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Young returnees' sustainability of return: The case of Bulgaria 年轻海归回国的可持续性:保加利亚的案例
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023023
M. Misheva, Antoaneta Getova
Return migration flow to Bulgaria is constant but not high, except for the past two years. Here, we argue that subjective and objective reasons should both be considered in line to explain life prospects of young returnees at home. An innovative approach to balancing the subjective-objective dichotomy in return migration phenomena is measuring sustainability of return through re-emigration, captured by and tested through a re-emigration index based on a national representative survey of returning Bulgarian migrants. The main hypothesis is that the sustainability of the return of young people depends on a complex group of factors, including social and emotional motives. The main findings are about the magnitude of the return migration flow and its sustainability: The factors for the return of young Bulgarians in the pre-Covid research show strong non-economic character, which intensifies in times of crisis. There are no significantly different tendencies for re-emigration/return among young people compared with all returnees.
除过去两年外,返回保加利亚的移民人数不变,但并不多。在此,我们认为在解释海归青年回国后的生活前景时,主观原因和客观原因都应该考虑在内。平衡回返移徙现象的主观-客观二分法的一个创新办法是衡量通过再移徙回返的可持续性,这是根据对回返保加利亚移徙者进行的全国代表性调查得出的再移徙指数所记录和检验的。主要假设是,年轻人回国的可持续性取决于一系列复杂的因素,包括社会和情感动机。主要发现是关于返回移民流的规模及其可持续性:在新冠疫情前的研究中,年轻保加利亚人返回的因素显示出强烈的非经济特征,这种特征在危机时期会加剧。与所有回返者相比,年轻人再移民/返回的趋势没有明显不同。
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引用次数: 0
Flood spatial location in a Mediterranean coastal city: Ibiza (Balearic Islands) from 2000 to 2021 2000 - 2021年地中海沿海城市:伊比沙岛(巴利阿里群岛)的洪水空间定位
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023013
Joan Rosselló-Geli, M. Grimalt-Gelabert
Floods are a common occurrence in the Western Mediterranean basin, causing daily life disturbances, economic impacts and fatalities as the population living near the Mediterranean shores face a great risk. The city of Ibiza has been historically affected by floods of different magnitudes. After almost three decades without large events, with the 1977 flood being the latest, 20 floods have been identified within the city boundaries since the beginning of the 21st century, causing a great social impact. The aim of the research herein presented is to identify the locations of floods and their possible causes. The methodology is based on a comprehensive survey of newspapers articles and technical reports, thus allowing mapping of the location of the events over a city map. Among the causes, there are the lack of a runoff network and deficient infrastructure planning. Regarding the spatial distribution of floods, the most affected areas are the circumvallation freeways around the city and the neighborhoods urbanized after the 1960's. The results highlight the importance of the urban sprawl and malpractices related to flood risk areas, which increase the occurrence of floods. Moreover, the identification of the most affected areas can help city planners to create prevention measures and systems to reduce flood hazards and vulnerability.
洪水在西地中海盆地经常发生,给生活在地中海沿岸附近的人们带来日常生活混乱、经济影响和死亡,因为他们面临着巨大的风险。伊比沙岛历史上曾受到不同程度的洪水的影响。以1977年的大洪水为例,近30年没有发生大洪水,进入21世纪以来,全市范围内共发生洪水20次,造成了巨大的社会影响。本文提出的研究目的是确定洪水的位置及其可能的原因。该方法基于对报纸文章和技术报告的全面调查,从而可以在城市地图上绘制事件的位置。原因之一是缺乏径流网络和基础设施规划不足。从洪水的空间分布来看,受影响最大的区域是城市环城高速公路和60年代以后城市化的街区。研究结果强调了城市扩张和与洪水风险区域相关的不当行为的重要性,这些行为增加了洪水的发生。此外,确定受影响最严重的地区可以帮助城市规划者制定预防措施和系统,以减少洪水的危害和脆弱性。
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引用次数: 0
Bulgarian community in Chicago: A model of development 芝加哥的保加利亚社区:发展的典范
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023029
Dilyana Ivanova Zieske, William F. Zieske
This paper presents the first comprehensive model of development of the Bulgarian settlement in the Chicago area from its earliest traces to the present day, from historical and anthropological perspectives. In the process, we distinguish five periods of Bulgarian presence spanning more than a century and discuss the patterns of Bulgarian settlement, economic profiles and community life for each of those periods. The paper highlights the struggle for survival and recognition of early Bulgarian migrants during the late nineteenth and early twentieth century, the political rivalry of the Cold War Bulgarian refugees preventing their consolidation and the contemporary, post-1989, Bulgarian economic mass migration which becomes increasingly visible and emancipated, claiming Chicago as the Bulgarian City. In the process, we seek to explain why this long history of Bulgarian immigration has not resulted in the community's overt visibility, either in the literature and studies of Chicago's ethnic landscape or through the creation of an ethnic enclave with vernacular urban centralized space distinct from other ethnic migrant groups and their neighborhoods such as Little Italy, Ukrainian Village, Greek Town and Chinatown.
本文从历史和人类学的角度,提出了芝加哥地区保加利亚定居点从最早的痕迹到现在的第一个综合发展模型。在此过程中,我们区分了跨越一个多世纪的保加利亚人存在的五个时期,并讨论了每个时期保加利亚人的定居模式、经济概况和社区生活。本文强调了19世纪末和20世纪初早期保加利亚移民的生存和认可斗争,冷战时期保加利亚难民的政治竞争阻止了他们的巩固,当代,1989年后,保加利亚经济大规模移民变得越来越明显和解放,声称芝加哥是保加利亚城市。在这个过程中,我们试图解释为什么保加利亚移民的悠久历史没有导致社区的公开可见性,无论是在芝加哥民族景观的文学和研究中,还是通过创造一个具有本土城市集中空间的民族飞地,与其他民族移民群体及其社区(如小意大利、乌克兰村、希腊城和唐人街)截然不同。
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引用次数: 0
Mobility issues and multidimensional inequalities: exploring the limits of the National Strategy for Immigration and Asylum during the COVID-19 pandemic in Morocco 流动问题和多维不平等:探讨摩洛哥2019冠状病毒病大流行期间国家移民和庇护战略的局限性
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023011
Daniela Santus, S. Ansaloni
In December 2019, the severe respiratory syndrome coronavirus-2 was discovered in China. The virus spread rapidly and, by March 2020, the World Health Organization (WHO) declared COVID-19 to be a global pandemic. Scientists expected the African continent to be among the worst affected by the sanitary emergency in terms of prevalence, incidence and mortality. This prediction was refuted by evidence, considering that Africa reported the least number of cases and deaths compared to Europe, Asia and America. The first case in Africa was registered in Egypt on February 14, 2020. By the end of 2021, the continent recorded a cumulative of 7,110,817 cases and 155,505 deaths. Nonetheless, estimates are likely to be distorted due to the lack of available data about the impact of COVID-19 and the limited documentary capacity of most African countries. There are several theories to explain why, contrary to the expected trend, Africa had the fewest COVID-19 incidences compared to other continents. Africa is characterized by a young population, which is notoriously less susceptible to COVID-19, with an average age of 19.7 years. In addition, most of the Africans (59%) live in rural areas, with few opportunities to travel or get in contact with outsiders. Moreover, governments enforced outstanding measures to contain the spread of the virus and safeguard the national economy, such as strengthening their documentary capacity and enforcing effective social safety nets. However, most of these policies have aggravated entrenched patterns of discrimination, making certain populations uniquely vulnerable. Indeed, mobility restrictions and border closures severely affected people with mobile livelihoods. In Morocco, the emergency measures compromised the resilience capacity of sub-Saharan migrants, particularly women and girls. To study the phenomenon of African migration to Morocco, we conducted fieldwork research from October to December 2021, interrupted by the closure of the kingdom's borders, and continued remotely thanks to key informants.
2019年12月,中国发现了严重呼吸综合征冠状病毒2型。该病毒迅速传播,到2020年3月,世界卫生组织(世卫组织)宣布COVID-19成为全球大流行。科学家们预计,就流行率、发病率和死亡率而言,非洲大陆将是受卫生紧急情况影响最严重的地区之一。考虑到与欧洲、亚洲和美洲相比,非洲报告的病例和死亡人数最少,证据驳斥了这一预测。非洲第一例病例于2020年2月14日在埃及登记。到2021年底,非洲大陆累计记录了7110817例病例和155505例死亡。然而,由于缺乏关于COVID-19影响的可用数据以及大多数非洲国家的记录能力有限,估计可能会被扭曲。有几种理论可以解释为什么与预期趋势相反,与其他大陆相比,非洲的COVID-19发病率最低。非洲的特点是人口年轻,不易感染COVID-19,平均年龄为19.7岁。此外,大多数非洲人(59%)生活在农村地区,很少有机会旅行或与外界接触。此外,各国政府为遏制病毒传播和保护国民经济而采取了有效措施,例如加强其记录能力和建立有效的社会安全网。然而,这些政策大多加剧了根深蒂固的歧视模式,使某些群体特别容易受到伤害。事实上,流动限制和边境关闭严重影响了以流动为生的人。在摩洛哥,紧急措施损害了撒哈拉以南移徙者,特别是妇女和女孩的复原能力。为了研究非洲移民到摩洛哥的现象,我们于2021年10月至12月进行了实地调查,该调查因王国边境关闭而中断,并在关键线人的帮助下远程继续进行。
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引用次数: 0
Assessment of Hydrological Drought Index change over long period (1990–2020): The case of İskenderun Gönençay Stream, Türkiye 1990-2020年水文干旱指数的长期变化评价:以浙江<s:1> İskenderun Gönençay溪为例
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023024
Serin Değerli Şimşek, Ömer Çapar, E. Turhan
Recently, due to changes in the global climate, there have been significant increases in flood and drought events. The changes in wet and dry periods can be examined by various methods using hydrometeorological data to analyze climate disasters. In this study, Gönençay Stream in the Asi River Basin was chosen as the study area, which contains abundant underground and surface water reserves in Türkiye. Within this region, not only are the agricultural activities intense, but also hydraulic structure applications such as dams and reservoirs draw attention. Previous studies stated that meteorological and agricultural droughts have started to be noticed in the basin. Therefore, temporal variation analyses can positively contribute to assessing possible hydrological droughts in the following years. In this context, wet and drought periods were determined using the Streamflow Drought Index method at 3, 6, 9, and 12-month time scales with monthly average flow data observed between 1990 and 2020. At the same time, the number and probabilities of drought categories on a 12-month time scale, the first expected transition times between classifications, and the expected residence times between categories were specified. The study revealed that the most severe dry period occurred between 2013 and 2014 and was classified as Extremely Drought. The wettest period was around 2018–2019 and was classified as Extremely Wet. The largest expected time residence among all classifications was calculated for the Extremely Drought category with nine months, means that if the Extremely Drought period ever occurs, it remains for approximately nine months. While the Moderately Drought period occurred within one month following the Extremely Drought duration, and a Near Normal Wet period was observed three months after the Extremely Wet period. The most seen drought category for monthly calculations was the Near Normal Wet category, and was seen over 200 times with a 52.8% probability. Considering the Gönençay region, it is possible that any Extreme drought classification eventually regresses to normal.
最近,由于全球气候的变化,洪水和干旱事件显著增加。利用水文气象资料分析气候灾害,可以采用多种方法考察干湿期的变化。本次研究选取了阿西河流域Gönençay溪流作为研究区域,该流域蕴藏着丰富的地下水和地表水储量。在该地区,不仅农业活动密集,而且水坝和水库等水工结构的应用也引起了人们的注意。此前的研究表明,该流域的气象和农业干旱已经开始受到关注。因此,时间变化分析对未来几年可能发生的水文干旱有积极的贡献。在此背景下,利用1990 - 2020年观测到的月平均流量数据,利用径流干旱指数法在3、6、9和12个月的时间尺度上确定了湿期和旱期。同时,确定了12个月时间尺度上干旱类别的数量和概率、类别之间的首次预期过渡时间和类别之间的预期停留时间。研究显示,最严重的干旱期发生在2013年至2014年,被归类为极端干旱。最潮湿的时期是在2018年至2019年左右,被归类为极度潮湿。在所有分类中,极端干旱类别的预期停留时间最长,为9个月,这意味着如果极端干旱时期发生,它将持续大约9个月。中度干旱期发生在极端干旱期后1个月内,接近正常湿润期发生在极端湿润期后3个月。每月计算中最常见的干旱类别是近正常潮湿类别,出现次数超过200次,概率为52.8%。考虑到Gönençay区域,任何极端干旱分类最终都有可能回归正常。
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引用次数: 0
The effects of climate and soil properties on the magnitude of the visual soil quality indicators: a logistic regression approach 气候和土壤性质对目视土壤质量指标大小的影响:逻辑回归方法
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023027
F. Teixeira
Understanding how different climates and soil properties affect the soil processes requires quantifying these effects. Visual soil quality indicators have been proposed to assess the robustness of the soil processes and infer their ability to function. The scores of the visual soil quality indicators covary with climate features and soil properties, and their magnitude is different in acid-to-neutral and alkaline soils. These variables show collinearities and interactions, and the assessment of the individual effect of each variable on the scores of the visual indicators and the selection of the best set of explanatory variables can only be made with a definite set of variables. Logistic regression was used to calculate the effects of six climate variables and four soil properties, and their interactions, on the scores of eight visual soil quality indicators. Simple models featuring climate and soil variables explained a substantial part of the variation of the visual indicators. Models were fitted for each visual indicator for acid-to-neutral and alkaline soils. The sample size needed was calculated, and the method and its validity were discussed. For two possible outcomes, the sample size using the events per variable (EPV) criterium ranges between 62 and 183 observations, while using one variable and a variance inflation factor, it ranges between 22 and 234. Except for the model of soil structure and consistency for acid-to-neutral soils, with a C statistic of 0.67, all others had acceptable to excellent discrimination. The models built are adequate, for example, for the large-scale spatial outline of the soil health indices, to couple with soil morphological-dependent pedotransfer functions, and so on. Future models should consider (test) other explanatory variables: other climate variables and indices, other soil properties and soil management practices.
了解不同的气候和土壤性质如何影响土壤过程需要量化这些影响。视觉土壤质量指标已被提出,以评估土壤过程的稳健性和推断其功能的能力。土壤质量目视指标的得分随气候特征和土壤性质的变化而变化,在酸碱土壤和中性土壤中,其大小不同。这些变量表现出共线性和相互作用,评估每个变量对视觉指标得分的个别影响和选择最佳解释变量集只能用一组确定的变量来进行。采用Logistic回归计算了6个气候变量和4种土壤性质及其相互作用对8个目视土壤质量指标得分的影响。以气候和土壤变量为特征的简单模型解释了视觉指标变化的很大一部分。对酸转中性和碱性土壤的各视觉指标进行了模型拟合。计算了所需的样本量,讨论了该方法及其有效性。对于两种可能的结果,使用每个变量事件(EPV)标准的样本量范围在62到183个观察值之间,而使用一个变量和方差膨胀因子,其范围在22到234之间。除酸中性土壤结构和一致性模型的C统计量为0.67外,其余均为可接受的极优判别。所建立的模型能够较好地反映土壤健康指数的大尺度空间轮廓,能够与土壤形态相关的土壤转移函数相耦合等。未来的模型应该考虑(测试)其他解释变量:其他气候变量和指数、其他土壤特性和土壤管理实践。
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引用次数: 0
Rock strength degradation induced by salt precipitation: A new mechanical mechanism of sand production in ultra-deep fractured tight sandstone gas reservoirs 盐沉降引起岩石强度退化:超深裂缝性致密砂岩气藏出砂新力学机制
Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023032
Dujie Zhang, Yili Kang, Lijun You, Li Xiangchen

I take a typical ultra-deep tight sandstone gas reservoir located in Tarim Basin as an example to investigate the rare sand production problem. The situation of sand production was presented, and then conventional analyses were conducted. Six tight sandstone core plugs were selected to conduct rock mechanical tests before and after salt precipitation. Ultimately, a mathematical model was established to investigate the mechanism of rock strength degradation. The results of sand production prediction indicated that sand production from rock skeletons should never appear, but the rock skeletons was observed in the sand samples, and thus the impact of salt precipitation was taken into account. The experiments proved salt precipitation caused a degradation in rock strength, and the difference between actual- and predicted critical sand production pressure drop based on the weakened rock strength reduced significantly. Furthermore, the stress intensity factor on the fracture tip induced by salt precipitation reached up to 1.22 MPa·m1/2, which was greater than the fracture toughness of tight sandstone, and it was used to explain the rock strength degradation. The results are helpful to the knowledge of the sand production problem in ultra-deep fractured tight sandstone gas reservoirs.

& lt; abstract>本文以塔里木盆地某典型超深层致密砂岩气藏为例,研究其稀有出砂问题。介绍了出砂情况,并进行了常规分析。选取6个致密砂岩岩心塞,进行了盐沉淀前后的岩石力学试验。最后,建立了岩石强度退化的数学模型,探讨了岩石强度退化的机理。产砂预测结果表明,岩石骨架产砂不应出现,但在砂样中观察到岩石骨架,因此考虑了盐降水的影响。实验证明,盐降水导致岩石强度下降,岩石强度减弱后的临界出砂压降与实际值的差值显著减小。盐岩析出引起的裂隙尖端应力强度因子高达1.22 MPa·m<sup>1/2</sup>,大于致密砂岩的断裂韧性,可以用来解释岩石强度退化。研究结果有助于认识超深裂缝性致密砂岩气藏出砂问题。& lt; / abstract>
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引用次数: 0
Digital infrastructure strategies: the case of the province of Caserta 数字基础设施战略:以卡塞塔省为例
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023014
Paolo Pane, Federico de Andreis
The digital economy and the associated productivity gains generated by the diffusion of the Internet are considered fundamental components of growth models. Scientific reflection converges in considering balanced access to digital services as a diriment factor for the promotion of competitiveness, equity, economic development and social and environmental sustainability. Although the availability of infrastructure is not sufficient to achieve the full development of the territory and the community, it is nevertheless an unavoidable prerequisite for today's and future technological and digital applications and, therefore, investigating the type of association between the presence of communication networks and the socio-economic structure of the territories is essential to understanding the very nature of multidimensional inequalities and their spatial and geographical distribution, within a framework that sees infrastructure as a conversion factor and means of development for capabilities. Based on the theories of social exclusion, the capability approach and critical theory, the research presented aims to investigate, through the analysis of a case study, the possible association between the state of progress of broadband implementation and specific territorial configurations, considering also different variables of a geographical nature.
数字经济和互联网扩散所带来的相关生产率提高被认为是增长模型的基本组成部分。科学反思一致认为,平衡获取数字服务是促进竞争力、公平、经济发展以及社会和环境可持续性的不利因素。虽然现有的基础设施不足以实现香港和香港社会的全面发展,但它却是当今和未来科技和数码应用不可避免的先决条件,因此,在一个将基础设施视为转换因素和能力发展手段的框架内,调查通讯网络的存在与领土的社会经济结构之间的联系类型,对于了解多方面不平等的本质及其空间和地理分布是至关重要的。基于社会排斥理论、能力理论和批判理论,本研究旨在通过案例分析,在考虑不同地理变量的情况下,探讨宽带实施进展状况与特定地域配置之间的可能关联。
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引用次数: 0
COVID-19 and return intentions among mobile Bulgarian citizens living abroad COVID-19和居住在国外的流动保加利亚公民的回国意愿
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023020
Vanya Ivanova
The article presents the results from a virtual ethnographic study, focused on the return intentions of 11 mobile Bulgarian citizens living in several countries in the European Union and beyond, employed in highly qualified jobs. In-depth interviews were conducted online in the months of April-May 2020, at the time of the first lockdowns and restrictions on international travel both to/from Bulgaria and to multiple countries around the world. The core issues, analyzed in this article, are the motivations for potential return and how the Bulgarians abroad observe and feel the COVID-19 situation in their current destination country. The qualitative data shows that in this particular small number of respondents, the majority of the highly qualified mobile Bulgarians do not have intentions to return to Bulgaria, most of them prefer to stay in their current country. In several cases, COVID-19 blocked their opportunities to further move internationally, for example, to a new job position in a third destination country. Three figures of highly qualified mobile people are synthesized, explaining three models of return intentions at the beginning of the COVID-19 pandemic.
本文介绍了一项虚拟人种学研究的结果,重点关注11名居住在欧盟和其他国家的流动保加利亚公民的回国意愿,他们从事着高质量的工作。在2020年4月至5月期间,在保加利亚和世界多个国家的国际旅行首次封锁和限制期间,我们在网上进行了深入采访。本文分析的核心问题是潜在回国的动机,以及海外保加利亚人如何观察和感受当前目的地国的COVID-19形势。定性数据显示,在这一小部分受访者中,大多数高素质的流动保加利亚人并不打算返回保加利亚,他们中的大多数人更愿意留在目前的国家。在一些情况下,COVID-19阻止了他们进一步国际流动的机会,例如在第三目的地国找到新的工作岗位。综合了高素质流动人员的三个数字,解释了COVID-19大流行开始时的三种回归意愿模型。
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引用次数: 0
Revisiting European migration industries amid the Covid-19 pandemic: Changes in the recruiting practices of Bulgarian agencies 在2019冠状病毒病大流行期间重新审视欧洲移民行业:保加利亚机构招聘实践的变化
IF 1.3 Q4 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-01-01 DOI: 10.3934/geosci.2023022
Boris Popivanov, S. Kovacheva
Workforce mobility in the European Union (EU) has faced enormous challenges regarding the outbreak of Covid-19 in 2020. Member-states reacted by imposing border closures and eliciting travel restrictions and sanitary measures, some of which continued well into 2022, with far-reaching consequences in all areas of mobility experience. In a time of constant changes in the regulations of the internal market, the work of labour market intermediaries deserves special attention. Recent studies have shown that, being a relatively new EU member-state, Bulgaria managed to develop an important migration industry comprising a complex network of public and private actors. We focus on an interpretative analysis of ten in-depth interviews conducted in 2017 with practitioners working in such agencies, and ten follow-up interviews five years later. The comparative analysis of these intermediaries' reflections on the mobility policies and practices before and during the pandemic allows us to examine the processes of structural and functional adaptation in the industry in multiple dimensions: assessment of changes in mobility practices, perceptions of employers' and migrants' needs and expectations, and the challenges facing their agencies vis-à-vis the role of other actors in the field. The conclusion underlines trends and transformations which are of interest for the developing recruitment sectors in other Central and East European countries, as well as for the dynamics of the East-West labour mobility throughout the entire EU.
由于2020年新冠肺炎疫情的爆发,欧盟的劳动力流动面临巨大挑战。会员国的反应是关闭边境,采取旅行限制和卫生措施,其中一些措施一直持续到2022年,对所有流动领域都产生了深远的影响。在内部市场规则不断变化的时代,劳动力市场中介机构的工作值得特别注意。最近的研究表明,作为一个相对较新的欧盟成员国,保加利亚成功地发展了一个重要的移民产业,包括一个由公共和私人行动者组成的复杂网络。我们重点对2017年对在这些机构工作的从业人员进行的10次深度访谈以及5年后的10次后续访谈进行了解释性分析。对这些中介机构在大流行之前和期间对流动政策和做法的反思进行比较分析,使我们能够从多个方面审查该行业的结构和功能适应过程:评估流动做法的变化,对雇主和移民的需求和期望的看法,以及他们的机构面临的挑战-à-vis以及该领域其他行为者的作用。结论强调了其他中欧和东欧国家发展中的招聘部门以及整个欧盟东西方劳动力流动的动态所关心的趋势和变化。
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引用次数: 0
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AIMS Geosciences
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