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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.

Hot deformation studies of a newly designed γ + α2 based TiAl alloy of composition Ti–42Al–6Nb–3Cr–0.1B at.% (nominal) realized through ingot metallurgy route using double vacuum arc remelting were carried out. Hot isothermal compression testing was performed in Gleeble™ 3500 at different temperatures ranging from 1123 to 1373 K at 50 K intervals and strain rates of 0.001–1 s−1. Processing maps were developed using an approach of dynamic material modeling of the flow curves to establish the safe hot working regime. Strain rate sensitivity and Zener–Holloman parameters were calculated and constitutive equation was derived. Microstructural investigation revealed dynamic recrystallization and activation of multiple twin systems as the main softening mechanisms operating at optimum hot working conditions. Safe hot working temperature and strain rate regime for the alloy was found to be in the temperature range of 1323–1373 K and strain rate range of 0.001–0.01 s−1. [ABSTRACT FROM AUTHOR]

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.

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Starch gelatinization and water penetration into starch granules are studied in the presence of sucrose by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). The water content of the samples ranged from 70% to 20% (w/w wsb) and two modes of preparation are used: All‐In‐One (AIO) and Sucrose‐Syrup mixed with Flour (SS + F). A shift of the gelatinization to higher temperatures is observed and an increase in its enthalpy, thus implying stabilization of the granular structure during heating. In addition, the AIO method shows that sucrose has priority over wheat starch in terms of access to water. With either an excess of water or a limited water content, the AIO method shows that the solubilization of sucrose is favored water penetration into the starch granules. XRD analysis is performed in a heating cell using the same time‐temperature profile, showing that there is a link between the endotherm of gelatinization and the moment when the amorphous regions of the granules are sufficiently mobile to impose stresses on the lamellar crystals and thereby trigger their destruction. This work provides new information showing the importance of sucrose dissolution and water content on starch gelatinization in the cake and biscuits application. [ABSTRACT FROM AUTHOR]

High temperature service capability and deformation behavior of γ + α2 TiAl alloy made through ingot melting route has been studied under tensile load at temperature (T = 750–900 °C) and strain rate ( ε ˙ = 10−1–10−3 s−1). Reduction in strength is not seen till 800 °C at all the three strain rates, indicating safe use of alloy up to this temperature. Further, it has been observed that % elongation to failure (ef) increases with increase in T or decreasing ε ˙ . Significant increase in ef is observed with decrease in ε ˙ from 10−2 to 10−3 s−1 at test temperature of 850 °C or above. At 900 °C and 10−3 s−1, ef is observed to be 47%. Microstructure consisting of γ and α2 phases with lamellar morphology and β phase are distributed uniformly along grain boundaries. Refinement of lamellae and dynamic recrystallization (DRX) assisted by twinning is found to be the primary reason for flow softening, which lead to improvement in ef of alloy at T ≥ 850 °C. It is observed that temperature plays a major role in initiation of DRX as observed with increasing T whereas ε ˙ plays major role in twinning as observed with decreasing ε ˙ even at lower temperatures. [ABSTRACT FROM AUTHOR]

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]

The hot deformation behavior of pre-forged AZ80 magnesium alloy is investigated by the isothermal compression tests at temperatures of 523–683 K and strain rates of 0.0001–0.1 s−1, and analyzed by the processing maps for guiding isothermal die forging. Flow localization and even cracking occurs at low temperatures and high strain rates, where shear deformation degree shows a positive correlation with the ξ ε ˙ value. Two stability regions with high efficiency is found out by the processing maps. At common stability region with high temperatures and low strain rates, peak power dissipation efficiency does not represent optimum deformation condition as reported in other materials. A Z parameter criterion is introduced for parameters optimization. javascript:void(0); a new stability domain of 523–590 K and 0.0001–0.01 s−1 is observed, which is typical for fine microstructure composed of equiaxed clean α-Mg grains and big particles both about 1 µm (573 K/0.01 s−1). Super plasticity is speculated to occur at that condition. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of Mg-Ga-Sn alloys at 360–450 °C and 0.001–1 s−1 was systematically studied by using a thermal simulator. The flow stress is affected by temperature and strain rate, which basically accords with hyperbolic sine constitutive equations. Based on the experimental data, the prediction accuracy of the stress correction model and the artificial neural network (ANN) model was comprehensively compared for the alloy system. The ANN model has good prediction accuracy and a certain degree of extrapolation and generalization ability. By observing the microstructures, the hot processing maps of the ANN modified model were ultimately determined to be closer to the real situation, and the hot processing maps were partially expanded (450–480 °C, 1-2 s−1). Based on the hot processing maps, the suitable processing range (360–450 °C, 0.001–0.01 s−1; 390–420 °C, 0.4–1 s−1) was determined, and a possible processing range (450–480 °C, 0.001–2 s−1; 390–450 °C, 1-2 s−1) was predicted. The EBSD results revealed two typical dynamic recrystallization mechanisms (CDRX and DDRX) in the alloy, corresponding to a strong <0001>//CD texture. In the region of higher temperature and lower strain rate, an obvious bimodal texture is found in the alloy, which is related to the promotion of nonbasal slip by Ga. [Display omitted] • The ANN model exhibits higher prediction accuracy than the stress correction model. • The processing map modified by ANN more closely reflects to the actual situation. • The formation of LAGBs is promoted at high strain rates. • The bimodal texture is related to the addition of Ga. [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]

Al-Cu-Li alloys exhibit enhanced performance when possessing a high substructure proportion and a low recrystallization proportion. To achieve this, it necessitates a thorough understanding of recrystallization behavior during its hot working and heat treatment. To this end, isothermal compression tests were conducted on an Al-Cu-Li alloy in the temperature range of 350–500 °C and strain rate range of 0.01–10 s−1. The deformed specimens underwent solution treatment at 530 °C/2 h followed by water quenching, and aging treatment at 155 °C/27 h. The microstructures of the deformed and heat-treated specimens were characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). During hot deformation, continuous dynamic recrystallization (CDRX) dominates when the natural logarithm of the Zener-Hollomon parameter (lnZ) >26 and discontinuous dynamic recrystallization (DDRX) predominates when lnZ ≤ 26. A low proportion kinetic model associated with lnZ was constructed to describe the DRX behavior, and the model parameters were optimized using genetic algorithm (GA) to improve accuracy. During heat treatment, substantial static recrystallization (SRX) occurs following deformation at lnZ > 30, while it is limited when lnZ < 27. The comparison of average geometrically necessary dislocations (GNDs) before and after heat treatment reveals that the consumption of dislocations increases with increasing lnZ. Statistical analysis indicates that the density of low/medium angle grain boundaries (L/MAGBs) can be increased and the recrystallization fraction can be decreased within the lnZ range of 24 to 27. Therefore, these specific hot deformation conditions are recommended as the optimal hot working window for the Al-Cu-Li alloy. • The effect of secondary phases on the DRX behavior of the Al-Cu-Li alloy was analyzed. • A GA-optimized low proportion kinetic model for DRX of the Al-Cu-Li alloy was constructed. • The effect of hot deformation on SRX behavior during heat treatment was revealed. • A specific lnZ range that resulted in high substructure volume fraction and low recrystallization volume fraction was determined. [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.

Improved mobile device battery lifetime and latency minimization are critical requirements for enhancing the mobile broadband services and user experience. Long-term evolution (LTE) networks have adopted discontinuous reception (DRX) as the baseline solution for prolonged battery lifetime. However, in every DRX cycle, the mobile device baseband processing unit monitors and decodes the control signaling, and thus, all instances without any actual data allocation leads to unnecessary energy consumption. This fact together with the long start-up and power-down times can prevent adopting frequent wake-up instants, which, in turn, leads to considerable latency. In this work, a novel wake-up scheme is described and studied, to tackle the trade-off between latency and battery lifetime in future 5G networks, seeking thus to facilitate an always-available experience, rather than always-on. Analytical and simulation-based results show that the proposed scheme is a promising approach to control the user plane latency and energy consumption, when the device is operating in the power saving mode. The aim of this article is to describe the overall wake-up system operating principle and the associated signaling methods, receiver processing solutions and essential implementation aspects. Additionally, the advantages compared to DRX-based systems are shown and demonstrated, through the analysis of the system energy-efficiency and latency characteristics, with special emphasis on future 5G-grade mobile devices. [ABSTRACT FROM AUTHOR]

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.

Presentamos los resultados experimentales obtenidos del análisis microestructural de películas delgadas de ZnO con 20, 50 y 100 nm de espesor, crecidas sobre el sustrato de vidrio comercial por pulverización catódica reactiva. Analizamos la información cuantitativa sobre tamaño de los dominios cristalinos, dirección de textura de las nanocolumnas, sus densidades, espesores, rugosidad supercial y interfacial obtenida a través de técnicas de caracterización como la microscopía electrónica de barrido (MEB), la reflectividad de rayos X (XRR) y la difracción de rayos X (DRX).

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.

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.

The thermal deformation behaviour of Mg-9Gd-4Y-2Zn-0.5Zr alloy at temperatures of 360–480 °C, strain rates of 0.001–1 s−1 and a maximum deformation degree of 60% was investigated in uniaxial hot compression experiments on a Gleeble 3800 thermomechanical simulator. A constitutive equation suitable for plastic deformation was constructed from the Arrhenius equation. The experimental results indicate that due to work hardening, the flow stress of the alloy rapidly reached peak stress with increased strain in the initial deformation stage and then began to decrease and stabilize, indicating that the deformation behaviour of the alloy conformed to steady-state rheological characteristics. The average deformation activation energy of this alloy was Q = 223.334 kJ·mol−1. Moreover, a processing map based on material dynamic modelling was established, and the law describing the influence of the machining parameters on deformation was obtained. The experimental results indicate that the effects of deformation temperature, strain rate and strain magnitude on the peak dissipation efficiency factor and instability range were highly significant. With the increase in the strain variable, the flow instability range increased gradually, but the coefficient of the peak power dissipation rate decreased gradually. The optimum deformation temperature and strain rate of this alloy during hot working were 400–480 °C and 0.001–0.01 s−1, respectively.

Poly(vinyl chloride) (PVC)/Zinc oxide (ZnO) nanocomposite films were synthesized by the sol–gel (spin coating) method using tetrahydrofuran as a solvent. Structural, Optical properties and photocatalytic activities with different nanosize zinc oxide (ZnO) concentrations (8%, 10% and 20%) have been studied. The samples were characterized by XRD, RAMAN, FTIR, UV–Vis spectrophotometer, and photoluminescence. X-ray diffraction measurements indicated that the average particle size of the ZnO is varying between 17 and 24 nm. Characterization by Raman spectrometry of the nanocomposites studied revealed the additional low-intensity lines which characterize the wurtzite phase of hexagonal ZnO (wurtzite type) in the host matrix (thin film) of PVC and highlights the good crystalline quality (low density of defects) of ZnO nanocomposites. The results of the FTIR infrared spectroscopy analysis of the PVC/ZnO nanocomposites confirmed the presence of peaks characteristic of the vibration of the Zn–O bond. This characterization also shows an increase in the visibility of the absorption band of ZnO with the increase in doping percentages. UV–Vis optical spectra revealed that the optical band of nanocomposites decreases with increasing concentration of ZnO nanoparticles in the PVC matrix. It was found that the band gap is 3.69, 3.64 and 3.52 eV for xZnO/PVC nanocomposites (x: 8%, 10%, and 20%). The photoluminescence spectra of the samples were found to be strong green luminescence. PVC/ZnO nanocomposites have revealed a wide band of luminescence that stretches from visible to near UV. These results confirm the introduction of ZnO in nanoscale form into PVC matrix. The photocatalytic reaction was depicted using MB in the UV-irradiation action of stacked films in methylene blue (MB) solution. The result showed 20ZnO/PVC films gave efficiency to remove MB by 80% at 60 min, similar to the films (8ZnO/PVC) and (10ZnO/PVC), which gave lower efficiency. The occurrence of dye degradation under light might attribute to the high-charge separation of ē-h pairs at the interfaces of PVC and ZnO nanoparticles in its excited state under irradiation. [ABSTRACT FROM AUTHOR]

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The isothermal compression test was employed to study the influence of deformation temperature and strain rate on the hot deformation behavior of C71500 copper-nickel alloy. According to the characteristics of dynamic recovery (DRV) and dynamic recrystallization (DRX), the Zener–Hollomon parameter lnZ is used as an important parameter to measure the influence of temperature and strain rate on the hot deformation behavior. The critical deformation conditions of DRX are determined by its different values. By analyzing the critical change of work hardening rate, the relationship among critical stress, peak stress and saturation stress transition point is obtained, and the dynamic mathematical model of the whole deformation process is established, which can predict the volume fraction of DRV and DRX well. The DRX nucleation and growth mechanism of C71500 copper-nickel alloy was determined by metallographic analysis. In the current work, the thermodynamic parameters are introduced to determine the critical conditions of the transformation of the deformation state, the transformation process of the hot deformation structure is predicted by the dynamic model, the nucleation and growth mechanism is analyzed, which could provide a complete set of important references for the DRV-based hot deformation alloy, and provide a theoretical basis for the control of the structure state after hot processing. [ABSTRACT FROM AUTHOR]

En este aporte se presentan resultados de estudios experimentales, petrográficos y de difracción de rayos X (DRX) tendientes a determinar el origen de las materias primas utilizadas por los alfareros de El Sunchal (Anfama, Tucumán) durante el primer milenio de la Era. Para ello, se ha identificado la ubicación de probables fuentes de aprovisionamiento en el valle, evaluando la factibilidad de utilización y calidad de distintas vetas mediante la realización de muestras experimentales. Las briquetas resultantes de la experimentación se compararon con las pastas arqueológicas de los grupos tecnológicos principales, a partir de la observación petrográfica de veintidós cortes delgados, y de DRX de siete fragmentos. Los resultados obtenidos permitirían plantear la proveniencia local de las materias primas utilizadas.

During the deformation of Mg alloys, {10-12} extension twin, as one of the most active deformation mechanisms, contributed much to the formation of basal texture, yet little to dynamic recrystallization (DRX) grains, i.e., effective grain refinement. In this work, {10-12} extension twin had been creatively utilized to achieve grain refinement and property improvement in a Mg-Gd-Y alloy by multi-directional impact forging (MDIF). Firstly, flourishing {10-12} extension twins divided the parent grain into many fine independent regions (~10 μm). Meanwhile, a large number of twin boundaries were pinning mainly by interaction with neighboring dislocations in twin or matrix. Secondly, those pinned twin boundaries can effectively accumulate dislocation slips and promote the formation of extensive low angle grain boundaries (LAGBs). These high densities of LAGBs can further subdivide the independent regions provided by extension twins into micro-regions (~5 μm). Thirdly, those fine micro-regions developed to be DRX after a dynamic recovery. Finally, we obtained a yield isotropy high-strength Mg alloy with an ultimate tensile strength of 354 MPa after MDIF of 110 passes. This work proposed a brand new insight to prepare wrought Mg alloy with fine grain, yet without strong texture, which is beneficial to better formability and mechanical property isotropy.

Este artículo estudia la capa de óxido formada en acero al carbono expuesto a ambientes marinos naturales y urbano-continentales durante 50 años. La composición de la fase mineralógica de la capa de óxido se evaluó mediante difracción de rayos-X (DRX), se identificaron las fases akaganeita, goetita, lepidocrocita, magnetita y amorfa. La caracterización morfológica de las muestras se realizó mediante microscopía electrónica de barrido (MEB) y microanálisis por dispersión de energía de rayos-X (EDX). La tensión mecánica generada durante la formación del óxido provoca la ruptura mediante exfoliación de la capa de herrumbre. La variación de volumen causada por las transformaciones estructurales y la presión de cristalización (Δp) de las fases cristalinas se analizaron para evaluar la tensión mecánica sobre la herrumbre y se encontró una relación lineal entre el coeficiente de expansión de volumen molar (α) y el parámetro Δp. La Δp más elevada fue producida por la goethita (374.99 MPa), mientras que la akaganeita presentó el valor α más alto (3.29).

Sobre la superficie de la aleación de magnesio AZ61 se aplicaron recubrimientos de sol-gel basados en el precursor GPTMS-TMOS, incluyendo como agentes dopantes L-Cysteína y ZrO2 en diferentes concentraciones. Su resistencia a la corrosión se estudió en solución de 0,6M NaCl, por inmersión hasta 14 días. Los patrones de DRX revelaron que el principal producto de corrosión en las superficies recubiertas es Mg(OH)2, mientras que en la de AZ61 no tratada adicionalmente se formaron varios compuestos de Zn con cloro. El ataque de la corrosión localizada en el AZ61 no tratada se manifiesta en forma de grietas y cavernas, mientras que en las superficies recubiertas la corrosión fue principalmente a través de picaduras. Dos métodos electroquímicos no destructivos fueron empleados en este estudio, que contrastan el comportamiento electroquímico del AZ61 recubierto con el de la aleación no recubierta. La tendencia en los cambios del potencial de corrosión en circuito abierto se correlacionó positivamente con el análisis SEM-EDS y DRX. Los diagramas EIS se ajustaron satisfactoriamente al modelo de circuito equivalente y los valores obtenidos de resistencia a la corrosión Rcorr (Rs + Rct) disminuyen drásticamente con el tiempo de exposición. El efecto de ZrO2 y L-cisteína están marcadamente influenciados por los cambios del pH de la solución, el potencial Zeta de la carga superficial, los procesos de quimisorción y desorción, el estrés interno en el precursor sol-gel, así como el cambio en su estructura, después de la encapsulación de ambos dopantes.

Se estudió el efecto del cromatizado, por ser un recubrimiento de conversión utilizado para lograr mayor protección sobre infinidad de recubrimientos metálicos. Se hace por inmersión del recubrimiento de Zn o ZnNi en la solución acuosa de cromatizado que contiene sales de Cr3+ (cromatos de sodio y de potasio). Los estudios de caracterización se han realizado por SEM, EIS, Curvas de Polarización, Espesores y Contenidos de Ni que se midieron por Fluorescencia (FRX). Los resultados y conclusiones relevantes con cromatizado Cr3+ indican que los contenidos de Ni aumentan a 16%, los potenciales se desplazan a valores más positivos o nobles (100 mV) y las corrientes de corrosión son menores. Los porcentajes de Ni son mayores con Cr3+, porque se produce disolución del metal de base y ocurre luego la formación de una película barrera con cromo, más protectora. La fase , que es típica del ZnNi, se intensifica con cromatizado.

El primer componente para la fabricación de productos de mampostería para la construcción es la arcilla, la cual aporta la plasticidad que facilita el moldeo y el manejo del producto. El segundo componente es el feldespato en su formación como alúmina ( Al2O3 ) que se utiliza como fundente. La tercera es la sílice ( SiO2 ) que se utiliza como un material de relleno y estabilizador. Estos elementos se determinan mediante la composición química por análisis de fluorescencia o difracción de rayos X, la cual es la base de la clasificación moderna de los minerales. De esta manera, el principal objetivo de este trabajo es estudiar las características superficiales de muestras de arcilla de una empresa dedicada a producción de bloques H-10 en la región Norte Santandereana, mediante el estudio de las superficies de las muestras seleccionadas a través de la técnica de Microscopía de Fuerza Atómica con el propósito de comparar los resultados con los obtenidos en la bibliografía teniendo en cuenta los elementos químicos en su mayor composición. Los resultados demuestran que ésta es una técnica que permite identificar los componentes de la arcilla validando de esta manera lo encontrado en los análisis físicos y químicos, con lo cual se espera brindar un aporte científico por AFM o MFA, debido a que existe poca información relacionada en la caracterización topográfica de materiales arcillosos.

Power saving is a salient issue regarding the 4G LTE network. In wireless networks, the frequent checking of the usage of the user equipment may lead to excessive power consumption, and the discontinuous reception mechanism of the LTE is implemented to avoid such excess. The DRX trade-off metrics between power saving and the delay constraint are investigated here for an improvement in the performance. In order to meet the UE QoS, this paper suggests a predictive mechanism with a delay constraint for the traffic patterns. The results for various traffic patterns show that the suggested mechanism offers beneficial power-saving effects while satisfying the UE QoS. [ABSTRACT FROM AUTHOR]