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1
Chun, Y. B., i Chris H. J. Davies. "Twinning-Induced Negative Strain Rate Sensitivity in Wrought Magnesium Alloy AZ31". Materials Science Forum 654-656 (czerwiec 2010): 707–10. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.707.
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Measurements of strain rate sensitivity (SRS) provide a key link between dislocation-based interpretations of plastic deformation and macroscopic measurements made in mechanical tests. It is well known that plastic deformation of hexagonal close-packed (hcp) metals is achieved not only by dislocation glide but also by twinning and that the atomic rearrangement underlying the latter mode is different from that of slip. This leads to an expectation that co-activation of twinning may affect SRS of hcp metals. This assumption was tested in the present work where strain rate jump tests in both tension and compression were conducted on highly textured AZ31 plate. It was found that the SRS of the alloy in tension decreased with strain whereas that in compression increased with strain, exhibiting negative values at low strain and positive values at higher strain. Microstructure analyses revealed that the strain regimes where negative SRS or decreasing trend in SRS with strain was observed correspond to extensive twinning, implying a negative SRS of twinning. It is concluded that dislocation model alone cannot explain the strain rate dependence of flow stress in metals whose deformation is assisted by twinning.
2
Vigié, Héloise, Thalita de Paula, Martin Surand i Bernard Viguier. "Low Temperature Strain Rate Sensitivity of Titanium Alloys". Solid State Phenomena 258 (grudzień 2016): 570–73. http://dx.doi.org/10.4028/www.scientific.net/ssp.258.570.
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Titanium alloys are widely used in many industrial applications such as in aeronautics due to their combination of good mechanical properties, excellent corrosion resistance and low density. The mechanical behaviour of titanium alloys is known to exhibit a peculiar dependence on both deformation temperature and strain rate. Titanium alloys show significant room temperature creep and they are very sensitive to dwell fatigue and sustained load cracking. This behaviour is related to the viscosity of plastic deformation in titanium alloys, which can be represented by a strain rate sensitivity (SRS) parameter. The present study aims to compare the tensile behavior of two different titanium alloys, Ti-6Al-4V and β21S, which exhibit dissimilar microstructures. Results of tensile tests, performed under constant strain rate and including strain rate changes, are reported in terms of flow stress, ductility and SRS over a wide range of temperatures.
3
May, Johannes, Heinz Werner Höppel i Matthias Göken. "Strain Rate Sensitivity of Ultrafine Grained FCC- and BCC-Type Metals". Materials Science Forum 503-504 (styczeń 2006): 781–86. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.781.
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The dependence of the strain rate sensitivity (SRS) of α-Fe and Al 99.5, as typical representatives of fcc- and bcc-type metals, on the testing temperature and with respect to the microstructure is investigated. In particular, the differences between conventional grain size (CG) and ultrafine grain size (UFG) are pointed out. UFG Al 99.5 generally shows an elevated SRS compared to CG Al 99.5. In case of α-Fe the SRS of the UFG state is decreased at room temperature, but increased at 200 °C, compared to the CG state. It is shown that the SRS also influences the ductility of UFG-metals in tensile tests.
4
Vevecka-Priftaj, Aferdita, Andreas Böhner, Johannes May, Heinz Werner Höppel i Matthias Göken. "Strain Rate Sensitivity of Ultrafine Grained Aluminium Alloy AA6061". Materials Science Forum 584-586 (czerwiec 2008): 741–47. http://dx.doi.org/10.4028/www.scientific.net/msf.584-586.741.
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The strain rate sensitivity of the aluminium alloy AA6061 has been investigated in a conventional grain sized (CG) state and in two different ultrafine grained (UFG) conditions processed by Equal Channel Angular Pressing (ECAP) for 2 and 6 passes at 100o C. Strain rate jump tests in compression were performed at different temperatures and the strain-rate sensitivity exponent m was determined. The tests were accomplished by microstructural investigations before and after compression testing in CG and UFG conditions. It is shown that all UFG microstructures exhibit strongly increased strain-rate sensitivity (SRS) compared to the CG state. The SRS increases with increasing temperature and is more pronounced for the UFG material processed using 6 ECAP passes. The microstructural investigations show a rather high stability of the grain structure for the UFG conditions up to 250o C. The results are discussed with respect to the relevant deformation mechanisms.
5
Lee, Min-Su, Yong-Taek Hyun i Tea-Sung Jun. "Effect of oxygen contents on strain rate sensitivity of commercially pure titanium". MATEC Web of Conferences 321 (2020): 04009. http://dx.doi.org/10.1051/matecconf/202032104009.
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In this study, we have investigated the effect of oxygen contents on strain rate senstivitiy (SRS) within Gr. 1 and 4 commercially pure titanium (CP-Ti). The SRS was evaluated in multi-scales using macro-scopic tensile test with constant strain rate (CSR) method and strain rate jump (SRJ) method, and nanoindentation test with SRJ method. Electron backscatter diffraction (EBSD) has been used to characterise crystallographic texture and individual grain orientation of samples. Slip and twin activities of each CP-Ti were compared by EBSD measurements and the associated Schmid factor (SF) analysis. The active slip system is anticipated to be different in each relation between loading directions and textures, but twin activity is much similar. The texture dependent global SRS is thus thought to be resulted from the different slip activity. Local SRS was dependent not only on the grain orientation but also on the oxygen contents, leading to the fact that the impact of oxygen contents is closely correlated in macro- and micro-scopic level.
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Jun, Tea-Sung. "Local strain rate sensitivity of α+β phases within dual-phase Ti alloys". Journal of Physics: Conference Series 2169, nr 1 (1.01.2022): 012040. http://dx.doi.org/10.1088/1742-6596/2169/1/012040.
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Abstract Using in-situ micropillar compression, the local strain rate sensitivity in Ti6242 and Ti6246 has been investigated to strengthen our understanding on the rate- and slip system-sensitive deformation of dual-phase Ti alloys. Electron backscatter diffraction (EBSD) was used to find target grains anticipating basal and primatic slip activities under compression test. Micropillars with similar α orientation and incomparable β morphology were made by a focused ion beam (FIB). Strain rate sensitivity (SRS) was determined based on the constant strain rate method (CSRM). The marked difference of SRS is found in the α+β of both alloys such that in Ti6242 the SRS in the basal slip is considerably higher than that in the prism whilst both slips in Ti6246 show somewhat similar SRS, inferring that either local chemical effects or the β morphology could affect rate-sensitive deformation behaviour.
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Zhang, Fan, Cheng Wen Tan i Hong Nian Cai. "Influence of Precipitate Phase on the Strain Rate Sensitivity of Mg-Gd-Y Alloy". Advanced Materials Research 311-313 (sierpień 2011): 792–97. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.792.
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Supersaturated Mg-Gd-Y alloy followed by aging at 225 °C with different times were subjected to quais-static and dynamic strain rates to determine the influence of precipitate phase β′ on the strain rate sensitivity of magnesium alloy. Strain rate sensitivity (SRS) decreases with the increase of the size of β′. SRS decreases from initial condition to peak-aged condition due to the β′ increases the athermal component of flow stress. On the other hand, the influence of precipitate interfaces on dislocation generation and storage mechanisms may be responsible for the decrease of SRS from peak-aged to over-aged condition.
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Li, Mingcan. "Effect of Annealing on Strain Rate Sensitivity of Metallic Glass under Nanoindentation". Metals 10, nr 8 (6.08.2020): 1063. http://dx.doi.org/10.3390/met10081063.
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The influence of isothermal annealing on the strain rate sensitivity (SRS) of a Zr-based bulk metallic glass (BMG) was investigated by nanoindentation. A more positive SRS is observed with a decrease in the content of the free volume (FV) of the sample. Furthermore, the SRS becomes nearly constant with increasing annealing time when the FV is annealed out. By taking into consideration the FV-assisted activation and combination of the shear transformation zones (STZs), the underlying mechanism is well understood. The current work may offer useful insights into the correlation between the microstructure and mechanical properties of BMGs.
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Wang, Xiang, Zhi Qiang Ren, Wei Xiong, Si Nan Liu, Ying Liu, Si Lan i Jing Tao Wang. "Negative Strain Rate Sensitivity Induced by Structure Heterogeneity in Zr64.13Cu15.75Ni10.12Al10 Bulk Metallic Glass". Metals 11, nr 2 (18.02.2021): 339. http://dx.doi.org/10.3390/met11020339.
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The negative strain rate sensitivity (SRS) of metallic glasses is frequently observed. However, the physical essence involved is still not well understood. In the present work, small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM) reveal the strong structure heterogeneity at nanometer and tens of nanometer scales, respectively, in bulk metallic glass (BMG) Zr64.13Cu15.75Ni10.12Al10 subjected to fully confined compression processing. A transition of SRS of stress, from 0.012 in the as-cast specimen to −0.005 in compression processed specimen, was observed through nanoindentation. A qualitative formulation clarifies the critical role of internal stress induced by structural heterogeneity in this transition. It reveals the physical origin of this negative SRS frequently reported in structurally heterogeneous BMG alloys and its composites.
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Chinh, Nguyen Q., Tamás Csanádi, Jenő Gubicza, Ruslan Valiev, Boris Straumal i Terence G. Langdon. "The Effect of Grain Boundary Sliding and Strain Rate Sensitivity on the Ductility of Ultrafine-Grained Materials". Materials Science Forum 667-669 (grudzień 2010): 677–82. http://dx.doi.org/10.4028/www.scientific.net/msf.667-669.677.
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Most ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) exibit only limited ductility which is correlated with the low strain rate sensitivity (SRS) of these materials. Recently, it was demonstrated that SPD is capable of increasing the room temperature ductility of aluminum-based alloys attaining elongations up to 150%, together with relatively high strain rate sensitivity. In the present work, additional results and discussions are presented on the effect of grain boundary sliding (GBS) and SRS on the ductility of some UFG metals and alloys. The characteristics of constitutive equations describing the steady-state deformation process are quantitatively analyzed for a better understanding of the effects of grain boundaries and strain rate sensitivity.
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Matsunaga, Tetsuya, Hidetoshi Somekawa, Hiromichi Hongo i Masaaki Tabuchi. "Strain-Rate Sensitivity Enhanced by Grain-Boundary Sliding in Creep Condition for AZ31 Magnesium Alloy at Room Temperature". Materials Science Forum 838-839 (styczeń 2016): 106–9. http://dx.doi.org/10.4028/www.scientific.net/msf.838-839.106.
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This study investigated strain-rate sensitivity (SRS) in an as-extruded AZ31 magnesium (Mg) alloy with grain size of about 10 mm. Although the alloy shows negligible SRS at strain rates of >10-5 s-1 at room temperature, the exponent increased by one order from 0.008 to 0.06 with decrease of the strain rate down to 10-8 s-1. The activation volume (V) was evaluated as approximately 100b3 at high strain rates and as about 15b3 at low strain rates (where b is the Burgers vector). In addition, deformation twin was observed only at high strain rates. Because the twin nucleates at the grain boundary, stress concentration is necessary to be accommodated by dislocation absorption into the grain boundary at low strain rates. Extrinsic grain boundary dislocations move and engender grain boundary sliding (GBS) with low thermal assistance. Therefore, GBS enhances and engenders SRS in AZ31 Mg alloy at room temperature.
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SUO, TAO, LU MING, FENG ZHAO, YULONG LI i XUELING FAN. "TEMPERATURE AND STRAIN RATE SENSITIVITY OF ULTRAFINE-GRAINED COPPER UNDER UNIAXIAL COMPRESSION". International Journal of Applied Mechanics 05, nr 02 (czerwiec 2013): 1350016. http://dx.doi.org/10.1142/s1758825113500166.
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Uniaxial compressive experiments of ultrafine-grained (UFG) copper fabricated by equal channel angular pressing method were performed at temperatures ranging from 77 K to 573 K under quasi-static and dynamic loading conditions. Based on the experimental results, the influence of temperature on flow stress, strain hardening rate and strain rate sensitivity (SRS) were investigated carefully. The results show that the flow stress of UFG copper displays much larger sensitivity to testing temperature than that of coarse grained copper. Meanwhile, both the strain hardening rate and its sensitivity to temperature of UFG copper are lower than those of its coarse counterpart. The SRS of UFG copper also shows apparent dependence on temperature. Although the estimated activation volume of UFG- Cu is on the order of ~10 b3, which is on the same order with that of grain boundary diffusion processes, these processes should be ruled out as dominant mechanisms for UFG- Cu at our experimental temperature and strain rate range. Instead, it is suggested that the dislocation-grain boundary interactions process might be the dominant thermally activated mechanism for UFG- Cu .
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Hu, Shao Wei. "The Simulation and Role of Discontinuous Yield Behaviors of Material". Advanced Materials Research 163-167 (grudzień 2010): 4590–94. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.4590.
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Discontinuous yield of material as Jerky flow was explained. Then, the strain rate sensitivity (SRS) and instability criterion was given out. Some tests were carried out at constant stress rate, so Jerky flow is manifested as a discontinuity in the stress-strain curves in form of strain bursts. Finally, the dynamic behaviors of specimens during instability of thermal origin were simulated with COLSYS software, whose results are good with test ones.
14
Xiao, Xiazi, Hao Liu i Long Yu. "On the Size Effect of Strain Rate Sensitivity and Activation Volume for Face-Centered Cubic Materials: A Scaling Law". Crystals 10, nr 10 (3.10.2020): 898. http://dx.doi.org/10.3390/cryst10100898.
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In a recent experimental study of indentation creep, the strain rate sensitivity (SRS) and activation volume v* have been noticed to be dependent on the indentation depth or loading force for face-centered cubic materials. Although several possible interpretations have been proposed, the fundamental mechanism is still not well addressed. In this work, a scaling law is proposed for the indentation depth or loading force-dependent SRS. Moreover, v* is indicated to scale with hardness H by the relation ∂ln(v*/b3)/∂lnH=−2 with the Burgers vector b. We show that this size effect of SRS and activation volume can mainly be ascribed to the evolution of geometrically necessary dislocations during the creep process. By comparing the theoretical results with different sets of reported experimental data, the proposed law is verified and a good agreement is achieved.
15
Suo, Tao, Yu Long Li, Feng Zhao i Kui Xie. "Temperature Effects on the Mechanical Behavior of Ultrafine-Grained Material". Materials Science Forum 667-669 (grudzień 2010): 827–32. http://dx.doi.org/10.4028/www.scientific.net/msf.667-669.827.
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The quasi-static and dynamic compression experiments of ultrafine-grained copper fabricated by equal channel angular pressing method were performed at temperatures ranging from 77 to 573K. The influence of temperature on flow stress, strain hardening rate and strain rate sensitivity were investigated. The results show that the flow stress of ultrafine-grained copper shows much larger sensitivity to testing temperature than that of coarse grained copper. However, the temperature sensitivity of ultrafine-grained copper to true strain is comparative weaker than that of coarse grained copper. For the ultrafine-grained copper, both the strain hardening rate and its sensitivity to temperature of ultrafine-grained copper are lower than those of its coarse counterpart. The SRS also displays apparent dependence on temperature. The activation volume for UFG-Cu is estimated to be on the order of ~10b3 in current experiment temperature. It is suggested that the dislocation-grain boundary interactions process might be the dominant thermally activated mechanism for UFG-Cu.
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Alkorta, Jon, José Manuel Martínez-Esnaola i Javier Gil Sevillano. "On the elastic effects in power-law indentation creep with sharp conical indenters". Journal of Materials Research 23, nr 1 (styczeń 2008): 182–88. http://dx.doi.org/10.1557/jmr.2008.0011.
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The elastic deformation contribution can significantly affect the measurement of the strain-rate sensitivity (SRS) of the plastic flow stress by indentation methods. In this paper, the effect of such elastic contribution is critically analyzed using an extension of a previous treatment developed by the authors for the elastic effects on the indentation of strain-hardening materials [J. Alkorta et al., J. Mater. Res.20, 432 (2005)]. The analytical model is calibrated and validated through finite element calculations. The results show that when the elastic contribution to the total deformation is not negligible then the measured SRS is significantly lower than the real one. A satisfactory correction factor for the apparent SRS exponent is proposed based on parameters directly accessible to instrumented indentation test results.
17
Park, Geon-Woo, Haeju Jo, Minha Park, Byung-Jun Kim, Wookjin Lee, Sunmi Shin, Sung Soo Park, Yong-Sik Ahn i Jong Bae Jeon. "Effect of Heat Treatment and Drawing on High-Manganese Steel Pipe Welded by Gas Tungsten Arc". Metals 10, nr 10 (13.10.2020): 1366. http://dx.doi.org/10.3390/met10101366.
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This study investigated the effect of post-weld processes including annealing and drawing on the microstructure and mechanical properties of high-Mn steel pipes welded by gas tungsten arc welding. The weld metal showed a solidified microstructure having coarse and elongated grains due to coalescence of columnar dendrite into welding heat direction. After post-annealing, the solidified microstructure changed into equiaxed grains due to recrystallization and grain growth. Mn segregation occurred during welding solidification and caused lower stacking fault energy (SFE) in the Mn-depleted region. Although ε-martensite formation in the as-welded state and during deformation was expected due to decreased SFE of the Mn-depleted zone, all regions showed a fully austenitic phase. The annealing process decreased strength due to grain coarsening but increased ductility. The drawing process increased strength of weld metal through work hardening. All pipes showed decreasing strain rate sensitivity (SRS) with deformation and negative SRS after certain strain levels. It was confirmed that negative SRS is related to less formation of mechanical twinning at a higher strain rate. This work provides fundamental insights into manufacturing a high-Mn steel pipe and manipulating its properties with annealing and drawing processes.
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Wang, Shiyu, Lihua Wen, Jinyou Xiao, Ming Lei, Xiao Hou i Jun Liang. "The Out-of-Plane Compression Response of Woven Thermoplastic Composites: Effects of Strain Rates and Temperature". Polymers 13, nr 2 (14.01.2021): 264. http://dx.doi.org/10.3390/polym13020264.
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The dynamic mechanical response of high-performance thermoplastic composites over a wide range of strain rates is a challenging research topic for extreme environmental survivability in the field of aerospace engineering. This paper investigates the evolution of the dynamic properties of woven thermoplastic composites with strain rate and damage process at elevated temperatures. Out-of-plane dynamic-compression tests of glass-fiber (GF)- and carbon-fiber (CF)-reinforced polyphenylene sulfide (PPS) composites were performed using a split Hopkinson pressure bar (SHPB). Results showed that thermoplastic composites possess strain-rate strengthening effects and high-temperature weakening dependence. GF/PPS and CF/PPS composites had the same strain-rate sensitivity (SRS) below the threshold strain rate. The softening of the matrix at elevated temperatures decreased the modulus but had little effect on strength. Some empirical formulations, including strain-rate and temperature effects, are proposed for more accurately predicting the out-of-plane dynamic-compression behavior of thermoplastic composites. Lastly, the final failure of the specimens was examined by scanning electron microscopy (SEM) to explore potential failure mechanisms, such as fiber-bundle shear fracture at high strain rates and stretch break at elevated temperatures.
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Alkorta, Jon, C. J. Luis-Pérez, E. N. Popova, Martin Hafok, Reinhard Pippan i J. Gil Sevillano. "Microstructure and Indentation Size-Effect in Pure Niobium Subjected to SPD via ECAP and HPT". Materials Science Forum 584-586 (czerwiec 2008): 215–20. http://dx.doi.org/10.4028/www.scientific.net/msf.584-586.215.
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A commercially pure niobium has been subjected to SPD at room temperature ( ~0.11 TM) via ECAP (90º, route BC) up to 16 passes and via HPT up to shear strains γ =1000. ECAP-ed samples show an equiaxed structure after 8 and 16 passes with a decreasing average grain size. The results show that both the microstructure and mechanical properties of ECAP-ed samples do not reach a steady state up to at least 16 passes. HPT samples show at outer region a finer structural size but similar hardness values at similar equivalent strains. The nanoindentation results show an evident indentation size-effect even for the most deformed samples. The hardness values at the nano level converge for the recrystallized, the ECAP-ed and the HPT samples. This implies that, at the nano level, when the geometrically necessary dislocation density overcomes significantly the (initial) statistically stored dislocation density, hardness depends mainly on the physical intrinsic properties of the material (Burgers modulus, bulk modulus...) and the contribution of bulk mechanical properties (i.e., bulk yield strength) to hardness is smoothed down. Strain-rate sensitivity (SRS) of plastic strength has been also measured by means of rate-jump nanoindentation tests. The SRS is proportional to the inverse of hardness.
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Zhang, Hengning, Meng Liu, Yinggang Miao, Han Wang, Tao Chen, Xuezhong Fan i Hai Chang. "Dynamic Mechanical Response and Damage Mechanism of HTPB Propellant under Impact Loading". Materials 13, nr 13 (7.07.2020): 3031. http://dx.doi.org/10.3390/ma13133031.
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The dynamic mechanical behaviors of Hydroxyl-terminated polybutadiene (HTPB) propellant was studied by a split Hopkinson pressure bar apparatus (SHPB) at strain rates ranging from 103 to 104 s−1. The obtained stress–strain curves indicated that the mechanical features, such as ultimate stress and strain energy, were strongly dependent on the strain rate. The real time deformation and fracture evolution of HTPB propellant were captured by a high-speed digital camera accompanied with an SHPB setup. Furthermore, microscopic observation for the post-test specimen was conducted to explore the different damage mechanisms under various conditions of impact loading. The dominated damage characteristics of HTPB propellant were changed from debonding and matrix tearing to multiple cracking modes of ammonium perchlorate (AP) particles, along with the increase of the strain rate. For the first time, the influence of AP particle density on the dynamic response of HTPB propellant was studied by analyzing the strain-rate sensitivity (SRS) index of HTPB propellant with two different filler content (80 wt.% and 85 wt.%), which deduced from a power function of ultimate stress and strain energy density. The result of this study is of significance for evaluating the structural integrity and security of HTPB propellant.
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MAHMUDI, REZA, H. MHJOUBI i P. MEHRARAM. "SUPERPLASTIC INDENTATION CREEP OF FINE-GRAINED Sn-1% Bi ALLOY". International Journal of Modern Physics B 22, nr 18n19 (30.07.2008): 2823–32. http://dx.doi.org/10.1142/s021797920804764x.
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Creep and superplasticity of the fine-grained Sn -1wt.% Bi alloy, processed by conventional rolling (CNR), cryorolling (CRR) and equal channel angular pressing (ECAP) routes, were investigated by indentation testing at room temperature (T > 0.6T m ). Based on the steady-state power law creep relationship, the stress exponents of 4.1, 2.8 and 2.5 were obtained for the CNR, CRR and ECAP routes, respectively. The corresponding strain rate sensitivity (SRS) indices of 0.24, 0.36 and 0.40, corresponding respectively to the grain sizes of 2.8, 2.1 and 1.2 μm, indicate that the materials processed by ECAP and CRR exhibit superplastic deformation behavior for which, grain boundary sliding is the possible creep mechanism.
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Tao, J. M., Xin Kun Zhu, P. Z. Wong, Ron O. Scattergood i Carl C. Koch. "Mechanical Properties of Nanocrystalline Cu and Cu-Zn Using Tensile and Shear Punch Tests". Materials Science Forum 633-634 (listopad 2009): 373–82. http://dx.doi.org/10.4028/www.scientific.net/msf.633-634.373.
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Shear punch test (SPT) has been used to study the mechanical properties of Cu, Cu–10 wt.% Zn, Cu–20 wt.% Zn and Cu–30 wt.% Zn after ball milling with an average grain size in the range of 33-12nm. The strain rate sensitivity (SRS) and physical activation volume have been determined. The magnitude observed for these characteristic deformation parameters is very different from their course-grained (cg) counterpart. This suggests that the thermally activated process in nanocrystalline (nc) metal/alloys is different from the conventional forest dislocation cutting mechanism. The stacking fault energy (SFE) of Cu-Zn alloys decreased with the adding of Zn, and deformation twins are anticipated to introduce into the nc Cu-Zn alloys during process of ball milling. Dislocations could accumulate along the TBs and carry the plastic strain, so the ductility of nc Cu-Zn alloys could be improved.
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Malomo, B. O., O. O. Fadodun, K. M. Oluwasegun, A. T. Ogunbodede, S. A. Ibitoye i L. O. Adekoya. "The Effect of Controlled Melt-Solidification on the Strain Rate Sensitivity of a Squeeze-Cast Hybrid-Reinforced Aluminum AA 6061 Matrix Composite". International Journal of Engineering Research in Africa 16 (czerwiec 2015): 1–16. http://dx.doi.org/10.4028/www.scientific.net/jera.16.1.
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A framework based on the relationship between variations in cooling rates and volume fraction of reinforcements during solidification processing to enhance the deformation behavior of aluminum alloy AA6061 matrix composite produced with a hybrid system of reinforcements is investigated in this study. The aluminum matrix composite with 5 %, 10 % and 20 % volume fraction of reinforcements (Al2O3-SiC) was synthesized by infiltrating molten aluminum AA 6061 at a pouring temperature of 740 °C into prefabricated preforms of reinforcements at a pressure of 80 MPa, die preheat temperature of 300 °C and pressure holding time of 15 s using the squeeze casting method. By employing water jet spraying at the rate of 0.1, 0.2 and 0.3 kg/s and taking measurements using a K-type thermocouple, cooling rates were obtained in correspondence with varying volume fractions of reinforcements. The developed composites were sectioned and microstructural features were examined by optical microscopy. Tensile testing was conducted according to ASTM B557 standard using an MTS testing machine. It was observed that cooling rates decreased as the volume fraction of reinforcements was increased and the cooling time also increased accordingly during this process. With respect to deformation behavior, higher cooling rates are associated with an improvement in mechanical properties at 5 % and 10 % additions of hybrid reinforcement particles but this effect diminishes as the volume fraction of reinforcements was increased to 20 %. Also, the strain rate sensitivity (SRS) exponent increased considerably with strain rates and volume fraction of reinforcements, but the tensile elongation values decreased with increasing volume fraction of reinforcements; and the variations in these properties were most significant for samples containing 20% volume fraction of hybrid reinforcements.From the foregoing, it follows that an experimentally-determined optimal solidification range is critical to the enhancement of deformation parameters as the volume fraction of reinforcements is varied in a squeeze casting process.
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Hildreth, Cara M., James R. Padley, Paul M. Pilowsky i Ann K. Goodchild. "Impaired serotonergic regulation of heart rate may underlie reduced baroreflex sensitivity in an animal model of depression". American Journal of Physiology-Heart and Circulatory Physiology 294, nr 1 (styczeń 2008): H474—H480. http://dx.doi.org/10.1152/ajpheart.01009.2007.
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Serotonin (5-HT) is crucial to normal reflex vagal modulation of heart rate (HR). Reduced baroreflex sensitivity [spontaneous baroreflex sensitivity (sBRS)] and HR variability (HRV) reflect impaired neural, particularly vagal, control of HR and are independently associated with depression. In conscious, telemetered Flinders-Sensitive Line (FSL) rats, a well-validated animal model of depression, we tested the hypothesis that cardiovascular regulatory abnormalities are present and associated with deficient serotonergic control of reflex cardiovagal function. In FSL rats and control Flinders-Resistant (FRL) and Sprague-Dawley (SD) rat strains, diurnal measurements of HR, arterial pressure (AP), activity, sBRS, and HRV were made. All strains had normal and similar diurnal variations in HR, AP, and activity. In FRL rats, HR was elevated, contributing to the reduced HRV and sBRS in this strain. In FSL rats, sBRS and high-frequency power HRV were reduced during the night, indicating reduced reflex cardiovagal activity. The ratio of low- to high-frequency bands of HRV was increased in FSL rats, suggesting a relative predominance of cardiac sympathetic and/or reflex activity compared with FRL and SD rats. These data show that conscious FSL rats have cardiovascular regulatory abnormalities similar to depressed humans. Acute changes in HR, AP, temperature, and sBRS in response to 8-hydroxy-2-(di- n-propylamino)tetralin, a 5-HT1A, 5-HT1B, and 5-HT7 receptor agonist, were also determined. In FSL rats, despite inducing an exaggerated hypothermic effect, 8-hydroxy-2-(di- n-propylamino)tetralin did not decrease HR and AP or improve sBRS, suggesting impaired serotonergic neural control of cardiovagal activity. These data suggest that impaired serotonergic control of cardiac reflex function could be one mechanism linking reduced sBRS to increased cardiac risk in depression.
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Yan, Jiangpeng, Zhimin Zhang, Jian Xu, Yaojin Wu, Xi Zhao, Yong Xue i Haijun Liu. "Microstructure evolution of TC4 powder by spark plasma sintering after hot deformation". High Temperature Materials and Processes 39, nr 1 (10.09.2020): 457–65. http://dx.doi.org/10.1515/htmp-2020-0002.
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AbstractThe cylindrical samples of TC4 titanium alloy prepared by spark plasma sintering (SPS) were compressed with hot deformation of 70% on the thermosimulation machine of Gleeble-1500. The temperature of the processes ranged from 850°C to 1,050°C, and the strain rates varied between 0.001 and 5 s−1. The relative density of the sintered and compressed samples was measured by the Archimedes principle. During hot deformation, the microstructure of the sample was observed. The results show that the average relative density of the samples was 90.2% after SPS. And the relative density was about 98% after the hot deformation of 70%. Under high temperature (>950°C), the sensitivity of flow stress to temperature was reduced. At low strain rate (0.001 s−1), the increase in the deformation temperature promoted the growth of dynamic recrystallization (DRX). At the same temperature, the increase in strain rate slowed down the growth of DRX grains. And the variation tendency was shown from the basket-weave structure to the Widmanstätten structure at a low strain rate (<0.1 s−1), with increase in the strain rate.
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Mohammad Sohan, Arif, MSI Tipu Chowdhury, Khaled Mohammad Iqbal, Najnin Akhter, ATM Iqbal Hasan i Chowdhury Meshkat Ahmed. "Echocardiographic Assessment of Myocardial Viability and Prediction of Left Ventricular Functional Recovery after Acute Myocardial Infarction Using Strain and Strain Rate". University Heart Journal 17, nr 1 (21.12.2020): 22–30. http://dx.doi.org/10.3329/uhj.v17i1.50876.
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Background: Extent of viable myocardial tissue has been recognized as a major determinant of recovery of left ventricular (LV) function after myocardial infarction. The present research was aimed at assessment of myocardial viability and prediction of left ventricular functional recovery in patients after acute anterior ST-elevated myocardial infarction using Tissue Doppler strain.
Methods: In this prospective observational research, 47 patients admitted into the hospital with acute anterior ST-elevated myocardial infarction were included. All patients underwent two-dimensional and strain echocardiography within 48-72 hours of admission. Follow up two-dimensional echocardiography had performed at 6 months after baseline examination.
Results: Total 47 patients (mean age, 57±5 years) underwent two-dimensional and strain echocardiography within 48-72 hours of admission. Significant relations were observed between baseline global systolic lengthening strain and wall motion score index (r=0.67), change in left ventricular ejection fraction (LVEF, r= -.844), Global Ses (r=.441) and on admission troponin I (r =0.397). At 6-months follow-up, LV ejection fraction was reassessed. Patients with absolute improvement in LV ejection fraction ≥5% at 6-months follow-up (n=24; 51%) had a higher (more negative) baseline global Ses strain (P<0.001) and lower global systolic lengthening (P<.001). A cutoff value for baseline global systolic lengthening strain of 7.6% yielded a sensitivity of 83% and a specificity of 87% to predict LV functional recovery at 6-months follow-up.
Conclusions: Global Left ventricular strain (Ses and Systolic lengthening) early after acute anterior ST-elevated myocardial infarction reflects myocardial viability and predicts recovery of LV function at 6-monts follow-up.
University Heart Journal Vol. 17, No. 1, Jan 2021; 22-30
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Krüger, Lutz, Steffen Grützner, Sabine Decker i Ines Schneider. "Spark Plasma Sintering and Strength Behavior under Compressive Loading of Mg-PSZ/Al2O3-TRIP-Steel Composites". Materials Science Forum 825-826 (lipiec 2015): 182–88. http://dx.doi.org/10.4028/www.scientific.net/msf.825-826.182.
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Composite materials, which consist of a metastable austenitic TRIP-steel matrix (CrMnNi TRIPsteel; TRansformation Induced Plasticity) reinforced by alumina particles (25 vol.% ceramic, designated as AT 25/75) and reinforced by alumina and MgO partially stabilized zirconia particles (Mg-PSZ) (35 vol.% ceramic, designated as AT 25/75 + MgPSZ) were synthesized through spark plasma sintering (SPS). In the AT 25/75 + MgPSZ, the steel particles were mainly surrounded by alumina. Hence, mostly steel/alumina and alumina/MgPSZ interfaces existed. The mechanical behavior of the as-sintered samples was characterized by compression tests at room temperature and 40 °C and in a range of strain rates between 103s-1and 103s1. The influence of the ceramic content, strain rate and temperature on TRIP-effect of the steel matrix was investigated. Due to the increasing ceramic volume fraction, AT 25/75 + MgPSZ exhibits the highest compressive yield strength under all loading conditions and no strain rate sensitivity. This composite showed no measurable TRIP-effect, due to the low fracture strain. The deformation-induced α’martensite within the steel particles in pure steel and AT 25/75 primary depends on the testing temperature and the strain rate. This is attributed to an increase of stacking fault energy with rising temperature. High strain rates cause adiabatic heating, counteracting the martensitic transformation.
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Qian, Xu, Hua Zhou i Heng Cai. "UDP-Glucose Pyrophosphorylase ugp1 is Required in Heat Stress Response of Saccharomyces cerevisiae". Journal of Biobased Materials and Bioenergy 15, nr 2 (1.04.2021): 188–93. http://dx.doi.org/10.1166/jbmb.2021.2037.
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UDP-glucose pyrophosphorylase (UGP1) is an important metabolic enzyme in Saccharomyces cerevisiae. In this research, we built a strain with reduced ugp1 level for exploring its biological roles. The survival rate, trehalose, glucan, and the sensitivity to cell wall perturbing agents were tested. Intracellular trehalose and glucan of ugp1 knockdown (ugp1KD) strain showed 37.4% and 56.69% of WT strain at 42 °C. Meanwhile, the survival rate declined to 33.83% after 2 hours and to 8.44% after 8 hours. The cell wall was more susceptible to Congo red, SDS, and Calcofluor white. After complementing ugp1(UGP1C), the resistance to heat-stress and cell wall perturbing agents were rescued markedly. The 1,3-β-D-glucan synthase (FKS1) expression level was affected by knocking down ugp1, as well. Our data suggest that ugp1 is required in the heat stress response of S. cerevisiae by influencing trehalose and glucan, and provides a foundation elucidating the essence of survival under heat stress.
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Caplea, Ann, Darcie Seachrist, Gail Dunphy i Daniel Ely. "Sodium-induced rise in blood pressure is suppressed by androgen receptor blockade". American Journal of Physiology-Heart and Circulatory Physiology 280, nr 4 (1.04.2001): H1793—H1801. http://dx.doi.org/10.1152/ajpheart.2001.280.4.h1793.
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Our objective was to test the hypothesis that 1) a high Na (HNa, 3%) diet would increase blood pressure (BP) in male Wistar-Kyoto (WKY) and spontaneously hypertensive Y chromosome (SHR/y) rat strains in a territorial colony; 2) sympathetic nervous system (SNS) blockade using clonidine would lower BP on a HNa diet; and 3) prepubertal androgen receptor blockade with flutamide would lower BP on a HNa diet. A 2 × 4 factorial design used rat strains (WKY, SHR/y) and treatment [0.3% normal Na (NNa), 3% HNa, HNa/clonidine, and HNa/flutamide]. BP increased in both strains on the HNa diet ( P < 0.0001). There was no significant decrease in BP in either strain with clonidine treatment. Androgen receptor blockade with flutamide significantly decreased BP in both strains ( P < 0.0001) and normalized BP in the SHR/y colony. Neither heart rate nor activity could explain these BP differences. In conclusion, a Na sensitivity was observed in both strains, which was reduced to normotensive values by androgen blockade but not by SNS blockade.
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Liu, Hua, Xiaotao Han, Xiaofen Lin, Xinjie Zhu i Yumei Wei. "Impact of vaccine measures on the transmission dynamics of COVID-19". PLOS ONE 18, nr 8 (25.08.2023): e0290640. http://dx.doi.org/10.1371/journal.pone.0290640.
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In many nations, efforts to prevent and control COVID-19 have been significantly impeded by the SARS-CoV-2 virus ongoing mutation. The Omicron strain, a more recent and prevalent strain, has had more significant detrimental effects in countries worldwide. To investigate the impact of the Omicron BA.2 strain on vaccine efficacy, we proposed a model with vaccination and immunological decline in this research. Then, we fitted our model based on the number of daily new instances reported by the government in Jilin and Shanghai, China. We estimated the effective reproduction number Re = 4.71 for the Jilin and Re = 3.32 for Shanghai. Additionally, we do sensitivity analysis to identify the critical factors affecting the effective reproduction number Re. It was found that vaccination rate, effectiveness rate, and declining rate had a significant effect on Re. Further, we investigate the relevant parameter thresholds that make Re lower than unity. Finally, rich numerical experiments were then carried out. We observed that even when vaccine efficiency was not high, increasing vaccination rates had a significant effect on early disease transmission, that limiting social distance was the most economical and rational measure to control the spread of disease, and that for a short period, reducing immune decline was not significant in curbing disease transmission.
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Burtniak, Julian, Adam Hedley, Kerry Dust, Paul Van Caeseele, Jared Bullard i Derek R. Stein. "Dorfman pooling enhances SARS-CoV-2 large-scale community testing efficiency". PLOS Global Public Health 3, nr 4 (18.04.2023): e0001793. http://dx.doi.org/10.1371/journal.pgph.0001793.
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PCR-based analysis is the gold standard for detection of SARS-CoV-2 and was used broadly throughout the pandemic. However, heightened demand for testing put strain on diagnostic resources and the adequate amount of PCR-based testing required exceeded existing testing capacity. Pooled testing strategies presented an effective method to increase testing capacity by decreasing the number of tests and resources required for laboratory PCR analysis of SARS-CoV-2. We sought to conduct an analysis of SARS-CoV-2 pooling schemes to determine the sensitivity of various sized Dorfman pooling strategies and evaluate the utility of using such pooling strategies in diagnostic laboratory settings. Overall, a trend of decreasing sensitivity with larger pool sizes was observed, with modest sensitivity losses in the largest pools tested, and high sensitivity in all other pools. Efficiency data was then calculated to determine the optimal Dorfman pool sizes based on test positivity rate. This was correlated with current presumptive test positivity to maximize the number of tests saved, thereby increasing testing capacity and resource efficiency in the community setting. Dorfman pooling methods were evaluated and found to offer a high-throughput solution to SARS-CoV-2 clinical testing that improve resource efficiency in low-resource environments.
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Menapace, Cinzia, Bhupendra Sharma i Kei Ameyama. "Hot Deformation Behavior of PM Ni with Harmonic Microstructure". Metals 12, nr 1 (4.01.2022): 90. http://dx.doi.org/10.3390/met12010090.
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The hot deformation behavior of a harmonic-structured pure nickel has been studied and compared with the hot deformability of a homogeneously structured nickel. Both materials were produced via the powder metallurgy route through the Spark Plasma Sintering (SPS) of mechanical milled and un-milled powders. Hot deformation was evaluated through compression tests at three different temperatures (400 °C, 800 °C, and 1300 °C), covering a wide range in the homologous temperature spectrum for Ni (from 0.39 to 0.91), and at three different strain rates (0.001, 0.01, and 0.1 s−1). The evaluation of the stress–strain curves showed a higher hot compression resistance for the harmonic-structured nickel, together with higher strain hardening and strain rate sensitivity, thanks to the peculiar microstructural features of this material. Through the metallographic analysis of the specimens after hot compression, different mechanisms were identified as responsible for the deformation behavior in relation to the temperature of testing. While at 400 °C dynamic recrystallization has slightly started, at 800 °C it is widely diffused, and at 1300 °C it is replaced by grain growth and diffusion creep phenomena.
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Duplan, Yannick, Dominique Saletti i Pascal Forquin. "Identification of the Quasi-Static and Dynamic Behaviour of Projectile-Core Steel by Using Shear-Compression Specimens". Metals 9, nr 2 (12.02.2019): 216. http://dx.doi.org/10.3390/met9020216.
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Armour-Piercing (AP) projectiles constitute a major threat to be considered for the design of bi-layer-armour configurations constructed using a ceramic front plate backed with a composite/metal layer. When they are not made of tungsten-carbide the cores of these projectiles are made of hard steel, and are the main part that defines the penetration performance of the projectile. However, due to specific testing difficulties, the dynamic behaviour of these high-strength steel AP projectiles has not been investigated in sufficient detail. In this study, a detailed experimental investigation of the dynamic behaviour of the steel used for the steel core of 7.62 mm BZ-type AP projectiles was analysed through the use of Shear-Compression Specimens (SCS). In this study, results from both quasi-static and dynamic experiments were examined. The data processing method employed was set and validated based on numerical simulations. Both quasi-static and dynamic SCS experiments were done with the steel tested which clearly indicated the steel cores exhibit a very high elastic limit, little strain-hardening, and very little strain-rate sensitivity despite the wide range of strain-rates considered. This experimental characterisation paves the way to the numerical modelling for the analysis of ballistic impact of 7.62 mm AP projectile against lightweight armour configurations.
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Tanabe, Shigeru, Naoko Ishii-Minami, Ken-Ichiro Saitoh, Yuko Otake, Hanae Kaku, Naoto Shibuya, Yoko Nishizawa i Eiichi Minami. "The Role of Catalase-Peroxidase Secreted by Magnaporthe oryzae During Early Infection of Rice Cells". Molecular Plant-Microbe Interactions® 24, nr 2 (luty 2011): 163–71. http://dx.doi.org/10.1094/mpmi-07-10-0175.
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The biological role of a secretory catalase of the rice blast fungus Magnaporthe oryzae was studied. The internal amino acid sequences of the partially purified catalase in the culture filtrate enabled us to identify its encoding gene as a catalase-peroxidase gene, CPXB, among four putative genes for catalase or catalase-peroxidase in M. oryzae. Knockout of the gene drastically reduced the level of catalase activity in the culture filtrate and supernatant of conidial suspension (SCS), and increased the sensitivity to exogenously added H2O2 compared with control strains, suggesting that CPXB is the major gene encoding the secretory catalase and confers resistance to H2O2 in hyphae. In the mutant, the rate of appressoria that induced accumulation of H2O2 in epidermal cells of the leaf sheath increased and infection at early stages was delayed; however, the formation of lesions in the leaf blade was not affected compared with the control strain. These phenotypes were complimented by reintroducing the putative coding regions of CPXB driven by a constitutive promoter. These results suggest that CPXB plays a role in fungal defense against H2O2 accumulated in epidermal cells of rice at the early stage of infection but not in pathogenicity of M. oryzae.
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Yao, Hongru, Tao Wang, Qiang Wang, Yadong Cao i Xiaolong Zhou. "Applicability of Standard Rheological Evaluation Methods for High Content SBS Polymer Modified Asphalts". Buildings 13, nr 5 (27.04.2023): 1156. http://dx.doi.org/10.3390/buildings13051156.
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High content SBS polymer modified asphalt (HCPMA) can serve as pavements under heavy traffic and a wide range of temperatures. However, the applicability and validity of standard rheological evaluation methods to characterize HCPMA are still unclear. In this study, the influence of SBS content on the conventional properties and rheological behavior of HCPMA was analyzed. A higher content of SBS can improve the performance grade of the asphalt binder to PG100-34. The slope of the Jnr-σ linear curves from the MSCR under various stress levels decreases when the SBS content increases. The slope of the Jnr-σ linear curves can replace Jnrdiff as an indicator of stress sensitivity. A higher content of SBS can also decrease the flexural creep stiffness and increase the creep rate of the binders. The binder fatigue resistance parameter increases and the binder yields at higher strain, with increasing SBS content. These results show that a higher content of SBS can further improve the resistance to rutting, thermal cracking, and fatigue. Current standard rheological methods should be modified when evaluating HCPMA. The results also show that conventional tests are not valid for evaluating the performance of HCPMA.
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Qurat-, ul-Ain Amjad, Saeed Umar, Piracha Zahra Zahid, Kanwal Kashmala, Munir Madiha, Waseem Atika, Nisar Tayyaba, Shoukat Arisha i Uppal Rizwan. "Contemplating SARS-CoV-2 infectivity with respect to ABO blood groups". International Journal of Clinical Virology 5, nr 2 (26.10.2021): 082–86. http://dx.doi.org/10.29328/journal.ijcv.1001039.
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COVID-19 is a disease that is caused by SARS-CoV-2 and very speedily spreading all over the world. The blood group’s effect on COVID-19 is not clear. The main aim of this article is to determine the relationship between sensitivity of COVID-19 and ABO blood group. For this study we have observed that the individuals with blood group A are at higher risk of getting COVID-19 because they contain the higher concentration of Angiotensin-converting enzyme-2 that provide the site to virus for entry. But in other blood groups the natural Anti A antibodies block the interaction between host receptor and virus and disturb their interaction. Certain studies show that the infectivity and mortality rate in covid patients is not affected by AB blood group system. But according to research, increased ventilator usage, ICU stay was observed in critically ill patients with AB blood group than of other blood groups. O blood group has proved to be protective against SARS-CoV-2 due to the presence of both anti-A and anti-B antibodies as they prevent the binding of the spike protein S of the virus with the ACE2 receptors which are present on the surface of cells. Moreover, furin also plays a major role in penetration of virus in the host cells. Furin is required for the activation of the spike protein S of the virus and due to the low efficiency of furin cleavage in blood group O it is protected from SARS-CoV-2 and other chronic diseases. Mortality rate of covid 19 depends upon the environmental factors, number of people living in the area and also some economic factors. The different strains of COVID-19 effect the different people differently and as the time passes the strain of COVID-19 has changed and thus according to this the mortality rate of different provinces and areas varies due to environmental factors. Pregnant women have no any kind of transportation of covid to their fetuses but mostly patients of blood group A are being affected by COVID-19 and hence their fetuses are somehow effected. And those pregnant women having blood group O does not have any risk of COVID-19 of severe stages.
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Fu, Hao, ChinYin Chen, Chongchong Wang, MinChiang Chao, Qiang Zhou, Guilin Yang i Guozhi Wang. "Quartz crystal based sensor head design and analysis for robot torque sensor application". Cobot 1 (26.04.2022): 11. http://dx.doi.org/10.12688/cobot.17474.1.
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Background: In recent years, with the gradual development of robot human-computer interaction, robots need to meet the precise control of more complex motion. Torque sensors play an important role. The traditional strain gauge sensor uses a metal strain gauge as the sensitive element, which means that the sensor has a slow response, low resolution and can easily be affected by external signal noise. Aiming at these deficiencies of strain gauge sensors, a sensor with cutting quartz square sheet as the sensor head is proposed. Methods: In order to study the application of quartz square sensing head in the sensor, firstly, COMSOL (5.6) simulation modeling is used to obtain the stress relationship between square quartz sheet and circular quartz sheet. Then the calculation formula of the force frequency coefficient of the circular quartz sheet is modified to obtain the calculation formula of the force frequency coefficient of the square quartz sheet, and the feasibility of the formula is verified by practical experiments. Next, the theoretical simulation and experimental research on the buckling limit force of quartz wafer are carried out, and the formula of buckling limit force in the process of quartz wafer installation is modified. Finally, the designed sensitive head is installed on the elastomer structure for verification. The frequency signal is collected by SGS-THOMSON Microelectronics 32 with a sampling rate of 1000Hz. Results: The main performances of the sensor are range 150nm, sensitivity 350Hz / nm, linearity 98.14%, hysteresis 0.51%, repeatability 98.44%, resolution 0.02%. Conclusions: As the sensitive unit of the torque sensor, the designed quartz wafer can obtain high response time and high resolution, solve the problems of low resolution and slow response time of the traditional strain gauge torque sensor, and reduce the use cost of the sensor.
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Fu, Hao, ChinYin Chen, Chongchong Wang, MinChiang Chao, Qiang Zhou, Guilin Yang i Guozhi Wang. "Quartz crystal based sensor head design and analysis for robot torque sensor application". Cobot 1 (26.04.2022): 11. http://dx.doi.org/10.12688/cobot.17474.1.
Pełny tekst źródłaStreszczenie:
Background: In recent years, with the gradual development of robot human-computer interaction, robots need to meet the precise control of more complex motion. Torque sensors play an important role. The traditional strain gauge sensor uses a metal strain gauge as the sensitive element, which means that the sensor has a slow response, low resolution and can easily be affected by external signal noise. Aiming at these deficiencies of strain gauge sensors, a sensor with cutting quartz square sheet as the sensor head is proposed. Methods: In order to study the application of quartz square sensing head in the sensor, firstly, COMSOL (5.6) simulation modeling is used to obtain the stress relationship between square quartz sheet and circular quartz sheet. Then the calculation formula of the force frequency coefficient of the circular quartz sheet is modified to obtain the calculation formula of the force frequency coefficient of the square quartz sheet, and the feasibility of the formula is verified by practical experiments. Next, the theoretical simulation and experimental research on the buckling limit force of quartz wafer are carried out, and the formula of buckling limit force in the process of quartz wafer installation is modified. Finally, the designed sensitive head is installed on the elastomer structure for verification. The frequency signal is collected by SGS-THOMSON Microelectronics 32 with a sampling rate of 1000Hz. Results: The main performances of the sensor are range 150nm, sensitivity 350Hz / nm, linearity 98.14%, hysteresis 0.51%, repeatability 98.44%, resolution 0.02%. Conclusions: As the sensitive unit of the torque sensor, the designed quartz wafer can obtain high response time and high resolution, solve the problems of low resolution and slow response time of the traditional strain gauge torque sensor, and reduce the use cost of the sensor.
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Maache, Mimoun, Florence Komurian-Pradel, Alain Rajoharison, Magali Perret, Jean-Luc Berland, Stéphane Pouzol, Audrey Bagnaud i in. "False-Positive Results in a Recombinant Severe Acute Respiratory Syndrome-Associated Coronavirus (SARS-CoV) Nucleocapsid-Based Western Blot Assay Were Rectified by the Use of Two Subunits (S1 and S2) of Spike for Detection of Antibody to SARS-CoV". Clinical and Vaccine Immunology 13, nr 3 (marzec 2006): 409–14. http://dx.doi.org/10.1128/cvi.13.3.409-414.2006.
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ABSTRACT To evaluate the reactivity of the recombinant proteins expressed in Escherichia coli strain BL21(DE3), a Western blot assay was performed by using a panel of 78 serum samples obtained, respectively, from convalescent-phase patients infected with severe acute respiratory syndrome-associated coronavirus (SARS-CoV) (30 samples) and from healthy donors (48 samples). As antigen for detection of SARS-CoV, the nucleocapsid protein (N) showed high sensitivity and strong reactivity with all samples from SARS-CoV patients and cross-reacted with all serum samples from healthy subjects, with either those obtained from China (10 samples) or those obtained from France (38 serum samples), giving then a significant rate of false positives. Specifically, our data indicated that the two subunits, S1 (residues 14 to 760) and S2 (residues 761 to 1190), resulted from the divided spike reacted with all samples from SARS-CoV patients and without any cross-reactivity with any of the healthy serum samples. Consequently, these data revealed the nonspecific nature of N protein in serodiagnosis of SARS-CoV compared with the S1 and S2, where the specificity is of 100%. Moreover, the reported results indicated that the use of one single protein as a detection antigen of SARS-CoV infection may lead to false-positive diagnosis. These may be rectified by using more than one protein for the serodiagnosis of SARS-CoV.
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Hamid, Abdulrahman, Hassan Baaj i Mohab El-Hakim. "Rutting Behaviour of Geopolymer and Styrene Butadiene Styrene-Modified Asphalt Binder". Polymers 14, nr 14 (7.07.2022): 2780. http://dx.doi.org/10.3390/polym14142780.
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Modifying asphalt binders is an effective method of improving the performance of asphalt pavement, such as its resistance to rutting. However, because modification changes the behaviour of binders, substantial laboratory testing is required before field application to determine the best mixtures. This research aimed to evaluate the impacts of temperature, stresses, polymer type, and modification rate on the rutting behaviour of the asphalt binder modified with fly-ash-based geopolymer (GF), styrene butadiene styrene (SBS), and a combination of SBS and GF. The rheological properties of asphalt binders were investigated using the frequency sweep test at various temperatures. Additionally, the multiple stress creep recovery test was conducted at various temperatures and stresses to calculate the non-recoverable creep compliance (Jnr) and the percent strain recovery (R). The rutting resistance of asphalt mixture was assessed using the Hamburg wheel rut test. The results revealed that the asphalt binder with 8% geopolymer (8%GF) exhibited the best response in terms of complex shear modulus (G*), rutting factor (G*/sinδ), R, and Jnr compared to the 4%GF and 12%GF at different temperatures. Another interesting finding is that GF’s use in the hybrid binder (2%SBS + 8%GF) led to a significant increase in the shear complex modulus and a decrease in the phase angle compared to the binder modified with 2%SBS. The geopolymer decreased the binder’s sensitivity to temperature for both unaged and RTFO asphalt binders. The hybrid binder would also improve strain recovery under high stress and temperatures and the ability to withstand severe traffic loads. Furthermore, there is a crucial relationship between temperature and Jnr, which could help asphalt pavement designers select suitable modifiers considering the local climate and traffic volume.
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Bintu, Alexandra, Gabriela Vincze, Catalin R. Picu, Augusto B. Lopes, Jose J. Grácio i Frederic Barlat. "Strain hardening rate sensitivity and strain rate sensitivity in TWIP steels". Materials Science and Engineering: A 629 (kwiecień 2015): 54–59. http://dx.doi.org/10.1016/j.msea.2015.01.080.
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Ding, Z. Y., Y. X. Song, Y. Ma, X. W. Huang i T. H. Zhang. "Nanoindentation Investigation on the Size-Dependent Creep Behavior in a Zr-Cu-Ag-Al Bulk Metallic Glass". Metals 9, nr 5 (27.05.2019): 613. http://dx.doi.org/10.3390/met9050613.
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Nanoindentation technology has been widely adopted to study creep behavior in small regions. However, nanoindentation creep behavior of metallic glass is still not well understood. In the present work, we investigated nanoindentation size effects on creep deformation in a Zr-based bulk metallic glass at room temperature. The total creep strain and strain rate of steady-state creep were gradually decreased with increasing holding depth under a Berkovich indenter, indicating a length-scale-dependent creep resistance. For a spherical indenter, creep deformations were insignificant in elastic regions and then greatly enhanced by increasing holding strain in plastic regions. Strain rate sensitivities (SRS) decreased with increasing holding depth and holding strain at first, and then stabilized as holding depth was beyond about 500 nm for both indenters. SRS values were 0.4–0.5 in elastic regions, in which atomic diffusion and free volume migration could be the creep mechanism. On the other hand, evolution of the shear transformation zone was suggested as a creep mechanism in plastic regions, and the corresponding SRS values were in the range of 0.05 to 0.3.
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Ma, Yi, Yuxuan Song i Taihua Zhang. "Revealing Nanoindentation Size-Dependent Creep Behavior in a La-Based Metallic Glassy Film". Nanomaterials 9, nr 12 (1.12.2019): 1712. http://dx.doi.org/10.3390/nano9121712.
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We systematically studied nanoindentation size effect on creep deformation in a La-based metallic glassy film, including holding depth effect and indenter size effect. Creep displacement was mainly dependent on both holding strain and deformation volume beneath indenter. Under elastic holding, creep strain was merely holding strain–dependent. While for plastic holding, creep strain was greatly enhanced by adopting smaller indenter and/or decreasing holding depth at the same holding strain. A strong nanoindentation size effect on creep resistance was validated. Strain rate sensitivities (SRS) were calculated, which were obviously higher at elastic regions than at plastic holdings. The relationship between SRS value and creep mechanism in metallic glass was discussed.
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Sharma, Krishna K., NK Jain, S. Jindal i N. Jain. "Reliability of Anti-Mycobacterial Drug Susceptibility Testing and Importance of Accreditation of Laboratory Performing the Test". SAARC Journal of Tuberculosis, Lung Diseases and HIV/AIDS 10, nr 1 (15.09.2013): 1–6. http://dx.doi.org/10.3126/saarctb.v10i1.8643.
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Introduction: Tuberculosis (TB) is one of the major causes of disease and death in the developing world. World Health Organization recommends that drug resistance surveillance should be carried out regularly in high-burden countries, not only to determine the level of drug resistant TB, but also to strengthen the laboratory capacity. The objective of the study was to evaluate drug susceptibility test (DST) and to observe on DST reports with high variability between the results of two laboratories. Methodology: The study was conducted at Hospital for Chest Diseases and Tuberculosis, SMS Medical College, Jaipur. This was an observational prospective study to analyze DST results, obtained from two different laboratories (Lab A and Lab B), of newly diagnosed sputum positive pulmonary tuberculosis patients registered on DOTS category I. Treatment outcome of patients was obtained from records at the referred clinics and hospitals. Results: Higher proportion of resistance was observed from Lab A (29%) than Lab B (16%), Proportion of MDR strains were higher from Lab A (12.5%) than Lab B (6.0%). Out of the patients whose treatment outcome were available, proportion of patients with treatment success were almost similar in both cohorts (84.6% vs. 85.2%), despite the difference in DST results. Success rate after treatment from Lab A was 60% even in patients with MDR strain, compared to 22% from Lab B. Conclusions: Disparity in DST results was observed from the two laboratories (non accredited and accredited) which does not correlate with the treatment outcome. This study points towards the need of proper quality assurance of the drug sensitivity testing in Mycobacterial testing laboratories. SAARC Journal of Tuberculosis, Lung Diseases & HIV/AIDS; 2013; X(1); 1-6 DOI: http://dx.doi.org/10.3126/saarctb.v10i1.8643
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Limbach, Rene, Bruno P. Rodrigues i Lothar Wondraczek. "Strain-rate sensitivity of glasses". Journal of Non-Crystalline Solids 404 (listopad 2014): 124–34. http://dx.doi.org/10.1016/j.jnoncrysol.2014.08.023.
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Entemeyer, D., E. Patoor, A. Eberhardt i M. Berveiller. "Strain rate sensitivity in superelasticity". International Journal of Plasticity 16, nr 10-11 (styczeń 2000): 1269–88. http://dx.doi.org/10.1016/s0749-6419(00)00010-3.
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Yun, H. M., i R. H. Titran. "Tensile strain-rate sensitivity of". Metallurgical Transactions A 23, nr 11 (listopad 1992): 3121–33. http://dx.doi.org/10.1007/bf02646131.
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Reda, Sherif M., Sampath K. Gollapudi i Murali Chandra. "Developmental increase in β-MHC enhances sarcomere length–dependent activation in the myocardium". Journal of General Physiology 151, nr 5 (2.01.2019): 635–44. http://dx.doi.org/10.1085/jgp.201812183.
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Shifts in myosin heavy chain (MHC) isoforms in cardiac myocytes have been shown to alter cardiac muscle function not only in healthy developing hearts but also in diseased hearts. In guinea pig hearts, there is a large age-dependent shift in MHC isoforms from 80% α-MHC/20% β-MHC at 3 wk to 14% α-MHC/86% β-MHC at 11 wk. Because kinetic differences in α- and β-MHC cross-bridges (XBs) are known to impart different cooperative effects on thin filaments, we hypothesize here that differences in α- and β-MHC expression in guinea pig cardiac muscle impact sarcomere length (SL)–dependent contractile function. We therefore measure steady state and dynamic contractile parameters in detergent-skinned cardiac muscle preparations isolated from the left ventricles of young (3 wk old) or adult (11 wk old) guinea pigs at two different SLs: short (1.9 µm) and long (2.3 µm). Our data show that SL-dependent effects on contractile parameters are augmented in adult guinea pig cardiac muscle preparations. Notably, the SL-mediated increase in myofilament Ca2+ sensitivity (ΔpCa50) is twofold greater in adult guinea pig muscle preparations (ΔpCa50 being 0.11 units in adult preparations but only 0.05 units in young preparations). Furthermore, adult guinea pig cardiac muscle preparations display greater SL-dependent changes than young muscle preparations in (1) the magnitude of length-mediated increase in the recruitment of new force-bearing XBs, (2) XB detachment rate, (3) XB strain-mediated effects on other force-bearing XBs, and (4) the rate constant of force redevelopment. Our findings suggest that increased β-MHC expression enhances length-dependent activation in the adult guinea pig cardiac myocardium.
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Klepaczko, J. R., i C. Y. Chiem. "On rate sensitivity of f.c.c. metals, instantaneous rate sensitivity and rate sensitivity of strain hardening". Journal of the Mechanics and Physics of Solids 34, nr 1 (styczeń 1986): 29–54. http://dx.doi.org/10.1016/0022-5096(86)90004-9.
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Jiang, Zhiqun, Xuezhi Zhang, Xichen Wan, Minjun Wei, Yue Liu, Cong Ding i Yilv Wan. "Efficacy and Safety of Combined Endovascular Embolization and Stereotactic Radiosurgery for Patients with Intracranial Arteriovenous Malformations: A Systematic Review and Meta-Analysis". BioMed Research International 2021 (14.04.2021): 1–11. http://dx.doi.org/10.1155/2021/6686167.
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Whether the use of endovascular embolization could provide additional benefits in patients treated with stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations (IAVMs) remains controversial. The current meta-analysis was conducted to assess the efficacy and safety of SRS with and without prior endovascular embolization in patients with IAVMs. The electronic databases of PubMed, EmBase, and Cochrane Library were systematically searched for eligible studies published from inception to August 12, 2020. The pooled results for obliteration rate, rehemorrhage rate, and permanent neurological deficits were calculated by odds ratios (ORs) with 95% confidence intervals (CIs) using the random-effects model. The sensitivity analysis, subgroup analysis, and publication bias for investigated outcomes were also evaluated. Nineteen studies (two prospective and 17 retrospective studies) involving a total of 3,454 patients with IAVMs were selected for the final meta-analysis. We noted that prior embolization and SRS were associated with a lower obliteration rate compared with SRS alone (OR, 0.57; 95% CI, 0.44–0.74; P < 0.001 ). However, prior embolization and SRS were not associated with the risk of rehemorrhage (OR, 1.05; 95% CI, 0.81–1.34; P = 0.729 ) and permanent neurological deficits (OR, 0.80; 95% CI, 0.48–1.33; P = 0.385 ) compared with SRS alone. The sensitivity analysis suggested that prior embolization might reduce the risk of permanent neurological deficits in patients with IAVMs treated with SRS. The treatment effects of prior embolization in patients with IAVMs could be affected by nidus volume, margin dose, intervention, and follow-up duration. This study found that prior embolization was associated with a reduced risk of obliteration in patients with IAVMs treated with SRS. Moreover, prior embolization might reduce the risk of permanent neurological deficits in patients with IAVMs.