1,172 research outputs found
Behavior of ar plasma formed in a high-density plasma source - an ecr reactor
No full textIn order to develop the ultra-large scale integration(ULSI), low pressure and high density plasma apparatus are required for etching and deposit of thin films. To understand critical parameters such as the pressure, temperature, electrostatic potential and energy distribution of ions impacting on the wafer, it is necessary to understand how these parameters are influenced by the power input and neutral gas pressure. In the present work, a 2-D hybrid electron fluid-particle ion model has been developed to simulate one of the high density plasma sources-an Electron Cyclotron Resonance (ECR) plasma system with various pressures and power inputs in a non-uniform magnetic field. By means of numerical simulation, the energy distributions of argon ion impacting on the wafer are obtained and the plasma density, electron temperature and plasma electrostatic potential are plotted in 3-D. It is concluded that the plasma density depends mainly on both the power input and neutral gas pressure. However, the plasma potential and electron temperature can hardly be affected by the power input, they seem to be primarily dependent on the neutral gas pressure. The comparison shows that the simulation results are qualitatively in good agreement with the experiment measurements
Generalized TASE-RK methods for stiff problems
No full textA family of Time-Accurate and Stable Explicit (TASE) methods for the numerical integration of Initial Value Problems in stiff Ordinary Differential Equations (ODEs) y'(t) = f (t, y) was recently introduced in [1]. The main idea was to make local extrapolation of a stabilized Euler method. More recently, in [3] a similar approach by considering the stabilization of arbitrary explicit Runge-Kutta methods (TASE-RK) was analyzed. In this case the explicit Runge-Kutta method integrates a transformed ODE obtained by multiplying the vector field f (t, y) by a certain operator which approximates the identity mapping up to a given order p. The main inconvenience of both approaches is that to reach order p the solution of p2 linear systems plus the evaluation of p derivatives are required per integration step.In order to substantially reduce the computational costs of the former approaches in the linear system solution, but maintaining the good accuracy and stability properties, a new family of TASE-RK methods which allow to introduce a few more free parameters are considered. The formulation of the methods was conceived to be implemented not only in sequential mode but it admits parallelism in a straightforward way. Furthermore, since these methods are linearly implicit, connections to the class of W-methods [19] are properly established. The order conditions for the new class of methods are widely studied by using the rooted tree theory. For p = 3, 4, new methods with p sequential stages and order p are derived and compared on semidiscrete 1D and 2D Partial Differential Equations (PDEs) to those in [1,3] and other standard Rosenbrock and W-methods in the literature.(c) 2023 The Author(s). Published by Elsevier B.V. on behalf of IMACS. This is an open access article under the CC BY-NC-ND license (http:// creativecommons .org /licenses /by-nc -nd /4 .0/)
The morphological effects of sediment diversions the Lower Mississippi River
No full textThe wetlands in the Mississippi delta (USA) are drastically subsiding and eroding. Many projects and researches are ongoing to determine how this “drowning effect” of the delta can be stopped. One of the solutions that could be feasible is implementing sediment diversions in the levees of the Lower Mississippi River in order to divert sediment into the delta. This thesis addresses the morphological effects of river diversions on the Lower Mississippi River. The main objective is to analyze and optimize trade-offs between delta building and river navigability. For this purpose a 2DH numerical model with Delf3D has been created; the model simulates the hydro- and morphodynamic behavior. The river reach which has been studied is the final 110 km of the river from Point a la Hache at River Kilometer 78 (RK 78) down to the mouth of the river (RK -30), below Head of Passes. The hydrodynamic model has been calibrated and verified with flow and stage data from daily observations on the river. With the available sediment data a calibration has been carried out of the morphological behavior in the river. The model has been used to simulate several scenarios to get insight in the problems in the delta. From analysis of the model results the river bed in the study area can be divided into three categories. Upstream of RK 4 the bed is subject to erosion, around RK 4 the bed is practically in equilibrium and downstream of RK 4 the bed is subject to sedimentation. The reach downstream of RK 4 is the dredging reach; after analyzing the long-term simulation of 20 years it is not expected that the dredging quantities will decrease in the future. Closing off West Bay diversion has a positive effect on the dredging quantities. The best diversion site for this study area is found in the inner bend of the river upstream of Empire (RK 47) at RK 53. This site is most efficient and diverts the largest quantities of sand through the diversion.Hydraulic EngineeringCivil Engineering and Geoscience
The Dunston Manuscript
No full textVariously titled 80 Slides and a Memory, Fit for a King and others this is the definitive performed version as an invited reading in 2001 to the Urban Design Group. It describes in blank verse the early stages of the Gateshead Garden Festival illustrated with slide
Common Genetic Variants Explain the Majority of the Correlation Between Height and Intelligence : The Generation Scotland Study
No full textCreative Commons Attribution LicensePeer reviewe
Evolution in the genus Arum: a comparative analysis of morpohological and genetic variation.
No full textTesting the correlation of morphological and genetic marker variation enables the investigation of evolutionary processes. Knowledge of evolutionary processes can be used
to identify those morphological characters that could be used to produce evolutionary meaningful taxonomies. This thesis aims to test the correlation between morphological and genetic marker variation to further understand the evolution of species within the genus Arum and identify those morphological characters that correspond with evolutionary groups. The investigation is carried out at the intraspecific level, intrageneric level and in a
putative hybrid zone. At the intraspecific level, genetic (ISSR) and morphological variation was quantified in
populations of the morphologically similar species A. maculatum and A. italicum. Populations of A. maculatum showed evidence of isolation by distance, presumably a result of pollinator behaviour and seed dispersal. Leaf patterning in A. maculatum did not correspond to evolutionary lineages. However, similar leaf patterning characters in A. italicum are used to classify the two subspecies neglectum and italicum and the ISSR analysis confirmed that these taxa are genetically distinct. These two subspecies were shown to be interbreeding in sympatric populations. The interbreeding has created a morphological and genetic difference between subsp. neglectum in sympatric populations compared with allopatric populations.
At the intrageneric level, a phylogenetic analysis of Arum (using trnL and ITS 1 sequences) indicated that both vegetative and reproductive characters are convergent within the genus. The apparent convergent evolution of reproductive and vegetative characters indicates that
both have been important during the diversification of the genus. These convergent characters are not useful for producing classifications that reflect evolutionary groups as the groups they produce are polyphyletic. In the putative hybrid zone, ISSR markers confirmed the presence of A. creticum and A. idaeum hybrids. There appears to be introgression of the A. idaeum genome into A. creticum; this could have implications for the future genetic integrity of A. creticum. Within this hybrid zone, continuous characters were found to be representative of genetic variation, however categorical characters were not.
In conclusion, this thesis has shown that even within a single genus, the correlation between morphological and genetic marker variation is influenced by both the taxa being studied and the nature of the morphological trait. In particular, if morphological characters are found to be adaptively important, their correspondence to genetic groups should be tested before their use in taxonomies. The findings of this thesis also suggest there is great value in the complementary use of genetic and morphological analysis for taxonomic studies as well as evolutionary studies. For example, the importance of reproductive characters in the diversification of Arum species has produced a wide range of morphological variation, with
limited taxonomic utility due to a tendency for homoplasy. Vegetative characters were also found to need careful testing before use in taxonomies as leaf patterning was found to correspond to sub-species status for one species of Arum but not another. Finally, this thesis has shown that, if closely related taxa are hybridising, variation of continuous reproductive characters may be used as an indicator of hybridisation, even if the morphological
characters are potentially polygenic
Associating Gender with Neighbourhood Deprivation in Lagos State, Nigeria
No full textAJOL has removed this paper from the website after it was found to be published in another academic publication. AJOL has requestd that both journal editorial boards investigate this matter further with the author
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Transcriptions of Albanian Violin Music for Viola: History, Musical Style and Teaching Tools for the Intermediate to Advanced Player
No full textABSTRACTTranscriptions of Albanian Violin Music for Viola: History, Musical Style and Teaching Tools for the Intermediate to Advanced Player byBesnik YzeiriThe aim of the present study was fourfold: to add valuable new pieces to the viola repertoire; to do so specifically highlighting Albanian classical music; to develop a methodology for making transcriptions for that instrument; and to demonstrate the usefulness of such works specifically to guide intermediate and advanced viola performance students toward higher technical levels. The author accomplished these goals by carefully choosing appropriate pieces, exploring and comparing the transcribing methodologies of William Primrose, Watson Forbes, and Lionel Tertis, and synthesizing a framework for accomplishing the best transcription method for the task. The author then applied this framework specifically to Albanian composer Pjetër Gaci’s Concertino and Concerto for Violin and Piano, transcribing them for viola and piano, and finally using these transcriptions as case studies as teaching tools for intermediate to advanced viola students
Rankine models for time-dependent gravity spreading of terrestrial source flows over subplanar slopes
No full textGeological mass flows extruding from a point source include mud, lava, and salt issued from subsurface reservoirs and ice from surface feeders. The delivery of the material may occur via a salt stock, a volcanic pipe (for magma and mud flows), or a valley glacier (for ice). All these source flows are commonly skewed by a superposed far-field velocity vector imposed by the topographic slope and thus develop plumes having a wide range of shapes. The morphological evolution of the perimeter of the plumes (in plan view) can be simulated by varying the key parameters in a simple analytical flow description on the basis of Rankine equations. Our model systematically varies the strength of the point source relative to the downslope far-field velocity of its expelled mass. The flow lines are critically controlled by the relative speed of the two rates, which can be concisely expressed by the dimensionless Rankine number (Rk, introduced in this study). For steady flows, plume widths can be expressed as a function of Rk. The viscosity of the rock, mud, or lava mass involved in the gravity flow affects Rk and thus the appearance of the plumes. For unsteady source strength, Rk becomes time dependent and the plume width varies over time. The model flow shapes suggest that the plume shapes of natural gravity flows of terrestrial surface materials (mud, lava, salt, and ice) commonly express fast initial flux of the source, followed by an exponential decline of the source strength. Flows having initially higher Rk but otherwise equal life cycles create broader plumes. Peaks in the source flux due to magmatic pulsing during the eruption cycle can explain the formation of pillow lavas. Rather than instantaneously reaching full strength before declining, some natural source flows start by swelling slowly, leading to the creation of unique plume shapes like a flying saucerGeoscience & EngineeringCivil Engineering and Geoscience
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