Search

In this work the investigation results of harvesting the RF energy of a 2.4 GHz Wi-Fi signal for supply of smart home leak sensors network are presented. The collected RF energy has been used as an additional source to power the sensors. The main goal of the work was to conduct research on determining the limit values of the RF signal source power and the limit distances between the RF energy harvesting system and the RF signal source, at which it is possible to harvest the RF energy and charge the energy storage capacitor. The PCB-based Yagi-Uda type antenna for RF signal receiving and a suitable RF energy harvesting system was designed for this purpose. The hardware model of the harvesting system was investigated with the designed antenna, as well as with other antennas using a signal generator and Wi-Fi router as a sources of RF signal. The obtained results demonstrate that at typical Wi-Fi router transmitting power, which is 10–17 dBm, RF energy can only be collected when the router is several tens of centimeters away from the harvesting antenna. When a router with a maximum allowed power of 20dBm is used, the distance at which it is possible to collect the RF energy, reaches 120 cm just in the case when both the transmitting and receiving antennas are Yagi-Uda directional antennas.

Communicating information to employees is identified as one of the most important and effective measures. However, there is a lack of research publications that specifically examine what specific information is relevant to employees, what specific content of information can encourage employees to resist change or reduce their negative reactions towards change. In this context, the problem of the study is what specific content of information can reduce or increase employee resistance to change. The subject is the impact of the content of information on employee resistance to change. The aim is to examine the impact of the content of information on employee resistance to change. Objectives: 1) To define the concept of employee resistance to change; 2. To analyse the impact of communicating information to employees on employee resistance to changes; 3) To determine the impact of the content of specific information on employee resistance to change in specific organizations. An empirical survey– an anonymous paper questionnaire of employees of public passenger transportation companies - was carried out. The results may be instrumental for devising efficient economic policies.

The Grid computing environment is very important for solving scientific problems. To get the best performance from Grid, it is important to know where to send tasks. This paper is about one of the suggested methods for a Grid resource broker to find the best resources for the task. This method requires defining the parameters of the resources and knowing the importance of the weights of parameters. This paper also presents the self-learning method of parameter weights.

The search for active, stable, and cost-efficient electrocatalysts for hydrogen production via water splitting could make a substantial impact on energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high-surface-area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction and oxygen evolution reaction compared to Rh/C and Pt/C catalysts. The atomic structure of the Rh2P NCs was directly observed by annular dark-field scanning transmission electron microscopy, which revealed a phosphorus-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorus plays a crucial role in determining the robust catalyst properties.

Video streaming service delivery is a challenging task for mobile network operators. Knowing which services clients are using could help ensure a specific quality of service and manage the users’ experience. Additionally, mobile network operators could apply throttle, traffic prioritization, or differentiated pricing. However, due to the growth of encrypted Internet traffic, it has become difficult for network operators to recognize the type of service used by their clients. In this article, we propose and evaluate a method for recognizing video streams solely based on the shape of the bitstream on a cellular network communication channel. To classify bitstreams, we used a convolutional neural network that was trained on a dataset of download and upload bitstreams collected by the authors. We demonstrate that our proposed method achieves an accuracy of over 90% in recognizing video streams from real-world mobile network traffic data.

Open-source software and its components are widely used in various products, solutions, and applications, even in closed-source. Majority of them are made on Linux or Unix based systems. Netfilter framework is one of the examples. It is used for packet filtering, load-balancing, and many other manipulations with network traffic. Netfilter based packet filter iptables has been most common firewall tool for Linux systems for more than two decades. Successor of iptables – nftables was introduced in 2014. It was designed to overcome various iptables limitations. However, it hasn’t received wide popularity and transition is still ongoing. In recent years researchers and developers around the world are searching for solution to increase performance of packet processing tools. For that purpose, many of them trying to utilize eBPF (Extended Berkeley Packet Filter) with XDP (Express Data Path) data path. This paper focused on analyzing Linux OS packet filters and comparing their performances in different scenarios. Article in English. Linux OS paketų filtravimo ir apdorojimo saugumo priemonų analizė Santrauka Atvirojo kodo priemonės plačiau naudojamos skirtinguose produktuose ir programose. Dauguma iš jų yra padaryta panaudojant Linux arba Unix sistemas. Netfiler tvarkyklė yra vienas iš pavyzdžių. Ji naudojama paketams filtruoti, apkrovai paskirstyti ir kitoms manipuliacijoms su paketais atlikti. Netfilter paketų filtras ipatables jau du dešimtmečius yra populiariausia Linux ugniasienė. Nauja ugniasienė nftables buvo pristatyta 2014 metais ir turėjo įveikti iptables trūkumus. Tačiau nftables taip ir negavo visuotinio pripažinimo, daug sistemų taip ir nebuvo perkeltos į iptables. Todėl pastaruosius metus mokslininkai ir programinės įrangos kūrėjai ieško naujo sprendimo padidinti paketų apdorojimo našumą. Tam jie bando išnaudoti tokias technologijas kaip eBPF ir XDP. Šio straipsnio tikslas padaryti Linux OS paketų filtro analizę ir palyginti jų našumą skirtinguose scenarijuose. Reikšminiai žodžiai: Linux, Netfilter, iptables, nftables, eBPF, XDP, ugniasienė, paketų filtrai.

The topology of the static synchronous compensator of reactive power for a low-voltage three-phase utility grid capable of asymmetric reactive power compensation in grid phases has been proposed and analysed. It is implemented using separate, independent cascaded H-bridge multilevel inverters for each phase. Every inverter includes two H-bridge cascades. The first cascade operating at grid frequency is implemented using thyristors, and the second one—operating at high frequency is based on the high-speed MOSFET transistors. The investigation shows that the proposed compensator is able to compensate the reactive power in a low-voltage three-phase grid when phases are loaded by highly asymmetrical reactive loads and provides up to three times lower power losses in the compensator as compared with the situation when the compensator is based on the conventional three-level inverters implemented using IGBT transistors.

The thyristor-controlled reactor (TCR) compensator for smooth asymmetric compensation of reactive power in a low-voltage utility grid is proposed in this work. Two different topologies of compensator were investigated: topology based on a single-cored three-phase reactor and topology with separate reactors for every phase. The investigation of the proposed TCR compensator was performed experimentally using a developed experimental test bench for 12 kVAr total reactive power. The obtained results show that employment of separate reactors for every phase allows us to control the reactive power in every phase independently, and that the TCR compensator with three single-phase reactors is suitable for smooth and asymmetric compensation of reactive power in a low-voltage utility grid.

The superconducting critical temperature Tc of YBa2Cu3Ox single crystals (6.35 7) has been measured resistively as a function of pressure P (0P 20 kbar). The initial rate dTc/dP exhibits three distinct regimes, a narrow plateau near 7 with dTc/dP 0.04 K/kbar, a plateau in the range 6.4 6.8, where dTc/dP 0.43 K/kbar, and a maximum value 0.8 K/kbar at 6.35. An analysis of the Tc(x,P) data using a phenomenological model yields a pronounced peak near x=6.8 in dnh(x)/dP, where nh(x) is the change in the hole density in the CuO2 planes relative to the value corresponding to the fully oxygenated sample. © 1992 The American Physical Society.

The superconducting critical temperature Tc of YBa2Cu3Ox single crystals (6.35 7) has been measured resistively as a function of pressure P (0P 20 kbar). The initial rate dTc/dP exhibits three distinct regimes, a narrow plateau near 7 with dTc/dP 0.04 K/kbar, a plateau in the range 6.4 6.8, where dTc/dP 0.43 K/kbar, and a maximum value 0.8 K/kbar at 6.35. An analysis of the Tc(x,P) data using a phenomenological model yields a pronounced peak near x=6.8 in dnh(x)/dP, where nh(x) is the change in the hole density in the CuO2 planes relative to the value corresponding to the fully oxygenated sample. © 1992 The American Physical Society.

We have performed angle-integrated and angle-resolved photoemission measurements at 20 K on well-characterized single crystals of high Tc cuprates (both 1:2:3-type and 2:2:1:2-type) cleaved in situ, and find a relatively large, resolution limited Fermi edge which shows large amplitude variations with photon energy, indicative of band structure final state effects. The lineshape of the spectra of the 1:2:3 materials as a function of photon energy are well reproduced by band structure predictions, indicating a correct mix of 2p and 3d orbitals in the calculations, while the energy positions of the peaks agree with calculated bands to within approx;;0.5 eV. This may yet prove to reflect the effects of Coulomb correlation. We nevertheless conclude that a Fermi liquid approach to conductivity is appropriate. Angle-resolved data, while still incomplete, suggest agreement with the Fermi surface predicted by the LDA calculations. A BCS-like energy gap is observed in the 2:2:1:2 materials, whose magnitude is twice the weak coupling BCS value (i.e., 2Δ approx;; 7kTc). © 1990 IOP Publishing Ltd.

We have performed angle-integrated and angle-resolved photoemission measurements at 20 K on well-characterized single crystals of high Tc cuprates (both 1:2:3-type and 2:2:1:2-type) cleaved in situ, and find a relatively large, resolution limited Fermi edge which shows large amplitude variations with photon energy, indicative of band structure final state effects. The lineshape of the spectra of the 1:2:3 materials as a function of photon energy are well reproduced by band structure predictions, indicating a correct mix of 2p and 3d orbitals in the calculations, while the energy positions of the peaks agree with calculated bands to within approx;;0.5 eV. This may yet prove to reflect the effects of Coulomb correlation. We nevertheless conclude that a Fermi liquid approach to conductivity is appropriate. Angle-resolved data, while still incomplete, suggest agreement with the Fermi surface predicted by the LDA calculations. A BCS-like energy gap is observed in the 2:2:1:2 materials, whose magnitude is twice the weak coupling BCS value (i.e., 2Δ approx;; 7kTc). © 1990 IOP Publishing Ltd.

The BitTorrent client application is a popular utility for sharing large files over the Internet. Sometimes, this powerful utility is used to commit cybercrimes, like sharing of illegal material or illegal sharing of legal material. In order to help forensics investigators to fight against these cybercrimes, we carried out an investigation of the artifacts left by the BitTorrent client. We proposed a methodology to locate the artifacts that indicate the BitTorrent client activity performed. Additionally, we designed and implemented a tool that searches for the evidence left by the BitTorrent client application in a local computer running Windows. The tool looks for the four files holding the evidence. The files are as follows: *.torrent, dht.dat, resume.dat, and settings.dat. The tool decodes the files, extracts important information for the forensic investigator and converts it into XML format. The results are combined into a single result file.

The first low-temperature photoemission spectra from well-oxygenated and characterized, cleaved single crystals of the 1:2:3-type superconductors, specifically EuBa2Cu3O7-x, are presented. In contrast with polycrystalline or higher-temperature single-crystalline studies, a distinct and very stable density of states is found at the Fermi edge below 20 K. As the crystal is warmed even to 80 K the emission is rapidly lost from both the upper and lower portions of the Cu-O hybrids. At room temperature there is a loss of intensity at the Fermi edge with an accompanying change in the Ba 4d core-level line shape and the presence of a charging effect indicative of an insulating surface. These results imply that upon warming from 20 K there is very rapid oxygen loss from the cleaved surface with a resulting loss of superconducting behavior. This suggests that future photoemission experiments, especially those investigating detailed band structure, should be performed at low temperatures. © 1988 The American Physical Society.

We have performed angle-integrated photoemission measurements at 20 K on well-oxygenated (Tc=92 K) single crystals of YBa2Cu3O6.9 cleaved n situ, and find a relatively large, resolution-limited Fermi edge which shows large amplitude variations with photon energy, indicative of band-structure final-state effects. Some dispersion is seen even in our angle-integrated measurements. Our best estimate of N(EF) per Cu atom is that it is about 20% that of Cu metal with about a 20-80 mix of Cu 3d and O 2p orbitals. Dispersive and final-state effects are seen throughout the valence bands. The line shapes of the spectra as a function of photon energy are very well reproduced by band-structure predictions, indicating a correct mix of 2p and 3d orbitals in the calculations, while the energy positions of the peak agree with calculated bands to within 0.5 eV. We conclude that a Fermi-liquid approach to conductivity is appropriate. © 1989 The American Physical Society.