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A new formulation of cracking in concrete structures based on lumped damage mechanics
Daniel V.C. Teles,Rafael N. Cunha,Ricardo A. Picón,David L.N.F. Amorim,Yongtao Bai,Sergio P.B. Proença,Julio Flórez-López 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.5
Lumped Damage Mechanics (LDM) is a theory proposed in the late eighties, which assumes that structural collapse may be analyzed as a two-phase phenomenon. In the first (pre-localization) stage, energy dissipation is a continuous process and it may be modelled by means of the classic versions of the theory of plasticity or Continuum Damage Mechanics (CDM). The second, post-localization, phase can be modelled assuming that energy dissipation is lumped in zones of zero volume: inelastic hinges, hinge lines or localization surfaces. This paper proposes a new LDM formulation for cracking in concrete structures in tension. It also describes its numerical implementation in conventional finite element programs. The results of three numerical simulations of experimental tests reported in the literature are presented. They correspond to plain and fiber-reinforced concrete specimens. A fourth simulation describes also the experimental results of a new test using the digital image correlation technique. These numerical simulations are also compared with the ones obtained using conventional Cohesive Fracture Mechanics (CFM). It is then shown that LDM conserves the advantages of both, CDM and CFM, while overcoming their drawbacks.
José Daniel Barquero-Cabrero,Arnulfo Luévanos-Rojas,Sandra López-Chavarría,Manuel Medina-Elizondo,Francisco Velázquez-Santillán,Ricardo Sandoval-Rivas 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.6
This paper presents a model of the elastic curve for rectangular beams with straight haunches under uniformly distributed load and moments in the ends considering the bending and shear deformations (Timoshenko Theory) to obtain the deflections and rotations on the beam, which is the main part of this research. The traditional model of the elastic curve for rectangular beams under uniformly distributed load considers only the bending deformations (Euler-Bernoulli Theory). Also, a comparison is made between the proposed and traditional model of simply supported beams with respect to the rotations in two supports and the maximum deflection of the beam. Also, another comparison is made for beams fixed at both ends with respect to the moments and reactions in the support A, and the maximum deflection of the beam. Results show that the proposed model is greater for simply supported beams in the maximum deflection and the traditional model is greater for beams fixed at both ends in the maximum deflection. Then, the proposed model is more appropriate and safe with respect the traditional model for structural analysis, because the shear forces and bending moments are present in any type of structure and the bending and shear deformations appear.
Elena Molina,,Ivan López-Expósito,Daniel Lozano-Ojalvo,Rosina López-Fandiño,Elena Molina 대한천식알레르기학회 2016 Allergy, Asthma & Immunology Research Vol.8 No.3
Purpose: Two mouse strains, BALB/c and C3H/HeOuJ, broadly used in the field of food allergy, were compared for the evaluation of the allergenic potential of ovalbumin (OVA). Methods: Sensitization was made by administering 2 different OVA doses (1 and 5 mg), with cholera toxin as Th2-polarizing adjuvant. Antibody levels, severity of anaphylaxis, and Th1 and Th2 responses induced by the allergen were assessed. In addition, because the mice selected had functional toll-like receptor 4, the influence of contamination with lipopolysaccharide (LPS) on the immunostimulating capacity of OVA on spleen cells was also evaluated. Results: Both strains exhibited similar susceptibility to OVA sensitization. The 2 protein doses generated similar OVA-specific IgE and IgG1 levels in both strains, whereas C3H/HeOuJ mice produced significantly more IgG2a. Oral challenge provoked more severe manifestations in C3H/HeOuJ mice as indicated by the drop in body temperature and the severity of the anaphylactic scores. Stimulation of splenocytes with OVA led to significantly higher levels of Th2 and Th1 cytokines in BALB/c, and these were less affected by protein contamination with LPS. Conclusions: The antibody and cytokine levels induced by OVA in BALB/c mice and the observation that BALB/c spleen cell cultures were more resistant than those of C3H/HeOuJ mice to the stimulus of LPS make this strain prone to exhibit Th2-mediated food allergic reactions and very adequate for the study of the features of OVA that make it allergenic.
Salguero Joseba,Gómez-Gómez Enrique,Valero-Rosa José,Carrasco-Valiente Julia,Mesa Juan,Martin Cristina,Campos-Hernández Juan Pablo,Rubio Juan Manuel,López Daniel,Requena María José 대한영상의학회 2021 Korean Journal of Radiology Vol.22 No.4
Objective: To evaluate the impact of multiparametric magnetic resonance imaging (mpMRI) before confirmatory prostate biopsy in patients under active surveillance (AS). Materials and Methods: This retrospective study included 170 patients with Gleason grade 6 prostate cancer initially enrolled in an AS program between 2011 and 2019. Prostate mpMRI was performed using a 1.5 tesla (T) magnetic resonance imaging system with a 16-channel phased-array body coil. The protocol included T1-weighted, T2-weighted, diffusion-weighted, and dynamic contrast-enhanced imaging sequences. Uroradiology reports generated by a specialist were based on prostate imagingreporting and data system (PI-RADS) version 2. Univariate and multivariate analyses were performed based on regression models. Results: The reclassification rate at confirmatory biopsy was higher in patients with suspicious lesions on mpMRI (PI-RADS score ≥ 3) (n = 47) than in patients with non-suspicious mpMRIs (n = 61) and who did not undergo mpMRIs (n = 62) (66%, 26.2%, and 24.2%, respectively; p < 0.001). On multivariate analysis, presence of a suspicious mpMRI finding (PI-RADS score ≥ 3) was associated (adjusted odds ratio: 4.72) with the risk of reclassification at confirmatory biopsy after adjusting for the main variables (age, prostate-specific antigen density, number of positive cores, number of previous biopsies, and clinical stage). Presence of a suspicious mpMRI finding (adjusted hazard ratio: 2.62) was also associated with the risk of progression to active treatment during the follow-up. Conclusion: Inclusion of mpMRI before the confirmatory biopsy is useful to stratify the risk of reclassification during the biopsy as well as to evaluate the risk of progression to active treatment during follow-up.
Recent introduction of Gracilaria parvispora (Gracilariales, Rhodophyta) in Baja California, Mexico
Garcí,a-Rodrí,guez, Luis Daniel,Riosmena-Rodrí,guez, Rafael,Kim, Su Yeon,Ló,pez-Meyer, Melina,Orduñ,a-Rojas, Javier,Ló,pez-Vivas, Juan Manuel,Boo, Sung Min Walter de Gruyter GmbH 2013 Botanica marina Vol.56 No.2