MECHATRONIC CLAMPING MECHANISM WITH ELECTRO-HYDRAULIC ACTUATOR FOR MACHINE SPINDLE UNITS

The design of the clamping mechanism for fixing workpieces and tools in the spindle assemblies of machines that is equipped with an additional subsystem to provide the possibility of programmable settings to the required clamping force is presented. The electronic unit and electromechanical energy converters provide the possibility of reconfiguration by reprogramming the clamping mechanism according to the different tasks comparatively easily. The obtained results help to expand the functionality of clamping mechanisms, and consequently the functionality of machine tools and their technological flexibility.

Leadership behaviour, team effectiveness, technological flexibility, work engagement and performance during COVID-19 lockdown: An exploratory study

Orientation: The coronavirus disease 2019 (COVID-19) pandemic has taken the world by storm. Little is known about leadership, motivation and employee performance during pandemics and associated lockdowns.Research purpose: The current study investigated a model of leadership behaviour, team effectiveness, technological flexibility, work engagement and performance in the context of a ‘hard lockdown’ in South Africa.Motivation for the study: As a result of the COVID-19 pandemic and the resulting lockdown, it was considered from an academic-practitioner perspective to explore leadership behaviour, team effectiveness, technological flexibility, work engagement and performance.Research approach/design and method: Specifically, remote workers were sampled online via social media (n = 229). Structural equation modelling methods were used to analyse the data, also controlling optimism and pessimism at the item level.Main findings: The results showed that the resources of leadership behaviour and team effectiveness had direct positive paths to work engagement and that work engagement had a positive path to two performance factors: adaptivity and proactivity. Furthermore, there were significant indirect relationship present from leadership behaviour and team effectiveness to both adaptability and proactivity through work engagement.Practical/managerial implications: From the evidence it seems appropriate to recommend that organisations explore fostering the employee job resources in order to positively impact work engagement, which in turn can have beneficial performance outcomes for organisations who have employees working remotely whilst the COVID-19 regulations remain in force.Contribution/value-add: This study was unique as it sampled from employees ‘locked down’ during a pandemic and gauged their perceptions of leadership behaviour, team effectiveness, technological flexibility, work engagement and performance.

Анализ и исследование материаловедческих и технологических факторов при создании пленочных преобразователей

Проведены анализ и исследование материаловедческих и технологических факторов при создании пленочных преобразователей, определены требования к материалам и их свойствам, технологии формирования элементов преобразователя. Показано, что учет материаловедческих и технологических факторов обеспечивает соответствие параметров пленочного преобразователя с требуемыми, устойчивость к внешним воздействующим факторам, получение пленок исходного состава, стабильность технологии производства. Выбор параметров материалов производится с учетом режимов и условий эксплуатации, статических и динамических нагрузок, действующих на элементы преобразователя, свойств исходных материалов и пленочных элементов. При сопряжении разнородных материалов учитывают коэффициенты линейного расширения. В процессе создания пленочных преобразователей исходные материалы, конструктивные элементы обрабатываются в различных технологических средах и подвергаются тепловым воздействиям, формируются заданные структуры и параметры пленочного преобразователя, и вместе с этим усиливаются несовершенства, имевшиеся в исходных материалах и элементах преобразователя, которые прямо или косвенно влияют на выходные параметры пленочного преобразователя. При изготовлении пленочных элементов преобразователя выбор метода получения тонких пленок определяется назначением пленки, совместимости метода с другими технологическими операциями микроэлектронной технологии. Воспроизводимость электрофизических свойств тонких пленок имеет место при их осаждении с контролируемым составом, что существенно при получении пленок на основе полупроводниковых соединений и формировании чувствительных элементов преобразователя. Анализ и исследования методов получения пленок показали, что энергетическая эффективность процесса ионного распыления материалов и получения тонких пленок заданного состава, технологическая гибкость, возможность регулирования толщины пленок путем изменения величины тока, времени осаждения и давления, при котором оно проводится, являются наиболее оптимальными. The analysis and research of material science and technological factors in the creation of film converters is carried out, the requirements for materials and their properties, the technology for the formation of converter elements are determined. It is shown that taking into account materials science and technology factors ensures that the parameters of the film converter meet the required parameters, resistance to external factors, obtaining films of the original composition, and stability of the production technology. The choice of material parameters is made taking into account operating conditions and conditions, static and dynamic loads acting on the converter elements, the properties of the starting materials and film elements. When pairing dissimilar materials, linear expansion coefficients are taken into account. In the process of creating film converters, the starting materials, structural elements are processed in various technological environments and exposed to thermal influences, the specified structures and parameters of the film converter are formed, and at the same time, the imperfections in the starting materials and converter elements are amplified, which directly or indirectly affect the output parameters film converter. In the manufacture of film elements of the converter, the choice of the method for producing thin films is determined by the purpose of the film, the compatibility of the method with other technological operations of microelectronic technology. The reproducibility of the electrophysical properties of thin films takes place when they are deposited with a controlled composition, which is essential when producing films based on semiconductor compounds and the formation of sensitive elements of the transducer. Analysis and research of methods for producing films showed that the energy efficiency of the process of ion sputtering of materials and the production of thin films of a given composition, technological flexibility, the ability to control the thickness of the films by changing the current, deposition time and pressure at which it is carried out, are the most optimal.

Covalent Adaptable Networks (CANs)

Thermosets are known to be very reliable polymeric materials for high-performance and light-weight applications, due to their retained dimensional stability, chemical inertia and rigidity over a broad range of temperatures. However, once fully cured, they cannot be easily reshaped or reprocessed, thus leaving still unsolved the issues of recycling and the lack of technological flexibility. Vitrimers, introduced by Leibler et al. in 2011, are a valiant step in the direction of bridging the chasm between thermoplastics and thermosets. Owing to their dynamic covalent networks, they can retain mechanical stability and solvent resistance, but can also flow on demand upon heating. More generally, the family of Covalent Adaptable Networks (CANs) is gleaming with astounding potential, thanks to the huge variety of chemistries that may enable bond exchange. Arising from this signature feature, intriguing properties such as self-healing, recyclability and weldability may expand the horizons for thermosets in terms of improved life-span, sustainability and overall enhanced functionality and versatility. In this review, we present a comprehensive overview of the most promising studies featuring CANs and vitrimers specifically, with particular regard for their industrial applications. Investigations into composites and sustainable vitrimers from epoxy-based and elastomeric networks are covered in detail.

The Impact of Vitrimers on the Industry of the Future: Chemistry, Properties and Sustainable Forward-Looking Applications

Thermosets are known to be very reliable polymeric materials for high-performance and light-weight applications, due to their retained dimensional stability, chemical inertia and rigidity over a broad range of temperatures. However, once fully cured, they cannot be easily reshaped or reprocessed, thus leaving still unsolved the issues of recycling and the lack of technological flexibility. Vitrimers, introduced by Leibler et al. in 2011, are a valiant step in the direction of bridging the chasm between thermoplastics and thermosets. Owing to their dynamic covalent networks, they can retain mechanical stability and solvent resistance, but can also flow on demand upon heating. More generally, the family of Covalent Adaptable Networks (CANs) is gleaming with astounding potential, thanks to the huge variety of chemistries that may enable bond exchange. Arising from this signature feature, intriguing properties such as self-healing, recyclability and weldability may expand the horizons for thermosets in terms of improved life-span, sustainability and overall enhanced functionality and versatility. In this review, we present a comprehensive overview of the most promising studies featuring CANs and vitrimers specifically, with particular regard for their industrial applications. Investigations into composites and sustainable vitrimers from epoxy-based and elastomeric networks are covered in detail.

Realistic and Robust Reproducible Research for Biostatistics

The complexity of analysis pipelines in biomedical sciences poses a severe challenge for the transparency and reproducibility of results. Researchers are increasingly incorporating software development technologies and methods into their analyses, but this is a quickly evolving landscape and teams may lack the capabilities to set up their own complex IT infrastructure to aid reproducibility. Basing a reproducible research strategy on readily available solutions with zero or low set-up costs whilst maintaining technological flexibility to incorporate domain-specific software tools is therefore of key importance. We outline a practical approach for robust reproducibility of analysis results. In our examples, we rely exclusively on established open-source tools and free services. Special emphasis is put on the integration of these tools with best practices from software development and free online services for the biostatistics domain.

African seaports and development in historical perspective

This article presents a long-term explanation of port evolution in Africa. It focuses on the economic, political and social characteristics that influenced the development of maritime infrastructures and their interaction with inland transport systems. This article demonstrates how seaport evolution in Africa has been heavily affected by path-dependence patterns. In addition, this study provides evidence of the insertion of the African economy into the waves of globalization through the modernization of seaports and the necessary institutional and technological flexibility.

Production data of wine grape gene bank (Vitis spp.) of University of Debrecen, east Hungary

National wine strategy of Hungary promotes the use of “flexible” grape cultivars. These enable producers’ best fit to wine market changes and expectations. This study is aimed to present data on the gene bank of the University of Debrecen, Hungary. Data were collected at a single site, between 2010 and 2018 in east Hungary lowland on acidic sandy soil, own rooted planting material. Our results showed that besides high yield and adequate cane production desired sugar content at convenient pH is to be awaited with moderate deviation between vintages. Presented concept demonstrate technological flexibility of cultivars by their average deviation from regression equation between increasing sugar and pH typical for the vintage composed of data of cultivars of the gene bank. Average positive deviation means higher sugar content at specific pH, thus higher sugar content at desired, conveniently low pH (3.0-3.2 pH).