Showing papers by "YuanTong Gu published in 2016"
TL;DR: In this paper, a two-dimensional (2D) ionic boron structure was predicted using ab initio evolutionary structure search, which consists of a graphene-like plane and B2 atom pairs with the P6/mmm space group and six atoms in the unit cell.
Abstract: Recently, partially ionic boron (γ-B28) has been predicted and observed in pure boron, in bulk phase and controlled by pressure [Nature 2009, 457, 863]. By using ab initio evolutionary structure search, we report the prediction of ionic boron at a reduced dimension and ambient pressure, namely, the two-dimensional (2D) ionic boron. This 2D boron structure consists of graphene-like plane and B2 atom pairs with the P6/mmm space group and six atoms in the unit cell and has lower energy than the previously reported α-sheet structure and its analogues. Its dynamical and thermal stability are confirmed by the phonon-spectrum and ab initio molecular dynamics simulation. In addition, this phase exhibits double Dirac cones with massless Dirac Fermions due to the significant charge transfer between the graphene-like plane and B2 pair that enhances the energetic stability of the P6/mmm boron. A Fermi velocity (vf) as high as 2.3 × 106 m/s, which is even higher than that of graphene (0.82 × 106 m/s), is predicted for...
214 citations
TL;DR: In this paper, the authors studied the thermal conductivities of diamond nanothread (DNT) based on non-equilibrium molecular dynamics simulations, and found that the properties of DNT are different from those of single-wall carbon nanotubes.
73 citations
TL;DR: In this article, two types of space-time fractional diffusion equations (STFDE) on a finite domain were considered and two schemes to approximate the time derivative and finite element methods for the space derivative were presented.
Abstract: In this paper, we consider two types of space-time fractional diffusion equations(STFDE) on a finite domain. The equation can be obtained from the standard diffusion equation by replacing the second order space derivative by a Riemann-Liouville fractional derivative of order s (1
68 citations
TL;DR: In this article, a sp3-bonded diamond nanothread (DNT) was shown to transition from brittle to ductile behavior by varying the length of the polybenzene sections, suggesting that DNT possesses entirely different mechanical responses than other 1D carbon allotropes.
Abstract: As a potential building block for the next generation of devices/multifunctional materials that are spreading in almost every technology sector, one-dimensional (1D) carbon nanomaterial has received intensive research interests. Recently, a new ultra-thin diamond nanothread (DNT) has joined this palette, which is a 1D structure with poly-benzene sections connected by Stone–Wales (SW) transformation defects. Using large-scale molecular dynamics simulations, we found that this sp3 bonded DNT can transition from brittle to ductile behaviour by varying the length of the poly-benzene sections, suggesting that DNT possesses entirely different mechanical responses than other 1D carbon allotropes. Analogously, the SW defects behave like a grain boundary that interrupts the consistency of the poly-benzene sections. For a DNT with a fixed length, the yield strength fluctuates in the vicinity of a certain value and is independent of the “grain size”. On the other hand, both yield strength and yield strain show a clear dependence on the total length of DNT, which is due to the fact that the failure of the DNT is dominated by the SW defects. Its highly tunable ductility together with its ultra-light density and high Young's modulus makes diamond nanothread ideal for the creation of extremely strong three-dimensional nano-architectures.
67 citations
TL;DR: In this article, a series of in-silico pull-out studies of the diamond nanothread (DNT) in polyethylene (PE) matrix was conducted, and the authors found that the load transfer between DNT and PE matrix is dominated by the non-covalent interactions, in particular the van der Waals interactions.
Abstract: This work explores the application of a new one-dimensional carbon nanomaterial, the diamond nanothread (DNT), as a reinforcement for nanocomposites. Owing to the existence of Stone-Wales transformation defects, the DNT intrinsically possesses irregular surfaces, which is expected to enhance the non-covalent interfacial load transfer. Through a series of in silico pull-out studies of the DNT in polyethylene (PE) matrix, we found that the load transfer between DNT and PE matrix is dominated by the non-covalent interactions, in particular the van der Waals interactions. Although the hydrogenated surface of the DNT reduces the strength of the van der Waals interactions at the interface, the irregular surface of the DNT can compensate for the weak bonds. These factors lead to an interfacial shear strength of the DNT/PE interface comparable with that of the carbon nanotube (CNT)/PE interface. Our results show that the DNT/PE interfacial shear strength remains high even as the number of Stone-Wales transformation defects decreases. It can be enhanced further by increasing the PE density or introduction of functional groups to the DNT, both of which greatly increase the non-covalent interactions.
64 citations
TL;DR: In this paper, the effectiveness of three different analytical wake models (PARK model, Larsen model and B-P model) is thoroughly compared over a wide range of wake properties, and the results show that when using the PARK model the surface roughness value (z0) must be carefully tuned to achieve good performance in predicting wind farm power production.
59 citations
Journal Article•
TL;DR: In this article, the thermal conductivities of diamond nanothread (DNT) were studied based on non-equilibrium molecular dynamics simulations, and strong length dependence in thermal conductivity was observed in DNTs with different lengths of poly-benzene rings.
Abstract: Based on the non-equilibrium molecular dynamics simulations, we have studied the thermal conductivities of a novel ultra-thin one-dimensional carbon nanomaterial - diamond nanothread (DNT). Unlike single-wall carbon nanotube (CNT), the existence of the Stone-Wales transformations in DNT endows it with richer thermal transport characteristics. There is a transition from wave-dominated to particle-dominated transport region, which depends on the length of poly-benzene rings. However, independent of the transport region, strong length dependence in thermal conductivity is observed in DNTs with different lengths of poly-benzene ring. The distinctive SW characteristic in DNT provides more degrees of freedom to tune the thermal conductivity not found in the homogeneous structure of CNT. Therefore, DNT is an ideal platform to investigate various thermal transport mechanisms at the nanoscale. Its high tunability raises the potential to design DNTs for different applications, such as thermal connection and temperature management.
55 citations
TL;DR: In this paper, the authors studied the mechanical properties of three representative diamond nanothreads using molecular dynamics simulations and found that the tensile properties of NTHs can vary significantly due to morphology differences, which originate from the different stress distributions determined by its structure.
45 citations
TL;DR: A new phase of transition metal dichalcogenides is discovered (labelled as T''), which is confirmed to be energetically, dynamically and kinetically stable by first-principles calculations and to offer a feasible way to control the electronic states of 2D topological insulators for the fabrication of high-speed spintronics devices.
Abstract: Single layered transition metal dichalcogenides have attracted tremendous research interest due to their structural phase diversities. By using a global optimization approach, we have discovered a new phase of transition metal dichalcogenides (labelled as T′′), which is confirmed to be energetically, dynamically and kinetically stable by our first-principles calculations. The new T′′ MoS2 phase exhibits an intrinsic quantum spin Hall (QSH) effect with a nontrivial gap as large as 0.42 eV, suggesting that a two-dimensional (2D) topological insulator can be achieved at room temperature. Most interestingly, there is a topological phase transition simply driven by a small tensile strain of up to 2%. Furthermore, all the known MX2 (M = Mo or W; X = S, Se or Te) monolayers in the new T′′ phase unambiguously display similar band topologies and strain controlled topological phase transitions. Our findings greatly enrich the 2D families of transition metal dichalcogenides and offer a feasible way to control the electronic states of 2D topological insulators for the fabrication of high-speed spintronics devices.
44 citations
Journal Article•
TL;DR: This paper considers two types of space-time fractional diffusion equations (STFDE) on a finite domain and presents two schemes to approximate the time derivative and finite element methods for the space derivative, finding the optimal convergence rate can be reached.
Abstract: In this paper, we consider two types of space-time fractional diffusion equations(STFDE) on a finite domain. The equation can be obtained from the standard diffusion equation by replacing the second order space derivative by a Riemann-Liouville fractional derivative of order β (1 < β ≤ 2), and the first order time derivative by a Caputo fractional derivative of order γ (0 < γ ≤ 1). For the 0 < γ < 1 case, we present two schemes to approximate the time derivative and finite element methods for the space derivative, the optimal convergence rate can be reached O(τ2−γ + h2) and O(τ2 + h2), respectively, in which τ is the time step size and h is the space step size. And for the case γ = 1, we use the Crank-Nicolson scheme to approximate the time derivative and obtain the optimal convergence rate O(τ2 + h2) as well. Some numerical examples are given and the numerical results are in good agreement with the theoretical analysis.
43 citations
Journal Article•
TL;DR: In this article, a new phase of transition metal dichalcogenides (labeled as T′′), which is confirmed to be energetically, dynamically and kinetically stable by first-principles calculations was discovered.
Abstract: Single layered transition metal dichalcogenides have attracted tremendous research interest due to their structural phase diversities By using a global optimization approach, we have discovered a new phase of transition metal dichalcogenides (labelled as T′′), which is confirmed to be energetically, dynamically and kinetically stable by our first-principles calculations The new T′′ MoS2 phase exhibits an intrinsic quantum spin Hall (QSH) effect with a nontrivial gap as large as 042 eV, suggesting that a two-dimensional (2D) topological insulator can be achieved at room temperature Most interestingly, there is a topological phase transition simply driven by a small tensile strain of up to 2% Furthermore, all the known MX2 (M = Mo or W; X = S, Se or Te) monolayers in the new T′′ phase unambiguously display similar band topologies and strain controlled topological phase transitions Our findings greatly enrich the 2D families of transition metal dichalcogenides and offer a feasible way to control the electronic states of 2D topological insulators for the fabrication of high-speed spintronics devices
TL;DR: In this paper, a series of in-silico pull-out studies of the diamond nanothread (DNT) in polyethylene (PE) matrix was conducted, and the authors found that the load transfer between DNT and PE matrix is dominated by the non-covalent interactions, in particular the van der Waals interactions.
Abstract: This work explores the application of a new one-dimensional carbon nanomaterial, the diamond nanothread (DNT), as a reinforcement for nanocomposites. Owing to the existence of Stone-Wales transformation defects, the DNT intrinsically possesses irregular surfaces, which is expected to enhance the non-covalent interfacial load transfer. Through a series of in silico pull-out studies of the DNT in polyethylene (PE) matrix, we found that the load transfer between DNT and PE matrix is dominated by the non-covalent interactions, in particular the van der Waals interactions. Although the hydrogenated surface of the DNT reduces the strength of the van der Waals interactions at the interface, the irregular surface of the DNT can compensate for the weak bonds. These factors lead to an interfacial shear strength of the DNT/PE interface comparable with that of the carbon nanotube (CNT)/PE interface. Our results show that the DNT/PE interfacial shear strength remains high even as the number of Stone-Wales transformation defects decreases. It can be enhanced further by increasing the PE density or introduction of functional groups to the DNT, both of which greatly increase the non-covalent interactions.
TL;DR: In this article, the authors investigated the adsorption dynamics, BMPRs-recruitment, and bioactivity of recombinant human BMP-2 on the HAP and Mg-HAP surfaces.
Abstract: Biomaterial surface functionalized with bone morphogenetic protein-2 (BMP-2) is a promising approach to fabricating successful orthopedic implants/scaffolds. However, the bioactivity of BMP-2 on material surfaces is still far from satisfactory and the mechanism of related protein-surface interaction remains elusive. Based on the most widely used bone-implants/scaffolds material, hydroxyapatite (HAP), we developed a matrix of magnesium-substituted HAP (Mg-HAP, 2.2 at% substitution) to address these issues. Further, we investigated the adsorption dynamics, BMPRs-recruitment, and bioactivity of recombinant human BMP-2 (rhBMP-2) on the HAP and Mg-HAP surfaces. To elucidate the mechanism, molecular dynamic simulations were performed to calculate the preferred orientations, conformation changes, and cysteine-knot stabilities of adsorbed BMP-2 molecules. The results showed that rhBMP-2 on the Mg-HAP surface exhibited greater bioactivity, evidenced by more facilitated BMPRs-recognition and higher ALP activity than on the HAP surface. Moreover, molecular simulations indicated that BMP-2 favoured distinct side-on orientations on the HAP and Mg-HAP surfaces. Intriguingly, BMP-2 on the Mg-HAP surface largely preserved the active protein structure evidenced by more stable cysteine-knots than on the HAP surface. These findings explicitly clarify the mechanism of BMP-2-HAP/Mg-HAP interactions and highlight the promising application of Mg-HAP/BMP-2 matrixes in bone regeneration implants/scaffolds.
TL;DR: The ability of pristine and calcined HT getters to effectively capture radioactive cations which can be securely stabilized at the getter surface is explored and it is found that calcine HT outperforms its pristine counterpart in cation removal ability.
Abstract: Hydrotalcite (HT)-based materials are usually applied to capture anionic pollutants in aqueous solutions. Generally considered anion exchangers, their ability to capture radioactive cations is rarely exploited. In the present work, we explored the ability of pristine and calcined HT getters to effectively capture radioactive cations (Sr2+ and Ba2+) which can be securely stabilized at the getter surface. It is found that calcined HT outperforms its pristine counterpart in cation removal ability. Meanwhile, a novel anion removal mechanism targeting radioactive I– is demonstrated. This approach involves HT surface modification with silver species, namely, Ag2CO3 nanoparticles, which can attach firmly on HT surface by forming coherent interface. This HT-based anion getter can be further used to capture I– in aqueous solution. The observed I– uptake mechanism is distinctly different from the widely reported ion exchange mechanism of HT and much more efficient. As a result of the high local concentrations of pr...
TL;DR: In this paper, a coupled finite volume and discrete element numerical method is used to numerically investigate the mechanisms that govern particle-laden gas flows and particulate fouling in idealized metal foam air-cooled heat exchangers.
TL;DR: In this paper, the deformation mechanisms of a monolayer graphene membrane under hypervelocity impact (from 2 to 6 km/s) were investigated and it was found that cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation.
Abstract: The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield. By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies. It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation. Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth. For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane. Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile. The higher kinetic energy, the more number the cracks. This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft.
Journal Article•
TL;DR: In this article, the authors studied the mechanical properties of three representative NTHs using molecular dynamics simulations and found that the NTH can vary significantly due to morphology differences, which are believed to originate from the different stress distributions determined by its structure.
Abstract: The ultrathin one-dimensional sp3 diamond nanothreads (NTHs), as successfully synthesised recently, have greatly augmented the interests from the carbon community. In principle, there can exist different stable NTH structures. In this work, we studied the mechanical behaviours of three representative NTHs using molecular dynamics simulations. It is found that the mechanical properties of NTH can vary significantly due to morphology differences, which are believed to originate from the different stress distributions determined by its structure. Further studies have shown that the temperature has a significant impact on the mechanical properties of the NTH. Specifically, the failure strength/strain decreases with increasing temperature, and the effective Young's modulus appears independent of temperature. The remarkable reduction of the failure strength/strain is believed to be resulted from the increased bond re-arrangement process and free lateral vibration at high temperatures. In addition, the NTH is found to have a relatively high bending rigidity, and behaves more like flexible elastic rod. This study highlights the importance of structure-property relation and provides a fundamental understanding of the tensile behaviours of different NTHs, which should shed light on the design and also application of the NTH-based nanostructures as strain sensors and mechanical connectors.
Journal Article•
TL;DR: This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft.
Abstract: The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile The higher kinetic energy, the more number the cracks This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft
TL;DR: In this paper, a new approach named simultaneous layout plus control optimization is developed to reduce power losses caused by the wake interactions of the air flow induced by the upstream turbines to the downstream turbines.
TL;DR: The point interpolation method (PIM), a meshfree method, is further developed to solve SFADE, where the polynomial point-interpolation functions and their fractional derivatives with explicit expressions are substituted into Galerkin weak form of SFADE to obtain the discrete approximation system.
TL;DR: In this article, an advanced finite element analysis (FEA) model combining porohyperelastic (PHE) constitutive model and cohesive zone formulation is developed to explore the mechanism of adhesion.
Abstract: It is well-known that cell adhesion is important in many biological processes such as cell migration and proliferation. A better understanding of the cell adhesion process will shed insight into these cellular biological responses as well as cell adhesion-related diseases treatment. However, there is little research which has attempted to investigate the process of cell adhesion and its mechanism. Thus, this paper aims to study the time-dependent adhesion properties of single living chondrocytes using an advanced coupled experimental-numerical approach. Atomic Force Microscopy (AFM) tips will be used to apply lateral forces to detach chondrocytes that are seeded for three different periods. An advanced Finite Element Analysis (FEA) model combining porohyperelastic (PHE) constitutive model and cohesive zone formulation is developed to explore the mechanism of adhesion. The results revealed that the cells can resist normal traction better than tangential traction in the beginning of adhesion. This is when the cell adhesion molecules establish early attachment to the substrates. After that when the cells are spreading, stress fiber bundles generate tangential traction on the substrate to form strong adhesion. Both simulation and experimental results agree well with each other, providing a powerful tool to study the cellular adhesion process.
TL;DR: In this paper, an elastic spring network based on the discrete element method (DEM) is employed to model the three-dimensional red blood cells (RBCs) membrane and the haemoglobin in the RBC and the plasma in the blood are modeled as smoothed particle hydrodynamics (SPH) particles.
Abstract: Blood continuously flows through the blood vessels in the human body. When blood flows through the smallest blood vessels, red blood cells (RBCs) in the blood exhibit various types of motion and deformed shapes. Computational modelling techniques can be used to successfully predict the behaviour of the RBCs in capillaries. In this study, we report the application of a meshfree particle approach to model and predict the motion and deformation of three-dimensional RBCs in capillaries. An elastic spring network based on the discrete element method (DEM) is employed to model the three-dimensional RBC membrane. The haemoglobin in the RBC and the plasma in the blood are modelled as smoothed particle hydrodynamics (SPH) particles. For validation purposes, the behaviour of a single RBC in a simple shear flow is examined and compared against experimental results. Then simulations are carried out to predict the behaviour of RBCs in a capillary; (i) the motion of five identical RBCs in a uniform capillary, (ii) the motion of five identical RBCs with different bending stiffness (K
b
) values in a stenosed capillary, (iii) the motion of three RBCs in a narrow capillary. Finally five identical RBCs are employed to determine the critical diameter of a stenosed capillary. Validation results showed a good agreement with less than 10% difference. From the above simulations, the following results are obtained; (i) RBCs exhibit different deformation behaviours due to the hydrodynamic interaction between them. (ii) Asymmetrical deformation behaviours of the RBCs are clearly observed when the bending stiffness (K
b
) of the RBCs is changed. (iii) The model predicts the ability of the RBCs to squeeze through smaller blood vessels. Finally, from the simulations, the critical diameter of the stenosed section to stop the motion of blood flow is predicted. A three-dimensional spring network model based on DEM in combination with the SPH method is successfully used to model the motion and deformation of RBCs in capillaries. Simulation results reveal that the condition of blood flow stopping depends on the pressure gradient of the capillary and the severity of stenosis of the capillary. In addition, this model is capable of predicting the critical diameter which prevents motion of RBCs for different blood pressures.
TL;DR: In this paper, the porohyperelastic (PHE) model was used to investigate the strain-rate-dependent responses under the loading and osmotic pressure conditions, and the results revealed that the hypo-osmotic external environment increased chondrocyte dimensions and reduced Young's modulus.
Abstract: It has been demonstrated that most cells of the body respond to osmotic pressure in a systematic manner. The disruption of the collagen network in the early stages of osteoarthritis causes an increase in water content of cartilage which leads to a reduction of pericellular osmolality in chondrocytes distributed within the extracellular environment. It is therefore arguable that an insight into the mechanical properties of chondrocytes under varying osmotic pressure would provide a better understanding of chondrocyte mechanotransduction and potentially contribute to knowledge on cartilage degeneration. In this present study, the chondrocyte cells were exposed to solutions with different osmolality. Changes in their dimensions and mechanical properties were measured over time. Atomic force microscopy (AFM) was used to apply load at various strain-rates and the force-time curves were logged. The thin-layer elastic model was used to extract the elastic stiffness of chondrocytes at different strain-rates and at different solution osmolality. In addition, the porohyperelastic (PHE) model was used to investigate the strain-rate-dependent responses under the loading and osmotic pressure conditions. The results revealed that the hypo-osmotic external environment increased chondrocyte dimensions and reduced Young's modulus of the cells at all strain-rates tested. In contrast, the hyper-osmotic external environment reduced dimensions and increased Young's modulus. Moreover, using the PHE model coupled with inverse FEA simulation, we established that the hydraulic permeability of chondrocytes increased with decreasing extracellular osmolality which is consistent with previous work in the literature. This could be due to a higher intracellular fluid volume fraction with lower osmolality.
TL;DR: It is found that pressure/strain has a significant impact on the electronic structure of PbO2/SnO2, and not only can the band gap be substantially tuned by pressure/Strain, but also a transition between a semiconductor and a gapless/band-inverted semimetal can be manipulated.
Abstract: By first-principle calculations, we have systematically studied the effect of strain/pressure on the electronic structure of rutile lead/stannic dioxide (PbO2/SnO2). We find that pressure/strain has a significant impact on the electronic structure of PbO2/SnO2. Not only can the band gap be substantially tuned by pressure/strain, but also a transition between a semiconductor and a gapless/band-inverted semimetal can be manipulated. Furthermore, the semimetallic state is robust under strain, indicating a bright perspective for electronics applications. In addition, a practical approach to realizing strain in SnO2 is then proposed by substituting tin (Sn) with lead (Pb), which also can trigger the transition from a large-band-gap to a moderate-gap semiconductor with enhanced electron mobility. This work is expected to provide guidance for full utilization of the flexible electronic properties in PbO2 and SnO2.
TL;DR: In this article, the analysis of two-dimensional magnetohydrodynamic (MHD) flow past a circular cylinder wrapped with a porous layer in different laminar flow regimes is presented.
TL;DR: In this article, a coupled smoothed particle hydrodynamics (SPH) and discrete element method (DEM) model was used to model the motion and deformation of two 2D (two-dimensional) RBCs in capillaries.
Abstract: Red blood cells (RBCs) are the most common type of blood cells in the blood and 99% of the blood cells are RBCs. During the circulation of blood in the cardiovascular network, RBCs squeeze through the tiny blood vessels (capillaries). They exhibit various types of motions and deformed shapes, when flowing through these capillaries with diameters varying between 5 10 µm. RBCs occupy about 45 % of the whole blood volume and the interaction between the RBCs directly influences on the motion and the deformation of the RBCs. However, most of the previous numerical studies have explored the motion and deformation of a single RBC when the interaction between RBCs has been neglected. In this study, motion and deformation of two 2D (two-dimensional) RBCs in capillaries are comprehensively explored using a coupled smoothed particle hydrodynamics (SPH) and discrete element method (DEM) model. In order to clearly model the interactions between RBCs, only two RBCs are considered in this study even though blood with RBCs is continuously flowing through the blood vessels. A spring network based on the DEM is employed to model the viscoelastic membrane of the RBC while the inside and outside fluid of RBC is modelled by SPH. The effect of the initial distance between two RBCs, membrane bending stiffness (Kb) of one RBC and undeformed diameter of one RBC on the motion and deformation of both RBCs in a uniform capillary is studied. Finally, the deformation behavior of two RBCs in a stenosed capillary is also examined. Simulation results reveal that the interaction between RBCs has significant influence on their motion and deformation.
TL;DR: In this paper, first-principles calculations showed that monolayer and bilayer γ-B28 films are intrinsically metallic while the thicker films possess intriguing electronic states that exhibit moderate to large bandgaps in all the interior layers but are nearly gapless at the surface.
Abstract: Recent reports of successful synthesis of atomically thin boron films have raised great prospects of discovering novel electronic and transport properties in a new type of 2D materials. Here we show by first-principles calculations that monolayer and bilayer γ-B28 films are intrinsically metallic while the thicker films possess intriguing electronic states that exhibit moderate to large bandgaps in all the interior layers but are nearly gapless at the surface. Remarkably, these surface electronic states are tunable by strain, allowing the outermost layer to transition between a semimetal and a narrow-gap semiconductor. Moreover, these surface states almost exclusively occupy a wide energy range around the Fermi level, thus dominating the electronic transport in γ-B28 films. The dispersions of the surface electronic bands are direction sensitive, and with hole injection producing anisotropic and very high carrier mobility up to 104 cm2 V−1 s−1. Surprisingly, surface passivation can open a sizable bandgap, which offers an additional avenue for effective band engineering and explains the experimental observation of a large bandgap in the synthesized film. These results make few-layer γ-B28 films desirable candidate materials for catalysis and electronics applications.
Journal Article•
TL;DR: In this article, the analysis of two-dimensional magnetohydrodynamic (MHD) flow past a circular cylinder wrapped with a porous layer in different laminar flow regimes is presented.
Abstract: The present study focuses on the analysis of two-dimensional Magnetohydrodynamic (MHD) flow past a circular cylinder wrapped with a porous layer in different laminar flow regimes The Darcy-Brinkman-Forchheimer model has been used for simulating flow in porous medium using finite volume based software, Fluent 63 In order to analyze the MHD flow, the mean and instantaneous drag and lift coefficients and stream patterns are computed to elucidate the role of Stuart number, N and Darcy number, Da It is revealed that the magnetic fields are capable to stabilize flow and suppress the vortex shedding of vortices The N-Re plane shows the curves for separating steady and periodic flow regimes, Ncr and disappearing of vortex, Ndiss For validate the solution, the obtained CD and St are compared with available results of literature
Journal Article•
TL;DR: A three-dimensional spring network model based on DEM in combination with the SPH method is successfully used to model and predict the motion and deformation of RBCs in capillaries and is capable of predicting the critical diameter which prevents motion of R BCs for different blood pressures.
Abstract: Background - Blood continuously flows through the blood vessels in the human body. When blood flows through the smallest blood vessels, red blood cells (RBCs) in the blood exhibit various types of motion and deformed shapes. Computational modelling techniques can be used to successfully predict the behaviour of the RBCs in capillaries. In this study, we report the application of a meshfree particle approach to model and predict the motion and deformation of three-dimensional RBCs in capillaries. Method - An elastic spring network based on the discrete element method (DEM) is employed to model the three-dimensional RBC membrane. The haemoglobin in the RBC and the plasma in the blood are modelled as smoothed particle hydrodynamics (SPH) particles. For validation purposes, the behaviour of a single RBC in a simple shear flow is examined and compared against experimental results. Then simulations are carried out to predict the behaviour of RBCs in a capillary:
(i) the motion of five identical RBCs in a uniform capillary; (ii) the motion of five identical RBCs with different bending stiffness (Kb) values in a stenosed capillary;
(iii) the motion of three RBCs in a narrow capillary. Finally five identical RBCs are employed to determine the critical diameter of a stenosed capillary.
Results - Validation results showed a good agreement with less than 10% difference. From the above simulations, the following results are obtained:
(i) RBCs exhibit different deformation behaviours due to the hydrodynamic interaction between them; (ii) Asymmetrical deformation behaviours of the RBCs are clearly observed when the bending stiffness (Kb) of the RBCs is changed;
(iii) The model predicts the ability of the RBCs to squeeze through smaller blood vessels. - Finally, from the simulations, the critical diameter of the stenosed section to stop the motion of blood flow is predicted.
Conclusions - A three-dimensional spring network model based on DEM in combination with the SPH method is successfully used to model the motion and deformation of RBCs in capillaries. Simulation results reveal that the condition of blood flow stopping depends on the pressure gradient of the capillary and the severity of stenosis of the capillary. In addition, this model is capable of predicting the critical diameter which prevents motion of RBCs for different blood pressures.
TL;DR: The newly developed PVHE model is compared thoroughly with the standard neo-Hookean solid and PHE models and it has been found that the PVHE can accurately capture both creep and stress relaxation behaviors of chondrocytes better than other two models.
Abstract: The aim of this paper is to use a poroviscohyperelastic (PVHE) model, which is developed based on the porohyperelastic (PHE) model to explore the mechanical deformation properties of single chondrocytes. Both creep and relaxation responses are investigated by using finite element analysis models of micropipette aspiration and atomic force microscopy experiments, respectively. The newly developed PVHE model is compared thoroughly with the standard neo-Hookean solid and PHE models. It has been found that the PVHE can accurately capture both creep and stress relaxation behaviors of chondrocytes better than other two models. Hence, the PVHE is a promising model to investigate mechanical properties of single chondrocytes.