18 research outputs found
Uncertainty quantification of residual strength post lightning strike: a coupled stochastic thermal-electrical-mechanical simulation framework for composite laminates
No full textThe strength of composite laminates can be significantly impacted by the damage caused due to lightning strikes. Quantifying such impact of lightning strikes, taking the inevitable compound influence of material and lightning current uncertainty into consideration, is of utmost importance to ensure the operational safety and serviceability in critical composite structural applications such as aircraft and wind turbines. We introduce a machine learning-enabled stochastic framework of hybrid thermal–electrical–mechanical simulations for the uncertainty quantification of residual strength post lightning strike in composite laminates. A comprehensive probabilistic analysis is presented for accurately assessing the uncertainty associated with the residual tensile strength of carbon/epoxy laminates considering stochastic temperature-dependent material properties and lightning current waveform. The results reveal that source uncertainty of the unprotected laminates significantly influences the structural strength with considerable stochastic variability. The machine learning models are exploited further for conducting global sensitivity analysis to examine the relative impact of the influencing parameters on the residual strength after lightning strikes. Seamless coupling of the Gaussian process-driven machine learning model in the finite element based multi-physical lightning strike analysis, integrating multi-stage computationally intensive simulations, leads to an efficient quantification of uncertainty for complete probabilistic characterization of the residual strength and subsequent serviceability analysis
Multi-fidelity machine learning based uncertainty quantification of progressive damage in composite laminates through optimal data fusion
No full textRecently machine learning (ML) based approaches have gained significant attention in dealing with computationally intensive analyses such as uncertainty quantification of composite laminates. However, high-fidelity ML model construction is computationally demanding for such high-dimensional problems due to the required large amount of high-fidelity training data. We propose to address this issue effectively through multi-fidelity ML based surrogates which can use a training dataset consisting of optimally distributed high- and low-fidelity simulations. For forming multi-fidelity surrogates of progressive damage in composite laminates, we combine low-fidelity finite element analysis data obtained using Matzenmiller damage model with Hasin failure criteria and high-fidelity finite element analysis data obtained using three-dimensional continuum damage mechanics based model with P Linde's failure criteria. It is shown that there is a significant computational advantage to using the multi-fidelity surrogate approach as compared to conventional single-fidelity surrogates. Such computational advantage through optimal data fusion without compromising accuracy becomes crucial for the subsequent data-driven uncertainty quantification and sensitivity analysis of composites involving thousands of realizations. Ply orientations come out to be the most sensitive parameters to matrix damage, fibre damage and reaction force in composite laminates. The degree of uncertainty in the output quantities depend on the input-level stochastic variations. For example, a combined stochastic variation of ±10% in material properties and ±10° in ply orientations lead to 1.85%, 16.98% and 11.24% coefficient of variation in the matrix damage, fibre damage and reaction force respectively. In general, the numerical results obtained based on the efficient data-driven approach strongly suggest that source-uncertainty of composites significantly influences the progressive damage evolution and global mechanical behaviour, leading to the realization of the importance of adopting an inclusive analysis framework considering such inevitable random variabilities.</p
On quantifying uncertainty in lightning strike damage of composite laminates: A hybrid stochastic framework of coupled transient thermal-electrical simulations
No full textLightning strike damage can severely affect the thermo-mechanical performance of composite laminates. It is essential to quantify the effect of lightning strikes considering the inevitable influence of material and geometric uncertainties for ensuring the operational safety of aircraft. This paper presents an efficient support vector machine (SVM)-based surrogate approach coupled with computationally intensive transient thermal-electrical finite element simulations to quantify the uncertainty in lightning strike damage. The uncertainty in epoxy matrix thermal damage and electrical responses of unprotected carbon/epoxy composite laminates is probabilistically quantified considering the stochasticity in temperature-dependent multi-physical material properties and ply orientations. Further, the SVM models are exploited for variance-based global sensitivity analysis to investigate the input parameters' relative influence on the lightning strike-induced damage behavior. Due to the adoption of a coupled SVM-based simulation approach here, it has become possible to carry out a comprehensive uncertainty quantification leading to complete probabilistic descriptions of the electrical and lightning damage parameters despite the requirement of performing a large number of computationally intensive function evaluations. The results reveal that source-uncertainty of the unprotected laminates significantly influences the epoxy matrix decomposition, electrical current density and electric potential, wherein longitudinal electrical conductivity is most sensitive to stochastic variations followed by other electrical, thermal and geometric parameters
Compile time aanalysis for hardware transactional memory architectures
No full textTransactional Memory is a parallel programming paradigm in which tasks are executed, in forms of transactions, concurrently by different resources in a system and resolve conflicts between them at run-time. Conflicts, caused by data dependencies, result in aborts and restarts of transactions, thus, degrading the performance of the system. In case these data dependencies are known at compile time, then the transactions can be scheduled in a way that conflicts are avoided, thereby, reducing the number of aborts and improving significantly the system’s performance. This thesis presents the Compiler insights to Transactional memory (CiT) tool, an architecture independent static analyzer for parallel programs, which detects all potential data dependencies between parallel sections of a program. It provides feedback about load-store instructions in a transaction, dependencies inside of a loop and branches, and severals warnings related to system calls which can affect the performance. The efficiency of the tool was tested on an application including different types of induced data dependencies, as well as several applications in the STAMP benchmark suit. In the first experiment, a 20% performance improvement was observed when the two versions of the application were executed on the TMFv2 HTM simulator.Circuits and SystemsMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Genesis and evolution of the sonnet (chahar-pare) composing in Iran
No full textAbstract Persian "Sonnets" (chahar-pare) or "continuous quatrains" are already mentioned briefly here and there but the emergence, evolution and the influence of the modern ottoman poetry on the inclination of Persian poets to this new poetic form have not been thoroughly discussed yet. The author of this paper, while studying the origin of this form of poetry by referring to its currency in French literature, seeks to answer the following questions: 1 â Did the Iranian poets compose sonnets under the influence of European and especially French literature? 2 â How much did the ottoman modern poetry influence the inclination of Iranian poets to this form? 3 âWhen did sonnet composing begin exactly and who first composed his poem in this form?   It seems that there is no doubt about the idea that this form of sonnets or continuous quatrains as a new form in Persian poetic was borrowed from the European and especially French literature, but it is disputable whether the Iranians received this form and its special rhyme scheme directly from Europeans or they got accustomed with it through an intermediary language?   From the viewpoint of the author these continuous quatrains were first considered by modern Turkish poets of Tanzimat and constitutional Revolution period such as Akif PaÅa (1316 AH), and later Ibrahim Åinasi (d. 1871 CE), Ziya PaÅaa (d. 1881 CE), Namik Kemal (d. 1888 CE) and the poets of the next generation such as Recaizade Ekrem Beik (d. 1914 CE) and Abdülhak Hamit Tarhan (d. 1937 CE) Tevfik Fikret (d. 1915 CE) who were familiar with french poetry and literature (Habib, 1340: 95) then this form entered Iranian literature via Turkish language and literature. On the one hand the distant priority of the Turkish modernist poets in using this form and on the other hand the familiarity of the first Iranian sonnet-composer poets such as Jaâfar Xameneâi, Lahuti and Taqi Rafâat with the modern ottoman poetry and literature confirms the correctness of this hypothesis. First sonnets and first iranian sonnet-composers   The researchers of the contemporary persian poem have generally considered the poem âFulfillment of the Covenantâ ( vafa be âahd) of Ab al-Qasem Lahuti, which is composed in 1908 CE/1327 AH, the first persian sonnet (cf. SHafiâi Kadkani, 1390: 423-425 SHams Langrudi, 65/1). However it is difficult to accept this opinion. Doubt about this view stems from this fact that there is no witness which shows that he was familiar with french literature and ottoman modern literature when composing this poem. The available evidences show that lahuti has composed his poem according to his iranian models of sonnet. In other words before Lahuti some other iranian poets such as Jaâfar Xameneâi who were familiar with french and modern ottoman literature have composed such sonnets and Lahuti has been accustomed with this poetic form via their poems. The sonnet which is published two years before âFulfillment of the Covenantâ by Lahuti in Azarbayejan newspaper at 15 rabiâ al-Äxar 1325 confirms this opinion (cf. Maqá¹£udi, 1356: 697). With regard to what Brown and Ariyan-pur (Brown, 1335: 317 Ariyan-pur, 1372: 454/2) have stated about Xameneâi and his poem and also considering the existing examples of his poetry one can infer that because of his familiarity with french language and also modern turkish literature he has had definitely more necessary literary and theoretical capabilities than Lahuti for composing sonnets, and he began to compose sonnets before Lahuti. So with regard to these evidences one can consider Jaâfar Xameneâi the first or one of the first iranian sonnet-composers during the Constitutional Revolution. The sonnet form in its historical trend has undergone changes in regard to the rhyme (in this paper five sorts of it are discussed). In the end one kind of it, in which the second and fourth hemistiches rhyme with each other, has gained popularity and acceptance. This form of poetry, because of its concomitance with a kind of romantic poetry, in the course of time has changed to the original form of the poems with the romantic theme
Boring Esfahan's North-South line: An assessment of the influence on the adjacent structures due to tunnelling underneath the Chahar Bagh Abbasi street in Esfahan, Iran
No full textCivil Engineering and Geoscience
Understanding school dropout among adolescents in a rural site of southern Zambia
No full textIncludes bibliographical references (p. 222-233).The study of school dropout in Zambia is still in its infancy. Apart from the countrywide annual surveys conducted by the Ministry of Education, no in-depth study on school dropout seems to have been conducted. These surveys have consistently indicated that school dropout is most common among rural adolescents. Thus, this study sought to have an in-depth understanding of the factors that influenced rural adolescents to drop out of school by drawing a purposive sample of 10 dropouts, 10 parents of the dropouts, five teachers from the school attended by the dropouts in a rural site of southern Zambia
Garden of memory : regeneration of a Persian garden. Case of Chahar-Bagh, Ishafan, Iran
No full textLAUREA MAGISTRALEIl motivo principale e l'ispirazione per lo sviluppo di questa tesi è il concetto di "Giardino Persiano" e la sensibilizzazione su questo tesoro piuttosto dimenticato. Il giardino persiano è una delle tipologie di progettazione del giardino in un'immagine di un recinto completo di abbellimento e piantumazione - curato e irrigato, che escludeva la natura selvaggia. In questo studio, l'autore mette in evidenza la storia, la disposizione, l'ascesa e la fine del giardino persiano per proporre in seguito una piattaforma per celebrare questo archetipo e invitare la società a riconnettersi con esso e trasmettere la conoscenza a riguardo alle giovani generazioni all'interno di un contemporaneo realizzazione di un giardino.
La comprensione della filosofia e della storia del giardino persiano ha incoraggiato un'indagine sulla sua connessione con la vita sociale in passato e ha portato a definire una serie di attività e interventi architettonici per ricordare alla comunità i loro valori architettonici perduti da tempo e per introdurli a i modi non materiali che hanno contribuito a salvare l'immagine del giardino persiano insieme alla sua forma fisica. E in ultima analisi, per coinvolgerli attivamente per salvaguardare la memoria del giardino persiano all'interno di una versione contemporanea di se stesso.
Questo studio è diviso in quattro temi principali: in primo luogo, la ricerca sulla Genesi e la fine dei giardini persiani, anche la sua storia attraverso la storia e diversi territori geografici. In secondo luogo, il caso di studio, Charbagh a Isfahan e i giardini ad esso adiacenti, dove possiamo assistere a uno dei migliori esempi di impegno pubblico con il paesaggio urbano in Iran. In terzo luogo, indagare altri metodi che hanno contribuito a preservare la memoria del giardino persiano negli ultimi 400 anni attraverso arti e mestieri e, infine, una proposta di design per rigenerare e rivitalizzare un giardino persiano in rovina in un giardino pubblico contemporaneo per fornire un'esposizione a coloro che preservano le arti e incoraggiare l'impegno sociale per il recupero di questo patrimonio architettonico per le generazioni future.The main motive and inspiration for developing this thesis is the concept of “Persian Garden” and raising awareness about this rather forgotten treasure. Persian garden is one of the typologies of garden design in a picture of an enclosure complete with landscaping and planting – tended and watered, which excluded the wilderness. In this study, the author highlights the history, layout, the rise and demise of the Persian garden to later propose a platform for celebrating this archetype and inviting the society to reconnect with it and pass on the knowledge about it to younger generations within a contemporary embodiment of a garden.
Understanding the philosophy and history of the Persian garden encouraged an investigation in its connection with the social life in the past and has led to defining a series of activities and architectural interventions to remind the community of their long-lost architectural values and to introduce them to the non-material ways which helped to save the image of the Persian garden along with its physical shape. And ultimately to engage them actively for safeguarding the Persian garden’s memory within a contemporary version of itself.
This study is divided into four main themes: First, research about the Genesis and demise of the Persian gardens, also its story throughout the history and different geographical territories. Second, the case study, Charbagh in Isfahan and the gardens attached to it where we can witness one of the best examples of public engagement with urban landscaping in Iran. Third, to investigate other methods that helped to preserve the memory of Persian garden in the past 400 years through arts and crafts and ultimately a design proposal for regenerating and revitalizing a ruined Persian garden into a contemporary public garden to provide a display for those preserving arts and encouraging social engagement for reclaiming this architectural heritage for future generations
The Persian Mirrors for Princes Written in the Saljuq Period: the Book Series
No full textThe article begins with a concise description of the genre, period, and classical Persian texts
covered by the announced book series of three books: 1) Amir Mu‘izzi Nishapuri. The Siyasatnama/
Siyar al-muluk: A Fabrication Ascribed to Nizam al-Mulk — this text is still being published
and reprinted under the authorship of Nizam al-Mulk, an outstanding Prime Minister
of the Saljuqids. However, the results of historical, codicological and textual analyzes show that
the text was compiled by Muhammad Mu‘izzi Nishapuri, the head of poets department under
the Saljuqid rulers Malik-shah and his son Sanjar, and then attributed by him to the dead
Nizam al-Mulk with completely definite goals; 2) The Writings of Imam al-Ghazali is a book
that includes six texts. Three of them are authentic: a student manual entitled by the author
as the Zad-i Akhirat (Provisions for the Hereafter); an authentic part of al-Ghazali’s epistle to
Sultan Sanjar entitled the Nasihat al-muluk (Counsel for Kings) and a medieval collection of
letters addressed by the Imam to various recipients and entitled the Fada’il al-anam min rasa’il
Hujjat al-Islam (The Virtues of People [drawn] from the Epistles of the Proof of Islam). The
remaining three texts are fabrications; 3) Kay Kawus b. Iskandar b. Qabus. Qabus-nama (The
Book of Qabus) and Nizami ‘Aruzi Samarqandi. Chahar maqala/Majma‘ al-nawadir (Four
Discourses/The Miscellany of rarities) is a book that includes two authentic texts. After this,
the article touches upon the problem of existence of literary and physical forgeries in medieval
Islamic literature, their categories and methods of their identification
Quasi-states and autonomies of northeast China as the instrument of ensuring economic stability of Japan (Based on the materials of the American mass media the 1930s)
No full text© 2016, International Journal of Economics and Financial Issues. All rights reserved.In article based on the materials of the American mass media the author constructs the autonomy process of Northeast China during the period preceding the Japanese-Chinese war of 1937-1945. The Japanese policy main stages on the creation of the semi-autonomous territories, the reasons interfering this plan implementation in whole, which it should be noted major confrontation in the Japan Cabinet, when the moderate politicians group supporting peaceful resolution of contradictions was headed by the Minister of Foreign Affairs, and the militarists group - The Minister of Army and the Command of Kwantung army supporting him, are established. Concluded that, first, Japan, being afraid of the negative international reaction, tried to solve the problem not military, but diplomatic and methods, and secondly, the Japanese policy on the continent was inconsistent and it was expressed in impossibility at an initial stage to achieve the status of the autonomy for five Chinese provinces and to declare the Autonomous Council of East Hebei, which under control territory covered only small part of one of the Chinese provinces. Creation of the Hopei-Chahar Political Council allowed both the Japanese, and the Chinese sides “to save face,” and the military campaign, which began in the summer of 1937, finished the transition process of the China northeast provinces under the Japan control through the creation of the quasi-state the Chinese Republic by the end of 1937. Invaders received in the order such tools as the circulation of the precious metals and drugs, finance, oil monopoly, customs points, etc., thereby having provided complete control over the region economy
