Showing papers by "Universidad del Norte, Colombia published in 2015"
07 Jun 2015
TL;DR: This paper introduces ActivityNet, a new large-scale video benchmark for human activity understanding that aims at covering a wide range of complex human activities that are of interest to people in their daily living.
Abstract: In spite of many dataset efforts for human action recognition, current computer vision algorithms are still severely limited in terms of the variability and complexity of the actions that they can recognize. This is in part due to the simplicity of current benchmarks, which mostly focus on simple actions and movements occurring on manually trimmed videos. In this paper we introduce ActivityNet, a new large-scale video benchmark for human activity understanding. Our benchmark aims at covering a wide range of complex human activities that are of interest to people in their daily living. In its current version, ActivityNet provides samples from 203 activity classes with an average of 137 untrimmed videos per class and 1.41 activity instances per video, for a total of 849 video hours. We illustrate three scenarios in which ActivityNet can be used to compare algorithms for human activity understanding: untrimmed video classification, trimmed activity classification and activity detection.
2,158 citations
TL;DR: A state-of-the-art survey on the vehicle routing problem with multiple depots (MDVRP) is presented, considered papers published between 1988 and 2014, in which several variants of the model are studied.
373 citations
07 Jun 2015
TL;DR: This work characterize the nature of the relationship between abstract concepts learned by popular and high performing convolutional networks (conv-nets) and established mid-level representations used in computer vision and shows empirical evidence of the existence of Attribute Centric Nodes (ACNs) within a conv-net, which is trained to recognize objects (not attributes) in images.
Abstract: One of the cornerstone principles of deep models is their abstraction capacity, i.e. their ability to learn abstract concepts from ‘simpler’ ones. Through extensive experiments, we characterize the nature of the relationship between abstract concepts (specifically objects in images) learned by popular and high performing convolutional networks (conv-nets) and established mid-level representations used in computer vision (specifically semantic visual attributes). We focus on attributes due to their impact on several applications, such as object description, retrieval and mining, and active (and zero-shot) learning. Among the findings we uncover, we show empirical evidence of the existence of Attribute Centric Nodes (ACNs) within a conv-net, which is trained to recognize objects (not attributes) in images. These special conv-net nodes (1) collectively encode information pertinent to visual attribute representation and discrimination, (2) are unevenly and sparsely distribution across all layers of the conv-net, and (3) play an important role in conv-net based object recognition.
107 citations
TL;DR: A hybrid framework is proposed to analyse the pedestrians' choice on how to cross an urban road where three crossing options are available: crossing directly, crossing by using a pedestrian bridge or using a crosswalk at a signalized intersection.
Abstract: As pedestrians are the most exposed and vulnerable road users to traffic accidents, urban planners frequently propose alternatives to improve their safety. However, some solutions, such as pedestrian bridges and crosswalks at signalized intersections, usually imply longer walking distances compared to the direct crossing alternative which, in its turn, involves a higher risk. In this article, a hybrid framework is proposed to analyse the pedestrians' choice on how to cross an urban road where three crossing options are available: crossing directly, crossing by using a pedestrian bridge or using a crosswalk at a signalized intersection. The decision process is modelled as a discrete choice model incorporating latent variables to consider perceptions and psychological factors, using stated preference data coming from a survey applied in Bogota, Colombia. RESULTS show that the latent variables security/safety and attractiveness of each crossing alternative are relevant to understand the pedestrian crossing behaviour. These latent variables are strongly determined by socioeconomic characteristics of the individual (age, gender, level of study) and conditioned by the circumstances of the trip (main mode of transport, walking or not with children). It was found that a longer walking distance to a pedestrian bridge or a signalized crosswalk increases the probability of direct crossing, having a more relevant effect in the case of the pedestrian bridge.
102 citations
TL;DR: In this paper, the impact of hydrous ethanol and n-butanol fumigation on the combustion characteristics, performance, pollutant emissions, particle number concentration and size distribution of an automotive diesel engine was studied.
88 citations
TL;DR: In this article, it was shown that the intrinsic defects are photo-oxidation sites because they lower the chemisorption barrier of ideal black phosphorus (>10 eV and out of visible-range light excitations) right into the visible and ultraviolet range (1.6 to 6.8 eV), thus enabling photoinduced oxidation and dissociation of oxygen dimers.
Abstract: Black phosphorus is a monatomic semiconducting layered material that degrades exothermically in the presence of light and ambient contaminants. Its degradation dynamics remain largely unknown. Even before degradation, local-probe studies indicate non-negligible local curvature—through a nonconstant height distribution—due to the unavoidable presence of intrinsic defects. We establish that these intrinsic defects are photo-oxidation sites because they lower the chemisorption barrier of ideal black phosphorus (>10 eV and out of visible-range light excitations) right into the visible and ultraviolet range (1.6 to 6.8 eV), thus enabling photoinduced oxidation and dissociation of oxygen dimers. A full characterization of the material’s shape and of its electronic properties at the early stages of the oxidation process is presented as well. This study thus provides fundamental insights into the degradation dynamics of this novel layered material.
80 citations
TL;DR: In this article, small copper clusters on the (101) and (100) surfaces of anatase have been investigated by first-principles simulations based on density functional theory, to shed light on their atomic and electronic structure, and to understand their effect on the photocatalytic process.
Abstract: Copper-modified titania is a system of interest for its potential for photocatalytic applications in the production of solar fuels. Still, the role of copper in the process is unclear. In this work, small copper clusters on the (101) and (100) surfaces of anatase have been investigated by first-principles simulations based on density functional theory, to shed light on their atomic and electronic structure, and to understand their effect on the photocatalytic process. The main effects of copper on the electronic structure are to provide states above the edge of the valence band of titania and to lead to the formation of midgap states. There are two types of midgap states, respectively, associated with direct Cu–Ti bonds and to Ti3+ polarons. The latter are the result of charge donation from copper and lie in the vicinity of the surface. Moreover, the copper tetramer (Cu4) displays empty states at the bottom of the conduction band that play a key role in accommodating excess electrons. We discuss how these...
73 citations
TL;DR: Repurposing existing molecules offers immense promise to tackle extensively drug-resistant TB infections.
65 citations
TL;DR: The properties of phosphorene are explored, a drastic reduction of its electronic gap is documented when under a conical structure, and a decrease of the semiconducting gap that is directly linked to its nonplanar shape is documented.
Abstract: Lattice kirigami, ultralight metamaterials, polydisperse aggregates, ceramic nanolattices, and 2D atomic materials share an inherent structural discreteness, and their material properties evolve with their shape. To exemplify the intimate relation among material properties and the local geometry, we explore the properties of phosphorene––a new 2D atomic material––in a conical structure, and document a decrease of the semiconducting gap that is directly linked to its nonplanar shape. This geometrical effect occurs regardless of phosphorene allotrope considered, and it provides a unique optical vehicle to single out local structural defects on this 2D material. We also classify other 2D atomic materials in terms of their crystalline unit cells, and propose means to obtain the local geometry directly from their diverse 2D structures while bypassing common descriptions of shape that are based from a parametric continuum.
62 citations
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TL;DR: This study establishes that intrinsic defects in black phosphorus are photo-oxidation sites because they lower the chemisorption barrier of ideal black phosphorus right into the visible and ultraviolet range (1.6 to 6.8 eV), thus enabling photoinduced oxidation and dissociation of oxygen dimers.
Abstract: Black phosphorus is a monoatomic semiconducting layered material that degrades exothermically in the presence of light and ambient contaminants. Its degradation dynamics remain largely unknown. Even before degradation, local-probe studies indicate non-negligible local curvature --through a non-constant height distribution-- due to the unavoidable presence of intrinsic defects. We establish that these intrinsic defects are photo-oxidation sites because they lower the chemisorption barrier of ideal black phosphorus (> 10 eV and out of visible-range light excitations) right into the visible and ultra-violet range (1.6 to 6.8 eV), thus enabling photo-induced oxidation and dissociation of oxygen dimers. A full characterization of the material's shape and of its electronic properties at the early stages of the oxidation process is presented as well. This study thus provides fundamental insights into the degradation dynamics of this novel layered material.
61 citations
TL;DR: Two cases had positive anti-dengue IgM, but dengue coinfection was rejected based on the clinical features and results of real-time reverse transcription polymerase chain reaction, which illustrates the challenges of the diagnosis and management of severe Chikungunya infection.
Smithsonian Tropical Research Institute1, University of Rochester2, Florida Museum of Natural History3, Natural History Museum of Los Angeles County4, University of Saskatchewan5, Universidad del Norte, Colombia6, Ecopetrol7, Senckenberg Museum8, University of Zurich9, EAFIT University10, Cornell University11, University of Los Andes12, University of Nebraska–Lincoln13
TL;DR: In this paper, a formal re-description of the Jimol and Castilletes formations, including a revised contact, and a description of a new lithostratigraphic unit, the Ware Formation (late Pliocene) were presented.
Abstract: The Cocinetas Basin of Colombia provides a valuable window into the geological and paleontological history of northern South America during the Neogene.
Two major findings provide new insights into the Neogene history of this Cocinetas Basin: (1) a formal re-description of the Jimol and Castilletes formations, including a revised contact; and (2) the description of a new lithostratigraphic unit, the Ware Formation (Late Pliocene). We conducted extensive fieldwork to develop a basin-scale stratigraphy, made exhaustive paleontological collections, and performed 87Sr/86Sr geochronology to document the transition from the fully marine environment of the Jimol Formation (ca. 17.9–16.7 Ma) to the fluvio-deltaic environment of the Castilletes (ca. 16.7–14.2 Ma) and Ware (ca. 3.5–2.8 Ma) formations. We also describe evidence for short-term periodic changes in depositional environments in the Jimol and Castilletes formations. The marine invertebrate fauna of the Jimol and Castilletes formations are among the richest yet recorded from Colombia during the Neogene. The Castilletes and Ware formations have also yielded diverse and biogeographically significant fossil vertebrate assemblages. The revised lithostratigraphy and chronostratigraphy presented here provides the necessary background information to explore the complete evolutionary and biogeographic significance of the excellent fossil record of the Cocinetas Basin.
TL;DR: It is concluded that POLD1 germline mutations can result in a variably expressed and probably underdiagnosed segmental progeroid syndrome.
Abstract: Segmental progeroid syndromes are rare, heterogeneous disorders characterized by signs of premature aging affecting more than one tissue or organ. A prototypic example is the Werner syndrome (WS), caused by biallelic germline mutations in the Werner helicase gene (WRN). While heterozygous lamin A/C (LMNA) mutations are found in a few nonclassical cases of WS, another 10%–15% of patients initially diagnosed with WS do not have mutations in WRN or LMNA. Germline POLD1 mutations were recently reported in five patients with another segmental progeroid disorder: mandibular hypoplasia, deafness, progeroid features syndrome. Here, we describe eight additional patients with heterozygous POLD1 mutations, thereby substantially expanding the characterization of this new example of segmental progeroid disorders. First, we identified POLD1 mutations in patients initially diagnosed with WS. Second, we describe POLD1 mutation carriers without clinically relevant hearing impairment or mandibular underdevelopment, both previously thought to represent obligate diagnostic features. These patients also exhibit a lower incidence of metabolic abnormalities and joint contractures. Third, we document postnatal short stature and premature greying/loss of hair in POLD1 mutation carriers. We conclude that POLD1 germline mutations can result in a variably expressed and probably underdiagnosed segmental progeroid syndrome.
TL;DR: In this paper, the authors present a systematic study to determine the reduced partition function ratio (β -factor) of aqueous Mg 2+ using several levels of theory within the simulations.
TL;DR: The results suggest that the use of simvastatin, 20 mg once daily for 4 days, since hospital admission did not reduce the time to clinical stability and the levels of inflammatory cytokines in hospitalised patients with CAP.
Abstract: Objectives It has been suggested that statins have an effect on the modulation of the cytokine cascade and on the outcome of patients with community-acquired pneumonia (CAP). The aim of this prospective, randomised, double-blind, placebo-controlled trial was to determine whether statin therapy given to hospitalised patients with CAP improves clinical outcomes and reduces the concentration of inflammatory cytokines. Setting A tertiary teaching hospital in Barcelona, Spain. Participants Thirty-four patients were randomly assigned and included in an intention-to-treat analysis (19 to the simvastatin group and 15 to the placebo group). Intervention Patients were randomly assigned to receive 20 mg of simvastatin or placebo administered in the first 24 h of hospital admission and once daily thereafter for 4 days. Outcome Primary end point was the time from hospital admission to clinical stability. The secondary end points were serum concentrations of inflammatory cytokines and partial pressure of arterial oxygen/fractional inspired oxygen (PaO2/FiO2) at 48 h after treatment administration. Results The trial was stopped because enrolment was much slower than originally anticipated. The baseline characteristics of the patients and cytokine concentrations at the time of enrolment were similar in the two groups. No significant differences in the time from hospital admission to clinical stability were found between study groups (median 3 days, IQR 2–5 vs 3 days, IQR 2–5; p=0.47). No significant differences in PaO2/FiO2 (p=0.37), C reactive protein (p=0.23), tumour necrosis factor-α (p=0.58), interleukin 6 (IL-6; p=0.64), and IL-10 (p=0.61) levels at 48 h of hospitalisation were found between simvastatin and placebo groups. Similarly, transaminase and total creatine kinase levels were similar between study groups at 48 h of hospitalisation (p=0.19, 0.08 and 0.53, respectively). Conclusions Our results suggest that the use of simvastatin, 20 mg once daily for 4 days, since hospital admission did not reduce the time to clinical stability and the levels of inflammatory cytokines in hospitalised patients with CAP. Trial registration number ISRCTN91327214.
TL;DR: ANP and DEMATEL-ANP effectively supported six sigma project selection processes, helping to create a complete framework that guarantees the prioritization of projects that provide maximum benefits to healthcare organizations.
Abstract: The project selection process is a crucial step for healthcare organizations at the moment of implementing six sigma programs in both administrative and caring processes. However, six-sigma project selection is often defined as a decision making process with interaction and feedback between criteria; so that it is necessary to explore different methods to help healthcare companies to determine the Six-sigma projects that provide the maximum benefits. This paper describes the application of both ANP (Analytic Network process) and DEMATEL (Decision Making trial and evaluation laboratory)-ANP in a public medical centre to establish the most suitable six sigma project and finally, these methods were compared to evaluate their performance in the decision making process. ANP and DEMATEL-ANP were used to evaluate 6 six sigma project alternatives under an evaluation model composed by 3 strategies, 4 criteria and 15 sub-criteria. Judgement matrixes were completed by the six sigma team whose participants worked in different departments of the medical centre. The improving of care opportunity in obstetric outpatients was elected as the most suitable six sigma project with a score of 0,117 as contribution to the organization goals. DEMATEL-ANP performed better at decision making process since it reduced the error probability due to interactions and feedback. ANP and DEMATEL-ANP effectively supported six sigma project selection processes, helping to create a complete framework that guarantees the prioritization of projects that provide maximum benefits to healthcare organizations. As DEMATEL- ANP performed better, it should be used by practitioners involved in decisions related to the implementation of six sigma programs in healthcare sector accompanied by the adequate identification of the evaluation criteria that support the decision making model. Thus, this comparative study contributes to choosing more effective approaches in this field. Suggestions of further work are also proposed so that these methods can be applied more adequate in six sigma project selection processes in healthcare.
07 Jun 2015
TL;DR: This paper proposes a new framework for estimating the Manhattan Frame (MF) of an indoor scene from a single RGB-D image by formulating this problem as the estimation of a rotation matrix that best aligns the normals of the captured scene to a canonical world axes.
Abstract: This paper proposes a new framework for estimating the Manhattan Frame (MF) of an indoor scene from a single RGB-D image. Our technique formulates this problem as the estimation of a rotation matrix that best aligns the normals of the captured scene to a canonical world axes. By introducing sparsity constraints, our method can simultaneously estimate the scene MF, the surfaces in the scene that are best aligned to one of three coordinate axes, and the outlier surfaces that do not align with any of the axes. To test our approach, we contribute a new set of annotations to determine ground truth MFs in each image of the popular NYUv2 dataset. We use this new benchmark to experimentally demonstrate that our method is more accurate, faster, more reliable and more robust than the methods used in the literature. We further motivate our technique by showing how it can be used to address the RGB-D SLAM problem in indoor scenes by incorporating it into and improving the performance of a popular RGB-D SLAM method.
Arizona State University1, Universidad del Norte, Colombia2, University of Pennsylvania3, Pontifical Catholic University of Peru4, Columbia University5, University of Talca6, Caribbean Meteorological Institute7, University of the West Indies8, University of the Republic9, Instituto Tecnológico Autónomo de México10, University of California, Berkeley11
TL;DR: In this paper, an analytical model for conceptualizing the contribution of existing information and communication technologies (ICTs) to adaptation, and a framework for evaluating ICT success is presented.
Abstract: Despite ongoing interest in deploying information and communication technologies (ICTs) for sustainable development, their use in climate change adaptation remains understudied. Based on the integration of adaptation theory and the existing literature on the use of ICTs in development, we present an analytical model for conceptualizing the contribution of existing ICTs to adaptation, and a framework for evaluating ICT success. We apply the framework to four case studies of ICTs in use for early warning systems and managing extreme events in the Latin American and the Caribbean countries. We propose that existing ICTs can support adaptation through enabling access to critical information for decision-making, coordinating actors and building social capital. ICTs also allow actors to communicate and disseminate their decision experience, thus enhancing opportunities for collective learning and continual improvements in adaptation processes. In this way, ICTs can both communicate the current and potential imp...
TL;DR: It was found that workers and individuals with the highest education level are more prone to use a mobile phone while driving than others and the cost of the fine is an important attribute in order to control mobile phone use while driving.
TL;DR: In this paper, the shrinkage covariance matrix is estimated using the Rao-Blackwell Ledoit and Wolf estimator, which has been specifically developed to approximate high-dimensional covariance matrices using a small number of samples.
Abstract: This paper develops efficient ensemble Kalman filter (EnKF) implementations based on shrinkage covariance estimation. The forecast ensemble members at each step are used to estimate the background error covariance matrix via the Rao-Blackwell Ledoit and Wolf estimator, which has been specifically developed to approximate high-dimensional covariance matrices using a small number of samples. Two implementations are considered: in the EnKF full-space (EnKF-FS) approach, the assimilation process is performed in the model space, while the EnKF reduce-space (EnKF-RS) formulation performs the analysis in the subspace spanned by the ensemble members. In the context of EnKF-RS, additional samples are taken from the normal distribution described by the background ensemble mean and the estimated background covariance matrix, in order to increase the size of the ensemble and reduce the sampling error of the filter. This increase in the size of the ensemble is obtained without running the forward model. After the assimilation step, the additional samples are discarded and only the model-based ensemble members are propagated further. Methodologies to reduce the impact of spurious correlations and under-estimation of sample variances in the context of the EnKF-FS and EnKF-RS implementations are discussed. An adjoint-free four-dimensional extension of EnKF-RS is also discussed. Numerical experiments carried out with the Lorenz-96 model and a quasi-geostrophic model show that the use of shrinkage covariance matrix estimation can mitigate the impact of spurious correlations during the assimilation process.
TL;DR: Canonical correlations revealed that there was a significant relationship between caregivers’ mental health and HRQOL, such that caregivers with better satisfaction with life and less symptoms of depression had more vitality and better general health.
Abstract: Existing published studies about health-related quality of life (HRQOL) in caregivers of dementia patients living in Latin American countries are very limited. However, cultural aspects, personal values, and social structure may affect the way caregivers experience their role in different societies. The current study investigated the relationship between HRQOL and psychological factors using a cross-sectional design. The sample consisted of 102 informal caregivers of patients with dementia from Bogota, Colombia, South America. Measures included the Patient Health Questionnaire (PHQ-9) for depression, the Satisfaction with Life Scale (SWLS), the Zarit Burden Interview, and the Short Health Questionnaire (SF36) for HRQOL. Canonical correlations revealed that there was a significant relationship between caregivers’ mental health and HRQOL, such that caregivers with better satisfaction with life and less symptoms of depression had more vitality and better general health. There is a strong relationship between mental health and health-related quality of life in Colombian caregivers of dementia patients living in their country of origin. Specific aspects of mental health, including satisfaction with life and depression, need to be addressed in order to improve caregivers’ quality of life. Given that mental health care resources may be scarce in Latin American countries, culturally appropriate interventions should focus on preventing/treating depression and promote life satisfaction, as a way to improve their quality of life.
TL;DR: The developed tool, CODESIGHT, is based on a modification of the Greedy String Tiling algorithm and verified the efficiency of the tool at the first five levels of the plagiarism spectrum for programming code, in addition to supporting suspicions of plagiarism in real scenarios.
Abstract: This article presents a proposal for the detection of programming source code similitude in academic environments. The objective of this proposal is to provide support to professors in detecting plagiarism in student homework assignments in introductory computer programming courses. The developed tool, CODESIGHT, is based on a modification of the Greedy String Tiling algorithm. The tool was tested in one theoretical and three real scenarios, obtaining similitude detections for assignments ranging from those that contained code without modifications to assignments containing insertions of procedural instructions inside the main code. The results verified the efficiency of the tool at the first five levels of the plagiarism spectrum for programming code, in addition to supporting suspicions of plagiarism in real scenarios. © 2013 Wiley Periodicals, Inc. Comput Appl Eng Educ 23:13–22, 2015; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21571
TL;DR: In this paper, the authors investigated the impact of service consumption practices on the well-being of base of the pyramid consumers and found that informal service offerings are non-discriminatory, hassle-free, jargon-free and reputation-based.
Abstract: There is a lack of research on service consumption practices of Base of the Pyramid consumers. This study contributes to the Transformative Service Research agenda by understanding stigmatized service consumption practices and their effect on the well-being of these consumers; this has not been fully addressed until now. Additionally, it is shown that understanding the relations among consumers, communities, and informal service offerings results in the design of services with unintentional positive effects on well-being at individual, collective, and relational levels. Findings show that informal service offerings are non-discriminatory, hassle-free, jargon-free, and reputation-based. These findings pave the way to further explore such complex contexts to better understand the impact of service design on the well-being of such consumers. Positive practices can be adopted by any service industry that intends to serve that segment through the intentional redesign of offerings that are engaging, inclusive, ...
TL;DR: The importance of innovation for the competitive development of a company and how the adoption of an open innovation strategy could be effective to face typical barriers associated with the implementation of such processes is explored in this paper.
Abstract: This paper explores, through a company case study, the importance of innovation for the competitive development of a company and how the adoption of an open innovation strategy could be effective to face typical barriers associated with the implementation of such processes. The case analysis shows the importance of the University-Industry relationship and the relevant role that the government plays in fomenting these relationships. Likewise, we point out the value of adopting an integral vision of the innovation process that not only considers its technological dimension (new product development), but also the elements associated to marketing and organizational change practices. The case studied herein exemplifies the systemic character of innovation and the relevance it has for companies, particularly for SME’s, to open its innovation strategy and integrate themselves with other actors to leverage its cognitive and financial resources as well as to explore new routes to bring the best of its internal technological capacities.
TL;DR: A group of experts convened to discuss the topic and develop recommendations for implementation should enable countries to accurately document the safety and performance of a biosimilar as experienced by patients under real-life conditions and have a significant impact on the successful implementation of pharmacovigilance of biosimilars throughout the region.
Abstract: The use of biotechnology-derived medicines has significantly increased in recent decades. Although biosimilars undergo rigorous characterization as well as clinical studies to document their safety and effectiveness, they are highly complex molecules and small changes in the purification and production process of a biosimilar can have major implications in its safety and effectiveness profile. In Latin America, regulatory authorities have begun to establish well-described and standardized pathways that permit a biosimilar to gain commercial licensure. In order to be certain that a biosimilar reaches its potential in ordinary clinical use, an intensive post-licensing monitoring system must be established since it is the only means to ascertain the true similarity between the original biologic and its biosimilar. Pharmacovigilance allows national authorities to determine a drug’s performance in the marketplace. An effective tracking and pharmacovigilance system for biological medicines has many steps and processes. To aid policy makers in Latin American in addressing the many issues surrounding the establishment of an effective pharmacovigilance system, the Americas Health Foundation convened a group of experts to discuss the topic and develop recommendations for implementation. The group discussed current challenges and gaps in pharmacovigilance in Latin America, paying close attention to the major issues associated with traceability and pharmacovigilance of biosimilars following their approval. The recommendations developed should enable countries to accurately document the safety and performance of a biosimilar as experienced by patients under real-life conditions and have a significant impact on the successful implementation of pharmacovigilance of biosimilars throughout the region.
TL;DR: In this paper, the results of a laboratory investigation on cold foamed recycled mixes and the effect on the mechanical properties of various additives, including foam additive, fiber reinforcement and active filler, were evaluated.
TL;DR: Traditional multiple-constrained-shortest-path heuristics are improved in this paper using the novel concept “potential feasibility” and one of them demonstrates a significantly smaller average runtime.
Abstract: Composite services are widely popular for solving complex problems where the required QoS levels are often demanding. The composite service that provides the best utility while meeting the QoS requirements has to be found. This paper proposes a network model where many complementary candidates could be selected for each service class to improve the benefits, while the conventional model limits the selection to a single service candidate or service level per service class. The selection of services step is NP-hard because it can be reduced to a multi-constraint knapsack problem. Yet, the decision has to be reached rapidly so that it does not increase the overall workflow time. Large-size networks and problems with high restriction levels (strong QoS requirements) are the most problematic. Traditional multiple-constrained-shortest-path (MCSP) heuristics are improved in this paper using the novel concept “potential feasibility”. When our modified MCSP heuristic algorithms are compared to the CPLEX solver, one of them demonstrates a significantly smaller average runtime. Further, it provides solutions within a 2.6 percent optimality gap on average for small networks, and a 10 percent optimality gap on average for large networks, regardless of the restriction level. Our algorithm uses a general utility function, not derived from the QoS parameters.
TL;DR: A high prevalence of physical inactivity was found in college students and males showed higher levels of physical activity than females.
Abstract: Background: Sedentariness is an important risk factor for chronic diseases in Western societies Aim: To determine the sociodemographic and motivational factors associated with physical activity in college students. Material and methods: The International Physical Activity Questionnaire (IPAQ) -short form- and the “motives for physical activities measure-revised” (MPAM–R) questionnaire were applied to 900 university students aged 20 ± 3 years (60% women). The frequency, level and motivations for engaging in physical activity and associated demographic factors were analyzed. Results: Twenty two percent of students were classified as having a high level of physical activity, 54.8% had a low level and 13.9% were considered inactive. According to MET consumption, 68.9% of students are inactive and only 16.8% of students classified as very active. Ninety two percent of active students performed physical activity for health reasons. A significant association between gender and social motivation was observed. Conclusions: A high prevalence of physical inactivity was found in these students. Males showed higher levels of physical activity than females.
15 Nov 2015
TL;DR: The proposed implementation outperforms in terms of accuracy the well-known local ensemble transform Kalman filter (LETKF) for all the model variables and for the largest number of processors, is 400 times faster than the serial version of the proposed method.
Abstract: This paper discusses an efficient parallel implementation of the ensemble Kalman filter based on the modified Cholesky decomposition. The proposed implementation starts with decomposing the domain into sub-domains. In each sub-domain a sparse estimation of the inverse background error covariance matrix is computed via a modified Cholesky decomposition; the estimates are computed concurrently on separate processors. The sparsity of this estimator is dictated by the conditional independence of model components for some radius of influence. Then, the assimilation step is carried out in parallel without the need of inter-processor communication. Once the local analysis states are computed, the analysis sub-domains are mapped back onto the global domain to obtain the analysis ensemble. Computational experiments are performed using the Atmospheric General Circulation Model (SPEEDY) with the T-63 resolution on the Blueridge cluster at Virginia Tech. The number of processors used in the experiments ranges from 96 to 2,048. The proposed implementation outperforms in terms of accuracy the well-known local ensemble transform Kalman filter (LETKF) for all the model variables. The computational time of the proposed implementation is similar to that of the parallel LETKF method (where no covariance estimation is performed). Finally, for the largest number of processors, the proposed parallel implementation is 400 times faster than the serial version of the proposed method.
TL;DR: The location routing problem with stochastic transportation cost and vehicle travel speeds is considered and a hybrid solution procedure based on Ant Colony Optimisation and Discrete-Event Simulation is proposed.
Abstract: The location routing problem with stochastic transportation cost and vehicle travel speeds is considered in this paper. A hybrid solution procedure based on Ant Colony Optimisation (ACO) and Discrete-Event Simulation (DES) is proposed. After using a sequential heuristic algorithm to solve the location subproblem, the subsequent capacitated vehicle routing problem is solved using ACO. Finally, a DES model evaluates those vehicle routes in terms of their impact on the expected total costs. The approach is tested using well-known randomly generated datasets. Since no previous works in the literature studied exactly the same SLRP, the proposed procedure is compared against its deterministic version. Numerical results show the efficiency and efficacy of the hybrid ACO-DES approach.