2,750 research outputs found
Target Tracking in Non-Gaussian Environment
Masreliez filter which is a Kalman type of recursive filter
is implemented and validated. The main computation in
Masreliez filter is to evaluate the score function which
directly influences the estimates of the target states. Scalar
approximation for score function evaluation is extended to
vector observations, implemented and validated. The
simulation studies have shown that the performance of the
Masreliez filter is relatively better than that of the
conventional Kalman filter in the presence of significant
glint noise in the observation
Low temperature hopping magnetotransport in paramagnetic single crystals of cobalt doped ZnO
Long needle-shaped single crystals of Zn1-xCoxO were grown at low
temperatures using a molten salt solvent technique, up to x=0.10. The
conduction process at low temperatures is determined to be by Mott variable
range hopping. Both pristine and cobalt doped crystals clearly exhibit a
crossover from negative to positive magnetoresistance as the temperature is
decreased. The positive magnetoresistance of the Zn1-xCoxO single crystals
increases with increased Co concentration and reaches up to 20% at low
temperatures (2.5 K) and high fields (>1 T). SQUID magnetometry confirms that
the Zn1-xCoxO crystals are predominantly paramagnetic in nature and the
magnetic response is independent of Co concentration. The results indicate that
cobalt doping of single crystalline ZnO introduces localized electronic states
and isolated Co2+ ions into the host matrix, but that the magnetotransport and
magnetic properties are decoupled.Comment: 7 pages, 9 figures, submitted to Physical Review
The Transformation of the U.S. Banking Industry: What a Long, Strange Trips It's Been
macroeconomics, Transformation, U.S. Banking Industry
Determination and Correlation of Anticardiolipin Antibody with High Sensitivity C- reactive Proteins and its Role in Predicting Short Term Outcome in Patients with Acute Coronary Syndrome
Anticardiolipin antibody (aCL) is considered to be an independent risk factor while high sensitivity C reactive protein (hsCRP) is an established marker for coronary artery disease. This study was conducted to determine levels of aCL antibodies and hsCRP, their correlation and role in predicting recurrence of events in patients presenting with Acute Coronary Syndrome (ACS). Sixty patients admitted with Acute Coronary Syndrome were followed up for 7 days or until discharge. Patients were classified into two groups as those having experienced an ischemic event needing intervention within 7 days (Group I) and other having an event free recovery (Group II). aCL antibody and hsCRP levels were estimated and compared in these two groups. Twenty age and sex matched disease free persons served as controls. The levels of aCL were significantly higher in patients with ACS as compared to the controls (p=0.020). However the levels of aCL in Group I (13.39±9.46 GPL-U/ml) and Group II (13.51±9.93 GPL-U/ml) were not significantly different (p =0.838). The mean hsCRP levels were higher in cases with an event (23.30±10.68 mg/dl) than in cases without an event (20.60±11.45mg/dl) though it was not significant statistically (p=0.389). aCL and CRP were not found to be significantly correlated in causing the recurrence of events(p=0.178). Therefore anticardiolipin antibody is an independent risk factor which could be implicated in the pathogenesis of ACS. However it is not significantly associated with recurrence of short-term events in patients with ACS. Also, aCL antibody does not have significant correlation with hSCRP in causing recurrence of events in the patients of acute coronary syndrome
Detection of Runway and Obstacles using Electro-optical and Infrared Sensors before Landing
For safe aircraft operations, detection of runway incursions especially during landing and takeoff is essential. And it is important that such detection technique is capable of detecting the distant objects so that pilot has enough response time to take corrective action. This paper presents techniques to detect runway and runway incursions using electro-optical color camera and medium wave infrared sensor on-board the aircraft during approach for landing. The detection process consists of horizon detection to reduce runway search space in sensor image and then detect runway and obstacles. The information is then presented to the pilot to improve pilot situational awareness. The performance of the proposed techniques are evaluated in flight simulators with simulated images of electro-optical and infrared sensors on-board the aircraft during approach for landing at a distance of 3 nautical miles from runway threshold during day/night and in low visibility CAT II foggy conditions. Effectiveness of the techniques with statistics of runway detection, miss detection and false alarm for different case studies have been provided and discussed.Defence Science Journal, Vol. 64, No. 1, January 2014, DOI:10.14429/dsj.64.276
Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel
We theoretically investigate the process of coupling cold atoms into the core
of a hollow-core photonic-crystal optical fiber using a blue-detuned
Laguerre-Gaussian beam. In contrast to the use of a red-detuned Gaussian beam
to couple the atoms, the blue-detuned hollow-beam can confine cold atoms to the
darkest regions of the beam thereby minimizing shifts in the internal states
and making the guide highly robust to heating effects. This single optical beam
is used as both a funnel and guide to maximize the number of atoms into the
fiber. In the proposed experiment, Rb atoms are loaded into a magneto-optical
trap (MOT) above a vertically-oriented optical fiber. We observe a
gravito-optical trapping effect for atoms with high orbital momentum around the
trap axis, which prevents atoms from coupling to the fiber: these atoms lack
the kinetic energy to escape the potential and are thus trapped in the laser
funnel indefinitely. We find that by reducing the dipolar force to the point at
which the trapping effect just vanishes, it is possible to optimize the
coupling of atoms into the fiber. Our simulations predict that by using a
low-power (2.5 mW) and far-detuned (300 GHz) Laguerre-Gaussian beam with a
20-{\mu}m radius core hollow-fiber it is possible to couple 11% of the atoms
from a MOT 9 mm away from the fiber. When MOT is positioned further away,
coupling efficiencies over 50% can be achieved with larger core fibers.Comment: 11 pages, 12 figures, 1 tabl
Robust Techniques for Bearing Estimation in Contaminated Gaussian Noise
The problem of estimating directions-of-arrival (DOA) of radiating sources from measurements provided by a passive array of sensors is frequently encountered in radar, sonar, radio astronomy and seismology. In this study various robust methods for the DOA estimation problem are developed, where the term robustness refers to insensitivity against small deviation in the underlying Gaussian noise assumption. The first method utilizes an eigenvector method and robust reconstruction of the correlation matrix by time series modeling of the array data; Secondly, a decentralized processing scheme is considered for geographically distributed array sites. The method provides reliable estimates even when a few of the subarray sites are malfunctioning. The above two techniques are useful for narrow band and incoherent sources. The third robust method, which utilizes Radon Transform, is capable of handling both the narrow band and wide band sources as well as the incoherent or coherent sources. The technique is also Useful in situations of very low SNR and colored noise with unknown correlation structure. The fourth method is an efficient narrow band robust maximum likelihood DOA estimation algorithm which is capable of handling coherent signals as well as the single snapshot cases. Furthermore, relationships between eigenvector methods and a ML DOA estimation, where the source signals are treated as sample functions of Gaussian random processes, are investigate
INTERACTING MULTIPLE MODEL SEEKER FILTER FOR TRACKING EVASIVE TARGETS
Seeker filter is an important subsystem in modern homing guidance system of advanced intercepting missiles. Seeker filter design for homing guidance requirements are highly demanding and challenging. Very low filter lag, high noise attenuation are some of the challenges that need to be addressed. This paper presents an interacting multiple model augmented extended Kalman filter (IMM-AEKF) design to operate as seeker filter in close loop homing guidance of an interceptor to track evasive targets. The performance of the seeker filter is verified with six degree of freedom interceptor-target engagement simulation with seeker filter in guidance loop of the interceptor. Different filter performance criteria have been used to verify the performance of the seeker filter. The seeker filter efficiently handles the various seeker noise and provides a smooth estimate of target states to generate guidance command for intercepting missile. The miss distance achieved is within the acceptable limits
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