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2022 ◽  
Vol 9 ◽  
Ioanna Kyriakou ◽  
Dimitris Emfietzoglou ◽  
Sebastien Incerti

The development of accurate physics models that enable track structure simulations of electrons in liquid water medium over a wide energy range, from the eV to the MeV scale, is a subject of continuous efforts due to its importance (among other things) in theoretical studies of radiation quality for application in radiotherapy and radiation protection. A few years ago, the Geant4-DNA very low-energy extension of the Geant4 Monte Carlo code had offered to users an improved set of physics models for discrete electron transport below 10 keV. In this work we present refinements to this model set and its extension to energies up to 1 MeV. Preliminary comparisons against the existing Geant4-DNA physics models with respect to total and differential ionization cross sections of electrons in liquid water are reported and discussed.

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8545
Patrik Kovář ◽  
Adam Tater ◽  
Pavel Mačák ◽  
Tomáš Vampola

This work investigates loss model sets based on empirical loss correlations for subsonic centrifugal compressors. These loss models in combination with off-design performance prediction algorithms make up an essential tool in predicting off-design behaviour of turbomachines. This is important since turbomachines rarely work under design conditions. This study employs an off-design performance prediction algorithm based on an iterative process from Galvas. Modelling of ten different loss mechanisms and physical phenomena is involved in this approach and is thoroughly described in this work. Geometries of two subsonic compressors were reconstructed and used in the evaluation of individual loss correlations in order to obtain a suitable loss model. Results of these variations are compared to experimental data. In addition, 4608 loss model sets were created by taking all possible combinations of individual loss estimations from which three promising candidates were selected for further investigation. Finally, off-design performance of both centrifugal compressors was computed. These results were compared to experimental data and to other loss model sets from literature. The newly composed loss model set No. 2137 approximates experimental data over a 21.2% better in relative error than the recent Zhang set and nearly a 36.7% better than the outdated Oh’s set. Therefore, set No. 2137 may contribute to higher precision of centrifugal turbomachines’ off-design predictions in the upcoming research.

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Xiuxiang Chi ◽  
Liguo Liu

With the overall weakening of the macroeconomic situation, the investment growth in Beijing-Tianjin-Hebei continued to slow down. This article focuses on the reform and innovation of investment and financing models in the vertical and horizontal collaborative construction of Beijing-Tianjin-Hebei infrastructure. Under the framework of the PPP model, this article discusses how to design a market-oriented platform of infrastructure investment and financing model, introduce and use private capital, build remote capital access and exit mechanism, measure the government’s financial capacity and financial risks in the PPP model, set up PPP institutions, and improve relevant laws and regulations to make the infrastructure construction and operation more efficient, thus promoting the coordinated development of infrastructure construction in the Beijing-Tianjin-Hebei region.


Abstract In this paper we study the existence of higher dimensional arithmetic progressions in Meyer sets. We show that the case when the ratios are linearly dependent over ${\mathbb Z}$ is trivial and focus on arithmetic progressions for which the ratios are linearly independent. Given a Meyer set $\Lambda $ and a fully Euclidean model set with the property that finitely many translates of cover $\Lambda $ , we prove that we can find higher dimensional arithmetic progressions of arbitrary length with k linearly independent ratios in $\Lambda $ if and only if k is at most the rank of the ${\mathbb Z}$ -module generated by . We use this result to characterize the Meyer sets that are subsets of fully Euclidean model sets.

2021 ◽  
pp. 155-160 ◽  

We describe a necessary stage in preparing the frontal approach of designing specialized applications. Such applications enable services dedicated to assisting the learning process (CAE). Therefore, our topic is dedicated to services, which assist the learning process. The novelty of the approach consists in the cybernetic analysis of the role and possible ways of working under conditions in which features of a set of automatic systems that work autonomously for each individual student and/or in an integrated manner for the training group, are considered the determinant process. This process is derived from the software dedicated to computer-assisted education. The preparation stage led to introducing a reticular structure of action, with multiple argumentations, in which some of the principles of traditional school were discussed. The model set of requirements enabled to introduce the design steps for developing the automation the learning process.

2021 ◽  
Vol 2 (3) ◽  
pp. 149-169
Daniel Pérez del Prado

Decentralisation of collective bargaining has been one of the key trends concerning labour market regulation of the last decades. Most of European countries have developed – with different breath and scope – procedures and reforms to strengthen the company level of bargaining. The Great Recession has stressed this orientation, particularly in those countries which were under financial pressure. This paper focuses on the cases of four Mediterranean countries – France, Italy, Spain, and Portugal – in order to assess how decentralisation has been carried out and, most importantly, what kind of practical results have been achieved. On the base of these outcomes, it highlights how the debate concerning the structure ofcollective bargaining is changing from a black or white perspective to a new one in which mixed models are possible if the whole system is coordinated, taking into consideration the type of collective bargaining model set in the country.  

2021 ◽  
Vol 2121 (1) ◽  
pp. 012004
Weijie Du ◽  
Miao Yu ◽  
Jinglin Li ◽  
Shouzhi Zhang ◽  
Jingxuan Hu

Abstract Identification and control are important problems of closed-loop power system. At present, most studies are separate identification methods. This paper studies an online and real-time integrated identification method, which can solve the problems of model set and controller design of closed-loop power system. This paper investigates a new iterative identification algorithm and its convergence problem of closed-loop power system based on ambient signals. Firstly, the whole algorithm procedure is given. This algorithm uses the iterative process under the closed-loop condition, which combines system model identification with controller design. Then the complementary of model identification and control design has been realized. Secondly, because of the dynamic performance of the iterative identification algorithm, it has characteristics described from the perspective of a partitioned dynamic system. Regard each iterative identification step as a state node. In this situation, the algorithm guarantees all the state nodes converge to the Lyapunov stable equilibrium. Finally, the simulation results show the correctness and effectiveness of the proposed method through the simulation of a power system with four-machine-two-region.

2021 ◽  
Ding Ding ◽  
Xinyue Liu ◽  
Haoran Xu

University students’ stress management is a core topic in educational research; however, limited research has ever focused on how personality would impact students’ perception of stress level. Thereby, this quantitative study, based on the Big Five Personality Trait Model, set out to investigates how openness, conscientiousness, extraversion, agreeableness, and neuroticism affect the college students’ perception of their study stress. As a result of a survey with sixty college students in China, it is found that whilst students’ demographic factors may not significantly predict their stress level, psychographic factors including conscientiousness, agreeableness and neuroticism can positively and significantly determine the college students’ perception of stress. Based on the findings of the study, implications for future students’ mental health management and ensuing educational research are put forward.

Minghui Wu ◽  
Canghong Jin ◽  
Wenkang Hu ◽  
Yabo Chen

Understanding mathematical topics is important for both educators and students to capture latent concepts of questions, evaluate study performance, and recommend content in online learning systems. Compared to traditional text classification, mathematical topic classification has several main challenges: (1) the length of mathematical questions is relatively short; (2) there are various representations of the same mathematical concept(i.e., calculations and application); (3) the content of question is complex including algebra, geometry, and calculus. In order to overcome these problems, we propose a framework that combines content tokens and mathematical knowledge concepts in whole procedures. We embed entities from mathematics knowledge graphs, integrate entities into tokens in a masked language model, set up semantic similarity-based tasks for next-sentence prediction, and fuse knowledge vectors and token vectors during the fine-tuning procedure. We also build a Chinese mathematical topic prediction dataset consisting of more than 70,000 mathematical questions with topics. Our experiments using real data demonstrate that our knowledge graph-based mathematical topic prediction model outperforms other state-of-the-art methods.

James J. Walton ◽  
Michael F. Whittaker

Abstract We present a single, connected tile which can tile the plane but only nonperiodically. The tile is hexagonal with edge markings, which impose simple rules as to how adjacent tiles are allowed to meet across edges. The first of these rules is a standard matching rule, that certain decorations match across edges. The second condition is a new type of matching rule, which allows tiles to meet only when certain decorations in a particular orientation are given the opposite charge. This forces the tiles to form a hierarchy of triangles, following a central idea of the Socolar–Taylor tilings. However, the new edge-to-edge orientational matching rule forces this structure in a very different way, which allows for a surprisingly simple proof of aperiodicity. We show that the hull of all tilings satisfying our rules is uniquely ergodic and that almost all tilings in the hull belong to a minimal core of tilings generated by substitution. Identifying tilings which are charge-flips of each other, these tilings are shown to have pure point dynamical spectrum and a regular model set structure.

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