Structure Segregation Research Articles

Self‐Powered Organic Photodetectors with High Detectivity for Near Infrared Light Detection Enabled by Dark Current Reduction

AbstractOrganic photodetectors (OPDs) for near infrared (NIR) light detection represents cutting‐edge technology for optical communication, environmental monitoring, biomedical imaging, and sensing. Herein, a series of self‐powered OPDs with high detectivity are constructed by the sequential deposition (SD) method. The dark currents (Jd) of SD devices are effectively reduced in comparison to blend casting (BC) ones due to the vertical phase segregation structure. Impressively, the Jd values of SD devices based on D18 and Y6 system is reduced to be 2.1 × 10−11 A cm−2 at 0 V, which is two orders of magnitude lower than those of the BC devices. The D* value of the SD device is superior to that of BC device under different bias voltages (0, −0.5, −1.0, and −2.0 V) due to the reduction of dark current, which originates from the fine vertical phase separation structure of the SD device. The mechanism studies shows that the vertical phase segregation structure can effectively suppress the unfavorable charge injection, thus reducing the dark current. Also, the surface energy is proven to play a key role in the photocurrent stability. In addition, the flexible OPDs demonstrate excellent performance in photoplethysmography test.

Twin Roll Casting and Secondary Cooling of 6.0 wt.% Silicon Steel

Iron–silicon alloys with up to 6.5 wt.% Si offer an improvement of soft magnetic properties in electrical steels compared to conventional electrical steel grades. However, steels with high Si contents are very brittle and cannot be produced by cold rolling. In addition to solid solution hardening, it is assumed that the B2- and DO3-superlattice structures are responsible for the poor cold workability. In this work, two cast strips with 6.0 wt.% Si were successfully produced by the twin roll strip casting process and cooled differently by secondary cooling. The aim of the different cooling strategies was to suppress the formation of the embrittling superlattice structures and thus enable further processing by cold rolling. A comprehensive material characterization allows for the understanding of the influence of casting parameters and cooling strategies on segregation, microstructure and superlattice structure. The results show that both cooling strategies are not sufficient to prevent the formation of B2- and DO3-structures. Although the dark field images show a condition which is far from equilibrium, the achieved condition is not sufficient to ensure cold processing of the material.

Surface segregation of 3 mol % yttria-doped tetragonal zirconia particle studied by atomic-resolution scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy

Atomic structure of the surfaces in commercial 3 mol % yttria-doped tetragonal zirconia (TZP) nano-particulate powders were studied by atomic resolution scanning transmission electron microscopy (STEM), and the surface segregation of Y were investigated by STEM energy-dispersive X-ray spectroscopy (EDS) at atomic scale. STEM-EDS observations revealed that the Y cations tend to segregate on the top surface layer, forming a monolayer segregation structure. Static lattice calculations revealed that the surface segregation of Y is energetically favorable. These results indicate that Y surface segregation occurs in the TZP powders, which might partially account for the grain boundary segregation in the sintered body of TZP ceramics.

Inclusive education is another country; developments, obstacles and resistance to inclusive education

ABSTRACT Inclusive education has been part of the global educational vernacular for more than 25 years, based on the premise that for education to achieve its goal of providing access to an inclusive society and its common goods, education itself should be inclusive. Universalism underpins inclusive education, but it is commonly perceived as relating to specific populations, namely disabled students. Developments in inclusive education have been multi-levelled, influenced by international and national policy, as well as grassroots advocacy. Even in systems with strong segregation and exclusion structures, islands of inclusive practice are to be found but fully inclusive systems are elusive, and the nature of inclusive education remains contested. This paper uses Australia as a case study to explore this complexity by illustrating the arguments surrounding inclusive education, the evidence used to support these arguments, and the implications for future developments. The analysis indicates that in the Australian context there is tremendous noise around inclusive education, but very little evidence of realising it. The separation of inclusion as a broader value from inclusive education has been successful in operating as a smokescreen, detracting attention from a system that becomes more selective, exclusive and with increased segregation.

Segregation competition and complexion coexistence within a polycrystalline grain boundary network

Interfacial segregation can stabilize grain structures and even lead to grain boundary complexion transitions. However, understanding of the complexity of such phenomena in polycrystalline materials is limited, as most studies focus on bicrystal geometries. In this work, we investigate interfacial segregation and subsequent complexion transitions in polycrystalline Cu-Zr alloys using hybrid Monte Carlo/molecular dynamics simulations. No significant change in the grain size or structure is observed upon Zr dopant addition to a pure Cu polycrystal at moderate temperature, where grain boundary segregation is the dominant behavior. Segregation within the boundary network is inhomogeneous, with some boundaries having local concentrations that are an order of magnitude larger than the global value and others having almost no segregation, and changes to physical parameters such as boundary free volume and energy are found to correlate with dopant concentration. Further, another alloy sample is investigated at a higher temperature to probe the occurrence of widespread transitions in interfacial structure, where a significant fraction of the originally ordered boundaries transition to amorphous complexions, demonstrating the coexistence of multiple complexion types, each with their own distribution of boundary chemical composition. Overall, this work highlights that interfacial segregation and complexion structure can be diverse in a polycrystalline network. The findings shown here complement existing computational and experimental studies of individual interfaces and help pave the way for unraveling the complexity of interfacial structure in realistic microstructures.

Disconnection-Mediated Transition in Segregation Structures at Twin Boundaries.

Twin boundaries play an important role in the thermodynamics, stability, and mechanical properties of nanocrystalline metals. Understanding their structure and chemistry at the atomic scale is key to guide strategies for fabricating nanocrystalline materials with improved properties. We report an unusual segregation phenomenon at gold-doped platinum twin boundaries, which is arbitrated by the presence of disconnections, a type of interfacial line defect. By using atomistic simulations, we show that disconnections containing a stacking fault can induce an unexpected transition in the interfacial-segregation structure at the atomic scale, from a bilayer, alternating-segregation structure to a trilayer, segregation-only structure. This behavior is found for faulted disconnections of varying step heights and dislocation characters. Supported by a structural analysis and the classical Langmuir-McLean segregation model, we reveal that this phenomenon is driven by a structurally induced drop of the local pressure across the faulted disconnection accompanied by an increase in the segregation volume.

The Spatial Structure and Local Experience of Residential Segregation

This study examines the extent to which road connectivity and physical barriers—such as highways, railroad tracks, and waterways—structure spatial patterns of racial and ethnic residential segregation and shape how segregation is locally experienced by residents. Our focus is on physical barriers that are also social boundaries—features of the built environment that reduce physical connectivity and mark a social boundary between geographic areas. We measure residential segregation with attention to the proximity and road connectivity between locations, which allows us to identify areas where physical barriers mark a social boundary between geographic areas with different racial and ethnic compositions. Our approach integrates ethnographic observation of three such areas in Houston, Texas, to investigate residents' perceptions and local experience of social and spatial division. The results reveal that physical barriers are associated with heightened levels of ethnoracial segregation, and residents experience the barriers as symbolic markers of perceived distinctions between groups and physical impediments to social connection. Although barriers like highways, railroad tracks, and bayous are not inherently harbingers of ethnoracial segregation, our study demonstrates that physical barriers can provide the infrastructure for social boundaries and facilitate durable neighborhood racial divisions.

“A New Ethnology”: The Legal Expansion of Whiteness under Early Jim Crow

The segregation laws known as “Jim Crow” are often understood as legislative efforts to promote White supremacy by shielding White southerners from contact with other races. This was not the case, however. By analyzing early railway segregation laws–in particular, the 1890 Louisiana law that was challenged in Plessy v. Ferguson–this article shows that the first post-Reconstruction segregations laws used an expansive definition of the “white race” as everyone who was not Black. In short, White purity and separation were the pretext, not the purpose, of early Jim Crow laws. Instead, the structure of legal segregation was initially determined by White, Democratic legislators' efforts to isolate and subjugate Black Americans by reinstating the racial logic of slavery, which had divided the world into Black people and everyone else. To achieve this end, White supremacist lawmakers framed laws that strategically integrated “white” train cars, all the while claiming the laws did the opposite.

Solute enrichment induced dendritic fragmentation in directional solidification of nickel-based superalloys

Dendritic fragmentation should be strictly prevented to avoid introducing new equiaxed grains of arbitrary orientations (known as freckles) in the single crystal blade, whose mechanism properties are extremely sensitive to the grain boundaries. However, the mechanism of the formation and distribution of freckles in superalloy castings remains debatable. Here the interactions among thermal-solutal convection, solute segregation and dendritic structure in the directional solidification is revealed via a cellular automaton-finite volume model developed and validated for nickel-based single-crystal superalloys. The simulated channel distribution, morphology of residual liquid region, dendritic tip velocity and freckle grains are in good agreement with the previous experimental observations. The present work directly predicts solute enrichment induced dendritic fragmentation, that is, the middle of the over-growing dendritic trunk is melted by the superheated liquid metal in the channel and thus the top of the dendrite becomes isolated fragments. These dendritic fragments rather than the newly nucleated grains are proved to be the root cause of freckle grains. The simulation results also provide new insight into the effect of the operating parameters on the solute distribution and dendritic structure. The undesired lateral heat flux in the directional solidification promotes the transfer of the solute-enriched solute and the migration of the channels, and thus results in the dendritic detachment. Increasing cooling rate makes significant effects on eliminating the freckle defect, because a higher cooling rate promotes the growth of the ternary dendritic arms on the side branches and inhibits the transfer of solute-enriched melt to the over-growing dendrite.

A Systemic Perspective

A Systemic Perspective

A Method for Studying Differences in Segregation Across Time and Space

An important topic in the study of segregation are comparisons across space and time. This article extends current approaches in segregation measurement by presenting a five-term decomposition procedure that can be used to understand more clearly why segregation has changed or differs between two comparison points. Two of the five terms account for differences in segregation that are due to the differing marginal distributions (e.g., the gender and occupational distributions), while one term accounts for differences in segregation due the different structure of segregation (what might be termed “pure” segregation). The decomposition thus presents a solution to the problem of margin dependency, frequently discussed in the segregation literature. Finally, two terms account for the appearance or disappearance of units when analyzing change over time. The method can be further extended to attribute structural changes to individual units, which makes it possible, for instance, to quantify the effect of each occupation on changing gender* segregation. The practical advantages of the decomposition are illustrated by two examples: a study of changing occupational gender segregation in the United States and a study of changing residential segregation in Brooklyn, New York.

Polycrystalline and Single‐Crystalline Edge Layer of Mg–Gd–TM (TM=Ni, Ag) Alloys Prepared by Ion Thinner

The different segregation and lattice structure in the sample edge layer (SEL) of Mg–Gd–TM (TM: solute element, mainly Ni or Ag) alloys prepared by ion thinner have been investigated in this study. The result displays that the polycrystalline phase, Mg2GdNi9, is found in the SEL zone of Mg–Gd–Ni alloys, and the single‐crystalline phase, MgGdAg2, is found in the SEL zone of Mg–Gd–Ag alloys. The investigation of different lattice structures contributes to the distinguishment and analysis of the illusionary phases in the SEL zone of Mg–Gd–TM ternary alloys by electron microscopy sampling.

Effect of M-EMS current intensity on the subsurface segregation and internal solidification structure for bloom casting of 42CrMo steel

ABSTRACT As-cast inherited defects are usually observed especially in quenched and tempered (QT) steels, such as 42CrMo due to macro-segregation. A three-dimensional numerical model has been presented to reveal the heat mass transportation and solidification behaviour of the molten steel in a 250 mm × 280 mm continuously cast bloom with and without M-EMS application. The reliability of the coupled model was proved by comparing the measured data of magnetic flux density with the calculated one along the centreline. The research indicates that the phenomena of a decrease in the solidification rate and an increase in molten steel washing velocity are observed as the current intensity increases from 0 to 450 A, which leads to a decrease of the minimum segregation degree by 0.039 and an increase of the width of the harmful negative segregation band by 3.6 mm. The washing effect that increases with the current intensity can reinforce the heat transfer between molten steel and solidification front and stimulate the formation of the equiaxed crystal. Accordingly, the average, local temperature gradient, and the superheat degree at the centre of mould exit decrease by 0.12, 2.62 K·mm−1, and 2.9 K, respectively, together with an increase of the equiaxed crystal ratio by about 9.44%. It suggests that the M-EMS may lead to the more serious subsurface negative segregation but can improve the equiaxed crystal ratio of bloom castings, which influences the heat treatment performance and flaw detection pass rate of subsequent rolled products.

Effect of dislocation configuration on Ag segregation in subgrain boundary of a Mg-Ag alloy

Interfacial segregation has been reported to play a critical role in the thermal-mechanical stability of nanocrystalline Mg alloys. Here we report Ag-segregation-assisted formation of nanocrystalline Mg-Ag alloy with high proportion of sub-grain boundaries during conventional rolling. The segregation structure is determined by dislocation configurations and subsequent strain field and misorientation of the sub-grain boundary. It indicates that the alloying elements, which induce <c+a> dislocations, would help to improve the stability of interfaces.

Microstructural development in DED stainless steels: applying welding models to elucidate the impact of processing and alloy composition

Austenitic stainless steel microstructures produced by directed energy deposition (DED) are analogous to those developed during welding, particularly high energy density welding. To better understand microstructural development during DED, theories of microstructural evolution, which have been established to contextualize weld microstructures, are applied in this study to microstructural development in DED austenitic stainless steels. Phenomenological welding models that describe the development of oxide inclusions, compositional microsegregation, ferrite, matrix austenite grains, and dislocation substructures are utilized to clarify microstructural evolution during deposition of austenitic stainless steels. Two different alloys, 304L and 316L, are compared to demonstrate the broad applicability of this framework for understanding microstructural development during the DED process. Despite differences in grain morphology and solidification mode for these two alloys (which can be attributed to compositional differences), similar tensile properties are achieved. It is the fine-scale compositional segregation and dislocation structures that ultimately determine the strength of these materials. The evolution of microsegregation and dislocation structures is shown to be dependent on the rapid solidification and thermomechanical history of the DED processing method and not the composition of the starting material.

Color-Metallographic Characterization of Alloyed White Cast Irons Ni-Hard Type

The Ni-hard alloys white-cast irons are generally used for high wear work. Among them, those with better impact resistance because of its low carbon content compared to the rest of the family, are studied in this paper. One experimental technique of characterizing the metallic materials is the microstructural study. Several metallographic attacks intended to reveal qualitatively each microconstituent that forms the alloy, as well as the segregation and solidification structure of casting, are studied in this article. The use of color metallography is fundamental in this case to distinguish clearly the microconstituents. The main objective of this paper is to propose a series of attacks that identify each one of the microconstituents present in the alloy that has not been reported up to date.

'When the walls come tumbling down': The role of intergroup proximity, threat, and contact in shaping attitudes towards the removal of Northern Ireland's peace walls.

Institutional structures of segregation typically entrench social inequality and sustain wider patterns of intergroup conflict and discrimination. However, initiatives to dismantle such structures may provoke resistance. Executive proposals to dismantle Northern Ireland's peace walls by 2023 provide a compelling case study of the nature of such resistance and may thus provide important clues about how it might be overcome. Drawing on a field survey conducted in north Belfast (n=488), this research explored the role of physical proximity, realistic and symbolic threat, and past experiences of positive and negative cross-community contact on Catholic and Protestant residents' support for removing the walls. Structural equation modelling suggested that both forms of contact and proximity were significantly related to such support and that these relationships were partially mediated by realistic threat. It also suggested that positive contact moderated the effects of proximity. That is, for residents who had more frequent positive interactions with members of the other community, proximity to a peace wall had a weaker relationship with resistance to their removal than residents who had less frequent contact.

Segregation and urban spatial structure in Barcelona

AbstractWe propose an analysis to identify the degree of spatial segregation among different communities of residents in Barcelona. We elaborate a theoretical setting as an extension of the monocentric framework, yielding the creation of mixed spatial units. Our idea is to assess the extent to which spatial segregation is connected to the urban spatial structure, the neighbourhood's status, and the spatial autocorrelation. As a novelty, we perform the empirical exercise by relying on an original database that gathers information for the period 1947–2011. Estimations emphasize that Barcelona increasingly shows a spatial segregation pattern that is based mostly on the gentrification of high‐skill workers.

Willem Banning and the Reform of Socialism in the Netherlands

AbstractIn 1947 the liberal Protestant minister Willem Banning drafted a new programme for the Labour Party, in which the party dropped the Marxist view of history and class struggle. New Labour in the Netherlands was envisioned as a party that strove for a democratic and just society. Banning's role in reforming the Labour Party was part of his broader project of breaking down structures of socio-political segregation that had existed since the end of the nineteenth century. Banning argued that the Labour Party had to abandon its atheist ideology to open up to Protestants and Catholics. This article will examine Banning's views and ideals and show how he contributed to the transformation of Labour into a social democratic party and seek answer to the question: how could a liberal Protestant minister become the main ideologue of the Labour Party?

Exclusion-Driven Segregation and Dalits: Evidence from Selected Colonies in Kerala

Dalit-centred social exclusion largely stems from structures of spatial segregation which is rooted in the Indian caste system. The caste system placed Dalits at the lowest and weakest social stratum; their segregated housing-spaces further marginalised them. The history of Dalits ghetto in Kerala can be traced back to 1936 when the T ravancore Government opened a colony for the lower castes at Kottayam. The Government might have had a view of providing cultivable land to Dalits in an isolated locality will provide them with economic freedom and as a result, there will be less violation of caste rules. Over the years, the provided colonies began to be conceived as merely a housing scheme. In particular, it appeared when the Land Reforms Act (1963) is re-amended in 1969. Also, the provided land under the schemes was just 4 or 5 cents. That was meagre and unsuitable for the families to live. Moreover, the land size reduced further because of the intergenerational subdivision and fragmentation of holdings. A study conducted by KILA (2013) found that there are 26,198 Dalit colonies and about 60% of lower castes in Kerala are living. The colonies in the State are so remote either in hilly areas, marshy lands or away from public gaze as it leads to excluding Dalits from the broader social and economic system. The study attempted to explore the position of Dalits in the exclusion-driven segregation by comparing the Dalits who are living in a colony with the non-Dalits living at the outside colony. While doing so, the study found that the surveyed colonies are away from mainstream society. Also, most of them are living without land but with abject poverty when compared to non-colony dwellers. Furthermore, the study emphasised with the evidence that the exclusion of Dalits in the past is continuing with the contemporary differences in their living conditions in colonies.