Showing papers by "Brno University of Technology published in 2018"
TL;DR: Supercapacitors represent the alternative to common electrochemical batteries, mainly to widely spread lithium-ion batteries as discussed by the authors, and their properties are between batteries and capacitors, where they are able to quickly accommodate large amounts of energy (smaller than in the case of batteries).
Abstract: Energy accumulation and storage is one of the most important topics in our times. This paper presents the topic of supercapacitors (SC) as energy storage devices. Supercapacitors represent the alternative to common electrochemical batteries, mainly to widely spread lithium-ion batteries. By physical mechanism and operation principle, supercapacitors are closer to batteries than to capacitors. Their properties are somewhere between batteries and capacitors. They are able to quickly accommodate large amounts of energy (smaller than in the case of batteries – lower energy density from weight and volume point of view) and their charging response is slower than in the case of ceramic capacitors. The most common type of supercapacitors is electrical double layer capacitor (EDLC). Other types of supercapacitors are lithium-ion hybrid supercapacitors and pseudo-supercapacitors. The EDLC type is using a dielectric layer on the electrode − electrolyte interphase to storage of the energy. It uses an electrostatic mechanism of energy storage. The other two types of supercapacitors operate with electrochemical redox reactions and the energy is stored in chemical bonds of chemical materials. This paper provides a brief introduction to the supercapacitor field of knowledge.
427 citations
TL;DR: A review of the most significant implementations of the Pinch analysis can be found in this article, where the authors identify and substantiate future directions of research for Pinch Methodology applications.
Abstract: The emergence of Pinch Analysis from more than four decades ago opened a new area of intense research development that has even accelerated in recent years. Initially, Pinch Analysis (PA) provided a systematic thermodynamic-based approach to address the need for large energy savings around the 1970s oil crises. Since inception, the Pinch Methodology (PM) has flourished considerably, finding meaningful application to a wide range of industrial, regional, and global challenges well beyond heat – it’s most well-known and first application. This review represents an attempt to identify and substantiate future directions of research for the most significant implementations of Pinch Methodology. Reported applications in the literature range from Heat Integration, Total Site and Water Integration through to Emergy and even Financial Investment Planning; cutting across multiple engineering fields – Mechanical, Chemical, Process, Power, and Environmental Engineering – as well as entering the research domains of Management and Finance. Key findings of this review include: (1) the need for more awareness within the engineering and science research communities of the latest and continuing developments of the Pinch Methodology; (2) a need for complete tool sets covering targeting through to engineering design for many of the Pinch Methodology applications; and, (3) the full benefits of Pinch Methodology can only be achieved in developing design solutions with an appreciation for the most recent developments.
235 citations
TL;DR: In this article, the authors highlight the importance of considering air pollutants in optimisation studies and evaluate the limitation of the current assessments for air emissions, particularly in relation to transportation, and develop a methodology to measure greenhouse gas and air pollutants simultaneously by considering the synergistic effect and the discussed limitation.
231 citations
TL;DR: In this paper, the authors compared the characteristics of food waste to biogas potential and proposed process improvement for enhanced Biogas production, and concluded that the variation in the characteristic of the food waste, in terms of physical and biochemical properties, can affect the efficiency of the applied treatment for process improvement, including nutrient balance, mechanical treatment, thermal treatment and two-stage configuration.
178 citations
15 Apr 2018
TL;DR: This paper addresses the problem of single channel speech recognition of a target speaker in a mixture of speech signals by exploiting auxiliary speaker information provided by an adaptation utterance from the target speaker to extract and recognize only that speaker.
Abstract: This paper addresses the problem of single channel speech recognition of a target speaker in a mixture of speech signals. We propose to exploit auxiliary speaker information provided by an adaptation utterance from the target speaker to extract and recognize only that speaker. Using such auxiliary information, we can build a speaker extraction neural network (NN) that is independent of the number of sources in the mixture, and that can track speakers across different utterances, which are two challenging issues occurring with conventional approaches for speech recognition of mixtures. We call such an informed speaker extraction scheme “SpeakerBeam”. SpeakerBeam exploits a recently developed context adaptive deep NN (CADNN) that allows tracking speech from a target speaker using a speaker adaptation layer, whose parameters are adjusted depending on auxiliary features representing the target speaker characteristics. SpeakerBeam was previously investigated for speaker extraction using a microphone array. In this paper, we demonstrate that it is also efficient for single channel speaker extraction. The speaker adaptation layer can be employed either to build a speaker adaptive acoustic model that recognizes only the target speaker or a mask-based speaker extraction network that extracts the target speech from the speech mixture signal prior to recognition. We also show that the latter speaker extraction network can be optimized jointly with an acoustic model to further improve ASR performance.
176 citations
TL;DR: TiO2 selectively adsorbs atmospheric carboxylic acids that are typically present in parts-per-billion concentrations while effectively repelling other adsorbates, such as alcohols, that are present in much higher concentrations.
Abstract: Researchers around the world have observed the formation of molecularly ordered structures of unknown origin on the surface of titanium dioxide (TiO2) photocatalysts exposed to air and solution. Using a combination of atomic-scale microscopy and spectroscopy, we show that TiO2 selectively adsorbs atmospheric carboxylic acids that are typically present in parts-per-billion concentrations while effectively repelling other adsorbates, such as alcohols, that are present in much higher concentrations. The high affinity of the surface for carboxylic acids is attributed to their bidentate binding. These self-assembled monolayers have the unusual property of being both hydrophobic and highly water-soluble, which may contribute to the self-cleaning properties of TiO2. This finding is relevant to TiO2 photocatalysis, because the self-assembled carboxylate monolayers block the undercoordinated surface cation sites typically implicated in photocatalysis.
176 citations
TL;DR: In this paper, the authors present a review of the composition of SCGs, the methods used for the isolation of individual compounds present in SCGs and the ways of utilizing SCGs presented in the literature so far, including SCGs bioactive compounds, carbohydrates, oil fraction, as well as SCGs as the whole composite without treatment or with some physical and chemical modifications.
156 citations
TL;DR: A new module for the estimation of thermodynamic stabilities using the Rosetta and FoldX suites has been introduced which prevents destabilizing mutations among pre-selected variants entering experimental testing.
Abstract: HotSpot Wizard is a web server used for the automated identification of hotspots in semi-rational protein design to give improved protein stability, catalytic activity, substrate specificity and enantioselectivity. Since there are three orders of magnitude fewer protein structures than sequences in bioinformatic databases, the major limitation to the usability of previous versions was the requirement for the protein structure to be a compulsory input for the calculation. HotSpot Wizard 3.0 now accepts the protein sequence as input data. The protein structure for the query sequence is obtained either from eight repositories of homology models or is modeled using Modeller and I-Tasser. The quality of the models is then evaluated using three quality assessment tools-WHAT_CHECK, PROCHECK and MolProbity. During follow-up analyses, the system automatically warns the users whenever they attempt to redesign poorly predicted parts of their homology models. The second main limitation of HotSpot Wizard's predictions is that it identifies suitable positions for mutagenesis, but does not provide any reliable advice on particular substitutions. A new module for the estimation of thermodynamic stabilities using the Rosetta and FoldX suites has been introduced which prevents destabilizing mutations among pre-selected variants entering experimental testing. HotSpot Wizard is freely available at http://loschmidt.chemi.muni.cz/hotspotwizard.
143 citations
TL;DR: Dramatic improvement in flexibility of poly(ε-caprolactone) based nanofiber matrix prepared by electrospinning method is showed whereas solvent casting method without any plasticizer produced very brittle, inflexible film of PCL.
Abstract: We put forth our opinion regarding the enhanced plasticity and modulation of mechanical properties of polymeric films obtained through electrospinning process in this article. In majority of the pharmaceutical, biomedical, and packaging applications, it is desirable that polymer based matrices should be soft, flexible, and have a moderate toughness. In order to convert inflexible and brittle polymers, adjuvants in the form of plasticizers are added to improve the flexibility and smoothness of solvent casted polymer films. However, many of these plasticizers are under scrutiny for their toxic effects and environmental hazards. In addition, plasticizers also increase the cost of end products. This has motivated the scientific community to investigate alternate approaches. The changes imparted in membrane casted by electrospinning were tried to be proved by SEM, Mechanical property study, DSC and XRD studies. We have showed dramatic improvement in flexibility of poly(e-caprolactone) based nanofiber matrix prepared by electrospinning method whereas solvent casting method without any plasticizer produced very brittle, inflexible film of PCL. Modulation capacity of mechanical properties is also recorded. We tried to support our opinion by citing several similar findings available in the open literature. The electrospinning method helps in plasticization and in tuning mechanical properties.
126 citations
TL;DR: In this article, a systematic review and meta-analysis of the life cycle environmental impacts of pulp making and paper making systems was carried out by means of quantification and harmonization.
Abstract: The pulp and paper industry, which provides cellulose pulp and paper, bio-based energy and chemicals, is one of the largest energy consumers, greenhouse gases (GHG) and pollutant emitters among manufacturing industries. Although the environmental impact of the pulp and paper industry has been extensively studied, life cycle assessment (LCA) results have not yet reached a consensus. By means of a systematic review and meta-analysis, this article contributes to the quantification and harmonization of the life cycle environmental impacts of pulp making and paper making systems. Based on the screening of 45 cases of paper making and 18 cases of pulp making, we found that 1 t of paper results in about 950 kg carbon dioxide (CO2) equivalent (CO2-eq) GHG emissions on average. However, there are distinct differences between countries and pulp and paper categories. The dominant factor influencing GHG emissions is energy use. In paper making, the pulp making process is responsible for 62% of energy use, 45% of GHG emissions, 48% of acidification potential, and 49% of eutrophication potential. The kg CO2-eq emissions of three different types of pulp were as follows: Kraft, 508 kg CO2-eq/t; chemi-mechanical, 513 kg CO2-eq/t; and recycled pulp, 408 kg CO2-eq/t. Excluding emissions from electricity and steam production, the convergence of carbon emissions is observed within the same categories of pulp. Straw-based pulp caused far more environmental impact than any other type because of the intensive inputs in agricultural activities as well as in the pulp making process. This research highlighted the inconsistencies in functional units, system boundaries, and methodologies and carbon neutrality assumptions in different LCA studies of pulp and paper making. Future studies should focus on the environmental impact of straw-based pulp making, system boundary unification, and calculation of biogenic carbon emissions.
120 citations
TL;DR: In this paper, several alkali activated aluminosilicate (AAA) materials prepared using waste brick powder as a precursor are analyzed from both functional and environmental points of view.
TL;DR: This work demonstrates that the grain size and cation distribution in Gd3+ doped cobalt ferrite nanoparticles synthesized by sonochemical method, is effective in controlling the structural, magnetic, and electrical properties, and can be find very promising applications.
TL;DR: The results suggest that TGA-MS can be an easy and viable complement to existing methods such as pyrolysis or thermogravimetry-thermal desorption assays followed by gas chromatography/mass spectrometry detection or to spectral microscopy techniques.
Abstract: The use of plastic materials in daily life, industry, and agriculture can cause soil pollution with plastic fragments down to the micrometer scale, i.e., microplastics. Quantitative assessment of microplastics in soil has been limited so far. Until now, microplastic analyses in soil require laborious sample cleanup and are mostly restricted to qualitative assessments. In this study, we applied thermogravimetry-mass spectrometry (TGA-MS) to develop a method for the direct quantitative analysis of poly(ethylene terephthalate) (PET) without further sample pretreatment. For this, soil samples containing 1.61 ± 0.15 wt % organic matter were spiked with 0.23-4.59 wt % PET bottle recyclate microplastics. dl-Cysteine was used as the internal standard (IS). Sample mixtures were pyrolyzed with a 5 K min-1 ramp (40-1000 °C), while sample mass loss and MS signal intensity of typical PET pyrolysis products were recorded. We found MS signal intensities linearly responding to microplastic concentrations. The most-promising results were obtained with the IS-corrected PET pyrolysis product vinylbenzene/benzoic acid ( m/ z = 105, adj. R2 = 0.987). The limits of detection and quantification were 0.07 and 1.72 wt % PET, respectively. Our results suggest that TGA-MS can be an easy and viable complement to existing methods such as pyrolysis or thermogravimetry-thermal desorption assays followed by gas chromatography/mass spectrometry detection or to spectral microscopy techniques.
TL;DR: In this article, a 3D magnetohydrodynamic model of the solar corona driven by measured magnetic fields was used to predict what the corona would look like one week before the eclipse.
Abstract: The total solar eclipse that occurred on 21 August 2017 across the United States provided an opportunity to test a magnetohydrodynamic model of the solar corona driven by measured magnetic fields. We used a new heating model based on the dissipation of Alfven waves, and a new energization mechanism to twist the magnetic field in filament channels. We predicted what the corona would look like one week before the eclipse. Here, we describe how this prediction was accomplished, and show that it compared favourably with observations of the eclipse in white light and extreme ultraviolet. The model allows us to understand the relationship of observed features, including streamers, coronal holes, prominences, polar plumes and thin rays, to the magnetic field. We show that the discrepancies between the model and observations arise from limitations in our ability to observe the Sun’s magnetic field. Predictions of this kind provide opportunities to improve the models, forging the path to improved space weather prediction. A 3D magnetohydrodynamic model forecasted the state of the solar corona during the eclipse that occurred on 21 August 2017, using observations taken ten days before the eclipse as boundary conditions. The agreement between the predicted images and those observed during the eclipse is very good.
TL;DR: The overall results suggested the positive effect provided by EM notably in odour control and humification.
04 Oct 2018
TL;DR: Experimental results show that the transfer learning approach from the multilingual model shows substantial gains over monolingual models across all 4 BABEL languages.
Abstract: Sequence-to-sequence (seq2seq) approach for low-resource ASR is a relatively new direction in speech research. The approach benefits by performing model training without using lexicon and alignments. However, this poses a new problem of requiring more data compared to conventional DNN-HMM systems. In this work, we attempt to use data from 10 BABEL languages to build a multilingual seq2seq model as a prior model, and then port them towards 4 other BABEL languages using transfer learning approach. We also explore different architectures for improving the prior multilingual seq2seq model. The paper also discusses the effect of integrating a recurrent neural network language model (RNNLM) with a seq2seq model during decoding. Experimental results show that the transfer learning approach from the multilingual model shows substantial gains over monolingual models across all 4 BABEL languages. Incorporating an RNNLM also brings significant improvements in terms of %WER, and achieves recognition performance comparable to the models trained with twice more training data.
TL;DR: In this article, a binary geopolymer system composed of metakaolin (MK), waste red brick (WRB) powder and sodium silicate solution as an alkaline activator was investigated.
TL;DR: A review of the current knowledge about the synthesis, magnetic properties, and applications of magnetic cylindrical nanowires and nanotubes can be found in this article, where the authors consider diameters reasonably smaller than a micrometer.
Abstract: We propose a review of the current knowledge about the synthesis, magnetic properties, and applications of magnetic cylindrical nanowires and nanotubes. By nano we consider diameters reasonably smaller than a micrometer. At this scale, comparable to micromagnetic and transport length scales, novel properties appear. At the same time, this makes the underlying physics easier to understand due to the limiter number of degrees of freedom involved. The three-dimensional nature and the curvature of these objects contribute also to their specific properties, compared to patterns flat elements. While the topic of nanowires and later nanotubes started now decades ago, it is nevertheless flourishing, thanks to the progress of synthesis, theory and characterization tools. These give access to ever more complex and thus functional structures, and also shifting the focus from material-type measurements of large assemblies, to single-object investigations. We first provide an overview of common fabrication methods yielding nanowires, nanotubes and structures engineered in geometry (change in diameter, shape) or material (segments, core–shell structures), shape or core–shell. We then review their magnetic properties: global measurements, magnetization states and switching, single domain wall statics and dynamics, and spin waves. For each aspect, both theory and experiments are surveyed. We also mention standard characterization techniques useful for these. We finally mention emerging applications of magnetic nanowires and nanotubes, along with the foreseen perspectives in the topic.
TL;DR: Various approaches and stages in the AD of MSW, which used to optimise the biogas production and quality are reviewed, to facilitate further development and extended implementation of AD.
TL;DR: This work proposes an additional millimeter-wavelength radio-frequency (RF)-FSO link, used as a backup for FSO-based backhaul networks, and demonstrates that the FSO/RF-FSO topology performs better than a single FSO link in terms of outage probability and BER.
Abstract: Free-space optical (FSO) links are considered as cost-effective, noninvasive alternative to fiber optic cables for 5G cellular backhaul networking. For FSO-based backhaul networks, we propose an additional millimeter-wavelength (MMW) radio-frequency (RF)-FSO link, used as a backup. Uninterrupted and reliable network connection is possible by switching between primary FSO link and the secondary RF-FSO link; when the primary link is under atmospheric turbulence, the secondary link maintains connectivity as the MMW RF link exhibits complementary characteristics to atmospheric effects. In order to analytically assess the improvement, we also derive concise mathematical expressions for different performance metrics, such as outage probability, average bit error rate (BER), and capacity. Our results demonstrate that the FSO/RF-FSO topology performs better than a single FSO link in terms of outage probability and BER. The dual-hop mixed RF-FSO link is realized with an amplify and forward (AF) relay that adapts an average power scaling strategy. The irradiance fluctuations in the FSO links are modeled by gamma–gamma distribution, assuming strong atmospheric turbulence while it is assumed that the RF link experiences multipath Rayleigh fading. For switching between links, a single FSO threshold is considered first, followed by a dual FSO threshold to prevent unnecessary switching.
TL;DR: In this article, a structural taxonomy of insider threat incidents is presented, which is based on existing taxonomies and the 5W1H questions of the information gathering problem.
Abstract: Insider threats are one of today's most challenging cybersecurity issues that are not well addressed by commonly employed security solutions. Despite several scientific works published in this domain, we argue that the field can benefit from the proposed structural taxonomy and novel categorization of research that contribute to the organization and disambiguation of insider threat incidents and the defense solutions used against them. The objective of our categorization is to systematize knowledge in insider threat research, while leveraging existing grounded theory method for rigorous literature review. The proposed categorization depicts the workflow among particular categories that include: 1) Incidents and datasets, 2) Analysis of attackers, 3) Simulations, and 4) Defense solutions. Special attention is paid to the definitions and taxonomies of the insider threat; we present a structural taxonomy of insider threat incidents, which is based on existing taxonomies and the 5W1H questions of the information gathering problem. Our survey will enhance researchers' efforts in the domain of insider threat, because it provides: a) a novel structural taxonomy that contributes to orthogonal classification of incidents and defining the scope of defense solutions employed against them, b) an updated overview on publicly available datasets that can be used to test new detection solutions against other works, c) references of existing case studies and frameworks modeling insiders' behaviors for the purpose of reviewing defense solutions or extending their coverage, and d) a discussion of existing trends and further research directions that can be used for reasoning in the insider threat domain.
TL;DR: This work explores molecular, morphological as well as biotechnological features of the highly promising polyhydroxyalkanoates (PHA) producer Halomonas halophila and its potential for industrial PHB production.
TL;DR: In this article, the capacity of lignite as a parent source of humic acids for agricultural applications is appreciated mainly on the base of extractability and ash content, and the results of X-ray photoelectron spectroscopy and fluorescence spectrometry are not commonly used for the investigation of Lignite humic acid, although they may provide relevant information.
TL;DR: It is revealed here that the supporting gold substrate uniquely favors a flexible cobalt-oxyhydroxide/Au interface in the electrochemically active potential window and thus suppresses the formation of less active bulk cobalt oxide morphologies.
Abstract: The catalytic synergy between cobalt oxide and gold leads to strong promotion of the oxygen evolution reaction (OER)-one half-reaction of electrochemical water splitting. However, the mechanism behind the enhancement effect is still not understood, in part due to a missing structural model of the active interface. Using a novel interplay of cyclic voltammetry (CV) for electrochemistry integrated with scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) on an atomically defined cobalt oxide/Au(111) system, we reveal here that the supporting gold substrate uniquely favors a flexible cobalt-oxyhydroxide/Au interface in the electrochemically active potential window and thus suppresses the formation of less active bulk cobalt oxide morphologies. The findings substantiate why optimum catalytic synergy is obtained for oxide coverages on gold close to or below one monolayer, and provide the first morphological description of the active phase during electrocatalysis.
TL;DR: In this article, the microstructural and mechanical properties of face-centred cubic Ni15Co15CrFeTi05 high-entropy alloy strengthened by nano-sized titanium oxide dispersion and coherent precipitates of Ni3Ti intermetallic phase produced by powder metallurgy were evaluated.
TL;DR: The results showed that the SLM-processed 2618 alloy could only reach one half of the yield strength and tensile strength of extruded material, mainly due to the occurrence of small cracks in the structure of the built material.
Abstract: This paper deals with various selective laser melting (SLM) processing strategies for aluminum 2618 powder in order to get material densities and properties close to conventionally-produced, high-strength 2618 alloy. To evaluate the influence of laser scanning strategies on the resulting porosity and mechanical properties a row of experiments was done. Three types of samples were used: single-track welds, bulk samples and samples for tensile testing. Single-track welds were used to find the appropriate processing parameters for achieving continuous and well-shaped welds. The bulk samples were built with different scanning strategies with the aim of reaching a low relative porosity of the material. The combination of the chessboard strategy with a 2 × 2 mm field size fabricated with an out-in spiral order was found to eliminate a major lack of fusion defects. However, small cracks in the material structure were found over the complete range of tested parameters. The decisive criteria was the elimination of small cracks that drastically reduced mechanical properties. Reduction of the thermal gradient using support structures or fabrication under elevated temperatures shows a promising approach to eliminating the cracks. Mechanical properties of samples produced by SLM were compared with the properties of extruded material. The results showed that the SLM-processed 2618 alloy could only reach one half of the yield strength and tensile strength of extruded material. This is mainly due to the occurrence of small cracks in the structure of the built material.
TL;DR: Enev et al. as mentioned in this paper compared ultraviolet-visible spectroscopy, Fourier transform infrared (FTIR), and 13 C nuclear magnetic resonance (13 C NMR) for the characterization of selected humic substances.
Abstract: Enev V., Pospisilova L., Klucakova M., Liptaj T., Doskocil L. (2014): Spectral characterization of selected humic substances. Soil&Water Res., 9 : 9-17. Current concern for soil quality has stimulated research on soil organic matter (OM). Humic substances (HS) of different origin were compared applying ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), "steady-state" fluorescence spectroscopy, and 13 C nuclear magnetic resonance ( 13 C NMR). Sodium humates samples were isolated from soil (Gleyic Luvisol), compost, and South-Moravian lignite from the mine Mir in Mikulcice. Sodium humates (SH) were extracted by a conventional procedure recommended by the International Humic Substances Society (IHSS). Results showed that the presence of O-containing functional groups (carbonyl in aldehydes and ketones, carboxyl in carboxylic acids, ester and ether groups) are in the order of compost > soil > lignohumate > lignite. Further, results of FTIR, fluorescence spectroscopy, and 13 C NMR suggested that samples of sodium humates isolated from soil, compost, and lignite were a more polycondensed, oxidized, unsaturated, humified, and aromatic structure. On the other hand, commercial lignohumate (LH) had very simple structural components and wide molecular heterogeneity. Furthermore, a small molecular size and weight, low degree of aromatic polycondensation, low level of conjugated chromophores and fluorophores, and low humification degree were characteristic for commercial LH. It should be noted that the sample of commercial LH was characterized by 13 C NMR analysis with a slightly higher value of aromaticity α in comparison with the sample of compost. The application of non-destructive analytical methods such as UV-VIS, FTIR, 13 C NMR, and fluorescence spectroscopy help us to provide main characteristics of selected humic substances.
TL;DR: In this paper, a special volume devoted to presenting feasible cleaner technologies supported by environmental assessment tool to enable the transition of Asia into a low-carbon-emission economy is presented.
TL;DR: In this article, hot-press sintering of nanoparticles at temperature 925°C for 10min in vacuum atmosphere under 30MPa mechanical pressure was investigated by superconducting quantum interface device (SQUID) magnetometer at room temperature.