Segregation Effects Research Articles

Particle size and shape effect of Crumbler® rotary shear-milled granular woody biomass on the performance of Acrison® screw feeder: A computational and experimental investigation

Physical experiments and discrete element model (DEM) simulations are conducted to evaluate particle characteristics and operation parameter effects on screw feeding performance for rotary shear-milled Douglas fir. Three performance metrics are used: mass flow rate, shaft driving torque, and specific energy consumption. The impact of particle size, particle size distribution (PSD), shaft rotational speed (rpm), and hopper dimensions on the performance are investigated. All employed performance metrics reveal the superior flowability of the 2-mm particles in contrast to the larger 6-mm counterpart. Remarkably, wider PSD results in poorer flowability than the two mono-sized particles, proving the flowability enhancement achieved by narrower PSD of the woody feedstock. More importantly, DEM simulations unveil PSD-induced degradation in flowability is attributed to mechanical interlocking and particle segregation effects. Furthermore, higher shaft rpm causes higher mass flow rate at the cost of higher specific energy consumption due to viscous dissipation and changes in flow pattern.

Effects of solute segregation on the mobility and mechanical properties of {10[formula omitted]2} coherent twin boundary in magnesium

The effects of solute segregation on the mobility and mechanical properties of {101¯2} coherent twin boundary (CTB) are studied using first-principles calculation methods. 16 alloying elements are chosen to test the effects. The mobility of {101¯2} CTB is limited by the pinning effect led by the solute segregation. The pinning limit is shown to be highly dependent on the solute element segregating at the CTB, and the pinning efficiency is revealed to be only associated with the position that the solute atoms segregate in. Solute segregation affects the toughness and strength of the {101¯2} CTB. Ba and Li are CTB embrittlement elements while Ca, Si, Zn, Al, Ag, La, Ce, Nd, Gd, Tb, Y, Lu, and Zr are CTB toughening elements. Ba, Li, together with Sr, Ca, are found to be CTB weakening elements, and La, Ce, Nd, Al, Zn, Gd, Tb, Y, Lu, Ag, Si, and Zr are CTB strengthening elements. The pinning effect, and the effects on the CTB toughness and strength are relative to the solute segregation propensity in the CTB. Higher segregation propensity at the compression site of {101¯2} CTB is revealed to result in stronger pinning effects, stronger CTB toughening and strengthening effects, while for the segregations at the extension site, the trend is opposite.

The strong hardening effect of Re segregation on edge dislocation lines in W

We investigate the radiation hardening induced by the segregation of solute Re atoms along edge dislocation lines in W. Given the Re content and the irradiation temperature (which are chosen to represent both ITER and DEMO conditions), reference atomic configurations are first obtained with Metropolis Monte Carlo, where the equilibrium Re content at the dislocation core is evaluated. Next, the critical unpinning shear stress is evaluated with a molecular dynamics tool and the classical method of Barnett et al. The study reveals that the effect of Re segregation is strong, its magnitude could be compared with the pinning effect of other radiation defects such as nanovoids, dislocation loops and Re-rich precipitates formed in bulk. This form of hardening is therefore important and should be taken into account in higher scale models.

Structural racism through Sundown towns and its relationship to COVID-19 local risk and racial and ethnic diversity

“Sundown towns” across the US prevented racial and ethnic minorities from living and working within their borders as they forced minorities to leave these towns after sunset. The objective of this study was to explore the relationship between sundown town status, COVID-19 local risk index and racial and ethnic diversity. A multi-level hierarchical model was used to examine the effect of historical segregation through sundown towns status on present day COVID-19 local risk index and city-level diversity. Over 2,400 Sundown towns were cataloged across the United States, with the greatest density in the Midwest. Sundown towns, which historically excluded racial and ethnic minorities, had significantly less city-level diversity and lower COVID-19 local risk index compared to non-Sundown towns. Findings show that Sundown towns perpetuate residual segregation which continues to impact current inequities in COVID-19 risk among racial and ethnic minorities at the neighborhood level. We recommend that public health officials for pandemic preparedness should devote greater resources to these historically segregated racial and ethnic minority areas because of the historic structural racism that has placed these places at higher risk.

A partial least squares analysis of gender inequality, occupational segregation, and economic growth: Evidence from Sub‐Saharan Africa

AbstractThe biggest barrier to an egalitarian Sub‐Saharan Africa (SSA) appears to be deeply ingrained structural obstacles and gender imbalances. The significant prevalence of gender inequities, which have both structural and economic ramifications, must be addressed if SSA is committed to achieving the Africa 2063 Agenda (the Africa we want) and Sustainable Development Agenda 2030: gender equity and equality, and economic development. Using partial least squares simultaneous equation modeling (PLS‐SEM), this study examines the effects of gender inequality and occupational segregation on economic growth in Sub‐Saharan Africa. The explanatory power of the structural path model indicated that 17.3% of the variations in latent endogenous variable economic growth in SSA are explained by gender inequality and occupational segregation. This is evidence that gender inequality and occupational segregation account for a significant portion of economic growth in the SSA region. The results of a bootstrapping simulation indicate that, in SSA nations, the direct impact of gender inequality on economic growth is insignificant (β = 0.068, p > 0.05) while occupational segregation, macroeconomic policies, and globalization have a significant impact. However, the indirect effects of both gender inequality (β = −0.048, p < 0.05) and occupational segregation (β = −0.011, p < 0.05) on economic growth via the coordinating power of macroeconomic policy and globalization are significant. This demonstrated that macroeconomic policies are not gender‐neutral. It is therefore recommended that the most significant progress toward achieving an egalitarian SSA be made through an adequate fiscal policy interplay that considers the socioeconomic level of SSA people. Advocate for trade liberalization policies and globalization to benefit from the spillover effects of greater demand for female labor, which promotes gender equality and economic expansion. Even though the gender gap in education and health is closing, SSA countries should fully implement the International Labour Organization (ILO) treaties on gender equality. This will help to lessen social consumption spending and encourage investment spending, which generates returns to develop the economy in the realization of the Sustainable Development Agenda 2030 and the Africa 2063 Agenda (the Africa we want).

A Comparison between the Standard Heterogeneity Test and the Simplified Segregation Free Analysis for Sampling Protocol Optimisation

Estimating the heterogeneity of base and precious metal mineralisation is a great challenge for mining engineers and geologists who undertake resource evaluation, grade control and reconciliation. The calculation of the minimum broken sample mass to represent a given lot of mineralisation at a given comminution size is based on the estimation of IHL, the constant factor of constitution heterogeneity. IHL can be derived by different heterogeneity testwork or calibration approaches. Three methodologies are well known in the mining industry: the standard heterogeneity test, the segregation free analysis, and the sampling tree experiment or duplicate sample analysis. However, the methodologies often show different results, especially when it comes to gold. These differences are due to many reasons. Assuming the variances added by sample preparation and analysis to be equivalent for all tests, the reasons for the differences may include the nugget effect (particularly the presence of coarse gold), the segregation effect and the procedure of collecting/splitting the samples when performing the tests. This paper analyses and compares two heterogeneity tests: the original heterogeneity test and the simplified segregation free analysis, both performed on mineralisation from different Brazilian operations. The results show clear differences between the tests, highlighting the complexity of estimating the heterogeneity of mineral deposits. The study reports the importance of using proper methodologies for constitution heterogeneity estimation so that minimum sample masses and relative standard deviations of the fundamental sampling error can be relied upon. It also provides recommendations for practitioners on the application of testwork/calibration studies.

The Most Vulnerable Hispanic Immigrants in New York City: Structural Racism and Gendered Differences in COVID-19 Deaths.

This paper explores the structural and group-specific factors explaining the excess death rates experienced by the Hispanic population in New York City during the peak years of the coronavirus pandemic. Neighborhood-level analysis of Census data allows an exploration of the relation between Hispanic COVID-19 deaths and spatial concentration, conceived in this study as a proxy for structural racism. This analysis also provides a more detailed exploration of the role of gender in understanding the effects of spatial segregation among different Hispanic subgroups, as gender has emerged as a significant variable in explaining the structural and social effects of COVID-19. Our results show a positive correlation between COVID-19 death rates and the share of Hispanic neighborhood residents. However, for men, this correlation cannot be explained by the characteristics of the neighborhood, as it is for women. In sum, we find: (a) differences in mortality risks between Hispanic men and women; (b) that weathering effects increase mortality risks the longer Hispanic immigrant groups reside in the U.S.; (c) that Hispanic males experience greater contagion and mortality risks associated with the workplace; and (d) we find evidence corroborating the importance of access to health insurance and citizenship status in reducing mortality risks. The findings propose revisiting the Hispanic health paradox with the use of structural racism and gendered frameworks.

Effect of Intragranular Solute Atom Segregation on the Mechanical Properties of the Ni–Co Alloy

In the present contribution, a certain amount of Co atoms was added to the grains (GI) of nano-polycrystalline Ni by a molecular dynamics method to study the effect of solute atom content on the mechanical properties of the alloy. It was found that the tensile strength and yield strength of the alloy increased with the increase of Co atomic content. With the increase of Co content, the grain boundary atomic potential energy decreased and the grain boundary became more stable. As the strain increased, the Co atoms in the grain migrated to the grain boundary, the lattice distortion at the grain boundary increased, and the dislocation nucleation at the grain boundary increased, forming a stable dislocation network and hindering the grain boundary migration. The 1/6⟨112⟩ Shockley incomplete dislocation formed at the grain boundary became the stacking fault source, which was also the source of transformation from the internal stacking fault to the external stacking fault, finally transforming into deformation twins. As the strain increased, the content of Shockley incomplete dislocations in the crystal increased, interacting with other dislocations to dominate the deformation process.

Metallurgical characterization and high-temperature tensile failure of Inconel 617 alloy welded by GTAW and SMAW—a comparative study

Two types of the weld joint of Inconel 617 alloy were produced using gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) processes with ERNiCrCoMo-1 filler metal and ENiCrCoMo-1 electrode, respectively. The weld metal showed the segregation of the principle alloying elements like Mo and Cr along the inter-dendritic spaces, triggering the formation of secondary phases. The microstructure characterization of the interface ensured the high dilution, which could be attributed to the closeness in melting point and chemistry of base and filler metal. Microhardness variation, tensile testing at room and high temperature, and Charpy impact test were conducted to investigate the effect of the Mo segregation in the weld zone and heterogeneity in the microstructure of weldments on the mechanical behavior of both the welded joints. The cross-weld tensile tests were conducted at room temperature and 550°C. The tensile test samples failed from the weld zone for each condition with a tensile strength value close to the base metal, which ensured the applicability of the joint for end service. The tensile strength of GTAW-RT, GTAW-HT, SMAW-RT, and SMAW-HT were measured as 766 ± 22 MPa, 570 ± 5 MPa, 760 ± 7 MPa, and 600 ± 8 MPa, respectively. A non-uniform hardness plot was witnessed with the hardness of the GTAW-weld and SMAW-weld zone of 257 ± 8 HV and 285 ± 5 HV, respectively, in the transverse direction. The impact toughness of the weld zone was 84 ± 2 J and 48 ± 4 J for GTAW and SMAW weld zone. The average impact toughness of the GTAW-weld zone was approximately 42% higher than the value of the SMAW-weld zone. In a nutshell, it can be concluded that the welded joint of Inconel 617 produced using the GTAW process with ERNiCrCoMo-1 filler had the best metallurgical and mechanical properties.

Molecular Weight Segregation and Thermal Conductivity of Polydisperse Wax-Graphene Nanocomposites.

Paraffin waxes are a promising material for heat storage with high energy density. Their low thermal conductivity, which limits the speed of charging and discharging in heat buffers, was previously shown to be improved by adding graphene nanofillers. In the present study, using molecular dynamics simulations, the segregation by molecular weight of polydisperse paraffin near graphene flakes is investigated. In liquid bidisperse paraffin composed of decane and triacontane, an aligned layer containing mainly triacontane was observed next to the graphene. Upon slow cooling, the wax crystallised into distinct layers parallel to the graphene sheet, with much stronger segregation by molecular weight than in the crystallised bidisperse wax without graphene. For polydisperse wax, the segregation effect was much less pronounced. The molten paraffin had a somewhat higher concentration of the longest chains in the first layers next to the graphene, but during crystallisation, the molecular weight segregation was only slightly increased. Measurements of crystallinity using an alternative version of the method developed by Yamamoto showed that the layers of wax were highly aligned parallel to the graphene, both in the solid state with all wax crystallised and in the liquid state with one layer of aligned wax above and below the graphene. Thermal conductivity was increased in planes parallel to the graphene flakes. The strong segregation of chain lengths in the bidisperse wax resulted in clear differences in thermal conductivity in the segregated regions. The less segregated polydisperse wax showed less variation in thermal conductivity.

Racial Residential Segregation and the Health of Black Youth With Type 1 Diabetes.

Black youth with type 1 diabetes (T1D) are at heightened risk for suboptimal glycemic control. Studies of neighborhood effects on the health of youth with T1D are limited. The current study investigated the effects of racial residential segregation on the diabetes health of young Black adolescents with T1D. A total of 148 participants were recruited from 7 pediatric diabetes clinics in 2 US cities. Racial residential segregation (RRS) was calculated at the census block group level based on US Census data. Diabetes management was measured via self-report questionnaire. Hemoglobin A1c (HbA1c) information was gathered from participants during home-based data collection. Hierarchical linear regression was used to test the effects of RRS while controlling for family income, youth age, insulin delivery method (insulin pump versus syringe therapy), and neighborhood adversity. HbA1c was significantly associated with RRS in bivariate analyses, whereas youth-reported diabetes management was not. In hierarchical regression analyses, whereas family income, age, and insulin delivery method were all significantly associated with HbA1c in model 1, only RRS, age, and insulin delivery method were significantly associated with HbA1c in model 2. Model 2 explained 25% of the variance in HbA1c (P = .001). RRS was associated with glycemic control in a sample of Black youth with T1D and accounted for variance in HbA1c even after controlling for adverse neighborhood conditions. Policies to reduce residential segregation, along with improved screening for neighborhood-level risk, hold the potential to improve the health of a vulnerable population of youth.

Tailoring of the nonlinear optical rectification in vertically and laterally coupled InxGa1-xAs/GaAs quantum dots for Tera-hertz applications: Under In/Ga inter-diffusion, indium segregation, and strains effects

We numerically investigate the Nonlinear Optical Rectification (NOR) of two laterally coupled lens-shaped InxGa1-xAs/GaAs quantum dots and two layers of InxGa1-xAs/GaAs coupled QDs along the growth axis. In addition, we have examined the impact of applying an external electric field, hydrostatic pressure, and temperature on the NOR under indium segregation inside the wetting layer (WL) and In/Ga inter-diffusion in the QD region. The three-dimensional Schrödinger equation (3D) is solved numerically using the finite difference method (FDM) within the framework of the effective mass. We have used the compact density matrix formalism to compute the NOR coefficient. Our findings reveal that the indium segregation and inter-diffusion phenomena significantly affect the NOR coefficient and should be considered appropriately. It is also found that the lateral and vertical coupling thicknesses significantly impact the NOR coefficient, and the structure under investigation has a resonant behavior in the terahertz domain (0.1–10 THz). Moreover, obtained results reveal that the applied electric field orientation and intensity significantly affect the NOR magnitude. Therefore, the NOR intensity reaches the maximum value, χ(0)(2)=50.10-7m/V, for a negative applied electric field, F = −10 kV/cm. Additionally, it was shown that the increase in the hydrostatic pressure shifts the NOR spectrum to higher energies (blue-shift), whereas increasing temperature has the contrary effect. It is worth noting that the NOR magnitude and its attributed resonance energy can be adjusted for THz devices with a good choice of the external factors mentioned above.

Effect of Copper Segregation at Low-Angle Grain Boundaries on the Mechanisms of Plastic Relaxation in Nanocrystalline Aluminum: An Atomistic Study.

The paper studies the mechanisms of plastic relaxation and mechanical response depending on the concentration of Cu atoms at grain boundaries (GBs) in nanocrystalline aluminum with molecular dynamics simulations. A nonmonotonic dependence of the critical resolved shear stress on the Cu content at GBs is shown. This nonmonotonic dependence is related to the change in plastic relaxation mechanisms at GBs. At a low Cu content, GBs slip as dislocation walls, whereas an increase in Cu content involves a dislocation emission from GBs and grain rotation with GB sliding.

Influence of the twin boundary and Cr segregation on the spalling of Ni-base alloys by large-scale molecular dynamic simulations

Large-scale nonequilibrium molecular dynamics simulation is used to study the effect of grain size and Cr segregation at the twin boundary (TB) on the spalling fracture mechanism of nickel based alloys. In particular, loading waves are designed so that the maximum tensile stress first appears in the grain interior for all the crystals with different grain sizes. In contrast to traditional understandings, no monotonous relationship between the spall strength and the grain size appears in our results. The spall strength is found to depend on the wave attenuation distance measured from the first maximum tensile stress position to the spalled TB as well as the accompanied microstructure evolutions. The number of spalling plane increases with the increase of TB or the decrease of the grain size. As the grain size continues to decrease, a greater impact strength is required to cause spallation fracture at multiple TBs. In this case, the spall strength becomes insensitive to the first maximum tensile stress position. With the increment of solute atom concentration, the number of the spalling plane increases when the solution is segregated. But it decreases when the solution is uniformly distributed. Such a result is explained by segregation-enhanced energy dissipation and interactions between the waves and the microstructures nearby TBs. In particular, the shock wave would induce a local lattice reorientation nearby the TB depending on its segregation degree and the lattice reorientation would modify the slip manner of stacking faults and, thus, affect void nucleation and growth. The lattice reorientation would also contribute to the generation of sub-grain boundaries inside the grains in terms of the movement of stacking faults. Void nucleation at the sub-GB is the main cause of fracture at the grain interior.

Directly-coupled well-wire hybrid quantum confinement lasers with the enhanced high temperature performance

It is well known that the laser diode performance will inevitably deteriorate when the device is heated. It has been a difficult issue to solve to date. In this letter, we are reporting a new solution to improve high-temperature performance of the laser diodes. The device uses a kind of directly-coupled well-wire hybrid quantum confinement (HQC) structure of the active medium based on the InGaAs–GaAs–GaAsP material system. This special HQC structure is constructed based on the strain-driven indium (In)-segregation effect and the growth orientation-dependent on-GaAs multi-atomic step effect. The measurement and analysis for the HQC laser sample show that the carrier leakage loss, the Auger recombination and gain-peak shifting due to heating are reduced in the HQC structure. It therefore increases the optical gain for lasing at high temperature. The power conversion efficiency is enhanced by >57% and the threshold carrier density drops by >24% at T ⩾ 360 K, in comparison to the traditional quantum-well laser performance. A higher characteristic temperature of 240 K is obtained as well. It implies the better thermal stability of the HQC laser structure. These achievements show a significant prospect for developing high thermo-optic performance of laser diodes.

Segregation effects of Tl and Li ions on the scintillation properties of NaI:Tl,Li single crystals

In this work, high quality NaI:Tl and NaI:Tl,Li single crystals with a size of 11 mm in diameter and 135 mm in length were grown by the multi-ampoule Bridgman method. The concentrations of Tl and Li ions along the solidification direction were measured by the inductively coupled plasma optical emission spectrometer. The effective segregation coefficients of Tl and Li in NaI single crystals were estimated as 0.26 and 0.35, respectively. The radioluminescence spectra under X-ray excitation, pulse height spectra and scintillation decay kinetics under γ-ray excitation of the samples taken from different solidification positions in NaI:Tl and NaI:Tl,Li single crystals were systematically studied. For RL spectrum and scintillation decay time, there is a negligible position-dependent difference for both NaI:Tl and NaI:Tl,Li single crystals. In contrast, the energy resolution at 662 keV gradually deteriorates along the solidification direction, and the light yield maintains almost the same until reaching the last-to-freeze region.

Effect of grain boundary segregation on aging resistance and mechanical properties of tetravalent element-doped 3Y-TZP ceramics for dental restoration

ABSTRACT In the humid oral environment, 3Y-TZP ceramics always suffer from low-temperature degradation (LTD) for a long time, which results in the degradation of mechanical properties and catastrophic failure. The low-temperature degradation (LTD) and mechanical properties of low-cost tetravalent (Ge4+, Ti4+) element-doped 3Y-TZP were investigated by analysing grain boundary segregation in samples with deferent contents. The results show that GeO2 is superior to TiO2 in limiting LTD but results in lower flexural strength and fracture toughness when the content is ≥1.5 mol%. This dilemma can be improved by adding only 0.1%-0.5 wt% Al2O3, and the flexural strength and fracture toughness of 0.25 wt% Al2O3 zirconia are then increased to 898 MPa and 4.68 MPa·m1/2 compared with 1Ge-3Y, respectively. This work is expected to provide an effective reference for the development and application of budget dental materials.

The Segregation Effect: How Residential Isolation Shapes Ethnic Minority Representation in England

AbstractExtant literature argues that ethnic minority representation in plurality systems will benefit from the presence of sizable co-ethnic populations. I argue that the threshold for election depends not only on a minority population's group size but a district's level of segregation. I show that residential segregation can facilitate the increased representation of ethnic minority populations. Contrary to the prevailing literature, however, I find that increased segregation levels in cities with sizable minority populations decrease the percentage of co-ethnics elected to office. I support this argument with evidence from an original dataset on the local representation outcomes of Muslims in England between 2011 and 2021, which covers 434 district council elections. Using threshold modelling, I introduce the concept of the population threshold, above which increases in segregation level decrease Muslim representation. This article contributes to the electoral geography literature on ethnic minority representation.

Effects of nanoscale Sn segregation on corrosion behavior of laser powder bed fusion Cu-15Ni-8Sn alloy

Corrosion resistance of laser powder bed fusion (LPBF) Cu-15Ni-8Sn alloys is crucial towards its practical application in marine engineering. In this work, corrosion behavior of LPBF Cu-15Ni-8Sn alloy was comprehensively investigated. The results suggest that LPBF Cu-15Ni-8Sn alloy exhibits superior corrosion resistance than the conventional casting counterpart and their corrosion behavior is highly associated with Sn segregation. Generally, a triple-layer film will be formed on the surface of LPBF Cu-15Ni-8Sn alloy when being exposed to 3.5 wt% NaCl solution. To be more detailed, the abundance of nanoscale Sn-rich precipitates at the molten pool boundaries promotes the initial formation of a thick inner layer, where Ni and Sn tend to be distributed at inner and outer positions of the layer, respectively. In contrast, the inner layer on molten pools is much thinner ascribed to a lower Sn content, facilitating the earlier nucleation and growth of a compact middle layer that is mainly composed of numerous Cu-rich nanoparticles. At the outmost position, CuO, Cu(OH)2 and Ni(OH)2 constitute the major composition of the loose layer. The results of this study could contribute to the optimal design and processing of additively manufactured Cu-Ni-Sn alloys.

Sexual Orientation, Workplace Authority and Occupational Segregation: Evidence from Germany

An extensive body of research has documented the relationship between sexual orientation and income, but only a few studies have examined the effects of sexual orientation on workplace authority. This article investigates the probability of lesbian, gay and bisexual (LGB) people having (high-level) workplace authority and the effects of occupational gender segregation. It analyses four waves of data from the German Socio-Economic Panel study (N=37,288 heterosexual and N=739 LGB observations). The results show that gay and bisexual men do not differ from heterosexual men in their probability of having workplace authority, but they have a lower probability of attaining high-level authority. Lesbian and bisexual women have a higher probability than heterosexual women of having workplace authority, but no advantages in attaining high-level authority. These insights into occupational segregation suggest that gay and bisexual men experience similar levels of disadvantages across occupations, whereas lesbian and bisexual women have an advantage in female-dominated occupations.