bluuebunny/crossref_metadata_2025 huggingface dataset:
Concentrating Solar Collectors for a Trigeneration System—A Comparative Study
Authors: Bellos Evangelos , Tzivanidis Christos
Published: June 2020

The objective of this study is the investigation of different solar concentrating collectors for application in a trigeneration system. Parabolic trough collectors, linear Fresnel reflectors and solar dishes are the examined solar concentrating technologies in this work. The trigeneration unit includes an organic Rankine cycle coupled with an absorption heat machine that operates with LiBr/water. The analysis is performed throughout the year by using the weather data of Athens in Greece. The results of this work indicate that the selection of parabolic trough collectors is the best choice because it leads to the maximum yearly system energy efficiency of 64.40% and to the minimum simple payback period of 6.25 years. The second technology is the solar dish with the energy efficiency of 62.41% and the simple payback period of 6.95 years, while the linear Fresnel reflector is the less efficient technology with the energy efficiency of 35.78% and with a simple payback period of 10.92 years. Lastly, it must be stated that the thermodynamic investigation of the system is performed with a created model in Engineering Equation Solver, while the dynamic analysis is performed with a code in the programming language FORTRAN.
NSHT: New Smart Hybrid Transducer for Structural and Geotechnical Applications
Authors: Minutolo Vincenzo , Cerri Enis , Coscetta Agnese , Damiano Emilia , De Cristofaro Martina , Di Gennaro Luciana , Esposito Luca , Ferla Paolo , Mirabile Maurizio , Olivares Lucio , Zona Renato
Published: June 2020

This work describes the application of a new transducer prototype for continuous monitoring in both the structural and geotechnical fields. The transducer is synthetically constituted by a wire of optical fiber embedded between two fiber tapes (fiberglass or carbon fiber) and glued by a matrix of polyester resin. The fiber optical wire ends have been connected to a control unit whose detection system is based on Brillouin optical time-domain frequency analysis. Three laboratory tests were carried out to evaluate the sensor’s reliability and accuracy. In each experiment, the transducer was applied to a sample of inclinometer casing sets in different configurations and with different constraint conditions. The experimental collected data were compared with theoretical models and with data obtained from the use of different measuring instruments to perform validation and calibration of the transducer at the same time. Several diagrams can compare the transducer and highlight its suitability for the monitoring and maintenance of structures. The characteristic of the transducer suggests its use as a mixed system for reinforcing and monitoring, especially in the lifetime maintenance of critical infrastructures such as transportation and service networks, and historical heritage.
Familiarization and Reliability of the Isometric Knee Extension Test for Rapid Force Production Assessment
Authors: Courel-Ibáñez Javier , Hernández-Belmonte Alejandro , Cava-Martínez Alejandro , Pallarés Jesús G.
Published: June 2020

Despite the rising interest in the use of portable force sensors during isometric exercises to inform on neuromuscular performance, the design of practical field-based methods to obtain reliable measures is an ongoing challenge. We aim at identifying the intra-session and test-retest reliability of a rapid, isometric knee extension test to evaluate the maximal voluntary concentric force (MVC), rate of force development (RFD) and impulse following a field-based approach. On two occasions, 14 athletes unfamiliar with the test completed three sets of 2 s ballistic contractions (as fast and hard as possible) with 30 s rest. Raw and filtered data were collected in real time using a portable force sensor. RFD and impulse were highly reliability during “late” phases of the contraction (0–250 ms) since the first session (coefficient of variation (CV) < 9.8%). Earlier phases (0–150 ms) achieved a moderate reliability after one familiarization session (CV < 7.1%). Measures at 0–50 ms did not reach sufficient reliability (CV~14%). MVC was accurately assessed. Dominant limbs were not importantly altered by the familiarization. In opposite, non-dominant limbs showed large variations. New evidence is provided about the positive effects of a single familiarization session to improve the reliability the isometric knee extension test for rapid force production assessment. Coaches and practitioners may benefit of from these findings to conduct practical and reliable assessments of the rapid force production using a portable force sensor and a field-based approach.
Metallic Ribbon-Core Sandwich Panels Subjected to Air Blast Loading
Authors: Abada Mahmoud , Ibrahim Ahmed
Published: June 2020

Sandwich structures provide a quite promising solution for blast alleviation techniques owing to their lightweight, high strength, and impressive energy absorption capabilities relative to solo metallic plates with equivalent density. The ability of the sandwich structure to withstand blast loading relies on its core topology. This paper numerically investigates the effectiveness of using ribbon shapes as an innovative core topology for sandwich structures subjected to blast loading. The hydro-code program (Autodyn) supported by the finite element program (ANSYS) is adopted to study the dynamic response of various sandwich panels. The accuracy of the finite element (FE) models were verified using available experimental results for a field blast test in the literature. The results show that the developed finite element model can be reliably exploited to simulate the dynamic behavior of the sandwich panels. The trapezoidal (TZ) and triangular (T) corrugated core topologies were selected to highlight the blast-resistant performance of the new ribbon core topology. Applying the ribbon topology to the traditional corrugated core topologies improved their blast performance. The facing front-plate’s deflection of the trapezoidal corrugated ribbon core sandwich structure (TZRC) has been improved by 45.3% and by 76.5% for the back-plate’s deflection, while for the triangular ribbon corrugated core (TRC), the front plate’s defection has been enhanced by 69.3% and by 112.1% for the back plate. The effect of various design parameters on the blast behavior of the Ribbon-Core Sandwich Panels (RCSPs) was investigated. A parametric study was conducted to evaluate performance indicators, including energy dissipated through plastic deformation and plate deflections. Finally, based on the parametric study, the results of this paper were recommended to be used as a guide for designing metallic ribbon sandwich structures with different protection levels.
Influence of TiO2 Nanoparticles Addition on the Hydrophilicity of Cementitious Composites Surfaces
Authors: Hegyi Andreea , Szilagyi Henriette , Grebenișan Elvira , Sandu Andrei Victor , Lăzărescu Adrian-Victor , Romila Claudiu
Published: June 2020

The effect of the use of TiO2 nanoparticles in the production of cementitious composites, worldwide already known, represents an area of interest for the development of materials with self-cleaning capacity; antimicrobial, antibacterial, antifungal properties; and to contribute to the reduction of environmental pollution. This paper aims to analyze the influence that TiO2 nanoparticles have on the cementitious matrix regarding hydrophilicity, this being one of the two main parameters of the self-cleaning mechanism. Experimental tests, conducted by using the indirect method of measuring the surface water absorption, indicated that an addition of 3%-6% (relative to the amount of cement) of TiO2 nanoparticles is effective in terms of increasing the surface hydrophilicity of the cementitious composites. An excess of TiO2 nanoparticles in the composite matrix (10% TiO2 nanoparticles relative to the amount of cement) not only does not improve surface performance in terms of hydrophilicity, but also reduces them. However, in practice on a case-by-case basis, an analysis is required regarding the optimal amount of nanoparticles used as an addition in the mix-design of the cementitious materials that are intended to induce the quality of self-cleaning process, depending on the intended use, climate, degree and duration of sunlight, and so on.
Effect of Cyclic Loading Frequency on Liquefaction Prediction of Sand
Authors: Nong Zhenzhen , Park Sung-Sik , Jeong Sueng-Won , Lee Dong-Eun
Published: June 2020

The frequency of ground motions during earthquakes is typically in the order of a few hertz. As the earthquake-induced liquefaction of soils is widely assessed by performing laboratory tests, it is necessary to consider various loading frequencies generated by real earthquakes. The effect of loading frequency has been studied by cyclic triaxial tests; however, it has rarely been investigated by cyclic direct simple shear tests, which are more similar to the cyclic loading conditions associated with earthquakes. In this study, a series of cyclic direct simple shear tests were performed on clean sand with a relative density (Dr) of 40% (loose sand) and 80% (dense sand), obtained from Nakdong River. The parameters considered are the initial vertical effective stresses (σv0′ = 50, 100, and 200 kPa) and the loading frequencies (f = 0.05, 0.1, 0.5, and 1 Hz) to evaluate the effect of the loading frequency on the liquefaction prediction of clean sand. The results showed that the liquefaction resistance of the sand increases with the increase in the loading frequency, regardless of the initial vertical effective stress and relative density. When the loading frequency increased from 0.1 to 0.5 or 1 Hz, the maximum increase in the cyclic resistances were 15%, and 19% for loose and dense sand, respectively. For a given loading frequency, the liquefaction resistance of the sand decreased when the initial vertical effective stress increased.
Modeling and Simulation of Processes in a Factory of the Future
Authors: Grznár Patrik , Gregor Milan , Krajčovič Martin , Mozol Štefan , Schickerle Marek , Vavrík Vladimír , Ďurica Lukáš , Marschall Martin , Bielik Tomáš
Published: June 2020

Current trends in manufacturing, which are based on customisation and gradually customised production, are becoming the main initiator for the development of new manufacturing approaches. New manufacturing approaches are counted as the application of new behavioural management patterns that calculate the retained competencies of decision-making by the individual members of the system agent; the production becomes decentralised. The interaction of the members of such a system creates emergent behaviour, where the result cannot be accurately determined by ordinary methods and simulation must be applied. Modelling and simulation will, therefore, be an integral part of the planning and control of the processes of factories of the future. The purpose of the article is to describe the use of modelling and simulation processes in factories of the future. The first part of the article describes new manufacturing concepts that will be used in factories of the future, with a description of modelling and simulation routing in the frame of Industry 4.0. The next section describes how simulation is used for the control of manufacturing processes in factories of the future. The included subsection describes the implementation of this suggested pattern in the laboratory of ZIMS (Zilina Intelligent Manufacturing System), with an example of a metamodeling application and the results obtained.
Low-Loss and Broadband Silicon Photonic 3-dB Power Splitter with Enhanced Coupling of Shallow-Etched Rib Waveguides
Authors: Nguyen Vinh Huu , Kim In Ki , Seok Tae Joon
Published: June 2020

A silicon photonic 3-dB power splitter is one of the essential components to demonstrate large-scale silicon photonic integrated circuits (PICs), and can be utilized to implement modulators, 1 × 2 switches, and 1 × N power splitters for various PIC applications. In this paper, we reported the design and experimental demonstration of low-loss and broadband silicon photonic 3-dB power splitters. The power splitter was realized by adiabatically tapered rib waveguides with 60-nm shallow etches. The shallow-etched rib waveguides offered strong coupling and relaxed critical dimensions (a taper tip width of 200 nm and gap spacing of 300 nm). The fabricated device exhibited an excess loss as low as 0.06 dB at a 1550-nm wavelength and a broad operating wavelength range from 1470 nm to 1570 nm. The relaxed critical dimensions (≥200 nm) make the power splitter compatible with standard fabrication processes of existing silicon photonics foundries.
Physicochemical and Antioxidant Properties of Potentilla anserina L. Polysaccharides Affected by Ultrasonication
Authors: Huang Yulong , Guo Jie , Zhang Ji
Published: June 2020

The effects of ultrasonic treatment on the physicochemical and antioxidant properties of Potentilla anserina L. polysaccharides (PAPs) were investigated. A Box–Behnken design (BBD) was applied to optimize the parameters of ultrasound-assisted extraction (UAE). A maximum yield of 9.43% was achieved at an extraction temperature of 66 °C, ultrasonic power of 205 W, and extraction time of 2.6 h. The chemical structure analyses illustrated that the two PAP extracts using UAE and hot water extraction (HWE) had the same monosaccharide composition but displayed a significant difference in the monosaccharide content, and the molecular weight of PAPUAE was significantly lower than PAPHWE. Fourier-transform infrared (FT-IR) spectroscopy confirmed that the ultrasonic treatment did not change the type of glycosidic bonds compared with HWE. In addition, the results from thermogravimetric analysis indicated that different extraction methods had effects on the physical properties of PAPs to some degree. Antioxidant activity assays demonstrated that PAPUAE had higher superoxide dismutase and glutathione peroxidase activities when cells were exposed to exogenous H2O2 than PAPHWE, and the malondialdehyde levels were also lowered following exposure to PAPUAE. These findings indicated that ultrasound irradiation is a promising technique for polysaccharide extraction from plant materials.
Rapid and Positive Effect of Bicarbonate Addition on Growth and Photosynthetic Efficiency of the Green Microalgae Chlorella Sorokiniana (Chlorophyta, Trebouxiophyceae)
Authors: Salbitani Giovanna , Bolinesi Francesco , Affuso Mario , Carraturo Federica , Mangoni Olga , Carfagna Simona
Published: June 2020

Bicarbonate ions are the primary source of inorganic carbon for autotrophic organisms living in aquatic environments. In the present study, we evaluated the short-term (hours) effects of sodium bicarbonate (NaHCO3) addition on the growth and photosynthetic efficiency of the green algae Chlorella sorokiniana (211/8k). Bicarbonate was added to nonaxenic cultures at concentrations of 1, 2, and 3 g L−1 leading to a significant increase in biomass especially at the highest salt concentration (3 g L−1) and also showing a bactericidal and bacteriostatic effect that helped to keep a reduced microbial load in the algal culture. Furthermore, bicarbonate stimulated the increase in cellular content of chlorophyll a, improving the photosynthetic performance of cells. Since microalgae of genus Chlorella spp. show great industrial potential for the production of biofuels, nutraceuticals, cosmetics, health, and dietary supplements and the use of bicarbonate as a source of inorganic carbon led to short-term responses in Chlorella sorokiniana, this method represents a valid alternative not only to the insufflation of carbon dioxide for the intensive cultures but also for the production of potentially bioactive compounds in a short period.
Polarization-Sensitive Digital Holographic Imaging for Characterization of Microscopic Samples: Recent Advances and Perspectives
Authors: Coppola Giuseppe , Ferrara Maria Antonietta
Published: June 2020

Polarization-sensitive digital holographic imaging (PS-DHI) is a recent imaging technique based on interference among several polarized optical beams. PS-DHI allows simultaneous quantitative three-dimensional reconstruction and quantitative evaluation of polarization properties of a given sample with micrometer scale resolution. Since this technique is very fast and does not require labels/markers, it finds application in several fields, from biology to microelectronics and micro-photonics. In this paper, a comprehensive review of the state-of-the-art of PS-DHI techniques, the theoretical principles, and important applications are reported.
Policy Framework for Energy Retrofitting of Built Heritage: A Critical Comparison of UK and Turkey
Authors: Jahed Negin , Aktaş Yasemin D. , Rickaby Peter , Bilgin Altınöz Ayşe Güliz
Published: June 2020

Energy efficiency is one of the most prominent global challenges of our era. Heritage buildings usually have a poor energy performance, not necessarily because of their intrinsic constructive features but due to their mostly dilapidated condition owed to age and previous damage, exacerbated by other factors such as the limited maintenance allowed by the restrictive legal framework and/or residents not being able to afford retrofit. On both national and international levels, energy efficiency measures are considered the key to answering the global challenge of climate change. This article aims to provide a critical discussion of the policy framework for energy retrofitting targeting built heritage in the UK and in Turkey. To this end, the development of guidance and legislation on cultural heritage, energy efficiency and climate change in both countries were thoroughly reviewed, and the retrofit incentives and constraints were determined in order to identify existing policy gaps and potential problems with implementation in the realm of energy retrofitting and climate resiliency of heritage buildings. As a result of a critical comparative analysis, the paper is concluded with suggestions on policy frames for the retrofitting of heritage buildings for improved energy efficiency.
Are Empirical Equations an Appropriate Tool to Assess Separation Distances to Avoid Odour Annoyance?
Authors: Brancher Marlon , Piringer Martin , Knauder Werner , Wu Chuandong , Griffiths K. David , Schauberger Günther
Published: June 2020

Annoyance due to environmental odour exposure is in many jurisdictions evaluated by a yes/no decision. Such a binary decision has been typically achieved via odour impact criteria (OIC) and, when applicable, the resultant separation distances between emission sources and residential areas. If the receptors lie inside the required separation distance, odour exposure is characterised with the potential of causing excessive annoyance. The state-of-the-art methodology to determine separation distances is based on two general steps: (i) calculation of the odour exposure (time series of ambient odour concentrations) using dispersion models and (ii) determination of separation distances through the evaluation of this odour exposure by OIC. Regarding meteorological input data, dispersion models need standard meteorological observations and/or atmospheric stability typically on an hourly basis, which requires expertise in this field. In the planning phase, and as a screening tool, an educated guess of the necessary separation distances to avoid annoyance is in some cases sufficient. Therefore, empirical equations (EQs) are in use to substitute the more time-consuming and costly application of dispersion models. Because the separation distance shape often resembles the wind distribution of a site, wind data should be included in such approaches. Otherwise, the resultant separation distance shape is simply given by a circle around the emission source. Here, an outline of selected empirical equations is given, and it is shown that only a few of them properly reflect the meteorological situation of a site. Furthermore, for three case studies, separation distances as calculated from empirical equations were compared against those from Gaussian plume and Lagrangian particle dispersion models. Overall, our results suggest that some empirical equations reach their limitation in the sense that they are not successful in capturing the inherent complexity of dispersion models. However, empirical equations, developed for Germany and Austria, have the potential to deliver reasonable results, especially if used within the conditions for which they were designed. The main advantage of empirical equations lies in the simplification of the meteorological input data and their use in a fast and straightforward approach.
Characterization and Source Identification of Elements and Water-Soluble Ions in Submicrometre Aerosols in Brno and Šlapanice (Czech Republic)
Authors: Mikuška Pavel , Vojtěšek Martin , Křůmal Kamil , Mikušková-Čampulová Martina , Michálek Jaroslav , Večeřa Zbyněk
Published: June 2020

Submicrometre aerosol particles (particulate matter, PM1) were collected in two Czech cities (Brno and Šlapanice) during week campaigns in winter and summer of 2009 and 2010. The aerosols were analysed for 14 elements and 12 water-soluble ions using inductively coupled plasma–mass spectrometry and ion chromatography techniques. The average PM1 mass concentration was 14.4 and 20.4 µg m−3 in Brno and Šlapanice, respectively. Most of the analysed elements and ions exhibit distinct seasonal variability with higher concentrations in winter in comparison to summer. The determined elements and ions together accounted for about 29% of total PM1 mass, ranging between 16% and 44%. Ion species were the most abundant components in collected aerosols, accounting for 27.2% of mass of PM1 aerosols, and elements accounted for 1.8% of mass of PM1 aerosols. One-day backward trajectories were calculated using the Hysplit model to analyse air masses transported towards the sampling sites. The Pearson correlation coefficients between individual PM1 components and PM1 mass and air temperature were calculated. To identify the main aerosol sources, factor analysis was applied. Six factors were identified for each locality. The following sources of PM1 particles were identified in Brno: a municipal incinerator, vehicle exhausts, secondary sulphate, a cement factory, industry and biomass burning. The identified sources in Šlapanice were as follows: a combustion source, coal combustion, a cement factory, a municipal incinerator, vehicle exhausts and industry.
Lessons from SARS-CoV-2 Pandemic: Evolution, Disease Dynamics and Future
Authors: Pandey Saurabh , Yadav Bharat , Pandey Arvind , Tripathi Takshashila , Khawary Masuma , Kant Sashi , Tripathi Deeksha
Published: June 2020

The COVID-19 pandemic is rising at an unprecedented rate. The surging number of deaths every day, global lockdown and travel restrictions have resulted in huge losses to society. The impact is massive and will leave a historical footprint. The Spanish Flu of 1918, which was the last pandemic that had a similar impact, was shadowed under the consequences of World War I. All the brilliance, strength and economies of countries worldwide are aimed at fighting the COVID-19 pandemic. The knowledge about coronavirus dynamics, its nature and epidemiology are expanding every day. The present review aims to summarize the structure, epidemiology, symptoms, statistical status of the disease status, intervention strategies and deliberates the lessons learnt during the pandemic. The intervention approaches, antiviral drug repurposing and vaccine trials are intensified now. Statistical interpretations of disease dynamics and their projections may help the decision-makers.
She Thinks in English, But She Wants in Mandarin: Differences in Singaporean Bilingual English–Mandarin Maternal Mental-State-Talk
Authors: Cheng Michelle , Setoh Peipei , Bornstein Marc H. , Esposito Gianluca
Published: June 2020

Chinese-speaking parents are believed to use less cognitive mental-state-talk than their English-speaking counterparts on account of their cultural goals in socializing their children to follow an interdependence script. Here, we investigated bilingual English–Mandarin Singaporean mothers who associate different functions for each language as prescribed by their government: English for school and Mandarin for in-group contexts. English and Mandarin maternal mental-state-talk from bilingual English–Mandarin mothers with their toddlers was examined. Mothers produced more ‘’cognitive’’ terms in English than in Mandarin and more ‘’desire’’ terms in Mandarin than in English. We show that mental-state-talk differs between bilingual parents’ languages, suggesting that mothers adjust their mental-state-talk to reflect the functions of each language.
Sustainable Urban Development in Slum Areas in the City of Rio de Janeiro Based on LEED-ND Indicators
Authors: de Siqueira Ana Carolina Hyczy , Najjar Mohammad K. , Hammad Ahmed W. A. , Haddad Assed , Vazquez Elaine
Published: June 2020

The accelerated urban transition and its consequent unsustainability is a problem registered in several global scenarios. This issue has been identified in the city of Rio de Janeiro in Brazil. One of the solutions provided for this theme is the application of specific methodologies to measure sustainability in urban areas such as the case of Leadership in Energy and Environmental Design for Neighborhood Development (LEED-ND). This work aims to analyze a real urban project, still in the executive project phase, Morro do Encontro project, in the scenario of the slum area of Rio de Janeiro based on the LEED-ND indicator system. The novelty of this study is to evaluate the existing relationships, between urban development actions and sustainability, through LEED-ND indicators, in the proposals of the Brazilian government plan PAC2, as a means of verifying their effectiveness. A total of 12 boards of the discipline of Urbanism in the executive project phase are studied. The analyzed items are divided into credit items and mandatory items. A total of 8% of credit items (CI) and 33% of mandatory items (MI) are attended. The results found indicated 47 sustainability items were not met and, therefore, can be improved. This comes back to the fact that 100% of the mandatory LEED-ND items were not achieved, which means that this project as it was conceived cannot be considered as a sustainable urban solution.
CFD Simulations of Radiative Heat Transport in Open-Cell Foam Catalytic Reactors
Authors: Sinn Christoph , Kranz Felix , Wentrup Jonas , Thöming Jorg , Wehinger Gregor D. , Pesch Georg R.
Published: June 2020

The heat transport management in catalytic reactors is crucial for the overall reactor performance. For small-scale dynamically-operated reactors, open-cell foams have shown advantageous heat transport characteristics over conventional pellet catalyst carriers. To design efficient and safe foam reactors as well as to deploy reliable engineering models, a thorough understanding of the three heat transport mechanisms, i.e., conduction, convection, and thermal radiation, is needed. Whereas conduction and convection have been studied extensively, the contribution of thermal radiation to the overall heat transport in open-cell foam reactors requires further investigation. In this study, we simulated a conjugate heat transfer case of a µCT based foam reactor using OpenFOAM and verified the model against a commercial computational fluid dynamics (CFD) code (STAR-CCM+). We further explicitly quantified the deviation made when radiation is not considered. We studied the effect of the solid thermal conductivity, the superficial velocity and surface emissivities in ranges that are relevant for heterogeneous catalysis applications (solid thermal conductivities 1–200 W m−1 K−1; superficial velocities 0.1–0.5 m s−1; surface emissivities 0.1–1). Moreover, the temperature levels correspond to a range of exo- and endothermal reactions, such as CO2 methanation, dry reforming of methane, and methane steam reforming. We found a significant influence of radiation on heat flows (deviations up to 24%) and temperature increases (deviations up to 400 K) for elevated temperature levels, low superficial velocities, low solid thermal conductivities and high surface emissivities.
Highly Active Catalysts for the Dehydration of Isopropanol
Authors: Murat Martyna , Tišler Zdeněk , Šimek Josef , Hidalgo-Herrador José M.
Published: June 2020

Due to the high costs and low selectivity associated with the production of propylene, new routes for its synthesis are being sought. Dehydration has been widely investigated in this field, but, thus far, no study has produced efficient results for isopropanol. Vanadium-zirconia catalysts have been shown to be effective for the dehydration of ethanol. Therefore, we investigated the activity of such catalysts in the dehydration of isopropanol. The catalysts were synthetized on a SBA-15 base, supplemented with zirconia or combined zirconia and vanadium. Tests were conducted in a continuous flow reactor at 150–300 °C. Samples were analyzed using a gas chromatograph. The most active catalyst showed 96% conversion with 100% selectivity to propylene. XRD, SEM and Raman spectroscopy analyses revealed that as the vanadium content increases, the pore size of the catalyst decreases and both isopropanol conversion and propylene selectivity are reduced. Thus, without the addition of vanadium, the Zr-SBA-15 catalyst appears to be suitable for the dehydration of isopropanol to propylene.
Comparison of Photocatalytic Membrane Reactor Types for the Degradation of an Organic Molecule by TiO2-Coated PES Membrane
Authors: Regmi Chhabilal , Lotfi Shabnam , Espíndola Jonathan Cawettiere , Fischer Kristina , Schulze Agnes , Schäfer Andrea Iris
Published: June 2020

Photocatalytic membrane reactors with different configurations (design, flow modes and light sources) have been widely applied for pollutant removal. A thorough understanding of the contribution of reactor design to performance is required to be able to compare photocatalytic materials. Reactors with different flow designs are implemented for process efficiency comparisons. Several figures-of-merit, namely adapted space-time yield (STY) and photocatalytic space-time yield (PSTY), specific energy consumption (SEC) and degradation rate constants, were used to assess the performance of batch, flow-along and flow-through reactors. A fair comparison of reactor performance, considering throughput together with energy efficiency and photocatalytic activity, was only possible with the modified PSTY. When comparing the three reactors at the example of methylene blue (MB) degradation under LED irradiation, flow-through proved to be the most efficient design. PSTY1/PSTY2 values were approximately 10 times higher than both the batch and flow-along processes. The highest activity of such a reactor is attributed to its unique flow design which allowed the reaction to take place not only on the outer surface of the membrane but also within its pores. The enhancement of the mass transfer when flowing in a narrow space (220 nm in flow-through) contributes to an additional MB removal.
Corrosion Resistance of Hard Coat Anodized AA 6061 in Citric–Sulfuric Solutions
Authors: Cabral-Miramontes José , Gaona-Tiburcio Citlalli , Estupinán-López Francisco , Lara-Banda María , Zambrano-Robledo Patricia , Nieves-Mendoza Demetrio , Maldonado-Bandala Erick , Chacón-Nava José , Almeraya-Calderón Facundo
Published: June 2020

Aluminum is a material widely used in aeronautical and transport industries due to its excellent mechanical and corrosion resistance properties. Unfortunately, aluminum alloys are susceptible to corrosion, which limits their use in some corrosive environments. The aim of this work is to characterize hard coat film fabricated by anodizing in a citric–sulfuric acid system using electrochemical techniques. The anodization process was carried out using an aluminum alloy AA 6061 anodization bath: a mix of citric and sulfuric acid solutions were used. For the anodizing process, two current densities were used, 1 and 7.2 A·cm−2. Anodized specimens obtained under different conditions were exposed to a 3.5 wt.% NaCl solution, and their electrochemical behavior was studied by electrochemical impedance spectroscopy (EIS) and cyclic potentiodynamic polarization (CPP) according to ASTM G106-15 and ASTM G5-13, respectively. Scanning electron microscopy (SEM) was employed to determinate the morphology and thickness of coatings. The results showed improved corrosion resistance in 6061 aluminum anodized in citric–sulfuric acid electrolyte compared to those anodized in sulfuric acid solution.
Polysulfone Composite Membranes with Carbonaceous Structure. Synthesis and Applications
Authors: Pandele Andreea Madalina , Serbanescu Oana Steluta , Voicu Stefan Ioan
Published: June 2020

The present review deals with the latest progress in the field of polysulfone composite membranes with carbon nanotubes, carbon fiber and graphene from both perspectives-synthesis and applications. These two fillers, extensively used in the last few years due to their remarkable properties, induce a high value character to the composite materials. On the other hand, polysulfone is one the most used polymers for preparing polymeric membranes due to its high versatility in a wide range of solvents and also to the properties of this remarkable polymer. All types of synthesis method were presented and also a large number of applications from industrial to biomedical were presented and discussed.
Cattaneo-Christov Heat Flux Model for Second Grade Nanofluid Flow with Hall Effect through Entropy Generation over Stretchable Rotating Disk
Authors: Wakeel Ahmad Muhammad , McCash Luthais B. , Shah Zahir , Nawaz Rashid
Published: June 2020

The second grade nanofluid flow with Cattaneo-Christov heat flux model by a stretching disk is examined in this paper. The nanofluid flow is characterized with Hall current, Brownian motion and thermophoresis influences. Entropy optimization with nonlinear thermal radiation, Joule heating and heat absorption/generation is also presented. The convergence of an analytical approach (HAM) is shown. Variation in the nanofluid flow profiles (velocities, thermal, concentration, total entropy, Bejan number) via influential parameters and number are also presented. Radial velocity, axial velocity and total entropy are enhanced with the Weissenberg number. Axial velocity, tangential velocity and Bejan number are heightened with the Hall parameter. The total entropy profile is enhanced with the Brinkman number, diffusion parameter, magnetic parameter and temperature difference. The Bejan number profile is heightened with the diffusion parameter and temperature difference. Arithmetical values of physical quantities are illustrated in Tables.
Correlations for Easy Calculation of the Critical Coalescence Concentration (CCC) of Simple Frothers
Authors: Karakashev Stoyan I. , Grozev Nikolay A. , Batjargal Khandjamts , Guven Onur , Ozdemir Orhan , Boylu Feridun , Çelik Mehmet Sabri
Published: June 2020

Can the critical coalescence concentration (CCC) of the flotation frothers be predictable? What is the relation between their molecular structure and their CCC values? A literature survey found specific correlations between the hydrophilic-lipophilic balances (HLB) and HLB/Mw (where Mw stands for the molecular mass) of homologue series of frothers and their CCC values, but the results are invalid when the molecule’s functional groups change. For this reason, 37 frothers with known values of CCC were analyzed. The CCC values of seven frothers were determined, and the rest were taken from the literature. The frothers were subdivided in homologue series with an increasing number of the carbon atoms with an account for the type and the location of the functional group, thus deriving three types of correlations lnCCC = f(HLB) applicable for: (i) alcohols; (ii) propylene glycols alkyl ethers and propylene glycols; (iii) ethylene glycols alkyl ethers. The average accuracy of these correlations between CCC and HLB is 93%.
The Preparation and Properties of the Brown Film by Micro-arc Oxidized on In-Situ TiB2/7050Al Matrix Composites
Authors: Xia Cunjuan , Huang Jie , Tao Jiongming , Wang Shuyang , Cai Ling , Wang Mingliang , Chen Dong , Wang Haowei
Published: June 2020

The brown or grayish-white color films were prepared by the micro-arc oxidation (MAO) method on in-situ TiB2/7050Al composites using these alkaline electrolytes with/without KMnO4 as an additive. The microstructure, elemental composition, chemical state and corrosion behavior have been investigated by the microstructure characterizations and electrochemistry measurements on the MAO films comparatively. The results indicated that a brown film was obtained via adding KMnO4 into the alkaline electrolyte. The coloration mechanism of the brown color can be ascribed to the existence of MnO inside the film. Furthermore, the initiation of corrosion to the Al composite was intensively hindered by the brown MAO film. Compared with the Al substrate and grayish-white film, the brown MAO film exhibited the elevated corrosion potential and reduced corrosion current. Therefore, the brown film has presented an optimized corrosion resistance for the composite.
Effect of Current Density on the Performance of Ni–P–ZrO2–CeO2 Composite Coatings Prepared by Jet-Electrodeposition
Authors: Song Zhaoyang , Zhang Hongwen , Fu Xiuqing , Lin Jinran , Shen Moqi , Wang Qingqing , Duan Shuanglu
Published: June 2020

The objective of this study was to improve the surface properties, hardness, wear resistance and electrochemical corrosion resistance of #45 steel. To this end, Ni–P–ZrO2–CeO2 composite coatings were prepared on the surface of #45 steel using the jet-electrodeposition technique by varying the current density from 20 to 60 A/dm2. The effect of current density on the performance of the composite coatings was evaluated. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were applied to explore the surface topography, elemental composition, hardness and electrochemical corrosion resistance of the composite coatings. The results showed that with the increase in the current density, the hardness, wear resistance, and electrochemical corrosion resistance tends to increase first and then decrease. At a current density of 40 A/dm2, the hardness reached a maximum of 688.9 HV0.1, the corrosion current reached a minimum of 8.2501 × 10−5 A·cm−2, and the corrosion potential reached a maximum of −0.45957 V. At these values, the performance of the composite coatings was optimal.
Investigation of Wettability, Drying and Water Condensation on Polyimide (Kapton) Films Treated by Atmospheric Pressure Air Dielectric Barrier Discharge
Authors: Khomiakova Natalia , Hanuš Jan , Kuzminova Anna , Kylián Ondřej
Published: June 2020

In this study, we report on the investigation of influence of air atmospheric pressure dielectric barrier discharge on polyimide (Kapton) films. It is shown that plasma treatment causes a significant increase of Kapton wettability that is connected with alterations of its chemical composition (oxidation) induced by dielectric barrier discharge. Observed variations in the wettability of Kapton were also found to be accompanied by changes in the dynamics of water droplets drying on plasma-treated Kapton, namely by the reduction of the constant contact angle phase of the droplet drying. This effect may be ascribed to the higher surface heterogeneity of plasma-treated Kapton that causes pinning of the edges of drying droplet on the Kapton surface. Finally, the differences in wettability induced by the plasma treatment led to a different way, how the water condensates on the Kapton surface: while the condensing water forms large amount of small droplets on untreated Kapton, much bigger water structures were found on the Kapton exposed to atmospheric plasma.
Experimental Study on Tool Wear and Delamination in Milling CFRPs with TiAlN- and TiN-Coated Tools
Authors: Ozkan Dervis , Panjan Peter , Gok Mustafa Sabri , Karaoglanli Abdullah Cahit
Published: June 2020

Carbon fiber-reinforced polymers (CFRPs) have very good mechanical properties, such as extremely high tensile strength/weight ratios, tensile modulus/weight ratios, and high strengths. CFRP composites need to be machined with a suitable cutting tool; otherwise, the machining quality may be reduced, and failures often occur. However, as a result of the high hardness and low thermal conductivity of CFRPs, the cutting tools used in the milling process of these materials complete their lifetime in a short cycle, due to especially abrasive wear and related failure mechanisms. As a result of tool wear, some problems, such as delamination, fiber breakage, uncut fiber and thermal damage, emerge in CFRP composite under working conditions. As one of the main failure mechanisms emerging in the milling of CFRPs, delamination is primarily affected by the cutting tool material and geometry, machining parameters, and the dynamic loads arising during the machining process. Dynamic loads can lead to the breakage and/or wear of cutting tools in the milling of difficult-to-machine CFRPs. The present research was carried out to understand the influence of different machining parameters on tool abrasion, and the work piece damage mechanisms during CFRP milling are experimentally investigated. For this purpose, cutting tests were carried out using a (Physical Vapor Deposition) PVD-coated single layer TiAlN and TiN carbide tool, and the abrasion behavior of the coated tool was investigated under dry machining. To understand the wear process, scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) was used. As a result of the experiments, it was determined that the hard and abrasive structure of the carbon fibers caused flank wear on TiAlN- and TiN-coated cutting tools. The best machining parameters in terms of the delamination damage of the CFRP composite were obtained at high cutting speeds and low feed rates. It was found that the higher wear values were observed at the TiAlN-coated tool, at the feed rate of 0.05 mm/tooth.
Estimations of the Optical Equivalence Theorem for Opto-Mechanical Systems for Investigation in General Relativity and High-Energy Physics
Authors: Lecian Orchidea Maria
Published: June 2020

The optical equivalence principle is analyzed according to the possibility of describing unbounded states, and the suitable approximations are calculated for highly energetic phenomena. Among these possibilities, the relevance for laser fields, interferometers, and optomehcanical systems are implemented. Their suitableness for research in General Relativity, Cosmology, and High-Energy Physics are outlined.
Lake Zeiļu Clay Application Induced Changes in Human Skin Hydration, Elasticity, Transepidermal Water Loss and PH in Healthy Individuals
Authors: Misiņa Samanta Marija , Tretjakova Rasma , Kodors Sergejs , Zavorins Aleksejs
Published: June 2020

Clay has a great biomedical application potential, however there are just a few instrumental studies and the impact of lake clay on the skin has not yet been studied. The DermaLab skin analysis system (Cortex Technology) was used for hydration, elasticity, transepidermal water loss (TEWL) and pH measurements after lake clay facial applications. Research included short-term tests (measurements 20 and 60 min after clay application) and long-term tests (application every 4th day for 3 weeks with measurements 20–24 h post-application). Control measurements and application tests to exclude contact allergy were made beforehand. No volunteer (n = 30) had positive allergic reaction. The matched-pairs design was applied: the right and left parts of forehead were used for the test and control groups. The Wilcoxon signed-rank test (significance level p = 0.001) was applied for statistical analysis. There were statistically significant pH changes demonstrated during the short-term measurements. The long-term measurements provided data that clay significantly improves skin hydration and elasticity.
Quantum-Sized Zinc Oxide Nanoparticles Synthesised within Mesoporous Silica (SBA-11) by Humid Thermal Decomposition of Zinc Acetate
Authors: Aqeel Tariq , Greer Heather F.
Published: June 2020

A modified facile method is presented to synthesise quantum-sized zinc oxide nanoparticles within the pores of a mesoporous silica host (SBA-11). This method eliminates the 3 h alcohol reflux and the basic solution reaction steps of zinc acetate. The mesoporous structure and the ZnO nanoparticles were analysed by X-ray diffractometry, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, nitrogen sorption analysis and UV–VIS spectroscopy. These tests confirm the synthesis of ~1 nm sized ZnO within the pores of SBA-11 and that the porous structure remained intact after ZnO synthesis.
Molecular and Serological Tests for COVID-19. A Comparative Review of SARS-CoV-2 Coronavirus Laboratory and Point-of-Care Diagnostics
Authors: Kubina Robert , Dziedzic Arkadiusz
Published: June 2020

Validated and accurate laboratory testing for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a crucial part of the timely management of Coronavirus Disease 2019 (COVID-19) disease, supporting the clinical decision-making process for infection control at the healthcare level and detecting asymptomatic cases. This would facilitate an appropriate treatment, a prompt isolation and consequently deceleration of the pandemic. Various laboratory tests can identify the genetic material of SARS-CoV-2 that causes COVID-19 in specimens, or specific anti-viral antibodies in blood/serum. Due to the current pandemic situation, a development of point-of-care diagnostics (POCD) allows us to substantially accelerate taking clinical decisions and implement strategic planning at the national level of preventative measures. This review summarizes and compares the available POCD and those currently under development, including quantitative reverse transcription PCR (RT-qPCR), serology immunoassays (SIAs) and protein microarray method (PMM) designed for standard and rapid COVID-19 diagnosis.
COVID-19 as a Vascular Disease: Lesson Learned from Imaging and Blood Biomarkers
Authors: Zamboni Paolo
Published: June 2020

COVID-19, a disease initially thought to be prominently an interstitial pneumonia with varying degrees of severity, can be considered a vascular disease with regards to serious complications and causes of mortality. Quite recently, blood clots have emerged as the common factor unifying many of the symptoms initially attributed without an explanation to COVID-19. Cardiovascular biomarkers and particularly, D-dimer and troponin appear to be very powerful prognostic markers, signaling the need for earlier and more aggressive interventions and treatments in order to avoid and/or minimize arterial/venous thromboembolism and myocardial infarct. The ultrasound imaging patterns at both the lung and peripheral vascular level can also be very useful weapons that have the advantage of being able to monitor longitudinally the clinical picture, something that real-time PCR/nasopharyngeal swab is not able to do and that CT can only pursue with significant radiation exposure. A lesson learned in the early phase of the COVID-19 pandemic suggests quitting and starting again with targeted imaging and blood vascular biomarkers.