Flávio Cunha, James J. Heckman, Susanne M. Schennach
This paper formulates and estimates multistage production functions for child cognitive and noncognitive skills. Output is determined by parental environments and investments at different stages of childhood. We estimate the elasticity of substitution between investments in one period and stocks of skills in that period to assess the benefits of early investment in children compared to later remediation. We establish nonparametric identification of a general class of nonlinear factor models. A by-product of our approach is a framework for evaluating childhood interventions that does not rely on arbitrarily scaled test scores as outputs and recognizes the differential effects of skills in different tasks. Using the estimated technology, we determine optimal targeting of interventions to children with different parental and personal birth endowments. Substitutability decreases in later stages of the life cycle for the production of cognitive skills. It increases in later stages of the life cycle for the production of noncognitive skills. This finding has important implications for the design of policies that target the disadvantaged. For some configurations of disadvantage and outcomes, it is optimal to invest relatively more in the later stages of childhood.
Face recognition technology is a biometric technology, which is based on the identification of facial features of a person. People collect the face images, and the recognition equipment automatically processes the images. The paper introduces the related researches of face recognition from different perspectives. The paper describes the development stages and the related technologies of face recognition. We introduce the research of face recognition for real conditions, and we introduce the general evaluation standards and the general databases of face recognition. We give a forward-looking view of face recognition. Face recognition has become the future development direction and has many potential application prospects.
Abstract Quality education is one of the pillars in the United Nations 2030 Agenda for Sustainable Development, which aims to ensure inclusive and equitable quality education and promote lifelong learning opportunities for all. This overall goal can be connected to some general trends affecting education in the information age. We argue that education is key to the future quality of human life and the sustainability of the world. Generally, education is being transformed in both formal and informal learning contexts by new digital technologies. Overall, some of these major innovations and how they are changing education can be summarized into the following aspects: 1) our educational aims and objectives; 2) educational ecologies and contexts of learning; 3) the processes of learning; 4) the processes of teaching; and 5) educational governance and policy. Meanwhile, we note some of the potential risks and downsides of these technology trends. From the sustainable perspective, our review points to a great potential for educational reform, but it can only be achieved if we are willing to rethink and even abandon some of our traditional ways of doing things in education.
This review provides an overview of the literature regarding digital technology use and adolescent well-being. Overall, findings imply that the general effects are on the negative end of the spectrum but very small. Effects differ depending on the type of use: whereas procrastination and passive use are related to more negative effects, social and active use are related to more positive effects. Digital technology use has stronger effects on short-term markers of hedonic well-being (eg, negative affect) than long-term measures of eudaimonic well-being (eg, life satisfaction). Although adolescents are more vulnerable, effects are comparable for both adolescents and adults. It appears that both low and excessive use are related to decreased well-being, whereas moderate use is related to increased well-being. The current research still has many limitations: High-quality studies with large-scale samples, objective measures of digital technology use, and experience sampling of well-being are missing.
Balkar Yildirim, Alan Albert Coley, Diego Fernando López
We investigate whether black holes can persist through the bounce with a minimal scale factor in a non-singular cosmology, whereby black holes from a previous contracting phase survive into the current expanding one. We do so by studying a generalized McVittie spacetime which embeds a spherically symmetric black hole in a positive spatial curvature bouncing FLRW cosmological background within the modified theory of teleparallel new general relativity. There are no further assumptions on the spacetime (e.g., on the form of the scale factor) initially, and the local evolution is derived from the field equations of the theory, utilizing a perturbative scheme which is valid ``near the bounce". To leading order we obtain a simple bounce solution similar to that in general relativity for a closed FLRW model with a positive cosmological constant, but in which the curvature term in the Friedmann equation is re-normalized within new general relativity. Qualitatively the minimum of the bounce at $t=0$ changes, but near the bounce the evolution remains symmetric. The central inhomogeneity evolves at higher perturbative orders, where the details depend on the arbitrary constants of the perturbative solution. Hence the evolution of the local horizon during the bounce changes qualitatively, where the effects depend on the signs of the perturbation, and the symmetry across the bounce is disrupted due to a linear term.
Este artigo explora a aplicação de métodos probabilísticos na análise da fiabilidade e no dimensionamento do reforço de taludes rochosos sujeitos a mecanismos de rotura planar. O estudo incide no caso de um maciço rochoso intersetado por uma família de descontinuidades paralela à face do talude. O volume com potencial de instabilização é idealizado como um modelo de blocos, para o qual se desenvolve uma formulação em sistemas de componentes. Como termo de comparação, analisa-se igualmente um modelo simplificado que considera o mesmo volume como um bloco único. Os resultados evidenciam a influência da inclinação do plano de deslizamento. Verifica-se que o modelo constituído por múltiplos blocos conduz a índices de fiabilidade inferiores. Contudo, a sua utilização para o dimensionamento probabilístico do reforço tem vantagens apenas para inclinações baixas do plano de deslizamento. A análise sugere ainda que o modelo de blocos múltiplos pode ser adequadamente representado por um modelo simplificado de dois blocos.
Geology, Engineering geology. Rock mechanics. Soil mechanics. Underground construction
This paper explores how epistemic artifacts have transformed our understanding of scientific observation. It examines the historical evolution from basic instruments such as Mayan quadrants and Galileo’s telescope to today’s sophisticated electron microscopes. The study focuses on how these devices have reshaped the traditional concept of observation in the philosophy of science, particularly within the field of nanotechnology. Against the backdrop of historical figures such as Descartes, Hooke, Newton, and Leeuwenhoek, it highlights how each contributed to the development of the «microscopic artifactual tradition». The paper introduces the concept of nanoepistemology to describe how knowledge of the nano-world fundamentally depends on instrument-processed images rather than traditional direct observation. It concludes that these technological transformations have weakened the role of classical theories and have shifted the philosophy of science toward a philosophy of technology.
To accurately evaluate the dynamic characteristics of helical gear transmission systems under high-speed operating conditions and to address the problem that the lumped parameter model fails to accurately reflect the system’s dynamic performance because its degrees of freedom are imperfectly considered, the full-degree-of-freedom dynamic model of the high-speed shaft-bearing-helical gear transmission system was established. The system’s dynamic equations were derived, and the natural frequencies calculated from the theoretical model, as well as the corresponding mode shapes for each degree of freedom, were compared with the finite element model simulation results. The relationship between the critical rotational speed within the system’s 3 × 104 rpm range of rotational speed and the system frequency was analyzed. The dynamic characteristics of the driving wheel and driven wheel in terms of amplitude and motion trajectory were investigated, and the influence of eccentricity on these characteristics was discussed. Results indicate that the relative deviation of the first six natural frequencies between the proposed model and finite element model ranges from 0.09 % to 13.1 %, and the deviations of the higher-order modes are within 1 %. This effectively validates that the full-degree-of-freedom model can accurately reflect the dynamic characteristics of the system, providing a theoretical basis for the design of high-speed-helical gear transmission system.
Abstract Underwater robot technologies are crucial for marine resource exploration and autonomous manipulation, and many breakthroughs have been achieved with key indicators (e.g., dive depth and navigation range). However, due to the complicated underwater environment, the state-of-the-art sensing technologies cannot handle all the needs of underwater observations. To improve the autonomous operating capacity of underwater robots, there is an urgent need to develop underwater sensing technology. Therefore, in this paper, we first introduce the development of underwater robot platforms. We then review some key sensing technologies such as underwater acoustic sensing, underwater optical sensing, underwater magnetic sensing, and underwater bionic sensing. Finally, we point out the challenges of underwater sensing technology and future directions in addressing these challenges, e.g., underwater bionic sensing, new underwater material development, multisource information fusion, and the construction of general test platforms.