wear resistance

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Wear Resistance of Fe-based Nanostructured Hardfacing

Wear Resistance of Fe-based Nanostructured Hardfacing

These materials have a high hardness due to their extremely small crystallite size, about 30 to 50 nm. They can also form ultra-hard precipitates as niobium, boron or tungsten carbides which improve abrasive wear resistance. They are applied on new or worn working surfaces of machine parts or elements to provide specific properties as abrasive and adhesive wear resistance, erosion resistance, corrosion resistance, heat resistance and many of their combinations (Linnert, G, 1994). It is reported that 50-60% of machine elements are worn due to erosive and abrasive wear which has many forms including low stress, high stress, dry or wet abrasion (Linnert, G, 1994; Merrick et al., 1998; Klimpel et al., 2005).
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10 Lee mas

Wear resistance of thermal spray WC Co VC nanostructured coatings

Wear resistance of thermal spray WC Co VC nanostructured coatings

As final conclusion, the friction coefficient of bimodal WC-Co + 2% VC coatings was less than the commercial coatings. The addition of VC in bimodal coatings resulted in a slight increase in the mechanical and wear resistance properties. The same behavior is described by Guile- many et al. [25] for bimodal WC-Co coatings, who showed lower values of friction coefficient (μ) in nanostructured systems and in commercial, both with the same chemical composition. The wear resistance of WC-Co coatings can be explained by the limited amount of debris removed during the sliding wear tests, the nanostructured WC-Co coatings contain a lower volume fraction of cobalt than commercial coatings. Therefore, it has been shown in various studies that a bimodal particle size distribution of WC improves response to wear on WC-Co coatings use conditions without lubrication (Luyckx and Machio [39]). Therefore, this work shows that a combination of micro- and nanostructures is beneficial to improve the wear resistance of WC-Co coatings.
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17 Lee mas

Tribology of Duplex Process of Plasma Nitriding Plus Hard Nanostructured Coating for Wear Resistance Applications in Tool Steels

Tribology of Duplex Process of Plasma Nitriding Plus Hard Nanostructured Coating for Wear Resistance Applications in Tool Steels

We performed successful formation of high-quality tungsten carbide coating with a very good adhesion to the surface of tool steel material. Such protective coatings are extremely important to improve tribological behavior of steel surfaces. Both friction coefficient and wear rate of the materials tested increased with increasing load; samples with higher hardness featured lower friction coefficient. The discussed duplex coating process allowed to achieve the most pronounced improvement to CPM10V steel, increasing its wear resistance in several times and extending working life at least in 500%.
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20 Lee mas

Surface modification of Al2O3–ZrO2(Y2O3) eutectic oxides by laser melting: processing and wear resistance

Surface modification of Al2O3–ZrO2(Y2O3) eutectic oxides by laser melting: processing and wear resistance

colonies, elongated along the traveling direction, whose micro- structural features (colony diameter, intercolony thickness, and interlamellar spacing) decreased as the traveling speed increased. The Vickers hardness, friction coefficient, and specific wear resistance were measured at room temperature in a dry labora- tory atmosphere. Hardness was at a maximum in the samples processed at a traveling speed of 500 mm/h, corresponding to a minimum in the friction coefficient and wear rate. This optimum behavior was correlated to the microstructural characteristics of the laser-melted material. Specimens grown at a lower traveling speed presented a coarser microstructure, while those grown at a higher speed revealed a higher population of defects (voids) at the intercolony regions. The wear rate of the optimum laser- melted specimens was almost an order of magnitude smaller than that of the conventionally sintered eutectic oxide material.
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8 Lee mas

SLIDING WEAR CHARACTERIZATION OF CEMENTED CARBIDES FOR HIGH PERFORMANCE CUTTING TOOLS

SLIDING WEAR CHARACTERIZATION OF CEMENTED CARBIDES FOR HIGH PERFORMANCE CUTTING TOOLS

In general, friction and wear is believed to result from three components: adhesion, ploughing and asperity deformations [7], several mechanisms have been proposed to explain how material is removed from the surface of WC-Co during sliding test because friction contacting bodies is a complicated phenomenon. The applied load is initially carried by only a few surface asperities, as sliding proceeds, the load is distributed over a large contact area since the surface roughness decreases. As indicated by [5,7,8] and based on the recorded responses from the sliding test, the wear resistance of WC based cemented carbides generally increases with reduced carbide grain size and decrease binder content, and thus, with increases hardness. Fig. 7 shows the values of friction coefficient, the 2608 grade have the lowest friction coefficient and the highest hardness (Fig 6), it is well know that coarse- grained cermets usually have lower abrasive wear resistance than that of fine or medium grain size and it is clear that the heterogeneity in the particles morphology and the gaps between them is obviously related to the sizes and all this is critical to the wear behavior and coefficient of friction observed in WC-Co structure. Based on the experiments completed during this test program and the interpretation of the sliding tribological testing, the following is a summary obtained in this investigation:
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8 Lee mas

Wear resistant coatings: Silica sol¿gel reinforced with carbon nanotubes

Wear resistant coatings: Silica sol¿gel reinforced with carbon nanotubes

However, little attention has been given, up to now, to the wear characterization of ceramic coatings reinforced with carbon nano- tubes. Agarwal et al. [13] reported the improvement (27% drop in the volume loss) of the wear resistance of plasma sprayed alumina coatings reinforced with CNTs, mainly because of the graphitization of the nanotubes due to pressure applied with the counterbody (50 N). Wear and corrosion protection of light metallic alloys with structural applications have increased the interest of the scienti fi c community. For instance, magnesium alloys are among the most promising materials to minimize weight in the transportation industry and in the portable electronics market. However, several drawbacks restrict the application of bare magnesium alloys, especially their low wear and corrosion resistance. Sol – gel silica coating is one of the few techniques that allow obtaining wear and corrosion protective ceramic layers at temperatures below the melting temperature of these alloys. Therefore, the more the mechanical performance of the silica coating the more the protection offered to the metallic substrate.
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7 Lee mas

Preparation and characterization of poly(methyl methacrylate)  chitosan/hydroxyapatite composite coating on ultra high molecular weight polyethylene substrate

Preparation and characterization of poly(methyl methacrylate) chitosan/hydroxyapatite composite coating on ultra high molecular weight polyethylene substrate

PMMA-CTS/HA coating show better tribological performance at higher loads compared with others studies that proposed a surface treatment method in order to enhance the wear resistance of UHMWPE. Besides its low costs and simple processing, we consider that PMMA-CTS/HA hybrid coating presented in this work could offer the advantage of supporting the early stages of UHMWPE wear in dry friction.

6 Lee mas

Transjugular intrahepatic portosystemic shunt is associated with significant changes in mitral inflow parameters

Transjugular intrahepatic portosystemic shunt is associated with significant changes in mitral inflow parameters

In our study, the diastolic dysfunction (impaired relaxation) was present in 45 % of patients before the procedure. 24 h later, the E/A ratio increased and the number of patients with impaired relaxation decreased. Further increase was observed until the end of the follow-up. This was caused by the increa- se of peak early filling velocity (E). In contrast to E wave, the peak late atrial filling velocity (A) only slightly increased 24 h after the TIPS procedure. De- celeration time had biphasic response: a rise in the first 24 h was followed by a decrease to baseline value. It is not easy to explain these changes. In our study, major changes were observed in increasing velocity of the E wave. It is known that E velocity is influenced by left atrial pressure at mitral valve ope- ning, the relative driving force between the left atrium and left ventricle, minimal left ventricular diastolic pressure, compliance of the left atrium and the rate of ventricular relaxation. Creation of the porto-systemic shunt leads to the changes in a num- ber of parameters (increase in cardiac output, cardiac index, heart rate, etc.), but the most important seems to be a decrease in systemic vascular resistance. 13,20
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7 Lee mas

Wearables: Análisis de dispositivos y recogida de datos en Android para estudios biométricos

Wearables: Análisis de dispositivos y recogida de datos en Android para estudios biométricos

Una de las partes más complicadas del proyecto fue implementar correctamente el envío de datos entre un dispositivo Android Wear y el smartphone. Para poder obtener muestras de datos útiles en el estudio de biometrías es necesario que la frecuencia de recogida de datos de los sensores sea bastante elevada. Los dispositivos wearables, debido a la funcionalidad para la que están pensados, no tienen una gran capacidad de procesamiento. Esto suponía un problema al recoger una muestra ya que, con el paso del tiempo, las mediciones comenzaban a encolarse y el sistema acababa bloqueándose produciendo que éstas no fueran útiles. Para solucionar esto se tuvo que optimizar todo lo posible esta parte del código hasta conseguir que las mediciones de los sensores no se encolasen al ser enviadas.
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120 Lee mas

Combatting resistance in intensive care: the multimodal approach of the Spanish ICU "Zero Resistance" program.

Combatting resistance in intensive care: the multimodal approach of the Spanish ICU "Zero Resistance" program.

Criteria for defining MDR pathogens vary from institution to institution and are also not uniform in the published literature, although the most highly resistant strains are readily recognizable. Based on the pathogens considered most problematic in Spanish ICUs, “Zero Resistance” collects information on episodes of infection and colonization of the pathogens listed in Table 1. Finally, because acquiring an infection may be the result of errors in patient-care, all three programs were designed to reduce and prevent these by incorporating an integral patient safety program [16].

8 Lee mas

Informe de un caso de resistencia mltiple a ixodicidas en Boophilus microplus Canestrini (Acari: Ixodidae) en Tamaulipas, Mxico

Informe de un caso de resistencia mltiple a ixodicidas en Boophilus microplus Canestrini (Acari: Ixodidae) en Tamaulipas, Mxico

A report of a multiple resistance case of Boophilus microplus (Acari: Ixodidae) in Padilla, Tamaulipas state, Mexico, is presented. Ticks larvae showed resistance against all ixodicides tested in the larval packages resistance test: chlorfenvinphos, coumaphos, diazinon, lindane, cipermethrine, deltamethrine and flumethrine. The greatest resistance was related to the permethrine group, being higher than 47%. For organophosphorus, larvae resistance was less than 31%. The less effective ixodicide was cipermethrine, having more than 85% resistance.

6 Lee mas

Future prospects for "Neisseria gonorrhoeae" treatment / Beatriz Suay García and María Teresa Pérez Gracia

Future prospects for "Neisseria gonorrhoeae" treatment / Beatriz Suay García and María Teresa Pérez Gracia

Abstract: Gonorrhea is a sexually transmitted disease with a high morbidity burden. Incidence of this disease is rising due to the increasing number of antibiotic-resistant strains. Neisseria gonorrhoeae has shown an extraordinary ability to develop resistance to all antimicrobials introduced for its treatment. In fact, it was recently classified as a “Priority 2” microorganism in the World Health Organization (WHO) Global Priority List of Antibiotic-Resistant Bacteria to Guide Research, Discovery and Development of New Antibiotics. Seeing as there is no gonococcal vaccine, control of the disease relies entirely on prevention, diagnosis, and, especially, antibiotic treatment. Different health organizations worldwide have established treatment guidelines against gonorrhea, mostly consisting of dual therapy with a single oral or intramuscular dose. However, gonococci continue to develop resistances to all antibiotics introduced for treatment. In fact, the first strain of super-resistant N. gonorrhoeae was recently detected in the United Kingdom, which was resistant to ceftriaxone and azithromycin. The increase in the detection of resistant gonococci may lead to a situation where gonorrhea becomes untreatable. Seeing as drug resistance appears to be unstoppable, new treatment options are necessary in order to control the disease. Three approaches are currently being followed for the development of new therapies against drug-resistant gonococci: (1) novel combinations of already existing antibiotics; (2) development of new antibiotics; and (3) development of alternative therapies which might slow down the appearance of resistances. N. gonorrhoeae is a public health threat due to the increasing number of antibiotic-resistant strains. Current treatment guidelines are already being challenged by this superbug. This has led the scientific community to develop new antibiotics and alternative therapies in order to control this disease.
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10 Lee mas

Abiotic factors modulate post-drought growth resilience of Scots pine plantations and rear-edge Scots pine and oak forests

Abiotic factors modulate post-drought growth resilience of Scots pine plantations and rear-edge Scots pine and oak forests

The proportion of planted forests in the Mediterranean Basin is one of the largest in the world. These plantations are dominated by pine species and present a series of characteristics such as low elevation, high competition or small tree size that make them more vulnerable to droughts. However, quantitative assessments of their post-drought growth resilience in accordance with species, site factors and tree characteristics are lacking. In this study we sampled 164 trees at four forest sites located in the drought- prone Sierra Nevada, southeastern Spain. We compared growth responsiveness to drought in rear-edge planted vs. relic natural Scots pine (Pinus sylvestris) and coexisting Pyrenean oak (Quercus pyrenaica) stands. Our objective was to characterize and compare the different growth responses to drought between species and sites and the effect of the main physiographic factors (altitude, aspect, and slope) on these responses since the influence of these factors on post-drought resistance and resilience has received little attention to date. Our results reveal that the planted pine sites with the lowest mean growth rates displayed greater resistance during drought, and that higher altitude was associated with improved resistance and/or resilience for all species and sites. Natural pine and Pyrenean oak stands were better adapted to the dry climatic conditions of the Mediterranean region where the study was undertaken, displaying greater resistance and/or resilience and lower influence of drought on growth in comparison to stands of planted pines. These results suggest that promoting the conservation of high-elevation pine plantations and enhancing the regeneration of natural pine and oak may improve the resistance and resilience of these drought-prone forest ecosystems.
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47 Lee mas

Standard Test Method for

Standard Test Method for

9.1.4 In situations where both the pin and the disk wear significantly, it will be necessary to measure the wear depth profile on both members. A suitable method uses stylus profiling. Profiling is the only approach to determine the exact final shape of the wear surfaces and thereby to calculate the volume of material lost due to wear. In the case of disk wear, the average wear track profile can be integrated to obtain the track cross-section area, and multiplied by the average track length to obtain disk wear volume. In the case of pin wear, the wear scar profile can be measured in two orthogonal directions, the profile results averaged, and used in a figure-of-revolution calculated for pin wear volume.
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6 Lee mas

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Besides plant extracts also an etheric oil has been tested against E. amylovora on its resistance induction effect. Although the essential oil of thyme has been described as an antibacterial natural agent against the fire blight pathogen besides others from origanum, savory, cinnamon, the etheric oil of the thyme variety Thymbra spicata showed in a low concentration of 0,05% also a reaction of systemic acquired resistance (SAR). In the meantime this thyme oil has been registered in Turkey and Germany under the names Aksebio 2 and BioZell-2000B and was tested in several experiments under greenhouse and field conditions. Reduction of disease index was correlated with a significantly lower bacterial population in the plant tissue of M26 rootstocks compared to untreated inoculated plants. In the studies with the extract of ivy (Hedera helix), which showed a suppressed disease development and bacterial multiplication of E. amylovora in various host plants local induced resistance was caused resulting in significant increase of polyphenol oxidation activity with higher activities of enzymes of phenol metabolism as peroxidase (PO), polyphenoloxidase (PPO) and phenylalanin-lyase (PAL). Recently Baysal and Zeller (2005) analyzed the mechanism of action of H. helix- extract, concerning alterations in the levels of key defense-relating enzymes, PO, chitinase and 1,3 β- glucanase. In this study a correlation was found between plant extract treatment and increase of PO and these both PR-proteins, which possess direct antimicrobial activity by degrading microbial cell walls. From these findings the authors concluded, that the extract of H. helix was responsible for a stimulation of resistance to fire blight in the host plant and can accelerate the defense response to stop bacterial migration in the plant tissue up to seven days. Also with BioZell-2000B, the natural compound of the etheric oil of thyme (Thymbra spicata) a similar resistance inducing effect could be observed [Zeller et al., 2004]. Besides a marked reduction in the severity of the disease in M26 rootstock shoots and apple blossom blight and decrease of the multiplication of E. amylovora in the host plant, the following physiological changes in inoculated and non-inoculated apple shoots could be found:
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5 Lee mas

WEAR AND FRICTION BEHAVIOR OF POLY (METHYL METHACRYLATE)/CALCIUM OXIDE COATING COMPOSITES UNDER DRY CONDITIONS

WEAR AND FRICTION BEHAVIOR OF POLY (METHYL METHACRYLATE)/CALCIUM OXIDE COATING COMPOSITES UNDER DRY CONDITIONS

Poly(methyl methacrylate)/calcium oxide (PMMA/CaO) composite in the form of solution, has been successful prepared for its application as coating on ultra high molecular weight polyethylene (UHMWPE). The hybrid coating was prepared by mixing the CaO powder in situ with PMMA polymerization from its monomer methyl methacrylate (MMA) using benzoyl peroxide (BPO) as initiator and toluene as solvent. The FTIR technique was used to study the hybrid composite coatings. Coating surface morphology was characterized by Scanning Electron Microscopy founding out CaO particles on the polymer surface; by image analysis was found that the incorporation of CaO powder increases the PMMA/CaO coating thickness obtaining a mean value of 107.57 µm. Wear test of PMMA/CaO coatings on UHMWPE were carried out on a pin-on-disk tribometer in dry conditions with a normal load of 5 N against stainless steel.
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10 Lee mas

Analysis of bio anode performance through electrochemical impedance spectroscopy

Analysis of bio anode performance through electrochemical impedance spectroscopy

of one. The appearance of a single arc is often interpreted as a charge transfer resistance, however, in this case it is caused by the presence of a very large capacitance in the bioanode (around 1 mF·cm −2 ), as was also reported in previous work on biocathodes [5]. This very large capacitance may mask the presence of two processes: charge transfer and diffusion resistance, resulting in a single arc that we do observe at potentials higher than − 0.45 V vs Ag/AgCl. This effect is illustrated in Fig. 2(a), where the simulated impedance of a Randles circuit using a capacitance of 1 mF·cm −2 (black line) is compared with the simulat- ed impedance provided by the same parameters but smaller, 0.2 mF·cm −2 (red line) and a much smaller, 10 μ F·cm −2 (green line) capacitances.
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9 Lee mas

Antimicrobial resistance: An emerging water, sanitation and hygiene issue

Antimicrobial resistance: An emerging water, sanitation and hygiene issue

The potential for human exposure to such wastes is great. It is estimated that up to 90% of all wastewater is discharged untreated directly into rivers, lakes or the oceans (Corcoran et al., 2010). Therefore, the collection, prevailing management and purposeful or unplanned use of such wastes often result in increased prevalence and environmental release of antimicrobial contaminants, including antibiotics and other antimicrobial agents, their metabolites, antimicrobial-resistant bacteria and AMR genes (Schwartz et al., 2003; Lupo, Coyne & Berendonk, 2012). Municipal wastewaters in particular are major environmental reservoirs for antimicrobial agents, antimicrobial-resistant bacteria and AMR genes, and they also provide an environment that is conducive to the transfer of resistance genes to other bacteria before or after being discharged into the environment (Rizzo, Fiorentino & Anselmo, 2013; Rizzo et al., 2013).
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16 Lee mas

Revista Ingeniería Investigación y Tecnología | Facultad de Ingeniería UNAM

Revista Ingeniería Investigación y Tecnología | Facultad de Ingeniería UNAM

In part a) of Figure 3 it can be seen the wear mecha- nisms on bare steel and the spherical counterpart bone. There are two wear mechanisms: abrasive wear and ad- hesive wear. Second zoom shows plow lines indicating abrasive wear likely because of some steel particle came off due to fatigue and strain hardened generated abra- sion to disk. The zoom shows bone adhesion to the disk; it is also observed that adhered material fractures because of fatigue forming wear debris acting as a third body. In part b) we observe wear mechanisms of coated steel. Abrasive wear is not observed and EDX probe re- vealed no bare steel, so it follows that the coating main- tained its integrity after testing. The only wear mecha- nism observed is adhesive and fatigue fracture of bon- ded bone forming wear particles. Figure 4 shows the wear mechanisms of bare steel and coated steel in Hank’s solution. It can be seen that the only wear me- chanisms both cases is bone adhesion, there is no abra- sive wear in neither case, there is no detachment of the coating, and there is salts precipitations.
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8 Lee mas

Some English names of clothing ending in -wear

Some English names of clothing ending in -wear

Rocawear is the name of a brand of clothing (at least T-shirts and jeans) sold at least since 1999. “Jay-Z says he’s over the whole ‘ghetto fabulous’ diamonds-and-furs look, and the flashy lifestyle that goes with it. To see his new Rocawear women’s line, you’d believe him. The collection [...] features low-waisted velour track suits, satin bomber jackets, dropped tops and drawstring short shorts. It’s young and sporty -- but not ripping with logos. ‘It’s funwear, not thugwear,’ explained Damon Dash, CEO of Rocawear, who is also working on ladies. ‘It’s a reflection of us. Not too dressy, not too couture-ish” (Alev Aktar and Holly Russel, “Rocawear for Ladies,” Daily News, New York, 13 December 2001, p. 73). Were the spellings Rock-A-Wear and Rockawear, once used and possibly now obsolete, ever official?
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23 Lee mas

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