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Design and experimental characterization of a novel passive magnetic levitating platform
E. Diez-Jimenez,R. Alcover-Sanchez,J.M. Soria,J. Pérez-Aracil,E. Pereira 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.3
This work proposes a novel contactless vibration damping and thermal isolation tripod platform based on Superconducting Magnetic Levitation (SML). This prototype is suitable for cryogenic environments, where classical passive, semi active and active vibration isolation techniques may present tribological problems due to the low temperatures and/or cannot guarantee an enough thermal isolation. The levitating platform consists of a Superconducting Magnetic Levitation (SML) with inherent passive static stabilization. In addition, the use of Operational Modal Analysis (OMA) technique is proposed to characterize the transmissibility function from the baseplate to the platform. The OMA is based on the Stochastic Subspace Identification (SSI) by using the Expectation Maximization (EM) algorithm. This paper contributes to the use of SSI-EM for SML applications by proposing a step-by-step experimental methodology to process the measured data, which are obtained with different unknown excitations: ambient excitation and impulse excitation. Thus, the performance of SSI-EM for SML applications can be improved, providing a good estimation of the natural frequency and damping ratio without any controlled excitation, which is the main obstacle to use an experimental modal analysis in cryogenic environments. The dynamic response of the 510 g levitating platform has been characterized by means of OMA in a cryogenic, 77 K, and high vacuum, 1E-5 mbar, environment. The measured vertical and radial stiffness are 9872.4 N/m and 21329 N/m, respectively, whilst the measured vertical and radial damping values are 0.5278 Nm/s and 0.8938 Nm/s. The first natural frequency in vertical direction has been identified to be 27.39 Hz, whilst a value of 40.26 Hz was identified for the radial direction. The determined damping values for both modes are 0.46% and 0.53%, respectively.
Improving the mechanical properties of pure magnesium by three-roll planetary milling
Diez, M.,Kim, H.E.,Serebryany, V.,Dobatkin, S.,Estrin, Y. Elsevier Sequoia 2014 Materials science & engineering. properties, micro Vol.612 No.-
In this study three-roll planetary milling was used to trial its potential for enhancing the mechanical properties of pure magnesium. The material was subjected to several passes of planetary milling at progressively decreased temperatures, down to room temperature for the last pass. It was shown that with increased number of passes the grain size was reduced, eventually to the micron range. Concurrently, the microstructure became increasingly more uniform across the billet. After six passes pure magnesium showed an excellent combination of tensile properties at room temperature, with a yield stress of 116MPa and a strain to failure of 13%.
L. Garcés,C. Vásquez,E. Contreras,J. Urra,M.C. Diez,L. Guerrero,C. Palma 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.5
Recycling industrial wastes is one of the major goals of bioengineering research. Agricultural wastes are often rich in natural sources of organic and inorganic compounds. The present study investigates the use of banana peel waste as a non-conventional alternative to nitrogen-enriched glucose media for a white rot fungus (WRF), Inonotus sp. SP2, recently isolated in southern Chile. WRF are known to produce biodegrading enzymes,such as peroxidases, that can have industrial and biotechnological applications. To that end, the metabolic characteristics and catalytic properties of peroxidases produced by Inonotus sp. SP2 were compared between glucose and banana peel-based growth mediums. The results establish that this strain of WRF produces high concentrations of a Mn+2-dependent peroxidase, with greater enzymatic activity in extracellular fluid and crude enzyme extracted from fungus grown in banana peel and glucose media,respectively. H2O2 has an inhibiting effect that is greater for enzymes produced in glucose media, and greater biomass can be obtained in banana-peel based media. This demonstrates that banana peel is a suitable and more cost-effective alternative to conventional glucose-based media for the production of biodegradative enzymes, such as peroxidase. Unlike other strains of WRF, the metabolic characteristics of Inonotus sp. SP2 demonstrate that it enters secondary metabolism with the production oxidative enzymes after both carbon and nitrogen sources are depleted. This suggests that with further investigation, this strain of WRF may be useful in industrial applications that require the biodegradation of nitrogen and carbon-based wastes and recalcitrant compounds.
Antonio Tienza,Petra L. Graham,Jose E. Roble,Fernando Diez-Caballero,David Rosell,Juan I. Pascual,Manish I. Patel,Sean F. Mungovan 대한배뇨장애요실금학회 2020 International Neurourology Journal Vol.24 No.2
Purpose: Continence assessment is an essential component of follow-up after radical prostatectomy (RP). Several methods exist to assess the severity of urinary incontinence (UI). Our study examined the relationship and degree of agreement between International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF) scores and the number of pads used in a 24-hour period in the assessment of UI following RP. Methods: Continence was prospectively assessed in 746 men from a Spanish urology clinic 12 months after RP using the ICIQ-SF and pad usage. The relationship between ICIQ-SF scores and pad usage was assessed using Spearman rank correlation coefficients. The Jonckheere-Terpstra trend test was used to determine whether the ICIQ-SF score and the component question scores increased with increasing pad usage. The Bonferroni-corrected pairwise Wilcoxon rank-sum test was used to determine which pairs of pad usage levels differed. The weighted kappa was used to evaluate the agreement between pad usage levels and ICIQ-SF questions. Results: The continence rate was 82% using the “no pad usage” definition of continence versus 78% using the definition of an ICIQ-SF score of 0 (P<0.001). Strong positive correlations were observed between the number of pads and the ICIQ-SF total and component question scores (rs>0.85, P<0.001). The ICIQ-SF total and component question scores increased significantly with increasing pad usage (P<0.001). The ICIQ-SF scores (P<0.018) for all pairs of pad usage levels (0, 1, 2, or 3 or more) differed significantly. The agreement between the ICIQ-SF leakage amount question and pad usage was very good (rs=0.861, P<0.001). Conclusions: At 12 months post-RP, 24-hour pad usage was closely correlated with ICIQ-SF, although the continence rate differed depending on the definition used. Higher levels of pad usage were associated with higher questionnaire scores, more leakage, and poor quality of life (interference with everyday life).
Li Wang, Y.,Molotnikov, A.,Diez, M.,Lapovok, R.,Kim, H.E.,Tao Wang, J.,Estrin, Y. Elsevier Sequoia 2015 Materials science & engineering. properties, micro Vol.639 No.-
In this study a gradient grain structure was produced by processing rod billets through three roll planetary milling (also known as PSW process). This kind of gradient structure is reported to provide an excellent combination of strength and ductility owing to an ultrafine-grained surface layer and a coarse-grained interior of the billet. Specifically, copper rod samples were subjected to up to six passes of PSW at room temperature. To study the evolution of the microstructure during the deformation, microhardness measurements and Electron Backscatter Diffraction (EBSD) analysis were performed after one, three and six passes. Additionally, the distributions of the equivalent stress during PSW and the equivalent strain after processing were studied by finite element analysis using the commercial software QFORM. The results showed the efficacy of PSW as a means of imparting a gradient ultrafine-grained structure to copper rods. A good correlation between the simulated equivalent strain distribution and the measured microhardness distribution was demonstrated.