Influencia del material de aporte en la resistencia a corrosión por picadura en uniones soldadas de un acero inoxidable dúplex 2205

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Múnez, C. J.

2007-08-01

Full Text Available In this work, it has been studied the pitting corrosion resistance of welding duplex stainless steel 2205. Unions were made by GMAW process with different fillers: duplex ER 2209 and two austenitic (ER 316LSi and ER 308LSi. The microstructure obtained with the duplex ER 2209 filler is similar to the duplex 2205 base material, but the unions produced with the austenitic fillers cause a decrease of the phases relation a/g. To evaluate the influence of the filler on the weld, the pitting corrosion resistance was determined by electrochemical critical pitting temperature test (TCP and the mechanical properties by the hardness. The phases imbalance produced for the dissimilar fillers bring out a variation of the pitting corrosion resistance and the mechanical properties.

En este trabajo se ha estudiado la resistencia a la corrosión localizada por picadura, de soldaduras realizadas sobre un acero inoxidable dúplex 2205. Se hicieron uniones mediante el proceso GMAW, utilizando como material de aporte un hilo dúplex ER 2209 y dos austeníticos ER 316LSi y ER 308LSi. Metalúrgicamente, se observa como para el hilo ER 2209 las microestructuras que se obtienen son similares a la del dúplex 2205, mientras que en las uniones con hilo austenítico, pueden verse microestructuras muy diferentes en las que la relación de fases a/g disminuye. Al evaluar la resistencia a la corrosión por picadura, mediante la Temperatura Crítica de Picadura (TCP, se comprobó como el desequilibrio entre las fases, generado por el aporte, provoca la variación en la resistencia a la corrosión localizada por picadura. También, se estudió la variación en las propiedades mecánicas del material mediante ensayos de dureza.

Evaluación de la adherencia del biofilm sobre salivaderas dentales de acero inoxidable, cerámica y opalina

OpenAIRE

Butler, Teresa Adela

2009-01-01

El objetivo principal de esta investigación fue estudiar el desarrollo de la biopelícula depositada sobre las salivaderas dentales de tres materiales diferentes (acero inoxidable, cerámica y opalina), de equipos odontológicos correspondientes a dos zonas diferentes del casco urbano de la ciudad de La Plata (Z1 y Z2). Para ello se realizaron 38 cortes de salivaderas dentales de los tres materiales, de cada zona En primer lugar se realizó el análisis de la microbiota planctónica y sé...

Estudio de electrodeposición de cobre sobre electrodos porosos de grafito y acero inoxidable vía SEM-DRX y análisis de imagen

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Constanzo-R., Robinson; Pagliero-N., Antonio; Vergara-G., Froilán

2014-01-01

El objetivo de este trabajo fue realizar un análisis cualitativo de la distribución de un electrodepósito de cobre en el interior de electrodos porosos (EP) de acero inoxidable y carbono grafito. Para ello, se realizaron pruebas de electrodepositación de cobre a nivel de laboratorio, con un posterior análisis de cortes de muestras de acero y grafito vía Microscopía Estereoscópica, Microscopía SEM-DRX y Análisis de Imagen, los cuales mostraron que el cobre no se deposita en forma uniforme al i...

Oxidación en vapor de agua del acero inoxidable aisi 317 a 700 y 750ºc

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MARULANDA AREVALO, JOSE LUDDEY; REMOLINA MILLAN, ADULJAY; BARON, JAIRO ALBERO

2013-01-01

Se realizó la oxidación del acero inoxidable austenítico AISI SAE 317, a temperaturas de 700 y 750ºC, en un ambiente con 100% vapor de agua, para evaluar su comportamiento a la corrosión. Se realizaron curvas de ganancia de masa y las películas de óxidos se analizaron por medio de Microscopia Electrónica de Barrido (SEM) y difracción de rayos X (DRX), para observar cómo se forman las capas de óxidos y discutir el posible mecanismo de oxidación en vapor de agua. Se encontró que el mecanismo de...

OXIDACIÓN EN VAPOR DE AGUA DEL ACERO INOXIDABLE AISI 317 A 700 Y 750ºC

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José Luddey Marulanda Arevalo; Aduljay Remolina Millan; Jairo Alberto Barón

2013-01-01

Se realizó la oxidación del acero inoxidable austenítico AISI SAE 317, a temperaturas de 700 y 750ºC, en un ambiente con 100% vapor de agua, para evaluar su comportamiento a la corrosión. Se realizaron curvas de ganancia de masa y las películas de óxidos se analizaron por medio de Microscopia Electrónica de Barrido (SEM) y difracción de rayos X (DRX), para observar cómo se forman las capas de óxidos y discutir el posible mecanismo de oxidación en vapor de agua. Se encontró que el mecanismo de...

Influencia de la fase sigma en la laminación en frío de los aceros inoxidables dúplex

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Fargas, G.

2004-04-01

Full Text Available One of the steps in the industrial rolling process of duplex stainless steels is the annealing heat treatment after hot rolling. If this annealing is performed in a temperature range that favours the precipitation of intermetallic phases, the mechanical properties can be modified considerably. The formation of these precipitates has a detrimental effect on the DSS ductility and toughness, so it will be a drawback for further cold rolling. In the present investigation, the effect of the sigma phase during cold rolling of a duplex stainless steel type EN 1.4462 has been studied. To simulate this process, compression tests up to a thickness reduction similar to that performed at industrial level have been done. The testing samples were studied by optical microscopy, SEM (scanning electronic microscopy and TEM (transmission electronic microscopy. Afterwards, some of the annealing conditions were selected in order to carry out cold rolling, using a laboratory scale machine, with the aim to observe if they offered a similar behaviour as that experienced in the compression tests. The results show that only the annealing condition at 975ºC during 10 minutes allows to produce sheets without rolling defects.

Una de las etapas en el proceso de fabricación industrial de los aceros inoxidables dúplex laminados es el tratamiento térmico de recocido posterior a la laminación en caliente. Si dicho recocido se efectúa en un rango de temperaturas que favorezca la formación de fases intermetálicas, las propiedades mecánicas del material pueden modificarse notablemente. La presencia en la microestructura bifásica de dichos precipitados provoca efectos muy perjudiciales sobre la ductilidad y la tenacidad del material, pudiendo llegar a hacer inviable la posterior etapa de laminación en frío. En el presente trabajo se ha estudiado el efecto sobre el proceso de laminación en frío de la presencia de fase sigma en un acero dúplex tipo E.N. 1

Elasto-plastic hardening models adjustment to ferritic, austenitic and austenoferritic Rebar; Ajuste de los aceros corrugados ferríticos, austeníticos y austenoferríticos a los modelos de endurecimiento elastoplástico por deformación

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Hortigóna, B.; Gallardo, J.M.; Nieto-García, E.J.; López, J.A.

2017-09-01

The elastoplastic behaviour of steel used for structural member fabrication has received attention to facilitate a mechanical-resistant design. New Zealand and South African standards have adopted various theoretical approaches to describe such behaviour in stainless steels. With respect to the building industry, describing the tensile behaviour of steel rebar used to produce reinforced concrete structures is of interest. Differences compared with the homogenous material described in the above mentioned standards and related literatures are discussed in this paper. Specifically, the presence of ribs and the TEMPCORE® technology used to produce carbon steel rebar may alter the elastoplastic model. Carbon steel rebar is shown to fit a Hollomon model giving hardening exponent values on the order of 0.17. Austenitic stainless steel rebar behaviour is better described using a modified Rasmussen model with a free fitted exponent of 6. Duplex stainless steel shows a poor fit to any previous model. [Spanish] Uno de los principales factores tenidos en cuenta en la fabricación de aceros estructurales es su comportamiento durante la fase elastoplástica o de endurecimiento por deformación. Normas neozelandesas y sudafricanas plantean diversas aproximaciones teóricas para describir dicho comportamiento en el caso de los aceros inoxidables. En el campo de la construcción resulta de interés la descripción del comportamiento tenso-deformacional de los aceros corrugados utilizados en las estructuras de hormigón armado. En este artículo se discuten los modelos planteados en las normas citadas anteriormente así como los existentes en la literatura tanto para los aceros corrugados inoxidables como para los aceros al carbono fabricados mediante el proceso denominado TEMPCORE® Los aceros TEMPCORE® analizados arrojan un valor del exponente de endurecimiento por deformación según el modelo de Hollomon de 0.17. Los aceros inoxidables austeníticos se ajustan mejor al modelo

PROTECCIÓN CONTRA LA CORROSIÓN EN SALES FUNDIDAS DE UN ACERO HOT ROLLED, EN EL RANGO DE TEMPERATURAS DE 400 ºC-600 ºC, RECUBIERTO POR ROCIADO TÉRMICO CON ACERO INOXIDABLE 312

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JOSE LUDDEY MARULANDA

2009-01-01

Full Text Available Se evaluó la corrosión por sales fundidas mediante la técnica gravimétrica en un acero de bajo carbono tipo hot rolled, rociado térmicamente con una aleación de acero inoxidable tipo 312, con el equipo Rototec, en una mezcla de sal 20% Na2SO4 - 80% V2O5, entre 400ºC - 600ºC, durante tiempos de 1-7-22 horas. Los resultados mostraron una moderada protección de la capa rociada térmicamente y se presentó alta degradación en el recubrimiento a 600ºC. Se concluyó que la velocidad de corrosión aumenta con la temperatura y disminuye con el tiempo de exposición.

Estudio comparativo de la cavidad de acceso radicular en conductos curvos con limas de níquel-titanio y taladros de acero inoxidable

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Oncins Rodríguez, J.; Pumarola Suñé, José; Canalda Sahli, Carlos

2005-01-01

El propósito de este estudio fue comparar la cantidad de dentina radicular removida y evaluar el mantenimiento de la forma del conducto tras la instrumentación de los dos tercios coronarios radiculares, utilizando instrumentos de acero inoxidable (taladros de Gates Glidden) y de níqueltitanio (limas GT Flare y limas Orifice Shaper). Un total de 42 dientes humanos extraídos con conductos radiculares curvos fueron divididos en tres grupos. Los conductos se instrumentaron mecánicamente usando ta...

Estudio de la calidad de recubrimientos de hidroxiapatita sobre acero inoxidable implantable aplicados mediante proyección térmica con plasma

OpenAIRE

Bernal Gaona, Sandra Paola

2013-01-01

El objetivo de este trabajo de investigación se basó en el estudio de los parámetros del proceso de deposición de recubrimientos de hidroxiapatita sobre substratos de acero inoxidable implantable mediante el proceso de proyección térmica con plasma atmosférico, que pueden afectar de forma significativa la calidad de los recubrimientos, en cuanto a su cristalinidad y adherencia al substrato. Como parámetros a evaluar se tomaron el tamaño de grano de la hidroxiapatita, el espesor...

Estudio de la resistencia a la corrosión por picadura de aceros inoxidables austeníticos: influencia de la adición de manganeso en solución sólida

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José Wilmar Calderón-Hernández; Lara Beatriz Braga Luz; Duberney Hincapie-Ladino; Neusa Alonso-Falleiros

2015-01-01

Este documento presenta los resultados de una investigación sobre la influencia del Mn en solución sólida sobre la resistencia a la corrosión por picadura de dos aceros inoxidables austeníticos, uno denominado 17Cr6Mn5Ni y un acero comercial UNS S304L utilizado como material de referencia. Fueron usadas soluciones electrolíticas de 0,6M NaCl en tres diferentes condiciones de concentración de oxígeno (solución desaireada, naturalmente aireada y aireada artificialment...

Soldadura TIG de los aceros inoxidables dúplex del tipo 22-05 (Uranus 45N y Avesta. Estudio de la microestructura y de las propiedades mecánicas

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Gómez de Salazar, J. M.

1998-05-01

Full Text Available TIG welding of two different duplex stainless steels is carried out. Arc-discharge on base-material plates by means of the TIG technique without filler metal and varying the energetic conditions (E.N.A. has been performed, A comparative study concerning the microstructural evolution as well as mechanical properties is carried out, The relation between hardness profiles, the microstructural variations and the ferrita δ concentration is established. Further, the above mentioned properties are related to the E.N.A. for each welded joint.

Se estudia la soldadura TIG de dos aceros inoxidables dúplex. Para ello, se ha descargado un arco sobre las chapas de material base mediante la técnica TIG, sin aportación de material y variando las E.N.A. Se realiza un estudio comparativo de la evolución microestructural, así como de las propiedades mecánicas. Se establece la relación entre los perfiles de dureza obtenidos y la variación microestructural y de la concentración de ferrita δ, así como estas propiedades con el E.N.A, de cada cordón.

Efecto del contenido de azufre y del grado de desoxidación sobre la ductilidad en caliente de aceros inoxidables austeníticos resulfurados en estado de solidificación

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Botella, J.

1998-05-01

Full Text Available The manufacture of free machining austenitic stainless steels features a specific drawback derived from their high sulphur content, which is needed for generating, into the austenitic matrix, inclusions to optimize the different machining operations. However, sulphur has a harmful effect on hot workability. This paper deals with assessing the effect of sulphur content and deoxidation level on the hot ductility of resulphurized austenitic stainless steels in as cast condition. Hot tensile tests were conducted on a Gleeble machine, at temperatures between 1,150 and 1,250°C, studying a ductility factor as a function of sulphur content, deoxidation degree, as well as type, size and distribution of sulfides. Results point out the harmful effect of increasing sulphur and oxygen contents on the hot workability of resulphurized austenitic stainless steels, and the need to control carefully the level of oxides of these steels.

La fabricación de aceros inoxidables austeníticos de alta maquinabilidad presenta una problemática específica derivada de su elevado contenido de azufre; elemento necesario para generar en la matriz austenítica inclusiones que faciliten las diferentes operaciones de mecanizado, pero perjudicial en cuanto al deterioro que produce en la deformabilidad en caliente. Este artículo describe el estudio realizado para evaluar el efecto del contenido de azufre y el grado de desoxidación sobre la ductilidad en caliente de aceros inoxidables austeníticos resulfurados, partiendo de una estructura de solidificación (as cast condition. Se realizaron ensayos de tracción en un sistema Gleeble, a temperaturas entre 1.150 y 1.250°C, analizándose el parámetro de ductilidad en función del contenido de azufre, nivel de desoxidación, y del tipo, tamaño y distribución de los sulfuros presentes. Los resultados ponen de manifiesto el efecto perjudicial de los contenidos de azufre y oxígeno sobre la deformabilidad en

Corrosión en caliente de un acero inoxidable 304h para calderas en presencia de sales fundidas de vanadatos y sulfatos

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Sonia Rincón

2003-01-01

Full Text Available El presente trabajo busca indagar y establecer el tipo de mecanismo de daño que sufre el acero inoxidable 304H en contacto con depósitos de sal fundida, junto con un estudio preliminar de la cinética de la corrosión. Para ello, se analizarán los depósitos fundidos, la composición química de éstos y se medirá la pérdida de material luego de ser sometido a períodos continuos de ataque, con el uso de la técnica gravimétrica en crisol. Con esto se pretende conocer las variables que influyen directamente sobre el deterioro del acero 304H, para en un futuro, adoptar medidas predictivas y/o preventivas que incrementen su vida útil, aumentando de ésta manera la eficiencia de las calderas y disminuyendo el tiempo entre paradas programadas.

Efecto de los ciclos térmicos sobre la ZAT de una soldadura multipasos de un acero inoxidable superdúplex SAF 2507 Effect of thermal cycles on the HAZ of a stainless steel multipass weld of superduplex SAF 2507

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D. Villalobos

2010-09-01

Full Text Available Los ciclos térmicos de una soldadura multipasos que experimenta un acero inoxidable superdúplex SAF 2507, pueden promover la precipitación de fases secundarias reduciendo significativamente las propiedades mecánicas y la resistencia a la corrosión. Debido a su aplicación en la industria petroquímica, el estudio de las aleaciones superdúplex es de suma importancia para predecir su comportamiento en servicio cuando están involucrados procesos de soldadura por arco eléctrico. En este trabajo, se estudia el cambio microestructural de la zona afectada térmicamente correspondiente al primer cordón depositado de una unión multipasos de acero inoxidable superdúplex SAF 2507 mediante el proceso GTAW y bajo tres temperaturas de interpasos. Los resultados muestran que la temperatura de interpasos tiene una influencia sobre la precipitación de fase sigma en la zona afectada térmicamente del primer cordón depositado.Thermal cycles experienced by a superduplex stainless steel SAF 2507 when is welded, can promote the precipitation of secondary phases which decrease the mechanical properties as well as the corrosion resistance. Due to the application of the duplex alloys in the petrochemical industry, the study of these alloys has become very important in order to predict its service behavior. The aim of this work is to study the microstructural changes in the superduplex stainless steel weld joint after applying the GTAW process under three interpass temperatures after the deposition of every single pass. The results showed that slow cooling rates promoted by the deposition of the subsecuent passes and the higher interpass temperature, promote the precipitation of sigma phase in the HAZ while rapid cooling rates promoted by the lower interpass temperature do not promote the sigma phase precipitation.

Efecto de las variables del procedimiento de soldadura sobre las propiedades mecánicas y la resistencia a la corrosión en depósitos de soldadura de aceros inoxidables supermartensíticos

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Zappa, Sebastián

2011-01-01

La soldadura de los aceros inoxidables martensíticos ha presentado ciertas dificultades y el uso de tratamientos térmicos es normalmente obligatorio. Las razones son diferentes para cada grado de acero, pero en general, es común obtener alta dureza y baja tenacidad en la zona afectada por el calor. Este hecho está asociado con la estructura martensítica en sí misma y el contenido de carbono. Una posible solución a este problema y para alcanzar determinadas propiedades en condición como soldad...

Some pitfalls in welding of duplex stainless steels Algumas armadilhas na soldagem de aços inoxidáveis duplex

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Demian J. Kotecki

2010-12-01

Full Text Available Duplex stainless steels (DSS, including super duplex stainless steels {SDSS} have proven to be very useful engineering materials, albeit with somewhat different welding requirements than those of the more familiar austenitic stainless steels. Despite a generally good track record in welding of duplex stainless steels, certain pitfalls have been encountered with enough frequency that they deserve review. Inappropriate base metal specification often leads to unsuitable heat affected zone (HAZ properties. Autogenous fusion zones are also of concern. This issue centers around nitrogen limits. The most frequently encountered is applying the UNS S31803 composition for 2205 DSS, instead of the S32205 composition. Inappropriate welding heat input arises most frequently with SDSS. While 0.5 to 1.5 kJ/mm is a normal heat input recommendation for SDSS, either a root pass or many small beads towards the low end of this heat input range tends to result in precipitation and/or secondary austenite formation in weld metal subjected to repeated thermal cycles from multiple weld passes. Inappropriate PWHT occurs when the enhanced nickel filler metals (typically 9% Ni are used. DSS are not normally given PWHT, but extensive forming of heads, for example, or repair welding of castings, may require a postweld anneal. Specifications such as ASTM A790 and A890 call for annealing at 1040ºC minimum, and the fabricator tends to use temperatures close to that minimum. However, the enhanced nickel filler metals require higher temperatures to dissolve sigma phase that forms during heating to the annealing temperature.Aços inoxidáveis duplex (AID, incluindo os aços super duplex, AISD provaram ser materiais de engenharia muito úteis, embora com requerimentos de soldagem em alguma medida diferentes daqueles dos aços inoxidáveis austeníticos mais usuais. Apesar do histórico geralmente bom dos aços inoxidáveis duplex quanto a soldagem, algumas dificuldades têm sido

Efectos gammágenos del cobre en los aceros inoxidables 18Cr8Ni

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Botella, J.

1997-10-01

Full Text Available From a series of 22 typical 18Cr8Ni stainless steel 40 kg ingots, with copper variable concentrations from 0.6 to 3.0 weight %, δ-ferrite is measured with a ferrite-meter device, calculating a nickel equivalent of 0.27 for copper. Some differences between the 8-ferrite and that on calculated by DeLong -excluding the copper γ-gene action- have been found because of different solidification and cooling regimes in ingot and weld cases.

A partir de una serie de 22 lingotes de 40 kg de aceros inoxidables típicos 18Cr8Ni, con concentraciones variables de cobre entre 0,6 y 3,0 % en masa, se mide la ferrita δ mediante un medidor de ferrita y se deduce para el cobre un equivalente en níquel de 0,27, a la vez que se establecen ciertas diferencias entre los contenidos de ferrita δ medida y la deducida según DeLong -excluida la acción gammágena del cobre- por el hecho de solidificar en lingotes en vez de la típica solidificación de soldaduras.

Correlaciones entre la microestructura y la atenuación sonora en un acero inoxidable martensítico

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Daniel Ramírez C.

2004-01-01

Full Text Available En este trabajo se exploró la relación entre la microestructura de un acero inoxidable martensítico y las variaciones en el sonido producido por un instrumento metalófono construido con dicho material. Para lograr este propósito, se hicieron copias de una de las placas de un glockenspiel y éstas fueron sometidas a diferentes tratamientos térmicos. Se construyeron montajes que permitieron producir sonidos mediante la excitación por percusión o electromagnética de las placas y se desarrollaron procedimientos para el análisis de las señales adquiridas usando programas de que permitían un análisis automático de la información. A partir de los resultados fue posible establecer correlaciones entre la microestructura obtenida con los diferentes tratamientos térmicos y características de los sonidos tales como la envolvente de atenuación y frecuencias predominantes.

Caracterización y propiedades mecánicas a alta temperatura de un acero inoxidable dúplex

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Jiménez, J. A.

1998-05-01

Full Text Available The microstructure and mechanical behavior at high temperature of a thermomechanical processed duplex stainless steel have been studied. Recrystalization of the material takes place during heating to test temperature, and a microstructure consisting of islands of austenitic grains of about 10-15 μm in size included in a more or less continuous matrix of ferrite is observed. Tensile tests at temperatures above 1,000°C and at low strain rates show a stress exponent of about 2 and elongations to failure up to 290 %. These values suggest that deformation is controlled by a grain boundary sliding mechanism, which causes a decrease in the size of the islands during deformation. Finally, an activation energy for plastic deformation of 167 kJ/mol was observed that was related to the activation energy for grain boundary diffusion of iron.

Se ha estudiado la microestructura y el comportamiento mecánico a alta temperatura de un acero inoxidable dúplex procesado termomecánicamente. Durante el calentamiento a la temperatura de ensayo, el material recristaliza y se obtiene una microestructura de granos austeníticos de tamaños comprendidos entre 10 y 15 μm agrupados en islas incluidas en una matriz más o menos continua de ferrita. Ensayos de tracción a temperaturas superiores a 1.000°C y bajas velocidades de deformación muestran un exponente de la tensión igual a 2 y alargamientos a rotura de hasta 290 %. Estos valores permiten asociar el mecanismo de deformación al deslizamiento de fronteras de grano, el cual determina la desaparición progresiva de las islas de granos austeníticos durante la deformación. Finalmente, se encontró un valor de 167 kJ/mol para la energía de activación de la deformación plástica, la cual se relacionó con la energía de autodifusión del hierro a lo largo de las fronteras de grano.

Formación de maclas durante el enfriamiento en aceros inoxidables superferríticos envejecidos

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Salán, M. N.

2005-12-01

Full Text Available Superferritic stainless steels show a BCC structure free of austenite at any temperature. Intermediate ageing temperatures, close to 475 °C, induce a-chromium content modulation and only after long periods of time, it is possible to detect chromium rich α' phase, which is responsible for embrittlement (475 °C embrittlement. In this work, ageing thermal treatments at intermediate temperatures in the superferritic stainless steel DIN 1.4575, have allowed to relate the associated hardness increase with time and temperature by means of a relationship that is compatible with a thermally activated process. After quenching from ageing temperature, twinning formation has been observed, and the extent of twinning is proportional to the increase in hardness, showing in this way that twinning density is proportional to embrittlement level.

Los aceros inoxidables superferríticos se caracterizan por su estructura cúbica centrada, libre de austenita a cualquier temperatura. Sometidos a temperaturas intermedias, próximas a 475 °C, revelan una modulación del contenido en Cr de la red. Después de tiempos prolongados se forma fase α', fragilizante y rica en cromo, fenómeno conocido como fragilización a 475 °C. En este trabajo, los tratamientos de envejecimiento realizados a temperaturas intermedias para un superferrítico DIN 1.4575 han permitido relacionar el incremento de dureza asociado a éstos con el tiempo de tratamiento, mediante una expresión coherente con un proceso térmicamente activado. Por otra parte, se ha detectado la presencia de maclas en el acero envejecido y templado en agua, siendo proporcional su densidad al grado de endurecimiento provocado por el tratamiento.

Oxidación en vapor de agua a 700 ºC y 750 ºC del acero inoxidable AISI 317 recubierto con aluminio por CVD-FBR.

OpenAIRE

Jose L. Marulanda; Saul I. Castañeda; Aduljay Remolina

2014-01-01

Se realizó la oxidación del acero inoxidable austenítico AISI 317 recubierto con aluminio por deposición química de vapor en lecho fluidizado, a temperaturas de 700 °C y 750ºC, en un ambiente con 100% vapor de agua, para evaluar su comportamiento. Se realizaron curvas de ganancia de masa y las películas de óxidos se analizaron por medio de SEM y difracción de rayos X, para observar la morfología de los óxidos. Se realizó la simulación termodinámica del proceso de oxidación en vapor de agua de...

Cinéticas de transformación de fases a 850 ºC de aceros inoxidables dúplex clásicos (2205 y 2507 y de uno nuevo de bajo contenido en níquel y alto en manganeso (DBNi

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Rodríguez, M. P.

2004-04-01

Full Text Available Austenitic-ferritic stainless steels are formed by ferrite and austenite in a variable proportion between 30 % and 70 %. Their chemical composition conditions the ageing processes that can happen during heat treatments, where phases that hardens and brittles the material can be generated. Evolution of a new duplex stainless steel with lower nickel and higher nitrogen and manganese content maintained at 1123 K (critical precipitation temperature up to 8 hours compared to classical ones (2205 and 2507 is presented. The study, done by magnetic measurements, XRD, optical and scanning electron microscopy and microanalysis, revealed a roughly similar behaviour for the three steels. The new one presents a higher initial stability, probably due to the high nitrogen and manganese contents; however, it also produces the higher final transformation due to the higher initial ferrite. A fine comparative analysis was done to correctly identify any phase; an accurate microanalysis in every generated phase was performed. All the steels tested are initially made on ferrite and austenite. After the ageing treatment, 8 hours at 1123 K, in the 2205 duplex steel a strong precipitation of sigma phase is observed, austenite and some of the original ferrite are also present; ferrite completely transforms in the 2507 duplex and austenite, sigma, secondary austenite and chromium nitride can be found; regarding the new duplex steel DBNi, austenite, ferrite, sigma, chi and chromium nitrides are detected.

Los aceros dúplex austeno-ferríticos están constituidos por ferrita y austenita en proporciones variables del 30 % al 70 %. Su composición química condiciona los procesos de envejecimiento que sufren durante los tratamientos térmicos, cuando se generan fases que endurecen y fragilizan el material. Este trabajo estudia la evolución de un nuevo inoxidable dúplex con bajo contenido en níquel y alto en nitrógeno y manganeso a 1123 K (temperatura crítica de

Optimización topológica y fabricación aditiva de un soporte aeronáutico mediante sinterizado láser de acero inoxidable 15-5PH

OpenAIRE

Marchal Montes, Álvaro

2016-01-01

El objetivo de este trabajó será la aplicación de la optimización topológica a un soporte usado en el sector aeronáutico para reducir su masa que posteriormente se fabricará mediante fabricación aditiva con tecnología DMLS (Direct Metal Laser Sintering) en acero inoxidable 15-5PH. Para llegar a una buena optimización topológica será necesario estudiar todos los caminos de optimización posibles hasta llegar a una correcta mediante softwares adecuados además de adaptarla a la fabricación ad...

Caracterización mecánica de recubrimientos de aluminio por CVD-FBR sobre aceros inoxidables y resistencia a la oxidación en vapor de agua

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Diego Pérez-Muñoz; José Luddey Marulanda-Arévalo; Juan Manuel Meza-Meza

2015-01-01

Los recubrimientos de aluminio depositados sobre el acero inoxidable austenítico AISI 317 por Deposición Química de Vapor en Lecho Fluidizado (CVD-FBR) presentan a altas temperaturas una reducción de la velocidad de corrosión de más de 80 veces. Se realizó la caracterización mecánica de los recubrimientos por medio de microdureza, nanoindentación, para conocer cómo se vieron afectas las propiedades mecánicas (en especial la dureza y el módulo de Young) del recubrimiento y del sustrato luego d...

Nitrocarburación mediante el proceso TENIFER QDQ de aceros inoxidables austeníticos estabilizados : caracterización química y estudio de su comportamiento frente al desgaste y la corrosión

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Bellas Muiño, Leonardo

2016-01-01

[Resumen]La nitrocarburación en baño de sales se utiliza para mejorar las propiedades tribológicas de los aceros inoxidables. Sin embargo, la aparición de carburos y nitruros de elementos de aleación en la capa externa puede tener efectos contraproducentes para su resistencia a la corrosión. Por este motivo, el proceso TENIFER®QPQ introduce una etapa de oxidación a altas temperaturas con objeto de formar una capa de magnetita (Fe3O4) que incrementa la resistencia a la corrosión...

A comparison of tensile, fracture and fatigue mechanical behaviour of structural reinforcing bars made with different steels

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Rodríguez, C.

2013-09-01

Full Text Available The use of austenitic stainless steels as rebar is an option increasingly used in reinforced concrete structures exposed to aggressive environments and especially those that have to work in marine environments. The same is true for duplex stainless steel rebars, although nowadays they have a lower use, mainly due to the fact that their inclusion in the reinforced concrete standards was delayed 10 years compared to austenitic stainless steel ones, and consequently their in-service behavior is not as well known. A study of the mechanical properties, including fracture toughness, fatigue behaviour and corrosion resistance in saline alkaline environments of austenitic (AISI 304LN and 316LN and duplex (D2205 stainless steel reinforcing bars was performed in this work. Bars made on a high ductility carbon steel (B500SD that are normally used to reinforce concrete were also characterized and used as a comparison. Stainless steel reinforcing bars show mechanical properties at least similar but usually higher than one of the best carbon steel re-bars (B500SD, along with a significantly higher ductility and, of course, much better corrosion behaviour in saline alkaline environments.El uso de aceros inoxidables austeníticos como armaduras de refuerzo es una opción cada vez más utilizada en estructuras de hormigón armado expuestas a ambientes agresivos y especialmente en las que han de trabajar en ambientes marinos. Lo mismo cabe decir de las armaduras de acero inoxidable dúplex, si bien su uso es menor, debido sobre todo a que su inclusión en la normativa aplicable al armado de hormigón se retrasó 10 años con respecto a los inoxidables austeníticos y, consecuentemente, su comportamiento en servicio es menos conocido. En este trabajo se analiza el comportamiento mecánico, incluyendo fractura y fatiga, así como la resistencia a la corrosión en medios que simulan un hormigón contaminado de cloruros, de armaduras fabricadas tanto con

Evaluación del grado de sensibilización en el acero inoxidable AISI

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González, O.

2003-12-01

Full Text Available Austenitic stainless steel, when heat-treated at 550-850 °C, became susceptible to intergranular corrosion in acids. This phenomenon, know as sensitization, it is result from the precipitation of chrome carbides in the grain boundary, making these areas less resistant to corrosion. Two different electrochemical reactivation tests are compared with a destructive test and related to the classification of its respective microstructures. It was established a quantitative methodology to evaluate the degree of sensitization in AISI 304 and also to compare the correspondence of the results with the data of the automatic and portable EPR device for non-destructive field measurement of the degree of sensitization. The used electrochemical techniques were the EPR (Electrochemical Potentiokinetic Reactivation or single loop test and the PRP (Pasivation Reactivation Potentiokinetic or double loop test. The destructive test used was boiling, 120 h ferric sulfate-50 % sulfuric acid, according to the standard practices ASTM A-262 practices B. The classifications of each structures were according to the standard practices ASTM A-262 practices B.

El acero inoxidable austenítico, cuando se calienta en un rango de temperatura entre 550 y 850 °C es susceptible a corrosión intergranular en ácidos. Este fenómeno, conocido como sensibilización, es resultado de la precipitación de carburos de cromo en el límite de grano, haciendo esas áreas menos resistentes a la corrosión. Se comparan dos pruebas diferentes de reactivación electroquímica con una prueba destructiva, relacionándolas con su respectiva microestructura. Se estableció una metodología cuantitativa para evaluar el grado de sensibilización del acero AISI 304 y se comparó con los datos generados de una herramienta no destructiva de campo, automática y portátil, para medir el grado de sensibilización. Las técnicas electroquímicas usadas fueron: la EPR (Reactivación electroqu

Estudio de la influencia microbiológica en la corrosión de latones (UNS C68700, UNS C443 y acero inoxidable AISI 316;

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Ohanian, Mauricio

2014-06-01

Full Text Available Microorganisms may play an important role in the corrosion process and generate conditions which affect the rate and/or the mechanism of deterioration. They become visible by the formation of biofilms: clusters of microorganisms and extracellular polymers. These biofilms affect not only the durability of the material, but also reduce the heat transfer. The present work studied the growth of aerobic and anaerobic heterotrophic microorganisms and sulfate reducing bacteria on aluminum brass (UNS C68700, admiralty brass (UNS C443 and stainless steel AISI 316 in exposure experiments held in the Bay of Montevideo (Uruguay. The influence of the biofilm growth on the corrosion behavior was studied by electrochemical techniques: polarization curves and Electrochemical Impedance Spectroscopy (EIS. The selection of the most suitable material for the exposure conditions is discussed and hypotheses of the corrosion mechanism are presented. Although stainless steel AISI 316 presented the lowest corrosion rate it showed localized deterioration.Los microorganismos influyen de manera significativa en el proceso corrosivo y generan condiciones que afectan la velocidad y/o el mecanismo de deterioro. Su presencia se manifiesta por la formación de bio-películas: conglomerados de bacterias y polímeros extracelulares. Dichas bio-películas afectan la durabilidad del material, la velocidad de flujo y la transferencia de calor. En el presente trabajo se evalúa el crecimiento de microorganismos heterótrofos aerobios, heterótrofos anaerobios y bacterias sulfato-reductoras sobre latón aluminio (UNS C68700, latón almirantazgo (UNS C443 y acero inoxidable AISI 316. Asimismo, se estudia la influencia del crecimiento de la bio-película sobre el comportamiento corrosivo mediante técnicas electroquímicas: curvas de polarización y espectroscopia de impedancia electroquímica. Las exposiciones se realizan en la Bahía de Montevideo, estuario del Río de la Plata

Influencia de la soldadura sobre la rotura por tensiones en tubos de acero inoxidable austenitico del tipo 18-11NB(TP347

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Gutiérrez de Saiz-Solabarria, S.

2000-06-01

Full Text Available This work has been undertaken to study the stress cracking failure in various 18Cr11Ni [TP347 (18-11Nb, TP 321 (18-11 Ti, TP304 (18-11 and TP316 (18-11-2] types austenitic stainless steel tubes. The material used was produced hot-rolling at 76,2 mm φ (3"φ x 2,54 mm (1/10" thickness. The study was carried out at 593ºC and applied stress of 50 Ton/in2.

Se estudia el efecto de la soldadura sobre la rotura por tensiones en tubos de acero inoxidable austenítico estabilizado con Nb o Ti de los tipos 18-11Nb (TP 347 y 18-11Ti (TP 321 así como sin estabilizar del tipo 18-11 (TP 304 y con Mo del tipo 18-11-2 (TP 316. Los tubos, en todos los casos, son de dimensiones 76,2 mm (3” φ x 2,54 mm (1/10” de espesor y la tensión aplicada (σ de 10 Ton/in2, para una temperatura de servicio de 593ºC.

PROTECCIÓN CONTRA LA CORROSIÓN POR SALES FUNDIDAS DE UN ACERO AL CARBONO POR ROCIADO TERMICO

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JOSE MARULANDA; ANDRÉS GARCÍA; JOSE VITOLA

2009-01-01

Se evaluó la corrosión por sales fundidas mediante la técnica gravimétrica en un acero de bajo carbono rociado térmicamente con una aleación de acero inoxidable, en una mezcla de sal con 20% Na2SO4 - 80% V2O5, entre 700ºC - 850ºC. Los resultados de las pruebas gravimétricas mostraron una deficiente protección de la capa rociada térmicamente y se presentó alta degradación en el recubrimiento protector, debido a que las temperaturas de exposición fueron mayores que las temperaturas de fusión de...

Losas de concreto reforzadas con acero inoxidable de desecho Reinforced concrete slabs with stainless steel waste

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Jorge Alberto Pérez González

2008-08-01

Full Text Available Se muestran los resultados de un programa experimental que explora la reutilización de materiales de desecho industrial (específicamente láminas de acero inoxidable producto de la acuñación de moneda como refuerzo en losas de concreto. Para ello se elaboraron 23 especímenes tipo viga-losa a escala natural con dicho refuerzo a fin de determinar su comportamiento en términos de resistencia, ductilidad y formas de falla; el análisis experimental de modelos ensayados con diferentes cantidades de refuerzo muestra que en algunos casos, bajo ciertas condiciones de cuantías y colocación del mismo, es posible alcanzar capacidades de carga y formas de falla similares a las de especímenes de control con refuerzo tradicional. En base a estos resultados se concluye en la factibilidad de utilizar el material arriba descrito como refuerzo alternativo en elementos estructurales de concreto, tratando de encontrar alternativas más económicas en la construcción de vivienda popular.The results from an experimental program that explores the use of industrial waste materials (specifically sheets of stainless steel that result of the currency coinage as reinforcement for concrete slabs are presented. Twenty three full size beam-deck specimens were built in order to measure resistance, ductility and failure modes; the experimental analysis in models with reinforcement in different quantities shows that in some cases, under certain quantities and location, it is possible to reach similar load capacities and failure modes as specimens with traditional reinforcement. Based on these results, it is concluded the feasibility of using the material described above as alternative reinforcement in structural concrete elements, as an economic option in the construction of social housing.

CATALIZADOR ESTRUCTURADO DE Pt/Al2O3 SOBRE UNA ESPUMA DE ACERO INOXIDABLE (AISI 314 PARA LA OXIDACIÓN DE CO

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Juan P. Bortolozzi

2011-01-01

Full Text Available Se obtuvo un catalizador estructurado por recubrimiento de Pt/Al2O3 sobre las paredes de una espuma de acero inoxidable AISI 314. Para estabilizar térmicamente e incrementar la rugosidad de la superficie de la espuma original se realizó un tratamiento a 900°C por 2 h. El soporte, Al2O3, y el metal activo, Pt, se incorporaron por inmersión. Las técnicas de caracterización aplicadas, XRD, LRS y SEM-EDX, permiten concluir que el tratamiento térmico previo indujo la formación de óxido de cromo y de las espinelas Mn1+xCr2-xO4-x y FeCr2O4 como fases principales en las paredes del sustrato. El espesor de la capa formada es cercano a 1 μm y los cristales producidos tienen forma octaédrica. El cubrimiento de alúmina presentó en general una apariencia homogénea, sin interacción con los óxidos formados durante el tratamiento. El Pt se distribuyó de manera uniforme, resultando un catalizador muy activo para la reacción test elegida: oxidación de monóxido de carbono.

Simulación del efecto de la irradiación mediante el trabajado en frío y los tratamientos térmicos en dos aceros inoxidables austeníticos

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de Diego, G.

1998-10-01

Full Text Available In the present study, annealed type 304 SS was cold worked and heat treated to simúlate irradiation hardening, ductility loss and grain boundary segregation. Constant Extension Rate Tensile (CERT tests were conducted to reproduce Irradiation Assisted Stress Corrosion Cracking (IASCC in BWR (Boiling Water Reactor environment.

En este trabajo se simulan los efectos que produce la irradiación, pérdida de ductilidad y segregación de impurezas en borde de grano, mediante trabajado en frío y posterior tratamiento térmico, para aceros inoxidables austeníticos AISI 304. Mediante ensayos de velocidad de extensión constante y en medios similares a los de los reactores de agua en ebullición se intenta relacionar la susceptibilidad a la corrosión bajo tensión con la susceptibilidad a la corrosión asistida por irradiación.

Stainless-Steel-Gadolinium Alloys; Alliages Acier Inoxydable-Gadolinium; Splavy iz nerzhaveyushchej stali i gadoliniya; Aleaciones de Acero Inoxidable-Gadolinio

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Copeland, M.; Kato, H. [Albany Metallurgy Research Center, Bureau Of Mines, United States Department of the Interior, Albany, OR (United States)

1964-06-15

mineures ont une grande influence sur les structures resultant de traitements equilibrants et sur les possibilites de transformation des aciers. Lorsque le gadolinium est melange a de l 'acier au chrome et au nickel, deux phases mineures, Fe{sub 9}Gd et Ni{sub 7}Gd, fondent a 1080 Degree-Sign C, ce qui impose une limite superieure aux temperatures de traitement a chaud et de transformation. Les auteurs ont pu facilement transformer des alliages comprenant jusqu'a 5 Degree-Sign Io en poids de gadolinium et determiner leurs caracteristiques mecaniques et leur resistance a la corrosion. Ils n'ont observe aucun changement dans les caracteristiques mecaniques de l'acier ou sa resistance a la corrosion par l'eau chaude, lorsqu'ils lui ont ajoute'jusqu'a 3% en poids de gadolinium. En raison des limites imposees aux temperatures de transformation des aciers au chrome et au nickel par le point de fusion des phases mineures, les auteurs ont etudie les effets du gadolinium sur des aciers au chrome. Ils ont releve une seule phase mineure qui fond a 1320 Degree-Sign C en etudiant l 'isoplethe du gadolinium a 10% en poids dans l 'alliage chrome-fer-gadolinium. Cette propriete permettrait d'equilibrer et de transformer ces aciers au gadolinium aux temperatures auxquelles on opere normalement. (author) [Spanish] En vista de la excelente resistencia a la corrosion de los aceros inoxidables y del interes que presenta el gadolinio como veneno nuclear, se han estudiado aleaciones de esos dos metales. El gadolinio fue aleado con aceros inoxidables de tipo AISI-304 y al cromo, y se estudiaron las relaciones de fase, la facilidad de trabajo y las propiedades de estas aleaciones. Se observo que en las aleaciones que contienen bajos porcentajes de gadolinio, los puntos de fusion de las fases menores ejercen un efecto muy marcado sobre las estructuras resultantes de los tratamientos de equilibracion y sobre la facilidad de trabajo de los afceros. Cuando se alea el gadolinio con acerce al cromo

Efecto de la biopelícula en la corrosión de aceros inoxidables

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Bethencourt, M.

2010-02-01

Full Text Available In this work, the influence of the biofilms in the corrosion process of different alloys of stainless steel was studied in two sampling points in a wastewater treatment plant during 4 years. The physicochemical microenvironment within the biofilms was characterized through O₂, H₂S and pH microelectrodes. Corrosion rates were quantified from the number, diameter and depth of pits. The results show a remarkable development of the biofilm and a significantly greater number of pits in the grit removal channel than in the sludge recirculation channel. Based on the characteristics of the water phase and microelectrode measurements, our results suggest that biofilms induced corrosion throughout 3 mechanisms: creation of differential aeration cells, areas with different pH and areas having high sulphide production which may react with metal ions.

En este trabajo se ha estudiado la influencia de las biopelículas en los procesos de corrosión de diferentes aleaciones de acero inoxidable, situadas durante 4 años en dos puntos de una estación depuradora de aguas residuales. Se caracterizó el microambiente físico-químico en el interior de las biopelículas mediante microelectrodos de O₂, H_2S y pH, y se cuantificaron las tasas de corrosión a partir del número, diámetro y profundidad de picadura. Los resultados obtenidos muestran un desarrollo más notable de las biopelículas y un número de picaduras significativamente mayor en el canal de salida de desbastes que en el canal de recirculación de fangos. Con base en las características del agua sobrenadante y en las medidas realizadas con microelectrodos, se sugiere que la biopelícula induce la corrosión a través de tres posibles mecanismos: creación de celdas de aireación diferencial, zonas con diferente pH y zonas con elevada producción de sulfuro capaz de reaccionar con iones metálicos.

Avaliação da soldagem multipasse de chapas espessas de aços inoxidáveis lean duplex UNS S32304 soldadas pelos processos SMAW, GMAW e FCAW: parte 1: propriedades mecânicas Evaluation of multipass welding of thick lean duplex stainless steel UNS S32304 plates welded by SMAW, GMAW and FCAW: part 1: Mechanical Properties

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Ronaldo Cardoso Junior

2012-12-01

Full Text Available Os aços inoxidáveis duplex (AID vêm se apresentando como uma excelente alternativa para aplicações em que alta resistência à corrosão e alta resistência mecânica são requeridas. Contudo, os AID, incluindo os aços inoxidáveis lean duplex, apresentam soldabilidade inferior em relação aos aços inoxidáveis austeníticos. Nesse sentido, esse trabalho tem como objetivo a avaliação da soldagem multipasse de chapas 22 mm de espessura da liga inoxidável lean duplex UNS S32304, utilizando-se os processo SMAW, GMAW e FCAW e consumíveis com dois tipos de composição química, 22%Cr9%Ni3%Mo e 23%Cr7%Ni, totalizando seis experimentos. Foram empregados chanfros em V com 60º e suporte cerâmico para soldagem do passe de raiz, sendo que o aporte térmico foi mantido praticamente constante em 1,6 kJ.mm-1. Determinou-se os tempos de soldagem e a seqüência de passes, objetivando uma análise de produtividade, em seguida as juntas soldadas foram submetidas à END por raios x. Foram extraídos corpos de prova para ensaios de tração, dobramento, Charpy a -30 ºC e microdureza. A produtividade dos processos semi-automáticos se mostrou pelo menos 63 % maior que a do processo SMAW, enquanto o processo FCAW se mostrou de 6 a 18% mais rápido que o GMAW. Foram encontradas descontinuidades (porosidade consideradas aceitáveis segundo ASME B31.3 em alguns dos experimentos, que não influenciaram negativamente os resultados mecânicos, os quais se apresentaram acima requerimento do metal de base e especificado por normas de fabricação.The duplex stainless steels (DSS's have been placed as an excellent alternative for applications where high corrosion resistance and high mechanical strength are required. However, DSS's, including the lean duplex, present lower weldability than the austenitic stainless steels. Thus, this study aims to evaluate the multipass welding of 22 mm plates of lean duplex stainless steel alloy UNS S32304, using the process

Evaluación de diferentes aceros para la evolución de hidrógeno en KOH

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Falk Michel Julke

2014-05-01

Full Text Available Se estudió el comportamiento electroquímico de los diferentes tipos de aceros comerciales de bajo costo (A36, 430 y 304 como electrodos para la obtención de hidrógeno. El propósito de este trabajo fue estudiar la evolución de hidrógeno, para lo cual se utilizaron técnicas electroquímicas como cronoamperometría y curvas voltamperométricas, en diferentes concentraciones de KOH (5% y 25% m/m. El acero inoxidable 304 en una concentración de 25%m/m tuvo el mejor desempeño, pues en estas condiciones el inicio de liberación de hidrógeno disminuyó y presentó el menor requerimiento de potencial para su uso como placa bipolar.

Brasagem dos aços inoxidáveis duplex 'baixa liga' UNS S32101, UNS S32304 e superduplex UNS S32750 com metal de adição AWS A5.3 tipo BNi-7 (Ni-Cr-P

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Dany Michell Andrade Centeno

2013-12-01

Full Text Available Os aços inoxidáveis duplex, devido à sua resistência à corrosão, têm uma grande aplicação em diversos segmentos industriais, onde a resistência à corrosão é uma propriedade requerida. Por terem resistência mecânica superior aos aços inoxidáveis ferríticos e austeníticos convencionais, podem produzir equipamentos mais leves. Quando ciclados termicamente, estes aços podem ter suas propriedades alteradas, principalmente quando se emprega processos de junção, como a brasagem, e quando ocorre o desbalanceamento da fração volumétrica ferrita/austenita. O objetivo deste trabalho é caracterizar a brasagem de aços inoxidáveis duplex 'baixa liga' e superduplex, verificando o efeito da folga e do tempo de brasagem na formação de intermetálicos contínuos no interior da junta brasada. Neste trabalho foram brasados, em forno continuo com atmosfera de hidrogênio, corpos-de-prova de aço inoxidável duplex UNS S32101, UNS S32304 e UNS S32750 com a adição para brasagem BNi-7 (Ni-Cr-P, na temperatura de 1100ºC, por tempos de 12 min e 32 min, utilizando-se folgas das juntas de 0,0 e 0,3 mm, seguidos de resfriamento em forno. Os corpos de prova foram caracterizados utilizando-se microscópio óptico, microscópio eletrônico de varredura com EDS e difração de raios X. Os resultados mostraram que a melhor condição para a brasagem em forno empregado foi a brasagem com a folga de 0,0 mm. Ambas as folgas apresentaram microestruturas variadas, porém a folga de 0,0 mm mostrou a presença de uma fase contínua CFC (cúbica de face centrada, rica em níquel, que é denominada, frequentemente, de γ-Ni. Para folgas de 0,3 mm, forma-se uma região eutética contínua no centro da junta, que pode prejudicar as propriedades mecânicas da mesma. Esta região é composta de fases intermetálicas ricas em fósforo. Foram observadas precipitações de fase sigma no metal de base no AID UNS S35750, nas condições de brasagem estudadas.

Caracterización mecánica de recubrimientos de aluminio por CVD-FBR sobre aceros inoxidables y resistencia a la oxidación en vapor de agua

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Diego Pérez-Muñoz

2015-09-01

Full Text Available Los recubrimientos de aluminio depositados sobre el acero inoxidable austenítico AISI 317 por Deposición Química de Vapor en Lecho Fluidizado (CVD-FBR presentan a altas temperaturas una reducción de la velocidad de corrosión de más de 80 veces. Se realizó la caracterización mecánica de los recubrimientos por medio de microdureza, nanoindentación, para conocer cómo se vieron afectas las propiedades mecánicas (en especial la dureza y el módulo de Young del recubrimiento y del sustrato luego de ser sometidos a la oxidación a alta temperatura. También se hicieron análisis por medio de Microscopia Electrónica de Barrido (MEB, para observar los cambios microestructurales, y de Microscopia de Fuerza Atómica (MFA, para observar cómo varía la topografía y el gradiente de rugosidad en función de la distancia recorrida por la punta del cantiléver durante los barridos.

Efeito da energia de soldagem sobre a microestrutura e propriedades mecânicas da zona afetada pelo calor de juntas de aço inoxidável duplex Effect of the welding heat input on the microstructure and mechanical properties of the heat affected zone of multipass welded joints of duplex stainless steel

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Everton Barbosa Nunes

2011-09-01

Full Text Available O objetivo deste trabalho é analisar a influência da energia de soldagem na zona afetada pelo calor (ZAC, de juntas soldadas do aço inoxidável duplex UNS S31803. Foram realizadas soldagens com eletrodo revestido AWS E2209-17 em junta tipo V de Aço Inoxidável Duplex UNS S31803, com dois níveis de energia (15 e 20 kJ/cm. A condição soldada com energia mais elevada apresentou uma ZAC mais extensa e microestrutura mais grosseira nos passes de acabamento. No entanto, nos passes de enchimento e de raiz, as ZAC's destas regiões foram mais refinadas e menos extensa. Em relação à microdureza, a condição soldada com energia de 15 kJ/cm apresentou níveis menores. Em relação à tenacidade, não foi verificada diferença significativa nos resultados.The aim this work is to evaluate the influence of multipass welding heat input on the microstructure and mechanical properties of the heat affected zone (HAZ of UNS S31803 duplex stainless steel multipass welded joints. The shielded metal arc welding process using as filler metal the AWS E2209-17 covered electrode were employed had been carried through V joint groove UNS S31803 DSS, so that two levels of energy (15 and 20 kJ/cm had been used in this experiment. The condition welded with higher energy higher a HAZ extensive and coarser microstructure in the finishing passes. On the other hand, in the wadding passes and root pass, the HAZ this region was more refined and less extensive. In respect of microhardness, the condition welded with energy of 15 kJ/cm got lower levels. In relation to toughness, it was not observed significant differences.

Aplicación del ensayo miniatura de embutido para la evaluación de la tenacidad a temperaturas criogénicas de aceros inoxidables austeníticos envejecidos isotérmicamente

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Saucedo-Muñoz, M. L.

2003-10-01

Full Text Available Two types of austenitic stainless steels JJl and JNl were isothermally aged at temperatures from 873 to 1173 K for 10 to 1000 min in order to study the microstructural evolution and its effect on fracture toughness at cryogenic temperatures. The Charpy V-Notch (CVN and Small-Punch (SPTesting methods were conducted at 77 K to evaluate the toughness of both solution treated and aged specimens. The fracture energy at 77 K determined for both methods showed a significant decrease with aging time for both steels. A linear correlation between the fracture energies of both methods was found. The intergranular precipitation of carbides and nitrides was responsible for the fracture toughness deterioration. The scanning electron microscope fractographs showed an intergranular brittle fracture and its fraction also increased with aging time and temperature. The presence of a more abundant intergranular precipitation resulted in a more rapid decrease in fracture toughness with aging time in JNl steel due to its higher content of C and N, compared to that of JJl steel.

Dos tipos de aceros inoxidables austeníticos, JJl y JNl, se envejecieron isotérmicamente a temperaturas entre 873 y 1.173 K por tiempos de 10 a 1.000 min, para estudiar la evolución microestructural y su efecto sobre la tenacidad a la fractura a temperaturas criogénicas. Los métodos de ensayo de impacto Charpy y el ensayo miniatura de embutido se llevaron a cabo a 77 K para evaluar la tenacidad de las muestras tratadas térmicamente. La energía de fractura determinada por ambos métodos mostró una disminución con el tiempo de envejecido para ambos aceros. Se encontró una relación lineal entre ambos valores de energía. La precipitación intergranular de carburos y nitruros fue la responsable de la pérdida de la tenacidad en las muestras envejecidas. La fractografía indicó que la fractura intergranular se incrementa con la temperatura y el tiempo de envejecido. La presencia

Separación selectiva de hierro y cromo de las lejías agotadas del decapado de acero inoxidable

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Gálvez, J. L.

2005-12-01

Full Text Available Stainless steel spent pickling baths are very complex solutions of metals and acids (HNO₃ and HF and are a very important environmental concern. Several processes have been developed for acid recovery (free and bounded acid with techniques like acid retardation, solvent extraction, evaporation and dialysis diffusion. In these processes, metallic content is precipitated and treated for its disposal. We have developed a process that permits the separation of metals by means of a selective precipitation, induced by adding free fluoride. Iron (Fe and chromium (Cr precipitate as pentafluorides and nitrogennickel (Ni remains in solution. After this stage, complex fluorides can be hydrolized with alkali to give iron and chromium hydroxides, releasing fluoride in solution

Los baños ácidos agotados del decapado de acero inoxidable son disoluciones muy complejas debido al alto contenido de metales y ácidos (HNO₃ y HF, por lo que constituyen un grave problema medioambiental. Existen tratamientos comerciales para la recuperación del ácido (libre o complejado que se basan en técnicas de retardo ácido, extracción con disolventes, evaporación o membranas. En estos procesos el contenido metálico es precipitado y tratado como un residuo. El grupo de investigación formado por los autores del presente trabajo ha desarrollado un procedimiento que permite el aprovechamiento de dichos metales mediante su recuperación selectiva con una técnica de precipitación modificada inducida por fluoruro libre. Se consigue la precipitación de hierro (Fe y cromo (Cr como pentafluoruros (pH 3-4,5 dejando el níquel en disolución. Posteriormente, los fluoruros complejos son hidrolizados con álcali dando lugar a hidróxidos de hierro y cromo, mientras que el fluoruro es redisuelto.

Influência da temperatura interpasse nas propriedades do aço inoxidável duplex durante a soldagem pelo processo a arco submerso

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Tatiana Resende Alvarez

2014-06-01

Full Text Available Os aços inoxidáveis duplex (AID são materiais que apresentam elevada resistência à corrosão com altos valores de resistência mecânica motivando sua utilização em diversos componentes de processo na indústria offshore. No entanto, existem grandes desafios na soldagem destes materiais em termos de produtividade e qualidade da junta produzida, tendo em vista sua ampla utilização desde componentes de pequenas espessuras, tais como umbilicais, até de grandes espessuras, como tubulações de linhas de injeção de água salgada. No que concerne a tubulações de espessuras pequenas é empregado satisfatoriamente o processo de soldagem Gas Tungsten Arc Welding (GTAW conhecido como TIG. No que diz a respeito a tubulações de paredes espessas foi implementado, recentemente, o processo automático de soldagem por arco submerso (SAW na linha de pré-montagem de tubulações, aumentando consideravelmente a produtividade das juntas produzidas. No entanto, existe uma grande demanda de tempo para a realização de um novo passe de solda, em virtude da máxima temperatura interpasse exigida ser inferior a 150ºC. Portanto, o presente trabalho apresenta os resultados da caracterização e avaliação da resistência à corrosão de uma junta soldada correspondente a uma tubulação de aço inoxidável duplex (AID UNS S31803 de 21,4 mm de espessura de parede soldada pelos processos de soldagem MIG (GMAW na raiz e arco submerso (SAW no enchimento e acabamento, empregando-se temperaturas interpasses entre 150 e 290ºC. Os resultados da caracterização das propriedades mecânicas, composição química e resistência à corrosão em diversas regiões da junta soldada foram comparadas com os obtidos para o metal de base (MB da tubulação, assim como com os valores mínimos exigidos pelas normas de projeto. Deste modo, o presente trabalho permite avaliar a influência da temperatura interpasse nas propriedades da junta em decorrência de um poss

Estudio de corrosión galvánica en pares latón/acero inoxidable y latón/fundición de hierro

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Ohanian, M.

2011-08-01

Full Text Available Corrosion attack in heat exchanger systems is a topic of main interest for the maintenance in each industrial plant. These are multigalvanic systems with particular geometric and fluidodynamic complexity. Corrosive damages include zinc selective dealeation in copper alloys. In order to explain zinc dealeation attack, this paper deals with laboratory scale testing, characterization and interactions between two copper and zinc alloys (Yellow brass –UNS C268– and Admiralty brass –UNS C443– compared to AISI 316 stainless steel and cast iron. The tests were performed at 20 °C in 1.5 % NaCl and 1.5 % Na₂SO₄ solutions, pH 8 and each material was characterized by potentiodynamic sweeps. The couples are analyzed by studying transient galvanic currents. We conclude about the cause of the analyzed pathology, brass protection potential ranges and its coupling compatibility with other metals.

El ataque por corrosión en los sistemas intercambiadores de calor constituye un problema para el mantenimiento de cualquier planta industrial. Se trata de sistemas multigalvánicos con particular complejidad geométrica y fluidodinámica. Las patologías corrosivas incluyen el fenómeno de dealeación selectiva de cinc en las aleaciones de cobre. A fin de explicar un caso particular de ataque por decinficación (deterioro en placa de intercambiador de calor de tubos de inoxidable, el presente trabajo aborda en ensayos a escala de laboratorio, la caracterización e interacciones entre dos aleaciones de cobre y cinc, (Yellow brass –UNS C268– y Admiralty brass –UNS C443–, respecto a acero inoxidable AISI 316 y fundición gris de hierro. Los ensayos se realizan a 20 °C en disoluciones de NaCl 1,5 % y Na₂SO₄ 1,5 % y pH 8. Se caracterizan electroquímicamente las aleaciones y materiales involucrados mediante barridos potenciodinámicos. Los pares galvánicos formados se analizan mediante el

Decapado de un acero inoxidable austenítico mediante mezclas ecológicas basadas en H2O2 - H2SO4 - iones F-

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Narváez, L.

2013-04-01

Full Text Available This study reports the pickling of 316L stainless steel using mixtures of hydrogen peroxide (H2O2, sulphuric acid (H2SO4 and fluoride ions as hydrofluoric acid (HF, sodium fluoride (NaF and potassium fluoride (KF. The decomposition of H2O2 in the mixtures was assessed at different temperatures 25 °C to 60 °C, with ferric ion contents from 0 to 40 g/l. According to the results obtained, were established the optimal condition pickling at 20 g/l of ferric ions, 25 °C and p-toluensulphonic acid as stabilizer of H2O2. The HF pickling mixture was the only capable to remove totally the oxide layer from the 316L stainless steel after 300 s. The fluoride salts pickling mixtures only remove partially the oxide layer (20 to 40 % aprox. after 300 s. When the pickling time was increased until 1200 s, the removal percentages were around to 80 %.En este estudio se presenta el decapado del acero inoxidable austenítico 316L utilizando mezclas de peróxido de hidrógeno (H2O2/ácido sulfúrico (H2SO4/iones fluoruro; los iones fluoruro provienen del ácido fluorhídrico (HF, fluoruro de sodio (NaF y fluoruro de potasio (KF. La estabilidad del H2O2 fue valorada modificando las concentraciones del ión férrico de 0 a 40 g/l y las temperaturas de 25 °C a 60 °C en las mezclas decapantes. Se establecieron las condiciones óptimas de decapado utilizando 20 g/l de iones férrico a 25 °C empleando el ácido p-toluensulfónico como estabilizante del H2O2. La mezcla que contenía HF fue la única capaz de eliminar completamente los óxidos superficiales del acero a tiempos de 300 s. Las mezclas a base de sales fluoradas eliminaron parcialmente los óxidos (20 y 40 % aprox. en 300 s. Al incrementar el tiempo de decapado hasta 1200 s se obtuvieron porcentajes de eliminación alrededor de un 80 %.

Estudo da soldagem de tubos de aço inoxidável duplex e superduplex na posição 5G Study of the welding of duplex and superduplex stainless steel pipes in the 5G position

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Pedro Ivo Guimarães de Vasconcellos

2010-09-01

Full Text Available Os aços inoxidáveis duplex e superduplex possuem uma microestrutura austeno-ferrítica com fração média de cada fase de cerca 50%. A microestrutura duplex é responsável pelas excelentes propriedades mecânicas, especialmente o limite de escoamento e a tenacidade, e pela elevada resistência a corrosão por pites e sob tensão em meios contendo cloretos. A soldagem destes aços é frequentemente uma operação crítica. Neste trabalho, um tubo de superduplex SAF 2207 foi soldado pelo processo TIG (GTAW no passe de raiz e eletrodo revestido (SMAW nos passes de enchimento, e um tubo de duplex SAF 2205 foi todo soldado pelo processo GTAW. A microestrutura do metal base, zona afetada termicamente (ZTA e metal de solda foi caracterizada e quantificada. As propriedades de tenacidade, resistência a corrosão e composição química foram avaliadas e correlacionadas. Os valores de tenacidade ao impacto Charpy-V foram considerados adequados. Não foi observada a precipitação de intermetálicos, carbonetos e nitretos. O melhor resultado no teste de corrosão da junta soldada de aço inox superduplex, comparado ao duplex, foi atribuído ao baixo teor de ferrita delta na solda e ZTA, e composição química da solda enriquecida em Cr, Mo, W e N.The duplex and superduplex stainless steels have an austenitic-ferritic microstructure with an average fraction of each phase of approximately 50%. This duplex microstructure is responsible for the excellent mechanical properties, specially the yield strength and toughness, and for the improved pitting and stress corrosion cracking resistance in chloride environments. Welding of these steels is often a critical operation. In this work, a superduplex stainless steel SAF 2507 pipe was welded by the GTAW process in the root pass and by SMAW process on filler passes, and one pipe of duplex SAF 2205 was entirely welded by the GTAW process. The microstructure of the base metal, heat affected zone (HAZ and weld

Recubrimientos de aluminio-silicio realizados por deposición química de vapor en lecho fluidizado sobre el acero inoxidable AISI 316

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José Luddey Marulanda Arevalo

2013-12-01

Full Text Available Los recubrimientos de aluminio-silicio fueron depositados sobre el acero inoxidable AISI 316 mediante deposición química de vapor en lecho fluidizado (CVD-FBR, en el rango de temperaturas de 540 a 560 ºC, utilizando un lecho formado por 2,5 g de silicio y 7,5 g de aluminio en polvo, y 90 g de lecho inerte (Alúmina, el cual se hizo fluidizar con Ar. Como gases activadores se usó una mezcla de HCl/H2, en relaciones de 1/10 a 1/16. Además, se varió el tiempo de deposición de los recubrimientos de 45 minutos a 1.5 horas, con una relación en volumen de 50% de gases activos y 50% de gases neutros. Se realizó una simulación termodinámica con la ayuda del programa informático Thermocalc, para obtener información de la posible composición y cantidad de material depositado, para las condiciones seleccionadas. En los recubrimientos se encuentran FeAl2Si, Fe2Al5 y FeAl2. Los recubrimientos aluminio-silicio fueron tratados térmicamente, para mejorar sus propiedades mecánicas y su comportamiento frente a la oxidación, por la interdifusión de los elementos de aleación, ya que el tratamiento térmico hace que el aluminio difunda hacia el substrato, y el hierro difunda hacia la superficie del recubrimiento, logrando la transformación de los compuestos anteriores en FeAl, Al2FeSi, Cr3Si, AlCrFe y AlFeNi.

Oxidación en vapor de agua a 700 ºC y 750 ºC del acero inoxidable AISI 317 recubierto con aluminio por CVD-FBR.

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Jose L. Marulanda

2014-01-01

Full Text Available Se realizó la oxidación del acero inoxidable austenítico AISI 317 recubierto con aluminio por deposición química de vapor en lecho fluidizado, a temperaturas de 700 °C y 750ºC, en un ambiente con 100% vapor de agua, para evaluar su comportamiento. Se realizaron curvas de ganancia de masa y las películas de óxidos se analizaron por medio de SEM y difracción de rayos X, para observar la morfología de los óxidos. Se realizó la simulación termodinámica del proceso de oxidación en vapor de agua de los substratos para conocer las posibles fases sólidas y gaseosas que se podrían formar, en presencia de una ambiente con 100% vapor de agua y una atmosfera de presión. La forma de ataque a 750 ºC es similar a 700 ºC, aunque la velocidad de oxidación es mayor, ya que la difusión de los elementos de aleación y las reacciones de oxidación son más rápidas. Los recubrimientos de aluminio tienen una buena resistencia a la oxidación en vapor de agua, ya que forman una capa superficial de Al 2 O 3 , que es compacta y adherente, la cual protege al substrato del ataque corrosivo.

Caracterización de una nueva membrana cerámica de microfiltración con soporte de tejido en acero inoxidable flexible

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Palacio, L.

1999-04-01

Full Text Available In this work we present the characterization of a ceramic flexible membrane, made by SynthesechemieⓇ, with a nominal pore size of 0.45 μm. This membrane consists in an α-alúmina porous support which has an embedded stainless steel metallic network, onto what a selective layer of titanium dioxide has been deposited. Membrane characterization has been realized with the aid of several techniques as: atomic force microscopy (AFM, air-liquid displacemente porosimetry and mercury porosimetry. Each tecnique giving information on different aspects: surface characteristics, bulk pores and active pores. Although the total pore size distribution is rather broad, the active pores (those opened to flux present a narrow distribution with a mean pore size very close to the manufacturer nominal value.

En este trabajo se ha abordado la caracterización de una membrana cerámica de microfiltración flexible, fabricada por SynthesechemieⓇ con tamaño de poro nominal de 0.45 μm. Ésta consiste en un soporte poroso de α-alúmina que posee un armazón formado por una red metálica de acero inoxidable sobre el cual existe una capa selectiva de óxido de titanio. La caracterización de la membrana ha sido realizada con diversas técnicas como: microscopia de fuerza atómica (AFM, porometría de desplazamiento aire-líquido y porosimetría de mercurio. Cada técnica da información sobre aspectos diferentes: superficie, poros totales y poros activos. Si bien la distribución total de tamaños de poro es bastante ancha, los poros activos (abiertos al flujo presentan una distribución de tamaños estrecha con un valor medio muy próximo al nominal.

Relaciones cuantitativas entre los contenidos de azufre y de sulfuros en los aceros inoxidables tipo AISI 303: influencia de la composición química de los sulfuros

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Botella, J.

1999-06-01

Full Text Available The work has been done with ten AISI 303 stainless steel rods which have similar chemical compositions, except for sulphur which varies between 0.25 and 0.36%. These steels are studied by Scanning Electron Microscopy (SEM and Energy Dispersive X-Ray Spectrometry (EDX. The sulphides are chemically microanalysed and the occupied volume determined by automatic image analysis. It can be inferred that the chemical composition of sulphides in AISI 303 steels is variable to some extent even though the steel chemistry is almost invariable. This could mean that solidification conditions and thermomechanical transformations are able to affect resulting in variations of sulphide compositions. Quantitative relations between sulphur and sulphide contents are established and the influence of sulphide chemical compositions on those relations is studied. The experimental results are compared with those obtained from theoretical calculations. A good approach is obtained when the difference between chemical compositions of real sulphides and the theoretical one, MnS, is taken into account.

Se trabaja con una serie de diez redondos de aceros inoxidables tipo AISI 303 de composiciones químicas prácticamente iguales a excepción del azufre que varía entre 0,25 y 0,36%. Se examinan los aceros mediante Microscopía Electrónica de Barrido (MEB y Espectrometría de Dispersión de Energías de Rayos X (EDX acoplada al MEB, analizándose químicamente los sulfuros y determinando, mediante análisis automático de imágenes, los volúmenes ocupados por los sulfuros. Parece deducible que la composición química de los sulfuros en el AISI 303 puede ser discretamente variable aún siendo prácticamente invariable la composición química del acero. Ello podría significar que las condiciones de solidificación y las transformaciones termomecánicas pueden influir, dando como resultado variaciones en la composición química de los sulfuros. Se establecen

EFICACIA DE LA PREPARACIÓN BIOMECÁNICA DE CONDUCTOS RADICULARES EN EL CRECIMIENTO MICROBIOLÓGICO EN PIEZAS DENTARIAS ANTERIORES CON NECROSIS PULPAR EN PACIENTES DE LA CLÍNICA ODONTOLÓGICA UANCV. JULIACA, PUNO. 2013

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TAPIA CONDORI, RILDO PAÚL

2015-01-01

RESULTADOS TABLAS DE INFORMACIÓN GENERAL TABLAS QUE RESPONDEN A LOS OBJETIVOS MICROBIOLOGÍA ENDODÓNTICA VÍAS MICROBIANAS DE ACCESO TÚBULOS DENTINARIOS CAVIDAD ABIERTA MEMBRANA PERIODONTAL REQUERIMIENTOS PARA UN PATÓGENO ENDODÓNTICO POTENCIAL DE OXIDO-REDUCCIÓN ANTAGÓNICOS INTERMICROBIANOS NECROSIS PULPAR TIPOS DE NECROSIS PREPARACIÓN BIOMECÁNICA EN PIEZAS CON NECROSIS PULPAR INSTRUMENTOS CONVENCIONALES DE ACERO INOXIDABLE CARACTERÍSTICAS DE LAS LIMAS K DE ACERO INOXIDABLE PROPIEDADES FÍSICAS ...

Aceros aluminotérmicos. Nuevas aplicaciones

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Duart Blay, J. M.

2004-02-01

. Particular aplicación o interés presentan en la tecnología de los ferrocarriles para la obtención del carril continuo, prácticamente implantado en todo el mundo y en soldaduras cable de cobre-carril de acero empleadas en las señalizaciones para control de tráfico. En este trabajo se aportan las bases termodinámicas de la aluminotermia del hierro y su aplicación a la soldadura compleja de cruzamientos, juntas de dilatación y desvíos en FF.CC, que combinan aceros Hadfield, aceros inoxidables y aceros perlíticos de diferentes propiedades mecánicas. Las uniones deben ser compactas, resistentes y duras en los niveles que se citan en el trabajo, según requisitos exigidos por la circulación en líneas de alta velocidad (350 km/h., actualmente en construcción en España, pero que resultan generalizables a otro tipo de líneas menos exigentes y a ferrocarriles mineros.

Vida a la fatiga de juntas soldadas del acero inoxidable AISI 316L obtenidas mediante el proceso GMAW

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Puchi-Cabrera, E. S.

2007-06-01

Full Text Available An investigation has been conducted in order to determine the effect of both the metallic transfer mode (pulsed arc or short circuit and the O2 content in the Ar/O2 gas mixture, of the gas-metal arc welding process (GMAW, on the fatigue life under uniaxial conditions of welded joints of 316L stainless steel. It has been concluded that the mixture of the protective gases employed in the process could have an important influence on the fatigue life of the welded joints of such steel in two different ways. Firstly, through the modification of the radius of curvature at the joint between the welding toe and the base metal and, secondly, through a more pronounced degree of oxidation of the alloying elements induced by a higher O2 content in the mixture. As far as the metallic transfer mode is concerned, it has been determined that the welded joints obtained under a pulsed arc mode show a greater fatigue life in comparison with the joints obtained under short circuit for both gas mixtures.

Se ha llevado a cabo una investigación con la finalidad de determinar el efecto, tanto del modo de transferencia metálica (arco pulsado o cortocircuito como del contenido de O2 en la mezcla de gases protectores Ar/O2, del proceso de soldadura a tope mediante arco metálico con protección gaseosa (GMAW, sobre la vida a la fatiga en condiciones uniaxiales de juntas soldadas del acero inoxidable AISI 316L. Dicho trabajo ha permitido concluir que la composición de la mezcla de gases protectores del proceso GMAW pudiera tener una influencia importante en la vida a la fatiga de las juntas soldadas de dicho material, a través de dos formas distintas: primero, mediante la modificación del radio de curvatura entre la raíz del cordón de soldadura y el metal base y, en segundo lugar, a través del mayor grado de oxidación de los elementos de aleación. En cuanto al modo de transferencia metálica, se determinó que las juntas soldadas mediante arco pulsado

Viabilidad de nuevos materiales frente a materiales convencionales en la construcción de pantalanes

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Marín Gallego, Enric

2012-01-01

Este proyecto estudia la viabilidad de nuevos materiales estructurales, tales como los materiales compuestos, comparándolos con materiales convencionales como el acero, el acero inoxidable o el hormigón.

Desarrollo de un modelo matemático de diferencias finitas para el análisis del campo de temperaturas en la soldadura por arco de chapas finas de acero inoxidable

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Miguel, V.

2010-12-01

Full Text Available This work develops a finite difference method to evaluate the temperature field in the heat affected zone in butt welding applied to AISI 304 stainless steel thin sheet by GTAWprocess. A computer program has been developed and implemented by Visual Basic for Applications (VBA in MS-Excel spreadsheet. The results that are obtained using the numerical application foresee the thermal behaviour of arc welding processes. An experimental methodology has been developed to validate the mathematical model that allows to measure the temperature in several points close to the weld bead. The methodology is applied to a stainless steel sheet with a thickness lower than 3 mm, although may be used for other steels and welding processes as MIG/MAG and SMAW. The data which has been obtained from the experimental procedure have been used to validate the results that have been calculated by the finite differences numerical method. The mathematical model adjustment has been carried out taking into account the experimental results. The differences found between the experimental and theoretical approaches are due to the convection and radiation heat losses, which have not been considered in the simulation model.With this simple model, the designer will be able to calculate the thermal cycles that take place in the process as well as to predict the temperature field in the proximity of the weld bead.

En este trabajo se desarrolla un método de diferencias finitas para calcular el campo de temperaturas en la zona afectada por el calor en la soldadura de dos chapas de acero inoxidable AISI 304, soldadas mediante el procedimiento GTAW. Se ha desarrollado un programa informático implementado en libros de cálculo MS-Excel con Visual Basic para Aplicaciones (VBA. Los experimentos modelizados a través de la aplicación numérica predicen el comportamiento térmico de un procedimiento de soldadura. Para la validación del modelo matemático se ha desarrollado un

Efecto de la velocidad y ángulo de impacto en la resistencia a corrosión - erosión de aceros inoxidables recubiertos con TiN

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José Ricardo Cano Rodas

2004-01-01

Full Text Available Fueron estudiados los mecanismos de degradación superficial en aceros inoxidables austenítico AISI 304 y martensítico AISI 420, con y sin recubrimiento cerámico de TiN, aplicado mediante técnica de deposición física de vapor PVD por arco pulsado, sometidos a erosión (solución de agua destilada con 30% en peso de partículas de sílice, corrosión (solución ½ M H2SO4 + 3.5% NaCl y efectos sinérgicos corrosión - erosión. Fue construido un dispositivo para realizar los ensayos descritos con la posibilidad de variar la velocidad y el ángulo medio de impacto de las partículas sobre la superficie de las muestras. Marcas características fueron observadas en las superficies desgastadas, siendo la condición de ángulo rasante la de mayor efecto nocivo tanto para las superficies desnudas como para las recubiertas con TiN. El nivel de deterioro superficial aumentó con la velocidad de impacto, al tiempo que se evidenció la importancia de la adherencia de las películas protectoras al substrato para la obtención de una buena resistencia a corrosiónerosión. La sinergia corrosión-erosión presentó, en algunas ocasiones, un efecto positivo para la superficie, ya que el impacto de las partículas duras causó intensa deformación plástica pero no consiguió remover material de la superficie.

Formación de fase sigma en uniones soldadas de acero inoxidable súper dúplex fundido

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Garin, J. L.

2011-08-01

Full Text Available This paper decribes the microstructural characteristics of weldments of cast super duplex stainless steel (J93404, being subjected to annealing processes to induce formation of sigma-phase at high temperatures. The influence of heating time at 1073 K, 1123 K and 1173 K upon precipitation of sigma in the heat affected zone, base metal and fusion zone of the weldments was analyzed. The experimental results revealed the formation of this intermetallic compound throughout decomposition of the ferritic phase into austenite and sigma. At earlier stages of the transformation the phase rapidly nucleates and growth along the ferrite-austenite grain boundaries, and then massively advances towards the bulk of the ferritic zone with greater effectiveness as temperature increases. The formation of sigma-phase in all weldments resembles the Johnson-Mehl-Avrami’s mechanism stated for nucleation and growth.

El presente trabajo describe las características microestructurales de uniones soldadas de acero súper dúplex fundido (J93404, al ser sometidas a procesos de recocido para inducir la formación de fase sigma a altas temperaturas. Se analizó la influencia del tiempo de calentamiento a 1.073 K, 1.123 K y 1.173 K sobre la precipitación de fase sigma en la zona afectada térmicamente, metal base y zona de fusión de los conjuntos soldados. Los resultados experimentales evidenciaron la formación de este compuesto intermetálico por descomposición de la fase ferrítica en austenita y sigma. Al comienzo de la transformación la fase nuclea y crece rápidamente en los bordes de grano austenita-ferrita, extendiéndose luego masivamente hacia el seno de la zona ferrítica, con mayor efectividad en términos del aumento de la temperatura de proceso. La formación de sigma en todas las uniones soldadas obedece a un mecanismo de nucleación y crecimiento del tipo Jonson-Mehl-Avrami.

Resistencia a la oxidación de aleaciones Ni-Cr-Al plaqueadas por láser sobre aceros al carbono e inoxidables austeníticos

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de Damborenea, J.

1995-04-01

Full Text Available Laser surface cladding has been carried out by means of a 5 kW CO₂ continuous wave laser on both a mild and a stainless steel. A powder injection technique has been used to deliver a Ni-Cr-Al alloy onto the steel molten pool. After processing, samples were analyzed by optical and scanning electron microscopy in order to know the microstructure and composition of present phases. High temperature corrosion resistance tests were done in an oxidant environment at temperatures of 950 °C. Phase transformations and corrosion behaviour are discussed. A general conclusion is the suitability of these alloys to bear oxidation due to the formation of protective oxide layers on their surface.

Se realiza un estudio sobre la obtención de recubrimientos de superficie mediante un láser continuo de CO₂ de 5 kW de potencia de salida. Mediante la técnica de inyección de partículas, se realizaron plaqueados en superficie de Ni-Cr-Al sobre un acero suave y otro inoxidable de tipo 316. Tras el procesado, se estudió la microestructura de las probetas obtenidas. Posteriormente, se procedió a su ensayo en atmósfera oxidante a 950 °C, observándose la evolución de la microestructura, la formación de las capas de óxido y la cinética del proceso. Como conclusión general, destaca, independientemente de la base sobre la que se obtienen los recubrimientos, la gran resistencia del material a la oxidación, seguramente debida a la formación de capas de alúmina que actúan como barreras frente al ataque del oxidante.

Cobre antimicrobiano contra patógenos intrahospitalarios en Perú

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Edwin Neciosup

2015-01-01

Full Text Available Introducción: Las infecciones intrahospitalarias (IIH constituyen un problema de salud pública que generan grandes gastos por parte de los gobiernos, debido a que los patógenos causantes de IIH presentan resistencia a fármacos y generan una mayor permanencia de los pacientes, pues la infraestructura hospitalaria constituye un reservorio favorable para los patógenos. Las superficies de cobre surgen como opción sanitaria y efectiva para controlar el crecimiento y propagación de estos patógenos. Objetivos: Evaluar la actividad bactericida de las superficies de cobre contra los principales bacterias patógenas causantes de IIH (Escherichia coli, Pseudomonas aeruginosa y Staphylococcus aureus. Diseño: Estudio experimental con muestreo no probabilístico. Lugar: Hospital Regional Docente las Mercedes (HRDLM y Hospital Provincial Docente Belén (HPDB, Lambayeque, Perú. Materiales: Nueve cepas bacterianas, 3 de E. coli , 3 de P. aeruginosa y 3 de S. aureus; superficies metálicas (1 cm² de cobre y acero inoxidable (control . Intervenciones: Las 9 cepas bacterianas fueron proporcionadas por los hospitales HRDLM (4 cepas y HPDB (5 cepas. Los análisis de ANOVA y de Tukey fueron aplicados para evaluar la actividad bactericida de las superficies de cobre y acero inoxidable contra las 9 cepas causantes de IIH, usando los programas estadísticos Minitab y Sigmaplot, respectivamente. Principales medidas de resultados: Diferencias en el crecimiento bacteriano sobre superficies de cobre o acero inoxidable, con respecto al tiempo de exposición. Resultados: Las 9 cepas -3 de P. aeruginosa, 3 de E. coli y 3 de S. aureus - expuestas a superficies de cobre fueron eliminadas en 10, 15 y 60 minutos, respectivamente. La carga bacteriana de las células expuestas en superficies de acero inoxidable permaneció constante y viable por periodos mayores a 60 minutos. Además, las superficies de cobre eliminaron más rápido a las bacterias Gram negativas (P

Deposición electroforética de una porcelana dental sobre acero inoxidable austenítico 304

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Vargas, G.

2003-02-01

Full Text Available An alternative technique for the production of dental restorations with porcelain, is the electrophoretic deposition (EPD. In this work, deposits of dental porcelain on stainless steel were obtained by EPD using water, ethanol and isopropanol as suspension mediums. The effect of the porcelain concentration, the intensity of the electric field and the suspension medium on the quantity of deposited mass were studied. All the tests were carried out at constant voltage, using a deposition time of 3 min. The particle size of the dental porcelain was in the range between 1.5 and 2.3 μm in the suspension. The results showed that the porcelain in the aqueous medium presented the major deposition velocity, in comparison with both ethanol and isopropanol. However, due to low the low suspension stability and hydrolysis of the water problems, the best coating finishes were obtained with ethanol. These results were obtained applying voltages between 70 and 150 V, for a deposition time of 3 min. Using isopropanol heterogeneous deposits were obtained due to the low suspension stability and to electrochemical reactions problems in the working electrodes, resulted from the high voltages application.

Una técnica alternativa para la fabricación de restauraciones dentales con porcelana, es la deposición electroforética (EPD. En este trabajo depósitos de porcelana dental sobre acero inoxidable fueron obtenidos por EPD utilizando como medios de suspensión: agua, etanol e isopropanol. Se estudió el efecto de la concentración de porcelana, de la intensidad del campo eléctrico y del medio de suspensión sobre la cantidad de masa depositada. Todas las pruebas fueron realizadas a voltaje constante, utilizando un tiempo de deposición de 3 min. La porcelana dental utilizada presentó un intervalo de tamaño de partícula entre 1,5 y 2,3 μm. Los resultados mostraron que la porcelana en el medio acuoso presentó la mayor velocidad de deposición, en

Análisis experimental del desgaste entre UHMWPE y acero inoxidable 316l empleados en la manufactura de prótesis coxofemorales

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Ricardo Gustavo Rodríguez Cañizo

2010-07-01

Full Text Available Título en inglés: Experimental wear analysis of UHMWPE and stainless 316l used in the manufacturing of coxofemoral prosthesis. Resumen La causa más común de falla en prótesis coxofemorales es el aflojamiento entre los componentes que conforman el sistema, de manera específica la copa acetabular y la cabeza femoral. En esta investigación se presenta un análisis tribológico del desgaste en los componentes mencionados, ya que cuando las superficies en contacto se desgastan, la funcionalidad mecánica del sistema se compromete, debido al cambio de geometría de los mismos, dando como resultado un juego mecánico entre la copa y la cabeza. Los materiales considerados en este estudio son el polietileno de ultra elevado peso molecular (UHMWPE, por sus siglas en inglés para la copa acetabular, y acero inoxidable 316L para la cabeza femoral. Esta combinación de materiales representa hoy en día la recomendación más usual por parte de los cirujanos para pacientes de la tercera edad. La tasa anual de desgaste se determinó de manera experimental y se cuantificó la cantidad de material desprendido durante el contacto. Se establecieron las condiciones de carga de forma analítica, considerando las que actúan sobre la cabeza femoral a lo largo del área de desgaste durante la marcha humana. Posteriormente, se realizó el análisis experimental de desgaste utilizando una máquina tribológica de configuración perno-sobre-disco (pin-on-disk, diseñada de manera específica para este estudio. Las pruebas para determinar la pérdida volumétrica de los componentes se realizaron bajo tres condiciones de operación: en seco, lubricada con agua destilada y lubricada con suero bovino. El marco experimental considerado consistió en pernos de UHMWPE sobre discos de acero inoxidable 316L simulando el desgaste equivalente a diez años de uso de la prótesis. Finalmente, de los resultados obtenidos se puede establecer que el desgaste y la cantidad de part

Estudio de microestructura y composición de la oxidación en vapor a 700 y 750oC de los aceros austeníticos AISI 304, 316 y 317

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José Luddey Marulanda

2013-01-01

Full Text Available Se ha investigado la oxidación de los aceros inoxidables austeníticos AISI SAE: 304, 316 y 317; a temperaturas de 700 y 750oC, en una atmósfera próxima al 100% de vapor de agua, y de 10 a 1000h de exposición. La finalidad es comprobar la calidad de los aceros austeníticos y estudiar la morfología, composición y estructura de la fases de las capas formadas en la cascarilla del óxido de las muestras por Microscopía Electrónica de Barrido (SEM, Análisis de Rayos X por Dispersión de Energía (EDAX y Difracción de Rayos X (XRD, respectivamente. Así como también, se ha realizado a diferentes tiempos un estudio sistemático de termogravimetría de las muestras oxidadas, donde se ha observado que el acero AISI 304 presentó la menor ganancia de masa y el acero AISI 316 fue el de mayor de masa respecto a los tres aceros del trabajo. Adicionalmente fue realizado un estudio teórico de simulación termodinámica de oxidación en vapor de los tres aceros, en las mismas condiciones experimentales y mediante el programa Thermo-calc. En estos aceros oxidados se han comprobado la presencia de estructuras de fases de óxidos como: Fe2O3, espinelas protectoras Fe3O4 y Cr2NiO4, y óxidos mixtos de tipo (CrxFey2O3, (Fe,Cr,Mn3O4 y Ni6MnO8. Finalmente, se discute un posible mecanismo de la formación de las capas de óxidos de las muestras ensayadas.

Soldagem por Difusão de Aços Inoxidáveis para Fabricação de Trocadores de Calor Compactos

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Marcus Vinícius Volponi Mortean

2016-03-01

Full Text Available Resumo A união de materiais diferentes ou componentes com geometrias complexas muitas vezes requer processos de uniões especiais, como por exemplo, uma fonte de energia de alta densidade como laser ou feixe de elétrons para soldagem por fusão ou mesmo um processo de soldagem no estado sólido. Em particular, este trabalho descreve os experimentos recentes da aplicação da soldagem por difusão no estado sólido (SDES para diferentes tipos de aços inoxidáveis: austenítico AISI 316L, duplex UNS 31803 e superduplex UNS 327250. A soldagem por difusão foi realizada sob alto vácuo a 1050 °C, durante 60 minutos, empregando uma pressão uniaxial de 18-35 MPa. A qualidade da união foi avaliada por microscopia óptica e testes mecânicos. Os resultados preliminares indicam a necessidade de otimização dos parâmetros de processo para os aços duplex e superduplex. Os resultados positivos alcançados no presente trabalho permitiram a fabricação de protótipos de trocadores de calor compacto em aço inoxidável, utilizando o novo método de fabricação, desenvolvido por LABTUCAL / UFSC, através do qual o processo de corte a jato de água é aplicado para confeccionar com precisão os canais do núcleo do permutador de calor.

Evaluación electroquímica de soldaduras en tubos capilares de acero inoxidable

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Javier E. Rodríguez-Yáñez

2014-02-01

Full Text Available La recuperación de capilares de acero 316L utilizados en pozos geotérmicos neutros, por medio de soldadura orbital autógena, se evalúa desde el punto de vista de su resistencia a la corrosión en las condiciones de utilización, mediante técnicas electroquímicas básicas. En el pretratamiento se encuentra que es más conveniente realizar un decapado químico previo a la soldadura por 5 minutos. Mientras que posteriormente a la soldadura, la aplicación de tratamiento térmico de reducción de tensiones no se justifica desde el punto de vista de la resistencia a la corrosión. También se plantea la comparación de los capilares soldados respecto a capilares nuevos y usados, teniendo los capilares soldados un comportamiento intermedio entre ambos.

PROPIEDADES MECÁNICAS DE PELÍCULAS HÍBRIDAS (ORGÁNICO-INORGÁNICO SOBRE ACERO INOXIDABLE 304 Mechanical Properties of Hybrid Films (Organic-Inorganic on Stainless Steel 304

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Jorge H. Bautista-Ruiz

2011-12-01

Full Text Available This article shows the creation of ceramic films of the SiO2-TiO2 Organic Polymer hybrid system from Tetraethyl-Orthosilicate (Si (OC2H54 and Titanium Tetrabutoxide (Ti(OBu4 synthesized through the sol-gel method in several volumetric concentrations of precursors. This hybrid system was deposited on AISI 304 stainless steel substrates through the dip-coating technique. Feasibility for obtaining hybrid and homogeneous coatings on this type of substrate and evaluating the surface properties was studies. For such a purpose, the coating microhardness and adhesion were studies. Additionally, the film surface was characterized through the SEM (Scanning Electron Microscopy. The study concluded that characteristics of films change in function of the volumetric amount of precursors used for creating films.Este trabajo muestra la conformación de películas cerámicas del sistema híbrido SiO2-TiO2-Polímero Orgánico, a partir de tetraetil-ortosilicato (Si (OC2H54, y tetra-butoxido de titanio (Ti(OBu4 y sintetizado por el método sol-gel en diferentes concentraciones volumétricas de los precursores. Este sistema híbrido se depositó sobre sustratos de acero inoxidable AISI 304 mediante la técnica de inmersión (dip-coating. Se estudió la viabilidad de obtener recubrimientos híbridos homogéneos sobre este tipo de sustrato y evaluar las propiedades superficiales. Para tal efecto, se estudió microdureza y adhesión del recubrimiento. Adicionalmente, se caracterizó la superficie de las películas por microscopía electrónica de barrido (MEB. Del estudio se concluye que las características de las películas cambian en función de la cantidad volumétrica de los precursores utilizados en la conformación de las mismas.

Caracterização e avaliação da resistência à corrosão na soldagem de tubulação de aço inoxidável duplex UNS S31803 pelo processo a arco submerso Characterization and evaluation of corrosion resistance of welded joint of duplex stainless steel pipe UNS S31803 by submerged arc process

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Juan Manuel Pardal

2011-12-01

Full Text Available O presente trabalho apresenta os resultados da caracterização e avaliação da resistência à corrosão de uma junta soldada correspondente a uma tubulação de aço inoxidável duplex (AID UNS S31803 de 35 mm de espessura de parede soldada pelos processos de soldagem TIG (GTAW na raiz e arco submerso (SAW no enchimento e acabamento. Foram empregados como consumíveis de soldagem metais de adição de liga 25Cr-9Ni-4Mo (% em peso. Os resultados da caracterização das propriedades mecânicas, composição química e resistência à corrosão em diversas regiões da junta soldada foram comparados com os obtidos para o metal de base da tubulação, assim como com os valores mínimos exigidos pelas normas de projeto. Os resultados obtidos demonstram claramente a possibilidade da implementação do processo SAW na pré fabricação de tubulações de paredes espessas de AID, tendo em vista os resultados das propriedades analisadas e a grande demanda na construção e montagem de tubulações desta família de aço inoxidáveis na indústria offshore.This work presents the mechanical properties, microstructural and corrosion resistance evaluation of a welded joint of duplex stainless steel (DSS pipe with 35 mm wall thickness. The joint was welded by gas tungsten arc welding (GTAW process in the root passes and submerged arc welding (SAW in the filling and cap passes using filler metals with composition 25Cr-9Ni-4Mo (%wt.. The results of mechanical properties, chemical composition and corrosion resistance characterization in different regions of the welded joint were compared to the base metal and to the specifications required by the standards applied in the project. The main focus of this work was to show the successful utilization of SAW process in the welding of thick wall pipes of DSS. The application of high productivity process such as SAW has a crescent demand in offshore industry.

DEFORMACIÓN ELÁSTICA RESIDUAL EN LÁMINAS DE ACERO AISI 304 RECUBIERTAS CON UNA PELÍCULA DE NITRURO DE TITANIO DEPOSITADA POR PVD-MAGNETRON SPUTTERING

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H. A. COLORADO

2009-01-01

Full Text Available Se realizó una caracterización mediante difracción de rayos x (DRX en láminas de acero inoxidable AISI 304 recubierto con una capa de nitruro de titanio de 3 um de espesor, obtenida mediante deposición física de vapor (PVD-MAGNETRON SPUTTERING a una temperatura de 200 °C. se tomaron imágenes de microscopía electrónica de barrido (MEB, microscopía óptica (MO y microscopía de fuerza atómica (MFA para caracterizar el sustrato, la capa y la zona cercana a la intercara. adicionalmente se determinó la deformación elástica residual asociada con el ensanchamiento de los picos de DRX.

Electrochemical noise transient analysis for 316 and Duplex 2205 stainless steels in NaCl and FeCl; Analisis de los transitorios de ruido electroquimico para aceros inoxidables 316 Y - DUPLEX 2205 en NaCl Y FeCl

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Almeraya-Calderaon, F.; Estupinan, F.; Zambrano, P.; Martinez-Villafane, A.; Borunda, A.; Colas, R.; Gaona-Tiburcio, C.

2012-11-01

This work shows the results obtained from electrochemical noise measurements for different materials exhibiting pitting corrosion. The transients presented in the potential and current time, correlates with the scanning electron microscopy (SEM) surface analysis. Electrochemical measurements were made at different exposure times to obtain the correlation. The materials used were stainless steel austenitic 316 and duplex 2205, immersed in ferric chloride (FeCl3) and sodium chloride (NaCl) electrolytes. SEM analysis shows that the transients observed in the time series, really correspond to the activity of pit nucleation developed over the surface of the electrodes. (Author) 31 refs.

INFLUENCIA DE LOS RECUBRIMIENTOS DÚPLEX SOBRE LAS PROPIEDADES MECÁNICAS Y RESISTENCIA AL DESGASTE DEL ACERO AISI 4140 BONIFICADO

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Francisco Javier Bolívar Osorio

Full Text Available El acero AISI 4140 es un acero de baja aleación al cromo/molibdeno de elevada resistencia mecánica y buena tenacidad, el cual se utiliza para la fabricación de piezas de maquinaria como piñones, cigüeñales, ejes de levas, etc. Sin embargo, su resistencia al desgaste es bastante limitada y suele ser mejorada mediante el tratamiento superficial de la nitruración. El propósito de este trabajo consistió en mejorar las propiedades mecánicas e incrementar la resistencia al desgaste del acero 4140 mediante la aplicación de un tratamiento superficial DUPLEX consistente en la nitruración líquida (conocida como Teniffer seguido del depósito de un recubrimiento duro de nitruro de titanio (TiN. La microestructura cristalina fue evaluada mediante difracción de rayos X, la morfología y la composición química fue determinada por microscopía SEM y espectroscopía de energía dispersiva de rayos X (EDS, las propiedades tribológicas fueron analizadas mediante mediciones en un tribómetro de tipo esfera sobre disco y la microdureza se determinó por el método Vickers. Las muestras tratadas con el recubrimiento dúplex mostraron una resistencia al desgaste 4 veces mayor que la muestra en estado bonificado, lo cual demuestra la aplicación potencial que tiene el acero 4140 sometido a este tratamiento dúplex.

“MEDICION DE PARAMETROS GENERADORES DE ESFUERZOS RESIDUALES DURANTE EL PROCESO DE SOLDADURA DE ACERO INOXIDABLE AUSTENITICO AISI 304L”.

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García López, Christian Jesus

2012-01-01

En la actualidad los procesos de soldadura por arco eléctrico se han convertido en la técnica por excelencia para la unión del acero y sus aleaciones. Se puede mencionar que la importancia de la soldadura, es tal, que sin ella no serían posibles muchos de los productos y servicios que cotidianamente son consumidos o requeridos por las sociedades contemporáneas actuales. Cada vez con mayor longitud y diámetro se instalan líneas de tubería para la distribución y conducción de tod...

Estudio in vitro de la citotoxicidad y genotoxicidad de los productos liberados del acero inoxidable 316L con recubrimientos cerámicos bioactivos Cytotoxic and genotoxic study of in Vitro released products of stainless Steel 316l with bioactive ceramic Coatings

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María Elena Márquez Fernández

2007-03-01

Full Text Available El acero inoxidable AISI 316L es el biomaterial mas utilizado para la fabricación de implantes temporales, pero presenta limitaciones para implantes permanentes debido a la liberación de iones metálicos hacia los tejidos circundantes, produciendo especies reactivas de oxígeno (ERO y daño en ADN, factores que aumentan el riesgo de aparición de tumores locales y fallas mecánicas del implante. Una estrategia utilizada para disminuir la liberación de iones es la modificación superficial de los implantes metálicos por medio de recubrimientos inorgánicos, cerámicos o vítreos, aplicados por el método sol-gel, el cual presenta una serie de ventajas comparativas con otras técnicas de deposición, como buena adherencia, aplicación sencilla, mínimos problemas de secado, bajas temperaturas de densificación y posibilidad de agregar partículas y/o grupos orgánicos que mejoran la adherencia celular al implante aumentando su biocompatibilidad. En el presente trabajo se evaluaron los efectos citotóxico por medio de la técnica MTT, y genotóxico por electroforesis en gel de células individuales (Ensayo Cometa, sobre células de la línea celular CHO, de los productos liberados en medio MEM por el acero inoxidable 316L sin recubrir, recubierto con una monocapa de vidrio de sílice (MC, o con doble capa que contiene partículas bioactivas de hidroxiapatita (HA, vidrio (V o vitrocerámico (VC, después de un periodo de 30 días. Los resultados muestran que a los 30 días de envejecimiento en medio MEM no se encuentra ningún efecto citotóxico, pero se encontró efecto genotóxico en las probetas de A y MC que no representa un peligro inminente a sistemas celulares. The stainless steel AISI 316L is the must used biomaterial for the making of temporal prosthesis, but it presents severe limitations for permanent implants due to the generation and migration of metallic ions to the surrounding peripheral tissues, which produces oxygen reactive

Avaliação da proporção de fases em juntas soldadas de tubulações de aço inoxidável duplex mediante aplicação de ensaios não destrutivos Evaluation of phases proportions in welded joints of duplex stainless steel by non-destructive testing

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Guttemberg Chagas de Souza

2013-06-01

Full Text Available Os aços inoxidáveis Duplex (AID aliam uma excelente resistência à corrosão com elevada resistência mecânica devido à fina microestrutura bifásica composta por quantidades similares de ferrita (δ e austenita (γ. Portanto, estas ligas são utilizados em tubulações e equipamentos industriais onde se requer elevada relação resistência/peso, especialmente em empreendimentos de construção e montagem off-shore. Entretanto, as condições operacionais, na soldagem de campo, podem promover um significativo desbalanço microestrutural destas fases, resultando em decréscimo das propriedades mencionadas. A inspeção com o ferritoscópio é uma avaliação normalmente utilizada nestas atividades. Durante a avaliação com esta técnica pode ocorrer a rejeição da junta soldada quando o metal de solda se encontra com valores de ferrita fora das faixas estabelecidas pelas especificações de projeto. Assim, torna-se importante a análise destas juntas, com outras técnicas complementares, tal como a utilização das réplicas metalográficas. Este fato motivou a avaliação da proporção de fases em spools de AID de espessuras relativamente finas, soldados no campo, comparando-se as técnicas não destrutivas descritas. Os resultados denotam valores semelhantes, contudo o resultado pode ser influenciado pela forma e condições superficiais da junta soldada.Duplex stainless steels are high strength and corrosion resistant alloys, whose properties are devoted to the fine microstructure composed by similar amounts of ferrite and austenite and also to the high concentrations of Cr, Mo and N in solid solution. Not for coincidence, duplex steels are extensively used in chemical and petrochemical industries. However, welding operations conditions can promote the unbalance of the ferrite/austenite proportions mainly in the welding metal, with decrease of the properties mentioned. For this reason, non destructive measurements of ferrite content

Estudo do processo de fabricação de tubos flexíveis de aço inoxidável duplex UNS 32304 utilizados na indústria de petróleo e gás Study of the manufacturing process of UNS 32304 flexible pipes for the oil and gas industry

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Ida Paula Gusmão de Oliveira

2013-03-01

Full Text Available A principal característica dos aços inoxidáveis duplex é o equilíbrio entre as fases austenita e ferrita, que garantem ao material melhores índices de resistências à corrosão e mecânica. No entanto, durante o processo de soldagem, ocorrem modificações estruturais, principalmente no balanço destas fases. Este desbalanceamento, em função dos níveis de solicitações mecânicas, pode levar tais regiões soldadas ao colapso. No intuito de minimizar o desequilíbrio das fases na região soldada, diversas técnicas são utilizadas, tais como inserção de metal de adição com elementos austenitizantes, uso de gás de proteção com nitrogênio ou, em outros casos, controle pós soldagem. Buscou-se identificar o verdadeiro efeito dos parâmetros de soldagem e do tratamento térmico especificado pela literatura em situações de campo. Através de uma avaliação temporal, observando uma linha de produção de tubulação flexível de aço inoxidável duplex UNS 32304 durante três anos, utilizando-se de procedimentos convencionais de soldagem com e sem a utilização de tratamento térmico foram observadas as falhas por fratura na zona termicamente afetada (ZTA. Foi utilizado um indutor localizado para o tratamento térmico, gerando um intenso fluxo de calor que promoveu temperaturas da ordem de 1000 ºC a altíssimas taxas de subida e descida, conforme estabelecem algumas literaturas.The main characteristic of duplex stainless steels is the balance between ferrite and austenite phases, wich ensures to such material the best levels of corrosion and mechanical resistance. However, during the welding process, structural modifications occur, especially with regard to the balance of these phases. This imbalance, depending on the levels of mechanical stress, may lead welded regions to collapse. In order to minimize the imbalance of the phases in the welded steel, several techniques are used, such as the insertion of filler metal with

Soldabilidad del acero inoxidable austenitico

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Pedro Pablo Torres-Medina

2002-01-01

Full Text Available This work involves welding stainless steel AISI 321H applying technical specifications according to welding standards, know the properties and phenomena that occur in the base metal and select the appropriate input material to ensure good quality of the process.

Reciclado de las aguas de decapado

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López, F. A.

1998-05-01

Full Text Available Pickling liquors from steel industry, listed as hazardous wastes in most industrializated countries, have been treated by means of several procedures in order to recover the iron and other metals and to obtain an environmental friendly effluent. Depending on the treatment employed, different valuable ferrous products have been obtained. Ammoniojarosite and zinc ferrite were precipitated from the previously oxidised ferrous solutions.

En la mayoría de los países industrializados, se incluyen las aguas de decapado, tanto las procedentes de los aceros al carbono como de aceros inoxidables, dentro de las listas de residuos tóxicos y peligrosos. Se presentan en este trabajo los resultados obtenidos en las investigaciones realizadas en los últimos años en los que se ha estudiado el tratamiento y recuperación de aguas de decapado de aceros comunes e inoxidables. Su tratamiento se ha enfocado hacia la consecución de dos objetivos: la recuperación del contenido total de metales y la obtención de un efluente de menor impacto ambiental. Se presentan los procedimientos estudiados para la obtención de compuestos de hierro, amoniojarosita y ferritas de zinc, con cierto valor añadido.

Dermatitis de contacto por prótesis ortopédicas Contact dermatitis for orthopaedic prostheses

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C.A. Danielo

2007-09-01

Full Text Available Diversas aleaciones son utilizadas en la fabricación de prótesis ortopédicas (ej: titanio, vitalio, etc, dentro de las cuales la más utilizada es la de acero inoxidable. El níquel, parte importante de esta aleación, es capaz de liberarse y provocar sensibilización, desencadenando reacciones cutáneas locales y sistémicas. De los materiales que componen la aleación para formar acero inoxidable, el níquel es el que más frecuentemente se ve implicado en reacciones cutáneas por sensibilidad, en tanto que otros como el cromo y cobalto, la posibilidad de pérdida de material a partir de la prótesis es discutida. Presentamos el caso de una paciente con dermatitis alérgica al níquel con lesiones generalizadas, que aparecieron luego del implante de prótesis ortopédicas de acero inoxidable, dando positivo para níquel sulfato en las pruebas epicutáneas.Several alloys are used in the manufacture of orthopaedics prostheses (ie: titanium, vitalium. Stainless steel is the most frequently used among them. Nickel is an important component of this alloy and may release and provoke sensitivity. Arising local and systemic cutaneous reactions. Nickel is the material composing stainless steel that ordinary is implicated in cutaneous reactions of sensitivity; the role of chrome or cobalt is still uncertain. Our patient is a woman affected of nickel contact dermatitis, with generalized reactions that appear after an implant of a stainless steel orthopaedic prosthesis. Epicutaneous tests were performed, confirming a strong sensitivity to nickel sulphate.

Estudo dos efeitos da restrição na microestrutura, microdureza e tenacidade em juntas soldadas em aço inoxidável duplex Study of restriction effects on mMicrostructure, microhardness and toughness in welded joints of duplex stainless steel

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Everton Barbosa Nunes

2011-06-01

Full Text Available Os aços inoxidáveis duplex (AID apresentam em sua microestrutura ferrita e austenita, de modo a aliar boas propriedades mecânicas e resistência à corrosão. Estes materiais possuem grande aplicação na indústria petroquímica, sendo o UNS S31803 um dos mais conhecidos. Existem poucos trabalhos referentes ao estudo da influência da restrição na soldagem da junta na formação de Widmanstätten. Logo, este trabalho tem como objetivo analisar a influência da restrição no balanceamento de fases, na morfologia da austenita, na microdureza e na tenacidade da Zona Afetada pelo Calor (ZAC e da Zona Fundida (ZF. Foram realizadas soldagens em juntas tipo V utilizando eletrodo revestido AWS E2209-17com dois níveis de energia: 15 kJ/cm e 20 kJ/cm, com e sem restrição. De maneira geral, houve maior quantidade de ferrita nos passes de acabamento em relação aos passes de enchimento e de raiz. Foram observadas maiores quantidades de Widmanstätten nas condições soldadas com restrição. A ZAC apresentou uma microestrutura mais grosseira nos passes de acabamento. No entanto, não foram observadas diferenças significativas nas microestruturas quando comparadas as condições com e sem restrição. As condições que apresentaram maior quantidade de Widmanstätten obtiveram menores níveis de microdureza. Não foram observadas diferenças na energia absorvida na ZAC e ZF.Duplex stainless steels present ferrite and austenite in their microstructure in order to join good mechanical properties and corrosion resistance. These materials are very used in petrochemical industry, being the DSS UNS S31803 one of the most commercially known. There were not much published literature to study the influence of the precipitation of Widmanstätten austenite in joins with some restriction. This work has as objective to analyze the influence of the restriction in the phase balance of austenite and ferrite, in the morphology of the austenite, in the

The Cementation of Boron to Steels by the Method of Electrolytic Deposition; Cementation Electrolytique d'Aciers par le Bore; Tsementirovanie bora v stali putem ehlektroliticheskogo osazhdeniya; Cementacion de Aceros con Boro por Deposito Electrolitico

Energy Technology Data Exchange (ETDEWEB)

Kawakami, M. [Tokyo Institute of Technology (Japan)

1964-06-15

aceros al carbono, aceros inoxidables, acero de elevado contenido de cromo, etc.; todos ellos dan resultados satisfactorios. (author) [Russian] Privoditsja metod izgotovlenija upravljajushhego sterzhnja s cementirovaniem bora. Jetot process osushhestvljaetsja posredstvom jelektroliza rasplavlennogo tetrabornokislogo natrija pri temperature okolo 900 Degree-Sign S . Obrabatyvaemyj stal'noj sterzhen' sluzhit katodom, v k a chestve anoda ispol'zuetsja grafitovyj jelektrod. V processe jelektroliza bor osazhdaetsja na stal'noj sterzhen' i diffundiruet v sta l'. Pri podhodjashhih uslovijah jelektroliza legko udaetsja poluchit' stal'noj sterzhen', soderzhashhij po 20% bora. Issledovalis' sledujushhie tipy stali: uglerodistaja, nerzhavejushhie, hromistaja i t.d. , vo vseh sluchajah byli polucheny polozhitel'nye rezul'taty. (author)

Influência da energia de soldagem na microestrutura e na microdureza de revestimentos de aço inoxidável duplex Influence of the heat input on the microstructure and microhardness of weld overlay of duplex stainless steel

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Everton Barbosa Nunes

2012-06-01

Full Text Available Aços inoxidáveis duplex (AID são caracterizados por apresentar interessante boas propriedades mecânicas e resistência à corrosão, possuindo um vasto campo de aplicação na indústria química e petroquímica. Geralmente, os reparos dos equipamentos ou estruturas são realizados por soldagem, sendo importante a seleção de parâmetros. É de suma importância a obtenção do teor adequado de ferrita no metal de solda, sendo que a variação da energia de soldagem pode influenciar de forma direta no percentual de ferrita. Logo, o objetivo deste trabalho é avaliar a influência da variação da energia de soldagem na microestrutura e na microdureza do metal de solda do AID. Foram realizadas soldagens de revestimento com sobreposição de duas camadas sobre o aço estrutural ASTM A516 Gr.60, utilizando eletrodo revestido AWS E2209-17. Três níveis de energia (15, 20 e 24 kJ/cm foram empregados, variando-se a corrente e a velocidade de soldagem. Foi verificado que para os níveis de energia empregados não houve diferença significativa no percentual de ferrita, porém o primeiro cordão depositado apresentou maior teor de austenita em relação aos demais cordões. De forma geral, foi verificado que o primeiro cordão depositado obteve níveis maiores de microdureza. Todas as condições apresentaram microdurezas abaixo do valor crítico.Duplex stainless steels (DSS are characterized by the presentation of an interesting combination of good mechanical properties and corrosion resistance, having a wide application in chemical and petrochemical industry. Generally, the manufacture and repair of any industrial equipment involve welding operations, even though it is very important to evaluate the influence of welding parameters. It is very important to obtain appropriate ferrite content in the weld metal, so that the variation of heat input can influence on the ferrite content directly. Therefore, the aim this work is to evaluate the

Study of copper deposit on a porous electrode of carbon and stainless steel by sem-xrd and image analysis

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Constanzo-R., Robinson; Pagliero-N., Antonio; Vergara-G., Froilán

2014-01-01

El objetivo de este trabajo fue realizar un análisis cualitativ o de la distribución de un electrodepósito de cobre en el inter ior de electrodos porosos (EP) de acero inoxidable y carbono grafito. Para ello, se reali zaron pruebas de electrodepositación de cobre a nivel de labora torio, con un posterior análisis de cortes de muestras de acero y grafito vía Microscopía Estereoscópica, Microscopía SEM-DRX y Análisis de Imagen, los cuales mostraron que el cobre no se deposita en forma uniforme ...

Resistencia a la corrosión localizada de juntas soldadas en un acero inoxidable duplex saf 2205

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LEÓN, JOSÉ B; ARIAS, RAFAEL; SÁNCHEZ, ABBY; SUÁREZ, MARIBEL; QUINTERO, AMADO

2008-01-01

La corrosión por picadura es uno de los mecanismos de falla más frecuentes que se presentan en la industria química, petrolera y petroquímica. El hecho de que metales o aleaciones metálicas estén expuestos a ambientes agresivos inducen a fenómenos de corrosión como la «corrosión por picadura». El conocimiento de cómo se originan y la detección temprana de este mecanismo se traducen en ahorros económicos considerables debido a que se evitaría la interrupción momentánea de operaciones de una ac...

Characterization of gold and nickel coating on AISI 304 stainless steel for use in the fabrication of current collector plates for fuel cells; Caracterizacion de recubrimientos de oro y niquel realizados sobre acero inoxidable AISI 304 para su empleo en la fabricacion de placas colectoras de corriente para celdas de combustible

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Flores Hernandez, J. Roberto [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)] e-mail: jrflores@iie.org.mx; Aguilar Gama, M. Tulio [UNAM. Facultad de Quimica, Mexico D.F. (Mexico); Cano Castillo, Ulises; Albarran, Lorena [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico); Olvera, J. Carlos; Orozco, German [CIDETEQ, Pedro Escobedo, Queretaro (Mexico)

2009-09-15

Among the different components that compose fuel cell technology (MEA, bipolar plates, seals, etc.) current collector plates play an important role in the good performance of fuel cells, since they collect all of the current generated and distribute it to the external circuit. Therefore, the most important properties that the current collector plates should have are excellent conductivity and good resistance to the corrosive conditions present in the fuel cell. This document presents results obtained during the nickel and gold electrodeposition process on AISI 304 stainless steel and the morphology and thickness of each coating, their adhesion, hardness and conductivity values. Finally, results obtained during some of the electrochemical tests performed on the coatings are shown. [Spanish] De los diferentes componentes que integran la tecnologia de celdas de combustible (MEA's, placas bipolares, sellos, etc.), las placas colectoras de corriente tienen un importante rol en el buen desempeno de la celdas de combustibles, ya que en estas placas se colecta toda la corriente generada y se distribuye al circuito externo. Debido a esto, las propiedades mas importantes que deben tener las placas colectaras de corriente son: excelente conductividad y buena resistencia a las condiciones corrosivas presentes en la celda de combustible. En este documento se presentan los resultados obtenidos en el proceso de electrodeposicion de niquel y oro sobre acero inoxidable AISI 304, asi como la morfologia y el espesor de cada recubrimiento, sus valores de adherencia, dureza y conductividad. Finalmente se muestran tambien los resultados obtenidos de algunas pruebas electroquimicas a los que fueron sometidos los recubrimientos.

Recubrimiento de acero con polidopamina

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Carrasco Rodríguez, Javier

2013-01-01

Se ha obtenido recubrimientos de polidopamina en acero mecánicamente resistentes y con tiempos de obtención relativamente pequeños a través de la polimerización de la dopamina bajo diferentes condiciones.

Influencia de la atmósfera de sinterización en las propiedades mecánicas de los aceros P/M AISI 430L

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Iglesias, F. Javier

2014-03-01

Full Text Available It has studied the stainless steel powder metallurgy AISI 430L. It has compared the sintering in two different atmospheres; in vacuum, and in an atmosphere containing nitrogen. It has developed a heat treatment with the aim of improving the mechanical properties. This has been done through microstructural modification of complex nitrides of iron and chromium precipitates during the phase of sintering. Physical properties have been evaluated and are been performing a microstructural analysis for microstructure related to the increase in mechanical properties.Se ha estudiado el acero inoxidable pulvimetalúrgico AISI 430L, comparando la sinterización en dos atmósferas diferentes; en vacío, y en una atmósfera que contiene nitrógeno. Se ha desarrollado un tratamiento térmico con objeto de incrementar las propiedades mecánicas, mediante la modificación microestructural de los nitruros complejos de hierro y cromo precipitados durante la etapa de sinterización. Se han evaluado las propiedades físicas y a la vez se ha realizado un análisis microestructural con el fin de relacionar la microestructura con el incremento en las propiedades mecánicas.

Oxidación cíclica de un acero refractario AISI 310 a alta temperatura en atmósferas con contenidos de oxígeno variables

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Higuera-Hidalgo, V.

2005-06-01

Full Text Available High temperature oxidation tests of an AISI 310 stainless steel was performed in two different environments: in an standard atmosphere (21 % oxygen at 704, 800, 884 and 1,000 °C and in the typical environment of a gas turbine and vapor generator of a combined-cycle electric generation unit (10 % oxygen at 800 and 1,000 °C. The oxidation kinetics was determined by means of the measurement of the weight gain per unit surface of the specimen and also determining the thickness of the oxide layer. Comparable results have been obtained using both methodologies and the effect of the oxygen content along with the other experimental differences were determined observing the oxidation kinetics in both environments. The cyclic oxidation of AISI 310 deteriorates at temperatures higher than 1,000 °C.

Se ha llevado a cabo un estudio experimental sobre la oxidación a altas temperaturas de un acero inoxidable refractario AISI 310, en dos ambientes diferentes: en una atmósfera convencional (21 % de O₂, a 704, 800, 884 y 1.000 °C y en un ambiente simulativo de una turbina de gas y del generador de vapor de uña central eléctrica de ciclo combinado (10-11 % de O₂, a 800 y 1.000 °C. La cinética de la oxidación del material se ha determinado a partir, tanto de la ganancia de peso por unidad de superficie experimentada por las probetas objeto de ensayo como por la determinación de los espesores de las capas de óxido formados. Se han obtenido resultados comparables con ambas metodologías y se ha puesto de manifiesto el efecto del contenido de oxígeno y de las demás diferencias experimentales a partir de la comparación de las cinéticas de oxidación del acero en los dos medios oxidantes analizados. La oxidación del acero AISI 310 en situaciones térmicas cíclicas empieza ya a ser importante a partir de una temperatura de 1.000 °C.

Efeito do Pré-aquecimento e de Único e Múltiplos Passes no Grau de Porosidade, Oxidação e Microdureza de um Revestimento de Aço Inoxidável Duplex Depositado por Aspersão Térmica Chama Arame

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Valdir Celestino da Silva

Full Text Available Resumo: Este trabalho tem como objetivo estudar o efeito do pré-aquecimento e de único e múltiplos passes no grau de porosidade, oxidação e microdureza no processo de revestimento obtido por aspersão térmica chama arame. A oxidação ao ar de partículas aspergidas após ancoragem afeta o desempenho para o aço inoxidável duplex AF2209 depositado por aspersão térmica chama arame em substrato de aço estrutural pré-aquecido com maçarico à diferentes temperaturas. O percentual de óxidos e poros foram medidos e quantificados por microscopia óptica com auxilio de software de análise de imagem. Imagens por MEV e a dureza Vickers dos óxidos e panquecas indicam que a oxidação aumenta com o pré-aquecimento e com a deposição de múltiplos passes. Os resultados indicam que maiores pré-aquecimentos e a deposição de múltiplos passes reduzem a fragmentação das partículas, mas aumenta a quantidade de óxidos. Observa-se também que o reaquecimento da camada reduz a microdureza Vickers média dos óxidos e panquecas da condição de único passe para a condição de múltiplos passes.

Propiedades mecánicas del acero de refuerzo utilizado en Colombia Propiedades mecánicas del acero de refuerzo utilizado en Colombia

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Victoria González Quintana; Juan Carlos Botero; Roberto Rochel; Julián Vidal; Martha Cecilia Alvarez Uribe

2005-01-01

Se presentan resultados del análisis estadístico aplicado al estudio experimental que de- termina las propiedades mecánicas de aceros colombianos sometidos a cargas monotónicas de tracción. Se obtienen curvas típicas de esfuerzo-deformación que permiten caracterizar aceros nacionales estudiados haciendo énfasis en las variables que determinan el cambio de comportamiento del materialA statistical analysis applied to a experimental study that determines the mechanical properties of steels produ...

Probabilistic Medium Access Control for Full-Duplex Networks with Half-Duplex Clients

OpenAIRE

Chen, Shih-Ying; Huang, Ting-Feng; Lin, Kate Ching-Ju; Hong, H. -W. Peter; Sabharwal, Ashutosh

2016-01-01

The feasibility of practical in-band full-duplex radios has recently been demonstrated experimentally. One way to leverage full-duplex in a network setting is to enable three-node full-duplex, where a full- duplex access point (AP) transmits data to one node yet simultaneously receives data from another node. Such three-node full-duplex communication however introduces inter-client interference, directly impacting the full-duplex gain. It hence may not always be beneficial to enable three-nod...

Corrosión en soldaduras de aparatos de ortodoncia

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Vázquez, S. M.

1997-10-01

Full Text Available The study of corrosion-related problems of dental materials has undergone a considerable development in recent years in order to avoid the use of materials with insufficient corrosion resistance in patients' mouth. The subject of the present work was to study a particular type of corrosion: galvanic corrosion. One of the most common case of galvanic couples in patients' mouth are the orthodontic appliances. The materials studied in the present work were stainless steel strips and silver-copper wires, isolated and welded between them. The electrochemical tests were performed in a NaCl 0.1M and Lactic Acid 0.1M solution (pH 2.3, and after test, the specimens were observed using the optical and scanning electron microscope. The results show that when stainless steel is coupled with a silver solder, the last is the anode of the galvanic couple. As a consequence of this, the silver solder undergone a severe attack. Stainless steel orthodontic appliances with silver solder are feasibly destroyed due to a severe attack on the filler metal disjoining the welded parts.

En los últimos años se ha desarrollado considerablemente el estudio de los problemas relacionados con la corrosión de aleaciones dentales a efectos de evitar la utilización de materiales con una deficiente resistencia a la corrosión en la boca de los pacientes. El objetivo del presente trabajo fue estudiar la corrosión de aparatos de ortodoncia fabricados con acero inoxidable con soldadura por punto o por aporte de aleación de plata. Los resultados obtenidos mostraron que cuando el acero inoxidable contiene aportes de soldadura de material de base plata, ésta actúa como ánodo disolviéndose preferencialmente a una velocidad considerable. Los aparatos de ortodoncia construidos con acero inoxidable soldado con aporte de material de base plata, corren el riesgo de destrucción debido a un ataque intenso en el cordón de soldadura con el consiguiente despegue de las piezas

Estudio de corrosión bajo tensión en los aceros inoxidables 17-4PH y 17-7PH en presencia de NaCl y NaOH (20 % a 90 °C

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Gaona-Tiburcio, Citlalli

2000-04-01

Full Text Available One of the problems that affects to the electric industry is the not programmed stoppages in the power plants, due to the failure of any main component: boiler, turbine and generator. In the turbine, the combined action of a corrosive agent (humid polluted vapor and a mechanical effort generally will result in Stress Corrosion Cracking (SCC. In this work the SCC susceptibility of the precipitation hardening stainless steels 17-4PH and 17- 7PH, thoroughly used in steam turbine blades of power stations is analyzed. The specimens were tested in the presence of NaCl and NaOH (20 % to 90 °C and different pH. The CERT test (Constant Extension Rate Test was used, at 10^-6 s^-1 supplementing it with electrochemical noise; the aim was to identify the conditions of maximum susceptibility and the performance of the studied materials. The fractographic analysis revealed ductile and brittle fracture. Intergranular crackings, characteristic of the anodic dissolution mechanism of the material was observed. Nevertheless, the main mechanism responsible the failure was hydrogen embrittlement.

Uno de los problemas que afecta a la industria eléctrica es el de los paros no programados en las plantas generadoras de electricidad, debidos al fallo de algún componente principal: caldera, turbina y generador. En la turbina, la acción combinada de un agente corrosivo (vapor húmedo contaminado y un esfuerzo mecánico, generalmente provocará corrosión bajo tensión (CBT. En este trabajo se analiza la susceptibilidad a la CBT de los aceros inoxidables, endurecibles por precipitación, 17-4PH y 17-7PH, ampliamente usados en alabes de turbina de vapor de centrales termoeléctricas. Las muestras se ensayaron en presencia de NaCl y NaOH (20 % a 90 °C, y distintos valores de pH. Se empleó el ensayo CERT (Constant Extensión Rate Test, a velocidades de 10^-6 s^-1, complementándolo con ruido electroquímico, buscando

Estudio de la susceptibilidad de un acero inoxidable austenítico estabilizado con niobio al dañado por tensocorrosión en medio H₂S (SSC y corrosión intergranular (IGC en otros medios agresivos

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Gutiérrez de Saiz-Solabarría, S.

1998-05-01

Full Text Available Behavior to hydrogen damage caused by stress corrosion in a H₂S medium (SSC and to intergranular corrosion (IGC in different mediums, such as oxalic acid (C2H₂O₄-2H₂0, iron sulphate-50 % sulfuric acid [Fe₂(SO₄₃-50 % H₂SO₄], nitric acid (HNO₃, copper sulphate-16 % sulfuric acid (CuSO₄-5H₂O-16 % H₂SO₄ and cooper sulphate-50 % sulfuric acid (CuSO₄-5H₂O-50 % H₂SO₄, is studied in an AISI 347 austenitic stainless steel stabilized with 0.61 mass % Nb and hot rolled to a seamless pipe with 273.1 mm in diameter and 18.2 mm in thickness.

Se estudia el comportamiento de un acero inoxidable austenítico del tipo AISI 347 estabilizado con un 0,61 % en masa de Nb, laminado en caliente para producir una tubería sin soldadura de 273,1 mm de diámetro y 18,2 mm de espesor, frente al dañado por hidrógeno generado por tensocorrosión en medio H₂S (SSC y frente a la corrosión intergranular (IGC en diferentes medios agresivos tales como ácido oxálico (C₂H₂O₄∙2H₂O, sulfato de hierro-50% ácido sulfúrico [Fe₂ (SO₄₃-50 % H₂SO₄], ácido nítrico (HNO₃, sulfato de cobre-16% ácido sulfúrico (CuSO₄-5H₂O-16 % H₂SO₄ y sulfato de cobre-50 % ácido sulfúrico (CuSO₄-5H₂O-50 % H₂SO₄, respectivamente.

Corrosion behavior of powder metallurgical stainless steels in urban and marine environments

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Bautista, A.

2006-06-01

Full Text Available This work studies the development of corrosive attack on sintered components manufactured from AISI 316L and AISI 304L powders. The stainless steels were sintered in vacuum and in nitrogen-base atmosphere at 1,120 and 1,250 ºC, and their corrosion resistance was then analyzed by electrochemical techniques and by atmospheric corrosion testing (two years at urban and marine test sites. Images are shown of the morphology of the attack on the surface of the stainless steels and the development of this attack in the interior of the material.

Este trabajo estudia el desarrollo del proceso corrosivo en componentes sinterizados fabricados a partir de polvos de AISI 316L y AISI 304L. Los aceros inoxidables fueron sinterizados en vacío y en atmósfera base nitrógeno a 1.120 y 1.250 ºC y, su resistencia a corrosión se ha analizado mediante técnicas electroquímicas y mediante ensayos de corrosión atmosférica (dos años en ambientes urbano y marino. Se muestran imágenes de la morfología del ataque en la superficie de los aceros inoxidables y del desarrollo de este ataque en el interior del material.

Microestrutura de uma Solda Dissimilar entre o Aço Inoxidável Ferrítico AISI 410S e o Aço Inoxidável Austenítico AISI 304L Soldado pelo Processo FSW

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Tathiane Caminha Andrade

2015-12-01

Full Text Available Resumo O presente trabalho visa investigar a microestrutura formada na soldagem dissimilar entre chapas de aços inoxidáveis ferríticos AISI 410S e aços inoxidáveis austeníticos AISI 304L pelo processo friction stir welding. A soldagem foi realizada com o ajuste dos seguintes parâmetros: rotação 450 rpm; velocidade de soldagem de 1,0 mm/s; e força axial 40 kN. O aço AISI 410S foi posicionado no lado de avanço enquanto que o aço AISI 304L foi posicionado no lado de retrocesso. A análise consistiu de preparação metalográfica e caracterização microestrutural por microscopia ótica e microscopia eletrônica de varredura. Para o aço AISI 410S foi observada a formação de martensita associada com ferrita na zona de mistura (ZM, zona termomecanicamente afetada (ZTMA e na zona afetada pelo calor (ZAC. As características do processo de soldagem FSW resultaram num refino de grão para o aço inoxidável ferrítico, posicionado no lado de avanço, tanto na ZM quanto nas ZTMA e ZAC. O mesmo comportamento não foi observado para o lado austenítico.

Diseño y evaluación de un procedimiento on-line para la biorremediación de aguas radiactivas en centrales nucleares

OpenAIRE

Belinchón Vergara, Julio Angel

2016-01-01

Recientemente se ha demostrado la existencia de microorganismos en las piscinas de almacenamiento de combustible nuclear gastado en las centrales nucleares utilizando técnicas convencionales de cultivo en el laboratorio. Estudios posteriores han puesto de manifiesto que los microorganismos presentes eran capaces de colonizar las paredes de acero inoxidable de las piscinas formando biopelículas. Adicionalmente se ha observado la capacidad de estas biopelículas de retener radionúclidos, lo que ...

Propiedades mecánicas del acero de refuerzo utilizado en Colombia Propiedades mecánicas del acero de refuerzo utilizado en Colombia

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Victoria González Quintana

2005-04-01

Full Text Available Se presentan resultados del análisis estadístico aplicado al estudio experimental que de- termina las propiedades mecánicas de aceros colombianos sometidos a cargas monotónicas de tracción. Se obtienen curvas típicas de esfuerzo-deformación que permiten caracterizar aceros nacionales estudiados haciendo énfasis en las variables que determinan el cambio de comportamiento del materialA statistical analysis applied to a experimental study that determines the mechanical properties of steels produced in Colombia subjected to monotonic loads of tension is presented. Typical stress-strain diagram that allow to characterize these steels making emphasis in the variables that determine the change of behaviour of the materia are presented.

Mejora de la tenacidad de un acero de ultraalto contenido en carbono nnediante unión por laminación con un acero al cromo y molibdeno

Directory of Open Access Journals (Sweden)

Pozuelo, M.

2005-12-01

Full Text Available Laminated composite materials containing five layers of ultrahigh carbon steel, 1.35%C, and five layers of a Cr-Mo steel were processed by roll bonding. The rolling procedure improves the bonding of layers and refines the microstructure, diminishing grain size and removing the pearlitic zones. Charpy impact tests were carried out to evaluate the impact properties. Toughness of the laminated composite was highly improved respect to the ultrahigh carbon steel. Moreover, it was double than that of the Cr-Mo steel in the arrester orientation. These results reveal the important role of the interfaces in the mechanical properties of the composite materials.

Se procesaron mediante unión por laminación, dos materiales compuestos laminados de 10 capas: cinco capas de un acero de ultraalto contenido en carbono con 1,35 % C, alternadas con otras cinco de un acero al cromo y molibdeno. La laminación en caliente consolida la unión entre las capas y afina la microestructura, reduciendo el tamaño de grano y eliminando las zonas de perlita presentes inicialmente. Se realizaron ensayos de impacto Charpy para evaluar su resistencia al impacto. El material compuesto laminado mejoró sustancialmente la tenacidad del acero de ultraalto carbono, además de duplicar la resiliencia del acero al cromo y molibdeno en la orientación "en serie". Estos resultados ponen de manifiesto la importancia de las intercaras en las propiedades mecánicas de los materiales compuestos.

Potencial de demanda energética cero en envolventes industriales: El caso de la vinificación en zonas de gran amplitud térmica.

Directory of Open Access Journals (Sweden)

Alba Inés Ramos Sanz

2017-12-01

Full Text Available En el estudio presentado en este artículo se desarrolla un modelo matemático para la simulación en tiempo real de un envolvente de vinificación representativo de la tecnología de vinificación nacional -de hormigón armado-, y se lleva a cabo un seguimiento térmico tanto del vino almacenado en este interior como en uno de acero inoxidable, con el empleo de sensores de temperatura HOBO U-12. Mediante tal simulación, se contempla el efecto producido sobre la estabilidad térmica del vino y la demanda térmica originada en la convección forzada -causada por las brisas-, bajo diversas configuraciones de bodegas. Con la herramienta validada, se realiza una sencilla optimización pasiva sobre el caso representativo. Finalmente, comparando los resultados de los casos simulados optimizados y de los casos reales, se concluye una mayor eficiencia termo-energética del caso representativo, frente a los de acero inoxidable. Asimismo, se observa que la estabilidad térmica del vino con demanda cero es factible a partir del empleo de envolventes adecuadas al clima analizado; con sencillas medidas de optimización, dicha estabilidad se acerca al prototipo de demanda cero perseguida en los modelos de referencia para la gestión de la energía.

Profundidad del surco gingival en dientes primarios restaurados con coronas de acero cromo

Directory of Open Access Journals (Sweden)

Rubén Muñoz Delgado

2015-01-01

Full Text Available Objetivo: Evaluar la relación entre el ajuste marginal y la profundidad del surco gingival en dientes primarios restaurados con coronas de acero cromo. Métodos: Se midió la profundidad del surco gingival de 114 dientes primarios restaurados con coronas de acero cromo en 67 niños, ambos sexos, de 3 a 6 años de edad de la clínica de Estomatología Pediátrica de la UATx, México. La población en estudio fue dividida en tres grupos: a experimental (n=30, b control (n=8, y c control negativo (n=29. Previo consentimiento informado se tomaron los índices de placa (LöeSilness 1967 e índice gingival en seis superficies; se midió el surco gingival con sonda periodontal y las coronas de acero cromo fueron evaluadas clínica y radiográficamente según su ajuste marginal y longitud cervical. Resultados: Los índices de placa y gingival no mostraron diferencias significativas para los grupos experimental y control negativo. El 34% de las coronas mostraron buen ajuste marginal, 33% un mal ajuste, 10.5% cortas, 7.9% largas y el 14% otro tipo de mal ajuste. La profundidad del surco gingival fue estadísticamente significativa para el primer y segundo molar inferior derechos y en los caninos inferiores (p >0.05; la superficie disto-vestibular presentó la mayor profundidad del surco gingival (2.34 mm, siendo estadísticamente significativa (p>0.05. Conclusiones: La profundidad del surco gingival fue mayor en los dientes rehabilitados con coronas de acero cromo mal ajustadas y sobre contorneadas (largas. La presencia de placa bacteriana y gingivitis estuvo relacionada con las coronas de acero cromo mal ajustadas.

Predicción del desgaste del flanco de la herramienta de corte durante el torneado en seco de alta velocidad para piezas de acero AISI 316L en la industria minera

Directory of Open Access Journals (Sweden)

Yusimit K. Zamora-Hernández

2015-07-01

Full Text Available Se realizó un estudio experimental sobre la influencia de los parámetros de corte en el torneado del acero inoxidable AISI 316L con insertos recubiertos de TiCN, Al2O3, TiN. Un microscopio electrónico de barrido fue utilizado para medir y analizar el desgaste de las herramientas de corte. Los resultados fueron comparados utilizando el análisis de varianza y el análisis de regresión múltiple para describir la relación entre el desgaste del flanco de las herramientas de corte, el tiempo de maquinado y el avance de corte, obteniéndose las ecuaciones de los modelos ajustados. La investigación demostró el efecto significativo del avance y del tiempo de maquinado en el desgaste del flanco. El inserto de tres capas no sobrepasó el criterio de fin de vida del desgaste, mientras que el inserto de una capa sufrió un desgaste elevado para la mayor velocidad de corte. El desgaste del flanco tuvo mejor comportamiento para el avance de 0,08 mm/rev en todas las velocidades empleadas en este estudio. Los errores medios absolutos no superaron el 15 %.

Vesicoureteral Reflux and Duplex Systems

OpenAIRE

Thomas, John C.

2008-01-01

Vesicoureteral reflux (VUR) is the most common anomaly associated with duplex systems. In addition to an uncomplicated duplex system, reflux can also be secondary in the presence of an ectopic ureterocele with duplex systems. Controversy exists in regard to the initial and most definitive management of these anomalies when they coexist. This paper will highlight what is currently known about duplex systems and VUR, and will attempt to provide evidence supporting the various surgical approa...

Hormigones de alta resistencia con nano-adiciones y fibras de acero

OpenAIRE

Alizo Mirabal, Manuel Arturo

2015-01-01

El presente Trabajo Fin de Máster consistió en determinar la influencia que pueden poseer las nano-adiciones de Sílice y Alúmina y fibras de acero en un Hormigón de Alta Resistencia. Partiendo de una dosificación de Hormigón de Alta Resistencia conocida, que contenía humo de Sílice (10%) y fibras de poliolefina (3kg/m3), se les procedió a sustituir por la incorporación de nano-adiciones de Sílice y Alúmina (7% y 3% respectivamente) y añadiendo fibras de acero en lugar de poliolefina. En el pr...

Ductility in a new low nickel stainless steel for reinforced concrete

Directory of Open Access Journals (Sweden)

Cobo, A.

2011-12-01

Full Text Available This paper discusses the stress-strain curves for a new low nickel stainless steel, a conventional AISI 304 stainless steel and a carbon steel commonly used in reinforced concrete structures. Ductility was studied in terms of ultimate tensile strength (f_max, elastic limit (f_y and total elongation at maximum force [ultimate strain; uniform elongation] (ε_max. The three materials were assessed with internationally accepted criteria, such as plastic rotational capacity, necking region and the toughness index (total energy absorbed at uniform elongation. The findings were compared to the properties of three types of conventional reinforcing steel: 500SD, 500N and 500H (EC-2.

En este trabajo se presentan los diagramas tensióndeformación de un nuevo acero inoxidable con bajo contenido en níquel, un inoxidable convencional AISI 304 y un acero al carbono de uso común en estructuras de hormigón armado. Dicha ductilidad se ha estudiado determinando la tensión máxima (f_max, la tensión en el límite elástico (f_y y la deformación bajo carga máxima (ε_max. Los tres materiales se han evaluado utilizando criterios aceptados internacionalmente, como son el índice p (capacidad de rotación plástica, el índice A* (área plástica de endurecimiento y el índice de tenacidad I_d (energía total absorbida en el punto de alargamiento bajo carga máxima, los resultados obtenidos se han comparado con los aceros convencionales de armaduras 500SD, 500N y 500H (EC-2.

Análisis comparativo de la calidad del acero de refuerzo distribuido en Boyacá

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Jimmy Vergara Silva, Óscar Javier Gutiérrez Junco

2011-05-01

Full Text Available Presenta  los  resultados  del  análisis  comparativo  de barras de acero de refuerzo, según las exigencias de la Norma Técnica Colombiana NTC 2289 [1], realizado a cinco marcas diferentes distribuidas para la industria de  la  construcción  en  Boyacá.  Inicialmente  se caracterizaron  las barras de  acero mediante  ensayos, para  determinar  su  composición  química  y  sus propiedades físicas y mecánicas; las características de la fractura del acero de refuerzo se observaron con el microscopio  electrónico  de  barrido  (MEB. Adicionalmente,  se  analizaron  muestras  conmicroscopio óptico, con  técnicas de espectrometría paraobservar y determinar las características del metal base de  las probetas. Los resultados  indican que la calidad del acero de refuerzo distribuido en Boyacá cumple en un alto  porcentaje con las exigencias sismo-resistentes para construcción; sin embargo, es importante que los constructores realicen control de calidad.

Ductilidad en caliente y mecanismos de fractura de un acero de construcción

Directory of Open Access Journals (Sweden)

Calvo, J.

2006-02-01

Full Text Available The hot ductility of a structural steel produced from scrap recycling has been studied to determine the origin of the transverse cracks in the corners that appeared in some billets. Samples extracted both from a billet with transverse cracks and from a billet with no external damage were tested. To evaluate the influence of residual elements and inclusions, the steel was compared to another one impurity free. Reduction in area of the samples tensile tested to the fracture was taken as a measure of the hot ductility The tests were carried out at temperatures ranging from 1000ºC to 650ºC and at a strain rate of 1·10- 3 s-1. The fracture surfaces of the tested samples were observed by scanning electron microscopy in order to determine the embrittling mechanisms that could be acting. The steel with residuals and impurities exhibited lower ductility values for a wider temperature range than the clean steel. The embrittling mechanisms also changed as compared to the impurity free steel.

Se evaluó la ductilidad en caliente de un acero de construcción procedente del reciclaje de chatarra con el fin de determinar el origen de las grietas transversales que aparecen en las esquinas de algunas palanquillas. Para ello, se extrajeron probetas de dos palanquillas de una misma calidad de acero. Una de las palanquillas había presentado agrietamiento transversal al ser colada y, la otra, no. Para conocer la influencia de los elementos residuales e inclusiones en la ductilidad en caliente, otro acero, con la misma composición pero sin impurezas, se fabricó en laboratorio y fue sometido al mismo análisis que los aceros comerciales. La ductilidad en caliente se midió como la reducción del área de las probetas ensayadas a tracción hasta la rotura. Las condiciones a las que se realizaron los ensayos fueron temperaturas de 1.000 a 650 ºC y a una velocidad de deformación de 1·10-3 s-1. Las superficies de fractura de las probetas ensayadas se

Welding of duplex and super-duplex stainless steels

International Nuclear Information System (INIS)

Van Nassau, L.; Meelker, H.; Hilkes, J.

1994-01-01

After a recall of the commercial designation of duplex or super-duplex steels (22-27% Cr, 4-8% Ni, 0.1-0.3% N with or without Mo (1.5-4%)) and of some metallurgical properties (phase diagrams, microstructure, ferrite determination, heat treatment and aging), welding technologies are synthetically presented (advantages-disadvantages of each process, metals filler, parameters of the welding processes, heat treatments after welding, cleaning, passivation, properties (mechanical, corrosion resistance) of the welded pieces). (A.B.). 28 refs. 5 figs., 15 tabs., 1 annexe

Backbone conformation affects duplex initiation and duplex propagation in hybridisation of synthetic H-bonding oligomers.

Science.gov (United States)

Iadevaia, Giulia; Núñez-Villanueva, Diego; Stross, Alexander E; Hunter, Christopher A

2018-06-06

Synthetic oligomers equipped with complementary H-bond donor and acceptor side chains form multiply H-bonded duplexes in organic solvents. Comparison of the duplex forming properties of four families of oligomers with different backbones shows that formation of an extended duplex with three or four inter-strand H-bonds is more challenging than formation of complexes that make only two H-bonds. The stabilities of 1 : 1 complexes formed between length complementary homo-oligomers equipped with either phosphine oxide or phenol recognition modules were measured in toluene. When the backbone is very flexible (pentane-1,5-diyl thioether), the stability increases uniformly by an order of magnitude for each additional base-pair added to the duplex: the effective molarities for formation of the first intramolecular H-bond (duplex initiation) and subsequent intramolecular H-bonds (duplex propagation) are similar. This flexible system is compared with three more rigid backbones that are isomeric combinations of an aromatic ring and methylene groups. One of the rigid systems behaves in exactly the same way as the flexible backbone, but the other two do not. For these systems, the effective molarity for formation of the first intramolecular H-bond is the same as that found for the other two backbones, but additional H-bonds are not formed between the longer oligomers. The effective molarities are too low for duplex propagation in these systems, because the oligomer backbones cannot adopt conformations compatible with formation of an extended duplex.

ESTUDIO DE LA CORROSIÓN DEL ACERO EMBEBIDO EN CONCRETO AAS SOMETIDO A CLORUROS

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ROBINSON TORRES GÓMEZ

2010-01-01

Full Text Available Se presenta un estudio sobre el comportamiento frente a la corrosión de barras de acero de refuerzo de un concreto de escoria activado alcalinamente. La escoria de alto horno fue activada mediante el uso de silicato sódico al 5% obteniéndose un material con buenas propiedades cementantes. Las probetas de concreto fueron fabricadas a partir de este cemento, después de mezclar con los agregados fueron reforzadas con barras de acero sismoresistente ASTMA706. Las probetas de concreto reforzado estuvieron sometidas en ambientes contaminados con iones cloruro para simular condiciones marinas. La evaluación electroquímica se realizo aplicando las técnicas de resistencia a la polarización lineal (LPR y espectroscopia de impedancia electroquímica (EIS. Se logra determinar el comportamiento de la capa pasiva del acero y electroquímico del metal cuando está inmerso en estos materiales cerámicos novedosos.

Full Duplex Emulation via Spatial Separation of Half Duplex Nodes in a Planar Cellular Network

DEFF Research Database (Denmark)

Thomsen, Henning; Kim, Dong Min; Popovski, Petar

2016-01-01

A Full Duplex Base Station (FD-BS) can be used to serve simultaneously two Half-Duplex (HD) Mobile Stations (MSs), one working in the uplink and one in the downlink, respectively. The same functionality can be realized by having two interconnected and spatially separated Half Duplex Base Stations...... (HD-BSs), which is a scheme termed CoMPflex (CoMP for In-Band Wireless Full Duplex). A FD-BS can be seen as a special case of CoMPflex with separation distance zero. In this paper we study the performance of CoMPflex in a two-dimensional cellular scenario using stochastic geometry and compare...

Fragilización por hidrógeno en tuberías de acero

OpenAIRE

Gutiérrez-Solana Salcedo, Federico

2011-01-01

Se pretende analizar el comportamiento en presencia de hidrogeno de las tuberías de acero de sistemas de transporte de combustibles gaseosos en uso para ello: 1.- Se estudia la sensibilidad a la fragilización por hidrogeno del acero de estas tuberías por dos métodos diferentes: polarización catódica y ambiente de hidrogeno gaseoso diseñando y construyendo una cámara para ensayos mecánicos en hidrogeno a presión primera de su genero en España. 2.- Se determina la tenacidad a fractura kic de es...

CÁLCULO DE LA TENSIÓN DE FLUENCIA EN ACEROS DEFORMADOS EN CALIENTE

OpenAIRE

Béjar, L; Hernández, C. A

2001-01-01

Se ha desarrollado un modelo matemático para la predicción de la curva de fluencia de la austenita deformada en aceros de baja aleación. Las ecuaciones constitutivas tienen en cuenta los mecanismos gobernantes durante la deformación plástica -responsables de la forma de la curva- y emplea las variables de proceso y la composición química del acero. Para una demostración de su precisión, el modelo propuesto se ha comparado con las curvas de fluencia clásicas de Cook en condiciones hasta dos ór...

Harvesting full-duplex rate gains in cellular networks with half-duplex user terminals

KAUST Repository

Alammouri, Ahmad; Elsawy, Hesham; Alouini, Mohamed-Slim

2016-01-01

Full-Duplex (FD) transceivers may be expensive in terms of complexity, power consumption, and price to be implemented in all user terminals. Therefore, techniques to exploit in-band full-duplex communication with FD base stations (BSs) and half

Achieving single channel, full duplex wireless communication

KAUST Repository

Choi, Jung Il; Jain, Mayank; Srinivasan, Kannan; Levis, Phil; Katti, Sachin

2010-01-01

This paper discusses the design of a single channel full-duplex wireless transceiver. The design uses a combination of RF and baseband techniques to achieve full-duplexing with minimal effect on link reliability. Experiments on real nodes show the full-duplex prototype achieves median performance that is within 8% of an ideal full-duplexing system. This paper presents Antenna Cancellation, a novel technique for self-interference cancellation. In conjunction with existing RF interference cancellation and digital baseband interference cancellation, antenna cancellation achieves the amount of self-interference cancellation required for full-duplex operation. The paper also discusses potential MAC and network gains with full-duplexing. It suggests ways in which a full-duplex system can solve some important problems with existing wireless systems including hidden terminals, loss of throughput due to congestion, and large end-to-end delays. Copyright 2010 ACM.

Structural Properties of G,T-Parallel Duplexes

Directory of Open Access Journals (Sweden)

Anna Aviñó

2010-01-01

Full Text Available The structure of G,T-parallel-stranded duplexes of DNA carrying similar amounts of adenine and guanine residues is studied by means of molecular dynamics (MD simulations and UV- and CD spectroscopies. In addition the impact of the substitution of adenine by 8-aminoadenine and guanine by 8-aminoguanine is analyzed. The presence of 8-aminoadenine and 8-aminoguanine stabilizes the parallel duplex structure. Binding of these oligonucleotides to their target polypyrimidine sequences to form the corresponding G,T-parallel triplex was not observed. Instead, when unmodified parallel-stranded duplexes were mixed with their polypyrimidine target, an interstrand Watson-Crick duplex was formed. As predicted by theoretical calculations parallel-stranded duplexes carrying 8-aminopurines did not bind to their target. The preference for the parallel-duplex over the Watson-Crick antiparallel duplex is attributed to the strong stabilization of the parallel duplex produced by the 8-aminopurines. Theoretical studies show that the isomorphism of the triads is crucial for the stability of the parallel triplex.

INFLUENCIA DE LA NITRURACIÓN POR PLASMA SOBRE EL COMPORTAMIENTO A LA CORROSIÓN Y LA ADHESIÓN DE RECUBRIMIENTOS DLC SOBRE ACERO INOXIDABLE AISI 420

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Jorge N. Pecina

2016-01-01

Full Text Available En este trabajo se estudió el comportamiento a la corrosió n y la adhesión de dos rec ubrimientos DLC (“Diamond Like Carbon ” , “Soft” y “Hard”, depositados por PACVD (“Plasma Assisted Chemical Vapour Deposition” sobre acero AISI 420, templado y revenido y /o nitrurado por plasma . Se analizaron por espectroscopía Raman y midió dureza en superficie. Se observó la microestructura por OM y SEM. Se realizaron pruebas de adhesión con indentación Rockwell C . S e practicaron ensayos de Niebla Salina e inmersión en HCl . Los DLC “ Soft ” presentaron una dureza de 5 00 HV y un espesor de 2 0 μm , mientras que los “ Hard ” tuvieron 1400 HV y 2 ,5 μm. Ambos recubrimientos presentaron bajo coeficiente de fricción y buena adhesión sobre el sustrato nitrurado . También presentaron buena resistencia a la corrosión atmosférica. En HCl el DLC retardó la degradación que se presentó rápidamente en las muestras sin recubrir.

Duplex gall bladder: bystander or culprit.

Science.gov (United States)

Kumar, Jogender; Yadav, Arushi

2017-08-30

Gall bladder (GB) duplication is a rare anatomical malformation, which can be detected by preoperative imaging study. We present a case of duplex gall bladder in a 14-year-old boy who presented with abdominal pain. On ultrasound, he had right nephrolithiasis and duplex gall bladder. Duplex gall bladder was confirmed on MR cholangiopancreatography. There was a dilemma for surgical management of duplex gall bladder; however, he became asymptomatic after conservative treatment. Prophylactic surgery is not recommended for asymptomatic incidentally detected duplex gall bladder. Radiologists and paediatric surgeons should be sensitised about the exact anatomy of this entity. © BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Overall performance of the duplex Stirling refrigerator

International Nuclear Information System (INIS)

Erbay, L. Berrin; Ozturk, M. Mete; Doğan, Bahadır

2017-01-01

Highlights: • Overall performance coefficient of duplex Stirling refrigerator was investigated. • A definite region for the coefficient of performance of the refrigerator in duplex Stirling is identified. • A definite region for the thermal efficiency of the heat engine in duplex Stirling is identified. • Benchmark values and design bounds of the duplex Stirling refrigerator were obtained. - Abstract: The duplex Stirling refrigerator is an integrated refrigerator consists of Stirling cycle engine and Stirling cycle refrigerator used for cooling. The equality of the work generation of the heat engine to the work consumption of the refrigerator is the primary constraint of the duplex Stirling. The duplex Stirling refrigerator is investigated thermodynamically by considering the effects of constructional and operational parameters which are namely the temperature ratios for heat engine and refrigerator, and the compression ratios for both sides. The primary concern is given to the parametric effects on the overall coefficient of performance of the duplex Stirling refrigerator. The given diagrams provide a design bounds and benchmark results that allows seeing the big picture about the cooling load and heat input relation. Moreover they ease to determine the corresponding work rate to the target cooling load. As regard to the obtained results, a definite region for coefficient of performance of the refrigerator and a definite region for the thermal efficiency of the heat engine of the duplex Stirling are identified.

Evaluation of structural behaviour and corrosion resistant of austenitic AISI 304 and duplex AISI 2304 stainless steel reinforcements embedded in ordinary Portland cement mortars; Evaluacion del comportamiento estructural y de resistencia a la corrosion de armaduras de acero inoxidable austenitico AISI 304 y duplex AISI 2304 embebidas en morteros de cemento Portland

Energy Technology Data Exchange (ETDEWEB)

Medina, E.; Cobo, A.; Bastidas, D. M.

2012-07-01

The mechanical and structural behaviour of two stainless steels reinforcements, with grades austenitic EN 1.4301 (AISI 304) and duplex EN 1.4362 (AISI 2304) have been studied, and compared with the conventional carbon steel B500SD rebar. The study was conducted at three levels: at rebar level, at section level and at structural element level. The different mechanical properties of stainless steel directly influence the behaviour at section level and structural element level. The study of the corrosion behaviour of the two stainless steels has been performed by electrochemical measurements, monitoring the corrosion potential and the lineal polarization resistance (LPR), of reinforcements embedded in ordinary Portland cement (OPC) mortar specimens contaminated with different amount of chloride over one year time exposure. Both stainless steels specimens embedded in OPC mortar remain in the passive state for all the chloride concentration range studied after one year exposure. (Author) 26 refs.

Low temperature plasma carburizing of AISI 316L austenitic stainless steel and AISI F51 duplex stainless steel Cementação sob plasma à baixa temperatura do aço inoxidável austenítico AISI 316L e do aço inoxidável duplex AISI F51

OpenAIRE

Carlos Eduardo Pinedo; André Paulo Tschiptschin

2013-01-01

In this work an austenitic AISI 316L and a duplex AISI F51 (EN 1.4462) stainless steel were DC-Plasma carburized at 480ºC, using CH4 as carbon carrier gas. For the austenitic AISI 316L stainless steel, low temperature plasma carburizing induced a strong carbon supersaturation in the austenitic lattice and the formation of carbon expanded austenite (γC) without any precipitation of carbides. The hardness of the carburized AISI 316L steel reached a maximum of 1000 HV due to ∼13 at% c...

Buffer management in wireless full-duplex systems

KAUST Repository

Bouacida, Nader

2015-10-19

Wireless full-duplex radios can simultaneously transmit and receive using the same frequency. In theory, this can double the throughput. In fact, there is only little work addressing aspects other than throughput gains in full-duplex systems. Over-buffering in today\\'s networks or the so-called “bufferbloat” phenomenon creates excessive end-to-end delays resulting in network performance degradation. Our analysis shows that full-duplex systems may suffer from high latency caused by bloated buffers. In this paper, we address the problem of buffer management in full-duplex networks by using Wireless Queue Management (WQM), which is an active queue management technique for wireless networks. Our solution is based on Relay Full-Duplex MAC (RFD-MAC), an asynchronous media access control protocol designed for relay full-duplexing. We compare the performance of WQM in full-duplex environment to Drop Tail mechanism over various scenarios. Our solution reduces the end-to-end delay by two orders of magnitude while achieving similar throughput in most of the cases.

Practical, real-time, full duplex wireless

KAUST Repository

Jain, Mayank; Choi, Jung Il; Kim, Taemin; Bharadia, Dinesh; Seth, Siddharth; Srinivasan, Kannan; Levis, Philip; Katti, Sachin; Sinha, Prasun

2011-01-01

This paper presents a full duplex radio design using signal inversion and adaptive cancellation. Signal inversion uses a simple design based on a balanced/unbalanced (Balun) transformer. This new design, unlike prior work, supports wideband and high power systems. In theory, this new design has no limitation on bandwidth or power. In practice, we find that the signal inversion technique alone can cancel at least 45dB across a 40MHz bandwidth. Further, combining signal inversion cancellation with cancellation in the digital domain can reduce self-interference by up to 73dB for a 10MHz OFDM signal. This paper also presents a full duplex medium access control (MAC) design and evaluates it using a testbed of 5 prototype full duplex nodes. Full duplex reduces packet losses due to hidden terminals by up to 88%. Full duplex also mitigates unfair channel allocation in AP-based networks, increasing fairness from 0.85 to 0.98 while improving downlink throughput by 110% and uplink throughput by 15%. These experimental results show that a re- design of the wireless network stack to exploit full duplex capability can result in significant improvements in network performance. © 2011 ACM.

EFECTO DE LA TEMPERATURA SOBRE LA RESISTENCIA A LA TRACCIÓN DE ALGUNOS REFUERZOS DE FIBRAS PARA MATRICES CERÁMICAS O POLIMÉRICAS EFEITO DA TEMPERATURA SOBRE A RESISTÊNCIA À TRAÇÃO DE ALGUNS REFORZOS DE FIBRAS PARA MATRIZES CERÁMICAS OU POLIMÉRICAS EFFECT OF TEMPERATURE ON TH E TENSILE STRENGTH OF SOME FIBER REINFORCEMENTS FOR CERAMIC OR POLYMER MATRICES

Directory of Open Access Journals (Sweden)

MARYORY ASTRID GÓMEZ

2009-07-01

Full Text Available Este artículo presenta un estudio de las propiedades termomecánicas de fibras de acero de bajo carbono, de acero inoxidable ASI-SAE 304, de aramida y de carbono. Además, se analizó el aspecto superficial de refuerzos de lana mineral de roca y lana de aluminosilicatos antes y después de someterlos a tratamientos térmicos a 1000 ºC. La resistencia a la tracción de las fibras se evaluó antes y después de someterlas a tratamientos térmicos a temperaturas de 400, 600, 800 y 1000 ºC dependiendo de la degradación que mostraran. Además, se efectuó un análisis termogravimétrico a cada tipo de fibra para determinar los cambios de peso a diferentes temperaturas. Las fibras de acero inoxidable mostraron la mayor estabilidad termomecánica, mientras que las fibras de aramida con tratamientos a 400 ºC mostraron propiedades mecánicas prácticamente nulas.Este artigo apresenta um estudo das propriedades termomecánicas de fibras de aço baixo carbono, de aço inoxidável ASI-SAE 304, de aramida e de carbono. Além disso, se analisou o aspecto superficial de reforços de lã mineral de rocha e lã de aluminosilicatos antes e depois que submetê-las a tratamentos térmicos a 1000 ºC. A resistência à tração das fibras se avaliou antes e depois de submetê-las a tratamentos térmicos a temperaturas de 400, 600, 800 e 1000 ºC dependendo da degradação que mostraram. Além disso, se efetuou uma análise termogravim étrica a cada tipo de fibra para determinar as mudanças de peso a diferentes temperaturas. As fibras de aço inoxidável mostraram a maior estabilidade termomecânica, enquanto as fibras de aramida com tratamentos a 400 ºC mostraram propriedades mecânicas praticamente nulas.This paper presents a study of the thermomechanical properties of low carbon steel, AISI-SAE 304 stainless steel, aramid and carbon fibers. Moreover, surface aspect of mineral rock wool of and aluminosilicate wool reinforcements was analyzed prior and after

Rietveld and impedance analysis of cold and hot rolled duplex and lean duplex steels for application in paper and pulp industry

Energy Technology Data Exchange (ETDEWEB)

Esteves, Luiza; Lins, Vanessa de Freitas Cunha, E-mail: luizaeq@yahoo.com.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Quimica; Paiva, Paulo Renato Perdigao [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET), Belo Horizonte, MG (Brazil); Viana, Adolfo Kalergis do Nascimento [APERAM South America, Timoteo, MG (Brazil)

2017-01-15

In this study, X-Ray Diffraction (XRD) and Rietveld Refinement were performed to identify and quantify the ferrite and austenite phase of cold and hot rolled duplex stainless steels (UNS S31803) and lean duplex stainless steels (UNS S32304). Electrochemical impedance spectroscopy (EIS) was applied to evaluate the chemical behavior of duplex and lean duplex stainless steels in white, green, and black liquors of paper and pulp industry. Rietveld analysis results showed a higher austenite content than the standard limit for duplex steels in the hot rolled condition. The hot rolling condition plays a major role in improving corrosion resistance in white liquor mainly for the lean duplex steel. (author)

Rietveld and impedance analysis of cold and hot rolled duplex and lean duplex steels for application in paper and pulp industry

International Nuclear Information System (INIS)

Esteves, Luiza; Lins, Vanessa de Freitas Cunha; Viana, Adolfo Kalergis do Nascimento

2017-01-01

In this study, X-Ray Diffraction (XRD) and Rietveld Refinement were performed to identify and quantify the ferrite and austenite phase of cold and hot rolled duplex stainless steels (UNS S31803) and lean duplex stainless steels (UNS S32304). Electrochemical impedance spectroscopy (EIS) was applied to evaluate the chemical behavior of duplex and lean duplex stainless steels in white, green, and black liquors of paper and pulp industry. Rietveld analysis results showed a higher austenite content than the standard limit for duplex steels in the hot rolled condition. The hot rolling condition plays a major role in improving corrosion resistance in white liquor mainly for the lean duplex steel. (author)

Thermal stability of DNA quadruplex-duplex hybrids.

Science.gov (United States)

Lim, Kah Wai; Khong, Zi Jian; Phan, Anh Tuân

2014-01-14

DNA has the capacity to adopt several distinct structural forms, such as duplex and quadruplex helices, which have been implicated in cellular processes and shown to exhibit important functional properties. Quadruplex-duplex hybrids, generated from the juxtaposition of these two structural elements, could find applications in therapeutics and nanotechnology. Here we used NMR and CD spectroscopy to investigate the thermal stability of two classes of quadruplex-duplex hybrids comprising fundamentally distinct modes of duplex and quadruplex connectivity: Construct I involves the coaxial orientation of the duplex and quadruplex helices with continual base stacking across the two components; Construct II involves the orthogonal orientation of the duplex and quadruplex helices with no base stacking between the two components. We have found that for both constructs, the stability of the quadruplex generally increases with the length of the stem-loop incorporated, with respect to quadruplexes comprising nonstructured loops of the same length, which showed a continuous drop in stability with increasing loop length. The stability of these complexes, particularly Construct I, can be substantially influenced by the base-pair steps proximal to the quadruplex-duplex junction. Bulges at the junction are largely detrimental to the adoption of the desired G-quadruplex topology for Construct I but not for Construct II. These findings should facilitate future design and prediction of quadruplex-duplex hybrids.

Prolonged CT urography in duplex kidney.

Science.gov (United States)

Gong, Honghan; Gao, Lei; Dai, Xi-Jian; Zhou, Fuqing; Zhang, Ning; Zeng, Xianjun; Jiang, Jian; He, Laichang

2016-05-13

Duplex kidney is a common anomaly that is frequently associated with multiple complications. Typical computed tomography urography (CTU) includes four phases (unenhanced, arterial, parenchymal and excretory) and has been suggested to considerably aid in the duplex kidney diagnosi. Unfortunately, regarding duplex kidney with prolonged dilatation, the affected parenchyma and tortuous ureters demonstrate a lack of or delayed excretory opacification. We used prolonged-delay CTU, which consists of another prolonged-delay phase (1- to 72-h delay; mean delay: 24 h) to opacify the duplicated ureters and affected parenchyma. Seventeen patients (9 males and 8 females; age range: 2.5-56 y; mean age: 40.4 y) with duplex kidney were included in this study. Unenhanced scans did not find typical characteristics of duplex kidney, except for irregular perirenal morphology. Duplex kidney could not be confirmed on typical four-phase CTU, whereas it could be easily diagnosed in axial and CT-3D reconstruction using prolonged CTU (prolonged-delay phase). Between January 2005 and October 2010, in this review board-approved study (with waived informed consent), 17 patients (9 males and 8 females; age range: 2.5 ~ 56 y; mean age: 40.4 y) with suspicious duplex kidney underwent prolonged CTU to opacify the duplicated ureters and confirm the diagnosis. Our results suggest the validity of prolonged CTU to aid in the evaluation of the function of the affected parenchyma and in the demonstration of urinary tract malformations.

Zoster duplex: a clinical report and etiologic analysis.

Science.gov (United States)

Zhang, Feng; Zhou, Jin

2015-01-01

Herpes zoster (HZ) duplex is a rare disease presentation. The mechanisms of varicella zoster virus (VZV) reactivation in multiple dermal regions are unknown. To present a HZ duplex case occurring in an immunocompetent woman and to analyze the possible underlying causes of HZ duplex. We present a HZ duplex case in an immunocompetent woman and analyzed the possible contributing factors in 36 HZ duplex cases. Continuously distributed variables were categorized by numbers and percentages. In our study, 24 cases (66.7%) were from Asia, 16 cases (44.4%) were in individuals ≥ 50 years of age, and 17 cases (47.2%) occurred in immunocompromised patients. Of the 36 cases, 23 involved women (63.9%) and 13 involved men. Eighteen patients suffering from HZ duplex, 13 of which were women (72.2%), did not suffer from any chronic systemic disease or have a long history of taking drugs. HZ duplex is a rare event that can occur in both immunocompetent and immunosuppressed individuals. HZ duplex might be associated with the Asia region, advanced age, immunosuppression, and being female.

Maximizing synchronizability of duplex networks

Science.gov (United States)

Wei, Xiang; Emenheiser, Jeffrey; Wu, Xiaoqun; Lu, Jun-an; D'Souza, Raissa M.

2018-01-01

We study the synchronizability of duplex networks formed by two randomly generated network layers with different patterns of interlayer node connections. According to the master stability function, we use the smallest nonzero eigenvalue and the eigenratio between the largest and the second smallest eigenvalues of supra-Laplacian matrices to characterize synchronizability on various duplexes. We find that the interlayer linking weight and linking fraction have a profound impact on synchronizability of duplex networks. The increasingly large inter-layer coupling weight is found to cause either decreasing or constant synchronizability for different classes of network dynamics. In addition, negative node degree correlation across interlayer links outperforms positive degree correlation when most interlayer links are present. The reverse is true when a few interlayer links are present. The numerical results and understanding based on these representative duplex networks are illustrative and instructive for building insights into maximizing synchronizability of more realistic multiplex networks.

Microestructura de una unión disímil AISI 321 y una aleación A 351 grado HK-40 obtenida mediante soldadura manual por arco eléctrico

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Reilis Fuentes-Guilarte

2016-05-01

Full Text Available El objetivo fue establecer el comportamiento microestructural de una unión disímil de acero inoxidable austenítico AISI 321 y de la aleación A 351 grado HK 40 obtenida por fundición mediante soldadura manual por arco eléctrico y electrodos revestidos del tipo E 309 L-16. La estructura ferrita–austeníta que se forma en la unión del acero con la aleación es resultado del elevado contenido de carbono de la segunda. La baja velocidad de enfriamiento del cordón de soldadura revela ausencia de discontinuidades en el retículo cristalino de la zona afectada térmicamente y atenúa la formación de carburos de cromo del tipo Cr23C6, que puede formar la aleación A 351 grado HK 40 durante la difusión del volumen de fracción en masa del cromo.

Comportamiento a fatiga del vástago de una prótesis para cadera al caminar//Fatigue behavior stem hip prosthesis for walking

OpenAIRE

Ángel Martínez-Delfín; Javier García-de-la-Figal-Costales; Luís Manuel Rodríguez-Milián; Reynaldo Rodríguez-Pérez

2014-01-01

La prótesis de cadera consiste en sustituir la parte superior fracturada del fémur por una pieza de material biocompatible. Debido a las cargas aleatorias que sobre esta prótesis actúan al caminar la persona injertada, surge la fatiga sobre la prótesis. En este trabajo se realiza el cálculo a fatiga del vástago de una prótesis de caderas fabricada con acero inoxidable austenítico AISI 316L GrQ y de uso actual. Para ellose emplea el método de los elementos finitos, considerando la compleja geo...

Modelamiento del proceso de recubrimiento de instrumental quirúrgico con cromoduro

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Jairo Ruiz

2003-01-01

Full Text Available En este artículo se presenta un modelo estadístico que describe el comportamiento de la variable respuesta espesor del recubrimiento de cromoduro en los portagujas quirúrgicos, de acero inoxidable martensítico, como función del tiempo de exposición, la densidad de corriente y la temperatura; el modelo fue ajustado por medio de un diseño experimental rotacional compuesto de segundo orden. El modelo tiene un poder de explicación del 75% en la variabilidad de la respuesta, que se considera muy satisfactorio dada la complejidad del proceso.

On the Secrecy Degrees of Freedom with Full-Duplex Communication

DEFF Research Database (Denmark)

Mahmood, Nurul Huda; Mogensen, Preben Elgaard

2017-01-01

of such an application. The potential of full duplex nodes in improving the physical layer security of a communication link is investigated in this contribution. We specifically derive the information theoretic secrecy degrees of freedom measure for a pair of nodes communicating in full duplex mode. Moreover, closed...... and the delay reduction of full duplex communication are somewhat limited in realistic network settings, leading researchers to study other possible applications of full duplex communication which can provide significantly higher gains over half duplex communication. Physical layer security is an example...... form expressions for the instantaneous and ergodic throughput gain of full duplex communication over conventional half duplex is derived. The secrecy degrees of freedom with full duplex is shown to be two as opposed to that of zero in half duplex mode....

Full-Duplex Relay Selection in Cognitive Underlay Networks

KAUST Repository

Khafagy, Mohammad Galal; Alouini, Mohamed-Slim; Aissa, Sonia

2017-01-01

In this work, we analyze the performance of full-duplex relay selection (FDRS) in spectrum-sharing networks. Contrary to half-duplex relaying, full-duplex relaying (FDR) enables simultaneous listening/forwarding at the secondary relay(s), thereby

AUMENTO EN LA RESISTENCIA A LA CORROSIÓN DE UN ACERO T91 ALUMINIZADO

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LUZ S. QUINTERO

2011-01-01

Full Text Available El acero ferrítico T91 ha sido ampliamente utilizado en plantas de generación de energía eléctrica, calderas y plantas nucleares. Sin embargo, su resistencia a la oxidación se ve gravemente afectada a temperaturas superiores a los 600ºC. En esta investigación se empleó la técnica de cementación empacada para aluminizar un acero T91 y se encontraron las condiciones óptimas para la formación de un recubrimiento libre de porosidad y con espesor uniforme (300 micras. Se evaluó la capa de óxido formada luego de una exposición a 800ºC en atmósfera de aire. La caracterización del recubrimiento y de la capa de óxido (Al2O3 se llevó a cabo empleando un microscopio electrónico de barrido (SEM, Espectroscopia de Rayos X (EDX y mapping. Se comprobó una buena resistencia a la oxidación del acero T91 aluminizado, debido a la formación de una fina capa continua de óxido de aluminio de aproximadamente 6 micras de espesor luego de una exposición de 7 días.

Análise microestrutural e tenacidade ao impacto da ZAC do aço inoxidável ferrítico com 11%Cr

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Temístocles de Sousa Luz

2013-09-01

Full Text Available O aço inoxidável ferrítico possibilita, em função de suas características, o uso em diversos campos da engenharia. Dentre esses é possível citar a industria do petróleo e gás, de celulose açucareira, de transporte, entre outras. Atualmente, o desenvolvimento de novas ligas para a substituição dos aços ao carbono no que se refere ao setor de transporte de carga, levou muitos fabricantes a adotarem a liga ferrítica com base de cromo entre 11% e 12%, implementando a tal situação, uma maior vida util. A utilização dessa nova classe de aço inoxidável ferrítico gera uma demanda no que tange à pesquisas das soldas desses aços. Neste trabalho, buscou-se analisar a região soldada de um aço inoxidável ferrítico experimental contendo 11% de cromo, realizando para tal um estudo de sua microestrutura, e tenacidade ao impacto do metal de base e da zona afetada pelo calor (ZAC. A avaliação mostrou bons resultados nas propriedades mecânicas medidas nas duas regiões analisadas. Entretanto, verificou-se uma perda acentuada da tenacidade ao impacto na ZAC em relação ao metal de base.

Aumento en la resistencia a la corrosión de un acero t91 aluminizado

OpenAIRE

QUINTERO, LUZ S.; LAVERDE, DIONISIO; ESCALANTE, HUMBERTO

2011-01-01

El acero ferrítico T91 ha sido ampliamente utilizado en plantas de generación de energía eléctrica, calderas y plantas nucleares. Sin embargo, su resistencia a la oxidación se ve gravemente afectada a temperaturas superiores a los 600ºC. En esta investigación se empleó la técnica de cementación empacada para aluminizar un acero T91 y se encontraron las condiciones óptimas para la formación de un recubrimiento libre de porosidad y con espesor uniforme (300 micras). Se evaluó la capa de óxido f...

Harvesting full-duplex rate gains in cellular networks with half-duplex user terminals

KAUST Repository

AlAmmouri, Ahmad

2016-07-26

Full-Duplex (FD) transceivers may be expensive in terms of complexity, power consumption, and price to be implemented in all user terminals. Therefore, techniques to exploit in-band full-duplex communication with FD base stations (BSs) and half-duplex (HD) users\\' equipment (UEs) are required. In this context, 3-node topology (3NT) has been recently proposed for FD BSs to reuse the uplink (UL) and downlink (DL) channels with HD terminals within the same cell. In this paper, we present a tractable mathematical framework, based on stochastic geometry, for 3NT in cellular networks. To this end, we propose a design paradigm via pulse-shaping and partial overlap between UL and DL channels to maximize the harvested rate gains in 3NT. The results show that 3NT achieves a close performance to networks with FD BSs and FD UEs, denoted by 2-node topology (2NT) networks. A maximum of 5% rate loss is reported when 3NT is compared to 2NT with efficient self-interference cancellation (SIC). If the SIC in 2NT is not efficient, 3NT highly outperforms 2NT. Consequently, we conclude that, irrespective to the UE duplexing scheme, it is sufficient to have FD BSs to harvest FD rate gains.

stainless steel by SEM-XRD and image analysis

Directory of Open Access Journals (Sweden)

Robinson Constanzo-R.

2014-01-01

Full Text Available El objetivo de este trabajo fue realizar un análisis cualitativ o de la distribución de un electrodepósito de cobre en el inter ior de electrodos porosos (EP de acero inoxidable y carbono grafito. Para ello, se reali zaron pruebas de electrodepositación de cobre a nivel de labora torio, con un posterior análisis de cortes de muestras de acero y grafito vía Microscopía Estereoscópica, Microscopía SEM-DRX y Análisis de Imagen, los cuales mostraron que el cobre no se deposita en forma uniforme al interior del electrodo. En el electrodo de acero, la penetra ción del depósito en el espesor fue alrededor de 50%, mientras que para el grafito a lrededor de 90%. En forma general, se observó un aumento de la cantidad de depósito hacia el extremo frente al ánodo y con sitios de difer ente crecimiento en depósito de cobre. Esto demuestra una distr ibución de corriente y potencial, función de parámetros físicos de electrodo y de la s características fisicoquímicas e hidrodinámicos del electroli to.

Identificación de aceros por espectroscopia de rompimiento inducido por láser (LIBS) y análisis de componentes principales

OpenAIRE

Contreras, U.; Meneses-Nava, M.A.; Torres-Armenta, D.; Robles-Camacho, J.; Barbosa-García, O.

2012-01-01

En la actualidad existe una producción de mas de 100 000 aceros diferentes de acuerdo a su composición química y propiedades mecánicas; sin embargo, una vez en el mercado, no existe técnica alguna capaz de identificar y clasificar cualquier acero según su clase o grado. En este trabajo se describe un método capaz de identificar y clasificar aceros a través de la determinación de su composición química. El método propuesto se basa en un análisis de espectroscopia atómica procedente de la técni...

Estudio del comportamiento a fluencia en caliente de un acero avanzado de alta resistencia de bajo contenido en carbono NiCrVCu microaleado con boro

OpenAIRE

González Sala, Sara

2009-01-01

Una de las líneas de investigación prioritarias en el contexto internacional es el desarrollo de aceros avanzados de alta resistencia (AHSS) con excelentes propiedades de resistencia y tenacidad para aplicaciones en la industria automotriz, naval, aeronáutica y de generación de energía, que permitan disminuir el peso de los componentes y sustituyan aceros tradicionales de contenidos mayores de carbono. Los aceros AHSS microaleados al boro, debido a sus cualidades, tecnología de...

Fenómenos de corrosión galvánica en las uniones aluminio y acero

OpenAIRE

Domínguez Parra, Alberto

2009-01-01

La corrosión es un proceso de degradación de un material al interactuar con el ambiente que le rodea. El presente proyecto trata de la corrosión galvánica de aceros y fundiciones, en contacto con aleaciones de aluminio. Su experimentación se ha realizado con acero AE 275 B, y fundición EN-GS 400 12. Se utilizó lingote de aluminio A356 obtenido por colada por gravedad, y dos tipos de muestras, con y sin tratamiento térmico T6, de A 356 producidas por el procedimiento de sub-liquidus casting...

Duplex kidney: not just a drooping lily.

Science.gov (United States)

Doery, Ashlea J; Ang, Eileen; Ditchfield, Michael R

2015-04-01

Duplex kidneys are common, mostly asymptomatic and of no clinical significance. However, they can be associated with significant pathology, often with long-term morbidity. There is minimal literature on the review of the duplex kidney, its associated anomalies and complications. The purpose of this paper is to review our experience of imaging the spectrum of abnormalities associated with duplex kidneys in the paediatric population and correlate this with contemporary literature. A retrospective review of the radiology database in a tertiary paediatric centre was performed. A word search of the Radiology Information System for 'duplex' of patients under the age of 16 was undertaken and limited to studies performed between 2006 and 2013. Two hundred seventy-four patients were identified (age range 0-16, median 3 years, gender 59.9% female) who had 836 studies: ultrasound 598/836 (71.6%), nuclear medicine 180/836 (21.5%), micturating cystourethrogram 52/836 (6.2%), MRI 5/836 (duplex and no complication (151/274 = 55.1%), upper moiety obstruction, lower moiety reflux/scarring, multicystic dysplastic kidney, abnormal ureteric insertion and other pathology. Duplex kidneys are common and often not clinically significant. However, this study demonstrates almost 50% of paediatric patients investigated for duplex kidneys had complications requiring treatment. The most common complications were upper moiety obstruction associated with a ureterocele and lower moiety vesicoureteric reflux. Ultrasound was the most common modality for early detection of these complications. © 2015 The Royal Australian and New Zealand College of Radiologists.

Full Duplex Communications in 5G Small Cells

DEFF Research Database (Denmark)

Mahmood, Nurul Huda; Gatnau, Marta; Berardinelli, Gilberto

2017-01-01

Full duplex communication promises system performance improvement over conventional half duplex communication by allowing simultaneous transmission and reception. However, such concurrent communication results in strong self interference and an increase in the overall network interference, and can...... only be exploited when traffic is available in both directions. The potential throughput gains of full duplex communication over conventional half duplex transmission in a small cell network with asymmetric traffic conditions is investigated in this contribution. The throughput performance gains...... are analysed using tools from stochastic geometry, and further confirmed through extensive system level simulations. Our findings explicitly quantify how the gains from full duplex communication depend on the traffic profile and the inter-cell interference coupling. The demonstrated throughput gains and delay...

Alternativa de protección contra la corrosión del acero AISI 310S mediante recubrimiento de aluminio bajo condiciones de platos separadores en celdas de combustible de carbonatos fundidos

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R. Orozco-Cruz

2016-01-01

Full Text Available Introducción: La celda de combustible de carbonatos fundidos (MCFC, por sus siglas en inglés convencional opera a 650°C. Consiste de un cátodo de NiO poroso y litiado, una mezcla eutéctica de carbonato de litio (Li2CO3 y carbonato de potasio (K2CO3 fundido en una matriz electrolitica de óxido de aluminio litiado (LiAlO2 y un ánodo poroso de Ni. Los platos separadores entre cada celda presentan problemas de corrosión. Ante eso, un acero inoxidable AISI 310S con recubrimiento fue estudiado en condiciones de un plato separador en una MCFC. Método: Se utilizó un acero inoxidable AISI 310S como sustrato (muestra A, aplicándole un recubrimiento de Al con (B y sin tratamiento térmico (C. Fueron expuestos en carbonatos fundidos (62 mol% Li2CO3 -38 mol% K2CO3 a 650 °C en crisoles de alúmina. El comportamiento electroquímico fue estudiado mediante la técnica de Espectroscopía de Impedancia Electroquimica (EIS. Para el análisis de los diagramas de impedancia, se utilizó el software de simulación “Boukamp Equivalent Circuit”. La sección transversal de las muestras corroídas fue caracterizada mediante Microscopía Electrónica de Barrido (SEM, por sus siglas en inglés y los productos formados por Difracción de rayos X (XRD, por sus siglas en inglés. Resultados: Los diagramas de EIS presentan aumentos y disminuciones en los semicírculos formados a altas frecuencias indicativo de disolución de la capa externa, aumento y disminución de la resistencia de esta última así como el posible rompimiento de ella. La técnica de XRD presentó fases LiFeO2, LiCrO2, -LiAlO2 y -LiAlO2 así como fases intermetálicas para las distintas condiciones de la muestra. De la misma manera, los análisis de SEM presentaron los espesores de cada una de las capas formadas. Discusión o Conclusión: En la muestra A, se formaron capas de LiFeO2 y LiCrO2 después de 200 horas de exposición. La capa de LiCrO2 aumenta por la difusión de Li hacia el

Efectos del tratamiento térmico en la fractura de aceros

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Héctor Hernández A.

1992-05-01

Full Text Available No obstante de los avances logrados en otros tipos de aleaciones, los aceros se siguen utilizando en forma extensiva en la construcción de elementos estructurales, porque con una adecuada selección y tratamiento técnico, los aceros permiten obtener una conveniente combinación de propiedades mecánicas ante unas exigencias específicas de servicio. La fractura en elementos de máquinas frecuentemente se encuentra asociada a una discontinuidad, la cual provoca una concentración de esfuerzo, lo que puede originar sitios de iniciación de una falla por fractura. La carga límite de fractura es afectada por parámetros geométricos, naturaleza y tipo de carga y propiedades mecánicas del material. La mayoría de fallas por fractura de elementos de máquinas son fallas por fatiga; por lo general una fractura por fatiga tiene lugar por una progresiva generación y crecimiento de grietas hasta obtenerse una condición crítica de fractura súbita de la sección residual resistente. Frecuentemente en una fractura por fatiga se observan marcas de playa, las cuales son evidencias de la posición del frente de grietas antes que se alcance la condición de fractura súbita final. En este trabajo se muestra como el tratamiento térmico de temple y revenido de los aceros afecta el esfuerzo límite de falla por fractura para carga de tracción estática y carga de fatiga uniaxial con la presencia de una entalla severa. También se estudia el efecto del tratamiento térmico en la tenacidad de fractura, propiedad que cuantifica la resistencia al crecimiento súbito de una grieta bajo carga estática.

Influencia sobre los tratamientos térmicos del contenido de aluminio de aceros no aleados

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Carreras, L.

1999-08-01

Full Text Available The main purpose of this article is to determine the optimal level of aluminum content in plain steels to have the optimal mechanical properties by means of surface heat treatments. Various plain steels with different aluminium content have been studied. The importance of treatment temperature is analyzed. The influence of other factors, like nitrogen content or the homogenous distribution of particles, is evaluated. It is concluded that the aluminum composition of plain steels that are subjected to heat treatments should not exceed 0.02 %.

El objetivo de este trabajo es determinar el intervalo óptimo de contenidos de aluminio en aceros no aleados para los que se consiguen las propiedades mecánicas óptimas mediante tratamientos térmicos de superficie. Se estudian diferentes coladas de acero en las que varía el contenido de aluminio y las temperaturas de tratamiento. Se evalúa la importancia de otros factores tales como el contenido de nitrógeno y la homogeneidad en la distribución de partículas endurecedoras. Se llega a la conclusión de que los aceros no aleados destinados a tratamientos térmicos no deben tener un contenido de aluminio superior al 0,02 %.

Desgaste por deslizamiento en seco de aceros perlíticos y bainíticos

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Cristian Camilo Viáfara Arango

2004-01-01

Full Text Available El desgaste por deslizamiento tiene una gran influencia sobre el desempeño de los sistemas rueda-riel, en particular, por el deslizamiento de la pestaña de la rueda sobre la parte interna del riel en una pista curva. Dado que el deslizamiento entre la rueda y el riel involucra efectos de adhesión, altos porcentajes de deslizamiento/rodadura afectan fuertemente el desgaste por fatiga de contacto por rodadura, que actúa en las superficies de contacto. En una máquina Pin sobre Disco se llevaron a cabo ensayos de desgaste por deslizamiento para estudiar el comportamiento del acero perlítico AISI 1070 y el bainítico AISI 15B30. La velocidad de deslizamiento fue 1 ms-1 para todas las pruebas y se utilizaron cargas normales de 10, 30 y 50 N. La resistencia al desgaste fue relacionada con la pérdida de masa medida después de las pruebas y las superficies desgastadas, al igual que las partículas removidas, fueron analizadas por medio de los microscopios óptico y electrónico. Se realizaron perfiles de microdureza bajo las superficies de contacto para analizar el efecto del endurecimiento por deformación. El acero perlítico mostró mayor resistencia al desgaste que el acero bainítico, debido al excelente comportamiento de endurecimiento por deformación de la perlita comparado con el de la bainita. En el acero perlítico se observaron regímenes de desgaste oxidativo, mientras que en el bainítico el principal mecanismo de remoción de material fue el adhesivo, llevando a un daño mucho más fuerte en la superficie. De hecho, el régimen de desgaste para las probetas bainíticas fue siempre severo, aún con la menor carga normal aplicada.

Análisis de falla en cable de acero Análisis de falla en cable de acero

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E. A. Ossa

2005-12-01

Full Text Available Este artículo describe el análisis de falla realizado en dos muestras de cables de acero que sufrieron falla súbita bajo condiciones de carga de trabajo normales. La falla fue causada por una carga menor a la capacidad nominal. Luego de inspección óptica se evidenció que la falla fue ocasionada por fatiga del material de uno de los cables.This paper describes the failure analysis of two wire ropes fractured during normal working conditions. The failure was caused by a load well below the nominal maximum resistance of the ropes. Optical microscopy indicated fatigue failure of one of the cables.

Procesos de unión y estudio de interfaces en Si3N4 y ZrO2

OpenAIRE

Polanco Rodríguez, Raquel

2007-01-01

Esta memoria se ha centrado en la obtención de uniones en dos tipos de materiales cerámicos alto interés tecnológico, como son el nitruro de silicio y el óxido de circonio. El trabajo desarrollado en esta tesis ha consistido, principalmente, en el estudio y caracterización de las interfaces metaVcerámica generadas tras el proceso de unión en estos materiales consigo mismos, o bien con piezas metálicas. En el' caso del ShN4 se utilizó acero inoxidable como lámina de unión. Por o...

Development of UO{sub 2}-Stainless Steel Fuel Plates Containing 30-50 Vol. % Oxide; Fabrication de plaques de combustible en acier inoxydable-UO{sub 2} contenant 30 a 40% d'oxyde (en volume); Razrabotka toplivnykh ehlementov iz nerzhaveyushchej stali i UO{sub 2}, soderzhashchikh 30 - 50 OB.% okisi; Elaboracion de placas de combustible de acero inoxidable UO{sub 2} conteniendo 30 a 40% de oxido (en volumen)

Energy Technology Data Exchange (ETDEWEB)

Lloyd, H. [Atomic Energy Research Establishment, Harwell (United Kingdom)

1963-11-15

lesquelles les particules de UO{sub 2} sont reparties uniformement dans la matrice en acier inoxydable, ainsi que le procede de revetement des plaques de combustible par rechargement a chaud. On a etudie des operations de laminage comprenant des deformations allant de 40% a 90%, a des temperatures allant jusqu'a 1300{sup o}C pour determiner les conditions optimums de production des noyaux de densite elevee et pour realiser une bonne cohesion entre les elements constitutifs des plaques, la fissuration des particules de UO{sub 2} etant reduite au minimum. L'auteui decrit la fabrication de grandes plaques de combustible composees de plaques a plusieurs noyaux, liees ensemble par laminage a chaud. L'auteur donne des indications sur les proprietes mecaniques de cermets UO{sub 2}-Inox contenant 30, 40 et 50% de UO{sub 2}(en volume), fabriques comme on l'a indique plus haut et essayes bruts de laminage et recuits a diverses temperatures allant jusqu'a 700{sup o}C. Il a utilise a cet effet des echantillons preleves les uns perpendiculairement, les autres parallelement au sens du laminage. Il examine en outre l'influence de la taille des particules de UO{sub 2} et de l'uniformite de leur repartition sur les proprietes mecaniques. Il a determine egalement les forces de liaison entre le noyau et la gaine pour des cermets similaires dans la meme gamme de temperatures. Le memoire contient encore les resultats d'essais de cyclage thermique entre 50 et 800{sup o}C entrepris pour determiner les effets de ce cyclage sur la structure du cermet et la stabilite de la liaison, apres 100, 500 et 1000 cycles. (author) [Spanish] La memoria expone los recientes progresos en lo relativo a la elaboracion de elementos combustibles del tipo de UO{sub 2} y acero inoxidable en placas, que contienen hasta 50% de UO{sub 2} en volumen. Describe la preparacion de particulas esfericas de UO{sub 2} sinterizado, de elevada densidad, de granulome tria comprendida entre 100 y 500, y la compactacion y sinterizacion

EFECTO DEL PRECALENTAMIENTO Y LA SEVERIDAD DE TEMPLE SOBRE LA RESISTENCIA AL DESGASTE ADHESIVO DEL ACERO AUSTENÍTICO AL MANGANESO

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OSCAR FABIÁN HIGUERA COBOS

2010-01-01

Full Text Available En este trabajo de investigación se estudió el efecto del precalentamiento y la severidad de temple sobre la resistencia al desgaste adhesivo del acero austenítico al manganeso ASTM A 128 grado C. El material se sometió a ciclos térmicos de temple y revenido con y sin precalentamiento con el fin de evaluar su influencia sobre la resistencia al desgaste. Posteriormente el material fue sometido a prueba según norma ASTM G83 y se determinó que el acero Austenítico al manganeso, es un material que presenta una microestructura metaestable en condiciones estables y no debe ser sometido a tratamiento térmico de revenido a altas temperaturas debido que favorece la descomposición de esta a ferrita (fase blanda de los acero y por ende disminuye su resistencia al desgaste.

Mejoramiento de la resistencia a la corrosión del acero AISI 4140 utilizando multicapas de titanio/nitruro de titanio

Directory of Open Access Journals (Sweden)

Faber Correa

2008-01-01

Full Text Available El acero 4140 se utiliza ampliamente en la fabricación de partes de máquinas con durezas entre 25-35 Rockwell C. Sin embargo, su vida útil se ve limitada por su baja resistencia al desgaste y a la corrosión. Con el fin de mejorar su comportamiento frente a la corrosión se depositaron multicapas de Titanio/Nitruro de Titanio (Ti/TiN sobre substratos de acero 4140 mediante un sistema multi-blanco d.c. magnetrón sputtering a partir de un blanco de Ti de alta pureza (99,99% en una atmósfera de Ar/N2. Con el objeto de estudiar el efecto del número de capas sobre la velocidad de corrosión de las películas depositadas, se crecieron multicapas con 1, 5, 10, 15, y 20 bicapas de [Ti /TiN], manteniendo un espesor total constante de 3 um en todas ellas. Las fases existentes y composición química de los recubrimientos fueron analizados mediante espectroscopía de difracción de rayos X (XRD y espectroscopía de energía dispersiva de rayos X (EDX respectivamente. Las muestras de acero sin y con recubrimiento se caracterizaron además por Espectroscopía de Impedancia Electroquímica (EIS y curvas de polarización Tafel. Se encontró que la velocidad de corrosión tuvo una disminución alrededor del 87% en el acero recubierto con 20 bicapas de Ti/TiN en comparación al acero sin recubrir y del 25% respecto a la muestra recubierta con 1 bicapa, lo cual evidencia el efecto positivo del incremento del período en las películas delgadas basadas en multicapas de Ti/TiN.

Buffer management in wireless full-duplex systems

KAUST Repository

Bouacida, Nader; Showail, Ahmad; Shihada, Basem

2015-01-01

, we address the problem of buffer management in full-duplex networks by using Wireless Queue Management (WQM), which is an active queue management technique for wireless networks. Our solution is based on Relay Full-Duplex MAC (RFD

Energy balance and deformation mechanisms of duplexes

Science.gov (United States)

Mitra, Gautam; Boyer, Steven E.

A duplex consists of a series of imbricate faults that are asymptotic to a roof thrust and a floor thrust. Depending on the final orientations of the imbricate faults and the final position of the branch lines, a duplex may be hinterland-dipping, foreland-dipping, or an antiformal stack. The exact geometry depends on various factors such as the initial dimensions of the individual slices (horses), their lithology, the amount of displacement (normalized to size of horse) on each fault, and the mechanics of movement along each fault. The energy required in duplex formation can be determined by calculating the total work involved in emplacing each horse: this is given by where W t=W p+W b+W g+W iWp is the work involved in initiating and propagating a fracture. Wb is the work involved in basal sliding, which may be frictional or some form of ductile flow, Wg is the work done against gravity during the emplacement of the horse, and Wi is the work involved in the internal deformation of the horse. By calculating and comparing these work terms it is possible to predict the conditions under which the different types of duplexes will form. Normally, the development of a hinterland-dipping duplex is most likely. However, if deformation conditions are favorable, displacements on individual imbricate faults may be very large compared to the size of the horses, leading to the formation of either antiformal stacks or foreland-dipping duplexes.

Duplex ultrasound surveillance after carotid artery endarterectomy.

Science.gov (United States)

Al Shakarchi, Julien; Lowry, Danielle; Nath, Jay; Khawaja, Aurangzaib Z; Inston, Nicholas; Tiwari, Alok

2016-06-01

After carotid endarterectomy (CEA), patients have been regularly followed up by duplex ultrasound imaging. However, the evidence for long-term follow-up is not clear, especially if the results from an early duplex scan are normal. This study assessed and systematically reviewed the evidence base for long-term surveillance after CEA and a normal early scan. Electronic databases were searched for studies assessing duplex surveillance after CEA in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The primary outcome for this study was the incidence of restenosis after a normal early scan. The secondary outcome was the number of reinterventions after a normal early scan. The review included seven studies that reported 2317 procedures. Of those patients with a normal early scan, 2.8% (95% confidence interval, 0.7%-6%) developed a restenosis, and 0.4% (95% confidence interval, 0%-0.9%) underwent a reintervention for their restenosis during the follow-up period. This review confirms that routine postoperative duplex ultrasound surveillance after CEA is not necessary if the early duplex scan is normal. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Optimización del acero usado como soporte y gancho de sujeción del acero de refuerzo en cimentaciones de concreto

OpenAIRE

Sánchez Trujillo, Bryan; Sánchez Trujillo, Bryan; Sánchez Trujillo, Bryan

2015-01-01

Para el proceso constructivo de cimentaciones de concreto se usan diversos accesorios, algunos estandarizados y otros no; uno de los no estandarizados es el acero usado como soporte y gancho de sujeción de las barras de refuerzo, (comúnmente llamado "burro", "burrito" o "silletas" de soporte), pues en los planos estructurales no se detalla la forma de colocar y sostener las barras de refuerzo y en obra las silletas se colocan de forma empírica según las experiencias previas de los encargados ...

Estudio mediante difracción de rayos X de las tensiones residuales producidas durante el depósito de películas delgadas de TiN sobre sustratos metálicos

Directory of Open Access Journals (Sweden)

Mónica Monsalve

2010-01-01

Full Text Available En este trabajo se analizó la influencia que tiene el espesor de la película y el tipo de sustrato en el nivel y tipo de esfuerzos residuales generados en recubrimientos de TiN obtenidos por dos técnicas de deposición física en fase vapor: pulverización catódica con magnetrón e implantación iónica. Los sustratos utilizados fueron un acero inoxidable AISI 304 y un acero de herramientas AISI M2. Las tensiones residuales, las fases presentes y la orientación cristalográfica de las películas depositadas fueron obtenidas mediante análisis de difracción de rayos X por incidencia rasante. Se encontró que los esfuerzos residuales fueron mayores en las películas depositadas por la técnica de pulverización catódica con magnetrón que en las depositadas por la técnica de implantación iónica. En ambos casos estos esfuerzos son de compresión y disminuyen en la medida que aumenta el espesor de la película. Esto se debe a la forma como se entrega la energía, la capa en crecimiento y el momentum de las partículas ionizadas, lo que influye directamente en la microestructura y aumento o disminución de los esfuerzos residuales. En cuanto al tipo de sustrato se obtuvieron esfuerzos mayores en las películas depositadas sobre el acero AISI 304 que en las depositadas sobre el acero AISI M2, lo cual se debe posiblemente a que este último acero tiene un menor coeficiente de expansión térmica.

On the Performance of In-Band Full-Duplex Cooperative Communications

KAUST Repository

Khafagy, Mohammad Galal

2016-01-01

-duplex potentials. Full-duplex relaying (FDR), where intermediate nodes may now support source-destination communication via simultaneous listening/forwarding, represents one of two full-duplex settings currently recommended for deployment in future fifth

Full-Duplex MIMO Small-Cell Networks: Performance Analysis

OpenAIRE

Atzeni, Italo; Kountouris, Marios

2015-01-01

Full-duplex small-cell relays with multiple antennas constitute a core element of the envisioned 5G network architecture. In this paper, we use stochastic geometry to analyze the performance of wireless networks with full-duplex multiple-antenna small cells, with particular emphasis on the probability of successful transmission. To achieve this goal, we additionally characterize the distribution of the self-interference power of the full-duplex nodes. The proposed framework reveals useful ins...

Caracterización mecánica de aceros empleados en el sector de la construcción de Almería

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Senoboua, A. J.

2003-12-01

Full Text Available Various tests have been conducted on the steel bars used in the construction of civil works in Almería (Spain during the period 18 January 2000-7 May 2001, with the aim of mechanically characterizing the different types of steel (weldable: B400S, B500S and ductile weldable: B400SD to determine whether there is a technical reason for the increase in the use of ductile weldable steel. For this, we have used a hydraulic machine to break by traction all the test samples that arrived to the laboratory, following the specifications of the UNE 7474-1:1992 and the UNE 7474-2:1992. The results indicate that only in 86 % of the cases does the steel B400SD satisfy the limits specified by the UNE 36065:1999-EX, as opposed to 95 and 94 % of the B400S and B500S steels. In addition, the ductile weldable steel registered mean values lower than those of B400S. This finding disagrees with expectations set by the specifications.

Se realizaron varios ensayos sobre las barras de acero utilizadas en la construcción de obra civil en Almería, durante el período comprendido entre 18/1/2000 y 7/05/2001, con el fin de caracterizar, mecánicamente, los diferentes tipos de aceros (soldables: B400S, B500S y soldable dúctil: B400SD y, de esta forma, determinar si existe alguna razón técnica para un incremento del consumo del acero soldable dúctil. Para ello, se ensayaron a tracción todas las muestras que llegaron al laboratorio, siguiendo las normas UNE 7474-1:1992 y UNE 7474-2:1992. Los resultados indican que el acero B400SD cumple, sólo, en un 86 % los límites especificados en la norma UNE 36065:1999 -EX, frente al 95 y 94 % de los aceros B400S y B500S. Además, el acero soldable dúctil muestra unos valores medios inferiores al B400S. Este hecho discrepa de lo que se podría esperar según la norma que lo regula.

Influence of microstructure on the microbial corrosión behaviour of stainless steels

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Moreno, Diego Alejandro

2000-08-01

Full Text Available Several stainless steels (Types UNS S30300, S30400, S30403, S31600, S31603 and S42000 with different microstructural characteristics have been used to study the influence of heat treatments on microbiologically influenced corrosion (MIC. Biocorrosion and accelerated electrochemical testing was performed in various microbiological media. Two species of sulphate-reducing bacteria (SRB have been used in order to ascertain the influence of microstructure. The morphology of corrosion pits produced in both chloride and chloride plus sulphide -SRB metabolites- was inspected by optical and scanning electron microscopy (SEM complemented with energy-dispersive X-ray (EDX analysis. Results have shown different behaviours regarding corrosion resistance in each case studied. Sensitized austenitic stainless steels were more affected by the presence of aggressive anions and pitting potential (Ep values were more cathodic than those of as-received state. A corrosion enhancement is produced by the synergistic action of biogenic sulphides and chloride anions. Pitting corrosion in martensitic stainless Steel Type UNS S42000 was found in a- biocorrosion test. The pitting morphology is correlated to the chemical composition, the microstructure and the electrolyte.

Se han utilizado aceros inoxidables de los tipos UNS S30300, S30400, S30403, S31600, S31603 y S42000, en diferentes estados microestructurales, para estudiar la influencia de los tratamientos térmicos sobre la corrosión microbiana. Para ello, se han realizado ensayos electroquímicos y ensayos de biocorrosión, en diferentes medios microbiológicos, utilizándose dos especies de bacterias reductoras de sulfatos (SRB. La morfología de las picaduras, producidas en presencia de cloruros y en presencia de cloruros más sulfuros -metabolitos de SRB-, se ha analizado por microscopía óptica y por microscopía electrónica de barrido (SEM complementada con análisis por energía dispersiva de rayos X

Tribological properties of BixTiyOz films grown via RF sputtering on 316L steel substrates

Directory of Open Access Journals (Sweden)

Johanna Parra

2015-01-01

Full Text Available En este trabajo se presentan los resultados obtenidos en el análisis químico superficial, la caracterización morfológica y evaluación de las propiedades tribológicas de recubrimientos de titanato de bismuto amorfo (BixTiyOz depositados sobre sustratos de acero inoxidable 316L utilizando la técnica de pulverización catódica rf. El análisis químico elemental se realizó por medio de espectroscopia de electrones Auger (EEA, la morfología de los recubrimientos se determinó mediante microscopia de fuerza atómica (MFA. Las medidas del coeficiente de fricción y la tasa de desgaste fueron obtenidas mediante pruebas de bola sobre disco. Los análisis de EEA permitieron establecer que los primeros 10 nm de los recubrimientos están formados probablemente por óxidos de Bi4Ti3O12 y Ti2O3, las medidas de AFM indican que los recubrimientos tienen una rugosidad promedio de 22.28nm y un tamaño de grano de 50nm. Finalmente, las pruebas tribológicas establecieron que el coeficiente de fricción y la tasa de desgaste del acero recubierto tiene valores similares al acero desnudo.

Consideraciones teórico prácticas acerca de la soldadura de los aceros al carbono

Directory of Open Access Journals (Sweden)

Osmundo Héctor Rodríguez Pérez

2006-01-01

Full Text Available Se analizan los tres tipos de aceros al carbono y su clasificación desde el punto de vista de su soldabilidad. Se pueden observar los aspectos físico - químicos en la zona fundida, zona de transición y zona afectada por el calor. Existen varios aspectos en la tecnología de la soldadura de los aceros al carbono, tales como: preparación de los bordes, limpieza superficial, posición relativa de las piezas, precalentamiento, selección del material de aporte, deposición de los cordones, postcalentamiento, tratamiento térmico posterior y el control de la calidad de las uniones soldadas a tomar en cuenta para realizar la soldadura.

Joint duplex mode selection, channel allocation, and power control for full-duplex cognitive femtocell networks

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Mingjie Feng

2015-02-01

Full Text Available In this paper, we aim to maximize the sum rate of a full-duplex cognitive femtocell network (FDCFN as well as guaranteeing the quality of service (QoS of users in the form of a required signal to interference plus noise ratios (SINR. We first consider the case of a pair of channels, and develop optimum-achieving power control solutions. Then, for the case of multiple channels, we formulate joint duplex model selection, power control, and channel allocation as a mixed integer nonlinear problem (MINLP, and propose an iterative framework to solve it. The proposed iterative framework consists of a duplex mode selection scheme, a near-optimal distributed power control algorithm, and a greedy channel allocation algorithm. We prove the convergence of the proposed iterative framework as well as a lower bound for the greedy channel allocation algorithm. Numerical results show that the proposed schemes effectively improve the sum rate of FDCFNs.

Improper Signaling for Virtual Full-Duplex Relay Systems

KAUST Repository

Gaafar, Mohamed; Amin, Osama; Schaefer, Rafael F.; Alouini, Mohamed-Slim

2017-01-01

Virtual full-duplex (VFD) is a powerful solution to compensate the rate loss of half-duplex relaying without the need to full-duplex capable nodes. Inter-relay interference (IRI) challenges the operation of VFD relaying systems. Recently, improper signaling is employed at both relays of the VFD to mitigate the IRI by imposing the same signal characteristics for both relays. To further boost the achievable rate performance, asymmetric time sharing VFD relaying system is adopted with different improper signals at the half-duplex relays. The joint tuning of the three design parameters improves the achievable rate performance at different ranges of IRI and different relays locations. Extensive simulation results are presented and analyzed to show the achievable rate gain of the proposed system and understand the system behavior.

Improper Signaling for Virtual Full-Duplex Relay Systems

KAUST Repository

Gaafar, Mohamed

2017-02-14

Virtual full-duplex (VFD) is a powerful solution to compensate the rate loss of half-duplex relaying without the need to full-duplex capable nodes. Inter-relay interference (IRI) challenges the operation of VFD relaying systems. Recently, improper signaling is employed at both relays of the VFD to mitigate the IRI by imposing the same signal characteristics for both relays. To further boost the achievable rate performance, asymmetric time sharing VFD relaying system is adopted with different improper signals at the half-duplex relays. The joint tuning of the three design parameters improves the achievable rate performance at different ranges of IRI and different relays locations. Extensive simulation results are presented and analyzed to show the achievable rate gain of the proposed system and understand the system behavior.

Ultra-short silicon MMI duplexer

Science.gov (United States)

Yi, Huaxiang; Huang, Yawen; Wang, Xingjun; Zhou, Zhiping

2012-11-01

The fiber-to-the-home (FTTH) systems are growing fast these days, where two different wavelengths are used for upstream and downstream traffic, typically 1310nm and 1490nm. The duplexers are the key elements to separate these wavelengths into different path in central offices (CO) and optical network unit (ONU) in passive optical network (PON). Multimode interference (MMI) has some benefits to be a duplexer including large fabrication tolerance, low-temperature dependence, and low-polarization dependence, but its size is too large to integrate in conventional case. Based on the silicon photonics platform, ultra-short silicon MMI duplexer was demonstrated to separate the 1310nm and 1490nm lights. By studying the theory of self-image phenomena in MMI, the first order images are adopted in order to keep the device short. A cascaded MMI structure was investigated to implement the wavelength splitting, where both the light of 1310nm and 1490nm was input from the same port, and the 1490nm light was coupling cross the first MMI and output at the cross-port in the device while the 1310nm light was coupling through the first and second MMI and output at the bar-port in the device. The experiment was carried on with the SOI wafer of 340nm top silicon. The cascaded MMI was investigated to fold the length of the duplexer as short as 117μm with the extinct ratio over 10dB.

Influencia de la transformación austenita-martensita en la estabilidad dimensional de un nuevo acero para herramientas aleado con niobio (0,08% y vanadio (0,12%

Directory of Open Access Journals (Sweden)

Conejero Ortega, Gerardo

2014-09-01

Full Text Available Austenite-martensite transformation influence on the dimensional stability of a new experimental tool steel alloyed with niobium (0.08% wt. and vanadium (0.12% wt. has been studied. The dimensional stability of this new steel was compared with the dimensional stability of commercial steel, after and before two thermal treatments, T1 (860 °C and T2 (900 °C. The thermal treatments consisted on heating and cooling, at 1 atmosphere of pressure, in N2 atmosphere furnace, fol lowing by heating in a conventional furnace at 180 °C during 1 hour. Initially, the experimental steel composition and Ac1 and Ac3 transformation temperatures were determined by glow-discharge luminescence (GDL and dilatometric tests, respectively, in order to select the austenization temperatures of T1 and T2 treatments. After hardness measurement, the microstructure of both steels was characterized by X-Ray Diffraction (XRD and optical metallography, before and after of T1 and T2 thermal treatments. Finally, longitudinal and angular dimensional stability analyses were realized for both commercial and experimental steels. After a contrastive hypothesis analysis, the results showed that the longitudinal relative variation of the experimental steel calculated was around 0.2% and the angular relative variation was not significantSe ha estudiado la influencia de la transformación de austenita a martensita en la estabilidad dimensional de un acero experimental para herramientas aleado con niobio (0,08% en peso y vanadio (0,12% en peso. La estabilidad dimensional del acero experimental fue comparada con la de un acero comercial antes y después de ser sometidos, ambos aceros, a dos tratamientos térmicos diferentes. Los tratamientos térmicos consistieron en un calentamiento y mantenimiento durante una hora a temperaturas de 860 °C (T1 y 900 °C (T2 y un enfriamiento final en horno con nitrógeno (N2 a 1 atmósfera de presión. Inicialmente, se determinaron las composiciones del

Full-duplex optical communication system

Science.gov (United States)

Shay, Thomas M. (Inventor); Hazzard, David A. (Inventor); Horan, Stephen (Inventor); Payne, Jason A. (Inventor)

2004-01-01

A method of full-duplex electromagnetic communication wherein a pair of data modulation formats are selected for the forward and return data links respectively such that the forward data electro-magnetic beam serves as a carrier for the return data. A method of encoding optical information is used wherein right-hand and left-hand circular polarizations are assigned to optical information to represent binary states. An application for an earth to low earth orbit optical communications system is presented which implements the full-duplex communication and circular polarization keying modulation format.

l-Proline and RNA Duplex m-Value Temperature Dependence.

Science.gov (United States)

Schwinefus, Jeffrey J; Baka, Nadia L; Modi, Kalpit; Billmeyer, Kaylyn N; Lu, Shutian; Haase, Lucas R; Menssen, Ryan J

2017-08-03

The temperature dependence of l-proline interactions with the RNA dodecamer duplex surface exposed after unfolding was quantified using thermal and isothermal titration denaturation monitored by uv-absorbance. The m-value quantifying proline interactions with the RNA duplex surface area exposed after unfolding was measured using RNA duplexes with GC content ranging between 17 and 83%. The m-values from thermal denaturation decreased with increasing GC content signifying increasingly favorable proline interactions with the exposed RNA surface area. However, m-values from isothermal titration denaturation at 25.0 °C were independent of GC content and less negative than those from thermal denaturation. The m-value from isothermal titration denaturation for a 50% GC RNA duplex decreased (became more negative) as the temperature increased and was in nearly exact agreement with the m-value from thermal denaturation. Since RNA duplex transition temperatures increased with GC content, the more favorable proline interactions with the high GC content duplex surface area observed from thermal denaturation resulted from the temperature dependence of proline interactions rather than the RNA surface chemical composition. The enthalpy contribution to the m-value was positive and small (indicating a slight increase in duplex unfolding enthalpy with proline) while the entropic contribution to the m-value was positive and increased with temperature. Our results will facilitate proline's use as a probe of solvent accessible surface area changes during biochemical reactions at different reaction temperatures.

The role of duplex stainless steels for downhole tubulars

International Nuclear Information System (INIS)

Francis, R.

1993-01-01

In sour conditions there is an increasing trend to turn to corrosion resistant alloys for downhole tubulars. The most commonly used CRA tubular is 13Cr, and there are thousands of feet in service. However, there are limits to the use of 13Cr, ie., the risk of sulphide stress corrosion cracking at high H 2 S levels, and the possibility of pitting or high corrosion rates in waters with high chloride contents. Where the service conditions are felt to be too severe for 13Cr alloys it has been traditional to switch to nickel base alloys such as alloys 825 and C-276 (UNS N08825 and N10276). The alloys are much more expensive than 13Cr, and in recent years the duplex stainless steels have been selected as alloys with superior corrosion and SSCC resistance compared with 13Cr, and having lower cost than nickel alloys. Originally the 22Cr duplex alloy (UNS 31803) was used, but more recently the 25Cr super duplex alloys (UNS S32760 and S32750) have become more available. The present paper reviews the data available for 13Cr and the limits of applicability. Data is also presented for laboratory tests for both the 22Cr and 25Cr super duplex alloys. There is extensive service experience with both 22Cr and 25Cr super duplex in the North Sea, covering both downhole tubulars, manifold and post wellhead equipment. Data is presented showing some of the sour condition being experienced in the North Sea by super duplex alloys. These results show that there is a substantial gap between the limits of use for 13Cr and the 25Cr super duplex stainless steel alloys. This means that in many sour environments super duplex stainless steel provides a cost effective alternative to nickel-base alloys

Transcranial Duplex Sonography Predicts Outcome following an Intracerebral Hemorrhage.

Science.gov (United States)

Camps-Renom, P; Méndez, J; Granell, E; Casoni, F; Prats-Sánchez, L; Martínez-Domeño, A; Guisado-Alonso, D; Martí-Fàbregas, J; Delgado-Mederos, R

2017-08-01

Several radiologic features such as hematoma volume are related to poor outcome following an intracerebral hemorrhage and can be measured with transcranial duplex sonography. We sought to determine the prognostic value of transcranial duplex sonography in patients with intracerebral hemorrhage. We conducted a prospective study of patients diagnosed with spontaneous intracerebral hemorrhage. Transcranial duplex sonography examinations were performed within 2 hours of baseline CT, and we recorded the following variables: hematoma volume, midline shift, third ventricle and lateral ventricle diameters, and the pulsatility index in both MCAs. We correlated these data with the CT scans and assessed the prognostic value of the transcranial duplex sonography measurements. We assessed early neurologic deterioration during hospitalization and mortality at 1-month follow-up. We included 35 patients with a mean age of 72.2 ± 12.8 years. Median baseline hematoma volume was 9.85 mL (interquartile range, 2.74-68.29 mL). We found good agreement and excellent correlation between transcranial duplex sonography and CT when measuring hematoma volume ( r = 0.791; P duplex sonography measurements showed that hematoma volume was an independent predictor of early neurologic deterioration (OR, 1.078; 95% CI, 1.023-1.135) and mortality (OR, 1.089; 95% CI, 1.020-1.160). A second regression analysis with CT variables also demonstrated that hematoma volume was associated with early neurologic deterioration and mortality. When we compared the rating operation curves of both models, their predictive power was similar. Transcranial duplex sonography showed an excellent correlation with CT in assessing hematoma volume and midline shift in patients with intracerebral hemorrhage. Hematoma volume measured with transcranial duplex sonography was an independent predictor of poor outcome. © 2017 by American Journal of Neuroradiology.

A most spectrum-efficient duplexing system: CDD

Science.gov (United States)

Lee, William C. Y.

2001-10-01

The game to play in wireless communications when it comes to increasing spectrum efficiency is to eliminate interference. Currently, all cellular systems use FDD (Frequency Division Duplexing) in an attempt to eliminate the interference from the adjacent cells. Through the use of many technologies only one type of interference remains and that is the adjacent base-tohome mobile interference. TDD (Time Division Duplexing) has not been used for mobile cellular systems, not only because of the adjacent base-to-home mobile interference, but also because of the additional adjacent base-to-home base interference, and adjacent mobile-to-home mobile interference. Therefore, TDD can only be used for small, confined area systems. CDD (Code Division Duplexing) can eliminate all three kinds of interference; the adjacent base-to-home mobile, the adjacent baseto-home base, and the adjacent mobile- to- home in cellular systems. Eliminating each of these interferences makes CDD the most spectrum efficient duplexing system. This talk will elaborate on a set of smart codes, which will make an efficient CDD system a reality.

Transferencia de calor en la colada continua de aceros. I parte. El molde

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Cicutti, C.

1997-10-01

Full Text Available The continuous casting mold plays the important role of receiving the liquid steel and allowing an uniform and defect free solidified skin to be developed. In this work, the different heat transfer mechanisms which are present from the liquid steel to the mold cooling water are reviewed. The effect of operating variables on heat extraction and the relationship between global and distributed heat flux are also analyzed.

El molde de colada continua cumple la importante función de recibir el acero líquido y permitir que se desarrolle una capa solidificada uniforme y libre de defectos. En este trabajo se revisan los distintos mecanismos implicados en el proceso de transferencia de calor, desde el acero líquido hasta el agua de refrigeración del molde. Se analiza también el efecto de las distintas variables de funcionamiento en la extracción calórica producida y la relación entre el flujo global de calor y su distribución a lo largo del molde.

Reducing duplex examinations in patients with iatrogenic pseudoaneurysms.

Science.gov (United States)

Stone, Patrick A; Aburahma, Ali F; Flaherty, Sarah K

2006-06-01

Ultrasound-guided thrombin injection has become the initial treatment of choice for femoral access-related pseudoaneurysms. Patients typically undergo serial duplex examinations to assess for spontaneous resolution of small iatrogenic pseudoaneurysms (IPSAs) (IPSAs (>2.5 cm). We evaluated the impact of a revised treatment algorithm that includes primary treatment of both small (2.5 cm), rather than observation of smaller ones, and attempts to establish a single duplex examination via a point-of-care treatment strategy. We reviewed 105 consecutive patients treated with ultrasound-guided thrombin injection from July 2001 through September 2004. Patient, IPSAs, characteristics, and treatment methods were examined. The number of duplex examinations per patient was evaluated over the treatment interval. Also, published cost data were used to compare primary treatment of small ISPAs vs observation with serial duplex examinations. Successful thrombosis occurred in 103 (98.1%) of 105 treated pseudoaneurysms. No minor or major complications occurred after thrombin injection in either small or large ISPAs, and both failures requiring operation were in the large aneurysm group. The recurrence rate for the series was 1.9% (2/105), and both recurrences were successfully treated with an additional thrombin injection. A single injection was successful in treating 43 (97.7%) of 44 small (IPSAs, and one required a second injection. Patients had an average of 3.3 duplex examinations in our first year of treatment experience, which declined to 1.5 by our third year with the institution of a point-of-care service model for all pseudoaneurysms. Based on this decreased use of duplex examination and an average treatment cohort of 35 IPSA patients per year our institution, we determined this results in a reduction of 35 hours of laboratory time and nearly 70 ultrasounds per year. Similarly for small pseudoaneurysms, a point-of-service primary treatment program rather than observation

Force-Induced Rupture of a DNA Duplex: From Fundamentals to Force Sensors.

Science.gov (United States)

Mosayebi, Majid; Louis, Ard A; Doye, Jonathan P K; Ouldridge, Thomas E

2015-12-22

The rupture of double-stranded DNA under stress is a key process in biophysics and nanotechnology. In this article, we consider the shear-induced rupture of short DNA duplexes, a system that has been given new importance by recently designed force sensors and nanotechnological devices. We argue that rupture must be understood as an activated process, where the duplex state is metastable and the strands will separate in a finite time that depends on the duplex length and the force applied. Thus, the critical shearing force required to rupture a duplex depends strongly on the time scale of observation. We use simple models of DNA to show that this approach naturally captures the observed dependence of the force required to rupture a duplex within a given time on duplex length. In particular, this critical force is zero for the shortest duplexes, before rising sharply and then plateauing in the long length limit. The prevailing approach, based on identifying when the presence of each additional base pair within the duplex is thermodynamically unfavorable rather than allowing for metastability, does not predict a time-scale-dependent critical force and does not naturally incorporate a critical force of zero for the shortest duplexes. We demonstrate that our findings have important consequences for the behavior of a new force-sensing nanodevice, which operates in a mixed mode that interpolates between shearing and unzipping. At a fixed time scale and duplex length, the critical force exhibits a sigmoidal dependence on the fraction of the duplex that is subject to shearing.

Downlink Error Rates of Half-duplex Users in Full-duplex Networks over a Laplacian Inter-User Interference Limited and EGK fading

KAUST Repository

Soury, Hamza; Elsawy, Hesham; Alouini, Mohamed-Slim

2017-01-01

This paper develops a mathematical framework to study downlink error rates and throughput for half-duplex (HD) terminals served by a full-duplex (FD) base station (BS). The developed model is used to motivate long term pairing for users that have

Combinación de fibras de acero de última generación para el refuerzo de hormigón autocompactante

OpenAIRE

Alberti, Marcos; Enfedaque, Alejandro; Galvez, Jaime; Cortez, Adriana

2018-01-01

[ES] Dado que la mayor desventaja mecánica del hormigón son sus propiedades en tracción, las fibras normalmente se utilizan para mejorar la respuesta frente a solicitaciones de tracción y flexión, siendo las fibras de acero las más comúnmente utilizadas. Este tipo de fibras se ha utilizado con éxito en aplicaciones estructurales en los últimos 50 años y, como consecuencia, se han desarrollado nuevas fibras de acero de última generación de las que existe una bibliografía muy lim...

Capturing a DNA duplex under near-physiological conditions

Science.gov (United States)

Zhang, Huijuan; Xu, Wei; Liu, Xiaogang; Stellacci, Francesco; Thong, John T. L.

2010-10-01

We report in situ trapping of a thiolated DNA duplex with eight base pairs into a polymer-protected gold nanogap device under near-physiological conditions. The double-stranded DNA was captured by electrophoresis and covalently attached to the nanogap electrodes through sulfur-gold bonding interaction. The immobilization of the DNA duplex was confirmed by direct electrical measurements under near-physiological conditions. The conductance of the DNA duplex was estimated to be 0.09 μS. We also demonstrate the control of DNA dehybridization by heating the device to temperatures above the melting point of the DNA.

Full-duplex wireless communications systems self-interference cancellation

CERN Document Server

Le-Ngoc, Tho

2017-01-01

This book introduces the development of self-interference (SI)-cancellation techniques for full-duplex wireless communication systems. The authors rely on estimation theory and signal processing to develop SI-cancellation algorithms by generating an estimate of the received SI and subtracting it from the received signal. The authors also cover two new SI-cancellation methods using the new concept of active signal injection (ASI) for full-duplex MIMO-OFDM systems. The ASI approach adds an appropriate cancelling signal to each transmitted signal such that the combined signals from transmit antennas attenuate the SI at the receive antennas. The authors illustrate that the SI-pre-cancelling signal does not affect the data-bearing signal. This book is for researchers and professionals working in wireless communications and engineers willing to understand the challenges of deploying full-duplex and practical solutions to implement a full-duplex system. Advanced-level students in electrical engineering and computer ...

Tensile properties of duplex UNS S32205 and lean duplex UNS S32304 steels and the influence of short duration 475 ºC aging

Directory of Open Access Journals (Sweden)

Sérgio Souto Maior Tavares

2012-12-01

Full Text Available Duplex stainless steels are high strength and corrosion resistant steels extensively used in the petrochemical and chemical industries. The aging at 475 ºC for long periods of time provokes embrittlement and deterioration of corrosion resistance. However, short duration aging at 475 ºC may be used as heat treatment to improve mechanical resistance with small decrease in the other properties. In this work the flow stress curves of lean duplex UNS S32304 and duplex UNS S32205 steels were modeled with Hollomon's equation and work hardening exponents (n were determined. The analyses were conducted in specimens annealed and heat treated at 475 ºC for short periods of time. The aging at 475 ºC for 4 hours, 8 hours and 12 hours promoted significant hardening with small decrease of ductility. The work hardening exponents of both steels were compared, being higher in the duplex steel than in the lean duplex grade.

Clinical utility of carotid duplex ultrasound prior to cardiac surgery.

Science.gov (United States)

Lin, Judith C; Kabbani, Loay S; Peterson, Edward L; Masabni, Khalil; Morgan, Jeffrey A; Brooks, Sara; Wertella, Kathleen P; Paone, Gaetano

2016-03-01

Clinical utility and cost-effectiveness of carotid duplex examination prior to cardiac surgery have been questioned by the multidisciplinary committee creating the 2012 Appropriate Use Criteria for Peripheral Vascular Laboratory Testing. We report the clinical outcomes and postoperative neurologic symptoms in patients who underwent carotid duplex ultrasound prior to open heart surgery at a tertiary institution. Using the combined databases from our clinical vascular laboratory and the Society of Thoracic Surgery, a retrospective analysis of all patients who underwent carotid duplex ultrasound within 13 months prior to open heart surgery from March 2005 to March 2013 was performed. The outcomes between those who underwent carotid duplex scanning (group A) and those who did not (group B) were compared. Among 3233 patients in the cohort who underwent cardiac surgery, 515 (15.9%) patients underwent a carotid duplex ultrasound preoperatively, and 2718 patients did not (84.1%). Among the patients who underwent carotid screening vs no screening, there was no statistically significant difference in the risk factors of cerebrovascular disease (10.9% vs 12.7%; P = .26), prior stroke (8.2% vs 7.2%; P = .41), and prior transient ischemic attack (2.9% vs 3.3%; P = .24). For those undergoing isolated coronary artery bypass grafting (CABG), 306 (17.8%) of 1723 patients underwent preoperative carotid duplex ultrasound. Among patients who had carotid screening prior to CABG, the incidence of carotid disease was low: 249 (81.4%) had minimal or mild stenosis (duplex scanning and those who did not. Primary outcomes of patients who underwent open heart surgery also showed no difference in the perioperative mortality (5.1% vs 6.9%; P = .14) and stroke (2.6% vs 2.4%; P = .85) between patients undergoing preoperative duplex scanning and those who did not. Operative intervention of severe carotid stenosis prior to isolated CABG occurred in 2 of the 17 patients (11.8%) identified who

Perancangan dan Implementasi Duplexer Mikrostrip untuk Frekuensi LTE pada band ke-7

Directory of Open Access Journals (Sweden)

ENCENG SULAEMAN

2013-07-01

The necessary of mobile communication has increased in technology, now it released the new of technology is Long Term Evolution (LTE. Type of duplex is Frequency Division Duplex (FDD, designed a duplexer which it is capable for transmitting and receiving process at the same time with the different of frequency between uplink and downlink. Research of designed and implemented a duplexer using Hybrid Coupler and Bandstop filters based on Split Ring Resonators for the frequency band 7th on LTE technology at Base Transceiver Station (BTS. Duplexer is made by combining two coupler and two bandstop filter. The results of duplexer measurements, when Tx port transmit the signal to antenna port with attenuation at the downlink frequency center at 3.168 dB. Attenuation from antenna port to Rx port about 6 dB. Isolation between Tx port and Rx port about 15 dB. Keywords: Duplexer, Bandstop Filter, Split Ring Resonator, Hybrid Coupler, and Long Term Evolution.

Electron Beam Welding of Duplex Steels with using Heat Treatment

Science.gov (United States)

Schwarz, Ladislav; Vrtochová, Tatiana; Ulrich, Koloman

2010-01-01

This contribution presents characteristics, metallurgy and weldability of duplex steels with using concentrated energy source. The first part of the article describes metallurgy of duplex steels and the influence of nitrogen on their solidification. The second part focuses on weldability of duplex steels with using electron beam aimed on acceptable structure and corrosion resistance performed by multiple runs of defocused beam over the penetration weld.

Perancangan dan Implementasi Duplexer Mikrostrip untuk Frekuensi LTE pada band ke-7

Directory of Open Access Journals (Sweden)

ENCENG SULAEMAN

2017-06-01

Full Text Available ABSTRAK Kebutuhan akan komunikasi bergerak semakin mengalami peningkatan dalam dunia teknologi yang ada saat ini, maka hadirlah teknologi terbaru yaitu Long Term Evolution (LTE. Dengan teknik duplex jenis Frequency Division Duplex (FDD, dirancanglah duplexer yang mampu melakukan proses pengiriman dan penerimaan dalam satu waktu dengan frekuensi yang berbeda antara uplink dan downlink. Pada penelitian ini dirancang dan diimplementasikan sebuah duplekser dengan menggunakan metoda Hybrid Coupler dan Bandstop Filter berbasis Split Ring Resonator untuk band frekuensi ke-7 pada teknologi LTE di sisi Base Transceiver Station (BTS. Duplekser dibuat dengan menggabungkan dua buah hybrid Coupler dan dua buah Bandstop Filter. Hasil pengukuran duplexer saat port Tx mengirimkan sinyal ke antena dengan nilai redaman pada frekuensi tengah downlink sebesar 3.168 dB. Lalu pada saat antena menerima sinyal untuk diteruskan ke Rx terdapat redaman di frekuensi tengah uplink sebesar 6 dB. Sedangkan untuk isolasi dari port Tx-port Rx dihasilkan sebesar 15 dB. Kata kunci: Duplexer, Bandstop Filter, Split Ring Resonator, Hybrid Coupler, dan Long Term Evolution. ABSTRACT The necessary of mobile communication has increased in technology, now it released the new of technology is Long Term Evolution (LTE. Type of duplex is Frequency Division Duplex (FDD, designed a duplexer which it is capable for transmitting and receiving process at the same time with the different of frequency between uplink and downlink. Research of designed and implemented a duplexer using Hybrid Coupler and Bandstop filters based on Split Ring Resonators for the frequency band 7th on LTE technology at Base Transceiver Station (BTS. Duplexer is made by combining two coupler and two bandstop filter. The results of duplexer measurements, when Tx port transmit the signal to antenna port with attenuation at the downlink frequency center at 3.168 dB. Attenuation from antenna port to Rx port about 6 d

Desarrollo de aceros reforzados con carburos primarios vía metalurgia líquida

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Agote, I.

2005-12-01

Full Text Available The steel reinforcement by means of the addition of primary carbides via liquid metallurgy needs to fulfill two essential requirements to be technically viable: the development of a solid reinforcing product which is appropriate to be mixed with the steel and the optimization of the metallurgic addition of these reinforcing particles into the liquid steel. Besides, the improvement of the reinforced alloy characteristics is directly related to the particles' nature of reinforcing particles, their homogeneous and uniform distribution in the matrix and their size and morphology. The manufacture of these carbides by SHS ('Self propagating High temperature Synthesis' and their addition before steel is poured into moulds allows achieving the above-mentioned conditions.

Para que el reforzamiento de los aceros con carburos primarios vía metalurgia líquida sea técnicamente viable se requiere del desarrollo de un tipo de producto reforzante sólido, adecuado para su incorporación al acero, así como de la optimización de dicha vía metalúrgica de adición del producto reforzante al material base en estado líquido. Además, la mejora de características de la aleación reforzada es función directa de la naturaleza de las partículas, de su homogénea y uniforme distribución en la matriz y del tamaño y morfología regular de las mismas. Estas condiciones se consiguen cuando las partículas de carburo se elaboran previamente mediante la técnica SHS (selfpropagating high temperature synthesis y se añaden al baño de acero líquido previo a su colada en moldes o lingoteras.

The Duplex Society.

Science.gov (United States)

Schorr, Alvin L.

1984-01-01

The duplex society, in which the poor live in close proximity to others but in a separate compartment, is already with us. Unless something deeply changes about family income, more than one-third of future generations will come to adulthood having spent a portion of their childhood in official poverty. (RM)

On the Performance of In-Band Full-Duplex Cooperative Communications

KAUST Repository

Khafagy, Mohammad Galal

2016-06-01

In-band full-duplex, by which radios may simultaneously transmit and receive over the same channel, has been always considered practically-unfeasible due to the prohibitively strong self-interference. Indeed, a freshly-generated transmit signal power is typically ten orders of magnitude higher than that of a naturally-attenuated received signal. While unable to manage such an overwhelming interference, wireless communications resorted to half-duplex operation, transmitting and receiving over orthogonal channel resources. Recent research has demonstrated the practical feasibility of full-duplexing via successive sophisticated stages of signal suppression/cancellation, bringing this long-held assumption down and reviving the promising full-duplex potentials. Full-duplex relaying (FDR), where intermediate nodes may now support source-destination communication via simultaneous listening/forwarding, represents one of two full-duplex settings currently recommended for deployment in future fifth-generation (5G) systems. Theoretically, it has been widely accepted that FDR potentially doubles the channel capacity when compared to its half-duplex counterpart. Although FDR doubles the multiplexing gain, the effective signal-to-noise ratio (SNR) can be significantly degraded due to the residual self-interference (RSI) if not properly handled. In this work, efficient protocols are devised for different FDR settings. Selective cooperation is proposed for the canonical three-terminal FDR channel with RSI, which exploits the cooperative diversity offered by the independently fading source/relay message replicas arriving at the destination. Closed-form expressions are derived for the end-to-end SNR cumulative distribution function (CDF) under Rayleigh and Nakagami-m fading. Further, the offered diversity gain is presented as a function of the RSI scaling trend with the relay power. We show that the existing diversity problem in simple FDR protocols can be considerably fixed via

On full duplex Gaussian relay channels with self-interference

KAUST Repository

Behboodi, Arash; Chaaban, Anas; Mathar, Rudolf; Alouini, Mohamed-Slim

2016-01-01

Self interference (SI) in full duplex (FD) systems is the interference caused by the transmission stream on the reception stream. Being one of the main restrictive factors for performance of practical full duplex systems, however, not too much

Distance-dependent duplex DNA destabilization proximal to G-quadruplex/i-motif sequences

Science.gov (United States)

König, Sebastian L. B.; Huppert, Julian L.; Sigel, Roland K. O.; Evans, Amanda C.

2013-01-01

G-quadruplexes and i-motifs are complementary examples of non-canonical nucleic acid substructure conformations. G-quadruplex thermodynamic stability has been extensively studied for a variety of base sequences, but the degree of duplex destabilization that adjacent quadruplex structure formation can cause has yet to be fully addressed. Stable in vivo formation of these alternative nucleic acid structures is likely to be highly dependent on whether sufficient spacing exists between neighbouring duplex- and quadruplex-/i-motif-forming regions to accommodate quadruplexes or i-motifs without disrupting duplex stability. Prediction of putative G-quadruplex-forming regions is likely to be assisted by further understanding of what distance (number of base pairs) is required for duplexes to remain stable as quadruplexes or i-motifs form. Using oligonucleotide constructs derived from precedented G-quadruplexes and i-motif-forming bcl-2 P1 promoter region, initial biophysical stability studies indicate that the formation of G-quadruplex and i-motif conformations do destabilize proximal duplex regions. The undermining effect that quadruplex formation can have on duplex stability is mitigated with increased distance from the duplex region: a spacing of five base pairs or more is sufficient to maintain duplex stability proximal to predicted quadruplex/i-motif-forming regions. PMID:23771141

Optimization of welding variables for duplex stainless steel by GTAW and SMAW

International Nuclear Information System (INIS)

Ajmal, M.; Anwar, M.Y.; Nawaz, A.

2006-01-01

The main problems faced during the welding of duplex stainless steels are cleanliness and slag inclusions. In the present work the methods to eliminate these problems were studied during the welding of duplex stainless steel by Gas Tungsten Arc Welding (GTAW) and Shielded Metal Arc Welding (SMAW). Since the duplex stainless steel is an expensive material, the initial experiments for optimization of welding variables were. carried out on low carbon steel (CS) plates with duplex consumables. Welding of butt groove joints on CS plates was carried with various sets of welding variables i.e. current, voltage and arc energy using duplex consumables. The. radiographic inspection, micro-structural observations and hardness testing of the welds suggested the welding variables that will produce a sound weld on CS plate. These optimized variables were then used for the welding of edge groove joint and T -joint on duplex stainless steel by GTAW and SMAW processes. The hardness and micro-structural study of the joints produced on duplex stainless steel by GTAW and SMAW with duplex consumables were also studied. No slag inclusions and porosity were observed in the microstructure of these weldments and their properties were found similar to the parent metal. (author)

Duplex/quadruplex oligonucleotides: Role of the duplex domain in the stabilization of a new generation of highly effective anti-thrombin aptamers.

Science.gov (United States)

Russo Krauss, Irene; Napolitano, Valeria; Petraccone, Luigi; Troisi, Romualdo; Spiridonova, Vera; Mattia, Carlo Andrea; Sica, Filomena

2018-02-01

Recently, mixed duplex/quadruplex oligonucleotides have attracted great interest for use as biomedical aptamers. In the case of anti-thrombin aptamers, the addition of duplex-forming sequences to a G-quadruplex module identical or very similar to the best-known G-quadruplex of the Thrombin Binding Aptamer (HD1) results in new or improved biological properties, such as higher activity or different recognition properties with respect to HD1. Remarkably, this bimodular fold was hypothesized, based on its sequence, for the only anti-thrombin aptamer in advanced clinical trial, NU172. Whereas cation modulation of G-quadruplex conformation and stability is well characterized, only few data from similar analysis on duplex/quadruplex oligonucleotides exist. Here we have performed a characterization of structure and stability of four different duplex/quadruplex anti-thrombin aptamers, including NU172, in the presence of different cations and in physiological-mimicking conditions in comparison to HD1, by means of spectroscopic techniques (UV and circular dichroism) and differential scanning calorimetry. Our data show a strong reciprocal influence of each domain on the stability of the other and in particular suggest a stabilizing effect of the duplex region in the presence of solutions mimicking the physiological conditions, strengthening the idea that bimodular aptamers present better therapeutic potentialities than those containing a single G-quadruplex domain. Copyright © 2017 Elsevier B.V. All rights reserved.

EFFECT OF INTERMETALLIC PHASES ON CORROSION BEHAVIOR AND MECHANICAL PROPERTIES OF DUPLEX STAINLESS STEEL AND SUPER-DUPLEX STAINLESS STEEL

OpenAIRE

Prabhu Paulraj; Rajnish Garg

2015-01-01

Duplex Stainless Steels (DSS) and Super Duplex Stainless Steel (SDSS) have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic pha...

Comparación de la microestructura y propiedades de impacto de dos materiales compuestos laminados de acero de ultraalto contenido de carbono

Directory of Open Access Journals (Sweden)

Pozuelo, M.

2004-04-01

Full Text Available Two ferrous laminated composites containing six layers have been processed by roll bonding. One of them consists of three layers of an ultrahigh carbon steel (1.3%C UHCS interlayered with other three layers of a microalloyed steel. The other composite consists of three layers of UHCS and three layers of a mild steel. Microstructure, Vickers hardness and impact properties have been studied. The absorbed energy values of the two laminated composites were higher than that of the UHCS.

Se procesaron mediante laminación en caliente dos materiales compuestos laminados de acero de ultraalto contenido de carbono (AUAC, 1,3%C de seis capas cada uno: El primero está compuesto por tres capas de AUAC alternadas con tres capas de un acero microaleado, y el segundo con tres del mismo AUAC alternadas con tres de un acero suave. Se ha realizado un estudio de sus microestructuras, dureza Vickers y propiedades de impacto. Se han mejorado los valores de energía absorbida de los dos materiales compuestos laminados respecto al del AUAC.

S-N Curves of high resistance steels in the gigacyclic regime; Curvas S-N de aceros de alta resistencia dentro del regimen gigaciclico

Energy Technology Data Exchange (ETDEWEB)

Marinez G, I [Conservatoire National des Arts et Metiers-Institut des Technologies et des Materiaux Avances (CNAM-ITMA), Paris (France); Dominguez A, G [Instituto Tecnologico de Celaya, Guanajuato (Mexico); Bathias, C [Conservatoire National des Arts et Metiers-Institut des Technologies et des Materiaux Avances (CNAM-ITMA), Paris (France)

2004-04-15

In this paper, the fatigue behavior of high strength steel used for mechanical parts has been investigated in the gigacycle fatigue regime. An experimental study has been carried out with both: R = 0.1 (perlitic-ferritic steel) and R = -1 (perlitic-ferritic steel, bainitic steel, martensitic steels) loads, at a high frequency of 20 khz up to 1010 cycles, to determine the S-N curves when fatigue life is more than 107 cycles. Comparison of experimental results at frequencies of 20 khz and 30 Hz with R = -1, shows that the S-N curve has a good agreement between 105 and 107 cycles for the high strength steels, Furthermore, fracture surface observations are made by SEM; the transition of crack initiation site is described. The generalization of gigacycle fatigue behavior is analyzed. More often initiation of fatigue crack at 109 cycles is a bulk phenomenon with an important effect of stress concentration due to mineral inclusions or perlitic platelets. Thus, the Murakami model is efficient when we can measure the defects associated with fracture, but it can not take into account the microstructure effect related to platelets phenomenon. [Spanish] En este trabajo se investigo el comportamiento en fatiga gigaciclica de varios aceros de alta resistencia utilizados en la industria automotriz. El estudio experimental se llevo a cabo utilizando dos diferentes valores de carga: R = 0.1 (acero perlitoferritico) y R = -1 (acero perlito-ferritico, acero bainitico, aceros martensiticos), a una frecuencia de ensayo de 20 kHz y hasta 1010 ciclos, para determinar las curvas S-N arriba de 107 ciclos. La comparacion de resultados experimentales obtenidos utilizando frecuencias de ensayo de 20 kHz y 30 Hz con la relacion de carga R = - 1, muestran la continuidad de las curvas S-N entre 105 y 107 ciclos para estos aceros de alta resistencia. Por otro lado, observaciones de la superficie de fractura se efectuaron utilizando el microscopio electronico de barrido; se describe la transicion

Water-evaporation reduction by duplex films: application to the human tear film.

Science.gov (United States)

Cerretani, Colin F; Ho, Nghia H; Radke, C J

2013-09-01

Water-evaporation reduction by duplex-oil films is especially important to understand the physiology of the human tear film. Secreted lipids, called meibum, form a duplex film that coats the aqueous tear film and purportedly reduces tear evaporation. Lipid-layer deficiency is correlated with the occurrence of dry-eye disease; however, in-vitro experiments fail to show water-evaporation reduction by tear-lipid duplex films. We review the available literature on water-evaporation reduction by duplex-oil films and outline the theoretical underpinnings of spreading and evaporation kinetics that govern behavior of these systems. A dissolution-diffusion model unifies the data reported in the literature and identifies dewetting of duplex films into lenses as a key challenge to obtaining significant evaporation reduction. We develop an improved apparatus for measuring evaporation reduction by duplex-oil films including simultaneous assessment of film coverage, stability, and temperature, all under controlled external mass transfer. New data reported in this study fit into the larger body of work conducted on water-evaporation reduction by duplex-oil films. Duplex-oil films of oxidized mineral oil/mucin (MOx/BSM), human meibum (HM), and bovine meibum (BM) reduce water evaporation by a dissolution-diffusion mechanism, as confirmed by agreement between measurement and theory. The water permeability of oxidized-mineral-oil duplex films agrees with those reported in the literature, after correction for the presence of mucin. We find that duplex-oil films of bovine and human meibum at physiologic temperature reduce water evaporation only 6-8% for a 100-nm film thickness pertinent to the human tear film. Comparison to in-vivo human tear-evaporation measurements is inconclusive because evaporation from a clean-water surface is not measured and because the mass-transfer resistance is not characterized. Copyright © 2013 Elsevier B.V. All rights reserved.

Physical-Layer Security of a Buffer-Aided Full-Duplex Relaying System

KAUST Repository

El Shafie, Ahmed

2016-07-07

This letter proposes a novel hybrid half-/full-duplex relaying scheme to enhance the relay channel security. A source node (Alice) communicates with her destination node (Bob) in the presence of a buffer-aided full-duplex relay node (Rooney) and a potential eavesdropper (Eve). Rooney adopts two different relaying, namely randomize-and-forward and decode-andforward relaying strategies, to improve the security of the legitimate system. In the first relaying strategy, Rooney uses a codebook different from that used at Alice. In the second relaying strategy, Rooney and Alice use the same codebooks. In addition, Rooney switches between half-duplex and full-duplex modes to further enhance the security of the legitimate system. The numerical results demonstrate that our proposed scheme achieves a significant average secrecy end-to-end throughput improvement relative to the conventional bufferless full-duplex relaying scheme.

Physical-Layer Security of a Buffer-Aided Full-Duplex Relaying System

KAUST Repository

El Shafie, Ahmed; Salem, Ahmed Sultan; Al-Dhahir, Naofal

2016-01-01

This letter proposes a novel hybrid half-/full-duplex relaying scheme to enhance the relay channel security. A source node (Alice) communicates with her destination node (Bob) in the presence of a buffer-aided full-duplex relay node (Rooney) and a potential eavesdropper (Eve). Rooney adopts two different relaying, namely randomize-and-forward and decode-andforward relaying strategies, to improve the security of the legitimate system. In the first relaying strategy, Rooney uses a codebook different from that used at Alice. In the second relaying strategy, Rooney and Alice use the same codebooks. In addition, Rooney switches between half-duplex and full-duplex modes to further enhance the security of the legitimate system. The numerical results demonstrate that our proposed scheme achieves a significant average secrecy end-to-end throughput improvement relative to the conventional bufferless full-duplex relaying scheme.

Characterization of thermal aging of duplex stainless steel by SQUID

International Nuclear Information System (INIS)

Isobe, Y.; Kamimura, A.; Aoki, K.; Nakayasu, F.

1995-01-01

Thermal aging is a growing concern for long-term-aged duplex stainless steel piping in nuclear power plants. Superconducting QUantum Interference Device (SQUID) was used for the detection of thermal aging of SUS329 rolled duplex stainless steel and SCS16 cast duplex stainless steel. It was found that the SQUID output signal pattern in the presence of AC magnetic field applied to the specimen was sensitive to the changes in electromagnetic properties due to thermal aging

Métodos electroquímicos semicuantitativos de estudio de lo corrosión por picaduras del acero para armaduras de hormigón

Directory of Open Access Journals (Sweden)

Andrade Perdrix, M. C.

1977-12-01

Full Text Available El acero embebido en el hormigón se encuentra sometido a un medio de elevada alcalinidad (pH comprendido entre 12 y 13, debido a la cal libre, a los álcalis que contiene el cemento, y al Ca(0H₂ que se forma durante la hidratación de los silicatos. En esta situación, el acero se halla recubierto por una capa de óxidos e hidróxidos estables que lo mantienen pasivado, interponiendo una barrera entre él y los agentes agresivos.

Comportamiento del acero de baja aleación SA-508 y del acero al carbono A-410b en las condiciones de operación y parada del circuito primario de los reactores de agua ligera tipo PWR

Directory of Open Access Journals (Sweden)

García-Redondo, María del Sol

2000-04-01

Full Text Available The corrosion rate of low alloy steel SA-508 and carbon steel A-410b in simulated operation and shutdown conditions of pressurized water reactor has been determined. Moreover potentiodynamic polarization curves and galvanic effect through coupling of AISI-304 have been carried out under shutdown simulated condition.

En este trabajo se ha determinado la cinética de corrosión del acero de baja aleación SA-508 y del acero al carbono A-410b en condiciones que simulan la operación y la parada de los reactores de agua ligera a presión. También se han realizado curvas de polarización potenciodinámica y se ha estudiado el acoplamiento galvánico con AISI-304 en condiciones de parada de los reactores de agua ligera a presión.

GEL DE ALOE-VERA COMO POTENCIAL INHIBIDOR DE LA CORROSIÓN DEL ACERO DE REFUERZO ESTRUCTURAL

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Héctor Herrera-Hernández

2015-01-01

Full Text Available En el presente trabajo se estudiaelectroquímicamente un GELextracto de las hojas de ALOE VERAcomo un posible inhibidor de la corrosión del acero de refuerzo estructuraldel concreto.Los estudiosde corrosiónse llevaron a cabo en 1M de HCl y utilizando la técnica de espectroscopia de impedancia electroquímica (EISse evaluó la resistencia a la corrosión en presencia y ausencia del GEL.Los diagramas de impedancia mostraronque la adición en diferentes proporcionesdel GELinhibe notablemente el proceso de la corrosión del acero inmerso en la solución ácida. También se determinó que las moléculas del GEL obedecena un mecanismo de fisisorciónsobre la superficie del metal de acuerdo con el modelo de isoterma de Langmuircon unG°adsde alrededor de 14.17 kJ/mol. El GEL se clasificócomo un inhibidor orgánico del tipo mixto.

Influencia de la termodependencia de las propiedades físicas del acero en la simulación por elementos finitos del proceso de soldadura

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Félix Ramos Morales

2009-01-01

Full Text Available En el presente trabajo se desarrolló un modelo de elementos finitos para simular la unión a tope, con electrodo E 7018 de 3,2 mm de diámetro, de dos placas de acero con bajo contenido de carbono y baja aleación. Adicionalmente, se estudia la influencia sobre la distribución de temperaturas en la placa al considerar la termo-dependencia de diferentes propiedades físicas del acero (conductividad térmica y calor específico.

Soldadura de aceros dual phase en chapa fina: GMAW, PAW y RSW

OpenAIRE

Svoboda,Hernán; Lorusso,Hernán N.; Burgueño,Alejandro

2011-01-01

Los aceros Dual Phase (DP) han encontrado recientemente una fuerte aplicación en elementos estructurales en la industria automotriz, debido a la necesidad de disminuir peso. La soldadura de estos materiales cobra particular importancia considerando su aplicación estructural y los procesos relacionados en su fabricación. En particular la soldadura de resistencia por punto (RSW) y semiautomática con alambre macizo y protección gaseosa (GMAW) son ampliamente utilizados en la industria automotriz...

Conformado por vía coloidal de recubrimientos en la cara interna de un tubo de acero

Directory of Open Access Journals (Sweden)

Ferrari, B.

2004-04-01

Full Text Available The development of new coating processes has important limitations related to the films thickness and the geometry of the coating substrates. In this work, two colloidal forming processes are proposed for manufacturing ceramic and metallic coatings on the inner surface of a steel pipe. Ceramic coatings of CaCO3 have been formed by electrophoretic deposition (EPD. Aqueous stable suspensions were prepared and a electrophoretic cell was designed, in which the steel tube to be coated acted simultaneously as container and working electrode. Nickel films were prepared by filling the pipe with the suspension and rotating to fully wet the steel surface. Nickel suspensions were formulated focusing an improved wettability and adherence to the steel surface by using binders. From these processes, ceramic and metallic coatings with 300- 350 μm in thickness, homogeneous and strongly adhered to the inner surface of the steel pipe have been obtained.

El desarrollo de las tecnologías de fabricación de recubrimientos presenta importantes limitaciones relativas a los espesores de las capas fabricadas y a la geometría de los substratos a recubrir. En este trabajo se proponen dos procesos de conformado coloidal de revestimientos cerámicos y metálicos en la cara interna de un tubo de acero. El revestimiento cerámico (CaCO3 se ha conformado por deposición electroforética (EPD. Para ello se han preparado suspensiones estables de CaCO3 en agua, y se ha diseñado una célula electroforética en la que el tubo es a la vez el contenedor y el electrodo de trabajo. El revestimiento metálico (níquel se ha fabricado por vertido de una suspensión estable sobre el propio tubo de acero. Para ello se han acondicionado las suspensiones con el objetivo de mejorar el mojado y la adherencia sobre el acero. A partir de los procesos de EPD y vertido se han obtenido revestimientos cerámicos y metálicos, respectivamente, con espesores de 300-350 μm, homogéneos y

Duplex ultrasound: Indications and findings in a newly created ...

African Journals Online (AJOL)

Duplex ultrasound: Indications and findings in a newly created facility at the University of Calabar Teaching Hospital, Calabar. ... It is recommended that timely referrals be made, and mobile Doppler units be acquired to save more lives and limbs in the developing world. Keywords: Calabar, deep venous thrombosis, duplex ...

Mejora de la calidad del acero obtenido por colada continua mediante influencias electrofísicas

Directory of Open Access Journals (Sweden)

Shklyar, V.

1998-12-01

Full Text Available Laboratory tests with tin smelted in a crucible and industrial tests with crude steel poured in moulds had been carried out. These metals were subjected to electrophysical influences. As a result of the applied electric field, it is observed in tin that during the solidification, the crystalization temperature and the solidification time are changed. Crystal growth in the electric field direction and an increase of the fracture limit in the steel ingot are observed.

Se han realizado ensayos de laboratorio con estaño fundido en crisol y a escala industrial con acero líquido vertidos en moldes, sometiendo estos metales a influencias electrofísicas. Como resultado del campo aplicado, en el estaño se observa que durante la solidificación varía la temperatura de cristalización y el tiempo de solidificación. En el lingote de acero se observa un crecimiento de los cristales en dirección del campo eléctrico y un aumento del límite de rotura.

An unusual mode of DNA duplex association: Watson-Crick interaction of all-purine deoxyribonucleic acids.

Science.gov (United States)

Battersby, Thomas R; Albalos, Maria; Friesenhahn, Michel J

2007-05-01

Nucleic acid duplexes associating through purine-purine base pairing have been constructed and characterized in a remarkable demonstration of nucleic acids with mixed sequence and a natural backbone in an alternative duplex structure. The antiparallel deoxyribose all-purine duplexes associate specifically through Watson-Crick pairing, violating the nucleobase size-complementarity pairing convention found in Nature. Sequence-specific recognition displayed by these structures makes the duplexes suitable, in principle, for information storage and replication fundamental to molecular evolution in all living organisms. All-purine duplexes can be formed through association of purines found in natural ribonucleosides. Key to the formation of these duplexes is the N(3)-H tautomer of isoguanine, preferred in the duplex, but not in aqueous solution. The duplexes have relevance to evolution of the modern genetic code and can be used for molecular recognition of natural nucleic acids.

Two-dimensional 1H and 31P NMR spectra of a decamer oligodeoxyribonucleotide duplex and a quinoxaline ([MeCys3, MeCys7]TANDEM) drug duplex complex

International Nuclear Information System (INIS)

Powers, R.; Olsen, R.K.; Gorenstein, D.G.

1989-01-01

Assignment of the 1H and 31P NMR spectra of a decamer oligodeoxyribonucleotide duplex, d(CCCGATCGGG), and its quinoxaline ([MeCys3, MeCys7]TANDEM) drug duplex complex has been made by two-dimensional 1H-1H and heteronuclear 31P-1H correlated spectroscopy. The 31P chemical shifts of this 10 base pair oligonucleotide follow the general observation that the more internal the phosphate is located within the oligonucleotide sequence, the more upfield the 31P resonance occurs. While the 31P chemical shifts show sequence-specific variations, they also do not generally follow the Calladine rules previously demonstrated. 31P NMR also provides a convenient monitor of the phosphate ester backbone conformational changes upon binding of the drug to the duplex. Although the quinoxaline drug, [MeCys3, MeCys7]TANDEM, is generally expected to bind to duplex DNA by bis-intercalation, only small 31P chemical shift changes are observed upon binding the drug to duplex d(CCCGATCGGG). Additionally, only small perturbations in the 1H NMR and UV spectra are observed upon binding the drug to the decamer, although association of the drug stabilizes the duplex form relative to the other states. These results are consistent with a non-intercalative mode of association of the drug. Modeling and molecular mechanics energy minimization demonstrate that a novel structure in which the two quinoxaline rings of the drug binds in the minor groove of the duplex is possible

Criteria for the Segmentation of Vowels on Duplex Oscillograms.

Science.gov (United States)

Naeser, Margaret A.

This paper develops criteria for the segmentation of vowels on duplex oscillograms. Previous vowel duration studies have primarily used sound spectrograms. The use of duplex oscillograms, rather than sound spectrograms, permits faster production (real time) at less expense (adding machine paper may be used). The speech signal can be more spread…

Evaluación del trabajo esencial de fractura en chapa de un acero de alta resistencia de fase dual

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Gutiérrez, D.

2013-02-01

Full Text Available Fracture toughness of advanced high strength steels (AHSS, can be used to optimize crash behavior of structural components. However it cannot be readily measured in metal sheet because of the sheet thickness. In this work, the Essential Work of Fracture (EWF methodology is proposed to evaluate the fracture toughness of metal sheets. It has been successfully applied in polymers films and some metal sheets. However, their information about the applicability of this methodology to AHSS is relatively scarce. In the present work the fracture toughness of a Dual Phase (strength of 800 MPa and drawing steel sheets has been measured by means of the EWF. The results show that the test requirements are met and also show the clear influence of notch radii on the measured values, specially for the AHSS grade. Thus, the EWF is postulated as a methodology to evaluate the fracture toughness in AHSS sheets.

La tenacidad de fractura de aceros de alta resistencia (AHSS, es una propiedad interesante para optimizar el comportamiento a impacto, pero su caracterización experimental en chapas metálicas es compleja debido a su espesor. En este trabajo se plantea el método del Trabajo Esencial de Fractura (TEF, como alternativa al cálculo de la tenacidad. Este método ya ha sido utilizado con éxito en polímeros y aceros dúctiles, aunque la información sobre su aplicación en AHSS es escasa. Se ha evaluado la tenacidad en un acero de fase dual de 800 MPa de resistencia y se ha comparado con la de un acero de embutición. Los resultados muestran que se cumplen los requisitos del método y ponen en evidencia la influencia del radio de entalla en el valor obtenido de TEF, especialmente para AHSS. Con todo ello, el método TEF se puede usar para caracterizar la tenacidad de AHSS en formato chapa.

Duplex-guided percutaneous transluminal angioplasty in iliac arterial occlusive disease.

Science.gov (United States)

Krasznai, A G; Sigterman, T A; Welten, R J; Heijboer, R; Sikkink, C J J M; van de Akker, L H J M; Bouwman, L H

2013-11-01

Chronic renal insufficiency (CRI) is a growing global problem. PTA can be performed without nephrotoxic contrast, utilizing Doppler-ultrasound (Duplex) guidance. Duplex-guided infra-inguinal interventions and access-related interventions have been reported. Duplex-guided iliac interventions have not been performed to any extent because of the anatomic location. In our study we evaluated the safety and efficacy of Duplex-guided percutaneous transluminal angioplasty (DuPTA) in iliac arteries. From June 2012 until February 2013, 31 patients (35 iliac lesions), underwent DuPTA. Indications ranged from Rutherford 3 to 5. Preoperative evaluation included Ankle Brachial Index (ABI), Duplex and MRA. Procedural success was defined as crossing the lesion with a guidewire and dilating or stenting the lesion. Clinical success was defined as 50% reduction in peak systolic velocity (PSV) or clinical improvement. PSV was evaluated after PTA, then at 2 weeks. Clinical results were assessed 2 weeks after the procedure. Procedural success was achieved in 94% of patients (33/35), all of whom also had clinical success. Post-procedural PSV reduction showed an average improvement of 63% (431 cm/s to 153 cm/s). Mean preoperative ABI was 0.72 and improved to 0.88 postoperatively. PTA using Duplex-guidance in significant iliac stenosis is a safe method with major advantages in patients at high risk for developing contrast-induced nephropathy. Copyright © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

A Full-Duplex MAC Tailored for 5G Wireless Networks

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Lucas de Melo Guimarães

2018-01-01

Full Text Available The increasing demands for high-data rate traffic stimulated the development of the fifth-generation (5G mobile networks. The envisioned 5G network is expected to meet its challenge by devising means to further improve spectrum usage. Many alternatives to enhance spectrum usage are being researched, such as massive MIMO, operation in mmWave frequency, cognitive radio, and the employment of full-duplex antennas. Efficient utilization of the potential of any of these technologies faces a set of challenges related to medium access control (MAC schemes. This work focuses on MAC schemes tailored for full-duplex antennas, since they are expected to play a major role in the foreseeable 5G networks. In this context, this paper presents a MAC layer technique to improve total transmission time when full-duplex antennas are employed. Several evaluations in different scenarios are conducted to assess the proposed MAC scheme. Numerical results show that the proposed scheme provides gains up to 156% when compared to a state-of-the-art full-duplex antenna MAC protocol. Compared to traditional half-duplex antenna MAC protocols, the proposed scheme yields gain up to 412%.

Analysing Self Interference Cancellation in Full Duplex Radios

DEFF Research Database (Denmark)

Mahmood, Nurul Huda; Shafique Ansari, Imran; Berardinelli, Gilberto

2016-01-01

Full duplex communication promises a theoretical $100\\%$ throughput gain by doubling the number of simultaneous transmissions. Such compelling gains are conditioned on perfect cancellation of the self interference power resulting from simultaneous transmission and reception. Generally, self...... interference power is modelled as a noise-like constant level interference floor. However, experimental validations have shown that the self interference power is in practice a random variable depending on a number of factors such as the surrounding wireless environment and the degree of interference...... cancellation. In this study, we derive an analytical model for the residual self interference power, and demonstrate various applications of the derived model in analysing the performance of a Full Duplex radio. In general, full duplex communication is found to provide only modest throughput gains over half...

Nanopore Analysis of the 5-Guanidinohydantoin to Iminoallantoin Isomerization in Duplex DNA.

Science.gov (United States)

Zeng, Tao; Fleming, Aaron M; Ding, Yun; Ren, Hang; White, Henry S; Burrows, Cynthia J

2018-04-06

In DNA, guanine oxidation yields diastereomers of 5-guanidinohydantoin (Gh) as one of the major products. In nucleosides and single-stranded DNA, Gh is in a pH-dependent equilibrium with its constitutional isomer iminoallantoin (Ia). Herein, the isomerization reaction between Gh and Ia was monitored in duplex DNA using a protein nanopore by measuring the ionic current when duplex DNA interacts with the pore under an electrophoretic force. Monitoring current levels in this single-molecule method proved to be superior for analysis of population distributions in an equilibrating mixture of four isomers in duplex DNA as a function of pH. The results identified Gh as a major isomer observed when base paired with A, C, or G at pH 6.4-8.4, and Ia was a minor isomer of the reaction mixture that was only observed when the pH was >7.4 in the duplex DNA context. The present results suggest that Gh will be the dominant isomer in duplex DNA under physiological conditions regardless of the base-pairing partner in the duplex.

Development of oxide dispersion strengthened 2205 duplex stainless steel composite

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Oladayo OLANIRAN

2015-05-01

Full Text Available Composites of duplex stainless steel were produced by oxide dispersion strengthening with comparatively improved mechanical properties by hot press sintering of partially stabilized Zirconia (PSZ, 3% yttria, mole fraction dispersion in 2205 duplex stainless steels. Ceramic oxide was added as reinforcement, while chromium (Cr and Nickel (Ni were incorporated to maintain the austenitic/ferritic phase balance of the duplex stainless steel. The powders and sintered were characterized in detail using scanning electron microscopy (SEM and X-ray diffraction (XRD. The microstructural evolution and phase formation during oxide dispersion strengthening of duplex stainless steel composites were investigated. The influence of composition variation of the reinforcements on the microstructural and corrosion behaviour in simulated mine water of the composites were investigated. In this manuscript, it was established that composition has great influence on the structure/properties relationship of the composites developed.

Measuring secondary phases in duplex stainless steels

Science.gov (United States)

Calliari, I.; Brunelli, K.; Dabalà, M.; Ramous, E.

2009-01-01

The use of duplex stainless steels is limited by their susceptibility to the formation of dangerous intermetallic phases resulting in detrimental effects on impact toughness and corrosion resistance. This precipitation and the quantitative determinations of the phases have received considerable attention and different precipitation sequences (σ phase, χ phase, and carbides) have been suggested. This study investigates the phase transformation during continuous cooling and isothermal treatments in commercial duplex stainless steel grades and the effects on alloy properties, and compares the most common techniques of analysis.

Analysis of Structural Flexibility of Damaged DNA Using Thiol-Tethered Oligonucleotide Duplexes.

Directory of Open Access Journals (Sweden)

Masashi Fujita

Full Text Available Bent structures are formed in DNA by the binding of small molecules or proteins. We developed a chemical method to detect bent DNA structures. Oligonucleotide duplexes in which two mercaptoalkyl groups were attached to the positions facing each other across the major groove were prepared. When the duplex contained the cisplatin adduct, which was proved to induce static helix bending, interstrand disulfide bond formation under an oxygen atmosphere was detected by HPLC analyses, but not in the non-adducted duplex, when the two thiol-tethered nucleosides were separated by six base pairs. When the insert was five and seven base pairs, the disulfide bond was formed and was not formed, respectively, regardless of the cisplatin adduct formation. The same reaction was observed in the duplexes containing an abasic site analog and the (6–4 photoproduct. Compared with the cisplatin case, the disulfide bond formation was slower in these duplexes, but the reaction rate was nearly independent of the linker length. These results indicate that dynamic structural changes of the abasic site- and (6–4 photoproduct-containing duplexes could be detected by our method. It is strongly suggested that the UV-damaged DNA-binding protein, which specifically binds these duplexes and functions at the first step of global-genome nucleotide excision repair, recognizes the easily bendable nature of damaged DNA.

Methodology for calculating the thickness free of sigma phase in duplex stainless steels large section parts during hiperquenching; Metodologia para el calculo de espesores limite libres de fase sigma durante el hipertemple en piezas de aceros duplex de gran seccion

Energy Technology Data Exchange (ETDEWEB)

Jimbert, P.; Guraya, T.; Torregary, A.; Bravo, P.

2013-06-01

To achieve the mechanical properties and corrosion resistance desired by duplex stainless steels used by the petrochemical and nuclear industry, parts are subjected to a hiperquenching heat treatment from about 1050 degree centigrade. This avoids the risk of intermetallic precipitation which drastically reduces the properties of these materials. However with increasing depth to which the deposits are present, the thicknesses for such pipes have been increased, resulting in higher levels of demand on all its manufacturing process, including the heat treatment. To avoid the precipitation of intermetallic phases such as sigma phase it is necessary to know the cooling profile in the center of the work piece and for this purpose to know the value of the Surface Heat Transfer Coefficient (h) is essential. This coefficient changes during the hiperquenching and its value is determined experimentally as it depends on several process parameters. Studies reveal that its value is stabilized within a few seconds. We can then assume that to know the cooling profile in the center of large sections it is only necessary to know the stabilized value of h. However, all the studies found in the literature are referred to diameters smaller than 100 mm. This paper has developed a methodology to predict the precipitation of intermetallic phases in duplex stainless steel parts with large thicknesses in industrial facilities from the calculation of h. This methodology allows us to calculate the cooling profiles without wasting any work piece using one or more sensorized patterns with thermocouples and a subsequent simulation with ANSYS. (Author)

Duplex tab exhaust nozzle

Science.gov (United States)

Gutmark, Ephraim Jeff (Inventor); Martens, Steven (nmn) (Inventor)

2012-01-01

An exhaust nozzle includes a conical duct terminating in an annular outlet. A row of vortex generating duplex tabs are mounted in the outlet. The tabs have compound radial and circumferential aft inclination inside the outlet for generating streamwise vortices for attenuating exhaust noise while reducing performance loss.

Caracterización de los aceros sinterizados obtenidos a partir de polvos prealeados Fe-1,5% Mo

Directory of Open Access Journals (Sweden)

Torralba, J. M.

1995-02-01

Full Text Available Sintered molybdenum-, copper-, nickel- alloyed steels, have been studied through the influence of the Chemical composition on different mechanical and physical properties. In all the studied steels, a constant percentage of carbon has been used, as well Fe-Mo prealloyed powders, with a 1,5% Mo content. Selected sintering conditions were close to those used in the P/M industry, potential consumer of the studied steels.

Se estudian los aceros aleados sinterizados con molibdeno, cobre, níquel y grafito, a partir de la influencia de su composición sobre distintas propiedades mecánicas y físicas. En todos los aceros, se utilizó una composición de carbono constante, así como polvos prealeados de Fe-Mo, con 1,5% Mo. Las condiciones de sinterización elegidas han sido las más próximas a las utilizadas en la industria pulvimetalúrgica, que es el usuario potencial de los materiales estudiados.

Qualitative comparison of duplex Stirling and absorption refrigerators in domestic applications

Energy Technology Data Exchange (ETDEWEB)

Shao, H. [Global Cooling BV, Zutphen (Netherlands)

2000-07-01

A qualitative comparison has been carried out between the duplex Stirling and the absorption refrigerator for domestic applications. The duplex Stirling has many advantages over the absorption refrigerator on efficiency, modulation, suitability, operating costs, pollution reduction. Based on the state of the art of free-piston gas-bearing and linear-motor Stirling engines and coolers, it appears technically and economically feasible to develop the duplex Stirling to compete with the absorption refrigerator for heat-driven domestic refrigeration. (orig.)

MODIFICACIÓN DEL SISTEMA CONCRETO-ACERO DE REFUERZO MEDIANTE LA ADICIÓN DE FIBRAS DE BAGAZO DE CAÑA PARA FACILITAR SU PROTECCIÓN ANTICORROSIVA.

OpenAIRE

GARCIA DELGADO, AMERICA

2015-01-01

Los sistemas concreto-acero de refuerzo son considerados estructuras durables y resistentes; sin embargo, con el paso del tiempo se ven afectados por problemas de corrosión, la cual, se desarrolla cuando los cloruros se encuentran más allá de un cierto nivel umbral, en el que se inicia la despasivación o la ruptura la capa pasiva que protege al acero de refuerzo. Para contrarrestar los daños ocasionados por la corrosión, se han propuestos varios métodos para disminuir y/o preve...

El acero que nunca se fundió. Una reseña sobre Stalin

Directory of Open Access Journals (Sweden)

Iñaki Oneca Agurruza

2004-02-01

Full Text Available Era el 5 de marzo de 1953 cuando murió el fetiche, el gurú, el símbolo. Stalin significa “acero”, y precisamente una de las cosas que se reprochó al joven revolucionario, tras la adopción de este apodo, era que el acero era duro pero también frío. Así iniciamos esta breve nota sobre la figura de uno de los personajes clave del siglo XX.

Comportamiento a la Corrosión del Acero API X70 Soldado por el Proceso de Doble Arco Sumergido Inmerso en Diferentes Medios Corrosivos

OpenAIRE

Montes, Omar Francisco; Garcés, Rocío Saldaña; Reyes, Felipe A. Reyes; Robledo, Patricia del Carmen Zambrano; López, Francisco H. Estupiñán; Calderón, Facundo Almeraya

2016-01-01

Resumen Los aceros API X70 son aplicados en fabricación y construcción de tuberías para el transporte de hidrocarburos, sin embargo, a un lapso de tiempo se degradan debido al medio ambiente al cual están expuestos; influyendo en la velocidad y tipo de corrosión sobre las superficies del metal base (MB), zona afectada por el calor (ZAC) y zona de fusión (ZF). A fin de conocer y evaluar la susceptibilidad a la corrosión en uniones del acero API X70 sometido a diferentes medios corrosivos, vari...

COMPORTAMIENTO DEL CONCRETO REFORZADO CON FIBRAS DE ACERO ZP-306 SOMETIDO A ESFUERZOS DE COMPRESIÓN

Directory of Open Access Journals (Sweden)

Lina P. Gallo-Arciniegas

2013-01-01

Full Text Available En Colombia, el uso del concreto reforzado con fibras de acero (CRFA es muy limitado, debido a que en el país no existe suficiente evidencia experimental y requisitos reglamentarios al respecto. En el artículo se presentan los resultados de una investigación experimental y analítica sobre el comportamiento del CRFA elaborado con fibras ZP-306, sometidas a esfuerzos de compresión. El estudio involucra la revisión y discusión de los modelos disponibles en la literatura, así como un programa experimental que incluye el ensayo de 48 especímenes. A partir de un análisis de regresión de los datos medidos, se proponen ecuaciones para estimar las principales propiedades mecánicas del CRFA, tales como resistencia a compresión, módulo de elasticidad y relación de Poisson. Las ecuaciones correlacionan las propiedades mecánicas con las principales características de las fibras de acero, tales como dosificación y relación de aspecto.

Fuego y acero

Directory of Open Access Journals (Sweden)

Sfintesco, D.

1965-03-01

Full Text Available In a brief and appealing manner the author analysis the basic considerations which should be taken into account to deal effectively with the safety of steel structures in case of fire. He makes it clear that the safety measures must not be the result of a rather intuitive and hasty reaction to the possibility of a fire: for example, the costly covering of steel columns with fire resisting material, which in most cases is not necessary. A careful assessment of possible risks must be made, available means to reduce these must be adopted, and the potential losses in case of fire must be taken into account. The article is completed with a brief commentary on the new Italian Regulations, which are probably the most modern and advanced on this matter.El autor expone en este trabajo, en forma breve y llamativa, las bases en que conviene apoyarse para poder resolver racionalmente el problema de la seguridad de las estructuras de acero frente al fuego. Su lectura hace comprender claramente que no puede constituir esta base el temor irreflexivo, con sus secuelas de revestimientos y precauciones onerosos, e innecesarios la mayor parte de las veces, sino la ponderación prudente de los riesgos posibles, de los medios disponibles para combatir el peligro y de los daños probables que del incendio se puedan derivar. Termina el artículo con un rápido comentario del nuevo Reglamento italiano, probablemente el más moderno y avanzado de todos los existentes sobre esta materia de protección contra el fuego.

A Dual-Specific Targeting Approach Based on the Simultaneous Recognition of Duplex and Quadruplex Motifs.

Science.gov (United States)

Nguyen, Thi Quynh Ngoc; Lim, Kah Wai; Phan, Anh Tuân

2017-09-20

Small-molecule ligands targeting nucleic acids have been explored as potential therapeutic agents. Duplex groove-binding ligands have been shown to recognize DNA in a sequence-specific manner. On the other hand, quadruplex-binding ligands exhibit high selectivity between quadruplex and duplex, but show limited discrimination between different quadruplex structures. Here we propose a dual-specific approach through the simultaneous application of duplex- and quadruplex-binders. We demonstrated that a quadruplex-specific ligand and a duplex-specific ligand can simultaneously interact at two separate binding sites of a quadruplex-duplex hybrid harbouring both quadruplex and duplex structural elements. Such a dual-specific targeting strategy would combine the sequence specificity of duplex-binders and the strong binding affinity of quadruplex-binders, potentially allowing the specific targeting of unique quadruplex structures. Future research can be directed towards the development of conjugated compounds targeting specific genomic quadruplex-duplex sites, for which the linker would be highly context-dependent in terms of length and flexibility, as well as the attachment points onto both ligands.

Full-Duplex opportunistic relay selection in future spectrum-sharing networks

KAUST Repository

Khafagy, Mohammad Galal; Alouini, Mohamed-Slim; Aï ssa, Sonia

2015-01-01

We propose and analyze the performance of full-duplex relay selection in primary/secondary spectrum-sharing networks. Contrary to half-duplex relaying, full-duplex relaying (FDR) enables simultaneous listening/forwarding at the secondary relay, thereby allowing for a higher spectral efficiency. However, since the source and relay simultaneously transmit in FDR, their superimposed signal at the primary receiver should now satisfy the existing interference constraint which can considerably limit the secondary network throughput. In this regard, relay selection can offer an adequate solution to boost the secondary throughput while satisfying the imposed interference limit. We first analyze the performance of opportunistic relay selection among a cluster of full-duplex decode-and-forward relays with self-interference by deriving the exact cumulative distribution function of its end-to-end signal-to-noise ratio. Second, we evaluate the end-to-end performance of relay selection with interference constraints due to the presence of a primary receiver. Finally, the presented exact theoretical findings are verified by numerical simulations.

Full-Duplex opportunistic relay selection in future spectrum-sharing networks

KAUST Repository

Khafagy, Mohammad Galal

2015-06-01

We propose and analyze the performance of full-duplex relay selection in primary/secondary spectrum-sharing networks. Contrary to half-duplex relaying, full-duplex relaying (FDR) enables simultaneous listening/forwarding at the secondary relay, thereby allowing for a higher spectral efficiency. However, since the source and relay simultaneously transmit in FDR, their superimposed signal at the primary receiver should now satisfy the existing interference constraint which can considerably limit the secondary network throughput. In this regard, relay selection can offer an adequate solution to boost the secondary throughput while satisfying the imposed interference limit. We first analyze the performance of opportunistic relay selection among a cluster of full-duplex decode-and-forward relays with self-interference by deriving the exact cumulative distribution function of its end-to-end signal-to-noise ratio. Second, we evaluate the end-to-end performance of relay selection with interference constraints due to the presence of a primary receiver. Finally, the presented exact theoretical findings are verified by numerical simulations.

[A Duplex PCR Method for Detection of Babesia caballi and Theileria equi].

Science.gov (United States)

Zhang, Yang; Zhang, Yu-ting; Wang, Zhen-bao; Bolati; Li, Hai; Bayinchahan

2015-04-01

To develop a duplex PCR assay for detection of Babesia caballi and Theileria equi. Two pairs of primers were designed according to the BC48 gene of B. caballi and 18 s rRNA gene of T. equi, and a duplex PCR assay was developed by the optimization of reaction conditions. The specificity, sensitivity and reliability of the method were tested. The horse blood samples of suspected cases were collected from Yili region, and detected by the duplex PCR, microspopy, conventional PCR, and fluorescence quantitative PCR, and the results were compared. Using the duplex PCR assay, the specific fragments of 155 bp and 280 bp were amplified from DNA samples of B. caballi and T. equi, respectively. No specific fragment was amplified from DNA samples of B. bigemina, Theilerdia annulata, Theilerdia sergenti, Toxoplasma gondii, Neospora caninum, and Trypanosoma evansi. The limit of detection was 4.85 x 10(5) copies/L for B. caballi DNA and 4.85 x 10(4) copies/µl for T. equi DNA, respectively. Among the 24 blood samples, 11 were found B. caballi-positive by the duplex PCR assay, and 18 were T. equi-positive. The coincidence rate of microscopy, conventional PCR, and fluorescence quantitative PCR with duplex PCR was 91.7% (22/24), 95.8% (23/24), and 95.8% (23/24), respectively. A duplex PCR assay for simultaneous detection of B. caballi and T. equi is established.

Duplex Ultrasonography Has Limited Utility in Detection of Postoperative DVT After Primary Total Joint Arthroplasty.

Science.gov (United States)

Vira, Shaleen; Ramme, Austin J; Alaia, Michael J; Steiger, David; Vigdorchik, Jonathan M; Jaffe, Frederick

2016-07-01

Duplex ultrasound is routinely used to evaluate suspected deep venous thrombosis after total joint arthroplasty. When there is a clinical suspicion for a pulmonary embolism, a chest angiogram (chest CTA) is concomitantly obtained. Two questions were addressed: First, for the population of patients who receive duplex ultrasound after total joint arthroplasty, what is the rate of positive results? Second, for these patients, how many of these also undergo chest CTA for clinical suspicion of pulmonary embolus and how many of these tests are positive? Furthermore, what is the correlation between duplex ultrasound results and chest CTA results? A retrospective chart review was conducted of total joint replacement patients in 2011 at a single institution. Inclusion criteria were adult patients who underwent a postoperative duplex ultrasonography for clinical suspicion of deep venous thrombosis (DVT). Demographic data, result of duplex scan, clinical indications for obtaining the duplex scan, and DVT prophylaxis used were recorded. Additionally, if a chest CTA was obtained for clinical suspicion for pulmonary embolus, results and clinical indication for obtaining the test were recorded. The rate of positive results for duplex ultrasonography and chest CTA was computed and correlated based on clinical indications. Two hundred ninety-five patients underwent duplex ultrasonography of which only 0.7% were positive for a DVT. One hundred three patients underwent a chest CTA for clinical suspicion of a pulmonary embolism (PE) of which 26 revealed a pulmonary embolus, none of which had a positive duplex ultrasound. Postoperative duplex scans have a low rate of positive results. A substantial number of patients with negative duplex results subsequently underwent chest CTA for clinical suspicion for which a pulmonary embolus was found, presumably resulting from a DVT despite negative duplex ultrasound result. A negative duplex ultrasonography should not rule out the presence of a

Development of a lean duplex stainless steel

Energy Technology Data Exchange (ETDEWEB)

Liljas, M.; Johansson, P.; Liu Hui-Ping; Olsson, C.O.A. [Avesta Research Centre, Avesta (Sweden). Outokumpu Stainless

2008-06-15

The classic series of duplex stainless steels shows very high corrosion resistance and can be used for very demanding applications. A new lean duplex steel, LDX 2101 {sup registered} (EN 1.4162, UNS S32101), has been developed with corrosion resistance on a par with standard austenitic grades. Application areas include: structural components, chemical industry, tanks and containers. The steel was designed to have equal amounts of ferrite and austenite in annealed condition and with an austenite that is stable against strain-induced martensite. Thanks to its high nitrogen content, the steel has a fast austenite reformation when subjected to thermal cycling, e.g. welding. Unlike conventional duplex grades, the formation of intermetallic phase is very sluggish, although precipitation of nitrides and carbides has a certain impact on material properties after exposure in the temperature range 600 to 800 C. The precipitation behaviour after different isothermal treatments is described and its influence on different product properties is shown. A good agreement was found between impact toughness and corrosion resistance for a wide range of thermal treatments. (orig.)

Full-Duplex Communications in Large-Scale Cellular Networks

KAUST Repository

AlAmmouri, Ahmad

2016-04-01

In-band full-duplex (FD) communications have been optimistically promoted to improve the spectrum utilization and efficiency. However, the penetration of FD communications to the cellular networks domain is challenging due to the imposed uplink/downlink interference. This thesis presents a tractable framework, based on stochastic geometry, to study FD communications in multi-tier cellular networks. Particularly, we assess the FD communications effect on the network performance and quantify the associated gains. The study proves the vulnerability of the uplink to the downlink interference and shows that the improved FD rate gains harvested in the downlink (up to 97%) comes at the expense of a significant degradation in the uplink rate (up to 94%). Therefore, we propose a novel fine-grained duplexing scheme, denoted as α-duplex scheme, which allows a partial overlap between the uplink and the downlink frequency bands. We derive the required conditions to harvest rate gains from the α-duplex scheme and show its superiority to both the FD and half-duplex (HD) schemes. In particular, we show that the α-duplex scheme provides a simultaneous improvement of 28% for the downlink rate and 56% for the uplink rate. We also show that the amount of the overlap can be optimized based on the network design objective. Moreover, backward compatibility is an essential ingredient for the success of new technologies. In the context of in-band FD communication, FD base stations (BSs) should support HD users\\' equipment (UEs) without sacrificing the foreseen FD gains. The results show that FD-UEs are not necessarily required to harvest rate gains from FD-BSs. In particular, the results show that adding FD-UEs to FD-BSs offers a maximum of 5% rate gain over FD-BSs and HD-UEs case, which is a marginal gain compared to the burden required to implement FD transceivers at the UEs\\' side. To this end, we shed light on practical scenarios where HD-UEs operation with FD-BSs outperforms the

Ultrasensitive Detection of RNA and DNA Viruses Simultaneously Using Duplex UNDP-PCR Assay.

Directory of Open Access Journals (Sweden)

Yong Huang

Full Text Available Mixed infection of multiple viruses is common in modern intensive pig rearing. However, there are no methods available to detect DNA and RNA viruses in the same reaction system in preclinical level. In this study, we aimed to develop a duplex ultrasensitive nanoparticle DNA probe-based PCR assay (duplex UNDP-PCR that was able to simultaneously detect DNA and RNA viruses in the same reaction system. PCV2 and TGEV are selected as representatives of the two different types of viruses. PCV2 DNA and TGEV RNA were simultaneously released from the serum sample by boiling with lysis buffer, then magnetic beads and gold nanoparticles coated with single and/or duplex specific probes for TGEV and PCV2 were added to form a sandwich-like complex with nucleic acids released from viruses. After magnetic separation, DNA barcodes specific for PCV2 and TGEV were eluted using DTT and characterized by specific PCR assay for specific DNA barcodes subsequently. The duplex UNDP-PCR showed similar sensitivity as that of single UNDP-PCR and was able to detect 20 copies each of PCV2 and TGEV in the serum, showing approximately 250-fold more sensitivity than conventional duplex PCR/RT-PCR assays. No cross-reaction was observed with other viruses. The positive detection rate of single MMPs- and duplex MMPs-based duplex UNDP-PCR was identical, with 29.6% for PCV2, 9.3% for TGEV and 3.7% for PCV2 and TGEV mixed infection. This duplex UNDP-PCR assay could detect TGEV (RNA virus and PCV2 (DNA virus from large-scale serum samples simultaneously without the need for DNA/RNA extraction, purification and reverse transcription of RNA, and showed a significantly increased positive detection rate for PCV2 (29% and TGEV (11.7% preclinical infection than conventional duplex PCR/RT-PCR. Therefore, the established duplex UNDP-PCR is a rapid and economical detection method, exhibiting high sensitivity, specificity and reproducibility.

Ultrasensitive Detection of RNA and DNA Viruses Simultaneously Using Duplex UNDP-PCR Assay

Science.gov (United States)

Wang, Zengguo; Zhang, Xiujuan; Zhao, Xiaomin; Du, Qian; Chang, Lingling; Tong, Dewen

2015-01-01

Mixed infection of multiple viruses is common in modern intensive pig rearing. However, there are no methods available to detect DNA and RNA viruses in the same reaction system in preclinical level. In this study, we aimed to develop a duplex ultrasensitive nanoparticle DNA probe-based PCR assay (duplex UNDP-PCR) that was able to simultaneously detect DNA and RNA viruses in the same reaction system. PCV2 and TGEV are selected as representatives of the two different types of viruses. PCV2 DNA and TGEV RNA were simultaneously released from the serum sample by boiling with lysis buffer, then magnetic beads and gold nanoparticles coated with single and/or duplex specific probes for TGEV and PCV2 were added to form a sandwich-like complex with nucleic acids released from viruses. After magnetic separation, DNA barcodes specific for PCV2 and TGEV were eluted using DTT and characterized by specific PCR assay for specific DNA barcodes subsequently. The duplex UNDP-PCR showed similar sensitivity as that of single UNDP-PCR and was able to detect 20 copies each of PCV2 and TGEV in the serum, showing approximately 250-fold more sensitivity than conventional duplex PCR/RT-PCR assays. No cross-reaction was observed with other viruses. The positive detection rate of single MMPs- and duplex MMPs-based duplex UNDP-PCR was identical, with 29.6% for PCV2, 9.3% for TGEV and 3.7% for PCV2 and TGEV mixed infection. This duplex UNDP-PCR assay could detect TGEV (RNA virus) and PCV2 (DNA virus) from large-scale serum samples simultaneously without the need for DNA/RNA extraction, purification and reverse transcription of RNA, and showed a significantly increased positive detection rate for PCV2 (29%) and TGEV (11.7%) preclinical infection than conventional duplex PCR/RT-PCR. Therefore, the established duplex UNDP-PCR is a rapid and economical detection method, exhibiting high sensitivity, specificity and reproducibility. PMID:26544710

Ultrasensitive Detection of RNA and DNA Viruses Simultaneously Using Duplex UNDP-PCR Assay.

Science.gov (United States)

Huang, Yong; Xing, Na; Wang, Zengguo; Zhang, Xiujuan; Zhao, Xiaomin; Du, Qian; Chang, Lingling; Tong, Dewen

2015-01-01

Mixed infection of multiple viruses is common in modern intensive pig rearing. However, there are no methods available to detect DNA and RNA viruses in the same reaction system in preclinical level. In this study, we aimed to develop a duplex ultrasensitive nanoparticle DNA probe-based PCR assay (duplex UNDP-PCR) that was able to simultaneously detect DNA and RNA viruses in the same reaction system. PCV2 and TGEV are selected as representatives of the two different types of viruses. PCV2 DNA and TGEV RNA were simultaneously released from the serum sample by boiling with lysis buffer, then magnetic beads and gold nanoparticles coated with single and/or duplex specific probes for TGEV and PCV2 were added to form a sandwich-like complex with nucleic acids released from viruses. After magnetic separation, DNA barcodes specific for PCV2 and TGEV were eluted using DTT and characterized by specific PCR assay for specific DNA barcodes subsequently. The duplex UNDP-PCR showed similar sensitivity as that of single UNDP-PCR and was able to detect 20 copies each of PCV2 and TGEV in the serum, showing approximately 250-fold more sensitivity than conventional duplex PCR/RT-PCR assays. No cross-reaction was observed with other viruses. The positive detection rate of single MMPs- and duplex MMPs-based duplex UNDP-PCR was identical, with 29.6% for PCV2, 9.3% for TGEV and 3.7% for PCV2 and TGEV mixed infection. This duplex UNDP-PCR assay could detect TGEV (RNA virus) and PCV2 (DNA virus) from large-scale serum samples simultaneously without the need for DNA/RNA extraction, purification and reverse transcription of RNA, and showed a significantly increased positive detection rate for PCV2 (29%) and TGEV (11.7%) preclinical infection than conventional duplex PCR/RT-PCR. Therefore, the established duplex UNDP-PCR is a rapid and economical detection method, exhibiting high sensitivity, specificity and reproducibility.

Corrosión microbiológica en aceros de bajo carbono

OpenAIRE

Medina-Custodio, O; Ortiz-Prado, A; Jacobo-Armendáriz, V.H.; Schouwenaars-Franssens, R

2009-01-01

La corrosión microbiológica es un tipo común de deterioro que afecta diversas industrias, una de ellas es la petrolera en la que se estiman que el 20% o 30% de fallas en las tuberías de trasporte de hidrocarburos es favorecida por microorganismos. Las reacciones químicas que sustentan éstos, generan transferencia de iones, lo que justifica el empleo de técnicas electroquímicas para su análisis. En este trabajo, se estudiaron probetas de acero de bajo carbono SAE 1018, sumergidas en un medio n...

Considerations in Duplex Investment.

Science.gov (United States)

Wright, Arthur; Goen, Tom

Problems of duplex investment are noted in the introduction to this booklet designed to provide a technique by which the investment decision can be approached, develop estimates of typical costs and returns under differing conditions, and encourage investors to analyze objectives and conditions before the decision to buy or build is made. A…

Effect of Cavity Size of Mesoporous Silica on Short DNA Duplex Stability.

Science.gov (United States)

Masuda, Tsubasa; Shibuya, Yuuta; Arai, Shota; Kobayashi, Sayaka; Suzuki, Sotaro; Kijima, Jun; Itoh, Tetsuji; Sato, Yusuke; Nishizawa, Seiichi; Yamaguchi, Akira

2018-05-15

We studied the stabilities of short (4- and 3-bp) DNA duplexes within silica mesopores modified with a positively charged trimethyl aminopropyl (TMAP) monolayer (BJH pore diameter 1.6-7.4 nm). The DNA fragments with fluorescent dye were introduced into the pores, and their fluorescence resonance energy transfer (FRET) response was measured to estimate the structuring energies of the short DNA duplexes under cryogenic conditions (temperature 233-323 K). The results confirmed the enthalpic stability gain of the duplex within size-matched pores (1.6 and 2.3 nm). The hybridization equilibrium constants found for the size-matched pores were 2 orders of magnitude larger than those for large pores (≥3.5 nm), and this size-matching effect for the enhanced duplex stability was explained by a tight electrostatic interaction between the duplex and the surface TMAP groups. These results indicate the requirement of the precise regulation of mesopore size to ensure the stabilization of hydrogen-bonded supramolecular assemblies.

Renal pelvis urothelial carcinoma of the upper moiety in complete right renal duplex: a case report.

Science.gov (United States)

Zhang, Yiran; Yu, Quanfeng; Zhang, Zhihong; Liu, Ranlu; Xu, Yong

2015-01-01

Urothelial carcinoma (UC) originated from renal pelvis is the common tumor of the urinary system, however, neoplasia of the renal pelvis in duplex kidneys is extremely rare, especially in the complete renal and ureteral duplex cases. We present the first case of renal pelvis UC of the upper moiety in a complete right renal duplex. This male patient has bilateral complete renal and ureteral duplex. To the best of our knowledge, this is the first reported case of renal pelvis UC in a complete renal duplex system. After this experience we feel that the diagnosis of renal pelvis UC in duplex kidneys is not so easy, and once the diagnosis is determined, the whole renal duplex units and bladder cuff or ectopic orifice should be excised radically.

Full-Duplex Relay Selection in Cognitive Underlay Networks

KAUST Repository

Khafagy, Mohammad Galal

2017-09-30

In this work, we analyze the performance of full-duplex relay selection (FDRS) in spectrum-sharing networks. Contrary to half-duplex relaying, full-duplex relaying (FDR) enables simultaneous listening/forwarding at the secondary relay(s), thereby allowing for a higher spectral efficiency. However, since the source and relay simultaneously transmit in FDR, their superimposed signal at the primary receiver should now satisfy the existing interference constraint, which can considerably limit the secondary network throughput. In this regard, relay selection can offer an adequate solution to boost the secondary throughput while satisfying the imposed interference limit. We first analyze the performance of opportunistic FDRS with residual self-interference (RSI) by deriving the exact cumulative distribution function of its end-to-end signal-to-interference-plus-noise ratio under Nakagami-m fading. We also evaluate the offered diversity gain of relay selection for different full-duplex cooperation schemes in the presence/absence of a direct source-destination link. When the adopted RSI link gain model is sublinear in the relay power, which agrees with recent research findings, we show that remarkable diversity gain can be recovered even in the presence of an interfering direct link. Second, we evaluate the end-to-end performance of FDRS with interference constraints due to the presence of a primary receiver. Finally, the presented exact theoretical findings are verified by numerical simulations.

THE INFLUENCE OF POSTHEAT TREATMENT ON FERRITE REDISTRIBUTION IN DUPLEX STEELS ELECTRON BEAM WELDS

OpenAIRE

Zita Iždinská; František Kolenič

2009-01-01

The duplex stainless steel is two-phase steel with the structure composed of austenite and ferrite with optimum austenite/ferrite proportion 50%. At present, classical arc processes for welding duplex steels are generally regarded as acceptable. On the other hand electron and laser beam welding is up to now considered less suitable for welding duplex steels. The submitted work presents the results of testing various thermal conditions at welding duplex stainless steel with electron beam. It w...

In-Band α-Duplex Scheme for Cellular Networks: A Stochastic Geometry Approach

KAUST Repository

Alammouri, Ahmad

2016-07-13

In-band full-duplex (FD) communications have been optimistically promoted to improve the spectrum utilization and efficiency. However, the penetration of FD communications to the cellular networks domain is challenging due to the imposed uplink/downlink interference. This paper presents a tractable framework, based on stochastic geometry, to study FD communications in cellular networks. Particularly, we assess the FD communications effect on the network performance and quantify the associated gains. The study proves the vulnerability of the uplink to the downlink interference and shows that FD rate gains harvested in the downlink (up to 97%) come at the expense of a significant degradation in the uplink rate (up to 94%). Therefore, we propose a novel fine-grained duplexing scheme, denoted as -duplex scheme, which allows a partial overlap between the uplink and the downlink frequency bands. We derive the required conditions to harvest rate gains from the -duplex scheme and show its superiority to both the FD and half-duplex (HD) schemes. In particular, we show that the -duplex scheme provides a simultaneous improvement of 28% for the downlink rate and 56% for the uplink rate. Finally, we show that the amount of the overlap can be optimized based on the network design objective.

An evaluation of nuclear design characteristics of duplex burnable poison rods for extended cycle core

International Nuclear Information System (INIS)

Lee, D. J.; Kim, M. H.; Song, K. W.

2003-01-01

Nuclear design characteristics of duplex burnable poison rod were evaluated for three integral type burnable absorbers; Gadolinia, Erbia and IFBA. Inter-comparison was done for both 12 and 24 month cycle for Korean Standard Nuclear Plant. Fuel assemblies with duplex BP was designed to the equivalent assembly with 8 and 16 gadolinia BP 2 . Duplex BP is composed of inner region of natural U-Gd 2 O 3 , and outer shell of, UO 2 -Er2O 3 . In order to evaluate the duplex BP, assemblies with erbia and IFBA were compared with alternative options. A sensitivity studies were performed to the size of region, compositions and location of duplex BPs. It was shown that duplex BP gave favorable k-infinite curve to burnup, but IFBA provided the least residual reactivity penalty as EOC. Erbia was good for more negative MTCs. IFBA and erbia had better neutronic performance than gadolinia od duplex BP in the aspect of pin power peaking

Ecuaciones constitutivas de la fluencia en caliente de aceros microaleados

Directory of Open Access Journals (Sweden)

Cabrera, J. M.

1998-05-01

Full Text Available Over centuries, the hot forming has been employed to provide shape to metáis. Nowadays, the deformation at high temperatures gives also the required final mechanical properties. From this point of view, the obtention of a constitutive equation describing the hot flow behaviour of microalloyed steels in particular is a very important task. The main difficulty in modelling the high temperature flow arises from the simultaneity of two opposite phenomena, namely, work hardening and dynamic softening due to recovery and recrystallization. In this is work a review of constitutive equations (including the effect of the chemical composition describing the flow behaviour of microalloyed steels deformed under high temperature conditions.

Durante siglos el conformado en caliente se ha utilizado para proporcionar a los metales la forma deseada. Hoy en día la deformación en caliente no sólo genera la geometría deseada sino las características mecánicas requeridas. Así, la obtención de una ecuación constitutiva para la fluencia en caliente de un acero en particular, es una tarea ineludible para efectuar simulaciones por ordenador de procesos industriales. La complicación de la modelización de la fluencia a alta temperatura proviene de la simultaneidad de dos fenómenos contrapuestos durante la deformación, a saber, endurecimiento por deformación y ablandamiento por recuperación de la estructura. Este último a su vez puede constar de restauración y recristalización dinámicas. En este trabajo se revisan y plantean las ecuaciones constitutivas que describen las curvas de fluencia bajo condiciones de deformación en caliente, y se presenta una aplicación de las mismas a aceros microaleados.

CMOS serial link for fully duplexed data communication

Science.gov (United States)

Lee, Kyeongho; Kim, Sungjoon; Ahn, Gijung; Jeong, Deog-Kyoon

1995-04-01

This paper describes a CMOS serial link allowing fully duplexed 500 Mbaud serial data communication. The CMOS serial link is a robust and low-cost solution to high data rate requirements. A central charge pump PLL for generating multiphase clocks for oversampling is shared by several serial link channels. Fully duplexed serial data communication is realized in the bidirectional bridge by separating incoming data from the mixed signal on the cable end. The digital PLL accomplishes process-independent data recovery by using a low-ratio oversampling, a majority voting, and a parallel data recovery scheme. Mostly, digital approach could extend its bandwidth further with scaled CMOS technology. A single channel serial link and a charge pump PLL are integrated in a test chip using 1.2 micron CMOS process technology. The test chip confirms upto 500 Mbaud unidirectional mode operation and 320 Mbaud fully duplexed mode operation with pseudo random data patterns.

Estudio de inteligencia de mercados para la importación de tubería de acero carbón para PSA Colombia S.A.S.

OpenAIRE

2012-01-01

Estudio de inteligencia de mercados para la importación de tuberia de acero carbon para PSA Colombia S.A.S, SCH 40 de 2" revisar la viabilidad de la compra local versus la compra en el exterior analizando tres proveedores Estados Unidos, China y Brasil. En el presente trabajo se estudian los mercados para la importación de tubería de Acero Carbón SCH40, se realiza el análisis de cada área del proceso de comercialización y se establece en términos técnicos, comerciales, financieros, logísticos...

ESTUDIO DE LA PROTECCIÓN ANTICORROSIVA SOBRE ACERO DE BAJO CARBONO MEDIANTE TRATAMIENTO DE CONVERSIÓN QUÍMICA BASE CERIO COMO PREPARACIÓN DE SUPERFICIE

OpenAIRE

MATA GALLARDO, LUIS JAIME

2014-01-01

En este trabajo, se propone un tratamiento de conversión química base cerio sobre acero de bajo carbono para obtener un incremento en las propiedades de protección y ser utilizado como una preparación de superficie para un pintado posterior. El nitrato de cerio fue elegido como precursor y se utilizaron tres métodos para la obtención de películas sobre la superficie de acero al carbono. Las películas son formadas utilizando o no el H2O2, sin embargo, el papel del H2O2 es el de ...

Producción de aceros al carbono en hornos de arco eléctrico en condiciones de mineral de manganeso.

Directory of Open Access Journals (Sweden)

E. E. Navas Medina

2007-05-01

Full Text Available El presente trabajo constituye una segunda etapa de investigación relacionada con la producción de acero en hornos de arco eléctrico con revestimiento básico en condiciones de utilización de mineral de manganeso como sustituto del ferro-manganeso. En la investigación se caracteriza el acero producido utilizando el mineral de manganeso en dos variantes tecnológicas diferentes y se determinan parámetros importantes, tales como la estructura del acero obtenido, la influencia de la composición química y la temperatura en la reducción del Mn. Adicionalmente, se determina la composición química de la escoria, su basicidad e influencia en el aprovechamiento del Mn del mineral, así como, lo que significa la sustitución del FeMn en la problemática medioambiental. This present work constitutes the second stage of investigation in relation with the steel production by means of electric arc furnaces in the condition of use of manganese ores as a substitute of the ferromanganese. In the investigation, the steel manufactured is analyzed the manganese ore in two different technological variants and some important parameters are determined such as: the chemical composition's structure of the steel, the influence of temperature in the reduction of Mn. Moreover, an analysis of the chemical composition of the slag and the influence in the environmental is realized.

Optimisation of welding procedures for duplex and superduplex stainless steels

International Nuclear Information System (INIS)

Westin, Elin M.

2014-01-01

Austenitic stainless steels are increasingly being replaced by duplex grades that can offer similar corrosion resistance with far higher strength. This increased strength makes it possible to reduce material consumption whilst also decreasing transport and construction costs. Although established welding methods used for austenitic steels can be used for duplex steels, modification of the procedures can lead to improved results. This paper reviews the welding of duplex stainless steel and examines precautions that may be required. The advantages and disadvantages of different welding methods are highlighted and some high productivity solutions are presented. The application of a more efficient process with a high deposition rate (e.g. flux- cored arc welding) can decrease labour costs. Further close control of heat input and interpass temperature can result in more favourable microstructures and final properties. Although welding adversely affects the corrosion resistance of austenitic and duplex stainless steels, particularly the pitting resistance, relative to the parent material, this problem can be minimised by proper backing gas protection and subsequent pickling.

Features of residual stresses in duplex stainless steel butt welds

Science.gov (United States)

Um, Tae-Hwan; Lee, Chin-Hyung; Chang, Kyong-Ho; Nguyen Van Do, Vuong

2018-04-01

Duplex stainless steel finds increasing use as an alternative to austenitic stainless steel, particularly where chloride or sulphide stress corrosion cracking is of primary concern, due to the excellent combination of strength and corrosion resistance. During welding, duplex stainless steel does not create the same magnitude or distribution of weld-induced residual stresses as those in welded austenitic stainless steel due to the different physical and mechanical properties between them. In this work, an experimental study on the residual stresses in butt-welded duplex stainless steel is performed utilizing the layering technique to investigate the characteristics of residual stresses in the weldment. Three-dimensional thermos-mechanical-metallurgical finite element analysis is also performed to confirm the residual stress measurements.

Estudio de la resistencia a la abrasión de capas vitrocerámicas depositadas sobre acero

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Gómez de Salazar, J. M.

2002-12-01

Full Text Available Wear test has been completed on two types of layered materials: a non-reinforced enamel plate and a ceramic reinforced enamel plate. The latter has been tested in two forms: with 10 wt. % and 20 wt. % ceramic particles reinforcement. For comparison the same test has also been completed on polished steel. Wear resistance was measure using a tribometer, equipped with a chromium steel sphere of 6 mm diameter. The sphere-plate surface contact area increases with distance covered, which in the polished steel provokes exponential increments in wear values. This exponential behaviour was not observed in the enamel plates due to their greater wear resistance. The reinforcement of the enamel plates with ceramic particles increases the wear resistance. A higher percentage of ceramic reinforcement results in a greater wear resistance of the plates.

Se han realizado ensayos de desgaste, tanto en placas esmaltadas sin refuerzo como en esmaltes con distinto porcentaje de carga cerámica (10 y 20% en peso, y se han comparado frente al del acero base pulido. Las medidas de resistencia a la abrasión se han obtenido utilizado un tribómetro con bola de acero al cromo de 6 mm de diámetro. El aumento de la superficie de contacto bola-placa a medida que aumenta la distancia recorrida, provoca aumentos exponenciales en los desgastes en el caso del acero pulido. Sin embargo, en el caso de las chapas esmaltadas no se observa este comportamiento, debido a la mayor resistencia al desgaste de las mismas. Cuando las capas esmaltadas están reforzadas con cargas cerámicas, la resistencia al desgaste aumenta con el porcentaje de refuerzo cerámico.

Micromechanics of base pair unzipping in the DNA duplex

International Nuclear Information System (INIS)

Volkov, Sergey N; Paramonova, Ekaterina V; Yakubovich, Alexander V; Solov’yov, Andrey V

2012-01-01

All-atom molecular dynamics (MD) simulations of DNA duplex unzipping in a water environment were performed. The investigated DNA double helix consists of a Drew-Dickerson dodecamer sequence and a hairpin (AAG) attached to the end of the double-helix chain. The considered system is used to examine the process of DNA strand separation under the action of an external force. This process occurs in vivo and now is being intensively investigated in experiments with single molecules. The DNA dodecamer duplex is consequently unzipped pair by pair by means of the steered MD. The unzipping trajectories turn out to be similar for the duplex parts with G⋅C content and rather distinct for the parts with A⋅T content. It is shown that during the unzipping each pair experiences two types of motion: relatively quick rotation together with all the duplex and slower motion in the frame of the unzipping fork. In the course of opening, the complementary pair passes through several distinct states: (i) the closed state in the double helix, (ii) the metastable preopened state in the unzipping fork and (iii) the unbound state. The performed simulations show that water molecules participate in the stabilization of the metastable states of the preopened base pairs in the DNA unzipping fork. (paper)

Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by super duplex filler metal

Energy Technology Data Exchange (ETDEWEB)

Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shamanian, Morteza [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandarian, Masoomeh [Department of Materials Engineering, Shiraz University, Shiraz 71348-51154 (Iran, Islamic Republic of); Zabolian, Azam [Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Szpunar, Jerzy A. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon SK S7N 5A9 (Canada)

2015-08-15

In the present paper, microstructural changes across an as-welded dissimilar austenitic/duplex stainless steel couple welded by a super duplex stainless steel filler metal using gas tungsten arc welding process is characterized with optical microscopy and electron back-scattered diffraction techniques. Accordingly, variations of microstructure, texture, and grain boundary character distribution of base metals, heat affected zones, and weld metal were investigated. The results showed that the weld metal, which was composed of Widmanstätten austenite side-plates and allotriomorphic grain boundary austenite morphologies, had the weakest texture and was dominated by low angle boundaries. The welding process increased the ferrite content but decreased the texture intensity at the heat affected zone of the super duplex stainless steel base metal. In addition, through partial ferritization, it changed the morphology of elongated grains of the rolled microstructure to twinned partially transformed austenite plateaus scattered between ferrite textured colonies. However, the texture of the austenitic stainless steel heat affected zone was strengthened via encouraging recrystallization and formation of annealing twins. At both interfaces, an increase in the special character coincident site lattice boundaries of the primary phase as well as a strong texture with <100> orientation, mainly of Goss component, was observed. - Graphical abstract: Display Omitted - Highlights: • Weld metal showed local orientation at microscale but random texture at macroscale. • Intensification of <100> orientated grains was observed adjacent to the fusion lines. • The austenite texture was weaker than that of the ferrite in all duplex regions. • Welding caused twinned partially transformed austenites to form at SDSS HAZ. • At both interfaces, the ratio of special CSL boundaries of the primary phase increased.

Comportamiento termomecánico de un acero microaleado al Nb-V

OpenAIRE

Cartaya, E. A.; Varela, G.; Cabrera Marrero, José M.; Prado Pozuelo, José Manuel

2012-01-01

Empleando ensayos de compresión simple en ca- liente y relajación de tensiones después de la de - formación en un dilatómetro modelo DIL805T, se obtuvieron las curvas de fluencia y relajación de dos aceros, el primero de ellos al C – Mn y otro HS- LA con idéntica composición química base, micro- aleado con Nb – V. Los ensayos de compresión simple fueron efectua- dos a temperaturas en el rango austenítico, desde 900 – 1.200 ºC y velocidades de deformación de 0....

Analyzing the Potential of Full Duplex in 5G Ultra-Dense Small Cell Networks

DEFF Research Database (Denmark)

Gatnau, Marta; Berardinelli, Gilberto; Mahmood, Nurul Huda

2016-01-01

Full duplex technology has become an attractive solution for future 5th Generation (5G) systems for accommodating the exponentially growing mobile traffic demand. Full duplex allows a node to transmit and receive simultaneously in the same frequency band, thus, theoretically, doubling the system...... throughput over conventional half duplex systems. A key limitation in building a feasible full duplex node is the self-interference, i.e., the interference generated by the transmitted signal to the desired signal received on the same node. This constraint has been overcome given the recent advances...... in the self-interference cancellation technology. However, there are other limitations in achieving the theoretical full duplex gain: residual self-interference, traffic constraints and inter-cell and intra-cell interference. The contribution of this article is twofold. Firstly, achievable levels of self...

Duplex-tube sodium-indication steam generator

International Nuclear Information System (INIS)

Matal, O.; Martoch, J.

1984-01-01

The steam generator with duplex tubes and sodium indication is connected to the main sodium input and output via the inlet and outlet chambers and has indication spaces connected to the interspaces of the duplex tubes. The first indication space is linked with the auxiliary inlet pipe to the inlet chamber and the second indication space is connected with the auxiliary pipe to the outlet chamber. Mounted to the auxiliary inlet pipe is at least one closure, i.e., a valve or electromagnetic stop. Mounted on the auxiliary outlet pipe is an indication sensor, e.g., a sodium flow sensor. At least one indication space is provided with an alarm sensor, e.g., a thermocouple, a pressure gauge and one sensor to monitor the hydrogen content of sodium. (J.P.)

Probing of miniPEGγ-PNA-DNA Hybrid Duplex Stability with AFM Force Spectroscopy.

Science.gov (United States)

Dutta, Samrat; Armitage, Bruce A; Lyubchenko, Yuri L

2016-03-15

Peptide nucleic acids (PNA) are synthetic polymers, the neutral peptide backbone of which provides elevated stability to PNA-PNA and PNA-DNA hybrid duplexes. It was demonstrated that incorporation of diethylene glycol (miniPEG) at the γ position of the peptide backbone increased the thermal stability of the hybrid duplexes (Sahu, B. et al. J. Org. Chem. 2011, 76, 5614-5627). Here, we applied atomic force microscopy (AFM) based single molecule force spectroscopy and dynamic force spectroscopy (DFS) to test the strength and stability of the hybrid 10 bp duplex. This hybrid duplex consisted of miniPEGγ-PNA and DNA of the same length (γ(MP)PNA-DNA), which we compared to a DNA duplex with a homologous sequence. AFM force spectroscopy data obtained at the same conditions showed that the γ(MP)PNA-DNA hybrid is more stable than the DNA counterpart, 65 ± 15 pN vs 47 ± 15 pN, respectively. The DFS measurements performed in a range of pulling speeds analyzed in the framework of the Bell-Evans approach yielded a dissociation constant, koff ≈ 0.030 ± 0.01 s⁻¹ for γ(MP)PNA-DNA hybrid duplex vs 0.375 ± 0.18 s⁻¹ for the DNA-DNA duplex suggesting that the hybrid duplex is much more stable. Correlating the high affinity of γ(MP)PNA-DNA to slow dissociation kinetics is consistent with prior bulk characterization by surface plasmon resonance. Given the growing interest in γ(MP)PNA as well as other synthetic DNA analogues, the use of single molecule experiments along with computational analysis of force spectroscopy data will provide direct characterization of various modifications as well as higher order structures such as triplexes and quadruplexes.

The value and economic analysis of routine postoperative carotid duplex ultrasound surveillance after carotid endarterectomy.

Science.gov (United States)

AbuRahma, Ali F; Srivastava, Mohit; AbuRahma, Zachary; Jackson, Will; Mousa, Albeir; Stone, Patrick A; Dean, L Scott; Green, Jason

2015-08-01

Several studies have reported on the role of postoperative duplex ultrasound surveillance after carotid endarterectomy (CEA) with varying results. Most of these studies had a small sample size or did not analyze cost-effectiveness. We analyzed 489 of 501 CEA patients with patch closure. All patients had immediate postoperative duplex ultrasound examination and were routinely followed up both clinically and with duplex ultrasound at regular intervals of 1 month, 6 months, 12 months, and every 12 months thereafter. A Kaplan-Meier analysis was used to estimate the rate of ≥50% and ≥80% post-CEA restenosis over time and the time frame of progression from normal to ≥50% or ≥80% restenosis. The cost of post-CEA duplex surveillance was also estimated. Overall, 489 patients with a mean age of 68.5 years were analyzed. Ten of these had residual postoperative ≥50% stenosis, and 37 did not undergo a second duplex ultrasound examination and therefore were not included in the final analysis. The mean follow-up was 20.4 months (range, 1-63 months), with a mean number of duplex ultrasound examinations of 3.6 (range, 1-7). Eleven of 397 patients (2.8%) with a normal finding on immediate postoperative duplex ultrasound vs 4 of 45 (8.9%) with mild stenosis on immediate postoperative duplex ultrasound progressed to ≥50% restenosis (P = .055). Overall, 15 patients (3.1%) had ≥50% restenosis, 9 with 50% to duplex ultrasound), which equals $1,408,320, to detect only four patients with ≥80% to 99% restenosis who may have been potential candidates for reintervention. This study shows that the value of routine postoperative duplex ultrasound surveillance after CEA with patch closure may be limited, particularly if the finding on immediate postoperative duplex ultrasound is normal or shows minimal disease. Copyright © 2015 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Mecanismos de fractura a alta temperatura en aceros eléctricos no-orientados

Directory of Open Access Journals (Sweden)

García-Sánchez, E. O.

2007-08-01

Full Text Available In this research work the effect of deformation temperature on the hot ductility of non-oriented electrical steels (0.6 % Si-0.3 Al % was studied using high temperature tensile tests. The specimens were machined from two thin slabs (50 mm thickness produced by CSP process (Compact Strip Process, one of them using 100 % sponge iron and the other using 67 % scrap and 33 % sponge iron. The tensile tests were carried out at constant strain rate (5×1010^–4 s^–1, and a temperature range from 850 to 1,200 °C. The results showed that the ductility decreased with the increment in the temperature until approximately 1,000 °C. At higher temperatures, a ductility recovery was observed only in the steel fabricated without scrap. Scanning Electron Microscopy on fracture surfaces showed that the loss of ductility is associated with intergranular cracking promoted by the austenitic transformation and AlN grain boundaries precipitation.

Se investigó el efecto de la temperatura de deformación sobre la ductilidad de aceros eléctricos de grano no-orientado (0,6 % Si-0,3 % Al mediante ensayos de tracción uniaxial. Las probetas se obtuvieron de planchones delgados (50 mm de espesor tipo CSP (Continuous Strip Processing fabricados a partir de 100 % hierro esponja y una mezcla de 67 % chatarra y 33 % de hierro esponja. El rango de temperatura de estudio fue de 850 a 1.200 °C y los ensayos se llevaron a cabo a una velocidad de deformación constante de 5×10^–4 s^–1. Los resultados experimentales demostraron que la ductilidad (% RA disminuye con el aumento en la temperatura hasta un mínimo a ~1.000 °C. A temperaturas mayores, la ductilidad del acero fabricado a partir de 100 % hierro esponja se recupera. Este efecto no fue observado en el acero fabricado a partir de chatarra. La caracterización de las superficies de fractura mediante microscopía electrónica de barrido demostró que la pérdida de

Impact of Duplex arterial mapping on decision making in non-acute ischemic limb patients.

Science.gov (United States)

Elbadawy, A; Aly, H; Ibrahim, M; Bakr, H

2015-12-01

The aim of this study was to demonstrate the impact of Duplex arterial mapping on decision making in non-acute ischemic limb patient group reporting pain onset between 15 days and 3 months. We prospectively evaluated patients presented with critical limb ischemia who reported pain onset of duration between 15 days and 3 months in one-year period. Our series included thirty cases (mean age=61.3 years old), as Duplex arterial mapping was the sole preoperative imaging tool performed in all of them. All patients, in whom duplex indicated thrombosis in long occluded segments, were candidates for fluoroscopically guided thrombectomy. When Duplex defined chronic arterial occlusions, patients underwent endovascular or bypass revascularisation procedures. Impact of Duplex wall interrogation on decision-making between the two groups (subacute and chronic) was measured. Duplex arterial mapping categorized correctly all 30 patients into either subacute ischemia with removable clot (N.=14) or chronic ischemia (N.=16). Fluoroscopic guided thrombectomy was performed in 14 cases when Duplex advised long occluded arterial segments as indicted by intact intima with echogenic thrombus inside. Bypass surgery was performed in 8 patients. Percutaneous transluminal angioplasty (PTA) was done in 7 cases and thrombendartrectomy of common femoral artery in a single case. One-year patency rate in our series was 86.6%. It was 71.4% in thrombosis group. Limb salvage rate was 93.3%. Duplex arterial mapping could be used to differentiate the subacute ischemia with removable thrombus and chronic arterial occlusions guiding for the best revascularization procedure accordingly.

On the Potential of Full Duplex Performance in 5G Ultra-Dense Small Cell Networks

DEFF Research Database (Denmark)

Gatnau, Marta; Fleischer, Marko; Berardinelli, Gilberto

2016-01-01

inter-cell interference and traffic constraints. In this paper, we first study the self-interference cancellation capabilities by using a real demonstrator. Results show that achieving ~110 dB of cancellation is already possible with the current available technology, thus providing the required level...... of isolation to build an operational full duplex node. Secondly, we investigate the inter-cell interference and traffic constraints impact on the full duplex performance in 5th generation systems. System level results show that both the traffic and the inter-cell interference can significantly reduce...... the potential gain of full duplex with respect to half duplex. However, for large traffic asymmetry, full duplex can boost the performance of the lightly loaded link....

THE INFLUENCE OF POSTHEAT TREATMENT ON FERRITE REDISTRIBUTION IN DUPLEX STEELS ELECTRON BEAM WELDS

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Zita Iždinská

2009-04-01

Full Text Available The duplex stainless steel is two-phase steel with the structure composed of austenite and ferrite with optimum austenite/ferrite proportion 50%. At present, classical arc processes for welding duplex steels are generally regarded as acceptable. On the other hand electron and laser beam welding is up to now considered less suitable for welding duplex steels. The submitted work presents the results of testing various thermal conditions at welding duplex stainless steel with electron beam. It was shown, that application of suitable postheat made possible to reduce the ferrite content in weld metal.

Quality assurance of lower limb venous duplex scans performed by vascular surgeons.

Science.gov (United States)

Kordowicz, A; Ferguson, G; Salaman, R; Onwudike, M

2015-02-01

Duplex scanning is the gold standard for investigating venous reflux; increasingly surgeons perform these scans themselves. There has been no data published analysing the accuracy of Duplex scans performed by vascular surgeons. We aimed to evaluate an objective method of comparing the results of lower limb Duplex scans performed by one consultant vascular surgeon with those performed by a vascular technologist. We assessed 100 legs with symptomatic varicose veins. Each patient underwent two lower limb venous Duplex scans; one performed by a consultant vascular surgeon and one by a vascular technologist. Scan results were randomised and sent to two consultant vascular surgeons blinded to the identity and experience of the sonographer. They were asked to recommend treatment. A k score was calculated in each case to assess the level of agreement between the scans performed by the consultant and the technologist. Eighty-one patients were studied (53 females). The kappa score for assessor 1 was 0.60 (95%CI:0.44-0.75) and for assessor 2 was 0.62 (95%CI:0.48-0.75). k scores >0.60 represent a substantial strength of agreement. Duplex scans performed by this surgeon were comparable to those performed by a vascular technologist. It is possible to quality-assure duplex performed by vascular surgeons without directly observing the scanning process or reviewing digitally recorded images. We propose standardisation of training, assessment and quality assurance for vascular surgeons wishing to perform ultrasound scans.

Selection of patients with infrainguinal arterial occlusive disease for percutaneous transluminal angioplasty with duplex scanning

International Nuclear Information System (INIS)

Bostroem Ardin, A.; Hellberg, A.; Ljungman, C.; Logason, K.; Karacagil, S.; Loefberg, A.M.; Andren, B.

2002-01-01

Aim: To evaluate the role of duplex scanning in the selection of patients with infrainguinal arterial occlusive disease for percutaneous transluminal angioplasty (PTA). Material and Methods: From January 1995 through May 2000, 702 patients (952 limbs), with chronic lower extremity ischemia due to infrainguinal atherosclerotic disease diagnosed by duplex scanning, were retrospectively studied. Diagnostic angiography (130 limbs) or infrainguinal PTA (108 limbs) was performed in 238 limbs. Two investigators retrospectively analyzed the duplex examinations and angiographies in a blinded manner and used similar criteria for the interpretation of lesions suitable or not suitable for PTA. Results: The superficial femoral, popliteal and crural artery lesions were correctly selected for PTA in 85%, 66% and 32%, respectively. The accuracy, sensitivity, specificity, negative predictive value and positive predictive value of duplex scanning to appropriately categorize femoropopliteal lesions as suitable or unsuitable for PTA were 89%, 83%, 92%, 94% and 78%, respectively. The accuracy of duplex scanning for predicting the performance of infrainguinal PTA was 83%. Conclusion: Duplex scanning has an important impact on the selection of treatment modalities in limbs with infrainguinal arterial occlusive disease. Femoropopliteal lesions can be reliably selected to PTA according to duplex scan findings

Duplex evaluation following femoropopliteal angioplasty and stenting: criteria and utility of surveillance.

Science.gov (United States)

Baril, Donald T; Marone, Luke K

2012-07-01

Surveillance following lower extremity bypass, carotid endarterectomy, and endovascular aortic aneurysm repair has become the standard of care at most institutions. Conversely, surveillance following lower extremity endovascular interventions is performed somewhat sporadically in part because the duplex criteria for recurrent stenoses have been ill defined. It appears that duplex surveillance after peripheral endovascular interventions, as with conventional bypass, is beneficial in identifying recurrent lesions which may preclude failure and occlusion. In-stent stenosis following superficial femoral artery angioplasty and stenting can be predicted by both peak systolic velocity and velocity ratio data as measured by duplex ultrasound. Duplex criteria have been defined to determine both ≥50% in-stent stenosis and ≥80% in-stent stenosis. Although not yet well studied, it appears that applying these criteria during routine surveillance may assist in preventing failure of endovascular interventions.

Templated Chemistry for Sequence-Specific Fluorogenic Detection of Duplex DNA

Science.gov (United States)

Li, Hao; Franzini, Raphael M.; Bruner, Christopher; Kool, Eric T.

2015-01-01

We describe the development of templated fluorogenic chemistry for detection of specific sequences of duplex DNA in solution. In this approach, two modified homopyrimidine oligodeoxynucleotide probes are designed to bind by triple helix formation at adjacent positions on a specific purine-rich target sequence of duplex DNA. One fluorescein-labeled probe contains an α-azidoether linker to a fluorescence quencher; the second (trigger) probe carries a triarylphosphine, designed to reduce the azide and cleave the linker. The data showed that at pH 5.6 these probes yielded a strong fluorescence signal within minutes on addition to a complementary homopurine duplex DNA target. The signal increased by a factor of ca. 60, and was completely dependent on the presence of the target DNA. Replacement of cytosine in the probes with pseudoisocytosine allowed the templated chemistry to proceed readily at pH 7. Single nucleotide mismatches in the target oligonucleotide slowed the templated reaction considerably, demonstrating high sequence selectivity. The use of templated fluorogenic chemistry for detection of duplex DNAs has not been previously reported and may allow detection of double stranded DNA, at least for homopurine-homopyrimidine target sites, under native, non-disturbing conditions. PMID:20859985

Podiatry Ankle Duplex Scan: Readily Learned and Accurate in Diabetes.

Science.gov (United States)

Normahani, Pasha; Powezka, Katarzyna; Aslam, Mohammed; Standfield, Nigel J; Jaffer, Usman

2018-03-01

We aimed to train podiatrists to perform a focused duplex ultrasound scan (DUS) of the tibial vessels at the ankle in diabetic patients; podiatry ankle (PodAnk) duplex scan. Thirteen podiatrists underwent an intensive 3-hour long simulation training session. Participants were then assessed performing bilateral PodAnk duplex scans of 3 diabetic patients with peripheral arterial disease. Participants were assessed using the duplex ultrasound objective structured assessment of technical skills (DUOSATS) tool and an "Imaging Score". A total of 156 vessel assessments were performed. All patients had abnormal waveforms with a loss of triphasic flow. Loss of triphasic flow was accurately detected in 145 (92.9%) vessels; the correct waveform was identified in 139 (89.1%) cases. Participants achieved excellent DUOSATS scores (median 24 [interquartile range: 23-25], max attainable score of 26) as well as "Imaging Scores" (8 [8-8], max attainable score of 8) indicating proficiency in technical skills. The mean time taken for each bilateral ankle assessment was 20.4 minutes (standard deviation ±6.7). We have demonstrated that a focused DUS for the purpose of vascular assessment of the diabetic foot is readily learned using intensive simulation training.

Toughness and other mechanical properties of the duplex stainless steel 2205

International Nuclear Information System (INIS)

Sieurin, H.; Sandstroem, R.

2003-01-01

The use and range of potential applications of duplex stainless steel continuously increase. An overview of the mechanical properties of duplex stainless steel 2205 is presented with focus on toughness properties. Impact and fracture toughness as well as strength results from the European research project, EcoPress, are presented. (orig.)

Acero de alto silicio producido por inmersión en Al-Si y recocido de difusión

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Ros-Yáñez, Tanya

2000-10-01

Full Text Available It is difficult to process steel sheet with a high Si content (>3.5%Si, mainly because of its brittleness and the appearance of cracks during rolling and oxidation. However, there is a market for this steel in electrical applications because of the favourable influence of Si on magnetostriction and electrical resistivity. As an alternative process, 3% Si-steel substrates were coated with hypereutectic Al-Si-alloys in a "hot-dip simulator" using different preheating and dipping times. The obtained layers were characterised by SEM and EDS analysis. Diffusion annealing experiments were performed to obtain sufficient amount of Si in the steel. It was observed that:

• intermetallic phases appear in the coating layers as according to the ternary Fe-Si-Al diagram
• with a double dipping primary silicon crystals are formed in the surface layer
• the ordered DO₃ structure is present if the dipping and/or diffusion time is long enough
• homogeneous silicon gradients in the whole substrate thickness have not yet been achieved
• theoretic calculations show that Si-gradient, also have beneficial effects on magnetic behaviour

Estudio para la optimización de la composición de un HACFRA (hormigón autocompactante reforzado con fibras de acero estructural

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Orbe, A.

2015-03-01

Full Text Available The interest of HACFRA (self compacting concrete reinforced with steel fibers, is the combination of the residual strength increase and cracking decrease compared to plain concrete by the introduction of steel fibers in the mass with the advantages of the self-compacting. The paper presents an analysis of the influence of different components of the HACRFA and provides their selection, refered to the granular skeleton and to different steel fiber types and amount, in order to obtain an optimization of its features and structural behavior.El interés de un HACFRA (Hormigón autocompactante reforzado con fibras de acero, radica en la combinación del incremento de capacidad resistente con respecto al hormigón y disminución de la fisuración, aportada por la introducción de fibras de acero, con las ventajas de la puesta en obra que supone la autocompactación. El artículo analiza la influencia de los diferentes componentes que integran el HACRFA, proponiendo una selección de los mismos, referidos tanto al esqueleto granular como a los diferentes tipos y densidades de fibras de acero, en base a la obtención de sus características y de un comportamiento estructural optimizado.

Base Pair Opening in a Deoxynucleotide Duplex Containing a cis-syn Thymine Cyclobutane Dimer Lesion

Science.gov (United States)

Wenke, Belinda B.; Huiting, Leah N.; Frankel, Elisa B.; Lane, Benjamin F.; Núñez, Megan E.

2014-01-01

The cis-syn thymine cyclobutane dimer is a DNA photoproduct implicated in skin cancer. We compared the stability of individual base pairs in thymine dimer-containing duplexes to undamaged parent 10-mer duplexes. UV melting thermodynamic measurements, CD spectroscopy, and 2D NOESY NMR spectroscopy confirm that the thymine dimer lesion is locally and moderately destabilizing within an overall B-form duplex conformation. We measured the rates of exchange of individual imino protons by NMR using magnetization transfer from water and determined the equilibrium constant for the opening of each base pair Kop. In the normal duplex Kop decreases from the frayed ends of the duplex toward the center, such that the central TA pair is the most stable with a Kop of 8×10−7. In contrast, base pair opening at the 5’T of the thymine dimer is facile. The 5’T of the dimer has the largest equilibrium constant (Kop =3×10−4) in its duplex, considerably larger than even the frayed penultimate base pairs. Notably, base pairing by the 3’T of the dimer is much more stable than by the 5’T, indicating that the predominant opening mechanism for the thymine dimer lesion is not likely to be flipping out into solution as a single unit. The dimer asymmetrically affects the stability of the duplex in its vicinity, destabilizing base pairing on its 5’ side more than on the 3’ side. The striking differences in base pair opening between parent and dimer duplexes occur independently of the duplex-single strand melting transitions. PMID:24328089

Effects of trimethylamine N-oxide and urea on DNA duplex and G-quadruplex.

Science.gov (United States)

Ueda, Yu-Mi; Zouzumi, Yu-Ki; Maruyama, Atsushi; Nakano, Shu-Ichi; Sugimoto, Naoki; Miyoshi, Daisuke

2016-01-01

We systematically investigated effects of molecular crowding with trimethylamine N -oxide (TMAO) as a zwitterionic and protective osmolyte and urea as a nonionic denaturing osmolyte on conformation and thermodynamics of the canonical DNA duplex and the non-canonical DNA G-quadruplex. It was found that TMAO and urea stabilized and destabilized, respectively, the G-quadruplex. On the other hand, these osmolytes generally destabilize the duplex; however, it was observed that osmolytes having the trimethylamine group stabilized the duplex at the lower concentrations because of a direct binding to a groove of the duplex. These results are useful not only to predict DNA structures and their thermodynamics under physiological environments in living cells, but also design of polymers and materials to regulate structure and stability of DNA sequences.

Influence of the filler material on the pitting corrosion in welded duplex stainless

International Nuclear Information System (INIS)

Munez, C. J.; Utrilla, M. V.; Urena, A.; Otero, E.

2007-01-01

In this work, it has been studied the pitting corrosion resistance of welding duplex stainless steel 2205. Unions were made by GMAW process with different fillers: duplex ER 2209 and two austenitic (ER 316LSi and ER 308LSi). the microstructure obtained with the duplex ER 2209 filler is similar to the duplex 2205 base material, but the unions produced with the austenitic fillers cause a decrease of the phases relationα/γ. To evaluate the influence of the filler on the weld, the pitting corrosion resistance was determined by electrochemical critical pitting temperature test (TCP) and the mechanical properties by the hardness. The phases imbalance produced for the dissimilar fillers bring out a variation of the pitting corrosion resistance and the mechanical properties. (Author)

Duplex sonography of the near-surface leg veins

International Nuclear Information System (INIS)

Mendoza, E.

2007-01-01

The book contains the following contributions: The ultrasonograph, selection of the ultrasonic transducer, anatomy of the near-surface vein system, physiology of the near-surface vein system, varicose status classification, systematics of the duplex sonography of near-surface leg veins, provocational maneuver for the duplex sonographic varicose diagnostics, exploration of vena saphena parva, perforans veins, side branches, phlebitis, sonography for varicose therapy, postsurgical sonography, deep leg veins, examination of near-surface leg veins for the pathology of the deep vein system, differential diagnostic clarification of leg oedema from the phlebologic-lymphological view, diagnostic side features along the near-surface leg veins

Dwell-Time Distribution, Long Pausing and Arrest of Single-Ribosome Translation through the mRNA Duplex.

Science.gov (United States)

Xie, Ping

2015-10-09

Proteins in the cell are synthesized by a ribosome translating the genetic information encoded on the single-stranded messenger RNA (mRNA). It has been shown that the ribosome can also translate through the duplex region of the mRNA by unwinding the duplex. Here, based on our proposed model of the ribosome translation through the mRNA duplex we study theoretically the distribution of dwell times of the ribosome translation through the mRNA duplex under the effect of a pulling force externally applied to the ends of the mRNA to unzip the duplex. We provide quantitative explanations of the available single molecule experimental data on the distribution of dwell times with both short and long durations, on rescuing of the long paused ribosomes by raising the pulling force to unzip the duplex, on translational arrests induced by the mRNA duplex and Shine-Dalgarno(SD)-like sequence in the mRNA. The functional consequences of the pauses or arrests caused by the mRNA duplex and the SD sequence are discussed and compared with those obtained from other types of pausing, such as those induced by "hungry" codons or interactions of specific sequences in the nascent chain with the ribosomal exit tunnel.

Duplex Healing of Selectively Thiolated Guanosine Mismatches through a Cd2+ Chemical Stimulus.

Science.gov (United States)

Lunn, Samantha M L; Hribesh, Samira; Whitfield, Colette J; Hall, Michael J; Houlton, Andrew; Bronowska, Agnieszka K; Tuite, Eimer M; Pike, Andrew R

2018-03-25

The on-column selective conversion of guanosine to thioguanosine (tG) yields modified oligomers that exhibit destabilisation over the fully complementary duplex. Restoration to a stabilised duplex is induced through thio-directed Cd 2+ coordination; a route for healing DNA damage. Short oligomers are G-specifically thiolated through a modified on-column protocol without the need for costly thioguanosine phosphoramidites. Addition of Cd 2+ ions to a duplex containing a highly disrupted tG central mismatch sequence, 3'-A 6 tG 4 T 6 -5', suggests a (tG) 8 Cd 2 central coordination regime, resulting in increased base stacking and duplex stability. Equilibrium molecular dynamic calculations support the hypothesis of metal-induced healing of the thiolated duplex. The 2 nm displacement of the central tG mismatched region is dramatically reduced after the addition of a chemical stimuli, Cd 2+ ions, returning to a minimized fluctuational state comparable to the unmodified fully complementary oligomer. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Breaking the Transmitter-Receiver Isolation Barrier in Mobile Handsets with Spatial Duplexing

DEFF Research Database (Denmark)

Alrabadi, Osama; Tatomirescu, Alexandru; Knudsen, Mikael

2013-01-01

In full-duplex radio communication systems like eUTRAN, CDMA-2000, the radio transmitter (Tx) is active at the same time as the radio receiver (Rx). The Tx and the Rx will be using separate dedicated frequency bands and the Tx-Rx isolation is ensured by duplex filters. However, agile duplexers...... required for multiband operation are almost non-existent while dedicating a bank of narrowband filters is bulky and incurs considerable switching losses. In this article we propose an approach that dramatically reduces the complexity of the RF frontend, first by replacing the duplex filter with a spatial...... frequency bands as long as the antennas are made tunable. Moreover, the spatial filter may directly benefit from the balanced architecture of the power amplifiers (PAs) thus reducing the total system complexity and insertion loss. Finally, simulation and initial measurement results are provided...

Can Full Duplex reduce the discovery time in D2D Communication?

DEFF Research Database (Denmark)

Gatnau, Marta; Berardinelli, Gilberto; Mahmood, Nurul Huda

2016-01-01

Device-to-device (D2D) communication is considered as one of the key technologies to support new types of services, such as public safety and proximity-based applications. D2D communication requires a discovery phase, i.e., the node awareness procedure prior to the communication phase. Conventional...... half duplex transmission may not be sufficient to provide fast discovery and cope with the strict latency targets of future 5G services. On the other hand, in-band full duplex, by allowing simultaneous transmission and reception, may complete the discovery phase faster. In this paper, the potential...... of full duplex in providing fast discovery for the next 5th generation (5G) system supporting D2D communication is investigated. A design for such system is presented and evaluated via simulations, showing that full duplex can accelerate the discovery phase by supporting a higher transmission probability...

On full duplex Gaussian relay channels with self-interference

KAUST Repository

Behboodi, Arash

2016-08-15

Self interference (SI) in full duplex (FD) systems is the interference caused by the transmission stream on the reception stream. Being one of the main restrictive factors for performance of practical full duplex systems, however, not too much is known about its effect on the fundamental limits of relaying systems. In this work, we consider the full duplex three-node relay channel with SI where SI is modeled as an additive Gaussian noise whose variance is dependent on instantaneous input power. The classical achievable rates and upper bounds for the single three-node relay channel no longer apply due to the structure of SI. Achievable rates for Decode-and-Forward (DF) and Compress-and-Forward (CF) and upper bounds on the capacity are derived assuming Gaussian inputs and SI. The deterministic model is also introduced and its capacity is characterized. The optimal joint source-relay distributions is discussed. Numerical results are provided comparing the achievable rates and upper bound. © 2016 IEEE.

Duplex recombinase polymerase amplification assays incorporating competitive internal controls for bacterial meningitis detection.

Science.gov (United States)

Higgins, Owen; Clancy, Eoin; Forrest, Matthew S; Piepenburg, Olaf; Cormican, Martin; Boo, Teck Wee; O'Sullivan, Nicola; McGuinness, Claire; Cafferty, Deirdre; Cunney, Robert; Smith, Terry J

2018-04-01

Recombinase polymerase amplification (RPA) is an isothermal nucleic acid amplification technology that provides rapid and robust infectious disease pathogen detection, ideal for point-of-care (POC) diagnostics in disease-prevalent low-resource countries. We have developed and evaluated three duplex RPA assays incorporating competitive internal controls for the detection of leading bacterial meningitis pathogens. Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae singleplex RPA assays were initially developed and evaluated, demonstrating 100% specificity with limits of detection of 4.1, 8.5 and 3.9 genome copies per reaction, respectively. Each assay was further developed into internally controlled duplex RPA assays via the incorporation of internal amplification control templates. Clinical performance of each internally controlled duplex RPA assay was evaluated by testing 64 archived PCR-positive clinical samples. Compared to real-time PCR, all duplex RPA assays demonstrated 100% diagnostic specificity, with diagnostic sensitivities of 100%, 86.3% and 100% for the S. pneumoniae, N. meningitidis and H. influenzae assays, respectively. This study details the first report of internally controlled duplex RPA assays for the detection of bacterial meningitis pathogens: S. pneumoniae, N. meningitidis and H. influenzae. We have successfully demonstrated the clinical diagnostic utility of each duplex RPA assay, introducing effective diagnostic technology for POC bacterial meningitis identification in disease-prevalent developing countries. Copyright © 2018 Elsevier Inc. All rights reserved.

Sigma phase morphologies in cast and aged super duplex stainless steel

International Nuclear Information System (INIS)

Martins, Marcelo; Casteletti, Luiz Carlos

2009-01-01

Solution annealed and water quenched duplex and super duplex stainless steels are thermodynamically metastable systems at room temperature. These systems do not migrate spontaneously to a thermodynamically stable condition because an energy barrier separates the metastable and stable states. However, any heat input they receive, for example through isothermal treatment or through prolonged exposure to a voltaic arc in the welding process, cause them to reach a condition of stable equilibrium which, for super duplex stainless steels, means precipitation of intermetallic and carbide phases. These phases include the sigma phase, which is easily identified from its morphology, and its influence on the material's impact strength. The purpose of this work was to ascertain how 2-hour isothermal heat treatments at 920 deg. C and 980 deg. C affect the microstructure of ASTM A890/A890M GR 6A super duplex stainless steel. The sigma phase morphologies were found to be influenced by these two aging temperatures, with the material showing a predominantly lacy microstructure when heat treated at 920 deg. C and block-shaped when heat treated at 980 deg. C.

Tricriticality in the q-neighbor Ising model on a partially duplex clique.

Science.gov (United States)

Chmiel, Anna; Sienkiewicz, Julian; Sznajd-Weron, Katarzyna

2017-12-01

We analyze a modified kinetic Ising model, a so-called q-neighbor Ising model, with Metropolis dynamics [Phys. Rev. E 92, 052105 (2015)PLEEE81539-375510.1103/PhysRevE.92.052105] on a duplex clique and a partially duplex clique. In the q-neighbor Ising model each spin interacts only with q spins randomly chosen from its whole neighborhood. In the case of a duplex clique the change of a spin is allowed only if both levels simultaneously induce this change. Due to the mean-field-like nature of the model we are able to derive the analytic form of transition probabilities and solve the corresponding master equation. The existence of the second level changes dramatically the character of the phase transition. In the case of the monoplex clique, the q-neighbor Ising model exhibits a continuous phase transition for q=3, discontinuous phase transition for q≥4, and for q=1 and q=2 the phase transition is not observed. On the other hand, in the case of the duplex clique continuous phase transitions are observed for all values of q, even for q=1 and q=2. Subsequently we introduce a partially duplex clique, parametrized by r∈[0,1], which allows us to tune the network from monoplex (r=0) to duplex (r=1). Such a generalized topology, in which a fraction r of all nodes appear on both levels, allows us to obtain the critical value of r=r^{*}(q) at which a tricriticality (switch from continuous to discontinuous phase transition) appears.

Magnetic resonance urography in duplex kidney with ectopic ureteral insertion

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Conjeevaram Rajendrarao Thambidorai

2011-01-01

Full Text Available This is a report on the use of magnetic resonance urography (MRU in a 6-year-old girl who presented with urinary incontinence. She had a left duplex kidney with poorly functioning upper moiety and ectopic insertion of the dilated upper pole ureter. MRU has been shown to be superior to conventional imaging techniques in delineating poorly functioning moieties of duplex kidneys and ectopic ureters.

Venous filling time using air-plethysmography correlates highly with great saphenous vein reflux time using duplex.

Science.gov (United States)

Lattimer, C R; Azzam, M; Kalodiki, E; Geroulakos, G

2014-03-01

Venous filling time (VFT90) is the time taken to reach 90% of the venous volume in the calf. It is recorded by air-plethysmography (APG(®)) and is assumed to measure global venous reflux duration. However, this has never been confirmed by duplex. The aim of the study was to compare VFT on APG to venous reflux time/duration (RT) measured simultaneously with duplex on the same patients. Twenty-six consecutive patients, M:F = 16:10, age (25-78), C1 = 1, C2 = 4, C3 = 8, C4a = 6, C4b = 4, C5 = 2, C6 = 1, underwent simultaneous APG with duplex. The venous filling index (VFI, mL/second), VFT90 (seconds), great saphenous vein (GSV) RT on duplex, averaged thigh GSV diameter and thigh length (length) between the APG sensor air-cuff and duplex transducer were recorded. The VFT100 was calculated by VFT90/0.9. The additional time taken to fill the thigh was achieved using the VFI, length and deep vein diameter (d), to determine the corrected reflux duration: CRD = VFT100 + (length × πd(2)/4 (1/VFI)). Twenty-five patients are presented. One patient with very mild reflux (VFT90 = 55.9 seconds) had an indeterminate endpoint on duplex and was excluded. The median (range) VFI and GSV diameter was 4.9(1.3-15.5) mL/second and 7(4-17) mm, respectively. The VFT90 and VFT100 both correlated with RT on duplex (Spearman, P duplex RT at 24 (16.9) versus 28 (20) seconds respectively, P duplex by performing simultaneous measurements. There was an excellent correlation between the VFT90 versus duplex RT, thereby comparing reverse flow in a single superficial vein against the legs overall venous haemodynamic status. These tests can both be used in the quantification of reflux.

Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

Science.gov (United States)

Rahmani, Mehdi; Eghlimi, Abbas; Shamanian, Morteza

2014-10-01

To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.

La fatiga en las barras de acero corrugado para refuerzo de hormigón

OpenAIRE

Avila Kildal, Francisco

2003-01-01

Para conseguir aprovechar los recursos que la sociedad invierte en infraestructuras de manera óptima es imprescindible, para la ingeniería civil, un buen conocimiento de los materiales y de sus propiedades. Partiendo de esta premisa, el objetivo de esta tesina es aportar conocimiento a la caracterización de las barras de acero corrugado para refuerzo de hormigón en su funcionamiento frente a la fatiga. Definimos fatiga como la alteración mecánica de los materiales bajo el ef...

Color-coded duplex sonography in the study of thyroid pathologic conditions

International Nuclear Information System (INIS)

Anguissola, R.; Bozzini, A.; Campani, R.; Bottinelli, O.; Genovese, E.; Guglielmoni, B.; Fulle, I.; Bandi, G.

1991-01-01

The authors examined 110 patients with suspected pathologic conditions of the thyroid by means of color-coded duplex US. In addition to the information yielded by conventional US, this technique allows organ vascularization to be demonstrated. Five normal patients were considered as a control group: no tissue vascularization was demonstrated in these cases. In 8 patients presenting with carcinoma or recurrences, vascularization was markedly increased both peripheral and central to the nodule. A few doubts are still to be solved as to the diagnostic value of color-coded duplex US in the evaluation of non-carcinomas nodular pathologic conditions. As a matter of fact, non-functioning avascular adenomas can be demonstrated only in a very low percentage of cases (66%). Color-coded duplex US proved extremely sensitive and specific in depicting malignant neoplasms. Moreover, the use of fine.needle biopsy could be optimized and subsequently reduced. Color-coded duplex US proved to be markedly superior to othe rmethods and techniques in the study of thyroid diseases, especially thyroiditis and multiple pathologic conditions. The simultaneous presence of hypocapture at scintigraphy and peripheral and central vascularization in a single nodule or within multinodular struma at color-Doppler was highly suggestive of malignant thyroid neoplasm. Color-coded duplex US is a low-cost technique, which can be performed on an outpatient basis. Moreover, it is not invasive, nor does it damage the thyroid. That is why its use is almost mandatory in the study of pathologic conditions of the thyroid

Influencia del Calor Aportado y Metal de Aporte Sobre las Propiedades Mecánicas y la Microestructura de Juntas Soldadas por FCAW de Acero Microaleado de Alta Resistencia

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César Marconi

2015-06-01

Full Text Available ResumenActualmente, los aceros microaleados son ampliamente utilizados en reemplazo de los aceros al C y C-Mn por sus ventajas en cuanto a propiedades mecánicas, resistencia a la corrosión y soldabilidad, permitiendo una reducción de peso de los vehículos y estructuras sin detrimento de su resistencia. Cuando estos aceros son soldados, el ciclo térmico de la soldadura provoca cambios microestructurales que modifican sus propiedades originales. El calor aportado (HI: heat input es una de las principales variables a tener en cuenta cuando se evalúan estas modificaciones. Las propiedades finales de la unión soldada también se definen por el tipo de consumible utilizado. El objetivo de este trabajo es analizar las propiedades mecánicas y la microestructura de juntas soldadas a tope de un acero microaleado con dos grados de metal de aporte y diferentes HI. Como resultado del trabajo se observó un aumento considerable de tamaño de grano en la ZAC adyacente a la línea de fusión para todas las condiciones, siendo este efecto más marcado cuando se soldó con alto HI; y un ablandamiento en la ZAC de grano fino. Prácticamente se mantuvieron los valores de resistencia a la tracción al soldar con ambos consumibles, con un mejor desempeño cuando se soldó con bajo HI. La tenacidad en la ZAC mejoró con la disminución del HI.

Development of a panel of seven duplex real-time PCR assays for detecting 13 streptococcal superantigens.

Science.gov (United States)

Yang, Peng; Peng, Xiaomin; Cui, Shujuan; Shao, Junbin; Zhu, Xuping; Zhang, Daitao; Liang, Huijie; Wang, Quanyi

2013-07-30

Streptococcal superantigens (SAgs) are the major virulence factors of infection in humans for group A Streptococcus (GAS) bacteria. A panel consisting of seven duplex real-time PCR assays was developed to simultaneously detect 13 streptococcal SAgs and one internal control which may be important in the control of GAS-mediated diseases. Primer and probe sequences were selected based on the highly conserved region from an alignment of nucleotide sequences of the 13 streptococcal SAgs. The reaction conditions of the duplex real-time PCR were optimized and the specificity of the duplex assays was evaluated using SAg positive strains. The limit of detection of the duplex assays was determined by using 10-fold serial dilutions of the DNA of 13 streptococcal SAgs and compared to a conventional polymerase chain reaction (PCR) method for evaluating the duplex assays sensitivity. Using the duplex assays, we were able to differentiate between 13 SAgs from Streptococcus strains and other non-Streptococcus bacteria without cross-reaction. On the other hand, the limit of detection of the duplex assays was at least one or two log dilutions lower than that of the conventional PCR. The panel was highly specific (100%) and the limit of detection of these duplex groups was at least ten times lower than that obtained by using a conventional PCR method.

Comportamiento frente al desgaste y fricción de aceros empleados en líneas de manutención aérea ensayados con y sin lubricación

Directory of Open Access Journals (Sweden)

Castro Regal, G.

2005-06-01

Full Text Available The sliding friction and wear behaviour of different steel qualities were investigated with and without lubrication conditions. Steel qualities tested are normally used in the overhead conveyor system of many industrial fields, like the automotive sector. Sliding wear tests have been conducted by means of a pin-on-disk machine. A 100Cr6 steel similar to that used within the overhead conveyor trolleys has been employed as a pin. Friction coefficient values obtained under lubrication conditions were three times smaller than those obtained without lubrication. The mechanism that controls wear behaviour under lubrication conditions is an abrasive one and the wear values obtained are almost worthless. On the other hand, mechanism controlling wear during non lubrication tests, was a combination of abrasion and adhesion

Se ha evaluado el comportamiento frente a fricción y el desgaste de distintas calidades de acero ensayadas bajo condiciones de lubricación y sin lubricación. Las calidades de acero seleccionadas son las que normalmente se emplean en los sistemas de manutención aérea de numerosos procesos de producción, como la fabricación de automóviles. Se han realizado ensayos de desgaste tipo punzón-disco mediante un punzón de acero de calidad100Cr6, empleado en los carros que circulan por las líneas de manutención aérea. Se ha observado que el valor del coeficiente de fricción obtenido bajo condiciones de lubricaciones, aproximadamente, tres veces menor que el obtenido sin lubricación. Por otro lado, el mecanismo que controla el proceso de desgaste de los aceros ensayados con lubricación es un mecanismo de desgaste abrasivo y los valores de desgaste obtenidos son prácticamente despreciables. El desgaste de los aceros ensayados sin lubricación se produjo por combinación de dos mecanismos de desgaste: abrasión y adhesión.

Producción electroquímica de gluconato de calcio

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Mario Grajales T.

2010-07-01

Full Text Available Se estudió experimentalmente el efecto del potencial anódico, densidad de corriente y concentración del ion bromuro en la producción electroquímica de gluconato de calcio a partir de glucosa, usando el sistema Br2 / Br' como mediador. Las condiciones de operación de la celda electroquímica con ánodo de grafito y cátodo de acero inoxidable fueron: Potencial anódico 1.3 V (vs ESC, 46 °C, densidad de corriente 26 mA / cmS y un medio acuoso compuesto por una solución de Glucosa 0.60 M -I- NaBr 0.20 M conteniendo CaCO, en suspensión (0. 30 mol / L. La eficiencia de corriente fue del 98% y la.pureza del gluconato obtenido del 99.7 %.

Numerical simulation of hydrogen-assisted crack initiation in austenitic-ferritic duplex steels

International Nuclear Information System (INIS)

Mente, Tobias

2015-01-01

Duplex stainless steels have been used for a long time in the offshore industry, since they have higher strength than conventional austenitic stainless steels and they exhibit a better ductility as well as an improved corrosion resistance in harsh environments compared to ferritic stainless steels. However, despite these good properties the literature shows some failure cases of duplex stainless steels in which hydrogen plays a crucial role for the cause of the damage. Numerical simulations can give a significant contribution in clarifying the damage mechanisms. Because they help to interpret experimental results as well as help to transfer results from laboratory tests to component tests and vice versa. So far, most numerical simulations of hydrogen-assisted material damage in duplex stainless steels were performed at the macroscopic scale. However, duplex stainless steels consist of approximately equal portions of austenite and δ-ferrite. Both phases have different mechanical properties as well as hydrogen transport properties. Thus, the sensitivity for hydrogen-assisted damage is different in both phases, too. Therefore, the objective of this research was to develop a numerical model of a duplex stainless steel microstructure enabling simulation of hydrogen transport, mechanical stresses and strains as well as crack initiation and propagation in both phases. Additionally, modern X-ray diffraction experiments were used in order to evaluate the influence of hydrogen on the phase specific mechanical properties. For the numerical simulation of the hydrogen transport it was shown, that hydrogen diffusion strongly depends on the alignment of austenite and δ-ferrite in the duplex stainless steel microstructure. Also, it was proven that the hydrogen transport is mainly realized by the ferritic phase and hydrogen is trapped in the austenitic phase. The numerical analysis of phase specific mechanical stresses and strains revealed that if the duplex stainless steel is

EFFECT OF INTERMETALLIC PHASES ON CORROSION BEHAVIOR AND MECHANICAL PROPERTIES OF DUPLEX STAINLESS STEEL AND SUPER-DUPLEX STAINLESS STEEL

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Prabhu Paulraj

2015-08-01

Full Text Available Duplex Stainless Steels (DSS and Super Duplex Stainless Steel (SDSS have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic phases and their effects on corrosion and mechanical properties. First the effect of various alloying elements on DSS and SDSS has been discussed followed by formation of various intermetallic phases. The intermetallic phases affect impact toughness and corrosion resistance significantly. Their deleterious effect on weldments has also been reviewed.

Mechanical properties of welded joints of duplex steels

International Nuclear Information System (INIS)

Kawiak, M.; Nowacki, J.

2003-01-01

The paper presents the study results of mechanical properties of duplex steels UNS S31803 welded joints as well as duplex and NV A36 steels welded joints. They have ben welded by FCAW method in CO 2 using FCW 2205-H flux-cored wire. The joints have been subjected: tensile tests, impact tests, bending tests, hardness tests and metallographic investigations. The influence of welding parameters and mechanical properties of the joints was appreciated. The welding method assured high tensile strength of the joints (approximately 770 MPa) and high impact strength of the welds (approximately 770 J). All samples were broken outside of welds. (author)

Preoperative Duplex Scanning is a Helpful Diagnostic Tool in Neurogenic Thoracic Outlet Syndrome.

Science.gov (United States)

Orlando, Megan S; Likes, Kendall C; Mirza, Serene; Cao, Yue; Cohen, Anne; Lum, Ying Wei; Freischlag, Julie A

2016-01-01

To evaluate the diagnostic role of venous and arterial duplex scanning in neurogenic thoracic outlet syndrome (NTOS). Retrospective review of patients who underwent duplex ultrasonography prior to first rib resection and scalenectomy (FRRS) for NTOS from 2005 to 2013. Abnormal scans included ipsilateral compression (IC) with abduction of the symptomatic extremity (>50% change in subclavian vessel flow), contralateral (asymptomatic side) compression (CC) or bilateral compression (BC). A total of 143 patients (76% female, average age 34, range 13-59) underwent bilateral preoperative duplex scanning. Ipsilateral compression was seen in 44 (31%), CC in 12 (8%), and BC in 14 (10%). Seventy-three (51%) patients demonstrated no compression. Patients with IC more often experienced intraoperative pneumothoraces (49% vs. 25%, P duplex ultrasonography can assist in NTOS diagnosis. Ipsilateral compression on abduction often correlates with Adson testing. © The Author(s) 2016.

Efecto de las sales fundidas en la termofluencia del acero inoxidable tipo 304

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González-Rodríguez, G.

1995-06-01

Full Text Available Problems caused by both hot corrosion and creep type-damage occurring on superheater and reheater tubes of power plants using heavy oil as fuel shorten their design lives. The acceleration of hot corrosion attack of boilers is caused by the presence of fuel ash deposits containing mainly vanadium, sodium and sulphur, in the form of Na₂SO₄ y V₂O₅ and V₂O₅ which form low melting point compounds. In addition to this, the tubes are exposed to the action of both high stresses and high temperatures, producing the so called creep damage. In this work, creep rupture tests were carried out in the temperature range of 620 to 660 °C in static air and in corrosive environments. The corrosive environments included 100 % Na₂SO₄, 100 % V₂O₅ and a 80 % V₂O₅ + 20 % Na₂SO₄ mixture.

Los problemas causados tanto por la corrosión por sales fundidas, así como por la termofluencia en los tubos de los sobrecalentadores y recalentadores de una planta de potencia que usa combustibles fósiles, reducen su vida prevista en diseño. La aceleración de la corrosión por sales fundidas es causada por la presencia de cenizas que contienen principalmente vanadio, sodio y azufre en la forma de Na₂SO₄ y V₂O₅, los cuales forman mezclas con eutécticos de bajo punto de fusión. Adicionalmente, los tubos están expuestos a la acción de altos esfuerzos y altas temperaturas, lo cual propicia la termofluencia del material. En este trabajo, se han realizado ensayos de termofluencia hasta la rotura en aire y en ambientes corrosivos en el rango de temperaturas de 620 a 660 °C. Los ambientes corrosivos fueron 100 % Na₂SO₄, 100 % V₂O₅, y una mezcla 20 % Na₂SO₄-80 % V₂O₅.

Microestructura y propiedades mecánicas de dos aceros para herramientas con ultra alto contenido de boro

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Jiménez, J. A.

1998-05-01

Full Text Available In the present work, two selected tool steels have been modified by a boron addition of 0.5 and 1 mass %. Both steels were processed by powder metallurgy methods, including argon atomization and hot isostatic pressing. The Consolidated materials presented a microstructure consisting of a fine and homogeneous distribution borocarbides M₂₃(C,B₆ in a ferrite-martensite matrix. No changes are observed in the microstructure after deformation by compression-strain-rate-change tests at temperatures ranging from 700 to 1,100 °C. For the Fe-lB-lC steel, a stress exponent of 4.5 was obtained, that suggests that slip creep is the controlling deformation mechanism. On the other hand, a stress exponent between 2 and 3 was obtained for the Fe-0.5B-1.5C steel that suggests that grain boundary sliding is the controlling deformation mechanism. In both cases, the activation energy for creep was related to the activation energy for iron self-diffusion.

En el presente trabajo se han modificado dos aceros para herramientas convencionales por la presencia de un contenido de boro entre 0,5 y 1 % en masa. Ambos aceros se procesaron por la ruta pulvimetalúrgica, incluyendo atomización por argón y compactación isostática en caliente. El material compactado presentó una microestructura caracterizada por una distribución de partículas de borocarburos M₂₃(C,B₆ fina y homogénea en una matriz de ferrita-martensita. Esta microestructura permanece prácticamente inalterada tras los ensayos de cambios en la velocidad de deformación durante el ensayo de compresión a temperaturas entre 750 y 1.000 °C. En el caso del acero Fe-lB-lC se obtuvo un valor para el exponente de la tensión de 4,5, que sugiere que la deformación plástica está controlada por un mecanismo de fluencia por movimiento de dislocaciones. Por otro lado, para el acero Fe-0,5B-1,5C, se obtuvieron valores para el exponente de la tensión comprendidos

Triple helical DNA in a duplex context and base pair opening

Science.gov (United States)

Esguerra, Mauricio; Nilsson, Lennart; Villa, Alessandra

2014-01-01

It is fundamental to explore in atomic detail the behavior of DNA triple helices as a means to understand the role they might play in vivo and to better engineer their use in genetic technologies, such as antigene therapy. To this aim we have performed atomistic simulations of a purine-rich antiparallel triple helix stretch of 10 base triplets flanked by canonical Watson–Crick double helices. At the same time we have explored the thermodynamic behavior of a flipping Watson–Crick base pair in the context of the triple and double helix. The third strand can be accommodated in a B-like duplex conformation. Upon binding, the double helix changes shape, and becomes more rigid. The triple-helical region increases its major groove width mainly by oversliding in the negative direction. The resulting conformations are somewhere between the A and B conformations with base pairs remaining almost perpendicular to the helical axis. The neighboring duplex regions maintain a B DNA conformation. Base pair opening in the duplex regions is more probable than in the triplex and binding of the Hoogsteen strand does not influence base pair breathing in the neighboring duplex region. PMID:25228466

Interference alignment for degrees of freedom improvement in 3-relay half-duplex systems

KAUST Repository

Park, Seongho; Ko, Youngchai; Park, Kihong; Alouini, Mohamed-Slim

2011-01-01

In a half-duplex relaying, the capacity pre-log factor is a major drawback in spectral efficiency. This paper proposes a linear precoding scheme and an alternate relaying protocol in a dual-hop half-duplex system where three relays help

Value of Duplex scanning in the selection of patients for percutaneous transluminal angioplasty

NARCIS (Netherlands)

van der Heijden, F. H.; Legemate, D. A.; van Leeuwen, M. S.; Mali, W. P.; Eikelboom, B. C.

1993-01-01

Duplex scanning is becoming increasingly important in the diagnosis and follow-up of arterial lesions, though most surgeons and radiologists currently still prefer diagnostic angiography prior to percutaneous transluminal angioplasty (PTA). We performed PTA based on Duplex scanning alone in 31

Oxide thickness measurement technique for duplex-layer Zircaloy-4 cladding

International Nuclear Information System (INIS)

McClelland, R.G.; O'Leary, P.M.

1992-01-01

Siemens Nuclear Power Corporation (SNP) is investigating the use of duplex-layer Zircaloy-4 tubing to improve the waterside corrosion resistance of cladding for high-burnup pressurized water reactor (PWR) fuel designs. Standard SNP PWR cladding is typically 0.762-mm (0.030-in.)-thick Zircaloy-4. The SNP duplex cladding is nominally 0.660-mm (0.026-in.)-thick Zircalloy-4 with an ∼0.102-mm (0.004-in.) outer layer of another, more corrosion-resistant, zirconium-based alloy. It is common industry practice to monitor the in-reactor corrosion behavior of Zircaloy cladding by using an eddy-current 'lift-off' technique to measure the oxide thickness on the outer surface of the fuel cladding. The test program evaluated three different cladding samples, all with the same outer diameter and wall thickness: Zircaloy-4 and duplex clad types D2 and D4

Renal duplex Doppler ultrasound findings in diabetics

International Nuclear Information System (INIS)

Shim, Hyang Yee; Kim, Young Geun; Kook, Cheol Keu; Yoon, Chong Hyun; Lee, Shin Hyung; Lee, Chang Joon

1993-01-01

The correlation between clinical-laboratory findings and renal duplex Doppler ultrasound findings was studied in 45 patients with diabetes mellitus to see the role of duplex Doppler ultrasound in the detection of diabetic nephropathy. The resistive indices in patients with elevated serum creatinine, BUN, proteinuria, and systolic blood pressure levels were statistically significantly higher than those in patients with normal levels (p<0.05). Also resistive indics in patients with retinopathy were higher than that in patients without retinopathy (p<0.05). But the ultrasound morphologic changes of kidney such as renal length, cortical eye-catching, and corticomedullarycontrast were not well correlated with clinical-laboratory data and resistive index. The resistive index of the kidney in conjunction with clinical-laboratory data in diabetics may be helpful in the evaluation of diabetic nephropathy

Renal duplex Doppler ultrasound findings in diabetics

Energy Technology Data Exchange (ETDEWEB)

Shim, Hyang Yee; Kim, Young Geun; Kook, Cheol Keu; Yoon, Chong Hyun; Lee, Shin Hyung; Lee, Chang Joon [National Medical Center, Seoul (Korea, Republic of)

1993-12-15

The correlation between clinical-laboratory findings and renal duplex Doppler ultrasound findings was studied in 45 patients with diabetes mellitus to see the role of duplex Doppler ultrasound in the detection of diabetic nephropathy. The resistive indices in patients with elevated serum creatinine, BUN, proteinuria, and systolic blood pressure levels were statistically significantly higher than those in patients with normal levels (p<0.05). Also resistive indics in patients with retinopathy were higher than that in patients without retinopathy (p<0.05). But the ultrasound morphologic changes of kidney such as renal length, cortical eye-catching, and corticomedullarycontrast were not well correlated with clinical-laboratory data and resistive index. The resistive index of the kidney in conjunction with clinical-laboratory data in diabetics may be helpful in the evaluation of diabetic nephropathy

Simulación de la precipitación de inclusiones en diferentes etapas del procesamiento del acero líquido

Directory of Open Access Journals (Sweden)

Carreño, V.

1998-05-01

Full Text Available Steelmaking processes are continuously improved in order to attend the increasing requirements of the cleanness of the liquid metal. At the refining stages, as deoxidation and desulphuration, the formation of inclusions of oxides and sulphides is promoted, which on the other hand, are the most frequent inclusions. In this work a mathematical simulator of the precipitation and chemical composition of non-metallic inclusions at different steps of the steelmaking process is presented. To this purpose, it is assumed that inclusions formed by reoxidation can be simulated by increasing arbitrarily the oxygen levels consumed by the residual elements (aluminium, calcium, etc. and starting the chemical reaction with less powerful deoxidants (silicium and manganese. Accordingly, different operative conditions can be simulated. Numerical predictions are compared with experimental results of industrial trials, as well as results included in the bibliography.

Los procesos de fabricación de acero se mejoran constantemente en respuesta a las demandas del consumidor que exige un mayor control de limpieza del metal líquido en las diversas etapas de su elaboración. En las etapas de refinación, como son desoxidación y desulfuración, se promueve la formación de inclusiones de óxidos y sulfuros, que por otra parte son las más frecuentes en el acero líquido. En este trabajo se presenta un simulador matemático que predice la precipitación y composición de las inclusiones no metálicas que se encuentran en el acero líquido en diferentes etapas de su procesamiento, asumiendo que las inclusiones formadas por reoxidación también se pueden simular al incrementar arbitrariamente los niveles de oxígeno que deberán consumir los elementos residuales altamente oxidables (Al, Ca, y empezar la reacción con los desoxidantes menores (Si y Mn. De esta manera se simulan diferentes condiciones de operación. Las predicciones numéricas se comparan con los

Circularly polarized luminescence of helically assembled pyrene π-stacks on RNA and DNA duplexes.

Science.gov (United States)

Nakamura, Mitsunobu; Ota, Fuyuki; Takada, Tadao; Akagi, Kazuo; Yamana, Kazushige

2018-05-01

In this report, we describe the circularly polarized luminescence (CPL) of the RNA duplexes having one to four 2'-O-pyrene modified uridines (Upy) and the DNA duplexes having two, four, and six pyrene modified non-nucleosidic linkers (Py). Both the pyrene π-stack arrays formed on the RNA and DNA double helical structures exhibited pyrene excimer fluorescence. In the pyrene-modified RNA systems, the RNA duplex having four Upys gives CPL emission with g lum value of <0.01 at 480 nm. The structure of pyrene stacks on the RNA duplex may be rigidly regulated with increase in the Upy domains, which resulted in the CPL emission. In the DNA systems, the pyrene-modified duplexes containing two and four Pys exhibited CPL emission with g lum values of <0.001 at 505 nm. The pyrene π-stack arrays presented here show CPL emission. However, the g lum values are relatively small when compared with our previous system consisting of the pyrene-zipper arrays on RNA. © 2018 Wiley Periodicals, Inc.

Cy3 and Cy5 dyes attached to oligonucleotide terminus stabilize DNA duplexes: predictive thermodynamic model.

Science.gov (United States)

Moreira, Bernardo G; You, Yong; Owczarzy, Richard

2015-03-01

Cyanine dyes are important chemical modifications of oligonucleotides exhibiting intensive and stable fluorescence at visible light wavelengths. When Cy3 or Cy5 dye is attached to 5' end of a DNA duplex, the dye stacks on the terminal base pair and stabilizes the duplex. Using optical melting experiments, we have determined thermodynamic parameters that can predict the effects of the dyes on duplex stability quantitatively (ΔG°, Tm). Both Cy dyes enhance duplex formation by 1.2 kcal/mol on average, however, this Gibbs energy contribution is sequence-dependent. If the Cy5 is attached to a pyrimidine nucleotide of pyrimidine-purine base pair, the stabilization is larger compared to the attachment to a purine nucleotide. This is likely due to increased stacking interactions of the dye to the purine of the complementary strand. Dangling (unpaired) nucleotides at duplex terminus are also known to enhance duplex stability. Stabilization originated from the Cy dyes is significantly larger than the stabilization due to the presence of dangling nucleotides. If both the dangling base and Cy3 are present, their thermodynamic contributions are approximately additive. New thermodynamic parameters improve predictions of duplex folding, which will help design oligonucleotide sequences for biophysical, biological, engineering, and nanotechnology applications. Copyright © 2015. Published by Elsevier B.V.

Assessing the effect of different operation techniques on postoperative duplex ultrasound quality after carotid endarterectomy.

Science.gov (United States)

Grambow, E; Heller, T; Wieneke, P; Weiß, C; Klar, E; Weinrich, M

2018-01-01

Duplex ultrasound is the first choice in diagnostics and surveillance of stenoses of the internal carotid arteries before and even after surgery. Therefore, the quality of duplex ultrasound is crucial to investigate these vascular pathologies. Aim of this study was the evaluation whether different surgical techniques affect the postoperative quality of duplex ultrasound. In a time period from January to May 2015 duplex ultrasound of the cervical vessels was performed in 75 patients after unilateral endarterectomy of the internal carotid artery at our department between 2006 and 2012. Thereby, the non-operated contralateral side served as a control. Study groups were defined by the surgical techniques of eversion- or thrombendarterectomy with patch plasty using different patch materials and/or a haemostatic sealant. Duplex ultrasound analysis included acoustic impedance, extinction of ultrasound, thickness of skin and individual anatomic aspects of the patients. Carotid endarterectomy itself reduced intravascular grey levels, skin thickness and increased extinction of duplex ultrasound when compared to the non-operated side of the neck. In contrast, neither the kind of chosen operative technique nor the use of different patch materials or the application of a haemostatic sealant showed an effect in this regards. Whereas carotid endarterectomy per se worsens the quality of postoperative duplex ultrasound, the different analysed surgical techniques as well as used patches and the application of a haemostatic sealant can be assumed to be equal regarding the quality of postoperative ultrasound.

Um novo fio de aço inoxidável para aplicações ortodônticas A new stainless steel wire for orthodontic purposes

Directory of Open Access Journals (Sweden)

André Itman Filho

2011-08-01

Full Text Available OBJETIVO: desenvolver uma metodologia para fabricação de fios ortodônticos de aço inoxidável austeno-ferrítico SEW 410 Nr. 14517 por meio dos processos convencionais de laminação e trefilação. MÉTODOS: o aço austeno-ferrítico foi elaborado em um forno elétrico de indução. A qualidade dos fios foi avaliada por ensaios de tração e medidas de microdureza. A ductilidade e a manuseabilidade foram analisadas por meio da confecção de componentes ortodônticos. RESULTADOS E CONCLUSÕES: os valores encontrados mostraram que os fios de aço inoxidável austeno-ferrítico atenderam às normas BS 3507:1976 e ISO 5832-1, e apresentaram ótima ductilidade para confecção de componentes ortodônticos com dobras complexas.OBJECTIVE: To develop a method to manufacture austenitic-ferritic stainless steel orthodontic wires (SEW 410 Nr. 14517 using conventional rolling and wiredrawing processes. METHODS: Austenitic-ferritic steel was produced in an induction furnace. Traction trials and microhardness measurements were used to evaluate wire quality. Orthodontic parts were fabricated to assess ductility and malleability. RESULTS AND CONCLUSIONS: Austenitic-ferritic stainless steel wires meet the BS 3507:1976 and ISO 5832-1 norms and have excellent ductility for the fabrication of orthodontic parts with complex folds.

Plastomes of the green algae Hydrodictyon reticulatum and Pediastrum duplex (Sphaeropleales, Chlorophyceae

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Hilary A. McManus

2017-05-01

Full Text Available Background Comparative studies of chloroplast genomes (plastomes across the Chlorophyceae are revealing dynamic patterns of size variation, gene content, and genome rearrangements. Phylogenomic analyses are improving resolution of relationships, and uncovering novel lineages as new plastomes continue to be characterized. To gain further insight into the evolution of the chlorophyte plastome and increase the number of representative plastomes for the Sphaeropleales, this study presents two fully sequenced plastomes from the green algal family Hydrodictyaceae (Sphaeropleales, Chlorophyceae, one from Hydrodictyon reticulatum and the other from Pediastrum duplex. Methods Genomic DNA from Hydrodictyon reticulatum and Pediastrum duplex was subjected to Illumina paired-end sequencing and the complete plastomes were assembled for each. Plastome size and gene content were characterized and compared with other plastomes from the Sphaeropleales. Homology searches using BLASTX were used to characterize introns and open reading frames (orfs ≥ 300 bp. A phylogenetic analysis of gene order across the Sphaeropleales was performed. Results The plastome of Hydrodictyon reticulatum is 225,641 bp and Pediastrum duplex is 232,554 bp. The plastome structure and gene order of H. reticulatum and P. duplex are more similar to each other than to other members of the Sphaeropleales. Numerous unique open reading frames are found in both plastomes and the plastome of P. duplex contains putative viral protein genes, not found in other Sphaeropleales plastomes. Gene order analyses support the monophyly of the Hydrodictyaceae and their sister relationship to the Neochloridaceae. Discussion The complete plastomes of Hydrodictyon reticulatum and Pediastrum duplex, representing the largest of the Sphaeropleales sequenced thus far, once again highlight the variability in size, architecture, gene order and content across the Chlorophyceae. Novel intron insertion sites and unique

Validation of a novel duplex ultrasound objective structured assessment of technical skills (DUOSATS) for arterial stenosis detection.

Science.gov (United States)

Jaffer, U; Singh, P; Pandey, V A; Aslam, M; Standfield, N J

2014-01-01

Duplex ultrasound facilitates bedside diagnosis and hence timely patient care. Its uptake has been hampered by training and accreditation issues. We have developed an assessment tool for Duplex arterial stenosis measurement for both simulator and patient based training. A novel assessment tool: duplex ultrasound assessment of technical skills was developed. A modified duplex ultrasound assessment of technical skills was used for simulator training. Novice, intermediate experience and expert users of duplex ultrasound were invited to participate. Participants viewed an instructional video and were allowed ample time to familiarize with the equipment. Participants' attempts were recorded and independently assessed by four experts using the modified duplex ultrasound assessment of technical skills. 'Global' assessment was also done on a four point Likert scale. Content, construct and concurrent validity as well as reliability were evaluated. Content and construct validity as well as reliability were demonstrated. The simulator had good satisfaction rating from participants: median 4; range 3-5. Receiver operator characteristic analysis has established a cut point of 22/ 34 and 25/ 40 were most appropriate for simulator and patient based assessment respectively. We have validated a novel assessment tool for duplex arterial stenosis detection. Further work is underway to establish transference validity of simulator training to improved skill in scanning patients. We have developed and validated duplex ultrasound assessment of technical skills for simulator training.

Four-Tap RF Canceller Evaluation for Indoor In-Band Full-Duplex Wireless Operation

Science.gov (United States)

2016-07-24

I. INTRODUCTION In-band full-duplex (IBFD) wireless operation can help alleviate the frequency spectrum congestion issues faced by current system...Valkama, “Wideband self-adaptive rf cancellation circuit for full- duplex radio: Operating principle and measurements,” in 2015 IEEE 81st Vehicular

Interactions Between Fibroblast Cells and Laser Beam Welded AISI 2205 Duplex Stainless Steel

Directory of Open Access Journals (Sweden)

Ceyhun KÖSE

2018-05-01

Full Text Available Because of their high mechanical strength, excellent corrosion resistance and good weldability, duplex stainless steels are mostly used in industries such as oil, chemistry, petrochemistry, food and occasionally used in medical industry. These properties have enabled us to use duplex stainless steels in biomedical applications recently. Accordingly, duplex stainless steel material can be highly important to examine the toxic effect on the cells. In this study, the effect of the AISI 2205 duplex stainless steels which are joined by CO2 laser beam welding on viability of L929 fibroblast cells has been studied in vitro for the first time. For this aim, the cells were kept in DMEM/F-12 (Thermofisher Scientific 31331-028 medium for 7 days. The viability study was experimentally studied using the MTT (Thiazolyl Blue Tetrazolium Bromide method for 7 days. The cell viability of the laser beam welded sample has been detected to be higher than that of the base metal and the control based on 7th day data. According to the obtained results, it was revealed that laser beam welded and base metal AISI 2205 duplex stainless steel has been found suitable to study for biomedical applications. DOI: http://dx.doi.org/10.5755/j01.ms.24.2.18006

Electroless Ni-P/Ni-B duplex coatings: preparation and evaluation of microhardness, wear and corrosion resistance

International Nuclear Information System (INIS)

Narayanan, T.S.N. Sankara; Krishnaveni, K.; Seshadri, S.K.

2003-01-01

The present work deals with the formation of Ni-P/Ni-B duplex coatings by electroless plating process and evaluation of their hardness, wear resistance and corrosion resistance. The Ni-P/Ni-B duplex coatings were prepared using dual baths (acidic hypophosphite- and alkaline borohydride-reduced electroless nickel baths) with both Ni-P and Ni-B as inner layers and with varying single layer thickness. Scanning electron microscopy (SEM) was used to assess the duplex interface. The microhardness, wear resistance and corrosion resistance of electroless nickel duplex coatings were compared with electroless Ni-P and Ni-B coatings of similar thickness. The study reveals that the Ni-P and Ni-B coatings are amorphous in their as-plated condition and upon heat-treatment at 450 deg. C for 1 h, both Ni-P and Ni-B coatings crystallize and produce nickel, nickel phosphide and nickel borides in the respective coatings. All the three phases are formed when Ni-P/Ni-B and Ni-B/Ni-P duplex coatings are heat-treated at 450 deg. C for 1 h. The duplex coatings are uniform and the compatibility between the layers is good. The microhardness, wear resistance and corrosion resistance of the duplex coating is higher than Ni-P and Ni-B coatings of similar thickness. Among the two types of duplex coatings studied, hardness and wear resistance is higher for coatings having Ni-B coating as the outer layer whereas better corrosion resistance is offered by coatings having Ni-P coating as the outer layer

Effect of ultrafine grain on tensile behaviour and corrosion resistance of the duplex stainless steel.

Science.gov (United States)

Jinlong, Lv; Tongxiang, Liang; Chen, Wang; Limin, Dong

2016-05-01

The ultrafine grained 2205 duplex stainless steel was obtained by cold rolling and annealing. The tensile properties were investigated at room temperature. Comparing with coarse grained stainless steel, ultrafine grained sample showed higher strength and plasticity. In addition, grain size changed deformation orientation. The strain induced α'-martensite was observed in coarse grained 2205 duplex stainless steel with large strain. However, the grain refinement inhibited the transformation of α'-martensite;nevertheless, more deformation twins improved the strength and plasticity of ultrafine grained 2205 duplex stainless steel. In addition, the grain refinement improved corrosion resistance of the 2205 duplex stainless steel in sodium chloride solution. Copyright © 2016 Elsevier B.V. All rights reserved.

Procesos de conversión de acero y efecto de variables en convertidores tipo L.B.E.

Directory of Open Access Journals (Sweden)

Blanco, C.

1995-10-01

Full Text Available In order to determine control equations based on qualitative and quantitative changes of the raw materials, an analysis of the efficiency of the steel production process was carried out in converters under specified operation conditions. Empirical equations to obtain the final composition of the steel as a function of the additives, the initial concentrations of the hot metal and the blowing oxygen patterns are established. The resulting relationships depend on the considered variables and therefore could be used to determine operational strategies in order to obtain steels of a certain quality.

Se analiza la eficacia de los procesos de transformación en convertidores en condiciones de trabajo determinadas, para deducir relaciones aplicables al control basadas en la modificación de cantidades y composiciones de las materias primas. Se plantean ecuaciones empíricas para determinar la composición final del acero como función de los aditivos y de las concentraciones iniciales del arrabio tratado, así como el patrón de soplado de oxígeno. Las relaciones obtenidas establecen las dependencias entre cada una de las variables consideradas y, por tanto, permiten determinar estrategias de operación para obtener aceros con unas calidades finales dadas.

Inclusion of methoxy groups inverts the thermodynamic stabilities of DNA-RNA hybrid duplexes: A molecular dynamics simulation study.

Science.gov (United States)

Suresh, Gorle; Priyakumar, U Deva

2015-09-01

Modified nucleic acids have found profound applications in nucleic acid based technologies such as antisense and antiviral therapies. Previous studies on chemically modified nucleic acids have suggested that modifications incorporated in furanose sugar especially at 2'-position attribute special properties to nucleic acids when compared to other modifications. 2'-O-methyl modification to deoxyribose sugars of DNA-RNA hybrids is one such modification that increases nucleic acid stability and has become an attractive class of compounds for potential antisense applications. It has been reported that modification of DNA strands with 2'-O-methyl group reverses the thermodynamic stability of DNA-RNA hybrid duplexes. Molecular dynamics simulations have been performed on two hybrid duplexes (DR and RD) which differ from each other and 2'-O-methyl modified counterparts to investigate the effect of 2'-O-methyl modification on their duplex stability. The results obtained suggest that the modification drives the conformations of both the hybrid duplexes towards A-RNA like conformation. The modified hybrid duplexes exhibit significantly contrasting dynamics and hydration patterns compared to respective parent duplexes. In line with the experimental results, the relative binding free energies suggest that the introduced modifications stabilize the less stable DR hybrid, but destabilize the more stable RD duplex. Binding free energy calculations suggest that the increased hydrophobicity is primarily responsible for the reversal of thermodynamic stability of hybrid duplexes. Free energy component analysis further provides insights into the stability of modified duplexes. Copyright © 2015 Elsevier Inc. All rights reserved.

Follow-up of renal and mesenteric artery revascularization with duplex ultrasonography

Science.gov (United States)

Taylor, David C.; Houston, Gordon T.M.; Anderson, Caroline; Jameson, Margot; Popatia, Shelley

1996-01-01

Objective To evaluate the long-term anatomic results of renal revascularization procedures using duplex ultrasonography. Design A case series. Setting A university-affiliated hospital. Patients Twenty-five patients who had undergone renal percutaneous transluminal angioplasty (PTA) (18 arteries), renal bypass (10 arteries) and mesenteric bypass (6 arteries). The mean follow-up was 22 months (range from 3 to 48 months) for those who underwent renal PTA, 23 months (range from 1.5 to 70 months) for those who underwent renal bypass and 34 months (range from 8 to 144 months) for those who underwent mesenteric bypass. Main Outcome Measures Patency rates for the three procedures as assessed by duplex ultrasonography. Results Duplex ultrasonography demonstrated patency without stenosis after renal and mesenteric artery revascularization in 14 arteries subjected to renal PTA, 9 arteries subjected to renal bypass and 6 arteries subjected to mesenteric bypass. Three arteries that had renal PTA had recurrent vessel stenosis and one had occlusion. One artery that had renal bypass showed occlusion. Conclusions Renal PTA, renal bypass and mesenteric bypass are durable procedures at 2 years of follow-up, and duplex ultrasonography is a valuable method for assessing the patency of arteries after renal and mesenteric revascularization. PMID:8599785

Characterization of duplex stainless steel weld metals obtained by hybrid plasma-gas metal arc welding

OpenAIRE

Yurtisik,Koray; Tirkes,Suha; Dykhno,Igor; Gur,C. Hakan; Gurbuz,Riza

2013-01-01

Despite its high efficiency, autogenous keyhole welding is not well-accepted for duplex stainless steels because it causes excessive ferrite in as-welded duplex microstructure, which leads to a degradation in toughness and corrosion properties of the material. Combining the deep penetration characteristics of plasma arc welding in keyhole mode and metal deposition capability of gas metal arc welding, hybrid plasma - gas metal arc welding process has considered for providing a proper duplex mi...

Diseño de puesto de trabajo para la fabricación de eslingas de cable de acero

Directory of Open Access Journals (Sweden)

Téllez Chavarro Luz Ángela

2015-04-01

Full Text Available Introducción: Para la realización de eslingas se demanda alto nivel físico y adopción de diferentes posturas en largas jornadas laborales. Los desórdenes músculo esqueléticos relacionados con el trabajo son comunes, potencialmente discapacitantes y evitables. Objetivos: Proponer un diseño de puesto de trabajo que facilite la tarea de armado de eslingas de cable de acero bajo condiciones ergonómicas para el trabajador, luego identificar las características sociodemográficas, determinar las condiciones de salud de los trabajadores, establecer las dimensiones antropométricas de los trabajadores y del puesto de trabajo y evaluar el riesgo ergonómico del puesto actual. Metodología: Estudio cuali-cuantitativo, transversal descriptivo con dos trabajadores que fabricaban eslingas de cable de acero. Criterios de inclusión: desarrollo de su labor diaria únicamente en área, más de 12 meses trabajando con la empresa. La recolección de datos se hizo a través de videos, entrevistas y fotografías. Para la evaluación del riesgo ergonómico se aplicó el método REBA (Rapid Entire Body Assessment y la herramienta antropométrica "Dimensiones de Puesto de Trabajo". Este fue validado por expertos. Posteriormente se realizó la propuesta del diseño de puesto de trabajo en AutoCad®. Resultados: La puntuación total de REBA para el grupo A fue 9, del grupo B fue 9, para una puntuación final de 11. Conclusiones: La manipulación del cable de acero es un factor de riesgo mecánico. Para la implementación del puesto de trabajo se debería realizar: definición del modelo de prueba, documentación del proceso productivo, capacitación a los trabajadores, seguimiento permanente y ajustes al proceso.

Effects of chitosan inhibitor on the electrochemical corrosion behavior of 2205 duplex stainless steel

Science.gov (United States)

Yang, Se-fei; Wen, Ying; Yi, Pan; Xiao, Kui; Dong, Chao-fang

2017-11-01

The effects of chitosan inhibitor on the corrosion behavior of 2205 duplex stainless steel were studied by electrochemical measurements, immersion tests, and stereology microscopy. The influences of immersion time, temperature, and chitosan concentration on the corrosion inhibition performance of chitosan were investigated. The optimum parameters of water-soluble chitosan on the corrosion inhibition performance of 2205 duplex stainless steel were also determined. The water-soluble chitosan showed excellent corrosion inhibition performance on the 2205 duplex stainless steel. Polarization curves demonstrated that chitosan acted as a mixed-type inhibitor. When the stainless steel specimen was immersed in the 0.2 g/L chitosan solution for 4 h, a dense and uniform adsorption film covered the sample surface and the inhibition efficiency (IE) reached its maximum value. Moreover, temperature was found to strongly influence the corrosion inhibition of chitosan; the inhibition efficiency gradually decreased with increasing temperature. The 2205 duplex stainless steel specimen immersed in 0.4 g/L water-soluble chitosan at 30°C displayed the best corrosion inhibition among the investigated specimens. Moreover, chitosan decreased the corrosion rate of the 2205 duplex stainless steel in an FeCl3 solution.

A morphological evaluation of a duplex stainless steel processed by high energy Ball Mill

International Nuclear Information System (INIS)

Yonekubo, Ariane Emi; Cintho, Osvaldo Mitsuyuki; Aguiar, Denilson Jose Marcolino de; Capocchi, Jose Deodoro Trani

2009-01-01

The duplex stainless steels are formed by a ferrite and austenite mixture, giving them a combination of properties. Commercially, these steels are hot rolled, developing an anisotropic, alternated ferrite and austenite elongated lamellae microstructure. In this work, a duplex stainless steel was produced by the mixture of elementary powders with the composition Fe-19.5Cr-5Ni processed in an ATTRITOR ball mill during periods up to 15 hours. The powders obtained were compressed in specimens and were heat treated in the temperatures of 900, 1050 and 1200 °C during 1 hour and analysed by x ray diffraction, optic microscopy, scanning electron microscopy and energy dispersion spectroscopy. An optimized microstructure with ultrafine, equiaxial and regular duplex microstructure was obtained in the 15 hour milling and 1200 °C heat treatment. Afterwards, a commercially super duplex stainless steel UNS S32520 was aged at 800 °C aiming the precipitation of σ phase in order to reduce its toughness and then, milled in SPEX mill. The resulting microstructure was a very fine duplex type with irregular grain boundary morphology duo to the grain growth barrier promoted by the renascent σ phase particles during sintering process. (author)

Selección automatizada de electrodos para la soldadura manual de los aceros al carbono

Directory of Open Access Journals (Sweden)

Alexander Velázquez Font

2008-01-01

Full Text Available Se aborda lo relativo a un sistema para la selección automatizada de electrodos en la soldadura de los aceros al carbono. Se inicia con una breve revisión de los problemas que presentan estos en su soldabilidad y los factores concernientes a la selección correcta del electrodo en los mismos. En el mismo se expone el fundamento teórico sobre el diseño del sistema el cual da solución a lo anteriormente expuesto. En la elaboración del software se tiene en cuenta los siguientes principios: propiedades mecánicas de la unión soldada, tipo de revestimiento, posición de la soldadura, etc. Se tienen en cuenta en el trabajo diferentes firmas y normas de fabricantes de electrodos y países que mas se utilizan en la industria mecánica en Cuba. El software tiene la ventaja de ser sencillo, rápido y seguro, garantizando la selección correcta de los electrodos para cada caso y situación. El software supone que el usuario no tenga que tener conocimientos profundos de soldadura, debido a que el sistema se encarga de la mayor parte de las decisiones para la selección del electrodo, procedimiento que con métodos convencionales, exigen del usuario una determinada experiencia en la selección de estos materiales para la soldadura de los aceros al carbono.

Corrosion behavior of duplex and reference cladding in NPP Grohnde

International Nuclear Information System (INIS)

Besch, O.A.; Yagnik, S.K.; Eucken, C.M.; Bradley, E.R.

1996-01-01

The Nuclear Fuel Industry Research (NFIR) Group undertook a lead test assembly (LTA) program in NPP Grohnde PWR in Germany to assess the corrosion performance of duplex and reference cladding. Two identical 16 by 16 LTAs, each containing 32 peripheral test rods, completed four reactor cycles, reaching a peak rod burnup of 46 MWd/kgU. The results from poolside examinations performed at the end of each cycle, together with power histories and coolant chemistry, are reported. Five different cladding materials were characterized during fabrication. The corrosion performance of the cladding materials was tracked in long-term tests in high-pressure, high-temperature autoclaves. The relative ranking of corrosion behavior in such tests corresponded well with the in-reactor corrosion performance. The extent and distribution of hydriding in duplex and reference specimens during the autoclave testing has been characterized. The in-reactor corrosion data indicate that the low-tin Zircaloy-4 reference cladding, R2, had an improved corrosion resistance compared to high-tin Zircaloy-4 reference cladding, R1. Two types of duplex cladding, D1 (Zr-2.5% Nb) and D2 (Zr-0.4% Fe-0.5% Sn), showed an even further improvement in corrosion resistance compared to R2 cladding. The third duplex cladding, D3 (Zr-4 + 1.0% Nb), had significantly less corrosion resistance, which was inferior to R1. The in-reactor and out-reactor corrosion performances have been ranked

Approximation methods for the stability analysis of complete synchronization on duplex networks

Science.gov (United States)

Han, Wenchen; Yang, Junzhong

2018-01-01

Recently, the synchronization on multi-layer networks has drawn a lot of attention. In this work, we study the stability of the complete synchronization on duplex networks. We investigate effects of coupling function on the complete synchronization on duplex networks. We propose two approximation methods to deal with the stability of the complete synchronization on duplex networks. In the first method, we introduce a modified master stability function and, in the second method, we only take into consideration the contributions of a few most unstable transverse modes to the stability of the complete synchronization. We find that both methods work well for predicting the stability of the complete synchronization for small networks. For large networks, the second method still works pretty well.

Migración de hierro y níquel, y estabilidad oxidativa del aceite refinado de soja calentado en utensilios culinarios de diversos materiales

Directory of Open Access Journals (Sweden)

Almeyda Haj-Isa, Niurka Maritza

2007-12-01

Full Text Available Cookware may release some inorganic components into foods during cooking, some of which have undesirable consequences. In fried foods, for instance, oil oxidation is favored by metals. The present study evaluated oxidative stability (AOCS method and iron and nickel migration (inductively coupled plasma-optical emission spectrometry into refined soybean oil in four cycles, with intervals of 24 hours. The cookware materials were glass, aluminum, stainless steel, iron and soapstone. The results demonstrated that the lowest metal migration occurred from glass and aluminum pans while the oil heated in these pans showed the highest oxidative stability. The highest migration of Fe and Ni into the oil occurred from the soapstone and iron pots (3.94 and 3.21 mg _ kg-1, respectively.Nevertheless, increasing loss of oxidative stability was evident in the oils heated in the soapstone, stainless steel and iron cookware, in this order. Since iron migration was lower from glass and aluminum pans, these were considered the best type of materials for fryingDurante la elaboración de alimentos los utensilios culinarios pueden liberar componentes inorgánicos ocasionalmente no deseables. La oxidación del aceite es durante la fritura es favorecida por la presencia de metales. Fue evaluada la migración de hierro y níquel (espectrometría de emisión óptica y la estabilidad oxidativa (método AOCS del aceite de soja sometido a cuatro calentamientos con intervalos de 24 horas en cazuelas de vidrio, aluminio, acero inoxidable, hierro y piedra-jabón. La mayor migración de hierro al aceite ocurrió en las cazuelas de hierro (3,94 mg•kg–1 y piedra (3,21 mg _ kg–1, sin diferencia estadística entre ellas. La pérdida progresiva de estabilidad oxidativa fue acentuada en los aceites calentados en utensilios de piedra, acero inoxidable e hierro, en tal orden. Vidrio y aluminio fueron considerados los mejores materiales para la fabricación de cazuelas

Prototipo autotérmico móvil para producción de biocarbón con biomasa de esquilmos de aguacate

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Lenin Ejecatl Medina Orozco

2018-04-01

Full Text Available El estado de Michoacán, México, es el principal productor mundial de aguacate, con un impacto social y económico en función de la superficie cultivada. Productos secundarios de esta actividad, son los esquilmos agrícolas derivados de las podas de mantenimiento de los árboles. El biocarbón (biochar de subproductos de aguacate, se vislumbra como una alternativa económica, ambiental y socialmente viable, para producir biocarbón en grandes volúmenes, sin extracción de maderas de bosque y selvas prístinas. El objetivo del presente estudio, fue construir y evaluar el desempeño en condiciones de campo, de un prototipo de biocarbón-pirólisis autotérmico y móvil, con volumen útil de 1.7 m3 de biomasa triturada. El equipo fue construido de acero inoxidable, para darle un periodo de vida útil de 7 años bajo condiciones intensivas de uso, con movilidad dentro de los campos agrícolas y auto térmico para no depender de una fuente de calor externa. El equipo fue de bajo costo comparado con equipos comerciales ($ 700 000.00 pesos MN y con un potencial futuro en la cogeneración de energía. La principal variable en el costo de fabricación es el precio del acero inoxidable en el mercado. El equipo reportó una tasa de conversión de biomasa a biocarbón, en condiciones de campo, de entre 300 y 400 kg por día, con una tasa promedio de recuperación del 16% en biocarbón. Las principales variables en la transformación de la biomasa a biocarbón fueron: humedad, el tamaño de la astilla y condiciones atmosféricas. Se encontró una Capacidad de Intercambio Catiónico (CIC de 46 Cmolc kg-1 y pH 10.25. El equipo transformó satisfactoriamente la biomasa de aguacate y el biocarbón presentó características adecuadas para su uso en suelos volcánicos.

Standard test methods for characterizing duplex grain sizes

CERN Document Server

American Society for Testing and Materials. Philadelphia

2002-01-01

1.1 These test methods provide simple guidelines for deciding whether a duplex grain size exists. The test methods separate duplex grain sizes into one of two distinct classes, then into specific types within those classes, and provide systems for grain size characterization of each type. 1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to consult appropriate safety and health practices and determine the applicability of regulatory limitations prior to its use.

Comportamiento a fatiga del acero sae 4140 usando alta rugosidad superficial y ambiente corrosivo

OpenAIRE

CEBALLOS, WILSON FERNANDO; GÓMEZ, ADOLFO LEÓN; CORONADO, JOHN JAIRO

2010-01-01

En este artículo se presenta el estudio del comportamiento a fatiga del acero SAE 4140 en condiciones diferentes: superficie pulida (acabado espejo), ambiente corrosivo (jugo de caña de azúcar), alta rugosidad superficial (superficie equivalente a la encontrada típicamente en los ejes de molino de caña) y una condición que involucra la combinación de las dos últimas. Las anteriores condiciones están presentes en los ejes de maza de molino de caña de azúcar durante el proceso de molienda. Se r...

COMPORTAMIENTO A FATIGA DEL ACERO SAE 4140 USANDO ALTA RUGOSIDAD SUPERFICIAL Y AMBIENTE CORROSIVO

OpenAIRE

CEBALLOS, WILSON FERNANDO; GÓMEZ, ADOLFO LEÓN; CORONADO, JOHN JAIRO

2010-01-01

En este artículo se presenta el estudio del comportamiento a fatiga del acero SAE 4140 en condiciones diferentes: superficie pulida (acabado espejo), ambiente corrosivo (jugo de caña de azúcar), alta rugosidad superficial (superficie equivalente a la encontrada típicamente en los ejes de molino de caña) y una condición que involucra la combinación de las dos últimas. Las anteriores condiciones están presentes en los ejes de maza de molino de caña de azúcar durante el proceso de molienda. Se r...

Problems in repair-welding of duplex-treated tool steels

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T. Muhič

2009-01-01

Full Text Available The present paper addresses problems in laser welding of die-cast tools used for aluminum pressure die-castings and plastic moulds. To extend life cycle of tools various surface improvements are used. These surface improvements significantly reduce weldability of the material. This paper presents development of defects in repair welding of duplex-treated tool steel. The procedure is aimed at reduction of defects by the newly developed repair laser welding techniques. Effects of different repair welding process parameters and techniques are considered. A microstructural analysis is conducted to detect defect formation and reveal the best laser welding method for duplex-treated tools.

NMR studies of abasic sites in DNA duplexes: Deoxyadenosine stacks into the helix opposite acyclic lesions

International Nuclear Information System (INIS)

Kalnik, M.W.; Chang, Chienneng; Johnson, F.; Grollman, A.P.; Patel, D.J.

1989-01-01

Proton and phosphorus NMR studies are reported for two complementary nonanucleotide duplexes containing acyclic abasic sites. The first duplex, d(C-A-T-G-A-G-T-A-C)·d(G-T-A-C-P-C-A-T-G), contains an acyclic propanyl moiety, P, located opposite a deoxyadenosine at the center of the helix (designated AP P 9-mer duplex). The second duplex, d(C-A-T-G-A-G-T-A-C-)·d(G-T-A-C-E-C-A-T-G), contains a similarly located acyclic ethanyl moiety, E (designated AP E 9-mer duplex). The ethanyl moiety is one carbon shorter than the natural carbon-phosphodiester backbone of a single nucleotide unit of DNA. The majority of the exchangeable and nonexchangeable base and sugar protons in both the AP P 9-mer and AP E 9-mer duplexes, including those at the abasic site, have been assigned by recording and analyzing two-dimensional phase-sensitive NOESY data sets in H 2 O and D 2 O solution between -5 and 5 degree C. These spectroscopic observations establish that A5 inserts into the helix opposite the abasic site (P14 and El14) and stacks between the flanking G4·C15 and G6·C13 Watson-Crick base pairs in both the AP P 9-mer and AP E 9-mer duplexes. Proton NMR parameters for the Ap P 9-mer and AP E 9-mer duplexes are similar to those reported previously. These proton NMR experiments demonstrate that the structures at abasic sites are very similar whether the five-membered ring is open or closed or whether the phosphodiester backbone is shortened by one carbon atom. Phosphorus spectra of the AP P 9-mer and AP E 9-mer duplexes (5 degree C) indicate that the backbone conformation is similarly perturbed at three phosphodiester backbone torsion angles

Surgical retroperitoneoscopic and transperitoneoscopic access in varicocelectomy: duplex scan results in pediatric population.

Science.gov (United States)

Mancini, Stefano; Bulotta, Anna Lavinia; Molinaro, Francesco; Ferrara, Francesco; Tommasino, Giulio; Messina, Mario

2014-12-01

This is a retrospective study to compare duplex scan results of laparoscopic Palomo's technique through retroperitoneal and transperitoneal approach for varicocelectomy in children. We statistically analyzed recurrence, testicular volume growth and complications. Surgical intervention was performed utilizing transperitoneoscopic (group A) or retroperitoneoscopic access (group B). Duplex scan control was performed after 12 months (T1), after 2 years (T2) and the last one at 18 years old in most patients. Statistical analysis was performed using the t-test for parametric data. Differences in proportions were evaluated using χ2 or Fisher's exact test. We treated 120 children (age range 10-17 years) who presented an asymptomatic IV grade of reflux, Coolsaet 1, associated with a left testicular hypotrophy in 36.6% of the cases (44 patients). No post-operative complications were verified. Duplex scan exam showed an increase of left testicular growth in both groups, with complete hypotrophy disappear in patients in both groups after 24 months. Hydrocele, diagnosed clinically and confirmed with duplex scan, was the most frequent post-operative complication (22/120 cases; 18.3%). This study showed the importance of duplex scan at all steps of this vascular pathology in children, and that there is no significantly difference in results between the two surgical techniques except for hydrocele in transperitoneoscopic access. Copyright © 2014 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

Técnicas para revelar el borde de grano austenítico en aceros microaleados

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García de Andrés, Carlos

2001-08-01

Full Text Available The prior austenite grain size (PAGS exerts an important influence on the microstructures forged by continuous cooling in the steel and on their mechanical properties. Since microalloyed steels have received considerable attention in the last years and enormous difficulties have been repetitively to reveal the austenite grain boundaries in these steels, this work analyzes the different techniques effective in that sense, which enable thus an accurate determination of the PAGS. This paper presents results obtained applying different conventional techniques such us chemical etching of quenched microstructures, the application of thermal cycles that enable the formation of phases around the prior austenite grain boundaries or oxidation etching which reveals the austenite grain boundaries by the preferential accumulation of oxides. Finally, an innovative and effective technique to reveal the prior austenite grain boundaries is presented. This technique is based on the preferential transfer of matter from the grain boundaries to the surrounding austenite by complicated mechanisms such as evaporation-condensation and volume and surface diffusion of atoms.

El tamaño de grano austenítico (TGA tiene una gran influencia sobre la microestructura final y sobre las propiedades mecánicas de los productos obtenidos por transformación anisotérmica del acero. Debido a la considerable atención que se está prestando a los aceros microaleados en los últimos años y a las dificultades que se encuentran en muchos casos para poder revelar los bordes de grano austenítico de estos aceros, en este trabajo se han analizado las técnicas que lo hacen posible, permitiendo así la determinación fiable del TGA. En este sentido, se presentan los resultados obtenidos al aplicar aislada y combinadamente distintas técnicas tradicionales, como el ataque químico de microestructuras obtenidas directamente por temple, la aplicación de diferentes tipos de ciclos t

Duplex ultrasound for identifying renal artery stenosis

DEFF Research Database (Denmark)

Zachrisson, Karin; Herlitz, Hans; Lönn, Lars

2017-01-01

Background Renal artery duplex ultrasound (RADUS) is an established method for diagnosis of renal artery stenosis (RAS), but there is no consensus regarding optimal RADUS criteria. Purpose To define optimal cutoff values for RADUS parameters when screening for RAS using intra-arterial trans...

Duplex Design Project: Science Pilot Test.

Science.gov (United States)

Center for Research on Evaluation, Standards, and Student Testing, Los Angeles, CA.

Work is reported towards the completion of a prototype duplex-design assessment instrument for grade-12 science. The student course-background questionnaire and the pretest section of the two-stage instrument that was developed were administered to all 134 12th-grade students at St. Clairsville High School (Ohio). Based on the information obtained…

Electrolytic pickling of duplex stainless steel

Energy Technology Data Exchange (ETDEWEB)

Ipek, N.; Holm, B.; Pettersson, R. [Swedish Institute for Metals Research, Drottning Kristinas vaeg 48, 11428 Stockholm (Sweden); Runnsjoe, G.; Karlsson, M. [Outokumpu Stainless AB, 77422 Avesta (Sweden)

2005-08-01

Pickling of duplex stainless steels has proved to be much more difficult than that of standard austenitic grades. Electrolytic pre-pickling is shown to be a key process towards facilitating the pickling process for material annealed both in the production-line and in laboratory experiments. The mechanism for the neutral electrolytic process on duplex 2205 and austenitic 316 steels has been examined and the oxide scale found to become thinner as a function of electrolytic pickling time. Spallation or peeling of the oxide induced by gas evolution did not play a decisive role. A maximum of about 20% of the current supplied to the oxidised steel surface goes to dissolution reactions whereas about 80% of the current was consumed in oxygen gas production. This makes the current utilisation very poor, particularly against the background of reports that in indirect electrolytic pickling only about 30% of the total current, supplied to the process, actually goes into the strip. A parametric study was therefore carried out to determine whether adjustment of process variables could improve the current utilisation. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

Molecular architecture: construction of self-assembled organophosphonate duplexes and their electrochemical characterization.

Science.gov (United States)

Cattani-Scholz, Anna; Liao, Kung-Ching; Bora, Achyut; Pathak, Anshuma; Hundschell, Christian; Nickel, Bert; Schwartz, Jeffrey; Abstreiter, Gerhard; Tornow, Marc

2012-05-22

Self-assembled monolayers of phosphonates (SAMPs) of 11-hydroxyundecylphosphonic acid, 2,6-diphosphonoanthracene, 9,10-diphenyl-2,6-diphosphonoanthracene, and 10,10'-diphosphono-9,9'-bianthracene and a novel self-assembled organophosphonate duplex ensemble were synthesized on nanometer-thick SiO(2)-coated, highly doped silicon electrodes. The duplex ensemble was synthesized by first treating the SAMP prepared from an aromatic diphosphonic acid to form a titanium complex-terminated one; this was followed by addition of a second equivalent of the aromatic diphosphonic acid. SAMP homogeneity, roughness, and thickness were evaluated by AFM; SAMP film thickness and the structural contributions of each unit in the duplex were measured by X-ray reflection (XRR). The duplex was compared with the aliphatic and aromatic monolayer SAMPs to determine the effect of stacking on electrochemical properties; these were measured by impedance spectroscopy using aqueous electrolytes in the frequency range 20 Hz to 100 kHz, and data were analyzed using resistance-capacitance network based equivalent circuits. For the 11-hydroxyundecylphosphonate SAMP, C(SAMP) = 2.6 ± 0.2 μF/cm(2), consistent with its measured layer thickness (ca. 1.1 nm). For the anthracene-based SAMPs, C(SAMP) = 6-10 μF/cm(2), which is attributed primarily to a higher effective dielectric constant for the aromatic moieties (ε = 5-10) compared to the aliphatic one; impedance spectroscopy measured the additional capacitance of the second aromatic monolayer in the duplex (2ndSAMP) to be C(Ti/2ndSAMP) = 6.8 ± 0.7 μF/cm(2), in series with the first.

Deformation induced martensite in AISI 316 stainless steel

Directory of Open Access Journals (Sweden)

Solomon, N.

2010-04-01

Full Text Available The forming process leads to a considerable differentiation of the strain field within the billet, and finally causes the non-uniform distribution of the total strain, microstrusture and properties of the material over the product cross-section. This paper focus on the influence of stress states on the deformation-induced a’ martensitic transformation in AISI Type 316 austenitic stainless steel. The formation of deformation-induced martensite is related to the austenite (g instability at temperatures close or below room temperature. The structural transformation susceptibility is correlated to the stacking fault energy (SFE, which is a function not only of the chemical composition, but also of the testing temperature. Austenitic stainless steels possess high plasticity and can be easily cold formed. However, during cold processing the hardening phenomena always occurs. Nevertheless, the deformation-induced martensite transformation may enhance the rate of work-hardening and it may or may not be in favour of further material processing. Due to their high corrosion resistance and versatile mechanical properties the austenitic stainless steels are used in pressing of heat exchanger plates. However, this corrosion resistance is influenced by the amount of martensite formed during processing. In order to establish the links between total plastic strain, and martensitic transformation, the experimental tests were followed by numerical simulation.

El proceso de conformación da a lugar a una considerable diferenciación del campo de tensiones dentro de una barra de extrusión y, finalmente, causa una distribución no uniforme de la tensión total, la microestructura y propiedades del material sobre el corte transversal. En este trabajo se estudia la influencia de los estados de tensión sobre la transformación martensítica inducida por deformación en un acero inoxidable austenítico tipo AISI 316. La formación de martensita inducida por

Duplex Schemes in Multiple Antenna Two-Hop Relaying

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Anja Klein

2008-04-01

Full Text Available A novel scheme for two-hop relaying defined as space division duplex (SDD relaying is proposed. In SDD relaying, multiple antenna beamforming techniques are applied at the intermediate relay station (RS in order to separate downlink and uplink signals of a bi-directional two-hop communication between two nodes, namely, S1 and S2. For conventional amplify-and-forward two-hop relaying, there appears a loss in spectral efficiency due to the fact that the RS cannot receive and transmit simultaneously on the same channel resource. In SDD relaying, this loss in spectral efficiency is circumvented by giving up the strict separation of downlink and uplink signals by either time division duplex or frequency division duplex. Two novel concepts for the derivation of the linear beamforming filters at the RS are proposed; they can be designed either by a three-step or a one-step concept. In SDD relaying, receive signals at S1 are interfered by transmit signals of S1, and receive signals at S2 are interfered by transmit signals of S2. An efficient method in order to combat this kind of interference is proposed in this paper. Furthermore, it is shown how the overall spectral efficiency of SDD relaying can be improved if the channels from S1 and S2 to the RS have different qualities.

Internal Carotid Artery Hypoplasia: Role of Color-Coded Carotid Duplex Sonography.

Science.gov (United States)

Chen, Pei-Ya; Liu, Hung-Yu; Lim, Kun-Eng; Lin, Shinn-Kuang

2015-10-01

The purpose of this study was to determine the role of color-coded carotid duplex sonography for diagnosis of internal carotid artery hypoplasia. We retrospectively reviewed 25,000 color-coded carotid duplex sonograms in our neurosonographic database to establish more diagnostic criteria for internal carotid artery hypoplasia. A definitive diagnosis of internal carotid artery hypoplasia was made in 9 patients. Diagnostic findings on color-coded carotid duplex imaging include a long segmental small-caliber lumen (52% diameter) with markedly decreased flow (13% flow volume) in the affected internal carotid artery relative to the contralateral side but without intraluminal lesions. Indirect findings included markedly increased total flow volume (an increase of 133%) in both vertebral arteries, antegrade ipsilateral ophthalmic arterial flow, and a reduced vessel diameter with increased flow resistance in the ipsilateral common carotid artery. Ten patients with distal internal carotid artery dissection showed a similar color-coded duplex pattern, but the reductions in the internal and common carotid artery diameters and increase in collateral flow from the vertebral artery were less prominent than those in hypoplasia. The ipsilateral ophthalmic arterial flow was retrograde in 40% of patients with distal internal carotid artery dissection. In addition, thin-section axial and sagittal computed tomograms of the skull base could show the small diameter of the carotid canal in internal carotid artery hypoplasia and help distinguish hypoplasia from distal internal carotid artery dissection. Color-coded carotid duplex sonography provides important clues for establishing a diagnosis of internal carotid artery hypoplasia. A hypoplastic carotid canal can be shown by thin-section axial and sagittal skull base computed tomography to confirm the final diagnosis. © 2015 by the American Institute of Ultrasound in Medicine.

Condiciones térmicas de un dispositivo electrónico en caso de incendio Primera parte: estudio experimental

Directory of Open Access Journals (Sweden)

Bruno Chine

2007-11-01

Full Text Available En este trabajo se presentan los resultados de un estudio experimental para determinar las condiciones térmicas a la cual un sistema electrónico, usado para radiocomunicaciones en túneles, podría estar sujeto en caso de incendio. El sistema se compone de un dispositivo electrónico contenido en una caja metálica de acero inoxidable 316, un cable coaxial interno y un cable coaxial externo de cobre. Sobre el sistema, que se alberga en una cámara de polímero concreto, ha sido realizada una prueba al fuego con registro experimental de los valores de temperatura en diferentes puntos del sistema mismo. El trabajo experimental ha permitido analizar eficazmente la respuesta del dispositivo electrónico y de los distintos materiales que lo componen a las severas condiciones térmicas de prueba.

RESISTENCIA A LA CORROSIÓN DE LAS MULTICAPAS DE [TIN/ALTIN]n DEPOSITADAS SOBRE ACERO AL CARBONO AISI 1045

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WILLIAM APERADOR

2011-01-01

Full Text Available En este artículo se presenta el mejoramiento frente a la corrosión de los recubrimientos multicapas de [TiN/AlTiN]n con periodos de 2, 6, 12 y 24 bicapas depositados mediante la técnica de PVD magnetrón Sputtering sobre acero al carbono AISI 1045. La evaluación electroquímica se realizó mediante las técnicas espectroscopia de impedancia electroquímica (EIS y curvas de polarización Tafel, en una solución de 0.5M de H2SO4 + 3.5% wt. de NaCl. La resistencia a la corrosión aumentó de forma gradual en función del número de bicapas en comparación al sustrato encontrando valores de velocidad de corrosión de 18.51 mpy para el sustrato sin recubrir y de 1x10 6 mpy para la muestra con 24 bicapas. Los resultados electroquímicos revelan el efecto positivo en cuanto a la protección superficial del acero 1045 con el incremento del periodo en las multicapas de [TiN /AlTiN]n.

Development and properties of duplex MgF2/PCL coatings on biodegradable magnesium alloy for biomedical applications.

Science.gov (United States)

Makkar, Preeti; Kang, Hoe Jin; Padalhin, Andrew R; Park, Ihho; Moon, Byoung-Gi; Lee, Byong Taek

2018-01-01

The present work addresses the performance of polycaprolactone (PCL) coating on fluoride treated (MgF2) biodegradable ZK60 magnesium alloy (Mg) for biomedical application. MgF2 conversion layer was first produced by immersing Mg alloy substrate in hydrofluoric acid solution. The outer PCL coating was then prepared using dip coating technique. Morphology, elements profile, phase structure, roughness, mechanical properties, invitro corrosion, and biocompatibility of duplex MgF2/PCL coating were then characterized and compared to those of fluoride coated and uncoated Mg samples. The invivo degradation behavior and biocompatibility of duplex MgF2/PCL coating with respect to ZK60 Mg alloy were also studied using rabbit model for 2 weeks. SEM and TEM analysis showed that the duplex coating was uniform and comprised of porous PCL film (~3.3 μm) as upper layer with compact MgF2 (~2.2 μm) as inner layer. No significant change in microhardness was found on duplex coating compared with uncoated ZK60 Mg alloy. The duplex coating showed improved invitro corrosion resistance than single layered MgF2 or uncoated alloy samples. The duplex coating also resulted in better cell viability, cell adhesion, and cell proliferation compared to fluoride coated or uncoated alloy. Preliminary invivo studies indicated that duplex MgF2/PCL coating reduced the degradation rate of ZK60 Mg alloy and exhibited good biocompatibility. These results suggested that duplex MgF2/PCL coating on magnesium alloy might have great potential for orthopedic applications.

Funcionalización electroquímica y tribológica de películas de quitosano en fosfato tricálcico depositados en acero 316L

Directory of Open Access Journals (Sweden)

Alexis Mina Escobar

2013-12-01

Full Text Available Se depositaron recubrimientos de fosfato tricálcico-β/quitosano sobre sustratos de acero 316L vía electrodeposición, a una temperatura de 60 °C, aplicando una corriente de 260 mA. Con el fin de estudiar el efecto del contenido de quitosano en la velocidad de corrosión y la respuesta tribológica de los aceros recubiertos, se utilizaron seis concentraciones de quitosano en la mezcla acuosa. Los enlaces químicos presentes en las capas fueron estudiados mediante Espectroscopia de Infrarrojo con Transformada de Fourier (FTIR; la cristalinidad de los depósitos fue examinada mediante difracción de rayos-X (DRX; la resistencia a la corrosión del TCP-β/quitosano depositado sobre los aceros se estudió mediante Espectroscopia de Impedancia Electroquímica (EIS y curvas anódicas Tafel, encontrándose una disminución del 54% en la velocidad de corrosión para la relación 50-50, con respecto a 100% TCP. La respuesta tribológica se analizó mediante pin-on-disc, evidenciando una reducción del 73% en el coeficiente de fricción con mayor concentración de quitosano.

Modelación de fenómenos metalúrgicos en laminación en caliente de acero

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Zambrano, P.

2008-02-01

Full Text Available Modelling of hot rolling of steel strip involves metallurgical phenomena such as restoration of deformed structures, transformation to ferrite and growth of the oxide layer on top of the steel strip. The effect of composition is taken into account when restoration and phase transformation is considered, whereas it is assumed that the chemical composition of the steel substrate does not affect the oxide crust, being common place to consider the oxide just as a thermal barrier and to assume sticking conditions within the roll-gap. Observations indicate that elements such as silicon and manganese, more susceptible to oxidize than iron, affect the growth kinetics, adhesion and the behaviour during deformation of the oxide layer. This work deals with the way used to model various superficial and metallurgical phenomena, and how this knowledge is used to simulate hot rolling of steel strip.

La modelación del proceso de laminación en caliente de acero incorpora fenómenos metalúrgicos como son la restauración de la estructura deformada, la trasformación de fase y el crecimiento de la capa de óxido sobre la superficie del acero. Se reconoce el efecto de la composición química sobre la transformación de fase y la restauración, sin embargo se considera que el crecimiento del óxido no es afectado por la presencia de elementos aleantes en el acero y es común que se maneje a la costra de óxido como una barrera térmica y que se supongan condiciones de fricción adhesivas en el entrehierro. Determinadas observaciones indican que elementos como el silicio y el manganeso, más susceptibles a oxidarse que el hierro, afectan la cinética de crecimiento, la adhesión y el comportamiento de la costra al ser deformada. En este trabajo se presenta la forma en que diversos fenómenos metalúrgicos y de superficie se modelan y se utilizan para simular el proceso de laminación en caliente.

Potential of duplex fuel in prebreeder, breeder, and power reactor designs: tests and analyses (AWBA Development Program)

International Nuclear Information System (INIS)

Chao, T.L.; Brennan, J.J.; Duncombe, E.; Schneider, M.J.; Johnson, R.G.R.

1982-09-01

Dual region fuel pellets, called duplex pellets, are comprised of an outer annular region of relatively high uranium fuel enrichment and a center pellet of fertile material with no enrichment. UO 2 and ThO 2 are the fissile and fertile materials of interest. Both prebreeders and breeders are discussed as are the performance advantages of duplex pellets over solid pellets in these two pressurized water reactor types. Advantages of duplex pellets for commercial reactor fuel rods are also discussed. Both irradiation test data and analytical results are used in comparisons. Manufacturing of duplex fuel is discussed

Can duplex Doppler ultrasound replace computerized tomography in staging patients with renal cell carcinoma?

NARCIS (Netherlands)

Bos, SD; Mensink, HJA

The purpose of this study was to evaluate the accuracy and reliability of duplex Doppler ultrasound (US) and computerized tomography (CT) in staging patients with renal cell carcinoma (RCC). Sixty-six patients were evaluated pre-operatively with duplex Doppler ultrasound and CT. The results were

miRNA-like duplexes as RNAi triggers with improved specificity

Directory of Open Access Journals (Sweden)

Juan G. Betancur

2012-07-01

Full Text Available siRNA duplexes, the most common triggers of RNA interference, are first loaded into an Argonaute (Ago protein and then undergo unwinding via passenger strand cleavage, which requires the slicer activity of the Ago protein. In mammals, only Ago2 out of the four Ago proteins possesses such slicer activity. In contrast, miRNA/miRNA* duplexes often contain central mismatches that prevent slicer-dependent unwinding. Instead, mismatches in specific regions (seed and 3´-mid regions promote efficient slicer-independent unwinding by any of the four mammalian Ago proteins. Both slicer-dependent and slicer-independent unwinding mechanisms produce guide-containing RNA-induced silencing complex (RISC, which silences target mRNAs by cleavage, translational repression, and/or deadenylation that leads to mRNA decay. In this review, we summarize our current knowledge of the RISC assembly pathways, and describe a simple method to rationally design artificial miRNA/miRNA*-like duplexes and highlight its benefits to reduce the unwanted off-target effects without compromising the specific target silencing activity.

Duplex System with Ectopic Ureter Opens into the Posterior Urethra: Case Report.

Science.gov (United States)

Milicevic, Snjezana; Bijelic, Radojka; Krivokuca, Vladimir; Jakovljevic, Branislava

2018-04-01

Duplicated ureter or Duplex Collecting System is a congenital condition in which the ureteric bud, the embryological origin of the ureter, arises twice, resulting in two ureters draining a single kidney. This congenital anomaly is rare, and even rarer when the duplex system with ectopic ureter is present. This type of congenital anomaly is even more rarely diagnosed and surgically treated in adulthood. This case report presents a case of a 32-year-old male, who had a duplex collecting system with two ureters on the left side. Ectopic ureter, draining the upper pole of the left kidney, opened into the posterior urethra. In our patient, taking into account the clinical perspective, the renal tissue damaging of the upper pole which was not functional, partial nephrectomy and ureterectomy was successfully performed.

Aluminum coating by fluidized bed chemical vapor deposition on austenitic stainless steels AISI 304 and AISI 316

Directory of Open Access Journals (Sweden)

Jose Luddey Marulanda-Arevalo

2015-01-01

Full Text Available Los revestimientos de aluminio f ueron depositados sobre aceros inoxidables AISI 304 y AISI 316 en el rango de temperatura de 5 60 a 600 °C por deposición química de vapor en lecho fluidizado(CVD – FBR. Se utilizó un lecho que consistía en 10 % de aluminio en polvo y 90 % de lecho inerte (alúmina, el cual fue fluidizado con Ar y como ga ses activadores se utilizó una mezcla de ácido clorhídrico con hidrógeno (HCl/H 2 . En el recubrimiento si n tratamiento térmico están las siguiente s especies: Al 13 Fe 4 , Fe 2 Al 5 , FeAl 2 y Al 5 FeNi, las cuales están presentes para ambos aceros. Además, el tratamiento térmico provoca la difusa de alu minio hacia el sustrato y la difusa de hierro del sustrato haci a la superficie del recubrimiento, haciendo la trans formación de los compuestos ant eriores a FeAl, Fe 2 Al 5 , FeAl 2 , Al 0.99 Fe 0.99 Ni 0.02 , AlNi y el Fe 2 AlCr. Se realizó la simulación termodinámica con el s oftware Thermo Calc para obt ener información de la posible composición y la cantidad de mat erial depositado, para condiciones seleccionadas. Las muestras recubi ertas y sin recubrir, se expus ieron a 750 ºC en una atmósfera d onde el vapor agua se transporta a las muestras usando un flujo de N 2 de 40 ml/min, más 100 % vapor de agua (H 2 O. Los dos sustratos sin revestir se comportaron de manera diferente, ya que el acero AISI 304 soportó bien el a taque y ganó poco peso (0.49 mg/cm 2 , en comparación con el acero AISI 316 que perdió mucho peso (25.4 mg/cm 2 . Los aceros recubiertos ganaron poco de peso durante las mil horas de exposición (0.26 mg/cm 2 y soportaron muy bien el ataque corrosivo en c omparación con sustratos sin r ecubrimiento.

Duplex investigations in children: Are clinical signs in children with venous disorders relevant?

Science.gov (United States)

Birgitte Maessen-Visch, M; Smeets, L; van Vleuten, C

2015-12-01

Ultra sound colored duplex sonography is the preferred method in diagnosing chronic venous disease. Data in children on incidence, indications, and results are lacking. From the total of 9180 duplex investigations performed in our hospital from 2009 to 2012, data on indication and results of the investigation as well as patient characteristics were evaluated retrospectively for the proportion of pediatric patients. Duplex investigations were performed 49 times in 38 children (6-18 years), with an average of 1.3 times (1-6 times) per child. Forty percent showed abnormalities: 17 times deep venous thrombosis was suspected; deep venous thrombosis was objectified in 18%. In the 21 investigations performed for varicosis-related complaints, varicose veins or venous malformations were objectified in 57%. Edema was never a symptom of chronic venous disease. Duplex investigation is not often performed in children. In children with established deep venous thrombosis, a family history with deep venous thrombosis is common. In general, edema was not seen in children with varicose veins and, therefore, does not seem a reliable clinical sign at young age. © The Author(s) 2014.

Stress corrosion (Astm G30-90 standard) in 08x18H10T stainless steel of nuclear fuel storage pool in WWER reactors; Corrosion bajo esfuerzo (Norma ASTM G30-90) en acero inoxidable 08x18H10T de piscinas de almacenamiento de combustible nuclear en reactores V.V.E.R

Energy Technology Data Exchange (ETDEWEB)

Herrera, V.; Zamora R, L. [Centro de Estudios Aplicados al Desarrollo Nuclear (Cuba)

1997-07-01

At the water storage of the irradiated nuclear fuel has been an important factor in its management. The actual pools have its walls covered with inoxidable steel and heat exchangers to dissipate the residual heat from fuel. It is essential to control the water purity to eliminate those conditions which aid to the corrosion process in fuel and at related components. The steel used in this research was obtained from an austenitic inoxidizable steel standardized with titanium 08x18H10T (Type 321) similar to one of the two steel coatings used to cover walls and the pools floor. the test consisted in the specimen deformation through an U ply according to the Astm G30-90 standard. The exposition of the deformed specimen it was realized in simulated conditions to the chemical regime used in pools. (Author)

Development of duplex RT-PCR-ELISA for the simultaneous detection of hepatitis A virus and hepatitis E virus.

Science.gov (United States)

Tahk, Hongmin; Lee, Min Hwa; Lee, Kang Bum; Cheon, Doo-Sung; Choi, Changsun

2011-07-01

This study aimed to develop a specific and sensitive duplex reverse transcription polymerase chain reaction enzyme-linked immunosorbent assay (duplex RT-PCR-ELISA) for hepatitis A virus (HAV) and hepatitis E virus (HEV). Duplex RT-PCR-ELISA could detect and differentiate HAV and HEV with specific probes. When ELISA technique was used to detect probe-bound RT-PCR products, duplex RT-PCR-ELISA could detect as little as 0.1 ng/μL HAV and HEV from clinical samples. Human norovirus, enterovirus, poliovirus, murine norovirus and feline calicivirus were used for the specificity test; all were negative. Therefore duplex RT-PCR-ELISA can be used for the simultaneous detection of HAV and HEV in contaminated fecal samples. Copyright © 2011 Elsevier B.V. All rights reserved.

Fatigue crack propagation behavior and acoustic emission characteristics of the heat affected zone of super duplex stainless steel

International Nuclear Information System (INIS)

Do, Jae Yoon; Kim, Jin Hwan; Ahn, Seok Hwan; Park, In Duck; Kang, Chang Yong; Nam, Ki Woo

2002-01-01

Because duplex stainless steel shows the good strength and corrosion resistance properties, the necessity of duplex stainless steel, which has long life in severe environments, has been increased with industrial development. The fatigue crack propagation behavior of Heat Affected Zone(HAZ) has been investigated in super duplex stainless steel. The fatigue crack propagation rate of HAZ of super duplex stainless steel was faster than that of base metal of super duplex stainless steel. We also analysed acoustic emission signals during the fatigue test with time-frequency analysis method. According to the results of time-frequency analysis, the frequency ranges of 200-400 kHz were obtained by striation and the frequency range of 500 kHz was obtained due to dimple and separate of inclusion

Weld oxide formation on lean duplex stainless steel

Energy Technology Data Exchange (ETDEWEB)

Westin, E.M. [Outokumpu Stainless, Avesta Research Centre, P.O. Box 74, SE-774 22 Avesta (Sweden)], E-mail: elin.westin@outokumpu.com; Olsson, C.-O.A. [Outokumpu Stainless, Avesta Research Centre, P.O. Box 74, SE-774 22 Avesta (Sweden); Hertzman, S. [Outokumpu Stainless Research Foundation, Brinellvaegen 23, SE-100 44 Stockholm (Sweden)

2008-09-15

Weld oxides have a strong influence on corrosion resistance, but have hitherto only been studied to a limited extent for duplex stainless steels. X-ray photoelectron spectroscopy (XPS) has here been used to study heat tint formed on gas tungsten arc (GTA) welds on the commercial duplex grades LDX 2101 (EN 1.4162/UNS S32101) and 2304 (EN 1.4362/UNS S32304) welded with and without nitrogen additions to the shielding gas. The process of heat tint formation is discussed in terms of transport phenomena to explain the effect of atmosphere, temperature and composition. The oxides formed were found to be enriched in manganese and corrosion testing shows that nitrogen has a strong influence on the weld oxide. A mechanism is proposed including evaporation from the weld pool and subsequent redeposition.

Weld oxide formation on lean duplex stainless steel

International Nuclear Information System (INIS)

Westin, E.M.; Olsson, C.-O.A.; Hertzman, S.

2008-01-01

Weld oxides have a strong influence on corrosion resistance, but have hitherto only been studied to a limited extent for duplex stainless steels. X-ray photoelectron spectroscopy (XPS) has here been used to study heat tint formed on gas tungsten arc (GTA) welds on the commercial duplex grades LDX 2101 (EN 1.4162/UNS S32101) and 2304 (EN 1.4362/UNS S32304) welded with and without nitrogen additions to the shielding gas. The process of heat tint formation is discussed in terms of transport phenomena to explain the effect of atmosphere, temperature and composition. The oxides formed were found to be enriched in manganese and corrosion testing shows that nitrogen has a strong influence on the weld oxide. A mechanism is proposed including evaporation from the weld pool and subsequent redeposition

Modelos de pérdida de masa de acero por corrosión atmosférica en Colombia usando inteligencia computacional

Directory of Open Access Journals (Sweden)

Esteban Velilla

2009-01-01

Full Text Available Con el fin de clasificar la corrosividad de las diferentes atmósferas colombianas, como parte de un proyecto de investigación extenso [1], se expusieron placas de acero al carbono en 21 estaciones distribuidas a lo largo de la infraestructura eléctrica del país (líneas de transmisión y subestaciones. En estas estaciones se midieron entre otros, el tiempo de humectación y la deposición de sulfatos y cloruros durante 12 meses; además, bimensualmente se tomaban placas de acero para medir en laboratorio la pérdida de masa sufrida por estas durante el tiempo de exposición. La clasificación de las 21 estaciones se hizo en 4 grupos, considerando: el tiempo de humectación, contenidos de cloruros y sulfatos, la altura sobre el nivel del mar y el tiempo de exposición de las placas; variables consideradas linealmente independientes según la técnica de descomposición en valores singulares (SVD realizada. El criterio utilizado para la clasificación fue el de similitud de las variables utilizando la norma Euclidiana considerada en la red neuronal no supervisada tipo Kohonen. Adicionalmente, se implementaron modelos para la pérdida de masa del acero para cada uno de los grupos usando redes neuronales (RN tipo Feed-Forward, definiéndose como entradas las variables antes mencionadas y como única salida la pérdida de masa. Complementariamente se presenta una comparación entre el modelo de RN para el grupo 1, con otros modelos obtenidos usando Algoritmos Genéticos (AG y el método Simplex.

Investigation of hot cracking resistance of 2205 duplex steel

Energy Technology Data Exchange (ETDEWEB)

Adamiec, J; Scibisz, B, E-mail: janusz.adamiec@polsl.pl [Silesian University of Technology, Faculty of Materials Science and Metallurgy, ul. Krasinskiego 8, PL-40019 Katowice (Poland)

2010-02-15

Austenitic duplex steel of the brand 2205 according to Avesta Sheffield is used for welded constructions (pipelines, tanks) in the petrol industry, chemical industry and food industry. It is important to know the range of high-temperature brittleness in designing welding technology for constructions made of this steel type. There is no data in literature concerning this issue. High-temperature brittleness tests using the simulator of heat flow device Gleeble 3800 were performed. The tests results allowed the evaluation of the characteristic temperatures in the brittleness temperature range during the joining of duplex steels, specifically the nil-strength temperature (NST) and nil-ductility temperatures (NDT) during heating, the strength and ductility recovery temperatures (DRT) during cooling, the R{sub f}parameter (R{sub f} = (T{sub liquidus} - NDT)/NDT) describing the duplex steel inclination for hot cracking, and the brittleness temperature range (BTR). It has been stated that, for the examined steel, this range is wide and amounts to ca. 90 deg. C. The joining of duplex steels with the help of welding techniques creates a significant risk of hot cracks. After analysis of the DTA curves a liquidus temperature of T{sub L} = 1465 deg. C and a solidus temperature of T{sub S} = 1454 deg. C were observed. For NST a mean value was assumed, in which the cracks appeared for six samples; the temperature was 1381 deg. C. As the value of the NDT temperature 1367 deg. C was applied while for DRT the assumed temperature was 1375 deg. C. The microstructure of the fractures was observed using a Hitachi S-3400N scanning electron microscope (SEM). The analyses of the chemical composition were performed using an energy-dispersive X-ray spectrometer (EDS), Noran System Six of Thermo Fisher Scientific. Essential differences of fracture morphology type over the brittle temperature range were observed and described.

Investigation of hot cracking resistance of 2205 duplex steel

Science.gov (United States)

Adamiec, J.; Ścibisz, B.

2010-02-01

Austenitic duplex steel of the brand 2205 according to Avesta Sheffield is used for welded constructions (pipelines, tanks) in the petrol industry, chemical industry and food industry. It is important to know the range of high-temperature brittleness in designing welding technology for constructions made of this steel type. There is no data in literature concerning this issue. High-temperature brittleness tests using the simulator of heat flow device Gleeble 3800 were performed. The tests results allowed the evaluation of the characteristic temperatures in the brittleness temperature range during the joining of duplex steels, specifically the nil-strength temperature (NST) and nil-ductility temperatures (NDT) during heating, the strength and ductility recovery temperatures (DRT) during cooling, the Rfparameter (Rf = (Tliquidus - NDT)/NDT) describing the duplex steel inclination for hot cracking, and the brittleness temperature range (BTR). It has been stated that, for the examined steel, this range is wide and amounts to ca. 90 °C. The joining of duplex steels with the help of welding techniques creates a significant risk of hot cracks. After analysis of the DTA curves a liquidus temperature of TL = 1465 °C and a solidus temperature of TS = 1454 °C were observed. For NST a mean value was assumed, in which the cracks appeared for six samples; the temperature was 1381 °C. As the value of the NDT temperature 1367 °C was applied while for DRT the assumed temperature was 1375 °C. The microstructure of the fractures was observed using a Hitachi S-3400N scanning electron microscope (SEM). The analyses of the chemical composition were performed using an energy-dispersive X-ray spectrometer (EDS), Noran System Six of Thermo Fisher Scientific. Essential differences of fracture morphology type over the brittle temperature range were observed and described.

Investigation of hot cracking resistance of 2205 duplex steel

International Nuclear Information System (INIS)

Adamiec, J; Scibisz, B

2010-01-01

Austenitic duplex steel of the brand 2205 according to Avesta Sheffield is used for welded constructions (pipelines, tanks) in the petrol industry, chemical industry and food industry. It is important to know the range of high-temperature brittleness in designing welding technology for constructions made of this steel type. There is no data in literature concerning this issue. High-temperature brittleness tests using the simulator of heat flow device Gleeble 3800 were performed. The tests results allowed the evaluation of the characteristic temperatures in the brittleness temperature range during the joining of duplex steels, specifically the nil-strength temperature (NST) and nil-ductility temperatures (NDT) during heating, the strength and ductility recovery temperatures (DRT) during cooling, the R f parameter (R f = (T liquidus - NDT)/NDT) describing the duplex steel inclination for hot cracking, and the brittleness temperature range (BTR). It has been stated that, for the examined steel, this range is wide and amounts to ca. 90 deg. C. The joining of duplex steels with the help of welding techniques creates a significant risk of hot cracks. After analysis of the DTA curves a liquidus temperature of T L = 1465 deg. C and a solidus temperature of T S = 1454 deg. C were observed. For NST a mean value was assumed, in which the cracks appeared for six samples; the temperature was 1381 deg. C. As the value of the NDT temperature 1367 deg. C was applied while for DRT the assumed temperature was 1375 deg. C. The microstructure of the fractures was observed using a Hitachi S-3400N scanning electron microscope (SEM). The analyses of the chemical composition were performed using an energy-dispersive X-ray spectrometer (EDS), Noran System Six of Thermo Fisher Scientific. Essential differences of fracture morphology type over the brittle temperature range were observed and described.

The possibilities for reuse of steel scrap in order to obtain blades for knives; Posibilidades de reutilización de la chatarra de acero para la obtención de cuchillas para cortar

Energy Technology Data Exchange (ETDEWEB)

Štrbaca, N.; Markovića, I.; Mitovskia, A.; Balanovića, L.; Živkovića, D.; Grekulović, V.

2017-09-01

The purpose of this study is to determine fracture toughness of Resistance Spot Welded (RSW) Dual Phase (DP) steels. RSW of galvanized and ungalvanized DP 450 steel sheets was carried out on spot welding machine. Fracture toughness of RSW joints of galvanized and ungalvanized DP 450 steel sheets was calculated from tensile-shear tests. New empirical equations were developed using Least Squares Method (LSM) between energy release rate, fracture toughness and critical crack size depending on the relationship between hardness and fracture toughness values. Results indicated that fracture toughness of joints welded by using RSW increased exponentially while the hardness decreased. In addition, fracture toughness and energy release rate of RSW galvanized DP 450 steel sheets were lower compared to RSW ungalvanized DP 450 steel sheets which had approximately the same hardness. [Spanish] El trabajo presenta los resultados de la caracterización de diversos tipos de aceros que han llegado al final de su ciclo de vida útil, y de los que se desconocía su composición química, propiedades mecánicas y tratamiento termomecánico aplicado previamente. El estudio se realizó con el objetivo de analizar las posibilidades de reutilización de algunos de estos materiales en aplicaciones agrícolas e industriales, obteniendo hojas de corte. Las formas exigidas a las hojas de corte se consiguieron aplicando diversos tipos de tratamientos termomecánicos. El análisis químico de la chatarra de acero de acero se realizó utilizando Energías Dispersivas de Rayos X. La microestructura se estudió utilizando Microscopía Óptica y Microscopía Electrónica de Barrido. La dureza de la chatarra de acero y de las cuchillas obtenidas se midió utilizando la escala Rockwell C. Los valores de dureza de las cuchillas obtenidas indican una buena selección de los productos finales de acero.

GEL DE ALOE-VERA COMO POTENCIAL INHIBIDOR DE LA CORROSIÓN DEL ACERO DE REFUERZO ESTRUCTURAL

OpenAIRE

Héctor Herrera-Hernández

2015-01-01

En el presente trabajo se estudiaelectroquímicamente un GELextracto de las hojas de ALOE VERAcomo un posible inhibidor de la corrosión del acero de refuerzo estructuraldel concreto.Los estudiosde corrosiónse llevaron a cabo en 1M de HCl y utilizando la técnica de espectroscopia de impedancia electroquímica (EIS)se evaluó la resistencia a la corrosión en presencia y ausencia del GEL.Los diagramas de impedancia mostraronque la adición en diferentes proporciones...

Influencia de la ductilidad de las armaduras de acero en el comportamiento y la seguridad de losas de hormigón armado

Directory of Open Access Journals (Sweden)

Ortega, H.

1999-10-01

Full Text Available This work is based on the results and basic conclusions of author's doctoral thesis, directed by Professor José Calavera. On the one hand, a new form to measure the ductility of those steels used like reinforcement of concrete, is proposed, in order to be compared and classified in accordance with this one. On the other hand it has been studied the results of the tests on 12 continuous slabs of two equal spans, reinforced with four different steel types chosen so that, in the more requested section the steel will reach, in first place, its collapse (situation in the 2 domain, A pivot. The reinforcement to allow the mentioned extent, is provided with same nominal resistance steels and same diameter, but with - different ductility. The results of this experimental study, reveals the importance of the steel ductility concerning the behaviour and real security of the structure in front of the collapse, and furnish a group of conclusions and proposals concerning this interesting subject.

Este trabajo se basa en los resultados y conclusiones básicas de la tesis doctoral del autor, dirigida por el Profesor D. José Calavera. Se propone, por un lado, una forma de medir mediante un único parámetro la ductilidad de los aceros utilizados como armaduras para hormigón armado, de forma que se puedan comparar y clasificar con arreglo al mismo. Por otro, se estudian los resultados de los ensayos sobre 12 losas continuas de dos vanos, de sección maciza, armadas con cuatro cuantías diferentes elegidas de forma que, en la sección más solicitada, sea el acero el que alcance, en primer lugar, su agotamiento (situación en el dominio 2, pivote A . El armado para conseguir las citadas cuantías se realiza con aceros de la misma resistencia nominal y del mismo diámetro, pero con distinta ductilidad. Los resultados de este estudio experimental, ponen de manifiesto la importancia de la ductilidad del acero en relación con el comportamiento, as

The Contribution of the Activation Entropy to the Gas-Phase Stability of Modified Nucleic Acid Duplexes

Science.gov (United States)

Hari, Yvonne; Dugovič, Branislav; Istrate, Alena; Fignolé, Annabel; Leumann, Christian J.; Schürch, Stefan

2016-07-01

Tricyclo-DNA (tcDNA) is a sugar-modified analogue of DNA currently tested for the treatment of Duchenne muscular dystrophy in an antisense approach. Tandem mass spectrometry plays a key role in modern medical diagnostics and has become a widespread technique for the structure elucidation and quantification of antisense oligonucleotides. Herein, mechanistic aspects of the fragmentation of tcDNA are discussed, which lay the basis for reliable sequencing and quantification of the antisense oligonucleotide. Excellent selectivity of tcDNA for complementary RNA is demonstrated in direct competition experiments. Moreover, the kinetic stability and fragmentation pattern of matched and mismatched tcDNA heteroduplexes were investigated and compared with non-modified DNA and RNA duplexes. Although the separation of the constituting strands is the entropy-favored fragmentation pathway of all nucleic acid duplexes, it was found to be only a minor pathway of tcDNA duplexes. The modified hybrid duplexes preferentially undergo neutral base loss and backbone cleavage. This difference is due to the low activation entropy for the strand dissociation of modified duplexes that arises from the conformational constraint of the tc-sugar-moiety. The low activation entropy results in a relatively high free activation enthalpy for the dissociation comparable to the free activation enthalpy of the alternative reaction pathway, the release of a nucleobase. The gas-phase behavior of tcDNA duplexes illustrates the impact of the activation entropy on the fragmentation kinetics and suggests that tandem mass spectrometric experiments are not suited to determine the relative stability of different types of nucleic acid duplexes.

Microstructure and Antiwear Property of Laser Cladding Ni-Co Duplex Coating on Copper.

Science.gov (United States)

Wang, Yiyong; Liang, Zhipeng; Zhang, Junwei; Ning, Zhe; Jin, Hui

2016-07-28

Ni-Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al₂O₃/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni-Co duplex coatings comprised a Co-based solid solution, Cr₇C₃, (Fe,Ni) 23 C₆, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV). The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni-Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni-Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties.

Microstructure and Antiwear Property of Laser Cladding Ni–Co Duplex Coating on Copper

Science.gov (United States)

Wang, Yiyong; Liang, Zhipeng; Zhang, Junwei; Ning, Zhe; Jin, Hui

2016-01-01

Ni–Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al2O3/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni–Co duplex coatings comprised a Co-based solid solution, Cr7C3, (Fe,Ni)23C6, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV). The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni–Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni–Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties. PMID:28773755

Microstructure and Antiwear Property of Laser Cladding Ni–Co Duplex Coating on Copper

Directory of Open Access Journals (Sweden)

Yiyong Wang

2016-07-01

Full Text Available Ni–Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al2O3/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni–Co duplex coatings comprised a Co-based solid solution, Cr7C3, (Fe,Ni23C6, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV. The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni–Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni–Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties.

Metodología para el cálculo de espesores límite libres de fase sigma durante el hipertemple en piezas de aceros dúplex de gran sección

Directory of Open Access Journals (Sweden)

Jimbert, P.

2013-04-01

Full Text Available To achieve the mechanical properties and corrosion resistance desired by duplex stainless steels used by the petrochemical and nuclear industry, parts are subjected to a hiperquenching heat treatment from about 1050 °C. This avoids the risk of intermetallic precipitation which drastically reduces the properties of these materials. However with increasing depth to which the deposits are present, the thicknesses for such pipes have been increased, resulting in higher levels of demand on all its manufacturing process, including the heat treatment. To avoid the precipitation of intermetallic phases such as sigma phase it is necessary to know the cooling profile in the center of the workpiece and for this purpose to know the value of the Surface Heat Transfer Coefficient (h is essential. This coefficient changes during the hiperquenching and its value is determined experimentally as it depends on several process parameters. Studies reveal that its value is stabilized within a few seconds. We can then assume that to know the cooling profile in the center of large sections it is only necessary to know the stabilized value of h. However, all the studies found in the literature are referred to diameters smaller than 100 mm. This paper has developed a methodology to predict the precipitation of intermetallic phases in duplex stainless steel parts with large thicknesses in industrial facilities from the calculation of h. This methodology allows us to calculate the cooling profiles without wasting any workpiece using one or more sensorized patterns with thermocouples and a subsequent simulation with ANSYS.Para conseguir las propiedades mecánicas y de corrosión deseadas en los aceros dúplex utilizados por la industria petro-química y nuclear se les somete a un tratamiento de hipertemple desde unos 1.050 °C. Con ello se evita el riesgo de aparición de precipitados intermetálicos que reducen drásticamente las propiedades de estos materiales. Sin

A duplex DNA-gold nanoparticle probe composed as a colorimetric biosensor for sequence-specific DNA-binding proteins.

Science.gov (United States)

Ahn, Junho; Choi, Yeonweon; Lee, Ae-Ree; Lee, Joon-Hwa; Jung, Jong Hwa

2016-03-21

Using duplex DNA-AuNP aggregates, a sequence-specific DNA-binding protein, SQUAMOSA Promoter-binding-Like protein 12 (SPL-12), was directly determined by SPL-12-duplex DNA interaction-based colorimetric actions of DNA-Au assemblies. In order to prepare duplex DNA-Au aggregates, thiol-modified DNA 1 and DNA 2 were attached onto the surface of AuNPs, respectively, by the salt-aging method and then the DNA-attached AuNPs were mixed. Duplex-DNA-Au aggregates having the average size of 160 nm diameter and the maximum absorption at 529 nm were able to recognize SPL-12 and reached the equivalent state by the addition of ∼30 equivalents of SPL-12 accompanying a color change from red to blue with a red shift of the maximum absorption at 570 nm. As a result, the aggregation size grew to about 247 nm. Also, at higher temperatures of the mixture of duplex-DNA-Au aggregate solution and SPL-12, the equivalent state was reached rapidly. On the contrary, in the control experiment using Bovine Serum Albumin (BSA), no absorption band shift of duplex-DNA-Au aggregates was observed.

The Role of Duplex Scanning in the Selection of Patients with Critical Lower-Limb Ischemia for Infrainguinal Percutaneous Transluminal Angioplasty

International Nuclear Information System (INIS)

Loefberg, Anne-Marie; Karacagil, Sadettin; Hellberg, Anders; Bostroem, Annika; Ljungman, Christer; Ostholm, Goerel

2001-01-01

Purpose: To investigate the role of duplex scanning in the selection of patients with critical lower-limb ischemia (CLI) for infrainguinal percutaneous transluminal angioplasty (PTA).Methods: One hundred and sixty-two limbs with CLI (150 patients) that underwent duplex scanning within 3 months prior to conventional diagnostic angiography (n = 88) or infrainguinal PTA (n = 74) were retrospectively studied. The findings obtained from duplex scanning and angiography were analyzed in a masked fashion by two different investigators.Results: The accuracy, sensitivity, specificity, and negative and positive predictive values of duplex scanning in the selection of patients for infrainguinal PTA were 86%, 84%, 89%, 86%, and 87% respectively. Forty-two procedures (57%) were performed at multiple arterial segments. The accuracy of duplex scanning in the selection of femoropopliteal and crural lesions for PTA was over 85%. However, the sensitivity of duplex scanning in the selection of popliteal and crural lesions for PTA was 49% and 38% respectively, compared with 80% for superior femoral artery lesions. In 39% of patients who were correctly selected for PTA, duplex scanning misdiagnosed one of the multiple lesions treated by PTA.Conclusion: Duplex scanning can safely be used for the selection of patients for infrainguinal PTA. The sensitivity of duplex scanning in the selection of lesions for PTA was less satisfactory in the popliteal and crural arteries compared with the femoropopliteal arteries

Duplex geometry: an example from the Moine Thrust Belt

Science.gov (United States)

Bowler, S.

1987-04-01

The geometry and microstructure of a small duplex formed in one bed from the Moine Thrust Belt of northwest Scotland is reported. The structure is seen in oblique section, within the Cambrian Pipe-rock, in an area of low strain. A range of movement direction indicators are present in the structure. An early grain shape fabric developed close to the roof thrust is taken as the best estimate of the overall movement direction towards 287°. Slickensides in the gouge developed on movement planes within the duplex show varied orientations on a given plane, and are not considered useful indicators of thrust transport direction. Branch lines exposed converge and diverge, suggesting little lateral continuity of the exposed structure. The microstructures present within the structure indicate an increase in localised deformation, and in cataclastic behavior as the duplex evolved. Early layer parallel shear is ubiquitous, giving rise to an elongate grain shape fabric close to bedding surfaces. In early formed horses, a layer-parallel, oblate grain shape fabric, which shows localised slip zones, is overprinted by gouge formation. Later formed horses show only fracturing and gouge development. This sequence is attributed to stick-slip behavior in the propagation or displacement of the original fault, now the floor thrust.

Microstructures and mechanical properties of duplex low carbon steel

Science.gov (United States)

Alfirano; Eben, U. S.; Hidayat, M.

2018-04-01

The microstructures behavior of duplex cold-rolled low carbon steel for automotive applications has been investigated. Intercritical annealing treatment is commonly used to develop a duplex low carbon steel containing ferrite and martensite. To get a duplex phase ferrite and martensite, the specimens were heated at inter-critical annealing temperature of 775°C - 825°C, for heating time up to 20 minutes, followed by water-quenched. The hardness of specimens was studied. The optical microscopy was used to analyze the microstructures. The optimal annealing conditions (martensite volume fraction approaching 20%) at 775°C with a heating time of 10 minutes was achieved. The highest hardness value was obtained in cold-rolled specimens of 41% in size reduction for intercritical annealing temperature of 825°C. In this condition, the hardness value was 373 HVN. The correlation between intercritical annealing temperature and time can be expressed in the transformation kinetics as fγ/fe = 1-exp(-Ktn) wherein K and n are grain growth rate constant and Avrami’s exponent, respectively. From experiment, the value of K = 0.15 and n = 0.461. Using the relationship between temperatures and heating time, activation energy (Q) can be calculated that is 267 kJ/mol.

Design of duplex low carbon steels for improved strength: weight applications

Energy Technology Data Exchange (ETDEWEB)

Koo, J.

1977-08-01

Duplex ferrite-martensite (DFM) steels with excellent combinations of strength and formability have been selected from first principles, and their microstructure-property relationships established through a systematic investigation of a series of ternary Fe/X/0.1 C steels (X being varying amount of Cr and Si). Duplex processing consists of initial austenitization and quenching to form 100% martensite, followed by annealing in the (..cap alpha.. + ..gamma..) range and subsequent quenching. The resultant DFM morphology is controlled by the type and amount of alloying element X.

Residual stresses and fatigue in a duplex stainless steel

International Nuclear Information System (INIS)

Johansson, Johan

1999-01-01

Duplex stainless steels, consisting of approximately equal amounts of austenite and ferrite, often combine the best features of austenitic and ferritic stainless steels. They generally have good mechanical properties, including high strength and ductility, and the corrosion resistance is often better than conventional austenitic grades. This has lead to a growing use of duplex stainless steels as a material in mechanically loaded constructions. However, detailed knowledge regarding its mechanical properties and deformation mechanisms are still lacking. In this thesis special emphasis has been placed on the residual stresses and their influence on mechanical behaviour of duplex stainless steels. Due to the difference in coefficient of thermal expansion between the two phases, tensile microstresses are found in the austenitic phase and balancing compressive microstresses in the ferritic phase. The first part of this thesis is a literature survey, which will give an introduction to duplex stainless steels and review the fatigue properties of duplex stainless steels and the influence of residual stresses in two-phase material. The second part concerns the evolution of the residual stress state during uniaxial loading. Initial residual stresses were found to be almost two times higher in the transverse direction compared to the rolling direction. During loading the absolute value of the microstresses increased in the macroscopic elastic regime but started to decrease with increasing load in the macroscopic plastic regime. A significant increase of the microstresses was also found to occur during unloading. Finite element simulations also show stress variation within one phase and a strong influence of both the elastic and plastic anisotropy of the individual phases on the simulated stress state. In the third part, the load sharing between the phases during cyclic loading is studied. X-ray diffraction stress analysis and transmission electron microscopy show that even if

Residual stresses and fatigue in a duplex stainless steel

Energy Technology Data Exchange (ETDEWEB)

Johansson, Johan

1999-05-01

Duplex stainless steels, consisting of approximately equal amounts of austenite and ferrite, often combine the best features of austenitic and ferritic stainless steels. They generally have good mechanical properties, including high strength and ductility, and the corrosion resistance is often better than conventional austenitic grades. This has lead to a growing use of duplex stainless steels as a material in mechanically loaded constructions. However, detailed knowledge regarding its mechanical properties and deformation mechanisms are still lacking. In this thesis special emphasis has been placed on the residual stresses and their influence on mechanical behaviour of duplex stainless steels. Due to the difference in coefficient of thermal expansion between the two phases, tensile microstresses are found in the austenitic phase and balancing compressive microstresses in the ferritic phase. The first part of this thesis is a literature survey, which will give an introduction to duplex stainless steels and review the fatigue properties of duplex stainless steels and the influence of residual stresses in two-phase material. The second part concerns the evolution of the residual stress state during uniaxial loading. Initial residual stresses were found to be almost two times higher in the transverse direction compared to the rolling direction. During loading the absolute value of the microstresses increased in the macroscopic elastic regime but started to decrease with increasing load in the macroscopic plastic regime. A significant increase of the microstresses was also found to occur during unloading. Finite element simulations also show stress variation within one phase and a strong influence of both the elastic and plastic anisotropy of the individual phases on the simulated stress state. In the third part, the load sharing between the phases during cyclic loading is studied. X-ray diffraction stress analysis and transmission electron microscopy show that even if

"Estudio tribologico de aceros para moldes. Aplicacion al moldeo por inyeccion de polibutilentereftalato reforzado con fibra de vidrio"

Science.gov (United States)

Martinez Mateo, Isidoro Jose

fabricacion del molde, tienen una gran influencia sobre su comportamiento en servicio a lo largo de la vida util del molde. En la primera parte del presente estudio, a partir de ensayos punzon sobre disco, se ha determinado la relacion entre la resistencia al desgaste y la dureza de aceros para moldes obtenidos a partir de bloques de gran espesor, estudiando los principales mecanismos de desgaste que tienen lugar. A continuacion, con el fin de determinar el dano superficial que sufren los aceros para moldes en condiciones reales de inyeccion, se han estudiado distintos tipos de aceros utilizados comercialmente en moldes de inyeccion de polimeros y materiales compuestos, seleccionando las condiciones de operacion para determinar la variacion de la rugosidad superficial del acero en funcion del material inyectado, del numero de operaciones sucesivas de inyeccion y de la orientacion del flujo de inyeccion, mediante tecnicas de perfilometria optica y microscopia electronica de barrido. Ademas del dano superficial sufrido por el acero con el numero de piezas inyectadas, tambien se ha determinado la evolucion de la rugosidad superficial de los materiales inyectados, polibutilentereftalato (PBT) puro y materiales compuestos derivados de PBT por adicion de un 20 o un 50% en peso de fibra de vidrio. En el caso de las piezas inyectadas, se ha caracterizado su microestructura en funcion del flujo de inyeccion y de la densidad de fibra, se han determinado sus propiedades termicas y dinamico-mecanicas, asi como la variacion de la rugosidad superficial de las piezas inyectadas con el numero de operaciones de inyeccion y con la geometria de las distintas secciones de las piezas. Finalmente, se ha evaluado la resistencia a la abrasion de PBT reforzado con un 50% de fibra, en funcion del numero de piezas inyectadas y de la direccion de rayado con respecto a la orientacion del flujo de inyeccion.

Microestructuras producidas en la soldadura de unión de aceros para tuberías de gran diámetro

Directory of Open Access Journals (Sweden)

Salazar, M.

1998-12-01

Full Text Available This is an evaluation of the microstructure in the heat affected zone (HAZ of steel weldings used in pipe lines. The welding was made by shielding metal are welding. This is a welding process with multiple run and low heat input, however local brittle zones are present in the HAZ. These are originated by a complex mechanism that is influenced by welding parameters and chemical composition of the steel. The welding sequences that help to eliminate the local brittle zones are studied.

En este trabajo se estudian las microestructuras producidas en la zona afectada por el calor (HAZ de la soldadura de unión en aceros utilizados en la construcción de poliductos. Se analizan las juntas obtenidas mediante soldadura manual con electrodo revestido. A pesar de que este es un proceso de soldadura con un bajo aporte térmico, se encuentran zonas frágiles locales que se originan por un mecanismo complejo influido por parámetros de soldadura y composición química del acero. Se analizan secuencias de soldaduras que ayuden a la desaparición de las mismas.

Producción de aceros al carbono en hornos de arco eléctrico en condiciones de mineral de manganeso. // Steel production in electric arc furnaces in the condition of use of manganese.

Directory of Open Access Journals (Sweden)

E. E. Navas Medina

2007-05-01

Full Text Available El presente trabajo constituye una segunda etapa de investigación relacionada con la producción de acero en hornos de arcoeléctrico con revestimiento básico en condiciones de utilización de mineral de manganeso como sustituto del ferromanganeso.En la investigación se caracteriza el acero producido utilizando el mineral de manganeso en dos variantes tecnológicasdiferentes y se determinan parámetros importantes, tales como la estructura del acero obtenido, la influencia de lacomposición química y la temperatura en la reducción del Mn. Adicionalmente, se determina la composición química de laescoria, su basicidad e influencia en el aprovechamiento del Mn del mineral, así como, lo que significa la sustitución delFeMn en la problemática medioambiental.Palabras claves: Producción de aceros al carbono, hornos de arco eléctricos, mineral de manganeso.______________________________________________________________________________Abstract:This present work constitutes the second stage of investigation in relation with the steel production bymeans of electric arc furnaces in the condition of use of manganese ores as a substitute of theferromanganese. In the investigation, the steel manufactured is analyzed the manganese ore in twodifferent technological variants and some important parameters are determined such as: the chemicalcomposition's structure of the steel, the influence of temperature in the reduction of Mn. Moreover, ananalysis of the chemical composition of the slag and the influence in the environmental is realized.Key words: Carbon steel production, electric arc furnaces, manganese mineral.

Phase transformations evaluation on a UNS S31803 duplex stainless steel based on nondestructive testing

International Nuclear Information System (INIS)

Macedo Silva, Edgard de; Costa de Albuquerque, Victor Hugo; Pereira Leite, Josinaldo; Gomes Varela, Antonio Carlos; Pinho de Moura, Elineudo; Tavares, Joao Manuel R.S.

2009-01-01

Duplex stainless steel presents special mechanical properties such as, for example, mechanical and corrosion strength, becoming competitive in relation to the other types of stainless steel. One of the great problems of duplex stainless steel microstructural changes study is related to embrittlement above 300 deg. C, with the precipitation of the α' phase occurring over the ferritic microstructure. Aiming to characterise embrittlement of duplex stainless steel, hardening kinetics, from 425 to 475 deg. C, was analysed through the speed of sound, Charpy impact energy, X-ray diffraction, hardness and microscopy parameters. The presence of two hardening stages, detected through the speed of sound, was observed, one being of brittle characteristic and the other ductile. Moreover, the speed of sound showed a direct correlation with the material's hardness. Thus, it is concluded that the speed of sound is a promising nondestructive parameter to follow-up embrittlement in duplex stainless steel.

Increased Y-chromosome detection by SRY duplexing

DEFF Research Database (Denmark)

Hansen, Morten Høgh; Clausen, Frederik Banch; Dziegiel, Morten Hanefeld

2012-01-01

Determining fetal sex noninvasively is dependent of a robust assay. We designed a novel SRY assay and combined it with a SRY assay from literature forming a duplex assay with the same fluorescent dye to increase detection of Y-chromosome at low cell-free fetal DNA or chimeric DNA concentrations....

Mechanical Deformation Behavior of Lean Duplex 329LA Steel

Energy Technology Data Exchange (ETDEWEB)

Yoon, Byung-Jun [Research Institute of Industrial Science and Technology, Pohang (Korea, Republic of); Choi, Jeom-Yong [POSCO Technical Research Lab., Pohang (Korea, Republic of); Park, Kyung-Tae [Hanvat National University, Daejeon (Korea, Republic of); Lee, Ho Seong [Kyungpook National University, Daegu (Korea, Republic of)

2015-09-15

The tensile response of Lean Duplex 329LA stainless steel was investigated over various strain rates. It was observed that the mechanical response, including in particular the total elongation of the tested alloy, was strongly affected by the strain rate. As the strain rate decreased from 10-1 s-1 to 10-4 s-1, the elongation increased. As the strain rate increased, the deformation mode in an austenite phase was dominated by dislocation glide, resulting in deterioration of the elongation. The substructure of the ferritic phase showed a dislocation cell structure, independent of the applied strain rate. The optimum mechanical properties of lean duplex stainless steel thus can be obtained by controlling the deformation mode in the austenitic phase.

Mechanical Deformation Behavior of Lean Duplex 329LA Steel

International Nuclear Information System (INIS)

Yoon, Byung-Jun; Choi, Jeom-Yong; Park, Kyung-Tae; Lee, Ho Seong

2015-01-01

The tensile response of Lean Duplex 329LA stainless steel was investigated over various strain rates. It was observed that the mechanical response, including in particular the total elongation of the tested alloy, was strongly affected by the strain rate. As the strain rate decreased from 10-1 s-1 to 10-4 s-1, the elongation increased. As the strain rate increased, the deformation mode in an austenite phase was dominated by dislocation glide, resulting in deterioration of the elongation. The substructure of the ferritic phase showed a dislocation cell structure, independent of the applied strain rate. The optimum mechanical properties of lean duplex stainless steel thus can be obtained by controlling the deformation mode in the austenitic phase.

Aging behaviour of 25Cr-17Mn high nitrogen duplex stainless steel

OpenAIRE

Machado, I. F.; Padilha, A. F.

2000-01-01

The precipitation behaviour of a nickel free stainless steel containing 25% chromium, 17% manganese and 0.54% nitrogen, with duplex ferritic-austenitic microstructure, was studied using several complementary techniques of microstructural analysis after aging heat treatments between 600 and 1 000 degrees C for periods of lime between 15 and 6 000 min. During aging heat treatments, ferrite was decomposed into sigma phase and austenite by a eutectoid reaction, like in the Fe-Cr-Ni duplex stainle...

Comparison of simulated and measured quantities of a duplex reactor

Energy Technology Data Exchange (ETDEWEB)

Koskela, M.; Kajava, M. [ABB Marine, Helsinki (Finland)

1997-12-31

The purpose of this article is to illustrate the use of an analog simulator as a design tool when designing new power electric equipment. The purpose of simulation is to predict the functionality of electrical equipment to be constructed. Duplex reactor is an electromagnetic device designed to reduce voltage harmonics and short circuit currents in the ship electrical network. In this report a comparison between simulated and measured electrical quantities of a duplex reactor has been made. The purpose of the measurements was to show the correct functioning of the reactor. The simulation results and the measured waveforms corresponds well to each other. (orig.) 4 refs.

Phosphate coating on stainless steel 304 sensitized;Recubrimiento fosfatado sobre acero inoxidable 304 sensibilizado

Energy Technology Data Exchange (ETDEWEB)

Cruz V, J. P. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira, Km. 14.5 Carretera Tampico-Puerto Industrial Altamira, 89600 Altamira, Tamaulipas (Mexico); Vite T, J. [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico); Castillo S, M.; Vite T, M., E-mail: jpcruz@ipn.m [IPN, Escuela Superior de Ingenieria Mecanica y Electrica, Seccion de Estudios de Posgrado e Investigacion, Unidad Profesional -Adolfo Lopez Mateos-, Zacatenco, 07738 Mexico, D. F. (Mexico)

2009-07-01

The stainless steel 304 can be sensitized when welding processes are applied, that causes the precipitation of chromium carbide in the grain limits, being promoted in this way the formation of galvanic cells and consequently the corrosion process. Using a phosphate coating is possible to retard the physiochemical damages that can to happen in the corrosion process. The stainless steel 304 substrate sensitized it is phosphate to base of Zn-Mn, in a immersion cell very hot. During the process was considered optimization values, for the characterization equipment of X-rays diffraction and scanning electron microscopy was used. The XRD technique confirmed the presence of the phases of manganese phosphate, zinc phosphate, as well as the phase of the stainless steel 304. When increasing the temperature from 60 to 90 C in the immersion process a homogeneous coating is obtained. (Author)

Characterization of duplex stainless steel weld metals obtained by hybrid plasma-gas metal arc welding

Directory of Open Access Journals (Sweden)

Koray Yurtisik

2013-09-01

Full Text Available Despite its high efficiency, autogenous keyhole welding is not well-accepted for duplex stainless steels because it causes excessive ferrite in as-welded duplex microstructure, which leads to a degradation in toughness and corrosion properties of the material. Combining the deep penetration characteristics of plasma arc welding in keyhole mode and metal deposition capability of gas metal arc welding, hybrid plasma - gas metal arc welding process has considered for providing a proper duplex microstructure without compromising the welding efficiency. 11.1 mm-thick standard duplex stainless steel plates were joined in a single-pass using this novel technique. Same plates were also subjected to conventional gas metal arc and plasma arc welding processes, providing benchmarks for the investigation of the weldability of the material. In the first place, the hybrid welding process enabled us to achieve less heat input compared to gas metal arc welding. Consequently, the precipitation of secondary phases, which are known to be detrimental to the toughness and corrosion resistance of duplex stainless steels, was significantly suppressed in both fusion and heat affected zones. Secondly, contrary to other keyhole techniques, proper cooling time and weld metal chemistry were achieved during the process, facilitating sufficient reconstructive transformation of austenite in the ferrite phase.

Concurrent infections of pseudorabies virus and porcine bocavirus in China detected by duplex nanoPCR.

Science.gov (United States)

Luo, Yakun; Liang, Lin; Zhou, Ling; Zhao, Kai; Cui, Shangjin

2015-07-01

Nanoparticle-assisted polymerase chain reaction (nanoPCR) is a novel method for the simple, rapid, and specific amplification of DNA and has been used to detect viruses. A duplex nanoPCR molecular detection system was developed to detect pseudorabies virus (PRV) and porcine bocavirus (PBoV). Primers were selected to target conserved regions within the PRV gE gene and the PBoV NS1 gene. Under optimized nanoPCR reaction conditions, two specific fragments of 316 bp (PRV) and 996 bp (PBoV) were amplified by the duplex nanoPCR with a detection limit of 6 copies for PRV and 95 copies for PBoV; no fragments were amplified when other porcine viruses were used as template. When used to test 550 clinical samples, the duplex nanoPRC assay and a conventional duplex PCR assay provided very similar results (98.1% consistency); single PRV infections, single PBoV infections, and concurrent PRV and PBoV infections were detected in 37%, 15%, and 9% of the samples, respectively. The results indicate that the novel duplex nanoPCR assay is useful for the rapid detection of PRV and PBoV in pigs. Copyright © 2015 Elsevier B.V. All rights reserved.

Recubrimiento de Stellite 6 sobre acero inoxidable realizado con láser de CO₂ para válvulas de escape de motores diesel

Directory of Open Access Journals (Sweden)

Cadenas, M.

2002-12-01

Full Text Available To reduce the recovery or the replacement costs of diesel engine exhaust valves, they are manufactured with an economic base material, and a coating which is deposited on the seat valve in order to reach high hardness and good impact, corrosion and high temperature wear resistance (>550 °C and without lubrication. In this work, appropriate laser cladding parameters have been determined to obtain Stellite 6 coatings over AISI 304 steel (as plane test specimens and SAE EV8 steel (as valves substrates. One and two superimposed tracks were deposited on the seat valves, and modifying the laser power as a function of the rotated angle at the beginning and the end of the circular tracks, pores and cracks have been minimized and the thickness of the track were made uniform. Hardness, dilution and final microstructure of the different coatings have been analysed. A 10 % dilution and 550 HV in the tracks over plane test specimens was observed, while valves with one track showed 25 % and 430 HV respectively. With two superimposed tracks the hardness was up to 470 HV in the upper track.

Para abaratar el coste de recuperación o sustitución de válvulas de escape en motores diesel, estas se fabrican con un material base económico, recubriéndose el asiento de la válvula con otro material al que se exigirá elevada dureza y buena resistencia al impacto, a la corrosión y al desgaste erosivo en caliente (>550 °C y sin lubricación. Partiendo de esta idea, en el presente trabajo se han determinado los parámetros adecuados para realizar, mediante la técnica de plaqueado láser, un recubrimiento con Stellite 6, sobre sustratos de acero AISI 304 (probetas planas y SAE EV8 (válvulas reales. Sobre las válvulas, se depositaron uno y dos cordones superpuestos, se minimizó la presencia de poros y grietas, modificando el grado de solape inicial y final de los cordones circulares y la potencia en función del ángulo girado. Así, se

Interference alignment for degrees of freedom improvement in 3-relay half-duplex systems

KAUST Repository

Park, Seongho

2011-12-01

In a half-duplex relaying, the capacity pre-log factor is a major drawback in spectral efficiency. This paper proposes a linear precoding scheme and an alternate relaying protocol in a dual-hop half-duplex system where three relays help the communication between the source and the destination. In our proposed scheme, we consider a phase incoherent method in relays in which the source alternately transmits message signals to the different relays. In addition, we propose a linear interference alignment scheme which can eliminate the inter-relay interference resulted from the phase incoherence of relaying. Based on our analysis of degrees of freedom and our simulation results, we show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying. © 2011 IEEE.

Structural Insights into the Quadruplex-Duplex 3' Interface Formed from a Telomeric Repeat: A Potential Molecular Target.

Science.gov (United States)

Russo Krauss, Irene; Ramaswamy, Sneha; Neidle, Stephen; Haider, Shozeb; Parkinson, Gary N

2016-02-03

We report here on an X-ray crystallographic and molecular modeling investigation into the complex 3' interface formed between putative parallel stranded G-quadruplexes and a duplex DNA sequence constructed from the human telomeric repeat sequence TTAGGG. Our crystallographic approach provides a detailed snapshot of a telomeric 3' quadruplex-duplex junction: a junction that appears to have the potential to form a unique molecular target for small molecule binding and interference with telomere-related functions. This unique target is particularly relevant as current high-affinity compounds that bind putative G-quadruplex forming sequences only rarely have a high degree of selectivity for a particular quadruplex. Here DNA junctions were assembled using different putative quadruplex-forming scaffolds linked at the 3' end to a telomeric duplex sequence and annealed to a complementary strand. We successfully generated a series of G-quadruplex-duplex containing crystals, both alone and in the presence of ligands. The structures demonstrate the formation of a parallel folded G-quadruplex and a B-form duplex DNA stacked coaxially. Most strikingly, structural data reveals the consistent formation of a TAT triad platform between the two motifs. This triad allows for a continuous stack of bases to link the quadruplex motif with the duplex region. For these crystal structures formed in the absence of ligands, the TAT triad interface occludes ligand binding at the 3' quadruplex-duplex interface, in agreement with in silico docking predictions. However, with the rearrangement of a single nucleotide, a stable pocket can be produced, thus providing an opportunity for the binding of selective molecules at the interface.

Development of duplex real-time PCR for the detection of WSSV and PstDV1 in cultivated shrimp.

Science.gov (United States)

Leal, Carlos A G; Carvalho, Alex F; Leite, Rômulo C; Figueiredo, Henrique C P

2014-07-05

The White spot syndrome virus (WSSV) and Penaeus stylirostris penstyldensovirus 1 (previously named Infectious hypodermal and hematopoietic necrosis virus-IHHNV) are two of the most important viral pathogens of penaeid shrimp. Different methods have been applied for diagnosis of these viruses, including Real-time PCR (qPCR) assays. A duplex qPCR method allows the simultaneous detection of two viruses in the same sample, which is more cost-effective than assaying for each virus separately. Currently, an assay for the simultaneous detection of the WSSV and the PstDV1 in shrimp is unavailable. The aim of this study was to develop and standardize a duplex qPCR assay for the simultaneous detection of the WSSV and the PstDV1 in clinical samples of diseased L. vannamei. In addition, to evaluate the performance of two qPCR master mixes with regard to the clinical sensitivity of the qPCR assay, as well as, different methods for qPCR results evaluation. The duplex qPCR assay for detecting WSSV and PstDV1 in clinical samples was successfully standardized. No difference in the amplification of the standard curves was observed between the duplex and singleplex assays. Specificities and sensitivities similar to those of the singleplex assays were obtained using the optimized duplex qPCR. The analytical sensitivities of duplex qPCR were two copies of WSSV control plasmid and 20 copies of PstDV1 control plasmid. The standardized duplex qPCR confirmed the presence of viral DNA in 28 from 43 samples tested. There was no difference for WSSV detection using the two kits and the distinct methods for qPCR results evaluation. High clinical sensitivity for PstDV1 was obtained with TaqMan Universal Master Mix associated with relative threshold evaluation. Three cases of simultaneous infection by the WSSV and the PstDV1 were identified with duplex qPCR. The standardized duplex qPCR was shown to be a robust, highly sensitive, and feasible diagnostic tool for the simultaneous detection of the

The first example of a Hoogsteen base-paired DNA duplex in dynamic equilibrium with a Watson-Crick base-paired duplex--a structural (NMR), kinetic and thermodynamic study.

Science.gov (United States)

Isaksson, J; Zamaratski, E; Maltseva, T V; Agback, P; Kumar, A; Chattopadhyaya, J

2001-06-01

A single-point substitution of the O4' oxygen by a CH2 group at the sugar residue of A6 (i.e. 2'-deoxyaristeromycin moiety) in a self-complementary DNA duplex, 5'-d(C1G2C3G4A5A6T7T8C9G10C11G12)2(-3), has been shown to steer the fully Watson-Crick basepaired DNA duplex (1A), akin to the native counterpart, to a doubly A6:T7 Hoogsteen basepaired (1B) B-type DNA duplex, resulting in a dynamic equilibrium of (1A)(1B): Keq = k1/k(-1) = 0.56+/-0.08. The dynamic conversion of the fully Watson-Crick basepaired (1A) to the partly Hoogsteen basepaired (1B) structure is marginally kinetically and thermodynamically disfavoured [k1 (298K) = 3.9 0.8 sec(-1); deltaHdegrees++ = 164+/-14 kJ/mol; -TdeltaS degrees++ (298K) = -92 kJ/mol giving a deltaG degrees++ 298 of 72 kJ/mol. Ea (k1) = 167 14 kJ/mol] compared to the reverse conversion of the Hoogsteen (1B) to the Watson-Crick (1A) structure [k-1 (298K) = 7.0 0.6 sec-1, deltaH degrees++ = 153 13 kJ/mol; -TdeltaSdegrees++ (298K) = -82 kJ/mol giving a deltaGdegrees++(298) of 71 kJ/mol. Ea (k-1) = 155 13 kJ/mol]. Acomparison of deltaGdegrees++(298) of the forward (k1) and backward (k-1) conversions, (1A)(1B), shows that there is ca 1 kJ/mol preference for the Watson-Crick (1A) over the double Hoogsteen basepaired (1B) DNA duplex, thus giving an equilibrium ratio of almost 2:1 in favour of the fully Watson-Crick basepaired duplex. The chemical environments of the two interconverting DNA duplexes are very different as evident from their widely separated sets of chemical shifts connected by temperature-dependent exchange peaks in the NOESY and ROESY spectra. The fully Watson-Crick basepaired structure (1A) is based on a total of 127 intra, 97 inter and 17 cross-strand distance constraints per strand, whereas the double A6:T7 Hoogsteen basepaired (1B) structure is based on 114 intra, 92 inter and 15 cross-strand distance constraints, giving an average of 22 and 20 NOE distance constraints per residue and strand, respectively. In addition

Base pairing and structural insights into the 5-formylcytosine in RNA duplex

Science.gov (United States)

Wang, Rui; Luo, Zhipu; He, Kaizhang; Delaney, Michael O.; Chen, Doris; Sheng, Jia

2016-01-01

Abstract 5-Formylcytidine (f5C), a previously discovered natural nucleotide in the mitochondrial tRNA of many species including human, has been recently detected as the oxidative product of 5-methylcytidine (m5C) through 5-hydroxymethylcytidine (hm5C) in total RNA of mammalian cells. The discovery indicated that these cytosine derivatives in RNA might also play important epigenetic roles similar as in DNA, which has been intensively investigated in the past few years. In this paper, we studied the base pairing specificity of f5C in different RNA duplex contexts. We found that the 5-formyl group could increase duplex thermal stability and enhance base pairing specificity. We present three high-resolution crystal structures of an octamer RNA duplex [5′-GUA(f5C)GUAC-3′]2 that have been solved under three crystallization conditions with different buffers and pH values. Our results showed that the 5-formyl group is located in the same plane as the cytosine base and forms an intra-residue hydrogen bond with the amino group in the N4 position. In addition, this modification increases the base stacking between the f5C and the neighboring bases while not causing significant global and local structure perturbations. This work provides insights into the effects of 5-formylcytosine on RNA duplex. PMID:27079978

Phase transformations evaluation on a UNS S31803 duplex stainless steel based on nondestructive testing

Energy Technology Data Exchange (ETDEWEB)

Macedo Silva, Edgard de, E-mail: edgard@cefetpb.edu.br [Centro federal de Educacao Tecnologica da Paraiba (CEFET PB), Area da Industria, Avenida 1o de Maio, 720 - 58015-430 - Joao Pessoa/PB (Brazil); Costa de Albuquerque, Victor Hugo, E-mail: victor.albuquerque@fe.up.pt [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Cidade Universitaria, S/N - 58059-900 - Joao Pessoa/PB (Brazil); Pereira Leite, Josinaldo, E-mail: josinaldo@ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Cidade Universitaria, S/N - 58059-900 - Joao Pessoa/PB (Brazil); Gomes Varela, Antonio Carlos, E-mail: varela@cefetpb.edu.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Cidade Universitaria, S/N - 58059-900 - Joao Pessoa/PB (Brazil); Pinho de Moura, Elineudo, E-mail: elineudo@pq.cnpq.br [Universidade Federal do Ceara (UFC), Departamento de Engenharia Metalurgica e de Materiais, Campus do Pici, Bloco 715, 60455-760 - Fortaleza/CE (Brazil); Tavares, Joao Manuel R.S., E-mail: tavares@fe.up.pt [Faculdade de Engenharia da Universidade do Porto (FEUP), Departamento de Engenharia Mecanica e Gestao Industrial (DEMEGI)/Instituto de Engenharia Mecanica e Gestao Industrial - INEGI, Rua Dr. Roberto Frias, s/n, 4200-465 Porto (Portugal)

2009-08-15

Duplex stainless steel presents special mechanical properties such as, for example, mechanical and corrosion strength, becoming competitive in relation to the other types of stainless steel. One of the great problems of duplex stainless steel microstructural changes study is related to embrittlement above 300 deg. C, with the precipitation of the {alpha}' phase occurring over the ferritic microstructure. Aiming to characterise embrittlement of duplex stainless steel, hardening kinetics, from 425 to 475 deg. C, was analysed through the speed of sound, Charpy impact energy, X-ray diffraction, hardness and microscopy parameters. The presence of two hardening stages, detected through the speed of sound, was observed, one being of brittle characteristic and the other ductile. Moreover, the speed of sound showed a direct correlation with the material's hardness. Thus, it is concluded that the speed of sound is a promising nondestructive parameter to follow-up embrittlement in duplex stainless steel.

Influencia del acabado superficial en la permeación de hidrógeno del acero API 5L-X52

Directory of Open Access Journals (Sweden)

Réquiz, R.

2004-02-01

Full Text Available The influence of surface roughness on the corrosion and hydrogen permeation behaviour was evaluated on a type API 5L-X52 steel in deaerated 0.1 M Na₂SO₄ at pH=2. Potentiodynamic polarization curves were employed to determine the electrochemical behaviour of the steel, while the Devanathan-Stachurski technique was used to estimate the hydrogen permeation rate. Additionally, the surface roughness profiles were obtained in order to correlate the changes in the hydrogen permeation rate with different metal surface finishings. The obtained results clearly demonstrate that when the roughness parameters have larger values, the cathodic current of hydrogen evolution increases while the hydrogen entry rate decreases. This effect can be attributed to the microstructural defects induced at the steel surface, such as dislocations, which increase the catalytic activity of the atomic hydrogen favouring its recombination. Also, these defects could allow the atomic hydrogen to remain adsorbed on the steel surface. Both effects could hinder the hydrogen diffusion into the metal since the possibility for this atom of becoming absorbed has been reduced

En el presente trabajo de investigación se evalúa la influencia del acabado superficial, tanto en la corrosión generalizada como en la permeación de hidrógeno del acero API 5L-X52 en solución de Na₂SO₄ 0,1M, a pH=2. El comportamiento electroquímico del acero se estudió mediante las curvas de polarización potenciodinámicas, mientras que la susceptibilidad al daño por hidrógeno se evaluó mediante la técnica de permeación de Devanathan- Stachurski. Además, se determinaron los parámetros de rugosidad a las muestras de acero con diferentes acabados superficiales, para luego correlacionarlos con los cambios en las corrientes de permeación de hidrógeno. Los resultados obtenidos demuestran, claramente, que, cuando la rugosidad superficial del acero

Circumferential welding applied for inox steel super duplex UNS S32750 using the process MIG using CMT® control; Soldagem circunferencial do aço inoxidável super duplex UNS S32750 pelo processo MIG com controle CMT®

Energy Technology Data Exchange (ETDEWEB)

Invernizzi, Bruno Pizol

2017-07-01

This study carried out circumferential welding experiments in UNS S32750 Super Duplex Stainless Steel tubes using diameters of 19,05 mm and 48,20 mm. Welds were performed using various welding parameters on a MIG machine with Cold Metal Transfer® CMT control. The weld joints were evaluated by visual and dimensional inspection in addition to the Vickers microhardness and traction tests, as well as the microstructural analysis in conjunction with phase precipitation analysis, which was performed according to practice A of ASTM A923, and corrosion test in accordance with practice A of ASTM G48 in conjunction with ASTM A923. The results indicated that welds performed in pipes with a diameter of 19.05 mm showed a weld joint with unacceptable dimensions according to the standard, this condition being attributed the use of a high wire diameter for the welding conditions used. Welding performed for pipes with a diameter of 48.20 mm showed a lack of penetration under the conditions employed when welded by the conventional CMT® process. In the case of the use of CMT® combined with pulsed arc, under conditions that generated greater heat input during welding, this resulted in total penetration of the joint and adequate surface finish. The results indicated that welding using the CMT® process combined with pulsed arc, under the conditions (parameters) employed generated good surface finish, combined mechanical properties, meeting standards requirements, as well as a balanced microstructure and high resistance to corrosion. (author)

Development and test evaluation of duplex steam reformer tube

International Nuclear Information System (INIS)

Allen, D.C.; Meyer, D.J.; Pflasterer, G.R.

1980-01-01

For HTR applications involving a steam reformer (SR), it is uncertain whether an intermediate heat exchanger (IHX) is required. There are several system configurations that could be developed for the application of nuclear heat using the steam reformer reaction. The considerations (advantages vs. disadvantages) for each of the system configurations are summarized. The approach that technically and economically appears to be the most attractive, in studies conducted by General Electric, combines the SR process heat exchanger and the IHX in a single component using a duplex tube. A central question concerning the duplex tube concept is whether the design would provide adequate leak monitoring capability and significant reduction in tritium and hydrogen diffusion, while introducing only a small increase in overall temperature difference from the helium to the process gas. A cooperative GE-KFA effort was undertaken to develop, fabricate, test, and evaluate a duplex steam reformer tube. GE was responsible for the development and fabrication of the tube, and KFA was responsible for testing the tube in the EVA I facility at Juelich. Both GE and KFA are evaluating the thermochemical and metallurgical test data. Actual fabrication of the tube was performed by Foster-Wheeler in accordance with the GE design. This paper reviews the highlights of the fabrication development and preliminary evaluation of the test data

Listen and talk full-duplex cognitive radio networks

CERN Document Server

Liao, Yun; Han, Zhu

2016-01-01

This brief focuses on the use of full-duplex radio in cognitive radio networks, presenting a novel spectrum sharing protocol that allows the secondary users to simultaneously sense and access the vacant spectrum. This protocol, called “Listen-and-talk” (LAT), is evaluated by both mathematical analysis and computer simulations in comparison with other existing protocols, including the listen-before-talk protocol. In addition to LAT-based signal processing and resource allocation, the brief discusses techniques such as spectrum sensing and dynamic spectrum access. The brief proposes LAT as a suitable access scheme for cognitive radio networks, which can support the quality-of-service requirements of these high priority applications. Fundamental theories and key techniques of cognitive radio networks are also covered. Listen and Talk: Full-duplex Cognitive Radio Networks is designed for researchers, developers, and professionals involved in cognitive radio networks. Advanced-level students studying signal pr...

Interference Management in Full-Duplex Cellular Networks with Partial Spectrum Overlap

KAUST Repository

Randrianantenaina, Itsikiantsoa

2017-03-31

Full-duplex (FD) communication is promoted to double the spectral efficiency when compared to the halfduplex (HD) counterpart. In the context of cellular networks, however, FD communication exacerbates the aggregate uplink and downlink interference, which diminishes the foreseen FD gains. This paper considers a flexible duplex system, denoted by -duplex (-D) system, wherein a fine-grained bandwidth control for each uplink/downlink channel pair in each base station (BS) is allowed, which also leads to partial spectrum overlap between the uplink and downlink channels. The paper addresses the resulting interference management problem by maximizing a network-wide rate-based utility function subject to uplink/downlink power constraints, so as to determine userto- BS association, user-to-channel scheduling, the UL and DL transmit powers, and the fraction of spectrum overlap between UL and DL for every user, under the assumption that the number of available channels and users are equal. The paper solves such a non-convex mixed-integer optimization problem in an iterative way by decoupling the problem into several subproblems. Particularly, the user-to-BS association problem is solved using a matching algorithm that is a generalization of the stable marriage problem. The scheduling problem is solved by iterative Hungarian algorithm. The power and spectrum overlap problem is solved by successive convex approximation. The proposed iterative strategy guarantees an efficient one-toone user to BS and channel assignment. It further provides optimized flexible duplexing and power allocation schemes for all transceivers. Simulations results show appreciable gains when comparing the proposed solution to different schemes from the literature.

Hybrid recursive active filters for duplexing in RF transmitter front-ends

Science.gov (United States)

Gottardo, Giuseppe; Donati, Giovanni; Musolff, Christian; Fischer, Georg; Felgentreff, Tilman

2016-08-01

Duplex filters in modern base transceiver stations shape the channel in order to perform common frequency division duplex operations. Usually, they are designed as cavity filters, which are expensive and have large dimensions. Thanks to the emerging digital technology and fast digital converters, it is possible to transfer the efforts of designing analog duplex filters into digital numeric algorithms applied to feedback structures, operating on power. This solution provides the shaping of the signal spectrum directly at the output of the radio frequency (RF) power amplifiers (PAs) relaxing the transmitter design especially in the duplexer and in the antenna sections. The design of a digital baseband feedback applied to the analog power RF amplifiers (hybrid filter) is presented and verified by measurements. A model to describe the hybrid system is investigated, and the relation between phase and resonance peaks of the resulting periodic band-pass transfer function is described. The stability condition of the system is analyzed using Nyquist criterion. A solution involving a number of digital feedback and forward branches is investigated defining the parameters of the recursive structure. This solution allows the closed loop system to show a periodic band pass with up to 500 kHz bandwidth at the output of the RF amplifier. The band-pass magnitude reaches up to 17 dB selectivity. The rejection of the PA noise in the out-of-band frequencies is verified by measurements. The filter is tested with a modulated LTE (Long Term Evolution) signal showing an ACPR (Adjacent Channel Power Ratio) enhancement of 10 dB of the transmitted signal.

Interference Management in Full-Duplex Cellular Networks with Partial Spectrum Overlap

KAUST Repository

Randrianantenaina, Itsikiantsoa; Dahrouj, Hayssam; Elsawy, Hesham; Alouini, Mohamed-Slim

2017-01-01

Full-duplex (FD) communication is promoted to double the spectral efficiency when compared to the halfduplex (HD) counterpart. In the context of cellular networks, however, FD communication exacerbates the aggregate uplink and downlink interference, which diminishes the foreseen FD gains. This paper considers a flexible duplex system, denoted by -duplex (-D) system, wherein a fine-grained bandwidth control for each uplink/downlink channel pair in each base station (BS) is allowed, which also leads to partial spectrum overlap between the uplink and downlink channels. The paper addresses the resulting interference management problem by maximizing a network-wide rate-based utility function subject to uplink/downlink power constraints, so as to determine userto- BS association, user-to-channel scheduling, the UL and DL transmit powers, and the fraction of spectrum overlap between UL and DL for every user, under the assumption that the number of available channels and users are equal. The paper solves such a non-convex mixed-integer optimization problem in an iterative way by decoupling the problem into several subproblems. Particularly, the user-to-BS association problem is solved using a matching algorithm that is a generalization of the stable marriage problem. The scheduling problem is solved by iterative Hungarian algorithm. The power and spectrum overlap problem is solved by successive convex approximation. The proposed iterative strategy guarantees an efficient one-toone user to BS and channel assignment. It further provides optimized flexible duplexing and power allocation schemes for all transceivers. Simulations results show appreciable gains when comparing the proposed solution to different schemes from the literature.

Duplex-assisted carotid artery stenting without administration of contrast medium for patients with chronic kidney disease or allergic reaction.

Science.gov (United States)

Mizowaki, Takashi; Fujita, Atsushi; Imahori, Taichiro; Uyama, Atsushi; Inoue, Satoshi; Kohta, Masaaki; Hamaguchi, Hirotoshi; Sasayama, Takashi; Hosoda, Kohkichi; Kohmura, Eiji

2016-07-01

We aimed to investigate the safety and feasibility of duplex-assisted carotid artery stenting (CAS) without administration of contrast medium for the prevention of adverse reactions. Fifteen patients (9 % of all CASs) with severe carotid stenosis (≥70 %) associated with chronic kidney disease (CKD) (stage ≥3) or allergy to contrast medium underwent duplex-assisted CAS without administration of contrast medium over 4 years. The procedural success rate and perioperative complication rates were compared between the duplex-assisted CAS (n = 15) and conventional CAS (n = 153) groups. The technical success rate was 100 % in both groups. Combined stroke or death rates during the post-procedural period did not differ significantly between the duplex-assisted CAS group (0/15, 0 %) and conventional CAS group (4/153, 2.6 %). None of the 14 patients with CKD in the duplex-assisted CAS group experienced further deterioration of renal function. The mean surface radiation dose of participants in the duplex-assisted CAS group (n = 13, 312 ± 131 mGy) was significantly lower than that of the conventional CAS group (n = 31, 1036 ± 571 mGy) (p duplex-assisted CAS group (156 ± 39.7 min) and the conventional CAS group (156 ± 37.4 min). Duplex-assisted CAS without administration of contrast medium could be an alternative option in selected patients deemed to be at high risk for renal failure from nephrotoxic contrast medium or who have an allergy to contrast medium.

Thermal ageing of duplex stainless steels

International Nuclear Information System (INIS)

Massoud, J.P.; Van Duysen, J.C.; Zacharie, G.; Auger, P.; Danoix, F.

1992-03-01

The evolution of the mechanical properties of Mobearing anf Mo-free cast duplex stainless steels, induced by long term ageing in the range 300-400 deg C, has been studied in relation with the evolution of their microstructure. The unmixing of the ferritic Fe-Cr-Ni, solid solution by three-dimensional (sponge-like) spinodal decomposition and the precipitation of intermetallic G-phase particles are the main characteristics of this microstructural evolution

DISEÑO DE UN PROTOTIPO FERMENTADOR DE LECHE SEMIAUTOMÁTICO PARA LA ELABORACIÓN DE SUERO COSTEÑO

Directory of Open Access Journals (Sweden)

BASHIR YACUB B.

Full Text Available El Suero Costeño es un producto lácteo fermentado, artesanalmente en la costa atlántica colombiana. Para cumplir con las normas sanitarias el fermentador está constituido por un tanque diseñado y fabricado en acero inoxidable 304, con un volumen neto de 30 L. Se garantizó una temperatura de 35°C en la fermentación de la leche, con un sistema de enfriamiento mediante una chaqueta. La temperatura se medió con un sensor de temperatura, tipo PT-100, con el sistema microcontrolado se programó su set-point, para separar el espiche del suero se utilizó una válvula; la finalización de la fermentación se determinó con la medición del pH con un pH-metro. La cantidad de materia prima y producto se mide con un sensor de nivel y se muestra de manera continua en la pantalla LCD del panel de control.

Comments on process of duplex coatings on aluminum alloys

Institute of Scientific and Technical Information of China (English)

Samir H.A.; QIAN Han-cheng(钱翰城); XIA Bo-cai(夏伯才); WU Shi-ming(吴仕明)

2004-01-01

Despite the great achievements made in improvement of wear resistance properties of aluminum alloys,their applications in heavy surface load-bearing are limited. Single coating is insufficient to produce the desired combination of surface properties. These problems can be solved through the duplex coatings. The aim of the present study is to overview the research advances on processes of duplex coatings on aluminum alloys combined with micro plasma oxidation process and with other modern processes such as physical vapour deposition and plasma assisted chemical vapour deposition and also to evaluate the performance of micro plasma oxidation coatings in improving the load-bearing, friction and wear resistance properties of aluminum alloys in comparison with other coatings. Wherein, a more detailed presentation of the processes and their performances and disadvantages are given as well.

Duplex surface treatment of AISI 1045 steel via plasma nitriding of chromized layer

International Nuclear Information System (INIS)

Hakami, F.; Sohi, M. Heydarzadeh; Ghani, J. Rasizadeh

2011-01-01

In this work AISI 1045 steel were duplex treated via plasma nitriding of chromized layer. Samples were pack chromized by using a powder mixture consisting of ferrochromium, ammonium chloride and alumina at 1273 K for 5 h. The samples were then plasma-nitrided for 5 h at 803 K and 823 K, in a gas mixture of 75%N 2 + 25%H 2 . The treated specimens were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and Vickers micro-hardness test. The thickness of chromized layer before nitriding was about 8 μm and it was increased after plasma nitriding. According to XRD analysis, the chromized layer was composed of chromium and iron carbides. Plasma nitriding of chromized layer resulted in the formation of chromium and iron nitrides and carbides. The hardness of the duplex layers was significantly higher than the hardness of the base material or chromized layer. The main cause of the large improvement in surface hardness was due to the formation of Cr x N and Fe x N phases in the duplex treated layers. Increasing of nitriding temperature from 803 to 823 K enhanced the formation of CrN in the duplex treated layer and increased the thickness of the nitrided layer.

Development of dansyl-modified oligonucleotide probes responding to structural changes in a duplex.

Science.gov (United States)

Suzuki, Yoshio; Kowata, Keiko; Komatsu, Yasuo

2013-11-15

We have synthesized a nonnucleoside amidite block of dansyl fluorophore to prepare dansyl-modified oligonucleotides (ONTs). The fluorescence intensities of dansyl-ONT specifically increased by the presence of adjacent guanosine residues but, significantly reduced in a dansyl-flipping duplex. These changes were caused by solvatochromism effect due to the number of guanine which is hydrophobic functional group and the external environment of dansyl group. The fluorescence intensities could be plotted as a function of the ONTs concentrations and the increase in the fluorescence was observed to equimolar concentrations of target DNA. This duplex exhibited higher melting temperature relative to the corresponding duplexes containing other base pairs. Similar changes in fluorescence could be detected upon hybridization with complementary RNAs. Thus, the dansyl-modified ONTs provide sequence specific fluorescent probe of DNA and RNA. Copyright © 2013 Elsevier Ltd. All rights reserved.

Law of mixture used to model the flow behavior of a duplex stainless steel at high temperatures

International Nuclear Information System (INIS)

Momeni, A.; Dehghani, K.; Poletti, M.C.

2013-01-01

In this investigation the flow curves of a duplex stainless steel were drawn by performing hot compression tests over a wide temperature range of 950–1200 °C and strain rates of 0.001–100 s −1 . The flow curves of ferrite and austenite phases in the duplex structure were depicted by conducting similar hot compression tests on two steels that were cast and prepared with the same chemical compositions. The flow curves of the austenitic steel were found typical of dynamic recrystallization. They were successfully modeled by using the experimental exponential equation proposed by Cingara and McQueen. The flow curves of the ferritic steel were typical of dynamic recovery. They were modeled by the dislocation density evolution function proposed by Estrin and Meckning. Comparing the flow curves of three studied steels, it was found that the flow curves of the duplex steel were very similar and close to those of the ferrite steel. It was understood that in a duplex structure of ferrite and austenite the flow behavior is mostly controlled by the softer phase, i.e. ferrite. The law of mixture was modified to consider the strain partitioning between ferrite and austenite. The distribution coefficients of ferrite and austenite were described and determined at different deformation conditions. The results of modeling satisfactorily predicted the experimental curves. It was shown that the influence of austenite on the flow behavior of the duplex structure is almost low. However, it increases as strain rate or temperature rises. - Highlights: ► Flow curves of austenite and ferrite in the duplex steel were modeled separately. ► The flow behavior of the duplex steel is mostly controlled by ferrite. ► The effect of austenite on flow curve increases with temperature and strain rate. ► The flow curve of the duplex steel is modeled by the modified law of mixture

Contribution to the metallurgy of welding processes in stainless ferritic-austenitic (duplex) steels

International Nuclear Information System (INIS)

Perteneder, E.; Toesch, J.; Rabensteiner, G.

1989-01-01

Duplex steels have a ferritic austenitic structure. Therefore, to obtain a successful welding, special metallurgical regulations must be observed. The effect of energy per unit length and plate thickness onto the heat influence zone in case of manual arc welding is examined. Practice-oriented instructions for the welding technique to be applied are deduced from the results. Finally, the effect of the alloy composition onto the welding capacity of duplex steels is examined. (orig.) [de

Structural studies of the 5'-phenazinium-tethered matched and G-A-mismatched DNA duplexes by NMR spectroscopy.

Science.gov (United States)

Maltseva, T; Sandström, A; Ivanova, I M; Sergeyev, D S; Zarytova, V F; Chattopadhyaya, J

1993-05-01

The mechanism through which modified oligo-DNA analogues act as antisense repressors at the transcriptional and translational level of gene expression is based on the information content in the nucleotide sequence which is determined by the specific base pairing. The efficiency of such action is largely determined by the stability of the duplex formed between the oligonucleotide reagent and the target sequence and also by the mismatched base pairing, such as G-A, that occurs during replication or recombination. We herein report that the phenazinium (Pzn)-tethered matched duplex p(d(TGTTTGGC)):(Pzn)-p(d(CCAAACA)) (III) (Tm = 50 degrees C) has a much larger stability than the parent matched duplex p(d(TGTTTGGC)):p(d(CCAAACA)) (I) (Tm = 30 degrees C). On the other hand, the Pzn-tethered G-A-mismatched duplex p(d(TGTTTGGC)):(Pzn)-p(d(ACAAACA)) (IV) (Tm = 34 degrees C) is only slightly more stable than its parent mismatched duplex p(d(TGTTTGGC)):p(d(ACAAACA)) (Tm = 25 degrees C). A detailed 500 MHz NMR study and constrained MD refinements of NMR-derived structures have been undertaken for the DNA duplexes (I), (II), (III) and (IV) in order to understand the structural basis of stabilization of Pzn-tethered matched DNA duplex (delta Tm = 20 degrees C) compared to mismatched duplex (delta Tm = 9 degrees C). Assignment of the 1H-NMR (500 MHz) spectra of the duplexes has been carried out by 2D NOESY, HOHAHA and DQF-COSY experiments. The torsion angles have been extracted from the J-coupling constants obtained by simulation of most of the DQF-COSY cross-peaks using program SMART. The solution structure of the duplexes were assessed by an iterative hybride relaxation matrix method (MORASS) combined with NOESY distances and torsion angles restrained molecular dynamics (MD) using program Amber 4.0. The standard Amber 4.0 force-field parameters were used for the oligonucleotide in conjunction with the new parameters for Pzn residue which was obtained by full geometry

A full-duplex CATV/wireless-over-fiber lightwave transmission system.

Science.gov (United States)

Li, Chung-Yi; Lu, Hai-Han; Ying, Cheng-Ling; Cheng, Chun-Jen; Lin, Che-Yu; Wan, Zhi-Wei; Chen, Jian-Hua

2015-04-06

A full-duplex CATV/wireless-over-fiber lightwave transmission system consisting of one broadband light source (BLS), two optical interleavers (ILs), one intensity modulator, and one phase modulator is proposed and experimentally demonstrated. The downstream light is optically promoted from 10Gbps/25GHz microwave (MW) data signal to 10Gbps/100GHz and 10Gbps/50GHz millimeter-wave (MMW) data signals in fiber-wireless convergence, and intensity-modulated with 50-550 MHz CATV signal. For up-link transmission, the downstream light is phase-remodulated with 10Gbps/25GHz MW data signal in fiber-wireless convergence. Over a 40-km single-mode fiber (SMF) and a 10-m radio frequency (RF) wireless transport, bit error rate (BER), carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple-beat (CTB) are observed to perform well in such full-duplex CATV/wireless-over-fiber lightwave transmission systems. This full-duplex 100-GHz/50-GHz/25-GHz/550-MHz lightwave transmission system is an attractive alternative. This transmission system not only presents its advancement in the integration of fiber backbone and CATV/wireless feeder networks, but also it provides the advantages of a communication channel for higher data rates and bandwidth.

Determinación de los parámetros de corrosión y desgaste del par acero/aluminio en presencia de líquidos iónicos

OpenAIRE

Jerez Mesa, Ramón

2008-01-01

El presente proyecto presenta resultados obtenidos en ensayos utilizando LI combinados con aluminio 2011 y acero F-1310, tanto en ensayos de corrosión como de tribología. Escuela Técnica Superior de Ingeniería Industrial

Aplicabilidad de un concreto de escoria activada alcalinamente como material protector del acero de refuerzo

OpenAIRE

Robinson de Jesús Torres Gómez, William A. Aperador Ch., Enrique Vera López,Rubi Mejía de Gutiérrez

2011-01-01

Se presentan los resultados del análisis electroquímico de las  barras  de  acero  embebidas  en  un  concreto  no convencional usado internacionalmente para reparación de estructuras. Este concreto utiliza materiales de desecho de otros procesos; en este caso específico se empleó escoria siderúrgica de  la empresa Acerías Paz del Río S.A. Se estudio el comportamiento frente a la corrosión generada por  los iones cloruro, con el uso de la técnica de resistencia lineal a la polarización LPR y ...

Yield stress of duplex stainless steel specimens estimated using a compound Hall–Petch equation

Directory of Open Access Journals (Sweden)

Noriaki Hirota, Fuxing Yin, Tsukasa Azuma and Tadanobu Inoue

2010-01-01

Full Text Available In this study, the 0.2% yield stress of duplex stainless steel was evaluated using a compound Hall–Petch equation. The compound Hall–Petch equation was derived from four types of duplex stainless steel, which contained 0.2–64.4 wt% δ-ferrite phase, had different chemical compositions and were annealed at different temperatures. Intragranular yield stress was measured with an ultra-microhardness tester and evaluated with the yield stress model proposed by Dao et al. Grain size, volume fraction and texture were monitored by electron backscattering diffraction measurement. The kγ constant in the compound equation for duplex stainless steel agrees well with that for γ-phase SUS316L steel in the temperature range of 1323–1473 K. The derived compound Hall–Petch equation predicts that the yield stress will be in good agreement with the experimental results for the Cr, Mn, Si, Ni and N solid-solution states. We find that the intragranular yield stress of the δ-phase of duplex stainless steel is rather sensitive to the chemical composition and annealing conditions, which is attributed to the size misfit parameter.

Study of Sigma Phase in Duplex SAF 2507

Science.gov (United States)

Fellicia, D. M.; Sutarsis; Kurniawan, B. A.; Wulanari, D.; Purniawan, A.; Wibisono, A. T.

2017-05-01

Super duplex stainless steel is one of the stainless steel which has a combination between high strength properties and excellent corrosion resistance. However, the resistance can decrease by precipitation of sigma phase which is formed at high temperature, for example after welding processes. A series of experiments has been performed to study the effect of solution annealing to existence of sigma phase on super duplex SAF 2507. Variations of solution-annealing temperatures were 1000 °C, 1065 °C and 1125 °C with holding time of 15 and 30 minutes for each temperature. Effect of solution annealing process was characterized by using XRD, SEM, and Optical Microscopy. The result showed precipitation of sigma phase completely dissolved at 1065 °C and 1125 °C because it reformed to austenite. After it was heated at 1065 °C, chromium carbide appeared in ferrite site and grain boundary. The amount of chromium carbide increased with the increasing of solution annealing temperature.

The effects of laser welding parameters on the microstructure of ferritic and duplex stainless steels welds

Science.gov (United States)

Pekkarinen, J.; Kujanpää, V.

This study is focused to determine empirically, which microstructural changes occur in ferritic and duplex stainless steels when heat input is controlled by welding parameters. Test welds were done autogenously bead-on-plate without shielding gas using 5 kW fiber laser. For comparison, some gas tungsten arc welds were made. Used test material were 1.4016 (AISI 430) and 1.4003 (low-carbon ferritic) type steels in ferritic steels group and 1.4162 (low-alloyed duplex, LDX2101) and 1.4462 (AISI 2205) type steels in duplex steels group. Microstructural changes in welds were identified and examined using optical metallographic methods.

Dilution and Ferrite Number Prediction in Pulsed Current Cladding of Super-Duplex Stainless Steel Using RSM

Science.gov (United States)

Eghlimi, Abbas; Shamanian, Morteza; Raeissi, Keyvan

2013-12-01

Super-duplex stainless steels have an excellent combination of mechanical properties and corrosion resistance at relatively low temperatures and can be used as a coating to improve the corrosion and wear resistance of low carbon and low alloy steels. Such coatings can be produced using weld cladding. In this study, pulsed current gas tungsten arc cladding process was utilized to deposit super-duplex stainless steel on high strength low alloy steel substrates. In such claddings, it is essential to understand how the dilution affects the composition and ferrite number of super-duplex stainless steel layer in order to be able to estimate its corrosion resistance and mechanical properties. In the current study, the effect of pulsed current gas tungsten arc cladding process parameters on the dilution and ferrite number of super-duplex stainless steel clad layer was investigated by applying response surface methodology. The validity of the proposed models was investigated by using quadratic regression models and analysis of variance. The results showed an inverse relationship between dilution and ferrite number. They also showed that increasing the heat input decreases the ferrite number. The proposed mathematical models are useful for predicting and controlling the ferrite number within an acceptable range for super-duplex stainless steel cladding.

The design and analysis of AVTMR (all voting triple modular redundancy) and dual-duplex system

International Nuclear Information System (INIS)

Kim, Hyunki; Lee, Hyeuntae; Lee, Keyseo

2005-01-01

In this paper, we design AVTMR (All Voting Triple Modular Redundancy) and dual-duplex system which have a fault-tolerant characteristic, and two systems are compared in the evaluation of RAMS (Reliability, Availability, Maintainability and Safety) and MTTF (Mean Time To Failure). AVTMR system is designed in a triplicated voter technique and dual-duplex system in a comparator, and two systems are based on MC68000. To evaluate system characteristic, Markov modeling method is designed for reliability, availability, safety and MTTF (Mean Time To Failure), and RELEX6.0 tool is used for the calculation of failure rate of electrical components that is based on MILSPEC-217F. In this paper, we can see two systems are more high dependability than a single system, and AVTMR or dual-duplex system can be selected for a specific application system. Especially, because AVTMR and dual-duplex system have high RAMS better than a single system, they can be applied to life critical system such as an airplane and a high-speed railway system

Estimation of brachial artery volume flow by duplex ultrasound imaging predicts dialysis access maturation.

Science.gov (United States)

Ko, Sae Hee; Bandyk, Dennis F; Hodgkiss-Harlow, Kelley D; Barleben, Andrew; Lane, John

2015-06-01

This study validated duplex ultrasound measurement of brachial artery volume flow (VF) as predictor of dialysis access flow maturation and successful hemodialysis. Duplex ultrasound was used to image upper extremity dialysis access anatomy and estimate access VF within 1 to 2 weeks of the procedure. Correlation of brachial artery VF with dialysis access conduit VF was performed using a standardized duplex testing protocol in 75 patients. The hemodynamic data were used to develop brachial artery flow velocity criteria (peak systolic velocity and end-diastolic velocity) predictive of three VF categories: low (800 mL/min). Brachial artery VF was then measured in 148 patients after a primary (n = 86) or revised (n = 62) upper extremity dialysis access procedure, and the VF category correlated with access maturation or need for revision before hemodialysis usage. Access maturation was conferred when brachial artery VF was >600 mL/min and conduit imaging indicated successful cannulation based on anatomic criteria of conduit diameter >5 mm and skin depth 800 mL/min was predicted when the brachial artery lumen diameter was >4.5 mm, peak systolic velocity was >150 cm/s, and the diastolic-to-systolic velocity ratio was >0.4. Brachial artery velocity spectra indicating VF 800 mL/min. Duplex testing to estimate brachial artery VF and assess the conduit for ease of cannulation can be performed in 5 minutes during the initial postoperative vascular clinic evaluation. Estimation of brachial artery VF using the duplex ultrasound, termed the "Fast, 5-min Dialysis Duplex Scan," facilitates patient evaluation after new or revised upper extremity dialysis access procedures. Brachial artery VF correlates with access VF measurements and has the advantage of being easier to perform and applicable for forearm and also arm dialysis access. When brachial artery velocity spectra criteria confirm a VF >800 mL/min, flow maturation and successful hemodialysis are predicted if anatomic criteria

Throughput maximization for buffer-aided hybrid half-/full-duplex relaying with self-interference

KAUST Repository

Khafagy, Mohammad Galal

2015-06-01

In this work, we consider a two-hop cooperative setting where a source communicates with a destination through an intermediate relay node with a buffer. Unlike the existing body of work on buffer-aided half-duplex relaying, we consider a hybrid half-/full-duplex relaying scenario with loopback interference in the full-duplex mode. Depending on the channel outage and buffer states that are assumed available at the transmitters, the source and relay may either transmit simultaneously or revert to orthogonal transmission. Specifically, a joint source/relay scheduling and relaying mode selection mechanism is proposed to maximize the end-to-end throughput. The throughput maximization problem is converted to a linear program where the exact global optimal solution is efficiently obtained via standard convex/linear numerical optimization tools. Finally, the theoretical findings are corroborated with event-based simulations to provide the necessary performance validation.

Importance of diastolic velocities in the detection of celiac and mesenteric artery disease by duplex ultrasound

DEFF Research Database (Denmark)

Perko, M J; Just, S; Schroeder, T V

1997-01-01

To assess the predictive value of ultrasound duplex scanning in the detection of superior mesenteric artery (SMA) and celiac artery (CA) occlusive disease.......To assess the predictive value of ultrasound duplex scanning in the detection of superior mesenteric artery (SMA) and celiac artery (CA) occlusive disease....

Alternate transmission relaying based on interference alignment in 3-relay half-duplex MIMO systems

KAUST Repository

Park, Seongho; Park, Kihong; Ko, Youngchai; Alouini, Mohamed-Slim

2012-01-01

In a half-duplex relaying, the capacity pre-log factor 1/2 is a major drawback in spectral efficiency. This paper proposes a linear precoding/decoding scheme and an alternate relaying protocol in a dual-hop half-duplex system where three relays help the communication between the source and the destination. In our proposed scheme, we consider a phase incoherent method in relays in which the source alternately transmits message signals to the different relays. In addition, we propose a linear interference alignment scheme which can suppress the inter-relay interference resulting from the phase incoherence of relaying. Based on our analysis of degrees of freedom and our simulation results, we show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying. © 2012 IEEE.

Alternate transmission relaying based on interference alignment in 3-relay half-duplex MIMO systems

KAUST Repository

Park, Seongho

2012-09-01

In a half-duplex relaying, the capacity pre-log factor 1/2 is a major drawback in spectral efficiency. This paper proposes a linear precoding/decoding scheme and an alternate relaying protocol in a dual-hop half-duplex system where three relays help the communication between the source and the destination. In our proposed scheme, we consider a phase incoherent method in relays in which the source alternately transmits message signals to the different relays. In addition, we propose a linear interference alignment scheme which can suppress the inter-relay interference resulting from the phase incoherence of relaying. Based on our analysis of degrees of freedom and our simulation results, we show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying. © 2012 IEEE.

Una herramienta para la selección automatizada de aceros en el contexto // A tool for the automated selection of steels in the Mechanical Engineering´s context

Directory of Open Access Journals (Sweden)

L. Dumitrescu

2010-01-01

Full Text Available ResumenEl diseno de Ingenieria de un producto o componente constituye una actividad dificil, compleja ymultidisciplinaria, enfocada a la resolucion de problemas. En el presente trabajo se muestra eldesarrollo de una herramienta automatizada para la seleccion de los aceros mas utilizados en laconstruccion de maquinarias. La herramienta constituye una ayuda para la seleccion de losmateriales desde la etapa conceptual del proceso de diseno, donde se identifican las diferentescategorias de materiales a utilizar. La herramienta comprende las caracteristicas y propiedades masrelevantes de los aceros de Ingenieria disponibles en seis normas internacionales: Japonesa (JIS,Alemana (DIN, Vbn, DIN-Vbn, Rusa (GOST, Americana (AISI, SAE, AISI-SAE, ASTM, Inglesa (BS, EN,GB, Francesa (AFNOR y la Norma Cubana (NC vigente.Palabras claves: materiales, automatizada, aceros, ingenieria.____________________________________________________________AbstractThe product or component design constitutes a difficult, complex and multidisciplinary activity,focused to the resolution of problems. Presently work show the development of an automated toolfor the selection of the more used steels in the construction of machineries. The tool constitute ahelp for the selection of the materials from the conceptual stage of the design process, where thedifferent categories of materials are identified to use. The tool analyze the characteristics and morecommon properties of the available steels in six international standards: JIS (Japan, DIN, Vbn, DINVbn(Germany, GOST (Russia, AISI, SAE, AISI-SAE, ASTM (USA, BS, IN, GB (England, AFNOR(France and NC (Cuba.Key words: materials, automated, steels, engineering.

A full-duplex working integrated optoelectronic device for optical interconnect

Science.gov (United States)

Liu, Kai; Fan, Huize; Huang, Yongqing; Duan, Xiaofeng; Wang, Qi; Ren, Xiaomin; Wei, Qi; Cai, Shiwei

2018-05-01

In this paper, a full-duplex working integrated optoelectronic device is proposed. It is constructed by integrating a vertical cavity surface emitting laser (VCSEL) unit above a resonant cavity enhanced photodetector (RCE-PD) unit. Analysis shows that, the VCSEL unit has a threshold current of 1 mA and a slop efficiency of 0.66 W/A at 849.7 nm, the RCE-PD unit obtains its maximal absorption quantum efficiency of 90.24% at 811 nm with a FWHM of 4 nm. Moreover, the two units of the proposed integrated device can work independently from each other. So that the proposed integrated optoelectronic device can work full-duplex. It can be applied for single fiber bidirectional optical interconnects system.

Diseño de redes neuronales con aprendizaje combinado de retropropagación y búsqueda aleatoria progresiva aplicado a la determinación de austenita retenida en aceros TRIP

Directory of Open Access Journals (Sweden)

Capdevila, C.

2010-12-01

Full Text Available At the beginning of the decade of the nineties, the industrial interest for TRIP steels leads to a significant increase of the investigation and application in this field. In this work, the flexibility of neural networks for the modelling of complex properties is used to tackle the problem of determining the retained austenite content in TRIP-steel. Applying a combination of two learning algorithms (backpropagation and creeping-random-search for the neural network, a model has been created that enables the prediction of retained austenite in low-Si / low-Al multiphase steels as a function of processing parameters.

A partir de los años noventa, el interés que los aceros TRIP despiertan en la industria ha producido un incremento considerable de su estudio y aplicación. En este trabajo, aprovechando la flexibilidad que las redes neuronales proporcionan para la modelización de propiedades complejas, se ha abordado el problema de la determinación de la austenita retenida en los aceros TRIP. Una combinación de dos algoritmos de aprendizaje (retropropagación y búsqueda aleatoria progresiva de la red neuronal ha permitido crear un modelo que predice la cantidad de austenita retenida en aceros multifase con bajo contenido en aluminio y silicio en función de los parámetros de procesado.

Modelado de Control de Nivel en Molde para Vaciado Continuo de Palanquillas de Acero

Directory of Open Access Journals (Sweden)

Guillermo González Yero

2014-01-01

Full Text Available Resumen: Este trabajo presenta un modelo del sistema de control de nivel en molde de una máquina de vaciado continuo de palanquillas de acero. El objetivo fue realizar el modelado de cada elemento del sistema incluyendo las perturbaciones y transformaciones de la planta que más afectan la calidad del control. Se obtuvo y validó un modelo aproximado, utilizando leyes físicas, la identificación experimental mediante señales especiales e identificación paramétrica fuera de línea. En el modelo se incluyen de forma explícita los fenómenos de obstrucción y erosión en la válvula, que tienen una incidencia significativa en el funcionamiento de la planta. Para el servosistema hidráulico de la instalación se logró un modelo de caja gris que contribuye a un mejor entendimiento del comportamiento del proceso y a evaluar la incidencia de una implementación multifrecuencia bajo esquema convencional. Con el modelo obtenido es posible estudiar la operación del sistema a escala de simulación y la efectividad de soluciones de control avanzadas. El trabajo desarrollado es parte de un proceso de I+D que en el transcurso de más de 10 años ha contribuido a que en la acería donde se realiza la investigación, exista un sistema de control de nivel en molde que tiene impacto positivo sobre la calidad del acero producido. Abstract: This paper presents a model of system for the mould level control in a continuous casting machine for steel billets. The objective was to carry out the modeling of each element of the system including disturbances and transformations of the plant that affect the quality of control in the installation study object. It was obtained and validated an approximate model of the control system using physical laws governing the same one, experimental identification by special signals and parametric identification off- line. The model explicitly includes the phenomena of obstruction and erosion of the valve which have a

Efficient Cooperative Protocols for Full-Duplex Relaying over Nakagami-m Fading Channels

KAUST Repository

Khafagy, Mohammad Galal

2015-02-24

In this work, efficient protocols are studied for full-duplex relaying (FDR) with loopback interference over Nakagami-m block fading channels. Recently, a selective decodeand- forward (DF) protocol was proposed for FDR, and was shown to outperform existing protocols in terms of outage over Rayleigh-fading channels. In this work, we propose an incremental selective DF protocol that offers additional power savings, yet yields the same outage performance. We evaluate their outage performance over independent non-identically distributed Nakagami-m fading links, and study their relative performance in terms of the signal-to-noise ratio cumulative distribution function via closed-form expressions. The offered diversity gain is also derived. In addition, we study their performance relative to their half-duplex counterparts, as well as known non-selective FDR protocols. We corroborate our theoretical results with simulation, and confirm that selective cooperation protocols outperform the known non-selective protocols in terms of outage. Finally, we show that depending on the loopback interference level, the proposed protocols can outperform their half-duplex counterparts when high spectral efficiencies are targeted.

Efficient Cooperative Protocols for Full-Duplex Relaying over Nakagami-m Fading Channels

KAUST Repository

Khafagy, Mohammad Galal; Tammam, Amr; Alouini, Mohamed-Slim; Aissa, Sonia

2015-01-01

In this work, efficient protocols are studied for full-duplex relaying (FDR) with loopback interference over Nakagami-m block fading channels. Recently, a selective decodeand- forward (DF) protocol was proposed for FDR, and was shown to outperform existing protocols in terms of outage over Rayleigh-fading channels. In this work, we propose an incremental selective DF protocol that offers additional power savings, yet yields the same outage performance. We evaluate their outage performance over independent non-identically distributed Nakagami-m fading links, and study their relative performance in terms of the signal-to-noise ratio cumulative distribution function via closed-form expressions. The offered diversity gain is also derived. In addition, we study their performance relative to their half-duplex counterparts, as well as known non-selective FDR protocols. We corroborate our theoretical results with simulation, and confirm that selective cooperation protocols outperform the known non-selective protocols in terms of outage. Finally, we show that depending on the loopback interference level, the proposed protocols can outperform their half-duplex counterparts when high spectral efficiencies are targeted.

Standard duplex criteria overestimate the degree of stenosis after eversion carotid endarterectomy.

Science.gov (United States)

Benzing, Travis; Wilhoit, Cameron; Wright, Sharee; McCann, P Aaron; Lessner, Susan; Brothers, Thomas E

2015-06-01

The eversion technique for carotid endarterectomy (eCEA) offers an alternative to longitudinal arteriotomy and patch closure (pCEA) for open carotid revascularization. In some reports, eCEA has been associated with a higher rate of >50% restenosis of the internal carotid when it is defined as peak systolic velocity (PSV) >125 cm/s by duplex imaging. Because the conformation of the carotid bifurcation may differ after eCEA compared with native carotid arteries, it was hypothesized that standard duplex criteria might not accurately reflect the presence of restenosis after eCEA. In a case-control study, the outcomes of all patients undergoing carotid endarterectomy by one surgeon during the last 10 years were analyzed retrospectively, with a primary end point of PSV >125 cm/s. Duplex flow velocities were compared with luminal diameter measurements for any carotid computed tomography arteriography or magnetic resonance angiography study obtained within 2 months of duplex imaging, with the degree of stenosis calculated by the methodology used in the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST) as well as cross-sectional area (CSA) reduction. Simulations were generated and analyzed by computational model simulations of the eCEA and pCEA arteries. Eversion and longitudinal arteriotomy with patch techniques were used in 118 and 177 carotid arteries, respectively. Duplex follow-up was available in 90 eCEA arteries at a median of 16 (range, 2-136) months and in 150 pCEA arteries at a median of 41 (range, 3-115) months postoperatively. PSV >125 cm/s was present at some time during follow-up in 31% of eCEA and pCEA carotid arteries, each, and in the most recent duplex examination in 7% after eCEA and 21% after pCEA (P = .003), with no eCEA and two pCEA arteries occluding completely during follow-up (P = .29). In 19 carotid arteries with PSV >125 cm/s after angle correction (median, 160 cm/s; interquartile range

Empleo de la cáscara de arroz en la fundición de piezas de acero al carbono//Using of rice husk in the carbon steel casting parts process

Directory of Open Access Journals (Sweden)

Juan Carlos Cruz-Pérez

2012-05-01

Full Text Available Los materiales auxiliares desempeñan un papel importante en el aumento de la eficiencia tecnológica del proceso de fundición de piezas de acero al carbono. En este artículo se exponen los primeros resultados del empleo de la cáscara de arroz como material termoaislante en la obtención de piezas fundidas de acero al carbono. En los experimentos se evaluó la influencia  de seis combinaciones de las variables espesor de pared del casquillo y capa de cobertura. En la confección de los casquillos se utilizó cáscara de arroz triturada, la que posteriormente fue aglutinada con silicato de sodio, apisonada y endurecida con CO2, mientras que la cobertura se utilizó sin procesamiento previo. El mayor nivel de entrega de acero se obtuvo al emplear un espesor de casquillo de 65 mm y una altura de cobertura de 85 mm. El valor del ASAF generado por las variantes experimentales resultó igual o inferior a 0,48. Palabras claves: casquillo termoaislante, polvo de cobertura, cáscara de arroz, acero fundido.______________________________________________________________________________ Abstract Feeding auxiliary materials perform a very important role in improves technological efficiency of carbon steel casting parts process. In this article are exposing the first results in the rice husk using as an insulating material in such process. The variables sleeve thickness and covering thickness’ influence were evaluated in six combinations by means of experiments. In sleeves preparation was used crushed rice husk, which was agglutinated with sodium silicate, compacted and hardened with CO2, meanwhile as covering it was uses without previous preparation. The mayor liquid steel delivering level was get employing 65 mm sleeve thickness and 85 mm covering thickness. The ASAF value generated for experimental variants was equal or inferior to 0.48. Key words: insulating sleeve, riser sleeve, hot topping, rice husk, steel cast.

Estudio de los mecanismos de degradación de la interfase acero (limpio u oxidado-recubrimiento clorocaucho en su exposición al ensayo de condensación de humedad

Directory of Open Access Journals (Sweden)

Chico, B.

1998-05-01

Full Text Available The effect of time of exposure to the humidity on the behaviour of the system chlorinated rubber paint-steel substrate (cleaned or pre-rusted is investigated from the interfacial chemistry and adhesion points of view. After one day of humidity exposure, the paint-rust free steel substrate system shows an increase of adhesion. A maximum adhesion value is obtained after 15 days of exposure. This behaviour is similar to that previously described for a pre-rusted steel substrate. After 30-60 days of exposure, the adhesion strength values show an important reduction and the locus of adhesion loss shifts from the paint inside to the interphase between the metallic substrate and the paint.

En el presente trabajo se analiza el efecto de la exposición a la humedad de un recubrimiento orgánico de clorocaucho aplicado a un sustrato de acero (únicamente limpio o previamente oxidado sobre los valores de adherencia del sistema y la composición química de la interfase metal-pintura. Se ha intentado establecer posibles relaciones entre la degradación de la interfase acero-recubrimiento clorocaucho en su exposición a condiciones de alta humedad y la presencia o ausencia de una capa de óxido sobre el sustrato original. Después de 1 día de exposición a la humedad, se observó un aumento en los valores de adherencia del sistema pintura-acero sin oxidar. Sorprendentemente, estos valores alcanzan un máximo después de 15 días de exposición. Este mismo comportamiento se había encontrado ya en el sistema acero preoxidado-recubrimiento clorocaucho. Tiempos de exposición a la humedad suficientemente largos (30-60 días producen una acusada disminución en los valores de adherencia y un desplazamiento del lugar donde ocurre el fallo desde el seno de la pintura a la región interfacial entre la pintura y el sustrato.

Electrodos austeníticos inoxidables semisintéticos para la soldadura manual por arco eléctrico: Una variante económica para las pequeñas y medianas empresas (PIME. // Semi-synthetic austenitics stainless steel electrodes for shielded metal arc welding: A

Directory of Open Access Journals (Sweden)

A. Paz Iglesias

2002-09-01

Full Text Available En el presente trabajo se brinda una valoración económica para la producción de electrodos austeníticos inoxidables tiposE308L, E309, E312 y E316L en las pequeñas y medianas empresas (PIME. Lo significativo de la presente valoración esque se brindan los resultados obtenidos al fabricar los electrodos de forma semisintética; es decir, utilizando un solo tipo dealambre inoxidable (308L y añadiendo las ferroaleaciones necesarias en el revestimiento. Los resultados que se muestranestán basados en las experiencias de investigación, producción y comercialización de una planta con capacidad para 200toneladas al año, a la cual le es muy difícil insertarse en el mercado utilizando los mismos procedimientos tecnológicos yfinancieros de una gran empresa con grandes capitales y recursos.Palabras claves: Electrodos austeníticos inoxidables, electrodos sintéticos, ferroaleaciones, electrodossemisintéticos, electrodos convencionales, metal depositado.___________________________________________________________________Abstract.This paper offers an economic valuation for the production of stainless electrodes type E308L, E309, E312 and E316L,for small and middle companies (PIME. The significant part of the present valuation gives the results obtained in theproduction of semi-synthetic electrodes; using just one type of stainless wire (308L and adding the ferroalloys neededin the coat. The results shown are based on investigation experiences, production and trading of companies with acapacity for 200 T/year, so it is very difficult to enter in the market using the same technological procedures of a bigcompany with higher capital and financial resources.Key words: Nonrusting austenistic electrodes, sintetic electrodes, semisintetic electrodes, iron alloy,conventional electrodes, metal deposition.

Role of magnetic resonance urography in diagnosis of duplex renal system: Our initial experience at a tertiary care institute

Directory of Open Access Journals (Sweden)

Milind P Joshi

2009-01-01

Full Text Available Aim: To determine diagnostic value of magnetic resonance urography in cases of duplex renal system. Method: Twenty cases between five month to nine years with suspected or known duplex renal system were evaluated by ultrasound (USG, micturating cystourethrography (MCU, intravenous urography (IVU and magnetic resonance urography (MRU. The findings of these diagnostic imaging studies were then compared with each other and against the results of final diagnosis established at surgery. Results: Duplex renal system could be identified in two of these cases on USG, was diagnosed in four in IVU and could be diagnosed in all cases with MRU. Conclusion: MRU is superior and far accurate than IVU, MCU and USG in diagnosing duplex renal system.

Fabricación de matrices de corte con aceros rápidos para herramientas mediante metalurgia de polvos

Directory of Open Access Journals (Sweden)

Talacchia, S.

1996-02-01

Full Text Available The present work summarizes the results obtained by compacting water atomized powders of T42 modified carbon and vanadium, M3/2 and M2 high speed steels. The powders were compacted under complex forms (cut off dies and sintered under a 90 N₂-9 H₂-I CH₄ industrial atmosphere. Heat treatments in different severity media were performed. Hardness of 1,100 HV can be obtained in the case of T42 modified steel. Also, the shrinking of the sintered specimens was study.

Se estudia la fabricación de matrices de corte de aceros rápidos para herramientas mediante procesos de metalurgia de polvos. Los polvos de los aceros T42 con contenidos de carbono y vanadio modificados, M3/2 y M2, obtenidos por atomización en agua, se compactaron de tal modo que quedaron dotados de formas geométricas complejas. Después de sinterizados en una atmósfera industrial 90 N₂-9 H₂-I CH₄, se trataron térmicamente en medios de distintas severidades. Tras el temple desde temperaturas de austenización cercanas a la temperatura óptima de sinterizado, se lograron durezas de hasta 1.100 HV. Se determinaron, también, las contracciones sufridas por las piezas sinterizadas.

In-Band Full-Duplex Communications for Cellular Networks with Partial Uplink/Downlink Overlap

KAUST Repository

Alammouri, Ahmad; Elsawy, Hesham; Amin, Osama; Alouini, Mohamed-Slim

2015-01-01

In-band full-duplex (FD) communications have been optimistically promoted to improve the spectrum utilization in cellular networks. However, the explicit impact of spatial interference, imposed by FD communications, on uplink and downlink transmissions has been overlooked in the literature. This paper presents an extensive study of the explicit effect of FD communications on the uplink and downlink performances. For the sake of rigorous analysis, we develop a tractable framework based on stochastic geometry toolset. The developed model accounts for uplink truncated channel inversion power control in FD cellular networks. The study shows that FD communications improve the downlink throughput at the expense of significant degradation in the uplink throughput. Therefore, we propose a novel fine-grained duplexing scheme, denoted as α-duplex scheme, which allows a partial overlap between uplink and downlink frequency bands. To this end, we show that the amount of the overlap can be optimized via adjusting α to achieve a certain design objective.

In-Band Full-Duplex Communications for Cellular Networks with Partial Uplink/Downlink Overlap

KAUST Repository

AlAmmouri, Ahmad

2015-12-06

In-band full-duplex (FD) communications have been optimistically promoted to improve the spectrum utilization in cellular networks. However, the explicit impact of spatial interference, imposed by FD communications, on uplink and downlink transmissions has been overlooked in the literature. This paper presents an extensive study of the explicit effect of FD communications on the uplink and downlink performances. For the sake of rigorous analysis, we develop a tractable framework based on stochastic geometry toolset. The developed model accounts for uplink truncated channel inversion power control in FD cellular networks. The study shows that FD communications improve the downlink throughput at the expense of significant degradation in the uplink throughput. Therefore, we propose a novel fine-grained duplexing scheme, denoted as α-duplex scheme, which allows a partial overlap between uplink and downlink frequency bands. To this end, we show that the amount of the overlap can be optimized via adjusting α to achieve a certain design objective.

Microstructure and properties of duplex (Ti:N)-DLC/MAO coating on magnesium alloy

Energy Technology Data Exchange (ETDEWEB)

Yang, Wei; Ke, Peiling [Ningbo Key Laboratory of Marine Protection Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Fang, Yong [Sir Run Run Shaw Hospital, School of Medicine, Zhe Jiang University, Zhejiang 310016 (China); Zheng, He [Ningbo Key Laboratory of Marine Protection Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Wang, Aiying, E-mail: aywang@nimte.ac.cn [Ningbo Key Laboratory of Marine Protection Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

2013-04-01

Ti and N co-doped diamond-like carbon ((Ti:N)-DLC) film was deposited on the MAO coated substrate using a hybrid beam deposition system, which consists of a DC magnetron sputtering of Ti target and a linear ion source (LIS) with C{sub 2}H{sub 2} and N{sub 2} precursor gas. The microstructure and properties of the duplex (Ti:N)-DLC/MAO coating were investigated. Results indicate that the (Ti:N)-DLC top film with TiN crystalline phase was formed. Ti and N co-doping resulted in the increasing I{sub D}/I{sub G} ratio. The significant improvement in the wear and corrosion resistance of duplex (Ti:N)-DLC/MAO coating was mainly attributed to the increased binding strength, lubrication characteristics and chemical inertness of (Ti:N)-DLC top film. The superior low-friction and anti-corrosion properties of duplex (Ti:N)-DLC/MAO coating make it a good candidate as protective coating on magnesium alloy.

Duplex sonography and magnetic resonance imaging in the clarification of nephrological complications after renal transplant

International Nuclear Information System (INIS)

Gueckel, C.; Krestin, G.P.; Wienand, P.

1989-01-01

A prospective study compared Duplex sonography and magnetic resonance imaging in evaluating renal transplant. Hundred and two Duplex sonographic and 24 MR examinations were performed and correlated with clinical course or biopsy. All normal renal allografts, 6 transplants with acute tubular necrosis and 2 cases of cyclosporin toxicity had normal Doppler waveforms, whereas 9 renal transplants with evidence of interstitial rejection by biopsy showed an obliteration or reversal of diastolic flow. MR imaging was less specific in identifying allograft rejection. There were false positive results in normal renal transplants, allografts with acute tubular necrosis and after rejection therapy. With regard to cost, accessibility and specificity, Duplex sonography is the method of choice for the evaluation of renal allografts. (orig.) [de

Reliability Capacity of Half-Duplex Channels with Strict Deadlines

DEFF Research Database (Denmark)

Costa, Rui; Roetter, Daniel Enrique Lucani; Vinhoza, Tiago

2015-01-01

A fundamental characterization of a half-duplex wireless system with packet losses under traffic with hard deadlines is instrumental to understanding and developing efficient, coding aware policies for real-time applications. We set forth the concept of reliability capacity with a limited number ...

Duplex sonography of the near-surface leg veins; Duplexsonographie der oberflaechlichen Beinvenen

Energy Technology Data Exchange (ETDEWEB)

Mendoza, E.

2007-07-01

The book contains the following contributions: The ultrasonograph, selection of the ultrasonic transducer, anatomy of the near-surface vein system, physiology of the near-surface vein system, varicose status classification, systematics of the duplex sonography of near-surface leg veins, provocational maneuver for the duplex sonographic varicose diagnostics, exploration of vena saphena parva, perforans veins, side branches, phlebitis, sonography for varicose therapy, postsurgical sonography, deep leg veins, examination of near-surface leg veins for the pathology of the deep vein system, differential diagnostic clarification of leg oedema from the phlebologic-lymphological view, diagnostic side features along the near-surface leg veins.

Characterization of Duplex steel Uranus 76N during deformation and heat treatment

Energy Technology Data Exchange (ETDEWEB)

Lecomte-Beckers, J.; Carton, M. [ASMA Department - Sector, Special Metallic Materials, University of Liege, Chemin des Chevreuils 1, 4000 Liege 1 (Belgium); Moureaux, P.; Habraken, A.M. [M and S Department - Sector, Mechanic of Solids and Material, University of Liege, Chemin des Chevreuils 1, 4000 Liege 1 (Belgium)

2006-12-15

Duplex Uranus 76N is characterized by metallography, thermal and mechanical analysis. The investigation shows that the microstructure of such a Duplex strongly depends on the cooling conditions determining the quantity of austenite formed in the ferrite matrix. Numerical simulations of 76N behavior during the rolling process and service life require the knowledge of the recrystallization state during rolling steps at high temperature, thermal parameters such as dilatation, density, specific heat, thermal diffusivity, thermal conductivity and mechanical constitutive laws. These material parameters are determined and presented in this study. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Automatización del proceso de curvado de flejes de acero para el conformado de sierras de corona

OpenAIRE

Guerrero González, Edgar

2004-01-01

El documento que se presenta a continuación es la Memoria del Proyecto de Final de Carrera titulado “Automatización del curvado de flejes de acero para el conformado de sierras de corona”. Proyecto solicitado por la empresa SAEGEN IBERICA, dedicada a la fabricación de coronas de sierra entre otros productos, y motivada por la incapacidad de su sistema productivo y de los procesos existentes, de alcanzar la calidad y la producción exigidas por el mercado. El proyecto queda enmarcado d...

COMPORTAMIENTO DE CORROSIÓN-EROSIÓN EN RECUBRIMIENTOS DE TiN/ZrN DEPOSITADOS SOBRE ACERO AISI 4140

OpenAIRE

Aperador, Willian; Mejía, Aura S; Caicedo, Julio

2014-01-01

Se depositaron películas delgadas de nitruro de titanio/nitruro de zirconio sobre acero AISI 4140 mediante un sistema multi-blanco magnetrón pulverización (sputtering) con radiofrecuencia. El proceso se desarrolló bajo el sistema de rotación del sustrato que permitió situar el sustrato de frente a los blancos de titanio y zirconio, generando la super-red con periodos de 1, 50, 100 y 200 bicapas. Las multicapas fueron evaluadas frente a la sinergia corrosión-erosión en una solución compuesta p...

The value of pre-discharge Duplex scanning in infrainguinal graft surveillance.

Science.gov (United States)

Wilson, Y G; Davies, A H; Currie, I C; McGrath, C; Morgan, M; Baird, R N; Lamont, P M

1995-08-01

Protocols and criteria for Duplex-based graft surveillance programmes (GS) vary widely as to the optimum regimens for maximising detection of "at risk" grafts. Few centres recommend starting GS before discharge. The aim of this study was to audit our experience with respect to early scanning. Vascular Studies Unit, Bristol Royal Infirmary. The records of 123 patients entering GS from January 1992 were reviewed. Patients were scanned at 1 week, 6 weeks and 3, 6, 9 and 12 months post-bypass. Haemodynamic criteria used were a peak mean velocity (PMV) less than 45 cm/s and a focal velocity disturbance with a V2/V1 ratio of 1.5 or more. Forty-six abnormalities (37% detection rate) were identified on scans within one week. In all cases, on-table completion studies with either arteriography and/or flow measurements had failed to identify the anomalies subsequently detected by Duplex. At 1 week, six grafts had occluded, 27 had a focal PMV increase (mean V2/V1 ratio: 2.6; range 1.5-4.3), four had low flow velocities, four had arteriovenous fistulae, one contained mobile thrombus, two had retained cusps and two had hamstring entrapment. Of 40 patent, but compromised grafts, 18 warranted immediate investigation. Of the 27 patients with velocity disturbances on Duplex, 25 were simply observed but, eight have since required intervention for definitive stenoses at these sites which, in retrospect, were evident within the first postoperative week. Pre-discharge scanning is a useful modality for detecting technical problems. Intrinsic graft abnormalities, possibly the sites of future definitive stenoses, have been visualised even at 1 week and once identified, can be more closely scrutinised thereafter. Pre-discharge colour Duplex is recommended as standard practice for quality control after infrainguinal bypass.

La celda Avesta: Un método para evitar problemas de corrosión por resquicios en los ensayos electroquímicos de corrosión por picaduras

Directory of Open Access Journals (Sweden)

Fosca, C.

1996-06-01

Full Text Available A very common problem, that occurs during the electrochemical pitting corrosion tests of CRAs (corrosion resistant alloys as stainless steels, is the simultaneous occurrence of crevice corrosion that difficults the evaluation of the electrochemical behaviour in presence of pitting corrosion mechanism only. Crevice corrosion appears as a consequence of the formation of crevices during the mountage of the specimen in the electrochemical cell. Several forms have been developed to avoid the presence of crevice during the electrochemical pitting corrosion test, but without satisfactory results. In the present study a relatively new and innovative method to eliminate the risk of crevice corrosion in the electrochemical tests is evaluated the Avesta cell. Anodic polarization electrochemical tests were carried out in a high alloy stainless steel in 3 % NaCl solution. The experimental results obtained using the Avesta cell were more reliable, reproducible and representative of the electrochemical behaviour of the material that those obtained using other methods of samples preparation to avoid the crevice formation.

Uno de los grandes problemas que suelen presentarse en los ensayos electroquímicos ideados para evaluar la resistencia a la corrosión por picaduras de materiales como los aceros inoxidables es la presencia simultánea de corrosión por resquicios, que suele dificultar e impedir muchas veces la interpretación de los resultados electroquímicos. Este mecanismo de corrosión localizada se produce como consecuencia de la presencia de resquicios en el ensamble de la muestra con la celda electroquímica de ensayo. Se han ideado numerosas formas de evitar este inconveniente, pero ninguna ha resultado completamente satisfactoria. En el presente estudio se evalúa uno de los más nuevos e ingeniosos procedimientos para eliminar el riesgo de corrosión por resquicios en los ensayos de corrosión por picaduras: la celda Avesta. Se efectuaron

Plasma spot welding of ferritic stainless steels

Directory of Open Access Journals (Sweden)

Lešnjak, A.

2002-06-01

Full Text Available Plasma spot welding of ferritic stainless steels is studied. The study was focused on welding parameters, plasma and shielding gases and the optimum welding equipment. Plasma-spot welded overlap joints on a 0.8 mm thick ferritic stainless steel sheet were subjected to a visual examination and mechanical testing in terms of tension-shear strength. Several macro specimens were prepared. Plasma spot welding is suitable to use the same gas as shielding gas and as plasma gas, i.e., a 98 % Ar/2 % H ₂ gas mixture. Tension-shear strength of plasma-spot welded joints was compared to that of resistance-spot welded joints. It was found that the resistance welded joints withstand a somewhat stronger load than the plasma welded joints due to a larger weld spot diameter of the former. Strength of both types of welded joints is approximately the same.

El artículo describe el proceso de soldeo de aceros inoxidables ferríticos por puntos con plasma. La investigación se centró en el establecimiento de los parámetros óptimos de la soldadura, la definición del gas de plasma y de protección más adecuado, así como del equipo óptimo para la realización de la soldadura. Las uniones de láminas de aceros inoxidables ferríticos de 0,8 mm de espesor, soldadas a solape por puntos con plasma, se inspeccionaron visualmente y se ensayaron mecánicamente mediante el ensayo de cizalladura por tracción. Se realizaron macro pulidos. Los resultados de la investigación demostraron que la solución más adecuada para el soldeo por puntos con plasma es elegir el mismo gas de plasma que de protección. Es decir, una mezcla de 98 % de argón y 2 % de hidrógeno. La resistencia a la cizalladura por tracción de las uniones soldadas por puntos con plasma fue comparada con la resistencia de las uniones soldadas por resistencia por puntos. Se llegó a la conclusión de que las uniones soldadas por resistencia soportan una carga algo mayor que la uniones

Diseño óptimo de tableros de puentes mixtos de carretera hormigón-acero

OpenAIRE

Taveras Mendoza, Carlos Tomás

2014-01-01

El desarrollo de la nanotecnología de los materiales, la búsqueda de la optimización en los proyectos de ingeniería, ha emergido una verdadera evolución en el diseño de los puentes a nivel mundial. Europa surge como el génesis de los puentes mixtos en el mundo, grandes puentes y viaductos se hacen con la tipología de viga cajón y viga bijácena mixta. España, concibe la tipología de la doble acción mixta, como alternativa de optimizar los costes del acero. En este trabajo de fin...

99Tcm-DTPA renography in evaluating the function of duplex kidneys in pediatric patients

International Nuclear Information System (INIS)

Zhang Lixia; Wang Xiaoming; Chen Jinyan; Su Junmei

2013-01-01

Objective: To study the value of 99 Tc m -DTPA dynamic renography in evaluating the function of duplex kidneys in pediatric patients. Methods: Twenty-five pediatric patients with duplex kidneys diagnosed by ultrasound or MR urography (MRU) were included (9 males, 16 females; mean age:(23.80 ± 20.97) months, range: 2-72 months). Twenty patients (9 males,11 females; mean age: (32.95 ± 23.58) months, range: 2-72 months) with urinary tract infection but without duplex kidneys confirmed by ultrasound or MRU were chosen as control group during the same period of this study. All patients and controls were divided into two subgroups according to their ages (group Ⅰ, 0-24 months; group Ⅱ, 25-72 months). The research was approved by the ethics committee, and all patients' parents (or guardians) signed informed consents. The time-activity curve was generated on the dynamic imaging data automatically with GFR calculated. The uptake rates of the upper and lower moieties were measured by drawing the corresponding ROIs in the duplex kidney. Dunnett-t test was used for statistical analysis. Results: There were 25 patients with 26 duplex kidneys (1 case bilateral), 16 on the left and 10 on the right. The time-activity curve of 6 cases was normal, 9 with continuously upward type, 4 with high level plateau type, 2 with parabolic type and 5 with low level plateau type. There were 19 abnormal kidneys in group Ⅰ and 7 in group Ⅱ, and 20 kidneys in each control subgroup. The GFR of patients with normal renography was (78.81 ± 15.97) ml/min (group Ⅰ) and (64.68 ± 11.15) ml/min (group Ⅱ), continuously upward type was (72.11 ±22.76) ml/min (group Ⅰ) and (63.41 ± 16.42) ml/min (group Ⅱ), high level plateau and parabolic types were (68.74 ± 16.17) ml/min and (65.26 ± 15.27) ml/min in group Ⅰ, respectively. There was no statistically significant difference between the GFR of different renography type groups and that of the controls (group Ⅰ: (79.35 ±13.31) ml

A Commentary on "Updating the Duplex Design for Test-Based Accountability in the Twenty-First Century"

Science.gov (United States)

Brandt, Steffen

2010-01-01

This article presents the author's commentary on "Updating the Duplex Design for Test-Based Accountability in the Twenty-First Century," in which Isaac I. Bejar and E. Aurora Graf propose the application of a test design--the duplex design (which was proposed in 1988 by Bock and Mislevy) for application in current accountability assessments.…

Three-dimensional shuffling of horses in a strike-slip duplex: an example from the Lambertville sill, New Jersey

Science.gov (United States)

Laney, Stephen E.; Gates, Alexander E.

1996-06-01

Detailed analysis of a dextral strike-slip duplex within the relatively isotropic rocks of the Lambertville sill, New Jersey indicates that horses have experienced vertical, horizontal and oblique movements resulting from extrusional shuffling within a restraining bend. This is the first documentation of the three-dimensional movement of horses within a strike-slip duplex. Deformation within the duplex shows a complex system of early synthetic fractures and reverse faults followed by antithetic fractures which dissect previously continuous slab-shaped horses into diamond-shaped lenses. Most faults are oblique slip. Antithetic fault movements and clockwise rigid rotation of horses dominate the south half of the duplex and synthetic movements and counterclockwise rotations dominate the north half. Slickenline plunges on curved horse-bounding fault surfaces within the duplex range from nearly horizontal to 40° resulting in both lateral movements (middle) to normal movements (tails) on a single horse. Curved slickensides commonly have opposite senses of movement on either side of individual horses indicating relative emergence or submergence. Such a geometry could also result from a group of horses moving in the same oblique direction but at different rates. These complex extrusional-type movements were observed in both cross-sectional and plan views. The net result of the movements is a contraction or flattening of the duplex normal to the bounding faults. The horses shifted to accommodate this flattening as overall displacement was transferred between the bounding faults along curved internal faults.

NMR and molecular modeling evidence for a G·A mismatch base pair in a purine-rich DNA duplex

International Nuclear Information System (INIS)

Li, Ying; Wilson, W.D.; Zon, G.

1991-01-01

1 H NMR experiments indicate that the oligomer 5'-d(ATGAGCGAATA) forms an unusual 10-base-pair duplex with 4 G·A base pairs and a 3' unpaired adenosine. NMR results indicate that guanoxine imino protons of the F·A mismatches are not hydrogen bonded but are stacked in the helix. A G→ I substitution in either G·A base pair causes a dramatic decrtease in duplex stability and indicates that hydrogen bonding of the guanosine amino group is critical. Nuclear Overhauser effect spectroscopy (NOESY) and two-dimensional correlated spectroscopy (COSY) results indicate that the overall duplex conformation is in the B-family. Cross-strand NOEs in two-dimensional NOESY spectra between a mismatched AH2 and an AH1' of the other mismatched base pair and between a mismatched GH8 and GNH1 of the other mismatch establish a purine-purine stacking pattern, adenosine over adenosine and guanosine over guanosine, which strongly stabilizes the duplex. A computer graphics molecular model of the ususual duplex was constructed with G·A base pairs containing A-NH 2 to GN3 and G-NH 2 to AN7 hydrogen bonds and B-form base pairs on both sides of the G·A pairs [5'-d(ATGAGC)]. The energy-minimized duplex satisfies all experimental constraints from NOESY and COSY results. A hydrogen bond from G-NH 2 of the mismatch to a phosphate oxygen is predicted

Block compressed sensing for feedback reduction in relay-aided multiuser full duplex networks

KAUST Repository

Elkhalil, Khalil

2016-08-11

Opportunistic user selection is a simple technique that exploits the spatial diversity in multiuser relay-aided networks. Nonetheless, channel state information (CSI) from all users (and cooperating relays) is generally required at a central node in order to make selection decisions. Practically, CSI acquisition generates a great deal of feedback overhead that could result in significant transmission delays. In addition to this, the presence of a full-duplex cooperating relay corrupts the fed back CSI by additive noise and the relay\\'s loop (or self) interference. This could lead to transmission outages if user selection is based on inaccurate feedback information. In this paper, we propose an opportunistic full-duplex feedback algorithm that tackles the above challenges. We cast the problem of joint user signal-to-noise ratio (SNR) and the relay loop interference estimation at the base-station as a block sparse signal recovery problem in compressive sensing (CS). Using existing CS block recovery algorithms, the identity of the strong users is obtained and their corresponding SNRs are estimated. Numerical results show that the proposed technique drastically reduces the feedback overhead and achieves a rate close to that obtained by techniques that require dedicated error-free feedback from all users. Numerical results also show that there is a trade-off between the feedback interference and load, and for short coherence intervals, full-duplex feedback achieves higher throughput when compared to interference-free (half-duplex) feedback. © 2016 IEEE.

Block compressed sensing for feedback reduction in relay-aided multiuser full duplex networks

KAUST Repository

Elkhalil, Khalil; Eltayeb, Mohammed; Kammoun, Abla; Al-Naffouri, Tareq Y.; Bahrami, Hamid Reza

2016-01-01

Opportunistic user selection is a simple technique that exploits the spatial diversity in multiuser relay-aided networks. Nonetheless, channel state information (CSI) from all users (and cooperating relays) is generally required at a central node in order to make selection decisions. Practically, CSI acquisition generates a great deal of feedback overhead that could result in significant transmission delays. In addition to this, the presence of a full-duplex cooperating relay corrupts the fed back CSI by additive noise and the relay's loop (or self) interference. This could lead to transmission outages if user selection is based on inaccurate feedback information. In this paper, we propose an opportunistic full-duplex feedback algorithm that tackles the above challenges. We cast the problem of joint user signal-to-noise ratio (SNR) and the relay loop interference estimation at the base-station as a block sparse signal recovery problem in compressive sensing (CS). Using existing CS block recovery algorithms, the identity of the strong users is obtained and their corresponding SNRs are estimated. Numerical results show that the proposed technique drastically reduces the feedback overhead and achieves a rate close to that obtained by techniques that require dedicated error-free feedback from all users. Numerical results also show that there is a trade-off between the feedback interference and load, and for short coherence intervals, full-duplex feedback achieves higher throughput when compared to interference-free (half-duplex) feedback. © 2016 IEEE.

Half-Duplex and Full-Duplex AF and DF Relaying with Energy-Harvesting in Log-Normal Fading

KAUST Repository

Rabie, Khaled M.

2017-08-15

Energy-harvesting (EH) and wireless power transfer in cooperative relaying networks have recently attracted a considerable amount of research attention. Most of the existing work on this topic however focuses on Rayleigh fading channels, which represent outdoor environments. In contrast, this paper is dedicated to analyze the performance of dual-hop relaying systems with EH over indoor channels characterized by log-normal fading. Both half-duplex (HD) and full-duplex (FD) relaying mechanisms are studied in this work with decode-and-forward (DF) and amplify-and-forward (AF) relaying protocols. In addition, three EH schemes are investigated, namely, time switching relaying, power splitting relaying and ideal relaying receiver which serves as a lower bound. The system performance is evaluated in terms of the ergodic outage probability for which we derive accurate analytical expressions. Monte Carlo simulations are provided throughout to validate the accuracy of our analysis. Results reveal that, in both HD and FD scenarios, AF relaying performs only slightly worse than DF relaying which can make the former a more efficient solution when the processing energy cost at the DF relay is taken into account. It is also shown that FD relaying systems can generally outperform HD relaying schemes as long as the loop-back interference in FD is relatively small. Furthermore, increasing the variance of the log-normal channel has shown to deteriorate the performance in all the relaying and EH protocols considered.

Counterpart synchronization of duplex networks with delayed nodes and noise perturbation

International Nuclear Information System (INIS)

Wei, Xiang; Wu, Xiaoqun; Lu, Jun-an; Zhao, Junchan

2015-01-01

In the real world, many complex systems are represented not by single networks but rather by sets of interdependent ones. In these specific networks, nodes in one network mutually interact with nodes in other networks. This paper focuses on a simple representative case of two-layer networks (the so-called duplex networks) with unidirectional inter-layer couplings. That is, each node in one network depends on a counterpart in the other network. Accordingly, the former network is called the response layer and the latter network is the drive layer. Specifically, synchronization between each node in the drive layer and its counterpart in the response layer (counterpart synchronization (CS)) in these kinds of duplex networks with delayed nodes and noise perturbation is investigated. Based on the LaSalle-type invariance principle, a control technique is proposed and a sufficient condition is developed for realizing CS of duplex networks. Furthermore, two corollaries are derived as special cases. In addition, node dynamics within each layer can be varied and topologies of the two layers are not necessarily identical. Therefore, the proposed synchronization method can be applied to a wide range of multiplex networks. Numerical examples are provided to illustrate the feasibility and effectiveness of the results. (paper)

X-Ray diffraction technique applied to study of residual stresses after welding of duplex stainless steel plates

International Nuclear Information System (INIS)

Monin, Vladimir Ivanovitch; Assis, Joaquim Teixeira de; Lopes, Ricardo Tadeu; Turibus, Sergio Noleto; Payao Filho, Joao C.

2014-01-01

Duplex stainless steel is an example of composite material with approximately equal amounts of austenite and ferrite phases. Difference of physical and mechanical properties of component is additional factor that contributes appearance of residual stresses after welding of duplex steel plates. Measurements of stress distributions in weld region were made by X-ray diffraction method both in ferrite and austenite phases. Duplex Steel plates were joined by GTAW (Gas Tungsten Arc Welding) technology. There were studied longitudinal and transverse stress components in welded butt joint, in heat affected zone (HAZ) and in points of base metal 10 mm from the weld. Residual stresses measured in duplex steel plates jointed by welding are caused by temperature gradients between weld zone and base metal and by difference of thermal expansion coefficients of ferrite and austenite phases. Proposed analytical model allows evaluating of residual stress distribution over the cross section in the weld region. (author)

Detection of 12 respiratory viruses by duplex real time PCR assays in respiratory samples.

Science.gov (United States)

Arvia, Rosaria; Corcioli, Fabiana; Ciccone, Nunziata; Della Malva, Nunzia; Azzi, Alberta

2015-12-01

Different viruses can be responsible for similar clinical manifestations of respiratory infections. Thus, the etiological diagnosis of respiratory viral diseases requires the detection of a large number of viruses. In this study, 6 duplex real-time PCR assays, using EvaGreen intercalating dye, were developed to detect 12 major viruses responsible for respiratory diseases: influenza A and B viruses, enteroviruses (including enterovirus spp, and rhinovirus spp), respiratory syncytial virus, human metapneumovirus, coronaviruses group I (of which CoV 229E and CoV NL63 are part) and II (including CoV OC43 and CoV HKU1), parainfluenza viruses type 1, 2, 3 and 4, human adenoviruses and human bocaviruses. The 2 target viruses of each duplex reaction were distinguishable by the melting temperatures of their amplicons. The 6 duplex real time PCR assays were applied for diagnostic purpose on 202 respiratory samples from 157 patients. One hundred fifty-seven samples were throat swabs and 45 were bronchoalveolar lavages. The results of the duplex PCR assays were confirmed by comparison with a commercial, validated, assay; in addition, the positive results were confirmed by sequencing. The analytical sensitivity of the duplex PCR assays varied from 10(3) copies/ml to 10(4) copies/ml. For parainfluenza virus 2 only it was 10(5) copies/ml. Seventy clinical samples (35%) from 55 patients (30 children and 25 adults) were positive for 1 or more viruses. In adult patients, influenza A virus was the most frequently detected respiratory virus followed by rhinoviruses. In contrast, respiratory syncytial virus was the most common virus in children, followed by enteroviruses, influenza A virus and coronavirus NL63. The small number of samples/patients does not allow us to draw any epidemiological conclusion. Altogether, the results of this study indicate that the 6 duplex PCR assays described in this study are sensitive, specific and cost-effective. Thus, this assay could be