188,875 research outputs found
Variable stress orientations in the offshore Nile Delta: The role of salt as a mechanical detachment horizon
The offshore Nile Delta is characterized by variations of the maximum horizontal stress orientation in subsalt and supra-salt sequences. Margin-parallel SH, typical for tertiary deltas, is observed for regions that are below or do not contain evaporites. In sequences underlain by evaporates pre-dominantly margin-normal SH is observed. This observation yielded the first conclusive in situ evidence that salt acts as a mechanical detachment layer. In this study, 3D finite element analysis (FEA) is used to simulate the total stress distribution in the offshore Nile Delta featuring evaporate sequences. Several parameters such as different salt sequence geometries, friction coefficient on faults, and salt viscosity are considered. The numerical modeling results are used to evaluate if possible basal drag forces or mechanical property contrast effect induced by gravitational gliding result in varying stress orientations and if the observed stress orientations in the Nile Delta can be explained and correlated by the numerical modeling results. Implication of the modeling results for hydrocarbon production will be analyzed and discussed. --Abstract, page iii
Hydrogeology and hydrogeochemistry of the Spring Mountains, Clark County, Nevada
The Spring Mountains are the largest ground-water recharge area in southern Nevada and supply a significant amount of ground water to the Las Vegas\u27 Pahrump, and Indian Springs Valleys; The high quality of ground water in the study area is controlled by the predominance of carbonate rock in the central portion of the mountain block. Modeling of {dollar}\delta\sp{13}{dollar}C in ground water suggest low P{dollar}\sb{\rm CO\sb2}{dollar} and enriched {dollar}\delta\sp{13}{dollar}C in soil, and open system conditions at high elevations. Analysis of {dollar}\sp{14}{dollar}C in ground water and geochemical modeling of ground water using PHREEQE and BALANCE suggest ground water from the Spring Mountain bedrock aquifer and alluvial-fan aquifers are mixing with water from the regional aquifer in the Las Vegas shear zone. Modeling also suggests mixing of 90 percent Las Vegas shear zone water with 10 percent water from the western portion of the Las Vegas Valley in the Las Vegas well field. (Abstract shortened with permission of author.)
Category Theory and Model-Driven Engineering: From Formal Semantics to Design Patterns and Beyond
There is a hidden intrigue in the title. CT is one of the most abstract
mathematical disciplines, sometimes nicknamed "abstract nonsense". MDE is a
recent trend in software development, industrially supported by standards,
tools, and the status of a new "silver bullet". Surprisingly, categorical
patterns turn out to be directly applicable to mathematical modeling of
structures appearing in everyday MDE practice. Model merging, transformation,
synchronization, and other important model management scenarios can be seen as
executions of categorical specifications.
Moreover, the paper aims to elucidate a claim that relationships between CT
and MDE are more complex and richer than is normally assumed for "applied
mathematics". CT provides a toolbox of design patterns and structural
principles of real practical value for MDE. We will present examples of how an
elementary categorical arrangement of a model management scenario reveals
deficiencies in the architecture of modern tools automating the scenario.Comment: In Proceedings ACCAT 2012, arXiv:1208.430
Prototyping Formal System Models with Active Objects
We propose active object languages as a development tool for formal system
models of distributed systems. Additionally to a formalization based on a term
rewriting system, we use established Software Engineering concepts, including
software product lines and object orientation that come with extensive tool
support. We illustrate our modeling approach by prototyping a weak memory
model. The resulting executable model is modular and has clear interfaces
between communicating participants through object-oriented modeling.
Relaxations of the basic memory model are expressed as self-contained variants
of a software product line. As a modeling language we use the formal active
object language ABS which comes with an extensive tool set. This permits rapid
formalization of core ideas, early validity checks in terms of formal invariant
proofs, and debugging support by executing test runs. Hence, our approach
supports the prototyping of formal system models with early feedback.Comment: In Proceedings ICE 2018, arXiv:1810.0205
A Decidable Confluence Test for Cognitive Models in ACT-R
Computational cognitive modeling investigates human cognition by building
detailed computational models for cognitive processes. Adaptive Control of
Thought - Rational (ACT-R) is a rule-based cognitive architecture that offers a
widely employed framework to build such models. There is a sound and complete
embedding of ACT-R in Constraint Handling Rules (CHR). Therefore analysis
techniques from CHR can be used to reason about computational properties of
ACT-R models. For example, confluence is the property that a program yields the
same result for the same input regardless of the rules that are applied.
In ACT-R models, there are often cognitive processes that should always yield
the same result while others e.g. implement strategies to solve a problem that
could yield different results. In this paper, a decidable confluence criterion
for ACT-R is presented. It allows to identify ACT-R rules that are not
confluent. Thereby, the modeler can check if his model has the desired
behavior.
The sound and complete translation of ACT-R to CHR from prior work is used to
come up with a suitable invariant-based confluence criterion from the CHR
literature. Proper invariants for translated ACT-R models are identified and
proven to be decidable. The presented method coincides with confluence of the
original ACT-R models.Comment: To appear in Stefania Costantini, Enrico Franconi, William Van
Woensel, Roman Kontchakov, Fariba Sadri, and Dumitru Roman: "Proceedings of
RuleML+RR 2017". Springer LNC
Abstract delta modeling : software product lines and beyond
To prevent a large software system from collapsing under its own complexity, its code needs to be well-structured. Ideally we want all code related to a certain feature to be grouped together __called feature modularization__ and code belonging to different features not to mix __ called separation of concerns. But many concerns are known as 'cross-cutting concerns'. By their very nature their implementation needs to be spread around the code base. The software engineering discipline that has the most to gain from those properties is Software Product Line Engineering. It is concerned with the development and maintenance of multiple software systems at the same time, each possessing a different (but often overlapping) set of features. This gives rise to an additional need: The code for a given feature must not only be separated and modular; it also needs to be composable and able to deal gracefully with the presence or absence of other features. This thesis presents Abstract Delta Modeling, a formal framework developed to achieve these goals in software. The thesis is a product of the European HATS project. It formalizes the techniques of delta modeling, the main approach to variability used by HATSAlgorithms and the Foundations of Software technolog
Accurate and simple modeling of amplifier dc gain nonlinearity in switched-capacitor circuits
This paper presents an accurate and simple model for dc gain nonlinearity of operational amplifiers used in the switched-capacitor circuits such as the sigma-delta modulators. The proposed model can simply be used in the time-domain system level simulation of sigma-delta modulators to evaluate the effect of amplifier's dc gain nonlinearity on the overall linearity of the modulator as well as in the other switched- capacitor circuits as explored in the paper.Comisión Interministerial de Ciencia y Tecnología TIC2003-0235
Evaluation of Variability Concepts for Simulink in the Automotive Domain
Modeling variability in Matlab/Simulink becomes more and more important. We
took the two variability modeling concepts already included in Matlab/Simulink
and our own one and evaluated them to find out which one is suited best for
modeling variability in the automotive domain. We conducted a controlled
experiment with developers at Volkswagen AG to decide which concept is
preferred by developers and if their preference aligns with measurable
performance factors. We found out that all existing concepts are viable
approaches and that the delta approach is both the preferred concept as well as
the objectively most efficient one, which makes Delta-Simulink a good solution
to model variability in the automotive domain.Comment: 10 pages, 7 figures, 6 tables, Proceedings of 48th Hawaii
International Conference on System Sciences (HICSS), pp. 5373-5382, Kauai,
Hawaii, USA, IEEE Computer Society, 201
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