Scielo RSS <![CDATA[Computación y Sistemas]]> vol. 21 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Editorial]]> <![CDATA[Humanitarian Logistics and Cultural Diversity within Crowd Simulation]]> Abstract: Human stampedes occur frequently because of abnormal events (e.g., a fire or explosion) produced in collective events (e.g., religious pilgrimages, music concerts and sportive events). These events provoke panic and when people are agglomerated they try to escape pushing each other without realizing that others are being crushed. Since crowds can consist of individuals with diverse physical and social characteristics determined by cultural diversity, it is difficult to configure the space in advance and find solutions in real-time to save people and reduce catastrophe. This paper proposes an approach to explore the impact of anthropometry and cultural diversity in the behaviour of crowds in panic situations. Our approach includes techniques for reproducing and simulating the behaviour of the crowd to generate models that can help decision making to control such situations. The main contribution of our work is to use computational science, data processing and visualization techniques to perform our simulation and study, for eventually supporting critical decision making. <![CDATA[CAREGIVERSPRO-MMD: Community Services, Helping Patients with Dementia and Caregivers Connect with Others for Evaluation, Support and to Improve the Care Experience]]> Abstract: In this paper, we present the design of a mHealth application that is specifically targeted to caregivers and persons with mild to moderate dementia. The result is CAREGIVERSPRO-MMD: a tool integrating a broader diagnostic approach, incorporating the live-in family caregiver-patient dyad and considering this dyad as the unit of care. CAREGIVERSPRO-MMD will provide value-added services based on social networks, tailored interventions, clinical strategies and gamification for improving the quality of life for people living with dementia and their caregivers, allowing them to live in the community for as long as possible. CAREGIVERSPRO-MMD is an EU project funded under the H2020 program. <![CDATA[Planet Boundary Layer Parameterization in Weather Research and Forecasting (WRFv3.5): Assessment of Performance in High Spatial Resolution Simulations in Complex Topography of Mexico]]> Abstract: This paper presents the application of the Weather Research and Forecasting (WRF version 3.5) with high spatial resolution (3 and 1 km) testing four Planet Boundary Layer (PBL) schemes to the complex topography of Mexico in different numerical experiments that have tried to find the best configuration. The WRF is a Numerical Weather Prediction (NWP) model giving support for weather forecasting and modeling in Chemical Transport (CTM) or Air Quality Models as CMAQ or CHIMERE. For the above, the objectives in this work were assess the performance, the best grid parameterization, meteorological initial conditions, temporal resolution, time step and PBL schemes used in order to minimize the execution time and to show changes in speedup and efficiency. Mare Nostrum III supercomputer was used for the computational processing in the cluster. The computational performance indicators were execution time, speedup and efficiency. The sensitivity analysis was performed using the mean bias (MB) and root mean square error (RMSE) from variables obtained by WRFv3.5 such as temperature, wind-speed, sea level pressure and the METAR Veracruz airport station observations. The results show that Mellor-Yamada-Janjic (MYJ) scheme was better in computational parallel execution with at least 8 processors and a time step of 18 seconds. The sensitivity analyses show that time step is not a key in the accuracy of the meteorological values obtained. It is necessary consider the lack of data in METAR stations in Mexico. <![CDATA[Simulating the Fractal growth of Quintana Roo’s Subaquatic Caves by the Diffusion Limited Aggregation Model]]> Resumen: Las cuevas subacuáticas son el resultado de un proceso de disolución que ocurre desde hace millones de años entre la piedra caliza y el agua. Para llevar a cabo un estudio teórico del proceso de crecimiento de estos sistemas utilizamos como marco el modelo de crecimiento de agregación limitada por difusión (DLA). Unas modificaciones de este modelo generan patrones fractales que son apropiados para describir las estructuras fractales observadas en las cuevas subacúaticas de Quintana-Roo. Como resultado de este trabajo encontramos que con reglas simples que toman en cuenta la anisotropía y la heterogeneidad del medio rocoso se pueden formar estructuras fractales complejas, similares a las que muestran las cuevas subacuáticas.<hr/>Abstract: Subaquatic caves are formed by dissolution processes between limestone and water that have been taking place for millions of years. These natural systems exhibit spatial patterns that can be studied using the theory of fractal geometry. Here we modify the Diffusion Limited Aggregation (DLA) model to simulate the fractal growth Quinta-Roo's subaquatic caves. We show that with simple dynamical rules it is possible to generate complex fractal structures similar to real caves. <![CDATA[Modelling Crowds in Urban Spaces]]> Abstract: Large scale crowd simulation and visualization combine computer graphics, artificial intelligence and high performance computing among other areas. Crowd sourced location data is used to compute spatio-temporal people and vehicle flows, while map and geometric data describe specific real places. With all this data, we can visualize both real trajectories and data driven on-line crowd simulation. We have some initial results using vehicle trajectory data. <![CDATA[Development and Validation of Software CRISIS to Perform Probabilistic Seismic Hazard Assessment with Emphasis on the Recent CRISIS2015]]> Abstract: The probabilistic seismic hazard assessment (PSHA) is a fundamental step to generate information that can contribute to reduce the seismic risk in cities. This reduction is essential to increase the resilience of the cities. Nowadays, there are different types of software that can be used to perform PSHA. In the present document a recent version of the CRISIS software to perform PSHA is described. CRISIS2015 is a versatile tool to perform PSHA. The first version of CRISIS was done more than fifteen years ago. In order to highlight the progress of CRISIS since then, in the present document some comparison between features of the recent CRISIS2015 and earlier versions are included. Additionally, different versions of CRISIS have been tested according to different validation procedures. In the present document results of tests that were applied to an earlier version of CRISIS2015 and also that were applied to the recent CRISIS2015 are included. According to the results of different tests, it is possible to conclude that the recent CRISIS2015 can compute PSHA with high precision. CRISIS2015 was included in an international project to validate software to compute seismic hazard. Representative results of this validation project are included in this document. The results computed by CRISIS2015 are in total agreement with the results considered as valid in the recent edition 2014-2015 of the PEER project to validate software to compute seismic hazard. Finally, examples of the kind of projects where some version of CRISIS has been applied to perform PSHA in the last fifteen years are included. <![CDATA[Energy-Efficient Medium Access Control Using Distributed Hash-based Elections]]> Abstract: In this paper we introduce the Energy-Efficient Multiple Access (EE-MA) protocol for wireless networks where nodes participate in a distributed election to gain interference-free access to the wireless channel. By taking advantage of the information used in the distributed elections, nodes can infer if they are not the intended receiver of a transmission and set their radios in sleeping state to save energy. To save even more energy and avoid false positives derived from the nature of the protocol, EE-MA also implements a sleeping scheme where nodes switch to the sleeping state if no message is received during the beginning of a time-slot. We show that the individual channel access plans computed by the proposed distributed algorithm are collision-free at the intended receivers and that intended receivers are always in receiving state. We also present a simulation-based performance analysis that shows that EE-MA outperforms a state of the art election-based channel access protocol in terms of energy efficiency with no cost in terms of network capacity. Simulations also show that EE-MA outperforms 802.11 contention based protocol in terms of goodput and channel access delay. <![CDATA[A Model Checker for the Verification of Browser Based Protocols]]> Abstract: A browser based protocol is the chief security component of a safety critical web application, such as e-banking. Accordingly, browser based protocols need to be thoroughly verified in order to guarantee they are up to comply with key security properties. To this end, we have developed WebMC, a model checker especially designed to consider web standards, with the aim of analyzing browser based protocol execution, as encompassed by the interactions of a typical user, a browser, and active attacker playing the role of the network, and one or more servers. In this paper, we shall show how to use WebMC in the design and the development of browser based protocols. Our tool has been successfully validated: WebMC has been able to reproduce a number of the verification results found in the literature, but fully automatically. <![CDATA[LinearTag Models: Recommendations Using Linear User Profiles Based on Tags]]> Abstract: Recommender systems allow the exploration of large collections of products, the discovery of patterns in the products, and the guidance of users towards products that match their interests. Collaborative tagging systems allow users to label products in a collection using a free vocabulary. The aggregation of these tags, also called a Folksonomy, can be used to build a collective characterization of the products in a simple and recognizable vocabulary. In this paper, we propose a family of methods called LinearTag recommenders, which infer users preferences for tags to formulate recommendations for them. We dubbed these inferred user profiles as TagProfiles. We present experiments using them as an interaction artifact that allows users to receive new recommendations as they delete, add or reorder tags in their profiles. Additional experiments using the Movielens dataset, show that the proposed methods generate recommendations with an error margin similar, or even lower than the results reported by methods based on latent factors. Next, we compared TagProfiles against KeywordProfiles, which are profiles based on keywords extracted automatically from textual descriptions of products. This comparison showed that TagProfiles are not only more precise in their predictions, but they are also more understandable by users. At last, we developed a user interface of a movie recommender based on TagProfiles, which we tested with 25 users. This experience showed that TagProfiles are easier to understand and modify by users, allowing them to discover new movies as they interact with their profiles. <![CDATA[Obtaining the Dicrotic Notch by Numerical Simulation Using the Ogden Model]]> Resumen: En este trabajo se hace una propuesta para un mejor entendimiento del comportamiento de la arteria aorta ascendente. Se propone que la onda dicrota que aparece en la curva de presión es el resultado del estímulo a un material hiperelástico. Dicha propuesta es puesta a prueba mediante la simulación numérica de la interacción del flujo sanguíneo con la pared arterial. Se resuelven las ecuaciones de Navier-Stokes con las condiciones iniciales y propiedades físicas propias del flujo sanguíneo para una persona en promedio sana; de manera simultánea los campos obtenidos, (presión y velocidad), alimentan los forzamientos de la estructura sólida, (pared arterial), para así obtener el comportamiento de la arteria aorta bajo la influencia del flujo sanguíneo. La aproximación a las soluciones de las ecuaciones dictaminantes y el acoplamiento de ambas estructuras se realiza mediante un conjunto de algoritmos para resolver el problema de la interacción del flujo sanguíneo con la pared arterial en 3D utilizando un método que proporciona acoplamiento débil y que es, en general, válido para modelos constitutivos no-lineales y con grandes deformaciones. Los resultados obtenidos son similares a los obtenidos en la clínica<hr/>Abstract: A proposal for the better understanding of the ascending aorta mechanical behavior is made. It is proposed that the dicrotic notch on the cardiac cycle is the result to the stimulus of an hyper elastic material. This proposal is sustained by the numerical study of the interaction between the blood flow and the arterial walls. The Navier-Stokes equations for the blood flow are solved with the initial conditions and the physical properties corresponding to an average healthy human aorta. The obtained velocity and pressure fields increase the stress on the solid wall (arterial wall), consequently the behavior of the aorta under the blood flow is obtained. Solutions to the 3D governing equations are obtained through algorithms that solve for the weak form of the coupling between the blood flow and arterial wall. This method is valid for non-linear models subjects to large deformations. Computational results are verified by available experimental data for tensile tests of the ascending aorta. Realistic parameters for both the isotropic hyper elastic Ogden and neo-Hookean models were obtained. <![CDATA[The Lineal Prediction Applied to Distributed Speech Recognition in IP Nets]]> Resumen: Este trabajo presenta resultados en la aplicación de técnicas de compresión al reconocimiento del habla en redes IP. Por lo que las tres áreas fundamentales del conocimiento que están involucradas son: la compresión de voz, la simulación de canales de transmisión y el reconocimiento del habla. Dichas áreas se integran para lograr una aplicación desarrollada en MATLAB, capaz de realizar un reconocimiento del habla de forma remota mediante la transmisión de voz comprimida, con la peculiaridad de que se considera la probabilidad de ocurrencia de pérdidas de información en los canales de transmisión, de forma tal que queda demostrada la robustez del sistema propuesto.<hr/>Abstract: This work presents results in the application of speech compression to speech recognition technics in IP nets. That’s why the three fundamental areas of the knowledge that are involved are: the voice compression, the transmission channels simulation and the speech recognition. This areas are integrated to achieve an application developed in MATLAB, able to carry out a remote speech recognition by means of the transmission of compressed voice, with the peculiarity that it is considered the probability of occurrence of losses of information in the transmission channels, in such way that the robustness of the proposed system is demonstrated. <![CDATA[Digital Rate MEMS Vibratory Gyroscope Modeling, Tuning and Simulation Results]]> Abstract: This paper is dealing with modeling, tuning and simulation of standing wave control and information processing algorithm for rate MEMS ring-type vibratory gyroscope. Standing wave control algorithm is presented in the form allowing transition from rate to rate integrating and to differential modes of MEMS gyro operation by simple switching command. It enables to implement triple-mode MEMS gyro. Block diagrams of the standing wave control algorithm and resonance frequency tracking subsystem are presented. Drive and compensation signal phases tuning criteria are described and implemented. Detailed explanations to the main operations which are used in information processing algorithm are given. Also, simulation results in case of measurement of a constant and variable angle rates are presented.