Mobility Gap Research Articles

A tale of two Americas: Socio-economic mobility gaps within and across American cities before and during the pandemic

We examine differences in mobility outcomes between residents of highest and lowest socio-economic index (SEI) at the Census block group (CBG) level in nine major US cities prior to and during the COVID-19 pandemic. While low-SEI groups generally traveled shorter distances but visited more city-wide CBGs before the pandemic, high-SEI residents universally reduced their mobility to a greater extent during the pandemic. Although high-SEI residents were making more trips to parks and health-care providers, and fewer subsistence trips to retail stores already before the pandemic, COVID-19 significantly widened these differences thereby exacerbating “mobility gaps” between low-SEI and high-SEI groups. We further examine how such “mobility gaps” can be mitigated by spatial advantages of home locations, controlling for political inclination. We find that living in better transit-served or more walkable neighborhoods generally benefited high-SEI residents more than low-SEI residents, with some variation across cities. This suggests that built environments not only impact mobility outcomes during “normal” times, but also influence how different socio-economic groups are able to adapt during times of crisis.

Enhanced photoresponse of InxMo1-xS2 (X = 0.05 and 0.1) nanosheets for PEC type photodetector

Transition metal chalcogenides (TMDCs) have great potential in the field of solid state photodetectors and photoelectrochemical (PEC) type photodetector owing to high carrier mobility and suitable energy band gap. Two dimensional MoS2, most intensively investigated member of TMDCs, has shown excellent photoresponsivity in the visible range owing to excitonic transition and suitable electronic structure. Herein, we demonstrate the PEC photodetector based on InxMo1-xS2 nanosheets. High yield liquid phase exfoliation techniques have been employed for the synthesis of InxMo1-xS2 nanosheets. InxMo1-xS2 nanosheets have hexagonal lattice structure with highly crystalline behavior and X-ray diffraction confirms the doping of indium in 2H–MoS2. PEC type detectors show 582 μA/W and 107 μA/W photoresponsivity for In0.05Mo0.95S2 and In0.1Mo0.9S2 nanosheets by optimized concentration of indium. Present investigation advocates the significant development in the field of opto-electronics and photoelectrochemical cells for generation clean energy.

Gender Gap in Intergenerational Educational Persistence: Can Compulsory Schooling Reduce It?

We analyze the impact of an increase in compulsory schooling policy on the gender gap in intergenerational educational persistence using the nationally representative Turkish Adult Education Survey. Prior to the reform, there is a gender gap in the association of parents’ educational attainment with their offspring’s. Daughters’ educational attainment is more dependent on their parents’ education background. We show that the education reform that increased compulsory schooling from 5 to 8 years reduced the impact of parental education on completion of new compulsory schooling (8 years) and post-compulsory schooling (high school) for both sons and daughters. The gender gap in intergenerational education transmission has decreased by about 5 percentage points in the completion of new compulsory schooling level but remains unchanged at the post-compulsory schooling level after the reform. Heterogeneous effects of the reform indicate that mandating additional years of education is an ineffective intervention in the eastern regions with poorer economic conditions, larger rural population, and more traditional gender views in reducing the gender gap in educational mobility, even at the compulsory level of education.

Influence of nuclear quantum effects on the electronic properties of amorphous carbon

We carry out quantum simulations to study the physical properties of diamond-like amorphous carbon by coupling first-principles molecular dynamics with a quantum thermostat, and we analyze multiple samples representative of different defective sites present in the disordered network. We show that quantum vibronic coupling is critical in determining the electronic properties of the system, in particular its electronic and mobility gaps, while it has a moderate influence on the structural properties. We find that despite localized electronic states near the Fermi level, the quantum nature of the nuclear motion leads to a renormalization of the electronic gap surprisingly similar to that found in crystalline diamond. We also discuss the notable influence of nuclear quantum effects on band-like and variable-hopping mechanisms contributing to electrical conduction. Our calculations indicate that methods often used to evaluate electron-phonon coupling in ordered solids are inaccurate to study the electronic and transport properties of amorphous semiconductors composed of light atoms.

Just because I’m a woman: Gender happiness gap in human mobility

This study explores the gender happiness gap in human mobility using smartphone-collected data from 355 residents in the Minneapolis-St. Paul Metropolitan Area. We develop a panel-ordered logit model to estimate how the factors of a trip and person are associated with the happiness change induced by the trip within both male and female participant groups. Trip-induced happiness, defined as the change in the level of happiness at the start of the trip and the end of the trip, is found to be affected by trip- and personal-level factors. We find that the magnitude of impact is different between males and females. For trip-level factors, the top three elements yielding the highest magnitude of impact for females are associated with biking, discretionary trip destinations, and walking. Males are impacted the most by walking, biking, and taking transit, with the highest magnitude of impact associated with biking. The likelihood of gain to loss of happiness is four times for male bikers and two and a half times for female bikers. Leisure destinations and afternoon trips have magnitudes greater than one. Results of both discretionary and mandatory trip origins have the least magnitude of impact for both females and males. For personal-level factors, the magnitude of impact is low for African-American females and not significant for males. In relation to the results of personal-level factors, we caution implementation due to the small number of participants in our data collection process. Our findings offer new insights into potential planning and policy strategies that could improve travel experiences and well-being for both genders.

Epitaxial Growth of Crystalline CaF2 on Silicene.

Silicene is one of the most promising two-dimensional (2D) materials for the realization of next-generation electronic devices, owing to its high carrier mobility and band gap tunability. To fully control its electronic properties, an external electric field needs to be applied perpendicularly to the 2D lattice, thus requiring the deposition of an insulating layer that directly interfaces silicene, without perturbing its bidimensional nature. A promising material candidate is CaF2, which is known to form a quasi van der Waals interface with 2D materials as well as to maintain its insulating properties even at ultrathin scales. Here we investigate the epitaxial growth of thin CaF2 layers on different silicene phases by means of molecular beam epitaxy. Through electron diffraction images, we clearly show that CaF2 can be grown epitaxially on silicene even at low temperatures, with its domains fully aligned to the lattice of the underlying 2D structure. Moreover, in situ X-ray photoelectron spectroscopy data evidence that, upon CaF2 deposition, no changes in the chemical state of the silicon atoms can be detected, proving that no Si–Ca or Si–F bonds are formed. This clearly shows that the 2D layer is pristinely preserved underneath the insulating layer. Polarized Raman experiments show that silicene undergoes a structural change upon interaction with CaF2; however, it retains its two-dimensional character without transitioning to a sp3-hybridized silicon. For the first time, we have shown that CaF2 and silicene can be successfully interfaced, paving the way for the integration of silicon-based 2D materials in functional devices.

African American Intergenerational Economic Mobility since 1880

We document the intergenerational mobility of Black and White American men from 1880 through 2000 by building new historical datasets for the late nineteenth and early twentieth century and combining them with modern data to cover the middle and late twentieth century. We find large disparities in mobility, with White children having far better chances of escaping the bottom of the distribution than Black children in every generation. This mobility gap was more important in proximately determining each generation's racial gap than was the initial gap in parents' economic status. (JEL D31, J15, J62, N31, N32)

Study of High field conduction in Se based Chalcogenide glasses

The present work reports the study of high field conduction in thin films of Se90Ge10-x Inx (x=2,6) because high field conduction in chalcogenide glasses is affected by the presence of localised states at the band edges as well as the defect states present in the mobility gap.To measure the density of states in these thin films , space charge limited conduction technique is used. I-V characteristics have been measured at various fixed temperatures. An ohmic behaviour is observed at low electric fields upto 102V/cm. Superohmic behaviour is observed at high electric fields (103 -104 V/cm).High field conduction theory of space charge limited conduction for uniform distribution of localised states in the mobility gap fits well with the experimental data.Using this theory, the density of defect states near Fermi level is calculated for all glassy alloys.

Impact of Urban Spatial Transformation on the Mobility of Commuters with Different Transportation Modes in China: Evidence from Kunming 2011–2016

Many emerging economies, including China, are undergoing rapid and large-scale urban spatial transformation. Thus, the daily mobility of transportation-disadvantaged groups, especially non-car users, has received increased attention, as these people may experience significant restrictions in their daily activities. Such restrictions raise issues with respect to transport-related social exclusion, which are detrimental to the sustainability of urban transportation systems. Activity participation and time use have been used to measure the spatial barriers and inequalities that travelers face in their daily lives. However, limited research has been conducted on how the daily mobility of different transportation modes has evolved over a longer period relative to urban development. Therefore, this study aimed to investigate the activity participation and time use of car travelers in comparison with other transportation mode groups in Kunming from 2011 to 2016, a period of rapid growth in motorization. A three-layer activity structure was used to characterize the hierarchy of activity requirements. Propensity score matching was used to compare the mobility of commuters across different urban periods and transportation modes while controlling several confounding factors. Three conclusions were drawn from the results of the study: First, changes in urban form and transportation system cause residential suburbanization and a considerable increase in private-car and public transportation at the expense of non-motorized transportation modes. Second, the degree of impact of urban space transformation on personal mobility is ranked in descending order of public transit, cycling and walking, e-bike, and cars. Third, the traffic disadvantage of non-car users is obvious, and the mobility gap of commuters with different travel modes tends to widen over time. We discuss the consequences of transport-related social exclusion and highlight directions for future sustainable transportation planning research.

The Government Policy on Online-Based Transportation in the Era of Disruption

The purpose of this study is to analyze the challenges and constraints of government policy on online-based land transportation in the era of disruption. This research uses qualitative research design. The type of data used in this research is seconddary data. Sufficient data is needed as material for analysis in the discussion of this article. The data collection method used in this research is a literature study. Based on the analysis results, it can be concluded that the implementation of online transportation system policies in Indonesia has been able to improve the social welfare of some Indonesian people. However, there are still some obstacles in the social sphere in its implementation, such as government organizational structure, umbrella act, facilities, human resources, and the process. Meanwhile, blocks were also found from the driver's side, such as mobility gaps, differences in inaccessibility, the potential for accidents, and congestion, which can be a waste of energy.

An effect of nitrogen incorporation on the structure and properties of amorphous SiC: First-principles molecular dynamics simulations

The structural, mechanical and electronic structure properties of amorphous silicon carbide and silicon carbonitride alloys were studied depending on chemical ordering, and nitrogen content, respectively, by using first-principles molecular dynamics simulations. The structure, chemical bonding, electronic structure, frequency-dependent dielectric functions, and mechanical properties (elastic moduli, Poisson ratio, bulk modulus to shear modulus ratio, ideal shear strength, Vickers hardness, Debye temperature and fracture toughness) were studied. It was established that an increase of nitrogen content in carbonitride alloys and a decrease of chemical ordering in carbide alloys cause the weakening of the Si–C network, strengthening of the C–C network, decrease in four-fold coordination and increase in three-fold coordination of Si and C atoms. All these factors lead to a deterioration of mechanical properties. The highly nitrided alloys are supposed to be wide-gap semiconductors with estimated mobility gaps in the range of 2.9–4.2 eV. The calculated data were used to elucidate available experimental results.

The quantum confinement effects on the electronic properties of monolayer GeS nanoribbon with tube-edged reconstruction

Monolayer α-phase GeS is promising for many novel applications due to its high carrier mobility and suitable band gap. Recently, the metal and nonmetal zigzag edges of monolayer α-phase GeS have been predicted to undergo universal ZZ(Ge-Tube)/ZZ(S-R) edge reconstruction. Therefore, studies on GeSNR should be reconsidered. In this paper, we study the quantum confinement effects on the electronic properties of edge reconstructed monolayer GeS nanoribbon (GeSNR) by using first-principles calculations. As width of the nanoribbon increases from 10 to 41 Å, the band gap keeps indirect and linearly decreases from 1.57 to 0.87 eV. Robust spatial separation of valence band maximum and conduction band minimum exist in reconstructed GeSNR with width larger than 19 Å. Moreover, high carrier mobility is expected in the reconstructed GeSNR. Our results suggest that reconstructed GeS nanoribbon is an important candidate for optoelectronics and photocatalytic.

Casting light on black phosphorus-based catalysts for water electrolysis: Approaches, promotion manners, and perspectives

Low-dimensional black phosphorus (BP) has attracted surging interest for electronics, optoelectronics, and catalysts. It has been regarded as a promising candidate in electrical device since 2014 due to its high carrier mobility and controllable band gap, especially in the application of water splitting electrocatalysis. However, the low intrinsic activity and weak stability of low-dimensional BP severely hinder its further application as efficient electrocatalyst. To improve the hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting activity of low-dimensional BP, many facile methods have been developed and explored for preparation of BP-based activated catalysts. In this regards, certain strategies have been tried to overcome their weaknesses of intrinsic activity and stability, including metal/nonmetal doping, building of heterostructure, and covalent functionalization. This work discusses the promotion strategies of high-efficient electrocatalysts for HER/OER and overall water splitting based on low-dimensional BP materials, providing an effective orientation of development and practical application of low-dimensional BP-based materials. Finally, a comment is also made on the recent developments, future outlook and challenges ahead in BP-based electrocatalysts.

Bridging the Gaps of Clean Mobility and Transport through Engineering Interventions

Transportation plays a significant role in sustainable development, civilization, industrialization and commercialization in many countries around the globe. This paper looked into bridging the gaps in clean mobility and transport through engineering interventions and other innovative ideas. Salient issues affecting clean mobility and an effective transport system were highlighted and possible solutions were suggested. The methodology includes a literature survey and consultation of environmental experts. A deeper understanding of the gaps between mobility and transportation management can provide insightful information into how cities must be structured. Clean mobility refers to all forms of transportation that do not require the use of fossil fuels exclusively. Mobility specializes in making ground-breaking solutions that enable mobility and industry to attain zero-emissions status. It was concluded that engineering interventions and other innovative ideas can be used to bridge the gaps in clean mobility and transport. Monitoring climate change and reduction of environmental pollution are very vital for the sustainable green environment in African urban communities. There is a need to strengthen digital advancements for integrated solutions in infrastructural development and transportation networks. Proper planning, adequate funding and sustainable development are very crucial for bridging the gap and attaining of a cleaner environment.

Gender and financial inclusion: does technology make a difference?

Using district-level survey data, the analysis assesses the impact of technology in fostering the financial inclusion of women in India. The findings show that women are 12% less likely to use a mobile phone while opening accounts and 9% less likely to actively use such accounts. Relatedly, account ownership and its use are less likely for women with mobile phones, especially in the post-PMJDY period. The evidence also reveals a differential impact of mobile phones on women across strata and primarily for below-poverty line respondents. The analysis suggests the need for carefully-crafted policies to address this mobile gender gap in order to further reduce the gender gap in financial inclusion.

Striving and Thriving: A Life Course Trade-Off?

Striving and Thriving: A Life Course Trade-Off?

ICT and Women's Health: An Examination of the Impact of ICT on Maternal Health in SADC States.

Attainment of sexual and reproductive health is regarded as a human rights matter. Notwithstanding this, maternal mortality continues to be a major public health concern in low-income countries, especially those in sub-Saharan Africa. Maternal mortality remains high in Africa, yet there are information communication technologies (ICTs) (such as the internet, mobile communication, social media, and community radios) that have the potential to make a difference. Making effective use of all of these ICTs can considerably decrease preventable maternal deaths. ICTs, particularly mobile devices, offer a platform for access to health information and services that can bring change in areas where health infrastructure and resources are often limited. However, for Southern Africa, maternal mortality remains high despite the presence of ICT tools that have transformative potential to improve maternal health. In light of this, this study sought to examine the impact of ICT on maternal health. The study was quantitative in nature, and it used panel data that covered the period from 2000–2018. The Mean Group and Pooled Mean Group cointegration techniques and a generalised method of moments panel technique were used for estimation purposes. Results showed that ICT has a negative effect on maternal health. This shows that ICT tools contribute positively to maternal health. The study gave a number of recommendations. The mobile gender gap should be closed (digital inclusion), mobile network connectivity boosted, and digital platforms must be created in order to enhance the transformative potential of ICT in improving health outcomes.

Raman Spectroscopic Studies on Graphene Oxide – Europium Nano Composites

Graphene based nano composites are receiving much importance in recent years due to the two-dimensional topology, high carrier mobility, luminescent nature, and ultra wide band gap transition. Here graphene oxide is prepared by modified Hammers method. Resultant residue of dark yellow color is filtered using Watt man No. 1 filter paper and is further cleaned by washing several times with 5% HCl solution and de-ionized water. Unexfoliated oxide is eliminated from the sample by ultra-sonication procedure for 30 minutes followed by micro-centrifugation under 4000 rpm for another 30 minutes. Vacuum annealing is done at sample at 60OC for 12 hours to get black graphene oxide powder and is labelled as Sample4. Europium (III) nitrate is added to 3g each of graphene oxide powder in 0.1g, 0.2g, and 0.3g concentration respectively labelled as Sample1, Sample2, and Sample3. Uniform mixing is done in composite samples. Morphological properties are analyzed through SEM. Surface topology of GO is like thin folded sheet, while that of Eu-GO is like that of spreading small nano materials on folded surface. Average particle size distribution is found to be 79.09 nm. Chemical composition and stotiometric ratio of different elements in the composites are quantitatively shown by EDX analysis. Raman spectra for Samples 1, 3, and 4 are shown. We can see that no shifting of peaks are observed in composites with respect to pure GO is an evidence of stable sp2 hybridisation and rigid oxygenated functional groups.

Building a spatial decision support system for tourism and infrastructure planning: technical solution and data integration challenges

Mobility planning in rural areas with a high number of tourists is important for creating sustainable destinations. By identifying mobility gaps in the transportation system, measures to improve the situation can be implemented. In order to identify such mobility gaps, decision-makers need a spatial decision support system (SDSS). The aim of this paper is to identify vital aspects of creating such an SDSS and to build a prototype. Two important aspects were identified, data and system design. The result of the analysis of available data shows a lack of data portals with disaggregated socio-economic and intra-destination travel data. Further, it shows that data on points of interest (POI) and public transit data are primarily found in company databases. The system design analysis showed that most SDSS today are relying on public data and are not designed to integrate disparate data sources. They are primarily developed to be used by experts. Based on these findings an SDSS that automatically integrates both public and private data was developed. It comprises of a self-hosted web mapping system and several geospatial tools. Our main conclusion is that both data and system design are important aspects to consider when building an SDSS for mobility planning. By using the architecture proposed in this article, new data can easily be incorporated in an SDSS. Furthermore, the system design also facilitates the involvement of stakeholders in the planning process.

Computer simulation on photoconductivity in hydrogenated amorphous silicon thin films

Abstract: We used a computer simulation for photoconductivity as a function of temperature in a-Si:H thin films. Utilizing a two level model for photoconductivity, calculated stationary photoconductivity values in a wide range of temperature. The nonlinear differential equations system (1) was solved numerically by iteration technique. For the mobility edge of a-Si:H films, we assumed a model with two level dangling bond centers in the mobility gap. It was shown that the computer modeling results describe well influences of such parameters, as exciting light intensities, capture coefficients for electrons and holes and state densities of dangling bond center levels on behavior of temperature dependence curves of photoconductivity in a-Si:H films.