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Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The self-assembled monolayers (SAMs) process is one of the techniques used for the production of ultra-thin layers. The present work is therefore devoted to the study of the inhibition of zinc corrosion in a marine environment rich in H2S by SAMs based on Sargassum fluitans III. The protective effect of crude extracts of Sargassum fluitans on the surface of zinc using the SAMs process was evaluated by gravimetry and impedance on two different sites after three months of exposure. The formation of SAMs was characterized by FTIR, and the corrosion products formed on the surfaces were analyzed by XRD. The results obtained show that SAMs based on Sargassum fluitans III effectively inhibit zinc corrosion. [ABSTRACT FROM AUTHOR]

Controlling the evolution process of columnar grains is benefits to achieve microstructure regulation during subsequent hot processing in superalloys. In present research, it takes a Ni–Co–W superalloy as an example, aims to clarify the underlying connections between the compression direction and dynamic recrystallization (DRX) behaviors in microstructure evolution. The compression direction (CD) was parallel or perpendicular to [001] columnar has been defined as CD∥[001] and CD⊥[001], respectively. The columnar evolution and DRX characteristics under two sets of experimental during hot deformation were identified deeply. The results show that complete DRX is more easily to occur when CD⊥[001], but fine DRX grains are tendency to form when CD∥[001]. DRX nucleation within CD∥[001] and CD⊥[001] deformed microstructure under dislocation energy was discussed deeply. The critical size of nucleation is decreased while the nucleation density is increased in CD∥[001] with high dislocation density, which benefits to form numerous fine DRX grains along the original columnar boundaries. In addition, according to Taylor factors (TFs) criterion, TFs difference will always existed in CD∥[001], which promotes the necklace structure gradually replaced columnar structure and some of them developed into fine DRX bands. With increasing of trues strain, TFs difference gradually decreased in CD⊥[001], DRX nucleation was inhibited, thus the existed DRX grains further grow and finally coarse DRX grains were obtained. The findings clarified the flow behaviors and DRX characteristics of [001] columnar in two directions, and then proposed a microstructure control mechanism of superalloys with [001] columnar based on deformation vector and evolution decomposition.

Limited QCIs (QoS Class Identifiers) restrict the handling different service types with varying quality requirements. This necessitates research on QoS management to minimize latency and improve user experience, particularly for real-time applications like video conferencing and online gaming. This paper proposes a combined optimization scheme targeting QCI 3 to reduce latency. The approach involves disabling DRX, optimizing pre-allocation, and reducing the PDCP discard timer. The optimization performance is studied by taking the case of an e-sport game that demands low network latency, affecting the quality of the players' experience. The optimization scheme was validated through functionality, resource allocation, and air interface latency tests conducted under actual e-sport gaming conditions. Network latency was measured every minute to evaluate the impact of optimization on esports games running under QCI 7, QCI 3, and optimized QCI 3. In addition, air interface latency for optimized QCI 3 under networks with poor coverage and very high-capacity networks was compared to latency under QCI 8 (basic), QCI 7, and regular QCI 3. The optimization strategy demonstrated a significant reduction in air interface latency, up to 19% improvement compared to non-optimized QCI 3. It has reduced air interface latency's maximum, minimum, and standard deviation values during gameplay. The strategy also ensured concurrent operation with multiple QCI values without compromising other application’s throughput. The proposed optimization strategy effectively enhances the user experience by significantly reducing average latency and jitter.

The dissolution mechanism of the η-Ni3(Al0.5Nb0.5) phase during hot compression in Ni-based ATI718Plus superalloy has been investigated. The results indicate that with increasing deformation, the amount of dynamic recrystallization grains in the γ matrix increases, and the dissolution of the η phase tends to be accelerated. At the precipitation temperature of the η phase of 950 °C, the η phase area fraction decreased from 9.8% to 3.0% after deformation. The deformation promotes dislocation accumulation at the boundaries of the η phase, developing into subgrains and then evolving into DRX grains due to subgrain rotation. With increased strain, the subgrain rotations and DRX grain growths result in extrusion and subsequent fracture of the η phase. Due to strain incompatibility between the η phase and γ matrix, dislocation sustains are accumulated at their interfaces, which disrupts the η/γ semi-coherent interface, leading to localized amorphization and the decomposition of the η phase. Furthermore, dislocation surrounding the η phase can act as diffusion channels for solute elements, promoting the dissolution of the η phase and resulting in the element concentration gradient distribution from the η phase to the γ matrix.

The microstructure evolution of Mg-13Gd-4Y-2Zn-0.5Zr (wt.%) alloy with long-period stacking ordered (LPSO) phases after compression-torsion deformation (thereinafter referred to as CT deformation) at different temperatures was analyzed by optical microscopy (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) analysis, especially the evolution of LPSO phases during CT deformation. In addition, dynamic recrystallization (DRX) behavior during CT deformation and the impact of LPSO phase evolution on DRX behavior was explicated. The results showed the structures by order of appearance: lamellar LPSO phase (light kink—moderate kink—severe kink—almost no kink) and bulk LPSO phase (needle-like projections—tearing—dissolution—crushing) at increased CT deformation temperature. The proportion of DRXed grains gradually increased with CT deformation temperature, ranged from 11.6% at 350 °C to 40.9% at 480 °C. Apart from the increases in atomic thermal vibration and diffusion rate owing to increase in CT deformation temperature, the bulk LPSO phases at the grain boundary showed enhanced lattice rotation, which provided an ideal position for the nucleation of DRXed grains, and promoted the accumulation of strain gradient during deformation. Meanwhile, the second-phase particles distributed in the grain and grain boundary promoted DRX nucleation through PSN mechanism. [ABSTRACT FROM AUTHOR]

In this paper, the electron backscatter diffraction (EBSD) technique was used to analyze the dynamic recrystallization (DRX), twinning, slip behavior, and texture evolution during forging and subsequent extruding deformation. The results show that, as the degree of strain increased (forging to extruding), the degree of DRX increased, and the DRX mechanism changed from discontinuous DRX (DDRX) during forging to DDRX and continuous DRX (CDRX) during extruding. Particle stimulation nucleation (PSN) promoting DRX occurred during deformation. The deformation process mainly produced {10–12} twins (TTW) and played a role in coordinating the deformation. The slip behavior also changed according to an analysis of in-grain misorientation axes (IGMA) results, changing from slip-dominated with a basal slip to co-dominated with multiple slip modes, with the activation of mainly prismatic and pyramidal slip. Meanwhile, the strong basal texture at the beginning of the deformation also changed, and the texture strength decreased from 24.81 to 15.56. The weakening of the texture was mainly due to the formation of DRX grains and twins, as the newly formed DRX and twins reoriented. In the later stages of deformation, the activation of prismatic slip and pyramidal slip changed the basal texture component. Based on microstructural analysis, the improvement in mechanical properties was due to fine-grain strengthening and load-transfer strengthening. The ultimate tensile strength (UTS) was 370.5 MPa, the yield strength (YS) was 340.1 MPa, and the elongation (EL) was 15.6%. [ABSTRACT FROM AUTHOR]

To achieve a broad range of gradient strain from the rim to the center of a single specimen, the size of the high-throughput double-cone (DC) specimen was optimized using finite-element-model (FEM) simulation. As the deformation increased, the flow stress of the DC specimen quickly reached the maximum value, then gradually declined, and finally tended to be stable. The gradient microstructures corresponding to the gradient strains from the rim to the center of the DC specimen compressed at a certain temperature and strain rate were obtained by only one compression testing. As the equivalent strain increased, the degree of dynamic recrystallization (DRX) gradually rose from the rim to the center of the compressed DC specimen. However, when the equivalent strain and strain rate remained constant, the degree of DRX increased steadily with rising deformation temperature in the compressed DC specimens. Furthermore, during compression of the DC specimens at temperatures of 250 °C and 300 °C, the primary DRX mechanism was continuous dynamic recrystallization (CDRX). At temperatures of 350 °C and 400 °C, the DRX mechanism shifted, as both CDRX and discontinuous dynamic recrystallization (DDRX) were observed. This suggested that the DRX mechanism underwent a change as the deformation temperature increased.

The hot deformation behavior and the associated microstructural evolution (which were the keys to decide mechanical properties) were studied using different deformation conditions for the quaternary Al–Cu–Li–Zn alloy containing 1.0 wt% Zn. The constitutive equations and processing map were established. Dynamic recrystallization (DRX) was related to the orientation of the initial grains. The DRX rarely occurred in the grains with an orientation near Al and mainly occurred in the grains with an orientation near Al. Particle simulated nucleation (PSN) promoted by pre-existed coarse T1 phase particles was the main mechanism of the DRX when the deformation temperature was below 450 °C. In the temperature range of 450–500 °C with a strain rate of 0.01 s−1, the DRX occurred by grain boundary bulging or the increase in the cumulative misorientation, but only small fraction of the DRX grains appeared. This work provided an important guideline for the optimization of deformation techniques and microstructures.

Copyright of Brazilian Dental Science is the property of Brazilian Dental Science Journal-ICT-UNESP and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the hot-deformation behavior of a die-casted Mg–Al–Zn–Ca–Mn–Zr alloy was investigated in the temperature range of 548–673 K and the strain rate range of 0.0001–1 s−1. The constitutive equation and processing maps were also developed to describe the flow stress behavior. The numerical simulation result revealed an average activation energy of ∼139.4 kJ mol−1, which is lower than the previously reported AZ31 Mg alloys. Subsequently, the low activation energy imparted a high degree of dynamic recrystallization and was mainly attributed to alloying elements Ca, Mn, and Zr. For optimum hot working parameters, processing maps displayed two different domains, the temperature range of 573–673 K for a strain rate range of 0.001–0.01 s−1 with a peak efficiency of 33% and a temperature of 673 K at a high strain rate of 0.01 s−1 with a peak efficiency of 31%. The microstructure evolution confirmed the validity of parameters and revealed high dynamic recrystallization. The average grain size ∼21.1 μm, ∼15.4 μm, and ∼16.1 μm were achieved at temperatures of 573 K, 623 K, and 673 K under a strain rate of 0.001 s−1. The profuse grain refinement is attributed to the pronounced accumulation of dislocation on grain boundaries and on the eutectic phases. In addition, the morphology of the eutectic phases was broken with the increase in the strain rate and temperature. Thus, the α-Mg and eutectic phases bear the compressive stresses and promote the dynamic recrystallization activity. Last but not least, the double peak texture after hot deformation was developed, which is one of the engineers' main requirements for enhancing the Mg alloy's ductility. Based on the above discussion, the hot deformed specimens exhibited an ultimate compressive strength of ∼340 MPa and elongated to fracture >25%. Consequently, this study enables the understanding of the broad use of Mg–Zn–Al–Ca–Mn–Zr alloys for automobile applications.

In this study, {10–12} tensile twins (TTs) were induced in hot-rolled AZ31 Mg sheets via hot tension along the normal direction. The results demonstrate that the volume fraction of TTs at 2 mm/min is greatly lower than their counterparts at 0.5 mm/min at 100 °C and 200 °C. Dynamic recrystallization (DRX) can decrease twin nucleation rate during hot tensile when the strain rate reaches 2 mm/min. Decrease in critical resolved shear stress of non-basal slips at 200 °C enhances the deformation capability among grains, which dramatically reduces the volume fraction of TTs. Hence, TTs are hardly observed in 200°C-2mm/min sample. Tensile temperature significantly affects the morphology of TT lamellae. Grain boundaries prevents the longitudinal growth of the TTs, and then the thickness of TTs begins to grow to coordinate the deformation, resulting in fine TT lamellae in 100°C-0.5 mm/min. Compared with AR, the basal texture intensity of 100°C-2mm/min and 200°C-2mm/min increases and the occurrence of DRX is the main reason, while basal texture weakening of 100°C-0.5 mm/min and 200°C-0.5 mm/min depends on the formation of TTs. Compared with samples at 200 °C, the samples at 100 °C have higher tensile stresses. The maximum stress of 100°C-0.5 mm/min is 64.97 MPa when tensile strain reaches 0.15 owing to its highest dislocation density. 200°C-2mm/min possesses the highest hardness among the four tension samples, which is associated with the largest fraction of DRXed grains (68.8%) and its refinement strengthening effect. Dislocation strengthening exerts more influence on the hardness of 100°C-0.5 mm/min.

Nano partículas de (LaF3)0.75Er0.025Yb0.225 y (LaF3)0.75Er0.015Yb0.235 fueron sintetizadas utilizando el método de coprecipitación química y sometidas a tratamiento térmico de 200 °C, 400 °C y 600 °C respectivamente durante 2 horas. La estructura de las muestras fue analizada a través de la técnica de difracción de rayos X (DRX) y modelamiento RIETVELD por parámetros fundamentales usando el software TOPAS. El tamaño de los cristalitos se determinó a nivel nanométrico (entre 11.9 nm y 140.7 nm) y se verifico el aumento del tamaño de los cristalitos a medida que la temperatura del tratamiento térmico se incrementaba. Se pudo verificar el cambio de estructura hexagonal a romboédrica para las muestras sometidas a 600 °C de temperatura y un aumento significativo en la cristalinidad de las muestras por efecto del tratamiento térmico. Las imágenes SEM-EDS muestran los efectos descritos y proporcionan una vía para corroborar el crecimiento de las partículas (entre los 538 nm y 778 nm ), así como para obtener la composición elemental de las muestras. Finalmente los espectros Raman muestran una baja energía fonónica de las muestras, asegurando así que la perdida de las propiedades de emisión anti Stokes de los estados excitados de los iones lantánidos en las muestras por el efecto de quenching sea mínima.

In this paper, the electron backscatter diffraction (EBSD) technique was used to analyze the dynamic recrystallization (DRX), twinning, slip behavior, and texture evolution during forging and subsequent extruding deformation. The results show that, as the degree of strain increased (forging to extruding), the degree of DRX increased, and the DRX mechanism changed from discontinuous DRX (DDRX) during forging to DDRX and continuous DRX (CDRX) during extruding. Particle stimulation nucleation (PSN) promoting DRX occurred during deformation. The deformation process mainly produced {10–12} twins (TTW) and played a role in coordinating the deformation. The slip behavior also changed according to an analysis of in-grain misorientation axes (IGMA) results, changing from slip-dominated with a basal slip to co-dominated with multiple slip modes, with the activation of mainly prismatic and pyramidal slip. Meanwhile, the strong basal texture at the beginning of the deformation also changed, and the texture strength decreased from 24.81 to 15.56. The weakening of the texture was mainly due to the formation of DRX grains and twins, as the newly formed DRX and twins reoriented. In the later stages of deformation, the activation of prismatic slip and pyramidal slip changed the basal texture component. Based on microstructural analysis, the improvement in mechanical properties was due to fine-grain strengthening and load-transfer strengthening. The ultimate tensile strength (UTS) was 370.5 MPa, the yield strength (YS) was 340.1 MPa, and the elongation (EL) was 15.6%.

Magnesium and magnesium-based alloys are widely used in the transportation, aerospace and military industries because they are lightweight, have good specific strength, a high specific damping capacity, excellent electromagnetic shielding properties and controllable degradation. However, traditional as-cast magnesium alloys have many defects. Their mechanical and corrosion properties cause difficulties in meeting application requirements. Therefore, extrusion processes are often used to eliminate the structural defects of magnesium alloys, and to improve strength and toughness synergy as well as corrosion resistance. This paper comprehensively summarizes the characteristics of extrusion processes, elaborates on the evolution law of microstructure, discusses DRX nucleation, texture weakening and abnormal texture behavior, discusses the influence of extrusion parameters on alloy properties, and systematically analyzes the properties of extruded magnesium alloys. The strengthening mechanism is comprehensively summarized, the non-basal plane slip, texture weakening and randomization laws are comprehensively summarized, and the future research direction of high-performance extruded magnesium alloys is prospected. [ABSTRACT FROM AUTHOR]

To suppress the edge crack of the magnesium alloy sheet during the ordinary rolling process, a new rolling process named width-limited rolling was proposed in this paper. Width-limited rolling is a rolling method in which the width of the alloy sheet is limited by modifying the shape of the rollers, allowing a compressive stress field to form at the edge portion of the alloy sheet during rolling, resulting in the reduction of edge cracks. At present work, magnesium alloy sheets were separately subjected to ordinary rolling and width-limited rolling. The microstructure evolution and mechanical properties of the rolled sheets were investigated by EBSD, TEM, and XRD. The results exhibited that under the same rolling conditions, the sheet after ordinary rolling exhibited obvious edge cracks while no crack was found at the edge of the sheet after width-limited rolling. The edge crack suppressing effect was attributed to the reduction of the tensile stress along rolling direction during WLR, promoting the synchronous extension of the edge and center regions to suppress edge crack tendency. Microstructure observation showed that the compressive twins formed in the sheet after ordinary rolling usually exhibited as thin plates and cannot continue to fully develop due to the premature generation of the edge cracks. However, the compressive twins developed maturely in some of which double twins formed and various slip systems with different dislocation Burgers vectors occurred in the rolled sheet after WLR. More twin intersections and shear bands, providing more potential recrystallization nucleation sites, which are beneficial to weaken basal texture. With the cooperation of twinning and dislocation slip, the texture of the sheet after the width-limited rolling is weakened and the mechanical properties are improved.

Cobalt-based superalloys are common materials for the manufacturing of various components used in aerospace applications. Conventional cobalt-based superalloys with a unimodal grain structure generally exhibit low strength and ductility at high temperatures. A bimodal grain structure of a cobalt-based superalloy, Co–20Cr–15W–10Ni (CCWN), was designed to achieve both high strength and ductility at high temperatures. The deformation behavior and tensile properties of a CCWN alloy with unimodal fine-grain (FG), coarse-grain (CG), and bimodal (FG/CG) structures were investigated at 900 °C. The microstructures and substructures after high-temperature deformation were examined via electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) to determine the deformation mechanisms. The microstructural observation showed that the bimodal grain structure consisted of FG and CG domains. During high-temperature deformation at 900 °C, the FG structure was mainly deformed by dynamic recrystallization (DRX), maintaining a similar FG structure. The CG structure was mainly deformed by DRV, resulting in a small amount of DRX grains and a large amount of dynamic recovery (DRV) grains. However, the bimodal grain structures were mainly softened via DRX and transformed into a new bimodal structure, ultrafine grain (UFG) and FG. The FG domains tended to deform via dislocations, and the CG domains via twinning. The high-temperature tensile tests revealed that the bimodal-structured alloy exhibited both higher strength and ductility than those of the alloy samples with unimodal FG or CG structure. This is associated with the newly developed UFG/FG structures in the bimodal grain-structured samples during high-temperature deformation. This work may provide new insight into the development of high-temperature alloys with bimodal grain structures. [ABSTRACT FROM AUTHOR]

Las cáscaras de naranja (Citrus sinensis) son residuos lignocelulósicos abundantes que pueden ser utilizados como fuente de carbono para obtener sólidos con potencial catalítico en la transformación de terpenos y sus óxidos en productos de valor agregado. Esta investigación buscó evaluar la isomerización de óxido de α-pineno a aldehído canfolénico, utilizando un catalizador obtenido de cáscaras de naranja. El material OAC-Zn se obtuvo por activación de las cáscaras con ZnSO4.7H2O, seguido de tratamiento térmico a 500 °C; también se obtuvo un sólido de la pirólisis de la cáscara a 500 °C (OC-500). Mediante DRX se identificó la presencia de ZnO y ZnS en OAC-Zn; los análisis por TGA indicaron estabilidad térmica en OAC-Zn y OC-500; las imágenes SEM mostraron superficies porosas de diferente morfología, así como la presencia de microporosidad en OC-500 y de mesoporosidad en OAC-Zn, que fueron confirmadas mediante adsorción física de nitrógeno. En los análisis EDX se identificaron los elementos C, O, Zn y S en OAC-Zn; los resultados de TPD-NH3 mostraron que los sólidos contenían acidez media y débil. Se sintetizó aldehído canfolénico con selectividad de 96 % sobre un material carbonoso mesoporoso, a partir de cáscaras de naranja utilizando ZnSO4.7H2O como agente activador

Orange peels (Citrus sinensis) are an abundant lignocellulosic residue that can be used as a carbon source to obtain solids with catalytic potential in the transformation of terpenes and their oxides into value-added products. This research seeks to evaluate the isomerization of a-pinene epoxide to campholenic aldehyde using a catalyst obtained from orange peels. The material OAC-Zn was obtained by activation of orange peel with ZnSO4.7H2O followed by thermal treatment at 500 °C; an additional solid was obtained from orange peel by pyrolysis at 500 °C (OC-500). XRD revealed the presence of ZnO and ZnS in OAC-Zn; TGA analysis indicated thermal stability in OAC-Zn and OC-500 materials; SEM images showed porous surfaces of different morphology, and the presence of microporosity in OC-500 and mesoporosity in the OAC-Zn that was confirmed by physical nitrogen adsorption. The elements C, O, Zn and S were identified in OAC-Zn by EDX analysis. The results of TPD-NH3 showed that the solids contained medium and weak acidity. Campholenic aldehyde was synthesized with a 96 % selectivity over the material OAC-Zn. [ABSTRACT FROM AUTHOR]

After years of intense research using structural, biological, and biochemical experimental procedures, it is clear that myosin molecules are essential for striated muscle contraction. However, this is just the tip of the iceberg of their function. Interestingly, it has been shown recently that these molecules (especially myosin heavy chains) are also crucial for cardiac and skeletal muscle resting state. In the present review, we first overview myosin heavy chain biochemical states and how they influence the consumption of ATP. We then detail how neighboring partner proteins including myosin light chains and myosin binding protein C intervene in such processes, modulating the ATP demand in health and disease. Finally, we present current experimental drugs targeting myosin ATP consumption and how they can treat muscle diseases. [ABSTRACT FROM AUTHOR]

Copyright of Revista Ciencia y Tecnología Agropecuaria is the property of Agrosavia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study opens up exciting possibilities for the application of Co-MOF, a Metal-Organic Framework ([Co(5-NH 2 -bdc)(bpy)0.5(H 2 O)]3·2H 2 O), in the efficient removal of heavy metals (Pb2+, Hg2+, Cd2+, Cu2+) from water. The removal mechanism combines ion exchange and adsorption, influenced by the ionic radius of the metal ions. Langmuir's model determined maximum adsorption capacities (Qm), showing a proportional increase with the ionic radius of heavy metals: 75.47 mg/g (Cu2+), 344.82 mg/g (Cd2+), 485 mg/g (Hg2+), and 526.31 mg/g (Pb2+). Free Gibbs energy, inversely proportional to the metal's ionic radius, was determined as −36.43 kKj/mol (Cu2+), −28.67 Kj/mol (Cd2+), −24.13 Kj/mol (Pb2+), and −21.67 Kj/mol (Hg2+). The pseudo-second-order mechanism explained heavy metal removal, except for Cu2+, due to continuous ion exchange. Reutilization experiments showed a decrement in efficacy in the second cycle. Filtration experiments demonstrated a lower removal percentage (close to 60 %) and confirmed the competitive activity of Co-MOF compared to other MOFs, particularly in Cd2+ removal, with superior rate constants and maximum adsorption capacities. [Display omitted] • Removal of Heavy Metals Pb2+, Hg2+, Cd2+ and Cu2+ from Water using crystalline MOFs. • Kinetic and isothermal studies on the adsorption process of Pb2+, Hg2+, Cd2+ and Cu2+. • Co-MOF with high adsorption activity for the removal of Cd2+ from water. • Combination of ion exchange and adsorption mechanisms for heavy metal removal from water. • Pseudo-second-order mechanism confirmed for the removal of heavy metals Pb2⁺, Hg2⁺, Cd2⁺, and Cu2⁺. [ABSTRACT FROM AUTHOR]

actualmente, se están produciendo ceras por hidrotratamiento de aceite de palma, sin embargo, los productos obtenidos no siempre alcanzan las condiciones de punto de fusión y dureza requeridas por la industria cosmética. Debido a esta problemática, el interés de este trabajo fue evaluar un proceso de cristalización sin solvente con el objetivo de incrementar la temperatura de fusión y los rendimientos másicos de la biocera, acercándolos a los intervalos de los valores de las propiedades fisicoquímicas que requiere el mercado. Para cumplir con este propósito, se determinó el rango operativo de la temperatura de cristalización por calorimetría diferencial de barrido (dsc) y difracción de rayos X (drx). Una vez conocidos los puntos de cristalización, se procedió a calentar la muestra hasta los 50 °C y seguidamente se realizó un enfriamiento controlado hasta que la biocera 1 alcanzara los 40 °C para y de 30 °C para la biocera 2, y a estas temperaturas se consiguieron dos fracciones (líquida y sólida). Las fracciones sólidas presentaron un incremento en la temperatura de fusión de 47 °C a 49 °C para la biocera 1, y de 45 ºC a 47 ºC para la biocera 2. El proceso de cristalización no separó las diferentes familias de compuestos presentes en las bioceras, por lo que no se evidenciaron cambios significativos en los parámetros índice de acidez, saponificación y yodo. Además, futuras investigaciones en otras técnicas de refinación complementarias a la cristalización, como neutralización y decoloración, permitirán a la biocera de palma cumplir con los criterios de calidad internacionales para ser utilizada como ingrediente en las industrias cosmética y farmacéutica.

Flow behavior of three near eutectic Al–Si alloys with the same chemical composition but different average eutectic Si sizes (A1, 1.7 μm; A2, 4.4 μm; A3, 8.2 μm) was investigated by isothermal compression tests conducted on a Gleeble-3500 thermal simulator under four different temperatures (350 °C, 400 °C, 450 °C, and 500 °C) and four different strain rates (0.01 s−1, 0.1 s−1, 1 s−1, and 5 s−1), with a focus on the effect of eutectic Si size. Not only the flow behavior but also the processing map of near eutectic Al–Si alloys are affected by eutectic Si size. The overall trends of the flow stress–strain curves of the three alloys are similar, but their steady flow stresses σs are different: A1 alloy has the largest σs, followed by that of A3. Strain-compensated constitutive equations in the hyperbolic sine form were constructed to describe the flow stress behavior of the three alloys. Materials constants of the constitutive equations depend on eutectic Si size. The processing maps of the three alloys exhibit different characteristics. The instability domain of A2 alloy is restricted to strain rates larger than about 0.4 s−1, in contrast to the case of A1 and A3 alloys in which the instability domain occurs at both low and high strain rates. The results presented in this study indicate that eutectic Si size is an indispensable factor to be considered when dealing with the hot working of Al–Si alloys.

This article presents the results of applying three archaeometry techniques in archaeological ceramics from the upper river Madeira region in Amazonia. The first consists of the nuclear technique, neutron activation analysis (INAA), to identify the trace elements of the clay sources used in the production of the vessels. The second, non-nuclear X-ray diffraction (XRD), was used to characterise the mineral phases of each clay source. The third technique, electron paramagnetic resonance spectroscopy (EPR), estimated burning temperature related to the production stage of the artefacts. This approach made it possible to understand technological choices linked to selecting specific clay sources. The results suggest that different indigenous groups that inhabited the region between 940 and 760 B.P selected three clay sources to produce their vessels.

Resumen En la arqueología del Nordeste argentino son escasos los trabajos que estudian las condiciones de quema de la alfarería prehispánica, no habiéndose aplicado técnicas físico-químicas que midan las transformaciones que sufre la pared cerámica durante el proceso de cocción. Con el propósito de revertir este estado de situación, aplicamos difracción de rayos X, análisis térmico diferencial y termogravimétrico, y dilatometría sobre 31 muestras de cerámicas arqueológicas recuperadas en los sitios Los Tres Cerros 1 y Cerro Tapera Vázquez (Delta Superior del río Paraná). La mayoría de las muestras (i.e., contenedores restringidos y no restringidos, campanas y cuchara) fue cocida a temperaturas superiores a 550/650 ºC e inferiores a 800 ºC; cuatro no superaron los 550/650 ºC y dos fueron sometidas a temperaturas superiores a los 800/900 ºC. A partir de la integración de estos resultados con evidencia etnoarqueológica, experimental y arqueológica interpretamos el amplio rango de temperaturas de cocción detectado (< 550 ºC y > 800 ºC) como un indicador de quemas en estructuras abiertas (i.e., fogones o pozos). Esta información nos permitió discutir hipótesis sobre las condiciones de cocción propuestas en investigaciones previas y plantear a futuro un programa experimental que permitirá conocer distintos aspectos de las quemas prehispánicas.

To suppress the edge crack of the magnesium alloy sheet during the ordinary rolling process, a new rolling process named width-limited rolling was proposed in this paper. Width-limited rolling is a rolling method in which the width of the alloy sheet is limited by modifying the shape of the rollers, allowing a compressive stress field to form at the edge portion of the alloy sheet during rolling, resulting in the reduction of edge cracks. At present work, magnesium alloy sheets were separately subjected to ordinary rolling and width-limited rolling. The microstructure evolution and mechanical properties of the rolled sheets were investigated by EBSD, TEM, and XRD. The results exhibited that under the same rolling conditions, the sheet after ordinary rolling exhibited obvious edge cracks while no crack was found at the edge of the sheet after width-limited rolling. The edge crack suppressing effect was attributed to the reduction of the tensile stress along rolling direction during WLR, promoting the synchronous extension of the edge and center regions to suppress edge crack tendency. Microstructure observation showed that the compressive twins formed in the sheet after ordinary rolling usually exhibited as thin plates and cannot continue to fully develop due to the premature generation of the edge cracks. However, the compressive twins developed maturely in some of which double twins formed and various slip systems with different dislocation Burgers vectors occurred in the rolled sheet after WLR. More twin intersections and shear bands, providing more potential recrystallization nucleation sites, which are beneficial to weaken basal texture. With the cooperation of twinning and dislocation slip, the texture of the sheet after the width-limited rolling is weakened and the mechanical properties are improved. [ABSTRACT FROM AUTHOR]

Magnesium and magnesium-based alloys are widely used in the transportation, aerospace and military industries because they are lightweight, have good specific strength, a high specific damping capacity, excellent electromagnetic shielding properties and controllable degradation. However, traditional as-cast magnesium alloys have many defects. Their mechanical and corrosion properties cause difficulties in meeting application requirements. Therefore, extrusion processes are often used to eliminate the structural defects of magnesium alloys, and to improve strength and toughness synergy as well as corrosion resistance. This paper comprehensively summarizes the characteristics of extrusion processes, elaborates on the evolution law of microstructure, discusses DRX nucleation, texture weakening and abnormal texture behavior, discusses the influence of extrusion parameters on alloy properties, and systematically analyzes the properties of extruded magnesium alloys. The strengthening mechanism is comprehensively summarized, the non-basal plane slip, texture weakening and randomization laws are comprehensively summarized, and the future research direction of high-performance extruded magnesium alloys is prospected.

The thermal compression tests of Ti–Nb alloy under T = 790–940 °C and ε˙ = 0.001–10s−1 were carried out on the thermal simulation testing machine of Gleeble-3500. The flow stress curves were obtained, and the high-temperature rheological properties of the alloy were analyzed. The 3D activation energy maps were calculated and constructed. The LSSVM model of constitutive relation was established, and the penalty coefficient γ and kernel parameter δ of the LSSVM model were optimized by the genetic algorithm (GA). The constitutive model of the alloy based on the GA-LSSVM algorithm was constructed. The predicted value of the model was also compared with the experimental data. The polar reciprocity model (PRM) and dynamic material model (DMM) were used to establish the 3D processing map of the alloy and appropriate thermal processing parameters. The results indicated that T and ε˙ have a great influence on the flow stress of Ti–Nb alloy. Ti–Nb alloy is a negative temperature-sensitive and a positive strain rate-sensitive material. The correlation coefficient (R) of the GA-LSSVM algorithm constitutive model is 0.9958. The model has high prediction accuracy and strong generalization ability, which provide a new method for establishing a high-temperature constitutive model of materials. The PRM processing map is more accurate in optimizing the processing parameters of Ti–Nb alloy than that of the DMM processing map through analyzing the 3D processing map and observing the microstructure. The instability modes in the instability region of the alloy mainly include local flow. The stability region's predominant deformation mechanism is DRX. The 870–940 °C and 0.001–0.01s−1 are the best parameters during the processing of Ti–Nb alloy.

Thermal deformation behavior of a Ni-Cr-Fe superalloy billet were investigated by hot compression experiments under temperatures of 900–1200 °C and strain rates of 0.001–1 s−1, and the corrosion properties of the superalloy after thermal deformation were also evaluated by electrochemical tests. Compression experiments determined that lower strain rates and higher temperatures reduce the superalloy's stress levels. The Arrhenius-type model accurately described the thermal deformation behavior of the superalloy. Furthermore, the optimal hot working domain was identified between 1120 and 1170 °C and strain rates of 0.001–0.01 s−1. Microstructure observations showed that the dynamic recrystallization (DRX), characterized by grain boundary bending nucleation and consumption of numerous dislocations is the main mechanism leading to grain refinement during thermal deformation. The results of the electrochemical corrosion tests proved that the corrosion predominantly occurred near the grain boundaries (GBs) of deformed grains, worsening with increased deformation temperatures. • Thermal deformation of a Ni-Cr-Fe superalloy over a wide range of temperatures and strain rates. • The Arrhenius-type model and hot processing maps were established. • The microstructure and DRX mechanisms depend on compression process parameters. • The difference in corrosion resistance was closely associated with the evolution of microstructure. [ABSTRACT FROM AUTHOR]

The hot deformation behavior and dynamic recrystallization (DRX) of Fe-15Mn-15Al-5Ni-1C low-density steel in the as-cast state was investigated via hot compression experiments over temperature and strain rate ranges of 925 to 1150 °C and 0.01 to 10 s−1, respectively. A constitutive equation and a critical DRX model of the Fe-15Mn-15Al-5Ni-1C low-density steel were also constructed. The results showed that higher strain rates resulted in significant work hardening and subsequent rapid softening of the Fe-15Mn-15Al-5Ni-1C low-density steel, while lower strain rates resulted in predominantly steady-state flow behavior. The activation energy of deformation for the Fe-15Mn-15Al-5Ni-1C low-density steel was Q = 540 kJ mol−1 and the stress index was n = 4. The hot deformation mechanism was solute dragging and dislocation climbing, which was controlled by the strain rate. Increasing the deformation temperature or strain rate reduced the critical stress value σc of the DRX of the Fe-15Mn-15Al-5Ni-1C low-density steel and contributed to the DRX of austenite and δ-ferrite. The Fe-15Mn-15Al-5Ni-1C low-density steel after the hot compression deformation was mainly composed of austenite, ferrite, and κ carbide phases. [ABSTRACT FROM AUTHOR]

The prominence of Machine-to-Machine (M2M) communications in the future wide area communication networks place various challenges to the cellular technologies such as the Long Term Evolution (LTE) standard, owing to the large number of M2M devices generating small bursts of infrequent data packets with a wide range of delay requirements. The channel structure and Quality of Service (QoS) framework of LTE networks fail to support M2M traffic with multiple burst sizes and QoS requirements while a bottleneck often arises from the limited control resources to communicate future uplink resource allocations to the M2M devices. Moreover, many of the M2M devices are battery-powered and require a low-power consuming wide area technology for wide-spread deployments. To alleviate these issues, in this article we propose an adaptive semi-persistent scheduling (SPS) scheme for the LTE uplink which caters for multi-service M2M traffic classes with variable burst sizes and delay tolerances. Instead of adhering to the rigid LTE QoS framework, the proposed algorithm supports variation of uplink allocation sizes based on queued data length yet does not require control signaling to inform those allocations to the respective devices. Both the eNodeB and the M2M devices can determine the precise uplink resource allocation related parameters based on their mutual knowledge, thus omitting the burden of regular control signaling exchanges. Based on a control parameter, the algorithm can offer different capacities and levels of QoS satisfaction to different traffic classes. We also introduce a pre-emptive feature by which the algorithm can prioritize new traffic with low delay tolerance over ongoing delay-tolerant traffic. We also build a model for incorporating the Discontinuous Reception (DRX) mechanism in synchronization with the adaptive SPS transmissions so that the UE power consumption can be significantly lowered, thereby extending their battery lives. The simulation and performance analysis of the proposed scheme shows significant improvement over the traditional LTE scheduler in terms of QoS satisfaction, channel utilization and low power requirements of multi-service M2M traffic. [ABSTRACT FROM AUTHOR]

In this work, we prepared thin films of nickel sulfide by spray pyrolysis on substrates of the glass at temperature of 300°C. The solution used is a mixture of nickel acetate and thiourea as a source of nickel and sulfur respectively, acetic acid was used as a complexing agent, and then heated the resulting layers in an ordinary furnace at 300°C at different times of 1h, 2h and 3h to study the annealing time effect on the physical and chemical properties. The characterization methods used indicate remarkable changes in the structural, electrical, morphological and optical properties of NiS films under annealing time. The results obtained have shown that the prepared NiS films contain good crystallization, dense morphology, good stochiometric ratio and high conductivity, and these specifications make them a potential candidate as electrode material for application in super-capacitors. [ABSTRACT FROM AUTHOR]

The evolution of the communication and computation systems enables the user equipment (UE) to handle tremendous transmission data. However, the high-speed data processing also makes UEs release heat and might burn the chips inside the devices. The thermal issue would be more critical in millimeter-wave communications. The massive antenna arrays and the radio frequency modules not only drain the UE battery but also heat the devices. 3GPP also identified the thermal issue and suppressed heat generation by temporarily reducing UE capability in Release 15. In this work, instead of reducing the UE capability, we propose to apply the beam-aware Discontinuous Reception (DRX) mechanism to manage the power consumption and temperature of UEs simultaneously. We are the first to analyze the temperature for UEs with DRX configured. A semi-Markov model is provided, and we employ it to estimate the sleep ratio, packet delay, and steady temperature. We use a simulation program to verify the proposed analytical model. When comparing the beam-aware DRX with the baseline 5G NR DRX operation, we find that the beam-aware scheme reduces the steady temperature from $38.2^\circ C$ to $26.7^\circ C$ . The results show that Beam-Aware DRX could solve the thermal issue without sacrificing much performance of packet delivery latency.

Los minerales translúcidos fueron apreciados por las sociedades prehistóricas por su rareza, y fueron utilizados como elementos altamente simbólicos. Este trabajo aborda el uso y la caracterización de las cuentas translúcidas de la península ibérica, mediante análisis químico (espectroscopía Raman, espectrómetro de fluorescencia de rayos X portátil, difracción de rayos X y espectroscopia en región visible y en infrarrojo cercano) y contextual, junto a una revisión de la bibliografía arqueológica sobre la producción y uso de adornos y elementos translúcidos durante la Prehistoria Reciente ibérica. Un total de 54 cuentas de 47 yacimientos, mayoritariamente funerarios, han sido analizadas; 33 fueron trabajadas en fluorita, mientras que las restantes 21 fueron realizadas en distintos minerales translúcidos (calcita, cuarzo y varios silicatos). La escasez de adornos translúcidos en el registro arqueológico, su escala regional y suprarregional de intercambio, y su asociación recurrente a otros elementos de prestigio en contextos singulares refuerzan la hipótesis del alto estatus de sus poseedores/portadores.

To improve the deformation uniformity and plasticity of AZ80-Ag magnesium alloy, solid solution treatment was introduced before deformation. Isothermal compression tests for both as-homogenized specimens and pre-solution treated specimens were carried out and compared systematically. The results show that the coarse discontinuous precipitates (CDP) of β-Mg17Al12 were fully dissolved by the pre-solution pre-treatment, and the flow stresses were decreased greatly by 12.4–26.3 MPa. Moreover, the unstable region with the local plastic flow and cracking defects was significantly reduced. Eventually, uniform deformation is achieved for AZ80-Ag magnesium alloy by the pre-solution treatment, which shows great potential for magnesium alloy engineering application. Then, microstructure observations such as OM and EBSD were carried out and analyzed. Abundant lamellar {10–12} extension twinning appear 86.3° relationship occurs after pre-solution treatment, rather than few needle-like {10–12} extension twinning appear 7.4° relationship in as-homogenized specimen, is found out to be responsible for deformation plasticity improvement and defects eliminating. On the one hand, stress concentration along deformation twins are released by {10–12} extension twinning appear 86.3° effectively, which is verified by Kernel Average Misorientation (KAM) of the as-homogenized and pre-solution treated specimen. In the other hand, twinning induced dynamic recrystallization (TDRX) inside high dense lamellar twins is the main DRX mechanism for the pre-solution treated specimen, which accelerates DRX and further releases stress concentration.

Cu–0.65%Cr–0.08%Zr alloys display a superior combination of mechanical and electrical properties than pure copper. This is due to the solid solution hardening solubility of Zr and Cr as low content alloying elements in copper. However, for some applications, such as coils for high-power magnet, a CuCrZr alloy needs a mechanical strength substantially improved as well as good electrical conductivity. The main objective of this work is to investigate the influence of an equal channel angular pressing processing followed by aging heat treatment in the microstructure, mechanical and electrical properties of a CuCrZr commercial alloy. This procedure produced a very refined microstructure with high dislocation density in association with finely dispersed precipitates and minimum amount of elements in solid solution in the Cu matrix. The mechanical and electrical properties of the alloy were evaluated by Vickers hardness while the electrical conductivity was measured using the 4-point technique. The microstructural evolution was accompanied by the grain size measurements distribution, using backscattered electron diffraction (EBSD). Dislocation density was disclosed via X-ray diffraction (XRD). The alloy presented a remarkable improvement both in mechanical strength from 53 to 562 MPa and hardness from 96 to 192 HV/10, as well as sensible increase in electrical conductivity from 82% to 92% IACS. The resulting microstructure was characterized by an average smaller grain size of 0.7 μm and a higher dislocation density of 1014 m−2. These results reveal a promising potential for applying this commercial alloy in coils of high-power magnets.

In the fifth-generation (5G) wireless communication system, the Discontinuous Reception (DRX) is indispensable to user equipment (UE) to support evolved technologies. However, the directionality of wireless links, especially in millimeter wave bands, leads the existing DRX mechanism to unnecessary power consumption. In this paper, we first identify the problems of beam pattern mismatching. Then, we proposed a dynamic beam-aware DRX mechanism, which could be applied along with dynamic mmWave beam configuration. The proposed framework jointly optimizes beam-aware DRX operation and dynamic mmWave beam configuration for better energy efficiency. A semi-Markov model is proposed to evaluate a UE sleeping ratio and packet delay. The simulation validates the proposed model. Compared to the baseline 5G NR DRX operation, the proposed scheme achieves 41.6% improvement in the sleep ratio without sacrificing the packet delivery latency performance.

Silica submicronic particles doped with Dy and Gd paramagnetic ions were successfully synthesized by using chemical synthesis based on the modified Stöber method, having potential applications as contrast agents for magnetic resonance imaging (MRI).Structural characterization analyses show an amorphous character of the particles (XRD), good thermal stability (DTA), and spheroid shape (SEM). The integration of paramagnetic ions into the silica network was demonstrated by the TEM, EPR and FTIR spectroscopies.The magnetic resonance (MR) relaxivity examinations of the samples show a high rate of relaxivity for the particles doped with Dy, making them suitable as T2 contrast agent for magnetic resonance imaging. This is in contrast to the results obtained on the particles doped with Gd, which are an effective T1-weighted MRI contrast agent. Notably, if the silica structure incorporates both Gd and Dy the particles are suitable for contrast enhancement in both T1 and T2 weighted images. These characteristics of the samples are also supported by the value of the relaxivity ratio (r2/r1) for the three samples doped with paramagnetic ions. The results confirm the sustainability of MRI contrast agent applications for all three synthesized samples.

Extrusion of unhomogenized castings of the 7075 aluminum (Al) alloy has been accomplished using shear assisted processing and extrusion (ShAPE). The simultaneous plastic deformation and heat generation during ShAPE rapidly fracture and dissolve interdendritic and intragranular secondary phases of Al-Zn-Mg-Cu, accomplishing homogenization in seconds rather than many hours in a furnace before extrusion. ShAPE thereby eliminates the energy-intensive and time-consuming homogenization step required to prepare as-cast microstructures for conventional extrusion. Concurrently, extensive grain refinement occurs due to gradient activation of dynamic recrystallization during ShAPE, which facilitates a threefold increase in extrusion speed compared to the conventional extrusion method. Evident enhancement of the mechanical properties of ShAPE + T6 samples is achieved, compared to the ASTM standard values for conventional extrusion products. The microstructural evolution pathway, involving the processes of grain refinement and secondary particle dissolution, is explained using scanning and transmission electron microscopy.

Cobalt-based superalloys are common materials for the manufacturing of various components used in aerospace applications. Conventional cobalt-based superalloys with a unimodal grain structure generally exhibit low strength and ductility at high temperatures. A bimodal grain structure of a cobalt-based superalloy, Co–20Cr–15W–10Ni (CCWN), was designed to achieve both high strength and ductility at high temperatures. The deformation behavior and tensile properties of a CCWN alloy with unimodal fine-grain (FG), coarse-grain (CG), and bimodal (FG/CG) structures were investigated at 900 °C. The microstructures and substructures after high-temperature deformation were examined via electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) to determine the deformation mechanisms. The microstructural observation showed that the bimodal grain structure consisted of FG and CG domains. During high-temperature deformation at 900 °C, the FG structure was mainly deformed by dynamic recrystallization (DRX), maintaining a similar FG structure. The CG structure was mainly deformed by DRV, resulting in a small amount of DRX grains and a large amount of dynamic recovery (DRV) grains. However, the bimodal grain structures were mainly softened via DRX and transformed into a new bimodal structure, ultrafine grain (UFG) and FG. The FG domains tended to deform via dislocations, and the CG domains via twinning. The high-temperature tensile tests revealed that the bimodal-structured alloy exhibited both higher strength and ductility than those of the alloy samples with unimodal FG or CG structure. This is associated with the newly developed UFG/FG structures in the bimodal grain-structured samples during high-temperature deformation. This work may provide new insight into the development of high-temperature alloys with bimodal grain structures.

Carbon steel AISI 1020 was exposed to environmental conditions along a transect of the Atacama Desert to gather experimental evidence to identify the local atmospheric mechanism that triggers corrosion through a buildup of water layer formation on the metal surface in addition to corrosion evolution. Coupons initially left in selected sites were periodically collected to determine weight loss and surface attributes by scanning electron microscopy and X-ray diffraction. In addition, meteorological conditions were measured in addition to a fog water collector in one site. During the study period, the predominant conditions were the absence of rain, clear skies, and large daily oscillations in temperature and relative humidity. The evidence indicates a water film formation on a metal surface either from a vertical water flux as fog water droplets and/or by the dew water harvesting mechanism. The uptakes of oxygen and chlorides during the corrosion process were highest in the coastal site P0 and gradually decreased with the increasing distance from the coast. This is attributed to both humidity and saline marine fog intrusion from the coast. The oxide layer evolved to form a compact layer with main constituents of lepidocrocite, goethite, and lesser amounts of akageneite. The corrosion depth can be modelled by a simple power function d=AtB with B < 1, indicating a deceleration process.

This study deals with the investigation of synthesized (NH2CONH2)CdCl2(Urea-CdCl2) complex properties. X-ray diffraction (XRD) and infrared (IR) measurements are carried out to characterize structural properties. XRD indicates that this compound crystallizes in triclinic system withP1¯space group. IR spectrum proved that the cohesion between the organic and inorganic groups is insured by the CdO bonds. Besides, the optical properties were examined by ultraviolet visible (UV–vis) and photoluminescence (PL) spectroscopies. The Urea-CdCl2 exhibits high absorbance in the UV and good transparency in the visible domain. Besides, Urea-CdCl2 shows a broad bluish emission. Moreover, the toxicity of the Urea-CdCl2 Complex was tested against normal kidney cell line (HEK293) and two cancers cell lines (MDA and T47D). The obtained results showed that Urea-CdCl2 improved the toxicity against the breast cancer line T47D.

The study of oxygen reduction reaction (ORR) in 0.5 M NaCl on copper revealed that oxygen reduction reaction rates are markedly influenced by the surface condition and increased in the following order: covered with PDTC < pre-reduced < passivated surfaces. On pre-reduced and passivated surfaces, the ORR proceeded via a four electron pathway limited by oxygen diffusion. When the surface is passivated, the ORR is influenced by a combination of the reduction of copper oxide and the normal kinetics of ORR at a pre-reduced surface. The partial reduction of Cu2O oxide enhances the ORR kinetics. A surface covered with PDTC represents the least reactive site towards ORR process. The current densities decreased significantly due to the limitation of O2 access to the surface by the formation of a protective barrier layer. PDTC molecules are bonded on copper surface and form an inhibitive adsorption layer, which plays a major role in slowing down O2 reduction by blocking the active cathodic sites.

Characterization of Ceiba aesculifolia (CA) fibers by various techniques is herein reported. The seed pods were collected, and the fibers surrounding the seeds were characterized or treated in an oven at 100 °C prior to characterization by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis coupled with a differential scanning calorimeter (TGA-DSC). The SEM micrographs showed that the natural material is comprised of tubes of external diameter of approximately 27 µm and a mean wall thickness of about 0.62 µm. The results also indicated that the tubes begin to decompose at approximately 220 °C. [ABSTRACT FROM AUTHOR]

Hot deformation plays a crucial role in strengthening and toughening of aluminum matrix composites, but the high hot deformation resistance and the microstructure defects generated after deformation need to be solved urgently. In this paper, a new material, B 4 C@B 2 O 3 /Al composites, with the low melting point B 2 O 3 phase at the interface, has been successfully prepared and the hot deformation behavior was studied in detail. By comparison, the hot deformation resistance and activation energy of the B 4 C@B 2 O 3 /Al composites is significantly lower than that of the B 4 C/Al composites. The softening mechanism of the B 4 C@B 2 O 3 /Al composites is mainly dynamic recrystallization (DRX) and the critical stress of DRX is much lower for the B 4 C@B 2 O 3 /Al composites than for the B 4 C/Al composites, while the volume fraction of DRX is higher than for the B 4 C/Al composites. Compared with the B 4 C/Al composites with similar particle content, the hot deformation temperature of the B 4 C@B 2 O 3 /Al composites decreases, but with high strength-plasticity compatibility (with tensile strength of 560 MPa and elongation of 4.2 %). This work provides an effective method to reduce the hot deformation resistance of the B 4 C/Al composites and explains the micro mechanism, guiding low-stress forming of the B 4 C/Al composites with high volume fraction and good mechanical properties. [ABSTRACT FROM AUTHOR]

In this work, we have studied two Kaolin .kaolin DD1 which consists of two main phases (kaolinite and Halloysite) and Tamazert kaolin .kaolin KT2 whose main constituents are kaolinite, quartz and mica. Our choice was set on the component that is Kaolinite because of the existence of the latter in both kaolins. A correction of Lorentz-Polarization was carried out prior to the diffraction data, which has been achieved using LWL program dome. The true profile was extracted by this program. The methods used for the micro structural analysis of the present in the two Kaolins are the Warren - Averbach and the Williamson – Hall methods Scherrer's relationship has been applied in cases where the compound is devoid of strains. The study revealed that the kaolin Kaolinite DD1 is devoid of micro constraints. Which similar analysis has shown that the Kaolinite in KT2 incorporates the strains. This was confirmed by the Williamson - Hall method as well as Fourier analysis. The evaluation of strains in the Kaolinite of KT2 has been dome the method of Warren - Averbach and Williamson – Hall diagram. The average value of this constraint found by the first method us 0.15 and 0.21 by the second method gave. The average size of crystallites of the Kaolinite in DD1 was found between 29 Å and 230 Å. by the method of Warren - Averbach and about 118 Å by the method of Williamson - Hall. Range the second Kaolinite the Kaolinite KT2, the size obtained was respectively 98 Å and 130 Å using to by methods. The study of the size distribution showed that the dominant size of Kaolinite in DD1 and KT2 is about 40 Å (42%) and 58 Å (32%). respectively.

The device-to-device (D2D) communication integrated with the millimeter-wave (mmWave) air interface will play a significant role in the future mobile communication in terms of high transmission rate and deployment flexibility. Meanwhile, unmanned aerial vehicles (UAVs) are promoted as D2D nodes to support D2D-enabled networks for broad coverage. In this paper, we provide a new D2D-based UAV mmWave communication framework, in which the UAVs are mobile nodes and have stringent energy constraints. Therefore, the energy-efficient technology which can turn on the UAVs' radio only when necessary and overcome the resulting easily-occurred beam misalignments due to the radio OFF periods and the aircrafts' agile mobility is required urgently. To tackle this issue, we propose a novel fast beam tracking discontinuous reception (FBT-DRX) mechanism. A new Semi-Markov model is designed to analytically investigate the statistical property of the proposed scheme. Different from many published works on DRX with beamforming, we take the impact of UAV movements into account when deriving the exact closed-form expressions of sleep ratio and average packet delay. Finally, the numerical results are supplied to evaluate the effects of different key parameters on the system performance, and demonstrate that the FBT-DRX mechanism can perform well both in power saving and packet delay in the considered framework.

La correcta identificación de los materiales que conforman los bienes muebles del patrimonio científico-técnico y de las interacciones entre los mismos es necesaria para establecer estrategias de conservación eficaces con criterios de intervención adaptados. En este trabajo se presenta un estudio del estado de conservación, materiales y patologías de la colección de extintores del Museo Nacional de Ciencia y Tecnología. Se ha realizado una base de datos con 56 extintores, documentando cada pieza, tipología y estado de conservación. Los análisis realizados en varias de ellas (por fluorescencia de rayos X y difracción de rayos X) han permitido identificar los materiales de los extintores, en algunos casos del contenido de los mismos, y establecer mecanismos de degradación. En el caso de los extintores de espuma y de agua, se ha mostrado que el agente extintor es altamente corrosivo y ha causado daños severos a la pieza. En estos casos, resulta aconsejable eliminar el contenido si se quiere asegurar una correcta conservación de los extintores.