Advanced engineering - Communications systems research

Communications systems research on information systems and on digital telemetry and command in Deep Space Networ

When in doubt ask the crowd : leveraging collective intelligence for improving event detection and machine learning

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Detection algorithms for spatial data

This dissertation addresses the problem of anomaly detection in spatial data. The problem of landmine detection in airborne spatial data is chosen as the specific detection scenario. The first part of the dissertation deals with the development of a fast algorithm for kernel-based non-linear anomaly detection in the airborne spatial data. The original Kernel RX algorithm, proposed by Kwon et al. [2005a], suffers from the problem of high computational complexity, and has seen limited application. With the aim to reduce the computational complexity, a reformulated version of the Kernel RX, termed the Spatially Weighted Kernel RX (SW-KRX), is presented. It is shown that under this reformulation, the detector statistics can be obtained directly as a function of the centered kernel Gram matrix. Subsequently, a methodology for the fast computation of the centered kernel Gram matrix is proposed. The key idea behind the proposed methodology is to decompose the set of image pixels into clusters, and expediting the computations by approximating the effect of each cluster as a whole. The SW-KRX algorithm is implemented for a special case, and comparative results are compiled for the SW-KRX vis-à-vis the RX anomaly detector. In the second part of the dissertation, a detection methodology for buried mine detection is presented. The methodology is based on extraction of color texture information using cross-co-occurrence features. A feature selection methodology based on Bhattacharya coefficients and principal feature analysis is proposed and detection results with different feature-based detectors are presented, to demonstrate the effectiveness of the proposed methodology in the extraction of useful discriminatory information --Abstract, page iii

Short-Time Estimation of Fractionation in Atrial Fibrillation with Coarse-Grained Correlation Dimension for Mapping the Atrial Substrate

[EN] Atrial ¿brillation (AF) is currently the most common cardiac arrhythmia, with catheter ablation (CA) of the pulmonary veins (PV) being its ¿rst line therapy. Ablation of complex fractionated atrial electrograms (CFAEs) outside the PVs has demonstrated improved long-term results, but their identi¿cation requires a reliable electrogram (EGM) fractionation estimator. This study proposes a technique aimed to assist CA procedures under real-time settings. The method has been tested on three groups of recordings: Group 1 consisted of 24 highly representative EGMs, eight of each belonging to a different AF Type. Group 2 contained the entire dataset of 119 EGMs, whereas Group 3 contained 20 pseudo-real EGMs of the special Type IV AF. Coarse-grained correlation dimension (CGCD) was computed at epochs of 1 s duration, obtaining a classi¿cation accuracy of 100% in Group 1 and 84.0¿85.7% in Group 2, using 10-fold cross-validation. The receiver operating characteristics (ROC) analysis for highly fractionated EGMs, showed 100% speci¿city and sensitivity in Group 1 and 87.5% speci¿city and 93.6% sensitivity in Group 2. In addition, 100% of the pseudo-real EGMs were correctly identi¿ed as Type IV AF. This method can consistently express the fractionation level of AF EGMs and provides better performance than previous works. Its ability to compute fractionation in short-time can agilely detect sudden changes of AF Types and could be used for mapping the atrial substrate, thus assisting CA procedures under real-time settings for atrial substrate modi¿cation.This research has been supported by grants DPI2017-83952-C3 from MINECO/AEI/FEDER EU, SBPLY/17/180501/000411 from JCCM and AICO/2019/036 from GVA.Vraka, A.; Hornero, F.; Bertomeu-Gonzalez, V.; Osca, J.; Alcaraz, R.; Rieta, JJ. (2020). Short-Time Estimation of Fractionation in Atrial Fibrillation with Coarse-Grained Correlation Dimension for Mapping the Atrial Substrate. Entropy. 22(2):1-20. https://doi.org/10.3390/e22020232S120222Go, A. S., Hylek, E. M., Phillips, K. A., Chang, Y., Henault, L. E., Selby, J. V., & Singer, D. E. (2001). Prevalence of Diagnosed Atrial Fibrillation in Adults. JAMA, 285(18), 2370. doi:10.1001/jama.285.18.2370Goette, A., Honeycutt, C., & Langberg, J. J. (1996). Electrical Remodeling in Atrial Fibrillation. Circulation, 94(11), 2968-2974. doi:10.1161/01.cir.94.11.2968Chugh, S. S., Roth, G. A., Gillum, R. F., & Mensah, G. A. (2014). Global Burden of Atrial Fibrillation in Developed and Developing Nations. Global Heart, 9(1), 113. doi:10.1016/j.gheart.2014.01.004Cappato, R., Calkins, H., Chen, S.-A., Davies, W., Iesaka, Y., Kalman, J., … Biganzoli, E. (2010). Updated Worldwide Survey on the Methods, Efficacy, and Safety of Catheter Ablation for Human Atrial Fibrillation. Circulation: Arrhythmia and Electrophysiology, 3(1), 32-38. doi:10.1161/circep.109.859116Cox, J. L., Canavan, T. E., Schuessler, R. B., Cain, M. E., Lindsay, B. D., Stone, C., … Boineau, J. P. (1991). The surgical treatment of atrial fibrillation. The Journal of Thoracic and Cardiovascular Surgery, 101(3), 406-426. doi:10.1016/s0022-5223(19)36723-6Haïssaguerre, M., Jaïs, P., Shah, D. C., Takahashi, A., Hocini, M., Quiniou, G., … Clémenty, J. (1998). Spontaneous Initiation of Atrial Fibrillation by Ectopic Beats Originating in the Pulmonary Veins. New England Journal of Medicine, 339(10), 659-666. doi:10.1056/nejm199809033391003Kornej, J., Schumacher, K., Zeynalova, S., Sommer, P., Arya, A., Weiß, M., … Hindricks, G. (2019). Time-dependent prediction of arrhythmia recurrences during long-term follow-up in patients undergoing catheter ablation of atrial fibrillation: The Leipzig Heart Center AF Ablation Registry. 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Circulation: Arrhythmia and Electrophysiology, 7(5), 825-833. doi:10.1161/circep.113.001251Takahashi, Y., O’Neill, M. D., Hocini, M., Dubois, R., Matsuo, S., Knecht, S., … Haïssaguerre, M. (2008). Characterization of Electrograms Associated With Termination of Chronic Atrial Fibrillation by Catheter Ablation. Journal of the American College of Cardiology, 51(10), 1003-1010. doi:10.1016/j.jacc.2007.10.056Atienza, F., Almendral, J., Jalife, J., Zlochiver, S., Ploutz-Snyder, R., Torrecilla, E. G., … Berenfeld, O. (2009). Real-time dominant frequency mapping and ablation of dominant frequency sites in atrial fibrillation with left-to-right frequency gradients predicts long-term maintenance of sinus rhythm. Heart Rhythm, 6(1), 33-40. doi:10.1016/j.hrthm.2008.10.024Nademanee, K., McKenzie, J., Kosar, E., Schwab, M., Sunsaneewitayakul, B., Vasavakul, T., … Ngarmukos, T. (2004). A new approach for catheter ablation of atrial fibrillation: mapping of the electrophysiologic substrate. Journal of the American College of Cardiology, 43(11), 2044-2053. doi:10.1016/j.jacc.2003.12.054Ciaccio, E. J., Biviano, A. B., Whang, W., Coromilas, J., & Garan, H. (2011). A new transform for the analysis of complex fractionated atrial electrograms. BioMedical Engineering OnLine, 10(1), 35. doi:10.1186/1475-925x-10-35Ciaccio, E. J., Biviano, A. B., & Garan, H. (2013). Computational method for high resolution spectral analysis of fractionated atrial electrograms. Computers in Biology and Medicine, 43(10), 1573-1582. doi:10.1016/j.compbiomed.2013.07.033TSAI, W.-C., LIN, Y.-J., TSAO, H.-M., CHANG, S.-L., LO, L.-W., HU, Y.-F., … CHEN, S.-A. (2010). The Optimal Automatic Algorithm for the Mapping of Complex Fractionated Atrial Electrograms in Patients With Atrial Fibrillation. Journal of Cardiovascular Electrophysiology, 21(1), 21-26. doi:10.1111/j.1540-8167.2009.01567.xTeh, A. W., Kistler, P. M., Lee, G., Medi, C., Heck, P. M., Spence, S. J., … Kalman, J. M. (2011). The relationship between complex fractionated electrograms and atrial low-voltage zones during atrial fibrillation and paced rhythm. Europace, 13(12), 1709-1716. doi:10.1093/europace/eur197Lin, Y.-J., Lo, M.-T., Chang, S.-L., Lo, L.-W., Hu, Y.-F., Chao, T.-F., … Chen, S.-A. (2016). Benefits of Atrial Substrate Modification Guided by Electrogram Similarity and Phase Mapping Techniques to Eliminate Rotors and Focal Sources Versus Conventional Defragmentation in Persistent Atrial Fibrillation. JACC: Clinical Electrophysiology, 2(6), 667-678. doi:10.1016/j.jacep.2016.08.005Verma, A., Jiang, C., Betts, T. R., Chen, J., Deisenhofer, I., Mantovan, R., … Sanders, P. (2015). Approaches to Catheter Ablation for Persistent Atrial Fibrillation. New England Journal of Medicine, 372(19), 1812-1822. doi:10.1056/nejmoa1408288Ammar-Busch, S., Reents, T., Knecht, S., Rostock, T., Arentz, T., Duytschaever, M., … Deisenhofer, I. (2018). Correlation between atrial fibrillation driver locations and complex fractionated atrial electrograms in patients with persistent atrial fibrillation. Pacing and Clinical Electrophysiology, 41(10), 1279-1285. doi:10.1111/pace.13483Almeida, T. P., Chu, G. S., Salinet, J. L., Vanheusden, F. J., Li, X., Tuan, J. H., … Schlindwein, F. S. (2016). Minimizing discordances in automated classification of fractionated electrograms in human persistent atrial fibrillation. Medical & Biological Engineering & Computing, 54(11), 1695-1706. doi:10.1007/s11517-016-1456-2De Bakker, J. M. T., & Wittkampf, F. H. M. (2010). The Pathophysiologic Basis of Fractionated and Complex Electrograms and the Impact of Recording Techniques on Their Detection and Interpretation. Circulation: Arrhythmia and Electrophysiology, 3(2), 204-213. doi:10.1161/circep.109.904763Luca, A., Buttu, A., Pruvot, E., Pascale, P., Bisch, L., & Vesin, J.-M. (2016). Nonlinear analysis of right atrial electrograms predicts termination of persistent atrial fibrillation within the left atrium by catheter ablation. Physiological Measurement, 37(3), 347-359. doi:10.1088/0967-3334/37/3/347Corana, A., Casaleggio, A., Rolando, C., & Ridella, S. (1991). Efficient computation of the correlation dimension from a time series on a LIW computer. Parallel Computing, 17(6-7), 809-820. doi:10.1016/s0167-8191(05)80068-7Fraser, A. M., & Swinney, H. L. (1986). Independent coordinates for strange attractors from mutual information. Physical Review A, 33(2), 1134-1140. doi:10.1103/physreva.33.1134Martínez-Iniesta, M., Ródenas, J., Alcaraz, R., & Rieta, J. J. (2017). Waveform Integrity in Atrial Fibrillation: The Forgotten Issue of Cardiac Electrophysiology. Annals of Biomedical Engineering, 45(8), 1890-1907. doi:10.1007/s10439-017-1832-6Theiler, J., Eubank, S., Longtin, A., Galdrikian, B., & Doyne Farmer, J. (1992). 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The Annals of Mathematical Statistics, 18(1), 50-60. doi:10.1214/aoms/1177730491Křemen, V., Lhotská, L., Macaš, M., Čihák, R., Vančura, V., Kautzner, J., & Wichterle, D. (2008). A new approach to automated assessment of fractionation of endocardial electrograms during atrial fibrillation. Physiological Measurement, 29(12), 1371-1381. doi:10.1088/0967-3334/29/12/002Haley, C. L., Gula, L. J., Miranda, R., Michael, K. A., Baranchuk, A. M., Simpson, C. S., … Redfearn, D. P. (2012). Validation of a novel algorithm for quantification of the percentage of signal fractionation in atrial fibrillation. EP Europace, 15(3), 447-452. doi:10.1093/europace/eus361Nollo, G., Marconcini, M., Faes, L., Bovolo, F., Ravelli, F., & Bruzzone, L. (2008). An Automatic System for the Analysis and Classification of Human Atrial Fibrillation Patterns from Intracardiac Electrograms. 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A design tool for sizing thermosyphon solar water heaters

Today, thermosyphon solar water heaters are the most popular type of solar water heaters for providing households with the required hot water for domestic purposes. However, sizing and designing these systems is still based on experience or on trial and errors methods, which are based more on intuition rather than scientific methods. The present study is aimed at addressing this problem (sizing thermosyphon systems) through the development of a design tool that can be used by engineers and manufacturers to arrive at optimised systems designed according to the weather and operating conditions of particular geographical locations. The design tool developed during the course of this study is based on the TRNSYS simulation programme for evaluating the thermal performance of thermosyphon systems, and on the genetic algorithm approach for the purpose of optimising selected design parameters of thermosyphon systems. A thorough literature review of the available models and software packages that are capable of evaluating the performance of thermosyphon systems has shown that the best available programme is TRNSYS, namely the component Type 45 (thermosyphon collector-storage component). However, the component Type 45 in its current form cannot be used directly for the purpose of optimisation, because this component relies on information that must be determined experimentally. This means that the component is mainly used for evaluating the thermal performance of already-made and tested systems under varying operating and climatic conditions. For this reason, two components developed in this research have been added to the TRNSYS suite to account for information that would otherwise have to be determined experimentally. The new components are: solar collector characteristics component Type 210; and pipes - tank heat loss coefficients Type 211. Furthermore, the component Type 45 is also modified to accept as, inputs, the outputs from the previous two new components. The modified component is named as modified thermosyphon component Type 245. The new components are validated experimentally and by using reports of tests conducted according to the appropriate European standard. The modified component Type 245 does not require any validation, as no changes were made in the main programme, except that of altering the experimentally-determined information from being parameters to instead being inputs in the TRNSYS terminology. The newly validated components were added to the original TRNSYS model so as to constitute a modified TRNSYS model which is used throughout this work. The modified TRNSYS model was· then used to perform a parametric study of the design parameters of thermosyphon systems. A genetic algorithm routine for constrained single objective optimisation problem was used, and the constraints are handled by using the stochastic ranking procedure. The genetic algorithm programme is combined with the modified TRNSYS model to constitute the final design tool. The design tool is used in this study to find the optimum thermosyphon system design that best suits Libyan families (as a case study in this research) according to the weather conditions of Tripoli and a simple, but representative, hot water load pattern. The design tool is shown to have significant potential, and with further development and validation would be capable of commercial application

LSENS, a general chemical kinetics and sensitivity analysis code for homogeneous gas-phase reactions. 2: Code description and usage

LSENS, the Lewis General Chemical Kinetics Analysis Code, has been developed for solving complex, homogeneous, gas-phase chemical kinetics problems and contains sensitivity analysis for a variety of problems, including nonisothermal situations. This report is part 2 of a series of three reference publications that describe LSENS, provide a detailed guide to its usage, and present many example problems. Part 2 describes the code, how to modify it, and its usage, including preparation of the problem data file required to execute LSENS. Code usage is illustrated by several example problems, which further explain preparation of the problem data file and show how to obtain desired accuracy in the computed results. LSENS is a flexible, convenient, accurate, and efficient solver for chemical reaction problems such as static system; steady, one-dimensional, inviscid flow; reaction behind incident shock wave, including boundary layer correction; and perfectly stirred (highly backmixed) reactor. In addition, the chemical equilibrium state can be computed for the following assigned states: temperature and pressure, enthalpy and pressure, temperature and volume, and internal energy and volume. For static problems the code computes the sensitivity coefficients of the dependent variables and their temporal derivatives with respect to the initial values of the dependent variables and/or the three rate coefficient parameters of the chemical reactions. Part 1 (NASA RP-1328) derives the governing equations describes the numerical solution procedures for the types of problems that can be solved by lSENS. Part 3 (NASA RP-1330) explains the kinetics and kinetics-plus-sensitivity-analysis problems supplied with LSENS and presents sample results

Data reduction analysis and application technique development for atmospheric trace gas constituents derived from remote sensors on satellite or airborne platforms

The applicability of the gas filter correlation radiometer (GFCR) to the measurement of tropospheric carbon monoxide gas was investigated. An assessment of the GFRC measurement system to a regional measurement program was conducted through extensive aircraft flight-testing of several versions of the GFRC. Investigative work in the following areas is described: flight test planning and coordination, acquisition of verifying CO measurements, determination and acquisition of supporting meteorological data requirements, and development of supporting computational software

Surface and solvent influences on protein crystallization

The role of water in protein crystallization was explored by investigating the effects of three factors (salts, point mutations and pressure) on subtilisin crystallization.;Solubility and growth kinetics of three subtilisin mutants in three salt solutions were measured. The decrease of the solubility of Properase RTM and PurafectRTM subtilisin followed the reverse order of the Hofmeister series: SCN- \u3e NO3- \u3e Cl-. The solubility of ProperaseRTM was higher than other two mutants. Crystal morphology changed with the nature of salts and the substitution of surface residues. The required supersaturation (c-s)/s for a given growth rate increased when solubility was decreased. The effect of anion on protein growth was related to the molar Gibbs free energy of hydration of the anion.;Structural and energetic considerations for crystallization of two subtilisin mutants (ProperaseRTM and PurafectRTM) were compared. The average hydrophobicity, solvent accessible surface area (ASA) and the number of hydrogen bonds and salt bridges were calculated to quantify surface properties of proteins in intermolecular contact patches. All three amino acid substitutions are present in the contact patches. Properase RTM lattice involves more atomic contacts and hydrogen bonds and larger accessible surface area, which corresponding to the faster growth of ProperaseRTM crystals. Non-electrostatic interaction energy was calculated for each contact direction and the competition of misoriented molecules with correctly oriented ones was considered to explain the variation of growth kinetics;The increase of solubility with pressure gave a total volume change for crystallization of 37 cm3/mol, whereas the decrease of nucleation rate with pressure gave an activation volume for nucleation of 226 cm 3/mol. 983 water molecules were estimated to attend Properase RTM crystallization.;The second virial coefficients (B2) of Properase RTM and PurafectRTM subtilisin under crystallization conditions were measured by static light scattering as a function of salt type and salt concentration, showing that conditions with slight negative B2 are suitable for protein crystallization. A DLVO-type model was used to fit the effective Hamaker constants for subtilisin and solubility was quantitatively correlated with B2 using a theoretically based correlation