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Experimental Investigation of the Effect of Wall Adaptation on Flow Over a Cylinder in a Modernized Adaptive-Wall Wind TunnelBishop, Michael Joseph January 2010 (has links)
A renovation of an adaptive-wall wind tunnel was completed to improve flow quality, automate data acquisition, integrate a three-axis traversing mechanism, and regain functionality of an adaptive-wall test section. Redesign of the settling chamber significantly improved flow quality, with the resulting turbulence intensity of 0.3% and flow uniformity of ±0.6% matching characteristics of research-grade wind tunnels. The functionality of the adaptive-wall test section was tested by analyzing the effect of wall adaptation on flow development over a circular cylinder. Experiments were carried out for a Reynolds number (Red) of 57,000 for three blockage ratios: 5%, 8%, and 17%. Measurements were made in three wall configurations: geometrically straight walls (GSW), aerodynamically straight walls (ASW), and streamlined walls (SLW). Solid blockage effects were clearly evident in cylinder surface pressure distributions for the GSW and ASW configurations, manifested by an increased peak suction and base suction. Upon streamlining the walls, pressure distributions for each blockage ratio matched distributions expected for low blockage ratios. Wake blockage limited wake growth in the GSW configuration at 7.75 and 15 diameters downstream of the cylinder for blockages of 17% and 8%, respectively. This adverse effect was rectified by streamlining the walls with the resulting wake width development matching that expected for low blockage ratios. Wake vortex shedding frequency and shear layer instability frequency increased in the GSW and ASW configurations with increasing blockage ratio. Invariance of the near wake width with wall configuration suggests that frequency increase is caused by the increased velocity due to solid blockage effects. For all the blockage ratios investigated, the increased wake vortex shedding frequency observed in the ASW and GSW configurations was corrected in the SLW configuration, with the resulting Strouhal numbers of about 0.19, matching that expected for low blockage ratios at the investigated Red.
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Experimental Investigation of the Effect of Wall Adaptation on Flow Over a Cylinder in a Modernized Adaptive-Wall Wind TunnelBishop, Michael Joseph January 2010 (has links)
A renovation of an adaptive-wall wind tunnel was completed to improve flow quality, automate data acquisition, integrate a three-axis traversing mechanism, and regain functionality of an adaptive-wall test section. Redesign of the settling chamber significantly improved flow quality, with the resulting turbulence intensity of 0.3% and flow uniformity of ±0.6% matching characteristics of research-grade wind tunnels. The functionality of the adaptive-wall test section was tested by analyzing the effect of wall adaptation on flow development over a circular cylinder. Experiments were carried out for a Reynolds number (Red) of 57,000 for three blockage ratios: 5%, 8%, and 17%. Measurements were made in three wall configurations: geometrically straight walls (GSW), aerodynamically straight walls (ASW), and streamlined walls (SLW). Solid blockage effects were clearly evident in cylinder surface pressure distributions for the GSW and ASW configurations, manifested by an increased peak suction and base suction. Upon streamlining the walls, pressure distributions for each blockage ratio matched distributions expected for low blockage ratios. Wake blockage limited wake growth in the GSW configuration at 7.75 and 15 diameters downstream of the cylinder for blockages of 17% and 8%, respectively. This adverse effect was rectified by streamlining the walls with the resulting wake width development matching that expected for low blockage ratios. Wake vortex shedding frequency and shear layer instability frequency increased in the GSW and ASW configurations with increasing blockage ratio. Invariance of the near wake width with wall configuration suggests that frequency increase is caused by the increased velocity due to solid blockage effects. For all the blockage ratios investigated, the increased wake vortex shedding frequency observed in the ASW and GSW configurations was corrected in the SLW configuration, with the resulting Strouhal numbers of about 0.19, matching that expected for low blockage ratios at the investigated Red.
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Pro- and Anti-Capitalism : in Wall Street and Wall Street. Money Never SleepsLi, Xu January 2012 (has links)
This thesis aims at comparatively analyzing the representation of financial capitalism in Wall Street (1987) and Wall Street. Money Never Sleeps (2010) with focusing on exploring in which ways the films promote/criticize the financial capitalism they portray. Theoretical approaches concerning film theories are mainly through ideological analysis, and supplemented by structuralist and semiotic theories. As methods used in data gathering and analyzing, basic film content analyses are principally applied through illustrating with film contents extracted from the films in qualitative and comparative ways in order to describe and distinguish the ideological positions of pro- and anti-capitalism in the two films. The results show an interesting fact that positions from the villain to the moral center are symbolized by both different characters separately and the key character (Gorden Gekko) alone. The analysis also shows that both of the films promote capitalism of freedom, which inspire people to work hard and create property for society, and criticize it of greed and immorality. However, Wall Street II is not nearly as merciless as the original, and it seems more fascinated than critical.
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Effect Of Inelastic Behaviour Of Load Bearing Walls On The FrameGuler, Gokay 01 June 2009 (has links) (PDF)
The purpose of this study is to investigate the influence of material and geometric nonlinearities occurring in beams, columns and walls of RC frame-wall structural systems when undergoing severe ground excitations. For this purpose, a low-rise RC building is considered with and without walls, and the joining beams and columns are designed with the strong-column weak-beam concept. The dimensions, material properties and the reinforcement amounts are calculated in accordance with the values suggested in design codes. Each structure is analyzed for various levels of applied vertical force and change in wall stiffness / where the effect of geometric nonlinearity is considered for each case. Force formulation frame elements with spreading inelasticity over the span are used for the modelling of each beam, column and wall. The coupling of the section forces is obtained by the fibre discretization of the section into several material points. Each section is divided into confined and unconfined regions and appropriate material properties are used for concrete and steel for cyclic loading. Both static pushover and dynamic analyses are performed in order to replicate the worst case scenario for a possible earthquake. From this study, it is concluded that the beams and columns of a frame-wall structural system should be designed carefully for load redistributions resulting from the yielding of the wall in the case of a strong earthquake, thus the design codes should address this situation for both in the retrofit of existing frame buildings with walls and in the construction of new frame-wall type buildings.
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Feedback control of resistive wall modes in the reversed field pinchYadikin, Dimitry January 2004 (has links)
<p>A wide range of unstable current driven MHD modes is present in the re- versed τeld pinch (RFP) conτguration. An ideally conducting wall facing the plasma can stabilize the ideal MHD modes. In the presence of a resistive wall characterized by the wall time τw, fast mode rotation with the frequency exceeding the inverse wall time gives stabilization for resistive MHD modes. The ideal MHD modes in the RFP are non-rotating modes and can not be stabilized by the resistive wall. Instead they are converted into resistive wall modes (RWM) growing with a growth rate proportional to the inverse of the wall time τw. EXTRAP T2R is an RFP device equipped with a thin resistive wall having the wall time shorter than the plasma pulse duration τw < τp. This feature allows the study of non-resonant non-rotating resistive wall modes. Resistive wall modes dynamics has been studied in EXTRAP T2R . RWM growth rates has been measured and compared with linear MHD stability calculations. Quantitative agreement is observed. In the case τw < τp the RWM can cause discharge degradation and should be stabilized. Active feedback is the way to stabilize the RWM in the RFP. An intelligent shell scheme is one possible feedback scenario. An active feed- back system including a set of sensors and discrete active coils is installed in EXTRAP T2R. The intelligent shell tries to keep the magnetic flux zero at the positions of the sensor. The analog PID controller for the intelligent shell feedback scheme has been studied. A model of the active control system was developed and comparison with the experimental results showed good agree- ment. Encouraging experimental results on the active feedback stabilization of multiple RWMs in the RFP plasmas were obtained.</p>
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Molecular Dynamics Study of Sodium Octanoate Self-assembly in Parallel-Wall ConfinementsRahman, Mohammod Hafizur 23 April 2012 (has links)
The practical applications of surfactant solutions in confined geometries require a thorough understanding of the system properties. Coarse-grained simulation techniques are useful for studying the qualitative behaviour of these systems, whereas the atomistic molecular dynamics (MD) technique can be used to obtain a molecular-level description. In this work, canonical MD simulations were performed using GROMACS version 4.0 to investigate the self-assembling behaviour of sodium octanoate (SO) confined between two parallel walls. In particular, the effects of gap size, wall type, and surfactant concentrations on the morphology of the surfactant aggregates were studied to gain in-depth knowledge of the system.
The simulation results reveal that the morphology of the micelles formed between two parallel walls are affected not only by the gap size and surfactant concentration, but also by the nature and characteristics of the confining walls. With the graphite walls, most octanoate molecules are adsorbed at lower concentrations, but they form micellar aggregates as the surfactant concentration increases. Spherical micelles were found in the larger gaps (4 nm and 5 nm) but not in the smaller gap (3 nm), and the micellar shape also changes with increasing surfactant concentration. SO forms bilayer structures instead of spherical micelles between two silica walls. Interestingly, in the hydrophilic silica confinement, the orientation of these bilayers changes with gap sizes, whereas in the hydrophobic silica confinement, these bilayers remain perpendicular to the wall in all cases.
Potentials of mean force between different molecules and atomic groups were determined under different conditions in order to develop a better understanding of the simulation results. It reveals, the presence of the confinement can alter the intermolecular interactions among the surfactant molecules, which, in turn, directly affects the self-assembling process, particularly the size and shape of the aggregates. Indeed, the formation of bilayers in silica wall confinement, as opposed to spherical micelles in graphite confinement, is caused by the enhanced electrostatic interactions between the charged atoms in the solution. The results of this study are expected to provide further insight into the self-assembling behaviour of confined surfactant systems, and may ultimately lead to the development of novel nanomaterials.
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Gastroschisis in KwaZulu-Natal.Sekabira, John. 25 September 2013 (has links)
Gastroschisis is a full thickness abdominal wall defect, usually to the right of the umbilicus,
through which a variable amount of viscera herniates, without a covering membrane. Newborns
with gastroschisis present challenging problems to paediatric surgeons. The incidence of
gastroschisis is rising worldwide. In developed countries, advances in neonatal intensive care
have improved survival of patients with gastroschisis. In the few reported studies from Africa,
mortality rates of patients with gastroschisis are high. The aim of this study was to evaluate
outcome of gastroschisis from a centre in Africa with modern neonatal intensive care facilities.
Methods: A retrospective analysis of all neonates admitted with the diagnosis of gastroschisis
at Inkosi Albert Luthuli Central Hospital (IALCH) over a 6-year period (2002-2007).
Proportions in percentages were used for categorical variables. For continuous variables the
mean with standard deviation (SD) were derived. Two sampled t-test was used to show the pvalue
for the time to reduction between the non-survivors and survivors with a 95% confidence
interval.
Results: There was a significant increase in the prevalence of gastroschisis among neonatal
surgical admissions from 6.2% in 2003 to 15.2% in 2007. There were more females 53.4%, the
majority (71.7% had low birth weight and 64.2% were born prematurely. Although 75% (n=79)
of the mothers attended antenatal clinic, antenatal diagnosis by ultrasound was made in only 13
(n=12%)). Most of the babies 90.6% were out-born, with 70.8% delivered by normal vaginal
delivery (NVD), and 57.4% of the mothers were primiparous. Primary closure was achieved in
73.5% of the patients. The overall mean (SD) time from birth to primary surgical intervention
was 16 (13.04) hours and was higher 17(9.1) hours in those who died compared to survivors 15
(16.0), but the difference was not statistically significant, p=0.4465 and mortality was 43% with
sepsis as the leading cause. Staged closure with a plastic silo bag was associated with more than
double the mortality as compared to primary closure.
Conclusion: The prevalence of gastroschisis among neonatal surgical admissions has increased
in accordance with international trends. Due to lack of antenatal diagnosis, most of the babies
were out-born resulting into delay in offering surgical treatment. Mortality is still high despite
the presence of modern intensive care. / Thesis (M.Med.)-University of KwaZulu-Natal, Durban, 2008.
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Lateral Load Analysis Of Shear Wall-frame StructuresAkis, Tolga 01 January 2004 (has links) (PDF)
The purpose of this study is to model and analyze the nonplanar shear wall assemblies of shear wall-frame structures. Two three dimensional models, for open and closed section shear wall assemblies, are developed. These models are based on conventional wide column analogy, in which a planar shear wall is replaced by an idealized frame structure consisting of a column and rigid beams located at floor levels. The rigid diaphragm floor assumption, which is widely used in the analysis of multistorey building structures, is also taken into consideration. The connections of the rigid beams are released against torsion in the model proposed for open section shear walls. For modelling closed section shear walls, in addition to this the torsional stiffness of the wide
columns are adjusted by using a series of equations. Several shear wall-frame systems having different shapes of nonplanar shear wall assemblies are analyzed by static lateral load, response spectrum and time history methods where the proposed methods are used. The results of these analyses are compared with the results obtained by using common shear wall modelling techniques.
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Effects Of Masonry Infill Walls On The Seismic Performance Of BuildingsOzturk, Mehmet Selim 01 December 2005 (has links) (PDF)
In Turkey, in most of the reinforced concrete buildings, hallow masonry infill walls are used as a non-structural element, during design stage, their contribution to overall building behavior is not well known. Observations made after the earthquakes revealed that these non-structural elements had beneficial effects on the lateral capacity of the building.
In this study, the contribution of the hallow masonry infill walls to the lateral behavior of reinforced concrete buildings was investigated. For this purpose, two different buildings were chosen as case studies. Three and six story symmetric buildings are modeled as bare and infilled frames. The parameters that were investigated are column area, infill wall area, distribution of masonry infill walls throughout the story. To determine the effect of each parameter, global drift ratios are computed and are compared for each case.
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Lateral load response of Cikarang brick wall structures : an experimental studyBasoenondo, Essy Arijoeni January 2008 (has links)
Despite their poor performance, non-standard clay bricks are commonly used in construction of low-rise buildings and rural houses in Indonesia. These clay bricks are produced traditionally in home industries. Indonesia is located in an active seismic region and many masonry buildings were badly damaged or collapsed during recent earthquakes. Such buildings are classified as non-engineered structures as they are built without using any proper design standard. Lateral load response of un-reinforced masonry walls is investigated in this research project, with the aim of better understanding the behaviour of these masonry walls using low quality local bricks. A comprehensive experimental program was undertaken with masonry wall elements of 600 mm x 600 mm x 110 mm constructed from local bricks from Cikarang in West Java - Indonesia. Wall specimens were constructed and tested under a combination of constant vertical compression load and increasing horizontal or lateral in-plane loads, of monotonic, repeated and cyclical nature. The vertical compressive loading was limited to 4% of maximum brick compressive strength. Masonry mortar mix used to construct the specimens was prepared according to Indonesian National Standard. Three different types of masonry wall panels were considered, (i) (normal) brick masonry walls, (ii) surface mortared brick masonry walls and (iii) comforted surface mortared brick masonry walls. The results indicated that the lateral load bearing capacity of masonry wall is usually lower than that of mortared and comforted walls. Despite this, the lateral load capacity under cyclic loads decreased 50 % of the average capacity of the walls under monotonic and repeated lateral loads. Using the results from the experimental program, a simplified model for the equivalent diagonal spring stiffness of local clay brick walls was developed. This stiffness model derived from experimental results in then used to simplify the structural analysis of clay brick wall panels in Indonesia. The design guideline for brick masonry houses and low-rise buildings in six Indonesian seismic zones was developed, as a contribution towards the development of design guidance for constructing brick masonry houses in Indonesia.
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