Increasing suburban development has impaired water resources in the Charles River Watershed. Growing populations in the suburban fringes of Boston, Massachusetts have had a significant impact on ecosystems in the region. According to the EPA, one of the primary pollutants in the Charles River is phosphorus (EPA, 2010b). Phosphorus pollution contributes to algal blooms in the Charles that are harmful to ecosystems and toxic to humans (EPA, 2010b). In order to prevent existing suburban residential areas from contributing additional phosphorus to the Charles River, stormwater best management practices (BMPs) were studied to determine which BMPs effectively contain phosphorus. Infiltration trenches, bio-retention areas, and dry swales were selected and tested in scenarios developed for a neighborhood on Hartford Road in Bellingham, Massachusetts. The scenarios were intended to test a prioritized implementation strategy based on phosphorus loading hotspots and flow accumulation patterns. This study is intended to provide designers and planners a process through which site design can more effectively fit into broader ecological systems, specifically hydrological systems. The methodology developed in this study provides the ability to identify land cover types that contribute to phosphorus loading while also allowing phosphors loading hotspots to be identified at a scale as fine as 16 x 16 meters. Recognizing land cover types that contribute to phosphorus loading and prioritizing BMP implementation according to phosphorus loading hotspots within those land cover types allows for both economic BMP implementation efficiency and pollutant removal efficiency.

No description available.

Inlet distortion is an important consideration in fan performance. Distortion can be generated through flight conditions and airframe-engine interfaces. The focus of this paper is a series of high-fidelity, time-accurate Computational Fluid Dynamics (CFD) simulations of a multistage fan, investigating distortion transfer, distortion generation, and the underlying flow physics under different operating conditions. The simulations are full annulus and include 3 stages and the inlet guide vane (IGV). The code used to carry out these simulations is a modified version of Overflow2.2 that was developed as part of the Computational Research and Engineering Acquisition Tools and Environment (CREATE) program. The inlet boundary condition is a single revolution (sinusoidal pattern with one period over the circumference ) total pressure distortion. Simulations at choke, design, and near stall are analyzed and compared to experimental data. Distortion transfer and generation is analyzed under these different operating conditions. Analysis includes the phase and amplitude of total temperature and pressure distortion through each stage of the fan, level of distortion transfer and generation in each stage, and blade loading. An understanding of the flow physics associated with distorted flows will help fan designers account for unsteady flow physics at design and off-design operating conditions, in order to build more robust fans offering a greater stability margin.

Intervertebral disc (IVD) degeneration is a prevalent health problem that is highly linked to back pain. To understand the disease and tissue response to therapies, ex-vivo whole IVD organ culture systems have recently been introduced. The goal of this study was to develop and validate a whole spinal segment culturing system that loads the disc in complex loading similar to the in-vivo condition, while preserving the adjacent endplates and vertebral bodies. The complex loading applied to the spinal segment was achieved with three pneumatic cylinders. The pneumatic cylinders were rigidly attached to two triangular alumni plates at each corner, comprising the loading mechanism. By extending or compressing the pneumatic cylinders, three modes of loading were achieved: flexion-extension, bi-lateral bending, and cyclic compression. The cylinders were controlled via microcontroller, and the entire system was fully automated. The culture container, which housed the spinal segment during culturing, was a flexible silicone container with an aluminum base and lid. The culture container attached to the loading mechanism allows for loading of the spinal segment. It had a vent attached to the aluminum lid that allowed for gas exchange in the system. The dynamic bioreactor was able to achieve physiologic loading conditions with 100 N of applied compression and approximately 2-4 N-m of applied torque. The function of the bioreactor was validated through testing of bovine caudal IVDs with intact endplates and vertebral bodies that were isolated within 2 hours of death and cultured for 14 days under a diurnal cycle. The resulting IVD cell viability following 14 days of loading was approximately 43% and 20% for the nucleus pulposus and annulus fibrosus respectively, which was significantly higher than the unloaded controls. The loading system accurately mimicked flexion-extension, bi-lateral bending, and compression motions seen during daily activities. Results indicate that this complex dynamic bioreactor may be appropriate for extended pre-clinical testing of vertebral mounted spinal devices and therapies.

Ultra-high performance fiber-reinforced concrete (UHPFRC) is an advanced cement-based composite with enhanced compressive strength, tensile resistance and toughness when compared to conventional concrete. Interest in the application of UHPFRC as a retrofit material has been rapidly increasing, and a few existing studies have examined the ability of UHPFRC to retrofit and strengthen existing reinforced concrete (RC) structures under static loading; however, very limited studies have examined the effectiveness of UHPFRC to improve the response of RC members under blast loading. This thesis aims at filing this research gap and investigates the behavior of UHPFRC retrofitted RC flexural members under both static and blast loads. A total of twenty-one (21) specimens, in two different series are tested. Series 1 includes nine (9) singly-reinforced beams built with high-strength concrete (HSC) and strengthened by UHPFRC to improve shear and flexural behaviour. Series 2 includes a further twelve (12) doubly-reinforced beams/columns built with normal-strength concrete (NSC), and strengthened by UHPFRC to improve response under blast, or combined blast-axial loading. Various test parameters are examined including the effects of varying retrofit types (full jacket, U-jacket or T-sided), surface roughening methods, longitudinal steel reinforcement ratio, single vs. repeated blasts, and the effects of axial loading. The results from this thesis are presented in six journal articles. Papers 1 and 2 study the effects of UHPFRC jacketing on the static and blast behaviour of the singly-reinforced HSC beams in Series 1, while Paper 3 discusses the effects of additional parameters such as: the effect of retrofit type, roughening method and steel detailing on blast behaviour. Under static loading (Paper 1), the UHPFRC jacketing was found to be effective in increasing shear resistance (by preventing shear failure), and improving flexural behaviour (by increasing strength, stiffness, ductility and overall toughness) when compared to control beams built without UHPFRC. Similarly, under blast loads (Paper 2) the use of UHPFRC jacketing prevented shear failure, and improved flexural behaviour by reducing displacements at equivalent blasts, increasing overall blast capacity, and improving damage tolerance. On the other hand, the results show that UHPFRC-retrofitted beams with low longitudinal steel ratios may be vulnerable to brittle bar fracture failures. As part of the numerical research, finite element (FE) modelling is used to predict the static and blast behaviour of the test beams using software LS-DYNA (Papers 1 and 2). The results from Paper 3, provide further insights into the effects of retrofit type (FJ, UJ and T) and roughening method on blast performance; both the UJ and FJ retrofits were found to be effective in increasing shear resistance, reducing blast-displacements and increasing blast capacity, while the benefit of the T-sided retrofit was limited by the crushing capacity of HSC concrete. The effect of roughening method was found to be negligible, except at the very late stages of blast loading. Papers 4, 5 and 6 present the experimental results from the doubly-reinforced NSC beams tested in Series 2, with a focus on the effect of UHPFRC jacketing, UHPFRC retrofitting type and Axial loading, respectively. Paper 4 shows that the UHPFRC jacketing increased the stiffness and strength of the beams under both static and blast loading, however the high bond capacity of the UHPFRC and relatively low tension steel ratio increased the vulnerability of bar rupture failure. The numerical parametric study investigates the effects of steel ratio and blast load scenario, jacket thickness and interface location on blast performance and failure model. Paper 5 confirms that the blast performance of the beams is influenced by the retrofit type, with optimal performance obtained when using full- or U-jacketing. The efficient use of localized "hinge" retrofits was also found to be effective, and reduced the vulnerability to bar rupture. The numerical parametric study investigates the effects of steel ratio and blast load scenario (single vs. repeated) on the blast performance of the beams. Paper 6, studies the effect of UHPFRC jacketing in columns tested under combined axial and blast loading. The retrofit is shown to increase blast capacity and reduce blast-induced displacements and damage, though the final failure of the columns was governed by bar rupture. As part of the numerical parametric study the effects of axial load ratio, boundary conditions, steel ratio, jacket thickness and jacket design are studied numerically and found to have significant effects on blast behaviour and failure mode.

Advanced breast cancer predominantly metastasizes to the skeleton, at which point patients suffer bone loss, pain, heightened fracture risk and their prognosis significantly declines. The skeleton is sensitive to its highly dynamic mechanical environment whereby bone mass is increased when applied loads are increased whereas bone loss occurs when applied loads are reduced. Increased mechanical loading inhibited bone metastatic tumor formation and progression in vivo, but the underlying mechanisms are currently under investigation. Here, we focus on the osteocyte, a specialized bone cell well-known as the primary mechanosensor and director of remodeling in the skeleton. Osteocytic dendrites are important for mechanosensing, and their number and length increase with applied loading. Dendrite connections are also known to suppress breast cancer growth and bone metastasis. How breast cancer cells affect loading-induced changes in dendrites, or downstream effects on mechanosensing and remodeling, is unknown. To examine how breast cancer cells modulate osteocyte function, we exposed osteocytes (MLO-Y4 cells) to medium conditioned by breast cancer cells (MDA-MB231 cells) and to fluid shear stress using a rocker platform (2 hrs per day for 3 days, shear stress 1.1 Pa). In the absence of loading, treatment with tumor conditioned media alone did not alter dendrite number per MLO or overall cell number. When loading was applied to MLOs treated with conditioned media, dendrite formation increased in MLOs despite the presence of tumor-derived factors. Conditioned media and loading together reduced MLO cell number, suggesting that the combination of these two factors may be stimulating apoptosis and dendrite formation increases in the remaining viable cells. Next, to model the more physiological situation in which both cell populations undergo loading, we exposed MLOs to loading as well as media conditioned by breast cancers that were also similarly loaded. When control (nonloaded) MLOs were treated with conditioned media from loaded breast cancer cells, their dendrite formation increased in a manner similar to that observed due to loading alone. When MLOs simultaneously underwent loading and treatment with loaded conditioned media, dendrite formation was greatest. Loaded conditioned media also decreased MLO cell number independent of MLO loading status. The results suggested that loading stimulates breast cancer cells to induce both osteocyte dendrite formation and apoptosis, which is a possible mechanism for the inhibitory role of applied loading on bone metastasis.

When a clay soil is sheared, clay particles along the shear plane become aligned in the direction of shear, forming "slickensided" surfaces. Slickensided surfaces are often observed along the sliding plane in field landslides. Because the clay particles along a slickensided surface are already aligned in the direction of shear, the available shear resistance is significantly less than that of the surrounding soil. During an earthquake, ground shaking often causes landslide movement. For existing landslides or repaired landslides that contain slickensided rupture surfaces, it is reasonable to expect that the movement will occur along the existing slickensided surfaces, because they are weaker than the surrounding soil. The amount of movement that occurs is controlled by the dynamic resistance that can be mobilized along the slickensided surfaces. The objective of this study was to investigate, through laboratory strength tests and centrifuge model tests, the shearing resistance that can be mobilized on slickensided rupture surfaces in clay slopes during earthquakes. A method was developed for preparing slickensided rupture surfaces in the laboratory, and a series of ring shear tests, direct shear tests, and triaxial tests was conducted to study the static and cyclic shear resistance of slickensided surfaces. Two dynamic centrifuge tests were also performed to study the dynamic shear behavior of slickensided clay slopes. Newmark's method was used to back-calculate cyclic strengths from the centrifuge data. Test results show that the cyclic shear resistance that can be mobilized along slickensided surfaces is higher than the drained shear resistance that is applicable for static loading conditions. These results, coupled with a review of existing literature, provide justification for using cyclic strengths that are at least 20% larger than the drained residual shear strength for analyses of seismic stability of slickensided clay slopes. This represents a departure from the current state of practice, which is to use the drained residual shear strength as a "first-order approximation of the residual strength friction angle under undrained and rapid loading conditions" (Blake et al., 2002). / Ph. D.

Traditional mortise and tenon timber frames have been used in modern construction for a substantial period of time with acceptable performance against weather phenomena and other hazards. However, performance criteria for this style of timber framing are not well defined in current codes and standards. To determine performance criteria for free-standing timber frames with knee-braces, three tasks were undertaken: (1) Two timber frame specimens were tested under cyclic loads to determine hysteretic behavior, damage states, and to explore rehabilitation of a damaged member using self-tapping screws. Three damage states for were identified: peg shear, tenon tearout, and post or beam splitting. Self-tapping screws were able to restore the strength of the 2-peg timber frame with the damaged beam, but not the stiffness of the frame. (2) Four timber frame mortise and tenon connection specimens were subjected to damp conditions for six months and then tested under monotonic tensile load to determine the effect of joint details. The results indicated that connection types tested had similar strength and stiffness. (3) Twelve free-standing timber frames with knee braces located at various sites across the United States were tested in the field under impulse loading to determine the fundamental period of vibration and to estimate damping. A relationship between the fundamental period and the mean roof height was fit to the test data using a power-law equation, and three sets of parameters were determined: a lower-bound equation for seismic loads, an upper-bound equation for wind loads, and mean equation for human-induced vibration performance criteria.

No description available.

<p> This thesis describes the analytical study of the stability of the structural system under circulatory loading and/or parametric excitation. The model is a double pendulum, composed of two rigid weightless bars of equal length and two concentrated masses at the ends of each bar, on an oscillating base. The vertical oscillation of the base produces parametric excitation to the system. A circulatory force is applied at the free end. At the joints the restoring moments are produced by spring and damping. The damping coefficients are taken as positive, and the gravitational effects are included. </p> <p> The combined effect of the circulatory loading and parametric excitation on stability of the system is investigated. The problem is so formulated that the stability of the system is represented by coupled Mathieu equations. The effect of damping on the boundary of stability is also determined. </p> / Thesis / Master of Engineering (ME)