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Sample records for aco rapido aisi

  1. Comparative study of AISI M3:2 high speed steel produced through different techniques of manufacturing; Estudo comparativo de acos rapidos AISI M3:2 produzidos por diferentes processos de fabricacao

    Araujo Filho, Oscar Olimpio de

    2006-07-01

    In this work AISI M3:2 high speed steels obtained through different techniques of manufacturing, submitted to the same heat treatment procedure were evaluated by measuring their mechanical properties of transverse rupture strength and hardness. Sinter 23 obtained by hot isostatic pressing (HIP), VWM3C obtained by the conventional route and a M3:2 high speed steel obtained by cold compaction of water atomized powders and vacuum sintered with and without the addition of a small quantity of carbon were evaluated after the same heat treatment procedure. The vacuum sintered M3:2 high speed steel can be an alternative to the more expensive high speed steel produced by hot isostatic pressing and with similar properties presented by the conventional one. The characterization of the vacuum sintered M3:2 high speed steel was performed by measuring the densities of the green compacts and after the sintering cycle. The sintering produced an acceptable microstructure and densities near to the theoretical. The transverse rupture strength was evaluated by means of three point bending tests and the hardness by means of Rockwell C and Vickers tests. The technique of scanning electronic microscopy (SEM) was used to evaluate the microstructure and to establish a relation with the property of transverse rupture strength. The structure was determined by means of X-ray diffraction (XRD) patterns and the retained austenite was detected to all the conditions of heat treatment. The main contribution of this work is to establish a relation between the microstructure and the mechanical property of transverse rupture strength and to evaluate the AISI M3:2 vacuum sintered high speed steel as an alternative to the similar commercial high speed steels. (author)

  2. Machining tools in AISI M2 high-speed steel obtained by spray forming process; Ferramentas de usinagem em aco rapido AISI M2 obtido por conformacao por 'spray'

    Jesus, Edilson Rosa Barbosa de. E-mail: erbjesus@usp.br

    2004-07-01

    The aim of the present work was the obtention of AISI M2 high-speed steel by spray forming technique and the material evaluation when used as machining tool. The obtained material was hot rolled at 50% and 72% reduction ratios, and from which it was manufactured inserts for machining tests. The performance of inserts made of the spray formed material was compared to inserts obtained from conventional and powder metallurgy (MP) processed materials. The spray formed material was chemical, physical, mechanical and microstructural characterised. For further characterisation, the materials were submitted to machining tests for performance evaluation under real work condition. The results of material characterisation highlight the potential of the spray forming technique, in the obtention of materials with good characteristics and properties. Under the current processing, hot rolling and heat treatments condition, the analysis of the results of the machining tests revealed a very similar behaviour among the tested materials. Proceeding a criterious analysis of the machining results tests, it was verified that the performance presented by the powder metallurgy material (MP) was slight superior, followed by conventional obtained material (MConv), which presented a insignificant advantage over the spray formed and hot rolled (72% reduction ratio) material. The worst result was encountered for the spray forming and hot rolled (50% reduction ratio) material that presented the highest wear values. (author)

  3. Modification and characterization of the AISI 410 martensitic stainless steels surface; Modificacao e caracterizacao da superficie do aco inoxidavel martensitico AISI 410

    Bincoleto, A.V.L. [Universidade Federal de Sao Carlos (PPG-CEM/UFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Nascente, P.A.P. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    Steam turbines are used in the generation of more than half the electric energy produced in the world nowadays. It is important the study which aims to improve the efficiency by means of the optimization of leaks and of the aerodynamic profiles, as well as to maintain the integrity of the components. The martensitic stainless steels are widely employed due to the combination of their good mechanical properties with higher corrosion resistance. However, their lower wear resistance and their poor tribological behavior limit their use, since they decrease the component life time. In order to evaluate the improvement in the performance of the AISI 410 stainless steel, several process of surface modification were employed. Five samples were produced: the first one was not treated, the second one received liquid nitriding, the third, gas nitriding, the forth, thermal aspersion of tungsten carbide, and the fifth, boronizing. The samples were characterized by optical microscopy, surface microhardness, and X-ray diffractometry. (author)

  4. Evaluation of performance of AISI 444 steel for application in distillation towers; Avaliacao do desempenho do aco AISI 444 para aplicacao como 'lining' em torres de destilacao

    Guimaraes, R.F.; Miranda, H.C. de; Farias, J.P. [Universidade Federal do Ceara (DEMM/UFC), Fortaleza, CE (Brazil). Dept. de Engenharia Metalurgica e de Materiais. Lab. de Caracterizacao de Materiais], e-mail: rf.guimaraes@yahoo.com.br

    2008-07-01

    In this work, the behavior of the AISI 444 ferritic stainless steel submitted to thermal fatigue test and their corrosion resistance in heavy crude oil was evaluated. The AWS E309MoL-16 and E316L-17 weld metal was employed as filler metal. Plates of the AISI 444 were welded on ASTM A-516 Gr. 60 plates and submitted to fatigue thermal cycle. Samples were extracted from plates welded and heat treated immersed in heavy crude oil at 300 deg C. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive of X-ray analysis (EDX) were used to characterize the microstructure and the corroded surface. The results show that the AISI 444 stainless steels did not present cracks after the thermal fatigue cycle and the heat treated immerse in heavy crude oil. The electrode AWS E309MoL-16 show better corrosion resistance than the AWS E316L-17. (author)

  5. Study of corrosion resistance of AISI 444 ferritic stainless steel for application as a biomaterial; Estudo da resistencia a corrosao do aco inoxidavel ferritico AISI 444 para aplicacao como biomaterial

    Marques, Rogerio Albuquerque

    2014-09-01

    Ferritic stainless steels are ferromagnetic materials. This property does not allow their use in orthopedic prosthesis. Nevertheless, in some specific applications, this characteristic is very useful, such as, for fixing dental and facial prostheses by using magnetic attachments. In this study, the corrosion resistance and cytotoxicity of the AISI 444 ferritic stainless steel, with low nickel content, extra-low interstitial levels (C and N) and Ti and Nb stabilizers, were investigated for magnetic dental attachments application. The ISO 5832-1 (ASTM F-139) austenitic stainless steel and a commercial universal keeper for dental attachment (Neo-magnet System) were evaluated for comparison reasons. The first stainless steel is the most used metallic material for prostheses, and the second one, is a ferromagnetic keeper for dental prostheses (NeoM). In vitro cytotoxicity analysis was performed by the red neutral incorporation method. The results showed that the AISI 444 stainless steel is non cytotoxic. The corrosion resistance was studied by anodic polarization methods and electrochemical impedance spectroscopy (EIS), in a saline phosphate buffered solution (PBS) at 37 °C. The electronic properties of the passive film formed on AISI 444 SS were evaluated by the Mott-Schottky approach. All tested materials showed passivity in the PBS medium and the passive oxide film presented a duplex nature. The highest susceptibility to pitting corrosion was associated to the NeoM SS. This steel was also associated to the highest dopant concentration. The comparatively low levels of chromium (nearly 12.5%) and molybdenum (0.3%) of NeoM relatively to the other studied stainless steels are the probable cause of its lower corrosion resistance. The NeoM chemical composition does not match that of the SUS444 standards. The AISI 444 SS pitting resistance was equivalent to the ISO 5832-1 pointing out that it is a potential candidate for replacement of commercial ferromagnetic alloys used

  6. Study of carbonitriding thermochemical treatment by plasma screen in active with pressures main austenitic stainless steels AISI 409 and AISI 316L; Estudo do tratamento termoquimico de carbonitretacao por plasma em tela ativa com pressoes variaveis nos acos inoxidaveis austenitico AISI 316L e ferririco AISI 409

    Melo, M.S.; Oliveira, A.M.; Leal, V.S.; Sousa, R.R.M. de; Alves Junior, C. [Centro Federal de Educacao Tecnologica do Maranhao (CEFET/MA), Sao Luis, MA (Brazil); Centro Federal de Educacao Tecnologica do Piaui (CEFET/PI), Teresina, PI (Brazil); Universidade Federal do Rio Grande do Norte (DF/UFRN), Natal, RN (Brazil). Dept. de Fisica. Labplasma

    2010-07-01

    The technique called Active Screen Plasma Nitriding (ASPN) is being used as an alternative once it offers several advantages with respect to conventional DC plasma. In this method, the plasma does not form directly in the sample's surface but on a screen, in such a way that undesired effects such as the edge effect is minimized. Stainless steels present not very satisfactory wearing characteristics. However, plasma carbonitriding has been used as to improve its resistance to wearing due to the formation of a fine surface layer with good properties. In this work, samples of stainless steel AISI 316L and AISI 409 were treated at pressures of 2.5 and 5 mbar. After the treatments they were characterized by microhardness, microscopy and Xray diffraction. Microscopy and hardness analysis showed satisfactory layers and toughness in those steels. (author)

  7. Pioneer ACO PUF

    U.S. Department of Health & Human Services — Pioneer ACO PUF - To address the increasing number of requests for Pioneer ACO data, the Centers for Medicare and Medicaid Services (CMS) has created a standard...

  8. Development of Nb{sub 2}O{sub 5}|Cu composite as AISI 1020 steel thermal spray coating for protection against corrosion by soil in buried structures; Desenvolvimento e uso do composito de Nb{sub 2}O{sub 5}|Cu como revestimento aplicado por aspersao termica sobre o aco AISI 1020 para protecao contra a corrosao pelo solo em estruturas enterradas

    Regis Junior, Oscar [Universidade Tecnologica Federal do Parana, Ponta Grossa, PR (Brazil). Dept. de Mecanica; Silva, Jose Maurilio da; Portella, Kleber Franke [Instituto de Tecnologia para o Desenvolvimento, Curitiba, PR (Brazil). Dept. de Pesquisa em Engenharia Civil; Paredes, Ramon Sigifredo Cortes, E-mail: regis@utfpr.edu.br [Universidade Federal do Parana, Curitiba, PR (Brazil). Dept. de Mecanica

    2012-07-01

    An Nb{sub 2}O|Cu corrosion-resistant coating was developed and applied onto AISI 1020 steel substrate by Powder Flame Spray. A galvanostatic electrochemical technique was employed, with and without ohmic drop, in four different soils (two corrosively aggressive and two less aggressive). Behavior of coatings in different soils was compared using a cathodic hydrogen reduction reaction (equilibrium potential, overvoltage and exchange current density) focusing on the effect of ohmic drop. Results allow recommendation of Nb{sub 2}O{sub 5}|Cu composite for use in buried structure protection. (author)

  9. Pioneer ACO Model

    U.S. Department of Health & Human Services — The Pioneer ACO Model is designed for health care organizations and providers that are already experienced in coordinating care for patients across care settings....

  10. Fluorescent lighting system of modified fast starting system; Sistema de alumbrado fluorescente de arranque rapido modificado

    Mendoza E, Ernesto J. [Manufacturera De Reactores, S. A., Mexico, D. F. (Mexico)

    1993-12-31

    This paper puts into perspective the possible energy saving in using hybrid ballasts for the operation of fast starting lamps. It presents in summarized form some fundamentals of the fluorescent lamps operation, as well as the fast starting modified systems. Also the results of field operation are shown, as well as the effects on the useful life of the lamp T12 as well as the T8. [Espanol] Este trabajo pone en perspectiva el ahorro de energia posible, al emplear balastros hibridos para operar lamparas de arranque rapido. Presenta en forma resumida algunos fundamentos de la operacion de lamparas fluorescentes, asi como de los sistemas de arranque rapido modificado. Se muestran tambien resultados de operacion de campo, asi como los efectos sobre la vida util de las lamparas, tanto T12 como T8.

  11. ASSESSMENT OF STOCK AND SPATIAL DISTRIBUTION OF SOLE (SOLEA SOLEA, L. IN ALBANIAN COAST USING RAPIDO TRAWL

    Enton Spaho

    2012-06-01

    Full Text Available Common sole (Solea solea Linnaeus, 1758 is still not a specific target of fishery in Albania, but it represents an important target of the mixed-species catches of bottom trawlers and set netters operating in the coastal areas in the upper part of Albanian Adriatic Sea. Sole landings are low, amounting very few tonnes, but the demand will likely increase in the next future, because of the high quality of the fish fillet and the increase of consumers demand for wild sea fish. In order to identify the spawning areas and assess the spatial distribution and biomass of this species a rapido trawl survey was performed in year 2007. The smallest specimens were mostly concentrated in the shallowest stratum and the largest ones between 30 and 100 m depth. Solea Stock Biomass (SSB was 354 t, corresponding to 64% of the overall population recorded at sea at that time. In the context of fisheries, the Albanian fishing fleet involve a number of different fishing gears, while rapido trawl is introduced recently. The special technical and operating characteristics of rapido trawl makes it very effective in sole fishery and less harmful for the sea benthos and the species inhabiting it. This study aimed the estimation of spatial distribution of common sole and its biomass in the Albanian coast using rapido trawl gear.

  12. The RAPIDOS project—European and Chinese collaborative research on biomaterials

    David Eglin

    2015-04-01

    Full Text Available The research project entitled “rapid prototyping of custom-made bone-forming tissue engineering constructs” (RAPIDOS is one of the three unique projects that are the result of the first coordinated call for research proposals in biomaterials launched by the European Union Commission and the National Natural Science Foundation of China in 2013 for facilitating bilateral translational research. We formed the RAPIDOS European and Chinese consortium with the aim of applying technologies creating custom-made tissue engineered constructs made of resorbable polymer and calcium phosphate ceramic composites specifically designed by integrating the following: (1 imaging and information technologies, (2 biomaterials and process engineering, and (3 biological and biomedical engineering for novel and truly translational bone repair solutions. Advanced solid free form fabrication technologies, precise stereolithography, and low-temperature rapid prototyping provide the necessary control to create innovative high-resolution medical implants. The use of Chinese medicine extracts, such as the bone anabolic factor icaritin, which has been shown to promote osteogenic differentiation of stem cells and enhance bone healing in vivo, is a safe and technologically relevant alternative to the intensely debated growth factors delivery strategies. This unique initiative driven by a global consortium is expected to accelerate scientific progress in the important field of biomaterials and to foster strong scientific cooperation between China and Europe.

  13. Including Language Access into Medicaid ACO Design.

    Gershon, Rachel; Morris, Lisa; Ferguson, Warren

    2016-09-01

    Quality health care relies upon communication in a patient's preferred language. Language access in health care occurs when individuals are: (1) Welcomed by providers regardless of language ability; and (2) Offered quality language services as part of their care. Federal law generally requires access to health care and quality language services for deaf and Limited English Proficient (LEP) patients in health care settings, but these patients still find it hard to access health care and quality language services.Meanwhile, several states are implementing Medicaid Accountable Care Organization (ACO) initiatives to reduce health care costs and improve health care quality. Alternative payment methods used in these initiatives can give Accountable Care Organizations more flexibility to design linguistically accessible care, but they can also put ACOs at increased financial risk for the cost of care. If these new payment methods do not account for differences in patient language needs, ACO initiatives could have the unintended consequence of rewarding ACOs who do not reach out to deaf and LEP communities or offer quality language services.We reviewed public documents related to Medicaid ACO initiatives in six states. Some of these documents address language access. More could be done, however, to pay for language access efforts. This article describes Medicaid ACO initiatives and explores how different payment tools could be leveraged to reward ACOs for increased access to care and quality language services. We find that a combination of payment tools might be helpful to encourage both access and quality. PMID:27587453

  14. Integrating III-V, Si, and polymer waveguides for optical interconnects: RAPIDO

    Aalto, Timo; Harjanne, Mikko; Offrein, Bert-Jan; Caër, Charles; Neumeyr, Christian; Malacarne, Antonio; Guina, Mircea; Sheehan, Robert N.; Peters, Frank H.; Melanen, Petri

    2016-03-01

    We present a vision for the hybrid integration of advanced transceivers at 1.3 μm wavelength, and the progress done towards this vision in the EU-funded RAPIDO project. The final goal of the project is to make five demonstrators that show the feasibility of the proposed concepts to make optical interconnects and packet-switched optical networks that are scalable to Pb/s systems in data centers and high performance computing. Simplest transceivers are to be made by combining directly modulated InP VCSELs with 12 μm SOI multiplexers to launch, for example, 200 Gbps data into a single polymer waveguide with 4 channels to connect processors on a single line card. For more advanced transceivers we develop novel dilute nitride amplifiers and modulators that are expected to be more power-efficient and temperatureinsensitive than InP devices. These edge-emitting III-V chips are flip-chip bonded on 3 μm SOI chips that also have polarization and temperature independent multiplexers and low-loss coupling to the 12 μm SOI interposers, enabling to launch up to 640 Gbps data into a standard single mode (SM) fiber. In this paper we present a number of experimental results, including low-loss multiplexers on SOI, zero-birefringence Si waveguides, micron-scale mirrors and bends with 0.1 dB loss, direct modulation of VCSELs up to 40 Gbps, +/-0.25μm length control for dilute nitride SOA, strong band edge shifts in dilute nitride EAMs and SM polymer waveguides with 0.4 dB/cm loss.

  15. Recent results of the ACO storage ring

    A permanent magnet undulator has been built and installed on the ACO Storage Ring. The undulator design, the spontaneous emission and gain of the system, as well as the laser induced bunch lengthening of the electron bunch, are presented. A low-loss optical cavity has been also recently built and operated on the ring. Its performance and the degradation problems of the mirrors are discussed. Amplification of the spontaneous emission stored in the optical cavity has been observed. Also, preliminary results on the operation of an optical klystron are reported and interpreted

  16. ALOHA Cabled Observatory (ACO): Acoustic Doppler Current Profiler (ADCP): Temperature

    National Oceanic and Atmospheric Administration, Department of Commerce — The University of Hawaii's ALOHA ("A Long-term Oligotrophic Habitat Assessment") Cabled Observatory (ACO) is located 100 km north of the island of Oahu, Hawaii (22...

  17. ALOHA Cabled Observatory (ACO): Acoustic Doppler Current Profiler (ADCP): Velocity

    National Oceanic and Atmospheric Administration, Department of Commerce — The University of Hawaii's ALOHA ("A Long-term Oligotrophic Habitat Assessment") Cabled Observatory (ACO) is located 100 km north of the island of Oahu, Hawaii (22...

  18. ACO-AFSA Algorithm in Function Optimization and Its Application

    Wang Shi Gang

    2016-01-01

    Full Text Available ACO and AFSA as two kinds of new intelligent bionic algorithm, has better robustness, and the design method is simple and easy to understand. At present, in many engineering fields, they have been a pivotal position, but there are some defects in solving function optimization problems. Because of the lack of pheromone in the initial stage of ACO, the speed of the solution is relatively slow, and AFSA has the advantages of strong global convergence ability and fast speed. In this paper, based on the advantages and disadvantages of ACO and AFSA, two kinds of algorithms are integrated, and the advantage is enhanced, a better optimization algorithm is put forward: ACO-AFSA. The initial solution and improved state transition probabilities are obtained by AFSA, and the basic ACO is improved, the congestion degree of AFSA is introduced in the algorithm, makes most of ants’ initial optimization will not be randomly selected at a strong crowding restrictions. Experimental results show that the new algorithm can get the optimal solution with less number of iterations, which greatly saves computation time, and has higher accuracy and better convergence performance. Engineering, computing the shortest distance between the surface and plane of the problem has also been good results, the experimental results are satisfactory.

  19. Improving Network Performance using ACO Based Redundant Link Avoidance Algorithm

    B. Chandra Mohan

    2010-05-01

    Full Text Available In the wide spread internet, response time and pocket loss are inappropriate due to network traffic, as a result the network efficiency becomes worst and the system provides poor Quality of Service (QoS. An optimal routing protocol, especially multipath may avoid such traffic in the network. But existing routing protocols, both single path and multi path, concentrates only on finding the routes based on any one or some set of metrics, that not always suitable for dynamic, cloud natured network environment. Ant Colony Optimization (ACO based multipath routing protocol was suggested as an alternate to this problem by many researchers. The multipath ACO also provides same set of link(s for the source to destination, so that traffic merging again becomes a critical problem. This paper proposes an optimal solution to avoid the problem of traffic merging in the network by removing redundant link in the route. The Proposed algorithm, called 'Redundant Link Avoidance (RLA algorithm', is an ACO based multi path routing methodology, avoiding copious link in the suggested routes of ACO multipath protocol.

  20. Characterization of AISI 4140 borided steels

    The present study characterizes the surface of AISI 4140 steels exposed to the paste-boriding process. The formation of Fe2B hard coatings was obtained in the temperature range 1123-1273 K with different exposure times, using a 4 mm thick layer of boron carbide paste over the material surface. First, the growth kinetics of boride layers at the surface of AISI 4140 steels was evaluated. Second, the presence and distribution of alloying elements on the Fe2B phase was measured using the Glow Discharge Optical Emission Spectrometry (GDOES) technique. Further, thermal residual stresses produced on the borided phase were evaluated by X-ray diffraction (XRD) analysis. The fracture toughness of the iron boride layer of the AISI 4140 borided steels was estimated using a Vickers microindentation induced-fracture testing at a constant distance of 25 μm from the surface. The force criterion of fracture toughness was determined from the extent of brittle cracks, both parallel and perpendicular to the surface, originating at the tips of an indenter impression. The fracture toughness values obtained by the Palmqvist crack model are expressed in the form KC(π/2) > KC > KC(0) for the different applied loads and experimental parameters of the boriding process.

  1. Corrosion of AISI 316 and AISI 304 stainless steel with iodine vapor

    The weight loss of stainless steel in corrosion with iodine vapor was studied at 500 to 10000C and an iodine vapor pressure range of 0.05 to 0.5 mm Hg, using a thermobalance. In the initial stage of corrosion, the weight loss rate is largely influenced by solution treatment or surface treatment; the induction period, observed for solution-treated samples, is shortened or eliminated by fission-fragment irradiation, ion-bombardment or mechanical polishing, and in some cases corrosion is even accelerated by the surface treatments. A constant weight loss region follows the initial stage of corrosion. In this region, the weight loss rate is not dependent on treatment to the samples, and has a linear relationship with the vapor pressure of iodine. The rate is the largest at about 800 and 7500C for AISI 316 s. s. and AISI 304 s. s. The rates in general are larger for AISI 304 s. s. than for AISI 316 s. s. below 7000C but almost the same above 8000C. Corrosion product layer is observed on the surface of the sample below 7000C. Based on these findings, the corrosion process is discussed. The deposition of corrosion product in a temperature gradient tube is also described

  2. An ACO approach for the Parallel Machines Scheduling Problem

    Gatica, Claudia R.; Esquivel, Susana Cecilia; Leguizamón, Guillermo

    2008-01-01

    The parallel machines scheduling problem (Pm) comprises the allocation of jobs on the system’s resources, i.e., a group of machines in parallel. The basic model consists of m identical machines and n jobs. The jobs are assigned according to resource availability following some allocation rule. In this work, we apply the Ant Colony Optimization (ACO) metaheuristic which includes in the construction solution process different specific heuristic to solve Pm for the minimization Maximum Tardiness...

  3. ACO in e-Learning: Towards an adaptive learning path

    Pushpa. M

    2012-03-01

    Full Text Available Today we are in an era where drastic advancements in networking and information technology are in action. The learning process has also taken these advancements, as a result of which e-learning came to thescene. Personalization in e-learning will improve the performance of the system. Recent researches are concentrating on providing adaptability to the learning management systems, depending upon the varying user needs and contexts. Adaptability can be provided at different levels .Providing an adaptive learning path according to the context of the learners’ is an important issue. An optimal adaptive learning path will help the learners in reducing the cognitive overload and disorientation, and thereby improving the efficiency of the Learning Management System (LMS. Ant Colony Optimization (ACO is a widely accepted technique since it provides an adaptive learning path to the learners. Meta-heuristic which is used in intelligent tutoring systems provides the learning path in an adaptive way. The most interesting feature of ACO is its adaptation and robustness in an environment where the learning materials and learners are changing frequently. In this paper we can have a look through the existing ACO approaches towards providing an adaptive learning path and an introduction towards an enhanced attribute ant for making the e-learning system more adaptive.

  4. ACO a Metaheuristic Technique for solving Network Problems and a Precise of Network Models

    Manila Pahwa

    2013-09-01

    Full Text Available With the growing importance of telecommunication and internet, more complex networked systems are being designed and developed. The challenges of dealing with vast complexity of networking problems such as load balancing, routing and network congestion accentuate the need of more sophisticated technique to solve these problems. Ant colony optimisation (ACO is one of the best and efficient solutions to cope up with these problems. This paper presents the following:- Theoretical study of Metaheuristic technique commonly named as Ant Colony Optimisation (ACO and how it is better than conventional algorithms, An Overview of ACO models and the reason behind being ACO better than other Conventional algorithms?

  5. Dolor mandibular de origen cardíaco

    MR Sáez Yuguero; A Bermejo Fenoll; JL Calvo Guirado; E. Álvarez Martínez

    2003-01-01

    En las complejas estructuras anatómicas orofaciales, asientan muchos procesos dolorosos. Las algias orofaciales más comunes tienen su origen a nivel dental, periodontal o en estructuras musculoesqueleticas. Sin embargo, el paciente puede manifestar dolor en esta región, bien en dientes o estructuras musculoesqueleticas, y la fuente originaria localizarse a distancia. A este tipo de dolor se le llama dolor heterotópico. Una posible fuente de dolor heterotópico es el dolor de origen cardíaco. E...

  6. A comparative study of mechanical and tribological properties of AISI-304 and AISI-316 submitted to glow discharge nitriding

    Fabiana Cristina Nascimento; Carlos Eugênio Foerster; Silvio Luiz Rutz da Silva; Carlos Mauricio Lepienski; Carlos José de Mesquita Siqueira; Clodomiro Alves Junior

    2009-01-01

    Mechanical and tribological properties os AISI 304 and AISI 316 stainless steels submited to glow discharge ion nitriding are reported.The atmosphere was 20:80 - N2:H2 with substrate temperatures ranging from 300 to 500 °C. Treatment at 300 °C produced expanded austenite (γN) in both steels. Increasing the temperature, the phases γ´-Fe4N and - Fe2+xN were present and the latter is the major phase for AISI 304. At 500 °C, the CrN phase was also identified in both steels. Hardnesses o...

  7. MODELO ACO PARA LA RECOLECCIÓN DE RESIDUOS POR CONTENEDORES ACO MODEL APPLIED TO THE WASTE COLLECTION BY CONTAINERS

    Eduardo Salazar Hornig

    2009-08-01

    Full Text Available ACO es una metaheurística inspirada en el comportamiento de las colonias de hormigas para solucionar problemas de optimización combinatoria, por medio de la utilización de agentes computacionales simples que trabajan de manera cooperativa y se comunican mediante rastros de feromona artificiales. En este trabajo se presenta un modelo para resolver el Problema de Recolección de Residuos Domiciliarios por Contenedores, el que aplica un concepto de secuencias parciales de recolección que deben ser unidas para minimizar la distancia total de recolección. El problema de unir las secuencias parciales se representa como un TSP, el que es resuelto mediante un algoritmo ACO. En base a recomendaciones de la literatura, se calibran experimentalmente los parámetros del algoritmo y se recomiendan rangos de valores que representan buenos rendimientos promedio. El modelo se aplica a un sector de recolección de la comuna de San Pedro de la Paz, Chile, obteniéndose rutas de recolección que reducen la distancia total recorrida respecto de la actual ruta utilizada y de la solución obtenida con otro modelo desarrollado previamente.ACO is a metaheuristic inspired in the behavior of natural ant colonies to solve combinatorial optimization problems, based on simple agents that work cooperatively communicating by artificial pheromone trails. In this paper a model to solve the municipal waste collection problem by containers is presented, which applies a concept of partial collection sequences that must be joined to minimize the total collection distance. The problem to join the partial collection sequences is represented as a TSP, which is solved by an ACO algorithm. Based on the literature, algorithm parameters are experimentally calibrated and range of variations that represents good average solutions are recommended. The model is applied to a waste collection sector of the San Pedro de la Paz commune in Chile, obtaining recollection routes with less total

  8. Process Parameter Optimization of WEDM for AISI M2 & AISI H13 by Anova & Analytic Hierarchy Process

    Rajkamal Singh Banga; Mukesh Verma

    2014-01-01

    WEDM is a widely recognized unconventional material cutting process used to manufacture components with complex shapes and profiles of hard materials. In this thermal erosion process, there is no physical contact between the wire tool and work materials. AISI M2 and AISI H13 materials are taken for studyand molybdenum wire electrode diameter (0.18mm); experiment is conducted according to Taguchi‟s L16 OA, with input parameters as Peak current, Pulse on, Pulse off their respons...

  9. Effect of temperature on the level of corrosion caused by heavy petroleum on AISI 304 and AISI 444 stainless steel

    João Paulo Sampaio Eufrásio Machado; Cleiton Carvalho Silva; Ana Vládia Cabral Sobral-Santiago; Hosiberto Batista de Sant'Ana; Jesualdo Pereira Farias

    2006-01-01

    This work presents a study on the influence of national heavy petroleum in the corrosion of the AISI 444 and AISI 304 stainless steels in simulated refining operation conditions. The petroleum was first characterized through physicochemical analysis (density, fluidity point, viscosity, sulfur concentration). In an attempt to understand the corrosion effect of temperature and of the type of heating the referred types of steel thermal treatments were carried out at three levels of temperature (...

  10. Physicians' Participation In ACOs Is Lower In Places With Vulnerable Populations Than In More Affluent Communities.

    Yasaitis, Laura C; Pajerowski, William; Polsky, Daniel; Werner, Rachel M

    2016-08-01

    Early evidence suggested that accountable care organizations (ACOs) could improve health care quality while constraining costs, and ACOs are expanding throughout the United States. However, if disadvantaged patients have unequal access to physicians who participate in ACOs, that expansion may exacerbate health care disparities. We examined the relationship between physicians' participation in both Medicare and commercial ACOs across the country and the sociodemographic characteristics of their likely patient populations. Physicians' participation in ACOs varied widely across hospital referral regions, from nearly 0 percent to over 85 percent. After we adjusted for individual physician and practice characteristics, we found that physicians who practiced in ZIP Code Tabulation Areas where a higher percentage of the population was black, living in poverty, uninsured, or disabled or had less than a high school education-compared to other areas-had significantly lower rates of ACO participation than other physicians. Our findings suggest that vulnerable populations' access to physicians participating in ACOs may not be as great as access for other groups, which could exacerbate existing disparities in health care quality. PMID:27503961

  11. Hospitals Participating In ACOs Tend To Be Large And Urban, Allowing Access To Capital And Data.

    Colla, Carrie H; Lewis, Valerie A; Tierney, Emily; Muhlestein, David B

    2016-03-01

    Relationships between physicians and hospitals have changed considerably over the past decade, as hospitals and physician groups have integrated and new public and private payment policies have created financial interdependence. The extent to which accountable care organizations (ACOs) involve hospitals in their operations may prove to be vitally important, because managing hospital care is a key part of improving health care quality and lowering cost growth. Using primary data on ACO composition and capabilities paired with hospital characteristics, we found that 20 percent of US hospitals were part of an ACO in 2014. Hospitals that were in urban areas, were nonprofit, or had a smaller share of Medicare patients were more likely to participate in ACOs, compared to hospitals that were in more rural areas, were for-profit or government owned, or had a larger share of Medicare patients, respectively. Qualitative data identified the following advantages of including a hospital in an ACO: the availability of start-up capital, advanced data sharing, and engagement of providers across the care continuum. Although the 63 percent of ACOs that included hospitals offered more comprehensive services compared to ACOs without hospitals, we found no differences between the two groups in their ability to manage hospital-related aspects of patient care. PMID:26953297

  12. MOEA/D-ACO: a multiobjective evolutionary algorithm using decomposition and AntColony.

    Ke, Liangjun; Zhang, Qingfu; Battiti, Roberto

    2013-12-01

    Combining ant colony optimization (ACO) and the multiobjective evolutionary algorithm (EA) based on decomposition (MOEA/D), this paper proposes a multiobjective EA, i.e., MOEA/D-ACO. Following other MOEA/D-like algorithms, MOEA/D-ACO decomposes a multiobjective optimization problem into a number of single-objective optimization problems. Each ant (i.e., agent) is responsible for solving one subproblem. All the ants are divided into a few groups, and each ant has several neighboring ants. An ant group maintains a pheromone matrix, and an individual ant has a heuristic information matrix. During the search, each ant also records the best solution found so far for its subproblem. To construct a new solution, an ant combines information from its group's pheromone matrix, its own heuristic information matrix, and its current solution. An ant checks the new solutions constructed by itself and its neighbors, and updates its current solution if it has found a better one in terms of its own objective. Extensive experiments have been conducted in this paper to study and compare MOEA/D-ACO with other algorithms on two sets of test problems. On the multiobjective 0-1 knapsack problem,MOEA/D-ACO outperforms the MOEA/D with conventional genetic operators and local search on all the nine test instances. We also demonstrate that the heuristic information matrices in MOEA/D-ACO are crucial to the good performance of MOEA/D-ACO for the knapsack problem. On the biobjective traveling salesman problem, MOEA/D-ACO performs much better than the BicriterionAnt on all the 12 test instances. We also evaluate the effects of grouping, neighborhood, and the location information of current solutions on the performance of MOEA/D-ACO. The work in this paper shows that reactive search optimization scheme, i.e., the "learning while optimizing" principle, is effective in improving multiobjective optimization algorithms. PMID:23757576

  13. Casting AISI 316 steel by gel cast

    The feasibility of producing AISI 316 steel components from their powders and avoiding their compaction is analyzed. A casting technique is tested that is similar to gel casting, used for ceramic materials. In the initial stage, the process consists of the formulation of a concentrated barbotine of powdered metal in a solution of water soluble organic monomers, which is cast in a mold and polymerized in situ to form a raw piece in the shape of the cavity. The process can be performed under controlled conditions using barbotines with a high monomer content from the acrylimide family. Then, the molded piece is slowly heated until the polymer is eliminated, and it is sintered at temperatures of 1160oC to 1300oC under a dry hydrogen atmosphere, until the desired densities are attained. The density and micro structure of the materials obtained are compared with those for the materials compacted and synthesized by the conventional processes. The preliminary results show the feasibility of the process for the production of certain kinds of structural components (CW)

  14. Optimization of tensile strength of friction welded AISI 1040 and AISI 304L steels according to statistics analysis (ANOVA)

    Kirik, Ihsan [Batman Univ. (Turkey); Ozdemir, Niyazi; Firat, Emrah Hanifi; Caligulu, Ugur [Firat Univ., Elazig (Turkey)

    2013-06-01

    Materials difficult to weld by fusion welding processes can be successfully welded by friction welding. The strength of the friction welded joints is extremely affected by process parameters (rotation speed, friction time, friction pressure, forging time, and forging pressure). In this study, statistical values of tensile strength were investigated in terms of rotation speed, friction time, and friction pressure on the strength behaviours of friction welded AISI 1040 and AISI 304L alloys. Then, the tensile test results were analyzed by analysis of variance (ANOVA) with a confidence level of 95 % to find out whether a statistically significant difference occurs. As a result of this study, the maximum tensile strength is very close, which that of AISI 1040 parent metal of 637 MPa to could be obtained for the joints fabricated under the welding conditions of rotation speed of 1700 rpm, friction pressure of 50 MPa, forging pressure of 100 MPa, friction time of 4 s, and forging time of 2 s. Rotation speed, friction time, and friction pressure on the friction welding of AISI 1040 and AISI 304L alloys were statistically significant regarding tensile strength test values. (orig.)

  15. Asthma-COPD Overlap Syndrome (ACOS): Single disease entity or not? Could exhaled nitric oxide be a useful biomarker for the differentiation of ACOS, asthma and COPD?

    Karampitsakos, Theodoros; Gourgoulianis, Konstantinos I

    2016-06-01

    Asthma and chronic obstructive pulmonary disease (COPD) represent two major public health problems. However, there is a significant proportion of patients with a mixed asthma-COPD phenotype. This condition is defined as asthma-COPD overlap syndrome (ACOS). Since there are no internationally accepted criteria for the diagnosis of that syndrome, its management remains difficult. Given the fact that patients with ACOS have an increased risk of exacerbation and hospitalization, there is a pressing need for a more targeted approach and better management. We propose that fractional exhaled nitric oxide (FeNO), a marker of eosinophilic inflammation, could help clinicians differentiate ACOS from asthma and COPD. We evaluate this hypothesis, using data derived from the existing literature. PMID:27142135

  16. The Impact Of Medicare ACOs On Improving Integration And Coordination Of Physical And Behavioral Health Care.

    Fullerton, Catherine A; Henke, Rachel M; Crable, Erica; Hohlbauch, Andriana; Cummings, Nicholas

    2016-07-01

    The accountable care organization (ACO) model holds the promise of reducing costs and improving the quality of care by realigning payment incentives to focus on health outcomes instead of service volume. One key to managing the total cost of care is improving care coordination for and treatment of people with behavioral health disorders. We examined qualitative data from ninety organizations participating in Medicare ACO demonstration programs from 2012 through 2015 to determine whether and how they focused on behavioral health care. These ACOs had mixed degrees of engagement in improving behavioral health care for their populations. The biggest challenges included a lack of behavioral health care providers, data availability, and sustainable financing models. Nonetheless, we found substantial interest in integrating behavioral health care into primary care across a majority of the ACOs. PMID:27385242

  17. Methodology to Optimize Manufacturing Time for a CNC Using a High Performance Implementation of ACO

    Oscar Montiel-Ross

    2012-10-01

    Full Text Available In this paper, an efficient methodology to generate optimal and/or quasi‐optimal sequences of G commands to minimize the manufacturing time is presented. Our solution starts from original G codes provided by application CAD/CAM software. Here, first we tackled the problem of reducing the time of the travel path for drilling of an industrial robotic manufacturing machine. The methodology can be easily implemented for free distribution or commercial CAD/CAM software without achieving any modification to it. Several experiments that demonstrate how this proposal can help to outperform solutions provided by application software are presented, consistent improvements around 62% were obtained. Moreover, for optimizing the time along the travel path, we present a high performance implementation of Ant Colonies (ACO known as Parallel ACO (P‐ACO that allows achieving the optimization task efficiently by speeding up the original ACO. A Graphical User Interface that integrates the whole process is shown.

  18. An ACO model for a non-stationary formulation of the single elevator problem

    Molina, Silvia; Leguizamón, Mario Guillermo; Alba Torres, Enrique

    2007-01-01

    The Ant Colony Optimization (ACO) metaheuristic is a bio-inspired approach for hard combinatorial optimization problems for stationary and non-stationary environments. In the ACO metaheuristic, a colony of artificial ants cooperate for finding high quality solutions in a reasonable time. An interesting example of a non-stationary combinatorial optimization problem is the Multiple Elevators Problem (MEP) which consists in finding a sequence of movements for each elevator to perform in a buildi...

  19. Comparative electrochemical study of 08H18N10T, AISI 304 and AISI 316L stainless steels

    The aim of this work was to determine the main characteristics of the passivation and surface oxidation of 08H18N10T, AISI304 and AISI316L stainless steels, which serve as structural materials of VVER and PWR nuclear reactors. With the help of electrochemical experiments these materials were ranked according to their resistance against uniform corrosion. The measurements were done as a function of temperature in the range between room temperature and 80 deg. C. A sample of 08H18N10T steel was irradiated in the Budapest research reactor. With cyclic voltammetry we found that AISI 304 exhibits a very large passivation peak as a classical example for passivation. The peak is much smaller for AISI 316L and it is very small for 08H18N10T. This implies that the native oxide layer on AISI 316L and 08H18N10T is more protective than on AISI 304. The 08H18N10T steel has the best protective passive oxide layer which forms already in air and it is very difficult to remove it even at negative potentials. By comparing impedance spectra of the various stainless steels results lead to the same conclusions we obtained from cyclic voltammetry. Our experimental results of the irradiated steel are in accord with the fact that neutron irradiation increases the number of defect sites within the oxide layer. We found that irradiation has no considerable effect on the active-to-passive transition process. The small variations in the alloy composition do not alter the transition process significantly, as well

  20. Comparative electrochemical study of 08H18N10T, AISI 304 and AISI 316L stainless steels

    Kerner, Zsolt; Horvath, Akos [KFKI Atomic Energy Research Institute, H-1525 Budapest 114, P.O. Box 49 (Hungary); Nagy, Gabor [KFKI Atomic Energy Research Institute, H-1525 Budapest 114, P.O. Box 49 (Hungary)], E-mail: nagyg@sunserv.kfki.hu

    2007-10-10

    The aim of this work was to determine the main characteristics of the passivation and surface oxidation of 08H18N10T, AISI304 and AISI316L stainless steels, which serve as structural materials of VVER and PWR nuclear reactors. With the help of electrochemical experiments these materials were ranked according to their resistance against uniform corrosion. The measurements were done as a function of temperature in the range between room temperature and 80 deg. C. A sample of 08H18N10T steel was irradiated in the Budapest research reactor. With cyclic voltammetry we found that AISI 304 exhibits a very large passivation peak as a classical example for passivation. The peak is much smaller for AISI 316L and it is very small for 08H18N10T. This implies that the native oxide layer on AISI 316L and 08H18N10T is more protective than on AISI 304. The 08H18N10T steel has the best protective passive oxide layer which forms already in air and it is very difficult to remove it even at negative potentials. By comparing impedance spectra of the various stainless steels results lead to the same conclusions we obtained from cyclic voltammetry. Our experimental results of the irradiated steel are in accord with the fact that neutron irradiation increases the number of defect sites within the oxide layer. We found that irradiation has no considerable effect on the active-to-passive transition process. The small variations in the alloy composition do not alter the transition process significantly, as well.

  1. The study on the properties of AISI 4140 and AISI 1040 steel rods welded by friction welding

    Thanee Toomprasen; Chawalit Thinvongpituk; Sukangkana Talangkun

    2014-01-01

    This paper is aimed to investigate the properties of joint between AISI 4140 and AISI 1040 welded by friction welding. The specimens were prepared in round shape of 13 mm diameter and 100 mm long. They were welded by friction welding method under the following conditions; friction pressure of 183 MPa, friction time of 12 sec, upset pressure of 428 MPa, upset time of 7 sec. and rotational speed of 1400 rpm. The strength and hardness were tested on the welded area. The result showed finer grain...

  2. Investigation of residual stress in laser welding between carbon steel AISI 1010 and stainless AISI 304

    The dissimilar materials union has the residual stress formation as one of the most critical problems, which occurs mainly because these materials have both different thermal expansion coefficients and thermal conductivities. In this study, it was investigated the laser welding technique between steels, AISI 1010 and AISI 304. The materials were joined by butt autogenous welding with a continuous Nd:YAG laser. The main objective was to identify the welding parameters influence by the residual stresses analysis in the heat affected zone (HAZ). It was executed a factorial design with three-factor at two levels with a replica, which were varied power, welding speed and focal position of the laser beam. Residual stress measurements by the diffraction of X-rays were performed on the sample surface, to study their variation as a function of the parameters investigated. The blind hole method was also used to evaluate the residual stress along the samples depth, up to depth of 1mm. Besides residual stress measurement, weld seams were evaluated by optical and scanned electron microscopy, which were aimed to determine the weld geometry and changes in the microstructure. It was also made Vickers hardness measurements to evaluate the extent of HAZ. To evaluate the mechanical properties of the union were performed tensile and fatigue test. The MINITAB 15 software was used to analyze the residual stresses obtained by the blind hole method at different depths of the HAZ. It was also used statistical regression based on both the influences different and the combination of this input factors, in the residual stress of union. The results indicate that the models can satisfactorily predict the responses and provide users a guide to better define the welding parameters. (author)

  3. Dolor mandibular de origen cardíaco

    MR Sáez Yuguero

    2003-10-01

    Full Text Available En las complejas estructuras anatómicas orofaciales, asientan muchos procesos dolorosos. Las algias orofaciales más comunes tienen su origen a nivel dental, periodontal o en estructuras musculoesqueleticas. Sin embargo, el paciente puede manifestar dolor en esta región, bien en dientes o estructuras musculoesqueleticas, y la fuente originaria localizarse a distancia. A este tipo de dolor se le llama dolor heterotópico. Una posible fuente de dolor heterotópico es el dolor de origen cardíaco. Este articulo presenta un caso clínico en el que el dolor mandibular bilateral fue el síntoma inicial de una cardiopatía isquémica que fue erróneamente etiquetada de artrosis de la articulación temporomandibular.In the complex orofacial anatomic structures, many painful processes are felt. The most common orofacial pains have their origin at dental or periodontal level, or in muscle -skeletical structures. However, the patient can have pain in this area- either in teeth or muscle-eskeletical structures- and the originating source can be located at a distance. This type of pain is called heterotopic pain. A possible source of heterotopic pain is the pain of cardiac origin. This paper presents a clinical case in which the bilateral mandibular pain is the initial symptom of an ischemic cardiopathy that was erroneously labeled as temporomandibular arthrosis.

  4. CACONET: Ant Colony Optimization (ACO) Based Clustering Algorithm for VANET

    Bajwa, Khalid Bashir; Khan, Salabat; Chaudary, Nadeem Majeed; Akram, Adeel

    2016-01-01

    A vehicular ad hoc network (VANET) is a wirelessly connected network of vehicular nodes. A number of techniques, such as message ferrying, data aggregation, and vehicular node clustering aim to improve communication efficiency in VANETs. Cluster heads (CHs), selected in the process of clustering, manage inter-cluster and intra-cluster communication. The lifetime of clusters and number of CHs determines the efficiency of network. In this paper a Clustering algorithm based on Ant Colony Optimization (ACO) for VANETs (CACONET) is proposed. CACONET forms optimized clusters for robust communication. CACONET is compared empirically with state-of-the-art baseline techniques like Multi-Objective Particle Swarm Optimization (MOPSO) and Comprehensive Learning Particle Swarm Optimization (CLPSO). Experiments varying the grid size of the network, the transmission range of nodes, and number of nodes in the network were performed to evaluate the comparative effectiveness of these algorithms. For optimized clustering, the parameters considered are the transmission range, direction and speed of the nodes. The results indicate that CACONET significantly outperforms MOPSO and CLPSO. PMID:27149517

  5. CACONET: Ant Colony Optimization (ACO) Based Clustering Algorithm for VANET.

    Aadil, Farhan; Bajwa, Khalid Bashir; Khan, Salabat; Chaudary, Nadeem Majeed; Akram, Adeel

    2016-01-01

    A vehicular ad hoc network (VANET) is a wirelessly connected network of vehicular nodes. A number of techniques, such as message ferrying, data aggregation, and vehicular node clustering aim to improve communication efficiency in VANETs. Cluster heads (CHs), selected in the process of clustering, manage inter-cluster and intra-cluster communication. The lifetime of clusters and number of CHs determines the efficiency of network. In this paper a Clustering algorithm based on Ant Colony Optimization (ACO) for VANETs (CACONET) is proposed. CACONET forms optimized clusters for robust communication. CACONET is compared empirically with state-of-the-art baseline techniques like Multi-Objective Particle Swarm Optimization (MOPSO) and Comprehensive Learning Particle Swarm Optimization (CLPSO). Experiments varying the grid size of the network, the transmission range of nodes, and number of nodes in the network were performed to evaluate the comparative effectiveness of these algorithms. For optimized clustering, the parameters considered are the transmission range, direction and speed of the nodes. The results indicate that CACONET significantly outperforms MOPSO and CLPSO. PMID:27149517

  6. Colloquium on Large Scale Improvement: Implications for AISI

    McEwen, Nelly, Ed.

    2008-01-01

    The Alberta Initiative for School Improvement (AISI) is a province-wide partnership program whose goal is to improve student learning and performance by fostering initiatives that reflect the unique needs and circumstances of each school authority. It is currently ending its third cycle and ninth year of implementation. "The Colloquium on Large…

  7. RNA Interference of 1-Aminocyclopropane-1-carboxylic Acid Oxidase (ACO1 and ACO2 Genes Expression Prolongs the Shelf Life of Eksotika (Carica papaya L. Papaya Fruit

    Rogayah Sekeli

    2014-06-01

    Full Text Available The purpose of this study was to evaluate the effectiveness of using RNA interference in down regulating the expression of 1-aminocyclopropane-1-carboxylic acid oxidase gene in Eksotika papaya. One-month old embryogenic calli were separately transformed with Agrobacterium strain LBA 4404 harbouring the three different RNAi pOpOff2 constructs bearing the 1-aminocyclopropane-1-carboxylic acid oxidase gene. A total of 176 putative transformed lines were produced from 15,000 calli transformed, selected, then regenerated on medium supplemented with kanamycin. Integration and expression of the targeted gene in putatively transformed lines were verified by PCR and real-time RT-PCR. Confined field evaluation of a total of 31 putative transgenic lines planted showed a knockdown expression of the targeted ACO1 and ACO2 genes in 13 lines, which required more than 8 days to achieve the full yellow colour (Index 6. Fruits harvested from lines pRNAiACO2 L2-9 and pRNAiACO1 L2 exhibited about 20 and 14 days extended post-harvest shelf life to reach Index 6, respectively. The total soluble solids contents of the fruits ranged from 11 to 14° Brix, a range similar to fruits from non-transformed, wild type seed-derived plants.

  8. A comparative study of mechanical and tribological properties of AISI-304 and AISI-316 submitted to glow discharge nitriding

    Fabiana Cristina Nascimento

    2009-06-01

    Full Text Available Mechanical and tribological properties os AISI 304 and AISI 316 stainless steels submited to glow discharge ion nitriding are reported.The atmosphere was 20:80 - N2:H2 with substrate temperatures ranging from 300 to 500 °C. Treatment at 300 °C produced expanded austenite (γN in both steels. Increasing the temperature, the phases γ´-Fe4N and - Fe2+xN were present and the latter is the major phase for AISI 304. At 500 °C, the CrN phase was also identified in both steels. Hardnesses of about 13-14 GPa at near surface regions were obtained in both steels. Moreover, AISI 316 nitrided at 500 °C has the deepest hard layer. Tribological tests showed that wear can be reduced by up to a factor of six after the nitriding processes, even for a working temperature of 300 °C. The profiles during and after nanoscratch tests did not reveal significant differences after nitriding processes in both steels.

  9. Process Parameter Optimization of WEDM for AISI M2 & AISI H13 by Anova & Analytic Hierarchy Process

    Rajkamal Singh Banga

    2014-10-01

    Full Text Available WEDM is a widely recognized unconventional material cutting process used to manufacture components with complex shapes and profiles of hard materials. In this thermal erosion process, there is no physical contact between the wire tool and work materials. AISI M2 and AISI H13 materials are taken for studyand molybdenum wire electrode diameter (0.18mm; experiment is conducted according to Taguchi‟s L16 OA, with input parameters as Peak current, Pulse on, Pulse off their response on MRR, Surface Roughness, Kerf width & Spark Gap is analysed to check the significance of each using ANOVA. Process parameter optimization is done by Analytic Hierarchy Process with the criteria Maximum MRR, minimum kerf and surface roughness. It is observed that for material AISI M2 at low value of peak current (1 A, pulse off (20µs and pulse on (30µs we can minimize surface roughness (3.30µm, kerf width (0.195 mm and maximize MRR (0.022 g/min,from the selected levels whereas for material AISI H13 Peak current (1A, Pulse On (40µs and high Pulse Off (30µs we get better Surface roughness (3.71 µm, kerf width (0.196mm and maximum MRR (0.020g/min, from the selected levels.

  10. The study on the properties of AISI 4140 and AISI 1040 steel rods welded by friction welding

    Thanee Toomprasen

    2014-06-01

    Full Text Available This paper is aimed to investigate the properties of joint between AISI 4140 and AISI 1040 welded by friction welding. The specimens were prepared in round shape of 13 mm diameter and 100 mm long. They were welded by friction welding method under the following conditions; friction pressure of 183 MPa, friction time of 12 sec, upset pressure of 428 MPa, upset time of 7 sec. and rotational speed of 1400 rpm. The strength and hardness were tested on the welded area. The result showed finer grains. in the welded area. This is the result of friction pressure and upset pressure in the welding process. In addition, the observation result indicated some changes of Ferrite and Pearlite in welded zone. This phase change resulted in the increment of hardness in AISI 4140 at the contact area and adjacent. In part of AISI 1040, the portion of Pearlite and Ferrite are not significantly changed, therefore the value of hardness is almost constant.

  11. MGA trajectory planning with an ACO-inspired algorithm

    Ceriotti, Matteo; Vasile, Massimiliano

    2010-11-01

    Given a set of celestial bodies, the problem of finding an optimal sequence of swing-bys, deep space manoeuvres (DSM) and transfer arcs connecting the elements of the set is combinatorial in nature. The number of possible paths grows exponentially with the number of celestial bodies. Therefore, the design of an optimal multiple gravity assist (MGA) trajectory is a NP-hard mixed combinatorial-continuous problem. Its automated solution would greatly improve the design of future space missions, allowing the assessment of a large number of alternative mission options in a short time. This work proposes to formulate the complete automated design of a multiple gravity assist trajectory as an autonomous planning and scheduling problem. The resulting scheduled plan will provide the optimal planetary sequence and a good estimation of the set of associated optimal trajectories. The trajectory model consists of a sequence of celestial bodies connected by two-dimensional transfer arcs containing one DSM. For each transfer arc, the position of the planet and the spacecraft, at the time of arrival, are matched by varying the pericentre of the preceding swing-by, or the magnitude of the launch excess velocity, for the first arc. For each departure date, this model generates a full tree of possible transfers from the departure to the destination planet. Each leaf of the tree represents a planetary encounter and a possible way to reach that planet. An algorithm inspired by ant colony optimization (ACO) is devised to explore the space of possible plans. The ants explore the tree from departure to destination adding one node at the time: every time an ant is at a node, a probability function is used to select a feasible direction. This approach to automatic trajectory planning is applied to the design of optimal transfers to Saturn and among the Galilean moons of Jupiter. Solutions are compared to those found through more traditional genetic-algorithm techniques.

  12. Relative Study of CGS with ACO and BCO Swarm Intelligence Techniques

    T.Hashni

    2012-09-01

    Full Text Available Swarm intelligence is the collective-level, problem-solving behavior of groups of relatively simple agents.Local interactions among agents, either direct or indirect through the environment, are fundamental for theemergence of swarm intelligence. Ant Colony Optimization (ACO is a swarm based meta-heuristic method that isinspired by the behavior of real ant colonies. Bee Colony Optimization (BCO meta-heuristic belongs to the groupof Swarm Intelligence techniques. Consultant Guided Search (CGS is a new hybrid meta heuristic, which combinesnew ideas with concepts found in Ant colony Optimization (ACO, Bee Colony Optimization (BCO technique. Thispaper presents comparative study of CGS, ACO, BCO techniques and the flexibility of CGS.

  13. Weldability of AISI 304 to copper by friction welding

    Kirik, Ihsan [Batman Univ. (Turkey); Balalan, Zulkuf [Firat Univ., Elazig (Turkey)

    2013-06-01

    Friction welding is a solid-state welding method, which can join different materials smoothly and is excessively used in manufacturing industry. Friction welding method is commonly used in welding applications of especially cylindrical components, pipes and materials with different properties, for which other welding methods remain incapable. AISI 304 stainless steel and a copper alloy of 99.6 % purity were used in this study. This couple was welded in the friction welding machine. After the welding process, samples were analyzed macroscopically and microscopically, and their microhardness was measured. Tensile test was used to determine the bond strength of materials that were joined using the friction welding method. At the end of the study, it was observed that AISI 304 stainless steel and copper could be welded smoothly using the friction welding method and the bond strength is close to the tensile strength of copper. (orig.)

  14. Experimental evaluation of mechanical properties of friction welded AISI steels

    Amit Handa

    2014-12-01

    Full Text Available In the present study, an experimental setup was designed and fabricated in order to accomplish friction welded joints between austenitic stainless steel and low-alloy steel. Thereafter, the effect of axial pressures on the mechanical properties of friction welded AISI 304 with AISI 1021 steels, produced by mechanical joining, have been investigated. Samples were welded under different axial pressures ranging from 75 to 135 MPa, at constant speed of 1250 rpm. The tensile strength, impact strength, and micro-hardness values of the weldments were determined and evaluated. Simultaneously, the fractrography of the tensile-tested specimens were carried out, so as to understand the failure analysis.

  15. Magnetic Barkhausen emission in lightly deformed AISI 1070 steel

    Capo Sanchez, J., E-mail: jcapo@cnt.uo.edu.cu [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, Av. Patricio Lumumba s/n, 90500 Santiago de Cuba (Cuba); Campos, M.F. de [EEIMVR-Universidade Federal Fluminense, Av. dos Trabalhadores 420, Vila Santa Cecilia, 27255-125 Volta Redonda, RJ (Brazil); Padovese, L.R. [Departamento de Engenharia Mecanica, Escola Politecnica, Universidade de Sao Paulo, Av. Prof. Mello Moraes, 2231, 05508-900 Sao Paulo (Brazil)

    2012-01-15

    The Magnetic Barkhausen Noise (MBN) technique can evaluate both micro- and macro-residual stresses, and provides indication about the relevance of contribution of these different stress components. MBN measurements were performed in AISI 1070 steel sheet samples, where different strains were applied. The Barkhausen emission is also analyzed when two different sheets, deformed and non-deformed, are evaluated together. This study is useful to understand the effect of a deformed region near the surface on MBN. The low permeability of the deformed region affects MBN, and if the deformed region is below the surface the magnetic Barkhausen signal increases. - Highlights: > Evaluated residual stresses by the magnetic Barkhausen technique. > Indication about the relevance of micro-and macro-stress components. > Magnetic Barkhausen measurements were carried out in AISI 1070 steel sheet samples. > Two different sheets, deformed and non-deformed, are evaluated together. > Magnetic Barkhausen signal increases when deformed region is below the surface.

  16. 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

    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...

  17. Hot forming of AISI A2 tool steel

    Večko Pirtovšek, T.; Peruš, I.; Kugler, G.; Turk, R.; M. Terčelj

    2008-01-01

    For further increase of economy of production of AISI A2 tool steel a study of possibility of expanding the hot working range and better prediction of flow stress has been carried out. By employing hot compression tests it was proved, that initial microstructures have influence on the lower limit and chemical composition on upper limit of hot working range. A CAE Neural Networks was applied to predict the flow stresses for intermediate values of strain rates and temperatures. For optimization...

  18. Corrosion under stress of AISI 304 steel in thiocyanate solutions

    Corrosion susceptibility under stress of AISI 304 steel sensitized in a sodium thiocyanate solution has been studied and results were compared with those obtained with solutions of thiosulfate and tetrathionate. Sensitized steel type 304 is highly susceptible to corrosion when under intergranular stress (IGSCC) in thiocyanate solutions but the aggressiveness of this anion is less than that of the other sulphur anions studied (thiosulfate and tetrathionate). This work has been partly carried out in the Chemistry Department. (Author)

  19. An investigation on fatigue life of borided AISI 1010 steel

    O.N. Celik

    2009-01-01

    Full Text Available Purpose: This study aims to investigate the fatigue life of box borided AISI 1010 steel materials.Design/methodology/approach: Fatigue specimens firstly have been prepared according to ASTM E466-96 standard and normalized. Then their surfaces have been cleaned by polishing. Boriding heat treatment has been applied in solid media with the help of Ekabor2 powder. Specimens have been borided at 1173-1223-1273 and 1323 K temperatures for 2-4 and 6 hours respectively. Fatigue tests have been made in rotating-bend test device. Separate S-N diagram has been formed for each boriding condition and then their results were compared with the results of the specimens on which any heat treatment has not been made.Findings: As a result it has been seen that boriding has no positive effect on fatigue life of AISI 1010 steel materials. And also it has been determined that fatigue life of the materials on which boriding heat treatment applied, decreases in between 14 %-55 %.Research limitations/implications: It can be noted that the reasons of short fatigue life determination are the boride layer’s much higher hardness than the substrate material’s, and the micro cracks existed between boride phases formed onto the surface.Originality/value: The investigations on fatigue life of borided AISI 1010 steel were made.

  20. An improved adaptive ACO meta heuristic for scheduling multimedia traffic across the 802.11e EDCA

    Ditze, Michael; Becker, Markus

    2008-01-01

    This paper presents an adaptive near-optimal scheduler for multimedia traffic for the 802.11e Enhanced Distributed Channel Access (EDCA) medium access control scheme. The scheduler exploits the ant colony optimization (ACO) meta heuristic to tackle the challenge of packet scheduling. ACO is a biologically inspired algorithm that is known to find near-optimal solutions for combinatorial optimization problems. Thus, we expect that ACO scheduling produces more efficient schedules than comparable deterministic scheduling approaches at the expenses of a computational overhead it introduces. We compare ACO scheduling relevant deterministic scheduling approaches, and in particular the MLLF scheduler that is specifically designed for the needs of compressed multimedia applications. The purpose of the evaluation is twofold. It allows to draw conclusions on the feasibility of ACO scheduling for multimedia traffic while it serves as a benchmark to determine to what extent deterministic schedulers fall short of a near-optimal solution.

  1. Effect of temperature on the level of corrosion caused by heavy petroleum on AISI 304 and AISI 444 stainless steel

    João Paulo Sampaio Eufrásio Machado

    2006-06-01

    Full Text Available This work presents a study on the influence of national heavy petroleum in the corrosion of the AISI 444 and AISI 304 stainless steels in simulated refining operation conditions. The petroleum was first characterized through physicochemical analysis (density, fluidity point, viscosity, sulfur concentration. In an attempt to understand the corrosion effect of temperature and of the type of heating the referred types of steel thermal treatments were carried out at three levels of temperature (200, 300 and 400 °C. The procedure was done in conditions close to those in the distillation column. Heat was gradually increased from room temperature, and directly heated to working temperature. Each treatment took 4 hours to be completed. Scanning electronic microscopy (SEM and the analysis of X rays dispersive energy (EDX were used after the trials to characterize the samples. The results show that treatment temperature, as well as the type of heating, has distinct influences on each type of steel.

  2. ACO Based Feature Subset Selection for Multiple k-Nearest Neighbor Classifiers

    Shailendra Kumar Shrivastava

    2011-05-01

    Full Text Available The k-nearest neighbor (k-NN is one of the most popular algorithms used for classification in various fields of pattern recognition & data mining problems. In k-nearest neighbor classification, theresult of a new instance query is classified based on the majority of k-nearest neighbors. Recently researchers have begun paying attention to combining a set of individual k-NN classifiers, each using adifferent subset of features, with the hope of improving the overall classification accuracy. In this paper we proposed Ant Colony Optimization (ACO based feature subset selection for multiple k-nearest neighbor classifiers. The ACO is an iterative meta-heuristic search technique, which inspired by the foraging food behavior of real ant colonies. In ACO, real ants become artificial ants with the particular abilities such as distance determination & tour memory. The solution is constructed in a probabilistic waybased on pheromone model in the form of numerical values. The concept of this approach is selecting the best possible subsets of feature from the original set with the help of ACO and combines the outputs from multiple k-NN classifiers. The experimental results show that this proposed method improves the average classification accuracy of k-NN classifier.

  3. Postharvest Analysis of Lowland Transgenic Tomato Fruits Harboring hpRNAi-ACO1 Construct

    Bita Behboodian

    2012-01-01

    Full Text Available The plant hormone, ethylene, is an important regulator which involved in regulating fruit ripening and flower senescence. In this study, RNA interference (RNAi technology was employed to silence the genes involved in ethylene biosynthetic pathway. This was achieved by blocking the expression of specific gene encoding the ACC oxidase. Initially, cDNA corresponding to ACO1 of lowland tomato cultivar (MT1, which has high identity with ACO1 of Solanum lycopersicum in GenBank, was cloned through RT-PCR. Using a partial coding region of ACO1, one hpRNAi transformation vector was constructed and expressed ectopically under the 35S promoter. Results showed that transgenic lines harboring the hpRNA-ACO1 construct had lower ethylene production and a longer shelf life of 32 days as compared to 10 days for wild-type fruits. Changes in cell wall degrading enzyme activities were also investigated in cases where the transgenic fruits exhibited reduced rates of firmness loss, which can be associated with a decrease in pectin methylesterase (PME and polygalacturonase (PG activities. However, no significant change was detected in both transgenic and wild-type fruits in terms of β-galactosidase (β-Gal activity and levels of total soluble solid, titratable acid and ascorbic acid.

  4. Squeeze Casting Method Of AI-Si Alloy For Piston Material

    The AI-Si alloy is an alloy used as piston material. This alloys could be as AI-Si hypereutectic alloy (Si content more than 12.5 % wt.), as AI-Si eutectic alloy (Si cuntent 12.5 % wt, and as AI-Si hypoeutectic alloy (Si content less than 12.5 % wt.). The synthesize of AI-Si alloy piston generally using the technique of gravity casting in a dies. This method is causing high porousity. By using the squeeze technique, amount ofporousity in AI-Si alloy is possibly reduced and the density of this alloy should be higher. The other factors such as alloying elements of AI-Si alloy (Mg. Cu, Zn) would increase the mechanical properties especially the hardness. The focuses of this research are the microstructure and the maximum hardness during the heat treatment of AI-Si alloy which was added by alloying elments. The result of hardness at test shows the maximum hardness at 94.7 kg/mm2 obtained at aging temperature of 210oC for hours with homogenous dendritic microstructure

  5. Plasma nitriding of AISI 304L and AISI 316L stainless steels: effect of time in the formation of S phase and the chromium nitrides

    Plasma nitriding can improve hardness and wear resistance of austenitic stainless steels without losses in corrosion resistance. This fact relies on a nitrided layer constituted only by S phase, without chromium nitrides precipitation. In this work, the effect of nitriding time on phases formed on nitrided layer was investigated in two austenitic stainless steels: AISI 304L e AISI 316L. The samples were nitrided at 420 deg C, using a mixture of 60 % N2 and 40% H2, during 5, 7 and 9 hours. It was noted that chromium nitrides were formed on samples of AISI 304L, nitrided for 7 e 9 hours, while all nitrided samples of AISI 316L showed only formation of S phase. The nitrided layers were characterized using optical microscope and x-ray diffraction. (author)

  6. Microstructural Characteristic of Dissimilar Welded Components (AISI 430 Ferritic-AISI 304 Austenitic Stainless Steels) by CO2 Laser Beam Welding (LBW)

    Caligulu, Ugur; Dikbas, Halil; Taskin, Mustafa

    2012-01-01

    In this study, microstructural characteristic of dissimilar welded components (AISI 430 ferritic-AISI 304 austenitic stainless steels) by CO2 laser beam welding (LBW) was investigated. Laser beam welding experiments were carried out under argon and helium atmospheres at 2000 and 2500 W heat inputs and 100-200-300 cm/min. welding speeds. The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy, SEM, EDS and XRD analysis. The tensile strengt...

  7. Effects of X-rays Radiation on AISI 304 Stainless Steel Weldings with AISI 316L Filler Material: A Study of Resistance and Pitting Corrosion Behavior

    Francisco Javier Cárcel-Carrasco; Manuel Pascual-Guillamón; Miguel Angel Pérez-Puig

    2016-01-01

    This article investigates the effect of low-level ionizing radiation, namely X-rays, on the micro structural characteristics, resistance, and corrosion resistance of TIG-welded joints of AISI 304 austenitic stainless steel made using AISI 316L filler rods. The welds were made in two different environments: natural atmospheric conditions and a closed chamber filled with inert argon gas. The influence of different doses of radiation on the resistance and corrosion characteristics of the welds i...

  8. Mössbauer studies on an AISI 1137 type steel

    E Güler; H Akta

    2006-06-01

    An AISI 1137 type medium carbon steel was studied by means of scanning electron microscopy and Mössbauer spectroscopy. This steel in as received state at room temperature was ferritic. Different heat treatments on related steel exhibited different microstructures such as pearlite and bainite. Also magnetism of these product phases was determined as 32.7 T and 32.6 T relatively where ferromagnetism of ferritic phase in as received state was 33.05 T. Mössbauer parameters such as isomer shifts and % volumes were also determined before and after transformations.

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

    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.

  10. In pile AISI 316L. Low cycle fatigue. Final report

    In pile testing of the effect of neutron irradiation on the fatigue life of the reference material AISI 316L was performed in the framework of the European fusion technology program. The overall programme, carried out at SCK CEN (Mol,Belgium), exists of two instrumented rigs for low cycle fatigue testing, which were consecutively loaded in the BR-2 reactor during periods Jan (94) June (94) and Aug (94)-Dec(94). In each experiment, two identical samples were loaded by means of a pneumatically driven system. The samples were instrumented with thermocouples, strain gages, linear variable displacement transducers, and activation monitors. The experimental conditions are given. Type of fatigue test: load controlled, symmetric, uniaxial, triangular wave shape; stress range: about 580 MPa; sample shape: hourglass, diameter 3.2 mm, radius 12.5 mm; environment: NaK (peritectic); temperature: 250 C; maximum dpa value up to fracture: 1.7. Two of four samples were broken (one in each experiment) after having experienced 17 419 respectively 11 870 stress cycles. These new data points confirm earlier results from pile fatigue tests: irradiation causes no degradation of fatigue life of AISI 316L steel, at least for the parameters corresponding to these experiments

  11. Fiber laser welding of AISI 304 stainless steel plates

    Compared with conventional lasers, fiber laser welding is characterized by high melting efficiency, deferent keyhole modes and power density characteristics, which could affect the heat and melt flow of the molten pool during welding. The objective of the present work was to study the fiber laser weldability of 5 mm thick AISI 304 austenitic stainless steel plates; therefore, bead-on-plate welding was exploited on AISI 304 stainless steel plates with different laser powers, welding speeds, defocused distances with different types of shielding gas and their effects on the weld zone geometry and properties and final solidification microstructure at room temperature. Laser power, welding speed and defocused distance have a great effect on the bead appearance and weld zone shape while almost no significant effect on both the type of microstructure and mechanical properties of welds. The microstructure of all laser welds was always austenitic including about 3-5 % ferrite. However, the lower the laser power and/or the higher the welding speed, the finer solidification structure, primary ferrite or mixed-mode solidification resulted in crack-free welds. (author)

  12. New data association technique based on ACO with directional information considered

    2008-01-01

    Due to the advantages of ant colony optimization (ACO) in solving complex problems, a new data association algorithm based on ACO in a cluttered environment called DACDA is proposed. In the proposed method, the concept for tour and the length of tour are redefined. Additionally, the directional information is incorporated into the proposed method because it is one of the most important factors that affects the performance of data association. Kalraan filter is employed to estimate target states. Computer simulation results show that the proposed method could carry out data association in an acceptable CPU time, and the correct data association rate is higher than that obtained by the data association (DA) algorithm not combined with directional information.

  13. A Novel Framework Based on ACO and PSO for RNA Secondary Structure Prediction

    Gang Wang

    2013-01-01

    Full Text Available Prediction of RNA structure is a useful process for creating new drugs and understanding genetic diseases. In this paper, we proposed a particle swarm optimization (PSO and ant colony optimization (ACO based framework (PAF for RNA secondary structure prediction. PAF consists of crucial stem searching (CSS and global sequence building (GSB. In CSS, a modified ACO (MACO is used to search the crucial stems, and then a set of stems are generated. In GSB, we used a modified PSO (MPSO to construct all the stems in one sequence. We evaluated the performance of PAF on ten sequences, which have length from 122 to 1494. We also compared the performance of PAF with the results obtained from six existing well-known methods, SARNA-Predict, RnaPredict, ACRNA, PSOfold, IPSO, and mfold. The comparison results show that PAF could not only predict structures with higher accuracy rate but also find crucial stems.

  14. Ant Colony Optimization ACO For The Traveling Salesman Problem TSP Using Partitioning

    Alok Bajpai; Raghav Yadav

    2015-01-01

    Abstract An ant colony optimization is a technique which was introduced in 1990s and which can be applied to a variety of discrete combinatorial optimization problem and to continuous optimization. The ACO algorithm is simulated with the foraging behavior of the real ants to find the incremental solution constructions and to realize a pheromone laying-and-following mechanism. This pheromone is the indirect communication among the ants. In this paper we introduces the partitioning technique ba...

  15. Experimental evaluation of a R134a/CO2 cascade refrigeration plant

    Sanz Kock, Carlos; Llopis Doménech, Rodrigo; Sánchez García-Vacas, Daniel; Cabello López, Ramón; Torrella Alcaraz, Enrique

    2014-01-01

    We present the experimental evaluation of a R134a/CO2 cascade refrigeration plant designed for low evaporation temperature in commercial refrigeration applications. The test bench incorporates two single- stage vapour compression cycles driven by semi hermetic compressors coupled thermally through two brazed plate cascade heat exchangers working in parallel and controlled by electronic expansion valves. The experimental evaluation (45 steady-states) covers evaporating temperatures from -40 to...

  16. Relative Study of CGS with ACO and BCO Swarm Intelligence Techniques

    T.Hashni; T Amudha

    2012-01-01

    Swarm intelligence is the collective-level, problem-solving behavior of groups of relatively simple agents.Local interactions among agents, either direct or indirect through the environment, are fundamental for theemergence of swarm intelligence. Ant Colony Optimization (ACO) is a swarm based meta-heuristic method that isinspired by the behavior of real ant colonies. Bee Colony Optimization (BCO) meta-heuristic belongs to the groupof Swarm Intelligence techniques. Consultant Guided Search (CG...

  17. Tailoring Systems Engineering Processes in a Conceptual Design Environment: A Case Study at NASA Marshall Spaceflight Center's ACO

    Mulqueen, John; Maples, C. Dauphne; Fabisinski, Leo, III

    2012-01-01

    This paper provides an overview of Systems Engineering as it is applied in a conceptual design space systems department at the National Aeronautics and Space Administration (NASA) Marshall Spaceflight Center (MSFC) Advanced Concepts Office (ACO). Engineering work performed in the NASA MFSC's ACO is targeted toward the Exploratory Research and Concepts Development life cycle stages, as defined in the International Council on Systems Engineering (INCOSE) System Engineering Handbook. This paper addresses three ACO Systems Engineering tools that correspond to three INCOSE Technical Processes: Stakeholder Requirements Definition, Requirements Analysis, and Integration, as well as one Project Process Risk Management. These processes are used to facilitate, streamline, and manage systems engineering processes tailored for the earliest two life cycle stages, which is the environment in which ACO engineers work. The role of systems engineers and systems engineering as performed in ACO is explored in this paper. The need for tailoring Systems Engineering processes, tools, and products in the ever-changing engineering services ACO provides to its customers is addressed.

  18. PERFORMANCE STUDY ON AISI316 AND AISI410 USING DIFFERENT LAYERED COATED CUTTING TOOLS IN CNC TURNING

    K. RAJA

    2015-01-01

    Full Text Available Stainless steel (SS is used for many commercial and industrial applications owing to its high resistance to corrosion. It is too hard to machine due to its high strength and high work hardening property. A surface property such as surface roughness (SR is critical to the function-ability of machined components. SS is generally regarded as more difficult to machine material and poor SR is obtained during machining. In this paper an attempt has been made to investigate the SR produced by CNC turning on austenitic stainless steel (AISI316 and martensitic stainless steel (AISI410 by different cases of coated cutting tool used at dry conditions. Multilayered coated with TiCN/Al2O3, multilayered coated with Ti(C, N, B and single layered coated with TiAlN coated cutting tools are used. Experiments were carried out by using Taguchi’s L27 orthogonal array. The effect of cutting parameters on SR is evaluated and optimum cutting conditions for minimizing the SR are determined. Analysis of variance (ANOVA is used for identifying the significant parameters affecting the responses. Confirmation experiments are conducted to validate the results obtained from optimization.

  19. Predicting coal ash fusion temperature based on its chemical composition using ACO-BP neural network

    Coal ash fusion temperature is important to boiler designers and operators of power plants. Fusion temperature is determined by the chemical composition of coal ash, however, their relationships are not precisely known. A novel neural network, ACO-BP neural network, is used to model coal ash fusion temperature based on its chemical composition. Ant colony optimization (ACO) is an ecological system algorithm, which draws its inspiration from the foraging behavior of real ants. A three-layer network is designed with 10 hidden nodes. The oxide contents consist of the inputs of the network and the fusion temperature is the output. Data on 80 typical Chinese coal ash samples were used for training and testing. Results show that ACO-BP neural network can obtain better performance compared with empirical formulas and BP neural network. The well-trained neural network can be used as a useful tool to predict coal ash fusion temperature according to the oxide contents of the coal ash

  20. De la Locura de doble forma a la Psicosis maníaco-depresiva.

    - Consejo de Redacción

    1995-01-01

    Full Text Available Sin entrar en polémicas sobre a quién atribuir la primera descripción de lo que actualmente llamamos Psicosis maníaco-depresiva, es decir, sin tomar partido por Baillarger o J.-P. Falret, lo cierto es que a mediados del pasado siglo los alienistas franceses orquestaron un saber nosológico en el que se reunían en una única categoría dos manifestaciones extremas del humor: la manía y la melancolía. Tras las descripciones fundacionales de Baillarger y de Falret, fechadas ambas en el mismo año, 1854, se abrió un espacio nosológico opuesto al terreno de los delirios crónicos: las psicosis del humor frente a las psicosis de la razón, o bien psicosis maníaco-depresiva frente a esquizofrenia-paranoia. De la última cosecha del nosógrafo por excelencia, Emil Kraepelin, proviene la descripción clínica más completa y matizada de la locura maníaco-depresiva (das manisch-depressive Irresein. Dos años después, en 1915, S. Freud mostró en Duelo y Melancolía la infraestructura metapsicológica de la manía y de la melancolía.

  1. Solving optimum operation of single pump unit problem with ant colony optimization (ACO) algorithm

    For pumping stations, the effective scheduling of daily pump operations from solutions to the optimum design operation problem is one of the greatest potential areas for energy cost-savings, there are some difficulties in solving this problem with traditional optimization methods due to the multimodality of the solution region. In this case, an ACO model for optimum operation of pumping unit is proposed and the solution method by ants searching is presented by rationally setting the object function and constrained conditions. A weighted directed graph was constructed and feasible solutions may be found by iteratively searching of artificial ants, and then the optimal solution can be obtained by applying the rule of state transition and the pheromone updating. An example calculation was conducted and the minimum cost was found as 4.9979. The result of ant colony algorithm was compared with the result from dynamic programming or evolutionary solving method in commercial software under the same discrete condition. The result of ACO is better and the computing time is shorter which indicates that ACO algorithm can provide a high application value to the field of optimal operation of pumping stations and related fields.

  2. Enfermedad inflamatoria intestinal en pacientes celíacos Inflammatory bowel disease in celiac patients

    M. Masachs

    2007-08-01

    Full Text Available Introducción: se ha sugerido una potencial asociación entre la enfermedad celíaca y la enfermedad inflamatoria intestinal, que puede justificar que ambas enfermedades puedan presentarse en un mismo enfermo o en sus familiares de primer orden con mayor frecuencia de lo esperado. Objetivo: determinar la prevalencia de la enfermedad de Crohn y la colitis ulcerosa en los enfermos celíacos y en sus familiares. Método: estudio epidemiológico prospectivo transversal en un grupo de pacientes celíacos, sus familiares de primer grado y un grupo control de características epidemiológicas similares, constituido por familiares de pacientes que acuden al Servicio de Urgencias por un problema agudo. Para detectar la existencia de colitis ulcerosa y enfermedad de Crohn en los celíacos y sus familiares, se realizó una entrevista semiestructurada. Resultados: se han incluido 86 celíacos y 432 familiares, que se han comparado con 809 controles (129 pacientes con una enfermedad aguda y 680 familiares de primer grado suyos. Se han detectado 3 casos de enfermedad de Crohn en el grupo de los enfermos celíacos y 4 casos de enfermedad de Crohn en sus familiares. Sólo se ha detectado 1 caso de enfermedad de Crohn en el grupo control (p Introduction: a potential association between celic disease and inflammatory bowel disease hs been suggested, which may explain the fact that both disorders occasionally present in one patient or in his/her first-degree relatives more frequently than expected. Objective: to establish the prevalence of Crohn's disease and ulcerative colitis in celiac patients and their relatives. Method: a cross-sectional, prospective epidemiological study in a group of celiac patients, their first-degree relatives, and a control group with similar epidemiological characteristics including the relatives of patients presenting at the ER for acute conditions. A semistructured interview was used to identify the presence of Crohn's disease and

  3. Fractographic studies of hydrogen embrittlement of AISI 316L austenitic stainless steel

    This paper concerns a fractographic examination of hydrogen embrittlement of a stable AISI 316L type austenitic stainless steel. The objective is a better understanding of the possible role of hydrogen in stress corrosion cracking processes. (author)

  4. Computer Aided Design of Heat Treatment for AISI P20+Ni Mold Steel with Good Machinability

    HU Xin-bin; GAO Wen; HE Yan-lin; LI Lin

    2004-01-01

    Computer aided design of heat treatment for AISI P20 mold steel with good machinability is attempted to proceed by the commercial software package Thermo-Calc (TCP+DICTRA). Through experimental and theoretical analysis of phase transformation during heat treatment, further knowledge of designing proper heat treatment is obtained. Then the machinability of AISI P20+Ni steel under given heat treatment condition is studied and the influencing factors to their machinability are analyzed. It is shown that heat treatment designed by computer simulation of carbide transformation is applicable to AISI P20+Ni steel with good machinability; AISI P20+Ni steel with tempered sorbite treated by quenching &tempering has optimal machinability; normalizing at the temperature of 910℃ & tempering can avoid cracking and result in acceptable machinability in small thickness module.

  5. Pileup Behavior in Sharp Nanoindentation of AISI 1045 Steel

    Zhu, L. N.; Xu, B. S.; Wang, H. D.; Wang, C. B.

    Experimental measurements have been used to investigate the pileup behavior during nanoindentation with a sharp indenter. The AISI 1045 steels treated by quenching and annealing were examined. The results show that during sharp nanoindentation process, the amount of pileup is related to the residual stress state, the indentation depth and the work hardening. The quenched steel with compressive residual stress will tend to pile up, and the stress-free annealed steel can decrease the pileup height. It is found that the pileup height gradually increases for the two steels as the indentation depth becomes larger. It is also shown that the low work hardening of the two steels can also result in the pileup deformation.

  6. Stress Ratio Effect on Ratcheting Behavior of AISI 4340 Steel

    Divya Bharathi, K.; Dutta, K.

    2016-02-01

    Ratcheting is known as accumulation of plastic strain during asymmetric cyclic loading of metallic materials under non-zero mean stress. This phenomenon reduces fatigue life of engineering materials and thus limits the life prediction capacity of Coffin-Manson relationship. This study intends to investigate the ratcheting behavior in AISI 4340 steel which is mainly used for designing of railway wheel sets, axles, shafts, aircraft components and other machinery parts. The effect of stress ratio on the ratcheting behaviour in both annealed and normalised conditions were investigated for investigated steel. Ratcheting tests were done at different stress ratios of -0.4, -0.6 and -0.8. The results showed that the material responds to hardening behavior and nature of strain accumulation is dependent on the magnitude of stress ratio. The post ratcheted samples showed increase in tensile strength and hardness which increases with increasing stress ratio and these variations in tensile properties are correlated with the induced cyclic hardening.

  7. Radiation-induced phase development in AISI 316

    During irradiation at temperatures between 460 and 6500C, the alloy AISI 316 decomposes into an austenite matrix of altered composition and some mixture of six possible precipitate phases. These phases are γ', G, eta-silicide, M23C6, M6C, and Laves. The balance of phases developed is exceptionally sensitive to a large number of material and environmental variables and frequently varies within a single grain. All of these phases are found to be either naturally rich in nickel and silicon or to become progressively enriched in these elements as the irradiation proceeds. The precipitates can be considered to be classified as thermally stable but modified, irradiation-enhanced, irradiation-induced, and irradiation-transformed

  8. Study of discordancy mobility in the AISI 304 steel

    Internal Friction (IF), measurements were carried out in a type AISI 304 austenitic stainless steels at approximately 1HZ of frequency in the temperature interval from 120 to 573K. The IF spectra and the vibration frequency were obtained in samples were submitted to specific heat treatments. The results showed IF spectra with a well defined peak at 260K. The intensity dependes on the amount of plastic deformation previously introduced in the sample. Another broad peak was detected between 300 and 400K. Both peaks could only be detected after plastic deformation in uniaxial tension or torsion. In torsionably deformed samples at liquid nitrogen temperature, 77 K, the IF spectrum is observed only after linear annealing at 400K. This apparently results from a high damping due to a possible phase transformation which occurs around room temperature. The broad peak at higher temperature is sensitive to recovery induced by linear annealings. (Author)

  9. Hot forming of AISI A2 tool steel

    T. Večko Pirtovšek

    2008-10-01

    Full Text Available For further increase of economy of production of AISI A2 tool steel a study of possibility of expanding the hot working range and better prediction of flow stress has been carried out. By employing hot compression tests it was proved, that initial microstructures have influence on the lower limit and chemical composition on upper limit of hot working range. A CAE Neural Networks was applied to predict the flow stresses for intermediate values of strain rates and temperatures. For optimization purposes the activation energies and constants of the hyperbolic sine function for two temperatures ranges (850-1000°C and 1000-1150°C were calculated.

  10. CO2 laser welding of AISI 321stainless steel

    CO2 laser welding of AISI 321austenitic stainless steel has been carried out. Bead on plate welds on 2 mm thick steel were performed with 450W CO2 laser at speeds ranging from 200 to 900 mm/min. It was observed that weld depth and width was decreased with increasing the speed at constant laser power. Butt welds on different sheet thickness of 1, 2 and 2.5 mm were performed with laser power of 450 W and at speed 750, 275 and 175 mm/min, respectively. The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy and SEM. The austenite/delta ferrite microstructure was reported in the welded zone. The microhardness and tensile strength of the welded joints were measured and found almost similar to base metal due to austenitic nature of steel

  11. Simulation of Thermo-viscoplastic Behaviors for AISI 4140 Steel

    Li, Hong-Bin; Feng, Yun-Li

    2016-04-01

    The thermo-viscoplastic behaviors of AISI 4140 steel are investigated over wide ranges of strain rate and deformation temperature by isothermal compression tests. Based on the experimental results, a unified viscoplastic constitutive model is proposed to describe the hot compressive deformation behaviors of the studied steel. In order to reasonably evaluate the work hardening behaviors, a strain hardening material constant (h0) is expressed as a function of deformation temperature and strain rate in the proposed constitutive model. Also, the sensitivity of initial value of internal variable s to the deformation temperature is discussed. Furthermore, it is found that the initial value of internal variable s can be expressed as a linear function of deformation temperature. Comparisons between the measured and predicted results confirm that the proposed constitutive model can give an accurate and precise estimate of the inelastic stress-strain relationships for the studied high-strength steel.

  12. Corrosion of AISI 304 stainless steel in polluted seawater

    The sequence of microbiofouling settlement on AISI 304 stain steel samples exposed to polluted harbor sea water of a power cooling water intake is studied. The firts sates of bacterial colonization are followed by means of scanning electron microscopy during two weeks of exposure. The relation between microbiofouling and corrosion is also followed by scanning electron microscopy and evaluated through electrochemical polarization experiments. The results obtained show that microbial colonization and extracellular polimeric substances forming the biofilms have a marked influence on the electrochemical behaviour of stainless steel in sea water. Laboratory experiments using inorganic chloride solutions or artificial sea water show a considerably lesser attack of the metal than those performed 'in situ' with natural sea water. Passivity breadown is highly facilitated when complex biological and inorganic deposits (fouling) have settled on the metal surface. (Author)

  13. Comportamiento termomecánico de aceros AISI 304

    El Wahabi, M.

    2001-04-01

    Full Text Available The hot deformation behaviour of three AISI 304 (H, L and HP austenitic stainless steel with different carbon contents has been studied. An analysis of the parameters describing their hot flow curves was carried out. No heavy effect of the carbon content was found on most of the latter parameters. However, the work hardening and dynamic recovery behaviour showed clear differences depending on the given alloy, especially at high temperatures and low strain rates where the high carbon steel displayed larger work hardening and dynamic recovery rates than the other steels. The high purity steel (interstitial free displayed the lower stress levels as its hardening rate was slower than in the other two steels.

    Se llevó a cabo un estudio del comportamiento termomecánico de tres aceros inoxidables austeníticos tipo AISI 304 (H, L y HP con diferentes contenido en carbono, mediante la determinación de los parámetros que describen las etapas de deformación en caliente. No se notó un fuerte efecto del carbono en dichos parámetros, excepto en los que describen los procesos de endurecimiento y de restauración dinámica que muestran una cierta dependencia con la composición química, especialmente a bajos valores del parámetro de Zener-Hollomon, donde el acero de alto carbono (304H endurece y restaura más rápido que el de bajo carbono (304L, alcanzándose valores de tensión de pico similares en ambos casos. El material de alta pureza (libre de intersticiales toma valores de tensión de pico más bajos que los otros aceros, endureciendo más lentamente y con una velocidad de restauración similar a la del 304H.

  14. Linear friction welding of AISI 316L stainless steel

    Research highlights: → Linear friction welding is a feasible process for joining AISI316L. → Most welds had tensile strengths superior to the parent material. → Welding parameters had a significant impact on weld microstructure. → Control of microstructure by controlling welding parameters is a process benefit. - Abstract: Linear friction welding is a solid state joining process established as a niche technology for the joining of aeroengine bladed disks. However, the process is not limited to this application, and therefore the feasibility of joining a common engineering austenitic steel, AISI 316L, has been explored. It was found that mechanically sound linear friction welds could be produced in 316L, with tensile properties in most welds exceeding those of the parent material. The mechanical properties of the welds were also found to be insensitive to relatively large changes in welding parameters. Texture was investigated in one weld using high energy synchrotron X-ray diffraction. Results showed a strong {1 1 1} type texture at the centre of the weld, which is a typical shear texture in face centre cubic materials. Variations in welding parameters were seen to have a significant impact on the microstructures of welds. This was particularly evident in the variation of the fraction of delta ferrite, in the thermo-mechanically affected zone of the welds, with different process parameters. Analysis of the variation in delta ferrite, with different welding parameters, has produced some interesting insights into heat generation and dissipation during the process. It is hoped that a greater understanding of the process could help to make the parameter optimisation process, when welding 316L as well as other materials, more efficient.

  15. Kepekaan Retak Korosi Tegangan Baja Tahan Karat Austenitik AISI 304 Dalam Lingkungan Air Laut Buatan

    Daud, Marzuki

    2012-01-01

    The component of AISI 304 stainless steel construction is used as a prop of linking up the ropes on the boat on the sea, such as socket swaged, chain plate, turnbuckle, and so on. This component usually has a failure problem of Stress Corrosion Cracking (SCC) although the stress which operates mechanically is far from its yield strength. The aim of this research is to analyze the SCC susceptibility of AISI 304 austenite stainless steel in artificial sea water which is represent...

  16. Texture evolution in thin-sheets on AISI 301 metastable stainless steel under dynamic loading

    Kim, K.Y. [Posco Steels, Pohan, South Korea (Korea, Republic of); Kozaczek, K. [Oak Ridge National Lab., TN (United States); Kulkarni, S.M. [TRW Vehicle Safety Systems, Mesa, AZ (United States); Bastias, P.C.; Hahn, G.T. [Vanderbilt Univ., Nashville, TN (United States)

    1995-05-08

    The evolution of texture in thin sheets of metastable austenitic stainless steel AISI 301 is affected by external conditions such as loading rate and temperature, by inhomogeneous deformation phenomena such as twinning and shear band formation, and by the concurent strain induced phase transformation of the retained austenitc ({gamma}) into martensite ({alpha}). The present paper describes texture measurements on different gauges of AISI 301 prior and after uniaxial stretching under different conditions.

  17. Resistencia al desgaste de recubrimientos Fe-Nb-Cr-W, Nb, AISI 1020 y AISI 420 producidos por proyección térmica por arco eléctrico

    López-Covaleda, E. A.; Mercado-Velandia, J. L.; Olaya-Flórez, J. J.

    2013-01-01

    The commercial materials 140MXC (with iron, tungsten, chrome, niobium), 530AS (AISI 1015 steel) and 560AS (AISI 420 steel) on AISI 4340 steel were deposited using thermal spray with arc. The aim of work was to evaluate the best strategy abrasive wear resistance of the system coating-substrate using the following combinations: (1) homogeneous coatings and (2) coatings depositing simultaneously 140MXC + 530AS and 140MXC + 560AS. The coatings microstructure was characterized using Optical micros...

  18. Study on residual stress of AISI304 TIG welding line with laser shock processing by x-ray stress analyzer

    Zhang, Y. K.; Kong, D. J.; Yin, S. M.; Feng, A. X.; Lu, J. Z.; Ge, T.

    2006-02-01

    The surface of AISI304 TIG welding line was processed by LSP (laser shock processing). The effects on the microstructure, hardness and residual stress of AISI304 welding line by LSP were observed, and its mechanical properties were researched by SEM (scanning electron microscope) and test device of mechanical property. Residual stresses of AISI304 TIG welding line by LSP were measured with Model X-350A X ray analyzer. The test results show that compressive residual stress values of AISI304 TIG welding line by LSP are about 110MPa. Strengthening effects of AISI304 TIG welding line by LSP is very obvious, and fatigue properties of welding line is improved, and tensile residual stresses of welding line are obviously reduced, the distribution of residual stress tends to equality, and service life of AISI304 TIG welding line is improved.

  19. Breakdown and evolution of the protective oxide scales of AISI 304 and AISI 316 stainless steels under high-temperature oxidation

    Habib, K. A.; Damra, M. S.; Saura, J. J.; Cervera, I.; Bellés, J.

    2011-01-01

    The failure of the protective oxide scales of AISI 304 and AISI 316 stainless steels has been studied and compared at 1,000°C in synthetic air. First, the isothermal thermogravimetric curves of both stainless steels were plotted to determine the time needed to reach the breakdown point. The different resistance of each stainless steel was interpreted on the basis of the nature of the crystalline phases formed, the morphology, and the surface structure as well as the cross-section structure of...

  20. Corrosion and microstructural analysis data for AISI 316L and AISI 347H stainless steels after exposure to a supercritical water environment

    Ruiz, A.; Timke, T.; van de Sande, A.; Heftrich, T.; Novotny, R.; Austin, T.

    2016-01-01

    This article presents corrosion data and microstructural analysis data of austenitic stainless steels AISI 316L and AISI 347H exposed to supercritical water (25 MPa, 550 °C) with 2000 ppb of dissolved oxygen. The corrosion tests lasted a total of 1200 h but were interrupted at 600 h to allow measurements to be made. The microstructural data have been collected in the grain interior and at grain boundaries of the bulk of the materials and at the superficial oxide layer developed during the corrosion exposure. PMID:27158647

  1. Corrosion and microstructural analysis data for AISI 316L and AISI 347H stainless steels after exposure to a supercritical water environment.

    Ruiz, A; Timke, T; van de Sande, A; Heftrich, T; Novotny, R; Austin, T

    2016-06-01

    This article presents corrosion data and microstructural analysis data of austenitic stainless steels AISI 316L and AISI 347H exposed to supercritical water (25 MPa, 550 °C) with 2000 ppb of dissolved oxygen. The corrosion tests lasted a total of 1200 h but were interrupted at 600 h to allow measurements to be made. The microstructural data have been collected in the grain interior and at grain boundaries of the bulk of the materials and at the superficial oxide layer developed during the corrosion exposure. PMID:27158647

  2. Blastocystis hominis en pacientes celíacos sintomáticos

    Oscar Manuel Villa Jiménez; Ángel Escobedo Carbonell; Olga Marina Hano García; Lisette Wood Rodríguez; Frank Pérez Triana; Licet González Fabián

    2012-01-01

    Introducción. La enfermedad celíaca (EC) no diagnosticada o no tratada compromete histológica, inmunológica y nutricionalmente a quienes la sufren. Estas alteraciones permitirían la infección por parásitos que no causarían síntomas en pacientes inmunocompetentes, como por ejemplo el Blastocystis hominis (Bh). Objetivo. Analizar la presencia de Bh en celíacos sintomáticos y describir el cuadro clínico, estado histológico, inmunológico y nutricional en dichos pacientes. Material y métodos. E...

  3. Taponamiento cardíaco por hipotiroidismo: descripción de 2 casos

    José Rafael Rojas-Solano

    2005-07-01

    Full Text Available Rara vez el derrame pericárdico en el hipotiroidismo evoluciona al taponamiento cardíaco, complicación que es mortal si no se diagnostica y trata a tiempo. En este artículo describimos dos singulares casos y discutimos aspectos importantes de la fisiopatología, diagnóstico y manejo de esta enfermedad.Pericardial effusion in hypothyroidism seldom evolves to cardiac tamponade, a fatal complication if diagnosis and treatment are delayed. In this article, we describe 2 singular cases and discuss important facts about the pathophysiology, diagnosis and management of this disease.

  4. Actualización en legislación de alimentos para celíacos

    Pellicer, K.; Huber, Bárbara; Benítez, F.; Bigeon, G.; Barbero, R.; Salum, L.; Copes, Julio

    2014-01-01

    Se realizó un análisis de la normativa sanitaria sobre alimentos para celíacos y su impacto en la población celíaca, mediante la investigación y comparación de las normativas sanitarias argentina e internacional sobre alimentos libres de gluten y el análisis de las consultas realizadas al listado oficial argentino de productos libres de gluten. La norma CODEX STAN 118/1979 y la normativa de la Comunidad Europea reconocen como alimentos “exentos de gluten” a los que contienen hasta 20 mg/kg y ...

  5. Domainwise Web Page Optimization Based On Clustered Query Sessions Using Hybrid Of Trust And ACO For Effective Information Retrieval

    Dr. Suruchi Chawla

    2015-08-01

    Full Text Available Abstract In this paper hybrid of Ant Colony OptimizationACO and trust has been used for domainwise web page optimization in clustered query sessions for effective Information retrieval. The trust of the web page identifies its degree of relevance in satisfying specific information need of the user. The trusted web pages when optimized using pheromone updates in ACO will identify the trusted colonies of web pages which will be relevant to users information need in a given domain. Hence in this paper the hybrid of Trust and ACO has been used on clustered query sessions for identifying more and more relevant number of documents in a given domain in order to better satisfy the information need of the user. Experiment was conducted on the data set of web query sessions to test the effectiveness of the proposed approach in selected three domains Academics Entertainment and Sports and the results confirm the improvement in the precision of search results.

  6. Study on tempering behaviour of AISI 410 stainless steel

    Martensitic stainless steels find extensive applications due to their optimum combination of strength, hardness and wear-resistance in tempered condition. However, this class of steels is susceptible to embrittlement during tempering if it is carried out in a specific temperature range resulting in significant reduction in toughness. Embrittlement of as-normalised AISI 410 martensitic stainless steel, subjected to tempering treatment in the temperature range of 673–923 K was studied using Charpy impact tests followed by metallurgical investigations using field emission scanning electron and transmission electron microscopes. Carbides precipitated during tempering were extracted by electrochemical dissolution of the matrix and identified by X-ray diffraction. Studies indicated that temper embrittlement is highest when the steel is tempered at 823 K. Mostly iron rich carbides are present in the steel subjected to tempering at low temperatures of around 723 K, whereas chromium rich carbides (M23C6) dominate precipitation at high temperature tempering. The range 773–823 K is the transition temperature range for the precipitates, with both Fe2C and M23C6 types of carbides coexisting in the material. The nucleation of Fe2C within the martensite lath, during low temperature tempering, has a definite role in the embrittlement of this steel. Embrittlement is not observed at high temperature tempering because of precipitation of M23C6 carbides, instead of Fe2C, preferentially along the lath and prior austenite boundaries. Segregation of S and P, which is widely reported as one of the causes for temper embrittlement, could not be detected in the material even through Auger electron spectroscopy studies. - Highlights: • Tempering behaviour of AISI 410 steel is studied within 673–923 K temperature range. • Temperature regime of maximum embrittlement is identified as 773–848 K. • Results show that type of carbide precipitation varies with temperature of tempering

  7. Studies on Pumice Lightweight Aggregate Concrete with Quarry Dust Using Mathematical Modeling Aid of ACO Techniques

    J. Rex

    2016-01-01

    Full Text Available The lightweight aggregate is an aggregate that weighs less than the usual rock aggregate and the quarry dust is a rock particle used in the concrete for the experimentation. The significant intention of the proposed technique is to frame a mathematical modeling with the aid of the optimization techniques. The mathematical modeling is done by minimizing the cost and time consumed in the case of extension of the real time experiment. The proposed mathematical modeling is utilized to predict four output parameters such as compressive strength (Mpa, split tensile strength (Mpa, flexural strength (Mpa, and deflection (in mm. Here, the modeling is carried out with three different optimization techniques like genetic algorithm (GA, particle swarm optimization (PSO, and ant colony optimization (ACO with 80% of data from experiment utilized for the training and the remaining 20% for the validation. Finally, while testing, the error value is minimized and the performance obtained in the ACO for the parameters such as compressive strength, split tensile strength, flexural strength, and deflection is 91%, 98%, 87%, and 94% of predicted values, respectively, in the mathematical modeling.

  8. Marcadores cardíacos na medicina veterinária Cardiac markers in veterinary medicine

    Letícia Andreza Yonezawa

    2010-02-01

    Full Text Available Os marcadores cardíacos são utilizados com o intuito de auxiliar no diagnóstico clínico de animais com doença cardíaca com maior acurácia e em menor tempo possível, possibilitando o estabelecimento do prognóstico e a terapia precocemente. Entretanto, em medicina veterinária, no Brasil, sua aplicabilidade ainda é, em geral, restrita a pesquisas. Esta revisão tem como objetivo abordar os principais marcadores cardíacos para que futuramente estes possam se tornar índices essenciais na avaliação cardíaca.Cardiac markers have been used in order to assist clinical diagnosis of animals with heart disease, more accurately, enabling the establishment of earlier prognosis and therapy. However, in Brazilian veterinary medicine, these markers are generally still restricted to researches. This review aims to approach the major cardiac markers, which further may become essential indexes in heart assessment.

  9. Optimization of Vibration Reduction Ability of Ladder Tracks by FEM Coupled with ACO

    Hao Jin

    2015-01-01

    Full Text Available Ladder track, which has drawn increased attention in scientific communities, is an effective method for reducing vibrations from underground railways. In order to optimize the vibration reduction ability of ladder track, a new method, that is, the finite element method (FEM coupled with ant colony optimization (ACO, has been proposed in this paper. We describe how to build the FEM model verified by the vibration tests in the Track Vibration Abatement and Control Laboratory and how to couple the FEM with ACO. The density and elasticity modulus of the sleeper pad are optimized using this method. After optimization, the vibration acceleration level of the supporting platform in the 1–200 Hz range was reduced from 102.8 dB to 94.4 dB. The optimized density of the sleeper pad is 620 kg/m3, and the optimized elasticity modulus of the sleeper pad is 6.25 × 106 N/m2.

  10. Application of GA, PSO, and ACO Algorithms to Path Planning of Autonomous Underwater Vehicles

    Mohammad Pourmahmood Aghababa; Mohammad Hossein Amrollahi; Mehdi Borjkhani

    2012-01-01

    In this paper,an underwater vehicle was modeled with six dimensional nonlinear equations of motion,controlled by DC motors in all degrees of freedom.Near-optimal trajectories in an energetic environment for underwater vehicles were computed using a numerical solution of a nonlinear optimal control problem (NOCP).An energy performance index as a cost function,which should be minimized,was defined.The resulting problem was a two-point boundary value problem (TPBVP).A genetic algorithm (GA),particle swarm optimization (PSO),and ant colony optimization (ACO) algorithms were applied to solve the resulting TPBVP.Applying an Euler-Lagrange equation to the NOCE a conjugate gradient penalty method was also adopted to solve the TPBVP.The problem of energetic environments,involving some energy sources,was discussed.Some near-optimal paths were found using a GA,PSO,and ACO algorithms.Finally,the problem of collision avoidance in an energetic environment was also taken into account.

  11. Plasma post oxidation of nitrocarburized AISI 4140 steel

    LEE Insup

    2006-01-01

    Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of AISI 4140 steel.Plasma nitrocarburizing was conducted for 3 h at 570 ℃ in the nitrogen, hydrogen and methane atmosphere to produce the ε-Fe2-3(N,C) phase.It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of ε-phase, with a small proportion of γ'-Fe4(N,C) phase.The thickness of the compound layer was about 10 μm and the diffusion layer was about 300 μm in thickness, respectively.Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at a constant temperature of 500 ℃ for 1 h.The very thin magnetite (Fe3O4) layer 1-2 μm in thickness on top of the compound layer was obtained by plasma post oxidation.It was confirmed that the corrosion characteristics of the nitrocarburized compound layer can be further improved by the application of the superficial magnetite layer.

  12. Qualification criteria verification for aisi-4340 steel suspension lug

    All external loads carried underneath an aircraft are mounted onto it through mechanism generally known as suspension system. The externally mounted attachments like bombs, missiles and fuel tanks etc. experience enormous aerodynamic and inertial forces in the flights. These forces are transferred to the interface point of suspension system, known as 'Suspension Lug'. Thus lugs are considered critical component and have extremely stringent qualification criteria standards used in the aviation industry in USA, Europe, Russia, etc. Different standards prevail in different parts of the world about qualification and testing of these lugs. As Pakistan is entering into aviation industry, therefore there is a need to fulfill the requirements of these standards, to suit Pakistani environment. The suspension lug under study is 2000 Ibs. load class made from AISI-4340 Steel having good mechanical properties as per required standard. The manufacturing processes included forging, machining and vacuum heat treatment. The prototypes of suspension lugs were manufactured in the local industry and subjected to the required mechanical tests such as tensile testing at 5 to 35 degree angles. Impact testing at cryogenic temperatures of -50 to -70 degree C, and breaking load testing were performed. The acceptable results were obtained and mechanical testing for qualification of lugs was finalized and standardized. The options were compared with practical viability, utilization of product and cost effectiveness. (author)

  13. High-temperature oxidation behavior of aluminized AISI 4130 steel

    Badaruddin, Mohammad; Wang, Chaur Jeng; Wardono, Herry; Tarkono, Asmi, Dwi

    2016-02-01

    AISI 4130 steel was dipped into a molten aluminum bath at 700°C for 16 s to produce an aluminide coating on the steel substrate. The coating, which consisted of an Al-rich layer and an FeAl3 and Fe2Al5 intermetallic layer, strongly adhered to the steel substrate. High-temperature oxidation of the bare steel and aluminized steel was performed by thermogravimetry at 850°C for 49 h in static air. The oxidation products were characterized by scanning electron microscopy and energy-dispersive spectroscopy. The aluminide coating could increase the oxidation resistance of the bare steel by a factor of ˜19. The increase in high-temperature oxidation resistance of the aluminized steel is attributed to the formation of protective alumina scale (α-Al2O3). Although iron oxide nodules grew on the aluminide coating surface, the oxidation rate of the aluminide coatings was very low. After 49 h of oxidation, agglomerates of α-Al2O3 fine grains grew on the rod-shaped FeAl phases.

  14. AISI waste oxide recycling program. Final technical report

    Aukrust, E.; Downing, K.B.; Sarma, B.

    1995-08-01

    In March 1995 AISI completed a five-year, $60 million collaborative development program on Direct Steelmaking cost-shared by DOE under the Metals Initiative. This program defined an energy-efficient and environmentally-friendly technology to produce hot metal for steelmaking directly from coal and iron ore pellets without incurring the high capital costs and environmental problems associated with traditional coke oven and blast furnace technology. As it becomes necessary to replace present capacity, this new technology will be favored because of reduced capital costs, higher energy efficiency, and lower operating costs. In April 1994, having failed to move forward with a demonstration plant for direct ironmaking, despite substantial efforts by both Stelco and Geneva Steel, an alternative opportunity was sought to commercialize this new technology without waiting until existing ironmaking capacity needed to be replaced. Recycling and resource recovery of steel plant waste oxides was considered an attractive possibility. This led to approval of a ten-month, $8.3 million joint program with DOE on recycling steel plant waste oxides utilizing this new smelting technology. This highly successful trial program was completed in December 1994. The results of the pilot plant work and a feasibility study for a recycling demonstration plant are presented in this final technical report.

  15. Deformation induced martensite in AISI 316 stainless steel

    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, microstructure 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. (Author) 21 refs.

  16. Environment-tensile property relationship in AISI 1018 steel

    Environment-material interaction depends on several concurrent and mutually competitive variables ranging from nature of the environment to composition of the steel and including: the test temperature; the time of exposure of the material to the environment; the deformation rate; and intrinsic microstructural effects; The present work is a characterization of strain rate and environment influences on the tensile properties of a steel, AISI 1018, having a fully spheroidized microstructure. Tensile tests were performed at ambient temperature (300 K) in environments which are mildly aggressive (moist laboratory air-relative humidity 50%) and inert (dry gaseous nitrogen). The specimens were deformed to failure at strain rates of 10-4sec-1 and 10-5sec-1. No appreciable increase in yield and tensile strengths was observed at the strain rate of 10-4sec-1. However, the increase in both was of the order of 10 to 12% at the strain rate of 10-5sec-1. Ductility showed no variation with strain rate, but increased in the inert environment at both strain rates. Both environment and strain rate were found to have little to no influence on reduction in area of the test specimens. The true fracture stress followed a similar trend to the yield strength and ultimate tensile strength. (author)

  17. Characterization of AISI 1005 corrosion films grown under cyclic voltammetry of low sulfide ion concentrations

    Highlights: •The corrosion of AISI 1005 in sulfide solutions was investigated. •The mechanism of film growth on carbon steel in sulfide solutions was studied. •Film growth was characterized using SEM, EDX, XRD and Mössbauer spectroscopy. •Growth of AISI 1005 corrosion films under cyclic voltammetry. -- Abstract: The mechanism of AISI 1005 corrosion in sulfide ion solutions has been investigated using cyclic voltammetry, electrochemical impedance spectroscopy, X-ray diffraction (XRD) and Mössbauer spectroscopy (MS). The proposed mechanism occurs with the initial formation of oxygenated ferrous species followed by adsorption of HS− species, precipitation of iron monosulfides and their partial conversion to bisulfide iron. This mechanism was demonstrated by XRD results that revealed Fe-O and Fe-S phases and by MS results that detected pyrite as the major proportion (94%) of the iron species in the corrosion product

  18. NHETS - Estudo de Necrópsias de Pacientes Submetidos a Transplante Cardíaco

    Thiago Ninck Valette

    2014-06-01

    Full Text Available Fundamento: Discordâncias entre diagnóstico pre e post-mortem são relatadas na literatura, podendo variar de 4,1 a 49,8% dentre os casos encaminhados para exame necroscópico, com importante repercussão no tratamento dos pacientes. Objetivo: Analisar pacientes com óbito após o transplante cardíaco e confrontar os diagnósticos pre e post-mortem. Métodos: Por meio da revisão de prontuários, foram analisados dados clínicos, presença de comorbidades, esquema de imunossupressão, exames laboratoriais, causa clínica do óbito e causa do óbito à necrópsia. Foram confrontadas, então, a causa clínica e a causa necroscópica do óbito de cada paciente. Resultados: Foram analisados 48 óbitos submetidos à necrópsia no período de 2000 a 2010; 29 (60,4% tiveram diagnósticos clínico e necroscópico concordantes, 16 (33,3% tiveram diagnósticos discordantes e três (6,3% tiveram diagnóstico não esclarecido. Entre os discordantes, 15 (31,3% apresentaram possível impacto na sobrevida e um (2,1% não apresentou impacto na sobrevida. O principal diagnóstico clínico feito equivocadamente foi o de infecção, com cinco casos (26,7% dos discordantes, seguido por rejeição hiperaguda, com quatro casos (20% dos discordantes, e tromboembolismo pulmonar, com três casos (13,3% dos discordantes. Conclusão: Discordâncias entre o diagnóstico clínico e achados da necrópsia são comumente encontradas no transplante cardíaco. Novas estratégias no aperfeiçoamento do diagnóstico clínico devem ser introduzidas, considerando-se os resultados da necrópsia para melhoria do tratamento da insuficiência cardíaca por meio do transplante cardíaco.

  19. Corrosion Behavior of TiN Coated AISI D2 Steel

    ÇEĞİL, Özkan; Şen, Şaduman

    2014-01-01

    In this study, the corrosion behaviors of nitride and titanium nitride (TiN) layers deposited on AISI D2 steel samples are reported. Steel was at first nitrided in a nitrogen and ammonia atmosphere at 575 °C for 8 h and then titanium nitride coating treatment was performed in the powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000°C for 2h by pack diffusion coating. TiN coating layer thickness realized on the AISI D2 steel is 6,71 ± 0,9 μm. The hardness of TiN l...

  20. 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

    Carlos Eduardo Pinedo

    2013-06-01

    Full Text Available 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% carbon supersaturation and expansion of the FCC lattice. For the duplex stainless steel AISI F51, the austenitic grains transformed to carbon expanded austenite (γC, the ferritic grains transformed to carbon expanded ferrite (αC and M23C6 type carbides precipitated in the nitrided case. Hardness of the carburized case of the F51 duplex steel reached 1600 HV due to the combined effects of austenite and ferrite lattice expansion with a fine and dispersed precipitation of M23C6 carbides.O aço inoxidável austenítico AISI 316L e o aço inoxidável duplex AISI F51 (EN 1.4462 foram cementados sob plasma-DC na temperatura de 480ºC, utilizando-se CH4 como gás de arraste. A cementação sob plasma à baixa temperatura conduziu a uma elevada supersaturação do reticulado cristalino em carbono com a formação de austenita expandida(γC, sem a precipitação de carbonetos. A dureza do aço 316L, após a cementação, atingiu um valor máximo de 1000 HV, devido à supersaturação de ∼ 13 at% de carbono e à expansão do reticulado cristalino CFC. Para o aço inoxidável duplex AISI F51, os grãos de austenita se transformaram em austenita expandida pelo carbono e os grãos de ferrita se transformaram para ferrita expandida com a precipitação de carbonetos do tipo M23C6, na camada cementada. A dureza da camada cementada, no aço F51, atingiu 1600HV, devido ao efeito combinado da expansão dos reticulados cristalinos da austenita e da ferrita com a precipitação fina e

  1. Laser gas assisted treatment of AISI H12 tool steel and corrosion properties

    Yilbas, B. S.; Toor, Ihsan-ul-Haq; Malik, Jahanzaib; Patel, F.

    2014-03-01

    Laser gas assisted treatment of AISI H12 tool steel surface is carried out and the electrochemical response of the laser treated surface is investigated. Morphological and metallurgical changes in the treated layer are examined using a scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Potentiodynamic polarization tests are carried out for untreated and laser treated specimen in 0.2 M NaCl solution at room temperature. It is found that the laser treated AISI H12 workpiece surfaces exhibit higher corrosion resistance as compared to untreated specimen as confirmed by lower corrosion rate, higher pitting potential, and lower passive current density.

  2. Study of radiation damages in AISI 316 and 347 steels

    The CV-28 cyclotron at IEN (Nuclear Engineering Institute) has been used to simulated, in a short time scale, uniform He concentrations produced during neutron irradiation of metals by (n, α) reactions. Helium was implanted at concentrations of 1 to 300 ppm in 100 μm thick sheet samples of AISI 316 and 347 S S by degrading a 28 MeV alpha particle beam with a rotating energy degrader. The effects of He on the mechanical properties of the steels were studied by both non-destructive (positron annihilation) and destructive tests (tensile, creep, TEM and SEM). The positron lifetime measurements of irradiated and annealed samples were used as the base to discuss the He diffusion mechanism. Activation energies of 0.34±0.04 eV for 316 S S and 0.57±0.06 eV for 347 S S, characterized a dissociative process above 6500 C. TEM analyses have suggested the Ostwald ripening process for bubble growth over the full range of He concentrations studied. It was shown, in agreement with theoretical calculations that, by themselves the displacements produced during the helium implantation, at rate of 1.8 x 10-3 d pa/ppm, were not sufficient to cause significant changes in ductility. However, a strong ductility loss with increasing He concentration was observed for both types of steel for tensile tests at 250 C, as well as in creep at 7500 C over the range of strain (100 to 200 MPa). Finally, it was shown that charged particle simulation associated with positron annihilation techniques provides a fast, relatively low cost, and useful method to study different kinds of neutron damage in materials. (author)

  3. Biomaterial Studies on AISI 316L Stainless Steel after Magnetoelectropolishing

    Massimiliano Filippi

    2009-03-01

    Full Text Available The polarisation characteristics of the electropolishing process in a magnetic field (MEP – magnetoelectropolishing, in comparison with those obtained under standard/conventional process (EP conditions, have been obtained. The occurrence of an EP plateau has been observed in view of the optimization of MEP process. Up-to-date stainless steel surface studies always indicated some amount of free-metal atoms apart from the detected oxides and hydroxides. Such a morphology of the surface film usually affects the thermodynamic stability and corrosion resistance of surface oxide layer and is one of the most important features of stainless steels. With this new MEP process we can improve metal surface properties by making the stainless steel more resistant to halides encountered in a variety of environments. Furthermore, in this paper the stainless steel surface film study results have been presented. The results of the corrosion research carried out by the authors on the behaviour of the most commonly used material - medical grade AISI 316L stainless steel both in Ringer’s body fluid and in aqueous 3% NaCl solution have been investigated and presented earlier elsewhere, though some of these results, concerning the EIS Nyquist plots and polarization curves are also revealed herein. In this paper an attempt to explain this peculiar performance of 316L stainless steel has been undertaken. The SEM studies, Auger electron spectroscopy (AES and X-ray photoelectron spectroscopy (XPS were performed on 316L samples after three treatments: MP – abrasive polishing (800 grit size, EP – conventional electrolytic polishing, and MEP – magnetoelectropolishing. It has been found that the proposed magnetoelectropolishing (MEP process considerably modifies the morphology and the composition of the surface film, thus leading to improved corrosion resistance of the studied 316L SS.

  4. A new VUV high resolution undulator-based beamline at Super-ACO

    The VUV undulator-based high resolution SU5 beamline, designed to operate in the 5-45 eV photon energy range, is under construction at Super-ACO. It is composed of three toroidal mirrors around a 6.65 m Eagle off-plane normal incidence monochromator, whose induced-astigmatism is negligible owing to an horizontal focusing onto the gratings. With an optical design minimizing the aberrations and optimizing the throughput through the entrance slit, and with a careful choice of the optical coatings, the SU5 beamline should provide in the near future more than 1010 ph/s at the sample level for a 1/50000 bandwidth in the 5-25 eV energy range. The ultimate resolving power should be higher than 105. (orig.)

  5. Transplante cardíaco humano: experiência inicial Human cardiac transplant: initial experience

    Noedir A. G Stolf; Edimar Bocchi; Pedro C. P Lemos; Fábio Biscegli Jatene; Pablo M. A. Pomerantzeff; Lourdes Higushi; Jorge Kalil; Alfredo I. FIORELLI; José Otávio C Auler Júnior; Giovanni Bellotti; Lélio A Silva; Fúlvio Pileggi; Adib D Jatene

    1986-01-01

    No Instituto do Coração, de março de 1985 a fevereiro de 1986,11 pacientes foram submetidos a transplante cardíaco ortotópico. Eram todos do sexo masculino, com idade variando de 39 a 54 anos; 6 com cardiopatia isquémica, 4 com cardiomiopatia dilatada e um com cardiomiopatia chagásica. Foi realizado estudo hemodinâmico através de catéter de Swan-Ganz, no pré-operatório, no pós-operatório, após estabilização na unidade de recuperação, e trinta ou mais dias após o transplante. Os dados mostram ...

  6. As Camélias Oitocentistas do Buçaco

    Cordeiro, Liliana Margarida Correia

    2014-01-01

    Durante séculos, o género Camellia desempenhou um papel importante como ornamental. Em Portugal, o fascínio por estas plantas teve o seu clímax no século XIX, principalmente no noroeste e na cidade de Sintra, onde as condições são particularmente favoráveis para o seu cultivo. A Mata do Buçaco, uma floresta no centro do país, é das áreas menos conhecidas de camélias. As suas camélias datam deste período, quando estas plantas eram itens de colecção para os nobres. Alfredo Allen, Visconde da Qu...

  7. Experimental evaluation of a R134a/CO2 cascade refrigeration plant

    We present the experimental evaluation of a R134a/CO2 cascade refrigeration plant designed for low evaporation temperature in commercial refrigeration applications. The test bench incorporates two single-stage vapour compression cycles driven by semi hermetic compressors coupled thermally through two brazed plate cascade heat exchangers working in parallel and controlled by electronic expansion valves. The experimental evaluation (45 steady-states) covers evaporating temperatures from −40 to −30 °C and condensing from 30 to 50 °C. In each steady-state, we conducted a sweep of the condensing temperature of the low temperature cycle with speed variation of the high temperature compressor. Here, the energy performance of the plant is analysed, focussing on the compressors' performance, temperature difference in the cascade heat exchanger, cooling capacity, COP and compressors discharge temperatures. - Highlights: • The experimental evaluation of a R134a/CO2 cascade refrigeration plant is presented. • Temperature difference in cascade heat exchanger varied from 3.3 to 5.3 °C. • Variation of intermediate level produced maximum COP variations of 6%. • Cooling capacity ranged from 4.5 kW (−40 and 40 °C) to 7.5 kW (−30 and 30 °C). • COP ranged from 1.05 (−40 and 40 °C) to 1.65 (−30 and 30 °C)

  8. Study of carbonitriding thermochemical treatment by plasma screen in active with pressures main austenitic stainless steels AISI 409 and AISI 316L

    The technique called Active Screen Plasma Nitriding (ASPN) is being used as an alternative once it offers several advantages with respect to conventional DC plasma. In this method, the plasma does not form directly in the sample's surface but on a screen, in such a way that undesired effects such as the edge effect is minimized. Stainless steels present not very satisfactory wearing characteristics. However, plasma carbonitriding has been used as to improve its resistance to wearing due to the formation of a fine surface layer with good properties. In this work, samples of stainless steel AISI 316L and AISI 409 were treated at pressures of 2.5 and 5 mbar. After the treatments they were characterized by microhardness, microscopy and Xray diffraction. Microscopy and hardness analysis showed satisfactory layers and toughness in those steels. (author)

  9. THE EFFECT OF SMALL AMOUNTS OF ELEMENTS ON SHAPES OF POTENTIODYNAMIC AND POTENTIOSTATIC CURVES OF AISI 304L AND AISI 316L STAINLESS STEELS IN CHLORIDE MEDIA

    D. Pulino-Sagradi

    1997-06-01

    Full Text Available Abstract - Samples of high purity grade and commercial purity grade type AISI 304L and AISI 316L steels were studied by the potentiodynamic and potentiostatic techniques in a naturally aerated 3.5% NaCl aqueous solution at a controlled temperature of (23±2°C. The anodic polarization curves of the potentiodynamic technique showed that not always is it possible to determine pitting potential: most of the curves of commercial purity grade steels displayed a smooth curvature in the region where the current density should increase sharply. The density current versus time potentiostatic curves also showed different shapes according to the purity grade steels: for the commercial purity grade steels, the current density showed large oscillations with time (related to unstable pits, whereas for the high purity grade steels, a regular behavior of current density as a function of time was found (related to stable pits

  10. Evaluation of structural behaviour and corrosion resistant of austenitic AISI 304 and duplex AISI 2304 stainless steel reinforcements embedded in ordinary Portland cement mortars

    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.

  11. Structure and properties of the Stainless steel AISI 316 nitrided with microwave plasma; Estructura y propiedades del acero inoxidable AISI 316 nitrurado con plasmas de microondas

    Becerril R, F

    1999-07-01

    In this work were presented the results obtained by nitridation on stainless steel AISI 316 using a plasma generated through a microwave discharge with an external magnetic field using several moistures hydrogen / nitrogen to form a plasma. The purpose of nitridation was to increase the surface hardness of stainless steel through a phase formation knew as {gamma}N which has been reported that produces such effect without affect the corrosion resistance proper of this material. (Author)

  12. Wear resistance of Fe-Nb-Cr-W, Nb, AISI 1020 and AISI 420 coatings produced by thermal spray wire arc

    The commercial materials 140MXC (with iron, tungsten, chrome, niobium), 530AS (AISI 1015 steel) and 560AS (AISI 420 steel) on AISI 4340 steel were deposited using thermal spray with arc. The aim of work was to evaluate the best strategy abrasive wear resistance of the system coating-substrate using the following combinations: (1) homogeneous coatings and (2) coatings depositing simultaneously 140MXC + 530AS and 140MXC + 560AS. The coatings microstructure was characterized using Optical microscopy, Scanning electron microscopy and Laser con focal microscopy. The wear resistance was evaluated through dry sand rubber wheel test (DSRW). We found that the wear resistance depends on the quantity of defects and the mechanical properties like hardness. For example, the softer coatings have the biggest wear rates and the failure mode was characterized by plastic deformation caused by particles indentation, and the other hand the failure mode at the harder materials was grooving. The details and wear mechanism of the coatings produced are described in this investigation. (Author)

  13. Influence of plasma nitriding on the hardness of AISI 304 and low carbon steel

    Nitriding with plasma/ion nitriding technique for surface treatment of AISI 304 and low carbon steel as a machine component material has been done. Surface treatment is meant to improve the surface quality of metal especially its hardness. To reach the optimum condition it has been done a variation of nitriding pressure, while to analyse the result it has been done the hardness and microstructure test, and the nitrogen content. Result of the test indicates that: the optimum hardness obtained at 1.8 mbar of pressure that is 624.9 VHN or 2.98 times while the initial hardness is 210.3 VHN for AISI 304 and 581.6 VHN or 3.07 times compare with initial hardness 142.9 VHN for low carbon steel. The thickness of nitride layer for AISI 304 and low carbon steel is around 30 µm. Nitrogen contents after nitriding are 10.74% mass or 30.32% atom for AISI 304 and 6.81% mass or 21.76% atom for low carbon steel. (author)

  14. The adhesion of hot-filament CVD diamond films on AISI type 316 austenitic stainless steel

    Buijnsters, J.G.; Shankar, P.; Enckevort, W.J.P. van; Schermer, J.J.; Meulen, J.J. ter

    2004-01-01

    Steel ball indentation and scratch adhesion testing of hot filament chemical vapour deposited diamond films onto AISI type 316 austenitic stainless steel substrates using two different interlayer systems, namely chromium nitride and borided steel, have been investigated. In order to compare the adhe

  15. Microstructural characterization of an AISI-SAE 4140 steel without nitridation and nitrided

    It was micro structurally characterized an AISI-SAE 4140 steel before and after of nitridation through the nitridation process by plasma post-unloading microwaves through Optical microscopy (OM), Scanning electron microscopy (SEM) by means of secondary electrons and retrodispersed, X-ray diffraction (XRD), Energy dispersion spectra (EDS) and mapping of elements. (Author)

  16. Influence of the surface finishing on electrochemical corrosion characteristics of AISI 316L stainless steel

    Dundeková, S.; Hadzima, B.; Fintová, Stanislava

    2015-01-01

    Roč. 22, č. 2 (2015), s. 77-84. ISSN 1335-0803 Institutional support: RVO:68081723 Keywords : AISI 316L stainless steel * EIS * Corrosion Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://ojs.mateng.sk/index.php/Mateng/article/view/167/278

  17. Produção de amoníaco e sua optimização

    Roque, Marta de Jesus

    2008-01-01

    Com este trabalho pretendeu-se estudar o estado da arte de produção de amoníaco que é uma matéria-prima importante para a produção de fertilizantes nitrogenados e é usado frequentemente em sistemas de refrigeração industrial. A sua obtenção via reacção catalítica em meio gasoso baseado no processo Haber-Bosch é o método mais utilizado. Com base nos dados recolhidos e diagramas de processos relativos à produção de amoníaco foi desenvolvido uma folha de simulação que per...

  18. Taponamiento cardíaco secundario a carcinoma papilar esclerosante difuso de tiroides

    Verónica Riva

    2011-12-01

    Full Text Available El carcinoma papilar, variante esclerosante difusa, corresponde al 2% de todos los carcinomas papilares de la tiroides. Se caracteriza por comprometer de manera difusa y bilateral a la glándula tiroides. Clínicamente se manifiesta con metástasis ganglionares y pulmonares, afectando predominantemente a mujeres jóvenes. Se describe un caso de taponamiento cardíaco como presentación inicial de un carcinoma papilar de tiroides variante esclerosante difusa. Una mujer de 32 años concurrió al servicio de emergencias médicas refiriendo epigastralgia y tos seca. Durante el examen físico se constató hipotensión arterial, taquicardia y ruidos cardíacos disminuidos. Se realizó un ecocardiograma, observándose derrame pericárdico. Por medio de una pericardiocentesis se obtuvo líquido pericárdico, cuyo análisis mostró células neoplásicas. Durante la evolución la paciente presentó recurrencia del derrame pericárdico por lo que se realizó una ventana pleuropericárdica, detectándose durante la cirugía una lesión nodular subpleural, la cual fue biopsiada e informada posteriormente como una metástasis de carcinoma papilar vinculable a origen tiroideo. Se realizó una tiroidectomía total con linfadenectomía cervical bilateral. El diagnóstico final fue carcinoma papilar, variante esclerosante difusa. Esta variante infiltra el tejido conectivo de los espacios interfoliculares, simulando una tiroiditis y se caracteriza por una permeación vascular temprana. En oposición a la variante clásica, la esclerosante difusa presenta mayor agresividad y mayor tasa de recurrencia. El carcinoma papilar de tiroides debe tenerse presente como diagnóstico diferencial en nuestro medio, en todas aquellas lesiones neoplásicas papilares metastásicas, más aún si se trata de mujeres jóvenes.

  19. No ROI in ACO. Risk, expense of Medicare program has most for-profit groups shying away.

    Kutscher, Beth

    2012-04-23

    For-profit healthcare companies aren't beating down the door to get in on Medicare ACOs. Several of the big chains say there is too much uncertainty about the experiment, and they're waiting to see how the program evolves. One company on the sideline is Capella Healthcare. Chairman and CEO Daniel Slipkovich, left, says there is a potential for high patient dropout rates and risks in population management. PMID:22571000

  20. Effect of heat treatment on an AISI 304 austenitic stainless steel evaluated by the ultrasonic attenuation coefficient

    The properties of metals can be substantially changed by various methods, one of them is using heat treatment processes. Moreover, ultrasonic testing is the most preferred and effective, nondestructive testing technique for characterization of mechanical material properties. Austenitic stainless steel AISI 304 serves in many applications due to high strength and corrosion resistance. In certain applications, it is important to evaluate the mechanical properties of AISI 304 stainless steel. In this study, the ultrasonic method (attenuation measurement technique) is used to evaluate the hardness of AISI 304 stainless steel samples which were heat treated at different levels. Due to the heat treatment process, each sample has its specific microstructure and hardness which attenuate ultrasonic waves appropriately. The ultrasonic and hardness test show that it is possible to evaluate the hardness of AISI 304 stainless steel by ultrasonic attenuation coefficient. In addition, the relationship between ultrasonic attenuation coefficients and time of heat treatment is investigated.

  1. Effect of heat treatment on an AISI 304 austenitic stainless steel evaluated by the ultrasonic attenuation coefficient

    Moghanizadeh, Abbas; Farzi, Abolfazl [Islamic Azad Univ., Esfarayen (Iran, Islamic Republic of). Dept. of Civil Engineering

    2016-07-01

    The properties of metals can be substantially changed by various methods, one of them is using heat treatment processes. Moreover, ultrasonic testing is the most preferred and effective, nondestructive testing technique for characterization of mechanical material properties. Austenitic stainless steel AISI 304 serves in many applications due to high strength and corrosion resistance. In certain applications, it is important to evaluate the mechanical properties of AISI 304 stainless steel. In this study, the ultrasonic method (attenuation measurement technique) is used to evaluate the hardness of AISI 304 stainless steel samples which were heat treated at different levels. Due to the heat treatment process, each sample has its specific microstructure and hardness which attenuate ultrasonic waves appropriately. The ultrasonic and hardness test show that it is possible to evaluate the hardness of AISI 304 stainless steel by ultrasonic attenuation coefficient. In addition, the relationship between ultrasonic attenuation coefficients and time of heat treatment is investigated.

  2. Microstructural changes of AISI 316L due to structural sensitization and its influence on the fatigue properties

    Dundeková, S.; Nový, F.; Fintová, Stanislava

    2014-01-01

    Roč. 21, č. 4 (2014), s. 172-177. ISSN 1335-0803 Institutional support: RVO:68081723 Keywords : AISI 316L * Structural sensitization * Rotating bending fatigue test Subject RIV: JL - Materials Fatigue, Friction Mechanics

  3. Eight reasons payer interoperability and data sharing are essential in ACOs. Interoperability standards could be a prerequisite to measuring care.

    Mookencherry, Shefali

    2012-01-01

    It makes strategic and business sense for payers and providers to collaborate on how to take substantial cost out of the healthcare delivery system. Acting independently, neither medical groups, hospitals nor health plans have the optimal mix of resources and incentives to significantly reduce costs. Payers have core assets such as marketing, claims data, claims processing, reimbursement systems and capital. It would be cost prohibitive for all but the largest providers to develop these capabilities in order to compete directly with insurers. Likewise, medical groups and hospitals are positioned to foster financial interdependence among providers and coordinate the continuum of patient illnesses and care settings. Payers and providers should commit to reasonable clinical and cost goals, and share resources to minimize expenses and financial risks. It is in the interest of payers to work closely with providers on risk-management strategies because insurers need synergy with ACOs to remain cost competitive. It is in the interest of ACOs to work collaboratively with payers early on to develop reasonable and effective performance benchmarks. Hence, it is essential to have payer interoperability and data sharing integrated in an ACO model. PMID:22352172

  4. EFFECTS OF CARBURIZING AND NITRIDING PROCESSES ON THE COST AND QUALITY OF GEARS PRODUCED WITH AISI 4140 AND 8620 STEELS

    Claudio José Leitão; Paulo Roberto Mei; Rodolfo Libard

    2012-01-01

    This study compares the effects of nitriding and carburizing processes applied to gears subjected to contact stresses below 1300 MPa. The manufacturing cost, as well the depth of hardened layer and the distortion produced by two processes are analyzed. AISI 4140 gears quenched, tempered, liquid and gas nitriding and AISI 8620 gears after liquid carburizing, quenching and tempering are analyzed. The dimensional control of the gears was carried out before and after heat and thermoch...

  5. Corrosion behavior of stainless steel in bio diesel production; Comportamento quanto a corrosao de acos inoxidaveis na producao do biodiesel

    Miranda, E.F. de [ArcelorMittal Sao Paulo Servicos, SP (Brazil); Moreira, M.C.; Lebrao, S.M.G. [Centro Universitario do Instituto Maua de Tecnologia, Sao Paulo, SP (Brazil)], e-mail: susana.lebrao@maua.br

    2010-07-01

    Biodiesel has become more attractive due to the benefits to the environment, mainly because it is a renewable resource. However, the main barrier to biodiesel is it cost. One factor which is charged to marketing is the use of stainless steel throughout the production line, the most used is AISI 304. To evaluate more economical stainless steels, weight loss and stress corrosion tests were performed on samples of AISI 304 and 439 in methanol PS X30% sodium methylate solution, crude soybean oil, glycerol and biodiesel for about two hundred and fifty days. The mass loss was negligible, and there was complete absence of pitting and stress corrosion cracking in all media studied, showing that both alloys are suitable for the manufacture of such equipment. (author)

  6. AISI 316L under electron radiolysis at high temperature and pressure in PWR modelling conditions

    temperature (HT), 280-320 deg. C, and high pressure (HP), 15.5 MPa. Very few data are available in the literature on the role of HTHP water radiolysis on the corrosion of metallic reactor components. The present approach use electron beam to control the production of radiolytic species at a AISI 316L/PWR solution interface in a high temperature and high pressure (HTHP) electrochemical cell working at the range [25 deg. C, 1 bar] - [300 deg. C, 90 bar]. The cell is designed to record the free corrosion potential of the AISI 316L/PWR solution interface mounted on line at the SIRIUS pelletron delivering the electron beam (LSI, Ecole Polytechnique, France). The PWR primary solutions are simulated by aqueous solutions prepared at room temperature by adding boric acid and lithium hydroxide to high purity water and, in some cases, purged with Ar/H2 flow. At the AISI 316L/PWR solution interfaces irradiated between 25 deg. C/ 1 bar and 300 deg. C/ 90 bar, electrons emerge at ∼0.6 MeV and the flux varies from ∼1010 to 1012 e-.cm-2.s-1. The results clearly show that the response of the free potential between the AISI316L/water interface and a pseudo-reference electrode, i.e. a platinum wire during the irradiation (from electron beam switch-on until cut-off) depends on many parameters: the energy of the electron beam, the temperature and pressure, the concentration of hydrogen in the solution, the ageing of the disc electrode, the growth conditions of the initial oxide passive layers, etc... These results can be compared with those which have obtained by using the proton beam (CEMHTI, CNRS Orleans, France). Surface characterization experiments (XPS, SEM, Raman spectroscopy, photoluminescence...) on the oxide layer of AISI316L which are formed under the irradiation could also bring new information about the irradiation influence on the AISI316L. (authors)

  7. 向日葵ACC氧化酶基因(HaACO1)的克隆及表达分析%Cloning and Expression Analysis of ACC Oxidase Gene (HaACO1) from Sunflower (Helianthus annuus L.)

    孙瑞芬; 张艳芳; 郭树春; 于海峰; 李素萍; 乔慧蕾; 聂惠; 安玉麟

    2015-01-01

    目的:克隆向日葵中的ACC氧化酶基因(HaACO1),并对其进行生物信息学分析及盐胁迫表达分析,为理解向日葵ACC氧化酶生理功能并加强对ACO基因的利用奠定基础.方法:以前期从盐胁迫的内葵杂4号根中获得的ACC氧化酶基因片段4-4-7TDF(KM823963)为基础,通过RT-PCR和5'/3' RACE技术克隆ACO基因的全长cDNA序列,利用生物信息学软件对获得的eDNA序列及编码的蛋白质序列进行分析.同时采用PCR方法克隆基因组DNA(genemic DNA,gDNA)序列,并对其进行结构分析.利用实时荧光定量PCR分析NaCl胁迫下向日葵根、下胚轴、叶中HaACO1的表达量和不同NaCl浓度及不同胁迫时间下根中HaACO1的表达量.结果:HaACO1的cDNA序列全长为1 135bp,其开放阅读框为942bp,编码313个氨基酸.预测其分子质量和等电点分别为35.84kDa和5.13,基因登录号为KP966508.HaACO1与已报道的多种植物的ACO基因核苷酸序列及其推导的氨基酸序列有较高的相似性,分别为76% ~ 83%和77% ~88%.gDNA起始密码子至终止密码子序列长1 018bp,包含2个外显子和1个内含子,基因登录号为KP988289.实时荧光定量PCR分析表明向日葵HaACO1在不同器官及不同NaCl浓度、不同时间诱导下存在特异性表达差异.结论:获得的向日葵HaACO1是植物ACO家族成员之一,该基因应答盐胁迫具有独特的表达模式.

  8. The cluster lens ACO 1703: redshift contrast and the inner profile

    Saha, Prasenjit

    2008-01-01

    ACO 1703 is a cluster recently found to have a variety of strongly lensed objects: there is a quintuply-imaged system at z=0.888 and several other lensed objects from z=2.2 to 3.0 (the cluster itself is at z=0.28). It is not difficult to model the lens, as previous work has already done. However, lens models are generically non-unique. We generate ensembles of models to explore the non-uniqueness. When the full range of source redshifts is included, all models are close to \\rho \\propto r^{-1} out to 200 kpc. But if the quint is omitted, both shallower and steeper models (e.g., \\rho \\propto r^{-2}) are possible. The reason is that the redshift contrast between the quint and the other sources gives a good measurement of the enclosed mass at two different radii, thus providing a good estimate of the mass profile in between. This result supports universal profiles and explains why single-model approaches can give conflicting results. The mass map itself is elongated in the NW-SE direction, like the galaxy distrib...

  9. Task Scheduling problem in distributed systems considering communication cost and precedence by population-based ACO

    Hossein Erfani

    2012-09-01

    Full Text Available With regard to the fact of the rapid growth of distributed systems and their large spectrum of usage of proposing and representing controlling solutions and optimization of task execution procedures is one of the most important issues. Task scheduling in distributed systems has determining role in improving efficiency in applications such as communication, routing, production plans and project management. The most important issues of good schedule are minimizing makespan and average of waiting time. However, the recent and previous effort usually focused on minimizing makespan. This article presents and analyze a new method based on Ant Colony Optimization (ACO algorithm with considerations to precedence and communication cost for task scheduling problem. In the mentioned method in addition to optimization of finish time, average of waiting time and number of needed processors are also optimized. In this method, by using of a new heuristic list, an algorithm based on ant colony is proposed. The results obtained in comparison with the latest similar models of random search algorithms, proves the higher efficiency of algorithm.

  10. NASA GES DISC support of CO2 Data from OCO-2, ACOS, and AIRS

    Wei, Jennifer C; Vollmer, Bruce E.; Savtchenko, Andrey K.; Hearty, Thomas J; Albayrak, Rustem Arif; Deshong, Barbara E.

    2013-01-01

    NASA Goddard Earth Sciences Data and Information Services Centers (GES DISC) is the data center assigned to archive and distribute current AIRS, ACOS data and data from the upcoming OCO-2 mission. The GES DISC archives and supports data containing information on CO2 as well as other atmospheric composition, atmospheric dynamics, modeling and precipitation. Along with the data stewardship, an important mission of GES DISC is to facilitate access to and enhance the usability of data as well as to broaden the user base. GES DISC strives to promote the awareness of science content and novelty of the data by working with Science Team members and releasing news articles as appropriate. Analysis of events that are of interest to the general public, and that help in understanding the goals of NASA Earth Observing missions, have been among most popular practices.Users have unrestricted access to a user-friendly search interface, Mirador, that allows temporal, spatial, keyword and event searches, as well as an ontology-driven drill down. Variable subsetting, format conversion, quality screening, and quick browse, are among the services available in Mirador. The majority of the GES DISC data are also accessible through OPeNDAP (Open-source Project for a Network Data Access Protocol) and WMS (Web Map Service). These services add more options for specialized subsetting, format conversion, image viewing and contributing to data interoperability.

  11. REGISTRO DE PARO CARDÍACO EN EL ADULTO Registries of outer hospital cardiac arrest in Bogotta-Colombia

    Ricardo Navarro Vargas

    2005-07-01

    Full Text Available En nuestro país no hay un registro estandarizado de los eventos cardíacos que requieren reanimación cerebro-cardio-pulmonar (RCCP siguiendo los lineamientos "Utstein". El propósito de este estudio fue determinar la calidad de los registros extrahospitalarios de paro cardíaco en el adulto, en Bogotá-Colombia. Entre enero y marzo de 2005 se realizó un análisis retrospectivo de los casos que correspondieron a paro cardíaco en el adulto atendidos por el "Centro Regulador de Urgencias del Distrito (CRU". El estudio reveló un registro deficiente de los eventos que requirieron RCCP realizados a nivel prehospitalario, e identificó al trauma como causa de paro cardíaco en 22% de los casos, una cifra particularmente elevada si se compara con los reportes mundiales, que oscilan entre 5% y 8%. Recomienda la estandarización del registro de paro cardíaco en el adulto, para lo cual se sugiere utilizar el formato de registro que sigue los lineamientos "Utstein".There is not a standardized registry form of cardiac events requiring cardiopulmonary resuscitation (CPR in our country such as the Utstein style. The purpose of this study was to determine the quality of the registries of out-ofhospital cardiac arrests in Bogotá-Colombia. A retrospective survey of registries of cardiac events assisted by a regulatory center "Centro Regulador de Urgencias del Distrito (CRU" was conducted, between January and March, 2005. The study reveals a poor registry of outof-hospital cardiac arrest in Bogotá-Colombia, and identifies trauma as the cause of cardiac arrest in 22% of cases, a particularly high figure compared with 5-8% registered worldwide. Recommend the standardization of the registry form of out-of-hospital cardiac arrest and suggest to use the "uniform reporting of data following cardiac arrest - the Utstein style". The registry forms are shown in appendix 1-2. Suggestions are welcome.

  12. Hot rolling of the superaustenitic stainless steel AISI 904L: Vroče valjanje superavstenitnega nerjavnega jekla AISI 904L:

    Arh, Boštjan; Burja, Jaka; PODGORNIK, Bojan; Tehovnik, Franc; Žužek, Borut

    2014-01-01

    The AISI 904L superaustenitic stainless steel has a narrow processing window. In this work the hot rolling of steel, specifically the hot deformation behavior, is investigated. Specimens of steel were hot rolled at temperatures from 1000 °C to 1250 °C with 50 °C increments and the rolling loads were measured and recorded. Microstructural changes were examined, with the accent on the recrystallization. From changes of the hot-rolling loads and microstructure it is concluded that the recrystall...

  13. Análisis experimental del torneado de alta velocidad del acero AISI 1045 // Experimental analysis of high speed turning of AISI 1045 steel gears

    Luís Wilfredo Hernández‐González

    2012-01-01

    Full Text Available El objetivo de este trabajo es el estudio experimental de la evolución del desgaste del flanco de dosinsertos de carburo recubiertos y un cermet, durante el torneado en seco del acero AISI 1045 con 500 y600 m/min de velocidad de corte. Los resultados fueron comparados utilizando el análisis de varianza y deregresión. La investigación mostró un efecto significativo de la velocidad de corte y del tiempo demaquinado en el desgaste del flanco. El mejor desempeño fue para el carburo recubierto con tres capas,mientras que a elevada velocidad de corte el carburo con dos capas sufrió el mayor desgaste, lo cual sedebe a que cuando pierde sus recubrimientos el substrato del inserto queda desprotegido y el desgastecrece rápidamente por la extremas condiciones del mecanizado por alta velocidad. Además, se planteanrecomendaciones del tiempo de maquinado de los insertos dadas las condiciones de elaboración por altavelocidad.Palabras claves: torneado de alta velocidad, desgaste del flanco, acero AISI 1045, estudio experimental.__________________________________________________________________________AbstractThis work deals with the experimental study of the flank wear evolution of two coating carbide inserts and acermet insert during the dry turning of AISI 1045 steel with 500 and 600 m/min cutting speed. The resultswere compared using the variance and regression analysis. The investigation showed a significant effectof cutting speed and machining time on the flank wear in high speed machining. The three coating layersinsert showed the best performance while the two layers insert had the worst behaviour of the cutting toolwear at high cutting speed, this is because once the coating film is peeled off, the substrate of the insertbecomes uncovered and the wear grows rapidly due to the extreme machining conditions for high speed.Besides, the machining time recommendations of inserts for the cutting conditions at high speed areexposed.Key words: high

  14. Qualidade de vida de pacientes submetidos ao transplante cardíaco: aplicação da escala Whoqol-Bref Calidad de vida de pacientes sometidos a transplante cardíaco: aplicación de la escala Whoqol-Bref Quality of life of patients that had a heart transplant: application of Whoqol-Bref scale

    Maria Isis Freire de Aguiar; Deisiana Rios Farias; Mabel Leite Pinheiro; Emília Soares Chaves; Isaura Letícia Tavares Palmeira Rolim; Paulo César de Almeida

    2011-01-01

    FUNDAMENTO: O sucesso do transplante cardíaco significa garantir a sobrevida dos pacientes com cardiopatia e permitir-lhes desenvolver suas atividades diárias. O transplante cardíaco apresenta-se como a primeira opção de tratamento na falência cardíaca, representando um aumento de sobrevida e qualidade de vida dos transplantados. OBJETIVO: Avaliar a qualidade de vida de pacientes submetidos ao transplante cardíaco através da aplicação de uma escala padronizada (Whoqol-Bref). MÉTODOS: Estudo e...

  15. Radiation-induced evolution of austenite matrix in silicon-modified AISI 316 alloys

    The microstructures of a series of silicon-modified AISI 316 alloys irradiated to fast neutron fluences of about 2-3 and 10 x 1022 n/cm2 (E > 0.1 MeV at temperatures ranging from 4000C to 6000C have been examined. The irradiation of AISI 316 leads to an extensive repartition of several elements, particularly nickel and silicon, between the matrix and various precipitate phases. The segregation of nickel at void and grain boundary surfaces at the expense of other faster-diffusing elements is a clear indication that one of the mechanisms driving the microchemical evolution is the Inverse Kirkendall effect. There is evidence that at one sink this mechanism is in competition with the solute drag process associated with interstitial gradients

  16. Martensitic transformation on AISI 304 stainless steel produced by a coaxial plasma gun

    Full text: In a previous paper, a surface treatment of AISI 304 stainless steel irradiated by a Nitrogen ion beam generated in a coaxial plasma gun has been reported. The device is operated with a Titanium insert at the end of the inner electrode, producing a TiN coating on the surface of the sample. Because of the ion and plasma energy deposition, the sample surface is strongly heated during the treatment resulting in titanium diffusion. Preliminary X-ray diffraction (XRD) studies have shown the presence of a martensitic transformation on AISI 304 samples, probably induced by Ti atoms. In this work, the transformation depth is studied with grazing-incidence XRD on samples subjected to several superimposed shots. For this purpose, multiple low angles of incidence are used, allowing the analysis at different depths of the substrate

  17. Analysis of pulsed Nd:YAG laser welding of AISI 304 steel

    Kim, Kwan Woo; Lee, Jung Kil; Cho, Hae Yong [Chungbuk National University College of Medicine, Jeonju (Korea, Republic of)

    2010-11-15

    Pulsed laser welding of AISI 304 stainless steel plate was simulated using commercial finite element software to determine the optimal welding conditions. Due to geometric symmetry, only one plate was modeled to reduce the simulation computation time. User subroutines were created to account for a moving three-dimensional heat source and to apply boundary conditions. The material properties such as conductivity, specific heat, and mass density were determined as functions of temperature. The latent heat was considered within the given temperature range. The three-dimensional heat source model for pulsed laser beam butt welding was designed by comparing the finite element analysis results and experimental data. This successful simulation of pulsed Nd:YAG laser welding for AISI 304 stainless steel will prove useful for determining optimal welding conditions

  18. Experimental Investigation of the Effect of Burnishing Force on Service Properties of AISI 1010 Steel Plates

    Gharbi, F.; Sghaier, S.; Morel, F.; Benameur, T.

    2015-02-01

    This paper presents the results obtained with a new ball burnishing tool developed for the mechanical treatment of large flat surfaces. Several parameters can affect the mechanical behavior and fatigue of workpiece. Our study focused on the effect of the burnishing force on the surface quality and on the service properties (mechanical behavior, fatigue) of AISI 1010 steel hot-rolled plates. Experimental results assert that burnishing force not exceeding 300 N causes an increase in the ductility. In addition, results indicated that the effect of the burnishing force on the residual surface stress was greater in the direction of advance than in the cross-feed direction. Furthermore, the flat burnishing surfaces did not improve the fatigue strength of AISI 1010 steel flat specimens.

  19. Behavior of AISI SAE 1020 steel implanted by titanium and exposed to bacteria sulphate deoxidizer

    A hybrid technology to treat solid surfaces with the pulse high voltage and electric arc discharges of low pressure with a three-dimensional ion implantation technique (3DII) is applied. This technology is used to protect AISI SAE 1020 steel against a microbiological corrosion. The titanium ion implanted steel samples (coupons) are subjected to a medium of bacteria sulphate deoxidizer (BSD) which are very typical of the hydrocarbon industry and are potentially harmful for structures when are in contact with petroleum and some of its derivatives. The used technology aims to find an effective hybrid procedure to minimize the harmful effects of bacteria on AISI SAE 1020 steel. The hybrid technology efficiency of superficial titanium implantation is estimated through the measurements of the point corrosion characteristics obtained after testing both the treated and non-treated coupons. The three-dimensional surface structures of the samples are reconstructed with help of a confocal microscope.

  20. Experimental study of mechanical properties of friction welded AISI 1021 steels

    Amit Handa; Vikas Chawla

    2013-12-01

    Friction welding is widely used as a mass production method in various industries. In the present study, an experimental set-up was designed in order to achieve friction welding of plastically deformed AISI 1021 steels. In this study, low alloy steel (AISI 1021) was welded under different welding parameters and afterwards the mechanical properties such as tensile strength, impact strength and hardness were experimentally determined. On the basis of the results obtained from the experimentation, the graphs were plotted. It is the strength of welded joints, which is fundamental property to the service reliability of the weldments and hence present work was undertaken to study the influence of axial pressure and rotational speed in friction welded joints. Axial pressure and rotational speed are the two major parameters which can influence the strength and hence the mechanical properties of the friction welded joints. Thus the axial pressure and rotational speed were taken as welding parameters, which reflect the mechanical properties.

  1. 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

    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.

  2. AFM surface imaging of AISI D2 tool steel machined by the EDM process

    The surface morphology, surface roughness and micro-crack of AISI D2 tool steel machined by the electrical discharge machining (EDM) process were analyzed by means of the atomic force microscopy (AFM) technique. Experimental results indicate that the surface texture after EDM is determined by the discharge energy during processing. An excellent machined finish can be obtained by setting the machine parameters at a low pulse energy. The surface roughness and the depth of the micro-cracks were proportional to the power input. Furthermore, the AFM application yielded information about the depth of the micro-cracks is particularly important in the post treatment of AISI D2 tool steel machined by EDM

  3. AFM surface imaging of AISI D2 tool steel machined by the EDM process

    Guu, Y.H. [Department of Mechanical Engineering, National United University, 1 Lien Da, Kung-Ching Li, Miaoli 360, Taiwan (China)]. E-mail: yhorng@nuu.edu.tw

    2005-04-15

    The surface morphology, surface roughness and micro-crack of AISI D2 tool steel machined by the electrical discharge machining (EDM) process were analyzed by means of the atomic force microscopy (AFM) technique. Experimental results indicate that the surface texture after EDM is determined by the discharge energy during processing. An excellent machined finish can be obtained by setting the machine parameters at a low pulse energy. The surface roughness and the depth of the micro-cracks were proportional to the power input. Furthermore, the AFM application yielded information about the depth of the micro-cracks is particularly important in the post treatment of AISI D2 tool steel machined by EDM.

  4. Tool life and surface roughness of ceramic cutting tool when turning AISI D2 tool steel

    The tool life of physical vapor deposition (PVD) titanium nitride (TiN) coated ceramic when turning AISI D2 tool steel of hardness 54-55 HRC was investigated. The experiments were conducted at various cutting speed and feed rate combinations with constant depth of cut and under dry cutting condition. The tool life of the cutting tool for all cutting conditions was obtained. The tool failure mode and wear mechanism were also investigated. The wear mechanism that is responsible for the wear form is abrasion and diffusion. Flank wear and crater wear are the main wear form found when turning AISI D2 grade hardened steel with 54-55 HRC using KY 4400 ceramic cutting tool. Additionally catastrophic failure is observed at cutting speed of 183 m/min and feed rate of 0.16 mm/ rev. (author)

  5. Analysis of pulsed Nd:YAG laser welding of AISI 304 steel

    Pulsed laser welding of AISI 304 stainless steel plate was simulated using commercial finite element software to determine the optimal welding conditions. Due to geometric symmetry, only one plate was modeled to reduce the simulation computation time. User subroutines were created to account for a moving three-dimensional heat source and to apply boundary conditions. The material properties such as conductivity, specific heat, and mass density were determined as functions of temperature. The latent heat was considered within the given temperature range. The three-dimensional heat source model for pulsed laser beam butt welding was designed by comparing the finite element analysis results and experimental data. This successful simulation of pulsed Nd:YAG laser welding for AISI 304 stainless steel will prove useful for determining optimal welding conditions

  6. Embrittlement and strain hardining of the hydrogenated AISI 304 austenitic stainless steel

    The influence of hydrogen the mechanical properties of type AISI 304 austenitic stainless steel was analysed. Hydrogenation was performed cathodically, at room temperature, in a 1N H2SO4 solution. The variables controlled for analysis were current density and time. Uniaxial tensile tests were conducted with constant nominal strain rate. Fracture morphology was analysed by scanning electron microscopy and the kinetics of strain hardening by applying Ludwick's equation to the resulting stress-strain curves. It was verified that hydrogen embrittles markedly, the austenitic AISI 304 steel, leading to a significant loss of ductility and modifying the fracture made, from essentially ductile to a transgrannular fragile fracture, containing small regions of intergranular fracture. With increasing amounts of hydrogen there was also a decrease in the maximum uniform stress, the strength coefficient, the strain hardening exponent and in the range the deformation stages II and III extended. (Author)

  7. Corrosion resistance of the welded AISI 316L after various surface treatments

    Tatiana Liptáková

    2014-01-01

    Full Text Available The main aim of this work is to monitor the surface treatment impact on the corrosion resistance of the welded stainless steel AISI 316L to local corrosion forms. The excellent corrosion resistance of austenitic stainless steel is caused by the existence of stable, thin and well adhering passive layer which quality is strongly influenced by welding. Therefore surface treatment of stainless steel is very important with regard to its local corrosion susceptibility Surfaces of welded stainless steel were treated by various mechanical methods (grinding, garnet blasting. Surface properties were studied by SEM, corrosion resistance was evaluated after exposition tests in chlorides environment using weight and metalographic analysis. The experimental outcomes confirmed that the mechanical finishing has a significant effect on the corrosion behavior of welded stainless steel AISI 316L.

  8. Microhardness measurement in AISI 321 stainless steel with niobium additions before and after fast neutron irradiation

    Data about influence of neutron irradiation on the microhardness of stainless steel of type AISI 321 with 0.05 and 0.1wt.% Nb additions are presented. The microhardness measurements were made in the range of 300 to 6500C, before and after fast neutron irradiation with fluences about 1017n/cm2. Our results indicate that radiation damage peaks occur around 4800C for the stainless steel of type AISI 321 without Nb addition, around 5000C for the composition with 0.05 wt.% Nb addition and around 5700C for the composition with 0.1 wt.% Nb addition. Microhardness data are in agreement with those obtained by means of electrical resistivity measurements, performed at the same conditions. (Author)

  9. INFLUENCE OF AISI 316Ti STAINLESS STELL SURFACE TREATMENT ON PITTING CORROSION IN VARIOUS SOLUTIONS

    Pavol Fajnor

    2010-12-01

    Full Text Available Investigation of the surface treatment effect on the resistance of AISI 316Ti stainless steel to pitting corrosion is presented in this paper. The grinded surfaces without additional chemical treatment, grinded and pickled, grinded, pickled and passivated surfaces are tested. The corrosion tests are carried out by exposition in solution which evoke pitting and by electrochemical cyclic potential - sweep method. According to the results the surface treatment has a great influence on the resistance of the tested material to pitting. It is not possible to estimate the best surface treatment because behavior of AISI 316Ti stainless steel with different surface state depends on the mechanism of corrosion processes which vary in the used experimental methods.

  10. Oxidation behavior of 26Cr-16Ni and AISI 309 austenitic stainless steels in air flow at 1,173 K

    Pipatnukun, Peeraya; Wangyao, Panyawat; Lothongkum, Gobboon [Chulalongkorn Univ., Bangkok (Thailand). Dept. of Metallurgical Engineering

    2015-11-01

    This work investigates the isothermal oxidation behavior of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 at 1,173 K in air flow rate of 40 cm{sup 3} x min{sup -1} using thermogravimetric analysis (TGA). In 33 hours, the oxidation resistance declines from high to low are as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309, respectively. The oxidation kinetic results show that the exponential rate constant of the as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 8.79 x 10{sup -6}, 4.02 x 10{sup -5} and 4.35 x 10{sup -5} g x cm{sup -2} x s{sup -n}, respectively. The exponential growth rates of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 0.42, 0.29 and 0.32, respectively. It indicates that the oxidation kinetic of as cast 26Cr-16Ni approaches a parabolic rate law, but those of as cold-rolled and as cast AISI 309 approach the cubic rate law. The sequence of oxide scale formations on the tested samples is also discussed.

  11. Oxidation behavior of 26Cr-16Ni and AISI 309 austenitic stainless steels in air flow at 1,173 K

    This work investigates the isothermal oxidation behavior of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 at 1,173 K in air flow rate of 40 cm3 x min-1 using thermogravimetric analysis (TGA). In 33 hours, the oxidation resistance declines from high to low are as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309, respectively. The oxidation kinetic results show that the exponential rate constant of the as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 8.79 x 10-6, 4.02 x 10-5 and 4.35 x 10-5 g x cm-2 x s-n, respectively. The exponential growth rates of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 0.42, 0.29 and 0.32, respectively. It indicates that the oxidation kinetic of as cast 26Cr-16Ni approaches a parabolic rate law, but those of as cold-rolled and as cast AISI 309 approach the cubic rate law. The sequence of oxide scale formations on the tested samples is also discussed.

  12. Sub-surface Fatigue Crack Growth at Alumina Inclusions in AISI 52100 Roller Bearings

    Cerullo, Michele

    2014-01-01

    damage factor is highest. Subsequently the stress history is imposed as boundary conditions in a periodic unit cell model, where an alumina inclusion is embedded in a AISI 52100 matrix. Cracks are assumed to grow radially from the inclusion under cyclic loading. The growth is predicted by means of...... irreversible fatigue cohesive elements. Different orientations of the cracks and different matrix-inclusion bonding conditions are analyzed and compared....

  13. Metallurgical response of an AISI 4140 steel to different plasma nitriding gas mixtures

    Adão Felipe Oliveira Skonieski; Giovanni Rocha dos Santos; Thomas Karl Hirsch; Alexandre da Silva Rocha

    2013-01-01

    Plasma nitriding is a surface modification process that uses glow discharge to diffuse nitrogen atoms into the metallic matrix of different materials. Among the many possible parameters of the process, the gas mixture composition plays an important role, as it impacts directly the formed layer's microstructure. In this work an AISI 4140 steel was plasma nitrided under five different gas compositions. The plasma nitriding samples were characterized using optical and scanning electron microscop...

  14. Deposition and characterization of duplex treated coating system applied on hot work steel AISI H13

    Bejarano Gait??n, Gilberto; Arroyave Franco, Mauricio; G??mez Botero, Maryori

    2015-01-01

    AISI H13 steel is widely used for extrusion moulds and other hot work tools fabrication, due to its high toughness, strength and hardness around 56 HRC (Rockwell C) -- However, this steel possesses a relatively low wear resistance, which reduces its life time under high loading conditions -- The aim of this work was to enhance the wear resistance of the steel H13 using the following surface treatments:austenitizing + quenching + tempering (further called ???tempering???), tempering and bath n...

  15. Corrosion behaviour of AISI 316L steel in artificial body fluids

    W. Kajzer

    2008-12-01

    Full Text Available Purpose: The paper presents the comparison of corrosion resistance of AISI 316L stainless steel in various corrosive media such as artificial urine, Tyrode’s physiological solution and artificial plasma.Design/methodology/approach: The tests were carried out on samples of the following surfaces: grinded – average roughness Ra = 0.31 μm and electropolished and chemically passivated average roughness Ra = 0.10 μm. The corrosion tests were realized by recording of anodic polarization curves with the use of the potentiodynamic method. The VoltaLab® PGP 201 system for electrochemical tests was applied. The tests were carried out in electrolyte simulating urine (pH = 6-6.4, Tyrode’s physiological solution (pH = 6.8-7.4 and plasma (pH = 7.2-7.6 at the temperature of 37±1°C.Findings: Surface condition of AISI 316L stainless steel determines its corrosion resistance. The highest values of breakdown potentials were recorded for all electropolished and chemically passivated samples in all simulated body fluids. The highest values of anodic current density were recorded for samples tested in artificial urine, the lowest values were recorded for samples tested in Tyrode’s physiological solution.Research limitations/implications: The obtained results are the basis for the optimization of physicochemical properties of the AISI 316L stainless steel.Practical implications: On the basis of the obtained results it can be stated that stainless steel meets the basic biocompatibility criteria and can be applied in reconstruction surgery, operative cardiology and urology.Originality/value: The paper presents the influence of various corrosive media simulating human body fluids on corrosion resistance of AISI 316L stainless steel.

  16. Study of corrosion resistance of AISI 444 ferritic stainless steel for application as a biomaterial

    Ferritic stainless steels are ferromagnetic materials. This property does not allow their use in orthopedic prosthesis. Nevertheless, in some specific applications, this characteristic is very useful, such as, for fixing dental and facial prostheses by using magnetic attachments. In this study, the corrosion resistance and cytotoxicity of the AISI 444 ferritic stainless steel, with low nickel content, extra-low interstitial levels (C and N) and Ti and Nb stabilizers, were investigated for magnetic dental attachments application. The ISO 5832-1 (ASTM F-139) austenitic stainless steel and a commercial universal keeper for dental attachment (Neo-magnet System) were evaluated for comparison reasons. The first stainless steel is the most used metallic material for prostheses, and the second one, is a ferromagnetic keeper for dental prostheses (NeoM). In vitro cytotoxicity analysis was performed by the red neutral incorporation method. The results showed that the AISI 444 stainless steel is non cytotoxic. The corrosion resistance was studied by anodic polarization methods and electrochemical impedance spectroscopy (EIS), in a saline phosphate buffered solution (PBS) at 37 °C. The electronic properties of the passive film formed on AISI 444 SS were evaluated by the Mott-Schottky approach. All tested materials showed passivity in the PBS medium and the passive oxide film presented a duplex nature. The highest susceptibility to pitting corrosion was associated to the NeoM SS. This steel was also associated to the highest dopant concentration. The comparatively low levels of chromium (nearly 12.5%) and molybdenum (0.3%) of NeoM relatively to the other studied stainless steels are the probable cause of its lower corrosion resistance. The NeoM chemical composition does not match that of the SUS444 standards. The AISI 444 SS pitting resistance was equivalent to the ISO 5832-1 pointing out that it is a potential candidate for replacement of commercial ferromagnetic alloys used

  17. The influence of microstruture on fracture toughness of vacuum heat treated HSS AISI M2

    Leskovšek, Vojteh; Ule, Boris; Liščić, Božidar

    2015-01-01

    The microstructure of AISI M2 high-speed can be substantially modified by vacuum heat treatment in order to optimize the ratio between hardness and fracture toughness, which is, however, significantly affected by the volume fractions of retained austenite and undissolved eutectic carbides, as well as the mean distance between these carbides. Calculated fracture toughness values, which were obtained using a newly developed semi-empirical equation, based on the stress-modified critical strain c...

  18. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    Rômulo Ribeiro Magalhães de Sousa

    2012-04-01

    Full Text Available AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN, with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

  19. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    Rômulo Ribeiro Magalhães de Sousa; Francisco Odolberto de Araújo; José Alzamir Pereira da Costa; Antonio Maia de Oliveira; Mineia Sampaio Melo; Clodomiro Alves Junior

    2012-01-01

    AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN), with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

  20. Multi-scale modelling of AISI H11 martensitic tool steel surface anisotropic mechanical behaviour

    Zouaghi Ahmed; Velay Vincent; Soveja Adriana; Rézaï-Aria Farhad

    2014-01-01

    In this work, a numerical investigation is carried out on the anisotropic and heterogeneous behaviour of the AISI H11 martensitic tool steel surface using finite element method and a multi-scale approach. An elasto-viscoplastic model that considers nonlinear isotropic and kinematic hardenings is implemented in the finite elements code ABAQUS using small strain assumption. The parameters of the constitutive equations are identified using macroscopic quasi-static and cyclic material responses b...

  1. Optimization of Machining Parameters for improved Surface Integrity of AISI H13 Tool Steel

    OUTEIRO, José

    2012-01-01

    The surface integrity plays a very important rule in this functional performance, being dependent of a large number of machining parameters. The major concern of the industry is to know which combination of machining parameters provides a better surface integrity of the machined components. AISI H13 tool steel has been applied widely to produce many different types of hot working dies due to its excellent mechanical properties, such as: good resistance to thermal softening, high hardenabil...

  2. Laser welding of butt joints of austenitic stainless steel AISI 321

    A. Klimpel

    2007-11-01

    Full Text Available Purpose: of this paper: A study of an automated laser autogenous welding process of butt joints of austenitic stainless steel AISI 321 sheets 0.5 [mm] and 1.0 [mm] thick using a high power diode laser HPDL has been carried out.Design/methodology/approach: Influence of basic parameters of laser welding on shape and quality of the butt joints and the range of optimal parameters of welding were determined.Findings: It was showed that there is a wide range of laser autogenous welding parameters which ensures high quality joints of mechanical strength not lower than the strength of the base material (BM. The butt joints of austenitic steel AISI 321 sheets welded by the HPDL diode laser at optimal parameters are very high quality, without any internal imperfections and the structure and grain size of weld metal and HAZ is very small and also the HAZ is very narrow and the fusion zone is very regular.Research limitations/implications: Studies of the weldability of stainless steels indicate that the basic influence on the quality of welded joints and reduction of thermal distortions has the heat input of welding, moreover the highest quality of welded joints of austenitic stainless steel sheets are ensured only by laser welding.Practical implications: The technology of laser welding can be directly applied for welding of butt joints of austenitic steel AISI 321 sheets 0.5 and 1.0 [mm] thick.Originality/value: Application of high power diode laser for welding of austenitic stainless steel AISI 321.

  3. Structure and properties of the Stainless steel AISI 316 nitrided with microwave plasma

    In this work were presented the results obtained by nitridation on stainless steel AISI 316 using a plasma generated through a microwave discharge with an external magnetic field using several moistures hydrogen / nitrogen to form a plasma. The purpose of nitridation was to increase the surface hardness of stainless steel through a phase formation knew as γN which has been reported that produces such effect without affect the corrosion resistance proper of this material. (Author)

  4. Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading

    Heinz Werner Höppel

    2012-02-01

    Full Text Available The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cyclic stress response is three times larger for the ultrafine-grained condition.

  5. Carbides crystalline structure of AISI M2 high-speed steel

    The aim of this study was to identify the crystallographic structure of the extracted carbides of AISI M2 steel spray formed The structure determination of these carbides. The structure determination of these carbides is a very hard work. Since these structures were formed by atom migration it is not possible to reproduce them by a controlled process with a determined chemical composition. The solution of this problem is to obtain the carbide by chemical extraction from the steel. (Author)

  6. Influence of the surface finishing on the corrosion behaviour of AISI 316L stainless steel

    Dundeková, S.; Zatkalíková, V.; Fintová, Stanislava; Hadzima, B.; Škorík, Viktor

    2015-01-01

    Roč. 22, č. 1 (2015), s. 48-53. ISSN 1335-0803 R&D Projects: GA MŠk(CZ) EE2.3.30.0063 Institutional support: RVO:68081723 Keywords : AISI 316L stainless steel * Corrosion * Immersion test * Corrosion rate Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://ojs.mateng.sk/index.php/Mateng/article/view/166/251

  7. AN ELECTROCHEMICAL PROCESSING STRATEGY FOR IMPROVING TRIBOLOGICAL PERFORMANCE OF AISI 316 STAINLESS STEEL UNDER GREASE LUBRICATION

    JIAOJUAN ZOU; MAOLIN LI; NAIMING LIN; XIANGYU ZHANG; LIN QIN; BIN TANG

    2014-01-01

    In order to improve the tribological performance of AISI 316 stainless steel (316 SS) under grease lubrication, electrochemical processing was conducted on it to obtain a rough (surface texturing-like) surface by making use of the high sensitivity of austenitic stainless steel to pitting corrosion in Cl--rich environment. Numerous corrosion pits or micro-ditches acted as micro-reservoirs on the obtained surface. While the grease could offer consistent lubrication, and then improve the tribolo...

  8. Stoichiometric titanium dioxide ion implantation in AISI 304 stainless steel for corrosion protection

    Hartwig, A.; Decker, M.; Klein, O.; Karl, H.

    2015-12-01

    The aim of this study is to evaluate the applicability of highly chemically inert titanium dioxide synthesized by ion beam implantation for corrosion protection of AISI 304 stainless steel in sodium chloride solution. More specifically, the prevention of galvanic corrosion between carbon-fiber reinforced plastic (CFRP) and AISI 304 was investigated. Corrosion performance of TiO2 implanted AISI 304 - examined for different implantation and annealing parameters - is strongly influenced by implantation fluence. Experimental results show that a fluence of 5 × 1016 cm-2 (Ti+) and 1 × 1017 cm-2 (O+) is sufficient to prevent pitting corrosion significantly, while galvanic corrosion with CFRP can already be noticeably reduced by an implantation fluence of 5 × 1015 cm-2 (Ti+) and 1 × 1016 cm-2 (O+). Surface roughness, implantation energy and annealing at 200 °C and 400 °C show only little influence on the corrosion behavior. TEM analysis indicates the existence of stoichiometric TiO2 inside the steel matrix for medium fluences and the formation of a separated metal oxide layer for high fluences.

  9. Structure and low-cycle fatigue of steel AISI 316 after ECAP

    M. Greger

    2008-05-01

    Full Text Available Purpose: Main aim of this paper is to describe the plastic deformation executed by ECAP on low cycle fatigueof steel AISI 316. Among others was attention fixed on mechanical properties after this treatment.Design/methodology/approach: Experiments were planned and realised at the temperature ranging fromroom temperature up to 280 °C. After application of deformation the structure was investigated in dependence onaccumulation of deformation and deformation temperature as well as abovementioned final properties.Findings: Accumulated real (logarithmic deformation varied from the value 2 to 8. Investigation of structure byelectron microscopy was made with use of microscope JEOL JEM 2100. Mechanical properties were investigatedby conventional tensile test and penetration test. Selected samples were subjected to low-cycle fatigue. Statisticevaluation of angular disorientation and of size of grains/sub-grains was also made with use of electron diffraction(EBSD in combination with scanning electron microscope FEG SEM Philips.Practical implications: The Technology ECAP was applied on austenitic steel AISI 316. It was verificationof ECAP application possibility on steel AISI 316 importantly for following applying on similar kinds of steel,because ECap technology influence on fatigue properties was confirmed.Originality/value: It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue theultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatiguecharacteristics, particularly fatigue limit.

  10. The structure of austenitic steel AISI 316 after ECAP and low-cycle fatigue

    L. Kander

    2008-06-01

    Full Text Available Purpose: The article presents results of investigation of structure and properties of austenitic steel grade AISI 316 after application of Equal Channel Angular Pressing (ECAP at the temperature of approx. 290ºC.Design/methodology/approach: The ECAP method led to significant improvement of strength of investigated material. Experiments were planned and realised at the temperature ranging from room temperature up to above mentioned temperature.Findings: It was established with use of the EBSD technique that after 8 passes through the ECAP die the sub-grains with an angle of disorientation smaller than 10º formed less than 20% of resulting structure. Average size of austenitic grains with high angle boundary after 8 passes was approx. 0.32 µm. It was proven that the ECAP method enables obtaining of ultra fine-grained austenitic structure formed by recrystallised grains with very low density of dislocations.Practical implications: The Technology ECAP was applied on austenitic steel AISI 316. It was verification of ECAP application possibility on steel AISI 316 importantly for following applying on similar kinds of steel, because ECAP technology influence on fatigue properties was confirmed.Originality/value: It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue the ultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatigue characteristics, particularly fatigue limit.

  11. Wear resistance of Fe-Nb-Cr-W, Nb, AISI 1020 and AISI 420 coatings produced by thermal spray wire arc; Resistencia al desgaste de recubrimientos Fe-Nb-Cr-W, Nb, AISI 1020 y AISI 420 producidos por proyeccion termica por arco electrico

    Lopez-Covaleda, E. A.; Mercado-Veladia, J. L.; Olaya-Florez, J. J.

    2013-07-01

    The commercial materials 140MXC (with iron, tungsten, chrome, niobium), 530AS (AISI 1015 steel) and 560AS (AISI 420 steel) on AISI 4340 steel were deposited using thermal spray with arc. The aim of work was to evaluate the best strategy abrasive wear resistance of the system coating-substrate using the following combinations: (1) homogeneous coatings and (2) coatings depositing simultaneously 140MXC + 530AS and 140MXC + 560AS. The coatings microstructure was characterized using Optical microscopy, Scanning electron microscopy and Laser con focal microscopy. The wear resistance was evaluated through dry sand rubber wheel test (DSRW). We found that the wear resistance depends on the quantity of defects and the mechanical properties like hardness. For example, the softer coatings have the biggest wear rates and the failure mode was characterized by plastic deformation caused by particles indentation, and the other hand the failure mode at the harder materials was grooving. The details and wear mechanism of the coatings produced are described in this investigation. (Author)

  12. Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

    Research highlights: → The surface roughness of the bare substrate influence the oxide layer growth. → The oxide layer roughness follows power laws and belongs to universality class. → At low growth temperature, the p-n heterojunction disappears in some places. → SKPFM images allow the direct visualization of local corrosion sites. → Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. - Abstract: Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

  13. A study on the control of melting ratio to increase mechanical properties of laser welded joints between AISI 440C and AISI 430F

    Romoli, L.; Rashed, C. A. A.; Lovicu, G.; Ishak, R.

    2015-05-01

    Laser beam welding of dissimilar AISI 440C and AISI 430F stainless steels was investigated in a circular constrained configuration. The beam incidence angle and the offset of the focusing position respect to the contact point between the two materials were used as main control parameters to vary the melting ratio inside the seam. The objective of the study is twofold: to avoid surface microcracks related to the high percentage of carbon of the martensitic steel and to enhance the shear strength of the weld by making it less brittle. To reach this scope the effects of incidence angle and offset on weld bead geometry and melting ratio were studied by means of metallographic analyses, microstructure and microhardness characterization. As last step, the weld mechanical strength was tested by tensile-shear stress test on the whole seam. Experiments demonstrated that varying incidence angle and offsetting the focal position is a reliable method to modify the melting ratio and maintaining the expected resistance length at the material interface, as well. It was found that increasing the percentage of ferritic steel into the joint has beneficial effects on the weld quality and on the shear resistance. The critical carbon content determining the mechanical properties in the fusion zone can be calculated by taking into account the melting ratio.

  14. Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

    Maachi, B. [Universite d' Oran, Laboratoire de Physique des Couches Minces et Materiaux pour l' Electronique (LPC2ME), BP 1524, El M' Naouer, 31000 Oran (Algeria); Pirri, C.; Mehdaoui, A. [Universite de Haute Alsace (UHA), Institut de Science des Materiaux de Mulhouse (IS2M), LRC 7228 - CNRS, 4 rue des freres Lumiere, 68093 Mulhouse (France); Hakiki, N.E., E-mail: hakiki.nourredine@yahoo.f [Universite d' Oran, Laboratoire de Physique des Couches Minces et Materiaux pour l' Electronique (LPC2ME), BP 1524, El M' Naouer, 31000 Oran (Algeria); Bubendorff, J.L., E-mail: jean-luc.bubendorff@uha.f [Universite de Haute Alsace (UHA), Institut de Science des Materiaux de Mulhouse (IS2M), LRC 7228 - CNRS, 4 rue des freres Lumiere, 68093 Mulhouse (France)

    2011-03-15

    Research highlights: {yields} The surface roughness of the bare substrate influence the oxide layer growth. {yields} The oxide layer roughness follows power laws and belongs to universality class. {yields} At low growth temperature, the p-n heterojunction disappears in some places. {yields} SKPFM images allow the direct visualization of local corrosion sites. {yields} Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. - Abstract: Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

  15. Transplante cardíaco humano: experiência inicial Human cardiac transplant: initial experience

    Noedir A. G Stolf

    1986-12-01

    Full Text Available No Instituto do Coração, de março de 1985 a fevereiro de 1986,11 pacientes foram submetidos a transplante cardíaco ortotópico. Eram todos do sexo masculino, com idade variando de 39 a 54 anos; 6 com cardiopatia isquémica, 4 com cardiomiopatia dilatada e um com cardiomiopatia chagásica. Foi realizado estudo hemodinâmico através de catéter de Swan-Ganz, no pré-operatório, no pós-operatório, após estabilização na unidade de recuperação, e trinta ou mais dias após o transplante. Os dados mostram melhora progressiva em relação ao índice cardíaco, pressão em artéria pulmonar, pressão de capilar pulmonar, resistência vascular pulmonar e resistência vascular sistêmica. Três dos 11 pacientes apresentaram disfunção renal transitória no pós-operatório imediato e que regrediram até o 15º dia, enquanto que 2 pacientes apresentaram aumento moderado da creatinina plasmática. Apenas 3 pacientes não apresentaram qualquer episódio de rejeição; nos demais, esses episódios foram um diagnóstico histológico sem repercussões clínicas. Complicações infecciosas ocorreram em 9 pacientes e foram de fácil controle clínico. No pós-operatório tardio, a hipertensão esteve presente em 8 pacientes, sendo mais acentuada em 2 deles. Não houve óbitos, nesta série de pacientes; todos estão assintomáticos e os 6 primeiros estão trabalhando.At the Instituto do Cora��ão, University of São Paulo Medical School, 11 patients were submitted to heart transplantation from march 1985 up to february 1986. All were male, with ages of 39-59 years, 6 with coronary heart disease, 4 with dilated cardiomyopathy and 1 with Chagas cardiomyopathy. The patients were studied hemodynamically with a Swan-Ganz catheter pre-operatively, at the arrival in the intensive care unit, in the first postoperative day and 30 or more days after the transplant. The data showed that there was a progressive increase of cardiac index and decreases of

  16. Changes in oxidative stress in transgenic RNAi ACO1 tomato fruit during ripening

    Eglous, Najat Mohamed; Ali, Zainon Mohd; Hassan, Maizom; Zainal, Zamri

    2013-11-01

    Tomato (Solanum Lycopersicum L.) is the second most cultivated vegetable in the world and widely used as a system for studying the role of ethylene during fruit ripening. Our objective was to study the oxidative stress and antioxidative metabolism during ripening of non transgenic tomato and transgenic line-21 tomato which reduced ethylene. The line-21 of transgenic tomato plants (RNAi ACO1) had lower ethylene production and longer shelf-life more than 32 days as compared to the wild-type fruits which have very short shelf-life. In this study, tomato fruit were divided into five different stages (MG: mature green 5%, B: breaker 25%, T: turning 50%, O: orange75%, RR: red ripe100%). The activity of lipoxygenase (LOX) and lipid peroxidation (MDA) were measured to assess changes in oxidative stress. The LOX activity and MDA content decreased significantly obtaining 2.6-fold and 1.2-fold, respectively, as compared to the wild type fruit. However, superoxide dismutase (SOD) and catalase (CAT) activities were increased to 1.9 and 1.2 folds from the mature green to the fully ripe stage in transgenic tomatoes. Furthermore, the wild type tomato increases 1.3 in SOD and 1.6 in CAT activities. The overall results indicate that the wild type tomato fruit showed a faster rate of ripening, parallel to decline in the rate of enzymatic antioxidative systems as compared to the transgenic line-21 tomato fruit. In addition, the results show that the antioxidant capacity is improved during the ripening process and is accompanied by an increase in the oxidative stress.

  17. Ultrasonic evaluation of friction stud welded AA 6063/AISI 1030 steel joints

    Highlights: • Friction stud welding of AA 6063 and AISI 1030 was done successfully. • Ultrasonic evaluation of interfacial properties. • EDX analysis confirms intermetallic compound (FeAl) in the interfacial region. - Abstract: Friction stud welding is a promising technique in many applications related to oil and gas industries. It is used to attach grating to offshore oil platforms in areas where arc welding is not permitted because of the risk of causing a fire or explosion. Attachment of anodes inside seawater discharge pipelines in a gas processing plant is performed by this process. This solid state joining process permits metal combinations such as welding of aluminum studs to steel which would be problematic with arc welding because of the formation of thick and brittle inter-metallic compounds. In the present work, AA 6063 is joined to AISI 1030 steel using friction stud welding machine. Properties that are of interest to manufacturing applications such as Young’s modulus, longitudinal velocity, bulk modulus and shear modulus are evaluated by means of an ultrasonic flaw detector. At the interface of the joint, there is an increase of 4.4%, 1.8%, 1.15% and 4.42% is observed for the properties Young’s modulus, longitudinal velocity, bulk modulus and shear modulus respectively. This is due to the formation of intermetallic compound and increase in hardness at the interfacial region. Energy Dispersive X-ray analysis confirms the presence of FeAl as the intermetallic compound. Scanning Electron Microscope evaluation shows the presence of an unbound zone at the center of the inner region which is due to the minimum rotational speed and low axial load experienced at that point. In the unbound zone, there is an incomplete bond between dissimilar metals and it is detrimental to joint strength. Optimum value of friction time and usage of pure aluminum interlayer during the friction stud welding process hinders the formation of unbound zone and enhances the

  18. SmartPATH: An Efficient Hybrid ACO-GA Algorithm for Solving the Global Path Planning Problem of Mobile Robots

    Imen Châari

    2014-07-01

    Full Text Available Path planning is a fundamental optimization problem that is crucial for the navigation of a mobile robot. Among the vast array of optimization approaches, we focus in this paper on Ant Colony Optimization (ACO and Genetic Algorithms (GA for solving the global path planning problem in a static environment, considering their effectiveness in solving such a problem. Our objective is to design an efficient hybrid algorithm that takes profit of the advantages of both ACO and GA approaches for the sake of maximizing the chance to find the optimal path even under real-time constraints. In this paper, we present smartPATH, a new hybrid ACO-GA algorithm that relies on the combination of an improved ACO algorithm (IACO for efficient and fast path selection, and a modified crossover operator to reduce the risk of falling into a local minimum. We demonstrate through extensive simulations that smartPATH outperforms classical ACO (CACO, GA algorithms. It also outperforms the Dijkstra exact method in solving the path planning problem for large graph environments. It improves the solution quality up to 57% in comparison with CACO and reduces the execution time up to 83% as compared to Dijkstra for large and dense graphs. In addition, the experimental results on a real robot shows that smartPATH finds the optimal path with a probability up to 80% with a small gap not exceeding 1m in 98%.

  19. Sedação com sufentanil e clonidina em pacientes submetidos a cateterismo cardíaco

    Anita Perpetua Carvalho Rocha

    2011-03-01

    Full Text Available FUNDAMENTO: A sedação para a realização de cateterismo cardíaco tem sido alvo de preocupação. Benzodiazepínicos, agonistas alfa-2 adrenérgicos e opioides são utilizados para esse fim, entretanto, cada um destes medicamentos possui vantagens e desvantagens. OBJETIVO: Avaliar a eficácia do sufentanil e da clonidina como sedativos em pacientes submetidos a cateterismo cardíaco, observando o impacto dos mesmos sobre os parâmetros hemodinâmicos e respiratórios, a presença de efeitos colaterais, além da satisfação do paciente e do hemodinamicista com o exame. MÉTODOS: Trata-se de um ensaio clínico prospectivo, duplo-cego, randomizado e controlado, que envolveu 60 pacientes que receberam 0,1 µg/kg de sufentanil ou 0,5 µg/kg de clonidina antes da realização do cateterismo cardíaco. O escore de sedação segundo a escala de Ramsay, a necessidade de utilização de midazolam, os efeitos colaterais, os parâmetros hemodinâmicos e respiratórios foram registrados, sendo os dados analisados em 06 diferentes momentos. RESULTADOS: O comportamento da pressão arterial, da frequência cardíaca e da frequência respiratória foi semelhante nos dois grupos, entretanto, no momento 2, os pacientes do grupo sufentanil (Grupo S apresentaram menor escore de sedação segundo a escala de Ramsay, e a saturação periférica da oxihemoglobina foi menor que o grupo clonidina (Grupo C no momento 6. Os pacientes do Grupo S apresentaram maior incidência de náusea e vômito pós-operatório que os pacientes do Grupo C. A satisfação dos pacientes foi maior no grupo clonidina. Os hemodinamicistas mostraram-se satisfeitos nos dois grupos. CONCLUSÃO: O sufentanil e a clonidina foram efetivos como sedativos em pacientes submetidos a cateterismo cardíaco.

  20. Influencia de los regímenes de lubricación en la vida de la herramienta y el acabado superficial del fresado de aceros endurecidos AISI D2 y AISI D6

    Maritza Mariño-Cala; Yanier Sánchez-Hechavarría

    2015-01-01

    Se realizó un análisis de la calidad superficial y la vida de la herramienta durante el mecanizado con altas velocidades de los aceros endurecidos AISI D2 y AISI D6, en dos regímenes de lubricación. Los ensayos fueron realizados en un centro de mecanizado MORI SEIKI SV 40 y se emplearon herramientas intercambiables de metal duro recubiertas. La evaluación de la calidad superficial se realizó mediante el monitoreo off-line de la rugosidad superficial media Ra en el sentido del avance y perpend...

  1. Acute Care of At-Risk Newborns (ACoRN): quantitative and qualitative educational evaluation of the program in a region of China

    Singhal Nalini; Lockyer Jocelyn; Fidler Herta; Aziz Khalid; McMillan Douglas; Qiu Xiangming; Ma Xiaolu; Du Lizhong; Lee Shoo K

    2012-01-01

    Abstract Background The Acute Care of at-Risk Newborns (ACoRN) program was developed in Canada for trained health care providers for the identification and management of newborns who are at-risk and/or become unwell in the first few hours or days after birth. The ACoRN process follows an 8-step framework that enables the evaluation and management of babies irrespective of the experience or expertise of the caregiving individual or team. This study assesses the applicability of the program to ...

  2. TIG AISI-316 welds using an inert gas welding chamber and different filler metals: Changes in mechanical properties and microstructure

    Pascual, M.; Salas, F.; Carcel, F.J.; Perales, M.; Sanchez, A.

    2010-07-01

    This report analyses the influence of the use of an inert gas welding chamber with a totally inert atmosphere on the microstructure and mechanical properties of austenitic AISI 316L stainless steel TIG welds, using AISI ER316L, AISI 308L and Inconel 625 as filler metals. When compared with the typical TIG process, the use of the inert gas chamber induced changes in the microstructure, mainly an increase in the presence of vermicular ferrite and ferrite stringers, what resulted in higher yield strengths and lower values of hardness. Its effect on other characteristics of the joins, such as tensile strength, depended on the filler metal. The best combination of mechanical characteristics was obtained when welding in the inert gas chamber using Inconel 625 as filler metal. (Author). 12 refs.

  3. Numerical-experimental analysis of a rin AISI{sub 7}Mg Alloy; Analisis numerico experimental de un rin de aleacion AISi{sub 7}Mg

    Sauceda Mesa, Israel; Mata Lucero, Omar; Tirado Delgado, Luis; Ocampo Diaz, Juan de Dios [Universidad Autonoma de Baja California, Mexicali, Baja California (Mexico)

    2005-10-15

    The present work shows the results obtained from an investigation mode on the behaviour of a rin of alloy AISi{sub 7}Mg, which is used in compact Volkswagen's cars. Due to two kind of analysis were realized, firstly an experimental and numerical analysis was done, using a special machine for test the flexionante torque and material fatigue, besides was used an equipment of laser to scanner zone with strength concentrations and the maximum displacement amplitudes. The second analysis was done with the finite element technique, using the software ANSYS and CATIA. The difference between life fatigue cycles obtained from the two analyses was 0.6%. While the time optimize by MEF, was of 85% less than experimental analysis. [Spanish] En el presente trabajo se hicieron investigaciones del comportamiento de un rin de aleacion AISi{sub 7}Mg, el cual es usado en automoviles compactos de volkswagen (VW). Para esto, se realizo analisis experimental y numerico. En el primero se utilizo una maquina para prueba de fatiga de momento flexionante, un equipo de medicion de laser escaner donde se detectaron las zonas de concentraciones de esfuerzos y la maxima amplitud de desplazamiento en el rin. Mientras que en el segundo se obtuvieron los esfuerzos que ocasionaban la fatiga por el elemento finito, utilizando los paquetes de computo Ansys y Catia. La diferencia de los ciclos de vida de fatiga obtenidos entre ambos analisis fue del 0.6%. Mientras que el tiempo que se optimizo por el MEF, fue de un 85% menos que el analisis experimental.

  4. Effect of aging at 700 deg. C on precipitation and toughness of AISI 321 and AISI 347 austenitic stainless steel welds

    A detailed knowledge of changes in microstructures and mechanical behaviour that occur in austenitic stainless steels with or without Nb/Ti-stabilized weld during heat treatment is of great interest, since the ductility and toughness of the material may change drastically after long aging times. Two kinds of materials, i.e. AISI 321 base and without Ti-stabilized weld steel and AISI 347 base with Nb-stabilized weld steel, were compared during aging at 700 deg. C up to 6000 h. Both materials present increased amount of precipitate and decreased impact energy as the aging time increases. The decreased extent of impact energy with aging is almost the same for both base materials. However, it presents differences for 347 and 321 weld samples. The latter shows a more drastic decrease of impact energy than the former due to the different amount of precipitates. 321 weld sample precipitates more numerously than 347 weld sample due to the absence of stabilized Ti/Nb on the former. Large amount of carbides is formed on 321 weld sample immediately after welding. The carbides are transformed to sigma phase, which is mainly responsible for the much more sigma phase precipitation compared with other samples, after high-temperature aging. The fractographs showed, in general, brittle fracture mode in 321 weld impact-fractured specimens after aging at 700 deg. C for 6000 h. However, other samples show ductile fracture mode in general. Several approaches should be employed to control sigma phase precipitation in weld material. These approaches include: decreasing content of ferrite and M23C6 carbide in weld and selecting Nb added weld wire during welding

  5. Transient absorption spectroscopy in biology using the Super-ACO storage ring FEL and the synchrotron radiation combination

    Renault, E; De Ninno, G; Garzella, D; Hirsch, M; Nahon, L; Nutarelli, D

    2001-01-01

    The Super-ACO storage ring FEL, covering the UV range down to 300 nm with a high average power (300 mW at 350 nm) together with a high stability and long lifetime, is a unique tool for the performance of users applications. We present here the first pump-probe two color experiments on biological species using a storage ring FEL coupled to the synchrotron radiation. The intense UV pulse of the Super-ACO FEL is used to prepare a high initial concentration of chromophores in their first singlet electronic excited state. The nearby bending magnet synchrotron radiation provides, on the other hand a pulsed, white light continuum (UV-IR), naturally synchronized with the FEL pulses and used to probe the photochemical subsequent events and the associated transient species. We have demonstrated the feasibility with a dye molecule (POPOP) observing a two-color effect, signature of excited state absorption and a temporal signature with Acridine. Applications on various chromophores of biological interest are carried out,...

  6. Manejo de las dislipidemias en pacientes cardíacos trasplantados. Hallazgos sobre nuevos factores de riesgo

    Walter Masson

    2008-01-01

    Full Text Available En pacientes cardíacos trasplantados, el desarrollo de enfermedad vascular coronaria es una complicación frecuente y la dislipidemia es uno de los predictores más importantes. Los inmunosupresores predisponen a las dislipidemias y dificultan la utilización de hipolipemiantes. En este grupo particular de pacientes se recomienda alcanzar las metas terapéuticas de prevención secundaria. Las estatinas son los hipolipemiantes de elección. No existen recomendaciones claras sobre nuevos factores de riesgo, como la homocisteína y la lipoproteína (a [Lp(a].Con el objetivo de conocer el perfil lipídico, la prevalencia de homocisteinemia y de Lp(a elevadas, el cumplimiento de las metas terapéuticas y la tolerancia a la medicación, se incluyeron en el estudio 23 pacientes cardíacos trasplantados. Los resultados mostraron que el cumplimiento de las metas lipídicas fue aceptable y que el 65% recibía tratamiento hipolipemiante. El uso de estatinas fue seguro. Se encontró una prevalencia alta de homocisteína y Lp(a elevadas. Su implicación en la modificación del tratamiento se desconoce.

  7. A Web-Based Egg-Quality Expert Advisory System using Rule Based and Ant Colony (ACO Optimization Algorithms

    J. Anitha

    2010-10-01

    Full Text Available This paper deals with the development of Web based online expert systems using Evolutionary Algorithms. An expert system is a computer application that performs a task that would otherwise be performed by a human expert. Here one of the evolutionary algorithms (ACO Algorithm is considered to find a good match of symptoms in the database. In the present paper, Ant Colony Optimization1 (ACO algorithm has been taken as the base and the concept of optimization is included, so that the new algorithm mainly focuses on the determination of the quality of eggs in the poultry farms. At first, the symptoms provided by the user are processed by a rule based expert system for identifying the quality of the eggs. If the rules required for processing the data by the above are not present in the database, then the system automatically calls the machine learning algorithm technique. As a whole, the system results good optimized solution for recognizing the quality and viruses if any affected to eggs in poultry farms. And corresponding treatments to the viruses may also be suggested to the users. This expert system is designed with JSP as front end and MySQL as backend.

  8. Interacciones entre dispositivos cardíacos implantables y modalidades fisioterapéuticas: ¿Mito o realidad?

    Genevieve C. Digby

    2011-04-01

    Full Text Available La fisioterapia se ha transformado en una especialidad que claramente incide en la calidad de vida de nuestros pacientes. En poblaciones añosas, el uso de fisioterapia incluye múltiples modalidades para un alto número de distintas enfermedades. Varios informes sobre posibles interacciones negativas entre las distintas modalidades de fisioterapia y los dispositivos cardíacos implantables (marcapasos y cardiodesfibriladores han sido publicados en los últimos aňos. A pesar de ello, existe muy poca evidencia y guías precisas para identificar cuáles son las modalidades de fisioterapia seguras a utilizar en esta población de pacientes. En la siguiente revisión, nos propusimos resumir las interacciones documentadas entre fisioterapia y dispositivos cardíacos implantables (DCI, discutir el estándar actual de estas prácticas e identificar las principales consideraciones que existen desde la perspectiva de un servicio de electrofisiología cardíaca, para el tratamiento adecuado en estos pacientes. Finalmente, abogamos por fortalecer la colaboración entre fisioterapeutas y electrofisiólogos, con el fin de asegurar una óptima y segura atención de este grupo de pacientes.

  9. TIG AISI-316 welds using an inert gas welding chamber and different filler metals: Changes in mechanical properties and microstructure

    Sánchez, A.

    2010-12-01

    Full Text Available This report analyses the influence of the use of an inert gas welding chamber with a totally inert atmosphere on the microstructure and mechanical properties of austenitic AISI 316L stainless steel TIG welds, using AISI ER316L, AISI 308L and Inconel 625 as filler metals. When compared with the typical TIG process, the use of the inert gas chamber induced changes in the microstructure, mainly an increase in the presence of vermicular ferrite and ferrite stringers, what resulted in higher yield strengths and lower values of hardness. Its effect on other characteristics of the joins, such as tensile strength, depended on the filler metal. The best combination of mechanical characteristics was obtained when welding in the inert gas chamber using Inconel 625 as filler metal.

    En este estudio se analiza la influencia que el uso de una cámara de soldadura de gas inerte tiene sobre la microestructura y las propiedades mecánicas de las soldaduras TIG en el acero inoxidable austenítico AISI-316L cuando se emplean AISI ER316L, AISI 308L e Inconel 625 como materiales de aporte. Cuando se compara con el típico proceso de TIG, el uso de una cámara de gas inerte induce cambios en la microestructura, incrementando la presencia de ferrita vermicular y de laminillas de ferrita, resultando en un aumento del límite elástico y una pérdida de dureza. Su influencia sobre otras características de las soldaduras como la carga de rotura depende de la composición del material de aporte. La mejor combinación de propiedades mecánicas se obtuvo usando el Inconel 625 como material de aporte y soldando en la cámara de gas inerte.

  10. Imunocitomonitorização em pacientes transplantados cardíacos Immunocytomonitorization in patients submitted to cardiac transplantation

    Ricardo Manrique

    1990-04-01

    Full Text Available A técnica de Imunocitomonitorização (CIM - Cytologrcal and Immunologic Monitoring, fundamenta-se na avaliação de mudanças nas subpopulações de linfócitos e seus precursores celulares, durante o processo rejeição aguda. O método avalia a ativação precoce pela contagem do número de: linfócitos ativados, linfoblastos e prolinfócitos (aqui chamados em conjunto de linfócitos ativos, quando esses se apresentam acima do limite superior normal. Utilizamos essa técnica para seguimento e controle da atividade da imunologia celular em 9 pacientes transplantados cardíacos. Também foram submetidos ao CIM para verificar a faixa de normalidade de ativação linfocítica 20 voluntários normais e cinco pacientes candidatos ao transplante cardíaco. Ambos os grupos não tinham antecedentes de quadro de infecção ou alteração imunológica. Para obtenção do controle positivo, testamos 10 pacientes com infecção bacteriana ou virai, previamente diagnosticados por exames bacterianos e/ou sorológicos. Foram observados valores de 1,8% de linfócitos ativos nos indivíduos normais e 3,2% nos candidatos ao transplante cardíaco. Dos 63 testes realizados nos transplantados cardíacos, quatro deles se mostraram positivos, onde três desses tratavam-se de casos de infecção e um confirmado como processo de rejeição aguda em evolução. O tempo médio necessário para a realização da CIM foi de aproximadamente duas horas. A técnica utiliza mostrou-se valiosa no reconhecimento imunológico dos pacientes transplantados cardíacos, pela sua sensibilidade diagnostica, baixo custo e rapidez.The immunocytomonitorization technique (CIM - Cytological and Immunologic Monitoring is based on assessment of changes in the subpopulations of lyphocyte and their precursor cells, while under the acute rejection. The method assesses the precocious activation by counting the number of the lymphocytes normal and actives, lymphoblasts and prolymphocytes (here

  11. Characterization Of Oxide Layers Produced On The AISI 321 Stainless Steel After Annealing

    Bochnowski W.

    2015-09-01

    Full Text Available In this study, the structure, chemical composition and topography of oxide layers produced on the surface of the AISI 321 austenitic steel in the annealing process were analyzed. Heat treatment was done at 980°C temperature for 1 hour time in different conditions. The annealing was done in a ceramic furnace in oxidation atmosphere and in vacuum furnaces with cylindrical molybdenum and graphite chambers. The analysis was carried out using the following methods: a scanning electron microscope (SEM equipped with an energy-dispersive X-ray spectrometer (EDX, a transmission electron microscope (TEM equipped with an energy-dispersive X-ray spectrometer (EDX, an X-ray diffractometer (XRD, a secondary ion mass spectrometer with time-of-flight mass analyzer (TOF SIMS and an atomic force microscope (AFM. The oxide layer formed during annealing of the AISI 321 steel at 980°C consisted of sub-layers, diversified in the chemical composition. The thickness of the oxidized layer is depended on the annealing conditions. In a ceramic furnace in oxidation atmosphere, the thickness of the oxide layer was of 300-500 nm, in a vacuum furnace with molybdenum and graphite heating chambers, it ranged from 40 to 300 nm and from a few to 50 nm, respectively. TOF SIMS method allows to get average (for the surface of 100 μm × 100 μm depth profiles of concentration of particular elements and elements combined with oxygen. In oxide layers formed in vacuum furnaces there are no iron oxides. Titanium, apart from being bounded with carbon in carbides, is a component of the oxide layer formed on the surface of the AISI 321 steel.

  12. Creep behaviour and microstructural evolution in AISI 316LN + Nb steels at 650 deg. C

    Research highlights: → We studied the effect of Nb additions to AISI 316LN steels on creep and microstructure at 650 deg. C. → Nb additions resulted in a reduction of secondary creep rate and shortening of the tertiary stage. → Two nitrogen rich minor phases were present in the niobium-bearing casts: Z-phase and M6X. → The dimensional stability of Z-phase during creep at 650 deg. C was much better than that of M6X. → Nb accelerated σ-phase and η-Laves formation and this surpassed the positive effect of Z-phase. - Abstract: The paper deals with the effect of niobium in the wrought AISI 316LN steels on the long-term creep characteristics at 650 deg. C. Casts B and C contained 0.1 and 0.3 wt.%Nb, respectively. As a reference material the niobium free Cast A was used. Small additions of niobium to the AISI 316LN steel resulted in a significant reduction of the minimum creep rate and shortening of the tertiary creep stage. At time to rupture exceeding 104 h the creep rupture strength of the niobium-bearing Casts B and C was slightly inferior to the Cast A. Two nitrides formed in the Casts B and C: Z-phase and M6X. The minimum creep rate in niobium-bearing casts was favourably affected by precipitation of the Z-phase. The dimensional stability of Z-phase particles was very high, but niobium additions also accelerated the formation and coarsening of η-Laves and σ-phase. Coarse σ-phase particles at grain boundaries contributed significantly to the shortening of the tertiary creep stage.

  13. Elastic-plastic fracture toughness characteristics of irradiated AISI 316 H stainless steel

    The objective of this research is the FM assessment of neutron damage to AISI 316 H steel commonly used in LMFBR's permanent primary circuit components. The material FM characteristics studied are the crack-initiation toughness and the crack-resistance curves. The AISI 316 H stainless steel has been considered in the base condition, the welded deposit and the HAZ material. The specimens tested are 3PB bars. The results presented cover the 0, 0.1 dpa and 0.3 dpa fluences at 350 deg. C and 550 deg. C. The crack-growth-resistance curves were obtained following the dimensional analysis approach together with the deformation theory of plasticity concepts. This method, using key curves has effectively shown trends in the above-mentioned fracture mechanics characteristics of the irradiated AISI 316 H steel. The results obtained so far indicate generally low degradation at both temperatures between the non-irradiated and the irradiated base material, one note-worthy exception being the significant lowering at 550 deg. C and 0.1 dpa of sup(dJ)/da by about 35% and of sup(J)Ic by about 50% with respect to those parameters values in the other conditions of fluences and temperatures. As far as the weld material is concerned, it exhibits significantly lower initiation toughness and tearing moduli in the pre and post irradiation conditions with respect to the base material but those FM parameters values are practically unaltered at both temperatures and all fluence levels. The HAZ material was studied too and it was found that all J values corresponding to various crack advances fell within the base material results at 350 deg. C as upper bound and the welded material at 550 deg. C as lower bound at corresponding fluence levels. (author)

  14. Compatibility studies of AISI type 316 stainless steel with lead-lithium eutectic alloy

    Spent fuel subassemblies from the Fast Breeder Test Reactor (FBTR) are to be stored in leak tight cotainers until they are required to be sent for reprocessing. Use of advanced fuels like uranium carbides and plutonium carbides, which are known to be highly chemically active with oxygen and moisture demands adequate leak tightness during long term storage to avoid undesirable chemical reactions. Use of low melting alloys which acts as liquid/solid sealants in the storage containers in which fuel subassemblies are to be kept is being considered for this purpose. Lead-lithium (0.7 wt % lithium) eutectic alloy was chosen as one of the candidate alloys for the purpose on the basis of theoretical assessments. The candidate sealing alloy should have good compatibility with the structural materials of fuel subassemblies as well as the fuel and fission products. AISI type 316 stainless steel in solution annealed, ten and twenty percent cold worked condition is the clad and wrapper material used for the fabrication of fuel pins and subassemblies. Compatibility studies between eutectic Pb-Li alloy and AISI type 316 stainless steel material in the above conditions were undertaken at different temperatures and time durations. The studies indicate that the tensile properties of AISI type 316 stainless steel are not subject to any serious jeopardisation through contact with this molten Pb-Li eutectic alloy for periods extending even upto 7000 hours at 873 K. Thus use of Pb-Li eutectic alloy would be suitable for the storage of irradiated fuel. (author). 16 refs., 38 figs., 3 tabs

  15. Microstructure and corrosion behaviour of pulsed plasma-nitrided AISI H13 tool steel

    Basso, Rodrigo L.O. [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Pastore, Heloise O. [Instituto de Quimica, Universidade Estadual de Campinas, 13084-862 Campinas, SP (Brazil); Schmidt, Vanessa [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Baumvol, Israel J.R. [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Instituto de Fisica, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Abarca, Silvia A.C.; Souza, Fernando S. de; Spinelli, Almir [Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900 Florianopolis, SC (Brazil); Figueroa, Carlos A. [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Giacomelli, Cristiano, E-mail: cgiacomelli@pq.cnpq.b [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil)

    2010-09-15

    The effect of pulsed plasma nitriding temperature and time on the pitting corrosion behaviour of AISI H13 tool steel in 0.9% NaCl solutions was investigated by cyclic polarization. The pitting potential (E{sub pit}) was found to be dependent on the composition, microstructure and morphology of the surface layers, whose properties were determined by X-ray diffraction and scanning electron microscopy techniques. The best corrosion protection was observed for samples nitrided at 480 {sup o}C and 520 {sup o}C. Under such experimental conditions the E{sub pit}-values shifted up to 1.25 V in the positive direction.

  16. Microstructure and corrosion behaviour of pulsed plasma-nitrided AISI H13 tool steel

    The effect of pulsed plasma nitriding temperature and time on the pitting corrosion behaviour of AISI H13 tool steel in 0.9% NaCl solutions was investigated by cyclic polarization. The pitting potential (Epit) was found to be dependent on the composition, microstructure and morphology of the surface layers, whose properties were determined by X-ray diffraction and scanning electron microscopy techniques. The best corrosion protection was observed for samples nitrided at 480 oC and 520 oC. Under such experimental conditions the Epit-values shifted up to 1.25 V in the positive direction.

  17. Anodic behaviour of the stainless steel AISI 430 in aqueous solutions of chloride and sulphate ions

    The kinetics of the dissolution of stainless steel AISI 430 in the presence of chloride and sulphate ions has been studied in terms of the ion concentration, the pH variation, and the velocity of the working electrode. The experimental method utilized was the potentiostatic anodic polarization, and the reactants used were NaCl and Na2 SO4 at room temperature. Atomic Absorption spectrophotometry and Auger Electrons spectroscopy (AES) analyses were made in order to support the interpretation of results obtained by means of the potentiostatic polarization method. (author)

  18. XPS Analysis of AISI 304L Stainless Steel Surface after Electropolishing

    Rokosz K.

    2015-03-01

    Full Text Available In the paper, the passive surface layers of AISI 304L after standard (EP50 and very-high-current density electropolishing (EP1000 in a mixture of orthophosphoric and sulfuric acids in a 1:4 ratio, are presented. The main finding of the presented studies is enrichment of the steel surface film in chromium: total chromium to total iron ratio was equal to 6.6 after EP50 and to 2.8 after EP1000; on the other hand, chromium compounds to iron compounds ratio was equal to 10.1 after EP50, and 3.9 after EP1000.

  19. Effects of the stress reduction tests in the creep of AISI-316 austenitic stainless steel

    Stress Reduction Tests were performed at the temperature of 1006 K (7330C) in AISI-316 stainless steel and the evolution of the microstructure was followed. After the stress reduction a rapid decrease in the dislocation density, a continuous increase in the average carbide size and a decrease in the mean particle spacing are observed. No change in the subgrain size occurs after the stress reduction. An increase in the creep resistance is observed after the stress reductions and is interpreted based on the microstructural modifications. (Author)

  20. Wear Properties of TiN Coating Formed on AISI D2 Surface

    ÇEĞİL, Özkan; KILINÇ, Bülent; Şen, Şaduman

    2014-01-01

    In this work, the wear test of uncoated and titanium nitride coated AISI D2 cold work tool steel against silicon nitride ball was realized at 0.3 m/s sliding speed and under the loads of 2.5N, 5N and 10N. Steel samples were nitrided at 575°C for 8 h in the first step of the coating process, and then titanium nitride coating was performed by pack diffusion coating in a powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000°C for 2h. Nitro-titanized samples were char...

  1. Effect of Welding Current on Energy Absorption of AISI 304 Resistance Spot Welds

    M. Pouranvari

    2012-08-01

    Full Text Available In this study, the effect of welding current on the energy absorption capability of austenitic stainless steel AISI304 resistance spot welds during the quasi-static tensile-shear test is investigated. Results showed that there is a direct relationship between the fusion zone size and failure energy in expulsion free samples. However, when expulsion occurred, the energy absorption capability reduced significantly. Failure energy for samples experiencing expulsion is lower compared to expulsion free samples with identical or even smaller weld nugget size.

  2. Estimation of embrittlement during aging of AISI 316 stainless steel TIG welds

    J Nayak; K R Udupa; K R Hebbar; H V S Nayak

    2004-12-01

    Weldments of AISI grade 316 stainless steel, having a ferrite content of 4–6% and a variety of nitrogen concentrations were prepared using a modified element implant technique. Charpy impact specimens prepared from these weldments were subjected to a variety of aging treatments. Impact toughness decreases with aging time at all aging temperatures. Nitrogen is found to be beneficial to toughness. An empirical relation connecting the aging temperature, aging time and nitrogen content with toughness has been developed which can be used to estimate the time for embrittlement.

  3. Estudio de las fuerzas de corte en el fresado de AISI 316

    González López, Diego

    2015-01-01

    Este trabajo trata sobre el comportamiento que tiene un acero AISI 316-L ASS al ser fresado mediante dos tipos de procedimiento: fresado en concordancia y fresado en oposición. Para realizar este estudio se ha instalado un dinamómetro Kistler en la herramienta, con el objetivo de medir las fuerzas de corte que intervienen en el mecanizado.Estas fuerzas se procesan con el sistema de adquisición de datos " WaveBook-512" y se analizan posteriormente con el software " Dasylab 8.0", un sistema d...

  4. Microstructural Evolution and Wear Resistance of Friction Stir-Processed AISI 52100 Steel

    Seraj, R. A.; Abdollah-zadeh, A.; Hajian, M.; Kargar, F.; Soltanalizadeh, R.

    2016-04-01

    Friction stir processing (FSP) was successfully applied on AISI 52100 steel. The influence of process parameters on the microstructure and mechanical properties of the material was evaluated. It was observed that the initial ferritic-pearlitic microstructure of the base metal is transformed to the martensitic microstructure with retained austenite in the stir zone. The results also showed that microhardness and wear resistance of the FSP samples are, respectively, at least 2 and 15 times higher than those of the base metal. The improvement of the mechanical properties of FSP samples was attributed to their microstructural characteristics. The mechanisms controlling the wear behavior of the base metal and FSP samples were also discussed.

  5. CRYOGENIC AND STRESS RELIEF THERMAL TREATMENTS IN AN AISI D2 STEEL

    Paula Fernanda da Silva Farina; Alexandre Bellegard Farina; Celso Antonio Barbosa; Helio Goldenstein

    2012-01-01

    The effects of cryogenic treatments on an AISI D2 cold work tool steel using X-ray diffraction from syncronton radiation are studied. The aim of this work is to verify the effects of: i) time at cryogenic temperatures (3, 10 and 30 hours); ii) cryogenic temperatures (–80°C and –196°C); iii) stress relief heat treatment (130°C) before cryogenic treatments; iv) effect of double tempering at 520°C for 2 hours each time, after cryogenic treatment at –196°C for 30 hours, with and witho...

  6. Effects of ageing on the ductile fracture of AISI type 316 stainless steel

    The micromechanisms of ductile fracture have been studied in a commercial AISI type 316 austenitic stainless steel. Tensile, Charpy impact and ductile fracture toughness testing has been performed on unaged material and samples aged at 7000C for times up to 4380 h. Examination of the specimens after testing has demonstrated that the microstructural changes occurring at grain boundaries are reponsible for the observed losses of ductility and crack growth resistance. The relative magnitude of the observed changes in mechanical properties has been accounted for using a simple model to describe the ductile fracture process. (author)

  7. 1020 AISI-SAE steel Austenitic Nitrocarburising with alcohol and triethanolamine

    Álvaro Castro P

    2010-04-01

    Full Text Available The present work shows AISI-SAE 1020 steel's nitrocarbide layer's microstructure and micro-hardness profile following 4 hours at 700ºC using methanol, isopropanol and triethanolamine. The steel was then hardened by quenching it in water and then tempered at 350ºC for 1 hour. Its surface had been partially oxidised by heating it at 400ºC for 1 hour. An example is given of other researchers analysing microstructure and propierties in steel having 0,5% C, using endothermic gas and different amounts of ammoniac.

  8. Thermo-mechanical and isothermal fatigue behavior of austenitic stainless steel AISI 316L

    Škorík, Viktor; Šulák, Ivo; Obrtlík, Karel; Polák, Jaroslav

    Ostrava: TANGER Ltd, 2015. ISBN 978-80-87294-58-1. [METAL 2015 - International Conference on Metallurgy and Materials /24./. Brno (CZ), 03.06.2015-05.06.2015] R&D Projects: GA MŠk(CZ) EE2.3.30.0063; GA ČR(CZ) GA15-20991S; GA ČR(CZ) GA13-23652S Institutional support: RVO:68081723 Keywords : Thermo-mechanical fatigue (TMF) * In-phase cycling (IP) * Isothermal fatigue (IF) * AISI 316L * Fatigue life Subject RIV: JL - Materials Fatigue, Friction Mechanics

  9. Study of Carbide Evolution During Thermo-Mechanical Processing of AISI D2 Tool Steel

    Bombac, D.; Fazarinc, M.; Podder, A. Saha; Kugler, G.

    2013-03-01

    The microstructure of a cold-worked tool steel (AISI D2) with various thermo-mechanical treatments was examined in the current study to identify the effects of these treatments on phases. X-ray diffraction was used to identify phases. Microstructural changes such as spheroidization and coarsening of carbides were studied. Thermodynamic calculations were used to verify the results of the differential thermal analysis. It was found that soaking temperature and time have a large influence on dissolution, precipitation, spheroidization, and coalescence of carbides present in the steel. This consequently influences the hot workability and final properties.

  10. Investigation into some tribological properties of plasma nitrided hot-worked tool steel AISI H11

    Yilbas, B.S.; Sahin, A.Z.; Said, S.A.M.; Nickel, J.; Coban, A. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Dept. of Mechanical Engineering

    1996-04-01

    Interest in the tribological properties of plasma nitriding has increased substantially over the past years because plasma nitriding provides a high nitride depth and improved hard facing. The present study examines the tribological properties of AISI H11 plasma nitrided, hot-worked steel. Different nitriding temperatures and durations were considered. Characterization of the composite structures was investigated with wear tests, x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and microhardness tests. The depth profile of the nitrided zone was measured using the nuclear reaction analysis (NRA) technique. Plasma nitriding affected the microhardness, wear properties, and morphology considerably. Increase in process temperature increased the nitride zone depth.

  11. Laser welding of butt joints of austenitic stainless steel AISI 321

    A. Klimpel; A. Lisiecki

    2007-01-01

    Purpose: of this paper: A study of an automated laser autogenous welding process of butt joints of austenitic stainless steel AISI 321 sheets 0.5 [mm] and 1.0 [mm] thick using a high power diode laser HPDL has been carried out.Design/methodology/approach: Influence of basic parameters of laser welding on shape and quality of the butt joints and the range of optimal parameters of welding were determined.Findings: It was showed that there is a wide range of laser autogenous welding parameters w...

  12. Microstructural Evolution and Wear Resistance of Friction Stir-Processed AISI 52100 Steel

    Seraj, R. A.; Abdollah-zadeh, A.; Hajian, M.; Kargar, F.; Soltanalizadeh, R.

    2016-07-01

    Friction stir processing (FSP) was successfully applied on AISI 52100 steel. The influence of process parameters on the microstructure and mechanical properties of the material was evaluated. It was observed that the initial ferritic-pearlitic microstructure of the base metal is transformed to the martensitic microstructure with retained austenite in the stir zone. The results also showed that microhardness and wear resistance of the FSP samples are, respectively, at least 2 and 15 times higher than those of the base metal. The improvement of the mechanical properties of FSP samples was attributed to their microstructural characteristics. The mechanisms controlling the wear behavior of the base metal and FSP samples were also discussed.

  13. The structural characterization of some biomaterials, type AISI 310, used in medicine

    Minciuna, M. G.; Vizureanu, P.; Hanganu, C.; Achitei, D. C.; Popescu, D. C.; Focsaneanu, S. C.

    2016-06-01

    Orthopedics biomaterials are intended for implantation in the human body and substituted or help to repair of bones, cartilage or organ transplant, and tendons. At the end of the 20th century, the availability of materials for the manufacture implants used in medicine has been the same as for other industrial applications. The most used metals for manufacturing the orthopedics implants are: stainless steels, cobalt-chrome-molybdenum alloys, titanium and his alloys. The structural researches which are made in this paper, offer a complete analysis of AISI310 stainless steels, using: optical spectrometry, X-ray diffraction and scanning electronic microscopy.

  14. Comparative study of the microbiological corrosion among an AISI 304L and an API X65

    Metallic samples of AISI 304L sensitized and API X65, were subjected to the action of an inoculated media with reductive sulphate microorganisms (SBR), carrying out electrochemical evaluations by means of the techniques of Polarization Resistance (RP), Tafel extrapolation (ET) and Electrochemical Noise (RE). The generated information was complemented with the analysis and diagnostic of the present damage in the surfaces exposed in both metals. The used electrochemical techniques allow to determine the corrosion velocities associated to each system, establishing that the uniform corrosion is not affected by the effect of the microorganisms; however, electrochemical noise, evidenced the formation of stings associated to the presence of bacteria. (Author)

  15. The influence of sulphate-reducing bacteria biofilm on the corrosion of stainless steel AISI 316

    This work investigates microbially-influenced corrosion (MIC) of stainless steel AISI 316 by two sulphate-reducing bacteria, Desulfovibrio desulfuricans and a local marine isolate. The biofilm and pit morphology that developed with time were analyzed using atomic force microscopy (AFM). Electrochemical impedance spectroscopy (EIS) results were interpreted with an equivalent circuit to model the physicoelectric characteristics of the electrode/biofilm/solution interface. D. desulfuricans formed one biofilm layer on the metal surface, while the marine isolate formed two layers: a biofilm layer and a ferrous sulfide deposit layer. AFM images corroborated results from the EIS modeling which showed biofilm attachment and subsequent detachment over time

  16. Effect of Niobium on Microstructure of Cast AISI H13 Hot Work Tool Steel

    Shahram Kheirandish; Ahmad Noorian

    2008-01-01

    The effect of niobium addition on the microstructure of cast AISI H13 hot work tool steel was evaluated by using EDX analyzer attached to the scanning electron microscope.The volume percent of eutectic area and eutectic cell size and also volume percent of different carbides of new steel,which is heat treated under different conditions,are also determined.The results show that the a niobium addition modifies the cast structure of Nb-alloyed hot work tool steel,and reduces the size and volume of eutectic cells,and increases the maximum hardness of the steel.

  17. Aspects of plasma arc cutting process in the AISI 321 type stainless steel

    Some aspects of plasma arc cutting process in the AISI321 stainless steel, used in nuclear industry, are analysed. The maximum values of the velocity of cutting and, the minimum quantity of energy per unit of length necesary for the plasma were determined. The localization of irregularities in the cut surface in function of the velocity of cutting was investigated. The cut surfaces were evaluated by surface roughness, using as measurement parameter, the distance between the sharpest salience and the deepest reentrance of the sample profile. The width of layer from thermal action of the plasma was influenced by the velocity of cutting. (Author)

  18. Fatigue of welded joint in a stainless steel AISI 304 L

    The flexion fatigue behavior for the base metal and welded joint of an AISI 304 L stainless steel type, used in the Angra-1 reactor, was determined. An automatic welding process was used with improved procedures in order to assure better welding metallurgy. Fatigue tests samples reinforcements were done to allow the evaluation of metallurgical variables, specially the role played by delta ferrite. The resulting welded joint showed better fatigue life than the base metal. Delta ferrite was found to play an important role on the initiation and propagation processes of the fatigue cracks. (Author)

  19. Microstructural changes due to laser surface melting of an AISI 304 stainless steel

    d?Oliveira A.S.C.M.

    2001-01-01

    Full Text Available Several techniques can be used to improve surface properties. These can involve changes on the surface chemical composition (such as alloying and surface welding processes or on the surface microstructure, such as hardening and melting. In the present work surface melting with a 3kW CO2 cw laser was done to alter surface features of an AISI 304 stainless steel. Microstructure characterisation was done by optical and scanning electron microscopy. Vickers and Knoop microhardness tests evaluated mechanical features after surface melting. Phase transformation during rapid solidification is analysed and discussed.

  20. Microstructural origins of yield strength changes in AISI 316 during fission or fusion irradiation

    The changes in yield strength of AISI 316 irradiated in breeder reactors have been successfully modeled in terms of concurrent changes in microstructural components. Two new insights involving the strength contributions of voids and Frank loops have been incorporated into the hardening models. Both the radiation-induced microstructure and the yield strength exhibit transients which are then followed by saturation at a level dependent on the irradiation temperature. Extrapolation to anticipated fusion behavior based on microstructural comparisons leads to the conclusion that the primary influence of transmutational differences is only to alter the transient behavior and not the saturation level of yield strength

  1. Optimization of the contact mechanical strength of magnetron-sputtered nitrogen-doped AISI 316L physically vapour deposited coatings

    The reactive magnetron sputtering technique adopted produces perfectly adhering nitrogen-doped AISI 316L coatings on construction and stainless steel substrates (AISI 316L and 4135). Surface mechanical testing was done by indentation and sclerometric, frictional, low cycle fatigue. The major damage parameters adopted were the critical coating cracking loads, track depression and lateral pile-up volumes. It is shown that the detrimental effect of growth defects on coating brittleness can be controlled to some extent by optimizing substrate surface treatment prior to and bias voltage during deposition. (orig.)

  2. Numerical Simulation on Temperature and Microstructure during Quenching Process of Large-sized AISI P20 Steel Die Blocks

    SONGDong-li; GUJian-feng; ZHANGWei-min; LIUYang; PANJian-sheng

    2004-01-01

    In this paper, a model of coupled thermal and phase transformation is described. The temperature and microstructure during the quenching process for large-sized AISI P20 steel die blocks have been simulated using the finite element method (FEM). The optimum quenching technology of large-sized AISI P20 steel die blocks has been proposed based on the simulation results, which not only can effectively avoid quenching cracks and obtain deeper hardened depth, but also can improve the microstructure and properties of the large-sized die blocks.

  3. Numerical Simulation on Temperature and Microstructure during Quenching Process of Large-sized AISI P20 Steel Die Blocks

    SONG Dong-li; GU Jian-feng; ZHANG Wei-min; LIU Yang; PAN Jian-sheng

    2004-01-01

    In this paper, a model of coupled thermal and phase transformation is described. The temperature and microstructure during the quenching process for large-sized AISI P20 steel die blocks have been simulated using the finite element method (FEM). The optimum quenching technology of large-sized AISI P20 steel die blocks has been proposed based on the simulation results, which not only can effectively avoid quenching cracks and obtain deeper hardened depth,but also can improve the microstructure and properties of the large-sized die blocks.

  4. Intelligent Search Method Based ACO Techniques for a Multistage Decision Problem EDP/LFP

    Mostefa RAHLI

    2006-07-01

    the algorithm getting to him a rate preferably more or less justifiable. In operational research, this subject is known under the name of CPO [14] (combinatory problem optimization.The choice of a numerical method to use for a merged case study and calculation of the LFP/Fitting/EDP what is [7, 8, 9, 10, 18, 19, 20] (in theoretical form of a problem compensates the final decision to adopt and a strategy of optimal production (which is a practical problem form and the final task most wanted.Each method is imposed by:· The algorithm complexity.· In an application gathering all calculations, the number of uses of method compared to the total number of later issues.· The maximum number of iterations for a given use.· The maximum iterations count allowed for this algorithm kind.· The limitations of the algorithm such as: applicability of a method (algorithm adapted or not to the problem; does the problem constrained or not; problem dimension or order N (N ≤ Nmax; the algorithm stability.It's well-known that for an approached calculation method, the propagation of errors strongly conditions the need of making its adequate choice and if it can be adopted compared to others for the same area.More is the number of the elementary operations is large more the final result misses precision and especially if the finality of the study is a responsible decision to make and a satisfaction of constraints and multiple conditions. Our study proposes an inference based solution (AI with the use of ACO technique (Ant colony Optimization2.

  5. Meta-heurística ACO (Ant Colony Optimization) para la resolución de problemas en líneas de producción

    Bautista Valhondo, Joaquín; Bretón Blas, Javier; Fernández Ros, José Antonio; De la Rosa Herrero, Marcela

    2000-01-01

    La meta-heurística ACO (Ant Colony Optimization) es un procedimiento heurístico para la resolución de problemas de optimización discreta basado en el comportamiento de las hormigas. Sus principales características son: (1) la utilización de

  6. Niobium boride layers deposition on the surface AISI D2 steel by a duplex treatment

    In this paper, we investigated the possibility of deposition of niobium boride layers on the surface of AISI D2 steel by a duplex treatment. At the first step of duplex treatment, boronizing was performed on AISI D2 steel samples at 1000oC for 2h and then pre-boronized samples niobized at 850°C, 900°C and 950°C using thermo-reactive deposition method for 1–4 h. The presence of the niobium boride layers such as NbB, NbB2 and Nb3B4 and also iron boride phases such as FeB, Fe2B were examined by X-ray diffraction analysis. Scanning electron microscope (SEM) and micro-hardness measurements were realized. Experimental studies showed that the depth of the coating layers increased with increasing temperature and times and also ranged from 0.42 µm to 2.43 µm, depending on treatment time and temperature. The hardness of the niobium boride layer was 2620±180 HV0.005

  7. Improvement in cavitation erosion resistance of AISI 316L stainless steel by friction stir processing

    Hajian, M.; Abdollah-zadeh, A.; Rezaei-Nejad, S. S.; Assadi, H.; Hadavi, S. M. M.; Chung, K.; Shokouhimehr, M.

    2014-07-01

    Commercial AISI 316L plates with the initial grain size of 14.8 μm were friction stir processed (FSP) with different processing parameters, resulting in two fine-grained microstructures with the grain sizes of 4.6 and 1.7 μm. The cavitation erosion behavior, before and after FSP, was evaluated in terms of incubation time, cumulative mass loss and mean depth of erosion. A separate cavitation erosion test was performed on the transverse cross section of a FSP sample to reveal the effect of grain structure. It was observed that FSP samples, depending on their grain size, are at least 3-6 times more resistant than the base material against cavitation erosion. The improvement in cavitation erosion resistance is attributed to smaller grain structure, lower fraction of twin boundaries, and favorable crystallographic orientation of grains in FSP samples. The finer the grain size, the more cavitation erosion resistance was achieved. Moreover, the microstructures of eroded surfaces were studied using a scanning electron microscope equipped with EBSD, and an atomic force microscope. The mechanisms controlling the cavitation erosion damage in friction stir processed AISI 316L are also discussed.

  8. Improvement in cavitation erosion resistance of AISI 316L stainless steel by friction stir processing

    Hajian, M. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Abdollah-zadeh, A., E-mail: zadeh@modares.ac.ir [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Rezaei-Nejad, S.S.; Assadi, H. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Hadavi, S.M.M. [Department of Materials Science and Engineering, MA University of Technology, Tehran (Iran, Islamic Republic of); Chung, K. [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Engineering Research Institute, Seoul National University, Seoul (Korea, Republic of); Shokouhimehr, M. [Department of Chemical Engineering, College of Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2014-07-01

    Commercial AISI 316L plates with the initial grain size of 14.8 μm were friction stir processed (FSP) with different processing parameters, resulting in two fine-grained microstructures with the grain sizes of 4.6 and 1.7 μm. The cavitation erosion behavior, before and after FSP, was evaluated in terms of incubation time, cumulative mass loss and mean depth of erosion. A separate cavitation erosion test was performed on the transverse cross section of a FSP sample to reveal the effect of grain structure. It was observed that FSP samples, depending on their grain size, are at least 3–6 times more resistant than the base material against cavitation erosion. The improvement in cavitation erosion resistance is attributed to smaller grain structure, lower fraction of twin boundaries, and favorable crystallographic orientation of grains in FSP samples. The finer the grain size, the more cavitation erosion resistance was achieved. Moreover, the microstructures of eroded surfaces were studied using a scanning electron microscope equipped with EBSD, and an atomic force microscope. The mechanisms controlling the cavitation erosion damage in friction stir processed AISI 316L are also discussed.

  9. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    Highlights: • AlN coating was applied on AISI 1045 steel via plasma nitriding and aluminizing. • Plasma nitriding and post-aluminizing result in AlN single phase layer on the steel. • PN–Al coated steel had better corrosion resistance than Al–PN one. • Formation of oxide layer provided protection of PN–Al coated steel against corrosion. • Pitting and surface defects was the dominant corrosion mechanism in Al–PN coated steel. - Abstract: Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN–Al), while the others were pack aluminized followed by plasma nitriding (Al–PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (Rp) resistances were obtained in PN–Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al–PN specimens

  10. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    Haftlang, Farahnaz, E-mail: f.haftlang@students.semnan.ac.ir [Department of Metallurgy and Materials Engineering, Faculty of Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Habibolahzadeh, Ali [Department of Metallurgy and Materials Engineering, Faculty of Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Sohi, Mahmoud Heydarzadeh [School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-02-28

    Highlights: • AlN coating was applied on AISI 1045 steel via plasma nitriding and aluminizing. • Plasma nitriding and post-aluminizing result in AlN single phase layer on the steel. • PN–Al coated steel had better corrosion resistance than Al–PN one. • Formation of oxide layer provided protection of PN–Al coated steel against corrosion. • Pitting and surface defects was the dominant corrosion mechanism in Al–PN coated steel. - Abstract: Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN–Al), while the others were pack aluminized followed by plasma nitriding (Al–PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (R{sub p}) resistances were obtained in PN–Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al–PN specimens.