“When Boys Become the Second Sex”: The New Gender Gap Among Chinese Middle School Students

This paper studies the gender gap in academic achievement using a nationally representative survey of middle school students in China. Chinese girls outperform boys in Mathematics, Chinese, and English by 13.5%, 62.1%, and 61.5% of a standard deviation, respectively, which is one of the largest gender gaps in the world. Using the OLS regression with interactions between gender and family-, teacher-, and school-level variables, I show that girls benefit from having a same-sex teacher in Mathematics and Chinese. For boys, however, the effect of sex congruence with the subject teacher is insignificant in all three subjects. Girls’ resilience in the face of adverse family and school environments also contributes to the gap. In dysfunctional families and lower-ranking schools, the female advantage is even more pronounced

Decision-aid or Controller? Steering Human Decision Makers with Algorithms

Algorithms are used to aid human decision makers by making predictions and recommending decisions. Currently, these algorithms are trained to optimize prediction accuracy. What if they were optimized to control final decisions? In this paper, we study a decision-aid algorithm that learns about the human decision maker and provides ''personalized recommendations'' to influence final decisions. We first consider fixed human decision functions which map observable features and the algorithm's recommendations to final decisions. We characterize the conditions under which perfect control over final decisions is attainable. Under fairly general assumptions, the parameters of the human decision function can be identified from past interactions between the algorithm and the human decision maker, even when the algorithm was constrained to make truthful recommendations. We then consider a decision maker who is aware of the algorithm's manipulation and responds strategically. By posing the setting as a variation of the cheap talk game [Crawford and Sobel, 1982], we show that all equilibria are partition equilibria where only coarse information is shared: the algorithm recommends an interval containing the ideal decision. We discuss the potential applications of such algorithms and their social implications

Nondestructive determination of subsurface grain morphology

Recent progress in experimental and numerical methods enables to scrutinize simulated polycrystal surface micromechanics at high spatial resolution. For the correct interpretation of similarities and deviations between experiment and simulation, the consideration of subsurface grain morphology is imperative because of its significant impact on the surface layer boundary condition. A novel method is presented that coarsely scans a relatively large area for subsurface crystallite orientation up to depths of ~0.2 mm by means of differential aperture X-ray microscopy. The resulting point set is categorized into grains according to proximity in physical and orientation space. Reconstruction of the subsurface grain structure starts with a Voronoi tessellation using the categorized set as seed points. Progressive smoothing of the resulting ragged grain boundary surfaces is achieved through mean curvature flow. As it turns out that the reconstruction quality of the bulk and on the surface are related, the latter can serve as guidance for optimum subsurface reconstruction

Characterising Ion-Irradiated FeCr : Hardness, Thermal Diffusivity and Lattice Strain

Ion-irradiated FeCr alloys are useful for understanding and predicting neutron damage in the structural steels of future nuclear reactors. Previous studies have largely focused on the structure of irradiation induced defects, probed by transmission electron microscopy (TEM), as well as changes in mechanical properties. Across these studies, a wide range of irradiation conditions has been employed on samples with different processing histories, which complicates the analysis of the relationship between defect structures and material properties. Furthermore, key properties, such as irradiation-induced changes in thermal transport and lattice strain, are little explored. Here we present a systematic study of Fe3Cr, Fe5Cr and Fe10Cr binary alloys implanted with 20 MeV Fe3+ ions to nominal doses of 0.01 dpa and 0.1 dpa at room temperature. Nanoindentation, transient grating spectroscopy (TGS) and X-ray micro-beam Laue diffraction were used to study the changes in hardness, thermal diffusivity and strain in the material as a function of damage and Cr content. Our results suggest that Cr leads to an increased retention of irradiation-induced defects, causing substantial changes in hardness and lattice strain. However, thermal diffusivity varies little with increasing damage and instead degrades significantly with increasing Cr content in the material. We find significant lattice strains even in samples exposed to a nominal displacement damage of 0.01 dpa. The defect density predicted from the lattice strain measurements is significantly higher than that observed in previous TEM studies, suggesting that TEM may not fully capture the irradiation-induced defect population. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Variation in superconducting transition temperature due to tetragonal domains in two-dimensionally doped SrTiO₃

Strontium titanate is a low-temperature, non-Bardeen-Cooper-Schrieffer superconductor that superconducts to carrier concentrations lower than in any other system and exhibits avoided ferroelectricity at low temperatures. Neither the mechanism of superconductivity in strontium titanate nor the importance of the structure and dielectric properties for the superconductivity are well understood. We studied the effects of twin structure on superconductivity in a 5.5-nm-thick layer of niobium-doped SrTiO$_{3}$ embedded in undoped SrTiO$_{3}$. We used a scanning superconducting quantum interference device susceptometer to image the local diamagnetic response of the sample as a function of temperature. We observed regions that exhibited a superconducting transition temperature $T_{c}$ $\gtrsim$ 10% higher than the temperature at which the sample was fully superconducting. The pattern of these regions varied spatially in a manner characteristic of structural twin domains. Our results emphasize that the anisotropic dielectric properties of SrTiO$_{3}$ are important for its superconductivity, and need to be considered in any theory of the mechanism of the superconductivity.Comment: 14 pages, 11 figures, Supplemental Information available at http://stanford.edu/group/moler/papers/Noad_STOsuperconductivity_SI.pd