Ing. Jiří Hájek, Ph.D.

In this article, we deal with the problem of Hybrid Energy Harvesting control strategies, while paying attention to their properties and suggesting criteria to assess their suitability for specific energy harvesting techniques, as well as their application in different areas of technology—especially Wireless Sensor Networks and the Internet of Things. Many research works have already been published on the topic of combining resources for Energy Harvesting; nevertheless, a comprehensive review of the control strategies for such systems and a comparison of their most important properties is missing. This is the genesis and the main subject of this article. We have performed a deep research investigation of available resources. We have identified eight different control strategies and defined a set of the most important parameters (including their possible ranges/states) as criteria to be able to compare them. The corresponding sections of this article begin with a general description of the respective strategies and their principles (including generalized schemes), which is followed by specific examples of best practices. The key conclusions of the performed analysis are summarized in a comparison table that allows the readers to make their own conclusions and choices.

Increasing the efficiency of the solar energy harvesting system is an urgent need in light of the climate changes we live in nowadays. The most significant data to be processed in the photovoltaic harvesters are the curve of solar radiation intensity to achieve the maximum benefits of the solar incident light. This processing contains complicated procedures, and the used algorithms are also high computational power-consuming which makes using special software and high potential hardware essential requirements. An explanation of the Minimum Energy Effect method is presented in this article. Our proposed algorithm uses this method to provide a simple and high-accuracy mathematical tool for generating a simple alternative curve instead of the complicated original nonlinear curve of solar radiation intensity. The produced curve is suitable for further operations, such as derivatives, integrals, or even simple addition/subtraction. Our algorithm provides a gradual procedure to find an optimum solution of the equation system, unlike the iterative methods. In addition, the results of analyzing the effect of time-division density showed the relationship between the speed of solving the task and the accuracy of results.

The paper describes the vibration laboratory stand solution, developed and realized by authors. The stand is used to reduce the influence of the environment on the measured system, so only required vibration sources are present (and captured). The stand itself is presented in the paper, as well as its finite element analysis. These are followed by an initial set of measurements, including the description of the used hardware and settings.

The prototype of remote-controlled emulator of communication channel was designed, assembled and tested in industry use-case. The radiocommunication channel in mobile network and wired channel in fixed network, for example broadband power line, can be emulated. The communication technologies for Smart Grid, Smart Cities and Industry 4.0 can be tested and verificated with designed emulator. The channel capacity, data performance, error rate and other parameters of the communication systems are depended on the signal-tonoise ratio. The test conditions nearly real systems can be emulated by the laboratory devices. Simply, the attenuator sets value of the signal on input of receiver, the generator sets value of the noise in communication channel.

The paper deals with transmission of communication signals over low-voltage power distribution lines. Narrowband data transmission for Smart Metering systems is considered. The probability of data frame loss is derived, based on practical experiments, and its impact on the efficiency of reading data records from electricity meters is discussed. Furthermore, communication system with frequency-shift keying modulation is considered. The system performance can be extended using wider frequency band and OFDM modulation.

New designed power systems of electric and hybrid vehicles influence other systems by generated disturbing electromagnetic field. One of the promising measures to mitigate this negative effect can be found in additional shielding of cables, which can be provided by electrically conductive textile materials. This paper focuses on verification of utilization of specifically designed shielding textile material, which are used as additional cable shielding in order to prevent undesirable effects of electromagnetic disturbance on data transmission. The results of our measurements verify that this concept provides advantageous characteristics of electrically conductive textile materials such as shielding capability, elasticity and easy handling.

The paper describes a design of global navigation satellite system (GNSS)/Radio frequency identification (RFID) active transponder which is primarily designed for localization of objects as a part of localization system designated for efficient handling of situations with mass casualties. The precise localization is improved by differential GNSS. The block diagram of such GNSS/RFID active transponder is described including main operation procedures of the firmware. Measurement of the localization by algorithms of RTKLIB library and by algorithms of GNSS module is compared. Dynamic tests, i.e. GNSS/RFID active transponder placed in the moving car (50~kmph), and static tests, i.e. GNSS/RFID active transponder placed in the position for 15~min, are performed.

Technical textile materials can be successfully used also as a protection against external electromagnetic field. There are available technologies to improve the material surface – with use of different (galvanize, plate, etc.) technologies. The paper deals with woven textiles – compound of cotton, polyester and conductive fibers. The paper presents the impact of electromagnetic field on special woven textile materials and describes the shielding principles. The measurement technique used at FEL CTU in Prague is also described and the base measuring technologies are discussed. Nevertheless, the major part of the paper is dedicated to experience of authors with numerical (FE) modeling of shielding textiles and to description of designed and used methodology of FE model evaluation. The numerical results are compared to measurement and to mathematical (Matlab) model results.

Global trends in the development of modern electrical devices include also eco-friendly demands. One of the areas is seen in environmentally friendly batteries (electrochemical power sources) which do not contain poisonous and heavy metals. Modern structures based on coated textile materials are an alternative to the current all-metal electrodes. The use of environmentally friendly metals often entails the necessity to apply multiple layers of metals, which negatively affects the lifetime of the electrodes and battery cells. Accordingly, this paper focuses on the design and manufacture of monometallic textile electrodes for "green" batteries, i.e. the use of ecological technologies for eco-friendly electronics, especially the new-generation electrochemical power sources. The proposed technological processes were verified by realization of specimens and measurement in laboratory conditions with good results. Industrially applicable technologies were used for applying a thick monometallic deposit to create the specimens. This will allow future mass production and deployment in electrical engineering applications.

Fourth generation (4G) of cellular wireless standards includes small base stations, located at individual buildings as homes or other separated areas, called femtocells. They provide higher transfer rate and level of received signal. These small and low-power cellular base stations can provide a wide-range of military applications – while they can easily be set for closed and from environment isolated areas (or buildings) such as headquarters, ships, airplanes, trains etc. [1]. This technology allows to extend service coverage indoors or at the edges where direct access would be unavailable or limited. The safe and secure internal communication and data exchange channels are offered with possibility of external (internet) connection. Several standards bodies, such as 3GPP, WiMAX Forum, and IEEE 802.16, have started to develop standard solutions to enable and optimize femtocells operation [2]. Despite of possible advantages of WiMAX solution [3] the whole technology is solved by 3GPP group, including emergency call cases. However, they are not described and published in deep detail for close subscriber group (CSG). The paper focuses on proposal of two control procedures which allow an access to CSG in the case of emergency calls.

Modern textile materials with increased electric surface conductivity or the ability to shield electromagnetic fields find their application mainly in electrical engineering.

Hlavním cílem tohoto článku je představit nové výukové pomůcky, které jsou vyvíjeny v rámci mezinárodního projektu IMProVET, spadajícího pod evropský Program celoživotního učení - Leonardo da Vinci. Kro-mě průmyslové automatizace pokrývají několik dalších oblastí techniky, mimo jiné například mobilní komunikace či problematiku sítí založených na IPv6. Primární cílovou skupinou jsou studenti středních odborných škol v pěti partnerských zemích, nicméně využitelnost výstupů projektu je díky jejich vhodně zvolené modulární koncepci mnohem širší.

The unique project based on cooperation of universities and primary or secondary schools is transformed to Czech Republic. The project, realized at Czech Technical University in Prague, Faculty of Electrical Engineering is focused on support of technical education and knowledge between primary and secondary schools' students (and teachers). The main idea is based on "Engineer Olympics" realized at Faculty of Mechanical Engineering, STU in Bratislava [1], and "Technical Olympics - Science-Research-Development" realized at Faculty of Mechatronics in Trencin, Slovakia (both projects started at 2008), and project "Science-Research-Development in a View of Children".

PC/ABS/PMMA blends with a varied content of PMMA were studied. TEM microscopy was employed to reveal the individual phases. Uniaxial tensile testing and instrumented macro-hardness indentation were carriedout to quantify the hardness, indentation modulus, elastic and plastic deformation work during indentation, yield strain and stress values.

The paper summarizes the ways leading to modernization of engineering education in the area of electronic communications. In order to maximize the positive impact on quality, the considered methods are continuously optimized. We describe the fundamental elements and their integration into a brand-new concept of education.

Detailed and complete derivation of published models misses in scientific literature and published approximated equations differ from each other in many cases. It can cause unwanted repetition of mistakes in published equations. This paper is therefore focused on derivation of electromagnetic shielding efficiency of planar materials. Derivation obviates discrepancy published in scientific literature and consequently possible incorrect applications in technical practice. Results of modeling and measurement show a strong dependence of shielding efficiency and material electric conductivity and related equivalent sheet model thickness. This result is in accordance with practical experience from EMC branch.

Data protection of personal information contained in electronic identifiers is one of the most important tasks in RFID technology development. This paper is focused on design and development of data hardware protection of electronic identifiers. New developed textile materials based on metallic and polymeric fibers reach electromagnetic shielding efficiency of tens of decibel in a wide frequency spectrum. The paper describes a development of specific application and its testing.

Článek se věnuje realizaci měřicího pracoviště pro měření elektromagnetické stínicí účinnosti planárních materiálů v pásmu 100 kHz až 1,5 GHz. Pracoviště slouží jak pro výuku studentů, tak pro výzkumné doktorandské projekty.

Článek se zabývá návrhem směrování hypotetického tranzitního poskytovatele Internetu střední velikosti. V návrhu je zohledněno připojení zákazníků, propojení s poskytovateli stejné velikosti a připojení do sítě dalšího tranzitního poskytovatele. Popisuje virtuální laboratoř, vytvořenou programem GNS3, pomocí které byl proveden návrh a simulace sítě prostřednictvím virtuálních směrovačů.

Článek se zabývá porovnáním metod kompenzace chromatické disperze u klasického jednovidového optického vlákna. Popisuje dvě metody kompenzace: disperzi kompenzujícím vláknem a čerpovanou Braggovou mřížkou. Uvažuje i metody předkompenzace u zkoumané optické trasy o délce 100 km.

Tento článek se zabývá směrováním a analýzou směrovacích protokolů OSPFv3 a BGP4+, které se používají pro směrování v sítích IPv6. Rozebírá atributy směrovacího protokolu BGP4+, pomocí kterých se navrhuje směrovací politika autonomní oblasti (AS) poskytovatele Internetu (ISP). A v poslední řadě se zabývá základy ISP peeringu.

Tento článek stručně popisuje základy síťového protokolu IP verze 6 (IPv6) a ICMP verze 6 (ICMPv6). Dále se zabývá směrováním a analýzou směrovacích protokolů OSPFv3 a BGP4+, které se používají pro směrování v sítích IPv6. Rozebírá atributy směrovacího protokolu BGP4+, pomocí kterých se navrhuje směrovací politika autonomní oblasti (AS) poskytovatele Internetu (ISP). A v poslední řadě se zabývá základy ISP peeringu.

This paper introduces a self-service laboratory concept based on the current trend respecting the needs of students as well as those of the education: accumulation of laboratory lessons to larger blocks (occupying the laboratory for a longer continuous periods of time) and, on the other hand, preserving enough flexibility of the individual students' schedules.

Two prototypes of human head protective hood were developed in the project called BE-TEX "Human and technology protection against high frequency radiation - research and development of new textiles". Interesting results of shielding efficiency were achieved by specially prepared yarn and suitable construction of full face hood. The shielding efficiency defines an attenuation of high frequency signal after spill by shielding material. Measurement results were gained in 500 MHz frequency range. Electric field intensity was compared for situations with ad without fool head hood.

New types of textiles were developed in the project Be-Tex, which is focused on human and technology protection against high frequency radiation. The shielding effectiveness defines an attenuation of high frequency signal after spill by shielding material. These textiles can reduce an effect of intensities of electromagnetic fields, which protect human body.

This paper analyzes modern education methods used in subjects dealing with data communications, more specifically with modulation methods

Článek popisuje základy síťového protokolu IP verze 6 (IPv6) a podpůrného protokolu ICMP verze 6 (ICMPv6). Je prvním ze seriálu článků, které popisují návrh směrování v síti IP verze 6.

We were looking for a way to prepare a modern curriculum for education in data communications and we decided for a procedure based on a project of a new Data Communications Laboratory that should become a core element in the modernized pedagogical process.

The main contribution of the presented project consists in the development and evaluation of e-learning tools - two independent courses - that support the placement of people from the target groups in the job market.

The purpose of this paper is to summarize the purposes and partial results of the Leonardo da Vinci project ELefANTS (E-Learning for Acquiring New Types of Skills) as we approach the final stage of its implementation.

The purpose of this paper is to introduce a mobile technical solution for IP video streaming that is usable for live broadcasts of lectures over the IP-based networks.

Příspěvek seznamuje s výsledky mezinárodního projektu ELefANTS (v rámci programu Leonardo da Vinci), k nimž patří rekvalifikační kurs nabízející zájemcům možnost získat či doplnit si vzdělání v oblasti průmys-lové automatizace a komunikačních technologií, a to primárně formou online (distančního) vzdělávání. V pilotní etapě je účast v kursu nabízena bezplatně.

The paper describes arrangement of a studio for streaming and the technologies it uses

The paper presents the introduction of the most modern telecommunication transmission technologies in education of the course "Transmission and Switching Systems".

The paper describes particular technical implementation of a mobile streaming workplace and explains the used forms, formats and technologies.

The paper describes the principles and use of higher-order QAM modulation in CATV

Tento článek se zabývá základním popisem přenosu dat v moderních sítích kabelové televize podle doporučení druhé generace telekomunikační unie ITU-T a laboratoře pro průmyslové standardy CableLabs.

Description and explanation of basic mechanisms of multistate modulations that are used for data transmission in CATV (cable TV) networks

Rozvody kabelové televize (CATV) jako vysoce kvalitní širokopásmové médium vhodné pro aplikaci datových přenosů

Standardy, které našly uplatnění v různých částech světa a v různých aplikacích

An efficient instrument to calm traffic down.

This article presents a short introduction to history and evolution of recommendations for cable modems.