ABSTRACT
The design of musical instruments is a discipline that is still carried out in an artisanal way, with limitations and high costs. With the additive manufacturing technique, it is possible to obtain results for the generation of not only electrical but also acoustic instruments. However, it is necessary to generate a procedure to evaluate the influence of the process on the final result of the acoustics obtained. This study focuses on investigating the relationship between the construction of acoustic guitars and their final sound. The reinforcement structures at the top of the instrument are analysed, as well as how this design affects the vibratory behaviour of the top in the first five vibratory modes. Specifically, this article presents a procedure for the design of customised acoustic guitars using additive manufacturing through parametrisation and a vibrational analysis of the designed tops using finite element (FEA) and experimental physical tests, in order to develop a methodology for the study of stringed instruments. As a result, an 11% increase in the high-frequency response was achieved with a printing direction of +45°, and a reduction in the high-frequency response with ±45°. In addition, at high frequencies, a relative error of 5% was achieved with respect to the simulation. This work fulfils an identified need to study the manufacture of acoustic guitars using polylactic acid (PLA), and to be able to offer the musician a customised instrument. This represents a breakthrough in the use of this manufacturing technology, extending its relationship with product design.
ABSTRACT
Objetivos: evaluar la utilidad de la prueba de inclinación (PI) en el adulto mayor con historia de síncope, presíncope o mareo de causa no aclarada. Secundariamente, describir el patrón hemodinámico durante la PI para subclasificar en diferentes grupos a los pacientes. Material y métodos: pacientes mayores de 60 años con historia de síncope o mareos que acudieron consecutivamente al Servicio de Arritmias de nuestro centro. Determinación de la aparición de alteraciones hemodinámicas y/o reproducción de la sintomatología a través de la PI. Se realizó masaje carotídeo en pacientes seleccionados. Resultados: el número total de pacientes fue de 141, edad media ± desviación estándar 74,0 ± 7,1 años (intervalo, 61-93), 51,1% mujeres. Ciento cuatro pacientes tenían historia de síncope previo (89 casos tuvieron 2 o más episodios). La PI fue positiva por síntomas en el 41,8% de pacientes: 36 presentaron mareos y 23, síncope. En 82 pacientes no se apreciaron síntomas, pero el comportamiento hemodinámico fue anormal en 9 casos. Se pudo identificar un patrón hemodinámico típico en el 61,7% de las PI: hipotensión ortostática en 63 pacientes y síncope mediado neuralmente en 24 pacientes. Conclusiones: la PI aportó un diagnóstico probable en dos tercios de los pacientes estudiados (suma del patrón hemodinámico típico más pruebas anormales), lo que permite documentar, medir y analizar estos cambios para orientar el tratamiento. La PI muestra gran utilidad en pacientes con síncope y otras manifestaciones clínicas inducidas por el ortostatismo
Objectives: the primary aim of this study was to evaluate the usefulness of the head-up tilt (HUT) test in the diagnosis of patients with history of syncope, presyncope or dizziness of unknown origin. A secondary aim was to describe the hemodynamic pattern during the HUT test in order to subclassify patients into distinct groups. Material and methods: patients aged more than 60 years old with a history of syncope or dizziness consecutively attending the arrhythmia unit in our center. The development of hemodynamic alterations and/or symptom reproduction was determined through the HUT test. Selected patients underwent carotid sinus massage. Results: we studied 141 patients. The mean age and standard deviation was 74 ± 7.1 years (range, 61-93); 72 (51.1%) were women. Of 104 patients with a history of syncope, 89 had had two or more episodes. The HUT test was positive for symptoms in 59/141 (41.8%) patients: 36 developed dizziness and 23 syncope. Eighty-two patients showed no symptoms, but hemodynamic abnormalities were observed in 9/82 (11%). A typical hemodynamic pattern was identified in 87/141 (61.7%): 63 patients developed orthostatic hypotension, and 24 patients developed neurally mediated syncope. Conclusions: the HUT test gave a probable diagnosis in two-thirds of the patients studied (typical hemodynamic pattern plus an abnormal test) and allowed hemodynamic changes to be measured and analyzed with a view of guiding treatment. This test was highly useful in patients with syncope and symptoms related to orthostatic stress
