Abstract
Molecular dynamics is applied to explore the deformation mechanism and crystal structure development of the AlCoCrFeNi high-entropy alloys under nanoimprinting. The influences of crystal ...structure, alloy composition, grain size, and twin boundary distance on the mechanical properties are carefully analyzed. The imprinting load indicates that the highest loading force is in ascending order with polycrystalline, nano-twinned (NT) polycrystalline, and monocrystalline. The change in alloy composition suggests that the imprinting force increases as the Al content in the alloy increases. The reverse Hall–Petch relation found for the polycrystalline structure, while the Hall–Petch and reverse Hall–Petch relations are discovered in the NT-polycrystalline, which is due to the interactions between the dislocations and grain/twin boundaries (GBs/TBs). The deformation behavior shows that shear strain and local stress are concentrated not only around the punch but also on GBs and adjacent to GBs. The slide and twist of the GBs play a major in controlling the deformation mechanism of polycrystalline structure. The twin boundary migrations are detected during the nanoimprinting of the NT-polycrystalline. Furthermore, the elastic recovery of material is insensitive to changes in alloy composition and grain size, and the formability of the pattern is higher with a decrease in TB distance.
The figure shows the microstructure evolution of AlCoCrFeNi high-entropy alloy with different crystallographic orientations (a), twin boundary spacings (b), twin boundary inclination angles (c).
...Display omitted
•Microstructure evolution reveals the formation of Lomer-Cottrell and Hirth dislocation locks.•Both the Hall–Petch and inverse Hall–Petch relationships are observed with the change of twin boundary spacing.•Microstructure evolution and atomic flow are greatly dependent on the spacing and inclination angle of the twin boundary.•Surface morphology and wear volume depend on the microstructure of the material.
Surface nanotribological properties and subsurface damage of Al0.4CoCrFeNi high-entropy alloy during the nano-scratching processes are investigated using molecular dynamics. The results show that the surface wear characteristics and scratching-caused surface damage significantly depend on the crystallographic orientation, spacing and inclination angle of the twin boundary. For the variation of crystallographic orientation, the largest friction coefficient belongs to the crystallographic orientation 001, indicating that the movement of the indenter in this substrate is most restricted. The microstructure evolution reveals the formation of Lomer-Cottrell and Hirth dislocation locks because of the distinctness of angle between various slip systems. Both the Hall–Petch and inverse Hall–Petch relationships are observed for the difference of twin boundary spacing, and the maximum indentation force is achieved with a tilt angle of 0° resulting from the various interactions among the dislocations and twin boundaries. The microstructure evolution and the atomic flow are greatly dependent on the spacing and the inclination angle of twin boundary, where the twin boundary migration is the significant factor. Furthermore, the surface morphology is distinct between workpieces due to the elastic recovery at the surface, nucleation and slipping of dislocation, which implies that the wear volume depends on the material microstructure.
Summary
Background
Lipid‐lowering effect was observed during treatment with tenofovir disoproxil fumarate (TDF) for chronic hepatitis B (CHB). However, the metabolic features in patients switching ...from TDF to tenofovir alafenamide (TAF) remain unclear.
Aims
To compare the impacts of switching from TDF to TAF or from entecavir to TAF on body weight and metabolic features in patients with CHB.
Methods
This was a multi‐centre, prospective, observational study in patients with CHB on TDF or entecavir who switched to TAF. Baseline characteristics, lipid profile and sugar profile were determined. This study received IRB approval from each hospital.
Results
We enrolled 177 patients on TDF (99) or entecavir (78) and followed them for 48 weeks after the switch to TAF. At baseline, TDF‐experienced patients had lower serum triglyceride, total cholesterol, high‐density lipoprotein (HDL) cholesterol and low‐density lipoprotein (LDL) cholesterol than entecavir‐experienced patients. The switch from TDF to TAF significantly increased body weight, triglyceride, total cholesterol, HDL, LDL, fasting glucose, glycaemic haemoglobin, insulin and insulin resistance. The switch from entecavir to TAF did not affect these measures. There was no significant difference in atherosclerotic cardiovascular disease risk scores between groups.
Conclusions
The switch from TDF to TAF was associated with weight gain, derangements of lipid profile, and increased insulin resistance in patients with CHB. Long‐term effects on these metabolic features need further investigation.
Body weight increase and metabolic derangements after TDF switch to TAF in patients with chronic hepatitis B.
Molecular dynamics (MD) simulation is applied to investigate the mechanical response of AlCrCuFeNi high-entropy alloy (HEA) under the conventional cutting and ultrasonic elliptical vibration-assisted ...cutting (UEVAC). The influences of vibration frequency, amplitude ratio, and phase angle on the material removal mechanism are investigated. The results show that the strain and stress are concentrated on the contact area between the workpiece and cutting tool, as well as at the grain boundaries in both cutting methods. The temperature of workpiece under the UEVAC is significantly larger than the conventional cutting, which can have a positive impact on the phase transformation and makes UEVAC easier. The analysis of structure and dislocation exposes that the deformation behavior of polycrystalline is strongly influenced by the grain boundaries, the evolution of stacking fault and dislocation is obstructed by the grain boundaries. Moreover, the average cutting force of the UEVAC is reduced as rising the vibration frequency and amplitude ratio, while the average force under the UEVAC with various phase angles has no significant difference. The number of chip atoms shows that the material removal rate is greater under the UEVAC with a larger vibration frequency, lower amplitude ratio and phase angle. The plastic deformation of chip becomes more serious under the UEVAC with a vibration frequency of 150 GHz, amplitude ratio of 4, and phase angle of 75° due to the smallest cutting ratio.
The figure shows the physical model (a), von Mises stress clouds (b) and relationship of force-cutting length (c) of AlCrCuFeNi HEA under the conventional cutting (b1 and c1) and UEVAC with vibration frequency of 150 GHz (b2 and c2). Display omitted
•The mechanism of UEVAC and the conventional nano-cutting method are exhibited and compared.•Effects of vibration frequency, amplitude ratio and phase angle on deformation behavior of AlCrCuFeNi HEA are investigated.•The cutting forces of UEVAC and conventional nanocutting show significant differences.•The UEVAC can produce the higher material removal rate compared to conventional cutting.
The figure shows the physical property of Cu47.5Zr47.5Al5 alloy in the various structures: polycrystalline (a) and twinned polycrystalline (b).
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•GB and TB play a significant role in ...preventing the spread of deformation.•High stress is located in front of the indenter and in the vicinity of GB.•Plastic deformation is governed by the interaction of dislocation-GB-TB.•The inverse Hall-Petch relationship is observed with different grain sizes.
Molecular dynamics (MD) simulation is applied to study the plastic deformation response of the nanoscratching process via the investigation of an indenter sliding on the surface of CuZrAl nanocrystalline. The effects of different crystal structures, alloy compositions, grain sizes, and twin lamellar thicknesses are paid special attention. The results show that the force and hardness are decreased in the order of single crystalline, twinned polycrystalline and polycrystalline. The average force value during the scratching stage is larger when the Cu content decreases. Interestingly, the inverse Hall-Petch relationship is observed from the change of grain sizes and twin lamellar thicknesses. Furthermore, the grain boundary (GB), twin boundary (TB) and grain growth play a significant role in preventing the spread of deformation in the polycrystalline and twinned polycrystalline structures. The plastic deformation of single crystalline is controlled by the interaction of dislocations. Whereas the plastic deformation of polycrystalline is dominated by the interaction of dislocation and GB. For twinned polycrystalline, the interaction of dislocation-GB-TB has simultaneously occurred in the deformation process. A comparison of the special wear rates, this value is the largest with the polycrystalline structure in different crystal structures, while it tends to rise as decreasing the grain size.
Molecular dynamics simulations are employed to study indentation/scratching tests on the mechanical properties of Cu64Zr36/Cu amorphous/crystalline nanolaminates. The formation of narrow shear bands ...is the major cause of plastic deformation in the single indentation. In cyclic indentation, the deformation behavior has no significant difference with the various number of cycles. The cyclic load and hardness increase as rising the cyclic number. The hysteresis loop appears and is wider with increasing loading/reloading steps. In the scratching test, the shear deformation process occurs in the shear plane. The forces increase rapidly in the first stage; then the normal forces increase gradually, the tangential forces fluctuate horizontally. The friction coefficient increases higher with the increasing cutting depth; its value oscillates from 1.0 to 1.21.
The figure is shown the local stress distribution (a), the atomic configuration (b and c), and the temperature (d) of Cu64Zr36/Cu A/C nanolaminates under different processes. Display omitted
•The shear bands do not appear in the crystalline layers too thin.•The thicker crystalline layers effectively prevent the spread of stress and strain.•The friction between the indenter and substrate also induces a local heat gain.•The hysteresis loop appears and is wider as increasing unloading/reloading steps.•The shear deformation process occurs in the shear plane during the scratching test.
•Sliding of grain boundary and grain growth play a key role in the plastic deformation mechanism.•Atoms in a state of high stress-strain are located around the abrasive tip and in the grain ...boundary.•The reverse Hall-Petch relationship is observed within the grain size range of this study.•The ability to lose the material volume of a polycrystalline is larger than a single-crystalline.
The mechanical response of CuAlNi nanocrystalline under the nanoscratch through an abrasive tip sliding on the workpiece is investigated using molecular dynamics (MD) simulation. The influences of the grain size, alloy composition, temperature and scratch speed on the plastic deformation characteristic and wear mechanism are surveyed. The results represent that increasing the grain size leads to higher force and hardness, which suggests the reverse Hall-Petch relationship. Meanwhile, the indentation and scratch forces tend to increase when reducing the Cu content and temperature, increasing the scratch speed. The deformation behavior exhibits that grain boundaries play a key role in inhibiting the spread of strain and stress. The results show that the stress and strain are concentrated not only in the contact region between the abrasive tip and substrate but also in the grain boundary and adjacent grain boundary areas. Notably, the sliding, twisting of grain boundary and the fusion of grains are a significant mechanism in the deformation behavior of polycrystalline, resulting in the dislocation is strongly developed in the grain boundary. Furthermore, the movement of atoms in various directions leads to different morphology of pile-up. From quantitative results of the special wear rate show that the ability to lose material volume is larger with Cu86Al11Ni3 alloy and at a temperature of 600 K, as well as the polycrystalline is higher than the single-crystalline. Finally, the residual depth ratios exhibit more strain recovery at the grain size of 6.17 nm and lower temperature.
The figure shows the workpiece model (a) and the evolution of grain of CuAlNi alloy at different positions: (b1) before scratching, (b2) an indentation depth of 2.0 nm, (b3) a scratching distance of 1.0 nm, (b4) a scratching distance of 4.0 nm, (b5) a scratching distance of 8.0 nm. Display omitted
TiNi intermetallic alloys were prepared with 2, 4 and 6 at.% niobium (Nb) addition. The mechanical properties and microstructures of the alloys were investigated under both static (1 × 10
to 1 × 10
s
...) and dynamic (4 × 10
to 6 × 10
s
) loading conditions. The intermetallic alloy structures and surface morphologies of the alloys were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. In addition, the fracture morphologies were observed by optical microscopy (OM). It was shown that the addition of 2 to 4 at.% Nb increased the strength of the TiNi alloy. However, as the level of Nb addition was further increased to 6 at.%, a significant reduction in strength occurred. For a constant Nb addition, the plastic flow stress and strain rate sensitivity increased with increasing strain rate under both loading conditions (static and dynamic). The XRD and SEM results showed that the original surface morphologies were composed primarily of dendritic structures and fine β-Nb + TiNi eutectic systems. Moreover, the OM results showed that the alloys underwent a transition from a brittle fracture mode to a ductile fracture mode as the level of Nb addition increased.
Countries are paying increasing attention to environmental issues and are moving towards the goal of energy saving and carbon reduction. This research presents a method to analyse the effects of the ...use of non-thermal plasma (NTP) and water injection (WI) devices on the efficiency of internal combustion engines. The devices were installed on the intake manifold to investigate the effects of additional substances produced by electrolysis on the engine performance and exhaust emissions. According to the results, the addition of the NTP and WI devices affected the power efficiency and the rate of change of the brake-specific fuel consumption (BSFC) of the internal combustion engines. In addition, the change rate of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in the exhaust gases was affected. In conclusion, the study found that the additional substances generated by the NTP-electrolysed water mist or air influenced the fuel combustion efficiency and exhaust emissions.
Background and Aim
Reducing post‐absorptive (fasting) phase by eating late evening snacks (LESs) is a potential intervention to improve substrate utilization and reverse sarcopenia. This study ...analyzed the results of published randomized controlled trials and controlled clinical trials to evaluate the effects of LES on liver function of patients with cirrhosis.
Methods
A meta‐analysis was conducted. The search strategy included electronic database searches, and 300 articles were searched. Eight of these articles provided qualified data for pooling and analysis. Outcomes assessments included serum albumin, total bilirubin, alanine aminotransferase, prothrombin time, and aspartate aminotransferase, complications of cirrhosis, severity of liver disease, and blood glucose levels.
Results
Our analysis included eight studies comprising 341 patients (167 in LES groups and 174 in control groups). The results showed that LES intervention helped to maintain liver reserves. These eight studies demonstrated that LES intervention had significant effects for liver biochemical parameters on albumin, ammonia, and prothrombin time, with respective effect sizes of 0.233, −0.425, and −0.589; liver enzymes include aspartate aminotransferase and alanine aminotransferase, with respective effect sizes of −0.320 and −0.284. Studies on clinical signs of liver dysfunction showed lower occurrence rates of ascites and hepatic encephalopathy than in the control group. LES had no significant effect on Child–Pugh score.
Conclusions
The overall results of the meta‐analysis indicated that having LES can improve liver function reserve for patients with liver cirrhosis, with or without hepatocellular carcinoma. LES is a promising intervention for reversing anabolic resistance and the sarcopenia of cirrhosis, resulting in an improved quality of life for patients with cirrhosis.
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