Analysis of Digital Twin Definition and Its Difference from Simulation Modelling in Practical Application

The digital twin is widely known as a tool for digitalization of a product, but there is no common definition concerning this term. This article discusses the definition and utilization of digital twin. Areas of use, it’s implementation in the product lifecycle and most importantly it’s benefits. The lack of a standardized concept of a digital  twin leads to a misunderstanding between mathematical models and digital twin. Several definitions of digital twin were analyzed and compared with the definition of mathematical model and simulation modelling. The basic concept of areas of use for digital twin is introduced. The differences and similarities between the two definitions were found. The article aims first of all to help the management of digital twins in practical application. Keywords: Digital twin, Mathematical modelling, Mathematical model, Lifecycle of a product, Simulation modelling, Practical use of digital twin, Difference between the digital twin and mathematical model, Simulation

Технология бережливого производства и минимизация потерь от аварий

[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT In railway sector there are many dangerous destabilizing factors. One of the most common problems is collision of a train with a vehicle which is stuck on or entered out of driver’s negligence into a railway crossing. In the article methods of minimization of losses from this type of accidents are considered. They comprise construction of tunnels and overpasses at the intersections of the railway and the road, use of a 3D-laser radar to warn the locomotive crew about the stuck transport. In addition, it is possible to use web cameras, the image from which, using a router installed within 4-5 km far from the crossing, is transferred to the train driver’s cab on a separate display in advance to see the stuck vehicle and to have time to take emergency braking measures. Keywords: lean manufacturing, safety factors, railway crossing, emergency situation, visual perception, 3D-laser radar, web camera.Текст аннотации на англ. языке и полный текст статьи на англ. языке находится в прилагаемом файле ПДФ (англ. версия следует после русской версии).В железнодорожном деле существует множество опасных дестабилизирующих факторов. Одна из самых распространённых проблем - столкновение поезда с застрявшим или выехавшим по неосторожности водителя на железнодорожный переезд транспортным средством. В статье рассмотрены способы минимизации потерь от такого вида аварий. Ими могут быть постройка тоннелей и путепроводов в местах пересечения железнодорожного полотна и автомобильной дороги, применение 3D-лазерного радара для предупреждения локомотивной бригады о застрявшем транспорте. Кроме того, возможно использование веб-камер, изображение с которых при помощи роутера, установленного за 4-5 км от переезда, передается в кабину машиниста на отдельный дисплей, чтобы заранее увидеть застрявшее транспортное средство и было время принять меры по экстренному торможению

Canadians Should Travel Randomly

We study online algorithms for the Canadian Traveller Problem (CTP) introduced by Papadimitriou and Yannakakis in 1991. In this problem, a traveller knows the entire road network in advance, and wishes to travel as quickly as possible from a source vertex s to a destination vertex t, but discovers online that some roads are blocked (e.g., by snow) once reaching them. It is PSPACE-complete to achieve a bounded competitive ratio for this problem. Furthermore, if at most k roads can be blocked, then the optimal competitive ratio for a deterministic online algorithm is 2k + 1, while the only randomized result known is a lower bound of k + 1. In this paper, we show for the first time that a polynomial time randomized algorithm can beat the best deterministic algorithms, surpassing the 2k + 1 lower bound by an o(1) factor. Moreover, we prove the randomized algorithm achieving a competitive ratio of (1 + [√2 over 2])k + 1 in pseudo-polynomial time. The proposed techniques can also be applied to implicitly represent multiple near-shortest s-t paths.NSC Grant 102-2221-E-007-075-MY3Japan Society for the Promotion of Science (KAKENHI 23240002

Quantum Diffusion and Eigenfunction Delocalization in a Random Band Matrix Model

We consider Hermitian and symmetric random band matrices $H$ in $d \geq 1$ dimensions. The matrix elements $H_{xy}$, indexed by $x,y \in \Lambda \subset \Z^d$, are independent, uniformly distributed random variables if \abs{x-y} is less than the band width $W$, and zero otherwise. We prove that the time evolution of a quantum particle subject to the Hamiltonian $H$ is diffusive on time scales $t\ll W^{d/3}$. We also show that the localization length of an arbitrarily large majority of the eigenvectors is larger than a factor $W^{d/6}$ times the band width. All results are uniform in the size \abs{\Lambda} of the matrix.Comment: Minor corrections, Sections 4 and 11 update