bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of ethnic tourism in poverty and drug deduction (the case study of Chiangrai Province, Thailand)
Authors: Sitikarn Bussaba
Published: July 2021

Despite significant economic growth in Thailand, in northern Thailand in particular, a growing number of indigenous communities have been turning to tourism as an alternative to expanding their commercial agriculture. However, in recent years, tourism resources have begun to deteriorate both culturally and environmentally in addition to problem of poverty. Thus, a growing gap between rich and poor, inadequate attention to the special needs of ethnic minorities, gender inequities and lack of access to basic health and education are significant problems. This paper presents the ethnic minorities’ context and their demands on tourism development as well as the key players’ roles and interests effecting on ethnic tourism promotion. The paper concluded with key issues for an achievement of creative ethnic tourism promotion in Chiang Rai Province.
Transformation of essential approaches to the semantics of the relationship between recreation and tourism
Authors: Vasilieva Anastasia
Published: July 2021

The paper examines the process of transformation of scientific and scientific-organizational approaches to the semantics of the relationship between recreation and tourism. There is no well-established terminological apparatus for the determination of phenomena, processes and relations in the sphere of human life, which are described with such definitions as “recreation”, “tourism”, “tourist activity”, “recreational system”, “recreational activity”, etc. in everyday communication and in Russian literature. In turn, to manage such a regional economic subsystem as a recreational one, it is important to present its structure and relations between its spatially distributed elements within a certain conceptual framework. The result of the analysis and comparison of the approaches of different groups of scientists and regulations to the definition and content of the concepts of “tourism” and “recreation” was the opportunity to draw several conclusions: recreational activities are a meaningful basis for the development of many types of tourism; separate recreational activities are not tourism; some types of tourism (business, shopping tourism, etc.) are not based on recreational activities; both residents and non-residents of the regional recreational subsystem use its recreational services; the concepts of tourism and recreation and their derivatives are not identical, they intersect and complement each other in the economic dimension.
Foreign labor migration control in Russian regions using multicultural barometer (by the example of the Republic of Karelia)
Authors: Pitukhina Maria , Tolstoguzov Oleg , Kulakova Lyubov , Pitukhin Eugene , Radikov Ivan
Published: July 2021

The article deals with foreign labor migration flows control as well as migration monitoring which are important for the Russian Federation regions’economy development. A new migration monitoring toolkit is proposed by the authors - Multicultural Barometer. It allows to quantify migration indicators in a region from 4 various angles: labor market; national identity; migrants’ adaptation; migrants’integration. The research data is coming from open sources (Kareliastat, Federal Migration Service of the Republic of Karelia, Ministry of Labor and Employment of the Republic of Karelia, data obtained from Centers for Interethnic Cooperation in Karelian municipalities); both migrants’ pilot survey and host community survey organized in 18 municipalities of the Republic of Karelia. The study conducted in Karelia seems to be important in a context of its geographical location (on a border with Finland) highlighting both successful practices and developing new tools for migration monitoring aimed at scientifically based solutions for migration control. Multicultural barometer as a tool was recommended by the Federal Agency on Ethnic Issues of Russia (FADN) and Strategic Initiatives Agency in 2017 as best regional practice for further implementation all over the Russian Federation.
Development of green environmental: policy in education
Authors: Sarbassova Saule , Abdugalina Sairan , Burganova Roza , Shaikheslyamova Kazna , Abdrasheva Banugul , Jamaliyeva Gaziza
Published: July 2021

The need to overcome the environmental problems of our time has set a task for pedagogical theory and practice: on the basis of the biosphere approach, to prepare an environmentally literate person who understands the importance of life as the highest value, who is able to determine his place in the world, participate in environmental protection, rationally use natural resources, make conscious decisions in the spheres of life where the interests of man as a living being, society and the environment overlap. In the system of training an environmentally literate person, an important role belongs to educational organizations of all levels, which can be considered as the initial link in enriching a person with knowledge about the natural and social environment, familiarizing him with a holistic picture of the world and forming a scientifically grounded, humane attitude towards society. Environmental education is designed to provide the young generation with scientific knowledge about the relationship between nature and society, to help understand the multifaceted significance of nature for society in general and for each person in particular, to form an understanding that nature is the primary basis of human existence, and man is a part of nature, to educate a conscious attitude towards it, a sense of responsibility for the environment as a universal value, develop creative activities to protect and transform the environment, cultivate love for nature. Environmental education and upbringing is a systematic pedagogical activity that is aimed at developing the environmental culture of a person. Environmental education of a person is a continuous process of learning and development throughout his life, which is expressed in the formation of an ecological culture, which manifests itself in an emotional and positive attitude towards nature, in compliance with certain moral norms, in a system of value orientations.
Necessity and problems of formation of mechanisms of environmental and economic development of the regional industrial complex
Authors: Geieva Larisa , Israilova Yaha , Khatsieva Larisa , Yakubov Timur
Published: July 2021

The paper assesses the rationality of creating mechanisms for state regulation of investment activities at the level of regional government, in particular using the example of the Chechen Republic, as well as the dynamics of changes in the degree of attractiveness of the investment climate in the region, and the share of investments directed to environmental protection and rational use of natural resources. The need to form mechanisms of state regulation that ensure the sustainable development of industrial complexes on the territory of Russia and its regions, in particular the Chechen Republic, is currently based on the requirements of the Constitution of the Russian Federation.
Problems of competitiveness of industries in ensuring the economic security of Russia
Authors: Mottaeva Angela , Kopteva Ludmila
Published: July 2021

The dynamics of the development of the domestic industrial complex shows significant changes in the organization and management of enterprises in recent years. Undoubtedly, global changes in industrial technologies in developed countries have had a significant impact, taking into account digital transformation, intelligent automation and artificial intelligence. In the present conditions, the Russian industrial complex faces a difficult task-to find the necessary resources to improve its own industrial production and thus maintain the ability to compete with foreign manufacturers. The resolution of this issue is complicated by the weakening Russian economy crisis and the growing sanctions pressure from Western partners against the background of a reduced to a minimum investment inflow. The imposed sanctions packages against the Russian economy not only hinder foreign investors, but also act as obstacles to the supply of modern technologies and high-tech industrial equipment to our country, as well as reduce opportunities for organizing cooperation between foreign and domestic developers. In fact, the goals of such sanctions are considered to be the maximum isolation of Russia’s industrial and economic systems for the gradual weakening of our country’s economy.
Waste-free stores in Russia: a retrospective analysis, criticism, and analysis of the visitor’s attitude
Authors: Ikramov Ruslan , Mityashin Gleb , Bakharev Vladimir
Published: July 2021

The paper presents a retrospective analysis of the concept of waste-free stores in Russia. The main feature of a waste-free store is described: the need to use reusable containers for purchases. The advantages and disadvantages of waste-free stores for visitors and operators are presented in the form of a 2x2 strategic table. The impact of the pandemic on their activities is further discussed. It is recommended to change the service model from self-service to over-the-counter trading during the pandemic. Using the example of the “B12 Zero Waste” store, the possibility of creating a waste-free online store is considered. Actions that reduce the cost of creating a web representation and organizing delivery were discussed. It is emphasized that an online store is necessary for any commercial enterprise in the current conditions. It is noted that the integration of the two most relevant trends in retail (e-commerce and greening) can be a real breakthrough. The authors point out that waste-free stores simultaneously reduce the amount of discarded packaging, but significantly increase the cost of detergents and fresh water, so the waste-free concept cannot be called completely eco-friendly. The survey revealed that in Russia, most visitors have a positive attitude to the waste-free model of the store. Depending on the factors that motivate customers to make a purchase, a waste-free store can be divided into two groups: environmentally responsible and economical.
Theoretical modeling of the logical-procedural system organizations of the history of society
Authors: Bakhtin Maxim , Rybakov Nikolay , Yarmolich Natalya , Sokolovskaya Irina
Published: July 2021

This article focuses on the metaphysical foundations of educational philosophy. They are considered as the sources of future human modeling and the commission of certain actions. The article explores the evolution of these principles in the development of human civilization. The causality principle is considered as the entity's fundamental ontological characteristic. It suggests that a human being can realize his desire for freedom only by submitting his life to the universal objective law. In the causal perspective, any phenomenon is considered as the consequence of a cause and at the same time as the cause of some other consequence. The model of the world of primitive man could not and did not contain a picture of nature as a certain arrangement of phenomena, united by unified cause-and-effect laws. However, it does not mean that our primitive ancestors did not imagine the world around them without the categories of order, just in his mind, there was a different order.
Valorization on the energy potential of Pistia stratiotes in sustainable agriculture-review
Authors: Matache Andreea , Vanghele Nicoleta Alexandra , Matache Mihai Gabriel , Petre Ancuța Alexandra
Published: July 2021

Of late years, aquatic plants have received increased attention due to their energy potential in sustainable agriculture.Pistia stratiotesalso belongs to this category. A vital aspect in sustainable agriculture, to which there is a growing tendency, is the use of environmentally friendly methods. Aquatic plants are used as raw materials for various applications, such as food industry, health, agriculture and aquaculture, ecosystem management, being an essential renewable resource. Due to population growth, both developed and developing countries are mainly facing problems related to future energy security and the proper use of natural resources. As the search for renewable energy resource intensifies, there is a growing drive to identify and develop promising, environmentally friendly, low-carbon and low-carbon bioenergy raw materials. Fuel demand is rising, while food costs and waste are gradually rising. It is therefore necessary to address waste management and reduce pollution caused by excessive energy use and industrialization. The current study focuses on the potential for harnessing renewable energy in the Nile lettuce (Pistia stratiotes), namely, highlighting the process of residual biomass, biofuel and compost.
Investigation of the thermodynamic and physicochemical properties of lavender oil (Lavandula angustifoliaMill.)-ethanol-water system
Authors: Gandova Vanya , Tasheva Stanislava , Prodanova-Stefanova Vanya , Dobreva Krasimira , Dincheva Ivayla , Stoyanova Albena
Published: July 2021

The thermodynamic and physicochemical properties of lavender oil (Lavandula angustifoliaMill.)-ethanol-water system were measured. The chemical composition of solutions of the lavender oil in 70%, 75%, 80%, 85%, 90%, and 95% ethanol was determined using GC/MS analysis. The main compounds in the solutions are oxygenated monoterpenes (β-linalool, terpinen-4-ol,α-terpineol, and linalyl acetate), followed by monoterpene hydrocarbons ((Z)-β-ocimene and (E)-β-ocimene), and sesquiterpene hydrocarbons (β-caryophyllene and (E)-β-farnesene). The ternary phase diagrams were constructed. By multiply linear regression model for surface tension prediction was applied. The thermodynamic and kinetic parameters of lavender oil – ethanol - water system were calculated (energy of Gibb’s, enthalpy, entropy, energy of activation, and coefficient of diffusion).
Archimedean screw as fish-friendly turbines for harnessing hydropower potential
Authors: Purece Cristian , Corlan Lilica
Published: July 2021

Hydraulic energy is one of the most important sources of renewable energy today. It is also a complementary source to other renewable energy sources, being the only one that offers an important nonpolluting storage capacity (through pump storage facilities). Another essential quality of hydraulic energy is its ability to regulate the energy system to allow the integration of other sources, in which the process of generating energy depends on factors that cannot be controlled (sun, wind, etc.). However, hydropower plants can damage ecosystems, especially by affecting fish within their turbines. Usually, fish cannot pass unharmed through most of the turbines. The main exceptions generally include some low head (below 8 m) turbines, such as the Very Low Head (VLH) turbine and the screw turbine, but lately strategies have also been developed for high head hydropower plants such as: fish passage facilities and fish friendly turbines such as Alden turbine, Minimal Gap Runner turbine (MGR). However, this article only deals with screw-type turbines, low-head fish-friendly turbines and how to implement them in order to obtain sustainable green energy.
Pollutants resulting from intensive poultry farming activities and their impact on the environment
Authors: Mitroi Roxana , Stoian Oana , Covaliu Cristina Ileana , Manea Dragoş
Published: July 2021

Poultry farming activities can have a negative impact on the environment, namely: acidification (with NH3 mainly, H2S, NOx etc.); pollution of surface water and groundwater (with NO3- and NH4+); eutrophication (N, P); air pollution with NH3, N2O, NO, dust (PM10 and PM2.5), bioaerosols; increasing the greenhouse effect (CO2, CH4, N2O etc); drying (use of groundwater); smells, noise; pollution with heavy metals, pesticides and toxic substances; the spread of pathogens that are resistant to antibiotics; pollution of waters with residues of pharmaceutical products. As a result, in order to prevent or reduce the negative impact on the environment, in the production process it is necessary to use BREF/BAT techniques (Best Available Techniques). The activity of poultry farming must be done according to the best available techniques: the farming system, production halls and related facilities are designed and built according to the latest standards in the field; implicitly the consumption of raw materials, waste emissions, wastewater, air pollutants values being according to the legislation [1].
Studies and research on the tribological behavior of the braking systems of vehicles. Review
Authors: Cristescu Andreea-Catalina , Filip Ilie , Ipate George , Voicu Gheorghe , Stefan Vasilica
Published: July 2021

Given the current context and the advanced stage of technology, which the braking systems of vehicles have reached, the main purpose of the studies and research is focused on presenting the main tribological aspects that contribute at improving the performance of braking systems, in order to ensure the vehicles’ safety and stability at braking, in any conditions. The performance of the braking system is a key factor for both producers and vehicle passengers, due to safety requirements, everincreasing. Thus, over time, numerous studies and research have been carried on in order to improve the performance of the braking system. In this paper are studied tribological phenomena through those, which contribute to the improvement of the braking system as performance, safety and stability.
Estimation of the stress state of agricultural harrows with vertical axis rotor, using mathematical models with finite elements
Authors: Iordache Valentin Cornel , Saracin Ion
Published: July 2021

In this paper we simulated through mathematical models the interaction between the agricultural harrow with vertical rotor (equipped with 4 boxes per rotor) and soil. Due to the large or even very large number of mathematical models that can be developed and can receive a solution using the finite element method, there are also many new possibilities to approach and improve some already developed models. The most important benefits of using finite element modeling are: increasing the quality of projects by checking the resistance, noticing dangerous vibration problems, remedying deficiencies reported in the testing of experimental models or even in operation. Normal optimization aims to reduce material consumption, its own vibration spectrum or other mechanical qualities.By using mathematical methods, a resistance check of the subassemblies of the working member (knife), connected to the action device, is obtained.
Electronic system for control of temperature of exhaust gases and pressure in turbochargers of diesel automobile engines
Authors: Kadirova Seher , Okishelov Stiliyan , Kolev Zhivko
Published: July 2021

The paper presents design and experimental investigation of an electronic system for control of the temperature of exhaust gases and the turbocharging air pressure in turbochargers of diesel automobile engines. The existing problems are faults in the fuel system of an engine. The indicators are changes in the values of the temperature and pressure in exact areas of the turbocharger. The presented device is a controller that monitors precisely the temperature and pressure, which are so vital for the long operation of the automobile. The control system is based on Arduino microcontroller. OLED Display has been added to visualize the obtained results. A schematic diagram of an electronic module for control of the temperature of exhaust gases and turbocharging air pressure in turbochargers of diesel automobile engines has been synthesized. The system has been investigated in laboratory conditions and practically implemented in a real automobile. As a result of laboratory experimental investigation, results were obtained for the time-monitored parameters temperature of the exhaust gases and turbocharging air pressure in the turbocharger system of a diesel automobile engine.
Miroirs temporels instantanés : une nouvelle approche du retournement temporel
Authors: Eddi Antonin , Fort Emmanuel
Published: July 2021

Peut-on faire revivre à une onde sa vie passée ? Ce problème a été largement étudié, en particulier au moyen de miroirs à retournement temporel digitaux utilisant des ordinateurs pour effectuer l’opération.

Récemment, en nous appuyant sur les symétries entre temps et espace, nous avons introduit le concept de miroir temporel instantané basé sur une brusque modification des propriétés du milieu. Nous avons testé expérimentalement ce nouveau type de retournement temporel à l’aide d’ondes de surface dans des liquides et montré l’efficacité d’un tel procédé.

Cette approche nous a également permis de revisiter les miroirs à conjugaison de phase.
A conjecture on a continuous optimization model for the Golomb Ruler Problem
Authors: Duxbury Phil , Lavor Carlile , de Salles-Neto Luiz Leduino
Published: July 2021

A Golomb Ruler (GR) is a set of integer marks along an imaginary ruler such that all the distances of the marks are different. Computing a GR of minimum length is associated to many applications (from astronomy to information theory). Although not yet demonstrated to be NP-hard, the problem is computationally very challenging. This brief note proposes a new continuous optimization model for the problem and, based on a given theoretical result and some computational experiments, we conjecture that an optimal solution of this model is also a solution to an associated GR of minimum length.
Designing a new mathematical model based on ABC analysis for inventory control problem: A real case study
Authors: Abdolazimi Omid , Shishebori Davood , Goodarzian Fariba , Ghasemi Peiman , Appolloni Andrea
Published: July 2021

In modern business today, organizations that hold large numbers of inventory items, do not find it economical to make policies for the management of individual inventory items. Managers, thus, need to classify these items according to their importance and fit each item to a certain asset class. The method of grouping and inventory control available in traditional ABC has several disadvantages. These shortcomings have led to the development of an optimization model in the present study to improve the grouping and inventory control decisions in ABC. Moreover, it simultaneously optimizes the existing business relationships among revenue, investment in inventory and customer satisfaction (through service levels) as well as a company’s budget for inventory costs. In this paper, a mathematical model is presented to classify inventory items, taking into account significant profit and cost reduction indices. The model has an objective function to maximize the net profit of items in stock. Limitations such as budget even inventory shortages are taken into account too. The mathematical model is solved by the Benders decomposition and the Lagrange relaxation algorithms. Then, the results of the two solutions are compared. The TOPSIS technique and statistical tests are used to evaluate and compare the proposed solutions with one another and to choose the best one. Subsequently, several sensitivity analyses are performed on the model, which helps inventory control managers determine the effect of inventory management costs on optimal decision making and item grouping. Finally, according to the results of evaluating the efficiency of the proposed model and the solution method, a real-world case study is conducted on the ceramic tile industry. Based on the proposed approach, several managerial perspectives are gained on optimal inventory grouping and item control strategies.
Who Called Team Europe? The European Union’s Development Policy Response During the First Wave of COVID-19
Authors: Burni Aline , Erforth Benedikt , Friesen Ina , Hackenesch Christine , Hoegl Maximilian , Keijzer Niels
Published: July 2021

The COVID-19 pandemic is a critical juncture for global development. Under the label of “Team Europe”, the EU has sought to mobilize rapid development assistance to support partners in addressing the impacts of the crisis, while promoting joined-up approaches among European actors to assert itself in a changing and competitive geopolitical context. This article assesses how substantive and process-oriented EU development policy norms are reflected in the Union’s global COVID-19 response. Focusing on the EU’s response during the first wave of the COVID-19 pandemic in the first half of 2020, the article shows that the EU’s response to this extraordinary crisis consisted of a deepening of EU integration. In so doing, the EU emphasized process-oriented over substantive norms in its development policy.
Observation of synergy between lower hybrid waves at two frequencies in EAST
Authors: Choi W. , Poli F. M. , Li M. H. , Baek S. G. , Gorenlenkova M. , Ding B. J. , Gong X. Z. , Chan A. , Duan Y. M. , Hu J. H. , Lian H. , Lin S. Y. , Liu H. Q. , Qian J. P. , Wallace G. , Wang Y. M. , Zang Q. , Zhao H. L.
Published: July 2021

Synergistic effects between two frequencies of lower hybrid (LH) waves—operating at 2.45 and 4.6 GHz—were observed in experiment on EAST for the first time. At low density (ne,lin≈2.0×1019 m−3), simultaneous injection of a 65/35 mix of 2.45/4.6 GHz power achieved an lower hybrid current drive efficiency that was 25% higher than what should be expected from the linear combination of the two sources. The experiment was interpreted with time-dependent simulations, using the equilibrium and transport solver TRANSP, coupled with the ray-tracing code GENRAY and the Fokker–Planck solver CQL3D. For each discharge, profiles of current and hard x-rays from simulation and measurement agree within uncertainties. An examination of the electron distribution function indicates that the LH synergy is supported by the increased width of the LH resonance plateau in the simultaneous injection case compared to independent injection.
Metallization of ZnSb and contact resistance
Authors: Song X. , Riis H. , Prytz Ø. , Finstad T. G.
Published: July 2021

We present results on electrical resistance of metal contacts to ZnSb. We synthesized the thermoelectric semiconductor ZnSb with specific doping concentrations by adding Cu as an acceptor to the melt, followed by solidification, crushing, ball-milling, hot-pressing, sawing, and polishing yielding wafers suitable for substrates for further processing. Many batches were made yielding different doping concentrations. We defined transmission line geometries in deposited metal films for specific contact resistance measurements. We prepared sets of Cu, Ti, and Ni films, respectively. We measured the contact resistance vs annealing temperatures. For Cu/ZnSb samples, we observed a specific contact resistance from 5 × 10−7 to 4 × 10−5 Ω cm2. We also measured the carrier concentration of ZnSb. The measurement data of the specific contact resistance had systematic dependence on doping concentration and annealing temperature and were analyzed by a model incorporating different transport mechanisms across the energy barrier at the metal–semiconductor interface. The data were discussed in terms of systematic variation in barrier height and density of states effective mass. We proposed these arising as a consequence of interactions at the interface and a nonparabolic valence band. We have also monitored the interface of the ZnSb substrate and metal films with transmission electron microscopy.
Strain engineering in metal halide perovskite materials and devices: Influence on stability and optoelectronic properties
Authors: Wang Mengru , Ni Zhenyi , Xiao Xun , Zhou Ying , Huang Jinsong
Published: July 2021

Metal halide perovskites (MHPs) have been extensively studied for their promising applications in solar cells and other devices due to their extraordinary optoelectronic properties, low cost, and easy fabrication by versatile processes. Different from bulk crystals grown from solutions, polycrystalline perovskite films deposited on substrates generally are strained due to multiple mechanisms, which significantly impact their optoelectronic properties, defect physics, and photostability. The fabrication and operation of perovskite solar panels inevitably introduce strains in perovskite. Strain has been broadly applied to stabilize the photoactive phase of several perovskite compositions that would otherwise show a thermodynamically stable photoinactive phase at room temperature. There is increasing research on strain engineering of MHPs to enhance device performance. However, a systematic review and understanding of strain engineering in MHP is still lacking. Herein, an overview of strain engineering on MHP materials and solar cells is provided. In this review, we start with a general review on strain in semiconductors, including the characteristics of strain, characterization techniques, and the effects of strain on the lattice structure, electronic, and optical properties of semiconductors. We then summarize progress in understanding the generation of strain categorized by local and global strains and their impacts on the multi-faceted properties of MHPs, including phase stability, photostability, and other optoelectronic properties. Both positive and negative impacts have been observed on these properties. Strain engineering has shown to be promising in making much more efficient and stable perovskite solar cells.
Analytic models for interdiffusion in dense plasma mixtures
Authors: Stanek Lucas J. , Murillo Michael S.
Published: July 2021

The characteristics of atomic-scale mixing are determined by diffusive processes driven by gradients. One such process is interdiffusion, a process driven by density gradients. We consider the various options for formulating interdiffusion in terms of Green–Kubo autocorrelation functions and the thermodynamic factor. Through models for the direct correlation function, we generalize expressions for the thermodynamic factor to include different electron and ion temperatures, electron degeneracy, finite-temperature exchange, and strong coupling. Additionally, a Gaussian autocorrelation function (GAF) is employed for a binary ionic mixture, yielding a simple analytic transport model for interdiffusion. The GAF model is shown to be accurate for moderately and strongly coupled plasmas.
Reduced order model using convolutional auto-encoder with self-attention
Authors: Wu Pin , Gong Siquan , Pan Kaikai , Qiu Feng , Feng Weibing , Pain Christopher
Published: July 2021

In this paper, a novel reduced order model based on a convolutional auto-encoder with self-attention (SACAE ROM) is proposed. The proposed model is a non-intrusive reduced order model, which uses a convolutional neural network and a long short-term memory network to extract temporal feature relationships from high-fidelity numerical solutions. The self-attention is introduced into the convolutional neural network to enhance the non-local information perception ability of the convolutional neural network and improve the feature extraction ability of the network. The model adopts a joint construction method, which overcomes the problem of propagating error in each process of the model. The model proposed in this paper has been verified on the problem of the flow around a cylinder. The experimental results indicate that the SACAE ROM has higher robustness and accuracy. Compared with the ROM based on a convolutional auto-encoder, the prediction error of the SACAE ROM is reduced by 42.9%. As with other ROMs based on deep neural networks, the SACAE ROM takes a long time to train. To solve this problem, the transfer and generalization ability of the model is studied in this paper. In the experiment, the flow velocity and spoiler of the flow around the cylinder were changed, and the training time of the transfer model was reduced by about 50% to 60%. This result demonstrates that the problem of too long training time can be solved by transfer learning.
Short-wavelength soliton in ultrarelativistic electron–positron–ion plasmas
Authors: Lashkin V. M.
Published: July 2021

We derive a nonlinear equation governing dynamics of short-wavelength longitudinal waves in ultrarelativistic electron–positron–ion plasmas. In contrast to the recent work by Lashkin [Phys. Plasmas 27, 102302 (2020)], where a similar equation was suggested in the framework of the Wigner function approach for a nonrelativistic electron–ion degenerate plasma, in our case which is based on the Vlasov kinetic equation, all three species of particles (electrons, positrons, and ions) should be present. The nonlinearity arises only in the presence of a population of ions. By numerical simulations, we demonstrate that collisions between even four solitons are fully elastic.
Study of quasi-particle dynamics using the optical pulse response of a superconducting resonator
Authors: Hu J. , He Q. , Yu F. , Chen Y. , Dai M. , Guan H. , Ouyang P. , Han J. , Liu C. , Dai X. , Mai Z. , Liu X. , Zhang M. , Wei L. F. , Vissers M. R. , Gao J. , Wang Y.
Published: July 2021

We study the optical pulse response of a superconducting half-wavelength coplanar waveguide (CPW) resonator. We apply a short optical pulse to the center strip of the CPW resonator, where the current distribution shows antinodes or nodes for different resonance modes, and measure the frequency response. We develop a time-dependent variable inductance circuit model with which we can simulate the optical pulse response of the resonator. By fitting this model to experimental data, we extract the temporal kinetic inductance variations, which directly reflect the quasi-particle recombination with time and diffusion in space. We also retrieve the spatial size of the quasi-particle distribution and the quasi-particle diffusion constant. Our study is very useful for the design of photon-counting kinetic inductance detectors, and the method developed in this work provides a useful way to study the quasi-particle dynamics in the superconductor.
Enhanced resistance switching in ultrathin Ag/SrTiO3/(La,Sr)MnO3 memristors and their long-term plasticity for neuromorphic computing
Authors: Hu Haihua , Li Yuke , Yang Yihao , Lv Wenxin , Yu Han , Lu Wencai , Dong Yuehang , Wen Zheng
Published: July 2021

Neuromorphic computing is a promising candidate for next-generation information technologies. In the present work, we report the realization of long-term plasticity and synapse emulations in Ag/SrTiO3/(La,Sr)MnO3 memristors with the SrTiO3 active layers down to 3 unit cells (u.c.) in thickness. In the 3 u.c.-thick SrTiO3 device, efficient control of Ag+-ion migration gives rise to enhanced memristive properties with the conductance continuously modulated within a large memory window of ∼26 000% between an Ohmic low resistance state (LRS) and an electron-tunneling high resistance state (HRS). In addition, long-term plasticity of the Ag/SrTiO3/(La,Sr)MnO3 memristors is found to be dependent upon the resistance state. In the HRS, the devices exhibit excellent spike-timing-dependent plasticity characteristics with a large modulation of synaptic weight of ∼3500% and sensitive response to electrical stimuli of as low as ∼1.0 V and as fast as ∼0.01 ms. Adopting the spike-timing-dependent plasticity results as database, supervised learning simulations are demonstrated in the Ag/SrTiO3/(La,Sr)MnO3-based neural networks and a high accuracy rate of 95.5% is achieved for recognizing handwritten digits. These results provide more insights into the ionic migration at nanoscale for continuous resistance modulation and facilitate the design of ultrathin memristors for high-density 3D stacking artificial neural networks.
Comparison of conventional and Lorentz transmission electron microscopy in magnetic imaging of permanent magnets
Authors: Pierobon Leonardo , Schäublin Robin E. , Löffler Jörg F.
Published: July 2021

Magnetization structures in magnetic materials are usually imaged in dedicated Lorentz transmission electron microscopes. Compared to conventional transmission electron microscopes, the magnetic field of the objective lens at the sample is removed by replacing the objective lens with a Lorentz lens below the sample. While this modification is critical for soft-magnetic materials whose magnetic state is affected by the strong magnetic field of the objective lens, we propose that this is not necessary for permanent magnets such as Sm–Co and Nd–Fe–B. Conventional and Lorentz microscopes are compared for imaging divergent and convergent domain walls in a Sm(Co,Fe,Cu,Zr)7.7 magnet. Both techniques provide an almost identical resolution and accuracy in the measurement of the domain-wall width parameter using focal-series imaging of divergent domain walls. It is further demonstrated that both techniques can be utilized to analyze the intensity profile of convergent domain walls. From this, the product of sample thickness and magnetic induction is extracted. These results illustrate that conventional microscopes can be used to image the magnetic state of permanent magnets with a resolution comparable to dedicated Lorentz microscopes, which make magnetic imaging experiments significantly more accessible to a wider scientific community.
Highly efficient implementation of the analytical gradients of pseudospectral time-dependent density functional theory
Authors: Cao Yixiang , Halls Mathew D. , Friesner Richard A.
Published: July 2021

The accuracy and efficiency of time-dependent density functional theory (TDDFT) excited state gradient calculations using the pseudospectral method are presented. TDDFT excited state geometry optimizations of the G2 test set molecules, the organic fluorophores with large Stokes shifts, and the Pt-complexes show that the pseudospectral method gives average errors of 0.01–0.1 kcal/mol for the TDDFT excited state energy, 0.02–0.06 pm for the bond length, and 0.02–0.12° for the bond angle when compared to the results from conventional TDDFT. TDDFT gradient calculations of fullerenes (Cn, n up to 540) with the B3LYP functional and 6-31G** basis set show that the pseudospectral method provides 8- to 14-fold speedups in the total wall clock time over the conventional methods. The pseudospectral TDDFT gradient calculations with a diffuse basis set give higher speedups than the calculations for the same basis set without diffuse functions included.
Uncovering near-wall blood flow from sparse data with physics-informed neural networks
Authors: Arzani Amirhossein , Wang Jian-Xun , D'Souza Roshan M.
Published: July 2021

Near-wall blood flow and wall shear stress (WSS) regulate major forms of cardiovascular disease, yet they are challenging to quantify with high fidelity. Patient-specific computational and experimental measurement of WSS suffers from uncertainty, low resolution, and noise issues. Physics-informed neural networks (PINNs) provide a flexible deep learning framework to integrate mathematical equations governing blood flow with measurement data. By leveraging knowledge about the governing equations (herein, Navier–Stokes), PINN overcomes the large data requirement in deep learning. In this study, it was shown how PINN could be used to improve WSS quantification in diseased arterial flows. Specifically, blood flow problems where the inlet and outlet boundary conditions were not known were solved by assimilating very few measurement points. Uncertainty in boundary conditions is a common feature in patient-specific computational fluid dynamics models. It was shown that PINN could use sparse velocity measurements away from the wall to quantify WSS with very high accuracy even without full knowledge of the boundary conditions. Examples in idealized stenosis and aneurysm models were considered demonstrating how partial knowledge about the flow physics could be combined with partial measurements to obtain accurate near-wall blood flow data. The proposed hybrid data-driven and physics-based deep learning framework has high potential in transforming high-fidelity near-wall hemodynamics modeling in cardiovascular disease.
GaN nanorods on V-groove textured Si (111): significant light trapping for photoelectrocatalytic water splitting
Authors: Reddeppa Maddaka , Thota Chandrakalavathi , Nam Dong-Jin , Woo Hyeonseok , Kim Song-Gang , Kim Moon- Deock
Published: July 2021

Although gallium nitride (GaN) nanostructures are auspicious for photocatalytic activity, geometrical optimization has paid much attention for a significant light trapping in photoelectrochemical applications. To minimize the optical losses, we designed a prototype V-groove textured Si (100) with (111) facets, and GaN nanorods (NRs) were grown over a prototype substrate using plasma-assisted molecular beam epitaxy. The photocurrent density of V-groove textured GaN NRs in the NaOH electrolyte is found to be 801.62 μA/cm2 at 1.14 V vs reversible hydrogen electrode, which was 2.1-fold larger than that of GaN NRs on plain Si (111). Using this prototype V-groove textured Si(100) with (111) facets, a significant light can be trapped and modulated into GaN NRs. Furthermore, the heterostructure between GaN NRs and V-groove textured Si stimulates effective charge separation and transportation. These results represent an important forward step in solar photoelectrolysis.
Compressibility effects on hypersonic turbulent channel flow with cold walls
Authors: Yu Ming , Xu Chun-Xiao
Published: July 2021

Compressibility effects on velocity and temperature fluctuations in hypersonic turbulence over cold walls are investigated by exploiting a direct numerical simulation database. We found that the compressibility effects are enhanced by the decrease in wall temperature, which is directly reflected by the rapid increase in velocity divergence and turbulent Mach number. Helmholtz decomposition is adopted to evaluate the genuine compressibility effects by splitting the velocity fluctuation into a solenoidal component and a dilatational component. As the wall temperature decreases, the vertical motion is gradually dominated by the dilatational component, while the wall-parallel motions still by the solenoidal component. The dilatational components tend to decrease the skin friction by around 4%–6%. The instantaneous and conditionally averaged field around strong compressive motions further suggests that the dilatational structures behave as traveling-wave packets surrounded by vortex clusters. To improve the strong analogy between temperature and velocity fluctuations, their correlation in spectral space is studied. The results show that they are strongly correlated at the scales of energy-containing motions, but they are mutually independent at small scales.
Dipolar Poisson models in a dual view
Authors: Berthoumieux Hélène , Monet Geoffrey , Blossey Ralf
Published: July 2021

In this work, we study the continuum theories of dipolar-Poisson models. Both the standard dipolar-Poisson model and the dipolar-Poisson–Langevin model, which keeps the dipolar density fixed, are non-convex functionals of the scalar electrostatic potential ϕ. Applying the Legendre transform approach introduced by Maggs [Europhys. Lett. 98, 16012 (2012)], the dual functionals of these models are derived and are given by convex vector-field functionals of the dielectric displacement D and the polarization field P. We compare the convex functionals in P-space to the non-convex functionals in electric field E-space and apply them to the classic problem of the solvation of point-like ions. Since the dipolar-Poisson model does not properly describe polarization saturation, we argue that only the dipolar-Poisson–Langevin functional can be used to provide a nonlinear generalization of the harmonic polarization functional used in the theory of Marcus for the electron transfer rate to nonlinear regimes. We show that the model can be quantitatively parameterized by molecular dynamics simulations.
Electrochemistry from first-principles in the grand canonical ensemble
Authors: Bhandari Arihant , Peng Chao , Dziedzic Jacek , Anton Lucian , Owen John R. , Kramer Denis , Skylaris Chris-Kriton
Published: July 2021

Progress in electrochemical technologies, such as automotive batteries, supercapacitors, and fuel cells, depends greatly on developing improved charged interfaces between electrodes and electrolytes. The rational development of such interfaces can benefit from the atomistic understanding of the materials involved by first-principles quantum mechanical simulations with Density Functional Theory (DFT). However, such simulations are typically performed on the electrode surface in the absence of its electrolyte environment and at constant charge. We have developed a new hybrid computational method combining DFT and the Poisson–Boltzmann equation (P–BE) capable of simulating experimental electrochemistry under potential control in the presence of a solvent and an electrolyte. The charged electrode is represented quantum-mechanically via linear-scaling DFT, which can model nanoscale systems with thousands of atoms and is neutralized by a counter electrolyte charge via the solution of a modified P–BE. Our approach works with the total free energy of the combined multiscale system in a grand canonical ensemble of electrons subject to a constant electrochemical potential. It is calibrated with respect to the reduction potential of common reference electrodes, such as the standard hydrogen electrode and the Li metal electrode, which is used as a reference electrode in Li-ion batteries. Our new method can be used to predict electrochemical properties under constant potential, and we demonstrate this in exemplar simulations of the differential capacitance of few-layer graphene electrodes and the charging of a graphene electrode coupled to a Li metal electrode at different voltages.
On the theory of Biot-patchy-squirt mechanism for wave propagation in partially saturated double-porosity medium
Authors: Sun Weitao
Published: July 2021

Reservoir rocks have a coherent heterogeneous porous matrix saturated by multiple fluids. At long wavelength limit, the composite material of solid skeleton is usually regarded as homogeneous media. However, at grain scale or high loading rate, non-uniform fluid flow plays an essential role in wave dispersion and attenuation. Formulating wave propagation in partially saturated and fractured rocks is challenging and is of great interest in geoscience. Recent studies have shown that the mechanisms of wave attenuation caused by viscous dissipation, patchy-saturation, and squirt flow are different. However, the relationship among these mechanisms and the combined effect on wave attenuation are not clear. Here, a Biot-patchy-squirt (BIPS) model is proposed to characterize wave dispersion/attenuation in fractured poroelastic media saturated by immiscible fluids. BIPS model incorporates local fluid-interface flow (LFIF) and squirt flow into global fluid flow simultaneously. Theoretical analysis shows that BIPS is consistent with the Biot theory, squirt flow, and LFIF models, and is reduced to these models under extreme conditions. More interestingly, numerical simulations reveal that the existence of squirt flow partially counterbalances the dissipative effect of LFIF at the patch interface. The attenuation-frequency relationship observed in experiments capturing evidence of squirt flow and patchy-saturation interface flow is reproduced by using the BIPS model. The results show that BIPS model is computationally reliable and is in reasonably good agreement with laboratory data. The findings advance understanding of the physics of wave propagation in natural reservoir rocks and push forward the potential applications of the triple dispersion/attenuation mechanism to wave velocity prediction.
The coloured Tverberg theorem, extensions and new results
Authors: Jojić D. , Panina G. Yu. , Živaljević R.
Published: July 2021

We prove amultiple coloured Tverberg theoremand abalanced coloured Tverberg theorem, applying different methods, tools and ideas. The proof of the first theorem uses a multiple chessboard complex (as configuration space) and the Eilenberg–Krasnoselskii theory of degrees of equivariant maps for non-free group actions. The proof of the second result relies on the high connectivity of the configuration space, established by using discrete Morse theory.