Search

Your search keyword '"Núñez, Alfredo"' showing total 126 results
Start Over Author "Núñez, Alfredo" Language english
126 results on '"Núñez, Alfredo"'

31. Binational Dengue Outbreak Along the United States–Mexico Border — Yuma County, Arizona, and Sonora, Mexico, 2014

Author

Dengue Investigative Team, Jones, Jefferson M., Lopez, Benito, Adams, Laura, Gálvez, Francisco Javier Navarro, Núñez, Alfredo Sánchez, Santillán, Nubia Astrid Hernández, Plante, Lydia, Hemme, Ryan R., Casal, Mariana, Hunsperger, Elizabeth A., Muñoz-Jordan, Jorge, Acevedo, Veronica, Ernst, Kacey, Hayden, Mary, Waterman, Steve, Gomez, Diana, Sharp, Tyler M., and Komatsu, Kenneth K.

Published
2016

32. An Interpretable Method for Operational Modal Analysis in Time-Frequency Representation and Its Applications to Railway Sleepers

Author

Zeng, Yuanchen, Shen, Chen, Núñez, Alfredo, Dollevoet, Rolf, Zhang, Weihua, and Li, Zili

Abstract

Operational modal analysis (OMA) enables the identification of modal characteristics under operational loads and conditions. Traditional frequency-domain methods cannot directly capture modal changes over time, while existing time-frequency representations are not sufficiently interpretable due to spurious modes and implicit parameter design. This paper develops a new OMA method in time-frequency representation based on frequency-domain decomposition (FDD). Short-time FDD and a convolution-based strategy are proposed to obtain singular values and local mode shape similarity, respectively, which are further fused into mode indicators by a fuzzy-based strategy mimicking the modal assurance criterion. The method provides not only a global view of the modal characteristics over time and frequency but also estimates of the modal parameters. It is applicable to strongly nonstationary responses under time-varying loads and conditions. All the parameters explicitly affect the time-frequency representation, and the interpretability is enhanced by including physical information from the user’s prior knowledge in selecting parameters and peak bands. The proposed method is validated based on a study of railway sleepers under train passage. The rigid-body motions and bending modes are identified at frequencies up to 6,500 Hz in laboratory tests and 4,500 Hz in field tests at speeds up to 200 km/h. The identified natural frequencies and mode shapes agree with experimental modal analysis (EMA). The proposed method outperforms EMA in terms of broad frequency range and low measurement cost and can be potentially applied to structural health monitoring under operational conditions.

Published
2023
Full Text
View/download PDF

46. Effect of Rail Vehicle–Track Coupled Dynamics on Fatigue Failure of Coil Spring in a Suspension System.

Author

Sharma, Sunil Kumar, Sharma, Rakesh Chandmal, Lee, Jaesun, and Núñez, Alfredo

Subjects
MOTOR vehicle springs & suspension, STRAINS & stresses (Mechanics), RAILROAD trains, STRESS fractures (Orthopedics), MODAL analysis
Abstract

In a rail vehicle, fatigue fracture causes a significant number of failures in the coil spring of the suspension system. In this work, the origin of these failures is examined by studying the rail wheel–track interaction, the modal analysis of the coil springs and the stresses induced during operation. The spring is tested experimentally, and a mathematical model is developed to show its force vs. displacement characteristics. A vertical 10-degree-of-freedom (DOF) mathematical model of a full-scale railway vehicle is developed, showing the motions of the car body, bogies and wheelsets, which are then combined with a track. The springs show internal resonances at nearly 50–60 Hz, where significant stresses are induced in them. From the stress result, the weakest position in the innerspring is identified and a few guidelines are proposed for the reduction of vibration and stress in rail vehicles. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

47. Train Wheel Condition Monitoring via Cepstral Analysis of Axle Box Accelerations.

Author

Baasch, Benjamin, Heusel, Judith, Roth, Michael, Neumann, Thorsten, and Núñez, Alfredo

Subjects
CEPSTRUM analysis (Mechanics), RAILROAD maintenance & repair, GLOBAL Positioning System, JOINT use of railroad facilities
Abstract

Featured Application: Online wheel condition monitoring for condition based and predictive maintenance. Continuous wheel condition monitoring is indispensable for the early detection of wheel defects. In this paper, we provide an approach based on cepstral analysis of axle-box accelerations (ABA). It is applied to the data in the spatial domain, which is why we introduce a new data representation called navewumber domain. In this domain, the wheel circumference and hence the wear of the wheel can be monitored. Furthermore, the amplitudes of peaks in the navewumber domain indicate the severity of possible wheel defects. We demonstrate our approach on simple synthetic data and real data gathered with an on-board multi-sensor system. The speed information obtained from fusing global navigation satellite system (GNSS) and inertial measurement unit (IMU) data is used to transform the data from time to space. The data acquisition was performed with a measurement train under normal operating conditions in the mainline railway network of Austria. We can show that our approach provides robust features that can be used for on-board wheel condition monitoring. Therefore, it enables further advances in the field of condition based and predictive maintenance of railway wheels. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

49. Virus‐Based Nanomotors for Cargo Delivery.

Author

Tejeda‐Rodríguez, José A., Núñez, Alfredo, García‐Gradilla, Víctor, Cadena‐Nava, Rubén, Vazquez‐Duhalt, Rafael, Soto, Fernando, and Wang, Joseph

Subjects
NANOMOTORS, FABRICATION (Manufacturing), MONODISPERSE colloids, IONIC strength, NANOCARRIERS, BROME mosaic virus, CANCER treatment
Abstract

Self‐propelled nanomotors based on virus structure were designed, fabricated and characterized. Capsids from plant virus were covered on one hemisphere with platinum layer to promote motion in the presence of hydrogen peroxide. The Janus viral nanomotors (JVNs) with 25–30 nm diameter from brome mosaic virus (BMV) and cowpea chlorotic mottle virus (CCMV) showed motion speeds of up to 9 μm/sec, depending of the peroxide fuel concentration in the medium. The JVNs can carry and deliver the chemo‐therapeutic drug Tamoxifen, and they are able to internalize into breast tumor cells without any functionalization. The therapeutic payload is released by a pH‐driven delivery action of the nanomotor. Here, the first proof of concept of a self‐propelled virus‐like nanoparticle is demonstrated. The attractive capabilities of nanomotors based on virus‐like nanoparticles (VLPs) pave the way to diverse biomedical applications. The first self‐propelled nanomotors based on a virus structure have been designed. Virus capsids were covered on one hemisphere with a Pt layer to promote motion in the presence of H2O2. The nanomotor can carry and deliver the drug, and they are able to internalize into tumor cells. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

50. Cuando la realidad supera a la ficción. Los Naufragios de Alvar Núñez Cabeza de Vaca

Author

Jiménez Núñez, Alfredo

Subjects
Alvar Núñez Cabeza de Vaca, Etnoliteratura, GN301-674, alvar núñez cabeza de vaca, etnoliteratura, Ethnoliterature, Ethnology. Social and cultural anthropology
Abstract

In order to pinpoint the thin line separating literature from reality, the author makes reference to Alvar Núñez Cabeza de Vaca's Relación, popularly known as Naufragios, which the famous explorer wrote sometime after his first returning from America. Jiménez Núñez suggests the convenience of using literary texts as ethnographic documents in anthropological analysis. In addition, he touches upon related issues, such as the veracity and credibility of the literary texts, the difference between fact and fiction, and whether or not only facts are suitable objects for analysis in anthropology. In an attempt to take his position to its limit, he reminds us that facts can overcome fiction and thereby become, at first sight, even less credible than fiction. El autor se refiere a la Relación que escribió Alvar Núñez Cabeza de Vaca a poco de su primer regreso de América —popularmente conocida como Naufragios— como un texto básico para plantear la frágil línea que delimita la literatura y la realidad. A partir de dicha fuente destaca el posible valor de los textos literarios como documentos etnográficos útiles para el análisis antropológico, así como la cuestión de la veracidad y credibilidad de los textos, la diferencia entre realidad y ficción, si sólo puede ser verdad y creíble lo que es real, y si sólo los hechos reales pueden ser objeto de la antropología. Como una manera de llevar hasta sus extremos estos condicionantes, propone la posibilidad de que la realidad supere a la ficción y resulte a primera vista menos creíble que la propia ficción.

Published
2005
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results