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Number of results: 26
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Abstract

The Ti15Mo alloy has been studied towards long-term corrosion performance in saline solution at 37°C using electrochemical impedance spectroscopy. The physical and chemical characterization of the material were also investigated. The as-received Ti15Mo alloy exhibits a single β-phase structure. The thickness of single-layer structured oxide presented on its surface is ~4 nm. Impedance measurements revealed that the Ti15Mo alloy is characterized by spontaneous passivation in the solution containing chloride ions and formation of a double-layer structured oxide composed of a dense interlayer being the barrier layer against corrosion and porous outer layer. The thickness of this oxide layer, estimated based on the impedance data increases up to ~6 nm during 78 days of exposure. The observed fall in value of the log|Z|f = 0.01 Hz indicates a decrease in pitting corrosion resistance of Ti15Mo alloy in saline solution along with the immersion time. The detailed EIS study on the kinetics and mechanism of corrosion process and the capacitive behavior of the Ti15Mo electrode | passive layer | saline solution system was based on the concept of equivalent electrical circuit with respect to the physical meaning of the applied circuit elements. Potentiodynamic studies up to 9 V vs. SCE and SEM analysis show no presence of pitting corrosion what indicates that the Ti15Mo alloy is promising biomaterial to long-term medical applications.

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Authors and Affiliations

M. Szklarska
B. Łosiewicz
G. Dercz
M. Zubko
R. Albrecht
D. Stróż
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Abstract

In the paper, the authors discuss the possibility to apply the "Nodalised Beam" method for vibroinsulation of manually operated tools. They indicate the difficulties in applying the original method for this purpose. On the bases of the reciprocity principle, the authors propose a method for modifying the system that allows them to avoid the mentioned disadvantages. Equations derived for the modified system that makes it possible to define the position of nodal points. The relations were verified at a test station. Furthermore, a method of tuning the system was proposed.
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Authors and Affiliations

Leszek Majkut
Jerzy Michalczyk
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Abstract

The aim of this paper is to show that a real order generalization of the dissipative concepts is a useful tool to determine the stability (in the Lyapunov and in the input-output sense) and to design control strategies not only for fractional order non-linear systems, but also for systems composed of integer and fractional order subsystems (mixed-order systems). In particular, the fractional control of integer order system (e.g. PIλ control) can be formalized. The key point is that the gradations of dissipativeness, passivity and positive realness concepts are related among them. Passivating systems is used as a strategy to stabilize them, which is studied in the non-adaptive as well as in the adaptive case.

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Authors and Affiliations

J.A. Gallegos
M.A. Duarte-Mermoud
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Abstract

In this publication the effect of the operating temperature on the effective inductance of a controllable inductor is analysed. The main difference compared to a coil with a simple single core lies in the current-controlled inductance-value. This is achieved by a second core implemented perpendicular upon the load-toroid affecting the saturation within a limited shared volume. Corresponding to the presented analysis, the dependencies on the core temperatures are investigated by measurements.
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Authors and Affiliations

Guido Schierle
1
ORCID: ORCID
Michael Meissner
1
Klaus F. Hoffmann
1

  1. Helmut Schmidt University, Germany
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Abstract

In recent years, assessing supply system impedance has become crucial due to the concerns on power quality and the proliferation of distributed generators. In this paper, a novel method is shown for passive measurement of system impedances using the gapless waveform data collected by a portable power quality monitoring device. This method improves the overall measurement accuracy through data regrouping. Compared with the traditional methods that use the consecutive measurement data directly, the proposed method regroups the data to find better candidates with less flotation on the system side. Simulation studies and extensive field tests have been conducted to verify the effectiveness of the proposed method. The results indicate that the proposed method can serve as a useful tool for impedance measurement tasks performed by utility companies.
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Authors and Affiliations

Shuangting Xu
1
Xianyong Xiao
1
Yang Wang
1
Jun Wu
2
ORCID: ORCID

  1. Sichuan University, The College of Electrical and Engineering, Chengdu 610065, China
  2. Electric Power Research Institute of State Grid Zhejiang Electric Power Company, Hangzhou 310014, China
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Abstract

The author defines the semantic category of diathesis as grammaticalized information about the hierarchy of arguments inscribed into the semantic structure of a predicate. She demonstrates that we can perceive an event from different perspectives depending on which argument is for the moment in the center of our interest. Thus, unlike aspect, mood or tense, diathesis is not an inflectional category of the constitutive predicate of a proposition, but a category of a pro-position as such, notwithstanding the fact that there are oppositions as active ~ passive, or possession ~ appertainance/belonging to which affect directly the surface form of the constitutive predicate. There is also something as a natural diathesis depending on the semantic role of the top argument - it is characteristic of propositions with argument referring to the agens at the top of the hierarchy. Understood this way diathetical hierarchy can serve as a criterion for a fun-ctional classification of propositions and the place of an argument in that hiararchy as a criterion for a functional classification of arguments.

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Authors and Affiliations

Zuzanna Topolińska
ORCID: ORCID
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Abstract

As a result of introduction of the Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings, all of the EU member states are obliged to introduce legal regulations for energy performance of all newly constructed buildings. The key aim is to achieve close to zero energy use starting from the year 2021. Estimating effectiveness of the actions and the new possibilities requires an analysis of the multiple criteria. They comprise both the current conditions as well as the changes that have occurred in the recent years due to new legislation, the eff ects of the subsidies and the development of the housing stock. This paper presents a broad overview and diagnosis of current situation. The development of the energy-efficient and passive housing in Poland is considered in the context of financial incentives, availability of design knowledge and building technology as well as the role of the green building certification.

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Authors and Affiliations

Monika Arczyńska
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Abstract

The viability of epitaxial regrowth of non-intentionally doped InP to passivate lateral mesa surfaces of InGaAs photodiodes lattice-matched to InP is investigated, evaluating whether the residual doping of the regrown layer can be responsible for an unexpected increase of the surface current. The effect of residual doping is evaluated via numerical calculations of dark current, considering the range of doping concentrations expected for non-intentionally doped InP. The calculations show that the increase in dark current due to the residual doping of the regrown InP layer is not enough to justify the observed increase in surface current. On the other hand, the technique is still valid as a passivation method if the photodetector pixel is isolated by etching only the top contact layer.
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Authors and Affiliations

Osvaldo M. Braga
1
Cristian A. Delfino
1
Rudy M. S. Kawabata
2
Luciana D. Pinto
2
Gustavo S. Vieira
1
Maurício P. Pires
3
Patricia L. Souza
2
Euclydes Marega
4
John A. Carlin
5
Sanjay Krishna
5

  1. Institute for Advanced Studies, IEAV, 12228-001, São Paulo, Brazil
  2. LabSem, CETUC, Pontifícia Universidade Católica, PUC-Rio, R. Marquês de São Vicente 124, Gávea, 22451-900 Rio de Janeiro, Brazil
  3. Physics Institute, Federal University of Rio de Janeiro, Av. Athos da Silveira Ramos 149, 21941-909 Rio de Janeiro, Brazil
  4. Universidade de São Paulo, USP-São Carlos, 13566-560 São Carlos, SP, Brazil
  5. Ohio State University, 281 W Lane Ave., Columbus, OH 43210, USA
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Abstract

A double balanced passive mixer-based receiver operating in the 3-5 GHz UWB for medical applications is described in this paper. The receiver front-end circuit is composed of an inductorless low noise amplifier (LNA) followed by a fully differential voltage-driven double-balanced passive mixer. A duty cycle of 25% was chosen to eliminate overlap between LO signals, thereby improving receiver linearity. The LNA realizes a gain of 25.3 dB and a noise figure of 2.9 dB. The proposed receiver achieves an IIP3 of 3.14 dBm, an IIP2 of 17.5 dBm and an input return loss (S11) below -12.5dB. Designed in 0.18μm CMOS technology, the proposed mixer consumes 0.72pW from a 1.8V power supply. The designed receiver demonstrated a good ports isolation performance with LO_IF isolation of 60dB and RF_IF isolation of 78dB.
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Authors and Affiliations

Thaar A. Kareem
1
Hatem Trabelsi
1

  1. Systems Integration & Emerging Energies Laboratory, Electrical Engineering Department, National Engineers School of Sfax, University of Sfax, Sfax, Tunisia
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Abstract

The structural concept of the dome dates back to the Pantheon in Rome. It is used as the cover of many churches and mosques all around the world. Light solutions, with a well-visible dome-shaped truss skeleton, are often preferred in modern architecture. Base isolation techniques can be adopted to mitigate the seismic effects. This paper aims to investigate the efficiency of different designs for the truss skeleton. To solve the problem, one has to assign the constraints, the materials and the geometry of the dome, its supporting structure and the isolation devices (number, locations, and type). The screening of the effects of different scheme assumptions on structural behaviour provides a better insight into the problem.
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Authors and Affiliations

Sara Casciati
1
ORCID: ORCID

  1. SIART srl, Pavia, Italy
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Abstract

One of the most energy-intensive activities for a vehicle is space air conditioning, for either cooling or heating. Considerable energy savings can be achieved if this can be decoupled from the use of fuel or electricity. This study analyzes the opportunities and effectiveness of deploying the concept of passive cooling through the atmospheric window (i.e. the 8– 14 nm wavelength range where the atmosphere is transparent for thermal radiation) for vehicle temperature control. Recent work at our institute has resulted in a skylight (roof window) design for passive cooling of building space. This should be applicable to vehicles as well, using the same materials and design concept. An overall cooling effect is obtained if outgoing (long wavelength greater than 4 nm) thermal radiation is stronger than the incoming (short wavelength less than 4 nm) thermal radiation. Of particular interest is to quantify the passive cooling of a vehicle parked under direct/indirect sunlight equipped with a small skylight, designed based on earlier designs for buildings. The work involved simulations using commercial computational fluid dynamics software implementing (where possible) wavelengthdependency of thermal radiation properties of materials involved. The findings show that by the use of passive cooling, a temperature difference of up to 7–8 K is obtained with an internal gas flow rate of 0.7 cm/s inside the skylight. A passive cooling effect of almost 27 W/m2 is attainable for summer season in Finland. Comparison of results from Ansys Fluent and COMSOL models shows differences up to about 10 W/m2 in the estimations.
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Bibliography

[1] Welstand J.S., Haskew H.H., Gunst R.F., Bevilacqua O.M.: Evaluation of the effects of air conditioning operation and associated environmental conditions on vehicle emissions and fuel economy. SAE Tech. Pap. (2003), 2003-01-2247.
[2] Lambert M.A., Jones B.J.: Automotive adsorption air conditioner powered by exhaust heat. Part 1: Conceptual and embodiment design. P.I. Mech. Eng. D-J. Aut. Eng. Vol. 220(2006), 7, 959–972.
[3] Johnson V.H.: Fuel used for vehicle air conditioning: A state-by-state thermal comfort-based approach. SAE Tech. Pap. (2002), 2002-01-1957.
[4] Fayazbakhsh M., Bahrami M.: Comprehensive modeling of vehicle air conditioning loads using heat balance method. SAE Tech. Pap. (2013), 2013-01-1507.
[5] Zevenhoven R., Fält M.: Radiative cooling through the atmospheric window: A third, less intrusive geoengineering approach. Energy 152(2018), 27–33.
[6] Zevenhoven R., Fält M., Gomes L.P.: Thermal radiation heat transfer: Including wavelength dependence into modelling. Int. J. Therm. Sci. 86(2014), 189–197.
[7] Fält M., Pettersson F.: Modified predator-prey algorithm approach to designing a cooling or insulating skylight. Build. Environ. 126(2017), 331-338.
[8] Fält M.: The utilisation of participating gases and long-wave thermal radiation in a passive cooling skylight. PhD thesis. Åbo Akademi, Turku 2016.
[9] Kuczynski P., Białecki R.: Radiation heat transfer model using Monte Carlo ray tracing method on hierarchical ortho-Cartesian meshes and non-uniform rational basis spline surfaces for description of boundaries. Arch. Thermodyn. 35(2014), 2, 65–92.
[10] Hanjalic K., Kenjereš S., Tummers M.J., Jonker H.J.J.: Analysis and Modelling of Physical Transport Phenomena. VSSD, Delft 2009.
[11] Bielinski H., Mikielewicz J.: Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical side. Arch. Thermodyn. 31(2010), 4, 51–59.
[12] www.comsol.fi (accessed 20 June 2020).
[13] https://www.ansys.com/products/fluids/ansys-fluent (accessed 20 June 2020).
[14] Finnish Meteorological Institute. Weather and sea / Local weather. https://en.ilmatieteenlaitos.fi/weather/turku (accessed 2 Aug. 2018).
[15] Zevenhoven R., Fält M.: Heat flow control and energy recovery using carbon dioxide in double glass arrangements. In: Proc. ASME 2010 4th Int. Conf. on Energy Sustainability, Volume 2. Phoenix, May 17-22, 2010, 201–206 (ES2010-90189).
[16] Cucumo M., De Rosa A., Marinelli V.: Experimental testing of correlations to calculate the atmospheric “transparency window” emissivity coefficient. Sol. Energy 80(2006), 8, 1031–1038.
[17] Meinel A.B., Meinel M.P.: Applied Solar Energy. An Introduction. Addison- Wesley, 1977.
[18] Opto-Technological Laboratory (LLC Opto-TL). Zinc Sulfide ZnS Cleartran https://optotl.com/upload/pdf_en/zns_cleartnan.pdf (accessed 20 June 2020).
[19] https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node115.htm (accessed 17 Aug. 2020).
[20] Siegel R. Howell J.R.: Thermal Radiation Heattransfer (3rd Edn.). Hemisphere, Washington, DC 1992.
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Authors and Affiliations

Umara Khan
1
Ron Zevenhoven
1

  1. Abo Akademi University, Process and Systems Engineering Laboratory, Henrikinkatu 2, 20500 Turku, Finland
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Abstract

Marine mammal identification and classification for passive acoustic monitoring remain a challenging task. Mainly the interspecific and intraspecific variations in calls within species and among different individuals of single species make it more challenging. Varieties of species along with geographical diversity induce more complications towards an accurate analysis of marine mammal classification using acoustic signatures. Prior methods for classification focused on spectral features which result in increasing bias for contour base classifiers in automatic detection algorithms. In this study, acoustic marine mammal classification is performed through the fusion of 1D Local Binary Pattern (1D-LBP) and Mel Frequency Cepstral Coefficient (MFCC) based features. Multi-class Support Vector Machines (SVM) classifier is employed to identify different classes of mammal sounds. Classification of six species named Tursiops truncatus, Delphinus delphis, Peponocephala electra, Grampus griseus, Stenella longirostris, and Stenella attenuate are targeted in this research. The proposed model achieved 90.4% accuracy on 70–30% training testing and 89.6% on 5-fold cross-validation experiments.

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Authors and Affiliations

Maheen Nadir
Syed Muhammad Adnan
Sumair Aziz
Muhammad Umar Khan
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Abstract

This article provides an optimized solution to the problem of passive shielding against static magnetic fields with any number of spherical shells. It is known, that the shielding factor of a layered structure increases in contrast to a single shell with the same overall thickness. For the reduction of weight and cost by given material parameters and available space the best system for the layer positions has to be found. Because classic magnetically shielded rooms are very heavy, this system will be used to develop a transportable Zero-Gauss-Chamber. To handle this problem, a new way was developed, in which for the first time the solution with regard to shielding and weight was optimized. Therefore, a solution for the most general case of spherical shells was chosen with an adapted boundary condition. This solution was expanded to an arbitrary number of layers and permeabilities. With this analytic solution a differential evolution algorithm is able to find the best partition of the shells. These optimized solutions are verified by numerical solutions made by the Finite Element Method (FEM). After that the solutions of different raw data are determined and investigated.
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Bibliography

[1] Schiebold K., Zerstörungsfreie Werkstoffprüfung – Magnetpulverprüfung, Springer-Verlag (2015).
[2] Farolfi A., Trypogeorgos D., Colzi G., Fava E., Lamporesi G., Ferrari G., Design and characterization of a compact magnetic shield for ultracold atomic gas experiments, Review of Scientific Instruments, 90.11, 115114 (2019), DOI: 10.48550/arXiv.1907.06457.
[3] Report Buyer Ltd., Degaussing System Market by Solution, End User, Vessel Type and Region – Global Forecast to 2023, June (2018).
[4] Rücker A.W., VII. On the magnetic shielding of concentric spherical shells, The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 37.224, pp. 95–130 (1894).
[5] Baum E., Bork J., Systematic design of magnetic shields, Journal of Magnetism and Magnetic materials, 101.1-3, pp. 69–74 (1991).
[6] Clerk Maxwell J., Electricity and magnetism, vol. 2, New York: Dover (1954).
[7] David Jackson J., Classical Electrodynamics, American Association of Physics Teachers (1999).
[8] Karaboga D., Ökdem S., A simple and global optimization algorithm for engineering problems: differential evolution algorithm, Turkish Journal of Electrical Engineering and Computer Sciences, 12.1, pp. 53–60 (2004).
[9] Bronstein I.N., Hromkovic J., Luderer B., Schwarz H.R., Blath J., Schied A., Gottwald S., Taschenbuch der Mathematik, compact disc, Springer-Verlag (2008).
[10] Bartelmann M., Feuerbacher B., Krüger T., Lüst D., Rebhan A., Wipf A., Theoretische Physik 2 |Elektrodynamik, Springer-Verlag (2018).
[11] Rohner M., Magnetisch anhaftende Partikel zuverlässig entfernen, JOT Journal für Oberflächentechnik, 53, pp. 51–53 (2013).
[12] Maurer MagneticAG, Restmagnetismus – das verkannte Problem, JOT Journal für Oberflächentechnik, 57, pp. 104–105 (2017).
[13] Wilson E., Nicholson J.W., On the magnetic shielding of large spaces and its experimental measurement, Proceedings of the Royal Society of London, Series A, Containing Papers of a Mathematical and Physical Character, pp. 529–549 (1916).
[14] King L.V., XXI. Electromagnetic shielding at radio frequencies, The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 15.97, pp. 201–223 (1933).
[15] Reutov Y.Y., Choice of the number of shells for a spherical magnetostatic shield, Russian Journal of Non-destructive Testing, 37.12, pp. 872–878 (2001).
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Authors and Affiliations

Patrick Alexander Ralf
1
ORCID: ORCID
Christian Kreischer
1

  1. Helmut Schmidt University, University of the Federal Armed Forced Hamburg, Germany
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Abstract

Cube Satellites are miniaturized satellites used for space research with a mass of not more than 1.33 kg per unit. They are widely used in space applications because of its low cost of manufacturing and flexibility of applications. Since, they use commercial off-the-shelf components, thermal consideration of internal components of 1-unit cube satellites becomes a necessity. In this paper, transient thermal analysis of a 1-unit cube satellite is conducted to analyze its behavior during the first 29 seconds of orbit insertion from the launch vehicle. Transient thermal analysis yielded a temperature range that exceeded the optimum limit. As a result, to reduce heat dissipation, two main types of thermal management systems for satellites: active control and passive control systems are included. To maintain critical components at their operating temperature, a passive thermal control is implemented. Thermal strap and multi-layer insulation are used to analyze internal components of 1-unit cube satellite. Using graphite fiber thermal strap and aerogel multi-layer insulation for internal components, the 1-unit modular cube satellite is found to be more suitable under low earth orbit conditions.
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Authors and Affiliations

Sunidhi Kubade
1
ORCID: ORCID
Shruti Kulkarni
1
ORCID: ORCID
Pankaj N. Dhatrak
1
ORCID: ORCID

  1. Dr. Vishwanath Karad Mit World Peace University, Pune, India
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Abstract

This research was conducted to examine the corrosion behaviour of mild steel bar embedded in geopolymer paste based fly ash Class F during curing and non-curing process. The geopolymer paste was fabricated by blending in the fly ash with alkaline activators (NaOH solution with molarity of 12 M, 2.5 ratio of solution Na2SiO3/NaOH). The paste was produced in 50 mm × 50 mm × 50 mm mould where the mild steel bar of 100 mm (length) × 12 mm (diameter) was embedded at the center of geopolymer paste. This is to comprehend the corrosion behaviour of mild steel embedded in geopolymer paste with and without curing process. Process of curing is carried out for 24 hours at a temperature of 60°C in oven. While on the contrary, the non-curing process will only be leave at room temperature. Both samples were tested after 28 days of curing to determine the corrosion behaviour, phase analysis and morphology analysis. In accordance with the morphology analysis, it shows that the fly ash was totally reacted with alkaline solutions in curing geopolymer paste sample while the non-curing geopolymer paste has shown the unreacted fly ash with high number of pores. The phase analysis of mild steel embedded in this geopolymer paste during curing and without curing process has proven that the presence of new crystallographic peak which also known as passive layer occurred. The potential values result by OCP testing shows the curing sample has highest potential values as compared to the non-curing sample ones.
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Authors and Affiliations

Fatin Shahira Shaharudin
1
ORCID: ORCID
Farah Farhana Zainal
1
ORCID: ORCID
Nur Farhana Hayazi
1
ORCID: ORCID
Noraziana Parimin
1
ORCID: ORCID
Nur Izzati Muhammad Nadzri
1
ORCID: ORCID
Sri Hastuty
2
ORCID: ORCID
Andri Kusbiantoro
3
ORCID: ORCID

  1. Universiti Malaysia Perlis (UniMAP), Faculty of Chemical Engineering and Technology, Center of Excellence Geopolymer and Green Technology (CEGeoGTech), 01000 Perlis, Malaysia
  2. Universitas Pertamina, Department of Mechanical Engineering, Jakarta 12220, Indonesia
  3. Universiti Tun Hussein Onn Malaysia, Faculty of Engineering Technology, Johor, Malaysia
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Abstract

The generalized magnetizing curve series for the nonlinear magnetic circuit is proposed. Subsequently, three definitions of selfinductance for the nonlinear magnetic circuit are compared. The passivity of the magnetic circuit is reconsidered. Three theorems that describe features of Fourier harmonics of distorted waveforms have been proved.
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Authors and Affiliations

Dariusz Spałek
1
ORCID: ORCID

  1. Silesian University of Technology, Electrical Engineering Faculty, Akademicka 10, 44-100 Gliwice Poland
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Abstract

The work discusses numerical and experimental researches, which are focused on developing a coherent model of magnetic interactions causing the levitation of the starting trolley of the unmanned aerial vehicle (UAV) catapult. The starting trolley is levitating over the catapult’s tracks, which generate the magnetic field. The levitation is made possible by the diamagnetic properties of high-temperature superconductors, placed in supports of the starting trolley. The introduction of the article briefly analyzes the catapult structure. Next, it explains the nature of associated with the Meissner and flux pinning effect magnetic interactions which causes the levitation phenomenon. The paper presents the results of numerical analysis of the magnetic field, generated by the catapult’s tracks arranged in two configurations: a “chessboard” and a “gutter” pattern. The numerical model was solved, using the finite element method. Parameterization of the numerical model was made based on the measurements of the magnetic field, generated by a single magnet.

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Authors and Affiliations

A. Sibilska-Mroziewicz
E. Ładyżyńska-Kozdraś
K. Falkowski
K. Sibilski
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Abstract

Distributed generation is an issue intensively studied in recent years. It concerns, among others protection systems of distributed generation units connected to electric power grids. The main goal of this paper is to present the issue of functional reliability of selected passive loss of mains (LoM) protection systems, i.e. methods of detecting island operation in distribution power grids, which are implemented in PV inverters installed in sample MV and LV grids, typical for Polish conditions. First, different methods of detecting island operation have been distinguished and shortly characterized. Some problems concerning their action have also been presented. Then commonly used passive methods of island grid operation detection have been described. Next sample distribution grid has been presented and chosen disturbances modelled in the grid to test mentioned passive methods have been defined. For each of the determined type of disturbance the dynamic simulation has been carried out, as well as voltage and frequency plots for two selected RES nodes have been recorded and observed. All considered passive methods of island grid operation detection have been implemented in a Matlab/Simulink environment. Models of RoCoF, U/OVP and U/ OFP algorithms have been presented in diagrams. Then, results of carried out extensive studies have been shown in tables and discussed. The results are a consequence of a realized research project concerning electric grids in rural areas. Summary, final conclusions, and future research possibilities constitute the last part of the paper. The conclusions are mainly concentrated on evaluation of action of passive methods of island operation detection as well as possibility of using the methods in Polish conditions, particularly in rural distribution grids.

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Authors and Affiliations

M. Parol
M. Połecki
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Abstract

Arsenic is the only beneficial impurity for copper electrorefining through inhibiting anode passivation and the formation of floating slimes. The behaviour of copper anodes with different content of arsenic were studied at high current density (>280 A/m 2). It showed that low arsenic anodes (As < 300 ppm) easily generated anode passivation, floating slimes and cathode nodules during the electrorefining proccess. The floating slimes, electrolyte, cathode and anode were observed and analyzed. As result, low arsenic anodes were more likely to be passivated due to their microstructure defects and irregular microstructure. Increasing electrolyte temperature and addition of glycerol were propitious to reduce low arsenic anodes’ passivation. The floating slimes occured when the concentration of As(III) in electrolyte decreased to 1 g/L, and they would be precipitated by polyacrylamide. All measures greatly improved the cathode quality at current density of 300 A/m 2.
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Authors and Affiliations

Xuyong Zhang
1
ORCID: ORCID
Silei Chen
1
ORCID: ORCID
Lu Li
1
ORCID: ORCID
Peng Yang
1
ORCID: ORCID

  1. Jiangxi Copper Technology Institute Co., Ltd, Nanchang 330096, Jiangxi, PR China
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Abstract

This paper presents a study of the damping of nonlinear vibrations in a two-mass model of mechanical system containing a torsion damper. The starting of the system by harmonic excitation is considered on the assumption of uniformly varying frequency and constant amplitude of the forced moment. Simultaneous structural friction phenomena (passive damping) and piezoelectric effect (active damping) have been considered as well. The problem is considered on the assumption of a uniform unit pressure distribution between the contacting surfaces of friction discs and plunger. The aim of the analysis is to asses the influence of angular acceleration, unitary pressure, external load and electric parameters on the resonance curves of the starting vibrations. The equations of motion of the tested system were solved by means of the Krylov-Bogolubov-Mitropolski method and digital simulation method.
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Authors and Affiliations

Zbigniew Skup
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Abstract

The first part of this article brings the author’s reply to the participants of the panel discussion of his book Culture as Verb (Anna Łebkowska, Jakub Momro, Tomasz Rakowski and Dorota Wolska). In the second part he outlines his premises and explains the analytical vocabulary that has enabled him to move from an active to a passive ‘verbal’ understanding of culture. He also draws a broad outline of prospective new research that would complement his project. Central to it is the exploration of what he believes is the dominant contemporary cultural experience, which is based on active participation. To characterize its most important features and forms we should make use of the following, newly defi ned analytical concepts – passivity, the present moment, immersion, and testimonial authority.

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Authors and Affiliations

Ryszard Nycz
ORCID: ORCID
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Abstract

Concentrator photovoltaic (CPV) systems have proven the capability of competing with traditional photovoltaic (PV) systems due to their high efficiency and low area occupancy. Such CPV systems require efficient heat removal auxiliary systems, especially for medium and high optical concentration ratios. Operating a CPV system under a high optical concentration (ratio > 200 X) might require active cooling techniques, which have high operating costs and maintenance. On the other hand, heat pipes (HPs) are widely used in electronic devices for cooling purposes. This work discusses the possibility of operating a CPV system coupled with HPs as a passive cooling technique. Two different HPs with different lengths are used to compare cooling efficiency. Each HP length was tested either in a single or double configuration. Long HPs showed better heat removal compared to a traditional fin-cooling system. CVP cooling with HP systems enhanced the entire electrical output of the cell, mainly at high optical concentration ratios.
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Authors and Affiliations

Mohammed Al Turkestani
1
ORCID: ORCID
Mohamed Sabry
1 2
ORCID: ORCID
Abdelrahman Lashin
1 3
ORCID: ORCID

  1. Physics Department, College of Science, Umm Al Qura University, Makkah, Kingdom of Saudi Arabia
  2. Solar Physics Lab, National Research Institute of Astronomy and Geophysics, Cairo, Egypt
  3. Physics Department, Faculty of Science, Mansoura University, Mansoura, Egypt
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Abstract

The LLC resonant converter is a widely used DC/DC converter that offers the benefit of enabling soft switching compared to classical DC/DC converters. However, traditional PI control strategy based on a linear model has drawbacks such as slow dynamic response and poor anti-interference performance. To overcome the shortage, a passivitybased control strategy based on the Euler–Lagrange (EL) model is proposed in this paper to improve the dynamic performance of the half-bridge LLC resonant converter. In addition, the stability of the system based on the proposed strategy is analyzed and verified. Further, the effectiveness and performance of the proposed strategy is verified in the simulation by comparing with the traditional PI controller. Finally, a prototype was built to verify the dynamic performance of the LLC resonant converter based on the proposed control strategy.
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Authors and Affiliations

Yajing Zhang
1
Weihao Liang
1
Xiuteng Wang
2
Lifen Li
3

  1. School of Automation, Beijing Information Science & Technology University No. 12 Qinghe Xiaoying East Road, Haidian District, Beijing, China
  2. Branch of Resource and Environment, China National Institute of Standardization No. 4 Zhi Chun Road, Haidian District, Beijing, China
  3. School of Information Science and Technology, Yanching Institute of Technology No. 808 Yingbin Road, National High-tech Industrial Development Zone Dongyanjiao, Beijing, Hebei, China

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