OALib Journal期刊

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匹配条件: “Erik Ortiz Guerra” ,找到相关结果约13209条。
Comparison between MACAW and T_Lohi protocols for underwater networks. Comparación de los protocolos MACAW y T_Lohi para redes subacuáticas.
Erik Ortiz Guerra,Vitalio Alfonso Reguera
Revista Cubana de Ingeniería , 2011, DOI: 10.1234/rci.v2i1.41
Abstract: The development of underwater networks presents great challenges, most of which are related to the complexity of the communication channel. The main difficulties to face in the underwater channel are the restricted bandwidth and the low propagation speed. Due to these difficulties, it is necessary the development of new and more competent communication protocols in order to obtain higher performance and minimize the energy consumption. Therefore, this paper presents a comparative evaluation between two medium access controls (MAC): MACAW and T_Lohi. Both protocols are based on random access mechanism, the first uses request to send (RTS); clear to send (CTS) and acknowledgement (ACK) messages to regulate transmissions while the second uses short duration tones which can be detected instantaneously. Thus, this study focuses on the performance, collisions and efficiency of these protocols in order to reserve the communication channel, whereby it highlights the advantages and deficiencies of each protocol in the underwater communication networks. El desarrollo de las redes subacuáticas presenta grandes desafíos, la mayoría de los cuales están relacionados con las complejidades del canal de comunicación. El limitado ancho de banda y la baja velocidad de propagación son las principales dificultades a vencer en las redes subacuáticas. Debido a estas complejidades es necesario el desarrollo de nuevos protocolos de comunicación capaces de obtener un alto desempe o minimizando el consumo de energía. En este trabajo se presenta un estudio comparativo entre dos protocolos de acceso al medio: MACAW (Múltiple Access with Collision Avoidance for Wireless) y T_Lohi, ambos constituyen mecanismos de acceso aleatorio, el primero emplea mensajes RTS (request to send), CTS (clear to send) y ACK (acknowledgement) para regular las transmisiones mientras que el segundo utiliza tonos de corta duración que pueden ser detectados simultáneamente. Este estudio se centra en la evaluación del desempe o, las colisiones y la eficiencia para reservar el canal de comunicación de estos protocolos, con el objetivo de poner al descubierto sus ventajas y deficiencias para la comunicación subacuática.
Análisis mediante simulación de mecanismos de control de acceso al medio para redes RFID
Erik Ortiz Guerra,Yusniel Ruiz Reyez
Ingenier?-a Electr?3nica, Autom??tica y Comunicaciones , 2011, DOI: 10.1234/rielac.v32i1.70
Abstract: La identificación por radio frecuencia constituye una tecnología que permite la identificación de manera única de objetos. El empleo de un canal compartido para la comunicación entre los objetos a identificar y los lectores, determinan la presencia de colisiones que se producen cuando dos o más objetos intentan identificarse de manera simultánea. El estándar EPCglobal Clase 1 Generación 2 define un protocolo de control de acceso al medio para ser empleado en sistemas RFID pasivos definiendo para ello ciclos de identificación que son marcados por el lector y cada uno de ellos es divido en ranuras de tiempo o slot; de esta manera el protocolo se puede implementar siguiendo tres posibles variantes: trama estática, trama adaptativa ciclo a ciclo y trama adaptativa slot a slot. En este trabajo se realiza un estudio de cada una de estas variantes y son mostrados los resultados obtenidos mediante simulación que demuestran cuál de ellas presenta los mejores resultados así como las limitaciones e inconvenientes de cada una.
Contribution to the phytochemical study and biological activity of plants of Cuban flora
Nogueiras,Clara; Spengler,Iraida; Guerra,José O; Ortiz,Yarelys; Torres,Susana; García,Trina H; Romeu,Carlos R; Regalado,Erik L; González,Telce A; Perera,Wilmer H; Lacret,Rodney;
Biotecnolog?-a Aplicada , 2010,
Abstract: interest in natural products as a source for innovation in drug discovery and agrochemicals is still growing worldwide. natural products, whose immense diversity has been appreciated for many years, may become in a rich source of novel chemical structures. our country is a rich source of both biological and chemical diversity which may be useful as a source of novel chemical structures. even when natural products have been used as medicinal agents for many years in cuba, their use as agrochemicals are still limited. thus, the present review focuses on recent advances in the studies on natural products performed by the "centro de estudios de productos naturales, cepn" during the past ten years, highlighting on those with potential use as biomedical and agrochemicals. 15 plant species were studied; agave brittoniana trel. subsp. brachypus a álvarez de zayas (agavaceae); juniperus barbadensis l. var. lucayana (britt.) rp adams (cupressaceae); melia azedarach linn. (meliaceae); tectona grandis linn. f. (lamiaceae); lantana camara linn. (verbenaceae); lantana trifolia cham. (verbenaceae); citrus sinensis (linn.) osbeck cv valencia (rutaceae); maytenus buxifolia (a rich) griseb (celastraceae); maytenus elaeodendroides griseb (celastraceae); maytenus urquiolae b mory (celastraceae); solanum americanum w. mill (solanaceae); thalassia testudinum kon. (hydrocharitaceae); sesbania rostrata bremek & oberm (fabaceae); pluchea carolinensis g don (asteraceae) and ageratina havanensis (hb & k) rm king & robinson (asteraceae). by means of a bio-guided fractionation, isolated structures as well as semi-purified fractions were assayed as antioxidant, antiparasitic, antibiotic, insecticides, antifungal, and skin regenerating and healing effects. the strategy employed allows us to discover novel secondary metabolites with potential for industrial development as pharmaceuticals and/or agrochemicals. besides, in addition to the goal of discovering new bioactive agents, the presence of uni
Estudio del efecto de la dirección de medición y contenido de humedad en la velocidad de ultrasonido en madera de pinus radiata D. Don a través de análisis de varianza
Ortiz Mansilla,Rodrigo; Baradit A.,Erik; Navarrete A.,José;
Ingeniería e Investigación , 2009,
Abstract: this study was carried out in order to analyse the ultrasound technique as an alternative form of assessing the structural state of different wooden buildings. this work studies the effect and relative importance of measurement direction and moisture content on ultrasound speed in wood. radiata pine wood samples were subjected to 1 mhz longitudinal ultrasound pulses. a 22 factorial design was run in a completely random experiment. measurement direction was the significant factor, as shown by the analysis of variance, explaining 95% of total ultrasound velocity variability. average tangential and radial propagation speeds were between 0% and 15% moisture content, 1644 m/s and 2130 m/s, respectively. the results of this study showed that wave propagation direction is the most important factor during wood structure ultrasound evaluation. future studies with combined planes are underway.
Complementary feeding: inappropriate practices in infants
Michelle Cavalcante Caetano,Thaís Tobaruela Ortiz Ortiz,Simone Guerra Lopes Da Silva,Fabíola Isabel Suano De Souza
Revista chilena de pediatría , 2012,
Patrón electroencefalográfico brote-supresión en intoxicación por baclofeno Electroencephalographic burst-suppression pattern due to baclofen intoxication
M.I. Montes,O.H. Hernández Ortiz,A. Guerra Palacio
Medicina Intensiva , 2011,
Profesor Dr. Ariel Nodarse Tápanes, Padre de la Neurocirugía Matancera Professor Dr. Ariel Nodarse Tápanes, Father of the Matanzazan Neurosurgery
Juan Milián Giradles,Rafael Guerra Sánchez,Eglys Rodríguez Ramos,Letier Pérez Ortiz
Revista M??dica Electr?3nica , 2011,
Classification, Identification, and Manipulation of Relevant Factors for Adaptation and Behavioural Adjustment from a Psychological Point of View  [PDF]
Gerardo Ortiz
Psychology (PSYCH) , 2014, DOI: 10.4236/psych.2014.513162
Abstract: Generally, the study of animal welfare is based on the identification and promotion of speciestypical behaviors of the individual or target group. The adjustment to new conditions (i.e. captivity) is easier for some species, while for others it may be very difficult or even impossible. The adjustment to captive conditions is a basic element for the development of conservation strategies (i.e. translocation, introduction, and reintroduction) and can be measured by different variables related to an animal’s psychological well-being. From a psychological point of view, we assume that organisms can adjust their behavior in correspondence to changes in their environment, adjustment that is enabled by an ecological contact medium (e.g. Ribes, 2007; Ribes & Perez-Almonacid, 2011). Under this assumption, we propose a methodology that allows the classification, identification and manipulation of relevant factors for an individual’s adjustment to different conditions (i.e. freedom and captivity) and a more rational handling of organisms and their specific life condition. The main elements of this methodology are: 1) adaptive and survival circumstances; 2) description of ecological milieu; 3) interactive processes (i.e. intra-individual, inter-individual, and inter-individual dependence); and 4) interaction-situation relationship.
Alimenta??o complementar: práticas inadequadas em lactentes
Caetano, Michelle Cavalcante;Ortiz, Thaís Tobaruela Ortiz;Silva, Simone Guerra Lopes da;Souza, Fabíola Isabel Suano de;Sarni, Roseli Oselka Saccardo;
Jornal de Pediatria , 2010, DOI: 10.1590/S0021-75572010000300006
Abstract: objective: to assess feeding practices and dietary intake of healthy infants in three brazilian municipalities. methods: by means of a prospective study, we analyzed the food record of 7 consecutive days of an intentional sample (quota and weighted sampling) of 179 healthy infants, aged between 4 and 12 months, from the municipalities of curitiba, s?o paulo, and recife, who were not being exclusively breastfed. mothers received oral and written information provided by a nutritionist with the purpose of standardizing the feeding data. the computer program nutwin was used to calculate the dietary intake. results: the median of the infants' age was 6.8 months (4.0-12.6 months). we found that 50.3% of the infants were no longer being exclusively breastfed. of these, 12.0 and 6.7% among the infants younger and older than 6 months, respectively, were fed with infant formulae instead of breast milk. therefore, most infants received whole cow's milk. infant formula dilution was correct in only 23.8 and 34.7% of the infants younger and older than 6 months old, respectively. with regards to complementary feeding, we found that the median age was 4 months for its introduction and 5.5 months for the introduction of family diet. there was high quantitative inappropriateness of micronutrient intake for infants between 6 and 12 months old who were not exclusively breastfed, mainly in terms of zinc (75%) and iron (45%). conclusion: the present study showed a high frequency of inappropriate feeding practices and dietary intake in very young infants. these practices may lead to an increased risk of development of chronic diseases in the future.
Irrigación intravesical continua con amikacina como tratamiento adyuvante en la cistitis enfisematosa
Cortés González,Jeff R.; Ortiz Lara,Gerardo E.; Arratia Maqueo,Jorge A.; Gómez Guerra,Lauro S.;
Archivos Espa?oles de Urología (Ed. impresa) , 2007, DOI: 10.4321/S0004-06142007001000014
Abstract: objective: to demonstrate that continuos intravesical irrigation with amikacin is an efective adyuvant treatment in emphisematous cistitis therapy. methods: a 3 way transurethral foley catheter was placed and a continuous intravesical irrigation was initiated with amikacin 500mg in 1l of normal saline (500 micrograms per ml) within 6 hours 4 times a day and three consecutive days. results: after 3 days of treatment the patient showed significant clinical response. a new ct scan showed the absence of gas in the bladder wall compared to the previews ct and negative urine culture was obtained. conclusions: we established that treatment using adjuvant continuous intravesical irrigation with amikacin can reduce hospital stay and accelerate the patient?s healing process, as well as an earlier negativisation of urine cultures. a comparative prospective study is needed to evaluate if in fact this treatment variant produces a real benefit compared to conventional therapy.

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