A microcontinuum analysis of the self propulsion of the spermatozoa in the cervical canal

The hydrodynamics of the self propulsion of a spermatozoa, swimming through the mucus filling the cervical channel, is investigated. The mucus is modeled as a micropolar fluid and the spermatozoa as a 2-dimensional sheet swimming at low Reynolds number between two rigid walls. The wavelengths of the propulsive waves passing down the sheet are assumed to be very large compared to the channel spacing, but the amplitude of the propulsive waves is arbitrary. Expressions for the propulsive velocity and the energy expended by the swimming sheet are obtained in terms of various parameters involved. The results are elaborated through graphs. It is found that both the propulsive velocity and the rate of working by the sheet increase as the value of the micropolar parameters $\text{N}$ increases and that of $\text{L}$ decreases.     

Parallel heap: An optimal parallel priority queue

We describe a new parallel data structure, namely parallel heap, for exclusive-read exclusive-write parallel random access machines. To our knowledge, it is the first such data structure to efficiently implement a truly parallel priority queue based on a heap structure. Employing p processors, the parallel heap allows deletions of (p) highest priority items and insertions of (p) new items, each in O(log n) time, where n is the size of the parallel heap. Furthermore, it can efficiently utilize processors in the range 1 through n.This work was supported by U.S. Army's PM-TRADE contract N61339-88-g-0002, Florida High Technology and Industry grant 11-28-716, and Georgia State University's internal research support during spring and summer quarters, 1991.     

UAV Path Following in Windy Urban Environments

This paper considers UAV path following in cluttered environments under windy conditions. Unstructured wind patterns in cluttered environments can make path following difficult resulting in high errors and possibly collisions with buildings. Combining a pursuit guidance law philosophy with a line-of-sight guidance law, we develop a novel guidance law that has low computational complexity and can track straight line paths, circular paths, a combination of both and waypaths accurately in the presence of wind blowing as high as fifty percent of the UAV’s air speed. Performance of the guidance law is demonstrated through numerical simulations.     

Detecting localized homogeneous anomalies over spatio-temporal data

The last decade has witnessed an unprecedented growth in availability of data having spatio-temporal characteristics. Given the scale and richness of such data, finding spatio-temporal patterns that demonstrate significantly different behavior from their neighbors could be of interest for various application scenarios such as—weather modeling, analyzing spread of disease outbreaks, monitoring traffic congestions, and so on. In this paper, we propose an automated approach of exploring and discovering such anomalous patterns irrespective of the underlying domain from which the data is recovered. Our approach differs significantly from traditional methods of spatial outlier detection, and employs two phases—(i) discovering homogeneous regions, and (ii) evaluating these regions as anomalies based on their statistical difference from a generalized neighborhood. We evaluate the quality of our approach and distinguish it from existing techniques via an extensive experimental evaluation.     

Product property and production rate control of styrene polymerization

A multivariable multi-rate nonlinear model predictive control (NMPC) strategy is applied to styrene polymerization. The NMPC algorithm incorporates a multi-rate Extended Kalman Filter (EKF) to handle state variable and parameter estimation. A fundamental model is developed for the styrene polymerization CSTR, and control of polymer properties such as number average molecular weight (NAMW) and polydispersity is considered. These properties characterize the final polymer distribution and are strong indicators of the polymer qualities of interest. Production rate control is also demonstrated. Temperature measurements are available frequently while laboratory measurements of concentration and molecular weight distribution are available infrequently with substantial time delays between sampling and analysis. Observability analysis of the augmented system provides guidelines for the design of the augmented disturbance model for use in estimation using the multi-rate EKF. The observability analysis links measurement sets and corresponding observable disturbance models, and shows that measurements of moments of the polymer distribution are essential for good estimation and control. The CSTR is operated at an open-loop unstable steady state. Control simulations are performed under conditions of plant-model structural mismatch and in the presence of parameter uncertainty and disturbances, and the proposed multi-rate NMPC algorithm is shown to provide superior performance compared to linear multi-rate and nonlinear single-rate MPC algorithms. The major contributions of this work are the development of the multi-rate estimator and the measurement design study based on the observability analysis.     

Safety,liveness and fairness in temporal logic

In this paper we present syntactic characterization of temporal formulas that express various properties of interest in the verification of concurrent programs. Such a characterization helps us in choosing the right techniques for proving correctness with respect to these properties. The properties that we consider include safety properties, liveness properties and fairness properties. We also present algorithms for checking if a given temporal formula expresses any of these properties.This work is partly supported by NSF grant CCR-9212183. A preliminary version of this paper appeared in the Fourth ACM Symposium on Principles of Distributed Computing.     

Design of decentralized robust load-frequency controller based on SVD method

A decentralized robust control scheme is presented for the load-frequency control of interconnected power systems with uncertain parameters. A singular value decomposition (SVD) technique and Lyapunov stability theory are adopted to implement a decentralized robust controller. The stability analysis of the closed-loop interconnected systems for all admissible uncertainties is discussed. The performance robustness of the proposed decentralized robust control scheme has been verified through simulation studies on a two-area power system model. The effectiveness of the decentralized control algorithm is compared to that of a centralized robust one. It has been found that both control schemes have almost the same performance with integral control action in the presence of parametric uncertainty in the plant.     

Sparse NMF based speech enhancement with bases update

In this paper, a combination of methods based on statistical modelling and Non-negative Matrix Factorization (NMF) for speech enhancement using speech and noise bases with on-line update is proposed. Template-based approaches are known to be more robust in the presence of non-stationary noises than methods based on statistical modeling. However, template-based approaches depend on a-priori information. The drawbacks of both the approaches can be avoided by combining them. In NMF approach, speech bases and noise bases are simultaneously adapted to further improve the performance. The proposed method outperforms other benchmark algorithms in terms of perceptual evaluation of speech quality (PESQ) and source-to-distortion ratio (SDR) in stationary and non-stationary noise environment conditions with matched and mismatched noise basis.