Using a damper amplification factor to increase energy dissipation in structures

AbstractFluid dampers are an important tool for dissipating unwanted vibrations in a range of engineering structures. This paper examines the effects of amplifying the displacements transferred to a non-linear damper, to increase the effectiveness of the damper in a range of situations commonly encountered in civil engineering structures. These include, (i) the ability to “fine tune” the required damping for a particular size damper, (ii) the ability to have a set of the same size dampers, but with different amplification factors to achieve a specific damping task, and (iii) to increase the sensitivity of the damper to small movements which effectively extends the range over which the damper works. Through numerical simulations and experimental tests conducted on a non-linear damper, we quantify the potential advantages of adding an amplification factor and the range of parameters where the benefit to this device is significant. The example of a two-storey structure is used as a test case and real-time dynamic substructuring tests are used to assess the complete system performance using a range of different amplification factors. The results show that the structural performance is most improved for frequencies close to resonance and that the amplification factor has an effective limit that for the case considered in this study is of approximately 3. The effects of the mechanism compliance are also assessed

Supporting brace sizing in structures with added linear viscous fluid dampers: A filter design solution

Viscous fluid dampers have proved to be effective in suppressing unwanted vibrations in a range of engineering structures. When dampers are fitted in a structure, a brace is typically used to attach them to the main structure. The stiffness of this brace can significantly alter the effectiveness of the damper, and in structures with multiple dampers, this can be a complex scenario to model. In this paper, we demonstrate that the effects of the brace compliance on the damper performance can be modelled by way of a first-order filter. We use this result to formulate a procedure that calculates the stiffness required by the supporting brace to provide a specified effectiveness of the damping action. The proposed procedure assumes that viscous dampers have been sized in a previous design step based on any optimal methodology in which, as is usually the case, the presence of supporting braces and their dynamic effects were neglected. Firstly considering a one degree-of-freedom system, we show that the proposed method ensures a desired level of damper efficiency for all frequencies within a selected bandwidth. Then the analysis is extended to the case of multi-degree-of-freedom systems to show that the design criteria can be applied in a straightforward and successful manner to more complex structures

Influencia del tiempo de gelificación sobre las propiedades estructurales, vibracionales y eléctricas del compósito PEG0.2/V2O5

Se estudiaron las propiedades estructurales, vibracionales y eléctricas de películas V2O5·nH2O y PEG0.2/V2O5 en función del tiempo de gelificación. Las películas fueron sinterizadas por sol-gel mediante la ruta del pentóxido de vanadio sobre sustratos de vidrio previamente tratados. La caracterización se llevo a cabo mediante Difracción de Rayos-X, Espectroscopía Raman y el método de las cuatro puntas convencional de van der Pauw. Los resultados indican que el aumento en el tiempo de gelificación del sol precursor (V2O5.nH2O) incrementa la calidad cristalina, el grado de hidratación, y la concentración de iones V5+ en las películas. En el compósito híbrido (PEG0.2/V2O5) los iones VO2+ actúan como enlazantes entre las cadenas poliméricas haciéndolas más compactas, lo cual facilita la movilidad de los portadores de carga eléctrica entre los iones vanadios. Los resultados mostraron una transición de fase semiconductormetal alrededor de 34°C, una transición óptica del tipo indirecta (para V2O5·nH2O) y una transición vítrea alrededor de Tg=-69°C.Structural, vibrational and electrical properties of V2O5·nH2O and PEG0.2/V2O5 films as a function of gelation time were studied. The films were sintered by sol-gel using vanadium pentoxide route on glass substrates previously treated. Films were characterized by X-Ray Diffraction, Raman Spectroscopy and the four-point van der Pauw conventional method. The results indicated that when the gelation time of the precursor (V2O5·nH2O) is increased, the crystalline quality, the degree of hydration, and V5+ ion concentration are increased. In the hybrid composite (PEG0.2/V2O5), VO2+ ions act as bonding between the polymer chains, making them more compact to facilitate the mobility of electric charge carriers between vanadium ions. The results showed a semiconductor-metal transition about 34°C, an indirect optical transition (V2O5·nH2O) and a vitreous transition around Tg=-69°C.Fil: Londoño Calderon, Cesar Leandro. Universidad Nacional de Colombia; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jurado, J. F.. Universidad Nacional de Colombia; ColombiaFil: Vargas Hernández, C.. Universidad Nacional de Colombia; Colombi

Riesgos y soluciones de seguridad existentes en el Internet de las cosas (IoT) en relación con Big Data

El avance tecnológico de la nueva era ha dado pie a la interconexión de dispositivos, aplicaciones, personas y datos, dando paso a la generación del Internet de las Cosas (IoT). Los múltiples datos recolectados son tan voluminosos y variables que deben ser almacenados en arquitecturas Big Data. Esta evolución ha brindado la oportunidad de tener mejor acceso, calidad y análisis de la información, pero a su vez existe un desafío para prevenir y mitigar los riesgos de seguridad asociados a la relación entre IoT y Big Data, poniendo en peligro la información recolectada y los datos sensibles del usuario, entre otros. El propósito del presente documento es realizar una revisión de literatura con el fin de recolectar los riesgos de seguridad encontrados entre la relación de Big Data e IoT, así mismo evaluar las soluciones actuales implementadas y concluir si éstas últimas cubren la necesidad de prevención y mitigación del riesgo

Ketorolac, a new non-opioid analgesic: a single-blind trial versus buprenorphine in pain after orthopaedic surgery

A randomized single-blind, double-observer trial was performed to evaluate the efficacy of a new non-steroidal anti-inflammatory analgesic drug, ketorolac, in the treatment of post-orthopaedic surgery pain. Sixty patients with moderate to severe pain were studied; 30 patients were treated with ketorolac at a dose of 30 mg intramuscularly up to 4-times a day, whilst the other 30 patients received 0.3 mg buprenorphine intramuscularly up to 4-times a day. A significant reduction in the severity of the pain was recorded in both groups. Throughout the study, comparable efficacy was found between the two therapies although buprenorphine showed greater efficacy during the first 8 hours. Interestingly, the withdrawals due to adverse events were significantly less in the ketorolac group (p less than 0.001). This study, therefore, suggests that ketorolac may be a useful and more acceptable alternative to buprenorphine in the treatment of post-orthopaedic surgery pain

Femtosecond pulses and dynamics of molecular photoexcitation: RbCs example

We investigate the dynamics of molecular photoexcitation by unchirped femtosecond laser pulses using RbCs as a model system. This study is motivated by a goal of optimizing a two-color scheme of transferring vibrationally-excited ultracold molecules to their absolute ground state. In this scheme the molecules are initially produced by photoassociation or magnetoassociation in bound vibrational levels close to the first dissociation threshold. We analyze here the first step of the two-color path as a function of pulse intensity from the low-field to the high-field regime. We use two different approaches, a global one, the 'Wavepacket' method, and a restricted one, the 'Level by Level' method where the number of vibrational levels is limited to a small subset. The comparison between the results of the two approaches allows one to gain qualitative insights into the complex dynamics of the high-field regime. In particular, we emphasize the non-trivial and important role of far-from-resonance levels which are adiabatically excited through 'vertical' transitions with a large Franck-Condon factor. We also point out spectacular excitation blockade due to the presence of a quasi-degenerate level in the lower electronic state. We conclude that selective transfer with femtosecond pulses is possible in the low-field regime only. Finally, we extend our single-pulse analysis and examine population transfer induced by coherent trains of low-intensity femtosecond pulses.Comment: 25 pages, 12 figure

Artículo 1162 del Código de Comercio carácter de las normas del C. de Co. en materia del contrato de seguro : según la teoría general del Seguro - El Contrato de J. Efrén Ossa. Editorial Temis 1991

La autonomía de la voluntad era el criterio rector de los contratantes de seguros hasta que empezó a regir el código de comercio de 1971, pues el maestro J. Efrén Ossa, como consta en el Acta número 100 del Comité Asesor para su revisión, propuso y obtuvo la aprobación del que hoy es el artículo 1162 del Código de Comercio, considerado como el "testigo de excepción del sustancial viraje legislativo operado en torno al alcance de la autonomía privada"Especialista en Derecho de SegurosEspecializació

Didactics in the explanation of modern architectural works: four architectural pieces seen from the viewpoint of six authors

La historia de la arquitectura en la docencia cuenta con los textos como un soporte fundamental y dentro de estos, con la explicación que se hace de las obras. ¿Qué sistema didáctico emplean sus autores? ¿Cómo se articula en estas explicaciones la descripción textual con las imágenes? ¿Qué relación hay entre las explicaciones y el predicamento que sigue cada autor? Todas esas preguntas fueron tratadas aquí a partir de examinar cuatro obras canónicas a través de los textos de seis autores, igualmente importantes dentro de la historiografía de la arquitectura moderna. El objetivo fue descifrar el sistema didáctico y los dispositivos que intervienen en esta forma explicativa que bien podría considerarse un género literario en sí mismo.Teaching History of Architecture is primarily performed by text- based approach; in this case, books present the description of architectural pieces. This poses certain queries like: What didactic method is used by their authors? How do these explanations articulate textual description with images? What is the connection between the explanations and the predicament every author faces? These questions are addressed here after analyzing four canonical pieces through the books of six different authors, all of them equally relevant within architecture’s modern historiography. The purpose was to unravel the didactic method and the mechanisms involved in this explanatory form which mayitself be considered a literary genre

Medidas experimentales de desplazamientos micrométricos basadas en vórtices ópticos

In this work, a system for measuring micrometer-displacements based on the characteristics of optical vortices is presented. In the proposal, a binary vortex-producing lens (BVPL) programmed to generate optimized optical vortices is transversally displaced from the optical axis, inducing perturbations on the optical characteristics of the vortices that are used as transduction parameters. Specifically, the method proposed theoretically by Anzolin et al. [18], which is based on the asymmetry of the intensity patterns of the off-axis optical vortices, is studied experimentally by using BVPLs. Experimental implementation is completely described and compared with theoretical results, likewise, metrological characteristics of the experimental metrological system are analyzed. Based on the results, we experimentally confirm the possibility of creating high sensitivity metrological systems by using optical vortices, opening the door for new vortex metrology techniques.En este trabajo, un sistema para medir desplazamientos micrométricos basados en las características de vórtices ópticos es presentado. En la propuesta, una lente productora de vórtices binaria (BVPL) programada para generar vórtices ópticos optimizados es desplazada transversalmente del eje óptico, induciendo perturbaciones en las características ópticas de los vórtices que son usadas como parámetros de transducción. Específicamente, el método propuesto por Anzolín et al [18], el cuál es basado en la asimetría de los patrones de intensidad de los vórtices ópticos fuera del eje, es estudiado experimentalmente usando BVPLs. Se describe completamente la implementación experimental y se compara con los resultados teóricos, así mismo, se analizan características metrológicas del sistema metrológico experimental. En base a los resultados, confirmamos experimentalmente la posibilidad de crear sistemas metrológicos de alta sensibilidad utilizando vórtices ópticos, abriendo la puerta para nuevas técnicas de metrología de vórtices.Centro de Investigaciones Óptica