Search Results (8)

The hot deformation behavior of a Mg-9.2Er-4.9Sm-2.2Zn-0.6Zr (wt.%) alloy, with emphasis on the role of grain size and long-period stacking-ordered (LPSO) phases, was examined via comparison experiments. Two types of samples were obtained through distinct heat treatment schedules: sample A had a smaller grain size, featuring block-shaped LPSO phases at grain boundaries and lamellar LPSO phases within grains, while sample B had a larger grain size and few LPSO phases. The hot deformation behavior was characterized by the true stress–strain curve within the processing window of 300–450 °C and 0.001–1 s⁻¹. The block-shaped LPSO phases contributed more significantly to strain hardening, leading to elevated flow stress in sample A, particularly under low-temperature and high-strain-rate conditions. Through the particle-stimulated nucleation (PSN) mechanism, block-shaped LPSO phases demonstrated greater efficiency in promoting Dynamic recrystallization (DRX) compared to lamellar LPSO phases; additionally, the synergistic effect between LPSO phases and grain boundary density further improved DRX efficiency. During hot deformation, dynamic precipitation of both block-shaped and lamellar LPSO phases occurred. The formation of block-shaped phases required a longer duration than that of lamellar ones. The presence of the LPSO kink exerted an influence on DRX, while a significant angle kink can promote DRX. Full article

Organic photovoltaics (OPVs) differ from their inorganic counterparts because of inevitable electronic disorders and structural heterogeneity. Charge carrier traps are inevitable in organic semiconductors. A common failure mechanism of OPVs is the development of an S-shaped current density–voltage characteristic (J-V curve). Herein, we focus on investigating the underlying physical mechanism of S-shaped deformation of J-V curve of the inverted organic photovoltaic devices with bulk-heterojunction, proven by experiments with the n-doped electron extraction layer and numerical simulations assuming electron traps (0.1 eV deeper) in the electron extraction layer. The numerical simulations are quite consistent with the experimental results. In addition, the open circuit voltage induced by S-kink is exemplified to be enhanced after removing the electron traps in the interlayer by introducing a dopant of cesium carbonate. Full article

Despite numerous studies on energy productivity and efficiency, only a few focus on the electricity intensity (EI) of economic output. As these studies largely examine the declining trend in EI, the increasing and/or fluctuating trends in EI have not been studied. We analyze EI trends by estimating the progress ratios from experience curves of 91 countries from 1991 to 2011. The results reveal wide variation in progress ratios, ranging from 53% to 135%, with an average of 101.5%. Furthermore, more than half of the 91 countries displayed a kinked slope, indicating the fluctuating rate of change in EI. The rate of population growth seems to be related to the increasing EI trends. A clear understanding of the relative performance of each country in terms of the progress ratio and the pattern of EI trends would be useful for the country’s policymakers to develop strategic options for the future. Full article

According to the basic principle of the hydraulic anti-kink system and flow continuity equation, this paper takes the low-floor tram as the research object and the four vehicles as the research carrier. Based on the correlation parameters between the vehicle subsystem and the hydraulic subsystem, a co-simulation platform of a low-floor tram with hydraulic an anti-kink system is built. The co-simulation results show that the anti-kink system can well maintain the relative yaw angle consistency between the vehicle body and bogie. The anti-kink system restrains the maximum yaw angle and excessive lateral displacement of the vehicle body effectively. The consistency between the experiment results and the simulation results shows the accuracy of the model. The co-simulation model of the low-floor tram with hydraulic anti-kink system can be used to research the dynamic performance when it passes through curve line. Full article

Despite the fact that fine particulate matter (PM_2.5) causes serious health issues, few studies have investigated the level and annual rate of PM_2.5 change across a large number of countries. For a better understanding of the global trend of PM_2.5, this study classified 190 countries into groups showing different trends of PM_2.5 change during the 2000–2014 period by estimating the progress ratio (PR) from the experience curve (EC), with PM_2.5 exposure (PME)–the population-weighted average annual concentration of PM_2.5 to which a person is exposed—as the dependent variable and the cumulative energy consumption as the independent variable. The results showed a wide variation of PRs across countries: While the average PR for 190 countries was 96.5%, indicating only a moderate decreasing PME trend of 3.5% for each doubling of the cumulative energy consumption, a majority of 118 countries experienced a decreasing trend of PME with an average PR of 88.1%, and the remaining 72 countries displayed an increasing trend with an average PR of 110.4%. When two different types of EC, classical and kinked, were applied, the chances of possible improvement in the future PME could be suggested in the descending order as follows: (1) the 60 countries with an increasing classical slope; (2) the 12 countries with an increasing kinked slope; (3) the 75 countries with a decreasing classical slope; and (4) the 43 countries with a decreasing kinked slope. The reason is that both increasing classical and kinked slopes are more likely to be replaced by decreasing kinked slopes, while decreasing classical and kinked slopes are less likely to change in the future. Population size seems to play a role: A majority of 52%, or 38 out of the 72 countries with an increasing slope, had a population size of bigger than 10 million inhabitants. Many of these countries came from SSA, EAP, and LAC regions. By identifying different patterns of past trends based on the analysis of PME for individual countries, this study suggests a possible change of the future slope for different groups of countries. Full article

Beam deflection experiments were used to systematically examine size effects on the low cyclic fatigue (LCF) deformation behaviour of micro-sized bending beams of copper (Cu) single crystals oriented for single slip, critical and coplanar double slip. We present cyclic hardening curves and fatigue surface roughness, as well as dislocations structures of the micro-sized beams with sizes between 1 and 15 µm. A clear crystal orientation and size effect on the cyclic hardening curves, surface roughness, and the dislocation microstructures were observed. Based on the experimental results, the fatigue damage in single slip orientations clearly decreased with decreasing the sample size, however, below a critical size regime, the surface damage suddenly increases. Additionally, samples with sizes larger than 5 µm clearly revealed, besides PSBs-like structures, the emergence of kink bands leading to larger surface roughness in comparison to the smaller ones. Fatigue surface damages in microcrystals oriented for critical double slip became more prevalent compared to single slip orientations. Quantitatively, the correlation of the fatigue surface damage was also demonstrated with the formation of PSBs-like structures. Full article

In this study, we performed off-axis transverse loading experiments to study the stress concentration developed in a high-performance yarn with different indenters. A universal testing machine was utilized to perform quasi-static transverse loading experiments on Twaron^® yarns. Seven different round indenters possessing radius of curvature ranging from 0.20 to 4.50 mm were employed in the experiments. In addition, post-mortem failure analysis was performed on the recovered specimens via a scanning electron microscope. From the transverse loading experiments, the results showed that, as the radius of curvature of the indenters increased, the concentrated load decreased, causing the failure surfaces to change from a combination of kink band, snapped-back, and localized shear to only fibrillations. The concentrated stresses were predicted by a strain energy model when loaded by an indenter with a radius of curvature smaller than 1.59 mm. For indenters larger than 1.59 mm, the specimens failed in fibrillation, the concentrated stresses agreed well with the stresses predicted by quasi-static circular curved beam theory. Full article

Many countries in the world have been experiencing widely varying rates of change in their carbon intensity (CI) of economic output. The dynamic trend of CI in this research is measured by the progress ratio (PR) from an experience curve (EC) involving 127 countries during the period of 1980–2011. The overall average PR of 88.8% estimated for the total group of 127 indicates a decreasing trend of carbon intensity. This means that each doubling of the cumulative CO₂ emission by this group has reduced carbon intensity by 11.2%. While a majority of 83 countries experienced a decreasing trend with an average PR of 73.1%, the remaining 44 countries have experienced an increasing trend with an average PR of 114.5%. When two different types of EC, classical and kinked, were applied, 73 countries displayed a kinked slope with an average PR of 73.4%, and 54 countries displayed a classical slope with an average PR of 104.2%. Examination of the type of trend and slope of EC suggests the chance of a major improvement of the future CI in the following order: (1) the 35 countries with a classical slope and an increasing trend of CIs; (2) the nine countries with a kinked slope and an increasing trend of CIs; (3) the 19 countries with a classical slope and a decreasing trend of CIs; and (4) the 64 countries with a kinked slope and a decreasing trend of CIs. Further implications from these findings are discussed. Full article