534 research outputs found
Experimental investigation of multiphase flow and acoustics during voice production
No full textThis dissertation advances the understanding of human phonation by integrating biomechanical modeling, aerosol analysis, and acoustic evaluation in a single comprehensive framework. First, a biomimetic, multi-layered synthetic larynx model was developed to replicate key features of human vocal fold physiology. By embedding ligament fibers with varying diameters and tensile strengths, the model allows controlled posturing (elongation, abduction, adduction) and dynamic manipulation of vocal fold stiffness. Systematic experiments revealed that increased fiber tension raises fundamental frequency and subglottal pressure, closely mirroring physiological observations of pitch regulation and providing a robust platform for studying both healthy and pathological voice conditions.
In a second step, the thesis elucidates aerosol formation mechanisms during phonation by combining the synthetic larynx model with synthetic mucus formulations that replicate human laryngeal mucus properties. Detailed high-speed imaging and particle image velocimetry showed that reduced surface tension and increased airflow reinforce aerosol particle generation, emphasizing the influence of mucus rheology and vocal fold dynamics on droplet release at the glottal level. These findings have direct implications for understanding transmission risks of airborne pathogens during speech and singing.
Finally, the acoustic effects of professional singing masks were investigated to reconcile infection control measures with vocal performance demands. Tests on a KEMAR head phantom demonstrated that although specialized fabrics and plastic face shields can mitigate frontal aerosol dispersion, they also introduce measurable spectral filtering of the acoustics, especially at higher frequencies. Some designs additionally cause low frequency amplification or altered directional radiation, potentially compromising vocal quality and clarity.
Collectively, this work integrates advanced physical modeling of physiological vocal fold oscillation with applied aerosol dispersion during phonation and the impact on the resulting acoustics. The outcomes not only enhance fundamental knowledge of vocal fold biomechanics but also support evidence-based strategies for safeguarding public health improving vocal performance in professional and educational settings, as well as addressing clinical needs.Diese Dissertation erweitert das Verständnis der menschlichen Stimmgebung, indem sie biomechanische Modellierung, Aerosolgenerierung und -ausbreitung und akustische Untersuchungen in einem umfassenden Forschungsansatz vereint. Zunächst wurde ein biomimetisches, mehrschichtiges synthetisches Larynxmodell entwickelt, das zentrale Aspekte der menschlichen Stimmlippenphysiologie abbildet. Durch die Integration von Ligamentfasern unterschiedlicher Durchmesser und Zugfestigkeiten ermöglicht das Modell eine gezielte Veränderung von Elongation, Adduktion und Abduktion sowie eine dynamische Anpassung der Steifigkeit der Stimmlippen. Systematische Experimente zeigten, dass eine höhere Faserspannung sowohl die Grundfrequenz als auch den subglottalen Druck erhöht und somit die menschliche Stimmgebung realistisch nachbildet. Damit bietet das Modell eine robuste Plattform, um gesunde und pathologische Zustände der Phonation zu untersuchen.
Im zweiten Schritt beleuchtet die Arbeit die Entstehung von Aerosolen während der Phonation, indem das synthetische Larynxmodell mit synthetischem Mukus kombiniert wurde, der die viskoelastischen Eigenschaften von menschlichem laryngealen Mukus nachahmt. High-speed Videoaufzeichnungen der Stimmlippenschwingung und Strömungsvisualisierung im supraglottalen Bereich zeigen, dass eine verringerte Oberflächenspannung des Mukus und ein erhöhter Luftstrom die Bildung von Aerosolpartikeln verstärken. Dies unterstreicht den Einfluss der Mukusrheologie und Stimmlippendynamik auf die Partikelentstehung auf glottaler Ebene und liefert wertvolle Erkenntnisse für die Bewertung von Infektionsrisiken bei Sprech- und Gesangstätigkeiten.
Abschlie\ss end wurden die akustischen Auswirkungen professioneller Sängermasken untersucht, um Infektionsschutzmaß nahmen mit den Anforderungen an die stimmliche Lei\-stungsfähigkeit zu vereinen. Versuche an einem KEMAR-Kopf belegten, dass spezielle Stoffe und transparente Kunststoffe zwar den frontalen Aerosolausstoß reduzieren, jedoch gleichzeitig deutlich hörbare akustische Filtereffekte, insbesondere bei hohen Frequenzen, hervorrufen. Zusätzlich können bestimmte Maskentypen zu einer Verstärkung tiefer Frequenzen oder einer veränderten räumlichen Schallabstrahlung führen und damit Klangqualität und Verständlichkeit beeinträchtigen.
Zusammenfassend vereint diese Arbeit die physikalische Modellierung physiologischer Stimmlippenschwingungen mit der praxisnahen Untersuchung von Aerosolausbreitung während der Phonation und den Einfluss auf die resultierende Akustik beim Tragen von Masken, um die Ausbreitung von Aerosolen zu reduzieren. Die Ergebnisse tragen nicht nur zu einem vertieften Grundlagenverständnis der Biomechanik der Stimmlippen bei, sondern unterstützen auch evidenzbasierte Strategien zum Schutz der öffentlichen Gesundheit, zur Verbesserung der stimmlichen Leistungsfähigkeit in beruflichen und pädagogischen Kontexten sowie zu Optimierungen im klinischen Betrieb
Mestizajes, exclusiones y alianzas étnicas en las pampas y el Chaco rioplatenses: (Segunda mitad del siglo XIX). Antropología. Boletín Oficial del Instituto Nacional de Antropología e Historia: Cien años. Anales del Museo Nacional de México (1877-1977). Num. 69 Nueva Época (2003) enero-marzo
No full textÁlvarez, Juan, Historia de Rosario, Buenos Aires, s/e, 1943.Bertoni, Lilia Ana, Patriotas, cosmopolitas y nacionalistas. La construcción de la nacionalidad argentina a fines del siglo XIX, Buenos Aires, Fondo de Cultura Económica, 2001.Gallo, Ezequiel, Colonos en armas. Las revoluciones radicales en la provincia de Santa Fe, Buenos Aires, Instituto Di Teila, 1977.———, La pampa gringa, Buenos Aires, Sudamericana, 1982.Rodríguez Mola, Ricardo, Historia social del gaucho, Buenos Aires, CEAL, 1986.
Sbarra, Noei H., Historia del alambrado en Argentina, Buenos Aires, Eudeba, 1964.Scobie, James, Revolución en las pampas. Historia social del trigo argentino, Buenos Aires, Solar-Hachette, 1967.Schobinger, Juan, Inmigración y colonización suizas en la República Argentina, Buenos Aires, s/e, 1963.Tur, Carlos M. y J. Alberto Tur, “El marco histórico”, en Santa Fe: el paisaje y los hombres, Rosario, Editorial Biblioteca, 1971.———, “La conquista de la pampa por la colonización Gringa”, en Revista Agro Nuestro, Rosario, 1971
Ramsey multiplicity and the Tur\'an coloring
No full textExtending an earlier conjecture of Erd\H{o}s, Burr and Rosta conjectured that
among all two-colorings of the edges of a complete graph, the uniformly random
coloring asymptotically minimizes the number of monochromatic copies of any
fixed graph . This conjecture was disproved independently by Sidorenko and
Thomason. The first author later found quantitatively stronger counterexamples,
using the Tur\'an coloring, in which one of the two colors spans a balanced
complete multipartite graph.
We prove that the Tur\'an coloring is extremal for an infinite family of
graphs, and that it is the unique extremal coloring. This yields the first
determination of the Ramsey multiplicity constant of a graph for which the
Burr--Rosta conjecture fails.
We also prove an analogous three-color result. In this case, our result is
conditional on a certain natural conjecture on the behavior of two-color Ramsey
numbers.Comment: 39 pages, final version to appear in Advances in Combinatoric
Pavlova, Tur, and 'Razdel': What's in a Name?
No full textThis article concerns an authorship problem that raises issues of canonical aesthetics. What does it mean to say a literary work is ‘good’? And does knowing the author’s literary reputation affect our ability to appreciate the work? Nineteenth-century Russian critics divided women authors into ‘extraordinary women’, i.e. honorary men, and perpetrators of ‘women’s writing’—categories that have persisted in Russia. It seems useful to look at what ‘women’s writing’ is, and on what basis ‘Razdel’, regardless of its author, can be evaluate
Tur\'{a}n numbers of general hypergraph star forests
No full textLet be a family of -uniform hypergraphs, and let be an
-uniform hypergraph. Then is called -free if it does not
contain any member of as a subhypergraph. The Tur\'{a}n number of
, denoted by , is the maximum number of
hyperedges in an -free -vertex -uniform hypergraph. Our
current results are motivated by earlier results on Tur\'{a}n numbers of star
forests and hypergraph star forests. In particular, Lidick\'{y}, Liu and Palmer
[Electron. J. Combin. 20 (2013)] determined the Tur\'{a}n number of a
star forest for sufficiently large . Recently, Khormali and Palmer
[European. J. Combin. 102 (2022) 103506] generalized the above result to three
different well-studied hypergraph settings, but restricted to the case that all
stars in the hypergraph star forests are identical. We further generalize these
results to general hypergraph star forests.Comment: arXiv admin note: substantial text overlap with arXiv:2001.05631 by
other author
Neural network-based estimation of biomechanical vocal fold parameters
No full textVocal fold (VF) vibrations are the primary source of human phonation. High-speed video (HSV) endoscopy enables the computation of descriptive VF parameters for assessment of physiological properties of laryngeal dynamics, i.e., the vibration of the VFs. However, underlying biomechanical factors responsible for physiological and disordered VF vibrations cannot be accessed. In contrast, physically based numerical VF models reveal insights into the organ’s oscillations, which remain inaccessible through endoscopy. To estimate biomechanical properties, previous research has fitted subglottal pressure-driven mass–spring–damper systems, as inverse problem to the HSV-recorded VF trajectories, by global optimization of the numerical model. A neural network trained on the numerical model may be used as a substitute for computationally expensive optimization, yielding a fast evaluating surrogate of the biomechanical inverse problem. This paper proposes a convolutional recurrent neural network (CRNN)-based architecture trained on regression of a physiological-based biomechanical six-mass model (6 MM). To compare with previous research, the underlying biomechanical factor “subglottal pressure” prediction was tested against 288 HSV ex vivo porcine recordings. The contributions of this work are two-fold: first, the presented CRNN with the 6 MM handles multiple trajectories along the VFs, which allows for investigations on local changes in VF characteristics. Second, the network was trained to reproduce further important biomechanical model parameters like VF mass and stiffness on synthetic data. Unlike in a previous work, the network in this study is therefore an entire surrogate of the inverse problem, which allowed for explicit computation of the fitted model using our approach. The presented approach achieves a best-case mean absolute error (MAE) of 133 Pa (13.9%) in subglottal pressure prediction with 76.6% correlation on experimental data and a re-estimated fundamental frequency MAE of 15.9 Hz (9.9%). In-detail training analysis revealed subglottal pressure as the most learnable parameter. With the physiological-based model design and advances in fast parameter prediction, this work is a next step in biomechanical VF model fitting and the estimation of laryngeal kinematics
Influence of flow rate and fiber tension on dynamical, mechanical and acoustical parameters in a synthetic larynx model with integrated fibers
No full textIntroductionThe human voice is generated by the oscillation of the vocal folds induced by exhalation airflow. Consequently, the characteristics of these oscillations and the primary sound signal are controlled by the longitudinal tension of the vocal folds, the flow rate, and their prephonatoric position. To facilitate independent control of these parameters, a synthetic larynx model was developed, as detailed in a previous publication.MethodsThis study aims to statistically analyze the influence of airflow and fiber tension on phonation characteristics, such as periodicity and symmetry, glottis closure during vocal fold oscillations, as well as tissue elasticity and generated sound. A total of 76 experiments were conducted and statistically analyzed with a systematic variation of flow rate and longitudinal tension within the vocal folds.During these experiments, vocal fold motion, subglottal pressure, and emitted sound were meticulously measured and analyzed.ResultsGroupwise statistical testing identified the flow rate as the main influencing parameter on nearly all phonation characteristics. However, the fundamental frequency, stiffness parameters, and quality parameters of the primary sound signal are predominantly controlled by the longitudinal tension within the vocal folds.DiscussionThe results demonstrated a complex interplay between the flow rate and tension, resulting in different characteristics of the produced sound signal
Comparison of Re-TUR results in primary patients with non-muscle-invasive bladder cancer (NMIBC) of low, intermediate, and high-risk for recurrence based on the EORTC scoring system
No full textBackground: Bladder cancer is the second mostcommonurologic malignancy. Transurethral resection (TUR) is the standard initial treatment for non-muscle-invasive bladder cancer (NMIBC). The high prevalence of residualtumorinsomepatients has necessitated repeat TUR (re-TUR). Previous studies have shown the quality of primary resection to impact re-TUR outcomes, but the role of tumor biology remains unclear. Objectives: This study aimed to evaluate the impact of tumor biology on re-TUR results in primary (non-recurrent) patients with superficial bladder tumors. Methods: We studied a cohort of consecutive primary patients with superficial bladder cancer undergoing resection and routine re-TUR between March 2018 and February 2019 at our unit. Patients with TaG1 or T2 on primary pathologic report, deliberately incomplete initial resection, or absence of detrusor muscle on the initial specimen were excluded from the study. Re-TUR was performed in the sixth week. All procedures were performed by the same surgeon. The patients were divided into three groups according to the European Organization for Research and Treatment of Cancer (EORTC) risk scoring system and compared for recurrence of NMIBC. Results: Of 58 primary patients, 16 were classified as low-risk, 32 as intermediate-risk, and 10 as high-risk. The mean age of subjects was 62.1 years. Residual tumor was detected on re-TUR in 19 (32.7) cases. Also, 3 (5.2) cases entailed stage progression to pT2, all of whombelonged to the high-risk group. Residual tumor rate was 0, 40.6, and 60 in the low-, intermediate-, and high-risk groups, respectively. In addition, 13 patients had macroscopic residual. Conclusions: Despite the modest study size, our results suggest that tumor biology might have an impact on residual tumor characteristics, and the EORTC scoring system may help to predict the risk of progression and residual tumor rate on re-TUR. © 2021, Author(s)
DataSheet1_Neural network-based estimation of biomechanical vocal fold parameters.PDF
No full textVocal fold (VF) vibrations are the primary source of human phonation. High-speed video (HSV) endoscopy enables the computation of descriptive VF parameters for assessment of physiological properties of laryngeal dynamics, i.e., the vibration of the VFs. However, underlying biomechanical factors responsible for physiological and disordered VF vibrations cannot be accessed. In contrast, physically based numerical VF models reveal insights into the organ’s oscillations, which remain inaccessible through endoscopy. To estimate biomechanical properties, previous research has fitted subglottal pressure-driven mass–spring–damper systems, as inverse problem to the HSV-recorded VF trajectories, by global optimization of the numerical model. A neural network trained on the numerical model may be used as a substitute for computationally expensive optimization, yielding a fast evaluating surrogate of the biomechanical inverse problem. This paper proposes a convolutional recurrent neural network (CRNN)-based architecture trained on regression of a physiological-based biomechanical six-mass model (6 MM). To compare with previous research, the underlying biomechanical factor “subglottal pressure” prediction was tested against 288 HSV ex vivo porcine recordings. The contributions of this work are two-fold: first, the presented CRNN with the 6 MM handles multiple trajectories along the VFs, which allows for investigations on local changes in VF characteristics. Second, the network was trained to reproduce further important biomechanical model parameters like VF mass and stiffness on synthetic data. Unlike in a previous work, the network in this study is therefore an entire surrogate of the inverse problem, which allowed for explicit computation of the fitted model using our approach. The presented approach achieves a best-case mean absolute error (MAE) of 133 Pa (13.9%) in subglottal pressure prediction with 76.6% correlation on experimental data and a re-estimated fundamental frequency MAE of 15.9 Hz (9.9%). In-detail training analysis revealed subglottal pressure as the most learnable parameter. With the physiological-based model design and advances in fast parameter prediction, this work is a next step in biomechanical VF model fitting and the estimation of laryngeal kinematics.</p
An Investigation of Acoustic Back-Coupling in Human Phonation on a Synthetic Larynx Model
No full textIn the human phonation process, acoustic standing waves in the vocal tract can influence the fluid flow through the glottis as well as vocal fold oscillation. To investigate the amount of acoustic back-coupling, the supraglottal flow field has been recorded via high-speed particle image velocimetry (PIV) in a synthetic larynx model for several configurations with different vocal tract lengths. Based on the obtained velocity fields, acoustic source terms were computed. Additionally, the sound radiation into the far field was recorded via microphone measurements and the vocal fold oscillation via high-speed camera recordings. The PIV measurements revealed that near a vocal tract resonance frequency fR, the vocal fold oscillation frequency fo (and therefore also the flow field’s fundamental frequency) jumps onto fR. This is accompanied by a substantial relative increase in aeroacoustic sound generation efficiency. Furthermore, the measurements show that fo-fR-coupling increases vocal efficiency, signal-to-noise ratio, harmonics-to-noise ratio and cepstral peak prominence. At the same time, the glottal volume flow needed for stable vocal fold oscillation decreases strongly. All of this results in an improved voice quality and phonation efficiency so that a person phonating with fo-fR-coupling can phonate longer and with better voice quality
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