Enhanced spin injection efficiency in a four-terminal double quantum dot system

Within the scheme of quantum rate equations, we investigate the spin-resolved transport through a double quantum dot system with four ferromagnetic terminals. It is found that the injection efficiency of spin-polarized electrons can be significantly improved compared with single dot case. When the magnetization in one of four ferromagnetic terminals is antiparallel with the other three, the polarization rate of the current through one dot can be greatly enhanced, accompanied by the drastic decrease of the current polarization rate through the other one. The mechanism is the exchange interaction between electrons in the two quantum dots, which can be a promising candidate for the improvement of the spin injection efficiency.Comment: 10 pages and 5 figure

Fireball/Blastwave Model and Soft Gamma-ray Repeaters

Soft gamma-ray repeaters are at determined distances and their positions are known accurately. If observed, afterglows from their soft gamma-ray bursts will provide important clues to the study of the so called "classical gamma-ray bursts". On applying the popular fireball/blastwave model of classical gamma-ray bursts to soft gamma-ray repeaters, it is found that their X-ray and optical afterglows are detectable. Monitoring of the three repeaters is solicited.Comment: Already published in 1998 in "Chinese Physics Letters", replaced with the published version. See astro-ph/0502452 for a more detailed versio

BPDST: Blockchain-Based Privacy-Preserving Data Sharing on Thin Client for Electronic Medical Records

Sharing medical data can improve the quality of medical services and reduce costs. However, the current Electronic Medical Records (EMRs) are scattered and easily tampered with, which is not conducive to the sharing of EMRs and is not compatible with thin clients. Fortunately, blockchain technology is tamper-proof, decentralized, auditable, and meets the above requirements. To solve these problems, we first propose Blockchain-Based Privacy-Preserving Data Sharing on Thin-Client for Electronic Medical Records (BPDST) approach that combines the k-anonymity and cloud storage, which thin clients can run like a full-node user and safeguard user\u27s EMRs privacy concurrently. Using this approach, patients can control their own EMRs, while the consortium blockchain is responsible for the transaction process and sending the correct results to the patients. BPDST can also share information without leaking or tampering with EMRs\u27 privacy, achieving the purpose of sharing medical data and privacy protection. In the medical field, this study can effectively protect users\u27 privacy when sharing medical data to provide convenience for users and break the "island" phenomenon among various medical institutions. Security analysis and extensive experiments show that BPDST is secure and practical for sharing EMRs

GeohashTile: Vector Geographic Data Display Method Based on Geohash

© 2020 MDPI AG. All rights reserved. In the development of geographic information-based applications for mobile devices, achieving better access speed and visual effects is the main research aim. In this paper, we propose a new geographic data display method based on Geohash, namely GeohashTile, to improve the performance of traditional geographic data display methods in data indexing, data compression, and the projection of different granularities. First, we use the Geohash encoding system to represent coordinates, as well as to partition and index large-scale geographic data. The data compression and tile encoding is accomplished by Geohash. Second, to realize a direct conversion between Geohash and screen-pixel coordinates, we adopt the relative position projection method. Finally, we improve the calculation and rendering efficiency by using the intermediate result caching method. To evaluate the GeohashTile method, we have implemented the client and the server of the GeohashTile system, which is also evaluated in a real-world environment. The results show that Geohash encoding can accurately represent latitude and longitude coordinates in vector maps, while the GeohashTile framework has obvious advantages when requesting data volume and average load time compared to the state-of-the-art GeoTile system