Effect of granular shape on radial segregation in a two-dimensional drum

Granular segregation is widely observed in nature and industry.Most research has focused on segregation caused by differences in the size and density of spherical grains.However,due to the fact that grains typically have different shapes,the focus is shifting towards shape segregation.In this study,experiments are conducted by mixing cubic and spherical grains.The results indicate that spherical grains gather at the center and cubic grains are distributed around them,and the degree of segregation is low.Through experiments,a structured analysis of local regions is conducted to explain the inability to form stable segregation patterns with obviously different geometric shapes.Further,through simulations,the reasons for the central and peripheral distributions are explained by comparing velocities and the number of collisions of the grains in the flow layer.

Segregation of Mg-6Gd alloy under natural convection:From macro solute distribution to micro dendrite growth

Segregation is a serious defect in alloy ingots which severely deteriorates materials performance.The segregation defect in Mg-6Gd alloy is studied by coupling macro thermal-solutal-convection transport and micro dendrite growth.The macroscopic fluid dynamics and mass transfer equations are resolved to forecast the segregation behavior under conditions of continuous temperature variation during the solidification process.The numerical model is validated by testing double-diffusive natural convection in a closed square cavity.A phase field model is then applied to simulate the micro dendrite growth,using macro undercooling and liquid flow velocity as boundary conditions.Results show that the multiscale segregation behavior,including macro solute distribution and micro dendritic morphology,is strongly dependent on the temperature condition and the liquid convection,which provides guidance for reducing and eliminating the segregation defect.

Effect of casting process on the inner-wall band segregation of high-strength antisulfur pipes

Controlling inner-wall band segregation is one of the difficulties in the production of high-strength antisulfur pipes.Comparative tests were carried out on different casting processes(superheat,mold electromagnetic stirring,end electromagnetic stirring,casting speed and soft reduction)for the smelting of high-strength antisulfur pipes.The microstructures of continuous-casting billets and hot-rolled or tempered pipes were analyzed using a metallographic microscope and scanning electron microscope.The mechanism and evolution law regarding the inner-wall band segregation of high-strength antisulfur pipes were studied,and the influence of different casting processes was explored.

Towards designing high mechanical performance low-alloyed wrought magnesium alloys via grain boundary segregation strategy:A review

Low-alloyed magnesium(Mg)alloys have emerged as one of the most promising candidates for lightweight materials.However,their further application potential has been hampered by limitations such as low strength,poor plasticity at room temperature,and unsatisfactory formability.To address these challenges,grain refinement and grain structure control have been identified as crucial factors to achieving high performance in low-alloyed Mg alloys.An effective way for regulating grain structure is through grain boundary(GB)segregation.This review presents a comprehensive summary of the distribution criteria of segregated atoms and the effects of solute segregation on grain size and growth in Mg alloys.The analysis encompasses both single element segregation and multi-element co-segregation behavior,considering coherent interfaces and incoherent interfaces.Furthermore,we introduce the high mechanical performance low-alloyed wrought Mg alloys that utilize GB segregation and analyze the potential impact mechanisms through which GB segregation influences materials properties.Drawing upon these studies,we propose strategies for the design of high mechanical performance Mg alloys with desirable properties,including high strength,excellent ductility,and good formability,achieved through the implementation of GB segregation.The findings of this review contribute to advancing the understanding of grain boundary engineering in Mg alloys and provide valuable insights for future alloy design and optimization.

Solute atom segregation to I1 stacking fault and its bounding partial dislocations in a Mg–Bi alloy

Stacking faults(SFs)and the interaction between solute atoms and SFs in a Mg–Bi alloy are investigated using aberration-corrected scanning transmission electron microscopy.It is found that abundant I_(1)SFs are generated after cold rolling and are mainly distributed inside{1012}twins.After aging treatment,the formation of single-layer and three-layer Bi atom segregation in the vicinity of I_(1)fault are clearly observed.Bi segregation also occurs at the 1/6<2203>bounding Frank partial dislocation cores.The segregation behaviors in I_(1)fault and Frank dislocations are discussed and rationalized using first-principles calculations.

The occurrence,inheritance,and segregation of complex genomic structural variation in synthetic Brassica napus

"Synthetic"allopolyploids recreated by interspecific hybridization play an important role in providing novel genomic variation for crop improvement.Such synthetic allopolyploids often undergo rapid genomic structural variation(SV).However,how such SV arises,is inherited and fixed,and how it affects important traits,has rarely been comprehensively and quantitively studied in advanced generation synthetic lines.A better understanding of these processes will aid breeders in knowing how to best utilize synthetic allopolyploids in breeding programs.Here,we analyzed three genetic mapping populations(735 DH lines)derived from crosses between advanced synthetic and conventional Brassica napus(rapeseed)lines,using whole-genome sequencing to determine genome composition.We observed high tolerance of large structural variants,particularly toward the telomeres,and preferential selection for balanced homoeologous exchanges(duplication/deletion events between the A and C genomes resulting in retention of gene/chromosome dosage between homoeologous chromosome pairs),including stable events involving whole chromosomes("pseudoeuploidy").Given the experimental design(all three populations shared a common parent),we were able to observe that parental SV was regularly inherited,showed genetic hitchhiking effects on segregation,and was one of the major factors inducing adjacent novel and larger SV.Surprisingly,novel SV occurred at low frequencies with no significant impacts on observed fertility and yield-related traits in the advanced generation synthetic lines.However,incorporating genome-wide SV in linkage mapping explained significantly more genetic variance for traits.Our results provide a framework for detecting and understanding the occurrence and inheritance of genomic SV in breeding programs,and support the use of synthetic parents as an important source of novel trait variation.

No basalt accumulation and segregation atop the 660-km discontinuity beneath the Sea of Okhotsk

Recent seismic evidence shows that basalt accumulation is widespread in the mantle transition zone(MTZ),yet its ubiquity or sporadic nature remains uncertain.To investigate this phenomenon further,we characterized the velocity structure across the 660-km discontinuity that separates the upper mantle from the lower mantle beneath the Sea of Okhotsk by modeling the waveform of the S660P phase,a downgoing S wave converting into a P wave at the 660-km interface.These waves were excited by two regional>410-km-deep events and were recorded by stations in central Asia.Our findings showed no need to introduce velocity anomalies at the base of the MTZ to explain the S660P waveforms because the IASP91 model adequately reproduced the waveforms.This finding indicates that the basalt accumulation has not affected the bottom of the MTZ in the study area.Instead,this discontinuity is primarily controlled by temperature or water content variations,or both.Thus,we argue that the basalt accumulation at the base of the MTZ is sporadic,not ubiquitous,reflecting its heterogeneous distribution.

NUMERICAL SIMULATION OF CHANNEL SEGREGATION IN Al-4.5wt-%Cu ALLOY

Equations for numerical simulation of channel segregation based on a model of continuum ap- proach to porous medium were advanced.In order to solve the non-linear computation prob- lem caused by the interactions between unknown variables in the equations,the trial-and-er- ror method is used.The computation results showed that the radial back-flow due to natural convection in mushy zone indeed exists in A1-4.5wt-%Cu alloy ingot under the condition of low cooling rate,and that the numerical simulation of channel segregation is applicable due to the coincidence of calculated concentration with the experimental values.

Potassium and calcium channels in different nerve cells act as therapeutic targets in neurological disorders

The central nervous system, information integration center of the body, is mainly composed of neurons and glial cells. The neuron is one of the most basic and important structural and functional units of the central nervous system, with sensory stimulation and excitation conduction functions. Astrocytes and microglia belong to the glial cell family, which is the main source of cytokines and represents the main defense system of the central nervous system. Nerve cells undergo neurotransmission or gliotransmission, which regulates neuronal activity via the ion channels, receptors, or transporters expressed on nerve cell membranes. Ion channels, composed of large transmembrane proteins, play crucial roles in maintaining nerve cell homeostasis. These channels are also important for control of the membrane potential and in the secretion of neurotransmitters. A variety of cellular functions and life activities, including functional regulation of the central nervous system, the generation and conduction of nerve excitation, the occurrence of receptor potential, heart pulsation, smooth muscle peristalsis, skeletal muscle contraction, and hormone secretion, are closely related to ion channels associated with passive transmembrane transport. Two types of ion channels in the central nervous system, potassium channels and calcium channels, are closely related to various neurological disorders, including Alzheimer's disease, Parkinson's disease, and epilepsy. Accordingly, various drugs that can affect these ion channels have been explored deeply to provide new directions for the treatment of these neurological disorders. In this review, we focus on the functions of potassium and calcium ion channels in different nerve cells and their involvement in neurological disorders such as Parkinson's disease, Alzheimer's disease, depression, epilepsy, autism, and rare disorders. We also describe several clinical drugs that target potassium or calcium channels in nerve cells and could be used to treat these disorders. We concluded that there are few clinical drugs that can improve the pathology these diseases by acting on potassium or calcium ions. Although a few novel ion-channelspecific modulators have been discovered, meaningful therapies have largely not yet been realized. The lack of target-specific drugs, their requirement to cross the blood–brain barrier, and their exact underlying mechanisms all need further attention. This review aims to explain the urgent problems that need research progress and provide comprehensive information aiming to arouse the research community's interest in the development of ion channel-targeting drugs and the identification of new therapeutic targets for that can increase the cure rate of nervous system diseases and reduce the occurrence of adverse reactions in other systems.

Formation mechanism and criterion of linear segregation in ZL205A alloy

The experiments and numerical simulation were conducted for ZL205A aluminum alloy cylindrical shell casting. The formation mechanism of the linear segregation produced by the low pressure die casting (LPDC) process was investigated. And the heat transfer of the casting during solidification process was analyzed by simulation technique, resulting from the information of linear segregation obtained by plenty of experiments. The new linear segregation criterion was proposed through the simulation and experimental results. It was found that the melting metal with high Cu contents was feeding the crack shrinkage formed by the tearing under the effect of feeding pressure during the later solidification, which led to the formation of linear segregation. The control methods for the linear segregation were suggested based on the proposed mechanism. Finally, the criterion of linear segregation was confirmed by the production of the actual castings.

Effect of carbon and boron additions on segregation behavior of directionally solidified nickel-base superalloys with rhenium

The phase transformation temperature, segregation behavior of elements and as-cast microstructure were investigated in experimental nickel-base superalloys with different levels of carbon and boron. The results show that the liquidus temperature decreases gradually but the carbide solvus temperature increases obviously with increasing carbon addition. Minor boron addition to the alloy decreases the liquidus temperature, carbide solvus temperature and solidus temperature slightly. Apart from rhenium, the segregation coefficients of the elements alter insignificantly with the addition of carbon. The segregation behavior of rhenium, tungsten and tantalum become more severe with boron addition. The volume fraction and size of primary carbides increase with increasing carbon addition. The main morphology of the carbides is script-like in the alloys with carbon addition while the carbide sheets tend to be concentrated and coarse in the boron-containing alloys

Non-equilibrium grain-boundary segregation of Bi in Cu bicrystals

The observations of grain-boundary segregation of Bi in Cu bicrystals were analyzed. According to equilibrium grain boundary segregation （EGS） model and non-equilibrium grain-boundary segregation （NGS） model, respectively, the segregation kinetics of isothermal annealing at 500 ＆#176;C and that of isochronal annealing for 24 h of Bi in Cu bicrystals were investigated. By qualitative analysis and quantitative analysis, it is concluded that the grain-boundary segregation of Bi agrees well with the theory of NGS. Based on the kinetics model of NGS, some parameters that are useful to predicting and controlling the Bi-induced embrittlement in Cu alloys are calculated as follows：the diffusion coefficient of Bi-vacancy complexes Dc=7.8×10^-5exp[-1.46/（kT）];the apparent diffusion coefficient of Bi atoms Di^A=7.66×10^at＋bexp[–1.76/（kT）], where a=8.45×10^-8 and b=-13.37.

Microstructure evolution and segregation behavior of thixoformed Al-Cu-Mg-Mn alloy

A commercial wrought Al-Cu-Mg-Mn alloy（2024） was thixoformed based on the recrystallization and partial melting（RAP） route, and the microstructure evolution and segregation behavior during the indirect thixoforming process were studied. The results show that fine spheroidal microstructures can be obtained by partial remelting of commercial extruded 2024 alloys without additional thermomechanical processing. During the indirect thixoforming, the stress distribution can be optimized by increasing the thickness of base region. Under three-dimensional compression stress state, the microstructures are homogeneous among different regions with no evidence of liquid segregation and micro-porosities, and the grains in the columns are deformed plastically. The distribution of tensile mechanical properties is consistent with the microstructures. Moreover, the distribution of deformation mechanism was discussed, and a technical method for improving the stress distribution was proposed.

Segregation and diffusion behavior of niobium in a highly alloyed nickel-base superalloy

The segregation during solidification and high temperature diffusion during homogenization of niobium in a highly alloyed nickel-base superalloy were investigated.Niobium is seriously segregated into the interdendritic regions with segregation coefficient as high as 4.30.Various niobium-enriched phases including Laves phase,δ phase,（γ＋γ＇） eutectic,MC and M6C types of carbides precipitated in the interdendritic regions.The soluble temperature of niobium-enriched phases and the degree of dendritic segregation were determined by differential thermal analysis and homogenization treatments at varied temperatures and times.The calculation of elemental diffusion indicates that the diffusion rate of niobium increases remarkably with the homogenization temperature increasing,so that the annealing time can be effectively reduced.A three-step homogenization treatment technology without incipient melting was established to eliminate the segregation of niobium and to obtain a uniform microstructure.

COMPUTER SIMULATION OF GRAIN BOUNDARY SEGREGATION BEHAVIOR AND MECHANISMS OF STRENGTHENING OF Mg IN Ni-BASED SUPERALLOYS

This paper used EAM and static relaxation method to simulate the grain boundary segregation behavior of Mg in Ni-based superalloys. The results offer a better understanding in the strengthening mechanism of Mg addition in superalloys. The segregation of Mg increases the grain boundary cohesive bond and the vacancy formation energy, and decreases the mobility of grain boundary dislocation. It results in the retardation of creep voids initiation and growth.

Radial mixing and segregation of granular bed bi-dispersed both in particle size and density within horizontal rotating drum

Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.

A Novel Segregation Distortion in Intraspecific Population of Asian Cotton(Gossypium arboretum L.)Detected by Molecular Markers

The segregation ratio of markers in an F2 population derived from Rudongjijiaoyaguo （Rdjjyg） and Zhongmian971 （Zm971） was studied using 3 morphological markers, 20 SSR markers, and ll SRAP markers. Totally, 24 markers （77.42%） showed a distorted segregation and all of them skewed toward the female genotype, which was peculiar in recent cotton research. All the three types of SSR markers and SRAP marker showed distorted segregation, but the morphological markers （Purple stem, Okra leaf, and Red spot color） were normally segregated. This indicated that such a novel segregation distortion phenomenon resulted from interior genetic factors, The allele frequency and the distribution of different genotype frequencies in the F2 population were analyzed in codominant markers, to find out factors attributed to distorted segregation. Most of them implied distorted allele frequency, but it was normal genotype frequency, which showed that these markers were influenced at the gamete level.

Effect of atomic structure on migration characteristic and solute segregation of ordered domain interfaces formed in Ni_(75)Al_xV_(25-x)

Based on the microscopic phase-field model, ordered domain interfaces formed between D022 （Ni3V） phases along [001] direction in Ni75AlxV25-x alloys were simulated, and the effects of atomic structure on the migration characteristic and solute segregation of interfaces were studied. It is found that the migration ability is related to the atomic structure of interfaces, and three kinds of interfaces can migrate except the interface （001）//（002） which has the characteristic of L12 （Ni3Al） structure. V atoms jump to the nearest neighbor site and substitute for Ni, and vice versa. Because of the site selectivity behaviors of jumping atoms, the number of jumping atoms during the migration is the least and the jumping distance of atoms is the shortest among all possible modes, and the atomic structures of interfaces are unchanged before and after the migration. The preferences and degree of segregation or depletion of alloy elements are also related to the atomic structure of interface.

Segregation of AFLP Markers in A ( Populus tomentosa× P. bolleana) ×P. tomentosa Carr. BC_1 Family

To investigate the levels of polymorphisms and Mendelian segregation ratio in clone “TB01” (P. tomentosa×P. bolleana) ×clone “LM50” (P. tomentosa) BC 1 population at the entire genome level, amplified fragment length polymorphisms (AFLPs) analysis was conducted for both parents and 120 progenies. Forty one pairs of selective primers were used to detect 2?707 bands, of which 712 (26.4%) were polymorphic. Chi\|square tests were performed to examine if the observed genotypic frequencies of AFLP loci deviated from expected 1∶1 Mendelian segregation ratio ( P <0.01) in BC 1 population. Among the 712 loci 571 (80.2%) fit to Mendelian 1∶1 segregation ratio, corresponding to DNA polymorphisms heterozygous in one parent and a null in the other. The result shows that the AFLP markers are very suitable for fingerprinting and genetic mapping in the Chinese white poplar (Populus tomentosa Carr.).

Segregation of niobium in laser cladding Inconel 718 superalloy

Inconel 718 superalloy is widely used in the aerospace and turbine industry. Segregation of niobium appears in the laser cladding Inconel 718 superalloy and consequently influences the phase transformation during the rapid solidification. In order to control the microstructure and improve the mechanical properties of the deposited coating, the the influence of solidification conditions on the segregation of niobium and the resultant formation of Nb-rich Laves phase was studied using the microstructure observation and EDS analysis. The results show that the cooling rate has considerable influence on the microstructure of the deposited coating. High cooling rate is beneficial for suppressing the segregation of Nb and reducing the formation of Laves phase, which is believed to be detrimental to the performance of the Inconel 718 alloy.