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Mejia-Nava, Rosa Adela,Ibrahimbegovic, Adnan,Lozano-Leal, Rogelio Techno-Press 2020 Coupled systems mechanics Vol.9 No.1
In this paper we study the control for nonlinear geometric instability problem of a deep or a shallow truss or yet a frame structure. All the structural models are built with geometrically exact truss and beam finite elements.The proposed models can successfully handle large overall motion under static or dynamic conservative load.The control strategy considers adding a damping from either friction device or viscous damper.This kind of control belong to well-known concept of passivity. Different examples are presented in order to illustrate the proposed theoretical developments.
Viscoelastic behavior of concrete structures subject to earthquake
Mejia-Nava, Rosa Adela,Ibrahimbegovic, Adnan,Dominguez-Ramirez, Norberto,Flores-Mendez, Esteban Techno-Press 2021 Coupled systems mechanics Vol.10 No.3
This paper investigates an alternative way to the Raleigh formula to catch con- tributions of damping effects. Nowadays, thanks to the power of new software and effi- cient computational methods, there exist possibility to implement new analysis of damping through multiscale approach. The corresponding homogenization of a representative elemen-tal volume of concrete is used to calculate the effective properties of the composite, since energy dissipation properties such as viscoelasticity are not taken into account. At the end of this work, these methodologies are incorporated into a column of a building subject to seismic action. More precisely, with concrete as a composite material (aggregate+cement), we can use homogenization methods to calculate its effective properties by using the classical approach of a representative elemental volume. This can help to take into account properties of energy dissipation, such as produced by viscoelasticity. Finally, for illustration, the pro- posed methodology is applied to structural analysis of a column under the most unfavorable conditions in a building subject to earthquake action.
Extraction of Pectinesterase from Jalapeno Chili Pepper (Capsicum annuum) and Its Thermal Stability
Sonia Marisela Mejia-Cordova,Julio Cesar Montanez,Cristobal Noe Aguilar,Maria de la Luz Reyes-Vega,Heliodoro de la Garza,Roque Alberto Hours,Juan Carlos Contreras-Esquivel 한국식품과학회 2005 Food Science and Biotechnology Vol.14 No.2
Mateo Restrepo Mejia,Juan Sebastian Arroyave,Michael Saturno,Laura Chelsea Mazudie Ndjonko,Bashar Zaidat,Rami Rajjoub,Wasil Ahmed,Ivan Zapolsky,Samuel K. Cho 대한척추신경외과학회 2024 Neurospine Vol.21 No.1
Objective: Large language models like chat generative pre-trained transformer (ChatGPT) have found success in various sectors, but their application in the medical field remains limited. This study aimed to assess the feasibility of using ChatGPT to provide accurate medical information to patients, specifically evaluating how well ChatGPT versions 3.5 and 4 aligned with the 2012 North American Spine Society (NASS) guidelines for lumbar disk herniation with radiculopathy. Methods: ChatGPT's responses to questions based on the NASS guidelines were analyzed for accuracy. Three new categories—overconclusiveness, supplementary information, and incompleteness—were introduced to deepen the analysis. Overconclusiveness referred to recommendations not mentioned in the NASS guidelines, supplementary information denoted additional relevant details, and incompleteness indicated omitted crucial information from the NASS guidelines. Results: Out of 29 clinical guidelines evaluated, ChatGPT-3.5 demonstrated accuracy in 15 responses (52%), while ChatGPT-4 achieved accuracy in 17 responses (59%). ChatGPT-3.5 was overconclusive in 14 responses (48%), while ChatGPT-4 exhibited overconclusiveness in 13 responses (45%). Additionally, ChatGPT-3.5 provided supplementary information in 24 responses (83%), and ChatGPT-4 provided supplemental information in 27 responses (93%). In terms of incompleteness, ChatGPT-3.5 displayed this in 11 responses (38%), while ChatGPT-4 showed incompleteness in 8 responses (23%). Conclusion: ChatGPT shows promise for clinical decision-making, but both patients and healthcare providers should exercise caution to ensure safety and quality of care. While these results are encouraging, further research is necessary to validate the use of large language models in clinical settings.
Structural and optical characterization of InGaN/GaN quantum wells grown in cubic phase by MBE
Luis Faustino MEJIA-CUELLAR,Yenny Lucero CASALLAS-MORENO,Alberto PIEDRA-LORENZANA,Carlos Alberto HERNANDEZ-GUTIE,Dagoberto CARDONA,Saul ARIAS-CERON,Juan HERNANDEZ-ROSAS,Jose Luis HERRERA-PEREZ,Emmanue 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8
Christopher A. Febres-Aldana,Odille Mejia-Mejia,Kritika Krishnamurthy,Thomas Mesko,Robert Poppiti 한국유방암학회 2020 Journal of breast cancer Vol.23 No.1
Breast adenomyoepitheliomas are composed of a biphasic proliferation of myoepithelial cells around small epithelial-lined spaces. Due to the rarity of adenomyoepitheliomas, the molecular data describing them are limited. Adenomyoepitheliomas are considered to be benign or have low malignant potential, and be prone to local recurrence. Malignant transformation has been associated with homozygous deletion of CDKN2A or somatic mutations in TERT, but remains unexplained in many cases. Here, we describe a case of carcinomatous transformation of both epithelial and myoepithelial cells in an estrogen receptor-negative adenomyoepithelioma caused by amplification of MYC. Break-apart fluorescence in situ hybridization revealed an increase in the MYC gene copy number (3–4 copies/cell in 37%, > 4 copies/cell in 40%). Deregulation of MYC is responsible for uncontrolled proliferation and cellular immortalization in basal-like breast cancers. Our case demonstrates that genomic instability events associated with gene amplification may be involved in the carcinogenesis of malignant adenomyoepitheliomas.
Hajdo, Emina,Mejia-Nava, Rosa Adela,Imamovic, Ismar,Ibrahimbegovic, Adnan Techno-Press 2021 Coupled systems mechanics Vol.10 No.1
In this paper we deal with instability problems of structures under nonconservative loading. It is shown that such class of problems should be analyzed in dynamics framework. Next to analytic solutions, provided for several simple problems, we show how to obtain the numerical solutions to more complex problems in efficient manner by using the finite element method. In particular, the numerical solution is obtained by using a modified Euler-Bernoulli beam finite element that includes the von Karman (virtual) strain in order to capture linearized instabilities (or Euler buckling). We next generalize the numerical solution to instability problems that include shear deformation by using the Timoshenko beam finite element. The proposed numerical beam models are validated against the corresponding analytic solutions.
Instability of (Heterogeneous) Euler beam: Deterministic vs. stochastic reduced model approach
Ibrahimbegovic, Adnan,Mejia-Nava, Rosa Adela,Hajdo, Emina,Limnios, Nikolaos Techno-Press 2022 Coupled systems mechanics Vol.11 No.2
In this paper we deal with classical instability problems of heterogeneous Euler beam under conservative loading. It is chosen as the model problem to systematically present several possible solution methods from simplest deterministic to more complex stochastic approach, both of which that can handle more complex engineering problems. We first present classical analytic solution along with rigorous definition of the classical Euler buckling problem starting from homogeneous beam with either simplified linearized theory or the most general geometrically exact beam theory. We then present the numerical solution to this problem by using reduced model constructed by discrete approximation based upon the weak form of the instability problem featuring von Karman (virtual) strain combined with the finite element method. We explain how such numerical approach can easily be adapted to solving instability problems much more complex than classical Euler's beam and in particular for heterogeneous beam, where analytic solution is not readily available. We finally present the stochastic approach making use of the Duffing oscillator, as the corresponding reduced model for heterogeneous Euler's beam within the dynamics framework. We show that such an approach allows computing probability density function quantifying all possible solutions to this instability problem. We conclude that increased computational cost of the stochastic framework is more than compensated by its ability to take into account beam material heterogeneities described in terms of fast oscillating stochastic process, which is typical of time evolution of internal variables describing plasticity and damage.
Classical and Quantum Chaos and Control of Heat Flow
Giulio Casati,C. Mejia-Monasteo 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.1I
We discuss the problem of heat conduction in classical and quantum low-dimensional systems from a microscopic point of view. At the classical level we provide convincing numerical evidence for the validity of the Fourier law of heat conduction in linear mixing systems, i.e., in systems without exponential instability. At the quantum level, where motion is characterized by the lack of exponential dynamical instability, we show that the validity of the Fourier law is in direct relation to the onset of quantum chaos. We then study the phenomenon of thermal recti.cation and brie°y discuss the dierent types of microscopic mechanisms that lead to the recti.cation of heat °ow. The control of heat conduction by nonlinearity opens the possibility to propose new devices, such as a thermal recti.er.