122 research outputs found
Low-Complexity Gridless 2D Harmonic Retrieval via Decoupled-ANM Covariance Reconstruction
No full textThis paper aims at developing low-complexity solutions for super-resolution two-dimensional (2D) harmonic retrieval via covariance reconstruction. Given the collected sample covariance, a novel gridless compressed sensing approach is designed based on the atomic norm minimization (ANM) technique. The key is to perform a redundancy reduction (RR) transformation that effectively reduces the large problem size at hand, without loss of useful frequency information. For uncorrelated sources, the transformed 2D covariance matrices in the RR domain retain a salient structure, which permits a sparse representation over a matrix-form atom set with decoupled 1D frequency components. Accordingly, the decoupled ANM (DANM) framework can be applied for super-resolution 2D frequency estimation, at low computational complexity on the same order of the 1D case. An analysis of the complexity reduction of the proposed RR-D-ANM compared with benchmark methods is provided as well, which is verified by our simulation resultsGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Efficient Super-Resolution Two-Dimensional Harmonic Retrieval with Multiple Measurement Vectors
No full textThis paper develops an efficient solution for super-resolution two-dimensional (2D) harmonic retrieval from multiple measurement vectors (MMV). Given the sample covariance matrix constructed from the MMV, a gridless compressed sensing approach is proposed based on the atomic norm minimization (ANM). In the approach, our key step is to perform a redundancy reduction (RR) transformation that effectively reduces the large problem size at hand, without loss of useful frequency information. For uncorrelated sources, the transformed 2D covariance matrices in the RR domain retain a salient structure, which permits a sparse representation over a matrix-form atom set with decoupled 1D frequency components. Accordingly, the decoupled ANM (D-ANM) framework can be applied for super-resolution 2D frequency estimation. Moreover, the resulting RR-enabled D-ANM technique, termed RR-D-ANM, further allows an efficient relaxation under certain conditions, which leads to low computational complexity of the same order as the 1D case. Simulation results verify the advantages of our solutions over benchmark methods, in terms of higher computational efficiency and detectability for 2D harmonic retrieval.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Efficient Super-Resolution Two-Dimensional Harmonic Retrieval Via Enhanced Low-Rank Structured Covariance Reconstruction
No full textThis paper develops an enhanced low-rank structured covariance reconstruction (LRSCR) method based on the decoupled atomic norm minimization (D-ANM), for super-resolution two-dimensional (2D) harmonic retrieval with multiple measurement vectors. This LRSCR-D-ANM approach exploits a potential structure hidden in the covariance by transferring the basic LRSCR to an efficient D-ANM formulation, which permits a sparse representation over a matrix-form atom set with decoupled 1D frequency components. The new LRSCR-D-ANM method builds upon the existence of a generalized Vandermonde decomposition of its solution, which otherwise cannot be guaranteed by the basic LRSCR unless a very conservative condition holds. Further, a low-complexity solution of the LRSCR-D-ANM is provided for fast implementation with negligible performance loss. Simulation results verify the advantages of the proposed LRSCR-D-ANM over the basic LRSCR, in terms of the wider applicability and the lower complexity.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Aircraft fuel system prognostics and health management
No full textThis thesis contains the specific description of Group Design Project (GDP) and
Individual Research Project (IRP) that are undertaken by the author and form
part of the degree of Master of Science.
The target of GDP is to develop a novel and unique commercial flying wing
aircraft titled FW-11. FW-11 is a three-year collaborative civil aircraft project
between Aviation Industry Corporation of China (AVIC) and Cranfield University.
According to the market analysis result conducted by the author, 250 seats
capacity and 7500 nautical miles were chosen as the design targets.
The IRP is the further study of GDP, which is to enhance the competitive
capability by deploying prognostics and health management (PHM) technology
to the fuel system of FW-11. As a novel and brand-new technology, PHM
enables the real-time transformation of system status data into alert and
maintenance information during all ground or flight operating phases to improve
the aircraft reliability and operating costs. Aircraft fuel system has a great
impact on flight safety. Therefore, the development of fuel system PHM concept
is necessary.
This thesis began with an investigation of PHM, then a safety and reliability
analysis of fuel system was conducted by using FHA, FMEA and FTA.
According to these analyses, fuel temperature diagnosis and prognosis were
chosen as a case study to improve the reliability and safety of FW-11. The PHM
architecture of fuel temperature had been established. A fuel temperature
prediction model was also introduced in this thesis
Advanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters: homogeneous vs. heterogeneous photocatalytic processes
No full textAdvanced oxidation processes (AOPs) for the mineralization of azo-dyes from wastewaters: homogeneous vs. heterogeneous photocatalytic processes
Francesco Conte 1, Cristina Calloni 2, Ilenia Rossetti 3 and Gianguido Ramis 4*
1 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
2 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
3 Chemical Plants and Industrial Chemistry Group, Dipartimento di Chimica, Università degli Studi di Milano, Milan, Italy
4* DICCA, Università degli Studi di Genova, Genoa, Italy, presenting author, corr. author ([email protected])
INTRODUCTION
Textiles industries huge production determines a strong environmental impact: the yearly total impact per person is estimated to be 1.3 tonnes of raw material and over 100 m3 of water. Ca. 700,000 – 1,000,000 tons/years of dyes are produced and more than 280,000 tons are lost in the effluent and often remain as persistent pollutants. Heterogeneous and homogeneous phototreatments can be efficiently used as Advanced Oxidation Processes to degrade such contaminants and a comparison between different technologies has been carried out on the azo-dye Dystar’s Levafix Brilliant Red E-6BA.
EXPERIMENTAL
Oas a model molecule for this study because it is characterized by low biodegradability
TiO2 P25 was employed as a commercial nanostructured material supplied by Evonik and compared with TiO2 FSP, prepared through a homemade flame spray pyrolysis apparatus. Metallic co-catalysts were deposited over the surface by wet impregnation and then reduced at different temperature (Ag, Au, Pt, Pd, Fe).
The catalysts were characterised by XRD, N2 physisorption and DR-UV-VIS analyses.
The photo-degradation tests were carried out in different cylinder-type double-wall glass reactors of 300-1000 mL capacity, open to air and equipped with a suitable lamp in case of photocatalyzed processes.
The Fenton process was carried out either in light or dark conditions by adding Fe salts and H2O2 and compared with UV/H2O2 and Heterogeneous photodegradation processes with the above described catalysts.
The light sources employed were characterized by different emission wavelength and power output: a LED-type lamp (white light, 30 W, 2700 lm), an external UV lamp (200W, maximum emission at 365 nm) and two different low power immersed-UV lamp (125 W, maximum emission at 365 nm); natural sunlight. The average irradiance was measured for the different setups through a photo-radiometer sensitive to the UVA fraction and were 116 W/m2 in case of the external-UV lamp and respectively 60 and 260 W/m2 for the low irradiance (lamp 1) and high irradiance (lamp 2) immersed-UV lamp. The progress of the reaction was monitored by UV-Vis and Total Organic Carbon (TOC).
Toxicity tests on the treated solutions were also carried out using the Crustacean Daphnia magna.
RESULTS AND DISCUSSION
The fastest degradation process was Photo-Fenton with the highest power immersion UV lamp (10 min to 97.4% conversion), strictly followed by the UV/H2O2 process (20 min to 100% conversion). The degradation time increased with the other light sources, i.e. sun and LED, but overall, the total reaction time did not exceed 30 min. On the other hand, when it comes to the heterogeneous process, the titania synthetized via flame pyrolysis takes longer time to reach full conversion. At first glance it seems that the homogeneous treatment outperforms the heterogeneous ones, however, in the first case these results were achieved using a large amount of hydrogen peroxide, about 3.5 equivalents, which of course boost the reaction and lowers the time required to achieve a good conversion of the substrate.
Figure 9: Degradation of Levafix dye: comparison.
No organic carbon was detected after the treatment, except when employing gold deposited catalyst. Acute toxicity tests revealed that the Levafix Briliant Red resulted in a 48h-LC50 of 117 mg/L. The toxic response was dramatic in case of the solutions treated with UV/H2O2 and (Photo)Fenton processed, since a higher mortality of Daphnia magna specimens was observed due to the residual amounts of hydrogen peroxide. Overall, the best toxicity results were achieved in case of the samples treated with titania photocatalyst (P25), since the toxicity of the solutions was lower than the ones containing the bare dye.
CONCLUSION
Photo-degradation of Levafix Brilliant Red was compared for different AOPs. The homogeneous treatments were more efficient in the degradation of the selected dye, but the main advantages of employing solid nanostructured photocatalyst is that it is not compulsory to add hydrogen peroxide (low toxicity) and the catalyst can be recovered easily
Wideband Direction of Arrival Estimation with Sparse Linear Arrays
No full textThis paper concerns wideband direction of arrival (DoA) estimation with sparse linear arrays (SLAs). We rely on the assumption that the power spectrum of the wideband sources is the same up to a scaling factor, which could in theory allow us to resolve not only more sources than the number of antennas but also more sources than the number of degrees of freedom (DoF) of the difference co-array of the SLA. We resort to the Jacobi-Anger approximation to transform the coarray response matrices of all frequency bins into a single virtual uniform linear array (ULA) response matrix. Based on the obtained model, two super-resolution DoA estimation approaches based on atomic norm minimization (ANM) are proposed, one with and one without prior knowledge of the power spectrum. Simulation results show that our proposed methods outperform the state of the art and are indeed capable of resolving more sources than the number of DoF of the difference co-array.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Integration and control of lithium-ion BESSs for active network management in smart grids : Sundom smart grid backup feeding case
No full textLithium-ion battery energy storage systems (Li-ion BESS), due to their capability in providing both active and reactive power services, act as a bridging technology for efficient implementation of active network management (ANM) schemes for land-based grid applications. Due to higher integration of intermittent renewable energy sources in the distribution system, transient instability may induce power quality issues, mainly in terms of voltage fluctuations. In such situations, ANM schemes in the power network are a possible solution to maintain operation limits defined by grid codes. However, to implement ANM schemes effectively, integration and control of highly flexible Li-ion BESS play an important role, considering their performance characteristics and economics. Hence, in this paper, an energy management system (EMS) has been developed for implementing the ANM scheme, particularly focusing on the integration design of Li-ion BESS and the controllers managing them. Developed ANM scheme has been utilized to mitigate MV network issues (i.e. voltage stability and adherence to reactive power window). The efficiency of Li-ion BESS integration methodology, performance of the EMS controllers to implement ANM scheme and the effect of such ANM schemes on integration of Li-ion BESS, i.e. control of its grid-side converter (considering operation states and characteristics of the Li-ion BESS) and their coordination with the grid side controllers have been validated by means of simulation studies in the Sundom smart grid network, Vaasa, Finland.© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.fi=vertaisarvioitu|en=peerReviewed
Incidence of intradialytic complications and their risk factors in patients undergoing hemodialysis in hospitals affiliated to Medical University of Hamadan Iran
No full textIncidence of intradialytic complications and their risk factors in patients undergoing hemodialysis in hospitals affiliated to Medical University of Hamadan Iran Ghahri Sarabi, AR.1 (MSN); Torabi, M.2 (MSN); Abed Saeedi, Zh.3 (PhD); Akbarzadeh Baghban, A.4 (PhD) 1. Lecture, Dept. of Medical Surgical, Faculty of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran. Iran.2. Alumnus, Faculty of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences. Tehran. Iran3. Assistant Professor, Dept. of Medical Surgical, Faculty of Nursing & Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 4. Assistant Professor, Dept. of Biostatistics. Faculty of Paramedical, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Abstract Background and aimHemodialysis is one the most common renal replacement therapies in end stage renal disease. Despite progress in dialysis technology, intradialytic complications occur frequently. The aim of this study was to determine the rate of intradialytic complications and their risk factors in patients undergoing hemodialysis in hospitals affiliated to Medical University of Hamedan Iran in 2009. Materials and methods192 patients undergoing hemodialysis participated in this descriptive correlational study. These patients were included in the study using census method. Data were collected by1- a questionnaire which consisted of 3 sections (demographic information, person – related factors and therapy- related factors),2-a check list and clinical examination ( blood pressure and weight measurement). Content validity of the questionnaire was assessed by 10 nursing experts, 5 staff of hemodialysis wards and 2 nephrologists. Reliability of check list was measured using inter-rater reliability (r=0.98). Data were collected by the second author. Data were analyzed by SPSS 15. Findings Findings showed that the most frequent complications include: hypotension (%15.1), muscle cramp(%11.5), nausea(%9.4), headache(%7.8), angina(%2.6), vomiting (%2.1) and itching(%1.6) respectively. Logistic regression analysis, showed a significant correlation between age and cramp (person – related causes) and a significant correlation between hypotension, cramp with vomiting and headache. Moreover, findings showed a significant correlation between nausea with eating during dialysis (patient- related causes); and between hypotension with dialysis solution (therapy- related causes). ConclusionBased on the results of this study, most of intradialytic complications can be prevented. Use of these findings can improve the process of dialysis. Keywords: Hemodialysis, Intradialytic hemodialysis complications *Corresponding Author: Alireza Ghahri Sarabi, department of Medical-Surgical nursing, school of nursing and midwifery, Shahid beheshti University of Medical Sciences and Health Services, Tehran, Iran. E-mail: [email protected]
Numerical simulation of the initial particle parking structure of cement/geopolymer paste and the dissolution of amorphous silica using real-shape particles
No full textMany particle-based numerical models have been used to simulate the hydration process of cementitious materials. Most of those models employ regular shape particles, like the commonly used spheres, to represent cement, slag, or fly ash, which neglects the influence of particle shape. To deal with this issue, this study extended the Anm material model and used irregular shape particles to simulate the initial particle parking structures of cement/geopolymer pastes. The irregular shapes of cement, slag and fly ash particles were characterized by spherical harmonic series. Compared to the initial particle structures simulated using spherical particles, those using irregular shape particles had total surface areas and bulk specific surface areas with up to 37.40% and 36.84% larger, respectively. However, the pore size distributions of the simulated initial particle structures did not show significant influence of particle shape. As a demonstration to illustrate the influence of particle shape on dissolution, the initial particle parking structure of amorphous silica in alkaline solution was generated using irregular shape particles, and was used as input to simulate the dissolution of silica particles. The Lattice Boltzmann method was used to simulate the transport process of aqueous ions and thermodynamics was employed to consider the rate of dissolution of silica. The dissolved fractions of silica at different temperatures in the simulations agreed well with experimental measurements. The influences of continuous stirring, concentration of alkali and particle shape on the dissolution kinetics of silica were investigated numerically.Accepted Author ManuscriptMaterials and EnvironmentRailway Engineerin
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