482 research outputs found
The role of part structure in the perceptual localization of a shape
No full textThe process of object localization may be accomplished with respect to a particularreference location, such as the center of gravity, COG (eg Vishwanath and Kowler, 2003 VisionResearch 43 1637-1653). Here, we investigated how part structure affects an object's referencelocation. The reference location was evaluated with a measure of the illusory displacement of an internal target element embedded within a larger object (Morgan et al, 1990 Vision Research 30 1793-1810). To examine whether the reference location is different for shapes with part structure, two shapes were tested: circle (small and large; no part structure) and bell (shape with two parts, one larger than the other). Results were examined with respect to two predictions: either the location of an object is based on its shape as a whole, disregarding part structure (ie a single, overall COG), or the parts are processed separately (different COGs).With the circles, the results showed a systematic illusory displacement of the internal target toward the COG. With the bell, the illusion was significantly weaker than with both circles--even though the main part of the bell had the same size as the small circle, and its horizontal axis had the same extent as the large circle. Moreover, the distance judgments for the bell were consistent with a (weaker) reference point being located at the COG of the larger part, rather than at the COG of the entire bell. These results show that the part structure of a shape plays a role in the representation of its location, and that for complex shapes the perceived location of an embedded element depends more on the parts within which it is embedded, rather than on the whole shape.Supported by the Air Force Office of Scientific Research, Grant AF 49620- 02-1-0112, Life Sciences Directorate to Eileen Kowler, and by NSF, Grant BCS-0216944 to Manish Singh.AF 29620-02-1-0112; to Eileen KowlerNSF BCS-0216944; to Manish SinghDenisova, Kristina, Manish Singh, Eileen Kowler, 2006. The definitive, peer-reviewed and edited version of this article is published in Perception, 35, 1073-1087, DOI:10.1068/p5518
Dynamic modeling and forecasting algorithms for financial data systems
No full textIt is a valid question that why a Control Systems Engineer would be interested in dealing with financial instruments. Financial instruments involving option theory are very elegant, math oriented and practical. These mathematical tools have created a new industry known as 'Derivative Industry' or 'Hedge-Fund Industry' or so called 'Risk-Management Industry'. This thesis is aimed at developing investment strategies involving the decision making needs via control system techniques. The problem, in general, is computationally challenging particularly when investment of many securities is involved resulting in a high dimensional computational framework. Furthermore, complications may arise due to realistic restrictions and non-linearities. The various areas of financial engineering are very fertile for the application of the system methodology and control theory techniques. Modeling, optimization, identification and computational methods used in the Systems Engineering can be successfully applied to the financial instruments. The ideas developed in this thesis are more about the scientific reasoning involving financial instruments rather than specific situations alone. Major contribution of this thesis is the time series optimal prediction filter and the development of the Dynamic Modeling and Forecasting Algorithm (DMFA). The proposed algorithm predicts the next data point of the financial time series while dynamically computing the parameters from existing data. The computation of the parameters is optimized by use of the recursive matrix inversion algorithm. The system is solved via an innovative technique of inversion such that it avoids explicit inversion of more than a 2 X 2 matrix and computation of higher dimensional determinants and co-factors. This results in new contributions to computation finance and numerical methodology along with arbitrage decision and hedging strategies under market uncertainties as well as robust control applications. The minimum mean-square algorithm used assures system stability via poles within the unit circle. The DMFA method is a superior auto regression (AR) model as a general system of time-series realizations in-order to calculate the coefficients that fit the model for a better prediction. Theoretical modeling and market specific volatility models, updated volatility computation are derived from the observation data.Ph.D.Includes bibliographical referencesIncludes vitaby Manish Mahaja
Isolated nuclear oculomotor nerve palsy due to a solitary midbrain metastasis: A rare presentation
No full textFirst Principles Study of Oxides : Bulk, Interfaces and Defects
No full textIn the recent years, oxides have been the focus of numerous theoretical and experimental
studies. This is because of a wide variety of exotic physical phenomenon,
such as multiferroicity, charge ordering, metal-insulator transitions, high-Tc superconductivity
etc that have been observed in these materials. Moreover, most
oxides are earth-abundant, stable, non-toxic and easy to produce in a wide range
of environmental conditions. As a result, they have also been used in a variety of
technological applications. In this thesis, we study bulk oxides, interfaces between
different oxides, and defects in bulk oxides. We use first-principles methods to
calculate different properties of these systems as discussed below. These state-of-the-
art methods based on density functional theory (for ground-state properties)
and many-body perturbation theory (for excited-state properties) have been shown
to predict properties that are in excellent agreement with experiments.
Our study of bulk properties of oxides is motivated by the possibility of constructing
an efficient all-oxide solar cell. We explore two ferroelectric transition metal
oxides, YMnO3 and Zn2Mo3O8, as potential candidates for photoabsorbers. We
calculate the electronic structure and optical properties of these materials and
compare our results with available experiments.
A technologically and fundamentally interesting phenomenon at oxide interfaces
is the formation of a two-dimensional electron gas (2DEG). We propose a novel
oxide heterostructure system, consisting of two materials with chemical formula
A2Mo3O8 (A = Zn, Mg, Cd), which has the potential to host a 2DEG. Our calculations
predict the formation of 2DEG at this interface with electron densities
and localization comparable to that of other well-known 2DEG systems.
In the last part of the thesis, we investigate the electronic structure and optical
properties of the oxygen vacancies (F-centers) in -alumina. -Alumina or sapphire
is a widely used and well-studied material. We propose a modi fication of the
existing method for calculation of defect charge transition levels (CTLs) in solids.
Using this modi fication we calculate CTLs for F-centers in -alumina. We show
that our modi fication improves the accuracy of the results signifi cantly. Furthermore,
we calculate excited state properties of these F-centers to understand and
explain photoluminescence experiments performed on these system
The relationship between spatial pooling and attention in saccadic and perceptual tasks
No full textAbstractSaccades aimed at spatially extended targets land reliably at central locations determined by pooling information across the target shape [Melcher, D., & Kowler, E. (1999). Shape, surfaces and saccades. Vision Research, 39, 2929–2946; Vishwanath, D., & Kowler, E. (2003). Localization of shapes: Eye movements and perception compared. Vision Research, 43, 1637–1653]. Previous findings of saccadic errors when attempting to look at a target in the midst of distractors encouraged suggestions that pooling occurs indiscriminately, with little or no influence of a selective filter to eliminate the influence of nearby distractors. To determine the effectiveness of filtering, saccadic localization was studied for saccades made to a set of target elements (discs) interleaved with an equivalent set of distractors of a different color. With such interleaved elements, selection and spatial pooling are constrained to occur over the same spatial region. The results showed that filtering was effective and saccadic landing position was determined mainly by the target elements. Concurrent perceptual judgments made about the same stimuli (estimating the mean size of either target or distractor discs) showed better performance for the target discs than distractors, confirming that perceptual attention was allocated to the set of target elements. These results: (1) support the role of attention in setting the input to the spatial pooling process that guides saccades to spatially extended targets, and (2) show that perceptual judgments of mean value, often thought to impose modest attentional demands, are not immune to the constraints of this pre-saccadic filter
Susceptibility evaluation of combinational logic in VLSI circuits
No full textA number of errors occur in digital systems operating in a harsh radiation environment. These errors are due to transient faults which may cause a temporary change in the state of the system without any permanent damage. These transient faults are referred to as Single Event Upsets (SEUs). Because of their random and non-recurring nature, such faults are very difficult to detect and hence are of source of great concern.
This thesis examines the logical response of combinational logic circuits to SEUs. Time domain analyses of a large number of circuits attempts to determine the affect of an SEU on a flip-flop which might lay at the end of a chain of combinational logic gates. In this way, the concept of an upset window, as it pertains to different types of logic gates is introduced. The results of the simulations carried out on various blocks of combinational logic are discussed. A program called SUPER (SUsceptibility PrEdiction pRogram) is developed. SUPER predicts the probability of a circuit fault occurring given that a cosmic ray with certain energy characteristics impinges on an arbitrary point within an IC. IC. The input variables to SUPER include the radiation level, the duration of the radiation, the types of gates the radiation affects, the signal path, the type of voltage pulse that the radiation produces (rising or falling) and the time (with respect to the clock pulse) that the radiation is incident on the circuit. The output of SUPER consists of a prediction as to whether or not the incident radiation causes a change in the output of a flip-flop.Master of Scienc
Adaptive particle encapsulation using digital opto-fluidic lithography
No full textEncapsulation of living cells using microgels has a wide range of applications in pharmaceutical research, tissue engineering, regenerative medicine, and personalized drug screening. Various cell encapsulation techniques have been proposed thus far focusing on creating cell-laden microgel particles. However, current techniques have limited control over the shape and size of the encapsulating particles and lack ability to address individual cells. This research aims to develop a method for adaptive encapsulation of particles with geometrically and biochemically complex micro-particles. To this end, we demonstrate image-based particle detection in a microfluidic channel and real-time in-flow lithography to encapsulate suspended particle employing a digital micro display as a dynamically reconfigurable virtual photomask. Digital dynamic mask is economical and offers the flexibility of rapidly changing the mask on demand. Microfluidic environment allows for mass production of micro-particles having various chemical composition in a continuous manner. Combining these unique capabilities, we present encapsulation of individual particles with graphically encoded information. Visual information (shape, size, and location) of polystyrene micro-beads suspended in a photo-curable liquid resin is acquired through digital imaging and subsequent image analysis, based on which desired digital patterns, possibly with graphical information, are created and optically projected on the target beads for lithographical in-flow encapsulation. The work presented in this thesis provides a new method for particle encapsulation, which has the potential to lead to a breakthrough solution in pharmaceutical engineering, cancer research, and tissue engineering.M.S.Includes bibliographical referencesby Manish Boorug
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