Migration Trajectories Research Articles

Influence mechanism of hydrocyclone main diameter on separation performance

The main diameter of hydrocyclone (HC) has significant effects on separation performance. However, the differences of flow field characteristics within different HCs have not been understood well yet, which makes it impossible to grasp the influence mechanism of the main diameter on the separation performance. Through the study of the migration trajectories of particles, it is found that the greater the diameter and the finer the particles, the more particles escape from the overflow outlet. The relationships between the longest residence time and the HC main diameter for particles with 10 and 15 μm were, respectively, clarified. The high-speed video and particle image velocimetry experiments were performed and found although the main diameter of a large-HC (LHC) is twice that of a mini-HC (MHC), its air-core diameter is much larger than twice that of MHC, which is not beneficial for separations. The axial velocity around the central axis area in LHC is higher than that of the MHC, which helps separate low-density discrete phases from the overflow outlet at a faster speed but not for the separations of high-density discrete phases from the underflow outlet. The angle of the locus of zero vertical velocity in MHC is larger than that of LHC, which is anticipated to enhance the separation efficiency for the high-density discrete phase. This study first reveals the influence mechanism of the HC main diameter on its separation performance from the perspective of the flow field characteristics, which would hopefully provide significant references for the applications of HCs.

Childhood internal migration in Europe: Developments across cohorts and countries

AbstractInternal migration is the driving force behind population re‐distribution within countries. Although internal migration has been extensively studied among adults, little is known about patterns in childhood migration, and even less so in a comparative manner. This study, therefore, adopts a child‐centred approach and contributes to the literature by exploring cross‐national changes in childhood migration across birth cohorts. Moreover, it examines how patterns of childhood migration relate to the postponement of childbearing. Drawing on retrospective residential histories from the SHARE survey, we analyzed childhood migration trajectories of 178,476 individuals born between 1935 and 1994 in 28 European countries. Cohort analyses confirm a country gradient in childhood migration, with the highest migration rates in Northern Europe and the lowest in Southeastern Europe. Nonetheless, across nearly all countries, childhood migration has consistently declined since the 1970s. Furthermore, when children relocate, it happens at increasingly younger ages. Finally, we find that these patterns are related to the increasing childbearing age across Europe. Our results thereby highlight the interplay between childhood migration and adult family life's changing dynamics, offering a novel perspective on the link between these two demographic components.

University Architectures Re-Invented: Re-Conceptualizing Forced Migration, Historical Consciousness, and Coalition Building in Ukraine After the Full-Scale Russian Invasion

The purpose of this article is to describe the creation of displaced universities (DUs) as spaces for coalition building, resistance, and decolonial practice that have re-invented the university architecture. This article offers a multi-perspectival and historical exploration of higher education in Ukraine before and after the full-scale invasion of Russia in Ukraine on February 24, 2022, with particular focus on the coalitions around Ukrainian DUs. DUs can be seen as one form of decolonial creations, as a unique organic coalition and intellectual community. This organic coalition includes a process of social resistance, resilience, and policy, which are being shaped by people whose lives were and still are uncertain. These people affiliated with higher education created invisible connections that re-shaped the vision and relationality of DUs. The interwoven life trajectories of forced migrants, Ukrainian academics, administrators, and students who made the decision to move to mainland Ukraine and establish (in)visible DUs while continuing their work and education in Ukrainian territories under the control of the Ukrainian government.

Double transition of young migrants in Luxembourg: vulnerable, resilient and empowering integration trajectories in the period of youth.

Migrant integration trajectories have become more complex, open, uncertain, and continuously changing, over time. For young migrants, their integration endeavour intersects with their process of transition to adulthood, a double transition that poses additional challenges. Recent theoretical perspectives such as "liquid integration" aim at focusing on the dynamic, processual, and temporal nature of migrant integration. The present article focuses on the dynamic interplay of obstacles and enablers that, over time, interact to construct complex, often non-linear, and open-ended integration and coming of age trajectories of young migrants (aged from 18 to 30 years) coming from outside the European Union (EU) to EU countries. Empirical results from the H2020 MIMY (Empowerment through liquid Integration of Migrant Youth in vulnerable conditions) research project in Luxembourg will be presented. In order to address the goal of the research, qualitative data were gathered by means of N = 38 interviews with young migrants with different migratory paths, characteristics and experiences, and specifically included: young migrants from non-EU Portuguese-speaking countries (N = 16), refugees living in reception centres (N = 15), migrants who since arriving in Luxembourg have become publicly visible (N = 7). Content analysis of the interviews allowed a twofold purpose: (1) capturing the unfolding of intersectional integration obstacles that over time play a decisive role in the building of conditions of vulnerability of the double transition under analysis; (2) capturing the multidimensional resources that interactively build up to give rise to resilient and empowering integration and coming of age experiences. The identification of decisive multidimensional obstacles and resources present in the integration endeavour during the process of coming of age allowed us to capture differentiated routes of vulnerability, on the one hand, and resilience/ empowerment on the other. Key ingredients of both vulnerable and more resilient and empowering integration and coming of age trajectories are identified as well as their relational dynamics, enabling to address key challenges for the resilience and empowerment of young migrants in the process of negotiating their transition to adulthood amidst their integration challenges in the Luxembourgish society.

The Merchant Networks of Afghan Sikhs: The Cold War, its Legacies and Beyond

This article documents the migration of Afghanistan’s Sikh communities to Asia and Europe during the Cold War and its aftermath. It analyses these migratory trajectories both in the context of conflict in Afghanistan and the refugee flows it created as well as in relation to the long-term role of Afghan Sikhs in transregional trade. The article argues that exploring Sikh migration from Afghanistan through the twin analytical lenses of trade networks and the Cold War helps to illuminate a more complex range of identities and experiences than allowed for by a singular focus on their status as either ‘refugees’ or migrants from ‘the Global South’.

Migration Activity of Spodoptera litura (Lepidoptera: Noctuidae) between China and the South-Southeast Asian Region.

The common cutworm, Spodoptera litura (F.), feeds on a wide variety of food and cash crops and is one of the most widespread and destructive agricultural pests worldwide. Migration is the biological basis of its regional population outbreaks but the seasonal movement of this pest between east and south Asia regions remains unknown. In this study, searchlight traps were used to monitor the seasonal migration of S. litura from 2019 to 2023 in Ruili City (Yunnan, China), located along the insect migratory route between China and the south Asia region. The results showed that migratory activity could occur throughout the year, with the main periods found in spring (April-May) and autumn (October-December). The ovarian development and mating status of the trapped females indicated that most individuals were in the middle or late stages of migration and that Ruili City was located in the transit area of the long-distance migration of the pest. In the migration trajectory simulation, populations of S. litura moved from northeast India, Bangladesh, and northern Myanmar to southwestern China along the southern margin of the Himalayas in spring and returned to the south Asia region in autumn. Our findings clarify the seasonal migration patterns of S. litura in China and South Asia and facilitate the development of regional cross-border monitoring and management systems for this pest.

Abundance and Seasonal Migration Patterns of Green Lacewings (Neuroptera: Chrysopidae) across the Bohai Strait in Eastern Asia.

Many insects, including green lacewings, migrate seasonally to exploit suitable breeding and winter habitats. Green lacewings are important natural enemies of insect pests worldwide. Here, four dominant green lacewing species, Chrysoperla nipponensis (Okamoto), Chrysopa pallens (Rambur), Chrysoperla furcifera (Okamoto), and Chrysopa formosa Brauer, were investigated for their ability to migrate between northern and northeastern China across the Bohai Strait from late May to late October each year. Furthermore, there were significant interannual and seasonal differences in the number of migratory green lacewings collected. The number of green lacewings in spring was significantly lower than that in summer and autumn, and the highest average number of green lacewings occurred in June. In addition, there were differences in the sex ratio of migrating green lacewings between months, with a greater proportion of females than males. Finally, the seasonal migration trajectories simulated by the HYSPLIT model revealed that the green lacewings captured on Beihuang Island primarily originated from Shandong Province. Accordingly, these findings contribute to our understanding of green lacewing migration in eastern Asia and aid its incorporation within integrated pest management (IPM) packages for several crop pests. Furthermore, long-term tracking of migrant insect populations can reveal ecosystem services and trophic dynamic processes at the macroscale.

UKRAINIAN FORCED MIGRANTS’ INTEGRATION IN EUROPEAN LABOUR MARKET: GERMAN VS POLISH CASE

The tsunami of forced migration caused by Russia's full-scale invasion of Ukraine in 2022 poses a significant challenge to the socio-economic systems of host European countries, in particular Germany and Poland, which are the two main destination countries for displaced Ukrainians. Despite relatively similar statistics on the number and demographic structure of Ukrainian forced immigrants, the two countries differ significantly in terms of the level of labour market integration of refugees, which is a key factor determining their social integration and economic outcomes. The purpose of this paper is to study the peculiarities and common features of the integration of Ukrainian forced migrants in the labour markets of Germany and Poland, taking into account the pre-war experience of these countries in attracting Ukrainian economic migrants. Methodology. The study is a comparative analysis of the pre-war and forced migration trajectories of the two countries based on data from the German and Polish statistical services and Eurostat in 2010-2022. Results. The article discusses the redistribution of the main demographic characteristics in the profile of Ukrainian migrants in the post-war period, which led to an increase in the share of women with higher education in the demographic structure of migrants. These demographic differences, coupled with the peculiarities of European labour markets, have affected the employment prospects of Ukrainian refugees in European countries of destination. The pre-war experience of temporary labour migration from Ukraine and social ties between refugees and members of the diaspora were recognised as factors that facilitated the integration of Ukrainian refugees. The analysis showed that in addition to the geographical and cultural proximity between Ukraine and Poland, the circular labour migration model that dominated relations between Ukraine and Poland contributed to the rapid integration of Ukrainian refugees into the labour market after the outbreak of full-scale war. The lack of German language skills is the most common reason for the lower participation of Ukrainians in the German labour market compared to the Polish one. In Germany, favourable labour market conditions combined with integration policies facilitate access to the labour market for Ukrainian refugees in the long term. Practical implications. By examining the previous circular seasonal migration of Ukrainians over the past decade and their labour market integration in specific destination countries after the outbreak of war, this paper provides a broader perspective for the study of the transition from forced to permanent migration. Value/Originality. Given the global growth of both seasonal labour migrants and forms of movement, the key findings of the study provide a better understanding of these changing categories of mobility and their implications.

Petromagnetism and paleomagnetism of kimberlite pipesof the Verkhnemunskoe deposit (Yakutsk diamondiferous province)

The purpose of the studies of kimberlite pipes of the Verkhnemunskoe diamond field is to calculate the Middle Paleozoic paleomagnetic pole to clarify the trajectory of the apparent migration of the pole and reconstructions of the paleogeographic position of the Siberian platform at the time of the manifestation of active tectono-magmatic processes. The Verkhnemunskoye deposit is located within the Verkhnemunskoye kimberlite field of the Yakutsk diamondiferous province and includes five kimberlite pipes (Deimos, Zapolyarnaya, Komsomolskaya-Magnitnaya, Novinka and Poiskovaya), the age of which according to geological and isotopic data is estimated as Late Devonian-Early Carboniferous (372–347 Ma). For the first time scalar and vector physical parameters of kimberlites and captured xenoliths from different structural-material complexes of the Earth’s crust, as well as the host terrigenous sedimentary rocks of the Early Paleozoic were obtained, which are necessary for the development of physical-geological models of the Verkhnemunskoe field deposits. A relatively deep level of erosional shearing of the field has been established. The primary (synchronous with the formation of the field) natural residual magnetization was preserved in the kimberlite cohesive mass. The main carrier minerals of natural remanent magnetization vectors of kimberlites are unaltered magnesioferrite and magnetite, which indicates their thermo-sufficient nature. The natural remanent magnetization vectors of captured xenoliths indicate that the influence of hypergenic processes did not strongly affect the NRM vectors of kimberlites. Firing test is positive. The paleomagnetic pole with coordinates Φ = 26.5°N, Λ = 142.2°E, dp/dm = 6.2/7.8° was calculated from the obtained clusters of N = 10 vectors of the primary natural remanent magnetization of kimberlite pipes. On its basis, we reconstructed the paleogeographic position of the Siberian Platform, which at the time of the kimberlite intrusion was located in the middle latitudes of the northern hemisphere and was facing north with its southern edge.

Parameter Optimization of a Conveying and Separating Device Based on a Five-Stage Screw and Vibrating Screen for Tiger Nut Harvesters

To tackle problems such as the difficult separation from sand and the high power consumption of tiger nut harvesting in the sandy areas of Xinjiang, a conveying and separating device for tiger nut harvesters was designed. The axial and radial migrations of materials under screw action and the separation process of materials under vibratory action were analyzed dynamically. A simulation analysis was carried out on the conveying and separating process based on EDEM software. The migration trajectories of tiger nuts and sand particles were extracted, the displacement variations of sand particles on the X-axis, Y-axis, and Z-axis were analyzed in the action area of the screen-cleaning spike teeth and the screw action area, respectively, and the conveying and separation law of the tiger nut harvest mixture was clarified. With key parameters such as the screw velocity ratio, amplitude, vibration frequency, and machine operation velocity as test factors, and with the sand removal rate, crushing rate, and power consumption as test evaluation indicators, a four-factor, five-level orthogonal central composite test design was implemented. The test results were analyzed via the regression variance analysis method, and relation models between variable factors and evaluation indicators were constructed. The test results show that under the combined conditions of a screw velocity ratio of 0.88, an amplitude of 4.7 mm, a vibration frequency of 7.5 Hz, and a machine operation velocity of 0.92 km/h, the sand removal rate is 90.40%, the crushing rate is 1.66%, and the power consumption is 2.24 kW in theory. The optimized results were verified by tests. The sand removal rate was 88.92%, the crushing rate was 1.71%, the total power consumption was 2.29 kW, and the errors from the predicted values were 1.6%, 3.0%, and 2.2%, respectively, meeting the requirements for tiger nut harvesting conveyance and separation. This research can provide support for the development of technology and equipment for mechanized harvesting of tiger nuts in the sandy areas of Xinjiang.

Weaving Borders, Resorting to Beliefs: The Role of Religion in the Migratory Trajectories of Intracontinental Migrants in Latin America

Weaving Borders, Resorting to Beliefs: The Role of Religion in the Migratory Trajectories of Intracontinental Migrants in Latin America

From collective centres to private accommodation: housing trajectories of asylum migrants in Switzerland

This paper examines the housing trajectories of complete cohorts of asylum migrants in Switzerland. It emphasizes the logistics of housing allocation by local authorities and how it shapes individual opportunity structure. We use full-population register data and analyse one key transition: the transition out of collective centre assigned upon arrival to the private and subsidized housing sectors. Event history models show the association between individual and contextual factors and the speed of access to private housing. Despite the quasi-autonomous management of refugee housing by region, priority rules regarding access to private housing were found to apply across the country. When choosing between different profiles, women, older asylum migrants, married individuals, and members of larger national groups are favoured in obtaining access to private housing. Nevertheless, the time spent in collective centres largely depends on the region to which a claimant is assigned, pointing to the minimal agency asylum migrants have during their first years of residence.

Population dynamics and seasonal migration patterns of Spodoptera exigua in northern China based on 11 years of monitoring data.

The beet armyworm, Spodoptera exigua (Hübner), is an important agricultural pest worldwide that has caused serious economic losses in the main crop-producing areas of China. To effectively monitor and control this pest, it is crucial to investigate its population dynamics and seasonal migration patterns in northern China. In this study, we monitored the population dynamics of S. exigua using sex pheromone traps in Shenyang, Liaoning Province from 2012 to 2022, combining these data with amigration trajectory simulation approach and synoptic weather analysis. There were significant interannual and seasonal variations in the capture number of S. exigua, and the total number of S. exigua exceeded 2,000 individuals in 2018 and 2020. The highest and lowest numbers of S. exigua were trapped in September and May, accounting for 34.65%±6.81% and 0.11%±0.04% of the annual totals, respectively. The average occurrence period was 140.9±9.34 days during 2012-2022. In addition, the biomass of S. exigua also increased significantly during these years. The simulated seasonal migration trajectories also revealed varying source regions in different months, primarily originated from Northeast China and East China. These unique insights into the migration patterns of S. exigua will contribute to a deeper understanding of its occurrence in northern China and provide a theoretical basis for regional monitoring, early warning, and the development of effective management strategies for long-range migratory pests.

Skill the low-skilled: the knowledge-driven stepwise migration of Vietnamese workers in South China

This article investigates the interplay between knowledge acquisition and the stepwise migration trajectories of low-skilled Vietnamese workers in China. Utilizing a rich array of data garnered from face-to-face interviews, customized surveys, on-site observations, media narratives, and an archival review of government regulations in Guangxi—a province bordering Vietnam—and in Guangdong, a non-adjacent province, this study proposes an analytical framework, skill-driven migration, to highlight the synergy between the pre-migratory socio-demographic attributes of migrants and the circumstances prevailing in both the places of origin and destination which orchestrates distinct job allocations and skill augmentation avenues. Notably, our study underscores that the competencies acquired in manufacturing employments potentially broaden the horizon of destinations for migrants in their subsequent stepwise migration endeavors. This phenomenon, in turn, poses intricate immigration management quandaries for newly emerged destination nations like China, spotlighting a nuanced dimension of labor mobility and policy frameworks in the evolving regional economic integration. Last, our findings challenge the conventional dichotomy of high-skilled and low-skilled categories of labor migration, as well as the dichotomy of explicit-tacit knowledge.

Migration trajectories and blocking effect of the fine particles in porous media based on particle flow simulation

The particle flow code method based on the discrete element method was used to establish the seepage migration model of fine particles [fine particles (FPs), i.e., suspended particles] in a porous medium. A series of numerical simulations were carried out by changing the particle size, seepage velocity, particle injection number, and wide particle size gradation. The research showed that large FPs play a major role in blocking porous medium channels when the injected FPs have a wide size gradation. Due to the blocking effect, small FPs that would not otherwise have deposited also deposit. Moreover, by increasing the number of large FPs in the mixed particles, the total number of particles deposited and the number of smaller FPs deposited will also increase. The distribution of FPs in porous mediums can be divided into three types: surface deposition, internal deposition, and non-deposition. When the seepage velocity increases and reaches a seepage threshold, which is the critical seepage velocity, the deposited FPs will once again be in a suspended state and undergo migration. On the contrary, the FPs will continue to maintain their sedimentary state, and the critical seepage velocity will also increase correspondingly with increasing particle size.

Ethnography of exploitation in seasonal agricultural labor. The case of Bulgarian Roma laborers in Apulia, Southern Italy

This paper analyses a case of severe labour exploitation, involving a group of Bulgarian fruit and vegetable pickers of Roma origin employed in the seasonal harvest, especially of tomatoes, in the Foggia area involved in a 10-year cycle of seasonal migration between Italy and Bulgaria. The essay presents the general characteristics and factors affecting the form of extreme exploitation in farm work in Italy and reconstructs the working conditions and migration trajectories of this group of farm laborers of Roma origin to see how ethnicity, widespread anti-Gypsyism, and forms of extreme social exclusion accentuate the dynamics of labor exploitation. This group experiences the most intense forms of exploitation on the ground compared to other exploited foreign laborers. The case study is based on ethnographic that lasted about 2 years and interviews with privileged witnesses.

Higher education trajectories of migrants and the role of age of arrival: evidence from native and migrant students in Chile

Higher education trajectories of migrants and the role of age of arrival: evidence from native and migrant students in Chile

An unlevel playing field: Immigrant assimilation and welfare utilization

This paper investigates the existence and mechanisms of segmentation in the welfare assimilation process of first-generation immigrants in the Netherlands. Using longitudinal administrative data (2007–2015) from Statistics Netherlands (CBS), we estimate the welfare utilization trajectories of migrants over the working-age life course vis-à-vis two reference groups representing different economic segments from the population, namely: average Dutch natives and Dutch natives with low education level. Empirical evidence shows a predominant trend of mainstream assimilation; however, two findings with more concerning implications should be highlighted. Welfare assimilation into the economically disadvantaged segment is found to concentrate among first-generation immigrants characterized by structural and human capital disadvantages, despite the notable extent of upward intragenerational mobility observed. In the worst-case scenario, there seems to be a lack of welfare assimilation to the comparison segments, raising concerns over the prospective emergence of marginalized ethnic groups at the bottom of the economic ladder. The implications of this finding are twofold. Firstly, automatic closing of the migrant-native gap over time should not be presumed in the absence of a level playing field for all regardless of their migration backgrounds. Secondly, systematic discrepancies observed between refugees and other types of migrants in terms of welfare assimilation patterns and determinants point to the need to have a clear distinction between immigration policy and refugee policy, which explicitly avoids bundling all migrants as one homogenous group.

Spatial-temporal evolution and influencing factors of ecological resilience in urban agglomerations: a case study of Shanxi section of the Yellow River Basin

Scientific assessment of the development status and factors influencing the urban ecological resilience of the Yellow River Basin (YRB) is highly significant for promoting its development. This study constructed an evaluation index system for urban ecological resilience considering the four dimensions of pressure, state, response, and innovation. The spatiotemporal ecological resilience of the urban agglomeration (UA) in the Shanxi section of the YRB from 2012 to 2021 was studied using kernel density estimation, Dagum Gini coefficient, and standard deviation ellipse, and the influencing factors of urban ecological resilience were analyzed using a geographic detector. This research revealed that (1) the ecological resilience of cities in the Shanxi section of the YRB experienced a fluctuation process of rise—fall—rise. The urban ecological resilience generally reflected a gradient decreasing spatial pattern of Central Shanxi UA > South Shanxi UA > North Shanxi UA, and gradually changed from the dual core of “Taiyuan—Jincheng City” to the single core of Taiyuan City. (2) The migration trajectory of urban ecological resilience center of gravity fluctuated in the direction of “northwest-southeast,” and moved 12.63 km to the southeast overall. (3) The water supply per ten thousand Yuan GDP, occupied area of construction land per ten thousand Yuan GDP, green coverage rate in built-up areas, ratio of research and experimental development funds (R&D) to GDP, proportion of science and technology expenditure in local fiscal expenditure, and patent licensing quantity index have a high influence on urban ecological toughness at all stages. This influence was further strengthened by the interaction between factors. This study provides an important scientific basis for shaping high-quality development advantages in the YRB and creating a resilient and livable environment.

Moment tensor potential for static and dynamic investigations of screw dislocations in bcc Nb

A new machine-learning interatomic potential, specifically a moment tensor potential (MTP), is developed for the study of screw-dislocation properties in body-centered-cubic (bcc) Nb in the thermally- and stress-assisted temperature regime. Importantly, configurations with straight screw dislocations and with kink pairs are included in the training set. The resulting MTP reproduces with near density-functional theory (DFT) accuracy a broad range of physical properties of bcc Nb, in particular, the Peierls barrier and the compact screw-dislocation core structure. Moreover, it accurately reproduces the energy of the easy core and the twinning-anti-twinning asymmetry of the critical resolved shear stress (CRSS). Thereby, the developed MTP enables large-scale molecular dynamics simulations with near DFT accuracy of properties such as for example the Peierls stress, the critical waiting time for the onset of screw dislocation movement, atomic trajectories of screw dislocation migration, as well as the temperature dependence of the CRSS. A critical assessment of previous results obtained with classical embedded atom method potentials thus becomes possible.