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[en] Ti–15Nb–xGe alloys with x = 0.8, 1, 1.2, 1.4, 1.6 and 1.8 (wt%) compositions for the first time. Theoretical calculations were performed with the generalized gradient approximation (GGA) functional within density functional theory (DFT). We employed the Perdew–Burke–Ernzerhof (PBE) scheme and the virtual crystal approximation (VCA) in this study. We determined the elastic constants, bulk, shear and Young’s moduli, Pugh ratio, Poisson’s ratio, universal anisotropy and hardness of all the alloys under varying Ge% concentrations. All studied compositions of the alloys show structural stability. Young’s moduli values were obtained as 43 and 14.8 GPa for Ti–15Nb–0.8Ge and Ti–15Nb–1.8Ge alloys, respectively, which compare well to the Young’s moduli range of human cortical bone with 10–30 GPa. Except the Poisson’s and Pugh ratios, all other computed parameters of the alloys were found to decrease under increasing Ge concentrations. Further, all investigated alloys exhibit desired ductile mechanical behaviour of biomaterials and calculated hardness values of these alloys are satisfactory with the hardness of human teeth dentin. (author)
[en] Phase-change material (PCMs) store data using the contrast (electrical or optical) between two phases: a conductive crystalline phase and a weakly conductive amorphous phase. Most PCMs have a distorted octahedral structure. The contrast comes mainly from the electronic structure. In PCMs, a spontaneous symmetry breaking mechanism, the Peierls distortion, transforms the metallic crystalline structure into a lower-density semiconducting structure. In a simple tight-binding model of the covalent bond, the parameters that control this distortion, characterized by a parameter η, are analyzed. The effective interatomic potential E(η) is developed in a Landau-type series in η: E(η) = E + Eη + Eη. The PCMs with the largest contrast are those for which the effective potential E(η) of the crystalline phase has a disappearing harmonic contribution (E = 0) and a vanishing electronic gap. This is called as an ''incipient Peierls distortion.'' It coincides with the so-called ''incipient metal''. The hardness of the repulsive potential and the number of electrons per atom play an important role. The vibrational properties and the anomalous Grüneisen parameter, specific to PCMs, are also studied. (© 2021 Wiley‐VCH GmbH)
[en] Fibre-reinforced concrete (FRC) allows reduction in, or substitution of, steel-bars to reinforce concrete and led to the commonly named structural FRC, with steel fibres being the most widespread. Macro-polymer fibres are an alternative to steel fibres, being the main benefits: chemical stability and lower weight for analogous residual strengths of polyolefin-fibre-reinforced concrete (PFRC). Furthermore, polyolefin fibres offer additional advantages such as safe-handling, low pump-wear, light weight in transport and storage, and an absence of corrosion. Other studies have also revealed environmental benefits. After 30 years of research and practice, there remains a need to review the opportunities that such a type of fibre may provide for structural FRC. This study seeks to show the advances and future challenges of use of these polyolefin fibres and summarise the main properties obtained in both fresh and hardened states of PFRC, focussing on the residual strengths obtained from flexural tensile tests.
[es]El hormigón reforzado con fibras (HRF) permite la reducción parcial o total de barras de acero en el hormigón armado, acuñándose término HRF estructural, siendo las fibras de acero las más usadas. Las macro-fibras poliméricas son una alternativa a las de acero, aportando estabilidad química y menor peso para resistencias residuales iguales. Además, las fibras de poliolefina ofrecen beneficios adicionales tales como mayor seguridad de trabajo, menor desgaste de equipos de bombeo, menor peso en el transporte y almacenamiento, y ausencia de corrosión. Otros estudios también han revelado beneficios medio-ambientales. Después de 30 años de investigación y práctica, sigue siendo necesario analizar las oportunidades que estas fibras de poliolefina pueden proporcionar al HRF estructural. Este estudio muestra los avances y posibilidades del uso de estas fibras y resume las principales propiedades obtenidas tanto en estado fresco como endurecido, centrándose en la resistencia residual obtenida en los ensayos de tracción por flexión.
[en] In this study, arc stud welding process was employed for welding AISI 316 stainless steel studs to AISI 1060 high carbon steel plates. A disc of Ni powder prepared and used as a buffering layer to enhance the properties of welding area. Optical and scanning electron microscopy were used to examine the microstructure. Energy-Dispersive X-ray (EDX) and X-Ray Diffraction (XRD) tests were performed to analyse and identify elements and phases, respectively in the weld region. The results observed that Ni powder prevented the direct contact between the dissimilar base metals. Existing of Ni altered the microstructure of the weld zone and encouraged dendritic type over cellular. Hardness reduced in the weld region from 600 HV to 200 HV due to the effect of Ni powder which prevented the formation of brittle Fe-Cr phase. (author)
[en] Thermomechanically controlled processed steels have gained attention increasingly by many industries. In this research S700MC steel is successfully welded using low power pulsed Nd:YAG laser and the microstructure and mechanical properties are investigated. It is shown that the average power and overlapping factor both affect the weld geometry. Full penetration with double-sided welding achieved on 2 mm thick plates autogenously. Optical metallographic methods and SEM/EDS were used to evaluate the resulting microstructures. The evaluations revealed that the weld metal microstructure contains different morphologies of ferrite such as acicular, allotriomorphic and Widmanstätten as well as bainaite and martensite structure in the weld zone. Also, no noticeable heat affected zone was detected near the fusion zone of the weldments. In addition to microstructures investigation, micro hardness and tensile tests were performed to evaluate mechanical properties. Hardness measurement results exhibit higher hardness values in weld zone than that of in the base metal. The tensile test revealed a ductile fracture behavior which happened in the base metal, due to proper weld zone microstructure. The strength and elongation of the prepared joints were 774 ± 14 MPa and 26.5 ± 2.5%, respectively. (author)
[en] This communication reviews results and toxicity of image-guided high-dose-rate endorectal brachytherapy (HDREBT) boost after external beam radiotherapy (ERT) in medically inoperable patients with rectal cancer. A total of 18 patients with rectal cancer and clinical stage T2-4N0‑2 treated with HDREBT boost after ERT were retrospectively reviewed. Following treatment with a median total dose (EQD2, α/β = 10) of 66 Gy (range 48–92 Gy), the incidence of early and late rectal grade 3 toxicity was 11% and 19%, respectively. There was no correlation between the occurrence of acute and late toxicity. With proper technique, a combined approach using EBRT and HDREBT was associated with acceptable toxicity in medically inoperable rectal cancer patients.
[en] The risks involved in materials deterioration and equipment failures due to corrosion associated with mechanical demands are increasing the challenge to search for new materials, alloys, coatings, inhibitors and new design solutions on plants and equipment for better performance and service life. Duplex stainless steel (DSS) has been gaining more and more space because it has many of those requirements mentioned above. High mechanical and corrosion resistance are related to balanced microstructure in approximately 50% ferrite and 50% austenite. In present work, UNS S31803 DSS plates were welded in a 45° bevel by conventional short circuit MIG/MAG process, using three different welding energies at 0.5-0.8 kJ/mm. The results showed that the effect of welding energy on the ferrite volumetric fraction was very marked in the heat affected zone (HAZ) and not so pronounced in the weld metal. Hardness and corrosion resistance (intergranular corrosion) were evaluated as a function of welding energy employed and, in general, both were not influenced when the various welding conditions were compared. (author)
[en] Non-thermal plasma has been studied for medical purposes such as sterilization, bacterial deactivation, wound healing, and cancer treatment. One of the problem is that the concept of plasma dosimetry has not been defined yet. Most of laboratories set up the operational parameters usually treatment time to control the dose based on empirical data. In this study, we suggest the concept of quantification of plasma dose by comparing with radiation dose. Non-thermal plasma generates physical factors including electromagnetic fields, heat and UV and also chemical factors including reactive oxygen and nitrogen species (RONS). Several studies reported ROS, especially hydroxyl radical (OH radical), play main roles in the plasma medicine. Low linear energy transfer (LET) radiation mostly induces cell death by producing OH radical via water radiolysis. Considering that both non-thermal plasmas and radiations produce OH radical as main mediator, plasma treatment could be quantified by comparing OH radical production with equivalent radiation dose. In this study, atmospheric pressure plasma jet (APPJ) reactor was used to generate non-thermal plasma and hard X-ray beam facility was used to generate X-ray. To measure OH radical generated in medium which has very short half-life, spin trapping material was used to measure by ESR spectrometry. DMPO-OH adduct has relatively long half-life (870s). Low LET radiation (X-ray) and plasma has difference for producing OH radicals. In contrast, X-ray produced OH radicals homogeneously with penetrating effect, APPJ produced most of OH radicals at medium surface without penetrating effect. Measuring intracellular OH radical was conducted to assess OH production inside the cells. The clonogenic surviving fraction (SF) assay was conducted to assess cell proliferation ability after treatment. The equivalent radiation doses were derived from comparing DMPO-OH concentration, intracellular OH concentration, and clonogenic SF of plasma treatments. We could conclude that the correlation between intracellular ROS and clonogenic SF was stronger than the correlation between medium OH and clonogenic SF, which means equivalent radiation for intracellular ROS could be considered as common index for the bioeffects of radiation and plasma. In this study, we quantitated plasma dose in terms of equivalent radical production compared with radiation dose. We concluded that plasma treatment can be estimated by quantitating the equivalent radiation dose
[en] There is high expectation for advanced remote technology and robotics to reduce the radiation exposure for workers in harsh nuclear environments such as the decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS). However, the radiation tolerance of state-of-the-art key components, sensors and electronic devices, for remote operation is still limited. In order to extend the application of robotics in nuclear energy, it is pertinent to develop “Radiation hardness” of components and “Radiation smartness” in operation procedures. Furthermore, developments of “Radiation measurement” and “Technology to recognize the location and to grasp the surrounding environment”, including the radiation imaging of the high dose-rate fields inside the FDNPS and the detection of nuclear fuel debris, are necessary for the future nuclear fuel debris retrieval. The 5th Fukushima Research Conference aims to share the future vision for advancing the remote technology among experts from diverse fields. (author)
[en] The present work is focused on the investigation of hardness and scratch behavior of mechanically alloyed and various temperature (300 °C–500 °C) spark plasma sintered AlNiY glassy alloys. Glassy alloy sintered at higher temperature, exhibited significantly improved hardness attributed to the increase in metallurgical bonding, relative density and nanocrystalline phases. A large variation in hardness of sintered alloys was attributed to the diffusion controlled crystallization mechanism depending on the nucleation rate during spark plasma sintering, which led to the different degree of microstructural phase evolution in a different part of the sample as confirmed by the scanning probe microscopy revealing the varying depth of indentation. Nanoindentation conducted at lower load resulted in higher hardness attributed to the indentation size effect. The scratch test exhibited decrease in coefficient of friction from 0.40 to 0.30 with the increase in sintering temperature from 300 °C to 500 °C, attributed to decrease in surface roughness.