Repair of Second-Generation Recycled Fine Aggregate of Waste Concrete from Freeze-Thaw Environment by Carbonation Treatment

The reuse of waste recycled concrete from harsh environments has become a research hotspot in the field of construction.This study investigated the repair effect of carbonation treatment on second-generation recycled fine aggregate(SRFA)obtained from recycled fine aggregate concrete(RFAC)subjected to freeze-thaw(FT)cycles.Before and after carbonation,the properties of SRFA were evaluated.Carbonated second-generation recycled fine aggregate(CSRFA)at five substitution rates(0%,25%,50%,75%,100%)to replace SRFA was used to prepare carbonated second-generation recycled fine aggregate concrete(CSRFAC).The water absorption,porosity and mechanical properties of CSRFAC were tested,and its frost-resisting durability was evaluated.The results showed after carbonation treatment,the physical properties of SRFA was improved and met the requirements of II aggregate.The micro-hardness of the interfacial transition zone and attached mortar in CSRFA was 50.5%and 31.2%higher than that in SRFA,respectively.With the increase of CSRFA replacement rate,the water absorption and porosity of CSRFAC gradually decreased,and the mechanical properties and frost resistance of CSRFAC were gradually improved.Carbonation treatment effectively repairs the damage of SRFA caused by FT cycles and improves its application potential.

Effect of High Temperature Curing on the Frost Resistance of Recycled Aggregate Concrete and the Physical Properties of Second-Generation Recycled Coarse Aggregate under Freeze-Thaw Cycles

With the emphasis on environmental issues,the recycling of waste concrete,even recycled concrete,has become a hot spot in the field of architecture.But the repeated recycling of waste concrete used in harsh environments is still a complex problem.This paper discusses the durability and recyclability of recycled aggregate concrete(RAC)as a prefabricated material in the harsh environment,the effect of high-temperature curing(60℃,80℃,and 100℃)on the frost resistance of RAC and physical properties of the second generation recycled coarse aggregate(RCA_(2))of RAC after 300 freeze-thaw cycles were studied.The frost resistance of RAC was characterized by compressive strength,relative dynamic elastic modulus,and mass loss.As the physical properties of RCA_(2),the apparent density,water absorption,and crushing value were measured.And the SEM images of RAC after 300 freeze-thaw cycles were shown.The results indicated that the frost resistance of RAC cured at 80℃ for 7 days was comparable to that cured in the standard condition(cured for 28 days at 20℃±2℃ and 95%humidity),and the RAC cured at 100℃ was slightly worse.However,the frost resistance of RAC cured at 60℃ deteriorated seriously.The RAC cured at 80℃ for 7 days is the best.Whether after the freeze-thaw cycle or not,the RCA that curd at 60℃,80℃,and 100℃ for 7 days can also meet the requirements of Grade III RCA and be used as the aggregate of non-bearing part of prefabricated concrete components.RCA_(2) which is cured at 80℃ for 7 days had the best physical properties.

What Drives Migrants Back to Set up Firms?Return-home Entrepreneurial Intention of Rural Migrant Workers in China

The extant literature on international immigrants has discussed migrants’entrepreneurial activities in the context of Western countries but has paid little attention to return-home entrepreneurial intention(RHEI).Rural migrant workers(RMWs)in China,who used to promote rural development by remittances and were characterized by similarities with early international migrants,have gradually returned to their hometowns to initiate entrepreneurial activities.Based on the structured questionnaire conducted in 2015 and 2020in Anhui Province,China,this article combines the concept of mixed embeddedness with the idea of double-layered embeddedness and analyzes the impacts of the social,economic and institutional context in RMWs’hometowns and migration destinations on RMWs’RHEI by using binary logistic regression.The article shows that the social,economic,and institutional environments of RMWs’hometowns and migration destinations have effects on their RHEI.The embeddedness in the economic and informal institutional context in RMWs’RHEI is even more important than personal characteristics.Compared with migration destinations,RMWs’hometowns exert a more influential effect on their RHEI.However,that does not mean that the role of migration destinations can be undervalued.Actually,the better the social,economic,and institutional environments of migration destinations RMWs moved into is,the higher entrepreneurial intention they will have after returning to their hometowns.The article proposes a modified framework in combination of mixed embeddedness with double-layer embeddedness and proves that it is suitable for analyzing RMWs’RHEI.The framework has important implications for strengthening China’s RMWs to return home to start their own businesses.

Neighborhood Effects and Political Trust: A Multi-level Analysis of Chinese Rural-to-Urban Migrants’ Trust in County Government

Massive rural-to-urban migration in China is consequential for political trust: rural-to-urban migrants have been found to hold lower levels of trust in local government than their rural peers who choose to stay in the countryside (mean 4.92 and 6.34 out of 10, respectively, p < 0.001). This article explores why migrants have a certain level of political trust in their county-level government. Using data of rural-to-urban migrants from the China Family Panel Survey, this study performs a hierarchical linear modeling (HLM) to unpack the multi-level explanatory factors of rural-to-urban migrants’ political trust. Findings show that the individual-level socio-economic characteristics and perceptions of government performance (Level-1), the neighborhood-level characteristics-the physical and social status and environment of neighborhoods (Level-2), and the objective macroeconomic performance of county-level government (Level-3), work together to explain migrants’ trust levels. These results suggest that considering the effects of neighborhood-level factors on rural-to-urban migrants’ political trust merits policy and public management attention in rapidly urbanizing countries.

Intergenerational Trauma and Resilience among Im/Migrant Families: Child Mental Health Outcomes and Psychosocial Mechanisms of Transmission

Research Background: Psychological stressors leading to poor mental health outcomes accumulate throughout the migration process. The impact of a parent or caregiver’s posttraumatic stress on non-traumatized children is significant and may lead to adverse development and mental health outcomes. Research Objectives: The objective of this review is to explore both the consequences of parental trauma transmission on descendants’ psychological adjustment and well-being, and the mechanisms through which trauma has been transmitted among im/migrant populations. Methods: Criteria outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guided this systemic review. The questions guiding this review are: (a) What are the consequences of parental trauma transmission on the psychological adjustment and well-being of im/migrant offspring? And (b) What are the psychosocial mechanisms of trauma and resilience transmission among im/migrant populations? Each potential study was assessed based on relevance to the review question(s). Results: Parental trauma can lead to adverse mental health outcomes among descendants including increased internalizing and externalizing problems, the adoption of coping behaviors and worldviews, and worsening school performance. Mechanisms that influence trauma transmission include parental trauma symptom severity, the parent-child dyad, social learning, and family stressors. Pathways of resilience exist across socioecological levels to include individual resilience such as coping skills and meaning making, family resilience, structural protective factors, and social and cultural protective factors. Conclusions: Despite the prevalence of traumatic events throughout the migration process, im/migrant families display strong levels of resilience. Mental health services and providers should incorporate a strength-based approach in designing interventions that are culturally responsive and take into accounts the broader ecological contexts in which im/migrant families live.

Impact of Migrant Populations on Tuberculosis Rates in Saudi Arabia: Assessing How Migration Patterns Affect TB Incidence and Control Measures: A Narrative Review

This research focuses on the effects of migration on the TB infection rate and its prevention in Saudi Arabia, which has a large number of expatriates from TB-affected countries. Despite, based on the current global statistics of TB occurrence, it is evident that the national incidence of TB has reduced from 10.55 per 100,000 in 2015 to 8.36 per 100,000 in 2019;despite this, there are still some difficulties because migrants bring new strains of Mycobacterium tuberculosis. Hindrances, including language barriers and perceived immigration status, hinder patients from seeking medical attention or doctors from diagnosing diseases. Each patient and each cultural group need special attention to public health, enhancing living circumstances, and health care support. Community participation, inclusion of TB control programs into functional healthcare facilities, and the functioning of TB programs need to be stressed to address TB issues. Considering the focus on social, economic, and cultural approaches, the country can make severe advancements in TB control and population protection. This holistic analysis is critical for a long-term effective strategy to combat TB in the Kingdom.

Maternal Mortality Rates among Im/Migrant Populations in the United States

Introduction: Maternal mortality rates have more than doubled in the U.S over the last two decades, making it one of the few places in the world where maternal mortality is increasing. Differences in maternal mortality among certain races and ethnicities are known but few studies examine maternal mortality among immigrants. Since immigrants represent 13.7% of the U.S. population, it is essential to examine immigrant subsets to understand maternal mortality among this vulnerable population. Methods: A literature search identified 318 articles on maternal mortality and immigrants, with 12 articles from the U.S. The keywords included maternal mortality, United States, migrants, asylum seekers, immigrants, and disparities. Maternal mortality statistics were obtained from the World Health Organization and Center for Disease Control. Results: Studies analyzed in this review found an overall lower maternal mortality rate among immigrant women compared to U.S.-born women, except for Hispanic immigrant women. Black women had the highest maternal mortality rate, regardless of immigration status. Conclusion: Although the literature points to lower maternal mortality among immigrants, the data is still somewhat mixed, making it challenging to draw comprehensive conclusions. Additional research examining maternal mortality among Im/migrants in the U.S. is needed to guide future training among healthcare professionals and policymakers.

Economic Growth:The Fundamental Path to the Realization of Social Security Rights for Migrant Workers

The International Labour Organization seems to only see the aspect of social security promoting economic growth,while neglecting the aspect of economic growth supporting social security.From the standpoint of materialism and the practice of social security,the realization of social security rights for migrant workers fundamentally depends on economic growth.The Belt and Road Initiative has provided a Chinese solution for creating a strong material and technological foundation to meet the social security needs of all people,including migrant workers.

The Second-generation Wavelet Transform and its Application in Denoising of Seismic Data

This paper discusses the principle and procedures of the second-generation wavelet transform and its application to the denoising of seismic data. Based on lifting steps, it is a flexible wavelet construction method using linear and nonlinear spatial prediction and operators to implement the wavelet transform and to make it reversible. The lifting scheme transform -includes three steps： split, predict, and update. Deslauriers-Dubuc （4, 2） wavelet transforms are used to process both synthetic and real data in our second-generation wavelet transform. The processing results show that random noise is effectively suppressed and the signal to noise ratio improves remarkably. The lifting wavelet transform is an efficient algorithm.

Sustainable Livelihood of Ecological Migrants in Qinling-Daba Mountains of Southern Shaanxi

The severe environment in Qinling-Daba Mountains has made it not suitable for the long-term residence due to the large amounts of ＂ecological migrants＂, and these migrants have moved out of the mountains and changed their economic and life styles, resulting in many problems. In this paper, the problems of ＂ecological migrants＂ were analyzed, including the education problem, different life styles, incomplete national protecting measures and policies, with the aim to provide governments with constructive suggestions for the establishment of the education and training system, acceleration of the development of industries （especially the tertiary industry, subsidiary business）, and labor transferring, increasing the incomes of ＂ecological migrants＂, and making the ＂ecological migrants＂ have the financial resources for a long time, thereby better stabilizing the ＂ecological migrants＂.

Analysis of Social Integration Models of Tourism Labor Migrants——A Case Study of Jiuhua Mountain of Anhui Province, China

The grounded theory of qualitative methods was applied to researching the social integration of tourism la-bor migrants in the Jiuhua Mountain of Anhui Province, China. The research was conducted based on the in-depth in-terviewing of 15 samples, open-consultation and the analysis of secondhand data. The integration models of tourism labor migrants in the Jiuhua Mountain were formed through four processes including theoretic sampling, cod-ing-analysis, cross-tabulation and contextualization. The result shows that modes of production and life styles decide self-integration orientation of tourism labor migrants in the Jiuhua Mountain. Cultural differences are fundamental dis-similarity between tourism labor migrants and natives. There are three kinds of integration models including rapid, free and gradually advancing integration. The differences among different types of migrants’ integration models are re-markable. Taking the working integration as the abscissa and taking the life integration as the coordinate, an "S" model of integration matrix appears in the gradually advancing integration of intermediate and high administers from the working to the life which should be paid special attention to.

Risk of overweight and obesity among migrants in Switzerland

We assessed the risk of overweight and obesity for six large migrant groups in Switzerland. We used population-based survey data form the Swiss Migrant Health Survey 2010 and the Swiss Health Survey 2007. The sample comprised permanent residents aged 17 - 64 years (n = 14,637). Multivariate logistic regressions have been used to estimate odds ratios (OR). Compared with Swiss nationals, the odds of being obese were 1.97 times higher for Turkish nationals (CI-95 1.26, 3.07), 1.73 times higher for Kosovan nationals (CI-95 1.09, 2.74) and 3.42 times higher for Serbs (CI-95 2.28, 5.12). The chance of being obese was not statistically different between Swiss nationals and those from Portugal, Italy, and Germany. The chance of being overweight or obese (BMI ≥ 25) was higher for migrants than for Swiss nationals. The respective odds were 1.54 times higher for nationals from Portugal (CI-95 1.13, 2.11), 2.05 times higher for those from Turkey (CI-95 1.50, 2.78), 2.67 times higher for those from Serbia (CI-95 1.93, 3.68), 2.68 times higher for those from Kosovo (CI-95 2.01, 3.56), and 2.16 times higher for nationals from Italy (CI-95 1.54, 3.02). We suggest that preventive initiatives should take into account the specific needs of migrants as well as the needs of persons with low education from all nationalities.

Body Mass Index and Hypertension Hemodynamic Subtypes in Yi Farmers and Migrants

Objective To examine the relationship between overweight or obesity and the risk of the various hypertension hemodynamic subtypes in Yi farmers and migrants. Methods A cross-sectional study of 2 358 Yi farmers and 2 392 Yi migrants was carried out in the Liangshan Yi autonomous prefecture, Sichuan, China in 2007. Results The standardized prevalence of overweight in female Yi farmers （6.22%） was higher than in males （3.25%）, whereas in Yi migrants 32.56% of males and 28.78% of females were overweight. The standardized prevalence of obesity was 0 and 0.62% in male and female Yi farmers, compared to 3.91% and 5.57% in male and female Yi migrants, respectively. For both genders the standardized prevalence of ISH, IDH, and SDH was higher in Yi migrants than Yi farmers. Overweight and obese Yi men and women had a higher risk for IDH and SDH （P〈O.002） than non-overweight/obese individuals. However, an association of overweight or obesity with ISH was observed only in men. Conclusion Yi migrants have substantially higher proportion of overweight and obese individuals, as well as individuals affected by ISH, IDH, and SDH, than do Yi farmers. Overweight and obesity are significant risk factors for the development of hypertension in Yi people.

Regular Observation of De-Acclimatization and Randomized Controlled Research of Diagnostic Criteria of High Altitude De-Acclimatization Syndrome among Different Plateau Migrants Crowd after Their Return to the Plain

Objective: The objective of this study was to investigate the diagnostic methods of high altitude de-acclimatization syndrome and to formulate diagnostic criteria. Methods: This study was conducted using epidemiological surveys and a multi-center randomized controlled clinical trial. A total of 3011 subjects were studied, and the following indices were collected after their return to low altitude areas from the plateau: general health status, blood, urine and stool samples, myo-cardial enzyme levels, liver and kidney function, nerve function, sex hormone levels, microalbuminuria, electrocardiogram (ECG), echocardiography, pulmonary function, and hemorheological markers. These data were compared to those of randomized healthy subjects in the same age range who lived at the same altitude to determine the characteristics of high altitude de-acclimatization syndrome. Based on these characteristics, diagnostic criteria for high altitude de-acclimatization syndrome were formulated. Results: This study demonstrated that the incidence of high altitude de-acclimatization syndrome was 84.36%. Sixty percent of the cases were mild, 30% were medium, and 10% were severe. The incidence was higher among those who returned to a place of lower altitude, resided at a high altitude for a longer period of time, or engaged in heavy labor while at high altitude. Patients with high altitude de-acclimatization syndrome manifested hematological abnormalities and abnormal ventricular function, notably a right ventricular diastolic function, which recovered to baseline function after one to five years. Exposure to long-term hypoxia often caused obvious changes in cardiac morphology, i.e., left and right ventricular hypertrophy, particularly within the right ventricle. In addition, patients with high altitude de-acclimatization syndrome often presented with low blood pressure, low pulse pressure, and microalbuminuria. A few patients presented with occult blood in their feces. The diagnosis of high altitude de-acclimatization syndrome can be made if a patient who recently returns to the plain from the plateau complains of dizziness, weakness, sleepiness, chest tightness, edema, memory loss, and other symptoms and signs that do not alleviate under short-term rehabilitation or symptomatic treatment, and if organic diseases of the heart, lung, kidney, and other organs have been excluded. Conclusion: The diagnosis of high altitude de-acclimatization syndrome should be made after a comprehensive analysis of the patient’s clinical symptoms and signs.

Second-generation wavelet finite element based on the lifting scheme for GPR simulation

Ground-penetrating radar(GPR)is a highly efficient,fast and non-destructive exploration method for shallow surfaces.High-precision numerical simulation method is employed to improve the interpretation precision of detection.Second-generation wavelet finite element is introduced into the forward modeling of the GPR.As the finite element basis function,the second-generation wavelet scaling function constructed by the scheme is characterized as having multiple scales and resolutions.The function can change the analytical scale arbitrarily according to actual needs.We can adopt a small analysis scale at a large gradient to improve the precision of analysis while adopting a large analytical scale at a small gradient to improve the efficiency of analysis.This approach is beneficial to capture the local mutation characteristics of the solution and improve the resolution without changing mesh subdivision to realize the efficient solution of the forward GPR problem.The algorithm is applied to the numerical simulation of line current radiation source and tunnel non-dense lining model with analytical solutions.Result show that the solution results of the secondgeneration wavelet finite element are in agreement with the analytical solutions and the conventional finite element solutions,thereby verifying the accuracy of the second-generation wavelet finite element algorithm.Furthermore,the second-generation wavelet finite element algorithm can change the analysis scale arbitrarily according to the actual problem without subdividing grids again.The adaptive algorithm is superior to traditional scheme in grid refinement and basis function order increase,which makes this algorithm suitable for solving complex GPR forward-modeling problems with large gradient and singularity.

Impact on Mountainous Agricultural Development in the Three Gorges Reservoir Area forced by Migrants of the Three Gorges Project

The Three Gorges Project attracts worldwide attention because of the Three Gorges migrants, and the agriculture of the Three Gorges Reservoir Area is a foundation for the development of the Three Gorges migrants. The Three Gorges Reservoir Area is situated at the mountainous area with bad agricultural development conditions and relatively low levels of development. As a result, the large-scale migration fias special influence on its agricultural development, which has attracted much attention. The paper analyzes influence that the migrants have forced on its agricultural development based on the scientific data, and makes some explorations on the models that are suitable for the development of mountainous agriculture in the Three Gorges Reservoir Area.

Rural migrants' participation in old-age insurance: a case study of the inter-provincial migrant workers from Sichuan, China

Old-age pension, a fundamental part of the Chinese social security system, is perceived by the Chinese government as the last support for rural-to-urban migrant workers upon retreating from the labor market. Using survey data collected by the authors, this paper examines a host of factors which influence migrant workers' participation in the old-age scheme. The result shows that individual characteristics, employment status, attitudes toward old-age support and perception of the old-age pension system significantly differentiate two groups of migrant workers between those that have participated in and their counterparts who have not participated in the old-age pension schemes. Among a number of factors, age, educational attainment, holding labor contract, etc. are found to be significant factors influencing migrants' behavior participating(or not participating) the available age-pension schemes. Policy implications for how to improve the rate of participation in existing old-age pension schemes among migrant workers are drawn from the findings.

An Empirical Analysis of Employment Stability and the Wage Gap of Rural Migrants in China Based on Quantile Regression

Under the background of accelerated integrated urban-rural development, this paper offers an analysis on the short-term employment of rural migrants in China and resulting wage gap between long-term and short-term rural migrants. On the basis of correcting for sample selection problems arising from labor market participation and short-term employment, rural migrants＇ wage function is estimated using quantile regression method, and wage gap between long-term and short-term rural migrants is decomposed using MM method. Our empirical results suggest that those with a higher level of education, training experience and local employment recommended by family relations or in formal labor market are more likely to secure long-term labor contract,＂ region and education have significant contributions to the wage of rural migrants,＂ rural migrants of both long- and short-term contract types have great gaps at the bottom of salary distribution; and there exists a sticky floor effect in wage difference of rural migrants. These results have important policy implications in enhancing employment stability of rural migrants, improving income distribution equity, speeding up the process of urbanization, and balancing regional development.

Alternating-current losses in two-layer superconducting cables consisting of second-generation superconductors coated by U-shaped ferromagnetic materials

Alternating-current losses in a two-layer superconducting cable, each layer being composed of 15 closely-spaced rectangular wires made up of second-generation superconductors when the ends of wires are coated by either a non-magnetic or strong ferromagnetic material having a U profile is numerically investigated. Computations are carried out through the finite-element method. The alternating-current losses do not increase significantly if the relative permeability of the coating is increased three orders of magnitude, provided that the current amplitude is less than half of the critical current in a superconducting wire. However, the losses are much higher for ferromagnetic coating if the amplitude of the applied current oscillating at 50 Hz is close to the critical current. The ferromagnetic coating is seen to accumulate the magnetic field lines normally on its surfaces, while the field lines are parallel to the long axes of the wires, leading to more significant flux penetration in the coated regions. This facilitates a uniform low-loss current flow in the uncoated regions of the wires. In contrast, coating with a non-magnetic material gives rise to a considerably smaller current flow in the uncoated regions, whereas the low-loss flow is maintained in the coated regions. Moreover, the current flows in opposite directions in the coated and uncoated regions, where the direction in each region is converse for the two materials.

Limited Focus on the Use of Health Care by Elderly Migrants——A Literature Review

Our premise for this literature review is the global demographic change caused by the world’s population living longer and becoming older, and extensive international migration leading to multicultural societies. Increasing age leads to health problems, often long-term or chronic, requiring investments in health care. Worse health and dissimilarities in pattern of morbidity/ mortality have been found in foreign-compared to Swedish-born persons, so it is reasonable to assume that this affects use of health care. The exploratory review focuses on elderly migrants’ (>65 years) use of healthcare. The databases Pub Med, EBSCO, CINAHL and ERIC were searched in 2000-2013. A limited number of studies were found;few had a comparative approach, most were from the USA, and focused on migrants from the former Soviet Union or countries in South-East Asia. A range of factors were identified that influence patterns of health care use: language fluency, ability to communicate, self-reported health status, prevalence of chronic disease, physical distance from care provision, availability of transport to reach care, cost of care, the health insurance system, cultural norms and values regarding different forms of care, level of education, and length of residence in the host country. Most studies treated health care from a general perspective and collected data from community and hospital settings, without analysing usage separately. Some studies indicated elderly migrants making use of health care less than other groups but the pattern is not unambiguous: other studies show that there is an overuse of health care. It is therefore difficult to show any particular pattern, or possible differences in use, regarding community versus in-patient care. Studies focusing on migrants’ actual use of health care are few and further research is needed, especially because elderly people form the largest group of users of health care and will be even larger in the future.