575 research outputs found
Numerical Analysis of Damage Iinitiation and Development in Bends of Steel Pipelines
No full textGasses and fluids are transported via an extensive infrastructure of steel pipelines. In the design of pipeline systems the use of elbows (pipe bends) is important because their flexibility makes them able to sustain significant deformations. These bends can be subjected to permanent deformations due to various load combinations which can lead to progressive material damage. There are three stages commonly observed in ductile damage: void nucleation, growth and coalescence. When subjected to varying bending loads low cycle fatigue damage may occur. Within this research project Finite Element Analysis is used to simulate the response of pipeline bends. Two element types are implemented to model a pipe bend, the classical shell element and an efficient tube element (pipe elbow element), respectively. To predict the structural response when subjected to monotonic loading a damage model is implemented for both elements. When subjected to cyclic loading three phases can be identified. During the first few cycles the permanent deformation increases rapidly. After some cycles, the rate of permanent deformation stabilizes until the point of response degradation. In order to capture this response a new material model, based upon the afore mentioned model, is proposed. Experiments have indicated that this model is well suited to determine the point of material failure.Structural MechanicsCivil Engineering and Geoscience
Policy options in a worst case climate change world
No full textClimate policy, Geoengineering, Governance, Extreme climate change, Mitigation,
Applications of Relations and Graphs to Coalition Formation
No full textA stable government is by definition not dominated by any other government. However, it may happen that all governments are dominated. In graph-theoretic terms this means that the dominance graph does not possess a source. In this paper we are able to deal with this case by a clever combination of notions from different fields, such as relational algebra, graph theory, social choice and bargaining theory, and by using the computer support system RelView for computing solutions and visualizing the results. Using relational algorithms, in such a case we break all cycles in each initial strongly connected component by removing the vertices in an appropriate minimum feedback vertex set. So, we can choose an un-dominated government. To achieve unique solutions, we additionally apply social choice rules. The main parts of our procedure can be executed using the RelView tool. Its sophisticated implementation of relations allows to deal with graph sizes that are sufficient for practical applications of coalition formation.Graph Theory, RELVIEW, Relational Algebra, Dominance, Stable Government
Novitates burseracearum
No full textThis paper contains the diagnoses in Latin of a new genus, new sections of some genera, several new species and a number of new varieties which will be dealt with by the author in English in a publication entitled: “A monograph of the genus Protium and some allied genera (Burseraceae)”, to be published in Rec. Trav. bot. néerl. XXXIX, p. 211 (1942) and in Meded. bot. Mus. en Herb. Utrecht 90 (1942).
Protium BURM.f. sectio Eu-Protium SWART n. sect
From trauma to well-being: how music and trauma can transform us
No full textTraumatic events can have a profound influence on the way musicians experience
“musicing” as well as on their actual performance. An interpretative phenomenological
analysis of two case histories is presented here – one being that of a professional singer
whose family members were brutally murdered, and the other of a conductor whose
mentor committed suicide and who was paralysed for three months after a serious motor
vehicle accident. Before turning the focus to the two musicians, issues pertaining to the
subject of trauma are highlighted and the author “brackets out” her own experiences with
particular reference to work as repétiteur for the opera Winnie and postgraduate piano
studies in Warsaw. For the two case study participants, healing comprised a journey
consisting of various phases in which music played an integral role. Traumatic influence
was seen to have a discernible impact on expression of emotion in music, memory for
music, career choices and interpersonal relationships. It was through music that they reestablished
their connection to self and others, and, after a period of struggling with
emotional expression, experienced a deepening of affect. For the conductor, drumming
played an essential role in recovering lost motor function and memory. Counselling
formed the other pillar in their recovery process, and for the conductor this also entailed
a journey leading to spiritual growth. The participants offered advice to others. Both
these case histories provide striking examples of how musicing can first suffer in the wake
of experiencing overwhelming traumatic events, yet later prove to be instrumental in
restoring well-being and bringing about transformation.https://doi.org/10.4102/td.v10i2.10
Volatility bursts and order book dynamics
No full textTitle: Volatility bursts and order book dynamics Author: Jana Plačková Department: Department of Probability and Mathematical Statistics Supervisor: Dr. Jan M. Swart Supervisor's e-mail address: [email protected] Abstract: The presented paper studies the dynamics of supply and demand through the electronic order book. We describe and define the basic rules of the order book and its dynamics. We also define limit and market orders and describe the differences between them and how they influenced the evolution of ask, bid price and spread. Next part of the paper is dedicated to the de- scription and definition of volatility and its basic models. The brief overview about volatility clustering and its modeling by economists and physicists can be found in the following part. In the last part we introduce a simple model of order book in which we observe ask, bid price and spread. Then we study the empirical distribution of spread and try to find its probability distribu- tion. The volatility clustering is then observed through the relative returns of spread. In the last part we introduce some possible improvement of the model. Keywords: volatility clustering, order book, limit orders, market orders
Protes in Suid-Afrika : kommentaar van prominente swart leiers op die Naturellen Grond Wet, 1913-1936
No full textHierdie artikel ondersoek 'n aspek van die nadraai van die Naturellen Grond Wet van 1913, naamlik die kommentaar van swart Suid-Afrikaanse leiers op die Wet en die gevolge daarvan van 1913 tot 1936. Die artikel beklemtoon die deurlopende woede van geleerde swart Suid-Afrikaners teenoor die Grond Wet. Die outeur dui verder aan dat swart leiers talle geleenthede gehad het om hulle menings oor die politiese en ekonomiese lewe in Suid- Afrika te lug en teen regeringsbeleid wat toenemend diskriminerend geraak het, te protesteer. Hierdie geleenthede het die skryf van insette vir swart koerante, toesprake by byeenkomste van swart organisasies byvoorbeeld die African National Congress (ANC), ontmoetings met witmense (beide individue uit die privaat sektor en staatsamptenare) by konferensies, en getuienis voor kommissies of parlementêre komitees ingesluit. Vir prominente swart Suid-Afrikaners het grondsake tot in die vroeë 1930's van die grootste belang gebly, en hulle bitterheid teenoor en veroordeling van die Naturellen Grond Wet het nie afgeneem nie. As gevolg van hulle houding, het geleerde swartes 'n klousule in dié wet, wat die staat toegelaat het om nuwe aankope van grond deur swartes buite reservate goed te keur, geïgnoreer. Verder het die swart leiers nie in die openbaar erken dat duisende swart Suid-Afrikaners by hierdie klousule gebaat het, deur na 1913 plase en persele aan te koop nie.ENGLISH:This article examines one aspect of the aftermath of the Natives Land Act of 1913, namely the commentary of black South African leaders about the Act and its impact from 1913 to 1936. The article emphasises the continuing anger of educated Africans towards the Land Act. The author also demonstrates that black leaders had many opportunities to discuss their opinions about political and economic life in South Africa and to protest against government policies which were increasingly discriminatory. These opportunities included writing for black newspapers, speaking to black organisations such as the ANC, meeting with whites (private individuals or government officials) at conferences, and testifying before commissions or parliamentary committees. To prominent Africans, the land issue continued to be very important into the early 1930s, and their bitterness towards and denunciation of the Land Act did not diminish. Because of their attitudes, educated Africans ignored a clause in the Natives Land Act which allowed the government to approve new purchases by Africans of land outside the reserves. In addition, black leaders failed to admit that thousands of Africans benefited from this exception clause in the Land Act by purchasing farms and lots after 1913.http://www.journals.co.za/ej/ejour_hist.htm
Mistieke klankwêrelde in Stefans Grové se musiek met spesifieke verwysing na sy Towermusiek vir klavier
No full textStefans Grové’s compositional ideas often come to him in dreams. This article explores the
processes inherent in the creation, re-creation by the performer, and appreciation of Grové’s
unique soundscapes, where the silences between the notes and the overtones are often as important
as the dissonances – which he describes as “colourful harmonies” – themselves.
Grové’s music is often regarded as relatively inaccessible and elusive. This article explores
how it can be better understood if the listener can develop the ability to appreciate its programmatic
nature, to draw on strong visual imagination when “translating” sound into images, and to
approach his music with openness to non-traditional structures and harmonies. Only by these
means can access be gained to the richness of the mystical soundscapes and musical imagery.
Primarily an autodidact, the 90-year-old Grové underwent a gradual stylistic transformation
during his career; his oeuvre ranged from music rooted in the neo-classical, impressionist and
expressionist styles of the Western tradition, to the predominantly African inspiration of the post-
1984 period. The transitions between these periods are not sharply demarcated but rather constitute
a gradual development. Neither is his African-inspired style exclusive of the other styles, as is
evident in such recent works as 8 Lieder nach Texten von Conrad Meyer for soprano, flute and piano (2007) and Haunting Music (2010). The latter, a work for solo piano, has strong similarities
to Gaspard de la nuit by Maurice Ravel. Both works belong to the impressionist style, both are
programmatic works and both contain strong mystical elements. Fascinated by the supernatural,
Grové chose a fantastical programme for this work, which consists of three separate pieces,
namely Strange valley of the mists, Wandering through an enchanted forest and Hobgoblin at
midnight. The work by Maurice Ravel, in turn, is based on three phantasmagoric poems by
Aloysius Bertrand, namely Ondine, Le Gibet and Scarbo, which deal respectively with a water
nymph, a man on the gallows, and an evil dwarf. Grové briefly alluded to drawing inspiration
from Ravel but later denied this – an argument is made for musical borrowing at the subconscious
level. Similarities between the works are not to be found in the melodic material per se, but in
melodic gestures, rhythm, character, style and programmatic content. Correspondences in the
first piece include falling melodic opening motifs, the evocation of water and mists through
shimmering effects and similar accompaniment patterns; in the second, notated in both cases on
three staves, rhythmically almost identical pedal points, representing the knocking of the hanged
man’s feet against the gallows and footsteps through a forest respectively; and in the second and
third pieces, the complete fading away of sound at the end. A diabolical nocturnal apparition
provides the inspiration for both the third pieces; in both, the composer uses pianistic acrobatics
encompassing a wide range on the keyboard. If properly understood, the complexities and dynamics inherent in the creation of Grové’s
music can be translated effectively by the performer into the soundscapes that originated in the
composer’s imagination. This entails a process of “re-creation” by the performer.
The author first encountered Grové as a lecturer in her class at the University of Pretoria,
and she later, as a performer and exponent of his works, received generous guidance from the
composer himself. The article is interspersed with four Vignettes depicting the circumstances at
the time. As in Grové’s own use of chain form, the Vignettes look first forward and then back in
chronological time. Essential elements in the performance of his music, as illustrated throughout
in the comparison of these works, include the exquisite control of sound and overtones, the ability
to create a rich variety of timbres, the dramatic use of silence, a secure sense of rhythm and fluency
in articulation. The processes of “creation”, “re-creation” and “appreciation” all entail application of the
mind, not least on the part of the listener. The mystical in Grové’s music can be appreciated through
a thorough understanding of the programme which inspired any given creation, keeping track of
the permutations of the original germ cells throughout a work, and imagining what can happen
but has not necessarily happened. In Strange valley of the mists, according to Grové himself, the
imagination must lead to what the listener thinks is there, and not to what he or she sees.
Grové draws inspiration from indigenous African music and cultures, and especially from
Venda legends. Many scholars and performers regard Stefans Grové as one of the most important
composers in Africa. He has an unlimited musical imagination with regard to sources from which
he chooses to draw upon for inspiration, his musical language and the creation of unconventional
sounds and structures. By transcending our traditional way of listening to music, we can gain
access to his special soundscapes and unique musical idiomhttp://www.scielo.org.za/scielo.php?script=sci_serial&pid=0041-4751&lng=e
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