A new modal-based damage location indicator

Vibration-based damage detection techniques use the change in modal data as an indicator to assess damages in the structure. Knowing the structural dynamic characteristics of the healthy and damaged structure, the estimation of the damage location and severity is possible by solving an inverse problem. This paper presents a mathematical expression relating damage location and depth to the frequency shifts of the bending vibration modes. This expression permits the extraction of a series of coefficients that characterize each damage location and are independent of the damage severity. The vector aggregating these coefficients for a given location constitutes a Damage Location Indicator (DLI) that unambiguously characterizes the position of a geometrical discontinuity in the beam. A set of vectors typifying all locations along the beam may be used as patters opposable to the damage signature found by measurements. The similarity between the signature and one of the patterns indicates the location of damage

Geometrically nonlinear isogeometric analysis of laminated composite plates based on higher-order shear deformation theory

In this paper, we present an effectively numerical approach based on isogeometric analysis (IGA) and higher-order shear deformation theory (HSDT) for geometrically nonlinear analysis of laminated composite plates. The HSDT allows us to approximate displacement field that ensures by itself the realistic shear strain energy part without shear correction factors. IGA utilizing basis functions namely B-splines or non-uniform rational B-splines (NURBS) enables to satisfy easily the stringent continuity requirement of the HSDT model without any additional variables. The nonlinearity of the plates is formed in the total Lagrange approach based on the von-Karman strain assumptions. Numerous numerical validations for the isotropic, orthotropic, cross-ply and angle-ply laminated plates are provided to demonstrate the effectiveness of the proposed method

Performance of locally developed sunflower (Helianthus annuus L.) hybrids under irrigation

    A field experiment was carried out at two locations, New Halfa and Rahad, for two cropping seasons, summer (2003/04) and winter (2004/05) at each location in a randomized complete block design with four replicates, to estimate the phenotypic and genotypic variability, heritability in broad sense and genetic advance for yield, yield components and other agronomic characters among 20 locally developed sunflower (Helianthus annuus L.) hybrids. Highly significant differences found between the evaluated hybrids for almost all characters at the four environments, except plant height at New Halfa, in summer, 1000- seed weight and seed yield at both locations in winter. Most of the variation for the morphological traits was due to genetic factors, whereas, the variation in yield and its components was due to environmental factors. High heritability estimate (>60 %) coupled with low genetic advance for the morphological characters indicate epistatic and dominance nature of inheritance, while, the low heritability (<60 %) coupled with high genetic advance for yield and its components, would indicate additive nature of inheritance. Therefore, direct selection for the morpholo-gical traits, based on the phenotype, among the hybrids may be effective, while selection for yield and yield components may not be effective. Thus, there is a need for a mechanism, other than simple selection, to improve yield in sunflower

Application of numerical modeling for optimization of selective hot water extraction of taxifolin from ‘milk thistle’ seeds

The term flavonoid is used for a class of plant chemicals known for their activity as highly potent antioxidants and accordingly their ability to protect the body against oxidative and free radical damage. Taxifolin has attracted our attention because it constitutes the flavonoid moiety in ‘milk thistle’ seeds. In this research, a novel optimization-extraction method of taxifolin from ‘milk thistle’ seeds has been developed. Total antioxidant content was measured to monitor the efficiency of the extraction under different experimental conditions (solid- liquid ratio, extraction time and extraction temperature /pressure). Response surface methodology based on numerical modeling was adopted for optimization of extraction procedures. High pressure liquid chromatograph (HPLC) analysis was applied to identify taxifolin and some other phenolics in the ‘milk thistle’ extract. Using this method allowed the development of an empirical polynomial model for the production of antioxidants compounds from ‘milk thistle’ seeds. Application of such models is of great importance for pharmaceutical industries.Key words: Milk thistle, extraction, numerical modeling, antioxidant, high pressure liquid chromatograph (HPLC)