154 research outputs found
Study of Atmospheric Ice Accretion on Wind Turbine Blades
No full textThis Ph.D. work concerns itself with the atmospheric ice accretion on wind turbine blades. The wind energy has been at the forefront of the renewable energy generation for the last several decades, with the amount and capacity of installed wind turbines steadily increasing. The cold climate (CC) regions around the world like Finland, Germany, Slovak Republic, Norway, Czech Republic, UK, Sweden, Bulgaria, Hungary, Russia, Canada and USA have great potential of wind resources. Estimated wind energy capacity in CC is about 60 GW. [1] However, due to this steady increase in the installed power capacity, more and more turbines have to be placed in regions with harsh geographical conditions, such as arctic regions, in which the temperatures below the normal operating conditions can result in the atmospheric icing to accumulate on the wind turbines particularly along blades. The icing on wind turbines blades leads to negative effects, such as, decreased lift and increased drag, increased mechanical wear and fatigue, possibility of ice throw, which negatively impacts the personnel and life in the area, aeroacoustics noise, generated from iced wind turbines, etc. The icing on wind turbines occurs when super-cooled water droplets collide with the wind turbine structure in the passing clouds (in-cloud icing) and/or freezing rain or drizzle freezes on the exposed wind turbine structure (precipitation icing). Within the scope of this Ph.D. work, the focus is made on the in-cloud icing on the wind turbines.
While there are existing standards and guidelines for the design and operation of wind turbines in normal, temperate climates, for example, the International Electrotechnical Commission standards for offshore turbines, including IEC 61400-1, IEC 61400-3, and the standards for the processes of type certification, which are commonly used to certify turbines in Europe (IEC 2001, 2005, 2010a, 2010b). However, no such definite framework exists for the design, operation and maintenance of wind turbines in cold, ice-prone regions. Thus, the better understanding of the atmospheric ice accretions on wind turbines and their negative effects, such as losses in power production due to the icing is a critical objective for the successful operation of the wind power in CC, ice-prone regions.
For the purposes of better understanding of the icing physics, involved in the icing on the wind turbines, the analytical, numerical and the experimental tools are used in this project. The analytical modelling is done by using the ISO 12494 standard: “Atmospheric Icing on Structures” with some modifications done to it, in order to permit analytical modelling of ice accretion on wind turbines, using basic circular cylinders from ISO 12494 as a reference collector. The numerical modelling scheme employs the usage of modern Computational Fluid Dynamics (CFD) tools such an ANSYS FENSAP-ICE and ANSYSFluent which are used to study the ice accretion process on airfoils and blades. These CFD tools allow for the study of icing physics in greater detail than the analytical model allows, for example by simulating the resultant ice shapes and their impact on the aerodynamic performance of the iced airfoils, when compared to the clean ones. The experimental methodology of this work encompasses usage of the icing tunnel experimental data, for the validation purposes of the numerical modelling, and the field measurements data from the Supervisory Control and Data Acquisition (SCADA) system, taken from a wind park operating in the CC region. The main reason for this is to perform a wind resource assessment study in the CC, ice prone region, in addition to the use of supplementary statistical and numerical modelling tools, such as T19IceLossMethod and WindSim.
The results of atmospheric ice accretion on the wind turbine blades show that the aerodynamic performance changes mainly due to difference in droplet freezing fraction as due to low freezing fraction for the glaze ice conditions, higher amount of the water runback and the aerodynamic heat flux along leading edge is observed which results in the complex horn type ice shapes. The phenomenon of the flow interaction in the third dimension results in the velocity magnitudes being reduced in the 3D simulations, when compared to the 2D simulations. This, in turn, affects the ice accretion process, as the higher velocity magnitudes in the 2D cases result in the higher droplet inertia, collision efficiencies and the maximum impingement angles, which results in more ice mass accreted along the leading edge with the thicker and larger ice shapes present in the 2D simulations.
The results of wind resource assessment of ice prone region show that power production for wind parks can be lower in CC regions when compared to identical wind parks/turbines situated in warmer temperate climates. However, the icing-related issues and the associated power losses need to be solved. It shows that duration and timing of the icing event is different for different wind turbines in a wind park, which clearly indicates that the icing events depend upon the meteorological conditions, airflow behaviour and also the location of the wind turbine. Even in the same wind park, it is not given that ice will accrete on all wind turbines under the same instrumental and on-site conditions. The wind park layout and changes in flow behaviour affects the occurrence of ice accretion, despite the favourable conditions for icing events being present.
Two main topics have been considered in this Ph.D. work: the atmospheric ice accretion on wind turbine blade and the performance losses associated with it; and the wind resource assessment in the ice prone region. Both of these topics are of major importance for the wind industry in CC, ice prone regions, due to the challenges present in the form of potential icing conditions and events and the resultant energy production losses. The results obtained in this Ph.D. thesis can be summarized, in short, as follows: power losses due to icing on wind turbines occur not because of a single reason, but through a combination of effects that need to be taken into account carefully during the wind park design process. These effects include the blade profile surface roughness and heat fluxes, which change significantly during the ice accretion process, and, in turn, affect the airflow and droplet behaviour. The change in the accreted ice shape affects both the airflow behaviour and the aerodynamics performance. With the increase in the atmospheric temperature, the type of accreted ice also changes from dry rime to wet glaze ice, which leads to a change in the ice density and also the accreted ice shapes on the wind turbine blades. Generally, wet ice growth is more damaging for wind turbine operations in icing conditions as compared to dry rime ice growth, due to higher degradation of aerodynamic characteristics under the glaze icing conditions.
The results obtained in this work also provide the need and motivation for improving the understanding about icing effects on the wind turbine blades and the improvement of the existing (or creating new) anti-/de-icing technologies
Fc-gamma receptor polymorphisms, cetuximab therapy, and survival in the NCIC CTG CO.17 trial of colorectal cancer
No full textAbstract not availableGeoffrey Liu, Dongsheng Tu, Marcia Lewis, Dangxiao Cheng, Leslie A. Sullivan, Zhuo Chen, Eric Morgen, John Simes, Timothy J. Price, Niall C. Tebbutt, Jeremy D. Shapiro, G. Mark Jeffery, J. Daniel Mellor, Thomas Mikeska, Shakeel Virk, Lois E. Shepherd, Derek J. Jonker, Christopher J. O'Callaghan, John R. Zalcberg, Christos S. Karapetis, and Alexander Dobrovi
LITERARY THEMES IN ESSAYS BY TOMO VIRK
No full textV magistrski nalogi je obravnavana esejistika Toma Virka. Prvi del naloge povzema teorijo eseja in hkrati razčlenjuje pojme, ki so pomembni za nadaljnjo analizo. Drugi del pa je posvečen interpretaciji in tematski delitvi esejistike Toma Virka. Med najbolj opazne tematske kroge novejše slovenske esejistike, kamor spada tudi esejistika Toma Virka, sodijo: književna vprašanja, eseji na temo kulture in umetnosti, eseji, ki obravnavajo bivanjsko problematiko itd.
Številni avtorji sodobne esejistike, med njimi tudi Tomo Virk, se obračajo na literarno ustvarjanje slovenskih pesnikov in pisateljev, ki so s svojim delom zaznamovali slovenski prostor. Tomo Virk spada med tiste pisce, ki jih zanimajo predvsem avtorji v slovenskem literarnem kanonu. V svoje razmišljanje vključujejo teoretske predpostavke in zaključke, do katerih so prišli priznani slovenski ali tuji literarni zgodovinarji ter kritiki. Svoj predmet obravnavajo sistematično, pregledno, v esejistično pisanje se vriva strokovna terminologija, notranjeslogovno pa so usmerjeni k literarni kritiki in zgodovini.
Tomo Virk književna dela v izbranih esejih tolmači, primerja, ocenjuje ter krati poskuša prikazati svoj osebni vidik, ki je velikokrat drugačen od že uveljavljenih interpretacij. Delo poskuša predstaviti natančno in objektivno, v nekaterih esejih pa želi poudariti subjektivni vidik, in sicer takrat ko želi izpostaviti vprašanja, ki imajo za avtorja osebni pomen.
Za Virkove eseje so značilne osebne, bivanjske teme, in sicer takrat ko se avtor postavlja v razmerje do obravnavane problematike, o njej premišljuje s subjektivnega vidika in sebe postavlja v širši kontekst bivanjskih vprašanj. V ospredju Virkovih esejev pa je tudi tematika ustvarjanja slovenskih avtorjev.In this master\u27s thesis the essay writing of Tomo Virk is being discussed. The first part of the work summarizes the theory of the essay and at the same time analyses the notions which are important for a further analysis. The second part, however, is dedicated to an interpretation and a thematic division of Tomo Virk’s essay writing. The most noticeable thematic circles of contemporary Slovene essay writing, including Tomo Virk’s essay writing, are: literature questions, essays on culture and art, essays on existentialism, etc.
Numerous authors of contemporary essay writing, including Tomo Virk, appeal to literary creativeness of Slovene poets and writers who have marked the Slovene area with their work. Tomo Virk belongs to a group of writers who are first of all interested in authors of Slovene literary standard. In their deliberation they include the theoretical suppositions and conclusions reached by acknowledged Slovene and foreign literary historians and critics. They discuss their subject matter systematically and clearly. The professional terminology is put in their essay writing and their internal way of writing is aimed at literary criticism and history.
Tomo Virk interprets, compares and reviews the literary works in selected essays and at the same time he tries to present his personal point of view which is often different from already established interpretations. He tries to present the work accurately and objectively and in some essays, when he wants to set out the questions that have a personal meaning for the author, he emphasizes the subjective viewpoint.
The personal and existential themes are characteristic of Virk’s essays when he relates to the discussed issue, thinking about it from a subjective point of view and putting himself in a wider context of existential questions. The themes of creativeness of Slovene authors are also in the forefront of Virk’s essays
Feasibility Study of Hydrogen Production from Wind Energy in Narvik
No full textThe use of renewable energy sources is gaining momentum globally as possible replacements for fossil fuels which have proven to be serial contributors to global warming. Hydrogen is one such environmentally friendly fuel with zero carbon emission proven to be reliable for use in the transport sector. Since hydrogen is an energy carrier, its mode of production has for a long time relied on high carbon emission fuels that negate its authority as emission-free fuel.
Therefore, this study investigates a green hydrogen production method based on water electrolysis using electrical energy from wind power. The project entails a detailed wind resource assessment around Narvik region through historical meteorological data analysis, and CFD simulations using Windographer and WindSim software programs to ascertain the viability of the wind power potential of the area. Thereafter, the project establishes suitable location(s) for appropriate wind turbine siting to generate optimal net AEP for use in the electrolysers. Subsequently, a detailed analytical calculation is conducted on the possible amount of hydrogen that can be produced when a water electrolyser system is installed at the Djupvik site based on the net AEP values obtained. Finally, there is determination of the probable cost estimates for such a venture
Wind resource assessment in cold climate regions
No full textCold regions have good potential for wind energy development, but icing on wind turbines is recognize as a hindrance limiting the wind energy production in ice prone cold regions. This master thesis work is linked with Wind-CoE project of Arctic Technology Research Team and is aimed on better understanding of wind resource assessment in cold regions. Three years (2013-15) field SCADA data from Nygårdsfjellet wind park located in an ice prone region near Narvik is used for this study. This work encompass both analytical and numerical analysis to better estimate the annual energy production (AEP) and study of wind flow physics over complex terrain. Computational fluid dynamics based numerical techniques has been used. A good agreement is found between analytical and numerical results
Book Review by Hardev Singh Virk - Science and Sikhism : Conflict and Coherence (Book Author: Dr. D. P. Singh)
No full textDr. D P Singh is a prolific writer in many areas of Science, Religion and Literature. He came into my contact almost four decades back when he started his teaching career in Shivalik College, Nangal. In my note published on the blurb of this book, I wrote: " I expect his forthcoming book" Science and Sikhism : Conflict or Coherence" will prove to be a landmark in the area of Science-Religion Dialogue, with special reference to Sikh religion". I can declare without an iota of doubt that DP has more than justified my claim on his book.
The title of the book is followed by a note "Anthology of Essays on various Concepts in Sri Guru Granth Sahib" which may be considered as a sub-title to the book. Nearly a dozen titles have appeared in the global market projecting scientific vision of Sikh Gurus enshrined in the holy pages of Sri Guru Granth Sahib but there is no rival to this volume in my view till date. The coverage of topics by DP Singh is very exhaustive. All Chapters of the book open with an appropriate quotation from Science, Religion or Literature.
The book is dedicated to "Inquisitive Human Spirit" which is displayed by the author throughout this volume. The dedication is followed by the famous quote of Freeman Dyson, the renowned Physicist: "Science and religion are two windows that people look through, trying to understand the big universe outside, trying to understand why we are here. The two windows give different views, but they look out at the same universe. Both views are one-sided, neither is complete. Both leave out essential features of the real world. And both are worthy of respect". Surprisingly, Dyson is contradicted as SGGS and Science are compatible in their world-view and there is no conflict but harmony between these two
windows
The literary work and it\u27s (implied) author
No full textVlogo avtorja v literarnem delu najprej preverimo preko kontroverznega koncepta implicitni avtor, pri katerem najprej pokažemo njegovo genezo. Magistrsko delo vsebuje izvirno sintezo rekonceptualizacij implicitnega avtorja, ki je vsebinsko razvrščena glede na osnovne kazalnike: povezava z empiričnim avtorjem in antropomorfnost ter trije vidiki opredeljevanja: vidik literarne produkcije, vidik literarne recepcije, vidik literarnega dela kot fenomena. Ta razdelitev je nastala preko vsebinske analize večine sodobnih in izbranih ključnih starejših razprav na to temo. Sinteza omogoča, da razkrijemo osrednje anomalije teorij, med temi problematično težnjo k simultanemu definiranju vloge avtorja v literarnem delu za vse procese, ki so povezani s književnostjo, hkrati. Posebej izpostavimo tiste teorije, ki koncept opredeljujejo z vidika literarnega bralca: gre za bralčev konstrukt, ki nastane preko znotrajbesedilnih lastnosti in poznavanja zunajbesedilnih dejstev o empiričnem avtorju ter širših kontekstov nastanka literarnega dela, pa tudi kasnejše recepcije literarnega dela. Tako opredeljen koncept je temelj za razpravo o vlogi dejstev o empiričnem avtorju v šolski praksi, pri čemer temeljimo na pouku slovenščine na gimnazijah. Za integriranje znanja o zunajliterarnih kontekstih v znanje o samem literarnem delu je ključno kognitivno branje. Omogoča namreč povezovanje literarnega dela v širše (kulturno-, duhovnozgodovinske in druge) kontekste. Kognitivna naratologija opaža, da bralci besedilno strukturo pripišejo določenemu delovalniku, empirična raziskava literarnega branja z vidika predstav o literarnem avtorju pa kaže, da emotivnih spodbud pri bralcu ne sproža le vsebina literarnega dela, pač pa tudi poznavanje dejstev o implicitnem avtorju. Na temelju sistemske književnodidaktične paradigme z elementi recepcijske zagovarjamo, da temelji spoznavanje avtorja na teh osnovah. Učenčevo zanje o literarnem avtorju ne sme biti ločeno od drugih kontekstualnih elementov produkcije in kasnejše recepcije književnosti. Med temi elementi književnega znanja naj bodo vzročno-posledične in logične povezave, ki jih zagotavlja znanje z(a) razumevanje(m). Dosežemo ga s poukom, kjer je na prvem mestu komunikacija s književnostjo in v katerem usvajanje znanja poteka dejavno % problemsko. Dokument Evropski literarni okvir za učitelje v srednjih šolah (2012) pri spoznavanju sistema književnosti izhaja iz učenčevega zanimanja za literarnega avtorja. Literarna zmožnost, ki jo določa, je tesno speta s književnim znanjem, ki empiričnega avtorja locira v kompleks okoliščin, ki določajo produkcijo in kasnejšo recepcijo literarnega dela. Višje stopnje literarne zmožnosti terjajo problemske obravnave zunajbesedilnih dejstev o literarnem delu, v tesni navezavi s slednjim.We check the role of the author in a literary work through the controversial concept of the implied author, in which we first check the establishment of it. This master\u27s thesis contains an original synthesis of the reconceptualizations of the implied author, which is substantially classified in terms of basic indicators: the link between the empirical author and the personification and three other defining aspects: the aspect of literary production, the aspect of literary reception and the aspect of the literary work as a phenomenon. This division was created through a content analysis of the most modern and even of some older discussions on this topic. The synthesis allows to reveal the abnormalities in the central theories, one of these is the troublesome tendency to define the role of the author in a literary work simultaneously for all the processes that are associated with literature. We particularly expose the theories that are determined in terms of the literary reader: the implied author is a construct of the reader that occurs via intratextual characteristics and knowledge of the extratextual empirical facts about the author and the broader contexts of the emergence of a literary work, as well as the subsequent reception of the literary work. Thus defined concept is the basis for a discussion on the role of the empirical facts about the author in the school practice at the Slovene grammar schools. To integrate the knowledge of the contexts in the knowledge about the literary work itself is a key for cognitive reading. It enables the integration of the literary works in the broader (cultural and historical) contexts. Cognitive narratology notes that the readers of the text attribute the structure to a factor, the empirical study of literary reading in terms of performances of literary author shows that emotional stimulus for the reader not only raises the content of a literary work, but also the knowledge of the facts about the implied author. Based on the systemic paradigm of literature didactics the reception of literature advocates to meet the author. Pupils\u27 knowledge of the literary author can not be separated from other contextual elements of the production and the subsequent reception of literature. These factors include literary knowledge to be causally and logically connected that provides the learning for understanding and learning by understanding. This is achieved by the classes where the first communication with literature and the acquisition of knowledge take place actively. The Literary framework for teachers in secondary education (2012) stems from a student\u27s interest in literary author to get to know the system of literature. It provides a literary ability, which is closely coupled with literary knowledge that the empirical author locates in the complex circumstances that determine the production and subsequent reception of a literary work. Higher levels of literary abilities for solving a problem require the treatment of the extratextual facts about the literary work that is closely linked to the latter
A Path to Truthful Living (A Way of Life based on Guru Nanak's Panj Khand of Jap Hymns) AUTHOR: Dr. D. P. Singh; REVIEWER: Dr. H.S. Virk
No full textDr. D.P. Singh is a brilliant Physicist by training, a practicing Gursikh, and a dedicated researcher of Science and Sikhism. I was wondering how a physicist would justify his new venture as the Director of the Centre for Understanding Sikhism? After reading his half a dozen books on the Sikh religion, I am fully satisfied and testify that DP Singh is one of the best Sikh theologians in the Sikh world. He has not only imbibed the spirit of Sikhi based on the core principles of the Sikh scripture, Sri Guru Granth Sahib, but also interpreted its message for Sikhs in general and Sikh Youth in particular using scientific methodology. Dr. Bhai Harbans Lal, a celebrated Scientist and a Theologian himself, mentions briefly in the introduction that DP Singh deems it necessary to give a background of the contents of this book before the discussion of the main theme. He presents the main topics under discussion by DP Singh and elaborates on the social and cultural background in which Guru Nanak launched his revolutionary mission to reform society, which was riven by the decadent religiosity of his times. The author explains the purpose of writing “A Path to Truthful Living” in his Foreword: “This book is not a mere intellectual exercise or a scholarly treatise. It is a heartfelt exploration of Guru Nanak’s timeless teachings, presented in a way that seeks to touch the very core of our being”. The author further elaborates the central theme of his book: “The Panj Khands are five distinct domains of existence described by Guru Nanak in his profound compositions. Through the exploration of the Dharam Khand (Domain of Righteousness), Gyan Khand (Domain of Knowledge), Saram Khand (Domain of Endeavour), Karam Khand (Domain of Grace), and Sach Khand (Domain of Truth), we are encouraged to reflect on the nature of our thoughts, actions, and beliefs”
Book Review: "Mystic Echoes: Stories Rooted in Sikh Spiritual Realms" (Book Author: Dr. Devinder Pal Singh; Book Reviewer: Prof. Hardev Singh Virk)
No full textDr. Devinder Pal (DP) Singh joined the Physics Department in 1983 as an Ad-hoc Lecturer to teach Physics and complete his doctorate degree in Physics (Acoustics). I found him as a dedicated teacher and researcher. Upon moving to Canada as an immigrant, he initiated a new venture, the “Center for Understanding Sikhism”. A similar organization, the “Institute for Understanding Sikhism,” was established in 1999 by Dr. D. S. Chahal in Montreal. I was perplexed as to why a hardcore physicist was meddling in Sikhism. My curiosity was satisfied after reviewing his book, “Science and Sikhism: Conflict or Coherence.” I started rating him as one of the greatest exponents of Sikhism (Sikhi) in the modern age.
The Foreword “A Sacred Mirror: Seeing Ourselves Through Sikh Narratives” is by Bhai Harbans Lal, Ph.D., D. Litt (Hons). Bhai Lal appreciates the technique used by D. P. Singh: “It brings the living essence of Gurbani into our day-to-day existence. These are not abstract theological exercises, nor are they simply nostalgic tales of rural life. Instead, they are powerful spiritual parables, immersive narratives that reveal how the universal truths embedded in Sikh teachings manifest in the hearts, struggles, and transformations of everyday people”.
The author introduces his UNIQUE work in the Preface “Bridging the Temporal and the Timeless” as follows: “The stories in Mystic Echoes: Stories Rooted in Sikh Spiritual Realms emerge from the convergence of profound spiritual reflection, lived experience, and the enduring resonance of Sikh philosophy. They are not merely works of fiction, but narrative expressions of spiritual truths rooted in the teachings of the Sikh Gurus”. Further, D. P. Singh explains the relevance and importance of chosen topics: “Each story in Mystic Echoes is an attempt to explore a specific spiritual theme from within the Sikh tradition: Naam (Divine Name), Hukam (Divine Order), Haumai (Ego), Maya (Worldly Illusion), Raza (Divine Will), Sunn (Primal Void), Sahaj (Equilibrium), Bhaau and Bhae (Devotional Love and Reverent Fear), Nadar (Grace), Wismad (Wondrous Bliss), Anhad Naad (Unstruck Melody), Chautha Pad (Fourth State), Dasam Duar (Tenth Gate), Panj Tat (Five classical elements), and Daya (Compassion) among others
Ice Accretion on Fixed-Wing Unmanned Aerial Vehicle—A Review Study
No full textIce accretion on commercial aircraft operating at high Reynolds numbers has been extensively studied in the literature, but a direct transformation of these results to an Unmanned Aerial Vehicle (UAV) operating at low Reynolds numbers is not straightforward. Changes in Reynolds number have a significant impact on the ice accretion physics. Previously, only a few researchers worked in this area, but it is now gaining more attention due to the increasing applications of UAVs in the modern world. As a result, an attempt is made to review existing scientific knowledge and identify the knowledge gaps in this field of research. Ice accretion can deteriorate the aerodynamic performance, structural integrity, and aircraft stability, necessitating optimal ice mitigation techniques. This paper provides a comprehensive review of ice accretion on fixed-wing UAVs. It includes various methodologies for studying and comprehending the physics of ice accretion on UAVs. The impact of various environmental and geometric factors on ice accretion physics is reviewed, and knowledge gaps are identified. The pros and cons of various ice detection and mitigation techniques developed for UAVs are also discussed
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