Technische Universitat Ilmenau Research Articles

The hot spot transformation in the research evolution of maker

The rapid development of digital technology together with the grassroots innovation has led to a new landmark of maker culture. Recently, a search with the query of ‘‘makerspace’’, ‘‘maker movement’’ and ‘‘maker culture’’ in Google Scholar found over 10,000 documents in total. As the volume of the literature grows rapidly, thus, a systematic review of maker research and its current challenges becomes essential. This study surveys the literature of maker between 1975 and 2016. The overall structure of its intellectual landscape is illustrated in terms of thematic concentrations of knowledge clusters of maker study, hot research categories and keywords, major contributing factors including contributing countries, organizations, and authors. Our review is based on 836 bibliographic records retrieved from the ISI Web of Science and visualized by the scientometric software of CiteSpace. This application results in comprehensive knowledge maps of maker research. The study identifies major intellectual cooperation network, co-occurrence keywords, research clusters and landmark articles, including: (1) the thematic clusters of ‘‘maker movement’’, ‘‘DIY culture and extended milieu’’, ‘‘craftsman hero’’ reflects the biggest knowledge base clusters of maker study. (2) “Physical computing”, “maker space”, “maker movement”, “3D printer” are the major frontiers of maker research based on analysis of citation burst. (3) In terms of contributing countries, institutions, authors, the major driving force of maker research is from the United States of America, England and Germany, with University of California Berkeley, Georgia Institute of Technology and Massachusetts Institute of Technology being major contributing institutions. Paulo Blikstein from Stanford University USA, Vasilis Kostakis from Tallinn University of Technology Estonia, Hans-Joachim Bohme from Technische Universitat Ilmenau German all have published three articles and rank at the top of the author list.

Dry Block Calibrator with Improved Temperature Field and Integrated Fixed-Point Cells

To reduce uncertainty of calibrations of contact thermometers using dry block calibrators, a concept was developed at Institute for Process Measurement and Sensor Technology of Technische Universitat Ilmenau. This concept uses a multi-zone heating, heat flux sensors and a multiple fixed-point cell. The paper shows the concept and its validation on the basis of a dry block calibrator with a working temperature range of \(70\,^{\circ }\hbox {C}\) to \(430\,^{\circ }\hbox {C}\). The experimental results show a stability of \({\pm } 4\,\hbox {mK}\) for the reference temperature and axial temperature differences in the normalization block less than \({\pm }55\,\hbox {mK}\).

From the editors' desk

The first article is "Transient and Steady-State DC Behavior of Oil-Impregnated Pressboard," by Fabian Schober, Stephan Harrer, and Andreas Kuchler of the University of Applied Sciences, Schweinfurt, Germany; Frank Berger of the Technische Universitat Ilmenau, Germany; and Wolfgang Exner and Christoph Krause of Weidmann Electrical Technology AG, Rapperswil, Switzerland. The article investigates the influence of pressboard density and oil conductivity on the conductivity of oil-impregnated pressboard, and both are shown to be important for achieving a desired conductivity of oil-impregnated pressboard for HVDC applications. Two pressboard types, low and high density, and two types of mineral oils, low conductive and high conductive, were used in the investigation. Both pressboard types exhibited similar apparent conductivities when impregnated with low-conductive oil, but when impregnated with high-conductive oil, an apparent conductivity 2.8 times higher was observed as a consequence of the larger oil volume. Yet, the numeric assessment of oil-impregnated pressboard conductivity by simple linear superposition of pressboard conductivity and oil conductivity does not provide the measured apparent conductivity. In addition, the influence of oil conductivity on the apparent oil-impregnated pressboard conductivity was evaluated. Pressboard impregnated with four types of mineral oil, spanning an apparent conductivity of 2.5 orders of magnitude, was found to be only in an apparent conductivity range of oil-impregnated pressboard of only 0.5 orders of magnitude. As an explanation for the observed phenomenon, it appears that new and modified charge transport paths in the oil volume altered the transport paths along pressboard fibers. Conduction processes therefore interact with each other, and this interaction opens a new and interesting field of further research. Selecting a suitable pressboard density and the right choice of mineral oil can be used to achieve the desired conductivity for the oil-pressboard insulation system, which may be an option for the optimization of HVDC insulation systems.

Calculation of electrical circuits with fractional characteristics of construction elements

Based on the memristor and applications in the field of filter technique, the elements of higher order have been developed at Technische Universitat Ilmenau as an extension of the classical bipolar construction elements. The elements of higher order form a set of points in the α,β-range. For these points only integer coordinates are allowed. Elements along a straight line with α-β=const. show the same characteristic behaviour. To close the gap between the points of integer coordinates Riemann–Liouville fractional calculus is applied. So the class of construction elements of higher, integer order ist extended to the one of higher, real order. The differences are shown by calculations of the voltage-current behaviour of electrical circuits.