An Estimate of the Vibrational Frequencies of Spherical Virus Particles

The possible normal modes of vibration of a nearly spherical virus particle are discussed. Two simple models for the particle are treated, a liquid drop model and an elastic sphere model. Some estimates for the lowest vibrational frequency are given for each model. It is concluded that this frequency is likely to be of the order of a few GHz for particles with a radius of the order of 50 nm.Comment: 6 pages, 1 figur

MIDV-500: a dataset for identity document analysis and recognition on mobile devices in video stream

A lot of research has been devoted to identity documents analysis and recognition on mobile devices. However, no publicly available datasets designed for this particular problem currently exist. There are a few datasets which are useful for associated subtasks but in order to facilitate a more comprehensive scientific and technical approach to identity document recognition more specialized datasets are required. In this paper we present a Mobile Identity Document Video dataset (MIDV-500) consisting of 500 video clips for 50 different identity document types with ground truth which allows to perform research in a wide scope of document analysis problems. The paper presents characteristics of the dataset and evaluation results for existing methods of face detection, text line recognition, and document fields data extraction. Since an important feature of identity documents is their sensitiveness as they contain personal data, all source document images used in MIDV-500 are either in public domain or distributed under public copyright licenses. The main goal of this paper is to present a dataset. However, in addition and as a baseline, we present evaluation results for existing methods for face detection, text line recognition, and document data extraction, using the presented dataset.This work is partially supported by Russian Foundation for Basic Research (projects 17-29-03170 and 17-29-03370). All source images for MIDV-500 dataset are obtained from Wikimedia Commons. Author attributions for each source images are listed in the description table at ftp://smartengines.com/midv-500/documents.pdf

Weighted combination of per-frame recognition results for text recognition in a video stream

The scope of uses of automated document recognition has extended and as a result, recognition techniques that do not require specialized equipment have become more relevant. Among such techniques, document recognition using mobile devices is of interest. However, it is not always possible to ensure controlled capturing conditions and, consequentially, high quality of input images. Unlike specialized scanners, mobile cameras allow using a video stream as an input, thus obtaining several images of the recognized object, captured with various characteristics. In this case, a problem of combining the information from multiple input frames arises. In this paper, we propose a weighing model for the process of combining the per-frame recognition results, two approaches to the weighted combination of the text recognition results, and two weighing criteria. The effectiveness of the proposed approaches is tested using datasets of identity documents captured with a mobile device camera in different conditions, including perspective distortion of the document image and low lighting conditions. The experimental results show that the weighting combination can improve the text recognition result quality in the video stream, and the per-character weighting method with input image focus estimation as a base criterion allows one to achieve the best results on the datasets analyzed.This work is partially supported by the Russian Foundation for Basic Research (projects 17-29-03236 and 18-07-01387)

Electronic structure multiconfiguration calculation of a small cluster embedded in an LDA host

The present paper proposes a method for electronic-structure calculations on a type of system that cannot be handled by present methods. It considers a system where a multideterminant wave function is essential for an atom or a small cluster of atoms embedded in a large system, normally a solid, which can be treated by density-functional methods such as with the local-density approximation (LDA). A suitable example is a transition-metal atom in a semiconductor or MgO host. In this method the embedding potential for the cluster is generated from a LDA calculation but applied in a multiconfiguration calculation. The method and the concept of the embedding potential are validated by application to a simple system of a cluster Li2Mg2 of four pseudoatoms