4,341 research outputs found
The Effect of Thermal Cycling on Crystal-Liquid Separation During Lunar Magma Ocean Differentiation
Differentiation of magma oceans likely involves a mixture of fractional and equilibrium crystallization [1]. The existence of: 1) large volumes of anorthosite in the lunar highlands and 2) the incompatible- rich (KREEP) reservoir suggests that fractional crystallization may have dominated during differentiation of the Moon. For this to have occurred, crystal fractionation must have been remarkably efficient. Several authors [e.g. 2, 3] have hypothesized that equilibrium crystallization would have dominated early in differentiation of magma oceans because of crystal entrainment during turbulent convection. However, recent numerical modeling [4] suggests that crystal settling could have occurred throughout the entire solidification history of the lunar magma ocean if crystals were large and crystal fraction was low. These results indicate that the crystal size distribution could have played an important role in differentiation of the lunar magma ocean. Here, I suggest that thermal cycling from tidal heating during lunar magma ocean crystallization caused crystals to coarsen, leading to efficient crystal-liquid separation
Development of a Ligno-Cellulosic Polymeric and Reinforced Sheet Molding Compound (SMC)
The overall objective of this dissertation was to study the surface energy and acid-base characteristics of natural fibers, glass, a wood extract, and a sheet molding compound prepreg to facilitate the fabrication of totally synthetic and partially renewable sheet molding compounds (SMCs). The water absorption and micro-mechanical performance of the totally synthetic and partially renewable SMC composites were compared through accelerated aging experiments. Reinforcing glass sized for polyester, bast kenaf fibers, hot water extract from Acer rubrum, and a dicyclopentadiene modified polyester prepreg were analyzed by inverse gas chromatography to evaluate and help predict how the various components may interact in a crosslinked composite SMC. Dynamic Mechanical Thermal Analysis (DMTA) was used to determine how the components in the SMC changed as a function of hygrothermal aging by analyzing the glass transitions of the individual components in the SMC. Inverse gas chromatography (IGC) results indicated that the polyester prepreg material had an experimental dispersive surface energy value of 47 mJ/m2 that compared well with a rule of mixture analysis of the components in the SMC giving a value of 50 mJ/m2 both at 30?C. IGC results also indicated that the kenaf-prepreg material has a higher acid base interaction then the glass-prepreg material. The IGC results indicated that surface sizing of the kenaf fibers with styrene-maleic anhydride might improve the cohesiveness of the final kenaf based SMC. IGC results also indicated that hot water extract from Acer rubrum had a dispersive energy close to polystyrene and should be miscible in the prepreg material. Hygrothermal aging was done by soaking SMC samples at 70?C for 3, 168, and 1032 hour time intervals. Standard SMC fabricated with glass reinforcement had water uptakes of less than 5 weight percent after 1032 hours. SMC fabricated with kenaf had water uptakes at 1032 hours approaching 20 weight percent indicating the kenaf based SMC is not suitable for exterior applications or applications where water contact occurs. SMC fabricated with hot water extract from Acer rubrum had water uptake similar to, and in some cases, better then the standard SMC references. DMTA results indicated that thickening reactions took place without thickening agents in the SMC in the presence of excess absorbed water. The temperature range of â50?C to 260?C during DMTA testing effectively destroyed the kenaf based SMC. The glass based synthetic SMC was the most resilient to the heat ramps followed by the extract based SMC. Inverse gas chromatography is a useful tool for analyzing the dispersive and acid-base properties of components of a composite. Kenaf based and extract based SMCâs can be fabricated and the extract based SMCâs compare well with standard synthetic SMCâs for water absorption and micro-mechanical properties
Citrus:Orchestrating Security Mechanisms via Adversarial Deception
Despite the Internet being an apex of human achievement for many years, sophisticated targeted attacks are becoming more prevalent than ever before. Large scale data collection using threat sources such as honeypots have recently been employed to gather information relating to these attacks. While this data naturally details attack properties, there exists challenges in extracting the relevant information from vast data sets to provide valuable insight and a standard description of the attack. Traditionally, threats are identified through the use of signatures that are crafted manually through the composition of IOCs (Indicators of Compromise) extracted from telemetry captured during an attack process, which is often administered by an experienced engineer. These signatures have been proven effective in their use by IDSs (Intrusion Detection Systems) to detect emerging threats. However, little research has been made in automating the extraction of emerging IOCs and the generation of corresponding signatures which incorporate host artefacts. In this paper we present Citrus: a novel approach to the generation of signatures by incorporating host based telemetry extracted from honeypot endpoints. Leveraging this visibility at an endpoint grants a detailed understanding of bleeding edge attack tactics, techniques, and procedures gathered from host logs
Whither Communism: A Comparative Perspective on Constitutionalism in a Postsocialist Cuba
For over fifty years, Cuba has been a source of high-spirited political and policy debates. Its history and geostrategic position make it unique in American diplomatic and socioeconomic history. Interest in the island has not waned with the collapse of Communism in Eastern Europe and the former Soviet Union. On the contrary, Raul Castroâs assumption of Government has led many to begin asking how and under what circumstances political liberalization and economic transformation may occur in Cuba. This article examines the possible constitutional outcomes of a Cuba transition and introduces a framework for analyzing both Cuban economic reforms and US policy decisions. Both pre- and post-Communist Cuban constitutional law is examined, as are Cubaâs nationalizations and recent economic reforms. After, examining the economic nationalizations in Eastern Europe, a legal paradigm is developed on what this article calls âmodes of constitutionalism.â By looking at how legitimacy vests, or illegitimacy develops in a nation, we can them predict how constitutional change may occur. This article examines three paradigms based on the transitions of Eastern Europe that are candidates for how an analogous transition may occur in Cuba. By looking at three levels - the state, government, and policy - we can project how democratic transitions, and new constitutional frameworks develop. From the models presented, this article examines the possibility of a US-Cuban claims settlement agreement. The current state of American law and politics as it pertains to Cuba is examined as are previous settlement agreements concluded for former Warsaw Pact nations. This article concludes with a discussion of how a claims settlement agreement may be negotiated in light of the various modes Cuban constitutionalism may take, and how US policymakers may increase the likelihoods of securing compensations for those aggrieved by the Castro regime
Enhancing Anomaly Detection Techniques for Emerging Threats
Despite the Internet being an apex of human achievement for many years, criminal behaviour and malicious activity are continuing to propagate at an alarming rate. This juxtaposition can be loosely attributed to the myriad of vulnerabilities identified in existing software. Cyber criminals leverage these innovative infection and exploitation techniques to author pervasive malware and propagate devastating attacks. These malicious actors are motivated by the financial or political gain achieved upon successful infiltration into computer systems as the resources held within are often very valuable in nature. With the widespread developments in the Internet of Things (IoT), 5G, and Starlink satellites, unserved areas of the world will experience a pervasive expansion of connected devices to the Internet. Consequently, a barrage of potential new attack vectors and victims are unfolding which requires constant monitoring in order to manage this ever growing problem. Conventional rule-based intrusion detection mechanisms used by network management solutions rely on pre-defined attack signatures and hence are unable to identify new attacks. In parallel, anomaly detection solutions tend to suffer from high false positive rates due to the limited statistical validation of ground truth data, which is used for profiling normal network behaviour. When considering the explosive threat landscape and the expanse of connected devices, current security solutions also face challenges relating to the scale at which attacks need to be monitored and detected. However, recent innovations in Big Data processing have revealed a promising avenue in which scale is addressed through cluster computing and parallel processing. This thesis advances beyond current solutions and leverages the coupling of anomaly detection and Cyber Threat Intelligence (CTI) with parallel processing for the profiling and detection of emerging cyber attacks. This is demonstrated through the design, implementation, and evaluation of Citrus: a novel intrusion detection framework which is adept at tackling emerging threats through the collection and labelling of live attack data by utilising diverse Internet vantage points in order to detect and classify malicious behaviour using graph-based metrics, as well as a range of Machine Learning (ML) algorithms. This research provides innovative contributions to the cyber security field, including the public release of an open flow-based intrusion detection data set. This data set encompasses emerging attack patterns and is supported by a robust ground truth. Furthermore, Citrus advances the current state of the art through a novel ground truth development method. Citrus also enables both near real-time and offline detection of emerging cyber attacks under optimal computational costs. These properties demonstrate that it is a viable and practical solution for next generation network defence and resilience strategies
Scale of pluton/wall rock interaction near May Lake, Yosemite National Park, California, USA
The western outer granodiorite of the Tuolumne Intrusive Suite intruded a variety of metasedimentary wall rocks at 93.1 ± 0.1 Ma. The May Lake metamorphic screen (4500 x 550 m) is a remnant of the chemically diverse metasedimentary host rocks. Their chemical contrast with the invading pluton provides an excellent location to study pluton/wall rock interactions. Outside the screen, visible wall-rock xenoliths (mostly pelitic quartzite) are predominantly located in an elongate horizon surrounded by a hybridized fine-grained granodiorite. Initial Sr and Nd isotopic ratios of the hybridized granodiorite indicate incorporation of crustal material. Major- and trace-element geochemical data indicate contamination of the granodiorite with pelitic metasedimentary rocks occurred in two modes, selective assimilation of 1) a high-K partial-melt derived from pelitic quartzite, and 2) a low-K partial-melt derived from pelitic quartzite. However, there is little evidence for contamination of granodiorite beyond the immediate vicinity of wall rock inclusions
Re-evaluating pluton/volcano connections and igneous textures in light of incremental magma emplacement
Zircon U-Pb geochronologic data collected within the past ten years indicate that plutons are emplaced incrementally over time periods of 105 to 106 annum at magma accumulation rates on the order of 10-4-10-3 km3/a. Although incremental emplacement of magmas is now widely accepted, evaluation of the wide-ranging effects on pluton-volcano connections and the generation of magma diversity has just begun. Magma emplacement rates calculated for large ignimbrites (10-2 km3/a) are higher than most estimates for plutons (10-4-10-3 km3/a). Thermal models for magma emplacement in the crust predict this rate disparity and suggest that magma emplacement rates of 10-2 km3/a or greater are needed to produce large ignimbrites. Thus, there is a fundamental difference in the rates of accumulation of ignimbrite and pluton magmas but little is known on how individual magmatic centers behave. Geochemistry and U-Pb zircon data from the Mt. Princeton batholith and spatially associated ignimbrites in central Colorado indicate that the vast majority of the batholith was emplaced between periods of ignimbrite eruption at a rate of 1.6x10-3 km3/a. The temporal disconnect supports the hypothesis that ignimbrites are generated during periods of high magma flux, without significant fractionation in the upper crust and that plutons represent similar magmas that froze in the crust during periods of low magma flux. Thermal models and geochronology also indicate that pluton emplacement must be episodic with only small fractions (<5%) of mobile magma existing at any one time. The episodic emplacement of plutons also leads to temperature cycling of the magma, which is hypothesized to affect crystal textures. Experiments on crystal growth of ammonium thiocyanate in a magma analog at approximately 50ÂșC and plagioclase and olivine growth in an alkali basalt at approximately 1150ÂșC indicate that temperature cycling changes the texture of magmas dramatically; creating large crystals and decreasing crystal number density. Also, crystal alignment is observed in the magma analog experiments coincident with the thermal gradient. Together, these results indicate that temperature cycling of magmas can affect the crystal size distribution and fabric of the resultant rock and is a variable that needs to be assessed when interpreting igneous textures.Doctor of Philosoph
Diagnosis, Investigation and Management of Patients with Acute and Chronic Myocardial Injury
The application of high-sensitivity cardiac troponins in clinical practice has led to an increase in the recognition of elevated concentrations in patients without myocardial ischaemia. The Fourth Universal Definition of Myocardial Infarction encourages clinicians to classify such patients as having an acute or chronic myocardial injury based on the presence or absence of a rise or a fall in cardiac troponin concentrations. Both conditions may be caused by a variety of cardiac and non-cardiac conditions, and evidence suggests that clinical outcomes are worse than patients with myocardial infarction due to atherosclerotic plaque rupture, with as few as one-third of patients alive at 5 years. Major adverse cardiovascular events are comparable between populations, and up to three-fold higher than healthy individuals. Despite this, no evidence-based strategies exist to guide clinicians in the investigation of non-ischaemic myocardial injury. This review explores the aetiology of myocardial injury and proposes a simple framework to guide clinicians in early assessment to identify those who may benefit from further investigation and treatment for those with cardiovascular disease
Prospectus, November 9, 2016
RADIO DRAMA BY COMM. STUDENTS TO AIR ON WPCD; Humans of Parkland: Thom Schnarre; Club Latino a \u27family-like community\u27; Official: 40 to 50 buildings damaged in Oklahoma quake; Parkland Cobra soccer teams 2016; Reasons to go to China; Obama reveals private living areas of White House; Register for Parkland College Spring 2017 Classes; Google speaker is secretary, radio...and work in progress; Students from Okinawa, Japan visit Parklandhttps://spark.parkland.edu/prospectus_2016/1027/thumbnail.jp
Implications of Wide-Area Geographic Diversity for Short- Term Variability of Solar Power
Worldwide interest in the deployment of photovoltaic generation (PV) is rapidly increasing. Operating experience with large PV plants, however, demonstrates that large, rapid changes in the output of PV plants are possible. Early studies of PV grid impacts suggested that short-term variability could be a potential limiting factor in deploying PV. Many of these early studies, however, lacked high-quality data from multiple sites to assess the costs and impacts of increasing PV penetration. As is well known for wind, accounting for the potential for geographic diversity can significantly reduce the magnitude of extreme changes in aggregated PV output, the resources required to accommodate that variability, and the potential costs of managing variability. We use measured 1-min solar insolation for 23 time-synchronized sites in the Southern Great Plains network of the Atmospheric Radiation Measurement program and wind speed data from 10 sites in the same network to characterize the variability of PV with different degrees of geographic diversity and to compare the variability of PV to the variability of similarly sited wind. The relative aggregate variability of PV plants sited in a dense 10 x 10 array with 20 km spacing is six times less than the variability of a single site for variability on time scales less than 15-min. We find in our analysis of wind and PV plants similarly sited in a 5 x 5 grid with 50 km spacing that the variability of PV is only slightly more than the variability of wind on time scales of 5-15 min. Over shorter and longer time scales the level of variability is nearly identical. Finally, we use a simple approximation method to estimate the cost of carrying additional reserves to manage sub-hourly variability. We conclude that the costs of managing the short-term variability of PV are dramatically reduced by geographic diversity and are not substantially different from the costs for managing the short-term variability of similarly sited wind in this region
- âŠ