RESUMO
The integration of machine learning techniques and metaheuristic algorithms is an area of interest due to the great potential for applications. In particular, using these hybrid techniques to solve combinatorial optimization problems (COPs) to improve the quality of the solutions and convergence times is of great interest in operations research. In this article, the db-scan unsupervised learning technique is explored with the goal of using it in the binarization process of continuous swarm intelligence metaheuristic algorithms. The contribution of the db-scan operator to the binarization process is analyzed systematically through the design of random operators. Additionally, the behavior of this algorithm is studied and compared with other binarization methods based on clusters and transfer functions (TFs). To verify the results, the well-known set covering problem is addressed, and a real-world problem is solved. The results show that the integration of the db-scan technique produces consistently better results in terms of computation time and quality of the solutions when compared with TFs and random operators. Furthermore, when it is compared with other clustering techniques, we see that it achieves significantly improved convergence times.
Assuntos
Algoritmos , Inteligência Artificial , Simulação por Computador , Aprendizado de Máquina , Análise por Conglomerados , Análise de DadosRESUMO
To investigate the determinants of acute mountain sickness (AMS) and of summiting in expedition-style mountaineering, 919 mountaineers (15.4% female) leaving Aconcagua Provincial Park at the end of an expedition to Mt. Aconcagua (6962 m) via the normal route were retrospectively evaluated by questionnaires. Symptoms of AMS were reported from the day when mountaineers felt worst. The prevalence of AMS, defined as a Lake Louise Score (self-assessment) > 4, was 39%. Low AMS scores were associated with faster ascent rates. The following parameters were independent predictors for AMS: no susceptibility for AMS (odds ratio, OR, 0.24; 95% confidence interval 0.17 to 0.35) more than 10 exposures per year above 3000 m (OR 0.60; 0.41 to 0.86), and previous exposures above 6000 m (OR, 0.48; 0.33 to 0.68). This last variable increased the OR for summiting 3.7-fold while female gender reduced this OR to 0.41 (0.25 to 0.67). Susceptibility and few exposures to high altitude are major predictors for AMS on Aconcagua, but AMS does not substantially reduce the chances for summiting. Those who are often in the mountains and who have already climbed to altitudes above 6000 m and are not susceptible for AMS have the best options for summiting Aconcagua.
Assuntos
Aclimatação , Doença da Altitude/diagnóstico , Doença da Altitude/epidemiologia , Montanhismo , Doença Aguda , Adulto , Doença da Altitude/etiologia , Argentina/epidemiologia , Intervalos de Confiança , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Montanhismo/estatística & dados numéricos , Razão de Chances , Prevalência , Análise de Regressão , Reprodutibilidade dos Testes , Estudos Retrospectivos , Fatores de Risco , Índice de Gravidade de Doença , Inquéritos e QuestionáriosRESUMO
Se analizan en forma retrospectiva las historias clinicas y los registros de anestesia para realizar 40 trasplantes renales entre Abril de 1985 y Abril de 1989. Los pacientes estaban sometidos a hemodialisis periodica, representativos de una fase final de falla renal cronica con un alto indice de alteraciones cardiovasculares y bioquimico, seleccionado para trasplante renal intrafamiliar y de cadaver, segun protocolo por su compabilidad inmunologica, edad, estado clinico, consentimiento familiar y condiciones anatomo-quirurgicos de donantes y receptores. La mayoria recibio anestesia general con barbiturico intravenoso, relajante muscular, agentes inhalatorios con suplemento narcotico, otros en menor numero, anestesia raquidea o peridural y en pequena proporcion una combinacion de las tecnicas. No ocurrieron decesos intraoperatorios, una muerte postoperatoria en recuperar se atribuyo a diuresis excesiva y profunda hipokalemia; no se presentaron complicaciones cardiovasculares y respiratorias inmediatas. Un pequeno numero de pacientes requirio nuevos procesos anestesicos inmediatos y taridos por sospecha de rechazo agudo compresion o torsion venosa y arterial, obstruccion ureteral, coagulos sanguineos vesicales o fistulas del trayecto uretero-vesical. A dos enfermos se les retiro tardiamente el injerto trasplantado