Metamodeling live sequence charts for code generation

This article presents a metamodeling study for Live Sequence Charts (LSCs) and Message Sequence Charts (MSCs) with an emphasis on code generation. The article discusses specifically the following points: the approach to building a metamodel for MSCs and LSCs, a metamodel extension from MSC to LSC, support for model-based code generation, and finally action model and domain-specific data model integration. The metamodel is formulated in metaGME, the metamodel language for the Generic Modeling Environment.

Optimization of coal liquefaction reactors

The method of Lagrangian multipliers of classical calculus is applied to obtain the optimum operating conditions of three continuous stirred tank reactors (CSTR) in series, to liquefy coal with minimum gas yield. In the formulation of the problem, the gas conversion was assumed to be the cost function. Results obtained were supported by the experimental findings in terms of liquefaction temperatures, reaction times, and conversion of coal into various liquefaction products.     

Memory Coalescing Implementation of Metropolis Resampling on Graphics Processing Unit

Owing to many cores in its architecture, graphics processing unit (GPU) offers promise for parallel execution of the particle filter. A stage of the particle filter that is particularly challenging to parallelize is resampling. There are parallel resampling algorithms in the literature such as Metropolis resampling, which does not require a collective operation such as cumulative sum over weights and does not suffer from numerical instability. However, with large number of particles, Metropolis resampling becomes slow. This is because of the non-coalesced access problem on the global memory of the GPU. In this article, we offer solutions for this problem of Metropolis resampling. We introduce two implementation techniques, named Metropolis-C1 and Metropolis-C2, and compare them with the original Metropolis resampling on NVIDIA Tesla K40 board. In the first scenario where these two techniques achieve their fastest execution times, Metropolis-C1 is faster than the others, but yields the worst results in quality. However, Metropolis-C2 is closer to Metropolis resampling in quality. In the second scenario where all three algorithms yield similar quality, although Metropolis-C1 and Metropolis-C2 get slower, they are still faster than the original Metropolis resampling.     

A survey on location estimation techniques for events detected in Twitter

Detection of events using voluntarily generated content in microblogs has been the objective of numerous recent studies. One essential challenge tackled in these studies is estimating the locations of events. In this paper, we review the state-of-the-art location estimation techniques used in the localization of events detected in microblogs, particularly in Twitter, which is one of the most popular microblogging platforms worldwide. We analyze these techniques with respect to the targeted event type, granularity of estimated locations, location-related features selected as sources of spatial evidence, and the method used to make aggregate decisions based on the extracted evidence. We discuss the strengths and advantages of alternative solutions to various problems related to location estimation, as well as their preconditions and limitations. We examine the most widely used evaluation methods to analyze the accuracy of estimations and present the results reported in the literature. We also discuss our findings and highlight important research challenges that may need further attention.     

Modelling and simulation of vertebrate retina: extended network

Dissections reveal that each lymphatic organ characteristic of species is supplied with lymph hearts, smooth muscles, or striated muscles whose contractions (along with tranmitted arterial pulsations and changing gravitational forces) coordinately propel lymph centrally during breathing, swallowing, food absorption and joint flexion. In aquatic vertebrates and amphibians lymph hearts, closely related to the gills, propel central lymph into the jugular veins. In aerial vertebrates with well-developed lungs, the striated muscles which enable ventilation, propel central lymph into large veins coursing through the thoracic inlet at rates commensurate with oxygen consumption under normal conditions.     

Optimal control of walking with functional electrical stimulation: a computer simulation study.

Bipedal locomotion was simulated to generate a pattern of activating muscles for walking using electrical stimulation in persons with spinal cord injury (SCI) or stroke. The simulation presented in this study starts from a model of the body determined with user-specific parameters, individualized with respect to the lengths, masses, inertia, muscle and joint properties. The trajectory used for simulation was recorded from an able-bodied subject while walking with ankle-foot orthoses. A discrete mathematical model and dynamic programming were used to determine the optimal control. A cost function was selected as the sum of the squares of the tracking errors from the desired trajectories, and the weighted sum of the squares of agonist and antagonist activations of the muscle groups acting around the hip and knee joints. The aim of the simulation was to study plausible trajectories keeping in mind the limitations imposed by the spinal cord injury or stroke (e.g., spasticity, decreased range of movements in some joints, limited strength of paralyzed, externally activated muscles). If the muscles were capable of generating the movements required and the trajectory was achieved, then the simulation provided two kinds of information: 1) timing of the onset and offset of muscle activations with respect to the various gait events and 2) patterns of activation with respect to the maximum activation. These results are important for synthesizing a rule-based controller.     

Optimal reactor size distribution with fixed terminal constraints

The method of Lagrange multipliers is applied to find the optimal size distributions of isothermal continuous stirred tank reactors (CSTR) with fixed terminal constraints, to carry out a simple reaction. The control variables minimizing the Lagrangian of the problem can be found by the well known first and second order gradient techniques, or simply by using a non-linear root finder computer program. The technique is also applicable to non- isothermal CSTR optimization.     

Attribute-based variability in feature models

Extended feature models enable the expression of complex cross-tree constraints involving feature attributes. The inclusion of attributes in cross-tree relations not only enriches the constraints, but also engenders an extended type of variability that involves attributes. In this article, we elaborate on the effects of this new variability type on feature models. We start by analyzing the nature of the variability involving attributes and extend the definitions of the configuration and the product to suit the emerging requirements. Next, we propose classifications for the features, configurations, and products to identify and formalize the ramifications that arise due to the new type of variability. Then, we provide a semantic foundation grounded on constraint satisfaction for our proposal. We introduce an ordering relation between configurations and show that the set of all the configurations represented by a feature model forms a semilattice. This is followed by a demonstration of how the feature model analyses will be affected using illustrative examples selected from existing and novel analysis operations. Finally, we summarize our experiences, gained from a commercial research and development project that employs an extended feature model.