bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic analysis of a five degree of freedom robotic arm using MATLAB-Simulink Simscape
Authors: Crenganis Mihai , Barsan Alexandru , Tera Melania , Chicea Anca
Published: August 2021

In this paper, a dynamic analysis for a 5 degree of freedom (DOF) robotic arm with serial topology is presented. The dynamic model of the robot is based on importing a tri-dimensional CAD model of the robot into Simulink®-Simscape™-Multibody™. The dynamic model of the robot in Simscape is a necessary and important step in development of the mechanical structure of the robot. The correct choice of the electric motors is made according to the resistant joint torques determined by running the dynamic analysis. One can import complete CAD assemblies, including all masses, inertias, joints, constraints, and tri-dimensional geometries, into the model block. The first step for executing a dynamic analysis is to resolve the Inverse Kinematics (IK) problem for the redundant robot. The proposed method for solving the inverse kinematic problem for this type of structure is based on a geometric approach and validated afterwards using SimScape Multibody. Solving the inverse kinematics problem is a mandatory step in the dynamic analysis of the robot, this is required to drive the robot on certain user-imposed trajectories. The dynamic model of the serial robot is necessary for the simulation of motion, analysis of the robot’s structure and design of optimal control algorithms.
Design of a modular locomotion system for autonomous mobile robots
Authors: Maroşan Iosif-Adrian , Constantin George
Published: August 2021

Autonomous mobile robots are becoming more popular today and are successfully integrated into many civil and industrial projects. In the industrial sectors flexibility and modularity have an important role, so the production can be diversified and achieved with low costs. This paper presents the conceptual and functional design of a modular locomotion system for an autonomous mobile platform that can be configured according to the needs of the industrial environment it serves. The architecture of the locomotion system is based on a spring suspension system and three types of wheels: conventional wheels, omnidirectional wheels and mechanum wheels. The calculations for the chosen suspension system are presented, which ensure the contact with the ground for each type of wheel and the resignation calculations for the engine that will drive the wheel. Finally, some variants of configurations are presented that can be made on an autonomous mobile platform with these modules.
Modular Transport and Sorting System with Omnidirectional Wheels
Authors: Rizescu Ciprian Ion , Pleşea Andrei Ioan , Rizescu Dana
Published: August 2021

The paper refers to the development of an intelligent sorting and transport system. This research aims to develop such systems and solve problems in multi-directional transport as well as the development of a sorting, transport and positioning system that can be used in various fields. At the same time, the omnidirectional transport system is a modular transport and sorting system. It consists of several small hexagonal transport cells, each with three individually operated omnidirectional wheels. By individually controlling the wheels, objects can be transported freely in all directions. This opens unlimited possibilities to create new concepts for handling materials or to improve existing classic ones. Due to the modular construction and the individual control of the omnidirectional wheels, the sorting tasks can be adapted very quickly. This will allow you to perform different tasks in very small areas. Individual control of objects also allows for exact alignment or individual rejection of objects. The system has been designed to transport work objects. To design the module, it was necessary to create its scale geometric model using the Autodesk Inventor Professional 2018 design environment. To make the module, it was used through the rapid prototyping process with Fused Deposition Modelling, the material used being Polylactic Acid. The solution adopted allows any transported object to always be supported on at least three wheels, this allows the direction of movement of the object to be controlled by the movement of the wheels.
Pro and con features regarding underground gas storage in depleted reservoirs versus saline deposits
Authors: Lungu Ionuţ , Dinu Florinel , Stoicescu Maria , Suditu Silviu , Mitrea (Rosu) Ioana-Cornelia
Published: August 2021

Underground storage of natural gas represents an efficient solution to cover fluctuations in natural gas consumption during the cold season and/or special situations like emergencies. The paper aims to presents the natural gas underground storages technologies in saline deposits and depleted reservoirs, as well as the pros and cons features of using of those methods..
Half a century of continuous oil production by in-situ combustion in Romania – case study Suplacu de Barcau field
Authors: Branoiu Gheorghe , Dinu Florinel , Stoicescu Maria , Ghetiu Iuliana , Stoianovici Doru
Published: August 2021

Thermal oil recovery is a special technique belonging to Enhanced Oil Recovery (EOR) methods and includes steam flooding, cyclic steam stimulation, and in-situ combustion (fire flooding) applied especially in the heavy oil reservoirs. Starting 1970 in-situ combustion (ISC) process has been successfully applied continuously in the Suplacu de Barcau oil field, currently this one representing the most important reservoir operated by ISC in the world. Suplacu de Barcau field is a shallow clastic Pliocene, heavy oil reservoir, located in the North-Western Romania and geologically belonging to Eastern Pannonian Basin. The ISC process are operated using a linear combustion front propagated downstructure. The maximum oil production was recorded in 1985 when the total air injection rate has reached maximum values. Cyclic steam stimulation has been continuously applied as support for the ISC process and it had a significant contribution in the oil production rates. Nowadays the oil recovery factor it’s over 55 percent but significant potential has left. In the paper are presented the important moments in the life-time production of the oil field, such as production history, monitoring of the combustion process, technical challenges and their solving solutions, and scientific achievements revealed by many studies performed on the impact of the ISC process in the oil reservoir.
Using GIS for management of conflicts in natural protected area in Cindrel mountains
Authors: Alexandru Bratu Iulian , Dincă Lucian
Published: August 2021

This study reflects the possibility of using the GIS technology for the management and resolution of conflicts between stakeholders in the management of protected natural areas that cover large surfaces, such as Natura 2000 sites. The research is accomplished in Frumoasa site from Cindrel Mountains, where a conflict of a legal nature was analysed, in the extinguishment of which the technology of geographical information systems was used. In this sense, the presence of the species and habitats that are found on the surface of the incriminated forest was analysed and the comparison with the list of species and habitats that was the basis for declaring the surface as a nature 2000 site. In the next stage, both the site management plan and the forest management plan were analysed in order to identify inconsistent potentials. Then, maps of the presence and distribution of species and habitats were made, with the protection and conservation measures adopted. Also, special attention was paid to the identification of primary and old-growth forest, their distribution and measures for their conservation. The conclusions include improvements can be made to the management of the incriminated areas, accompanied by the geo-database.
Deciphering the Reservoir Rocks Lithology by Mineralogical Investigations Techniques for an Oilfield in South-West Romania
Authors: Branoiu Gheorghe , Avram Lazar , Ghetiu Iuliana , Suditu Silvian , Pelin Stefan
Published: August 2021

An important element of the geological modeling of oil reservoirs is represented by determining of the mineralogical composition and rock types as part of the reservoir characterization process. In the paper we provide a comprehensive mineralogo-petrographic study based on petrographic observations and X-rays diffraction investigations made on several Miocene rock samples collected in the wells spudded in an oil field belonging to the Getic Basin. Getic Basin is a prolific petroleum province in Romania and belongs to petroleum systems of the Carpathian Foredeep. The oil exploration in the Getic Basin started more than 100 years ago and resulted in thousands of wells drilled and tens of fields discovered. The oil field is located in the Gorj County, geologically belongs to the internal zone of the Getic Basin, and is a faulted anticline with hydrocarbon accumulations in Burdigalian and Sarmatian deposits. The petrographic study led to the interpreting of the rock samples analyzed as epiclastic sedimentary rocks represented by conglomerates, breccias, sands, sandstones, claystones and marlstones, and carbonate rocks (limestones). X-rays diffraction investigations indicated the phyllosilicates (smectite and illite) as main minerals in the Sarmatian samples, while in the Burdigalian samples were found as main minerals: quartz, feldspars and carbonate minerals. The paper provides detailed information (like petrographic types, composition and microtexture) on the Miocene reservoir rocks belonging to the Getic Basin. Also the data obtained may be used as basis for future reservoir modeling studies in the region.
Sizing Particles in Gases by an Advanced Optical Procedure
Authors: Chicea Dan , Leca Cristian , Olaru Sorin
Published: August 2021

Several types of sensors capable of detecting fumes are commercially available. A well-established procedure for sizing particles suspended in liquid solvent is called Dynamic Light Scattering (DLS) and is based on assessing the diffusion coefficient of the particles from the fluctuations of the scattered light recorded in the scattered light intensity time series. This work highlights the difficulties encountered in an attempt to use DLS for sizing particles suspended in air and the particular, narrow experimental conditions chosen in designing and setting such a DLS experiment. The experimental setup was tested on combustion gases and the results of the preliminary experiment are presented in detail. The results stand as a proof of concept for using DLS in sizing particle in gases and in designing a sensor for fumes detection that can indicate the average size of the particles over an extended range.
The risk of static electricity at handling diesel fuel
Authors: Părăian Mihaela , Ghicioi Emilian , Vătavu Niculina , Gabor Dan , Mangu Sorin Iuliu
Published: August 2021

Diesel fuel in motion when is transporting by pipes when is mixing, pumping, filtering, agitating or by pouring them from one vessel to another can generate static charges. Also, static electricity may occur if the liquid is splashes and forms a mist inside the tank. Accumulation of static electricity can, under certain conditions, be discharge and ignite the flammable/explosive atmosphere. Ignition hazards from static discharges can be eliminated by controlling the generation or accumulation of static charges or by eliminating a flammable mixture where static electricity may be discharged. Factors that need to be considered to reduce the risk of ignition sunt flammability characteristics of explosive atmosphere (the vapor pressure, flash point, temperature, and pressure) and the factors that determine the charging of static electricity (fuel type, electrical conductivity, sulfur content, viscosity, vehicle process: flow rate, pipe diameter, filters, pumps, spark promoters). In this paper are presented some aspects regarding the technical, organizational requirements and responsibilities of the personnel designated to prevent the formation and accumulation of static electricity when loading diesel fuel tanks, starting from a case study, respectively some explosions which occurred to a company during the loading operation.
The importance of performance indicators in occupational safety and health management - a review
Authors: Caldarescu Gabriela , Florea Laura , Nagit Gheorghe , Bernevig Mihai-Adrian
Published: August 2021

Reports on the incidence of accidents at work in Romania show that there is poor management of injury risks, and the component called management has a defining role, which is why performance indicators can be used to increase performance in occupational OSH (occupational safety and health) management and implicitly contribute to reduce the number of accidents and occupational diseases. The paper is a review that aims to perform an analysis of key performance indicators (KPIs) given the relevance of the indicators used in the field of OSH. The first part includes the current use of these indicators and a summary of their effectiveness in the field, which presents lagging performance indicators applicable to OSH, which can measure the results of activities carried out and leading indicators, which are proactive, preventive and predictive, to provide information about the performance of the management system in the field. In the second part, using the survey method for which the research tool is a questionnaire with 10 items, an analysis is performed to test the relationship between the two types of performance indicators. Finally, the results obtained highlighted the existence of direct correlations between the types of selected indicators, but also the existence of limits on their use.
Indoor air quality monitoring and human perception survey on air quality in public buildings in Timisoara
Authors: Bere Semeredi Iudit , Valceanu Mihai Eugen , Nica Diana Mihaela , Sipetan Ella Anca , Corlan Romulus
Published: August 2021

The paper presents a study aimed at investigating the indoor air quality (IAQ) and people’s perception regarding the indoor environment of schools and public buildings in Timisoara. The indoor air quality monitoring was performed during the cold season, in the period January 2020 – February 2021. Six public buildings – schools and administrative edifices belonging to the municipality were subject of monitoring. An Andersen microbial air sampler was used to enumerate the numbers and different kinds of respirable bacteria and fungi inside of the selected classrooms and offices. The results of the specialized laboratory analyses indicate that the microbiological contaminant counts, expressed in colonyforming unit (CFU/m3), fall within the permissible limits for all monitored rooms. No beta-hemolytic streptococci or Staphylococcus aureus were identified, conditionally pathogenic bacteria for the upper respiratory tract. Most moulds were of the genus Penicillium, without having a pathogenic significance for humans. Occupants’ perception on indoor air quality, thermal comfort, health complaints and symptoms such allergies or respiratory illnesses with possible connection to the Sick building syndrome were surveyed by questionnaire. The findings were analysed and a plan to improve IAQ in the public buildings was proposed, with specific measures to increase the comfort and health of the learning and working environment.
Using new digital technologies in employee training to avoid occupational accidents in the industry
Authors: Muresan Petru Iulian , Milosan Ioan , Machedon-Pisu Teodor , Reit Adrian , Senchetru Dorin , Oancea Gheorghe
Published: August 2021

The most frequent workplace accidents in the industry are most of the times caused by the employer’s failure to fulfill their obligation to provide appropriate on-the-job training. Starting from this state of affairs, this paper analyzes the main cause of workplace accidents in the industry, which is the lack of training, or incomplete or inadequate training of employees, a situation indicated by the latest studies and the latest activity report of Labor Inspectorate. The solution identified by most employers was to use the online environment, this being the only way that allows the achievement of both of the aforementioned objectives at the same time. In this context, the paper identifies and proposes the use of the online environment, especially in the process of distance training of workers, giving them the opportunity to receive training documents, to analyze them, to electronically sign them and send them to the employer in electronic format. This proposal of supplementing the current legislation with the possibility of using the online environment in the field of occupational health and safety (OHS) also takes into account other categories of benefits that this solution brings, such as streamlining OHS and optimizing costs incurred in fulfilling these legal obligations.
Development of a conceptual model of sustainable building from a university
Authors: Olteanu Alexandru , Kifor Claudiu-Vasile
Published: August 2021

Introduction: In this paper, the authors aim is to develop a conceptual model that aims to facilitate the processes of implementing sustainability and / or assessment of sustainable performance in a Higher Education Building (HEB). The conceptual model could also be used to compare two or more buildings of higher education in terms of sustainability. Methodology: The authors started the scientific research with the literature review in order to identify and analyze the most relevant aspects that are frequently assess and could influencing the components of sustainability in higher education institutions. These aspects were clustered into categories and for each of them were established objectives and key performance indicators. Results: The main results obtained were presented synthetically in graphical, tabular and mathematical manner. This way of presentation was preferred by the authors for defining and developing the proposed conceptual model. Conclusions: Finally, the authors propose a piloting of the conceptual model in order to validate it, because until now, no testing in physical circumstances of the model has been implemented, it based only on the results identified in the literature review.
Developing adult motivation for continuous training
Authors: Mara Elena Lucia
Published: August 2021

Traditional education focused primarily on the moment of teaching, on the moment of transmitting information, knowledge, and only then on aspects related to ethical, motivational, moral nature. Contemporary society in a continuous remodeling and change, no longer coincides, no longer accepts such a system. Traditional learning does not keep pace with contemporary society. The aim of this study is to investigate the motivation of learning in adulthood. In the motivational structure of the investigated adults, extrinsic reasons predominated, indirectly related to the learning activity, such as: the need to advance professionally, to keep up with the times, to obtain a social status as high as possible, to meet current requirements, to earn the respect of others, for a diploma, a change of job. Among the intrinsic reasons invoked by the study participants, directly related to the learning activity, we mention: the desire for knowledge and personal development, curiosity, the desire to teach others. In conclusion, we want to offer a better perspective and a well-understanding of motivational factors implicated in adult learning, ensuring the ease of triangulation of sources of information collection, thus improving the credibility of findings.
Using Design Thinking to Redesign the Educational Experience
Authors: Baltador Lia Alexandra , Grecu Valentin , Pentescu Alma
Published: August 2021

In a world that is ever changing and full of uncertainties, there is an undeniable need to equip students with competencies that exceed cognitive knowledge, thus enabling them to develop their individual potentials. Using case study methodology, Design Thinking and ProblemBased Learning, this paper presents a program that brought together students and teachers from different faculties with the purpose of developing innovative solutions to important and pressing societal challenges. Given the unprecedented context generated by the worldwide spread of SARS–COV2 Virus, the program challenged students to find solutions to redesign the educational process. The aim was to equip them with the skills and competencies necessary to adapt in a globalized world, where remote work with team members from different backgrounds is the norm. The Problem-Based Learning approach and the visually attractive collaborative online platform used to implement the Design Thinking methodology generated an overall increased student engagement and creative solutions for wicked problems.
Home ergonomics – lessons learned
Authors: Boatca Maria-Elena , Draghici Anca , Gaureanu Alin
Published: August 2021

The current pandemic conditions generated new ways of working and learning by shifting from face-to-face to remote and online working environment. From an ergonomics perspective, this change involved a large variety of adaptations to ‘the new normal’, especially inappropriate furniture, and inadequate social and physical environment conditions. Therefore, the paper aims to provide a deeper understanding on the role of education in ergonomics on the basis of a study on students at Politehnica University of Timisoara. There is little to no information available on ergonomic conditions in which students attend online classes and prepare their projects. The study involved several steps: (1) attendance to an educational session where they were informed on how to sit and organise their working space; (2) presentation of their current and wished working space; and (3) response to a detailed checklist targeted at understanding both their perception and effects on their health regarding online schooling. The results were, to an extent, predicted by the authors: students do not have adequate furniture and lighting conditions; furthermore, the effects on their health are already visible, although not severe.
Quality management assessment within Erasmus+ Programme according to the perception of the participating students
Authors: Răulea Rebecca-Clara , Dumitraşcu Dănuţ-Dumitru
Published: August 2021

The aim of the paper was to analyze the perception of students regarding the quality of management within Erasmus+ programme carried out by Lucian Blaga University of Sibiu and their partner academic institutions from Romania and abroad. Through this paper we also tried to determine a classification of the evaluated variables, their correlation and the factor which influences most the quality of the management of Erasmus mobility projects. In order to assess these goals, the research consisted of collecting, processing and analyzing the responses to questionnaires from 66 Romanian students and 165 foreign students who have benefited from an Erasmus+ study or placement mobility in the last years. The findings highlighted that Romanian students compared to foreign students assessed better the quality of management in general, more exactly the variables related to promotion and information activities, quality and professionalism of the Erasmus selection competition, support in filling out the Erasmus documents, the level of support throughout the application process, information and support provided by the home university during their mobility and the support for the administrative part after returning from mobility.
Herausforderungen der Opioid-Agonistentherapie aus der Perspektive der Mitarbeitenden in Behandlungszentren
Authors: Köck Patrick , Schmalz Ann-Marie , Walter Marc , Strasser Johannes , Dürsteler Kenneth M. , Vogel Marc
Published: August 2021

Dank verbesserter Behandlungsmöglichkeiten opioidabhängiger Menschen ist ein Anstieg der Zahl älterer Patienten in Opioid-Agonistentherapie (OAT) zu verzeichnen. Insgesamt verbesserte sich die Lebenserwartung dieser Patienten in den letzten Jahren deutlich und das Durchschnittsalter der Patienten in OAT nahm zu. Bei den über 50-jährigen OAT-Patienten fiel auf, dass sich diese Population im Vergleich zur gleichaltrigen Normalbevölkerung in schlechterem Gesundheitszustand sowie auf niedrigerem sozialen Funktionsniveau befindet. Die Entstehung eines neuen Patientenkollektives stellt komplexe Ansprüche an das Gesundheitssystem. Insbesondere betrifft dies die somatische, psychiatrische und psychosoziale Versorgung dieser Patientengruppe. Diese Herausforderungen wurden kaum untersucht. Mittels einer Online-Umfrage wurde eine Analyse der Situation aus Sicht der Behandlungsanbieter in der deutschsprachigen Schweiz durchgeführt. Dabei wurden aus Sicht der Mitarbeitenden Bedarf an verbesserter altersgerechter Infrastruktur, ausgearbeitete Konzepte im Umgang mit älteren Patienten sowie Fortbildungen im Bereich „Palliative Care“ festgestellt. Einigkeit bestand darüber, dass die OAT auch für ältere Patienten weiterhin ermöglicht werden sollte.
Anti-Craving-Substanzen bei Alkoholabhängigkeit
Authors: Rösner Susanne , Soyka Michael
Published: August 2021

Die Therapieerfolge von Anti-Craving-Substanzen bewegen sich im Bereich geringer bis moderater Effekte. Gleichzeitig macht die starke Heterogenität der Effekte innerhalb von Studien deutlich, dass sich Patienten im Ansprechen auf Anti-Craving-Substanzen unterscheiden und in bestimmten Patientengruppen stärkere Effekte als im Stichprobenmittel erzielt werden. Eine daraus ableitbare therapeutische Strategie basiert auf der Individualisierung der pharmakologischen Rückfallprophylaxe unter Berücksichtigung der zugrunde liegenden Wirkmechanismen 1. Ein weiterer Ansatz besteht in der Modifikation von Faktoren, die für das Ansprechen von Patienten von Bedeutung sind. Voraussetzung dafür ist die Identifikation individueller Einflussfaktoren und die Etablierung von Methoden, diese in positiver Richtung zu verändern.

Der folgende Beitrag gibt einen Überblick über die aktuelle Befundlage zur Wirksamkeit von Anti-Craving-Substanzen, wobei der Schwerpunkt auf die Darstellung individueller Effektmoderatoren als Grundlage für die Ableitung optimierender Strategien gelegt wird.
Classic Psychedelic Coadministration with Lithium, but Not Lamotrigine, is Associated with Seizures: An Analysis of Online Psychedelic Experience Reports
Authors: Nayak Sandeep M. , Gukasyan Natalie , Barrett Frederick S. , Erowid Earth , Erowid Fire , Griffiths Roland R.
Published: August 2021

Introduction Psychedelics show promise in treating unipolar depression, though patients with bipolar disorder have been excluded from recent psychedelic trials. There is limited information on the use of classic psychedelics (e. g., LSD or psilocybin) in individuals using mood stabilizers to treat bipolar disorder. This is important to know, as individuals with bipolar depression may attempt to treat themselves with psychedelics while on a mood stabilizer, particularly given enthusiastic media reports of the efficacy of psilocybin for depression.

Methods This study analyzed reports of classic psychedelics administered with mood stabilizers from 3 websites (Erowid.org, Shroomery.org, and Reddit.com).

Results Strikingly, 47% of 62 lithium plus psychedelic reports involved seizures, and an additional 18% resulted in bad trips while none of 34 lamotrigine reports did. Further, 39% of lithium reports involved medical attention. Most of the lamotrigine reports (65%) but few (8%) of the lithium reports were judged to not affect the psychedelic experience.

Discussion Although further research is needed, we provisionally conclude that psychedelic use may pose a significant seizure risk for patients on lithium.
Husten und Belastungsdyspnoe nach ölhaltiger Mentholinhalation
Authors: Friedrich Juliane , Michels Berthold , Lohfink-Schumm Sylvia , Mackert Heide Isabell , Bargon Joachim
Published: August 2021

Ein 48-jähriger Patient mit einem seit 5 Wochen bestehenden nichtproduktiven Husten und Belastungsdyspnoe stellte sich in der pneumologischen Ambulanz vor. Eine Lungenfunktion enthüllte eine leichtgradige Diffusionsstörung. In einer durchgeführten Computertomografie des Thorax ergab sich das Bild einer atypischen Pneumonie mit beidseitigen, im rechten Oberlappen-betonten Konsolidierungen.

In einer transbronchialen Biopsie aus dem Bereich der Veränderungen ließen sich mittels der Sudan-Schwarz-Färbung mit Lipid-beladene Makrophagen nachweisen. Damit konnte die Diagnose einer Lipidpneumonie gesichert werden, die im Rahmen einer Inhalation mentholhaltiger Substanzen entstanden ist.

Nach Absetzen des auslösenden Agens sowie hochdosierter Steroidgabe zeigten sich die Beschwerden regredient.
Time matters: civic engagement and the development of anti-immigrant attitudes among adolescents
Authors: Lundberg Erik , Abdelzadeh Ali
Published: August 2021

A recurring claim in the literature is that civic engagement in voluntary associations is crucial for the formation of a variety of interpersonal attitudes, such as social trust, tolerance, and intolerance. In this article, we study the role of membership in voluntary associations and volunteer work in the development of anti-immigrant attitudes among adolescents. Using a four-wave longitudinal design with a target sample comprising approximately 2000 adolescents between the ages of 13 and 16 at the first measurement occasion, this study contributes to previous research by analysing the impact on anti-immigrant attitudes of different dimensions of membership in voluntary associations and volunteer work. The results showed that membership in voluntary associations and volunteer work over several years serve to decrease anti-immigrant attitudes among adolescents over time. In addition, volunteering over several years seems to have a somewhat stronger impact on anti-immigrant attitudes than do various aspects of membership in associations. Our study also shows that anti-immigrant attitudes become more firmly established with age and that membership in only certain types of voluntary associations relates to attitudes toward immigrants. In sum, this study contributes to previous research focusing on the role of civic engagement in the development of interpersonal attitudes.
Measuring interest group agendas in regulatory proposals: a method and the case of US education policy
Authors: Workman Samuel , Carlson Deven , Bark Tracey , Bell Elizabeth
Published: August 2021

We introduce a new way to measure interest group agendas and demonstrate an approach to extending the CAP topic coding scheme to policy domains at lower levels of analysis. We use public comments on regulatory proposals in US education policy to examine the topics contained in policy arguments. We map the education policy space using a data set of 493 comments and 5315 hand-coded comment paragraphs. A unique measurement model accounts for group and topic diversity and allows us to validate our approach. The findings have implications for measuring topic agendas in lower-level policy domains and understanding group coalitions and competition in education policy. We contribute to text-as-data approaches tracing policy change in the study of public policy. The findings suggest the relationship between issue attention observed by scholars and larger policy reform movements.
Grand challenges and emergent modes of convergence science
Authors: Petersen Alexander M. , Ahmed Mohammed E. , Pavlidis Ioannis
Published: August 2021

To address complex problems, scholars are increasingly faced with challenges of integrating diverse domains. We analyzed the evolution of this convergence paradigm in the ecosystem of brain science, a research frontier that provides a contemporary testbed for evaluating two modes of cross-domain integration: (a) cross-disciplinary collaboration among experts from academic departments associated with disparate disciplines; and (b) cross-topic knowledge recombination across distinct subject areas. We show that research involving both modes features a 16% citation premium relative to a mono-domain baseline. We further show that the cross-disciplinary mode is essential for integrating across large epistemic distances. Yet we find research utilizing cross-topic exploration alone—a convergence shortcut—to be growing in prevalence at roughly 3% per year, significantly outpacing the more essential cross-disciplinary convergence mode. By measuring shifts in the prevalence and impact of different convergence modes in the 5-year intervals up to and after 2013, we find that shortcut patterns may relate to competitive pressures associated with Human Brain funding initiatives launched that year. Without policy adjustments, flagship funding programs may unintentionally incentivize suboptimal integration patterns, thereby undercutting convergence science’s potential in tackling grand challenges.
Beyond optimization—supervised learning applications in relativistic laser-plasma experiments
Authors: Lin Jinpu , Qian Qian , Murphy Jon , Hsu Abigail , Hero Alfred , Ma Yong , Thomas Alexander G. R. , Krushelnick Karl
Published: August 2021

We explore the applications of a variety of machine learning techniques in relativistic laser-plasma experiments beyond optimization purposes. With the trained supervised learning models, the beam charge of electrons produced in a laser wakefield accelerator is predicted given the laser wavefront change caused by a deformable mirror. Feature importance analysis using the trained models shows that specific aberrations in the laser wavefront are favored in generating higher beam charges, which reveals more information than the genetic algorithms and the statistical correlation do. The predictive models enable operations beyond merely searching for an optimal beam charge. The quality of the measured data is characterized, and anomaly detection is demonstrated. The model robustness against measurement errors is examined by applying a range of virtual measurement error bars to the experimental data. This work demonstrates a route to machine learning applications in a highly nonlinear problem of relativistic laser-plasma interaction for in-depth data analysis to assist physics interpretation.
Unsteady flow of igniter combustion-gas heating base bleed propellant by convection
Authors: Xue Xiaochun , Yu Yonggang
Published: August 2021

The performance and launching accuracy of the vehicle with the base-bleed unit (BBU) depend strongly on the complex flow field characteristics and reignition delay time of the base bleed propellant in the combustion chamber of the BBU because the rapid depressurization process will occur in the BBU with a significantly altered flow field structure and induced extinguishment of the base bleed propellant located on both sides of the BBU when the vehicle is out of the muzzle at an initial time. However, the base bleed propellant will be reignited under the continuous convective heating effect of the igniter combustion-gas jet in the BBU at a later time. In this study, numerical simulations are carried out to investigate the coupling flow field characteristics and heating mechanism of the igniter of an actual BBU under a rapid depressurization process. Indeed, it is found that when the base bleed vehicle is out of the muzzle, the BBU experiences a rapid depressurization process due to the pressure difference between the combustion chamber of the BBU and the atmosphere, resulting in a strong unsteady flow field structure under the Kelvin–Helmholtz instability effect from the velocity difference between the igniter combustion-gas and gun propellant combustion-gas. Meanwhile, the high-temperature combustion-gas from the igniter is pressed on the end face of the igniter, and then, the axial expansion becomes quicker than the radial expansion with the development of the depressurization process. Afterward, the continuous convective heating effect of the igniter combustion-gas jet on the base bleed propellant occurs due to the direct contact of the high-temperature combustion-gas jet from the igniter with the surface of the base bleed propellant.
Manipulating the three-phase contact line of an evaporating particle-laden droplet to get desirable microstructures: A lattice Boltzmann study
Authors: Nath Gaurav , Ray Bahni
Published: August 2021

The lattice Boltzmann method (LBM) is used to study a novel inkjet printing scheme for making three-dimensional (3D) microstructures from evaporating droplets laden with the nanoparticles. The scheme involves pinning the three-phase contact line (TCL) on the specific points of a chemically heterogeneous pattern, leading to an asymmetric retraction of the TCL and a corresponding particle deposition morphology. A simple isothermal LBM model incorporating diffusion-limited evaporation, contact line pinning, and an Eulerian treatment of particles is employed to study the said scheme. The results show that TCL retraction plays a significant role in determining the final shape of the pattern when the particle concentration is low (<1 wt.  %), enabling a pure liquid approach to approximate the deposition. For the particle Peclet number greater than one, the coffee-ring effect leads to undesirable non-uniform deposits close to the pinning regions. Increasing the pattern dimensions and the surface energy difference between the pattern and the substrate result in a more stereoscopic morphology. The shape of the pattern and the pinning points can be altered to control the shape and the dimensions of the final 3D microstructure. A premature unpinning of the pure liquid drop is observed at the sharp edges of the pinning points owing to the higher contact line curvature in that region.
Wafer-scale integration of graphene for waveguide-integrated optoelectronics
Authors: Mišeikis Vaidotas , Coletti Camilla
Published: August 2021

As the focus of graphene research shifts from fundamental physics to applications, the scalability and reproducibility of experimental results become ever more important. Graphene has been proposed as an enabling material for the continuing growth of the telecommunications industry due to its applications in optoelectronics; however, the extent of its adoption will depend on the possibility to maintain the high intrinsic quality of graphene when processing it using the industry-standard approaches. We look at the challenges of scalable graphene integration and the opportunities presented by the recent technological advances.
Electronic properties of intrinsic vacancies in single-layer CaF2 and its heterostructure with monolayer MoS2
Authors: Li Zhenzhen , Baskurt Mehmet , Sahin Hasan , Gao Shiwu , Kang Jun
Published: August 2021

Exploring gate insulator materials for 2D transistors and their defect properties is of importance for device performance optimization. In this work, the structural and electronic properties of intrinsic vacancies in the CaF2 single layer and its heterostructures with monolayer MoS2 are investigated from first-principles calculations. VCa introduces a shallow defect level close to the VBM, whereas VF introduces a deep level below the CBM. In both cases, spin polarization is observed. Overall, VF has a relatively lower formation energy than VCa, except for the extreme Ca-rich case. Thus, VF should be dominant in CaF2. The band offset between CaF2 and MoS2 is determined to be type-I, with large offsets at both the conduction band and valence band. With the presence of vacancies in CaF2, the type-I band offset is preserved. The electron or hole on the defect states will transfer from CaF2 to MoS2 due to the large band offset, and spin polarization vanishes. Nevertheless, there are no defect states inside the gap or around the band edge of MoS2, and the electronic properties of MoS2 are almost intact. Compared with h-BN that has a small valence band offset with MoS2 and could introduce in-gap defect states, CaF2 can be a good candidate to serve as the dielectric layer of MoS2-based transistors.
Thermal conductivity of strongly coupled Yukawa fluids
Authors: Khrapak Sergey A.
Published: August 2021

A vibrational model of heat conduction in liquids with soft pairwise interactions is applied to estimate the thermal conductivity coefficient of strongly coupled Yukawa fluids. A reasonable agreement with the available data from numerical simulations is observed. The results can be useful in the context of strongly coupled plasma and complex (dusty) plasma fluids, when Yukawa (or screened Coulomb) interaction potential is applicable.
Effect of the aspect ratio on the velocity field of a straight open-channel flow
Authors: Shinneeb A.-M. , Nasif G. , Balachandar R.
Published: August 2021

This study investigates numerically the effect of the aspect ratio (AR) on the velocity field characteristics of the turbulent flow of a straight open-channel flow. Five aspect ratio cases (AR = channel width/flow depth) are investigated ranging from a narrow case of AR = 1 to a wide case of AR = 9. The transient three-dimensional Navier–Stokes equations were numerically solved using a finite-volume approach with an improved–delayed detached-eddy simulation turbulence model. The objective of this study is to enhance our understanding of the effect of AR on the formation of secondary currents in a channel flow. The results revealed the formation of a pair of counter-rotating recirculation zones near the bottom corners of the channel, whose axes are aligned with the main flow direction. Each pair consists of a mean recirculation zone that resides near the bed (bed recirculation zone), and another one that resides near the sidewall (side recirculation zone). The AR appears to significantly influence the size and strength of the recirculation zones. With decreasing the AR, the momentum transport by the streamwise-vertical Reynolds shear stress in the horizontal direction appears to be inhibited at higher vertical locations, the momentum transport by streamwise-transverse Reynolds shear stress is considerably enhanced, and the momentum transport by vertical-transverse Reynolds shear stress is slightly enhanced.
Non-thermal plasma multi-jet platform based on a flexible matrix
Authors: Corbella Carles , Portal Sabine , Lin Li , Keidar Michael
Published: August 2021

A new plasma source design that merges the main characteristics of capacitive dielectric barrier discharge (DBD) and cold atmospheric plasma jet (CAPJ) is discussed. The DBD system contains a flexible, porous matrix consisting of silica aerogel, which is comprised between two biased electrodes. The helium flow supply subjected to a sinusoidal voltage of around 5 kV in amplitude and 15 kHz in frequency provides a set of plasma jets that propagates more than 1 cm beyond the active DBD region. The studied plasma multi-jet system consists of an array of three aligned jets that flow in the laminar regime, and it is intended for treating the surfaces of 3D objects and large areas. CAPJ performance is discussed as a hypothetical morphing source in flat and bent configurations. Electrical characterization and optical emission spectroscopy diagnostics have provided current–voltage waveforms and the composition of the CAPJ through the aerogel layer, respectively. This novel source is promising for biomedical applications that require full adaptation of plasma parameters to delicate samples, such as wound healing and treatment of surgical margins in plasma-based cancer surgery.
The electron acoustic waves in plasmas with two kappa-distributed electrons at the same temperatures and immobile ions
Authors: Guo Ran
Published: August 2021

The linear electron acoustic waves propagating in plasmas with two kappa-distributed electrons and stationary ions are investigated. The temperatures of the two electrons are assumed to be same, but the kappa indices are not. It shows that if one kappa index is small enough and the other one is large enough, a weak damping regime of the electron acoustic waves exists. The dispersions and damping rates are numerically studied. The parameter spaces for the weakly damped electron acoustic waves are analyzed. Moreover, the electron acoustic waves in the present model are compared with those in other models, especially the plasmas with two-temperature electrons. At last, we perform Vlasov–Poisson simulations to verify the theory.
Direct simulations and subgrid modeling of turbulent channel flows asymmetrically heated from both walls
Authors: David M. , Toutant A. , Bataille F.
Published: August 2021

Thermal large-eddy simulations (T-LES) and a direct numerical simulation are carried out in a bi-periodical channel with hot and cold wall temperatures of, respectively, 900 and 1300 K. The mean fluid temperature is lowered below the cold wall temperature thanks to a heat source, resulting in a both walls heating of the fluid. The hot and cold wall friction Reynolds numbers are, respectively, 640 and 1000. These conditions are representative of the working conditions of gas-pressurized solar receiver of solar power tower. The low Mach number Navier–Stokes equations are solved. The coupling between the dynamic and the temperature effects is considered. In the T-LES, both the momentum convection and the density–velocity correlation subgrid terms are modeled. Functional models, structural models, and mixed models are considered. A tensorial version of the anisotropic minimum-dissipation (AMD) model is also investigated. The Quick and the second-order-centered schemes are tested for the discretization of the mass convection term. First, an overview of the results of 17 T-LES on first- and second-order statistics is proposed. It permits selecting 6 of these simulations for a detailed analysis consisting in the investigation of profiles of mean quantities and turbulent correlations. Particular attention is given to the wall heat fluxes because they are a critical point for the design and the optimization of solar receivers. Overall, the first-order statistics are better predicted than the second-order's. The tensorial AMD model takes advantage of the classical AMD model properties and better reproduces the anisotropy of the flow thanks to its formulation. The tensorial AMD model produces the most reliable and efficient results among the considered models.
The effect of droplet coalescence on drag in turbulent channel flows
Authors: Cannon Ianto , Izbassarov Daulet , Tammisola Outi , Brandt Luca , Rosti Marco E.
Published: August 2021

We study the effect of droplet coalescence on turbulent wall-bounded flows by means of direct numerical simulations. In particular, the volume-of-fluid and front-tracking methods are used to simulate turbulent channel flows containing coalescing and non-coalescing droplets, respectively. We find that coalescing droplets have a negligible effect on the drag, whereas the non-coalescing ones steadily increase drag as the volume fraction of the dispersed phase increases: indeed, at 10% volume fraction, the non-coalescing droplets show a 30% increase in drag, whereas the coalescing droplets show less than 4% increase. We explain this by looking at the wall-normal location of droplets in the channel and show that non-coalescing droplets enter the viscous sublayer, generating an interfacial shear stress, which reduces the budget for viscous stress in the channel. On the other hand, coalescing droplets migrate toward the bulk of the channel forming large aggregates, which hardly affect the viscous shear stress while damping the Reynolds shear stress. We prove this by relating the mean viscous shear stress integrated in the wall-normal direction to the centerline velocity.