de/R<=3.3) and large (de/R>3.3) inserted depths, respectively, after seabed consolidation, (2) the aforementioned effects are relatively more significant for small inserted depth, large external loading, and small Young’s modulus, (3) the shear failure mainly occurs around the inserted pile foundation, rather than below the foundation as previously found for the located marine structures, and (4) wave-induced momentary liquefaction near the inserted pile foundation significantly increases with the increase of inserted depth, due to the change of seabed consolidation state. / National Natural Science Foundation for Distinguished Young Scholars (51425901), the National Natural Science Foundation of China (51209082, 51209083), the Natural Science Foundation of Jiangsu Province (BK20161509), the Fundamental Research Funds for the Central Universities (2015B15514), Jiangsu Graduate Research and Innovation Plan Grant (#CXLX11_0450) and the 111 project (B12032).

Exploring the mechanical properties of soft tissues under compressive loading is crucial for understanding their role in automobile incidents. Soft tissues, which serve as cushions or padding between bone and vehicle interiors, significantly influence contact duration and forces, thereby altering incident kinematics and injury risk assessment. In this investigation, muscle and soft connective tissues from post-mortem human subjects (PMHS) forearms were excised and subjected to compression and indentation testing methods at various rates and strains. Anthropomorphic Test Devices (ATDs) upper extremity foam and vinyl foam composite material surrogate tissues underwent similar testing for comparison. High impact rates simulating those in high-speed car collisions were achieved using a custom-built drop tower. The results revealed substantial differences in stiffness between soft tissues and ATD materials across most loading rates and strains, although some exceptions were noted at higher rates and strains. Indentation and modified Zener models were used to quantify material parameters. The indentation model could characterize human muscle, soft connective tissues and ATD vinyl foam composites, but fell short with ATD foam materials. The Zener model effectively derived material parameters for the tested human tissues but encountered difficulties characterizing both ATD materials. This highlights the need for further refinement to develop a constitutive model for both materials. These findings provide a solid basis for advancing ATD surrogate materials and have broader implications for soft tissue research. Moreover, this work represents a crucial step towards enhancing safety standards in the automotive industry. / Thesis / Master of Science in Biomedical Engineering / Soft tissues are crucial in mitigating impact effects in various loading scenarios, yet their specific roles are complex and poorly understood. Understanding soft tissues' role in these loading scenarios is critical for understanding injury risk tolerances. This study aimed to characterize muscle and soft connective tissue behaviour during compressive loading scenarios using various techniques and modelling approaches. This was done through compressive loading tests on soft tissues and comparing these same tests with data from current crash test dummy surrogate tissues. The results showed that the soft tissues were less stiff than the crash test dummy materials in most scenarios. It was also apparent that different stiffnesses were seen depending on soft connective tissue and muscle tissue composition. This study provides insights into the rate dependence of materials, alongside the relevance of how different compositions affect their loading properties. This characterization also revealed significant discrepancies between the responses of current surrogates and human muscle and soft connective tissues. This work offers valuable observations and data for refining ATD surrogates and enhancing their fidelity in simulating real-world impact scenarios. Such advancements are pivotal for improving safety standards.

Evaluating the performance of filter media for filtration applications is essential to assure design engineers and users that filter device will deliver promised performance for specific applications under the environmental stress. The study of particle loading characteristics of filter media in the laboratory setting is typically performed under the steady flow conditions, i.e., at the constant particle concentration and flow rate. In reality, filtration products are operated under the situations that the flow rate and mass concentration of particles are varied in time. The success of translating the laboratory data to estimate the performance of filter media in the fields is thus limited. It is necessary to investigate the performance of filter media under the real-world conditions, i.e., unsteady flow rate and mass concentration to bridge the gap. The overall goals of this research are (1) to study the performance of filter medium under unsteady conditions (i.e., the performance of respirator filter media under simulated breathing conditions); and (2) to investigate the issue of non-uniform particle deposition on HVAC filter panels. A new experimental setup was developed to accomplish the former goal. Numerical modeling tool, Computational fluid dynamics (CFD), was applied to achieve the latter objective……

Title of thesis: Evaluation of psychologically and physically load in competitors of Winter Survival; including incorporation of knowhow to hold the competition. Aim of thesis: 1. Creation of a manual to order competition of Winter Survival type in civil and army. 2. Valorize and confront physically load in Winter Survival 2007, 2008, 2011. 3. Valorize and confront psychologically load in Winter Survival 2007, 2008, 2011. Methods: 1. For the creation of the manual was used qualitative research with exploitation of interview with abstract questions. 2. To valorizing and fixing of physically load was used quantitative study. 3. To valorizing and fixing of psychologically load was used quantitative study. Results: 1. We created the "manual" to ordering and organising of cometition for trainee officials of competitions like Winter Survival. 2. The results prove, that competitors of WS moved around middle zone of physical load. WS 2008 was, in light of physical load, much easier, than WS 2007 and 2011. Effect of the extension in 2. part of competition is the extension of physical work in middle zone of physical load to the prejudice moderate zone. 3. Mental condition is impressed with physical load in "state" and "activity" parameter, less connections are between physical load and "mood" parameter; the...