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Search Results: 1 - 10 of 385579 matches for " C. Cuevas; Chavarín "
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Corrosion Evaluation of SS-304 Stainless Steel for the Application to Heat Pumps
Arteaga,C. Cuevas; Chavarín,J. Uruchurtu; Martínez G.,Miguel A.;
Portugaliae Electrochimica Acta , 2005,
Abstract: studies of the corrosion evaluation of ss-304 stainless steel exposed in aqueous lithium bromide solution have been carried out applying the electrochemical noise technique, polarization curves and the weight loss method. the test temperatures were 50, 60 and 70 °c, and the exposure time was for fifteen days. the main objective was to determine the corrosion rates and the type of corrosion that ss-304 suffers under the mentioned conditions with the purpose of evaluating its application to heat pumps/transformers. the results showed that at the three test temperatures the type of corrosion was a mixed and pitting process. at 60 °c, it was observed some anodic peaks at the fifth day of exposure, indicating pitting nucleation. from 7 to 12 days a regular and continue pitting process was observed, and then the corrosion process became in generalized type. at 70 °c, some isolated and medium intensity peaks were observed, presenting behaviour of some mixed and pitting corrosion. the resistance noise was calculated through a statistical analysis, and then the stern-geary equation and faraday law were applied to determine the mass loss, which was compared to that obtained from weight loss method. tafel slopes were determined from experimental polarization curves. to support the metallic oxidation carried out on the stainless steel surface, atomic absorption analysis was made to the solution corrosion products.
Corrosion Evaluation of SS-304 Stainless Steel for the Application to Heat Pumps
C. Cuevas Arteaga,J. Uruchurtu Chavarín,Miguel A. Martínez G.
Portugaliae Electrochimica Acta , 2005,
Abstract: Studies of the corrosion evaluation of SS-304 stainless steel exposed in aqueous lithium bromide solution have been carried out applying the electrochemical noise technique, polarization curves and the weight loss method. The test temperatures were 50, 60 and 70 °C, and the exposure time was for fifteen days. The main objective was to determine the corrosion rates and the type of corrosion that SS-304 suffers under the mentioned conditions with the purpose of evaluating its application to heat pumps/transformers. The results showed that at the three test temperatures the type of corrosion was a mixed and pitting process. At 60 °C, it was observed some anodic peaks at the fifth day of exposure, indicating pitting nucleation. From 7 to 12 days a regular and continue pitting process was observed, and then the corrosion process became in generalized type. At 70 °C, some isolated and medium intensity peaks were observed, presenting behaviour of some mixed and pitting corrosion. The resistance noise was calculated through a statistical analysis, and then the Stern-Geary equation and Faraday Law were applied to determine the mass loss, which was compared to that obtained from weight loss method. Tafel slopes were determined from experimental polarization curves. To support the metallic oxidation carried out on the stainless steel surface, atomic absorption analysis was made to the solution corrosion products.
PRIMER REPORTE DEL ENROLLADOR DE BANDAS OBLICUAS, CHORISTONEURA ROSACEANA (HARRIS) (LEPIDOPTERA: TORTRICIDAE), EN MANZANO EN EL EJIDO VISTA HERMOSA, CIUDAD CUAUHTéMOC, CHIHUAHUA, MéXICO
N. Bautista Martínez,C. Chavarín Palacio,E. López Bautista
Acta zoológica mexicana , 2011,
Abstract: Choristoneura rosaceana (Harris) is recorded for the first time in apple crops variety "Golden Delicious" in the Ciudad Cuauhtémoc, Chihuahua, Mexico. Immature stages were described briefly and its damage in foliage and fruits; also the adults main characteristics. The way of arrivalby this pest to the apple crops region was hypothesized.
Nylon/Porphyrin/Graphene Oxide Fiber Ternary Composite, Synthesis and Characterization  [PDF]
César García-Pérez, Carmina Menchaca-Campos, Miguel A. García-Sánchez, Elsa Pereyra-Laguna, Ociel Rodríguez-Pérez, Jorge Uruchurtu-Chavarín
Open Journal of Composite Materials (OJCM) , 2017, DOI: 10.4236/ojcm.2017.73009
Abstract: This research was based on the manufacture of new composite materials that offer technological possibilities in the development of new devices with greater efficiency. Electrospinning was used to form nylon 66/-tetra-(para-aminophenyl) porphyrin (H2T(p-NH2)PP)/graphene oxide (GO) composite film. Graphene oxide coatings were obtained from graphite, through mechanical exfoliation followed by calcination and ultrasonic agitation in an oxidant solution. These samples were characterized under SEM, FTIR, Raman spectroscopy, UV-vis and R-X techniques. On the other hand, H2T(p-NH2)PP was synthesized in two steps?process by the Rothemun reaction and the Adler Method and it was integrated within nylon polyamide fibers by direct addition of a hexamethylenediamine/adipoyl chloride reactant mixture. The polymerization of the nylon/H2T(p-NH2)PP species occurs in such a way that it starts or ends on the four peripherals-NH2 groups, connected and located in the same molecular plane of H2T(p-NH2)PP, forming nylon chains at the periphery of the macrocycle. The association of GO with nylon/H2T(p-NH2)PP fibers is performed
La arquitectura organizacional y gobierno corporativo de los Grupos Económicos en México
Rubén Chavarín Rodríguez
Ciencia Ergo Sum , 2006,
Abstract: Un rasgo importante de la organización industrial en diversos países es la presencia de Grupos Económicos, que son redes de negocios en donde las empresas establecen relaciones de largo plazo. Para una definición y entendimiento más extensos de los Grupos Económicos resulta útil referirse a los conceptos de arquitectura organizacional y gobierno corporativo. En este documento se da una breve explicación de la arquitectura y gobierno de los Grupos Económicos en México, así como de su evolución histórica. Un aspecto relevante de esta evolución fue la incorporación de empresas controladoras en la arquitectura de las redes de negocios.
Identidad de la rana austral chilena Eupsophus coppingeri (Amphibia, Anura, Neobatrachia): evidencias morfológicas, cromosómicas y moleculares
FORMAS,J. RAMóN; Nú?EZ,JOSé; CUEVAS,CéSAR;
Revista chilena de historia natural , 2008, DOI: 10.4067/S0716-078X2008000100001
Abstract: comparative analyses that include: external morphology of adults and larvae, osteology, chromosomes and sequences of the mitochondrial gen cytochrome b show that the austral chilean frog eupsophus coppingeri (günther 1881) is a species of the genus alsodes that should be named alsodes coppingeri (günther 1881). based on the holotype and new specimens collected in the type locality the taxon is redescribed and compared with its congeners. the synonymy between alsodes montícola and a. coppingeri is discussed
Identidad de la rana austral chilena Eupsophus coppingeri (Amphibia, Anura, Neobatrachia): evidencias morfológicas, cromosómicas y moleculares Identity of the austral Chilean frog Eupsophus coppingeri (Amphibia, Anura, Neobatrachia): morphological, chromosomic and molecular evidences
J. RAMóN FORMAS,JOSé Nú?EZ,CéSAR CUEVAS
Revista chilena de historia natural , 2008,
Abstract: Análisis comparativos que incluyen: morfología externa de adultos y larvas, osteología, cromosomas y secuencias del gen mitocondrial citocromo b muestran que la rana austral chilena Eupsophus coppingeri (Günther 1881) es una especie del género Alsodes que debe nominarse Alsodes coppingeri (Günther 1881) nueva combinación. Basados en el holotipo y nuevos especímenes recolectados en la localidad típica, el taxón es redescrito y comparado con otros taxa congenéricos. Se discute la sinonimia entre Alsodes montícola y A. coppingeri Comparative analyses that include: external morphology of adults and larvae, osteology, chromosomes and sequences of the mitochondrial gen cytochrome b show that the austral Chilean frog Eupsophus coppingeri (Günther 1881) is a species of the genus Alsodes that should be named Alsodes coppingeri (Günther 1881). Based on the holotype and new specimens collected in the type locality the taxon is redescribed and compared with its congeners. The synonymy between Alsodes montícola and A. coppingeri is discussed
Telmatobius philippii, una nueva especie de rana acuática de Ollagüe, norte de Chile (Leptodactylidae)
CUEVAS,CéSAR C.; FORMAS,J. RAMóN;
Revista chilena de historia natural , 2002, DOI: 10.4067/S0716-078X2002000100022
Abstract: a new species of aquatic frog, telmatobius philippii, is described in the proximity of ollagüe, ii región, andes range, northern chile. the new taxon has moderate-sized (46.10-53.70 mm), granular flanks, tongue oval, unnotched; attached anteriorly about 75 % of its length, maxillary and premaxillary teeth present, tadpole with lateral line system conspicuous. the description of the new species is completed with, osteological, chromosomic, ecological and larval information. telmatobius philippii is compared with other chilean species of the genus telmatobius
Telmatobius philippii, una nueva especie de rana acuática de Ollagüe, norte de Chile (Leptodactylidae) Telmatobius philippii, a new species of aquatic frog from Ollagüe, northern Chile (Leptodactylidae)
CéSAR C. CUEVAS,J. RAMóN FORMAS
Revista chilena de historia natural , 2002,
Abstract: Se describe una nueva especie de rana acuática, Telmatobius philippii, de las proximidades de Ollagüe, II Región, Cordillera de Los Andes, norte de Chile. El nuevo taxón se caracteriza por su tama o moderado (46,10-53,70 mm), flancos granulares, lengua ovalada sin escotadura; adherida anteriormente al piso de la boca en 75 % de su longitud, dientes maxilares y premaxilares presentes y renacuajos con sistema de la línea lateral conspicua. La descripción de la nueva especie se completa con información osteológica, cromosómica ecológica y larvaria. Telmatobius philippii es comparada con otras especies chilenas del género Telmatobius A new species of aquatic frog, Telmatobius philippii, is described in the proximity of Ollagüe, II Región, Andes range, northern Chile. The new taxon has moderate-sized (46.10-53.70 mm), granular flanks, tongue oval, unnotched; attached anteriorly about 75 % of its length, maxillary and premaxillary teeth present, tadpole with lateral line system conspicuous. The description of the new species is completed with, osteological, chromosomic, ecological and larval information. Telmatobius philippii is compared with other Chilean species of the genus Telmatobius
Recurrence Quantification Analysis of Rough Surfaces Applied to Optical and Speckle Profiles  [PDF]
Oscar Sarmiento Martinez, Darwin Mayorga Cruz, Jorge Uruchurtu Chavarín, Estela Sarmiento Bustos
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.44083
Abstract: In this paper, Recurrence Quantification Analysis (RQA) is set as a practical nonlinear data tool to establish and compare surface roughness (Ra) through percentage parameters of a dynamical system: Recurrence (%REC), Determinism (%DET) and Laminarity (%LAM). Variations in surface roughness of different machining procedures from a typical metallic casting comparator are obtained from scattering intensity of a laser beam and expressed as changes in the statistics of speckle patterns and profiles optical properties. The application of the analysis (RQA) by Recurrence Plots (RPs), allowed to distinguish between machining procedures, highlighting features that other methods are unable to detect.
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