In the present study, the influence of the quenching temperature and partitioning conditions (temperature and time) have been investigated on a 0.6%C-1.2%Mn-1.6%Si-1.75%Cr alloy. Maps of hardness, impact toughness and amount of retained austenite have been developed for three quenching temperatures as a function of partitioning temperature and partitioning time. Results demonstrate that, in this material, the carbon depletion of the martensite and the stabilization of austenite can be achieved significantly faster at high partitioning temperatures, promoting higher retained austenite fractions, lower hardness, and maximizing the energy absorbed in a Charpy V‑Notch test. In addition, the effect of the partitioning time was also analysed, presenting different behaviour at high and low partitioning temperatures. Whereas an increment of time at high partitioning temperatures (>400 ºC) leads to an austenite consumption, at low partitioning temperatures it is effective to retain a higher amount of austenite.  Furthermore, tensile properties are shown to be better than in conventional alloys utilized in industry. Whilst, for example, the AISI 52100 alloy achieves 2 GPa of tensile strength and 1‑2% of fracture deformation, in the present study the notable combination of 2.5 GPa of tensile strength and 5.7 % of fracture deformation was achieved in samples quenched until room temperature. Untempered martensite transformed during final cooling in samples quenched until higher temperatures was shown to be detrimental for tensile properties. A comparison between the Q&P process and the austempering process on this alloy has been carried out. Results reveal that the quenching and partitioning heat treatment is presented as a promising alternative to reach higher hardness (>700 HV) and similar specific wear rates in dry conditions performing a shorter heat treatment.    Finally, a complementary study about the effect of micro-segregation on the Q&P process and an optimization method to minimize the inhomogeneity of the structure by a correct selection of the quenching temperature were established.

The complexity of SPARQL queries and RDF applications poses great challenges on distributed RDF management systems. SPARQL workloads are dynamic and con- sist of queries with variable complexities. Hence, systems that use static partitioning su↵er from communication overhead for workloads that generate excessive communi- cation. Concurrently, RDF applications are becoming more sophisticated, mandating analytical operations that extend beyond SPARQL queries. Being primarily designed and optimized to execute SPARQL queries, which lack procedural capabilities, exist- ing systems are not suitable for rich RDF analytics. This dissertation tackles the problem of accelerating SPARQL queries and RDF analytics on distributed shared-nothing RDF systems. First, a distributed RDF en- gine, coined AdPart, is introduced. AdPart uses lightweight hash partitioning for sharding triples using their subject values; rendering its startup overhead very low. The locality-aware query optimizer of AdPart takes full advantage of the partition- ing to (i) support the fully parallel processing of join patterns on subjects and (ii) minimize data communication for general queries by applying hash distribution of intermediate results instead of broadcasting, wherever possible. By exploiting hash- based locality, AdPart achieves better or comparable performance to systems that employ sophisticated partitioning schemes. To cope with workloads dynamism, AdPart is extended to dynamically adapt to workload changes. AdPart monitors the data access patterns and dynamically redis- tributes and replicates the instances of the most frequent patterns among workers.Consequently, the communication cost for future queries is drastically reduced or even eliminated. Experiments with synthetic and real data verify that AdPart starts faster than all existing systems and gracefully adapts to the query load. Finally, to support and accelerate rich RDF analytical tasks, a vertex-centric RDF analytics framework is proposed. The framework, named SPARTex, bridges the gap between RDF and graph processing. To do so, SPARTex: (i) implements a generic SPARQL operator as a vertex-centric program. The operator is coupled with an optimizer that generates e cient execution plans. (ii) It allows SPARQL to invoke vertex-centric programs as stored procedures. Finally, (iii) it provides a unified in- memory data store that allows the persistence of intermediate results. Consequently, SPARTex can e ciently support RDF analytical tasks consisting of complex pipeline of operators.

The Caprellidae are a specialized suborder of Amphipoda, which are highly modified for a semisessile life. Caprellids exhibit direct development and brood their young. The suborder is exclusively marine and commonly found on filamentous algae, sea grasses and fouling communities. Most published works on caprellids have been primarily concern~d with systematics (Caine, 1974; Dougherty, 1943; Laubitz, 1970, 1972; McCain, 1968, 1975), although a few recent studies have dealt with ecology and ethology (Bynum, 1978; Caine, 1977; Keith, 1969, 1971; Lewbel, 1978; Saunders, 1966). This study examines·spatial and temporal variations in distribution, abundance and population structure as well as describing intraspecific aggressive behavior of Caprella californica Stimpson. ~- californica is dioecious and has marked sexual dimorphism in both its size and secondary sex characteristics. It is found from San Diego to the South China Sea (Laubitz, 1970), and is the dominant caprellid in the Zostera marina beds of the local bays and is a major diet item for many of the eel grass associated fishes. There is a preponderance of females in the population as well as a size-specific distribution of the proportion of the sexes.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / Studies on snake competitive interactions have relatively been well documented globally, however, those examples tend to be dominated by non-African examples. Africa has a large and spectacular reptile diversity and yet robust and empirical studies on snake population ecology remain poorly understood or documented. Given the close phylogenetic relationship between the two species, as well as the remarkable similarities in overall appearance, morphology, reproductive biology, and most importantly geographic distribution, Psammophis crucifer and Psammophylax rhombeatus offered an ideal study system in which to ask questions related to interspecific competition and niche partitioning.

We investigate so-called partitioning oracle attacks against AES-GCM and ChaCha20-Poly1305 along with some improvements. Such attacks against these two cryptosystems are efficient because they can be reduced to solving linear systems of equations over finite fields. We show, with some randomness assumptions, that such linear systems must have at least as many columns as rows. We have also chosen two finite (non-field) rings, as replacement for the respective fields used by AES-GCM and ChaCha20-Poly1305 for message authentication. These rings make the problem of linear system arrangement in a partitioning oracle attack extremely hard for large linear system dimensions.

Vehicle to Vehicle (V2V) communication provides a flexible and real-time information dissemination mechanism through various applications of Intelligent Transportation Systems (ITS). Achieving seamless connectivity through multi-hop vehicular communication with sparse network is a challenging issue. In this paper, we have studied this multi-hop vehicular connectivity in an urban scenario using GPS traces obtained from San Francisco Yellow cabs. Our current work describes a new algorithm for the analysis of topological properties like connectivity and partitions for any kind of vehicular or mobile computing environment. The novel approach uses bitwise manipulation of sparse matrix with an efficient storage technique for determining multi-hop connectivity. The computation mechanism can be further scaled to parallel processing environment. The main contribution of this research is threefold. First, developing an efficient algorithm to quantify multi-hop connectivity with the aid of bitwise manipulation of sparse matrix. Second, investigating the time varying nature of multi-hop vehicular connectivity and dynamic network partitioning of the topology. Third, deriving a mathematical model for calculating message propagation rate in an urban environment.

Pocket gophers (family Geomyidae) are the dominant burrowing rodents in North America today. Their fossil record is also incredibly rich; in particular, entoptychine gophers, a diverse extinct subfamily of the Geomyidae, are known from countless teeth and jaws from Oligocene and Miocene-aged deposits of the western United States and Mexico. Their postcranial remains, however, are much rarer and little studied. Yet, they offer the opportunity to investigate the locomotion of fossil gophers, shed light on the evolution of fossoriality, and enable ecomorphological comparisons with contemporaneous rodents. We present herein a quantitative study of the cranial and postcranial remains of eight different species of entoptychine gophers as well as many contemporary rodent species. We find a range of burrowing capabilities within Entoptychinae, including semifossorial scratch-digging animals and fossorial taxa with cranial adaptations to burrowing. Our results suggest the repeated evolution of chisel-tooth digging across genera. Comparisons between entoptychine gophers and contemporaneous rodent taxa show little ecomorphological overlap and suggest that the succession of burrowing rodent taxa on the landscape may have had more to do with habitat partitioning than competition.

Purpose: This article provides an empirical identification of groups of marketing scholars who share common beliefs about the role of science and the logic of scientific discovery. Design: We use Topology Representing Network quantization to empirically identify classes of marketing researchers within a representative sample of marketing professors. Findings: We find six distinct classes of marketing scholars. They differ with regard to popularity (size) and productivity (levels of publication output). Comparing the sub-samples of German-speaking and US respondents shows cross-cultural differences. Value: The study enhances our understanding of the current scientific orientation(s) of marketing. It may help to motivate marketing scholars to ponder on their own positions and assist them in judging where they may belong. Future comparisons over time would give us indication about the future of the academic discipline of marketing.(author's abstract)

The subsumed work of this dissertation is comprised of three independent but interrelated studies which seek to further the understanding of processes which govern the coprecipitation of trace elements with calcite and aragonite minerals. These studies investigate the effects of: 1) pressure on crystal morphology and trace element incorporation to aragonite; 2) growth rate on uranium partitioning between calcite and fluid; 3) aqueous Mg/Ca on the magnesium partitioning to low-magnesium calcite. The importance of this work is to determine how the environment of formation and growth rate influences the geochemistry of CaCO3 in order to improve existing paleoproxies and develop new ones. In the first study a series of experiments were conducted at 1, 25, 75, 100, and 345 bars of nitrogen – this range covers pressures at the oceanic floor. Aragonite precipitation was induced by the one-time addition of a Na2CO3 solution to an artificial seawater. Results suggest that oceanic floor pressures could affect the crystallization of CaCO3 by altering mineralogical composition and aragonite crystal size. In the second study calcite crystallized from NH4Cl-CaCl2-U solution by diffusion of CO2. The calcite growth rate was monitored by sequential spiking of the calcite-precipitating fluids with REE dopants. The resulting crystals were analyzed using Secondary Ion Mass Spectrometry (SIMS). Results showed that the partitioning of uranium increases with increasing growth rate. Growth entrapment model (GEM) and unified uptake kinetics model (UUKM) explain the obtained data.In the third study CaCO3 precipitated in NaCl solution by continuous addition of CaCl2, MgCl2, and either Na2CO3 or NaHCO3. The Mg/Ca of the fluid was adjusted in an attempt to produce calcite where Mg/Ca would match Mg/Ca in foraminifera shells. It was observed that multiple CaCO3 polymorphs precipitated from fluids at high pH (Na2CO3 doping experiments). This result underscores the potential control of pH and/or supersaturation state on CaCO3 polymorph precipitated from low Mg/Ca solutions. Calcite was the only mineral crystallized at low pH (NaHCO3 doping experiments). It was determined that Mg partition coefficient between calcite and fluid (KMg) negatively correlates with Mg/Ca(Fluid) when it exceeds 0.5 mol/mol; no systematic correlation was observed when 0.05< Mg/Ca(Fluid)<0.5 mol/mol.

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