Modeling Techniques

Esta tesis presenta una estrategia en la Ingeniería de Requisitos, denominada SDRES, que intenta abordar temas poco tratados en la práctica real, tales como los cambios constantes en los requisitos, defectos del software originados en los requisitos, el contexto organizacional que rodea al sistema de software y la consideración de requisitos de calidad. Esta estrategia está dirigida por modelos (Léxico Extendido del Lenguaje, Escenarios y Documento de Requisitos) y orientada al cliente, por ello utiliza sus modelos escritos en lenguaje natural como medio de comunicación y elicitación. SDRES tiene en cuenta la calidad de los modelos que produce mediante procesos de verificación y validación. Para cada actividad de la estrategia se presenta un conjunto de heurísticas y recomendaciones. Se encara el tema de evolución y versionado de los modelos, así como distintas modalidades de utilizar la estrategia según la complejidad del problema, el conocimiento sobre el mismo y otras característ...

Magnetic field measurements are very valuable, as they provide constraints on the interior of the telluric planets and Moon. The Earth possesses a planetary scale magnetic field, generated in the conductive and convective outer core. This global magnetic field is superimposed on the magnetic field generated by the rocks of the crust, of induced (i.e. aligned on the current main field) or remanent (i.e. aligned on the past magnetic field). The crustal magnetic field on the Earth is very small scale, reflecting the processes (internal or external) that shaped the Earth. At spacecraft altitude, it reaches an amplitude of about 20 nT. Mars, on the contrary, lacks today a magnetic field of core origin. Instead, there is only a remanent magnetic field, which is one to two orders of magnitude larger than the terrestrial one at spacecraft altitude. The heterogeneous distribution of the Martian magnetic anomalies reflects the processes that built the Martian crust, dominated by igneous and cratering processes. These latter processes seem to be the driving ones in building the lunar magnetic field. As Mars, the Moon has no core-generated magnetic field. Crustal magnetic features are very weak, reaching only 30 nT at 30-km altitude. Their distribution is heterogeneous too, but the most intense anomalies are located at the antipodes of the largest impact basins. The picture is completed with Mercury, which seems to possess an Earth-like, global magnetic field, which however is weaker than expected. Magnetic exploration of Mercury is underway, and will possibly allow the Hermean crustal field to be characterized. This paper presents recent advances in our understanding and interpretation of the crustal magnetic field of the telluric planets and Moon.

This paper describes a general state-variable form of mathematical modeling which may be used to control the dynamic stability of a larger power system optimally. Based on the linearization about the operating point of the system, a complete model for dynamic stability control is ...

... Yoonho Seo*, Tae-Hoon Choi*, Suk-Hwan Suh ... public void MachineControlVrml(String AxisX, String AxisY, String AxisZ){ try{ AxisNodeX = browser.getNode(AxisX); AxisInX = (EventInSFVec3f ) AxisNodeX.getEventIn( "set-translation"); AxisOuiY = (EventOutSFVec3f) AxisNodeX ...

ABSTRACT In modern IT systems, data backup and restore operations are essential for providing protection against data loss from both natural and man-made incidents. On the other hand, data backup and restore operations can be resource-intensive and lead to performance degradation, or may require the system to be offline entirely. Therefore, it is important to properly choose backup and restore techniques and policies to ensure adequate data protection while minimizing the impact on system availability and performance. In this paper, we present an analytical modeling approach for such a purpose. We study a file service system that undergoes periodic data backups, and investigate metrics concerning system availability, data loss and rejection of user requests. To obtain the metrics, we combine a variety of model types, including Markov chains, queuing networks and Stochastic Reward Nets, to construct a set of analytical models that capture the operational details of the system. We then compute the metrics of interest under different backup/restore techniques, policies, and workload scenarios. The numerical results allow us to compare the effects of different backup/restore techniques and policies in terms of the tradeoff between protective power and impact on system performance and availability.

Along with numerous universities and large trading companies heavily relying on e-learning environments to train their students and employees, the design and development of adaptive educational hypermedia that customize the content and navigation for each student has gained importance and priority all around the world. This study aims to describe the concept of student modeling, heart of the adaptive learning systems, and analyze the information collection, construction and updating phases of a student modeling process. In the study, the classification of student models in numerous ways is explained, and the different methods employed in the representation of information in the student model are addressed. Moreover, the problem of uncertainty, which is one of the most important challenges in the student modeling process, is mentioned, and the trends in student modeling are discussed.

This paper aims to propose an approach to curriculum management modeling in universities based on the fundamentals of business processes and with a special focus on context-sensitive information. The importance of the context lies in the need to control more information of the surroundings to improve expressiveness in the representation and intelligent reasoning of knowledge. The context is modeled by entities related to the domain of execution, as well as by contextual situations associated with said environment. Automated reasoning is carried out by implementing an intelligent algorithm that uses clustering techniques. This algorithm considers the contextual information of a process and then generates contextual alerts that support decision making. For the automated processing of such information, we design a system that simulates and records process executions using data sets for the log of each process. Some of our findings include a formal representation of curriculum management based on situations that enrich the information of each business process. According to the results, we may conclude that curriculum-related information is context-sensitive and might, thus, affect the execution of the processes associated with curriculum management. Therefore, we recommend designing automated reasoning rules that consider the context for decision making in curriculum management processes.

In this paper, the estimation of a scalar field over a bidimensional scenario (e.g., the atmospheric pressure in a wide area) through a self-organizing wireless sensor network (WSN) with energy constraints is investigated. The sensor devices (denoted as nodes) are randomly distributed; they transmit samples to a supervisor by using a clustered network. This paper provides a mathematical framework to analyze the interdependent aspects of WSN communication protocol and signal processing design. Channel modelling and connectivity issues, multiple access control and routing, and the role of distributed digital signal processing (DDSP) techniques are accounted for. The possibility that nodes perform DDSP is studied through a distributed compression technique based on signal resampling. The DDSP impact on network energy efficiency is compared through a novel mathematical approach to the case where the processing is performed entirely by the supervisor. The trade-off between energy conservation (i.e., network lifetime) and estimation error is discussed and a design criterion is proposed as well. Comparison to simulation outcomes validates the model. As an example result, the required node density is found as a trade-off between estimation quality and network lifetime for different system parameters and scalar field characteristics. It is shown that both the DDSP technique and the MAC protocol choice have a relevant impact on the performance of a WSN.