Understanding the Hydromechanical Effects of Extreme Events To Improve the Performance of Infrastructure Foundations

Extreme hydroclimatic events like heavy rainfall, flooding, and prolonged drought can potentially cause the failure of infrastructure foundations, leading to socio-economic losses. The objective of this dissertation is to understand the deformation and bearing capacity behavior of drilled shafts subjected to extreme hydroclimatic events, including heavy rainfall, prolonged drought, and earthquake. The Finite Element Method (FEM) results show that during rainfall, the drilled shaft settled caused by a decrease in the porewater pressure in the sand leading to a decrease in the axial bearing capacity. The axial force variation from an experimental investigation showed good agreement with the FEM. The impact of natural hazards on deep foundations can be critical and highly unpredictable when extreme hydrological and seismic events occur simultaneously or in sequence. A multi-hazard analysis was carried out to understand the structural response of deep foundations. When the drilled shaft was subjected to the dynamic load from heavy rainfall followed by dynamic load from the earthquake, the vertical settlement for the drilled shaft was significantly high compared to the case where the drilled shaft was subjected to dynamic load from the earthquake. A case study was adopted to predict the structural response of drilled shaft at the end bent of a proposed bridge subjected to liquefaction-induced lateral spreading caused by extreme earthquake events. The structural response of the bridge foundation before, during, and after liquefaction-induced lateral spreading was predicted using analytical methods and FEM. The comparison results showed that the during-liquefaction scenario was the worst-case

The NEBULA RPC-Optimized Architecture

Large-scale online services are commonly structured as a network of software tiers, which communicate over the datacenter network using RPCs. Ongoing trends towards software decomposition have led to the prevalence of tiers receiving and generating RPCs with runtimes of only a few microseconds. With such small software runtimes, even the smallest latency overheads in RPC handling have a significant relative performance impact. In particular, we find that growing network bandwidth introduces queuing effects within a server’s memory hierarchy, considerably hurting the response latency of fine-grained RPCs. In this work we introduce NeBuLa, an architecture optimized to accelerate the most challenging microsecond-scale RPCs, by leveraging two novel mechanisms to drastically improve server throughput under strict tail latency goals. First, NeBuLa reduces detrimental queuing at the memory controllers via hardware support for efficient in-LLC network buffer management. Second, NeBuLa’s network interface steers incoming RPCs into the CPU cores’ L1 caches, improving RPC startup latency. Our evaluation shows that NeBuLa boosts the throughput of a state-of-the-art key- value store by 1.25–2.19x compared to existing proposals, while maintaining strict tail latency goals

Design of a flexing organ-chip to model in situ loading of the intervertebral disc

The leading cause of disability of all ages worldwide is severe lower back pain. To address this untreated epidemic, further investigation is needed into the leading cause of back pain, intervertebral disc degeneration. In particular, microphysiological systems modeling critical tissues in a degenerative disc, like the annulus fibrosus (AF), are needed to investigate the effects of complex multiaxial strains on AF cells. By replicating these mechanobiological effects unique to the AF that are not yet understood, we can advance therapies for early-stage degeneration at the cellular level. To this end, we designed, fabricated, and collected proof-of-concept data for a novel microphysiological device called the flexing annulus-on-a-chip (AoC). We used computational models and experimental measurements to characterize the device's ability to mimic complex physiologically relevant strains. As a result, these strains proved to be controllable, multi-directional, and uniformly distributed with magnitudes ranging from -10 % to 12% in the axial, radial, and circumferential directions, which differ greatly from applied strains possible in uniaxial devices. Furthermore, after withstanding accelerated life testing (66 K cycles of 10% strain) and maintaining 2000 bovine AF cells without loading for more than three weeks the AoC proved capable of long-term cell culture. Additionally, after strain (3.5% strain for 75 cycles at 0.5 Hz) was applied to a monolayer of AF cells in the AoC, a population remained adhered to the channel with spread morphology. The AoC can also be tailored for other annular structures in the body such as cardiovascular vessels, lymphatic vessels, and the cervix