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Darryll J. Pines

Bio: Darryll J. Pines is an academic researcher from University of Maryland, College Park. The author has contributed to research in topics: Hypersonic speed & Wave propagation. The author has an hindex of 32, co-authored 167 publications receiving 4136 citations. Previous affiliations of Darryll J. Pines include Massachusetts Institute of Technology.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors define the terms rotor disk area, sectional drag coefficient, and zero-lift drag coefficient for rotor disk areas, where the sectional coefficient is defined as the ratio of the area of the rotor disk to the length of the chord length.
Abstract: Nomenclature Ar = rotor disk area CD = sectional drag coefficient CD0 = zero-lift drag coefficient Clα = lift-curve slope CP = power coefficient CPi = induced power coefficient CP0 = profile power coefficient CT = thrust coefficient c = chord length D = drag force D.L . = disk loading L = lift force m = mass P.L . = power loading SF = separated flow T = rotor thrust V = local wind velocity perceived by flap W = weight W f = final weight Wo = gross takeoff weight α = blade section angle of attack η = efficiency μ = dynamic viscosity ρ = air density σ = rotor solidity = flapping amplitude (peak to peak)

559 citations

Journal ArticleDOI
TL;DR: Emerging research trends suggest that improvements in signal processing, sensor development and individual-tooth mesh waveform modelling could improve the performance of current and future helicopter transmission diagnostics.

497 citations

Journal ArticleDOI
TL;DR: The feasibility of determining spacecraft time and position using x-ray pulsars is explored in this article, where a detailed analysis of eight x-rays is presented to quantify expected spacecraft position accuracy based on described pulsar properties, detector parameters, and pulsar observation times.
Abstract: The feasibility of determining spacecraft time and position using x-ray pulsars is explored. Pulsars are rapidly rotating neutron stars that generate pulsed electromagnetic radiation. A detailed analysis of eight x-ray pulsars is presented to quantify expected spacecraft position accuracy based on described pulsar properties, detector parameters, and pulsar observation times. In addition, a time transformation equation is developed to provide comparisons of measured and predicted pulse time of arrival for accurate time and position determination. This model is used in a new pulsar navigation approach that provides corrections to estimated spacecraft position. This approach is evaluated using recorded flight data obtained from the unconventional stellar aspect x-ray timing experiment. Results from these data provide first demonstration of position determination using the Crab pulsar.

318 citations

Journal ArticleDOI
TL;DR: In this article, a new signal processing tool involving the use of empirical mode decomposition and its application to health monitoring of structures is discussed, which is used to process time-series data from a variety of 1-D structures with and without structural damage.

147 citations

Journal ArticleDOI
TL;DR: In this article, an overview of ongoing research and development in the field of structural health monitoring technologies in the US, with application to long-span bridges, is given, including sensor development, data processing, damage detection algorithms, data analysis and information processing.
Abstract: This paper gives an overview of ongoing research and development in the field of structural health monitoring technologies in the US, with application to long-span bridges. Specifically, this paper attempts to review various key structural health monitoring technologies, including sensor development, data processing, damage detection algorithms, data analysis and information processing. Several examples are cited from the aerospace, civil and mechanical communities. Monitoring of constructed systems are of considerable interest since the consequences of failure can have a significant effect on the society at large. For instance, consider the 1100 major long-span bridges in the USA (those with spans of 100 m or longer), many are over 50 years old, and several notable ones are over 100 years old. These bridges fall outside the Standard Specifications issued by AASHTO (1998), and there is little generic experience related to maintaining their performance, especially after they age and/or following any damage. More than 800 of the long-span bridges in the National Bridge Inventory are classified as fracture-critical. It follows that structural health monitoring techniques may prove to be useful for maintaining and preserving this population of aging civil infrastructure. It is hoped that the following will stimulate additional discussion regarding the importance of structural health monitoring as an emerging research area for a variety of aerospace, civil and mechanical applications.

145 citations


Cited by
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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Proceedings ArticleDOI
09 May 2011
TL;DR: An algorithm is developed that enables the real-time generation of optimal trajectories through a sequence of 3-D positions and yaw angles, while ensuring safe passage through specified corridors and satisfying constraints on velocities, accelerations and inputs.
Abstract: We address the controller design and the trajectory generation for a quadrotor maneuvering in three dimensions in a tightly constrained setting typical of indoor environments. In such settings, it is necessary to allow for significant excursions of the attitude from the hover state and small angle approximations cannot be justified for the roll and pitch. We develop an algorithm that enables the real-time generation of optimal trajectories through a sequence of 3-D positions and yaw angles, while ensuring safe passage through specified corridors and satisfying constraints on velocities, accelerations and inputs. A nonlinear controller ensures the faithful tracking of these trajectories. Experimental results illustrate the application of the method to fast motion (5–10 body lengths/second) in three-dimensional slalom courses.

1,875 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the possibility of dissipating mechanical energy with piezoelectric material shunted with passive electrical circuits, and derived the effective mechanical impedance for the piezolectric element shunted by an arbitrary circuit.

1,685 citations

Journal ArticleDOI
TL;DR: This paper is intended to serve as a summary review of the collective experience the structural engineering community has gained from the use of wireless sensors and sensor networks for monitoring structural performance and health.
Abstract: In recent years, there has been an increasing interest in the adoption of emerging sensing technologies for instrumentation within a variety of structural systems. Wireless sensors and sensor networks are emerging as sensing paradigms that the structural engineering field has begun to consider as substitutes for traditional tethered monitoring systems. A benefit of wireless structural monitoring systems is that they are inexpensive to install because extensive wiring is no longer required between sensors and the data acquisition system. Researchers are discovering that wireless sensors are an exciting technology that should not be viewed as simply a substitute for traditional tethered monitoring systems. Rather, wireless sensors can play greater roles in the processing of structural response data; this feature can be utilized to screen data for signs of structural damage. Also, wireless sensors have limitations that require novel system architectures and modes of operation. This paper is intended to serve as a summary review of the collective experience the structural engineering community has gained from the use of wireless sensors and sensor networks for monitoring structural performance and health.

1,497 citations

07 Apr 2002
TL;DR: An updated review covering the years 1996 2001 will summarize the outcome of an updated review of the structural health monitoring literature, finding that although there are many more SHM studies being reported, the investigators, in general, have not yet fully embraced the well-developed tools from statistical pattern recognition.
Abstract: Staff members at Los Alamos National Laboratory (LANL) produced a summary of the structural health monitoring literature in 1995. This presentation will summarize the outcome of an updated review covering the years 1996 2001. The updated review follows the LANL statistical pattern recognition paradigm for SHM, which addresses four topics: 1. Operational Evaluation; 2. Data Acquisition and Cleansing; 3. Feature Extraction; and 4. Statistical Modeling for Feature Discrimination. The literature has been reviewed based on how a particular study addresses these four topics. A significant observation from this review is that although there are many more SHM studies being reported, the investigators, in general, have not yet fully embraced the well-developed tools from statistical pattern recognition. As such, the discrimination procedures employed are often lacking the appropriate rigor necessary for this technology to evolve beyond demonstration problems carried out in laboratory setting.

1,467 citations