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Reliability and Resilience of Chiplets
Get PDFIndustry is moving towards large-scale systems where processor cores, memories, accelerators, etc. are bundled via 2.5D integration. These various components are fabricated separately as chiplets and then integrated using an interposer. This new design style benefits yield, as well as economies of scale, as many third-party vendor chiplets can be integrated into one system. These benefits, however, come at the cost of new challenges for the system's security and integrity when many third-party component chiplets, some from not fully trusted vendors, are integrated. Hardware Trojans are ���malicious hardware inserted by an attacker during a device���s design or manufacturing processor���. However, these Trojans can be designed to only be triggered under specific conditions, which makes their presence exponentially harder to detect. In addition, if a third-party IP is untrustworthy, these Trojans can even potentially be camouflaged by their IP, further increasing the difficulty of detectability [1]. All known previous works for 2.5D integrated systems have, upon Trojan detection, halted all system operation. Unfortunately, there are scenarios where shutdown is not feasible for all chip integration systems, especially in mission critical systems where execution must continue. Henceforth, recovery protocols have become increasingly more important and aim to minimize system shutdown and enhance performance. This paper continues previous research by Chacon et al., who developed several potential hardware Trojan attacks for 2.5D integrated systems that center around the memory system interconnect. However, the previous design of the Trojan attack only allowed for the processor to shut down when the Trojan was detected. This paper introduces a solution that is specifically focused on a recovery protocol and architecture, which will detect the hardware Trojan. After the Trojan has been detected, the protocol will cut off directory and chiplet communication so that the malicious chiplet effectively can no longer communicate with the system. Blocking the malicious chiplet requests is a multi-step process to ensure that the malicious chiplet can no longer impact the existing system functionality. In this paper, a hardware Trojan which targets the system���s coherence protocol is inserted onto a chiplet. Upon detection of the hardware Trojan, the recovery controller will become active, which will prevent the system from allowing the directory to communicate with the malicious chiplet. This means that the directory can no longer request information from the malicious chiplet and the malicious chiplet can no longer initiate a request to the directory for information. The system will continue to operate with one less chiplet and core balancing will be performed to optimize latency statistics
Study of the Optical Properties of Nonspherical Particles With the Physical Geometric Optics Method
Get PDFUnderstanding the optical properties of nonspherical particles such as ice particles and dust aerosols is critical in reducing the uncertainties in radiative transfer simulations, remote sensing technique implementations, and climate studies. Improvements in this regard allow us to better understand the role ice particles and dust aerosols have in the radiative budget. In the first part of the dissertation, we discuss the current light scattering methods, such as the invariant imbedding T-matrix method (IITM), the physical geometric optics method (PGOM), and a simplified version of PGOM called the improved geometric optics method (IGOM). PGOM and IGOM extinction efficiency calculations are underestimated mostly because a semiclassical effect called the edge effect is not included in the extinction and absorption efficiencies. The problem is that semi-empirical formulas for the edge effect contributions to the extinction and absorption efficiencies are available only for spheres, spheroids, and ellipsoids. One of the objectives of this research effort reported in this dissertation is to extend the edge effect formulas for the extinction and absorption efficiencies to a particular case superspheroid called the superegg. This research will help improve the accuracy of PGOM and IGOM extinction and absorption efficiencies.
The second part of this dissertation introduces a new type of surrogate aerosol model called the irregular triangular bipyramid or diamond ensemble, which might serve as an approximation to a ���roughened regular diamond���. Regular diamond and the irregular diamond ensemble are utilized to analyze the impact of particle surface roughness on the optical properties. The present study also assesses the capability of an irregular diamond ensemble as a surrogate to mimic the optical properties of dust aerosols in the Amsterdam-Granada light scattering database (AGLSD). The uncertainties of the size distribution measurements in the AGLSD are investigated. Furthermore, the applicability of the bulk scattering matrix of the irregular triangular bipyramid ensemble is assessed as input to the vector radiative transfer simulations and comparing the results to satellite observations for multiple locations.
Overall, the research reported in this dissertation represents a significant step toward reducing the uncertainties in obtaining the optical and microphysical properties of aerosols
Investigation Into the Influential Role of Stereo-Active Sulfur Lone Pairs in Metallodithiolate Complexes
No full textMetallodithiolates have been used as a unique class of ligands in organometallic chemistry. They can behave either as mono- or bidentate ligands, binding to various metals via their thiolate sulfur donor atoms. What sets them apart from other chelating ligands is the presence of the two lone pairs at each sulfur donor site, resulting in geometrically ordered aggregates in various topological forms. Additionally, the binding conformation of the N���S��� donor set can accommodate a range of metals, modifying the binding preference of the metallodithiolates. By modifying the N���S��� scaffold in (N���S���)Ni or changing Ni to either Fe(NO) or Co(NO), a series of pentametallic M���Ag��� C��� paddlewheel complexes was formed. These complexes were characterized through single-crystal X-ray diffraction, demonstrating the general binding preference difference between the (N���S���)Ni and the (N���S���)M(NO) (M = Fe, Co) metallodithiolates, influenced by the additional NO ligand and the neighboring sulfur lone pairs.
Insights into the formation of an asymmetric bis-nitrosylated trimetallic dication, CoMoCo���, were gained due to increased sterics and electronic effects, preventing nitrosylated metallodithiolates from accommodating large aggregates. This complex underwent an NO transfer redox process, initially expected to form a dimolybdenum C��� ���paddlewheel��� type complex. The CoMoCo��� complex, with S = 1, is composed of an intact (N���S���)Co(NO) (Co) with a bent NO ligand, S-bridged to a trans-Mo(NO)(MeCN) center, which is further S-bridged to an unusual pentacoordinate (N���S���)Co(MeCN) metalloligand denoted as Co���. The asymmetry in Mo-Co distances, 3.33 �� in Mo-Co and 2.73 �� in Mo-Co���, indicates a Mo-Co��� bonding interaction. Paramagnetism arising from an intermediate spin Co(III) and direct metal-metal interaction towards the {Mo(NO)}��� center was revealed by DFT calculations and magnetic measurements. The transfer of NO from (N���S���)Co(NO) was necessary to reductively cleave the strong Mo���Mo quadruple bond, with the energetic cost compensated through delocalization of charge and electron density throughout the (ON-Mo-Co���) unit.
Lastly, a designed approach to replicate the CoMoCo��� species resulted in the development of a new class of coordination complexes featuring different (N���S���)M metallodithiolates, (M = Ni�����, [Fe(NO)]�����, [Co(NO)]�����, and [Co(MeCN)]�����). These metallodithiolates act as bidentate chelating ligands, binding to a central trans-Cr(NO)(MeCN) unit. Similar to CoMoCo���, these complexes display a cisoid structural topology, due to the stereoactivity of the available lone pairs on the sulfur donors. This creates a dispersed, electropositive cavity within the N to S hydrocarbon linkers, accommodating the Cr-NO unit. With the help of DFT calculations, alternative isomers were explored, and the governing factors behind such specific geometrical selectively were found, involving a combination of electronic and steric effects between the nitrosyl ligand on chromium and the available S lone pairs on the metallodithiolates. These additional lone pairs work together with the ��-withdrawing ability of NO to push the Cr out of the S4 plane toward the NO ligand, ultimately stabilizing the cisoid configuration. Overall, this research displays the directional influential role of metallodithiolates in combination with the receiving secondary metal
Early Larvae Survivorship and Gamete Production of Hydroides dianthus with Notes on its Morphology
No full textHydroides dianthus is a non-native marine annelid worm that has been reported along the boat basin of Texas A&M University at Galveston (TAMUG). The genus Hydroides is notorious for biofouling and invasion due to its planktonic larval stage, easily transported in ballast water, vessel hulls, and aquaculture. Baseline information on this species in Galveston Bay remains limited, reflecting an incomplete understanding of biodiversity and geography at the species level. Ongoing research has revealed a high abundance of this species in the TAMUG boat basin. With this, the project had four objectives: i) brief taxonomic diagnosis, ii) comparison of early larval survivorship in different seasons, iii) morphometric analysis, and iv) evaluation of female gamete production across seasons. Hydroides dianthus specimens were collected from TAMUG's boat basin and subjected to controlled conditions (20 psu) in the lab. Females were photographed and numbered before gamete collection to obtain their gamete production, followed by larval testing through fertilization. A one-sample t-test showed significant differences in larval survival rates between Fall (71.38%) and Summer (80.02%). These results indicate significant differences in larval survival rates between seasons under controlled conditions. Morphological measurements revealed that females had larger thoracic and operculum lengths and widths, while males had a larger abdominal section, increasing their total length compared to females. The percentage of gamete production in females was significantly higher in Summer (19.6%) than in Fall (9.89%), confirming seasonal variation in reproductive activity. These findings contribute to understanding the taxonomy, morphology, and reproductive dynamics of Hydroides dianthus, providing valuable insight into its survivability and adaptability. Future research could explore the fluctuation of Hydroides dianthus or other non-native species along Galveston Bay and their effects on other sessile marine invertebrates
Nanotube-Stabilized Foams and the Effect of Polyacrylamide on Enhancing Oil Recovery Using Foam Flooding
No full textEnhancing oil recovery using foam flooding has been an interesting topic in the petroleum engineering literature in the last few decades. Despite the fact that foam flooding seems to be a very promising idea with great potential to boost oil recovery from brown fields, they are notorious for the lack of stability in the underground reservoir. In this dissertation, the idea of surfactant stabilized by nanotubes and polymers to create stable foam is presented.
The work presented in this dissertation is divided into two major parts: 1) experimentally investigating the effect of stabilizing foam using carbon nanotubes, and comparing the performance to silica-stabilized foam, 2) experimentally investigating the effect of adding polyacrylamide to the nanotube-stabilized foam.
In the first part of the study, silica nanoparticles and functionalized carbon nanotubes are put into experimental testing as foam stabilizers. Foam stability, salt tolerance and mobility reduction factor were measured and investigated in order to determine the better foam stabilizer. In the second part of the study, the effect of adding polyacrylamide to a nanotube-stabilized foam is experimentally investigated. Foam stability, salt tolerance, mobility reduction factors and oil recoveries were measured. Additionally, surface tension, interfacial tension with oil and contact angle on glass were measured.
The main findings in this study are that: 1) the nanotube-stabilized foam is 70% more stable than the silica stabilized-foam, 2) the carbon nanotubes can tolerate higher salinity levels compared to the silica nanoparticles, 3) during coreflood testing, the nanotubes produce foam with a higher mobility reduction compared to the silica nanoparticles, 4) adding polyacrylamide to the nanotube-stabilized foam increases its stability by 300%, 5) the polymer can enhance the nanofluid���s salt tolerance, and 6) adding the polymer increase the oil recovery to 68% compared to 47% when the nanotubes were used in the absence of the polymer
Listen to the Canary's Song: Barriers to Utilization of Title IX Resolution Processes Experienced by Queer Students in College
No full textMuch attention has been paid to addressing sexual violence on college and university campuses in recent years. Resources have been allocated and systems have been created to allow for the reporting of violations of Title IX of the Education Amendments Act of 1972 which prohibits discrimination from participation in Federally funded programs on the basis of sex. While progress has been made in standing up and administering systems of reporting, investigating, and resolving instances of sexual violence, much work remains to be done in assessing how these processes are utilized and by whom. There is reason to believe that Queer/non-cisgender or heterosexual students are more likely to experience sexual violence than their cisgender and heterosexual counterparts, and less likely to report these instances when they do. In order to address the gap in need and utilization in the face of available resources, this qualitative study interviewed ten Queer/non-cishet survivors of sexual violence in college since 2011, who declined to fully participate in Title IX resolution processes offered by their institutions.
Participants shared their perceptions of trust in their institutions prior to the instance of violence, how they cared for themselves after their violence, and why they ultimately declined to fully participate in the Title IX resolution processes offered by their institution. Barriers to reporting were characterized by the participants in terms of fear of the process based on their observed experiences, a lack of trust in their institutions to meet their needs and were heavily informed by the negative social capital they felt would gain with reporting. They universally expressed that while reporting sexual violence would impact them negatively in terms of social capital, that their Queer/non-cishet identities would not add social capital to them, and in most cases exacerbate their negative social capital
