A class of stochastic epidemic models and its deterministic counterpart

Raúl Fierro 한국통계학회 2010 Journal of the Korean Statistical Society Vol.39 No.4

A general stochastic model for the spread of an epidemic developing in a closed population is introduced. Each model consisting of a discrete-time Markov chain involves a deterministic counterpart represented by an ordinary differential equation. Our framework involves various epidemic models such as a stochastic version of the Kermack and McKendrick model and the SIS epidemic model. We prove the asymptotic consistency of the stochastic model regarding a deterministic model; this means that for a large population both modelings are similar. Moreover, a Central Limit Theorem for the fluctuations of the stochastic modeling regarding the deterministic model is also proved.

Finite element simulation of nanoindentation tests using a macroscopic computational model

Mourad Khelifa,Vanessa Fierro,Alain Celzard 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8

The aim of this work was to develop a numerical procedure to simulate nanoindentation tests using a macroscopic computational model. Both theoretical and numerical aspects of the proposed methodology, based on the coupling of isotropic elasticity and anisotropicplasticity described with the quadratic criterion of Hill are presented to model this behaviour. The anisotropic plastic behaviour accountsfor the mixed nonlinear hardening (isotropic and kinematic) under large plastic deformation. Nanoindentation tests were simulated toanalyse the nonlinear mechanical behaviour of aluminium alloy. The predicted results of the finite element (FE) modelling are in goodagreement with the experimental data, thereby confirming the accuracy level of the suggested FE method of analysis. The effects of sometechnological and mechanical parameters known to have an influence during the nanoindentation tests were also investigated.

Osborne-Cotterill Lesion a Forgotten Injury: Review Article and Case Report

Daniel Gaitan Vargas,Santiago Woodcock,Guido Fierro Porto,Juan Carlos Gonzalez 대한견주관절의학회 2020 대한견주관절의학회지 Vol.23 No.1

Osborne-Cotterill lesion is an osteochondral fracture located in the posterolateral margin of the humeral capitellum, which may be associated with a defect of the radial head after an elbow dislocation. This lesion causes instability by affecting the lateral ulnar collateral ligament over its capitellar insertion, which is associated with a residual capsular laxity, thereby leading to poor coverage of the radial head, and hence resulting in frequent dislocations. We present a 54-year-old patient, a physician who underwent trauma of the left elbow after falling from a bike and suffered a posterior dislocation fracture of the elbow. The patient subsequently presented episodes of instability, and additional work-up studies diagnosed the occurrence of Osborne-Cotterill lesion. An open reduction and internal fixation of the bony lesion was performed, with reinsertion of the lateral ligamentous complex. Three months after surgery, the patient was asymptomatic, having a flexion of 130° and extension of 0°, and resumed his daily activities without any limitation. Currently, the patient remains asymptomatic 2 years after the procedure. Elbow instability includes a large spectrum of pathological conditions that affect the biomechanics of the joint. The Osborne-Cotterill lesion is one among these conditions. It is a pathology that is often forgotten and easily overlooked. Undoubtedly, this lesion requires surgical intervention.

Circumnavigation of a Moving Target in 3D by Multi-agent Systems with Collision Avoidance: An Orthogonal Vector Fields-based Approach

Hang Zhong,Yaonan Wang,Zhiqiang Miao,Jianhao Tan,Ling Li,Hui Zhang,Rafael Fierro 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.1

The problem of circumnavigating a moving target in a three dimensional setting by a network of agentswhile avoiding inter-agent collisions is addressed in this paper. A distributed control strategy is proposed for themulti-agent system to achieve three objectives: reaching the target plane with predesigned orientation, circulatingaround the target with prescribed radius, and avoiding collisions among agents. After representing the controlobjectives by three potential functions, the gradient fields of which are orthogonal to each other, the control lawthen is developed using the gradient vector field-based approach. The novelty of the proposed controller lies in theorthogonality of the vector fields, which decouples the control objectives and ensures global asymptotic convergenceto the desired motion, subject to some mild initial condition constraints. The stability and convergence analysis arepresented using Lyapunov tools, and the effectiveness of the proposed control strategy is demonstrated throughnumerical simulations.

The effect of Sn on the electronic state of M/γ-Al₂O₃(M = Pd, Pt) catalysts and the influence in the catalytic combustion of methane

Grisel Corro,O. Vázquez-Cuchillo,F. Bañuelos,A. Cruz-López,J.L.G. Fierro 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6

Pd-Sn and Pt-Sn catalysts supported on γ-Al2O3 were prepared by co-precipitation and the Pt characterized dispersion of reduced samples was determined by H2 chemisorption for Pt and Pt-Sn catalysts, The Pd dispersion was determined by CO adsorption on Pd and Pd-Sn catalysts. The catalysts were characterized by the electron binding energy values determined by XPS. The results are explained on the basis of the Pt and Pd species electron binding energy changes due to the electronic properties of Sn. The catalytic activity in methane oxidation under lean burn conditions was measured. The results reveal that the tin addition causes a change in the catalytic activity of the supported catalysts, showing a greater catalytic activity on the CH4-O2 reaction for the bimetallic Pd-Sn/ γ-Al2O3. Pd-Sn and Pt-Sn catalysts supported on γ-Al2O3 were prepared by co-precipitation and the Pt characterized dispersion of reduced samples was determined by H2 chemisorption for Pt and Pt-Sn catalysts, The Pd dispersion was determined by CO adsorption on Pd and Pd-Sn catalysts. The catalysts were characterized by the electron binding energy values determined by XPS. The results are explained on the basis of the Pt and Pd species electron binding energy changes due to the electronic properties of Sn. The catalytic activity in methane oxidation under lean burn conditions was measured. The results reveal that the tin addition causes a change in the catalytic activity of the supported catalysts, showing a greater catalytic activity on the CH4-O2 reaction for the bimetallic Pd-Sn/ γ-Al2O3.

Induction-related mortality in adolescents and young adults with acute lymphoblastic leukemia in a resource-limited setting: do treatment-related complications create more impact than disease biology?

Sergio I. Inclan-Alarcon,Santiago Riviello-Goya,Kevin Teran-De-la-Sancha,Oscar M. Fierro-Angulo,Aldo A. Acosta-Medina,Roberta Demichelis-Gomez,Christianne Bourlon 대한혈액학회 2022 Blood Research Vol.57 No.1

Background Acute lymphoblastic leukemia (ALL) is a malignant clonal bone marrow disorder with a high mortality rate during the initial therapy. This retrospective study aimed to describe and analyze the risk factors and causes of induction-related mortality (IRM) in an adolescent and adult ALL population treated in a low- and middle-income country. Methods From 2009 to 2016, a total of 167 patients were included, of which 50.9% were male with a median age of 28 years. B-immunophenotype represented 97.6%, and high-risk cytogenetics were present in 23.3%. During induction therapy, 91% had at least 1 complication, most of which were infectious, with an IRM of 12%. Results Factors associated with increased mortality rate were central nervous system (CNS) status [CNS-3: hazard ratio (HR) 3.029; 95% confidence interval (CI), 0.79‒11.49; P =0.103 and CNS-2: HR, 9.98; 95% CI, 2.65‒37.65; P =0.001] and dialysis requirement (HR, 9.15; 95% CI, 2.44‒34.34; P =0.001). Conclusion Our study confirms that ALL patients treated in resource-constrained settings have high rates of IRM, mainly attributed to advanced disease and high tumor burden at diagnosis.