bluuebunny/crossref_metadata_2025 huggingface dataset:
Urban sustainable development using qualimetry procedures of digital transformation
Authors: Voronin Dmitry , Kuznetsov Pavel , Evstigneev Vladislav
Published: July 2021

The use of information technologies to improve the efficiency of organizing the functioning of urban processes and the provision of innovative services forms the basis of the concept of smart sustainable city. Society mistakenly identify the digital transformation of the urban environment with the unsystematic, redundant introduction of technical innovations into the citizens’ life. This is because the changes made to the habitual processes of citizens' life often do not pass the mandatory check for their balance in terms of compliance with principles of sustainable development. The article proposes a new conceptual approach for assessing the effectiveness of the implemented solutions related to the implementation of the paradigm that ensures the transition from technology-oriented to human-oriented concept of “Sustainable Smart Cities”. The main idea is to consider the transformation of the urban environment through the prism of changes in the functional state of its objects.
Media Noise: the problem of hygienic rationing and personal well-being
Authors: Polyanina Alla
Published: July 2021

The article raises the problem of hygienic rationing of a special type of noise, the nature of which stems from the sources of public information – the mass media. The author develops a new concept of comprehending this type of noise – the concept of Media Noise. Such noise is associated with the special nature of its perception and consumption in the background mode that acts as a risk factor for human health and well-being. The author points out such specific characteristics of the media noise that relate it to certain risk factors, namely: hyperstimulation of the auditory analyzer and the inability to control its implementation (work), that is, the compulsion of perception. This second key feature of the media noise is similar to mental violence, if the audio signal is used by an external subject, for example, in public places or transport, and its broadcasting excludes the possibility for the perceiving subject to influence upon the source of noise (a screen or a player).
Professional training at the university and digitalization of education: problems and prospects
Authors: Surin Aleksandr , Surina Marietta , Goltseva O.S. , Sunaeva S.G. , Gerasimenko I.I.
Published: July 2021

The article deals with the specifics of training specialists in creative professions (designers, architects) at the university and the general psychological and pedagogical conditions for the formation of specialized consciousness. The purpose and main objective of the study are to identify those conditions for the introduction of digital learning that enables to get a really stable positive result and create a basis for the effective application of electronic equipment and digital education methods. In this context, we study the psychological features of the formation of professional thinking and teaching methods of professional activity at the university level. The psychological conditions of the translation of visual and verbal information into the mental plane, the ways of transformation of students' learning activities and their formation as creative specialists are considered. The basic and special abilities in the field of color proficiency are revealed. The article examines the problematic and promising aspects of digitalization of education in the framework of design education. The ways of effective integration of digital education and traditional forms of professional training in the training of specialists in creative professions (designers, architects, artists, etc.) are determined.
“The Yakut Cold” as a brand
Authors: Nikolaeva Tatiana , Pribylykh Anna
Published: July 2021

The article considers the Yakut cold as a brand that forms a certain public image of a tourist destination, especially for inbound tourism. Currently, the republic possesses all the necessary prerequisites for the effective development of both inbound and domestic tourism. “The Yakut Cold” brand is an integration (unity) of images and associations, that appear as an emotional response to the word “Yakutia”. Formation of an attractive public image requires an integrative approach, including the creation of information services for tourists. The article contains an analysis of the interests and knowledge of foreigners about the Republic of Sakha (Yakutia) as potential visitors, which made it necessary to study the Yakut cold as an attractive brand of the region. The authors of the article consider that the ongoing work to create a textbook in German, with the consideration of the national culture peculiarities and the unique ways of survival in extreme conditions, will contribute to the formation of the “Yakut cold” as an interesting brand of a particular destination.
Forecasting the development of social infrastructure agriculture of the Chuvash republic
Authors: Ivanova Tatiana , Yakovchik Nikolay , Chainikov Valery , Kravchenko Tatiana , Mityugina Marina
Published: July 2021

The article discusses the development of the social infrastructure of agriculture in the Chuvash Republic for the period from 2009 to 2018. Agriculture occupies a special position in the region’s economy and is a backbone industry. Its share in the gross regional product is 9%, which is noticeably higher than in other regions of the country, and the share of residents living in rural areas is 36.6%. With the help of the Excel program, a forecast of the development of rural social infrastructure for the most important indicators for 2019–2022 is presented. according to three scenarios: optimistic, probabilistic and pessimistic. As studies have shown, a pessimistic scenario is more likely to be implemented, which requires immediate corrective measures to effectively manage the industry, in particular, by creating a single “Chuvash Center for the Development of Rural Areas”.
Training of volunteers for social services as an element of a participatory model of sustainable development paradigm
Authors: Ogorodnikova Ekaterina , Plakhin Andrey , Rostovtsev Konstantin
Published: July 2021

The relevance of the study of the processes of training volunteers working in social service organizations is due to the massive use of labor of non-professional participants to provide social services to needy groups of the population. The purpose of this article is to substantiate a conceptual model for organizing regional systems for vocational training and certification of volunteers in the field of social services. The research was carried out on the basis of studying, summarizing and systematizing scientific literature, regulatory documents, training programs for volunteers, and social service standards. As a method of empirical research, a survey of 54 volunteers in the field of social services was used, which revealed the main issues of training for the subsequent provision of services in the field of social services. A review of theoretical sources identified the characteristics of two approaches to training social service volunteers. The first assumes a hierarchical model with a gradual expansion of a volunteer functions, depending on the training programs completed with the receipt of a attestation certificate. The second model involves the training of volunteers directly at the sites of providing social services with the involvement of students from specialized universities. Empirical research has shown that in Russia, in most cases, the training of volunteers in the field of social services is carried out by specialists from institutions in which volunteer activities are carried out in the form of short-term seminars and an oral survey on the presented material. Consequently, it can be stated that there are no full-fledged systems of professional training and certification of volunteers in the field of social services, the construction methodology of which is considered in the works of a number of foreign authors. The formation of such a system in Russia should become one of the target priorities for the development of the volunteer movement, since the specificity of the problems of social services requires special knowledge, skills and abilities.
Sustainable functioning of the finances of organizations in various sectors of the economy
Authors: Piontkevich Nadezhda , Shatkovskaya Ekaterina
Published: July 2021

The current stage of development of the world economy is characterized by specific transformations that affect not only the state of the national economies of the countries of the world, but also the peculiarities of conducting financial and economic activities of individual organizations (enterprises) employed in various sectors of the economy. The emerging trends require the development of financial knowledge, skills, and financial management skills of an economic entity, which, in turn, confirms the need for in-depth theoretical and empirical studies of the organizational and economic aspects of the finances of organizations (enterprises) in various spheres of the economy. The purpose of the article is to develop theoretical and methodological provisions that form the basis for the formation of a financial management system for organizations in various sectors of the economy. The article uses modern methods of collecting and processing initial information, representative sample sets with the justification for the selection of financial indicators for the objects of financial management of organizations (enterprises). The leading method for the study of the problem of financial management of organizations (enterprises) has become the dynamic method. The problems in the world financial science in the field of studying the finances of organizations on a linear basis are identified and the need for an integrated approach is substantiated. The prospects of using a systematic approach to the formation of a financial management system for organizations in various sectors of the economy in science and practice have been proved. The theoretical significance of the study lies in the development of the theory of finance of organizations. The scientific theoretical provisions developed by the authors are aimed at improving the quality of financial management of organizations, depending on their belonging to the relevant sphere of the economy. The practical significance of the results of the work is reduced to determining the prospects for the practical use of the theory of financial management of organizations (enterprises) in various spheres of the economy in practice.
Investigation of the dependence of the significance of the links of the integrative structure on the factors of the institutional environment
Authors: Plakhin Andrey , Kochergina Tatiana , Khokholush Maria , Selezneva Maria
Published: July 2021

The formation of network integrative structures at the present stage is associated with the factors of the institutional environment. The article presents the results of a study of the impact of factors of the institutional environment on the stability of the links of the integrative network structure. The research method is based on the search for the correlation dependence of the indicator characterizing the stability of the relationships between subjects and factors of the institutional environment. The results of the study show that the factors associated with financial support, ensuring the availability of credit resources, and providing conditions for preferential taxation have the greatest impact on the stability of the subjects’ ties. This situation is directly related to the assessments of the owners and managers of companies included in the network structure of the effectiveness of their activities.
Modern problems of the oil industry development and their impact on the financial stability of oil production enterprises
Authors: Abedi Ahmed Abd Zaid
Published: July 2021

The oil industry is one of the main key points in the economies of Russia and Iraq, therefore, the state, social and economic life of the country depends on its productivity, functioning, and stability. The oil industry has several tasks: improving energy efficiency, modernizing equipment, and innovative developments. The oil industry has experienced ups and downs over the years, but the 2020 crisis hit the industry harder than in all years. The long-term decline in oil demand paints highly unfavorable prospects for the future. The Covid 19 crisis was the worst in the history of the oil industry. As companies and entire industries recoil from its effects, oil prices continue to fall. The pandemic has reduced the demand for oil to such an extent that the industry is unable to adapt to such a sharp decline. And the buildup of oil reserves further lowers fuel prices. This article is devoted to the reflection of the algorithm and the substantiation of the practical application of the developed automated model of analysis and forecasting of the financial condition of an enterprise using regression analysis in assessing the financial indicators of an oil production enterprise. In the course of the research, the methods of logical, statistical analysis were used. The developed prototype of an automated model for complex analysis and forecasting of the financial condition of oil production enterprises is a good basis for creating a full-fledged commercial system for the oil production business. It is concluded that the new automated model of analysis and forecasting provides an opportunity to analyze the financial condition of an oil production enterprise, including the identification of its financial difficulties and the study of financial attractiveness, as well as to predict the financial condition of an oil production enterprise within almost any time interval, determining ways to overcome its financial difficulties and increasing financial attractiveness.
MRT-LBM simulation of natural convection in square annulus with a porous coating: route to chaos
Authors: Bourada Abderrahmane , Boutra Abdelkader , Benzema Mahdi , Ameziani Djamel Eddine , Feddaoui M'barek , Benkahla Youb Khaled
Published: July 2021

In this work, multiple-relaxation-time lattice Boltzmann method is applied for examining transient natural convection in a square annulus of circular interior cylinder. This duct is covered by a porous deposit on all interior walls. The Darcy-Brinkman-Forchheimer equation is implemented to model the momentum equations in the porous matrix and the Boussinesq approximation is assumed for buoyancy term. The impact of Darcy number (10−6 ≤ Da ≤ 10−2), Rayleigh number (Ra ≥ 101), radius ratio of the circular cylinder (0.05 ≤ R ≤ 0.40) and the thickness of the porous layer (0.05 ≤ δ ≤ 0.15) on natural convection are analysed. The outcomes are represented under the form of stream functions, isotherms and mean Nusselt number. In addition, temporal evolution and phase portrait are plotted to examine the unsteady flow at elevated Rayleigh numbers. The results are coherent and show that natural convection develops from stable state to chaotic flow via periodic and quasi-periodic oscillatory regimes as the Rayleigh number increases.
Risk control mechanisms of third-party guarantee when financing newsvendor
Authors: Huang Jiazhou , Lu Qihui , Chen Xiangfeng , Zhan Jizhou
Published: July 2021

Two risk control mechanisms, namely, cash deposit, and loan limits based on retained profit or maximum expected guarantor profit, are developed for capital-constrained newsvendor financing. Results show that with a large initial capital or mortgage asset, the newsvendor reduces the order quantity to avoid bankruptcy risk. Under the risk control mechanism with a cash deposit, the guarantor gains greater profit when the newsvendor has a low initial capital. Setting a loan limit is thus an effective mechanism for newsvendors to not only reduce the bankruptcy risk, but also increase the guarantee profit. Numerical experiments also show that, compared with the risk control mechanism based on maximum expected profit, loan limits based on retained profit is more beneficial for the newsvendor, guarantee, and the bank.
Multinationals, innovation, and institutional context: IPR protection and distance effects
Authors: Bruno Randolph Luca , Crescenzi Riccardo , Estrin Saul , Petralia Sergio
Published: July 2021

We characterize the knowledge production process whereby the inventive capabilities of the firm generate innovation output in highly inventive multinational enterprises (MNEs). We explore the sensitivity of this relationship to the strength of intellectual property rights (IPR) protection across the MNEs R&D subsidiaries. We argue that MNE innovative performance will be enhanced when the firm’s R&D activities are based in locations where IPR protection is stronger. Moreover, when considering the internal geography of the MNEs R&D activities, innovation performance depends on the distance between the home- and host-country IPR regime. Thus, innovation performance is worse, as the difference between home and host IPR regimes increases. Finally, we explore asymmetries in this relationship, in particular that the deterioration is more marked when MNEs locate their R&D activities in host economies with IPR protection significantly less strict than in their home country. We test these ideas using a unique new dataset about the most innovative MNEs in the world, an unbalanced panel of around 900 MNEs observed for the period 2004 to 2013 and find strong support for all our hypotheses.
Human security at the Mediterranean borders: humanitarian discourse in the EU periphery
Authors: Panebianco Stefania
Published: July 2021

This article provides a re-conceptualization of human security by exploring humanitarian discourse in the EU periphery. It analyzes human security at the Mediterranean borders by focusing on humanitarian, migrant-centered discourse concerned with defending the world’s most vulnerable populations (Barnett in Annual Review of Political Science 16(1): 379-398, 2013). Empirical research has detected humanitarian discourse defending migrants’ rights, based on claims for the right to be free from inhuman treatment (Aradau in Millennium: Journal of International Studies 33(2): 251–77, 2004), as a counter-argument to the defense and closure of the borders. A humanitarian discourse focused on the alleviation of migrants’ physical and mental suffering erupted at the EU periphery when the Italian government denied a port of safety to the SeaWatch3 vessel in January 2019. This case study provides an example of center-periphery conflictual dynamics. The Italian government, defending the EU/Italian borders by closing the Italian ports, was challenged by actors mobilizing pressure, shaming the state into compliance and requesting pro-migrant legislation.
Laboratory plasma devices for space physics investigation
Authors: Liu Yu , Shi Peiyun , Zhang Xiao , Lei Jiuhou , Ding Weixing
Published: July 2021

In the past decades, laboratory experiments have contributed significantly to the exploration of the fundamental physics of space plasmas. Since 1908, when Birkeland invented the first terrella device, numerous experimental apparatuses have been designed and constructed for space physics investigations, and beneficial achievements have been gained using these laboratory plasma devices. In the present work, we review the initiation, development, and current status of laboratory plasma devices for space physics investigations. The notable experimental apparatuses are categorized and discussed according to the central scientific research topics they are related to, such as space plasma waves and instabilities, magnetic field generation and reconnection, and modeling of the Earth’s and planetary space environments. The characteristics of each device, including the plasma configuration, plasma generation, and control method, are highlighted and described in detail. In addition, their contributions to reveal the underlying physics of space observations are also briefly discussed. For the scope of future research, various challenges are discussed, and suggestions are provided for the construction of new and enhanced devices. The objective of this work is to allow space physicists and planetary scientists to enhance their knowledge of the experimental apparatuses and the corresponding experimental techniques, thereby facilitating the combination of spacecraft observation, numerical simulation, and laboratory experiments and consequently promoting the development of space physics.
Photonic rocket structure grown by site-selective and bottom-up approach: A directional and Gaussian-like quantum emitter platform
Authors: Choi Minho , Kim Sejeong , Choi Sunghan , Cho Yong-Hoon
Published: July 2021

Semiconductor quantum dots (QDs) integrated with photonic nanowires are one of the representative platforms for high-purity single photonic sources. However, conventional photonic nanowires suffer from severe scattering at the edge owing to the small footprint. For this reason, tapered structures have been adopted to achieve directional emission with minimized scattering, and hence, high light collection efficiency. So far, various tapered structures have been demonstrated by using top-down etching fabrication or catalyst-assisted growth. However, these approaches can induce critical issues for QD integrated photonic devices such as an etching damage, an inclusion of multiple QDs in a wire, a misalignment of QD with respect to the wire axis center, or a contamination of QD by the catalyst. Therefore, developing a catalyst-free, site-controlled growth technique is essential for high-quality tapered nanowire structures. In this work, we propose a site-selectively grown photonic rocket structure, which consists of a pencil-like nanowire and a pyramid acting as a single-mode waveguide and a coupler, respectively. Since this structure is defined by stable crystal facets, the dimensions of the structure, especially its tapering angle, are determined precisely. Most significantly, a single QD can be formed at the apex, deterministically aligned to the axis center of the photonic structure. We analyzed the propagating mode inside the photonic nanowire and pyramid coupler using finite-difference time-domain simulations. This photonic rocket structure produces directional emission owing to the pyramid coupler, resulting in 2.9 (2.0) times larger light collection efficiency with a numerical aperture of 0.3 (0.7), compared to the nanowire structure alone.
Hot-carrier radiative recombination through phonon confinement in silicon nanocrystals embedded in colloidal xerogel matrix
Authors: Biswas Susmita , Nandi Anupam , Ghanta Ujjwal , Jana Biswajit , Mukhopadhyay Sumita , Saha Hiranmay , Hossain Syed Minhaz
Published: July 2021

Colloidal suspension of free standing silicon/silicon oxide core/shell nanoparticles has been synthesized using a mechanochemical top-down approach. Quasi-mono-dispersed core size distribution of synthesized nanoparticles has been confirmed using different structural, morphological, and optoelectronic characterizations. Raman, continuous wave photoluminescence and time-resolved photoluminescence studies have been performed on synthesized colloidal nanoparticles in ethanol medium. Asymmetric broadening of the Raman peak (red shifted with respect to that of bulk silicon) has been observed. Intensities and positions of photoluminescence emission peaks are prominently dependent on excitation photon energy. Moreover, the photoluminescence decay time varies from sub-nanoseconds to tens of nanoseconds. The decay time also exhibits a strong dependence on the excitation wavelength, while the emission wavelength is kept unaltered. The abovementioned observations indicate the slow relaxation of photo-excited carriers in silicon quantum dots. This particular phenomenon takes place due to phonon mode discretization, which is further responsible for the radiative recombination of hot-carriers and consequent strong visible emission. The enhancement of hot-carrier lifetime in colloidal silicon quantum dots is the key requirement for the active material of the hot-carrier solar cell. Runny texture of the synthesized material inhibits practical device implementation; therefore, the synthesized nanoparticles have been embedded in the silica xerogel matrix. The impression of phonon mode confinement, in silicon quantum dots embedded in a hard matrix, has been observed, resulting in increased hot-carrier lifetime. The enhanced hot-carrier lifetime can lead to the realization of a silicon-based active material for the hot-carrier solar cell.
Artificial neural network-based standalone tunable RF sensor system
Authors: Seth Sachin , Banerjee Apala , Tiwari Nilesh K. , Akhtar M. Jaleel
Published: July 2021

An artificial neural network (ANN) based tunable automated standalone RF sensor system is proposed to realize an improved sensing module involving a quite accurate solution of the non-linear inverse characterization problem. The presented tunable sensor system is quite novel as it alleviates the need for any active tuning circuitry. Moreover, the proposed unified design topology facilitates a relatively higher tuning range (1900 MHz) than that of the earlier reported (580 MHz) capacitor-based tunable complementary split-ring resonator (CSRR). The higher tuning range of structures resulted from the improved design configuration comprising a modified CSRR design coupled with a modified microstrip line. The obtained dielectric sensitivity is ∼8.8%. The numerically generated S-parameters of various dielectric samples are used here as a training dataset for the ANN, which is trained using the Levenberg–Marquardt backpropagation algorithm in combination with the Bayesian regularization. Finally, several standard test samples at different unloaded tuned frequencies are measured to record the corresponding resonant frequency and magnitude of the S-parameter in order to process them using the proposed ANN-based sensor system. It is found that the developed ANN-based sensor system provides a reasonably accurate value of the extracted complex permittivity over the frequency range under consideration, which basically removes the need for designing multiple resonant structures unlikely to the conventional resonant sensors.
The post-impact dynamics of drop rebound on inclined hydrophobic surfaces of various wettabilities
Authors: Guan Yin , Fu Jingwei , Wu Shuang , Chen Xiyang , Zhou Cheng
Published: July 2021

In this work, the post-impact drop motions of the rebound regime on inclined hydrophobic surfaces are investigated using a numerical technique. The effects of impact velocity (Vi = 0.5–1.5 m/s), drop diameter (D0 = 1.0–2.5 mm), surface wettability (θeq = 120°–160°), and inclined angle (α = 0°–80°) on the post-impact regimes, contact time (tc) and spreading time (ts), nondimensionalized maximum spreading diameter (Ds_max*), and drop displacement prior to the rebound (ld_final) are examined and analyzed, some of which exhibit markedly different outcomes at α = 80° compared to α≤ 60°. It has been discovered that the rebound regime occurs in most impact conditions at θeq = 160° and 140° but transitions to sliding for all α = 80° cases at θeq = 120°. When α≤ 60°, tc and ts of θeq = 160° and 140° are very close and hardly affected by Vi and α, which are generally smaller than those of α = 80°, resulting from the rapid decline of the normal impact velocity that diminishes drop deformation and prolongs drop sliding motion. Ds_max* is barely influenced by θeq but increases with Vi and D0 and decreases when α increases owing to a greater normal inertial force. ld_final generally increases with Vi, D0, and α but with different mechanisms. More importantly, the nondimensionalized parameters tc*, Ds_max*, and ld_final* are found to scale with the normal or tangential Weber numbers according to the power law, while the exponents vary with θeq and α.
Graphene-based mid-infrared photodetectors using metamaterials and related concepts
Authors: Ye Ming , Zha Jiajia , Tan Chaoliang , Crozier Kenneth B.
Published: July 2021

Graphene, a semi-metal with a gapless band structure, has been used in mid-infrared (MIR) photodetectors (PDs) for some time. However, these detectors often suffer from low responsivity due to the intrinsically low absorption and ultra-short carrier lifetime in graphene, large dark current, and low detectivity due to the semi-metallic nature of graphene. Over the past decade, much effort has been devoted to addressing these issues. A variety of metamaterials and related concepts has been employed to improve the detector responsivity by enhancing the graphene absorption and/or the carrier collection efficiency. Here, we provide an overview of the graphene MIR PDs with and without the use of approaches for responsivity enhancement. We focus our attention on the state-of-the-art graphene MIR PDs whose performance is improved by employing metamaterials and related concepts, including band structure engineering, the photogating effect, integration with plasmonic nanostructures and waveguides, the use of asymmetric plasmons, coupled plasmon–phonon polaritons, and small-twist-angle bilayer graphene. We conclude by providing possible directions for further performance improvement of graphene MIR PDs and a discussion on future applications of these detectors.
Scaling up the throughput of microfluidic droplet-based materials synthesis: A review of recent progress and outlook
Authors: Wu Jingyu , Yadavali Sagar , Lee Daeyeon , Issadore David A.
Published: July 2021

The last two decades have witnessed tremendous progress in the development of microfluidic chips that generate micrometer- and nanometer-scale materials. These chips allow precise control over composition, structure, and particle uniformity not achievable using conventional methods. These microfluidic-generated materials have demonstrated enormous potential for applications in medicine, agriculture, food processing, acoustic, and optical meta-materials, and more. However, because the basis of these chips' performance is their precise control of fluid flows at the micrometer scale, their operation is limited to the inherently low throughputs dictated by the physics of multiphasic flows in micro-channels. This limitation on throughput results in material production rates that are too low for most practical applications. In recent years, however, significant progress has been made to tackle this challenge by designing microchip architectures that incorporate multiple microfluidic devices onto single chips. These devices can be operated in parallel to increase throughput while retaining the benefits of microfluidic particle generation. In this review, we will highlight recent work in this area and share our perspective on the key unsolved challenges and opportunities in this field.
Mechanism of control of the near-wall turbulence using a micro-cavity array
Authors: Bhat S. S. , Silvestri A. , Cazzolato B. S. , Arjomandi M.
Published: July 2021

Coherent structures in a turbulent boundary layer have been shown to have an influence on the skin-friction drag acting on surfaces beneath the boundary layer. The use of micro-cavities on a flat surface has recently shown the potential to passively control a turbulent boundary layer by attenuating the sweep events. Previous experiments have determined the design parameters of the cavity array for the optimal boundary-layer control by reducing the sweep events. However, investigating the flow physics behind the interaction of the boundary-layer flow with the cavities is challenging. High near-wall velocity gradients and very small scales and sizes of the cavity holes limit the experiments from investigating the flow characteristics very close to the wall and inside the holes. Therefore, in the present work, direct numerical simulations have been utilized to model the boundary layer flow over a flat surface with a micro-cavity array in order to understand the flow interactions. Detection of coherent structures in the boundary layer shows a reduction in the number of events over the cavity array. Reynolds stresses have been analyzed to determine the effect of micro-cavities. The reduction in the Reynolds shear stress results in a lower skin-friction drag. The flow fluctuations through the holes in the streamwise sequence have been found to be highly correlated using cross correlation. These flow fluctuations interact with the boundary layer to suppress the coherent structures. Overall, the use of the micro-cavity array has resulted in a reduced wall shear stress and approximately 5.6% lower local skin-friction drag.
Electric pulse heating device for the analysis of solid/solid phase transformations
Authors: Kaaden T. , Tympel V. , Kober M. , Schmidl F. , Rettenmayr M. , Lippmann S.
Published: July 2021

Ohmic pulse heating is applied to investigate diffusion and interface controlled solid-state phase transformations. The developed device uses extensive solid-state electronics providing a high current, low voltage approach that overcomes the limitations of existing setups, most notably the use of sample geometries that allow for the reliable measurement of local temperatures and their assignment to microstructures. Power for heating is supplied by a capacitor array with adjustable voltage, and the process is controlled by microcontrollers and a solid-state relay, which allows for controlled pulses that are adjustable in microseconds. Electric currents of up to 22 kA at 90 V can be realized by the setup. Electric data are monitored and collected during the experiments, and temperature data are captured using a high-resolution infrared camera at high frame rates (1200 fps). The capabilities of the setup are demonstrated by rapid heating (106 K/s) and subsequent cooling of a brass sample. Two distinct areas of the sample are analyzed in detail, showing similar heating, but different cooling curves with rates of 104 and 102 K/s. Local microstructure analysis shows that different phase transformation mechanisms were dominant, and thus, the setup fulfills its purpose.
Numerical study of non-gyrotropic electron pressure effects in collisionless magnetic reconnection
Authors: Sladkov A. , Smets R. , Aunai N. , Korzhimanov A.
Published: July 2021

We investigate the time evolution of the six-component electron pressure tensor in a hybrid code studying consequences for the two-dimensional reconnection process in an initially perturbed Harris sheet. We put forward that two tensor components (a diagonal and a non-diagonal one) grow in an unstable way unless an isotropization operator is considered. This isotropization term is physically associated with an electron heat flux. As a consequence, we put forward that an enhanced value of a diagonal component is observed in the very middle of field reversal at sub-ion scale. Because of the increase in the kinetic pressure, the magnetic field is decreased in this electron layer, hence increasing the associated out-of-plane current at its edges and leading to its bifurcation. The bifurcation mechanism is based on the presence of electron pressure anisotropy, related to the gradient of inflow electron bulk velocity. The gradient in the inflow direction of the enhanced diagonal electron pressure tensor component results in the deceleration of the ions entering the X-point region. We suggest that bifurcated current sheets resulting from the anisotropies/agyrotropies of the six-component electron pressure tensor correspond to smaller reconnection rates compared to non-bifurcated ones.
Thermal quench in ITER locked mode disruptions
Authors: Strauss H.
Published: July 2021

Simulations and theory are presented of an ITER locked mode thermal quench (TQ). In present experiments, locked mode disruptions have a long precursor phase, followed by a rapid termination and thermal quench, which can be identified with a resistive wall tearing mode (RWTM). In ITER, the RWTM will be slowed by the highly conductive vacuum vessel. The rapid termination might be absent, and the plasma could remain in the precursor phase. If the edge temperature is in the collisional regime, the TQ would proceed on a long timescale, limited by the RWTM to almost 100 ms. This is an important self-mitigating effect.
Viscoplastic flow in a pipe of complex cross section with stick–slip at the wall
Authors: Muravleva Larisa
Published: July 2021

The Poiseuille flow of a Bingham fluid with the yield slip condition at the wall is examined. The governing equations are solved employing the accelerated augmented Lagrangian method for both the viscoplastic model and the yield slip equation. We solve numerically the flow in pipes with different cross sections: equilateral and isosceles triangles, L-shape, and hourglass-shape. The combined effects of viscoplasticity and slip on the flow have been investigated. The evolution of the unyielded regions has been studied. The computations cover the full range of the two main dimensionless numbers and exhibit complex flow patterns: all the different flow regimes are identified in ducts of various cross sections.
Rationalizing the enhancement of the thermoelectric properties of PEDOT:PSS by secondary doping
Authors: Cassinelli Marco , Park Won-Tae , Kim Youngno , Kim Jung-Hyun , Noh Yong-Young , Caironi Mario
Published: July 2021

The enhancement of the thermoelectric (TE) properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) through secondary doping is well-known. In particular, the increase in the power factor (PF) following the addition of the strong polar solvent dimethyl sulfoxide (DMSO) in an aqueous solution is largely reported. However, systematic and comprehensive characterization of the morphological, compositional, and energetic evolution of the system with the addition of the secondary dopant is still missing. Here, the rationalization of the PF enhancement of PEDOT:PSS thin films with the addition of DMSO is presented. The system evolution is followed with morphological, by AFM and grazing incident wide angle x-ray scattering (GIWAXS), compositional, by x-ray photoelectron spectroscopy (XPS), and energetic, by ultraviolet photoelectron spectroscopy (UPS), measurements as varying the secondary dopant percentage from 0 to 50 vol. %. UPS measurements reveal no changes in the work function, substantiating the measured constant values of Seebeck coefficient (S) as varying the percentage of DMSO. On the other hand, XPS analysis confirms that the PSS to PEDOT ratio decreases with the addition of DMSO. However, the compositional changes do not influence the molecular packing and the thin film crystallinity, as reported by GIWAXS measurements. This comprehensive analysis of the system evolution makes possible to safely relate the increase in the electrical conductivity (σ) as a function of the secondary dopant to the sole enhancement of the charge carrier mobility, due to both morphological and chemical composition changes.
Sub-6 GHz ceramic inverted-L antenna with non-resonant structure and leaky-wave radiation
Authors: Fan Fei , Wang Shiyan , Zhu Lei , Yang Li , Li Yin , Zhang Gang , Wong Sai-Wai
Published: July 2021

With the arrival of the 5G era, the working frequencies of wireless devices are being transferred to a higher spectrum with a wider available bandwidth. However, conventional metal wire antennas used in 5G communication systems are often limited by their resonant structure, which inevitably leads to narrow operating bands and fixed sizes at integral multiples of λ/2 or λ/4. In this Letter, a ceramic inverted-L antenna with a non-resonant architecture is proposed to achieve a wide bandwidth and flexible size. Its leaky-wave radiation is based on the cutoff region of dielectric waveguides, which verifies that the working frequencies of the proposed antenna are related to the cross section rather than the length. Ceramic 3D printing technology is adopted for precise manufacturing of the proposed antenna, which covers the frequency range of 3.28–5.28 GHz, including the bands n77/n78/n79 of the sub-6 GHz spectrum.
Strong magnon–photon coupling with chip-integrated YIG in the zero-temperature limit
Authors: Baity Paul G. , Bozhko Dmytro A. , Macêdo Rair , Smith William , Holland Rory C. , Danilin Sergey , Seferai Valentino , Barbosa João , Peroor Renju R. , Goldman Sara , Nasti Umberto , Paul Jharna , Hadfield Robert H. , McVitie Stephen , Weides Martin
Published: July 2021

The cross-integration of spin-wave and superconducting technologies is a promising method for creating novel hybrid devices for future information processing technologies to store, manipulate, or convert data in both classical and quantum regimes. Hybrid magnon–polariton systems have been widely studied using bulk Yttrium Iron Garnet (Y3Fe5O12, YIG) and three-dimensional microwave photon cavities. However, limitations in YIG growth have, thus far, prevented its incorporation into CMOS compatible technologies, such as high-quality factor superconducting quantum technology. To overcome this impediment, we have used Plasma Focused Ion Beam (PFIB) technology—taking advantage of precision placement down to the micrometer scale—to integrate YIG with superconducting microwave devices. Ferromagnetic resonance has been measured at milliKelvin temperatures on PFIB-processed YIG samples using planar microwave circuits. Furthermore, we demonstrate strong coupling between superconducting resonators and YIG ferromagnetic resonance modes by maintaining reasonably low loss while reducing the system down to the micrometer scale. This achievement of strong coupling on-chip is a crucial step toward fabrication of functional hybrid quantum devices from spin-wave and superconducting components.
Photonic implementation of artificial synapses in ultrafast laser inscribed waveguides in chalcogenide glass
Authors: Ramos M. , Bharadwaj V. , Sotillo B. , Gholipour B. , Giakoumaki A. N. , Ramponi R. , Eaton S. M. , Soci C.
Published: July 2021

Simple and direct prototyping methods are ideal for large-scale delivery of cognitive photonic hardware. Here, we choose ultrafast laser writing as a direct fabrication technique to later demonstrate all-optical synaptic-like performance along the laser-written waveguides in a chalcogenide glass. Neuronal communication protocols, such as excitatory and inhibitory responses, temporal summations, and spike-timing-dependent plasticity, are shown in the glass chip. This work manifests the potential for large-scale delivery of fully integrated photonic chips based on cognitive principles by single-step fabrication procedures.
Stochastic heating of electrons due to Raman backscatter radiations in interaction of intense laser pulse with nitrogen atoms
Authors: Khalilzadeh E. , Jafari M. J. , Chakhmachi A.
Published: July 2021

In this paper, simulation study of electron stochastic heating arising from the Raman backscatter radiations during the interaction of the laser pulse with the nitrogen atoms is presented by use of a massively parallel particle-in-cell code. For this purpose, the self-consistent evolutions of the laser pulse via the time–space Fourier transforms of transvers vector potential are investigated at the different times of propagation. It is shown that since the ionization has effect on the emission of the Raman backscattered radiation; it noticeably contributes on the stochastic heating threshold of the electrons. According to our results, it has been found that, when there is the long rise time laser pulse (here 100 fs), the Raman backscattered radiations are seeded by a strong initial noise at the earlier times. Therefore, by considering the ionization, the necessary condition for chaos threshold is met sooner, which, in turn, causes the electron stochastic heating start quickly compared to the case the laser pulse is propagated in the pre-plasma. As a result, in agreement with chaotic nature of the motion, the electrons gain more energy through the stochastic mechanism in the field-ionized plasma.
Broadband 2DES detection of vibrational coherence in the Sx state of canthaxanthin
Authors: Mohan T. M. Nila , Leslie Chase H. , Sil Sourav , Rose Justin B. , Tilluck Ryan W. , Beck Warren F.
Published: July 2021

The nonadiabatic mechanism that mediates nonradiative decay of the bright S2 state to the dark S1 state of carotenoids involves population of a bridging intermediate state, Sx, in several examples. The nature of Sx remains to be determined definitively, but it has been recently suggested that Sx corresponds to conformationally distorted molecules evolving along out-of-plane coordinates of the isoprenoid backbone near a low barrier between planar and distorted conformations on the S2 potential surface. In this study, the electronic and vibrational dynamics accompanying the formation of Sx in toluene solutions of the ketocarotenoid canthaxanthin (CAN) are characterized with broadband two-dimensional electronic spectroscopy (2DES) with 7.8 fs excitation pulses and detection of the linear polarization components of the third-order nonlinear optical signal. A stimulated-emission cross peak in the 2DES spectrum accompanies the formation of Sx in <20 fs following excitation of the main absorption band. Sx is prepared instantaneously, however, with excitation of hot-band transitions associated with distorted conformations of CAN’s isoprenoid backbone in the low frequency onset of the main absorption band. Vibrational coherence oscillation maps and modulated anisotropy transients show that Sx undergoes displacements from the Franck–Condon S2 state along out-of-plane coordinates as it passes to the S1 state. The results are consistent with the conclusion that CAN’s carbonyl-substituted β-ionone rings impart an intramolecular charge-transfer character that frictionally slows the passage from Sx to S1 compared to carotenoids lacking carbonyl substitution. Despite the longer lifetime, the S1 state of CAN is formed with retention of vibrational coherence after passing through a conical intersection seam with the Sx state.
Energetic structures in the turbulent boundary layer over a spanwise-heterogeneous converging/diverging riblets wall
Authors: Bai Honglei , Gong Jinlai , Lu Zhenbo
Published: July 2021

Time-invariant (or mean) secondary flows, in terms of large-scale counter-rotating roll modes filling boundary layer, have been observed in turbulent boundary layer (TBL) flows over various spanwise-heterogeneous rough walls. Recent studies show that these mean secondary flows are inherently connected with instantaneous large-scale structures in TBL flows over such spanwise-heterogeneous rough walls. In this work, the technique of proper orthogonal decomposition (POD) is used to extract dominant energetic (and thus large-scale) structures from TBL flows over the surface with a spanwise-periodic converging/diverging riblets pattern, one of the spanwise-heterogeneous rough walls adopted previously. POD analyses are conducted on the three fluctuating components of velocities, measured by stereoscopic particle image velocimetry at Reθ = 13 000, in a cross-stream plane of the TBL flows over a spanwise section of the converging riblets pattern, where low-momentum eruptions consistently occur. It is found that first two POD modes with large temporal coefficients are linked to large-scale structures oscillating vigorously in the transverse direction within one section of the converging riblets. Superposition of these instantaneous large-scale structures reveals the observed pattern of mean secondary flows. Furthermore, these large-scale structures are associated with enhanced streamwise vortices and spanwise gradients of the streamwise velocity, compared with that in the smooth wall flow, thus rendering profound effects on the spatial correlations of velocities as well as the distributions of Reynolds stresses.