Capturing usage patterns in bike sharing system via multilayer network fused Lasso

Data collected from a bike-sharing system exhibit complex temporal and spatial features. We analyze shared-bike usage data collected in Seoul, South Korea, at the level of individual stations while accounting for station-specific behavior and covariate effects. For this, we adopt a penalized regression approach with a multilayer network fused Lasso penalty. These fusion penalties are imposed on networks which embed spatio-temporal linkages, and capture the homogeneity in bike usage that is attributed to intricate spatio-temporal features without arbitrarily partitioning the data. On the real-life dataset, we demonstrate that the proposed approach yields competitive predictive performance and provides a new interpretation of the data

Does Higher Education Affect Health and Health Behaviors?: Evidence from a Regression Discontinuity Design

This paper examines the causal effect of higher education on health related outcomes. To address the endogeneity in educational attainment, we exploit the educational reform in Korea which has increased the opportunity to engage in college education for affected cohorts. Using the regression discontinuity design, we do not find supportive evidence for health return of higher education. Moreover, we find that higher education has limited causal effects on health behaviors such as smoking and drinking. The limited effect might be a result of universal health care system in Korea which provides health insurance for practically all individuals

The Long-Term Effects of Labor Market Entry in a Recession: Evidence from the 1997-1998 Asian Financial Crisis

In this paper, we investigate the long-term effect of entering the job market during the 1997–1998 Asian financial crisis upon college graduation. We estimate the impact on labor market and family outcomes, such as employment, earnings, marriage, divorce, and child bearing. Using fluctuations in unemployment rates, previous research has documented the long-term adverse impacts on labor market outcomes of economic conditions at the time of labor market entry. Nevertheless, direct evidence on the consequences of an abrupt and severe recession stemming from a financial crisis has been understudied. We contribute to the literature in two aspects. First, by utilizing the shock from the Asian financial crisis, we estimate the long-term impact of labor market entry during a severe and abrupt downturn, which will have implications for the recent Great Recession. Second, by investigating both labor market and family formation outcomes, we are able to estimate the overall welfare impact of labor market entry during a crisis

The Long-Term Effects of Labor Market Entry in a Recession: Evidence from the Asian Financial Crisis

This study investigates the long-term effects of initial labor market conditions by comparing cohorts who graduated from college before, during, and after the 1997–1998 Asian financial crisis in South Korea. We measure the overall welfare effect by examining their labor market activities, family formation, and household finances. Using data from 20 waves of the Korean Labor and Income Panel Study, we find a substantial and persistent reduction in employment, earnings, marriage, fertility, and asset building among men who graduated during a recession. For women, limited job opportunities at graduation result in an increase in childbearing. Our results suggest that labor market entry in a large-scale recession has prolonged effects on a young worker’s life course even after the penalties in the labor market have disappeared

Stretchable Gold Nanomembrane Electrode with Ionic Hydrogel Skin-Adhesive Properties

Skin has a dynamic surface and offers essential information through biological signals originating from internal organs, blood vessels, and muscles. Soft and stretchable bioelectronics can be used in wearable machines for long-term stability and to continuously obtain distinct bio-signals in conjunction with repeated expansion and contraction with physical activities. While monitoring bio-signals, the electrode and skin must be firmly attached for high signal quality. Furthermore, the signal-to-noise ratio (SNR) should be high enough, and accordingly, the ionic conductivity of an adhesive hydrogel needs to be improved. Here, we used a chitosan-alginate-chitosan (CAC) triple hydrogel layer as an interface between the electrodes and the skin to enhance ionic conductivity and skin adhesiveness and to minimize the mechanical mismatch. For development, thermoplastic elastomer Styrene-Ethylene-Butylene-Styrene (SEBS) dissolved in toluene was used as a substrate, and gold nanomembranes were thermally evaporated on SEBS. Subsequently, CAC triple layers were drop-casted onto the gold surface one by one and dried successively. Lastly, to demonstrate the performance of our electrodes, a human electrocardiogram signal was monitored. The electrodes coupled with our CAC triple hydrogel layer showed high SNR with clear PQRST peaks

Free-standing two-dimensional ferro-ionic memristor

Abstract Two-dimensional (2D) ferroelectric materials have emerged as significant platforms for multi-functional three-dimensional (3D) integrated electronic devices. Among 2D ferroelectric materials, ferro-ionic CuInP2S6 has the potential to achieve the versatile advances in neuromorphic computing systems due to its phase tunability and ferro-ionic characteristics. As CuInP2S6 exhibits a ferroelectric phase with insulating properties at room temperature, the external temperature and electrical field should be required to activate the ferro-ionic conduction. Nevertheless, such external conditions inevitably facilitate stochastic ionic conduction, which completely limits the practical applications of 2D ferro-ionic materials. Herein, free-standing 2D ferroelectric heterostructure is mechanically manipulated for nano-confined conductive filaments growth in free-standing 2D ferro-ionic memristor. The ultra-high mechanical bending is selectively facilitated at the free-standing area to spatially activate the ferro-ionic conduction, which allows the deterministic local positioning of Cu+ ion transport. According to the local flexoelectric engineering, 5.76×102-fold increased maximum current is observed within vertical shear strain 720 nN, which is theoretically supported by the 3D flexoelectric simulation. In conclusion, we envision that our universal free-standing platform can provide the extendable geometric solution for ultra-efficient self-powered system and reliable neuromorphic device