Predictive modeling of an energy-absorbing sandwich structural concept using the building block approach

An energy-absorbing composite sandwich structural concept, comprised of a deep honeycomb core with carbon/epoxy facesheets, is subject to through-thickness crushing and penetration using a cylindrical pole. With the aid of the building block approach, the response of the structure is predicted by analysis supported by test evidence. Experiments are conducted at various levels of complexity, from the coupon level used to generate material properties to be used as input in the finite element models, through the element level used to calibrate the analysis models, and up to the component level to validate them. LS-DYNA is used to perform the analyses, including material models MAT 54 for the facesheets, MAT 126 for the honeycomb, and tie-break contact for the adhesive. Material models and contact formulations require extensive calibration of modeling parameters at the lower and intermediate levels of the building block pyramid, but eventually enable the prediction of the full-scale structure.     

Questioning the Shanghai Ranking methodology as a tool for the evaluation of universities: an integrative review

Scientometrics - This integrative review reports on methodological questions about the Shanghai Ranking as a tool for the evaluation of universities, questions that are extensible to other...     

Webometric analysis of Iranian universities of medical sciences

Introduction  There are many researches have been conducted on webometrics, especially the impacts of websites on each other and the web impact factor. However, there are few studies focusing on the websites of Iranian universities. This study analyzed the websites of Iranian universities of medical sciences according to the webometric indicators. Method and materials  In a cross-sectional study, the number of web pages, inlinks, external inlinks and also the overall and absolute web impact factors for Iranian universities of medical sciences with active exclusive websites were calculated and compared using AltaVista search engine. Finally, the websites were ranked based on these webometric indicators. Results  The results showed that the website of Tehran university of medical sciences with 49,300 web pages and 9860 inlinks was ranked first for the size and number of inlinks, while its impact factor was ranked 38th. Rafsanjan UMS with 15 web pages and 211 links had the highest rank for the web impact factor among Iranian universities of medical sciences. Discussions and conclusions  The study revealed that Iranian universities of medical sciences did not have much impact on the web and were not well known internationally. The major reason relies on linguistic barriers. Some of them also suffer from technical problems in their web design.     

Scientometric analysis of the major Iranian medical universities

Nowadays, scientometrics has become an important field of study to monitor the progresses in scientific performance of a research group, a department, a university etc. A number of scientometrical studies have been done about Iranian scientific outcome in recent years. But there is no comparison between major Iranian medical universities. In this study, by using Scopus as search engine, the scientific outcomes of the Iran University of Medical Sciences, Isfahan University of Medical Sciences, Mashhad University of Medical Sciences, Shahid Beheshti University of Medical Sciences, Shiraz University of Medical Sciences, Tabriz University of Medical Sciences, and Tehran University of Medical Sciences have been compared with each other. These universities were compared by the number of published articles per year, number of citations received per year, number of citations received per year per article, total H-indices, top ten authors, and top ten journals. The results of this study show that the order of the studied universities in research performance is as follow: Tehran > Shiraz = Shahid Beheshti > Isfahan = Iran > Tabriz = Mashhad universities of medical sciences. In addition, the data of Tehran University of Medical Sciences as the top medical university of Iran was compared with some of top medical universities around the world.     

A partial-least-squares approach to interpretative analysis of multivariate data

Kvalheim, O.M., 1988. A partial-least-squares approach to interpretative analysis of multivariate data. Chemometrics and Intelligent Laboratory Systems, 3: 189-197.A partial-least-squares (PLS) approach to the resolution of blocks of variables into interpretable factors is developed. The combination step necessary to obtain such factors from a PLS-decomposed matrix is similar to that of target-transformation of principal components.If the block of ‘dependent’ variables can be resolved into uncorrelated interpretable factors, the performance of the PLS method for interpretative data analysis is improved by using, in the decomposition step, these factors standardized to equal variance. This approach eliminates the effects of differences in relative size of factors in the ‘dependent’ variable block, and thus provides enhanced resolution of small factors which are often masked by the larger ones in truncated principal component (PC) and ordinary PLS decompositions. The ability of the present PLS approach to include small but relevant variation in the early components gives a sharper borderline between noise and information than is obtained with PC and ordinary PLS decompositions.     

Barriers in adoption of internet banking: A structural equation modeling - Neural network approach

Comparatively, less attention has been paid to the factors that obstruct consumers to use internet banking. Therefore, this study aims to analyze the barriers in the adoption of Internet banking in Karachi, Pakistan. A survey research questionnaire was adopted and, in total, 300 useable responses were used from the banks’ customers. First exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were applied for the establishment of measurement model and structural equation modeling (SEM) was used to find the significant influence barriers on Internet banking adoption. In the second phase, the neural network model was used to rank the relative influence of significant predictors obtained from SEM. The results indicate a significant positive relationship between value barrier, risk barrier, and image barrier with the usage of Internet banking. Only, the traditional barrier has a negative insignificant effect on the usage of Internet banking. The image barrier has a higher impact on usage of Internet banking followed by the value barrier and risk barrier. Results also indicate that males are facing high barriers in comparison with females. Findings provide guidelines to banks for developing facilities that enable the consumer to use Internet banking for their financial transactions. This study will be highly beneficial for the banking industry to improve their online services and revise their policies to facilitate consumers by meeting their needs.     

A thermomechanical modeling approach of the structural changes in semi-crystalline polymers under elongational strain

Different polymer processing techniques, like thermoforming, cast film, or spinning, involve deformation of the material in a rubber-like state. In the case of semi-crystalline materials the processing temperature can be near but lower than the melting point. Moreover, in these processes, elongational strains are generally very high which lead to important crystalline evolution and orientation. Concomitantly, the thermomechanical behavior of the film is linked to the morphological evolving and the crystalline orientation due to the strain. In the present work, the elongational behavior was studied for a polypropylene film at temperatures between 110 and 140 °C and constant elongation rates. Based on a two-phase approach (amorphous and crystalline), a thermomechanical modeling of the stress curves is proposed including the fragmentation and the fibrils formation mechanisms. Particularly, the originality of the model consists in taking into account the fibrils contribution to the stress only as far as they are generated. As a consequence the model takes an integral form. However, despite the simplicity of this approach, the stress curves are described relatively well.     

Ranking of research output of universities on the basis of the multidimensional prestige of influential fields: Spanish universities as a case of study

A university may be considered as having dimension-specific prestige in a scientific field (e.g., physics) when a particular bibliometric research performance indicator exceeds a threshold value. But a university has multidimensional prestige in a field of study only if it is influential with respect to a number of dimensions. The multidimensional prestige of influential fields at a given university takes into account that several prestige indicators should be used for a distinct analysis of the influence of a university in a particular field of study. After having identified the multidimensionally influential fields of study at a university their prestige scores can be aggregated to produce a summary measure of the multidimensional prestige of influential fields at this university, which satisfies numerous properties. Here we use this summary measure of multidimensional prestige to assess the comparative performance of Spanish Universities during the period 2006–2010.     

Flexible manufacturing systems: a structural approach

In the last five years, developed countries have seen more rapid advancement in the application of high technology to manufacturing than in the two preceding decades. Many of these applications have occurred under the banner of a new type of manufacturing called flexible manufacturing systems (FMSs). With the implementation of FMSs, a new awareness of the opportunities for manufacturing-cost reduction is emerging. In this paper, the FMS taxonomy and structure is presented. To exploit this structure, FMS process and problem views are presented, and various aspects of flexibility are discussed. To show the complexity of an FMS, its design and operational problems are defined. Basic functions of robots and vision systems are also presented. Finally, FMS modularity issues and future trends in FMS development are outlined.     

Effective mechanical properties of EM composite conductors: an analytical and finite element modeling approach

An analytical model and numerical approach to predict the effective mechanical properties of a composite conductor consisting of metallic core and insulation layers are presented in this paper. The analytical model was developed based on a two-step homogenizations and mechanics analysis for composite unit cell. The Step 1 homogenization derives the effective properties of the out-wrapped composite insulation layers. The Step 2 homogenization further smears the metallic core and the effective composite insulation layers to develop homogenized mechanical properties for composite conductor according to appropriate homogenization sequences. The procedure of using numerical approach and finite element method to determine the unit cell effective constants were also described and the results of the FEA prediction were presented. The analytical predictions were compared well to the numerical results for the nine material constants that characterize the effective mechanical properties of the composite conductor.     

Resin flow modeling in compliant porous media: an efficient approach for liquid composite molding

In Liquid Composite Molding (LCM) processes such as Resin Transfer Molding (RTM) and Vacuum Assisted Resin Transfer Molding (VARTM), complete saturation of reinforcement with resin during the injection step is necessary. In RTM, reinforcement experiences no deformation during infusion but for other methods reinforcement thickness changes during the injection. To model resin flow in compliant media, RTM flow simulation software is routinely used. It has been successful in predicting flow patterns if appropriate “effective” permeability is used. The proper approach requires new implementation that couples the deformation and pressure field which is computationally more demanding. Our work describes a computationally efficient methodology to add corrections into RTM simulation environment to account for deformation. This approach is verified with known solutions and experimental validation. The simulation is applied to a complex geometry which demonstrates better computational performance and confirms that the “effective” permeability may be used to model flow in complex geometries.     

A structural approach to estimating cracking resistance in an anisotropic metal

A form of the Hahn-Rosenfield model is used in a structural approach to evaluating cracking resistance in an anisotropic metal by standard test data for uncracked specimens subject to biaxial loading. The formulas incorporate a generalized function of the structural parameters covering the effect of the interaction between the preliminary strain path and the repeat-strain one on the yield point and the dimensional parameter for the terminal crack zone. The approach has been confirmed by experiments on low-cycle loading of 12KH18N10T steel containing a normal-detachment crack if the directions of the preliminary and repeat stretching coincide or are orthogonal. Translated from Problemy Prochnosti, No. 5, pp. 53–62, May 1996.     

Analysis of SCF under sales promotional schemes: an application of interpretive structural modelling approach

In the competitive market of today, supply chain flexibility (SCF) plays crucial way to address various supply chain uncertainties. But, in diverse situations, the supply chain needs different types of flexibilities. This paper analyses the flexibility of an automobile supply chain under sales promotional schemes (SPS) to meet the demand uncertainty. Taking the opinion of supply chain experts from automobile original equipment manufacturers (OEM’s), 14 SCF strategies have been identified and then using interpretive structural modelling (ISM) on the conducted survey, their interrelationships are established and a hierarchical model is developed. MICMAC analysis is done to classify the strategies into four categories viz. autonomous, dependent, linkage and independent strategies, which are based on their driving and dependence powers. Sensitivity analysis has been conducted to check the stability of the model. The thorough exposition of the model presents a handful of insights to supply chain managers to know the most important strategies affecting each other. The study helps in bridging the SCF with SPS, a huge gap existing in the literature.     

Knowledge mapping of the Iranian nanoscience and technology: a text mining approach

Nanoscience and technology (NST) is a relatively new interdisciplinary scientific domain, and scholars from a broad range of different disciplines are contributing to it. However, there is an ambiguity in its structure and in the extent of multidisciplinary scientific collaboration of NST. This paper investigates the multidisciplinary patterns of Iranian research in NST based on a selection of 1,120 ISI??indexed articles published during 1974?C2007. Using text mining techniques, 96 terms were identified as the main terms of the Iranian publications in NST. Then the scientific structure of the Iranian NST was mapped through multidimensional scaling, based upon the co-occurrence of the main terms in the academic publications. The results showed that the NST domain in Iranian publications has a multidisciplinary structure which is composed of different fields, such as pure physics, analytical chemistry, chemistry physics, material science and engineering, polymer science, biochemistry and new emerging topics.     

Fluid–structure interaction modeling of a patient-specific cerebral aneurysm: influence of structural modeling

Fluid–structure interaction (FSI) simulations of a cerebral aneurysm with the linearly elastic and hyper-elastic wall constitutive models are carried out to investigate the influence of the wall-structure model on patient-specific FSI simulations. The maximum displacement computed with the hyper-elastic model is 36% smaller compared to the linearly elastic material model, but the displacement patterns such as the site of local maxima are not sensitive to the wall models. The blood near the apex of an aneurysm is likely to be stagnant, which causes very low wall shear stress and is a factor in rupture by degrading the aneurysmal wall. In this study, however, relatively high flow velocities due to the interaction between the blood flow and aneurysmal wall are seen to be independent of the wall model. The present results indicate that both linearly elastic and hyper-elastic models can be useful to investigate aneurysm FSI.     

FINITE: An approach to structural mechanics systems

FINITE is a general purpose structural mechanics system which runs under the POLO II supervisor. It is unique in that it provides users with a very flexible recursive structural modeling capability. Engineers can communicate with FINITE through a problem-oriented language similar to STRUDL. Significant savings in computer and data entry times can be achieved when its recursive substructuring and condensation features are used appropriately. The structure of FINITE permits engineers to enter new elements with a minimal knowledge of the system operation. Nonsymmetric elements, hybrid elements, and elements with different degrees of freedom at the various nodes are all permissible. Various forms of linear constraints may be applied to the generalized displacements of a structure. The system runs under the POLO II supervisor and derives many of its attributes from the unique data base management facilities of this system. Among them are a limited working set size in a virtual memory environment and automatic restart capabilities.     

Ranking sensors using an adaptive fuzzy logic algorithm

A procedure to rank sensors according to their noise rates was developed based on an adaptive fuzzy logic algorithm for sensor fusion. No a priori knowledge of the sensors performance is assumed. Simulation analysis indicated 83.33% successful ranking with noise rates up to 50%. In an indoor experiment with a mobile robot equipped with three logical sensors, 88% of the rankings were correct. The ranking procedure also indicates the ranking results success probability.