In recent years, a flurry of interest has been shown for a relatively old technology called magneto-rheological fluids, or MR fluids. Multiple types of devices have been designed to implement this versatile fluid, including linear dampers, clutches, work-piece fixtures, and polishing machines. The devices have been used in automobiles, washing machines, bicycles, prosthetic limbs, and even smart structures. This thesis focuses on another application of MR dampers, involving super-sport motorcycles. This paper introduces the topics of MR dampers and motorcycle suspensions, and why the two would be a good combination. A detailed history of MR fluids, MR dampers, and motorcycle suspension technologies is given next. After a broad outline of MR dampers and motorcycle suspensions, the method of designing and manufacturing MR dampers is discussed. The damper design for this research is presented in detail, along with the design procedure used to make it. Next, laboratory testing for it is covered, including the test equipment, test procedure, and the laboratory test results. Upon laboratory test completion, the field test setup and procedure are presented. The results of field tests with stock dampers and MR dampers with a variety of control systems is discussed. The MR dampers provided a more stable ride than that of the OEM dampers. By reducing suspension displacement, settling time, and suspension oscillations, the MR dampers were able to reduce suspension geometry instability. Lastly, concluding remarks are made on the research presented. Design flaws are discussed, as well as recommendations for future work in the same area. / Master of Science

The thesis develops the acoustic theory of the propagation of the shook waves produced by an aircraft in supersonic flight through an atmosphere in which the speed of sound decreases linearly with altitude. The problem is first studied in terms of the geometry of the rays along which the shock wave travels away from its point of origin and into the surrounding atmosphere. The equation of the rays is derived and certain important properties of the rays are discussed. It is shown how these results lead to a systematic graphical procedure for determining the location of the shock wave of a maneuvering aircraft. The theory is then considered in terms of the geometry of the "wave fronts" which represent the instantaneous positions of the individual disturbances created along the flight path. The shape of a wave front and its growth with time are determined. From this the equations for the envelope of a one-parameter family of wave fronts are obtained. The envelope equations are solved in parametric form and several examples are worked out which show some effects of flight maneuvers upon shock wave propagation. / M.S.

Pallet durability is a key characteristic with significant impact on a company's supply chain. Physical durability is defined as the number of trips that the pallet will accomplish before requiring repairs. Numerous studies have focused on understanding how durability is affected by different pallet components and warehouse environment characteristics. The VPI FasTrack is a testing sequence created to predict the performance of a pallet in a warehouse environment through different handling modes. However, this simulation has not been updated since its creation in 1993; therefore, a revision is needed to make it more closely reflect the behavior of a pallet in terms of durability. The objective of the current research was to investigate the ability of the FasTrack procedure to replicate the damages caused by material handling and storage systems in modern warehouses. This investigation was conducted through visual inspections of the damages seen on pallets used in the field, and pallets tested with FasTrack. The results of this study show the differences between the simulation-tested pallets and those from the field. The FasTrack simulation focuses heavily on top lead deckboard and stringer damage. The occurrence of damage modes such as splits and missing wood, were identified for these components. It was found that most of the damages from this simulation are created due to forklift handling. Because of substantial forklift handling damages, an experimental design was developed to investigate the effects of entry speed, payload, forklift type, and pallet design on the stresses exerted on a pallet, measured in terms of peak acceleration. The factors with the greatest effect on forklift peak acceleration and pallet peak acceleration were identified. The research shows that the acceleration in the pallet is approximately 4.4 times greater than the acceleration recorded in the forklift; however, the model of pallet acceleration based on forklift acceleration as a predictor shows poor performance. Different modifications to FasTrack are proposed according to the findings of this research. It is advised that they continue the FasTrack procedure past the point of repairable damage in a pallet, which is the usual practice when pallets are handled in the field. Further investigation of steps such as the flow rack and the stack storage are proposed, due to their low damage output during the simulation. The experimental design also showed that different damage severity levels from the FasTrack simulation are possible with variations in top load and entry speed. These changes could improve the ability of the VPI FasTrack to replicate the damages that pallets experience in the field. / Master of Science / Pallet durability refers to the number of uses that can be expected from a pallet before it needs to be repaired. Durability is an important performance characteristic, with a direct effect on the supply chain for any company. By further understanding how the warehouse environment and material handling systems affect pallet durability, companies can significantly reduce costs and improve their supply chain operations. The FasTrack procedure was created to satisfy the need for an effective durability simulation procedure. Created in 1993, FasTrack features different handling modes and interactions with handling equipment to reproduce the damages that a pallet could suffer in a real warehouse environment. However, warehouse environments have changed since the creation of FasTrack, which makes it important to assess the performance of this procedure in predicting pallet durability. The goal of this research was to investigate the ability of the FasTrack procedure to replicate the damages caused by material handling and storage systems in modern warehouses. This study was conducted through visual inspection of damaged locations, damage types, and damage severity levels for pallets used in the field and for pallets tested with FasTrack. The results obtained show differences between FasTrack and the field. The damage distribution in FasTrack for components of the pallet such as stringers and top lead deckboard is significantly higher than that measured in the field. The interaction of the pallet with the forklift could explain common damage modes, such as splits and missing wood, which were identified as the most damaged components in the pallets. An experimental design was developed to investigate the effects of entry speed, top load, forklift type, and pallet design on the stresses produced during interactions between forklifts and pallets. This interaction was measured in terms of horizontal shock impact acceleration. The most influential factors for forklift and pallet peak accelerations were identified with this study. An opportunity to predict pallet acceleration with forklift acceleration was identified, which could allow further investigation of the FasTrack simulation compared to the field. The results of the investigation show that FasTrack does not accurately reproduce the damages that pallets experience in the field. To improve the performance of the VPI FasTrack, the research proposes a revision of the steps during which damage output is low, such as the flow rack and the stack storage. The experimental design identified forklift entry speed and top load on the pallet as potential variables that could be customized in FasTrack, reflecting different severity levels based on a customer's unique environment characteristics. These changes could improve the correlation of the damages seen from the FasTrack simulation and the field, which would grant the industry a more reliable prediction of pallet durability.

Corrosion of reinforcing steel embedded in concrete due to the presence of moisture, aggressive chemicals, inadequate cover, and other factors can lead to deterioration that substantially reduces the strength and serviceability of the affected structure. Accounting for corrosion degradation is critical for evaluation and assessment of the load carrying capacity of existing reinforced concrete (RC) structures. However, little is known about the relationship between high strain rate blast loading and the degradation effects that govern corrosion damaged structures such as concrete cover cracking, reduction in reinforcement areas, and deterioration of bond between concrete and steel. Ten identical RC beams were constructed and tested, half under blast loading conditions produced using the Virginia Tech Shock Tube Research Facility and the other half under quasi-static loading. The blast tests were conducted to investigate how increasing blast pressure and impulse affect the global displacement response and damage modes of beams subjected to blast loads. The quasi-static tests were performed to establish fundamental data on the load-deflection characteristics of corroded RC beams. One beam from each testing group served as a control specimen and was not corroded while the remaining beams were subjected to varying levels of corrosion (5%, 10%, 15%, and 20%) of the longitudinal reinforcement along the midspan region. The specimens were corroded using an accelerated corrosion technique in a tank of 3% sodium chloride solution and a constant electrical current, creating a controlled environment for varying levels of corrosion. An analytical model was also created using a single degree of freedom (SDOF) approach which predicted the performance of corroded RC beams under blast loading. The results of the quasi-static tests revealed that as corrosion levels increased, the load to cause yielding decreased, the yield displacements decreased, and failure occurred earlier for all specimens. This was accompanied by increased damage to the concrete cover and the addition of longitudinal corrosion induced cracking. For the blast loaded specimens, the results demonstrated that the maximum displacements and residual displacements increased beyond the expected response limits for corrosion levels greater than 5%, but at corrosion levels less than 5% there was no significant change in displacements. Damage levels increased by one or more categories with the introduction of even small levels of corrosion of less than 5%. At corrosion levels greater than 5%, before loading was applied, the specimens exhibited moderate damage due to the introduction of corrosion induced cracking. After loading, the specimens sustained hazardous damage at progressively lower blast volumes. The failure mode changed from ductile to sudden and brittle failure at corrosion levels greater than 5% but remained ductile with flexural failures at low corrosion levels below 5%. The experimental results could be predicted with a high level of accuracy using the SDOF approach, provided that the degraded strength of corroded concrete cover, degraded mechanical properties of corroded steel, length of the corroded region, and determination of either uniform or pitting corrosion are accounted for. Overall, the introduction of corrosion to an RC beam subjected to blast loading resulted in decreased strength and ductility across all specimens but with most disastrous effects occurring at corrosion levels of 5% or greater. A recommendation is made to adjust the response limits in ASCE/SEI 59 to account for corrosion in RC beams. / Master of Science / The threat of blast loads, resulting from either terrorist attacks or accidental explosions, poses a significant threat to the structural integrity of buildings, life safety of occupants, and the functionality of the structure. Corrosion of reinforcing steel embedded in concrete, due to the presence of moisture, aggressive chemicals, and other factors, can lead to deterioration that substantially weakens the affected structure. Accounting for corrosion degradation is critical for evaluation and assessment of the strength of existing reinforced concrete structures. However, little is known about the effects of blast loading on the adverse nature that governs corrosion damaged structures. Ten identical reinforced concrete beams were constructed and tested, half under blast loading and the other half under quasi-static loading. The blast loaded beams were subjected to a series of increasing blast volumes until failure was reached. Five identical beams were tested under quasi-static loading to provide a baseline comparison against the blast loaded beams. One beam from each testing group served as a control specimen and was not corroded while the remaining beams were subjected to varying levels of corrosion of the steel reinforcement. An analytical model was also created to predict the performance of corroded reinforced concrete beams under blast loading. The results of the study showed that as corrosion levels increased, the displacements increased beyond the expected response limits. Damage levels became increasingly more severe with the introduction of corrosion at all levels. The behavior changed from ductile to brittle at corrosion levels greater than 5% but remained ductile with flexural failures at corrosion levels below 5%. Overall, the introduction of corrosion to a concrete beam subjected to blast loading resulted in decreased strength and ductility across all specimens but with most disastrous effects occurring at corrosion levels of 5% or greater. A recommendation is made to adjust the response the limits in the code to account for corrosion in reinforced concrete beams.

Investigations on the design of controllable magnetorheological (MR) fluid devices have focused heavily on low velocity and low frequency applications. The extensive work in this area has led to a good understanding of MR fluid properties at low velocities and frequencies. However, the issues concerning MR fluid behavior in impact and shock applications are relatively unknown. To investigate MR fluid properties in this regime, MR dampers were subjected to impulsive loads. A drop-tower test facility was developed to simulate the impact events. The design includes a guided drop-mass released from variable heights to achieve different impact energies. Five drop-heights and two fundamental MR damper configurations were tested. The two configurations were a double-ended piston and a mono-tube with nitrogen accumulator. To separate the dynamics of the MR fluid from the dynamics of the current source, each damper received a constant supply current before the impact event. A total of five supply currents were investigated for each impact velocity. After reviewing the results, it was concluded that the effect of energizing the MR fluid only leads to "controllability" below a certain fluid velocity for the double-ended design. In other words, until the fluid velocity dropped below some threshold, the MR fluid behaved as if it was not energized, regardless of the strength of the magnetic field. Controllability was defined when greater supply currents yielded larger damping forces. For the mono-tube design, it was shown that the MR fluid was unable to travel through the gap fast enough during the initial impact. Consequently, the damper piston and accumulator piston traveled in unison until the accumulator bottomed out. After which, the fluid was forced through the gap. In conclusion, the two designs were compared and general recommendations on designing MR dampers for impulsive loading were made. Possible directions for future research were presented as well. / Master of Science

Several aesthetic, health, and plumbing quality issues can arise during new construction or renovation of premise plumbing. There has been little research done on many of these concerns and therefore few guidelines or regulations are in place to protect the health of the consumer or the integrity of the plumbing infrastructure. This work examines common construction practices including: 1) effect of residual construction debris, 2) shock chlorination of new plumbing lines, and 3) lead leaching propensity of new brass ball valves. During installation of plumbing systems, residual chemicals and debris including copper brass particles and flux, can be left in plumbing lines following construction and installation. This debris is considered undesirable from health, aesthetic, and corrosion perspectives. Soldering flux is of particular concern due to its corrosive nature. Experiments were conducted to determine the effects of residual solder flux, PVC glue, and metallic debris and to quantify flushing velocities and durations to effectively remove them from a new plumbing system. A flushing velocity of 3 fps for 30 minutes is needed to remove water soluble flux, while petroleum based flux still persists after extensive flushing at 7 fps. Currently a practice known as shock chlorination, whereby super chlorinated water is used for disinfection, is used in water mains after installation or repair as specified in the ANSI/AWWA C651 Standard. This practice is now starting to be required by some building codes in premise plumbing for new construction. Water mains are typically made of concrete where as premise plumbing using copper or PVC piping. Copper pipe is susceptible to attack by high chlorine, and this reaction will also remove the chlorine residual. There is concern about potential damage to copper from free chlorine and that in some systems targeted residuals of chlorine might not be obtained. Experiments did not detect serious damage to copper pipe, but in some waters it was not possible to meet targeted residual levels of chlorine. The addition of orthophosphate corrosion inhibitor or adjustment of pH can sometimes reduce the chlorine decay rate. Extremely high and persistent lead leaching in a brand new building at the University of North Carolina (UNC) traced to leaded bronze ball valves, prompted an extensive forensic evaluation how existing standards (National Sanitation Foundation Section 8) could allow for installation of products that could create a human health hazard due to high lead. Diffusion of lead from within the device to water in the pipe, high velocity, microbial activity and other factors caused more leaching in practice than would be expected based on NSF testing and normalization factors applied to certify a valve as safe. Moreover, use of flux during soldering of joints, increased lead leaching by orders of magnitude relative to results of NSF testing without flux. / Master of Science

Exploring the design space of tensegrity systems is the basis of the work presented in this thesis. The areas explored as part of this research include the optimization of tensegrity structures to minimize the size of a tensegrity structure given payload shock constraints, and the control and locomotion of an icosahedral tensegrity system using movable masses and using an accelerometer in conjunction with leveraging geometrical knowledge of an icosahedral tensegrity system to localize the system after the system moves. In the optimization design space, a simplified model was created to represent an icosahedral tensegrity structure. This was done by assuming that a system of springs could represent an icosahedral system with enough fidelity to be useful for optimization. These results were then validated and tested. The most extensive part of the research preformed was in regards to the control of a Tensegrity Icosahedron. This structure utilized novel locomotion techniques to allow the structure to move by changing its center of mass. Essentially, instead of actuating the system by changing the length of the strings that make up the system state, the system's center of mass is moved using movable masses. These masses make it so the system can rotate about one of the base pivot points. A controller was also created that allows for this system to go to a target point if the state of the system is known. Finally, work was done to attempt to localize a structure by combining a motion model based off the geometry of the structure and a measurement model based on accelerometer readings during the movement of the structure into an EKF. This EKF was then used to localize the structure based on the predicted motion model and the measurement model prescribed by the accelerometer. This allowed for the system's state to be estimated to within 3 standard deviations of the uncertainty of the motion and measurement models. Additional work on this system was also done to make a physical model of the system. This work includes making a bar so that movable masses can pass through it, creating an accelerometer model to roughly determine the system's state, and tracking the system’s displacement using some steady-state model assumptions.

Yes / Inhibition of the chaperone heat-shock protein 90 (HSP90) induces apoptosis, and it is a promising anti-cancer strategy. The mechanisms underpinning apoptosis activation following HSP90 inhibition and how they are modified during acquired drug resistance are unknown. We show for the first time that, to induce apoptosis, HSP90 inhibition requires the cooperation of multi BH3-only proteins (BID, BIK, PUMA) and the reciprocal suppression of the pro-survival BCL-2 family member MCL1, which occurs via inhibition of STAT5A. A subset of tumour cell lines exhibit dependence on MCL1 expression for survival and this dependence is also associated with tumour response to HSP90 inhibition. In the acquired resistance setting, MCL1 suppression in response to HSP90 inhibitors is maintained; however, a switch in MCL1 dependence occurs. This can be exploited by the BH3 peptidomimetic ABT737, through non-BCL-2-dependent synthetic lethality.

Yes / Functional genomics research can give us valuable insights into bacterial gene function. RNA Sequencing (RNA-seq) can generate information on transcript abundance in bacteria following abiotic stress treatments. In this study, we used the RNA-seq technique to study the transcriptomes of the opportunistic nosocomial pathogen Pseudomonas aeruginosa PAO1 following heat shock. Samples were grown at both the human body temperature (37 C) and an arbitrarily-selected temperature of 46 C. In this work using RNA-seq, we identified 133 genes that are differentially expressed at 46 C compared to the human body temperature. Our work identifies some key P. aeruginosa PAO1 genes whose products have importance in both environmental adaptation as well as in vivo infection in febrile hosts. More importantly, our transcriptomic results show that many genes are only expressed when subjected to heat shock. Because the RNA-seq can generate high throughput gene expression profiles, our work reveals many unanticipated genes with further work to be done exploring such genes products. / University of Malaya High Impact Research (HIR) UM-MOHE HIR Grants (UM.C/625/1/HIR/MOHE/CHAN/14/1, No. H-50001-A000027; UM.C/625/1/HIR/MOHE/CHAN/01, No. A000001-50001); PPP Grant (PG081-2015B)

A shock is essentially a propagating variation in the pressure or density of a medium. If the medium is transparent, such as air, and the shock radially symmetric, the refractive fringe diagnostic can be used to examine its general features. A laser beam probes the shock, the central part of the beam, refracted to different degrees by the different density features within the shock, interferes with itself and with the outer unrefracted part creating a series of coarse and fine fringes. By examining this interference pattern one can gain insight into the density profile underlying the shock. A series of such experiments was conducted by the Plasma Physics Research Institute at the University of Natal in 1990. To model the situation computationally, they developed a ray-tracer which produced interference patterns for modified theoretical density profiles based on those predicted by Sedov. After numerous trials, an intensity pattern was produced which agreed approximately with experimental observations. Thus encouraged, the institute then sought to determine density profiles directly from the interference patterns, but a true mathematical deconvolution proved non-trivial and is still awaited. The work presented in this thesis reconstructs the ray-tracer using software engineering techniques and achieves the desired deconvolution by training a neural network of the back-propagation type to behave as an inverse ray-tracer. The ray-tracer is first used to generate numerous density profile - interference pattern pairs. The neural network is trained with this theoretical data to provide a density profile when presented with an interference pattern. The trained network is then tested with experimental interference patterns extracted from captured images. The density profiles predicted by the neural network are then fed back to the ray-tracer and the resultant theoretically determined interference patterns compared to those obtained experimentally. The shock is examined at various times after the initial explosion allowing its propagation to be tracked by its evolving density profile and interference pattern. The results obtained prove superior to those first published by the institute and confirm the neural network's promise as a research tool. Instead of lengthy trial and error sessions with the unaided ray-tracer, experimental interference patterns can be fed directly to an appropriately trained neural network to yield an initial density profile. The network, not the researcher, does the pattern association. / Thesis (M.Sc.)-University of Natal, 1996.