9,214 research outputs found
Diagnostic investigation of flame spread mechanism in dual-thrust solid propellant rocket motors
No full textNumerical studies have been carried out to examine the flame spread mechanism and the chamber dynamics of high-performance dual-thrust solid propellant rocket motors during the starting transient period of operation. Using a three-dimensional unsteady, shear-stress transport k-ω turbulence model, detailed parametric studies have been carried out to examine the aerodynamic choking and the existence/non-existence of a fluid throat at the transition region during the startup transient of dual-thrust motors (DTMs). In the numerical study, a fully implicit finite volume scheme of the compressible, density based Navier-Stokes equation is employed. We confirmed that, at the subsonic inflow conditions, there is a possibility of the occurrence of internal flow choking in dual-thrust motors with large length-to-diameter ratio (L/d > 44) due to the formation of a fluid throat at the beginning of the transition region induced by area blockage caused by boundary layerdisplacement thickness. We also confirmed that in such motors the choked flow becomes unchoked flow during the flame spread period due to the mass injection from the wall as a result of the thinning of the boundary layer thickness. We have demonstrated that without altering the grain geometry one can alter the flame spread mechanism by altering the igniter jet turbulence intensity, igniter gas temperature and propellant conductivity. Additionally, the numerical results of inert simulators of dual-thrust motors are compared with that of the case with propellant injection for establishing the physical situations of the choked and unchoked flow conditions during the starting transient period of operation of dual-thrust motors with high-propellant loading density
3D flow visualization and geometry optimization of cavity based scramjet combustors using k-ω model
No full textIn this paper numerical studies have been carried out to examine the intrinsic flow features of cavity based scramjet combustors with backward facing step and forward ramp using 3D, density-based, implicit, SST k-omega turbulence model. The preliminary results show a wide variety of flow features resulting from the interactions between the injector flows, shock waves, boundary layers, and cavity flows. In all the cases the C2H6-CO2-H2O fuel is injected at three different jet angles for the optimization of the jet orientation. Through the 3D numerical simulation we have corroborated that an optimized cavity is a good choice to stabilize the flame in the scramjet combustor as it generates a benign recirculation zone in the scramjet combustor. We comprehended that the cavity based scramjet combustors have a bearing on the source of disturbance for the transverse jet oscillation, fuel/air mixing enhancement, and flame-holding improvement. We concluded that the cavity shaped combustor with backward facing step and 45° forward ramp having an injector location of 1.6 times of its hydraulic diameter from the inlet facilitating at an angle of injection of 45° opposing the inlet flow is a good choice to getting relatively higher temperature at the exit
Lubrication with Oil-Compatible Polymer Brushes
No full textISSN:1023-8883ISSN:1573-2711ISSN:1573-271
Colourful children’s author visits Notre Dame
No full textOne of Australia’s most cherished authors, Morris Gleitzman, spoke about his passion for writing, the impacts of his literature on children and the enjoyment he receives from exploring his imagination every day to a vast audience at Notre Dame’s Fremantle Campus on Monday 21 May.
Author of more than 30 books, including the timeless classics Worry Warts, Two Weeks with the Queen and Adults Only, Mr Gleitzman said his stories reflected the essential qualities and values each person held dear in their lives.
“I wanted to suggest that stories, while we use them often for entertainment, have been around the centre of human culture for millennia,” Mr Gleitzman said.
“These stories are modelling exactly the same skills, abilities and cultural traits via the main characters as teachers hope to develop in their students in the classroom.”
The British-born author was an avid reader as a child and soon found a love for writing after migrating to Australia in 1969. Prior to becoming a full-time writer, Mr Gleitzman’s colourful career included working as a department store Santa Claus, a frozen chicken defroster and as a paperboy.
Mr Gleitzman also worked as a television screenwriter for the popular Norman Gunston Show in the 1970s.
However, it was not until a publishing company presented Mr Gleitzman with an opportunity to turn his script about a schoolboy who drove his family and friends “bonkers” into a book that his vocation as an author was realised.
He says that, for him, writing is a technical process that is assisted by a love of language and the ability to explore and evolve characters in any given setting.
“The aspect of writing that I most enjoy is going into my imagination, a place free of all the constraints of the physical and social world where I can have adventures in the context of that freedom,” Mr Gleitzman said.
“When I’m looking for, as I do with each new character, the biggest problem in their life, the problem is almost always timeless and universal.
“The biggest problems we face in our lives today are problems that humans have faced forever and everywhere. Everyone has a need for love, friendship, recognition, validation and, sometimes, survival in their lives.”
Senior Lecturer in English Literature at the Fremantle Campus, Dr Angeline O’Neill, said Mr Gleitzman exemplified the power and importance of children’s literature in contemporary society.
Notre Dame was indeed fortunate to host the first week of Morris Gleitzman’s Perth visit,” Dr O’Neill said.
“He is a major Australian author with a significant global readership, ranging from child readers to adults.
“We see literature in action through Mr Gleitzman’s work. His novels simultaneously entertain and inform young readers, promoting social awareness through the pleasure of reading.
While in Perth, Mr Gleitzman was sponsored by Notre Dame to conduct a series of school visits which included Mercedes College and John XXIII College. These visits provided students with the opportunity to hear about his new book titled After and the chance to speak to the highly acclaimed author.
MEDIA CONTACT: Shelley Robinson: Tel (08) 9433 0610; Mob 0408 959 138 Leigh Dawson: Tel (08) 9433 0569; Mob 0405 441 09
Defining simple nD operations based on prismatic nD objects
No full textAn alternative to the traditional approaches to model separately 2D/3D space, time, scale and other parametrisable characteristics in GIS lies in the higher-dimensional modelling of geographic information, in which a chosen set of non-spatial characteristics, e.g. time and scale, are modelled as extra geometric dimensions perpendicular to the spatial ones, thus creating a higher dimensional model. While higher-dimensional models are undoubtedly powerful, they are also hard to create and manipulate due to our lack of an intuitive understanding in dimensions higher than three. As a solution to this problem, this paper proposes a methodology that makes nD object generation easier by splitting the creation and manipulation process into three steps: (i) constructing simple nD objects based on nD prismatic polytopes—analogous to prisms in 3D—, (ii) defining simple modification operations at the vertex level, and (iii) simple postprocessing to fix errors introduced in the model. As a use case, we show how two sets of operations can be defined and implemented in a dimension-independent manner using this methodology: the most common transformations (i.e. translation, scaling and rotation) and the collapse of objects. The nD objects generated in this manner can then be used as a basis for an nD GIS.Urban Data Scienc
Tailoring SU-8 surfaces: covalent attachment of polymers by means of nitrene insertion
No full textThe photoresist material SU-8 has found a variety of applications in microfabricated systems, such as microelectromechanical (MEMS) and lab-on-a-chip devices. Although the bulk properties of SU-8 are appropriate for many such applications, tailoring its surface-chemical properties has, until now, proven to be challenging but is essential in order to carry out any subsequent self-assembly steps. We have demonstrated that the SU-8 surface can be functionalized by the covalent grafting of a wide variety of polymers by means of nitrene insertion. This is readily achieved with poly(allylamine)-graft-perfluorophenyl azide (PAAm-g-PFPA) or poly(ethyleneimine)-graft-PFPA (PEI-g-PFPA), which can form covalent bonds to both the SU-8 surface and a functionalizing polymer. As examples, poly(diallyl-dimethylammonium chloride) (PDDA) and poly(styrenesulfonate) (PSS) have been covalently linked to a SU-8 substrate, yielding positively and negatively charged surfaces, respectively. The grafted polymers were characterized by means of X-ray photoelectron spectroscopy, and their charge characteristics were confirmed via charged-particle adsorption
Structural and magnetic characterization of Nd-based Nd-Fe and Nd-Fe-Co-Al metastable alloys
No full textThe aim of the present work is to characterize a metastable hard magnetic phase referred to as "A1" in Nd-Fe alloys, which forms as a part of the fine eutectic depending on the composition and cooling rate. In order to define the range of composition for the formation of A1, Nd100-xFex (x = 20, 25, 40) alloys are cooled at about 150 K/s. The results indicate that for a cooling rate of 150 K/s, the hypereutectic Nd100-xFex (x = 20) alloys solidify into hard magnetic A1 whilst the hypoeutectic alloys (x = 40) show the formation of Nd2Fe17 crystallites. However, no sample cooled at 150 K/s shows the peaks of Nd5Fe17 as expected from the equilibrium Nd-Fe phase diagram. The effect of cooling rate on the formation of hard magnetic A1 is studied by investigating the Nd80Fe20 alloys cooled at different rates. The microstructure of hard magnetic Nd80Fe20 alloys displays a fine eutectic-like matrix consisting of Nd-richer and Fe-richer regions. The Nd-richer regions are identified as dhcp Nd and fcc Nd-Fe solid solution. However, the Fe-richer regions also referred to as A1, are diffuse and give an average composition of Nd56Fe44. These regions yield complex electron diffraction patterns, which do not match with any known Nd-Fe phase. HRTEM images of the Fe-richer regions reveal the presence of 5-10 nm crystallites embedded in an amorphous phase. Thus the Fe-richer regions of the hard magnetic Nd80Fe20 specimens are not a single homogeneous phase rather they are mixture of finely dispersed nanocrystallites in an amorphous phase. The demagnetization curves the hard magnetic Nd80Fe20 measured at temperatures above 30 K are typical of a hard magnetic material. The coercivity increases from 0.48 to 4.4 T with the temperature decreasing from 300 to 55 K. The demagnetization curves change from single to two-phase type when the temperature approaches 29 K, ordering temperature of fcc Nd-Fe solid solution. The measurements of initial magnetization, field dependence of coercivity, and temperature dependence of coercivity suggest the Stoner-Wohlfarth type magnetization reversal process for the hard magnetic A1. The values of anisotropy constant are estimated by fitting the magnetization data to the law-of-approach to saturation. The temperature dependence of anisotropy constant and the coercivity indicate that the origin of coercivity is magnetic anisotropy. A cluster model with sperimagnetic arrangement of Nd and Fe spins is used to explain the hard magnetic behavior of the mold-cast Nd80Fe20. Structural and magnetic properties of multicomponent Nd60Co30-xFexAl10 (0 < x < 30) alloys are compared with the binary Nd-Fe alloys. Magnetic measurements of the multicomponent alloys show that the magnetic properties are controlled by the fraction of the Fe content. The coercivity of the Nd60Co30-xFexAl10 mold-cast rods does not vary much with the Fe-content for more than 10 at.% Fe but the remanence and the maximum magnetization increase linearly with the Fe content. The temperature dependence of coercivity, effective anisotropy constant, and anisotropy field are identical to those for the binary Nd80Fe20 mold-cast rod. These results clearly suggest that the binary Nd80Fe20 and the multicomponent Nd60Co30-xFexAl10 (x > 5) mold-cast rods are magnetically identical
Laser-based manufacturing processes: A comprehensive review
No full textLight is always a fascinating subject to humankind from the beginning of the modern age. It fulfils the purpose of sight and is used for various purposes such as in decorations, medical and many other research applications. Laser is one of the most widely used technologies based on the properties and phenomenon of light. Laser beams are always considered as supporting tools in the field of machining. It is merely considered a heat source that accelerates the machining operation. When a laser beam falls on the material surface, there are always three possibilities: (i) transmission, (ii) reflection and (iii) absorption. Nowadays, several industries use CO2 Laser, Nd: YAG laser, fibre laser and diode laser in their manufacturing units for fabrication and material removal processes. This chapter discusses the various application of laser in machining operation. The ongoing evolution of laser technology and the development of other sophisticated assisting tools established laser material processing technology as one of the trusted allied manufacturing operations
Executing convex polytope queries on nD point clouds
No full textEfficient spatial queries are frequently needed to extract useful information from massive nD point clouds. Most previous studies focus on developing solutions for orthogonal window queries, while rarely considering the polytope query. The latter query, which includes the widely adopted polygonal query in 2D, also plays a critical role in many nD spatial applications such as the perspective view selection. Aiming for an nD solution, this paper first formulates a convex nD-polytope for querying. Then, the paper integrates three approximate geometric algorithms – SWEEP, SPHERE, VERTEX, and a linear programming method CPLEX, developing a solution based on an Index-Organized Table (IOT) approach. IOT is applied with space filling curve based clustering and advanced querying mechanism which recursively refines hypercubic nD spaces to approach the query geometry for primary filtering. Results from experiments based on both synthetic and real data have confirmed the superior performance of SWEEP. However, the algorithm may lag behind CPLEX due to pessimistic intersection computation in high dimensional spaces. In a real application, by properly transforming a perspective view selection into a polytope query, the solution achieves a sub-second querying performance using SWEEP. In another flood risk query, SWEEP also leads the others. In general, the robust and efficient solution can be immediately used to address different polytope queries, including those abstract ones whose constraints on combinations of different dimensions are formed into a polytope model. Besides, the knowledge of high-dimensional computations acquired also provides significant guidance for handling more nD GIS issues.GIS Technologi
Award winning Indigenous author speaks at Notre Dame
No full textMultiple Miles Franklin Literary Award winning Indigenous author, Kim Scott, discussed the role of language in developing and exploring relationships between people of different cultures with guests at Notre Dame’s Fremantle Campus recently.
Scott spoke of the background and inspiration behind his recent publication That Deadman Dance to community members and Notre Dame’s Study Abroad students from the United States of America.
The event was hosted by the College of St Benedict (CSB) and St John’s University (SJU), Minnesota, with support from Notre Dame’s Study Abroad Office.
The students had been studying That Deadman Dance to further their understanding of Australia’s diverse and continually evolving culture.
The book explores the first contact between the Noongar people, European settlers and American whalers in a 19th century setting in the Great Southern region of Western Australia.
It follows the story of young Noongar man, Bobby Wabalanginy, and decisions that lay before him which could have potentially affected not only the lives of his ancestors, but the lives of his new-found settler friends in Australia.
Study Abroad Director from CSB and SJU, Janelle Hinchley, said the Study Abroad students responded well to the issues presented in the novel surrounding cultural diversity in Australia.
“He challenged our students to look at the layered dynamics involved in these early cultural exchanges and the propensity that the Aboriginal people had in the facilitation of multiculturalism in Australia,” Ms Hinchley said.
Study Abroad student Christine Schneider said That Deadman Dance provided her with an artistic outlook of the Aboriginal heritage in WA.
“After hearing Kim Scott speak, I realised how poetic and insightful he is which lent itself to the discovery of all the hidden meanings within his novel,” Ms Schneider said.
“It was a great example of being able to take written work and further develop our understanding of its impact on our lives.”
That Deadman Dance won several awards in 2011, including the Miles Franklin Literary Award for the best Australian novel or play which portrays the beauty, challenges and characteristics of Australian life. The novel also collected the Premier’s Prize and the Best Fiction Book prize at the Western Australian Premier’s Book Awards.
MEDIA CONTACT: Shelley Robinson: Tel (08) 9433 0610; Mob 0408 959 138 Leigh Dawson: Tel (08) 9433 0569; Mob 0405 441 09
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