Search results for: mechanism reaction

Authors: Sushish Baral, Pratibha Joshi, Yaman Maharjan

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Glaucoma is a chronic eye condition that causes vision loss that is irreversible. Early detection and treatment are critical to prevent vision loss because it can be asymptomatic. For the identification of glaucoma, multiple deep learning algorithms are used. Transformer-based architectures, which use the self-attention mechanism to encode long-range dependencies and acquire extremely expressive representations, have recently become popular. Convolutional architectures, on the other hand, lack knowledge of long-range dependencies in the image due to their intrinsic inductive biases. The aforementioned statements inspire this thesis to look at transformer-based solutions and investigate the viability of adopting transformer-based network designs for glaucoma detection. Using retinal fundus images of the optic nerve head to develop a viable algorithm to assess the severity of glaucoma necessitates a large number of well-curated images. Initially, data is generated by augmenting ocular pictures. After that, the ocular images are pre-processed to make them ready for further processing. The system is trained using pre-processed images, and it classifies the input images as normal or glaucoma based on the features retrieved during training. The Vision Transformer (ViT) architecture is well suited to this situation, as it allows the self-attention mechanism to utilise structural modeling. Extensive experiments are run on the common dataset, and the results are thoroughly validated and visualized.

Keywords: glaucoma, vision transformer, convolutional architectures, retinal fundus images, self-attention, deep learning

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Authors: Yeidy Sorani Montenegro Camacho, Samir Bensaid, Nunzio Russo, Debora Fino

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LiFeO2 nano-powders were prepared via solution combustion synthesis (SCS) method and were used as carbon gasification catalyst in a reduced atmosphere. The gasification of soot with CO2 and H2O in the presence of CO and H2 (syngas atmosphere) were also investigated under atmospheric conditions using a fixed-bed micro-reactor placed in an electric, PID-regulated oven. The catalytic bed was composed of 150 mg of inert silica, 45 mg of carbon (Printex-U) and 5 mg of catalyst. The bed was prepared by ball milling the mixture at 240 rpm for 15 min to get an intimate contact between the catalyst and soot. A Gas Hourly Space Velocity (GHSV) of 38.000 h-1 was used for the tests campaign. The furnace was heated up to the desired temperature, a flow of 120 mL/min was sent into the system and at the same time the concentrations of CO, CO2 and H2 were recorded at the reactor outlet using an EMERSON X-STREAM XEGP analyzer. Catalytic and non-catalytic soot gasification reactions were studied in a temperature range of 120°C – 850°C with a heating rate of 5 °C/min (non-isothermal case) and at 650°C for 40 minutes (isothermal case). Experimental results show that the gasification of soot with H2O and CO2 are inhibited by the H2 and CO, respectively. The soot conversion at 650°C decreases from 70.2% to 31.6% when the CO is present in the feed. Besides, the soot conversion was 73.1% and 48.6% for H2O-soot and H2O-H2-soot gasification reactions, respectively. Also, it was observed that the carbon gasification in mixed atmosphere, i.e., when simultaneous carbon gasification with CO2 and steam take place, with H2 and CO as co-reagents; the gasification reaction is strongly inhibited by CO and H2, as well has been observed in single atmospheres for the isothermal and non-isothermal reactions. Further, it has been observed that when CO2 and H2O react with carbon at the same time, there is a passive cooperation of steam and carbon dioxide in the gasification reaction, this means that the two gases operate on separate active sites without influencing each other. Finally, despite the extreme reduced operating conditions, it has been demonstrated that the 32.9% of the initial carbon was gasified using LiFeO2-catalyst, while in the non-catalytic case only 8% of the soot was gasified at 650°C.

Keywords: soot gasification, nanostructured catalyst, reducing environment, syngas

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Authors: Alessio Varotto, Lorenzo Freschi, Umberto Pasqual Laverdura, Anastasia Moschovi, Davide Pumiglia, Iakovos Yakoumis, Marta Feroci, Maria Luisa Grilli

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Dry reforming of Methane (DRM) is considered one of the most valuable technologies for green-house gas valorization thanks to the fact that through this reaction, it is possible to obtain syngas, a mixture of H₂ and CO in an H₂/CO ratio suitable for utilization in the Fischer-Tropsch process of high value-added chemicals and fuels. Challenges of the DRM process are the reduction of costs due to the high temperature of the process and the high cost of precious metals of the catalyst, the metal particles sintering, and carbon deposition on the catalysts’ surface. The aim of this study is to demonstrate the feasibility of the synthesis of catalysts using a leachate solution containing Pt coming directly from the recovery of spent diesel oxidation catalysts (DOCs) without further purification. An unusual perovskite support for DRM, the BaCe₁₋ₓ₋ᵧZrₓGdᵧO₃ (BCZG) perovskite, has been chosen as the catalyst support because of its high thermal stability and capability to produce oxygen vacancies, which suppress the carbon deposition and enhance the catalytic activity of the catalyst. BCZG perovskite has been synthesized by a sol-gel modified Pechini process and calcinated in air at 1100 °C. BCZG supports have been impregnated with a Pt-containing leachate solution of DOC, obtained by a mild hydrometallurgical recovery process, as reported elsewhere by some of the authors of this manuscript. For comparison reasons, a synthetic solution obtained by digesting commercial Pt-black powder in aqua regia was used for BCZG support impregnation. Pt nominal content was 2% in both BCZG-based catalysts formed by real and synthetic solutions. The structure and morphology of catalysts were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Thermogravimetric Analysis (TGA) was used to study the thermal stability of the catalyst’s samples. Brunauer-Emmett-Teller (BET) analysis provided a high surface area of the catalysts. H₂-TPR (Temperature Programmed Reduction) analysis was used to study the consumption of hydrogen for reducibility, and it was associated with H₂-TPD characterization to study the dispersion of Pt on the surface of the support and calculate the number of active sites used by the precious metal. Dry reforming of methane (DRM) reaction, carried out in a fixed bed reactor, showed a high conversion efficiency of CO₂ and CH4. At 850°C, CO₂ and CH₄ conversion were close to 100% for the catalyst obtained with the aqua regia-based solution of commercial Pt-black, and ~70% (for CH₄) and ~80 % (for CO₂) in the case of real HCl-based leachate solution. H₂/CO ratios were ~0.9 and ~0.70 in the first and latter cases, respectively. As far as we know, this is the first pioneering work in which a BCGZ catalyst and a real Pt-containing leachate solution were successfully employed for DRM reaction.

Keywords: dry reforming of methane, perovskite, PGM, recycled Pt, syngas

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Authors: Simon Guerin-Marthe, Marie Violay

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Thermal Pressurization (TP) has been proposed as a key mechanism involved in the weakening of faults during dynamic ruptures. Theoretical and numerical studies clearly show how frictional heating can lead to an increase in pore fluid pressure due to the rapid slip along faults occurring during earthquakes. In addition, recent laboratory studies have evidenced local pore pressure or local temperature variation during rotary shear tests, which are consistent with TP theoretical and numerical models. The aim of this study is to complement previous ones by measuring both local pore pressure and local temperature variations in the vicinity of a water-saturated calcite gouge layer subjected to a controlled slip velocity in direct double shear configuration. Laboratory investigation of TP process is crucial in order to understand the conditions at which it is likely to become a dominant mechanism controlling dynamic friction. It is also important in order to understand the timing and magnitude of temperature and pore pressure variations, to help understanding when it is negligible, and how it competes with other rather strengthening-mechanisms such as dilatancy, which can occur during rock failure. Here we present unique direct measurements of temperature and pressure variations during high-speed friction experiments under various load point velocities and show the timing of these variations relatively to the slip event.

Keywords: thermal pressurization, double-shear test, high-speed friction, dilatancy

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Authors: Berina Pilipović, Saša Pilipović, Maja Pašić-Kulenović

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Inflammation is the body's response to impaired homeostasis caused by infection, injury or trauma resulting in systemic and local effects. Inflammation causes the body's response to injury and is characterized by a series of events including inflammatory response, response to pain receptors and the recovery process. Inflammation can be acute and chronic. The inflammatory response is described in three different phases. Free radical is an atom or molecule that has the unpaired electron and is therefore generally very reactive chemical species. Biologically important example of reaction with free radicals is called Lipid peroxidation (LP). Lipid peroxidation reactions occur in biological membranes, and if at the outset is not stopped with the action of antioxidants, it will bring damage to the membrane, which results in partial or complete loss of their physiological functions. Calcium antagonists and beta-adrenergic receptor antagonists are known drugs, and for many years and widely used in the treatment of cardiovascular diseases. Some of these compounds also show antioxidant activity. The mechanism of antioxidant activities of calcium antagonists and beta-blockers is unknown, since their structure varies widely. This research investigated the possible local anti-inflammatory activity of ointments containing 1% carvedilol in the white petrolatum USP. Ear inflammation was induced by 3% croton oil acetone solution, in quantity of 10 µl on both mouse ears. Albino Swiss mouse (n = 8) are treated with 2.5 mg/ear ointment, and control group was treated on the same way as previous with hydrocortisone 1% ointment (2.5 mg/ear). The other ear of the same animal was used as control one. Ointments were administered once per day, on the left ear. After treatment, ears were observed for three days. After three days, we measured mass (mg) of 6 mm ear punch of treated and controlled ears. The results of testing anti-inflammatory effects of ointments with carvedilol in the mouse ear model show stronger observed effect than ointment with 1% hydrocortisone in the same basis. Identical results were confirmed by the difference between the mass of 6 mm ears punch. The results were also confirmed by histological examination. Ointments with carvedilol showed significant reduction of the inflammation process caused by croton oil on the mouse inflammation model.

Keywords: antioxidant, carvedilol, inflammation, mouse ear

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Authors: Ramya P, Lino Abraham Varghese, S. Bose

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By cloud storage services, the data can be stored in the cloud, and can be shared across multiple users. Due to the unexpected hardware/software failures and human errors, which make the data stored in the cloud be lost or corrupted easily it affected the integrity of data in cloud. Some mechanisms have been designed to allow both data owners and public verifiers to efficiently audit cloud data integrity without retrieving the entire data from the cloud server. But public auditing on the integrity of shared data with the existing mechanisms will unavoidably reveal confidential information such as identity of the person, to public verifiers. Here a privacy-preserving mechanism is proposed to support public auditing on shared data stored in the cloud. It uses group signatures to compute verification metadata needed to audit the correctness of shared data. The identity of the signer on each block in shared data is kept confidential from public verifiers, who are easily verifying shared data integrity without retrieving the entire file. But on demand, the signer of the each block is reveal to the owner alone. Group private key is generated once by the owner in the static group, where as in the dynamic group, the group private key is change when the users revoke from the group. When the users leave from the group the already signed blocks are resigned by cloud service provider instead of owner is efficiently handled by efficient proxy re-signature scheme.

Keywords: data integrity, dynamic group, group signature, public auditing

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Authors: M. E. Joret, F. Germeys, P. Van de Craen

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Background: Previous studies have shown that ‘full’ bilingualism seems to enhance the executive functions in children, young adults and elderly people. Executive functions refer to a complex cognitive system responsible for self-controlled and planned behavior and seem to predict academic achievement. The present study aimed at investigating whether similar effects could be found in children learning their second language at school in immersion education programs. Methods: In this study, 44 children involved in immersion education for 4 to 5 years were compared to 48 children in traditional schools. All children were between 9 and 11 years old. To assess executive functions, the Simon task was used, a neuropsychological measure assessing executive functions with reaction times and accuracy on congruent and incongruent trials. To control for background measures, all children underwent the Raven’s coloured progressive matrices, to measure non-verbal intelligence and the Echelle de Vocabulaire en Images Peabody (EVIP), assessing verbal intelligence. In addition, a questionnaire was given to the parents to control for other confounding variables, such as socio-economic status (SES), home language, developmental disorders, etc. Results: There were no differences between groups concerning non-verbal intelligence and verbal intelligence. Furthermore, the immersion learners showed overall faster reaction times on both congruent and incongruent trials compared to the traditional learners, but only after 5 years of training, not before. Conclusion: These results show that the cognitive benefits found in ‘full’ bilinguals also appear in children involved in immersion education, but only after a sufficient exposure to the second language. Our results suggest that the amount of second language training needs to be sufficient before these cognitive effects may emerge.

Keywords: bilingualism, executive functions, immersion education, Simon task

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Authors: Muhammad Fatahillah Akbar

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Criminal Procedural Law is established to protect the society from the abuse of authority. To achieve that purpose, the criminal procedural law shall be established in accordance with the laws of human right and the protection of the society. One of the mechanisms to protect human rights and to ensure the compliance of authorities in criminal procedural law is pre-trial mechanism. In many countries, there are various mechanisms of pre-trial. In the recent cases in Indonesia, pre-trial has been an interesting issue. The issue is also addressed by the Constitutional Court Decision Number 21/PUU-XII/2014 which enhance the competence of pre-trial which includes the suspect determination and the legality of seizure and search. Before that decision, some pre-trial decisions have made landmark decision by enhancing the competence of pre-trial, such as the suspect determination case in Budi Gunawan Case and legality of the investigation in Hadi Purnomo Case. These pre-trial cases occurred because the society needs protection even though it is not provided by written legislations, in this matter, The Indonesian Criminal Procedural Code (KUHAP). For instance, a person can be a suspect for unlimited time because the Criminal Procedural Code does not regulate the limit of investigation, so the suspect enactment shall be able to be challenged to protect human rights. Before the Constitutional Court Decision Suspect Determination cannot be challenged so that the society is not fully protected. The Constitutional Court Decision has provided more protections. Nowadays, investigators shall be more careful in conducting the investigation. However, those decisions, including the Constitutional Court Decision are not sufficient for society to be protected by abuse of authority. For example, on 7 March 2017, a single judge, in a Pre-Trial, at the Surabaya District Court, decided that the investigation was unlawful and shall be terminated. This is not regulated according to the Code and also any decisions in pre-trial. It can be seen that the reform of pre-trial is necessary. Hence, this paper aims to examine how pre-trial shall be developed in the future to provide wide access for society to have social justice in criminal justice system. The question will be answered by normative, historical, and comparative approaches. Firstly, the paper will examine the history of pre-trial in Indonesia and also landmark decisions on pre-trial. Then, the lessons learned from other countries regarding to the pre-trial mechanism will be elaborated to show how pre-trial shall be developed and what the competences of a pre-trial are. The focus of all discussions shall be on how the society is protected and provided access to legally complain to the authority. At the end of the paper, the recommendation to reform the pre-trial mechanism will be suggested.

Keywords: pre-trial, criminal procedural law, society

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Authors: Egor Stadnichuk

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Relativistic runaway electron avalanches (RREA) are a widely accepted source of thunderstorm gamma-radiation. In regions with huge electric field strength, RREA can multiply via relativistic feedback. The relativistic feedback is caused both by positron production and by runaway electron bremsstrahlung gamma-rays reversal. In complex multilayer thunderstorm electric field structures, an additional reactor feedback mechanism appears due to gamma-ray exchange between separate strong electric field regions with different electric field directions. The study of this reactor mechanism in conjunction with the relativistic feedback with Monte Carlo simulations or by direct solution of the kinetic Boltzmann equation requires a significant amount of computational time. In this work, a theoretical approach to study feedback mechanisms in RREA physics is developed. It is based on the matrix of feedback operators construction. With the feedback matrix, the problem of the dynamics of avalanches in complex electric structures is reduced to the problem of finding eigenvectors and eigenvalues. A method of matrix elements calculation is proposed. The proposed concept was used to study the dynamics of RREAs in multilayer thunderclouds.

Keywords: terrestrial Gamma-ray flashes, thunderstorm ground enhancement, relativistic runaway electron avalanches, gamma-rays, high-energy atmospheric physics, TGF, TGE, thunderstorm, relativistic feedback, reactor feedback, reactor model

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Authors: A. Banerjee, C. Grazon, B. Nadal, T. Pons, Y. Krishnan, B. Dubertret

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Quantum Dots (QDs) have emerged as novel fluorescent probes for biomedical applications. The photophysical properties of QDs such as broad absorption, narrow emission spectrum, reduced blinking, and enhanced photostability make them advantageous over organic fluorophores. However, for some biological applications, QDs need to be first targeted to specific intracellular locations. It parallel, base pairing properties and biocompatibility of DNA has been extensively used for biosensing, targetting and intracellular delivery of numerous bioactive agents. The combination of the photophysical properties of QDs and targettability of DNA has yielded fluorescent, stable and targetable nanosensors. QD-DNA conjugates have used in drug delivery, siRNA, intracellular pH sensing and several other applications; and continue to be an active area of research. In this project, a novel method to synthesise QD-DNA conjugates and their applications in bioimaging are investigated. QDs are first solubilized in water using a thiol based amphiphilic co-polymer and, then conjugated to amine functionalized DNA using a heterobifunctional linker. The conjugates are purified by size exclusion chromatography and characterized by UV-Vis absorption and fluorescence spectroscopy, electrophoresis and microscopy. Parameters that influence the conjugation yield such as reducing agents, the excess of salt and pH have been investigated in detail. In optimized reaction conditions, up to 12 single-stranded DNA (15 mer length) can be conjugated per QD. After conjugation, the QDs retain their colloidal stability and high quantum yield; and the DNA is available for hybridization. The reaction has also been successfully tested on QDs emitting different colors and on Gold nanoparticles and therefore highly generalizable. After extensive characterization and robust synthesis of QD-DNA conjugates in vitro, the physical properties of these conjugates in cellular milieu are being invistigated. Modification of QD surface with DNA appears to remarkably alter the fate of QD inside cells and can have potential implications in therapeutic applications.

Keywords: bioimaging, cellular targeting, drug delivery, photostability

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Authors: Huawei Bai, Jianguo Yao, Fellow, IEEE

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Atrial fibrillation (AF) is the most common form of heart arrhythmia and is closely associated with mortality and morbidity in heart failure, stroke, and coronary artery disease. The development of single spot optical sensors enables widespread photoplethysmography (PPG) screening, especially for AF, since it represents a more convenient and noninvasive approach. To our knowledge, most existing studies based on public and unbalanced datasets can barely handle the multiple noises sources in the real world and, also, lack interpretability. In this paper, we construct a large- scale PPG dataset using measurements collected from PPG wrist- watch devices worn by volunteers and propose an attention-based two-stream heterogeneous neural network (TSHNN). The first stream is a hybrid neural network consisting of a three-layer one-dimensional convolutional neural network (1D-CNN) and two-layer attention- based bidirectional long short-term memory (Bi-LSTM) network to learn representations from temporally sampled signals. The second stream extracts latent representations from the PPG time-frequency spectrogram using a five-layer CNN. The outputs from both streams are fed into a fusion layer for the outcome. Visualization of the attention weights learned demonstrates the effectiveness of the attention mechanism against noise. The experimental results show that the TSHNN outperforms all the competitive baseline approaches and with 98.09% accuracy, achieves state-of-the-art performance.

Keywords: PPG wearables, atrial fibrillation, feature fusion, attention mechanism, hyber network

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Authors: Zeyu Zhou, Ziyu Zhao, Xiaochen Yang, Ling AI, Heng Zhai, Stuart Holmes

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As a promising sustainable alternative to traditional fossil fuels, fuel cell technology is highly favoured due to its enhanced working efficiency and reduced emissions. In the context of high-temperature fuel cells (operating above 100 °C), the most commonly used proton exchange membrane (PEM) is the Polybenzimidazole (PBI) doped phosphoric acid (PA) membrane. Grafting is a promising strategy to advance PA-doped PBI PEM technology. The existing grafting modification on PBI PEMs mainly focuses on grafting phosphate-containing or alkaline groups onto the PBI molecular chains. However, quaternary ammonium-based grafting approaches face a common challenge. To initiate the N-alkylation reaction, deacidifying agents such as NaH, NaOH, KOH, K2CO3, etc., can lead to ionic crosslinking between the quaternary ammonium group and PBI. Polyvinylpyrrolidone (PVP) is another widely used polymer, the N-heterocycle groups within PVP endow it with a significant ability to absorb PA. Recently, PVP has attracted substantial attention in the field of fuel cells due to its reduced environmental impact and impressive fuel cell performance. However, due to the the poor compatibility of PVP in PBI, few research apply PVP in PA-doped PBI PEMs. This work introduces an innovative strategy to graft PVP onto PBI to form a network-like polymer. Due to the absence of quaternary ammonium groups, PVP does not pose issues related to crosslinking with PBI. Moreover, the nitrogen-containing functional groups on PVP provide PBI with a robust phosphoric acid retention ability. The nuclear magnetic resonance (NMR) hydrogen spectrum analysis results indicate the successful completion of the grafting reaction where N-alkylation reactions happen on both sides of the grafting agent 1,4-bis(chloromethyl)benzene. On one side, the reaction takes place with the hydrogen atoms on the imidazole groups of PBI, while on the other side, it reacts with the terminal amino group of PVP. The XPS results provide additional evidence from the perspective of the element. On synthesized PBI-g-PVP surfaces, there is an absence of chlorine (chlorine in grafting agent 1,4-bis(chloromethyl)benzene is substituted) element but a presence of sulfur element (sulfur element in terminal amino PVP appears in PBI), which demonstrates the occurrence of the grafting reaction and PVP is successfully grafted onto PBI. Prepare these modified membranes into MEA. It was found that during the fuel cell operation, all the grafted membranes showed substantial improvement in maximum current density and peak power density compared to unmodified one. For PBI-g-PVP 30, with a grafting degree of 22.4%, the peak power density reaches 1312 mW cm⁻², marking a 59.6% enhancement compared to the pristine PBI membrane. The improvement is caused by the improved PA binding ability of the membrane after grafting. The AST test result shows that the grafting membranes have better long-term durability and performance than unmodified membranes attributed to the presence of added PA binding sites, which can effectively prevent the PA leaching caused by proton migration. In conclusion, the test results indicate that grafting PVP onto PBI is a promising strategy which can effectively improve the fuel cell performance.

Keywords: fuel cell, grafting modification, PA doping ability, PVP

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Authors: Shyh-Ming Chern, Te-Hsiu Tang

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Hemicellulose is one of the major constituents of all plant cell walls, making up 15-25% of dry wood. It is a biopolymer from many different sugar monomers, including pentoses, like xylose, and hexoses, like mannose. In an effort to gasify real biomass in subcritical and supercritical water in a single process, it is necessary to understand the gasification of hemicellulose, in addition to cellulose and lignin, in subcritical and supercritical water. In the present study, xylose is chosen as the model compound for hemicellulose, since it has the largest amount in most hardwoods. Xylose is gasified in subcritical and supercritical water for the production of higher-valued gaseous products. Experiments were conducted with a 16-ml autoclave batch-type reactor. Hydrogen peroxide is adopted as the oxidant in an attempt to promote the gasification yield. The major operating parameters for the gasification include reaction temperature (400 - 600°C), reaction pressure (5 - 25 MPa), the concentration of xylose (0.05 and 0.30 M), and level of oxidant added (0 and 0.25 chemical oxygen demand). 102 experimental runs were completed out of 46 different set of experimental conditions. Product gases were analyzed with a GC-TCD and determined to be mainly composed of H₂ (10 – 74 mol. %), CO (1 – 56 mol. %), CH₄ (1 – 27 mol. %), CO₂ (10 – 50 mol. %), and C₂H₆ (0 – 8 mol. %). It has been found that the gas yield (amount of gas produced per gram of xylose gasified), higher heating value (HHV) of the dry product gas, and energy yield (energy stored in the product gas divided by the energy stored in xylose) all increase significantly with rising temperature and moderately with reducing pressure. The overall best operating condition occurred at 873 K and 10 MPa, with a gas yield of 54 mmol/g of xylose, a gas HHV of 440 kJ/mol, and an energy yield of 1.3. A seemingly unreasonably energy yield of greater than unity resulted from the external heating employed in the experiments to drive the gasification process. It is concluded that xylose can be completely gasified in subcritical and supercritical water under proper operating conditions. The addition of oxidant does not promote the gasification of xylose.

Keywords: gasification, subcritical water, supercritical water, xylose

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Authors: Sun Zhe, Ruggero Micheletto

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As discussed extensively in many studies, noise in neural networks have an important role in the functioning and time evolution of the system. The mechanism by which noise induce stochastic resonance enhancing and influencing certain operations is not clarified nor is the mechanism of information storage and coding. With the present research we want to study the role of noise, especially focusing on the frequency peaks in a three variable Hindmarsh−Rose Small−World network. We investigated the behaviour of the network to external noises. We demonstrate that a variation of signal to noise ratio of about 10 dB induces an increase in membrane potential signal of about 15%, averaged over the whole network. We also considered the integral of the whole membrane potential as a paradigm of internal noise, the one generated by the brain network. We showed that this internal noise is attenuated with the size of the network or with the number of random connections. By means of Fourier analysis we found that it has distinct peaks of frequencies, moreover, we showed that increasing the size of the network introducing more neurons, reduced the maximum frequencies generated by the network, whereas the increase in the number of random connections (determined by the small-world probability p) led to a trend toward higher frequencies. This study may give clues on how networks utilize noise to alter the collective behaviour of the system in their operations.

Keywords: neural networks, stochastic processes, small-world networks, discrete Fourier analysis

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Authors: Gayathri Devi V, Aravamudan Kannan, Amit Sircar

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In the inner fuel cycle system of a nuclear fusion reactor, the Hydrogen Isotopes Removal System (HIRS) plays a pivoted role. It enables the effective extraction of the hydrogen isotopes from the breeder purge gas which helps to maintain the tritium breeding ratio and sustain the fusion reaction. One of the components of HIRS, Cryogenic Molecular Sieve Bed (CMSB) columns with zeolites adsorbents are considered for the physisorption of hydrogen isotopes at 1 bar and 77 K. Even though zeolites have good thermal stability and reduced activation properties making them ideal for use in nuclear reactor applications, their modest capacity for hydrogen isotopes adsorption is a cause of concern. In order to enhance the adsorbent capacity in an informed manner, it is helpful to understand the adsorption phenomena at the quantum electronic structure level. Physicochemical modifications of the adsorbent material enhances the adsorption capacity through the incorporation of active sites. This may be accomplished through the incorporation of suitable metal ions in the zeolite framework. In this work, molecular hydrogen isotopes adsorption on the active sites of functionalized zeolites are investigated in detail using Density Functional Theory (DFT) study. This involves the utilization of hybrid Generalized Gradient Approximation (GGA) with dispersion correction to account for the exchange and correlation functional of DFT. The electronic energies, adsorption enthalpy, adsorption free energy, Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO) energies are computed on the stable 8T zeolite clusters as well as the periodic structure functionalized with different active sites. The characteristics of the dihydrogen bond with the active metal sites and the isotopic effects are also studied in detail. Validation studies with DFT will also be presented for adsorption of hydrogen on metal ion functionalized zeolites. The ab-inito screening analysis gave insights regarding the mechanism of hydrogen interaction with the zeolites under study and also the effect of the metal ion on adsorption. This detailed study provides guidelines for selection of the appropriate metal ions that may be incorporated in the zeolites framework for effective adsorption of hydrogen isotopes in the HIRS.

Keywords: adsorption enthalpy, functionalized zeolites, hydrogen isotopes, nuclear fusion, physisorption

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Authors: Kidane Workelul, Yohans Tekle, Guesh Negash, Haftay Abraha, Nigus Abebe Shumuye, Yisehak Tsegaye Redda

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Bovine papillomatosis (wart) is one of the economically important bovine skin diseases worldwide, caused by a group of viruses named papillomaviruses (PVs). However, it has often been misdiagnosed as other skin diseases and remained untreated. In order to determine the status of the diseases, twenty-two farms were visited, and fourteen infected cattle with cutaneous papillomatosis were identified from a total of 235. Papilloma biopsies were taken for molecular and histopathological characterization, the therapeutic trial of an autogenous vaccine was evaluated on infected animals. The overall status of bovine papillomatosis in this study was calculated as 5.96% (14/235). The disease was found to be statistically significant in the age groups less than two years (X² = 26.69, P = 0.0001). The more prominent histologically characterized lesions in the sampled tissue were identified as squamous papilloma and fibro-papilloma. The Polymerase Chain Reaction (PCR) based identification revealed that all the clinically and histo-pathologically characterized papillomatosis cases were found to be infected with Bovine Papilloma Virus1(BPV1), indicating that BPV1 was the most common and sole causative agent of the diseases in the study area. In immunizing active bovine papillomatosis, an autogenous vaccine therapeutic trial demonstrated excellent results, with practically full recovery and no recurrence of the infection. Hence, it is concluded that bovine papillomatosis is an economically important disease of young age group cattle as well as a treatable disease. So, the production of marketable autogenous vaccines against bovine papillomatosis should be started and given at an early stage.

Keywords: autogenous vaccine, bovine papillomatosis, bovine papilloma virus1 clinical-pathology, polymerase chine reaction, wart

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Authors: Bharat Kumar, Deepak Kumar, Vijay Chaudhry

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Zirconium alloys are widely used for the core components of a pressurized heavy water reactor (PHWR) or Canada deuterium (CANDU) reactor due to their low neutron absorption cross-section and excellent mechanical properties. The components made of Zirconium alloys are subjected to flow-induced vibrations, resulting in fretting wear at the interface of; pressure tubes and bearing pads, pressure tubes and calandria tubes, and calandria tubes and Liquid injection shutdown system (LISS) nozzles. There is a need to explore the tribological response under such conditions. Present work simulates the contact between calandria tube and LISS nozzle of PHWR/CANDU reactor as cylinder-on-cylinder contact configuration. Reciprocating tribo-tests were conducted on Zircaloy-4 (Zr-4) under the self-mated condition at varying amplitude, frequency, and sliding time. To understand the active wear mechanism, worn surfaces were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The change in amplitude severely affects the wear than other factors. The wear mechanism transits from adhesion to abrasion with increasing test amplitude. The dominant wear mechanisms are micro-cutting and micro-plowing followed by delamination in some areas. However, the coefficient of friction has indifferent behaviors.

Keywords: zircaloy-4, tribology, calandria tube, LISS nozzle, PHWR

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Authors: Szu-Kai Hsu, Po-Ching Lin

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As more and more multi-core processors emerge, traditional sequential programming paradigm no longer suffice. Yet only few modern dynamic programming languages can leverage such advantage. Ruby, for example, despite its wide adoption, only includes threads as a simple parallel primitive. The global virtual machine lock of official Ruby runtime makes it impossible to exploit full parallelism. Though various alternative Ruby implementations do eliminate the global virtual machine lock, they only provide developers dated locking mechanism for data synchronization. However, traditional locking mechanism error-prone by nature. Software Transactional Memory is one of the promising alternatives among others. This paper introduces a new virtual machine: GobiesVM to provide a native software transactional memory based solution for dynamic programming languages to exploit parallelism. We also proposed a simplified variation of Transactional Locking II algorithm. The empirical results of our experiments show that support of STM at virtual machine level enables developers to write straightforward code without compromising parallelism or sacrificing thread safety. Existing source code only requires minimal or even none modi cation, which allows developers to easily switch their legacy codebase to a parallel environment. The performance evaluations of GobiesVM also indicate the difference between sequential and parallel execution is significant.

Keywords: global interpreter lock, ruby, software transactional memory, virtual machine

Procedia PDF Downloads 280

Authors: Annapurna Basavaraju, Arianna Mastrodonato, Franz Heitmeir

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The Advisory Council for Aeronautics Research in Europe (ACARE) is creating awareness for the overall reduction of NOx emissions by 80% in its vision 2020. Hence this promotes the researchers to work on novel technologies, one such technology is the use of alternative fuels. Among these fuels hydrogen is of interest due to its one and only significant pollutant NOx. The influence of NOx formation due to hydrogen combustion depends on various parameters such as air pressure, inlet air temperature, air to fuel jet momentum ratio etc. Appropriately, this research is motivated to investigate the impact of the air to fuel jet momentum ratio onto the NOx formation in a hydrogen combustion chamber for aircraft engines. The air to jet fuel momentum is defined as the ratio of impulse/momentum of air with respect to the momentum of fuel. The experiments were performed in an existing combustion chamber that has been previously tested for methane. Premix of the reactants has not been considered due to the high reactivity of the hydrogen and high risk of a flashback. In order to create a less rich zone of reaction at the burner and to decrease the emissions, a forced internal recirculation flow has been achieved by integrating a plate similar to honeycomb structure, suitable to the geometry of the liner. The liner has been provided with an external cooling system to avoid the increase of local temperatures and in turn the reaction rate of the NOx formation. The injected air has been preheated to aim at so called flameless combustion. The air to fuel jet momentum ratio has been inspected by changing the area of fuel inlets and keeping the number of fuel inlets constant in order to alter the fuel jet momentum, thus maintaining the homogeneity of the flow. Within this analysis, promising results for a flameless combustion have been achieved. For a constant number of fuel inlets, it was seen that the reduction of the fuel inlet diameter resulted in decrease of air to fuel jet momentum ratio in turn lowering the NOx emissions.

Keywords: combustion chamber, hydrogen, jet momentum, NOx emission

Procedia PDF Downloads 287

Authors: Wei-Jing Li, Ren-Xuan Yang, Kui-Hao Chuang, Ming-Yen Wey

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Nowadays, plastic product and utilization are extensive and have greatly improved our life. Yet, plastic wastes are stable and non-biodegradable challenging issues to the environment. Waste-to-energy strategies emerge a promising way for waste management. This work investigated the co-production of hydrogen and carbon nanotubes from the syngas which was from the gasification of polypropylene. A nickel-silica core-shell catalyst was applied for syngas reaction from plastic waste gasification in a fixed-bed reactor. SiO2 were prepared through various synthesis solvents by Stöber process. Ni plays a role as modified SiO2 support, which were synthesized by deposition-precipitation method. Core-shell catalysts have strong interaction between active phase and support, in order to avoid catalyst sintering. Moreover, Fe or Co metal acts as promoter to enhance catalytic activity. The effects of calcined atmosphere, second metal addition, and reaction temperature on hydrogen production and carbon yield were examined. In this study, the catalytic activity and carbon yield results revealed that the Ni/SiO2 catalyst calcined under H2 atmosphere exhibited the best performance. Furthermore, Co promoted Ni/SiO2 catalyst produced 3 times more than Ni/SiO2 on carbon yield at long-term operation. The structure and morphological nature of the calcined and spent catalysts were examined using different characterization techniques including scanning electron microscopy, transmission electron microscopy, X-ray diffraction. In addition, the quality and thermal stability of the nano-carbon materials were also evaluated by Raman spectroscopy and thermogravimetric analysis.

Keywords: plastic wastes, hydrogen, carbon nanotube, core-shell catalysts

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Authors: Oshada Gamage, Chamal Wimalasooriya, Chrismal Boteju, W. K. Wimalsiri

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This paper presents a study on the feasibility of introducing a solar powered propelling mechanism to multi-day fishing boats as an alternative energy source. Since solar energy is readily available on the sea throughout the year, this free energy could be utilized to power multi-day fishing vessels. Multi-day boats have a large deck area where solar panels can be mounted above without much effort. This project involves studying the amount of power that can be generated using onboard solar panels and implementing an independent propelling system to run the boat. A chain drive system was designed to propel the boat, when the batteries are fully charged, from an electric motor using the same propeller. A 60 feet multi-day fishing boat built by a local boat manufacturer was chosen for the study. The service speed of the boat was around 6 knots with the electric motor, and the duration of cruising is 1 hour per day with around 11 hours of charging. 350-watt Mono-crystalline PV module, 75 kW HVH type motor, and 10 kWh lithium-ion battery packs were chosen for the study. From the calculations, it was obtained that the boat has 30 PV modules (10.5 kW), 5 batteries (47 kWh), The boat dimensions are 20 meter length of water line, 5.51 meter of beam, 1.8 meter of draught, and 77 ton of total displacement with the PV system net present value of USD 12445 for 20 years of operation and a payback period of around 8.2 years.

Keywords: multiday fishing boats, photovoltaic cells, solar energy, solar powered boat

Procedia PDF Downloads 143

Authors: Amjad Alsulami, Farah Albishri, Kholod Alzubidi, Lama Almehemadi, Salma Elhag

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Food allergy is a common and rising problem among children. Many students have their first allergic reaction at school, one of these is anaphylaxis, which can be fatal. This study discovered that several schools' processes lacked safety regulations and information on how to handle allergy issues and chronic diseases like diabetes where students were not supervised or monitored during the cafeteria purchasing process. There is no obvious prevention or effort in academic institutions when purchasing food containing allergens or negatively impacting the health status of students who suffer from chronic diseases. Students must always be stable to reflect positively on their educational development process. To address this issue, this paper uses a business reengineering process to propose the automation of the whole food-purchasing process, which will aid in detecting and avoiding allergic occurrences and preventing any side effects from eating foods that are conflicting with students' health. This may be achieved by designing a smart card with an embedded QR code that reveals which foods cause an allergic reaction in a student. A survey was distributed to determine and examine how the cafeteria will handle allergic children and whether any management or policy is applied in the school. Also, the survey findings indicate that the integration of QR technology into the food purchasing process would improve health condition detection. The suggested system would be beneficial to all parties, the family agreed, as they would ensure that their children didn't eat foods that were bad for their health. Moreover, by analyzing and simulating the as-is process and the suggested process the results demonstrate that there is an improvement in quality and time.

Keywords: QR code, smart card, food allergies, business process reengineering, health condition detection

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Authors: Fariba Jafari, Samaneh Heydarian

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Al2(HPO4)3 was easily prepared and used as a solid acid in acetalization of carbonyl compounds at room temperature and under solvent-free conditions. The protection was done in short reaction times and in good to high isolated yields. The cheapness and availability of this reagent with easy procedure and work-up make this method attractive for the organic synthesis.

Keywords: acetalization, acid catalysis, carbonylcompounds, green condition, protection

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Authors: Sara Rejeb, Catherine Duveau, Tabea Rebafka

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To monitor the production process of turbofan aircraft engines, multiple measurements of various geometrical parameters are systematically recorded on manufactured parts. Engine parts are subject to extremely high standards as they can impact the performance of the engine. Therefore, it is essential to analyze these databases to better understand the influence of the different parameters on the engine's performance. Self-organizing maps are unsupervised neural networks which achieve two tasks simultaneously: they visualize high-dimensional data by projection onto a 2-dimensional map and provide clustering of the data. This technique has become very popular for data exploration since it provides easily interpretable results and a meaningful global view of the data. As such, self-organizing maps are usually applied to aircraft engine condition monitoring. As databases in this field are huge and complex, they naturally contain multiple missing entries for various reasons. The classical Kohonen algorithm to compute self-organizing maps is conceived for complete data only. A naive approach to deal with partially observed data consists in deleting items or variables with missing entries. However, this requires a sufficient number of complete individuals to be fairly representative of the population; otherwise, deletion leads to a considerable loss of information. Moreover, deletion can also induce bias in the analysis results. Alternatively, one can first apply a common imputation method to create a complete dataset and then apply the Kohonen algorithm. However, the choice of the imputation method may have a strong impact on the resulting self-organizing map. Our approach is to address simultaneously the two problems of computing a self-organizing map and imputing missing values, as these tasks are not independent. In this work, we propose an extension of self-organizing maps for partially observed data, referred to as missSOM. First, we introduce a criterion to be optimized, that aims at defining simultaneously the best self-organizing map and the best imputations for the missing entries. As such, missSOM is also an imputation method for missing values. To minimize the criterion, we propose an iterative algorithm that alternates the learning of a self-organizing map and the imputation of missing values. Moreover, we develop an accelerated version of the algorithm by entwining the iterations of the Kohonen algorithm with the updates of the imputed values. This method is efficiently implemented in R and will soon be released on CRAN. Compared to the standard Kohonen algorithm, it does not come with any additional cost in terms of computing time. Numerical experiments illustrate that missSOM performs well in terms of both clustering and imputation compared to the state of the art. In particular, it turns out that missSOM is robust to the missingness mechanism, which is in contrast to many imputation methods that are appropriate for only a single mechanism. This is an important property of missSOM as, in practice, the missingness mechanism is often unknown. An application to measurements on one type of part is also provided and shows the practical interest of missSOM.

Keywords: imputation method of missing data, partially observed data, robustness to missingness mechanism, self-organizing maps

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Authors: Daria Grechishnikova, Maria Poptsova

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Transposable elements play an important role in the evolution of various species from bacteria to human. Long Interspersed Nuclear Elements (LINEs) and Short Interspersed Nuclear Elements (SINEs) are two major classes of retrotransposons that occupy a considerable part of any genome and their copy numbers can range form several hundreds to a million. Both LINEs and SINEs multiply through a copy-and-paste mechanism. LINEs encode proteins, which make them capable of self-propagation while SINEs are parasitic and require the machinery of LINEs to multiply. The mechanisms how LINE and SINE RNA is recognized by the LINE-encoded reverse transcriptase (RT) remain unclear. For some SINE-LINE pairs, it was shown that they share a common 3’-end with a stem-loop structure. Majority of the SINE-LINE pairs do not have a common 3’-end. Recently we have shown that in the human genome Alu-L1 pairs have structurally similar stem-loop structure at the 3’-end. Here we extended our analysis to a wide range of species and analyzed LINEs from 161 different species from Repbase and 217 SINE sequences from SINEBase. It appeared that all of the analyzed sequences contained stem-loop structures at the 3’-end. Here we conclude that it is very likely that a common evolutionary mechanism of transposon RNA recognition requires the presence of stem-loop structures at their 3’-end.

Keywords: LINE, SINE, mechanisms of retrotransposition, retrotransposons, stem-loop, stem-loop structures, transposons

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Authors: Anton S. Perin, Vladimir M. Shandarov

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Compensation for the nonlinear diffraction of narrow laser beams with wavelength of 532 and the formation of photonic waveguides and waveguide circuits due to the contribution of pyroelectric effect to the nonlinear response of lithium niobate crystal have been experimentally demonstrated. Complete compensation for the linear and nonlinear diffraction broadening of light beams is obtained upon uniform heating of an undoped sample from room temperature to 55 degrees Celsius. An analysis of the light-field distribution patterns and the corresponding intensity distribution profiles allowed us to estimate the spacing for the channel waveguides. The observed behavior of bright soliton beams may be caused by their coherent interaction, which manifests itself in repulsion for anti-phase light fields and in attraction for in-phase light fields. The experimental results of this study showed a fundamental possibility of forming optically complex waveguide structures in lithium niobate crystals with pyroelectric mechanism of nonlinear response. The topology of these structures is determined by the light field distribution on the input face of crystalline sample. The optical induction of channel waveguide elements by interacting spatial solitons makes it possible to design optical systems with a more complex topology and a possibility of their dynamic reconfiguration.

Keywords: self-action, soliton, lithium niobate, piroliton, photorefractive effect, pyroelectric effect

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Authors: Sukhwinder K. Bhullar, M. B. G. Jun

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The developments in biomedical industry have demanded the development of biocompatible, high performance materials to meet higher engineering specifications. The general requirements of such materials are to provide a combination of high stiffness and strength with significant weight savings, resistance to corrosion, chemical resistance, low maintenance, and reduced costs. Auxetic materials which come under the category of smart materials offer huge potential through measured enhancements in mechanical properties. Unique deformation mechanism, providing cushioning on indentation, automatically adjustable with its strength and thickness in response to forces and having memory returns to its neutral state on dissipation of stresses make them good candidate in biomedical industry. As simple extension and compression of tissues is of fundamental importance in biomechanics, therefore, to study the elastic behaviour of auxetic soft tissues implant is targeted in this paper. Therefore development and characterization of auxetic soft tissue implant is studied in this paper. This represents a real life configuration where soft tissue such as meniscus in knee replacement, ligaments and tendons often are taken as transversely isotropic. Further, as composition of alternating polydisperse blocks of soft and stiff segments combined with excellent biocompatibility make polyurethanes one of the most promising synthetic biomaterials. Hence selecting auxetic polyurathylene foam functional characterization is performed and compared with conventional polyurathylene foam.

Keywords: auxetic materials, deformation mechanism, enhanced mechanical properties, soft tissues

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Authors: D. Kuvshinov, A. Siswanto, J. Lozano-Parada, W. Zimmerman

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Ozone is well known as a powerful fast reaction rate oxidant. The ozone based processes produce no by-product left as a non-reacted ozone returns back to the original oxygen molecule. Therefore an application of ozone is widely accepted as one of the main directions for a sustainable and clean technologies development. There are number of technologies require ozone to be delivered to specific points of a production network or reactors construction. Due to space constrains, high reactivity and short life time of ozone the use of ozone generators even of a bench top scale is practically limited. This requires development of mini/micro scale ozone generator which can be directly incorporated into production units. Our report presents a feasibility study of a new micro scale rector for ozone generation (MROG). Data on MROG calibration and indigo decomposition at different operation conditions are presented. At selected operation conditions with residence time of 0.25 s the process of ozone generation is not limited by reaction rate and the amount of ozone produced is a function of power applied. It was shown that the MROG is capable to produce ozone at voltage level starting from 3.5kV with ozone concentration of 5.28E-6 (mol/L) at 5kV. This is in line with data presented on numerical investigation for a MROG. It was shown that in compare to a conventional ozone generator, MROG has lower power consumption at low voltages and atmospheric pressure. The MROG construction makes it applicable for emerged and dry systems. With a robust compact design MROG can be used as incorporated unit for production lines of high complexity.

Keywords: dielectric barrier discharge (DBD), micro reactor, ozone, plasma

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Authors: Yanxue Shang, Jingbin Zeng

Abstract:

Chlorobenzene homologues (CBHs) are a category of environmental pollutants that can not be ignored. They can stay in the environment for a long period and are potentially carcinogenic. The traditional degradation method of CBHs is dechlorination followed by sample preparation and analysis. This is not only time-consuming and laborious, but the detection and analysis processes are used in conjunction with large-scale instruments. Therefore, this can not achieve rapid and low-cost detection. Compared with traditional sensing methods, colorimetric sensing is simpler and more convenient. In recent years, chromaticity sensors based on fluorescence have attracted more and more attention. Compared with sensing methods based on changes in fluorescence intensity, changes in color gradients are easier to recognize by the naked eye. Accordingly, this work proposes to use single drop microextraction (SDME) technology to solve the above problems. After the dechlorination reaction was completed, the organic droplet extracts Cl⁻ and realizes fluorescence colorimetric sensing at the same time. This method was integrated sample processing and visual in-situ detection, simplifying the detection process. As a fluorescence colorimetric sensor material, CsPbBr₃ was encapsulated in MOF-5 to construct CsPbBr₃@MOF-5 fluorescence colorimetric composite. Then the fluorescence colorimetric sensor was constructed by dispersing the composite in SDME organic droplets. When the Br⁻ in CsPbBr₃ exchanges with Cl⁻ produced by the dechlorination reactions, it is converted into CsPbCl₃. The fluorescence color of the single droplet of SDME will change from green to blue emission, thereby realizing visual observation. Therein, SDME can enhance the concentration and enrichment of Cl⁻ and instead of sample pretreatment. The fluorescence color change of CsPbBr₃@MOF-5 can replace the detection process of large-scale instruments to achieve real-time rapid detection. Due to the absorption ability of MOF-5, it can not only improve the stability of CsPbBr₃, but induce the adsorption of Cl⁻. Simultaneously, accelerate the exchange of Br- and Cl⁻ in CsPbBr₃ and the detection process of Cl⁻. The absorption process was verified by density functional theory (DFT) calculations. This method exhibits exceptional linearity for Cl⁻ in the range of 10⁻² - 10⁻⁶ M (10000 μM - 1 μM) with a limit of detection of 10⁻⁷ M. Whereafter, the dechlorination reactions of different kinds of CBHs were also carried out with this method, and all had satisfactory detection ability. Also verified the accuracy by gas chromatography (GC), and it was found that the SDME we developed in this work had high credibility. In summary, the in-situ visualization method of dechlorination reaction detection was a combination of sample processing and fluorescence colorimetric sensing. Thus, the strategy researched herein represents a promising method for the visual detection of dechlorination reactions and can be extended for applications in environments, chemical industries, and foods.

Keywords: chlorobenzene homologues, colorimetric sensor, metal halide perovskite, metal-organic frameworks, single drop microextraction

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Authors: Atef Y. Shenouda, Anton A. Momchilov

Abstract:

Graphene and CdO with different stoichiometric ratios of Cd(CH₃COO)₂ and graphene samples were prepared by hydrothermal reaction. The crystalline phases of pure CdO and 3CdO:1graphene were identified by X-ray diffraction (XRD). The particle morphology was studied with SEM. Furthermore, impedance measurements were applied. Galvanostatic measurements for the cells were carried out using potential limits between 0.01 and 3 V vs. Li/Li⁺. The current cycling intensity was 10⁻⁴ A. The specific discharge capacity of 3CdO-1G cell was about 450 Ah.Kg⁻¹ up to more than 100 cycles.

Keywords: CdO, graphene, negative electrode, lithium battery

Procedia PDF Downloads 159