Renmin University of China

About: Renmin University of China is a education organization based out in Beijing, Beijing, China. It is known for research contribution in the topics: China & Population. The organization has 11325 authors who have published 15498 publications receiving 238419 citations. The organization is also known as: Renmin University & People's University of China.

Electrical contacts to monolayer black phosphorus: A first-principles investigation

Abstract: We report first-principles theoretical investigations of possible metal contacts to monolayer black phosphorus (BP). By analyzing lattice geometry, five metal surfaces are found to have minimal lattice mismatch with BP: Cu(111), Zn(0001), In(110), Ta(110), and Nb(110). Further studies indicate Ta and Nb bond strongly with monolayer BP causing substantial bond distortions, but the combined Ta-BP and Nb-BP form good metal surfaces to contact a second layer BP. By analyzing the geometry, bonding, electronic structure, charge transfer, potential, and band bending, it is concluded that Cu(111) is the best candidate to form excellent Ohmic contact to monolayer BP. The other four metal surfaces or combined surfaces also provide viable structures to form metal/BP contacts, but they have Schottky character. Finally, the band bending property in the current-in-plane (CIP) structure where metal/BP is connected to a freestanding monolayer BP, is investigated. By both work function estimates and direct calculations of the two-probe CIP structure, we find that the freestanding BP channel is $n$ type.

Learning Depth-Guided Convolutions for Monocular 3D Object Detection

Abstract: 3D object detection from a single image without LiDAR is a challenging task due to the lack of accurate depth information. Conventional 2D convolutions are unsuitable for this task because they fail to capture local object and its scale information, which are vital for 3D object detection. To better represent 3D structure, prior arts typically transform depth maps estimated from 2D images into a pseudo-LiDAR representation, and then apply existing 3D point-cloud based object detectors. However, their results depend heavily on the accuracy of the estimated depth maps, resulting in suboptimal performance. In this work, instead of using pseudo-LiDAR representation, we improve the fundamental 2D fully convolutions by proposing a new local convolutional network (LCN), termed Depth-guided Dynamic-Depthwise-Dilated LCN (D4LCN), where the filters and their receptive fields can be automatically learned from image-based depth maps, making different pixels of different images have different filters. D4LCN overcomes the limitation of conventional 2D convolutions and narrows the gap between image representation and 3D point cloud representation. Extensive experiments show that D$^4$LCN outperforms existing works by large margins. For example, the relative improvement of D4LCN against the state-of-the-art on KITTI is 9.1\% in the moderate setting. D4LCN ranks 1st on KITTI monocular 3D object detection benchmark at the time of submission (car, December 2019). The code is available at https://github.com/dingmyu/D4LCN

Enhanced Photocatalytic Degradation of RhB Driven by Visible Light-Induced MMCT of Ti(IV)−O−Fe(II) Formed in Fe-Doped SrTiO3

Abstract: It is important to reveal the origin of the visible light-induced photocatalytic activity of transition metal-doped SrTiO3 in which an isolated energy level is created by the dopant in the forbidden band gap. In this particle, the photocatalytic and photophysical properties of pure SrTiO3 and Fe-doped SrTiO3 were investigated comparatively. The Fe-doped SrTiO3 has been shown to have a much higher photocatalytic activity than pure SrTiO3 for the degradation of RhB under visible light irradiation. It was showed that doping Fe into SrTiO3 exhibited an absorption extending up to the visible region in the optical absorption spectrum and established the TiIV−O−FeII heterobimetallic linkages in the host. Difference diffuse reflectance spectra revealed that the absorption in the visible region is partly attributed to the metal-to-metal charge-transfer (MMCT) excitation of TiIV−O−FeII linkage formed in the Fe-doped SrTiO3. The visible light excitation of TiIV−O−FeII linkage was demonstrated to be the cause of the ...

Graphene spintronics: the role of ferromagnetic electrodes

Abstract: We report a first principles study of spin-transport under finite bias through a graphene-ferromagnet (FM) interface, where FM=Co(111), Ni(111). The use of Co and Ni electrodes achieves spin efficiencies reaching 80% and 60%, respectively. This large spin filtering results from the materials specific interaction between graphene and the FM which destroys the linear dispersion relation of the graphene bands and leads to an opening of spin-dependent energy gaps of roughly 0.4-0.5 eV at the K points. The minority spin band gap resides higher in energy than the majority spin band gap located near the Fermi level, a feature that results in large minority spin dominated currents.

Survey using incognito standardized patients shows poor quality care in China’s rural clinics

Abstract: Over the past decade, China has implemented reforms designed to expand access to health care in rural areas. Little objective evidence exists, however, on the quality of that care. This study reports results from a standardized patient study designed to assess the quality of care delivered by village clinicians in rural China. To measure quality, we recruited individuals from the local community to serve as undercover patients and trained them to present consistent symptoms of two common illnesses (dysentery and angina). Based on 82 covert interactions between the standardized patients and local clinicians, we find that the quality of care is low as measured by adherence to clinical checklists and the rates of correct diagnoses and treatments. Further analysis suggests that quality is most strongly correlated with provider qualifications. Our results highlight the need for policy action to address the low quality of care delivered by grassroots providers.