Robust Direction-of-Arrival Estimation using Array Feedback Beamforming in Low SNR Scenarios

A new spatial IIR beamformer based direction-of-arrival (DoA) estimation method is proposed in this paper. We propose a retransmission based spatial feedback method for an array of transmit and receive antennas that improves the performance parameters of a beamformer, viz. half-power beamwidth (HPBW), side-lobe suppression, and directivity. Through quantitative comparison, we show that our approach outperforms the previous feedback beamforming approach with a single transmit antenna, and the conventional beamformer. We then incorporate a retransmission based minimum variance distortionless response (MVDR) beamformer with the feedback beamforming setup. We propose two approaches, show that one approach is superior in terms of lower estimation error, and use that as the DoA estimation method. We then compare this approach with Multiple Signal Classification (MUSIC), Estimation of Parameters using Rotation Invariant Technique (ESPRIT), robust MVDR, nested-array MVDR, and reduced-dimension MVDR methods. The results show that at SNR levels of -60 dB to -10 dB, the angle estiation error of the proposed method is 20 degree less compared to that of prior methods

903-8 Mitogenic Effect of Thromboxane A2and Its Synergistic Interaction with Serotonin on Smooth Muscle Cell Proliferation is Reversed by Ridogrel

BackgroundThromboxane A2(TxA2) and serotonin (5HT) released from aggregating platelets are known mitogens for vascular smooth muscle cells (SMC). Recently we reported that TxA2and 5HT act synergistically in inducing proliferation of SMC and may contribute to the development of restenosis following vascular injury.PurposeIn this study, we examined whether ridogrel (a TxA2synthase inhibitor/receptor antagonist) can inhibit the TxA2induced SMC proliferation both in the presence and absence of 5HT.MethodsCanine aortic primary SMC were preincubated with either 30 μg/ml of Ridogrel in phosphate buffered saline (PBS) or equal volume of PBS, as control, for 2 hrs in serum free medium. Increasing concentrations of U46619 (a TxA2mimetic) with or without 5HT were then added and 3H-thymidine incorporated into DNA of the SMC was measured.ResultsControl (PBS) 5HT Concentration(μM)Rido9rel 30 μg/ml 5HT Concentration(μM)05500550TxA20 nM100236±37222±568±4306±3212±13TxA27.5 nM100±1394±201131±9784±8294±27*249±6*TxA275 nmM173±29541±691369±14674±117*283±24*279±17*TxA2750 nM282±8795±221569±10376±27*285±28*274±21*Values are % of control: Control=100% =9023±621 cpm/106cells. n =3*p<0.001 compared to corresponding PBS treated controlsThe data show that unlike the PBS treated controls, ridogrel reversed both the mitogenic effect of TxA2on SMC as well as its synergistic interaction with 5HT in inducing cellular proliferation.ConclusionThe data indicate the specificity of the interaction of TxA2with 5HT in inducing SMC proliferation. This suggests a potential role forthe combined use of TxA2synthase inhibitor/receptor antagonist and 5HT receptor antagonist for inhibiting SMC proliferation at sites of vascular injury

Multi target direction-of-arrival tracking using road priors

In this paper, we present a multi target particle filter DOA tracker that can incorporate road prior information at a single array node. The filter uses a batch of DON's to determine the state vector, based on an image template matching idea. The filter likelihood is derived with the joint probability density association principles so that no DOA measurement is associated to more than one target. The filter state update has the target DOA, the target velocity over range ratio, and the target heading parameters. We present two approaches for incorporating the road information. In the first approach, the road prior is injected at the weighting stage of the tracker, where a raised mixture Gaussian distribution, derived from the road headings at the target DOA, constraints the particles. The second approach is based on modifying the state update function with a compound model, where a mixture of the constant velocity model and the road information is used. In this case, the filter uses an online EM algorithm to update the state vector along with the mixture components. Computer simulations demonstrate the performance of the approaches

Acoustic multi target tracking using direction-of-arrival batches

In this paper, we propose a particle filter acoustic direction-of-arrival (DOA) tracker to track multiple maneuvering targets using a state space approach. The particle filter determines its state vector using a batch of DOA estimates. The filter likelihood treats the observations as an image, using template models derived from the state update equation, and also incorporates the possibility of missing data as well as spurious DOA observations. The particle filter handles multiple targets, using a partitioned state-vector approach. The particle filter solution is compared with three other methods: the extended Kalman filter, Laplacian filter, and another particle filter that uses the acoustic microphone outputs directly. We discuss the advantages and disadvantages of these methods for our problem. In addition, we also demonstrate an autonomous system for multiple target DOA tracking with automatic target initialization and deletion. The initialization system uses a track-before-detect approach and employs the matching pursuit idea to initialize multiple targets. Computer simulations are presented to show the performances of the algorithms

A range-only multiple target particle filter tracker

We propose a particle filter tracker to track multiple maneuvering targets using a batch of range measurements. The state update is formulated through a locally linear motion model and the observability of the state vector is proved using geometrical arguments. The data likelihood treats the range observations as an image using template models derived from the state update equation, and incorporates the possibility of missing data as well as spurious range observations. The particle filter handles multiple targets, using a partitioned state-vector approach. The filter proposal function uses a Gaussian approximation of the full-posterior to cope with target maneuvers for improved efficiency. By treating the range measurements as images and using smoothness constraints, the particle filter is able to avoid the data association problems. Computer simulations demonstrate the performance of the tracking algorithm

A multi target bearing tracking system using random sampling consensus

In this paper, we present an acoustic direction-of-arrival (DOA) tracking system to track multiple maneuvering targets using a state space approach. The system consists of three blocks: beamformer, random sampling, and particle filter. The beamformer block processes the received acoustic data to output bearing batches as point statistics. The random sampling block determines temporal clustering of the bearings in a batch to determine region-of-interests (ROIs). Based on the track-before-detect approach, each ROI indicates the presence of a possible target. We describe three random sampling algorithms called RANSAC, MSAC, and NAPSAC to use in the random sampling block. The particle filter then tracks the targets via its interactions with the beamformer and the random sampling blocks. We present a computational analysis of the random sampling blocks and show tracking results with field data

The Evolution of KTP Laser Vaporization of the Prostate

The search for a minimally invasive approach to the treatment of Lower Urinary Tract Symptoms (LUTS) suggestive of Benign Prostatic Hyperplasia (BPH) is probably as old as Transurethral Resection of the Prostate (TURP). In an effort to overcome the limitations and morbidities of TURP, and in light of evidence suggesting that medical treatment for BPH has a limited life-span, laser-based treatments have emerged during the last decade. Photoselective Vaporization of the Prostate (PVP) by the "GreenLight" KTP laser is considered one of the most promising options, one that is constantly evolving new technologies in prostate surgery. In this overview of KTP laser usage in BPH treatment, we will briefly discuss the evolution of this modality since it was first introduced and focus on the available evidence regarding safety, efficacy and cost parameters of its application