oalib

OALib Journal期刊

ISSN: 2333-9721

费用:600人民币/ 99美元

投稿

时间不限

2017 ( 74 )

2016 ( 470 )

2015 ( 8498 )

2014 ( 11153 )

自定义范围…

匹配条件: “Pedro Arco Ríos” ,找到相关结果约239113条。
列表显示的所有文章,均可免费获取
第1页/共239113条
每页显示
Evaluation of the Quality of Service of Voice Over Internet Protocol (VoIP) Using Active Queue Management (AQM) Evaluación de la calidad de servicios de VoIP en presencia de AQM
Vitalio Alfonso Reguera,Félix F. álvarez Paliza,Pedro Arco Ríos,Carlos A. Rodríguez López
Revista Cubana de Ingeniería , 2010, DOI: 10.1234/rci.v1i2.15
Abstract: This paper presents a comprehensive study about the impact of active queue management (AQM) on Voice over Internet Protocol (VoIP) quality of service. One of the most representative AQM scheme is analyzed through extensive simulation and its effect on the perceived quality of voice calls is evaluated. Different network scenarios, changing network loads and different scheme control parameters are investigated. Network impairments are related to user perception by means of well known algorithmic models, expressing user satisfaction in the MOS scale. The main results obtained show that the use of active queue management schemes like adaptive random early detection (ARED) significantly improve the perceived quality of voice calls. Se presenta un comprensivo estudio sobre el impacto del manejo activo de colas (AQM) en la calidad de servicio de las aplicaciones de voz sobre IP (VoIP). Se analiza uno de los algoritmos AQM más representativos mediante extensas simulaciones, evaluando su efecto en la calidad de voz percibida. Diferentes escenarios de red son investigados cambiando la carga de tráfico y alterando los parámetros de control. La degradación de la transmisión es vinculada a la percepción de los usuarios por medio de modelos algorítmicos bien conocidos, expresando la satisfacción de estos en la escala MOS. Los principales resultados obtenidos muestran que el uso de mecanismos para el manejo activo de colas, como el de detección temprana aleatoria en su versión adaptativa (ARED), mejora significativamente la calidad de voz percibida.
Telefonía móvil: percepción social y hechos The cellular mobile telephone: social perception and real facts
Pedro Javier Galache Ríos
Revista de Salud Ambiental , 2005,
Abstract: La telefonía móvil ha evolucionado desde un uso muy escaso y restringido hasta la universalización de sus servicios a toda la sociedad. La percepción social de que la telefonía móvil representa un riesgo para la salud, ha hecho necesario la realización de numerosos estudios científico-técnicos y la promulgación de legislación que garantice el desarrollo y aprovechamiento de la sociedad de información, con el objetivo último de la protección de la salud. The cellular mobil telephone has evolved, in a very short period of time, from a technology restricted and scarcely used to the universalitation of its use by all the societies. The social perception that cellular mobil telephone represents a public health risk has created the need of developing a great deal of scientific/tecnics studies and also the implementation of legislation that gaaranties the development and use of information with the uppermost aim of public health protection.
Urbanizaciones cerradas en áreas inundables del municipio de Tigre: ?producción de espacio urbano de alta calidad ambiental?
Ríos,Diego; Pírez,Pedro?;
EURE (Santiago) , 2008, DOI: 10.4067/S0250-71612008000100005
Abstract: from the last decades of the twentieth century, private economic agents began building gated communities over flood-prone areas of the periphery of the greater buenos aires agglomeration, via the incorporation of labour, major investments and specialized technology. this process of private production of urban space, which brings together public and private interests, has been legitimated through discourses relating to "sustainable development" and "environmental recovery". as a consequence, 'urban business' is generated that, in contradiction to what it claims, alters environmental functionality in an unprecedeted way. in this article, the contradictions that emerge in the processes associated with the production of'high environmental quality' urban space is addressed. this is pursued in terms of the conflict between the discourses and practices of thesocialactors that intervene, based on the paradigmatic case of the gated communities of the tigre municipality
Urbanizaciones cerradas en áreas inundables del municipio de Tigre: producción de espacio urbano de alta calidad ambiental?
Diego Ríos,Pedro Pírez
EURE (Santiago) , 2008,
Abstract: Desde la última década del siglo XX, los actores económicos privados comenzaron a producir urbanizaciones cerradas sobre áreas inundables de la periferia del Aglomerado Gran Buenos Aires, a partir de la incorporación de trabajo, grandes capitales y tecnologías especializadas. Este proceso de producción privada de espacio urbano, en el que convergen intereses tanto públicos como privados, ha sido legitimado a través de discursos referidos a las nociones de "desarrollo sustentable" y "recuperación ambiental", viabiüzando el avance de grandes "negocios urbanos" que, contradictoriamente a lo que se sostiene, tienden a una alteración de las funciones ambientales sin precedentes. En este trabajo se abordan las contradicciones que surgen de los procesos asociados a la producción de espacio urbano de "alta calidad ambiental" en términos de la confrontación entre los discursos y las prácticas de los actores sociales in te rvin lentes, a partir del caso paradigmático de las urbanizaciones cerradas del municipio de Tigre From the last decades of the twentieth century, private economic agents began building gated communities over flood-prone areas of the periphery of the Greater Buenos Aires Agglomeration, via the incorporation of labour, major investments and specialized technology. This process of private production of urban space, which brings together public and private interests, has been legitimated through discourses relating to "sustainable development" and "environmental recovery". As a consequence, 'urban business' is generated that, in contradiction to what it claims, alters environmental functionality in an unprecedeted way. In this article, the contradictions that emerge in the processes associated with the production of'high environmental quality' urban space is addressed. This is pursued in terms of the conflict between the discourses and practices of thesocialactors that intervene, based on the paradigmatic case of the gated communities of the Tigre municipality
Characteristics of Bromus cartharticus Vahl (Poaceae) natural populations collected in the central area of Argentina
Rosso, Beatriz;Pagano, Elba;Rimieri, Pedro;Ríos, Raúl;
Scientia Agricola , 2009, DOI: 10.1590/S0103-90162009000200019
Abstract: collection of bromus catharticus vahl was carried out in the argentine humid and sub-humid central area. sixty-eight natural populations are conserved for medium and long term in pergamino germplasm bank and in irb germplasm bank, and ten morphological and agronomic traits were evaluated in the field during two years. there was variability for the traits considered among the accessions. those populations from the subhumid area showed differences in valuable attributes for breeding. exploration of marginal areas for this species might be an effective way to add variability to this collection.
Propiedades de flujo a baja temperatura del biodiesel de aceite de palma
Benjumea,Pedro Nel; Agudelo,John Ramiro; Ríos,Luis Alberto;
Revista Facultad de Ingeniería Universidad de Antioquia , 2007,
Abstract: the faulty performance of palm oil biodiesel at low temperatures constitutes its main quality drawback and limitation to use this alternative fuel for diesel engines either as a neat fuel or blended with conventional diesel fuel derived from petroleum. in this work, several alternatives for improving the cold flow properties of palm oil biodiesel are evaluated. the production of biodiesel using branched-chain alcohols such as isopropyl alcohol, isobutyl alcohol, 2-butyl alcohol and isopentyl alcohol allows the production of palm oil alkyl esters having cloud and pour points lower than those of methyl esters. substituting isopropyl for the methyl group allows reductions in the cloud and pour points of 8 and 21 oc, respectively. palm oil isopropyl esters have a cloud point 10 oc lower than the corresponding methyl esters. the cloud point of the palm oil biodieseldiesel fuel blends linearly increases with mixture biodiesel content. in the case of the tested blends there may be fuel filterability problems only at temperatures below -4 oc. this work also presents the effectiveness of two commercial additives used to reduce the cold filter plugging point of neat biodiesel and the tested blends. the results obtained showed that by using such additives it is only possible to obtain reductions in the b5 blend cold filter plugging point when the lowest additive concentration was used.
Período óptimo de polinización del melón con abejas melíferas (Apis mellifera L.)
Reyes-Carrillo, José Luis;Cano-Ríos, Pedro;Nava-Camberos, Urbano;
Agricultura técnica en México , 2009,
Abstract: this research was carried out in the comarca lagunera region in order to answer the questions of when to introduce the beehives to the muskmelon fields and when to take them out. muskmelon hybrids gold rush (2001) and cruiser (2002) were used in this study. planting dates were in april 18 in 2001 and april 26 in 2002. four beehives per ha were used for pollination purposes. in 2001 nine treatments were studied: in treatments 1, 2, 3, 4, and 5 bee pollination began as follows: 1st, 2nd, 3rd, 4th and 5th week of blooming, respectively. for treatments 6-9, bee pollination was as follows: 6= bee pollination the 1st week and then covered with agribon? net the rest of the blooming period, therefore, treatment 9 was pollinated during the 1st, 2nd, 3rd, and 4th week of blooming and then covered with agribon? the rest of the blooming period. in 2002 a 10th treatment was added, which was covered all the blooming period. a significant quadratic relationship was found between the first five treatments and commercial yield with a determination coefficient of 92.5%. this quadratic model showed that when pollination began at the beginning of blooming the yield might be about 44.3 t ha-1 and 3.17 t ha-1 may be lost for each day in bee pollination delay. this data indicates that beehives should remain 28 days in the muskmelon field.
Uso de sustratos orgánicos para la producción de tomate en invernadero
Márquez Hernández, Cándido;Cano Ríos, Pedro;Rodríguez Dimas, Norma;
Agricultura técnica en México , 2008,
Abstract: organic food production is an alternative for consumers who prefer food free of synthetic pesticides and fertilizers, innocuous and with a high nutritional value. however, organic certification indicates a period of transition of three to five years without application of any synthetic product to the soil, period that most of the producers, are not willing to accept, because that implies a risk for their capital. on the other hand, the organic tomato in mexico reaches a price of 5.84 times greater than the conventional one; to produce it in greenhouse would increase considerably yield, and therefore the economic benefit for the producer. nevertheless, a substrate is necessary that besides, support contributes with considerable amounts of nutrients that satisfy the demands of the cultures. an alternative is compost, which mixed with inert materials, will improve its physical and chemical characteristics avoiding hypoxia. the objective of this work was to evaluate substrates made with mixtures between composts, biocomposta and vermicompost, and inert substrates, sand and perlite at various levels under greenhouse conditions. the experiment was carried out in matamoros, coahuila, mexico, in the experimental station la laguna facilities, from october 1st, 2003 up to march 30th, 2004, using the bosky genotype. the best four mixtures were vermicompost with sand at 50% level and vermicompost with perlita at 37,5 and 50% levels and biocomposta with perlita at 37.5% level with a mean yield of 91.42 t ha-1 surpassing the open field yields by 9.14 times, without affecting fruit quality.
NUEVOS ASPECTOS DE LA REACCIóN TIPO MANNICH EN MEDIO BáSICO DE 1,3,6,8-TETRAZATRICICLO;[4.4.1.1(3,8)] DODECANO (TATD) CON FENOLES
Rivera,Augusto; Ríos-Motta,Jaime; Quevedo,Rodolfo; Joseph-Nathan,Pedro;
Revista Colombiana de Química , 2005,
Abstract: several phenols were tested as nucleophilesin mannich-type reactions with the macrocyclic aminal 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane (tatd) in basic medium. depending on the degree of substitution of the phenol employed,1,3-bis-[2’-hydroxybenzyl]imidazolidines, 2,6-di[3’-(2’’-hydroxybenzyl)-1’- methyleneimidazolidin] phenols and 3,3’-ethylene-bis-(3,4-dihydro-2h-1,3- benzoxazines) were obtained.
Hindered Rotation in N-Carbomethoxylated Indole Derivatives
Martha S. Morales Ríos,Norma F. Santos Sánchez,Pedro Joseph Nathan
Revista de la Sociedad Química de México , 2001,
Abstract: Los derivados de indoles N-carbometoxilados exhiben procesos dinámicos en RMN 1H resultantes de la rotación restringida alrededor del enlace N-C del carbamato. El modelado teórico por mecánica molecular predice dos mínimos conformacionales A y B, debido a los isómeros E y Z del grupo carbamato. El confórmero A, que presenta al carbonilo del carbamato orientado hacia el anillo de benceno es, en la mayoría de los casos, más estable que el confórmero B. La preferencia del confórmero B en 2 se atribuye a la presencia de un puente de hidrógeno. Los perfiles energéticos indican que, entre las moléculas investigadas, el compuesto 3 tiene la menor barrera rotacional para la interconversión de los confórmeros A y B. Las energías relativas de 3 favorecen al confórmero A en amplia proporción (97:3). Estos resultados son consistentes con las se ales agudas observadas en el espectro de RMN 1H de 3, mientras que los compuestos 2, 6 y 7 muestran algunas se ales significativamente anchas en sus espectros de RMN de 1H y 13C.
第1页/共239113条
每页显示


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.