1,721,033 research outputs found
Interview with Mohamed Shaker
No full textمقابلة بين المراسلة إيمان رافع والسفير محمد شاكر حول خلل النظام العربي مؤكداً أنه يحتاج الي تجديد لاحيائه عن طريق السوق العربية المشتركة ويشارك في انشائها كل الدول العربية.An interview between the correspondent Iman Rafi and ambassador Mohamed Shaker about the flaw in the Arab system and how it might be revived through the establishment of an Arab common market in which all Arab nations would take part
Proper Generalized Decomposition solutions of composite laminates parameterized with fibre orientations for fast computations
Get PDFI materiali compositi stanno guadagnando popolarità come alternativa ai
materiali classici in molte diverse applicazioni. Inoltre, il loro design è sempre
più
essibile grazie al potenziale della manifattura additiva. Pertanto, è
possibile produrre un laminato composito su misura con i valori ottimali di
alcuni parametri di progettazione allo scopo di fornire le prestazioni meccaniche
desiderate. In questo contesto, disporre di un modello numerico parametrico
per la risposta meccanica del laminato composito è essenziale per calcolare i
parametri ottimali. In generale, risolvere un modello meccanico utilizzando
tecniche basate su mesh in 3D è computazionalmente costoso e ad un certo
punto potrebbe diventare irrealizzabile quando il problema è multidimensionale.
Inoltre, se il problema in esame è un'applicazione che richiede più query nei
problemi di ottimizzazione, i problemi inversi o la quanticazione dell'incertezza,
il problema diretto viene risolto numerose volte aumentando drasticamente il
carico computazionale.
Nella presente tesi, i parametri di progetto presi in considerazione sono gli
angoli che descrivono l'orientamento delle bre di rinforzo nei diversi strati o
nelle diverse zone dei laminati compositi. Presentiamo il criterio di rottura
di Tsai-Wu come funzione obiettivo del problema di ottimizzazione. Nel
presente lavoro, si raccomanda l'uso di una tecnica di "Model Order Reduction"
(MOR) per decrementare il costo computazionale menzionato; ovvero, si ricorre
alla "Proper Generalized Decomposition" (PGD) per ottenere la soluzione
generalizzata della risposta meccanica della struttura. In particolare, otteniamo
un vademecum computazionale 3D che fornisce un indice di rottura del laminato
e un fattore di sicurezza che dipendono esplicitamente dall'orientamento della
bra. PGD fornisce anche sensitività per un algoritmo di ottimizzazione basato
sul gradiente. La potenzialità e l'efficacia dell'approccio presentato è dimostrata
attraverso alcuni test numerici. Inne, viene presentato un accoppiamento tra
la metodologia proposta e le tecniche di clustering per migliorare le prestazioni
complessive del modello.Composite materials are gaining popularity as an alternative to classical
materials in many different applications. Moreover, their design is even more
flexible due to the potential of additive manufacturing. Thus, one can produce a
tailored composite laminate with the optimal values of some design parameters
providing the desired mechanical performance. In this context, having a
parametric numerical model for the mechanical response of the composite
laminate is essential to compute the optimal parameters. Generally, solving
a mechanical model using mesh-based techniques in 3D is computationally
expensive and at some point it could become infeasible when the problem
is multidimensional. Furthermore, if the problem under consideration is an
application requiring multiple queries such as optimization, inverse problems,
or uncertainty quantification, the direct problem is solved numerous times
increasing drastically the computational burden.
In the present thesis, the design parameters under consideration are the angles
describing the orientation of the reinforcement fibres in different layers or
patches of the composite laminates. We present the Tsai-Wu failure criterion as
the objective function of the optimization problem. The use of a Model Order
Reduction (MOR) technique is advocated to alleviate the mentioned computational
burden. Namely, we resort to the Proper Generalized Decomposition
(PGD) to obtain the generalized solution of the structure mechanical response.
Particularly, we obtain a computational vademecum which provides laminate
failure index and safety factor that depend explicitly on the fibre orientation.
The PGD vademecum provides also sensitivities for a gradient-based optimization
algorithm. The potentiality and effciency of the presented approach is
demonstrated through some numerical tests. Finally, a coupling between the
proposed methodology and clustering techniques is presented to enhance the
overall performance of the model
The dark side of intangibles? Organizational capital and corporate investment efficiency
Get PDFPurpose
Organizational capital (OK) represents an important intangible productive firm asset, yet one subject to agency problems. This paper provides a first examination of how OK impacts corporate investment inefficiency using an unbalanced panel of listed US companies from 2009 to 2020.
Design/methodology/approach
We utilize fixed-effect regressions to explore the relationship between OK and investment efficiency. Additionally, we implement a battery of robustness tests of the main study findings based on a variety of panel data techniques, including firm fixed effects, alternative measures of investment efficiency, estimators, including Newey–West as well as additional steps to address endogeneity concerns using system-GMM, two-stage least-squares and entropy balancing analyses.
Findings
OK is associated with reduced investment efficiency (underinvestment and overinvestment). A one-standard deviation increase in OK to total assets is associated with a 4.42% decrease in investment efficiency. Based on average firm investment, this represents a $390.88 million decrease in investment. CEO gender and career concerns as well as R&D intensity, positively moderate this relationship, while CEOs’ age, power, tenure and connections as well as corporate governance and disclosure quality, negatively moderate it. The findings can be understood from the perspective of agency theory, whereby informational asymmetries surrounding OK make it challenging for firm outsiders to monitor and evaluate managerial investment choices.
Originality/value
We lack understanding as to how it impacts the efficiency of corporate investment. We contribute the first evidence in this regard by demonstrating that OK is associated with lower investment efficiency.© Mohamed Shaker Ahmed and Timothy King. Published by Emerald Publishing Limited. This
article is published under the Creative Commons Attribution (CC BY 4.0) licence. Anyone may
reproduce, distribute, translate and create derivative works of this article (for both commercial and noncommercial purposes), subject to full attribution to the original publication and authors. The full terms of this licence may be seen at http://creativecommons.org/licences/by/4.0/legalcodefi=vertaisarvioitu|en=peerReviewed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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