Despite recent decreases in Black infant mortality, racial disparities persist, motivating continued research into factors related to these inequalities. While the inverse association between education and infant mortality has been documented across races, less is known about its geographic heterogeneity. Using vital statistics from the National Center for Health Statistics, this study considers Black-white disparities in infant mortality for births occurring between 2011 and 2015 across regions and metropolitan status of maternal residence. With logistic regressions, we investigate heterogeneity in maternal educational gradients of infant mortality by geographic residence both within and between races. Beyond confirming the well-known relationship between education and infant mortality, our findings document a slight metropolitan advantage for infants born to white mothers as well as lower returns to education for infants born to Black mothers residing in nonmetropolitan counties. We observe a metropolitan advantage for infants born to Black mothers with at least a bachelor's degree, but a metropolitan disadvantage for infants born to Black mothers with less than a high school degree. The South is driving this divergence, pointing to particular mechanisms limiting returns to education for Southern Black mothers in nonmetropolitan areas. This paper's geographic perspective emphasizes that racial infant health disparities are not uniform across the country and cannot be fully understood through individual and household characteristics. Infant mortality is a key indicator of population health as it reflects the mother's health, environmental context, and access to socioeconomic resources and healthcare . Within The heterogeneity of disparities in infant mortality across the country remain not well-understood. In this paper, we look at geographic patterns in infant mortality in the United States through their intersection with racial and educational inequalities. We bring together socioeconomic status, race, geography, and timing of death, which have been identified by previous papers as essential dimensions for understanding infant mortality in the United States. Using the National Center for Health Statistics' complete linked birth/infant death datasets from 2011 to 2015 and 1998 to 2002, we investigate the role of region and metropolitan status on infant mortality for children born to non-Hispanic white and non-Hispanic Black mothers across categories of educational attainment. Spatial approaches to health research have important implications for public policy through informing appropriate targeting of resources and intervention strategies. Additionally, better understanding the intricacies behind Black-white disparities provides insight into the systemic inequalities that Black communities face and their broad impacts on health more generally.Below we briefly outline related literature before discussing our data and methods. We then present our findings and conclude with a discussion of our results and their significance in the broader context of racial and geographic disparities in health.In the infant mortality literature, socioeconomic status is frequently proxied with maternal education. Education is expected to lower the probability of infant mortality through two main pathways. On one hand, women are expected to leverage higher education into improved social and economic conditions, such as better housing, financial stability, quality healthcare, and adequate nutrition. On the other hand, education—through increased knowledge—has an effect on the adoption of individual behaviors that impact health, such as smoking, exercising, assigning importance to nutrition, and seeking early prenatal care .Many have documented group disparities in both infant and adult health and mortality along educational gradients. With data from 2007 to 2010, Fishman et al.  estimateThe important role of geography in infant mortality in the United States has been described in numerous studies. With regard to region, the West and Northeast have historically had lower probabilities of infant mortality than the South and Midwest , 6, 15. Consistent with Sparks et al. , multiplThe timing of infant death across neonatal and postneonatal periods has important implications for understanding inequalities in infant mortality. Chen et al.  documentIn light of this review of the literature, this study brings together socioeconomic status, race, geography, and timing of death to further our understanding of the disparities in infant mortality across the United States. In particular, we examine the differences in educational gradients in infant mortality for native-born non-Hispanic Black and white mothers across metropolitan residence and region. First, in line with existing literature, we aim to confirm the negative association between education and infant mortality. Then, the following research questions guide our main analysis:Heterogeneity within race. For both Black and white mothers, do returns to education in infant mortality vary across metropolitan status and region?Heterogeneity in patterns across races. Do the geographic patterns in returns to education in infant mortality differ between Black and white mothers?In order to consider the distinct causes of infant mortality throughout the first year of life, we examine the above questions across both the neonatal and postneonatal periods.Identifying geographic patterns in infant mortality and determining whether Black and white populations share similar patterns is important for two main reasons: first, it informs appropriate allocation of resources; second, it assesses whether geographic heterogeneity contributes to the overall racial gap in infant mortality. We expect significant overlap between our results and the robust body of literature on infant mortality in the U.S., which has documented the persistence of racial disparities and educational gradients. Beyond these well-known characteristics of U.S. infant mortality, this study seeks to shed light on the understudied intersection of race, education, and geography. Our approach of estimating mortality across educational categories is in line with recent research drawing attention to the role of compositional differences in education in time-space comparisons of mortality , 25.This paper uses data from the National Vital Statistics Birth Cohort Linked Birth/Infant Death Data (LBID) from the National Center for Health Statistics (NCHS) . This dabridged race variable transforming multiple race responses into one single race, allowing for continuity with the older records. We use the NCHS bridged race in this analysis. In both time periods, we use NCHS's imputation when racial information was missing from the birth certificate. Additionally, in 2011, NCHS began only releasing maternal education and race data for births that were recorded with the revised birth certificate form. Therefore, in the 2011–2015 time period, we only observe these maternal characteristics for mothers who gave birth in states that had adopted the 2003 revised birth certificate.The revised birth certificate form affected the recording of maternal educational attainment and race. The revised birth certificate issued in 2003 reports educational attainment in terms of highest educational level completed, rather than years of schooling which was collected by the 1989 birth certificate format. With regard to race, the revised 2003 birth certificate allows for the reporting of multiple racial identities, whereas the 1989 birth certificate form only allowed one race to be recorded for each parent. With the revised form, the NCHS created a Thus, while the LBID has quasi-exhaustive coverage, we are limited to analyzing births that were recorded with the revised form. Because of our incomplete coverage of states in the period 2011–2015 and our focus on geography, we reproduce our analysis in two ways. First, we turn to the years 1998–2002, which are the 5 years that immediately precede the adoption of the revised birth certificate. Although the main purpose of this robustness check is to examine consistency and continuity in geographic patterns, this also allows us to consider long run trends in levels and compare our findings to previous work, notably Green and Hamilton . Next, rOur main geographic variable of interest is maternal county of residence's metropolitan status. This is a binary variable defined as metropolitan or nonmetropolitan according to whether or not the county was located in a metropolitan statistical area (MSA) as of 2005, i.e., an urban cluster with a population of at least 50,000. More precisely, we use the 2006 NCHS Urban-Rural Classification Scheme for Counties, which places U.S. counties into six categories: large central metropolitan, large fringe metropolitan, medium metropolitan, small metropolitan, micropolitan, and non-core. Large central metropolitan and large fringe metropolitan counties form the core and peripheral counties of MSAs of at least 1,000,000 people. All counties in MSAs with populations in the intervals 250,000–999,999 and 50,000–249,999 are categorized, respectively, as medium and small metropolitan counties. Micropolitan counties belong to urban clusters with population of less than 50,000 and, along with non-core—or rural—counties, form the nonmetropolitan counties in our analysis. We use the 2006 classification, because it is a midpoint between the two time periods under study.Across our analysis, we restrict the dataset to singletons born to U.S.-born mothers between the ages of 18 and 46 living in the United States at the time of giving birth and who reported a racial/ethnic identity of either non-Hispanic white or non-Hispanic BlackTo examine the relationship between infant mortality, education, and metropolitan county residence, we run separate logistic regressions on infant death for infants born to non-Hispanic white and non-Hispanic Black mothers between 2011 and 2015:mortalityi is infant mortality, Ci is county of residence's metropolitan status, Ei is mother's educational attainment, CiEi is the interaction between metropolitan residence and educational attainment, and mortalityi is infant death in days 0–27 and in days 28–364, respectively.where milton's  model spnt death . In the Then, to address the question of how the interaction between race and education varies over geography, we conduct this analysis broken out by U.S. region. The model specification is as follows:where variables are as defined above with the inclusion of the complete interaction between county of residence's metropolitan status, maternal educational attainment, and U.S. region of birth .In figures, we present the total predicted probabilities of infant, neonatal, and postneonatal mortality. These predicted probabilities are computed by averaging over predicted probabilities for each mother in the dataset, using the regression coefficients. Thus, the estimates shown in the figures below do not eliminate differences in distributions of covariates between subgroups and, rather, represent the average predicted probability of infant mortality for mothers in these subgroups.When logistic regression is used to model rare events, there are potential concerns related to the low number of events observed in the data . Past reWe conduct two supplemental analyses. First, to alleviate data quality concerns with the incomplete coverage of births in the 2011–2015 data and consider long run trends, we repeat the above analysis for births that occurred between 1998 and 2002. These are the 5 years that directly preceded the adoption of the revised birth certificate and are thus the most recent years for which data are complete with respect to our variables of interest. Moreover, this allows for direct comparison with Green and Hamilton , who useOur main analysis is conducted on 10, 343, 382 births which occurred between 2011 and 2015. Before restricting our sample, we have record of 19, 849, 690 infant births. Restricting to singletons born to U.S.-born non-Hispanic white or non-Hispanic Black mothers between the ages of 18 and 46 residing in the U.S. at the time of birth brings this figure down to 11, 786, 983. Before making this restriction, mother's country of birth and race were missing from 0.3% and 4.3% of records, respectively. We keep records with imputed maternal race; 18.85% of our final sample have an imputed value for race. In terms of our main independent variables of interest, we observe maternal county of residence—and thus metropolitan status—as well as U.S. region of birth for all births to mothers residing in the U.S. Due to the changes in the birth certificate format discussed above, we do not observe maternal education for over 1 million (8.67%) records. While unobserved maternal education is not correlated with metropolitan county status, it is not evenly distributed geographically: whereas 20.87% births in the Northeast are missing maternal education, almost all education is observed in the Midwest (99.36%). Of our covariates—maternal age, marital status, prenatal care, child's sex, birth order, birth year, and U.S. region of birth—we are only missing values for birth order (0.54%) and prenatal care (11.53%). Restricting to observations for which we observe maternal education and have non-missing covariates brings us to the final analytic sample of 10, 343, 382 births.The negative association between education and infant mortality is observed in Consistent with previous research, at each level of education, infant mortality tends to be higher in nonmetropolitan counties. In this section, we break out the above analysis by region of birth; thus we present educational gradients of infant mortality for white and Black mothers living in metropolitan and nonmetropolitan counties by U.S. region of birth . Before considering these findings, it is important to note that white and Black mothers are not evenly distributed across regions and metropolitan counties . The majadvantage for Black mothers with low education and, on the contrary, the nonmetropolitan disadvantage for Black mothers with high education.The next analysis considers how the educational gradients by metropolitan residence and race vary by timing of infant death. Next, we have repeated our analysis looking at educational gradients by metropolitan residence status for an earlier time period where all states could be included. As suggested by recent work, there was a sharp decline in infant mortality for infants born to Black mothers across levels of maternal education and metropolitan residence between 1998–2002 and 2011–2015. Despite this progress, infants born to Black mothers continue to face higher probabilities of infant mortality at any level of education when compared to infants born to white mothers. This time comparison shows a persistence in racial, geographic, and educational patterns in infant mortality, which provides support for our results despite incomplete data. However, it is not possible to more directly compare the two time periods, because, as noted above, the revised birth certificate format changed how maternal education was measured.Due to the staggered adoption of the revised birth certificate form, we do not observe maternal education in all states between 2011 and 2015. To address the possibility that the absence of some states in the more recent data is driving some of the changes between the two time periods, we also run the analysis for both time periods restricting the samples to the U.S. states that switched to the revised birth certificate before 2011 . Through our findings, we have documented the negative association between maternal education and infant death as well as within-race heterogeneity in the association between education and infant mortality, across both metropolitan status and region. These differences are subtle for infants born to white women but substantial and meaningful for infants born to Black women. The main finding of this paper is the remarkable flatness of the educational gradient of nonmetropolitan Black mothers, driven by Southern states and across both the neonatal and postneonatal periods. This observation could not have been made without this paper's approach looking at the intersection of education and geography. Below we discuss our main findings in more detail for white and Black mothers and some potential mechanisms before outlining this study's limitations and contributions.We find that geographic differences in infant mortality exist more starkly for infants born to Black mothers than to white mothers. The small regional differences for infants born to white mothers and the consistent, yet small, difference between metropolitan and nonmetropolitan counties suggest that, for white mothers, the detrimental effect of living in a nonmetropolitan county is fairly constant across educational levels at the national scale and for each of the four regions. This finding relates to a broader literature on rural disadvantage that has emphasized difficulties in accessing quality healthcare  and alsoThe relationship between education and geographic residence for infants born to Black mothers, however, requires a more nuanced discussion. Black mothers display distinct patterns of infant mortality when considered through the intersection of both education and geography. Although a marked racial gap exists in all four census regions, the metropolitan Midwest and South contribute the most to the overall Black-white gap in infant mortality. The flat educational gradient observed for nonmetropolitan mothers at the national level is driven by the South, where the vast majority of nonmetropolitan Black mothers live. The difference between metropolitan and nonmetropolitan counties is not constant across levels of maternal education, as evidenced by the crossover between the gradients. At the lowest level of maternal educational attainment, nonmetropolitan mothers fare better than their metropolitan counterparts. This is in contrast to the metropolitan advantage observed for infants born to white mothers as well as the metropolitan advantage that is present for infants born to Black mothers with at least a bachelor's degree.This geographic pattern has persisted in the past two decades despite the overall decline in infant mortality and the reduction of the absolute gap in infant mortality between Black and white infants, as documented by previous studies  and our These findings point to potentially crucial mechanisms of rural and micropolitan Black health in the United States, with important policy implications. It can be thought that this evidence of low returns to education for the nonmetropolitan Black population in the South, as it manifests through the first year of infancy, stems from more fundamental sources that likely affect a variety of outcomes for which an educational gradient is expected. This finding could be symptomatic of a wider phenomenon impacting multiple facets of life. Below we explore four potential mechanisms that could contribute to this finding. Rather than explanations, these should be taken as avenues for future research.First, it is possible that the Southern nonmetropolitan counties where these Black mothers live—which includes the Black Belt region known for its high proportions of African Americans and persistent disadvantage through legacies of slavery—offer few opportunities for highly educated mothers to leverage education into higher income and better living situations. Lower observed or perceived quality of education and racial employment discrimination could be a barrier to employment opportunities for college-educated Black mothers. Unfortunately, education is the only measure of socioeconomic status available on U.S. birth certificates, which prevents us from directly testing the hypothesis that the flat educational gradient in infant mortality for nonmetropolitan Black mothers derives from a flatter educational gradient in income.Second, the selection effect of migration to metropolitan areas could contribute to the Black infant mortality gap between metropolitan and nonmetropolitan areas. Positive selection of migrants with respect to health is generally observed with young internal migrants tending to be healthier than their non-migrant peers. Migration of young adults to metropolitan areas also signals motivation to access better opportunities and living conditions, which could also reflect in higher degrees of health consciousness. However, opportunity-motivated migration comes with potentially detrimental consequences, such as higher stress and weaker social networks –41. ThesThird, given the residential segregation that persists in the U.S. South between Black and white populations, it is possible that nonmetropolitan Black mothers, regardless of education, have worse access to healthcare than their white counterparts, and that health institutions present in predominantly Black counties are of lower quality. The history of racial discrimination in healthcare may also cause Black mothers to receive poorer services or be more reluctant to trust medical professionals even when they do have access to healthcare. For example, Pathman et al.  report tLastly, it can be thought that education has a weaker association with the adoption of beneficial health behaviors for Black mothers living in nonmetropolitan areas. This hypothesis is partly supported by research suggesting that education is a significant predictor of health consciousness for whites and Hispanics, but not for Blacks . This coThese last two potential explanations—access to healthcare and adoption of beneficial health behaviors—are related to our analysis of neonatal and postneonatal mortality insomuch as timing of infant mortality indicates different underlying patterns of causes of death. Because the nonmetropolitan advantage occurs during the neonatal period for Black mothers with less than a high school education, this could suggest that, contrary to initial expectations, it might be harder for mothers with low educational attainment to access quality obstetric and neonatal healthcare in metropolitan counties. Additionally, in all four census regions, Black mothers are much more likely than white mothers to reside in large central metropolitan counties . Higher Although our analysis highlights that nonmetropolitan residence limits Black mothers' returns to education with respect to infant mortality—particularly in the South—, this paper can only hypothesize about the mechanisms underlying this finding. Additional research is needed to shed light on these processes. This paper only provides a partial picture of infant mortality in the U.S. given the sample restrictions, excluding immigrants, Hispanics, Asians, Pacific Islanders, Indigenous peoples, and other ethnoracial groups. We also acknowledge that the data limit us to considering race through categorical identities, despite the complexity of this concept and the fuzzy boundaries between racial groups, especially for multiracial individuals.A further limitation to this study is the potential for intracategorical variation, both in terms of metropolitan status and education. While our analysis focuses on the distinction between metropolitan and nonmetropolitan counties, the distribution of mothers across the six NCHS urban-rural codes see  suggestsThis paper contributes to the literature on the ways through which mothers' situation and context impact infants' health and mortality. Beyond confirming the persistence of the well-known racial gap in infant mortality and the negative association with maternal educational attainment, we have documented the smaller returns to education for Black mothers living in nonmetropolitan counties, a pattern that is observed across the periods 1998–2002 and 2011–2015. This finding offers a new axis for research and policy intervention focusing on issues relating to limited returns to education for the nonmetropolitan Black population living in the U.S. South. While metropolitan residence and region cannot account for the overall racial gap, the fact that geographic variations are much more salient for Black mothers than for white mothers suggests broader issues related to availability and quality of healthcare and education as well as persistent social stress and discrimination in Black communities. This points to the importance of looking at infant health in a holistic perspective, beyond individual and household characteristics. Considering the geographic dimensions of these dynamics and their persistence over time helps to understand the systemic and ingrained nature of disparities.https://www.cdc.gov/nchs/nvss/nvss-restricted-data.htm.The data analyzed in this study is subject to the following licenses/restrictions: the datasets analyzed for this study are restricted and can be requested from NCHS. Public versions of these data, which do not include geographic information, can be downloaded from the National Bureau of Economic Research website. Requests to access these datasets should be directed to MCG wrote the first draft of the manuscript. KDM completed the statistical analysis. MCG and KDM contributed to the conception, manuscript writing and revision, and read and approved the submitted version.This publication was supported by the Princeton University Library Open Access Fund.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Multiphase flows are encountered in various industries, and the Coriolis flowmeter (CFM) is considered a high potential flowmeter for the metering of these flows. However, the decoupling effect and asymmetrical gas distribution in a CFM might decrease the accuracy of its multiphase flow metering The asymmetry of gas distribution in a CFM and its influence on the metering accuracy have only been qualitatively investigated in a few studies. The present paper quantitatively describes the gas distribution asymmetry in several CFMs under different flow conditions by numerical simulation. The simulation methodology is developed and validated by a results comparison with a conducted experiment and published data for bubbly, stratified and transitional flow regimes. U-shaped and triangle-shaped CFMs of different diameters are investigated at different gas volume fractions and flow rates. It is shown that the increase in the gas volume fraction and the reduction in the mixture flow rate lead to the increase in the gas distribution asymmetry. The strong correlation between the gas distribution asymmetry and the experimentally observed CFM error is demonstrated. The correction of the CFM error is proposed based on this correlation allowing the metering error to be decreased from 34% to 10% for the investigated conditions. Nowadays, multiphase fluids are one of the most common fluids, and may be found in medical equipment, and in the aerospace, energy storage and other industries. For example, promising energy storage liquids and fuels, i.e., hydrogen, liquefied natural gas and liquid air, often contain gaseous components, i.e., bubbles, due to their cryogenic nature ,2,3. At A Coriolis flowmeter (CFM) is considered one of the promising tools in multiphase fluid metrology ,8,9. Thiα is the gas volume fraction, and The CFM accuracy is supposedly aimed at being higher than 99.9% for multiphase fluids, including viscous fluids, emulsions, gases and bubbly flows . HoweverAt the same time, some other studies have shown that Equation (1) overestimates the negative CFM error and is not applicable in some cases at all ,25,26,27Pushnov  suggestsThe present paper aims to describe and quantify the gas distribution asymmetry in different CFMs by computational simulation at various flow conditions. Additionally, the correlation between the numerically calculated gas distribution asymmetry and the experimentally observed flowmeter error is demonstrated. Finally, the CFM error correction, which is based on the gas distribution asymmetry effect, is presented. It is compared with the previously used correction, based on the decoupling effect and the experimentally observed non-corrected error. Therefore, it is hoped that this study will further improve our understanding of the causes behind the CFM multiphase metering error and provide a correction methodology for the metering accuracy improvement for multiphase flow metering.Three different Coriolis flowmeters (CFMs) by Emerson are investigated in the present study by numerical and experimental approaches. Firstly, the performances of CMF200 and CMF050 at multiphase metering are experimentally investigated. Secondly, the multiphase flows inside of these CFMs are analyzed by conducting the computational simulation. Finally, the numerical simulation of D300, which has been experimentally studied by Sultan , is condIt should be noted that the investigated flowmeters are installed in different orientations: D300 is in the down-tube orientation, while CMF200 and CMF050 are in the up-tube position, as demonstrated in The experimental study is conducted to determine the error of the multiphase metering by a CFM at different flow rates and gas volume fractions. The experimental setup, which is shown in Firstly, water is pumped from storage tank (1) to the pipeline by pump (3), The different gas volume fractions (GVFs) at the CFM inlet . This is in accordance with the best practices for the analysis of the flowmeter operation at multiphase flow as demonstrated by TUV NEL  and someNumerical simulations were conducted to investigate the performance of CFM models and obtain the insight on the CFM operation. In this work, a set of transient simulations was performed using multiphase flow models in the commercial software ANSYS CFX. Air was modelled as compressible gas, while water was modelled as the incompressible liquid following the experimental study conditions. The Reynolds Stress turbulence model was selected for all conducted simulations of the flows through the selected CFMs. This model was selected as its high accuracy, above 95%, was confirmed by Shavrina et al.  for the t is the time, μ is the dynamic viscosity, p is the pressure, v is velocity and As highlighted above, three flow regimes are investigated in the present study, namely: stratified, bubbly and transitional. These regimes are modelled by different modifications of Eulerian–Eulerian multiphase model  followinq is the fluid phase, qth phase, qth phase stress–strain tensor and For the bubbly flow regime, the interface between the phases is of less interest. Moreover, the VOF approach requires a fine mesh to resolve the interface between phases, leading to a high computational cost. As such, a classic Eulerian–Eulerian technique is used for the simulation of the bubbly flows instead of VOF approach. In the classic Eulerian–Eulerian approach, the separate momentum equations are solved for each of the phases as followsThe bubbles’ coalescence is modelled by MUSIG approach  for the The numerically investigated operation conditions are described in The CFM geometry is discretized by hexahedral elements in the computational simulation. The average size of the element is selected following the study by Shavrina et al.  to ensurThe objective of the conducted computational analysis is the quantification of the gas distribution asymmetry. This variable is characterized as a difference between the volume-weighted gas volume fractions (GVFs) in the inlet part  and (b) in At the same time, the bubbles in CMF200 are too small and the inlet GVF is too low to ensure sufficient buoyancy force to overcome the flow momentum in the inlet vertical part of the CMF200 at 5% inlet GVF. Because of this, the bubbles are distributed almost perfectly following the flow field in CMF200 at 5% GVF, case (c) The relationship between the GVF at the inlet and the gas distribution asymmetry is investigated for different flow regimes and CFMs. According to Additionally, the relationship between the gas distribution asymmetry and the mixture flow rate is studied. As demonstrated in Overall, the gas distribution asymmetry depends on the mixture flow rate, gas volume fraction and CFM type, as demonstrated. The lowest value of the gas distribution asymmetry may be achieved by a low GVF at the inlet and a high mixture flow rate. This is explained by the influence of the buoyance force, which is the main reason behind the gas distribution asymmetry in bent tubes . The corAs indicated above, the CFM error at multiphase metering has previously been quantified based on the decoupling effect by Equation (1) ,23). How. How23])The CFM error estimation based on the gas distribution asymmetry effect  accuracy at multiphase metering is investigated in the present paper. Firstly, the numerical study of gas distribution asymmetry at different flow conditions is conducted. It is demonstrated through a numerical simulation that the gas asymmetry value grows with the increase in the gas volume fraction (GVF) value at the CFM inlet. Additionally, it is shown that the gas distribution asymmetry decreases with the increase in mixture flow rate. This is explained by the influence of buoyancy force, which becomes larger compared to momentum with the decrease in the mixture flow rate and the increase in the GVF at the CFM inlet.Secondly, the relationship between the CFM multiphase metering error and the gas distribution asymmetry is demonstrated. It is demonstrated that the change in the gas asymmetry is quite close to the change in the metering error with the change in operating conditions. Hence, it is suggested that the CFM error is primarily caused by the gas distribution asymmetry. This is supported by the fact that gas distribution asymmetry causes the overall CFM tube mass symmetry, which is the foundation of the CFM operation. The CFM error correction, which is based on the gas distribution asymmetry effect, decreases the CFM multiphase metering error range to ±10%. This is up to 3.5 times smaller than the non-corrected error range, which is between −17% and 34%. Moreover, this is a significant improvement in comparison with the error corrected based on decoupling, which does not take into account the gas distribution asymmetry effect and is between 5% and 68%.The investigated asymmetry value depends on the flow rate, gas volume fraction and CFM shape. Hence, the proposed error estimation methodology may be used for any CFM configuration. Additionally, it may be possible to measure the gas volume fractions before and after the CFM tube instead of the simulation to calculate the gas asymmetry value. The appropriate/optimal measurement location is to be determined. Furthermore, the asymmetry value may yet be ascertained as the best measure to quantify flow asymmetry for the CFM operation. There may be a more feasible way to determine the gas distribution asymmetry industrial settings.Overall, the gas distribution asymmetry in the CFM tube is numerically investigated in the present study. It is shown that this asymmetry depends on the GVF and mixture flow rate values due to the buoyancy force effect. Moreover, the demonstrated relationship between the gas distribution asymmetry and CFM error provides us with an improved understanding of the reasons behind the CFM error during the multiphase flow metering. Finally, the proposed correction of the CFM error, which takes into account the gas asymmetry effect, significantly increases the metering accuracy. The suggested correction might significantly decrease the expenses related to the multiphase flow metering error, which may reach as high as 9% . Therefo


Today, a diverse range of contraceptive techniques is available to women; this, coupled with continued positive trends in female children and adults’ educational attainment, will hasten declines in fertility and continue to slow population growth. With the advent of a sustained fertility rate lower than the replacement level in many countries, including China and India, we are already witnessing major economic, social, environmental, and geopolitical consequences .Hormonal contraception, which was initially available as a daily pill, can be administered through seven different routes today: intramuscularly, intranasally, intra-uterus, intravaginally, orally, subcutaneously, and transdermally. New advancements have also been made in intrauterine contraception with the development of “frameless” devices. Last, but not least, research is being undertaken to provide effective emergency contraception after unprotected intercourse. The use of selective progesterone receptor modulators (antiprogestins) is very promising in this area .The expansion of contraceptive use worldwide was a main priority during the second half of the twentieth century. As countries in the developed world  reached and even went below the replacement level of fertility, issues regarding contraception seem to have been placed on the back burner.Yet, since the milestone final declaration of the Cairo Conference on Population and Development in 1994 , contracBecause of this reality, the universal acceptance of methods of family planning, the best measure to prevent voluntary interruption of pregnancy (VIP), necessitates an integrated approach. Contraception must therefore be included in the broader concept of Sexual and Reproductive Health. This means that family planning and contraception must be placed within the wider paradigm of health, the health of the mother, and the health of her child. This in turn must be accepted as a task for individual couples, being a health and development issue, not a demographic one.Promoting the use of contraception within the framework of improving health, not demography, means placing the emphasis on individuals, not methods alone, and on quality of services, not simply on availability through better distribution. Indeed, there is increasing awareness that contraception can help women to reduce health risks associated with reproductive events and specifically with unwanted pregnancies. In conclusion, no matter how ideal a method may be considered from a purely scientific viewpoint, it will be challenged by the constraints of the system in which it will be applied.user-centered perspective, the present issue of the Journal of Clinical Medicine presents a series of articles in which technology is considered within the broader concept of women’s health.To contribute to the new To begin with, five articles deal with issues related to users’ and providers’ perspectives. The first reported on a National Contraception Survey conducted to explore the sexual and contraceptive habits of 1801 Spanish women of reproductive age . Among tWith regard to EC, a second investigation  tried toA third survey also from Spain , analyzeAccess to reproductive health and family-planning services during lockdowns in the COVID-19 pandemic was the subject of the fourth descriptive, cross-sectional study conducted in the Canary Islands (Spain) on a random sample stratified by age on a total of 1800 women (response rate: 98.72%) [The fifth report deals with an important question from users’ perspective of utilizing a contraceptive, namely the possibility that a given method  may modify a woman’s sexuality . To explThree of the published articles dealt with a modality that is gaining increasing amounts of attention: the so-called Long-Acting Reversible Contraception (LARC).The first article presented the results of a retrospective electronic chart review of 311 insertions of either the levonorgestrel-releasing intrauterine device (LNG-IUS), or the subcutaneous etonogestrel implant (SEI) in a center in the USA . Delays Some LARC methods, specifically the LNG-IUS, have been used for a variety of non-contraceptive indications; this was the subject of a review of the utility of the system in women with heavy menstrual bleeding and/or dysmenorrhea . Data frAn uncommon but important limitation in the use of the SEI is represented by social and psychiatric disorders, in which the ready accessibility of the device by the subject becomes a negative feature. To obviate this situation, a device was successfully inserted into the scapular region in a young woman with a chronic psychiatric disorder .The last three contributions to this Special Issue dealt with new advancements in oral hormonal contraception (OHC).An important unwanted effect in this field is bleeding irregularities, which is cited as one of the major reasons for the discontinuation of these methods, and therefore, bleeding irregularities have been the focus of numerous investigations. The first of the three articles regarding OHC in this issue provided an overview of bleeding data related to the recently marketed cyclic COC and one progestin-only pill (POP) . In thisThe issue of irregular bleeding patterns in POPs was discussed in the second article on OHC . StartinThe last article in the series summarized the present state of a COC in which DRSP is combined with E4 . ClinicaIn conclusion, the field of contraception continues to expand in search for more acceptable and safer modalities and routes of administration. At the same time, today, increased attention is paid to users’ perspective and needs. This new focus means the available methods must be made suitable for different categories of subjects, ranging from teenagers to pre-menopausal women.Today, contraception is much more than a technology; it has been the major instrument of a true social revolution that led to a—now often unwelcome—continued low fertility rate, while at the same time enhancing female reproductive health. Finding a correct balance between these aspects will be crucial in the years to come.


Phytoecdysteroids are a class of plant secondary compounds which are present in a wide diversity of vascular plant species, where they contribute to a reduction in invertebrate predation. Over the past 55 years, a significant body of heterogeneous literature on the presence, identities and/or quantities of ecdysteroids in plant species has accumulated, resulting in the compilation of a first database, the Ecdybase Literature Survey . A second extensive database on the distribution of ecdysteroids in vascular plants is available as the Exeter Survey , which used standardised extraction and analysis methods to survey seeds/spores. We compare the usefulness of these two databases to provide information on the occurrence of phytoecdysteroids at the order/family levels in relation to the recent molecular classifications of gymnosperms, pteridophytes/lycophytes and angiosperms. The study, in conjunction with the other published literature, provides insights into the distribution of phytoecdysteroids in the plant world, their role in plant protection in nature and their potential future contribution to crop protection. Furthermore, it will assist future investigations in the chemotaxonomy of phytoecdysteroids and other classes of plant secondary compounds. There are an estimated 300,000–400,000 species of terrestrial vascular plants on Earth, with about 2000 being discovered each year ,2. They Diploclisia glaucescens [Cyanotis arachnoidea [Phytoecdysteroids are analogues of arthropod steroid hormones, first identified from plant sources by several research groups almost simultaneously in 1966–7 ,9,10. Itucescens  and up tchnoidea ), while chnoidea ). The ecchnoidea ,18. The The original function attributed to phytoecdysteroids was in contributing to the deterrence of insect predators . SeveralSilene  and new ecdysteroid analogues. More recently, several studies have begun to assess the chemotaxonomical significance of phytoecdysteroids in the Chenopodiaceae  and theae; Ref. ) and theae; Ref. , pteridoae; Ref.  and angiae; Ref.  which haThe data concerning ecdysteroid presence at family and order levels are presented in the Neither database was generated for the specific purpose of determining the chemotaxonomic significance of phytoecdysteroids. Rather, ELS was compiled as a resource to provide researchers with ready access to the literature, while ES was the product of a survey of plant species to identify those which contained high levels of ecdysteroid agonists  or ecdysteroid antagonists. However, both databases are large in comparison to those which exist for other classes of plant secondary compounds, even if they are still small in comparison to the total number of vascular plant species . These findings concerning phytoecdysteroids deriving from the two databases will help to refine future studies on the occurrence of phytoecdysteroids in the plant world, and may have relevance to other classes of secondary compounds, especially triterpenoids  which are generated by similar biosynthetic routes and may have parts of their biosynthetic pathways in common.18-RP-HPLC). The most recent data are derived from methods which are both sensitive and specific, e.g., HPLC/DAD/MS and advanced NMR techniques. Furthermore, the reports incorporated into ELS concern all or various parts of the plants at diverse stages of development, sometimes not always specified in the publications. Thus, the studies used to compile ELS are very heterogeneous, but the database does accurately reflect the published knowledge. Finally, it should be mentioned that the tendency to publish positive data (the presence of ecdysteroids) over negative findings (the absence of ecdysteroids) will have inevitably biased the content of ELS.ELS reflects a large body of research performed over more than 50 years by a significant number of researchers of many disciplines with diverse goals. Over this time, the methods of extraction, detection, identification and quantification of ecdysteroids became more sensitive and refined. Many of the early studies were undertaken by phytochemists who isolated individual ecdysteroid analogues and identified them through diligent and time-consuming studies using the nascent spectroscopic methods available at the time. The advent of HPLC facilitated the purification of ecdysteroid analogues enormously, and also allowed their identification via co-chromatography and quantification based on their characteristic UV-absorbance, but in light of what we now know about the complexity of plant secondary metabolites, this may not have been specific enough for unambiguous identification since most were performed using only one separation system  samples. The uniformity of the methodology is generally beneficial, but one could argue that other stages of development might vary in their ecdysteroid content. Since the presence of phytoecdysteroids was detected by three ecdysteroid-specific RIAs and the agonist version of the BII cell bioassay, there is the capacity for detection on the basis of chemical similarity to ecdysone (black and white antisera) or 20-hydroxyecdysone (DBL-1 antiserum) and similar biological activity to 20-hydroxyecdysone (BII bioassay). The requirement for linearity in RIA response and the microscopical study of responding BII cells excludes a cytotoxic response and minimises false positives.The classification of ecdysteroid occurrence in this study is binary (present or absent), i.e., above or below the relevant detection threshold. This is more of a problem for ELS, where a range of methods with differing detection modalities and sensitivities were used, and this may contribute to the larger number of ‘uncertain’ species in the ELS database. However, as phytoecdysteroids are believed to contribute to a reduction in invertebrate predation, the biologically valid threshold concentration would be the level at which predators are deterred, but this would depend on ecdysteroid profile, predator  and any synergistic interaction with other plant secondary compounds and would thus be ecosystem-specific, so not useful for setting a universal threshold as required for this study.The proportion of an uncertain presence or absence of ecdysteroids in certain species is higher in the ELS than ES. This refers to situations where different samples of the same species have been assessed either within the same study or different studies and have been found to be contradictory. As mentioned above, this will in part be a result of the differing detection thresholds, but may also arise from different plant parts being compared. In the particular case of ferns, where ‘uncertain’ species are particularly common , most ofA previous comparison using the ES methodology for 180 species of the levels of phytoecdysteroids present in seeds and plants grown from these batches of seeds  found thOverall, 1.9% of the Lycophyte species have been assessed, but one of the four families, the Isoetaceae, has not been represented. The Equisetaceae (27%) have been overrepresented . The perTwo families (Welwitschiaceae and Ephedraceae) are not represented in the ELS , while mCyanotis arachnoidea [Silene otites [The ELS contains no data for 21 of the 64 angiosperm orders, while this is reduced to 13 for the ES, almost certainly because of the larger size of the latter database. Most correspond to the smaller orders with less than 150 species, but the Dilleniales (430 species), Pandanales (1610 species) and Santales (2373 species) are not represented in the ELS, while the Pandanales is the only larger order not represented in the ES, although the Dilleniales and Santales are still underrepresented. Overall, 0.77% and 1.37% of angiosperm species are covered in the ELS and ES, respectively . Amongste otites ), which The findings indicate that Lycophytes are ecdysteroid-negative, although it should be borne in mind that there are no data for the Isoetaceae . AmongstThe earlier evolving families  all appear to be ecdysteroid-negative, while the Pinaceae, Podocarpaceae, Cupressaceae and Taxaceae amongst the later evolving gymnosperms contain significant proportions of ecdysteroid-positive species. The data for the single-species Sciadopityaceae are contradictory for the two databases .The proportions of the assessed species found to be ecdysteroid-positive in each angiosperm order according to the ELS and ES are summarised numerically and visually in The ELS database suggests that the early evolved orders up to and including the Magnolids are ecdysteroid-negative, even if this is based on evidence from few species. However, the somewhat more extensive ES data show that this is not true, as positive species are present in all three orders of the Magnolids . In addition to the numbers of assessed species, other explanations may be greater sensitivity of the methods used in the ES or the presence of detectable ecdysteroids only in seeds of these orders and not at other stages of development .From the data for the larger later evolving orders where a greater number of species have been assessed, it would appear that species can always be encountered which are ecdysteroid-positive. A possible exception to this is the Proteales, which might infer a secondary loss of the capacity to biosynthesise/accumulate ecdysteroids in this order, but this would need much more extensive investigation.The percentage of ecdysteroid-positive seed extracts of randomly selected vascular plant species  was 7.1%, which is close to the preliminary value (6.6%) determined previously for 98 species , but whiIt is a widely accepted concept that the co-evolution of plants and insects has driven the wide diversity in both, since vascular plants and herbivorous insects account for more than half of all of the described species, but it has proved difficult to demonstrate that plant secondary compounds and other resistance mechanisms evolved as defensive functions . Since sThe first fossil plants and fungi have been dated to 480–460 mya. Arthropods began to invade the land in the Silurian period (440 mya) when land plants comprised mosses and lycophytes. The divergence in the ferns (400 mya) occurred at the start of the Devonian period as the first winged insects appeared, but many of the modern ferns did not appear until ca. 145 mya. Important orders of phytophagous insects, Orthoptera, Hemiptera, Coleoptera, Lepidoptera and Diptera emerged 310–240 mya . The divPteridium aquilinum), of which the mature fronds are highly resistant to predators of all sorts (invertebrate and vertebrate), and which contains a wide variety of defensive chemicals , but eads; Ref. ,59,60. Pon years . The ELSon years ; DBIF, Ron years ) or by bon years ), this pOne of the early goals in phytoecdysteroid research was to identify plant species which are high accumulators of 20-hydroxyecdysone and other analogues. These high accumulators were, and still are, our main source of pure ecdysteroids for studies in invertebrate physiology/biochemistry and the wide diversity in ecdysteroid analogues available from plant sources has proved to be an exceedingly useful natural resource for structure–activity relationship studies. Relating the occurrence of phytoecdysteroids to molecular phylogenetic trees will facilitate a more rational search for high accumulators. This search has recently received greater interest because of the pharmaceutical/medical potential of ecdysteroids for the treatment of various conditions in mammals (including humans). Ecdysteroids are non-toxic to mammals and were shown to have many beneficial effects in model animal systems. Recently, clinical trials have started to substantiate these findings. For such trials to proceed, kg amounts of pure 20-hydroxyecdysone are required, and for ultimate development as a commercial medication, tonnes would be needed. The only currently viable source of such large amounts of 20E is from high accumulating plants, since other methods  are too inefficient (reviewed in ).Since less than 2% of the known species of vascular plants have been investigated at any stage of development, there is plenty of scope to expand this study. This report, which pulls together all of the currently known surveys of the presence of phytoecdysteroids, reveals that the coverage is not fully satisfactory even for the consideration of the distribution at the order level, since some orders are underrepresented or not represented at all. Much more extensive studies  could only be envisaged as major international collaborations where botanists in different parts of the world collect and identify many samples from their local flora and these are analysed using standardised and optimised analytical procedures. A start in this direction has been made for the floras of north-east European Russia and northern Vietnam ,67. It wA further advance in this area would be to improve a high accumulator species so that it produces even larger amounts of 20-hydroxyecdysone and possesses a simpler ecdysteroid profile, which would considerably facilitate the purification of 20E considerably. Progress is currently hampered by our lack of knowledge of the biosynthetic pathway(s) for phytoecdysteroids and their regulation. What information we have about the biosynthesis is incomplete and derived from only a few species, but intriguingly suggests that the routes may be different in ferns and flowering plants. The data here confirm that phytoecdysteroids are widespread in pteridophytes, gymnosperms and angiosperms, but indicate that they are absent in earlier evolving lycophytes . Moreover, within the gymnosperms and angiosperms, there is some evidence to suggest that ecdysteroids are absent in the earlier evolving orders. The distribution pattern seen in Helleborus: [5 isopentenyl diphosphate units  to form C30 squalene which is then cyclised to generate the characteristic four-ring steroid nucleus and side chain [27–C30) which is converted in a committed step reaction to a core metabolite which will then be further metabolised via the permutation of modification reactions  to generate the characteristic triterpenoid profile for that plant species at that stage of its development. The types and locations of the various further modifications overlap considerably between the different classes of plant triterpenoids. It appears that these further modifications occur as a network of reactions (rather than a linear sequence), which implies lower substrate specificity of the reaction involved . Plade chain ,72. The nd Jones ), but prnd Jones ,74,75) aThe ELS . The thne; Ref. , and theThe plant species in the two databases were originally allocated to families according to Brummitt , which w


Orientation and Mobility training (O&M) is a specific program that teaches people with vision loss to orient themselves and travel safely within certain contexts. State-of-the-art research reveals that people with vision loss expect high-quality O&M training, especially at early ages, but the conventional O&M training methods involve tedious programs and require a high participation of professional trainers. However, there is an insufficient number of excellent trainers. In this work, we first interpret and discuss the relevant research in recent years. Then, we discuss the questionnaires and interviews we conducted with visually impaired people. On the basis of field investigation and related research, we propose the design of a training solution for children to operate and maintain direction based on audio augmented reality. We discuss how, within the perceptible scene created by EasyAR’s map-aware framework, we created an AR audio source tracing training that simulates a social scene to strengthen the audiometric identification of the subjects, and then to verify the efficiency and feasibility of this scheme, we implemented the application prototype with the required hardware and software and conducted the subsequential experiments with blindfolded children. We confirm the high usability of the designed approach by analyzing the results of the pilot study. Compared with other orientation training studies, the method we propose makes the whole training process flexible and entertaining. At the same time, this training process does not involve excessive economic costs or require professional skills training, allowing users to undergo training at home or on the sports ground rather than having to go to rehabilitation sites or specified schools. Furthermore, according to the feedback from the experiments, the approach is promising in regard to gamification. According to the World Health Organization (WHO), there are 185 million visually impaired people across the world, of which 39 million are completely blind, including 19 million children under the age of 15 [There are many schemes and programs designed to solve this problem or relieve the dilemma . OrientaPonchillia used indoor navigation concerns and prototype feature preferences, and perceptions of the relative importance and difficulties of certain building types were identified to guide the development of accurate and user-friendly indoor navigation applications . HoweverThe study by Plikynas surveyed blind experts and proved that, after outdoor navigation, the second-most-important directional electronic travel assistance (ETA) feature for visually impaired people is indoor navigation and orientation . Visually impaired people need directional electronic travel aids for orientation and navigation in unfamiliar indoor environments, with embedded capabilities for detecting and identifying obstacles  . PlikynaBased on these reviews, Nair et al. proposed an indoor navigation application that can guide blind and visually impaired (BVI) people through indoor environments with high accuracy, while enhancing their understanding of their surroundings. The application provides a personalized interface by considering the unique experience of BVI individuals with indoor wayfinding and offers multiple levels of multimodal feedback . HoweverRogge et al. demonstrated improvements in gait parameters and navigation performance by evaluating 14 blind and visually impaired children and adolescents (8–18 years) and 14 visually matched individuals; no differences were observed among the blind group, the visually impaired group, and the blindfolded participant group . GuerreiTraining in auditory orientation is usually a part of orientation and mobility (O&M) instruction for blind people. O&M instruction is usually conducted in a real environment, and trainees should acquire auditory orientation by listening to ambient sounds experientially . In ChinIn the United States, the Extended Core Curriculum (ECC-VI) proposed by Dr. Philip Hatlen was soon widely recognized by American schools for the blind and ordinary schools with visually impaired students. The ECC-VI includes nine significant fields: compensatory access, sensory efficiency, assistive technology, orientation and mobility (O&M), social interaction, recreation and leisure, independent living, self-determination, and career education. In terms of O&M, visually impaired students in the United States are divided into four stages: preschool, elementary school, junior high school, and high school. In the preschool years, the goal of blind children in the United States is to learn how to move toward objects, sounds, or stimuli. In elementary school, blind children practice holding a blind cane correctly or using other mobility aids to walk with simple instructions. In junior high school, blind children practice using blind sticks or other mobility aids to walk familiar routes under supervision. By the end of high school, blind teenagers need to be able to recognize and use landmarks while walking. They should be able to walk safely with blind sticks or other mobility aids and use these skills independently and appropriately ,18.In Europe, according to the research results of the European Blind Union, most blind people need detailed training methods, perfect laws and regulations, and complete facilities for the disabled. Commonly used devices are long canes, guide dogs, and (recently) GPS systems.Understand the environment: Learn about the scheme of the body, learn about the constant and moving objects in the environment, get to know the various ground surfaces, perceive noises and sounds, and perceive scents.Train the senses: Obtain a sense of movement and balance; improve hearing ; train hands, legs, and face to perceive tactile sensation; perceive aromas (recognize different scents); and identify areas depending on the destination.Grasp the walking technique: Walk with a sighted guide, walk independently without aids, and walk independently with a cane and other devices.In Slovenia, the main objective of the training is to enable people to become independent and be able to travel safely in their environment. The topics covered in the training are as follows:Slovenia has recently enacted comprehensive rehabilitation of blind and visually impaired people, regardless of the cause and age of the individual client .In Denmark, children are trained by special consultants, who visit them at their kindergarten or school. Children are also offered training in general use during courses at the resource center, where they receive specific dedicated training during internal courses. As for newly blind persons, some—especially if they are in a job and needing quick and expeditious rehabilitation—are trained via lengthy courses offered by The Institute for the Blind. Almost all other training is carried out by consultants that train at the local (home) level. On-site instruction is provided at the local level as per the needs of the persons with visual impairment, but often not to the degree and length that we find is needed .In Italy, the National Association of Instructors of Orientation and Mobility and Personal Autonomy (ANIOMAP), at the Institute for Research, Training and Rehabilitation (I.Ri.Fo.R), organizes special dedicated courses at the local level. Training is carried out in private facilities, at the Italian Union of the Blind and Partially Sighted (UICI) local branches, at the local health units when funded by them, at the Institutes of the Blind (resource centers), or at rehabilitation camps. The contents of a course can be summarized as follows: indoor training , training exercises in urban areas , training routes in commercial areas , use of public transport, and training with aids  .However, for novice trainees, training in a natural environment where actual vehicles operate can sometimes be dangerous and stressful. Furthermore, with this training method, the trainee must acquire auditory orientation because it is difficult for a novice trainee to selectively listen to essential sounds when these are mixed with many other ambient noises. To reduce the risk and stress of orientation training and shorten the training period, a new training method for reproducing an ideal sound field by acoustic simulation is presented; it is an effective method. Seki et al. developed a new auditory orientation training system for blind people using acoustic virtual reality (VR). This training system reproduces a virtual training environment for orientation and movement (O&M) instructions that produce sound sources and sound reflections and isolation, allowing trainees to learn sound localization and obstacle perception skills.However, all of the solutions for blind people give rise to some questions: Do they have special adaptations for blind children? Do their programs help visually impaired children with walking training? Do visually impaired children still have enough interest in these traditional training methods and methods?Meanwhile, some studies have proved that augmented reality (AR) is an up-and-coming technology, especially in disability education, and its role is becoming increasingly apparent ,23,24. FSuppose the immersive interaction advantage of AR can be combined with the orientation walking training course. In that case, it will improve the effect of orientation walking training for visually impaired children and expand the applications of AR.How to design and build a safe AR environment.How to ensure that the child can avoid obstacles on the way to the destination and reach the goal safely.How to guide the travel route from a child’s perspective. How to inform visually impaired children of specific travel routes.How to use AR to enhance the user’s perception when using it .The challenges that the project needed to face are as follows:This project aimed to design and develop a set of orientation walking aids based on using a smartphone, combined with Arduino intelligent hardware, as a carrier to help visually impaired children complete orientation walking training more efficiently and make the training interesting for the children. In this project, the sparse map technology of EasyAR4.0 was used as the primary technical means, combined with an immersive AR scene experience and an orientation walking space training course. Finally, an auxiliary device with the function of the orientation training course with sound scene gamification was designed to provide children with visual impairment. This research expands the applications of AR technology in special education for visually impaired children. At present, most AR application research focuses on vision-based AR applications. This study emphasizes that AR applications should focus more on auditory immersion, which is of great significance for the development of AR theory.(1)As a project with practical value, we expect our design to be feasible. Specifically, it means to limit the burden on users as much as possible under the premise of guaranteeing functions, especially economically, in terms of restricting the need for new equipment. Smartphones are the epitome of modern industrial production and technological progress. They integrate incredible computing power, sensing ability, and endurance on a banknote-sized board at an amazingly low cost. More importantly, computer vision solutions, such as EasyAR (in Unity), on mobile phones are at the forefront of technical societies. EasyAR (in Unity) was originally developed for multiplayer games with an indoor visual positioning functions. Therefore, the ubiquitous smartphone has become the choice for the brain of the solution we plan to design and develop.(2)To ensure that our work serves the people, we needed to consider their actual situation and the particularity of their interactions, so we planned to use external interactive devices to realize the functions beyond the intelligent core. We chose Arduino, which is friendly to both designers and developers. It has good platform compatibility, and clear and concise code, while it attaches importance to logic in the development process, and has a large number of directly adaptable sensors and interactive components, which can meet all the needs of the project at a reduced development cost.(3)The joint development of the mobile phone and the Arduino has the advantage of agility, which is particularly important for research in the prototype phase.The reasons we chose smartphones and Arduino are as follows:To evaluate the system, we conducted some experimental studies with subjects and collected process interview statistics in subsequent evaluations.A solution for orientation walking training for visually impaired children based on AR is proposed. It uses audio augmented reality to expand the training range and improve the fun of orientation and mobility training.We designed an AR solution prototype using EasyAR, Unity, and Arduino. We created an AR audio training scenario that simulates road and social scenarios and developed design guidelines specifically for the visually impaired children.The contributions of this work are as follows:The rest of this paper is organized as follows: (1)Research on tactile mapsAt present, there are the following solutions in terms of walking aids: tactile maps; virtual technology orientation aids; real-space, physical-simulation, 3D-sound-source aids; and AR-technology-based orientation aids. The general characteristics of these research programs are as follows:A tactile map is a topographic map that contains specific symbols and tactile cues for visually impaired students to touch. Some examples of tactile maps that can help visually impaired students are a campus’s tactile floor plan, a specific area’s (lot) tactile map, and a shopping mall’s (home) tactile floor plan. The group has a deep understanding of and familiarity with the conditions of the target environment. Ungar pointed out that tactile maps have at least two critical offerings in helping visually impaired people in spatial orientation: one is that they can help visually impaired people understand the spatial layout of an area; and the other is that they can represent the spatial environment in an environment-centric way. He also pointed out that visually impaired people obtain scene representations of the environment through tactile maps, and through orientational walking in this way, they can approach the target smoothly .The current tactile maps on the market are made of microcapsule paper technology, making them easy to carry and store and highly recognizable. It is easy for visually impaired people to replace the map pattern with the internal representation in their brains . There a(2)Oriented walking aids based on virtual technologyVirtual technology orientation aids rely on users’ perceptions and control of various objects in the virtual world by using sensing devices, such as helmet-mounted monitors, data clothing, data gloves, and force feedback, to create an immersive experience. Because they have no visual experience, visually impaired people can perceive information only through non-visual channels. Virtual reality technology allows visually impaired groups to perceive spatial information in the virtual environment mainly through hearing and touch. Virtual reality technology is immersive, interactive, and safe. In such a system, blind people can explore and navigate freely and happily. They can form their mental maps of the environment efficiently using virtual reality. However, VR equipment is relatively expensive and difficult to promote. Virtual technology is not suitable for all places, and if misused, it can bring about side effects. For example, in a secret room in a virtual space too much sensory perception may cause the subject to feel uncomfortable, causing the subject to distrust the system. In addition, in reality, blind people place great importance on using echo cues. In contrast, audio cues in virtual environments have not been addressed, causing distortions in virtual environments in this regard.(3)Real-space, physical-simulation, 3D-audio-source auxiliary equipmentThis equipment mainly simulates the sound in the natural environment through hardware sound sources in different directions in real space to train the orientation abilities of visually impaired children. The traditional real-space, physical-simulation, 3D-sound-source auxiliary equipment is mainly based on the 3D sound source space of the speaker array, and it is not easy to flexibly control the position of the sound source—the simulated sound source ,36,37,38(4)Oriented walking aids based on AR technologyAugmented reality (AR) technology can combine virtual objects  in natural scenes and allows users to interact with virtual objects in real space. This interactive method based on the natural world and enhanced by virtual data provides students with a learning space that can be explored in a way that is closest to natural interaction. AR is a cutting-edge technology, but some of its characteristics coincide with some points of education theory. At present, many studies have found ,25 that Researchers such as Lei Zhang of New York University have improved and developed a mobile phone application that combines AR and VR. Due to mixed reality (the fusion of VR and AR), the project is also called Mixed Reality Blind Combat (MR cane) . The proVisual impairment refers to the congenital or acquired impairment of visual function to a certain extent. Visually impaired children have lost direct access to visual information and can perceive external information only through the remaining senses. Hatwell found that visually impaired children face bigger challenges than ordinary children in spatial perception, especially in distance-related depth perception and accurate perception . Unlike To allow visually impaired children to perform activities, more reliable and safer barrier-free facilities are needed that encourage them to explore the environment. Accommodation should be provided for children to explore through non-visual senses, through which they can learn to move, practice their recognition, and memorize the environment . Our work aimed to examine the possibility of reconstructing audio-AR-based O&M orientation training. To design and provide a hybrid solution, we started by identifying the main problem experienced by blind subjects, as shown in In the study, eight visually impaired children and three adult guardians of visually impaired children were invited. Due to the difficulty of contacting visually impaired children offline during the epidemic, the authors strengthened their awareness of orientation training for visually impaired people by participating in the blind volunteering activities of the Guangzhou Association for the Blind and observing the work activities of five adult visually impaired persons.By observing their behaviors and interviewing them, we realized that with white canes, visually impaired people are capable of moving as fast as normal-sighted people in familiar environments. However, when it comes to unfamiliar sites, visually impaired subjects are prone to acquiring external assistance.Most of the users interviewed in the study were blind, and a few had low vision. Most of the interviewees were congenitally blind, and a few were blind due to acquired diseases. Nearly half of them had never received orientation training. It can be seen in the interview records that the spatial cognition of visually impaired children who have received orientation training is more effective than that of visually impaired children who have not received such training. Because the visually impaired children were not guided in their early orientation walking learning, some visually impaired children are unable to travel independently, which has a severe negative impact on their spatial cognitive ability and will have a severe negative impact on their future growth. Parents of most visually impaired children do not allow them to go out alone, which may stifle the essential living ability of visually impaired children and further widen the gap between visually impaired children and other children.Most of the respondents had not received orientation training before the age of 7 years. Even after training, the trainees will still have problems, such as inaccurate orientation judgment and the inability to walk straight in the early stages of training. Due to safety factors, visually impaired children can only train in a school environment. When they enter the later training period, problems such as boredom and low learning efficiency appear because they are too familiar with the campus space and have no extra space for further exploration. Visually impaired children generally like to learn orientational walking with specifically designed games. Most visually impaired children are reluctant to practice on the road by themselves because of their fear of the unknown external environment.The interviewed subjects are highly receptive to new orientation aids. However, they are still worried about the immaturity of the new technology and the lack of apparent training effectiveness. For assistive devices for orientation walking, most subjects believe it is necessary to simulate different kinds of roads; in addition, the device should make the training process more enjoyable. Most visually impaired children hope that friends or parents can join their training to improve training efficiency and improve their family and friends’ understanding of them.Spatial positioning and angle positioning are critical for visually impaired children to orient themselves in walking, thereby determining whether the visually impaired can reach their destinations smoothly.Parents of visually impaired children are expected to devote more energy and financial resources to educating and raising them. Most of the low- and middle-income families urgently need sufficient support from the government and society . The famTo experience the challenges in orientation, we also used simulated training. Keeping that in mind, we summarize the interviews and observations in three dimensions: basic, travel, and willingness to use and outline the relevant findings of the simulated content. The summary is as follows:According to the analysis of the characteristics of the visually impaired children and the needs of orientation training described in the preceding section, we designed and developed a set of orientation training systems using a smartphone as a carrier with separate audio devices to provide visually impaired children with more exciting and efficient orientation training. We combined immersive AR and key features from a conventional orientation training course, took EasyAR4.0 for localization, and adopted the audio prototype hardware for the voice to design the situational gamification training course, which is expected to deliver an entertaining experience in training. The design scheme also considers the social difficulties visually impaired children face, providing them with a way to invite friends or relatives to participate in their own training, as shown in The augmented reality module for orientation walking for visually impaired children is mainly based on the visual SLAM of EasyAR. It adopts the vision-based positioning scheme and plans the path by marking the sound source point of interest (POI), as shown in Facilitate the follow-up code development and research. EasyAR is built on the Unity engine, so it needs a platform with high computing power portability to support Unity. We chose the Arduino to program the size of the sound and change the sensor. It was relatively easy for our team to understand Arduino and smartphones. However, it is more challenging to develop if we use STM32 or 51 microcontroller and other microcontroller or FPGA development.The external expansion of the development environment of Arduino and mobile phones makes it easy to find highly compatible components, thus reducing the difficulty and cost of development.Almost every Chinese has a smartphone. Compared with development boards such as FPGA circuits and NVIDIA Jetson Nano, the cost of a smartphone APP and an Arduino development board is extremely low, and a smartphone is easy to use and promote.The reasons why we chose the Arduino and smartphones are as follows:2 experimental scene in an indoor environment. In the experimental site, more than 20 obstacles of unequal volumes were placed. These included tables, chairs, and daily household necessities to simulate reality and enrich the experimental system. We used comparative experiments to verify the effect of the training. The first experiment in this study involved an 8 × 4 m(1)Install the designed and developed AR orientation training application on the smartphone.(2)Use the mobile phone to check the outer surfaces of the objects in the experimental site to build up a sparse map.(3)Mark the POI of the sound source to determine the position of the target sound source and the position of the interfering sound source and situate the corresponding sound source hardware in the experimental scene.(4)Designate the movement path.(5)Generate the correct walking path, as shown in The tests involved the following steps: Specifically, the phone we used in the experiments was a Huawei P20, the SDK for development was Unity3D, and the onboard map builder we chose was the EasyAR platform.(1)Normal-sighted children were invited to first familiarize themselves with the relevant commands of the AR orientation training application.(2)The children were asked to wear a blindfold 10 min prior to the training tasks with the app. Each child was asked to participate in three trials. Here, we regarded the training as successful if the child could navigate to the destination in at least two trials.(3)The experimental and interview results were collected and analyzed. The interview questions are listed in The main experimental steps were as follows: In this experiment on the effectiveness of the proposed training, all six blindfolded participants were able to reach the target sound source. However, they did show a certain degree of drift in the experimental results. According to our interviews with the six subjects after the event, all six members knew they had deviated away from the sound source. There we two issues: (1) being more sensitive to car sound sources, and (2) choosing a relatively sizeable-in-relative-error route to avoid collision with the sound source. This phenomenon indicates that each user empirically predicted the relative position of the sound source in space and could react to it. Therefore, as long as the experimenter can avoid obstacles and reach the target sound source, the experiment can be regarded as a success.The feedback scores were collected by interviews, as shown in After our first experiment, to further verify the effectiveness of the orientation training, we conducted an inter-group comparison experiment. Two groups performed the comparative experiment. One group of children used the prototype intervention training of the orientation training aid, and the other group did not receive the aid. The test site of the verification experiment was an outdoor area of 8 m × 3 m. We built a simulated road scene in this area and prepared a tram and a cart. To better simulate the actual road conditions, the author placed several stools on the side of the road to act as vehicles and obstacles on the road. The specific arrangement is shown in (1)The researcher first used the AR orientation training application prototype to scan objects on the experimental site to construct a 3D visual map.(2)After scanning the map, we marked the POIs, determined the starting point, and generated navigation paths. (3)We turned off the navigation sound because the software only needs to be used to record the subjects’ movement path.(4)We informed the staff of issues and safety precautions. The participants were blindfolded for 10 min.Before starting the experiment, we needed to prepare for the investigation as follows:(1)Two staff members who participated in the experiment drove electric cars and bicycles back and forth in the simulated space. One of the staff members parked the tram on the road and honked the horn.(2)The tested children came to the simulated road and completed the task of crossing the road.(3)After the experiment, we interviewed the subjects about the usability scale.(4)We analyzed the experimental results.During the experiment, if the children could walk to the target position and avoid all vehicles and people in the simulated scene, the experiment was considered a success. However, if a subject encountered any vehicle or failed to reach the target position during the experiment, the experiment was considered a failure.A total of 12 children were involved in the inter-group comparison experiment. Six of the children were subjects who had undergone the training intervention in the previous investigation, and the other six were untrained. Ten minutes before the experiment, the children wore a blindfold to mimic the vision of a newly blind child.In the experiment, we controlled a simulated traffic light and produced different audio frequencies. When a traffic light emitted a high-frequency audio signal, indicating a green light, the children could cross the road. If the children were crossing the road with no pedestrians or cars in the middle, they were more likely to succeed. If there was a red light, the simulation environment had cars simulating the actual scene, and the participants were more likely to fail. In this experiment, participants in the intervention group reached the finish line during the green light. The authors screened the refined relevant experimental data and sorted the suitable and effective mobile data into the path graph shown in Compared with the trained children, the children without intervention training were less able to complete the task. Although four of the six subjects reached the final destination, the subjects repeatedly bumped into obstacles during walking. Three children ran into pedestrians and vehicles crossing the street during a red light. The fourth subject reached the destination by bypassing the barrier, but the subject seriously deviated from the actual walking path, even beyond the experimental range. The fifth and sixth children walked back and forth near the starting point but did not reach the end area. On analyzing the experience questionnaire results of the two groups of children , we founIn this work, we first discussed the relevant research in recent years and pointed out their shortcomings in the corresponding fields. Then, we developed an orientation training framework and application for a smartphone to help visually impaired children in orientation training in O&M. Next, we conducted questionnaires and interviews with visually impaired people, especially impaired children. Next, we used the advantage of immersive AR audio with training courses and designed an auxiliary device with AR-audio-scene gamification orientation training to provide visually impaired children with more interesting walking assistance training. It innovatively combines AR audio and physics to successfully improve the efficiency and entertainment of O&M training. After designing the equipment and curriculum, we recruited children with normal vision, conducted experiments after blindfolding them, and proved the effectiveness of the system through the experiments and post-test interviews.To conclude, in this work, we propose an orientation training method based on mobile computed audio augmented reality. This approach is based on the ubiquitous smartphone and on Arduino, which has superior usability and feasibility, low equipment and scheme costs, low requirements for professionally skilled coaches, and flexible demand in terms of the place of training.Compared with other orientation training studies ,5, our mThe equipment and curriculum we designed have some shortcomings. First, although the simulated environment constructed by the training equipment for visually impaired children provides a deeper understanding of the navigation and development of visually impaired people, a virtual training environment for visually impaired children cannot fully imitate the actual road training. Still, most trained experimenters believe that the project and the equipment achieved excellent results. Secondly, the system itself requires further testing and optimization. For example, if the light changes significantly and the moving range of the object is large, it may cause a slight position shift. In addition, due to time constraints, we could simulate only some functions of the designed solution for in-time testing, and the experimental conclusions do not fully reflect the experiences of all users.In recent decades, virtual reality and augmented reality have been widely used as promising technology, providing relatively feasible and inexpensive solutions for enhancing activities such as nursing care and physical rehabilitation of disabled people. However, visually impaired people have little access to the benefits of this technology. In addition, people facing inconveniences in social life also need the attention of relevant policymakers, rehabilitation experts, researchers, and developers. The augmented-reality-based orientation training designed in this project can more effectively train visually impaired children in terms of orientational walking ability. Visually impaired children can invite parents or friends to wear audio accessories to participate in the training to increase the fun of training and enhance friendship. Orientation walkers use a smartphone as the primary carrier. The cost of the whole set of equipment is low even after the device is combined with audio accessories, which is in line with the affordability requirement of ordinary families with visually impaired members in China and is suitable for large-scale promotion. The AR orientation walker conforms to the development trend of AR technology, expands the application scope of AR technology in visually impaired people, and contributes to the development of AR theory.Due to time constraints, the various sound source accessories we prepared were not enough to simulate complex road scenes. At the same time, considering factors such as the COVID-19 epidemic situation and time constraints, the main subjects of this research were children and college students with normal vision and only a limited number of visually impaired children were tested and interviewed. Although blind children have better hearing and touch abilities than normal blindfolded adolescents, we still need and will continue to conduct future experiments on blind children to demonstrate the effectiveness of our devices.Another interesting result that was not an intended goal of the experiment is as follows: when the participants were interviewed, many of them said that they felt the experiment and training we conducted were like a fun game. Although this was not part of our interview question, it made us feel like games are a possible way to train such children. Although gamified tasks are not the core of the study, we found in the course of the study that entertaining or gamification content can easily stimulate children’s curiosity and participation enthusiasm.