Nedelcu M.,Technical University of Cluj Napoca
Thin-Walled Structures | Year: 2012
This paper presents an original method based on the Generalised Beam Theory (GBT) capable to decompose the elastic buckling modes from a shell finite element analysis (FEA) of an isotropic thin-walled member, into pure buckling modes of global, distorsional or local nature. The main novelty lies in using only the GBT cross-sectional deformation modes instead of member base mode shapes. The contribution of each pure buckling mode can be calculated, allowing a better understanding of the member post-buckling behaviour and strength reserve. Following the GBT classical assumptions, the membrane shear strains and transverse extensions are neglected. The modal participations obtained from FEA are in good agreement with the values calculated via classical GBT approach. © 2012 Elsevier Ltd.
Berinde V.,Technical University of Cluj Napoca
Computers and Mathematics with Applications | Year: 2012
We obtain coupled coincidence and coupled common fixed point theorems for mixed g-monotone nonlinear operators F:X×X→X in partially ordered metric spaces. Our results are generalizations of recent coincidence point theorems due to Lakshmikantham and irić [V. Lakshmikantham, L. irić, Coupled fixed point theorems for nonlinear contractions in partially ordered metric spaces, Nonlinear Anal. 70 (2009) 4341-4349], of coupled fixed point theorems established by Bhaskar and Lakshmikantham [T.G. Bhaskar, V. Lakshmikantham, Fixed point theorems in partially ordered metric spaces and applications, Nonlinear Anal. 65 (7) (2006) 1379-1393] and also include as particular cases several related results in very recent literature. © 2012 Elsevier Ltd. All rights reserved.
Rosca D.,Technical University of Cluj Napoca
Astronomy and Astrophysics | Year: 2010
Aims. A method for constructing new uniform grids on the sphere is given. Methods. We define a bijection in R2, which maps squares onto discs and preserves areas. Then we use this bijection, combined with Lambert azimuthal projection, for lifting uniform grids from the square to the sphere. Results. We can obtain uniform spherical grids that allow a hierarchical data manipulation and have an isolatitudinal distribution of cells. Compared with HEALPix grids, nowadays the most used in astronomy and astrophysics, our grids have the advantage of allowing easier implementation, and in addition one can move approximating functions from the square to the sphere by a simple technique. © 2010 ESO.
Talu S.,Technical University of Cluj Napoca
Current Eye Research | Year: 2013
Objective: The purpose of this paper is to determine a quantitative assessment of the human retinal vascular network architecture for patients with diabetic macular edema (DME). Multifractal geometry and lacunarity parameters are used in this study. Materials and methods: A set of 10 segmented and skeletonized human retinal images, corresponding to both normal (five images) and DME states of the retina (five images), from the DRIVE database was analyzed using the Image J software. Statistical analyses were performed using Microsoft Office Excel 2003 and GraphPad InStat software. Results: The human retinal vascular network architecture has a multifractal geometry. The average of generalized dimensions (Dq) for q = 0, 1, 2 of the normal images (segmented versions), is similar to the DME cases (segmented versions). The average of generalized dimensions (Dq) for q = 0, 1 of the normal images (skeletonized versions), is slightly greater than the DME cases (skeletonized versions). However, the average of D2 for the normal images (skeletonized versions) is similar to the DME images. The average of lacunarity parameter, Λ, for the normal images (segmented and skeletonized versions) is slightly lower than the corresponding values for DME images (segmented and skeletonized versions). Conclusion: The multifractal and lacunarity analysis provides a non-invasive predictive complementary tool for an early diagnosis of patients with DME. © Informa Healthcare USA, Inc.
Fratila D.,Technical University of Cluj Napoca
Journal of Cleaner Production | Year: 2010
This paper focuses on investigating several aspects of the machining process from an ecological perspective, the result being a macro-level analysis. The analysis presented here considers not only the environmental impact of the material removal process itself, but also the impact of the associated processes such as the material preparation, and the scrap processing. A macro-level assessment of the comparative life cycle environmental performance of the near-dry machining (NDM) using TiN-coated carbide tools and the flood machining (FM) is performed by a case study referring to the gear milling. The assessment, using the SimaPro 7.1.5 software and the ecoinvent1.5 database, includes combined Life Cycle Assessment (LCA) of the workpiece material, the scrap processing, the use of lubrication, and the energy consumption. © 2010 Elsevier Ltd.